Commissioners called the meeting after learning that contaminated sediment had washed downstream in greater volumes than originally predicted following the March dam-breaching that restored the free flow of the Clark Fork and Blackfoot rivers at their confluence and that is part of the Superfund cleanup of old mine tailings in the bottom of Milltown Reservoir.
The concentration of mining contaminants in sediment along the river exceeded the U.S. Environmental Protection Agency's worst-case scenario, according to researchers with the University of Montana, U.S. Geological Survey and PPL Montana.
Wells, aquatic life and water quality along the Clark Fork are constantly monitored, and federal officials have tested sediment at recreational points between Milltown and Thompson Falls in response to community concerns.
Peter Nielsen, environmental health supervisor for the Missoula City-County Health Department, solicited calls this week from concerned folks wanting to know if their dogs could swim in the river - or if it was safe to use it to irrigate their crops.
Though recently collected data is not yet available, on Friday the Montana Department of Environmental Quality released results of sediment samples taken from a beach 1.5 miles downstream from Milltown in August, showing arsenic levels well below all recreational-risk standards.
Only once did arsenic in the water exceed the drinking-level standard, Forba said. It occurred the day after the dam breaching and lasted less than 48 hours.
As Nielsen explained Friday, the water is cleaner than it has been in years. Arsenic levels are “not as high as in some previous events,” such as during the 1996 ice scour. “It was enormously worse then.”
Plus, higher-than-normal river runoff this spring flushed out high concentrations of sediments and metals. The load is diluted as it moves downstream, as the Clark Fork picks up the flows of its many tributaries.
Commissioner Jean Curtiss was satisfied with the discussion and came away confident there is no public health threat.
Prior to the 2009 spring runoff, Forba promised to work toward “best management practices” to eliminate excess sediment and mining pollution from flowing downriver. That may include stabilizing the banks to eliminate erosion, if such work is affordable and effective.
“We don't know what's practical yet,” Forba said Friday.
Prior to high flow in 2010, the federal government will turn the project over to the state to begin the restoration phase. At that point, all monitoring of sediment dispersal downstream will fall to the state.
Meanwhile, Missoula County is making progress on a pedestrian walking bridge across the Blackfoot River. Weather caused some delay in the project, but workers finished painting it this week. Both the pedestrian and Highway 200 bridges are scheduled for completion by November or December.
A public meeting to update citizens on the Milltown Reservoir Superfund cleanup is scheduled for Tuesday, Oct. 14, in Bonner. EPA officials will be on the bluff south of the Clark Fork overlooking the project from 4-5:30 p.m. to answer questions and point out the work to date. Then at 6:30 p.m., the meeting will reconvene at the Bonner Elementary School gymnasium. It will last until 8:30 p.m. The public is invited to attend.
Shortly after that will come another historic benchmark in the Milltown Dam removal project. Removal of the spillway - the last remaining portion of the dam - is slated to disappear completely by the end of October. Workers are now removing portions of the spillway; eventually, the river will be allowed to take its natural course through that channel.
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