SITE INFORMATION AND CORRESPONDENCE

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Richard Powell - 2— Drainage 2— Drainage Channel Confirmation Report NCTS, Stockton in soil. Kerosene and fuel oil applied at 20 to 40 gallons per acre is a simple and effective [mosquito] larvacide for small bodies of water. Most larvaciding operations are conducted, using emulsions or granular formulations of DDT, dieldrin, chlordane, heptachlor, or lindane at 0.05 to 0.1 pound per acres (Metcalf, 1962). Based on communications with the San Joaquin County Agricultural Commissioner's Office, diesel oil was used as a carrier to DDT for weed control. Lightweight Superior brand oil was also used as a solvent for the DDT that came in powder form. A Senior Agricultural Biologist, who worked on the island in 1968 and then regulated the island between 1970 and 1985, stated that the Navy was known to dump crankcase oil, solvent from cleaning ships, and other waste oil/fuel in the landfill area. The biologist stated that you could smell the petroleum hydrocarbons when driving through the landfill area. According to the San Joaquin County Mosquito Abatement Agency, they performed surveillance activities on the island, as well as lab work to identify mosquitoes for the Navy. The Agency representative stated that#2 diesel oil was used as a larvacide and Weed Oil along the ditches for weed control. Therefore, we do not concur with the statement, "Because the pesticides and herbicides were routinely applied in a manner consistent with the standards for licensed application, they likely do not pose a threat to human health or the environment." 2. Leachability Evaluation. The Report states that, "The leachable limit for pesticides in NCTS, Stockton soils was determined from soil samples collected at Initial Assessment Study(IAS-9)." This is an incorrect statement. The leachable fraction of pesticides in soil for the contaminated road was developed for the specific Installation Restoration(IR) Site by using contaminated groundwater as the extract solution using the Waste Extraction Test(WET) methodology. This resulted in a leachable limit of 3.56 mg/kg for IAS-9. Ambient Screening Levels for pesticide concentrations in soil were developed in the Final Technical Memorandum Background Metal Concentrations and Ambient Pesticide Concentrations in Soil, October 1997. This document states that, "The WET analysis was performed on five of the 13 surface soil samples that recorded detection of pesticides. Pesticides were not detected in any of the WET analyses." The following table presents a comparison of maximum background concentrations versus drainage channel results. Maximum Background Maximum Constituent Concentration (pg/kg) Drainage Channel Concentration 4,4'-DDT 72 5,880 4,4'-DDD 8.8 5,700 4,4'-DDE 58 470 The table clearly shows that the drainage channel results are several orders of magnitude higher than background concentrations.