North Sharon Road Timber Bridge Project
Kalkaska Conservation District
Basin Program Funds:
An undersized culvert on the North Sharon Road crossing on the North Branch tributary of the Big Manistee River has caused severe sedimentation to the river. The site consists of a single culvert channeling the river under a gravel country road. Estimated sediment loading from this site was 84 tons per year. In addition to the sediment deposition from the unpaved surface, the undersized culvert had caused the development of a plunge pool on the downstream side of the culvert with the resultant bank erosion of 7-10 tons per year. The undersized culvert had a detrimental effect on the river upstream as well. The impeded water on the upstream side of the culvert was 25-30 percent wider than the unimpeded flow downstream.
For over ten years the upper reaches of Michigan’s Big Manistee River have been the focus of extensive stream bank and road crossing repair work in efforts to abate sediment loading. Nearly $3 million has been invested to date. Fish populations are on the rise, resulting in heavier recreational fishing activities on the rivers. One remaining problem area needing attention was the North Sharon Road crossing, which is within one-quarter mile of the main branch of the river.
This project removed an existing culvert at the North Sharon Road Crossing on the North Branch of the Manistee River, installed a clear span timber bridge, and pave 3,800 feet of approaches to the crossing. In addition, the following were installed: asphalt ditches with water spout “turnouts” to direct roadway water to wetland and upland retention areas, heavy rock rip-rap to armor bridge footings, and treated steps to allow access to the river by river users. The project produce a partnership agreement for project collaborators and set up tours of our project with local and regional decisionmakers, demonstrating the effectiveness of the collaborative soil erosion and sediment control projects.
Due to the diverse group involved and the financial logistics, a nine-way agreement for the construction of the bridge was signed. The existing culvert was removed and the new bridge was constructed. The hydraulics of the river is completely changed. Stream bank scouring has stopped and the downstream plunge pool is beginning to fill. Erosion control measures are in place, including heavy rip-rap channel lining, stream bank erosion protection and rock-lined downspouts diverting water from the roadway, and final grading has been done for the paving.
Summary of Problems Encountered
The actual construction of the bridge got started later than hoped. The late start meant a later finish time for the project and paving had to be pushed back until the spring of 2002. A gravel substrate caused several bridge pilings to shatter during the driving process. While excavating the old culvert, old concrete railroad abutments were unearthed. One of the abutments had to be removed to accommodate the new bridge installation.
Contact: Russ LaRowe, 231-258-3307