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HomeMy WebLinkAboutPD 2020-0007; FUKUDA ADDITION; FINAL SOILS REPORT; 2023-02-01@ COAST GEOTECH, INC. I CONSULTING ENGINEERS AND GEOLOGISTS February 1, 2023 Lane Fukuda 2726 Morning Glory Lane Carlsbad, California 92008 Subject: FINAL GEOTECHNICAL REPORT Proposed Second Story Addition and Basement 2726 Morning Glory Lane Carlsbad, California References: See Page 5 Dear Mr. Fukuda: w.o. 707419 In response to your request, enclosed is our Final Geotechnical Report on the above referenced property. This report presents a summary of our geotechnical observations during the grading and construction phases. PROPOSED DEVELOPMENT Grading plans for site development were prepared by Rancho Coastal Engineering and Surveying .. The project included the construction of an attached guest room on the southeast end of the residence with a basement storage and an expanded garage with a covered deck over the southwest end of the residence .. The structures are supported on basement wall and column pad footings with slab-on- grade floors. Coast Geotech, Inc. GEOTECHNICAL CONDITIONS February 1, 2023 w.o. 707419 Page 2 of 5 The subject property is located in the Coastal Plains Physiographic Province of San Diego. The property is underlain at relatively shallow depths by Pleistocene Very Old Paralic Deposits. The Very Old Paralic Deposits are underlain at depth by Eocene-age sedimentary rocks commonly correlated with Torrey Sandstone on published geological maps. The Very Old Paralic Deposits are covered by relatively thin soil deposits. Unweathered dense Very Old Paralic Deposits are considered dense and competent, which makes it suitable for the support of foundation and fill deposits. The Very O Id Paralic Deposits are composed of tan orangish brown fine to medium grained sand. CONSTRUCTION PHASE 1. Prior to the grading operations, surface vegetation was removed and trees were trimmed for the site, as appropriate. 2. Grading operations included the excavation of the basement. The total depth of the basement was approximately 10.0 feet and has been excavated to the designed rough grade. 3. Exposed bottom of basement excavation was observed and probed on July 8, 2022 to assure footings are founded into competent Very Old Paralic Deposits. Excavations were performed using a mini excavator. 4. Earth deposits generated from the site grading operations predominantly consisted of silty fine and medium grained sand (SM) and fine and medium grained sand (SP) deposits. The formation reflects an expansion potential in the low to very low range. 5. The basement footing excavations were observed by this firm on July 8, 2022. The footings are founded into Very Old Paralic Deposits with an expansion potential in the low to very low range. 6. Waterproofing was performed by AVM Industries, Inc. utilizing Aussie Skin 550G waterproofing membrane. The membrane was placed directly underneath the mat-type foundation slab. No special concrete design was necessary according to our previous discussion. Coast Geotech, Inc. February 1, 2023 w.o. 707419 Page 3 of 5 7. The continuous wall and column pad footing excavations for the support of the garage and covered deck were observed by this firm on September 26, 2022. 8. The basement wall and column pad footing excavations were founded into Very Old Paralic Deposits. The footing excavations were approved by this firm provided all loose deposits were removed from the base of the excavations prior to pouring concrete. The footing excavations were not reviewed for compliance with structural plans and location. 9. Based on visual classification and previous laboratory testing, the mixture of soils utilized as compacted fill reflect an expansion potential in the very low range. CONCLUSIONS The geotechnical conditions encountered on the site were in substantial conformance with those conditions anticipated in the Preliminary Geotechnical Investigation Report. The recommendations of the geotechnical reports were substantially implemented during the grading and construction phases. Footings and slabs on grade should be protected from root and/or moisture migration. Undermining and pressure from roots and/or saturated soil conditions from infiltration can adversely affect foundations and slabs on grade. Irrigation should be limited to that amount necessary to sustain plant life. Over zealous irrigation can result in slope instability and settlement of foundations and concrete flatwork. LIMIT A TIO NS This office assumes no responsibility for any alterations made without our knowledge and written approval, subsequent to the issuance of this report. All areas of disturbance which require the placement of compacted fill to restore them to the original condition will not be reviewed unless such backfilling operations are performed under our observation and tested for required compaction. It should be noted that density (compaction) testing is conducted on a very small volume of the fill. The intent is to provide an opinion, based on selective testing and observation during fill placement. Coast Geotech, Inc. REFERENCES 1. PRELIMINARY GEOTECHNICAL INVESTIGATION Proposed Second Story Addition and Basement 2726 Morning Glory Lane Carlsbad, California Prepared by Coast Geotech, Inc. Dated June 18, 2019 2. GRADING PLAN AND FOUNDATION PLAN REVIEW Proposed Second Story Addition and Basement 2726 Morning Glory Lane Carlsbad, California Prepared by Coast Geotech, Inc. Dated November 3, 2020 February 1, 2023 w.o. 707419 Page 5 of 5 3. ROUGH GRADING AND BASEMENT FOOTING EXCAVATION REPORT Proposed Second Story Addition and Basement 2726 Morning Glory Lane Carlsbad, California Prepared by Coast Geotech, Inc. Dated July 11, 2022