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r ` A-C7 12. This is a small aerial applicator facility serving just a few planes. Rinse water is discharged from a concrete pad and into a plastic-lined impound- ment constructed in 1980. The liner is deteriorated. Approximately 1/3 of the impoundment bottom was not under water and a thick layer of sulfur and discolored sediment was visible. A sample of the sediment and a sample of the liquid in the impoundment were collected. Analyses of the sediment was difficult, due to the large amount of sulfur. In particular, the detection limits for DDT and metabolites was elevated, but given the age of the facility, it is doubtful that any DDT was dis- charged into the impoundment. Several pesticides were detected in the pond liquid and sediment at levels which indicate that the impoundment is not adequate for the wastes being discharged and that it should be closed. Due to the deteriorated condition of the pondliner, additional soil testing will be necessary after the pond contents and liner are removed. The Facility owner has indicated that he could modify the existing wash pad to discharge to an above-ground tank. 13. This site was selected as an example of a fairly new facility that has been well designed and operated. The applicator business is a medium sized operation that applies pesticides to grains, row crops, and orchards in the Sacramento Valley. Washing is done on a concrete pad that drains into a hypalon-lined surface impoundment constructed in November 1980. Pesticide tanks on applicator planes have been field-rinsed and only exterior wash has been discharged to the impoundment. A sample of the liquid in the impoundment was analyzed and found to contain only low levels of carbamate pesticides and 0.8 ppb of DDE. The probable sources of the DDE are washing of equipment used to apply Kelthane (DDE is a contaminant of Kelthane) , or soil adhering to tires after the airplanes have utilized outlying airstrips where DDE residues remain from past operations. A bioassay was performed on the liquid to evaluate its toxicity. For the test conducted, a waste with a 96-hour LC50 of 500 mg/l is considered to be 'hazardous ' . The test indicated that the wastewater in the impoundment had a 96-hour LC50 of approximately 75,000 mg/1 . It appears that the current operation is not generating a waste that is hazardous or poses a significant threat to water quality based on the management system utilized. However, the operator has indicated that due to increasingly stringent laws directed at surface impoundments, he plans to close the impoundment and install above-ground tanks for rinse water• management. -,