A mile-long wall separating freight and light-rail trains on the Southwest light rail route will cost nearly $93 million — a 356% increase over what was initially budgeted four years ago.

The "corridor protection barrier" was a late addition to the light-rail line, which will connect downtown Minneapolis to Eden Prairie.

The wall will stretch just west of the Royalston Av./Farmers Market station and end at the Bryn Mawr station, along the route's northern spine.

BNSF Railway, which operates trains in the corridor and controls the land, insisted in 2017 that a barrier separate freight and light-rail trains. At the time, the Metropolitan Council, which is building Southwest, estimated that the cost to build the wall would be about $20 million.

"It's a very tight arrangement," said Southwest Project Director Jim Alexander at a council meeting Monday.

The wall will be heavily fortified to prevent a collision between freight and light-rail trains, he added.

The council said the cost of the wall will come out of the project's contingency fund, which now stands at 10% of the project's overall cost.

In January, the council approved a $10 million change order to Southwest's budget for "earthwork activities," including excavation and grading, to prepare the area for construction of the wall.

The most recent change order for $82.6 million will be considered by the full council on April 14. The project's contractor, Lunda/McCrossan Joint Venture, will build the wall.

Alexander said about 100 freight trains rumble through the area weekly, causing work on Southwest to shut down to accommodate them.

It's unclear what the current price tag is for Southwest — it had been $2 billion, making it the most expensive public works project in state history.

In January, the council said passenger service won't begin in 2023, as originally planned, due to issues related to construction of a shallow tunnel and another wall to separate freight and light-rail trains operating farther south in Minneapolis' Kenilworth corridor.

It's unclear how the delay and additional work will affect Southwest's overall price tag.

Janet Moore • 612-673-7752