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Working to Restore Nature <br /> hydrocarbons detected during that sampling event may have been due to contaminated <br /> equipment <br /> In November 1987, the tank cavity was over-excavated to 28 feet below grade in an effort <br /> to remove soil affected by hydrocarbons Analytical results of soil samples collected from <br /> the base of the excavation indicated that relatively low concentrations of gasoline <br /> hydrocarbons (0 20 parts per million [ppm] ethylbenzene, 020 ppm toluene, 325 ppm <br /> xylene) were detected in only one sample, which was collected nearest to well BH-1 <br /> In July 1993, RESNA observed the drilling three soil borings and installation of three <br /> monitoring wells (MW-2 through MW-4) in the three borings Results of analyses of soil <br /> and water samples Indicated that hydrocarbon concentrations were below laboratory <br /> detection limits <br /> GROUNDWATER MONITORING, FOURTH QUARTER 1993 <br /> On October 15, 1993, a technician from RESNA measured the depth to water, performed <br /> subjective analyses of groundwater, and collected groundwater samples from the four <br /> monitoring wells (Table 1) The technician noted no floating product or sheen 1n the four <br /> wells (MW-1 through MW-4) <br /> The wellhead elevations of the monitoring wells at the site were surveyed by Tom O <br /> Morrow, Inc of West Sacramento California, a licensed land surveyor (California Land <br /> Surveyors No 3275) The surveyed elevations and the depth-to-groundwater measurements, <br /> summarized in Table 2, were used to evaluate the potentiometric surface beneath the site <br /> The groundwater flow direction on October 15, 1993, was to the northeast with the hydraulic <br /> gradient ranging from 0 001 to 0 1 (Plate 3) <br /> The water samples were analyzed for TPHg using modified Environmental Protection <br /> Agency (EPA) Method 8015 and benzene, toluene, ethylbenzene, and total xylene isomers <br /> 1 (BTEX) using EPA Method 602 The samples were analyzed at Sequoia Analytical in <br /> Sacramento, California(Hazardous Waste Testing Laboratory Certificate No 1624) Results <br /> of analyses indicated TPHg and BTEX concentrations were below laboratory detection <br /> ' limits The results of analyses are summarized in Table 1 Copies of the laboratory <br /> Analysis Reports and Chain of Custody Record are attached <br /> WORK IN PROGRESS <br /> i <br /> RESNA has scheduled the next quarterly sampling event for the second week of January <br /> t 1994 <br /> t <br /> 1028glak/123009-1 2 <br />