ST. CLOUD, Minn. — Fifteen years after it opened, the popular Lake Wobegon Regional Trail in central Minnesota is showing signs of age.

Local officials are searching for money to confront cracks and bubbling in the trail surface, the St. Cloud Times reported (http://on.sctimes.com/1aOnuha ) Friday. They're considering user fees and also have their eyes on the state's Legacy Fund, which holds set-aside sales tax money from a voter-approved tax increase five years ago.

"It's easier to find money for building new things, of course," said Cliff Borgerding, president of the Lake Wobegon Trails Association. "But the repair and maintenance is really critical."

Minnesota's state trail system contained 560 miles of paved trails as of 2012, according to the Department of Natural Resources. That's up from 475 miles five years before, and doesn't count city-, county- or private-owned trails.

The 62-mile Lake Wobegon trail draws hundreds of thousands of bicyclists, walkers, snowmobilers and in-line skaters every year. Uneven trails can be hazardous.

The way trails age differs from roadways, where heavy vehicles help seal the asphalt, said Thomas Wood, research project supervisor with the Minnesota Department of Transportation. On trails, microcracks form and allow moisture and oxygen to seep in.

State grants have generally gone toward acquiring land and building new parks and trails. But the 25-year Legacy plan includes a goal of "taking care of what we have" through restoration projects.

Last year, Itasca County received $200,000 last year to reconstruct and widen 6 miles of the Mesabi Trail.

User fees are also a possibility. On the Cannon Valley Trail in Goodhue County, officials charge a $4 daily wheel pass for adults who use bicycles, skates or other wheeled modes of transportation during spring, summer and fall.

About $100,000 was set aside in the Stearns County highway budget this year for Lake Wobegon Trail repairs, along with about $94,000 from the county's regional rail authority.