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What’s Up with MATS? The Rule 28 Years in the Making and Still Cookin’


EPA’s long-suffering Mercury and Air Toxics Standards (MATS) rule regulates emissions of mercury and other air toxics from coal-fired power plants. The rule has its origins 28 years ago with the passage of the Clean Air Act of 1990. The Act required that EPA submit a Utility Air Toxics Study to Congress to determine whether it was “appropriate and necessary” to regulate power plants under the air toxics provisions of the Clean Air Act. And the saga begins…

Note: Red dates indicate key events

Bush 1 EPA

November 15, 1990 – President George H.W. Bush signs the Clean Air Act Amendments of 1990 into law. The statute includes the provision that requires EPA submit a Utility Air Toxics Study to Congress to determine whether it is “appropriate and necessary” to regulate power plants under the Section 112 air toxics provisions of the Act. This is due November 15, 1993. The Act also requires EPA to issue a Mercury Study Report addressing the broader question of the impact of mercury emissions from many sources.

Clinton EPA

November 15, 1993 – Nothing to report…

October 1994 – EPA enters into a settlement agreement to issue the study by November 15, 1995.

November 15, 1995 – Nothing to report…

December 1997 – EPA issues the Mercury Study Report to Congress. This is not the Utility Air Toxics Study but is a massive 8-volume report on mercury emissions and their effects from a wide range of sources. It is a snapshot of EPA’s current understanding of mercury and its environmental impact.

February 1998 – The Utility Air Toxic Study is issued! Note that this is not the determination of “appropriate and necessary” but just the data upon which that determination will be made. That determination is pushed into the future. One of the major conclusions from the study was that mercury from coal-fired utilities was the HAP of greatest public health concern and that there was a plausible link that mercury from electric utilities was adding to the existing environmental burden.

December 20, 2000 – During the Clinton-Bush transition period, the Clinton EPA issues a determination that based on the results of the Utility Air Toxic report, regulating electric utilities under Section 112 of the Clean Air Act is appropriate and necessary. This was the trigger for EPA to begin rule development.

Bush 2 EPA

January 30, 2004 – The Bush EPA issues proposed mercury regulations – the Clean Air Mercury Rule (CAMR). Much of the proposal preamble is an apology for having to issue the regulations. The Bush EPA blames the necessity of the rule (correctly) on the appropriate and necessary determination issued by the Clinton EPA. The proposal spells out two approaches to regulating mercury — 1) Applying Maximum Achievable Control Technology (MACT) and 2) Developing a market-based “cap and trade” program. BUT… In an interesting twist, EPA also proposes revising the appropriate and necessary determination to regulate mercury emissions from power plants under Section 111 (New Source Performance Standards) of the Clean Air Act as opposed to Section 112 (air toxics). The MACT approach requires “delisting” power plants from the list of sources regulated under Section 112. Needless to say, this is a controversial proposal for three reasons. First, of course, it is a modification of the Clinton EPA determination and is done without conducting additional research to support the decision. Second, a cap and trade program for air toxics had not been previously considered for any rule. And third, regulating an air toxic (mercury) under Section 111 allows for potentially less stringent control.

March 16, 2004– EPA issues a supplement to the January proposal that provides further details on the cap and trade program.

December 1, 2004– EPA issues a Notice of Data Availability summarizing the modeling analyses EPA is using to support the upcoming rule.

February 3, 2005– EPA’s Office of Inspector General (OIG) issues a report finding (among other things) that EPA did not follow prescribed guidelines in determining MACT reductions for the rule and that their analysis as to whether MACT or cap and trade provide the best cost/benefit ratio was flawed. OIG recommends re-analysis of the MACT data.

March 29, 2005 -EPA finds that it IS NOT appropriate and necessary to regulate power plants under Section 112 despite it’s earlier finding that it IS appropriate and necessary. It concluded that the Utility Air Toxics Study over-estimated mercury emissions becasue it did not take into account mecury reduction caused by other requirements of the Clean Air Air. EPA delists electic utilities from the Section 112 air toxics list setting the stage for regulating these units under Section 111. Law firms rejoice. Litigation ensues.

May 18, 2005– EPA promulgates CAMR using the cap and trade approach under Section 111. There is no indication in the final rule that EPA followed the recommendations of the OIG report. Even more litigation ensues.

February 8, 2008– In New Jersey v EPA, the D.C. Circuit finds that EPA’s delisting rule violated the Clean Air Act and vacates the rule. This means that mercury emissions from power plants must remain listed under Section 112. Since the Clean Air Act does not permit Section 112 listed sources to be regulated under Section 111 as required by CAMR, the court finds that CAMR must also be vacated. The rule is dead. Long live the rule. EPA requests a review by the Supreme Court.

Obama EPA

February 6, 2009– The Obama EPA asks the Supreme Court to dismiss the request for review filed by the Bush EPA.

December 24, 2009– EPA approves an Information Collection Request (ICR) requiring all coal- and oil-fired power plants to submit operating and emissions data for use in crafting a new rule. Merry Christmas for stack testers.

March 16, 2011– EPA proposes its replacement for CAMR. This is the MATS rule. The proposed rule would establish standards for both existing and future power plants following a traditional MACT approach under Section 112.

February 16, 2012– EPA promulgates the MATS rule. Litigation ensues.

July 20, 2012– EPA grants Petition for Reconsideration focusing on measurement issues related to mercury and how EPA established the new source standards for particulate matter and hydrochloric acid, as well as startup and shutdown provisions.

November 16, 2012– EPA issues a proposal to update requirements for new plants based on the Reconsideration. The proposal includes 1) Revised NSPS standards, 2) Requirements applicable during startups and shutdowns, 3) Changes in some monitoring requirements and definitions.

March 28, 2013– EPA promulgates the final rule for the update to new plant standards. Startup and shutdown provisions are not addressed pending further public comment.

June 25, 2013Re-opening of public comment on startups and shutdowns

November 7, 2014– EPA issues a direct final rule (and parallel proposal in case of adverse comment) on MATS e-reporting. EPA has developed two systems for submitting electronic data to the agency – 1) The Emissions Collection and Monitoring Plan System (ECMPS) developed by the Clean Air Markets division of EPA and 2) The Compliance and Emissions Data Reporting Interface (CEDRI) developed by the Office of Air Quality Planning and Standards (OAQPS) and home of the much-maligned Electronic Reporting Tool (ERT). The MATS rule requires that affected sources report data to BOTH systems depending on the type of data. Several commenters suggested this was inefficient particularly since most sources affected under MATS have already been reporting to ECMPS for many years. EPA agrees in this rule and pledges to consolidate reporting in ECMPS. To allow time for the transition, EPA amends MATS so that the CEDRI data can be submitted to ECMPS as a pdf attachment. EPA also sets a deadline of April 16, 2017 for this transition to ECMPS to be complete. If it is not, affected sources will be required to submit data collected after this data through CEDRI (via ERT).

November 7, 2014– EPA finalizes update of startup shutdowns provisions based on the Reconsideration. The rule revision affects both existing and new units and includes work standard practices during startup and shutdown periods and adjustments to monitoring and testing during these periods. 

December 19, 2014– EPA proposes technical corrections for MATS. A variety of small changes to various parts of the rule focusing on 1) Resolution of conflicts between the preamble and regulatory text, 2) Corrections made in response to comments that were inadvertently not made, and 3) clarification of language in the regulatory text. One significant proposal is to remove the affirmative defense to civil penalties caused by malfunctions and replace it with “enforcement discretion.” This is in response to NRDC v.EPA in which the DC Court of Appeals struck down the affirmative defense in the Portland Cement rule.

March 9, 2015– EPA promulgates final e-reporting rule given comments from November 7 proposal. In this rule, EPA states that, as part of a Phase 2 transition, they “plan to develop another rulemaking that requires affected source owners or operators to submit the data elements required in the rule in a structured XML format using the ECMPS Client Tool.”

April 21, 2015– EPA denies all outstanding Petitions for Reconsideration except for startup/shutdown petitions signaling that they have finalized their approach to the MATS rule.

June 29, 2015– In the landmark Michigan v EPA decision (also see here), the Supreme Court remands (but does not vacate) the rule to EPA for failing to conduct a cost/benefit analysis (CBA) at the start of the rule-making process. This decision, along with Entergy v Riverkeeper (also see here), is seen by many as removing EPA’s discretion regarding when to perform some type of CBA if the statute is not clear or is silent on the matter. Justice Scalia writing for the majority states that EPA “must consider cost — including, most importantly, cost of compliance — before deciding whether regulation is appropriate and necessary.” It is important to note that the remand did not halt implementation of the rule. Therefore, all regulatory deadlines remained in place as EPA reconsidered the cost of the rule. At this point, it is estimated that 70% of the affected units have already installed the control equipment necessary to comply with the standard. 

November 20, 2015Supplemental Cost Analysis to support appropriate and necessary determination. This, of course, is EPA’s response to the Michigan v EPA decision. This analysis only presents the data. It does not address whether the data continues to support EPA’s earlier finding that it is appropriate and necessary to regulate power plant under Section 112.

March 17, 2016– EPA issues final technical corrections including removal of the affirmative defense for malfunctions.

April 14, 2016– EPA issues its revised appropriate and necessary determination based on the November 20 Supplemental Cost Analysis required by the Supreme Court in Michigan v EPA. They find that even after reconsidering costs, it is still appropriate and necessary to regulate power plants under Section 112. Litigation ensues.

August 8, 2016– EPA denies Petitions for Reconsideration of startup/shutdown rule revisions. 

August 23, 2016– EPA proposes to extend  the e-reporting deadline to July 1, 2018. The transition to ECMPS is not going as quickly as EPA would like so they propose to extend the “return to CEDRI” deadline.

Trump EPA

April 6, 2017 – EPA finalizes rule to extend e-reporting deadline to July 1, 2018

April 27, 2017– At the request of the Trump EPA, DC Court of Appeals suspends MATS litigation resulting from the April 14, 2017 appropriate and necessary determination to allow EPA to evaluate the situation. EPA is required to file progress reports with the court every 90 days. MATS continues in effect with essentially all affected units having either installed the necessary control equipment to comply or shut down units that were not cost-effective to upgrade. 

September 10, 2017– President Trump nominates William Wehrum as EPA Assistant Administrator for Air and Radiation. Wehrum, who previously served in the Bush EPA as Assistant Administrator, was one of the chief architects of the legal strategy for the CAMR rule.

April 19, 2018– Administrator Wehrum, speaking at an American Bar Association conference in Orlando states, “Under the law, there are good reasons why the [MATS] standard shouldn’t exist because it’s not appropriate and necessary. But on the other hand, we cannot turn a blind eye toward the practical, the implications of the possibility of rescinding the rule and the uncertainty that that would cause within the regulated community.” He stated further, “We’re still thinking about it. We haven’t quite figured out what we’re going to do.”

June 26, 2018Another extension to the e-reporting deadline, this time until July 1, 2020. It’s taking even longer than EPA anticipated to modify ECMPS to accept MATS data.

So what lies in the future for MATS? Given that all of the plants subject to the rule have already made the investment in pollution control to comply with MATS or have shut down non-compliant units, maybe whatever happens at this point is moot. As of this writing, litigation is still suspended and EPA is still weighing options. The next couple of years will tell. It is too early to tell whether the newly appointed interim Administrator, Andrew Wheeler, will attempt to change the course of MATS. But the real decision maker here is Bill Wehrum. And he’s still scratching his head.

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