The city of Sedona’s latest study on the environmental effects of off-highway vehicles, which became available in June, revealed that there are no significant environmental or health problems resulting from the use of OHVs inside or outside the city. The members of the Sedona City Council have subsequently rejected the study’s results, questioning their validity.

Study Results

The purpose of the study, as outlined by City Manager Karen Osburn, was “to discern whether or not there were environmental impacts significant enough that would necessitate banning OHVs on city streets.” The study was conducted by the consulting firm Kimley-Horn, the only respondent to two separate RFPs the city had issued, at a cost of $99,000.

The study examined traffic at the trailheads on Soldier Pass Road, Forest Road 152C, Schnebly Hill Road, Dry Creek Road and Broken Arrow Road. The average daily number of OHVs observed at each location, including SUVs, ATVs and UTVs, was 111 for Broken Arrow, 114 for Dry Creek, 197 for Schnebly Hill, 153 for FR 152C and 25 for Soldier Pass. SUVs such as Jeeps accounted for 28% of traffic on FR 152C, 56% on Dry Creek, 70% on Schnebly Hill, 83% at Soldier Pass and 84% at Broken Arrow.

Only on FR 152C were side-by-side UTVs the dominant vehicle type, at 53%.

The majority of OHVs observed at all locations except Soldier Pass were personal vehicles, which accounted for 43% of trips on Dry Creek, 47% on Schnebly Hill, 53% on Broken Arrow and 57% on FR 152C.

Tours accounted for more than 30% of traffic on Broken Arrow, Dry Creek and Schnebly Hill; 15% on FR 152C; and 83% on Soldier Pass.

Ambient noise levels at trailheads were between 48.6 and 62.8 decibels, while noise levels observed during the passage of OHVs ranged from 72.9 to 98.7 dB. As the report noted, short-term hearing damage occurs at or above noise levels of 120 dB, or more than 100 times greater than those produced by the passage of an OHV — the decibel scale is logarithmic, not linear.

The average noise levels generated during periods of vehicle activity was 87 dB, below the level of 90 dB at which hearing damage can occur over periods of prolonged exposure. The report stated that the highest observed level of OHV noise was “similar to standing next to a gas-powered lawnmower.”

Average dust levels were measured for both 10-micron and 2.5-micron particle sizes. The results obtained for 10-micron particles were 16 micrograms per cubic meter at Dry Creek, 18 at Schnebly Hill, 21 at Soldier Pass and the upwind section of Broken Arrow, 41 on the downwind section of Broken Arrow and 66 on FR 152C, an unpaved road. For 2.5- micron particles, the results were 9 μg/m3 on Schnebly Hill, 11 on both sections of Broken Arrow, 13 at Soldier Pass and Dry Creek and 30 on FR 152C. Federal air quality standards for dust exposure include thresholds of 35 μg/m3 for 2.5-micron particles and 150 μg/m3 for 10-micron particles.

“None of the results were anywhere near a threshold,” Osburn summarized. “Yes, the rain was a factor, but they were nowhere near what they needed to be in order to have a justification from a health perspective to ban OHVs.”

Council Reception

“This report sits in city files and is subject to any kind of public request to see it,” Councilman Pete Furman said during the council’s priority retreat on Dec. 13. “I’m really quite concerned about this study … Not only did we have experts in the field come out and do a dust study two days after it rained … I just don’t know how that fits in any expert’s professional ethics.”

“We also know at this point that [Forest Road] 152 and [Forest Road] 525 were closed for parts of this study,” Furman said. The study did not examine traffic on FR 525.

“Where I would like to take this now is for us to put a cover page on that report that talks about all of our concerns and that this report is really not valid, and that anyone in the future that accesses that report sees that we have more questions, we really shouldn’t rely on that data,” Furman said.

“The report is accurate for what it was,” Osburn said. “That’s a point-in-time analysis, and that analysis is accurate for that point in time.”

She explained that Kimley-Horn’s air quality expert “was pretty adamant that even at the highest levels measured, it would not have necessitated or warranted a ban of OHVs because our lungs are built to take in bad stuff for short durations of time.”

“We’ve stood out at the Aerie Trailhead, and we’ve seen air quality there that exceeds the worst I’ve ever seen in Phoenix in the ’80s,” Furman said. “It’s terrible … We’ve done some work and we’re convinced ourselves that there are flaws in the study, but we’re not communicating that … That report didn’t meet our standards.”

“It was as bad as LA ever was,” Vice Mayor Holli Ploog said of a recent trip outside the city limits. “They kept coming and coming … Most of them were owner-owned. They were not rental company vehicles.”

“It’s unfortunate that the study was flawed,” Councilwoman Kathy Kinsella said. “I’m very disappointed in a company that we have had such an active relationship with on so many projects didn’t see fit to say, ‘These are not the right conditions’ … It really is a very poor reflection of their relationship with us.”

“When we start to look at their conclusions around noise, they didn’t measure noise next to where houses are,” Councilwoman Melissa Dunn said. “They measured where the trailheads were. So again, just flawed methodology … I would have expected better for our money.”

Sound pressure levels decrease as the inverse square of distance, so it is not possible for sound levels to be higher in a home at some distance from a trailhead than at the trailhead itself.

“Since we’re not going to rely on the draft but it exists, something simple could maybe go on there, like ‘unaccepted draft’ or ‘draft not used.’ I don’t see the harm in putting something on there that makes it clear that this is a document that has not informed positions that we’re taking,” Kinsella said.

“I would agree to have that ‘unaccepted’ — either a stamp put on it or a cover letter,” Mayor Scott Jablow said.

“Just as a reminder, we have no evidence whatsoever that the end result would be anything different,” Osburn said.

“Right. But we don’t have to accept it,” Jablow said.

“It sounds like many of you believe that there is a health issue,” Osburn said. “And if you believe that there’s a health issue … but we don’t want to assess whether or not it actually does exist, then I just want to make sure that we’re saying, ‘We think it does and we’re concerned about it, but we’re not wanting to do anything further.’”

Councilwoman Jessica Williamson expressed a dissenting view from that of her colleagues.

“I think we should drop this,” Williamson said. “We basically made an arrangement, an agreement, with the OHV people. They’re putting a lot of money into their vehicles on the understanding that if they did that, we would not move forward with banning their vehicles. I believe that’s an agreement we have, and I don’t believe we should seek to back out of that agreement by a different method at this point. I think we made our bed, we made our decision, and I would not support moving forward through another avenue … I would be morally against doing something at this point to try and get OHVs off the road given the conversations we’ve had with the owners.”