Built by the Army Corps of Engineers in the early twentieth century to provide clean drinking water for the District of Columbia, the 92-acre site included a reservoir fed by water from the Potomac River via the Washington Aqueduct, a pump station, concrete sand bins and sand washers, masonry regulator houses, and a grid of subterranean filter cells constructed below a leveled earthen plinth. Opened in 1905, the site was named for Senator James McMillan, chairman of the Senate Commission on the Improvement of the Park System of the District of Columbia. The site also functioned as a public park. Landscape improvements were implemented between 1908 and 1919 designed by Frederick Law Olmsted Jr. in collaboration with engineer Allen Hazen, architect Charles Platt, and sculptor Herbert Adams.

In 1986, a 25-acre portion of the site was decommissioned and sat unused for 35 years, eventually being added to the D.C. Inventory of Historic Sites in 1991. Through an initiative led by the Office of the Deputy Mayor for Planning and Economic Development (DMPED), Vision McMillan Partners (VMP) was selected in 2007 to deliver a mixed-use project that includes a grocery store, a healthcare facility, 12 acres of public open space, and more than 600 units of housing, retail, and restaurants. Although it took some time to get local groups on board with the proposal, plans were eventually approved by the Historic Preservation Review Board in 2016, only for court challenges to postpone demolition until 2021. The opening of Reservoir Park and Community Center in 2024 represents the inaugural phase of this transformative project, setting the stage for new mixed-use investment while enlivening an established - yet underserved - neighborhood.

Reclaiming
Inspired by the historic resources of the obsolete industrial facility and envisioning the remaining remnants as a framework, the designers introduced new civic uses for the site: a sunken plaza, a playground, a tree-lined promenade, an unprogrammed greenspace, and a shared-use street. The main gathering area is a 30,000-square-foot plaza inserted between the community center and stabilized earthen berms that form the perimeter. Terraced gardens, concrete amphitheater seating, and two splash fountains invite prolonged visits to the plaza, while a dramatic pedestrian portal incised through the berm connects it to the adjacent neighborhood. The grid of columns that once supported the roof of the filtration cells inspired the plaza's paving design. Stairs and accessible ramps provide access to the upper level of the earthen plinth and connect a tree-lined promenade that encircles the park.

 
Bioretention gardens, permeable paving, and vegetated roofs reestablish the function of the site as a place for water purification. The community center roof, vegetated with sedum, drains to the plaza level, where it enters bioretention features. All paved surfaces in the plaza comprise permeable pavers set atop deep gravel storage areas that drain into adjacent bioretention facilities. The engineered soil blend in these bioretention basins absorbs and retains water, preventing it from being flushed from the site to the city's storm system. Bioretention facilities are planted lushly with woody and herbaceous plants that utilize the captured stormwater. To ensure the health and longevity of new trees and to meet local green infrastructure requirements, it was necessary to provide 1,500 cubic feet of rootable soil for trees. Because many of the trees are in areas of permeable pavers, structural soil was used to suspend the paving near the trees.

A Paved Palimpsest
The former filtration site's engineered grid, designed topography, and industrial character inspired the design and materiality of the new park, which balanced new construction with preservation and reintroduced publicly accessible open spaces into an urban context. For example, concrete columns that once supported the roof of the subterranean water filtration cells and served as conduits for drinking water were preserved and integrated into the plaza. They now function as interpretive features that help visitors appreciate the scale of the former engineering works, transitioning from the interior of the filter cell to the openness of the plaza while projecting their design rhythm into the paving pattern.

This pattern presented one of the biggest challenges encountered during construction, as the design team attempted to relate the new features to the original site grid based on the regular rhythm of structural columns that supported the roof of the subterranean filter cells. However, the columns could not be effectively surveyed before demolition because they were below the artificial terrain. The design of the plaza elements - including the framework of the aquatic center and its canopy columns, the geometries of the bioretention facilities, and the layout of site furnishings, lighting, paving patterns, and interpretive features - all depended upon replicating the grid in relationship to the columns that remained in the preserved filter cell, which would be open to the plaza as a museum gallery. Site layout was carefully controlled with surveying during construction, and routine visual checks were made to ensure that the new site elements were aligned to the column grid that had been demolished. Making the site accessible to the public for social interaction, active and passive recreational interests, and historic interpretation inspired the conversion of unused space into a productive one that meets the diverse needs of the community.

Repurposing
Along the park's northern edge, the Landscape Architects transformed a former service court into a public courtyard. Serving as a formal entrance to the development, this shared-use loop road is designed as a woonerf, "a Dutch term for common space created to be shared by pedestrians, bicyclists, and low-speed motor vehicles" (Department of Transportation). Where traditional woonerfs slow drivers with trees, planters, and other obstacles, the preserved brick structures and iconic concrete silos at Reservoir Park produce the same effect. In subsequent phases of the project, residential and retail properties will be added just north of the service court in what will be called the Reservoir District. An identical area is planned on the other end of the future residential structures.

Restoring
The new composition also includes a memorial fountain, stone plaza, and ceremonial stair originally installed in 1913 in honor of Senator James McMillan and designed by sculptor Herbert Adams and architect Charles Platt. These commemorative features had been held in storage since 1941 and were returned to the site, restored, and positioned by the Landscape Architect as close to their original location as possible to reestablish views of the nearby reservoir. When the fountain was originally installed, stone steps extended from street level and up the berm to the fountain plaza on the West side of First Street. However, when restoration plans were discussed, the original location was not available because the Army Corps of Engineers still operates Washington, D.C.'s water filtration site on that land. So, a new location was determined nearby on the East side of First Street, marking the southwest entrance to Reservoir Park. The stones from the original steps and plaza were taken out of storage, restored, and assembled on site to lead visitors entering from the street up the berm to the fountain and the park's walking path.

While the bronze sculpture designed by Herbert Adams was in good condition, the fountain components needed to be replaced, and the Landscape Architects found a significant challenge in sourcing granite to match the original plaza, benches, and steps. These pieces had been in storage for decades at an open-air location in Maryland, and some pieces were unusable due to breakage. Thankfully, the quarry of the original stone was still in operation, allowing the design team to quickly determine which pieces were unusable and arrange for new pieces to be fabricated and shipped to the site for assembly.

A New Generation
The design of Reservoir Park seeks to balance the stewardship of historic resources with environmentally sustainable interventions. Rhodeside Harwell Inc. worked with the Commission of Fine Arts and D.C.'s Historic Preservation Office to ensure that the design paid homage to the site's nationally significant history, leading a multi-disciplinary team in site design considerations and technical detailing to accomplish the task. The transformation from an industrial relic to a unique, publicly accessible open space accommodates civic and recreational functions, promoting health and well-being.

As seen in LASN magazine, August 2025.