The United States Steel Corporation (USSC) National-Duquesne Works is composed of two separate plants, the National Plant and the Duquesne Plant on the east and west banks, respectively, of the Monongahela River. The plants are about 8 km (13 mi) upstream of the confluence of the Allegheny and Monongahela Rivers at Pittsburgh, Pennsylvania. The Duquesne Plant is primarily an iron and steel production facility with some finishing operations. Ancillary facilities include an oxygen plant, granulated slag operation and water treatment plant. Wastewater is discharged through seven major outfalls (011, 012, 013, 014, 015, 016 and 017) and four intermediate outfalls (111, 211, 112 and 114). All wastewaters are discharged untreated with the exception of process wastes from the blast furnaces, BOF, primary mills and bar mill. Blast furnace and BOF process wastewaters are treated for solids removal by gravity thickening and vacuum filtration of sludge. Scale pits are installed for the removal of mill scale from primary and bar mill wastewaters. U.S. EPA Region III, Philadelphia, Pennsylvania, requested the National Enforcement Investigations Center (NEIC) to conduct an intensive survey of wastewater discharges to the Monongahela River from U.S. Steel Corporation facilities.