SITE INFORMATION AND CORRESPONDENCE

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Wendy Cohen • - 2 - • 8 August 2003 We discussed the following points during the telephone conference: 1. The Board's concerns/expectations: a. The existing downgradient monitoring wells contain pollution, and there is no well downgradient that defines the extent of the plume. b. The cone of depression of the extraction system does not appear to reach the polluted downgradient wells, so there is still no control over the pollution leaving the facility. 2. LFC is resistant to chase the plume off site,preferring to spend money on remediation. The extent of pollutant migration off site is unknown. 3. LFC raised the question if they could show that the plume is stable, would we close the site. I stated that there are cases where monitored natural attenuation (NA) is an appropriate remediation action, but they would need to show that the plume is stable and then monitor it to show NA is occurring. Until the plume is defined,we cannot assume it is stable. In no case would we accept NA without monitoring. 4. LFC requested information on cleanup goals, and whether we would set cleanup goals based on risk. I said cleanup goals are based on the Basin Plan and non-degradation policy. Generally, we want to see cleanup to background levels. If that is not technically or economically feasible,we pick the most stringent water quality goal to protect beneficial uses. For diesel fuel, that level is usually 100 ug/l. 5. I concur that oxygenating the groundwater would probably accelerate biodegradation of the pollution and bring the site closer to closure. The extraction system appears close to creating hydraulic control of the source area plume, but the declining rate of fuel recovery means the pump and treat system is declining in efficiency. I would like to see a fence of oxygenation at the property line to mitigate pollution leaving the site. A second phase of oxygenation at the source area could be useful for accelerating biodegradation in the source area. LFC would have to gather some baseline data and propose a monitoring program to track progress of biodegradation, such as monitoring dissolved oxygen,nitrate, dissolved iron, and alkalinity. Jeff Reichmuth believes DO is the most critical monitoring parameter to track biodegradation. We would revise the MRP to reflect changes in the required monitoring if they proceed with the oxygenation proposal. 6. Extraction well RW-4A is located near the northwestern corner of the property. The closest monitoring wells to RW-4A are MW-5 and MW-14A. MW-5 last contained diesel fuel in June 2001, when it had 61 ug/I diesel. It also had no diesel fuel detections from June 1996 to March 2001. MW-14A was sampled quarterly 15 times since September 1999; 10 of the samples were non- detect, one contained 1,770 ug/1 TPHd(December 2000), and three contained about 100 ug/1 TPHd. Although it has been pumping about four gpm, it does not appear to be depressing the water table, especially since the cone of depression for extraction well EW-2 has developed. Because it is located downgradient from the source area, it may be creating a slight downgradient draw on the pollution. I believe it is worthwhile to shut down RW-4A for a trial period and monitor the response in the water table and pollution levels. If LFC is going to pump from a downgradient well, RW-1 or RW-2 would be more useful for capturing the escaping plume.