The largest source of leaks of the potent greenhouse gas methane may be the spider web of largely unregulated pipes transporting it from drilling sites to processing facilities, according to new research from the Environmental Defense Fund. This 425,000-mile network network of pipes is overseen by the little known Pipelines and Hazardous Materials Safety Administration, but according to the report less than 3% of the so-called gathering lines are actually regulated by the federal agency.

Research suggests gas gathering, transmission, and distribution account for a significant portion of methane leakage from the oil and gas industry, and gas distribution pipelines alone may leak about five times more methane than EPA assumes. Most of the nation’s gas delivery system falls under the regulatory purview of PHMSA, and leaking and venting gas into the atmosphere is a regular course of business for pipelines. In November, PHMSA rolled out new regulations to reduce leaks from gathering lines in rural areas, the location of which are often unknown even to the companies that own them, for the first time. (E&E $)