Ventilation Shaft, I-35W Stormwater Storage Facility, Minneapolis

The I-35W Stormwater Storage Facility sits beneath downtown Minneapolis as part of the Minnesota Department of Transportation's broader I-35W corridor project. Crews bored deep vertical shafts and connecting tunnels through bedrock to create underground storage capacity for runoff that would otherwise strain the city's combined sewer system. Ventilation ducting and mechanical equipment staged at the shaft collar support workers below during excavation, since the shafts extend far enough underground to require forced air circulation. MnDOT designed the system to hold stormwater temporarily during heavy rain events, releasing it gradually to reduce the risk of overflow into the Mississippi River. The project is one of several tunnel-and-shaft stormwater facilities MnDOT has built in the Twin Cities to modernize aging infrastructure without expanding surface-level footprint.

Photo taken in February 2022.