Tuesday, April 03, 2012
The Arcola Avenue Green Street Project integrates curbside swales, rain gardens and curb extensions right into the street design, to treat rainfall runoff from the street. The treatment system filters water through a mixture of highly permeable soils (sand, mulch, compost), then stores the water in an underlying gravel layer from which the water percolates into groundwater.
Environmentally-sensitive design (ESD) stormwater treatment systems like this one built right into the street, are much smaller in scope and complexity than standard stormwater facilities (e.g. stormwater ponds) which require much more space than available in dense urbanized or suburbanized areas. Arcola Avenue’s stormwater treatment is not only cost-effective and controls runoff pollution, but it also helps restore Sligo Creek.
The Arcola Green Street Project integrates curbside swales, rain gardens and curb extensions along the roadway. These rain gardens, curbside swales and curb extensions are integrated between the curb and the sidewalk and occasionally the curbs were extended into the parking lanes to expand the practices and provide for additional treatment. In larger storms, excess water is treated and discharges back into the curb and gutter system or into the storm drain system. These systems ultimately improve receiving stream and watershed health by improving water quality, reducing storm runoff and recharging the water table.
The Arcola Avenue Green Street Project is located along a heavily traveled arterial road in Silver Spring, Maryland. It uses ESD practices to treat 1.85 acres of impervious uncontrolled rainfall runoff draining to Sligo Creek, a tributary of the Anacostia River. The Arcola Avenue Green Street project was initiated in March 2011 as a pilot partnership between the Montgomery County Department of Environmental Protection (DEP) and the Montgomery County Department of Transportation (DOT). The partnership’s goal was to develop a process for constructing stormwater management practices along Montgomery County roads. The Arcola Avenue Green Street Project was originally identified as a stormwater management retrofit opportunity in the Anacostia River Restoration Plan (ARP). The ARP, completed in 2010, is a comprehensive 10-year restoration plan that identified restoration opportunities throughout the Anacostia River Watershed. The Arcola Avenue Green Street Project is one of hundreds of restoration opportunities identified in Montgomery County and is an integral part in fulfilling the overarching goal of restoring the Sligo Creek watershed.
Roadway bioretention facilities, rain gardens, and related “low impact development” or “environmental site design” projects are much smaller in scope and complexity than standard stormwater facilities. The Arcola Avenue Green Street required only twelve weeks to design, and three months to construct the 10 ESD practices. The resulting 1.85 treated acres of roadway rainfall runoff could not have been otherwise treated due to lack of available open space and real estate.