The price tag for the next light-rail transit project in the Twin Cities, linking Minneapolis to the northern suburbs, has increased by nearly $500 million and now stands at $1.48 billion.

Members of a Metropolitan Council advisory committee were briefed Thursday on the new cost of the 13-mile Bottineau Blue Line Extension, which would run from Target Field to Brooklyn Park.

Metro Transit officials have long maintained that the initial $1 billion cost estimate would increase as more details became available in the planning process.

But Met Council Chairman Adam Duininck acknowledged Wednesday "there might be an immediate reaction to the number."

He added, however, "But I do think as people process the information and talk about the value of the line, it will make the case for itself."

Last spring, a firestorm erupted when the Met Council revealed that the cost of the controversial Southwest light-rail line linking Minneapolis to Eden Prairie ballooned by $341 million to nearly $2 billion. The news prompted blowback from Gov. Mark Dayton, provided fresh fuel to transit critics and left Duininck questioning whether the line should even be built.

Since then, communities along the Southwest line agreed to substantial cuts, and contributed more local funds to keep the project afloat with a new $1.77 billion price tag.

But Duininck says the Bottineau cost hike is not a case of transit déjà vu.

"There are a lot of big differences between the two projects," he noted. "We've tried to learn important lessons from the [Southwest] project, and take some of those lessons and apply them to Bottineau."

Hennepin County Commissioner Peter McLaughlin said Wednesday the Bottineau budget revelation is not equivalent "in any way, shape or form" to Southwest's price surge. The $1.48 billion figure for Bottineau "is still a reasonable number, it still keeps us competitive for federal dollars," he said.

How costs added up

The cost increase for the Bottineau line crystallized after Metro Transit staff and consultants completed 15 percent of the engineering and environmental work. A Plymouth Avenue station was added near north Minneapolis, as well as seven additional bridges — infrastructure that is a significant cost driver in transit projects.

In addition, wetlands located primarily on the southern stretch of the route will add to the cost because they require additional pilings, piers and bridges to support the 200-plus light-rail trains using the tracks daily.

Contaminated soils — mostly along rail tracks that Bottineau would share with BNSF Railway freight trains — would have to be mitigated, as well, said Mark Fuhrmann, Metro Transit's deputy general manager.

Because Metro Transit wanted light-rail trains to run every 10 minutes, two additional light-rail cars are needed, and each car costs about $4 million. The trip from downtown to the final stop at Oak Grove Parkway, near Target Corp.'s Brooklyn Park campus, is expected to take about 30 minutes.

Metro Transit's decision to overhaul Olson Hwy., where the line will run from downtown Minneapolis to Golden Valley, was another factor in the Bottineau price increase. In addition to repaving the highway, underground utilities that currently run down the middle of the busy six-lane thoroughfare will have to be relocated, Fuhrmann said.

The Bottineau project still faces significant unknowns that could further push up the price.

Additional engineering could reveal more construction issues, and substantive negotiations with BNSF over the use of the railroad right of way have yet to begin.

Cities along the line — Minneapolis, Golden Valley, Robbinsdale, Crystal and Brooklyn Park — could fail to approve the project, although Met Council officials say that's unlikely.

And, there's the dogged issue of funding. Currently, the Federal Transit Administration is expected to pay 49 percent; the Counties Transit Improvement Board, 31 percent; with Hennepin County and the state each contributing 10 percent.

It's unclear whether state lawmakers will fully support both the Bottineau and Southwest projects.

The Southwest project will likely be part of a request for state bonding dollars during the 2016 legislative session, and Duininck supports a metro-area sales tax to support transit projects.

"If that doesn't happen, then we'll have to figure out what to do in 2017," he said. All of the transit projects are part of a broader system, he added, and "they rise and fall together."