SITE INFORMATION AND CORRESPONDENCE

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Mr. Eric Jenks • - 2 - • 13 March JJ00 The laboratory reported that some of the samples analyzed for diesel components showed an unidentified non -diesel hydrocarbon that eluted in the diesel range. JTF should fingerprint one of these samples to identify this compound. You may either obtain a new groundwater sample from the monitoring wells proposed near the east end of the former liquid tank farm, or you may fingerprint one of the previous samples that showed this non -diesel constituent that are stored at the analytical laboratory. Grab groundwater samples obtained near the concrete drainage swale identify ammonia, nitrate, 1,2-dichloropropane, and 1,2,3-trichloropropane at concentrations above initial screening levels. There is a storm drain downslope from the drainage swale. Most municipalities separate the storm drainage system from the sanitary sewer system. In these instances, storm drainage is routed to a ditch, drainage canal, creek or other untreated discharge point. Please investigate the discharge point(s) of the storm drain system at the site and report the findings in the monitoring well installation report. If the system is not connected to the sanitary sewer network, soil and water samples will be required from the discharge point. GeoSyntec used drinking water standards as the screening tool to gauge the relative impact a detected compound has on water quality. While this is a reasonable method to gauge health impacts to humans via drinking water, the California Water Code mandates that all beneficial uses of water be protected. At the JTF site in Stockton, beneficial uses of water include municipal, domestic and industrial water supply and protection of freshwater replenishment sources. The specific water quality standards that provide for this protection are identified in A Compilation of Water Quality Goals, published by the Central Valley Regional Water Quality Control Board. Many of these goals are lower than the drinking water standards, since small aquatic life cannot safely absorb the quantities of pollutants that the human body can. The State Water Resources Control Board recognizes that the quality of waters should be preserved, particularly when constituent concentrations in unpolluted water are lower than the water quality objectives. This is described in the Antidegradation Policy, Statement of Policy With Respect to Maintaining High Quality of Waters in California (Resolution 68-16). The corollary to the antidegradation policy Policies and Procedures for Investigation and Cleanup and Abatement of Discharges Under Water Code Section 13304 (Resolution 92-49) states that the Antidegradation Policy applies to cleanup of contaminated sites, and that the background pollutant concentrations are the primary cleanup goal. Several pollutants identified in the grab groundwater investigation at the JTF Stockton site are below drinking water standards, but greater than water quality goals and are therefore pollutants of concern here. These include chlorpyrifos, atrazine, diuron, and dacthal, in addition to 1,2,3 -TCP, 1,2-DCP, MTBE, bentazon and benzene identified above the screening level by GeoSyntec. Monitoring Well Work Plan The work plan portion of the report proposes five shallow groundwater wells bounding the identified source areas on three sides. As Ms. Carolyn Kneiblher and I discussed during our 29 February 2000 telephone conversation, it is not yet clear which direction groundwater flows, and an upgradient- monitoring well may be required once the direction is established. The proposed wells are positioned to provide constituent information from at least three of the identified source areas regardless of groundwater direction.