Several Ecolocity members joined the tour of McMillan Park, site of DC's early water reservoir and sand filtration system. The site was originally laid out by Frederick Law Olmsted. The 1905 completion of the McMillan Reservoir Slow Sand Filtration Site was a Washington public health milestone. Its innovative system of water purification, which relied on sand rather than chemicals, led to the elimination of typhoid epidemics and the reduction of many other communicable diseases in the city. The 25-acre site consists of regulator houses, sand bins, washers, and underground sand filtration beds. A legacy of the City Beautiful Movement, the complex is an engineering wonder that served its original purpose until 1986. Since its purchase by the District government in 1987, the site has deteriorated severely due to lack of maintenance. It is now threatened by pressure for commercial and residential development. McMillan Reservoir was designated a DC Historic Landmark in 1991.