The Marcellus Shale Coalition (MSC) on Tuesday published recommended practices to respond to stray gas incidents, the fourth in a series of guidance documents published by the industry group.

Stray gas may originate from various sources, including coalbeds, oil and natural gas wells, landfills, pipelines, naturally occurring methane and microbial gas, according to the MSC. Gas migrates from one of the sources into groundwater, a structure, surface water and soil. A “well documented history of stray gas incidents” has occurred in rural communities, including many areas of Appalachia, the coalition said.

“Over the past several years, our industry has frequently identified the presence of stray gas during pre-drill baseline water surveys,” said MSC President Kathryn Klaber. “This document provides detailed steps that operators can take when stray gas is encountered — from developing proper plans of action, to notification of regulators as well as initial response actions and performing site reconnaissance surveys. Each of these key steps helps ensure that public safety and environmental concerns are mitigated and resolved in a responsible and timely manner.”

Stray gas may be influenced by a number of factors, including changes in barometric pressure, soil and bedrock permeability, temperature contrasts and other weather related conditions, such as rain or snow among others, the MSC said.

“When responding to a stray gas incident, maintaining lines of communication with state regulators, local officials, first responders and homeowners is crucial,” according to the guidance. “Depending on the identified levels and location of the methane, oil and natural gas producers can take a number of steps based upon initial response and assessment. Should stray gas be detected in a structure, ventilation and methane-specific alarms may be installed as a precautionary measure.

“Similarly, vents may also be installed if methane is detected in water wells at heightened levels. When dissolved methane is detected in a water source servicing a structure, operators should consider providing an alternate water source until additional testing is completed to determine the source of the stray gas.”

“Our organization, as laid out in our guiding principles, is committed to operational transparency and environmental protection,” said Klaber. “This product will further assist operators in addressing cases of stray gas when encountered. Core to this document is the importance of safety of our employees, contractors and the general public.”

The MSC previously published guidance documents for operators on recommended practices for site planning development and restoration, supply chains, and water testing.