The Wisconsin Department of Natural Resources announced last Friday that it had forwarded the case of a sand mine which spilled fine sediments into the St. Croix River to the state’s attorney general for prosecution.

A containment berm constructed at the mine near Grantsburg to hold water in a settling pond is believed to have burst in April, causing soupy water to flow down a stream, through a wetland, and into the river just below the Highway 70 bridge. The pollution continued for five days until a hiker noticed it and notified authorities.

The DNR alleges the company violated the law in three ways: discharging water from the mine site without a permit, failing to maintain the containment berm which failed, and not notifying the DNR when it built the new settling pond which leaked into the river.

The Star Tribune reports:

For five days, massive amounts of ultra-fine sand and water flowed from a pond through an inadequate berm that was formed to contain it and into an environmentally sensitive area that included a wetland, creek and the federally protected St. Croix River. A hiker discovered the cream-colored spill as it flowed through the creek into the river.

Company officials did not immediately return phone calls Monday. But the Wisconsin DNR said the operators are working to fix the problem and, earlier, a company spokesperson said the company regretted the incident.

Dix said an investigation into the damage is underway. But a sand spill of that size could destroy a wetland and smother fragile fish spawning grounds and mussel beds in the river, environmental officials said.

“They used on-site soils that were too fine to maintain a tight seal” in the berm, Dix said.

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Department of Natural Resources spokeswoman Deb Dix told Minnesota Public Radio News, “They did not construct properly, were not out there on a daily basis to watch what’s going on, and with their permit conditions they should have an understanding of what they need to do so that we don’t need to be out there every day.”

Mussels and fish

One of the primary concerns from the incident is its possible impact on rare mussels that live in the St. Croix River, as well as on fish.

The Minnesota Department of Natural Resources provided the map below from its rare species database. It shows where surveys have found one of several aquatic species that are either rare, endangered, or of special concern.

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 a site where up to seven different species have been found. Mussels include:

• Elliptio dilatata (spike) – Special Concern
• Ligumia recta (black sandshell) – Special Concern
• Cyclonaias tuberculata (purple wartyback) – Threatened
• Actinonaias ligamentina (mucket) – Threatened
• Cumberlandia monodonta (spectacle case) – Listed as Endangered in Wisconsin
• Lasmigona costata (fluted shell) – Special Concern
• Pleurobema coccineum (round pigtoe) – Threatened
• Obovaria olivaria (hickory nut) – Special concern
• Alasmidonta marginata (elktoe) – Threatened

Potential penalties

In a letter to the mining companies, the DNR described several violations of Wisconsin laws.

The letter mentions two Wisconsin statutes, one of which carries maximum fines of $5,000 per day of violation, another which would mean fines of at most $10,000 per day. Both have minimum fines of just $10 per day.

Ultimately, the maximum fine possible for this incident is apparently $50,000. One of the statutes also has the potential for up to six months of jail time.

There has not been any news about possible federal charges for harming the federally-protected Wild & Scenic River.