Fifteen people donned bright orange safety vests, hard hats and safety glasses on Thursday to learn more about construction of the Southwest light-rail line at its most challenging spot: the Kenilworth corridor in Minneapolis.

The tour was one of dozens hosted by the Metropolitan Council to demystify for the public the complicated, multiyear construction process of the Twin Cities' third light-rail line.

"We want people to understand how complex this project is," explained David Davies, community outreach coordinator for the regional planning body.

Thursday's tour explored a half-mile-long tunnel being built along the Kenilworth corridor, a narrow recreation and freight passage between Cedar Lake and Lake of the Isles. It's the most expensive and complicated part of the 14.5-mile line linking downtown Minneapolis and Eden Prairie.

Southwest project director Jim Alexander began by addressing "the elephant on the beach" — the project's current cost and when the line will begin service. Both are unknown at this point.

Issues with what contractors called "poor soils" in the corridor caused the previous $2 billion price tag to rise by $200 million. "That cost will go up, we don't know yet by how much," Alexander said.

The project, which is halfway complete, has exhausted its original $204 million contingency fund. Hennepin County has set aside an additional $200 million to cover costs at the behest of the Federal Transit Administration (FTA), which is helping fund the project.

When passenger service begins all depends on how the tunnel progresses. The previous start date was 2023.

"This is the most difficult piece. This is a bear," Alexander said, nodding toward the site. "And it's a big bear."

He speculated that Southwest will end up costing $150 million to $200 million a mile, causing one woman to audibly gasp. But, he said, other transit projects across the United States have cost more.

The project's relationship with its neighbors in the Kenilworth corridor has been fraught over the years, including unsuccessful litigation lodged against the Met Council that sought to stop the project on environmental grounds. Tour participants on Tuesday were curious but polite.

Kenwood resident Evelyn Turner said she's endured her fair share of dust and noise during Southwest's construction. "It will be done sometime," she said, somewhat philosophically.

While Turner said she supports light-rail transit in general, she questioned locating it alongside Twin Cities and Western Railroad's freight trains, which will continue to operate in the corridor even after light-rail service begins.

When Southwest was being planned, Turner said, Hennepin County had promised the freight trains would be diverted, but that didn't happen. "A lot of people still are bitter," she said.

The more recent soil issue caused the Met Council to change its construction methods in a narrow stretch of the corridor close to the Calhoun Isles condominiums. Parts of the complex's foundation lie within 6 inches of the tunnel.

Builders are erecting a secant wall — intersecting reinforced concrete piles — on the east side of the tunnel to stabilize the soils during construction, a move intended to protect the foundations of nearby buildings, according to council officials.

Heading toward downtown, light-rail trains will emerge from the tunnel to cross a bridge over the channel between Cedar Lake and Lake of the Isles.

"I have grandkids, so we have to balance the disruption of our lives now for the benefit of future generations," said Dick Adair, who lives in the Bryn Mawr neighborhood of Minneapolis.

Janet Moore • 612-673-7752

Twitter: @ByJanetMoore