The Washington Aqueduct is an aqueduct that provides the public

water supply Water supply is the provision of water by public utilities, commercial organisations, community endeavors or by individuals, usually via a system of pumps and pipes. Public water supply systems are crucial to properly functioning societies. Th ...

system serving Washington, D.C., and parts of its suburbs, using water from the

Potomac River The Potomac River () drains the Mid-Atlantic United States, flowing from the Potomac Highlands into Chesapeake Bay. It is long,U.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map. Retrieved Augu ...

. One of the first major aqueduct projects in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

, the Aqueduct was commissioned by

Congress A congress is a formal meeting of the representatives of different countries, constituent states, organizations, trade unions, political parties, or other groups. The term originated in Late Middle English to denote an encounter (meeting of ...

in 1852, and construction began in 1853 under the supervision of

Montgomery C. Meigs Montgomery Cunningham Meigs (; May 3, 1816 – January 2, 1892) was a career United States Army officer and civil engineer, who served as Quartermaster General of the U.S. Army during and after the American Civil War. Meigs strongly opposed sec ...

and the

US Army Corps of Engineers , colors = , anniversaries = 16 June (Organization Day) , battles = , battles_label = Wars , website = , commander1 = ...

. Portions of the Aqueduct went online on January 3, 1859, and the full pipeline began operating in 1864. The system is owned and operated by the Corps of Engineers and has been in continuous use ever since. It is listed as a

National Historic Landmark A National Historic Landmark (NHL) is a building, district, object, site, or structure that is officially recognized by the United States government for its outstanding historical significance. Only some 2,500 (~3%) of over 90,000 places liste ...

, and the

Union Arch Bridge The Union Arch Bridge, also called the "Cabin John Bridge", is a historic masonry structure in Cabin John, Maryland. It was designed as part of the Washington Aqueduct. The bridge construction began in 1857 and was completed in 1864. The roadw ...

within the system is listed as a

Historic Civil Engineering Landmark __NOTOC__ The following is a list of Historic Civil Engineering Landmarks as designated by the American Society of Civil Engineers since it began the program in 1964. The designation is granted to projects, structures, and sites in the United State ...

Design and facilities

The centerpiece of the Aqueduct is a 12-mile (19 km) pipeline which connects the system's dam at Great Falls with the Dalecarlia Reservoir on the border with

Montgomery County, Maryland Montgomery County is the most populous county in the state of Maryland. As of the 2020 census, the county's population was 1,062,061, increasing by 9.3% from 2010. The county seat and largest municipality is Rockville, although the census-design ...

. Portions of the Aqueduct went online on January 3, 1859, and the full pipeline began operating in 1864. The pipeline runs along what is now MacArthur Boulevard, traversing some of the higher cliffs along the Potomac River. Washington Aqueduct dam - look SE - Great Falls of the Potomac River - 2007-10-31

Washington Aqueduct dam - look SE - Great Falls of the Potomac River - 2007-10-31

The

carries the pipeline and MacArthur Boulevard over Cabin John Creek and the Cabin John Parkway near the community of Cabin John, Maryland. This bridge was the longest

masonry Masonry is the building of structures from individual units, which are often laid in and bound together by mortar; the term ''masonry'' can also refer to the units themselves. The common materials of masonry construction are bricks, building ...

arch bridge An arch bridge is a bridge with abutments at each end shaped as a curved arch. Arch bridges work by transferring the weight of the bridge and its loads partially into a horizontal thrust restrained by the abutments at either side. A viaduct ...

in the world for 40 years after its completion. The Dalecarlia Reservoir serves as a primary

sedimentation Sedimentation is the deposition of sediments. It takes place when particles in suspension settle out of the fluid in which they are entrained and come to rest against a barrier. This is due to their motion through the fluid in response to the ...

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 The McMillan Reservoir is a reservoir in Washington, D.C. that supplies the majority of the city's municipal water. It was originally called the Howard University Reservoir or the Washington City Reservoir, and was completed in 1902 by the U.S. A ...

, 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.

System expansion

The system originally used a single pipe for water delivery, and did not have any

water purification Water purification is the process of removing undesirable chemicals, biological contaminants, suspended solids, and gases from water. The goal is to produce water that is fit for specific purposes. Most water is purified and disinfected for hu ...

plants, relying instead on the reservoirs to act as settling basins. By the turn of the 20th century, however, Washington's growth and the high amount of

sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand ...

in the Potomac's water kept the reservoirs from doing their jobs well, and so the first treatment plant, a massive

slow sand filter Slow sand filters are used in water purification for treating raw water to produce a potable product. They are typically deep, can be rectangular or cylindrical in cross section and are used primarily to treat surface water. The length and bre ...

bed system, was installed at McMillan Reservoir, and was completed in 1905. Publication No. EP 870-1-67. The regular use of

chlorine Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine i ...

as a

disinfectant A disinfectant is a chemical substance or compound used to inactivate or destroy microorganisms on inert surfaces. Disinfection does not necessarily kill all microorganisms, especially resistant bacterial spores; it is less effective than s ...

began in 1923 at the McMillan plant. The McMillan plant was not replaced until 1985, when a

rapid sand filter The rapid sand filter or rapid gravity filter is a type of filter used in water purification and is commonly used in municipal drinking water facilities as part of a multiple-stage treatment system. Rapid sand filters were first developed in the ...

plant was opened adjacent to it. In the 1920s, the aqueduct was upgraded with the addition of a second pipe from Great Falls to Dalecarlia, along with several new reservoirs and a pumping station, A rapid sand filter plant was built at Dalecarlia Reservoir, which went online in 1927. The Dalecarlia plant is the larger of the two plants in the system, having been upgraded in the 1950s, and is the plant that serves the

Virginia Virginia, officially the Commonwealth of Virginia, is a state in the Mid-Atlantic and Southeastern regions of the United States, between the Atlantic Coast and the Appalachian Mountains. The geography and climate of the Commonwealth are ...

communities that use the Aqueduct. In 1926, Congress approved selling water from the aqueduct to

Arlington County, Virginia Arlington County is a county in the Commonwealth of Virginia. The county is situated in Northern Virginia on the southwestern bank of the Potomac River directly across from the District of Columbia, of which it was once a part. The county ...

. A new water supply pipe was constructed at Chain Bridge and service to Arlington began in 1927. Additional pipes were built as Arlington's population grew, including a pipe built under the Potomac River. In 1947 Congress approved adding the city of

Falls Church, Virginia Falls Church is an independent city in the Commonwealth of Virginia. As of the 2020 census, the population was 14,658. Falls Church is included in the Washington metropolitan area. Taking its name from The Falls Church, an 18th-century Ch ...

to the aqueduct system, and nearby portions of

Fairfax County, Virginia Fairfax County, officially the County of Fairfax, is a county in the Commonwealth of Virginia. It is part of Northern Virginia and borders both the city of Alexandria and Arlington County and forms part of the suburban ring of Washington, D. ...

were added in the 1960s. The Corps built an additional intake and pumping station at Little Falls in 1959.

Operations and service area

The Aqueduct is a

wholesale Wholesaling or distributing is the sale of goods or merchandise to retailers; to industrial, commercial, institutional or other professional business users; or to other wholesalers (wholesale businesses) and related subordinated services. I ...

water supplier. The communities it serves are responsible for billing customers and managing water mains. The service area is: * Washington, D.C., and most of the federal installations in the city (via DC Water) * Arlington County * The city of Falls Church and part of Fairfax County (particularly McLean).

References

External links

U.S. Army Corps of Engineers: official Washington Aqueduct website

* ttp://tps.cr.nps.gov/nhl/detail.cfm?ResourceID=1401&resourceType=Structure 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 {{Authority control Aqueducts in the United States Water in Washington, D.C. Transportation buildings and structures in Montgomery County, Maryland Bridges in Montgomery County, Maryland Bridges in Washington, D.C. Transportation buildings and structures in Washington, D.C. Infrastructure completed in 1859 Water supply infrastructure on the National Register of Historic Places National Historic Landmarks in Washington, D.C. National Historic Landmarks in Maryland Transportation buildings and structures on the National Register of Historic Places in Maryland Transportation buildings and structures on the National Register of Historic Places in Washington, D.C. Chesapeake Bay watershed Potomac River watershed National Register of Historic Places in Montgomery County, Maryland Aqueducts on the National Register of Historic Places The Palisades (Washington, D.C.)

Design and facilities

System expansion

Operations and service area

References

Further reading

External links