Deep beneath our downtown streets, as well as in parts of Southeast Minneapolis, Public Works maintains several miles of large underground stormwater tunnels. These tunnels are 100 feet below the surface. They were carved out of the sandstone that lies beneath the bedrock limestone in the 1930s to funnel stormwater to the Mississippi River.
When the tunnels were installed 80-some years ago, the builders didn't backfill around them. That situation was exacerbated over the decades by groundwater pressure, allowing void spaces to open up around the outsides of the tunnels and causing some shifting and cracking in the tunnels themselves. The 20-person crew that inspects and maintains these tunnels has been working on filling the void spaces for several years. Because the storm tunnels can quickly fill with water during even a minor rain event, the crews can only undertake this type of major rehabilitation work during the winter months.
The work itself isn't for everyone. New employees are taken down to the tunnels for a mile walk underground before they're hired to ensure that they won't have issues with this specialized workplace. The crews need to be prepared to work in boots, raincoats and gloves in tunnels with water that is sometimes ankle-deep or higher.
Supplies are lowered through access points and then moved by wheelbarrow through tunnels that are often less than 6 feet high. In addition to the water, workers also encounter the occasional bewildered raccoon or albino fish in the tunnels close to the river.
Just like the streets one hundred feet above, the tunnels even have street signs (like the one for 1st Ave N at left) to let workers know where they are.
This stormwater tunnel work is just one example of the many jobs undertaken by the City of Minneapolis Public Works Department.
(Photos courtesy of Shannon McDonough)
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