Treasure Valley could be caught in ozone limbo

The Idaho Legislature enacted a law in 2008 requiring vehicle emission testing in areas of the state, including Ada and Canyon counties, where air quality is compromised and vehicle emissions are one of the main culprits.

Ada has had an emission testing program since 1984; Kuna and Canyon County came on board in 2010 under the new law.

The expanded program is a success, says the Idaho Department of Environmental Quality, reducing emissions in the two counties by more than it estimated and keeping the area from violating federal standards for ozone pollution.

But even an expanded testing program might not be enough to keep the Treasure Valley in the clear in the future.

Within the next two months, the U.S. Environmental Protection Agency is expected to announce whether it will tighten air quality standards for ground-level ozone. Ozone high in the atmosphere is an important element in protecting the planet from solar radiation. But when it’s emitted from ground-level sources, it’s a pollution that is unhealthy for humans.

The EPA has been “pretty tight-lipped” about its plans for the ozone standard, which is currently 75 parts per billion, said Mike Toole, DEQ regional air quality monitoring coordinator.

“We anticipate if there is a change it will be between 65 and 70,” he said.

The Treasure Valley’s ozone-pollution levels are fairly consistently in the 67 ppb to 68 ppb range, said Toole. The most recent three-year average for the Valley is 69 ppb.

“We are optimistic if the change is around 70 we will be under that standard. ... If it’s changed to between 65 and 68 we could be over that standard,” Toole said.

But DEQ is not panicking. “Once we see where that standard is set, we will have a lot better idea on how that will impact us and what we need to do moving forward,” said Toole.


Ground-level ozone is a key component of smog, which forms when emissions of nitrogen oxides and volatile organic compounds mix in the air and then “cook” in the sun.

In the Treasure Valley, the top sources of nitrogen oxides are vehicles (64.9 percent), construction equipment (7.4 percent) and industry (7.1 percent). The top sources of volatile organic compounds are vegetation (41 percent), vehicles (14 percent) and degreasing/cleaning solvents (13.5 percent), according to DEQ.

More than half of all vehicle pollution comes from just 10 percent of the vehicles. By identifying the dirtiest vehicles and getting them fixed, the emission-testing program has been able to reduce vehicular pollution by about 18 percent, according to the Ada County Air Quality Board, which manages Ada’s testing program. DEQ manages Kuna’s and Canyon’s programs.

In 2008, the Treasure Valley almost violated the ozone standard when the EPA dropped it from 80 ppb to 75 ppb. The valley’s 2008 level was right on the line at 75 ppb.

That same year the Idaho Legislature enacted the new emission-testing law, which forced testing in Kuna and Canyon County.

DEQ’s models in 2008 estimated the two-county vehicle emission testing would reduce the ingredients of ozone by 568 tons per year in Ada County and 252 tons in Canyon County.

Since 2010, estimated emission reductions have exceeded initial estimates each year. In 2013, Ada’s emission reductions were 4 percent greater than estimated and Canyon’s were 25 percent greater.

While the program has proved successful, it likely has reached its maximum potential in terms of emission reduction — dirty cars are getting fixed and newer cars run cleaner. Current testing protocols will keep pollution levels where they are, but may not provide a boost to efforts to get the air cleaner.

“We can assume that the reductions are going to become less significant as motorists comply with the program, and/or trade out older vehicles,” said Mike Hahn, DEQ vehicle inspection and maintenance program coordinator. “There are areas within the current structure of the emissions testing program that we could look at modifying to further increase emission reductions, however, until we know what the new standard is we haven’t started the process of formally determining what those are and what benefits we would gain,” he said.


Two factors affect Treasure Valley vehicle emissions — one helps improve conditions, the other worsens it.

Working in the valley’s favor is the fleet turning over as newer, cleaner cars replace older, less-efficient cars over time

Each year, the average age of vehicles registered in Ada County is 10 to 11 years, according to an Idaho Transportation Department report. In 2014, the average year of manufacture was 2003; by 2020, the average car will be a 2010 model. EPA plans call for future auto models and future gasoline to be even cleaner, which will help lower emissions even more.

Working against the Valley’s favor is growth. More people means more cars on the road.

Since 2004, the combined population Ada and Canyon counties has increased 28 percent to 629,379. During the same time, the number of registered passenger vehicles in both counties increased 12 percent.

In 2008, Ada and Canyon drivers logged 3.7 billion miles; by 2014 that number jumped to 4.7 billion and is expected to grow, according to Community Planning Association of Southwest Idaho.

Reducing ozone and its many potential ingredients is a complicated challenge, said Matt Stoll, Community Planning Association of Southwest Idaho director and former DEQ air quality manager.

“The control strategies employed across the country are pretty invasive,” said Stoll. “We hit industry and ag quite a bit, and we have gone after the motor vehicle fleet as far as emission-testing goes. The next logical step is how can we get a better public transportation system in the area. But it is not going to be the silver bullet.”

Getting people to drive less in the Treasure Valley poses a challenge, in part because of its limited public transportation system and lack of money and political will to improve it. “Public transportation should be one we look at, but on its own it is not going to be enough.”


When the EPA decides to ratchet down the ozone level, the new standard will not go into effect immediately, Toole said. States will have one year to develop a plan to meet the revised standard, and then the EPA will have one year to review and approve states’ plans.

EPA projections show the vast majority of U.S. counties, including Ada and Canyon, would be able to meet the proposed new standards by 2025 with the rules and programs now in place or underway.

EPA plans might be delayed, however, if a third party files a lawsuit and the new standards are tied up in court.

Either way, the DEQ is hopeful that the state will not face more serious nonattainment classification. Areas receiving higher classifications must contend with long-term, tighter pollution-control measures including limits on new construction or requirements for emission-reducing gasoline blends.

Typically, areas on the margin like the Treasure Valley can pursue voluntary measures under a short-term plan and do not have to face forced EPA actions, Toole said.

“It always benefits us to go the voluntary route,” Toole said. “Not only does that keep it at a state and local level, but it also involves the community. It is always great to get buy-in and cooperation from everybody.”