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OffilF. _ - - �` A' - _ k .. - ng OMM6 t GROUNDWATER REMEDIATION This section describes the groundwaier remediation proposed for the site. ' Water Quality and Hydrology nitoring Groundwater flows south to south-southwest beneath the site under a hydraulic gradient measured ranging from 0.002 to 0.0:5. The elevation of theinn April 1987 Grote d ac r elevathe tions and wells has declined approximately 8 to 11 feet stn p Appendix B. historical gradient data ase presented in Table 1 and 2 in The concentration of benzene, ethyibenzene, toluene, and xylenes (BETX) in individual oncentration of Table 3 C shows the c monitoring wells have varied over time. n groundwater r samples Collect from the BETX and total netroleum hydrocarbons as gas olut monitoring wells on a quarterly basis since 198'. 1991 sampling of rine monitoring A projected zero line based on analytical data from April welly Ls shown in Figure 4. HyDROGEOLOGIC MEASUREMENTS AND PREDICTIONS tter extraction NS step-drawdown pumping test was performed on A ermme the hy,�lraul c properties of the Installed on the site- The test was conducted to better d tuld yield water• pumping zone around E-1 and to determine the rates at which E-1 co Vg steps were used in the test. The first rate of l g llon per minute(gpm) was Two pumping maintained for 60 minutes a which es,the the water level in E-i had tZe1� 60 ft 'rninatsnatt which m m and continued for pp pump rate was stepped up to 2.31 gp intake and the test was stopped. time the water level in E-1 fell below the pump W-3,W-9,and W-2A periodically Water levels were measured in wells Vtlte aquifer t test data forms for each well. during the pumping. Appendix D provides The water level c E 1 was measured using a dedicated ORS interface tape. Water levels in the observation wells were measured using a single marine rnoisture interface tape mp rates were calculated by dividing the reading from a decontaminated between eac�ons}by the uartsptred time. continuous flow gauge(in g The data collected from observation well W-2 was analyzed using the Generalized Straight The method was used to determine the transmissivity Line Ivle[hod of Cooper and Jacob(1.946)1. ___.._ ----------- l0 of equivalent time. Equivalent (T) and hydraulic conducrvity (K)of the material ethos�grated zone-around-the-we tgur 5 is a plot of the drawdown(s)over discharge(Q) if had been time is the time at which the observed drawdown would haveoccurredaye aa given time.pumping done at a constant discharge rate equal to the actual discharge �y ry� �