Dissolved methane in New York groundwater, 1999—2011: U.S. Geological Survey Open-File Report 2012-1162, 6 p. by William M. Kappel and Elizabeth A. Nystrom, Prepared in cooperation with the New York State Department of Environmental Conservation, August 2012
In groundwater, methane can be dissolved or in a gaseous state. When methane is dissolved, it acts like the carbon dioxide gas used in carbonated beverages, where the gas is held within the fluid under the confining pressure of the sealed container. When the container is opened, pressure is reduced and some of the gas comes out of solution, which causes bubbling and fizzing in the beverage. In aquifers, methane may be confined by overlying fine-grained deposits or unfractured bedrock. Dissolved methane concentrations in confined aquifers can be much greater than the saturation concentration at atmospheric pressure. As groundwater enters a well at atmospheric pressure, the natural gas can be released from the water, which can cause a column of gas to form above the water surface in the well or be released within a pressure tank, at faucets inside a home, or in structures enclosing the well, where it can become flammable or explosive as a result (Eltschlager and others, 2001). Methane reaches saturation in water at 28 milligrams per liter (mg/L) at atmospheric pressure and becomes flammable in air at about 5 percent by volume (Eltschlager and others, 2001). The Office of Surface Mining recommends that methane concentrations greater than 28 mg/L in well water should be addressed immediately by removing any potential ignition source and venting the gas away from confined spaces (Eltschlager and others, 2001). The Office of Surface Mining also recommends that methane concentrations ranging from 10 to 28 mg/L in water (or 3 to 5 percent by volume in air) signify an action level where the situation should be closely monitored, and if the concentration increases, the area should be vented to prevent methane gas buildup.
Concentrations of methane less than 10 mg/L in water (or 1 to 3 percent by volume in air) are not as great a concern, but the gas should be monitored to observe if the concentrations increase over time (Eltschlager and others, 2001). Homeowners should contact their local or New York State Health Department for further information about measuring and mitigating ”action level” methane concentrations (as previously defined) in their water wells or in their homes. … Even though there are many gas-producing formations, relatively little data exist citing the occurrence, distribution, and concentration of methane in groundwater.
Since 2002, the USGS, in cooperation with New York State Department of Environmental Conservation (NYSDEC), has conducted groundwater-quality monitoring assessments in major river basins in New York. Since 2009, these assessments have included sampling for dissolved gases, including methane (Nystrom, 2011, 2012, and Reddy and Risen, 2011). By 2011, methane had been sampled in 8 of the 14 major river basins in the State. These data, combined with those from groundwater age-dating analyses, yielded dissolved methane concentrations from water wells at 239 locations in New York from 1999 to 2011 (fig. 3).
Samples collected through 2011 indicate that concentrations of methane in groundwater from most wells measured (91 percent of the wells) were at or below the Office of Surface Mining action level of 10 mg/L (Eltschlager and others, 2001), and a large number of wells (47 percent) had no detectable methane (fig. 4 and table 1). However, methane concentrations from several wells exceeded 10 mg/L (9 percent); in five cases, the measured concentrations were greater than 28 mg/L (2 percent).
In unconsolidated aquifers, 93 percent of the wells had non-detect to low-level methane concentrations (methane concentrations <1 mg/L), and less than 1 percent of the wells (one well) was greater than the saturation value of 28 mg/L. The greater methane concentrations are most likely associated with confined glacial aquifers over black shale bedrock. In bedrock formation aquifers, 73 percent of the methane concentrations were less than 1 mg/L, while nearly 4 percent had concentrations greater than 28 mg/L across the State. Three of the four highest methane values in bedrock wells were associated with Devonian-aged black shale bedrock; in total, many of the greater methane concentrations were most likely associated with wells drilled into these shales (fig. 3). …
The 1999–2011 analysis of dissolved methane in groundwater in New York is meant to document the natural occurrence of methane in the States aquifers. [Emphasis added]
[Depths of the water wells sampled is critical information not included in this report, nor is distance of the water wells to the more than 75,000 oil and gas wells drilled in the state since the late 1800’s of which 14,000 are still active, or rates of methane leakage from those energy wells especially those abandoned and poorly plugged (estimated at about 4,800)]
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