Sierra Club v. EPA, 972 F.3d 290

The Clean Air Act requires states to adopt State Implementation Plans (SIPs) meeting Reasonably Available Control Technology (RACT) for existing sources to attain ozone NAAQS; EPA reviews and approves those SIPs.
Pennsylvania’s 2016 SIP (RACT II) set a 0.12 lb NOx/MMBtu limit for SCR‑equipped coal units operating at SCR inlet temperatures ≥600°F, while allowing higher limits (0.16–0.40 lb/MMBtu) when operating below 600°F; the SIP used 30‑day averaging for compliance.
EPA provisionally approved Pennsylvania’s SIP in 2018 and gave final approval in 2019; neighboring states and environmental groups submitted adverse comments before and after approval.
Sierra Club challenged EPA’s approval, arguing (1) the 0.12 limit is unjustified and effectively an average of current emissions, (2) the 600°F temperature exemption is unsupported and creates a loophole, and (3) the SIP lacks enforceable temperature reporting requirements to police the exemption.
Post‑approval data showed at least one plant (Cheswick) operating below 600°F at night and producing much higher NOx rates thereafter, supporting Sierra Club’s claim that the temperature exemption enables evasion of the lower limit.
The Third Circuit found EPA’s approval arbitrary and capricious for failing to support the 0.12 limit, the 600°F threshold, and the lack of enforceable reporting; it vacated those provisions and remanded for a revised SIP or a federal implementation plan.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Adequacy of 0.12 lb NOx/MMBtu RACT limit for SCR units	0.12 is merely an average of existing emissions; record shows SCR units achieved substantially lower rates, so RACT should be stricter	EPA/PA DEP: RACT need not be the absolute lowest achievable; 0.12 reflects practicable, economically and technically achievable limits	Court: EPA failed to explain or justify selecting 0.12 given data showing lower achievable rates; approval arbitrary and capricious; vacated
Legitimacy of 600°F SCR temperature exemption	Threshold unsupported; SCR operates below 600°F and can still reduce NOx; 600°F creates a predictable loophole to evade lower limits	EPA/PA DEP: SCR efficiency declines at lower temps; 600°F reflects technical limitations and target efficiency	Court: Record does not support why 600°F (versus 550°F or 650°F) is the correct cut‑off; agency didn’t connect facts to choice; exemption arbitrary and capricious; vacated
Sufficiency of reporting/recordkeeping for inlet temperature	SIP lacks mandatory, specific, publicly accessible temperature reporting; without records plants can claim below‑600°F operation to avoid limits	EPA/PA DEP: existing state recordkeeping and Title V permit requirements provide oversight	Court: Record contained no clear, enforceable temperature‑reporting scheme or public access; delegation to state/operator was speculative/post‑hoc; reporting regime inadequate; vacated

Motor Vehicle Manufacturers Ass'n v. State Farm Mut. Auto. Ins. Co., 463 U.S. 29 (agency action arbitrary and capricious standard)
Friends of the Earth, Inc. v. Laidlaw Envtl. Servs. (TOC), Inc., 528 U.S. 167 (environmental standing for recreational and health interests)
Lujan v. Defenders of Wildlife, 504 U.S. 555 (standing requirements)
E.P.A. v. EME Homer City Generation, L.P., 572 U.S. 489 (Cooperative federalism under the CAA and SIP/FIP framework)
Nat'l Parks Conservation Ass'n v. E.P.A., 803 F.3d 151 (3d Cir.) (deference and remand where EPA approval relied on inadequate state analysis)
Sierra Club v. E.P.A., 884 F.3d 1185 (D.C. Cir.) (rejecting EPA reliance on unreliable technical data)
Prometheus Radio Project v. FCC, 373 F.3d 372 (line‑drawing review and requirement for a rational connection between facts and agency choice)
Navistar Intern. Transp. Corp. v. E.P.A., 941 F.2d 1339 (6th Cir.) (historical interpretation of RACT as the lowest emission limit reasonably available)