Laura Lundquist

(Missoula Current) The Forest Service will allow the use of some motorized equipment for the removal of the old McKinley Lake impoundment in the Rattlesnake Wilderness Area this summer.

On Tuesday, Lolo National Forest supervisor Carolyn Upton issued a draft decision notice saying she’s approving limited motorized equipment/mechanical transport use and limited helicopter and vehicle access needed to breach and decommission the century-old earth-and-timber dam on McKinley Lake high in the Rattlesnake Wilderness.

The proposal for limiting motorized or mechanical equipment was listed as Alternative 2 in the Lolo Forest’s environmental assessment issued in July. Alternative 1 was a no-action alternative where the Forest Service would have set no restrictions, leaving the city to use whatever equipment it wanted.

The 1964 Wilderness Act doesn’t usually allow the use of any mechanical equipment in wilderness areas unless something was grandfathered in when the wilderness was designated or if the Forest Service grants a waiver.

In her rationale, Upton explained her choice of allowing some mechanical equipment, based on activities that already exist. For example, the City of Missoula, and the previous water-rights owners, Mountain Water and the Montana Power Company, have flown annual maintenance flights into the eight lakes and 10 dams and have driven the dirt roads in the Rattlesnake Wilderness.

“Therefore, I am limiting helicopter use to one day to bring in equipment and supplies for the expected 12 to 13-week work window, and one day to remove equipment and supplies. This avoids the negative impacts that approximately 48 pack train trips (round-trip) would have on the trail and work area and enables the work to be completed in one field season,” Upton wrote.

Other allowed activities include: driving the roads twice a month to drop off crews; using a motorized pump to dewater the breach site; drilling holes for blast charges using a power auger; and the use of wheelbarrows and carts to move rock.

More than two years ago - after the Rattlesnake Dam had been removed on the lower section of Rattlesnake Creek, and after the city won its battle with the Mountain Water Company to own its own water supply - the city started debating what to do about the 10 dams built in the 1920s and ‘30s in what eventually became the Rattlesnake Wilderness.

Decades ago, the dams were needed, because the lakes were Missoula’s water source. So when the Rattlesnake Wilderness was designated in 1980, certain maintenance activities on the dams were grandfathered in. But, after a Giardia outbreak in 1983, the Mountain Water Company transitioned to well water, leaving the lakes only as a backup water source.

Even though the dams were really no longer necessary, the Lolo National Forest was required to maintain them, although most haven’t aged well and are in need of repair. The city is also required to maintain the roads and trails that access the dams.

The dams have deteriorated to the point where they need to be rehabilitated or decommissioned, but both options cost money. According to a 2018 feasibility study, it would cost about $7 million to rehabilitate all 10 dams or about $1.2 million to decommission them, so it would make economic sense to get rid of them.

The impoundments on eight lakes – two lakes have two dams each – are ancient constructions of dirt over wooden cribs filled with rocks. (Laura Lundquist/Missoula Current)
The impoundments on eight lakes – two lakes have two dams each – are ancient constructions of dirt over wooden cribs filled with rocks. (Laura Lundquist/Missoula Current)

But fisheries biologists pointed out that keeping two or three of the dams on the larger lakes could add more cold water to help fish, particularly bull trout in Rattlesnake Creek. As climate change worsens, the region is looking at more hot, dry summers that will put cold water at a premium.

With the help of Trout Unlimited, the city decided to use the dam on McKinley Lake as a pilot removal project. That’s what led to this draft decision.

Not everyone supported Alternative 2. Wilderness Watch, a Missoula-based organization, liked the idea of getting rid of the dams but didn’t support the use of mechanized or motorized equipment, because it violates the concept of wilderness. In its comments on the environmental assessment, Wilderness Watch advocated for the use of non-motorized, traditional skills and methods, “which is the same way this small, earthen dam was constructed a century ago,” and said using traditional methods would cost less than one-fifth of the $621,800 estimated for Alternative 2.

On Tuesday, Wilderness Watch conservation director Kevin Proescholdt expressed disappointment with the draft decision.

“It appears the Forest Service authorized helicopter and motor-vehicle use right up to the dam. Unfortunately, it seems as if the Forest Service chose expediency over wilderness values,” Proescholdt said in an email.

In her rationale, Upton said she chose actions that would allow the work to be completed in one season, because the state and the Forest Service have deemed the dam to be high-hazard and the spillway is failing.

“All cooperators involved, as well as the Montana Department of Environmental Quality and Watershed Education Network, agreed that the work should be completed in one field season to avoid having to secure the breach site for overwintering and risk a failure that could threaten important downstream fishery resources. This plan also allows the disruption to wilderness recreationists and wildlife to be limited to a single season,” Upton wrote.

The City of Missoula will breach McKinley Lake Dam as soon as the snow is gone from the site, likely in mid-June, according to the decision notice. The decision notice can be found online at this link.

Those who commented previously and still want to object should mail objections to: Objection Reviewing Officer, USDA Forest Service, Northern Region, P.O. Box 7669, Missoula, MT, 59807.

Contact reporter Laura Lundquist at