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ll � <br /> Mr Chuck Carmel <br /> August 12, 1992 <br /> Page 2 <br /> Results <br /> The groundwater extraction system at this site has been in operation since June 1991 The <br /> groundwater extraction system has influenced the groundwater flow pattern locally, as shown <br /> on Figure 1 In September 1991, the pumping rate was reduced to approximately 5 gpm <br /> because too large of an area was being influenced at a pumping rate of 10 1 gpm (rate prior <br /> to September 1991) Table 1 (Exhibit B) presents the water-level data for this site in tabular <br /> form, and Table 2 (Exhibit C) presents historical flow direction and gradient data for this site <br /> Figure i also shows the water-Ievel elevations for each well and the contours of equal water- <br /> level elevation calculated from the April 22, 1992, data <br /> Analytical results of current groundwater samples along with previous results are summanzed <br /> m Table 3 (Exhibit D) The complete laboratory report for the April 1992 sampling is <br /> presented in Exhibit E Figure 2 shows BETX and TPH-G concentrations for each well <br /> sampled In addition, Figure 2 presents an approximation (dashed line) of the lateral extent <br /> of benzene in the groundwater <br /> Discussion <br /> The general groundwater flow direction has not changed at this site since the last groundwater <br /> monitoring (January 1992) Water-level elevations have increased an average of 0 87 feet. <br /> This increase is most likely the result of the reduced groundwater extraction rate and recharge <br /> from precipitation <br /> Changes in concentration of constituents in groundwater since the last quarterly momtonng <br /> in January�l992-are=summarized=as-follows <br /> T The-BBETX and TP =G concon ions decreasedmin monitoring welly F_-2, E-7, and E�9.1 - Tf <br /> P��.;PR-2 and HB D-2 continue i acreo�rd_nvndetectable_BE'L'�_aud TPH;Q' Groundwater <br /> samples taken from well E-10 recorded de,�d 6enzene,_ethylbenzene, xylenes and TPH-G <br /> but increased toluene concentrations. The�nzene-coaceritrauon_in the sample from well`E=5� <br /> has d�_asecr d whole the`other`canstttucrrts-have increased since this well was_last..sampled <br /> (�pril-19 In wells E=$and-E=11;the BETX concentration has remained stable and the <br /> TPH-G concentration has increased. The BETX and TPH-G constituents detected in samples <br /> collected from the other wells remained relatively stable. <br /> product recov ry_system was-built-arount 1984 The system has been modified a number <br /> of tunes since then and operated periodically from 19$4 to 1990 Additional modifications <br /> were made in 1991, and the system has been operating nearly continuously since June 1991 <br /> The BETX and TPH-G concentrations have remained relatively stable in nearly all of the <br /> wells since the groundwater extraction system was started in June 1991 Based on this <br /> information, two reasonable assumptions can be made--(1) the hydrocarbon-affected 7 <br /> groundwater plume is not migrating off site, and (2) the operation of the groundwater �h <br /> extraction system is having a beneficial effect on the groundwater quality at this site The <br /> Brown and Caldwell <br /> Consultants 67ao�r�oxTsaQTxxiYr <br />