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.
Thanks for this interesting article. Were any monitoring systems installed and a monitoring program implemented to assess with time the performance of the storm water management systems constructed?
Monitoring was considered and a grant application submitted but not funded. The granting organization name escapes me at the moment. However, there was an effort made. Please keep in mind that there are many examples of monitored projects of various stormwater control measures in the research literature. For permeable pavements, there are over 30 water quality and water quantity studies. They all point to effectiveness in reducing pollutants and runoff.
Very impressive and probably very expensive application for perhaps a small amount of reduction of runoff. These systems seem somewhat effective to the point where the underlayment material gets clogged with dust and hydrocarbon contaminated materials. An Efficacy Study should be undertaken considering cost of maintenance of the surface as well as life span of the underlayment materials before requiring replacement.
Would like to see H&H Calculations.
Definitely agree that maintenance is key to removing accumulated sediment. Most collects at the surface and has to be periodically removed with vacuum equipment. There is some useful research literature on surface cleaning effectiveness of various equipment and some cities and private property owners have implemented routine cleaning to prevent the conditions from happening that you noted. While forensic studies on sediment deposition onto subgrades within permeable pavements might be useful, it is also quite expensive and in many cases impractical. And deposition likely depends much on the amount of contributing impervious drainage area. In the meantime, routine surface cleaning as well as occasional cleaning of underdrains before they clog can maintain vertical and horizontal infiltration into soil subgrades.
Impressive, but is this really needed. We need to compare cost data with that of a regular parking lot as well as water quality improvement if any. The alternative, of course, is to apply filtration only at the inlets. It appears that this project is feasible as a demonstration but not on a larger scale especially with cities strapped by budget demands.
What’s represented in the ASCE LID project goes beyond pollutant reduction and speaks to runoff volume reduction. Many cities are strapped with storm sewer systems working at capacity resulting in overflows and flooding. There are also older portions of cities with combined sewers. Permeable pavements are a way to mitigate this stress and damage to drainage systems. For example, the City of Atlanta installed 4 miles of permeable interlocking concrete pavement to reduce flooding from combined sewer overflows. New Orleans is another example. In September 2019, the City passed an ordinance requiring all new parking lots to be constructed with permeable pavement. There are some municipalities that don’t permit development unless permeable pavement is used because the storm sewer system is booked, so to speak. Permeable pavements are addressing the results of increased rainfall in many places that might be caused by global warming. Permeable pavements go beyond reducing pollutants, to reducing flooding and increasing the resilience of the drainage infrastructure. For more information, please consider purchasing and reading ASCE 68-18, a national design standard for permeable interlocking concrete pavement.