Traverse City Record-Eagle

September 11, 2013

Forum: Expensive Hammond bridge not needed


Traverse City Record-Eagle

---- — If you Google “Hammond Bridge Traverse City,” you will be inundated with hundreds of articles dating back to 1995. Most of these were printed in the Record-Eagle.

Numerous studies and meetings have been conducted over the years and to date no decision has been made regarding any of them. I realize this proposed bridge is very controversial because so many organizations have to agree to a solution.

However, one of the main reasons the linking of Cass-Hartman-Hammond roads with a bridge has been delayed so many times is the high cost of a bridge. It is my opinion that an expensive bridge is really not necessary.

About a mile downstream from that location is South Airport Road where the Boardman River flows through three 16-feet-wide steel culverts instead of under a bridge. Both locations have water flowing from the Boardman watershed except at the proposed bridge location, there is even less water flowing from the Boardman River than at the South Airport Road location.

When roads are being built over streams the hydrologists and engineers have to determine the quantity of water emanating from the watershed, including an estimated 100-year flood. Then they design a safe structure to handle the flow.

At the time the three 16-foot culverts were installed to convey the Boardman River under South Airport Road, 100-year flood information determined by hydrologists may not have been as accurate as it is today. What kind of structure would be required at South Airport if it was being considered today? Would three cheaper 16-foot culverts provide a safe design or is an expensive bridge really necessary?

Now let’s get back to the Boardman River flowing under the Cass-Hartman-Hammond upstream of South Airport Road. The water flowing at this site will actually have less water flowing under it than at South Airport Road. Why? There is a small tributary from the west flowing into the Boardman River (Jacks Creek) between Hartman and South Airport Road.

So in addition to the Boardman River watershed above Cass-Hartman-Hammond, the additive watershed below this site will send additional water to South Airport Road.

New 100-year flood flows, using current studies, will indicate what kind of structure would provide a safe design at the Cass-Hartman-Hammond site. Since these new studies will show that there is less water flowing at this site than at South Airport Road, it might even be determined that three smaller culverts or two culverts of a different diameter might provide a safe design.

So if I’m wrong and updated studies by hydrologists and engineers, using the latest research and design criteria, determined that a bridge at the proposed Cass-Hartman-Hammond is necessary, then a bridge would also be needed at South Airport Road.

About the author: Frank Lahde holds a degree in civil engineering and earned a Profesional Engineering License. He was an officer in the U.S. Army Corps of Engineers for more than eight years before resigning his commission as a Major. Most of his working career was with Ford Motor Company. He has lived in Grand Traverse County since 2004. Twice a year for the past five years he has assisted the Boardman River Clean Sweep organization in the removal of river debris. By email: franklahde@yahoo.com.

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