A TOUR OF DALECARLIA RESERVOIR

June, 2000 -- In the first half of the nineteenth century, when the District's population soared from 3,000 to 52,000, water supplies became alarmingly low. In an age of wooden buildings, fear of fire motivated an outcry for a larger source of water than government-operated springs and private wells could supply.
In 1851, when a room in the Capitol that housed the Library of Congress was destroyed by a fire because there was no way to put it out, Congress took steps to provide a more adequate water supply for the city.
In 1853, when a young army lieutenant, Montgomery C. Meigs, delivered to Congress his survey of possible new water sources for the city and his recommendations for how to deliver it, Congress provided the funds to start building the system. Meigs was appointed to oversee its construction.
Considering understandable delays caused by the Civil War and political bickering about having the military in charge of a civil works project, by 1863, water from the Potomac River was entering the city's water supply system.
On Saturday, May 6, twenty-five Palisades residents, the lucky first to sign up, were given a thorough tour of the Dalecarlia Water Treatment Plant and a fascinating lesson in the history of the Washington, DC water supply system, known as the Washington Aqueduct, by its Civilian Chief Engineer, Thomas P. Jacobus.
The three-hour tour was arranged for by John Finney, The Palisades News' on-the-spot reporter.
Much of the system that Meigs designed in the 1850's is still in use today and much of it is located in our Palisades neighborhood, or in nearby Maryland.
Meigs turned to the most obvious source of water in the region, the Potomac River.
Water would be drawn from the river upstream at Great Falls, a higher altitude than the city (as it was developed at the time - basically Georgetown across to Capitol Hill).
The Great Falls water was (and still is) carried to the Dalecarlia Reservoir by a 9 foot diameter conduit under MacArthur Boulevard (originally named "Conduit Road"). The conduit crosses over Cabin John Creek by means of the Union Arch Bridge, the single-lane automobile bridge linking Glen Echo and Cabin John.
A daring design for the 220-foot bridge was conceived by Meigs and, for forty years, it remained the longest single span arch bridge in the world.
Two reservoirs, Dalecarlia and Georgetown, were provided to settle out sediments and, from there, water (sometimes still muddy) ran downhill to the Capitol.
The original system could be almost completely gravity-fed, requiring little pumping to produce adequate water pressure all over town.
Water purification, other than the removal of some of the sediment, was not part of Meigs' plan, though by 1900, a prevalence of typhoid fever argued for filtration and sterilization.
In the 1900's, new elements were added to the system to meet growing water consumption and the spread of the city: the "Little Falls" dam and intake, the Dalecarlia water treatment plant, the water treatment elements at the McMillan Reservoir (near Children's Hospital), new holding reservoirs to distribute water to higher elevations as the city grew to the north (Ft. Reno, and behind the German Embassy on Foxhall Road, for example).
The Dalecarlia and Georgetown Reservoirs are the first step in treatment of the water. Some of the sediment in the river water settles out in the two reservoirs.
The Dalecarlia Reservoir was recently dredged, with the sediments trucked to Hains Point and disposal sites in Maryland and Virginia. The catchment basins at the Georgetown Reservoir, which sends water across town to the McMillan plant, are emptied for cleaning from time to time.
Water from the Dalecarlia Reservoir goes into four settling basins along Norton Street, which also have to be flushed out periodically. Currently these sediments are allowed to be flushed back into the river when the flow is high, but should the Environmental Protection Agency not renew the flushing permit, more heavy truck traffic through the neighborhood would be required.
Water purification, the last process, takes place at both the Dalecarlia Water Treatment plant and at the McMillan Reservoir and Water Treatment Plant, which receives about 30% of the Potomac waters directly from the Georgetown Reservoir. From these two plants, water distribution is managed by the Department of Public Works.
Don't worry: those gushers we see in the middle of MacArthur Boulevard are not from Meigs' conduit; they are damaged city water mains.
The neighborhood is fortunate to have the Washington Aqueduct within its boundaries.
The Dalecarlia plant and reservoir and the Georgetown Reservoir and Gate Houses are beautiful historic structures providing pleasant water vistas, attractions for wildlife and open space that we all enjoy.
But the Washington Aqueduct is a major industrial operation. It furnishes water not only to District residents, but to the Federal Government, including Andrews Air Force Base; to Northern Fairfax Country including Vienna and Falls Church; and to all of Arlington County!
It operates with no public funds but the fees it charges for its product.
For all of this, it is amazing that it operates in our low-density residential neighborhood without impairing our quality of life.
We should certainly stay informed about Aqueduct activities such as the trucking of sediments and the proximity of potentially dangerous chemicals (see Palisades News, April 2000), but after our visit with Tom Jacobus, we were all impressed by the highly professional manner in which the operation is conducted and by the Aqueduct's willingness to work with its Palisades neighbors.
--Lynn Scholz