Washington Aqueduct

The Washington Aqueduct is an aqueduct that brings water from the Potomac River to Washington, D.C., and parts of its suburbs. It was one of the first big aqueduct projects in the United States. The U.S. Congress approved it in 1852. Building started the next year under Montgomery C. Meigs and the U.S. Army Corps of Engineers.

Some parts of the aqueduct began working on January 3, 1859, and the whole system started in 1864. It has been used ever since. The Corps of Engineers owns and runs it. The aqueduct gives clean water to D.C. and nearby areas in Virginia, like Arlington County, Falls Church, and part of Fairfax County.

The aqueduct is a National Historic Landmark. The Union Arch Bridge, which carries part of the aqueduct, is also 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 began with one pipe to carry water. It didn’t have special cleaning places, so it used reservoirs to help clean the water. But as Washington grew, the water from the Potomac River had too much dirt, and the reservoirs couldn’t clean it well anymore.

In 1905, a big cleaning system called a slow sand filter was built at McMillan Reservoir to 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 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 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 gives water to many places. It brings water to Washington, D.C. and most of the important buildings there through the District of Columbia Water and Sewer Authority. It also gives water to Arlington County, Virginia, Falls Church, Virginia, and part of Fairfax County, including McLean. People in these areas use the water for their homes and businesses.