In December 2020 ASCE completed a project at its Reston, Virginia, headquarters that demonstrates low-impact development techniques, best management practices in stormwater control, and sustainable development — all funded by donations to ASCE’s Foundation.
Reston is located in northern Virginia, within the Difficult Run watershed, which drains into the Potomac River and eventually into the Chesapeake Bay. According to data from the U.S. Environmental Protection Agency cited by chesapeakebay.net, 80 percent of the bay’s tidal regions are partially or fully impaired by toxic contaminants.
By renovating the entire parking lot of its headquarters site with environmentally responsible techniques, ASCE is doing its part to help reduce stormwater runoff and improve the quality of the water that does discharge from its surfaces and into the watershed and bay. The new parking lot includes sections built with two types of permeable pavers and two types of underground stormwater filtration units. The remainder of the parking lot surface was milled and repaved with asphalt made with recycled tires.
Twenty-four parking spots at the front of the building were rebuilt with permeable interlocking concrete pavement supplied by the Interlocking Concrete Pavement Institute’s Foundation for Education and Research. The image in slide 1 above shows how the system works: The 80 mm thick pavers are made of solid concrete and spaced roughly 10 mm apart, their joints filled with a permeable aggregate that traps sediment as water flows through. Stormwater flows to stone base and subbase layers below that can store about 100 mm of water while infiltrating it into the sloped soil subgrade. Polyvinyl chloride vertical check dams, spaced roughly every 5 m, help detain and infiltrate the water.
Sidewalks at the front and side of the building, as well as 11 parking spaces on the side, are paved with Stormcrete precast porous concrete panels, made by Porous Technologies LLC, as seen in slide 2. The panels are made with a concrete mix that has uniform coarse aggregate and very little fine aggregate. This leaves roughly 15 to 20 percent of each panel as void space. Stormwater passes through those voids into the soils and a perforated underdrain below, as seen in slide 3. From there, it flows into an underground biofiltration structure called FocalPoint, made by ACF Environmental, which is covered with soil that is planted with trees and other vegetation to create a patio, as seen in slide 4.
Another innovative technology that is being tested as part of the project is a stormwater filtration system called Filterra, made by Contech Engineered Solutions LLC. This 13 by 7 ft filtering unit was installed beneath one of the building’s sidewalks and captures and treats stormwater from a curb inlet.
The remainder of the parking lot — some 105,750 sq ft — was repaved with 1,241 tons of asphalt made with recycled tires, supplied by Asphalt Plus LLC. Roughly 722 scrap tires were recycled and kept from landfills by using this innovative, durable product.
The project, which incorporated ASCE’s technical guidance and engineering standards in its design construction, will serve as a demonstration of all these technologies. Special signage explaining its various components will help tell the story to visitors, including Society members and local students, once COVID-19 restrictions are lifted.