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HomeMy WebLinkAboutPD 16-14; 1655 CHESTNUT AVENUE; FINAL SOILS REPORT; 2020-11-16Geotechnical C Geologic C Coastal C Environmental 5741 Palmer Way C Carlsbad, California 92010 C (760) 438-3155 C FAX (760) 931-0915 C www.geosoilsinc.com November 16, 2020 W.O. 7014-C-SC Mr. Ron Ozaki 1645 Chestnut Avenue Carlsbad, California 92008 Subject: Final Geotechnical Report of Grading and Improvements Construction, 1655 Chestnut Avenue, Carlsbad, San Diego County, California References: 1. Review of Pavement Design for a Residential Driveway, 1655 Chestnut Avenue, Carlsbad, San Diego County, California,” W.O. 7014-C-SC, dated February 14, 2019, by GeoSoils, Inc. 2. “Geotechnical Plan Review, 1655 Chestnut Avenue, Carlsbad, California,” W.O. 7014-B-SC, dated March 3, 2017, by GeoSoils, Inc. 3. “Geotechnical Report of Grading and Building Pad Construction, at 1655 Chestnut Avenue, Carlsbad, San Diego County, California,” W.O. 7014-B-SC, dated March 3, 2017, by GeoSoils, Inc. 4. “Geotechnical Evaluation for Proposed Construction at 1645 Chestnut Avenue, Carlsbad, San Diego County, California,” W.O. 7014-A-SC, dated February 22, 2016, by GeoSoils, Inc. 5. “Structural Plans for: Ozaki Residence, 1655 Chestnut Ave. Carlsbad, Ca 92008, Project No. 161275,” dated November 29, 2016, by Rons House Plans and Nelson Engineers. 6. “Minor Grading Plan, Ozaki Residence, 1655 Chestnut Avenue, Carlsbad,” 4 Sheets, Project ID: P.D. 16-14, Drawing No.:494-6A, dated October, 2016, by Tait Consulting, Inc.. Dear Mr. Ozaki: In accordance with your request, and as required by the City, GeoSoils, Inc. (GSI) has prepared this final geotechnical report with respect to grading and improvement of the subject site. In addition to grading operations for the support of the building pad, Geotechnical observations were provided with respect to driveway, retaining wall, and utility construction. Site Grading The primary purpose of grading was to mitigate potentially compressible soils within the influence of the planned residential structure, and to create a building pad for the planned residential structure and attached garage. Observations and field compaction testing for this specific construction task occurred periodically between mid December, 2016, and early February, 2017. Grading was observed and fill was selectively tested by a representative of GSI, on a part-time, as- Mr. Ron Ozaki W.O. 7014-C-SC 1655 Chestnut Avenue, Carlsbad November 16, 2020 File:e:\wp12\7000\7014c.fgr Page 2 needed basis. The scheduling of such was solely determined by your field representative. Line and grade was provided by others and not GSI. Site grading for the building pad appears to be in general conformance with the preliminary recommendations contained in Reference No. 4, GSI field recommendations, Appendix Chapter J of the 2013 California Building Code, and with the grading guidelines of the City, from a geotechnical standpoint. Field testing indicates that fills placed under the purview of this report have been minimally compacted to at least 90 percent of the laboratory standard (ASTM D 1557), where tested. Based on the observation and compaction testing performed during grading, GSI concludes that the residential building pad, constructed under GSI observation and testing, is suitable for its intended use. A comprehensive discussion of site grading is presented in Reference No. 3. Utility trench Backfill Where accessible within planter areas, and within constructed gaps between driveway pavement panels, selective mechanical probing of trench backfill soil was performed. Selective mechanical probing of trench backfill indicates that the backfill appears to have received compactive effort and is performing adequately, based on probe resistance and no visible settlement along the trench line(s), where observed. Driveway Pavement Pavement design and construction recommendations for the driveway pavement were provided in Reference No. 1. Based on our evaluation, a full depth Portland Concrete Cement (PCC) pavement section of 5½ inches (plain concrete) was recommended. Based on observations made in shallow excavations, it appears that the minimum recommended PCC pavement section thickness was constructed, where observed. Selective mechanical probing of the underlying soil subgrade between, and along the outer edges of pavement panels indicates that the subgrade soil appears to have received compactive effort, where observed. To date, the pavement appears to be performing adequately. Given the relative age of the pavement and the lack of visible distress, it appears that subgrade preparation is adequate for the intended use, based on readily accessible observations. Retaining Walls As part of the grading plan (Reference No. 6), it was necessary to construct a retaining wall along the southern portion of the eastern property line, with the wall continuing along the southern property line. This wall was planned to a maximum height of about 2 ½ feet and in accordance with Regional Standard Drawing C-1 (see Reference No. 6). Observations of as-built wall construction indicate that wall drainage is accommodated via open head joint weep holes long the exposed base of the wall. Selective mechanical probing of wall Mr. Ron Ozaki W.O. 7014-C-SC 1655 Chestnut Avenue, Carlsbad November 16, 2020 File:e:\wp12\7000\7014c.fgr Page 3 backfill (offsite) indicates that the backfill appears to have received compactive effort and is performing adequately, where observed, based on probe resistance and no significant settlement. 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, 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 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. If you have any questions or comments regarding this letter, please do not hesitate to contact the undersigned. Respectfully submitted, GeoSoils, Inc. Robert Crisman David W. Skelly Engineering Geologist, CEG 1934 Civil Engineer, RCE 47857 RGC/DWS/JPF/mn Distribution: (1) Addressee (via E-mail) Geotechnical C Geologic C Coastal C Environmental 5741 Palmer Way C Carlsbad, California 92010 C (760) 438-3155 C FAX (760) 931-0915 C www.geosoilsinc.com March 3, 2017 W.O. 7014-B-SC Mr. Kevin Ozaki 1645 Chestnut Avenue Carlsbad, California 92008 Subject: Geotechnical Report of Grading and Building Pad Construction, at 1655 Chestnut Avenue, Carlsbad, San Diego County, California References: 1. “Minor Grading Plan, Ozaki Residence, 1655 Chestnut Avenue, Carlsbad,” 4 Sheets, Project ID: P.D. 16-14, Drawing No.:494-6A, dated October, 2016, by Tait Consulting, Inc. 2. “Geotechnical Evaluation for Proposed Construction at 1645 Chestnut Avenue, Carlsbad, San Diego County, California,” W.O. 7014-A-SC, dated February 22, 2016, by GeoSoils, Inc. Dear Mr. Ozaki: In accordance with your request, and as required by the City, GeoSoils, Inc. (GSI) has prepared this geotechnical report of grading for the proposed residential structures. Observations and field compaction testing for this specific construction task occurred periodically between mid December, 2016, and early February, 2017. Grading was observed and fill was selectively tested by a representative of GSI, on a part-time, as- needed basis. The scheduling of such was solely determined by your field representative. Line and grade was provided by others and not GSI. Unless specifically superceded herein, the conclusions and recommendations in the referenced geotechnical reports prepared by this firm (see Reference No. 2) remain valid and applicable and should be appropriately implemented during the balance of construction. Purpose of Grading The primary purpose of grading was to mitigate potentially compressible soils within the influence of the planned residential structure, and to create a building pad for the planned residential structure and attached garage. Engineering Geology The geologic conditions exposed in excavations during the process of remedial grading for the planned residential structures were observed on a part-time basis by a representative from our firm. Earth materials encountered during grading consisted of existing Quaternary-age colluvium and underlying Quaternary-age, older paralic deposits (considered suitable formation). Evidence of adverse geologic structure was not observed in the earthwork excavations. The site plan prepared by Tait Consulting, Incorporated (Reference No. 1) was used a base for the Field Density Location Map (Plate 1). GeoSoils, Inc. Ron Ozaki W.O. 7014-B-SC 1645 Chestnut Avenue, Carlsbad March 3, 2017 File:e:\wp12\7000\7014b.gro Page 2 Groundwater Regional groundwater was not encountered within the earthwork excavations and therefore is not anticipated to be a major factor in the future performance of the planned residential structure, provided the recommendations contained in this and our prior report are properly incorporated into the balance of construction and post-development landscape practices. Due to the nature of the site earth materials, perched groundwater conditions may manifest in the future along zones of contrasting permeabilities and densities (i.e., fill/bedrock deposits contacts, fill lifts, geologic discontinuities), as a result of excessive precipitation, over-irrigation, and/or damaged underground utilities. The potential for perched groundwater occurrence should be anticipated and disclosed to all interested/affected parties. Should such conditions occur in the future, GSI could provide recommendations for mitigation. Geotechnical Engineering Remedial Earthwork 1. Prior to grading, existing vegetation was removed and hauled offsite. 2. During grading, potentially compressible unsuitable soils (i.e., existing Quaternary colluvium), were removed to expose suitable formational soils. The depth of excavations necessary to remove potentially compressible soils was approximately ±2-3 feet below the existing grade. The removal of unsuitable soils was completed to at least 5 feet outside the building footprint (as determined by others), or to a lateral distance equal to the depth of the removal, whichever is greater. Elevations of removal and/or undercut bottoms are shown on Plate 1. 3. In order to provide for the uniform support of the structure, the building pad was undercut to a minimum depth of at least 3 feet below pad grade to provide for a minimum 3-foot thick cap of engineered fill. The undercut portion of the pad was generally sloped toward the south in order to mitigate the potential for perched water along the fill/formational soils contact beneath the building. 4. Prior to fill placement, the bottoms of the remedial grading excavations (i.e., removals and undercuts) were scarified, moisture conditioned to slightly above optimum moisture conditions, and then re-compacted to at least 90 percent relative compaction (ASTM D 1557), where tested. 5. All processing of original ground in areas to receive fill, as shown on Plate 1, were observed by a representative of GSI. 6. Earthwork was performed to provide a uniform building pad for the planned new structure. Any planned, settlement-sensitive improvements spanning these transitions, and/or located within areas beyond the limits of fill placed under the GeoSoils, Inc. Ron Ozaki W.O. 7014-B-SC 1645 Chestnut Avenue, Carlsbad March 3, 2017 File:e:\wp12\7000\7014b.gro Page 3 purview of this report, will be subject to an elevated potential for adverse soil movement and associated distress, if these conditions are not mitigated in the future. Additional recommendations for treatment of soils in these areas may be provided on request. Engineered Fill Placement Engineered fill materials predominately consisted of the onsite soils derived from the remedial grading excavations. However, it should be mentioned that import fill materials were used during grading. Import fill materials used appeared to be consistent with the native terrace deposits. During grading, engineered fills were placed in approximately 6- to 8-inch lifts, moisture conditioned, mixed to achieve slightly greater than optimum moisture conditions, and mechanically compacted to a minimum relative compaction of 90 percent of the laboratory standard (ASTM D 1557), where tested. In general, the thickness of engineered fill placed under purview of this report was generally ±3 feet beneath the building pad. Field Testing 1. Field density tests were performed using the nuclear method in general accordance with ASTM test method D 6938-10 (Procedure A). The compaction test results are presented in the attached Table 1. The approximate locations of the field density tests performed during grading operations are presented on Plate 1. 2. The field dry densities of the engineered fill were evaluated as a percentage of the maximum dry density attained in the laboratory for the representative soil types encountered during grading. Where field density testing indicated inadequate compaction or moisture content, the failure area was reworked until at least 90 percent of the laboratory standard or slightly greater than optimum moisture (ASTM D 1557) was achieved. 3. Field density tests were taken at periodic intervals and selected locations to check the compaction and moisture content of the engineered fill placed by the contractor. Laboratory Testing Maximum Density Testing The laboratory maximum dry density and optimum moisture content for the major soil type encountered during grading, were evaluated in general accordance with test method ASTM D 1557. The following table presents the results: GeoSoils, Inc. Ron Ozaki W.O. 7014-B-SC 1645 Chestnut Avenue, Carlsbad March 3, 2017 File:e:\wp12\7000\7014b.gro Page 4 SOIL TYPE MAXIMUM DENSITY (PCF) MOISTURE CONTENT (PERCENT) A - Dark Yellow Brown, Silty Sand 130.0 9.5 Expansion Potential Expansion testing was performed on a representative sample of site soil in general accordance with ASTM D 4829. The results of expansion testing are presented in the following table. LOCATION AND DEPTH (FT) EXPANSION INDEX EXPANSION POTENTIAL Finished Grade <5 Very Low Saturated Resistivity, pH, and Soluble Sulfates, and Chlorides GSI conducted sampling of onsite earth materials for general soil corrosivity and soluble sulfates, and chlorides testing. The testing included evaluation of soil pH, soluble sulfates, chlorides, and saturated resistivity. Test results are presented in the following table: SAMPLE LOCATION pH SATURATED RESISTIVITY (ohm-cm) SOLUBLE SULFATES (wt. %) SOLUBLE CHLORIDE (ppm) Finished Grade 6.22 to 7.35 1,000 to 3,800 0.0135 to 0.0195 16 to 62 Laboratory testing indicates that a sample of the onsite soil evaluated is slightly acidic to mildly alkaline with respect to soil acidity/alkalinity, moderately corrosive to corrosive to exposed, buried metals when saturated; presents a negligible sulfate exposure to concrete; and chloride levels are low to slightly elevated. Reinforced concrete mix design for foundations, slab-on-grade floors, and pavements should minimally conform to “Exposure Class C1” in Table 4.2.1 of ACI 318-11, as concrete would likely be exposed to moisture. It should be noted that GSI does not consult in the field of corrosion engineering. The client and project architect should agree on the level of corrosion protection required for the project and seek consultation from a qualified corrosion consultant as warranted. I I GeoSoils, Inc. As defined in the California Business and Professions Code, Division 3, Chapter 15, Article 5,1 Section 8770.6. Ron Ozaki W.O. 7014-B-SC 1645 Chestnut Avenue, Carlsbad March 3, 2017 File:e:\wp12\7000\7014b.gro Page 5 Conclusions The work performed to date appears to be in general conformance with the preliminary recommendations contained in Reference No. 2, GSI field recommendations, Appendix Chapter J of the 2013 California Building Code, and with the grading guidelines of the City, from a geotechnical standpoint. Field testing indicates that fills placed under the purview of this report have been minimally compacted to at least 90 percent of the laboratory standard (ASTM D 1557), where tested. Based on the observation and compaction testing performed during grading, GSI concludes that the residential building pad, constructed under GSI observation and testing, is suitable for its intended use. Unless superceded herein, the conclusions and recommendations regarding site construction, including foundation design and construction recommendations presented in Reference No. 2 are considered valid and applicable. Regulatory Compliance The soil engineering and engineering geologic aspects of the construction are in general compliance with approved geotechnical report and geotechnical aspects of the construction. Furthermore, with respect to the grading plans, GSI will certify that the soil1 engineering and engineering geologic aspects of the grading are in general compliance with the approved geotechnical reports (see Reference 2) and the grading site plan (Reference 1). 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, 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 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. GeoSoils, Inc. Ron Ozaki W.O. 7014-B-SC 1645 Chestnut Avenue, Carlsbad March 3, 2017 File:e:\wp12\7000\7014b.gro Page 6 If you have any questions or comments regarding this letter, please do not hesitate to contact the undersigned. Respectfully submitted, GeoSoils, Inc. Robert Crisman David W. Skelly Engineering Geologist, CEG 1934 Civil Engineer, RCE 47857 ATS/RGC/DWS/jh Attachments: Table 1 - Field Density Test Results Plate 1 - Field Density Test Location Map Distribution: (3) Addressee (via US mail) Table 1 FIELD DENSITY TEST RESULTS TEST UTILITY DATE TEST LOCATION TRACT ELEV MOISTURE DRY REL TEST SOIL NO.TYPE NO.OR CONTENT DENSITY COMP METHOD TYPE DEPTH (ft)(%)(pcf)(%) 1 12/20/16 Bldg Pad 1655 Chestnut 168.0 9.5 117.3 90.2 ND A 2 12/21/16 Bldg Pad 1655 Chestnut 168.0 9.5 123.4 94.9 ND A 3 12/21/16 Bldg Pad 1655 Chestnut 169.0 9.5 122.3 94.0 ND A 4 12/27/16 Bldg Pad 1655 Chestnut 169.7 10.4 122.6 94.3 ND A 5 12/27/16 Bldg Pad 1655 Chestnut 169.5 11.9 120.1 92.4 ND A 6 12/28/16 Bldg Pad 1655 Chestnut 170.5 10.3 121.6 93.5 ND A 7 12/28/16 Bldg Pad 1655 Chestnut 170.6 9.9 123.5 95.0 ND A 8 12/28/16 Bldg Pad 1655 Chestnut 169.4 11.1 120.3 92.5 ND A 9 12/28/16 Bldg Pad 1655 Chestnut 170.9 10.9 121.5 93.4 ND A 10 12/28/16 Bldg Pad 1655 Chestnut 170.9 11.3 119.9 92.2 ND A 11 1/31/17 Garage 1655 Chestnut 169.9 9.6 121.9 93.7 ND A 12 2/1/17 Garage 1655 Chestnut 170.9 10.1 120.6 92.7 ND A 13 FG 2/1/17 Garage 1655 Chestnut FG 10.2 119.7 92.1 ND A 14 FG 2/1/17 Bldg Pad 1655 Chestnut FG 9.9 119.4 91.8 ND A 15 FG 2/1/17 Bldg Pad 1655 Chestnut FG 10.5 120.1 92.3 ND A LEGEND: * =Failed Test A =Retest FG =Finish Grade ND =Nuclear Densometer Ron Ozaki 1655 Chestnut Avenue, Carlsbad File: C:\excel\tables\7014tbl GeoSoils, Inc. W.O. 7014-B-SC March, 2017 Page 1 ----- f--- 6 -~ X-12 PRO OSED°9 X-11 2-AR "'---~ ~ 'eGA AGE~ f~ • ..-------' X-13 w 0::: LL'. 0 -.;;I- w 0-, 1/ I I I I <2> ,~ ,1,-~~ \1\•~ I ,1,, I ~ V RE:~R: AREA l 0) cs I\ "'-.. 169.9 EG GS/ LEGEND Af COMPACTED FILL PLACED UNDER THE PURVIEW OF THIS REPORT X-15 APPROX/MA TE LOCATION OF FIELD DENSITY TEST I 169.6 I -APPROX/MA TE ELEVATION IN FEET (MSL) OF EXCAVATION BOTTOM -■■--APPROXIMATE LIMITS OF COMPACTED FILL PLACED UNDER THE PURVIEW OF THIS REPORT BASE MAP: WI CITY OF CARLSBAD II SHEETS I tJ ENGINEERING DEPARTMENT 4 GRADING PLANS FOR: 1655 CH~STNUT AVENUE TAIT PLAN SWET CONSULTING, INC. AP=>ROVED: JASON S. CELDERT 818 Crestview Court CITY ENGINEER RCE 6 3912 EXPIRES 9 /30 /16 DATE San Marcos, CA 92078 DWN BY: ~-11 PROJECT ID II DRAWING NO. Cf-KD BY: __ P.D. 16-14 RVWC BY: 494-6A 10 GRAPHIC SCALE 0 5 10 20 1" = 10· ~- ALLLOCATIONSAREAPPROXIMATE This document or efi/e is not a part of the Construction Documents and should not be relied upon as being an accurate depiction of design. FIELD DENSITY TEST LOCATION MAP Plate 1 W.O. 7014-8-SC DATE: 03/17 SCALE: 1" = 10'