By Aaron Mitchell
Otsego City Manager
Many are not aware of the details, but we made some significant state-mandated improvements to our city-owned dam late last year.
When the expected costs made the repairs almost impossible, the DNR (Wildlife Division and Fisheries Division) played a vital role in the completion of the work and really saved the day.
Let me share some of the details.
This whole situation started in May of last year when we had our standard dam inspection conducted by EGLE. I should inform you that these inspections take place every three years and usually only require minor maintenance, such as the removal of vegetation from within the dam area.
This inspection was a little different.
The inspectors quickly identified that there was a small “rooster tail” coming off the northern spillway and informed us that it would need to be addressed immediately.
Below I will answer a series of questions that you likely have to better help you understand the situation and the severity of it.
What is the status of our dam? Wasn’t the EPA removing that?
Yes, and no …
The dam has been scheduled for removal for more than 20 years by the EPA as part of its Kalamazoo Superfund work. It was always in the plan for removal; however, the exact schedule has always been five to seven years away. That is mostly due to the nature of the work and out of the EPA’s hands.
So, it is coming out, just no guarantees when. And it needs to. It is more than 100 years old and has not been used for hydroelectric power for many decades (which was its original purpose).
Plus, did I mention the cost to do any and all maintenance on a dam?
What is a “rooster tail”?
A rooster tail is a noticeable agitation to the flow of water running down the spillway that is causing a noticeable redirection of the water.
Considering the location of the rooster tail on the spillway, it meant it was almost certainly from a crack in the very old foundation of the spillway.
We had many questions and few answers. The questions were more about why the crack was forming than anything else. It could be from the creation of a void under the spillway for some unknown reason, or a void could be created as a result of the crack.
Either way, a void could be very bad and create a catastrophic event that could blow out the entire dam.
What is needed to repair the spillway?
At this point, we did not know exactly the severity of the crack in the spillway or the potential void in the foundation.
In order to fully understand the situation, we would have to inspect it further. In order to do that, we needed to stop the water by hammering in sheet pilings upstream along the northern spillway and placing some sandbags to stop all water from entering the spillway.
Once the water was stopped, a deeper inspection could take place. Once the inspection was completed, maintenance would be expected to be completed at that very point—whatever the need or cost—since the water was already stopped.
What was the City’s response?
Considering this dam is already tentatively scheduled to come out, I asked anyone willing to listen to try and get someone else to pay for these repairs.
I have a hard time justifying spending a significant amount of taxpayer money to reinforce a dam only to have it completely removed in a matter of years.
Plus, at this point there was a very real possibility that when we got in there and inspected it, we would find that the whole dam was preparing to fail, which would trigger emergency work to repair it. That would put costs for the project into the multiple millions!
That had me more than a little nervous and not wanting to be the one on the hook, to be honest.
When it became obvious that we had no one coming in to save the day (i.e. EPA, contractors, responsible parties, EGLE, insurance), we dug into what exactly the costs were going to be and found the best estimate to be a little over $300,000.
That is just too much money for me to explain to the community to spend on this aging dam that we have been told for the last 20 years will be removed.
But we obviously cannot sit tight and let a failing dam only worsen.
What did the City do?
The good news is that state agencies have such a good relationship with the City of Otsego that word got out about the situation and agencies looked around for possibilities.
DNR’s Mark Mills had an amazing offer to transfer an unused grant of $300,000 to put toward the project. The grant required a 10-percent local match, which we happily complied with since it was such an incredible offer by the DNR.
How did the project go?
It took a bit to get the water to safely stop going over the northern spillway. But once we did that, we were pleasantly surprised by the findings.
We found everything to be intact.
There was definitely a large crack in the concrete that was causing the rooster tail. The vital data was found within and below that crack. The concern was that all of the rocks and boulders would be washed away under the spillways.
Once the water was stopped on the northern spillway, engineers were able to identify that no washout had occurred at this point.
This was great news!
However, the wide crack still had to be fixed. The contractors were able to apply some additional rocks and concrete to smooth and secure everything for at least another 20 years.
Overall, the project ended just under $350,000, which is not bad since we were able to secure the wall as well while the spillway was accessible.
It was pretty cool to stand on a location that has not been exposed for 100 years.
This was an extremely anxiety-ridden process that started with the initial inspection in May and concluded with the work being completed in December.
I am incredibly thankful that the work was able to be completed before the winter. There were multiple times that river flows were challenging communities across the state of Michigan.
If that work was not done, I do not know how well the dam would have held up to that stress in the late winter and early spring months.
And that work would not have been possible if it was not for the DNR grant.
We all owe the DNR a big “thank you!”
