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i1995 . Ground water gradient shows a relatively flat flow to the east, with a high mound at MW3 (probable residual high in ground water caused from the vapor extraction at this well) 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 venting of MW8 commenced on Janaury 25, 1995 and lasted a duration of two hours The average flow rate calculated during this time was 49 cfm with a vapor stream composed of 0 . 13 mg/L as gasoline, 0 . 001 mg/L benzene and 311 carbon dioxide The weekly two hour venting of MW8 again occurred on February 1 and 8, 1995 Flow rate calculations showed similar rates of 53 and 52 cfm respectively. The vapor stream on February 1 contained 0 . 14 mg/L gasoline range hydrocarbons, 0 001 mg/L benzene and 3 . 3o CO2 The sample bag (tedlar) broke during the February 8th test therefore, no analysis of the vapor stream was conducted The above results show that the weekly two hour venting of MW8, is removing excess carbon dioxide and allowing oxygen transfer to occur A calculated 0 05 pounds of gasoline range hydrocarbons in being removed from MW8 weekly, see Table 4 and Appendix - Field Notes MW8 VENTING PROCEDURES We are using LTT vacuum trucks to pull an estimated 11 feet of water vacuum on MW8, for 2 hours weekly and exhaust directly to atmosphere This vacuum generates a flow rate of approximately 52 cfm. COLLECTING SAMPLES The sample is obtained from a sample port located, prior to the vacuum pump from a sample port on the flow meter orifice Sterile Poly tubing was used to attach a one liter tedlar bag, fitted PAGE 2