Dredging can churn up historical contaminants

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Dredging on Lake Superior near Duluth, MN. While dredging can help commercial and recreational boating on the Great Lakes, it can also stir up harmful chemicals in the sediment. Photo: Minnesota Sea Grant, via U.S. Environmental Protection Agency.

By Max King

Dredging may be a solution to Great Lakes low water, but it can also lead to contaminated sediments re-merging into the water.

Michigan Gov. Rick Snyder recently signed a bill in March allowing an additional $20.9 million to be spent on dredging this year to help recreational and commercial boaters operate in low water levels.

The most common contaminant in the bottom of the Great Lakes is polychlorinated biphenyls, also known as PCBs, according to the Michigan Department of Natural Resources.

PCBs got into the Great Lakes because of the automobile industries near the lakes, said  Andy Buchsbaum, director of the Great Lakes office for the National Wildlife Federation.

There was a lot of PCB-laced oil used by the automobile industry before was banned, said Buchsbaum.

“There still was this old equipment that had PCB-contaminated oil in it which is leaked into the ground and ultimately found it way into the Great Lakes,”  Buchsbaum said.

When dredging moves contaminated sediments, chemicals are exposed. They can be harmful to wildlife and people who enter the water, said Kim Fish, assistant chief for the Water Resources Division at the Michigan Department of Environmental Quality.

“In areas where we know we have contamination that is impacting wildlife and water quality, removal of that sediment is usually a good thing overall,” said Fish. “However, (the Department of Environmental Quality) needs to consider where (they are) going to place that contaminated material and make sure (they) are not spreading the contamination.”

Humans who eat fish contaminated with PCBs and arsenic are at a high risk of cancer and other organ damage, but the largest effect these chemicals have is on reproductive health, said Buchsbaum.

“(The chemicals) can impair the development of the fetus in pregnant women who eat contaminated fish,” said Buchsbaum.

Dredging exposes older sediment that is more contaminated than the sediment on top of it, Fish said. Those older sediments were contaminated prior to 1972 when there were little or no regulations on what could be discharged into the lakes.

PCBs affect fish as well when stirred up from dredging, said Joe Bohr, an aquatic biology specialist with the resource agency.

Carp and channel catfish tend to accumulate the highest amounts of PCBs, said Bohr.

“With carp they live on the bottom and they stir up the sediments – similar with catfish,” he said. “Both of them tend to be fatty and these contaminants accumulate in the fat.”

Bohr said top predator fishes are at risk too when eating carp and channel catfish.

Lakes Erie, Ontario and Superior will also reach all-time low water levels resulting in the call for more dredging, Fish said.

“This has been a several year trend of lake levels declining. Primarily we are not getting a lot of ice cover in the winter on any of the lakes which allows evaporation to occur all winter long,” said Fish.

Fish said another reason the water levels are low is because snowfall has declined in northern areas of Michigan and parts of Canada. Snowfall maintains water levels when melted, or when snow goes directly into the lake.

At the federal level, an additional $4 million will be provided to fund dredging this year compared to last year , said Michael O’Bryan, chief of engineering and technical services at the U.S. Army Corps of Engineers in the Detroit district.

“Our needs are out there for more money…there is a significant increase in need for dredging funds in the Great Lakes area,” said O’Bryan.

O’Bryan said the U.S. Army Corps of Engineers in the Great Lakes region needs about $40 million each year to keep up with dredging needs for commercial vessels.

8 thoughts on “Dredging can churn up historical contaminants

  1. If you live in S.W. Michigan in a port community, whether your port is commercial or not, you realize just how important access into and out of Lake Michigan is. Our local economies depend on the commercial trade and tourism. Michigan supports the Port Initiative which calls for our ports and waterways to be the gateways to our communities (front doors). Dredging makes keeping our gateways open and economic stability possible.

    Lets quit using politics as a scapegoat for decision-making in Lansing. The reality is that between evaporation, a lack of precipitation and glacial upwelling of the Great Lakes basin, we have less water to safely navigate the Great Lakes, channels and tributaries. Perhaps exposing the lower lying sediments will give us an opportunity to clean up the contaminants.

  2. Doesn’t removal take out more than is stirs up? And Salmon are right behind Carp and Catfish for PCB retention rounding off the top 3 worst. There was an article here how salmon are transporting and dumping PCB in rivers with no other source for PCB. There’s other studies as well.

  3. Michigan Gov. Rick Snyder recently signed SB233 to help his politically corrupt Republican cohorts steal more dredging money from the NRTF for his marina campaign contributors. He also knows that by diverting the NRTF money there will be less competition for his lakefront developers by having less money for the minorities and public access sites in southern Michigan.

  4. I didn’t grow up in Port Huron…so I guess that multiple posters can sign up using the same name. That might be confusing…but at least “Harold” made a decent post.

  5. I grew up in Port Huron and would see dredgeing being done periodically. I witnessed it being done mainly on the Black River, from the mouth where it emptied into the St. Clair river, westward into the river. This was done to keep the shipping lanes open for the big freighters that would come into the river to deliever supplies to Mueller Brass and other industries along the river. It probably aided the pleasure crafts as well as it was a stopover for the Chicago to Mackinac boat race. I would also see dredgeing being done in the St Clair river. I would occasionally get down by Harsens Island and see dredging in the narrow shipping lane. It use to be very good fishing in the St Clair river, but in the late sixties and early seventies warnings were issued about PCB’s and other contaminates, being found in the fish. Some of these were found to come from the oil refineries on the Canadian shore line. Though the water levels are at an all time low, and dredging is probably necessary to aid the shipping lanes, I can be thankful for the regulations that we have. At least I don’t see contaminate slicks floating on the surface of the water when i visit. The waters are looking much cleaner than they were, But the scope of pollution from both the U.S. and Canadien sides are still being felt today.

  6. I live in Grand Bend, On. Yesterday, was the worst day for sighting more and more dead fish everywhere in the Channel. They don’t bite hooks. They are too sick. They are all hemoraging/ dying.

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