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GROUND WATER SAMPLE RESULTS These latest sample results showed levels declining at MW1, MW3 , MW10, and MW12 . MW2, MW7 and MW8 showed slight increases and MW4, MW5, MW6, MW9 and MW11 continue to be below laboratory detection limits Dissolved Oxygen measurements were obtained during sampling and show Oxygen saturation at vapor recovery well MW-10, with Oxygen lows at MW-4 and MW-8, both on the leading edge of the hydrocarbon plume, see Table 1, Figure 5, Figure 6- Charts and Appendix A. VAPOR RECOVERY OPERATIONS AND RESULTS The original REMOX unit operated for 14452 hours out of a total of 21048 hours (69s) From August 18, 1992 to March S. 1996, the new replacement unit operated 18786 hours out of 31095 hours (60°s) During the site visit on June 7, 1995, excessive noise generating from the blower prompted the noon shut down of the REMOX unit . The unit remained off until September 23 , 1995 . At that time the blower was replaced with 2 DR 505 Rotron blowers and the system was restarted As of March 5, 1996 an estimated 74849 pounds of gasoline range hydrocarbons have been destroyed, see Table 2 , in Appendix C - Air Monitoring Notes Since March 11, 1993 the vapor recovery/destruction has been declining when above 100 pounds per day of gasoline range hydrocarbons were being removed, down to 1 85 pounds per day on December 19, 1995 . A request for Modification to the system was made, to remove the TO and replace it with activated carbon vapor scrubs This modification was approved, see Update ##29-Appendix D. On March 6, 1996, start-up of the Carbon Adsorbtion system occurred, see Appendix C Table 2 is a summary of the Carbon Adsorbtion Vapor Recovery System and shows approximately 92 pounds of gasoline range hydrocarbons have been removed as of June 27, 1996 MW-8 BIO-VENTING/OXYGEN TRANSFER 0"n October 20, 1994 , a bio-venuing 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 The vapor extraction system at Former Regal Station 603 , PTO ## N- 1090-1-0 , was 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 source 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 PAGE 2 R603 UPDATE-44 7/19/96