Granbury coalition expands ozone monitoring after recent rise in readings

Granbury — The Hood County Clean Air Coalition told the Granbury City Council on June 17 that it has installed five air monitors around Hood County as part of a monitoring project intended to explain recent increases in ozone measurements and guide possible local responses.

The coalition, administered by the city of Granbury, said the monitoring project is funded through an interlocal agreement with the North Central Texas Council of Governments (NCTCOG) using a Texas Commission on Environmental Quality (TCEQ) Rider 7 ozone planning grant. Michelle McKenzie, the coalition’s air quality program manager, described hourly readings from five sites and said the county’s current design value sits at 72 parts per billion, a rise from earlier years.

The project matters because a sustained rise in ozone readings could put Hood County at risk of a federal “nonattainment” designation, which would trigger regulatory changes such as vehicle emissions inspections and could affect local industry and residents’ daily life. McKenzie told council members the coalition hopes the new measurements will help distinguish local emissions from ozone transported into the county.

McKenzie said the monitoring network includes one TCEQ regulatory monitor in Granbury and four additional monitor locations around the county, plus a fifth monitor placed in Somerville County to measure potential ozone transport from the south. "We were going down for several years, but since about 2022, it started going the opposite direction," McKenzie said of the county’s design value. She said four sites have sensors measuring ozone, nitrogen oxide and particulate matter; all five sites use federally equivalent method (FEM) ozone monitors and have weather stations to allow correlation of pollutant levels with wind and temperature.

McKenzie said the monitoring equipment is being operated by the Texas A&M Transportation Institute and that the project’s roughly $200,000 equipment-and-operations budget comes from the Rider 7 grant administered through NCTCOG. She noted that some of the low-cost, solar-powered sensors had early performance issues at sheltered locations but are working better in the summer.

Councilmembers pressed on what the data can show about sources. Councilmember Rodriguez asked whether the coalition could identify particular industrial zones or facilities; McKenzie said that is the goal of the combined monitoring and the county emission-inventory review, and that she expects to have more to share after TCEQ reviews the draft inventory. "Mostly, initially just to keep us going. But additionally... any outreach that if we do find that there are things that could be done with the industrial sites, any assistance in contacting those people... would be greatly appreciated," she said.

Mark Franco, the coalition board chairman, told the council he lives near the Wolf Hollow power plant and said the county’s design value began rising around 2022 when a peaker unit at Wolf Hollow became full-time to supply nearby cryptocurrency operations. "When we started increasing, the design value was in 2022, and that's when that peaker plant at Wolf Hollow became permanent and full time to supply the cryptocurrency plant with the energy that they need to operate," Franco said. He and McKenzie both said it is too early to draw a causal link and that the project is meant to provide factual data for analysis.

McKenzie also noted that particulate matter (PM2.5) readings have been higher at the Rancho Brazos site, and described PM2.5 as tied to cardiovascular and respiratory health risks. She said the coalition’s other work includes an emissions-inventory review covering on-road, off-road, point and area sources; the draft inventory has already been received by the coalition and awaits TCEQ review.

Council members and the mayor thanked the coalition for its work and for continued local support. McKenzie said the monitoring project is intended to produce data that can be layered with weather information and the emissions inventory to help determine whether local controls, outreach to industry, or other actions are needed.

Council members asked the coalition to return with analysis once the TCEQ-reviewed inventory is available. The coalition briefed the council but did not seek any formal council action at the June 17 meeting.