Measurements in recent years of naturally occurring methane in New York State wells could serve as a base line for assuring the quality of water supplies if and when fracking for natural gas gets under way in the state, the United States Geological Survey reported this week.
The agency said that 9 percent of groundwater samples taken from more than 200 wells between 1999 and 2011 showed levels of methane that were high enough to warrant further monitoring or concrete steps ?to avoid possible explosive conditions.?
Methane, a potent greenhouse gas, is highly flammable and can cause explosions in confined spaces if ignited by an open flame or an electrical spark. It can be present in dissolved form in water from wells and as gas in the air space above the well water.
Methane has also been associated with oil and gas drilling operations, a matter of concern for people whose water supplies are in close proximity to proposed fracking sites. Hydraulic fracturing involves drilling into underground shale deposits and injecting water and chemicals under high pressure to release natural gas.
?Any time you drill a hole into the ground, you?re creating potential pathways for gas to move,? said William Kappel, a hydrogeologist with the Geological Survey. ?It can bring gas from a deeper source up to the surface. That?s why it?s important? to understand what your base line is now.?
The methane levels measured in New York, where about 30 percent of the population, or six million people, get their drinking water from wells, are similar to those taken in other Northeastern states as part of the Geological Survey?s studies on groundwater quality, the agency said.
In New York, 91 percent of the samples tested either registered no dissolved methane or contained
it in levels below the threshold that would require monitoring. But 7 percent of the wells tested had methane levels above 10 milligrams per liter, the agency said, high enough to encourage owners to contact the local health department for information about how to monitor or fix the problem.
Another 2 percent had more than 28 milligrams per liter, ?a level that requires removal of any potential ignition source and venting the gas away from confined spaces to avoid possible explosive conditions,? the agency said.
?Methane in groundwater has been much in the news on account of the???potential association with unconventional energy development, but citizens need to be aware that methane occurs naturally in some?groundwater systems,? the Geological Survey?s director, Marcia McNutt, said in a statement. ?When present, methane can be dangerous and yet difficult to detect by the consumer, hence the importance of testing groundwater for the presence of this dissolved gas.?
Mr. Kappel said that ideally, well owners should have their wells tested at least once a year.
?People need to understand they can?t smell methane or taste it,? he said.
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