Oil and gas operations continue to fuel Front Range air pollution, and rules clamping down on emissions have had little effect in the past three years, a new study says.

Air samples from residential backyards in Erie and Longmont and near wells contained levels of chemicals as much as 77 times above regional background levels.

Ambient levels of benzene, a known carcinogen, were higher at the state's air monitor in Platte ville than in Houston, home to some of the nation's biggest refineries.

The study was done by researchers the University of Colorado and will appear Friday in the journal Elementa.

Comparing the readings with earlier studies showed no improvement even after Colorado adopted a rule in 2008 requiring capture of 90 percent of oil and gas emissions, the study said.

The effect of tightened controls may be limited by the acceleration of drilling in the Denver-Julesburg Basin, the study said.

The number of drilling permits issued annually in Weld County, the basin's core, has nearly tripled since 2005 to 2,468 in 2013, according to state data.


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"Even though the volume of emissions per well may be decreasing, the rapid and continuing increase in the number of wells may potentially negate any real improvements to the air quality situation," the study said.

State Air Pollution Control Division director Will Allison said oil and gas emissions have been reduced in the past decade.

"Without the tougher regulations you would have seen an uptick in emissions with the increased industry activity," Allison said. "We are constantly looking at what needs to be upgraded."

Oil tanks are becoming more visible as they encroach on the suburbs, leading to new concerns about leaks of volatile compounds.
Oil tanks are becoming more visible as they encroach on the suburbs, leading to new concerns about leaks of volatile compounds. (Andy Cross, Denver Post file)

In February, the state adopted tougher rules calling for 95 percent of oil and gas emissions to be captured.

"It will take several years to determine the impact of the new rules," said Chelsea Thompson, a postdoctoral researcher at CU and the study's lead author.

The new rules will allow 5 percent of oil and gas air emissions to escape from the basin's 25,000 wells, Thompson said.

"But the industry is investing billions of dollars in Colorado," Thompson said. "When it is 5 percent of 60,000 wells, that will be a great deal more."

The study was limited to 32 24-hour air samples taken in 2013 from backyards of seven homes that had oil and gas wells between 244 feet and 1,319 feet away.

Additional 24-hour samples were taken at state-operated ground monitors in Denver and in Platteville, in southwest Weld County.

Most of the chemicals detected are light hydrocarbons, such as propane, ethane and butane. Earlier studies in Erie and Boulder also recorded high levels of these chemicals.

These chemicals do not pose a direct health risks but do contribute to the formation of ozone or smog. The Front Range summer ozone levels are above the federal Clean Air Act health standards, and the state has to come up with a plan to reduce ozone.

The volatile organic chemicals that pose health risks, such as benzene and toluene, were below health standards in Erie and Longmont.

But the state's air monitor in Platteville registered benzene above the standard for long-term exposure standard, Thompson said. The federal Environmental Protection Agency's recommends no more than 0.4 parts per billion as its most protective standard.

While the single Platteville benzene reading in the study was more than 1 part per billion, Thompson said that doesn't necessarily reflect the long-term exposure level.

The Air Pollution Control Division's Allison said the CU study "corroborates a lot of what we already know."

Still, there has been progress, Allison said. In 2004 average benzene levels in Platteville were 4 parts per billion, in 2013 the average reading was 0.5 parts per billion, he said.

Thompson's research showed that while most of the benzene in Denver was associated with vehicle tailpipe emissions, more than 70 percent of the Platteville levels are linked to oil and gas emissions.

Encana Corp., one of the primary oil and gas companies operating in Erie, has a team devoted to managing emissions, spokesman Doug Hock said. "We are continually looking to reduce emissions."

Encana uses infrared cameras to inspect for leaks, Hock said, and like other large operators is adding pollution-control equipment and centralizing facilities to better manage production and emission.

The Denver-Julesberg Basin has been drilled since 1901, and many legacy wells and facilities also contribute to the emissions.

"It would good for the state to go after those older and larger emission sources first," Thompson said.

The study was funded in part by Patagonia, the outdoor gear company, and in part by the National Science Foundation.