Washington Aqueduct

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. Construction began the next year under the supervision of Montgomery C. Meigs and the U.S. Army Corps of Engineers.

Portions of the aqueduct started working on January 3, 1859, and the whole system began operating in 1864. It has been used ever since. Owned and operated by the Corps of Engineers, the aqueduct is part of the system that provides clean water to D.C. and nearby areas in Virginia, including Arlington County, Falls Church, and part of Fairfax County.

The aqueduct is recognized as a National Historic Landmark. The Union Arch Bridge, which carries part of the aqueduct, is also honored as a Historic Civil Engineering Landmark.

Design and facilities

The Washington Aqueduct has a main pipeline that is 12 miles long. It starts at a dam at Great Falls and ends at the Dalecarlia Reservoir near Montgomery County, Maryland. Parts of the aqueduct started working on January 3, 1859, and the whole system began operating in 1864. The pipeline runs along MacArthur Boulevard and passes over high cliffs by the Potomac River.

The Union Arch Bridge carries the pipeline and the road over Cabin John Creek and the Cabin John Parkway near Cabin John, Maryland. For 40 years, this bridge was the longest masonry arch bridge in the world. The Dalecarlia Reservoir helps clean the water. Some water from here is treated at the Dalecarlia Water Treatment Plant and sent to city water pipes. The rest goes to the Georgetown Reservoir in Washington's Palisades neighborhood. From there, the water moves through the Washington City Tunnel to the McMillan Reservoir for more treatment before being pumped into city water mains. The Dalecarlia Reservoir was changed in 1895 and 1935 to make the water cleaner and provide more water.

Expansion

The Washington Aqueduct started with just one pipe to carry water. It didn’t have special cleaning places for the water, so it depended on special areas called reservoirs to help clean it. But as Washington grew, the water from the Potomac River had too much dirt, and the reservoirs couldn’t do their job well anymore.

In 1905, a big cleaning system called a slow sand filter was built at McMillan Reservoir to help make the water safer. Later, in 1923, they started using chlorine to keep the water clean. The old McMillan plant was replaced in 1985 with a newer, faster kind of filter.

In the 1920s, a second pipe was added, along with new reservoirs and a place to push the water along. By 1927, a fast sand filter plant was ready at Dalecarlia Reservoir. In the 1950s, this plant became even bigger and now serves places in Virginia.

In 1926, Congress allowed the aqueduct to sell water to Arlington County, Virginia. A new pipe at Chain Bridge made this possible in 1927. As Arlington grew, more pipes were built, even one under the Potomac River. Later, Falls Church, Virginia, and parts of Fairfax County, Virginia, were also added.

In 1959, a new dam called Little Falls Dam was built, along with a new place to take in water and a pumping station. This new intake helps supply extra water, especially when there is very little rain.

Operations and service area

The Washington Aqueduct provides water to many places. It sends water to Washington, D.C. and most of the federal buildings there through the District of Columbia Water and Sewer Authority. It also supplies water to Arlington County, Virginia, Falls Church, Virginia, and part of Fairfax County, including McLean. These areas use the water for their homes and businesses.