Searching for a south-metro bridge over rising waters

At the Dunn Bros. in downtown Chaska, owner Mike Webb plays a game to find humor in the flood that has shut down the nearby Hwy. 41 river crossing -- again.

"We count the U-turns. It's kind of fun," he said wryly. "Yesterday, the over-under was 40. We hit 40 by about 2:30 [in the afternoon]."

It's the third time since spring 2010 that the Hwy. 41 bridge, which normally carries 14,000 cars daily, has been rendered impassable for weeks at a time, its southern approach submerged in the swollen Minnesota River. The Hwy. 101 bridge a few miles to the north provides no respite -- it's also closed by floodwaters, prompting the diversion of 20,000 more cars per day.

An expensive new Hwy. 41 bridge -- estimates peg it at $750 million -- is probably decades away, if it's built at all. So the Minnesota Department of Transportation (MnDOT) is instead looking at other ways to make flood season more bearable in the southwest metro. Those projects -- such as raising a road here or re-striping a road there -- would cost "tens of millions" instead of "hundreds of millions," said Diane Langenbach, MnDOT's south metro project manager.

"We know we definitely need to improve something in that area," she said.

A menu of possible solutions for Hwys. 41, 101 and 169, the road that carries most of the rerouted traffic, will be drawn up between now and September, with public input. Which projects go forward will depend on available funding, with MnDOT hoping to draw on a $50 million pot of money for flood mitigation projects.

"We're on parallel paths where we're focusing on the long-term plan while we're looking at short-term options," Langenbach said.

Other interim options, such as raising the roughly half-mile lowland approach to the Hwy. 41 bridge, present problems because of the floodplain and the protected environmental resources in the valley. "It's a tricky balance," she said.

Sticker shock

There are even more obstacles to an entirely new crossing. For starters, the estimated $750 million cost.

The cost is so high partly because a bridge across the valley would be one of the longest in the metro area -- a nearly two-mile span with another two miles of road on land.

The length would be necessary to lift the highway out of the 100-year floodplain and the environmentally sensitive river valley.

Add to that the challenge of weaving a highway around downtown Chaska, its ballpark and mobile home parks on both sides of the river.

"The whole southwest metro is just filled with sensitive resources," Langenbach said.

Diane Cooper, a hydrologist with the National Weather Service, said bringing a road out of the floodplain is tricky.

For example, raising the existing approach on an earthen berm could have the unintended effect of partially damming the river during high-water periods, potentially worsening floods upstream.

"It's just kind of a Catch-22," Cooper said.

The challenges are all too familiar for Shakopee Mayor John Schmitt, who has long lobbied for a new crossing.

MnDOT began studies of a new crossing in the 1970s, and Chaska acquired some land for a crossing that would have stretched northward across the river from Hwy. 169 toward Carver County Road 15.

"All that work went out the window," he said. "When the fen came up, we all got caught."

Fens gained recognition as special resources in the 1990s. Since then, the Minnesota Department of Natural Resources and nonprofit groups have worked to protect them.

Another big road project -- the Bloomington Ferry Bridge on Hwy. 169 -- also interfered.

Since that bridge opened in 1995, Scott County has grown faster than any other metro county, and even without flood detours, traffic backs up along Hwy. 169.

The Hwy. 41 bridge was rebuilt with four lanes in 2006, but the flood problem remained because there wasn't a plan or money to fix it.

MnDOT resumed the study of a new crossing in 2002 and just last year, after much controversy, settled on a preferred route. The future bridge would be at the same site, then snake south around downtown Chaska and the ballpark before heading west to connect with Hwy. 212. They plan to complete a final study of that route and officially name it as the preferred alternative this year.