September 23, 2008

Confluence September 21, 2008
Confluence Sept. 21, 2008

The Missoulian and the Clark Fork Valley Press featured articles on concerns residents in Thompson Falls area and officials of PPL Montana have over elevated levels of arsenic and metals in the Clark Fork River reported by University of Montana researchers. Based on data collected in early May, after the breach but before peak run-off, UM researchers found levels of arsenic and metals higher than EPA and state officials had predicted in their modeling. The higher and longer flows this spring scoured sediments above Milltown remediation area.

PPL Montana, owner of the dam at Thompson Falls, has called for revised modeling and additional measures by the state to reduce scour during restoration work. EPA and state officials, however, say concerns are overblown and based on early, preliminary data. “Those professors have not produced any kind of report,” said DEQ Milltown project manager Keith Large. “They’re looking at fine-grain sediments instead of all sediments. Those university professors need to step forward with written data instead of just showing bits and pieces. Once you look at the big picture and consider all the data, it’s a much different picture then. We’re not seeing any big problem.”

EPA community liaison, Diana Hammer, in a note that accompanied a biweekly update (PDF) from last week, said:

We are monitoring the surface water and groundwater downstream of the Milltown Reservoir project area after the dam breach on March 28, 2008. To date, the only time the arsenic level was measured higher than the drinking water standard was on March 29, 2008 — the day after the dam was breached.

Since then the arsenic levels in the Clark Fork River have been below drinking water standards. At these low levels, EPA sees no cause for human health or environmental concerns. Domestic wells, aquatic life, surface and groundwater monitoring results show no reason for concern.

We have also been sampling sediments at recreational access areas along the Clark Fork River downstream of the former dam. The highest result we have seen from these sediment samples is 21.5 ppm arsenic. This is well below any level that would pose a risk to human health or the environment. Therefore, we see no reason to tell people not to swim or eat fish caught in the river.

We will continue to monitor. We will continue to report results as they come in. We will discuss all of this at the public meetings in October in Bonner (10/14) and Thompson Falls (10/15).

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