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HomeMy WebLinkAboutCT 12-01; Miles Pacific Subdivision; Geotechnical Update Evaluation; 2014-06-23Geotechnical - Geotogic * Coastal > Environmental 5741 PalmerWay • Carlsbaa. CalriDmia 92010 • (760} 438-3155 • FAX (760) S31-0S15 • www.geo60jlsmc.coin May 8, 2015 W.O. 6649-A3-SC Shea Homes Limited Partnership 9990 Mesa Rim Road, Suite 200 San Diego, Calrfornia 92121 Attention: Ms. Sarah Morell Subject: Geotechnical Review of 20-Scale Grading PlansforMiles Pacific Subdivision (Second Plan Submittal), 2373 and 2375 Pio Pico Drive, Carlsbad, San Diego County, Califomia, APNs 156-351-03, -07, and -08^ City of Carlsbad Project No : CT 12-01 Dear Ms. Morrell: In accordance with your request and authorization, GeoSoils, Inc. (GSI) is presenting, herein, a summary of our geotechnical review ofthe subject grading plans prepared by bHA, Inc, {|bHAl, undated [see Appendix|). The subject plans were elect rom cal fy transmitted to our office on May 5,2015. The purpose of our review was to evaluate if the recommendations contained in the reports, listed in the Appendix, have been properly incorporated into the plans. The scope of our services has included areview oflhe subject ptans, analysis ot data, and preparation of this summary letter. GEOTECHNtCAL REVIEW OF GRADING PLANS {bHA. Undated) Based on our review, the plans are in general accordance with the recommendations provided in the referenced reports. Unless specifically superceded herein, the conclusions and recommendations in the referenced geotechnical and environmental reports, and team correspondence remain pertinent and applicable, and should be appropriately implemented during planning, design, and construction. r LAND DEVi-in- - CLOSURE 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. / /YSff, David W. Skelly ^ Civil Engineer, RCE 47857 John P.fFranklin L^Engineering Geologist, CEG 1340 RBB/JPF/DWS/jh Attachments - Appendix Distribution: (1) Addressee (via email) (1) bHA, Inc., Attention: Mr. Dale Clark (via email) Shea Homes Limited Partnership Sohaei 20-Scale Review File:e:\wp12\6600\6649a3.gro GeoSoils, Inc. w.o. 6649-A3-SC May 8, 2015 Page 2 APPENDIX REFERENCES bHA, Inc., undated. Grading plans for: Miles Pacific subdivision, 8 sheets, 20-scale, Drawing No. 483-4A, City of Carlsbad Project No.:, 12-01. GeoSoils, Inc., 2014a, Geotechnical update evaluation, Ayre Subdivision (Former Miles Pacific and Sohaei Properties), 2359, 2373, and 2375 Pio Pico Drive, Carlsbad, San Diego County, California, W.O. 6649-A-SC, dated June 23. , 2014b, Property mitigation plan, proposed 17 lot subdivision, APNs 156-351 -03, -07, and -08, 2373 and 2375 Pio Pico Drive, Carlsbad, San Diego County, California 92010, Voluntary Assistance Case DEH2013-LSAM-000194, W.O. E6649.1-SC, dated April 30. , 2012a, Qualitative evaluation of infiltration and soil runoff potentials, APNs 156-351 -03, -07, and -08,2373 and 2375 Pio Pico Drive, Carlsbad, San Diego County, California 92008, W.O. 6324-AI-SC, dated December 27. , 2012b, Preliminary geotechnical evaluation, APNs 156-351-03, -07, and -08, 2373 and 2375 Pio Pico Drive, Carlsbad, San Diego County, California 92008, W.O. 6324-A-SC, dated October 31. GeoSoilSf Inc. Geotechnical • Geologic • Coastal • Environmental 5741 PalmerWay • Carlsbad, California 92010 • (760)438-3155 • FAX (760) 931-0915 • www,geosoilslnc.com June 29, 2015 W.O. 6649-A4-SC Shea Homes Limited Partnership 9990 Mesa Rim Road, Suite 200 San Diego, California 92121 Attention: Ms. Sarah Morell Subject: Geotechnical Review of 20-Scale Grading Plans and Calculation Package for Miles Pacific Subdivision, 2373 and 2375 Pio Pico Drive, Carlsbad, San Diego County, California, 9 sheets, APNs 156-351-03, -07, and -08, City of Carlsbad Project No.: CT 12-01 Dear Ms. Morrell: In accordance with your request and authorization, GeoSoils, Inc. (GSI) is presenting, herein, a summary of our geotechnical review of the subject grading plans prepared by bHA, Inc. ([bHA], undated [see Appendix]). The subject plans and calculation package were revised and electronically re-transmitted to our office on June 25 and 27,2015. The purpose of our review was to evaluate if the recommendations contained in the reports, listed in the Appendix, have been properly incorporated into the plans. The scope of our services has included a review ofthe subject plans, associated calculation package (dated June 27, 2015), review of data, and preparation ofthis summary letter. GEOTECHNICAL REVIEW OF GRADING PLANS (bHA. Undated) Based on our review, the plans are in general accordance with the recommendations provided in the referenced reports. Unless specifically superceded herein, the conclusions and recommendations in the referenced geotechnical and environmental reports, remain pertinent and applicable, and should be appropriately implemented during planning, design, and construction. RECEIVED JUL 01 20i5 LAND DEVELOPMENT ENGINEERING CLOSURE The opportunity to be of service is sincerely appreciated. If you should have any questions, please do not hesitate to contact our office. Respectfully submitt GeoSoils, Inc. P. FrankliQii^Jj^n^ Anurew T. Guatelli /Engineering Geologislr€Ke4340 Geotechnical Engineer, GE 2320 RBB/JPF/ATG/jh Attachment: Appendix Distribution: (1) Addressee (wet signed, via email) (2) bHA, Inc., Attention: Mr. Dale Clark (wet signed, also via email) Shea Homes Limited Partnership Sohaei 20-Scale Review Flle:e:\wp12\6600\664ga4.gro GeoSoils, Inc. w.o. 6649-A4-SC June 29, 2015 Page 2 APPENDiX REFERENCES bHA, Inc., undated. Grading plans for: Miles Pacific subdivision, 9 sheets, 20-scale, Drawing No. 483-4A, City of Carlsbad Project No.: 12-01, with undated delta 1 revisions. GeoSoils, Inc., 2015, Geotechnical review of 20-scale grading plans for Miles Pacific Subdivision (second plan submittal), 2373 and 2375 Pio Pico Drive, Carlsbad, San Diego County, California, APNs 156-351-03, -07, and -08, City of Carlsbad project no.: CT 12-01, W.O. 6649-A3-SC, dated May 8. , 2014a, Geotechnical update evaluation, Ayre Subdivision (Former Miles Pacific and Sohaei Properties), 2359, 2373, and 2375 Pio Pico Drive, Carlsbad, San Diego County, California, W.O. 6649-A-SC, dated June 23. , 2014b, Property mitigation plan, proposed 17-lot subdivision, APNs 156-351 -03, -07, and -08, 2373 and 2375 Pio Pico Drive, Carlsbad, San Diego County, California 92010, Voluntary Assistance Case DEH2013-LSAM-000194, W.O. E6649.1-SC, dated April 30. , 2012a, Qualitative evaluation of infiltration and soil runoff potentials, APNs 156-351 -03, -07, and -08,2373 and 2375 Pio Pico Drive, Carlsbad, San Diego County, California 92008, W.O. 6324-AI-SC, dated December 27. , 2012b, Preliminary geotechnical evaluation, APNs 156-351-03, -07, and -08, 2373 and 2375 Pio Pico Drive, Carlsbad, San Diego County, California 92008, W.O. 6324-A-SC, dated October 31. Swanson & Associates, 2015, Retaining wall details and calculation package, sheets 8 and 9 of bHA, Inc.'s grading plans, dated June 27. GeoSoils, Inc. Geotechnical • Geologic • Coastal • Environmental 5741 PalmerWay • Carlsbad, California 92010 • (760)438-315? • FAX (760) 931:0915 • wwwgeosoilsinc.com December 27, 2012 l\/liles-Pacific, LLP c/o bHA, Inc. 5115 Avenida Encinas, Suite L Carlsbad, California 92008-8700 Attention: Mr. Mike Smith RECEIVED JUN 23 2014 ENGINEFPiMQ W.o. 6324-A-SC Subject: Qualitative Evaluation of Infiltration and Soil Runoff Potentials, APNs 156-351-03, -07, and -08, 2373 and 2375 Pio Pico Drive, Carlsbad, San Diego County, California 92008 Dear Mr. Smith: In accordance with your request and Mr. Robert Miles' authorization, GeoSoils, Inc. (GSI) has qualitatively evaluated the onsite soils' Infiltration and soil runoff potentials in orderto provide a Hydrologic Soil Group (HSG) classification to be used in the design ofthe onsite storm water treatment basins, shown on bHA, Inc. (bHA, 2012 [see the Appendix]). The scope of services performed forthis evaluation included a review ofthe documents listed in the Appendix and the preparation of this letter. Unless specifically superseded herein, the conclusions and recommendations provided in GSI (2012) are considered valid and applicable, and should be appropriately considered in project design and construction. The feasibility of infiltration for onsite storm water treatment is dependent on the onsite soils' ability to accept and absorb water (County of San Diego, 2007). As a guideline for the feasibility and design for onsite storm water treatment systems, the County of San Diego defers to Hydrologic Soil Group (HSG) classifications derived from soil surveys conducted bythe United States Department of Agricultural (USDA), on San Diego County soils (USDA, 1973). Soil survey mapping by the USDA indicates that the subject site is underlain by soils that include soils that belong to the Chesterson - Urban land complex (USDA [1973] map symbol - CgC). The USDA (1973) indicates the HSG classification for this soil is "D." Based on data gathered in preparation of GSI (2012), the subject site is underlain by both younger and older paralic deposits. Laboratory testing performed on these deposits indicates relatively high in-place density (i.e., ±108 to ±124 pounds per cubic foot [pcf]) and the locally occurrence of clay. Due to their relatively high in-place densities and local fine-grained nature, it is our opinion that the onsite soils generally exhibit slow infiltration and high runoff rates. Therefore, owing to direct subsurface investigation and laboratory testing, we assign a HSG classification of "D" to the onsite soils. Due to anticipated slow infiltration, GSI recommends thatthe onsite storm water treatment basins include an under-drain system consisting of pea gravel and perforated drain pipe (Schedule 40 or approved equivalent) placed within a trench beneath the filter media. The floor and sides of the basin, and the underdrain trench should be lined with an impermeable liner. The perforated drain pipe should be sleeved with Mirafi 140N filter fabric to mitigate clogging with silt and organic matter. The opportunity to be of service is sincerely appreciated, questions, please do not hesitate to contact our office. Respectfully submitt; GeoSoils, Inc. If you should have any n P. FranI' ineering Geologist, CEG 1340 David W. Skelly Civil Engineer, RCE'-^^BSfc-i;: Ryan B. Boehmer Staff Geologist RBB/JPF/DWS/jh Distribution: (2) Addressee (via email and US mail) (1) Miles-Pacific, LLC, Attention: Mr. Robert Miles Miles-Pacific, LLP 2373 and 2375 Plo Pico Dr., Carlsbad Flle:e:\wp12\6300\6324a.qeo GeoSoils, Inc. w.o. 6324-A-SC December 27, 2012 Page 2 APPENDiX REFERENCES bHA, Inc., 2012, Tentative map and coastal development plan CT 12-01/CDP 12-15 for: Miles-Pacific Subdivision, Carlsbad, CA, Sheetsi, 2, and 3 of 5,30-scale, plot dated August 29. County of San Diego, Department of Planning and Land Use, 2007, Low impact development (LID) handbook, stormwater management strategies, dated December 31. GeoSoils, Inc., 2012, Preliminary geotechnical evaluation, APNs 156-351-03, -07, and -08, 2373 and 2375 Pio Pico Drive, Carlsbad, San Diego County, California 92008, W.O. 6324-A-SC, dated October 31. United States Department of Agriculture, Soil Conservation Services and Forrest Services, 1973, Soil survey, San Diego area, California, dated December. GeoSoils, Inc. Geotechnical • Geologic • Coastal • Environmental 5741 PalmerWay • Carlsbad, California 92010 • (760)438-3155 • FAX (760) 931-0915 • www.geosollsinc.com March 18, 2014 W.O. 6637-A-SC i\1iies-Pacific, LP c/o BHA, Inc. 5115 Avenida Encinas, Suite L Carlsbad, California 92008-8700 AUG 8 ZOU Attention: Mr. Rod Bradley Subject: Addendum to Preliminary Geotechnical Evaluation, Proposed Residential Subdivision, 1833 Buena Vista Way, Carlsbad, San Diego County, California References: 1. "Preliminary Geotechnical Evaluation, Proposed Residential Subdivision, 1833 Buena Vlsta Way, Carlsbad, San Diego County, California," W.O. 6637-A-SC, dated March 17, 2014, by GeoSoils, Inc.. 2. "City of Carlsbad Engineering Standards, General Design Standards," Volume 1, 2004 Edition, by City of Carlsbad. Dear Mr. Bradley: GeoSoils, Inc. (GSI) is providing this addendum to our preliminary geotechnical evaluation report (see Reference 1). This addendum provides revised preliminary asphaltic concrete pavement sections that conform to City of Carlsbad minimum criteria, indicated in Reference 2. Unless specifically superceded herein, the conclusions and recommendations provided in Reference 1 are still considered valid and applicable and should be appropriately implemented during the balance of project design and construction. The revised preliminary asphaltic concrete pavement sections are included in the table below: ASPHALTIC CONCRETE PAVEMENT TRAFFIC AREA Private Street Private Street T.l.<'' 4.5 5.0 SUBGRADE R-VALUE 30'= 30'=' A.C. THICKNESS (Inches) 4.0C) CLASS 2 AGGREGATE BASE THICKNES8('> (Inches) 4.0 5.5 Assumed Tl values based on a review of Reference 2. The actual value should be confirmed by the Project Civil Engineer prior to construction. Denotes standard Caltrans Class 2 aggregate base R >78, SE >22). Assumed. City of Carlsbad minimum thickness. o o LIMiTATiONS 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 bythe 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. If you have any questions or comments regarding this letter, please do not hesitate to contact the undersigned. Respectfully submitted, GeoSoils, Inc. Engineering Geologist, CEG 1340 (yan B. Boehmer Project Geologist RBB/JPF/DWS/jh Distribution: (2) Addressee (wet-signed) David W. Skelly Civil Engineer, RCE 47857 Miles-Pacific, LP 1833 Buena Vista Street, Carlsbad File:e:\wp12\6600\6637a.atp GeoSoils, Inc. w.o. 6637-A-SC March 18, 2014 Page 2 1(0 Mli GEOTECHNICAL UPDATE EVALUATION AYRE SUBDIVISION (FORMER MILES PACIFIC AND SOHAEI PROPERTIES) 2359, 2373, AND 2375 PIOJPICO DRIVE^ CARIBAD, SAN ©lEGjOtdu SHEAH€^MES LlMit^f»AllTNER^HIP ! 999d l«ESA^RIM R6AD, SUiyE'200 S SAN-DtE<3 O, CAL^f ORf*tA"92 t2t W.O. 6649-A-SC JUNE 23, 2014 Geotechnical • Geologic • Coastal • Environmental 5741 PalmerWay • Carlsbad, California 92010 • (760)438-3155 • FAX (760) 931 0915 • www.geosoilsinc.com June 23, 2014 W.O. 6649-A-SC Shea Homes Limited Partnership 9990 Mesa Rim Road, Suite 200 San Diego, California 92121 Attention: Ms. Sarah Morell and Mr. Greg Ponce Subject: Geotechnical Update Evaluation, Ayre Subdivision (Former Miles Pacific and Sohaei Properties), 2359, 2373, and 2375 Pio Pico Drive, Carlsbad, San Diego County, California Dear Ms. Morrell and Mr. Ponce: In accordance with your request and authorization, GeoSoils, Inc. (GSI), is providing geotechnical update evaluation for the subject properties in the City of Carlsbad, San Diego County, California. The scope of our services has included a review of the referenced documents (see Appendix A), analysis of data, and the preparation of this summary report. Unless specifically superceded herein, the conclusions and recommendations contained in the referenced geotechnical reports (GSI; 2011, 2012a, 2012b, and 2014), remain pertinent and applicable, and should be appropriately implemented during the balance of project development. PROPOSED DEVELOPMENT Based on our review ofthe 20-scale grading plans prepared by bHA, Inc. ([bHA], 2014 and undated) proposed development consists of preparing the subject properties to receive a combined 20 residential lots with associated underground utility, surface drainage, wall, and pavement improvements. Cut and fill grading will be necessary to achieve the design grades with maximum planned cuts and fills on the order of 5V2 and 6V2 feet, respectively. The grading plans indicate that grade differentials will be accommodated by the construction of 2:1 (horizontahvertical [h:v]) orflatter cut and fill slopes and retaining walls. The maximum height of cut and fill slopes will be on the order of 6 and 7 feet, respectively. The maximum height retaining wall is approximately 5 feet high. GSI anticipates that one-to two-story single-family residential structures will be constructed upon the grade lots. We further anticipate that the residential structures will consist of wood framing with slab-on-grade floors. bHA (2014 and undated) do not indicate the need for import fill at this time. Sanitary sewage disposal will be tied into the regional system. UPDATE GEOTECHNiCAL RECOMMENDATIONS The update geotechnical recommendations provided in the following sections are based on our review of the existing subsurface data, laboratory testing, and our review of the proposed development currently shown on bHA (2014 and undated). Unless specifically superceded herein, the conclusions and recommendations contained in the referenced reports (GSI; 2011,2012a, 2012b, and 2014), remain pertinent and applicable, and should be appropriately implemented during the balance of project development. Seismic Design Parameters The following table summarizes the site-specific design criteria obtained from the 2013 California Building Code (2013 CBC), Chapter 16 Structural Design, Section 1613, Earthquake Loads. The computer program Seismic Design Maps, provided by the United States Geologic Survey (http://geohazards.usgs.gov/designmaps/us/application.php) was utilized to aid in design. 2013 CBC SEISMIC DESIGN PARAMETERS I PARAMETER VALUE 2013 CBC REFERENCE Risk Category II Table 1604.5 Site Class D Section 1613.3.2/ASCE 7 (p. 203-205) Spectral Response - (0.2 sec), Sg 1.138 g Figure 1613.3.1(1) Spectral Response - (1 sec), 0.437 g Figure 1613.3.1(2) Site Coefficient, F^ 1.045 Table 1613.3.3(1) Site Coefficient, F„ 1.563 Tablet 613.3.3(2) Maximum Considered Earthquake Spectral Response Acceleration (0.2 sec), S^s 1.189 g Section 1613.3.3 (Eqn 16-37) Maximum Considered Earthquake Spectral Response Acceleration (1 sec), 8^^ 0.683 g Section 1613.3.3 (Eqn 16-38) 5% Damped Design Spectral Response Acceleration (0.2 sec), Sfjg 0.793 g Section 1613.3.4 (Eqn 16-39) 5% Damped Design Spectral Response Acceleration (1 sec), Sp, 0.455 g Section 1613.3.4 (Eqn 16-40) 0.471 g ASCE 7-10 (Eqn 11.8.1) Seismic Design Category D Section 1613.3.5/ASCE 7-10 (Table 11.6-1 or 11.6-2) Shea Homes Limited Partnership 2359, 2373, and 2375 Pio Pico Drive Flle:e:\wp12\6600\6649a.gue GeoSoils, Inc. w.o. 6649-A-SC June 23, 2014 Page 2 GENERAL SEISMIC DESIGN PARAMETERS PARAMETER VALUE Distance to Seismic Source (Newport-Inglewood [Connected Alternatives 1 and 2] and Newport-Inglewood [Offshore segment]) 5.0 mi (8.1 km)'^' Upper Bound Earthquake (Newport-Inglewood [Connected Alternatives 1 and 2] and Newport-Inglewood [Offshore segment]) 7.1 United States Geological Survey (http://geohazards.usgs.gov/cfusion/hazfaults_search/hf_search_maln.cfm) Cao, et al. (2003) Conformance to the criteria above for seismic design does not constitute any kind of guarantee or assurance that significant structural damage, ground failure, or surface manifestations will not occur in the event of a large earthquake in this region. 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 2013 CBC (CBSC, 2013) and regular maintenance and repair following locally significant seismic events (i.e., M^ 5.5) will likely be necessary. It is important to keep in perspective that in the event of a maximum probable or credible earthquake occurring on any of the nearby major faults, strong ground shaking would occur in the subject site's general area. Potential damage to any structure(s) would likely be greatest from the vibrations and impelling force caused by the inertia of a structure's mass. This potential would be no greater than that for other existing structures and improvements in the immediate vicinity. Seismic Densification During seismic-induced ground shaking, natural or artificial soils deform under loading and volumetrically strain, potentially resulting in ground surface settlements. Some densification may occur on the adjoining un-mitigated properties or areas of the subject site where remedial grading is not performed. This may influence improvements located above a 1:1 (h:v) projection up from the perimeter of the site or the limits of remedial grading. Special settDacks and/or foundations would be recommended for settlement- sensitive improvements within the influence of densifiable soils. Our evaluation assumes that the current offsite conditions will not be significantly modified by future grading at the time ofthe design earthquake, which is a reasonably conservative assumption. Shea Homes Limited Partnership 2359, 2373, and 2375 Pio Pico Drive File:e:\wp12\6600\6649a.gue GeoSoils, Inc. w.o. 6649-A-SC June 23, 2014 Page 3 Previous Corrosion Testing Soil pH, saturated resistivity, and soluble sulfate, and chloride testing were previously performed on representative samples ofthe onsite soils. Testing indicated that these soils are mildly to moderately alkaline with respect to soil acidity/alkalinity, are corrosive to exposed, buried metals when saturated, possess negligible sulfate exposure ("not applicable") to concrete ("Exposure Class SO" inTable 4.3.1 of ACI 318-11), and are below the action level for chloride exposure (per State of California Department of Transportation, 2003). Reinforced concrete mix design for foundations, slab-on-grade floors, and pavements should minimally conform to "Exposure Class Cl" in Table 4.3.1 of ACI 318-11, as concrete would likely be exposed to moisture. GSI does not consult in corrosion engineering. Therefore, additional comments and recommendations may be obtained from a qualified corrosion engineer based on the level of corrosion protection desired or required for the project, as determined by the project architect and/or structural engineer. Earthwork Construction Recommendations General Remedial earthwork will be necessary for the support ofthe planned settlement-sensitive improvements (i.e., residential structures, walls, underground utilities, pavements, etc.). All earthwork should conform to the guidelines presented in 2013 CBC, the requirements ofthe City of Carlsbad and the County of San Diego Department of Environmental Health, and the Grading Guidelines presented in Appendix B, except where specifically superceded in the text of this report. In case of conflict, the more onerous code or recommendations should govern. Priorto grading, a GSI representative should be present at the pre-construction meeting to provide additional grading guidelines, if needed, and review the earthwork schedule. During earthwork construction, all site preparation and the general grading procedures of the contractor should be observed and the fill selectively tested by a representative(s) of GSI. If unusual or unexpected conditions are exposed in the field, they should be reviewed by this office and, if warranted, modified and/or additional recommendations will be offered. All applicable requirements of local and national construction and general industry safety orders, the Occupational Safety and Health Act (OSHA), and the Construction Safety Act should be met. It is the onsite general contractor's and individual subcontractors' responsibility to provide a safe working environment for our field staff who are onsite. GSI does not consult in the area of safety engineering. GSI also recommends that the contractor(s) take precautionary measure to protect work, especially during the rainy season. Failure to do so may result in additional remedial earthwork. Shea Homes Limited Partnership W.O. 6649-A-SC 2359,2373, and 2375 Plo Pico Drive . June 23,2014 File:e:\wp12\6600\6649a,gue GCOSoilS, InC. Page 4 Demolition/Grubbing 1. Vegetation, and any miscellaneous deleterious debris generated from the demolition of existing site improvements should be removed from the areas of proposed grading/earthwork. 2. Cavities or loose soils remaining after demolition and site clearance should be cleaned out and observed by the geotechnical consultant. 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 ofthe laboratory standard. 3. Any buried septic systems encountered during grading should be observed by the geotechnical consultant. Recommendationsforthe removal of septic structures will then be provided based on the conditions exposed. Mitigation of impacted Soiis Mitigation of impacted soils on 2373 and 2375 Pio Pico Drive should be performed in accordance with the approved property mitigation plan outlined in GSI (2014), prior to mass grading ofthe site. This will result in removal of much ofthe potentially compressible surficial soils, discussed below. Remedial Removals (Removai of Potentially Compressible Surficial Materiais) Where planned fills or settlement-sensitive improvements are proposed, potentially compressible undocumented artificial fill, Quaternary alluvium. Quaternary colluvium. Quaternary paleosol, and weathered paralic deposits should be removed to expose unweathered paralic deposits. Removed soils may be reused as properly engineered fill provided that major concentrations of organic and/or deleterious materials have been removed prior to placement. In general, the remedial grading excavations to remove potentially compressible soils are anticipated to be on the order of 2 to 6V2 feet across a majority ofthe site. However, local deeper remdial excavations cannot be precluded and should be anticipated. The removal of potentially compressible soils should be performed below a 1:1 (h:v) projection down from the bottom, outermost edge of proposed settlement-sensitive improvements and/or limits of planned fills. Once the unsuitable soils have been removed, the exposed paralic deposits should be scarified approximately 6 to 8 inches, moisture conditioned as necessary to achieve the soil's optimum moisture content and then be re-compacted to at least 90 percent ofthe laboratory standard prior to fill placement. All remedial removal excavations should be observed by the geotechnical consultant prior to scarification. Shea Homes Limited Partnership W.O. 6649-A-SC 2359, 2373, and 2375 Pio Pico Drive ^ June 23, 2014 File:e:\wp12\6600\6649a.gue GeoSoilS, InC. Page 5 Overexcavation bHA, Inc. (2014 and undated) indicates planned cut/fill transitions. As such, uniform support of foundations should be provided by overexcavating the cut portion of cut/fill transition lots or building pad areas where the planned plus remedial fill thickness does not allow for 2 feet of engineered fill beneath footings. This would require that all unweathered paralic deposits exposed within 2 feet of finish grade, following the removal of potentially compressible soils, be overexcavated to at least 2 feet below the lowermost foundation element (as approved by GSI field personnel) and be replaced with engineered fill compacted to at least 90 percent of the laboratory standard (ASTM D 1557). The bottom of the overexcavation should be sloped toward the street or other drainage facilities, scarified at least 6 to 8 inches, moisture-conditioned as necessary to achieve the soil's optimum moisture content, and then be recompacted to at least 90 percent of the laboratory standard priorto fill placement. Overexcavation should be laterally completed to at least 5 feet outside the outermost foundation element of settlement-sensitive improvements. Overexcavations should be observed bythe geotechnical consultant prior to scarification. The maximum to minimum fill thickness across building pads should not exceed a ratio of 3:1 (maximum:minimum), including the impacted soil placement area shown on the remedial grading exhibit (bHA, 2014). As an alternative to the 3:1 (maximum:minimum) fill thickness criteria (i.e., laying back the temporary cut slope to a 3:1 [h:v] inclination), the impacted soils may be minimally placed at 95 percent of the laboratory standard (ASTM D 1557), below the top 5 feet. Overexcavation need not be performed in street areas. Temporary Slopes Temporary slopes for excavations greaterthan 4 feet but less than 20 feet in overall height should conform to CAL-OSHA and/or OSHA requirements for Type "B" soils. Temporary slopes, up to a maximum height of ±20 feet, may be excavated at a 1:1 (h:v) gradient, or flatter, provided groundwater and/or running sands are not exposed. Construction materials or soil stockpiles should not be placed within 'H' of any temporary slope where 'H'equals the heightof the temporary slope. All temporary slopes should be observed by a licensed engineering geologist and/or geotechnical engineer prior to worker entry into the excavation. Based on the exposed field conditions, inclining temporary slopes to flatter gradients or the use of shoring may be necessary if adverse conditions are observed. If temporary slopes conflict with property boundaries, shoring or alternating slot excavations may be necessary. The need for shoring or alternating slot excavations could be further evaluated during the grading plan review stage, but is considered likely on the eastern and northern property lines. Shea Homes Limited Partnership W.O. 6649-A-SC 2359, 2373, and 2375 Pio Pico Drive , June 23, 2014 File:e:\wp12\6600\6649a.gue GeoSoilS, InC. Page 6 Engineered Fiii Placement All engineered fill should be well blended, placed in thin lifts, moisture conditioned, and mixed to achieve 1.1 to 1.2 times the soil's optimum moisture content, and then be mechanically compacted to at least 90 percent ofthe laboratory standard (ASTM D 1557). Engineered fill placement should be observed and selectively tested for moisture content and compaction bythe geotechnical consultant. Graded Slopes At this time maximum graded (cut and fill) slopes are anticipated to be ±6 and ±7 feet, respectively, in overall height and inclined at gradients no steeper than 2:1 (h:v). It is our professional opinion that graded fill slopes will be grossly and surficially stable following the completion of construction provided that site drainage is directed awayfrom the tops of slopes and the slope faces are protected with deep-rooted vegetative cover capable of surviving the prevailing climate without only the amount of irrigation water necessary to sustain plant vigor. Graded cut slopes will likely expose colluvium, weathered younger paralic deposits, and possibly a paleosol along the face at the conclusion of construction. Owing to the potential for perched/daylighted water on such soils, GSI recommends that all "in-tract" cut slopes receive stabilization fills with subdrains (see Appendix B), and/or be overexcavated and reconstructed as a fill slope. Subdrains should be shown on the final 20-scale grading plans, when available. Due to insufficient space for stabilization along the perimeter ofthe site, it is our opinion that cut slopes exposing these conditions will be more readily subject to erosion and sloughing. An erosion control mat such as MacMat-R (http://www.maccaferri.co.uk/PAGES00295.html) may be used to reduce erosion on perimeter cut slopes 5 feet or greater in overall height. Vegetative cover should be provided as soon as possible following slope construction. In the interim, GSI recommends the slope faces be covered with City of Carlsbad approved erosion control devices. Graded slope stability should be further evaluated during the grading plan review stage. Graded fill slopes should be properly keyed and benched, and be compacted to at least 90 percent relative compaction throughout, including the slope face. All graded cut slopes should be observed by this office following construction. If adverse geologic conditions (daylighted, out-of-slope bedding and/or joints/fractures, highly weathered paralic deposits, thick unsuitable soils, etc.) are noted in the slope face, GSI would provide recommendations for mitigation. Mitigation measures may included but not necessarily be limited to inclining the slope to gradients flatter than any adverse geologic structure, stabilization fills, or the use of an erosion control mat. Shea Homes Limited Partnership W.O. 6649-A-SC 2359,2373, and 2375 Pio Pico Drive _ June 23, 2014 File:e;\wp12\6600\6649a.gue GcoSoilS, InC. Page 7 Import Fill Materials Any import fill materials used onthis project should possess an E.I. of 20 or less with a P.I. not exceeding 15. All import fill material should be tested by GSI priorto placement within the site. GSI would also request environmental documentation (e.g.. Phase I Environmental Site Assessment) pertaining to any offsite export/borrow site, to evaluate if the proposed import could present an environmental risk to the planned residential development. At least five (5) business days of lead time will be necessary for the required laboratory testing and document review. Testing of As-Graded Soil Conditions Upon completion of grading, additional testing of soils (including import materials) for expansion and corrosion should be performed prior to the construction of utilities and foundations. Preliminary Foundation Design Recommendations General Thefoundation design and construction recommendations are based on laboratory testing and engineering evaluations of onsite earth materials by GSI. The following preliminary foundation construction recommendations are presented as a minimum criteriafrom a soi Is engineering viewpoint. Testing indicates that the expansion index ofthe representative majority of onsite soils is <5. However, Atterberg Limits testing suggests that some thin localized layers of paralic deposits may be moderately expansive (expansion index = 51 to 90). Provided that sufficient blending of sands and clays is undertaken during fill placement, GSI anticipates that finish grade soils will be non-detrimentally expansive (i.e., expansion index less than 21 and a plasticity index [PI] less than 15). However, there is some likelihood that detrimentally expansive soils may be detected in finish grade soils at the conclusion of site grading. As such, GSI is providing preliminary design and construction recommendations for conventional foundation recommendations for non-detrimentally expansive soil conditions as well as post-tensioned foundation recommendations for detrimental low to medium expansive soil conditions (i.e., soils with an expansion index = 21 to 90 and with a PI = 15 or greater). In addition, GSI is providing post-tension foundation systems for non-detrimentally expansive soil conditions if higher foundation performance is expected. This report presents minimum design criteria for the design of foundations, concrete slab-on-grade floors, and other elements possibly applicable to the project. These criteria should not be considered as substitutes for actual designs by the structural engineer. Recommendations by the project's design-structural engineer or architect, which may exceed the geotechnical consultant's recommendations, should take precedence overthe following minimum requirements. The foundation systems recommended herein may be Shea Homes Limited Partnership W.O. 6649-A-SC 2359,2373, and 2375 Pio Pico Drive , June 23,2014 File:e:\wp12\6600\6649a.gue GeoSoilS, InC. Page 8 used to support the proposed residences provided they are enti rely founded in compacted fill tested and approved by GSI. The proposed foundation systems should be designed and constructed in accordance with the guidelines contained in the 2013 CBC. In the event thatthe information concerning the proposed development plan is not correct, or any changes in the design, location or loading conditions ofthe proposed structure are made, the conclusions and recommendations contained in this report shall not be considered valid unless the changes are reviewed and conclusions of this report are modified or approved in writing by this office. The information and recommendations presented in this section are not meant to supercede design by the project structural engineer or civil engineer specializing in structural design. Upon request, GSI could provide additional input/consultation regarding soil parameters, as they relate to foundation design. General Foundation Design 1. The foundation systems should be designed and constructed in accordance with guidelines presented in the 2013 CBC. 2. An allowable bearing value of 2,000 pounds per square foot (psf) may be used for the design of continuous footings that maintain a minimum width of 12 inches and a minimum depth of 12 inches (belowthe lowest adjacent grade) and are founded into properlv 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. A similar allowable bearing value may be used in the design of ilsolated pad footings that have a minimum dimension of at least 24 inches square and a minimum embedment of 24 inches below the lowest adjacent grade into properly engineered fill. Foundation embedment excludes any landscaped zone, undocumented fill, topsoil/colluvium, weathered paralic deposits, concrete slabs-on-grade, and/or slab underlayment. 3. Passive earth pressure may be computed as an equivalent fluid having a density of 250 pcf, with a maximum earth pressure of 2,500 psf for footings founded into properly engineered fill. Lateral passive pressures for shallow foundations within 2013 CBC setback zones should be reduced following a review bythe geotechnical engineer unless proper setback can be established. 4. 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. 5. When combining passive pressure and frictional resistance, the passive pressure component should be reduced by one-third. Shea Homes Limited Partnership W.O. 6649-A-SC 2359, 2373, and 2375 Pio Pico Drive , June 23, 2014 Flle:e:\wp12\6600\6649a.gue GeoSoilS, InC. Page 9 6. All footing setbacks from slopes should comply with Figure 1808.7.1 of the 2013 CBC. GSI recommends a minimum horizontal setback distance of 7 feet as measured from the bottom, outboard edge ofthe footing to the slope face. 7. Footings for structures adjacent to retaining walls should be deepened so as to extend below a 1:1 projection from the heel ofthe wall. Alternatively, walls may be designed to accommodate structural loads from buildings or appurtenances as described in the "Retaining Wall" section ofthis report. 8. Code-compliant foundations may be conventional-type if soils within the influence of the foundation have an E.I. of 20 or less and a P.I. less than 15. Othenwise post- tension foundation systems should be used. Foundation Settlement Provided the recommendations in this report are properly followed, foundation systems should be minimally designed to accommodate a differential settlement of at least %-inch in a 40-foot horizontal span (angular distortion = 1/640). These preliminary settlement values do not apply to improvements constructed within 2013 CBC setbacks or within the influence of unmitigated soils. In addition, these values do not take seismic effects from strong ground motion into account, which may range up to 0.3 inches of differential seismic settlement. The foundation and wall designers should consider the above differential settlement values in their design. Preliminarv Foundation Construction Recommendations The following foundation construction recommendations are presented as a minimum criteria from a soils engineering viewpoint. Conventional foundations may be used to support the planned residential structures provided the soils within the upper 7 feet of pad grade possess an E.I. of 20 or less and a P.I. less than 15. Otherwise, post-tension foundations would be necessary to mitigate expansive soil effects in accordance with Sections 1808.6.1 or 1808.6.2 ofthe 2013 CBC. Conventional Foundations (Expansion index of 20 or Less with a Plasticity Index Less Than 15) 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 for a one- or two-story floor loads, respectively. For one- and two-story floor loads, footing widths should be 12 and 15 inches, respectively. Isolated, exterior column and panel pads, or wall footings, should be at least 24 inches, square, and founded at a minimum depth of 24 inches into properly compacted 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. Shea Homes Limited Partnership W.O. 6649-A-SC 2359, 2373, and 2375 Pio Pico Drive , June 23, 2014 File:e:\wp12\6600\6649a.gue GeoSoilS, InC. Page 10 4. 5. Al,in.eriorandexteriorcolumn,ootings,andp^^^^^^^^^^^ r g^eCrKrot me^eTntrd grade bsa. should be a, me sa.e elevation as the adjoining footings. A minimum concrete slab-on-grade thickness of 4y. inches is recommended. axis and short axis), acceptable method of positioning. soils generated from footing excavations to be u^d o-;*-^-;;;^^-"^'^^^^^ raLttC'ird^s:'::^^ 9 Reinforced concrete for foundations and slab-on-grade floors should have a maximum vxater to cement ratio of 0.50. Post-Tensioned Foundations Post-tensionfoundations may be usedto -'''Sf ^^f-^^ing e«e^^^^ on the planned building's foundation ""-Slf/,^"'^:^ j^^^^^^^ of encountered at finish grade. They may f "^^"^post-tension foundations constructed on foundation designermayelecttoe^^^^^^^^ sro^^^^r^gt^-^^^^^^ but has a thicker slab than the ribbed-type. 8. Shea Homes Limited Partnership 2359, 2373, and 2375 Pio Pico Drive File:e:\wp12\6600\6649a.gue GeoSoils, Inc. w.o. 6649-A-SC June 23, 2014 Page 11 The information and -mmenda^ns pr^^^^^^^^^^^ ;rrsro»nX:r^^ to post-tensioned foundation design. From a soii expansion/shrinkage standpoint a commo^^^^^^^^^^^ structures using post-tensioned slabs - ^ ^ish n^^^^^^^^ by the fluctuation of moisture content in tlie so,ls oeiowr p L to onsite and o^^^^''XZ'^^Tet^^ZTsZZ^iug^e^y^et^ot presence of expansive soils. When the soil env ro ^^.^^^^ ^^^^^ ,^ slab has a higher moisture content than the ^^t^^'^f^ ^^^ ,^3 slab edges referred migrate inward, underneath the slab «^9«='° f occurs, the volume of to as the moisture variation distanca When th^ ™grm^^^^^^ .^his the soils beneath slab edges expand and cau^^^^ 9 ^^.^ ^^...onnnent is is referred to as an edge-lift ,he soils underneath the slab drier, the moisture transmission regime is of the slab at the edges lose their moisture and shnnk. This P™ff f " °e center iift condition. A edges, v,hich leads to what is ^""^J^^^'V^ff^den sWness a^^^^^^^^ provides a weldesigned, POsMensioned slab ^^^;^^':^[^^:,Zt^y,ng and shrinKing slab ;X=rs%«^^^^^^^^ — Othermi.igationtechniguestypica.yu^ed«^^^^ of a combination of specific soil P ^-satur^ o" o^^^ioisture conditioning the slab subgrade wall grade beam. Soil pre-saturation reduces soil moisture soiis prior to the post-tension slab 0°"—Jfj^ towa d he soils underlying the migration from the area f^Sd e^^^^^ nnst-tension slab. Perimeter cut-off walls are tnicKeneu eua l^^pedes both outward and inward soil moisture migration. Slab Subgrade Pre-Soaking Pre-moistening of the slab subgrade f ^l^^—^^^^^^ conditions at the site. T^^. ^'^^^^^^^^^^^^^^^^^ grade beam or high and very high expansive soil conditions, respectively). pre-moistening and/or pre-soaking should be evaluated by the soils engineer 72 hours prior to vapor retarder placement. In summary: Shea Homes Limited Partnership 2359, 2373, and 2375 Pio Pico Dnve File:e:\wp12\6600\6649a.gue GeoSoils, Inc. w.o. 6649-A-SC June 23, 2014 Page 12 Very Low to Low (0-50) Medium (51-90) Upper 12 inches of pad soil moisture 2 percent over optimum (or 1.2 times) Upper 18 inches of pad soil moisture 2 percent over optimum (or 1.2 times) Wetting and/or reprocessing Berm and flood or wetting and reprocessing Periodically wet or cover with plastic after trenching. Evaluation 72 hours priorto lar.ement of concrete Perimeter Cut-Off Walls Perimeter cut-of, wails Should be12and18inchesdeepfo^^^^^^^ expansive soil conditions P^^!^^«''he cut of^'war^^^^ be L mfnimum of 6 inches fhlTTrSSrrpi^m^^^^^^^^ cable or reinforcement per the structural engineer. Post-Tensioned Foundation Design The following recommendations for ^-ign of post-tension^^^ prepa;.d (PTI, 2004), together with it's subsequent addendums (PTI, 2008). Soil Support Parameters mi^um "efficients™ be used in the Post-Tensioning Institute design method. Thornthwaite Moisture lnd<?x -20 inches/year Correction Factor for Irrigation 20 inches/year Deoth to Constant Soil Suction 7 feet Constant soil Suction (pf) 3.6 Moisture Velocity 0.7 inches/month Plasticitv Index (P.I.) 15-35 Shea Homes Limited Partnership 2359, 2373, and 2375 Pio Pico Drive File:e:\wp12\6600\6649a.gue GeoSoils, Inc. w.o. 6649-A-SC June 23,2014 Page 13 i^^ i kicrtlllM DESIGN PARAMETERS VERY LOW TO LOW EXPANSION (El = 0-50) MEDIUM EXPANSION <EI = 51-90j e„ center lift e„ edge lift y„ center lift y„ edge lift Bearing Value 9.0 feet 5.2 feet 8.7 feet 4.5 feet Lateral Pressure Subgrade Modulus (k) Minimum Perimeter 0.3 inches 0.7 inch 1,000 psf 250 psf 100 pci/inch 0.49 inches 1.3 inch 1,000 psf 175 psf 85 pci/inch 12 inches 18 inches IVlllllMUJiii . 1 _ IJ„, Footing Embedment^^_L__===^=^^ ^,000 psf for » AS measured below me loves. ad,ac ^^^^^^^ -;t.r u':nr:pe„ .o«o.edp^^o^-sa*— ^^oir|n parameters.. —^h sig^nlflc^uo. Trim^rnt" rtTa::e,trrS^^--^^ interested/affected parties^Thevaguest ^^^^^ '^'*°'^ns«utf (IPTll third for possible different —^.^.^ ,„e,na.ive Post-Tensioning institute (IP :S;Tra—Pe recommended. SgiLMOIbluricjri^ ^1 ^ 3 lbs/24 hours as an upper limit. T ne ^^^^ 2359 2373, and 2375 Pio Pico Dnve File:e:\wp12\6600\6649a.gue GeoSoils, Inc. w.o. 6649-A-SC June 23,2014 Page 14 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, 2011). These recommendations may be exceeded or supplemented by a water "proofing" specialist, project architect, or structural consultant. Thus, the client will need to evaluate the following in light of a cost vs. benefit analysis (owner expectations and repairs/replacement), along with disclosure to all interested/affected parties. It should also be noted that vapor transmission will occur in new slab-on-grade floors as a result of chemical reactions taking place within the curing concrete. Vapor transmission through concrete floor slabs as a result of concrete curing has the potential to adversely affect sensitive floor coverings depending on the thickness of the concrete floor slab and the duration of time between the placement of concrete, and the floor covering. It is possible that a slab moisture sealant may be needed prior to the placement of sensitive floor coverings if a thick slab-on-grade floor is used and the time frame between concrete and floor covering placement is relatively short. Considering the E.I. test results obtained for the site, 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 a minimum of 5 inches thick. Concrete slab underlayment should consist of a 10-mil vapor retarder, or equivalent, with all laps sealed per the 2013 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 302.1 R-04 and ASTM E 1643. The 10-mil vapor retarder (ASTM E 1745 - Class A) shall be installed per the recommendations ofthe 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 10 mil vapor retarder (ASTM E-1745 - Class, per Engineering Bulletin 119 [Kanare, 2005]) installed perthe recommendations of the manufacturer, including all penetrations (i.e., pipe, ducting, rebar, etc.). The manufacturer shall provide instructions for lap sealing, including minimum width of lap, method of sealing, and eithersupply or specify suitable products for lap sealing (ASTM E 1745), and per code. ACI 302.1 R-04 (2004) states "If a cushion or sand layer is desired between the vapor retarder and the slab, care must be taken to protect the sand layer from taking on additional water from a source such as rain, curing, cutting, or cleaning. Shea Homes Limited Partnership W.O. 6649-A-SC 2359,2373, and 2375 Pio Pico Drive _ June 23,2014 File:e:\wp12\6600\6649a.gue GCOSoilS, InC. Page 15 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/ortesting 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 soils 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 4.3.1 of Chapter 4 of the ACI (2011) for corrosion or other corrosive requirements. Additional concrete mix design recommendations should be provided by the structural consultant and/or waterproofing specialist. Concrete finishing and workablity should be addressed by the structural consultant and a waterproofing specialist. Where slab water/cement ratios are as indicated herein, and/or admixtures used, the structural consultant should also make changes to the concrete in the grade beams and footings in kind, so that the concrete used in the foundation and slabs are designed and/or treated for more uniform moisture protection. The owner(s) should be specifically advised which areas are suitable tortile flooring, vinyl flooring, or other types of water/vapor-sensitive flooring and which are not suitable. In all planned floor areas, flooring shall be installed per the manufactures recommendations. Additional recommendations regarding water or vapor transmission should be provided by the architect/structural engineer/slab or foundation designer and should be consistent with the specified floor coverings indicated by the architect. Regardless ofthe 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. Atechnical representative of the flooring contractor should reviewthe slab and moisture retarder plans and provide comment priorto the construction ofthe foundations or improvements. The vapor retarder contractor should have representatives onsite during the initial installation. Shea Homes Limited Partnership W.O. 6649-A-SC 2359, 2373, and 2375 Pio Pico Drive , June 23, 2014 File:e:\wp12\6600\6649a.gue GeoSoilS, InC. Page 16 WALL DESIGN PARAMETERS CONSIDERING EXPANSIVE SOILS General Based on our review of bHA (2014), conventional concrete masonry unit (CMU) retaining walls with an approximate maximum height of 5 feet are proposed. GSI recommends that retaining walls located at the top or within 15 horizontal feet from the top of descending slopes should be supported on deep foundations as indicated in the "Top-of-Slope Walls/Fences/lmprovements and Expansive Soils" section ofthis report to mitigate creep- related deformations. Recommendations for specialty walls (i.e., crib, earthstone, geogrid, etc.) can be provided upon request, and would be based on site specific conditions. Conventional Retaining Walls The design parameters provided below assume that either very low expansive soils (typically Class 2 permeable filter material or Class 3 aggregate base) or native onsite materials with an expansion index up to 20 are used to backfill any retaining wall. Please note that some ofthe onsite likely do not meet this criteria. The type of backfill (i.e., select or native), should be specified by the wall designer, and clearly shown on the plans. Waterproofing should be provided for site retaining walls in order to reduce the potential for efflorescence staining. Preliminary Retaining Wall Foundation Design Preliminary foundation design for retaining walls should incorporate the following recommendations: Minimum Footing Embedment - 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 thatthe footing maintains a minimum width of 24 inches and extends at least 18 inches into approved engineered fill overlying dense paralic deposits. This pressure may be increased by one-third for short-term wind and/or seismic loads. Passive Earth Pressure - A passive earth pressure of 250 pcf with a maximum earth pressure of 2,500 psf may be used in the preliminary design of retaining wall foundations provided the foundation is embedded into properly compacted silty to clayey sand fill. Shea Homes Limited Partnership W.O. 6649-A-SC 2359, 2373, and 2375 Pio Pico Drive _ June 23, 2014 File:e:\wp12\6600\6649a.gue GeoSoIlS, InC. Pagg 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 105 pcf and 115 pcf may be used in the design of retaining wall foundations. This assumes an average engineered fill compaction of at least 90 percent ofthe laboratory standard (ASTM D 1557). Any retaining wall footings near the perimeter of the site will likely need to be deepened into unweathered very old paralic deposits or unweathered Santiago Formation for adequate vertical and lateral bearing support. All retaining wall footing setbacks from slopes should complywith Figure 1808.7.1 ofthe 2013 CBC. GSI recommends a minimum horizontal setback distance of 7 feet as measured from the bottom, outboard edge ofthe footing to the slope face. Restrained Walls Any retaining walls that will be restrained priorto placing and compacting backfill material or that have re-entrant or male corners, should be designed for an at-rest equivalent fluid pressure (EFP) of 55 pcf and 65 pcf for select and very low expansive native backfill, respectively. The design should include any applicable surcharge loading. For areas of male or re-entrant corners, the restrained wall design should extend a minimum distance of twice the height of the wall (2H) laterally from the corner. Cantilevered Walls The recommendations presented below are for cantilevered retaining walls up to 10 feet high. Design parameters for walls less than 3 feet in height may be superceded by County of San Diego regional standard design. Active earth pressure may be used for retaining wall design, provided the top of the wall is not restrained from minor deflections. An equivalent fluid pressure approach may be used to compute the horizontal pressure againstthe wall. Appropriate fluid unit weights are given below for specific slope gradients ofthe retained material. These do not include other superimposed loading conditions due to traffic, structures, seismic events or adverse geologic conditions. When wall configurations are finalized, the appropriate loading conditions for superimposed loads can be provided upon request. For preliminary planning purposes, the structural consultant/wall designer should incorporate the surcharge of traffic on the back of retaining walls where vehicular traffic could occur within horizontal distance "H" from the back ofthe retaining wall (where "H" equals the wall height). The traffic surcharge may be taken as 100 psf/ft in the upper 5 feet of backfill for light truck and cars traffic. This does not include the surcharge of parked Shea Homes Limited Partnership W.O. 6649-A-SC 2359,2373, and 2375 Pio Pico Drive , June 23,2014 File:e:\wp12\6600\6649a.gue GeoSoilS, InC. Page 18 vehicles which should be evaluated at a higher surcharge to account for the effects of seismic loading. Equivalent fluid pressures for the design of cantilevered retaining walls are provided in the following table: SURFACE SLOPE OF RETAINED MATERIAL (HORIZONTAL:VERTICAL) EQUIVALENT FLUID WEIGHT P.C.F. (SELECT BACKFILL)'^' EQUIVALENT FLUID WEIGHT P.C.F. ! (NATIVE BACKFILL)'^* Level'^' 2 to 1 38 55 50 65 Level backfill behind a retaining wall is defined as compacted earth materials, properly drained, without a slope for a distance of 2H behind the wall, where H is the height of the wall. SE 30, P.I. < 15, E.I. < 21, and ^ 10% passing No. 200 sieve. E.I. = 0 to 50, SE > 30, P.I. < 15, E.I. < 21, and < 15% passing No. 200 sieve. Please note that site soils are marginally acceptable for use as backfill, and will require extensive testing during backfilling operations to evaluate compliance for potential use. This may hinder job progress, and should be considered during planning and design. Seismic Surcharge For engineered retaining walls, GSI recommends that the wall designer evaluate the walls for a seismic surcharge per the requirements of the 2013 CBC. 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. Please note this is for local wall stability only. 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 an inverted triangular distribution using 15H. 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° - ^12 plane away from the back ofthe wall. The 15H seismic surcharge is derived from the formula: Shea Homes Limited Partnership 2359, 2373, and 2375 Pio Pico Drive File:e:\wp12\6600\6649a.gue GeoSoils, Inc. w.o. 6649-A-SC June 23,2014 Page 19 P, = % . a, . YtH Where: Ph = Seismic increment = Probabilistic horizontal site acceleration with a percentage of "g" Yt = total unit weight (115 to 125 pcf for site soils @ 90% relative compaction. H = Height ofthe wall from the bottom ofthe footing or point of pile fixity. Retaining Wall Backfill and Drainage Positive drainage must be provided behind all retaining walls in the form of gravel wrapped in geofabric and outlets. A backdrain system is considered necessary for retaining walls that are 2 feet or greater in height. Details 1, 2, and 3, present the backdrainage options discussed below. Backdrains should consist of a 4-inch diameter perforated PVC or ABS pipe encased in either Class 2 permeable filter material or y4-inch to iy2-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 ofthe walls and upward at least 1 foot. For native backfill that has up to E.I. = 50, 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 greaterthan 20 should not be used as backfill for retaining walls. For more onerous expansive situations, backfill and drainage behind the retaining wall should conform with Detail 3 (Retaining Wall And Subdrain Detail Clean Sand Backfill). 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 useof weep holes, only, in walls higher than 2 feet, is not recommended. The surface ofthe backfill should besealed by pavement orthe 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. The geotechnical consultant should observe retaining wall backdrains priorto backfilling the walls. Retaining wall backfill should be moisture conditioned to at least optimum moisture content, placed in relatively thin 6-to 8-inch lifts, and then compacted to at least 90 percent of the laboratory standard (ASTM D 1557). Geotechnical observation and field density testing should be performed during retaining wall backfill. Shea Homes Limited Partnership W.O. 6649-A-SC 2359,2373, and 2375 Pio Pico Drive . June 23,2014 Flle:e:\wp12\6600\6649a.gue GeoSOllS, InC. Page 20 structural footing or settlement-sensitive improvement (1) Waterproofing membrane CMU or reinforced-concrete wall r- Proposed grade \ sloped to drain 1 per precise civil \ drawings \ (5) Weep hole Footing and wall design by others— Native backfill 11 (h:v) or flatter backcut to be properly benched (6) Footing (1) Waterproofing membrane. (2) Gravel: Clean, crushed, % to 1)^ inch. (3) Filter fabric: Mirafi MON or approved equivalent. (4) Pipe: 4-inch-diameter perforated PVC, Schedule 40, or approved alternative with minimum of 1 percent gradient sloped to suitable, approved outlet point (perforations down). (5) Weep hole: Minimum 2-inch diameter placed at 20-foot centers along the wall and placed 3 inches above finished surface. Design civil engineer to provide drainage at toe of wall. No weep holes for below-grade walls. (6) Footing: If bench is created behind the footing greater than the footing width, use level fill or cut natural earth materials. An additional "heel" drain will likely be required by geotechnical consultant. Gets$0§tsi line. RETAINING WALL DETAIL - ALTERNATIVE A Detail 1 (1) Waterproofing membrane (optional) CMU or reinforced-concrete wall Structural footing or settlement-sensitive improvement Footing and wall design by others— Native backfili 1:1 (h-v) or flatter backcut to be properly benched (6) 1 cubic foot of %-inch crushed rock (7) Footing (1) Waterproofing membrane (optional): Liquid boot or approved mastic equivalent. (2) Drain: Miradrain 6000 or J-drain 200 or equivalent for non-waterproofed walls; Miradrain 6200 or J-drain 200 or equivalent for waterproofed walls (all perforations down). (3) Filter fabric: Mirafi MON or approved equivalent; place fabric flap behind core. (4) Pipe: 4-inch-diameter perforated PVC, Schedule 40, or approved alternative with minimum of 1 percent gradient to proper outlet point (perforations down). (5) Weep hole: Minimum 2-inch diameter placed at 20-foot centers along the wall and placed 3 inches above finished surface. Design civil engineer to provide drainage at toe of wall. No weep holes for below-grade walls. (6) Gravel: Clean, crushed, % to 1>2 inch. (7) Footing: If bench is created behind the footing greater than the footing width, use level fill or cut natural earth materials. An additional "heel" drain will likely be required by geotechnical consultant. Chsf6S0f^Sf Inc. RETAINING WALL DETAIL - ALTERNATIVE B Detail 2 (1) Waterproofing membrane CMU or reinforced-concrete wall Structural footing or settlement-sensitive improvement Provide surface drainage slope Footing and wall design by others (5) Weep hole Proposed grade sloped to drain per precise civil drawings (3) Filter fabric (2) Gravel (4) Pipe (7) Footing (8) Native backfill (6) Clean sand backfill 1=1 (h:v) or flatter backcut to be properly benched (1) Waterproofing membrane: Liquid boot or approved masticequivalent. (2) Gravel: Clean, crushed, % to 1>2 inch. (3) Filter fabric: Mirafi MON or approved equivalent. (4) Pipe: 4-inch-diameter perforated PVC, Schedule 40, or approved alternative with minimum of 1 percent gradient to proper outlet point (perforations down). (5) Weep hole: Minimum 2-inch diameter placed at 20-foot centers along the wall and placed 3 inches above finished surface. Design civil engineer to provide drainage at toe of wall. No weep holes for below-grade walls. (6) Clean sand backfilh Must have sand equivalent value (S.E.) of 35 or greater; can be densified by water jetting upon approval by geotechnical engineer. (7) Footing: |f bench is created behind the footing greater than the footing width, use level fill or cut natural earth materials. An additional "heel" drain will likely be required by geotechnical consultant. (8) Native backfilh If E.I. <21 and S.E. >35 then all sand requirements also may not be required and will be reviewed by the geotechnical consultant. GmShH^f Inc. RETAINING WALL DETAIL - ALTERNATIVE C Detail 3 Wail/Retaining Wall Footing Transitions Site walls are anticipated to be founded on footings designed in accordance with the recommendations in this report. Should wall footings transition from cut to fill, the civil designer may specify either: a) A minimum of a 2-foot overexcavation and recompaction of cut materials for a distance of 2H, from the point of transition. b) Increase of the amount of reinforcing steel and wall detailing (i.e., expansion joints or crack control joints) such that a angular distortion of 1/360 for a distance of 2H on either side of the transition may be accommodated. Expansion joints should be placed no greater than 20 feet on-center, in accordance with the structural engineer's/wall designer's recommendations, regardless of whether or nottransition conditions exist. Expansion joints should be sealed with aflexible, non-shrink grout. c) Embed the footings entirely into native formational material (i.e., deepened footings). If transitions from cut to fill transect the wall footing alignment at an angle of less than 45 degrees (plan view), then the designer should follow recommendation "a" (above) and until such transition is between 45 and 90 degrees to the wall alignment. TOP-OF-SLOPE WALLS/FENCES/IMPROVEMENTS AND EXPANSIVE SOILS Expansive Soils and Slope Creep Some ofthe soils at the site are likely to be expansive and therefore, become desiccated when allowed to dry. Such soils are susceptible to surficial slope creep, especially with seasonal changes in moisture content. Typically in southern California, during the hot and dry summer period, these soils become desiccated and shrink, thereby developing surface cracks. The extent and depth of these shrinkage cracks depend on many factors such as the nature and expansivity of the soils, temperature and humidity, and extraction of moisture from surface soils by plants and roots. When seasonal rains occur, water percolates into the cracks and fissures, causing slope surfaces to expand, with a corresponding loss in soil density and shear strength near the slope surface. With the passage of time and several moisture cycles, the outer 3 to 5 feet of slope materials experience a very slow, but progressive, outward and downward movement, known as slope creep. For slope heights greater than 10 feet, this creep related soil movement will typically impact all rear yard flatwork and other secondary improvements that are located within about 15 feet from the top of slopes, such as swimming pools, concrete flatwork, etc., and in particular top of slope fences/walls. Where removal and recompaction of potentially compressible soils below a 1:1 (h:v) projection down from the toe of perimeter Shea Homes Limited Partnership W.O. 6649-A-SC 2359, 2373, and 2375 Pio Pico Drive , June 23, 2014 File:e:\wp12\6600\6649a.gue GCOSoilS, InC. Page 24 fill slopes are constrained by property lines, improvements located within about H/3 feet from the tops of fill slopes, where H is the height of the slope, may be adversely affected by creep. This influence is normally in the form of detrimental settlement, and tilting ofthe proposed improvements. The dessication/swelling and creep discussed above continues over the life of the improvements, and generally becomes progressively worse. Accordingly, the developer should provide this information to all interested/affected parties. Top of Slope Walls/Fences Due to the potential for slope creep for slopes higher than about 10 feet, some settlement and tilting ofthe walls/fence with the corresponding distresses, should be expected. To mitigate the tilting of top of slope walls/fences, we recommend that the walls/fences be constructed on a combination of grade beam and caisson foundations. The grade beam should be at a minimum of 12 inches by 12 inches in cross section, supported by drilled caissons, 12 inches minimum in diameter, placed at a maximum spacing of 6 feet on center, and with a minimum embedment length of 7 feet below the bottom of the grade beam. The strength of the concrete and grout should be evaluated by the structural engineer of record. The proper ASTM tests for the concrete and mortar should be provided along with the slump quantities. The concrete used should be appropriate to mitigate sulfate corrosion, as warranted. The design of the grade beam and caissons should be in accordance with the recommendations ofthe project structural engineer, and include the utilization ofthe following geotechnical parameters: Creep Zone: Creep Load: Point of Fixity: Passive Resistance: 5-footvertical zone belowthe slope face and projected upward parallel to the slope face. The creep load projected on the area of the grade beam should be taken as an equivalent fluid approach, having a density of 60 pcf. For the caisson, it should be taken as a uniform 900 pounds per linearfoot of caisson's depth, located above the creep zone. Located a distance of 1.5 times the caisson's diameter, below the creep zone. Passive earth pressure of 250 psf per foot of depth per foot of caisson diameter, to a maximum value of 2,500 psf may be used to determine caisson depth and spacing, provided that they meet or exceed the minimum requirements stated above. To determine the total lateral resistance, the contribution ofthe creep prone zone above the point of fixity, to passive resistance, should be disregarded. Shea Homes Limited Partnership 2359, 2373, and 2375 Pio Pico Drive File:e:\wp12\6600\6649a.gue GeoSoils, Inc. w.o. 6649-A-SC June 23,2014 Page 25 Allowable Axial Capacitv: Shaft capacity : 300 psf applied below the point of fixity over the surface area of the shaft in approved compacted fill (min. 90% relative compaction) or formational materials. Tip capacity: 3,000 psf in approved compacted fill (min. 90% relative compaction) or formational materials. This assumes the absence of water in the drilled shafts and the bottom of the drilled shaft will be free of all loose soils or debris. EXPANSIVE SOiLS, DRIVEWAY, FLATWORK, AND OTHER IMPROVEMENTS Some ofthe soil materials on site are likely to be expansive. The effects of expansive soils are cumulative, and typically occur over the lifetime of any improvements. On relatively level areas, when the soils are allowed to dry, the dessication and swelling process tends to cause heaving and distress to flatwork and other improvements. The resulting potential for distress to improvements may be reduced, but not totally eliminated. To that end, it is recommended that the developer should notify all interested/affected parties of this long-term potential for distress. 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, 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. The moisture content ofthe subgrade should be proof tested within 72 hours prior to pouring concrete. 2. Concrete slabs should be cast over a relatively 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. The layer should wet-down completely prior to pouring concrete, to minimize loss of concrete moisture to the surrounding earth materials. 3. Exterior slabs should be a minimum of 4 inches thick. Driveway slabs and approaches should additionally have a thickened edge (12 inches) adjacent to all landscape areas, to help impede infiltration of landscape water under the slab. 4. The use of transverse and longitudinal control joints are recommended to help control slab cracking due to concrete shrinkage or expansion. Two ways to mitigate such cracking are: a) add a sufficient amount of reinforcing steel, increasing tensile strength of the slab; and, b) provide an adequate amount of control and/or expansion joints to accommodate anticipated concrete shrinkage and expansion. Shea Homes Limited Partnership W.O. 6649-A-SC 2359,2373, and 2375 Pio Pico Drive . June 23, 2014 File:e:\wp12\6600\6649a.gue GCOSollS, InC. Page 26 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. The exterior slabs should be scored or saw cut, to ¥8 inches deep, often enough so that no section is greater than 10 feet by 10 feet. For sidewalks or narrow slabs, control joints should be provided at intervals of every 6 feet. The slabs should be separated from the foundations and sidewalks with expansion joint filler material. 5. No traffic should be allowed upon the newly poured concrete slabs until they have been properly cured to within 75 percentof design strength. Concrete compression strength should be a minimum of 2,500 psi. 6. Driveways, sidewalks, and patio slabs adjacent to the house should be separated from the house with thick expansion joint filler material. In areas directly adjacent to a continuous source of moisture (i.e., irrigation, planters, etc.), all joints should be additionally sealed with flexible mastic. 7. Planters and walls should not be tied to the house. 8. Overhang structures should be supported on the slabs, or structurally designed with continuous footings tied in at least two directions. 9. Any masonry landscape walls that are to be constructed throughout the property should be grouted and articulated in segments no more than 20 feet long. These segments should be keyed or doweled together. 10. utilities should be enclosed within a closed utilidor (vault) or designed with flexible connections to accommodate differential settlement and expansive soil conditions. 11. Positive site drainage should be maintained at all times. Finish grade on the lots 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 or homeowners association. 12. Due to expansive soils, air conditioning (A/C) units should be supported by slabs that are incorporated into the building foundation or constructed on a rigid slab with flexible couplings for plumbing and electrical lines. A/C waste water lines should be drained to a suitable non-erosive outlet. 13. Shrinkage cracks could become excessive if proper finishing and curing practices are not followed. Finishing and curing practices should be performed per the Portland Cement Association Guidelines. Mix design should incorporate rate of curing for climate and time of year, sulfate content of soils, corrosion potential of soils, and fertilizers used on site. Shea Homes Limited Partnership W.O. 6649-A-SC 2359, 2373, and 2375 Pio Pico Drive _ June 23, 2014 File:e:\wp12\6600\6649a.gue GeoSoilS, InC. Page 27 PRELIMINARY PAVEMENT DESIGN New Pavements Asphaltic concrete (AC) pavement sections were analyzed using an assumed R-value and an assumed traffic index (T.l.) value. For preliminary planning purposes, the minimum AC over aggregate base (AB) pavement structural sections are provided in the following table. Final pavement structural sections should be based on R-value testing of soils exposed near the subgrade elevation following grading and underground utility construction. New Asphaltic Concrete (AC) Pavement NEW ASPHALTIC CONCRETE PAVEMENT TRAFFIC AREA T.l.'^> SUBGRADE R-VALUE A.C. THICKNESS (inches) ! CLASS 2 AGGREGATE BASETHICKNESS'^> (inches) Private Streets 4.5 30 3.0 4.5 '^'TI value for private streets (City of Carlsbad, 2004) '^'Denotes standard Caltrans Class 2 aggregate base R >78, SE >22). The recommended pavement sections provided above are meant as minimums. If thinner or highly variable pavement sections are constructed, increased maintenance and repair could be expected. If the ADT (average daily traffic) beyond that intended, as reflected by the traffic index used for design, increased maintenance and repair could be required for the pavement section. The project civil engineer should consider the use of thicker pavement sections around intersections where turning and braking will occur. Best management construction practices should be in effect at all times. Pavement Grading Recommendations General Subgrade preparation and aggregate base preparation should be performed in accordance with the recommendations presented below, and the minimum subgrade (upper 12 inches) and Class 2 aggregate base compaction should generally be 95 percent ofthe maximum dry density (ASTM D 1557). If adverse conditions (i.e., saturated ground, etc.) are encountered during preparation of subgrade, special construction methods may need to be employed. These recommendations should be considered preliminary. Further R-value testing and pavement design analysis should be performed upon completion of grading and underground utility trench backfill. Shea Homes Limited Partnership 2359, 2373, and 2375 Pio Pico Drive File:e:\wp12\6600\6649a.gue GeoSoils, Inc. w.o. 6649-A-SC June 23,2014 Page 28 All section changes should be properly transitioned. If adverse conditions are encountered during the preparation of subgrade materials, special construction methods may need to be employed. Subgrade Within street areas, all surficial deposits of loose soil material generated underground utility construction should be removed or re-compacted as recommended. After the loose soils are removed, the exposed ground should be scarified to a depth of 12 inches, moisture conditioned as necessary and compacted to 95 percent of maximum laboratory density, as determined by ASTM Test Method D 1557. Deleterious material, excessively wet or dry pockets, concentrated zones of oversized rock fragments, and any other unsuitable materials encountered during roadway grading should be removed. The compacted fill material should then be brought to the elevation of the proposed subgrade for the pavement. The subgrade should be proof-rolled in order to ensure a uniformly firm and unyielding surface. All grading and fill placement should be observed by the project soil engineer and/or his representative. Aggregate Base Compaction tests are required for the recommended aggregate base section. The minimum relative compaction required will be 95 percent of the maximum laboratory density as determined by ASTM Test Method D 1557. Base aggregate should be in accordance to the "Standard Specifications for Public Works Construction" (green book) current edition. Paving Prime coat may be omitted if all ofthe following conditions are met: 1. The asphalt pavement layer is placed within two weeks of completion of base and/or sub base course. 2. Traffic is not routed over completed base before paving. 3. Construction is completed during the dry season of May through October. 4. The base is free of dirt and debris. If construction is performed during the wet season of November through April, prime coat may be omitted if no rain occurs between completion of base course and paving and the time between completion of base and paving is reduced to three days, provided the base Shea Homes Limited Partnership W.O. 6649-A-SC 2359,2373, and 2375 Pio Pico Drive _ June 23, 2014 File:e:\wp12\6600\6649a.gue GeoSoilS, InC. Page 29 is free of dirt and debris. Where prime coat has been omitted and rain occurs, traffic is routed over base course, or paving is delayed, measures shall be taken to restore base course, subbase course, and subgrade to conditions that will meet specifications as directed bythe soil engineer. Drainage Positive drainage should be provided for all surface water to drain towards an approved drainage facility. Positive site drainage should be maintained at all times. Water should not be allowed to pond or seep into the ground. If planters or landscaping are adjacent to paved areas, measures should be taken to minimize the potential for water to enter the pavement section. These measures may include, but not limited to, subdrainage devices, thickened curbs, or concrete cut-off walls. UNDERGROUND UTILITiES NEAR THE TOP OF THE SLOPE DESCENDING TO INTERSTATE 5 FREEWAY In order to help maintain the long-term stability of the slope descending to Interstate 5 freeway, GSI recommends that all sewer and storm drain trenches outside and between Basins "A" and "B" should be backfilled with a 2-sack sand-cement slurry to mitigate a potential conduit for subsurface water to discharge on the slope face and/or adversely affect improvements on the slope. Appropriately located cutoff walls (minimum12 inch embedment), should be constructed in the sewer and storm drain trenches. ONSITE INFILTRATION-RUNOFF RETENTION SYSTEMS General Should onsite infiltration-runoff retention systems (OIRRS) be planned for Best Management Practices (BMP's) 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. A key factor in these systems is the infiltration rate (often referred to as the percolation rate) which can be ascribed to, or determined for, the earth materials within which these systems are installed. Additionally, the infiltration rate ofthe designed system (which may include gravel, sand, mulch/topsoil, or other amendments, etc.) will need to be considered. The project infiltration testing is very site specific, any changes to the location of the proposed OIRRS and/or estimated size of the OIRRS, may require additional infiltration Shea Homes Limited Partnership W.O. 6649-A-SC 2359,2373, and 2375 Pio Pico Drive _ June 23, 2014 File:e:\wp12\6600\6649a.gue GcoSoilS, InC. Page 30 testing. Locally, relatively impermeable formations include: paralic deposits, claystone, siltstone, cemented sandstone, igneous and metamorphic bedrock, as well as expansive fill soils. Some ofthe methods which are utilized for onsite infiltration include percolation basins, drywells, bio-swale/bio-retention, permeable pavers/pavement, infiltration trenches, filter boxes and subsurface infiltration galleries/chambers. Some of these systems are constructed using native and import soils, perforated piping, and filter fabrics while others employ structural components such as stormwater infiltration chambers and filters/separators. Every site will have characteristics which should lend themselves to one or more ofthese 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. Previous evaluations by GSI (2011 and 2012a), indicate that site soils belong to County of San Diego (2007), Hydrologic Soil Group (HSG) "D" and correspondtosoilswith very slow infiltration rates. Infiltration testing (GSI, 2011), of <0.52 inches/hour indicates that the site is not feasible for infiltration (United States Environmental Protection Agency [USEPA], 2004). 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 is now requiring this for OIRRS purposes on many projects. Impermeable liners used in conjunction with OIRRS should consist of a 30-mil polyvinyl chloride (PVC) membrane that meets the following minimum specifications: Specific Gravity (ASTM D792): 120 (min.); Tensile (ASTM D882): 73 (Ib/in-width, min); Elongation at Break (ASTM D882: 380 (%min); Modulus (STM D882): 30 (Ib/in-width, min.); and Tear Resistance (ASTM D1004): 30 (Ib/in, min). • Wherever possible, infiltration systems should not be installed within ±50 feet ofthe tops of slopes steeper than 15 percent or within H/3 from the tops of slopes (where H equals the height of slope). Shea Homes Limited Partnership W.O. 6649-A-SC 2359, 2373, and 2375 Pio Pico Drive , June 23, 2014 File:e:\wp12\6600\6649a.gue GcoSoilS, InC. Page 31 Wherever possible, infiltrations systems should not be placed within a distance of H/2 from the toes of slopes (where H equals the height of slope). • The landscape architect should be notified of the location of the proposed OIRRS. If landscaping is proposed within the OIRRS, consideration should be given to the type of vegetation chosen and their potential effect upon subsurface improvements (i.e., some trees/shrubs will have an effect on subsurface improvements with their extensive root systems). Over-watering landscape areas above, or adjacent to, the proposed OIRRS could adversely affect performance ofthe system. • Areas adjacent to, or within, the OIRRS that are subject to inundation should be properly protected against scouring, undermining, and erosion, in accordance with the recommendations ofthe design engineer. • Seismic shaking may result in the formation of a seiche which could potential overtop the banks of an OIRRS and result in down-gradient flooding and scour. If subsurface infiltration galleries/chambers are proposed, the appropriate size, depth interval, and ultimate placement ofthe detention/infiltration system should be evaluated by the design engineer, and be of sufficient width/depth to achieve optimum performance, based on the infiltration rates provided. In addition, proper debris filter systems will need to be utilized for the infiltration galleries/chambers. Debris filter systems will need to be self cleaning and periodically and regularly maintained on a regular basis. Provisions for the regular and periodic maintenance of any debris filter system is recommended and this condition should be disclosed to all interested/affected parties. Infiltrations systems should not be installed within ±8 feet of building foundations utility trenches, and walls, or a 1:1 (h:v) slope (down and away) from the bottom elements of these improvements. Alternatively, deepened foundations and/or pile/pier supported improvements may be used. • Infiltrations systems should not be installed adjacent to pavement and/or hardscape improvements. Alternatively, deepened/thickened edges and curbs and/or impermeable liners may be utilized in areas adjoining the OIRRS. As with any OIRRS, localized ponding and groundwater seepage should be anticipated. The potential for seepage and/or perched groundwater to occur after site development should be disclosed to all interested/affected parties. • Installation of infiltrations systems should avoid expansive soils (Expansion Index [E.I.] >51) or soils with a relatively high plasticity index (P.I. > 20). • Infiltration systems should not be installed where the vertical separation of the groundwater level is less than ±10 feet from the base ofthe system. Shea Homes Limited Partnership W.O. 6649-A-SC 2359,2373, and 2375 Pio Pico Drive ^ June 23,2014 File:e:\wp12\6600\6649a.Que GcoSoilS, InC. Page 32 Where permeable pavements are planned as part of the system, the site Traffic Index (T.l.) should be less than 25,000 Average Daily Traffic (ADT), as recommended in Allen, et al. (2011). Infiltration systems should be designed using a suitable factor of safety (FOS) to account for uncertainties in the known infiltration rates (as generally required bythe controlling authorities), and reduction in performance overtime. As with any OIRRS, proper care will need to provided. Best management practices should be followed at all times, especially during inclement weather. Provisions for the management of any siltation, debris within the OIRRS, and/or overgrown vegetation (including root systems) should be considered. An appropriate inspection schedule will need to adopted and provided to all interested/affected parties. Any designed system will require regular and periodic maintenance, which may include rehabilitation and/or complete replacement of the filter media (e.g., sand, gravel, filter fabrics, topsoils, mulch, etc.) or other components utilized in construction, so that the design life exceeds 15 years. Due to the potential for piping and adverse seepage conditions, a burrowing rodent control program should also be implemented onsite. All or portions of these systems may be considered attractive nuisances. Thus, consideration ofthe effects of, or potential for, vandalism should be addressed. Newly established vegetation/landscaping (including phreatophytes) may have root systems that will influence the performance ofthe OIRRS or nearby LID systems. The potential for surface flooding, in the case of system blockage, should be evaluated by the design engineer. Any proposed utility backfill materials (i.e., inlet/outlet piping and/or other subsurface utilities) located within or near the proposed area of the OIRRS may become saturated. This is due to the potential for piping, water migration, and/or seepage along the utility trench line backfill. If utility trenches cross and/or are proposed near the OIRRS, cut-off walls or other water barriers will need to be installed to mitigate the potential for piping and excess water entering the utility backfill materials. Planned or existing utilities may also be subject to piping of fines into open-graded gravel backfill layers unless separated from overlying or adjoining OIRRS by geotextiles and/or slurry backfill. The use of OIRRS above existing utilities that might degrade/corrode with the introduction of water/seepage should be avoided. Shea Homes Limited Partnership W.O. 6649-A-SC 2359,2373, and 2375 Pio Pico Drive _ June 23, 2014 File:e:\wp12\6600\6649a.gue GeoSoilS, InC. Page 33 Plan Specific bHA, Inc. (2014) indicate the construction of stormwater bio-retention basins near the westerly margin ofthe 2373 and 2375 Pio Pico Drive site, and near the top ofthe cut slope descending to Interstate 5. bHA (undated) indicates stormwater treatment in a bio-retention basin near the westerly margin of the 2359 Pio Pico Drive site and beneath permeable pavers in the Private Street. Stormwater on 2359 Pio Pico Drive is currently planned to be disposed by infiltration into the onsite soils. In consideration ofthe long- term stability of the slope descending to Interstate 5 and the nearby planned improvements, GSI recommends the following in addition to the above: bHA (undated) indicates that storm water runoff will infiltrate into the onsite soils at 2359 Pio Pico Drive. As indicated in GSI (2011), a relatively conservative infiltration rate of 0.12 inches per hour was calculated for the soils located thereon. It should be noted, as indicated previously, that the calculated infiltration rate provided in GSI (2011) does not meet the minimum infiltration rate of 0.52 in/hr established by the United Stated Environmental Protection Agency (2004) for infiltration feasibility. Thus, infiltration for stormwater disposal does not appear feasible at this site. Thus, GSI recommends that stormwater be conveyed to an approved drainage facility following onsite treatment. The bottom of the basins and the bottoms and sides of all storm drain trenches located on Lots 18 and 19 (BHA, 2014) should lined with an impermeable 30-mil PVC liner as discussed above. Waterproofing should be provided on the backs of basin retaining walls to the design high-level water height in the basins to help mitigate efflorescence staining. Subdrains at the bottoms of Basins "A" and "B" (bHA, 2014) should consist of a 4-inch diameter Schedule 40 or SDR 35 perforated drain pipe with the perforations oriented downward. The perforated drain pipe should be sleeved with a filter sock. The subdrains should gravity flow (minimum 1 percent) to an approved drainage facility. The bottom of the footings forthe retaining walls associated with Basins "A" and "B" (bHA, 2014) should minimally extend at least 18 inches below the bottom ofthe basin excavations or be pier supported per the recommendations in the "Top-of-Slope Walls/Fences/lmprovements and Expansive Soils" section of this report where they are located at the top-of-slopes or within 15 horizontal feet from the top ofthe nearby descending slope. GSI recommends that the bottom and sides ofthe planned bio-retention basin near the westerly margin of 2359 Pio Pico Drive be lined with a 30-mil PVC impermeable liner that meets the aforementioned specifications. A 4-inch diameter Schedule 40 or SDR 35 perforated drain pipe should be placed above the impermeable liner with the perforations oriented downward. The perforated drain pipe should be sleeved Shea Homes Limited Partnership W.O. 6649-A SC 2359, 2373, and 2375 Pio Pico Drive , June 23, 2014 File:G:\wp12\6600\6649a.gue GCOSoilS, InC. Page 34 with a filter sock. The subdrains should gravity flow (minimum 1 percent) to an approved drainage facility. The bottoms of the planned permeable paver sections at 2359 Pio Pico Drive should be lined with a 30-mil PVC impermeable linerthat meets the aforementioned specifications. A sleeved, 4-inch diameter Schedule 40 or SDR 35 perforated drain pipe should be placed above the impermeable liner with the perforations oriented downward. The perforated drain pipe should be sleeved with a filter sock. The subdrains should gravity flow (minimum 1 percent) to an approved drainage facility. Concrete cut-off walls or collars should be provided around the margins of the permeable pavers. The cut off walls should be at least 6 inches wide and extend 1 foot below the paver section subgrade. In order to increase the performance of the permeable paver section, HP-570 geotextile should be placed along the subgrade. Proper maintenance and care of the basins will need to provided. Best management maintenance practices should be followed at all times, especially during inclement weather. Should regular inspection and/or required maintenance not be performed, the potential for malfunctioning of the detention systems will increase. All inlets, outlets and piping from these temporary drainage features should be properly backfilled and installed per City standards. Consideration should be given to increasing the width and height ofthe splash wall in the brow ditch on the slope descending to Interstate 5. The brow ditch will need to be cleaned of debris periodically, especially prior to, and following forecasted storm events. It has been our experience that poorly maintained brow ditches can result in overtopping and severe slope erosion/failures. PRELIMINARY OUTDOOR POOL/SPA DESIGN RECOMMENDATIONS The following preliminary recommendations are provided for consideration in pool/spa design and planning if part of the project or part of the homeowner landscaping scheme. Actual recommendations should be provided by a qualified geotechnical consultant, based on the presence of impacted soils, site specific geotechnical conditions, including supplemental subsurface investigation, differential settlement potential, expansive and corrosive soil potential, proximity ofthe proposed pool/spa to any slopes with regard to slope creep and lateral fill extension, as well as slope setbacks per code, and geometry of the proposed improvements. Recommendations for pools/spas and/or deck flatwork underlain by expansive soils, or for areas with differential settlement greater than y4-inch over 40 feet horizontally, will be more onerous than the preliminary recommendations presented below. The conditions and recommendations presented herein should be disclosed to all homeowners and any interested/affected parties. Shea Homes Limited Partnership W.O. 6649-A-SC 2359, 2373, and 2375 Pio Pico Drive , June 23, 2014 File:e:\wp12\6600\6649a.gue GcoSoilS, InC. Page 35 General 1. The equivalent fluid pressure to be used for the pool/spa design should be 60 pounds per cubic foot (pcf) for pool/spa walls with level backfill, and 75 pcf for a 2:1 sloped backfill condition. In addition, backdrains should be provided behind pool/spa walls subjacent to slopes. 2. Passive earth pressure may be computed as an equivalent fluid having a density of 150 pcf, to a maximum lateral earth pressure of 1,000 psf. 3. An allowable coefficient of friction between soil and concrete of 0.30 may be used with the dead load forces. 4. When combining passive pressure and frictional resistance, the passive pressure component should be reduced by one-third. 5. Where pools/spas are planned near structures, appropriate surcharge loads need to be incorporated into design and construction by the pool/spa designer. This includes, but is not limited to landscape berms, decorative walls, footings, built-in barbeques, utility poles, etc. 6. All pool/spa walls should be designed as "free standing" and be capable of supporting the water in the pool/spa without soil support. The shape of pool/spa in cross section and plan view may affect the performance of the pool, from a geotechnical standpoint. Pools and spas should also be designed in accordance with Section 1808.7.3 ofthe 2013 CBC (CBSC, 2013). Minimally, the bottoms ofthe pools/spas, should maintain a distance H/3, where H is the height ofthe slope (in feet), from the slope face. This distance should not be less than 7 feet, nor need not be greater than 40 feet. 7. The soil beneath the pool/spa bottom should be uniformly moist with the same stiffness throughout. If a fill/paralic deposits transition occurs beneath the pool/spa bottom, the paralic deposits should be overexcavated to a minimum depth of 48 inches, and replaced with compacted fill, such that there is a uniform blanket that is a minimum of 48 inches below the pool/spa shell. If very low expansive soil is used for fill, the fill should be placed at a minimum of 95 percent relative compaction, at optimum moisture conditions. This requirement should be 90 percent relative compaction at over optimum moisture if the pool/spa is constructed within or near expansive soils. The potential for grading and/or re-grading ofthe pool/spa bottom, and attendant potential for shoring and/or slot excavation, needs to be considered during all aspects of pool/spa planning, design, and construction. 8. Ifthe pool/spa is founded entirely in compacted fill placed during rough grading, the deepest portion of the pool/spa should correspond with the thickest fill on the lot. Shea Homes Limited Partnership W.O. 6649-A-SC 2359,2373, and 2375 Pio Pico Drive , June 23,2014 File:e;\wp12\6600\6649a.gue GCOSOllS, InC. Page 36 9. Hydrostatic pressure relief valves should be incorporated into the pool and spa designs. A pool/spa under-drain system is also recommended, with an appropriate outlet for discharge. 10. All fittings and pipe joints, particularly fittings in the side of the pool or spa, should be properly sealed to prevent water from leaking into the adjacent soils materials, and be fitted with slip or expandible joints between connections transecting varying soil conditions. 11. An elastic expansion joint (flexible waterproof sealant) should be installed to prevent water from seeping into the soil at all deck joints. 12. A reinforced grade beam should be placed around skimmer inlets to provide support and mitigate cracking around the skimmer face. 13. In order to reduce unsightly cracking, deck slabs should minimally be 4 inches thick, and reinforced with No. 3 reinforcing bars at 18 inches on-center. All slab reinforcement should be supported to ensure proper mid-slab positioning during the placement of concrete. Wire mesh reinforcing is specifically not recommended. Deck slabs should not be tied to the pool/spa structure. Pre-moistening and/or pre-soaking of the slab subgrade is recommended, to a depth of 12 inches (optimum moisture content), or 18 inches (120 percent of the soil's optimum moisture content, or 3 percent over optimum moisture content, whichever is greater), for very low to low, and medium expansive soils, respectively. This moisture content should be maintained in the subgrade soils during concrete placement to promote uniform curing of the concrete and minimize the development of unsightly shrinkage cracks. Slab underlayment should consist of a 1-to 2-inch leveling course of sand (S.E.>30) and a minimum of 4 to 6 inches of Class 2 base compacted to 90 percent. Deck slabs within the H/3 zone, where H is the height of the slope (in feet), will have an increased potential for distress relative to other areas outside of the H/3 zone. If distress is undesirable, improvements, deck slabs or flatwork should not be constructed closer than H/3 or 7 feet (whichever is greater) from the slope face, in order to reduce, but not eliminate, this potential. 14. Pool/spa bottom or deck slabs should be founded entirely on competent paralic deposits or properly compacted fill. Fill should be compacted to achieve a minimum 90 percent relative compaction, as discussed above. Prior to pouring concrete, subgrade soils belowthe pool/spa decking should be throughly watered to achieve a moisture content that is at least 2 percent above optimum moisture content, to a depth of at least 18 inches below the bottom of slabs. This moisture content should be maintained in the subgrade soils during concrete placement to promote uniform curing ofthe concrete and minimize the development of unsightly shrinkage cracks. Shea Homes Limited Partnership W.O. 6649-A-SC 2359,2373, and 2375 Pio Pico Drive _ June 23,2014 File:e:\wp12\6600\6649a.gue GeoSoilS, InC. Page 37 15. In order to reduce unsightly cracking, the outer edges of pool/spa decking to be bordered by landscaping, and the edges immediately adjacent to the pool/spa, should be underlain by an 8-inch wide concrete cutoff shoulder (thickened edge) extending to a depth of at least 12 inches below the bottoms ofthe slabs to mitigate excessive infiltration of water under the pool/spa deck. These thickened edges should be reinforced with two No. 4 bars, one at the top and one at the bottom. Deck slabs may be minimally reinforced with No. 3 reinforcing bars placed at 18 inches on-center, in both directions. All slab reinforcement should be supported on chairs to ensure proper mid-slab positioning during the placement of concrete. 16. Surface and shrinkage cracking of the finish slab may be reduced if a low slump and water-cement ratio are maintained during concrete placement. Concrete utilized should have a minimum compressive strength of 4,000 psi and a maximum water to cement ratio of 0.50. Excessive water added to concrete prior to placement is likely to cause shrinkage cracking, and should be avoided. Some concrete shrinkage cracking, however, is unavoidable. 17. Joint and sawcut locations for the pool/spa deck should be determined by the design engineer and/or contractor. However, spacings should not exceed 6 feet on-center. 18. Considering the nature ofthe onsite earth materials, it should be anticipated that caving or sloughing could be a factor in subsurface excavations and trenching. Shoring or excavating the trench walls/backcuts at the angle of repose (typically 25 to 45 degrees), should be anticipated. All excavations should be observed by a representative ofthe geotechnical consultant, including the project geologist and/or geotechnical engineer, 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 should be offered atthattime bythe geotechnical consultant. GSI does not consult in the area of safety engineering and the safety of the construction crew is the responsibility ofthe pool/spa builder. 19. It is imperative that adequate provisions for surface drainage are incorporated by the homeowners into their overall improvement scheme. Ponding water, ground saturation and flow over slope faces, are all situations which must be avoided to enhance long term performance ofthe pool/spa and associated improvements, and reduce the likelihood of distress. 20. Regardless ofthe methods employed, once the pool/spa is filled with water, should it be emptied, there exists some potential that if emptied, significant distress may occur. Accordingly, once filled, the pool/spa should not be emptied unless evaluated by the geotechnical consultant and the pool/spa builder. 21. For pools/spas built within (all or part) ofthe 2013 CBC setback and/or geotechnical setback, as indicated in the site geotechnical documents, special foundations are Shea Homes Limited Partnership W.O. 6649-A-SC 2359, 2373, and 2375 Pio Pico Drive , June 23,2014 File:e:\wp12\6600\6649a.gue GeoSoilS, InC. Page 38 recommended to mitigate the affects of creep, lateral fill extension, expansive soils and settlement on the proposed pool/spa. Most municipalities or County reviewers do not consider these effects in pool/spa plan approvals. As such, where pools/spas are proposed on 20 feet or more of fill, medium or highly expansive soils, or rock fill with limited "cap soils" and built within 2013 CBC setbacks, or within the influence ofthe creep zone, or lateral fill extension, the following should be considered during design and construction: OPTION A: Shallow foundations with or without overexcavation of the pool/spa "shell," such that the pool/spa is surrounded by 5 feet of very low to low expansive soils (without irreducible particles greater that 6 inches), and the pool/spa walls closer to the slope(s) are designed to be free standing. GSI recommends a pool/spa under-drain or blanket system (see Typical Pool/Spa Detail [Appendix B]). The pool/spa builders and owner in this optional construction technique should be generally satisfied with pool/spa performance underthis scenario; however, some settlement, tilting, cracking, and leakage ofthe pool/spa is likely overthe life ofthe project. OPTION B: Pier supported pool/spa foundations with or without overexcavation ofthe pool/spa shell such thatthe pool/spa is surrounded by 5 feet of very lowto low expansive soils (without irreducible particles greater than 6 inches), and the pool/spa walls closer to the slope(s) are designed to be free standing. The need for a pool/spa under-drain system may be installed for leak detection purposes. Piers that support the pool/spa should be a minimum of 12 inches in diameter and at a spacing to provide vertical and lateral support of the pool/spa, in accordance with the pool/spa designers recommendations, local code, and the 2013 CBC. The pool/spa builder and owner in this second scenario construction technique should be more satisfied with pool/spa performance. This construction will reduce settlement and creep effects on the pool/spa; however, it will not eliminate these potentials, nor make the pool/spa "leak-free." 22. The temperature of the water lines for spas and pools may affect the corrosion properties of site soils, thus, a corrosion specialist should be retained to review all spa and pool plans, and provide mitigative recommendations, as warranted. Concrete mix design should be reviewed by a qualified corrosion consultant and materials engineer. 23. All pool/spa utility trenches should be compacted to 90 percent of the laboratory standard, under the full-time observation and testing of a qualified geotechnical consultant. Utility trench bottoms should be sloped away from the primary structure on the property (typically the residence). 24. Pool and spa utility lines should not cross the primary structure's utility lines (i.e., not stacked, or sharing of trenches, etc.). Shea Homes Limited Partnership W.O. 6649-A-SC 2359, 2373, and 2375 Pio Pico Drive . June 23, 2014 File:e:\wp12\6600\6649a.gue GCOSoilS, InC. Page 39 25. The pool/spa or associated utilities should not intercept, interrupt, or otherwise adversely impact any area drain, roof drain, or other drainage conveyances. If it is necessary to modify, move, or disrupt existing area drains, subdrains, or tightiines, then the design civil engineer should be consulted, and mitigative measures provided. Such measures should be further reviewed and approved by the geotechnical consultant, priorto proceeding with any further construction. 26. The geotechnical consultant should review and approve all aspects of pool/spa and flatwork design prior to construction. A design civil engineer should review all aspects of such design, including drainage and setback conditions. Prior to acceptance of the pool/spa construction, the project builder, geotechnical consultant and civil designer should evaluate the performance ofthe area drains and other site drainage pipes, following pool/spa construction. 27. All aspects of construction should be reviewed and approved by the geotechnical consultant, including during excavation, priorto the placement of any additional fill, prior to the placement of any reinforcement or pouring of any concrete. 28. Any changes in design or location of the pool/spa should be reviewed and approved bythe geotechnical and design civil engineer priorto construction. Field adjustments should not be allowed until written approval of the proposed field changes are obtained from the geotechnical and design civil engineer. 29. Disclosure should be made to homeowners and builders, contractors, and any interested/affected parties, that pools/spas built within about 15 feet of the top of a slope, and/or H/3, where H isthe height ofthe slope (in feet), will experience some movement or tilting. While the pool/spa shell or coping may not necessarily crack, the levelness of the pool/spa will likely tilt toward the slope, and may not be esthetically pleasing. The same is true with decking, flatwork and other improvements in this zone. 30. Failure to adhere to the above recommendations will significantly increase the potential for distress to the pool/spa, flatwork, etc. 31. Local seismicity and/or the design earthquake will cause some distress to the pool/spa and decking or flatwork, possibly including total functional and economic loss. 32. The information and recommendations discussed above should be provided to any contractors and/or subcontractors, or homeowners, interested/affected parties, etc., that may perform or may be affected by such work. Shea Homes Limited Partnership W.O. 6649-A-SC 2359, 2373, and 2375 Pio Pico Drive June 23, 2014 File:e:\wp12\6600\6649a.gue GCOSOllS, InC. Page 40 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 ofthe fill soils which results in slow downslope movement. This type of movement is expected to occurthroughoutthe life ofthe slope, and is anticipated to potentially affect improvements or structures (e.g., separations and/or cracking), placed near the top-of-slope, up to a maximum distance of approximately 15 feet from the top-of-slope, depending on the slope height. This movement generally results in rotation and differential settlement of improvements located within the creep zone. LFE occurs due to deep wetting from irrigation and rainfall on slopes comprised of expansive materials. Although some movement should be expected, long-term movement from this source may be minimized, but not eliminated, by placing the fill throughout the slope region, wet of the fill's optimum moisture content. It is generally not practical to attempt to eliminate the effects of either slope creep or LFE. Suitable mitigative measures to reduce the potential of lateral deformation typically include: setback of improvements from the slope faces (per the 2013 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 ofthese measures are recommended for design of structures and improvements. The ramifications of the above conditions, and recommendations for mitigation, should be provided to all interested/affected parties. Slope Maintenance and Planting Water has been shown to weaken the inherent strength of all earth materials. Slope stability is significantly reduced by overly wet conditions. Positive surface drainage away from slopes should be maintained and only the amount of irrigation necessary to sustain plant life should be provided for planted slopes. Over-watering should be avoided as it adversely affects site improvements, and causes perched groundwater conditions. Graded slopes constructed utilizing onsite materials would be erosive. Eroded debris may be minimized and surficial slope stability enhanced by establishing and maintaining a suitable vegetation cover soon after construction. Compaction to the face of fill slopes would tend to minimize short-term erosion until vegetation is established. Plants selected for 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 Shea Homes Limited Partnership W.O. 6649-A-SC 2359,2373, and 2375 Pio Pico Drive . June 23, 2014 File:e:\wp12\6600\6649a.gue GCOSoilS, InC. Page 41 develop. A rodent control program to prevent burrowing should be implemented. Irrigation of natural (ungraded) slope areas is generally not recommended. These recommendations regarding plant type, irrigation practices, and rodent control should be provided to all interested/affected parties. Over-steepening of slopes should be avoided during building construction activities and landscaping. Drainage Adequate surface drainage is a very important factor in reducing the likelihood of adverse performance 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 2013 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. 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 awayfrom 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 barrierto prevent penetration of irrigation water Shea Homes Limited Partnership W.O. 6649-A-SC 2359,2373, and 2375 Pio Pico Drive . June 23, 2014 File:e:\wp12\6600\6649a.gue GcoSoilS, InC. Page 42 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 house, to an appropriate outlet, in accordance with the recommendations of the design civil engineer. Downspouts and gutters are not a requirement; however, from a geotechnical viewpoint, provided that positive drainage is incorporated into project design (as discussed previously). Subsurface and Surface Water Subsurface and surface water are not anticipated to affect site development, provided that the recommendations contained in this report are incorporated into final design and construction and that prudent surface and subsurface drainage practices are incorporated into the construction plans. Perched groundwater conditions along zones of contrasting permeabilities may not be precluded from occurring in the future due to site irrigation, poor drainage conditions, or damaged utilities, and should be anticipated. Should perched groundwater conditions develop, this office could assess the affected area(s) and provide the appropriate recommendations to mitigate the observed groundwater conditions. Groundwater conditions may change with the introduction of irrigation, rainfall, or other factors. Site Improvements If in the future, any additional improvements (e.g., pools, spas, etc.) are planned for the site, recommendations concerning the geological or geotechnical aspects of design and construction of said improvements could be provided upon request. Pools and/or spas should not be constructed without specific design and construction recommendations from GSI, and this construction recommendation should be provided to all interested/affected parties. This office should be notified in advance of any fill placement, grading ofthe site, or trench backfilling after rough grading has been completed. This includes any grading, utility trench and retaining wall backfills, flatwork, etc. Shea Homes Limited Partnership W.O. 6649-A-SC 2359,2373, and 2375 Pio Pico Drive , June 23,2014 File:e:\wp12\6600\6649a.gue GCOSoilS, InC. Page 43 Tile Flooring Tile flooring can crack, reflecting cracks in the concrete slab belowthe 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 ofthis firm subsequent to trenching and prior to concrete form and reinforcement placement. The purpose ofthe 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 ofthe subgrade materials would be recommended at that time. Footing trench spoil and any excess soils generated from utility trench excavations should be compacted to a minimum relative compaction of 90 percent, if not removed from the site. Trenching/Temporary Construction Backcuts Considering the nature ofthe 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 ofthis report]), should be anticipated. All excavations should be observed by an engineering geologist or soil engineer from GSI, prior to workers entering the excavation or trench, and minimally conform to CAL-OSHA, state, and local safety codes. Should adverse conditions exist, appropriate recommendations would be offered at that time. The above recommendations should be provided to any contractors and/or subcontractors, or homeowners, etc., that may perform such work. Shea Homes Limited Partnership W.O. 6649-A-SC 2359, 2373, and 2375 Pio Pico Drive , June 23, 2014 File:e;\wp12\6600\6649a.gue GeoSoilS, InC. Page 44 Utilitv 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 ofthe laboratory standard. As an alternative for shallow (12-inch to 18-inch) under-slab trenches, sand having a sand equivalent value of 30 or greater may be utilized and jetted or flooded into place. Observation, probing and testing should be provided to evaluate the desired results. 2. Exterior trenches adjacent to, and within areas extending below a 1:1 plane projected from the outside bottom edge of the footing, and all trenches beneath hardscape features and in slopes, should be compacted to at least 90 percent of the laboratory standard. Sand backfill, unless excavated from the trench, should not be used in these backfill areas. Compaction testing and observations, along with probing, should be accomplished to evaluate the desired results. 3. All trench excavations should conform to CAL-OSHA, state, and local safety codes. 4. Utilities crossing grade beams, perimeter beams, or footings should either pass below the footing or grade beam utilizing a hardened collar or foam spacer, or pass through the footing or grade beam in accordance with the recommendations ofthe structural engineer. SUMMARYOF 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. • 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.). Shea Homes Limited Partnership W.O. 6649-A-SC 2359, 2373, and 2375 Pio Pico Drive _ June 23, 2014 File:e:\wp12\6600\6649a.gue GeoSoilS, InC. Page 45 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 ofthis report. When any developer or homeowner improvements, such as flatwork, spas, pools, walls, etc., are constructed, prior to construction. A report of geotechnical observation and testing should be provided at the conclusion of each of the above stages, in order to provide concise and clear documentation of site work, and/or to comply with code requirements. OTHER DESIGN PROFESSIONALS/CONSULTANTS The design civil engineer, structural engineer, post-tension designer, architect, landscape architect, wall designer, etc., should review the recommendations provided herein, incorporate those recommendations into all their respective plans, and by explicit reference, make this report part of their project plans. This report presents minimum design criteria for the design of slabs, foundations and other elements possibly applicable to the project. These criteria should not be considered as substitutes for actual designs by the structural engineer/designer. Please note that the recommendations contained herein are not intended to preclude the transmission of water or vapor through the slab or foundation. The structural engineer/foundation and/or slab designer should provide recommendations to not allow water or vapor to enter into the structure so as to cause damage to another building component, or so as to limit the installation ofthe type of flooring materials typically used for the particular application. The structural engineer/designer should analyze actual soil-structure interaction and consider, as needed, bearing, expansive soil influence, and strength, stiffness and deflections in the various slab, foundation, and other elements in order to develop appropriate, design-specific details. As conditions dictate, it is possible that other influences will also have to be considered. The structural engineer/designer should consider all applicable codes and authoritative sources where needed. If analyses by the structural engineer/designer result in less critical details than are provided herein as minimums, the minimums presented herein should be adopted. It is considered likely that some, more restrictive details will be required. Shea Homes Limited Partnership W.O. 6649-A-SC 2359, 2373, and 2375 Pio Pico Drive , June 23, 2014 File:e:\wp12\6600\6649a.gue GeoSoilS, InC. Page 46 If the Structural engineer/designer has any questions or requires further assistance, they should not hesitate to call or othenA/ise 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, thatthe 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. Improvement plans should also be reviewed for subdrainage and piping (washing of fines) conditions, in light of the proposed sewer and storm drain's close proximity to the cut slope descending to Interstate 5. LIMITATIONS The materials encountered on the project site and utilized for our analysis are believed representative ofthe area; however, soil and bedrock materials vary in character between excavations and natural outcrops or conditions exposed during mass grading. Site conditions may vary due to seasonal changes or other factors. Inasmuch as our study is based upon our review and engineering analyses and laboratory data, the conclusions and recommendations are professional opinions. These opinions have been derived in accordance with current standards of practice, and no warranty, either express or implied, is given. Standards of practice are subject to change with time. GSI assumes no responsibility or liability for work or testing performed by others, or their inaction; or work performed when GSI is not requested to be onsite, to evaluate if our recommendations have been properly implemented. Use of this report constitutes an agreement and consent by the user to all the limitations outlined above, notwithstanding any other agreements that may be in place. In addition, this report may be subject to review by the controlling authorities. Thus, this report brings to completion our scope of services for this portion of the project. Shea Homes Limited Partnership W.O. 6649-A-SC 2359,2373, and 2375 Pio Pico Drive _ June 23,2014 File:e:\wp12\6600\6649a.gue GCOSoilS, InC. Page 47 The opportunity to be of service is sincerely appreciated. If you should have any questions, please do not hesitate to contact our office. Respectfully sub GeoSoils, inc. Engineering Geologist bavid W. Skelly Civil Engineer, RCE 4 Ryan B. Boehmer Project Geologist RBB/JPF/DWS/jh Enclosures: Appendix A - References Appendix B - General Earthwork and Grading Guidelines Distribution: (4) Addressee (2 wet signed) Shea Homes Limited Partnership 2359, 2373, and 2375 Pio Pico Drive File:e:\wp12\6600\6649a.gue GeoSoils, Inc. w.o. 6649-A-SC June 23, 2014 Page 48 APPENDIXA REFERENCES GeoSoils, Inc. APPENDIXA REFERENCES American Concrete Institute Committee 318, 2011, Building code requirements for structural concrete (ACI 318-11) and commentary, dated August. ACI Committee 302,2004, Guide for concrete floor and slab construction, ACI 302.1 R-04, dated June. Allen, v., Connerton, A., and Carlson, C, 2011, Introduction to Infiltration Best Management Practices (BMP), Contech Construction Products, Inc., Professional Development Series, dated December. American Society for Testing and Materials (ASTM), 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, 2006, Minimum design loads for buildings and other structures, ASCE Standard ASCE/SEI 7-05. bHA, Inc. 2014, Grading and erosion control plans for: Shea Homes - Ayre, 6 sheets, 20-scale, plot dated April 16. , undated. Grading and erosion control plans for: Sohaei Minor Subdivision, 4 sheets, 20-scale. California Building Standards Commission, 2013, California Building Code, California Code of Regulations, Title 24, Part 2, Volume 2 of 2, Based on the 2012 International Building Code, 2013 California Historical Building Code, Title 24, Part 8; 2013 California Existing Building Code, Title 24, Part 10. California Department of Water Resources, 1993, Division of Safety of Dams, Guidelines for the design and construction of small embankments dams, reprinted January. California Stormwater Quality Association (CASQA), 2003, Stormwater best management practice handbook, new development and redevelopment, dated January. 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 GeoSoils, Inc. City of Carlsbad, 2004, Engineering standards, general design standards, vol. 1. County of San Diego, Department of Planning and Land Use, 2007, Low impact development (LID) handbook, stormwater management strategies, dated December 31. East County Soil Consultation and Engineering, Inc., 2005, Limited site investigation update, three proposed two-story single-family residences, 2359 Pio Pico Drive, APN 156-351-06, Project No. 04-1106E3(A), dated August 11. GeoSoils, Inc., 2014, Property mitigation plan, proposed 17 lot subdivision, APNs 156-351-03, -07, and -08, 2373 and 2375 Pio Pico Drive, Carlsbad, San Diego County, California 92010, Voluntary Assistance Case DEH2013-LSAM-000194, W.O. E6649.1-SC, dated April 30. , 2012a, Qualitative evaluation of infiltration and soil runoff potentials, APNs 156-351 -03, -07, and -08,2373 and 2375 Pio Pico Drive, Carlsbad, San Diego County, California 92008, W.O. 6324-A1-SC, dated December 27. , 2012b, Preliminary geotechnical evaluation, APNs 156-351-03, -07, and -08, 2373 and 2375 Pio Pico Drive, Carlsbad, San Diego County, California 92008, W.O. 6324- A-SC, dated October 31. , 2011, Feasibility level infiltration testing for proposed bio-retention basin and preliminary design recommendations for interlocking pervious pavers, 2359 Pio Pico Drive, Carlsbad, San Diego County, California, W.O. 6252-A-SC, dated June 27. Hydrologic Solutions, StormChamber™ installation brochure, pgs. 1 through 8, undated. Kanare, H.M., 2005, Concrete floors and moisture. Engineering Bulletin 119, Portland Cement Association. State of California, 2014, Civil Code, Sections 895 et seq. United States Environmental Protection Agency, 2004, Stormwater Best Management Practice Design Guide, EPA/600/R-04/121B. GeoSoils, Inc. APPENDIX B 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 ofthe 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 bythe 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. Laboratorv and Field Tests Maximum dry density tests to determine the degree of compaction should be performed in accordance with American Standard Testing Materials test method ASTM designation D 1557. Random or representative field compaction tests should be performed in GeoSoils, Inc. 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 Responsibiiity All clearing, site preparation, and earthwork performed on the project should be conducted bythe 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 ofthe 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 ofthe contractorto 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 bythe 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 ofthe 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 Shea Homes Limited Partnership _ Appendix B Flle:e:\wp12\6600\6649a.gue GcoSoilS, InC. Page 2 or treated in a manner recommended by the geotechnical consultant. Soft, dry, spongy, highly fractured, or othenwise 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 bythe geotechnical consultant. After the scarified ground is brought to optimum moisture content, or greater and mixed, the materials should be compacted as specified herein. Ifthe 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 ofthe lowest bench or key is also 15 feet, with the key founded on firm material, as designated bythe geotechnical consultant. As a general rule, unless specifically recommended otherwise bythe geotechnical consultant, the minimum width of fill keys should be equal to 72 the height ofthe 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 Shea Homes Limited Partnership ^ Appendix B File:e:\wp12\6600\6649a.gue GeoSoilS, InC. Page 3 consultant. These materials should be free of roots, tree branches, other organic matter, or other deleterious materials. All unsuitable materials should be removed from the fill as directed by the geotechnical consultant. Soils of poor gradation, undesirable expansion potential, or substandard strength characteristics may be designated by the consultant as unsuitable and may require blending with other soils to serve as a satisfactory fill material. Fill materials derived from benching operations should be dispersed throughout the fill area and blended with other approved material. Benching operations should not result in the benched material being placed only within a single equipment width away from the fill/bedrock contact. Oversized materials defined as rock, or other irreducible materials, with a maximum dimension greater than 12 inches, should not be buried or placed in fills unless the location of materials and disposal methods are specifically approved bythe geotechnical consultant. Oversized material should be taken offsite, or placed in accordance with recommendations ofthe geotechnical consultant in areas designated as suitable for rock disposal. GSI anticipates that soils to be utilized as fill material for the subject project may contain some rock. Appropriately, the need for rock disposal may be necessary during grading operations on the site. From a geotechnical standpoint, the depth of any rocks, rock fills, or rock blankets, should be a sufficient distance from finish grade. This depth is generally the same as any overexcavation due to cut-fill transitions in hard rock areas, and generally facilitates the excavation of structural footings and substructures. Should deeper excavations be proposed (i.e., deepened footings, utility trenching, swimming pools, spas, etc.), the developer may consider increasing the hold-down depth of any rocky fills to be placed, as appropriate. In addition, some agencies/jurisdictions mandate a specific hold-down depth for oversize materials placed in fills. The hold-down depth, and potential to encounter oversize rock, both within fills, and occurring in cut or natural areas, would need to be disclosed to all interested/affected parties. Once approved by the governing agency, the hold-down depth for oversized rock (i.e., greaterthan 12 inches) in fills on this project is provided as 10 feet, unless specified differently in the text ofthis 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 ofthis material should be conducted by the geotechnical consultant as soon as possible. Shea Homes Limited Partnership _ Appendix B File:e:\wp12\6600\6649a.gue GCOSoilS, InC. Page 4 Approved fill material should be placed in areas prepared to receive fill in near horizontal layers, that when compacted, should not exceed about 6 to 8 inches in thickness. The geotechnical consultant may approve thick lifts if testing indicates the grading procedures are such that adequate compaction is being achieved with lifts of greater thickness. Each layer should be spread evenly and blended to attain uniformity of material and moisture suitable for compaction. Fill layers at a moisture content less than optimum should be watered and mixed, and wet fill layers should be aerated by scarification, or should be blended with drier material. Moisture conditioning, blending, and mixing of the fill layer should continue until the fill materials have a uniform moisture content at, or above, optimum moisture. After each layer has been evenly spread, moisture conditioned, and mixed, it should be uniformly compacted to a minimum of 90 percent ofthe maximum density as evaluated by ASTM test designation D 1557, or as othenwise 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, perthe latest adopted version ofthe 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. Afinal 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 Shea Homes Limited Partnership _ Appendix B Fjle:e:\wp12\6600\6649a.gue GeoSoilS, InC. Page 5 slopes, and extend out over the slope to provide adequate compaction to the face of the slope. 2. Loose fill should not be spilled out over the face of the slope as each lift is compacted. Any loose fill spilled over a previously completed slope face should be trimmed off or be subject to re-rolling. 3. Field compaction tests will be made in the outer (horizontal) ±2 to ±8 feet of the slope at appropriate vertical intervals, subsequent to compaction operations. 4. After completion of the slope, the slope face should be shaped with a small tractor and then re-rolled with a sheepsfoot to achieve compaction to near the slope face. Subsequent to testing to evaluate compaction, the slopes should be grid-rolled to achieve compaction to the slope face. Final testing should be used to evaluate compaction after grid rolling. 5. Where testing indicates less than adequate compaction, the contractor will be responsible to rip, water, mix, and recompact the slope material as necessary to achieve compaction. Additional testing should be performed to evaluate compaction. SUBDRAIN INSTALLATION Subdrains should be installed in approved ground in accordance with the approximate alignment and details indicated by the geotechnical consultant. Subdrain locations or materials should not be changed or modified without approval of the geotechnical consultant. The geotechnical consultant may recommend and direct changes in subdrain line, grade, and drain material in the field, pending exposed conditions. The location of constructed subdrains, especially the outlets, should be recorded/surveyed bythe 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 othenwise approved, the cut portion ofthe slope should be observed by the geotechnical consultant priorto placement of materials for construction ofthe fill portion ofthe slope. The geotechnical consultant should observe all cut slopes, and should be notified bythe 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 Shea Homes Limited Partnership _ Appendix B File:e:\wp12\6600\6649a.gue GeoSoilS, InC. Page 6 make appropriate recommendations for mitigation ofthese conditions. The need for cut slope buttressing or stabilizing should be based on in-grading evaluation by the geotechnical consultant, whether anticipated or not. Unless othenwise 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 bythe project civil engineer and should be constructed in compliance with the ordinances ofthe controlling governmental agencies, and/or in accordance with the recommendations ofthe 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 orfilling should be undertaken without prior notification ofthe 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 ofthe 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: Shea Homes Limited Partnership _ Appendix B File:e:\wp12\6600\6649a.gue GeoSoilS, InC. Page 7 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 Fiags: 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 belowthe 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 ofthe fill as soon as possible following testing. The technician's vehicle should be parked at the perimeter ofthe fill in Shea Homes Limited Partnership _ Appendix B File:e:\wp12\6600\6649a.gue GcoSoilS, InC. Page 8 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 ofthe contractor'sfailureto complywith any ofthe 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. Shea Homes Limited Partnership . Appendix B File:e:\wp12\6600\6649a.gue GCOSOllS, InC. Page 9 Toe of slope as shown on grading plan Natural slope to be restored with compacted fill Proposed grade i T 2-foot minimum in bedrock or approved earth material Backcut varies Bedrock or ap 2-Percent al 15-foot minimum or —H/2 where H is the slope height Subdrain geotechnical consultant NOTES: 1. Where the natural slope approaches or exceeds the design slope ratio, special recommendations would be provided by the geotechnical consultant. 2. The need for and disposition of drains should be evaluated by the geotechnical consultant, based upon exposed conditions. GeoSoiiSf Inc. FILL OVER NATURAL (SIDEHILL FILL) DETAIL Plate B-7 Cut/fill contact as shown on grading plan Proposed grade Subdrain as recommended by geotechnical consultant Bedrock or approved native material NOTE: The cut portion of the slope should be excavated and evaluated by the geotechnical consultant prior to construction of the fill portion. Ge0B(&Ukf lnc. FILL OVER CUT DETAIL Plate B-8 Natural slope Proposed finish grade Typical benching (4-foot minimum) Compacted stablization Bedrock or other approved native material If recommended by the geotechnical consultant, the remaining cut portion of the slope may require removal and replacement with compacted fill. Subdrain as recommended by geotechnical consultant NOTES: 1. Subdrains may be required as specified by the geotechnical consultant. 2 W shall be equipment width (15 feet) for slope heights less than 25 feet. For slopes greater than 25 feet, W shall be evaluated by the geotechnical consultant. At no time, shall W be less than H/2, where H is the height of the slope. Creo5»dllS) Inc. STABLIZATION FILL FOR UNSTABLE MATERIAL EXPOSED IN CUT SLOPE DETAIL Plate B-9 Proposed finish grade Natural grade Bedrock or approved native material Typical benching (4-foot minimum) 2-foot minimum key depth or H/2 if H>30 feet Subdrain as recommended by geotechnical consultant NOTES: 1. 15-foot minimum to be maintained from proposed finish slope face to backcut. 2. The need and disposition of drains will be evaluated by the geotechnical consultant based on field conditions. 3. Pad overexcavation and recompaction should be performed if evaluated to be necessary by the geotechnical consultant. Ge^Ststiis, Inc. SKIN FILL OF NATURAL GROUND DETAIL Plate B-10 Natural grade Subgrade at 2 percent gradient, draining toward street Typical benching Bedrock or approved native material 3- to 7-foot minimum* overexcavate and recompact per text of report CUT LOT OR MATERIAL-TYPE TRANSITION Proposed pad grade Natural grade Typical benching (4-foot minimum) Bedrock or approved native material 3- to 7-foot minimum* overexcavate and recompact per text of report * Deeper overexcavation may be recommended by the geotechnical consultant in steep cut-fill transition areas, such that the underlying topography is no steeper than 3:1 (H V) CUT-FILL LOT (DAYLIGHT TRANSITION) Ge&Scits^ Inc. TRANSITION LOT DETAILS Plate B-12 MAP VIEW NOT TO SCALE SEE NOT ES Concrete cut-off wall B Top of slope 4-inch perforated subdrain pipe (transverse) Gravity-flow, nonperforated subdrain pipe (transverse) Toe of slope 4-inch perforated subdrain pipe (longitudinal) B' Direction of drainage 2-inch-thick sand layer CROSS SECTION VIEW NOT TO SCALE SEE NOTES Coping Pool encapsulated in 5-foot thickness of sand Vapor retarder 6-inch-thick gravel layer 4-inch perforated subdrain pipe layer Gravity-flow nonperforated subdrain pipe ^Concrete cut-off wall Vapor retarder Perforated subdrain pipe NOTES: 1. 6-inch-thick, clean gravel i% to 1)^ inch) sub-base encapsulated in Mirafi MON or equivalent, underlain by a 15-mil vapor retarder, with 4-inch-diameter perforated pipe longitudinal connected to 4-inch-diameter perforated pipe transverse. Connect transverse pipe to 4-inch-diameter nonperforated pipe at low point and outlet or to sump pump area. 2. Pools on fills thicker than 20 feet should be constructed on deep foundations; otherwise, distress (tilting, cracking, etc.) should be expected. 3. Design does not apply to infinity-edge pools/spas. TYPICAL POOL/SPA DETAIL SIDE VIEW Test pit TOP VIEW Flag GSoS^ilSf Inc. TEST PIT SAFETY DIAGRAM Plate B-20