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Kennedy/Jenks/Chilton Mr. Charles Whitworth Cal -Farm Supply 14 July 1989 Page 11 Nitrates A possible nitrate source was not identified at the Cal-Farm facility during the investigation. The results of the soil boring and surface sampling indicate that low concentrations of nitrate are present in surface soils, subsurface soils, and groundwater. Concentrations of nitrate exceeded the EPA Maximum Contaminant Level (MCL) drinking water standard in the groundwater sample collected from MW-2. However, the higher concentration of nitrate (1350 mg/L) reported in Roy F. Weston Inc. 's previous analysis of a water sample was not duplicated. The apparent groundwater gradient at the site is to the north, indicating the source of nitrates may not be from the Cal-Farm Supply storage area, buy may be due to offsite agricultural uses or local septic tanks. Pesticides in Soil Concentrations of 4,4'-DDT in four surface soil samples from the yard exceeded the Total Threshold Limit Concentration (TTLC) set forth by the California Code of Regulations (CCR) Title 22 to define a hazardous waste. The highest concentrations of pesticides were present in sample SS-11 which was collected at the base of the ramp by the southern door of the warehouse building (see Figure 6) . Pesticide concentrations in this area are consistent with the reported practice of sweeping the warehouse floor and discarding the material t out of the southern door The soil samples which contained 4,4'-DDT at levels above the TTLC were collected from areas adjacent to the warehouse building (SS-5, SS-11 , SS-13), or in the case of SS-4 at a low spot in the yard. Sample SS-6, SS-8, and SS- 10 were collected in the estimated pathways from the main warehouse building to the storage trailers where pesticides were reportedly stored The DDT concentrations from these samples were all below the TTLC, therefore, indicating that the DDt concentrations above the TTLC are restricted to the proximity of the main warehouse building. As DDT is a neutral organic compound (NOC) and has a low water solubility, the mobility of this chemical vertically in these soils would be expected to be low It appears that the concentration of chemicals in surface soils at the " site is highest near the source areas (warehouse building and storage trailers) and to a low spot near the center of the yard where surface drainage could collect. i