Local air regulators on Friday upheld their approval of a major refinery upgrade in Carson, despite vociferous community and environmental opposition.

The South Coast Air Quality Management District board of governors unanimously voted to uphold staff approval of an upgrade of a Phillips 66 refinery in the South Bay city, rejecting an appeal by Communities for a Better Environment.

Phillips 66 is proposing a new 615,000 barrel oil storage tank and two new oil transfer pumps to increase the production capacity at the refinery. The Houston company has proposed the upgrades to increase capacity and to be able to handle oil imported from the Bakken fields in North Dakota, which is a different consistency than the oil the refinery currently handles.

Air district staff approved the project in December and issued what’s called a “negative declaration,” meaning staff deemed the project not to have a significant environmental impact.

But Communities for a Better Environment argued that the capacity expansion and the refining of Bakken crude increases air pollution, carbon emission and the risk of explosions. The group filed for an appeal early last month, then last week filed a lawsuit in state Superior Court in Los Angeles, seeking a full environmental impact report on the project.

The air board on Friday rejected the appeal, thereby upholding the staff approval. But, after several hours of contentious testimony, the board also left open the possibility that one of its committees could hold a hearing on the Phillips 66 project in coming weeks.