St. Paul Interceptor
- LocationSt. Paul, Minnesota
- TimelineNovember 2018 - October 2019
Michels Trenchless, Inc., one of North America's largest pipe rehabilitation contractors, restored more than a mile of sanitary sewer pipes on the St. Paul Interceptor. The project included 670 lineal feet of 56-inch, 4,418 lineal feet of 60-inch and 2,250 lineal feet of 72-inch diameter pipes.
Crews used cured-in-place pipe (CIPP) liners made of 5-8 layers of felt inside corrosion-resistant coated liners impregnated with resin. The liners were cured in place with hot water, with the exception of one installation. The 90-foot installation of 72-inch pipe had a 13 foot elevation change and was cured with steam.
Installing liners between 25 to 50 feet below ground was challenging. For example, when the 72-inch liner was filled with resin, it weighed nearly 200 pounds per foot. As a result, the crew added a special hydraulic brake to the roller setup to control the speed at which is was lowered into the manhole. In addition, one 90-foot section had a 13-percent grade change, far more than the typical 0.5 - 3 percent.
The second phase of the project had an extremely deteriorated pipe, a condition that was not known to the owner. The CIPP liner had to be re-sized and re-designed for the actual pipe conditions.
The project was completed in 12 installations ranging from 90 feet to 1,480 feet over the course of 4 months in November 2018 to February 2019. A 2,400-foot second phase was completed the following September and October.