Swine manure anaerobic lagoons have sometimes been constructed in sandy soil without clay liners. Although swine manure and other animal manures have been reported to physically ”seal” lagoons to various degrees, long-term studies with sandy soil have been lacking. Two swine manure, anaerobic lagoons located in sandy, coastal plain soil were investigated. Both continued to have significant seepage after 3.5 to 5 years of receiving waste. Monitoring wells indicated broad seepage plumes, and much variation in concentrations of several parameters with well location, time, and depth of well. The variations indicate the difficulty of accurately monitoring and quantifying seepage transport of nutrients, and the complexity of developing groundwater transport models to accurately predict transport and transformations of chemical compounds, particularly ammonium and nitrate nitrogen, at various distances from the lagoon.