Return to Overview Map
Visit a section of river between Great Falls and Georgetown...
Great Falls
Claude Moore Colonial Farm
Glen Echo, Md.
Potomac Overlook Regional Park
Little Falls
Chain Bridge
Georgetown, Washington, D.C.
|
Great Falls is the original intake for the Washington Aqueduct, the supply division of the District of Columbia water system. The Aqueduct facilities, built and operated by the U.S. Army Corps of Engineers, bring about 200 million gallons a day out of the Potomac, divert it through two conduits under MacArthur Boulevard, and treat it at the Dalecarlia and McMillan Water Treatment Plants. The original Aqueduct was built in the early 1860s by the Corps, and is still operated by the Corps. The city of Washington was served by a number of wells and springs for the first several decades of its existence. By 1802, the city was laying wooden pipes made of bored logs for supplying a few houses on Pennsylvania Avenue. But the main impetus for a reliable source of water for the city came from the need for adequate fire protection. Between 1832 and 1850, a number of studies for Congress indicated that springs and wells would not be adequate for the future growth and safety of the city. The British invasion of 1814 and burning of the White House had given evidence enough of that.
Water from the Potomac first entered the conduit in December 1863. When it was put in service, it worked perfectly and did not need draining for 27 years.
The most impressive structure of the Aqueduct, now a National Historic Landmark and source of local pride, is the Cabin John Bridge, also called the Union Arch. It was built from 1857 to 1863, and when completed, it was the longest masonry arch in the world. The main arch has a span 220 feet long, rising 57 feet above the creek. A plaque on the bridge lists Franklin Pierce as President of the U.S. and Jefferson Davis as Secretary of War.
Cabin John Bridge held the record as the longest stone masonry arch in the world from 1863 to 1903, when a similar bridge was built in Luxembourg. The bridge is not solid masonry, but consists of hollow spandrel arches inside the main arch, to relieve the loads. A second raw water conduit was constructed in 1926, parallel to the old conduit. At the Cabin John Valley, the Corps built an "inverted syphon" which dips into the valley. The syphon is visible as a box-like structure in the valley below the bridge. Together, the two conduits supply more than 200 million gallons of water for Washington, D.C., Falls Church, and Arlington, Va.
|
