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Working To Restore Nature <br /> 3,1 <br /> Histoa of Soil and Groundwater Investigation <br /> During precision testing at the facility (May 1988), leakage was detected from the product line <br /> of a 10,000 gallon unleaded gasoline tank Elevated levels of gasoline hydrocarbons were <br /> recorded in two of four soil samples collected June 9, 1988 from a trench located adjacent to <br /> ' the product lines (Figure 2) Although individual testing of the tanks indicated that they were <br /> mathematically tight, a small hole was found in the unleaded product line in the area of highest <br /> contamination Based upon these leak indicators PHSIEHD required further investigation to <br /> assess the extent of contamination <br /> On October 19, 1989, a soil boring was drilled to a total depth of 55 feet below grade to <br /> rdetermine the vertical extent of hydrocarbon impacted soils and to facilitate the installation of <br /> a groundwater monitoring well (MW1, Figure 2) The bonng/monitoring well was located as <br /> close as possible to the area of suspected soil contamination near the product line Laboratory <br /> analyses of soil samples collected at five foot intervals from 10 0 to 40 0 feet in the well boring <br /> did not detect the presence of gasoline constituents above the method detection limits (Table 1) <br /> Historical analyses of groundwater samples collected from monitoring well MW 1 indicate that <br /> groundwater beneath the site has not been impacted by petroleum hydrocarbons (Table 2) <br /> 3.2 Remedial Actions <br /> 3.2.1 July 1992 Excavation <br /> On July 23, 1992, under the direction of RESNA, approximately 300 cubic yards of native and <br /> backfilled soil were excavated by Falcon Energy Associates (Falcon Energy, license #584524) <br /> 1 using a backhoe tractor Visible hydrocarbon impaction of soil was evident to a depth of <br /> approximately 6 to 6 5 feet below grade PID measurements detected vapors intermittently to <br /> Iapproximately 8 feet below grade A layer of clay from approximately 7 to 10 feet below grade _ <br /> apparently limited the vertical extent of contaminant migration All excavated materials were <br /> OW01481REPORTS\CR-0694 FNL 3 <br /> 1 <br />