Surface Water Impairment from Storms and Swine in North Carolina

High-profile incidents of flooding, catastrophic lagoon breaches, and thousands of animal deaths have put a spotlight on the environmental risks associated with a geographically-concentrated hog industry and the annual storm season in North Carolina. The purpose of this paper is to quantify the impact of swine feeding operations on surface water quality given existing permit protocols, examine the role of precipitation in exacerbating outcomes, and evaluate whether the current regulatory/permit system can be revised to better protect North Carolina’s water resources. Using inorganic nitrogen, phosphorus, and fecal coliform readings from surface water quality monitoring locations throughout the state, daily precipitation, and the list of permitted animal feeding operations, we estimate difference-in-difference models to compare surface water quality outcomes before and after excessive precipitation across monitoring locations. Our results indicate that excessive rain triggers levels of fecal coliform that exceed the Environmental Protection Agency’s safety standards for drinking, swimming, and boating at monitoring locations downstream of swine feeding operations. Given the low incidence of reported lagoon overflows in our period of analysis, our results suggest that runoff from manure applied ahead of extreme rainfall is the primary mechanism by which hog feeding facilities damage water resources in North Carolina.