Seepage evaluation of older swine lagoons in North Carolina

Thirty-four swine waste lagoon systems in North Carolina were examined for evidence of seepage losses to the shallow groundwater. All were constructed prior to the state's January 1993 adoption of stricter construction standards. Mineral nitrogen concentrations (ammoniacal plus nitrate nitrogen) were used as the primary indicators of seepage impacts. Total mineral concentrations were compared to the U.S. EPA drinking water standard for nitrate-N of 10 mg/L. The shallow groundwater on approximately one-third of the 34 systems met the EPA standard at a distance of 38 m (125 ft) downgradient from the lagoon(s).