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• MEMORANDUM CALIFORNIA-REGIONAL WATER QUALITY CONTROL BOARD • CENTRAL VALLEY REGION 3443 Routier Road, Suite A Phone: (916) 255-3000 Sacramento, CA 95827-3098 CALNET: 8-494-3000 TO: Gordon L. Boggs FROM: Elizabeth A. Thayer UGT Program Manager Associate Engineer n/ DATE: 28 November 1995 SIGNATURE: �^- SUBJECT: MEETING, GEWEKE, 16 SOUTH CHEROKEE LANE, LODI, SAN JOAQUIN COUNTY A meeting was held 27 October 1995, to discuss the progress of insitu bioremediation at the Geweke site. An agenda and attendance list are attached. Geweke's consultant, Advanced GeoEnvironmental (AGE), provided handouts (also attached) during the meeting. In September, AGE collected numerous soil and ground water samples for analysis by an independent microbiologist, Keith Kauffman. Based on his analysis, AGE proposes to facilitate bioremediation in soil with the addition of oxidized nitrogen and water into the subsurface using inoculation wells. We discussed the moisture content of the soil. According to the consultants, the water table will not be affected by adding water to the soil. The original inoculum contained 100% biodegrading bacteria. The microbiologist determined that the current population includes up to 24% biodegraders. AGE is not certain if the bacteria are native or the bacteria which were inoculated in August 1994. Addition of nitrate will require application for Waste Discharge Requirements and hydraulic control or nitrogen removal. Benzene is the material of main concern, however, the handouts show cross sections of soil TPHg contamination at the depth interval 40 to 45 feet. High concentrations remain in soil at other depths as well. Soil contours at other levels and benzene concentrations in ground water were not provided. Geweke has an existing contingency plan consisting of soil vapor extraction, ground water extraction, and above ground biotreatment. The contingency plan was to be implemented upon failure of the insitu bioremediation plan to reach the goals. The original bioremediation plan was projected to clean up the soil in one to two years, and clean up ground water in six months to a year. The monitoring reports indicate that the treatment system has not achieved the goals. We required that a down gradient well be installed between existing wells MW-9 and MW-12 to ensure hydraulic control. AGE has been doing vapor monitoring monthly. The data shows an inverse relationship between oxygen and carbon dioxide concentrations in the vapor. However, it is difficult to relate the data to other site phenomena, such as hydrocarbon concentrations or bacterial populations. AGE requested to discontinue the vapor analysis. You requested that they continue data collection until further analysis confirms that the data is not needed. AGE stated that they have used this procedure at several sites regulated by our Fresno Office and they have worked with John Noonan and Russell Walls.