Loading...
HomeMy WebLinkAboutMS 11-02; SOHAEI MINOR SUBDIVISION; FINAL SOILS REPORT; 2016-02-17Geotechnical C Geologic C Coastal C Environmental 5741 Palmer Way C Carlsbad, California 92010 C (760) 438-3155 C FAX (760) 931-0915 C www.geosoilsinc.com February 17, 2016 W.O. 6649-B-SC Shea Homes Limited Partnership 9990 Mesa Rim Road, Suite 200 San Diego, California 92121 Attention:Ms. Sarah Morell Subject:Interim Compaction Report, Lots 14 and 15, Lanai Project (Miles Pacific Subdivision), Carlsbad, California, City of Carlsbad Project No.: CT 12-01, Drawing No.: DWG 483-4A Dear Ms. Morrell: In accordance with your request and authorization, GeoSoils, Inc. (GSI) presents this interim compaction report of grading for the subject lots. With the exception of the subject lots, grading for the encompassing tract commenced in late August 2015 and was substantially completed in November 2015. A summary of the geotechnical observation and testing during grading of the overall subdivision is provided in GSI (2016b [see the Appendix]). Unless specifically superceded herein, the conclusions and recommendations in the referenced geotechnical reports prepared by this firm (see the Appendix) remain valid and applicable and should be appropriately implemented during the balance of construction Grading of the subject lots generally occurred between August 2015 and January 2016. Earthwork performed during the process of grading for Lots 14 and 15 involved the mitigation of environmentally impacted soils, as summarized in GSI (2016b). Subsequently, the subject lots were overexcavated to at least 3½ to 4½ feet below pad grade. Fill materials generated from the onsite excavations (i.e., foundation excavations, underground utility trenches, and grading for pavement structural sections) were placed within the lots on a periodic basis until finish grade was achieved. The fill materials were moisturized and mixed to achieve at least optimum moisture conditions and mechanically compacted to at least 95 percent of the laboratory standard (ASTM D 1557), where tested. Observation and testing during grading of the subject lots was performed on a part-time, as-needed basis, as solely determined by your field representatives. Engineering Geology The geologic conditions exposed in excavations, during the process of planned and remedial grading for the subject lots, were observed by a representative from our firm. Earth materials, encountered during grading, consisted of localized areas of undocumented fill, Quaternary-age colluvium, and Quaternary-age paralic deposits. GeoSoils, Inc. Shea Homes Limited Partnership W.O. 6649-B-SC Lots 14 and 15, Lanai Project February 17, 2016 File:e:\wp12\6600\6649b.icr2 Page 2 Evidence of adverse geologic structures was not observed in the earthwork excavations. In general, the geologic conditions exposed during grading, were similar to those described in geotechnical reports prepared for the design phase of project development. The as-built geologic conditions within the subject lots are shown on Figure 1, which uses the 20-scale grading plan prepared by bHA, Inc. (2015a) as a base. Groundwater The regional groundwater table was not encountered within the earthwork excavations, completed in the subject lots; and therefore, is not anticipated to a major factor in the future performance of the currently planned improvements, provided the recommendations contained in this report are properly incorporated into the balance of construction and post-development landscape practices. Due to the nature of the site earth materials, perched groundwater conditions may manifest in the future along zones of contrasting permeabilities and densities (i.e., engineered fill/ paralic deposit contacts, fill lifts, geologic discontinuities, etc.) as a result of excessive precipitation, over-irrigation, and/or damaged underground utilities. The potential for perched groundwater occurrence should be anticipated and disclosed to all interested/affected parties. Should such conditions occur in the future, GSI could provide recommendations for mitigation, upon request. Field Testing 1.Field density tests were performed using the nuclear method in general accordance with ASTM D 6938-10 (Procedure A), and the sand cone method in general accordance with ASTM D 1556. The compaction test results are presented in the attached Table 1. The approximate locations of the field density tests performed during grading operations are presented on Figure 1. 2.The field dry densities of the engineered fill were evaluated as a percentage of the maximum dry density attained in the laboratory for the representative soil types encountered during grading. Where field density testing indicated inadequate compaction, the failure area was reworked until at least 95 percent of the laboratory standard (ASTM D 1557) was achieved. 3.Field density tests were taken at periodic intervals and random locations to check the compaction of the engineered fill placed by the contractor. 4.In general, the thickness of fill placed across the subject lots during grading was on the order of ±3½ to ±4½ feet, with the thicker fills occurring on Lot 14. GeoSoils, Inc. Shea Homes Limited Partnership W.O. 6649-B-SC Lots 14 and 15, Lanai Project February 17, 2016 File:e:\wp12\6600\6649b.icr2 Page 4 Laboratory Testing Maximum Dry Density/Optimum Moisture Content The maximum density and optimum moisture content were evaluated for the major soil types encountered during grading of the subject lots. Testing was performed in general accordance with the laboratory standard, ASTM D 1557. The moisture-density relationships obtained for these soils are shown on the following table: SOIL TYPES MAXIMUM DENSITY (PCF) OPTIMUM MOISTURE CONTENT (%) A - Brown Silty Sand 131.0 10.0 B - Brown Silty Sand 127.0 10.5 Expansion Index Expansion index (E.I.) testing was performed on a representative soil sample, exposed near finish grade. Testing and expansion potential classification was performed in general accordance with ASTM D 4829. The result of expansion testing is indicated in the following table: SAMPLE LOCATION AND DEPTH (FT)EXPANSION INDEX CBC CLASSIFICATION Lot 14 @ Finish Grade (Represents Lots 14 and 15)<5 Very Low Corrosion Testing (Saturated Resistivity, pH, and Soluble Sulfates, and Chlorides) Testing was performed on a representative sample of soils exposed near finish grade to evaluate saturated resistivity, pH, and soluble sulfates and chlorides. The testing was performed in general accordance with California Test Methods (CTM) 417, 422, and 532 (643). The results of the testing are provided in the following table: SAMPLE LOCATION AND DEPTH (FT)pH SATURATED RESISTIVITY (ohm-cm) SOLUBLE SULFATES (% by weight) SOLUBLE CHLORIDES (ppm) Lot 14 @ Finish Grade (Represents Lots 14 and 15)7.41 1,950 0.0085 80 GeoSoils, Inc. Shea Homes Limited Partnership W.O. 6649-B-SC Lots 14 and 15, Lanai Project February 17, 2016 File:e:\wp12\6600\6649b.icr2 Page 5 Corrosion testing indicates that the site soils are mildly alkaline with respect to soil acidity/alkalinity; are corrosive to exposed, buried metals when saturated; present negligible (“not applicable” per Table 4.2.1 of American Concrete Institute 318-11) sulfate exposure to concrete, and the soluble chloride content is somewhat elevated. Any metal building components in contact with the onsite soils should be protected from the corrosive effects of the onsite soils. Typical mitigation would include code-compliant concrete cover for steel reinforcement, wrapping buried metal piping in corrosion resistant tape or membranes, sleeving buried metal piping in plastic conduit, or the use of cathodic protection. GSI does not consult in corrosion engineering. Therefore, additional comments and recommendations should 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. CONCLUSIONS Based on our observations and field density test results, grading within Lots 14 and 15 of Tract CT 12-01 has been performed in general accordance with GSI recommendations and engineered fills have been compacted to at least 95 percent of the laboratory standard (ASTM D 1557), where tested. Therefore, it is our opinion that the subject lots are suitable for their intended use from a geotechnical perspective. Additional criteria for development are provided in GSI (2016b). RECOMMENDATIONS Foundations Owing to the very low expansion potential of soil exposed near finish grade of the subject lots, foundations for the residential structures, planned thereon, should conform to Foundation Category IA of the approved foundation plans for the project (Suncoast Post-Tension, Ltd., 2015a). Due to the variability of onsite soil expansion characteristics, the Client should consider pre-moisturizing slab subgrade soils on the lots. The slab subgrade should be pre-moisturized to at least the soil’s optimum moisture content to a depth of 12 inches below finish grade. The slab subgrade moisture content should be evaluated by GSI within 72 hours of the placement of the underlayment sand and vapor retarder. REGULATORY COMPLIANCE The soil engineering and engineering geologic aspects of the construction are in general compliance with approved geotechnical report and geotechnical aspects of the GeoSoils, Inc. As defined in the California Business and Professions Code, Division 3, Chapter 15, Article 5,1 Section 8770.6. Shea Homes Limited Partnership W.O. 6649-B-SC Lots 14 and 15, Lanai Project February 17, 2016 File:e:\wp12\6600\6649b.icr2 Page 6 construction. Furthermore, with respect to the grading plans, GSI will certify that the soil1 engineering and engineering geologic aspects of the grading are in general compliance with the approved geotechnical report and the grading plan (bHA, 2015a). LIMITATIONS 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 (such as site walls), 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 project. All samples will be disposed of after 30 days, unless specifically requested by the client, in writing. GeoSoils, Inc. Shea Homes Limited Partnership W.O. 6649-B-SC Lots 14 and 15, Lanai Project February 17, 2016 File:e:\wp12\6600\6649b.icr2 Page 7 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. John P. Franklin David W. Skelly Engineering Geologist, CEG 1340 Civil Engineer, RCE 47857 Ryan B. Boehmer Project Geologist RBB/JPF/DWS/jh Attachments:Table 1 - Field Density Test Results Appendix - References Distribution:(3) Addressee (wet signed, via email) (1) bHA, Inc., Attention: Mr. Dale Clark (via email) (1) Suncoast Post-Tension, Ltd., Attn: Mr. Derek Beckman (via email) Table 1 FIELD DENSITY TEST RESULTS TEST DATE TEST LOCATION TRACT ELEV MOISTURE DRY REL TEST SOIL NO.NO.OR CONTENT DENSITY COMP METHOD TYPE DEPTH (ft)(%)(pcf)(%) GRADING 128 11/4/15 Lot 14 CT 12-01 93.5 10.6 122.2 96.2 ND B 129 11/4/15 Lot 14 CT 12-01 94.5 10.7 121.7 95.8 ND B 130 11/4/15 Lot 15 CT 12-01 93.0 10.6 121.2 95.4 ND B 134 12/17/15 Lot 14 CT 12-01 94.5 12.6 125.1 95.4 ND A 135 12/18/16 Lot 14 CT 12-01 95.0 10.7 126.3 96.4 ND A 138 1/26/16 Lot 14 CT 12-01 94.5 10.1 126.0 96.7 ND A 139 1/26/16 Lot 14 CT 12-01 95.5 10.6 123.9 97.5 SC B 140 1/27/16 Lot 15 CT 12-01 93.5 10.1 124.6 95.1 ND A 141-FG 1/27/16 Lot 14 CT 12-01 96.0 10.2 129.9 99.2 ND A 142 1/27/16 Lot 15 CT 12-01 94.0 10.7 122.4 96.3 ND B 143-FG 1/28/16 Lot 15 CT 12-01 95.0 10.1 124.8 95.2 ND A LEGEND: FG =Finish Grade ND =Nuclear Densometer SC =Sand Cone Shea Homes Limited Partnership Lanai Subdivision, Carlsbad File:e:\wp12\6600\6649b.icr.lots14-15 GeoSoils, Inc. W.O. 6649-B-SC February 2016 Page 1 GeoSoils, Inc. APPENDIX REFERENCES American Concrete Institute, 2011, Building code requirements for structural concrete (ACI 318-11) and commentary, reported by ACI Committee 318, dated January. _____, 2008, Building code requirements for structural concrete (ACI 318-08) and commentary, reported by ACI Committee 318, dated January. _____, 2004, Guide for concrete floor and slab construction: reported by ACI Committee 302; Designation ACI 302.1R-04, dated March 23. American Society of Civil Engineers, 2010, Minimum design loads for buildings and other structures, ASCE Standard ASCE/SEI 7-10. bHA, Inc., 2015a, Grading plans for: Miles Pacific subdivision, 9 sheets, 20-scale, Drawing No. 483-4A, City of Carlsbad Project No.: 12-01, latest date of July 30. _____, 2015b, Grading plans for: Sohaei Minor subdivision, 4 sheets, 20-scale, Drawing No. 483-5A, City of Carlsbad Project No.: 12-01, latest date of April 10. 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. GeoSoils, Inc., 2016a, Pavement design report, Lanai Court and Moana Place, Lanai Project (Formerly Miles Pacific Subdivision), CT 12-01, Carlsbad, San Diego County, California, W.O. 6649-E-SC, dated January 6. _____, 2016b, Compaction report of grading, Lanai Subdivision (former Miles Pacific and Sohei Subdivisions), Carlsbad, San Diego County, California, City of Carlsbad Project Nos.: CT 12-01 and MS 11-02, W.O. 6649-B-SC, dated January 6. _____, 2015a, Pavement design report, Esmat Way, Lanai Project (Formerly Sohaei Minor Subdivision), MS 11-02, Carlsbad, San Diego County, California, W.O. 6649-E-SC, dated December 21. _____, 2015b, Interim compaction report, Lots 2 and 3, Lanai Project (Miles Pacific Subdivision), Carlsbad, California, City of Carlsbad Project No.: CT 12-01, Drawing No.: DWG 483-4A, W.O. 6649-B-SC, dated November 11. _____, 2015c, Preliminary as-graded lot conditions, Lanai Project (Miles Pacific Subdivision and Sohaei Minor Subdivision), Carlsbad, California, W.O. 6649-B-SC, dated November 10. GeoSoils, Inc.Shea Homes Appendix File:e:\wp12\sc6600\6649b.icr2 Page 2 _____, 2015d, Second foundation and post-tension plan review, Lanai Project (Miles Pacific Subdivision and Sohaei Minor Subdivision), Carlsbad, California, W.O. 6649-A7-SC, dated September 18. _____, 2015e, Foundation and post-tension plan review, Lanai Project (Miles Pacific Subdivision and Sohaei Minor Subdivision), Carlsbad, California, W.O. 6649-A6-SC, dated September 8. _____, 2015f, Geotechnical recommendations for mat slabs, Lanai Project, 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-A5-SC, dated July 15. _____, 2015g, 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, W.O. 6649-A4-SC, dated June 29. _____, 2015h, 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. _____, 2014, 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. _____, 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. Kanare, Howard, M., 2005, Concrete Floors and Moisture, Engineering Bulletin 119, Portland Cement Association. Post-Tensioning Institute, 2008, Addendum no. 2 to the 3 edition of the design ofrd post-tensioned slabs-on-ground, dated May. _____, 2004, Design and construction of post-tensioned slabs-on-ground, 3 edition,rd Phoenix, AZ. State of California, 2016, Civil Code, Sections 895 et seq. GeoSoils, Inc.Shea Homes Appendix File:e:\wp12\sc6600\6649b.icr2 Page 2 Suncoast Post-Tension Ltd., 2015a, Project: Lanai, Location: Carlsbad, CA, Builder: Shea Homes, Job No. 15-6414, latest revision dated July 28. _____, 2015b, Post Tension Foundation Calculation for: Shea Homes, Lanai, Carlsbad, CA, Job # 6414, dated July 10.