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369k cubic yards of sediment came through Morrow Dam, says river expert

KALAMAZOO, MI — The total shocked Stephen Hamilton.

Hamilton, an aquatic ecology professor at Michigan State University, had seen the Kalamazoo River sediment deposits that developed after a hydroelectric dam operator unexpectedly drained its impoundment.

He had seen the turbidity in the water, which was so dark with fine sediment particles last year that objects disappeared from view immediately upon immersion.

He had paddled through the reservoir behind Morrow Dam, which is owned by Eagle Creek Renewable Energy, a subsidiary of Ontario Power Generation of Canada.

But Hamilton was still floored by the total volume of sediment his measurements say has come through the dam — about 369,000 cubic yards. For context, that amount of sediment could fill 36,900 standard 10-yard dump trucks or about 113 Olympic-sized swimming pools.

“That’s enough sediment to cover the river bottom with one foot for 12-and-a-half miles,” said Hamilton, who has studied the Kalamazoo River watershed for more than 25 years and is considered to be the state’s foremost expert on the river.

“It’s a lot of sediment,” he said.

Hamilton’s assessment has been shared with the Michigan Department of Environment, Great Lakes and Energy (EGLE), which is negotiating with Eagle Creek on a potential consent agreement to resolve state law violations EGLE says happened when the company unexpectedly drew down Morrow Lake in late 2019 for spillway gate repairs.

The river has become a muddy mess since then, with the impoundment sludge smothering fish spawning habitat and recontouring bends in the river. Long-term impact on the fish and mussel populations are expected and local officials are worried about how the excess material might change flood risks as temperatures warm and snowmelt accelerates.

River advocates are upset, perceiving minor dredging efforts and no attempt to control downstream migration as showing a lack of urgency on the company and the state’s part.

This week, Eagle Creek began its first attempt to remove some of sediment by staging excavation equipment at Wenke Park. The company will dredge about 3,000 cubic yards from a side channel in Comstock Township during a six-week project that won’t make much dent in the overall problem.

Investigation maps and aerial photos show the bulk of deposits are located well downstream of the Wenke Park project, which was supposed to begin last month.

Regulators at EGLE say more dredging should follow.

Kyle Alexander, head of EGLE’s local water resources division office, said Eagle Creek has shared some preliminary plans to dredge a second nearby area around Merrill Park. The state hasn’t received any detail about additional dredging.

“There’s kind of a desire among all parties that we scale up the effort and start thinking bigger picture,” said Alexander. “I suspect some of these conversations are starting.”

In February, Eagle Creek submitted a field investigation report that estimated 114,000 cubic yards of sediment was coating about seven to eight miles of river downstream of Morrow Dam.

Bathymetric surveys and core sampling found sediment deposits more than an acre in size, ranging from two to 10 feet thick in some areas. Maps show deposits more than 9-feet thick near downtown Kalamazoo and more than 11 feet thick next to the city wastewater plant. One deposit stretches nearly 2,500 feet from the wastewater plant to Mosel Avenue.

The state says Eagle Creek’s estimate does not portray the full impact scope because consultants did not include deposits less than one foot deep and stopped taking samples and measurements at the northern border of Parchment.

Hamilton’s sediment estimate is based on regular total suspended solid (TSS) measurements taken from the river and Morrow Lake before and after the November 2019 drawdown. That data was then compared with past sediment density measurements taken in Morrow Lake.

Hamilton said some sampling was missed in late May due to COVID-19 restrictions, but given the overall wetness of that month in Michigan, a data gap there would be “more likely to bias it low than high.”

“This is the best information that we have available,” he said. “Nobody else was monitoring anything until August when the company started measuring turbidity.”

He said the 1,000-acre Morrow Lake impoundment may have been collecting sediment since the dam was built in 1941, about 80 years before the drawdown.

“As far as we know, this reservoir hasn’t been drained since it was created. It was probably filled about 1940,” Hamilton said. “That’s a lot of accumulation.”

David Fox, Eagle Creek licensing and compliance director, said the company has “reviewed Dr. Hamilton’s analysis and we appreciate his good work.”

“Our understanding is that Dr. Hamilton estimated the total volume of sediment that moved through the dam during the drawdown period by analyzing the sediment load in a relatively limited number of water quality samples,” Fox said, compared that to the field measurements taken by Eagle Creek consultants. “As one would expect, the different methodologies produced different estimates results.”

Meanwhile, fishermen with the Kalamazoo River Alliance are concerned about sediment migrating into more communities. They say new sediment deposits are becoming evident around the D Avenue Bridge in Cooper Township.

“Clearly, this sediment is moving further downstream,” said Ryan Baker, president of the Kalamazoo River Alliance angler group, who said he sunk into one deposit up to his knees while taking photos around D Ave. “We checked this area out last year and there wasn’t anything to take pictures of.”

Baker, whose group has been trying to raise alarm about the situation among the public and local governments, said there is evidence of accumulating sediment around the former paper mill complex in Plainwell and behind the Otsego city dam near the Bittersweet Ski Resort.

Members of the Kalamazoo River Superfund Community Advisory Group (CAG) say they’ve noticed sediment accumulation in Lake Allegan over the past year.

“All of a sudden at the end of the summer last year, the cranes didn’t have to land on the water. They could land on big piles of mud in the middle of the lake,” said Coco Soodek, a Chicago attorney with a home on Lake Allegan, at the Feb. 25 CAG meeting. “Now, I don’t have any evidence that’s from Morrow Dam, but we never had it before.”

Fox, who was presenting to the CAG about Eagle Creek’s field investigation results, told Soodek that he had “no idea” when the company might examine Lake Allegan,

The lake is approximately 40 river miles downstream of Morrow Dam. Absent removal, it would be the last deposition point for most of the Morrow Lake sediment because further advance downriver would be inhibited by Calkins Dam, which is owned by Consumers Energy.

“I expect the hydrodynamic modeling that we’re in the process of doing will shed some light on that question,” Fox said, adding later that Eagle Creeks is looking for places to landfill dredged material and reducing that cost “means I’ll have more ability to remove material from the river.”

“I’m hoping within the next couple months we’ll have a much better idea where we can put this,” Fox said.

Hamilton said there are methods the company or agencies could employ to remove sediment in a strategic manner. A temporary dam structure could be installed in the river to trap and continually remove sediment, but it would be an expensive undertaking. He floated the idea in a recent stakeholder meeting, but it was “not met with enthusiasm.”

“I was arguing that it should be on the table as a possibility, because it would actually be less environmentally harmful to stick a dam in and capture the sediments as they arrive,” he said, compared to spot dredging numerous locations along the river with heavy equipment.

Hamilton said he was told that Eagle Creek’s consultant AECOM is evaluating several options for sediment removal. He hopes a temporary dam is considered. He thinks the river flow is too strong to install something less expensive with the same goal, like turbidity curtains.

“It may be possible to recover most of it, but it’s tricky because it’s going to keep moving every time there’s a change in flow,” Hamilton said. “It’s going to be a moving target that they’re chasing just like it was for oil recovery after the Enbridge spill.”

Hamilton said phosphorus dispersal along with the sediment portends algae problems later this summer in downstream impoundments like Lake Allegan where water flow reduces.

Baker said river advocates are worried that as more time passes, the sediment deposits will disperse to the point that meaningful recovery becomes practically impossible.

“A lot of this stuff is along the shoreline a foot or two deep and all of it is going to keep blowing downstream with high water events,” Baker said. “Eventually, it’s going to become virtually impossible to clean this out of the river.”

“We’re still waiting for the first project to start.”

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