They've grassed over a park and put up a parking lot.

Finishing touches were applied last week on a unique $250,000 reinforced grass parking lot in Missoula County's Development Park.

The three-quarter-acre lot will provide spaces for 81 vehicles next to the expanding Mount Jumbo West Little League fields near DeSmet School.

The "reinforced" part entails a layer of gravel topped by a heavy plastic mesh geomatrix filled with sand. The grass went on top of it all. The design will enhance the capacity for stormwater runoff.

"It's strong enough to hold the weight of a vehicle, and with the gravel and sand, it helps it from getting muddy even in wet conditions," said Barbara Martens, special projects coordinator in the county commissioners' office.

While it's roughly 20 percent more expensive than asphalt, a grass lot helps follow one of the guiding principles county commissioners set for the development park, creating economic activity in a park-like setting.

"Providing green space for development park visitors in an area that can double as a parking lot is a real benefit," Martens said.

The new lot was financed with county funds from the development park's special tax increment district - not with federal stimulus funds, as the commissioners' office has heard bandied about.

Property taxes in a tax increment district don't go into the county's general fund, but stay within the park for infrastructure improvements - sewer, water, sidewalks and the like.

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The improvements include maintaining and enhancing 13 dedicated parklands within the larger park. The Little League complex leased by Mount Jumbo West is the busiest park each spring. The league has three fields either finished or under construction, with plans for two more.

The other parks are maintained by a property owners' association. Benches and picnic tables have popped up in one to the east of the Little League complex. They were also funded by the tax increment district, Martens said.

Plans for additional park work aren't in place yet, but they'll include landscaping in the medians at the main intersection of Airway Boulevard and Expressway.

"We try to keep maintenance costs as low as we can, but part of the vision of the park is that it's a park-like setting," said Martens. "So we'll be developing plans and working with the property owners and the Missoula Development Authority board and the commissioners."

The grass parking lot comes with stipulations based on air quality standards. One is that it can be used for only 61 days each year. Mount Jumbo West plays baseball and softball on the fields for 55 days each spring. It must be fenced and gated to block vehicle access when not in use.

The county bought the 450-acre development park in 1991. It's bordered by Interstate 90 and Highway 10 West on the north and south and Butler Creek on the west. Canyon Creek Village was part of the original park, but homeowners there aren't part of the development park property owners' association. The technological park that includes the DirectTV facilities is now on the eastern end.

Reporter Kim Briggeman can be reached at 523-5266 or at kbriggeman @missoulian.com.Missoula County goes green with parking lot