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Cedar Road at the North Branch of Tobacco River

Harrison, Michigan

Bridge Replacement

Installation:

October 2020

Technical Description:

• Open Bottom Aluminum Box Culvert
• Span: 28-ft. 8-in.
• Rise: 9-ft. 4-in.
• Length: 40.5 ft.

The existing dual 72” rise corrugated metal pipe culvert crossing at Cedar Road already had exceeded the useful service life when in June 2020, a 500 year flood event occurred. There was significant flooding throughout the area and the river level in this location was 10' higher than normal, eventually overtopping the road and causing the culverts to fail. 

The dual culvert approach has become an outdated design approach and is no longer acceptable through Michigan Department of Environment and Great Lakes and Energy (EGLE), the review and approval agency for crossing replacements. Undersized, single culverts or multiple culvert designs were an economical solution throughout the early and mid-1900s, but there was little attention paid to the long-term impact of the water course, the surrounding drainage area, and the limitations of fish passage. New structures need to recreate the natural water course to improve the overall drainage watershed, reestablish a natural water path for fish passage and allow for new clearance access for canoeing and kayaking.

Current design requirements of new structures is to span the full width of the bank or the width of the stream that corresponds with the depth where water fills the main channel prior to overflowing. For the Cedar Road crossing, the width of the bank was approximately 25' with rise limitations of 12' from streambed to road grade. As an added challenge, EGLE requested the new structure clear span the creek to limit construction-related impact, while also creating a natural bottom to further improve fish passage.

“Natural rivers have constant and significant flow where any approach used to manage the water creates a costly addition to the contract and impacts the aquatic environment,” noted DeWayne Rogers, Managing Director for Clare County Road Commission. “Working over the creek, rather than in the creek, is an economical approach while accelerating the project construction cycle."

Early on in the design, the Contech Engineered Solutions team worked closely with local engineering firms and agencies in Northern Michigan to design a clear span structure solution that addressed foundation design, long-term scour-counter measures and met the span/rise requirements for a given crossing by combining aluminum structures with a steel sheet pile cofferdam. Contech offers 143 standard aluminum box shapes spanning up to 35' with varied rise options. For any given crossing, multiple aluminum box solutions can be identified when considering EGLE design requirements, combined with a required hydraulic open area and height of cover limits.

The inclusion of a steel sheet pile cofferdam through the culvert allows for the contractor to complete construction without impacting the water course with temporary diversion methods or draw-down pumping. The cofferdam sheeting also acts as a spread foundation improvement and scour countermeasure protecting the structure during the largest storm events.

Due to Contech's previous experience working with Michigan's road agencies and non-profit organizations to replace structures along Michigan’s natural rivers, the team met with Contech to review product options and concepts. After evaluating the options, the team decided that an open bottom 28-8' span x 9'-4" rise Aluminum Box Culvert (ALBC) was the best replacement solution. Designed to MDOT HL-93 modified live loading requirements, the 40.5' long structure included an integral aluminum headwall and wingwall end treatment package. 

Even though the county crew did not have previous experience with this type of structure, they were able to complete the entire project in-house. Additionally, the project was completed during the winter months without disturbing the river. The entire structure replacement was completed for less than $300,000 including paving, guardrail and approach and reopened in January 2020.

Technical Description:

• Open Bottom Aluminum Box Culvert
• Span: 28-ft. 8-in.
• Rise: 9-ft. 4-in.
• Length: 40.5 ft.

800-338-1122 | www.ContechES.com

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