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Home My WebLink AboutCDP 2021-0024; BLAUVELT RESIDENCE; RESPONSE TO THIRD PARTY GEOTECHNICAL REVIEW FOR PROPOSED TWO STORY SINGLE FAMILY RESIDENCE; 2022-10-05Paul Blauvelt 1060 Northwood Drive EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. 10925 HARTLEY ROAD, SUITE "I" SANTEE, CALIFORNIA 92071 TEL. 619-258-7901 San Carlos, California 94070 October 5, 2022 Project No. 21-1106E6 Subject: Response to Third-Party Geotechnical Review for Proposed Two-Story, Single-Family Residence 3259 Lincoln Street Carlsbad, California 92008 References: 1. "Third Party Geotechnical Review, Proposed Blauvelt Residence, 3259 Lincoln Street, Carlsbad, California", Project No. 109343010, by Ninyo & Moore Geotechnical & Environmental Sciences Consultants, Dated July 20, 2022. 2. "Geotechnical Investigation for Proposed Two-Story, Single-Family Residence, 3259 Lincoln Street, Carlsbad, California 92008", Project No. 21-1106E6, Prepared by East County Soil Consultation and Engineering, Inc., Dated February 24, 2021. Dear Mr. Blauvelt: In accordance with your request, we have prepared this letter in response to the subject third- party geotechnical review by Ninyo & Moore Geotechnical & Environmental Sciences Consultants. Comment No. 1 We have reviewed the grading plans prepared by Rancho Coastal Engineering and Surveying and the foundation plans and details prepared by Morgan Structural Engineering for the proposed two-story single-family residence and associated improvements at the subject site. The grading, foundation plans and details were found to be in accordance with the recommendations presented in the referenced geotechnical report (Reference No. 2). Comments No. 2, 3 and 5 Please see attached Figure 1 showing a geologic/ geotechnical map/plot plan and cross section. Response to Third-Party Geotechnical Review for Proposed Two-Story Single- Family Residence 3259 Lincoln Street Carlsbad, California 92008 Comment No. 4 Page2 October 5, 2022 Project No. 21-1106E6 From published geologic maps, the site is underlain at depth by sedimentary terrace deposits. There are no known geologic hazards such as landslides, liquefaction-prone areas, or earthquake faults at the site. However, the proposed building is subject to ground shaking and possible damage from earthquakes on nearby, or more distant, active faults. There are no mapped earthquake faults at the site. The closest major active fault is the offshore Newport-Inglewood Fault Zone located about 2 miles to the southwest. Comment No. 6 Excavations for utility lines, which extend under structural areas should be properly backfilled and compacted. Utilities should be bedded and backfilled with clean sand or approved granular soil to a depth of at least one foot over the pipe. This backfill should be uniformly watered and compacted to a firm condition for pipe support. The remainder of the backfill should be on-site soils or non-expansive imported soils, which should be placed in thin lifts, moisture-conditioned and compacted to at least 90% relative compaction. Comment No. 7 Cantilevered retaining walls should be designed for an "active" lateral earth pressure of 35 psf/ft (35 pcf EFP) for approved granular backfill and level backfill conditions. Where cantilevered walls support 2: 1 (hor: vert) sloping backfill, the equivalent active fluid pressure should be increased to 45pcf. Cantilever walls subject to uniform surcharge loads should be designed for an additional uniform lateral pressure equal to one-third (1/3) the anticipated surcharge pressure. Another additional lateral earth pressure due to earthquake motions of 22 pcf (EFP) for unrestrained conditions may be applied using an inverted triangular distribution if required. Soil design criteria, such as bearing capacity, passive earth pressure and sliding resistance as recommended under the Foundation and Slab Recommendations section, may be incorporated into the retaining wall design. Footings should be reinforced as recommended by the structural engineer and appropriate back drainage provided to avoid excessive hydrostatic wall pressures. As a minimum we recommend a fabric-wrapped crushed rock and perforated pipe system. At least 2 cubic feet per linear foot of free-drainage crushed rock should be provided. The remaining wall backfill should consist of approved granular material. This fill material should be compacted to a minimum relative compaction of 90 percent as determined by ASTM D-1557 test method. Flooding or jetting of backfill should not be permitted. Granular backfill should be capped with 18 inches (minimum) of relatively impervious fill to seal the backfill and EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. Response to Third-Party Geotechnical Review for Proposed Two-Story Single- Family Residence 3259 Lincoln Street Carlsbad, California 92008 Page3 October 5, 2022 Project No. 21-ll06E6 prevent saturation. It should be noted that the use of heavy compaction equipment in close proximity to retaining structures can result in wall pressures exceeding design values and corresponding wall movement greater than that associated with active or at-rest conditions. In this regard, the contractor should take appropriate precautions during the backfill placement. Comment No. 8 Driveway and other exterior slabs may be supported on the existing soils provided they are scarified to a depth of 6 to 8 inches, moisture conditioned to near optimum moisture content and compacted to at least 90 percent relative compaction. Driveway and other exterior concrete slabs should be at least 5 inches thick and reinforced with No. 4 rebars spaced at 18 inches on centers in two directions and placed at mid-height in the slab. Driveway and other exterior slabs should be provided with construction joints spaced no more than 10 feet apart to minimize shrinkage cracking. Slab concrete should have a minimum compressive strength of 3,000 psi and maximum water-cement ratio of 0.5 to minimize shrinkage cracking. No special testing of concrete is necessary. Some shrinkage cracking is still possible. Comment No. 9 Please see attached a list of references. Comment No. 10 Based on the dense consistency of the terrace deposits underlying the site at shallow depths and the minor depth of surface soil removal, it is our opinion that the proposed site grading and construction will not impact adjacent properties and existing improvements. Comment No. 11 Based on site geotechnical conditions, the subject site is suitable for its intended use provided the recommendations contained in the referenced geotechnical report are implemented in the design and construction of the proposed single-family residence. EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. Re ponse to Third-Party Geotechnical Review for Proposed Two-Story Single- Fa ily Residence 32 9 Lincoln Street Ca lsbad, California 92008 Page4 October 5, 2022 Project No. 21-1106E6 is opportunity to be of service is appreciated. If you have any questions, or we can be of er service, please do not hesitate to call or contact us. pectfully Submitted, adou Saliou Diallo, P .E. 54071, GE 2704 achments: Figure 1 and References EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. •• Response to Third-Party Geotechnical Review for Proposed Two-Story Single- Family Residence 3259 Lincoln Street Carlsbad, California 92008 FIGURE 1 Pages October 5, 2022 Project No.21-1106E6 GEOLOGIC/ GEOTECHNICAL MAP/PLOT PLAN •a-2- PROPOSED RESIDENCE PAC•54.5 F'F'•SS.17 :..-::::- / ------- ___ /frf'l?a(//44f£ La:.HJpA/ tJ~ ?EST 1&121A/G 1Yt1A/1A1///r'! t/ft1IT5 t!J,.c-6-/?M/N~ .5~4or-/ ~ £>erpo/~ I I i EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. Response to Third-Party Geotechnical Review for Proposed Two-Story Single- Family Residence 3259 Lincoln Street Carlsbad, California 92008 REFERENCES Page 6 October 5, 2022 Project No. 21-1106E6 I. "2019 California Building Code, California Code of Regulations, Title 24, Part 2, Volume 2 of 2", Published by International Code Council. 2. "Geologic Map of the San Diego 30' x 60' Quadrangle, California", by Michael P. Kennedy and Siang S. Tan, 2008. 3. "Geotechnical and Foundation Engineering: Design and Construction", by Robert W. Day, 1999. 4. "Maps of Known Active Fault Near-Source Zones in California and Adjacent Portions of Nevada to be used with 1997 Uniform Building Code", Published by International Conference of Building Officials. 5. "Geologic Maps of the Northwestern Part of San Diego County, California", Department of Conservation, Division of Mines and Geology, by Siang S. Tan and Michael P. Kennedy, 1996. 6. "Bearing Capacity of Soils, Technical Engineering and Design Guides as Adapted from the US Army Corps of Engineers, No. 7", Published by ASCE Press, 1994. 7. "Foundations and Earth Structures, Design Manual 7.2", by Department of Navy Naval Facilities Engineering Command, May 1982, Revalidated by Change 1 September 1986. 8. "Ground Motions and Soil Liquefaction during Earthquakes", by H.B. Seed and J.M. Idriss, 1982. EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. Geotechnical & Environmental Sciences Consultants July 20, 2022 Project No. 109343010 Ms. Jessica Nishiura, P.E. Hunsaker & Associates Inc. 9707 Waples Street San Diego, California 92121 Subject: Third-Party Geotechnical Review Proposed Blauvelt Residence 3259 Lincoln Street Carlsbad, California ~ References: City of Carlsbad, 1993, Technical Guidelines For Geotechnical Reports: dated January. East County Soil Consultation and Engineering, Inc., 2021, Geotechnical Investigation for Proposed Two-Story, Single-Family Residence, 3259 Lincoln Street Carlsbad, California, 92008, Project No. 21-1106E6: dated February 24. Rancho Coastal Engineering & Surveying, Submittal Set from 2022, Grading Plans For: Blauvelt Residence, 3259 Lincoln Street, Sheets 1 through 5. Dear Ms. Nishiura: At your request, we have prepared this letter providing our review comments to the referenced geotechnical report prepared by East County Soil Consultation and Engineering, Inc. dated February 24, 2021. Our comments regarding the geotechnical report include the following: Comment 1: The Geotechnical Consultant should review the project grading and foundation plans and provide any additional geotechnical recommendations, as appropriate, and indicate if the plans have been prepared in accordance with the geotechnical recommendations provided in the referenced geotechnical report (East County Soil Consultation and Engineering, 2021 ). Comment 2: The Geotechnical Consultant should provide a geotechnical cross-section of the site or discussion as to why one is not presented. If a geologic cross section is prepared, an updated geotechnical map/plot plan showing the location of the cross-section should be provided. Comment 3: The Geotechnical Consultant should provide a geotechnical map/plot plan to clearly show the lateral limits of the recommended remedial grading and the planned structure. Comment 4: Per the City of Carlsbad's guidelines, the Geotechnical Consultant is to provide discussion regarding regional faulting and fault distances to the site. Comment 5: Per the City of Carlsbad's guidelines, the Geotechnical Consultant is to provide a geologic map. 5710 Ruffin Road I San Diego, California 92123 I p. 858.576.1000 I www.ninyoandmoore.com Comment 6: Per the City of Carlsbad's guidelines, the Geotechnical Consultant is to provide recommendations for the backfill of utility trenches. Comment 7: Per the City of Carlsbad's guidelines, the Geotechnical Consultant is to provide recommendations for retaining walls. Comment 8: Per the City of Carlsbad's guidelines, the Geotechnical Consultant is to provide recommendations for exterior concrete flatwork. Comment 9: Per the City of Carlsbad's guidelines, the Geotechnical Consultant is to provide a list of references. Comment 10: The Consultant should provide a statement regarding the impact of the proposed grading and construction on adjacent properties and improvements. Comment 11: The Geotechnical Consultant should provide conclusions regarding the site geotechnical conditions and a conclusion regarding the site's suitability for development. We appreciate the opportunity to be of service. Respectfully submitted, NINYO & MOORE Christina Tretinjak, PG, CEG Senior Project Geologist CAT/JTK/mp 11::.:::: Principal Engineer Ninyo & Moore I 3259 Lincoln Street, Carlsbad, California I 109343010 I July 20, 2022 2