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4_— "7� EDMO UEANO O.BROWN JR. <br /> NOR <br /> CALIFORNIA , <br /> SECRETARY FOR RoonsouEz <br /> WaterBoards ENVIRONMENTAL PROTECTION <br /> Central Valley Regional Water Quality Control Board <br /> 15 May 2018 <br /> Munir Obiad & Talal Nasser Nagi & Halima Saleh-Ali <br /> 3501 Kentucky Avenue 40 Jersey Lane <br /> Riverbank, CA 95367 Patterson, CA 95363 <br /> DOCUMENT REVIEW, RANCH MARKET, 23569 S. SANTA FE ROAD, RIVERBANK, SAN <br /> JOAQUIN COUNTY, CASE# 390609 <br /> Central Valley Regional Water Quality Control Board (Central Valley Water Board) staff <br /> reviewed the Soil Vapor and Groundwater Sampling Report(Report) dated 14 March 2018, <br /> received 22 March 2018, submitted on your behalf by Condor Earth Technologies (Condor), <br /> for the Ranch Market unauthorized petroleum release at 23569 S. Santa Fe Road in <br /> Riverbank (Site). In the Report, Condor details the activities and findings related to <br /> December 2017 confirmation soil gas sampling and 1st quarter 2018 groundwater sampling, <br /> and states that petroleum concentrations reported in Site well MW-7 are a result of an <br /> unknown release at a potential former fueling facility downgradient of the Site. In the Report, <br /> Condor recommends destroying deep monitoring well MW-5D and remaining Site remedial <br /> wells, and to continue semi-annual groundwater sampling only in monitoring wells MW-1, <br /> MW-3, MW-5, and MW-7 and domestic well DW-3. <br /> Central Valley Water Board staff has the following comments: <br /> 1. In the Report, Condor states that petroleum hydrocarbon concentrations in soil gas <br /> are below the thresholds established in the Low Threat Underground Storage Tank <br /> Case Closure Policy(LTCP). Central Valley Water Board staff concurs that maximum <br /> soil gas concentrations meet LTCP Direct Contact and Outdoor Air Exposure criteria. <br /> Table 1 —Maximum Soil Gas Concentrations <br /> Well Depth Maximum Concentrations A <br /> TPHg Benzene Ethylbenzene Napthalene 1,1-DFA Oxygen <br /> (ft) (Ug/m3) (Ug/m3) (Ug/m3) (Ug/m3) (Ug/m3) N <br /> SV-1 B 5 <440 18 23 <44 <32 -- <br /> SV-2c j 5 15,000 68 24 1 <46 <34 -- <br /> LTCP No 85 1,100 93 -- <4 <br /> Residential BAZ <br /> Thresholds BAZ -- 280 3,600 310 -- >4 <br /> TPHg=total petroleum hydrocarbons as gasoline; BAZ=bio-attenuation zone;ug/m'=micrograms per cubic meter <br /> A=Used as leak detection compound;B=Near Site building;C=Near adjacent residential property to the south <br /> KARL E. LONGLEV $CD, P.E.,CHAIR I PAMELA C. CREEDON P.E., 13CEE, EXECUTIVE OFFICER <br /> 11020 Sun Center Drive#200.Rancho Cordova.CA 95570 1 www.waterboards.ca.gov/centralvalley <br /> L♦RECVCLEO PAPER <br />