The Washington Aqueduct is an aqueduct that brings water from the Potomac River to Washington, D.C., and parts of its suburbs.

One of the first major aqueduct projects in the United States, it was commissioned by the U.S. Congress in 1852, and construction began the following year under the supervision of Montgomery C. Meigs and the U.S. Army Corps of Engineers. Portions of the aqueduct began operation on January 3, 1859, and the full pipeline began operating in 1864. It has been in continuous use ever since.

Owned and operated by the Corps of Engineers, the aqueduct is part of the system that supplies the public water systems that serve D.C. and nearby Virginia locations, including Arlington County, Falls Church, and part of Fairfax County.

It is listed as a National Historic Landmark. The Union Arch Bridge, which carries a portion of the aqueduct, is also listed as a Historic Civil Engineering Landmark.

Design and facilities

thumb|upright=1|The Washington Aqueduct Dam, upstream of the [[Potomac River's Great Falls]]

The centerpiece of the Aqueduct is a 12-mile (19 km) pipeline that connects the system's dam at Great Falls with the Dalecarlia Reservoir on the border with Montgomery County, Maryland. Portions of the Aqueduct went online on January 3, 1859, and the full pipeline began operating in 1864.

The Dalecarlia Reservoir serves as a primary sedimentation basin. A portion of the water from the reservoir is treated at the nearby Dalecarlia Water Treatment Plant and distributed to municipal water mains. The remainder of the water from the reservoir flows to the Georgetown Reservoir in the Palisades neighborhood of Washington. This facility serves as an additional sedimentation basin, and then the water flows through the Washington City Tunnel to the treatment facility at the McMillan Reservoir, after which it is pumped through city mains. The Dalecarlia Reservoir was modified in 1895 and 1935 to improve water quality and increase water supply. Improvements in the early 1900s were planned and supervised by Army engineer Henry C. Newcomer. The regular use of chlorine as a disinfectant began in 1923 at the McMillan plant. The McMillan plant was not replaced until 1985, when a rapid sand filter plant was opened next to it.

Operations and service area

The Aqueduct is a wholesale water supplier to utilities that bill customers and manage water mains. The service area is:

  • Washington, D.C., and most of the federal installations in the city through the District of Columbia Water and Sewer Authority
  • Arlington County, Virginia
  • Falls Church, Virginia, and part of Fairfax County, including McLean

References

Further reading

  • U.S. Army Corps of Engineers: official Washington Aqueduct website
  • National Park Service.gov: A longer history of the system, from the C&O Canal site
  • National Park Service.gov: National Historic Landmarks Program & the Washington Aqueduct
  • Maps of the Washington Aqueduct, Md. and Washington D.C. : to accompany supplemental report of Chief Engineer dated Feb. 22nd 1864
  • at Maryland Historical Trust website