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Epw„,o G.BnawV Jrt. <br /> CALIP86 L• �1TliB nYYA41P2 <br /> Water Boards ^ <br /> Central Valley Regional Water Quality,Control Board <br /> 1 September 2015 RECEIVED <br /> Ms. Georgia Rooks FEB 01 2016 <br /> STAND Affordable Housing <br /> 1209 east 8th Street ENVIRONMENTAL <br /> Stockton, CA 95206 HEALTH DEPARTMENT <br /> SOIL GAS INVESTIGATION, CASA DE OASIS, 1700 SOUTH EL DORADO STREET, STOCKON, <br /> SAN JOAQUIN COUNTY <br /> California Regional Water Quality Control Board, Central Valley Region (Central Valley Water Board) staff <br /> reviewed the Soil-Vapor Sampling Report(SVS Report), dated 30 July 2015, submitted by Advanced <br /> GeoEnvironmental Inc. (AGEI) on behalf of STAND Affordable Housing (STAND). We understand STAND <br /> is currently considering purchasing the property at 1700 South EI Dorado Street in Stockton (Casa De <br /> Oasis), for use as an adult (senior) apartment complex with a community center. <br /> In January 2015 a Phase I Environmental Assessment was conducted by AGEI on behalf of STAND and <br /> reported five underground storage tanks (USTs), identified in 1991, in the City of Stockton sidewalk adjacent <br /> to the proposed community center. Evidence of a fuel dispenser was found inside the community center. <br /> The USTs and associated piping were removed on 11 December 1991. Petroleum hydrocarbons or volatile <br /> organic compounds were not detected in the soil samples collected at the time of the tank removal activities. <br /> On 16 September 1992, the San Joaquin County Department of Public Health Services issued a closure <br /> letter to the City of Stockton for the USTs case. <br /> In March 2015 a Phase 11 Site Assessment Report was prepared by AGEI. AGEI reported the results of <br /> seven soil vapor samples collected at five and ten feet below ground surface (` bgs). Naphthalene was <br /> detected in the sample collected in the sidewalk near the former USTs. Naphthalene concentrations of <br /> 1.2 micrograms per Liter (Ng/L) in SV3-5 exceed the California Human Health Screening Level (CHHSLs) of <br /> 0.032 pg/L for residential exposures, developed by the Office of Environmental Health Hazard Assessment. <br /> Toluene and xylenes were detected in SV3-5 and also in SV4-5 (150' from the USTs) but results did not <br /> exceed the CHHSLs for residential exposures. AGEI recommended additional soil vapor sampling in the <br /> Phase II Site Assessment Report and submitted the 7 May 2015 Soil Vapor Survey Work Plan proposing <br /> installation of additional soil borings for the purpose of collecting additional soil vapor samples. The Soil <br /> Vapor Survey Work Plan was conditionally approved on 26 May 2015. <br /> On 1 July 2015 AGEI installed seven (7) vapor wells in soil borings along EI Dorado Street and 3'd Avenue <br /> and within the adult senior apartment complex. Soil vapor sampling occurred on 3 July 2015 and <br /> 7 July 2015 to investigate potential for petroleum vapors to migrate into indoor air. AGEI did not include <br /> oxygen sampling as requested by Central Valley Water Board staff in the 26 May 2015 letter. However, <br /> results of the soil vapor wells sampling did not exceed the CHHSLs for the following petroleum <br /> hydrocarbons: benzene, ethylbenzene, toluene, xylenes, methyl tert butyl ether (MTBE), tert amyl methyl <br /> ether, di-isopropyl ether, ethyl tent butyl ether, tertiary butyl alcohol, 1,2 dichloroethane, ethylene dibromide, <br /> and naphthalene by TO-14 and naphthalene by TO-17. In the SVS Report, AGEI recommends against <br /> KM E. Lcma ScD, P.E.,cw I PAMP"C.ONNO N P.E.,BCEE,66QIIIYE OcsaeFH <br /> f i0ft Surt C�Ofty f 4 Mrbc m Cmdw GA ON, I `rM1rArUMr60uW.aa.OdM rNy <br />