US Army Corps of Engineers
Baltimore District

Water Treatment Residuals Management Project

The Washington Aqueduct maintains and operates the Dalecarlia and McMillan Water Treatment Plants which serve reliable and safe potable water to the District of Columbia, Arlington County and the City of Falls Church, VA. Historically, river solids removed during the water treatment process have been disposed of by returning them to the Potomac River. The reissued version of the National Pollution Discharge Elimination System (NPDES) permit precludes the discharge of river solids or residuals to the river.

The Residuals Project Involves:

  • Construction of equipments and facilities that collects water treatment residuals from three different locations: Dalecarlia Sedimentation Basins, Georgetown Reservoir and the Dalecarlia Reservoir Forebay.

  • Construction of dredge system and pumping station at each location.

The residuals will be collected from the three locations and then pumped and transferred through piping system to a central processing facility for dewatering and loading of disposal.

To learn more about the steps Washington Aqueduct took to arrive at a residuals management process read the final Executive Summary in the Environmental Impact Statement.


Milestone Schedule

The construction contract was awarded in March 2008 and the builder Archer Western began mobilization activities in May 2008.

The schedule is governed by the provisions of a Federal Facilities Compliance Agreement (FFCA).  In May 2007, Washington Aqueduct requested an extension of the date for final completion due to delays incurred during project development and to allow for safe operation of the water treatment facilities during this major construction.  In May 2010, Washington Aqueduct requested a second extension of the date for final completion to compensate for delays in the installation of the complex foundation piling for the principal residuals processing facility and to accommodate the seasonal high water demand periods as well as the conditions of the NPDES permit and the FFCA that restrict current authorized discharges during the spring spawning seasons.  In June 2011 Washington Aqueduct requested a third extension.  EPA approved this request.

For further questions about the status of the residuals project please contact:

Chief, Planning & Engineering Branch
Tel:  202-764-2776
Fax: 202-764-2756
Email: Nathan.H.Cole@usace.army.mil