An earlier study tested an unlined swine lagoon and detected elevated mineral nitrogen concentrations 38 m down gradient from the lagoon. The current study conducted hydrologic and water quality monitoring of the site from March 1999 to September 2004, a period during which the lagoon went from being semi-active to completely closed out. It was found that the average hydraulic gradient decreased from 0.0033 m m‐1, prior to the activation of a groundwater pumping system (Mar. 1999 to Jan. 2000) to 0.0010m m‐1 after pumping was initiated (Sept. 2000 to Sept. 2004). Also, the average hydraulic gradient was reduced by 70%. Since the installation of the pumping system, approximately 17,900 m3 of subsurface water has been pumped, removing 1200 kg of TN from the groundwater plume. TAN concentrations steadily declined from 120 mg L‐1 at the onset of pumping in September 2000 to less than 6 mg L‐1 by September 2004.