Fish Lake Regional Park parking solution is friendly for fish & people
When the Three Rivers Park District needed to rehabilitate parking lots and roadways at Fish Lake Regional Park in Maple Grove, Minn, the desire to reduce runoff, complicated by the reality of less-than-optimum soil conditions, resulted in an innovative design using permeable concrete pavers.
Water and woods are the main attractions at Fish Lake Regional Park, an all-season recreation area in the Elm Creek Watershed District. Founded in 1957 by the Minnesota Legislature, Three Rivers Park District now includes 27,000 acres in 10 regional parks, seven park reserves and 10 regional trails.
With stewardship integral to the district's mission, park district engineers and planners are committed to minimizing stormwater runoff into the lake to strengthen stewardship of the watershed district for years to come.
"Being under government jurisdiction, we have certain sustainable guidelines we have to follow," says Mike Horn, a district project manager. "Because there are so many projects and limited budgets, we work with a team to determine which improvement project will be most cost effective and will give us the biggest payback — both budgetary and environmentally."
The challenge at Fish Lake Park was a clay subgrade, which results in slow rates of infiltration. Engineers selected permeable pavers to be used with an innovative filtration and sloping system, so water that didn't infiltrate naturally would have other chances to percolate before reaching the retention basin.
"We tried to supplement what the park district was already using for stormwater control, which is a filtration basin at the base of the lake where the stormwater would outlet before overflowing into the lake," says Toby Muse, project manager for SEH, the design/engineering firm selected for the project. "We left the parking grades as they were, and although the subsoil was clay, we determined we could provide a greater level of infiltration by installing permeable paving stones in the parking pads."
To maximize infiltration despite the clay subgrade, a drain system with perforated pipe was installed under the permeable pavement. The parking lot already sloped toward the lake, and asphalt driving aisles and curbs with integral gutters were located between each parking pad.
"Although the base material is mostly clay, infiltration to some degree will occur at each level of parking pad, which provides even more filtration before the stormwater reaches the basin, and ultimately, the lake," said Muse.
In heavy rain events, the new configuration allows sheeted runoff to flow over the other parking pads where infiltration can occur again before eventually reaching the retention basin. With this system, no additional catch basins or stormwater pipe installation was required.
"It is working well during heavy rains," said Josh Bowe, a project manager for Three Rivers Park District. "Water is not ponding anywhere."
In addition to the unique permeable paving system, unused parking bays also were eliminated to help meet Elm Creek Watershed Management Commission and city of Maple Grove stormwater requirements, said Bowe.
"We've found that permeable paving stones are ideal for retrofits, like this pavement maintenance project," said Bowe. "We were able to utilize the area under the parking pads for stormwater storage and treatment, while minimizing the disturbance of existing space by not adding basins and piping. Not only do permeable paving stones look great, but they also give you the multiple uses of parking and stormwater management."
Contractor Glacial Ridge Inc. of Willmar, Minn., used a machine installer for the 19,000 square feet of Willow Creek Brickstone permeable pavers in the Sedona color.
- Case Study (PDF) 675.43 KB