The battle lines over proposed rules governing new sources of methane emissions from the oil and natural gas industry continued to form, with nine states, the city of Chicago and a half-dozen environmental groups lining up to support the U.S. Environmental Protection Agency (EPA).

On Monday, the nine states — California, Connecticut, Illinois, Massachusetts, New Mexico, New York, Oregon, Rhode Island and Vermont — and the City of Chicago filed an unopposed motion to intervene as respondents in the case State of North Dakota et al v. EPA et al [16-1242] in U.S. District Court of Appeals for the District of Columbia Circuit.

Meanwhile, six environmental groups — the Natural Resources Defense Council, the Environmental Defense Fund, the Sierra Club, the Clean Air Council, Earthworks and the Environmental Integrity Project — filed a separate motion to intervene on behalf of the EPA on Monday.

At issue are three final rules governing methane emissions that the EPA unveiled in May (see Shale Daily, May 12). The rules, collectively updates to the New Source Performance Standards (NSPS), are designed to reduce methane, volatile organic compounds (VOC) and toxic air pollutants. The agency said its actions would help the Obama administration meet its goal of slashing methane emissions from the oil and gas sector by 40-45% from 2012 levels by the year 2025.

“By providing a national minimum standard for new and modified oil and gas sources, the final rule represents an important step toward addressing a significant nationwide source of potent greenhouse gas emissions, forms a strong foundation for further EPA efforts to limit methane emissions, and helps supplement and strengthen state efforts,” the states wrote in their petition. “Because the final rule would further the state and municipal intervenors’ goals and efforts, and would do so on a nationwide basis, [they] have a strong interest in defending it.”

Texas joined North Dakota in opposition to the new rules earlier this month (see Daily GPI, Aug. 2). Court records show 11 other states — Alabama, Arizona, Kansas, Kentucky, Louisiana, Montana, Ohio, Oklahoma, South Carolina, West Virginia and Wisconsin — plus the attorney general for Michigan are also petitioners opposed to the new rules.

Court records also show at eight other cases have so far been consolidated with State of North Dakota et al v. EPA et al. Oral arguments have not yet been scheduled.

Other petitioners include various state oil and gas industry groups, plus the Independent Petroleum Association of America, the Western Energy Alliance, the GPA Midstream Association, the American Petroleum Institute and the Interstate Natural Gas Association of America.

According to EPA, the NSPS will build upon VOC emission reduction requirements for new oil and gas wells that the agency first unveiled in April 2012 (see Daily GPI, April 19, 2012). Those requirements called for a two-phase process to reduce VOCs: requiring flaring followed by “green completions,” a term that means deploying equipment to capture and sell natural gas emissions that are otherwise lost.

EPA said it expects the NSPS will reduce 510,000 short tons of methane in 2025, which is the equivalent of reducing 11 million metric tons of carbon dioxide. The rules are also expected to reduce other pollutants, including 210,000 tons of VOCs and 3,900 tons of air toxics, in the year 2025.