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HomeMy WebLinkAboutCT 05-03; LINCOLN & OAK MIXED USE; GEOTECHNICAL REVIEW OF GRADING PLANS, LINCOLN AND OAK MIXED USE; 2011-02-11.r DT- o3 /OM- Ii Geotechnical • Geologic. Coastal • Environmental 5741 Palmer Way . Carlsbad, California 92010 • (760) 438-3155 • FAX (760)931-0915. www.geosoilsinc.com February 11, 2011 III4R 1,9~26 W. 4147-A2-SC Mr. Russell Bennett P.O. Box 356 Solana Beach, California 92075 Subject: Gedtechnical Review of Grading Plans, Lincoln and Oak Mixed Use, 3112 Lincoln Street, San Diego County, California Dear Mr. Bennett: I In accordance with your request and authorization, GeoSoils, Inc. (GSI) has performed a geotechnical review of the project grading plans, notes, and details prepared by Conway and Associates, Inc. (2011 [see the Appendix]), for the planned three-story mixed-use commercial and residential structure, as well as associated improvements at the subject site. The purpose of our review was to evaluate if the grading plans incorporate the recommendations provided in previous project geotechnical documents prepared by GSI (see Appendix), as required by EsGil Corporation (2010). GSI's scope of services included a review of Conway and Associates, Inc. (2011), EsGil Corporation (2010), GSI (2004a, 2004b, 2007, 2010, and 2011), and the preparation of this summary review letter. Recommendations contained in GSI (2004a, 2004b, 2007, 2010, and 2011), which are not specifically superceded by this review, should be properly incorporated into the design and construction phases of site development. Based on our review, the grading plans, and corresponding notes and details shown on Conway and Associates, Inc. (2011), appear to be in general accordance with the recommendations provided in GSI (2004a, 2004b, 2007, 2010, and 2011), from a geotechnical standpoint, with the following comments: GSI recommends that this review letter be referenced on Conway and Associates, Inc. (2011). o As previously indicated in GSI (2011), foundations should either. be uniformly• supported by unweathered terrace deposits or at least 2 feet of engineered fill. Foundations should not simultaneously bear on terrace deposits and compacted fill. If the client elects to support the footings on unweathered terrace deposits, and not performed complete site removals, GSI recommends that uniform support of the interior slab-on-grade floors be provided by removing all unsuitable soils below a 1:1 (horizontal:vertical) projection below the bottom outside edge of the concrete slab to where the 1:1 plane intersects the surface of the relatively unweathered terrace deposits. Once the unsuitable soils have been removed, the resultant excavation should be observed by GSI. Following GSI observation and approval of the remedial grading excavation, the bottom of the excavation should be scarified at least 6 inches, moisture conditioned to at least the soil's optimum moisture content and re-compacted to at least 95 percent relative compaction (ASTM D 1557). The excavation may then be backlilled to planned grade with the removed soils that have been generally cleaned of organics and/or deleterious debris, placed in relatively thin lifts, moisture conditioned to at least optimum moisture content, and compacted to at least 95 percent relative compaction. The purpose of the 95 percent compaction requirement is to reduce the potential for differential settlement between slab-on-grade floors supported by engineered fill and footings supported by terrace deposits. Should the client elect to support the slabs and footings entirely on engineered fill, any terrace deposits located within 2 feet below the lowest foundation element (including elevator pits) following the removal of unsuitable soils, should be overexcavated at least 2 feet below the elevation of the bottom of the lowest footing. The overexcavation should be completed to a lateral distance of at least 5 feet outside the outboard-most foundation element, and the bottom of the overexcavation should be sloped to drain toward the street(s). Once the overexcavation is complete, the overexcavation bottom should be observed by GSI. Following the GSI overexcavation bottom observation and approval, the bottom of the overexcavation should be scarified at least 6 inches, moisture conditioned to at least the soil's optimum moisture content and re-compacted to at least 90 percent relative compaction. The overexcavation may then be backfilled to the planned grade with the removed and overexcavated soils that have been generally cleaned of organics and/or deleterious debris, placed in relatively thin lifts, moisture conditioned to at least optimum moisture content, and compacted to at least 90 percent relative compaction (ASTM D 1557). As indicated in GSI (2007), the California Building Code, removals of unsuitable soils be performed across all areas under the purview of the grading permit graded, not just within the influence of the proposed structures/buildings. Relatively deep removals may also necessitate a special zone of consideration, on perimeter/confining areas. This zone would be approximately equal to the depth of removals, if removals cannot be performed offsite. Thus, any settlement-sensitive improvements (walls, curbs, flatwork, etc.), constructed within this zone may require dOepened foundations, reinforcement, etc., or will retain some potential for settlement and associated distress. This will require proper disclosure to all interested/affected parties, should this condition exist at the conclusion of grading. Mr. Russell Bennett W.O. 4147-A2-SC Lincoln and Oak Mixed Use Carlsbad February 11, 2011 FiIe:e:\wp12\41474147a2.gro Page 2 GeoSoUs, Inc. Detail 1 on Sheet 5 of Conway and Associates, Inc. (2011) indicates that the footing embedment for the building, where located adjacent to the bottom of the bioretention swale, should be measured relative to the bottom of the swale. GSI recommends that the project CMI and structural engineers coordinate the building locations where deepened footings are necessary. The project structural engineer should then show these locations and required footing depths on the foundation plan in order to minimize confusion during construction. GSI requests that revised plans (after the date of the plans reviewed herein) showing the design of the fountain be providedto this office for review when they become available. Based on our review amendments to the recommendations provided herein and in GSI (2004a, 2004b, 2007, 2010, and 2011) may be necessary. Provided that the above comments are properly incorporated into Conway and Associates, Inc. (2011), no further review is deemed necessary. Should any amendments to the grading plans be necessary following our review of the fountain plans, they should be incorporated into the project drawings prior to construction. Should any major revisions pertaining to design layout and/or elevations be made following this review, GSI recommends that such revisions be reviewed by this office prior to construction. Based on our review of any significant plan revisions, GSI may recommend additional analysis. LIMITATIONS The conclusions and recommendations presented herein are professional opinions. These opinions have been derived in accordance with current standards of practice, and no warranty is express or implied. Standards of practice are subject to change with time. 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. Mr. Russell Bennett W.O. 4147-A2-SC Lincoln and Oak Mixed Use Carlsbad February 11, 2011 FiIe:e:\wp12\4147\4147a2.gro Page 3 cecous,. I. The opportunity to be of service is greatly appreciated. • If you have any questions concerning this report, or if we may be of further assistance, please do not hesitate to contact any of the undersigned. Respectfully sub GeoSoils, In $• Fft411 <'0 ?Enginee No.134O Certified Engineering . Fran eoiogIet ring Geo C 1340 Ryan Boehmer Project Geologist RB/ATG/JPF/jh Geotechnical Engineer, GE 230 Attachment: Appendix - References Distnbution: (1) Addressee (via email) (4) Karnak Planning and Design, Attn: Robert Richardson (wet signed) (1) Concrode Consult Group, Inc., Attn: Kolaei Kripanarayanan (via email) (1) Conway and Associates, Attn: Mike Pasko (via email) Mr. Russell Bennett W.O. 4147-A2-SC Lincoln and Oak Mixed Use Carlsbad February 11, 2011 FiIe:e:wp12\4147\4147a2.gro Page 4 GeoSipils, Inc. } V APPENDIX REFERENCES California Building Standards Commission, 2007, California Building Code. Conway and Associates, Inc., 2011, Grading plans for: Lincoln &Oak Mixed Use, Submittal No. 3, 6 sheets, 10-scale, Drawing No. 451-7A, Project No. CT 05-03, dated February 1. EsGil Corporation, 2010, Lincoln & Oak Mix Use, 3112 Lincoln Street, City of Carlsbad, Plan Check No. PCi 0-41, dated October 28. GeoSoils, Inc., 2011, Geotechnical review of foundation plans, Lincoln and Oak mixed use, 3112 Lincoln Street, San Diego County, California, W.O. 4147-A3-SC, dated. January 28. . 2010, Geotechnical update for structural design, 3112 Lincoln Street, San Diego County, California, W.O. 4147-Al-SC, dated September 27. 2007, Geotechnical review of rough grading plans (first submittal), Lincoln and Oak Project, 3112 Lincoln Street, Carlsbad, San Diego County, California, W.O. 4147-A-SC, dated May 4. 2004a, Soil corrosivity results, 3112 Lincoln Street, Carlsbad, San Diego County, California, W.O. 4147-A-SC, dated January 22. 2004b, Preliminary geotechnical evaluation, 3112 Lincoln Street, Carlsbad, San Diego County, California, W.O. 4147-A-SC, dated January 14. GeoS€ils, Iw.