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GROUND WATER SAMPLE RESULTS The latest sample results showed a decline in contaminant levels associated with the ground water at MW2 , MW3 , MW8 and MW12 Monitor wells MW4 , MW5 , MW6, MW7, MW9 and MW11 continue to be below detection limits The other wells that have some degree of ground water contamination (MW1 and MW10) showed slight increases, see Table 1, and Figure 5 . VAPOR RECOVERY OPERATIONS AND RESULTS The original REMOX unit operated for a total of 14452 hours out of a total of 21048 hours (690-. ) . As of April 26 , 1995, the new replacement unit has operated 13913 hours out of 22459 hours (62%) An electrical problem associated with the REMOX make-up air blower and needed repair to the pilot assembly caused sporadic operation from September 2, 1994 through February 4 , 1995 As of April 19, 1995 an estimated 74496 pounds of gasoline range hydrocarbons have been destroyed, see Table 2, Chart-Figure 5 and Appendix A - Air Monitoring Report Since April 15, 1993 the vapor recovery/destruction has been declining, from an average above 100 pounds per day of gasoline range hydrocarbons to a low of 2 . 5 pounds per day on January 12 , 1995 . Presently, the system is destroying between 1 to 9 pounds per day of gasoline range hydrocarbons. MW-8 BIO-VENTING/OXYGEN TRANSFER On October 26, 1994, a bio-venting source test was performed on MW-8 The purpose of this test was to evaluate the benefit of performing a once a week evacuation of the well to enhance oxygen transfer and remove residual CO2 Presently the vapor extraction system at Former Regal Station 603 , PTO ## N-1090-1-0 , is only having only limited effect on the leading edge of the dissolved gasoline range plume that has traveled east from the site, across Pacific Avenue Two sources tests, of two hours each, were conducted on MW8 The well is near the leading edge of the plume and results indicate that a two hour vacuum extraction once a week will help control the migration of the plume and will enhance biodegradation by removing CO2 and enhancing oxygen transfer while limiting hydrocarbon removal to less than 0 1 pound per week. Mr Mark Schonhoff of San Joaquin Valley Unified Air Pollution Control District, evaluating this source test as it pertains to air quality conditions in the Stockton area and has allowed Wickland to perform the weekly two hour venting of this well The weekly venting of MW8 commenced on Janaury 25, 1995 and lasts a duration of two hours. The average flow rate calculated during during these venting events is 64 cfm with an average vapor stream containing 0 119 mg/L as gasoline and 2 5o carbon PAGE 2 R603 UPDATE-38 5/04/95