On September 4-5, 2003 boaters encountered a horrible surprise on the Potomac. Over 60 million gallons of raw and partially treated sewage spilled in Antietam Creek, a tributary of the Potomac. Over the following week, the spill moved downriver and eventually passed Great Falls and Washington, DC. The spill was caused by a 24-hour power outage and exacerbated by heavy rain (nearly 4.5 inches) in less than 2 hours.
This same plant in Hagerstown, MD also spilled in February 2002 when industrial solvents killed the bacteria used to process the sewage. We have provided more information at: http://www.americanwhitewater.org/archive/article/385/.