The U.S. Environmental Protection Agency (EPA) has updated oil and gas storage tank emission standards it released in April 2012 to allow the phase-in of emission control deadlines and to alleviate confusion over implementation of the requirements.

The oil and natural gas industry uses tanks for temporary storage of crude oil, condensate and other liquids before they are moved to a pipeline, sold or moved for disposal. Storage tanks can be sources of emissions of ozone-forming volatile organic compounds (VOC), along with several toxic air pollutants, including benzene.

Higher-emitting tanks will be affected by the new requirements first. The rule changes also provide time for operators to acquire and install necessary emissions controls, EPA said. The changes are in response to stakeholder comments that revealed that more storage tanks will be coming online than EPA had originally thought.

Storage tanks that emit six or more tons of VOCs per year must reduce emissions by 95%. Two control deadlines were established by the latest changes:

The updated standards also establish an alternative emissions limit that would allow owners/operators to remove controls from tanks if they can demonstrate that the tanks emit less than four tons per year of VOC emissions without controls. In addition, the rule streamlines compliance and monitoring requirements for tanks that have already installed controls, EPA said.

The updates respond to petitions for reconsideration of the “2012 New Source Performance Standards for Oil and Natural Gas Production.”