Bastrop and Elgin will soon become home to two air quality monitoring stations that will contribute to Central Texas’ system for measuring ground-level ozone levels.

The Capitol Area Council of Governments, which operates eight monitoring stations throughout its 10-county region, is reconfiguring its monitoring system to better scrutinize smog conditions in the Austin-Round Rock metropolitan statistical area, which includes Travis, Williamson, Hays, Bastrop and Caldwell counties.

One monitoring station will be moved from McKinney Roughs Nature Park near Cedar Creek to Bastrop. An analysis released by CAPCOG in May shows that the station in its current location “could be better position to capture the high concentrations (of ozone) in the county.” When trees are too close to where a monitor is sampling the air, “scrubbing” can occur that impacts the station’s readings.

Ground-level ozone, which is a major factor in urban smog, forms from car and coal plant emissions and can exacerbate respiratory illnesses and diseases.

“By relocating the equipment to Bastrop, the station would be able to better represent conditions for the entire county, it would be closer to a population center, and would be located in an area where we expect to see higher air pollution levels,” said CAPCOG Director of Regional Services Andrew Hoekzema.

Using air quality data collected over the years, CAPCOG created a model that projects ozone levels across the metro area in 2020 based on emission fluctuations across the county.

In Bastrop County, the highest levels of ozone exist along the northeastern edge of the county around Paige where modeled ozone levels were measured at 62.6 parts per billion, which “appears to be attributable to the influence of the Fayette Power Plant.”

For comparison, federal ozone standards set by the Obama administration allow a maximum of 70 parts per billion. If that threshold is exceeded, the Environmental Protection Agency can place a county within the “non-attainment designation,” which triggers stricter federal restrictions on new or existing businesses and transportation projects. In July, the EPA designated San Antonio in non-attainment after the city had been working for years to reduce its emissions.

The lowest measured level of ozone in Bastrop County was found in an area near McKinney Roughs Nature Park, where ozone levels were measured at 59.4 parts per billion.

CAPCOG is also planning to move a monitoring station from Fayetteville in Fayette County to Elgin, where it would monitor ozone levels directly upwind of the Austin urban area on “days when wind is blowing in from the northeast,” the CAPCOG analysis said.

Officials are still scouting sites for these monitoring stations, Hoekzema said. CAPCOG hopes to begin collecting data at the new sites by the end of February.

Elevated ozone concentrations

CAPCOG’s analysis shows elevated ozone concentrations over the Austin-Round Rock metro area, as well as within a group of counties east and northeast of the metro. An overhead view of ozone patterns show plumes emanating from large coal-fired power plants in Fayette and Robertson counties, as well as from the Sandow power plant in Milam County, which was shuttered earlier this year. The plumes emitted from the metro area and the power plants are fanned by northwestern winds that blow ozone emissions into neighboring counties.

Of CAPCOG’s five-county metropolitan statistical area, Williamson County contained both the highest and lowest ozone measurements, with 66.1 parts per billion measured in the northernmost edges of the Austin city limits — in between Cedar Park and Round Rock — and 58.7 parts per billion measured along the northern edge of the county.