The Monongahela River Watershed — the largest of the sub-watersheds with a drainage area of 7,386 square miles, a 128-mile waterway that begins near Fairmont, WV and joins Allegheny River in Pittsburgh to form the Ohio River. The Pennsylvania Department of Environmental Protection (PADEP) has classified this river as a Warm Water Fishery (WWF), meaning that this type of stream maintains and propagates fish species and additional flora and fauna that are indigenous to a warm water habitat. It also is protected under the Navigation (N) use, meaning that this type of stream is used for the commercial transfer and transport of persons, animals, and goods. The Monongahela River has played a significant role in the history of the region. It has served as a transport avenue for runaway slaves who were heading north, a major transportation route for westward settlement during colonial times and later propelled the industries along its shores to worldwide importance and unequaled production. Along with its changing roles and functions, the Monongahela River itself has adapted. It has been transformed from a wide and shallow river to a slow- moving, deeply pooled, body of water. The Monongahela River has approved TMDLs for two pollutantsóchlordane and PCBs. Chlordane was used from 1948 until 1988 in the United States as a pesticide; it is a persistent chemical (>20 years) and bioaccumulates in the environment and tissues of animals. PCBs are manmade chemicals that were used in transformers, paints, adhesives, caulking compounds, some filters, and carbonless copy paper. PCBs enter the environment in air, water, and soil during the manufacturing process. The Monongahela River Conservation Plan (RCP) was completed in 1998 and contains management objectives to assist in the future planning of the watershed.