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EPA Headquarters Low Impact Development Demonstration Projects – Constitution Avenue Entrances
In This Section
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Location: Constitution Avenue, NW, between 12th and 14th Streets, in Washington, DC.
Address: EPA Headquarters, 1200 Constitution Ave, NW, Washington, DC 20004 
Constitution Avenue Entrance High Density Plastic Grid
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Specifications:
- Bioretention cells: 1,264 square feet
- High density plastic grid: 600 square feet
Objective:
Constitution Avenue is a highly visible public area along Washington, DC's National Mall. This project is educational as both a self-guided and instructor-led demonstration area that shows how disconnection, storage, evaporation, and high-efficiency mechanical systems can be used to modify runoff processes and how sustainable plantings combined with high-efficiency irrigation systems can be used on a large scale. Educational signage and materials were installed at the site for self-guided tours.
Signage along Constitution Avenue
Description:
The low impact development (LID) demonstration project at Constitution Avenue is designed to demonstrate how LID strategies can be used in urban areas to manage stormwater in response to the Chesapeake Executive Council Directive No. 01-1: Managing Stormwater on State, Federal and District-Owned Lands and Facilities. The design incorporates a combination of conservation practices, strategic site design, pollution prevention, and distributed small-scale source control management practices that reduce the stormwater that would otherwise have been discharged into the city’s combined sewer system. The project was completed in April 2005.
LID Components:
- Bioretention cells (also called rain gardens)
- Soil amendments
- Sustainable landscaping
- High-efficiency irrigation
- High-density plastic grid (grass stabilization material) with structural soil
Benefits:
- Bioretention cells (rain gardens) were integrated into the existing planting beds for a seamless design. They are planted with sustainable, water-tolerant vegetation with similar height, texture, appearance, and growing season.
- The bioretention cells are graded to provide a 6- to 8-inch shallow depression with a layer of filtering soil on a bed of stone. Runoff is directed to the bioretention area, where it temporarily ponds in the contoured depression and is stored in the underlying stone bed as it infiltrates into the ground. The rain gardens provide more than 400 cubic feet of stormwater storage volume.
- Bioretention areas demonstrate how runoff water quantity can be reduced and water quality enhanced by using the filtration capacity of newly amended soils. Runoff from disconnected pavement areas flows and infiltrates into surrounding soils.
- The high-density plastic grid system provides structural support for high-traffic pedestrian areas while maintaining porosity of the soil, protecting turf, and providing conduits for root growth.