Design for Downtown St. Paul Airport's Floodwall Faulted

With industrial docks on one side of the Mississippi River and an airport on the other, the stretch near Holman Field is hardly the most scenic in St. Paul. But it could become even less so.

Not content to see the airport flooded occasionally, the Metropolitan Airports Commission wants to protect it by spending $28 million to build a lengthy perimeter dike along the river.

By every account, that floodwall would be ugly and intrusive, with the only questions being how ugly and how intrusive.

Now, the debate is headed to the St. Paul City Council, which has been asked to reverse a planning commission decision endorsing the project. The vote is expected to be close and could hinge on an array of aesthetic and environmental concerns.

To seal off the airport, which serves businesses, the military, small planes and State Patrol helicopters, the airports commission has proposed several big changes to the river corridor.

It wants to build a 1.7-mile dike system — consisting of sheet metal, earthen berm and temporary structures — that would largely end flood-related shutdowns such as those that occurred three times in the past 13 years, including a 78-day interruption in 2001. Such a system, however, would move floodwater from the airport back into the channel, creating a bottleneck that ordinarily would worsen flooding problems upstream.

To prevent that from happening, the commission has proposed widening the river slightly by excavating 160,000 cubic yards of soil along the airport bank. That would allow the same volume of water to pass through the corridor during flood conditions.

In a separate project, it's building a drainage system beneath runways to allow soil to dry more quickly.

Late last week, questions about the ownership of land that would be excavated threatened to delay action altogether.

Environmental groups have strong misgivings about the various projects, which carry a collective $47 million price tag.

Some say excavating soil could release contaminants into the river and could require dredging later. Others fear the dike will block future efforts to refurbish the river corridor. Still others contend the approach goes against modern flood-control measures, which increasingly emphasize backwater retention areas. With a permanent protective wall, the airport also could see increased airplane traffic, worsening neighborhood noise and affecting a heron rookery at nearby Pig's Eye Lake, environmental advocates add.

The most anxiety, however, is over the sheet-metal wall, which would rise from the riverbank and block views from the river. The top is slated to be 19 to 22 feet above the typical water level.

"It's going to be a big, ugly wall, and it's going to change the character of the river,'' said Steve Johnson, chief of resource management for the Mississippi National River and Recreation Area, a unit of the National Park Service.

Knowing he could get drawn into the debate, Mayor Chris Coleman asked the St. Paul Riverfront Corp. to prepare an analysis of the project's ecological issues.

Delivered last week, it confirmed the wall would be intrusive but said it could be set back from the riverbank, lowered and covered with vegetation. The analysis also said hydrologic models show no impact on flooding elsewhere and little chance of soil contamination from excavation work.

With only 210 days lost because of flooding at the airport in the past 70 years, the project simply isn't needed, critics said.

Furthermore, they contend shaving the riverbank to increase the channel's flood-related capacity hasn't been tried in the Upper Mississippi. Spokesmen for the U.S. Army Corps of Engineers and the Minnesota Department of Natural Resources agreed.

"What if, at some point, this fills in (with silt)?'' asked McGuiness, director of the Audubon Society's Upper Mississippi Campaign.

Warren said the concept is sound.

"It's not a new technique … although it's not common on the Mississippi,'' Warren said.

Clark, executive director of Friends of the Mississippi River, said the project is simply ill conceived.

"The biggest issue of all is the permanent alteration of the floodplain and the hydrological function of the river,'' Clark said. "Strip away all the rhetoric, all the mitigation, all the politics, and it's not the right thing to add infrastructure in the floodplain and the flood fringe. That is a 19th- and 20th-century model.''

Because the airport is built on old fill, Clark said, he's also concerned the drainage project eventually would funnel toxins to the river.

The National Park Service, which coordinates management in the corridor, also doesn't like the proposal, Johnson said.

"Their project is not consistent with our plan, but we don't have any regulatory teeth to stop it,'' he said. "We're all about keeping shoreline areas natural or restoring them to natural conditions if the opportunity arises, rather than creating some artificial condition.''

Pointing to the geologic significance of the river gorge through St. Paul, Johnson added: "It's an extraordinary place. Why build a wall and make it look ordinary?''

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