The Fairfax County Water Authority (FCW A) is one of the largest water purveyors in Virginia, producing an average of 111 million gallons of water per day for approximately 960,000 people. Located in Northern Virginia, FCW A supplies drinking water to Fairfax, Prince William, and Loudoun Counties, the Town of Herndon, the City of Alexandria, and several federal institutions within the area. The Potomac River and the Occoquan Reservoir constitute the raw surface water supplies for the service area.

On March 28, 1993, a 36-inch oil transportation line ruptured, spilling in excess of 400,000 gallons of No.2 fuel oil in the vicinity of Reston, Virginia. This massive spill severely contaminated the Potomac River and forced a complete shutdown of FCWA's Corbalis Water Treatment Plant (WTP) for 13 days. Since the Corbalis WTP normally meets 50 percent of the water demand, production from FCW A's other treatment facilities, drawing from the Occoquan Reservoir, had to be dramatically increased during a period of unusually harsh raw water conditions.