(CN) - Shell Offshore Inc. can move ahead with plans for exploratory drilling in the Chukchi and Beaufort Seas off the North Slope of Alaska, the 9th Circuit ruled Wednesday.
The federal appeals court in Anchorage found that the EPA's Environmental Appeals Board had properly upheld two air permits allowing the oil giant to explore the Arctic waters using its drillship "Discoverer" and a fleet of support vessels.
Resisting Environmental Destruction on Indigenous Lands and other environmental groups challenged the permits in 2010. The group wanted the agency to require the entire fleet to use "best available control technology" (BACT) to control emissions whenever it is operating within 25 miles of the drillship.
As it is, the permit requires that the Discoverer and its supply vessel use such technology only when the drillship is attached to the seabed at a drill site by at least one anchor. The permits do not place any technological requirements on the other vessels in the fleet. The groups also objected to an exemption of the area within a 500-meter radius of the drillship from ambient air quality standards.
The plaintiffs lost two rounds before the Environmental Appeals Board before taking the issue to the 9th Circuit. A unanimous three-judge panel affirmed on Wednesday, deferring to the EPA's interpretation of its own regulations because "the statute is ambiguous as to application of BACT to associated vessels within 25 miles of an OCS source.
"We defer to the EPA's reasonable construction of the statute, as adopted by the EAB, that BACT does not apply to mobile support vessels unattached to the drillship," wrote Judge M. Margaret McKeown for the panel.
Similarly, the panel agreed with the appeals board that the agency had properly allowed the ambient air exemption, which requires the U.S. Coast Guard's to establish "an effective safety zone precluding public access to the area."
"Constructing a fence in the Arctic Ocean would make little sense, and the EPA has previously recognized a safety zone established by the Coast Guard as evidence of sufficient ownership or control over open water areas to qualify as a boundary for defining ambient air,"McKeown wrote. "We conclude that the EPA's grant of an ambient air exemption to Shell conditioned on an effective safety zone excluding the public is a permissible interpretation of its ambient air regulation and earlier letter ruling."