Giant 'geopool' strains sediment from Black River water

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Posted August 24, 2020

A dredging project in Lorain’s Black River could be the future of keeping shipping channels open while reusing mud from the river bottom.

The city of Lorain Engineering Department, Coldwater Consulting LLC and the Ohio Department of Natural Resources have joined to create a pilot project to dredge the river and pump the mud upland.

There, the new “geopool 2.0,” a giant above-ground filtration lagoon, will strain out particles from the water, which will be pumped back into the river.

The mud will dry out and could be used for other purposes.

“It has exceeded expectations,” said Corry Platt, director of sediments, coastal and brownfield restoration for Coldwater Consulting LLC.

That firm has worked with Lorain staff to guide a number of environmental restoration projects along the Black River.

Platt discussed the project on site with Kristen Risch, principal and owner of Coldwater Consulting.

Geopool

The geopool, formally known as the City of Lorain Black River Dredge Reuse Facility, is a pilot project to examine if the method could be used in port cities where crews scoop out mud to maintain appropriate depth for freighters.

Previously, the dredging crews dumped the material in deeper waters of Lake Erie, but the state of Ohio will stop that practice this year.

On Nov. 19, 2019, Lorain’s first geopool collapsed when workers began pumping river mud into it.

No one was hurt, but it was a setback for the project schedule.

“We were so disappointed when the first pilot failed,” said Kate Golden, stormwater manager in the city Engineering Department. “But, it gave us some information on how to do better next time.

"We were able to build on that failure to ensure that this second round was successful.”

Try again

This month, the geopool remained stable operating four days a week starting Aug. 10.

The second geopool was built to be sturdier than the first one, but the design remains largely the same.

The Ohio Department of Natural Resources has supplied the hydraulic dredge barge that sits in the Black River.

It is located in the turning basin behind the steel mills, an area that has not been dredged in at least 20 years, Platt said.

The dredge acts much like a giant vacuum cleaner, sucking up mud from the river bottom to deepen the navigation channel that freighters move in.

Sediment and water is pumped through a mile-long pipeline to the geopool, Platt and Risch said.

The elevation change is 75 feet from the riverbed to the geopool.

“That’s a lot,” Risch said.

The geopool is set up like a giant above-ground pool, but with a screen mesh that collects particles while letting water trickle out.

Results so far

Researchers are collecting samples to examine at least three components of the project.

They want to analyze the dredge material coming in, the cleanliness of the water going out and whether the dirt that’s left could be used for purposes such as ecosystem restoration, residential use or general fill.

It appears to be an effective strainer, so far, Platt said.

Water comes in with an average of 40 grams of solids per liter.

The filtered water has about 40 milligrams of solids per liter — considerably cleaner —- when it returns to the Black River.

“That is a measure of the water quality," Platt said. "The more solids you have in it, the dirtier your water is.”

The clarified water collects in a sump, which looks like a moat dug around the pool.

The geopool is designed to be an effective method for drying the dirt that’s left, Risch said.

Eventually, workers could open the sides of the geopool and use a front end loader to scoop up the dirt into a dump truck.

That point is important, because generally, every time workers have to handle materials, there is a cost involved for labor, fuel and tools, Risch and Platt said.

Reducing the amount of handling should help push down operational costs.

Paying for research

The city received a $4 million grant to pay for the project, which is coordinated with the Ohio Department of Natural Resources, Ohio Environmental Protection Agency and U.S. Army Corps of Engineers.

It came to the attention of Lorain City Council in July, when members approved a contract amendment of more than $1.11 million for the work.

The geopool has a price tag of more than $2.78 million so far, according to city records.

“Understandably, the initiation of the facility is very costly,” Golden said. “From the other side of things, we have been incredibly impressed with the redesign of the geopool.”

Source: MJ