“...there are blocks of thick, inviting, deep-green grass cleanly edged with sleek granite curbs. There is also a set of strategies that any manager of a heavily used public green space, particularly one covered by turf, could appreciate for its comprehensiveness.”
Each year, the National Mall hosts 25 million visitors and 3,000 special events. Few public spaces can compare with its grandeur, intensity of use and cultural symbolism.
Though the US National Park Service has spent decades cultivating the lawn, its condition had deteriorated.
This project defines sustainable strategies for maintaining healthy soils and turf on the National Mall. It improves stormwater absorption and maintains existing vegetation while preserving the iconic quality of this historic landmark.
The team, which included several turf experts, identified types of grass that can withstand the National Mall’s heavy use and irrigation systems that are durable and environmentally sound. The design solutions alleviate soil compaction and provide proper air, water and nutrient infiltration. The plan replaces subsoil and surface soil with an engineered soil that is permeable, effective for plant growth, and that retains water within its subsurface structure.
Walkways and re-graded lawn panels drain into a new, deeper subsurface drainage structure featuring four 250,000-gallon cisterns. ADA-compliant granite curbs guide water to the cisterns and redefine the edge of the National Mall’s lawn panels.
With the first phase complete, three of the National Mall’s eight center grass panels and two cisterns have been installed.
To ensure that the Mall looks good well into the future, HOK also helped the National Park Service write a manual for operating and maintaining the turf in a sustainable way. The design and operations plan proved successful during the 2013 presidential inauguration, when the grass was preserved despite the large crowds.
Phase I: 11.3 acres / 4.6 hectares
Phase II+III: 17.9 acres / 7.2 hectares
American Society of Landscape Architects Maryland and Potomac – Merit Award, Built Design