MB2

 2020 will be a year not forgotten soon. A year fraught with global health concerns, political turmoil, and strife. Lost in the glare of these issues and concerns were also notable events from entities that persevered during those unsettling times. Not the least of which was the design, production, and installation of what arguably is the largest single cell precast concrete box culvert in the world.

The Michigan Department of Transportation needed to replace an obsolete twin culvert at the crossing of the Carp River under Marquette County’s M-35. A flat-bottom rigid box culvert was determined to be the preferred structure. Marginal soils at the site were found adequate when used in conjunction with a unique improved soils foundation and the distribution benefits of a rigid flat-bottom box culvert.  

The “problem” would be that the necessary hydraulic end area geometry would require a single cell box culvert to be larger in span and rise than any rigid precast concrete box culvert produced to date in the world (*1), i.e., 48’ span x 12’ rise conforming to MDOT’s HL 93 MOD (*2). Those requirements meant: 

• The span width / loading criteria could not be addressed with conventional bar steel reinforcement.
• The needed span geometry precluded the use of a conventional 4-sided precast box culvert due to handling and transportation limitations.