An Idea That's Soaking In: Parks Turn to Permeable Paving Systems to Help with Stormwater Management
Beard, Elizabeth, Parks & Recreation
From cows in the creek to bikes on the trail When Luray, Virginia, Parks and Recreation Director Pat O'Brien began planning to build a paved parking lot for the new greenway along Hawksbill Creek, water quality issues were a key consideration. The town had just established a riparian buffer along the creekside trail using Conservation Reserve Enhancement Program (CREP) funds.
"Cows used to be going straight into the creek and doing their business. So the CREP riparian buffer fences the cattle away, and then we put in alternative water sources," O'Brien says. "It also filters any runoff or fertilizer that would have been going directly in the creek."
The riparian buffer paid off with vastly improved water quality, turning a cow-trampled creek into a Class A trout stream. Not to mention creating an instantly popular greenway trail.
"I had a lot of folks when we were doing the first section who said it was the craziest thing that Luray has ever done," chuckles O'Brien. "But it's truly far exceeded our expectations in terms of usage; there are folks out there day and night on the trail."
So the question became how to improve parking along the trail without adversely affecting those water quality gains. The solution turned out to be permeable paving.
Using federal stimulus funds via the Virginia Department of Forestry's Urban and Community Forestry partnership program, the town installed a parking lot composed of two different types of permeable pavers over a bed of compacted gravel. Much of the lot consists of two different color permeable pavers, which are separated by small tabs and filled in with small grit gravel that allows the water to drain. A piping system under the last pad of the parking lot drains water into a rain garden. Another section of parking area is made of Turfstone, a honeycomb system of pavers that allows grass to grow through the middle of each block.
"It is more expensive than your traditional paving, but it was always the plan for along our award-winning Luray-Hawksbill Greenway," O'Brien says. "The environmental benefits are well worth the little bit larger investment than your traditional, old-school paving materials."
Comparing apples to asphalt
But do permeable paving options really cost that much more? Matt Kilmartin, a planner with the Tualatin Hills Park and Recreation District (THPRD) in Beaverton, Oregon, recently researched the costs and benefits of pervious paving for both new and retrofit construction.
"What we've found is that the overall project and lifetime costs tend to balance out or even warrant higher up-front costs of permeable pavement systems in terms of permitting, utility/infrastructure, and maintenance/replacement costs, and a better public image, plus the added benefit of reduced total footprint--i.e., avoiding constructing water quality facilities adjacent to paved areas means more land is available for other park, trail, and open space amenities," Kilmartin says.
Principal engineer John Howorth of 3J Consulting, Inc. in Beaverton, Oregon, notes that pervious paving may even save money in the short and long term. His company recently designed and managed the installation of a pervious concrete parking lot at THPRD's Aloha Swim Center.
"In order to accurately compare pervious with conventional impervious paving of a parking lot, for instance, you must also add into the equation the cost of the associated storm water facility, both conveyance systems and any water quality retention system you may be required to construct," Howorth says. "Another element that may also be a factor is the cost of the land that would otherwise be used for a retention pond. And finally, the life cycle cost of pervious versus convert tional paving that includes all the maintenance costs should also be considered."
Howorth cites the case of a townhouse development where pervious paving was a less-expensive option than constructing a stormwater pond, especially when that land could then be used for an additional unit of townhouses. …