Smoky skies returned to Mammoth this past weekend, reminding residents that the big Rim Fire near Yosemite is still kicking—and at almost 400 square miles, one of the biggest fires in the state’s history.
Forgetting the fire’s strength and size is a luxury northern Mono County hasn’t had. The region north of Bridgeport has largely been stuck in a pattern of smoke and haze for much of the past month and the sheer length of the time of exposure to the smoke is beginning to take an economic toll on the region.
The closure of a section of S.R. 120 West, which cut off access from the Eastside to Yosemite Valley just as the Labor Day weekend started, made an already bad situation in north county even worse.
“The smoke has become a big issue and a lot of businesses have been affected,” said Tim Fesko, the Mono County supervisor for much of the area of the county north of Conway summit. “Even though all of 120 wasn’t closed, businesses, especially in Lee Vining, took a big hit over Labor Day weekend because people thought the entire road was closed. The economy, my business included, is definitely hurting.”
“I was at Tenaya Lake on Sunday and I have never seen such thick smoke,” said Mono County Supervisor Byng Hunt. “I can see why people are leaving early. It’s not a fun experience.”
Unfortunately, the smoke—at least to some degree—isn’t likely to end anytime soon.
Although the Rim Fire was about 80 percent contained as of press time, it was still growing—and that, along with the sheer size of the fire, means it will likely continue to throw out smoke for several more weeks.
That said, the worst of the fire is considered to be past, according to fire managers.
And it’s not just the Eastern Sierra economy that has been affected.
The smoke has created day after day of unhealthy or hazardous air pollution ratings. It has even triggered a change in the way those ratings are established, according to Mono County Public Health Officer Dr. Rick Johnson.
That’s because the ratings are set up to measure the kind of air pollution that comes from the Owens Dry Lake and then make a determination if the amount of particles in the air at any one time is dangerous—and to what degree.
But fire smoke and the dust particles that spin off the Dry Lake during windstorms are very different from each other, said Johnson.
“The Owens Lake dust has particles that are much larger than particles that are in wildfire smoke. Owens Lake dust particles are usually about 10 microns in diameter (about 1/7 the thickness of human hair) but fire particulate matter is about 2.5 microns in diameter.”
Such small particles can get into the deepest recesses of the human lungs and that’s what makes them so damaging, he said.
But the region’s air pollution control district was issuing health advisories based on the larger particles, called PM10, which Johnson said didn’t always account for the impacts that the much-smaller-in-diameter fire–generated particulate matter might have—and in smaller amounts.
So he and the Great Basin Unified Air Pollution Control District agreed to a new protocol for how the district issued their health advisories.
“We had a very cordial conversation, and we came to agreement on all matters,” he said, which included changing the health advisory ratings to reflect the impact the smaller fire-generated air pollution particle would have.
“We agreed to continue the current policy and procedure of Great Basin issuing health advisories, since they have the monitoring equipment, and Public Health does not,” he said. “Our recommendations are now in line with all state and national recommendations.”
There is another issue too, he said, which is that in Mono County, there is no air pollution monitoring equipment north of Mono Lake until you get to Markleeville in Alpine County.
So he and the air pollution control district agreed to also include visual cues—how much visibility there was at any given time in health advisories.