The city of Minneapolis is in the midst of a $57 million expansion of a downtown stormwater tunnel system that’s designed to relieve pressure on existing tunnels, reduce long-term maintenance on those tunnels and provide enough additional capacity to handle expected larger rainfalls in the years to come.
The project’s main component is a new 12-foot-diameter, 4,000-foot-long tunnel that’s being bored about 70 feet underground. It runs parallel to an existing 6-foot-diameter main tunnel that’s the backbone of what’s known as the Central City tunnel system, originally built in the late 1930s to drain stormwater into the Mississippi River, says Kevin
