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A bill to require emissions tests for diesel vehicles in northern Utah areas that don't comply with federal air quality standards faces just one final hurdle in the state Legislature.

House Bill 134 passed a Senate committee unanimously Thursday. The bill, which passed the House 39-29 last week, is now headed for the Senate floor with one week left in the session.

Because most of the counties in Utah's nonattainment areas already test diesel emissions, the bill would affect only Utah County, according to Rep. Patrice Arent, D-Millcreek.

Utah County has required emissions tests for diesel vehicles in the past, but the county commission voted to stop doing so in 2006, said Ralph Clegg, executive director of the Utah County Health Department.

Utah County's three-person commission sent a letter to the Senate Business and Labor Committee asserting their opposition to the inspections. Orem and Provo cities sent letters supporting the proposal.

Bryce Bird, director of the Utah Division of Air Quality, said testing diesel vehicles for emissions compliance would remove 170 tons of pollution from Utah County's air each year. If non-compliant diesel vehicles were a factory, he said, they would be the third-largest source of emissions in Utah County.

Bird's figures were based on data from the Salt Lake County Health Department, which has required emissions tests for diesel vehicles since 1994. Corbin Anderson, who supervises the county health department's Bureau of Air Quality, said about 6 percent of the diesel vehicles tested fail to comply with emissions standards. Of those, more than half fail because their emissions systems have been deliberately disabled.

The Weber-Morgan Health Department, which began requiring emissions tests for diesel vehicles in January, has seen similar results, said Scott Braeden, the department's air quality program manager. The charge for the test is capped at $30, he said, and first-time offenders can get a waiver giving them more time to complete the necessary repairs.

So far, Braeden said, 15 percent of tested diesels fail, compared to 4.5 percent of gasoline vehicles. Approximately 40 percent of those that failed did so because their emissions systems showed signs of tampering.

Braeden said he wasn't surprised by the outcome.

"We had expected to have a higher than normal failure rate, if only because they hadn't tested before," he said. But the health department has also had a visual smoke program for some time, he added. "Vehicles could be turned in for intentionally blowing black smoke. We would do an inspection on those, and the vast majority had been tampered with."

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