History

From the discovery of gold on Silver Bow Creek< west of Butte in the 1860s, the Clark Fork River and surrounding ecosystems of western Montana have been heavily impacted by mining and smelting. With the discovery of gold and other valuable minerals in Montana, development quickly followed. By the turn of the 20th century, there were at least a dozen concentrators, smelters and precipitation plants on Silver Bow Creek just below the Butte Hill, where the urban center of the city of Butte was taking shape. Underground mines, marked by the large black headframes still seen today, were scattered throughout the city.

Early Environmental Damages

The intensive mining and smelting underway in Butte and Anaconda had serious environmental consequences for the entire Upper Clark Fork Basin, consequences that have persisted for over 100 years and that will continue to require community attention and management for the foreseeable future. The photo at left, taken around 2000, shows one such impact: mine tailings deposits along Silver Bow Creek, a primary headwater of the Clark Fork River. Tailings are particularly harmful to aquatic life. Ongoing remediation and restoration have greatly improved the health of the creek from Butte to Ramsay; work is underway on the remaining contaminated sections.

The amount of waste rock and tailings was immense. For every shovel of rock mined, a tiny bit of copper or other valuable ore is produced. Butte earned the nickname “Richest Hill on Earth” because of the richest veins on the hill, some of which were reportedly more than 30% copper. As a point of comparison, the ore mined today at the Continental Pit in Butte is roughly 0.25-0.35% copper. On average, the ore mined from the Butte hill over the last century is approximately 10% profitable metals (copper, silver, molybdenum).

The rest becomes waste, either waste piled at the mine site or the waste from processing, also known as tailings. Because of the tailings’ fine-grained nature, they were exported through Silver Bow Creek in the absence of any environmental laws. On the floodplain, when the water spread out, it slowed and the tailings dropped out; water without the tailings was allowed to drain back into the channel. This spread tailings across the Silver Bow Creek floodplain in the Butte valley and downstream to the west and north over a large area. As more tailings were flushed downstream, the floodplain deposits would grow thicker.

The coarse, granitic rock of the Butte ore body contains substantial amounts of pyrite. The Butte geology is a sulfide ore-body, meaning all of the metals found in the rock are sulfide minerals that can produce sulfuric acid as one of the products of their oxidation when exposed to air and water. Exposed minerals (copper, zinc, lead, cadmium, arsenic, etc.) are dissolved when pH is low (acidic), as in sulfuric acid. The dissolved minerals can be very toxic to fish, bugs, plants and other aquatic life in streams, and can potentially contaminate water supplies used by humans, such as groundwater. When pyrite mixes with air and water to produce sulfuric acid, iron is left to settle out, giving areas where this happens an orange rust color – a tell-tale sign of acid mine drainage. Although this process is often called acid mine drainage, it does not necessarily have to be caused by mining. Any time pyrite is exposed, this process can occur, which is why we refer to it as acid rock drainage.

Smelting is the final step in the process where copper concentrate from milling and processing is roasted into pure copper. Airborne byproducts of smelting include arsenic and acidic sulfur fumes. These fumes greatly affected public health; in the worst cases, people experienced bloody noses and vomiting, and sometimes, death. In Butte in the winter months before smelting operations were moved to Anaconda, air inversions would trap smelting pollution in the valley, and Butte death rates were higher than in New York and Chicago.

The fallout from smelting in Butte and, later, Anaconda spread as far north and west as Avon, Montana on the Blackfoot River. These impacts were more intense in the Deer Lodge Valley; Anaconda and its immense smelter sit at the south end of the valley. The northern portion near the town of Deer Lodge has traditionally been more agricultural. When Anaconda smelting was at its peak in the early 20th century, livestock in the valley were dying, and farmers and ranchers could not sell their hay because of high, potentially toxic levels of arsenic. The book Smoke Wars by Donald MacMillan is an excellent resource on this topic. The following information is excerpted from Smoke Wars: In 1902, in its first year of operation, the Anaconda Stack pumped 30 tons (60,000 pounds) of arsenic trioxide and 150 tons (300,000 pounds) of sulfur dioxide in the air each day. The stack was built to a height of 585 feet in order to further spread and dilute pollution in prevailing air currents. It did nothing to reduce the total volume of pollution. The acidic fumes and resulting fallout caused areas of dead vegetation around Anaconda and in the Deer Lodge Valley.

Later Environmental Damages

In Butte in 1955 excavation on what would become the Berkeley Pit<, named from one of several nearby historic underground mines that the Pit would later swallow, began in a transition from underground to open pit mining. The Pit would, in the next decade, swallow Butte neighborhoods like Meaderville, Dublin Gulch, and McQueen. The transition to open pit mining, a highly mechanized form of mining, also meant fewer jobs for the city’s miners. But mining had always been the lifeblood of Butte, and so the community embraced the new mine, and there was little objection to the sacrifice of some of the city’s neighborhoods. While some structures were moved elsewhere, many, like the Holy Savior church, were simply buried. Like the underground mines, the Pit led to unforeseen environmental consequences. Steep, continuous declines in copper prices in the 1970s led to the eventual shut down of Berkeley operations in 1982. Throughout the history of mining in Butte, pumps were used to de-water the underground mines and, later, the Berkeley Pit. On April 23, 1982, ARCO (now BP-ARCO), the owners of the former Anaconda Company holdings, announced that they were suspending their Butte operations. Along with the announcement, the underground pumps in the Kelley Mine were shut down. The result: the underground mines and the Berkeley Pit began to fill with acidic water. Over the active lifespan of the Berkeley, approximately 320 million tons of ore and over 700 million tons of waste rock were mined from the Pit. Put another way, “The Richest Hill on Earth” produced enough copper to pave a four-lane highway four inches thick from Butte to Salt Lake City and 30 miles beyond. Today, the Pit is managed as a federal Superfund site. Plans are in place to monitor water levels to ensure that contamination caused by the Pit does not spread. For much more on Berkeley Pit history and ongoing management, visit the www.pitwatch.org website.

Superfund & The Beginning of Restoration

In 1980, the U.S. Congress passed the Comprehensive Environmental Response, Compensation, and Liability Act, also known as CERCLA, or, more commonly, Superfund. Combined with the Clean Air Act of 1970 and the Clean Water Act of 1972, Superfund provided the impetus for the beginning of cleanup in the Clark Fork and in Butte. But actual on-the-ground remediation and restoration were still a decade or two away.

Starting in the mid-1980s, sites around the basic were gradually added to the Superfund National Priorities List. The EPA began to negotiate the details of remediation with the State of Montana, local communities, and the Potentially Responsible Parties (PRPs), the formal term for the business entities liable for cleanup costs. In the case of the Clark Fork, BP-ARCO, who purchased the old Anaconda Company in 1977, is the main PRP, although there are others.

Concurrently, the State of Montana filed a lawsuit against ARCO to cover costs for restoration, going beyond EPA-mandated reclamation. A portion of the lawsuit was settled in 1998, and $85 million was allocated for the restoration of Silver Bow Creek. Settlements soon followed for other sites, such as the Milltown Dam, although settlements for other sites in the basin are still being negotiated.

For more information on western Montana Superfund sites and ongoing reclamation and restoration, visit the EPA Montana Superfund page, the Montana Department of Environmental Quality Clark Fork River site, and the Montana Department of Environmental Quality Silver Bow Creek site.