I-35 Flooding, Rock-Filled Storm Sewer Under Review For Long-Term Fix

The I-35 Off-Ramp Of Lake Avenue Is The Center Of Flooding Concerns

DULUTH, Minn.- Lake Superior’s force and lack of access inside some storm sewers are causing a nightmare for engineers with the Minnesota Department of Transportation and the city of Duluth.

A normal roadway may be all that you see driving along Interstate-35 to the off ramp of Lake Avenue on a sunny day, but even the slightest amount of rain can cause flooding around the ramp. This is due to a backed-up storm drain running beneath I-35 and the city’s streets.

The system was originally installed in the 1980s. The four-foot tall storm sewers are packed with rocks from Lake Superior, leaving only inches of room for water to pass through.

MnDOT installed a newly designed grate at the end of the pipe last year as a temporary fix to keep sedimentary out. However, the grates were temporarily removed to repair damages caused to them from the storms this past fall. According to MnDOT engineer Perry Collins, during their time of maintenance, another storm brought in more rocks than before, enough to cause 75 feet of back-up from the lake.

MnDOT anticipates on starting the next fix on the pipe in the coming weeks, but as they wait to receive a permit from the U.S. Army Corp of Engineers, storm water pumps and other clean-up equipment are on standby for the next time flooding occurs.

Temporary fixes can cost up to $100,000, but a permanent fix to the problem could be time consuming and cost upwards of 1 million, according to MnDOT.

“Long term we’re also researching a permanent solution to this problem. We’ve hired a consultant to analyze the wave patterns on Lake Superior as well as what those waves do to move the sediment and rock around.”

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