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Home My WebLink AboutCT 2018-0002; AVIARA APARTMENTS; REVISED PRELIMINARY GEOTECHNICAL EVALUATION; 2019-04-01REVISED PRELIMINARY GEOTECHNICAL EVALUATION 2 VENTURE, SUITE 360 IRVINE, CALIFORNIA 92618 W .0. 7103-A-SC APRIL1 ,2019 ECEIVE APR O 5 2019 CITY OF CARLSBAD PLANNING DIVISION • Geotechnical •Geologic• Coastal• Environmental 5741 Palmer Way • Carlsbad, California 92010 • (760) 438-3155 • FAX (760) 931-0915 • www.geosoilsinc.com Summerhill Homes 2 Venture, Suite 360 INine, California 92618 Attention: Mr. Keven Doherty April 1, 2019 W.O. 7103-A-SC Subject: Revised Preliminary Geotechnical Evaluation, 9.2 Acres, APN 212-040-56-00, Laurel Tree Lane at Aviara Parkway, Carlsbad, San Diego County, California Dear Mr. Doherty: In accordance with your request and authorization, GeoSoils, Inc. (GSI) is pleased to present the results of our preliminary geotechnical evaluation of the subject site. The purpose of our study was to evaluate the site geologic and geotechnical conditions relative to the residential development proposed thereon, and to provide preliminary recommendations for earthwork construction and the design of foundations, slab-on-grade floors, and driveway pavement. EXECUTIVE SUMMARY Based upon our field exploration , geologic, and geotechnical engineering analysis, the proposed residential development appears feasible from a soils engineering and geologic viewpoint, provided that the recommendations presented in the text of this report are properly incorporated into the design and construction of the project. The most significant elements of our study are summarized below: • In general, surficial earth materials units at the site consist of undocumented artificial fill, roadway fill, underlain by alluvium (encountered on the eastern parcel only), and in turn underlain by bedrock of the Santiago Formation. The upper approximately 1 ½ feet of the Santiago Formation is weathered. • Due to their relative low density and compressibility, all undocumented fill, roadway fill , alluvium, and weathered Santiago Formation are considered unsuitable for the support of settlement-sensitive improvements (i.e., residential structures, walls, pavements, etc.) and/or new planned fills in their existing state. Based on the available data, the thickness of potentially compressible soils, excluding roadway fill areas, based on the available subsurface data, remedial grading excavations are anticipated to extend to depths on the order of 17 to 20 feet below existing grades, on the east parcel, and about 3 to 7 feet below existing grade on the west parcel. However, localized thicker sections of unsuitable soils cannot be precluded and should be anticipated. Conversely, the underlying unweathered Santiago Formation is considered suitable for the support of settlement-sensitive improvements and new planned fills. In order to provide uniform support of settlement-sensitive improvements, all undocumented fills , roadway fil , and weathered Santiago Formation should be removed to expose the underlying, unweathered bedrock (Santiago Formation). The excavated soils may then be reused as engineered fills provided they are relatively free of organic matter and deleterious debris prior to placement, and prepared in accordance with the recommendations in this report. Alternatively, the proposed residential structures may incorporate deep foundations and a structural concrete slab-on-grade floor. Please note, if the latter is selected, any ancillary site improvement (i.e., walls , hardscape, etc.) not supported by deep foundations or a structural slab may be subject to settlement and resultant distress. • It should be noted that the 2016 California Building Code ([2016 CBC], California Building Standards Commission [CBSC], 2016) indicates that the removal and recompaction of unsuitable soils be performed across all areas to be graded, under the purview of a grading permit, and not just within the influence of the proposed improvements. Relatively deep removals may also necessitate a special zone of consideration, on perimeter/confining areas. This zone would be approximately equal to the depth of removals , if removals cannot be performed onsite or offsite. Perimeter conditions and existing offsite improvements will limit the removal and recompaction of potentially compressible soils near the margins of the site. As such, any settlement-sensitive improvement at the property line would require deepened foundations, additional reinforcement, or would retain some potential for distress and therefore, a reduced serviceable life. The limits of the proposed remedial grading are indicated herein. On a preliminary basis, any planned settlement-sensitive improvements located approximately 17 to 20 feet from the property line on the east parcel, or within about 20 feet of the roadway fill would require deepened foundations or additional reinforcement by means of ground improvement or specific structural design. This should be considered during project design, planning and construction. This condition should be disclosed to all interested/affected parties should it exist at the conclusion of grading. • Visual classification and expansion index (E.I.) testing, performed on representative samples of the onsite soils, indicates expansion indices ranging from 32 up to 72, with the potential for the occurrence of even higher E.l.s. Thus, the expansion potential of the onsite soils ranges between low and medium, to perhaps highly expansive. Based on the available laboratory data, some of the near-surface, onsite soils meet the criteria for expansive soils, as indicated in Section 1803.5.3. of the 2016 CBC (CBSC, 2016). In order to comply with 2016 CBC requirements for the mitigation of expansive soils, the proposed residential structures will need specific foundation and slab-on-grade design that will tolerate the shrink/swell effects of highly expansive soils (see Sections 1808.6.1 and 1808.6.2 of the 2016 CBC). Alternatively, expansive soils within the influence of the proposed residential structures may be removed and replaced with very low expansive soils (E.I. less Summerhill Homes File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. W.O. 7103-A-SC Page Two .. ... .. ... ... ... .. .. ... .. ... -,.. .. ... .. .. ... .. ... .. .. .. JIil .. ,,. .. ,,,,. .. .. .. ,,. .. ... ... .. • • • • • • than 21) with a plasticity index (P.I.) less than 15 (see Section 1808.6.3 of the 2016 CBC), reducing foundation requirements . Laboratory testing indicates thattested samples of the onsite soils are: medium acid to slightly acid with respect to soil acidity/alkalinity; severely corrosive to exposed, buried metals when saturated; present a negligible sulfate exposure to concrete (Exposure Class SO per American Concrete Institute [ACI] 318-14); and have low to slightly elevated concentrations of soluble chlorides. The use of concrete conforming to Exposure Class C1 in American Concrete Institute (ACI) 318-14, should be utilized, as the concrete would likely be exposed to water. GSI does not practice in the field of corrosion engineering. Thus, the project architect and structural engineer should evaluate the level of corrosion protection required for the project and seek consultation from a qualified corrosion engineer, as warranted. Groundwater was encountered only in Boring B-1 at a depth of about 21 ½ feet. The piezometric surface associated with perched groundwater has been as high as 10 feet below original grade, on the northern margin of the property. Perched groundwater may be encountered during site earthwork, in excavations for deep utilities, and may not be precluded in shallow excavations. This should be considered in project planning and construction . Our evaluation indicates there are no known active faults crossing the site and the site has very low susceptibility to deep-seated landslides; however, the hills descending from the south toward the western parcel have been mapped as having a moderate to high potential for mud flows (Leighton and Associates, Inc., 1992) . Recommendations for the mitigation of mud flows are provided herein. The potential for the site to be adversely affected by liquefaction/lateral spreading is considered low, provided the geotechnical recommendations, presented herein, are properly incorporated into the project design and construction. Site soils are considered erosive. Thus, properly designed and maintained site drainage is considered necessary from a geotechnical standpoint to reduce damage to the planned improvements from erosion. The seismic acceleration values and design parameters provided herein should be considered during the design of the proposed development. The adverse effects of seismic shaking on the structure(s) will likely be wall cracks, some foundation/slab distress, and some seismic settlement. However, it is anticipated that the proposed structures will be repairable in the event of the design seismic event. This potential should be disclosed to all interested/affected parties. Additional adverse geologic features that would preclude project feasibility were not encountered, based on the available data . The recommendations presented in this report should be incorporated into the design and construction considerations of the project. Summerhill Homes File:e:\wp12\7100\7103a.rpge GeoSoils, Inc . W.O. 7103-A-SC Page Three The opportunity to be of service is sincerely appreciated. If you should have any questions, please do not hesitate to contact our office. Respectfully submi GeoSoils, Inc. ~!~ Engineering Geolog1 RB/JPF/DWS/jh Distribution: (3) Addressee Summerhill Homes File:e:\wp12\7100\7103a.pge ~~ Civil Engineer, RCE GeoSoils, Inc. W.O. 7103-A-SC Page Four .. .. .. .. , ... , .. .. . .. J ... ' .. ... I .. 11111 .. , .. ., .. .. ... ... ... .. ... ,.. ... .... .. .. .. ... ... .. ... ... ... -.. .. .. .. ... .. ,,.. ... .. .. ... .. ... .. .. ,. ill TABLE OF CONTENTS SCOPE OF SERVICES ................................................... 1 SITE DESCRIPTION AND PROPOSED DEVELOPMENT ......................... 1 FIELD STUDIES ......................................................... 3 REGIONAL GEOLOGY ................................................... 4 SITE GEOLOGIC UNITS .................................................. 6 Artificial Fill -Undocumented (Map Symbol -Afu) ........................ 6 Artificial Fill -Roadway (Map Symbol -Afr) .............................. 6 Quaternary Alluvium (Map Symbol -Qal) ............................... 7 Tertiary Santiago Formation (Map Symbol -Tsa) ......................... 7 GEOLOGIC STRUCTURE ................................................. 7 GROUNDWATER ........................................................ 7 ROCK HARDNESS/EXCAVATION DIFFICULTY ................................ 8 GEOLOGIC HAZARDS EVALUATION ........................................ 8 Mass Wasting/Landslide Susceptibility ................................. 8 FAULTING AND REGIONAL SEISMICITY ..................................... 9 Regional Faults .................................................... 9 Local Faulting .................................................... 1 O Surface Rupture .................................................. 1 O Seismicity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 O Seismic Shaking Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 SECONDARY SEISMIC HAZARDS ......................................... 12 Liquefaction/Lateral Spreading ...................................... 12 Seismic Densification .............................................. 13 Other Geologic/Secondary Seismic Hazards ........................... 13 LABORATORY TESTING ................................................. 13 Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Moisture-Density Relations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Laboratory Standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Expansion Index .................................................. 14 Atterberg Limits ................................................... 15 Grain Size Distribution ............................................. 15 Direct Shear Test ................................................. 15 GeoSoils, Inc . Consolidation Test ................................................ 15 Saturated Resistivity, pH, and Soluble Sulfates, and Chlorides ............. 16 Corrosion Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 PRELIMINARY SETTLEMENT EVALUATION ................................. 16 Post-Grading Settlement ........................................... 17 Seismic Settlement of Fill ........................................... 17 Foundation Settlement Due to Structural Loads . . . . . . . . . . . . . . . . . . . . . . . . . 17 Settlement Summary .............................................. 18 PRELIMINARY CONCLUSIONS AND RECOMMENDATIONS .................... 18 GENERAL RECOMMENDATIONS ......................................... 20 Alternative "A" .................................................... 21 Advantages ................................................ 21 Disadvantages .............................................. 21 Alternative "B" .................................................... 22 Advantages ................................................ 22 Disadvantages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 EARTHWORK CONSTRUCTION RECOMMENDATIONS -ALTERNATIVE "A" ....... 22 General ......................................................... 22 Site Preparation .................................................. 23 Removal and Recompaction of Potentially Compressible Earth Materials .... 23 Earthwork Mitigation of Detrimentally Expansive Soils .................... 24 Alternating Slot Excavations ........................................ 24 Perimeter Conditions .............................................. 24 Fill Placement .................................................... 25 Overexcavation ................................................... 25 Subdrains ....................................................... 25 Earthwork Balance (Shrinkage/Bulking) ............................... 25 Import Soils ...................................................... 26 Slope Considerations and Slope Design .............................. 26 Temporary Slopes ................................................ 26 Excavation Observation and Monitoring (All Excavations) ................. 27 Observation ................................................ 27 PRELIMINARY FOUNDATION RECOMMENDATIONS -ALTERNATIVE A .......... 28 General ......................................................... 28 General Foundation Design ......................................... 29 Preliminary Foundation and Fill Settlements -Alternative A ................ 30 Preliminary Conventional Foundation and Slab-On-Grade Construction Recommendations -Non Detrimentally Expansive Soils ............. 30 Summerhill Homes File:e:\wp 12\7100\7103a, rpge GeoSoils, Inc. Table of Contents Page ii .. ,, .. ... .. , .. ., .. , .. ., .. , .. , .. ... I .. .. • , "' .. .., ., .. ., .. ~ """ ... .. ... ... ,.. .. ... ,.. ... ... .. .... ... ... ... -,.. .. ... ,,. .. ,.. .. ,.. .. ,.. .. .. ... ,.. .. Post-Tensioned Slab Foundation Systems ............................. 32 Slab Subgrade Pre-Soaking ................................... 33 Perimeter Cut-Off Walls ....................................... 33 Post-Tensioned Foundation Design ............................. 33 Soil Support Parameters ...................................... 34 Preliminary Foundation Design and Construction Recommendations for Mat-Type Foundations -Alternative A .................................... 35 Mat Foundation Design ....................................... 35 Slab Subgrade Moisture Content ............................... 36 DRILLED PIER AND GRADE BEAM FOUNDATION RECOMMENDATIONS (ALTERNATIVE B) ................................................. 36 Passive Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Point of Fixity .................................................... 37 Allowable Axial Capacity ........................................... 37 Caisson Construction .............................................. 37 Drilled Pier and Grade Beam Foundation Settlement ..................... 38 Corrosion and Concrete Mix ........................................ 38 SOIL MOISTURE TRANSMISSION CONSIDERATIONS (BOTH ALTERNATIVES) .... 38 WALL DESIGN PARAMETERS ............................................ 40 General ......................................................... 40 Conventional Retaining Walls ....................................... 40 Preliminary Retaining Wall Foundation Design .................... 41 Restrained Walls ............................................ 42 Cantilevered Walls ........................................... 42 Seismic Surcharge ................................................ 43 Retaining Wall Backfill and Drainage .................................. 43 Wall/Retaining Wall Footing Transitions ............................... 47 TEMPORARY SHORING DESIGN AND CONSTRUCTION ...................... 48 Shoring of Excavations ............................................. 48 Lateral Pressure -Temporary Shoring ................................. 48 Temporary Shoring Construction Recommendations .................... 51 Monitoring of Shoring .............................................. 52 Monitoring of Existing Improvements ............................ 53 DEBRIS IMPACT WALLS ................................................. 53 WALLS/FENCES/IMPROVEMENTS ........................................ 54 Perimeter Walls/Fences ............................................ 54 DRIVEWAY, FLATWORK, AND OTHER IMPROVEMENTS ....................... 55 Summerhill Homes File:e:\wp12\7100\7103a.rpge GeoSoils, Inc . Table of Contents Page iii PRELIMINARY PAVEMENT DESIGN/CONSTRUCTION ........................ 57 Structural Section ................................................. 57 PAVEMENT GRADING RECOMMENDATIONS ............................... 58 General ......................................................... 58 Subgrade ....................................................... 59 Aggregate Base .................................................. 59 Paving .......................................................... 59 Drainage ........................................................ 60 PCC Cross Gutters ................................................ 60 Additional Considerations .......................................... 60 ONSITE INFILTRATION-RUNOFF RETENTION SYSTEMS ...................... 60 General ......................................................... 60 DEVELOPMENT CRITERIA ............................................... 66 Drainage ........................................................ 66 Erosion Control ................................................... 66 Landscape Maintenance ........................................... 66 Gutters and Downspouts ........................................... 67 Subsurface and Surface Water ...................................... 67 Site Improvements ................................................ 67 Tile Flooring ..................................................... 67 Additional Grading ................................................ 68 Footing Trench Excavation ......................................... 68 Trenching/Temporary Construction Backcuts .......................... 68 Utility Trench Backfill .............................................. 68 SUMMARY OF RECOMMENDATIONS REGARDING GEOTECHNICAL OBSERVATION AND TESTING ........................................................ 69 OTHER DESIGN PROFESSIONALS/CONSULTANTS .......................... 70 PLAN REVIEW ......................................................... 70 LIMITATIONS .......................................................... 71 FIGURES: Figure 1 -Site Location Map ......................................... 2 Figure 2 -Test Pit Location Map ...................................... 5 Detail 1 -Typical Retaining Wall Backfill and Drainage Detail .............. 44 Detail 2 -Retaining Wall Backfill and Subdrain Detail Geotextile Drain ....... 45 Detail 3 -Retaining Wall and Subdrain Detail Clean Sand Backfill ........... 46 Figure 3 -Lateral Earth Pressures for Temporary Shoring ................. 49 Figure 4 -USDNNRCS Soil Units Map ................................ 62 Summerhill Homes File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. Table of Contents Page iv , .. ., • .. t .. , .. , .. , .. ., • .. t .. , .. , .. ... 4 .. 1111 f .. , .. , .. , .. .. .. ,,,. .. ... .. ,.. .. ,,. .. ,,,. .. .. .. ... ... ,,,. ... ... ,,. -,,,. .. ,.. .. .. .. .. .. .. .. ,,. ... ATTACHMENTS: Appendix A -References ................................... Rear of Text Appendix B -Test Pit Logs .................................. Rear of Text Appendix C -Seismicity .................................... Rear of Text Appendix D -Laboratory Data ............................... Rear of Text Appendix E -Liquefaction Analysis ........................... Rear of Text Appendix F -Infiltration Data and Form 1-8 ..................... Rear of Text Appendix G -General Earthwork, Grading Guidelines, and Preliminary Criteria .. .................................................. Rear of Text Summerhill Homes File:e:\wp12\7100\7103a.rpge GeoSoils, Inc . Table of Contents Page v PRELIMINARY GEOTECHNICAL EVALUATION 9.2 ACRES, APN 212-040-56-00 LAUREL TREE LANE ATAVIARA PARKWAY CARLSBAD, SAN DIEGO COUNTY, CALIFORNIA SCOPE OF SERVICES The scope of our services has included the following: 1. 2. 3. 4. 5. Review of readily available published literature, aerial photographs, and maps of the site vicinity, including in-house nearby geotechnical reports (see Appendix A). Site reconnaissance mapping and sub-surface exploration using a hollow stem auger drill rig and cone penetrometer test soundings (CPT). Two (2) auger borings were drilled on the east and west parcels (one [1] on each parcel), to a depth of approximately 50 feet. Four (4) CPT explorations were conducted (two [2] on each parcel), although several more soundings were attempted, but were not successful (refusal). Accordingly, the CPT soundings are not in sequential order. Shear wave velocity and pore water pressure were measured in the CPTs. All exploratory borings were backfilled per DEH guidelines (see Appendix B). In addition, and concurrently, two (2) shallow supplemental borings were advanced for the purposes of infiltration testing in the soil type designated as "Hydrologic Group A," by the USDA. General areal geologic and seismic hazards evaluation (see Appendix C). Appropriate laboratory testing of representative undisturbed and bulk soil samples collected during our subsurface exploration program (see Appendix D). 6. Analysis of field and laboratory data relative to the proposed development. 7. 8. 9. Perform an evaluation of soil settlement and liquefaction potential (Appendix E). Infiltration data and City of Carlsbad Form 1-8 are included in Appendix F. Appropriate engineering and geologic analyses of data collected, and the preparation of this summary report and accompaniments. SITE DESCRIPTION AND PROPOSED DEVELOPMENT The subject site consists of two parcels located on the east and west sides of Aviara Parkway in the City of Carlsbad, San Diego County, California (see Figure 1, Site Location Map). Roadway/driveway fill associated with Aviara Parkway transects the eastern third of the site in a roughly north-south direction, descending to the west and east, separating the GeoSoils, Inc. ; .. • , .. .. , • , ... , .. , .. , .. ... ' .. ., .. ., .., , ... ., ... J Base Map: TOPO!@ @2003 National Geographic, U.S.G.S. Encinitas Quadrangle, California --San Diego Co., 7.5 Minute, dated 1997, current, 1999. Base Map: Google Maps, Copyright 2016 Google, Map Data Copyright 2016 Google w.o. This map Is copyrighted by Google 2016. ff Is unlawful lo copy or reproduce all or any part thereof, whether for personal use or resale, without permission. All rights reserved . 7103-A-SC • N SITE LOCATION MAP Figure 1 two parcels. Roadway fill associated with Laurel Tree Lane descends to the eastern parcel, from the south. The Laurel Tree Lane roadway fill ranges up to about 16 feet in overall height. The eastern portion of the site is bounded by Aviara Parkway to the west, Laurel Tree Lane to the south and east, and a natural channel leading to a vacant lot to the north. According to the topographic survey prepared by REC Consultants, Inc. ([REC], 2016), site elevations range between approximately 94 and 111 feet (datum is not labeled), for an overall relief of about 17 feet. The eastern site slopes to the northwest at a very gentle gradient. Low hanging power lines cross on the eastern margin of this parcel. Access is through a locked gate below the power lines on the east. The east site is vegetated with what appears to be native weeds and plants, with a few trees along Aviara Parkway and Laurel Tree Lane. The western portion of the site is bounded by Aviara Parkway to the east and vacant areas of vegetation on the remaining sides. Slopes exist on the east, south, and west sides, and the aforementioned drainage borders the northern margin of this site. A commercial building distributing wholesale flowers occupies the central-southerly portion of the western site. Roadway fill associated with Aviara Parkway and two driveways ranges up to about 23 feet in overall height. Site elevations range between a high of about 144 feet in the southeast corner on a hillside, to a low of about 82 feet in the east-west flowing drainage area at the northeast margin of the western property (REC, 2016), for an overall relief of ±62 feet. The commercial site is generally flat graded, with drainage directed to a drainage channel along the toe of the hillside to the west and southwest. The natural portion of the west site is sparsely to moderately covered by native weeds, grasses and shrubs, and the slopes and areas adjoining Aviara Parkway have been vegetated with shrubs and a few trees, including palm trees. The northern and western margins are lightly covered with grasses and weeds, with shrubs becoming more prolific to the north. Based on our review of the preliminary architectural plans prepared by KTGY Architecture + Planning ([KTGY], 2016), GSI understands that proposed development includes razing the existing building and improvements, and preparing the site to receive a new two-to four-story multi-family residential complex with associated parking either on grade surrounding the buildings, or in a centrally located four-story parking structure. KTGY (2016) illustrations are preliminary and do not have any additional design information at this time. FIELD STUDIES Site-specific field studies were conducted by GSI on June 15, 16, and 17, 2016, and consisted of reconnaissance geologic mapping, and advancing two (2) hollow-stem auger borings (one [1] on each parcel), followed by four (4) CPT soundings (two [2] on each parcel). GSI attempted to advance two (2) additional CPT soundings. However, these soundings encountered practical refusal essentially at the ground surface. Since practical Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. W.O. 7103-A-SC April 1, 2019 Page 3 ... .. .. ... .. -.. ,,,. .. ... .. ... ... .. ... ... .. ... .. .. -,,,,. .. ... ... ... refusal prevented the acquisition of useful subsurface data from these soundings, the associated CPT logs were not included herein. This is the reason for the non-consecutive numbering sequence for the CPT logs published herein. In addition to the hollow-stem auger borings and CPT soundings, two (2) shallow borings were advanced for infiltration purposes, one on each parcel. The borings were logged by a representative of this office who collected relatively undisturbed and representative bulk soil samples for appropriate laboratory testing. The logs of the explorations are presented in Appendix B. Site geology and the location of the borings and CPT soundings are presented on the Boring Location Map (see Figure 2), which uses REC (2016) as a base. REGIONAL GEOLOGY The site is located near the boundary between the coastal plain and the central mountain-valley physiographic sections of San Diego County. The coastal plain section is characterized by pronounced marine wave-cut terraces intermittently dissected by stream channels that convey water from the eastern highlands to the Pacific Ocean. The central mountain-valley section is characterized by ridges and intermontane basins. The basins or valleys range between 500 and 5,000 feet in elevation and are likely due to multiple erosion cycles. However, several of the larger intermontane basins owe their configuration to structural control and erosion of crystalline rocks. Mountain peaks in this physiographic section ascend to elevations greater than 6,000 feet. San Diego County lies within the Peninsular Ranges Geomorphic Province of southern California. This province is characterized as elongated mountain ranges and valleys that trend northwesterly (Norris and Webb, 1990). This geomorphic province extends from the base of the east-west aligned Santa Monica-San Gabriel Mountains, and continues south into Baja California, Mexico. The mountain ranges within this province are underlain by basement rocks consisting of pre-Cretaceous metasedimentary rocks, Jurassic metavolcanic rocks, and Cretaceous plutonic (granitic) rocks . The San Diego County region was originally a broad area composed of pre-batholithic rocks that were subsequently subjected to tectonism and metamorphism. In the late Cretaceous Period, the southern California Batholith was emplaced causing the aforementioned metamorphism of pre-batholithic rocks. Many separate magmatic injections originating from this body occurred along zones of structural weakness . Following batholith emplacement, uplift occurred, resulting in the removal of the overlying rocks by erosion. Erosion continued until the area was that of low relief and highly weathered. The eroded materials were deposited along the sea margins. Sedimentation also occurred during the late Cretaceous Period. However, subsequent erosion has removed much of this evidence. In the early Tertiary Period, terrestrial sedimentation occurred on a low-relief land surface. In Eocene time, previously fluctuating sea levels stabilized and marine deposition occurred. In the late Eocene, regional uplift produced erosion and thick deposition of terrestrial sediments. In the middle Miocene, the submergence of the Los Angeles Basin resulted in the deposition of thick marine beds in Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc . W.O. 7103-A-SC April 1 , 2019 Page 4 I I I I I I I I I I I I I • 4.12 112.JI. ...-------- \ ____ ,.,. ... -- I \ I \ . \ 112~ I I PT-6 I ..• V.J DIii 0,11 ~-En,lr-,witol Land Surw,lng 2+u..,,.,._ s.ca..r,.c,.mcn Cona,tta,ts. Inc. (flt):1»:-tJOO (111)232-fflO '• -•-' ....... ALL LOCATIONS ARE APPROXIMATE This document or efife is not a part of the Construction Documents and should not be relied upon as being an accurate depiction of design. II 87/ 100 6145 LAUREL TREE ROAD, CARLSBAD, CA Afu Afr Qal Tsa B-2 s TD=40' GRAPHIC SCALE 0 50 100 200 1"= 100' TOPOGRAPHY NOJF ntE UHDERl YlilG T0POGMPt.:: FEATURES SHCMN HEREON 1/EREIIAPPE>IY: SAN -1.0AERW. SIMVEYS tt300STl'tEET,SUTE7.~CAViZDSS _, ... .1081: 1"°17C,..VW't.AP~Y') OATE:M3'201t GS/ LEGEND ARTIFICIAL FILL UNDOCUMENTfD CPT-6 I -•-I ARTIFICIAL FILL ROADWAY 1-2 QUA TfRNARY ALLUVIUM DEPOSITS, CIRCLED Q9 WHERE BURIED -- TcR17ARY-AGE SANTIAGO FORMA 17ON, CIRCLED ··••?••·· WHERE BURIED APPROX/MA TE LOCATION OF ---------HOLLOW-STEM-AUGER BORING, GS/ ~ APPROX/MA TE LOCATION OF CONE PENETRATION TEST (CPT), GS/ APPROX/MA TE LOCATION OF INFILTRATION TEST, GS/ APPROXIMATE LOCATION OF GEOLOGIC CONTACT APPROX/MA TE QUERIED LOCA T/ON OF BURIED GEOLOGIC CONTACT APPROX/MA TE LOCATION OF STUDY AREA APPROX/MA TE LOCA T/ON OF RECOMMENDED DEBRIS IMPACT WALL BORING LOCATION MAP Fi ure 2 W.O. 7103-A-SC DATE: 04/19 SCALE: 1" = 100' -.. ... .. .. ... ... ,,,. .. .. ... -.. ... .. ,,,. .. .. .. .. .. ,... .. .. fllll' ... the northwestern portion of San Diego County. During the Pliocene, marine sedimentation was more discontinuous and generally occurred within shallow marine embayments. The Pleistocene saw regressive and transgressive sea levels that fluctuated with prograding and recessive glaciation. The changes in sea level had a significant effect on coastal topography and resultant wave erosion and deposition formed many terraces along the coastal plain. In the mid-Pleistocene, regional faulting separated highland erosional surfaces into major blocks lying at varying elevations. A later rise in sea level, during the late Pleistocene caused the deposition of thick alluvial deposits within the coastal river channels. In recent geologic time, crystalline rocks have weathered to form residuum, highland areas have eroded, and deposition of river, lake, and beach sediments has occurred. Regional geologic mapping by Kennedy and Tan (2005 and 2007) shows the site is underlain by late Holocene unconsolidated alluvial flood plain deposits. Kennedy and Tan (2005 and 2007) suggest that these site deposits are underlain by middle Eocene sedimentary bedrock belonging to the Santiago Formation. However, the surface and subsurface data acquired during our site-specific field investigation indicated somewhat differing geologic conditions, as discussed below . SITE GEOLOGIC UNITS The site geologic units encountered or observed during our subsurface exploration and site reconnaissance include roadway fill, undocumented artificial fill, Holocene unconsolidated alluvial flood plain deposits, and sedimentary bedrock belonging to the Tertiary Santiago Formation. The earth materials are generally described, below, from the youngest to the oldest. The distribution of these materials is shown on Figure 2 . Artificial Fill -Undocumented (Map Symbol -Afu) Undocumented artificial fill was observed mantling the site in Borings 8-1, B-2, CPT-1, CPT-2, CPT-4A, and CPT-6. As observed, the fill was generally comprised of reddish yellow to light brown, to yellow brown, to light gray, sandy clays to sandy silts, with local gravels and asphalt debris. The fill was dry to moist, and loose to medium stiff. The fill was observed to extend to depths on the order of 3 to perhaps ± 7 feet below the existing grades (b.e.g.), on the western parcel, and about 1 o to 13 feet thick on the eastern parcel. Owing to the lack of documentation regarding engineering suitability and the observed non-uniformity, the existing fill is considered potentially compressible in its existing state. Mitigation of the existing fill is recommended, should settlement-sensitive improvements or additional fill be proposed within its influence. Artificial Fill -Roadway (Map Symbol -Afr) Although not encountered in our borings, roadway fill is associated with the embankments ascending to Aviara Parkway on both parcels, and Laurel Tree Lane on the eastern parcel. Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc . W.O. 7103-A-SC April 1, 2019 Page 6 Roadway fill associated with Aviara Parkway and the two driveways on the western parcel ranges up to about 23 feet thick, or more. The Laurel Tree Lane roadway fill ranges up to about 16 feet thick, or more. Similar to the undocumented fill, the existing fill is considered potentially compressible in its existing state. Mitigation ofthe existing fill is recommended, should settlement-sensitive improvements or additional fill be proposed within its influence. Quaternary Alluvium (Map Symbol -Qal) Holocene unconsolidated alluvial flood plain deposits were encountered at shallow depth on the easterly parcel, underlying the undocumented fill. As observed, the alluvium extended to depths on the order of 9 to 13 feet below the undocumented fill. The alluvium typically consisted of dark reddish brown, fine-grained sandy clay, with traces of pebbles. The alluvium was generally damp and loose. The alluvial deposits are considered potentially compressible in their existing state. As such, they should not be used for the support of settlement-sensitive improvements and/or new planned fills without mitigation. Tertiary Santiago Formation (Map Symbol -Tsa) The site is underlain at the surface and shallow depth by the middle Eocene-age Santiago Formation. In general, the weathered portions of the Santiago Formation consisted of dark reddish brown, silty sandstone, that was moist and dense. Unweathered Santiago Formation was encountered at approximate depths of 0 to 6½ feet below the weathered portion. As observed, the unweathered Santiago Formation consisted of varying shades of light gray and yellowish brown silty sandstone, and light yellow brown to yellowish gray claystone. Unweathered Santiago Formation was generally very moist to wet to saturated, and medium dense/medium stiff-stiff to very dense. Unweathered Santiago Formation is considered suitable for the support of proposed settlement-sensitive improvements and/or new planned fills. GEOLOGIC STRUCTURE The alluvium is typically thickly bedded and is gently inclined in a southwesterly direction, mimicking areal topography. Kennedy and Tan (2005 and 2007) show that Santiago Formation bedding in the site vicinity is inclined about 1 0 degrees to the southwest. GROUNDWATER Groundwater was encountered only in Boring B-1 at a depth of about 21 ½ feet. Thus, it appears that perched groundwater forms a piezometric surface, at least on the east site. The piezometric surface associated with perched groundwater has been as high as 1 0 feet below original grade, on the northern margin of the property (Robert Prater Associates, 1997). Based on a review of in-house, proprietary data, the regional groundwater table is Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. W .0. 7103-A-SC April 1, 2019 Page 7 j ., .. J J J j , .. , "' ~ .,, J .. J ,... .. .. .. ... ... .. ,,,.. .... .. ,,. ... ... .. .. ,,. .. ... .. .. ,,,.. ..., ,,,,. ... estimated to be nearly coincident with sea level, or deeper than 50 feet. However, the elevation of the groundwater table may vary depending on the time of year and precipitation. Perched groundwater conditions along zones of contrasting permeabilities and/or densities (i.e., fill/alluvium contacts, younger and sandy/clayey fill lifts, bedrock discontinuities, etc.) may not be precluded from occurring in the future due to site irrigation, increased precipitation, poor drainage conditions, or damaged underground utilities, and should be anticipated. Should perched groundwater conditions develop after development, this office could assess the affected area(s) and provide the appropriate recommendations to mitigate the observed groundwater conditions Due to the potential for shallow perched water conditions, more onerous slab design is necessary for any new slab-on-grade floor (State of California, 2019). Recommendations for reducing the amount of water and/or water vapor through slab-on-grade floors are provided in the "Soil Moisture Considerations" sections of this report. ROCK HARDNESS/EXCAVATION DIFFICULTY Excavations with standard mechanized earth-moving equipment are anticipated to be relatively easy with respect to difficulty. However, localized areas of highly cemented Santiago Formation could present very difficult excavation, if encountered. Excavation equipment should be appropriately suited for the required excavation task. Excavations deeper than about 1 0 feet have an elevated potential to encounter groundwater and/or saturated soils, which could hinder job progress . GEOLOGIC HAZARDS EVALUATION Mass Wasting/Landslide Susceptibility Mass wasting refers to the various processes by which earth materials are moved down slope in response to the force of gravity. Examples of these processes include slope creep, surficial failures, and deep-seated landslides. Creep is the slowest form of mass wasting and generally involves the outer 5 to 1 0 feet of a slope surface. During heavy rains, such as those in El Nino years, creep-affected materials may become saturated, resulting in a more rapid form of downslope movement (i.e., landslides and/or surficial failures). Geomorphic expressions indicative of past significant mass wasting events (i.e., scarps and hummocky terrain) were not observed during our field studies. Further, no adverse geologic structures were encountered during our subsurface exploration nor during our review of regional geologic maps. Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. W.O. 7103-A-SC April 1, 2019 Page 8 According to Leighton and Associates, Inc. (1992), the slope descending from the south toward the west parcel has a moderate to high mud flow potential. However, based on our observations, mud flow potential would be limited to the mouths of the reentrant natural drainage courses that traverse the aforementioned slope and intersect the west parcel, near its southwesterly corner and southerly boundary. It is our opinion that coalescing factors, including wildfire burn scars in steep (>20 degrees), tightly confined drainage basins and rainfall rates of 0.4 inches per hour within 2 years of the formation the wildfire burn scar would be necessary to place the subject site at significant risk from mud flow (United States Geological Survey, 2005). At present, there are no wildfire burn scars on the slopes that descend to the west parcel from the South. Thus, the likelihood of the site to experience mud flows is presently considered low, but would be elevated in the event that wildfires were to occur in the reentrant natural drainage courses, previously mentioned. In addition, the relatively steep gradient of the slope does not promote sedimentation nor soil development. This would further limit mud flow potential. For the mitigation of mudflow potential on the west parcel, debris impact walls may be installed across the mouths of the natural drainage courses. Figure 2 shows the approximate locations of the recommended debris impact walls. Recommendations for debris impact walls are included herein. The onsite soils are considered highly erosive. Therefore, the project should include prudent surface drainage controls that direct water away from foundations and tops of slopes (if slopes are planned). FAULTING AND REGIONAL SEISMICITY Regional Faults Our review indicates that there are no known active faults crossing the project area and the site is not within an Alquist-Priolo Earthquake Fault Zone (California Geological Survey [CGS], 2018). However, the site is situated in a region subject to periodic earthquakes along active faults. The Rose Canyon fault is the closest known active fault to the site (located at a distance of approximately 5.3 miles [8.6 kilometers]) and should have the greatest effect on the site in the form of strong ground shaking, should the design earthquake occur. According to Cao, et al. (2003), the Rose Canyon fault has a slip rate of 1.5 (±0.5) millimeters per year; and therefore, is classified as a "B" fault. Cao, et al. (2003) further indicate that the Rose Canyon fault is capable of a maximum magnitude 7.2 earthquake. The location of the Rose Canyon fault and other major faults relative to the site are shown on the "California Fault Map" in Appendix C. The possibility of ground acceleration, or shaking at the site, may be considered as approximately similar to the southern California region as a whole. Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. W.O. 7103-A-SC April 1 , 2019 Page 9 , .. , .. , .. J J ., .. j J J J j ... 1 .. .. .. .. .. ,.. .. .. ,... -- ,.. ,.. .. - .. ... ,.. .. .. ... ... .. ,,. .. ... ,.. .... Local Faulting According to Kennedy and Tan (2005 and 2007), no known active faults specifically transect the subject site. An old, north-south trending fault transects the easterly parcel, and is generally coincident with that portion of Laurel Tree Lane that also trends north-south. Kennedy and Tan (2005 and 2007) show that this fault disrupts the Santiago Formation but does not displace very old paralic deposits approximately 698,000 years in age. Thus, this fault does not meet the definition of a Holocene-active fault (CGS, 2018) . Surface Rupture Owing to the lack of known Holocene-active faults crossing the site, the potential for the proposed development to be adversely affected by surface rupture from fault movement is considered very low. Seismicity The acceleration-attenuation relation of Bozorgnia, Campbell, and Niazi (1999) has been incorporated into EQFAULT (Blake, 2000a). EQFAULT is a computer program developed by Thomas F. Blake (2000a), which performs deterministic seismic hazard analyses using digitized California faults as earthquake sources. The program estimates the closest distance between each fault and a given site. If a fault is found to be within a user-selected radius, the program estimates peak horizontal ground acceleration that may occur at the site from an upper bound (formerly "maximum credible earthquake") on that fault. Upper bound refers to the maximum expected ground acceleration produced from a given fault. Based on the EQFAUL T program, a peak horizontal ground acceleration from an upper bound event on the Rose Canyon fault may be on the order of 0.55 g. The computer printouts of pertinent portions of the EQFAUL T program are included within Appendix C . Historical site seismicity was evaluated with the acceleration-attenuation relation of Bozorgnia, Campbell, and Niazi (1999), and the computer program EQSEARCH (Blake, 2000b, updated to January 2015). This program performs a search of the historical earthquake records for magnitude 5.0 to 9.0 seismic events within a 100-kilometer radius, between the years 1800 through January 2015. Based on the selected acceleration-attenuation relationship, a peak horizontal ground acceleration is estimated, which may have affected the site during the specific event listed. Based on the available data and the attenuation relationship used, the estimated maximum {peak) site acceleration during the period 1800 through January 2015 was about 0.31 g. A historic earthquake epicenter map and a seismic recurrence curve are also estimated/generated from the historical data. Computer printouts of the EQSEARCH program are presented in Appendix C . Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc . W.O. 7103-A-SC April 1, 2019 Page 10 Seismic Shaking Parameters Based on the site conditions, the following table summarizes the site-specific design criteria obtained from the 2016 CBC (CBSC, 2016), Chapter 16 Structural Design, Section 1613, Earthquake Loads. The seismic design parameters were calculated using Applied Technology Council's (ATC 's) "Hazards By Location" website (https://hazards.atcouncil.org/). The short spectral response utilizes a period of 0.2 seconds. 2016 CBC SEISMIC DESIGN PARAMETERS PARAMETER VALUE 2016 CBC/ASCE REFERENCE Site Class D Section 1613.3.2/ASCE 7-10 (p. 203-205) Spectral Response -(0.2 sec), S5 1.105 g Section 1613.3.1 Figure 1613.3.1 (1) Spectral Response -(1 sec), S1 0.425 g Section 1613.3.1 Figure 1613.3.1 (2) Site Coefficient, Fa 1.058 Table 1613.3.3(1 ) Site Coefficient, F v 1.575 Table 1613.3.3(2) Maximum Considered Earthquake Spectral 1.169 g Section 1613.3.3 Response Acceleration (0.2 sec), SMs (Eqn 16-37) Maximum Considered Earthquake Spectral 0.67 g Section 1613.3.3 Response Acceleration (1 sec), SM, (Eqn 16-38) 5% Damped Design Spectral Response 0.78 g Section 1613.3.4 Acceleration (0.2 sec), S05 (Eqn 16-39) 5% Damped Design Spectral Response 0.447 g Section 1613.3.4 Acceleration (1 sec), S01 (Eqn 16-40) PGAM 0.464 g ASCE 7-10 (Eqn 11.8.1) Seismic Design Category D Section 1613.3.5/ASCE 7-1 0 (Table 11 .6-1 or 11 .6-2) I GENERAL SEISMIC PARAMETERS I Distance to Seismic Source -(Rose Canyon fault) 5.3 mi (8.6 km)I1> Upper Bound Earthquake (Rose Canyon fault) 11> -From Blake (2000a) 12> -Cao, et al. (2003) Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp1 2\7100\7103a.rpge GeoSoils, Inc. Mw = 7.212> W.O. 7103-A-SC April 1, 2019 Page 11 .. .. .. ' .. .. ... ,.. .. '-.. Ila ... ... ... ,... ... .. .. lllr ,.. ,,. ... .,. ,,. .. .. ,,.. ... Conformance to the criteria above for seismic design does not constitute any kind of guarantee or assurance that significant structural damage or ground failure will not occur in the event of a large earthquake. The primary goal of seismic design is to protect life, not to eliminate all damage, since such design may be economically prohibitive. Cumulative effects of seismic events are not addressed in the 2016 CBC (CBSC, 2016) and regular maintenance and repair following locally significant seismic events (i.e., Mw5.5) will likely be necessary, as is the case in all of southern California. SECONDARY SEISMIC HAZARDS Liquefaction/Lateral Spreading Liquefaction describes a phenomenon in which cyclic stresses, produced by earthquake-induced ground motion, create excess pore pressures in relatively cohesion less soils. These soils may thereby acquire a high degree of mobility, which can lead to vertical deformation, lateral movement, lurching, sliding, and as a result of seismic loading, volumetric strain and manifestation in surface settlement of loose sediments, sand boils and other damaging lateral deformations. This phenomenon occurs only below the water table, but after liquefaction has developed, it can propagate upward into overlying non-saturated soil as excess pore water dissipates . One of the primary factors controlling the potential for liquefaction is depth to groundwater . Typically, liquefaction has a relatively low potential at depths greater than 50 feet and is unlikely and/or will produce vertical strains well below 1 percent for depths below 60 feet when relative densities are 40 to 60 percent and effective overburden pressures are two or more atmospheres (i.e., 4,232 pounds per square foot [Seed, 2005]) . The condition of liquefaction has two principal effects. One is the consolidation of loose sediments with resultant settlement of the ground surface. The other effect is lateral sliding. Significant permanent lateral movement generally occurs only when there is significant differential loading, such as fill or natural ground slopes within susceptible materials. These conditions do not exist at the site . Liquefaction susceptibility is related to numerous factors and the following five conditions should be concurrently present for liquefaction to occur: 1) sediments must be relatively young in age and not have developed a large amount of cementation; 2) sediments must generally consist of medium-to fine-grained, relatively cohesionless sands; 3) the sediments must have low relative density; 4) free groundwater must be present in the sediment; and 5) the site must experience a seismic event of a sufficient duration and magnitude, to induce straining of soil particles. Effects of liquefaction may include sand boils, settlement, and bearing capacity failures . Based on our review of in-house, proprietary data and our recent findings, the subject site has a low susceptibility to damaging deformations resulting from seismic-induced Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. W.O. 7103-A-SC April 1, 2019 Page 12 liquefaction, provided the recommendations in this report are incorporated into project design and construction. This assessment considers the consolidated, fine-grained nature of the Santiago Formation, which underlies the site at a relatively shallow depth. Seismic Densification Seismic densification is a phenomenon thattypically occurs in low relative density granular soils (i.e., United States Soil Classification System [USCS] soil types SP, SW, SM, and SC) that are above the groundwater table. These unsaturated granular soils are susceptible if left in the original density (unmitigated), and are generally dry of the optimum moisture content (as defined by the ASTM D 1557). During seismic-induced ground shaking, these natural or artificial soils deform under loading and volumetrically strain, potentially resulting in ground surface settlements. Provided that the earthwork and foundation recommendations contained in this report are implemented during project planning and construction, the potential for seismic densification to adversely affect the proposed development is considered low. However, some densification of the adjoining un-mitigated properties may influence improvements at the perimeter of the site and proposed improvements not supported by deep foundations or recompacted engineered fill may be susceptible to seismic densificaiton. Special setbacks and/or deepened foundations may be utilized if significant structures/improvements are placed close to the perimeter of the site. Our evaluation assumed that the current offsite conditions will not be significantly modified by future grading at the time of the design earthquake, which is a reasonably conservative assumption. Other Geologic/Secondary Seismic Hazards The following list includes other geologic/seismic related hazards that have been considered during our evaluation of the site. The hazards listed are considered negligible and/or mitigated as a result of site location, soil characteristics, and typical site development procedures: • Subsidence • Ground Lurching or Shallow Ground Rupture • Seiche • Tsunami LABORATORY TESTING Laboratory tests were performed on representative bulk and relatively undisturbed samples of site earth materials collected during our subsurface exploration in order to evaluate their physical characteristics. Test procedures used and results obtained are presented below. Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. W.O. 7103-A-SC April 1, 2019 Page 13 J , .. J J J J J J ... .J j Classification Soils were classified visually according to the Unified Soils Classification System, in general accordance with ASTM D 2487 and D 2488. The soil classifications are shown on the Boring Logs and CPT soundings in Appendix B. Moisture-Density Relations The field moisture contents and dry unit weights were determined for relatively undisturbed samples of site earth materials in the laboratory. Testing was performed in general accordance with ASTM D 2937 and ASTM D 2216. The dry unit weight was determined in pounds per cubic foot (pcf), and the field moisture content was determined as a percentage of the dry weight. The results of these tests are shown on the Boring Logs in Appendix B. Laboratory Standard The maximum density and optimum moisture content was evaluated for the major soil type encountered in the borings. The laboratory standard used was ASTM D 1557. The moisture-density relationships obtained for these soils are shown on the following table: SAMPLE LOCATION SOIL TYPE MAXIMUM DENSITY OPTIMUM MOISTURE AND DEPTH (FT) (PCF) CONTENT(%) B-1 @ 3-7 Brown, Silty SAND 123.0 11 .5 B-2@ 5 Grey, Sandy CLAY 122.0 13.0 Expansion Index A representative sample of near-surface site soils was evaluated for expansion potential. Expansion Index (E.I.) testing and expansion potential classification were performed in general accordance with ASTM Standard D 4829. The results of the expansion testing are presented in the following table. SAMPLE LOCATION AND DEPTH (FT) I B-1 @ 15 B-2 @ 5 Summerhill Homes Laurel Tree Lan e, Carlsbad File:e:\wp12\7100\7103a.rpge I EXPANSION INDEX I EXPANSION POTENTIAL I 32 I 72 GeoSoils, Inc. Low Medium I W.O. 7103-A-SC April 1, 2019 Page 14 Atterberg Limits Testing was performed on a representative fine-grained soil sample to evaluate the liquid limit, plastic limit, and plasticity index (P .1.) in general accordance with ASTM D 4318. The test results are presented below: SAMPLE LOCATION AND DEPTH (FT) I LIQUID LIMIT I PLASTIC LIMIT I PLASTICITY INDEX B-2 @ 5 45 16 29 I Grain Size Distribution An evaluation was performed on a selected representative soil sample in general accordance with ASTM D 422 . The grain-size distribution curve is presented in Appendix D. Direct Shear Test Shear testing was performed on a representative bulk sample of site soil in general accordance with ASTM test method D 3080 in a Direct Shear Machine of the strain control type. Prior to testing, the sample was remolded to 90 percent of the laboratory standard (ASTM D 1557). The shear test results are presented as follows: PRIMARY RESIDUAL LOCATION AND DEPTH (FT) COHESION FRICTION ANGLE COHESION FRICTION ANGLE (PSF) (DEGREES) (PSF) (DEGREES) B-1 @ 5 267 32 310 32 (U ndisturbed) B-2 @ 5 359 29 304 29 (Remolded) Consolidation Test Consolidation testing was performed on a selected , relatively undisturbed sample of the onsite soils. Testing was performed in general accordance with ASTM Test Method D 2435. Test results are presented in Appendix 0 . Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. W .O. 7103-A-SC April 1, 2019 Page 15 Saturated Resistivity, pH, and Soluble Sulfates, and Chlorides GSI conducted sampling of onsite earth materials for general soil corrosivity and soluble sulfates, and chlorides testing. The testing included evaluation of soil pH , soluble sulfates, chlorides, and saturated resistivity. Test results are presented in the following table: SAMPLE LOCATION SATURATED SOLUBLE SOLUBLE AND DEPTH (FT) pH RESISTIVITY SULFATES CHLORIDES (ohm-cm) (% by weight) (ppm) B-1 @ 3-7 6.43 350 0.0375 40 B-2 @ 5 5.53 240 0.0195 35 Corrosion Summary Laboratory testing indicates that tested samples of the onsite soils are: medium acid to slightly acid with respect to soil acidity/alkalinity; severely corrosive to exposed, buried metals when saturated ; present a negligible sulfate exposure to concrete (Exposure Class SO per ACI 318-14); and have low to slightly elevated concentrations of soluble chlorides. GSI does not practice in the field of corrosion engineering. Thus, the project architect and structural engineer should evaluate the level of corrosion protection required for the project and seek consultation from a qualified corrosion engineer, as warranted. PRELIMINARY SETTLEMENT EVALUATION GSI has estimated the potential total vertical settlement, differential settlement for the site. The analyses were based on laboratory test results and subsurface data collected from borings and CPT data completed in preparation of this study. Site specific conditions affecting settlement potential include the areal depositional environment, grain size and lithology of sediments, cementing agents, stress history, moisture history, material shape, density, void ratio, etc. Ground settlement should be anticipated due to primary consolidation and secondary compression of engineered fill and potential left-in-place alluvium, and weathered and unweathered Santiago Formation under new foundation and fill loads. The amount of total vertical settlement, and time over wh ich it occurs, is dependent upon various factors, including material type, depth of fill , depth of removals , initial and final moisture content (groundwater elevation), and in-place density of subsurface materials and new foundation loads. For the proposed buildings, GSI anticipates that wall loads will be on the order of 5 to 8 kips, and column loads will range between approximately 20 to 200 kips. Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. W.O. 7103-A-SC April 1, 2019 Page 16 Post-Grading Settlement Site grading is anticipated to consist of maximum planned cuts and fills on the order of 3 feet from existing grades. In planned fill areas remedial grading may add an additional 5 to 17 feet of compacted fill. Thus, the maximum thickness of engineered fill is anticipated to be 20 feet, on a preliminary basis. As such, the magnitude of this settlement is considered to be relatively low, with total vertical static settlements of approximately¾ to 2 inches anticipated after grading is complete. Total fill settlement may be revised, dependant on conditions exposed during grading and review of final foundation and grading plans. Monitoring following grading should be performed to evaluate expansion characteristics of the exposed subsurface soils and compaction due to mitigated fill. Seismic Settlement of Fill The magnitude of potential seismic settlement was evaluated. Based upon the assumed design configuration and the results of our seismic settlement analysis, the total ground settlement, across the site, during the design basis seismic event is anticipated to be on the order of½ to 1 inch, with a potential differential seismic settlement of approximately ¼ to¾ inch over 50 feet horizontally (i.e., angular distortion approximately 1/800), given recommended mitigation and current site conditions. This minimal level of deformation should be considered in foundation design and planning, in addition to foundation settlement under static loading conditions. This anticipated seismic-induced settlement may be mitigated by foundation type, grading and/or ground modification. If mitigated soils and foundations are completed, surface manifestations during the design basis earthquake should be limited to 1 inch total seismic settlement and differential seismic settlement of ¾ inches over 50 feet. Foundation Settlement Due to Structural Loads The settlement of the structures supported on structural concrete mats or slabs founded on compacted fill will depend on the actual foundation dimensions, the thickness and compressibility offill below the bottom of the foundation, and the imposed structural loads. GSI has assumed that the existing graded pad on the west parcel will not be altered by more than 2 feet (i.e., new fill loads Oto 2 feet). Provided the thickness of recompacted fill below the bottom of the foundation is based on a maximum allowable bearing pressure, provided in this report, post-construction total vertical static settlement of less than 1 inch should be anticipated; however, this assumes all fill is properly compacted. Given this condition, the majority of the foundation settlement should occur as the building loads are applied during construction. Differential settlement between the lightest and heaviest loading condition may occur across the foundation, and is anticipated to minimally be on the order of ½ to 1 inch in 30 feet (about 1 /350) or between the heaviest and lightest loaded areas of the foundation. Further review will be needed once draft foundation plans and building loads are provided. Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. W .0. 7103-A-SC April 1 , 2019 Page 17 J J J J :J J J j j :J J J J j -J .. .. ... .. .. r .. .. ... ... ... II""' Ill' - -.. .. 111111 IJIII 1111 ... Ila Settlement Summary Static differential settlement of up to 1 inch in 40 feet (1 /480) in should be incorporated into the foundation system design. Dynamic deformations (i.e., angular distortion approximately 1/800), should be evaluated in the design as part of the seismic performance of the building and other improvements onsite . PRELIMINARY CONCLUSIONS AND RECOMMENDATIONS Based on our field exploration, laboratory testing, and geotechnical engineering analysis, it is our opinion that the subject site is suitable for the proposed residential development from a geotechnical engineering and geologic viewpoint, provided that the recommendations presented in the following sections are incorporated into the design and construction phases of site development. The primary geotechnical concerns with respect to the proposed development and improvements are: • • • • • • • • • Earth materials characteristics and depth to competent bearing material. Presence of undocumented fill, should settlement-sensitive improvements be proposed within its influence. Presence of potentially compressible roadway fill, should settlement-sensitive improvements be proposed within its influence. Temporary slope stability and the need for alternating slot excavations or shoring along the roadway fill, if remedial earthwork is performed. On-going expansion and corrosion potential of site soils, and the presence of detrimentally expansive soils (as defined in the 2016 CBC). Erosiveness of site earth materials, and potential for mud flows to impact the western parcel, emanating from the hills to the south. Perimeter conditions and planned improvements near the property boundary . A relatively shallow groundwater table . Regional seismic activity and the potential for earthquake-induced ground motions to affect the proposed development. The recommendations presented herein consider these as well as other aspects of the site. The engineering analyses performed concerning site preparation and the recommendations presented herein have been completed using the information provided and obtained during our field work. In the event that any significant changes are made to proposed site development, the conclusions and recommendations contained in this report shall not be considered valid unless the changes are reviewed and the recommendations of this report verified or modified in writing by this office. Foundation design parameters are considered preliminary until the foundation design, layout, and structural loads are provided to this office for review. Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. W.O. 7103-A-SC April 1, 2019 Page 18 1. 2. 3. 4. 5. 6. 7. Soil engineering, observation, and testing services should be provided during grading to aid the contractor in removing unsuitable soils and in his effort to compact the fill. Geologic observations should be performed during any grading and foundation construction to verify and/or further evaluate geologic conditions. Although unlikely, if adverse geologic structures are encountered, supplemental recommendations and earthwork may be warranted. Based on our review, the site is susceptible to moderate to severe ground shaking should an earthquake occur on any of the regionally active fault systems. This will need to be considered in the structural design of the proposed residential structure. The primary purpose of building codes in regard to seismic design is to protect life and safety; not to eliminate all structural damage. All undocumented artificial fill, roadway fill, alluvium, and weathered bedrock are considered unsuitable for the support of the proposed settlement-sensitive improvements, and new planned fills. These potentially compressible earth materials will require mitigation, as recommended herein, where they are within the influence of the proposed settlement-sensitive improvements. Mitigation would include removal and recompaction of unsuitable soils. Expansion Index (E.I.) testing, performed on a representative sample of the site soils, indicates low to medium, and possibly highly expansive conditions. Based on classification index tests, site soils are considered detrimentally expansive and warrant special foundation and slab-on-grade floor designs to resist the damaging effects of expansive soils. Laboratory testing indicates that tested samples of the onsite soils are: medium acid to slightly acid with respect to soil acidity/alkalinity; severely corrosive to exposed, buried metals when saturated; present a negligible sulfate exposure to concrete (Exposure Class SO per ACI 318-14); and have low to slightly elevated concentrations of soluble chlorides. GSI does not practice in the field of corrosion engineering. Thus, the Client and project architect should agree on the level of corrosion protection required for the project and seek consultation from a qualified corrosion consultant as warranted. The use of concrete conforming to Exposure Class C1 in American Concrete Institute (ACI) 318-14, should be utilized, as the concrete would likely be exposed to water. Site soils are considered erosive. Surface drainage should be designed to eliminate the potential for concentrated flows. Positive surface drainage away from foundations is recommended. Temporary erosion control measures should be implemented until vegetative covering is well established. The property owners should maintain proper surface drainage over the life of the project. Summerhill Homes W.O. 7103-A-SC April 1, 2019 Page 19 Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. j J J J J , 111111 J J J J J j J J J .. ... ... .. ... .... .. ... ... ... ,,.. 1111111 ... ,. .. ,,.. ... ... ,.. ... .. .. ... .. 111111 ,.. 8. Groundwater was encountered only in Boring B-1 at a depth of about 21 ½ feet. The piezometric surface associated with perched groundwater has been as high as 10 feet below original grade, on the northern margin of the property. Perched groundwater may be encountered during site earthwork, in excavations for deep utilities, and may not be precluded in shallow excavations. This should be considered in project planning and construction. 9. Perimeter conditions and existing offsite improvements will limit the removal and recompaction of potentially compressible soils near the margins of the site. As such, any settlement-sensitive improvement at the property line would require deepened foundations, additional reinforcement, or would retain some potential for distress and therefore, a reduced serviceable life. Alternatively, unsuitable soils near the property lines may be removed and recompacted in alternating slot or shored excavations . 10. On a preliminary basis, temporary slopes should be constructed in accordance with CAL-OSHA guidelines for Type "B" soils, provided water, seepage, or other adverse geologic conditions are not present. All temporary slopes should be evaluated by the geotechnical consultant, prior to worker entry. Should adverse conditions be identified, the slope may need to be laid back to a flatter gradient or require the use of shoring. Alternating "A," "B," and "C" slot excavations may be used to perform the recommended remedial earthwork near the property lines/roadway fill in lieu of shoring. 11. The project civil design should incorporate the herein provided recommendations to mitigate potential mud flows, emanating from the hills to the south of the west parcel, from adversely affecting the proposed development. 12. The seismicity-acceleration values provided herein should be considered during the design and construction of the proposed development. 13. General Earthwork, Grading Guidelines, and Preliminary Criteria are provided at the end of this report as Appendix G. Specific recommendations are provided below. GENERAL RECOMMENDATIONS Owing to the depth to competent bearing materials, and the proximity of offsite improvements on adjoining properties, GSI is providing two (2) alternative geotechnical engineering scenarios for remedial earthwork and foundation construction. These are referred to hereinafter as Alternatives "A" and "B." Alternative "A" includes remedial earthwork to remove and recompact the low density, surficial undocumented fill and roadway fill, alluvium, and weathered bedrock deposits, if the proposed settlement-sensitive improvements on both parcels are proposed close to the existing roadways. Obviously, this would not be necessary if proposed improvements are kept well Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc . W.O. 7103-A-SC April 1, 2019 Page 20 away from the existing roadways and/or property lines. Alternative "B" includes very little to no remedial grading and the use of a drilled pier and grade beam foundation system with a structural slab-on-grade floor for the support of the proposed residential structures on the east parcel. Possible advantages and disadvantages of both alternatives are discussed below. GSI recommends that the selection of the preferred alternative be based on value engineering studies that at a minimum evaluate quality (i.e., long-term performance), speed of construction, and construction costs. Alternative "A" Advantages Possible advantages of Alternative "A" are: • • • The removal and recompaction of low density surficial soils would allow for the use of a shallow foundation system. Possible lower costs than a deep foundation system unless shoring is used . Less potential for distress to ancillary site improvements if remedial grading is performed across the entire property. Disadvantages Possible disadvantages of Alternative "A" are: • • • • • • Potential sloughing of the excavation walls at the property lines that may extend into the adjoining properties. This may require some repair of any damaged offsite property. Remedial excavations near Aviara Parkway and Laurel Tree Lane will need to be completed in alternating slot or shored excavations. Will require pre-construction surveys and excavation monitoring . Soils too saturated to properly compact may be encountered at depth, and would require drying back or blending with drier materials to achieve compaction. Heavy equipment vibrations could potentially damage offsite improvements . The speed of construction will likely be relatively slow as compared to Alternative "B." • Foundation settlements may be greater than Alternative "B." Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. W.O. 7103-A-SC April 1, 2019 Page 21 J J J , .. , ... J j J :J J J J J , 111111 ,,.. .. .. .. ,,.. .. ,,.. .. ,,.. ... ... ... .. .. ,,.. ,,.. ... ,,.. ... ,,.. -,.. ... ,,.. ,,.. .. ,,.. Ill ... .. ... Alternative "B" Advantages Possible advantages of Alternative "B" are: • A smaller magnitude of foundation settlement than Alternative "A." • • • A likely faster speed of construction than Alternative "A" as a result of the little to no remedial earthwork required . Increased foundation performance . Lower likelihood for damage to existing improvements on adjoining properties . • Would not require as much excavation and vibration monitoring as Alternative "A." Disadvantages Possible disadvantages of Alternative "B" are: • • • • • The possible need for casing of the drilled shafts, owing to the relatively cohesionless nature of some of the surficial earth materials and a potential perched groundwater table . The need for structural slab-on-grade floors that are capable of supporting the applied net loading conditions without the aid of the underlying soils . The possible need to penetrate grade beams to install the under-slab utilities . Reduced performance of ancillary site improvements if remedial grading is not performed and if the improvements are not pier-supported. The possible need for chloride resistant concrete and corrosion-protected reinforcing bars in drilled pier construction. EARTHWORK CONSTRUCTION RECOMMENDATIONS -ALTERNATIVE "A" General All earthwork should conform to the guidelines presented in Appendix J of the 2016 CBC (CBSC, 2016), the requirements of the City of Carlsbad, and the General Earthwork and Grading Guidelines presented in Appendix G, except where specifically superceded in the Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc . W.O. 7103-A-SC April 1 , 2019 Page 22 text of this report. Prior to earthwork, a GSI representative should be present at the pre-construction meeting to provide additional earthwork guidelines, if needed, and review the earthwork schedule. This office should be notified in advance of any fill placement, supplemental regrading of the site, or backfilling underground utility trenches and retaining walls after rough earthwork has been completed. This includes grading for driveway approaches, driveways, and exterior hardscape. During earthwork construction, all site preparation and the general grading procedures of the contractor should be observed and the fill selectively tested by a representative(s) of GSI. If unusual or unexpected conditions are exposed in the field, they should be reviewed by this office and, if warranted, modified and/or additional recommendations will be offered. All applicable requirements of local and national construction and general industry safety orders, the Occupational Safety and Health Act (OSHA), and the Construction Safety Act should be met. It is the onsite general contractor's and individual subcontractors' responsibility to provide a safe working environment for our field staff who are onsite. GSI does not consult in the area of safety engineering. It is also the responsibility of the contractor to provide protection of their work product. Surface drainage should be directed away from open excavations. Site Preparation Any existing improvements, vegetation and deleterious debris should be removed from the site, prior to the start of construction, if they are located in areas of proposed earthwork. Any remaining cavities should be observed by the geotechnical consultant. Mitigation of cavities would likely include removing any potentially compressible soils to expose unweathered Santiago Formation and then backfilling the excavation with a controlled engineered fill or soils that have been moisture conditioned to optimum moisture content and compacted to at least 90 percent of the laboratory standard (ASTM D 1557). Should the onsite sewage disposal/holding system be encountered during earthwork, this office should be contacted to provide recommendations for removal and disposal. Removal and Recompaction of Potentially Compressible Earth Materials Potentially compressible undocumented and roadway fill, alluvium, and weathered bedrock should be removed to expose unweathered bedrock (Santiago Formation). Excluding roadway fill areas, based on the available subsurface data, remedial grading excavations are anticipated to extend to depths on the order of 17 to 20 feet below existing grades, on the east parcel, and about 3 to 7 feet below existing grade on the west parcel. Following excavation, the exposed subsoils should be scarified at least 6 to 8 inches, moisture conditioned to at least optimum moisture content, and then compacted to at least 90 percent of laboratory standard (ASTM D 1557). The removed soils may be reused as engineered fill provided they are not too wet to compact, and cleaned of any vegetation Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. W.O. 7103-A-SC April 1, 2019 Page 23 , .. J J J j ., 111111 J J J , .. .. J J , ... , ... .. 111111 ,. .. ... ,,. .... .. ... .. 11111 .... ... .. ,,. 111111 ,. 11111 ,. 11111 ... .... ... .. ,,. ! .. and deleterious debris prior to placement. Remedial grading excavations should extend below a 1 :1 (h:v) plane down from the perimeter of the proposed building footprint at the bearing elevation, and should be observed by the geotechnical consultant prior to scarification and fill placement. Alternating slot excavations, as recommended below, should be used to complete the remedial excavations below a 1 ½: 1 (h:v) plane down from the bottom, outboard edge of any existing improvement along property lines or roadway fill. Once observed and approved, the bottom of the remedial grading excavations should be lightly scarified, moisture conditioned (moisture added or dried back, as warranted) to at least the soil's optimum moisture content, and then be recompacted in accordance with the recommendations in the "Fill Placement" section below. The use of vibratory compaction equipment should not be considered for compaction, owing to the potential for damage to neighboring improvements . Earthwork Mitigation of Detrimentally Expansive Soils As an alternative to using structural design for the mitigation of detrimentally expansive soils, earthwork may be performed to remove any soils possessing an expansion index (E.I.) greater than 20 and a plasticity index (P.I.) greater than 14, within the upper 7 feet of pad grade, and replacing these soils with very low expansive (E.I. < 21) soil with a P.l. less than 15. The lateral limits of the removal and replacement of detrimentally expansive soils should be at least 5 feet outside the perimeter footprint of the proposed residential structure. This mitigation may reduce foundation requirements to possibly include conventional foundations . Alternating Slot Excavations Remedial grading excavations extending below a 1 ½:1 (h:v) plane down from the bottom, outboard edge of any existing improvements along property lines or the roadway fill should be performed in alternating (A, B, and C) slots. Slot excavations should be a maximum of 6 feet in width. Multiple slots may be simultaneously excavated provided that open slots are separated by at least 6 feet of engineered fill or undisturbed soils. Perimeter Conditions On a preliminary basis, any proposed settlement-sensitive improvements located within approximately 17 to 20 feet from the property line on the east parcel, or within about 20 feet of the roadway fill, would likely require deepened foundations or additional reinforcement by means of ground improvement or specific structural design, if remedial grading in alternating slot or shored excavations is not performed. Otherwise, these improvements may be subject to distress and a reduced serviceable lifespan. This would require proper disclosure to all interested/affected parties should this condition exist at the conclusion of grading . Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc . W.O. 7103-A-SC April 1, 2019 Page 24 Fill Placement Following scarification of the bottom of the remedial grading excavation, the reused onsite soils and import (if necessary) should be placed in ±6-to ±8-inch lifts, cleaned of vegetation and debris, moisture conditioned (water added or dried back, as warranted) to at least the soil's optimum moisture content, and compacted to achieve a minimum relative compaction of 90 percent of the laboratory standard (ASTM D 1557). Overexcavation Overexcavation should be performed minimally to 5-foot outside the building footprint or a 1 :1 (h:v) projection from the building to suitable bedrock, whichever is more. Overexcavation should be completed to a depth of 2-foot below the lowest foundation element. Since plans showing foundation layout and footing depths are currently unavailable, the recommended overexcavation should be completed to at least 4 feet below finish pad grade, on a preliminary basis. Overexcavated materials should be replaced with engineered fill compacted to at least 90 percent of the laboratory standard (ASTM D 1557). The bottom of the overexcavation should be sloped toward the parking area or approved drainage facilities, scarified at least 6 to 8 inches, moisture-conditioned as necessary to achieve the soil's optimum moisture content, and then be recompacted to at least 90 percent of the laboratory standard prior to fill placement. Overexcavation should be completed across the entire building pad, as necessary, since building layouts are currently unknown. Overexcavations should be observed by the geotechnical consultant prior to scarification. The maximum to minimum fill thickness across building pads should not exceed a ratio of 3:1 (maximum:minimum). Subdrains Although generally not anticipated, local seepage along the contact between the fill lifts may require subdrain systems, based on depth offill, finish grade elevations, and potential flowline outlet areas. Subdrains should consist of a 4-inch diameter perforated Schedule 40 or SDR 35 drain pipe encased in 1 cubic foot of ¾-inch clean, crushed gravel, and wrapped in filter fabric (Mirafi 140N or approved equivalent). Subdrains should outlet into an approved drainage facility. Earthwork Balance (Shrinkage/Bulking) The volume change of excavated materials upon compaction as engineered fill is anticipated to vary with material type and location. The overall earthwork shrinkage and bulking may be approximated by using the following parameters: Existing Artificial Fill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0% to 10% shrinkage Alluvium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10% to 15% shrinkage Santiago Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2% to 3% shrinkage or bulk Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. W.O. 7103-A-SC April 1, 2019 Page 25 , .. J J .. J ., .. J .. J , .. J J J , "" , .. ,. ... ,. ... .. ... .. .. ,. .. ... .. .. .. ... ,. ,... .. ... ... .. .. ,,. .. ,. .. ,,. l ... It should be noted that the above factors are estimates only, based on preliminary data . Alluvium may achieve higher shrinkage if organics or clay content is higher than anticipated. Final earthwork balance factors could vary. In this regard, it is recommended that balance areas be reserved where grades could be adjusted up or down near the completion of grading in order to accommodate any yardage imbalance for the project. Subsidence in non-bedrock areas should be on the order of 0.1 feet. Import Soils If import fill is necessary, a sample of the soil import should be evaluated by this office prior to importing, in order to assure compatibility with the onsite soils and the recommendations presented in this report. If non-manufactured materials are used, environmental documentation for the export site should be provided for GSI review. At least three business days of lead time should be allowed by builders or contractors for proposed import submittals. This lead time will allow for environmental document review, particle size analysis, laboratory standard, expansion testing, and blended import/native characteristics as deemed necessary. Import soils should be non-detrimentally expansive (i.e., E.1. less than 21 and P.I. less than 15). The use of subdrains at the bottom of the fill cap may be necessary, and may be subsequently recommended based on compatibility with onsite soils . Slope Considerations and Slope Design All slopes should be designed and constructed in accordance with the minimum requirements of the City of Carlsbad, the 2016 CBC, and the recommendations in Appendix G. Temporary Slopes Temporary slopes for excavations greater than 2 feet but less than 20 feet in overall height should conform to CAL-OSHA and/or OSHA requirements for Type "B" soils, unless water or seepage is present, or other adverse conditions are exposed, in which case Type "C" soils would govern. Construction materials, soil stockpiles, and heavy equipment should not be stored and/or operated within 'H' of any temporary slope where 'H' equals the height of the temporary slope. All temporary slopes should be observed by a licensed engineering geologist and/or geotechnical engineer prior to worker entry into the excavation. Based on the exposed field conditions, inclining temporary slopes to flatter gradients or the use of shoring or alternating slot excavations may be necessary if adverse conditions are observed. The need for shoring or alternating slot excavations would be best evaluated during the grading plan review stage and in the field during grading. Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. W.O. 7103-A-SC April 1, 2019 Page 26 Excavation Observation and Monitoring (All Excavations) When excavations are made adjacent to an existing improvement (i.e., utility, wall, road, building, etc.) there is a risk of some damage even if a well designed system of excavation is planned and executed. We recommend, therefore, that a systematic program of observations be made before, during, and after construction to determine the effects (if any) of construction on existing improvements. We believe that this is necessary for two reasons: First, if excessive movements (i.e., more than ½ inch) are detected early enough, remedial measures can be taken which could possibly prevent serious damage to existing improvements. Second, the responsibility for damage to the existing improvement can be determined more equitably if the cause and extent of the damage can be determined more precisely. Monitoring should include the measurement of any horizontal and vertical movements of the existing structures/improvements. Locations and type of the monitoring devices should be selected prior to the start of construction. The program of monitoring should be agreed upon between the project team, the site surveyor and the Geotechnical Engineer-of-Record, prior to excavation. Reference points on existing walls, buildings, and other settlement-sensitive improvements should be placed as low as possible on the wall and building adjacent to the excavation. Exact locations may be dictated by critical points, such as bearing walls or columns for buildings; and surface points on roadways or curbs near the top of the excavation. For a survey monitoring system, an accuracy of a least 0.01 foot should be required. Reference points should be installed and read initially prior to excavation. The readings should continue until all construction below ground has been completed and the permanent backfill has been brought to final grade. The frequency of readings will depend upon the results of previous readings and the rate of construction. Weekly readings could be assumed throughout the duration of construction with daily readings during rapid excavation near the bottom of the excavation. The reading should be plotted by the Surveyor and then reviewed by the Geotechnical Engineer. In addition to the monitoring system, it would be prudent for the Geotechnical Engineer and the Contractor to make a complete inspection of the existing structures both before and after construction. The inspection should be directed toward detecting any signs of damage, particularly those caused by settlement. Notes should be made and pictures should be taken where necessary. Observation It is recommended that all excavations be observed by the Geologist and/or Geotechnical Engineer. Any fill which is placed should be approved, tested, and verified if used for Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. W .0. 7103-A-SC April 1, 2019 Page 27 J ., .. J , .. j , .. J J , .. , .. J , .. ,. .. .. .. .. ... .. .. ... .. ,. ... .. ... ... .. ,. .. ... .. ... ... ,. ... ,,.. I ... engineered purposes. Should the observation reveal any unforseen hazard, the Geologist or Geotechnical Engineer will recommend treatment. Please inform GSI at least 24 hours prior to any required site observation . PRELIMINARY FOUNDATION RECOMMENDATIONS -ALTERNATIVE A General The preliminary foundation design and construction recommendations, presented herein, are based on the geotechnical data obtained during our recent field studies, laboratory testing of the onsite earth materials, and engineering evaluations performed in conjunction with this investigation. The following preliminary foundation design and construction recommendations are presented as minimum criteria from a geotechnical engineering viewpoint. This section presents minimum design criteria for the design of foundations, concrete slab-on-grade floors, and other elements possibly applicable to the project. These criteria should not be considered as substitutes for actual designs by the structural engineer. Recommendations by the project's design-structural engineer or architect, which may exceed the geotechnical consultant's recommendations, should take precedence over the following minimum requirements. The foundation systems recommended herein may be used to support the proposed residential structure provided they are entirely founded in engineered fill tested and approved by GSI that overlies dense formational earth materials. Foundation and slab-on-grade floor systems constructed within the influence of detrimentally expansive soils (E.1. > 20 and P.I. > 14 [such as exists at the site]) should be designed in accordance with Sections 1808.6.1 and 1808.6.2 of the 2016 CBC. In the event that the information concerning the proposed development plan is not correct, or any changes in the design, location or loading conditions of the proposed structure are made, the conclusions and recommendations contained in this report shall not be considered valid unless the changes are reviewed and conclusions of this report are modified or approved in writing by this office. Upon request, GSI could provide additional input/consultation regarding soil parameters, as they relate to foundation design Based on the onsite soil conditions, anticipated loading conditions, and use (i.e., improvements), we have considered conventional shallow spread footings, a post-tensioned slab, and a mat-type foundation to be appropriate foundation designs from a geotechnical perspective, provided unsuitable soils are removed and recompacted, as indicated herein . Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. W.O. 7103-A-SC April 1, 2019 Page 28 General Foundation Design 1. 2. 3. 4. 5. 6. 7. 8. The foundation systems should be designed and constructed in accordance with guidelines presented in the 2016 CBC. An allowable bearing value of 2,000 psf may be used for the design of continuous spread footings that maintain a minimum width of 12 inches and a minimum depth of 12 inches below the lowest adjacent grade or isolated spread footings having a minimum dimension of 24 inches and a minimum embedment of 24 inches below the lowest adjacent grade. Footings should be entirely founded into properly engineered fill overlying dense formational materials. This value may be increased by 20 percent for each additional 12 inches in footing embedment to a maximum value of 2,500 psf. These values may also be increased by one-third when considering short duration seismic or wind loads. Foundation embedment excludes any landscaped zones, concrete slabs-on-grade, and/or slab underlayment. Allowable bearing values for post-tensioned slab and mat foundations are provided in their respective sections. The passive earth pressure may be computed as an equivalent fluid having a density of 200 pcf, with a maximum earth pressure of 2,000 psf for footings founded into properly engineered fill. Lateral passive pressures for shallow foundations within 2016 CBC setback zones or within the influence of retaining walls should be reduced following a review by the geotechnical engineer unless proper setbacks can be established. For lateral sliding resistance, a 0.35 coefficient of friction may be utilized for a concrete to soil contact when multiplied by the dead load. When combining passive pressure and frictional resistance, the passive pressure component should be reduced by one-third. All footing setbacks from slopes should comply with Figure 1808.7.1 of the 2016 CBC. GSI recommends a minimum horizontal setback distance of 7 feet as measured from the bottom (i.e., bearing elevation), outboard edge of the footing to any slope face. Footings for structures adjacent to retaining walls should be deepened so as to extend below a 1: 1 projection from the heel of the wall should this condition occur. Alternatively, walls may be designed to accommodate structural loads from buildings or appurtenances as described in the "Retaining Wall" section of this report. All interior and exterior column footings should be tied to the perimeter wall footings in at least two directions. The base of the reinforced grade beam should be at the same elevation as the adjoining footings. Summerhill Homes W.O. 7103-A-SC April 1 , 2019 Page 29 Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. .. t .. J .. .. J J , .. j J 111111 ~ ,,. .. .. ... ... .. .. ... ,,. ,,. ... .. la ... ,.. ,.. .. ,. ... ,,. ... .. ' .. ,,. ... ... ... ... .. .. ,,. ... Preliminary Foundation and Fill Settlements -Alternative A In addition to designing foundations for the corrosive and expansive soil conditions described herein, the project structural engineer should also evaluate the estimated vertical settlement and angular distortion values that an individual structure (including walls, footings, and/or other settlement-sensitive improvements, etc.), could be subjected to. The levels of angular distortion were evaluated on a 40-foot length assumed as the minimum dimension of building spans; if, from a structural standpoint, a decreased or increased length over which the differential settlement is assumed to occur is justified, this change should be incorporated into the design. Typical differential foundation settlement generally occurs between the lightest and heaviest foundation elements. Provided that the Alternative "A" earthwork recommendations are implemented, differential settlement of up to approximately 1 inch over 40 feet horizontally (i.e., angular distortion approximately 1/480), may be assumed. Differential vertical settlements of 1 inch in 30feet (about 1/350) should be applied between the heaviest and lightest foundation elements (i.e., between heaviest columns or wall footings). These localized static settlements are anticipated to be mostly complete at the conclusion of construction. Any post-construction settlement of the fill should be mitigated by proper foundation design, provided the design parameters indicated in this report are properly utilized in final design of foundation system(s). In addition to the above, the structural engineer should also consider estimated settlements due to short duration seismic loading and applicable load combinations, as required by the City and/or the 2016 CBC (CBSC, 2016). Preliminary Conventional Foundation and Slab-On-Grade Construction Recommendations -Non Detrimentally Expansive Soils The following recommendations are for conventional foundations and slab-on-grade floor systems underlain by at least 7 feet of non-detrimentally expansive engineered fill (i.e., E.I. < 21 and P.I. < 15) overlying dense, unweathered Santiago Formation. This would likely require selective grading and/or import to accomplish. The structural engineer's recommendations may be more onerous, based on actual floor loads. 1 . Exterior and interior footings should be founded into approved engineered fill at a minimum depth of 12, 18, or 24 inches below the lowest adjacent grade for a one-, two-, or three-story floor loads, respectively. For one-, two-, and three-story floor loads, footing widths should be at least 12, 15, and 18 inches, respectively. Isolated, exterior column and panel pads, or wall footings, should be at least 24 inches square, and founded at a minimum depth of 24 inches into approved engineered fill. All footings should be minimally reinforced with four No. 4 reinforcing bars, two placed near the top and two placed near the bottom of the footing. Depth of embedment does not include the slab or underlayment thickness, and is measured from the lowest adjacent grade . Summerhill Homes W.O. 7103-A-SC April 1, 2019 Page 30 Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc . 2. 3. 4. 5. 6. 7. 8. 9. All interior and exterior column footings, and perimeter wall footings, should be tied together via grade beams in at least one direction, for very low expansive soils, or two directions otherwise. The grade beams should be at least 12 inches square in cross section, and should be provided with a minimum of one No.4 reinforcing bar near the top, and one No.4 reinforcing bar near the bottom of the grade beam. The base of the reinforced grade beams should be at the same elevation as the adjoining footings. A stepped grade beam, constructed per the structural engineer's specifications, may be necessary where the base of footings occur at different elevations. A grade beam, reinforced as previously recommended and at least 12 inches square, should be provided across large (garage) entrances. The base of the reinforced grade beam should be at the same elevation as the adjoining footings. A stepped grade beam, constructed per the structural engineer's specifications, may be necessary where the base of footings occur at different elevations. A minimum concrete slab-on-grade floor thickness of 4.5 inches is recommended. A maximum water to cement ratio of 0.5 is recommended for foundations and slab-on-grade floors. Concrete slabs should be reinforced with a minimum of No. 3 reinforcement bars placed at 18 inches on center, in two horizontally perpendicular directions (i.e., long axis and short axis). The actual thickness and steel reinforcement for concrete slab-on-grade floors should be determined by the project structural engineer, based on the anticipated loading conditions and building use. However, the slab thickness and steel reinforcement, recommended above, are considered minimum guidelines. All slab reinforcement should be supported to ensure proper mid-slab height positioning during placement of the concrete. "Hooking" of reinforcement is not an acceptable method of positioning. Slab subgrade pre-soaking is not required for non-detrimentally expansive soil conditions. However, the Client should consider pre-wetting the slab subgrade materials to at least the soil's optimum moisture content to a minimum depth of 12 inches, within 72 hours of the placement of the underlayment sand and vapor retarder. Soils generated from footing excavations to be used onsite should be compacted to a minimum relative compaction of 90 percent of the laboratory standard (ASTM D 1557), whether the soils are to be placed inside the foundation perimeter or in the yard/right-of-way areas. This material must not alter positive drainage patterns that direct drainage away from the structural areas and toward traffic areas or approved drainage facilities. Summerhill Homes W .0. 7103-A-SC April 1, 2019 Page 31 Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. J ., -' J , .. J j J ,. .. ,.. 111111 ,.. 1111 .. .. .... .. .. ... .. .. .. .. ,,,. .. .. .. ,,. ... Post-Tensioned Slab Foundation Systems Post-tensioned slab foundations may be used to mitigate the damaging shrink/swell effects of expansive soils that exist onsite. The post-tensioned slab foundation designer may elect to exceed the minimal recommendations, provided herein, to increase slab stiffness performance. Post-tension (PT) design may be either ribbed or mat-type. The latter is also referred to as uniform thickness foundation (UTF). The use of a UTF is an alternative to the traditional ribbed-type. The UTF offers a reduction in grade beams. That is to say a UTF typically uses a single perimeter grade beam and possible "shovel" footings, but has a thicker slab than the ribbed-type . The information and recommendations presented in this section are not meant to supercede design by a registered structural engineer or civil engineer qualified to perform PT slab foundation design. PT foundations should be designed using sound engineering practice and be in accordance with local and 2016 CBC requirements. Upon request, GSI can provide additional data/consultation regarding soil parameters as related to PT foundation design. For the purpose of this study, GSI is providing recommended PT foundation design criteria for low, medium and highly expansive soil conditions (E.1. = 21 to 130). From a soil expansion/shrinkage standpoint, a common contributing factor to distress of structures using PT slabs is a "dishing" or "arching" of the slabs. This is caused by the fluctuation of moisture content in the soils below the perimeter of the slab primarily due to onsite and offsite irrigation practices, climatic and seasonal changes, and the presence of expansive soils. When the soil environment surrounding the exterior of the slab has a higher moisture content than the area beneath the slab, moisture tends to migrate inward, underneath the slab edges to a distance beyond the slab edges referred to as the moisture variation distance. When this migration of water occurs, the volume of the soils beneath the slab edges expands and causes the slab edges to lift in response. This is referred to as an edge-lift condition . Conversely, when the outside soil environment is drier, the moisture transmission regime is reversed and the soils underneath the slab edges lose their moisture and shrink. This process leads to dropping of the slab at the edges, which leads to what is commonly referred to as the center lift condition. A well-designed, PT slab having sufficient stiffness and rigidity provides a resistance to excessive bending that results from non-uniform swelling and shrinking slab subgrade soils, particularly within the moisture variation distance, near the slab edges. Other mitigation techniques typically used in conjunction with PT slabs consist of a combination of specific soil pre-saturation and the construction of a perimeter "cut-off" wall grade beam . Soil pre-saturation consists of moisture conditioning the slab subgrade soils prior to the PT slab construction. This effectively reduces soil moisture migration from the area located outside the building toward the soils underlying the post-tension slab. Perimeter cut-off Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. W.O. 7103-A-SC April 1, 2019 Page 32 walls are thickened edges of the concrete slab that impede both outward and inward soil moisture migration. Slab Subgrade Pre-Soaking Pre-moistening of the slab subgrade soil is recommended for detrimentally expansive soil conditions. The moisture content of the subgrade soils should be equal to or greater than optimum moisture to a depth equivalent to the perimeter grade beam or cut-off wall depth in the slab areas (typically 12, 18, and 24 inches) for low, medium, and high expansive soil conditions. Pre-moistening and/or pre-soaking should be evaluated by the soils engineer 72 hours prior to vapor retarder placement. In summary: EXPANSION PAD SOIL MOISTURE CONSTRUCTION SOIL MOISTURE POTENTIAL METHOD RETENTION Upper 12 inches of pad soil Periodically wet or cover with Low moisture 2 percent Wetting and/or reprocessing plastic after trenching . (21-50) over Evaluation 72 hours prior to optimum (or 1.2 times) placement of concrete. Upper 18 inches of pad soil Periodically wet or cover with Medium Berm and flood QI wetting plastic after trenching. moisture 2 percent over (E.1. = 51-90) optimum (or 1.2 times) and reprocessing Evaluation 72 hours prior to placement of concrete. Upper 24 inches of pad soil Periodically wet or cover with High Berm and flood QI wetting plastic after trenching. moisture 3 percent over (E.I. = 91-130) optimum (or 1.3 times) and reprocessing Evaluation 72 hours prior to olacement of concrete. Perimeter Cut-Off Walls Perimeter cut-off walls should be at least 12, 18, or 24 inches deep for low, medium, or highly expansive soil conditions, respectively. The cut-off walls may be integrated into the slab design or independent of the slab. The cut-off walls should be a minimum of 6 inches thick (wide). The bottom of the perimeter cut-off wall should be designed to resist tension, using cable or reinforcement per the structural engineer. Post-Tensioned Foundation Design The following recommendations for design of PT slabs have been prepared in general compliance with the requirements of the recent Post Tensioning lnstitute's (PTl's) publication titled "Design of Post-Tensioned Slabs on Ground, Third Edition" (PTI , 2004), together with it's subsequent addendums (PTI , 2008). Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. W.O. 7103-A-SC April 1, 2019 Page 33 Soil Support Parameters The recommendations for soil support parameters have been provided based on the typical soil index properties for soils that are medium to high in expansion potential. The soil index properties are typically the upper bound values based on our experience and practice in the southern California area. Additional testing is recommended either during or following grading, and prior to foundation construction to further evaluate the soil conditions within the upper 7 to 15 feet of pad grade. The following table presents suggested minimum coefficients to be used in the PTI design method. Thornthwaite Moisture Index -20 inches/year Correction Factor for Irrigation 20 inches/year Depth to Constant Soil Suction 7 feet or overexcavation depth to bedrock Constant soil Suction (pf) 3.6 Moisture Velocity 0.7 inches/month Effective Plasticitv Index (P.l.l* 25-35 * -The effective plasticity index should be evaluated for the upper 7 to 15 feet of foundation soils either durina or followina oradina. Based on the above, the recommended soil support parameters are tabulated below: DESIGN PARAMETERS LOW EXPANSION MEDIUM EXPANSION HIGH EXPANSION CE.I. = 21-50) CE.I.= 51-90) CE.I. = 91-130) em center lift 9.0 feet 8.7 feet 8.5 feet em edge lift 5.2 feet 4.5 feet 4.0 feet Ym center lift 0.4 inches 0.5 inches 0.66 inches Ym edge lift 0.7 inch 1.3 inch 1.7 inches Bearing Value 11> 1,000 psf 1,000 psf 1,000 psf Lateral Pressure 250 psf 175 psf 150 psf Subgrade Modulus (k) 100 pci/inch 85 pci/inch 70 pci/inch Minimum Perimeter 12inches 18inches 24inches Footing Embedment 12> 11> Internal bearing values within the perimeter of the post-tension slab may be increased to 1,500 psf for a minimum embedment of 12 inches, then by 20 percent for each additional foot of embedment to a maximum of 2,500 psf. 12> As measured below the lowest adjacent compacted subgrade surface without landscape layer or sand underlayment. Note: The use of ooen bottomed raised olanters adiacent to foundations will reauire more onerous desian oarameters. Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. W.O. 7103-A-SC April 1, 2019 Page 34 Preliminary Foundation Design and Construction Recommendations for Mat-Type Foundations -Alternative A Mat-type foundations and slabs may be utilized to mitigate the effects of expansive soils. For mat foundations founded at least 18 inches in properly compacted engineered fill, a maximum allowable bearing capacity of 2,500 psf is recommended. This value may be increased by one-third for short-term loads including wind or seismic. Reinforcement should be designed in accordance with local codes and structural considerations. Mat-type foundations or slabs may be uniform thickness or incorporate edge footings for moisture cut-off barriers as recommended herein. Edge footings should be at least 12 inches wide and extend 18 inches below the lowest adjacent grade. The bottom of the edge footing should be designed to resist tension, using reinforcement per the structural engineer. The need and arrangement of interior grade beams (stiffening beams) will be in accordance with the structural consultant's recommendations. Uniform thickness mat foundations/slabs should extend at least 18 inches below the lowest adjacent grade. Reinforcement bar sizing and spacing for mat foundations should be provided by the structural engineer. The parameters herein should be modified to mitigate the effects of the differential settlements reported earlier in this report. Mat Foundation Design The design of mat foundations should incorporate the vertical modulus of subgrade reaction. This value is a unit value for a 1-foot square footing and should be reduced in accordance with the following equation when used with the design of larger foundations. This assumes that the bearing soils will consist of engineered fills with an average relative compaction of 90 percent of the laboratory (ASTM D 1557), overlying dense formational earth materials. K = K [B+1]2 R s 2B where: Ks = unit subgrade modulus ~ = reduced subgrade modulus B = foundation width (in feet) The modulus of subgrade reaction (Ks) and effective plasticity index (Pl) to be used in mat foundation design for various expansive soil conditions is presented in the following table. The effective plasticity index (P.I.) for the upper 7 to 15 feet of the foundation soils should be evaluated during or following grading. Lateral pressures for mat foundation design should conform to those previously provided in the "Post-Tensioned Slab Foundation Systems" section of this report. Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. W.O. 7103-A-SC April 1, 2019 Page 35 , .. ., .. .,, J j ... J J ., ... ., .. J J , .. J LOW EXPANSION MEDIUM EXPANSION I HIGH EXPANSION (E.I. = 0-50) (E.I. = 51-90) (E.I. = 91-130) K~ =100 pci/inch, P.I. <15 K~ =85 pci/inch, P.I. = 25 I K~ =70 pci/inch, P.I. = 35 Slab Subgrade Moisture Content Pre-moistening/pre-soaking of the slab subgrade soil is recommended owing to expansive soil conditions at the site. The moisture content of the subgrade soils should be equal to or greater than optimum moisture to a depth equivalent to the perimeter grade beam or cut-off wall depth in the slab areas (typically 12, 18 and 24 inches for low, medium and highly expansive soil conditions, respectively). Pre-moistening and/or pre-soaking should be evaluated by the soils engineer 72 hours prior to vapor retarder placement. DRILLED PIER AND GRADE BEAM FOUNDATION RECOMMENDATIONS (ALTERNATIVE B) Alternative Bis primarily for the east parcel. The proposed residential structure, underlain by left in-place undocumented fill, roadway fill, alluvium, and weathered Santiago Formation may be supported by drilled, cast-in-place, concrete piers with structural concrete floors. All drilled piers should extend a minimum of 5 feet into competent formational materials, or a minimum tip elevation of 70 feet, on a preliminary basis. Actual pier embedment should be finalized by the project's structural engineer. The structural strength of the piers should be checked by the structural engineer or civil engineer specializing in structural analysis. Pier holes should be drilled straight and plumb. Locations (both plan and elevation) and plumbness should be the contractor's responsibility. The grade beam should be at a minimum of 24 inches by 24 inches in cross section and supported by drilled piers 24 inches in diameter which are placed at a minimum spacing of 8 to 1 0 feet on center and supporting all structural columns. The design of the grade beam and caissons should be in accordance with the recommendations of the project structural engineer, and utilize the following geotechnical parameters: Passive Resistance Passive earth pressure of 400 lbs/ft2 per foot of pier depth, to a maximum value of 4,000 psf may be used to determine pier depth and spacing, provided that pile embedment and spacing meet or exceed the minimum requirements stated above. Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. W.O. 7103-A-SC April 1, 2019 Page 36 Point of Fixity The point of fixity should be located at approximately 1 pier diameter below the top of the unweathered Santiago Formation, or approximately 16 to 19 feet below the existing grade, on the east parcel. Allowable Axial Capacity A shaft capacity of 400 psf should be applied over the surface area of the drilled pier located in the unweathered Santiago Formation only. The tip bearing capacity should be limited to 4,000 psf. Caisson Construction 1. 2. 3. 4. 5. The excavation and installation of the drilled piers should be observed and documented by the project geotechnical engineer to verify the recommended embedment depth. The drilled holes should be cased, specifically below the water table to prevent caving. The bottom of the casing should be at least 4 feet below the top of the concrete as the concrete is poured and the casing is withdrawn. Dewatering may be required for concrete placement. This should be considered during project planning. The bottom of the drilled pier should be cleared of any loose or soft soils before concrete placement. The exact depths of the piers should be determined during the final precise grading plan review. Proper slump underwater type concrete with a maximum water to cement ratio of 0.50 should be used, and should be delivered through a tremie pipe. We recommend that concrete be placed through the tremie pipe immediately subsequent to approved excavation and steel placement. Care should be taken to prevent striking the walls of the excavations with the tremie pipe during concrete placement. Drilled pier steel reinforcement cages should have spacers to allow for a minimum spacing of steel from the side of the pier excavation. The need for corrosion protected reinforcing steel in drilled pier construction should be evaluated by the structural consultant. 6. During pier placement, concrete should not be allowed to free fall more than 5 feet. 7. Concrete used in the foundation should be tested by a qualified materials testing consultant for strength and mix design. Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. W.O. 7103-A-SC April 1, 2019 Page 37 , .. j ., .. j , .. J ., .. .. t .. J J J ,,. .. ,. ... .. ... ,. ... ,. .. .. ... ... ,. .. .. .. flllll .. ,. .. ,. .. .. .. ... ,. ,,,,. Drilled Pier and Grade Beam Foundation Settlement Drilled pier and grade beam foundations should be designed to accommodate a differential settlement of½ inch over a 40-foot horizontal span. Corrosion and Concrete Mix Upon completion of grading, laboratory testing should be performed of site materials for corrosion to concrete and corrosion to steel. Additional comments may be obtained from a qualified corrosion engineer at that time . SOIL MOISTURE TRANSMISSION CONSIDERATIONS (BOTH ALTERNATIVES) GSI has evaluated the potential for vapor or water transmission through concrete floor slabs, in light of typical floor coverings and improvements. Please note that slab moisture emission rates range from about 2 to 27 lbs/24 hours/1,000 square feet from a typical slab (Kanare, 2005), while floor covering manufacturers generally recommend about 3 lbs/24 hours as an upper limit. The recommendations in this section are not intended to preclude the transmission of water or vapor through the foundation or slabs . Foundation systems and slabs shall not allow water or water vapor to enter into the structure so as to cause damage to another building component or to limit the installation of the type of flooring materials typically used for the particular application (State of California, 2019). These recommendations may be exceeded or supplemented by a water "proofing" specialist, project architect, or structural consultant. Thus, the client will need to evaluate the following in light of a cost vs. benefit analysis (owner expectations and repairs/replacement), along with disclosure to all interested/affected parties. It should also be noted that vapor transmission will occur in new slab-on-grade floors as a result of chemical reactions taking place within the curing concrete. Vapor transmission through concrete floor slabs as a result of concrete curing has the potential to adversely affect sensitive floor coverings depending on the thickness of the concrete floor slab and the duration of time between the placement of concrete, and the floor covering. It is possible that a slab moisture sealant may be needed prior to the placement of sensitive floor coverings if a thick slab-on-grade floor is used and the time frame between concrete and floor covering placement is relatively short. Considering the known soil conditions in the region, the anticipated typical water vapor transmission rates, floor coverings, and improvements (to be chosen by the Client and/or project architect) that can tolerate vapor transmission rates without significant distress, the following alternatives are provided: • Concrete slabs, including the garage slab, should be thickened . Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. W.O. 7103-A-SC April 1, 2019 Page 38 • • • • • Concrete slab underlayment should consist of a 15-mil vapor retarder, or equivalent, with all laps sealed per the 2016 CBC and the manufacturer's recommendation. The vapor retarder should comply with the ASTM E 1745 -Class A criteria (Stego Wrap or approved equivalent), and be installed in accordance with ACI 302.1 R-04 and ASTM E 1643. The 15-mil vapor retarder (ASTM E 17 45 -Class A) shall be installed per the recommendations of the manufacturer, including all penetrations (i.e., pipe, ducting, rebar, etc.). Concrete slabs, including the garage slab, should be underlain by 2 inches of clean, washed sand (SE > 30) above a 15-mil vapor retarder (ASTM E-17 45 -Class A, per Engineering Bulletin 119 [Kanare, 2005]) installed per the recommendations of the manufacturer, including all penetrations (i.e., pipe, ducting, rebar, etc.). The manufacturer shall provide instructions for lap sealing, including minimum width of lap, method of sealing, and either supply or specify suitable products for lap sealing (ASTM E 17 45), and per the 2016 CBC. ACI 302.1 R-04 (2004) states "If a cushion or sand layer is desired between the vapor retarder and the slab, care must be taken to protect the sand layer from taking on additional water from a source such as rain, curing, cutting, or cleaning. Wet cushion or sand layer has been directly linked in the past to significant lengthening of time required for a slab to reach an acceptable level of dryness for floor covering applications." Therefore, additional observation and/or testing will be necessary for the cushion or sand layer for moisture content, and relatively uniform thicknesses, prior to the placement of concrete. For very low expansive soil conditions (E.I. < 21 and P.I. < 15), the vapor retarder should be underlain by 2 inches of sand (SE > 30) placed directly on the prepared, moisture conditioned, subgrade and should be sealed to provide a continuous retarder under the entire slab, as discussed above. The underlying sand layer may be omitted provided testing indicates the SE of the slab subgrades soils is greater than or equal to 30. If the slab subgrade exposes soils with an E.I. > 20 and P.1. > 14, the vapor retarder shall be underlain by a capillary break consisting of at least 4 inches of clean crushed gravel with a maximum dimension of ¾ inch (less than 5 percent passing the No. 200 sieve). The maximum water to cement ratio for concrete used in foundation and slab-on-grade floor construction should not exceed 0.50. Additional concrete mix design recommendations should be provided by the structural consultant and/or waterproofing specialist. Concrete finishing and workablity should be addressed by the structural consultant and a waterproofing specialist. Summerhill Homes W.O. 7103-A-SC April 1, 2019 Page 39 Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. J , ... , .. , .. J J , .. j , • ., .. .. .J J , .. ., .. ... ,. - .. ... ... .. ... ,,. .. .. ... .. .. ,. .. ,,. 1111 • • • Where slab water/cement ratios are as indicated herein, and/or admixtures used, the structural consultant should also make changes to the concrete in the grade beams and footings in kind, so that the concrete used in the foundation and slabs are designed and/or treated for more uniform moisture protection. The property owner should be specifically advised which areas are suitable for tile flooring, vinyl flooring, or other types of water/vapor-sensitive flooring and which areas are not suitable for these types of flooring applications. In all planned floor areas, flooring shall be installed per the manufacturer's recommendations. Additional recommendations regarding water or vapor transmission should be provided by the architect/structural engineer/slab or foundation designer and should be consistent with the specified floor coverings indicated by the architect. Regardless of the mitigation, some limited moisture/moisture vapor transmission through the slab cannot be entirely precluded and should be anticipated. Construction crews may require special training for installation of certain product(s), as well as concrete finishing techniques. The use of specialized product(s) should be approved by the slab designer and water-proofing consultant. A technical representative of the flooring contractor should review the slab and moisture retarder plans and provide comment prior to the construction of the foundation or improvement. The vapor retarder contractor should have representatives onsite during the initial installation . WALL DESIGN PARAMETERS General The following recommendations for the design and construction of conventional masonry retaining walls have been provided should they be included in the proposed development plan. Recommendations for specialty walls (i.e., crib, earthstone, geogrid, etc.) can be provided upon request, and would be based on site-specific conditions. Conventional Retaining Walls The design parameters, provided below, assume that either very low expansive soils (typically Class 2 permeable filter material or Class 3 aggregate base) or native onsite materials with an E.I. up to 20 and a P.I. less than 15 are used to backfill any retaining wall (this latter case would require significant compliance testing). The type of backfill (i.e., selector native), should be specified by the wall designer, and clearly shown on the plans. Please note that the use of native backfill materials may require a more robust retaining wall design than if select backfill is used. In other words, there would likely be a need for additional/larger steel reinforcements, larger footing dimensions, larger masonry units, increased compressive strength for mortar and grout, etc. in the construction of a retaining wall with native backfill than would be needed if a select import backfill were used. It Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. W.O. 7103-A-SC April 1, 2019 Page 40 should also be noted that the onsite earth materials may not meet the herein recommended parameters for retaining wall backfill materials. Thus, import may be necessary to provide suitable retaining wall backfill. The use of non-compliant retaining wall backfill could potentially result in retaining wall distress. Any building walls, below grade (i.e., basement walls), should be water-proofed. Waterproofing should also be provided for site retaining walls in order to reduce the potential for efflorescence staining. Preliminary Retaining Wall Foundation Design Preliminary foundation design for retaining walls should incorporate the following recommendations: Minimum Footing Embedment -24 inches below the lowest adjacent grade (excluding landscape layer, 6 inches). Minimum Footing Width -24 inches Allowable Bearing Pressure -An allowable bearing pressure of 2,500 pcf may be used in the preliminary design of retaining wall foundations provided that the footing maintains a minimum width of 24 inches and extends at least 24 inches into approved engineered fill overlying dense unweathered formational deposits. This pressure may be increased by one-third for short-term wind and/or seismic loads. Passive Earth Pressure -A passive earth pressure of 200 pcf with a maximum earth pressure of 2,000 psf may be used in the preliminary design of retaining wall foundations. Lateral Sliding Resistance -A 0.35 coefficient of friction may be utilized for a concrete to soil contact when multiplied by the dead load. When combining passive pressure and frictional resistance, the passive pressure component should be reduced by one-third. Soil Density -Soil densities ranging between 115 pcf and 125 pcf may be used in the design of retaining wall foundations. This assumes an average engineered fill compaction of at least 90 percent of the laboratory standard. Any retaining walls near the perimeter of the site will likely need to be supported by drilled pier and grade beam foundations systems for adequate vertical and lateral bearing support. All retaining wall footing setbacks from any slopes should comply with Figure 1808.7.1 of the 2016 CBC. GSI recommends a minimum horizontal setback distance of 7 feet as measured from the bottom, outboard edge of the footing to any slope face. Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. W.O. 7103-A-SC April 1, 2019 Page 41 , ... J , .,, J ., "" j J J J J Restrained Walls Any retaining walls that will be restrained prior to placing and compacting backfill material or that have re-entrant or male corners, should be designed for an at-rest equivalent fluid pressure (EFP) of 55 pcf and 65 pcf for select and very low expansive native backfill, respectively. The design should include any applicable surcharge loading. For areas of male or re-entrant corners, the restrained wall design should extend a minimum distance of twice the height of the wall (2H) laterally from the corner. Cantilevered Walls The recommendations, presented below, are for cantilevered retaining walls up to 1 O feet high. Design parameters for walls less than 3 feet in height may be superceded by San Diego regional standard design. Active earth pressure may be used for retaining wall design, provided the top of the wall is not restrained from minor deflections. An equivalent fluid pressure approach may be used to compute the horizontal pressure against the wall. Appropriate fluid unit weights are given below for specific slope gradients of the retained material. These do not include other superimposed loading conditions due to traffic, structures, seismic events or adverse geologic conditions. When wall configurations are finalized , the appropriate loading conditions for superimposed loads can be provided upon request. For preliminary planning purposes, the structural consultant should incorporate the surcharge of traffic on the back of retaining walls where vehicular traffic will occur within a horizontal distance equal to "H" from the back of any retaining wall (where "H" equals the height of the retaining wall). The traffic surcharge may be taken as 100 psf/ft in the upper 5 feet of backfill for light truck and car traffic. This does not include the surcharge of parked vehicles which should be evaluated at a higher surcharge to account for the effects of seismic loading. SURFACE SLOPE OF EQUIVALENT EQUIVALENT RETAINED MATERIAL FLUID WEIGHT P.C.F. FLUID WEIGHT P.C.F. (HORIZONTAL:VERTICAL) (SELECT BACKFILL)<2> (NATIVE BACKFILL)<3> I Leve1<1> I 38 I 45 I 2 to 1 55 60 <1> Level backfill behind a retaining wall is defined as compacted earth materials, properly drained, without a slope for a distance of 2H behind the wall, where H is the height of the wall. <2> SE ~30, P.I. < 15, E.I. < 21 , and~ 10% passing No. 200 sieve. <3> E.I. = Oto 20, SE > 25, P.I. < 15, and < 15% passing No. 200 sieve. Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. W.O. 7103-A-SC April 1, 2019 Page 42 Seismic Surcharge For engineered retaining walls where the height of retained earth is 6 feet or greater, or incorporated into a building, and/or could pose ingress or egress constraints to the residential structure, GSI recommends that such walls be evaluated for a seismic surcharge (in general accordance with 2016 CBC requirements). The site walls in this category should maintain an overturning Factor-of-Safety (FOS) of approximately 1.25 when the seismic surcharge (increment) is applied. This seismic surcharge pressure (seismic increment) may be taken as 15H where "H" is the height of the retained backfill, measured from the top of the footing at its heel. The resultant force should be applied at a distance 0.6 H up from the bottom of the footing. For restrained walls, the seismic surcharge should be applied as a uniform surcharge load from the bottom of the footing (excluding shear keys) to the top of the backfill at the heel of the wall footing. For cantilevered walls, the pressure should be an inverted triangular distribution using 15H. The bearing pressure obtained during the seismic evaluation may exceed the static value by one-third, considering the transient nature of this surcharge. Please note this is for local wall stability only. The 15H is derived from a Mononobe-Okabe solution for both restrained cantilever walls. This accounts for the increased lateral pressure due to shakedown or movement of the sand fill soil in the zone of influence from the wall or roughly a 45° -cj)/2 plane away from the back of the wall. The 15H seismic surcharge is derived from the formula: Where: = = H Seismic increment Probabilistic horizontal site acceleration with a percentage of "g" total unit weight (115 to 125 pcf for site soils @ 90% relative compaction). Height of the wall from the bottom of the footing or point of pile fixity. Retaining Wall Backfill and Drainage Positive drainage must be provided behind all retaining walls in the form of gravel wrapped in geofabric and outlets. A backdrain system is considered necessary for retaining walls that are 2 feet or greater in height. Details 1, 2, and 3, present the backdrainage options discussed below. Backdrains should consist of a 4-inch diameter perforated PVC or ABS pipe encased in either Class 2 permeable filter material or ¾-inch to 1 ½-inch gravel wrapped in approved filter fabric (Mirafi 140 or equivalent). The backdrain should flow via gravity (minimum 1 percent fall) toward an approved drainage facility selected by a civil engineer. For select backfill, the filter material should extend a minimum of 1 horizontal foot behind the base of the walls and upward at least 1 foot. For native backfill that has up to E.I. = 20, continuous Class 2 permeable drain materials should be used behind the wall. Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. W.O. 7103-A-SC April 1, 2019 Page 43 , .. J j J J J j J .. ,,, (1) Waterproofing membrane -~ CMU or reinforced-concrete wall ±12 inches Proposed grade t - sloped to drain per precise civil drawings (5) Weep hole ~,~~v. Footing and wall design by others-""-~ Structural footing or settlement-sensitive improvement Provide surf ace drainage via an engineered V-ditch (see civil plans for details) 2=1 (h:v) slope -~ . . .. .. 4}Pi . · ~\" .: . \ -.·. . . . Native backfill 1=1 (h=v) or flatter backcut to be properly benched (6) Footing (1) Waterproofing membrane. (2) Gravel= Clean, crushed, ¾ to 1½ inch. (3) Filter fabric= Mirafi 140N or approved equivalent. (4) Pipe: 4-inch-diameter perforated PVC, Schedule 40, or approved alternative with minimum of 1 percent gradient sloped to suitable, approved outlet point (perforations down). (5) Weep hole= Minimum 2-inch diameter placed at 20-foot centers along the wall and placed 3 inches above finished surface. Design civil engineer to provide drainage at toe of wall. No weep holes for below-grade walls. (6) Footing= If bench is created behind the footing greater than the footing width, use level fill or cut natural earth materials. An additional "heel" drain will likely be required by geotechnical consultant. RETAINING WALL DETAIL -ALTERNATIVE A Detail 1 (1) Waterproofing membrane (optional) CMU or reinforced-concrete wall l 6 inches 1 - (5) Weep hole Proposed grade sloped to drain per precise civil drawings --,);\\:§(\~~~\~\ Footing and wall design by others -""'-__..,-1 Structural footing or settlement-sensitive improvement Provide surf ace drainage via engineered V-ditch (see civil plan details) 2:1 (h=v) slope Slope'.or-,fever · · .... ··· . . ..... . . -·-·._ ... --·, . · '· (2)Cornposite . · drain . •. . . (3} Filter• fa. ' '' Native backfill 1:1 (h=v) or flatter backcut to be properly benched -------(6) 1 cubic foot of ¾-inch crushed rock (7) Footing (1) Waterproofing membrane (optional): Liquid boot or approved mastic equivalent. (2) Drain: Miradrain 6000 or J-drain 200 or equivalent for non-waterproofed walls; Miradrain 6200 or J-drain 200 or equivalent for waterproofed walls (all perforations down). (3) Filter fabric: Mirafi 140N or approved equivalent; place fabric flap behind core. (4) Pipe: 4-inch-diameter perforated PVC, Schedule 40, or approved alternative with minimum of 1 percent gradient to proper outlet point (perforations down). (5) Weep hole: Minimum 2-inch diameter placed at 20-foot centers along the wall and placed 3 inches above finished surface. Design civil engineer to provide drainage at toe of wall. No weep holes for below-grade walls. (6) Gravel: Clean, crushed, ¾ to 1½ inch. (7) Footing= If bench is created behind the f coting greater than the f coting width, use level fill or cut natural earth materials. An additional "heel" drain will likely be required by geotechnical consultant. c. RETAINING WALL DETAIL -ALTERNATIVE B Detail 2 (1) Waterproofing membrane ---. Structural footing or settlement-sensitive improvement CMU or reinforced-concrete wall Provide surf ace drainage ±12 inches 7- (5) Weep hole H [ Proposed grade sloped to drain per precise civil drawings <B-~):::\\);(\ ~\/'.: Footing and wall design by others 2=1 (h:v) slope .._r--~· · . H/2 .. : ', minimum :• .-·-··.-•'' I ·:--... ~·• ... . I· .....,.~.,._.;..;........_.......,.;___, ........... . . . . . . . . . . . . . . . '.' ............... . . . . . ...... . . . . . . . . . . . . . . . . . . . Heel 1-width (3) Filter fabric (2) Gravel (4) Pipe (7) Footing (1) Waterproofing membrane: Liquid boot or approved masticequivalent. (2) Gravel: Clean, crushed, ¾ to 1½ inch. (3) Filter fabric: Mirafi 140N or approved equivalent. (8) Native backfill (6) Clean sand backfill 1=1 (h=v) or flatter backcut to be properly benched (4) Pipe: 4-inch-diameter perforated PVC, Schedule 40, or approved alternative with minimum of 1 percent gradient to proper outlet point (perforations down). (5) Weep hole: Minimum 2-inch diameter placed at 20-foot centers along the wall and placed 3 inches above finished surf ace. Design civil engineer to provide drainage at toe of wall. No weep holes for below-grade walls. (6) Clean sand backfill: Must have sand equivalent value (S.E.) of 35 or greater; can be densified by water jetting upon approval by geotechnical engineer. (7) Footing: If bench is created behind the footing greater than the footing width, use level fill or cut natural earth materials. An additional "heel" drain will likely be required by geotechnical consultant. (8) Native backfill: If E.I. (21 and S.E. L35 then all sand requirements also may not be required and will be reviewed by the geotechnical consultant. RETAINING WALL DETAIL -ALTERNATIVE C Detail 3 el This material should be continuous (i.e ., full height) behind the wall , and it should be constructed in accordance with the enclosed Detail 1 (Typical Retaining Wall Backfill and Drainage Detail). For limited access and confined areas, (panel) drainage behind the wall may be constructed in accordance with Detail 2 (Retaining Wall Backfill and Subdrain Detail Geotextile Drain). Materials with an expansion index (E.I.) potential of greater than 20 should not be used as backfill for retaining walls. For more onerous expansive situations, backfill and drainage behind the retaining wall should conform with Detail 3 (Retaining Wall And Subdrain Detail Clean Sand Backfill). Retaining wall backfill should be moisture conditioned to 1.1 to 1.2 times the soil's optimum moisture content, placed in relatively thin lifts, and compacted to at least 90 percent of the laboratory standard (ASTM D 1557). Outlets should consist of a 4-inch diameter solid PVC or ABS pipe spaced no greater than ± 100 feet apart, with a minimum of two outlets, one on each end. The use of weep holes, only, in walls higher than 2 feet, is not recommended. The surface of the backfill should be sealed by pavement or the top 18 inches compacted with native soil (E.I. s 50). Proper surface drainage should also be provided. For additional mitigation, consideration should be given to applying a water-proof membrane to the back of all retaining structures. The use of a waterstop should be considered for all concrete and masonry joints. Wall/Retaining Wall Footing Transitions Site walls are anticipated to be founded on footings designed in accordance with the recommendations in this report. Should wall footings transition from cut to fill , the civil designer may specify either: a) A minimum of a 2-foot overexcavation and recompaction of cut materials for a distance of 2H , from the point of transition. b) Increase of the amount of reinforcing steel and wall detailing (i.e., expansion joints or crack control joints) such that a angular distortion of 1 /360 for a distance of 2H on either side of the transition may be accommodated. Expansion joints should be placed no greater than 20 feet on-center, in accordance with the structural engineer's/wall designer's recommendations, regardless of whether or not transition conditions exist. Expansion joints should be sealed with a flexible, non-shrink grout. c) Embed the footings entirely into native formational material (i.e., deepened footings). If transitions from cut to fill transect the wall footing alignment at an angle of less than 45 degrees (plan view), then the designer should follow recommendation "a" (above) and until such transition is between 45 and 90 degrees to the wall alignment. Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. W .O. 7103-A-SC April 1, 2019 Page 47 TEMPORARY SHORING DESIGN AND CONSTRUCTION Shoring of Excavations GSI is providing the following recommendations should temporary shoring be necessary in order to temporarily retain existing offsite improvements that are to remain in service during the recommended remedial grading excavations (Alternative "A"). GSI anticipates that a system of cast-in-place soldier beams and wood lagging, would be necessary to retain excavation walls if the temporary slopes, recommended herein, would extend into offsite property or would pass below a 1 ½: 1 projection down from the bottom outboard edge of any offsite improvement that is to remain is serviceable use during and following construction. The incorporation of tiebacks or soil nails into the shoring system may not be feasible on this site due to the close proximity of the property lines and the City of Carlsbad right-of-way. If necessary, the use of internal braces and/or rakers may be used to achieve the maximum shoring height needed to complete the recommended excavations. Shoring of excavations of this size is typically performed by specialty contractors with knowledge of the City of Carlsbad ordinances, and current building codes, as well as the local area soil conditions. Since the design of retaining systems is sensitive to surcharge pressures behind the excavation, we recommend that this office be consulted if unusual load conditions are uncovered in the placement/installation. To that end, GSI should perform field reviews during shoring construction. Care should be exercised when excavating into the on-site soils since caving or sloughing of the earth materials is possible. Observation of soldier pile excavations and special inspections/testing should be performed during shoring construction. Shoring of the excavation is the responsibility of the shoring contractor. Extreme caution should be used to reduce damage to any adjacent improvements caused by settlement or reduction of lateral support. Accordingly, we recommend a system of surveying and monitoring until the excavations are backfilled to the design grade in order to evaluate the effects of shoring on existing onsite and offsite improvements. Pre-construction photo-documentation is also advisable. Unless incorporated into the shoring design, construction equipment storage or traffic, and/or stockpiled soils/building materials should not be stored or operated within 'H' feet of the top of any shored excavations (where 'H' equals the height of the retained earth). Temporary/permanent provisions should be made to direct any potential runoff away from the top of shored excavations. All applicable surcharges from vehicular traffic and existing structures within 'H' of a shored excavation should be evaluated. Lateral Pressure -Temporary Shoring 1. The active pressure to be utilized in the design of temporary shoring, retaining level backfill conditions, may be computed by the triangular pressure distribution shown in Figure 3. Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. W.O. 7103-A-SC April 1, 2019 Page 48 Cantilever Shoring System / --Surcharge Pressure p (psf) .__,....,.......,.\ __ ---Line Load al (pounds) T R H (feet) D (feet) 35 H (psf) H 0.35 P (psf) 400 D (psf) · I X 0.1 Y (feet) 0.3 0.5 0.7 X R i0.4 0.55 al >0.4 (0.64 al~ x2t 1 } y 0.6H 0.6H 0.56H 0.48H Tie-Back Shoring System _ -Surcharge Pressure P (psf) r \ ---Line Load a L (pounds) 0.21(ft.} H (feet) NOTES ..--Resistance ("-behind this line "' (D Include grol.lldwater effects below groundwater level @ Include water effects below groundwater level. Grouted length greater than 7 feet; field teat anchor strength. Y (feet RIVERSIDE CO. c. ORANGE CO. SAN DIEGO CO. LATERAL EARTH PRESSURES FOR TEMPORARY SHORING ® © Neglect paeeive pre881.re below base of excavation to a depth of ______ s .... r._S_TE __ M_s____,,__ __ Fi_gu_re_3-I one pier ciameter. W.O. 7103-A-SC DATE 04/19 SCALE None ,.. ... ... ... -... ... ... .. ,,. .. 1111 ,,.. 2. 3. 4. 5 . 6. Passive pressure may be computed as an equivalent fluid having a given density shown in Figure 3. The above criteria assumes that hydrostatic pressure is not allowed to build up behind excavation walls. Surcharge: These recommendations are for exposed excavation walls up to 10 feet high. An empirical equivalent fluid pressure approach may be used to compute the horizontal pressure against the wall. Appropriate fluid unit weights are provided for specific slope gradients of the retained material; these do not include other superimposed loading conditions such as traffic, structures, seismic events, expansive soils or adverse geologic conditions. The traffic surcharge for light passenger cars, trucks, and vans may be taken as 100 psf/ft in the upper 5 feet of the wall. For heavy emergency vehicle or multi-axle (HS20) truck traffic, the traffic surcharge should be 300 psf/ft in the upper 5 feet of the wall. This does not include the surcharge of parked vehicles which should be evaluated at a higher surcharge to account for the effects of seismic loading. It is not recommended to allow sloping surcharge (other than level backfill) within "H" behind the shored walls from either stockpiled soils or temporary/permanent graded slopes (where "H" equals the height of the exposed shoring wall). Steeper slope gradients (more than level) will increase the EFP for shoring design significantly as well as associated costs . Deflection: The shoring system should be designed such that the maximum lateral deformation at the top of the soldier pile not exceed 1 inch. The maximum lateral deformation for the drilled pier concrete shafts at the lowest grade level should not exceed½ inch. The point of fixity, given a CIDH diameter of 18 to 24 inches and the allowable deflection, should be on the order of 1 pile diameter from the depth of excavation (dredge line) into unweathered formational deposits. Lateral deflection may result in settlement of approximately½ percent the total shoring height behind the wall. Should a braced temporary shoring system be necessary, a maximum allowable bearing of 2,000 psf may be used for a temporary concrete raker footing (dead man) or by permanent lateral footings that are at least 12 inches wide by 12 inches below the lowest adjacent grade (deep) into unweathered formational deposits. These footings should be poured with the bearing surface normal to rakers inclined at 45 degrees. Alternatively, if a pile-supported raker is used, a passive pressure of 300 pcf may be used in the design of an 18-inch diameter cast-in-drilled hole (CIDH) pile embedded into unweathered formational deposits. This value may be increased by 20 percent for each additional foot of depth to a maximum lateral bearing of 3,000 psf. The coefficient of friction between concrete and Santiago Formation should be 0.35 when combined with the dead load forces. Summerhill Homes W.O. 7103-A-SC April 1, 2019 Page 50 Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. Temporary Shoring Construction Recommendations 1. 2. 3. 4. 5. 6. 7. 8. 9. The excavation and installation of the soldier piles should be observed and documented by the project geotechnical engineer to further evaluate the geologic conditions within the influence of the temporary shoring wall and to ensure the soldier pile construction conforms to the requirements of the shoring plan. Drilled excavations for soldier piles should be straight and plumb. If boulders and cobbles are encountered during drilling, the contractor should periodically recheck the drilled shaft for plumbness. Although not anticipated, casing should be provided in drilled shafts if perched water and/or caving conditions are encountered during drilling operations. The bottom of the casing should be at least 4 feet below the top of the concrete as the concrete is poured and the casing is withdrawn. Although not anticipated, dewatering may be required for concrete placement if significant seepage or groundwater is encountered during construction. This should be considered during project planning. The exact tip elevation of the soldier piles should be clearly indicated on the shoring plans. All concrete should delivered through a tremie pipe immediately subsequent to approved excavation and steel placement. Care should be taken to prevent striking the walls of the excavations with the tremie pipe during concrete placement. Concrete should not be allowed to free fall more than 5 feet. "Tailgating" concrete will not be permitted. Proper spacing (minimum of 3 inches) between H beams and the side walls, and bottoms of the drilled shafts should be provided. Concrete used in the shoring construction should be tested by a qualified materials testing consultant for strength and mix design. Excavation for lagging should not commence until the soldier pile concrete reaches its 28-day compressive strength. A complete and accurate record of all soldier pile locations, depths, concrete, strengths, quantity of concrete per pile should be maintained by the special inspector and geotechnical consultant. The shoring design engineer should be notified of any unusual conditions encountered during installation. Summerhill Homes W.O. 7103-A-SC April 1, 2019 Page 51 Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. 1111 "' lllf .i ., "" , "" ., "' J J ,,,. .. ,,. .. ... .... .. ,,. .. .... .. ... ... ,... ... ,.. .. ,,.. .. ,,. 1111 Monitoring of Shoring 1 . 2. 3. 4. 5. 6. 7. The shoring designer or his designee should make periodic inspections of the job site for the purpose of observing the installation of the shoring system and monitoring of the survey. Monitoring points should be established at the top of selected soldier piles and at intermediate intervals as considered appropriate by the Geotechnical Engineer . Control points should be established outside the area of influence of the shoring system to ensure the accuracy of the monitoring readings . Initial monitoring and photo-documentation should be performed prior to any excavation. Once the excavation has commenced, periodic readings should be taken weekly until the excavation is backfilled to the design grade. If the performance of the shoring system is within established guidelines, the shoring engineer may permit the periodic readings to be bi-weekly. Permission to conduct bi-weekly readings should be provided by the shoring design engineer in writing, and be distributed to the Geotechnical Engineer-of-Record, Structural Engineer-of-Record, Civil Engineer-of-Record, and shoring contractor. Once initiated, bi-weekly readings should continue until the excavation is backfilled to the design grade. Thereafter, readings can be made monthly. Additional readings should be taken when requested by the special inspector, Shoring Design Engineer, Structural Engineer-of-Record, Geotechnical Engineer-of-Record, or the Building Official. Monitoring readings should be submitted to the Shoring Design Engineer, and Engineer in Responsible Charge, within three business days after they are conducted. Monitoring readings should be accurate to within 0.01 feet. Results are to be submitted in tabular form showing at least the initial date of monitoring and reading, current monitoring date and reading and difference between the two readings . If the total cumulative horizontal or vertical movement (from start of shoring construction) of any nearby existing improvement reaches ½-inch or soldier piles reaches 1 inch, all excavation activities should be suspended until the Geotechnical Engineer and Shoring Design Engineer determine the cause of movement. Supplemental shoring should be devised to eliminate further movement. Supplemental shoring design will require review and approval by the Building Official. Excavation should not re-commence until written permission is provided by the Building Official. Summerhill Homes W.O. 7103-A-SC April 1 , 2019 Page 52 Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. Monitoring of Existing Improvements 1. The contractor should complete written and photographic logs of any existing improvement located within 100 feet or three times the depth of shoring (whichever is greater), prior to shoring construction. A licensed surveyor should document all existing substantial cracks (i.e., greater than 1/s inch horizontal or vertical separation) in the existing structures/improvements. 2. The contractor should document the condition of the existing improvements adjacent to the shoring wall prior to the start of shoring construction. 3. The contractor should monitor existing improvements for movement or cracking that may result from the adjacent shoring. 4. If excessive movement or visible cracking occurs, the shoring contractor should stop work and shore/reinforce the excavation, and contact the Shoring Design Engineer and the Building Official. 5. Monitoring of the existing improvements should be made at reasonable intervals as required by the registered design professional, subject to approval by the Building Official. Monitoring should be performed by a licensed surveyor. 6. Prior to commencing shoring construction, a pre-construction meeting should take place between the contractor, Shoring Design Engineer, Surveyor, and Geotechnical Engineer, to identify monitoring locations on existing improvements. 7. If in the opinion of the Building Official or Shoring Design Engineer, monitoring data indicate excessive movement or other distress, all excavation should cease until the Geotechnical Engineer and Shoring Design Engineer investigates the situation and makes recommendations for remedial actions or continuation. 8. All readings and measurements should be submitted to the Shoring Design Engineer. DEBRIS IMPACT WALLS On a preliminary basis, debris impact walls should be incorporated into the project civil design in order to mitigate potential mud flows, originating in reentrant natural drainage courses along the hillside descending toward the southerly and southwesterly boundaries of the west parcel. The debris impact walls should include at least 3 feet of free board and be designed for an active pressure of 125 pounds per cubic foot (pcf). Foundations for the debris impact walls should conform to the preliminary criteria recommended herein for retaining walls provided that remedial grading (i.e., removal and recompaction of potentially compressible earth materials) can be performed below a 1: 1 (horizontal:vertical Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. W.O. 7103-A-SC April 1, 2019 Page 53 -.---·-·· -··· ... ... .. .t J ~ .l J, j ... ·"" ... -' J ., "" lilt .J J , .. :J J ... .J ., "' J , .. ,,. -.. Illa. ,,. -... .... ,,. .. ... ... ,. .. ,.. ... ,,,,. .. ,.. ,. 11,., ,,... - [h:v]) plane projected down from the bottom, edges of the wall footing in all directions. If remedial grading cannot be performed below the aforementioned plane, footings for the debris impact walls would need to be deepened into unweathered Santiago Formation or the walls would need to be supported by a drilled pier and grade beam foundation system per the preliminary recommendations provided in this report. Debris impact walls may also be integrated into proposed site retaining walls. The approximate locations of the recommended debris impact walls are presented on Figure 2. Other mitigation methods, such as catchments, basins, gabions, and embankments may be employed depending on the available space . WALLS/FENCES/IMPROVEMENTS Perimeter Walls/Fences Due to the potential for some settlement and associated distress to proposed walls and fences within the unmitigated zones, adjacentto property lines (i.e., the area located above a 1 :1 (h:v) plane projected up from the bottom, outboard edge of remedial grading excavations near the property boundaries), we recommend that these improvements be constructed on deepened foundations utilizing a combination of grade beams and drilled piers (caissons). The grade beams should be a minimum of 12 inches by 12 inches in cross section, supported by the drilled piers embedded at least 5 feet into unweathered Santiago Formation. The diameter of the drilled piers should be at least 12 inches. The spacing of the piers should be no greater than 6 feet on center, unless the project structural engineer can demonstrate greater pier spacings in the structural calculations. The strength of the concrete and grout should be evaluated by the project structural engineer. The proper ASTM tests for the concrete and mortar should be provided along with the slump quantities. The design of the grade beam and piers should be in accordance with the recommendations of the project structural engineer, and utilize the following geotechnical parameters: Point of Fixity: Passive Resistance: Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge Located a distance of 1.5 times the pier's diameter, below the top of the unweathered Santiago Formation . Passive earth pressure of 200 psf per foot of depth per foot of caisson diameter, to a maximum value of 4,000 psf may be used to determine pier depth and spacing, provided that they meet or exceed the minimum requirements stated above. To determine the total lateral resistance, the contribution of the creep prone zone above the point of fixity, to passive resistance, should be disregarded. GeoSoils, Inc. W.O. 7103-A-SC April 1, 2019 Page 54 Allowable Axial Capacity: Shaft capacity: 400 psf applied below the point of fixity over the surface area of the shaft. Tip capacity: 4,000 psf. DRIVEWAY, FLATWORK, AND OTHER IMPROVEMENTS Some of the soil materials at the site are expansive. The effects of expansive soils are cumulative, and typically occur over the lifetime of any improvements. On relatively level areas, when the soils are allowed to dry, the dessication and swelling process tends to cause heaving and distress to flatwork and other improvements. The resulting potential for distress to improvements may be reduced, but not totally eliminated. To that end, all interested/affected parties should be informed of this long-term potential for distress. To reduce the likelihood of distress, the following recommendations are presented for all exterior flatwork: 1. 2. 3. 4. The subgrade area for concrete slabs should be compacted to achieve a minimum 90 percent relative compaction, and then be presoaked to 2 to 3 percentage points above (or 125 percent of) the soils' optimum moisture content, to a depth of 18 inches below subgrade elevation. If very low expansive soils are present, only optimum moisture content, or greater, is required and specific presoaking is not warranted. The moisture content of the subgrade should be proof tested within 72 hours prior to pouring concrete. Mitigation of any potentially compressible soils within the influence of the hardscape should be performed prior to subgrade preparation. Concrete slabs should be cast over a non-yielding surface, consisting of a 4-inch layer of crushed rock, gravel, or clean sand, that should be compacted and level prior to pouring concrete. If very low expansive soils are present, the rock or gravel or sand may be deleted. The layer or subgrade should be wet-down completely prior to pouring concrete, to minimize loss of concrete moisture to the surrounding earth materials. Exterior slabs should be a minimum of 4 inches thick. Driveway slabs and approaches should additionally have a thickened edge (12 inches) adjacent to all landscape areas, to help impede infiltration of landscape water under the slab. The use of transverse and longitudinal control joints are recommended to help control slab cracking due to concrete shrinkage or expansion. Two ways to mitigate such cracking are: a) add a sufficient amount of reinforcing steel, increasing tensile strength of the slab; or, b) provide an adequate amount of control Summerhill Homes W.O. 7103-A-SC April 1, 2019 Page 55 Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. J ... J ... .J J ., "" J J J J ., .,; J ,,. .. ,.. .... .. ,,. .... ... ... ,,,. ,,.. ... ,,.. --.... ,.. .. ,.. ... ... .. ,. 1111111 .. .... ,. ... ... ,. -,.. 5. 6. 7. 8. and/or expansion joints to accommodate anticipated concrete shrinkage and expansion. In order to reduce the potential for unsightly cracks, slabs should be reinforced at mid-height with a minimum of No. 3 bars placed at 18 inches on center, in each direction. If subgrade soils within the top 7 feet from finish grade are very low expansive soils (i.e., E.1. :,;20), then 6x6-W1 .4xW1 .4 welded-wire mesh may be substituted for the rebar, provided the reinforcement is placed on chairs, at slab mid-height. The exterior slabs should be scored or saw cut, ½ to % inches deep, often enough so that no section is greater than 1 O feet by 1 O feet. For sidewalks or narrow slabs, control joints should be provided at intervals of every 6 feet. The slabs should be separated from the foundations and sidewalks with expansion joint filler material. No traffic should be allowed upon the newly poured concrete slabs until they have been properly cured to within 75 percent of design strength. Concrete compression strength should be a minimum of 2,500 psi. Driveways, sidewalks, and patio slabs adjacent to the building should be separated from this structure with thick expansion joint filler material. In areas directly adjacent to a continuous source of moisture (i.e., irrigation, planters, etc.), all joints should be additionally sealed with flexible mastic . Planters and walls should not be tied to the building. Overhang structures should be supported on the slabs, or structurally designed with continuous footings tied in at least two directions. If very low expansion soils are present, footings need only be tied in one direction. 9. Any masonry landscape walls that are to be constructed throughout the property should be grouted and articulated in segments no more than 20 feet long. These segments should be keyed or doweled together . 10. Utilities should be enclosed within a closed utilidor (vault) or designed with flexible connections to accommodate differential settlement and expansive soil conditions. 11. Positive site drainage should be maintained at all times. Finish grade on the property should provide a minimum of 1 to 2 percent fall to the street, as indicated herein or conform to Section 1804.4 of the 2016 CBC (whichever is more conservative). It should be kept in mind that drainage reversals could occur, including post-construction settlement, if relatively flat yard drainage gradients are not periodically maintained by the HOA. Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. W.O. 7103-A-SC April 1, 2019 Page 56 12. Air conditioning (A/C) units should be supported by slabs that are incorporated into the building foundation or constructed on a rigid slab with flexible couplings for plumbing and electrical lines. A/C waste water lines should be drained to a suitable non-erosive outlet. 13. Shrinkage cracks could become excessive if proper finishing and curing practices are not followed. Finishing and curing practices should be performed per the Portland Cement Association Guidelines. Mix design should incorporate rate of curing for climate and time of year, sulfate content of soils, corrosion potential of soils, and fertilizers used on site. PRELIMINARY PAVEMENT DESIGN/CONSTRUCTION Structural Section As indicated in City of Carlsbad (2016), the Traffic Index (Tl) for private driveways and parking lots shall be 4.5. However, the City of Carlsbad (2016) requires that truck routes through parking lots and aisles with an Average Daily Traffic (ADT) shall be designed with a Tl of 5.0. Thus, GSI evaluated the preliminary design of pavements in consideration of the aforementioned Tl values. It is recommended that the Tl values for onsite pavements be reviewed by the project civil engineer for comment, and any revisions, as necessary. An R-value of 20 was assumed for preliminary planning purposes in this study. The recommended preliminary pavement sections for both asphaltic concrete and Portland Cement Concrete Pavement (P.C.C.P.) are provided in the following tables: I ASPHALTIC CONCRETE PAVEMENTS I ASPHALTIC AGGREGATE APPROXIMATE TRAFFIC SUBGRADE CONCRETE BASE TRAFFIC AREA INDEx<1> R-VALUE<2> THICKNESS THICKNEss<3> (INCHES) (INCHES) Private Street and Parking Lots 4.5 20 4.0 (4) 4.0 (4) Private Street and Parking Lots 5.0 20 4.0 (4) 6.0 (1> Per City of Carlsbad (2016). The Tl values should be reviewed and revised as necessary by the project civil engineer. Trash disposal areas, entry areas, fire vehicle access may require special design and/or detailing. (2> Estimate, to be verified during grading and prior to placement of the street section. (3l Denotes Class 2 Aggregate Base R ~78 , SE ~25). (4l City minimum . As indicated in City of Carlsbad (2016), all routes leading to trash enclosures shall be designed for heavy loading, and shall have a minimum section of 4.0 inches of asphaltic Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. W.O. 7103-A-SC April 1, 201 9 Page 57 concrete overlying 6.0 inches of approved aggregate base. The level loading area in front of trash enclosures shall be concrete with a minimum thickness of 7½ inches in conformance with City of Carlsbad Standard Drawing GS-16 (City of Carlsbad, 2017). I PORTLAND CONCRETE CEMENT PAVEMENTS (PCCP) I TRAFFIC CONCRETE PCCP TRAFFIC CONCRETE PCCP THICKNESS THICKNESS AREAS TYPE (INCHES) AREAS TYPE (INCHES) 520-C-2500 6.0 520-C-2500 8.0 Light Vehicles Heavy Truck Traffic 560-C-3250 5.0 560-C-3250 7.0 NOTE: All PCCP is designed as un-reinforced and bearing directly on compacted subgrade. However, a 4-inch thick leveling course of compacted aggregate base, or crushed rock may be considered to improve performance. All PCCP should be properly detailed (jointing, etc.) per the industry standard. Pavements may be additionally reinforced with #4 reinforcing bars, placed 12 inches on center, each way, for improved performance. Trash truck loading pads shall be 8 inches per the City standard and reinforced accordingly. All pavement installation, including preparation and compaction of subgrade, compaction of base material, and placement and rolling of asphaltic concrete, etc., shall be done in accordance with the City of Carlsbad guidelines, and under the observation and testing of the project geotechnical engineer and/or the City. The recommended pavement sections provided above are intended as minimum guidelines. If thinner or highly variable pavement sections are constructed, increased maintenance and repair could be expected. If the ADT or Average Daily Truck Traffic (ADTT) increases beyond that intended, as reflected by the Tl used for design, increased maintenance and repair could be required for the pavement section. Consideration should be given to the increased potential for distress from overuse of paved street areas by heavy equipment and/or construction related heavy traffic (e.g ., concrete trucks, loaded supply trucks, etc.), particularly when the final section is not in place (i.e ., topcoat). Best management construction practices should be followed at all times, especially during inclement weather. PAVEMENT GRADING RECOMMENDATIONS General All section changes should be properly transitioned. If adverse conditions are encountered during the preparation of subgrade materials, special construction methods may need to be employed. A GSI representative should be present for the preparation of subgrade, aggregate base, and asphaltic concrete. Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. W .O. 7103-A-SC April 1, 2019 Page 58 Subgrade Within street and parking areas, all surficial deposits of loose soil material should be removed and recompacted as recommended. After the loose soils are removed, the bottom is to be scarified to a depth of at least 6 inches, moisture conditioned as necessary and compacted to 95 percent of the maximum laboratory density, as determined by ASTM D 1557. Deleterious material, excessively wet or dry pockets, concentrated zones of oversized rock fragments, and any other unsuitable materials encountered during grading should be removed. The compacted fill material should then be brought to the elevation of the proposed subgrade for the pavement. The subgrade should be proof-rolled in order to promote a uniform firm and unyielding surface. All grading and fill placement should be observed by the project geotechnical consultant. Aggregate Base Compaction tests are required for the recommended aggregate base section. Minimum relative compaction required will be 95 percent of the laboratory maximum density as determined by ASTM D 1557. Base aggregate should be in accordance to the "Greenbook" crushed aggregate base rock (minimum R-value=78). Paving Prime coat may be omitted if all of the following conditions are met: 1. The asphalt pavement layer is placed within two weeks of completion of aggregate base and/or sub base course. 2. Traffic is not routed over completed base before paving 3. Construction is completed during the dry season of May through October. 4. The aggregate base is kept free of debris prior to placement of asphaltic concrete. If construction is performed during the wet season of November through April, prime coat may be omitted if no rain occurs between completion of the aggregate base course and paving and the time between completion of aggregate base and paving is reduced to three days, provided the aggregate base is free of loose soil or debris. Where prime coat has been omitted and rain occurs, traffic is routed over the aggregate base course, or paving is delayed, measures shall be taken to restore the aggregate base course, and subgrade to conditions that will meet specifications as directed by the geotechnical consultant. GSI has assumed that traffic will not be allowed on recently placed AC for a period of 24 hours or more. Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. W.O. 7103-A-SC April 1, 2019 Page 59 .. J ., .. , .. J ., "" J :J J j .. .. .. ... ... Ill" I .. ... .. ... .. .. ... .. .. I --i -... ... ,. ~ ,,,, .. .. Drainage Positive drainage should be provided for all surface water to drain towards the area swale, curb and gutter, or to an approved drainage channel. Positive site drainage should be maintained at all times. Water should not be allowed to pond or seep into the ground, such as from behind unprotected curbs, both during and after grading. If planters or landscaping are adjacent to paved areas, measures should be taken to minimize the potential for water to enter the pavement section, such as thickened edges, enclosed planters, etc. Also, best management construction practices should be strictly adhered to at all times to minimize the potential for distress during construction and roadway improvements. Seismic effects may reverse relatively flat gradients in streets and gutters . These should be periodically checked following a significant seismic event. PCC Cross Gutters PCC cross gutters should be designed in accordance with San Diego Regional Standard Drawing (SDRSD) G-12 . Additional Considerations To mitigate perched groundwater, consideration should be given to installation of subgrade separators (cut-offs) between pavement subgrade and landscape areas, although this is not a requirement from a geotechnical standpoint. Cut-offs, if used, should be 6 inches wide and at least 12 inches below the pavement subgrade contact or 12 inches below the crushed aggregate base rock, if utilized . ONSITE INFILTRATION-RUNOFF RETENTION SYSTEMS General Onsite infiltration-runoff retention systems (OIRRS) are anticipated to be used for Best Management Practices (BMPs) or Low Impact Development (LID) principles for the project. To that end, some guidelines should/must be followed in the planning, design, and construction of such systems. Such facilities, if improperly designed or implemented without consideration of the geotechnical aspects of site conditions, can contribute to flooding, saturation of bearing materials beneath site improvements, slope instability, and possible concentration and contribution of pollutants into the groundwater or storm drain and/or utility trench systems. A key factor in these systems is the infiltration rate (often referred to as the percolation rate) which can be ascribed to, or determined for, the earth materials within which these systems are installed. Additionally, the infiltration rate of the designed system (which may include gravel, sand, mulch/topsoil, or other amendments, etc.) will need to be considered. Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. W.O. 7103-A-SC April 1, 2019 Page 60 The project infiltration testing is very site specific, any changes to the location of the proposed OIRRS and/or estimated size of the OIRRS, may require additional infiltration testing. Some of the methods which are utilized for onsite infiltration include percolation basins, dry wells, bio-swale/bio-retention, permeable pavers/pavement, infiltration trenches, filter boxes and subsurface infiltration galleries/chambers. Some of these systems are constructed using native and import soils, perforated piping, and filter fabrics while others employ structural components such as stormwater infiltration chambers and filters/separators. Every site will have characteristics which should lend themselves to one or more of these methods; but, not every site is suitable for OIRRS. In practice, OIRRS are usually initially designed by the project design civil engineer. Selection of methods should include (but should not be limited to) review by licensed professionals including the geotechnical engineer, hydrogeologist, engineering geologist, project civil engineer, landscape architect, environmental professional, and industrial hygienist. Applicable governing agency requirements should be reviewed and included in design considerations. The following geotechnical guidelines should be considered when designing onsite infiltration-runoff retention systems: • Based on our review of the United States Department of Agriculture (USDA) Soil Survey, the onsite soils consist of the Diab lo clay (15 to 30% slopes), the Las Flores loamy fine sand (2 to 9% slopes), the Las Flores loamy fine sand (9 to 15% slopes), and the Visalia sandy loam (2 to 5% slopes). The approximate distribution of the mapped soil units within the subject parcels is shown on Figure 4. The capacity of the most limiting layer to transmit water (Ksat) for these soil units, and Hydrologic Soil Group (HSG) are reported as: Diablo clay (15 to 30 % slopes) -moderately low to moderately high (0.06 to 0.20 in/hr); and HSG classification as "D." Las Flores loamy fine sand (2 to 9% slopes) -very low to moderately low (0.00 to 0.06 in/hr); and HSG classification as "D." Las Flores loamy fine sand (9 to 15 % slopes) -very low to moderately low (0.00 to 0.06 in/hr); and HSG classification as "D." Visalia sandy loam (2 to 5% slopes) -High (1.98 to 5.95 in/hr); and HSG Classification as "A." During our feasibility screening level investigation, GSI has evaluated the infiltration rate of natural surface soils on the west parcel to potentially be about 0.2 inches/hour, and on the east parcel to potentially be about 0.5 inches/hour Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. W.O. 7103-A-SC April 1, 2019 Page 61 J J J -..J J J ., .. J , -.. 1 - J , - J J J J j I I I I I I I I I I I I I I I 111/7.J • 67.I ' ' •4&9 ' 8:3 1166.9 1141/S..9 - 0,l~--LandSlll"fW!ln!I ~--S.""'9,oCAIZ'JOI Cona,ltcr,lt., Inc. (t1t)2l:l-12DO (.i•)llZ-fflO '• ALL LOCATIONS ARE APPROXIMATE This document or efi/e is not a part of the Construction Documents and should not be relied upon as being an accurate depiction of design. ---- 100 6145 LAUREL TREE ROAD, CARLSBAD, CA -~--- _,,;,.-= __ .:_~::::::ii~/.·'._ -: --.· ' ·~. ." .,•' N GRAPHIC SCALE 0 50 100 200 1" = 100' DaE LeC LeD VaB r--'-' N.A.P TOPOGRAPHY NOTE THE I.NIBtl.Y1NG T0P0GIW'HIC nAT\JRES SMC1Mt HEREOH \IIIERE MAPPB> aY: GS/ LEGEND DIABLO CLAY, 15 TO 30 PERCENT SLOPES (HSG D) LAS FLORES LOAMY FINE SAND, 2 TO 9 PERCENT SLOPES (HSG D) LAS FLORES LOAMY FINE SAND, 9 TO 15 PERCENT SLOPES (HSG D) VISALIA SANDY LOAM, 2 TO 5 PERCENT SLOPES (HSG A) APPROX/MA TE LOCATION OF GEOLOGIC CONTACT NOT A PART OF THIS STUDY l i l ' i I I I i i • j .. ! . I ; . I USDA/ NRCS SOIL UNITS MAP Fi ure4 W.O. 7103-A-SC DATE: 04/19 SCALE: 1" = 100' ... .. ,. ... ,,.. .. ,. .. ... .. ,,.. .. ,.. ... ,.. .... ,. .. ,,. .. ,,,. .. ,. .. - ,,,. • • • • • • • • (both conducted in USDA-mapped Hydrologic Soil Group "A" areas). Prior development has resulted in the removal of natural surface soils, and for all intent and purposes, the west parcel is predominantly a cut lot exposing some surficial fill and dense sedimentary bedrock consisting of silty sandstone, and significant fill thickness exist on the east parcel. On the east parcel, artificial fill, created through removal/recompaction of onsite soils is of a similar, very low permeability. The City of Carlsbad "Form 1-8" is provided in Appendix F . Owing to the infiltration rate, and per the City of Carlsbad BMP Design Manual (2016), infiltration for onsite storm water treatment is not recommended. It is not good engineering practice to allow water to saturate soils, especially near slopes or improvements; however, the controlling agency/authority is now requiring this for OIRRS purposes on many projects. If infiltration is planned, infiltration system design should be based on actual infiltration testing results/data. Wherever possible, infiltration systems should not be installed within ±50 feet of the tops of slopes steeper than 15 percent or within H/3 from the tops of slopes (where H equals the height of slope) . Wherever possible, infiltrations systems should not be placed within a distance of H/2 from the toes of slopes (where H equals the height of slope) . Impermeable liners and subdrains should be used along the bottom of bioretention swales/basins located within the influence of slopes or settlement-sensitive improvements. Impermeable liners used in conjunction with bioretention basins should consist of a 30-mil polyvinyl chloride (PVC) membrane that is covered by a minimum of 12 inches of clean soil, free from rocks and debris, with a maximum 4: 1 (h:v) slope inclination, or flatter, and meets the following minimum specifications: Specific Gravity (ASTM 0792): 1.2 (g/cc, min.); Tensile (ASTM 0882): 73 (lb/in-width, min); Elongation at Break (ASTM 0882): 380 (%, min); Modulus (ASTM 0882): 30 (lb/in-width, min.); and Tear Strength (ASTM 01004): 8 (lb/in, min); Seam Shear Strength (ASTM 0882) 58.4 (lb/in, min); Seam Peel Strength (ASTM 0882) 15 (lb/in, min). Subdrains should consist of at least 4-inch diameter Schedule 40 or SOR 35 drain pipe with perforations oriented down. The drain pipe should be sleeved with a filter sock. The landscape architect should be notified of the location of the proposed OIRRS . If landscaping is proposed within the OIRRS, consideration should be given to the Summerhill Homes W.O. 7103-A-SC April 1, 2019 Page 63 Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. • • • • • • • • • type of vegetation chosen and their potential effect upon subsurface improvements (i.e., some trees/shrubs will have an effect on subsurface improvements with their extensive root systems). Over-watering landscape areas above, or adjacent to, the proposed OIRRS could adversely affect performance of the system. Areas adjacent to, or within, the OIRRS that are subject to inundation should be properly protected against scouring, undermining, and erosion, in accordance with the recommendations of the design engineer. Seismic shaking may result in the formation of a seiche which could potential overtop the banks of an OIRRS and result in down-gradient flooding and scour. If subsurface infiltration galleries/chambers are proposed, the appropriate size, depth interval, and ultimate placement of the detention/infiltration system should be evaluated by the design engineer, and be of sufficient width/depth to achieve optimum performance, based on the infiltration rates provided. In addition, proper debris filter systems will need to be utilized for the infiltration galleries/chambers. Debris filter systems will need to be self cleaning and periodically and regularly maintained on a regular basis. Provisions for the regular and periodic maintenance of any debris filter system are recommended and this condition should be disclosed to all interested/affected parties. Infiltrations systems should not be installed within ±8 feet of building foundations, utility trenches, and walls, or a 1 :1 (h:v) slope (down and away) from the bottom elements of these improvements. Alternatively, deepened foundations and/or pile/pier supported improvements may be used. Infiltrations systems should not be installed adjacent to pavement and/or hard scape improvements. Alternatively, deepened/thickened edges and curbs and/or impermeable liners may be utilized in areas adjoining the OIRRS. As with any OIRRS, localized ponding and groundwater seepage should be anticipated. The potential for seepage and/or perched groundwater to occur after site development should be disclosed to all interested/affected parties. Installation of infiltrations systems should avoid expansive soils (E.I. ;:: 51) or soils with a relatively high plasticity index (P.I. > 20). Infiltration systems should not be installed where the vertical separation of the groundwater level is less than ± 1 O feet from the base of the system. Where permeable pavements are planned as part of the system, the site Traffic Index (T.I.) should be less than 25,000 ADT, as recommended in Allen, et al. (2011 ). Summerhill Homes W.O. 7103-A-SC April 1, 2019 Page 64 Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. J J ... ... J J J ., .. , .,,; J J ,,. .. ,,. ... ,,.. ... ,. Ill ,.. .. ,,. ,,. ,.. .. ,.. -.. ... • • • • • • • • • Infiltration systems should be designed using a suitable factor of safety (FOS) to account for uncertainties in the known infiltration rates (as generally required by the controlling authorities), and reduction in performance over time. As with any OIRRS, proper care will need to be provided. Best management practices should be followed at all times, especially during inclement weather . Provisions for the management of any siltation, debris within the OIRRS, and/or overgrown vegetation (including root systems) should be considered. An appropriate inspection schedule will need to adopted and provided to all interested/affected parties. Any designed system will require regular and periodic maintenance, which may include rehabilitation and/or complete replacement of the filter media (e.g., sand, gravel, filter fabrics, topsoils, mulch, etc.) or other components utilized in construction, so that the design life exceeds 15 years. Due to the potential for piping and adverse seepage conditions, a burrowing rodent control program should also be implemented onsite. All or portions of these systems may be considered attractive nuisances. Thus, consideration of the effects of, or potential for, vandalism should be addressed. Newly established vegetation/landscaping (including phreatophytes) may have root systems that will influence the performance of the OIRRS or nearby LID systems. The potential for surface flooding, in the case of system blockage, should be evaluated by the design engineer. Any proposed utility backfill materials (i.e., inlet/outlet piping and/or other subsurface utilities) located within or near the proposed area of the OIRRS may become saturated. This is due to the potential for piping, water migration, and/or seepage along the utility trench line backfill. If utility trenches cross and/or are proposed near the OIRRS, cut-off walls or other water barriers will need to be installed to mitigate the potential for piping and excess water entering the utility backfill materials. Planned or existing utilities may also be subject to piping of fines into open-graded gravel backfill layers unless separated from overlying or adjoining OIRRS by geotextiles and/or slurry backfill. The use of OIRRS above existing utilities that might degrade/corrode with the introduction of water/seepage should be avoided . A vector control program may be necessary as stagnant water contained in OIRRS may attract mammals, birds, and insects that carry pathogens. Summerhill Homes W.O. 7103-A-SC April 1, 2019 Page 65 Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. DEVELOPMENT CRITERIA Drainage Adequate surface drainage is a very important factor in reducing the likelihood of adverse performance offoundations, hardscape, and slopes. Surface drainage should be sufficient to mitigate ponding of water anywhere on the property, and especially near structures and tops of slopes. Surface drainage should be carefully taken into consideration during fine grading, landscaping, and building construction. Therefore, care should be taken that future landscaping or construction activities do not create adverse drainage conditions. Positive site drainage within the property should be provided and maintained at all times. Drainage should not flow uncontrolled down any descending slope. Water should be directed away from foundations, tops, and toes of slopes, and not allowed to pond and/or seep into the ground. In general, site drainage should conform to Section 1804.4 of the 2016 CBC. Consideration should be given to avoiding construction of planters adjacent to the building. Building pad drainage should be directed toward the street or other approved area(s). Although not a geotechnical requirement, roof gutters, down spouts, or other appropriate means may be utilized to control roof drainage. Down spouts, or drainage devices, should outlet a minimum of 5 feet from structures or into a subsurface drainage system. Areas of seepage may develop due to irrigation or heavy rainfall, and should be anticipated. Minimizing irrigation will lessen this potential. If areas of seepage develop, recommendations for minimizing this effect could be provided upon request. Erosion Control Onsite earth materials have a moderate to high erosion potential. Consideration should be given to providing hay bales and silt fences for the temporary control of surface water, from a geotechnical viewpoint. Landscape Maintenance Only the amount of irrigation necessary to sustain plant life should be provided. Over-watering the landscape areas will adversely affect proposed site improvements. We would recommend that any proposed open-bottom planters adjacent to the structure be eliminated for a minimum distance of 1 O feet. As an alternative, closed-bottom type planters could be utilized. An outlet placed in the bottom of the planter, could be installed to direct drainage away from structures or any exterior concrete flatwork. If planters are constructed adjacent to the structure, the sides and bottom of the planter should be provided with a moisture barrier to prevent penetration of irrigation water into the subgrade. Provisions should be made to drain the excess irrigation water from the planters without saturating the subgrade below or adjacent to the planters. Consideration should be given to the type of vegetation chosen and their potential effect upon surface improvements (i.e., some trees will have an effect on concrete flatwork with their extensive root systems). From a geotechnical standpoint, leaching is not recommended for Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp1217100\7103a.rpge GeoSoils, Inc:. W.0. 7103-A-SC April 1, 2019 Page 66 J ., "" J J , "' ,. .. ,.. IJlllt ... 111111 ,. i 111111 ,. 1111 ,,. ,. .. ,,. .. .. .. ,. 1111111 .. ,,. ... .. Ill establishing landscaping. If the surface soils are processed for the purpose of adding amendments, they should be recompacted to 90 percent minimum relative compaction. Gutters and Downspouts As previously discussed in the drainage section, the installation of gutters and downspouts should be considered to collect roof water that may otherwise infiltrate the soils adjacent to the structures. If utilized, the downspouts should be drained into PVC collector pipes or other non-erosive devices (e.g., paved swales or ditches; below grade, solid tight-lined PVC pipes; etc.), that will carry the water away from the building, to an appropriate outlet, in accordance with the recommendations of the design civil engineer. Downspouts and gutters are not a requirement; however, from a geotechnical viewpoint, they may be used, provided that positive drainage is incorporated into project design (as discussed previously). Subsurface and Surface Water Subsurface and surface water are not anticipated to affect site development, provided that the recommendations contained in this report are incorporated into final design and construction and that prudent surface and subsurface drainage practices are incorporated into the construction plans. Perched groundwater conditions along zones of contrasting permeabilities may not be precluded from occurring in the future due to site irrigation, poor drainage conditions, or damaged utilities, and should be anticipated. Should perched groundwater conditions develop, this office could assess the affected area(s) and provide the appropriate recommendations to mitigate the observed groundwater conditions . Groundwater conditions may change with the introduction of irrigation, rainfall, or other factors . Site Improvements If in the future, any additional improvements (e.g., pools, spas, etc.) are planned for the site, recommendations concerning the geological or geotechnical aspects of design and construction of said improvements could be provided upon request. Pools and/or spas should be constructed in accordance with the preliminary guidelines in Appendix G. These recommendations should be provided to all interested/affected parties. This office should be notified in advance of any fill placement, grading of the site, or trench backfilling after rough grading has been completed. This includes any grading, utility trench and retaining wall backfills, flatwork, etc. Tile Flooring Tile flooring can crack, reflecting cracks in the concrete slab below the tile, although small cracks in a conventional slab may not be significant. Therefore, the designer should consider additional steel reinforcement for concrete slabs-on-grade where tile will be placed. The tile installer should consider installation methods that reduce possible Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc . W.O. 7103-A-SC April 1, 2019 Page 67 cracking of the tile such as slipsheets. Slipsheets or a vinyl crack isolation membrane (approved by the Tile Council of America/Ceramic Tile Institute) are recommended between tile and concrete slabs on grade. Additional Grading This office should be notified in advance of any fill placement, supplemental regrading of the site, or trench backfilling after rough grading has been completed. This includes completion of grading in the street, driveway approaches, driveways, parking areas, and utility trench and retaining wall backfills. Footing Trench Excavation All footing excavations should be observed by a representative of this firm subsequent to trenching and prior to concrete form and reinforcement placement. The purpose of the observation is to evaluate whether the excavations have been made into the recommended bearing material and to the minimum widths and depths recommended for construction. If loose or compressible materials are exposed within the footing excavation, a deeper footing or removal and recompaction of the subgrade materials would be recommended at that time. Footing trench spoil and any excess soils generated from utility trench excavations should be compacted to a minimum relative compaction of 90 percent, if not removed from the site. Trenching/Temporary Construction Backcuts Considering the nature of the onsite earth materials, it should be anticipated that caving or sloughing could be a factor in subsurface excavations and trenching. Shoring or excavating the trench walls/backcuts at the angle of repose (typically 25 to 45 degrees [except as specifically superceded within the text of this report]), should be anticipated. All excavations should be observed by an engineering geologist or soil engineer from GSI, prior to workers entering the excavation or trench, and all excavations must minimally conform to CAL-OSHA, state, and local safety codes. Should adverse conditions exist, appropriate recommendations would be offered atthattime. The above recommendations should be provided to any contractors and/or subcontractors, or property owner(s), etc., that may perform such work. Utility Trench Backfill 1. All interior utility trench backfill should be brought to at least 2 percent above optimum moisture content and then compacted to obtain a minimum relative compaction of 90 percent of the laboratory standard. As an alternative for shallow (12-inch to 18-inch) under-slab trenches, sand having a sand equivalent value of 30 or greater may be utilized and jetted or flooded into place. Observation, probing and testing should be provided to evaluate the desired results. Summerhill Homes W.O. 7103-A-SC April 1, 2019 Page 68 Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. ., "' ..., "' J .. .,J ., .. ., "" ... ~ J ., ,,,, , "' J ,,. .. ,,. ... ,,,. 111111 ,,. .... ... ,.. !11111 ,.. ,.. ,. .. ,,,. ... ,,. .. ,,,. ... ,,. .. ,,,. .. .. .. ,,,. .. 2. 3. 4. Exterior trenches adjacent to, and within areas extending below a 1 :1 plane projected from the outside bottom edge of the footing, and all trenches beneath hardscape features and in slopes, should be compacted to at least 90 percent of the laboratory standard. Sand backfill, unless excavated from the trench, should not be used in these backfill areas. Compaction testing and observations, along with probing, should be accomplished to evaluate the desired results. All trench excavations should conform to CAL-OSHA, state, and local safety codes. Utilities crossing grade beams, perimeter beams, or footings should either pass below the footing or grade beam utilizing a hardened collar or foam spacer, or pass through the footing or grade beam in accordance with the recommendations of the structural engineer. SUMMARY OF RECOMMENDATIONS REGARDING GEOTECHNICAL OBSERVATION AND TESTING We recommend that observation and/or testing be performed by GSI at each of the following construction stages: • • • • • • • • • During grading . During excavation . During placement of subdrains or other subdrainage devices, prior to placing fill and/or backfill. After excavation of building footings, retaining wall footings, and free standing walls footings, prior to the placement of reinforcing steel or concrete. Prior to pouring any slabs or flatwork, after presoaking/presaturation of building pads and other flatwork subgrade, before the placement of concrete, reinforcing steel, capillary break (i.e., sand, pea-gravel, etc.), or vapor retarders (i.e., visqueen, etc.). During retaining wall subdrain installation, prior to backfill placement. During placement of backfill for area drain, interior plumbing, utility line trenches, and retaining wall backfill. During any slope construction/repair. When any unusual soil conditions are encountered during any construction operations, subsequent to the issuance of this report. Summerhill Homes W.O. 7103-A-SC April 1, 2019 Page 69 Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc . • • When any improvements, such as flatwork, spas, pools, walls, etc., are constructed, prior to construction. A report of geotechnical observation and testing shall be provided by GSI at the conclusion of each of the above stages, in order to provide concise and clear documentation of site work, and/or to comply with code requirements. OTHER DESIGN PROFESSIONALS/CONSULTANTS The design civil engineer, structural engineer, post-tension designer, architect, landscape architect, wall designer, etc., should review the recommendations provided herein, incorporate those recommendations into all their respective plans, and by explicit reference, make this report part of their project plans. This report presents minimum design criteria for the design of slabs, foundations and other elements possibly applicable to the project. These criteria should not be considered as substitutes for actual designs by the structural engineer/designer. Please note that the recommendations contained herein are not intended to preclude the transmission of water or vapor through the slab or foundation. The structural engineer/foundation and/or slab designer should provide recommendations to not allow water or vapor to enter into the structure so as to cause damage to another building component, or so as to limit the installation of the type of flooring materials typically used for the particular application. The structural engineer/designer should analyze actual soil-structure interaction and consider, as needed, bearing, expansive soil influence, and strength, stiffness and deflections in the various slab, foundation, and other elements in order to develop appropriate, design-specific details. As conditions dictate, it is possible that other influences will also have to be considered. The structural engineer/designer should consider all applicable codes and authoritative sources where needed. If analyses by the structural engineer/designer result in less critical details than are provided herein as minimums, the minimums presented herein should be adopted. It is considered likely that more restrictive details will be required in some cases. If the structural engineer/designer has any questions or requires further assistance, they should not hesitate to call or otherwise transmit their requests to GSI. In order to mitigate potential distress, the foundation and/or improvement's designer should confirm to GSI and the governing agency, in writing, that the proposed foundations and/or improvements can tolerate the amount of differential settlement and/or expansion characteristics and other design criteria specified herein. PLAN REVIEW Final project plans (grading, precise grading, foundation, retaining wall, landscaping, etc.), should be reviewed by this office prior to construction, so that construction is in Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc. W.O. 7103-A-SC April 1, 2019 Page 70 ... "" ... .. , .. ., ... ,.. ... ,.. ... ... ,,,. ... ,,,. .. ,.. Ill ,,. ,,. ... ,,,. ... .. ... ,,,. ... ,,. ,.. .. .. ... ,.. .. accordance with the conclusions and recommendations of this report. Based on our review, supplemental recommendations and/or further geotechnical studies may be warranted . LIMITATIONS The materials encountered on the project site and utilized for our analysis are believed representative of the area; however, soil and bedrock materials vary in character between excavations and natural outcrops or conditions exposed during mass grading. Site conditions may vary due to seasonal changes or other factors. Inasmuch as our study is based upon our review and engineering analyses and laboratory data, the conclusions and recommendations are professional opinions. These opinions have been derived in accordance with current standards of practice, and no warranty, either express or implied, is given. Standards of practice are subject to change with time. GSI assumes no responsibility or liability for work or testing performed by others, or their inaction; or work performed when GSI is not requested to be onsite, to evaluate if our recommendations have been properly implemented. Use of this report constitutes an agreement and consent by the user to all the limitations outlined above, notwithstanding any other agreements that may be in place. In addition, this report may be subject to review by the controlling authorities. Thus, this report brings to completion our scope of services for this portion of the project. All samples will be disposed of after 30 days, unless specifically requested by the client, in writing. Summerhill Homes Laurel Tree Lane, Carlsbad File:e:\wp12\7100\7103a.rpge GeoSoils, Inc . W.O. 7103-A-SC April 1, 2019 Page 71 APPENDIX A REFERENCES GeoSoils, Inc. .., "' ... ... J ... .,J , .. ,,. .. ,,,. .. ,,,. .. ,,,. .. ,.. .. ,. ,,. .. ,.. .. ,. .. ,,. .. ,,. .. .. .. ... ,,. .. -.. ,,,. .. APPENDIX A REFERENCES American Concrete Institute, 2014, Building code requirements for structural concrete (ACI 318-14), and commentary (ACI 318R-14): reported by ACI Committee 318, dated September. American Concrete Institute (ACI) Committee 302, 2004, Guide for concrete floor and slab construction, ACI 302.1 R-04, dated June. Allen, V., Connerton, A., and Carlson, C., 2011, Introduction to Infiltration Best Management Practices (BMP), Contech Construction Products, Inc., Professional Development Series, dated December . American Society for Testing and Materials (ASTM), 2003, Standard test method for infiltration rate of soils in field using double-ring infiltrometer, Designation D 3385-03, dated August. __ , 1998, Standard practice for installation of water vapor retarder used in contact with earth or granular fill under concrete slabs, Designation: E 1643-98 (Reapproved 2005). __ , 1997, Standard specification for plastic water vapor retarders used in contact with soil or granular fill under concrete slabs, Designation: E 1745-97 (Reapproved 2004) . American Society of Civil Engineers, 2010, Minimum design loads for buildings and other structures, ASCE Standard ASCE/SEI 7-10. Blake, Thomas F., 2000a, EQFAULT, A computer program for the estimation of peak horizontal acceleration from 3-D fault sources; Windows 95/98 version. __ , 2000b, EQSEARCH, A computer program for the estimation of peak horizontal acceleration from California historical earthquake catalogs; Updated to January 2015, Windows 95/98 version . Bozorgnia, Y., Campbell K.W., and Niazi, M., 1999, Vertical ground motion: Characteristics, relationship with horizontal component, and building-code implications; Proceedings of the SMIP99 seminar on utilization of strong-motion data, September 15, Oakland, pp. 23-49 . Bryant, W.A., and Hart, E.W., 2007, Fault-rupture hazard zones in California, Alquist-Priolo earthquake fault zoning act with index to earthquake fault zones maps; California Geological Survey, Special Publication 42, interim revision . GeoSoils, Inc. California Building Standards Commission, 2016a, California Building Code, California Code of Regulations, Title 24, Part 2, Volume 2 of 2, based on the 2015 International Building Code, 2016 California Historical Building code, Title 24, Part 8, 2016 California Existing Building Code, Title 24, Part 10, and the 2015 International Existing Building Code. __ , 2016b, California Building Code, California Code of Regulations, Title 24, Part 2, Volume 1 of 2, Based on the 2015 International Building Code. __ , 2016c, California green building standard code of regulations, Title 24, Part 11, ISBN 978-1-60983-462-3. California Department of Conservation, California Geological Survey (CGS), 2018, Earthquake fault zones, a guide for government agencies, property owners/developers, and geoscience practitioners for assessing fault rupture hazards in California: California Geological Survey Special Publication 42 (revised 2018), 93 p. __ , 2008, Guidelines for evaluating and mitigating seismic hazards in California: California Geological Survey Special Publication 117A (revised 2008), 102 p. California Geological Survey, 2018, Earthquake Fault Zones, a guide for government agencies, property owners/developers, and geoscience practitioners for assessing fault rupture hazards in California, Special Publication 42, revised. Cao, T., Bryant, W.A., Rowshandel, B., Branum, D., and Wills, C.J., 2003, The revised 2002 California probabilistic seismic hazard maps, dated June, http://www.conservation.ca.gov/cgs/rghm/psha/fault_parameters/pdf/Documents /2002 _CA_ Hazard_ Maps. pdf. City of Carlsbad, 2017, Engineering standards, vol. 3, standard drawings and specifications, 2016 edition, dated April 12. __ , 2016b, Engineering standards, vol. 1, general design standards, 2016 edition, dated February 16. __ , 1992, Geotechnical Hazards analysis and mapping Study, November. Jennings, C.W., and Bryant, W.A., 2010, Fault activity map of California, scale 1 :750,000, California Geological Survey, Geologic Data Map No. 6. Kanare, H.M., 2005, Concrete floors and moisture, Engineering Bulletin 119, Portland Cement Association. Summerhill Homes File:e:\wp12\7000\7103a.rpge GeoSoils, Inc. Appendix A Page 2 ... "" ... .. ... .. 11111 ! ... ... "" ., .. ., "" ., .. ., .. ,.. ... ,.. ... ... ,.. .. 11111111 .. ,.. ,-... ,,,. .. ,,. .. .. .. ,.. .. Kennedy, MP., and Tan, SS., 2007, Geologic map of the Oceanside 30' by 60' quadrangle, California, regional geologic map series, scale 1: 100,000, California Geologic Survey Map No. 2. __ , 2005, Geologic map of the Oceanside 30' by 60' quadrangle, California, regional map series, scale 1: 100,000, California Geologic Survey and United States Geological Survey, www.conservation.ca.gov/cgs/rghm/ rgm/preliminary_geologic_maps.htm KTGY Architecture + Planning, 2016, Aviara Apartments, Capacity study-Options 1, 2 & 3, three sheets, job # 20160328, dated May 12, May 4, and May 4, respectively. Leighton and Associates, Inc., 1992, City of Carlsbad geotechnical hazards analysis and mapping study, 115 sheets, various scales, dated November. Norris, R.M. and Webb, R.W., 1990, Geology of California, second edition, John Wiley & Sons, Inc. REC Consultants, Inc., 2016, Site exhibit, 6145 Laurel Tree Toad, Carslbad, CA., plot date June 22. Robert Prater Associates, 2000, Earthwork observation, testing, and as-built geology services, Kelly Ranch corporate center-building pads 2A, 2B, and 3, Carlsbad, California, project no. 543-!B, 00-110, dated April 12. __ , 1997, Geotechnical investigation, Kelly Ranch corporate center, Carlsbad, California, project no. 543-1A. 97-145, dated April 30 . Robert Prater Associates, 1997, Geotechnical investigation for Kelly Ranch Corporate Center, job no. 543-1A, 97-145, dated April 30 Romanoff, M., 1957, Underground corrosion, originally issued April 1. Seed, 2005, Evaluation and mitigation of soil liquefaction hazard "evaluation of field data and procedures for evaluating the risk of triggering (or inception) of liquefaction," in Geotechnical earthquake engineering; short course, San Diego, California, April 8-9. Sowers and Sowers, 1979, Unified soil classification system (After U. S. Waterways Experiment Station and ASTM 02487-667) in Introductory Soil Mechanics, New York. State of California, 2019, Civil Code, Sections 895 et seq. Summerhill Homes File:e:\wp12\7000\7103a.rpge GeoSoils, Inc . Appendix A Page 3 State of California Department of Transportation, Division of Engineering Services, Materials Engineering, and Testing Services, Corrosion Technology Branch, 2003, Corrosion Guidelines, Version 1.0, dated September. Tan, S.S. and Giffen, D.G., 1995, Landslide hazards in the northern part of the San Diego metropolitan area, San Diego County, California, DMG open file report 95-04, landslide hazard identification map no. 35, relative landslide susceptibility and landslide distribution map, plate G, 1 :24,000 scale. U.S. Geological Survey, 2013, U.S. Seismic Design Maps, Earthquake Hazards Program, http://geohazards.usgs.gov/designmaps/us/application.php, version 3.1.0. Summerhill Homes File:e:\wp 12\7000\7103a.rpge GeoSoils, Inc. Appendix A Page 4 ... .. .. ' wl J ., .. ... i .. ., .. ,,. ... ,,.. .. ,,,.. ,.. .. ,,,.. .. ,. .. ,. ... ,. ... ,. 111111 ,,. -,,. .. ,,. ... ,,. ... ,,. ... ,,. .. APPENDIX B BORING LOGS AND CPT SOUNDINGS GeoSoils, Inc. UNIFIED SOIL CLASSIFICATION SYSTEM CONSISTENCY OR RELATIVE DENSITY Major Divisions Group Typical Names CRITERIA Symbols GW Well-graded gravels and gravel- sand mixtures, little or no fines Standard Penetration Test Q) C: .!!! > al Q) Q) Q) > oa! -al Poorly graded gravels and Penetration (.) ~ Q) CD > ~ ·u o GP gravel-sand mixtures, little or no Resistance N Relative Q) 1/) ·u; ai ~ Jg z fines (blows/ft) Density 0 > 0 al ~ Q) C: ~ 0 1/) 0 C\J CJ '# ~ -0 Silty gravels gravel-sand-silt 0-4 Very loose 1/) • al Q) ~£ GM ,: 0 0 8 -~ mixtures oz Lt) Cf) C: i al ·- -0 0 0 ~ 4-10 Loose -~ al GC Clayey gravels, gravel-sand-clay ~ -~ mixtures 10-30 Medium CD .S ' Q) Q) ~ Well-graded sands and gravelly 30-50 Dense ~ '# SW 00 Q) C: (/) sands, little or no fines (.) Lt) 15 C: a'i al -0 Very dense Q) C: > 50 C: -;RO·-[5 c)1l al b.:: en Poorly graded sands and = 1/) Lt) l;l ~ SP ~ -0 C-=: 0 gravelly sands, little or no fines 0 Iii~ Q) z ::!?: Cl) ..... ~ en SM Silty sands, sand-silt mixtures Q) al Q) ~ 0 1/) ~£~ 0 <..l 1/) E ~ C ·-C::: Clayey sands, sand-clay ci1l 3: u:: SC mixtures Inorganic silts, very fine sands, Standard Penetration Test ML rock flour, silty or clayey fine sands 1/) Q) ~::: ~ Unconfined > [5_!;; .!!! Inorganic clays of low to Penetration Compressive Q) -g ~ 0 medium plasticity, gravelly clays, ·u; CL Resistance N Strength 0 m 5-cf sandy clays, silty clays, lean (blows/ft) Consistency (tons/fl") 0 1/) C\J ~::Jg clays '5 . Cf) Cf) :£ Organic silts and organic silty <2 Very Soft <0.25 -0 1/) OL Q) Q) clays of low plasticity C: 1/) -~ 1/) 2-4 Soft 0.25-.050 al CD C. d, ~ Inorganic silts, micaceous or 4-8 Medium 0.50-1.00 C: 0 MH diatomaceous fine sands or silts, u:: E 1/) if. >, 0 elastic silts 0 CO:-~ LO 8 -15 Stiff 1.00-2.00 if. [5~ al Inorganic clays of high plasticity, 0 -g :g £ CH Lt) "' ::, ~ fat clays 15-30 Very Stiff 2.00-4.00 ~g~ ·-Q) Cf) ~ >30 Hard >4.00 OJ Organic clays of medium to high OH plasticity Highly Organic Soils PT Peat, mucic, and other highly organic soils 3" 3/4" #4 #10 #40 #200 U.S. Standard Sieve Unified Soil Gravel Sand Silt or Clay Classification Cobbles I I I coarse fine coarse medium fine MOISTURE CONDITIONS MATERIAL QUANTITY OTHER SYMBOLS Dry Absence of moisture: dusty, dry to the touch trace 0-5% C Core Sample Slightly Moist Below optimum moisture content for compaction few 5-10% s SPT Sample Moist Near optimum moisture content little 10-25 % B Bulk Sample Very Moist Above optimum moisture content some 25-45% . . Groundwater - Wet Visible free water; below water table Qp Pocket Penetrometer BASIC LOG FORMAT: Group name, Group symbol, (grain size), color, moisture, consistency or relative density. Additional comments: odor, presence of roots, mica, gypsum, coarse grained particles, etc. EXAMPLE: Sand (SP), fine to medium grained, brown, moist, loose, trace silt, little fine gravel, few cobbles up to 4" in size, some hair roots and rootlets. File:Mgr: c;\SoilClassif.wpd PLATE B-1 J ., "' ., .. ., .. ~ .c ii Q) 0 2 3 4 5 6 7 8 9 10 11 BORING LOG GeoSoi Is, Inc. WO. 7103-A-SC PROJECT: SUMMERHILL HOMES BORING B-1 Laurel Tree Lane At College Boulevard, Carslbad SHEET_1_ OF 2 6-15-16 Sample ] :, in .x: i5 :5 C CD :J 26 31 9 0 .0 E >, (f) (f) u (f) :J ML CL 6.8 103.2 8.0 17.8 C 0 ~ :, '" (f) DATE EXCAVATED SAMPLE METHOD: _H_oll_ow_S_te_m_A_u~ge_r ______________ --1 ,......, ,......, ,......, ,......, ,......, ,......, ,......, ,......, Standard Penetration Test Undisturbed, Ring Sample Approx. Elevation: 104' MSL 'SJ_ Groundwater ~ Seepage Description of Material UNDOCUMENTED FILL: @ O' SANDY SILT, reddish yellow to light brown, dry, medium dense; broken rock/concrete encountered, oxidation staining, fine grained. @ 3' SANDY CLAY, yellowish brown, damp, medium stiff; fine grained. @ 9' As per 3', moist, stiff; traces of gravel and asphalt fragments. 12 13-+---!-+----+---+----+---+---l½½+----------------------------, CL ALLUVIUM: 14 29 114.7 13.1 78.5 :a1~~cr.~~t ge~biei:~kc~~~~:r~gmwn, very moist, stiff; fine 15 16 17-+--+---+---+-=c,,...L-+----+---+---t.Hfft---=s-,-AN,...,.T=1cc-A-=G-=o-=F=--=oc-=R=M-=--Ac-=T=-1o=N,...,..:--------------; 18 @ 17' CLA YSTONE, light yellow brown to yellowish gray, very 19 20 21 22 11 32.1 moist to wet, stiff. @ 21 ½' Groundwater encountered. 23-+---+-+----+---+-----+---+--+<-'-,...,_ _________________________ __, SM @ 23' SILTY SANDSTONE with trace CLAY, yellowish brown, 24 22 wet to saturated, loose to medium dense; fine grained. 98.3 24.1 93.6 25 26 27 28 29 20 18.7 @ 29' As per 17', light gray, wet, medium stiff. Laurel Tree Lane At College Boulevard, Carslbad GeoSoi Is, Inc. PLATE 8-2 BORING LOG GeoSoils, Inc. W.O. 7103-A-SC PROJECT SUMMERHILL HOMES BORING B-1 Laurel Tree Lane At College Boulevard, Carslbad SHEET_2_ OF -2_ 6-15-16 ~ E. .s:: 15. Q) 0 31 - 32- 33- 34- 35- 36- 37- 38- 39- 40- 41 - 42- 43- 44- 45- 46- 47- 48- 49- -"" :'i co Sample 'u' 0 5 ,::, .0 ~ Q) E .0 u:: >, :5 (f) ·c U) cii (f) 'o ,:: u :;:) C: 0 (f) c:-:;:) ai :;:) 0 SM ~ 30 94.2 42 46 97.5 l l C: ~ 0 ~ ::, U) :5 ·5 '" :a (f) 29.7 100 28.8 29.4 100 DATE EXCAVATED SAMPLE METHOD: Hollow Stem Auger ffl Standard Penetration Test ~ Undisturbed, Ring Sample Approx. Elevation: 104' MSL 'SJ-Groundwater ~ Seepage Description of Material @ 35' SIL TY SANDSTONE, yellowish brown, saturated, medium dense; mottled, signs of oxidation. @ 40' As per 35'. @ 45' As per 35', trace CLAY. ■ n ~-9 ~ m -@49' SILTY SANDSTONE with trace CLAY, light gray brown, 50+---l""-'-"+----1--+------1---+---+-'""-"-!-,.'-cs=a""'t,.,,u""ra~t'°'e""d'.L.i-'m'-"e""d'=i'=u.;.-'m-'--"'d-"'e-'-'n""s""e,_· ,_,_in""te""re!Cb'-"e'-"d,..,,s:....:o""f'-'o""x"'i""d"'iz,.,,e""d'--'c"-'l"'a.L:-v. ____ __,r Total Depth = 50' 51- 52- 53- 54- 55- 56- 57- 58- 59- Laurel Tree Lane At College Boulevard, Carslbad No Caving Encountered Groundwater Encountered@ 21 ½' Backfilled 6-15-2016 Per DEH Requirements GeoSoi Is, Inc. PLA TE 8-3 BORING LOG GeoSoi Is, Inc. WO. 7103-A-SC PROJECT: SUMMERHILL HOMES BORING B-2 SHEET 1 OF 2 Laurel Tree Lane At College Boulevard, Carslbad ~ .c C. Q) 0 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 -" :i CD Sample "O Q) .0 '5 <ii '6 C :::) Li'. cii ;:: 0 iii 35 271 50-5" 50-6" 401 50-4" 50-3" 0 .0 E >, (/) (/) () (/) :::) CL SM 't _e, ~ ~ l C I!! 0 ·c ::, ~ :::) <ii '5 c:-·o ro 0 ::!': (/) 116.0 12.5 77.8 15.5 102.7 16.1 69.6 13.1 115.0 13.2 80.0 Laurel Tree Lane At College Boulevard, Carslbad DATE EXCAVATED 6-15-16 SAMPLE METHOD· _H_oll_ow_S_te_m_A_u_ge_r ______________ __, m WJ Standard Penetration Test Undisturbed, Ring Sample Approx. Elevation: 82' MSL 'Sl Groundwater ~ Seepage Description of Material UNDOCUMENTED FILL: @ O' SANDY CLAY with SILT inclusions, light yellow brown to light gray, moist, medium stiff. WEATHERED SANTIAGO FORMATION: @ 3' SIL TY SANDSTONE, dark reddish brown, moist, very dense; fine grained. SANTIAGO FORMATION: @ 9½' SIL TY SANDSTONE, light gray, damp to moist, dense; thinly bedded. @ 14' SIL TY SANDSTONE, light gray to dark red, damp, very dense; fine grained. @ 19' SIL TY SANDSTONE, light gray, moist, dense; fine grained, thinly bedded. @ 23½' As per 19', dark red hues, wet, very dense. @ 29' As per 23½', dusky red. GeoSoi Is, Inc. PLATE B-4 BORING LOG GeoSoi Is, I nc. WO 7103-A-SC PROJECT SUMMERHILL HOMES BORING B-2 Laurel Tree Lane At College Boulevard, Carslbad SHEET_2_ OF __3_ 6-15-16 ~ !E. .r. a. Q) 0 31- 32 - 33 - 34 - 35 - 36 37 - 38 -"' :5 00 Sample -0 Q) .0 u:: :5 iii ui 'o ~ C 0 ::> in 150-5½" 'n 0 5 .0 ~ E >, (J) ·c (J) <.) ::> (J) ~ ::> 0 SM l ~ 0 C I!! ::, 0 ~ iii ·o ~ :5 iii (J) 15.5 DATE EXCAVATED SAMPLE METHOD: Hollow Stem Auger ~ ~ ,_r, ,_r, ,_r, ,_r, ,_r, ,_r, ,_r, ,_r, ,_r, ,_r, ,_r, ,_r, ,_r, ,_r, ,_r, ,_r, ,_r, ,_r, ,_r, ,_r, Standard Penetration Test Undisturbed, Ring Sample Approx. Elevation: 82' MSL 'Sl-Groundwater ~ Seepage Description of Material @ 33½' As per 29', brownish yellow; weathered. @ 37' Water added for ease of boring material. ,_r, 98.5 ,_r, ,_r, 39-~ 50-2½" 99.6 24 .6 @ 39' As per 33½', wet due to water addition. 40 -l------,f<'-U4------l----l~-----l----l---i--=--'--+-------------------------------I Practical Refusal @ 40' 41 -No Groundwater/Caving Encountered 42 43 - 44 - 45- 46 - 47- 48- 49- 50- 51 - 52- 53- 54- 55- 56- 57- 58- 59- Laurel Tree Lane At College Boulevard, Carslbad Backfilled 6-15-2016 Per DEH Requirements GeoSoi Is, Inc. PLATE B-5 I f-a. w~ 0$ Net Area Ratio .8 0 Geosoils Project Summerhill Homes Operator Job Number 7103-A-SC Cone Number Hole Number CPT--01 Date and Time EST GW Depth During Test 17.20 ft TIP TSF 500 Io FRICTION TSF CPT DATA 1010 DG-RC DDG1366 6/17/2016 7:50:19 AM Fs/Qt 51 I~ I I I I I I 10 BI O Filename GPS Maximum Depth SPTN SDF(568).c1 50.52 ft 15 I{ I I I I I I I I I I fr I I I I I I I I I I I I b4 _,I < I I ?1 I I I I I I I I 20 25 0:: 0 > ....J <{ w -I a. O w ~ (/) Cl) "I ffl 1 1 1 1 1 1 1 ftt 1 1 1 1 1 1 1 111=1 %1 1 1 1 1 t 1 1 1 1 1 1 1 1 1111 m ■ 1 -sensitive fine grained ■ 4 -silty clay to clay ■ 2 -organic material ■ 5 -clayey silt to silty clay ■ 3 -clay ■ 6 -sandy silt to clayey silt Cone Size 10cm squared ■ 7 -silty sand to sandy silt 8 -sand to silty sand ■ 9 -sand S"Soil behavior type and SPT based on data from UBC-1983 ■ 10 -gravelly sand to sand ■ 11 -very stiff fine grained (*) ■ 12 -sand to clayey sand (*) 1-t CPT-01 Geosoils DepM.92ft ~ I Ref* ----=fl:_ Depth 10.01ft , t _ , J_ -L-1_' ~-Ref 4.92ft . l__ Depth 14.93ft __ j J±. ~ Ref 10.01ft Depth 20.01 ft I t __ +I: -•-Ref 14.93ft -7-- Depth 24.93ft -_1_ --t -f + Ref 20.01ft l Depth 30.02ft I -~ -± l+ Ref 24.93ft _l__ Depth 35.1 Oft --= i -_ ---1=_ -±= ± Ref 30.02ft Depth 40.03ft _± I 1-Ref 35.10ft Depth 44.95ft +----♦ Ref 40.03ft Depth 50.20ft I ____ Ref 44.95ft 0 10 20 1--• ...... ~.,~",,11,,,;;;;;u I .L ·, l"' ,r I ~ IL:.! '--I , f ..., ' I GPS DATA:,, L__ Summerhill Homes -+-- Arrival 9.61mS Velocity* ~ -----1 Arrival15.16mS -r--t---=-- Velocity 712.30ft/S Arrival 21.40mS Velocity 711. 15ft/S I- I + Arrival 28.90mS Velocity 642.55ft/S ' t Arrival 34.69mS ---+-------Velocity 823.70ft/S --:---Velocity 816.22ft/S ----1-_ ~ I Arrival 40.78mS 80 -+ Arrival 46.40mS ---Velocity 889.86ft/S 90 --Arrival 51 .87mS -Velocity 889.24ft/S Arrival 57.50mS Velocity 866.79ft/S 1 Arrival 63.28mS Velocity 901.28ft/S 100 Net Area Ratio .8 I I-a.. w ~ oE. _l..Q. 0 5 10 15 20 25 30 35 40 45 50 ■ 1 -sensitive fine grained ■ 2 -organic material ■ 3 -clay Geosoils Project Summerhill Homes Operator DG-RC Job Number 7103-A-SC Cone Number DDG1366 Hole Number CPT-03 Date and Time 6/17/2016 8:48:57 AM EST GW Depth During Test 17.00 ft CPT DATA TIP TSF FRICTION 500 Io TSF ■ 4 -silty clay to clay ■ 5 -clayey silt to silty clay ■ 6 -sandy silt to clayey silt 1010 Fs/Qt % ■ 7 -silty sand to sandy silt 8 -sand to silty sand ■ 9 -sand BI O Filename GPS Maximum Depth SDF(569).c 50.52 ft I a::: 0 > _J <( w -I a.. SPT N 200 I. 55 ~ ~ ■ 10 -gravelly sand to sand ■ 11 -very stiff fine grained(*) ■ 12 -sand to clayey sand (*) Cone Size 10cm squared S"Soil behavior type and SPT based on data from UBC-1983 1_!_ CPT-03 ___ Geosoils _____ ____ Summerhill Hornes Depth4.92ft +_±_ l--i !-] ---t -~Arrival6.72rnS Ref* -/ ' -_. · ----~---• ~ -Velocity• -------------~----1 ---~ ---~ Depth 10.01ft • , _ l _ _ Arrival 14.76rnS Ref 4.92ft t---~----_ -_ +-+ "'-~ __ i -j----1 ---f----=-. i --t---~-.~ Velocity 491.00ft/S Depth 14.93ft ~-----+" 1 _ . _ _ 1 _ I j -t _ Arrival 20.00rnS Ref 10.01ft __ _L_ -_ _ · -___ L___ ---l__ ---, ---'----· ~ Velocity 849.13ft/S ~=f~~2 9°3~ 1 ft 1------1-1 ---± + ~ '. ~ -· _-_ --:-I -~ -1--t-I ~~ e;,~~i~~:J~25ws Depth 24.93ft ,_____ 1 _ _,L____ ~ l t t-+-j ~ Arrival 30.78rnS Ref 20 01ft _ j --_._ ----~ ----· -------Velocity 896.38ft/S Depth 30.02ft 1 -=± ·---= + I _ -_ _ I __ _J._, _ _J___ Arriva.I 36.33rnS Ref24.93ft __L_ ---'------~ ~ ---~ ---~--_ ~r-____ ~----l ____ Velocity 896.?0ft/S Depth 34.94ft 1-----_ _._ __ ± _ j + ~ , + J Arrival 42.65rnS Ref 30.02ft ,_____ __,L__ _______ .,._ ----__L-~ --t -~.----------Velocity 765.42ft/S Depth 40.03ft + + ,• f -j , ~ A"i,a'47.97mS Ref 34.94ft i-----~----I · ~---_ ~::;---.-·---~------' -----t -~-· Velocity 945.86ft/S Depth 44.95ft t-----~,-..---~ _,..--+. i ._· ~~_: [-.-j _ _ Arrival 53.75rnS Ref 40.03ft / --?"' -. . -· -Velocity 843.36ft/S Depth50.03ft l-------· ---~-VF ~~~ --~ _ ----4 _0=Arrival59.21rnS Ref 44.95ft n r-v'""--.. · -Velocity 922.99ft/S 0 10 20 90 100 i\ ~ l , r~ ~~u;, 1 1 11J f "yul , GPS DATA:., ~ N :::, w 0:: :::, <I) <I) w 0:: a. 0 Location Summerhill Homes Job Number 7103-A.SC Hole Number CPT-03 Equilized Pressure 2.9 t Geosoils Operator DG-RC Cone Number DDG1366 Date and Time 6/17/2016 8:48:57 AM EST GW Depth Du!!!!9. Test 17.2 Time (Sec) Page 1 of 1 GPS " "&; 1400.00 ----------- re Geosoils Project Summerhill Homes Operator DG-RC Filename SDF(571).cet Job Number 7103-A-SC Cone Number DDG1366 GPS Hole Number CPT-04A Date and Time 6/17/2016 10:25:25 AM Maximum Depth 6.73 ft EST GW Depth During Test 17.00 ft Net Area Ratio .8 a:: CPT DATA 0 I > t--...J <( w Q_ -I Q. w ~ TIP FRICTION Fs/Qt SPT N 0 w ~ 0~ 0 TSF 500 0 TSF 10 0 % 8 0 '"Iii 0 1--5 ~ -~ t..--c---,i---f--_L---i.---~ _I ~ t:::== ,~ I---"--5 I------..J -~ >-- 10 15 20 25 30 35 40 45 50 ■ 1 -sensitive fine grained ■4-silty clay to clay ■ 7 -silty sand to sandy silt ■ 10 -gravelly sand to sand • 2-organic material ■ 5 -clayey silt to silty clay • 8 -sand to silty sand ■ 11 -very stiff fine grained (*) • 3 -clay ■ 6 -sandy silt to clayey silt • 9 -sand ■ 12 -sand to clayey sand (*) Cone Size 10cm squared S-Soil behavior type and SPT based on data from UBC-1983 c..a c~ &:.I ~ &.;I ~ L...a c... ~ C:I L~ ~ , ... ........ .._~ I[ • ..___. • • ........ Net Area Ratio .8 I I-a.. LU~ 0 !S _j_Q_ 0 5 10 15 20 Geosoils Project Summerhill Homes Operator Job Number 7103-A-SC Cone Number Hole Number CPT-06 Date and Time EST GW Depth During Test 17.00 ft TIP TSF 500 Io FRICTION TSF CPT DATA 1010 DG-RC DDG1366 6/17/2016 11:06:35 AM Fs/Qt % BIO Filename GPS Maximum Depth SPTN SDF(572).c1 42.49 ft 45 I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I 50 ■ 1 -sensitive fine grained ■ 2 -organic material ■ 3 -clay Cone Size 10cm squared ■ 4 -silty clay to clay ■ 5 -clayey silt to silty clay ■ 6 -sandy silt to clayey silt ■ 7 -silty sand to sandy silt 8 -sand to silty sand ■ 9 -sand S*Soil behavior type and SPT based on data from UBC-1983 ■ 10 -gravelly sand to sand ■ 11 -very stiff fine grained (*) ■ 12 -sand to clayey sand (*) 0:: 0 > -1 <( LU -I a.. 0 LU >-en m I- .!.!. Depth 4.92ft Ref• Depth 10.01ft Ref 4.92ft Depth 14.93ft Ref 10.01ft Depth 20.01 ft Ref 14.93ft Depth 25.1 Oft Ref 20.01ft Depth 30.02ft Ref 25.10ft Depth 34.94ft Ref30.02ft Depth 40.03ft Ref 34.94ft Depth 42.49ft Ref 40.03ft 0 CPT-06 Geosoils Summerhill Homes --- -_ / __ i_ _ t-_ ~ Arrival 10.47mS . -_ Velocity• + _ + _____ +· __ --1--__ · _ --+ _ _ Arriva_l 15.70mS ------~-I _____ ---~---~-_ _____ ----'----Velocity 754.82ft/S --f---+_ 1-L-~ 1-t=-+ ±--1 eZi~ii~~:;;18ws -+-· --=+ + 'J _-_ ~-------__ +~------=--=-'~-___ t-.___-_-_-__ -+_± ___ ~~~ eZi~ii~~1~\ms~ft/S ---L---__ I --=fil. ~ L-I j Arrival 29.22mS 1 j 1 ----i -I Velocity 1067.78ft/S -±--+ -__ ( + -j _ 1 t _ I -+-_ Arrival33.83mS ---~I ___ ·-----------'-T ___ __J__.___ Velocity 1044.42ft/S -+ --+ -----J --+t---r _J _ j L-. j _ ~ Arr;,a13851mS _ _ I L___ Velocity 1033.31ft/S f · J Arrival 43.67mS --J -Velocity 974.52ft/S · · , -1 Arrival 45.54mS --.,.. ...--~ -. Velocity 1299.48ft/S +-t --------------+--- 10 20 ~~ -. 100 1) ~ i 11 80 90 Gf'S DATA [ .. l l ::_ I 11 APPENDIX C SEISMICITY GeoSoils, Inc. 1000 900 800 700 600 500 400 300 200 100 0 CALIFORNIA FAULT MAP SUMMERHJLL -1 00 +.-JL......J_..J........L--!-L......J_..J........L--!-L.......!......J........L--!-L.......!......J........L-+-L......J_..J........L-+-L......J_..J........L-+-.1........L....J-J:Lf-.1........L...J........l.-+-.1........L...J.......J.-+-.L....L....J.......J.-1 -400 -300 -200 -100 0 100 200 300 400 500 600 W.O. 7103-A-SC PLATE C-1 7103-EQF *********************** -:: '" ;': E Q F A u L T •': -.': ..... * Version 3.00 •k ;'. * *********************** DETERMINISTIC ESTIMATION OF PEAK ACCELERATION FROM DIGITIZED FAULTS JOB NUMBER: 7103-A-SC DATE: 06-29-2016 JOB NAME: SUMMERHILL CALCULATION NAME : 7103 EQF FAULT-DATA -FILE NAME: (:\Program Files\EQFAULTl\CDMGFLTE.DAT SITE COORDINATES: SITE LATITUDE: 33.1220 SITE LONGITUDE: 117.3020 SEARCH RADIUS: 62 . 4 mi ATTENUATION RELATION: 11) Bozorgnia Campbell Niazi (1999) Hor.-Pleist. Soil -Cor. UNCERTAINTY (M=Median, S=Sigma): s Number of Sigmas: 1.0 DISTANCE MEASURE: cdist SCOND: 1 Basement Depth: .01 km Campbell SSR: 0 Campbell SHR: 0 COMPUTE PEAK HORIZONTAL ACCELERATION FAULT-DATA FILE USED: (:\Program Files\EQFAULTl\CDMGFLTE.DAT MINIMUM DEPTH VALUE (km): 3.0 Page 1 W.O. 7103-A-SC PLATE C-2 Page 1 7103-EQF EQFAULT SUMMARY DETERMINISTIC SITE PARAMETERS !ESTIMATED MAX . EARTHQUAKE EVENT APPROXIMATE 1------------------------------- ABBREVIATED DI STANCE I MAXIMUM I PEAK IEST . SITE FAULT NAME I mi (km) IEARTHQUAKE I SITE !INTENSITY I I MAG.(Mw) I ACCEL . g IMOD .MERC. --------------------------------==============l==========l==========I========= ROSE CANYON 5.3( 8 .6)1 6.9 I 0.552 I X NEWPORT-INGLEWOOD (Offshore) 8 .0( 12 .8)1 6.9 I 0 .420 I X CORONADO BANK 21.0( 33.8)1 7 .4 I 0 .240 I IX ELSINORE-TEMECULA 24.4( 39.2)1 6.8 I 0 .139 I VIII ELSINORE-JULIAN 24.4( 39.2) 7.1 0.170 I VIII ELSINORE-GLEN IVY 36.2( 58 .2) 6 .8 0.092 I VII PALOS VERDES 38.5( 62 .0) 7 .1 0.106 I VII EARTHQUAKE VALLEY 41.9( 67 .5) 6.5 0 .064 I VI SAN JACINTO-ANZA 47. 2 ( 75. 9) 7. 2 0 . 092 I VII SAN JACINTO-SAN JACINTO VALLEY 48.2( 77.6) 6.9 0 .073 I VII NEWPORT-INGLEWOOD (L.A.Bas i n) 49.2( 79.2) 6.9 0.071 I VI CHINO-CENTRAL AVE . (Elsinore) 50.6( 81.5) 6.7 0.085 I VII SAN JACINTO -COYOTE CREEK 51.4( 82.8) 6.8 0.064 I VI WHITTIER 54.2( 87.2) 6.8 0 .060 I VI ELSINORE-COYOTE MOUNTAIN 55.5 ( 89.3) 6.8 0 .059 I VI COMPTON THRUST 58.9( 94.8) 6.8 0 .078 I VII ELYSIAN PARK THRUST 61.8( 99.4) 6 .7 0 .070 I VI SAN JACINTO -SAN BERNARDINO 61.9( 99.6) 6.7 I 0.049 I VI ********************************~********************************************** -END OF SEARCH-18 FAULTS FOUND WITHIN THE SPECIFIED SEARCH RADIU S . THE ROSE CANYON FAULT IS CLOSEST TO THE SITE. IT I S ABOUT 5.3 MILES (8.6 km) AWAY. LARG EST MAXIMUM-EARTHQUAKE SITE ACCEL ERATION: 0.5518 g Page 2 W.0. 7103-A-SC PLATE C-3 STRIKE-SLIP FAULTS 11) Bozorgnia Campbell Niazi (1999) Hor.-Pleist. Soil-Cor. --0) ._. C 0 ....... co ~ Q) Q) () () <x: 1 . 1 .01 .001 1 10 100 Distance f adistl (km) W.O. 7103-A-SC PLATE C-4 .-. 0) --C 0 +-' ro ~ Q) Q) (.) (.) <( MAXIMUM EARTHQUAKES SUMMERHILL 1 .1 .01 .001 .1 1 10 Distance (mi) "' "' W.O. 7103-A-SC PLATE C-5 EARTHQUAKE EPICENTER MAP SUMMERHILL 1100 ,r----------------------------------, 1000 900 800 700 600 500 400 300 200 LEGEND M=4 M=5 100 M=6 M=7 -0 M=B -1 00 +-'--'--'-----'-+---'--...J........1-'--~..L-l.-'--j-'-.1,.....J........i......+-'---J'-----'---.1--j,-....L.....L-'--'-+-..L-L--'-'"-t-.L-L-...L.-L--+-'-'--'--'-+-'-........... ~ -400 -300 -200 -100 0 100 200 300 400 500 600 W.0. 7103-A-SC PLATE C-6 JOB NUMBER: 7103-A-SC 7103-EQS ************************* -:: .. ': * E Q s E A R C H * '1: ,~ -:: version 3.00 .. ": -.': ,~ ************************* ESTIMATION OF PEAK ACCELERATION FROM CALIFORNIA EARTHQUAKE CATALOGS DATE: 06-29-2016 JOB NAME: SUMMERHILL EARTHQUAKE-CATALOG-FILE NAME: (:\Program Files\EQSEARCH\ALLQUAKE.DAT MAGNITUDE RANGE : MINIM UM MAGNITUDE: 5.00 MAXIMUM MAGNITUDE: 9.00 SITE COORDINATES: SITE LATITUDE: 33 .1220 SITE LONGITUDE: 117.3020 SEARCH DATES: START DATE: 1800 END DATE: 2016 SEARCH RADIUS: 62. 4 mi 100.4 km ATTENUATION RELATION: 12) Bozorgnia Campbell Niazi (1999) Hor.-soft Rock-cor. UNCERTAINTY (M=Median, S=Sigma): S Number of Sigmas: 1.0 ASSUMED SOURCE TYPE: ss [SS=Strike-slip, DS=Reverse-slip, BT=Blind-thrust] SCOND: 1 Depth source: A Basement Depth: .01 km Campbell SSR: 1 Campbel l SHR: 0 COMPUTE PEAK HORIZONTAL ACCELERATION MINIMUM DEPTH VALUE (km): 3.0 Page 1 W.O. 7103-A-SC PLATE C-7 7103-EQS EARTHQUAKE SEARCH RESULTS Page 1 -------------------------------------------------------------------------------I I I TIME I SITE I SITE I APPROX. FILEI LAT . I LONG. I DATE I (UTC) IDEPTH IQUAKEI ACC. I MM I DISTANCE CODEI NORTH I WEST I I H M Seel (km)I MAG. I g IINT. I mi [km] ----+-------+--------+----------+--------+-----+-----+-------+----+------------DMG 33.00001117.3000 11/22/1800 2130 0.0 0.0 1 6.50 0.312 MGI 33.00001117.0000 09/21/1856 730 0.0 0.01 5.00 0.056 MGI 32 .80001117.1000 05/25/1803 0 0 0.0 0.01 5.00 0.043 DMG 32.70001117.2000 05/27/1862 20 0 0.0 0.01 5.90 0.062 T-A 32.67001117.1700 10/21/1862 0 0 0 .0 0.01 5.00 0.033 T-A 32.67001117.1700 12/00/1856 0 0 0.0 0.01 5.00 0.033 T-A 32.67001117.1700 05/24/1865 0 0 0.0 0 .01 5.00 0.033 PAS 32.97101117.8700 07/13/1986 1347 8.2 6 .01 5.30 0.037 DMG 33.20001116.7000 01/01/1920 235 0.0 0.0 5.00 0.030 DMG 32.80001116.8000 10/23/1894 23 3 0.0 0.0 5.70 0.044 DMG 33 .70001117.4000 05/13/1910 620 0.0 0.0 5.00 0.026 DMG 33 .70001117.4000 05/15/1910 1547 0.0 0.0 6 .00 0.048 DMG 33.7000 117.4000 04/11/1910 757 0.0 0.0 5.00 0.026 MGI 33.2000 116.6000 10/12/1920 1748 0.0 0.0 5.30I 0.031 DMG 33.6990 117.5110 05/31/1938 83455.4 10 .0 5.50 0.034 DMG 33.7100 116.9250 09/23/1963 144152.6 16.5 5.00 0.023 DMG 33.7500 117.0000 06/06/1918 2232 0 .0 0 .0 5.00 0.023 DMG 33.7500 117.0000104/21/1918 223225.0 0.0 6.80 0.069 MGI 33.8000 117.6000 04/22/1918 2115 0.0 0.0 5.00 0.021 DMG 33.8000 117.0000 12/25/1899 1225 0.0 0.0 6.40 0 .049 DMG 33.5750 117.9830 03/11/1933 518 4.0 0.0 5.20 0.023 DMG 33 .0000 116.4330 06/04/1940 1035 8.3 0.0 5.10 0.022 DMG 33.6170 117.9670 03/11/1933 154 7.8 0.0 6.30 0.045 PAS 33.5010 116.5130 02/25/1980 104738.5 13 .6 5.50 0.027 PDP 133.5080 116.5140 10/31/2001 075616.6 15 .01 5.10 0.021 DMG 133 .5000 116.5000 09/30/1916 211 0.0 0.01 5.00 0.020 DMG 133.6170 118.0170 03/14/1933 19 150.0 0.01 5.10 0.021 DMG 133.9000 117.2000 12/19/18801 0 0 0.0 0.01 6.00 0 .035 DMG 133 .3430 116.3460 04/28/19691232042.9 20.01 5.80 0 .029 DMG 133 .6830 118 .0500 03/11/1933 1 658 3.0 0.01 5.50 0.024 DMG 133 .7000 118.0670 03/11/1933I 85457.0 0.01 5.10 0.018 DMG 133.7000 118.0670 03/11/19331 51022.0 0.01 5.10 0 .018 DMG 134.0000 117 .2500 07/23/19231 73026.0I 0.01 6.25 0.036 DMG 133 .4000 116.3000 02/09/1890 l12 6 0.01 0.01 6.30 0.037 T-A 132.2500 117.5000 01/13/1877 120 0 0.01 0.01 5.00I 0.017 MGI 134.0000 117.5000 12/16/1858110 0 0 .01 0.0I 7.00I 0 .059 IX I 8 . 4 ( 13 . 5) VI I 19.4( 31.2) VI I 25.1( 40 .4) VI I 29.7( 47.8) v I 32.1( 51.7) V 32.1( 51.7) V 32.1( 51.7) V 34.5( 55.5) V 35.2( 56.7) VI 36.6( 58.9) V 40.3( 64 .9) VI 40.3( 64.9) V 40.3( 64.9) V 40.9( 65.9) V 41.6( 67.0) IV 46.0( 74 .1) IV 46.7( 75.2) VI 46.7( 75.2) IV 49.9( 80.2) VI 49.9( 80.4) IV 50 .2( 80.8) IV 51.0( 82.0) VI 51.4( 82.7) V 52.5( 84.5) IV 52.7( 84.8) IV 53 .1( 85.5) IV 53.5( 86.2) V 54 .0( 87.0) V 57.3( 92.2) V 58.0( 93 .3) IV 59.5( 95.7) IV 59.5( 95.7) V 60. 7 ( 97. 7) V 60.9( 98.1) IV 61. 3 ( 98. 6) VI 61. 7 ( 99. 3) ******************************************************************************* -END OF SEARCH-36 EARTHQUAKES FOUND WITHIN THE SPECIFIED SEARCH AREA. TIME PERIOD OF SEARCH: 1800 TO 2016 LENGTH OF SEARCH TIME: 217 years Page 2 W.O. 7103-A-SC PLATE C-8 7103-EQS THE EARTHQUAKE CLOSEST TO THE SITE IS ABOUT 8.4 MILES (13 .5 km) AWAY. LARGEST EARTHQUAKE MAGNITUDE FOUND IN THE SEARCH RADIUS: 7.0 LARGEST EARTHQUAKE SITE ACCELERATION FROM THIS SEARCH: 0.312 g COEFFICIENTS FOR GUTENBERG & RICHTER RECURRENCE RELATION: a -value= 0.608 b-value= 0.317 beta-value= 0 .730 TABLE OF MAGNITUDES AND EXCEEDANCES: Ea rthquake I Number of Times I Cumulative Magnitude I Exceeded I No. / Year -----------+-----------------+------------4.0 I 36 I 0.16590 4. 5 I 36 I o .16590 5.0 I 36 I 0.16590 5.5 I 15 I 0.06912 6.0 I 9 I 0.04147 6. 5 I 3 I 0.01382 7.0 I 1 I 0.00461 Page 3 W.O. 7103-A-SC PLATE C-9 ---0) -C 0 +-' ro :..... Q) Q) C) C) <! STRIKE-SLIP FAUL TS 12) Bozorgnia Campbell Niazi (1999) Hor.-Soft Rock-Car. 1 . 1 .01 .001 1 10 100 Distance f adistl (km) W.0 . 7103-A-SC PLATE C-10 ..--.. z -(/) ...... C (1) > w -0 ~ (1) .0 E :J z (1) > ...... ro :J E :J 0 Number of Earthquakes (N) Above Magnitude (M) SUMMERHILL 20 10 8 6 4 2 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 Magnitude (M) W.0. 7103-A-SC PLATE C-11 APPENDIX D LABORATORY DATA GeoSoils, Inc. VJ :::, ~ Cl. (!) "' 0 ;:: UJ N ui z ~ (!) VJ :::, U.S. SIEVE OPENING IN INCHES I U.S. SIEVE NUMBERS I HYDROMETER 6 4 3 2 1.5 1 3/4 1/23/8 3 4 6 810 1416 20 30 40 50 60 100 140200 100 I II I I 11 I I I I I I I I I 95 ---r--- 90 r-------. ~ 85 ■ " I'\ 80 • 75 \ 70 ;\ \ j: 65 <.9 w6o \ ~ ~ 55 \ 0::: UJ 50 \ z LL 1-45 z \ ~40 ii 0::: ~ 35 30 25 20 15 10 5 0 100 10 1 0.1 0.01 GRAIN SIZE IN MILLIMETERS I GRAVEL SAND I COBBLES I I I SILT OR CLAY coarse fi ne coarse medium fine Sample Depth Range Visual Classification/USCS CLASSIFICATION LL PL Pl Cc e B-1 15.1 Sandy Clay, Qal Sample Depth D100 D60 D30 D10 %Gravel %Sand %Silt I e B-1 15.1 9.5 0.18 2.5 52.5 40.8 GeoSoils, Inc. GRAIN SIZE DISTRIBUTION ~-~-" 5741 Pal mer Way Project: SU MMERHILL ~WU Carlsbad, CA 92008 Telephone: (760) 438-3155 Number: 71 03-A-SC Fax: (760) 931-0915 Date: July 2016 Plate: D -1 0.001 Cu %Clay (/J ::::, ~ (!) ,., 0 ;::. z ~ ~ i5 (/J z 0 (.) (/J ::::, -0.8 -0.6 4~ ~ ~ -0.4 I \ -0.2 \ 0.0 \ 0.2 I\ \ 0.4 [\ I ,R \ \ 0 z 4: 0.6 \ \ a:: I-I\ Cf) 0.8 "\. ~ 1.0 \ ~ \ 1.2 ~~ 1.4 \ ~ \ 1.6 ~ "~ \ 1.8 "-"~ \ 2.0 i"---, I 100 1,000 10,000 STRESS, psf Sample Depth/El. Visual Classification yd MC MC H20 Initial Initial Final e B-1 15.0 Sandy Clay, Qal 117.3 13.1 15.1 1000 Stress at which water was added: 500 psf Strain Difference: % ------ GeoSoils, Inc. CONSOLIDATION TEST ~-~~ 5741 Palmer Way Project: SUMMERHILL Carlsbad , CA 92008 ~-.D Telephone: (760) 438-3155 Number: 7103-A-SC Fax: (760) 931-0915 Date: July 2016 Plate: D -2 Cal Land Engineering, Inc. dba Quartech Consultant Geotechnical, Environmental, and Civil Engineering SUMMARY OF LABORATORY TEST DATA GeoSoils, Inc. 5741 Palmer Way, Suite D Carlsbad, CA 92010 W.O. 7103-A-SC Project Name: Summerhill Client: N/A Sample ID B-1 B-2 Sample Depth (ft) 3'-7' 5' QCI Project No.: 16-029-006n Date: June 28, 2016 Summarized by: KA Corrosivity Test Results pH Chloride CT-532 CT-422 (643) (ppm) 6.43 40 5.53 35 Sulfate CT-417 % By Weiqht 0.0375 0.0195 Resistivity CT-532 (643) (ohm-cm) 350 240 W.O. 7103-A-SC PLATE D-3 576 East Lambert Road, Brea, California 92821 ; Tel: 714-671-1050; Fax: 714-671-1090 APPENDIX E LIQUEFACTION ANALYSIS GeoSoils, Inc. SEISMIC INDUCED LIQUEFACTION ANALYSIS 7103-A-SC Summerhill, FOS = 1.0 Hole No.=B-2 Water Depth=16.5 ft Surface Elev.=100 Shear Stress Ratio (ft) O -0 ~~--.-----.--~---,~~--,----,----r----, -10 20 -30 40 fs1=1.00 so CRR -CSR fs1- Shaded Zone has Liquefaction Potential Factor of Safety Settlement O 1 5 O (in.) I I I I I I I I r ~,~,~,~1~1~1~1~1,-,1 S = 0.14 in. Saturated Unsaturat. - Magnitude= 7.2 Acceleration=0.464g Soil Description Remediated Fill: SANDY SILT, reddish yellow to light brown, dry, medium dense, broken rock/concrete encountered, oxidation staining, fine grained sand :j;j ALLUVIUM: Sandy Clay, dark reddish Y·z brown, very moist, stiff, fine grained 0!) -~. SANTIAGO FORMATION: Claystone, light yellow brown to yellowish gray, very moist to wet becomes saturated at 21.5 feet, soft Tokimatsu/M-Correction; No Fines Correction, No Liquefiable Clays GeoSoils, Inc. Plate E-1 < "' :::, !!! " J c5l 1l t::: :~ (J £ t ~ .!< ...J SEISMIC INDUCED LIQUEFACTION ANALYSIS 7103-A-SC Summerhill, FOS = 1.3 Hole No.=B-2 Water Depth=16.5 ft Surface Elev.=100 Shear Stress Ratio Factor of Safety Settlement Magnitude= 7.2 Acceleration=0.464g Soil Description (ft) o 0 01 5 ~O~(i~n-~)~~~ I I I I 10 __J ~ L 20 -30 -40 fs1 =1.30 I I T T I I I I I I I I I I I I I I I I u S = 0.22 in. Remediated Fill: SANDY SILT, reddish yellow to light brown, dry, medium dense, broken rock/concrete encountered, oxidation staining, fine grained sand ALLUVIUM: Sandy Clay, dark reddish brown, very moist, stiff, fine grained SANTIAGO FORMATION: Claystone, light yellow brown to yellowish gray, very moist to wet becomes saturated at 21.5 feet, soft SO CRR -CSR Isl--Saturated Unsaturat. - 60 70 Shaded Zone has Liquefaction Potential Tokimatsu/M-Correction; No Fines Correction, No Liquefiable Clays GeoSoils, Inc. Plate E-2 APPENDIX F INFILTRATION DATA AND FORM 1-8 GeoSoils, Inc. Appendix I: Forms and Checklists Categorization of Infiltration Condition Form 1-8 Part 1 -Full Infiltration Feasibility Screening Criteria Would infiltration of the full design volume be feasible from a physical perspective without any undesirable consequences that cannot be reasonably mitigated? Criteria Screening Question Is the estimated reliable infiltration rate below proposed facility locations greater than 0.5 inches per hour? The response to this Screening Question shall be based on a comprehensive evaluation oft he factors presented in Appendix C.2 and Appendix D. Provide basis: Yes No X GSI has evaluated the infiltration rate of natural surface soils on the west site to be about 0.2 inches/hour, and on the east site to be about 0.5 inches/hour (both conducted in Hydrologic Soil Group A areas). Prior development has resulted in the removal of natural surface soils, and for all intent and purposes, the west site is predominantly a cut lot exposing some surficial fill and dense sed imentary bedrock consisting of silty sandstone, and significant fill thickness exist on the east site. On the east site, artificial fill, created through removal/recompaction of on site soils is of a similar, very low permeability. See text of GSI (2019) for other related discussions and references. Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicability. 2 Can infiltration greater than 0.5 inches per hour be allowed without increasing risk of geotechnical hazards (slope stability, groundwater mounding, utilities, or other factors) that cannot be mitigated to an acceptable level? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.2. Provide basis: X See above. Groundwater was not encountered on the west site, and was encountered at a depth of about 21 1/2 feet on the east site. There is an increased potential for the creation of perched groundwater (mounding) conditions along zones of contrasting perm eabilities, including shallow cut/fill contacts, fill lifts, and transitions between clayey and sandy formational materials within the sedimentary bedrock. Due to the strong permeability contrast between bedrock and fill, utility trenches can potentially act as french drains and provide conduits for the movement of excessive moisture beneath the structure(s), exacerbating slope instability, and fill and/or trench backfill settlement, causing distress to structures. See text of GSI (2019) for other related discussions and references. Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicabi lity. 1-3 GeoSoils, Inc. February 2016 Appendix I: Forms and Checklists Criteria 3 Form 1-8 Page 2 of 4 Screening Question Can infiltration greater than 0.5 inches per hour be allowed without increasing risk of groundwater contamination (shallow water table, storm water pollutants or other factors) that cannot be mitigated to an acceptable level? The response to this Screening Question shall be based on a comprehensible evaluation of the factors presented in Appendix C.3. Provide basis: Yes No X While this study did not include an environmental assessment, visual observation did not indicate the presence of potential con tam in ants. The infiltration rate is less than 0.5 inches per hour. While the regional groundwater table is not considered a factor in the development of this site, the creation of a shallow "perched" water table can occur through infiltration. Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicability. 4 Can infiltration greater than 0.5 inches per hour be allowed without causing potential water balance issues such as a change of seasonality of ephemeral streams or increased discharge of contaminated groundwater to surface waters? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.3. Provide basis: X The infiltration rate is less than 0.5 inches per hour. The site currently appears to drain offsite and no runoff appears to be retained onsite. While an environmental site assessment has not been performed to evaluate the presence of contaminated groundwater, the regional groundwater table is not considered a factor in the development of this site. Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicability. Part I In the answers to rows 1-4 are "Yes" a full infiltration design is potentially feasible. TI1e feasibility Result* screening category is Full Infiltration l fany answer from row 1-4 is "No", infiltration may be possible to some extent but would not generally be feasible or desirable to achieve a "full infiltration" design. Proceed to Pan 2 •To be completed using gathered site information and best professional judgement considering the definition of MEP in the MS4 Pennit. Additional testing and/or studies may be required by [City Engineer] to substantiate findings. 1-4 GeoSoils, Inc. February 2016 I Appendix I: Forms and Checklists Form 1-11 Pai:e 3 of 4 Part 2 -Partial Infiltration vs. No Infiltration Feasibility Screening Criteria Would infiltration of water in an appreciable amount be physically feasible without any negative consequences that cannot be reasonably mitigated? Criteria 5 Screening Question Do soil and geologic conditions allow for infiltration in any appreciable rate or volume? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.2 and Appendix D. Provide basis: Yes No X GSI has evaluated the infiltration rate of natural surface soils on the west site to be about 0.2 inches/hour, and on the east site to be about 0.5 inches/hour (both Hydro logic Soil Group A areas). Prior development has resulted in the removal of natural surface soils, and for all intent and purposes, the west site is predominantly a cut lot exposing some surficial fill and dense sedimentary bedrock consisting of silty sandstone, and significant fill thickness exist on the east site. On the east site, artificial fill, created through removal/recompaction of on site soils is of a similar, very low permeability. See text of GSI (2019) for other related discussions and references. Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicability. 6 Can infiltration in any appreciable quantity be allowed without increasing risk of geotechnical hazards (slope stability, groundwater mounding, utilities, or other factors) that cannot be mitigated to an acceptable level? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.2. Provide basis: X No. The infiltration rate is less than 0.5 inches per hour. The limited permeability of sedimentary bedrock will tend to result in the lateral migration of water and saturated conditions at, or near the surface, increasing the potential for distress to foundations, floor slabs, and slope instability, etc. Onsite soils are expansive, saturation of some onsite soils has been shown, through laboratory testing, to generate uplift pressures on the order of 3,000 pounds per square. There is an increased potential for the creation of perched groundwater (mounding) conditions along zones of contrasting permeabilities, including shallow cut/fill contacts, fill lifts, and transitions between clayey and sandy formational materials within th e sedimentary bedrock. Due to the strong permeability contrast between bedrock and fill, utility trenches can potentially act as trench drains and provide conduits for the movement of excessive moisture beneath th e structure(s), exacerbating slope instability, and fill or backfill settlement, potentially causing distress to structures. See text of GSI (2019) for other related discussions and references. Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicabil ity. 1-5 GeoSoils, Inc. February 2016 Appendix I: Forms and Checklists Form 1-8 Page 4 of 4 Criteria Screening Question Yes No Can Infiltration in any appreciable quantity be allowed without posing significant 7 risk for groundwater related concerns (shallow water table, storm water X pollutants or other factors)? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.3. Provide basis: While the regional groundwater table is not considered a factor in the development of this site, the creation of a shallow "perched" water table can occur and increase the potential for distress to the structure(s) due to water vapor transmission through foundations, slabs, and any resultant corrosive effects on metal conduit in trenches. See text of report for other related discussions and references. Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicability. Can infiltration be allowed without violating downstream water rights? The 8 response to this Screening Question shall be based on a comprehensive evaluation of X the factors presented in Appendix C.3. Provide basis: The infiltration rate is less than 0.5 inches per hour. The site currently appears to drain offsite and no runoff appears to be retained on site. While an environmental site assessment has not been performed to evaluate the presence of contaminated groundwater, the regional groundwater table is not considered a factor in the development of this site. Sunm1arize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicability. Part 2 If all answers from row 5-8 are yes then partial infiltration design is potentially feasible. The Result• feasibility screening category is Partial Infiltration. No If any answer from row 5-8 is no, then infiltration of any volume is considered to be infeasible within Infiltration the drainage area. The feasibility screening category is No Infiltration. •Tobe completed using gathered site information and best professional judgement considering the definition of MEP in the MS4 Permit. Additional testing and/or studies may be required by Agency/Jurisdictions to substantiate findings. 1-6 GeoSoils, Inc. February 2016 ,,. ... ,.. .. ,,.. ... ,.. ,,. ,.. JIIIIII ... ,. .. .. \a. ,,.. ... ... 111.i ... .. ... .. .. ,.. .. APPENDIX G GENERAL EARTHWORK, GRADING GUIDELINES AND PRELIMINARY CRITERIA GeoSoils, Inc . GENERAL EARTHWORK, GRADING GUIDELINES, AND PRELIMINARY CRITERIA General These guidelines present general procedures and requirements for earthwork and grading as shown on the approved grading plans, including preparation of areas to be filled, placement of fill, installation of subdrains, excavations, and appurtenant structures or flatwork. The recommendations contained in the geotechnical report are part of these earthwork and grading guidelines and would supercede the provisions contained hereafter in the case of conflict. Evaluations performed by the consultant during the course of grading may result in new or revised recommendations which could supercede these guidelines or the recommendations contained in the geotechnical report. Generalized details follow this text. The contractor is responsible for the satisfactory completion of all earthwork in accordance with provisions of the project plans and specifications and latest adopted code. In the case of conflict, the most onerous provisions shall prevail. The project geotechnical engineer and engineering geologist (geotechnical consultant), and/or their representatives, should provide observation and testing services, and geotechnical consultation during the duration of the project. EARTHWORK OBSERVATIONS AND TESTING Geotechnical Consultant Prior to the commencement of grading, a qualified geotechnical consultant (soil engineer and engineering geologist) should be employed for the purpose of observing earthwork procedures and testing the fills for general conformance with the recommendations of the geotechnical report(s), the approved grading plans, and applicable grading codes and ordinances. The geotechnical consultant should provide testing and observation so that an evaluation may be made that the work is being accomplished as specified. It is the responsibility of the contractor to assist the consultants and keep them apprised of anticipated work schedules and changes, so that they may schedule their personnel accordingly. All remedial removals, clean-outs, prepared ground to receive fill, key excavations, and subdrain installation should be observed and documented by the geotechnical consultant prior to placing any fill. It is the contractor's responsibility to notify the geotechnical consultant when such areas are ready for observation. Laboratory and Field Tests Maximum dry density tests to determine the degree of compaction should be performed in accordance with American Standard Testing Materials test method ASTM designation D-1557. Random or representative field compaction tests should be performed in GeoSoils, Inc. , ""' ., "' .. .l ... J J ., I J J ,.. -- 11111 .. --.. - ... ... ... .. - ,--,. ... ,,. 11111 .. .. .. ,. .. ... accordance with test methods ASTM designation D-1556, D-2937 or D-2922, and D-3017, at intervals of approximately ±2 feet of fill height or approximately every 1,000 cubic yards placed. These criteria would vary depending on the soil conditions and the size of the project. The location and frequency of testing would be at the discretion of the geotechnical consultant. Contractor's Responsibility All clearing, site preparation, and earthwork performed on the project should be conducted by the contractor, with observation by a geotechnical consultant, and staged approval by the governing agencies, as applicable. It is the contractor's responsibility to prepare the ground surface to receive the fill, to the satisfaction of the geotechnical consultant, and to place, spread, moisture condition, mix, and compact the fill in accordance with the recommendations of the geotechnical consultant. The contractor should also remove all non-earth material considered unsatisfactory by the geotechnical consultant. Notwithstanding the services provided by the geotechnical consultant, it is the sole responsibility of the contractor to provide adequate equipment and methods to accomplish the earthwork in strict accordance with applicable grading guidelines, latest adopted codes or agency ordinances, geotechnical report(s), and approved grading plans. Sufficient watering apparatus and compaction equipment should be provided by the contractor with due consideration for the fill material, rate of placement, and climatic conditions. If, in the opinion of the geotechnical consultant, unsatisfactory conditions such as questionable weather, excessive oversized rock or deleterious material, insufficient support equipment, etc., are resulting in a quality of work that is not acceptable, the consultant will inform the contractor, and the contractor is expected to rectify the conditions, and if necessary, stop work until conditions are satisfactory. During construction, the contractor shall properly grade all surfaces to maintain good drainage and prevent ponding of water. The contractor shall take remedial measures to control surface water and to prevent erosion of graded areas until such time as permanent drainage and erosion control measures have been installed. SITE PREPARATION All major vegetation, including brush, trees, thick grasses, organic debris, and other deleterious material, should be removed and disposed of off-site. These removals must be concluded prior to placing fill. In-place existing fill, soil, alluvium, colluvium, or rock materials, as evaluated by the geotechnical consultant as being unsuitable, should be removed prior to any fill placement. Depending upon the soil conditions, these materials may be reused as compacted fills. Any materials incorporated as part of the compacted fills should be approved by the geotechnical consultant. Any underground structures such as cesspools, cisterns, mining shafts, tunnels, septic tanks, wells, pipelines, or other structures not located prior to grading, are to be removed Summerhill Homes File:e:\wp12\7103\7103a.rpge GeoSoils, Inc. Appendix G Page 2 or treated in a manner recommended by the geotechnical consultant. Soft, dry, spongy, highly fractured, or otherwise unsuitable ground, extending to such a depth that surface processing cannot adequately improve the condition, should be overexcavated down to firm ground and approved by the geotechnical consultant before compaction and filling operations continue. Overexcavated and processed soils, which have been properly mixed and moisture conditioned, should be re-compacted to the minimum relative compaction as specified in these guidelines. Existing ground, which is determined to be satisfactory for support of the fills, should be scarified (ripped) to a minimum depth of 6 to 8 inches, or as directed by the geotechnical consultant. After the scarified ground is brought to optimum moisture content, or greater and mixed, the materials should be compacted as specified herein. If the scarified zone is greater than 6 to 8 inches in depth, it may be necessary to remove the excess and place the material in lifts restricted to about 6 to 8 inches in compacted thickness. Existing ground which is not satisfactory to support compacted fill should be overexcavated as required in the geotechnical report, or by the on-site geotechnical consultant. Scarification, disc harrowing, or other acceptable forms of mixing should continue until the soils are broken down and free of large lumps or clods, until the working surface is reasonably uniform and free from ruts, hollows, hummocks, mounds, or other uneven features, which would inhibit compaction as described previously. Where fills are to be placed on ground with slopes steeper than 5: 1 (horizontal to vertical [h:v]), the ground should be stepped or benched. The lowest bench, which will act as a key, should be a minimum of 15 feet wide and should be at least 2 feet deep into firm material, and approved by the geotechnical consultant. In fill-over-cut slope conditions, the recommended minimum width of the lowest bench or key is also 15 feet, with the key founded on firm material, as designated by the geotechnical consultant. As a general rule, unless specifically recommended otherwise by the geotechnical consultant, the minimum width of fill keys should be equal to ½ the height of the slope. Standard benching is generally 4 feet (minimum) vertically, exposing firm, acceptable material. Benching may be used to remove unsuitable materials, although it is understood that the vertical height of the bench may exceed 4 feet. Pre-stripping may be considered for unsuitable materials in excess of 4 feet in thickness. All areas to receive fill, including processed areas, removal areas, and the toes of fill benches, should be observed and approved by the geotechnical consultant prior to placement of fill. Fills may then be properly placed and compacted until design grades (elevations) are attained. COMPACTED FILLS Any earth materials imported or excavated on the property may be utilized in the fill provided that each material has been evaluated to be suitable by the geotechnical Summerhill Homes File:e:\wp12\7103\7103a.rpge GeoSoils, Inc. Appendix G Page 3 11111 llllllt .. i .. J J .. .J , Iii J J J J J ... I 11111 ... ... ... 111111 - ... ... ... -.. ... ' -,. .. ... ... .. 1111 ... 11111 ,. 11111 ... .. ... consultant. These materials should be free of roots, tree branches, other organic matter, or other deleterious materials. All unsuitable materials should be removed from the fill as directed by the geotechnical consultant. Soils of poor gradation, undesirable expansion potential, or substandard strength characteristics may be designated by the consultant as unsuitable and may require blending with other soils to serve as a satisfactory fill material. Fill materials derived from benching operations should be dispersed throughout the fill area and blended with other approved material. Benching operations should not result in the benched material being placed only within a single equipment width away from the fill/bedrock contact. Oversized materials defined as rock, or other irreducible materials, with a maximum dimension greater than 12 inches, should not be buried or placed in fills unless the location of materials and disposal methods are specifically approved by the geotechnical consultant. Oversized material should be taken offsite, or placed in accordance with recommendations of the geotechnical consultant in areas designated as suitable for rock disposal. GSI anticipates that soils to be utilized as fill material for the subject project may contain some rock. Appropriately, the need for rock disposal may be necessary during grading operations on the site. From a geotechnical standpoint, the depth of any rocks, rock fills, or rock blankets, should be a sufficient distance from finish grade. This depth is generally the same as any overexcavation due to cut-fill transitions in hard rock areas, and generally facilitates the excavation of structural footings and substructures. Should deeper excavations be proposed (i.e., deepened footings, utility trenching, swimming pools, spas, etc.), the developer may consider increasing the hold-down depth of any rocky fills to be placed, as appropriate. In addition, some agencies/jurisdictions mandate a specific hold-down depth for oversize materials placed in fills. The hold-down depth, and potential to encounter oversize rock, both within fills, and occurring in cut or natural areas, would need to be disclosed to all interested/affected parties. Once approved by the governing agency, the hold-down depth for oversized rock (i.e., greater than 12 inches) in fills on this project is provided as 1 O feet, unless specified differently in the text of this report. The governing agency may require that these materials need to be deeper, crushed, or reduced to less than 12 inches in maximum dimension, at their discretion . To facilitate future trenching, rock (or oversized material), should not be placed within the hold-down depth feet from finish grade, the range of foundation excavations, future utilities, or underground construction unless specifically approved by the governing agency, the geotechnical consultant, and/or the developer's representative. If import material is required for grading, representative samples of the materials to be utilized as compacted fill should be analyzed in the laboratory by the geotechnical consultant to evaluate it's physical properties and suitability for use onsite. Such testing should be performed three (3) days prior to importation. If any material other than that previously tested is encountered during grading, an appropriate analysis of this material should be conducted by the geotechnical consultant as soon as possible . Summerhill Homes File:e:\wp12\7103\7103a.rpge GeoSoils, Inc. Appendix G Page 4 Approved fill material should be placed in areas prepared to receive fill in near horizontal layers, that when compacted, should not exceed about 6 to 8 inches in thickness. The geotechnical consultant may approve thick lifts if testing indicates the grading procedures are such that adequate compaction is being achieved with lifts of greater thickness. Each layer should be spread evenly and blended to attain uniformity of material and moisture suitable for compaction. Fill layers at a moisture content less than optimum should be watered and mixed, and wet fill layers should be aerated by scarification, or should be blended with drier material. Moisture conditioning, blending, and mixing of the fill layer should continue until the fill materials have a uniform moisture content at, or above, optimum moisture. After each layer has been evenly spread, moisture conditioned, and mixed, it should be uniformly compacted to a minimum of 90 percent of the maximum density as evaluated by ASTM test designation D 1557, or as otherwise recommended by the geotechnical consultant. Compaction equipment should be adequately sized and should be specifically designed for soil compaction, or of proven reliability to efficiently achieve the specified degree of compaction. Where tests indicate that the density of any layer of fill, or portion thereof, is below the required relative compaction, or improper moisture is in evidence, the particular layer or portion shall be re-worked until the required density and/or moisture content has been attained. No additional fill shall be placed in an area until the last placed lift of fill has been tested and found to meet the density and moisture requirements, and is approved by the geotechnical consultant. In general, per the latest adopted version of the California Building Code (CBC), fill slopes should be designed and constructed at a gradient of 2:1 (h:v), or flatter. Compaction of slopes should be accomplished by over-building a minimum of 3 feet horizontally, and subsequently trimming back to the design slope configuration. Testing shall be performed as the fill is elevated to evaluate compaction as the fill core is being developed. Special efforts may be necessary to attain the specified compaction in the fill slope zone. Final slope shaping should be performed by trimming and removing loose materials with appropriate equipment. A final evaluation of fill slope compaction should be based on observation and/or testing of the finished slope face. Where compacted fill slopes are designed steeper than 2:1 (h:v), prior approval from the governing agency, specific material types, a higher minimum relative compaction, special reinforcement, and special grading procedures will be recommended. If an alternative to over-building and cutting back the compacted fill slopes is selected, then special effort should be made to achieve the required compaction in the outer 1 O feet of each lift of fill by undertaking the following: 1. An extra piece of equipment consisting of a heavy, short-shanked sheepsfoot should be used to roll (horizontal) parallel to the slopes continuously as fill is placed. The sheepsfoot roller should also be used to roll perpendicular to the Summerhill Homes File:e:\wp12\7103\7103a.rpge GeoSoils, Inc. Appendix G Page 5 J J J J J J J J J J J J J J J J J J J .. .. .. .. .. .. ,. 111111 ,. 1111 ... Ill ... ,,,. ,... .. ... ... .. .... .. .. .. .. .. .. ... ... .. ... ,... 2. 3. 4 . 5. slopes, and extend out over the slope to provide adequate compaction to the face of the slope . Loose fill should not be spilled out over the face of the slope as each lift is compacted. Any loose fill spilled over a previously completed slope face should be trimmed off or be subject to re-rolling. Field compaction tests will be made in the outer (horizontal) ±2 to ±8 feet of the slope at appropriate vertical intervals, subsequent to compaction operations. After completion of the slope, the slope face should be shaped with a small tractor and then re-rolled with a sheepsfoot to achieve compaction to near the slope face. Subsequent to testing to evaluate compaction, the slopes should be grid-rolled to achieve compaction to the slope face. Final testing should be used to evaluate compaction after grid rolling. Where testing indicates less than adequate compaction, the contractor will be responsible to rip, water, mix, and recompact the slope material as necessary to achieve compaction. Additional testing should be performed to evaluate compaction. SUBDRAIN INSTALLATION Subdrains should be installed in approved ground in accordance with the approximate alignment and details indicated by the geotechnical consultant. Subdrain locations or materials should not be changed or modified without approval of the geotechnical consultant. The geotechnical consultant may recommend and direct changes in subdrain line, grade, and drain material in the field, pending exposed conditions. The location of constructed subdrains, especially the outlets, should be recorded/surveyed by the project civil engineer. Drainage at the subdrain outlets should be provided by the project civil engineer . EXCAVATIONS Excavations and cut slopes should be examined during grading by the geotechnical consultant. If directed by the geotechnical consultant, further excavations or overexcavation and refilling of cut areas should be performed, and/or remedial grading of cut slopes should be performed. When fill-over-cut slopes are to be graded, unless otherwise approved, the cut portion of the slope should be observed by the geotechnical consultant prior to placement of materials for construction of the fill portion of the slope . The geotechnical consultant should observe all cut slopes, and should be notified by the contractor when excavation of cut slopes commence . Summerhill Homes File:e:\wp12\7103\7103a.rpge GeoSoils, Inc . Appendix G Page 6 If, during the course of grading, unforeseen adverse or potentially adverse geologic conditions are encountered, the geotechnical consultant should investigate, evaluate, and make appropriate recommendations for mitigation of these conditions. The need for cut slope buttressing or stabilizing should be based on in-grading evaluation by the geotechnical consultant, whether anticipated or not. Unless otherwise specified in geotechnical and geological report(s), no cut slopes should be excavated higher or steeper than that allowed by the ordinances of controlling governmental agencies. Additionally, short-term stability of temporary cut slopes is the contractor's responsibility. Erosion control and drainage devices should be designed by the project civil engineer and should be constructed in compliance with the ordinances of the controlling governmental agencies, and/or in accordance with the recommendations of the geotechnical consultant. COMPLETION Observation, testing, and consultation by the geotechnical consultant should be conducted during the grading operations in order to state an opinion that all cut and fill areas are graded in accordance with the approved project specifications. After completion of grading, and after the geotechnical consultant has finished observations of the work, final reports should be submitted, and may be subject to review by the controlling governmental agencies. No further excavation or filling should be undertaken without prior notification of the geotechnical consultant or approved plans. All finished cut and fill slopes should be protected from erosion and/or be planted in accordance with the project specifications and/or as recommended by a landscape architect. Such protection and/or planning should be undertaken as soon as practical after completion of grading. PRELIMINARY OUTDOOR POOL/SPA DESIGN RECOMMENDATIONS The following preliminary recommendations are provided for consideration in pool/spa design and planning. Actual recommendations should be provided by a qualified geotechnical consultant, based on site specific geotechnical conditions, including a subsurface investigation, differential settlement potential, expansive and corrosive soil potential, proximity of the proposed pool/spa to any slopes with regard to slope creep and lateral fill extension, as well as slope setbacks per Code, and geometry of the proposed improvements. Recommendations for pools/spas and/or deck flatwork underlain by expansive soils, or for areas with differential settlement greater than ¼-inch over 40 feet horizontally, will be more onerous than the preliminary recommendations presented below. The 1 :1 (h:v) influence zone of any nearby retaining wall site structures should be delineated on the project civil drawings with the pool/spa. This 1 :1 (h:v) zone is defined as a plane up from the lower-most heel of the retaining structure, to the daylight grade of Summerhill Homes File:e:\wp12\7103\7103a.rpge GeoSoils, Inc. Appendix G Page 7 J , ... J J J .. l ... J :J ., .. J , ... :J j 11111111 .J , ... J .. ... ... ... ,,.. ... ,,.. ... ,.. ... ,.. ... ... I 11111 ,,,. ... ,.. ,.. ... .. ... ... .. ... .. -1111 ... ... .. II"' Ill the nearby building pad or slope. If pools/spas or associated pool/spa improvements are constructed within this zone, they should be re-positioned (horizontally or vertically) so that they are supported by earth materials that are outside or below this 1: 1 plane. If this is not possible given the area of the building pad, the owner should consider eliminating these improvements or allow for increased potential for lateral/vertical deformations and associated distress that may render these improvements unusable in the future, unless they are periodically repaired and maintained. The conditions and recommendations presented herein should be disclosed to all homeowners and any interested/affected parties . General 1. 2 . 3. 4. 5. 6. 7. The equivalent fluid pressure to be used for the pool/spa design should be 60 pounds per cubic foot (pcf) for pool/spa walls with level backfill, and 75 pcf for a 2:1 sloped backfill condition. In addition, backdrains should be provided behind pool/spa walls subjacent to slopes. Passive earth pressure may be computed as an equivalent fluid having a density of 150 pcf, to a maximum lateral earth pressure of 1,000 pounds per square foot (psf). An allowable coefficient of friction between soil and concrete of 0.30 may be used with the dead load forces. When combining passive pressure and frictional resistance, the passive pressure component should be reduced by one-third. Where pools/spas are planned near structures, appropriate surcharge loads need to be incorporated into design and construction by the pool/spa designer. This includes, but is not limited to landscape berms, decorative walls, footings, built-in barbeques, utility poles, etc . All pool/spa walls should be designed as "free standing" and be capable of supporting the water in the pool/spa without soil support. The shape of pool/spa in cross section and plan view may affect the performance of the pool, from a geotechnical standpoint. Pools and spas should also be designed in accordance with the latest adopted Code. Minimally, the bottoms of the pools/spas, should maintain a distance H/3, where H is the height of the slope (in feet), from the slope face. This distance should not be less than 7 feet, nor need not be greater than 40 feet. The soil beneath the pool/spa bottom should be uniformly moist with the same stiffness throughout. If a fill/cut transition occurs beneath the pool/spa bottom, the cut portion should be overexcavated to a minimum depth of 48 inches, and replaced with compacted fill, such that there is a uniform blanket that is a minimum of 48 inches below the pool/spa shell. If very low expansive soil is used for fill, the fill should be placed at a minimum of 95 percent relative compaction, at optimum Summerhill Homes File:e:\wp12\7103\7103a.rpge GeoSoils, Inc . Appendix G Page 8 moisture conditions. This requirement should be 90 percent relative compaction at over optimum moisture if the pool/spa is constructed within or near expansive soils. The potential for grading and/or re-grading of the pool/spa bottom, and attendant potential for shoring and/or slot excavation, needs to be considered during all aspects of pool/spa planning, design, and construction. 8. If the pool/spa is founded entirely in compacted fill placed during rough grading, the deepest portion of the pool/spa should correspond with the thickest fill on the lot. 9. Hydrostatic pressure relief valves should be incorporated into the pool and spa designs. A pool/spa under-drain system is also recommended, with an appropriate outlet for discharge. 10. All fittings and pipe joints, particularly fittings in the side of the pool or spa, should be properly sealed to prevent water from leaking into the adjacent soils materials, and be fitted with slip or expandible joints between connections transecting varying soil conditions. 11. An elastic expansion joint (flexible waterproof sealant) should be installed to prevent water from seeping into the soil at all deck joints. 12. A reinforced grade beam should be placed around skimmer inlets to provide support and mitigate cracking around the skimmer face. 13. In order to reduce unsightly cracking, deck slabs should minimally be 4 inches thick, and reinforced with No. 3 reinforcing bars at 18 inches on-center. All slab reinforcement should be supported to ensure proper mid-slab positioning during the placement of concrete. Wire mesh reinforcing is specifically not recommended. Deck slabs should not be tied to the pool/spa structure. Pre-moistening and/or pre-soaking of the slab subgrade is recommended, to a depth of 12 inches (optimum moisture content), or 18 inches (120 percent of the soil's optimum moisture content, or 3 percent over optimum moisture content, whichever is greater), for very low to low, and medium expansive soils, respectively. This moisture content should be maintained in the subgrade soils during concrete placement to promote uniform curing of the concrete and minimize the development of unsightly shrinkage cracks. Slab underlayment should consist of a 1-to 2-inch leveling course of sand (S.E. >30) and a minimum of 4 to 6 inches of Class 2 base compacted to 90 percent. Deck slabs within the H/3 zone, where H is the height of the slope (in feet), will have an increased potential for distress relative to other areas outside of the H/3 zone. If distress is undesirable, improvements, deck slabs or flatwork should not be constructed closer than H/3 or 7 feet (whichever is greater) from the slope face, in order to reduce, but not eliminate, this potential. 14. Pool/spa bottom or deck slabs should be founded entirely on competent bedrock, or properly compacted fill. Fill should be compacted to achieve a minimum Summerhill Homes File:e:\wp12\7103\7103a.rpge GeoSoils, Inc. Appendix G Page 9 .. .. t .. j J J J .., .. , .. J J j J , .. , .. ., .. .. .. .. .. ,,. 1111111 ,.. .. ... ,.. ... ,.. ... ,.. "'" 1111111 ,.. .. .. .. .. .. .. .. .. .. 1111111 ,.. ,.. 90 percent relative compaction, as discussed above. Prior to pouring concrete, subgrade soils below the pool/spa decking should be throughly watered to achieve a moisture content that is at least 2 percent above optimum moisture content, to a depth of at least 18 inches below the bottom of slabs. This moisture content should be maintained in the subgrade soils during concrete placement to promote uniform curing of the concrete and minimize the development of unsightly shrinkage cracks. 15. In order to reduce unsightly cracking, the outer edges of pool/spa decking to be bordered by landscaping, and the edges immediately adjacent to the pool/spa, should be underlain by an 8-inch wide concrete cutoff shoulder (thickened edge) extending to a depth of at least 12 inches below the bottoms of the slabs to mitigate excessive infiltration of water under the pool/spa deck. These thickened edges should be reinforced with two No. 4 bars, one at the top and one at the bottom. Deck slabs may be minimally reinforced with No. 3 reinforcing bars placed at 18 inches on-center, in both directions. All slab reinforcement should be supported on chairs to ensure proper mid-slab positioning during the placement of concrete. 16. Surface and shrinkage cracking of the finish slab may be reduced if a low slump and water-cement ratio are maintained during concrete placement. Concrete utilized should have a minimum compressive strength of 4,000 psi. Excessive water added to concrete prior to placement is likely to cause shrinkage cracking, and should be avoided. Some concrete shrinkage cracking, however, is unavoidable. 17. Joint and sawcut locations for the pool/spa deck should be determined by the design engineer and/or contractor. However, spacings should not exceed 6 feet on center . 18. Considering the nature of the onsite earth materials, it should be anticipated that caving or sloughing could be a factor in subsurface excavations and trenching. Shoring or excavating the trench walls/backcuts at the angle of repose (typically 25 to 45 degrees), should be anticipated. All excavations should be observed by a representative of the geotechnical consultant, including the project geologist and/or geotechnical engineer, prior to workers entering the excavation or trench, and minimally conform to Cal/OSHA ("Type C" soils may be assumed), state, and local safety codes. Should adverse conditions exist, appropriate recommendations should be offered at that time by the geotechnical consultant. GSI does not consult in the area of safety engineering and the safety of the construction crew is the responsibility of the pool/spa builder . 19. It is imperative that adequate provisions for surface drainage are incorporated by the homeowners into their overall improvement scheme. Ponding water, ground saturation and flow over slope faces, are all situations which must be avoided to enhance long-term performance of the pool/spa and associated improvements, and reduce the likelihood of distress . Summerhill Homes File:e:\wp12\7103\7103a.rpge GeoSoils, Inc. Appendix G Page 10 20. Regardless of the methods employed, once the pool/spa is filled with water, should it be emptied, there exists some potential that if emptied, significant distress may occur. Accordingly, once filled, the pool/spa should not be emptied unless evaluated by the geotechnical consultant and the pool/spa builder. 21. For pools/spas built within (all or part) of the Code setback and/or geotechnical setback, as indicated in the site geotechnical documents, special foundations are recommended to mitigate the affects of creep, lateral fill extension, expansive soils and settlement on the proposed pool/spa. Most municipalities or County reviewers do not consider these effects in pool/spa plan approvals. As such, where pools/spas are proposed on 20 feet or more of fill, medium or highly expansive soils, or rock fill with limited "cap soils" and built within Code setbacks, or within the influence of the creep zone, or lateral fill extension, the following should be considered during design and construction: OPTION A: Shallow foundations with or without overexcavation of the pool/spa "shell," such that the pool/spa is surrounded by 5 feet of very low to low expansive soils (without irreducible particles greater that 6 inches), and the pool/spa walls closer to the slope(s) are designed to be free standing. GSI recommends a pool/spa under-drain or blanket system (see attached Typical Pool/Spa Detail). The pool/spa builders and owner in this optional construction technique should be generally satisfied with pool/spa performance under this scenario; however, some settlement, tilting, cracking, and leakage of the pool/spa is likely over the life of the project. OPTION B: Pier supported pool/spa foundations with or without overexcavation of the pool/spa shell such that the pool/spa is surrounded by 5 feet of very low to low expansive soils (without irreducible particles greater than 6 inches), and the pool/spa walls closer to the slope(s) are designed to be free standing. The need for a pool/spa under-drain system may be installed for leak detection purposes. Piers that support the pool/spa should be a minimum of 12 inches in diameter and at a spacing to provide vertical and lateral support of the pool/spa, in accordance with the pool/spa designers recommendations current applicable Codes. The pool/spa builder and owner in this second scenario construction technique should be more satisfied with pool/spa performance. This construction will reduce settlement and creep effects on the pool/spa; however, it will not eliminate these potentials, nor make the pool/spa "leak-free." 22. The temperature of the water lines for spas and pools may affect the corrosion properties of site soils, thus, a corrosion specialist should be retained to review all spa and pool plans, and provide mitigative recommendations, as warranted. Concrete mix design should be reviewed by a qualified corrosion consultant and materials engineer. Summerhill Homes File:e:\wp12\7103\7103a.rpge GeoSoils, Inc. Appendix G Page 11 ... I .. J , 11111 , .. :J .. .J , .. j J J J J J J J , .. .. .. .. ... ,,,. ... ,,. .. ,,. ... .. .. 11111 -.. .. ,,. .. ,,,. ... ,,. .. .. .. ,. .. .. .. ,,,. .. 23. All pool/spa utility trenches should be compacted to 90 percent of the laboratory standard, under the full-time observation and testing of a qualified geotechnical consultant. Utility trench bottoms should be sloped away from the primary structure on the property (typically the residence) . 24. Pool and spa utility lines should not cross the primary structure's utility lines (i.e., not stacked, or sharing of trenches, etc.). 25. The pool/spa or associated utilities should not intercept, interrupt, or otherwise adversely impact any area drain, roof drain, or other drainage conveyances. If it is necessary to modify, move, or disrupt existing area drains, subdrains, or tightlines, then the design civil engineer should be consulted, and mitigative measures provided. Such measures should be further reviewed and approved by the geotechnical consultant, prior to proceeding with any further construction . 26. The geotechnical consultant should review and approve all aspects of pool/spa and flatwork design prior to construction. A design civil engineer should review all aspects of such design, including drainage and setback conditions. Prior to acceptance of the pool/spa construction, the project builder, geotechnical consultant and civil designer should evaluate the performance of the area drains and other site drainage pipes, following pool/spa construction . 27. All aspects of construction should be reviewed and approved by the geotechnical consultant, including during excavation, prior to the placement of any additional fill, prior to the placement of any reinforcement or pouring of any concrete . 28. Any changes in design or location of the pool/spa should be reviewed and approved by the geotechnical and design civil engineer prior to construction. Field adjustments should not be allowed until written approval of the proposed field changes are obtained from the geotechnical and design civil engineer. 29. Disclosure should be made to homeowners and builders, contractors, and any interested/affected parties, that pools/spas built within about 15 feet of the top of a slope, and/or H/3, where His the height of the slope (in feet), will experience some movement or tilting. While the pool/spa shell or coping may not necessarily crack, the levelness of the pool/spa will likely tilt toward the slope, and may not be esthetically pleasing. The same is true with decking, flatwork and other improvements in this zone . 30. Failure to adhere to the above recommendations will significantly increase the potential for distress to the pool/spa, flatwork, etc. 31. Local seismicity and/or the design earthquake will cause some distress to the pool/spa and decking or flatwork, possibly including total functional and economic loss. Summerhill Homes File:e:\wp12\7103\7103a.rpge GeoSoils, Inc . Appendix G Page 12 32. The information and recommendations discussed above should be provided to any contractors and/or subcontractors, or homeowners, interested/affected parties, etc., that may perform or may be affected by such work. JOB SAFETY General At GSI, getting the job done safely is of primary concern. The following is the company's safety considerations for use by all employees on multi-employer construction sites. On-ground personnel are at highest risk of injury, and possible fatality, on grading and construction projects. GSI recognizes that construction activities will vary on each site, and that site safety is the prime responsibility of the contractor; however, everyone must be safety conscious and responsible at all times. To achieve our goal of avoiding accidents, cooperation between the client, the contractor, and GSI personnel must be maintained. In an effort to minimize risks associated with geotechnical testing and observation, the following precautions are to be implemented for the safety of field personnel on grading and construction projects: Safety Meetings: GSI field personnel are directed to attend contractor's regularly scheduled and documented safety meetings. Safety Vests: Safety vests are provided for, and are to be worn by GSI personnel, at all times, when they are working in the field. Safety Flags: Flashing Lights: Two safety flags are provided to GSI field technicians; one is to be affixed to the vehicle when on site, the other is to be placed atop the spoil pile on all test pits. All vehicles stationary in the grading area shall use rotating or flashing amber beacons, or strobe lights, on the vehicle during all field testing. While operating a vehicle in the grading area, the emergency flasher on the vehicle shall be activated. In the event that the contractor's representative observes any of our personnel not following the above, we request that it be brought to the attention of our office. Test Pits Location, Orientation, and Clearance The technician is responsible for selecting test pit locations. A primary concern should be the technician's safety. Efforts will be made to coordinate locations with the grading contractor's authorized representative, and to select locations following or behind the established traffic pattern, preferably outside of current traffic. The contractor's authorized representative (supervisor, grade checker, dump man, operator, etc.) should direct Summerhill Homes File:e:\wp12\7103\7103a.rpge GeoSoils, Inc. Appendix G Page 13 , .. , ... J J .. . t .. J ., .. J J J J J J J J , .. , .. ,. ,,.. .. .. ,,,. ... ,.. .. ,,,. .. .. ... .. ... .. ... 1111 .. ... .. .. 1111 ... 1111 ,,,. .. .. ... ... ... ... .. excavation of the pit and safety during the test period. Of paramount concern should be the soil technician's safety, and obtaining enough tests to represent the fill. Test pits should be excavated so that the spoil pile is placed away from oncoming traffic, whenever possible. The technician's vehicle is to be placed next to the test pit, opposite the spoil pile. This necessitates the fill be maintained in a driveable condition . Alternatively, the contractor may wish to park a piece of equipment in front of the test holes, particularly in small fill areas or those with limited access. A zone of non-encroachment should be established for all test pits. No grading equipment should enter this zone during the testing procedure. The zone should extend approximately 50 feet outward from the center of the test pit. This zone is established for safety and to avoid excessive ground vibration, which typically decreases test results . When taking slope tests, the technician should park the vehicle directly above or below the test location. If this is not possible, a prominent flag should be placed at the top of the slope. The contractor's representative should effectively keep all equipment at a safe operational distance (e.g., 50 feet) away from the slope during this testing . The technician is directed to withdraw from the active portion of the fill as soon as possible following testing. The technician's vehicle should be parked at the perimeter of the fill in a highly visible location, well away from the equipment traffic pattern. The contractor should inform our personnel of all changes to haul roads, cut and fill areas or other factors that may affect site access and site safety . In the event that the technician's safety is jeopardized or compromised as a result of the contractor's failure to comply with any of the above, the technician is required, by company policy, to immediately withdraw and notify his/her supervisor. The grading contractor's representative will be contacted in an effort to affect a solution. However, in the interim, no further testing will be performed until the situation is rectified. Any fill placed can be considered unacceptable and subject to reprocessing, recompaction, or removal. In the event that the soil technician does not comply with the above or other established safety guidelines, we request that the contractor bring this to the technician's attention and notify this office. Effective communication and coordination between the contractor's representative and the soil technician is strongly encouraged in order to implement the above safety plan. Trench and Vertical Excavation It is the contractor's responsibility to provide safe access into trenches where compaction testing is needed. Our personnel are directed not to enter any excavation or vertical cut which: 1) is 5 feet or deeper unless shored or laid back; 2) displays any evidence of instability, has any loose rock or other debris which could fall into the trench; or 3) displays any other evidence of any unsafe conditions regardless of depth . Summerhill Homes File:e:\wp12\7103\7103a.rpge GeoSoils, Inc . Appendix G Page 14 All trench excavations or vertical cuts in excess of 5 feet deep, which any person enters, should be shored or laid back. Trench access should be provided in accordance with Cal/OSHA and/or state and local standards. Our personnel are directed not to enter any trench by being lowered or "riding down" on the equipment. If the contractor fails to provide safe access to trenches for compaction testing, our company policy requires that the soil technician withdraw and notify his/her supervisor. The contractor's representative will be contacted in an effort to affect a solution. All backfill not tested due to safety concerns or other reasons could be subject to reprocessing and/or removal. If GSI personnel become aware of anyone working beneath an unsafe trench wall or vertical excavation, we have a legal obligation to put the contractor and owner/developer on notice to immediately correct the situation. If corrective steps are not taken, GSI then has an obligation to notify Cal/OSHA and/or the proper controlling authorities. Summerhill Homes File:e:\wp12\7103\7103a.rpge GeoSoils, Inc. Appendix G Page 15 J , .. .. • .. , .. ., .. J J .. J J J .. J J J ., .. TYPE A ------------, ---------- Natural grade ~ Proposed grade , . \ \' '1/\ Colluvium and alluvium (remove) t?-=~~~;y \\< 1/ / ' ✓, ,......,/,.......;:.....,.,....~ ~-~-.,--~ --.........-..,,......,......,_; ,,' · , Typical benching / Bedrock or , approved native material See Alternate Details TYPE B ------------, ---------- Natural grade ~ Proposed grade \/ 0 v' 'V .y' \ \ ~ \ ~ ~ ......... ~ ;:;,\ / ----~ \\ \ -~~_:,...,.......,, ;A....,,.,..,....,.._ .......... ......,J_ 1/ -\ -""""'..,...;:~..,...,,--~,.,.,....,..,.,_ ypical benching ~~ 0 Bedrock or · ~\ , , ~ approved ' native material See Alternate Details Selection of alternate subdrain details, location, and extent of subdrains should be evaluated by the geotechnical consultant during grading. c. CANYON SUBDRAIN DETAIL Plate G-1 6 inc minim 6-inch minimum ------....._I I / 6-inch minimum ,-y I . \' // . . . ,\ . ~ \ . 1/, -----✓->::,\ . ------ 6-inch minimum A-1 Filter material= Minimum volume of 9 cubic feet per lineal foot of pipe. Perforated pipe= 6-inch-diameter ABS or PVC pipe or approved substitute with minimum 8 perforations (¼-inch diameter) per lineal foot in bottom half of pipe (ASTM D-2751, SDR-35, or ASTM D-1527, Schd. 40). For continuous run in excess of 500 feet, use 8-inch-diameter pipe (ASTM D-3034, SDR-35, or ASTM D-1785, Schd. 40). ---- I ---6-inch minimum Y'\\ ;(\\- \\ /-/.y J 6-incfl minimum 8-1 FIL TEA MATERIAL Sieve Size 1 inch ¾ inch ¾ inch No.4 No. 8 No. 30 No.50 No. 200 Percent Passing 100 90-100 40-100 25-40 18-33 5-15 0-7 0-3 AL TERNA TE 1= PERFORATED PIPE AND RL TEA MATERIAL \_,,----6-inch minimum \ ------....._1 I -------- 6-inch minimum I I --- 1 1 6-inch minimum I ~~ ---Filter fabric Filter fabric . 0-,~ 6-inch minimum J-6-inch minimum A-2 Gravel Material= 9 cubic feet per lineal foot. Perforated Pipe= See Alternate 1 8-2 Gravel= Clean ¾-inch rock or approved substitute. Filter Fabric= Mirafi 140 or approved substitute. -inch minimum ALTERNATE 2: PERFORATED PIPE, GRAVEL, AND FILTER FABRIC c. CANYON SUBDRAIN ALTERNATE DETAILS Plate G-2 ~-Toe of slope as shown on grading plan ~-. -. -. ..-.-.. : .-, .-. /·.· Original ground surf ace to be restored with compacted fill / ... ·.··•·. ·. , .. · .... ·.· ...... . <: .. · Compacted. Fill · ,/ . . I ,,,, .. 2D ~ / ii'~/ I \__Original ground surface ~ ~<.. / D -Anticipated removal of unsuitable material .cf/ (depth per geotechnical engineer) '~ ❖$/ i c) /~ ·\\\ ·~i:~w\ \ /, / y Back-cut varies. For deep removals, backcut should be made no steeper than 1:1 (HV), or flatter as necessary for safety considerations. Provide a l1 (HV) minimum projection from toe of slope as shown on grading plan to the recommended removal depth. Slope height, site conditions, and/ or local conditions could dictate flatter projections. c. FILL SLOPE TOEING OUT ON FLAT ALLUVIATED CANYON DETAIL Plate G-3 Blanket fill (if recommended by the geotechnical consultant) Design finish slope -----._ I 1s foot ~ .. ~ I minimum Drainage per design civil engineer . ~. -~. ~-,.-.-.- \/ ./.\1/V:::,\ \\'\\ /, 1 10-foot minimum / 25-foot maximum/ ---__,/_ ----- -...,,.....,·\, --:-:-:::: \ '\ \ -~----: ~ Typical benching 1 ---~ --/ But_t:es~ or_ 15-foot typical stab1hzat1on fill 1 to 2 drain spacing / .....,.,......-:,1 I foot J J / 2-Percent Gradient ~ ' --= ~i ✓' -----f~\1/,\Y: \' =-<<-✓• 2-foot minimum l Y(\ V _./;'\ Toe Heel ,), ' minimum) key depth ____ ~ 2-Percent Gradient--X: l --/1 /,..-: ;----,\ · 'v. Bedrock or Typical benching (4-foot I 15-foot minimum _____ _, approved native ·---or H/2 where H 18 the t · I slope height ma ena Subdrain as recommended by geotechnical consultant 4-inch-diameter non-perforated outlet pipe and backdrain (see detail Plate E-6). Outlets to be spaced at 100-f oot maximum intervals and shall extend 2 feet beyond the face of slope at time of rough grading completion. At the completion of rough grading. the design civil engineer should provide recommendations to convey any outlet's discharge to a suitable conveyance, utilizing a non-erosive device. c. TYPICAL STABILIZATION / BUTTRESS FILL DETAIL Plate G-5 Filter Material= Minimum of 5 cubic feet per lineal foot of pipe or 4 cubic feet per lineal feet of pipe when placed in square cut trench. Alternative in Lieu of Filter Material= Gravel may be encased in approved filter fabric. Filter fabric shall be Mirafi 140 or equivalent. Filter fabric shall be lapped a minimum of 12 inches in all joints. Minimum 4-lnch-Diameter Pipe: ABS-ASTM D-2751, SDR 35; or ASTM D-1527 Schedule 40, PVC-ASTM D-3034, SDR 35; or ASTM D-1785 Schedule 40 with a crushing strength of 1,000 pounds minimum, and a minimum of 8 uniformly-spa per foot of pipe. Must be installed with perforations down at bottom of pipe. Provide cap at upstream end of pipe. Slope at 2 percent to outlet pipe. Outlet pipe to be connected to subdrain pipe with tee or elbow. Notes= 1. Trench for outlet pipes to be backfilled and compacted with onsite soil. 2. Backdrains and lateral drains shall be located at elevation of every bench drain. First drain located at elevation just above lower lot grade. Additional drains may be required at the discretion of the geotechnical consultant. Filter Material shall be of the following specification or an approved equivalent. Sieve Size 1 inch ¾ inch ¾ inch No.4 No. 8 No. 30 No.SO No.200 Percent Passing 100 90-100 40-100 25-40 18-33 5-15 0-7 0-3 Gravel shall be of the following specification or an approved equivalent. Sieve Size 1½ inch No.4 No. 200 Percent Passing 100 50 8 c:. TYPICAL BUTTRESS SUBDRAIN DETAIL Plate G-6 Toe of slope as shown on grading plan Natural slope to be restored with compacted fill Backcut varies _,,,,,,-Proposed grade \ / / / / Compacted fill / / / / -----·• -·o~ . ~ -----· . . . . . . . s.\ef\o • -~ su\\a.tJ\.e ro . . -~ L / .. , --orun ~'7'"~ ......... -- • ' \1 N\1Jt1\, Y/, ;\ co\\\l · ' \ A/ 4 t t · · .·.· . . . 0 \a?~O11, . . . J"7'"~..,............,...,..........I __ _:_ oo m1n1mum ····. \\"""'~· .... ··. . . . ~ r ... ·.·· ·.·. ~~--:-7"'<"..........,....v I ~-foot minimum ~· ·' ~ '<Y _ ~ I 1n bedrock or ~ . · ., ~ • . ... ,_,,,,.,--:-r,:,""":....,,.'""""'...,.......,.........J-, Bench width approved . . ~'"'·• ~ ::,,;--; /, '----[ .~., =•~;"'---.:_ __ · _ ~ \\/, \ \ , , , Y. [ 3-foot mnmm 1 , •• ::' ~~ Bedrock or -,----~" -.-,;---,------'Y------~~:::iterial I 15-foot mininum or I I H/2 where H is ., the slope height I NOTES: -----r Subdrain as recommended by geotechnical consultant 1. Where the natural slope approaches or exceeds the design slope ratio, special recommendations would be provided by the geotechnical consultant. 2. The need for and disposition of drains should be evaluated by the geotechnical consultant, based upon exposed conditions. e. FILL OVER NATURAL (SIDEHILL FILL) DETAIL Plate G-7 Cut/fill contact as shown on grading plan Proposed grade / / Cut/fill contact as shown on as-built plan Maintain inimum 15-foot / Compacted fill H -height of slope I iTII section from back.cut to face I of finish slope I ~~---.~_,,.._,.,y\\Y,:""(u\v' / ~-·;,..-<0\\" I . ·. . ~e,\e~ ✓'' -· ~"'\e. / ---~ - 4-foot mnimum -~-. t Z\\\-;,\//.YT,,-\ ----7- ><,><<<>,<> ~.1/ I Original (existing) grade / < Bench width I r---mayvary-- c t I _ _.-:-:. .. ~ , . , "~ ___ / "✓" '" ,✓ ✓✓ ~ I (4-foot minimum) I u sope --------....... -~ . \< ~t minimum __J . ~__:_.,:...;...: ~1/\ key depth 1 15-foot minimum or I ~.., · · 1/ \ \ \ i--H/2 where H is v----,\\\j<'.~S\>,\\ :((V I the slope height7 Bedrock or approved native material Subdrain as recommended by geotechnical consultant NOTE= The cut portion of the slope should be excavated and evaluated by the geotechnical consultant prior to construction of the fill portion. c:. FILL OVER CUT DETAIL Plate G-8 H. Natural slope Proposed finish grade Remove Unsuitable · •· .Mate\rial. .• ·. . . .. ~--~··~·.·~.•·~·.~.~.~~ .J: ~;::~: t ···•·· :~ 76 __ _ ·.·~ ., ><✓ Typical benching ( 4-foot minimum) ·-~ •·.··.•~ ./ ···-----/" .·~· / . . : · ..... ,.. . . . / \ -mnimum tilt back . ·. ~ /4 ?CZ~~¾'. ~ ~' ~ ~ -/ ----/ , . t Compacted stablization fill '---Bedrock or other approved native material / , '-'=-------If recommended by the geotechnical 2-1~ consultant, the remaining cut portion of f Y 2 Percent Gradient . the slope may require removal and ¥0u'\¼\(\<, ✓. ,,, replacement with compacted fill. I ... w ►I Subdrain as recommended by geotechnical consultant NOTES= 1. Subdrains may be required as specified by the geotechnical consultant. 2 W shall be equipment width (15 feet) for slope heights less than 25 feet. For slopes greater than 25 feet, W shall be evaluated by the geotechnical consultant. At no time, shall W be less than H/2, where H is the height of the slope. c.1 STABLIZATION FILL FOR UNSTABLE MATERIAL EXPOSED IN CUT SLOPE DETAIL Plate G-9 Proposed finish grade ~ Natural grade --------------------------~ 3-foot minimum :,.?· </~\\'. \\\/., /, y\ ~y -t,\-~-e--:-~ j.,~\ \ \<\\0 i,,-,.t<.,,,,-:: ......... \~........,,\\\,,,-; H -height of elope 0:0'-';,::,\ ... ~ ..... ,....,\\'"'")...,.'\\ .... ~ Bedrock or k\/ d " , ,. « > /.~\ approve \ \:,,-: native material 9\ 7-<~~~ =s;:-v:0:'1' J ''7: .,, '' \/\, 2-fool -~ v 1 , A (:;:\ ~0\\\ ,.,_, , , ,,\'V\7,y\ ;:-:? Typical benching (4-foot minimum) rnmum ke' I .,. 15-foot m1· , , \ \,,-;: or H/2 H H) Y Wi1.1111 _ 30 feet .,;; , -Subdrain as recommended by geotechnical consultant NOTES: 1. 15-foot minimum to be maintained from proposed finish slope face to back cut. 2. The need and disposition of drains will be evaluated by the geotechnical consultant based on field conditions. 3. Pad overexcavation and recompaction should be performed if evaluated to be necessary by the geotechnical consultant. c. SKIN FILL OF NATURAL GROUND DETAIL Plate G-10 Natural grade ~ 0..->-;;. . ----------__ J_ Subgrade at 2 percent gradient, draining toward street CUT LOT OR MATERIAL -TYPE TRANSmON - Natural grade __ _L .. •· .•. ~-. ~ • • · , • · ·' ·3'_ to .7-!oot'mini~um• ... : .. ·, ·.: : · ~ \: overexcavate and recompact 'o\e 11\a~ ,.......,.,.,....,...,...,.,,........,,........,..... ;.--: per text of report ~a~ ~ · ·. ·' • Deeper overexcavation may be Typical benching ( 4-foot minimum) Bedrock or approved native material recommended by the geotechnical consultant in steep cut-fill transition areas, such that the underlying topography is no steeper than 3=1 (H=V) CUT -FILL LOT (DAYLIGHT TRANSITION) TRANSITION LOT DETAILS Plate G-12 Existing grade 5-f oot-high impact/ debris wall METHOD 1 1 Pad grade --__L__ --- Existing grade 5-f oot-high impact/ debris wall METHOD 2 Existing grade impact/ debris wall I 5-foot-wide catchment area [ 5-toot-high METHOD 3 \\\ ~ Pad grade ~ "';,,:/>.-:::,---------- <\ :,_,-;--; \ \, \ /,-'):/ /\ Existing grade NOT TO SCALE e. DEBRIS DEVICE CONTROL METHODS DETAIL Plate G-15 Rock-filled gabion basket Existing grade Filter fabric 5-foot minimum or as E!l.,,,,!~¥'1=:~"'1 recommended by 'f'ii9:~~~~ geotechnical consultant Drain rock Compacted fill Proposed grade " Gabion impact or diversion wall should be constructed at the base of the ascending slope subject to rock fall. Walls need to be constructed with high segments that sustain impact and mitigate potential for overtopping, and low segment that provides channelization of sediments and debris to desired depositional area for subsequent clean-out. Additional subdrain may be recommended by geotechnical consultant. From GSA, 1987 c. ROCK FALL MITIGATION DETAIL Plate G-16 MAP VIEW NOTTO SCALE Concrete cut-off wall SEE NoTE._I _ s _________ j Top of slope Bl ~ 2-inch-thick sand layer Gravity-flow, nonperforated subdrain I=== ,>pe (transverse) Toe of slope 4 Pool 4-inch perforated subdrain pipe (longitudinal) Coping A' 4-inch perforated subdrain pipe (transverse) Pool Direction of drainage B' CROSS SECTION VIEW Coping NOTTO SCALE SEE NOTES Pool encapsulated in 5-foot thickness of sand --- 6-inch-thick gravel layer 4-inch perforated subdrain pipe B NOTES: r H Gravity-flow nonperforated subdrain pipe Coping B' 2-inch-thick sand layer Vapor retarder Perforated subdrain pipe l 6-inch-thick, clean gravel(¾ to 1½ inch) sub-base encapsulated in Mirafi 140N or equivalent, underlain by a 15-mil vapor retarder, with 4-inch-diameter perforated pipe longitudinal connected to 4-inch-diameter perforated pipe transverse. Connect transverse pipe to 4-inch-diameter nonperforated pipe at low point and outlet or to sump pump area. 2. Pools on fills thicker than 20 feet should be constructed on deep foundations; otherwise, distress {tilting, cracking, etc.) should be expected. 3. Design does not apply to infinity-edge pools/ spas. c. TYPICAL POOL/SPA DETAIL Plate G-17 I I I ~ yv- 2-foot x 2-foot x ¼-inch steel plate Standard ¾-inch pipe nipple welded to top of plate ¾-inch x 5-foot galvanized pipe, standard pipe threads top and bottom; extensions threaded on both ends and added in 5-foot increments 3-inch schedule 40 PVC pipe sleeve, add in 5-f oot increments with glue joints 1------,...--r'----Proposed finish grade r ------------b __ J_ ! s,~ st-• ! 1 J l s ,ee, -121~ -// ''>-!- -__ '/ 1 . 1 tt 00 _ 1 \; .... '. __________ · _· ·_ ... J. · _· .... ' ___ Bottom of cleanout . :>::/-Provide a minimum 1-foot bedding of compacted sand NOTES= 1. Locations of settlement plates should be clearly marked and readily visible (red flagged) to equipment operators. 2. Contractor should maintain clearance of a 5-foot radius of plate base and withiin 5 feet (vertical) for heavy equipment. Fill within clearance area should be hand compacted to project specifications or compacted by alternative approved method by the geotechnical consultant (in writing, prior to construction). 3. After 5 feet (vertical) of fill is in place, contractor should maintain a 5-foot radius equipment clearance from riser. 4. Place and mechanically hand compact initial 2 feet of fill prior to establishing the initial reading. 5. In the event of damage to the settlement plate or extension resulting from equipment operating within the specified clearance area, contractor should immediately notify the geotechnical consultant and should be responsible for restoring the settlement plates to working order. 6. An alternate design and method of installation may be provided at the discretion of the geotechnical consultant. SETTLEMENT PLATE AND RISER DETAIL Plate G-18 Finish grade ~ c. ,1 <J <J ,1 3 to 6 feet ,1 <J ,1 <J ,1 <J <J .('.\ .('.\ ,1 <J ,1 <J ---¾-inch-diameter X 6-inch-long carriage bolt or equivalent 1 -6-inch diameter X 3½-inch-long hole Concrete backfill -· ---________ ... TYPICAL SURFACE SETTLEMENT MONUMENT Plate G-19 SIDE VIEW Test pit TOP VIEW Flag Flag Spoil pile Test pit Light Vehicle i-------SO!eet-----------50 feet------ -------------100feet------------------ TEST PIT SAFETY DIAGRAM Plate G-20