With the widening of I-15 from Farmington to the northwest side of Salt Lake City inching closer to reality, residents impacted by the proposed project are concerned about a myriad of things. A top issue is how the project will exacerbate the air quality problem along the Wasatch Front.
Denise and Clark Ward live in Bountiful. While the potential construction would disrupt their desire to drive to Salt Lake City or Ogden, they’re worried about what more cars on the freeway could mean for the air they breathe, especially with a shrinking Great Salt Lake.
“It's no secret that the dry lake beds are producing toxic dust,” Clark said. “So you combine that with the additional pollutants from additional traffic and you have a toxic Wasatch Front.”
Utah’s population is expected to double by 2050, which is part of the Utah Department of Transportation’s argument for the expansion. Whether or not lanes are added, Bradon Weston, director of environmental services for UDOT, said the traffic increase in the expansion corridor from 2019 to 2050 is projected to be around 28%.
Without the changes, the agency said traffic would only get worse, which would have a negative impact on air quality improvements since commuters would be idling for longer. UDOT believes the preferred solution to the traffic woes and cleaning up the air is adding an additional lane in each direction.
The draft environmental impact statement on the freeway expansion is already available and the public comment period is open till Nov. 13. One of the findings outlined in the draft report is that prominent pollutants, like PM2.5, would actually improve by 30% by 2050. Even then, without the expansion, they are eyeing roughly the same improvement — thanks to technology.
“A lot of that decrease is because of efficiencies in emission standards,” Weston said. “So car makers have to deliver more efficient fuel vehicles in the future and also the fuel mixes that the refineries are going to become more efficient.”
He added more air quality improvement will come from people spending less time on the road, less idling and less stop-and-go traffic because there will be decreased congestion on the freeway. The switch to electric cars in the future is also expected to play a role.
Gannet Hallar, a professor of atmospheric science at the University of Utah, isn’t sold on UDOT’s air quality projections.
“I am concerned about the time frame under which they're evaluating. And I think it would be more appropriate to evaluate under a much more relevant and shorter time frame,” she said. “I think there's a lot of uncertainty with projections out that far pertaining to vehicle emissions, both in gas and aerosols.”
By shortening the timeframe to between three and five years, Hallar said there would be a better understanding of “emissions, the vehicle traffic expected, fuel standards,” among other things.
Weston said their timeline was based on the Wasatch Regional Council’s transportation plan that goes out to 2050. There weren’t any talks about reducing the years in the air quality model presented in the environmental impact statement.
There is also a question about how long the air quality improvements will last. There are numerous studies that show highway expansions don't permanently solve traffic congestion — otherwise known as induced demand. A big chunk of Utah’s air quality problems are a direct result of vehicle emissions. As congestion inevitably returns to I-15, more vehicles will be idling with stop-and-go traffic, which will emit more pollution.
Weston said UDOT is “not under the disillusion” that expanding the freeway “is going to solve congestion.” As a result, he “would expect” the air quality projection numbers “to change” due to the amount of time people spend in their vehicles because of traffic.
Although PM2.5 is anticipated to decrease, PM10 is expected to worsen by 27%. There isn’t much UDOT can do to curb that spike, Weston said, aside from encouraging people to drive less.
“It's like your tires wearing down, it's your brakes wearing down and it's just grit from the road itself,” Weston said of the likely increase in particulate matter.
Even if the emissions are cleaner, Hallar said the increase of vehicles on the road will still have an immediate impact on human health, especially since the Wasatch Front suffers from severe summertime ozone and particulate matter pollution in the winter.
“Improving air quality means reducing the amount of fossil fuel burning in the valley,” she said.
The Clarks are already aware of the impact on their health. Deinse never experienced allergies until moving to Bountiful and Clark suffers from asthma attacks when the air quality is poor.
“The air quality is critical,” Deinse said. “We just don't feel well when we're in that air environment, whether it's an inversion or it's smog or it's windy and what's rolling off of the Great Salt Lake.”
