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Home My WebLink AboutPD 2021-0003; BRIDGEN RESIDENCE; FINAL SOILS REPORT; 2022-02-23 23 February 2022 Premier Pools and Spas Job No. 20-12991 5431 Avenida Encinas, Suite B Carlsbad, CA 92008 Attn: Mr. Aaron Temme Subject: Report of Observations and Soil Testing Brigden Property Retaining Wall 1953 Cobalt Drive Carlsbad, California Dear Mr. Temme: As requested and per our work agreement, Geotechnical Exploration, Inc. hereby presents this report of observations and soil testing for the work performed at the subject site. The work reported herein was performed between June 9 and July 28, 2021. We previously performed a limited soil investigation, the results of which were presented in our Report of Limited Soil Investigation and Bearing Value Evaluation dated January 13, 2021. We also issued a Response to the City of Carlsbad Third- Party Geotechnical Review letter dated March 5, 2021. FIELD OBSERVATIONS 1. Our representative was requested to be on-site on June 9, 2021, to evaluate the bottom bearing soils for the retaining wall footing excavation (per the new city standard drawing) located along the southwest side ascending slope. The bearing soils were observed to be adequately firm/dense to support the new city standard retaining wall. Brigden Property Retaining Wall Job No. 20-12991 Carlsbad, California Page 2 2. Our representative was requested to observe the backfill placement for the retaining wall on June 30 and July 28, 2021. Prior to backfill placement, our representative observed the drainboard had been placed incorrectly with the fabric side against the wall. He contractor removed the drainboard and fixed the orientation of the drainage board. It should be noted that it is not within the scope of our services to provide quality control oversight for surface or subsurface drainage construction or retaining wall sealing and base of wall drain construction. It is the responsibility of the contractor to verify proper wall sealing, geofabric installation, protection board installation (if needed), drain depth below interior floor or yard surfaces; pipe percent slope to the outlet, etc. The wall was backfilled with gravel material and capped off with a 2-foot soil cap. The soil cap placed behind the wall was observed and compaction tested by our representative. 3. Work pending as of the date of this report includes evaluating the bearing soils for the proposed swimming pool and testing backfill placement for pending exterior walls and hardscape improvements to be located around the swimming pool perimeter. We have not been requested to test backfill placement for any underground utilities or test the compaction of the finished grades of exterior improvements other than the previously described retaining wall. SOIL TESTING Representative soil samples were collected during the grading to determine laboratory maximum dry density of the soils. Field density tests were performed at approximate locations shown on Figure No. II. The complete list of field density tests Brigden Property Retaining Wall Job No. 20-12991 Carlsbad, California Page 3 results is shown on Table A of Figure No. IIIa, and laboratory soil compaction test results are shown on Table B of Figure No. IIIb. Equipment used for the earthwork compaction consisted of a pneumatic hand tamper. Water was added, when needed, to increase the soil moisture. Field density tests yielded a relative compaction of at least 90 percent of maximum dry density at the tested locations. Density tests were performed with a nuclear gauge testing apparatus in accordance with ASTM D6938-17a. The maximum dry density of the soils was determined per ASTM D1557-12e1. On-site soils used for the earthwork consisted of olive-brown clayey sand. The on-site soils were visually classified to have low expansion potential characteristics per ASTM D4829. Proper finish drainage for the site was to be implemented by the general contractor prior to completing construction. Field density tests are shown in the attached Plot Plan, Figure No. II. SITE SUITABILITY AND COMPLIANCE The observed and tested areas of the pre-manufactured homes are, in our professional opinion, suitable for their intended use. The stiff formational soils are, in our professional opinion, suitable to support te recompacted fill, structure foundations, and new exterior improvements. We certify that the soil engineering and engineering geologic aspects of the backfill placement are in compliance with the City of Carlsbad grading ordinance and per the city approved plans. Brigden Property Retaining Wall Job No. 20-12991 Carlsbad, California Page 4 LIMITATIONS The findings and opinions presented herein have been made in accordance with currently accepted principles and practice in the field of geotechnical engineering in the City of Carlsbad in the County of San Diego. No warranty, either expressed or implied, is made. All statements in this report are applicable only for the backfill operation observed and tested by our firm. The firm Geotechnical Exploration, Inc. shall not be held responsible for fill soils placed without our observations and testing at any other time, or subsequent changes to the site by others, which directly or indirectly cause poor surface or subsurface drainage, water erosion, and/or alteration of the strength of the compacted fill soils. As previously stated, it is not within the scope of our services to provide quality control oversight for surface or subsurface drainage construction or retaining wall sealing and base of wall drain construction. It is the responsibility of the contractor to verify proper wall sealing, geofabric installation, protection board installation (if needed), drain depth below interior floor or yard surfaces; pipe percent slope to the outlet, etc. In the event that any changes in the nature, design, or location of the building or improvements are planned, the conclusions and recommendations contained in this report should not be considered valid unless the changes are reviewed and the conclusions of this report modified or verified in writing. Brigden Property Retaining Wall Job No. 20-12991 Carlsbad, California Page 5 This opportunity to be of service is sincerely appreciated. If you have any questions regarding this letter, please contact our office. Reference to our Job No. 20-12991 will help expedite a response to your inquiry. Respectfully submitted, GEOTECHNICAL EXPLORATION, INC. _______________________________ ______________________________ Jaime A. Cerros, P.E. Jay K. Heiser R.C.E. 34422/G.E. 2007 Senior Project Geologist Senior Geotechnical Engineer _______________________________ Richard Cerros, E.I.T. Staff Engineer VICINITY MAP Brigden Residence 1953 Colbalt Drive Carlsbad, CA. Figure No. I Job No. 20-12991 SITE Thomas Bros. Guide San Diego County, pg 1127-E5 Approximate Limits of ObservationApproximate Location ofField Density Test13424FIELD DENSITY TEST LOCATIONSBrigden Residence1953 Cobalt DriveCarlsbad, CA.Figure No. IIJob No. 20-12991REFERENCE: This PLOT PLAN was prepared from an existing undated GRADING PLAN by bha, INC. and from on-site field reconnaissance performed by GEI.Scale: 1” =20’(approximate)LEGENDNOTE: This Plot Plan is not to be used for legal purposes. Locations and dimensions are approximate. Actual property dimensions and locations of utilities may be obtained from the Approved Building Plans or the “As-Built” Grading Plans.20-12991-p2.aiPLOT PLAN ANDSITE SPECIFICGEOLOGIC MAPFebruary 2022Artificial FillQafGEOLOGIC LEGENDTsaSantiago Formation (concealed)QafTsaQafTsa TABLE A ApproximateWater DryDegree of Test Elevation Content DensityCompaction Compaction No. Date of Test Test Location (Feet) (%) (pcf) (%) Curve No. Remarks 1 7/28/21 City Standard Retaining Wall Backfill 227' (F.S) 8.7 115.093 12 7/28/21 City Standard Retaining Wall Backfill 227' (F.S) 8.0 113.291 13 7/28/21 City Standard Retaining Wall Backfill 227' (F.S) 9.1 114.893 14 7/28/21 City Standard Retaining Wall Backfill 227' (F.S) 7.9 113.792 1 Job No. 20-12991 Figure No. IIIaSUMMARY OF FIELD DENSITY TEST RESULTS (ASTM D1556 and/or ASTM D6938)Notes: 1) Curve number refers to Table B 2) FSG denotes finish subgrade elevation 3) FBG denotes finish base grade elevation 4) FPG denotes finish pavement grade Job No. 20-12991 Figure No. IIIb TABLE B LABORATORY COMPACTION TEST RESULTS (ASTM D1557) Compaction Maximum Optimum Test Source of Dry Density Water Content Curve No. Description of Material Material (pcf) % 1 (SC) Clayey Sand; Olive-Brown On-site 124.0 10.6