Blankenship bank stabilization a short-term fix to a larger problem

In 1964, flood water collapsed the Blankenship bridge. Now, 60 years later, it is at risk again. 

Flathead County in partnership with the Forest Service is seeking to stabilize the northwest bank of the Middle Fork of the Flathead River as the water erodes ever-closer to Blankenship Bridge’s abutment. 

The proposed project, estimated to cost around $1 million from the county’s bridge funds in the general fund and/or the gas tax revenue fund, would include around 200 feet of shoreline owned mostly by the county and partially by Flathead National Forest, though ultimate say on the construction plans will come down to the Forest Service as the overseers of the National Wild and Scenic River. The bank stabilization will incorporate rip rap — boulders of varying sizes, as well as a 20-foot long Douglas fir-type tree, and other large woody debris with root balls. The bank will be replanted with native plants for stabilization and naturalization.

“To just put rip rap, throw rock onto the bank of a river that is considered wild and scenic, that’s the only treatment — you start to cross the line. There’s actually some language in the Wild and Scenic Rivers Act that says rip rap can have a negative effect to the free-flowing nature of a river,” Hungry Horse and Glacier View District Ranger Rob Davies said. Hence the Forest Service’s proposal to work with the county to protect public infrastructure in a way that is hoped to also aid fish habitat, namely cutthroat and bull trout. 

Davies made a preliminary determination in a January 9 scoping letter that the project “may fall within a category of actions listed in the Forest Service National Policy Act that is excluded from documentation in an environmental assessment or environmental impact statement under 36 CFR 220.6(e)(18) for restoring wetlands, streams, riparian areas, or other water bodies by removing, replacing, or modifying water control structures.”

Through the National Environmental Protection Act, the Forest Service is required to conduct an analysis to determine the environmental effects of proposed actions before making decisions. 

“Part of our NEPA process is evaluating the effects from that activity and basically, if there are any extraordinary circumstances, it kicks it into a higher level… it could be an environmental assessment, it could be a very detailed environmental impact statement, and there’s a whole bunch of categories, called categorical exclusions, from doing an environmental assessment. We felt like after we got a feel for what the project’s all about and what’s involved, it’s not going to meet the mark of any extraordinary circumstances,” Davies said.

Though the Forest Service will still conduct a detailed analysis of the project’s potential effects on the free-flowing nature of the river, they see no need for an environmental assessment at this time. The construction itself is not atypical, and has been proven to improve fish populations in isolated habitats. 

“It’s not super uncommon to build bank stabilization to protect public infrastructure on Wild and Scenic Rivers, but it is critical that the public be given the chance to review some more detailed plans and to point out any deficiencies that could be in the project in order to improve it,” Scott Bosse, Northern Rockies Regional Director of American Rivers said. 

The Forest Service’s comment period was officially Jan. 9 through Jan. 31,  with no intention to further scope or gather more information from the public, though Davies has noted that comments will be accepted until a decision is made. That timeline is undetermined, though if the county is able to obtain the seven or so permits needed in time to get started before spring runoff, Davies would like to have a final decision by the end of March. If an environmental assessment is determined to be necessary, there will be more opportunity for public comment on the project. A second construction timeline, if permissions can’t be obtained before runoff, would start later in the summer.

“There are not specific plans that we’ve seen, like diagrams showing what the bank stabilization work would look like and the exact extent of what it would be. That is actually what has us a little concerned, possibly seeking a categorical exclusion to avoid a more detailed environmental assessment of the project,” Bosse said. 

Regardless of the bank stabilization project, the long term issue seems to be Blankenship Bridge itself. According to Bosse, the bridge span is too short to accommodate the flow of water below, which is partially why the structure is threatened by erosion in the first place. Davies agreed, to some extent:

“There’s probably some legitimate concerns about any bridge in the Flathead River… a lot of the channels of the Flathead River are made up of unconsolidated, loosely packed gravel and rock that shift and move. So those channels, over time, will naturally shift and move laterally. They’re not stationary and stay where they are forever and ever. Essentially, from hydrologic standpoint, bridges or any kind of structure that spans that channel, eventually, at some point, may not [allow the river to] function naturally.”

Some say now may be the time for Blankenship. 

“Since Blankenship Bridge was installed, it has restricted flows, altered the river channel and caused possibly irreparable harm to the free flowing river in this area,” Blankenship resident Gary Saurey wrote in a recent letter to the editor.  “Furthermore, the single lane bridge is inadequate and unsafe. The County and Forest Service need to quit wasting time and money applying band aides and cooperate on the removal and replacement of the bridge with a new, longer, wider and safer structure as soon as possible.”

Two hundred and nineteen miles of the Flathead river system, including the Middle Fork, were added to the Wild and Scenic River System in 1976, long after the one-lane bridge’s construction. A new bridge, which would be determined necessary and funded by the county, would need to allow the water to migrate laterally, have two lanes of traffic and a pedestrian walkway. The price tag, estimated by Flathead County public works director Dave Prunty, would be $15 to $20 million. If the timeline for grants, permits, designs and contracts went as typical, it would be between a five and fifteen year project. 

Prunty said the bridge recently passed its county assessment, and is acceptable. The county would consider replacing it “at some point, when its service life is over.”

“It’s not uncommon for counties to replace bridges that pose flooding problems… Just because the bridge is not structurally deficient does not mean that it doesn’t need to be replaced,” Bosse said. 

For now, the bank stabilization is hoped to buy the county some time in case of a flood or heavy flow, though with current snow pack, that doesn’t seem to be a threat for this season. 

“Nobody wants to see that bridge fail and fall into a Wild and Scenic river,” Davies said.