Showing Value in Stormwater Management-Case Studies
A broad regional partnership, which includes TMACOG Stormwater Coalition members, the University of Toledo, and Clay High School, is working to quantify the value of stormwater best management practices. Following is an overview of the projects planned.
Rainwater and snowmelt present water pollution problems and water volume problems. In urban areas with lots of pavement, stormwater runs over parking lots and driveways collecting debris and chemicals. A heavy storm can overwhelm drainage systems and lead to flooding. Current practices say that stormwater is best managed close to where it falls, using natural percolation through the soil, and low-maintenance infrastructure. Stormwater managers in this region now employ several strategies to keep stormwater out of the storm sewer system, treat it naturally, and put the water to beneficial use.
A series of grants from the Great Lakes Restoration Initiative (GLRI) Surface Water Improvement Fund (SWIF) is funding the design and construction of a range of stormwater management projects in Lucas County. The University of Toledo, with funding from the University of Michigan Water Center, is evaluating those pilot projects. The goal is to provide information to builders and developers who want to reduce the amount of stormwater entering sewer systems, remove pollutants from the water, and do so cost effectively.
Engineers and builders must make complicated decisions about stormwater management in new construction and in renovations. There are several scenarios for paving, for example. Completely paving a parking lot with permeable concrete might cost four to eight times more than paving with asphalt. If data can show that paving half of the parking lot in permeable materials reduces stormwater volume and treats it effectively, then permeable pavement becomes a better option. If the choice is between extending a storm sewer, which controls water but doesn’t treat it, or using permeable paving, which facilitates both, the pricey pavers might be the better value. Hard data will help builders make the best decisions.
The City of Oregon has a pilot stormwater project in a soccer field parking area adjacent to Wolf Creek. Currently, the parking lot has catch basins that direct rain water directly to Wolf Creek. Oregon’s plan is to install bioretention cells in areas between parking lots to capture and hold stormwater. Builders will remove up to three feet of hard, impervious clay and replace it with engineered soil made up of sand and organic material. The cells will be planted with native species that have been selected for deep roots and a tolerance for both flood and dry conditions. Oregon Environmental Specialist Don Nelson expects a much reduced flow of water to underdrains. The water will drain gradually and some will be taken up by the plants. Water quality is also expected to improve. Most pollutants degrade naturally in the engineered soil or are taken up by plants.
To measure the effectiveness of the design, Oregon engineers and scientists have worked closely with ODNR and Ohio EPA to design the monitoring system.
The Lucas County maintenance garage on McCord Road in Holland recently repaved a dilapidated parking lot incorporating sections of permeable pavement. Challenges that they dealt with include selecting areas with less heavy truck traffic (permeable pavement is somewhat more brittle than asphalt) and choosing areas where water usually pooled so that the pervious concrete would be effective in drainage. Construction involved putting in an underlay of porous soils below the cement. They also graded an area for a rain garden which will be planted in the spring of 2014. There was no data collected before the renovation but Drainage Engineer Brian Miller will be monitoring the site and checking for flood management.
At another site managed by Lucas County engineers, University of Toledo students plan to collect data before and after a paving project. A parking lot at Larc Lane and Garden Lake in Toledo is currently all asphalt. Plans call for permeable paving in sections of the lot.
At both the Larc Lane and Oregon bioretention sites, University of Toledo students will be using placing tools in the catch basin to collect data on water volume before and after the stormwater systems are created. Samples to test water quality will be taken regularly. In Oregon, a Clay High School student has made a senior project out of the study and will be collecting and analyzing additional data.
Progress on these and other regional projects is being facilitated through meetings of the Stormwater Action Group, which is a subcommittee of TMACOG’s Stormwater Coalition.
A stormwater improvement project in the City of Toledo