Abstract

In 1998, the Millard County Commission approved a conditional use permit for a new poultry farm operation near Sugarville, Utah, which ultimately may house as many as 3 million chickens. The farm operation uses ground water to supply drinking water for the chickens and to wash the eggs. Water used in the egg-washing process is disposed of in an on-site wastewater lagoon. Much of the manure produced by the birds is used as fertilizer on adjacent farmlands. The land on which the wastewater lagoons are located and manure is applied is underlain by unconsolidated deposits forming the principal drinking-water aquifer for the area. The principal drinking-water aquifer system consists of a deep unconfined aquifer along the basin margins and one or more confined aquifers in the central parts of the basin; where confined, the principal aquifer is overlain by a shallow unconfined aquifer (not a drinking-water aquifer). Although ground water in the principal aquifer is generally of good quality, the potentially large amount of manure associated with the poultry farm operation and its potential impact on the quality of water resources has caused concern among local government officials.

We documented baseline ground-water quality in the area prior to the poultry farm becoming fully operational so that any adverse impact associated with manure applications from the farm could be documented. We established 35 shallow polyvinyl chloride (PVC) monitoring wells, and sampled ground water from these wells and from eight land-drain ditch locations quarterly for five sampling periods in 2000-01; the samples were analyzed for total-dissolved-solids (TDS) and nutrient concentrations. We also sampled 19 water wells in the study area that are completed in confined aquifers underlying the shallow unconfined aquifer in June 2003, and analyzed the ground water for general chemistry, nutrients, and TDS concentrations. For the shallow unconfined aquifer, TDS ranged from 1204 to 63,974 mg/L and averaged 13,293 mg/L, and nitrate concentrations ranged from <0.1 to 236 mg/L and averaged 6.34 mg/L. For the principal aquifer, TDS ranged from 240 to 372 mg/L and averaged 294 mg/L, and nitrate concentrations ranged from <0.1 to 0.51 mg/L and averaged 0.33 mg/L. Based on these data, the poorer quality water in the shallow unconfined aquifer appears to be partitioned from water in the confined aquifer.