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The Milltown Dam

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Clean-Up or Containment?

MISSOULA, Montana- A number of environmental policies were adopted in the final days of the Clinton Administration. Some of the policies dealt specifically with human health. One such policy limited the amount of acceptable levels of arsenic in drinking water. Last month the Bush Administration embraced the revised standards set by the Clinton Administration. This decision lowered the legally allowed amount of arsenic from 50 parts per billion (ppb) to 10 ppb. Amazingly, the aquifer surrounding Missoula’s Milltown Dam and Reservoir has found arsenic in levels of up to 1200 ppb. If not re-mediated, this pollution, according to Peter Nielsen of the Missoula City-County Health Department (MCCHD), may last hundreds of thousands of years. And it may get worse.

    Christie Todd Whitman, the Administrator of the Environmental Protection Agency (EPA), wrote in a recent letter to Congress that arsenic causes cancer, heart disease, and diabetes. With the new arsenic standards of 10 ppb, the EPA estimates that three Americans per 1,000 will succumb to the detrimental health effects of arsenic-tainted drinking water.  The MCCHD speculates that the Milltown Dam and the arsenic and copper-tainted mining pollution it accumulated has helped reduce the Clark Fork trout population to only 20% of its potential. No statistics apparently exist estimating death/disease in humans directly related to the Milltown Dam’s toxic mining pollution buildup.

    The national standard allowing arsenic levels at 10 ppb amounts to about  one teaspoon of arsenic per 1.3 million gallons of water. The Milltown Dam holds back an estimated 2100 tons of arsenic, and releases up to 7,300 pounds per year to the Missoula aquifer. Copper concentrations of up to 770 ppb have been measured, contrasted with the legal copper quality standard of 18 ppb. Copper kills aquatic life. Floods, ice jams, earthquakes, or vandalism can “cause significant damage or failure of the dam with potentially catastrophic impacts to the river and downstream drinking water supplies” according to the MCCHD. Sanders County, the Clark Fork River, and Lake Pend Oreille are downstream from the Milltown Dam.

    The Milltown Dam is located five miles upstream of Missoula at the confluence of the Blackfoot and Clark Fork Rivers. It is a Superfund site, contaminated with 2 million yards of tailings from mining operations in Butte and Anaconda. It is a decaying facility that was built in 1906 using a Timber Crib structure periodically encased with now deteriorating concrete. It is built on the Ninemile/Clark Fork Earthquake Fault. The north end was not built on bedrock, but on the proverbial “weak and shifting sand” subject to erosion in a large flood. In the opinion of some it has become the poster child for a dam from hell.  The MCCHD would like to help send it there, after first removing the polluted sediments it barely restrains.

    The MCCHD, in conjunction with the EPA and the Army Corps of Engineers, recommends removal of the sediment build-up by dredging, followed by removal of the dam itself.  The agencies advocate environmental dredging as a proven technology used in thousands of projects worldwide, including the Great Lakes, Hudson River and Puget Sound.  They maintain that the downstream impacts are small, and are far less polluting than what occurs when natural events, such as floods, cause the pollution to spill over the dam.

    The MCCHD’s two-part plan proposes sediment cleanup and dam removal first. The second phase would include wetland restoration and recreational development. The estimated cost of $250 million is proposed to be covered by a combination of private, federal, state, and local sources. An estimated $100 million or more will be spent in the local economy on cleanup. The MCCHD predicts good paying jobs associated with the cleanup. And they predict stimulated economic activity following the cleanup in the form of residential, commercial, and recreational development.

    The current owner of the Milltown Dam is British Petroleum Corporation (formerly ARCO).  They are opposed to the dredging and dam removal apparently due to the cleanup costs they would incur. Currently, the dam reports an annual operating loss of $190,000. It has averaged an output of 1.4 MW for the last five years. The lower Clark Fork Dams produce 700 MW. A portable natural gas generator produces 4.3 MW.

    The Milltown Dam provides no flood storage capability. Averaging only eight feet of water in the reservoir, it is a ‘run of the river’ dam. Therefore, what goes in comes out at the same rate. It is, however, an effective barrier to fish migration and spawning.  Its removal is supported by the officials of Missoula County and by the City of Missoula.

    Bruce Hall, of the Bonner Development Group, does not support either the removal of the dam or its sediments. In a September 19th letter to the Sanders County Board of Commissioners, he states that, “The Milltown Dam represents 15% of the Bonner-Milltown tax base.” And he maintains that it has the generating capacity to meet the demands of 3,000 homes or four school districts or the “greater part of the University of Montana demand for power.” Finally, he maintains that the Milltown Reservoir has “special meaning from both historical and recreational purposes.”

    Hall, working in conjunction with the dam’s owner and the Montana Power Company, wish to perpetuate the maintenance and operation of the dam.  They propose holding back the contaminated sediments through installation of a pneumatic crest, which they describe as a rubber dam. They maintain that, “The pneumatic crest will enable the dam operators to control water elevation in the pond during crisis situations, thereby foregoing the release of contaminated sediments.”

    A number of federal and state agencies are involved in the decision making process of this dam’s future and the future of the toxic payload of mining waste it harbors. The MCCHD is concerned that a lack of agency coordination may jeopardize the decision making process.

    For additional information call Peter Nielsen of the MCCHD (406-523-4890), or Bruce Hall, BDG  (406-258-5268.)


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Nancy Lynn Masten

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