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1 The GETS preliminary design outlined in this proposal is based in part on the results of bail and ' pumping tests conducted in May and September 1990 The remediation comprises the following tasks, some of which have been completed. TASK I Installation of one groundwater recovery well, two downgradient monitor- ing wells, an injection well, and two piezometers t TASK II Determination of groundwater chemistry TASK III Groundwater treatment system permitting and final design TASK IV System construction and installation TASK V System start-up, operation, maintenance, and reporting Tasks I and 11 have been completed to date, and EA is implementing Task III ' 2.2 TASK I - INSTALLATION OF ONE GROUNDWATER RECOVERY WELL, TWO DOWNGRADIENT MONITORING WELLS, ONE INJECTION WELL, ' AND TWO PIEZOMETERS EA has permitted and installed one additional groundwater recovery well (RW4,Figure 4) This additional well is required because well MW 10, formerly proposed for groundwater recovery, has an insufficient amount of water The groundwater elevation in the Stockton area is not expected to rise in the near future, and pumping of the upgradient recovery wells will also de- crease the water level in MW 10. To further define the extent of the plume, two additional monitoring wells (MW 11, MW 12) were installed at the locations shown in Figure 4 Both the recovery well and the monitoring wells were constructed to contain a water column of 15 feet The boreholes were drilled and sampled ' in accordance with the "Tri-Regional Board Staff recommendations ° Soil samples were collect- ed in both the saturated and unsaturated zones and scanned with an organic vapor analyzer (OVA) Appropriate samples were submitted to a certified laboratory and analyzed for total ' petroleum hydrocarbons (TPH) as gasoline by EPA Method 8015 and for the aromatic hydrocar- bons benzene, toluene,ethylbenzene, and xylenes (BTEX) by EPA Method 8020 The wells were developed more than 72 hours after installation and sampled more than 24 hours after development Groundwater samples were analyzed for TPH as gasoline and for BTEX, as described above The elevations of the tops of the well casings were surveyed relative to the same benchmark as the other wells on the site ' An additional injection well (IW 1) was installed midway between MW4 and MW7 (Figure 4) This well will be used to distribute the injected water evenly into the aquifer In order to monitor the capacity of these wells to create a sufficient barrier between the two sites, two piezometers (P1, P2) were installed at locations shown in Figure 4 The piezometers were installed according to RWQCB guidelines ' v6Ww.6n394ZrJu19tM 13