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HomeMy WebLinkAboutCDP 2017-0043; FRANCIS RESIDENCE; GEOTECHNICAL UPDATE EVALUATION; 2017-06-09GEOTECHNICAL UPDATE EVALUATION PROPOSED Sl'-:Glc-FAMll;;Y RESIOE-WCE-OFF OF-TRt'FON STREET CA~,t:SBAJl..-SAN D,EGO coµtHY, €ALIFOR~iA AS ESSO 'S P C L UMBER (A9-} 215-0710-51 -MR. MARK FRANCIS 3385 BLODGETT DRIVE COLORADO SPRINGS, COLORADO 80919 W .0 . 7279-A-SC JUNE 9, 2017 • REconncopy ~ _'lr.~0 -----ate ...... ~ .... ___ ~ • Geotechnical • Geologic • Coastal • Environmental 5741 Palmer Way • Carlsbad, California 9201 0 • (760) 438-3155 • FAX (760) 931-0915 • www.geosoilsinc.com Mr. Mark Francis 3385 Blodgett Drive Colorado Springs, Colorado 80919 June 9, 2017 W.0 . 7279-A-SC Subject: Geotechnical Update Evaluation, Proposed Single-Family Residence Off of Triton Street, Carlsbad, San Diego County, California, Assessor's Parcel Number (APN) 215-070-51 Dear Mr. Francis: In accordance with your request and authorization, GeoSoils, Inc. (GSI) is pleased to present the results of our geotechnical update evaluation of the subject site. The purpose of our study was three-fold. Firstly, this update serves as an assessment of the current site geologic and geotechnical conditions. Secondly, this update brings our previous site-specific work into accordance with the 2016 California Building Code ((2016 CBC], California Building Standards Commission [CBSC], 2016) and current standards of practice. Lastly, this update provides preliminary, project-specific geotechnical recommendations for earthwork and the design of foundations, retaining walls, pavements, and flatwork, as they relate to the proposed single-family residence at the property. 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, the site may be characterized as being mantled by localized undocumented fill and structural fill. These earth materials are underlain by Quaternary-age very old paralic deposits, which are considered formational earth materials. Structural fills were observed and tested by GSI during original grading of the lot. • Due to their relatively low density, lack of uniformity, and porous nature, all undocumented fill and weathered structural fill are considered potentially compressible and unsuitable for the support of settlement-sensitive improvements (i.e., foundation elements, slab-on-grade floors, flatwork, walls, etc.) and/or engineered fill in their existing state. These earth materials should be removed and • • • • Francis reused as properly prepared structural fill, per the recommendations in this report. Based on the available data, the thickness of potentially compressible soils, across the site, is anticipated to vary between approximately 1 foot to 1 ½ feet. However, localized thicker sections of unsuitable soils cannot be precluded and should be anticipated. Conversely, the underlying unweathered very old paralic deposits are considered suitable for the support of settlement-sensitive improvements and engineered fill. It should be noted that the 2016 CBC (CBSC, 2016) indicates that removals of unsuitable soils be performed across all areas to be graded, under the purview of the grading permit, and not just within the influence of the proposed residential structure. 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. In general, any planned settlement-sensitive improvement located above a 1 :1 (horizontal:vertical [h:v]) projection up from the bottom, outboard edge of the remedial grading excavation at the property boundary would be affected by perimeter conditions. On a preliminary basis, any planned settlement-sensitive improvements located within approximately 1 foot to 1 ½ feet from the property boundary would require deepened foundations or additional reinforcement by means of ground improvement or specific structural design. Otherwise, these improvements may be subject to distress and a reduced serviceable life . This will also require proper disclosure to all interested/affected parties should this condition exist at the conclusion of grading. In GSI (2002b and 2004), we identified paleoliquefaction features within the very old paralic deposits. These features are artifacts of ancient seismically-induced liquefaction, occurring prior to lithification of the very old paralic deposits, and do not present a current secondary seismic risk to the proposed development. However, due to density/permeability contrasts between these features and the intact very old paralic deposits, these features can act as conduits for subsurface water which could result in piping of fines and low magnitude settlement. Similar to GSI (2002b and 2004), we are recommending the use of post-tensioned (PT) foundations for support of the proposed residential structure. Expansion index (E.I.) testing, performed on a representative sample of the onsite soils, indicates an E.I. that is less than 5. Thus, on a preliminary basis, the expansion potential of the onsite soils is very low. Site soils are provisionally considered non-detrimentally expansive and do not require specific structural design for the mitigation of shrink/swell effects. Additional evaluations regarding the expansion potential of the onsite soils should be performed during remedial earthwork, and prior to foundation construction. Corrosion testing performed on a representative sample of the onsite soils indicates site soils are neutral with respect to soil acidity/alkalinity; are corrosive to exposed, File:e:\wp12\ 7200\7279a.gue GeoSoils, Inc. W.O. 7279-A-SC Page Two • • • Francis buried metals when saturated; present negligible ("not applicable"or "SO" per American Concrete Institute [ACI] 318-14) sulfate exposure to concrete; and contain relatively low concentrations of soluble chlorides. GSI does not consult in the field of corrosion engineering. Thus, consultation from a qualified corrosion consultant may be considered based on the level of corrosion protection required for the project, as determined by the Project Architect, Structural Engineer, Civil Engineer, and Plumbing/Mechanical Engineers. On a preliminary basis, site soils are classified as "SO," "WO," and "C1 ," per ACI (318-14). Based on our previous site work (GSI, 2002b and 2004), the very old paralic deposits are highly cemented and presented excavation difficulties during original earthwork performed at the property. Excavations using relatively lightweight excavation equipment such as backhoes or mini-excavators would likely encountered practical refusal during excavations completed into the very old paralic deposits. Thus, rock breaking equipment, such as a hoe ram, may be necessary to complete the planned excavations as well as the herein recommended remedial excavations. Based on our understanding of the proposed development, excavation difficulty would likely be experienced during the foundation excavation for the retaining wall, along the westerly property line and the fill slope keyway excavation near the southerly property boundary. Additional areas where excavation difficulty could be experienced can be provided following our review of the development plans. GSI recommends that all excavation equipment be properly sized and powered for the required excavation task. If further information pertaining to rock hardness/excavation difficulty, this office could perform a geophysical assay with seismic refraction equipment. It is our understanding that the proposed project includes the installation of a retaining wall near the westerly property line, and adjacent to an existing segmental retaining wall system. To date, GSI has not been provided with any as-built engineering documents pertaining to the construction of the existing segmental retaining wall. Owing to the currently unknown construction and the flexible nature of this retaining wall, GSI recommends that the foundation for the proposed retaining wall extend through any surficial soils and be founded into the underlying very old paralic deposits. The purpose of this recommendation is to reduce the potential for the proposed retaining wall to experience distress. GSI did not observe evidence of a regional groundwater table nor perched water within our subsurface explorations nor during our previous site work (GSI, 2002b and 2004). The regional groundwater table is anticipated to be coincident with sea level or approximately 361 feet below the lowest site elevation. Thus, the regional water table is not anticipated to affect site development. We did encounter relatively thin zones of saturation within the structural fill in our Test Pit TP-2 at approximately 3½ and 4½ feet below the existing grade. This is evidence that perched water conditions may occur during development or in the future, along zones of contrasting permeability and/or density. This potential should be disclosed to all File:e:\wp12\ 7200\7279a.gue GeoSoils, Inc. W.O. 7279-A-SC Pag e Three interested/affected parties. Our findings reflect the groundwater conditions at the time of our investigation and do not preclude future changes in local groundwater conditions from excessive irrigation, precipitation, or that were not obvious, at the time of our study. • On a preliminary basis, temporary slopes should be constru cted in accordance with CAL-OSHA guidelines for Type "B" soils, provided running sands, water, or seepage 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. If the recommended temporary slopes conflict with property lines or existing improvements that need to remain in serviceable use, alternating slot excavations or shoring may be necessary. • Our evaluation indicates that with the exception of moderate to strong ground shaking as a resu lt of a regional earthquake the proposed development has low susceptibility to be adversely affected by geologic and secondary seismic hazards. Site soils are considered erosive. Thus, properly designed and maintained site drainage is necessary in reducing erosion damage to the planned improvements. • The site is subject to moderate to strong ground shaking should an earthquake occur along any of a number of the regional fault systems. The seismic acceleration values and design parameters provided herein should be considered during the design of the proposed development. The adverse effects of seismic shakin g 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 any owners and all interested/affected parties. • On a preliminary basis, the feasibility of stormwater infiltration at the subject site is considered very low, owing to the highly cemented nature of the very old paralic deposits that occur in the near surface. If stormwater were to infiltrate, it would most likely perch upon the very old paralic deposits and migrate laterally. This may have detrimental effects on onsite and offsite improvements, including public and private underground utility trenches. • The recommendations presented in this report should be incorporated into the design and construction considerations of the project. Francis File:e:\wp 12\7200\7279a.pge GeoSoils, Inc. W.O . 7279-A-SC Page Four The opportunity to be of service is sincerely appreciated. If you should have any questions, please do not hesitate to contact our office. hnP ~:i, Engineering Geologist, CEG 1340 RBB/JPF/DWS/jh Distribution: (3) Addressee (2 wet signed) Francis File:e:\wp 12\7200\ 7279a. pge GeoSoils, Inc:. W.O. 7279-A-SC Page Five TABLE OF CONTENTS SCOPE OF SERVICES ................................................... 3 SITE DESCRIPTION AND PROPOSED DEVELOPMENT ......................... 4 PROJECT GEOTECHNICAL BACKGROUND .................................. 5 RECENT FIELD STUDIES ................................................. 5 PHYSIOGRAPHIC AND REGIONAL GEOLOGIC SETTINGS ...................... 6 Physiographic Setting .............................................. 6 Regional Geologic Setting ........................................... 6 SITE GEOLOGIC UNITS .................................................. 8 General .......................................................... 8 Undocumented Artificial Fill (Map Symbol -Afu) .................... 8 Structural Fill (Map Symbol -Afs) ................................ 9 Quaternary Very Old Paralic Deposits (Map Symbol -Qvop) .......... 9 Structural Geology ................................................. 9 GROUNDWATER ........................................................ 9 ROCK HARDNESS/EXCAVATION DIFFICULTY ............................... 10 GEOLOGIC/SEISMIC HAZARDS EVALUATION ............................... 10 UPDATED SEISMICITY .................................................. 11 Deterministic Site Acceleration ...................................... 11 Historical Site Acceleration ......................................... 11 Seismic Shaking Parameters ............................ : ........... 12 LABORATORY TESTING ................................................. 13 Classification ..................................................... 13 Moisture-Density Relations ......................................... 13 Expansion Index .................................................. 13 Saturated Resistivity, pH, and Soluble Sulfates, and Chlorides ............. 14 Corrosion Summary ......................................... 14 PRELIMINARY CONCLUSIONS AND RECOMMENDATIONS .................... 14 EARTHWORK CONSTRUCTION RECOMMENDATIONS ....................... 18 General ......................................................... 18 Site Preparation .................................................. 19 Removal and Recompaction of Potentially Compressible Earth Materials .... 19 Alternating Slot Excavations ........................................ 19 Perimeter Conditions .............................................. 20 GeoSoils, Inc. Overexcavation ................................................... 20 Structural Fill Placement ........................................... 20 Import Soils ...................................................... 20 Graded Slope Construction ......................................... 21 General ................................................... 21 Cut Slopes ................................................. 21 Fill Slopes ................................................. 21 Other Considerations Regarding Graded Slopes .................. 21 Temporary Slopes ................................................ 22 Excavation Observation and Monitoring (All Excavations) ................. 22 Observation ................................................ 23 Earthwork Balance (Shrinkage/Bulking) ............................... 23 PRELIMINARY RECOMMENDATIONS -FOUNDATIONS ....................... 24 General ......................................................... 24 Post-Tensioned Foundation Systems ................................. 25 Slab Subgrade Pre-Soaking ........................................ 26 Perimeter Cut-Off Walls/Beams ...................................... 26 Post-Tensioned Foundation Design .................................. 26 Soil Support Parameters ........................................... 26 PT Foundation Setbacks ........................................... 28 Foundation Settlement ............................................. 28 SOIL MOISTURE TRANSMISSION CONSIDERATIONS ........................ 28 SITE RETAINING WALL DESIGN PARAMETERS .............................. 30 General ......................................................... 30 Conventional Retaining Walls ....................................... 30 Preliminary Retaining Wall Foundation Design .................... 31 Additional Design Considerations .............................. 31 Restrained Walls ............................................ 32 Cantilevered Walls ........................................... 32 Seismic Surcharge ................................................ 33 Retaining Wall Backfill and Drainage .................................. 34 Wall/Retaining Wall Footing Transitions ............................... 34 Slope Creep ..................................................... 38 Top of Slope Walls/Fences ......................................... 38 DRIVEWAY, FLATWORK, AND OTHER IMPROVEMENTS ....................... 39 ONSITE INFILTRATION-RUNOFF RETENTION SYSTEMS ...................... 41 General ......................................................... 41 DEVELOPMENT CRITERIA ............................................... 44 Slope Deformation ................................................ 44 Slope Maintenance and Planting ..................................... 44 Francis File:e:\wp12\7200\7279a.pge GeoSoils, Inc. Table of Contents Page ii Drainage ........................................................ 45 Erosion Control ................................................... 45 Landscape Maintenance ........................................... 45 Gutters and Downspouts ........................................... 46 Subsurface and Surface Water ...................................... 46 Site Improvements ................................................ 46 Tile Flooring ..................................................... 47 Additional Grading ................................................ 47 Footing Trench Excavation ......................................... 47 Trenching(Temporary Construction Backcuts .......................... 47 Utility Trench Backfill .............................................. 48 SUMMARY OF RECOMMENDATIONS REGARDING GEOTECHNICALOBSERVATION AND TESTING ........................................................ 48 OTHER DESIGN PROFESSIONALS/CONSULTANTS .......................... 49 PLAN REVIEW ......................................................... 50 LIMITATIONS .......................................................... 50 FIGURES: Figure 1 -Site Location Map ......................................... 2 Figure 2 -Geotechnical Map ......................................... 4 Detail 1 -Typical Retaining Wall Backfill and Drainage Detail .............. 35 Detail 2 -Retaining Wall Backfill and Subdrain Detail Geotextile Drain ....... 36 Detail 3 -Retaining Wall and Subdrain Detail Clean Sand Backfill ........... 37 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 -General Earthwork, Grading Guidelines, and Preliminary Criteria .................................................. Rear of Text Francis File:e:\wp12\7200\7279a.pge GeoSoils, Inc. Table of Contents Page iii GEOTECHNICAL UPDATE EVALUATION PROPOSED SINGLE-FAMILY RESIDENCE OFF TRITON STREET CARLSBAD, SAN DIEGO COUNTY, CALIFORNIA ASSESSOR'S PARCEL NUMBER (APN) 215-070-51 SCOPE OF SERVICES The scope of our services has included the following: 1. 2. Reviewed existing site-specific geotechnical reports, and readily available published geologic maps of the vicinity (see Appendix A). Conducted site reconnaissance mapping and shallow subsurface exploration by excavating two (2) exploratory test pits and two (2) borings with non-mechanized, manual equipment (see Appendix B). 3. Performed an updated seismic hazards evaluation (see Appendix C). 4. Tested relatively undisturbed and representative bulk soil samples collected during our subsurface exploration program in the laboratory (see Appendix D). 5. Analyzed field and laboratory data relative to the proposed development. 6. Prepared this summary report and accompaniments. SITE DESCRIPTION AND PROPOSED DEVELOPMENT The subject property consists of an existing graded lot, located along the southerly side of Triton Street in Carlsbad, San Diego California (see Figure 1, Site Location Map). The aforementioned lot is situated approximately 165 feet westerly of the intersection of Triton Street and Black Rail Road. The latitude and longitude of the approximate centroid of the site is 33.1124 • and -1 17 .2884 °. The property is bounded by Triton Street to the north, by existing private drives to the east and west and by an undeveloped residential lot to the remaining quadrant. Topographically, the site is situated upon the westerly flank of a northwesterly trending mesa. According to a 10-scale grading plan prepared by Omega Engineering Consultants ([OE]) for a formerly proposed project (OE, 2012), site elevations range between approximately 361 feet and 372 feet (Datum = North American Vertical Datum of 1929 [NGVD29]), for an overall relief of about11 feet. The site is generally flat lying to moderately sloping to the south, west, and north. Existing slopes are on the order of 9 feet high or less with gradients of approximately 2: 1 (horizontal:vertical [h :v]) or flatter. However, recent brush removal has resulted in an approximately 1 foot high vertical slope along the toe of the westerly facing slope. Surface drainage appears to be controlled by sheet flow runoff, primarily directed to the west, north, and south. A temporary storm water detention basin occurs near the northwesterly property corner, which collects some of the site runoff. GeoSoils, Inc. Base Map: TOPO!® ©2003 National Geographic, U.S.G.S. Encinitas Quadrangle, California -- San Diego Co., 7.5 Minute, dated 1997, current, 1999. sale <OI :J!PolnteO ¥ .. \ \ r,, SITE : VIiia Loma Al)llt Triton St.--..__ ~l•~•leod•,. l Base Map: Google Maps, Copyright 2017 Google, Map Data Copyright 2017 Google This map Is copyrighted by Google 2017. It Is unlawful to copy or reproduce 11/ or any p1rt thlreof, whether for personal use or resale, without permission. All rights reserved. N w.o. 7279-A-SC SITE LOCATION MAP Figure 1 Based on communication with the Client and our review of a conceptual site plan you provided, GSI understands that proposed development consists of preparing the lot to receive a two-story single-family residence with associated driveway, retaining wall, and hardscape improvements. We understand that site preparation will include minor cut and fill grading; however, civi l engineering plans showing the proposed graded configuration have not been provided for GSI review. The Client has indicated that grading is intended to increase the area of the building pad by installing an approximately 4-foot high retaining wall along the toe of the westerly facing slope, and constructing a new 2: 1 (h :v) fill slope farther to the south of the current southerly facing slope's position. The latter may require some grading on the adjacent southerly property. GSI anticipates that the proposed residential structure will consists of a wood frame, supported by shallow foundations and a slab-on-grade floor. Building loads are currently unknown, but assumed to be typical for this type of relatively light residential construction. Sanitary sewage disposal is to be connected into the existing municipal system. PROJECT GEOTECHNICAL BACKGROUND In 2002, GSI performed a preliminary geotechnical evaluation of the subject site relative the original subdivision of 6575 Black Rail Road. A summary of this study was provided in GSI (2002b). In January 2004, GSI provided geotechnical observation and testing during grading of the subject lot. GSI (2004) provides a synopsis of our observations and testing during grading. In general, grading of the lot consisted of the removal of all potentially compressible soils to expose the underlying very old paralic deposits (formerly termed "terrace deposits" in GSI [2002b and 2004]). Following the removal of the unsuitable surficial soils, they were cleaned of significant concentrations of organic matter and deleterious debris, moisture conditioned to at least optimum moisture content, and then reused within the lot as structural fill. GSl's field density testing indicated that the fill materials were compacted to at least 90 percent of the laboratory standard (ASTM D 1557). Expansion index testing, performed on a sample of near-finish grade soils indicated a very low expansion potential. Due to the presence of pervasive paleo-liquefaction features identified during field work performed in preparation of GSI (2002b), the use of post-tension foundations were recommended to support any proposed residential structure within the subject lot. RECENT FIELD STUDIES Site-specific field studies were conducted by GSI on April 30, 2017, and consisted of reconnaissance geologic mapping, excavating two (2) shallow exploratory test pits, and advancing two (2) shallow boring. The test pits and borings were completed using non- mechanized, manual equipment, and were logged by a representative of this office. Representative bulk and relatively undisturbed soil samples were collected from the subsurface explorations for appropriate laboratory testing. The logs of the test pits and Francis APN 256-420-55, Carlsbad File:e:\wp12\7200\7249a.pge GeoSoils, Inc. W.O . 7279-A-SC June 9, 201 7 Page 6 1 borings are presented in Appendix B. Site geology and the location of the test pits and borings are shown on the Subsurface Exploration Location Map (see Figure 2), which uses Google Earth imagery as a base. PHYSIOGRAPHIC AND REGIONAL GEOLOGIC SETTINGS Physiographic Setting The site is located in the coastal plain physiographic section 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. Regional Geologic Setting 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 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 Francis APN 256-420-55, Carlsbad File:e:\wp12\7200\7249a.pge GeoSoils, Inc. W.O. 7279-A-SC June 9, 201 7 Page 7 ' Afu Afs Qvop TP-2 ~ HA-2 ® TD=2 ½' GSI LEGEND ARTIFICIAL FILL -UNDOCUMENTED ARTIFICIAL FILL -STRUCTURAL, PLACED UNDER THE PURVIEW OF GS/ (2004), CIRCLED WHERE BURIED QUA TERNARY VERY OLD PARAUC DEPOSITS, CIRCLED WHERE BURIED APPROX/MA TE LOCA 110N OF GEOLOGIC CONTACT, DOTTED WHERE BURIED APPROX/MA TE LOCA 110N OF EXPLORATORY TEST PIT APPROX/MA TE LOCA 110N OF EXPLORATORY HAND-AUGER BORING, WITH TOTAL DEPTH IN FEET NOT A PART OF THIS STUDY ALL LOCATIONS ARE APPROX/MA TE This document or efile is not a parl of the Construction Documents and should not be relied upon as being an accurate depiction of design. ~. GEOTECHNICAL MAP Fiaure2 w.o. 7219-A-SC I DATE: 06/17 I SCALE: 1" = 30' 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 soil residuum, highland areas have eroded, and deposition of river, lake, lagoonal , and beach sediments has occurred. Regional geologic mapping by Kennedy and Tan (2008) indicates that the site is underlain by very old paralic deposits (subunits 10-11), formerly termed "terrace deposits." The very old paralic deposits consist of marine and non-marine sediments deposited on wave cut platforms that emerged from the sea approximately 698,000 to 800,000 years before present. SITE GEOLOGIC UNITS General The earth material units that were observed and/or encountered at the subject site consist of localized undocumented fill, structural fill placed under the purview of GSI (2004), and Quaternary-age very old paralic deposits. A general description of each material type is presented as follows, from youngest to oldest. The general distribution of these materials across the site is presented on Figure 2. Undocumented Artificial Fill (Map Symbol -Afu) Undocumented fill was encountered at the surface in Test Pits TP-1 and TP-2, and in Hand-Auger Boring HA-2. It is the opinion of GSI that the undocumented fill was placed on the subject property, following the original rough grading. The undocumented fill in Test Pit TP-1 appears to be associated with the construction of the nearby driveway and segmental retaining wall. The undocumented fill in Hand-Auger Boring HA-2 may be associated with the repair of a surficial failure on the westerly facing fill slope. The undocumented fill observed in Test Pit TP-2 may be associated with the remnants of stockpiled materials. As observed, the undocumented fill primarily consisted of grayish brown and dark grayish silty sand with localized abundant ¾-inch gravel (TP-1) and trace asphaltic concrete and angular, cobble-sized rock fragments (TP-2). The undocumented fill also consisted of gray clayey sand (HA-2). In general, the undocumented fill was dry and loose to medium dense. The thickness of the undocumented fill encountered in our subsurface explorations was on the order of 213 foot to 1 foot. The undocumented fill is considered unsuitable for the support of the proposed improvements and engineered fills in its existing state. Francis APN 256-420-55, Carlsbad File:e:\wp12\7200\7249a.pge GeoSoils, Inc. W.O. 7279-A-SC June 9, 2017 Page 9 Structural Fill (Map Symbol -Afs) Structural fill, placed under the purview of GSI (2004), was encountered beneath the undocumented fill in Test Pits TP-1, TP-2, and HA-2, and at the surface in HA-1 . As observed therein, the structural fill consisted of dark yellowish brown, brown, and reddish yellow clayey sand and a mixture of dark brown, gray, and reddish yellow silty sand with trace clay and sandy clay. The structural fill locally contained trace fragments of reddish yellow and gray sandstone and trace rounded pebbles and cobbles. In general, the structural fill was dry to moist with localized zones of saturation, and medium dense to dense. Based on our review of current subsurface data and GSI (2004), the thickness of the structural fill within the subject property is on the order of 1 ½ to 11 feet. However, within the building pad area of the subject property, the thickness of the structural fill generally ranges between approximately 5 and 11 feet. The upper approximately 1 ½ feet of the structural fill in the vicinity of Hand-Auger Boring HA-1 will require some reprocessing, owing to weathering, to restore consistency. Quaternary Very Old Paralic Deposits (Map Symbol -Qvop) Quaternary very old paralic deposits were encountered underlying the surficial earth materials in the test pits and in Hand-Auger Boring HA-1 . The very old paralic deposits consisted of a reddish yellow and gray, very fine-to fine-grained sandstone. The very old paralic deposits were typically dry and very dense. Based on observations during our recent site investigation and during the original rough grading of the subject lot, the very old paralic deposits are highly cemented. Based on the recent subsurface data and a review of GSI (2004), the very old paralic deposits occur at depths on the order of 1 ½ and 11 feet below the existing grade, within the subject property. Structural Geology Regionally, the very old paralic deposits generally exhibit relatively thick, subhorizontal bedding. Adverse geologic structures that would preclude project feasibility were not observed or encountered during our recent or previous field work. GROUNDWATER GSI did not observe evidence of a regional groundwater table nor perched water within our subsurface explorations nor during our previous site work (GSI , 2002b and 2004). The regional groundwater table is anticipated to be coincident with sea level or approximately 361 feet below the lowest site elevation. Thus, the regional water table is not anticipated to affect site development. Our findings reflect the groundwater conditions at the time of our investigation and do not preclude future changes in local groundwater conditions from excessive irrigation, precipitation, or that were not obvious, at the time of our study. Francis APN 256-420-55, Carlsbad File:e:\wp12\7200\7249a.pge GeoSoils, Inc. W.O. 7279-A-SC June 9 , 2017 Page 1 o Seeps, springs, or other indications of subsurface water were not noted on the subject property during the time of our recent field investigation. However, we did observe minor saturated zones within Test Pit TP-2 at approximately 3½ and 4½ feet below the existing grades. This is evidence that perched water conditions can develop as the result of heavy precipitation and/or irrigation, or damaged wet utilities. Perched water conditions typically develop along zones of contrasting permeabilities/densities (i.e., fill/very old paralic deposit contacts, sandy/clayey fill lifts, etc.) or along geologic discontinuities. This potential should be anticipated and disclosed to all interested/affected parties. Due to the potential for post-development perched water to manifest near the surface, owing to as-graded permeability/density contrasts, more onerous slab design is necessary for any new slab-on-grade floor (State of California, 2017). 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 Based on our recent and previous observations, the very old paralic deposits are highly cemented and will likely present excavation difficulty for trenching equipment. The need for rock breaking equipment (i.e., hoe ram) should be anticipated, especially during foundation excavation for the proposed retaining along the westerly property line or the keyway excavation along the southerly property boundary. All excavation equipment should be appropriately sized and powered for the required excavation task. If more data pertaining to the excavation characteristics of the onsite earth materials is necessary, this office can perform seismic refraction(rock hardness) surveys. GEOLOGIC/SEISMIC HAZARDS EVALUATION Geologic/seismic hazard were previously addressed in GSI (2002b). Based on our review, other than the potential for the site to experience moderate to strong ground shaking in the event of an earthquake, the susceptibility of the site to other geologic/seismic hazards is relatively low. The occurrence of localized undocumented fill along the westerly facing fill slope is possible evidence that this slope experienced a surficial failure following its original construction. If a slope failure occurred, it was likely the result of unattended, poor surface drainage. Provided, that the recommendations contained herein are incorporated into project design and construction, the recurrence of failure is considered relatively low. Francis APN 256-420-55, Carlsbad File:e:\wp 12\7200\7249a.pge GeoSoils, Inc. W .O. 7279-A-SC June 9, 201 7 Page 11 UPDATED SEISMICITY The subject site is situated in a region subject to periodic earthquakes along active faults . According to Blake (2000a), the Rose Canyon fault is the closest known active fault to the site (located at a distance of approximately 5.6 miles [9.0 kilometers]) and should have the greatest effect on the site in the form of strong ground shaking, should the design earthquake occur. Cao, et al. (2003) indicate the slip rate on the Rose Canyon fault is 1.5 (±0.5) millimeters per year (mm/yr), and the fault is capable of a maximum magnitude 7.2 earthquake. The location of the Rose Canyon fault and other major faults within 100 kilometers of 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. Deterministic Site Acceleration 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. Site acceleration (g) was computed by one user-selected acceleration-attenuation relation that is contained in EQFAUL T. Based on the EQFAULT program, a peak horizontal ground acceleration from an upper-bound event on the Rose Canyon fault may be on the order of 0.60 g. The computer printouts of pertinent portions of the EQFAULT program are included within Appendix C. Historical Site Acceleration 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 December 15, 2016). This program performs a search of the historical earthquake records for magnitude 5.0 to 9.0 seismic events within a 1 GO-kilometer radius, between the years 1800 through December 15, 2016. Based on the selected acceleration-attenuation relationship, a peak horizontal ground acceleration is estimated, which may have affected the site during the specific time frame. Based on the available data and the attenuation relationship used, the estimated maximum (peak) site acceleration during the period 1800 through December 15, 2016 was about 0.34 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. Francis APN 256-420-55, Carlsbad File:e:\wp 12\7200\7249a.pge GeoSoils, Inc. W.O. 7279-A-SC June 9, 2017 Page 12 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 computer program "U.S. Seismic Design Maps, provided by the United States Geological Survey (2014) was utilized for design. The short spectral response utilizes a period of 0.2 seconds. 2016 CBC SEISMIC DESIGN PARAMETERS PARAMETER VALUE 2016 CBC AND/OR REFERENCE Site Class D Section 1613.3.2/ASCE 7-10 (Chapter 20) Spectral Response -(0.2 sec), s. 1.091 g Figure 1613.3.1 (1) Spectral Response -(1 sec), S1 0.421 g Figure 1613.3.1 (2) Site Coefficient, F. 1.064 Table 1613.3.3(1) Site Coefficient, F. 1.579 Table1613.3.3(2) Maximum Considered Earthquake Spectral 1.160g Section 1613.3.3 Response Acceleration (0.2 sec), SMs (Eqn 16-37) Maximum Considered Earthquake Spectral 0.664 g Section 1613.3.3 Response Acceleration (1 sec), SM, (Eqn 16-38) 5% Damped Design Spectral Response 0.774 g Section 1613.3.4 Acceleration (0.2 sec), S05 (Eqn 16-39) 5% Damped Design Spectral Response 0.443 g Section 1613.3.4 Acceleration (1 sec), S0 1 (Eqn 16-40) PGA., 0.459 g ASCE 7-10 (Eqn 11.8.1) Seismic Design Category D Section 1613.3.5/ASCE 7-10 {Table 11.6-1 or 11.6-2) GENERAL SEISMIC PARAMETERS PARAMETER VALUE Distance to Seismic Source (Rose Canyon fault) 5.6 mi (9.0 km)<'> Upper Bound Earthquake (Rose Canyon fault) Mw = 7.2<2> I 111 -Blake (2000a) : 12> -Cao, et al. (2003) I 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 Francis APN 256-420-55, Carlsbad File:e:\wp1 2\7200\7249a.pge GeoSoils, Inc. W.O. 7279-A-SC June 9, 2017 Page 13 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. LABORATORY TESTING Laboratory tests were performed on representative 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. Classification Soils were visually classified with respect to the Unified Soil Classification System (U.S.C.S.) in general accordance with ASTM D 2487 and D 2488. The soil classifications of the onsite soils are provided on the Test Pit and Hand-Auger Boring Logs 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 Test Pit and Hand-Auger Boring Logs in Appendix B. Expansion Index A representative sample of near-surface site soils was evaluated for expansion potential. Expansion Index (E.1.) testing and expansion potential classification was 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) TP-1 @ 1-3 & TP-2@1-3½ (Composite) Francis APN 256-420-55, Carlsbad File:e:\wp 12\7200\7249a.pge EXPANSION INDEX <5 GeoSoils, Inc. EXPANSION POTENTIAL Very Low W.O. 7279-A-SC June 9, 2017 Page 14 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) TP-1 @ 1-3 & 6.91 1,600 0.0315 76 TP-2@ 1-3½ (Composite) Corrosion Summary Laboratory testing indicates that tested samples of the onsite soils are neutral with respect to soil acidity/alkalinity; are corrosive to exposed, buried metals when saturated; present negligible ("not applicable" or "SO" per American Concrete Institute [ACI] 318-14) sulfate exposure to concrete; and contain relatively low concentrations of soluble chlorides. GSI does not consult in the field of corrosion engineering. Thus, consultation from a qualified corrosion consultant may be considered based on the level of corrosion protection required for the project, as determined by the Project Architect, Structural Engineer, Civil Engineer, and Plumbing/Mechanical Engineers. On a preliminary basis, site soils are classified as "SO," "WO," and "C1 ," per ACI (318-14). PRELIMINARY CONCLUSIONS AND RECOMMENDATIONS Based on a review of our previous site work (GSI, 2002b and 2004), and our recent 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: • The presence of undocumented fills and the depth to competent bearing material below the existing grades. • The presence of paleoliquefaction features within the very old paralic deposits, necessitating special foundation design for the proposed residential structure. • On-going expansion and corrosion potential of site soils. Francis APN 256-420-55, Carlsbad File:e:\wp 12\7200\7249a.pge GeoSoils, Inc. W.O. 7279-A-SC June 9, 2017 Page 15 • • • • • • • • • The highly cemented nature of the very old paralic deposits and its effect on planned excavations for retaining wall foundations or underground utilities. The proximity of a flexible retaining wall adjacent to the westerly property line and its effects on the proposed development. Erosiveness of site earth materials . Potential for perched water during and following site development. Perimeter conditions and planned improvements near the property boundary . Uniform support of building and retaining wall foundations . Excavations adjacent to existing improvements to remain in serviceable use . Temporary slope stability . Regional seismic activity . 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. 1. 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 . 2. 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 . 3. Undocumented artificial fill , weathered structural fills, and weathered very old paralic deposits are considered unsuitable for the support of the planned settlement- sensitive improvements (i.e., foundations, new slab-on-grade floors, walls, exterior hardscape, etc.) and new planned fills. Unsuitable soils within the influence of planned settlement-sensitive improvements and planned fill should be removed to expose unweathered very old paralic deposits and then be reused as properly engineered fill. Based on the available subsurface data, remedial grading excavations are anticipated to extend to depths of approximately 1 feet to 1 ½ feet below existing grades. However, locally deeper remedial grading excavations cannot be precluded and should be anticipated. Francis APN 256-420-55, Carlsbad File:e:\wp12\7200\7249a.pge GeoSoils, Inc. W.O. 7279-A-SC June 9, 2017 Page 16 4. In GSI (2002b and 2004), we identified paleoliquefaction features within the very old paralic deposits. These features are artifacts of ancient seismically-induced liquefaction, occurring prior to lithification of the very old paralic deposits, and do not present a current secondary seismic risk to the proposed development. However, due to density/permeability contrasts between these features and the intact very old paralic deposits, these features can act as conduits for subsurface water which could result in piping of fines and low magnitude settlement. Similar to GSI (2002b and 2004), we are recommending the use of post-tensioned (PT) foundations for support of the proposed residential structure. 5. Expansion Index (E.I.) testing performed on a representative sample of near-finish grade soils performed at the conclusion of original grading (GSI, 2004) and this study, indicates very low expansive conditions (E.I. < 5). On a preliminary basis, the onsite soils are considered non-detrimentally expansive and do not warrant special foundation design to resist the damaging shrink/swell effects of expansive soils. 6. Corrosion testing performed on a representative sample of the onsite soils in conjuction with this update indicates site soils are neutral with respect to soil acidity/alkalinity; are corrosive to exposed, buried metals when saturated; present negligible ("not applicable" or "SO" per American Concrete Institute [ACI] 318-14) sulfate exposure to concrete; and contain non-detectable to relatively low concentrations of soluble chlorides. GSI does not consult in the field of corrosion engineering. Thus, consultation from a qualified corrosion consultant may be considered based on the level of corrosion protection required for the project, as determined by the Project Architect, Structural Engineer, Civil Engineer, and Plumbing/Mechanical Engineers. On a preliminary basis, site soils are classified as "SO," "WO," and "C1 ," per ACI (318-14). 7. Based on our past and recent site work, it is our opinion that the highly cemented nature of the unweathered very old paralic deposits will present excavation difficulties for any planned excavation extending into this earth material, especially if relatively light excavation equipment (i.e., mini-excavator or rubber-tire backhoe). Thus, rock breaking equipment such as a hoe-ram may be necessary to achieve planned excavation depths. Based on our current understanding of the proposed development and the recommendations contained herein, such equipment would likely be warranted to excavate the foundation for the proposed retaining wall along the westerly property line as well as the keyway for the new fill slope along the southerly property line. 8. A segmental retaining wall occurs near the westerly property line. This type of wall system is flexible and subject to movement, which can lead to deformations within the backfilled area. To date, GSI has not been provided with engineering documents presenting the as-built condition of this wall. Thus, in order to reduce the potential for the proposed retaining wall along the westerly property line to Francis APN 256-420-55, Carlsbad File:e:\wp12\7200\7249a.pge GeoSoils, Inc. W .O. 7279-A-SC June 9, 201 7 Page 17 experience settlement and distress, GSI recommends that the proposed retaining wall foundation extend through the surficial fill materials and be founded into the underlying very old paralic deposits. Geogrid reinforcements associated with the existing segmental wall should not be disturbed by the construction of the proposed retaining wall. 9. Site soils are considered erosive. Surface drainage should be designed to eliminate the potential for concentrated flows, especially near slopes. Positive surface drainage away from foundations is recommended. Temporary erosion control measures should be implemented until vegetative covering is well established. The homeowner(s) will need to maintain proper surface drainage over the life of the project. 10. No evidence of a high regional groundwater table nor perched water was observed during our subsurface exploration within the property. However, minor zones of saturated existing structural fill were observed at approximately 3½ and 4½ feet below the existing grades in Test Pit TP-2. Due to the nature of site earth materials, there is a potential for perched water to occur both during and following site development. This potential should be disclosed to all interested/affected parties. Should perched water conditions be encountered, this office could provide recommendations for mitigation. Typical mitigation includes subdrainage system, cut-off barriers, etc. 11. The removal and recompaction of potentially compressible soils below a 1 :1 (h:v) projection down from the bottom outside of planned settlement-sensitive improvements and fill along the perimeter of the site will be limited due to boundary restrictions. As such, any settlement-sensitive improvement located above a 1 :1 (h:v) projection from the bottom outboard edge of the remedial grading excavation at the property line would require deepened foundations below this plane, additional reinforcement, or would retain some potential for distress and therefore, a reduced serviceable life. On a preliminary basis, any planned settlement-sensitive improvements located within approximately 1 foot to 1 ½ feet from the property lines would require deepened foundations or additional reinforcement by means of ground improvement or specific structural design. Otherwise, these improvements would retain a potential to exhibit distress. This should be considered during project design. Owing to boundary restrictions and the proximity of a segmental retaining wall, it is recommended that the foundation for the proposed retaining wall, along the westerly property line, extend through the surficial earth materials and be founded in . 12. On a preliminary basis, temporary slopes should be constructed in accordance with CAL-OSHA guidelines for Type "B" soils (i.e., 1 :1 [h:v] slope), provided running sands, water, or seepage is 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 Francis APN 256-420-55, Carlsbad File:e:\wp12\7200\7249a.pge GeoSoils, Inc. W.O. 7279-A-SC June 9, 2017 Page 18 use of shoring. If the recommended temporary slopes conflict with property lines or existing improvements that need to remain in serviceable use, alternating slot excavations or shoring may be necessary. 13. The site is subject to moderate to strong ground shaking should an earthquake occur along any of a number of the regional fault systems. 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 any owners and all interested/affected parties. 14. On a preliminary basis, the feasibility of stormwater infiltration at the subject site is considered very low, owing to the dense and highly cemented nature of the very old paralic deposits that occur in the near surface. If stormwater were to infiltrate, it would most likely perch upon the very old paralic deposits and migrate laterally. This may have detrimental effects on onsite and offsite improvements, including utility trench backfill, and may cause distress to such. 15. General Earthwork and Grading Guidelines are provided at the end of this report as Appendix E. Specific recommendations are provided below. EARTHWORK CONSTRUCTION RECOMMENDATIONS General All earthwork should conform to the guidelines presented in the 2016 CBC (CBSC, 2016), the requirements of the City of Carlsbad, and the General Earthwork and Grading Guidelines presented in Appendix E, except where specifically superceded in the text of this report. Prior to earthwork, a GSI representative should be present at the preconstruction 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 Francis APN 256-420-55, Carlsbad File:e:\wp 12\7200\ 7249a.pge GeoSoils, Inc. W.O. 7279-A-SC June 9, 2017 Page 19 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. Site Preparation All 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 very old paralic deposits 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). Removal and Recompaction of Potentially Compressible Earth Materials Potentially compressible undocumented fill, weathered structural fill, and weathered very old paralic deposits should be removed to expose either unweathered old paralic deposits. This includes the undocumented fill exposed along the westerly facing slope, if not removed during the construction of the backcutforthe proposed retaining wall in this area. The removed soils may be reused as structural fill , provided that it is cleaned of any organic matter and deleterious debris. Based on the available subsurface data, excavations necessary to remove unsuitable soils are anticipated to range between approximately 1 and 1 ½ feet below existing grades. The potential to encounter localized thicker sections of unsuitable soils that require deeper remedial grading excavations, than stated above, cannot be precluded and should be anticipated. Potentially compressible soils should be removed below a 1 :1 (h:v) projection down from the bottom, outboard edge of any settlement-sensitive improvement or limits of planned fill where not limited by property lines and existing improvements that need to remain in serviceable use. Remedial grading excavations should be observed by the geotechnical consultant prior to scarification and fill placement. Once observed and approved, the bottom of the remedial grading excavation should be scarified at least 6 to 8 inches, moisture conditioned to at leastthe soil's optimum moisture content, and then recompacted to a minimum 90 percent of the laboratory standard (ASTM D 1557). Alternating Slot Excavations Alternating (A, B, and C) slot excavations should be performed when conducting remedial earthwork adjacent to property lines and existing improvements that need to remain in serviceable use so as to not cause damage to offsite property or improvements. 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 12 feet of approved engineered fill or undisturbed soils. Francis APN 256-420-55, Carlsbad File:e:\wp 12\7200\7249a.pge GeoSoils, Inc. W .O. 7279-A-SC June 9, 2017 Page 20 Perimeter Conditions It should be noted that the 2016 CBC (CBSC, 2016) indicates that removals of unsuitable soils be performed across all areas to be graded, under the purview of the grading permit, not just within the influence of the proposed residential structure. 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 on site or offsite. In general, any planned improvement located above a 1: 1 (h:v) projection up from the bottom, outboard edge of the remedial grading excavation at the property boundary would be affected by perimeter conditions. On a preliminary basis, any planned settlement-sensitive improvements located within approximately 1 feet and 1 ½ feet from the property lines would require deepened foundations or additional reinforcement by means of ground improvement or specific structural design, for perimeter conditions discussed above. Otherwise these improvements may be subject to distress and a reduced serviceable life span. This will also require proper disclosure to any owners and all interested/affected parties should this condition exist at the conclusion of grading. Overexcavation Due to the thickness of the existing structural fill within the lot, overexcavation to mitigate fill/very old paralic deposit transitions or unbalanced structural fill thicknesses is not anticipated. Structural 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 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). Field density testing should be performed by the geotechnical consultant during structural fill placement. Keyways should be provided at the toes of all proposed fill slopes. Owing to the relatively small height of the proposed fill slopes, the keyway excavations should have a minimum width of 8 feet and extend at least 1 foot into unweathered very old paralic deposits along the toe. The bottom of the keyway should slope toward the heel (minimum 2 percent slope). Benching should be provided on all surfaces steeper than 5:1 (h:v) prior to fill placement. 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 Francis APN 256-420-55, Carlsbad File:e:\wp12\7200\ 7249a.pge GeoSoils, Inc. W.0. 7279-A-SC June 9, 201 7 Page 21 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.I. less than 21 and plasticity index [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. Graded Slope Construction General Graded cut and fill slopes are anticipated to be grossly and surficially stable provided the recommendations contained herein are properly implemented during construction and homeowner maintenance plans. Our opinion regarding graded slope stability assumes proper slope construction, normal rainfall , adequate vegetative covering, positive drainage away from the tops of slopes, and periodic maintenance by the homeowner(s) over the life of the project. Cut Slopes Cut slopes are not currently proposed. Fill Slopes Graded fill slopes should be properly keyed and benched, and be compacted to at least 90 percent relative compaction throughout, including the slope face. Compaction at the slope face may be achieved by either overbuilding and trimming back fill slopes or back-rolling fill slopes with compaction equipment every 4 vertical feet. Fill materials used in fill slope construction should have a minimum cohesion (C) of 200 and a minimum friction angle (cp) of 29 degrees. This may require some blending of the onsite materials or the use of import. If not removed during the construction of the backcut for the proposed retaining wall along the westerly property line, the undocumented fill along portions of the existing westerly facing fill slope should be removed. The slope should then be rebuilt to gradients no steeper than 2: 1 (h:v). Benching into suitable structural fills should be undertaken during slope reconstruction. The minimum height and width of the benches should be 2 and 4 feet, respectively. If the proposed retain ing wall along the toe of the westerly facing fill slope will not be constructed, the removed areas of the toe of this slope should be restored, following the remedial earthwork recommendations previously provided. Other Considerations Regarding Graded Slopes • Graded slopes should receive a deep-rooted, drought tolerant vegetative covering immediately following construction. In the interim between construction and the Francis APN 256-420-55, Carlsbad File:e:\wp12\7200\7249a.pge GeoSoils, Inc. W.O. 7279-A-SC June 9, 2017 Page 22 • • • establishment of landscape cover, the graded slopes should receive City-approved erosion control devices. The owner should consider the use of drip-system irrigation with moisture sensors on all graded slopes. Surface drainage should be directed away from the tops of graded slopes . Conveyance of surface runoff along the toe of slopes should be avoided or transported in lined swales or through piping. Storage or infiltration of surface runoff along the toe of slopes should be avoided. The homeowner should periodically review the condition of graded slopes and correct any deficiencies as soon as possible. If requested, this office can provide additional consultation regarding the maintenance of graded slopes. Temporary Slopes Temporary slopes for excavations greater than 4 feet, but less than 20 feet in overall height should conform to CAL-OSHA and/or OSHA requirements for Type "B" soils, provided water or seepage and/or running sands are not present. Temporary slopes, up to a maximum height of ±20 feet, may be excavated at a 1: 1 (h:v) gradient, or flatter, provided groundwater and/or running sands are not exposed. Construction materials or soil stockpiles should not be placed 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 may be necessary if adverse conditions are observed. If adverse conditions are exposed or if temporary slopes conflict with property boundaries, or existing improvements that need to remain in serviceable use, shoring or alternating slot excavations may be necessary. The need for shoring or alternating slot excavations could be further evaluated during the grading plan review stage and during site earthwork. 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 obseNations 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. Francis APN 256-420-55, Carlsbad File:e:\wp12\7200\7249a.pge GeoSoils, Inc. W.O. 7279-A-SC June 9, 201 7 Page 23 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. These points 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 su rv ey 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 constru ction below ground has been completed and the perm anent 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. Pre-construction notes should be made and photographs or video recordings 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 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 observati on. Earthwork Balance (Shrinkage/Bulking) The volume change of excavated materials upon compaction as engineered fill is anti cipated to vary with material type and location. The overall earthwork shrinkage and bulking may be approximated by using the following parameters: Undocumented Fill and Weathered Structural Fill . . . . . . . . . . . . 10% to 20% shrinkage Weathered Very Old Paralic Deposits ................ 2% to 3% shrinkage or bulking Unweathered Very Old Paralic Deposits . . . . . . . . . . . . . . . . . . . . . . . . 2% to 3% bulking Francis APN 256-420-55, Carlsbad File:e:\wp 12\7200\7249a.pge GeoSoils, Inc. W.O. 7279-A-SC June 9, 2017 Page 24 It should be noted that the above factors are estimates only, based on preliminary data. The undocumented fill, weathered structural fill, and weathered very old paralic deposits may achieve higher shrinkage if organics or clay content is higher than anticipated, if a high degree of porosity is encountered, or if compaction averages more than 92 percent of the laboratory standard (ASTM D 1557). In addition, due to extensive rodent burrowing, higher shrinkage may be encountered. 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. PRELIMINARY RECOMMENDATIONS -FOUNDATIONS General Preliminary recommendations for foundation design and construction are provided in the following sections. These preliminary recommendations have been developed from our understanding of the currently planned site development and our review of previous site work (GSI, 2002b and 2004). In addition, these recommendations have been developed from our recent site observations, subsurface exploration, laboratory testing, and engineering analyses. Foundation design should be re-evaluated at the conclusion of site grading/remedial earthwork for the as-graded soil conditions. Although not anticipated, revisions to these recommendations may be necessary. 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 residence 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. The information and recommendations presented in this section are not meant to supercede design by the project structural engineer or civil engineer specializing in structural design. Upon request, GSI could provide additional input/consultation regarding soil parameters, as they relate to foundation design. The preliminary geotechnical data indicates the subject site is underlain by very low expansive soils (E.1. of 20 or less) and a P.I. less than 15. As indicated in GSI (2002b and 2004), we identified the presence of paleoliquefaction features within the very old paralic deposits. These features are the product of ancient seismically-induced liquefaction, occurring prior to lithification of the very old paralic deposits, and do not present a current secondary seismic risk to the proposed development. However, due to density/permeability contrasts between these features and the intact very old paralic deposits, these features can act as conduits for subsurface water which could result in piping of fines and low magnitude settlement. Thus, we recommended the use of post- tensioned (PT) foundations in GSI (2002a and 2004) for support of residential structures. Updated recommendations for PT slab foundations underlain by very low to low expansive Francis APN 256-420-55, Carlsbad File:e:\wp 12\7200\ 7249a.pge GeoSoils, Inc. W.0. 7279-A-SC June 9, 201 7 Page 25 soil conditions are provided herein. Foundations for the residential structure should be supported by approved structural fill observed and tested by this office. Post-Tensioned Foundation S stems Post-tensioned (PT) foundations should be used to support the proposed residential structure, owing to the presence of paleoliquefaction features within the very old paralic deposits. The PT foundation designer may elect to exceed the minimal recommendations, provided herein, to increase slab stiffness performance. Post-tension (PT) foundation 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 UTE typically uses a single perimeter g rade 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 post-tensioned design. Post-tensioned foundations should be designed using sound engineering practice and be in accord ance with local and 2016 CBC requirements. Upon request, GSI can provide additional data/consultation regarding soil parameters as related to post-tensioned foundation design. From a soil expansion/shrinkage standpoint, a common contributing factor to distress of structures using post-tensioned 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 thei r 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, post-tensioned 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 post-tensioned 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 post-tension slab construction. Th is effectively reduces soil moisture migration from the area located outside the building toward the soils underlying the post-tension slab. Perimeter cut-off walls are thickened edges of the concrete slab that impedes both outward and inward soil moisture migration. Francis APN 256-420-55, Carlsbad File:e:\wp 12\7200\7249a.pge GeoSoils, Inc. W.O. 7279-A-SC June 9, 2017 Page 26 Slab Subgrade Pre-Soaking Specific geotechnical testing to evaluate the pre-moistening of the slab subgrade soil is not required for very low to low expansive soil conditions. However, the contractor should pre- moisten the slab subgrade to a depth of 12 inches prior to the placement of the slab underlayment section. Perimeter Cut-Off Walls/Beams Perimeter cut-off walls/beams should be at least 12 inches deep for very low to low expansive soil conditions. The cut-off walls/beams should be integrated into the slab design. The cut-off walls/beams should be a minimum of 6 inches thick (wide). The bottom of the perimeter cut-off wall/beam should be designed to resist tension, using cable or reinforcement per the structural engineer. Post-Tensioned Foundation Design The following recommendations for design of post-tensioned 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 and errata (PTI ; 2008, 2012, 2013, and 2014). Soil Support Parameters The recommendations for soil support parameters have been provided based on the typical soil index properties for soils that are very low to low 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 following grading, and prior to foundation construction to further evaluate the expansive properties of the finish grade soils. The following table presents suggested minimum coefficients to be used in the Post-Tensioning Institute 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 Plasticity Index (P.I.)* 15-25 Francis APN 256-420-55, Carlsbad File:e:\wp12\7200\7249a.pge GeoSoils, Inc. W.O. 7279-A-SC June 9, 2017 Page 27 Based on the above, the recommended soil support parameters are tabulated below: DESIGN PARAMETERS VERY LOW TO LOW EXPANSION (E.I. = 0-50) em center lift 9.0 feet em edge lift 5.2 feet Ym center lift 0.4 inches Ym edge lift 0.7 inch Bearing Value (1l 1,000 psf Lateral Pressure 250 psf Coefficient of Friction 0.35 (multiplied by the dead load) Subgrade Modulus (k) 1 00 pci/inch Minimum Perimeter 12 inches Footing Embedment (2> Minimum Slab Thickness 5 inches (1> 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. (2> As measured below the lowest adjacent compacted subgrade surface without landscape layer or sand underlayment. Note: The use of open bottomed raised planters adjacent to foundations will require more onerous design oarameters. The parameters are considered minimums and may not be adequate to represent all expansive soils and site conditions such as adverse drainage and/or improper landscaping and maintenance. The above parameters are applicable provided the structure has positive drainage that is maintained away from the structure. In addition, no trees with signifi cant root systems are to be planted within 15 feet of the perimeter of foundations. Therefore, it is important that information regarding drainage, site maintenance, trees, settlements, and effects of expansive soils be passed on to future all interested/affected parties. The values tabulated above may not be appropriate to account for possible differential settlement of the slab due to other factors, such as excessive settlements. If a stiffer slab is desired, alternative Post-Tensioning Institute ([PTI] third edition) parameters may be recommended. All exterior columns not supported by the post-tensioned foundation should be supported by 24 square inch isolated footings extending at least 24 in ches into approved engineered fill. Exterior column footings should be tied to the post-tensioned foundation with 12 square inch, reinforced grade beams in at least one direction. Francis APN 256-420-55, Carlsbad File:e:\wp12\7200\7249a.pge GeoSoils, Inc. W.O. 7279-A-SC June 9, 2017 Page 28 PT Foundation Setbacks 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, outboard edge of the perimeter beam to the slope face. Foundations should also extend below a 1 :1 (h:v) projection up from the bottom outside edge of remedial grading excavations. Foundation Settlement Provided that the earthwork and foundation recommendations in this report are adhered, foundations bearing on approved engineered fill overlying dense unweathered very old paralic deposits should be minimally designed to accommodate a total settlement of 1 ½ inches and a differential settlement of ¾-inch over a 40-foot horizontal span (angular distortion = 1 /640). SOIL MOISTURE TRANSMISSION CONSIDERATIONS GSI has evaluated the potential for vapor or water transmission through the concrete floor slab, 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. Th e 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, 2017). 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 E.I. test results presented herein, and 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: Francis APN 256-420-55, Carlsbad File:e:\wp 12\7200\7249a.pge GeoSoils, Inc. W.0. 7279-A-SC June 9, 2017 Page 29 • Concrete slabs, including garages, should be thicker than 5 inches. • 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 (i.e., 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 areas, 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 1745), and per code. 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 wil l 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, 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 2-inch sand layer may be omitted provided testing indicates the SE of the slab subgrades soils is greater than or equal to 30. • Concrete should have a maximum water/cement ratio of 0.50. This does not supercede Table 4.3.1 of Chapter 4 of the ACI (2008) for corrosion or other corrosive requirements. 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. • 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 Francis APN 256-420-55, Carlsbad File:e:\wp 12\7200\7249a.pge GeoSoils, Inc. W.O. 7279-A-SC June 9, 201 7 Page 30 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 homeowner 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 manufactures 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 techniq ues. 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. SITE RETAINING WALL DESIGN PARAMETERS General It is our understanding that the project includes the construction of one (1) site retaining wall, near the westerly property boundary. Recommendations for the design and construction of conventional masonry retaining walls are included herein. Recommendationsforspecialtywalls (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 expansion index up to 20 are used to backfill any retaining wall. The type of backfill (i.e., select or native), should be specified by the wall designer, and clearly shown on the plans. It is unlikely that the onsite earth materials qualify as select backfill. This should be considered in the design and construction of site retaining walls. The use of waterproofing should be considered for site retaining walls in order to reduce the potential for efflorescence staining at the face. Francis APN 256-420-55, Carlsbad File:e:\wp12\7200\7249a.pge GeoSoils, Inc. W.0. 7279-A-SC June 9, 2017 Page 31 Preliminary Retaining Wall Foundation Design Preliminary foundation design for retaining walls should incorporate the following recommendations: Minimum Footing Embedment -As previously stated, in order to reduce the potential for retaining wall distress due to deformations occurring within the nearby existing segmental retaining wall system that lacks as-built engineering documentation, GSI recommends that the footing for the proposed retaining wall extend through the surficial earth materials and be founded at least 12 inches into the underlying unweathered very old paralic deposits. Rather than a deepened footing, the wall designer should consider the use of a thickened footing that extends from the planned bottom-of-wall elevation to 12 inches into unweathered very old paralic deposits. This will help to reduce overall wall heights and assist with the wall subdrainage recommended herein. 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 thatthe footing maintains a minimum width of 24 inches and minimally extends at least 12 inches into unweathered very old paralic 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 250 pcf with a maximum earth pressure of 2,500 psf may be used in the preliminary design of retaining wall foundations provided the foundation is embedded into very low expansive, unweathered very old paralic deposits. 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. Backfill Soil Density-Soil densities ranging between 11 0 pcf and 11 5 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 (ASTM D 1557). Additional Design Considerations • Any retaining wall footings near the perimeter of the site will likely need to be deepened into unweathered very old paralic deposits for adequate vertical and lateral bearing support. All retaining wall footing setbacks from slopes should Francis APN 256-420-55, Carlsbad File:e:\wp 12\ 7200\7249a.pge GeoSoils, Inc. W .O. 7279-A-SC June 9, 2017 Page 32 • 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 the slope face. The wall designer should evaluate if the proposed retaining wall would surcharge the existing segmental retaining wall. Should this be the case, the foundation for the proposed retaining wall will need to extend below a 1: 1 (h:v) plane projected up from the heel of the segmental retaining wall. 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 10 feet high. Design parameters for walls less than 3 feet in height may be superceded by County of 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/wall designer should incorporate the surcharge of traffic on the back of retaining walls where vehicular traffic could occur within horizontal distance "H" from the back of the retaining wall (where "H" equals the wall height). The traffic surcharge may be taken as 100 psf/ft in the upper 5 feet of backfill for light truck and cars 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. Equivalent fluid pressures for the design of cantilevered retaining walls are provided in the following table: Francis APN 256-420-55, Carlsbad File:e:\wp 12\ 7200\7249a.pge GeoSoils, Inc. W.O. 7279-A-SC June 9, 201 7 Page 33 SURFACE SLOPE OF EQUIVALENT EQUIVALENT RETAINED MATERIAL FLUID WEIGHT P.C.F. FLUID WEIGHT P.C.F. (HOR IZONTAL:VERTICAL) (SELECT BACKFILL)12> (NATIVE BACKFILL)13l I Level(1) I 38 I 50 I 2 to 1 55 65 (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 .s._ 10% passing No. 200 sieve. (3) E.I. =Oto 50, SE > 30, P.I. < 15, E.I. < 21, and< 15% passing No . 200 sieve. Seismic Surcharge For retaining walls incorporated into th e residence, site retaining walls with more than 6 feet of retained materials as measured vertically from the bottom of the wall footing at the heel to daylight, or retaining walls that could present ingress/egress constraints in the event of failure, GSI recommends that the walls be evaluated for seismic surcharge in general accordance with 2016 CBC requirements. The retaining walls in this category should maintain an overturning Factor-of-Safety (FOS) of approximately 1.25 when the seismic surcharge (increment), is applied. For restrained walls, the seism ic 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. This seismic surcharge pressure (seismic increment) may be taken as 15H where "H" for restrained walls is the dimension previously noted as the height of the backfill to the bottom of the footing. For cantilevered walls, a seismic increment of 15H should be applied as an inverted tri angular pressure distribution from 0.6H from the bottom of the footing to the top of the wall. For the evaluation of the seismic surcharge, the bearing pressure may exceed the static value by one-third, considerin g 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 fi ll soil in the zone of influence from the wall or roughly a 45° -cp/2 plane away from the back of the wall. The 15H seismic surcharge is derived from the formula: Where: H Francis APN 256-420-55, Carlsbad File:e:\wp12\7200\7249a.pge Seismic increment Probabilistic horizontal site acceleration with a percentage of "g" Total unit weight (120 to 125 pcf for site soils@ 95% relative compaction). Height of the wall from the bottom of the footing or point of pile fixity. GeoSoils, Inc. W .0. 7279-A-SC June 9, 2017 Page 34 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. 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. 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 Wal l 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. _., 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 DETAIL Francis APN 256-420-55, Carlsbad File:e:\wp 12\7200\7249a.pge GeoSoils, Inc. W.0. 7279-A-SC June 9, 2017 Page 35 Structural footing or settlement-sensitive improvement (1) Waterproofing membrane ---. CMU or reinforced-concrete wall Proposed grade t- sloped to drain per precise civil drawings ( 5) Weep hole --------~II~~ Provide surf ace drainage via an engineered V-ditch (see civil plans for details) \ 2:1 (h:v) slope Slope or level (2) Gravel -::::::;'Y\ \v,\Y-~\ \.---:---~ .--\ \ \--:::::\_:----\ \ \·::::::::;:.-:----_\ \? (4) Pipe '/(<, 1/\ / Footing and wall / design by others ~,_J-~~~---t 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 // \ \'(\ ?.,'..(;\1/\Y:\ \\{\~,. /,~\ \.,.-\ \ '.::<',/41/.,.-\ \ ,,-\ \ \ Footing and wall design by others ----"-.-1 Structural footing or settlement-sensitive improvement Provide surface drainage via engineered V-ditch (see civil plan details) \ 2:1 (h=v) slope Slope or level (2) Composite drain (4) Pipe ~<, 1/\ / \ 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 fa bric 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 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 B Detail 2 (1) Waterproofing membrane --~ CMU or reinforced-concrete wall ---=t ±12 inches 7- (5) Weep hole H [ Proposed grade sloped to drain per precise civil drawings --(0~\\Y(\\~\1/ Structural footing or settlement-sensitive improvement l r---Provide surf ace drainage \ 2=1 (h: _v_) _sl_op_e _________ _ H/2 minimum I -- Slope or level (8) Native backfill (6) Clean sand backfill Footing and w;;;; -~------- design by others r~~~-~ -1 (3) Filter fabric (2) Gravel ~4)Pipe -1:1 (h:v) or flatter backcut to be properly benched (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. (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 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. TOP-OF-SLOPE WALLS/FENCES/IMPROVEMENTS Slope Creep Although unlikely, some soils at the site may be expansive and therefore, may become desiccated when allowed to dry. Such soils are susceptible to surficial slope creep, especially with seasonal changes in moisture content. Typically in southern California, during the hot and dry summer period, these soils become desiccated and shrink, thereby developing surface cracks. The extent and depth of these shrinkage cracks depend on many factors such as the nature and expansivity of the soils, temperature and humidity, and extraction of moisture from surface soils by plants and roots. When seasonal rains occur, water percolates into the cracks and fissures, causing slope surfaces to expand, with a corresponding loss in soil density and shear strength near the slope surface. With the passage of time and several moisture cycles, the outer 3 to 5 feet of slope materials experience a very slow, but progressive, outward and downward movement, known as slope creep. For slope heights greater than 1 O feet, this creep related soil movement will typically impact all rear yard flatwork and other secondary improvements that are located within about 15 feet from the top of slopes, such as swimming pools, concrete flatwork, etc., and in particular top of slope fences/walls. This influence is normally in the form of detrimental settlement, and tilting of the proposed improvements. The dessication/swelling and creep discussed above continues over the life of the improvements, and generally becomes progressively worse. Accordingly, the developer should provide this information to all interested/affected parties. Top of Slope Walls/Fences Due to the potential for slope creep for slopes higher than about 1 O feet, some settlement and tilting of the walls/fence with the corresponding distresses, should be expected. To mitigate the tilting of top of slope walls/fences, we recommend that the walls/fences be constructed on a combination of grade beam and caisson foundations with creep forces taken into account. The grade beam should be at a minimum of 12 inches by 12 inches in cross-section, supported by drilled caissons, 12 inches minimum in diameter, pl aced at a maximum spacing of 6 feet on center, and with a minimum embedment length of 7 feet Francis APN 256-420-55, Carlsbad File:e:\wp12\7200\7249a.pge GeoSoils, Inc. W .O. 7279-A-SC June 9, 2017 Page 39 below the bottom of the grade beam. The strength of the concrete and grout should be evaluated by the structural engineer of record. The proper ASTM tests for the concrete and mortar should be provided along with the slump quantities. The concrete used should be appropriate to mitigate sulfate corrosion, as warranted. The design of the grade beam and caissons should be in accordance with the recommendations of the project structural engineer, and include the util ization of the following geotechnical parameters: Creep Zone: Creep Load: Point of Fixity: Passive Resistance: Allowable Axial Capacity: Shaft capacity : Tip capacity: 5-foot vertical zone below the slope face and projected upward parallel to the slope face. The creep load projected on the area of the grade beam should be taken as an equivalent fluid approach, having a density of 60 pcf. For the caisson, it should be taken as a uniform 900 pounds per linearfoot of caisson's depth, located above the creep zone. Located a distance of 1.5 times the caisson's diameter, below the creep zone. Passive earth pressure of 300 psf per foot of depth per foot of caisson diameter, to a maximum value of 4,500 psf may be used to determine caisson 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. 350 psf applied below the point of fixity over the surface area of the shaft. 4,000 psf. DRIVEWAY, FLATWORK, AND OTHER IMPROVEMENTS Although not necessarily anticipated, some of the on site soil materials may be 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, it is recommended that the developer should notify any homeowners of this long-term potential for distress. To reduce the likelihood of distress, the following recommendations are presented for all exterior flatwork: Francis APN 256-420-55, Carlsbad File:e:\wp12\7200\7249a.pge GeoSoils, Inc. W.O. 7279-A-SC June 9, 2017 Page 40 1. 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 soi ls' 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. 2. 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. 3. Exterior concrete 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 and pervious pavements, to help impede infiltration of landscape water under the slab. 4. 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; and , b) provide an adequate amount of control 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.I. ~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 3/a inches deep, often enough so that no section is greater than 1 0 feet by 10 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. 5. 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. Francis APN 256-420-55, Carlsbad File:e:\wp 12\7200\7249a.pge GeoSoils, Inc. W.O. 7279-A-SC June 9, 2017 Page 41 6. Driveways, sidewalks, and patio slabs adjacent to the residential structure should be separated from the building with thick expansion joint fi ller 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. 7. Planters and walls should not be tied to the house. 8. 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 1804.3 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 homeowner. 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, su lfate content of soils, corrosion potential of soils, and fertilizers used on site. ONSITE INFILTRATION-RUNOFF RETENTION SYSTEMS General GSI is currently unaware if the proposed project qualifies as a Priority Development Project (PDP). Thus, it is currently unknown if permanent storm water Best Management Practices (BMPs) or Low Impact Development (LID) principles are required. If permanent storm water BMPs/LIDs are mandated by the controlling authorities, some guidelines Francis APN 256-420-55, Carlsbad File:e:\wp12\7200\7249a.pge GeoSoils, Inc. W.O. 7279-A-SC June 9, 2017 Page 42 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. The following geotechnical guidelines should be considered when designing onsite infiltration-runoff retention systems: • • According to the United States Department of Agriculture/National Resources Conservation Service (USDA/NRCS) web soil survey (https://websoilsurvey.sc.egov.usda.gov/App/WebSoilSurvey.aspx), the subject site is underlain by the Chesterton fine sandy loam, 5 to 9 percent slopes. The USDA/NRCS indicates the capacity of the most limiting layer to transmit water is very low (0.00 inches per hour) and the Hydrologic Soil Group (HSG) for this mapped soil unit is "D". HSG D soils are generally not compatible with infiltration facilities. The observed highly cemented nature of the very old paralic deposits corroborates the USDA/NRCS findings. It is our opinion that if an infiltration BMP/LID were to be used for permanent storm water treatment, the infiltrated water would perch upon the very old paralic deposits, and then migrate laterally. This could have damaging repercussions to both onsite and offsite improvements, including private and public underground utilities. Therefore, all storm water treatment should occur within lined bio-retention basins or another type of contained system. Impermeable liners and subdrains should be used along the bottom of bio-retention swales/basins. Impermeable liners should consist of a 30-mil polyvinyl chloride (PVC) membrane with the following properties: Specific Gravity (ASTM D792): 1.2 (g/cc, min.); Tensile (ASTM D882): 73 (lb/in-width, min); Elongation at Break (ASTM D882): 380 (%, min); Modulus (ASTM D882): 30 (lb/in-width, min.); and Tear Strength (ASTM D1004): 8 (lb/in, min); Seam Shear Strength (ASTM D882) 58.4 (lb/in, min); Seam Peel Strength (ASTM D882) 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. • If landscaping is proposed within the bio-retention basin, consideration should be given to the 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 bio-retention basin could adversely affect performance of the system. Francis APN 256-420-55, Carlsbad File:e:\wp12\7200\7249a.pge GeoSoils, Inc. W.O. 7279-A-SC June 9, 2017 Page 43 • Areas adjacent to, or within , the bio-retention basin 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 the bioretention basin and result in down-gradient flooding and scour. • As with any storm water LID/BMP, 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 bio-retention basin. • 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 p1p1ng and/or other subsurface utilities) located within or near the proposed area of the bio-retention basin 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 bio-retention basin, 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 the overlying or adjoining bio-retention basin by geotextiles and/or slurry backfill. • The use of storm water LID/BMPs above existing utilities that might degrade/corrode with the introduction of water/seepage should be avoided. Francis APN 256-420-55, Carlsbad File:e:\wp12\7200\7249a.pge GeoSoils, Inc. W.O. 7279-A-SC June 9, 2017 Page 44 • A vector control program may be necessary as stagnant water contained in the bio- retention basin may attract mammals, birds, and insects that carry pathogens. DEVELOPMENT CRITERIA Slope Deformation Compacted fill slopes designed using customary factors-of-safety for gross or surficial stability and constructed in general accordance with the design specifications should be expected to undergo some differential vertical heave or settlement in combination with differential lateral movement in the out-of-slope direction, after grading. This post-construction movement occurs in two forms: slope creep, and lateral fill extension (LFE). Slope creep is caused by alternate wetting and drying of the fill soils which results in slow downslope movement. Th is type of movement is expected to occur throughout the life of the slope, and is anticipated to potentially affect improvements or structures (e.g., separations and/or cracking), placed near the top-of-slope, up to a maximum distance of approximately 15 feet from the top-of-slope, depending on the slope height. This movement generally results in rotation and differential settlement of improvements located within the creep zone. LFE occurs due to deep wetting from irrigation and rainfall on slopes comprised of expansive materials. Although some movement should be expected, long-term movement from this source may be minimized, but not eliminated, by placing the fill throughout the slope region, wet of the fill 's optimum moisture content. It is generally not practical to attempt to eliminate the effects of either slope creep or LFE. Suitable mitigative measures to reduce the potential of lateral deformation typically include: setback of improvements from the slope faces (per the 2016 CBC), positive structural separations (i.e., joints) between improvements, and stiffening and deepening of foundations. Expansion joints in walls should be placed no greater than 20 feet on-center, and in accordance with the structural engineer's recommendations. All of these measures are recommended for design of structures and improvements. The ramifications of the above conditions, and recommendations for mitigation, should be provided to all interested/affected parties. Slope Maintenance and Planting Water has been shown to weaken the inherent strength of all earth materials. Slope stability is significantly reduced by overly wet conditions. Positive surface drainage away from slopes should be maintained and only the amount of irrigation necessary to sustain plant life should be provided for planted slopes. Over-watering should be avoided as it adversely affects site improvements, and causes perched groundwater conditions. Graded slopes constructed utilizing onsite materials would be erosive. Eroded debris may be minimized and surficial slope stability enhanced by establishing and maintaining a suitable vegetation cover soon after construction. Compaction to the face of fill slopes would tend to minimize short-term erosion until vegetation is established. Plants selected for Francis APN 256-420-55, Carlsbad File:e:\wp12\7200\7249a.pge GeoSoils, Inc. W.O. 7279-A-SC June 9, 2017 Page 45 landscaping should be light weight, deep rooted types that require little water and are capable of surviving the prevailing climate. Jute-type matting or other fibrous covers may aid in allowing the establishment of a sparse plant cover. Utilizing plants other than those recommended above will increase the potential for perched water, staining, mold, etc., to develop. A rodent control program to prevent burrowing should be implemented. Irrigation of natural (ungraded) slope areas is generally not recommended. These recommendations regarding plant type, irrigation practices, and rodent control should be provided to all interested/affected parties. Over-steepening of slopes should be avoided during building construction activities and landscaping. 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 and tops of slopes, and not allowed to pond and/or seep into the ground. In general, finish grade on the property should provide a minimum of 1 to 2 percent fall to the street or other approved areas, or conform to Section 1804.3 of the 2016 CBC (whichever is more conservative). Consideration should be given to avoiding construction of planters adjacent to the residential structure. 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 proposed structures be eliminated for a minimum distance of 10 feet. As an alternative, Francis APN 256-420-55, Carlsbad File:e:\wp1 2\7200\7249a.pge GeoSoils, Inc. W.O. 7279-A -SC June 9, 2017 Page 46 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 structures, 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 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 house, 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, 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 not be constructed without specific design and construction recommendations from GSI, and this construction recommendation should be provided to all interested/affected parties. This office should be notified in advance of any fill placement, grading of the site, Francis APN 256-420-55, Carlsbad File:e:\wp12\7200\7249a.pge GeoSoils, Inc. W.O. 7279-A-SC June 9, 2017 Page 47 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 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 observations is to evaluate that 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 minimally conform to CAL-OSHA, state, and local safety codes. Should adverse conditions exist, appropriate recommendations would be offered at that time. The above recommendations should be provided to any contractors and/or subcontractors, or homeowner(s), etc., that may perform such work. Francis APN 256-420-55, Carlsbad File:e:\wp 12\7200\7249a.pge GeoSoils, Inc. W.O. 7279-A-SC June 9, 2017 Page 48 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. 2. 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. 3. All trench excavations should conform to CAL-OSHA, state, and local safety codes. 4. 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, including remedial grading excavations and trenching for underground utilities, bio-retention basins, etc. • During the placement of structural fill s. • 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. Francis APN 256-420-55, Carlsbad File:e:\wp12\7200\7249a.pge GeoSoils, Inc. W.0. 7279-A-SC June 9, 2017 Page 49 • • • • • • • 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. When any homeowner improvements, such as fl atwork, spas, pools, walls, etc., are constructed, prior to construction. A report of geotechnical observation and testing should be provided 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 Francis APN 256-420-55, Carlsbad File:e:\wp12\7200\7249a.pge GeoSoils, Inc. W.O. 7279-A-SC J une 9, 2017 Page 50 structural engineer/designer resu lt in less critical details than are provided herein as minimums, the minimums presented herein should be adopted. It is considered likely that some, more restrictive details will be required. 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 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. In asmuch 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. Francis APN 256-420-55, Carlsbad File:e:\wp 12\7200\7249a.pge GeoSoils, Inc. W.O. 7279-A-SC June 9, 2017 Page 51 APPENDIX A REFERENCES GeoSoils, Inc. 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, 2014, Supplement No. 2, Minimum design loads for buildings and other structures, ASCE Standard ASCE/SEI 7-10, dated September 18. __ , 2013a, Expanded seismic commentary, minimum design loads for buildings and other structures, ASCE Standard ASCE/SEI 7-10 (included in third printing). __ , 2013b, Errata No. 2, minimum design loads for buildings and other structures, ASCE Standard ASCE/SEI 7-10, dated March 31 . __ , 2013c, Supplement No. 1, minimum design loads for buildings and other structures, ASCE Standard ASCE/SEI 7-10, dated March 31. , 201 Oa, Minimum design loads for buildings and other structures, ASCE Standard ASCE/SEI 7-10. __ , 201 Ob, Structural design of interlocking concrete pavement for municipal streets and roadways, ASCE Standard 58-10. GeoSoils, Inc. 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 December 15, 2016, 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. California Building Standards Commission, 2016, 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. California Department of Water Resources, 1993, Division of Safety of Dams, Guidelines for the design and constructi on of small embankments dams, reprinted January. California Stormwater Quality Association (CASQA), 2003, Stormwater best management practice handbook, new development and redevelopment, dated January. County of San Diego, Department of Planning and Land Use, 2007, Low impact development (LID) handbook, stormwater management strategies, dated December 31 . GeoSoils, Inc., 2004, Final compaction report of grading, Parcels 1 and 3, 6575 Black Rail Road, Carlsbad, San Diego County, California, W.O. 3460-B-SC, dated March 9. , 2002a, Soil corrosivity test results, 6575 Black Rail Road , City of Carlsbad, San Diego County, California, W.O. 3460-A1-SC, dated December 20. , 2002b, Preliminary geotechnical evaluation, 6575 Black Rail Road, proposed subdivision, Carlsbad, San Diego County, California, W.O. 3460-A-SC, dated November 27. Hydrologic Solutions, StormChamber™ installation brochure, pgs. 1 through 8, undated. Francis File:e:\wp 12\7200\7249a.pge GeoSoils, Inc. Appendix A Page 2 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. Kennedy, M.P., and Tan, SS., 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.html Omega Engineering Consultants, 2012, Grading plans for: Rhodes property, sheet 4 of 5, 10-scale, Project No.: CDP 11-17, Drawing No. 469-2A, dated June 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, 2017, Civil Code, Sections 895 et seq. 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. United States Geological Survey, 2014, U.S. Seismic Design Maps, Earthquake Hazards Program, http://geohazards.usgs.gov/designmaps/us/application.php, updated June 23, 2014. United States Geological Survey, 1999, Encinitas quadrangle, San Diego County, California, 7.5 minute series, 1 :24,000 scale. Francis File:e:\wp 12\7200\7249a.pge GeoSoils, Inc. Appendix A Page 3 APPENDIX B TEST PIT AND HAND-AUGER BORING LOGS GeoSoils , Inc. UNIFIED SOIL CLASSIFICATION SYSTEM CONSISTENCY OR RELATIVE DENSITY Major Divisions Group Typical Names CRITERIA Symbols GW Well-graded gravels and gravel- Cl) C ..!!1 sand mixtures. little or no fines Standard Penetration Test > Cl) <ti Cl) -C ·u, ..9! ~ Poorly graded gravels and Penetration Cl) 0 o v 0 ~ > Cl) ~ ·n o C, GP gravel-sand mixtures, little or no Resistance N Relative Cl) "iii ~~iz fines (blows/ft) Density 0 co: ..... a>c 0 N c3 0(/)0 Silty gravels gravel-sand-silt (I) • ~~~ Q) .c GM 0 -4 Very loose = 0 oz 0 C mixtures Cl) C l!) () 'iii in -~ 'O 0 "§ a~ 4 -10 Loose -~ al GC Clayey gravels, gravel-sand-clay ~ .!: mixtures 10 · 30 Medium C, 2 ' Cl) ~ ~ Well-graded sands and gravelly 30 • 50 Dense «; * SW sands, little or no fines oO 0 Cl) C v, 0 l!) C il; "' 'O C cf. 0 ·-..9! ~ > 50 Very dense <ti 0 -~ ti) 0 Cl) Poorly graded sands and -s v, l!) U V SP Q) -gcio gravelly sands, little or no fines 0 <tS"' Cl)z ~ en :5 ~ (I) SM Silty sands, sand-silt mixtures Cl)"' Cl) ~ 0 (I) ~ .c t/) ~ () (I) "' C -~ ~ a. ~ ;;= u: Clayey sands, sand-clay SC mixtures Inorganic silts, very fine sands, Standard Penetration Test ML rock flour. silty or clayey fine (I) sands >, -(I) Unconfined Cl) iLL~ > Inorganic clays of low to Penetration Compressive Cl) -g ~ 0 medium plasticity, gravelly clays, "iii CL Resistance N Strength 0 «s a-* sandy clays, silty clays, lean 0 (blows/ft) Consistenc~ (tons/ff} ..!!1 N ~:Jg clays ·5 . Cl) Cl) ~ Organic silts and organic silty <2 Very Soft <0.25 'O (/) Cl) Cl) OL clays of low plasticity C (I) -~ (/) 2-4 Soft 0.25 • .050 "' C, a. d, ~ Inorganic silts, micaceous or 4-8 Medium 0.50 · 1.00 C 0 MH diatomaceous fine sands or silts, u: E (/) cf. >, 0 elastic silts 0 ..!!! .. E lll 8 -15 Stiff 1.00 · 2.00 cf. o= ~ Inorganic clays of high plasticity, 0 -g ~ £ CH l!) "' ::, ~ fat clays 15 • 30 Very Stiff 2.00 • 4.00 ~g~ ·-Cl) CJ) ~ >30 Hard >4.00 0) 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 % T 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 EXCAVATION ELEV. DEPTH NO. (ft.) (ft.) TP-1 ±361 0-2/3 213-3 3 TP-2 ±369 0-¾ ¾-5½ 5½ W.O. 7279-A-SC Francis APN 215-070-51, Carlsbad Logged By: RBB April 30, 2017 LOG OF EXPLORATORY TEST PIT AND HAND-AUGER BORING GROUP SAMPLE MOISTURE FIELD DRY SYMBOL DEPTH (%) DENSITY DESCRIPTION (ft.) (pcf) SM UNDOCUMENTED ARTIFICIAL FILL: SIL TY SAND, grayish brown, dry, medium dense; trace clay, abundant ¾-inch angular pebbles. SM/CL UND@1 9.1 122.7 STRUCTURAL FILL: SILTY SAND with trace CLAY and SANDY CLAY, dark brown, gray, and reddish yellow, moist, dense; trace fragments of UND @ 2 8.2 128.2 reddish yellow and gray sandstone. SP QUATERNARY OLD PARALIC DEPOSITS: SANDSTONE, reddish yellow, dry, very dense; very fine to fine grained, highly cemented. UNO = Undisturbed Practical Refusal @ 3' No Groundwater/Caving Encountered Backfilled 4/30/17 SM SM BAG @½ ARTIFICIAL FILL-UNDOCUMENTED: SIL TY SAND, dark grayish brown dry, loose becoming dense at approximately -½'; trace clay, trace asphaltic concrete fragment (approximately 10 inches in dimension}, trace angular cobble (approximately 8 inches in dimension}. SM/CL UND@1 7.4 120.7 ARTIFICIAL FILL -STRUCTURAL: SILTY SAND with trace CLAY and SM BAG@ 1 SANDY CLAY, dark brown, gray, and reddish yellow, moist to saturated, SM BAG@2 medium dense to dense; saturated zones at approximately-3½' and -4½'. SM BAG @3 SM BAG @4½ SP QUATERNARY VERY OLD PARALIC DEPOSITS: SANDSTONE, reddish yellow and gray, dry, very dense; very fine to fine grained, highly cemented. Practical Refusal @ -5½' No Groundwater/Caving Encountered Backfilled 4/30/17 PLATE 8-2 EXCAVATION ELEV. DEPTH GROUP NO. (ft.) (ft.) SYMBOL HA-1 ±362 0-1½ SC 1½-2½ SC 2½ SP HA-2 ±365 0-1 SC 1-1 ½ SC W.O. 7279-A-SC Francis APN 215-070-51, Carlsbad Logged By: RBB April 30, 2017 LOG OF EXPLORATORY TEST PIT AND HAND-AUGER BORING SAMPLE MOISTURE FIELD DRY DEPTH (%) DENSITY DESCRIPTION (ft.) (pcf) ARTIFICIAL Fl LL -STRUCTURAL: CLAYEY SAND, dark yellowish brown and brown, dry, dense; trace rounded pebbles and cobbles. CLAYEY SAND, reddish yellowish and brown, moist, dense. QUATERNARY VERY OLD PARALIC DEPOSITS: SANDSTONE, reddish yellow, dry, very dense; very fine to fine grained, highly cemented. Practical Refusal @ 3' No Groundwater/Caving Encountered Backfilled 4/30/17 ARTIFICIAL FILL -UNDOCUMENTED: CLAYEY SAND, gray, dry, loose; porous, trace organics. ARTIFICIAL FILL -STRUCTURAL: CLAYEY SAND, reddish yellowish, damp, medium dense; trace cobbles. Practical Refusal @ 1 ½' Due to Cobble No Groundwater/Caving Encountered Backfilled 4/30/17 PLATE B-3 APPENDIX C UPDATED SEISMICITY GeoSoils, Inc. *********************** ·k * * E Q F A u L T * * * * version 3.00 °I( * "!( *********************** DETERMINISTIC ESTIMATION OF PEAK ACCELERATION FROM DIGITIZED FAU LTS JOB NUMB ER: 7279-A-SC DATE: 06-05-2017 JOB NAME: FRANCIS CALCULATION NAME: 7279 FAULT-DATA-FILE NAME: (:\Program Files\EQFAULTl\CGSFLTE.DAT SITE COORDINATES: SITE LATITUDE: 33.1124 SITE LONGITUDE: 117.2884 SEARCH RADIUS: 62. 2 mi ATTENUATION RELATION: 11) Bozorgnia Campbell Niazi (1999) Hor.-Pleist. s oil -car. UNCERTAINTY (M=Median, S=Sigma): s Number of Sigmas : 1.0 DISTANCE MEASURE: cdi st SCOND: 0 Basement Depth: 5.00 km Campbell SSR: 0 Campbell SHR: 0 COMPUTE PEAK HORIZONTAL ACCELERATION FAULT-DATA FILE USED: (:\Program Files\EQFAULTl\CGSFLTE.DAT MI NIMUM DEPTH VALUE (km): 3.0 Page 1 W.O. 7279-A-SC PLATE C-1 EQFAULT SUMMARY DETERMINISTIC SITE PARAMETERS Page 1 ABBREVIATED FAULT NAME APPROXIMATE DISTANCE mi (km) ESTIMATED MAX . EARTHQUAK E EVENT MAXIMUM PEAK EST . SITE EARTHQUAKE SITE INTENSITY MAG.(Mw) ACCEL. g MOD .MERC. ---------------------------------------------------------------------------ROSE CANYON 5.6( 9.0) 7.2 0.600 X NEWPORT-INGLEWOOD (Offshore) 8.9( 14 .3) 7.1 0.427 X CORONADO BANK 21.1( 33.9) 7.6 0.273 IX ELSINORE (JULIAN) 24.3( 39.1) 7.1 0.170 VIII ELSINORE (TEMECULA) 24.3( 39.1) 6.8 0.139 VIII ELSINORE (GLEN IVY) 36.8( 59.3) 6.8 0.090 VII PALOS VERDES 39.5( 63.6) 7.3 0.119 VII SAN JOAQUIN HILLS 39.6( 63.7)1 6.6 0.104 VII EARTHQUAKE VAL LEY 41.3( 66.4)1 6.5 0.066 VI SAN JACINTO -ANZA 47.2( 75.9)1 7.2 0.092 VII SAN JACINTO -SAN JACINTO VALLEY 48.4( 77.9)1 6.9 0.073 VII NEWPORT-I NGLEWOOD CL.A .Basi n) 50 .2( 80.8)1 7.1 0.080 VII SAN JACINTO -COYOTE CREEK 51.1( 82.2)1 6.6 0.056 VI CHINO -CENTRAL AVE. (Elsinore) 51.6( 83.0)I 6.7 0.084 VII ELSINORE (COYOTE MOUNTAIN) 54 .6( 87.9)1 6.8 0.060 VI WHITTIER 55 .5( 89.3)1 6.8 0.059 I VI ******************************************************************************* -END OF SEARCH -16 FAULTS FOUND WITHIN THE SPECIFIED SEARCH RADIUS. THE ROSE CANYON FAULT IS CLOSEST TO THE SITE. IT IS ABOUT 5.6 MILES (9.0 km) AWAY. LARGEST MAXIMUM -EARTHQUAKE SITE ACCELERATION : 0.6001 g Page 2 W.O. 7279-A-SC PLATE C-2 1000 900 800 700 600 500 400 300 200 100 0 CALIFORNIA FAULT MAP FRANCIS -400 -300 -200 -100 0 100 200 300 400 500 600 W.O. 7279-A-SC PLATE C-3 1 -C) -.1 C: 0 :;. ca ... Q) Q) 0 0 <( .01 .001 .1 MAXIMUM EARTHQUAKES FRANCIS 1 ~· ► ♦ ♦ 10 Distance (mi) ◄ ► ... a • r ◄ II" 100 W.O. 7279-A-SC PLATE C-4 JOB NUMBER: 7279-A-SC ************************* * 'i: * E Q s E A R C H * * * * version 3.00 * -!: "· ************************* ESTIMATION OF PEAK ACCELERATION FROM CALIFORNIA EARTHQUAKE CATALOGS DATE: 05 -13-2017 JOB NAME: FRANCIS EARTHQUAKE-CATALOG-FILE NAME: ALLQUAKE.DAT SITE COORDINATES: SITE LATITUDE: 33.1124 SITE LONGITUDE : 117.2884 SEARCH DATE S: START DATE: 1800 END DATE: 2017 SEARCH RADIUS: 62 .2 mi 100.1 km ATTENUATION RELATION: 11) Bozorgnia Campbel l Ni azi (1999) Hor.-Pleist. Soil -Cor. UNCERTAINTY (M=Medi a n, S=Sigma): s Number of Sigmas: 1.0 ASSUMED SOURCE TYPE : ss [SS=Stri ke-slip, DS=Reverse-s lip, BT=Blind-thrust] SCOND: 0 Depth s ource: A Ba sement Depth: 5.00 km Campb e ll SS R: 0 Campbell SHR: 0 COMPUTE PEAK HORIZONTAL ACCELERATION MINIMUM DEPTH VALU E (km): 3.0 Page 1 W.O. 7279-A-SC PLATE C-5 EARTHQUAKE SEARCH RESULTS Page 1 I I TIME I I I SITE I SITE I APPROX. FILEI LAT. I LONG. I DATE I (UTC) IDEPTHIQUAKEI ACC . I MM I DISTANCE CODE! NORTH I WEST I I HM See l (km)I MAG.I g IINT. I mi [km] ----+-------+--------+----------+--------+-----+-----+-------+----+------------ DMG 33.0000l117.3000lll/22/1800 2130 0.01 MGI 33.0000 117.0000 09/21/1856 730 0.0 MGI 32.8000 117.1000 05/25/1803 0 0 0.0 DMG 32 .7000 117.2000 05/27/1862 20 0 0.0 T-A 32.6700 117.1700 12/00/1856 0 0 0.0 T-A 32.6700 117.1700 10/21/1862 0 0 0.0 T-A 32.6700 117.1700 05/24/1865 0 0 0.0 DMG 33.2000 116.7000 01/01/1920 235 0.0 PAS 32.9710 117.8700 07/13/1986 1347 8.2 DMG 32.8000 116.8000 10/23/1894 23 3 0.0 MGI 33.2000 116.6000 10/12/1920 1748 0.0 DMG 33.7000 117.4000 05/13/1910 620 0.0 DMG 33.7000 117.4000 04/11/1910 757 0.0 DMG 33.7000 117.4000 05/15/1910 1547 0.0 DMG 33.6990 117.5110 05/31/1938 83455.4 DMG 33.7100 116.9250 09/23/1963 144152 .6 DMG 33.7500 117.0000 06/06/1918 2232 0.0 DMG 33.7500 117.0000 04/21/1918 223225.0 DMG 33.0000 116.4330 06/04/1940 1035 8.3 DMG 33.8000 117.0000 12/25/1899 1225 0.0 GSP 33 .5290 116.5720 06/12/2005 154146.5 MGI 33.8000 117.6000 04/22/1918 2115 0.0 GSG 33.4200 116.4890 07/07/2010 235333.5 DMG 33.5750 117.9830 03/11/1933 518 4.0 PAS 33 .5010 116.5130 02/25/1980 104738.5 GSP 33.5080 116.5140 10/31/2001 075616.6 DMG 33.6170 117.9670 03/11/1933 154 7.8 DMG 33.5000 116.5000 09/30/1916 211 0.0 GSP 33.4315 116.4427 06/10/2016 080438.7 DMG 33.6170 118.0170 03/14/1933 19 150.0 DMG 33 .9000 117.2000 12/19/1880 0 0 0.0 DMG 33.3430 116.3460 04/28/1969 232042 .9 DMG 33.6830 118.0500 03/11/1933 658 3.0 DMG 33.4000 116.3000 02/09/1890 12 6 0.0 DMG 33.7000 118.0670 03/11/1933 85457.0 DMG 33.7000 118.0670 03/11/1933 51022.0 T-A 132.2500 117.5000 01/13/1877 20 0 0.0 DMG 134.0000 117.2500 07/23/1923 73026.0 0.01 0.0 0.0 0.0 0.0 0.0 0.0 0.0 6.0 0.0 0.0 0.0 0.0 0.0 10.0 16.5 0.0 0.0 0.0 0.0 14.0 0.0 14.0 0.0 13.6 15.0 0.0 0.0 12.3 0.0 0.0 20.0 0.0 0.0 0.0 0.0 0.0 0.0 6. SOI 5.00 5.00 5.90 5.00 5.00 5.00 5.00 5.30 5.70 5.30 5.00 5.00 6.00 5.50 5.00 5.00 6.80 5.10 6.40 5.20 5.00 5.50 5.20 5.50 5.101 6. 301 5.001 5.191 5 .101 6.001 5.801 5.501 6.301 5.101 5.101 5.001 6.251 0.338 0.060 0.045 0.065 0.035 0.035 0.035 0.031 0.037 0.046 0.032 0.026 0.026 0.048 0.034 0.023 0.023 0.070 0.022 0.050 0.024 0.021 0.028 0.023 0.027 0.021 0.045 0 .020 0.022 0.021 0.035 0.030 0.024 0.038 0.018 0 .018 0.017 0.037 IX VI VI VI V V V V V VI V V V VI V IV IV VI IV VI IV IV V IV V IV VI IV IV IV V V IV V IV IV IV V 7.8( 12.5) 18.4( 29.6) 24.2( 38.9) 28.9( 46.6) 31.3( 50.4) 31.3( 50.4) 31.3( 50.4) 34.5( 55.6) 35.0( 56.4) 35 .6( 57.2) 40.2( 64.8) 41.1( 66.1) 41.1( 66.1) 41.1( 66.1) 42 .5( 68.4) 46.3( 74.5) 47.1( 75.7) 47.1( 75.7) 50.1( 80.6) 50. 3 ( 80. 9) 50.4( 81.0) 50.8( 81.7) 50.8( 81.7) 51.2( 82.4) 52.2( 84.0) 52.4( 84.3) 52.4( 84.3) 52.8( 84.9) 53.6( 86.2) 54.6( 87.8) 54 .6( 87.9) 56. 7( 91. 3) 59.0( 94 .9) 60 .4( 97.2) 60.5( 97.3) 60 .5 ( 97.3) 60.8( 97.8) 61. 3 ( 98. 7) ******************************************************************************* -END OF SEARCH -38 EARTHQUAKES FOUND WITHIN THE SPECIFIED SEARCH AREA. TIME PERIOD OF SEARCH: 1800 TO 2017 LENGTH OF SEARCH TIME: 218 years THE EARTHQUAKE CLOSEST TO THE SITE IS ABOUT 7.8 MILES (12.5 km) AWAY. LARGEST EARTHQUAKE MAGNITUDE FOUND IN THE SEARCH RADIUS: 6.8 Page 2 W.O. 7279-A-SC PLATE C-6 LARGEST EARTHQUAKE SITE ACCELERATION FROM THIS SEARCH : 0.338 g COEFFICIENTS FOR GUTENBERG & RICHTER RECURRENCE RELATION: a-val ue= 0.782 b-value= 0 .351 beta-value= 0 .809 TABLE OF MAGNITUDES AND EXCEEDANCES: Earthqu ake I Number of Times I cumul ati ve Magnitude I Exceeded I No. / Year -----------+-----------------+------------4.0 I 38 I 0.17512 4.5 I 38 I 0.17512 5. o I 38 I o .17512 5. 5 I 15 I o. 06912 6.0 I 8 I 0.03687 6. 5 I 2 I 0.00922 Page 3 W.O. 7279-A-SC PLATE C-7 EARTHQUAKE EPICENTER MAP FRANCIS 1100 -,,---------------------, 1000 900 800 700 600 500 400 300 200 100 LEGEND x M = 4 0 M =5 n M =6 M = 7 O ◊M=8 - -400 -300 -200 -100 0 100 200 300 400 500 600 W.O. 7279-A-SC PLATE C-8 100 10 :i... CtS Q) >--1 -z -en ... C: Q) > w -0 .1 :i... Q) .c E ::::s z Q) > ... CtS .01 ::::s E E ::::s (.) .001 EARTHQUAKE RECURRENCE CURVE FRANCIS io,,.__ ............ ...... 4 • ........ ~' --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 I I I I I I 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.O. 7279-A-SC PLATE C-9 APPENDIX D LABORATORY DATA GeoSoils, Inc. 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. 7279-A-SC Client: Francis Sample Sample ID Depth (ft) TP-1 /2 N/A Composite - QCI Project No.: 17-029-0059 Date: June 5, 2017 Summarized by: KA Corrosivity Test Results pH Chloride CT-532 CT-422 (643) (ppm) 6.91 76 Sulfate CT-417 % By Weight 0.0315 Resistivity CT-532 (643) (ohm-cm) 1600 W.O. 7279-A-SC PLATE D-1 576 East Lambert Road, Brea, California 92821; Tel: 714-671-1050; Fax: 714-671 -1090 APPENDIX E GENERAL EARTHWORK AND GRADING GUIDELINES GeoSoils, Inc. GENERAL EARTHWORK AND GRADING GUIDELINES 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 supercedethe 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 appri sed 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 Am erican Standard Testing Materi als test method ASTM designation D-1557. Random or representative field compaction tests should be performed in GeoSoils, Inc. accordance with test methods ASTM designation 0 -1556, 0-2937 or 0-2922, and 0-3017, 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 fill s. 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 Francis File:e:\wp12\7200\7279a.gue GeoSoils, Inc. Appendix E 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 Francis File:e:\wp 12\7200\7279a.gue GeoSoits, Inc. Appendix E Page 3 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. Francis File:e:\wp12\7200\7279a.gue GeoSoils, Inc. Appendix E 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 fl atter. 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 shou ld be based on observation and/or testing of th e 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 proced ures 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 10 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 Francis File:e:\wp12\7200\7279a.gue GeoSoils, Inc. Appendix E Page 5 slopes, and extend out over the slope to provide adequate compaction to the face of the slope. 2. 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. 3. 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. 4. 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 . 5. 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 th e geotechnical consultant, further excavations or overexcavation and refill ing of cut areas should be performed, and/or remedial grading of cut slopes should be performed. Wh en 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. Francis File:e:\wp12\ 7200\7279a.gue GeoSoils, Inc. Appendix E 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. Nofurtherexcavation orfilling 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 Francis File:e:\wp12\7200\7279a.gue GeoSoils, Inc. Appendix E Page 7 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. The equivalent fluid pressure to be used for the pool/spa design should be 60 pounds per cubic foot (pc0 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. 2. Passive earth pressure may be computed as an equivalent fluid having a density of 150 pct, to a maximum lateral earth pressure of 1,000 pounds per square foot (psD. 3. An allowable coefficient of friction between soil and concrete of 0.30 may be used with the dead load forces. 4. When combining passive pressure and frictional resistance, the passive pressure component should be reduced by one-third. 5. 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. 6. 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. 7. 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 Francis File:e:\wp12\7200\7279a.gue GeoSoils, Inc. Appendix E 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), wi ll 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 Francis File:e:\wp 12\ 7200\7279a.gue GeoSoits, Inc. Appendix E Page 9 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 durin g 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. Francis File:e:\wp12\7200\7279a.gue GeoSoils, Inc. Appendix E Page 1 O 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 fi ll 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 satisfi ed 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 th e 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. Francis File:e:\wp12\7200\7279a.gue GeoSoils, Inc. Appendix E Page 11 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. Francis File:e:\wp12\7200\7279a.gue GeoSoils, Inc. Appendix E 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: 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. Flashing Lights: 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 Francis File:e:\wp12\7200\7279a.gue GeoSoils, Inc. Appendix E Page 13 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 fi ll. 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 th e 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 th e 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. Francis File:e:\wp1 2\7200\7279a.gue GeoSoils, Inc. Appendix E 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. Francis File:e:\wp12\7200\7279a.gue GeoSoils, Inc. Appendix E Page 15 Toe of slope as shown on grading plan Proposed grade \ / \/ / .,,,,,,,- Natural slope to be restored with compacted fill / Compacted fill / / / / / ·0(:-/ _2-foot minimum~ --/ o{'c;--1/ in bedrock \ '4 1/ .-or , " approved \f § "-'/ :::_ l_ mth m,ted•I_ ~ \ ~1/ --------, ----~\ -~-I -, ;:'\--(\ ,,:--,,,....-'---· . ,,, -~, :ry;:::~~t-~"7"~.,4\.'\ I_ ----- 1 -r Subdrain as recommended by geotechnical consultant NOTES: 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. r' -,.-- ~ Gea~~lnc. FILL OVER NATURAL (SIDEHILL FILL) DETAIL Plate E-7 ......._.., I Proposed finish grade -~ Natural grade -------------------------~ H = height of slope ~ ~ minimum . "1/:0-·> \ \-''\ 1-\\\ /., /,\1/~ 'I ~'< I [\?/'~~ \~;::\ \ \<\\0 1,,-,,t<--:/"""":':~~~·~~ '),\ \ \ ' ,-\ ...... ~ .... , ,.....\\..,..),...,.\\....,~ Bedrock or ~\< d " , , « -✓,~\ approve \ \/( native material Typical benching (4-foot minimum) 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. ,,..i--.s-1 r:::::;:)0 G(!o§:o.@.ft rlnc. cl •. ,,.;rf....); SKIN FILL OF NATURAL GROUND DETAIL Plate E-10 MAP VIEW NOTTO SCALE Concrete cut-off wall SEE NOTr~-S---------~J Top of slope Bl ~ Gravity-flow, nonperforated subdrain pipe (transverse) Toe of slope 4-inch perforated _j subdrain pipe (longitudinal) 2-inch-thick sand layer Sleet Pool 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 B NOTES: Outlet per design civil engineer Gravity-flow nonperforated subdrain pipe 4-inch perforated subdrain pipe Coping I 1-S leel Pool B' ---_ 2-i~ch-thick sand layer Vapor retarder Perfor ated subdrain pipe 1. 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. r• °' I/ ' \J GeaSaiJs, tJnc. ., ' . TYPICAL POOL/SPA DETAIL Pla te E-17 SIDE VIEW ...._\ 1.,, Spoil pile Test pit TOP VIEW Flag Flag Spoil pile Test pit Light Vehicle ---50feet-----...-------50feel----------'l--t '-------------1001ee·t-----------.-t TEST PIT SAFETY DIAGRAM Plate E-20