A group of Twin Cities mountain bikers is attacking a proposal for a new paved trail the same way they’d attack a muddy hill: Crank harder.

Save the River Bottoms, which also includes trail runners and bird watchers, hopes to turn out dozens of supporters for a normally placid meeting of the Bloomington Planning Commission on Thursday.

Their goal is to keep up the pressure against a paved recreation trail along the Minnesota River bottom. It’s a project that many local officials say is a done deal, but the bikers aren’t giving up.

“The more people learn about this project, the more opposition grows,” said Dennis Porter, who’s gathered nearly 4,000 signatures on an online petition against the 12-mile trail. “We have a lot of paved trails. Can’t we keep one natural?”

The Legislature last session appropriated about $2.2 million to build the trail, which will be owned and maintained by the Minnesota Department of Natural Resources (DNR). It’s a key segment in a planned 72-mile regional trail running all the way from Fort Snelling to Le Sueur. But the paved trail would share the river bottom with a rugged natural trail that the bikers, birders and runners have carved out and maintained for decades.

There’s room for both, said Ann Lenczewski, who resigned this month from her Bloomington seat in the state House after several years as the No. 1 legislative supporter of the paved trail.

“This is one of the key trails in the entire state,” Lenczewski said. “This is a link that will put a lot of trails together. All Minnesota taxpayers own these lands and pay for these lands. It’s important to provide access for all.

“Most reasonable people understand that people of all abilities should have access to our assets.”

The Bloomington City Council earlier this year adopted a resolution in support of the two-trail proposal. But the city has nothing to do with planning, building or paying for the trail, said Julie Farnham, a senior city planner. The project is completely in the hands of the DNR.

The Planning Commission will be discussing long-range ideas for the river valley at Thursday’s meeting, not the trail proposal, Farnham said.

“Since there hasn’t really been an opportunity for public input at the state level, I think the opponents are using our [meeting] as their venue to vent,” she said. “I understand it. They’re raising questions that are legitimate, but they’re not necessarily issues that can’t be surmounted.”

Lenczewski noted that all four of the City Council members re-elected in November are trail supporters.

“So the voters have had a chance to speak,” she said. “Arguing that just a select group of people should have access is not reasonable.”

Porter pointed to the difficulty of building and maintaining a paved trail in a flood-prone area, and noted that the DNR already has a large backlog of trail maintenance projects.

The agency recently said it would forgo plowing the Gateway and Browns Creek state trails in the east-metro area, then quickly reversed its no-plow decision.

“There’s way too many questions remaining,” said Porter, who maintains that the trail will cost much more than the estimated amount, based on the reported cost of other regional trails. “We want to preserve this area in its natural state. Maybe this area is something that a land manager should look at and say, ‘This is something different.’ ”