Deployment Of Floodwall At St. Paul Downtown Airport Underway

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Deployment Of Floodwall At St. Paul Downtown Airport Underway By Jim Douglas

		March 15, 2011 - With spring flooding of the Mississippi River at St. Paul all but certain, work crews from the Metropolitan Airports Commission (MAC) began deploying temporary sections of floodwall at St. Paul Downtown Airport. St. Paul Downtown Airport also known as Holman Field, is an airport just across the Mississippi River from downtown Saint Paul, Minnesota. It is one of several reliever airports in the Twin Cities operated by the Metropolitan Airports Commission. The airport has three runways and serves aircraft operated by corporations in the local area, a flight training school and the Minnesota Army National Guard aviation unit, as well as transient general aviation aircraft. The airport is home to an installation of the Minnesota Army National Guard. The Holman Field Administration Building was added to the National Register of Historic Places in 1991.

Recently local debate has ensued over plans to build a flood wall around the airport. Three times in the last thirteen years the airport has been flooded due to its proximity to the Mississippi River. Supporters do not want to deal with the future inconvenience of having to deal with the flood again, while critics say that the proposed wall would ruin views and make the airport "ugly". A dike to protect the airport from the nearby river was considered since the National Guard stated that they may leave if the dike is not constructed in a timely manner. In 2009, a removable flood wall was installed that is only erected when flooding is imminent, leaving the views of the river intact for the rest of the year. Steel plates are embedded in the concrete on the river side of the runways. The flood wall is composed of steel posts that anchor to the embedded plates and aluminum planks that are stacked between the posts to form a flood barrier. These are then removed and stored when the flood event has passed. This is the fourth time the floodwall has been deployed at the airport, having been erected once in 2009 and twice in 2010. The 9,532? dike includes 4,563? of permanently installed sheet pile wall, 3,595? of temporary, deployable wall and 1,374? of earthen levee. MAC staff can deploy temporary sections of the wall in about a week. ?Prior to developing the floodwall in 2009, flooding sometimes caused hundreds of thousands of dollars of damage and expense and closed St. Paul Downtown Airport for weeks at a time,? said MAC Executive Director Jeff Hamiel. ?The floodwall is designed to protect the airport against a hundred-year flood, safeguarding infrastructure and minimizing operational impacts.?

Portions of the wall along Bayfield Street and those crossing the airport?s two shortest runways, 13-31 and 9-27, will be erected first, leaving the longest, primary runway, 14-32, unaffected as long as possible. As the water rises, the MAC will close storm sewer gates to prevent river water from backing up onto the airport, and pumps will be activated to drain water that does collect there.

If necessary, MAC also will install the deployable wall crossing the far southeastern end of 14-32, sealing off the airfield from the river. Barring unforeseen circumstances, Runway 14-32 will remain operational with the wall in place, but the landing threshold will be displaced, shortening the operational portion of runway pavement from 6,491? to 5,341?.

The two shorter runways already have been temporarily closed. The Federal Aviation Administration will remove navigational aids located outside the floodwall to protect them from water damage. The wall will remain in place until the danger of flooding has passed.

St. Paul Downtown Airport has the only runway longer than 5,000? in the MAC reliever airport system. The airport primarily serves corporate aviation needs. In 2010, nearly 89,000 aircraft landings and takeoffs occurred there, making St. Paul Downtown the second busiest airport in the MAC?s six-airport reliever system and the third busiest airport in Minnesota.

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