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HomeMy WebLinkAboutCT 02-16; ROBERTSON RANCH; COMPACTION REPORT OF BUILDING PAD RE-CERTIFICATION; 2010-12-13UT 0 2-\ —J_--' Geotechnical . Geologic. Coastal . Environmental 5741 Palmer Way • Carlsbad, California 92010 • (760) 438-3155 • FAX (760) 931-0915 www.geosoilsinc.com December 13, 2010 W.O. 5954-B-SC William Lyon Homes, Inc. 4490 Von Karman Avenue Newport Beach, California 92660 Attention: Mr. John Lux Subject: Compaction Report of Building Pad Re-certification, Lots 270 through 274, and 294 through 298, Phase 3 of Blossom Grove, Planning Area 18, Robertson Ranch Development, City of Carlsbad, San Diego County, California References: 1. "Report of Rough Grading, Planning Area 18 of Robertson Ranch, East Village (Lots 195 through 304, and 309) Carlsbad Tract 04-26, Drawing 453-8A, Carlsbad, San Diego County, California," W.O. 5353-131-SC, dated September 17, 2008, by GeoSoils, Inc.. "Discussion of Building Slab Subgrade Pre-Wetting, Planning Area 18 of Robertson Ranch, City of Carlsbad, California. Dated October 8, 2009, by GeoSoils, Inc. "California Building Code," dated 2007, by California Building Standards Commission. "California Building Code," dated 2001, by International Conference of Building Officials. Dear Mr. Lux: GeoSoils, Inc. (GSI) is providing this summary of our observation and testing services of grading within Lots 270 through 274, and 294 through 298, Phase 3 of Blossom Grove, Planning Area 18, at the Robertson Ranch Subdivision in the City of Carlsbad, California. Planning Area 18 was initially graded with observation and testing services provided by GSI (see Reference No. 1). The purpose of remedial grading was to re-condition the building pads in general accordance with Reference No. 2. Remedial grading consisted re-processing surficial soils, moisture conditioning, and compacting the soil to a minimum relative compaction of 90 percent per ASTM D 1557. Based on our observations and testing, the building pads appear to have been prepared in general accordance with the recommendations provided by this office (see Reference Nos. 1 and 2), and are considered suitable for their intended use, from a geotechnical viewpoint. Field Observation and Testing As previously indicated, the purpose of grading was to re-condition the subject building pads in general accordance with recommendations presented in Reference No. 2. In general, remedial earthwork consisted of reprocessing near surface soils in place, within Lots 294 through 298. Within Lots 270 through 274, the upper 12 inches was removed and the exposed bottom processed in place. These lots were then brought back to grade with properly compacted fill, in accordance with ASTM Dl 557. GSI was onsite on an as-needed, part-time bases, as solely determined by the client/contractor. Field density tests were performed using nuclear (densometer) ASTM test methods D 2922 and D 3017. The test results taken during grading operations are presented in the attached copies of our "Field Testing Report(s)." The laboratory maximum dry density and optimum moisture content for the major soil type within this construction phase were determined according to test method ASTM D 1557. The following table presents the results: - - SOIL TYPE MAXIMUM DENSITY(PCF) MOISTURE CONTENT (PERCENT) A - Brown, Silty SAND 127.0 10.0 L - Gray, Clayey SAND 121.0 12.5 S - Yellowish Gray, SAND w/CLAY 124.0 11.0 Where tested, field compaction testing indicates that the soils appear to meet the minimum compaction requirements previously established and adopted by the City of Carlsbad ([2007 California Building Code] i.e., at least 90 percent relative compaction per ASTM D 1557), and testing also indicates adequate soil moisture. However, based on the expansive character of site soils (see Reference No. 1), and the anticipated additional time that will pass prior to slab construction, additional moisture conditioning and verification will likely be necessary prior to placement of the underslab vapor retarder (see Table A, Note 11, and Page 11 of Reference No. 1). Soil Expansion, and Corrosion Potential A review of Reference No. 1 indicates that low expansive soils underlie Lots 294 through 298 (expansion index >20, <50), and medium expansive soils underlie Lots 270 through 274 (expansion index >50, <90), as classified by 2001 California Building Code ([CBC], International Conference of Building Officials [ICBO], 2001), Table 18-I-B. Please note that GSl utilizing this previous CBC code only to classify the soils, as the 2007 CBC (California Building Standards Commission [CBSC], 2007) does not provide this index. Corrosion William Lyon Homes W.O. 5954-13-SC Lots 270-274, 294-298, PA-18, Robertson Ranch December 13, 2010 FiIe:e:\wp12\5900\5954b.ph3 Page 2 GeoSoils, Inc. testing of soils within 3 feet of finish grade indicate that these soils present a negligible (sulfate class SO) sulfate exposure to concrete, per Table 4.2.1 and 4.3.1 of the American Concrete Institute (ACI) document 318-08 (2007 CBC [CBSC, 2007]). Soils are relatively neutral with respect to soil acidity/alkalinity (pH of 6.8), and are considered corrosive to exposed ferrous metals in a saturated state. The chloride ion content in soil was also noted to generally be below action levels (300 ppm [see Reference No. 1]). It is our understanding that standard concrete cover over reinforcing steel is usually appropriate for these conditions; however, a corrosion engineer should be consulted to provide specific recommendations regarding foundations and piping, etc. Foundation Design/Construction Based on a review of Reference No. 1 and observations/testing performed during this phase of site grading, foundations should be designed and constructed in accordance with recommendations presented in Reference No. 1 for Category I post-tension foundations within Lots 294 through 298, and Category II post-tension foundations for Lots 270 through 274. SI should review the foundation plans, prior to construction. As of this date, the pad conditions have not changed significantly from a geotechnical standpoint since the completion of grading. Unless specifically superceded herein, the geotechnical findings, conclusions, and recommendations presented in Reference No. 1 are generally considered valid and applicable with respect to the construction and development of the subject building pads. Based on the potential duration of time following pad completion, pre-wethng/saturation is recommended prior to construction, as indicated in the referenced GSl'reports. Closure The materials encountered on the project site and utilized for our analysis are believed representative of the area; however, soil and bedrock materials vary in character between excavations and natural outcrops or conditions exposed during mass grading. Site conditions may vary due to seasonal changes or other factors. Inasmuch as our study is based upon our review and engineering analyses and laboratory data, the conclusions and recommendations are professional opinions. These opinions have been derived in accordance with current standards of practice, and no warranty, either express or implied, is given. Standards of practice are subject to change with time. GSI assumes no responsibility or liability for work or testing performed by others, or their inaction; or work performed when GSl 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. William Lyon Homes W.O. 5954-B-SC Lots 270-274, 294-298, PA-18, Robertson Ranch December 13, 2010 File:e:\wpl2\5900\5954b.ph3 Page 3 GeoSoils, Inc. -I 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 134 ' No.G 23 0 33 Geologist 0 Robert G. Crisman Andrew TllI OF Eg Engineering Geologis ," 4 Geotechnical Engineer, RCG/ATG/JPF/jh Attachment: "Field Testing Reports" Distribution: (4) Addressee William Lyon Homes . Lots 270-274,.294-298, PA-1 8, Robertson Ranch Filé:e:\wpl2\5900\5954b.ph3 - GeoSoils, Inc. W.O. 5954-B-SC December 13, 2010 Page FIELD TESTING REPORT wo# 5954 C SC DATE 12107/10 NAME TODD '.. 0 4 HOURS 3 0 cL:IENv.: - ___..WILLIAM LYON TRACT PA-18 LOCATION CARLSBAD PER JOHNLUX __CONTRACTOR .SCM 0 0•' 00 ? EQUIP 1 LOADER 1-SKIP LOADER 4LOT RECERTIFICATION TESTt LOCATION . EL. Or DEPTH MOISTURE CONTENT% DRY DENSITY % RELATIVE COMPACTION TEST TYPE SOIL TYPE LOT274. 75.0 20.0% 100.6 90.6% ND L LOT 294 75.0 12.2% 114.7 92.5% ND S 50FG .LOT 295 74.0 11.9% 111.8 90.2% ND S LOT 296 . 74.5 12.0% 112.5 90.7% ND S ;52FG . LOT297 74.5 11.5% 111.7 90.1%. ND S 53F°G.I -, ........LOT 298 75.0 12.6% 112.0 90.3% ND s to. •. . _______ _______ LOTS 270-2 73 . ° . •00• 0 0 • O°0 A 0••0 00 j COMMENTS ON SITE AT CLIENTS REQUEST TO OBSERVE SITE GRADING RELATED TO PAD RECERTIFICATION TEST RESULTS MEET OUR RECOMMENDATIONS RECOMMEND CONTRACTOR EXTEND THE THE REPROCESSED AREA ON THE BACK SIDE OF LOTS 270-273 TO COMPLY WITH OUR RECOMMENDATIONS REGARDING OX ENVELOPE.. GeoSoils, Inc. BY: %4'24. PAGE: 1 OF 1 This field report presents a summary of observation and testing by Geosoils, Inc. personnel. Our work does not include supervision or direction of the actual work of the contractor, his employees, dr agents. The contractor should be informed that neitherth'é presence of our field representative, nor the observation and testing by our firm, shall excuse him in anyway for defects discovered in his work. It, is understood that our firm will not be responsible for job or site safety on this project. . FIELD TESTING REPORT Wo# 5954CSC DATE 12/08/10 NAME TODD HOURS 35 CLIENT WILLIAMLYON TRACT _PA_18 LOCATION CARLSBAD SUPER JOHNLUX ___CONTRACTOR __SCM 1-LOADER 1-SKIP LOADER TEST NO$ LOCATION . • EL Or DEPTH MOISTURE CONTENT% DRY DENSITY % RELATIVE COMPACTION TEST TYPE SOIL TYPE ______ LOT 272. 75.0 11.4%. 116.0 91.3% ND A LOT 270 • 750 20.1% 101.8 91.7% ND L wt N. J. 244 _ft :COMMENTS: •.. • • • S N SITE TO PERFORM OBSERVATION AND TESTING OF PAD RECERT J , EARTHWORK. TEST RESULTS MEET OUR RECOMMENDATIONS. GeoSoils, Inc. BY: PAGE: 1 OF 1 This field report presents a summary of observation and testing by Geosoils, Inc. personnel. Our work does not include supervision or direction of the actual work of the contractor, his employees, or agents. The contractor should be informed that neither the presence f our field representative, nor the observation and testing by our firm, shall excuse him in anyway for defects discovered in his wortc. t is understood that our firm will not be responsible for job or site safety on this project. FIELD TESTING REPORT wo# 5954 c Sc DATE 12109/10 NAME TODD HOURS:4 ............ ................................. .CLIENT .Y. . WILLIAM LYON TRACT PA-18 LOCATION CARLSBAD SUPER JOHNLUX __CONTRACTOR SCM EQUIP 1 SKIP LOADER 7:..PP RECERTIFICATION .: TESP LOCATION EL Or DEPTH MOISTURE CONTENT% DRY DENSITY % RELATIVE COMPACTION TEST TYPE SOIL TYPE 56, 1 .. LOT : 753 19.9% 95.6 86.1% ND L 6A'.' :.. . LOT 274 - 75.3 19.6% 102.0 91.9% ND L '..'. LOT 271 75.0 12.1% 115.7 91.1% ND A 58EG- LOT 273 . 75.3 1 11.5% 114.8 90.4% ND A .'..; .LOT 272 75.3 11.7% 115.0 90.6% ND A G:i ..............L0T271 . 75.4 12.2% 114.4 0.1% ND A 61FGs . LOT 270 75.4 19.8% 100.6 90.6% ND L 62FG .:.•..... _LOT 274 75.5 19.2% 100.0 90.1% ND L COMMENTS: ON SITE AT CLIENT'S REQUEST TO OBSERVE SITE EARTHWORK RELATED TO THE RECERTIFICATION OF LOTS 270-274. TESTS AND RETESTS MEET OUR RECOMMENDATIONS REGARDING RELATIVE COMPACTION AND WATER CONTENT. E AND GRADE FOR BUILDING ENVELOPE DETERMINED BY CONTRACTOR. GeoSoils, Inc. I BY: PAGE: 1 OF 1 . ........ This field report presents a summary of observation and testing by Geosoils, Inc.personneI. Our work does not include supervision or direction of the actual. work of the contractor, his employees, or agents. The contractor should be informed that neither the presence of our field representative, nor the observation and testing by our firm, shall excuse him in anyway for defects discovered in his work. It is understood that our firm will not be responsible for job or site safety on this project.