Tuesday, May 25, 2010

Bulltrout, The Blackfoot River & Milltown

While the last sediments contaminated by historic mine waste were shipped by rail away from the former Milltown Dam site at the confluence of the Clark Fork and Blackfoot Rivers near the end of 2009, much work remains to be done at the site. There are still roughly 4 million cubic yards of mining contaminated sediments left behind at the site. These additional contaminants were left because the removal of the dam and saturate sediments left them high and dry, where likelihood of them ever becoming entrained in the river or contaminating the groundwater is slim to nothing.

An April 11 article in The Missoulian described the concerns of some local residents regarding the impact on native bull trout from work at the site. Concerns for bull trout stem from work on the piers that support the Interstate 90 overpass over the Blackfoot, just before it joins with the Clark Fork. The Clark Fork River is currently diverted into a side channel running near I-90 while crews continue reclamation and restoration of the natural stream channel. This situation has caused the Blackfoot, as it flows under I-90, to narrow, and water velocity speeds up as a result. Some Bonner residents are concerned that this will make it difficult for bull trout to navigate.

Above: The diverted Clark Fork River now flows through an artificial channel near I-90 while crews continue to restore the historic floodplain and river channel.

Bull trout were listed as a threatened species by the U.S. Fish and Wildlife Service in 1998. The bulls are a sensitive species that do not tolerate high sediment levels in their spawning streams. Many Upper Clark Fork tributaries are considered spawning streams for bulls. The Fish and Wildlife Service is currently considering a proposal to increase the amount of land considered critical habitat for bull trout, noting that “Bull trout depend on cold, clear water and are excellent indicators of water quality. Protecting and restoring their habitat contributes to the water quality of rivers and lakes throughout the Northwest.”

Pat Saffel, Montana Fish, Wildlife and Parks (FWP) fisheries manager for the region, has said that no immediate action is necessary. Fish passage at the overpass is typically only an issue during short periods of high flow. When the water level comes back down, the fish can navigate the narrow, rapid channel. The EPA is currently reviewing the issue, and FWP is monitoring fish populations in the area to better understand the effects of the removal of the Milltown Dam.

Short-term impacts related to the reclamation and restoration of the old reservoir site may harm fish, but the long-term effects of the dam removal are likely to be very beneficial to the fishery, outweighing the short-term negatives. More remedial and redevelopment work remain in the Milltown cleanup project, which is expected to end in 2011. Once all is said and done, the connectivity of the Clark Fork Basin will be greatly improved, giving native fish like the bull and cutthroat trout increased opportunities to find suitable habitat and spawning grounds in the numerous Upper Clark Fork tributary streams and creeks.

No comments: