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DTSC-OMF r '�� ����1' `'+ t ✓ "Y: ?FeaC.0 - 7 a 7ArrR'r� <br /> I� <br /> Mr. Stevan Pinkerton <br /> Page 2 <br /> closure of the former USTs, it is not necessary for DTSC to make any additional <br /> recommendations concerning soil or groundwater issues associated with the UST <br /> releases from the former Schell station. <br /> Soil samples analyzed indicated that the Site contains lead as nigh as 184 milligrams <br /> per kilograms (mg/kg or part per million (ppm)), and lead in groundwater at 75.3 <br /> (groundwater sample:collected at south area of Site) micrograms per liter(ugA). This <br /> lead value in groundwater exceeds Federal primary drinking water standards <br /> established as Maximum Containment levels {MCL). 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 /> r Soil samples also contained benzo(a) pyrene at 0.33 ppm. Sediment samples <br /> oollected from the Stockton Channel below the pier supported parking lot contained <br /> lead levels as high as 200 ppm, arsenic at 22.1 ppm, and benzo(a) pyrene was <br /> detected as high as 1.2 ppm_ Samples collected from an offsite monitoring well <br /> (Well#4) indicated components associated with the underground tank release at a <br />�Ir <br /> former ARCO gas station including MTBE at 53 ppb, benzene at 300 ppb, vinyl chloride; <br /> at 81 ppb, and cis-1,2-dichloroethane at 120 ppb, which significantly exceed Federal <br /> MCL for drinking water. <br /> A human health screening evaivatfon was completed as part of the PEA investigation. <br /> Using the default residential land use scenario to calculate on site risk, theca Iculated <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'-with a total cumulative risk cf 3.3 x 10�. <br /> Based upon the data presented in the PEA report, the Site poses ae risk to human <br /> health and the environment as evaluated under unrestricted land use activities. <br /> Therefore DTSC has determined that further action -is necessary as outlined below to <br /> address investigative and remedial measures requirements associated with the <br /> hazardous substances at the Site. <br /> DTSC ooncurs with the recommendation in the PEA. Specifically, <br /> Recording a deed restriction on the property to, prevent future residential use <br /> and restrict use of the surface water and shallow groundwater underlying the <br />