A Maricopa County Superior Court judge overruled a decision by state regulators that cleared the way for a controversial gas power plant expansion in Mohave County.
Judge Dewain Fox’s ruling reversed a June 2024 decision by the Arizona Corporation Commission that would have allowed UNS Electric to construct a 200-megawatt expansion at its Black Mountain Generating Station without undergoing an environmental review.
The case highlights the complex web of laws, regulations and regulators that oversee power utilities in the state.
Arizona law requires utilities to obtain a certificate of environmental compatibility before building power plants larger than 100 megawatts, but the commission, which includes five commissioners elected by Arizona voters, found the project was exempt because it was divided into four 50-megawatt units.
That overturned an earlier vote by the Arizona Power Plant and Transmission Line Siting Committee, an unelected body created by state law to review new power plant and transmission line projects.
UNS Electric, the parent company of Tucson Electric Power and UniSource Energy, had asked the committee to find that dividing the expansion into four separate units exempted it the environmental review law.
Clean energy advocates and environmental groups argued that granting UNS Electric’s request would undermine the law passed in 1971 that requires a certificate of environmental compatibility for power plants larger than 100 megawatts and open the door for more utilities to bypass those rules.
“It is absurd to read the statute in a way that would require review of a project with one 100-megawatt turbine but no review of a project with 10 99-megawatt turbines,” Autumn Johnson with the Arizona Solar Energy Industries Association told the committee before the vote.
The committee voted 9-2 to reject the request, finding it ran counter to the way regulators have interpreted the law for decades and would have essentially rewritten the rulebook for building new power plants.
After the commission overturned the committee ruling, the Sierra Club, Western Resource Advocates and Arizona Attorney General Kris Mayes sued, arguing regulators misinterpreted state law.
The decision
While Fox overturned the Corporation Commission’s ruling, he sidestepped question about whether the commission correctly interpreted the state law.
Instead, Fox found that state law didn’t give the commission the power to review the committee’s rejection of UNS Electric’s request in the first place.
According to his decision, Fox found that state regulations do allow the commissioners to review committee decisions to grant or reject certificates of environmental review.
But, in the UNS Electric case, the committee never actually granted or denied a certificate. Instead, the committee simply rejected the utility’s request to be exempt from environmental review.
And that decision, Fox found, cannot be reversed by the commissioners.
“Because the regulations promulgated by the Commission do not provide for the Commission to review an order by the Committee denying a request to disclaim jurisdiction, the Court must conclude that the Commission exceeded its authority in issuing the Decision overturning the Committee Order,” according to the ruling.
A spokesman for UNS Electric declined to comment, saying it is “reviewing the decision and can’t provide further comment on pending legal matters.”
Next steps
The decision does not mean that UNS Electric cannot eventually build the Black Mountain expansion.
Fox sent the case back to regulators and directed the Power Plant and Line Siting Committee to consider the utility’s request for a certificate of environmental compatibility.
He also explained why he chose not to rule on who — the commission or the committee — correctly interpreted the state law requiring large power plants to undergo that environmental review.
Fox said doing so would be premature. He said the committee should first review the Black Mountain project and issue, or deny, a certificate.
“If that happens, the Commission then will have the opportunity to address the Committee’s findings and conclusions in that regard,” Fox wrote.
At that point, the issue could make it back to court.
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