"Remarkable" spikes in air pollution in northern Colorado this year

Air pollutants east of Longmont were recently measured at the highest ever seen by a scientist with 40 years experience in the field. On January 6 and February 1, readings from air monitoring equipment at Union Reservoir, east of Longmont, spiked so high for the chemical ethane, it was far above what the equipment could measure. Methane, propane and other petroleum hydrocarbons were also extremely high, according to Atmospheric Chemist, Dr. Detlev Helmig.

"I've never seen values this high anywhere else in my career," said Helmig, the owner of Boulder A.I.R., a company that contracts with the City of Longmont and other local governments to measure air quality on the Front Range.

The readings from the event at the Union Reservoir Monitoring Station stand out among the estimated 40,000 measurements Helmig has seen on the Front Range. "These were by far the highest concentrations, so these data are remarkable from that perspective," he said.

Helmig presented the air monitoring data in a semi-annual presentation to the Longmont City Council last week. He chose ethane as one example of the Volatile Organic Compounds, or VOCs, that are part of the monitoring program.

Because ethane saturated the equipment, scientists at Boulder A.I.R. had to estimate the actual reading through calculations based on the ratio of chemicals in samples from that particular wind direction in lower concentration samples.

According to those calculations, the peak of ethane was estimated at nearly 3500 times the background level during a ten-second interval on February 1. The background level represents the lowest levels of these pollutants in ambient air pollution that is transported into the region. The 10-minute mean reading that day was more than 500 times the background level. On January 6, the peak concentration of ethane was nearly 3000 times the background level.

Methane, a greenhouse gas that traps about 50 times more heat in the atmosphere than carbon dioxide, was 12 - 23 times higher than background levels, according to the data.

"We're very confident this is an oil and gas signature. This is not traffic, this is not a chemical plant releasing something. It's natural gas mostly," Helmig told Longmont City Council.

Maintenance work, including venting of wells, can be a source of VOC emissions along with leaks and accidents, which must be reported to the Colorado Oil and Gas Conservation Commission (COGCC)."I am not aware of any uncontrolled releases or spills that correlate with the timing of the spikes," said Dr. Jane Turner, air quality/oil and gas coordinator for the city of Longmont.

New oil and gas regulations went into effect in Colorado on January 15. One of the rules is that companies need to notify "proximate" cities, within a couple miles of a well, when there will be maintenance. Turner said notifications are typically made within 48 hours of the work.

One oil and natural gas company did notify the city of work to be done in January, according to Turner, who followed up with operators of well sites east of the monitoring station. "I discussed the January 6 data with Kerr McGee/Occidental representatives and was informed that their work logs did not list any maintenance activities occurring in the hours prior to the January 6 VOC spike," she said.

Without context, there is only so much information the data can provide about the source of the emissions. "The instruments cannot identify with certainty the specific locations where the pollutants were released," Turner said.

The exact source may be elusive, but an analysis of the wind direction at the time showed it blowing from the east and northeast for the two events. There are dozens of wells in those directions, though the short duration and sharp spike of the peak suggests to Boulder A.I.R. scientists that the source was likely within a few miles of Union Reservoir.

The VOCs instrument only takes readings 10 minutes out of each hour and the winds and atmospheric conditions have to line up just right to capture the spikes. "The odds for us to see this plume at the Union Reservoir are pretty low. Possible well sites are maybe two, three, four miles away and the wind can go 360 degrees in any direction it likes," Helmig said. "So these plumes may happen much more frequently. People living closer to these well sites are very likely subjected to even higher pollution levels than what we measured at the Union Reservoir monitoring station."

The Courier asked the Colorado Oil and Gas Association, COGA, for a comment on the air monitoring readings. "Looking at the data, I can tell you the benzene measurements are quite low, and well below federal health guideline values. At those low levels, it's hard to tell what the source could be, as these results could occur near a neighborhood gas station or a local manufacturing facility or even be seen with vehicle traffic," said COGA's Director of Communications, Scott Prestidge. When asked about ethane and methane, Prestidge chose not to comment on those readings.

A page on COGA's website states that "Thousands of air quality measurements have been taken near oil and natural gas sites in Colorado over the past decade, and no measurement attributable to oil and natural gas has been above EPA or Health and Human Services health guideline values, according to monitoring by the state, industry, and third parties."

Ozone pollution was also an issue for northern Colorado for March 19 - 21 when the region had the highest ozone levels in the nation as measured by EPA monitoring stations in Platteville and other stations north of Denver, according to EPA data presented to the Longmont City Council.

Ozone was also high at Boulder A.I.R. monitoring stations in Longmont, Broomfield and Boulder where it violated federal standards two of the three days in Longmont and one day at Boulder Reservoir. Ozone is formed when sunlight mixes with VOCs and nitrogen oxide from vehicle emissions.

Ozone is more typical in the warmer months. Boulder A.I.R. looked at 20 years of data for Boulder ozone readings. "The March event was thus far the most extreme occurrence of this wintertime ozone seen in Colorado," Helmig said.

Particulate matter, or smog, also violated federal air quality standards during those three days. Weather contributed to the high readings. Helmig said pollutants were trapped by a strong inversion that kept air close to the ground, temperatures were low, and sunlight came from above and reflected off the snow.

Chronic exposure to air pollution is a health risk. A 2018 study by the US Environmental Protection Agency in the journal "Environmental Science and Technology" estimates that by 2025, 70 people in Colorado will die prematurely each year because of ozone and particulate emissions.

Longmont's air monitoring program is just over a year old. Turner said she believes the data have already had an impact on the state's tighter oil and gas regulations and will continue to inform the scientific understanding of Front Range air quality. The public is also able to stay informed through national and local websites that monitor air quality.

• http://www.bouldair.com/ - Air monitoring for Longmont, Boulder and other cities.
• airnow.gov - Easy way to check daily ozone levels by zip code.
• https://www.colorado.gov/airquality/all_sites_map_ags.aspx Colorado's CDPHE monitoring sites.
• https://www.youtube.com/watch?v=E9vIwYRnotE - Semi-annual air quality study presentation for Longmont City Council. Starts at 26:40.