A 5.6 magnitude earthquake centered near Dillon on July 25, 2005 did not affect the Berkeley Pit. There was no Pit wall sloughing or change in the water levels in the Berkeley Pit, the underground mine shafts, the alluvial aquifer wells, or the majority of the bedrock monitoring wells.
However, two bedrock monitoring wells (A&B) showed changes. Well A showed an initial water level decline of about one (1) foot after the earthquake, and the level stayed lower for a number of days before rising again. Well B, which is located in an area that wasn’t dewatered as extensively by historic mining activities as other portions of the bedrock aquifer had a 9-foot drop in water levels in the month following the earthquake. Recently, the water elevation in Well B is rising again.
One possible explanation for the lower water level in these wells is that the earthquake opened up existing fractures in the bedrock surrounding the wells. Water then flowed into these fractures until the bedrock adjacent to them became saturated. When that happened, the water levels began to rise again.
Since the July earthquake, there have been two additional quakes in the region, one of which was centered in the Butte Basin. Both of these other quakes were considerably smaller in magnitude, and no effects were noted in the Berkeley Pit or bedrock monitoring wells.
Tsunamis, volcanoes and earthquakes in recent months have created an increased interest in seismic activity. Many readers have written, called, or stopped by questioning what will happen to the Berkeley Pit if an earthquake occurs in Butte, Montana. To help answer these questions, local experts were asked to explain the likelihood of an earthquake and what effect it would have on the Berkeley Pit.
Probability of an Earthquake in Butte
Mike Stickney, Director of the Earthquake Studies Office at the Montana Bureau of Mines and Geology says that Butte is not likely to suffer a severe earthquake anytime soon. Large earthquakes are certainly possible in western Montana as demonstrated by the 1959 Hebgen Lake earthquake (magnitude 7.3), but are most likely to occur in the more seismically active regions located to the north, east, or southeast of Butte. The state of Montana is unlikely to experience earthquakes larger than the 1959 earthquake because the faults are not large enough to produce earthquakes greater than magnitude 7.5.
Stickney also explained that Butte has been monitored closely for seismic activity over the past 25 years. There has never been any significant seismic activity recorded that suggests the nearby faults to be active enough to cause a large earthquake. Most seismic activity that registers in the Butte area is caused by blasting at the open mine site, and very minor underground subsidence, especially near the old block caving zones under the Kelley Mine.
Effects of an Earthquake
Even assuming a worst-case earthquake scenario, the Berkeley Pit would not overflow. Experts suggest that there would be far more damage to buildings and other structures in Uptown Butte than would be caused by adverse impacts from the waters in the Berkeley Pit.
Studies show that the Yankee Doodle Tailings Pond dam would withstand at least a 6.5 magnitude quake. It can also be assumed from similar studies that such a quake could cause some sloughing on the pit walls, but the resulting movements would not discharge enough rock and materials to cause the water in the pit to overflow.
Sloughing and Landslides
Although earthquakes are not likely to be a problem, landslides and sloughing of the Pit could occur. The majority of the Berkeley Pit walls are made of “solid” bedrock. However, the southeast wall is composed of “loose”silts, sands and gravels, and this is the area where sloughing is most likely to occur, with or without a major earthquake.
In September 1998, about 1.3 million cubic yards of “loose” alluvium on the southeast wall sloughed into the Pit. This event caused a 3-foot rise in the water level and surface waves greater than 20 feet.
The water rise associated with any pit wall sloughing would ultimately depend on the volume of material that breaks free and displaces the water. But it should be noted there is enough space for more significant events. For example, there is more than 150 feet between the current Pit water level (5,252′ above sea level) and the Critical Water Level (5,410′), and there is another 100′ feet up to the rim of the Pit.
If an earthquake were to occur, the effects of seismic activity at the Berkeley Pit would be the least of Butte’s worries. Since a large earthquake is not likely anytime soon, and because landslides are relatively manageable, the public should not be overly concerned. There will probably continue to be some sloughing on the benches and old roads, but not enough to cause the Pit water to rise more than a few feet.
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:
to eliminate direct contact with mine waste on the Hill, thus protecting human health; and
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.
Two Butte students – Alexandra Antonioli and Kels Phelps – have taken their school science projects to the highest levels of success. After claiming local awards from the Pit Committee, their impressive work has earned national awards and scholarships for their continuing education.
Alexandra, a Butte High senior, has spent most of her educational career working on science fair projects relating to solutions and issues regarding the Berkeley Pit. When she’s not swimming and playing piano, she’s working on her main project titled, “An Investigation of the Remediation of Berkeley Pit Water Using Genetically Modified Extremophilic Yeast”. Although it’s quite complicated, Alexandra’s simplified explanation is the project deals with evaluating microorganisms and their ability to sequester the complex mineral compounds contained within the water. The end result is the potential detoxification of Pit water. For her work, Alexandra has received a full scholarship ($78,000) to Drexel University for microbiology, as well as numerous other honors, including awards from the Navy, the University of Montana and Montana Tech.
Kels, a Butte High freshman, has also concentrated on microbiology and the Berkeley Pit for his science fair project. The project, “Do Microbes Growing in Unique Ecological Niches Contain Compounds with Redeemable Medicinal Value,” was one of 40 finalists (out of 60,000 nominations) in the Discovery Channel Young Scientist Challenge in Washington, D.C. in October 2002. At this national competition, Kels won a special award for leadership, a physics award, and a scholarship to attend an aviation camp in Wisconsin next summer. Kels says his project was looking for a possible medicine from a fungus that grows in the Berkeley Pit. Tested for its ability to fight cancer and five types of infections, it was discovered that this fungus was a possible anti-cancer agent and lethal to Staphylococcus aureus.
Others Butte students are encouraged to develop projects related to mining or the Berkeley Pit for the 2003 Science Fair next spring at Montana Tech.
The Berkeley Pit is one of the most high-profile examples of the adverse impacts of mining. Although the Berkeley Pit Superfund site is currently in a simple monitoring mode, an extensive amount of work is performed locally related to the understanding and remediation of the Pit and similar systems.
Ongoing projects include:
• treatability studies including metals recovery and in-situ treatment
• use of photocatalytic reactions to enhance water treatment
• demonstration of innovative technologies, such as a Biosulfide process for recovery of copper sulfide, zinc sulfide and sodium hydrosulfide products
• vertical and seasonal characterizations of Pit water
• biological surveys
• remediation using algae
• wall-rock interaction with water
• evaluation of organic carbon in the Pit
• use of neural networks to simulate the Pit system.
For more information about these and other projects, contact MaryAnn Harrington-Baker, EPA’s Mine Waste Technology Program at MSE Technology Applications, (406) 494-7240, James Madison, Montana Bureau of Mines and Geology, (406) 496-4619, and Steve Anderson, Montana Tech Mine Waste Technology Program, (406) 496-4409.
The Montana Bureau of Mines and Geology has issued a 15-year report containing water-level data collected from all of the mine flooding monitoring points from 1982 to 1997. The comprehensive document also includes numerous graphs, maps, and historic photographs, plus explanations of the various areas that comprise the Butte Mine Flooding Superfund Site. To request a copy, call 496-4167. In 1999, the Bureau will release a companion report on water quality in these monitoring wells and shafts. Both reports will be updated annually.