SITE INFORMATION AND CORRESPONDENCE FILE 1

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i 2.2 Performance of Test In well tests conducted with an above ground pump prior to the EVR pilot study, the aquifer produced no more than 0.5 gpm and only for a period of a few hours. A three hour non- enhanced vacuum recovery test was conducted with the newly constructed recovery well at the outset of the EVR pilot study. In this non-enhanced vacuum recovery test, groundwater was entrained with air through the stinger using vacuum, but the well head was open to atmosphere. This test corroborates previous findings that the aquifer would not sustain a flow greater than 0.5 gpm under conventional pumping conditions. Application of vacuum in the recovery well was achieved by closing the well head to atmosphere. Combinations of drawdown levels and vacuum pressures were used to determine the optimal parameters for maximizing groundwater recovery. Drawdown levels within the recovery well ranged from about 2.5 to 8.5 feet below static groundwater level. Vacuum pressures at the well head ranged from 0 to 55 inches of water column. Groundwater recovery rates ranged from 0.5 to 1.4 gpm and were determined by timing the duration I. required to fill a'unit volume container with water effluent discharged from the recovery/treatment system. in this study, optimal recovery well drawdown and well head vacuum are 8.5 feet and 45 inches of water column, respectively. Pertinent optimal recovery/treatment system settings are provided in Table 1. Once the optimal settings for natural and engineered systems were determined during the shake-down stage, the pilot study ' ensued at these settings, which consequently provided a well discharge of i gpm. s Groundwater levels in the recovery well were determined using pre-measured markings made j on the stinger during well head fabrication and accounting for the distance between the a stinger andAhe groundwater surface. Groundwater levels in the observations wells were made at regularly timed intervals using an electronic tape indicator. Table 2 summarizes the groundwater level measurements collected during the EVR pilot study. 3.0 Test Results A well yield of 1 gpm was sustained for a period of 72 hours in the pilot study. This represents a two-fold increase in groundwater recovery compared to standard pumping and non-enhanced vacuum techniques conducted at the test site prior to the pilot study. A maximum drawdown in the recovery well of 8.5 feet induced observation well drawdowns of about 0.5 and 0.4 feet at lateral distances of about 5 and 12 feet from the recovery well. Utilization of the vacuum generated by the specified treatment system to recover groundwater represents a new application for the system and demonstrates that groundwater can be effectively recovered from low yield aquifers without the use of pumps, downhole switches and timers. 4.0 Cost Considerations The EVR pilot study required approximately 130 in-field man hours to conduct. Capital expenditures totaled slightly less than $14,000. The more significant of the expenditures,were 519