McMillan Park


McMillan Sand Filtration Site is a twenty-five acre park and decommissioned water treatment plant in northwest Washington, D.C. connected to the McMillan Reservoir. Two paved courts lined by regulator houses, tower-like sand bins, sand washers and the gated entrances to the underground filter cells provided a promenade for citizens taking the air in the park before it was fenced off in WWII.


Below grade, there are twenty catacomb-like cells, each an acre in extent, where sand was used to filter water from the Potomac River by way of the Washington Aqueduct. The purification system was a slow sand filter design that became obsolete by the late 20th century. In 1985, a new rapid sand filter plant replaced it across First Street beside the reservoir. The treatment system is operated by the Army Corps of Engineers.


Public access to the site has been restricted since World War II, when the Army erected a fence to guard against sabotage of the city's water supply. Specially arranged biannual tours are supported by scores of visitors curious about the odd-looking structures. The park was never reopened to the public on the same basis as before the war.

For information concerning the McMillan Advisory Group (MAG), please contact your Bloomingdale Civic Association MAG Representatives: Betsy McDaniel ( or visit the MAG website: McMillan Advisory Group


For more information on Vision McMillan Partners (VMP) and the proposed master plan, visit the master plan website: Envision McMillan


For more information on the Friends of McMillan (FoM), visit the group’s website: Friends of McMillan Park


Read more about McMillan on Wikipedia.