by Laura Lundquist, Chronicle Staff Writer
This summer’s Millie fire prompted renewed calls for thinning the forests south of Bozeman to protect the city’s water supply from fire. However, upgrades to the water plant are nullifying the argument that the water supply needs protection.
The Bozeman water plant’s antiquated filtration system, built in 1984, couldn’t filter much more sediment than what is carried by the streams on a normal day. Any increase in the amount of sediment in Bozeman or Hyalite creeks was a source of concern.
But that will change when a new $43 million system comes online in a little more than a year, said water treatment supervisor Rick Moroney. Construction started a year ago.
“It adds an important extra step — sedimentation — which makes it vastly superior,” Moroney said. “I can’t guarantee it could handle everything, but it will be able to handle the sediment from a fire.”
The new facility removes the urgency from one side’s argument in what is now a 2-year-old battle over a forest-thinning project. In March 2010, the Gallatin National Forest published its Bozeman Municipal Watershed Project, a plan devised with the city to harvest, thin and burn 4,800 acres in the Hyalite and Bozeman creek watersheds.
The $2 million project had the stated objective of protecting the watersheds that provide 80 percent of the city’s summer water supply from being polluted after a severe fire.
But wildfire doesn’t pose the only risk to water quality.
The Alliance for the Wild Rockies, the Montana Ecosystems Defense Council and the Native Ecosystems Council opposed the project because more than seven miles of new logging roads would be required, and such roads can add as much sediment to area streams as a fire.
The groups challenged the plan with the Forest Service three times. In April, they finally filed a lawsuit challenging the project.
Hydrologist Mark Story said decades of research show roads are responsible for 90 percent of the sediment produced during logging.
The groups argued thinning wouldn’t prevent a wildfire, which would add still more sediment.
“There’s no science that will fireproof a watershed,” said Michael Garrity of the Alliance for the Wild Rockies. “We have no problem with thinning as long as they can do it without building roads that are just as bad for the watershed.”
With water supply vulnerability reduced, the argument may just come down to whether fire should be minimized in such a popular area.
In that case, recent studies have found that tree removal is not the primary driver in minimizing fire risk.
The studies emphasize that thinning projects should focus mainly on the removal of surface fuel — deadfall, debris and young trees — and not so much on logging larger trees.
“In fact, very effective fuel treatment in many studies consist solely of prescribed burning with no overstory tree removal,” wrote the authors of a recently published study that analyzed a 2010 fire in the Fourmile Canyon near Boulder, Colo.
According to the study, segments of the burned area had been thinned during the six previous years, but only in small areas. Chuck McHugh was a co-author of that study.
“The way the thinning was carried out wasn’t effective,” McHugh said. “There was no prescribed burn to remove accumulated surface fuels that piled up and it wasn’t done on a landscape level.”
Thinning makes little difference in a high-intensity fire, usually brought on by high winds, dry fuels, south-facing slopes and when burning uphill. One-fifth of the Millie fire burned with high intensity.
But when done right, repeatedly in the right locations, thinning can be effective when followed by prescribed burning. But it can’t be a one-time project.
“There is no cut-and-dried answer,” McHugh said. “We’re trying to deal with 100 years of fire suppression and a social-political world that makes it difficult.”
