By: angiehongmn
Partners and Updates, ,

Please, park on the grass

After tearing out the lawn grass, WCD staff seeded the area with prairie grasses and covered it with an erosion control blanket.
After tearing out the lawn grass, WCD staff seeded the area with prairie grasses and covered it with an erosion control blanket.

“There goes the neighborhood,” someone surely thought when cars began to pull in and park on the lawn in front of the building. After years of driving through cornfields while visiting with farmers, maybe the conservation district staff forgot how to park between the lines like the rest of the world. Later that summer, a large swath of turf grass north of the building disappeared, giving way to gentle hills where young prairie grasses grow. A phone call was made to the lawn care company, “This won’t be business as usual, you know.”

Matt Downing explains monitoring equipment installed in a pipe that connects the parking lot to a new raingarden in front of the wetland complex behind WCD's office.
Matt Downing explains monitoring equipment installed in a pipe that connects the parking lot to a new raingarden in front of the wetland complex behind WCD’s office.

When the Washington Conservation District moved into a new building in Oakdale three years ago, they immediately recognized the opportunity to demonstrate new ways of managing a commercial landscape. The Washington Conservation Center – shared with the Brown’s Creek Watershed District, Middle St. Croix Watershed Management Organization, and several staff from Washington County’s public works department – is located in a traditional business park in Oakdale northeast of the Hwy 94 and 694 interchange. There is a small wetland behind the building with condominiums on the other side. The office buildings are mostly nondescript and each comes with a small parking lot, a wide perimeter of turf grass, and a smattering of accent plants near the parking lot entrance and building foundation. Because of the crisscrossing freeways, you can no longer tell that the surrounding wetlands connect in a chain, with water flowing through culverts and pipes under roads until it reaches Battle Creek Lake on the southwest corner of the interchange. From there, the water flows on to Battle Creek and eventually the Mississippi River.

With an appraising eye, conservation district staff walked their new property, looking for opportunities to treat stormwater runoff, protect the wetland and downstream water resources, and create habitat for birds and pollinators. They settled on a retrofit design that includes a permeable parking lot, a large raingarden near the wetland, 5000 square feet of native prairie, and native plantings along the building foundation and parking lot entrance. Ramsey-Washington Metro Watershed District provided $100,000 in funding to make the demonstration project possible.

Part of the new parking area is made up of paver stones with gaps between them for water to soak through. The rest is grassy pave.
Part of the new parking area is made up of paver stones with gaps between them for water to soak through. The rest is grassy pave.

Perhaps the most unique component of Washington Conservation Center’s new landscaping is the 15,325 square foot overflow parking area in front of the building, which features permeable paver stones, as well as parking stalls planted with grass. When it rains, water soaks through the grass and paver stones into a gravel bed that can hold 783 cubic feet of water – the equivalent of 0.6 inches of rain. The system effectively treats runoff from small storms, which would otherwise wash dirt, grit and oil off of the pavement and into the wetland. During larger rainstorms, water overflows through a buried underdrain and into a swale that flows round the prairie to the wetland.

Tara Kline described the Conservation Center project during a recent Water Consortium tour.
Tara Kline described the Conservation Center project during a recent Water Consortium tour.

Though the grassy-pave looks like a lawn from a distance, it is actually a structural system, designed to withstand the weight of cars and trucks without compacting the soil beneath. The process for installation consisted of excavating the ground to create a shallow square-shaped bowl, 18 inches deep, which was filled with layers of gravel and sand. Two different brands of planting frames – EcoGrid e50 by TerraFirm Enterprises and PG-45 grids by Green Innovations – were laid on top of the gravel bed in rows and then sod and soil were pressed into the frames. Paver stones were used instead of grass between the two rows of parking stalls. The system was designed by Washington Conservation District and installed by Nelco Landscaping.

District designer Tara Kline hopes that the Conservation Center’s demonstration project will get more business owners thinking about the ways that they can modify their parking lots and landscapes to create habitat and protect water resources. “If you’re planning to fix-up your parking lot,” she explains, “it’s a great opportunity to reach out to your local watershed district for advice and assistance. Often there are grants to incorporate water-friendly features such as raingardens, native plantings, and porous pavement and they can help provide a design as well.”

To learn more about stormwater management on commercial properties, contact the Washington Conservation District at www.mnwcd.org or 651-330-8220 x.35. If you come to visit the office, be sure to park on the grass.