District offers look into century-old tunnel system in St. Paul area

(KMSP) - The Capitol Region Watershed District posted photos and video on Monday showing the first glimpse of the century-old, six-mile underground tunnel system that travels from Como Lake to Lake McCarrons, carrying storm water to the Mississippi.

According to a release, the Trout Brook Storm Sewer System’s extensive maze of tunnels carries water from neighborhoods in St. Paul, Roseville, Falcon Heights and Maplewood.

Not open to the public, the underground tunnels are maintained by staff who receive specialized training and equipment in order to safely enter the tunnels for maintenance activities. 

The system’s unique limestone arch tunnels are often seen at local historic sites, and the tunnels play a vital role in moving rain water below ground to keep residents safe by preventing flooding and clearing runoff.

In 2016, the system carried almost 3.9 billion gallons of rain water and snow melt to the river.

The District is in the process of repairing the oldest section of the system by replacing missing or damaged mortar between the limestone blocks, installing a concrete liner where more defects occur and removing calcium deposits.

Watch the video here.