Fort Worth air study misses the mark on gas industry compressors

The three natural gas company representatives on Fort Worth's Air Quality Study Committee are angry about the $1 million-plus consultant's report that has resulted from the committee's work more than a year ago.

They have a right to be mad. The report paints an unfair picture of potentially hazardous emissions from gas pipeline compressor engines.

Predominantly, the report received last week from Eastern Research Group shows no significant danger to public health due to emissions from Barnett Shale natural gas wells and related operations. Gas drilling in and around Fort Worth has boomed since 2002, with almost 2,000 permits issued within the city so far.

After receiving conflicting reports from state officials about the air quality around those operations in late 2009 and early 2010, the City Council named a 10-person committee of local residents and others to help design a study of potential dangers. The committee included representatives of Chesapeake Energy, Devon Energy and XTO Energy.

ERG's study was commissioned by the council in August, following the committee's recommendation. It included using delicate instruments to test for emissions at 388 well pads, compressor stations, processing facilities and other sites.

ERG also set up monitors to sample for pollutants in ambient air downwind of natural gas sites.

From all the data gathered through that testing, ERG built models to show how natural gas site emissions might disperse throughout the city.

Only two pollutants were shown in that modeling to be potential dangers, ERG's report says. Those pollutants are acrolein and formaldehyde, both of which are respiratory irritants. They are byproducts of combustion, showing up in the exhaust from compressor engines.

ERG's modeling for large compressor stations, some with 1,500-horsepower engines, showed acrolein in concentrations exceeding regulatory limits for long-term exposure "several hundred feet" beyond the city's prescribed distance between gas facilities and homes or other protected properties. Levels were also too high for short-term exposure.

For sites with multiple large engines, the modeling predicted formaldehyde at nearly three times the short-term health-protective concentration set by the Texas Commission on Environmental Quality.

None of the pollutants reached levels known to cause adverse health effects. Regulatory limits are designed to be lower than that as a safety cushion.

Still, it's worrisome. But it's not real-world data.

ERG did not measure exhaust stack emissions from the compressor engines. In its modeling, the consultant used information from engine manufacturers as to what emissions levels could be expected.

More importantly, ERG's modeling assumed no pollution control equipment was used on the engines. The Air Quality Study Committee's natural gas industry representatives strongly objected.

Pollution control equipment is used on "100 percent of our engines," said XTO's Nina Hutton.

Chesapeake's John Satterfield called the projections "irresponsible."

Emotions both for and against urban natural gas drilling run high. From the Air Quality Study Committee's first meeting early last year until today, it has been clear that the study would have to be of the highest quality or it would lack credibility.

For the most part, ERG has achieved that. But to the extent that its report raises alarm about emissions from compressor engines, it is not fully credible. Without measuring exhaust stack emissions in the presence of whatever pollution control equipment is in use, it does not answer the questions it was supposed to answer.

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