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v :_.. ATC A S S O C I A T E S I N C - 1 Analytical results of groundwater samples are summarized in Table 2. -' 5.0 DISCUSSION �. The following paragraphs summarize the results of the subsurface investigations performed at the project site. r 1. Results of soil samples collected in the vadose zone (less than 16.5 feet deep) suggest that ' k shallow soil contamination is somewhat random and not laterally continuous across the site. Furthermore, no BTEX constituents are present at significant levels. Results of the most 1 recent investigation indicated that TPHd was present only in the samples collected between 14 and 16.5 feet bgs from borings adjacent to the former UST (SB 11, SB 12, and SB13). Soil samples SB11-15.5, SB12-16.5, and SB13-14.0 contained detectable concentrations of TPHd at concentrations of 390 ppm, 290 ppm and 1,100 ppm, respectively. Soil analytical results are contained in Table 1. 2. Soil beneath the site generally consists of gravel fill material from the surface to depths between 2 to 5 feet bgs. Soil from depths between 2 to 5 feet bgs and 16 to 25 feet bgs primarily consisted of clay and silt. Soil from depths between 16 to 25 feet bgs and approximately 30 to 36 feet bgs, the maximum depth explored, consisted of sand and silt. 3. Groundwater in the uppermost water bearing zone appears to be unconfined. Groundwater flow beneath the site is generally north-northwest with a magnitude of 0.007 ft/ft, or approximately 37 ft/mile. 4. Laboratory results from the most recent monitoring event indicate that TPHd was detected in groundwater samples collected from all wells at concentrations ranging from C 90.4 ppb in well AM to 8,890 ppb in well MW4. TPHd detected in wells MM3, MM5, and MW6 was reported by the laboratory as an unidentified hydrocarbon. The -:i concentrations of TPHd appear to decrease with distance from well MW-4. a 5. Floating petroleum product has previously been observed in well MW-4. Since December 1997, only a slight, unmeasurable sheen has been observed in well MW-4. `? To date, a total of approximately ten gallons of free product has been recovered from the well. Table 3 summarizes the product thickness measurements and volume of product =; removed from all monitoring events. 6. During the pumping test, approximately 6,000 gallons of groundwater were extracted from the subsurface and discharged to the sanitary sewer. Based on the analytical results, a total of approximately 0.00005 pounds of TPHd were removed from the subsurface during the twenty-four hour test. ,J w:162574.02Vcports\RPT-pump teAdoc 6