1-MN-341 Interceptor Rehabilitation
- Location Minnesota
- TimelineSpring 2014-March 2015
Parts of the sewer main linking south Minneapolis and St. Louis Park to the Metropolitan Council Environmental Services (MCES) Treatment Plant in St. Paul had deteriorated, posing a risk to public Safety. The Southwest Minneapolis Interceptor Sewer was built in 1918, and Minneapolis Chain of Lakes Regional Park — which the sewer main crosses — is now home to a bird sanctuary, peace garden and environmentally sensitive wetlands, making it one of the most popular destinations in the City's park system. Thanks to substantial residential growth, the sewer main surrounding the area serves more than 30,000 people.
Michels, one of the largest cured in place pipe companies in North America, was awarded the contract to complete the sewer manhole rehabilitation that spanned nearly two miles of sanitary sewer main in a challenging environment. It would require a significant amount of planning and coordination with the design team at Foth Infrastructure and Environment, MCES, and the Minneapolis Park and Recreation Board staff prior to work getting started. This involved wetland surveys, tree surveys, and soil exploration. As the site is in the heart of a dense urban area, there were many informational meetings open to the public.
Michels utilized a cured in place pipe (CIPP) lining system for sewer main and manhole rehabilitation to restore both to like-new conditions. To minimize impact on birds and the environment, we adhered to a non-linear, three-phase schedule allowing our crews to work in the bird sanctuary in the winter.
Our cured in place pipe restoration approach was to install 3,371 lf of 33-in. diameter main, followed by 3,474 lf of 39-in., followed by 3,605 lf of 60-in. The 33-in. main crossed under parkway roads, the 39-in. main crossed through the bird sanctuary and peace garden, and the 60-in. sewer was adjacent to a park and a residential neighborhood. To minimize any disruption to bird nesting and breeding times and meet the needs of our customer, the 39-in. main was completed last, from December to February.
The brutal Minnesota winter timeframe posed several challenges; the only accessible hydrant for use during water inversion was 2,000 ft away, and water supply lines periodically froze when temperatures dipped below -10 F. Fortunately, our crews and project managers knew what precautions are necessary to maintain health and safety when working in frigid temperatures. For example, all crew members were outfitted with boot cleats to improve traction.
In the summer, heavy infiltration from groundwater was challenging as heat and direct sunlight required tents, tarps and refrigerated trucks to be used to prevent the liners from prematurely curing. To minimize inconveniences to the surrounding public, Michels worked around the clock 24/7. In addition to diligent project management to overcome climate challenges, consistent, effective communication with all parties involved included updates on temporary parking and traffic restrictions, equipment parking, extended work hours, lights and the presence of diversion pumps, generators and other construction equipment.
Ultimately, the crews successfully completed the installation in the environmentally sensitive bird sanctuary within the contracted timeline and budget. Click here to read more about this project as featured in Trenchless Technology.