Interior Shaft, MnDOT I-35W Stormwater Storage Facility

The MnDOT I-35W Stormwater Storage Facility is an underground concrete vault built to hold runoff collected from the I-35W corridor through downtown Minneapolis before it's released into the municipal storm sewer system. The structure consists of a cylindrical shaft bored deep into bedrock, a construction method chosen to fit a large-capacity reservoir into a dense urban footprint without acquiring additional surface land. Its capacity allows the Minnesota Department of Transportation to manage peak flows during heavy rain events, reducing the risk of flooding and easing pressure on the city's older combined sewer infrastructure. Access shafts and maintenance hatches at the surface connect down to the reservoir for inspection and repair work.

Photo taken in February 2022.