Editor’s note: This is the second part of two-part story. See last week’s issue for the first part.
When contractors for the U.S. Environmental Protection Agency are done, the Kalamazoo River will take a significantly different course near the unused Otsego Township Dam.
The project was authorized with the aim of cleaning up time-critical PCB contamination in the river and along its banks, but part of the way it will do that is removing the more than 100-year-old dam.
Work will soon begin reshaping the river’s channel above and near the dam, which is near Bittersweet Ski Area along River Road.
EPA on scene coordinator Paul Ruesch said the channel would be reshaped.
“A pilot channel above the water control structure will get the water to go down a new channel right in the middle,” he said.
The machine, which sits on a barge, uses GPS to dig the channel precisely where engineers have calculated it needs to go. It then sucks up the soil from the river bottom along with water and pushes it through a pipe.
“It’s like a big wet vac,” Ruesch said.
The soil will be discharged into an area south of the dam that is currently a backwater area next to the old concrete spillway of the dam. Contractors will fill most of the area with soil and what open area is left will become a wetland.
“When he gets done, most of that will be filled in, but not all,” Ruesch said.
The water that carries the soil will be filtered through a mass of bundled Christmas trees and what the EPA calls turbidity currents to make sure that a minimum of the soil being pulled up ends up going down river.
If too much sediment gets into the water, it can crowd out the oxygen fish need to breath and kill them, so the EPA is focused on making sure that is kept to a minimum.
Sensors are placed in the river below the work area that monitor the amount of sediment in the water.
“If turbidity elevates, my phone gets a text and we’ll stop work,” Ruesch said.
At the dam, the concrete spillway will be broken up into smaller pieces and covered with soil.
Ruesch said that water has been infiltrating under the dam’s spillway. The soil under the spillway has also eroded away, causing a void at the front.
“The Allegan County Sheriff’s dive team has been out and explored it for us as a training exercise,” he said. “They measured how deep it is so we know how much we have to deal with.”
Ruesch said the fall was the best time of year for the work to happen, because the river would be too high in the spring.
The dam’s problems made failure to likely and caused the Michigan Department of Natural Resources to install the temporary water control structure the EPA is currently using to regulate the river’s level.
Once the work is done, the river’s surface will be about five feet below where it is now with the water control structure at work. The river’s course will stick toward the middle of the current river flow passing along an island south of the dam.
Also, once the EPA is done with the former dam site, it will leave behind a public access site for river users.
Time critical only
On the site, Ruesch pointed to examples of gray soil as examples of what old paper mill sludge looks like.
“That’s what it looks like, but the sludge doesn’t mean it has PCBs,” he said.
The contamination won’t all be removed when the project is finished (if it stays on schedule that will be next year) because the time-critical removal focuses only on the contamination that is likely to be discharged into the river if nothing is done, mainly that actually in the stream or along banks that eroding.
A major part of the work includes stopping that erosion.
In the part of the work that is very visible from the M-89 bridge west of Otsego was focused on that aspect as the river’s bend there was pushing the southeast bank back alarmingly quickly.
The rocky structures contractors installed in the river are called J Hook Vanes.
“They take the energy out of the water, the idea is to stop erosion on this bank,” Ruesch said.
The structures are anchored deep into the bank and shaped to withstand the water, so they should be a fairly permanent feature in the river.
A new channel was also dug in that section, also encouraging the water to stay away from the bank, which has been extended with clean fill.
“We did stream modeling and it showed the ideal depth to width ratio,” Ruesch said.
Odds, ends and misconceptions
This fall the EPA will continue work along the banks near Pine Creek and will also plant a wide variety of native plants and shrubs in the areas.
One they call a live stake, which is a cut willow tree branch which should take root and help provide bank stability.
One rumor Ruesch said he’d like to dispel was about the large white bags visible on site.
“I’ve heard a lot of people say the bags are full of chemicals that are dumped on the PCBs at night,” Ruesch said. “That’s not true, we can open one up and it’s nothing but clean sand.”
The contractors will be at work clearing some timber this fall, as they are prohibited from cutting trees during part of the year by the presence of several endangered bat species that migrate to Michigan in the summer and live in tree bark, but head back south for the winter.
Ruesch said the crews have been very welcomed by the community, but one resident, Maré Westin, was above and beyond.
One day this summer she hosted the whole crew for Cheboygan bratwurst.
Contact Dan Pepper at dpepper@allegannews.com or at (269) 673-5534.
.