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A-05 9. This aerial applicator site has been in use since 1962 and rinse water has been discharged to a borrow area created when dirt was used to construct the runway. During the rainy season, there is standing water on the disposal area due to its topography and restricted drainage caused by high clay content soils. The disposal site was registered as an impoundment under Cortese, but the owner has since indicated that he does not feel it meets the definition of a "surface impoundment" . Soil sampling of the disposal site was conducted in 1975 and 1976 and indicated that several pesticides were present in the soils and that OC pesticides were greatly attenuated in the upper 5 feet of soil . In 1980 testing of rinse water from tanks to which a neutralizer was added indicated that the rinse water was not hazardous waste; however, only a small percentage of the pesticides used at the facility were tested. For the current investigation, two composite soil samples were collected. One was comprised of four samples from 0-6" and the other was comprised of two samples from 18"-24". Analyses of the 0-6" samples revealed endosulfan and thiobencarb present at relatively high levels and several other pesticides present at low levels. The endosulfan interfered with testing for DDT and other pesticides in the 0-6" sample. At 18"-24", endosulfan, molinate, and thiobencarb were present at low levels; no other pesticides, including DDT or metabolites were detected. Disposal area soils need to be retested to confirm the absence of DDT in the upper few inches of soil . If DDT is not present at 1 ppm or above, then the disposal site will not be a hazardous waste site and can be regulated accordingly. The site owner has indicated that he will abandon land disposal and construct above-ground tanks for rinse ►,rater. 10. This facility has been utilized by three aerial applicator businesses over the last 40 years. The current operators acquired the facility from their parents and implemented changes in rinse water disposal practices. One change, made a few months before our inspection, was to install a sump, a submersible pump, and an above-ground tank for rinse water. Prior disposal was onto a paved area (part of which had numerous 'cracks ) or into a small pit from where it probably infiltrated. The first sampling site selected was a gravel area adjacent to the runway at the end where the wash area is located. The sampling site was approxi- mately 50 feet from the old pit in the wash area; the separating area is paved with asphalt. At approximately 8 inches depth, an underlying fill of large gravel was encountered. The large gravel was discolored and had a pesticide/hydrocarbon odor. Free water was encountered at 18 inches. Samples of the discolored gravel and of the water were collected. Two soil composite samples were taken from areas adjacent to other portions of the runway. One composite was from 1"-6" at five sites (surface debris was removed prior to sampling) , and the other sample was from 18-24" at two sites . A water sample was collected from a faucet supplied by an on-site well .