That’s when Mohawk Mining Co. shuttered its stamp mill in the town of Gay — a speck in Michigan’s far western Upper Peninsula. The company left as much as 23 million metric tons of crushed rock along the shore — enough to fill more than 1.4 million commercial dump trucks.

The whittled down pile now weighs about 2.4 million metric tons. The rest of the dark, course sands have seeped into the lake, bringing along metals like arsenic and copper. Drifting southward, the waste is damming stream outlets, covering wetlands and jeopardizing Buffalo Reef.

Buffalo Reef stretches 2,200 acres beneath the bay and supports a roughly $5 million-a-year recreational and commercial fishery that’s culturally and economically vital for the Keweenaw Bay Indian Community and other Ojibwe tribes.

The reef sustains nearly a quarter of tribal commercial harvests of lake trout (12,500 pounds a year) and whitefish (about 125,000 pounds a year), according to the Great Lakes Indian Fish and Wildlife Commission. Losing those fish would likely harm genetic diversity across the bay, perhaps making surviving fish more prone to diseases, researchers say.

The waste already covers more than 35 percent of the reef and could blanket up to 60 percent by 2025 without major intervention, according to the Michigan Department of Natural Resources.

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So what to do? First, officials are working to remove the sands traveling from Gay using heavy dredging machinery.

The U.S. Army Corps of Engineers last year announced a $2.7 million contract with a company that’s to clear about 27,500 cubic yards of mining waste from Grand Traverse Harbor, and an extra 80,000 cubic yards from a fast-filling trough north of Buffalo Reef.

Slated for this summer, that work would only remove a small fraction of the sands, and would protecting Buffalo Reef for little more than two years.

Meanwhile, questions loom about where to put what’s pumped from the lake. For now, the Army Corps plans to put it right back where it came from — the pile at Gay.

That’s where the task force’s analysis comes in, and the ideas range widely.

They include trying to find a “beneficial use” for the stamp sands.

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Suggestions over the years have ranged from using the sands to manufacture shingles to recovering the trace amounts of leftover copper in it.

“Most of the proposals being contemplated have not made it past the conceptual phase. Developing an end use for this product has proven to be challenging,” the task force wrote, citing logistical difficulties of permitting and transportation and other logistics. What’s more, demand for any developed materials could plummet over time.

The Michigan Legislature last year approved $3 million for projects related to saving Buffalo Reef, and the state may put $500,000 of that pot into researching “beneficial use” alongside the Army Corps of Engineers, according to the DNR.