Publication Summary

The Environmental Investigations and Laboratory Services Program of Ecology monitored ground water quality for one year at a seven-year-old dairy lagoon in Lewis County. Ecology's Water Quality Program requested this study as part of a larger effort to define the impact of dairy lagoons on ground water quality at four locations in Washington State. The results of these studies will be used to augment existing dairy waste management programs.

The Environmental Investigations and Laboratory Services Program of Ecology monitored ground water quality for one year at a seven-year-old dairy lagoon in Lewis County. Ecology's Water Quality Program requested this study as part of a larger effort to define the impact of dairy lagoons on ground water quality at four locations in Washington State. The results of these studies will be used to augment existing dairy waste management programs.

Monitoring wells were installed and subsequently sampled quarterly. Analytes included chloride, total dissolved solids, total organic carbon, chemical oxygen demand, total phosphorus, ammonia-N, nitrate+nitrite-N, and total and fecal coliform bacteria. The target aquifer consisted of a thin, confined or semi-confined gravel layer at a depth of about 30 feet. Silt and clay deposits overlie the gravel layer and act to separate the lagoon from the aquifer. The lagoon does not appear to have affected ground water quality to date. Although nitrate-nitrite-N concentrations were elevated relative to upgradient conditions in two downgradient wells, none of the other parameters tested, particularly chloride, were elevated.