Hydrogeologic, water-quality, and biogeochemical data were collected at the site of a septage- treatment facility in Orleans, Massachusetts, from October 1988 through December 1992, where a nitrogen-rich effluent is discharged to the underlying glacial aquifer. The data were collected as part of a study done by the U.S. Geological Survey, in cooperation with the Massachusetts Department of Environmental Protection, Office of Watershed Management, to investigate the effect of effluent discharge on ground-water quality and the transport of effluent nitrogen through the aquifer. Hydrogeologic data include lithologic logs and ground-water levels. Water-quality data include chemical analyses of the treated septage effluent, of ground water at the water table beneath the infiltration beds, and of ground water throughout the aquifer. Dissolved concentrations of dinitrogen gas, nitrous oxide, and dissolved inorganic carbon also were measured. Biogeochemical data include concentrations of total ammonium and solid-phase carbon and nitrogen in aquifer sediments and sediments from the effluent-infiltration beds.