Summary of Comments Received and EPA's Responses 
      The EPA received 20 sets of comments on the September 29, 2016 proposed amendments to the MATS rule (40 CFR 63, Subpart UUUUU).  The majority of them were submitted by utility companies; the remainder were from regulatory response groups, consultants, and data acquisition and handling system (DAHS) vendors.  No comments were received from environmental groups, State and local air agencies, or private citizens.  The commenters were generally supportive of EPA's initiative to have all of the MATS data reported through one data system, i.e., ECMPS.  However, fourteen of the commenters objected to the Agency's proposed extension of the current interim PDF reporting process to December 31, 2017.  Only one comment was received on the proposed amendments to Appendix A of Subpart UUUUU.  A summary of these comments and EPA's responses is presented below.  
Comment: One commenter stated that EPA has not allowed enough time to implement the proposed changes.  The proposed rule would require sources to begin following the new proposed requirements for data collected starting on January 1, 2018.  The commenter asserted that sources as well as EPA need more time to implement these changes.  The proposed changes would require sources (and/or their software vendors) to make substantial changes to the data acquisition and handing system (DAHS) software that they use for MATS reporting.  Programmers would need to interpret the regulations and reporting instructions to ensure that the DAHS software addresses the various reporting options that are allowed under the MATS rule and the different monitoring scenarios that might be used.  The software vendors would need to make these changes while supporting the on-going reporting under the existing requirements, which may necessitate cumbersome parallel revisions to their reporting platforms.  Iterative rounds of beta testing might be needed to ensure the proper performance of software.  The beta testing would require interaction between the software vendors, utility personnel and, at times, EPA to identify and resolve issues prior to the date that actual reporting begins.  Stack test companies would also have to develop spreadsheet and/or other tools to accommodate the proposed changes to the way performance test data are reported under Appendix E.  All these tasks would take time to do properly.  Further, implementation of the changes is also predicated on the Agency finalizing the rule changes and providing reporting instructions.  Based on past MATS-related revisions, the commenter believed that the Agency, at best, could not finalize the changes until mid-2017, which would only give sources and the EPA about six months to make the necessary changes.  The commenter asserted that this timeline is wholly inadequate, and recommended that the Agency extend the current interim reporting requirements for eight quarters following the date when the final rule published.  Thirteen other commenters also asked for EPA to extend the interim PDF reporting period beyond December 31, 2017, for similar reasons; their suggested alternative dates ranged from June 30, 2018 to December 31, 2019.  Five commenters urged EPA to issue a brief final rule extending the interim reporting period, and then to focus on finalizing the remainder of the September 29, 2016 proposal.
Response:  After careful consideration of the comments received, the Agency has decided to issue a final rule that changes the expiration date of the interim PDF reporting process from April 16, 2017 to June 30, 2018.  In a separate action, EPA intends to finalize the amendments to Subpart UUUUU that were proposed on September 26, 2016.  If those amendments are not finalized by June 30, 2018, the two data system approach for MATS reporting described in the original MATS rule will be reinstated, starting on July 1, 2018.

Comment: Only one comment was received on the proposed technical corrections to Appendix A of 40 CFR 63, subpart UUUUU.  The commenter supported the proposed amendments.
Response: The Agency appreciates the supportive comment and has finalized the amendments as proposed.
