Sixth Avenue viaduct repairs ongoing

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BROOKINGS – Physical barriers remain in the grass, ready to use if the viaduct on Sixth Avenue South between First Street South and Second Street becomes flooded due to the fact the crossing arms are still not working properly.

“The viaduct has been having some issues,” City Engineer Jackie Lanning said.

The viaduct has a history of accumulating water when it rains and filling quickly in heavy rains. Several vehicles have been caught in the swiftly rising waters, endangering drivers and passengers.

The Brookings City Council approved a bid of $399,568 by VJ Ahlers Excavating of Brookings in April 2018 for a viaduct drainage improvement project.

“The work will include installing new storm sewer pipe and inlets, concrete pavement, lighted flood warning system and articulated concrete mattress to stabilize the embankment on the east side of Sixth Avenue South. The articulated concrete mattress will provide stability of the slope at a lower cost than a retaining wall,” according to an attachment to a council agenda at the time.

The flood warning system was not meant to keep the viaduct from flooding, but is there to alert drivers and keep them from driving through the area when water is rising, Lanning said in 2018.

Although some work has been done in the past year, there’s still more to do, Lanning said this week.

“The contractors replaced one part so the lights are working, but there is another part for the arms that we are still waiting for. These are traffic signal related parts and we are seeing long lead times on traffic signals this year. … (It’s) an issue of too-few suppliers,” Lanning said.

Another problem, shown below, is the concrete retaining wall mattress located just south of the viaduct overpass. 

“The second issue is the concrete retaining wall matt is sliding. The last storm fell with a velocity that undermined the concrete and caused erosion. We alerted the design engineer and are trying to come up with a solution. Unfortunately, the contractor who installed it is no longer in business, but none-the-less, the city is trying to get it fixed,” Lanning said.

“The viaduct is one of those highly visible projects and so the community can see the issues. We are hoping to resolve them as soon as we can,” she added.