Passenger service for the Southwest light-rail line won't begin in 2023 as originally planned, officials say, due to "unforeseen conditions" that surfaced during construction of the project.

It's now unclear when the 14.5-mile line will open and how much the delay will affect Southwest's $2 billion price tag, according to the Metropolitan Council. The Green Line extension into the west metro suburbs is already the most expensive public works project in state history.

"With these large and complicated infrastructure projects it's not unusual to have areas of risk that rear their head, and you just have to manage through them," Met Council Chairman Charlie Zelle said Thursday.

Southwest is designed to link downtown Minneapolis with Eden Prairie through St. Louis Park, Hopkins and Minnetonka. Construction of the line, which began in late 2018, is about 35% complete, and some $971 million has been spent so far on the project.

But the Minneapolis portion of the route, which includes a shallow tunnel and a giant wall to separate light-rail and freight trains, has proved problematic for the council and the project's contractor, the Lunda/McCrossan joint venture. Builders have encountered "poor soils" in the Kenilworth corridor, a narrow stretch between Lake of the Isles and Cedar Lake, requiring contractors to use an "alternative construction method."

A planned half-mile tunnel in the corridor must squeeze through a crowded area to accommodate freight rail and the Kenilworth Trail, a popular thoroughfare for cyclists and pedestrians, above ground. In some spots, the tunnel for light-rail trains is located just a few feet away from private homes.

The Met Council said Thursday it will erect a special wall to stabilize soils while constructing the tunnel. "We are taking this approach out of an abundance of caution to protect the foundations of adjacent buildings," according to the regional planning agency.

Still, Thursday's news about the project attracted fresh criticism to an already controversial project.

"We told [transit planners] they were wrong about the cost, wrong about the geology, wrong about the geography, that it couldn't fit in the narrow bottleneck of the Kenilworth corridor, and we were right on all of these things," said Mary Pattock, chairwoman of the Cedar-Isles-Dean Neighborhood Association.

Neighbors sued to stop the project in 2014, claiming it violated federal environmental laws. But the suit was ultimately thrown out.

The Met Council on Thursday also attributed the delay to a $20 million mile-long crash protection wall between the Royalston/Farmers Market and Bryn Mawr stations, a late add to the project. Requested by BNSF Railway, the wall will separate freight and light-rail trains just west of Target Field.

"While this element is not a surprise, we have now completed analysis and design for the wall and have a fuller understanding of the challenges" involved with building the wall in an active freight corridor, the council said.

The project's budget has a 10% contingency fund built in, but any increases would come from local coffers since the federal contribution is capped at $929 million. The Hennepin County Board approved a measure in 2019 that added a $200 million cushion should Southwest run out of money.

"With a project of this size and complexity, this is why you have contingencies," said County Board Chairwoman Marion Greene, whose district includes southwest Minneapolis' part of the line. "We're not looking to spend the $200 million cushion."

Pattock noted that NASA's New Horizons space mission to Pluto cost much less — about $781 million — than the estimated $2 billion price of building the Southwest light rail extension. "With Southwest, we're only going to Eden Prairie," she said.

Pattock said Southwest's neighbors in Minneapolis support public transportation, "but instead of addressing the real needs of the community, [the Met Council] throws away money on a project that won't work."

"How can it be that the agency is so consistently wrong?" she asked.

Janet Moore • 612-673-7752