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Tuscola taking steps to assure dam safety
Mary Drier posted by Tom Greene
Mon, 22 Feb 2021 14:30:20 EST
click on the picture to enlarge
After seeing the disastrous dam failure in Midland last May, Tuscola County officials are paying close attention to the condition of its dam.
Murphy Lake is located approximately three miles northeast of Millington in southern Tuscola County. Originally, Murphy Lake was one of three small lakes interconnected by Goodings Creek as part of the Cass River system.
The original dam was constructed in the 1850s to enlarge Murphy Lake to facilitate the lumber industry.
Then, a new dam was installed in the early 1930s when the lake was enlarged to include Nest Lake and Robins Lake which transformed Murphy Lake into a 209 acre body of water.
There was a special presentation earlier this month on the need to replace the Murphy Lake Dam.
Before the presentation was hosted, Tuscola County Drain Commissioner Robert Mantey gave county commissioners a heads up about the condition of the dam, the special meeting regarding it, and that the matter will be coming before them to make decisions.
"The county is responsible for making sure this dam is kept up so you need to understand that, and what is going on," said Mantey, who is the manager of the dam.
A little work has been done here and there on the dam over the years despite recommendations.
"Two of the spill ways were coated with concrete to prevent further corrosion that was occurring. The corrosion was detected in 1974. It was recommended at that time to do something but nothing happened until 1983," said Mantey. "In 1997, there was a 48 niche metal main pipe that was recommended to be replaced with a concrete or plastic pipe; but instead, it was cleaned and coated onsite. The recommendations of a professional engineer were not followed. Here we are, 60 years later, with the metal pipes near the end of their lives according to EGLE (Michigan Department of Environment, Great Lakes, and Energy), and they've said several times they are nearing the end of their life."
The dam is on a lot owned by the county.
The lake water level is maintained with an earthen dam with a concrete/steel water control structure on the north shore.
Engineers from Spicer Group did visual presentations on the proposed new dam to control the level of the inland lake. Once it is built the new dam will have a life expectancy of 70 to 90 years.
Some of the plans outlined for the new dam is for a cement box culvert, a weir, and a new gate that can be manually controlled by cranking.
"Currently, I raise and lower the lake level. I physically get in the lake with waders. There is a ledge to stand on. I have to stand off to the side because the water comes through so fast when I pull the boards," said Mantey. "There are six-inch boards that are pulled to let the water come through a 36-inch chute."
The boards are wood. Over time some have rotted and had to be replaced, and they have been vandalized.
"There is nowhere else in the state where someone gets in the water to pull boards for a dam. This is an archaic system. Most stand on a platform and crank boards up or down. Most are going to aluminum boards," he said. "It needs a redesign."
The new design would also allow the lake to be drawn down for maintenance.
To do the work, the lake would have to be lowered. That would take about a month to do.
The drawn down and dam design are both pending EGLE approval.
The projected timeline is for bid letting to be done this September with the lake level lowering happening about Labor Day with construction being done in October through December, and the work to be finished in the spring of 2022.
Before that point, there will be public hearings, a draft of the assessment roll, and go to the county commissioners for approval.
The cost of the project would be spread over an assessment of the property owners along the lake, including the Michigan Department of Natural Resources (DNR).
On June 22, 2019, Tuscola County Circuit Judge Amy Grace Gierhart approved the Murphy Lake Level Order, which included establishing an assessment district boundary to finance improvements to maintain the lake's legal level, and to clarify when the summer and winter lake levels begin and end.
Once the bids come back, the cost of the project can be determined and the amount of the assessment set. Although the cost can be levied up to 40 years, the assessment level is anticipated to be about 10 years.
Goodings Creek is the primary inlet and outlet of Murphy Lake. The creek enters Murphy Lake from the south and exits to the north flowing to the Cass River and to the Saginaw River and Lake Huron.