Minneapolis has a new winner for most expensive bike-walk trail in the city.

Supporters say the $3 million trail and tunnel being built beneath two major bridges is a crucial connection between the University of Minnesota and downtown.

At less than one-fourth of a mile long, the Bluff Street Bike Trail project works out to a per-mile rate of more than $12 million, easily eclipsing the $9.2 million the city paid for the final mile of the Cedar Lake Trail through the North Loop, which opened in 2011.

The Midtown Greenway averaged about $6.5 million per mile, including its signature bridge. In comparison, the city's average project cost per mile of street reconstruction this year is roughly $8.5 million.

City Council Member Cam Gordon, whose ward includes part of the trail, admitted he swallowed hard at the cost but voted for it, saying the expense should be viewed in the context of it completing a key link in a larger network of bike-walk connections in the area.

But a 2013 mayoral candidate who has been critical of how the city prioritizes said the cost is another example of its misplaced priorities.

"I hope the City Council has the guts to go and look the young minority child in the eye whose neighborhood isn't safe because we can't afford enough police patrols," said Cam Winton, an attorney.

The trail, which is less than 400 yards long, runs under the west ends of the 10th Avenue and Interstate 35W bridges, just below and east of the U Law School and the nearby Riverview Towers condo building.

It will connect to a former railroad bridge that's now a pedestrian-walking bridge that crosses the Mississippi River just downriver of the 10th Avenue Bridge.

Costs are largely driven by grading along the steep riverbank, safety and construction of the tunnel itself. This week, crews are working on the tunnel and surrounding pathways, hauling dirt away in large trucks. The trail is expected to open in mid-July.

A link for the city

The walking-biking bridge, known as Northern Pacific Bridge No. 9, is already connected to downtown via bike and walking paths along West River Parkway. The existing trail winds gently downhill, a direct link to the bike path on West River Road.

Gordon said that means fewer cars on the road, and Council Member Jacob Frey, whose ward includes the west end of the trail, said it will connect grads with jobs downtown. "This is a relatively cheap measure to connect the two," he said.

The project will also link to off-road paths that reach as far as the Minnesota State Fairgrounds, and through downtown on 2nd Street to the North Side.

Bridge No. 9 draws an estimated 840 bikers and 370 pedestrians a day, according to 2013 counts. It's an abandoned rail bridge at the U that was converted to recreational use in 2000.

The new trail is wide, consisting of twin bike trails, each 6 feet wide, plus another 6-foot-wide walking path. It's a mix of concrete and asphalt surface.

The cost is driven up in part by lighting, cameras and an emergency phone that will be installed in the culvert, requiring an extension of electrical lines. Grading and storm sewer connections to make sure water doesn't pool in the tunnel also are issues. An old retaining wall had to be breached and new piling installed.

Divvying up the cost

According to the project budget, $800,000 of the project's funding comes from the federal pilot project for nonmotorized transportation that has funded numerous Twin Cities bike-walk projects in recent years. Property taxes fund the rest, with $1.1 million from city bonds and $300,000 from Hennepin County. The city earlier spent an additional $841,500 in 2008 to install a culvert for the trail.

The city missed a chance to have the federal government foot the bill for the culvert when the new I-35W bridge was being built. But the trail had not been formally added to the city's master bike plan so it paid for the project.

Steve Brandt • 612-673-4438

Twitter: @brandtstrib