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Home My WebLink AboutPD 2021-0021; 3460 ROOSEVELT STREET; RESPONSE TO THIRD-PARTY GEOTECHNICAL REVIEW FOR PROPOSED TWO-STORY SINGLE-FAMILY RESIDENCE; 2021-07-07EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. 10925 HARTLEY ROAD, SUITE “I” SANTEE, CALIFORNIA 92071 TEL. 619-258-7901 3460 Roosevelt, LLC July 7, 2021 c/o Craig Correll Project No. 20-1106E6 4245 Sunnyhill Drive Carlsbad, California 92008 Subject: Response to Third-Party Geotechnical Review for Proposed Two-Story Single-Family Residence 3460 Roosevelt Street Carlsbad, California 92008 References: 1. Third Party Geotechnical Review (First), 3460 Roosevelt Street, Carlsbad, California, PD 2021-0021 531-AA, by Hetherington Engineering Inc, dated May 24, 2021 2. “Geotechnical Investigation for Proposed Two-Story, Single-Family Residence, 3460 Roosevelt Street, Carlsbad, California 92008”, Project No. 20-1106E6, Prepared by East County Soil Consultation and Engineering, Inc., Dated October 10, 2020. Dear Mr. Correll: In accordance with your request, we have prepared this letter in response to the subject third- party geotechnical review by Hetherington Engineering, Inc. Comment No. 1 We have reviewed the grading plan prepared by BHA, Inc. of Carlsbad, California for the proposed two-story single-family residence and associated improvements at the subject site. The grading plans were found to be in accordance with the recommendations presented in the referenced geotechnical report (Reference No. 2). Comment No. 2 Based on a review of our geotechnical report (Reference No. 2), site grading will consist of the removal, moisture conditioning and recompaction of the upper 12 inches of subgrade for support of the proposed floor slab and exterior flatwork. The proposed two-story, single-family residence will be supported on medium dense to dense terrace deposits. The foundation will consist of continuous footings, 18 inches deep, 15 inches wide and reinforced with four #4 bars, two near the top and two near the bottom. The floor slabs will be 5 inches thick and reinforced with #4 bars at 18 inches on centers in both directions. Floor slabs will be underlain by 2 inches of clean sand over a 10-mil visqueen moisture barrier over 2 inches of clean sand. Response to Third-Party Geotechnical Review for Proposed Two-Story, Single- Family Residence Page 2 3460 Roosevelt Street July 7, 2021 Carlsbad, California 92008 Project No. 20-1106E6 ______________________________________________________________________________ EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. A review of the grading plan indicates that a majority of the exterior flat work will consist of permeable and impervious pavers. Based on the anticipated soil conditions following site grading, the following permeable concrete paver section is recommended in accordance with the Interlocking Concrete Pavement Institute (ICPI) specifications. • Minimum 3-1/8 inch permeable concrete pavers • 1.5 to 2 inch bedding course (Typ. No. 8 Aggregate) • 4 inch No. 57 stone open-graded base • 6 inch No. 2 stone subbase wrapped in Mirafi 180N geotextile or equivalent Impervious pavers may be placed over 2 inches of leveling sand over properly compacted fill or medium dense to dense terrace deposits. Comment No. 3 There are no mapped earthquake faults at the site. The closest major active fault is the offshore Newport-Inglewood Fault Zone located 2 about miles to the southwest. Comment No. 4 Please see attached figures showing an updated geotechnical map/plot plan (Figure 2) and geologic cross sections (Figure 3). Comment No. 5 Based on the recommended shallow depth of overexcavation and recompaction, it is our opinion that the proposed site grading and construction will not negatively impact the adjacent properties and improvements. Comment No. 6 As presented in the referenced geotechnical report (Reference No. 2), total and differential settlements of ½ inch may be assumed. Comment No. 7 Based on the distance of the site from the ocean and the relatively high elevation of the property, it is our opinion that the potential of a tsunami affecting the site is very low. Response to Third-Party Geotechnical Review for Proposed Two-Story, Single- Family Residence Page 3 3460 Roosevelt Street July 7, 2021 Carlsbad, California 92008 Project No. 20-1106E6 ______________________________________________________________________________ EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. Comment No. 8 Corrosivity tests were performed on a representative sample of the onsite soils. The attached test results (Figure 3) indicate a low degree of corrosivity. Accordingly, we recommend Type I/II Portland Cement for foundation construction. Comment No. 9 Proposed driveway and 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. Exterior slabs should be supported on the existing soils scarified to a depth of 6 to 8 inches, moisture conditioned and compacted to at least 90 percent relative compaction. Driveway and 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. In addition to the above, no subdrain is needed for the small retaining walls on the north and south property lines provided proper surface drainage is provided. Where the concrete walk meets the edge of the retaining wall on the north property line, a 2 percent minimum swale should be provided away from the wall. This opportunity to be of service is appreciated. If you have any questions, or we can be of further service, please do not hesitate to call or contact us. Respectfully Submitted, _______________________ Martin R. Owen, PE, GE Geotechnical Engineer Attachments: Figures 1, 2 and 3 Response to Third-Party Geotechnical Review for Proposed Two-Story, Single- Family Residence Page 4 3460 Roosevelt Street July 7, 2021 Carlsbad, California 92008 Project No. 20-1106E6 ______________________________________________________________________________ EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. FIGURE 1 GEOTECHNICAL MAP/PLOT PLAN Response to Third-Party Geotechnical Review for Proposed Two-Story, Single- Family Residence Page 5 3460 Roosevelt Street July 7, 2021 Carlsbad, California 92008 Project No. 20-1106E6 ______________________________________________________________________________ EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. FIGURE 2 GEOLOGIC CROSS-SECTIONS Response to Third-Party Geotechnical Review for Proposed Two-Story, Single- Family Residence Page 6 3460 Roosevelt Street July 7, 2021 Carlsbad, California 92008 Project No. 20-1106E6 ______________________________________________________________________________ EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. FIGURE 3 CORROSIVITY TEST RESULTS