Pesticide and PCB residues in the upper Snake River ecosystem, Southeastern Idaho, following the collapse of the Teton Dam 1976

Abstract

The Teton Dam in Southeastern Idaho collapsed on June 5, 1976. The resulting flood damaged a large area and caused the release of toxicants into the Snake River. A pesticide recovery team in a helicopter worked the flooded area for three weeks and collected 1,104 containers, about 35% of which contained toxicants. It was estimated that less than 60% of the lost pesticide containers were recovered.

This paper addresses the results of a one-time sampling effort designed to determine the magnitude of the chemical contamination. Over 300 samples of fish, plankton, waterfowl, sediments, water, stream drift, aquatic plants, and soil were taken. Pesticide residues were measured asμg/kg (ppb) wet weight, whole animal basis. Rainbow trout had as much as 1432μg/kg total DDT plus analogs, 66μg/kg dieldrin, and 1010μg/kg PCBs. Utah suckers had up to 1420μg/kg total DDT plus analogs, 32μg/kg dieldrin, and 1800μg/kg PCB. Rocky Mountain whitefish had as much as 2650μg/kg total DDT and analogs, 30μg/kg dieldrin and 1400μg/kg PCBs. These PCB and DDT levels were high, approaching the 2,000μg/kg FDA proposed tolerance, but were below the 5,000μg/kg present tolerance. Dieldrin levels were low and organophosphates were undetectable.

An undeveloped area (the Fort Hall Bottoms) showed higher levels of contaminants than did an industrialized area (the lower Portneuf River). This apparent discrepancy remains unexplained.

Very little pre-flood data on a whole fish basis were available for comparison (Johnsonet al 1977). However, it does not appear that any human health hazard due to pesticide levels exists in this portion of the Snake River.