A19-0134

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STATE OF MINNESOTA

IN SUPREME COURT

A19-0115
A19-0134

Court of Appeals Chutich, J.
Took no part, Thissen, J.

In the Matter of Issuance of Air Emissions
Permit No. 13700345-101 for PolyMet Mining, Inc., Filed: February 24, 2021
City of Hoyt Lakes, St. Louis County, Minnesota. Office of Appellate Courts

______________________________

Emily C. Schilling, Holland & Hart LLP, Salt Lake City, Utah; and

Adonis A. Neblett, Saint Paul, Minnesota, for appellant Minnesota Pollution Control
Agency.

Monte A. Mills, Davida S. McGhee, Greene Espel PLLP, Minneapolis, Minnesota; and

Kathryn A. Kusske Floyd, Jay C. Johnson, Amanda L. Crawford, Venable LLP,
Washington, D.C., for appellant PolyMet Mining, Inc.

Evan J. Mulholland, Ann E. Cohen, Jay E. Eidsness, Saint Paul, Minnesota, for respondents
Minnesota Center for Environmental Advoc acy, Friends of the Boundary Waters
Wilderness, Center for Biological Diversity, and Sierra Club.

Sean Copeland, Cloquet, Minnesota, for respond ent Fond du Lac Band of Lake Superior
Chippewa.

Keri N. Powell, Powell Environmental Law, LLC, Decatur, Georgia; and

Vanya S. Hogen, Hogen Adams PLLC, Sain t Paul, Minnesota, for amicus curiae
Environmental Integrity Project.

Jeremy P. Greenhouse, The Environmental Law Group, Ltd., Mendota Heights, Minnesota;
and

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Carroll W. McGuffey III, Troutman Pepper Hamilton Sanders LLP, Atlanta, Georgia, for
amicus curiae National Mining Association.

________________________

S Y L L A B U S
The Minnesota Pollution Control Agency is not required under the Clean Air Act,
42 U.S.C. §§ 7401–7671q, and its applicable regulations to investigate allegations of sham
permitting when a source first applies for a synthetic minor source permit.
Reversed and remanded.
O P I N I O N
CHUTICH, Justice.
At issue in this case is whether appellant, the Minnesota Pollution Control Agency
(the Agency), is required to investigate allegations of “sham” permitting when considering
whether to initially approve th e air-emissions permit of appellant PolyMet Mining, Inc.
(PolyMet) for its NorthMet mine project. In particular, we consider whether the federal
Clean Air Act, 42 U.S.C. §§ 7401–7671q, ma ndates that the Agency scrutinize whether
PolyMet intends to expand mining operations in the near future, ma king it subject to the
more stringent emissions limitations that appl y to a “major source” instead of those that
apply to a “synthetic minor source.”
1

1 A “synthetic minor source” is a source that accepts enforceable limits restricting its
potential to emit air pollutants to a level below the threshold limits set for a “major source”
by the Clean Air Act. See In re Shell Offshore, Inc., 15 E.A.D. 536, 550 (EAB 2012).

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Respondents—a coalition of environmental groups led by the Minnesota Center for
Environmental Advocacy and the Fond du La c Band of Lake Supe rior Chippewa—filed
two certiorari appeals challenging the decision of the Agency to gr ant an air-emissions
permit to PolyMet for the propos ed mine. They asserted that , before the Agency issued
the synthetic minor source permit, it had failed to conduct an adequate investigation into
whether PolyMet intended to operate within the limits of the permit or whether PolyMet
was instead seeking a “sham” permit.
The court of appeals concluded that the Agency’s factual findings were “insufficient
to facilitate judicial review of the perm itting decision” and remanded the matter to the
Agency for further fact-finding. In re Issuance of Air Emissions Permit No. 13700345-101
for PolyMet Mining Inc., 943 N.W.2d 399, 402 (Minn. App. 2020). Specifically, the court
of appeals concluded that th e Agency’s short response to the written concerns of the
environmental groups was not the sort of “hard look” required under the Minnesota
Administrative Procedure Act, Minn. Stat. § 14.69 (2020). In re Air Emissions Permit for
PolyMet Mining, Inc., 943 N.W.2d at 408–11.
The Agency and PolyMet each petitioned for further review, asserting that the court
of appeals incorrectly applied the relevant la ws and improperly considered extra-record
information. We granted their petitions. B ecause the applicable federal regulations and
guidance contemplate retrospective enforc ement after the applicant has obtained a
synthetic minor source permit—and do not mandate prospective investigation—we reverse
the decision of the court of appeals. Acco rdingly, we remand the matter to the court to
consider the remaining issues on appeal.

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FACTS
In 2005, PolyMet first proposed developing a copper-nickel-platinum mine, the first
of its kind in Minnesota, appr oximately six miles from Babb itt. The proposed facility
would include both new construction and refurbished equipment left from a previous iron
ore processing facility on the site. The proj ect proceeded through environmental review
until 2015. In 2016, the Minne sota Department of Natural Resources (DNR) deemed the
Final Environmental Impact Statement to be adequate.
On August 25, 2016, PolyMe t submitted its draft air emissions permit application
to the Agency. The application included de tails about the proposed facilities, projected
pollutant emissions, and expected air quality impact. PolyMet applied for the permit as a
synthetic minor source.
A brief review of air permitting terminology provides context to PolyMet’s choice
of air permit type and the core issues of th is case. Under the federal Clean Air Act, a
facility that emits or has the potential to emit over 250 tons per year of a regulated pollutant
is a “major stationary source” (major source). 40 C.F.R. § 52.21(b)(1)(i)(a)–(b) (2020).
Major sources must undergo an exacting review process before construction that includes
stringent pollution control measures known as “best available control technology.”
40 C.F.R. § 52.21(b)(12). A source that has the capacity to be a major source of
emissions—that is, to emit over 250 tons per year of a specified pollutant—but chooses
instead to adopt enforceable operational restrictions so as to reduce its actual emissions to
less than that limit is a “synthetic minor source.” See In re Shell Offshore, Inc., 15 E.A.D.
536, 550 (EAB 2012).

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A synthetic minor source is treated the same as a true minor source—that is, a source
that does not have the capacity to emit over 250 tons per year of a regulated pollutant.
40 C.F.R. § 52.21(aa)(2)(xv) (2020). Either type of minor source undergoes a review
process that is less demanding than that for a major source; neither type must use best
available control technology that major sour ces are required to in stall. 40 C.F.R.
§ 52.21(b)(12).
What qualifies as best available contro l technology depend s on a case-by-case
analysis weighing energy, environmental, and economic impacts. Id. As a general rule, it
is more expensive to retrofit pollution contro l measures onto existing equipment than to
construct new equipment with be tter pollution control measures. See United States v.
Cinergy Corp., 458 F.3d 705, 709 (7th Cir. 2006) (“ The Clean Air Act treats old plants
more leniently than new ones because of th e expense of retrofitting pollution-control
equipment.”). A source that first obtains a minor source permit and later, after construction
of the facility, seeks modification of the permit to become a major source could therefore,
depending upon the circumstances, be allowe d to install less stringent pollution control
technologies than if it had or iginally sought a major source permit. For example, if the
cost of retrofitting outweighs the environmental benefits of the available pollution control
measures, the facility may not be required to install the more stringent measures. See, e.g.,
United States v. Ameren Mo., 421 F. Supp. 3d 729, 808–09 (E.D. Mo. 2019).
This scenario raises the potential prob lem of a source improperly seeking and
receiving a synthetic minor sour ce permit and shortly thereaf ter actually emitting major
source levels of pollution. The Environmenta l Protection Agency (E PA) refers to such

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synthetic minor source permits as “sham permits.” See Terrell E. Hunt & John S. Seitz,
Guidance on Limiting Po tential to Emit in New Source Permitting , U.S. EPA (June 13,
1989) (EPA Guidance); see also Requirements for the Prep aration, Adoption, and
Submittal of Implementation Plans; Approval and Promulgation of Implementation Plans,
54 Fed. Reg. 27,274, 27,280–81 (June 28, 1989) (codified at 40 C.F.R. pts. 51, 52).
The EPA, which ordinarily delegates to states its authority to enforce the Clean Air
Act, has retained concurrent authority to en force federal law if a facility obtained a sham
permit. See Approval and Promulgation of Implementation Plans, 54 Fed. Reg. at 27,274,
27,280–81. In determ ining whether a permit is a sham, the “EPA will lo ok to objective
indicia to evaluate” whether the facility “obtained a minor source permit with the purpose
of obtaining, after construction, a major s ource permit, so as to evade preconstruction
review.” Id. at 27,281. Such objective indicia include whether the facility “would not be
economically viable for any appreciable period of time if it were restricted to emitting at
minor levels,” “how a project ’s projected level of opera tion was portrayed to lending
institutions,” and if the facility applies for a major source and minor source permit around
the same time. Id. If the EPA finds that the facility obtained a sham permit, it will consider
“seeking injunctive relief, civil penalties, and criminal sanctions” da ting back to “the
beginning of the actual construction.” Id. at 27,280.
The EPA emphasizes that thes e enforcement principles are not directed to sources
that “accept emissions limitations in pursuit of legitimate bus iness purposes, and who in
good faith later seek a relaxation of those limitations.” Id. at 27,281. But regardless, any
synthetic minor source that se eks relaxed restrictions, such as increasing “hours of

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operation,” which would then incr ease its emissions to the le vel of a major source, will
undergo control technology review as tho ugh “construction had not yet commenced.”
40 C.F.R. § 52.21(r)(4) (2020).
With this general background in mind, we turn to the facts he re. PolyMet applied
for a synthetic minor source permit, with its potential emissions capped by a key restriction
limiting the amount of ore that it processes (the “throughput”) to a proposed maximum of
32,000 tons per day, among other restrictions. The Agency’s permit requirements includes
numerous federal enforceable emission limits, as well as operational and production limits
that restrict emission of regulated pollutants. The permit further includes daily, weekly,
and monthly monitoring and recordkeeping re quirements to help ensure that PolyMet
actually remains below the 250 tons per year threshold for regulated pollutants that is
required to operate as a synthetic minor source.
Throughout the permitting pr ocess, the Agency prov ided for community and
stakeholder involvement. These measures included designing a dedicated web portal for
interested parties, emailing updates, and providing links to all public application materials.
The Agency also provided notice of, and held, two public meetings for the project. Before
the public comment period began, the Agency provided the draft permit to tribal authorities
and the EPA. On January 31, 2018, the Agency publicly announced a 45-day comment
period that ended on March 16, 2018. During this period, the Agency received 88 timely
comments; it did not receive a request for a contested case hearing.
Several environmental groups raised concerns during the comment period that, in
light of the capacity of the existing facilities at PolyMet’s mine site to process ore at a

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higher rate than set forth in the permit application, Poly Met was applying for a sham
permit. The Agency responded that the draft permit includes many limitations on mining
that can be enforced—including recordkeep ing requirements—to ensure that PolyMet’s
emissions will remain below the maximum limit of 250 tons per year.
In March 2018, ten days after the close of the public comment period, PolyMet’s
Canadian parent corporation filed a Form 43-101F1 Technical Re port (the March 2018
Report) with Canadian regulatory authorities. Such reports are directed to investors, or
potential investors, in publicly traded mining companies to inform them of the viability of
proposed mining operations. The approximately 270-page Report primarily addressed the
economic viability of the proposed mining fac ility at the 32,000 tons per day throughput
limit. At that throughput, the Report stated that the NorthMet project would produce an
internal rate of return of about 10 percent and fully recoup its startup costs in 7.5 years.
About 10 pages of the lengthy March 20 18 Report also provided preliminary
economic analysis of two higher throughput scenarios, 59,000 and 118,000 tons per day.
These preliminary projections suggested that , because of existing infrastructure at the
NorthMet site, PolyMet could increase internal rates of return, decrease payback time, and
increase revenues under the higher throughputs.
This section of the March 2018 Report, however, cautioned that “[t]he estimates for
these two scenarios are prelim inary in nature” and are “too speculative geologically” to
demonstrate economic viability. It emphasized that “further engine ering, environmental
studies, and permitting” woul d be required “to improve the economic uncertainties
associated with these [hi gher throughput] estimates.” The Report concluded that

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“PolyMet’s focus and intention is to put into oper ation the 32,000 [tons per day] plan
detailed in this Technical Report as soon as possible.”
In light of the March 2018 Report, th e Minnesota Center for Environmental
Advocacy (the Center) petitioned the DNR to prepare a Supplemental Environmental
Impact Statement. See In re Applications for a Supple mental Env’t Impact Statement for
the Proposed NorthMet Project , Nos. A18-1312, A18-152 4, A18-1608, 2019 WL
2262780, at *1 (Minn. App. May 28, 2019), rev. denied (Minn. Aug. 20, 2019). The Center
argued that the Report showed PolyMet’s intent to build a larger project than the one for
which it was seeking pe rmits, and that this “substantia l new information” required
preparation of a supplemental envi ronmental impact statement. Id. at *6–7 . The DNR
denied the petition, and the court of appeals affirmed that denial. Id. at 7. The court of
appeals deferred to the DNR’s judgment, noting that “the expansions are not part of the
project as currently proposed” and that th e 32,000 ton pe r day throughput was still
projected to be profitable. Id. at *6.
The Center wrote to the Agency on Dece mber 13, 2018, raising concerns that
PolyMet was applying for a sham permit. It requested that the Agen cy stay its permit
approval pending further investigation. The Ag ency responded by letter six days later,
stating that it had reviewed the March 2018 Report and disagreed that further investigation
was warranted. Specifically, the Agency quoted the various statements in the Report that
characterized the highe r throughput scenarios as “prelimin ary in nature,” “speculative,”
and uncertain. The Agency determined that the higher throughputs “reflect potential future
scenarios that would require significant additional study and for which economic viability

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has not been demonstrated.” It concluded that “[n]either the Technical Report, nor
PolyMet’s submittals in support of the Air Permit, indicate any intent by PolyMet to
circumvent major source permitting.” The next day, the Agency issued the approximately
700-page permit, accompanied by its Findings of Fact, Conclusions of Law, and Order that
incorporated by reference a 200-page Te chnical Support Document. The Technical
Support document detailed how the various rest rictions and reporting requirements are
designed to ensure that emissions limits are not exceeded.
The Center, other environmental groups , and the Fond du Lac Band of Lake
Superior Chippewa (collectively, the environmental groups) appealed by writ of certiorari,
challenging the Agency’s permit decision. In re Issuance of Air Emissions Permit No.
13700345-101 for PolyMet Mining Inc. , 943 N.W.2d 399 (Minn. App. 2020). The court
of appeals first addressed the scope of the record. The environmental groups moved to
correct and to supplement the record. They sought to add to the record two documents
submitted after the close of the public comment period (1) the earlier petition to the DNR
for a supplemental environmental impact statem ent, with the accomp anying exhibits and
(2) a November 8 letter sent by the Center to the Agency requesting a stay of all permits
pending appeal of the DNR’s denial of that petition. Id. at 406.
A special term panel of the court of appeals denied the motion to correct, but the
merits panel later granted the motion to supplement. 2 Id. at 406–07. In its ruling on the

2 A motion to correct or complete the reco rd under Minnesota Rule of Civil Appellate
Procedure 110.05 is limited to documents that are “material to either party” that were
omitted from the record “by error or accident, or . . . misstated in it.” A motion to
supplement, on the other hand, seeks to add evidence to the record that the agency did not

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merits, the court concluded that it had the authority to consider evidence outside the record
“as probative of whether the [Agency] ‘failed to consider information relevant to making
its decision.’ ” Id. at 407 (quoting White v. Minn. Dep’t of Nat. Res., 567 N.W.2d 724, 735
(Minn. App. 1997), rev. denied (Minn. Oct. 31, 1997)).
The court of appeals then ex amined whether the Agency took a “hard look” at the
evidence of sham permitting. Id. at 408–11. The court concluded that the EPA Guidance
is consistent with the requirement that the Agency “anticipate[] that the applicant will . . .
comply with all conditions of the permit.” Id. at 409 (quoting Minn. R. 7007.1000, subp.
1(G) (2019)). The court critiqued the Agency ’s “conclusory” Findings of Fact and its
“short” response to the Center’s letter reque sting a stay and further investigation. Id. at
409–10. The March 2018 Report, the court concluded, raised questions about whether the
proposed 32,000 tons per day throughput limit would enable NorthMet to remain “viable”
if metal prices fell. Id. at 410. And finally, the court stated that “if expansion is the current
intent, the time to comply with [major source review] requirements is now.” Id. Because
the Agency did not transmit “all documents that it considered or was invited to consider”
and did not make particulariz ed findings of fact on the sham permitting issue, the court
concluded that remand and a reop ening of the record were re quired to facilitate judicial
review. Id. at 410–11. The Agency and PolyMet each petitione d for review, which we
granted.

consider but is “necessary for the cour t to conduct a substantial inquiry.” See In re Air
Emissions Permit for PolyMet Mining, Inc. , 943 N.W.2d at 406 n. 8 (citation omitted)
(internal quotation marks omitted).

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ANALYSIS
Judicial review of the Agency’s issuance of a permit is governed by the Minnesota
Administrative Procedure Act. See Reserve Mining Co. v. Herbst , 256 N.W.2d 808,
826−27 (Minn. 1977); Minn. Stat. § 14.69. Under the Act, a reviewing court may “affirm
the decision of the agency or remand the case for further proceedings; or it may reverse or
modify the decision if the s ubstantial rights of the petitione rs may have been prejudiced
because the administrative finding, inferences, conclusion, or decisions are” affected by an
error in law, unsupported by substantial evidence , or arbitrary or capricious. Minn. Stat.
§ 14.69. We review questions of law, in cluding statutory interpretation, de novo. In re
Restorff, 932 N.W.2d 12, 18 (Minn. 2019).
A.
The central issue here is whether the a pplicable federal regulations require the
Agency to investigate allega tions of sham permitting before issuing a synthetic minor
source permit. Accordingly, we address those arguments first.
The Agency contends that the EPA Guidance supports issuing a synthetic minor
source permit when operational restrictions, like those in the PolyMet permit, are present.
The Agency further argues that the EPA Guidance is designed to determine whether a
facility has circumvented preconstruction review, which presents a different situation than
a facility intending to expand at some indefinite point in the future. Th e fundamental
question, according to the Agency, is whether PolyMet will comply w ith the terms of its
permit.

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PolyMet agrees that the key question is wh ether it will comply with the permit. It
adds that if it seeks to expand its throughput limits beyond the terms of its synthetic minor
source permit and becomes a major source, certain consequences will follow. For example,
it would have to undergo preconstruction review as though it had never begun construction.
See 40 C.F.R. § 52.21(r)(4).
The environmental groups respond that the EPA Guidance was written to help
permitting agencies determine whether a proposed synthetic minor source permit is a sham.
They assert that the EPA Guidance require s permitting agencies to look beyond material
submitted in the permit applicati on. To support this asserti on, they note that various
documents cited in the EP A Guidance—like “stockhold er reports”—would not be
submitted with the permit application. The groups maintain that the Clean Air Act’s
fundamental emphasis on preconstruction review, instead of retrofitting after construction
has occurred, suggests that a retrospective analysis of best available control technology is
not sufficient.
The parties cite two primary sources of au thority produced by the EPA. First are
the federal regulations defining appropriate restrictions in synthetic minor source permits
and the accompanying supporting comme ntary in the Federal Register. See 40 C.F.R.
§ 50.21; Approval and Promulgation of Implementation Plans, 54 Fed. Reg. at 27,280–81.
These regulations were passed through notice and comment and therefore have the force
of law. See United States v. Mead Corp., 533 U.S. 218, 231–32 (2001).
Second is the EPA Guidance, which was released in the same month as the federal
regulations. This memorandum primarily provides more detail for states to determine what

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restrictions are permissible in synthetic minor source permits and how to identify when a
facility has received a sham permit. The EP A Guidance, in contrast to the federal
regulations described above, is not a regulati on or agency adjudication; it is therefore not
legally binding and is only afforded deference to the extent that it is persuasive. See Mead
Corp., 533 U.S. at 227–28; Skidmore v. Swift & Co., 323 U.S. 134, 139–40 (1944).
Because the federal regulations are binding, we first look to those to determine what
obligations the Agency, which reviews applications for and issues synthetic minor source
permits, see Minn. R. 7007.0250, subps. 1, 5 (2019), has concerning sham permitting. The
federal regulations show that the EPA was concerned that some state permitting authorities
may not enforce the operational restricti ons in synthetic minor source permits, 3 which
would allow those sources to actually emit major source levels of pollution in violation of
their permit. Approval and Promulgation of Implementation Plans, 54 Fed. Reg. at 27,277.
The EPA’s proposed solution was to retain concurrent authority to enforce operational
restrictions in synthetic minor source permits. Id. at 27,274 (granting the EPA enforcement
authority under 40 C.F.R. § 52.23).
The EPA explained that its concurrent en forcement has two bene fits. First, the
specter of EPA enforcemen t “giv[es] sources more incentive to comply.” Id. at 27,278.
Second, having the EPA as backup would give state authorities “more leverage over
industrial sources.” Id. This federal authority an d the corresponding operational

3 Although “decisions of administrativ e agencies enjoy a presumption of
correctness,” Reserve Mining Co. , 256 N.W.2d at 824, stat e agency decisions cannot
supersede the EPA’s lawfully promulgated regulations.

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restrictions required in synthetic minor source permits were ultimately designed to ensure
that synthetic minor sources comply with their permits and emit less than 250 tons per year
of regulated pollutants.4
The EPA identified another potential problem in issuing and enforcing synthetic
minor source permits. A source could have an incentive to accept operational restrictions
as a synthetic minor source so that it coul d begin construction a nd operation relatively
quickly. Id. at 27,281. Then soon thereafter, the s ource could seek re laxation of those
restrictions—making it a major source—without undergoing preconstruction review. Id.
The EPA proposed three solutions to this potential problem. First, it could simply
deny the major source permit and require the s ource to continue operating as a synthetic
minor source. Id. at 27,280. Second, if the EPA were to approve the major source permit,
then it would require the source to u ndergo preconstruction review—including
determination of best available control technology—as though it never began construction
in the first place. Id.; see also 40 C.F.R. § 52.21(r)(4). Nota bly, even sources that seek

4 The synthetic minor source permit issued to PolyMet contains the very sort of
federally enforceable operational restrictions called for by the EPA Guidance and required
under Minnesota’s delegated permitting authority. These opera tional restrictions include
the ore throughput limit (measu red at two points in the process), limits on the hours of
operation during winter months, limits on the t ypes and quantities of fu el used in heaters
and vehicles, limits on vehicle miles traveled and the number and type of engines used, and
upgrading existing equipment for better efficien cy and pollution control. Each of these
restrictions requires monitoring and recordkeeping at regular intervals (between daily and
annually depending on the limitation) that must be s ubmitted to the Agency for regular
review. And each of these restrictions is federally enforceable, meaning that the EPA can
also review these records and bring an enforcement action if PolyMet is not in compliance.

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relaxation of restrictions in good faith be cause of changing business plans must undergo
this review. Approval and Promulgation of Implementation Plans, 54 Fed. Reg. at 27,280.
A final enforcement option allows the EPA to penalize bad faith actors. If the EPA
believes that a source obtained a synthetic minor source permit with “an intent to construct,
and possibly begin operation of, a major new source or modification without first obtaining
a [] permit,” then the EPA would consider the initial synthetic minor source permit to be a
sham. Id. If such bad faith intent is shown, the EPA “deems the new source or modification
to have been major” from th e outset, and it will then consid er “seeking injunctive relief,
civil penalties, and criminal sanctions . . . from the beginning of actual construction.” Id.
Essentially, this enforc ement alternative allows the EPA to look back to the first day of
construction and view the source as having been in violation of its synthetic minor source
permit because it was, in fact, a major source.5
The EPA then identified seve ral “objective indicia” that , in the context of an
enforcement action, suggest that a source in tended to evade precon struction review by
obtaining a sham permit. Id. at 27,281. These indicia include seeking a minor and major
source permit simultaneously, constructing a new source that would not be economically

5 We note that civil penalties alone for such a violation could be substantial. Under
the Clean Air Act, a permit violation can result in a civil penalty as high as $100,000 per
day per violation. 40 C.F.R. § 19.4 (2020) (adjusting for inflation the $25,000 maximum
civil penalty under 42 U.S.C. § 7413(b)). If a source, for example, gets caught violating
only one operating condition of its synthetic minor source permit 5 years after receiving a
sham permit, the civil penalties alone could amount to nearly $200 million. The EPA could
also seek an injunction forcing the source to cease operations until it enacts best available
control technology. 42 U.S.C. § 7413(b).

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viable under operation restrictions, and portrayi ng its operations to lenders as though it
were or would soon be a major source. Id.
Critically, the EPA’s discussion of enforc ement is entirely retrospective. See id.
(noting that the EPA would only seek reme dies “where it believes it could show to the
satisfaction of a court that a source . . . had obtained a minor source permit with the
purpose of obtaining, after construction , a major source perm it, so as to evade
preconstruction review” (emphasis added)). At no point do the relevant regulations suggest
that the objective indicia of a sham permit necessarily disqualify a source from obtaining
a synthetic minor source permit in the first inst ance. In fact, the EPA specifically leaves
open the possibility of a synthetic minor source seeking relaxation of operating restrictions,
noting that it “in no way seeks to discourage or intends to penalize [sources that] accept
emissions limitations in pursuit of legitimate business purposes, and who in good faith later
seek a relaxation of those limitations.” Id. Under those circumstances, the preconstruction
review procedures under 40 C.F.R. § 52.21(r)(4) and enforcement actions for “any period
in which minor source permit lim its are actually ex ceeded” would “provide a complete
remedy.” Id.
B.
With this analysis in mind, we next a ddress whether the federal regulations and
guidance require the Agency to investigate sham permitting at the synthetic minor source
permit application stage. Critically, nothing in the non-binding EPA Guidance contradicts
the retrospective enforcement regime derived from the binding federal regulations laid out
above. The first half of the EPA Guidance explains in greater detail what types of

18
limitations in synthetic minor source permits are “federally enforceable” and “enforceable
as a practical matter.” See EPA Guidance at 2, 5–10. And it stresses that recordkeeping is
required so that agencies may review records to determine whether operational limits have
been exceeded and consequently that the emissions limits of the permit have been violated.
Id. at 6–7.
The EPA Guidance th en addresses situations in which a facility improperly
constructs a source with a synthetic minor s ource permit when it inte nds to operate as a
major source; the Guidance notes that these permits are “void ab initio.” Id. at 10. The
EPA Guidance also “provides guidelines for identifying these ‘sham’ permits.” Id. at
11−16. It concludes with a series of examples to illustrate the type of restrictions that are
and are not permissible in a synthetic minor source permit. Id. at 17–21. Nowhere in the
EPA Guidance does it dictate that a permitting agency must investigate sham permitting at
the synthetic minor source permit application stage.
Amicus Environmental Integrity Project (the Project) suggests that the EPA
Guidance is part of the minimum standards that the EPA considers when approving state
permitting programs. See Operating Permit Program, 57 Fed. Reg. 32,250, 32,284
(July 21, 1992) (codified at 40 C.F.R. pt. 70). The section of the re gulations cited by the
Project, however, deals specifically with modifications to existing minor source permits.
See id. This review of existing permits is, theref ore, entirely after the fact, looking at the
originally issued minor source permit, and is accordingly consistent with our interpretation
of the EPA Guidance. Several paragraphs after the passage cited by the Project, the EPA
specifically notes that “[s]tates that have serious nonattainment problems may wish to

19
adopt more stringent review procedures than those that do not.” Id. This latter statement
suggests a key point: based upon our review of the applicable federal regulations, the
Agency could, if it so desired, investigat e sham permitting during the synthetic minor
source permit application process, but it is not required to do so.
Instead, the legally binding regulations , passed through notice and comment, are
specifically designed to provide the EPA its own independent authority to enforce the
operational restrictions within synthetic minor source permits issued by the Agency and to
punish after the fact those sources that obtained a sy nthetic minor source permit through
deceit. Approval and Promulgation of Implementation Plans, 54 Fed. Reg. at 27,280–81.
Accordingly, because we conc lude that the Agency was un der no federal obligation to
investigate sham permitting during the synthetic minor source permit process, we reverse
the decision of the court of appeals ordering a remand on that basis.
C.
We now turn to the remaining issues presented by this appeal.
First, the Agency and PolyMet object to th e decision of the court of appeals to
remand without explicitly finding a violation of the Minnesota Administrative Procedure
Act. Each argues that the court’s decision to remand was improper because a reviewing
court should seek to affirm an agency decision if possible on the existing record. See In re
Excess Surplus of Blue Cro ss & Blue Shield of Minn. , 624 N.W.2d 264, 278–79 (Minn.
2001). Because we conclude above that th e court of appeals relied on an erroneous
interpretation of federal law to remand to the Agency, we need not decide this issue and
decline to do so here.

20
Second, in their appeals to the court of appeals, the environmental groups
challenged the Agency’s decision to issue the permit on grounds not specifically addressed
by the court of appeals. In particular, the groups asserted that the March 2018 Report and
other evidence undermined the Agency’s conclusion that Poly Met “will . . . comply with
all conditions of the permit,” Minn. R. 7007.1000, subp. 1(G). They also contend that the
Agency should have denied the permit because PolyMet “has failed to disclose fully all
facts relevant” to the permit and has “knowingly submitted false or misleading information
to the agency.” Id., subp. 2(C). These arguments shou ld be addressed by the court of
appeals on remand.
Finally, on appeal the partie s have disputed the proper scope of review. Because
this appeal must be remanded to the court of appeals to address the remaining issues, we
briefly address these arguments. In general, a ppellate review is confined to the record.
Minn. R. Civ. App. P. 110.01; 115.04. Th e court of appeals, however, granted the
environmental groups’ motion to supplement the record with two documents: the petition
to the DNR requesting a supplemental e nvironmental impact statement and the
November 8 letter to the Agency requesting a stay of permits pending appeal of the petition
denial.
Neither the Agency nor PolyMe t sought review of this decision, and they did not
challenge this decision in their briefs filed with our court; only at oral argument did the
Agency suggest that it was challenging the cour t of appeals’ decision to grant the motion
to supplement. Instead, the Agency challenged in its brief the court of appeals’ denial of
its motion to strike extra-record information from the environmental groups’ briefing.

21
Based on this record, we conclude th at the Agency and PolyMet forfeited any
challenge to the court of appeals’ deci sion to grant the motion to supplement. 6 See In re
Welfare of Children of J.D.T. , 946 N.W.2d 321, 326 n.3 (Minn. 2020); Rhodes v. State ,
875 N.W.2d 779, 784 n. 3 (Minn. 2016). As to the motion to strike, because the court of
appeals did not rely on any extra-record information contained in the briefing,7 we see no
error in denying the motion.
CONCLUSION
For the foregoing reasons, we reverse the decision of the court of appeals and
remand to that court to address the remaining issues on appeal.
Reversed and remanded.

6 Even if the Agency had not forfeited its challenge to that decision, the court of
appeals may look to federal administ rative law in granting the motion. See In re
Application of Minn. Power for Auth. to Increase Rates for Elec. Serv. in Minn. ,
838 N.W.2d 747, 766 (Minn. 2013) (Anderson, J., dissenting) (“[F]ederal courts have
considerable experience implementing a very similar standard of review, and . . . we
therefore find those federal decisions to be persuasive authority in many of our own
administrative law cases.”). Supplementing the record can be appropriate for “a limited
class of documents which should have been co nsidered by the [agency] in reaching the
challenged decision.” Ctr. for Native Ecosystems v. Salazar, 711 F. Supp. 2d 1267, 1281
(D. Colo. 2010). Here, there is no dispute that the two documents subject to the motion to
supplement were sent to the Agency months before it issued the permit.

7 The court of appeals stated the followi ng in remanding to the Agency: “[T]he
Canadian technical report raises questions concerning whethe r, if metal prices drop, the
project can remain viable with the 32,000 [tons per day] throughput limit that the synthetic-
minor permit necessitates.” In re Air Emissions Permit for PolyMet Mining, Inc. ,
943 N.W.2d at 410. The March 2018 Report a nd the potential that dropping metal prices
could lead to a lack of viability (as described in the Report) were each in the record as
submitted by the Agency to the court of appeals.

22
THISSEN, J., took no part in the consideration or decision of this appeal.