Water and the City


This hybrid park and civic infrastructure was originally the Slow Sand Filtration Plant. Fresh water from Great Falls in Virginia was brought cross-town through the Washington Aqueduct to the McMillan Reservoir Water was pumped into the catacombs where it was filtered naturally by the sand, collected through pipes at the base, stored and later distributed throughout the city. This plant was built by Congress in the early 20th century as a public health measure to provide pure water and eradicate typhoid and other water borne diseases. The innovative sand filtration system was very ecological and energy efficient, but it was also very labor



The slow sand filtration system was declared technically obsolete and replaced with a chemical plant in 1987.


McMillan Sand Filtration Plant

Underground sand-filtration vaults


Silo, used to filter dirty sand


Silo with entrance to vaults


McMillan Sand Filtration, McMillan Silo
Slow-Sand Filtration
McMillan Silo, Vaults entrance

Diagram of underground vaults, showing water level