Document 5zya38n48XbnQQd4oJae2GX8

Presidential Exemption Request GVEA Healy Power Plant March 31, 2025 CI on current Unit 2 correlation equation = 5.28% (Pass) o CI on Unit 2 correlation under new PM standard = 10.56% (Fail) 2) Tolerance Interval Half Range (TI) Performance Specification = 25% TI on current Unit 1 correlation equation = 14.7% (Pass) TI on Unit 1 correlation under new PM standard = 29.4% (Fail) TI on current Unit 2 correlation equation = 16.7% (Pass) TI on Unit 2 correlation under new PM standard = 33.4% (Fail) This means that the valid correlations currently established for the Unit 1 and Unit 2 PM CEMS would no longer be acceptable with the lower emissions limit, and new PM CEMS correlations would have to be developed meeting the more restrictive requirements. In public comments on the proposed MATS rule amendment, many commenters questioned the feasibility of obtaining valid PM correlations following PS-11 under the proposed lower PM emissions standard. EPA's response was to increase the volume of PM required to be collected during a test run from 1 dscm to 4 dscm. While this change may improve the poor accuracy of the empirical PM results at the lowest PM emission rates, it will also increase each test run duration from 1 hour to 3 hours. This means that a periodic PM correlation or RCA test that currently takes days will, under the new PM standard, instead take weeks. The longer duration of an already difficult test will increase the potential for test protocol upsets, personnel fatigue, and equipment failures, and will diminish GVEA's ability to dispatch its generating resources in accordance with electrical demand, maintenance and economic needs. Extending the duration of these already cumbersome periodic tests will result in an even greater cost to GVEA's member-owners and even more disruption to power plant operations. Based on GVEA's experience, it is not technically feasible to consistently complete an adequate number of valid test runs of the proposed duration to maintain compliance with the performance standard. If EPA elects to lower the PM emission standard, GVEA believes it should first develop a practical correlation method that is feasible at the lower emission limit, so regulated facilities can affordably and reasonably certify and maintain compliant PM GEMS. Please see the following attachments for additional information and technical issues previously provided to EPA regarding 40 CFR 63 Subpart UUUUU: Attachment 1: Comments provided by GVEA, Docket ID No. EPA-HQOAR-2018-0794, 88 FR 24854, June 23, 2023 Attachment 2: Comments provided by GVEA, Docket ID No. EPA-HQOAR-2018-0794, April 17, 2019 Page 6 of 8 Sierra Club FOIA 2025-EPA-04883 ED_018388_00000057-00006 SC_EVERSPLIT0005606