The Washington Suburban Sanitary Commission (WSSC) is a nonprofit organization that provides safe drinking water and wastewater treatment for Montgomery and Prince Georges Counties in Maryland except for a few cities in Montgomery County that continue to operate their own water facilities. It was established on May 1, 1918. It is the eighth largest water and wastewater utility in the United States. The WSSC serves about 1.8 million people in an approximately 1,000-square-mile (2,600 km2) area. It owns and manages about 10,000 miles (16,000 km) of water and sewer mains. A bi-county agency, WSSC has extensive regulatory functions. It promulgates and enforces the plumbing code for its jurisdiction as well as reviews and approves contract plans for extensions of water and sewer mains. The agency operates 3 reservoirs (plus shared access to a fourth reservoir), 2 drinking water filtration plants, and 6 wastewater treatment plants. It also collects wastewater which is treated at the Blue Plains Advanced Wastewater Treatment Plant (operated by DC Water) in Washington, D.C. * shared resource with Fairfax County Water Authority and Washington Aqueduct. Jennings Randolph Lake, operated by the U.S. Army Corps of Engineers, is also shared by these water suppliers.