Posted on August 13, 2025
Dredging crews returned to Grand Traverse Harbor this summer in a renewed push to protect Buffalo Reef, critical spawning habitat for lake trout and lake whitefish, from migrating stamp sand mining waste that threatens to wipe out up to 33% of these fish populations in Lake Superior.
Buffalo Reef, a 2,200-acre natural cobble feature beneath the waters of Lake Superior off Michigan’s Keweenaw Peninsula, is one of the most important spawning grounds for lake trout and lake whitefish in the Great Lakes. But a century-old industrial legacy, known as “stamp sands,” is threatening to bury the reef and destroy the fishery it supports.
The stamp sands are a waste product from copper ore processing at the Wolverine and Mohawk mines. Beginning in the mid-1800s, miners crushed basalt rock containing copper, extracting only a small fraction of the ore.
Charles Kerfoot, Biological Sciences professor at Michigan Tech University, explains, “The copper was only 1-2% of the rock. So, 97% of what came out were these stamp sands. We know that they discharged 22.7 million metric tons of stamp sands.” Deposited on the shoreline at Gay, Michigan, the black, sand-like waste began drifting south with Lake Superior’s powerful currents.
Source: Buffalo Reef – Final Alternatives Analysis (January 2024)
Underwater photo of migrating stamp sands. Screenshot: Saving Buffalo Reef Video
Mining ceased in 1932, but the migration of the sands never stopped. “It wasn’t until later on that the stamp sands made it all the way down to the Traverse River,” adds Kerfoot. “By the early 80s, the original string beach was covered by stamp sands.” Today, 1,426 acres of shoreline and lake bottom are coated in the waste. Kerfoot and his team estimate that 60% of Buffalo Reef is now unusable for fish spawning.
Traverse Bay (not to be confused with Grand Traverse Bay in the Lower Peninsula) resident Judy Kraska has watched the changes unfold. “When I was little… I remember seeing little black speckles of funny black rocks, and I didn’t know what that was,” she says. “Sadly, the beginning of the invasion just got worse and worse every year.”
Evelyn Ravindran, Natural Resources Director for Keweenaw Bay Indian Community, emphasizes that the reef is ecologically critical. “Buffalo Reef is one of the three big reefs in our home waters,” she says. “They make up the majority of spawning areas for lake trout and whitefish… when the biologists are out there and they’re investigating more… they’re finding that there is a habitat issue. It’s not overfishing.”
Graphic showing the impact of stamp sands. The left has more interstitial spaces for spawning. The right has those spaces filled in by the stamp sands. Source: Buffalo Reef – Final Alternatives Analysis (January 2024)
Studies show that once stamp sands cover more than half the substrate, aquatic life collapses. “When you’re getting out past 40, 50% stamp sand, you’re only picking up 30% of the density of the organisms,” explains Kerfoot. “Past 75, there’s nothing there. There’s just nothing living there.”
The economic and cultural stakes are high. The Keweenaw Bay Indian Community has treaty rights to the fishery and has led preservation efforts.
“The reef is in the catalog of one of the most effective reefs out in the Great Lakes,” says Kerfoot. “Models suggested that 60% of the reef would be covered within 10 years. If nothing were done, about 1.8 million a year would be lost if the Buffalo Reef collapsed, largely to the tribe in terms of commercial revenue, but also to the non-tribal commercial fisheries and to recreational fishing.” He notes that losing the reef would result in losing 33% of the lake trout and whitefish in the lake.
Crews have returned this summer to dredge the Grand Traverse Harbor and mouth of the Traverse River, an interim measure to keep the harbor open and slow the sands’ advance. “First phase is the dredging,” says Kerfoot. “It will save us for a little while, three to five years is the idea… the second phase is probably a combination of dredging and a revetment. And the third part would be to remove the stamp sands from the site.”
The Buffalo Reef Task Force, a coalition of tribal, state, and federal agencies, has endorsed a long-term plan to build a 2,000-foot jetty to intercept migrating sands and an upland facility to store dredged material. Geotechnical work for the jetty was completed last fall, and design is expected within months.
For the Keweenaw Bay Indian Community, the project is part of a deeper responsibility. “We have an older treaty… with creation,” explains Ravindran. “We were given responsibilities [to be] good stewards.” That stewardship is now guiding a broad partnership. “There may not be a perfect solution, but we’ll do the best we can with what we have. We’re willing to put that effort in together to save that reef,” she adds.
“It’s a sadness at what happened, and it’s a responsibility that we need to do something about it as a whole community, as all people,” Ravidran concludes. “You have to take care of the world you live in. You have a responsibility to do that.”
For more information and updates, visit Michigan.gov/BuffaloReef.
