Kansas City, Mo. ? Volunteers are building an urban mountain biking trail system in Kansas City that will eventually include more than 50 miles of trails.

The project could take up to eight years to complete but will eventually include natural single-track trails built to the standards of the International Mountain Bicycling Association, planners said.

“This is one of those once-in-a-lifetime opportunities,” bike shop manager Craig Stoeltzing, who is leading the project with architect Scott Capstack, said.

While many urban areas have developed mountain bike trails, the scope of the Kansas City project sets it apart, said Ryan Schutz, director of field programs at the IMBA in Boulder, Colo. He said the Kansas City area already was well-regarded for its mountain bike trails.

The three-section project calls for 20 miles of trails in the Swope Park system. Seven miles are finished, and the rest will take about four years to complete.

Work recently began on a 20-mile “connector” trail project that will follow the Blue River from Swope Park.

The third section, another 16 miles of Blue River trails, has already been completed and is maintained by Earth Riders Trails Association. The nonprofit maintains mountain biking and hiking trails in local parks through agreements with park managers and boards.

Capstack and Stoeltzing first scoped out Swope Park in 2007. Not only was the city park big — at 1,800 acres, it’s more than twice the size of New York’s Central Park — its undeveloped areas provided a blank canvas on which to paint single-track trails.

“Every time we came upon another stone outcropping, we’d say, ‘Can it get any better?’ And then it did,” Stoeltzing said.

Earth Riders’ project in Swope Park is a model partnership for the city because it provides new recreational opportunities and is sensitive to the park’s ecosystem, said Forest Decker, Kansas City’s acting superintendent of parks.