Field Notes: Three Hundred Feet High and Rising

When miners quit the Canisteo iron mine in 1985 and pulled the pumps, rain and groundwater flooded in, raising the level 70 feet a year and forming a 5-mile-long lake just north of Bovey, Coleraine, and Taconite. Ten years later the flood had slowed to 2 to 5 feet a year, "but it shows no sign of stopping," says Bob Leibfried, a DNR hydrologist who has studied the Canisteo for two years. "Pit walls are constantly eroding. As a result, there are potential safety hazards."

Indeed, the eroding walls are threatening a nearby railroad track. The DNR predicts that left to its own the pit will fill and overflow in four to nine years, depending on the weather. It will carve a new stream through Bovey, behind the grocery store, across Highway 169, past the Dairy Queen, and into Trout Lake.

In 1995, at the request of local citizens, the DNR Division of Lands and Minerals began measuring water levels in the pit with the intention of engineering an escape route before nature could take its own course. The Canisteo study involved collecting data from 18 groundwater wells around the pit and measuring flow out of Holman Lake and Trout Creek. It revealed three possible receiving waters for the Canisteo Pit drainage: Trout Lake, Holman Lake, and Prairie River.

If the Canisteo water were directed to Trout Lake, the lake level would increase approximately half a foot and could rise higher during extreme storms, flooding residences in low areas. Rainbow smelt, an exotic species now residing in the pit, would enter Trout Lake with unknown effects on the lake’s native fish.

Members of the Trout Lake Association, such as Darrel Hecimovich, would welcome the Canisteo’s pure water. "For years the mining companies dumped tailings and two cities discharged sewage into Trout Lake, so that water would help refresh our lake and clean it up," Hecimovich says. "We’d like to get back a little of what was taken away."

Holman Lake, east of Bovey, could receive the Canisteo overflow, rising half a foot on average. No homes would be affected. Raising the pit level high enough to flow into Holman Lake would result in considerable erosion of pit walls, however. Beaver would also need to be controlled in the upstream wetlands and Holman Creek to assure efficient discharge of the water.

The Prairie River plan would direct the water through a wetland, into the abandoned West Hill and Lind-Greenway mine pits, and then into the river, which has much more water than the runoff from the Canisteo pit and could easily accommodate the additional flow, according to flow records for the Prairie River. Unfortunately, routing the water to the Prairie River would raise the pit water level high enough to make erosion a real concern, Leibfried says. In addition, the West Hill pit still contains enough natural iron ore to spur talk of dewatering the pit to resume mining.

"We’ve got to look at the pluses and minuses of each of these receiving waters and determine which one is best," says Sam Dickinson, coordinator of the Western Mesabi Mine Planning Board. A task force, including the board, the Trout Lake Association, the DNR, and other government groups, is dealing with the situation. Lessons learned from the Canisteo study may be applied to other mine abandonment plans and potential flooding problems in the area. Says Dickinson, "The way it’s handled here is going to be very important, not only to the local area but also to the Range as a whole."

—Margaret A. Haapoja