The comment period has now begun on EPA’s proposal for replacing the Clean Power Plan, named the “Affordable Clean Energy”—or “ACE”—rule.  The rule was published in the Federal Register on August 31. And there is plenty to keep commenters busy over the next 60 days, given that EPA expressly identified 75 distinct requests for comment, not counting potential sub-issues and issues that EPA did not count.  Comments are due by October 30^th. Here are the top 10 key aspects of the rule that are likely to be the subject of the most fervent comments:

1. Section 111(d) Authority. As previously set forth in its proposed repeal of the Clean Power Plan, EPA has decided to return to its historical interpretation of Section 111(d) of the Clean Air Act—that it only authorizes EPA to establish the best system of emission reduction based on measures that can be employed within the fenceline of a source subject to the rule.  Conversely, EPA makes clear that its historical reading of Section 111(d) precludes the use of “generation-shifting,” “reduced utilization,” or “redefining the source” as part of a Section 111(d) emission guideline, all of which were relied upon heavily under the Clean Power Plan.  In the ACE proposal, EPA also characterizes its authority as merely providing “information” to states, that then have the authority to establish the enforceable, pound per megawatt hour “performance standards” on a unit-by-unit or source-category basis.  EPA also leaves to the states to determine the compliance deadlines associated with those performance standards.
2. The Best System of Emission Reduction (BSER). EPA has determined that the best system for reducing greenhouse gas emission reductions from existing power plants (consistent with its reading of Section 111(d)) is to improve the efficiency of those power plants.  Specifically, EPA listed six equipment upgrades and a seventh catch-all for improved operating practices that could be used to improve the efficiency with which power plants convert fuel into electricity.  EPA expressly rejected carbon capture and sequestration as insufficiently demonstrated and co-firing with gas or biomass as insufficiently available and unnecessarily costly.
3. Affected Sources Subject to the Rule. ACE, as proposed, would apply only to coal-fired power plants, not gas-fired plants (unlike the Clean Power Plan, which applied to both).  EPA’s basis for excluding gas-fired units is that it does not have enough information to establish a similar efficiency-based emission guideline for them.  However, ACE is likely to set a precedent that could be important if EPA later decides that a similar program might be appropriate for gas generators after all.  Exclusion from ACE might also mean that gas-fired plants will be unable to take advantage of EPA’s New Source Review reforms, summarized below.
4. No Presumptive Limits or Cumulative Targets: Unlike the Clean Power Plan, which focused on national and interconnection-level emission reduction targets to establish mandatory emission budgets for each state, ACE is not based on a cumulative emission reduction target, nor does it provide any presumptive limits or a prescriptive methodology for states to follow in setting performance standards.  That approach provides states maximum flexibility and authority, but it may also lead to significant variability from state-to-state, as plans are developed and submitted to EPA for approval. EPA did provide a range of expected efficiency improvement levels for each one of the seven measures proposed, which states must consider, but exactly how states are expected to incorporate those ranges into the process of establishing standards of performance remains unclear.
5. Some Averaging, But No Trading: In describing the requirements for states, EPA made clear that averaging between affected units within a single facility will be allowed, but averaging or trading of emission reductions between facilities will be out of bounds.  This aspect of the rule is likely to be trouble to states that have already sought to reduce greenhouse gas emissions via a trading program, such as the states participating in the Regional Greenhouse Gas Initiative.
6. Cost Implications: ACE expressly allows states to decide which measures are cost-effective, and therefore a valid basis for establishing a performance standard, and which measures might be too costly.  As noted above, that evaluation can be case-by-case, so states will need to conduct a detailed assessment of each covered facility’s economic characteristics.  EPA has also indicated a preference for including in that analysis the costs associated with any additional permitting or control requirements that could be triggered by the measures required—something EPA has not typically considered in the past.
7. New Source Review (NSR) Reform: EPA has resurrected a 2007 proposal for NSR reform that would add to the current NSR permitting applicability test a preliminary hourly emissions check.  In short, if maximum hourly emissions are not expected to increase, NSR will not apply.  The concept could be highly beneficial in simplifying and clarifying the controversial NSR program, and the hourly test squares nicely with the new 1-hour national ambient air quality standards.  However, the exact form of EPA’s proposed preliminary hourly test leaves much to be desired, in that it relies on either a single highest hour or a flawed statistical analysis that must be compared to every single hour of emissions in the future.  It also fails to implement the statutory requirement for evaluating only those emissions increases caused by a project.
8. State Plan Deadlines: EPA has proposed to significantly extend the deadline for state plans and for EPA action to approve those plans or issue federal plans for states that failed to submit an approvable one.  This timeline will give states much more time to work with EPA and make sure their plan is approvable, but it also means that the deadline for approving plans will not arrive until the next presidential administration.
9. Adopting Standards Less (or More) Stringent than Guidelines: EPA’s ACE proposal confirms that a state’s standards of performance may be less stringent than the “information” comprising EPA’s emission guidelines.  However, for a less-stringent state plan to be approvable, states must demonstrate the reasonableness of their decisions.  How much or little deference EPA will pay to the state’s demonstrations will be, as noted above, up to the next presidential administration.
10. Rule Benefits and Costs: In evaluating the potential impacts of its proposal—its costs and benefits—EPA compared its ACE proposal to two baselines, one with the Clean Power Plan in place, and one without it, which reflects the current state of the law in light of the Supreme Court’s stay of the Clean Power Plan.  EPA also relied on the social cost of carbon (but only domestic benefits) and co-benefits of particulate matter reductions (but noting that it has low confidence in the vast majority of the health benefits calculated).  All told, the rule predictably provides fewer benefits and imposes lower costs than the Clean Power Plan, but greater benefits and costs than doing nothing.