Forest thinning makes strides on Observatory Mesa
Mesa thinning

Forest thinning makes strides on Observatory Mesa

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The forest across Observatory Mesa is looking much more open these days. That's because this fall, the city of Flagstaff finished thinning and pile burning on nearly 700 acres on the mesa just west of downtown.

The work was part of the Flagstaff Watershed Protection Project, the taxpayer-funded initiative to reduce the threat of wildfire and post-fire flooding around the city’s watersheds.

The biggest project on the mesa was a 475-acre mechanical thinning zone where operators removed 60 percent to 70 percent of the trees, many of them small-diameter, to get the forest closer to its historical lower density and structure, said Paul Summerfelt, wildland fire management officer for the city of Flagstaff.

The project also contained several lessons for future forest thinning and restoration projects in the region, Summerfelt said.

The first had to do with the process the city used to direct the logging contractor’s work. Instead of marking the trees to be cut or those to be left, which is a strategy commonly used by the Forest Service in timber sales and stewardship contracts in the area, the city decided to take a different tack. It opted for a “designation by prescription” process in which the contractor on the job, Perkins Timber Harvesting, was given a description of the types of trees to be taken, those to be left and what the forest should look like when the work was complete. Perkins has about a decade of experience with that type of logging contract, owner James Perkins said.

To help provide direction, Mark Brehl, former FWPP field operations specialist who was working on the project, used smartphone mapping applications to pinpoint areas where openings should be made, or where groups of trees should be left, which were relayed to the operator’s cell phone.

While the designation by description route puts more responsibility in the hands of the logging company, doing so saved about $60,000 in marking paint, staff time, vehicle expenses and other costs, Summerfelt wrote in a brief to city council last month. It also sped up the pace of the thinning, with the contractor able to cut 15 to 20 acres of trees per day, he said.

The project was an attempt to see if such a strategy would work and result in a successful final product, and in the end it did, Summerfelt said in an interview.

“We’re really pleased with what occurred in there,” he said.

Looking back on the project, the city came up with a substantial list of lessons learned that can apply to similar work in the future. When it comes to the Four Forest Restoration Initiative, for example, where hundreds of thousands of acres need to be thinned, designating thinning by description instead of marking could result in immense cost savings, Summerfelt said.

The way costs broke down on the Observatory Mesa project also was instructive, Summerfelt said. Cost-per-acre came in at $781, half of which was covered with grant funding and half of which was paid for with money from the $10 million FWPP bond that voters approved in 2012. More than half that project budget — $450 per acre — was dedicated to chipping the slash from thinning and hauling it off site. That hefty expense raises important questions about how to accomplish biomass removal in a much bigger project like 4FRI, Summerfelt said.

“It’s a good eye-opener when you think about 4FRI. What are you going to do with that stuff?” he said.

For the city’s part, it decided to chip instead of pile and burn the slash to avoid producing smoke that would likely affect a substantial part of the city.

The Observatory Mesa work also serves as a good introduction to the type of mechanical thinning that this region will see more of in the coming years, said Brehl, who is now an assistant fire management officer with the Arizona State Forestry Division.

The region’s forests have already seen an immense amount of work over the past two decades, but “we’re moving into a time where we have to do more,” Brehl said. The use of big machines and the removal of larger volumes of trees is needed to get the ponderosa pine forests back into a healthy, resilient state, he said.

“It’s more intensive, we're going to see more mechanical operations in the woods but it’s nothing to be scared of, it’s something we should be excited for and proud of,” Brehl said. “We want people to understand that this is an industrial operation in the woods but it is the precise tool that's needed right now.”

Over the next two years, the city will continue FWPP-related thinning work on another 1,500 acres it owns in the Observatory Mesa area. It will also be doing prescribed burning on the acreage already thinned. After that, FWPP thinning work will transition nearly exclusively to Forest Service land in Dry Lake Hills, Mount Elden and Mormon Mountain areas, Summerfelt said.

Meanwhile, mechanical thinning on about 700 acres of Forest Service land at the base of Mount Elden, from the top of Fourth Street to Schultz Pass Road, is expected to begin this summer, Summerfelt said.

Emery Cowan can be reached at (928) 556-2250 or

 “We want people to understand that this is an industrial operation in the woods but it is the precise tool that's needed right now.”

--Mark Brehl, former FWPP field operations specialist


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