Originally constructed in 1884, the Thompson Mill dam on the Big Blue River failed. Town Council will now decide its fate after hearing an informative presentation.
Daily Journal file photo
The future of Edinburgh’s Thompson Mill dam is still uncertain, but the town council heard possible options for its fate Monday.
The Thompson Mill dam officially burst the weekend of Oct. 16, marking a critical turning point in the landmark’s future. At Monday evening’s meeting, the Edinburgh Town Council invited Jerry Sweeten, a senior ecologist at Ecosystems Connections Institute, to present an informative lecture on low-head dams and his advice on how to handle the current situation for the 19th-century dam on the Big Blue River.
Sweeten specializes in limnology, the study of inland water bodies such as lakes and streams. He is credited with using National Fish Passageway money to remove low-head dams across Indiana and has extensively researched the effects of low-head dam removal.
“We’ve learned a great deal,” Sweeten said. “There are hundreds of dams across Indiana. Many of them were built in the middle of the 1800s. Every one of them has a life and they are reaching the point in history where they are struggling to exist.”
Sweeten was part of a team that removed every dam in the Eel River, a waterway located in North Manchester. Since removing the final dam in 2021, they have detected 18 previously unseen fish species in that river, all deriving from the Wabash River.
A common misunderstanding regarding low-head dams is that they prevent flooding, he said. Sweeten insists they do not and were primarily used as barriers to prevent fish passage.
Calling the dams “culturally historic,” Sweeten realized over time the dangers these dams pose on community members. He emphasized how quickly these dams can change.
The power of the water below the dams is extremely dangerous and can cause death or severe injury if someone were to fall in, Sweeten said. Edinburgh’s dam has also seen its share of tragedies, notably causing the death of two Franklin teenagers in 2014.
Edinburgh’s situation
The Thompson Mill Dam was established in 1884 and has remained a prominent attraction to the Edinburgh community.
“It’s taken a lot of force from the river,” Sweeten said. “Moving water has tremendous power. It is constantly beating against this structure. Over time, as I mentioned, every day has a life expectancy; and it is sad, and it is hard to deal with. We happen to be in the generation where we are reaching the end of the life of this structure that we are all so familiar with.”
Some of the signs that the dam was in trouble included water flowing in between the blocks and a noticeable dip in the dam’s wall. Sweeten said that he predicted that the dam would not last through this winter.
“We know that [Indiana Department of Natural Resources] engineers have come out to look at the dam,” he said. “They knew this dam was structurally impaired. We looked at it and our conclusion was the same. The only thing we weren’t quite expecting was the dam to fail quite as quickly as it did.”
The town is not alone, and Sweeten says he’s seen this happen before. The best way for officials to preserve the history of the dam is to get it removed so that the blocks can be used across town in ways that help save the memory and history of what’s left, he said.
Sweeten said that their team works with an archaeologist who can offer a complete historical report on the dam’s legacy.
Can it be fixed?
The dam will undeniably continue to fail if no action is taken, Sweeten said.
“It has not experienced a large flow of water yet, but the structural integrity of this dam is compromised at the hole in the foundation,” he said. “As you are facing the dam off to the left, there is also some large cracks between those blocks. That is the same sign we saw in the spot in the dam where the foundation was compromised.”
Although repairing the dam is possible, Sweeten explained that it would be an experience and laborious undertaking.
First, all of the dam’s blocks would have to be completely removed from the river. The dam’s foundation is compromised, he said. The old wood foundation would have to also be removed and a new foundation would have to be poured or placed back into Big Blue River.
Then the stone blocks would have to be put back onto the new foundation.
Sweeten is not aware of any grants that would fund the dam’s repair, meaning that the money would most likely have to come from the public’s tax dollars. However, there is funding available for the removal of dangerous low-head dams through the National Fish Passageway program and the bipartisan infrastructure deal passed in 2021.
That bill has nearly $40 million to remove low-head dams around the country, he said.
“I was authorized to submit a proposal for funding to remove the Edinburgh dam,” Sweeten said. “It was competing nationally for those funds, and it received full funding. It would cost the town of Edinburgh zero dollars to remove the dam and to preserve the history that goes along with having the dam removed. In that proposal, we built in moving the blocks wherever would be convenient for the town to save the blocks for historical purposes.”
Sweeten is not aware of any resources that are available for repairing a dam like Thompson Mill, he said.
What if it’s removed?
Sweeten mentioned that he often hears speculation that if a dam is removed, the river would run out of water. That is not the case, he said.
“If you want to know what the river will look like, look downstream of the bridge at the river. That is what the river will look like after it heals if the dam should be removed,” he said.
If the dam is ultimately removed, Sweeten says that fishing will most certainly change in the area. But his research shows that it will actually change for the better, he said
“Rather than sitting in at the base of the dam and casting bait in the pool, it will open up the entire stretch of the river that was in the pool behind the dam for fishing,” he said. “In our research, we have plenty of data that it will actually improve the fishery, fishing and the biological community of the stream in every case.”
What happens if the dam collapses further?
The decision to either remove the dam or repair it must be decided promptly, Sweeten warned. If the dam collapses even further, Edinburgh may lose the funding available to remove the dam and they would be left with an expensive and worsening situation.
“If the dam collapses more and fish passage becomes available just because the dam collapsed, I cannot tell you for sure if the money to remove the dam would stay in place,” said Sweeten “The money is founded on fish passage.”
Council member Ryan Piercefield said that the town council does not yet know what direction they are going to pursue, but they are considering holding a town hall meeting once a decision has been made to get all of the information out to the public in a factual manner.
He also said he anticipated a larger crowd at the presentation on Monday evening due to the apparent passion displayed online for the dam. Regardless, the council plans to consider Sweeten’s presentation and come up with a solution.
There is an extreme amount of cost with rebuilding the dam, and the town doesn’t know if the Indiana Department of Natural Resources, or IDNR, would let this to happen, Piercefield said.
“We don’t even know if the IDNR would even permit for that because it is such a danger and it has proven bad for the ecology of the river,” Piercefield said. “Nobody up here [on the council] wants to maliciously see the dam go. It is just, at this point, what do you do with something that is past its life while trying to figure out how to honor it respectfully and share that to all the people who have enjoyed it all the years? It is all heavy in our hearts. We do need to figure out for the community what the next course of action is, we just don’t have that answer yet.”
