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page 2, 16 E. Harding <br /> The Additional Site Assessment Report documents fieldwork that took place from July 9-16, <br /> 2001, when two soil borings and five shallow groundwater monitoring wells were installed. The <br /> soil borings were advanced on-site to approximately 80-feet below surface grade (bsg)and depth <br /> discrete soil and groundwater samples were collected for the purpose of defining the vertical <br /> extent of the petroleum hydrocarbon contamination. Please note that this report was submitted to <br /> PHS/EHD approximately six weeks late. <br /> Analytical results from the soil samples were basically all non-detect, indicating that the limits of <br /> the soil contamination have been defined. The bulk of the soil contamination remaining at this <br /> site is in the area of the northern dispenser island, near MW-4 and SVE-1, to a depth of <br /> approximately 40-feet bsg. <br /> Analytical results of the discrete water samples collected from SBA and SB-2 indicate that <br /> significant petroleum hydrocarbon contamination in groundwater extends to above 65-feet bsg, <br /> and that it has not been defined laterally at this depth. Analytical results of the water samples <br /> collected from the shallow wells indicate that lateral definition of the methyl tertiary butyl ether <br /> (MtBE)plume at this depth is not complete, with high concentrations of MtBE present in the <br /> down-gradient well, MW-6. <br /> In this report SECOR recommends further investigation of the contaminant plume in the down- <br /> gradient direction, installation of one deep monitoring well on site, and that a file review be <br /> completed to research possible offsite sources of the contamination present in the up-gradient <br /> well, MW-9. <br /> PHS/EHD agrees with these recommendations. However, the lateral extent of the contaminant <br /> plume at depth must also be defined. PHS/EHD directs that a minimum of three deep, discretely <br /> screened monitoring wells be installed. The installation of these wells was previously directed by <br /> PHS/EHD, and was listed as a condition of the approval of the January 5, 2001 'Work Plan for <br /> Additional Site Assessment'. Submit to PHS/EHD by January 21, 2002 a work plan for further <br /> monitoring well installations to complete the plume definition at this site. <br /> A feasibility study must be completed for this site, and it must address the issue of remediation of <br /> the groundwater contamination. The feasibility study, or a work plan to complete further feasibility <br /> testing, is also due to PHS/EHD by January 21, 2002. As discussed in PHS/EHD <br /> correspondence dated November 21, 2000, interim remediation should be on going at this site to <br /> contain the MtBE plume. <br /> If you have any questions or comments please call Lori Duncan at(209)468-0337. <br /> Donna Heran, RENS, Director <br /> Environmental Health Division <br /> co-, � ✓� <br /> Lori Duncan, Senior REHS Margam Supervising REHS <br /> LOP/Site Mitigation Unit IV LOP/Site Mitigation Unit IV <br /> cc: Marty Hartzell, CVRW QCB <br /> Rusty Benkosky, SECOR <br />