Clean Production and Toxics

When is a hotspot no longer a hotspot?

With remediation activity completed, the push is on to delist Torch Lake as an Area of Concern. But with millions of tons of sediment still contaminated, delisting this site before these sediments are buried by natural processes may be hasty.

Until a few years ago, whenever the wind came up around Torch Lake in Michigan’s upper peninsula, copper-contaminated sands would whirl up from around its shores. Local residents describe it as looking like a sandstorm in the desert.

For over one hundred years, the towns of Houghton and Hancock, near the shore of Lake Superior, were the centre of a major copper mining, milling, and smelting industry. The contaminated sands are the byproduct of a stamp mill, which separated copper from rock by pounding the ore. From the mid-1800s to 1968, over 2.5 million tons of copper were processed at Torch Lake.

By 1969, this industry had closed down, leaving the hulking remnants of industrial plants that still remain to this day. But, when the industry closed, they left behind a devastated environment around Torch Lake. 200 million tons of copper mill stamp sands were dumped into the lake, taking up about 20 percent of the lake’s volume. In some areas, the contaminated sediments are believed to be seventy feet deep.

These sediments contain copper at levels up to 2,000 parts per million, as well as other heavy metals. Some of the tailings were dredged up and processed to reclaim the copper, after which the wastes were returned to the lake and the shoreline. This made the tailings finer, smothering the lake like a fine-woven blanket. The finer tailings are also more readily taken up by life on the bottom of the lake. This has severely degraded the bottom-dwelling communities that are essential to the Torch Lake food web.

The main activity to clean up the Torch Lake Area of Concern has been to stop the dust storms that swirl around the lake. The aim here is to stop more tailings from blowing into the lake, further contaminating the lake-bottom. Stopping the sand also reduces the risk to those people who would otherwise be breathing in these toxic particles. Between 1998 and 2005, 800 acres of stamp sands around the shores of Torch Lake were covered with a six-inch layer of soil, and vegetation was planted on top.

The dust storms have now ended, but 200 million tons of heavy-metal-contaminated stamp sands still remain in Torch Lake. The governments have decided to leave these sediments alone to gradually be covered over by natural deposits of soil. The U.S. Environmental Protection Agency (EPA) determined that the costs of taking any other action on the sediments would be extremely high and that contaminant levels are within “safe” levels for human health.

By the governments’ determination, all remedial activities in Torch Lake are completed. The issue is now deciding when Torch Lake can be delisted. The U.S. EPA estimates that it will take decades for enough soil to be deposited to sufficiently cover the contamination, bringing back a healthy benthic community. The state of Michigan and some local residents are pushing for delisting of the Torch Lake within the next couple of years, arguing that this is no longer an area of concern.

In two places, Spanish Harbour in Ontario and Presque Isle Bay (Erie) in Pennsylvania, AOCs have been declared to be in a “recovery stage.” This means that all planned remedial actions have been completed, but that it will take time for the system to naturally recover. Michigan, however, does not accept a recovery stage option. It prefers to instead push for immediate delisting.

The issue at Torch Lake is one that is likely to recur in other areas of concern as the push to delist AOCs continues.

It is critical to continue to call sites in which there still are impaired conditions “areas of concern” until they truly are restored. By saying that they are in a “recovery stage” instead of delisted properly conveys to the governments and the community that conditions are not yet restored and that we must keep a vigilant eye on these areas. Extensive monitoring is necessary to ensure that recovery is actually occurring. It also means being open to additional restoration actions if monitoring indicates that recovery is not happening to the extent or as quickly as predicted.

© 2009 Great Lakes News.