A proposal to build a smaller St. Croix River bridge with lower vehicle speeds fell to strong criticism from the Minnesota Department of Transportation in a report issued Wednesday.

The plan by Sensible Stillwater Bridge Partnership, drafted to counter a drive for a $690 million four-lane bridge project at Oak Park Heights, envisioned building a narrower bridge diagonally to connect with the Wisconsin end of the Stillwater Lift Bridge.

Proponents have said such a bridge would save Minnesota taxpayers millions of dollars and serve as a replacement for the 80-year-old Stillwater Lift Bridge without promoting urban sprawl in Wisconsin's St. Croix County.

But the MnDOT review said the alternative plan varies little from a proposal studied and rejected several years ago. The alternative plan would cost as much as the current proposal and would create "significant" disruption of historic properties and natural resources on the Minnesota side of the river, the review said. Construction couldn't start until 2019 because of permits, approvals, legalities and funding decisions necessary to move such a project forward, the review said.

A spokesman for the alternative plan, Roger Tomten, said the MnDOT review lacked depth, included errors and was written without any consultation with his group.

"I was pretty disappointed in the way it was handled," said Tomten, a Stillwater architect who helped design the alternative plan. "They didn't have the courtesy to meet with us and resolve these things."

Specific objections in MnDOT's review included insufficient space for stormwater ponds, traffic congestion at the point where the bridge would launch from the Stillwater side and possible interference with protected mussel habitat along the Wisconsin shoreline.

Wednesday's announcement was the second setback in recent weeks for opponents of the bigger bridge. In mid-August, Gov. Mark Dayton denied a request by 30 environmental and conservation organizations to reconsider the existing plan.

Construction of the bigger bridge awaits a decision in Congress to exempt it from the U.S. Wild and Scenic Rivers Act, which governs the St. Croix. Rep. Michele Bachmann, R-Minn., and Sen. Amy Klobuchar, D-Minn., have introduced legislation to amend federal law.

Klobuchar has requested an extension of a Sept. 30 deadline set by Dayton for a congressional decision. Dayton said federal funding will expire if Congress waits too long.

Adam Josephson, MnDOT's east metro manager, said Wednesday that the deadline remains intact but "it has been suggested that we will work with the congressional folks to accommodate their needs as things continue to move forward."

Kevin Giles • 651-925-5037 Twitter: @stribgiles