Getting one step closer to cleaner waters in Virginia and beyond
By Ana Constantinescu
Innovative software developed by a team of Virginia Tech faculty, researchers, and graduate students minimizes guesswork in the stormwater runoff management process.
If you take a stroll on Virginia Tech’s Blacksburg campus, chances are you will notice a handful of ponds, oases of calm harboring thriving aquatic life. Some ponds are landscaped with winding alleys and invite passersby to sit on a bench for a few minutes and enjoy the serene view. But while the water is shimmering and ducks are swimming playfully, something critical to the health of our water resources is happening below the surface: Pollutants are being removed from the urban stormwater runoff that flows into some of these so-called retention ponds.
The retention pond is just one of the dozens of methods that help remove contaminants from urban stormwater runoff, a major source of pollution in U.S. waters. Known as “best management practices,” or BMPs, in the water quality management field, these methods are essential to keeping the nation’s waters as clean as possible.
Choosing the optimal BMP for a given site is a taxing process. Stormwater experts often rely on their intuition and personal preference when they sort through the dozens of types of BMPs and criteria specific to each construction site. This means that the BMP selection has traditionally been a rather subjective procedure, sometimes lacking effectiveness and a rigorous scientific approach.
The selection of stormwater runoff BMPs will soon become more scientific, as an innovative approach to selecting BMPs for managing stormwater runoff is being developed by a team of researchers from Virginia Tech’s Via Department of Civil and Environmental Engineering (CEE), Virginia Water Resources Research Center (VWRRC), and Center for Geospatial Information Technology (CGIT).
The project, funded by the U.S. Environmental Protection Agency (EPA), brings together CEE and CGIT research associate Kevin Young; VWRRC associate director Tamim Younos, who is also research professor of water resources in the Department of Geography; CEE professor David Kibler; CGIT co-director and CEE associate professor Randy Dymond; and CEE graduate students David Lee and Dan Phipps.
Such contaminants as toxic motor oil, pesticides, metals, bacteria, and trash are washed off roads, parking lots, or other surfaces by stormwater. The Congressional Research Service reported in 2007 that as much as 50 percent of water pollution problems in the United States are attributed to urban stormwater runoff.
The issue of polluted stormwater runoff is closely related to the urban sprawl facing many regions of the U.S., including Virginia Tech’s home, the New River Valley. As new roads, parking lots, and other structures are built, the ground loses its natural ability to absorb and filter contaminated stormwater. Instead, rainwater flows over these impervious surfaces, collects harmful contaminants, and eventually reaches local streams, rivers, lakes, and estuaries.
The latest Virginia Water Quality Report issued by the Virginia Department of Environmental Quality (DEQ) in 2006 found that, overall, the number of impaired rivers, streams, lakes, and estuaries had increased during the past decade. A staggering 94 percent of the lakes and 98 percent of the estuary areas were reported as impaired in 2006. There seems to be better news for Virginia’s streams and rivers: Only 19 percent of the total mileage of monitored waters is impaired, according to DEQ. However, a decade-long analysis showed that in 2006 there was almost four times as much impaired river and stream mileage as in 1996.
Ever since the Clean Water Act’s enactment in the 1970s, engineers and planners have been faced with the difficult task of choosing the optimal BMPs. Among the popular BMPs are retention ponds that help deposit some pollutants onto the bottom, vegetated wetlands and sand filters to help filter the pollutants, and proprietary stormwater technologies, such as hydrodynamic separators.
So how does one go about deciding which BMP is best for a particular land development project? Traditionally, the selection of BMPs has been guided by little more than vaguely written regulations, experience, and intuition. “They rely heavily on past knowledge, tradition, or even personal preference for particular methods of controlling stormwater runoff,” explains Young. He adds that all too often personal bias has led to “cookie-cutter” solutions to very complex stormwater management needs, resulting in poor control of the pollutants.
This fairly subjective and time-consuming selection process will soon be made more efficient by an innovative software developed by the multidisciplinary team at A complex stormwater runoff cleaning process is performed by this bio-retention BMP near the Smithfield parking lot. Virginia Tech. The new BMP selection approach uses the Analytical Hierarchy Process (AHP) Optimization Tool. This novel software factors in dozens of site-specific criteria -- such as soil types, land slopes, depth of groundwater and bedrock, maintenance accessibility, and cost — when selecting the optimal BMPs for a particular location.
“Our technique is expected to reduce the BMP selection time and minimize human error from such a complex process,” says Younos.
The new tool is not designed to replace professional judgment, but rather to enhance it with the most accurate information available.
Young, who developed the principles of this application in his master’s degree thesis under the guidance of Kibler and the late CEE Professor G.V. Loganathan, explains that the program requires users to define and prioritize the project’s main characteristics and objectives. Users also need to assign weight to the various BMP selection criteria, allowing the software to determine the optimal BMP for the development project. Ultimately, the selected BMPs will need to be double-checked by the stormwater expert to ensure that it meets all the site’s requirements.
Pilot-testing of the AHP application began on the Town of Blacksburg’s stormwater system and the local Stroubles Creek watershed in the winter of 2007. The software was used by the research team to select BMPs within the watershed contributing runoff to Stroubles Creek, the town’s main receiving water body. Multiple computer software platforms were used to simulate how effective the selected BMPs were at removing the stormwater runoff pollutants.
“The best part about conducting a pilot test on Blacksburg is that the town will be able to implement our recommendations,” says Younos. “We are very pleased by the town’s enthusiasm and support for this project.”
Other stakeholders in the pilot-testing include the New River Planning District Commission, DEQ, and Virginia Department of Conservation and Recreation. Upon completion in summer 2008, the software will be available for free to all interested engineers and planners, localities, and BMP review authorities, and will be applicable in other states with geographic and climatic environments similar to Virginia’s.
So, next time you walk past a pond in a residential or retail area, you may find yourself thinking that something so unassuming was scientifically selected and built to keep our waters cleaner.