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40 Workrng to Restore Nature The hydhydrocarbons detected duringthat sampling may have due to contaminated equipment In November 1987, the tank cavity was over-excavated to 28 feet below grade in an effort to remove soil affected by hydrocarbons Analytical results of soil samples collected from • the base of the excavation indicated that relatively low concentrations of gasoline hydrocarbons (0 20 ppm) ethylbenzene, 0 20 ppm toluene, 3 25 ppm xylene) were detected in only one sample, which was collected nearest to well BH-1/ MW-1 In July 1993, RESNA observed the drilling of three soil borings and installation of three • monitoring wells (MW-2 through MW-4) in the three borings Results of analyses of soil and water samples indicated that hydrocarbon concentrations were below laboratory detection limits GROUNDWATER MONITORING, FIRST QUARTER 1994 • On November 23 and December 17, 1993 and January 14, 1994, a technician from RESNA measured the depth to water and performed subjective analyses of groundwater samples collected from the four monitoring wells (MW-1 through MW-4) The technician noted no floating product or sheen in the four wells (Table 1) On January 14, groundwater samples were collected for laboratory analyses. Our field procedures are described in an attachment 00 to this report The wellhead elevations of the monitoring wells at the site were surveyed by Tom O Morrow, Inc of West Sacramento California, a licensed land surveyor (California Land Surveyors No 3275) The surveyed elevations and the depth-to-groundwater measurements, 0 summarized in Table 1, were used to evaluate the potentiometric surface beneath the site The groundwater flow direction during the three monitoring events was to the east to southeast with hydraulic gradients ranging from 0 001 to 0 004 (Plates 3, 4, and 5) The water samples were analyzed for TPHg using modified Environmental Protection • Agency (EPA) Method 8015 and benzene, toluene, ethylbenzene, and total xvlene isomers (BTEX) using EPA Method 602 The samples were analyzed at Sequoia Analytical in Sacramento,California(Hazardous Waste Testing Laboratory Certificate No 1624) Results of analyses indicated TPHg and BTEX concentrations were below laboratory detection limits The results of analyses are summarized in Table 1 Concentrations of TPHg and benzene are shown on Plate 2 Copies of the laboratory Analysis Reports and Chain of Custody Record are attached • 0201giak/123009-1 2 0