Wisconsin engineers are gaining valuable information about storm water management and qualifying for environmental credits, thanks to the ongoing permeable pavement test plot project supported by County Materials.
With DNR regulations and an increasing number of cities requiring permeable surfaces for permitting, permeable pavers are becoming a preferred choice among engineers and business and home owners.
The test plot was constructed at the Sycamore Dog Park in Madison Wis., in 2014. Lead by US Geological Survey researcher, William R. Selbig, the permeable research project is intended to document storm water quality and quantity improvements through various permeable surface materials. While not the first research project of its kind, the test plot is unique in its comprehensiveness.
By request from the WDNR and WDOT the plot includes three cells, one for permeable concrete pavers, one for permeable concrete and one for permeable asphalt. In addition, it is fully lined and includes isolated equipment for measuring inflow, outflow and over flows. The project is designed to enable researches to measure the changes in quality and the mass balance of storm water through the system.
Permeable pavers are widely recognized as an effective solution for reducing total suspended solids (TSS) levels in storm water to EPA-mandated standards. Permeable pavers are often the preferred system where space is at a premium; they can also help avoid potential liability associated with retention and detention ponds that are open bodies of water in areas where children and adults may be present. The Wisconsin DNR has developed a technical standard for permeable pavers and will continually update the standard as data is collected. In February of 2016, the underdrain discharge pollutant removal credit was increased from 55% to 65%. Further updates are anticipated including more robust guidance on best practices for maintenance for each surface type.
“Without technical standards in place, engineers often hesitate to specify permeable pavers, even in cases when they may otherwise be the best option for a particular project,” comments Bob Roehrig, an architectural sales representative at County Materials and one of the driving forces behind the project.
Roehrig also serves on the Wisconsin DNR’s Standards Oversight Council to represent permeable pavers. He notes the importance of obtaining data from the test plot to ensure engineers have up-to-date standards for viable storm water management options.
Data from the test plot will help alleviate this problem. “One of the keys to doing these technical standards is having good data,” says Roger Bannerman, an environmental specialist with the Wisconsin DNR and member of the Standards Committee for permeable pavers. Road salt has become a serious issue for Wisconsin’s environmental quality, Banner adds. “Permeable pavers can significantly reduce the amount of salt that ends up in the water supply—some say by up to 70%. (Having standards in place) will make it easier for people to use permeable pavers.”
Bannerman says the results gained will prove invaluable in the future. “A standard like this is a living document. New research will often change our recommendation. Every time we improve them it makes them easier to implement. The bottom line is to do the most cost-effective thing possible and make sure we spend our money wisely in Wisconsin.” The data is also likely to affect best proactive recommendations in other areas of the country and the work, says Bannerman.
County Materials continues to be instrumental in identifying additional supporting partners, including manufacturers, engineers and contractors. The overall cost of the test plot for the first two years was approximately $640,000. Funding sources include the Wisconsin DNR, Wisconsin DOT, US Geological Survey, Oldcastle, Unilock and County Materials. In 2017, the Interlocking Concrete Pavement Institute donated $79,918 to expand the list of pollutant continuants tested.
The test plot continues to process rain events. The study is scheduled to run through 2018 with a re-evaluation in 2019. Further study at the site is anticipated beyond 2019.