The Michigan Ditch is located in Jackson County, Colorado and is part of the City of Fort Collins water supply system and conveys water from the west side of the Never Summer Mountains to Joe Wright Reservoir on the east side of the range. The 5.2-mile-long ditch was constructed in the early 1900’s and has been plagued by slope instability since it was built. An area known as the “Mudslide” experienced accelerated slope instability in recent years and the piped portion of the ditch through the landslide was destroyed in 2015 when the landslide moved over 20 feet horizontally and 7 feet vertically.
Design a solution to the destroyed portion of Michigan Ditch that could be built during 2016. The construction site was fraught with challenges including: elevation above 10,000FT, very small launch and receive areas for a tunnel machine, unknown geology in the probable tunnel path, and an available construction window from May through September depending on snowfall.
The City of Fort Collins utilized there Alternative Product Delivery System to procure the project. Extensive geotechnical investigation during the summer of 2015 allowed the team to develop a number of solutions that were analyzed with cost, risk, and long term viability as the main criteria evaluated. Ultimately the team decided on a 766FT long, 96” diameter tunnel to be installed with a TBM behind the landslide. The geology of the tunnel profile and site topography required the tunnel to have a 726FT long curve on a 630FT radius 40FT after launch. The TBM was a 720 Series II provided by Akkerman, Inc. out of Minnesota. The final carrier pipe was 60” diameter CCFRPM pipe supplied by Hobas out of Texas. The Michigan Ditch was back online in October of 2016.