Document 7O12Dg5aRzYJr30oExad7KXYB

Presidential Exemption Request GVEA Healy Power Plant March 31, 2025 estimate filterable PM emissions at any time using the PM CEMS. The initial correlation requires a minimum of 15 source test runs and must meet the performance criteria in PS-11. If the correlation does not meet the performance criteria, then additional runs must be performed. After the initial correlation, quarterly audits are required to ensure that the correlation remains accurate. The annual relative response audits (RRA) require a minimum of three additional source test runs, with triennial relative correlation audits (RCA) requiring twelve additional source test runs. Per a 2012 Consent Decree, GVEA operates PM GEMS on both Healy EGUs to demonstrate compliance with a PM emission limit of 0.020 lb/MMBtu. Over the last ten years GVEA has invested considerable funds and effort to establish and maintain the performance requirements for the PM CEMS, and in doing so, GVEA has learned a great deal about the challenges and limitations of operating PM CEMS. Based on this experience, GVEA does not believe it is technically feasible to establish and maintain PM GEMS correlations in compliance with PS11 under the new emission standard. GVEA has been required to re-establish the correlation of a PM CEMS on several occasions over the past decade when audit results did not meet the EPArequired performance standards. GVEA has struggled for years with the Healy Power Plant's Unit 1 and Unit 2 PM CEMS to obtain and maintain valid correlations, pass relative response audits and relative correlation audits in accordance with EPA requirements, and keep the instruments operating to maintain the required monitor availability. Each correlation requires contracting, coordination, regulatory notifications, and mobilization of specialized equipment and qualified source testing personnel to the power plant location in remote Healy, Alaska for multiple days of onsite testing. The tests are expensive, disruptive and cumbersome to balance with plant operations and power generation needs. Given GVEA's historic struggles in obtaining valid PM correlations under the existing performance specifications and applicable PM emissions limit, GVEA believes it is technically infeasible to obtain valid PM correlations under the new, lower MATS standard of 0.010 lb/MMBtu following the PS-11. The following PS11 performance criteria are inversely dependent on the emissions limit and therefore become increasingly difficult to attain as the emission limit is lowered. As an example, the effect the new PM standard will have on these performance criteria for GVEA's current correlation equations for the Healy Unit 1 and Unit 2 PM CEMS are noted. 1) Confidence Interval Half Range (CI) Performance Specification = 10% CI on current Unit 1 correlation equation = 4.58% (Pass) o CI on Unit 1 correlation under new PM standard = 9.16% (Pass) Page 5 of 8 Sierra Club FOIA 2025-EPA-04883 ED_018388_00000057-00005 SC_EVERSPLIT0005605