PORTLAND, Ore. (AP) — Federal regulators have approved the expansion of a natural gas pipeline in the Pacific Northwest over the protest of environmental groups and top officials in West Coast states.

The project, known as GTN Xpress, aims to expand the capacity of the Gas Transmission Northwest pipeline, which runs through Idaho, Washington and Oregon, by about 150 million cubic feet (4.2 million cubic meters) of natural gas per day. The Federal Energy Regulatory Commission gave it the green light in a vote on Thursday.

The pipeline belongs to TC Energy of Calgary, Canada — the same company behind the now-abandoned Keystone XL crude oil pipeline.

TC Energy plans to modify three compressor stations along the pipeline — in Kootenai County, Idaho; Walla Walla County, Washington; and Sherman County, Oregon. Compressor stations help maintain the pressure and flow of gas over long distances in a pipeline.

The company says the project is necessary to meet consumer demand.

The 1,377-mile (2,216-kilometer) pipeline runs from the Canadian border through a corner of Idaho and into Washington state and Oregon, connecting with a pipeline going into California.

Officials from Washington, Oregon and California called on federal regulators to reject the project, saying it would undermine their states’ efforts to reduce emissions to combat the effects of climate change.

The attorneys general of the three states, citing the Federal Energy Regulatory Commission’s draft environmental impact statement for the project, said it would result in more than 3.47 million metric tons of greenhouse gas emissions per year for at least the next three decades. The agency’s final environmental assessment revised that number downward by roughly half in calculations contested by environmental groups.

The agency’s chairman, Willie Phillips, reiterated its stance after Thursday’s vote.

“There was no evidence presented that this project would significantly increase greenhouse gas emissions,” he told reporters. “The commission determined that this project was needed and therefore we support its approval.”

In a joint letter to the federal agency the day before its vote, Democratic U.S. Senators Ron Wyden and Jeff Merkley of Oregon and Patty Murray and Maria Cantwell of Washington described the project as “incompatible with our climate laws.”

“GTN Xpress represents a significant expansion of methane gas infrastructure at a time when California, Oregon, and Washington are moving away from fossil fuels,” the senators said.

The senators also expressed concern about TC Energy’s safety record. Its Columbia Gas Transmission pipeline exploded in Strasburg, Virginia, in July and its existing Keystone pipeline spilled nearly 600,000 gallons of bitumen oil in Kansas last December.

Environmental groups criticized the decision of the Federal Energy Regulatory Commission, or FERC.

“FERC failed to listen to Senators, Governors, State Attorneys General, Tribes, and the public in its rubber stamp of unnecessary fracked gas in the Northwest,” said Audrey Leonard, staff attorney for Columbia Riverkeeper, an environmental nonprofit, in a statement.

Leonard said potential spills and explosions on the pipeline, which was built in the 1960s, would not only harm the environment but also present a heightened wildfire risk in the arid regions it passes through.

“An explosion of that level in eastern Washington or eastern Oregon would be catastrophic,” said Audrey Leonard, staff attorney for Columbia Riverkeeper, an environmental nonprofit.

Leonard said Columbia Riverkeeper will appeal the federal regulators’ decision and submit a petition for a rehearing.

In its final environmental impact statement for the project issued last November, the federal agency said the compressor stations were in non-forested areas with low to moderate fire hazard. It concluded the project “would result in limited adverse impacts on the environment.”

“Most adverse environmental impacts would be temporary or short-term,” the federal agency said.

The agency recommended certain steps, such as requiring the company to train its personnel and contractors on environmental mitigation measures before any construction begins.

But environmental groups say the assessment didn’t adequately address the harm caused by the project, including by fracking to obtain the natural gas that flows through the pipeline.

Fracking is a technique used by the energy industry to extract oil and gas from rock by injecting high-pressure mixtures of water, sand or gravel and chemicals. It has been criticized by climate and environment groups for increasing emissions of methane, an extraordinarily potent greenhouse gas.

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Claire Rush is a corps member for the Associated Press/Report for America Statehouse News Initiative. Report for America is a nonprofit national service program that places journalists in local newsrooms to report on undercovered issues.