State says H2S is not a public health risk in Garfield County |

State says H2S is not a public health risk in Garfield County

John Colson
Post Independent staff
Glenwood Springs, CO Colorado

Colorado’s agency overseeing the oil and gas industry has concluded that there is no public health risk from hydrogen sulfide at gas well pads in Garfield County.

A selective sample testing of wells in Garfield County operated by Antero Resources, Williams Production RMT, Laramie Energy and EnCana Oil and Gas (USA) indicated only very low levels of the gas, said David Neslin, director of the Colorado Oil and Gas Conservation Commission (COGCC).

“Based on the information we have collected to date, with respect to all of these wells, we have determined that there isn’t a risk to the public,” Neslin said.

The COGCC has been investigating the occurrence of hydrogen sulfide, or H2S, ever since reports were uncovered last March in the agency’s paperwork archives that showed deadly levels of the gas at well pads operated by Noble Energy.

In a presentation last month to the Northwest Colorado Oil and Gas Forum in Rifle, Stuart Ellsworth, engineering manager for the oil and gas commission, said a search of the agency’s records showed that hydrogen sulfide gas has been reported at 312 of Noble’s 353 producing wells in the area.

Most of the reports involved low levels of the gas, below 10 parts per million (ppm), considered safe for humans and detectable as an odor of rotten eggs, according to the U.S. Centers for Disease Control.

But at least one reading at a Noble well showed H2S at a level of 450 ppm.

The gas is considered lethal at 500 parts per million, and can cause sickness, respiratory distress, severe irritation of the eyes and other problems at lesser levels, according to the U.S. Centers for Disease Control and other sources.

If the exposure continues at 100 ppm for several hours, Ellsworth reported, “death may occur within the next 48 hours.”

Neslin said there have been no high H2S readings discovered at the wells of other operators in Garfield County, after operators conducted a “selective sample” of wells.

He said Antero reported testing for H2S at 24 wells, and that the gas was “undetectable” at 18 of those wells.

At six Antero wells, he said, the company reported readings between one-tenth of one part per million (0.1 ppm) and three-tenths of a part per million.

At Williams sites, Neslin said, two wells were tested and one came up clean for H2S, while the other showed 1 part per million.

The one Laramie well tested, Neslin reported, showed H2S at 5 parts per million.

EnCana, he said, tested three wells, and reported readings of zero at one well, 6.9 ppm at a second well, and 25 ppm at the third.

“If someone has additional information, we encourage them to report that to us,” Neslin said, particularly readings of higher levels.

Reports of readings in the 1,000 ppm range at Antero well pads, received in telephone calls to the Post Independent, are not accurate, according to Antero vice president Kevin Kilstrom.

“We deny any presence of H2S such as you are suggesting,” Kilstrom told the Post Independent in an e-mail.

“Such high levels of H2S are extremely dangerous,” Kilstrom continued, asking that any information about such high readings be sent to him “so we could thoroughly investigate.”

Neslin suggested that such high readings could only come from inside tanks that had contained H2S, rather than outside in the open air.

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