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Superfund Operable Units in the greater Butte area. Map from the EPA Record of Decision (ROD) for the Butte/Silver Bow Creek Superfund Site (2006).

What is an ‘Operable Unit’?

An operable unit is a subsection of a larger EPA Federal Superfund site. There are four Operable Units (OUs) in the Butte mining district.

Superfund Operable Units in the greater Butte area. Map from the EPA Record of Decision (ROD) for the Butte/Silver Bow Creek Superfund Site (2006).
Superfund Operable Units in the greater Butte area. Map from the EPA Record of Decision (ROD) for the Butte/Silver Bow Creek Superfund Site (2006). Click on the image to view a larger version.
  •  The Butte Mine Flooding Operable Unit, which includes the Berkeley Pit, the hydraulically-connected underground mine workings associated with the historic East Camp and West Camp tunnel systems, associated bedrock, and alluvial aquifers. The area covers approximately 23 square miles.
  • Butte Priority Soils is a five square mile area that includes the town of Walkerville, along with the part of the Butte Hill that is north of Silver Bow Creek, west of the Berkeley Pit, and east of Big Butte. It also includes a section of land extending south from Silver Bow Creek to Timber Butte. This Operable Unit includes residential yards, mine dumps, contaminated railroad beds, and stormwater drainages on the Butte Hill and in Walkerville.
  • Silver Bow Creek/Streamside Tailings Operable Unit, which follows Silver Bow Creek from just below the historic Colorado Tailings deposit in Butte and 25 miles downstream to the Warm Springs Ponds. The area includes Silver Bow Creek itself, as well as the adjacent mining wastes deposited along the creek bank and nearby floodplain, and railroad embankments adjacent to the stream that contain mining wastes.
  • West Side Soils Operable Unit includes lands that fall outside of the Butte Priority Soils OU. There are approximately 1,500 mine waste dumps located north and west of Butte. The dumps have not been sampled. A schedule for investigating this OU and selecting a remedy has not yet been set.

There are numerous additional operable units in the greater Clark Fork River Superfund site, which stretches from Butte and 120 miles downstream to the Milltown Dam near Missoula.

The Butte/Silver Bow Creek Superfund Site and separate Operable Units, in the context of the greater western Montana environment that was impacted by historic mining and smelting damages. Cleanup is ongoing across the basin. Map from the EPA Five Year Review of the Butte/Silver Bow Creek Superfund Site, Part 6: Butte Priority Soils Operable Unit, Figures.
The Butte/Silver Bow Creek Superfund Site and separate Operable Units, in the context of the greater western Montana environment that was impacted by historic mining and smelting damages. Cleanup is ongoing across the basin. Map from the EPA Five Year Review of the Butte/Silver Bow Creek Superfund Site, Part 6: Butte Priority Soils Operable Unit, Figures. Click on the image to view a larger version.

For more information on non-Berkeley Pit Superfund sites in Butte and the Clark Fork Basin on western Montana, visit the Citizens Technical Environmental Committee (Butte CTEC) website, or the Clark Fork Watershed Education Program (CFWEP) website.

Controlled groundwater areas for Butte Superfund sites, including Superfund Operable Unit borders and monitoring points, from the 2011 EPA Five Year Review on Butte/Silver Bow Creek.

Priority Soils: The Other Superfund cleanup project in the Butte area

Controlled groundwater areas for Butte Superfund sites, including Superfund Operable Unit borders and monitoring points, from the 2011 EPA Five Year Review on Butte/Silver Bow Creek.
Controlled groundwater areas for Butte Superfund sites, including Superfund Operable Unit borders and monitoring points, from the 2011 EPA Five Year Review on Butte/Silver Bow Creek. Click on the image to view a larger version.

When the Horseshoe Bend Water Treatment Plant starts operating later this year, the contaminated waters from the Berkeley Pit and underground mines should be managed safely for years to come. In the meantime, another cleanup project – called the Butte Priority Soils Operable Unit – is just now reaching its critical decision point (i.e., the Record of Decision, scheduled by the end of 2003). Over the next several months, there will be a series of public meetings about this project, and the Committee would like to share information to help citizens understand the issues and encourage participation in the decision-making process.

Where is the Butte Priority Soils cleanup site?

Generally, the project includes the residential yards and mine dumps on the Butte Hill and in Walkerville, and the water drainages weaving down the Hill to Silver Bow Creek. The site is about five square miles and includes most of the urban area from Walkerville on the north to Silver Bow Creek on the south, along with the Clark Tailings below Timber Butte.
It’s also important to understand what the Priority Soils does NOT include. It’s separate from the Berkeley Pit and underground mine flooding project, which, as we’ve reported in PITWATCH for several years, is the responsibility of Arco and Montana Resources. The Priority Soils is also separate from the Montana Pole cleanup and the Streamside Tailings project along Silver Bow Creek, both of which are ongoing and the responsibility of Montana Department of Environmental Quality. In the big picture, all these cleanup activities will have to fit together, but for now, Priority Soils stands alone.

What is the cleanup task?

The job is two-fold:

  1. to eliminate direct contact with mine waste on the Hill, thus protecting human health; and
  2. to prevent the heavy metals in those mine waste materials from getting into storm water and groundwater and finding their way to Silver Bow Creek, thereby protecting life in the stream and the DEQ’s $85 million creek cleanup project.

Is some work already complete?

Yes. In fact, a substantial amount of the cleanup of Priority Soils has occurred – about $50 million of work by current estimates. Over the past 15 years, several projects have been completed, with the understanding that all this work will be reviewed as part of the final decision. Major projects include: the Alice Pit/Dump (1998); several areas in Walkerville (1988, 1994, 2002); the Missoula Gulch, Buffalo Gulch and Kelley ditches and retention ponds (1997-99); railroad corridors (2001-03); and Lower Area One, including the reconstructed Silver Bow Creek, the Colorado Tailings removal, and the Clark Tailings project (1993-2000).

In all, more than 175 mine dumps covering more than 400 acres have been partially removed and capped, and more than 180 residential yards have been cleaned up (lead soil removals). The caps generally consist of placing 18″ of clean soil materials with organic amendments over the wastes and planting native vegetation to hold the soil in place and minimize erosion. To complement the caps, a system of storm water collection facilities – the new drainage ditches and retention ponds – has been installed to collect water that may still contain heavy metals and prevent those contaminants from reaching Silver Bow Creek.

What Other Areas and Issues Must Be Addressed?

The major cleanups still ahead include the Parrot Tailings near the Civic Center and the Metro Storm Drain corridor, which once was the historic Silver Bow Creek channel that flowed through town, and a large area north of the Kelley Mine, surrounding the Mountain Con Mineyard and the Granite Mountain Memorial.

In addition to cleanups, other issues include deciding what type of water treatment system should be used to ensure groundwater, surface water or storm water leaving the area will not pollute Silver Bow Creek heading west of town. Another big decision will be to determine whether the projects already completed were done satisfactorily and will be permanent, or whether additional work is needed.

Perhaps the most important issue is to determine how the reclaimed areas and water management facilities will perform in the long term and be effectively maintained. As part of the Record of Decision, it will be critical to set the right performance standards for treatment and long-term care, and then determine how much money it will take to get the job done properly.

Is Butte on the hook for the Priority Soils cleanup?

Unlike every other cleanup around Butte, where the citizens have been protected from any Superfund liability, Butte-Silver Bow was named as a Potentially Responsible Party or PRP to conduct the Priority Soils cleanup. In 1990, EPA decided that since the publicly owned storm water system carried wastes off the Hill to the creek, the community was partly liable for the problem.
However, Arco is also a PRP for Priority Soils, and for the most part over the past 15 years, Arco has paid all costs for cleanup work. As part of the upcoming Record of Decision and then a Consent Decree for the Priority Soils project, Butte’s “share” will be determined.

For much more on Butte Priority Soils and other area Superfund projects, visit the Citizens Technical Environmental Committee (Butte CTEC) website.