By Holly Crocco
The Town of Kent and Putnam County are working together to maintain the upper and middle South Lake dams in Kent, with the hopes of improving the culverts and reducing the costs associated with inspection and regulatory efforts required by the state Department of Environmental Conservation.
Neal Tomann, interim director of the Putnam County Soil & Water District, explained at the March 21 Kent Town Board meeting that while the town owns the lower dam, the county owns the upper and middle ones.
Currently, all three dams on South Lake have B ratings, meaning they are considered an “intermediate hazard,” so if they fail, they could potentially cause property damage.
An A rating means there would be no property damage if the dam failed, a C means there would be potential for serious property damage and/or loss of life, and a D rating means the dam is decommissioned.
Every 10 years, the state requires owners of dams rated with a B or a C to file an engineering assessment of the condition of their dams.
According to Tomann, the plan is to create a controlled breach of the upper dam, to equalize the water level between the upper and middle sections, then engineer a spillway that can go over without washing away the dam. This would give the upper dam a D rating, but then the middle would get an A rating.
“We don’t want to be Bs, we want to be As, which are minimal hazard, or we want to be D, which is decommissioned,” he said. That way, the municipalities won’t have to spend $20,000 to $30,000 to complete an engineering assessment every 10 years.
About a year and a half ago, the Town of Kent was awarded grant funding through Bridge NY to make improvements to the lower dam, and has since has engaged Burton & Loguidice to design the work. Now, the county has engaged the same firm to design the controlled breach of the upper dam, to determine the effect of the new, post-breach discharge flow rates on the lower dam and spillway.
“Since all the streams are in succession, we are all very much in the same boat,” said Tomann. “We don’t have a great idea, under a certain type of rain event, how these two upper damns are going to behave, and that makes it difficult for the Kent side of the project to really get a good look at what to do. I would rather have the dam be configured so the flow is far more predictable and the liability and hazard potential is down to an A, or a D grade.”
Currently, the upper and middle dams don’t have a spillway. They have areas of busted, corrugated pipes as well as areas of heavy beaver activity clogging them up. Tomann said the engineers will calculate how much water is flowing in, how much is penetrating the dams and how much will have to go through the system, in order to build a good dam.
Additionally, there is currently a roughly 4-foot difference in water elevation between the upper and middle sections. Engineers hope to reduce the level of the upper lake closer to what the middle section is, then there will be a small drop to the lower section.
“There’s a three-tier system and we’re trying to eliminate one of those tiers,” said Tomann. “So, it simplifies everything. It simplifies the dynamic of the whole system.” In doing this, he said engineers hope to avoid pouring any concrete, in creating “something simple, low maintenance, so it can carry the requisite amount of water.”
Tomann said the county is hoping to have a plan to present to the town by mid-summer. “It’s not a complicated build,” he said.
The dam would have to accommodate 150 percent of how much water is figured would get through during a “100-year flood,” so there is essentially no chance it will overflow. However, Tomann cautioned that the middle level is still going to have seasonal fluctuations, and there will still be beaver activity.
According to Kent Highway Superintendent Richard Othmer, the town is still about a year away from starting work on the lower dam, so waiting on the county’s plans this summer won’t hold up the project.
“The bridge is staring to collapse,” he said of the lower dam. “The bridge is in horrible shape. It’s really a danger… These things were built in the 1930s and they haven’t been touched. They are 100 years old.”
Specifically, he said there is a 10- to 12-foot spillway between the upper and middle dam that the beavers constantly clog up. “We’re there 10, 12 times a year cleaning it,” he said.
Othmer said the engineers “are going to do a mathematical study of hydraulics, so the output keeps the surrounding area safe and it equalizes with the input of water, because there are a lot of feeder drains going in there from up north. Right now, it’s not balanced,” he said.