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Mr.Harlin Knoll Environmental 24 May I994 Resources Page 2 Management Table 2 presents the results of samples analyzed to evaluate biodegradation at the site. The results of these samples indicate that biodegradation is occurring at the site. As stated in the Investigation Results Report, if biodegradation is occurring, the concentrations of electron acceptors (sulfate and nitrate) within the hydrocarbon ground water plumes should be less than in the upgradient ground water. Similarly, the concentrations of metabolic byproducts (dissolved iron, dissolved manganese, and methane) should be greater in the hydrocarbon ground water plumes than in the upgradient ground water. The sample results verify that biodegradation is occurring at UST 1. The concentrations of sulfate and nitrate are lower in samples collected from wells within the hydrocarbon plume (MW-1 and MW-4) than the well located upgradient of the plume (MW-3). Similarly,the concentrations of dissolved iron, dissolved manganese, and methane in samples collected from MW-1 and MW--4 are greater than in the sample collected from MW-3. The graphs included as Attachment B present the concentrations of each compound at each sampling location with distance from the upgradient well. Biodegradation is also occurring at UST 2. The results of samples collected at UST 2 are similar to those observed at UST 1. At UST 2, the concentrations of sulfate and nitrate are lower in the sample collected from MW-6 (located within the hydrocarbon plume) than the well located upgradient of the plume (MW-5). Similarly, the concentrations of dissolved iron, dissolved manganese, and methane in the sample collected from MW-6 are greater than in the sample collected from MW-5. At MW-2 (located downgradient of UST 2), the concentrations of organics is low to non-detectable, indicating that this well is at the downgradient edge of the plume at UST 2. The results of the biodegradation parameter samples at this location are consistent with the organics results. With the exception of dissolved manganese, the concentrations of each of the biodegradation indicator compounds are similar to the concentrations observed in the upgradient well (MW-5), indicating that little to no biodegradation is occurring at this location. Dissolved manganese at MW-2 is elevated relative to MW-5; however, since low organic concentrations are present at this location, little biodegradation is expected. The graphs included as Attachment B present the concentrations of each compound at each sampling location with distance from the upgradient well.