After months of preparing for what many saw as inevitable federal sanctions, the Treasure Valley might not exceed new ozone air quality standards this year after all - and it all may come down to how the federal government treats a few decimal points.

Idaho Department of Environmental Quality officials reported in July that the Valley had exceeded the three-year average standard, lowered last year by the federal government. But after taking a closer look at its monitoring data, state officials say the Valley could squeak by.

"It's incredibly close," DEQ Administrator Toni Hardesty told the Boise City Club Tuesday.

The Treasure Valley has met the standard of 75 parts per billion, Hardesty said, if the U.S. Environmental Protection Agency uses its new computing rule and cuts off the decimals instead of rounding them off. Idaho is awaiting a ruling from the federal agency and also completing its own quality assurance tests on its monitoring data.

"It depends on their interpretation, but that's how we interpreted the new rule," Hardesty said.

Ozone is a summertime problem, created when nitrogen oxides mix with volatile organic chemicals in the presence of heat and sunlight. It causes lung and heart disease.

Exceeding the standard would require industries to reduce pollution if they hope to expand and require even small businesses like auto body repair shops to meet new regulations.

But the biggest impact would be on our driving habits, since auto emissions are the biggest source of the pollutants. The federal rules would force state leaders to take a harder look at expanding public transportation instead of widening roads to handle growth. And Canyon County drivers might have to submit to vehicle emissions tests like those in Ada County.

Hardesty remains hopeful that even if the Treasure Valley exceeds the ozone standard this year, the state could avoid such mandatory federal controls if the Valley can reverse ozone pollution growth in 2009 and 2010. But that would take similarly dramatic state and local actions to reduce driving and curb ozone from other sources.

Cooler weather this year helped keep ozone levels down, and high gas prices caused Idaho drivers to reduce the miles they traveled in the Treasure Valley by 6 percent, Hardesty said.

If people continue to reduce their trips by car-pooling, riding the bus, riding bikes to work and telecommuting, they can help reduce both of the pollutants that create ozone.

"We've always said a 5 percent reduction in vehicle miles traveled can make a major difference in whether we exceed the standards," Hardesty said.

Regulations that require gas stations to capture volatile organic compounds - the vapors in underground gas tanks - should be in place next year.

But new emissions testing for Ada and Canyon counties, approved by the Idaho Legislature earlier this year, is not expected to be in place earlier than 2010.

State officials hope to hear in the next two months what the EPA decides.

Rocky Barker: 377-6484