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HomeMy WebLinkAboutCT 06-25; ROBERTSON RANCH EAST VILLAGE PA 21; GEOTECHNICAL UPDATES & COMPACTION TESTING;t '1 5741 Palmer Way Carlsbad, California 92010 (760) 438-3155 FAX (760) 931-0915 www.geosoilsinc.com W.O. 5981 -B-SC D.R. Horton do REDP 3549 Summit Trail Court Carlsbad, Carlsbad 92010 Attention: Mr. Kurt Hubbell Subject: Geotechnical Update for Planning Area 21, Robertson Ranch, East Village, City of Carlsbad, San Diego County, California References: 1. "Discussion of Building Slab Subgrade Pre-Wetting, Planning Area 21 of Robertson Ranch, City of Carlsbad, California," W.O. 5949-C-SC, dated January 21, 2010, by GeoSoils, Inc. "Report of Rough Grading, Planning Area 21 of Robertson Ranch, East Village Carlsbad, San Diego County, California," W.O. 5953-131-SC, dated November 24, 2008,. by GeoSoils, Inc. "California Building Code, California Code of Regulations, Title 24, Part 2, Volume 2 of 2, Based on the 2009 International Building Code, 2010 California Historical Building Code, Title 24, Part 8; 2010 California Existing Building Code, Title 24, Part 10," dated 2010, by the California Building Standards Commission. Dear Mr. Hubbell: In accordance with your request, GeoSoils, Inc. (GSI) has reviewed the referenced reports with respect to as-graded site conditions and have prepared this summary update report. Grading and processing of original ground within the subject building pads was observed and selectively tested by a representative of GSI during the earthwork phase of development for the subject property (see Reference No. 2). Based on our recent observations and testing, the subject lots are considered suitable for their intended residential use. Geotechnical observations and testing completed bythis office during site grading are summarized in Reference No. 2. As of this date, the remaining, undeveloped building pads have not changed significantly since the completion of grading and the issuance of Reference No. 2; thus, the findings, conclusions, and recommendations presented in that report are generally considered valid and applicable with respect to the construction and development of the subject building pads, and the current building code (see Reference No. 3) . ,'Based- an the duration of time following- pad completion, pre-wetting and/or surficial processing is recommended as indicated in Reference No 1 In addition to the recommendations presented in Reference No. 2, all foundation systems should be designed and constructed in accordance with guidelines presented in the latest edition of the CBC (Reference No. 3). Please note that Reference No. 2 referenced the 2007 Code; however, while some section numbers have changed from the 2007 Code to the 2010 CBC (see following table, and Reference No. 3), the geotechnical design parameters indicated in Reference No.2 are the same. Additional recommendations regarding peak horizontal ground acceleration and seismic surcharge are provided in the following sections. Seismic Shaking Parameters Based on the site conditions, the following table summarizes the site-specific design criteria obtained from the 2010 CBC (Reference No. 3), Chapter 16 Structural Design, Section 1613, Earthquake Loads, which is based on the 2009 edition of the IBC (International Building Code), and ASCE Standard 7-05 (American Society of Civil Engineers, 2005). The computer program Seismic Hazard Curves and Uniform Hazard Response Spectra, provided by the United States Geologic Survey (U.S.G.S.) was utilized for design. The short spectral response utilizes a period of 0.2 seconds. CBC SEISMIC DESIGN PARAMETERS I PARAMETER VALUE REFE16CE Site Class D Table 1613.5.2 Spectral Response - (0.2 sec), S 1.15g Figure 1613.5(1) Spectral Response - (1 sec), S 0.44g Figure 1613.5(2) Site Coefficient, F3 1.04 Table 1613.5.3(1) Site Coefficient, F3 1.56 Table 1613.5.3(2) Maximum Considered Earthquake Spectral Section 1613.5.3 Response Acceleration (0.2 sec), SMS 1.20g (Eqn 16-36) Maximum Considered Earthquake Spectral Section 1613.5.3 Response Acceleration (1 sec), SM1 068 g (Eqn 16-37) 5% Damped Design Spectral Response Section 1613.5.4 Acceleration (0.2 sec), SDS 0.79g (Eqn 16-38) 5% Damped Design Spectral Response Section 1613.5.4 Acceleration (1 sec), 046 . g (Eqn 16-39) GENERAL SEISMIC DESIGN PARAMETERS Distance to Seismic Source (Rose Canyon fault zone) 7.5 mi. (12.0 km) Upper Bound Earthquake (Rose Canyon fault zone) M 6 9** W D.R. Horton Planning Area 21, Robertson Ranch File:e:\wp9\5900\5981 b.guf.pa2l W.O. 5981-B-SC May 25, 2011 Page 2 Conformance to the criteria above for seismic design does not constitute any kind of guarantee or assurance that significant structural damage or ground failure will not occur in the event of a large earthquake. The primary goal of seismic design is to protect life, not to eliminate all damage, since such design may be economically prohibitive. Cumulative effects of seismic events are not addressed in the 2010 CBC (Reference No. 3) and regular maintenance and repair following locally significant seismic events (i.e., M5.0) will likely be necessary. Peak Horizontal Ground Acceleration A probabilistic peak horizontal ground acceleration (PHGA) of 0.28 g was evaluated forthis site (Reference No. 2). This value was chosen as it corresponds to a 10 percent probability of exceedence in 50 years (or a 475-year return period). Per the CBC (Reference No. 3), a PHGA of 0.39 was also evaluated. This value was chosen as it corresponds to a 2 percent probability of exceedence in 50 years (or a 2,475-year return period). Seismic Surcharge for Retaining Walls For retaining walls that are over 6 feet in height, or within 6 feet or less of residences, that may impede ingress/egress, GSI recommends that the walls be evaluated for a seismic surcharge (Section 1603.1 .5 of the 2010 CBC). If those conditions do not exist, evaluation of a seismic surcharge is not required. The site walls in this category should maintain an overturing Factor-of Safety (FOS) of about 1.3, when the seismic surcharge is applied. The seismic surcharge should be applied as a uniform load from the bottom of the footing (excluding shear keys), to the top of the backfill at the heel of the wall footing for restrained walls and an inverted triangular distribution for cantilever walls. This seismic surcharge pressure may be taken as 14H, where "H" is the dimension taken as the height of the retained material for the top of backfilL The resultant force should be applied at a distance 0.6H 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. LIMITATIONS Inasmuch as our study is based upon our review, engineering analyses, and laboratory data, these conclusions and recommendations are professional opinions. These opinions D.R. Horton W.O. 5981-B-SC Planning Area 21, Robertson Ranch May 25, 2011 FiIe:e:\wp9\5900\5981 b.gut.pa2l Page 3 GeoSofls, have been derived in accordance with current staridardsof practice, and no warranty is express or implied. 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. Site drainage is under the purview of the civil engineer. Use of this report constitutes an agreement and consent by the user to all the limitations Use above, notwithstanding any other agreements that may be in place. In addition, this report may be subject to review by the controlling authorities. The opportunity to be of service is greatly appreciated. If you have any questions, please do not hesitate to call our office. Respectfully su GeoSoils, Inc. G. \ tk. 1S4 CiJflad I \ Erjftwi1ng / Robert G. Engineering Geol RGC/ATG/JPF/jh Distribution: (4) Addressee Jo. Exp.f) /Andrewl. Guatelli Geotechnical Engineer, G 2320 D.R. Horton W.O. 5981-B-SC Planning Area 21, Robertson Ranch May 25, 2011 FiIe:e:\wp9\5900\5981 b.gul.pa2l Page 4 GcoSofls, Inc. Geotechnical • Geologic . Coastal . Environmental 5741 Palmer Way • Carlsbad, California 92010 • (760) 438-3155 • FAX (760)931-0915. www.geosoilsinc.com March 5, 2010 W.O. 5981 -C-SC D.R. Horton 1021 Costa Pacifica Way, Suite 2107 Oceanside, California 92054 Attention: Mr. Tom Lombardi Subject: Geotechnical Update and the Results of Compaction Testing for Production Phase 2, Lots 53 Through 56, and 65 Through 68, and Production Phase 3, Lots 57 Through 64, Planning Area 21, Robertson Ranch, East Village, Carlsbad Trabt 04-26, Drawing 453-8C, City of Carlsbad, San Diego County, California References: 1. "Report of Rough Grading, Planning Area 21 of Robertson Ranch, East Village Carlsbad, San Diego County, California," W.O. 5353-131-SC, dated November 24, 2008, by GeoSoils, Inc. "Memorandum: Discussion of Building Slab Subgrade Pre-Wetting, Planning Area 21 of Robertson Ranch, City of Carlsbad, California," W.O. 5981 -C-SC, dated January 6, 2010, by GeoSoils, Inc. "Grading plan for: Robertson Ranch, East Village PA 21," C.T. 06-25, 18 Sheets, Drawing No. 461-6A, Project No. C.T. 06-25, O'Day Job No. 011014, dated May 12, 2009, by O'Day Consultants, Inc. Dear Mr. Lombardi: In accordance with your request, GeoSoils, Inc. (GSl) has reviewed the referenced reports and plans (see above) with respect to the as-graded site conditions and has prepared this update report. Grading and processing of original ground within the subject building pads was observed and selectively tested by a representative of GSI during the rough earthwork phase of development for the subject property. A summary of observation and testing services provided during mass (rough) grading of the subject lots is presented in Reference No. 1. Based on the duration of time following pad completion (approximately 15 months), pre-wetting was recommended, as indicated in Reference No. 1. Owing to the passage of time, erosion, weathering, etc., some surlicial processing was also recommended (see Reference Nos. 1 and 2). Based on soil conditions evaluated within these lots, reprocessing of the building pads was recommended, and recently performed prior to foundation construction, in general accordance with recommendations presented in Reference No. 2. During reprocessing of Lots 53 through 68, GSI was onsite on an as-needed, part-time basis, as solely determined by the client/contractor. Field density (compaction) 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)." 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). Testing also indicates adequate soil moisture. 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 No. 2), and are considered suitable fortheir intended use. However, based on the medium expansive character of site soils within some of the subject lots (see Reference 1, Lots 53 through 60), and the anticipated additional time that will pass prior to slab construction, additional moisture conditioning and verification may be necessary prior to placement of the underslab vapor retarder (see Table A, Note 11, and Page 12 of Referenced No. 1), should the duration of the pads lying fallow exceed about 30 days. Unless superceded by recommendations presented herein, the conclusions and recommendations contained in our referenced reports remain pertinent and applicable. CLOSURE Inasmuch as our study is based upon our review, engineering analyses, and laboratory data, these conclusions and recommendations are professional opinions. These opinions have been derived in accordance with current standards of practice, and no warranty is express or implied. Standards of practice are subject to change with time. 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. D.R. Horton W.O. 5981-C-SC Lots 53-68, PA-21, Robertson Ranch March 5, 2010 File:e:\wp9\5900\5981 c.gua3 Page 2 GeoSoils, Inc. The opportunity to be of service is greatly appreciated. If you have any questions, please do not hesitate to call our office. Respectfully su GeoSoils, Inc. 1934 Ci)d / \ tr,cIneerirg / Robert-G. Crisma Engineering Geologist -134 RGC/ATG/J PF/jh Attachments: Field Testing Reports 0çOFESSiQ/" OF A T. ndrew Geotechnical Engineer, GE 2320 Distribution: (4) Addressee (Pick up) (1) Bausback Consulting, Attention: Mr. Kurt Bausback (E-mail) D.R. Horton W.O. 5981-C-SC Lots 53-68, PA-21, Robertson Ranch March 5, 2010 File:e:\wp9\5900\5981 c.gua3 Page 3 GeoSoils, Inc. ¶. 5 W.O. DATE ZI/.V NAME I HOURS 2. CLIENT Afh"TRACT______________ LOCATION SUPT. /AiJ CONTRACTOR EQUIPMENT I ~G'n B_V7'6r4'~ TEST NO. LOCATION ELEV. OR DEPTH MOISTURE CONTENT % DRY DENSITY P.C.F. % RELATIVE COMPACTION TEST TYPE SOIL TYPE jo;( /h!. '3' 90, / )( ar awp 1—Igge rS 37'_Pa'z. eo _'4/fl7 2M 4J/) B&?,i477J ,e- W-4 203 e i&i _7ar? vfi/e _ 77MT A4 $ ji k.#,i( ho i)_(uow2w., zi COMMENTS: GeoSoils, In. BY: PAGE OF This field report preseits a summary of observations and testing by Geosoils, Inc. personnel only where the tests were performed. 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 any way for defects discovered in his work. It is understood that our firm will not be responsible for job or site safety on this project. w.O.____ DATE NAME_____________ HOURS 3 CLIENT 4W hZ?VII TRACT PX LOCATION_____________________ SUPT. R4A1 CONTRACTOR EQUIPMENT 36 tAP7J LOCATION LE OR DEPTH MOISTURE CONTENT ___ % DRY DENSITY % RELATIVE P.C.F. COMPACTION Mz_L "IA ffiffl:n WA - N-1-A. M COMMENTS: GeoSoils, Inc. tO BY: PAGE. OF I This field report presents a summary of observations and testing by Geosoils, Inc. personnel only where the tests were performed. 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 any way 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 W.O. DATE ______________ NAME ' HOURS $ CLIENT IWA,eii TRACT LOCATION OAKUBAQ SUPT. _A'4' _Jnpg CONTRACTOR tIL i/*r EQUIPMENT 41A~'A & / TEST NO. LOCATION ELEV. OR DEPTH MOISTURE CONTENT % DRY DENSITY P.C.F. % RELATIVE COMPACTION TEST TYPE SOIL TYPE 4AP S-1;5_______________ ____ 9O I / /ce9i ________ ___ 17 18J /3 I?,:/2?,, -57 '79-z ~- it7ti IL 7 /sy ACO 71 4'zrp 74J &5r ____ 3 0 147P Moog ui iW COMMENTS: GeoScilsi In U) BY: PAGE / ______ This field report presents a summary of observations and testing by Geosoils, Inc. personnel only where the tests were performed. 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 any way for defects discovered in his work. It is understood that our firm will not be responsible for job or site safety on this project. Geotechnical • Geologic • Coastal • Environmental 5741 Palmer Way • Carlsbad, California 92010 (760) 438-3155 FAX (760) 931-0915 February 8, 2010 W.O. 5981 -C-SC D.R. Horton 1021 Costa Pacifica Way, Suite 2107 Oceanside, California 92054 Attention: Mr. Tom Lombardi Subject: Geotechnical Update and the Results of Campaction Testing for for Model Lots 1 through 3, Production Phase 1, Lots 7 through 12, and Temporary Parking Areas Within Lots 4 Through 6 of Planning Area 21, Robertson Ranch, East Village, Carlsbad Tract 04-26, Drawing 453-8C, City of Carlsbad, San Diego County, California References: 1. "Report of Rough Grading, Planning Area 21 of Robertson Ranch, East Village Carlsbad, San Diego County, California," W.O. 5353-131-SC, dated November 24, 2008, by GeoSoils, Inc. "Memorandum: Discussion of Building Slab Subgrade Pre-Wetting, Planning Area 21 of Robertson Ranch, City of Carlsbad, California," W.O. 5981-C-SC, dated January 6, 2010, by GeoSoils, Inc. "Grading plan for: Robertson Ranch, East Village PA 21," C.T. 06-25,18 Sheets, Drawing No. 461-6A, Project No. C.T. 06-25, O'Day Job No. 011014, dated May 12, 2009, by O'Day Consultants, Inc. Dear Mr. Lombardi: In accordance with your request, GeoSoils, Inc. (GSl) has reviewed the referenced reports and plans (see above) with respect to the as-graded site conditions and has prepared this update report. Grading and processing of original ground within the subject building pads was observed and selectively tested by a representative of GSI during the rough earthwork phase of development for the. subject property. A summary of observation and testing services provided during mass (rough) grading of the subject lots is presented in Reference No. 1. Based on the duration of time following pad completion (approximately 15 months), pre-wetting was recommended, as indicated in Reference No. 1. Owing to the passage of time, erosion, weathering, etc., some surficial processing was also recommended (see Reference Nos. 1 and 2). • Based on soil conditions evaluated within Lots 1 through 3, and 7 through 12, reprocessing of these pads was recommended, and recently performed prior to foundation construction on these lots in general accordance with recommendations presented in Reference No. 2. Lots 4 through 6 are planned to be used as temporary parking areas and were not reprocessed. During reprocessing of Lots 1 through., and 7 through 12, GSI was onsite on an as-need, part-time basis, as solely determined by the client/contractor. Field density (compaction) 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)." 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). Testing also indicates adequate soil moisture. 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 No. 2), and are considered suitable for their intended use. However, based on the medium expansive character of site soils (see Reference 1), and the anticipated additional time that will pass prior to slab construction, additional moisture conditioning and verification may be necessary prior to placement of the undersiab vapor retarder (see Table A, Note 11, and Page 12 of Referenced No. 1), should the duration of the pads lying fallow exceed about one month. Unless superceded by recommendations presented herein, the conclusions and recommendations contained in our referenced reports remain pertinent and applicable. CLOSURE Inasmuch as our study is based upon our review, engineering analyses, and laboratory data, these conclusions and recommendations are professional opinions. These opinions have been derived in accordance with current standards of practice, and no warranty is express or implied. Standards of practice are subject to change with time. 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. D.R. Horton W. 0. 5981 -C-SC Lots 1- 12, PA-21, Robertson Ranch • February 8, 2010 FUe:e:\wp9\5900\5981 c.gu2 Page 2 GeoSoils, Inc. The opportunity to be of service is greatly appreciated. If you have any questions, please do not hesitate to call our office. Respectfully sub rf%0 '\ / WGI?/\O GeoSoils, Inc. I !INo. I t Certified I ."It \Engineering / Geologist Robert G. Crisman N " Engineering Geologist, CEG 1934 FROW-0140-10., ;10" David W Skelly 4 Civil Engineer, RCE 4i - NO. RCE4?857 ! C vi CAU RGC/DWS/JPF/jh Attachments: Field Testing Reports Distribution: (4) Addressee (Pick up) (1) Bausback Consulting, Attention: Mr. Kurt Bausback (E-mail) D.R. Horton W.O. 5981 -C-SC Lots 1-12, PA721, Robertson Ranch February 8, 2010 File:e:\wp9\5900\5981 c.gu2 Page 3 GeóSoils, Inc. FIELD TESTING REPORT W.O. DATE NAME_____________ HOURS 1/ CLIENT R TRACT f LOCATION_____________________ SUPT. CM 6143/.,94e CONTRACTOR A EQUIPMENT /tY 2Z /8C4 hIsYIl[I]OR ELEV. DEPTH MOISTURE CONTENT _____ DRY DENSI % RELATIVE P.C.F. COMPACTION -, MEM ffliv M FEW,; 10T 119 "40W. 0 W-1-1 RIMM!Warl., FROM "4- 4 MR-1. COMMENTS: GeoSoils, mc If BY: PAGE ____________eF ( This field report presents a summary of observations and testing by Geosoils, Inc. personnel only where the tests were performed. 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 any way for defects discovered in his work. It is understood that our firm will not be responsible for job or site safety on this project. HELD TESTING REPORT W.O. DATE________ NAME_____________ HOURS CLIENT TRACT _____________________TRACT_ LOCATION SUPT TZI 1ZI't CONTRACTOR &L t2kr EQUIPMENT /JW4 /&'i hOZ34 I4 TEST NO. LOCATION ELEV. OR DEPTH MOISTURE CONTENT % DRY DENSITY P.C.F. % RELATIVE COMPACTION TEST TYPE SOIL TYPE 3 14&IZ Ii31 '/1 -c 1¼' jig *TMO Mq7 /I,/1f *iPi /724' '7Zf dWAAr i- ___d/697 £ P3 ?7fJ AITh 7 A g 66C 7-V wvf i/pi 77 rI £ 'A17t-i /Nf ( MA IiWfll A~~CVp mgiJ, m COMMENTS: GeoSoils, Inc. BY: PAGE ___________ OF This field report presents a summary of observations and testing by Geosoils, Inc. personnel only where the tests were performed. 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 any way for defects discovered in his work. It is understood that our firm will not be responsible for job or site safety on this project. HELD TESTING REPORT W.O. DATE ZJSiiD NAME HOURS 27- CLIENT ____________________TRAG T_1AI LOCATION____________________ SUPT._/fl1 £66-41 CONTRACTOR 44=W L-sr EQUIPMENT TEST NO. LOCATION ELEV. OR DEPTH MOISTURE CONTENT % DRY DENSITY P.C.F. % RELATIVE COMPACTION TEST TYPE SOIL TYPE qu dgAg/P ipz _____ çJ 1thD •7 rE&E/fl7#;'c47k/ 99417 7#) AM 27 caTrnuM 77W- A'44,: I/ 777 rzk ,, A rrr'. GeoSoils, in -WI This field report presents a summary of observations and testing by Geosoils, Inc. personnel only where the tests were performed. 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 any way for defects discovered in his work. It is understood that our firm will not be responsible for lob or site safety on this project.