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Ms Chuck Carmel <br /> January 12, 1993 <br /> Page 2 <br /> i' <br /> Discussion <br /> The general groundwater flow direction is to the northeast, except in the area of the recovery <br /> well, where the groundwater extraction system influences the water table Water-level <br /> elevations have decreased an average of 0 42 feet since the last quarterly monitoring <br /> (July 1992) <br /> Compared to July 1992 sampling results. BETX and TPH-G concentrations are lower or nearly <br /> the same in all wells sampled except for E-4 and E-9 Well E-9 showed an increase in all <br /> hydrocarbon constituents analyzed, and well E-4 showed an increase in benzene <br /> A product recovery system was installed at this site around 1984 After the free product was <br /> recovered, the system was modified for use as a groundwater extraction system and operated <br /> periodically from 1986 to 1991 The system was modified to incorporate groundwater <br /> extraction in 1991, and the system has been operating nearly continuously since June 1991 <br /> The operation of the groundwater extraction system has influenced the groundwater flow <br /> pattern locally as shown on Figure 1 In September 1991, the primping rate was reduced to <br /> between 3 and 5 gpm because too large of an area was being influenced at a pumping rate of <br /> 10 1 gpm (rate prior to September 1991) -The BETX and, TPH-G concentrations have <br /> remained relatively stable in nearly all ofthe wells since the groundwater extraction system <br /> #� was started in June 1991. Based on this'information, two reasonable assumptions can be <br /> made--(1) the hydrocarbon-affected groundwater plume is not migratmg off site, and (2) the <br /> operation of the groundwater extraction system is having a beneficial effect on the <br /> groundwater quality at this site. The slight fluctuations in the BETX and TPH-G levels may <br /> be caused by the changes in the flow rate of the groundwater extraction system or fluctuations <br /> in water levels. <br /> The current groundwater monitoring program will be continued through 1993 Please contact <br /> Mr. Misner at (916) 444-0123 if you have any questions about this report. <br /> EO G3E <br /> Sincerely, r <br /> BROWN AND CALDWELL CONSULTANTS �'� EN <br /> P P <br /> N 7 Oa <br /> .... <br /> Steven Misner C. Lucas <br /> Project Manager California Registe ogist #4301 <br /> SDM.irb <br /> Enclosures <br /> k <br /> CC. Mr. Jim Maughan, California Regional Water Quality Control Board, Central Valley <br /> r/Ms. Mary Meays, San Joaquin County Health Department <br /> Mr. Clint Rogers, Chevron <br /> Mr Frank Tucker, City of Stockton <br /> Brown and Caldwell <br /> C OnSU�TG r-S 6748�EtEPORTS�ACI92QIR RP r <br />