Trout Brook Storm Sewer Interceptor (TBI) Repairs

Capitol Region Watershed District (CRWD) owns, operates and maintains the Trout Brook Storm Sewer System, a “trunk conveyor” that receives runoff from the cities of Saint Paul, Roseville, Falcon Heights and Maplewood, as well as from Ramsey County and the Minnesota Department of Transportation. Originally built between the 1880s and 1950s as a combined sanitary and storm sewer, the combined systems were separated in 1988. Today, Trout Brook Storm Sewer Interceptor (TBI) carries rainwater and snowmelt from city streets, parking lots and other hard surfaces to the Mississippi River.

The Challenge

Some sections of the TBI infrastructure are more than one hundred years old. To ensure the system functions properly, CRWD completes entire system inspections on a five-year cycle and performs minor maintenance and capital repairs. When TBI was transferred to CRWD from the Metropolitan Council in 2006, the District repaired two sections of pipe that were in poor condition. TBI is in a highly built-up urban environment, and in some cases, repair work has required street closures, utility relocation and pipe realignment.

Tunnel inspections in 2018

Placing box culvert sections beneath railroad next to 1-35E in 2012.

“TBI drains more than 5,000 acres of the District. Keeping it properly maintained prevents thousands of pounds of sediment and other pollutants from entering the Mississippi River.” – Anna Eleria, Planning, Projects and Grants Division Manager, CRWD

The Solution

CRWD completes regular inspections, maintenance and capital repairs of TBI to ensure the system functions properly. Past and present repair projects include:

2007-2008 – Replacing and repairing two sections of pipe that were in poor condition from cracking and settlement beneath the streets.

2012-2013 – Rerouting a section of TBI to avoid conflicts with I-35E bridge construction, which included abandoning a 630-foot section of pipe and replacing it in a new location.

2017-2018 – Repairing a half-mile stretch of the oldest section of TBI, including repairing a 10×10-foot horseshoe arch, replacing missing mortar, and installing a concrete liner in a 500-foot section of the pipe.

2021-2022 – Repairing cracks, replacing access steps and hatches, and sealing exposed reinforcement in a 2,000-foot section of TBI adjacent to I-35E and the railroad. Work also includes repairing exterior defects and placing soil cover over a short, exposed section of pipe.

Plans for forthcoming years include regular inspections, general preventative maintenance and long-range planning for major reconstruction projects in the future.

CRWD Protects Communities by Repairing Century Old Tunnel, 2021-2022 Repairs


Maintenance work keeps TBI functioning efficiently and provides valuable insight into future maintenance priorities for the District and its partners. CRWD collects data from TBI as part of its comprehensive stormwater management program, assessing sediment control, illicit discharge, construction site erosion and pollution. Results of the District’s ongoing measurement programs at TBI can be found in CRWD annual reports. PDFs of recent annual reports are available on the Our Work page.


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