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Home My WebLink AboutCT 2017-0008; HARDING & PALM TOWNHOUSE; PRELIMINARY GEOTECHNICAL EVALUTION; 2017-10-27PRELIMINARY GEOTECHNICAL EVALUATION PRO NO S'F EET CAR 008 A -c...,_,~ ,~-~ 03 • ____ H_ DIN ALM, L C/O VECK BUILDING GROUP P.O. BOX 4492 CARLSBAD, CALIFORNIA 92018 W.O. 7355-A-SC OCTOBER 27, 2017 • Geotechnical • Geologic • Coastal • Environmental 5741 Palmer Way • Carlsbad, California 92010 • (760) 438-3155 • FAX (760) 931-0915 • www.geosoilsinc.com October 27, 2017 W.O. 7355-A-SC Harding Palm, LLC c/o Veck Building Group P.O. Box 4492 Carlsbad, California 92018 Attention: Ms. Elizabeth Temple Subject: Preliminary Geotechnical Evaluation, Proposed Townhouses, 3535 Harding Street, Carlsbad, San Diego County, California, Assessor's Parcel Number (APN) 204-210-03 Dear Ms. Temple: In accordance with your request and authorization, GeoSoils, Inc. (GSI) is pleased to present the results of our preliminary geotechnical evaluation of the subject site, relative to the proposed residential development thereon. The purpose of our study was to evaluate the site geologic and geotechnical conditions in order to develop preliminary recommendations for earthwork and the design of foundations, retaining walls, and pavements as well as other improvements possibly associated with the project. 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 a relatively thin layer of Quaternary-age colluvium (i .e., topsoil). These earth materials are in turn underlain by Quaternary-age old paralic deposits and thence Tertiary-age sedimentary bedrock belonging to the Santiago Formation . Unweathered old paralic deposits and the Santiago Formation are considered formational earth materials at the subject site. Locally, the upper approximately 2 to 2½ feet of the old paralic deposits are weathered in-place. • • • • • American Concrete Institute [ACI] 318-14); and have slightly elevated concentrations of soluble chlorides. GSI does not consult in the field of corrosion engineering. Thus, the Client, Structural, Civil, Plumbing, Mechanical, and Electrical Engineers, and Project Architect should agree on the level of corrosion protection required for the project and seek consultation from a qualified corrosion consultant as warranted. Foundations should be uniformly supported by at least 24 inches of engineered fill. Based on the available subsurface data, this will require some overexcavation of the unweathered old paralic deposits. Perched groundwater was encountered near the geologic contact of the old paralic deposits and the underlying Santiago Formation at an approximate depth of 17 feet BEG. The regional groundwater table is anticipated to be near sea level, or approximately 62 feet below the lowest site elevation. Groundwater is not anticipated to significantly affect the proposed development. provided that planned excavations do not extend greater than approximately 17 feet below the existing grades. Saturated soil conditions could be encountered a few feet above the perched water table. Groundwater conditions are subject to change and the potential for perched water to be encountered at higher elevations during or following site development cannot be precluded. This potential should be disclosed to all interested/affected parties. Our evaluation indicates there are no known active faults crossing the subject site and the site has very low susceptibility to deep-seated landslides. Owing to the depth to groundwater and the dense nature of the old paralic deposits and the underlying Santiago Formation, the potential for the site to be adversely affected by liquefaction/lateral spreading is considered low. 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 parameters, provided herein, should be considered during the design of the proposed development. The adverse effects of seismic shaking on the structure(s) will likely be wall cracks, some foundation/slab distress, and some seismic settlement. However, it is anticipated that the proposed structures will be repairable in the event of the design seismic event. This potential should be disclosed to all interested/affected parties. Additional adverse geologic features that would preclude project feasibility were not encountered, based on the available data. Harding Palm, LLC File:e:\wp12\7300\7355a.pge GeoSoils, Inc. W.O. 7355-A-SC Page Three • Due to their relatively low density, lack of uniformity, and porous nature, all Quaternary-age colluvium and weathered old paralic deposits are considered potentially compressible; and therefore, unsuitable for the support of proposed settlement-sensitive improvements (i.e., foundation elements, slab-on-grade floors, pavements, walls, etc.) and/or engineered fill in their existing state. Based on the available data, potentially compressible soils extend to an approximate depth of 3 feet below existing grades (BEG). However, the possibility of potentially compressible locally extending to greater depths cannot be precluded and should be anticipated. Conversely, the underlying unweathered old paralic deposits are considered suitable for the support of settlement-sensitive improvements and engineered fill in their existing state. • Based on the age of the existing residential structure, it is possible that onsite sewage disposal systems could be encountered during remedial earthwork. If encountered, this office should observe the exposed conditions to provide appropriate remedial recommendations. • It should be noted that the 2016 California Building Code ([2016 CBC], California Building Standards Commission [CBSC], 2016) requires the removal of unsuitable soils across all areas to be graded, under the purview of a grading permit, and not just within the influence of the proposed townhouses. 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 3 feet from the property boundaries 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 span. Proper disclosure to all interested/affected parties should occur if this condition exists at the conclusion of grading. • Expansion Index (E. I.) testing, performed on a representative sample of the onsite soils, indicates an E.1. that is less than 5. Thus, on a preliminary basis, the expansion potential of the onsite soils is very low. On a preliminary basis specific mitigation of the shrink/swell effects of expansive soils is not warranted at this time. 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 on site soils suggests site soils are moderately alkaline with respect to soil acidity/alkalinity; are moderately corrosive to exposed, buried metals when saturated; present negligible sulfate exposure to concrete (i.e., Exposure Class SO per Table 19.3.1.1 of Harding Palm, LLC File:e:\wp12\7300\7355a.pge GeoSoils, Inc. W .0. 7355-A-SC Page Two • On a preliminary basis, the feasibility of stormwater infiltration at the subject site is considered low to perhaps moderate, Owing to the dense and locally moderately cemented nature of the old paralic deposits that occur in the near surface full infiltration is unlikely. If stormwater were to infiltrate, it would most likely perch upon the old paralic deposits and migrate laterally. This may have detrimental effects on onsite and offsite improvements, including utility trenches. • The recommendations presented in this report should be incorporated into the design and construction considerations of the project. Harding Palm, LLC File:e:\wp12\7300\7355a.pge GeoSoils, Inc. W.O. 7355-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. Respectfully sub · GeoSoils, Inc. JI;!~ Engineering Geolog1 in~ Staff Geologist RBB/JPF/DWS/jh Distribution: (1) Addressee (via US Mail and email) (2) Karnak Planning and Design, Attention: Mr. Robert Richardson (wet signed/stamped) Harding Palm, LLC File:e:\wp12\7300\7355a.pge GeoSoils, Inc. W.O. 7355-A-SC Page Five TABLE OF CONTENTS SCOPE OF SERVICES ................................................... 1 SITE DESCRIPTION AND PROPOSED DEVELOPMENT ......................... 1 FIELD STUDIES ......................................................... 3 PHYSIOGRAPHIC AND REGIONAL GEOLOGIC SETTINGS ...................... 3 Physiographic Setting .............................................. 3 Regional Geologic Setting ........................................... 3 SITE GEOLOGIC UNITS .................................................. 5 General .......................................................... 5 Quaternary Colluvium (Not Mapped) ............................. 6 Quaternary Old Paralic Deposits (Map Symbol -Qop) ............... 6 Tertiary Santiago Formation (Map Symbol -Tsa) ................... 6 Structural Geology ................................................. 6 GROUNDWATER ........................................................ 7 ROCK HARDNESS/EXCAVATION DIFFICULTY ................................ 7 GEOLOGIC HAZARDS EVALUATION ........................................ 8 Mass Wasting/Landslide Susceptibility ................................. 8 FAUL TING AND REGIONAL SEISMICITY ..................................... 8 Regional Faults .................................................... 8 Local Faulting ..................................................... 9 Surface Rupture ................................................... 9 Seismicity ........................................................ 9 Seismic Shaking Parameters ........................................ 1 O SECONDARY SEISMIC HAZARDS ......................................... 11 Liquefaction/Lateral Spreading ...................................... 11 Seismic Densification .............................................. 12 Summary ........................................................ 12 Other Geologic/Secondary Seismic Hazards ........................... 12 LABORATORY TESTING ................................................. 13 Classification ..................................................... 13 Moisture-Density Relations ......................................... 13 Laboratory Standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Expansion Index .................................................. 14 Direct Shear ..................................................... 14 Saturated Resistivity, pH, and Soluble Sulfates, and Chlmirlcs ............ 14 Corrosion Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 GeoSoils, Inc. PRELIMINARY CONCLUSIONS AND RECOMMENDATIONS .................... 15 EARTHWORK CONSTRUCTION RECOMMENDATIONS ....................... 18 General ......................................................... 18 Site Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Removal and Recompaction of Potentially Compressible Earth Materials .... 19 Alternating Slot Excavations ........................................ 19 Perimeter Conditions .............................................. 19 Overexcavation ................................................... 20 Fill Placement .................................................... 20 Import Soils ...................................................... 20 Graded Slope Construction ......................................... 21 Temporary Slopes ................................................ 21 Excavation Observation and Monitoring (All Excavations) ................. 21 Observation ................................................ 22 Earthwork Balance (Shrinkage/Bulking) ............................... 22 PRELIMINARY RECOMMENDATIONS -FOUNDATIONS ....................... 23 General ......................................................... 23 Preliminary Foundation Design ...................................... 23 PRELIMINARY FOUNDATION CONSTRUCTION RECOMMENDATIONS ........... 24 Conventional Foundation and Slab-On-Grade Floor Systems .............. 24 Foundation Settlement ............................................. 25 SOIL MOISTURE TRANSMISSION CONSIDERATIONS ........................ 26 SITE RETAINING WALL DESIGN PARAMETERS (IF WARRANTED) ............... 28 General ......................................................... 28 Conventional Retaining Walls ....................................... 28 Preliminary Retaining Wall Foundation Design .................... 28 Restrained Walls ............................................ 29 Cantilevered Walls ........................................... 29 Seismic Surcharge ................................................ 30 Retaining Wall Backfill and Drainage .................................. 31 Wall/Retaining Wall Footing Transitions ............................... 35 Subgrade Preparation ............................................. 36 Unbound Granular Base Preparation ................................. 36 Sand Leveling Base ............................................... 36 Additional Recommendations for Permeable Brick Paver Sections .......... 37 FLATWORK AND OTHER IMPROVEMENTS ................................. 38 ONSITE INFILTRATION-RUNOFF RETENTION SYSTEMS ...................... 40 General ......................................................... 40 Harding Palm, LLC File:e:\wp12\7300\7355a.pge GeoSoils, Inc. Table of Contents Page ii DEVELOPMENT CRITERIA ............................................... 45 Drainage ........................................................ 45 Erosion Control ................................................... 45 Landscape Maintenance and Design of Open Bottom Planters ............ 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 GEOTECHNICAL OBSERVATION AND TESTING ........................................................ 48 OTHER DESIGN PROFESSIONALS/CONSULTANTS .......................... 49 PLAN REVIEW ......................................................... 50 LIMITATIONS .......................................................... 50 FIGURES: Figure 1 -Site Location Map ......................................... 2 Figure 2 -Boring Location Map ....................................... 4 Detail 1 -Typical Retaining Wall Backfill and Drainage Detail .............. 31 Detail 2 -Retaining Wall Backfill and Subdrain Detail Geotextile Drain ....... 32 Detail 3 -Retaining Wall and Subdrain Detail Clean Sand Backfill ........... 33 ATTACHMENTS: Appendix A -References ................................... Rear of Text Appendix B -Boring Logs .................................. Rear of Text Appendix C -Seismicity .................................... Rear of Text Appendix D -Laboratory Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Rear of Text Appendix E -General Earthwork and Grading Guidelines . . . . . . . . . Rear of Text Harding Palm, LLC File:e:\wp 12\7300\7355a.pge GeoSoils, Inc. Table of Contents Page iii PRELIMINARY GEOTECHNICAL EVALUATION PROPOSED TOWNHOUSES, 3535 HARDING STREET CARLSBAD, SAN DIEGO COUNTY, CALIFORNIA ASSESSOR'S PARCEL NUMBER (APN) 204-210-03 SCOPE OF SERVICES The scope of our services has included the following: 1. Review of readily available published geologic literature and maps, and aerial photographs (see Appendix A). 2. Site reconnaissance mapping and advancing three (3) exploratory hollow-stem auger borings to evaluate the near-surface soil/geologic profiles and sample representative earth materials (see Appendix B). 3. General areal geologic and seismic hazards evaluation (see Appendix C). 4. Appropriate laboratory testing of representative bulk and relatively undisturbed soil samples collected during our subsurface exploration program (see Appendix D). 5. Analysis of field and laboratory data relative to the proposed development. 6. The preparation of this summary report and accompaniments. SITE DESCRIPTION AND PROPOSED DEVELOPMENT The subject site consists of a rectangular-shaped, developed residential property located at the southwesterly corner of Harding Street and Palm Avenue in Carlsbad, San Diego, County, California 92018 (see Figure 1, Site Location Map). The actual physical address of the subject site is 3535 Harding Street, Carlsbad, California 92008. The latitude and longitude of the approximate centroid of the project area is 33.1561 • and -117 .3404 •. The study area is bounded by Harding Street to the northeast, by Palm Avenue to the northwest, and by existing residential development to the remaining quadrants. Topographically, the site is generally flat-lying to very gently sloping in a southwesterly direction. According to Google Earth satellite imagery, elevations across the site range between approximately 61 and 62 feet (unknown datum). Surface drainage appears to be controlled by sheet flow runoff, primarily directed to the southwest. An existing one-story residential structure and associated outbuilding occupies approximately one-quarter of the subject property. Other improvements consists of Portland Cement Concrete (PCC) hardscape (driveway and walkways). The remainder of the site is vacant and is sparsely covered with weeds, shrubbery, and a few trees. GeoSoils, Inc. Base Map: TOPO!® ©2003 National Geographic, U.S.G.S. San Luis Rey Quadrangle, California --San Diego Co., 7.5 Minute, dated 1997, current, 1999. Base Map: Google Maps, Copyright 2017 Google, Map Data Copyright 2017 Google w.o. This map Is copyrighted by Google 2017. It I• unlawful to copy or reproduce all or any part thereof, whether for personal use or resale, without pennlsslon. All rights reserved. 7355-A-SC SITE LOCATION MAP N Figure 1 Based on our review of architectural plans prepared by Karnak Planning and Design ([KP&D] 2017), GSI understands that proposed development consists of razing the existing structures and preparing the site to receive three (3) multi-family structures containing a total of six (6) townhouse units. GSI understands that the townhouses will be two-stories with a roof deck. KP&D (2017) also shows that proposed development includes the construction of a private driveway and hardscape. The proposed residential structures are anticipated to be serviced by underground utilities. GSI anticipates that the proposed structures will consist of wood frames with concrete slab-on-grade floors. Basements are not proposed. Building loads are currently unknown but assumed to be typical for this type of relatively light residential construction. Minor cut and fill grading is anticipated to bring the site to design grades. Based on site relief, maximum planned cut and fills on the order of½ foot or less is expected. Sanitary sewage disposal is to be connected into the municipal system. FIELD STUDIES Site-specific field studies were conducted by GSI on September 26, 2017, and consisted of reconnaissance geologic mapping, and advancing three (3) hollow-stem auger borings. The borings were logged by a representative of this office who collected representative bulk and relatively undisturbed soil samples for appropriate laboratory testing. The logs of the borings are presented in Appendix B. Site geology and the location of the borings are shown on the Boring Location Map (see Figure 2), which uses the Sheet A-1.0 of KP&D (2017) 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. 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( 7~__,/ .- I Ji OJ c;;r I : Qop Tsa 8-3 -$ TD=20 ½' --.J : Overal I Site Plan GS/ LEGEND QUA TERNARY OLD PARAL/C DEPOSITS TERTIARY SANTIAGO FORMATION, CIRCLED WHERE BURIED APPROXIMATE LOCATION OF EXPLORATORY HOLLOW-STEM AUGER BORING WITH TOTAL DEPTH IN FEET ( \ \ ) I \ . ··-----· Planning & Architecture ~t~ .iil..\;;J.A ~w -;~ Karnak Planning & Design 614 ca11e Via:n1e, ea, a~,T1e11-e ca 92673 75~~~;~~cr~::;t~f~~~~m CUE,'\JT Harding Palm LLC Veck BUlding Group P .0. Box 4492 Carlsbad, Ca 92018 Elizabeth Tern pie 819•204-4903 eli:z.abethlem ple@gmail.com PRJJECT ACORESS: 3535 Harding Street Carlsbad, Ca 92008 APN: 204-210-03-00 PRJJECT 1-1) DP.AV,J!NG F!LE: DRAWN BY Ct-ECl<E.O BY PRJJEcr· Harding & Palm Townhouse Project SI-EE rnTLE Plot Plan SI-EETNO.: A-1.0 COP'1RIGHT 2008 Prinl Date. 8-28-17 : i I ALLLOCATIONSAREAPPROXIMATE This document or efi/e is not a parl of the Construction Documents and should not be relied upon as being an accurate depiction of design. ~- BORING LOCATION MAP Fiaure2 w.o. 7355-A-SC I DATE: 10/17 I SCALE: 1" = 20' 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 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 (2007) indicates that the site is underlain by old paralic deposits (Subunits 6-7), formerly termed "terrace deposits" on older geologic maps and in GSI (1988). The old paralic deposits consist of marine and non-marine sediments deposited on a wave cut abrasion platform that emerged from the sea approximately 80,000 to 120,000 years before present. SITE GEOLOGIC UNITS General The earth material units that were observed and/or encountered at the subject site during our field exploration consisted of Quaternary-age colluvium (topsoil), weathered and unweathered Quaternary-age old paralic deposits, and the Tertiary Santiago Formation. 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. H.irding Palm, LLC 3535 Harding Street, Carlsbad File:e:\wp12\7300\7355a.pge GeoSoils, Inc. VV .0. 7355 /\-t:iC October 27, 2017 Page 5 Quaternary Colluvium (Not Mapped) Quaternary colluvium (topsoil) was encountered at the surface in all borings and generally consisted of dark brownish gray and brownish gray silty sand. The colluvium generally extended to depths ranging between approximately½ foot and 1 foot BEG. The colluvium was typically dry, loose, and porous. As such, it should not be used to support proposed settlement-sensitive improvements or engineered fill in is existing state. Quaternary Old Paralic Deposits (Map Symbol -Qop) Quaternary old paralic deposits were observed underlying the colluvium in all borings. These sediments were locally weathered in the upper 2 to 2½ feet of their vertical extent, and generally consisted of dark yellowish brown, very fine-to fine-grained silty sand and dark yellowish brown very fine-to fine-grained sand with trace silt. The weathered old paralic deposits were typically dry to damp and medium dense. Unweathered old paralic deposits were encountered at an approximate depth of 3 feet BEG. The unweathered old paralic deposits generally consisted of reddish yellow, yellowish brown, dark yellowish brown, brown, and dark gray very fine-to fine-grained sand; and reddish yellow and gray, very fine-to coarse-grained silty sand with localized traces of clay and subangular to subrounded gravels. Paleoliquefaction features (sand dikes) were observed at approximate depths of 1 O and 11 feet BEG in Borings B-1 and B-2, respectively. The paleoliquefaction features are artifacts of ancient seismically-induced liquefaction, occurring prior to lithification of the old paralic deposits, and do not present a current secondary seismic risk to the proposed development. Weathered old paralic deposits are considered potentially compressible in their existing state. Therefore, these surficial weathered sediments should not be used for the support of settlement-sensitive improvements and/or engineered fill without mitigation. Unweathered old paralic deposits are considered suitable formational (bedrock) materials for the site. Tertiary Santiago Formation (Map Symbol -Tsa) Sedimentary bedrock belonging to the Tertiary Santiago Formation was observed unconformably underlying the old paralic deposits in Borings B-1 and B-2 at an approximate depth of 17 feet BEG. As observed therein, the Santiago Formation generally consisted of light gray, very fine-grained silty sandstone and sandstone. The Santiago Formation was saturated becoming moist with depth, and dense. The Santiago Formation is also considered suitable formational earth materials for the site. Based on its depth and our understanding of the proposed development, the Santiago Formation is not anticipated to be encountered during construction. Structural Geology Owing to the subsurface investigative techniques, the geologic structure was not readily observed. However, based on our experience and observations in the site vicinity, the old :-iarding Palm, LLC 3535 Harding Street, Carlsbad File:e: \wp 12\ 7300\ 7355a. pg e GeoSoils, Inc. October 27, 2017 Page 6 paralic deposits are generally thickly bedded to massive with local subhorizontal to gentle westerly dipping bedding. A review of Kennedy and Tan (2008), indicates that Santiago Formation bedding in the vicinity of the subject site dips 10 degrees to the northeast and 8 degrees to the southwest, which may suggest a synclinal fold structure. No adverse geologic structures that would preclude or otherwise hinder project feasibility were observed on the site. GROUNDWATER GSI encountered perched groundwater within Borings B-1 and B-2 at an approximate depth of 17 feet BEG. The regional groundwater table is anticipated to be within a few feet of sea level or approximately 61 feet below the lowest site elevation. The groundwater is perched near the contact of the old paralic deposits and Santiago Formation owing to permeability/density contrasts between the two units. Groundwater is not anticipated to significantly affect proposed site development, provided that planned excavations do not extend to depths greater than approximate 17 feet BEG, and the recommendations contained in this report are properly incorporated into final design and construction. These observations reflect site 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 investigation. Seeps, springs, or other indications of subsurface water were not noted on the subject property during the time of our field investigation. However, perched water seepage may occur locally (as the result of heavy precipitation and/or irrigation, or damaged wet utilities) along zones of contrasting permeabilities/densities (fill/old paralic deposit contacts, 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 No significant difficulty was encountered while advancing the borings to the depths explored. GSI anticipates that easy to moderately difficult excavation would be experienced with standard mechanized earth-moving equipment in good working order. Localized areas of highly cemented old paralic deposits may present very difficult excavation. Excavation equipment should be appropriately sized and powered for the required excavation task. Harding Palm, LLC 3535 Harding Street, Carlsbad File:e:\wp12\7300\7355a.pge GeoSoils, Inc. W.O. 7355-/\ SC October 27, 2017 Page 7 GEOLOGIC HAZARDS EVALUATION Mass Wasting/Landslide Susceptibility Mass wasting refers to the various processes by which earth materials are moved down slope in response to the force of gravity. Examples of these processes include slope creep, surficial failures, and deep-seated landslides. Creep is the slowest form of mass wasting and generally involves the outer 5 to 1 O feet of a slope surface. During heavy rains, such as those in El Nino years, creep-affected materials may become saturated, resulting in a more rapid form of downslope movement (i.e., landslides and/or surficial failures). According to regional landslide susceptibility mapping by Tan and Giffen (1995), the site is located within landslide susceptibility Subarea 2, which is characterized as being "marginally susceptible" to landsliding. Owing to their strength characteristics, the old paralic deposits and underlying Santiago Formation have a very low susceptibility to deep-seated landslides. In addition, the site's flat-lying to gently sloping relief is not prone to significant mass wasting events. Geomorphic expressions indicative of past mass wasting events (i.e., scarps and hummocky terrain) were not observed during our field studies. Further, no adverse geologic structures were encountered during our subsurface exploration nor during our review of regional geologic maps. The onsite soils are, however, considered erosive. Therefore, any slopes comprised of these materials may be subject to rilling, gullying, sloughing, and surficial slope failures depending on rainfall severity and surface drainage practices. Such risks can be minimized through properly designed and regularly and periodically maintained surface drainage. FAULTING AND REGIONAL SEISMICITY Regional Faults Our review indicates that there are no known active faults crossing the project and the site is not within an Alquist-Priolo Earthquake Fault Zone (Jennings and Bryant, 201 O; Bryant and Hart, 2007). However, the site is situated in a region subject to periodic earthquakes along active faults. The offshore segment of the Newport-Inglewood fault (part of the Newport-Inglewood -Rose Canyon fault zone) is the closest known active fault to the site (located at a distance of approximately 5.5 miles [8.8 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 offshore segment of the Newport-Inglewood fault is 1.5 (±0.5) millimeters per year (mm/yr) and the fault is capable tlar.:::ing P;:;:m, LLC 3535 Harding Street, Carlsbad File:e:\wp12\7300\7355a.pge GeoSoils, Inc. W.O. 7335-A-SC October 27, 2017 Page 8 of a maximum magnitude 7.1 earthquake. The location of the offshore segment of the Newport-Inglewood 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. Local Faulting Although active faults lie within a few miles of the site, no active faults were observed to specifically transect the site during the field investigation. Additionally, a review of available regional geologic maps does not indicate the presence of active faults crossing the specific project site. Surface Rupture Owing to the lack of known active or potentially active faults crossing the site, the potential for the proposed development to be adversely affected by surface rupture from fault movement is considered very low. Seismicity The acceleration-attenuation relation of Bozorgnia, Campbell, and Niazi (1999) has been incorporated into EQFAULT (Blake, 2000a). EQFAULT is a computer program developed by Thomas F. Blake (2000a), which performs deterministic seismic hazard analyses using digitized California faults as earthquake sources. The program estimates the closest distance between each fault and a given site. If a fault is found to be within a user-selected radius, the program estimates peak horizontal ground acceleration that may occur at the site from an upper bound (formerly "maximum credible earthquake"), on that fault. Upper bound refers to the maximum expected ground acceleration produced from a given fault. Site acceleration (g) was computed by one user-selected acceleration-attenuation relation that is contained in EQFAUL T. Based on the EQFAUL T program, a peak horizontal ground acceleration from an upper bound event on the offshore segment of the Newport-Inglewood 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 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 100-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 Harding Palm, LLC 3535 Harding Street, Carlsbad File:e:\wp 12\7300\7355a.pge GeoSoils, Inc. W.O. 7355-A-SC October 27, 2017 Page 9 available data and the attenuation relationship used, the estimated maximum (peak) site acceleration during the period 1800 through December 15, 2016 was about 0.25 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. 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 (http://geohazards.usgs.gov/ designmaps/us/application.php) was utilized for design. The short spectral response utilizes a period of 0.2 seconds. 2_016 CBC SEISMIC DESIGN P~RAMETERS .. ' PARAMETER VALUE Site Class D Spectral Response -(0.2 sec), S5 1.145 g Spectral Response -(1 sec), S1 0.439 g Site Coefficient, Fa 1.042 Site Coefficient, F v 1.561 Maximum Considered Earthquake Spectral 1.193 g Response Acceleration (0.2 sec), SMs Maximum Considered Earthquake Spectral 0.685 g Response Acceleration (1 sec}, SM1 5% Damped Design Spectral Response 0.795 g Acceleration (0.2 sec), S05 5% Damped Design Spectral Response 0.457 g Acceleration (1 sec), S01 PGAM 0.474 g Seismic Design Category D Hardin~ ;,aim, LLC 3535 Harding Street, Carlsbad File:e:\wp12\7300\7355a.pge GeoSoils, Inc. 2013CBC AND/OR REFERENCE> Section 1613.3.2/ASCE 7-10 (Chapter 20) Figure 1613.3.1 (1) Figure 1613.3.1 (2) Table 1613.3.3(1) Table1613.3.3(2) Section 1613.3.3 (Eqn 16-37) Section 1613.3.3 (Eqn 16-38) Section 1613.3.4 (Eqn 16-39) Section 1613.3.4 (Eqn 16-40) ASCE 7-10 (Eqn 11.8.1) Section 1613.3.5/ASCE 7-10 (Table 11 .6-1 or 11.6-2) W .0. 735~-A-SC October 27, 2017 Page 10 GENERAL SEISMIC PARAMETERS PARAMETER VALUE Distance to Seismic Source 5.5 mi (8.8 km)I1 l (Newport Inglewood [offshore segment]) Upper Bound Earthquake Mw = 7.112) (Newport Inglewood [offshore segment]) 111) -Blake (2000a) : 12J -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 to eliminate all damage, since such design may be economically prohibitive. Cumulative effects of seismic events are not addressed in the 2016 CBC (CBSC, 2016) and regular maintenance and repair following locally significant seismic events (i.e., Mw5.5) will likely be necessary, as is the case in all of southern California. SECONDARY SEISMIC HAZARDS Liquefaction/Lateral Spreading Liquefaction describes a phenomenon in which cyclic stresses, produced by earthquake-induced ground motion, create excess pore pressures in relatively cohesion less soils. These soils may thereby acquire a high degree of mobility, which can lead to vertical deformation, lateral movement, lurching, sliding, and as a result of seismic loading, volumetric strain and manifestation in surface settlement of loose sediments, sand boils and other damaging lateral deformations. This phenomenon occurs only below the water table, but after liquefaction has developed, it can propagate upward into overlying non-saturated soil as excess pore water dissipates. One of the primary factors controlling the potential for liquefaction is depth to groundwater. Typically, liquefaction has a relatively low potential at depths greater than 50 feet and is unlikely and/or will produce vertical strains well below 1 percent for depths below 60 feet when relative densities are 40 to 60 percent and effective overburden pressures are two or more atmospheres (i.e., 4,232 pounds per square foot [Seed, 20051). The condition of liquefaction has two principal effects. One is the consolidation of loose sediments with resultant settlement of the ground surface. The other effect is lateral sliding. Significant permanent lateral movement generally occurs only when there is significant differential loading, such as fill or natural ground slopes within susceptible materials. No such loading conditions exist at the site. Hnrding Palm, LLC 3535 Harding Street, Carlsbad File:e:\wp12\7300\7355a.pge GeoSoils, Inc. ';': .0. 7355 A-SC October 27, 2017 Page 11 Liquefaction susceptibility is related to numerous factors and the following five conditions should be concurrently present for liquefaction to occur: 1) sediments must be relatively young in age and not have developed a large amount of cementation; 2) sediments must generally consist of medium-to fine-grained, relatively cohesionless sands; 3) the sediments must have low relative density; 4) free groundwater must be present in the sediment; and 5) the site must experience a seismic event of a sufficient duration and magnitude, to induce straining of soil particles. Only about two to perhaps three of these five necessary conditions have the potential to affect the site, concurrently. Seismic Densification Seismic densification is a phenomenon thattypically occurs in low relative density granular soils (i.e., United States Soil Classification System [USCS] soil types SP, SW, SM, and SC) that are above the groundwater table. These unsaturated granular soils are susceptible if left in the original density (unmitigated), and are generally dry of the optimum moisture content (as defined by the ASTM D 1557). During seismic-induced ground shaking, these natural or artificial soils deform under loading and volumetrically strain, potentially resulting in ground surface settlements. The herein provided earthwork recommendations would mitigate seismic densification onsite. However, some densification of the adjoining un-mitigated properties may influence improvements at the perimeter of the site. Special setbacks and/or foundations may be utilized if significant structures/improvements are placed close to the perimeter of the site. In order to mitigate seismic densification occurring on adjoining properties, foundations near the perimeter of the site should extend below a 1 : 1 (h :v) plane projected up and into the project area from the bottom the remedial grading excavation at the property lines. Our evaluation assumed that the current offsite conditions will not be significantly modified by future grading at the time of the design earthquake, which is a reasonably conservative assumption. Summary It is the opinion of GSI that the susceptibility of the site to experience damaging deformations from seismically-induced liquefaction and densification is relatively low owing to the dense, nature of the old paralic deposits that underlie the site in the near-surface. In addition, the recommendations for remedial earthwork and foundations would further reduce any significant liquefaction/densification potential. Some seismic densification of the adjoining un-mitigated site(s) may adversely influence planned improvements at the perimeter of the site. However, given the remedial earthwork and foundation recommendations provided herein, the potential for the site to be affected by significant seismic densification or liquefaction of adjoining offsite soils may be considered low. Other Geologic/Secondary Seismic Hazards The following list includes other geologic/seismic related hazards that have been considered during our evaluation of the site. The hazards listed are considered negligible 3535 Harding Street, Carlsbad File:e:\wp12\7300\7355a. pge GeoSoils, Inc. October 27, 2017 Page 12 and/or mitigated as a result of site location, soil characteristics, and typical site development procedures: • Subsidence • Ground Lurching or Shallow Ground Rupture • Tsunami • Seiche 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 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 (pct), and the field moisture content was determined as a percentage of the dry weight. The results of these tests are shown on the Boring Logs in Appendix B. Laboratory Standard The maximum density and optimum moisture content was evaluated for a representative, near-surface bulk soil sample collected from the borings. Testing was performed in general accordance with ASTM D 1557. The moisture-density relationships obtained for this soil are shown on the following table: SAMPLE LOCATION AND DEPTH {FT) I B-1 @ ½-5 Harding Palm, LLC 3535 Harding Street, Carlsbad File:e:\wp 12\7300\7355a.pge I MAXIMUM DENSITY {PCF) 132.0 I GeoSoils, Inc. OPTIMUM MOISTURE CONTENT{%) 7.7 I 'N.O. 7355 l\ SC October 27, 2017 Page 13 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 LOCATIOH :I EXPAN~11ON INDEX I EXPANSION POTENTIAL AND DEPTH (Fn B-1 @ ½-5 I <5 I Very Low I Direct Shear Shear testing was performed on a representative, remolded sample of near-surface site soils in general accordance with ASTM Test Method D 3080 in a Direct Shear Machine of the strain control type. Prior to testing, the bulk soil sample was remolded to 90 percent of the laboratory standard (ASTM D 1557). The shear test results are presented as follows and in Appendix D: : PRIMARY RESIDUAL SAMPLE LOCATION I AND DEfJTH (FT) COHESION I FRICTION ANGLE COHESION FRICTION ANGLE {PSF) (DEGREES) {PSF) . (DEGREES) I B-1 @ ½-5 I 2 I 33 I 2 I 30 I Saturated Resistivity, pH, and Soluble Sulfates, and Chlorides GSI conducted sampling of the near-surface 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 AND DEPTH (FT) I B-1 @ ½-5 I Harding Palm, LLC 3535 Harding Street, Carlsbad File:e:\wp12\7300\7355a.pge SATURATED pH RESISTIVITY {ohm-cm) 8.04 I 2,900 GeoSoils, Inc. SOLUBLE SU.LFATES {% by weight) I 0.0185 I SOLUBLE CHLORIDES {ppm) 60 I W.0. 735!:i-A-SC October 27, 2017 Page 14 Corrosion Summary Laboratory testing indicates thatthetested sample of the onsite soils is moderately alkaline with respect to soil acidity/alkalinity; is moderately corrosive to exposed, buried metals when saturated; presents negligible sulfate exposure to concrete (i.e., Exposure Class SO per Table 19.3.1.1 of American Concrete Institute [ACI] 318-14); and has slightly elevated concentrations of soluble chlorides. GSI does not consult in the field of corrosion engineering. Thus, the Client, Structural, Civil, Plumbing, Mechanical, and Electrical Engineers, and Project Architect should agree on the level of corrosion protection required for the project and seek consultation from a qualified corrosion consultant as warranted. PRELIMINARY CONCLUSIONS AND RECOMMENDATIONS Based on our field exploration, laboratory testing, and geotechnical engineering analysis, it is our opinion that the subject site is suitable for the proposed residential development from a geotechnical engineering and geologic viewpoint, provided that the recommendations presented in the following sections are incorporated into the design and construction phases of site development. The primary geotechnical concerns with respect to the proposed development and improvements are: • Earth materials characteristics and depth to competent bearing materials below the existing grades. • On-going corrosion potential of site soils. • Erosiveness of site earth materials. • A shallow perched groundwater table the potential to encounter perched groundwater both during and following site development. • Perimeter conditions and planned improvements near the property boundary. • Uniform support of building foundations. • 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. Harding Palm, :..:..c 3535 Harding Street, Carlsbad File:e:\wp 12\7300\7355a.pge GeoSoils, Inc. -.·: .0. 7355-A-SC October 27, 2017 Page 15 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. Quaternary-age colluvium and weathered 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 engineered fills. Unsuitable soils within the influence of proposed settlement- sensitive improvements and engineered fills should be removed to expose unweathered 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 a depth of approximately 3 feet below existing grades. However, locally deeper remedial grading excavations cannot be precluded and should be anticipated. 4. Expansion Index (E.I.) testing performed on a representative sample of the onsite soils indicates very low expansive soil conditions (E.I. < 5). On a preliminary basis, mitigation measures to protect the proposed development from the damaging shrink/swell effects of expansive soils is not warranted. 5. Corrosion testing performed on a representative sample of the on site soils suggests that site soils are moderately alkaline with respect to soil acidity/alkalinity; are moderately corrosive to exposed, buried metals when saturated; present negligible sulfate exposure to concrete (i.e., Exposure Class SO per Table 19.3.1.1 of American Concrete Institute [ACI] 318-14); and have slightly elevated concentrations of soluble chlorides. GSI does not consult in the field of corrosion engineering. Thus, the Client, Structural, Civil, Plumbing, Mechanical, and Electrical Engineers, and Project Architect should agree on the level of corrosion protection required for the project and seek consultation from a qualified corrosion consultant as warranted.; and contain elevated concentrations of soluble chlorides. 6. Site soils are considered erosive. Surface drainage should be designed to eliminate the potential for concentrated flows. Positive surface drainage away from foundations is recommended. Temporary erosion control measures should be implemented until vegetative covering is well established. The homeowners/homeowner's association (HOA) will need to maintain proper surface drainage over the life of the project. Harding Palm, LLt: 3535 Harding Street, Carlsbad File:e:\wp 12\7300\7355a.pge GeoSoils, Inc. 'IJ.O. 73::;5 A-SC October 27, 2017 Page 16 7. Perched groundwater was encountered near the geologic contact of the old paralic deposits and the underlying Santiago Formation at an approximate depth of 17 feet BEG. The regional groundwater table is anticipated to be near sea level, or approximately 62 feet below the lowest site elevation. Groundwater is not anticipated to significantly affect the proposed development. provided that planned excavations do not extend greater than approximately 17 feet below the existing grades. Saturated soil conditions could be encountered a few feet above the perched water table. Groundwater conditions are subject to change and the potential for perched water to be encountered at higher elevations during or following site development cannot be precluded. This potential should be disclosed to all interested/affected parties. 8. The removal and recompaction of potentially compressible soils below a 1 :1 (h:v) projection down from the bottom, outboard of planned settlement-sensitive improvements and engineered fill along the perimeter of the site will be limited due to boundary restrictions and existing improvements that are to remain in serviceable use. As such, any settlement-sensitive improvement located above a 1 :1 (h:v) projection from the bottom outboard edge of the remedial grading excavation atthe property boundaries 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 3 feet from the property boundaries would require deepened foundations or additional reinforcement by means of ground improvement or specific structural design. This should be considered during project design. 9. In order to provide uniform foundation support, all footings for the townhouse structures should be underlain by at least 24 inches of engineered fill. Based on the available subsurface data, this will require some overexcavation of the unweathered old paralic deposits. 10. On a preliminary basis, temporary slopes should be constructed in accordance with CAL-OSHA guidelines for Type "B" soils, provided 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 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. 11. 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 Harding Palm, L:..C 3535 Harding Street, Carlsbad File:e:\wp 12\7300\7355a.pge GeoSoils, Inc. ':J.0. 7355 /\ SC October 27, 2017 Page 17 repairable in the event of the design seismic event. This potential should be disclosed to any owners and all interested/affected parties. 12. On a preliminary basis, the feasibility of stormwater infiltration at the subject site is considered very low to perhaps moderate. Full infiltration is considered unlikely owing to the dense and typically moderately cemented nature of the old paralic deposits that occur in the near surface. If stormwater were to infiltrate, it would most likely perch upon the old paralic deposits and migrate laterally. This could have adverse effects onsite and offsite, including backfill settlement within utility trenches and subsequent distress to overlying or superjacent improvements. 13. 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 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. Harding Palm, LLC 3535 Harding Street, Carlsbad File:e:\wp12\7300\7355a.pge GeoSoils, Inc. October 27, 2017 Page 18 Any remaining cavities should be observed by the geotechnical consultant. Mitigation of cavities would likely include removing any potentially compressible soils to expose unweathered 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). Given the age of the existing residence, it is possible that an onsite sewage disposal system (i.e., cisterns, seepage pits, leach lines, etc.) may be present, Should such structures be encountered during earthwork, this office should be contacted to provide recommendations for removal and disposal. Removal and Recompaction of Potentially Compressible Earth Materials Potentially compressible colluvium and weathered old paralic deposits should be removed to expose unweathered old paralic deposits. Following removal, these soils should be cleaned of any vegetation and deleterious debris, moisture conditioned to at least the soil's optimum moisture content, and then be recompacted to at least 90 percent of the laboratory standard (ASTM D 1557). Based on the available data, excavations necessary to remove unsuitable soils are anticipated to extend to a depth of approximately 3 feet BEG (excluding the recommended fill blanket below footings). The potential for remedial grading excavations to extend to greater depths 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 or 5 feet outside the perimeter edges of the townhouse structure (whichever is greater), 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 least the 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 adjacent property and existing improvements that need to remain in serviceable use so as to not cause damage to such. 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. 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, Ha.ding Pa:m, :..LC 3535 Harding Street, Carlsbad File:e:\wp 12\7300\7355a.pge GeoSoils, Inc. October 27, 2017 Page 19 not just within the influence of the proposed townhouse structures. 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 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 3 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 potential should be disclosed to any owners and all interested/affected parties should this condition exist at the conclusion of grading. Overexcavation In order to provide uniform foundation support, any unweathered old paralic deposits exposed within 48 inches from pad grade or 24 inches below the lowest foundation (whichever is greater) should be overexcavated and replaced with compacted fill. The maximum to minimum fill thickness beneath the proposed townhouse structures should not exceed a ratio of 3:1 (maximum:minimum). 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). Fills placement and compaction should be observed and tested by the geotechnical consultant. Import Soils If import fill is necessary, a sample of the soil import should be evaluated by this office prior to importing, in order to assure compatibility with the onsite soils and the recommendations presented in this report. If non-manufactured materials are used, environmental documentation for the export site should be provided for GSI review. At least three business days of lead time should be allowed by builders or contractors for proposed import submittals. This lead time will allow for environmental document review, particle size analysis, laboratory standard, expansion testing, and blended import/native characteristics as deemed necessary. Import soils should have an E.I. of 20 or less and a plasticity index (P.I.) of 14 or less. 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. Harding Palm, L:..C 3535 Harding Street, Carlsbad File:e:\wp12\7300\7355a.pge GeoSoils, Inc. ',/V.O. 7355./\-SC October 27, 2017 Page 20 Graded Slope Construction Based on site relief, permanent graded slopes are not anticipated. Thus, recommendations for grade slope construction have not been provided, but could be provided upon request. Temporary Slopes Temporary slopes for excavations greater than 4 feet, but less than 15 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± 15 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 observations be made before, during, and after construction to determine the effects (if any) of construction on existing improvements. We believe that this is necessary for two reasons: First, if excessive movements (i.e., more than ½-inch) are detected early enough, remedial measures can be taken which could possibly prevent serious damage to existing improvements. Second, the responsibility for damage to the existing improvement can be determined more equitably if the cause and extent of the damage can be determined more precisely. Monitoring should include the measurement of any horizontal and vertical movements of the existing structures/improvements. Locations and type of the monitoring devices should be selected prior to the start of construction. The program of monitoring should be agreed upon between the project team, the site surveyor and the Geotechnical Engineer-of-Record, prior to excavation. Harding Palm, LLC 3535 Harding Street, Carlsbad File:e:\wp12\7300\7355a.pge GeoSoils, Inc. W.O. 7355-A-SC October 27, 2017 Page 21 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 survey monitoring system, an accuracy of a least 0.01 foot should be required. Reference points should be installed and read initially prior to excavation. The readings should continue until all construction below ground has been completed and the permanent backfill has been brought to final grade. The frequency of readings will depend upon the results of previous readings and the rate of construction. Weekly readings could be assumed throughout the duration of construction with daily readings during rapid excavation near the bottom of the excavation. The reading should be plotted by the Surveyor and then reviewed by the Geotechnical Engineer. In addition to the monitoring system, it would be prudent for the Geotechnical Engineer and the Contractor to make a complete inspection of the existing structures both before and after construction. The inspection should be directed toward detecting any signs of damage, particularly those caused by settlement. Notes should be made and pictures should be taken where necessary. Observation It is recommended that all excavations be observed by the Geologist and/or Geotechnical Engineer. Any fill which is placed should be approved, tested, and verified if used for engineered purposes. Should the observation reveal any unforseen hazard, the Geologist or Geotechnical Engineer will recommend treatment. Please inform GSI at least 24 hours prior to any required site observation. Earthwork Balance (Shrinkage/Bulking) The volume change of excavated materials upon compaction as engineered fill is anticipated to vary with material type and location. The overall earthwork shrinkage and bulking may be approximated by using the following parameters: Colluvium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5% to 8% shrinkage Weathered Old Paralic Deposits . . . . . . . . . . . . . . . . . . . . . . 2% to 3% shrinkage or bulk Unweathered Old Paralic Deposits . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2% to 3% bulking It should be noted that the above factors are estimates only, based on preliminary data. The colluvium and weathered 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 Harding Palm, LLC 3535 Harding Street, Carlsbad File:e:\wp12\7300\7355a.pge GeoSoils, Inc. '.\'.O. 7355 /\ SC October 27, 2017 Page 22 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, 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 townhouse structures 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 related to foundation design. The preliminary geotechnical data indicates the subject site is underlain by very low expansive soils (E.I. of 20 or less) and a P.1. of 14 or less In the following sections, GSI provides preliminary design and construction recommendations for foundations and slab-on-grade floor systems underlain by this type of soil conditions. Footings for the duplex structures should be founded into approved engineered fill observed and tested by this office. Preliminary Foundation Design 1. The foundation systems should be designed and constructed in accordance with guidelines presented in the 2016 CBC. 2. An allowable bearing value of 2,000 pounds per square foot (psf) may be used for the design of continuous spread footings that maintain a minimum width of 12 inches and a minimum depth of 12 inches (below the lowest adjacent grade), into approved engineered fill. A similar bearing value may be used in the design of isolated spread footings that have a minimum dimension of at least 24 inches square and a minimum embedment of 24 inches below the lowest adjacent grade, into approved engineered fill. Foundation embedment depth excludes concrete Marding Palm, LLC 3535 Harding Street, Carlsbad File:e:\wp 12\7300\7355a.pge GeoSoils, Inc. W.O. 7355-A-SC October 27, 2017 Page 23 slabs-on-grade, and/or slab underlayment. The bearing value may be increased by 20 percent for each additional 12 inches in footing depth to a maximum value of 2,500 psfforfootings founded into approved engineered fill. The bearing value may be increased by one-third when considering short duration seismic or wind loads. 3. For foundations deriving passive resistance from approved very low expansive engineered fill, a passive earth pressure may be computed as an equivalent fluid having a density of 250 pcf, with a maximum earth pressure of 2,500 psf. 4. The upper 6 inches of passive pressure should be neglected if not confined by slabs or pavement. 5. For lateral sliding resistance, a 0.35 coefficient of friction may be utilized for a concrete to soil contact when multiplied by the dead load. 6. When combining passive pressure and frictional resistance, the passive pressure component should be reduced by one-third. 7. Although significant slopes are not anticipated to be a part of the proposed development, 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 footing to the slope face. 8. Footings for structures adjacent to retaining walls should be deepened so as to extend below a 1 :1 projection up from the heel of the wall footing. PRELIMINARY FOUNDATION CONSTRUCTION RECOMMENDATIONS Conventional Foundation and Slab-On-Grade Floor Systems The following recommendations are intended to support foundations and slab-on-grade floor systems underlain by soils with an E.l.<20 and P.I. <14. 1. Exterior and interior continuous footings should be founded into approved engineered fill at a minimum depth of 12, 18, and 24 inches below the lowest adjacent grade for one-, two-, and three-story floor loads, respectively. For one-, two-, and three-story floor loads, continuous footing widths should be 12, 15, and 18 inches, respectively. Isolated, column, panel pad, or retaining wall footings, should be at least 24 inches square, and be founded at a minimum depth of 24 inches below the lowest adjacent grade into approved engineered fill. All footings should be minimally reinforced with four No. 4 reinforcing bars, two placed near the top and two placed near the bottom of the footing. Harding Palm, LLC 3535 Harding Street, Carlsbad File:e:\wp12\7300\7355a.pge GeoSoils, Inc. W .0. 7355 A-SC October 27, 2017 Page 24 2. All interior and exterior isolated column footings should be tied to the perimeter foundation via a reinforced grade beam in at least one direction. The grade beam should be at least 12 inches square in cross section, and should be provided with a minimum of one No.4 reinforcing bar at the top, and one No.4 reinforcing bar at the bottom of the grade beam. The base of the reinforced grade beam should be at the same elevation as the adjoining footings. This may require the use of a stepped grade beam if there are differences in the bearing elevations. 3. A grade beam, reinforced as previously recommended and at least 12 inches square, should be provided across large (garage) entrances. The base of the reinforced grade beam should be at the same elevation as the adjoining footings. 4. A minimum concrete slab-on-grade thickness of 4½ inches is recommended. This includes garage slabs-on-grade. 5. Concrete slabs should be reinforced with a minimum of No. 3 reinforcement bars placed at 18 inches on center, in two horizontally perpendicular directions (i.e., long axis and short axis). 6. All slab reinforcement should be supported to ensure proper mid-slab height positioning during placement of the concrete. "Hooking" of reinforcement is not an acceptable method of positioning. 7. Slab subgrade pre-soaking is not required for very low expansive soil conditions. However, the Client/Developer should consider pre-wetting the slab subgrade materials to at least the soil's optimum moisture content to a minimum depth of 12 inches, prior to the placement of the underlayment sand and vapor retarder. 8. Soils generated from footing excavations to be used onsite should be compacted to a minimum relative compaction of 90 percent of the laboratory standard (ASTM D 1557), whether the soils are to be placed inside the foundation perimeter or in the yard/right-of-way areas. This material must not alter positive drainage patterns that direct drainage away from the structural areas and toward the street. 9. Reinforced concrete mix design should consider the elevated concentrations of soluble chlorides in the onsite soils. Foundation Settlement Provided that the earthwork and foundation recommendations in this report are adhered, foundations bearing on approved engineered fill overlying dense unweathered 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). !-laiding Palm, LLC 3535 Harding Street, Carlsbad File:e:\wp 12\7300\7355a.pge GeoSoils, Inc. 'N.O. 7355ASC October 27, 2017 Page 25 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. The recommendations in this section are not intended to preclude the transmission of water or vapor through the foundation or slabs. Foundation systems and slabs shall not allow water or water vapor to enter into the structure so as to cause damage to another building component or to limit the installation of the type of flooring materials typically used for the particular application (State of California, 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, project architect, and/or individual homeowner[s]) that can tolerate vapor transmission rates without significant distress, the following alternatives are provided: • Concrete slabs, including garages, should be a minimum of 5 inches thick. • 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-1745 - Class A, per Engineering Bulletin 119 [Kanare, 2005]) installed per the Harding Palm, LLC 3535 Harding Street, Carlsbad File:e:\wp 12\7300\7355a.pge GeoSoils, Inc. ~•J.C. 7355 A SC October 27, 2017 Page 26 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 will be necessary for the cushion or sand layer for moisture content, and relatively uniform thicknesses, prior to the placement of concrete. • For very low expansive soil conditions, 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 19.3.2.1 of American Concrete Institute 318-14 ([ACI], 2014a and 2014b) 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 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(s)/tenants 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 Harding Palm, L:.C 3535 Harding Street, Carlsbad File:e:\wp12\7300\7355a.pge GeoSoils, Inc. 'N.0. 7355-A SC October 27, 2017 Page 27 techniques. The use of specialized product(s) should be approved by the slab designer and water-proofing consultant. A technical representative of the flooring contractor should review the slab and moisture retarder plans and provide comment prior to the construction of the foundation or improvement. The vapor retarder contractor should have representatives onsite during the initial installation. SITE RETAINING WALL DESIGN PARAMETERS (IF WARRANTED) General Based on our review of KP&D (2017), there are no proposed retaining walls associated with the project at this time. However, should they be needed or incorporated into future owner and/or HOA landscape improvements, we have included recommendations for the design and construction of conventional masonry retaining walls. Recommendations for specialty walls (i.e., crib, earthstone, geogrid, etc.) can be provided upon request, and would be based on site specific conditions. · Conventional Retaining Walls The design parameters provided below assume that either very low expansive soils (typically Class 2 permeable filter material or Class 3 aggregate base) or native onsite materials with an 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. Building walls, below grade, should be water-proofed. Waterproofing should also be provided for site retaining walls in order to reduce the potential for efflorescence staining. The onsite soils intended for retaining wall backfill should be evaluated for suitability prior to placement. Preliminary Retaining Wall Foundation Design Preliminary foundation design for retaining walls should incorporate the following recommendations: Minimum Footing Embedment -24 inches below the lowest adjacent grade (excluding landscape layer [upper 6 inches]). Minimum Footing Width -24 inches Allowable Bearing Pressure -An allowable bearing pressure of 2,500 pcf may be used in the preliminary design of retaining wall foundations provided that the footing maintains a minimum width of 24 inches and extends at least 24 inches into approved engineered fill overlying dense unweathered old paralic deposits, or suitable unweathered old paralic deposits. This pressure may be increased by one-third for short-term wind and/or seismic loads. Uarding Palm, L:..C 3535 Harding Street, Carlsbad File:e:\wp12\7300\7355a.pge GeoSoils, Inc. W.O. ?355 A-SC October 27, 2017 Page 28 Passive Earth Pressure -A passive earth pressure of 250 pct 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 properly compacted granular fill or granular 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 125 pct and 135 pct 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). Any retaining wall footings near the perimeter of the site will likely need to be deepened into unweathered old paralic deposits for adequate vertical and lateral bearing support. All retaining wall 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 footing to the slope face. 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 pct and 65 pct 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 Harding r'alrr., :..LC 3535 Harding Street, Carlsbad File:e:\wp 12\7300\7355a.pge GeoSoils, Inc. October 27, 2017 Page 29 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 passenger truck and car traffic. For heavy axle loads (HS-20), a 300 psf/ft traffic surcharge should be applied in the upper 5 feet of the wall. This does not include the surcharge of parked vehicles which should be evaluated at a higher surcharge to account for the effects of seismic loading. Equivalent fluid pressures for the design of cantilevered retaining walls are provided in the following table: SURFACE SLOPE OF EQUIVALENT EQUIVALENT RETAINED MATERIAL FLUID WEIGHT P.C.F. FLUID WEIGHT P.C.F. ·-::< .. / !,-:-:-, (HORIZONTAL:VERTICAL) (SELECT BACKFILL)<2> (NATJ\.fE BACKFILL)13> I LeveI(1l I 38 I 50 I 2 to 1 55 65 (1l Level backfill behind a retaining wall is defined as compacted earth materials, properly drained, without a slope tor a distance of 2H behind the wall, where H is the height of the wall. (2l SE~ 30, P .I. < 15, E.I. < 21, and~ 10% passing No. 200 sieve. (3l E.I. = 0 to 50, SE > 30, P.1. < 15, E.I. < 21, and < 15% passing No. 200 sieve. Seismic Surcharge For retaining walls incorporated into the 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 seismic surcharge should be applied as a uniform surcharge load from the bottom of the footing (excluding shear keys) to the top of the backfill at the heel of the wall footing. 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 triangular 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, considering the transient nature of this surcharge. Please note this is for local wall stability only. The 15H is derived from a Mononobe-Okabe solution for both restrained cantilever walls. This accounts for the increased lateral pressure due to shakedown or movement of the sand fill soil in the zone of influence from the wall or roughly a 45° -cp/2 plane away from the back of the wall. The 15H seismic surcharge is derived from the formula: Harding ralm, LL~ 3535 Harding Street, Carlsbad File:e:\wp12\7300\7355a.pge GeoSoils, Inc. October 27, 2017 Page 30 p h = 3/a • ah • y tH Where: Ph ah Yi H = = = = Seismic increment Probabilistic horizontal site acceleration with a percentage of "g" Total unit weight (120 to 125 pct for site soils @ 95% relative compaction). Height of the wall from the bottom of the footing or point of pile fixity. Retaining Wall Backfill and Drainage Positive drainage must be provided behind all retaining walls in the form of gravel wrapped in geofabric and outlets. A backdrain system is considered necessary for retaining walls that are 2 feet or greater in height. Details 1, 2, and 3, present the backdrainage options discussed below. Backdrains should consist of a 4-inch diameter perforated Schedule 40 or SDR 35 drain 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 slope) 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 Wall Backfill and Subdrain Detail Geotextile Drain). Materials with an expansion index (E.1.) 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 sol id 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. ltardir.g P~:m, LLC 3535 Harding Street, Carlsbad File:e:\wp12\7300\7355a.pge GeoSoils, Inc. 'N.O. 7355-A-SC October 27, 2017 Page 31 (1) Waterproofing membrane-~ CMU or reinforced-concrete wall ±12 inches Proposed grade t- sloped to drain per precise civil drawings (5) Weep hole /4~~~Ws\~ Footing and wall design by others~~ (1) Waterproofing membrane. (2) Gravel= Clean, crushed, ¾ to 1½ inch. Structural footing or settlement-sensitive improvement Provide surface drainage via an engineered V-ditch (see civil plans tor details) 2=1 (h=v) slope Slope or level (2) Gravel ::,,,.-:\1/ \\ ~ (3) Filter fabri fa Native backfill \\\/ 1=1 (h=v) or flatter backcut to be properly benched (6) Footing (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 reinf creed-concrete wall l 6 inches 1- (5) Weep hole Proposed grade sloped to drain per precise civil drawings /<)~\\y(\~~\)5\\0(\\ Footing and wall design by others-----"'~-, Structural f coting 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 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; Mira drain 6200 or J-drain 200 or equivalent for waterproofed walls (all perforations down). (3) Filter fabric= Mirafi 140N or approved equivalent; place fabric flap behind core. (4) Pipe= 4-inch-diameter perforated PVC, Schedule 40, or approved alternative with minimum of 1 percent gradient to proper outlet point (perforations down). (5) Weep hole= Minimum 2-inch diameter placed at 20-foot centers along the wall and placed 3 inches above finished surf ace. 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 ol (1) Waterproofing membrane --~ CMU or re inf creed-concrete wall Structural footing or settlement-sensitive improvement r-----Provide surf ace drainage ±12 inches l (5) Weep hole H [ Proposed grade sloped to drain per precise civil drawings -(0~\\j(\\~\/: Footing and wall design by others H/2 minimum 2=1 (h=v) slope Slope or level ... 1 I ':\\\ ~ ~,Y (3) Filter fabric (2) Gravel (4) Pipe (7) Footing (1) Waterproofing membrane= Liquid boot or approved masticequivalent. (2) Gravel= Clean, crushed, ¾ to 1½ inch. (3) Filter fabric= Mirafi 140N or approved equivalent. (8) Native backfill (6) Clean sand backfill 1=1 (h=v) or flatter backcut to be properly benched (4) Pipe: 4-inch-diameter perforated PVC, Schedule 40, or approved alternative with minimum of 1 percent gradient to proper outlet point (perforations down). (5) Weep hole= Minimum 2-inch diameter placed at 20-foot centers along the wall and placed 3 inches above finished surf ace. Design civil engineer to provide drainage at toe of wall. No weep holes for below-grade walls. (6) Clean sand backfill= Must have sand equivalent value (S.E.) of 35 or greater; can be densified by water jetting upon approval by geotechnical engineer. (7) Footing: If bench is created behind the footing greater than the footing width, use level fill or cut natural earth materials. An additional "heel" drain will likely be required by geotechnical consultant. (8) Native backfill= If E.I. (21 and S.E. ~35 then all sand requirements also may not be required and will be reviewed by the geotechnical consultant. /.Y'4--.._,,; 1 / ' F-t;:.')t \-i>--'/ ~~~!,jJl~e. '.,~'~«.;c,,,r •~<,-/,>;,-# "'-=<.-; •' RETAINING WALL DETAIL -ALTERNATIVE C Detail 3 el Wall/Retaining Wall Footing Transitions Site walls are anticipated to be founded on footings designed in accordance with the recommendations in this report. Should wall footings transition from cut to fill, the civil designer may specify either: a) A minimum of a 2-foot overexcavation and recompaction of cut materials for a distance of 2H, from the point of transition. b) Increase of the amount of reinforcing steel and wall detailing (i.e., expansion joints or crack control joints) such that a angular distortion of 1 /360 for a distance of 2H on either side of the transition may be accommodated. Expansion joints should be placed no greater than 20 feet on-center, in accordance with the structural engineer's/wall designer's recommendations, regardless of whether or not transition conditions exist. Expansion joints should be sealed with a flexible, non-shrink grout. c) Embed the footings entirely into native formational material (i.e., deepened footings). If transitions from cut to fill transect the wall footing alignment at an angle of less than 45 degrees (plan view), then the designer should follow recommendation "a" {above) and until such transition is between 45 and 90 degrees to the wall alignment. PRELIMINARY PERMEABLE INTERLOCKING CONCRETE PAVEMENT DESIGN Based on communication with a representative of Spear and Associates, Inc. (Project Civil Engineer), GSI understands that the proposed private driveway may incorporate permeable interlocking concrete pavement (i.e., brick pavers) in order to reduce the volume of storm water runoff. Thus, preliminary recommendations for the design and construction of the permeable interlocking concrete pavement structural section are included herein. Final pavement design should be based on R-value testing of the subgrade following grading and underground utility backfill. The preliminary design of the pavement structural section is based on guidelines presented in American Society of Civil Engineers (ASCE) Standard 58-10 (ASCE, 2010). The available subsurface data suggests that the pavement subgrade will likely consist of a mixture of poorly graded sand (USCS Symbol -SP) and silty sand (USCS Symbol -SM). For the preliminary design of the permeable interlocking concrete pavement structural section, GSI concludes that a Subgrade Soil Category No. 3 with fair to poor drainage characteristics is appropriate for the onsite soil conditions. We have also assumed Traffic Indices (T.l.s) ranging between 5.0 and 6.0 to account for heavy axle (HS20) vehicle loads and trash trucks. As indicated in Table 4-3 of ASCE (2010), the aforementioned subgrade and traffic conditions require a minimum permeable interlocking pavement section as shown in the following table: Harding Palm, :..:..c 3535 Harding Street, Carlsbad File:e:\wp 12\7300\7355a. pge GeoSolls, Inc. '.'.'.O. 7355-A SC October 27, 2017 Page 35 BRICK PAV,ERTHICKNES~.11>: I .. SAN!?, _LEVELING . ,;, UNBOUND. DENSE GRANULAR -BAsEm THICKNess·' ,, .. ·.· BASE'THICKNESS11> .. .. 3.15 inches (±80 millimeters) I 1 inch (±25 millimeters) 4 inches (±100 millimeters) (1) -Minimum specified thickness for vehicular traffic applications (American Society of Civil Engineers [ASCE], 2010) (2l-Minimum California Bearing Ratio (CBR) = 80 percent; maximum loss of 40 percent (per ASTM C131 ); maximum plasticity index = 6; and maximum liquid limit of 25. Subgrade Preparation Subgrade materials to receive permeable brick paver sections should be scarified at least 12 inches, moisture conditioned to at least optimum moisture content and compacted to at least 95 percent of the laboratory standard (ASTM D 1557). Prior to subgrade approval from the geotechnical consultant, it should be proof rolled either by heavy .equipment or a full water truck. Any areas observed to deform under vehicle loads should be mitigated per the geotechnical consultant's recommendations. Given the "permeable" nature of this pavement application, GSI recommends that following subgrade testing and approval, the subgrade be covered with Tencate HP570 stabilization geotextile to help reduce the potential for infiltrated runoff to weaken and deform the pavement subgrade. Unbound Granular Base Preparation Unbound granular base should placed atop the HP570 stabilization geotextile and the prepared subgrade. Care should be taken to prevent damage to the HP570 stabilization geotextile from delivery truck and construction equipment traffic, during aggregate base placement. This can be accomplished by spreading the dumped base materials over the HP570 stabilization geotextile before it receives traffic from construction equipment or delivery trucks. The base materials should be moisture conditioned to at least optimum moisture content and then compacted to at least 95 percent of the laboratory standard (ASTM D 1557). Aggregate within the base material should consist of at least 2 fractured faces to assist with interlock. Sand Leveling Base The sand leveling bed should consist of well-graded sand conforming to the following particle-size distribution: I US SIEVE SIZE" I PERCENT PASSING II .• US SIEVE SIZE %" No. 4 No. 8 No. 16 Harding Palii., :..:..c 3535 Harding Street, Carlsbad File:e:\wp12\7300\7355a.pge 100 No. 30 95 -100 No. 50 70 -100 No. 100 45 -85 No.200 GeoSoils, Inc. I PERCENT PASSING I 30 -65 10 -30 0 -10 0 -1 VV .C. 7355-A-SC October 27, 2017 Page 36 According to ASCE (2010), sands with predominant silica composition and sub-rounded to sub-angular particle shape are best suited for long-term performance of the brick paver section. The sand leveling base should be lightly moisture conditioned and then densified with a vibratory plate compactor. The geotechnical consultant should observe the preparation of the sand leveling base. Separation geotextile consisting of Mirafi 140N filter fabric should be placed atop the unbound granular base material if it consists of open- graded gravels in order to reduce the potential for piping of the sand leveling base into the underlying base layer. Additional Recommendations for Permeable Brick Paver Sections 1. An impermeable liner should be installed vertically around the perimeter of permeable pavements sections in order to reduce the lateral migration of perched water. The impermeable liner should be installed vertically along the outboard wall of a narrow trench excavated around the perimeter of the permeable pavement section and should extend at least 2 feet below the driveway subgrade elevation. The trench should be backfilled with slurry or a jetted clean sand with a Sand Equivalent (SE) of 50 or greater. Alternatively, concrete or slurry cut-off walls with a minimum width of 6 inches may be used around the perimeter of the permeable pavement section. Cut-off walls should extend at least 2 feet below the driveway subgrade elevation. 2. 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 Strength at Break (ASTM D882): 73 (lb/in-width, min); Elongation (ASTM D882): 380 (%, min); Modulus at 100 percent (ASTM D882): 32 (lb/in-width, min.); Tear Strength (ASTM D1004): 8 (lbs, min); Seam Strength (ASTM D882): 58.4 (lb/in, min); Seam Shear Strength (ASTM D882): 15 (lbs/in, min.); and Seam Peel Strength (ASTM D882) 2.6 (kN/m, min). 3. In order to improve structural capacity of the brick paver section, the brick pavers should be installed in a 45-or 90-degree herringbone pattern where they will receive vehicular traffic (ASCE, 2010). Provided that the pavers are confined by edge restraints such as a curb or gutter edge, a sailor or soldier course is not required to increase edge stability. However, a sailor or soldier course is recommended where utility structures and other protrusions occur in the pavement surface (ASCE, 2010). 4. Edge restraints (typically concrete curbs) should be installed around the perimeter of brick paver pavements to help maintain rotational and horizontal interlock in the pavement surface resulting from dynamic vehicular wheel loads such as turning, braking, and accelerating (ASCE, 2010). Harding Pal;";1, :..:..c 3535 Harding Street, Carlsbad File:e:\wp12\7300\7355a.pge GeoSoils, Inc. N.O. 7355-/\-SC October 27, 2017 Page 37 5. If a gravel reservoir layer is required for storage during draw down, it should consist of well-graded gravels (USCS Symbol -GW) with the following gradation: lu.s. SIEVE SIZE I PERCENT PASSING I 2½" 100 2" 65-100 ¾" 40-80 No. 4 <5 - No. 100 0-2 6. The minimum thickness of the gravel reservoir layer should be twice the dimension of the largest particle size. In addition, the portion of the gravel retained on the No. 4 sieve should have at least 2 fractured faces to assist with aggregate interlock. The gravel reservoir should be placed atop the HP570 stabilization geotextile and prepared subgrade, and densified using vibratory compaction equipment. If the overlying unbound base materials contains fine soil particles, GSI recommends that it be separated from the gravel reservoir layer with Mirafi 140N filter fabric to reduce the potential for piping of fines into the reservoir layer. FLATWORK AND OTHER IMPROVEMENTS Although not necessarily anticipated, some of the onsite 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: 1. Remedial grading, as recommended previously, should be performed below a 1 :1 (h:v) plane projected down from the bottom, outboard edges of driveways and flatwork. The subgrade area for concrete slabs should be compacted to achieve a minimum 90 percent relative compaction, and then be presoaked to 2 to 3 percentage points above (or 125 percent of) the soils' optimum moisture content, to a depth of 18 inches below subgrade elevation. If very low expansive soils are present, only optimum moisture content, or greater, is required and specific presoaking is not warranted. The moisture content of the subgrade should be proof tested within 72 hours prior to pouring concrete. Mitigation of any potentially Harding Pa:m, :..:..~ 3535 Harding Street, Carlsbad File:e:\wp12\7300\7355a.pge GeoSoils, Inc:. October 27, 2017 Page 38 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 slabs should be a minimum of 4 inches thick. Driveway slabs and approaches should additionally have a thickened edge (12 inches) adjacent to all landscape areas, to help impede infiltration of landscape water under the slab. 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. s: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/s inches deep, often enough so that no section is greater than 10 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. 6. Driveways, sidewalks, and patio slabs adjacent to the townhouse structures should be separated from the building with thick expansion joint filler material. In areas directly adjacent to a continuous source of moisture (i.e., irrigation, planters, etc.), all joints should be additionally sealed with flexible mastic. 7. Planters and walls should not be tied to the townhouse structures. ::ardlng Palm, LLC 3535 Harding Street, Carlsbad File:e:\wp12\7300\7355a.pge GeoSoils, Inc. October 27, 2017 Page 39 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. NC waste water lines should be drained to a suitable non-erosive outlet. 13. Shrinkage cracks could become excessive if proper finishing and curing practices are not followed. Finishing and curing practices should be performed per the Portland Cement Association Guidelines. Mix design should incorporate rate of curing for climate and time of year, sulfate content of soils, corrosion potential of soils, and fertilizers used on site. ONSITE INFILTRATION-RUNOFF RETENTION SYSTEMS General Onsite infiltration-runoff retention systems (OIRRS) are anticipated to be used for Best Management Practices (BMPs) or Low Impact Development (LID) principles for the project. To that end, some guidelines should/must be followed in the planning, design, and construction of such systems. Such facilities, if improperly designed or implemented without consideration of the geotechnical aspects of site conditions, can contribute to flooding, saturation of bearing materials beneath site improvements, slope instability, and possible concentration and contribution of pollutants into the groundwater or storm drain and/or utility trench systems. Harding Pi.hr., !..LC 3535 Harding Street, Carlsbad File:e:\wp12\7300\7355a. pge GeoSoils, Inc. October 27, 2017 Page 40 A key factor in these systems is the infiltration rate (often referred to as the percolation rate) which can be ascribed to, or determined for, the earth materials within which these systems are installed. Additionally, the infiltration rate of the designed system (which may include gravel, sand, mulch/topsoil, or other amendments, etc.) will need to be considered. The project infiltration testing is very site specific, any changes to the location of the proposed OIRRS and/or estimated size of the OIRRS, may require additional infiltration testing. GSI anticipates that relatively impermeable paralic deposits will occur near the surface at the conclusion of grading. Some of the methods which are utilized for onsite infiltration include percolation basins, dry wells, bio-swale/bio-retention, permeable pavers/pavement, infiltration trenches, filter boxes and subsurface infiltration galleries/chambers. Some of these systems are constructed using native and import soils, perforated piping, and filter fabrics while others employ structural components such as stormwater infiltration chambers and filters/separators. Every site will have characteristics which should lend themselves to one or more of these methods; but, not every site is suitable for OIRRS. In practice, OIRRS are usually initially designed by the project design civil engineer. Selection of methods should include (but should not be limited to) review by licensed professionals including the geotechnical engineer, hydrogeologist, engineering geologist, project civil engineer, landscape architect, environmental professional, and industrial hygienist. Applicable governing agency requirements should be reviewed and included in design considerations. The following geotechnical guidelines should be considered when designing onsite infiltration-runoff retention systems: • Based on our review of the United States Department of Agriculture (USDA) Web Soil Survey (http://websoilsurvey.sc.egov.usda.gov/ App/WebSoilSurvey.aspx), the onsite soils consist of the Marina loamy coarse sand, 2 to 9 percent slopes. The USDA reports that the capacity of the most limiting layer to transmit water (Ksat) of this mapped soil unit is moderately high to high (0.57 to 1.98 inches per hour [in/hr]). The USDA further indicates that this soil unit falls into Hydrologic Soil Group (HSG) "B." According to County of San Diego Department of Planning and Land Use (2014), HSG "B" soils have moderate infiltration rates when thoroughly wet. However, based on our observations, the old paralic deposits that underlie the site at a shallow depth may be more consistent with HSG "D" soils, locally, due to their induration. According to County of San Diego Department of Planning and Land Use (2014), HSG "D" soils have very low infiltration rates when thoroughly wet. On a preliminary basis, HSG "D" conditions and very slow infiltration rates should be considered when designing onsite storm water treatment BMPs. "Full infiltration" is considered unlikely at this time. The civil designer should also take into account that any infiltrated storm water would likely perch upon either the unweathered old paralic deposits or the underlying Santiago Formation and migrate laterally, potentially adversely impacting improvements on adjoining properties, including lluiding Palm, LLC' 3535 Harding Street, Carlsbad File:e:\wp12\7300\7355a.pge GeoSoils, Inc. '/'./.0. l:355 /\ SC October 27, 2017 Page 41 • • • • • • • utility trenches, distress to superjacent improvements. The recommended compacted fill mat will also perform like a HSG "O" soil. It is not good engineering practice to allow water to saturate soils, especially near slopes or improvements; however, the controlling agency/authority is now requiring this for OIRRS purposes on many projects. Wherever possible, infiltration systems should not be installed within ±50 feet of the tops of slopes steeper than 15 percent or within H/3 from the tops of slopes (where H equals the height of slope). Wherever possible, infiltrations systems should not be placed within a distance of H/2 from the toes of slopes (where H equals the height of slope). An impermeable liner or concrete, or slurry cut-off walls should be instaUed around the perimeter of permanent storm water infiltration BMPs in order to reduce the lateral migration of the infiltrated storm water. The impermeable liner or cut-off walls should extend at least 2 feet below the bottom of the basin. The impermeable liner should be installed vertically along the outboard wall of a narrow trench. The trench should be backfilled with slurry or a jetted clean sand with a Sand Equivalent (SE) of 50 or greater. Concrete or slurry cut-off walls should be at least 6 inches wide and utilize a low permeability mix design. Impermeable liners used in conjunction with permanent storm water BMPs should consist of a 30-mil polyvinyl chloride (PVC) membrane with the following properties: Specific Gravity (ASTM 0792): 1.2 (g/cc, min.); Tensile Strength at Break (ASTM 0882): 73 (lb/in-width, min); Elongation (ASTM 0882): 380 (%, min); Modulus at 100 percent (ASTM 0882): 32 (lb/in-width, min.); Tear Strength (ASTM 01004): 8 (lbs, min); Seam Strength (ASTM 0882): 58.4 (lb/in, min); Seam Shear Strength (ASTM 0882): 15 (lbs/in, min.); and Seam Peel Strength (ASTM 0882) 2.6 (kN/m, min). Subdrains used in conjunction with bioretention basins 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. Subdrains may be necessary down-gradient of permanent storm water BMPs. If necessary, the subdrain should consist of 4-inch diameter perforated Schedule 40 or SOR 35 drain pipe encased in ¾-inch clean gravels, and wrapped in approved filter fabric (Mirafi 140 or equivalent). The subdrain should flow via gravity (minimum 1 percent slope) toward an approved drainage facility. Marding Palm, LLC \"J.C. 7355A-SC October 27, 2017 Page 42 3535 Harding Street, Carlsbad File:e:\wp12\7300\7355a.pge GeoSoils, Inc. • • • • • • • • • The landscape architect should be notified of the location of the proposed OIRRS . If landscaping is proposed within the OIRRS, consideration should be given to the type of vegetation chosen and their potential effect upon subsurface improvements (i.e., some trees/shrubs will have an effect on subsurface improvements with their extensive root systems). Over-watering landscape areas above, or adjacent to, the proposed OIRRS could adversely affect performance of the system. Areas adjacent to, or within, the OIRRS that are subject to inundation should be properly protected against scouring, undermining, and erosion, in accordance with the recommendations of the design engineer. Seismic shaking may result in the formation of a seiche which could potential overtop the banks of an OIRRS and result in down-gradient flooding and scour. If subsurface infiltration galleries/chambers are proposed, the appropripte size, depth interval, and ultimate placement of the detention/infiltration system should be evaluated by the design engineer, and be of sufficient width/depth to achieve optimum performance, based on the infiltration rates provided. In addition, proper debris filter systems will need to be utilized for the infiltration galleries/chambers. Debris filter systems will need to be self cleaning and periodically and regularly maintained on a regular basis. Provisions for the regular and periodic maintenance of any debris filter system is recommended and this condition should be disclosed to all interested/affected parties. Infiltrations systems should not be installed within ±8 feet of building foundations utility trenches, and walls, or a 1 :1 (h:v) slope (down and away) from the bottom elements of these improvements. Alternatively, deepened foundations and/or pile/pier supported improvements may be used. Infiltrations systems should not be installed adjacent to pavement and/or hardscape improvements. Alternatively, deepened/thickened edges and curbs and/or impermeable liners may be utilized in areas adjoining the OIRRS. As with any OIRRS, localized ponding and groundwater seepage should be anticipated. The potential for seepage and/or perched groundwater to occur after site development should be disclosed to all interested/affected parties. Installation of infiltrations systems should av9id expansive soils (E.I. :::51) or soils with a relatively high plasticity index (P.I. > 20). Infiltration systems should not be installed where the vertical separation of the groundwater level is less than ± 1 O feet from the base of the system. V·J.0. 7:::!55·A-SC 3535 Harding Street, Carlsbad File:e:\wp12\7300\7355a.pge GeoSoils, Inc. October 27, 2017 Page 43 • • • • • • • • • Where permeable pavements are planned as part of the system, the site Traffic Index (T.1.) should be less than 25,000 Average Daily Traffic (ADT), as recommended in Allen, et al. (2011). Infiltration systems should be designed using a suitable factor of safety (FOS) to account for uncertainties in the known infiltration rates (as generally required by the controlling authorities), and reduction in performance over time. As with any OIRRS, proper care will need to be provided. Best management practices should be followed at all times, especially during inclement weather. Provisions for the management of any siltation, debris within the OIRRS, and/or overgrown vegetation (including root systems) should be considered. An appropriate inspection schedule will need to adopted and provided to all interested/affected parties. Any designed system will require regular and periodic maintenance, which may include rehabilitation and/or complete replacement of the filter media (e.g., sand, gravel, filter fabrics, topsoils, mulch, etc.) or other components utilized in construction, so that the design life exceeds 15 years. Due to the potential for piping and adverse seepage conditions, a burrowing rodent control program should also be implemented onsite. All or portions of these systems may be considered attractive nuisances. Thus, consideration of the effects of, or potential for, vandalism should be addressed. Newly established vegetation/landscaping (including phreatophytes) may have root systems that will influence the performance of the OIRRS or nearby LID systems. The potential for surface flooding, in the case of system blockage, should be evaluated by the design engineer. Any proposed utility backfill materials (i.e., inlet/outlet pIpIng and/or other subsurface utilities) located within or near the proposed area of the OIRRS may become saturated. This is due to the potential for piping, water migration, and/or seepage along the utility trench line backfill. If utility trenches cross and/or are proposed near the OIRRS, cut-off walls or other water barriers will need to be installed to mitigate the potential for piping and excess water entering the utility backfill materials. Planned or existing utilities may also be subject to piping of fines into open-graded gravel backfill layers unless separated from overlying or adjoining OIRRS by geotextiles and/or slurry backfill. The use of OIRRS above existing utilities that might degrade/corrode with the introduction of water/seepage should be avoided. Harding f'a!m, LLC ':✓.O. 7355-A-SC October 27, 2017 Page 44 3535 Harding Street, Carlsbad File:e:\wp 12\7300\7355a.pge GeoSoils, Inc. • A vector control program may be necessary as stagnant water contained in OIRRS may attract mammals, birds, and insects that carry pathogens. DEVELOPMENT CRITERIA Drainage Adequate surface drainage is a very important factor in reducing the likelihood of adverse performance of foundations, hard scape, 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 2013 CBC (whichever is more conservative). Consideration should be given to avoiding construction of planters adjacentto 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 and Design of Open Bottom Planters 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 1 O feet. As an alternative, closed-bottom type planters could be utilized. An outlet placed in the bottom of the planter, could be installed to direct drainage away from structures or any exterior concrete flatwork. If planters are constructed adjacent to structures, the sides and bottom of the Harding Palm, LLC 3535 Harding Street, Carlsbad File:e:\wp 12\7300\7355a.pge GeoSoils, Inc. 'IJ .0. 7355-A-SC October 27, 2017 Page 45 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, or trench backfilling after rough grading has been completed. This includes any grading, utility trench and retaining wall backfills, flatwork, etc. Mardi;;g Palm, LLC 3535 Harding Street, Carlsbad File:e:\wp 12\7300\7355a.pge GeoSoils, Inc. W.O. 7355 /\-SC October 27, 2017 Page 46 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. H.:;ding Pal:.., L:..C 3535 Harding Street, Carlsbad File:e:\wp12\7300\7355a.pge GeoSoils, Inc. October 27, 2017 Page 47 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. • During placement of subdrains or other subdrainage devices, prior to placing fill and/or backfill. • After excavation of building footings, retaining wall footings, and free standing walls footings, prior to the placement of reinforcing steel or concrete. • Prior to pouring any slabs or flatwork, after presoaking/presaturation of building pads and other flatwork subgrade, before the placement of concrete, reinforcing steel, capillary break (i.e., sand, pea-gravel, etc.), or vapor retarders (i.e., visqueen, etc.). Harding P.:.!;n, LLC 3535 Harding Street, Carlsbad File:e:\wp12\7300\7355a.pge GeoSoils, Inc. October 27, 2017 Page 48 • • • • • • 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 flatwork, 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 structural engineer/designer result in less critical details than are provided herein as minimums, the minimums presented herein should be adopted. It is considered likely that some, more restrictive details will be required. Hard;;-;~ r .. 1m, LLC 3535 Harding Street, Carlsbad File: e: \wp 12\ 7300\ 7355a. pge GeoSoils, Inc. W.O. 73b5 .'\. SC October 27, 2017 Page 49 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. Inasmuch as our study is based upon our review and engineering analyses and laboratory data, the conclusions and recommendations are professional opinions. These opinions have been derived in accordance with current standards of practice, and no warranty, either express or implied, is given. Standards of practice are subject to change with time. GSI assumes no responsibility or liability for work or testing performed by others, or their inaction; or work performed when GSI is not requested to be onsite, to evaluate if our recommendations have been properly implemented. Use of this report constitutes an agreement and consent by the user to all the limitations outlined above, notwithstanding any other agreements that may be in place. In addition, this report may be subject to review by the controlling authorities. Thus, this report brings to completion our scope of services forth is portion of the project. All samples will be disposed of after 30 days, unless specifically requested by the client, in writing. Harclir.g :·aim, L1.C 3535 Harding Street, Carlsbad File:e:\wp 12\7300\7355a.pge GeoSoils, Inc. October 27, 2017 Page 50 APPENDIX A REFERENCES GeoSoils, Inc. APPENDIX A REFERENCES American Concrete Institute, 2014a, Building code requirements for structural concrete (ACI 318-14), and commentary (ACI 318R-14): reported by ACI Committee 318, dated September. __ , 2014b, Building code requirements for concrete thin shells (ACI 318.2-14), and commentary (ACI 318.2R-14), dated September. __ , 2011, Building code requirements for structural concrete (ACI 318-11), an ACI standard and commentary: reported by ACI Committee 318; dated May 24. __ , 2004, Guide for concrete floor and slab construction, ACI 302.1 R-04, reported by ACI Committee 302. dated June. American Society of Civil Engineers, 2010, Structural design of interlocking concrete pavement for municipal streets and roadways, ASCE Standard 58-10. Allen, V., Connerton, A., and Carlson, C., 2011, Introduction to Infiltration Best Management Practices (BMP), Contech Construction Products, Inc., Professional Development Series, dated December. American Society for Testing and Materials (ASTM), 2003, Standard test method for infiltration rate of soils in field using double-ring infiltrometer, Designation D 3385-03, dated August. __ , 1998, Standard practice for installation of water vapor retarder used in contact with earth or granular fill under concrete slabs, Designation: E 1643-98 (Reapproved 2005). , 1997, Standard specification for plastic water vapor retarders used in contact with soil or granular fill under concrete slabs, Designation: E 1745-97 (Reapproved 2004). American Society of Civil Engineers, 2010, Minimum design loads for buildings and other structures, ASCE Standard ASCE/SEI 7-10. Blake, Thomas F., 2000a, EQFAUL T, A computer program for the estimation of peak horizontal acceleration from 3-D fault sources; Windows 95/98 version. __ , 2000b, EQSEARCH, A computer program for the estimation of peak horizontal acceleration from California historical earthquake catalogs; Updated to January 2015, Windows 95/98 version. GeoSoils, Inc. 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 construction of small embankments dams, reprinted January. California Stormwater Quality Association (CASQA), 2003, Stormwater best management practice handbook, new development and redevelopment, dated July. County of San Diego, Department of Public Works, 2014, Low impact development handbook, stormwater management strategies, dated December 31. Hydrologic Solutions, StormChamber™ installation brochure, pgs. 1 through 8, undated. International Conference of Building Officials, 2001, California building code, California code of regulations title 24, part 2, volume 1 and 2. __ , 1998, Maps of known active fault near-source zones in California and adjacent portions of Nevada. 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. Karnak Planning and Design, 2017, Plot plan for: Harding and Palm townhouse project, 3535 Harding Street, Carlsbad, CA 92008, APN: 204-210-03-00, Sheet A-1.0, 10- scale, dated August 28. Harding Palm, LLC File:e:\wp12\7300\7355a.pge GeoSoils, Inc. Appendix A Page 2 Kennedy, M.P., and Tan, SS., 2005, Geologic map of the Oceanside 30' by60' 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 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, 2016, 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. Tan, S.S., and Giffen, D.G., 1995, Landslide hazards in the northern part of the San Diego Metropolitan area, San Diego County, California, Landslide hazard identification map no. 35, Plate 35A, Department of Conservation, Division of Mines and Geology, DMG Open File Report 95-04. United States Geological Survey, 1997, San Luis Rey quadrangle, San Diego County, California, 7.5 minute series, 1 :24,000 scale. Harding Palm, LLC File:e:\wp12\7300\7355a.pge GeoSoils, Inc. Appendix A Page 3 APPENDIX B BORING LOGS GeoSoils, Inc. UNIFIED SOIL CLASSIFICATION SYSTEM CONSISTENCY OR RELATIVE DENSITY Major Divisions Group Symbols Typical Names CRITERIA GW Well-graded gravels and gravel- (I) C: .!!l sand mixtures, little or no fines Standard Penetration Test > «l (I) (I) (I)> -C ·u5 -«l Poorly graded gravels and Penetration (I) 0 ov (.) '- > oo ~ U 0 (!) GP gravel-sand mixtures, little or no Resistance N Relative (I) ·.; ai O «l Z fines (blows/ft) Density >E.t:: 0 ~ a m 5 0 C\J (!) 0 '--0 Silty gravels gravel-sand-silt 1/) • 0-4 Very loose =O ~ «l (I) ai .c GM oz 0 0 c: mixtures en c: LO(.) .iii i;j:!: -0 0 ~ (9 3: 4 -10 Loose ~ -0 GC Clayey gravels, gravel-sand-clay -~ -~ mixtures 10-30 Medium (!) «l (1) Q) Well-graded sands and gravelly 1/) '-30-50 Dense ca* SW oO 0 (I) C II) sands, little or no fines (.) LO C: ii, «l -0 C: Q) C > 50 Very dense ;;!!_ 0 ·--«l «l 0:;::; rn o en £ II) LO~~ SP Poorly graded sands and (I) -Oc.:=o gravelly sands, little or no fines 0 1;i «l (])Z ~ Cf) -E ~ 1/) SM Silty sands, sand-silt mixtures (I) «l (I) '-0 1/) ~=~ ~ (.) 1/) «l 0.. C: ·-C: Clayey sands, sand-clay ~ ::: u::: SC mixtures Inorganic silts, very fine sands, Standard Penetration Test ML rock flour, silty or clayey fine sands 1/) >--(/) Unconfined (I) ~:~ ~ > Inorganic clays of low to Penetration Compressive (I) -g ~ 0 medium plasticity, gravelly clays, ·.; CL Resistance N Strength 0 : .Q" ~ sandy clays, silty clays, lean 0 {blows/ft) Consistencx: {tons/ff) II) N ~.....Ill) clays '6 . en en ~ Organic silts and organic silty <2 Very Soft <0.25 -0 1/) (I) (I) OL clays of low plasticity C: 1/) -~ 1/) 2-4 Soft 0.25-.050 «l (!) 0.. Cl) ~ Inorganic silts, micaceous or 4-8 Medium 0.50-1.00 C: 0 MH diatomaceous fine sands or silts, u::: E 1/) ~ >-0 elastic silts 0 .!!! .E LO 8-15 Stiff 1.00-2.00 ?ft. (.)= 1ii Inorganic clays of high plasticity, 0 -0 -0 .c LO C ·-_, CH 15-30 Very Stiff <ll :::, '-fat clays 2.00-4.00 ~g~ u5 Q) 0) Organic clays of medium to high >30 Hard >4.00 OH plasticity Highly Organic Soils PT Peat, mucic, and other highly organic soils 3" 3/4" #4 #10 #40 #200 U.S. Standard Sieve Unified Soil Gravel Sand Silt or Clay Classification Cobbles I I I coarse fine coarse medium fine MOISTURE CONDITIONS MATERIAL QUANTITY OTHER SYMBOLS Dry Absence of moisture: dusty, dry to the touch trace 0-5% C Core Sample Slightly Moist Below optimum moisture content for compaction few 5-10 % s SPT Sample Moist Near optimum moisture content little 10-25 % B Bulk Sample Very Moist Above optimum moisture content some 25-45 % ... Groundwater Wet Visible free water; below water table Qp Pocket Penetrometer BASIC LOG FORMAT: Group name, Group symbol, (grain size), color, moisture, consistency or relative density. Additional comments: odor, presence of roots, mica, gypsum, coarse grained particles, etc. EXAMPLE: Sand (SP), fine to medium grained, brown, moist, loose, trace silt, little fine gravel, few cobbles up to 4" in size, some hair roots and rootlets. File:Mgr: c;\SoilClassif.wpd PLATE B-1 BORING LOG GeoSoils, Inc. W 0. 7355-A-SC PROJECT: HARDING PALM, LLC BORING B-1 SHEET_1_ OF_1_ 9-26-17 1- 2- 3535 Harding Street, Carlsbad Sample "O Q) -e ::, iii ~ u :5 C Ill :::> Li'. j 0 in 0 .0 E >, Cl) Cl) (.) Cl) :::> SM SM C 0 :;::; E ::, -;;; Cl) DATE EXCAVATED SAMPLE METHOD: Standard Penetration/Modified Cal Sampler, 140 Lb@30" Drop Standard Penetration Test Undisturbed, Ring Sample Approx. Elevation: ±62' MSL ¥ Groundwater ~ Seepage Description of Material QUATERNARY COLLUVIUM (TOPSOIL): @ O' SIL TY SAND, dark brownish gray, dry, loose; very fine to r '---7c=o=a"c-rs=e=-e:!carc=a=in=e=-d-o'cc1o"=r=ou=s=c.~~~~~~~~=~~=-----' WEATHERED QUATERNARY OLD PARALIC DEPOSITS: @½'SIL TY SAND, dark yellowish brown, dry to damp, medium 31 ------t'l1/1/racicoi---.::.ni~t--:;.,;,1 --:..,;-1-./'~r"----'::d~e'..',.n,gsgek· v~e~,rv~f~in~e'.dt~o~fic'--',mg:e~a~1r~a~in~e~d~-=~=~--------__,,,~ ~ 65 SP 119.5 6.4 44.o QUATERNARY OLD PARALIC DEPOSITS: 4- 5- 6- 7- 8- 9- ~ @ 3' SAND, reddish yellow, damp, dense; very fine to fine ~ 32 111.4 5.3 28.8 grained, trace silt. @ 5' SAND, dark yellowish brown, damp, medium dense; very fine to fine grained, trace silt. 10-+---+~.+-----+---+----+------+---+-----+--~------:-c------c---c-------c----------,-------+ ~ 64 SM 108.2 10.0 50.0 :::::: @ 1 O' SIL TY SAND, reddish yellow and gray, damp, dense; very 11-~ ._/' fine grained, trace clay, paleoliquecation feature (sand dike). 12- 13- 14- 15- 16- ~ 87 106.8 9.7 46.8 ._/' ._/' @ 15' SIL TY SAND, reddish yellow, damp, very dense; very fine to coarse grained, trace clay, trace gravel, subangular to subrounded . 174'7--1----+-----+--S-M-+-----+--+----+-:::-+-T-E_R_T_IA_RY_S_A_N_T_IA_G_O_F_O_R_MA_T_I_O_N_: __________ ---1 18- 19- 20- 21- 22- 23- 24- 1 I ~ 50-5½" ~ 50-5½" i I 3535 Harding Street, Carlsbad I I @ 17' SIL TY SANDSTONE, light gray, saturated, dense; very fine grained. @ 17' Groundwater encountered. @ 19' No recovery. @ 20' SIL TY SANDSTONE, light gray, saturated becoming ~m_o_i_st_w_it_h_d_e~oth~,_d_e_n_s_e~· _ve_,rv~f_in_e_a~r_a_in_e_d_. ________ ~( Total Depth= 20½' Perched Groundwater Encountered @ -17' No Caving Encountered Backfilled 9-26-17 GeoSoils, Inc. PLATE B-2 ~ .c ii Q) □ GeoSoils, Inc. PROJECT: HARDING PALM, LLC 3535 Harding Street, Carlsbad Sample u Q) .c 5 -;;; ~ =o "3 C: m => ~ VJ :3: ..Q m 0 .c E >-(/) (/) (.) (/) => SM BORING LOG BORING B-2 DATE EXCAVATED WO. 7355-A-SC SHEET_1_ OF_1_ 9-26-17 SAMPLE METHOD: Standard Penetration/Modified Cal Sampler, 140 Lb@ 30" Drop Standard Penetration Test Undisturbed, Ring Sample Approx. Elevation: ±61' MSL ¥ Groundwater ~ Seepage Description of Material :::= QUATERNARY COLLUVIUM (TOPSOIL): 1-+--+-+-----+----+-----+----+---f---"~'--t--, @ O' SIL TY SAND, brownish gray, dry, loose; very fine to fine f SP ~q~1ra_i_n~e_d~~p1o_r_o_u~s_. _________________ ~ 2-WEATHERED QUATERNARY OLD PARALIC DEPOSITS: @ 1' SAND, dark yellowish brown, dry, medium dense; very fine 311~7,7,7;,::;t---,;.1 ~~-.;;;,.--1 ,:---;,1 --;,;--;;--1-4'~t~o~fi~n~e~a~r~a~in~e~d~tr~a~ce~s~ilt~-c-=-7--c-=---=-==~=---------_/~ v.// 64 SP 123.1 5.7 44.2 QUATERNARY OLD PARALIC DEPOSITS: 4-@ 3' SAND, reddish yellow, damp, dense; very fine to fine grained, trace silt. 5- 6-32 7- 8- 9- 10- 11-47 12- 13- 14- 15- 16- 106.4 2.8 98.9 6.4 13.3 25.3 @ 6' SAND, yellowish brown, dry, medium dense; very fine to medium grained, friable. @ 11' SAND, yellowish brown, gray, and reddish yellow, dry, dense; very fine to fine grained, paleoliquefaction features, micaceous. 174'7c__-+,,,-,-A----l-----,--+-------+--+---:::------:---+--+----====-=---==-~-=---:c~=---==-:::==c--==-:-:------------7 ~ 16/ SP 109.4 15.1 77.9 TERTIARY SANTIAGO FORMATION: 18-+------+WLL~"-'1/,'f---=--50=---.-:_5"--+-----+--------+--+----+-------h @ 17' SAN DST ONE, light gray, saturated becoming wet with { depth, dense; very fine grained. 19_ ~@-1~7~'~G~r~o7u~nd~w-c-=at~e~r~e_n_c~o_u_nt_e_re~d_. ___________ ~ 20- 21- 22- 23- ?4 3535 Harding Street, Carlsbad Total Depth= 18' Perched Groundwater Encountered @ -17' No Caving Encountered Backfilled 9-26-17 GeoSoils, Inc. PLATE B-3 GeoSoils, Inc. PROJECT: HARDING PALM, LLC 3535 Harding Street, Carlsbad Sample u 'C Q) :E, -e -' :, b!::: ,= -;;; ~ C. -" '5 Q) 'S C: .Q Cl CD ::> CD 0 .e .0 ~ l E >, ~ en ·c en ::> ~ 0 en c::-·o ::> Cl ~ SM C C: ~ f! :, iii en BORING LOG BORING 8-3 DATE EXCAVATED W 0. 7355-A-SC SHEET_1_ OF_1_ 9-26-17 SAMPLE METHOD: Standard Penetration/Modified Cal Sampler, 140 Lb@ 30" Drop m ~ -/' -/' Standard Penetration Test Undisturbed, Ring Sample Approx. Elevation: ±62' MSL 'SJ_ Groundwater ~ Seepage Description of Material QUATERNARY COLLUVIUM (TOPSOIL): 1-+-----+-+----+---+-------+---+-------<~-+-, @ O' SIL TY SAND, dark brownish gray, dry, loose; very fine to ( '---ccfi=-=n=e-!'a:Sr='"-"a=inc=ec=de=~oo"""ro~u~s=. =~~~~~~~~=~~~---~ ~ SP 2-WEATHERED QUATERNARY OLD PARALIC DEPOSITS: @ 1' SAND, dark yellowish brown, dry to damp, medium dense; 3-+---+--+---+----+-----+---+---+-----+-.'---V='ec-'c:ry~fi=nc=ecc-t-c-coc-'cfi=-cn-=e_,a~1r-'=a='---in=e-=d-=. ~~~~==~--------~~ SP QUATERNARY OLD PARALIC DEPOSITS: 4- 5-31 109.0 6- 7- 8- 9- 6.8 35.1 @ 3' SAND, reddish yellow, damp, medium dense; very fine to fine grained. @ 5' SAND, reddish yellow, damp, medium dense; very fine to fine grained, trace silt and clay. 10-~ 43 103.3 6.0 26.5 @ 10' SAND, brown and dark gray, damp, dense; very fine to 11 -+---+W.~.,.._--+---+-----+---+----t------t--------"cf.._in"'e'---'Q""r,;:,a"-'-in-'--"e°"d'--'--'-'mc.c,:ac::,_n~1Q..,,:a'-'-n"'e'-"s-"'e-'o'--'-x""'id::.:e:c....::.st:=a::cin.c:i'-"na"'--.'--------------, Total Depth = 11' 12- 13- 14- 15- 16- 17- 18- 19- 20- 21- 22- 23- ?4- 3535 Harding Street, Carlsbad No Groundwater/Caving Encountered Backfilled 9-26-2017 GeoSoils, Inc. PLATE B-4 APPENDIX C SEISMIC ITV GeoSoils, Inc. JOB NUMBER: 7355-A-SC *********************** * * * * * E Q F A U L T version 3.00 * * * * * *********************** DETERMINISTIC ESTIMATION OF PEAK ACCELERATION FROM DIGITIZED FAULTS DATE: 09-26-2017 JOB NAME: HARDING PALM, LLC CALCULATION NAME: 7355 FAULT-DATA-FILE NAME: c:\Program Files\EQFAULTl\CGSFLTE.DAT SITE COORDINATES: SITE LATITUDE: 33.1561 SITE LONGITUDE: 117.3404 SEARCH RADIUS: 62. 2 mi ATTENUATION RELATION: 11) Bozorgnia Campbell Niazi (1999) Hor.-Pleist. Soil-Car. UNCERTAINTY (M=Median, S=Sigma): s Number of Sigmas: 1.0 DISTANCE MEASURE: cdist SCOND: 0 Basement Depth: 5.00 km Campbell SSR: 0 Campbell SHR: 0 COMPUTE PEAK HORIZONTAL ACCELERATION FAULT-DATA FILE USED: C:\Program Files\EQFAULTl\CGSFLTE.DAT MINIMUM DEPTH VALUE (km): 3.0 Page 1 W.O. 7355-A-SC PLATE C-1 Page 1 EQFAULT SUMMARY DETERMINISTIC SITE PARAMETERS I ESTIMATED MAX. EARTHQUAKE EVENT I APPROXIMATE ----------------------------- ABBREVIATED I DISTANCE MAXIMUM PEAK EST. SITE FAULT NAME I mi (km) EARTHQUAKE SITE INTENSITY I MAG.(Mw) ACCEL. g MOD.MERC. ================================I==============-----------------------------NEWPORT-INGLEwooD (offshore) I 5.5( 8.8) 7.1 0.586 X ROSE CANYON I 5.5( 8.9) 7.2 0.604 X CORONADO BANK 21.1( 34.0) 7.6 0.273 IX ELSINORE (TEMECULA) 24.2( 38.9) 6.8 0.140 VIII ELSINORE (JULIAN) 24.4( 39.3) 7.1 0.169 VIII ELSINORE (GLEN IVY) 33.7( 54.2) 6.8 0.099 VII SAN JOAQUIN HILLS 35.3( 56.8) 6.6 0.117 VII PALOS VERDES 35.8( 57.6) 7.3 0.132 VIII EARTHQUAKE VALLEY 44.0( 70.8) 6.5 0.061 VI NEWPORT-INGLEWOOD (L.A.Basin) 46.0( 74.0) 7.1 0.088 VII SAN JACINTO-ANZA 46.7( 75.2) 7.2 0.093 VII SAN JACINTO-SAN JACINTO VALLEY 47.2( 76.0)1 6.9 0.075 VII CHINO-CENTRAL AVE. (Elsinore) 47.7( 76.8)1 6.7 0.091 VII WHITTIER 51.6( 83.0)1 6.8 0.063 VI SAN JACINTO-COYOTE CREEK 52.5( 84.5)1 6.6 0.054 VI ELSINORE (COYOTE MOUNTAIN) 58.2( 93.6)1 6.8 0.056 VI SAN JACINTO-SAN BERNARDINO 59.8( 96.3)1 6.7 0.051 VI PUENTE HILLS BLIND THRUST 61.5( 98.9)1 7.1 0.092 I VII ******************************************************************************* -END OF SEARCH-18 FAULTS FOUND WITHIN THE SPECIFIED SEARCH RADIUS. THE NEWPORT-INGLEWOOD (Offshore) FAULT IS CLOSEST TO THE SITE. IT IS ABOUT 5.5 MILES (8.8 km) AWAY. LARGEST MAXIMUM-EARTHQUAKE SITE ACCELERATION: 0.6035 g Page 2 W.O. 7355-A-SC PLATE C-2 1000 900 800 700 600 500 400 300 200 100 0 CALIFORNIA FAULT MAP HARDING PALM, LLC -400 -300 -200 -100 0 100 200 300 400 500 600 W.O. 7355-A-SC PLATE C-3 -C) -C 0 .:; ca I.. Cl) -Cl) u u <( 1 .1 .01 .001 .1 MAXIMUM EARTHQUAKES HARDING PALM, LLC 1 ... • ► ♦ ♦ 10 Distance (mi) ~ .., .. " ... 1 ........ -I 100 W.O. 7355-A-SC PLATE C-4 JOB NUMBER: 7355-A-SC ************************* * * * * * E Q S E A R C H version 3.00 * * * * * ************************* ESTIMATION OF PEAK ACCELERATION FROM CALIFORNIA EARTHQUAKE CATALOGS DATE: 09-26-2017 JOB NAME: HARDING PALM, LLC EARTHQUAKE-CATALOG-FILE NAME: ALLQUAKE.DAT SITE COORDINATES: SITE LATITUDE: 33.1561 SITE LONGITUDE: 117.3404 SEARCH DATES: START DATE: 1800 END DATE: 2017 SEARCH RADIUS: 62. 2 mi 100.1 km ATTENUATION RELATION: 11) Bozorgnia Campbell Niazi (1999) Hor.-Pleist. Soil-car. UNCERTAINTY (M=Median, S=Sigma): s Number of sigmas: 1.0 ASSUMED SOURCE TYPE: ss [SS=Strike-slip, DS=Reverse-slip, BT=Blind-thrust] SCOND: 0 Depth source: A Basement Depth: 5.00 km Campbell SSR: 0 Campbell SHR: 0 COMPUTE PEAK HORIZONTAL ACCELERATION MINIMUM DEPTH VALUE (km): 3.0 Page 1 W.O. 7355-A-SC PLATE C-5 EARTHQUAKE SEARCH RESULTS Page 1 I I TIME I I I SITE ISITEI APPROX. FILE! LAT. I LONG. I DATE I (UTC) IDEPTHIQUAKEI ACC. I MM I DISTANCE CODE! NORTH I WEST I I HM Seel (km)I MAG. I g IINT. I mi [km] ----+-------+--------+----------+--------+-----+-----+-------+----+------------ DMG MGI MGI DMG PAS T-A T-A T-A DMG DMG DMG DMG DMG DMG MGI DMG DMG DMG MGI DMG DMG DMG DMG GSP DMG GSG PAS GSP DMG DMG DMG GSP DMG DMG DMG DMG MGI DMG DMG DMG DMG DMG GSG DMG 33.00001117.3000 11/22/1800 2130 0.01 33.0000 117.0000 09/21/1856 730 0.0 32.8000 117.1000 05/25/1803 0 0 0.0 32.7000 117.2000 05/27/1862 20 0 0.0 32.9710 117.8700 07/13/1986 1347 8.2 32.6700 117.1700 12/00/1856 0 0 0.0 32.6700 117.1700 05/24/1865 0 0 0.0 32.6700 117.1700 10/21/1862 0 0 0.0 33.2000 116.7000 01/01/1920 235 0.0 33.7000 117.4000 05/13/1910 620 0.0 33.7000 117.4000 04/11/1910 757 0.0 33.7000 117.4000 05/15/1910 1547 0.0 33.6990 117.5110 05/31/1938 83455.4 32.8000 116.8000 10/23/1894 23 3 0.0 33.2000 116.6000110/12/1920 1748 0.0 33.7100 116.9250109/23/1963 144152.6 33.7500 117.0000106/06/1918 2232 0.0 33.7500 117.0000104/21/1918 223225.0 33.8000 117.6000104/22/1918 2115 0.0 33.5750 117.9830103/11/1933 518 4.0 33.6170 117.9670103/11/1933 154 7.8 33.8000 117.0000112/25/1899 1225 0.0 33.6170 118.0170103/14/1933 19 150.0 33.5290 116.5720106/12/2005 154146.5 33.9000 117.2000112/19/1880 0 0 0.01 33.4200 116.4890107/07/2010 235333.51 33.5010 116.5130 02/25/1980 104738.51 33.50801116.5140 10/31/2001 075616.61 33.0000 116.4330 06/04/1940 1035 8.31 33.5000 116.5000 09/30/1916 211 0.01 33.6830 118.0500 03/11/1933 658 3.01 33.4315 116.4427 06/10/2016 080438.71 33.7000 118.0670 03/11/1933 85457.01 33.7000 118.0670 03/11/1933 51022.01 34.oooo 117.2500 07/23/1923 73026.0I 33.3430 116.3460 04/28/1969 232042.91 34.0000 117.5000 12/16/1858 10 0 0.01 33.7500 118.0830 03/11/1933 323 0.01 33.7500 118.0830 03/13/1933 131828.01 33.7500 118.0830 03/11/1933 2 9 0.01 33.7500 118.0830103/11/1933 230 0.01 33.7500 118.0830103/11/1933 910 0.01 33.9530 117.7610107/29/2008 184215.71 33.9500 116.8500109/28/1946 719 9.01 0.0 0.0 0.0 0.0 6.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 10.0 0.0 0.0 16.5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 14.0 0.0 14.0 13.6 15.0 0.0 0.0 0.0 12.3 0.0 0.0 0.0 20.0 0.0 0.0 0.0 0.0 0.01 0.01 14.01 0.01 Page 2 6. 50 5.00 5.00 5.90 5.30 5.00 5.00 5.00 5.00 5.00 5.00 6.00 5.50 5.70 5.30 5.00 5.00 6.80 5.00 5.20 6. 30 6.40 5.10 5.20 6.00 5.50 5.50 5.10 5.10 5 .00 5.50 5.19 5.10 5.10 6.25 5.80 7.00 5.00 5.30 5.00 5.10 5.10 5. 30 5.00 0.249 0.049 0.039 0.057 0.039 0.031 0.031 0.031 0.029 0.029 0.029 0.052 0.037 0.041 0.030 0.024 0.024 0.072 0.023 0.025 0.049 0.052 0.022 0.023 0.037 0.027 0.027 0.021 0.021 0.020 0.026 0.021 0.020 0.020 0.038 0.029 0.063 0.018 0.021 0.018 0.019 0.019 0.021 0.017 IX VI V VI V V V V V V V VI V V V IV IV VII IV V VI VI IV IV V V V IV IV IV V IV IV IV V V VI IV IV IV IV IV IV IV 11.0( 17. 7) 22.4( 36.1) 28.3( 45.5) 32.5( 52.3) 33.2( 53.4) 35.0( 56.3) 35.0( 56.3) 35.0( 56.3) 37.1( 59.7) 37. 7( 60. 7) 37.7( 60.7) 37. 7( 60. 7) 38.7( 62.4) 39.8( 64.0) 42.9( 69.0) 45.1( 72.6) 45.4( 73.1) 45 .4( 73 .1) 46.9( 75.5) 47.0( 75.6) 48.1( 77. 5) 48.6( 78.2) 50. 3( 81.0) 51.3( 82.5) 52.0( 83.7) 52.4( 84.3) 53.3( 85.8) 53.5( 86.1) 53.6( 86.2) 54.0( 86.9) 54.7( 88.1) 55.2( 88.8) 56.2( 90.5) 56.2( 90.5) 58. 5 ( 94 .1) 58.8( 94.7) 59.0( 94.9) 59.3( 95.4) 59.3( 95.4) 59.3( 95.4) 59.3( 95.4) 59.3( 95.4) 60.1( 96. 7) 61.6( 99.2) W.O. 7355-A-SC PLATE C-6 -END OF SEARCH-44 EARTHQUAKES FOUND WITHIN THE SPECIFIED SEARCH AREA. TIME PERIOD OF SEARCH: LENGTH OF SEARCH TIME: 1800 TO 2017 218 years THE EARTHQUAKE CLOSEST TO THE SITE IS ABOUT 11.0 MILES (17.7 km) AWAY. LARGEST EARTHQUAKE MAGNITUDE FOUND IN THE SEARCH RADIUS: 7.0 LARGEST EARTHQUAKE SITE ACCELERATION FROM THIS SEARCH: 0.249 g COEFFICIENTS FOR GUTENBERG & RICHTER RECURRENCE RELATION: a-value= 1. 012 b-value= 0.390 beta-value= 0.897 TABLE OF MAGNITUDES AND EXCEEDANCES: Earthquake I Number of Times I cumulative Magnitude I Exceeded I No. / Year -----------+-----------------+------------ 4.0 I 44 I 0.20276 4.5 I 44 I o.20276 5.0 I 44 I 0.20276 5. 5 I 15 I o. 06912 6.o I 8 I 0.03687 6.5 I 3 I o.01382 7.0 I 1 I 0.00461 Page 3 W.O. 7355-A-SC PLATE C-7 EARTHQUAKE EPICENTER MAP HARDING PALM , LLC 1100 -------------------------, 1000 900 800 700 600 500 400 300 200 100 LEGEND x M = 4 0 M =5 □ M =6 ;\ M = 7 o ◊M =8 -400 -300 -200 -100 0 100 200 300 400 500 600 W.O. 7355-A-SC PLATE C-8 100 10 :i.. m Cl) >--1 -z -en -C: Cl) > w -0 .1 :i.. Cl) .c E :::s z Cl) > :;: .01 m :::s E E :::s 0 .001 ... EARTHQUAKE RECURRENCE CURVE HARDING PALM, LLC """"-,,.. -~. .. "'~ -,-. ., ........... ,............. 0 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. 7355-A-SC PLATE C-9 APPENDIX D LABORATORY DATA GeoSoils, Inc. r-- ID 25 l-o (!) ID ::i VJ ::, -, a.. (!) :Jl "' r-- o:'. <! UJ J: C? l-o UJ Q:; 0 VJ ::, 2,000 1,500 • ..... <I) a. J: /' I-c., z w 1,000 a:: V I-Cl) a:: ~ w I Cl) 0 500 ~ ~ 0 0 500 1,000 1,500 2,000 NORMAL PRESSURE, psf Sample Depth/El. Primary/Residual Shear Sample Type yd MC% C <I> • B-1 5.0 Primary Shear Remolded 118.7 13.9 2 33 ■ B-1 5.0 Residual Shear Remolded 118.7 13.9 2 30 Note: Sample lnnundated prior to testing GeoSoils, Inc. DIRECT SHEAR TEST 5741 Palmer Way Proiect: Hardinq Palm, LLC ~ib,Ioe. ..-.. _ I I , ~ .... "' '"\''!-•, _. r, \..,ell 1;:,uau, \..,M. -1LU IV I Telephone: 760-438-3155 Number: 7355-A-SC Fax: 760-931-0915 Date: October 2017 Figure: D -1 Cal Land Engineering, Inc. dba Quartech Consultant Geotechni~, Environme~al,anst., Civil E~_gineering _ , •• ,.~ ·--··~-~,-· -~----··-·--~-M~ SUMMARY OF LABORATORY TEST DATA GeoSoils, Inc. 5741 Palmer Way, Ste D Carlsbad CA 92010 W .0. 7355-A-SC Client: Harding Palms, LLC QCI Project No.: 17-029-010a Date: October 11, 2017 Summarized by: MA Corrosivity Test Results Sc1rnple ,pH Chloride Sample ID Depth CT-532 CT-422 '(ft) (643) (ppm) 8-1 0.5-5 8.04 60 ' " ,., . ,, " , , ~" ~ Sulfate CT~417 % By Weight 0.0185 ResisUvity . CT-532 (643) (ohm-cm) 2900 W.O. 7355-A-SC PLATE D-2 57G Cast Lar11bc;11 :1oad, Orea, Ca:ifurti;a 82C~i; T t::: 714·C/1-1 G~G; :· aA: 714-Ci~ -i GSG APPENDIX E GENERAL EARTHWORK, GRADING GUIDELINES AND PRELIMINARY CRITERIA GeoSoils, Inc. GENERAL EARTHWORK, GRADING GUIDELINES, AND PRELIMINARY CRITERIA General These guidelines present general procedures and requirements for earthwork and grading as shown on the approved grading plans, including preparation of areas to be filled, placement of fill, installation of subdrains, excavations, and appurtenant structures or flatwork. The recommendations contained in the geotechnical report are part of these earthwork and grading guidelines and would 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 apprised of anticipated work schedules and changes, so that they may schedule their personnel accordingly. All remedial removals, clean-outs, prepared ground to receive fill, key excavations, and subdrain installation should be observed and documented by the geotechnical consultant prior to placing any fill. It is the contractor's responsibility to notify the geotechnical consultant when such areas are ready for observation. Laboratory and Field Tests Maximum dry density tests to determine the degree of compaction should be performed in accordance with American Standard Testing Materials test method ASTM designation D-1557 R::inrlnm or rA!XP.~ent,.iJivP. fiP.!r! r.omr,?.r.tion test!=; shr.uld he rertormerl in GeoSoils, Inc. accordance with test methods ASTM designation 0-1556, D-2937 or D-2922, and D-3017, at intervals of approximately ±2 feet of fill height or approximately every 1,000 cubic yards placed. These criteria would vary depending on the soil conditions and the size of the project. The location and frequency of testing would be at the discretion of the geotechnical consultant. Contractor's Responsibility All clearing, site preparation, and earthwork performed on the project should be conducted by the contractor, with observation by a geotechnical consultant, and staged approval by the governing agencies, as applicable. It is the contractor's responsibility to prepare the ground surface to receive the fill, to the satisfaction of the geotechnical consultant, and to place, spread, moisture condition, mix, and compact the fill in accordance with the recommendations of the geotechnical consultant. The contractor should also remove all non-earth material considered unsatisfactory by the geotechnical consultant. Notwithstanding the services provided by the geotechnical consultant, it is the sole responsibility of the contractor to provide adequate equipment and methods to accomplish the earthwork in strict accordance with applicable grading guidelines, latest adopted codes or agency ordinances, geotechnical report(s), and approved grading plans. Sufficient watering apparatus and compaction equipment should be provided by the contractor with due consideration for the fill material, rate of placement, and climatic conditions. If, in the opinion of the geotechnical consultant, unsatisfactory conditions such as questionable weather, excessive oversized rock or deleterious material, insufficient support equipment, etc., are resulting in a quality of work that is not acceptable, the consultant will inform the contractor, and the contractor is expected to rectify the conditions, and if necessary, stop work until conditions are satisfactory. During construction, the contractor shall properly grade all surfaces to maintain good drainage and prevent ponding of water. The contractor shall take remedial measures to control surface water and to prevent erosion of graded areas until such time as permanent drainage and erosion control measures have been installed. SITE PREPARATION All major vegetation, including brush, trees, thick grasses, organic debris, and other deleterious material, should be removed and disposed of off-site. These removals must be concluded prior to placing fill. In-place existing fill, soil, alluvium, colluvium, or rock materials, as evaluated by the geotechnical consultant as being unsuitable, should be removed prior to any fill placement. Depending upon the soil conditions, these materials may be reused as compacted fills. Any materials incorporated as part of the compacted fills should be approved by the geotechnical consultant. Any underground structures such as cesspools, cisterns, mining shafts, tunnels, septic tanks, wells, pipelines, or other structures not located prior to grading, are to be removed Harding Palm, LLC File:e:\wp12\7300\7355a.pge 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 Harding Palm, LLC File:e:\wp12\7300\7355a.pge GeoSoils, 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 10 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 feetfrom finish grade, the range offoundation 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. Harding Palm, LLC File:e:\wp12\7300\7355a.pge 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 flatter. Compaction of slopes should be accomplished by over-building a minimum of 3 feet horizontally, and subsequently trimming back to the design slope configuration. Testing shall be performed as the fill is elevated to evaluate compaction as the fill core is being developed. Special efforts may be necessary to attain the specified compaction in the fill slope zone. Final slope shaping should be performed by trimming and removing loose materials with appropriate equipment. A final evaluation of fill slope compaction should be based on observation and/or testing of the finished slope face. Where compacted fill slopes are designed steeper than 2:1 (h:v), prior approval from the governing agency, specific material types, a higher minimum relative compaction, special reinforcement, and special grading procedures will be recommended. If an alternative to over-building and cutting back the compacted fill slopes is selected, then special effort should be made to achieve the required compaction in the outer 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 Harding Palm, LLC File:e:\wp 12\7300\7355a.pge 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 the geotechnical consultant, further excavations or overexcavation and refilling of cut areas should be performed, and/or remedial grading of cut slopes should be performed. When fill-over-cut slopes are to be graded, unless otherwise approved, the cut portion of the slope should be observed by the geotechnical consultant prior to placement of materials for construction of the fill portion of the slope. The geotechnical consultant should observe all cut slopes, and should be notified by the contractor when excavation of cut slopes commence. Harding Palm, LLC File:e:\wp12\7300\7355a.pge 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. No further excavation or filling should be undertaken without prior notification of the geotechnical consultant or approved plans. All finished cut and fill slopes should be protected from erosion and/or be planted in accordance with the project specifications and/or as recommended by a landscape architect. Such protection and/or planning should be undertaken as soon as practical after completion of grading. PRELIMINARY OUTDOOR POOL/SPA DESIGN RECOMMENDATIONS The following preliminary recommendations are provided for consideration in pool/spa design and planning. Actual recommendations should be provided by a qualified geotechnical consultant, based on site specific geotechnical conditions, including a subsurface investigation, differential settlement potential, expansive and corrosive soil potential, proximity of the proposed pool/spa to any slopes with regard to slope creep and lateral fill extension, as well as slope setbacks per Code, and geometry of the proposed improvements. Recommendations for pools/spas and/or deck flatwork underlain by expansive soils, or for areas with differential settlement greater than ¼-inch over 40 feet horizontally, will be more onerous than the preliminary recommendations presented below. The 1 :1 (h:v) influence zone of any nearby retaining wall site structures should be delineated on the project civil drawings with the pool/spa. This 1 :1 (h:v) zone is defined as a plane up from the lower-most heel of the retaining structure, to the daylight grade of Harding Palm, LLC File:e:\wp12\7300\7355a.pge 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 (pcf) for pool/spa walls with level backfill, and 75 pcf for a 2:1 sloped backfill condition. In addition, backdrains should be provided behind pool/spa walls subjacent to slopes. 2. Passive earth pressure may be computed as an equivalent fluid having a density of 150 pcf, to a maximum lateral earth pressure of 1 ,000 pounds per square foot (psf). 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 His 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 Harding Palm, LLC File:e:\wp 12\7300\7355a.pge 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), will have an increased potential for distress relative to other areas outside of the H/3 zone. If distress is undesirable, improvements, deck slabs or flatwork should not be constructed closer than H/3 or 7 feet (whichever is greater) from the slope face, in order to reduce, but not eliminate, this potential. 14. Pool/spa bottom or deck slabs should be founded entirely on competent bedrock, or properly compacted fill. Fill should be compacted to achieve a minimum Harding Palm, LLC File:e:\wp12\7300\7355a.pge GeoSoils, 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 during concrete placement. Concrete utilized should have a minimum compressive strength of 4,000 psi. Excessive water added to concrete prior to placement is likely to cause shrinkage cracking, and should be avoided. Some concrete shrinkage cracking, however, is unavoidable. 17. Joint and sawcut locations for the pool/spa deck should be determined by the design engineer and/or contractor. However, spacings should not exceed 6 feet on center. 18. Considering the nature of the onsite earth materials, it should be anticipated that caving or sloughing could be a factor in subsurface excavations and trenching. Shoring or excavating the trench walls/backcuts at the angle of repose (typically 25 to 45 degrees), should be anticipated. All excavations should be observed by a representative of the geotechnical consultant, including the project geologist and/or geotechnical engineer, prior to workers entering the excavation or trench, and minimally conform to Cal/OSHA ("Type C" soils may be assumed), state, and local safety codes. Should adverse conditions exist, appropriate recommendations should be offered at that time by the geotechnical consultant. GSI does not consult in the area of safety engineering and the safety of the construction crew is the responsibility of the pool/spa builder. 19. It is imperative that adequate provisions for surface drainage are incorporated by the homeowners into their overall improvement scheme. Ponding water, ground saturation and flow over slope faces, are all situations which must be avoided to enhance long term performance of the pool/spa and associated improvements, and reduce the likelihood of distress. Harding Palm, LLC File:e:\wp 12\7300\7355a.pge GeoSoils, Inc. Appendix E Page 10 20. Regardless of the methods employed, once the pool/spa is filled with water, should it be emptied, there exists some potential that if emptied, significant distress may occur. Accordingly, once filled, the pool/spa should not be emptied unless evaluated by the geotechnical consultant and the pool/spa builder. 21. For pools/spas built within (all or part) of the Code setback and/or geotechnical setback, as indicated in the site geotechnical documents, special foundations are recommended to mitigate the affects of creep, lateral fill extension, expansive soils and settlement on the proposed pool/spa. Most municipalities or County reviewers do not consider these effects in pool/spa plan approvals. As such, where pools/spas are proposed on 20 feet or more of fill, medium or highly expansive soils, or rock fill with limited "cap soils" and built within Code setbacks, or within the influence of the creep zone, or lateral fill extension, the following should be considered during design and construction: OPTION A: Shallow foundations with or without overexcavation of the pool/spa "shell," such that the pool/spa is surrounded by 5 feet of very low to low expansive soils (without irreducible particles greater that 6 inches), and the pool/spa walls closer to the slope(s) are designed to be free standing. GSI recommends a pool/spa under-drain or blanket system (see attached Typical Pool/Spa Detail). The pool/spa builders and owner in this optional construction technique should be generally satisfied with pool/spa performance under this scenario; however, some settlement, tilting, cracking, and leakage of the pool/spa is likely over the life of the project. OPTION B: Pier supported pool/spa foundations with or without overexcavation of the pool/spa shell such that the pool/spa is surrounded by 5 feet of very low to low expansive soils (without irreducible particles greater than 6 inches), and the pool/spa walls closer to the slope(s) are designed to be free standing. The need for a pool/spa under-drain system may be installed for leak detection purposes. Piers that support the pool/spa should be a minimum of 12 inches in diameter and at a spacing to provide vertical and lateral support of the pool/spa, in accordance with the pool/spa designers recommendations current applicable Codes. The pool/spa builder and owner in this second scenario construction technique should be more satisfied with pool/spa performance. This construction will reduce settlement and creep effects on the pool/spa; however, it will not eliminate these potentials, nor make the pool/spa "leak-free." 22. The temperature of the water lines for spas and pools may affect the corrosion properties of site soils, thus, a corrosion specialist should be retained to review all spa and pool plans, and provide mitigative recommendations, as warranted. · Concrete mix design should be reviewed by a qualified corrosion consultant and materials engineer. Harding Palm, LLC File:e:\wp 12\7300\7355a.pge 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 H is 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. Harding Palm, LLC File:e:\wp12\7300\7355a.pge 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 Harding Palm, LLC File:e:\wp 12\7300\7355a.pge 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 fill. Test pits should be excavated so that the spoil pile is placed away from oncoming traffic, whenever possible. The technician's vehicle is to be placed next to the test pit, opposite the spoil pile. This necessitates the fill be maintained in a driveable condition. Alternatively, the contractor may wish to park a piece of equipment in front of the test holes, particularly in small fill areas or those with limited access. A zone of non-encroachment should be established for all test pits. No grading equipment should enter this zone during the testing procedure. The zone should extend approximately 50 feet outward from the center of the test pit. This zone is established for safety and to avoid excessive ground vibration, which typically decreases test results. When taking slope tests, the technician should park the vehicle directly above or below the test location. If this is not possible, a prominent flag should be placed at the top of the slope. The contractor's representative should effectively keep all equipment at a safe operational distance (e.g., 50 feet) away from the slope during this testing. The technician is directed to withdraw from the active portion of the fill as soon as possible following testing. The technician's vehicle should be parked at the perimeter of the fill in a highly visible location, well away from the equipment traffic pattern. The contractor should inform our personnel of all changes to haul roads, cut and fill areas or other factors that may affect site access and site safety. In the event that the technician's safety is jeopardized or compromised as a result of the contractor's failure to comply with any of the above, the technician is required, by company policy, to immediately withdraw and notify his/her supervisor. The grading contractor's representative will be contacted in an effort to affect a solution. However, in the interim, no further testing will be performed until the situation is rectified. Any fill placed can be considered unacceptable and subject to reprocessing, recompaction, or removal. In the event that the soil technician does not comply with the above or other established safety guidelines, we request that the contractor bring this to the technician's attention and notify this office. Effective communication and coordination between the contractor's representative and the soil technician is strongly encouraged in order to implement the above safety plan. Trench and Vertical Excavation It is the contractor's responsibility to provide safe access into trenches where compaction testing is needed. Our personnel are directed not to enter any excavation or vertical cut which: 1) is 5 feet or deeper unless shored or laid back; 2) displays any evidence of instability, has any loose rock or other debris which could fall into the trench; or 3) displays any other evidence of any unsafe conditions regardless of depth. Harding Palm, LLC File:e:\wp12\7300\7355a.pge 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. Harding Palm, LLC File:e:\wp12\7300\7355a.pge GeoSoils, Inc. Appendix E Page 15 Toe of slope as shown on grading plan Natural slope to be restored with compacted fill / / .,,,,,--Proposed grade \ / / / / Compacted fill / / / ----- . of ur-sut..a'Ole "'a\ef\al ~ I co\\u~1ul1\, ~ I .,f' / Ne \O\lsOl, . --------I\.\\ 1/ -' 2-foot m;n;m . .p""'/ l',el1'0 -------=----p:::~0\""--:,-,.,.....-,,,/ , \ \~,-- [ _in bedrock 0~~ \ ~ J1/ ~~\;('~?'7""o:""""" _ _y1/U\ \\\,:_,,,:,:;.,6--___ 4 -toot minimum appco,ed §-''/ ~ \ 1/ · \ • ''!\_ --- _ _ _ earth mate,;a1_ _ _ 4/ ----------~v~~~--_tx y\ \ :;;\:,:,,;.;:.\ \\ 1 ! ---· · -. . -\ -~ _ _ _ _ \\;(\\;'.(<,;)\;.-\\' _ . Bench w;dth I f ~ :~" 2 Percent Gradie ----\ \ -[ 3 foot minimum I~ may vary ----1 . I\ • \ \ / nt ~ ·', -(4-foof · · B d . \ // y\ ,.....,,._~\, ---""""""'I , e rock Backcut varies I -•' \\/-,1/ ---_ or 15-1001 m;n;m,m 1 ----approved I .~/2 whece H ;,o, I r . native material e olope he~hf j I 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. :;:i ~1.Cii~ <~;? ~-&~,J~~c. FILL OVER NATURAL (SIDEHILL FILL) DETAIL Plate E-7 Proposed finish grade ~~ Natural grade ------------------------=--- 3-fool minimum ~ .· >\VU>Y> ~y [\'("/~~ ~\\\<\\0 ~ H = height of slope f<,..,..,,, ....... <\..,....~~~\\' ');0\ -~\ ~' "\\);\\~ Bedrock or ~~~ , 1-:Y !<\ ;<\ \",<'(<--\ \ \,,.-;:~ <0\);:\\' J ~L .\ -\\\,,\1/L ~ /1/ 2-foot m;rnm,m ~~c--:;,\\"'~t G.-a_,__ \\ '(/C\~/0 Typical benching (4-foot minimum) key depth y).\\;(\~,Y '<\ '\:;{\/ 1-t5-foot m;,;m;.., v0-\c-c, \' \ or H/2 if H)30ey w1dtn _,,-\ \,,,-\ \ feet .., I ,\ \ Subdrain as recommended by geotechnical consultant NOTES: 1. 15-foot minimum to be maintained from proposed finish slope face to back cut. approved native material 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. ·"· ,·~. r: ·•-.J~'.) G~tr~fi~ )t,-c. ~ >>..-... '.~-/ ,,,:::;::1 {~) SKIN FILL OF NATURAL GROUND DETAIL Plate E-10 Natural grade Proposed pad grade ----- -~ a rno"e .,e \eria\ ·• b\e rna unsu1,a: ----------__ j_ --- CUT LOT OR MATERIAL-TYPE TRANSITION Proposed pad grade Natural grade ----- ·--~----_L Typical benching (4-foot minimum) Bedrock or approved native material CUT-FILL LOT (DAYLIGHT TRANSITION) TRANSITION LOT DETAILS Plate E.-12 MAP VIEW NOTTO SCALE SEE NOTES Concrete cut-off wall l~----------<J Top of slope Bl ~ Gravity-flow, nonperforated subdrain t=== pipe (transverse) <I Toe of slope I 4-inch perforated _j subdrain pipe (longitudinal) 2-inch-thick sand layer I 1 --steet Coping\ A' Pool 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 --~ Vapor retarder 6-inch-thick gravel layer 4-inch perforated subdrain pipe 8 r H NOTES= Outlet per design civil engineer Gravity-flow nonperforated subdrain pipe Concrete cut-off wall Coping B' Pool ~2-i~ch-thick sand layer Vapor retarder Perforated 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. TYPICAL POOL/SPA DETAIL Plate E-17 SIDE VIEW Spoil pile Test pit TOP VIEW Flag Flag Spoil pile Test pit Light Vehicle --------50 feet-------------,-------------------50 feet--------i --------------100 feet--------------- TEST PIT SAFETY DIAGRAM Plate E-20