On January 23, 2011, a pipe break at the Potomac River Substation in Alexandria, Virginia, owned by Pepco, LLC, resulted in the discharge of 17,000 gallons of mineral insulating oil from the No. 9 transformer. An underground secondary containment reservoir overflowed, resulting in a discharge of approximately 4,500 gallons of oil into the Potomac River, causing injury to natural resources, including birds, fish, and benthic habitat. Due to the oil's properties, the material spread quickly with river currents, sheer force of wind, and gravity. The resulting oil sheen was reported from the Washington Sailing Marina to National Harbor, a distance of 3.5 miles. Eleven subsequent discharges of accumulated storm water occurred from the site between February 1 and June 23, 2011. During spill response activities, portions of the Mount Vernon Trail, in George Washington Memorial Parkway, were closed, preventing visitors from accessing portions of the trail and nearby recreational opportunities. In addition, three bird mortalities were observed and two oiled birds were recovered or observed as oiled during surveys following the spill.