On Thursday, April 25, 2024 the Arizona Power Plant and Transmission Line Siting Committee (Siting Committee) voted to uphold the requirement that gas-fired power plants in Arizona must undergo environmental review before the Arizona Corporation Commission (Commission), and to apply that requirement to the proposed expansion of the gas-fired Black Mountain Generating Station. Sierra Club had intervened in the proceeding to support this result, presenting expert testimony and oral argument that persuaded the Siting Committee despite Commission staff’s arguments that the Committee lacked jurisdiction over the plant.
In March, UNS Electric proposed a 200 MW expansion at its gas-fired Black Mountain Generating Station. UNS attempted to skirt Arizona’s environmental review process for power plant siting by asserting that each of its four turbines should be considered individual 50 MW power plants rather than parts of a single 200 MW power plant. Because Arizona only requires review for plants over 100 MW, this interpretation would have allowed this expansion project to avoid environmental review. This could have set a dangerous precedent, since most new gas projects in the state consist of multiple turbines that are individually under 100 MW but collectively above the threshold. Arizona utilities are proposing to build thousands of MW of new gas capacity over the next decade, including over 1,000 MW this year alone.
Sierra Club presented expert witness testimony and oral argument at an April evidentiary hearing demonstrating why four units are not in fact or by law four separate power plants, and thus why environmental review is required for the project. At the end of the hearing, the Siting Committee determined that it had jurisdiction to review the Black Mountain project and that UNS must undergo environmental review, rejecting UNS's attempts to create a loophole in the siting statute. The Committee's decision affirms important precedent and protects the environmental review process for siting of multi-unit peaking gas plants.
Sierra Club was represented in this case by Environmental Law Program attorneys Patrick Woolsey and Nihal Shrinath. Managing Senior Analyst Cara Fogler provided expert witness testimony for Sierra Club. Sierra Club’s Grand Canyon Chapter raised public awareness, gathering petition signatures and organizing public commenters.
The press release is here.