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Dredging mindfully: taking special care to minimize impacts

24

July, 2017
G. Wilkins

 

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Miners in Copper Country Michigan, C. 1905

Copper-ore

Attribution: Brian Stansberry via Wikipedia Commons

Talks are in progress to establish an emergency dredging project that would save the Buffalo Reef in northern Michigan’s Grand Traverse Harbor.

The Michigan Natural Resources Commission led a meeting July 20 in Haughton to discuss the plight of the Buffalo Reef. According to Charles Kerfoot, professor at Michigan Technological University, the reef is the most productive spawning point for trout and whitefish in the area, and responsible for 8 percent of the fish in the Keweenaw Bay. Kerfoot spoke at the meeting about the threat that century-old stamp sand poses to the reef and its inhabitants.

Stamp sand is a type of mining tailings waste, finely-ground rock and mineral of little to no value. This stamp sand comes from the ‘mining era,’ before copper mining ended, well before the Environmental Protection Agency was founded in 1970, and before the modern mining practices of today that manage waste with as little harm to the environment as possible.

During the mining era, copper mining was big.

Stamp mills would crush mined copper ore to extract the copper from within it, dumping the rest as stamp sand. The Mohawk and Wolverine mills in this area of Michigan discharged 22.7 million metric tons of stamp sand onto shores off the coast of a small township called Gay, named after Joseph E. Gay, one of the founders of the Mohawk and Wolverine mining companies.

Today, currents have naturally pushed that stamp sand far from its original pile.

Among other problems, the waste is now threatening the critical fish breeding grounds and damming stream and river outlets, threatening to choke off access to the harbor and compromise beaches.

“We’re aware that there’s a large metal halo around the Keweenaw Peninsula,” said Kerfoot.

The Michigan Department of Natural Resources (DNR) will hold a second meeting Aug. 3 to officially propose the dredging project that would save the Buffalo Reef. Representatives from the U.S. Army Corps of Engineers, the U.S. Environmental Protection Agency, and the Michigan Department of Environmental Quality will be in attendance, among other involved groups. The DNR will discuss the project and gain feedback before putting the project into motion, removing 205,000 cubic feet of stamp sand from around the harbor and reef.

The $300,000 dredging project is a short-term solution. Some of the copper tailings dredged from the area would be placed back at their point of origin near Gay. The rest would depend on how the dredging company can best move the material. Dredging the stamp sand away in this manner would protect the reef for 5-7 years. A previous dredging attempt in 2015 was undone by a single storm due to high lake levels and the height of the tailings pile, which exceeded that of the breakwall designed to separate the two.

A long-term solution would be to create a barrier around the stamp sand pile to prevent erosion. That would protect the area for around 50 years, but it would be expensive. The U.S. Army Corps proposed such a barrier would cost $12.5 million.

Conversely, some companies are trying to determine a use for the stamp sand.

One company, Lesktech Limited, once proposed creating roof shingles with it. Some scientists are researching its ability to grow plants. In any case, the ultimate solution would be to remove the stamp sand completely from the water, but the copper tailings are expensive to move and have low value. Doing so would not be economically viable at the moment.

Today, the mining industry deposits tailings into special reservoirs called tailings ponds that are designed specifically for that purpose and, if part of a larger body of water, are dammed to ensure that the tailings do not escape and affect the environment around them.

  1. Header photo Attribution: JudyDruskovich, via Wikipedia Commons
  2. http://www.mininggazette.com/news/2017/07/stamp-sand%E2%80%88dredge-temp-fix-no-funds-for-permanent-solution/
  3. http://www.mininggazette.com/news/2017/06/stamp-sand-erosion-threatens-lake-coast-locals-urge-state-federal-funding-for-dredging-fix/
  4. https://cfpub.epa.gov/ncer_abstracts/index.cfm/fuseaction/display.highlight/abstract/8754
  5. https://www.sciencedaily.com/releases/2014/03/140305191717.htmhttp://www.miningfacts.org/Environment/How-are-waste-materials-managed-at-mine-sites/
  6. http://www.exploringthenorth.com/ghost/towns.html

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