The U.S. Environmental Protection Agency is approving a source-specific revision to the Arizona State Implementation Plan (SIP) that establishes an alternative to best available retrofit technology (BART) for Steam Units 2 and 3 (ST2 and ST3) at Arizona Electric Power Cooperative’s (AEPCO) Apache Generating Station.
Under the BART Alternative, ST2 will be converted from a primarily coal-fired unit to a unit that combusts pipeline-quality natural gas, while ST3 will remain as a coal-fired unit and would be retrofitted with selective non-catalytic reduction (SNCR) control technology, said EPA in a notice to be published in the April 10 Federal Register. The SIP revision also revises the emission limit for NOX applicable to Apache Steam Unit 1 (ST1), when it is operated in combined-cycle mode with Gas Turbine 1 (GT1).
“EPA has determined that the BART Alternative for ST2 and ST3 would provide greater reasonable progress toward natural visibility conditions than BART, in accordance with the requirements of the Clean Air Act (CAA) and EPA’s Regional Haze Rule (RHR),” the agency said. “Accordingly, we are approving all elements of the SIP revision, with the exception of a provision pertaining to affirmative defenses for malfunctions. In conjunction with this final approval, we are withdrawing those portions of the Arizona Federal Implementation Plan (FIP) that address BART for Apache.”
This final rule will be effective 30 days from the April 10 publication in the Federal Register.
In September 2014, EPA proposed to approve this revision to the Arizona Regional Haze SIP concerning Apache Generating Station. As described in the proposal, the Apache SIP Revision consists of two components: a BART alternative for ST2 and ST3 (“Apache BART Alternative”) and a revised NOX emission limit for ST1 and GT1 when operated in combined-cycle mode. The Apache BART Alternative was submitted under provisions of the Regional haze Rule (RHR) that allow states to adopt alternative measures in lieu of source-specific BART controls, if they can demonstrate that the alternative measures provide greater reasonable progress towards natural visibility conditions than BART.
Under the Apache BART Alternative, ST2 would be converted from a primarily coal-fired unit to a unit that combusts pipeline-quality natural gas, while ST3 would remain as a coal-fired unit and would be retrofitted with SNCR. Emission limits to implement the Apache BART Alternative and the revised limit for ST1 and GT1, as well as associated compliance deadlines and monitoring, recordkeeping, and reporting requirements, are incorporated into an addendum to Apache’s Operating Permit, which was submitted as part of the Apache SIP Revision.
In the April 10 notice, EPA responds to criticisms of this proposal from various environmental organizations that were filed after the September 2014 notice of intent to approve. Said one EPA response: “We do not agree that we can amend the Apache BART Alternative to provide greater emission reductions. Under the [Clean Air Act], if EPA determines that a SIP meets the requirements of the CAA and EPA’s implementing regulations, we are obligated to approve the SIP. For the reasons described in our proposal and elsewhere in this document, we have determined that the Apache SIP revision meets the applicable requirements of the CAA and EPA’s regulations, and we are therefore required to approve it.”
Apache was first constructed with the installation of Steam Unit 1 (ST1), a 72 net MW steam unit in 1963 and Gas Turbine 1 (GT1), a 10 net MW simple cycle gas turbine in 1964. In 1978-1979, AEPCO added ST2 and ST3, almost identical Riley Stoker turbo-fired boiler units with a 175 net MW capacity each. ST2 and ST3 are AEPCO’s only coal-fired units. Other simple cycle combustion turbines (GT2, GT3 and GT4) were added later.