Potomac Water Supply Program Trap Rock Water Treatment Facility

The new, $133.2 million Trap Rock Water Treatment Facility represents a landmark investment in regional infrastructure, delivering a state-of-the-art 20-mgd potable water treatment plant with the built-in scalability to reach 40 mgd. This project meets the demands of Loudoun Water’s rapidly growing population, ensuring long-term water security through advanced technology and sustainable design. A centerpiece of the facility’s operation is its LEED Gold-certified administration building, which operates alongside a general maintenance facility to support the site’s comprehensive utility needs.

The project’s technical complexity is highlighted by the 400-foot-long Goose Creek Tunnel with two 50-foot drop shafts, which required a hand-mined effort with less than 30 feet of cover between the top of the tunnel and the 20-foot-deep creek bed.

The new facility features a pre-ozone contactor facility and operations building housing flocculation basins, sediment basins, settled water ozone contactor, filters and a UV system. A deep-bed, dual-media Granular Activate Carbon (GAC) and sand biological filtration system was installed into the new facilities, including a nozzle and plenum underdrain system equipped with air scour, dissolved oxygen monitoring, and chemical feed. The residuals handling facilities include backwash, equalization, clarification, sludge thickening, and two clearwells. Completing the facility is a finished water pump station, 3,500 feet of 42-inch-diameter finished water transmission main, a sanitary pump station, and 10,000 feet of 12-inch-diameter force main.