Apr 23, 2014 4 min read

Results of air sampling conducted following the explosion at the Chevron Appalachia well site in Dunkard Township indicate no pollutants at concentration levels harmful to local residents or emergency responders, the state Department of Environmental Protection said Wednesday.

Chevron’s Lanco well pad exploded Feb. 11, killing one worker and injuring another. Two wells on the pad damaged by the explosion burned for several days and then continued to release gas until they were successfully capped.

DEP took samples at several sites, upwind and downwind of the well pad, from Feb. 12, the day following the explosion, to Feb. 20, the day the wells were capped. The samples were analyzed for 57 toxic air pollutants.

“It was a top priority of the department to be certain that emergency response workers and nearby residents were not harmed by any emissions caused by this incident,” DEP Secretary E. Christopher Abruzzo said.

DEP tested for a large number of pollutants, including those normally associated with a fire and an uncontrolled release at a natural gas well site, said John Poister, DEP spokesman.

“We wanted to test for as many chemicals as possible, even those remotely connected to this type of incident, to make sure we were covered,” he said.

None of the levels of pollutants detected during the nine-day period in which the sampling was conducted presented a threat to health, Poister said.

Propane, heptane and 1,2,4-trimethylbenzene, however, were detected at higher concentrations than are normally found in other rural areas across the state. DEP could not verify the higher concentration of these chemicals resulted from the fire and gas release at the well site, Poister said.

Heptane often comes from crude oil and is used in paints and solvents; 1,2,4-trimethylbenzene is usually found in coal tar or oil; and the higher concentrations of propane are believed to have come from nearby storage tanks, DEP said.

While these chemicals were “likely” associated with the release and burning of “wet” natural gas and equipment damaged on site, the detection of 1,2 dichlorotetrafluoroethane, was unexpected, the report said.

This chemical is a nonflammable refrigerant that may have been in materials used by emergency responders to fight the fire or was contained in on-site cooling or fire suppression equipment, DEP said.

To tests for air quality, DEP had used air sampling canisters to collect both instantaneous samples, referred to as grab samples, and 24-hour continuous samples.

Each day, two grab samples were collected near residences downwind of the well site. For an air quality benchmark, a single daily upwind grab sample was also taken. In addition, a 24-hour continuous sample was taken at one of the two downwind sample sites.

DEP compared the upwind and downwind samples to estimate the air toxics concentration during the nine days of the event. The samples were also compared to data gathered by the 24-hour method.

DEP also compared the sample readings with historic toxic air concentrations at three other air monitoring sites in the state to determine the extent of any toxic pollution during the incident.

Samples gathered at the Greene County site were compared to a rural site generally not impacted by air pollution in Arendtsville, Adams County, and two urban sites with differing toxic pollution sources, Charleroi, Washington County, and Marcus Hook, Delaware County.

The control sites served as a benchmark to indicate typical air quality for this region of the state, providing DEP with a better understanding of any impact that may have resulted from the incident, DEP said.

DEP continues to investigate the cause of the explosion, Poister said.

The department earlier released a report on radiation studies completed at the site that showed no radiation levels had exceeded normal “background” levels. No testing of groundwater was conducted. Poister said the agency didn’t believe that was necessary because the explosion and fire were confined to the well site.