Characterization of nutrients and fecal indicator bacteria at a concentrated swine feeding operation in Wake County, North Carolina, 2009-2011

Hydrologic and water-quality data were collected during October 2009–January 2011 to characterize nutrient and bacteria concentrations in stormwater runoff from agricultural fields that receive wastewater originating at a swine facility at North Carolina State University's Lake Wheeler Road Field Laboratory (LWRFL) in Wake County, North Carolina. The swine facility consists of six swine houses, two wastewater storage lagoons, and wastewater spray fields. The data-collection network consisted of 11 sampling sites, including 4 wastewater sites, 3 in-field runoff sites, and 4 stream sites. Continuous precipitation data were recorded with a raingage to document rainfall conditions during the study.

Study sites were sampled for laboratory analysis of nutrients, total suspended solids (TSS), and (or) fecal indicator bacteria (FIB). Nutrient analyses included measurement of dissolved ammonia, total and dissolved ammonia + organic nitrogen, dissolved nitrate + nitrite, dissolved orthophosphate, and total phosphorus. The FIB analyses included measurement of Escherichia coli and enterococci. Samples of wastewater at the swine facility were collected from a pipe outfall from the swine housing units, two storage lagoons, and the spray fields for analysis of nutrients, TSS, and FIB. Soil samples collected from a spray field were analyzed for FIB. Monitoring locations were established for collecting discharge and water-quality data during storm events at three in-field runoff sites and two sites on the headwater stream (one upstream and one downstream) next to the swine facility. Stormflow samples at the five monitoring locations were collected for four storm events during 2009 to 2010 and analyzed for nutrients, TSS, and FIB. Monthly water samples also were collected during base-flow conditions at all four stream sites for laboratory analysis of nutrients, TSS, and (or) FIB.