Utility regulators denied a request by Tucson Electric Power’s sister company to exempt a proposed 200-megawatt power plant expansion from environmental review. 

UniSource Energy filed a request with the Arizona Power Plant and Transmission Line Siting Committee, asking it to rule that the company should not have to undergo an environmental impact assessment for a proposed 200-megawatt expansion of the company’s Black Mountain Generation Station in Mohave County.

The request faced stiff opposition from multiple environmental and consumer advocacy groups, who cited a state law that requires a certificate of environmental compatibility for power plants larger than 100 megawatts.

“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,” said Autumn Johnson with the Arizona Solar Energy Industries Association.

But attorney Meghan Grabel, who represents the UniSource Energy, told the committee that requirement shouldn’t apply to UniSource Energy’s proposed expansion in Mohave County, citing the specific language in the law that defines a power plant as a “separate thermal electric, nuclear or hydroelectric generating unit with a nameplate rating of one hundred megawatts or more.”

Grabel said the Black Mountain expansion will be made up of four individual 50 megawatt units.

“There is no dispute that the nameplate rating for each of the new generators to be added to the Black Mountain Generation Station will be under 100 megawatts,” she said.

Grabel argued each unit will be “fully independent of one another,” though she acknowledged they will share some facilities. 

But critics argued Grabel’s interpretation of the law conflicted with the way regulators have interpreted the law since legislators passed it in 1971.

“UNS is proposing a novel and self-serving interpretation of the siting statute that would improperly evade the CEC requirement by treating four interconnected units within a single power plant as four separate plants,” said Patrick Woolsey, an attorney with the Sierra Club. 

UNS is the parent company of UniSource Energy. Woolsey argued that adopting its interpretation would stifle regulators’ ability to assess the environmental impact of new power plants moving forward.

The environmental groups pointed to similar power plant expansions that had to go before the committee and the Arizona Corporation Commission for a certificate of environmental compatibility in recent years. That includes Salt River Project’s Coolidge gas plant expansion, which features 12 units with a cumulative capacity of 575 megawatts.

The Arizona Power Plant and Transmission Line Siting Committee ultimately voted down the measure on a 9-2 vote. 

Gabby Saucedo Mercer, one of two committee members to vote in favor of approving UniSource’s request, said the law is flawed but agreed with Grabel that the plain language of the statute should exempt the UniSource plant from review.

“I have spoken to several legislators about it, and they agree that the statue is outdated and it does not fit with the new technology we have with renewable and sustainable energy as well as with solar and wind,” Mercer said. 

But Committee Chair Adam Stafford said that, despite the specific language of the law, the request to exempt the Black Mountain expansion from environmental review ran counter to the intent of legislators who passed the law 50 years ago.

“The Legislature hereby finds and declares that there is at present and will continue to be a growing need for electric service which will require the construction of major new facilities,” according to a legislative intent clause included in the law, which defined those major facilities as plants rated at 100 megawatts or more. “It is recognized that such facilities cannot be built without in some way affecting the physical environment where the facilities are located.”

“I think the logical interpretation of the statute is that if they share the same site, they are not separate. Period,” Stafford said.  

The decision does not put an end to the Black Mountain expansion. Instead, it means UniSource will have to undergo the standard certificate of environmental compatibility process. Under that process, the committee holds public hearings before voting to recommend approval or denial. If it votes to approve the certificate, the case goes to the Arizona Corporation Commission for a final vote.

The committee has not yet filed its official ruling denying UniSource's request. Nicole Garcia, a spokeswoman for the Corporation Commission, said UniSource can appeal the committee's decision within 15 days after the committee files that order.

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