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is V � TC �r f. _ A A S S O C I A T E S I N C groundwater extraction at the site is greater than 50 feet (Figure 4). Observation well MW-1 is located approximately.46 feet from pumping well MW-4 and the groundwater elevation dropped about 1.7 feet in this well. Observation wells MW-2, MW-3, and MW-5 are each located approximately 55 feet from pumping well MW-4 and the groundwater elevation dropped about 0.7`feet in each of these wells. In general, a small radius of influence is expected for pumping in an unconfined aquifer. 2_5 Groundwater Sampling and Analysis Grab groundwater samples were collected from well MW-4 approximately 7.5 hours after the start of the pump test and just prior to the completion of the pump test. Groundwater samples }_ were transferred to appropriate sample containers, using clean, disposable bailers with bottom r emptying devices to reduce volatilization. Sample containers were then labeled with sample t identification, placed on ice, and shipped under chain-of-custody to State-certified Sequoia Analytical for chemical analysis of TPHd utilizing EPA method 8015 modified. Groundwater analytical results are summarized in Table 2 and laboratory data sheets are presented in Appendix A. 3.0 SUBSURFACE CONDITIONS 3_1 Geology 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, L< the maximum depth explored, consisted of sand and silt. 3_2 Hydrosmologv Water level measurements were collected from wells MW-1 through MW-6 on September 22, 1999. Water levels ranged from 9.78 to 13.28 feet below the tops of the well casing elevations. The water level data were used to develop the groundwater elevation contour map (Figure 3). Assuming that horizontal isotropic conditions prevail, groundwater in the uppermost aquifer beneath the site flowed towards-th"orthwest. The average hydraulic gradient on September 22, f 1999 was calculated to Pe 0.007 ft/ft f'r approximately 37 ft/mile. A summary of groundwater monitoring data is presented in Table 4. 4.0 ANALYTICAL RESULTS i '-J The groundwater sample collected from well MW-4 on September 22, 1999 contained a J detectable concentration of TPHd at 1,340 ppb. The groundwater sample collected from well MW-4 on September 23, 1999 contained a detectable concentration of TPHd at 1,170 ppb. W:62574.02Veports\M-per tecaoc 5