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HomeMy WebLinkAboutCT 2017-0003; LA COSTA TOWN SQUARE - PARCEL 3; GEOTECHNICAL DUE DILIGENCE EVALUATION; 2021-06-17Geotechnical C Geologic C Coastal C Environmental 5741 Palmer Way C Carlsbad, California 92010 C (760) 438-3155 C FAX (760) 931-0915 C www.geosoilsinc.com M E M O R A N D U M DATE: February 9, 2023 W.O. 8144-A-SC Woodside 05S, LP 1250 Corona Pointe Court, Suite 500 Corona, California 92879 Attention: Mr. Craig Moreas From: Robert G. Crisman, CEG 1934 Stephen J. Coover, GE 2057 SUBJECT: Geotechnical Due Diligence Report and Attachments, La Costa Town Square Project, City of Carlsbad, California APN 223-050-73-00 References: 1. ”Third- Party Geotechnical Review (First), La Costa Town Square Parcel 3, La Costa Avenue, Carlsbad, California, GR2022-0001/CT2017-003, Project No. 9604.1, Log No. 21774, dated February 9, 2022, by Hetherington Engineering, Inc. 2. “Review and Response to Third Party Geotechnical Review Comments, La Costa Town Square Townhome Site, APN 223-050-73-00, La Costa Avenue, City of Carlsbad, San Diego County, California,” W.O. 8144-A-SC, dated March 24, 2022, by GeoSoils, Inc. 3. “Geotechnical Due Diligence Evaluation of the La Costa Town Square Townhome Site, APN 223-050-73-00, La Costa Avenue, City of Carlsbad, San Diego County, California 92011,” W.O. 8144-A-SC, dated June 17, 2021, by GeoSoils, Inc. Pursuant to a request from the City, GeoSoils, Inc. (GSI), has prepared this cover letter, the referenced Geotechnical report (Reference No. 3), and the attached referenced documents (Reference Nos. 1 and 2) in accordance with the following City review comment: “soils report should include the City’s 3rd party review comments and the applicant’s response to comments, incorporated as an attachment, addendum, etc. (not loose leafed or separate doc.” Attachments to the geotechnical report (Reference No. 3) include: the referenced third party review document prepared by Hetherington Engineering (Reference No. 1), and the review response document prepared by GeoSoils, Inc. (Reference No. 2). Distribution: (1) Addressee (PDF via email) • GEOTECHNICAL DUE DILIGENCE EVALUATION OF THE LA COSTA TOWN SQUARE TOWNHOME SITE APN 223-050-73-00 LA COSTA AVENUE, CITY OF CARLSBAD SAN DIEGO COUNTY, CALIFORNIA 92011 FOR WOODSIDE 05S, LP 1250 CORONA POINTE COURT, SUITE 500 CORONA, CALIFORNIA 92879 W.O. 8144-A-SC JUNE 17, 2021 Geotechnical C Geologic C Coastal C Environmental 5741 Palmer Way C Carlsbad, California 92010 C (760) 438-3155 C FAX (760) 931-0915 C www.geosoilsinc.com June 17, 2021 W.O. 8144-A-SC Woodside 05S, LP 1250 Corona Pointe Court, Suite 500 Corona, California 92879 Attention: Mr. Michael Jagels, Community Development Director Subject: Geotechnical Due Diligence Evaluation of the La Costa Town Square Townhome Site, APN 223-050-73-00, La Costa Avenue, City of Carlsbad, San Diego County, California 92011 Dear Mr. Jagels: In accordance with your request and authorization, GeoSoils, Inc. (GSI) is pleased to present the results of our geotechnical evaluation at the subject site. The purpose of our study was to evaluate the geologic and geotechnical conditions at the site in order to develop preliminary recommendations for site earthwork and the design of foundations, walls, and pavements related to the proposed residential construction at the property. It is our understanding that this project is governed by the City of Carlsbad and the current edition of the California Building Code (CBSC, 2019a). EXECUTIVE SUMMARY Based upon our field exploration, geologic and geotechnical engineering analyses, the proposed 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 proposed building area may be characterized as a relatively flat lying to very gently sloping graded super pad underlain with engineered fills, sedimentary bedrock (claystone), and fractured metamorphosed volcanic rock. The existing building pad appears to have been graded some time during late 2012 through mid 2013. Other than some surface drainage improvements (i.e., storm drains and desilting basins) the site appears to have remained fallow ever since. • Proposed development generally consists of preparing the site for the construction of 19 buildings including 76 three-story townhomes, and 19 apartments utilizing concrete slab-on-grade foundation systems for support. Additional improvements GeoSoils, Inc.Woodside 05S, LP W.O. 8144-A-SC File:e:\wp12\8100\8144a.gdd Page Two are anticipated to consist of traffic pavements, concrete flatwork (hardscapes), underground utilities, landscaping, and improvement of an existing storm water basin west of the site for use as a storm water BMP. • Due to the relatively compressible nature and/or degraded condition of near surface soils, these materials are considered unsuitable for the support of settlement-sensitive improvements (e.g., residential foundations, concrete slab-on-grade floors, site walls, exterior hardscape, etc.) and/or engineered fill in its existing state. As such, it is recommended that this material is removed, moisture conditioned, and recompacted, prior to foundation and improvements construction. Based on our site exploration, remedial removal depths up to about 5 feet are anticipated. • Options for remedial earthwork discussed herein consist of site grading with existing site soils only; site grading where the upper five (5) feet of soil from finish grade consists of a select import (requiring removal and export offsite of some onsite soil); and, soil cement treatment of existing soils within 5 feet of finish grades. • The 2019 California Building Code ([2019 CBC], California Building Standards Commission [CBSC], 2019a) indicates that removals of unsuitable soils be performed across all areas to be graded, under the purview of the grading permit, not just within the influence of the residential structure. Relatively deep removals may also necessitate a special zone of consideration on perimeter/confining areas. This zone would be approximately equal to the depth of removals, if removals cannot be performed onsite or offsite. Thus, any settlement-sensitive improvements (walls, curbs, flatwork, etc.), constructed within this zone may require deepened foundations, reinforcement, etc., or will retain some potential for settlement and associated distress. • Expansion index (E.I.) testing performed on a representative samples of the onsite soil indicates a range of E.I.’s between 51 and 130 (medium to highly expansive). The soils expansion potential should be re-evaluated at the conclusion of grading and provide updated data for final foundation design. • Site soils are considered to be neutral to mildly alkaline, moderately corrosive to exposed buried metals when saturated, present a negligible to moderate sulfate exposure to concrete, and a negligible chloride exposure, on a preliminary basis (Exposure Classes S1, C1, and W0 per ACI 318-14). Corrosion testing at the completion of earthwork is recommended in order to obtain corrosion data specific to the as-graded conditions. • Regional groundwater is not anticipated to significantly affect the planned improvements. Perched water may occur in the future along zones of contrasting permeability and/or density. GeoSoils, Inc.Woodside 05S, LP W.O. 8144-A-SC File:e:\wp12\8100\8144a.gdd Page Three • Our evaluation indicates there are no known active faults crossing the site and the site is located in an area that has generally low susceptibility to deep-seated landslides. Owing to the depth to groundwater and the relatively dense nature of the underlying bedrock, the potential for the site to be adversely affected by liquefaction is considered very low. Site soils are considered erosive. Thus, properly designed site drainage is necessary in reducing the potential for erosion damage to the planned improvements. • 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 structure will be repairable in the event of the design seismic event. • Additional adverse geologic features that would preclude project feasibility were not encountered, based on the available data. • Our review of site conditions indicates that a full or partial infiltration design is not considered feasible onsite, per City BMP criteria. However, it is our understanding from a review of the tentative map that an existing desilting basin immediately west of the site will be modified to function as a storm water BMP. • The recommendations presented in this report should be incorporated into the design and construction considerations of the project. GeoSoils, Inc.Woodside 05S, LP W.O. 8144-A-SC File:e:\wp12\8100\8144a.gdd 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 submitted, GeoSoils, Inc. Robert G. Crisman David W. Skelly Engineering Geologist, CEG 1934 Civil Engineer, RCE 47857 RGC/JPF/DWS/sh Distribution: (1) Addressee (3 copies, plus PDF via email) GeoSoils, Inc. TABLE OF CONTENTS SCOPE OF SERVICES ...................................................1 SITE DESCRIPTION AND PROPOSED DEVELOPMENT . . . . . . . . . . . . . . . . . . . . . . . . .1 FIELD STUDIES.........................................................4 REGIONAL GEOLOGY ...................................................4 SITE GEOLOGIC UNITS ..................................................4 General ..........................................................4 Engineered Fill (Map Symbol - Afe)....................................5 Tertiary - Age, Delmar Formation (Map Symbol - Td) . . . . . . . . . . . . . . . . . . . . . . 5 Mesozoic-Age, Metamorphosed Volcanic Rock (Map Symbol - Mzu) . . . . . . . . .5 Structural Geology .................................................5 GROUNDWATER........................................................6 GEOLOGIC HAZARDS EVALUATION........................................6 Mass Wasting/Landslide Susceptibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 FAULTING AND REGIONAL SEISMICITY.....................................7 Regional Faults....................................................7 Local Faulting.....................................................7 Seismicity ........................................................7 Seismic Shaking Parameters.........................................8 SECONDARY SEISMIC HAZARDS ..........................................9 SLOPE STABILITY......................................................10 ROCK HARDNESS EVALUATION..........................................10 LABORATORY TESTING.................................................10 Classification.....................................................11 Moisture Density..................................................11 Laboratory Standard...............................................11 Expansion Index..................................................11 Atterberg Limits...................................................12 Particle-Size Analysis ..............................................12 Direct Shear Test .................................................12 Resistance Value .................................................12 Saturated Resistivity, pH, and Soluble Sulfates, and Chlorides . . . . . . . . . . . . . 13 GeoSoils, Inc.Woodside 05S, LP Table of Contents File:e:\wp12\8100\8144a.gdd Page ii STORM WATER INFILTRATION RATE EVALUATION AND DISCUSSION . . . . . . . . . .13 USDA Study .....................................................13 Infiltration Feasibility...............................................13 Onsite Filtration/Infiltration-Runoff Retention Systems . . . . . . . . . . . . . . . . . . . .14 PRELIMINARY CONCLUSIONS AND RECOMMENDATIONS . . . . . . . . . . . . . . . . . . . . 16 EARTHWORK CONSTRUCTION RECOMMENDATIONS . . . . . . . . . . . . . . . . . . . . . . . 16 General .........................................................16 Grading Concept Discussion........................................17 Demolition/Grubbing ..............................................18 Treatment of Existing Ground .......................................18 Fill Suitability.....................................................19 Fill Placement....................................................19 Bulking and Shrinkage.............................................20 Perimeter Conditions ..............................................20 Graded Slope Construction .........................................20 Temporary Slopes ................................................21 Fill Drainage .....................................................21 PRELIMINARY RECOMMENDATIONS - FOUNDATIONS . . . . . . . . . . . . . . . . . . . . . . . 21 General .........................................................21 Expansive Soils...................................................22 Preliminary Foundation Design ......................................22 Preliminary Foundation Construction Recommendations . . . . . . . . . . . . . . . . . 23 Stiffened Slabs ...................................................25 Structural Mat Foundations - Design/Construction . . . . . . . . . . . . . . . . . . . . . . . 25 Post-Tension Slab Foundations......................................26 Corrosion and Concrete Mix ........................................27 SOIL MOISTURE TRANSMISSION CONSIDERATIONS . . . . . . . . . . . . . . . . . . . . . . . . 28 PRELIMINARY PAVEMENT DESIGN RECOMMENDATIONS . . . . . . . . . . . . . . . . . . . . 30 Asphaltic Concrete Pavement (ACP)..................................30 Portland Concrete Cement Pavement (PCCP) . . . . . . . . . . . . . . . . . . . . . . . . . . 30 PCC Pavement Joints..............................................31 Weakened Plane Joints.......................................31 Expansion Joints............................................31 Contact Joints ..............................................31 Slab Reinforcement ...............................................31 Concrete/Pervious Pavers ..........................................31 FLATWORK, AND OTHER IMPROVEMENTS.................................32 GeoSoils, Inc.Woodside 05S, LP Table of Contents File:e:\wp12\8100\8144a.gdd Page iii PRELIMINARY WALL DESIGN PARAMETERS................................34 General .........................................................34 Conventional Retaining Walls .......................................34 Preliminary Retaining Wall Foundation Design . . . . . . . . . . . . . . . . . . . . . . . . . .34 Restrained Walls ............................................35 Cantilevered Walls...........................................35 Seismic Surcharge ................................................36 Retaining Wall Backfill and Drainage..................................37 Wall/Retaining Wall Footing Transitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 DEVELOPMENT CRITERIA ...............................................41 Slope Deformation ................................................41 Slope Maintenance and Planting.....................................42 Drainage ........................................................42 Erosion Control...................................................43 Landscape Maintenance ...........................................43 Gutters and Downspouts ...........................................43 Subsurface and Surface Water ......................................43 Site Improvements ................................................44 Tile Flooring .....................................................44 Additional Grading ................................................44 Footing Trench Excavation .........................................44 Trenching/Temporary Construction Backcuts . . . . . . . . . . . . . . . . . . . . . . . . . .45 Utility Trench Backfill ..............................................45 SUMMARY OF RECOMMENDATIONS REGARDING GEOTECHNICAL OBSERVATION AND TESTING........................................................45 OTHER DESIGN PROFESSIONALS/CONSULTANTS . . . . . . . . . . . . . . . . . . . . . . . . . . 46 PLAN REVIEW .........................................................47 LIMITATIONS..........................................................47 FIGURES: Figure 1 - Site Location Map .........................................2 Detail 1 - Retaining Wall Detail - Alternative A . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Detail 2 - Retaining Wall Detail - Alternative B . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 Detail 3 - Retaining Wall Detail - Alternative C . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 GeoSoils, Inc.Woodside 05S, LP Table of Contents File:e:\wp12\8100\8144a.gdd Page iv ATTACHMENTS: Plate 1 - Geotechnical Map .................................Rear of Text Appendix A - References ...................................Rear of Text Appendix B - Boring Logs ..................................Rear of Text Appendix C - Seismicity ....................................Rear of Text Appendix D - Laboratory Testing.............................Rear of Text Appendix E - General Earthwork and Grading Guidelines . . . . . . . . . Rear of Text GeoSoils, Inc. GEOTECHNICAL DUE DILIGENCE EVALUATION OF THE LA COSTA TOWN SQUARE TOWNHOME SITE APN 223-050-73-00 LA COSTA AVENUE, CITY OF CARLSBAD SAN DIEGO COUNTY, CALIFORNIA 92011 SCOPE OF SERVICES The scope of our services has included the following: 1. Review of readily available published literature, aerial photographs, and maps of the vicinity (see Appendix A). 2. Site reconnaissance mapping and the excavation of nine (9) exploratory borings to evaluate the soil/bedrock profiles, sample representative earth materials, and delineate the horizontal and vertical extent of earth material units (see Appendix B). 3. General areal seismicity evaluation (see Appendix C). 5. Appropriate laboratory testing of relatively undisturbed and representative bulk and undisturbed soil samples collected during our geologic mapping and subsurface exploration program (Appendix D). 6. Analysis of field and laboratory data relative to the proposed development. 7. Appropriate engineering and geologic analyses of data collected, and the preparation of this summary report and accompaniments. SITE DESCRIPTION AND PROPOSED DEVELOPMENT The subject site consists of an irregular shaped, approximately 7.2 acre vacant property located on the north side of La Costa Avenue, and north of the intersection of La Costa Avenue and Calle Timiteo, in the La Costa community of the City of Carlsbad, San Diego County, California (see Site Location Map, Figure 1). The property is bounded by La Costa Avenue to the south, a commercial/retail development to the north, an existing residential development to the east, and an existing storm water basin on the west. Topographically, the majority of the site consists of a relatively flat lying to very gently sloping “super pad” with perimeter slopes descending away from the pad to the east, south, and west. The northern edge of the pad is defined by an existing retaining wall (ascending) and slope above the wall. The existing wall/slope configuration along the north side of the property varies from about 27 feet to 42 feet (total height) with the lower, wall portion ranging from about 14 to 22 feet in height. Perimeter slopes on the east, south, and west sides of the pad appear to vary from about 14 to 22 feet in height. All slopes appear to be constructed at gradients of 2:1 (h:v) or flatter. Based on a review of the “existing conditions and utilities” exhibit included in the vesting tentative map and W.O. SITE LOCATION MAP Figure 1 8144-A-SC Base Map: TOPO!® ©2003 National Geographic, U.S.G.S. Encinitas Quadrangle, California -- San Diego Co., 7.5 Minute, dated 1997, current, 1999. Base Map: Google Maps, Copyright 2021 Google, Map Data Copyright 2021 Google 0 1000 2000 3000 4000 This map is copyrighted by Google 2021. It is unlawful tocopy or reproduce all or any part thereof, whether forpersonal use or resale, without permission. All rightsreserved. NOT TO SCALE SITE SITE 11,no Creek ,ntary School N "IIY61110r ca\\e e,arcelona \.&oue1aLn RANCHO -------- - Canyon Park • l Delltey,4~e The Baked Bear 24 Hour Fitness Q Q La Costa Heights Elementary School C11viota C,r Santa Fe Ranch n Apartments T ¥ ! 8 caJ•o.iSul I Sprouts Farmers Market 0 Stagecoach -o.,, .. J" Community ,;<'<" ! \ Mission Estancia t"\ ••• Elementary School .., (\~fl ... Park c La Costa Canyon Q High School LA COSTA OAKS SOUTH .... GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 3 planned development permit for La Costa Town Square, Parcel 3, prepared by Hunsaker & Associates, San Diego, Inc. (H&A, 2018), pad elevations appear to range from about 299 feet to 291 feet (NAVD 29). Access to the pad is via an access road (unimproved) located at the south central portion of the pad. This road way generally splits the pad into an eastern and western area where drainage within the western area is directed southeasterly into an existing desilting basin and drainage within the eastern portion is directed southwesterly into an additional desilting basin. Drainage accumulated within these basins appears to be directed either offsite or into an existing BMP located along La Costa Avenue. Existing improvements onsite consist of the aforementioned graded pad, slopes, and retaining wall. Based on our review, mass grading and wall construction generally occurred during late 2012 and early to mid 2013. Based on a review of the grading plan for the site, prepared by O’Day Consultants (O’Day, 2012) plan cuts and fill appear to have ranged from about 18 to 24 feet, respectively. Based on our observations and a review of O’Day (2012) the retaining wall located along the north side of the building pad is a mechanically stabilized earth (MSE) wall, or segmental retaining wall. Two storm water runoff retention basins and associated storm drain improvements were also observed in the field and are shown on the existing site conditions exhibit prepared by H&A (2018). The grading plan (O’Day, 2012) also shows a “canyon subdrain.” The outlet for this drain was noted in the field as a 6 inch solid PVC pipe at about the same location as shown on O’Day (2012). Based on our review and site work, the existing retaining wall and graded slopes appear to be performing adequately to date. Of note is that the grading plan (O’Day, 2012) indicates pad grades ranging from about 289 to 298 feet, while the tentative map (H&A, 2018) indicates pad grades ranging from about 291 to 300 feet, or about 2 feet higher than the grading plan. It is our understanding that this difference in elevation is due to methods of elevation control used for the grading plan vs tentative map. Based on a review of the “site plan” included as Sheet 6 of H&A (2018), proposed development of the site appears to consist of site preparation for the construction of 76 three story townhomes and 19 apartments grouped into 19 buildings. Additional improvements are anticipated to consist of traffic pavements, concrete flatwork (hardscapes), underground utilities, landscaping, and improvement of an existing storm water basin west of the site for use as a storm water BMP. Cut and fill grading techniques are anticipated to bring the site to the desired grades. Based on a review of existing conditions (Sheet 5) and the site plan (Sheet 6) of H&A (2018), cuts and fills on the order of about 2 feet, or less are planned. GSI anticipates that construction would consist of wood frame with typical foundations and slab-on-grade ground floors. Building loads are assumed to be typical for this type of relatively light construction. Sewage disposal is anticipated to be accommodated by the regional system. Proposed site development is shown on Plate 1, which uses Sheet 6 of H&A (2018) as a base. GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 4 FIELD STUDIES Site-specific field studies were conducted by GSI on June 7, 2021, and consisted of reconnaissance geologic mapping and the excavation of nine (9) exploratory borings with a truck mounted hollow stem auger drill rig (Ingersoll-Rand A300). The test borings were logged by a representative of this office who also collected representative bulk and undisturbed soil samples for appropriate laboratory testing. The logs of the test borings are presented in Appendix B. The approximate location of the test borings are presented on the Geotechnical Map (see Plate 1). REGIONAL GEOLOGY The subject property lies within the coastal plain physiographic region of the Peninsular Ranges Geomorphic Province of southern California. This region consists of dissected, mesa-like terraces that transition inland to rolling hills. The encompassing Peninsular Ranges Geomorphic Province is characterized by elongated mountain ranges and valleys that trend northwesterly. This geomorphic province extends from the base of the east-west aligned Santa Monica - San Gabriel Mountains, and continues south into Baja California. The mountain ranges within this province are underlain by basement rocks consisting of pre-Cretaceous metasedimentary rocks, Cretaceous plutonic (granitic) rocks, and Jurassic metasedimentary and metavolcanic rocks. In the Southern California region, deposition occurred during the Cretaceous Period and Cenozoic Era in the continental margin of a forearc basin. Sediments, derived from Cretaceous-age plutonic rocks and Jurassic-age volcanic rocks, were deposited during the Tertiary Period (Eocene-age) into the narrow, steep, coastal plain and continental margin of the basin. These rocks have been uplifted, eroded, and deeply incised. During early Pleistocene time, a broad coastal plain was developed from the deposition of marine terrace deposits. During mid- to late- Pleistocene time, this plain was uplifted, eroded and incised. Alluvial deposits have since filled the lower valleys, and young marine sediments are currently being deposited/eroded within coastal and beach areas. Regional geologic mapping by Kennedy and Tan (2007) indicates the site is underlain by Tertiary sedimentary bedrock belonging to the Delmar formation, and Mesozoic-age, metamorphosed and un-metamorphosed volcanic and sedimentary rocks, undivided. Site specific field work indicates that the Mesozoic age formation primarily consists of metamorphosed volcanic bedrock, or “meta-volcanic” rock. SITE GEOLOGIC UNITS General The earth material units that were observed and/or encountered at the subject site consist of engineered artificial fill overlying bedrock consisting of either Tertiary age sedimentary rock, or Mesozoic age metamorphosed volcanic rock. A general description of each material type is presented as follows, from youngest to oldest. GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 5 Engineered Fill (Map Symbol - Afe) Where observed, engineered fill encountered onsite consist of gravelly clay, clay, clayey sand, and sandy clay in various colors of olive brown, brown, light olive brown, dark olive brown, greenish gray, and dark greenish gray. These soils were typically observed to be relatively dry to slightly moist, and firm to stiff within about 5 feet of existing surface grades, becoming moist and stiff (clays) and medium dense (clayey sands) at depth. Existing fill within about 5 feet of existing surface grades is not considered suitable for the support of engineered fill or structures unless this material is removed, cleaned of any deleterious material, such as large roots, and replaced as properly compacted fill. Tertiary - Age, Delmar Formation (Map Symbol - Td) Sedimentary bedrock belonging to the Delmar formation underlies portions of the site (see Plate 1) and consists of light olive brown and greenish gray claystones. Where observed, claystones are relatively dry and desiccated near the surface, becoming moist and stiff at depth. Sedimentary bedrock generally below the depth of desiccation (i.e., 2 to 3 feet below surface grades) is considered to be suitable bearing material for the support of new fills, or settlement-sensitive improvements. Mesozoic-Age, Metamorphosed Volcanic Rock (Map Symbol - Mzu) The metamorphosed volcanic member of this formation (or bedrock) appears to underlie the entire site either at the surface, or at depth beneath either engineered fill or the Delmar claystone. Where observed, this “crystalline bedrock” consist of highly weathered rock, producing light olive gray, moist and stiff clay upon excavation and relatively less weathered, dense, fractured rock, producing gravelly silty sand, gravelly sand, and angular gravels upon excavation. Where encountered, refusal of drilling generally occurs after drilling has advanced about one (1) to two (2) feet into the less weathered, denser zone of bedrock. Based on our review, and site exploration, the majority of the relatively dense zone of rock occurs within the approximate limits of private driveway “A” and the intersection of private drives “A” and “B.” Metavolcanic bedrock is considered to be suitable bearing material for the support of new fills, or settlement-sensitive improvements. Structural Geology Structural trends within sedimentary bedrock appear to be generally oriented northeasterly with bedding dipping to the northwest, or into slope (i.e., MSE wall). Metavolcanic rock is generally randomly fractured at high angles (i.e., greater than 45 degrees). Structural orientations should generally not affect site development. GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 6 GROUNDWATER GSI did not observe evidence of a regional groundwater table. However, some water seepage was observed from the side slope within western desilting basin and likely represents water accumulated along a cut/fill contact at depth that “daylights” into the basin. Groundwater is not anticipated to adversely affect proposed site development, provided that 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/bedrock contacts, fill lifts, etc.) or along geologic discontinuities such as fractures. Due to the potential for post-development perched water to manifest near the surface, owing to as-graded permeability/density contrasts, more robust slab design is necessary for any new slab-on-grade floor (State of California, 2021). 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. 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 10 feet of a slope surface. During heavy rains, such as those in El Niño 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 3-1, which is characterized as being "generally susceptible" to landsliding. However, as the site has been graded, the potential for mass wasting has likely been mitigated. Regional geologic maps do not indicate the presence of landslides on the property, nor did our field investigation. GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 7 The onsite soils are considered erosive. Therefore, 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 (California Geological Survey [CGS], 2018). However, the site is situated in an area of active faulting. The Rose Canyon fault is the closest known active fault to the site (located at a distance of approximately 7.1 miles [11.4 kilometers]) and should have the greatest effect on the site in the form of strong ground shaking, should the design earthquake occur. The location of the Rose Canyon fault and other major faults relative to the site is 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 local active faulting was noted in our review, nor observed to specifically transect the site during the field investigation. Additionally, a review of available regional geologic maps does not indicate the presence of local active faults crossing the specific project site. Seismicity It is our understanding that site-specific seismic design criteria from the 2019 California Building Code ([2019 CBC], California Building Standards Commission [CBSC], 2019a), are to be utilized for foundation design. Much of the 2019 CBC relies on the American Society of Civil Engineers (ASCE) Minimum Design Loads for Buildings and Other Structures (ASCE Standard 7-16). The seismic design parameters provided herein are based on the 2019 CBC. 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 GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 8 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 EQFAULT. Based on the EQFAULT program, a peak horizontal ground acceleration from an upper bound event on the Newport Inglewood fault may be on the order of 0.50g (1-sigma). 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 May 2021). 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 May 2021. Based on the selected acceleration-attenuation relationship, a peak horizontal ground acceleration is estimated, which may have affected the site during the specific event listed. Based on the available data and the attenuation relationship used, the estimated maximum (peak) site acceleration during the period 1800 through May 2021 was about 0.372 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 updated site-specific design criteria obtained from the 2019 CBC (CBSC, 2019a), Chapter 16 Structural Design, Section 1613, Earthquake Loads. The computer program “OSHPD Seismic design Maps,” provided by a joint effort between the Structural Engineers Association of California and the Office of Statewide Health Planning and Development ([OSHPD] SEAC/OSHPD, 2021) was utilized for design (http://seismicmaps.org). The short spectral response utilizes a period of 0.2 seconds. 2019 CBC SEISMIC DESIGN PARAMETERS PARAMETER VALUE 2019 CBC or REFERENCE Risk Category II Table 1604.5 Site Class C Section 1613.2.2/Chap. 20 ASCE 7-16 (p. 203-204) sSpectral Response - (0.2 sec), S 0.955 g Section 1613.2.1 Figure 1613.2.1(1) 1Spectral Response - (1 sec), S 0.348 g Section 1613.2.1 Figure 1613.2.1(2) aSite Coefficient, F 1.2 Table 1613.2.3(1) vSite Coefficient, F 1.5 Table 1613.2.3(2) GeoSoils, Inc. 2019 CBC SEISMIC DESIGN PARAMETERS PARAMETER VALUE 2019 CBC or REFERENCE Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 9 Maximum Considered Earthquake Spectral MSResponse Acceleration (0.2 sec), S 1.146 g Section 1613.2.3 (Eqn 16-36) Maximum Considered Earthquake Spectral M1Response Acceleration (1 sec), S 0.522 Section 1613.2.3 (Eqn 16-37) 5% Damped Design Spectral Response DSAcceleration (0.2 sec), S 0.764 g Section 1613.2.4 (Eqn 16-38) 5% Damped Design Spectral Response D1Acceleration (1 sec), S 0.348 Section 1613.2.4 (Eqn 16-39) MPGA - Probabilistic Vertical Ground Acceleration may be assumed as about 50% of these values. 0.50 g ASCE 7-16 (Eqn 11.8.1) Seismic Design Category D Section 1613.2.5/ASCE 7-16 (p. 85: Table 11.6-1 or 11.6-2) S* Seismic velocity (V ) > 2,500 fps top 100 feet. GENERAL SEISMIC DESIGN PARAMETERS PARAMETER VALUE Distance to Seismic Source (Rose Canyon) “B” fault ±7.1 mi (11.4 km)(1)(2) WUpper Bound Earthquake (Rose Canyon) “B” fault M = 7.2(1)(1) - Cao, et al. (2003). (1) - From Blake (2000a)(2) 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 2019 CBC (CBSC, 2019a) and regular wmaintenance and repair following locally significant seismic events (i.e., M 5.5) will likely be necessary, as is the case in all of southern California. SECONDARY SEISMIC HAZARDS The following list includes other geologic/seismic related hazards that have been considered during our evaluation of the site. The hazards listed are considered negligible and/or mitigated as a result of site location, soil characteristics, and typical site development procedures: GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 10 • Liquefaction • Lateral Spreading • Subsidence • Ground Lurching or Shallow Ground Rupture • Tsunami • Seiche SLOPE STABILITY Based on our review of existing geotechnical documents, site conditions and planned improvements, existing cut and fill slopes appear to be performing adequately. Slope are anticipated to continue to perform adequately assuming adequate maintenance and care over the like of the project. Temporary slopes for construction (i.e., trenching, etc.) are discussed in subsequent sections of our report. The existing MSE wall and slope configuration located along the northern side was observed to exhibit no significant sign of distress and appears to be performing adequately. ROCK HARDNESS EVALUATION Our review and site work indicates an area of hard rock at, or near the surface in the general vicinity of private street “A” and within private street “B” at the intersection of private streets “A” and “B.” Based on a refusal depth of about 2 feet with an Ingersoll-Rand A300 drill rig, bedrock in this area is not considered “trenchable” but can likely be excavated with heavy grading equipment (Cat D9L or equivalent with a single shank ripper tooth). As this appears to be located within an area planned for future underground utility construction, including deep utility construction (i.e., sewer) within street “B,” consideration should be given to undercutting the area to at least 1 foot below the lowest utility invert elevation and bringing back to grade with compacted fill. The need for local blasting, and/or rock breaking cannot be precluded, based on the available information. This area may also potentially generate oversize material which will need to be either reduced in size and placed as a controlled fill, or exported. 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. GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 11 Classification Soils were visually classified with respect to the Unified Soil Classification System (USCS) in general accordance with ASTM D 2487 and D 2488. The soil classifications of the onsite soils are provided on the Boring Logs (Appendix B). Moisture Density The field moisture contents and dry unit weights were determined for undisturbed ring samples for the soils encountered in the exploratory borings. The dry unit weight was determined in pounds per cubic foot and the field moisture content was determined as a percentage of the dry unit weight. The results of these tests are shown on the Boring Logs (Appendix B). Laboratory Standard The maximum density and optimum moisture content was evaluated for composite soil sample collected from Boring B-5. The test was performed in general accordance with the laboratory standard ASTM D 1557. The moisture-density relationships obtained for this composite soil sample is shown in the following table: SAMPLE LOCATION AND DEPTH (FT)SOIL TYPE MAXIMUM DENSITY (PCF) OPTIMUM MOISTURE CONTENT (%) B-5 @ 1'-5' Composite Clay w/gravel 118.6* 124.5** 13.7* 11.6** * Uncorrected value ** Rock correction applied Expansion Index Expansion Index testing was performed on representative samples of site soil in general accordance with ASTM D 4829. Test results and the soils expansion potential are presented in the following table: SAMPLE LOCATION DESCRIPTION EXPANSION INDEX EXPANSION POTENTIAL B-1 @ 1'-6'Clay w/gravel 71 MEDIUM B-5 @ 1' - 5'Clay w/gravel 94 HIGH I I I I I GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 12 Atterberg Limits Testing of representative soil samples to evaluate their liquid limit, plastic limit, and plasticity index (P.I.) was performed in general accordance with ASTM D 4318. The test results are presented in the following table: SAMPLE LOCATION DEPTH (FT)LIQUID LIMIT PLASTIC LIMIT PLASTICITY INDEX B-1 @ 1-6 55 18 37 B-5 @ 7 60 19 41 Particle-Size Analysis Testing on representative site soils was performed in accordance with ASTM D 422-63. The testing was utilized to evaluate the soil classification in accordance with the Unified Soil Classification System (USCS). Based on visual/tactile soil evaluations in the field, site soils generally consist of an admixture of clays and rock fragments. The results of our particle size analysis are presented in Appendix D. Direct Shear Test Shear testing was performed on a undisturbed soil sample in general accordance with ASTM test method D 3080. The results of the shear testing are presented in the following table, and Appendix D: SAMPLE LOCATION PRIMARY RESIDUAL COHESION (PSF) FRICTION ANGLE (DEGREES) COHESION (PSF) FRICTION ANGLE (DEGREES) B-5 @ 5’ (undisturbed) 547 31 314 28 Resistance Value Testing to evaluate the resistance value, or “R” value for a representative sample of site soil was evaluated in accordance with the latest revisions to the State of California, Department of Transportation, Material & Research Test Method No. 301. Based on testing, an R-value of R < 5 was evaluated. GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 13 Saturated Resistivity, pH, and Soluble Sulfates, and Chlorides Based on our review and experience, onsite soils are anticipated to be neutral to mildly alkaline with respect to soil acidity/alkalinity, corrosive to exposed, buried metals when saturated; present a negligible to moderate (“not applicable” to “moderate “per ACI 318R-14) sulfate exposure to concrete; and an elevated chloride exposure. On a preliminary basis reinforced concrete mix design for foundations, slab-on-grade floors, and pavements should minimally conform to “Exposure Classes S1, W1, and C1” in Table 19.3.1.1 of ACI 318R-14, as concrete would likely be exposed to moisture and a moderate sulfate exposure. It should be noted that GSI does not consult in the field of corrosion engineering. The client and project architect should agree on the level of corrosion protection required for the project and seek consultation from a qualified corrosion consultant as warranted. Conformation testing is recommended upon the completion of rough grading. Importing and placement of a select fill cap for foundation support may reduce overall corrosiveness of the soil, dependant on the nature of the import. STORM WATER INFILTRATION RATE EVALUATION AND DISCUSSION USDA Study A review of the United States Department of Agriculture database ([USDA]; 1973, 2021) indicates two (2) main soil groups onsite (pre-grading). Each soil type exhibits relatively low infiltration rates, between 0.06 to 0.02 inches per hour for the Altamont Clay, and 0.00 to 0.06 inches per hour for the Huerhuero Loam. The USDA study further indicates that site soils are classified as belonging to Hydrologic Soil Group C and D, respectively. However, as the site is graded, the “native” soils represented by these classifications have been remediated, i.e., removed, and recompacted (densified), and/or removed to expose the underlying “restrictive layer” or “paralithic bedrock” per the USDA. Infiltration Feasibility In general accordance with the City BMP design manual (City, 2016), the infiltration feasibility for this site was evaluated using “desk top” methodology, including the soils infiltration characteristics and potential impact on site development, and existing onsite and offsite improvements. Based on our review, including; presence of existing compacted fill, clayey site soils, adjacent properties, existing (or proposed) utility backfill, and/or existing moisture-sensitive improvements, such as pavements, foundations, exterior flatwork, etc., would likely be adversely affected by soil infiltration, including offsite improvements, causing settlement and distress, or subject to shallow surface, or near surface lateral seepage. As such, a “no infiltration” design for any planned storm water BMP onsite is recommended. However, it is our understanding from a review of H&A (2018) that the existing desilting basin immediately west of the site will be modified to function as a storm water BMP. GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 14 Storm water BMPs can adversely affect the performance of the onsite and offsite structures foundation systems by: 1) Increasing soil moisture transmission rates through concrete flooring; 2) reducing the stability of slopes 3) induce expansion; and 4) increase the potential for a loss in bearing strength of soil. Furthermore, any onsite mitigative grading of compressible near-surface soils for the support of structures generally involves removal and recompaction. This is anticipated to create a permeability contrast, and the potential for the development of a shallow “perched” and mounded water table, which can reasonably be anticipated to migrate laterally, beneath the structure(s), and offsite onto adjacent property, causing settlement and associated distress to public (offsite) and private improvements. Onsite Filtration/Infiltration-Runoff Retention Systems General design criteria regarding the use of onsite filtration-infiltration-runoff retention systems (OIRRS) are presented below. Should onsite infiltration-runoff retention systems (OIRRS) be required for Best Management Practices (BMPs) or Low Impact Development (LID) principles for the project, 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. 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 storm water 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. Based on our evaluation, the following issues should be addressed when considering any storm water BMP design: • The probability of limited space and proximity of settlement-sensitive improvements to potential treatment area BMPs. GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 15 • The presence of a thin layer of engineered fill overlying formation (future as-built condition) and the potential for developing a shallow, perched water table beneath foundations. • Potential for adverse performance of planned improvements such as floor slabs, below grade walls, and foundations, due to potential settlement from saturation, or other distress due to water vapor transmission. • The potential for the migration of subsurface water offsite, beneath adjacent residential properties, or streets, and/or into utility line trenches. The following geotechnical guidelines should be considered when designing onsite infiltration-runoff retention systems: • It is not good engineering practice to allow water to saturate soils, especially near slopes or improvements; however, the controlling agency/authority may now require this. • 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. • Should they be required, where infiltration systems are located near slopes or improvements, impermeable liners and subdrains should be used along the bottom of bioretention swales/basins located within the influence of such slopes and structures. Impermeable liners used in conjunction with bioretention basins should consist of a 30-mil polyvinyl chloride (PVC) membrane that is covered by a minimum of 12 inches of clean soil, free from rocks and debris, with a maximum 4:1 (h:v) slope inclination, or flatter, and meets the following minimum specifications: Specific Gravity (ASTM D792): 1.2 (g/cc, min.); Tensile (ASTM D882): 73 (lb/in-width, min); Elongation at Break (ASTM D882): 380 (%, min); Modulus (ASTM D882): 32 (lb/in-width, min.); and Tear Strength (ASTM D1004): 8 (lb/in, min); Seam Shear Strength (ASTM D882) 58.4 (lb/in, min); Seam Peel Strength (ASTM D882) 15 (lb/in, min). • Subdrains for basins should consist of at least 4-inch diameter Schedule 40 or SDR 35 drain pipe with perforations oriented down. The drain pipe should be sleeved with a filter sock. • Utility backfill within OIRRS should consist of a two-sack mix of slurry. Final project plans (infiltration, grading, precise grading, foundation, retaining wall, landscaping, etc.), should be reviewed by this office prior to construction, so that GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 16 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. It should be noted that structural and landscape plans were not available for review at this time. PRELIMINARY CONCLUSIONS AND RECOMMENDATIONS Based on our field exploration, laboratory testing, and geotechnical engineering analysis, it is our opinion that the subject site is suitable for the proposed residential development from a geotechnical engineering and geologic viewpoint, provided that the recommendations presented in the following sections are incorporated into the design and construction phases of site development. The primary geotechnical concerns with respect to the proposed development and improvements are: • Earth materials characteristics and depth to competent bearing material. • On-going expansion and corrosion potential of site soils. • Erosiveness of site earth materials. • Potential for perched water during and following site development. • Potential to encounter hard rock and oversized materials requiring special handling. • 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. EARTHWORK CONSTRUCTION RECOMMENDATIONS General All earthwork should conform to the guidelines presented in the 2019 CBC (CBSC, 2019a), the requirements of the City of Carlsbad, except where specifically superceded in the text, or Appendix E of this report. Prior to earthwork, a GSI representative should be present at the preconstruction meeting to provide additional earthwork guidelines, if needed, and GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 17 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 and individual subcontractors responsibility to provide a save working environment for our field staff who are onsite. GSI does not consult in the area of safety engineering. Grading Concept Discussion Existing engineered fills, sedimentary bedrock (claystone), and highly weathered meta- volcanic bedrock onsite range from medium to highly expansive (expansive index range between 51 and 130). The following Table presents various options for remedial earth work with respect to the nature of remedial earthwork, expansive soil conditions and corresponding foundation design. OPTION #GRADING CONCEPT CORRESPONDING FOUNDATION, MISC. 1 Removal/recompaction of existing fill and bedrock within 5 feet of existing grade, or 3 feet below deepest footing, whichever is greater. Remedial earthwork in plan cut areas would likely necessitate undercutting to provide 3 feet of compacted fill beneath footings. Post tension or equivalent design to accommodate medium to highly expansive soil conditions. Medium to highly expansive soils at grade will increase the potential for distress to ancillary surface improvements such as concrete flat work, necessitating the use of select substrates (base) for support. 2 Export onsite soil as necessary in order to provide a select cap of very low to low expansive soil (EI = 0-50). Cap thickness would be at least 5 feet. Remedial earthwork as per Option #1. Remedial earthwork in plan fill areas would still be required in order to remediate existing soils within 5 feet of existing grade. Post tension, or equivalent design to accommodate less onerous expansive conditions based on a weighted plasticity index evaluation of soils within 15 feet of finish grade. I I I I GeoSoils, Inc. OPTION #GRADING CONCEPT CORRESPONDING FOUNDATION, MISC. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 18 3 Soil cement, or lime treatment of existing site soil remediated as per Option #1. Typically 5% lime/soil cement by weight. Typically requires blending through a pug mill. Some gradation requirement as to maximum particle size (2½ inches) may be problematic with respect to the high percentage of gravel in some of the existing fill. Post tension (or equivalent) design for very low to low expansive soil conditions. Requires greater amount of care and testing during placement. Landscaping (vegetation) performance could be affected. All options would involve undercutting of hard rock areas within private streets “A” and “B” to at least 1 foot below lowest utility invert elevation Demolition/Grubbing 1. Vegetation and any miscellaneous debris should be removed from the areas of proposed grading. 2. Any existing subsurface structures uncovered during the recommended removal should be observed by GSI so that appropriate remedial recommendations can be provided. 3. Cavities or loose soils remaining after demolition and site clearance should be cleaned out and observed by the soil engineer. The cavities should be replaced with fill materials that have been moisture conditioned to at least optimum moisture content and compacted to at least 90 percent of the laboratory standard. Treatment of Existing Ground 1. Removals should consist of all soils within about 5 feet of existing grade, or within 3 feet of the bottom of new foundations, whichever is deeper. These soils may be re-used as fill, provided that the soil is cleaned of any deleterious material and moisture conditioned, and compacted to a minimum 90 percent relative compaction per ASTM D 1557. Alternatively, site soils may be treated in accordance with the options presented in the “Grading Concept Discussion” above. 2. Undercutting, or overexcavation of bedrock is recommended in order to mitigate existing and/or plan transitions. Undercutting should be performed to a depth of at least 5 feet below finish pad grade, or at least 3 feet below the bottom of footings, whichever is greater. Where the maximum as-built fill beneath any building exceeds 15 feet, the depth of the undercut shall be increased to H/3, where H is the maximum thickness of fill beneath the building. For example, a maximum fill thickness of 18 feet would require a minimum undercut of 18/3 or 6 feet. I I I I GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 19 3. Subsequent to the above removals/overexcavation, the exposed bottom should be scarified to a depth of at least 6 to 8 inches, brought to at least 2 to 3 percentage points above the soils optimum moisture content, and recompacted to a minimum relative compaction of 90 percent of the laboratory standard, prior to any fill placement. 4. Existing fill and removed natural ground materials may be reused as compacted fill provided that major concentrations of vegetation and miscellaneous debris are removed from the site, prior to or during fill placement. Alternatively, site soils may be treated in accordance with the option presented in the “Grading Concept Discussion” above. 5. Localized deeper removals may be necessary due to buried drainage channel meanders or dry porous materials, septic systems, etc. The project soils engineer/geologist should observe all removal areas during the grading. Fill Suitability Existing earth materials within about 5 feet below existing grades should generate relatively fine grained fill material with gravel to fine cobble size fragments of rock locally. Excavation within the area of private drive “A” and the intersection of private drive “A” and “B” will generate gravelly sands and abundant rock fragments. With depth, the relative percentage and size of rock will increase as excavation and “ripping” becomes more difficult, and excavation produces more rock fragments than fines. Due to the limited depth, and areal extent of any anticipated fill area, any oversize material encountered should be removed from the site. In order to facilitate fill placement, the maximum particle size used for fill should be 8 inches, or less, in long dimension within 3 feet of finish pad grade, with 12 inch minus material acceptable below the 3 foot capping layer. If soil cement treatment is to be considered, the maximum particle size would be reduced to 2½ inches. If soil importation is planned, samples of the soil import should be evaluated by this office prior to importing in order to assure compatibility with the onsite site soils and the recommendations presented in this report. Import soils, if used, should be relatively sandy and very low expansive (i.e., expansion index less than 50). Fill Placement 1. Subsequent to ground preparation, fill materials should be brought to at least 2 to 3 percentage point above the soils optimum moisture content, placed in thin 6- to 8-inch lifts, and mechanically compacted to obtain a minimum relative compaction of 90 percent of the laboratory standard. 2. Fill materials should be cleansed of major vegetation and debris prior to placement. GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 20 3. Oversize material (i.e., 12 inches, or greater in long dimension) should be either reduced in size to meet the maximum gradation, exported from the site, or placed in fill greater than 3 feet from pad grade. Rock fragments greater than 12 inches in long dimension shall either be reduced in size to 12 inch minus material, or exported from the construction area. If soil cement treatment is to be considered, the maximum particle size would be reduced to 2½ inches 4. Any import materials should be observed and deemed suitable by the soils engineer prior to placement on the site. Foundation designs may be altered if import materials have a greater expansion value than the onsite materials encountered in this investigation. Bulking and Shrinkage Existing fills should not appreciably shrink or bulk during regrading. Excavated soil from onsite sedimentary bedrock and weathered meta-volcanics may bulk on the order of about 3%, while excavated soil from the relatively dense, less weathered meta-volcanic rock may bulk 12% to 18%. If soil cement treatment is used, the treated soils may also bulk about 3 percent. Perimeter Conditions It should be noted, that the 2016 CBC (CBSC, 2016) indicates that removals of unsuitable soils be performed across all areas under the purview of the grading permit, not just within the influence of the proposed buildings. Relatively deep removals may also necessitate a special zone of consideration, on perimeter/confining areas. Any proposed improvement or future homeowner improvements such as walls, swimming pools, house additions, etc. that are located above a 1:1 (h:v) projection up from the outermost limit of the remedial grading excavations will require deepened foundations that extend below this plane. Other site improvements, such as pavements, constructed above the aforementioned plane would retain some potential for settlement and associated distress, which may require increased maintenance/repair or replacement. Graded Slope Construction Graded fill slopes should be constructed at gradients no steeper than 2:1 (h:v) to heights up to 15 feet, without further analysis. Fill slopes should be properly keyed and benched if constructed along surfaces steeper than 5:1 (h:v). All fill slopes should be compacted to at least 90 percent of the laboratory standard (ASTM D 1557) throughout, including the slope face. Keyways for any planned fill slope should be constructed in accordance with Appendix E. GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 21 Graded cut slopes should be constructed at gradients no steeper than 2:1 (h:v) to heights up to 10 feet without further evaluation. All cut slopes should be mapped by a geologist during construction. Although not anticipated at this time, should intersecting planes of joints/fractures daylight the cut slope face, or should undocumented fill, colluvium, or highly weathered bedrock be exposed in cut slopes, remedial grading including stabilization fills or inclining the cut slope to a gradient flatter than the adverse structure may be necessary. The type of remedial grading would be based on the conditions exposed during cut slope construction. Cut slopes may be difficult to vegetate. Temporary Slopes Temporary slopes for excavations greater than 4 feet, but less than 20 feet in overall height should conform to CAL-OSHA and/or OSHA requirements for Type “B” soils where slope expose compacted fill, sedimentary bedrock, or highly weathered meta-volcanic bedrock, and Type “A” soils where the slope exposes dense, meta-volcanic bedrock. Temporary slopes, up to a maximum height of ±20 feet, may be excavated at a 1:1 (h:v)(type B), to ½: 1 (h:v)(type A) 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. Fill Drainage Slope subdrainage may be recommended for any perimeter fill slope, based on conditions exposed during site grading. Schematic details of subdrains are provided in Appendix E. 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 anticipated 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 additions 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. GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 22 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. Expansive Soils Our review and current laboratory testing indicates that the onsite soils exhibit expansion index (E.I.) values ranging on the order of 51 to 130 (medium to highly expansive). As such, site soil meets the criteria of detrimentally expansive soils as defined in Section 1803.5.2 of the 2019 CBC. Foundation systems constructed within the influence of detrimentally expansive soils (i.e., E.I. > 20 and PI > 15) will require specific design to resist expansive soil effects per Sections 1808.6.1 or 1808.6.2 of the 2019 CBC, and should be reviewed by the project structural engineer. Preliminary Foundation Design The following foundation construction recommendations are presented as a minimum criteria from a soils engineering viewpoint, where the planned improvements are underlain by at least 7 feet of non-detrimentally expansive soils (i.e., E.I.<21 and P.I. <15). Should foundations be underlain by (detrimentally) expansive soils, they will require specific design to mitigate expansive soil effects as required in Sections 1808.6.1 or 1808.6.2 of the 2019 CBC. Recommendations for Code compliant foundations for the mitigation of expansive soils are presented in later sections of this report. 1. The foundation systems should be designed and constructed in accordance with guidelines presented in the 2019 CBC. 2. An allowable bearing value of 2,000 pounds per square foot (psf) may be used for the design of footings that maintain a minimum width of 12 inches and a minimum depth of 18 inches (below the lowest adjacent grade) and are founded entirely into properly compacted, engineered fill. This value may be increased by 20 percent for each additional 12 inches in footing depth to a maximum value of 2,500 psf. These values may be increased by one-third when considering short duration seismic or wind loads. Isolated pad footings should have a minimum dimension of at least 24 inches square and a minimum embedment of 24 inches below the lowest adjacent grade into properly engineered fill. Foundation embedment depth excludes concrete slabs-on-grade, and/or slab underlayment. Foundations should not simultaneously bear on bedrock and engineered fill. 3. For foundations deriving passive resistance from engineered fill, a passive earth pressure may be computed as an equivalent fluid having a density of 200 pcf, with a maximum earth pressure of 2,000 psf. GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 23 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. All footing setbacks from slopes should comply with Figure 1808.7.1 of the 2019 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 from the heel of the wall. Alternatively, walls may be designed to accommodate structural loads from buildings or appurtenances as described in the “Retaining Wall” section of this report. 9. Provided that the earthwork and foundation recommendations in this reported are adhered foundations bearing on engineered fill should be minimally designed to accommodate a differential settlement of 1 inch over a 40-foot horizontal span (angular distortion = 1/480). Preliminary Foundation Construction Recommendations Current laboratory testing indicates that some onsite soils meet the criteria of detrimentally expansive soils as defined in Section 1803.5.2 of the 2019 CBC. The following foundation construction recommendations are presented as a minimum criteria from a soils engineering viewpoint, where the planned improvements are underlain by at least 7 feet, and perhaps more (as determined during grading), of non-detrimentally expansive soils (i.e., E.I.<21 and P.I. <15). Should foundations be underlain by expansive soils, they will require specific design to mitigate expansive soil effects as required in Sections 1808.6.1 or 1808.6.2 of the 2019 CBC. 1. Exterior and interior footings should be founded into engineered fill at a minimum depth of 12 or 18 inches below the lowest adjacent grade, and a minimum width of 12 or 15 inches, for the planned one- or two-story floor load structures, respectively. Isolated, exterior column and panel pads, or wall footings, should be at least 24 inches, square, and founded at a minimum depth of 24 inches into properly 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. GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 24 2. All exterior column footings, and perimeter wall footings, should be tied together via grade beams in at least one direction. If detrimentally expansive soils are present (per the 2019 CBC), grade beams should be tied in two directions. The grade beam should be at least 12 inches square in cross section, and should be provided with a minimum of two No.4 reinforcing bars at the top, and two 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. 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 5 inches is recommended. Recommendations for floor slab underlayment are presented in a later section of this report. 5. Concrete slabs should be reinforced with a minimum of No. 3 reinforcement bars placed at 18-inch on centers, 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. Specific slab subgrade pre-soaking is recommended for these soil conditions. Prior to the placement of underlayment sand and vapor retarder, GSI recommends that the slab subgrade materials be moisture conditioned to at least optimum moisture content to a minimum depth of 12 inches for very low expansive soil conditions; to at least 2 percent over optimum moisture content (or 1.2 times) to a depth of 18 inches, for medium expansive soils; and 3 percent over optimum moisture content (or 1.3 times) to a depth of 24 inches, for highly expansive soils. Slab subgrade pre-soaking should be evaluated by the geotechnical consultant within 72 hours of 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 conform to “Exposure Class C1” in Table 19.3.2.1 of ACI 318-14 since concrete would likely be exposed to moisture. GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 25 Stiffened Slabs All foundations supported by expansive soils (as defined per Section 1803.5.3 of the 2019 CBC), shall be in compliance with Section 1808.6 of the 2019 CBC (CBSC, 2019), and the findings of this report. For a typical slab designed with interior ribs, or stiffeners, the slab should minimally be at least 5 inches thick. The ribs should be provided in both transverse and longitudinal directions. The interior rib spacing and depth should be provided by the project structural engineer. The perimeter beams, however, should be embedded at least 24 inches for soils with high expansion potential, and in consideration of the building type. The embedment depth should be measured downward from the lowest adjacent grade surface to the bottom of the beam. Structural Mat Foundations - Design/Construction The design of mat foundations should incorporate the vertical modulus of subgrade reaction. This value is a unit value for a 1-foot square footing and should be reduced in accordance with the following equation when used with the design of larger foundations. This is assumes that the bearing soils will consist of engineered fills with an average relative compaction of 90 percent of the laboratory (ASTM D 1557), overlying dense formational earth materials. S where: K = unit subgrade modulus R K = reduced subgrade modulus B = foundation width (in feet) SThe modulus of subgrade reaction (K ) and effective plasticity index (PI) to be used in mat foundation design for various expansive soil conditions are presented in the following table: LOW EXPANSION (E.I. = 0-50) MEDIUM EXPANSION (E.I. = 51-90) HIGH EXPANSION (E.I. = 91-130) SSSK =100 pci/inch, PI <20 K =85 pci/inch, PI = 30 K =70 pci/inch, PI = 41 Reinforcement bar sizing and spacing for mat slab foundations should be provided by the structural engineer. Mat slabs may be uniform thickness foundations (UTF) or may incorporate the use of edge footings for moisture cut-off barriers as recommended herein II l I I II l j GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 26 for post-tension foundations. Edge footings should be a minimum of 6 inches thick. The bottom of the edge footing should be designed to resist tension, using reinforcement per the structural engineer. The need and arrangement of interior grade beams (stiffening beams) will be in accordance with the structural consultant’s recommendations. The recommendations for a mat type of foundation assume that the soils below the slab are compacted fill overlying dense, unweathered formational earth materials. The parameters herein are to mitigate the effects of expansive soils and should be modified to mitigate the effects of the total and differential settlements reported earlier in this report. GSI recommends that the slab subgrade materials be moisture conditioned per recommendations presented in the previous section on general foundation construction. In order to mitigate the effects from post-development perched water and to impede water vapor transmission, structural mats, shall be in accordance with Table 19.3.2.1 of ACI 318-14 ACI (2014) per the 2019 CBC (CBSC, 2019), for low permeability concrete (i.e., a maximum water-cement ratio of 0.50). Recommendations for slab underlayment and soil moisture transmission considerations are presented in a later section of this report. Nuisance cracking may be lessened by the addition of engineered reinforcing fibers in the concrete and careful control of water/cement ratios. For below grade structures (garages, etc.) epoxy-coated reinforcing bars should be considered and are dependent on the structural consultant’s waterproofing and corrosion specialists’ recommendations. Post-Tension Slab Foundations Post-tension (PT) slab foundation may also be used to support structures overlying expansive soils. PT slab foundations should be designed in accordance with 2019 CBC (CBSC, 2019), the criteria for the expansive soil conditions prevalent onsite, and per the PTI Method (3 Edition).rd The following table presents foundation design parameters for post-tensioned slab foundations relative to a specific range of soil expansion potential in accordance with the 2019 CBC and the PTI Method (3 Edition):rd Correction Factor in Integration 20 inches/year Depth to Constant Soil Suction 7 feet or overexcavation depth to bedrock Constant Soil Suction (pf)3.6 Moisture Velocity 0.7 inches/month Plasticity Index (P.I.)*15-45 * The effective plasticity index should be evaluated for the upper 7 to 15 feet of earth materials. GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 27 Based on the above, the recommended soil support parameters are tabulated below: POST-TENSION FOUNDATION DESIGN DESIGN PARAMETER(3)EXPANSION POTENTIAL VERY LOW TO LOW MEDIUM HIGH me center lift 9.0 feet 8.7 feet 8.5 feet me edge lift 5.2 feet 4.5 feet 4.0 feet my center lift 0.4 inches 0.50 inches 0.66 inches my edge lift 0.7 inch 1.3 inch 1.7 inch Bearing Value 1,000 psf 1,000 psf 1,000 psf (1)(1)(1)(1) Lateral Pressure 250 psf 175 psf 150 psf Subgrade Modulus (k)100 pci/inch 85 pci/inch 70 pci/inch Minimum Perimeter Footing Embedment (2)12 inches 18 inches 24 inches Internal bearing values within the perimeter of the post-tension slab may be increased to 2,000 psf for a minimum(1) embedment of 12 inches, then by 20 percent for each additional foot of embedment to a maximum of 2,500 psf. As measured below the lowest adjacent compacted subgrade surface (not including slab underlayment layer thickness).(2) Post-tension slab design should also be evaluated with respect to the potential differential settlements provided in this(3) report. Note: The use of open bottomed raised planters adjacent to foundations will require more onerous design parameters. The parameters are considered minimums and may not be adequate to represent all expansive soils/drainage conditions such as adverse drainage and/or improper landscaping and maintenance. The above parameters are applicable provided the structure has positive drainage that is maintained away from the structure. In addition, no trees with significant root systems are to be planted within 15 feet of the perimeter of foundations. Therefore, it is important that information regarding drainage, site maintenance, trees, settlements, and effects of expansive soils be passed on to future owners. The values tabulated above may not be appropriate to account for possible differential settlement of the slab due to other factors, such as excessive settlements. If a stiffer slab is desired, alternative Post-Tensioning Institute ([PTI] third edition) parameters may be recommended. GSI recommends that the slab subgrade materials be moisture conditioned per recommendations presented in the previous section regarding general foundation construction. Corrosion and Concrete Mix Upon completion of grading, laboratory testing should be performed of site materials for corrosion to concrete and corrosion to steel. Additional comments may be obtained from a qualified corrosion engineer at that time. Current testing data indicates sulfate exposures ranging from S0 to S1 per Table 19.3.1.1 of ACI 318R-14. GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 28 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, 2020). 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). It should also be noted that vapor transmission will occur in new slab-on-grade floors as a result of chemical reactions taking place within the curing concrete. Vapor transmission through concrete floor slabs as a result of concrete curing has the potential to adversely affect sensitive floor coverings depending on the thickness of the concrete floor slab and the duration of time between the placement of concrete, and the floor covering. It is possible that a slab moisture sealant may be needed prior to the placement of sensitive floor coverings if a thick slab-on-grade floor is used and the time frame between concrete and floor covering placement is relatively short. Considering the E.I. test results presented herein, and known soil conditions in the region, the anticipated typical water vapor transmission rates, floor coverings, and improvements (to be chosen by the Client and/or project architect) that can tolerate vapor transmission rates without significant distress, the following alternatives are provided: • Concrete slabs should be increased in thickness (5 inches is considered the minimum). • Concrete slab underlayment should consist of a 15-mil vapor retarder, or equivalent, with all laps sealed per the 2019 CBC and the manufacturer’s recommendation. The vapor retarder should comply with the ASTM E 1745 - Class A criteria, and be installed in accordance with ACI 302.1R-04 and ASTM E 1643. • The 15-mil vapor retarder (ASTM E 1745 - 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, shall 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 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 GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 29 lap, method of sealing, and either supply or specify suitable products for lap sealing (ASTM E 1745), and per Code. ACI 302.1R-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. • The vapor retarder shall 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. As discussed previously, GSI indicated this layer of import sand may be eliminated below the vapor retarder, if laboratory testing indicates that the slab subgrade soil have a sand equivalent (SE) of 30 or greater. • Concrete should have a maximum water/cement ratio of 0.50. This does not supercede Table 19.3.2.1 of the ACI (2014) 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. • 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 should be anticipated. Construction crews may require special training for installation of certain product(s), as well as concrete finishing techniques. The use of specialized product(s) should be approved by the slab designer and water-proofing consultant. A technical representative of the flooring contractor should review the slab and moisture retarder plans and provide comment prior to the construction of the foundations or improvements. The vapor retarder contractor should have representatives onsite during the initial installation. GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 30 PRELIMINARY PAVEMENT DESIGN RECOMMENDATIONS The preliminary design for Asphaltic Concrete (AC), and Portland Cement Concrete Pavement (PCCP) was evaluated based on a preliminary resistance value, or “R” Value evaluated for a representative soil sample evaluated as R<5, and the use of concrete shoulders (curb and/or gutter) at the edge of PCC pavement. GSI does not recommend the use of an ADTT (Average Daily Truck Traffic) value of less than 25 for any pavement section, unless the ADTT significantly less than 25 is certified by a civil engineer specializing in traffic engineering. Asphaltic Concrete Pavement (ACP) Based on a preliminary resistance value (R-Value) of 5 and a traffic index (TI) of 5.0, preliminary ACP sections should consist of at least 3 inches AC over 10 inches of Class 2 aggregate base (AB). R-value testing and AC pavement design analysis should be performed upon completion of grading for the project. Per the City, subgrades within the City ROW with R-values less than 13 may require soil cement treatment, or alternatively the use of geotextiles, such as HP 570 (or equivalent) placed over the subgrade surface prior to base placement. In general, the use of a geotextile could elevate the effective subgrade R-value to about R = 20, resulting in a pavement section of 3 inches AC over 7 ½ inches of aggregate base, over a layer of geotextile (Mirafi HP 570, or equivalent). The use of a select import may potentially reduce this section and/or eliminate the need for geotextiles or soil cement treatment. Final pavement design should be based on additional R value testing of soils once finish subgrade elevations are made. Portland Concrete Cement Pavement (PCCP) The preliminary PCCP sections are provided in the following table: PORTLAND CONCRETE CEMENT PAVEMENTS (PCCP) TRAFFIC AREAS CONCRETE TYPE PCCP THICKNESS (INCHES) TRAFFIC AREAS CONCRETE TYPE PCCP THICKNESS (INCHES) Light Vehicles 520-C-2500 7.0 Heavy Truck Traffic 520-C-2500 8.0 560-C-3250 6.0 560-C-3250 7.0 NOTE: All PCCP is designed as un-reinforced and bearing directly on compacted subgrade. However, a 4-inch thick leveling course of compacted aggregate base, or crushed rock may be considered to improve performance. All PCCP should be properly detailed (jointing, etc.) per the industry standard. Pavements may be additionally reinforced with No. 4 reinforcing bars, placed 12 inches on center, each way, for improved performance. Trash truck loading pads shall be 8 inches per the City standard reinforced accordingly. The transition of the pavement from parking to traffic lanes should be made over a distance of 24 inches with crack control joints (weaken plane) or contact joints at the end of the transition. A minimum 4-inch layer of base rock in traffic and loading dock areas should I I I I I I I GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 31 be considered to improve traffic lane performance. Base rock may consist of either ¾-inch crushed rock or Caltrans Class 2 aggregate base. Crushed rock may be compacted by vibratory methods. Aggregate base should be compacted to a minimum relative compaction of 95 percent. R-value testing and PCC pavement design analysis should be performed upon completion of grading for the project. PCC Pavement Joints Weakened Plane Joints Transverse and longitudinal weakened plane joints may be constructed per Caltrans Standard specifications, Section 40-1.08B and 40-1.08B(1). Transverse weakened plane joints should be spaced no farther than 15 feet apart and no closer than 5 feet. Longitudinal weakened plane joints should be spaced no farther than 20 feet apart, but not less than 5 feet. Expansion Joints Transverse expansion joints should be constructed at 120-foot spacings. Contact Joints Transverse and longitudinal contact joints should be determined by the design engineer. Within large parking areas, joint spacings should be no greater than 20 feet. Slab Reinforcement PCC Pavements for this project are designed as plain concrete (i.e., unreinforced) and should perform adequately, assuming proper construction. If additional control of internal slab stresses (i.e., curing shrinkage, thermal expansion and contraction), and the effects of expansive soil subgrades is desired, then the use of No. 3 reinforcing bars, 18 inches on center each way, should be considered. Concrete/Pervious Pavers Concrete pavers should be underlain by a minimum of 9 inches of aggregate base, overlain by a leveling-course of sand, and/or per the manufacturer’s guidelines. Manufacturer’s guidelines should be reviewed for concordance with the intent of the geotechnical report and the underlying soil conditions. Prior to aggregate base placement the subgrade soils should be compacted to a minimum relative compaction of 95 percent. Aggregate base compaction should also be 95 percent of the maximum dry density (ASTM D-1557), and follow the pavement grading recommendations provided below, as warranted. GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 32 FLATWORK, AND OTHER IMPROVEMENTS 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 reduce the likelihood of distress, the following recommendations are presented for all exterior flatwork: 1. The subgrade area for concrete slabs should be compacted to achieve a minimum 90 percent relative compaction (sidewalks, patios) 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. 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 (sidewalks, patios, etc.) should be a minimum of 4 inches thick. 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. 5. In order to reduce the potential for unsightly cracks, slabs should be reinforced at mid-height with a minimum of No. 3 bars placed at 18 inches on center, in each direction. If subgrade soils within the top 7 feet from finish grade are very low expansive soils (i.e., E.I. #20), then 6x6-W1.4xW1.4 welded-wire mesh may be substituted for the rebar, provided the reinforcement is placed on chairs, at slab mid-height. The exterior slabs should be scored or saw cut, ½ to d 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. GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 33 6. 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 for sidewalks and patios, and a minimum 3,250 psi for traffic pavements. 7. Driveways, sidewalks, and patio slabs adjacent to the structure should be separated from the structure with thick expansion joint filler material. In areas directly adjacent to a continuous source of moisture (i.e., irrigation, planters, etc.), all joints should be additionally sealed with flexible mastic. 8. Planters and walls should not be tied to the structure. 9. 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. 10. 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. 11. Utilities should be enclosed within a closed utilidor (vault) or designed with flexible connections to accommodate differential settlement and expansive soil conditions. 12. Positive site drainage should be maintained at all times. Finish grade on the lot should provide a minimum of 1 to 2 percent fall to the street, as indicated herein. 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. 13. Air conditioning (A/C) units should be supported by slabs that are incorporated into the building foundation or constructed on a rigid slab with flexible couplings for plumbing and electrical lines. A/C waste water lines should be drained to a suitable non-erosive outlet. 14. 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. GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 34 PRELIMINARY WALL DESIGN PARAMETERS General Recommendations for the design and construction of conventional masonry retaining walls are provided below. Recommendations for specialty walls (i.e., crib, earthstone, mechanically stabilized earth [MSE], gravity, 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. Onsite soils are generally clayey and expansive and should not be used as backfill within the active zone behind the wall, where the active zone is defined as the area above a 1:1 projection up and away from the inside bottom of wall. Preliminary Retaining Wall Foundation Design Preliminary foundation design for retaining walls should incorporate the following recommendations: Minimum Footing Embedment - 18 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 18 inches into approved engineered fill overlying dense formational materials. This pressure may be increased by 20 percent for each additional foot of depth and 10 percent for each additional foot of width to a maximum value of 3,000 psf. This pressure may be increased by one-third for short-term wind and/or seismic loads. Passive Earth Pressure - A passive earth pressure of 250 pcf with a maximum earth pressure of 2,500 psf may be used in the preliminary design of retaining wall foundations provided the foundation is embedded into properly compacted fill or suitable native soil. GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 35 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 pcf and 135 pcf may be used in the design of retaining wall foundations. This assumes an average engineered fill compaction of at least 90 percent of the laboratory standard (ASTM D 1557). All retaining wall footing setbacks from slopes should comply with Figure 1808.7.1 of the 2019 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 62 pcf for low expansive native backfill (level backfill). 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 the wall(s) on the adjacent pool as necessary. Equivalent fluid pressures for the design of cantilevered retaining walls are provided in the following table: GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 36 SURFACE SLOPE OF RETAINED MATERIAL (HORIZONTAL:VERTICAL) EQUIVALENT FLUID WEIGHT P.C.F. (SELECT SOIL)(2) Level(1) 2 to 1 42 60 Level backfill behind a retaining wall is defined as compacted earth materials, properly drained, without(1) a slope for a distance of 2H behind the wall, where H is the height of the wall. SE > 20, P.I. < 15, E.I. < 21, and < 20% passing No. 200 sieve.(2) Seismic Surcharge For engineered 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 , GSI recommends that the walls be evaluated for a seismic surcharge (in general accordance with 2019 CBC requirements). The site walls in this category should maintain an overturning factor-of-safety (FOS) of approximately 1.25 when the seismic surcharge (increment), is applied. 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 retained walls is the dimension previously noted as the height of the backfill to the bottom of the footing. The resultant force should be applied at a distance 0.6 H up from the bottom of the footing. 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. For cantilevered walls, the pressure should be applied as an inverted triangular distribution using 15H. For restrained walls, the pressure should be applied as a rectangular distribution. 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/ - N/2 plane away from the back of the wall. The 15H seismic surcharge is derived from the formula: hhtP = d C a C (H hWhere:P = Seismic increment. ha = Probabilistic horizontal site acceleration with a percentage of “g”. t(=total unit weight (125 to 135 pcf for site soils @ 90% relative compaction). H=Height of the wall from the bottom of the footing or point of pile fixity. GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 37 Retaining Wall Backfill and Drainage Onsite soils are consider to be detrimentally expansive with respect to use as retaining wall backfill. As such, the use of a select soil, or gravel is recommended within the “active” zone behind the wall, defined as the zone above a 1:1 projection up and away from the inside outer edge of the wall footing. Positive drainage must be provided behind all retaining walls in the form of gravel wrapped in geofabric and outlets. A backdrain system is considered necessary for retaining walls that are 2 feet or greater in height. Details 1, 2, and 3, present the backdrainage options discussed below. Backdrains should consist of a 4-inch diameter perforated PVC or ABS pipe encased in either Class 2 permeable filter material or ¾-inch to 1½-inch gravel wrapped in approved filter fabric (Mirafi 140 or equivalent). 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.I.) potential of greater than 20 should not be used as backfill for retaining walls. Retaining wall backfill materials should be moisture conditioned and mixed to achieve the soil’s optimum moisture content, placed in relatively thin lifts (6 to 10 inches), and compacted to at least 90 percent relative compaction. 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). Outlets should consist of a 4-inch diameter solid PVC or ABS pipe spaced no greater than ±100 feet apart, with a minimum of two outlets, one on each end. The use of weep holes, only, in walls higher than 2 feet, is not recommended. The surface of the backfill should be sealed by pavement or the top 18 inches compacted with native soil (E.I. # 50). Proper surface drainage should also be provided. For additional mitigation, consideration should be given to applying a water-proof membrane to the back of all retaining structures. The use of a waterstop should be considered for all concrete and masonry joints. Wall/Retaining Wall Footing Transitions Site walls are anticipated to be founded on footings designed in accordance with the recommendations in this report. Should wall footings transition from cut to fill, the structural consultant/wall 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. GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 41 b) Increase of the amount of reinforcing steel and wall detailing (i.e., expansion joints or crack control joints) such that an 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. DEVELOPMENT CRITERIA Slope Deformation Compacted fill slopes designed using customary factors of safety for gross or surficial stability and constructed in general accordance with the design specifications should be expected to undergo some differential vertical heave or settlement in combination with differential lateral movement in the out-of-slope direction, after grading. This post-construction movement occurs in two forms: slope creep, and lateral fill extension (LFE). Slope creep is caused by alternate wetting and drying of the fill soils which results in slow downslope movement. This type of movement is expected to occur throughout the life of the slope, and is anticipated to potentially affect improvements or structures (e.g., separation and/or cracking), placed near the top-of-slope, up to a maximum distance of approximately 15 feet from the top-of-slope, depending on the slope height. This movement generally results in rotation and differential settlement of improvements located within the creep zone. LFE occurs due to deep wetting from irrigation and rainfall on slopes comprised of expansive materials. Although some movement should be expected, long-term movement from this source may be minimized, but not eliminated, by placing the fill throughout the slope region, wet of the fill’s optimum moisture content. It is generally not practical to attempt to eliminate the effects of either slope creep or LFE. Suitable mitigative measures to reduce the potential of lateral deformation typically include: setback of improvements from the slope faces (per 2019 CBC), positive structural separations (i.e., joints) between improvements, and stiffening and deepening of foundations. Expansion joints in walls should be placed no greater than 20 feet on-center, and in accordance with the structural engineer’s recommendations. All of these measures are recommended for design of structures and improvements. GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 42 Slope Maintenance and Planting Water has been shown to weaken the inherent strength of all earth materials. Slope stability is significantly reduced by overly wet conditions. Positive surface drainage away from slopes should be maintained and only the amount of irrigation necessary to sustain plant life should be provided for planted slopes. Over-watering should be avoided as it adversely affects site improvements, and causes perched groundwater conditions. Graded slopes constructed utilizing onsite materials would be erosive. Eroded debris may be minimized and surficial slope stability enhanced by establishing and maintaining a suitable vegetation cover soon after construction. Compaction to the face of fill slopes would tend to minimize short-term erosion until vegetation is established. Plants selected for landscaping should be light weight, deep rooted types that require little water and are capable of surviving the prevailing climate. Jute-type matting or other fibrous covers may aid in allowing the establishment of a sparse plant cover. Utilizing plants other than those recommended above will increase the potential for perched water, staining, mold, etc., to develop. A rodent control program to prevent burrowing should be implemented. Irrigation of natural (ungraded) slope areas is generally not recommended. Over- steepening of slopes should be avoided during building construction activities and landscaping. Drainage Adequate surface drainage is a very important factor in reducing the likelihood of adverse performance of foundations, hardscape, and slopes. Surface drainage should be sufficient to mitigate ponding of water anywhere on the property, and especially near structures and tops of slopes. Surface drainage should be carefully taken into consideration during fine grading, landscaping, and building construction. Therefore, care should be taken that future landscaping or construction activities do not create adverse drainage conditions. Positive site drainage within the property should be provided and maintained at all times. Drainage should not flow uncontrolled down any descending slope. Water should be directed away from foundations and tops of slopes, and not allowed to pond and/or seep into the ground. In general, site drainage should conform to Section 1804.3 of the 2019 CBC. Consideration should be given to avoiding construction of planters adjacent to structures (buildings, pools, spas, etc.). 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. GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 43 Erosion Control Cut and fill slopes will be subject to surficial erosion during and after grading. Onsite earth materials have a moderate to high erosion potential. Consideration should be given to providing hay bales and silt fences for the temporary control of surface water, from a geotechnical viewpoint. Landscape Maintenance Only the amount of irrigation necessary to sustain plant life should be provided. Over-watering the landscape areas will adversely affect proposed site improvements. We would recommend that any proposed open-bottom planters adjacent to proposed structures be eliminated for a minimum distance of 10 feet. As an alternative, closed-bottom type planters could be utilized. An outlet placed in the bottom of the planter, could be installed to direct drainage away from structures or any exterior concrete flatwork. If planters are constructed adjacent to structures, the sides and bottom of the planter should be provided with a moisture barrier to prevent penetration of irrigation water into the subgrade. Provisions should be made to drain the excess irrigation water from the planters without saturating the subgrade below or adjacent to the planters. Graded slope areas should be planted with drought resistant vegetation. 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 structure, 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 GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 44 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. This office should be notified in advance of any fill placement, grading of the site, or trench backfilling after rough grading has been completed. This includes any grading, utility trench and retaining wall backfills, flatwork, etc. Tile Flooring Tile flooring can crack, reflecting cracks in the concrete slab below the tile, although small cracks in a conventional slab may not be significant. Therefore, the designer should consider additional steel reinforcement for concrete slabs-on-grade where tile will be placed. The tile installer should consider installation methods that reduce possible 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. GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 45 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. 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- 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/recertification. • During excavation. GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 46 • During placement of subdrains or other subdrainage devices, prior to placing fill and/or backfill. • After excavation of building footings, retaining wall footings, and free standing walls footings, prior to the placement of reinforcing steel or concrete. • Prior to pouring any slabs or flatwork, after presoaking/presaturation of building pads and other flatwork subgrade, before the placement of concrete, reinforcing steel, capillary break (i.e., sand, pea-gravel, etc.), or vapor retarders (i.e., visqueen, etc.). • During retaining wall subdrain installation, prior to backfill placement. • During placement of backfill for area drain, interior plumbing, utility line trenches, and retaining wall backfill. • During slope construction/repair. • When any unusual soil conditions are encountered during any construction operations, subsequent to the issuance of this report. • 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 GeoSoils, Inc. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Square, Carlsbad June 17, 2021 File:e:\wp12\8100\8144a.gdd Page 47 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. 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 formation/bedrock materials vary in character between excavations and natural outcrops or conditions exposed during mass grading. Site conditions may vary due to seasonal changes or other factors. Inasmuch as our study is based upon our review and engineering analyses and laboratory data, the conclusions and recommendations are professional opinions. These opinions have been derived in accordance with current standards of practice, and no warranty, either express or implied, is given. Standards of practice are subject to change with time. GSI assumes no responsibility or liability for work or testing performed by others, or their inaction; or work performed when GSI is not requested to be onsite, to evaluate if our recommendations have been properly implemented. Use of this report constitutes an agreement and consent by the user to all the limitations outlined above, notwithstanding any other agreements that may be in place. In addition, this report may be subject to review by the controlling authorities. Thus, this report brings to completion our scope of services for this portion of the project. All samples will be disposed of after 30 days, unless specifically requested by the client, in writing. ALL LOCATIONS ARE APPROXIMATE This document or efile is not a part of the ConstructionDocuments and should not be relied upon as being anaccurate depiction of design. W.O.SCALE:8144-A-SC DATE: 07/21 1" = 100' Plate 1 GEOTECHNICAL MAP B-1 B-2B-3 B-4 B-5B-6 B-7 B-9 B-8 Td Td Td Afe Td Afe Td Afe TdMzu Mzu Mzu Td Mzu 1 GSI LEGEND Td Afe Mzu B-9 N BASE MAP FROM: 6" PVC SUBDRAIN OUTLET =:--'J½_/" -'.":"~ 4J .. 1 . 0 ,~, t ~ ~~ . ..:C.'''O @~>c4~/r ' w .• J ,/ ' '' •=· •---. .<-·J "'" ,Y -~,/--~ ,..01'>' --~~ , .J---'<>-' v:,. ·· . ,=•=~· ---• x•,> _c.--· -r ~~ -L .. --, __., ·fl' • ~-_ ...,c -• · ~ ,,, • .,.,.--_. x· = 4 \".. • / \,' " • ~~;"•• ;-'-"c~,1 < '='-w • ~--.·•~3,?ff:C" .,.,.;:;;. ~V ,-0'> • ', ['·';'/p J':''~"----,';J;.~ ---• --• -_.-• ~-•~~ ---.· --,•-~ • -c-r/1/' Cc ' o , • -t ._,, -C::. ~ -;---ro---...,._.:~~~ . -;,-'_~,,Jf&fil"'~ c:c_ ~1,..AcosrAAVf.---~~.,~'?' _-, . , ,,,.,',,f 1' 1 . • . • ----~----• . • -·--~~ -•· . -,o ' ' . 'I. <~ ;"'.°•----"~----~ ~;;;:.:,J;:1&ff,;• _ .~ -~·-.. _,"~-¥§fF" , .F ·~:::•, ·., .. \\o ~ ~ ·pir;: 1'~,, 1 f . ,-•. ------· _. ---__ .. --~---------~--,v ''. ·~ Q ;/ J~=•11·· . ,.-=~=~-·--•--= _, ______ .,..< ... --• -. ' 0 0 . ., .,,, " -. --·--~--~--·-..cc----" . " ' ~ " , "" , , ,, f "' , l · 4 1"' ~ .:~ "~-, •• ----·-· · " • -cc>-c;j;, ,, , "\· L\f' \ ~-;. \ , ' 0 fi '( -:~o\, . H~----.,-;-z-c.:••--.,/.,-,,'C:"" • ' -' ' . "" ---,-----. " . . --' c,, •• , ,:::J ~t:! '&: 1((;,{'-~. __ ,..,, __ , __ • y• ----. -" \ ·" /"' i ", r t , ./ . , . , " -,,. ,(:) ;:;;J 1//11,:,:11 ~ ,,.-,'. ,-.~ . :;::t;:5-) \ , \ ' I " ",", • I, , I 'I \ ,,;,, p \ •" '\ ,.·c-• . ,) ,.., 0 \ \ \ \ \ j ,:; GRAPHIC SCALE ENGINEERED FILL WITH A THICKNESS IN EXCESS OF 2 FEET 100 0 50 100 ---?-•. ·- s TERTIARY DELMAR FORMATION, CIRCLED WHERE BURIED MESOZOIC META-VOLCANIC ROBEDROCK, CIRCLED WHERE BURIED, CROSS HATCHED AREA REPRESENTS APPROX/MA TE LIMITS OF VERY DENSE/HARD BEDROCK APPROXIMATE LOCATION OF GEOLOGIC CONTACT, DOTTED WHERE BURIED, QUERIED WHERE UNCERTAIN APPROX/MA TE LOCATION OF EXPLORATORY BORING -HUNSAKER PLANNED DEVELOPMENT PERMIT PREPARED BY, I VESTING TENTATIVE MAP AND 11m1 :"..A:1~:'1~!"'' LA COSTA TOWN SQUARE PARCEL3 CITY OF CARLSBAD, CALIFORNIA 1---c-I I 1" = 100' ~~- SHEET 6 OF 12 200 I GeoSoils, Inc. 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. _____, 2004, Guide for concrete floor and slab construction: reported by ACI Committee 302; Designation ACI 302.1R-04, dated March 23. American Society for Testing and Materials (ASTM), 1998, Standard practice for installation of water vapor retarder used in contact with earth or granular fill under concrete slabs, Designation: E 1643-98 (Reapproved 2005). _____, 1997, Standard specification for plastic water vapor retarders used in contact with soil or granular fill under concrete slabs, Designation: E 1745-97 (Reapproved 2004). American Society of Civil Engineers, 2014, Supplement No. 2, Minimum design loads for buildings and other structures, ASCE Standard ASCE/SEI 7-10, dated September 18. _____, 2013a, Expanded seismic commentary, minimum design loads for buildings and other structures, ASCE Standard ASCE/SEI 7-10 (included in third printing). _____, 2013b, Errata No. 2, minimum design loads for buildings and other structures, ASCE Standard ASCE/SEI 7-10, dated March 31. _____, 2013c, Supplement No. 1, minimum design loads for buildings and other structures, ASCE Standard ASCE/SEI 7-10, dated March 31. Blake, Thomas F., 2000a, EQFAULT, A computer program for the estimation of peak horizontal acceleration from 3-D fault sources; Windows 95/98 version. _____, 2000b, EQSEARCH, A computer program for the estimation of peak horizontal acceleration from California historical earthquake catalogs; Updated to December 2016, Windows 95/98 version. Bozorgnia, Y., Campbell K.W., and Niazi, M., 1999, Vertical ground motion: Characteristics, relationship with horizontal component, and building-code implications; Proceedings of the SMIP99 seminar on utilization of strong-motion data, September 15, Oakland, pp. 23-49. GeoSoils, Inc.Woodside 05S, LP Appendix A File:e:\wp12\8100\8144a.gdd Page 2 California Building Standards Commission, 2019a, California Building Code, California Code of Regulations, Title 24, Part 2, Volume 2 of 2, based on the 2018 International Building Code, effective January 1, 2020. _____, 2019b, California Building Code, California Code of Regulations, Title 24, Part 2, Volume 1 of 2, Based on the 2018 International Building Code, effective January 1, 2020. California Department of Conservation, California Geological Survey (CGS), 2018, Earthquake Fault Zones, a guide for government agencies, property owners/developers, and geoscience practitioners for assessing fault rupture hazards in California, California Geological Survey Special Publication 42 (revised 2018), 93 p. California Department of Transportation (Caltrans), 2013, Highway design manual, http://www.dot.ca.gov/hq/oppd/hdm/pdf/english/HDM_Complete_06-21-13.pdf, dated June 21. California Department of Transportation (Caltrans), 1999, Standard Specifications, State of California, Business, Transportation, and Housing Agency, Department of Transportation, dated July. Cao, T., Bryant, W.A., Rowshandel, B., Branum, D., and Wills, C.J., 2003, The revised 2002 California probabilistic seismic hazard maps, dated June, http://www.conservation.ca.gov/cgs/rghm/psha/fault_parameters/pdf/Documents /2002_CA_Hazard_Maps.pdf Carlsbad, City of, 2016, Carlsbad BMP design manual and appendices, Volume 5 of Engineering design manual. Google Earth Imagery, 2021, Satellite imagery. Hunsaker & Associates, San Diego, Inc., 2018, Vesting tentative map and planned development permit, La Costa Town Square, Parcel 3, City of Carlsbad, California, Sheet 6 of 12, W.O. 3355-0001, dated 2018. Jennings, C.W., 1994, Fault activity map of California and adjacent areas: California Division of Mines and Geology, Map Sheet No. 6, scale 1:750,000. Kanare, H.M., 2005, Concrete floors and moisture, Engineering Bulletin 119, Portland Cement Association. GeoSoils, Inc.Woodside 05S, LP Appendix A File:e:\wp12\8100\8144a.gdd Page 3 Kennedy, M.P., and Tan, SS., 2007, Geologic map of the Oceanside 30' by 60' quadrangle, California, regional map series, scale 1:100,000, California Geologic Survey and United States Geological Survey, www.conservation.ca.gov/cgs/rghm/rgm/preliminary_geologic_maps.html Kennedy, M.P, and Tan, S.S, 2005, Geologic map of the Oceanside 30' x 60' quadrangle, California, United States Geological Survey, 1:100,000-scale. Land Advisors Organization, undated, Exclusive offering memorandum, La Costa town square townhome site, Carlsbad, San Diego County, California, undated, no job No. Norris, R.M. and Webb, R.W., 1990, Geology of California, second edition, John Wiley & Sons, Inc. O’Day Consultant, Inc., 2012, Grading plan for LaCosta Town Square office, Carlsbad Tract No. C.T. 01-09, DWG. 474-7A, J.N. 101290, dated January. Public Works Standards, Inc., 2018, “Greenbook” standard specifications for public works construction, 2018 edition. Rimrock Geophysics, 2004, SIPwin, BV-2.78, Seismic refraction interpretation program for Windows. Rimrock Geophysics, 2002, SIPwin, BV-2.7, A personal computer program for interpreting seismic refraction data using modeling and iterative ray tracing techniques. Romanoff, M., 1957, Underground corrosion, originally issued April 1. Structural Engineers Association of California (SEAC) and the Office of Statewide Health Planning and Development (OSHPD), 2020, OSHPD Seismic design maps, (http://seismicmaps.org). 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, 2021 Civil Code, Sections 895 et seq. GeoSoils, Inc.Woodside 05S, LP Appendix A File:e:\wp12\8100\8144a.gdd Page 4 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. GeoSoils, Inc. APPENDIX B BORING LOGS ~ .s:: i5.. Q) 0 - - - 5 - - - - - 10- - - - - 15 - - - - - 20 - - - - - 25- - - - - BORING LOG GeoSoils, Inc. W.O. K/1'-fA PROJECT.-LA LusrA Te?w'>-J S&uA/1.t' ~,¢/2..CGL 3 BORING /34 SHEET _.L_OF I b/7/z/ Hk//ZbC- :!" :::, (]) t.,,,v,DOLJ5"/J..>E cJS➔ L~ DA TE EXCAVATED Logged by Sample "O Q) -e :::, ~ ;;; ti C 0 ::::i a5 ~ ~ :z;,7; 50{ .;::-u 0 E, ~ .0 ~ ~ ,'._., E 0 C >, (/) ~ 0 :;:; (/) C :::, ~ (.) ::::i ;;; :::, (/) c'.' ·o iii ::::i 0 2 (/) cy c,-1 G£- ~ GM Elevation ~Cal Sampler SAMPLE METHOD: D 140 lb hammer@ 30-in drop Z13 □Hand Auger □Other: ~ Standard Penetration Test 5l_ Water Seepage into hole ~ Undisturbed, Ring Sample Description of Material MSL (circle one) ~&' bJ61.AJ~erL£:> ~;//: CLA'1 ✓ '1d/ot.J1..fl-l- l~12-0 w YI I D IZ '1 / fin. J,Y/. K!3 ' M €rAV Ol. CA Al I<-/3-6.J..)/'2oc:Jc: Merl voLL AJ'I//(_ IZDCI< ( w eATH£~€J;> j B;i__c4J<1~ '7 1t:> cl A. '1 u.. V) J... ANGu..,LA "-- bl'LA\J6L.5 l/P07 ~CAVA1/0"l.,1 /~0/St. I ✓6>L'1 0 6(} Sat/ SA!nPlf Plsrt4'ZC€t?. ..L.--.,J..:b.~·'..:....i--~e. ~-I P-5 P6JL 3 I bec..oM~S. l-?6=>J>l.sN /3JrK)1,J1 Molffj ✓E~'1 06.,JSE.,/ 9J,n~L..€ J/lffk.,l'l/5l:P. t!.., 1/z.' d,L P6"L 5"1 wGATH&t.J tv s1t-r'1 StJn1> ~..,,,9 /1.a,)L.. FM/;JnGl'7t~,1 01-111~ LJ/'kJU'? ~n--{ /i~jpJsH /3now>?✓ moisr: i/Cll-'-1 £?6'tls€; ~,o' 1,µs. Pe.i<. ,1/J .. ', ~AYhPL£-v1STI,L,1'2-8fP. -rcilA'-DePTI-1 -= IO i/4. 1 AJO Gn-~wY?:> w.kr6VL. {J,(J Gk:. h n ,£:b. Client: GeoSoils, Inc. PLATE E-s- GeoSoils, Inc. APPENDIX C SEISMICITY TEST.OUT *********************** * * * E Q F A U L T * * * * Version 3.00 * * * *********************** DETERMINISTIC ESTIMATION OF PEAK ACCELERATION FROM DIGITIZED FAULTS JOB NUMBER: 8144A DATE: 06-13-2021 JOB NAME: woodside la costa CALCULATION NAME: Test Run Analysis FAULT-DATA-FILE NAME: C:\EQ\EQFAULT\CGSFLTE.DAT SITE COORDINATES: SITE LATITUDE: 33.0804 SITE LONGITUDE: 117.2324 SEARCH RADIUS: 62.4 mi ATTENUATION RELATION: 12) Bozorgnia Campbell Niazi (1999) Hor.-Soft Rock-Cor. UNCERTAINTY (M=Median, S=Sigma): S Number of Sigmas: 1.0 DISTANCE MEASURE: cdist SCOND: 1 Basement Depth: .01 km Campbell SSR: 1 Campbell SHR: 0 COMPUTE PEAK HORIZONTAL ACCELERATION FAULT-DATA FILE USED: C:\EQ\EQFAULT\CGSFLTE.DAT MINIMUM DEPTH VALUE (km): 3.0 Page 1 W.O. 8144-A-SC PLATE C-1 TEST.OUT --------------- EQFAULT SUMMARY --------------- ----------------------------- DETERMINISTIC SITE PARAMETERS ----------------------------- Page 1 ------------------------------------------------------------------------------- | |ESTIMATED MAX. EARTHQUAKE EVENT | APPROXIMATE |------------------------------- ABBREVIATED | DISTANCE | MAXIMUM | PEAK |EST. SITE FAULT NAME | mi (km) |EARTHQUAKE| SITE |INTENSITY | | MAG.(Mw) | ACCEL. g |MOD.MERC. ================================|==============|==========|==========|========= ROSE CANYON | 7.1( 11.4)| 7.2 | 0.517 | X NEWPORT-INGLEWOOD (Offshore) | 12.7( 20.4)| 7.1 | 0.313 | IX CORONADO BANK | 21.8( 35.1)| 7.6 | 0.261 | IX ELSINORE (JULIAN) | 24.1( 38.8)| 7.1 | 0.169 | VIII ELSINORE (TEMECULA) | 24.2( 38.9)| 6.8 | 0.138 | VIII EARTHQUAKE VALLEY | 38.4( 61.8)| 6.5 | 0.070 | VI ELSINORE (GLEN IVY) | 39.5( 63.5)| 6.8 | 0.083 | VII PALOS VERDES | 43.3( 69.7)| 7.3 | 0.106 | VII SAN JOAQUIN HILLS | 43.4( 69.8)| 6.6 | 0.093 | VII SAN JACINTO-ANZA | 46.8( 75.3)| 7.2 | 0.091 | VII SAN JACINTO-SAN JACINTO VALLEY | 49.2( 79.1)| 6.9 | 0.070 | VI SAN JACINTO-COYOTE CREEK | 49.4( 79.5)| 6.6 | 0.057 | VI ELSINORE (COYOTE MOUNTAIN) | 51.1( 82.2)| 6.8 | 0.063 | VI NEWPORT-INGLEWOOD (L.A.Basin) | 54.1( 87.1)| 7.1 | 0.073 | VII CHINO-CENTRAL AVE. (Elsinore) | 54.8( 88.2)| 6.7 | 0.077 | VII WHITTIER | 58.7( 94.5)| 6.8 | 0.054 | VI SAN JACINTO - BORREGO | 60.7( 97.7)| 6.6 | 0.046 | VI ******************************************************************************* -END OF SEARCH- 17 FAULTS FOUND WITHIN THE SPECIFIED SEARCH RADIUS. THE ROSE CANYON FAULT IS CLOSEST TO THE SITE. IT IS ABOUT 7.1 MILES (11.4 km) AWAY. LARGEST MAXIMUM-EARTHQUAKE SITE ACCELERATION: 0.5172 g Page 2 W.O. 8144-A-SC PLATE C-2 SITE -100 0 100 200 300 400 500 600 700 800 900 1000 1100 -400 -300 -200 -100 0 100 200 300 400 500 600 CALIFORNIA FAULT MAP woodside la costa W.O. 8144-A-SC PLATE C-3 .001 .01 .1 1 .1 1 10 MAXIMUM EARTHQUAKES woodside la costa Acceleration (g)Distance (mi) W.O. 8144-A-SC PLATE C-4 X X X X 6.5 6.6 6.7 6.8 6.9 7.0 7.1 7.2 7.3 7.4 7.5 7.6 .1 1 10 EARTHQUAKE MAGNITUDES & DISTANCES woodside la costa Magnitude (M)Distance (mi) W.O. 8144-A-SC PLATE C-5 • • • • • • • • . ·- • -· • TEST.OUT ************************* * * * E Q S E A R C H * * * * Version 3.00 * * * ************************* ESTIMATION OF PEAK ACCELERATION FROM CALIFORNIA EARTHQUAKE CATALOGS JOB NUMBER: 8144a DATE: 06-13-2021 JOB NAME: woodside la costa EARTHQUAKE-CATALOG-FILE NAME: ALLQUAKE.DAT MAGNITUDE RANGE: MINIMUM MAGNITUDE: 5.00 MAXIMUM MAGNITUDE: 9.00 SITE COORDINATES: SITE LATITUDE: 33.0804 SITE LONGITUDE: 117.2324 SEARCH DATES: START DATE: 1800 END DATE: 2021 SEARCH RADIUS: 62.4 mi 100.4 km ATTENUATION RELATION: 12) Bozorgnia Campbell Niazi (1999) Hor.-Soft Rock-Cor. UNCERTAINTY (M=Median, S=Sigma): S Number of Sigmas: 1.0 ASSUMED SOURCE TYPE: SS [SS=Strike-slip, DS=Reverse-slip, BT=Blind-thrust] SCOND: 1 Depth Source: A Basement Depth: .01 km Campbell SSR: 1 Campbell SHR: 0 COMPUTE PEAK HORIZONTAL ACCELERATION MINIMUM DEPTH VALUE (km): 3.0 Page 1 W.O. 8144-A-SC PLATE C-6 TEST.OUT ------------------------- EARTHQUAKE SEARCH RESULTS ------------------------- Page 1 ------------------------------------------------------------------------------- | | | | TIME | | | SITE |SITE| APPROX. FILE| LAT. | LONG. | DATE | (UTC) |DEPTH|QUAKE| ACC. | MM | DISTANCE CODE| NORTH | WEST | | H M Sec| (km)| MAG.| g |INT.| mi [km] ----+-------+--------+----------+--------+-----+-----+-------+----+------------ DMG |33.0000|117.3000|11/22/1800|2130 0.0| 0.0| 6.50| 0.372 | IX | 6.8( 10.9) MGI |33.0000|117.0000|09/21/1856| 730 0.0| 0.0| 5.00| 0.074 | VII| 14.5( 23.4) MGI |32.8000|117.1000|05/25/1803| 0 0 0.0| 0.0| 5.00| 0.052 | VI | 20.8( 33.5) DMG |32.7000|117.2000|05/27/1862|20 0 0.0| 0.0| 5.90| 0.070 | VI | 26.3( 42.4) T-A |32.6700|117.1700|12/00/1856| 0 0 0.0| 0.0| 5.00| 0.038 | V | 28.6( 46.0) T-A |32.6700|117.1700|10/21/1862| 0 0 0.0| 0.0| 5.00| 0.038 | V | 28.6( 46.0) T-A |32.6700|117.1700|05/24/1865| 0 0 0.0| 0.0| 5.00| 0.038 | V | 28.6( 46.0) DMG |32.8000|116.8000|10/23/1894|23 3 0.0| 0.0| 5.70| 0.051 | VI | 31.7( 50.9) DMG |33.2000|116.7000|01/01/1920| 235 0.0| 0.0| 5.00| 0.034 | V | 31.9( 51.3) MGI |33.2000|116.6000|10/12/1920|1748 0.0| 0.0| 5.30| 0.034 | V | 37.5( 60.3) PAS |32.9710|117.8700|07/13/1986|1347 8.2| 6.0| 5.30| 0.034 | V | 37.7( 60.6) DMG |33.7000|117.4000|04/11/1910| 757 0.0| 0.0| 5.00| 0.024 | V | 43.9( 70.6) DMG |33.7000|117.4000|05/13/1910| 620 0.0| 0.0| 5.00| 0.024 | V | 43.9( 70.6) DMG |33.7000|117.4000|05/15/1910|1547 0.0| 0.0| 6.00| 0.044 | VI | 43.9( 70.6) DMG |33.6990|117.5110|05/31/1938| 83455.4| 10.0| 5.50| 0.031 | V | 45.6( 73.4) DMG |33.0000|116.4330|06/04/1940|1035 8.3| 0.0| 5.10| 0.024 | IV | 46.6( 75.0) DMG |33.7100|116.9250|09/23/1963|144152.6| 16.5| 5.00| 0.022 | IV | 46.9( 75.5) DMG |33.7500|117.0000|04/21/1918|223225.0| 0.0| 6.80| 0.067 | VI | 48.1( 77.5) DMG |33.7500|117.0000|06/06/1918|2232 0.0| 0.0| 5.00| 0.022 | IV | 48.1( 77.5) GSG |33.4200|116.4890|07/07/2010|235333.5| 14.0| 5.50| 0.029 | V | 48.9( 78.7) GSP |33.5290|116.5720|06/12/2005|154146.5| 14.0| 5.20| 0.024 | V | 49.1( 79.0) PAS |33.5010|116.5130|02/25/1980|104738.5| 13.6| 5.50| 0.028 | V | 50.7( 81.5) GSP |33.5080|116.5140|10/31/2001|075616.6| 15.0| 5.10| 0.022 | IV | 50.9( 81.9) DMG |33.5000|116.5000|09/30/1916| 211 0.0| 0.0| 5.00| 0.020 | IV | 51.2( 82.5) DMG |33.8000|117.0000|12/25/1899|1225 0.0| 0.0| 6.40| 0.048 | VI | 51.5( 82.8) GSP |33.4315|116.4427|06/10/2016|080438.7| 12.3| 5.19| 0.023 | IV | 51.6( 83.1) MGI |33.8000|117.6000|04/22/1918|2115 0.0| 0.0| 5.00| 0.019 | IV | 54.0( 86.9) DMG |33.3430|116.3460|04/28/1969|232042.9| 20.0| 5.80| 0.031 | V | 54.3( 87.4) DMG |33.5750|117.9830|03/11/1933| 518 4.0| 0.0| 5.20| 0.021 | IV | 55.1( 88.7) DMG |33.6170|117.9670|03/11/1933| 154 7.8| 0.0| 6.30| 0.041 | V | 56.3( 90.6) DMG |33.9000|117.2000|12/19/1880| 0 0 0.0| 0.0| 6.00| 0.033 | V | 56.6( 91.1) DMG |33.4000|116.3000|02/09/1890|12 6 0.0| 0.0| 6.30| 0.039 | V | 58.2( 93.6) DMG |33.6170|118.0170|03/14/1933|19 150.0| 0.0| 5.10| 0.019 | IV | 58.5( 94.1) T-A |32.2500|117.5000|01/13/1877|20 0 0.0| 0.0| 5.00| 0.017 | IV | 59.4( 95.6) DMG |32.7000|116.3000|02/24/1892| 720 0.0| 0.0| 6.70| 0.050 | VI | 60.1( 96.7) DMG |33.2000|116.2000|05/28/1892|1115 0.0| 0.0| 6.30| 0.038 | V | 60.3( 97.0) DMG |33.4080|116.2610|03/25/1937|1649 1.8| 10.0| 6.00| 0.031 | V | 60.5( 97.3) DMG |33.2830|116.1830|03/23/1954| 41450.0| 0.0| 5.10| 0.018 | IV | 62.2(100.1) DMG |33.2830|116.1830|03/19/1954|102117.0| 0.0| 5.50| 0.022 | IV | 62.2(100.1) DMG |33.2830|116.1830|03/19/1954| 95429.0| 0.0| 6.20| 0.034 | V | 62.2(100.1) DMG |33.2830|116.1830|03/19/1954| 95556.0| 0.0| 5.00| 0.017 | IV | 62.2(100.1) ******************************************************************************* Page 2 W.O. 8144-A-SC PLATE C-7 TEST.OUT -END OF SEARCH- 41 EARTHQUAKES FOUND WITHIN THE SPECIFIED SEARCH AREA. TIME PERIOD OF SEARCH: 1800 TO 2021 LENGTH OF SEARCH TIME: 222 years THE EARTHQUAKE CLOSEST TO THE SITE IS ABOUT 6.8 MILES (10.9 km) AWAY. LARGEST EARTHQUAKE MAGNITUDE FOUND IN THE SEARCH RADIUS: 6.8 LARGEST EARTHQUAKE SITE ACCELERATION FROM THIS SEARCH: 0.372 g COEFFICIENTS FOR GUTENBERG & RICHTER RECURRENCE RELATION: a-value= 0.581 b-value= 0.300 beta-value= 0.691 ------------------------------------ TABLE OF MAGNITUDES AND EXCEEDANCES: ------------------------------------ Earthquake | Number of Times | Cumulative Magnitude | Exceeded | No. / Year -----------+-----------------+------------ 4.0 | 41 | 0.18468 4.5 | 41 | 0.18468 5.0 | 41 | 0.18468 5.5 | 18 | 0.08108 6.0 | 11 | 0.04955 6.5 | 3 | 0.01351 Page 3 W.O. 8144-A-SC PLATE C-8 SITE LEGEND M = 4 M = 5 M = 6 M = 7 M = 8 -100 0 100 200 300 400 500 600 700 800 900 1000 1100 -400 -300 -200 -100 0 100 200 300 400 500 600 EARTHQUAKE EPICENTER MAP woodside la costa W.O. 8144-A-SC PLATE C-9 .001 .01 .1 1 10 100 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 EARTHQUAKE RECURRENCE CURVE woodside la costa Cummulative Number of Events (N)/ YearMagnitude (M) W.O. 8144-A-SC PLATE C-10 i..... ---.. ....... ., --~ ., ..... ~ --............ -.............. 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 2 4 6 8 10 20 40 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 Number of Earthquakes (N) Above Magnitude (M) woodside la costa Cumulative Number of Events (N)Magnitude (M) W.O. 8144-A-SC PLATE C-11 GeoSoils, Inc. APPENDIX D LABORATORY Tested By: TR Checked By: TR LIQUID AND PLASTIC LIMITS TEST REPORT PLASTICITY INDEX0 10 20 30 40 50 60 LIQUID LIMIT 0 10 20 30 40 50 60 70 80 90 100 110 CL-ML CL or O L CH or O H ML or OL MH or OH Dashed line indicates the approximate upper limit boundary for natural soils 47 SOIL DATA SYMBOL SOURCE NATURAL USCSSAMPLE DEPTH WATER PLASTIC LIQUID PLASTICITY NO.CONTENT LIMIT LIMIT INDEX (%)(%)(%)(%) Client: Project: Project No.:Plate Woodside Homes La Costa 8144-A-SC B-1 B-1 1-6 -18 55 37 CH B-5 B-5 7.0 -19 60 41 CH W.O. 8144-A-SC PLATE D-1 • ■ Tested By: TR Checked By: TR 6-15-21 (no specification provided) PL=LL=PI= D90=D85=D60= D50=D30=D15= D10=Cu=Cc= USCS=AASHTO= * Olive Brown Sandy Clay 2 1.5 1 .75 .5 .375 #4 #10 #20 #40 #60 #100 #200 100.0 99.2 95.0 91.3 87.2 85.6 79.6 76.8 74.3 72.3 70.3 64.8 55.8 18 55 37 17.0634 8.7933 0.1031 CH A-7-6(17) Woodside Homes La Costa 8144-A-SC Soil Description Atterberg Limits Coefficients Classification Remarks Source of Sample: B-1 Depth: 1-6 Sample Number: B-1 Date: Client: Project: Project No:Plate SIEVE PERCENT SPEC.*PASS? SIZE FINER PERCENT (X=NO)PERCENT FINER0 10 20 30 40 50 60 70 80 90 100 GRAIN SIZE - mm. 0.0010.010.1110100 % +3"Coarse % Gravel Fine Coarse Medium % Sand Fine Silt % Fines Clay 0.0 8.7 11.7 2.8 4.5 16.5 55.86 in.3 in.2 in.1½ in.1 in.¾ in.½ in.3/8 in.#4#10#20#30#40#60#100#140#200Particle Size Distribution Report W.O. 8144-A-SC PLATE D-2 ri' ~\ 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 ll I I I "' I I I ~I'-I I I .. , I I r -r--:: ~ I I I I ~~"' ""--K -~ ~'\j '," I I I I ~~f!. ~,'I • Tested By: TR Checked By: TR 7-6-21 (no specification provided) PL=LL=PI= D90=D85=D60= D50=D30=D15= D10=Cu=Cc= USCS=AASHTO= * Olive Brown Sandy Clay 1.5 1 .75 .5 .375 #4 #10 #20 #40 #60 #100 #200 100.0 98.8 95.6 92.8 90.4 83.1 79.7 77.0 74.6 72.2 62.7 51.2 9.1848 5.8226 0.1300 CL Woodside Homes La Costa 8144-A-SC Soil Description Atterberg Limits Coefficients Classification Remarks Source of Sample: B-5 Depth: 1-5 Sample Number: B-5 Date: Client: Project: Project No:Plate SIEVE PERCENT SPEC.*PASS? SIZE FINER PERCENT (X=NO)PERCENT FINER0 10 20 30 40 50 60 70 80 90 100 GRAIN SIZE - mm. 0.0010.010.1110100 % +3"Coarse % Gravel Fine Coarse Medium % Sand Fine Silt % Fines Clay 0.0 4.4 12.5 3.4 5.1 23.4 51.26 in.3 in.2 in.1½ in.1 in.¾ in.½ in.3/8 in.#4#10#20#30#40#60#100#140#200Particle Size Distribution Report W.O. 8144-A-SC PLATE D-3 ~ 1:'\ K ' I I I I I I I I I I I I I I I 'r--. I I I I I I r--,' I I ~ I I ...... I I ---~~ I "" i-,._ K I -~ \ '\ ', I I I I ~~f!. ~,'I • Tested By: TR Checked By: TR Client: Woodside Homes Project: La Costa Source of Sample: B-5 Depth: 5.0 Sample Number: B-5 Proj. No.: 8144-A-SC Date Sampled: Sample Type: Natural Description: Olive Brown Sandy Clay Specific Gravity= 2.75 Remarks: Plate Sample No. Water Content, % Dry Density, pcf Saturation, % Void Ratio Diameter, in. Height, in. Water Content, % Dry Density, pcf Saturation, % Void Ratio Diameter, in. Height, in. Normal Stress, psf Fail. Stress, psf Strain, % Ult. Stress, psf Strain, % Strain rate, in./min.InitialAt TestShear Stress, psf0 1000 2000 3000 4000 5000 6000 Strain, % 0 5 10 15 20 1 2 3Ult. Stress, psf Fail. Stress, psf 0 2000 4000 6000 Normal Stress, psf 0 2000 4000 6000 8000 10000 12000 C, psf f, deg Tan(f) Fail.Ult. 547 31 0.60 314 28 0.52 1 18.1 104.8 78.2 0.6378 2.38 1.00 19.9 105.8 87.9 0.6231 2.38 0.99 1100 1186 2.4 829 11.8 0.000 2 18.1 105.0 78.5 0.6355 2.38 1.00 20.8 106.2 92.8 0.6159 2.38 0.99 2200 1885 3.3 1548 10.7 0.001 3 18.1 102.2 73.4 0.6798 2.38 1.00 21.1 106.3 94.3 0.6143 2.38 0.96 4400 3163 4.8 2579 11.8 0.001 W.O. 8144-A-SC PLATE D-4 1 ..... ,"' ,, ,. I/ 1-•"' .... ,.,· V .. ,. .... ,. ,. _., ... I ,.,· I ..... ,. I )IC Cl 1 .... -· ,, ,. I I / ," I ,..,. , ...... ,, ,. / ,. ... .,. ,., .. 17 ,,. ... .... ,. .. .... ., ... _,. ,. ... .... . ... ,. -· ,. .... ,. ., .,, ... ,. ..,.-,, ,..,,, l,-C ,. .. ,. c.• ,. r-- I " I I I '-t -~ Ln:J~iH· ~'57~' • A B C D Compactor air pressure PSI Water added % Moisture at compaction % Height of sample IN Dry density PCF R-Value by exudation R-Value by exudation, corrected Exudation pressure PSI Stability thickness FT Expansion pressure thickness FT Traffic index, assumed 5.0 Sample Location: Gravel equivalent factor, assumed 1.25 Sample Description: Expansion, stability equilibrium 0 Notes: R-Value by expansion NA R-Value by exudation <5 Test Method: R-Value at equilibrium <5 * Four lights illuminated with soil exuding from under the mold at 800psi GeoSoils, Inc. 5741 Palmer Way Project:Woodside Carlsbad, CA 92008 Telephone: (760) 438-3155 Number:8144-A-SC Fax: (760) 931-0915 9/2/2010 Date:July 2021 TEST SPECIMEN R - VALUE TEST RESULTS - DESIGN CALCULATION DATA 9% Retained on 3/4 inch sieve Olive Brown Sandy Clay SAMPLE INFORMATION B-1, 1-6ft Cal-Trans Test 301 0.00 0.50 1.00 0.00 0.50 1.00 1.50 2.00Cover Thickness by Stability (ft)Cover Thickness by Expansion Pressure (ft) Expansion, Stability Equilibrium 0 10 20 30 40 50 60 70 80 90 100 0R-ValueExudation Pressure (psi) R-Value By Exudation W.O. 8144-A-SC PLATE D-5 V / V / / V V / / / / V / I/ / / / / I/ V GeoSoils, Inc. APPENDIX E GENERAL EARTHWORK AND GRADING GUIDELINES GeoSoils, Inc. GENERAL EARTHWORK AND GRADING GUIDELINES General These guidelines present general procedures and requirements for earthwork and grading as shown on the approved grading plans, including preparation of areas to be filled, placement of fill, installation of subdrains, excavations, and appurtenant structures or flatwork. The recommendations contained in the geotechnical report are part of these earthwork and grading guidelines and would supercede the provisions contained hereafter in the case of conflict. Evaluations performed by the consultant during the course of grading may result in new or revised recommendations which could supercede these guidelines or the recommendations contained in the geotechnical report. Generalized details follow this text. The contractor is responsible for the satisfactory completion of all earthwork in accordance with provisions of the project plans and specifications and latest adopted code. In the case of conflict, the most onerous provisions shall prevail. The project geotechnical engineer and engineering geologist (geotechnical consultant), and/or their representatives, should provide observation and testing services, and geotechnical consultation during the duration of the project. EARTHWORK OBSERVATIONS AND TESTING Geotechnical Consultant Prior to the commencement of grading, a qualified geotechnical consultant (soil engineer and engineering geologist) should be employed for the purpose of observing earthwork procedures and testing the fills for general conformance with the recommendations of the geotechnical report(s), the approved grading plans, and applicable grading codes and ordinances. The geotechnical consultant should provide testing and observation so that an evaluation may be made that the work is being accomplished as specified. It is the responsibility of the contractor to assist the consultants and keep them apprised of anticipated work schedules and changes, so that they may schedule their personnel accordingly. All remedial removals, clean-outs, prepared ground to receive fill, key excavations, and subdrain installation should be observed and documented by the geotechnical consultant prior to placing any fill. It is the contractor’s responsibility to notify the geotechnical consultant when such areas are ready for observation. Laboratory and Field Tests Maximum dry density tests to determine the degree of compaction should be performed in accordance with American Standard Testing Materials test method ASTM designation D 1557. Random or representative field compaction tests should be GeoSoils, Inc.Woodside 05S, LP Appendix E File:e:\wp12\8100\8144a.gdd Page 2 performed in accordance with test methods ASTM designation D-1556, D-2937 or D-2922, and D-3017, at intervals of approximately ±2 feet of fill height or approximately every 1,000 cubic yards placed. These criteria would vary depending on the soil conditions and the size of the project. The location and frequency of testing would be at the discretion of the geotechnical consultant. Contractor's Responsibility All clearing, site preparation, and earthwork performed on the project should be conducted by the contractor, with observation by a geotechnical consultant, and staged approval by the governing agencies, as applicable. It is the contractor's responsibility to prepare the ground surface to receive the fill, to the satisfaction of the geotechnical consultant, and to place, spread, moisture condition, mix, and compact the fill in accordance with the recommendations of the geotechnical consultant. The contractor should also remove all non-earth material considered unsatisfactory by the geotechnical consultant. Notwithstanding the services provided by the geotechnical consultant, it is the sole responsibility of the contractor to provide adequate equipment and methods to accomplish the earthwork in strict accordance with applicable grading guidelines, latest adopted codes or agency ordinances, geotechnical report(s), and approved grading plans. Sufficient watering apparatus and compaction equipment should be provided by the contractor with due consideration for the fill material, rate of placement, and climatic conditions. If, in the opinion of the geotechnical consultant, unsatisfactory conditions such as questionable weather, excessive oversized rock or deleterious material, insufficient support equipment, etc., are resulting in a quality of work that is not acceptable, the consultant will inform the contractor, and the contractor is expected to rectify the conditions, and if necessary, stop work until conditions are satisfactory. During construction, the contractor shall properly grade all surfaces to maintain good drainage and prevent ponding of water. The contractor shall take remedial measures to control surface water and to prevent erosion of graded areas until such time as permanent drainage and erosion control measures have been installed. SITE PREPARATION All major vegetation, including brush, trees, thick grasses, organic debris, and other deleterious material, should be removed and disposed of off-site. These removals must be concluded prior to placing fill. In-place existing fill, soil, alluvium, colluvium, or rock materials, as evaluated by the geotechnical consultant as being unsuitable, should be removed prior to any fill placement. Depending upon the soil conditions, these materials may be reused as compacted fills. Any materials incorporated as part of the compacted fills should be approved by the geotechnical consultant. Any underground structures such as cesspools, cisterns, mining shafts, tunnels, septic tanks, wells, pipelines, or other structures not located prior to grading, are to be removed GeoSoils, Inc.Woodside 05S, LP Appendix E File:e:\wp12\8100\8144a.gdd Page 3 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 GeoSoils, Inc.Woodside 05S, LP Appendix E File:e:\wp12\8100\8144a.gdd Page 4 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/formation 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. 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 feet from finish grade, the range of foundation excavations, future utilities, or underground construction unless specifically approved by the governing agency, the geotechnical consultant, and/or the developer’s representative. If import material is required for grading, representative samples of the materials to be utilized as compacted fill should be analyzed in the laboratory by the geotechnical consultant to evaluate it’s physical properties and suitability for use onsite. Such testing should be performed three (3) days prior to importation. If any material other than that previously tested is encountered during grading, an appropriate analysis of this material should be conducted by the geotechnical consultant as soon as possible. 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 GeoSoils, Inc.Woodside 05S, LP Appendix E File:e:\wp12\8100\8144a.gdd Page 5 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 slopes, and extend out over the slope to provide adequate compaction to the face of the slope. GeoSoils, Inc.Woodside 05S, LP Appendix E File:e:\wp12\8100\8144a.gdd Page 6 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. 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 GeoSoils, Inc.Woodside 05S, LP Appendix E File:e:\wp12\8100\8144a.gdd Page 7 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. 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: GeoSoils, Inc.Woodside 05S, LP Appendix E File:e:\wp12\8100\8144a.gdd Page 8 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 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 GeoSoils, Inc.Woodside 05S, LP Appendix E File:e:\wp12\8100\8144a.gdd Page 9 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. 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. February 9, 2022 Project No. 9604.1 Log No. 21774 City of Carlsbad Land Development Engineering 1635 Faraday Avenue Carlsbad, California 92008-7314 Attention: Ms. Emad Elias Subject: THIRD-PARTY GEOTECHNICAL REVIEW (FIRST) La Costa Town Square Parcel 3 La Costa Avenue Carlsbad, California GR2022-0001/CT2017-003 References: 1. “Geotechnical Due Diligence Evaluation of the La Costa Town Square Townhomes Site, APN 223-050-73-00, La Costa Avenue, City of Carlsbad, San Diego County, California 92011,” by Geosoils, Inc., dated June 17, 2021. 2. “Rough Grading/Public Improvements Plans For: La Costa Town Square,” by SB&O, Inc., dated January 14, 2022 (Sheets 1 through 10). Dear Mr. Elias: In accordance with your request, Hetherington Engineering, Inc. has provided third-party geotechnical review of Reference 1. The following comments are provided for analyses and/or response by the Geotechnical Consultant. 1. The Consultant should review the project grading/improvement plans (Reference 2), and foundation plans, provide any additional geotechnical analyses/recommendations considered necessary, and confirm that the plans have been prepared in accordance with the geotechnical recommendations. 2. The Consultant should provide an updated geotechnical map utilizing the current grading plan for the project to clearly show (at minimum): a) existing site topography, b) proposed structures/improvements, c) proposed finished grades, d) geologic conditions, e) locations of the subsurface exploration, f) temporary construction slopes, g) remedial grading, key locations, etc. 3. The Consultant should provide geologic cross-sections utilizing the current grading plan to clearly show (at minimum): a) existing topography, b) proposed structures/improvements, c) proposed finish grades, d) geologic contacts, e) geologic SOIL & FOUNDATION ENGINEERING ENGINEERING GEOLOGY HYDROGEOLOGY (760) 931-1917 Fax (760) 931-0545 333 Third Street Laguna Beach, CA 92651 (949) 715-5440 Fax (949) 715-5442 Carlsbad, CA 92008-43695365 Avenida Encinas, Suite A HETHERINGTON ENGINEERING, INC. www.hetheringtonengineering.com • • • • • • • • THIRD-PARTY GEOTECHNICAL REVIEW (FIRST) Project No 9604.1 Log No. 21774 February 9, 2022 Page 2 structure, f) locations of the subsurface exploration, g) temporary construction slopes, and h) remedial grading, etc. 4. The Consultant indicates the existing site fills are “engineered” but provides no references or discussion regarding documentation. The consultant should provide additional discussion and relevant references. 5. The Consultant should address the gross and surficial stability of existing and proposed site slopes. 6. The Consultant should address impacts to adjacent property and improvements as a result of site grading and construction. 7. The Consultant should specify the sulfate exposure category based on the soluble sulfate testing or default to a severe category. Please call if there are any questions. Sincerely, HETHERINGTON ENGINEERING, INC. Paul A. Bogseth Mark D. Hetherington Professional Geologist 3772 Civil Engineer 30488 Certified Engineering Geologist 1153 Geotechnical Engineer 397 Certified Hydrogeologist 591 (expires 3/31/22) (expires 3/31/22) Distribution: 1-via e-mail (Emad.Elias@carlsbadca.gov) 1-via e-mail (ldetrackingdesk@carlsbadca.gov) 1-via e-mail (Tim.Carroll@carlsbadca.gov) HETHERINGTON ENGINEERING, INC. -- Geotechnical C Geologic C Coastal C Environmental 5741 Palmer Way C Carlsbad, California 92010 C (760) 438-3155 C FAX (760) 931-0915 C www.geosoilsinc.com March 24, 2022 W.O. 8144-A-SC Woodside 05S, LP 1250 Corona Pointe Court, Suite 500 Corona, California 92879 Attention: Mr. Craig Moraes Subject: Review and Response to Third Party Geotechnical Review Comments, LaCosta Town Square Townhome Site (APN 223-050-73-00), La Costa Boulevard, City of Carlsbad, California Dear Mr. Moraes: In accordance with your request, GeoSoils, Inc. (GSI) has reviewed the 3rd party geotechnical review prepared by Hetherington Engineering, Inc. (HEI, 2022) with respect to the geotechnical documents prepared for this site (see Appendix A - References) and the planned improvement of the site. Based on our review of HEI (2022) and the existing body of geotechnical and civil work for the site (see Appendix A - References), GSI has prepared the following responses to comments presented in HEI (2022). For ease of review, the HEI (2022) comments are provided below in italics, followed by the appropriate GSI response. Comment No. 1 “The Consultant should review the project grading plan (Reference No. 2), and foundation plans, provide any additional geotechnical analyses/recommendations considered necessary, and confirm that the plans have been prepared in accordance with the geotechnical recommendations.” Response to Comment No. 1 Acknowledged. A review of the rough grading/public improvement plans for the site, prepared by SB&O, Inc. (SB&O, 2022) was performed by GSI. Based on our review, the plans appear to be is accordance with the intent of the geotechnical report. The “Soils Engineer’s Certificate” shown on Sheet 1 of SB&O (2022) would be completed once mylars are generated. As indicated in GSI (2021), dense/hard igneous rock will be encountered around the intersection between Driveways “A” and “B,” and along Driveway “A” and within the slope west of Driveway “A” (below Building Pad 1). Recommendations for undercutting of streets for utilities are included in GSI (2021). Planned wall construction GeoSoils, Inc. within the slope below Building Pad 1 will likely encounter hard rock, requiring special excavation techniques (rock breakers/saws, etc.) for foundation excavation. Alternatively, a stabilization fill slope could be constructed in order to facilitate wall construction. Stabilization fill slope construction guidelines are included in GSI (2021). Oversize material may be generated from hard rock excavation. Foundation plans do not appear to be available for review at this time. Once available, it is recommended that the foundation/structural plans are reviewed by the geotechnical engineer. Unless specifically superceded in the text of this report, the conclusions and recommendations presented in GSI (2021) are considered valid and applicable with respect to the subject site, and should be properly incorporated into the design and construction phases of site development. Comment No. 2 “The Consultant should provide an updated geotechnical map utilizing the current grading plan for the project to clearly show (at minimum): a) existing site topography, b) proposed structures/improvements, c) proposed finish grades, d) geologic conditions, e) locations of subsurface exploration, f) temporary construction slopes, g) remedial grading, key locations, etc.” Response to Comment No. 2 Acknowledged. An updated geotechnical map using SB&O (2022) as a base, is attached as Plate 1. Comment No. 3 “The Consultant should provide geologic cross-sections utilizing the current grading plan to clearly show (at minimum): a) existing site topography, b) proposed structures/improvements, c) proposed finish grades, d) geologic contacts, e) geologic structure, f) locations of subsurface exploration, g) temporary construction slopes, and h) remedial grading, etc.” Response to Comment No. 3 Acknowledged. A geologic cross section with the requested information is attached as Plate 2. Please note that plan grades are generally within 1 to 2 feet of existing grades across all building areas and will not result in a meaningful representation/comparison in cross section. Exceptions would include two (2) local areas of plan fills on the order of about 5-6 feet in depth to mitigate existing desilting basins located in the vicinity of building pads 1, 2, 18, and 19. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Center, Carlsbad March 24, 2022 File:e:\wp21\8100\8144a.rar Page 2 GeoSoils, Inc. Comment No. 4 “The Consultant indicates that the existing fills are “engineered” but provides no references or discussion regarding documentation. The consultant should provide additional discussion and relevant references.” Response to Comment No. 4 Compacted fills onsite were placed as part of mass grading operations for the larger La Costa Town Center project, with observation and testing services provided by Southern California Soils & Testing, Inc.(SCS&T). The results of SCS&T’s observation and testing are summarized in SCS&T (2013), and also discussed in SCS&T (2017). Based on SCS&T’s observations and testing, compacted fills have been placed to a minimum relative compaction of at least 90 percent. Comment No. 5 “The Consultant should address the gross and surficial stability of existing and proposed site slopes.” Response to Comment No. 5 Acknowledged. In preparation of SCS&T (2018) a reconnaissance assessment of the geotechnical conditions of the slope and segmental retaining wall above the subject site (norrth side) was performed. Based on their review and evaluation, they concluded that “the slope is not considered subject to slope failures or falling debris.” In addition, from GSI (2021): “Based on our review of existing geotechnical documents, site conditions and planned improvements, existing cut and fill slopes appear to be performing adequately. Slopes are anticipated to continue to perform adequately assuming adequate maintenance and care over the like of the project. Temporary slopes for construction (i.e., trenching, etc.) are discussed in subsequent sections of our report. The existing MSE wall and slope configuration located along the northern side was observed to exhibit no significant sign of distress and appears to be performing adequately.” Based on our review and evaluation, existing and planned slopes are anticipated to be stable from a gross (static/dynamic) and surficial perspective, provided that the slopes are properly constructed and/or maintained. Comment No. 6 “The Consultant should address the impacts to adjacent property and improvements as a result of site grading and construction.” Woodside 05S, LP W.O. 8144-A-SC La Costa Town Center, Carlsbad March 24, 2022 File:e:\wp21\8100\8144a.rar Page 3 GeoSoils, Inc. Response to Comment No. 6 Acknowledged. Based on the “infill” nature of site construction, including previous earthwork, etc., significant impacts to any offsite improvements are not anticipated, provided that the recommendations presented in the geotechnical evaluation of the site (GSI, 2021) are properly incorporated into the construction plans and site work methodology for this project. Comment No. 7 “The Consultant should specify the sulfate exposure category based on the soluble sulfate testing or default to severe category.” Response to Comment No. 7 Acknowledged. Sulfate testing was performed in preparation of SCST (2017) and generally evaluated a “not applicable” (S0) to “low” (S1) per ACI 318R-14) sulfate exposure to concrete. Test results are included in Appendix B of this document. Conformation testing is recommended during site grading. Importing and placement of a select fill cap for foundation support may reduce overall corrosiveness of the soil, dependant on the nature of the import. 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, engineering analyses, and laboratory data, the conclusions and recommendations presented herein are professional opinions. These opinions have been derived in accordance with current standards of practice, and no warranty is express or implied. Standards of practice are subject to change with time. This report has been prepared for the purpose of providing soil design parameters derived from testing of a soil sample received at our laboratory, and does not represent an evaluation of the overall stability, suitability, or performance of the property for the proposed development. GSI assumes no responsibility or liability for work or testing performed by others, or their inaction; or work performed when GSI is not requested to be onsite, to evaluate if our recommendations have been properly implemented. Use of this report constitutes an agreement and consent by the user to all the limitations outlined above, notwithstanding any other agreements that may be in place. In addition, this report may be subject to review by the controlling authorities. Thus, this report brings to completion our scope of services for this portion of the project. Woodside 05S, LP W.O. 8144-A-SC La Costa Town Center, Carlsbad March 24, 2022 File:e:\wp21\8100\8144a.rar Page 4 GeoSoils, Inc. The opportunity to be of service is sincerely appreciated. If you should have any questions, please do not hesitate to contact our office. Respectfully submitted, GeoSoils, Inc. Robert G. Crisman Stephen J. Coover Engineering Geologist, CEG 1934 Geotechnical Engineer, GE 2057 MJS/RGC/SJC/sh Attachment: Appendix A - References Appendix B - Soil Corrosion Test Results Plate 1 - Geotechnical Map Plate 2 - Cross Section A-A’ Distribution: (1) Addressee (PDF via email) Woodside 05S, LP W.O. 8144-A-SC La Costa Town Center, Carlsbad March 24, 2022 File:e:\wp21\8100\8144a.rar Page 5 GeoSoils, Inc. APPENDIX A REFERENCES GeoSoils, Inc. APPENDIX A REFERENCES American Concrete Institute, 2014, Building code requirements for structural concrete (ACI 318-14), and commentary (ACI 318R-14): reported by ACI Committee 318, dated September. California Building Standards Commission, 2019a, California Building Code, California Code of Regulations, Title 24, Part 2, Volume 2 of 2, based on the 2018 International Building Code, effective January 1, 2020. _____, 2019b, California Building Code, California Code of Regulations, Title 24, Part 2, Volume 1 of 2, Based on the 2018 International Building Code, effective January 1, 2020. GeoSoils, Inc., 2021, Geotechnical due diligence evaluation of the La Costa Town Square Townhome Site, APN 223-050-73-00, La Costa Avenue, City of Carlsbad, San Diego County, California 92011, W.O. 8144-A-SC, dated June 17. Hetherington Engineering, Inc., 2022, Third-party geotechnical review (first), La Costa Town Square, Parcel 3, La Costa Avenue, Carlsbad, California, GR2022-0001/CT2017-003, Project No. 9604.1, Log No. 21774, dated February 9. SB&O, Inc., 2022, Rough grading and public improvement plans for: La Costa Town Square, 10 Sheets, J.N. 76882RG04, plot dated January 14. Southern California Soils & Testing, Inc., 2018, Slope Assessment, La Costa Town Square multi-family housing, Parcel 3, La Costa Boulevard, Carlsbad, California, SCST No. 160518N, Report No. 2 , dated October 23. _____, 2017, Limited geotechnical investigation, La Costa Town Square multi-family housing, La Costa Boulevard, Carlsbad, California, SCST Report No. 160518N-1, dated February 28. _____, 2015, Final as-graded geotechnical report, La Costa Town Square, office development, La Costa Avenue, Carlsbad, California, Project No. C.T. 01-09, dated November 13. _____, 2013, Interim as-graded geotechnical report, La Costa Town Square commercial development, Pads 1 through 10, 14, and 22, and office development, La Costa Avenue, Carlsbad, California, Project No. C.T. 01-09 and C.T. 08-07, SCS&T No. 1211179, Report No. 25, dated July 31. GeoSoils, Inc. APPENDIX B CORROSION TESTING RESULTS (SCS&T, 2017) CLASSIFICATION OF EXPANSIVE SOIL 1 2. ACI 318, Table 4.2.1 SCST, INC. Date: Job Number:Figure: Severity S0 Not applicable High Above 130 Very High 1. ASTM - D4829 TP-16 290 6.9 0.006 104 108 116 1 - 20 Very Low DELMAR FORMATION: FAT CLAY, moderate brown EXPANSION INDEX POTENTIAL EXPANSION TP-17 METAMORPHIC ROCK SANDY CLAY, light brown, decomposed TP-9 TP-15 TP-16 TP-1 7.28 SO4 > 2.00 0.020 TP-17 0.0161796.82 0.001 S3 Very Severe S1 Moderate CHLORIDE (%)RESISTIVITY (Ω-cm) 288 pHSAMPLE 0.066 S2 SULFATE EXPOSURE CLASSES 2 Water-Soluble Sulfate (SO4) in Soil, Percent by Mass SO4 < 0.10 0.10 ≤ SO4 < 0.20 0.20 ≤ SO4 ≤ 2.00Severe Class WLV La Costa Town Square Multi-Family Housing Carlsbad, California By: II-1 )HEUXDU\, 2017 160518N ASTM D2489 EXPANSION INDEX EXPANSION INDEX DESCRIPTION FILL: LEAN SANDY CLAY, greenish gray 51TP-1 SAMPLE TP-9 TP-15 189 149 6.09 7.27 0.022 0.049 0.144 DELMAR FORMATION: FAT CLAY, greenish gray FILL: FAT SANDY CLAY, greenish gray 0.141 SULFATE (%) 0.171 110 21 - 50 Low RESISTIVITY, pH, SOLUBLE CHLORIDE and SOLUBLE SULFATE 51 - 90 Medium 91 - 130 W.O. 8144-A-SC PLATE B-1 ~ :sJ ii B-8 Afe Td 1 6" PVC SUBDRAIN OUTLET B-3 B-4 B-6 B-5 B-9 B-7 B-1 B-2 Td Mzu Mzu Mzu Td Td Afe Td Afe TdMzu Td Afe Td Afe TdAfe Td ALL LOCATIONS ARE APPROXIMATE This document or efile is not a part of the ConstructionDocuments and should not be relied upon as being anaccurate depiction of design. 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