Houghton, Mich., is one of America’s most walkable cities. City Manager Scott McInnes noted that the M-26 highway and increased traffic generated by development was an impediment to residents who wished to walk to Michigan Technological University (MTU), the downtown area or the city’s waterfront. Residents and visitors now benefit from a safer and more pleasant means of accessing these destinations because of a pedestrian and bicycle tunnel using precast concrete box sections.
The tunnel is under M-26 and connects Houghton’s waterfront park with residential areas. The 12-ft x 9-ft tunnel has a length of 160 ft. It was a collaborative effort between the Michigan Department of Transportation (MDOT), West Houghton Community Partnership and the city of Houghton.
M-26 is a major artery in the northern portion of the Upper Peninsula of Michigan. It joins U.S. 41 in Houghton to provide the only vehicle access onto the Keweenaw Peninsula via the Houghton lift bridge, recognizable to the thousands of engineers that have graduated from MTU. For those seeking to enjoy the waterfront development with its park and beaches, M-26 has been a dangerous and frustrating barrier to pedestrian access. When M-26 was built in 1980, there was little concern regarding pedestrian access to the canal area, but that changed with the development of the waterfront in 1994.
Wilcox Professional Services of Cadillac, Mich., undertook the design of the tunnel. Following a cost comparison, Connie Houk, P.E., of Wilcox commented Wilcox concurred with MDOT that precast concrete boxes provided a less expensive option to a cast-in-place structure, according to Andy Sikkema, P.E., Ishpeming Transportation Service Center. U.P. engineers and architects conducted an additional structural analysis on the box culvert because the dimensions of the box sections were not a standard size recognized by ASTM C1433. Also, specially designed traffic barriers were to be attached to the end box sections. The slope of the tunnel and the superelevated road surface resulted in varying depth of soil cover along the length of the tunnel requiring multiple design analyses. Additionally, the skew of the culvert with respect to the road centerline caused an increased span length that had to be accommodated in the design. The analysis was completed using a precast concrete design program and checked using methods detailed in ACI 318-02.
According to MDOT, the biggest problem in implementing this project was traffic flow. Use of 27 precast concrete box segments allowed construction without total road closures. Roadwork was managed by part-width construction. Work on the tunnel commenced in September 2003. Traffic was closed and diverted traffic to shared lanes on both phases of the part width construction, according to Jeff Moyle of Moyle Construction, Houghton, contractor for the project. The city of Houghton provided lighting, security cameras and gates for the tunnel, which is open from dawn until dusk with 24-hour monitoring by the security camera.
