ARCHIVED REPORTS XR0002747 - Laserfiche WebLink

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