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LII�A_-UM r Fax:916-255-3734 Mar 9 2000 11 :07 P.03 <br /> "M w-'rit- <br /> 7 <br /> Mr' Steven Pinkerton <br /> Page 2 <br /> Closure of the former USTs, it is n9l necessary for DTSC to make any additional <br /> recommendations concerning soil or groundwater issues associated Wth the UST <br /> releases from the former Shelf station. <br /> Soil samples analyzed indicated that the Site con ins lead as high as 184imilligrams <br /> per kilograms (mg/Kg or part per million (ppm)), ar d lead in groundwater at 75.3 <br /> (groundwater sample collected at'south area of Si 69) micrograms Per liter(ugfi). This <br /> lead value in groundwater exceeds Federal primadrinking water standards <br /> established as Maximum Containment Levels (M L). However, if the sample was <br /> prepared absent filtering the Sample, then the lead value may be overstated and not <br /> representative of lead in groundwater, For this reason another sample is required to <br /> definitively determine the lead levels in groundwater. <br /> Soil samples also contained benzb(a) pyrene at 0 33 ppm. Sediment samples <br /> collected from the Stockton Channel below the pie r supported parking lot contained <br /> lead levels as high as 200 ppm, arsenic at 22.1.p m, and benzo(a) pyrene was <br /> detected as high as 1.2 ppm- Samples collected ftm an offsite monitoring well <br /> (Well #4) indicated components associated with the underground tank release at a <br /> former ARCO gas station including IVITEE at 63 ppb, benzena at 300 ppb, vinyl chloride <br /> at 61 ppb, and cis-1.2-dichicroethane at 120 ppb, which significantly exceed Federal <br /> MCL for drinking water. <br /> A human health screening evaluation was completed as part of the PEA investigation. <br /> Using the default residential land use scenario to (21culate on site risk, the calculated <br /> excess risk from soil ingestion and dermal contact was 2.3 x 10-5 and the excess <br /> cancer risk from groundwater ingestion and showering/ bathing as calculated using <br /> onsite groundwater was 1.1 x: 10 ,m(jth a total curnulative risk of 3.3 x '10-6. <br /> Based upon the data presented in!the PEA report the Site poses aifsk to human <br /> health and the environment as evaluated under urr estricted land use activities. <br /> Therefore DTSC has determined that further actio f i is necessary as outlined below to <br /> address investigative and remedial measures requirements associated with the <br /> hazardous substances at the Site. <br /> DTSC concurs with the recommendation in the PEA. Specifically, <br /> Recording 2deed restriction on the property to, prevent future residential use <br /> and restrict use of the surface water and shdiow groundwater underlying the <br /> MOW-= <br />