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Y' Mr Chuck Carmel May 28, 1992 Page 2 (gpm) The groundwater extraction system has influenced the groundwater flow pattern locally, as shown on Figure 1 In September 1991, the pumping rate was reduced to approximately 5 gpm because too large of an area was being influenced when the pumping rate was 10 1 gpm Table 1 (Exhibit B) presents the water-level data for this site in tabular form, and Table 2 (Exhibit C)presents historical flow direction and gradient data for this site. Figure 1 also shows the water-level elevations for each well and the contours of equal water- level elevation calculated from the January 22, 1992, data Analytical results of current groundwater samples along with previous results are summarized in Table 3 (Exhibit D) The complete laboratory report for the January 1992 sampling is presented in Exhibit E Figure 2 shows BETX and TPH-G concentrations for each well sampled In addition, Figure 2 presents an approximation (dashed lune) of the lateral extent of benzene in the groundwater Discussion The general groundwater flow direction has not changed at this site since the last groundwater monitoring (October 1991) Water-level elevations have increased This increase is most likely the result of the reduced groundwater extraction rate .' In monitoring wells E-7, E-8, E-11, and E-12, BETX and TPH-G concentrations decreased. PR-1 and PR-2 continue to record nondetectable BETX and TPH-G constituents. Ground- water samples taken from well E-10 recorded higher BETX and TPH-G concentrations than the last quarterly groundwater sampling (October 1991) The BETX and TPH-G constituents detected in samples collected from the other wells remained relatively stable. The BETX and TPH-G concentrations have remained relatively stable in nearly all of the wells since the groundwater extraction system was started in June 1991 Based on this information, two reasonable assumptions can be made--(1) the hydrocarbon-affected groundwater plume is not migrating off site, and (2) the operation of the groundwater extraction system is having a beneficial effect on the groundwater quality at this site The slight fluctuations in the TPH-G and BETX levels may be caused by the change in the flow rate of the groundwater extraction system Samples from wells E-8,BHD-1, and BHD-2 were analyzed for fecal coliform The analytical results of these samples indicate that fecal coliform populations are not present in any of these wells The purge water generated during this sampling event was temporarily stored on site in 55-gallon barrels then transported off site by Balch Petroleum Company Brown and Caldwell 6746\RFP0RTSJAN92QMAVr Const.. ants