I visited the St. Croix Watershed Research Station last week — a Science Museum facility near Marine on St. Croix which hosts 20 or so scientists studying how land use affects rivers around the world.


At the entrance to the main building is a display of the couple dozen kinds of mussels that were once found in the Minnesota River. The Minnesota used to be home to more species of mussels than the St. Croix, although it’s now the St. Croix that is known for mussels, including some of which are rare and endangered.

The Minnesota River flows through primarily agricultural land, and it is nearly devoid of mussels now, largely due to excessive sediment. Some of the species of mussels displayed on the research station’s wall are extinct, others have disappeared from the river but can still be found in other rivers.

The health of the St. Croix’s mussels has been on many people’s minds recently because of the incident in April when a containment berm burst at a sand mine along the river near Grantsburg, WI. The mine spilled fine sediment into the river for five days before a hiker noticed it and alerted authorities. (The ultra-fine sand mined at the site is used in hydraulic fracturing, or “fracking.”)

What’s the harm of a little more sand?

The impacts to the river from the sand mine spill are still being analyzed, but this is not just a matter of a little more sand in the river. The Wisconsin DNR has acknowledged that the type of ultra-fine sand which got into the river is not “native” to the river.

Photo of contaminated stream taken by hiker who reported the issue.

Suspended in the creek which flowed from the mine to the river, the water gave the appearance of “coffee with a lot of cream.”

That is bad news for the St. Croix’s native mussels. These highly-specialized creatures depend on clean, fast-moving water and firm river bottoms to survive. The U.S. Fish and Wildlife Service reports that as little as a quarter-inch of sediment covering a stream bottom can kill 90 percent of the mussels in an area.

What mussels are there and why should I care?

The map below is pulled from the Minnesota DNR’s rare species inventory database, showing where rare mussels and fish have been found in the vicinity of the Grantsburg sand mine incident. The stream carrying the sediments from the mine enters the river just below the Highway 70 bridge.

The blue dots on the map represent vertebrae species, such as fish, which could include gilt darter, southern brook lamprey, and lake sturgeon.

The orange dots are survey sites where mussels have been found — each dot represents an inventory site where up to seven different species have been found. Mussels include:

Note: All species of mussels are protected by law, and it is illegal to take live mussels or even dead mussel shells from the St. Croix River.

Endangered Higgins Eye Mussels (USFWS photo)

Mussels are the proverbial canary in the coal mine for healthy rivers. They need specific habitat, certain fish species present which they depend on for reproducing, and clean water.

The U.S. Fish and Wildlife Service says the 38 mussel species that live in the St. Croix and Namekagon Rivers put it “among the world’s greatest mussel watersheds.”

But it’s just one incident, how big of a deal is that really?

Tiller Corporation, the Maple Grove, MN-based mining company behind the Grantsburg mine, is currently trying to get approval for another mine next to the river — this one a gravel mine downstream in Scandia.

Local residents have been fighting that mine for a couple years, both because of its location, proximity to the river, and the heavy truck traffic that will transport material from the mine and through the small community.

Photo taken on property adjacent to Tiller/Zavoral proposed mine site

The Scandia mine proposal is nearing the end of its environmental review. When the draft Environmental Impact Statement was released in April, local writer Laurie Allman published an in-depth article about it on St. Croix 360. She listed many concerns about the proposal and the adequacy of the environmental review, and then poetically described what is at stake:

Along most of its perimeter, the mine would abut land held in scenic easements by the St. Croix Scenic Riverway: the National Park we are privileged to enjoy and serve as citizen stewards. It is, without doubt, one of the most lovely, most vulnerable places along the St. Croix: a place characterized by the sounds of bird song, wind moving through the needles of towering white pines, and the trickle of spring water bound for the river. Continue reading …

The city’s plan does not currently allow mining at the location due to its scenic and natural character, but the mining company is seeking a variance. In comments on the draft EIS (PDF), the St. Croix National Scenic Riverway declared its opposition to the mine being permitted, specifically referencing the Grantsburg mine accident:

Soils at the proposed mine site are sandy and the area immediately to the east of the site down to the St. Croix River has very steep slopes and bluffs that are at a high risk of erosion. Portions of the proposed mine site discharge to three different creeks that run down the steep slopes to the St. Croix River. The DEIS correctly acknowledges that the potential for erosion exists after the start of construction when soils are exposed for overburden removal or other activity …

… The NPS, Wisconsin Department of Natural Resources (WDNR), and Burnett County have been involved in responding to a significant sediment discharge to the St. Croix River from Soderbeck Pit (frac sand mine) near Grantsburg, Wisconsin, that occurred in April 2012. Because the Riverway runs through the City of Scandia and the City has zoning authority that can help protect the Riverway, the NPS believes we have an obligation to inform you of this event. Soderbeck Pit is also operated by Tiller and was to be internally drained … Given the vulnerability of the sandy soils and steep slopes at Zavoral site, the potential for a similar sedimentation event exists, brought about by rainfall rather than wash water.

The Grantsburg mine — currently the only of its kind along the St. Croix — had been operating since just last July. In less than a year, the mining company built a containment berm out of the wrong material, didn’t monitor it, and didn’t notify the DNR when it failed.

So they will fix the problem and pay the price, right?

A settling pond at the Grantsburg mine, photo taken before the containment berm failed.

By all accounts, the companies involved have been very cooperative so far. The DNR just sent the case to the Wisconsin attorney general for prosecution. By my calculation, they could face total fines of up to $50,000. Perhaps a big enough fine will be incentive enough to mend their ways, but the Wisconsin DNR’s recent history suggests they won’t be punished severely.

Governor Scott Walker has made loosening environmental protections one of his top priorities. Last month, the Milwaukee Journal-Sentinel reported that inspections by the DNR had declined significantly from previous years. In one notorious incident, one of Walker’s appointees gave a slap on the wrist to a company which was illegally treating farm fields with human waste at three times the legal limit — bad enough to contaminate nearby drinking water wells.

The Grantsburg mine? It hadn’t been inspected since last fall.

Thinking downstream

Do unto those downstream as you would have those upstream do unto you.” – Wendell Berry (via Dan McGuiness)

I have canoed the stretch of the St. Croix around Grantsburg several times. We’ve gotten out and swam in the little rapids below the Highway 70 bridge where the contaminated stream flowed into the river.

The river is a paradise for me and a lot of people. I can’t wait to share it with my new daughter. The silence, the sandbars, the fish. And the mussels. I can already see the hot summer day several years from now when she will canoe, swim and fish it with us.

In April, a hiker saw a muddy stream flowing into the St. Croix River and said, “That isn’t right.” The only question which remains is if his government will agree.

The St. Croix downstream of Grantsburg

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