ARCHIVED REPORTS_XR0003094 - Laserfiche WebLink

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fe .� Working To Restore Nature On March 2, 1992, RESNA installed groundwater monitoring well MW-1 to a depth of 85 feet below grade Laboratory analyses of soil and groundwater samples collected from MW-1 indicated that groundwater and near-water soils had been impacted by gasoline hydrocarbons in the vicinity of MW-1 Three additional groundwater monitoring wells (MW-2, MW-3, and MW-4) were installed in October 1993 No hydrocarbons were detected in any soil samples from these borings (Table 1). Analysis of groundwater samples indicated that petroleum hydrocarbon contamination was limited to a relatively small area near the former gasoline tanks and dispenser island Well locations are shown on the Site Plan, Plate 2 Groundwater analytical results are summarized in Table 2 In October 1993, RESNA supervised the drilling of three borings which were completed as vapor extraction test wells (VW-1, VW-2 and VW-3) to collect volatilized hydrocarbons from the soils within the gasoline impacted area during a vapor extraction test. Locations of vapor extraction test wells are shown on Plate 2 Soil samples collected from borings VW-2 and VW- 3 contained low levels of petroleum hydrocarbon analytes RESNA conducted a one-day soil vapor extraction test (VET) using the newly installed vapor extraction wells in October 1993 Test results indicated that vapor extraction is a feasible method for remediating impacted soils in the vicinity of the former u/g gasoline storage tanks EXCAVATION ACTIVITIES The following scope of work was based upon the information collected during previous site investigations The work was designed to remove the remaining impacted soil in the vicinity of the former diesel and waste oil tanks All field work was performed in accordance with the Quality Assurance/Quality Control Plan and the site specific Health and Safety Plan on file with San Joaquin County Public Health Services, Environmental Health Division (PHS/EHD) The extent of the excavation and former tank locations are depicted on Plate 3 Excavation was conducted by Goins Environmental Construction (Lic #674281) under the direct supervision of a RESNA geologist Excavation activities were observed and approved by Ms. Linda Turkatte of PHS/EHD Former Diesel Tank Location On January 4, 1994, approximately 160 cubic yards of residual petroleum hydrocarbon contaminated soil was excavated from the vicinity of the former underground diesel storage tank Visual and olfactory methods were utilized during excavation to assist in evaluating the lateral and vertical extent of soil impaction Petroleum hydrocarbon odor and gray discoloration indicated that impacted soils remained in the area of the former diesel tank between approximately 3 and 8 feet below grade along the north wall where excavation was limited by California Street Excavation continued along the east, west and south sides of the pit, to a maximum depth of 14 feet until field evidence indicated that contamination was no longer present axcnv aril. 2