Massive filter keeps Detroit River contaminants in place

By BRIANNA M. LANE
Capital News Service

LANSING —Thanks to a spongy M&M-like technology, contaminated soil in the Detroit River downstream of Belle Isle’s MacArthur Bridge has been contained.

Powdered activated carbon absorbed the contaminated soil in the $3.6 million Detroit Riverwalk project that finished in December.

“Activated carbon is a pure form (of carbon) that’s used to absorb contaminants,” said John Collins, the general manager for AquaBlok, the Ohio contamination remediation company that created the carbon under the brand name of AquaGate+PAC.

“The powder functions similar to a Brita water filter you would put on your faucet,” Collins said. “We’re essentially doing the same thing but we’re doing it in the river.”

He compared the powdered activated carbon to M&Ms. The core is a hard stone-like material, while the coating is the powdered activated carbon.

Heavy metals, like lead, and chemicals called polycyclic aromatic hydrocarbons contaminated the sediment in the Detroit River Area of Concern, one of the toxic hotspots that U.S. and Canadian agencies have identified on the Great Lakes, Allison Lippert, an Environmental Protection Agency media relations officer, wrote in an email. 

Those chemicals are found naturally in gasoline, coal and crude oil, according to the Centers for Disease Control and Prevention. Burning coal, oil, gas, wood and garbage also creates polycyclic aromatic hydrocarbons.

The cleanup project was a partnership between the EPA and the Detroit Riverfront Conservancy and supported by the Great Lakes Restoration Initiative, a federal effort to restore and protect the Great Lakes.

Lippert said the powdered activated carbon was combined with sand for the Detroit River remediation project.

And Collins said, “You drop it in, and it goes where it’s supposed to go.”.

Once the contaminants are absorbed, they’re locked in.

A layer of stone was put in to cap and lock in the sentiments and to stabilize an old seawall before it is extended. The stone layer protects the carbon from currents and anything else that could disturb or damage it, Collins said.

The amount of contamination and the amount of powdered activated carbon needed influences how long it’s left in the water, he said. Many projects leave it in forever, as will happen to the Detroit River sediment. 

Activated carbon has advantages compared to other kinds of caps used to contain contaminants, Collins said. It’s a natural material that will support the natural habitat, while concrete disturbs natural habitat.

With activated carbon, less material is put down and it provides more protection, he said. It’s also cheaper since less material is needed, usually 10% or less of the overall project cost. 

The finished remediation will allow construction of a Riverwalk extension along the east riverfront. Work will begin soon.

Marc Pasco, the Detroit Riverfront Conservancy communications director, said, “Right now there’s a disconnect between the Gabriel Richard Park, the Uniroyal property and the Mount Elliott Park.” The Riverwalk extension will connect the three.

Extending the Riverwalk will create a safe and easy trip to Belle Isle, he said.

The extension will be 3.5 miles, making the total length of the Detroit Riverwalk 5.5 miles. Since the conservancy’s opening in 2003, its goal has been to revitalize 5.5 miles of the riverfront, Pasco said.

Brianna M. Lane writes for Great Lakes Echo.