ALJDEC decisions subject to certification as final

25-002-WQAB · Water Quality Appeals Board · 2026-07-17

IN THE OFFICE OF ADMINISTRATIVE HEARINGS

SAN CARLOS APACHE TRIBE, and ARIZONA MINING REFORM COALITION,

Appellants,

DEPARTMENT OF ENVIRONMENTAL QUALITY

Respondent

RESOLUTION COPPER MINING, LLC,

Intervenor.

No. 25-002-WQAB

ADMINISTRATIVE LAW JUDGE DECISION

HEARING: May 11, 2026

APPEARANCES: Bernard M. Velasco and James N. Saul appeared on behalf of Appellants San Carlos Apache Tribe and Arizona Mining Reform Coalition. Assistant Attorneys General James C. Olson II and Taylor Parmenter appeared on behalf of the Department of Environmental Quality. Christopher D. Thomas and Janet M. Howe appeared on behalf of Intervenor Resolution Copper Mining LLC.

ADMINISTRATIVE LAW JUDGE: Adam D. Stone

EXHIBITS ADMITTED INTO EVIDENCE: Exhibits 1-12 were admitted into evidence.

_____________________________________________________________________

FINDINGS OF FACT

In 1975, the United States Environmental Protection Agency (“EPA”) issued what is now Arizona Pollutant Discharge Elimination System (“AZPDES”) discharge permit No. 0020389 (“Permit”) to the Magma Copper Mine (“Magma”); that Permit has been serially renewed by EPA or, after 2002, by the Arizona Department of Environmental Quality (“ADEQ”).

Resolution Copper Mining LLC (“RCM”), the successor to Magma, applied to renew the Permit. RCM owned the copper mine north of the town of Superior in Pinal County, Arizona. Because it may eventually be necessary for the mine to discharge into a nearby Waters of the United States (“WOTUS”), Queen Creek, RCM holds the Permit. The Permit authorizes two separate discharges (“outfalls” in permitting parlance): Outfall 001 is the discharge of untreated stormwater from CP-105, a pond that collects precipitation runoff that is impacted by industrial activity. RCM is only authorized to discharge from Outfall 001 in the event of a large storm. Outfall 002 is the discharge of water—mostly stormwater or groundwater pumped as part of the mine’s “dewatering” efforts—treated by the industrial mine water treatment plant and discharged to Queen Creek. Despite having AZPDES permit coverage for decades, RCM has never discharged to Queen Creek and instead diverts treated water for reuse by a nearby irrigation district.

On July 23, 2021, RCM timely applied to renew the Permit. ADEQ published the draft renewal Permit on March 9, 2022, and notified the public that it would accept public comments until April 9, 2022. ADEQ held a public hearing on the Permit on April 11, 2022, and then extended the public comment period from April 13, 2022 until May 31, 2022—an extra month and a half. Meanwhile, the San Carlos Apache Tribe’s appeal of the previous (now current) RCM AZPDES permit (the “2017 Permit”) was argued at the Arizona Court of Appeals. On November 15, 2022, the Court of Appeals decided against ADEQ, temporarily upending the AZPDES permit program on grounds now irrelevant to this appeal. After the Supreme Court of Arizona accepted ADEQ and RCM’s appeal, the agency decided to pause the permitting process to ensure that the renewed permit complies with state law. On June 27, 2024, the uncertainty was resolved when the Arizona Supreme Court decided in favor of ADEQ and RCM. ADEQ granted the Permit renewal on September 20, 2024 (the “2024 Permit”).

On March 9, 2022, ADEQ published its final permit decision for public comment; during the comment period, ADEQ received comments contesting the Decision to change the prohibition on discharging untreated stormwater runoff from CP-105 from anything less than a 100-year, 24-hour storm event to a 10-year, 24-hour storm event.

In response to these comments, ADEQ stated (1) “[e]xemption provisions under 40 CFR 440.131(b) apply only to [Technology Based Emission Limits (“TBELs”)] under 40 CFR 440, not to any [Water Quality Based Effluent Limits (“WQBELs”)]; (2) “all permit limits from the CP-105 pond are WQBELs”; (3) “no exemptions under 40 CFR 440.131(b) are permissible”; and (4) “[t]he 100-year storm limitation . . . has no basis in rule.”

On September 20, 2024, ADEQ provided notice it would renew the Permit with a 10-year, 24-hour storm event limit, and, on December 13, 2025, the Permit took effect with that limit. Like RCM’s previous permits, the Renewed Permit authorizes two discharge points: (1) Outfall 001 for stormwater runoff collected from the West Plant site; and (2) Outfall 002 for treated mine water, industrial water, and seepage pumping. Both outfalls are subject to numeric effluent limitations that meet both TBELs and WQBELs. Those numeric limits are set forth in Tables 1.a and 1.b of the Renewed Permit. TBELs were established based on technology available when standards were first established and are accordingly almost always less stringent than WQBELs. WQBELs are calibrated to protect the quality of the receiving water body, in this case Queen Creek. RCM has never discharged from either outfall. Instead, RCM treats water that would otherwise be discharged from either outfall at the mine water treatment plant and sends it for irrigation purposes to the New Magma Irrigation and Drainage District.

The Renewed Permit was issued by ADEQ pursuant to its delegated

authority under the federal Clean Water Act, 33 U.S.C. §§ 1251 et seq. Section 402 of the Act, 33 U.S.C. § 1342, authorizes the EPA and approved States to issue permits to discharge “pollutants” into jurisdictional “waters of the United States.” Such permits are called National Pollutant Discharge Elimination System (“NPDES”) permits when issued by EPA.

Arizona received delegation to issue permits on non-tribal lands in Arizona, subject to ultimate EPA oversight, in 2002. Approval of Application by Arizona to Administer the NPDES Program, 67 Fed. Reg. 79629 (Dec. 30, 2002). When issued by ADEQ, discharge permits are AZPDES permits. All past and present owners and operators of the RCM facility have continuously held either an NPDES permit or an AZPDES permit since permits regulating mining and metallurgical facilities were first established in 1975.

On October 19, 2024, Appellants, the Arizona Mining Reform Coalition and San Carlos Apache Tribe (collectively, “Appellants”) appealed the decision to renew the Permit.

On December 11, 2024, the Waters Quality Board of ADEQ issued a Notice of Hearing in this matter to determine whether ADEQ’s decision to grant renewal of the RCM Copper Mining AZPDES Permit No. AZ0020389 (LTF No. 90471), was appropriate.

The hearing was held on May 11, 2026.

Although Appellants initially noticed seven issues for appeal, the list was later narrowed to four, and ultimately Appellants pursued only one issue during the Court’s May 11, 2026 hearing. The Renewed Permit authorizes discharge from two points, or “outfalls.” The challenged provision of the Renewed Permit pertains to Outfall 001, which authorizes discharge of collected stormwater provided that it meets specific numeric criteria and a triggering event occurs. The stormwater consists of rainfall that falls onto or crosses parts of RCM’s West Plant site.

The numeric discharge criteria in the Renewed Permit have not been relaxed, and Appellants do not challenge the same. Rather, Appellants challenge the alteration of another component of the permit that dictates the circumstances under which collected stormwater can be discharged. The Renewed Permit authorizes discharge whenever the RCM facility encounters a rainfall event whose magnitude is expected once in 10 years. The previous version of the permit allowed discharges of stormwater only in the event of a once-in-a-100-year rainfall event. For ease of reference, this provision will be called the “Stormwater Discharge Trigger.”

Appellants contended that ADEQ made its decision to change the Stormwater Discharge Trigger “unlawfully, unreasonably, and arbitrarily” based upon six separate grounds, namely:

First, Appellants contended that the Decision was unlawful because it will allow discharges of untreated stormwater runoff that will exceed Permit limits.

Second, Appellants contend that the Decision was unlawful because it applies a regulatory exemption for TBELs to discharges limited by Water Quality Based Effluent Limits WQBELs”.

Third, Appellants contend that the Decision was unlawful because the change from a prohibition on discharges from anything less than a 100-year, 24-hour storm event to any 10-year, 24-hour storm event constitutes impermissible backsliding in violation of the Clean Water Act (“CWA”).

Fourth, Appellants contended that the Decision was arbitrary and unreasonable because it contradicts sampling results (“Results”) that show concentration of copper and lead that exceed Permit limits and that ADEQ “deemed . . . representative” of any discharge of untreated stormwater runoff through Outfall 001.

Fifth, Appellants contended that the Decision was unreasonable to the extent it relies on RCM’s justifications for the 10-year storm limit, including (1) concerns about improbable “back to back to back” storms; and (2) a mistaken assumption that RCM is entitled to discharge untreated storm water.

Sixth, Appellants contended that the Decision was arbitrary because it demonstrated that ADEQ treated similarly situated permittees differently. Specifically, Appellants pointed to a fact sheet ADEQ published explaining that the Pinto Valley Mining Corp.’s (“Pinto Valley”) discharge permit would include a revised prohibition on discharges of untreated stormwater runoff from less than a 100-year, 24-hour storm event rather than the previous limit of a 10-year, 24-hour storm event. Appellants contended that like RCM, Pinto Valley was another copper mine that holds a permit authorizing discharge into a water body that is impaired for copper and that has the capacity to contain stormwater associated with a 100-year, 24-hour storm event.

ADEQ and RCM asserted that the Decision was not unlawful, unreasonable, or arbitrary, and presented three witnesses, namely Josephine Maressa of ADEQ and Dr. Casey McKeon and Darla Gage.

16. Ms. Maressa has been employed by ADEQ since March 2021 and was currently the Deputy Director of the ADEQ Water Quality Division. As part of her role, she oversees the AZPDES program delegated to ADEQ by EPA. She holds three degrees: a juris doctor, a master’s degree in environmental law and policy, and a bachelor’s degree in environmental studies.

17. Ms. Maressa testified that Arizona’s AZPDES program regulates, among other things, stormwater, or “runoff from a precipitation event that may pick up pollutants and carry them to a surface water.”

18. In addition, Ms. Maressa testified that the EPA reviews AZPDES permits to ensure they comply with the Clean Water Act, and that the EPA specifically reviewed the Renewed Permit and had no objections or concerns regarding the Renewed Permit’s compliance with the Clean Water Act.

19. Ms. Maressa reviewed the Renewed Permit before it was issued by the

ADEQ. ADEQ changed the 100-year Stormwater Discharge Trigger because it concluded it lacked the authority to impose it, since it had no basis in rule. During the renewal process, RCM asked ADEQ to clarify the legal basis for the 100-year Stormwater Discharge Trigger. In the prior permit, RCM had voluntarily agreed to the 100-year Stormwater Discharge Trigger provision. Upon review, ADEQ determined that it did not have legal authority under the Clean Water Act to impose the 100-year Stormwater Discharge Trigger. Further, Arizona state law prohibits ADEQ from imposing on regulated parties conditions more stringent than federal law.

20. Regardless of when any discharge from Outfall 001 occurs and the size of

the storm event, RCM’s discharge must always meet the numeric limitations in the

Renewed Permit Table 1.a. Ms. Maressa testified twice about this:

Q: Okay. So if RCM is – if the mine is hit by a 10-year storm and

RCM discharges, are there limits, concentration limits, that RCM is supposed to meet?

A: Every single time they discharge, they must meet these limits.

Q: Oh. So regardless of the size of the storm, if RCM discharges from Outfall 001, they need to meet these limits?

A: That is correct.

21. Ms. Maressa also testified regarding the inclusion of a 100-year Stormwater Discharge Trigger at a different mine, the Pinto Valley Mine. In that case, the legal basis for including the 100-year trigger was the agency’s completion of a total maximum daily load (“TMDL”) study. A TMDL is a diet for an impaired water body. It assigns maximum pollutant loading limits to dischargers along the impaired water body. The Pinto Valley Mine discharges into Pinto Creek, which has a completed TMDL. It is the completed TMDL and the corresponding pollutant allocation that provides the legal basis for the 100-year stormwater trigger in the draft Pinto Valley Mine permit. If RCM were to discharge from Outfall 001, it would discharge into Queen Creek, for which there is no TMDL. The existence of the completed TMDL for Pinto Creek and the absence of a TMDL for Queen Creek explains why ADEQ could impose the 100-year Stormwater Discharge Trigger in one permit and not the other. Ms. Maressa could not say whether the next Resolution permit renewal would be impacted by future completion of a Queen Creek TMDL, but it is possible.

22. Dr. Casey McKeon was Resolution’s principal advisor for permitting and

approvals, a position she has held since 2022. She previously worked at Resolution from April 2005 through 2019, starting as an environmental advisor and later serving as

environmental manager. She holds three degrees from the University of Arizona, including a doctorate in soil and water science (conferred in 2003), a master’s degree in soil and water science (earned in 1999), and a bachelor’s degree in microbiology (conferred in 1995). She also did post-doctoral work at the University of Arizona. Dr. McKeon helped prepare RCM’s application for the AZPDES permit immediately prior to the Renewed Permit.

23. Dr. McKeon also supervised most of the reclamation work conducted by

RCM to eliminate exposure of pollutants to stormwater flow. That work had not

been completed before the prior AZPDES permit was issued. Further, Dr. McKeon demonstrated how RCM Exhibit 6 depicts the areas in which exposed pollutants were relocated, closed, capped, or graded. The work was supervised by either ADEQ, under one of several programs, or by the State Mine Inspector. ADEQ was satisfied with the cleanup work it supervised. Work supervised by the State Mine Inspector was also completed to the Inspector’s satisfaction. RCM has completed remediation of all areas of the facility that received rainfall that would report to CP-105 and possibly be discharged from Outfall 001. RCM completed remediation of 11 impacted areas that could have reported to CP-105. All of those areas have been cleaned up to the satisfaction of the government.

24. Darla Gage was RCM’s principal advisor for the environment, a position she has held since April 2023. She ensures that the company maintains compliance with environmental permits including the Renewed Permit. She holds a master’s degree in mining and engineering (conferred by the University of Arizona in 2022) and a bachelor’s degree in geology (conferred by the University of North Dakota in 2002). She started working at RCM in 2018.

25. Ms. Gage helped complete RCM’s application for the Renewed

Permit, submitted in 2021. She was involved in RCM’s request to ADEQ to amend the Stormwater Discharge Trigger from a 100-year, 24-hour storm event to a 10-year, 24-hour storm event. At the time of the application for the Renewed Permit, RCM “had cleaned up the site and felt that the stormwater would meet standards if [it] ever had to discharge.” RCM was also concerned about the potential need to refrain from discharging in the event of back-to-back storm events lesser than 100-year events.

26. In addition, Ms. Gage testified all the reclamation in the areas exposed to rainfall and stormwater was “100 percent complete by the late 2020 with the approval from the ADEQ in 2021.” That was before submittal of the application for the Renewed Permit.

27. Ms. Gage testified further, that since RCM has never discharged from either outfall, it had no water quality data from discharged water when it submitted the Renewed Permit Application. The only stormwater capable of being sampled for the Renewed Permit Application was water collected in CP-105 during a storm event smaller than a 10-year, 24-hour event, but it was not representative of the quality of water that would potentially be discharged from Outfall 001 during a 10-year, 24-hour event or larger. CP-105 is normally only 25 percent full. If there was a discharge trigger storm event at the 10-year level, the concentration of pollutants would be much more diluted. A 10-year storm event produces a large volume of water, and the likelihood of it being contaminated is minimal. Ms. Gage’s opinion was informed by her 20 years of stormwater sampling at the facility. Additionally, were there any hint of a problem, the treatment plant has excess capacity—around 1600-1700 gallons per minute—to accommodate treatment of stormwater from CP-105 and routing the treated stormwater to the New Magma Irrigation District, rather than discharging through Outfall 001. In conclusion, Ms. Gage was confident that, were stormwater to ever be discharged from Outfall 001, it would comply with the discharge limitations in the Permit.

CONCLUSIONS OF LAW

The tribunal has jurisdiction in this matter pursuant to A.R.S. Title 49, Chapter 2, Article 3.1 and implementing rules.

This appeal of ADEQ’s decision to renew RCM’s AZPDES permit, No. AZ0020389, is governed by A.R.S. § 49-324(C), which provides:

Decisions by the director shall be affirmed by the appeals board unless, considering the entire record before the board, it concludes that the director’s decision is arbitrary, unreasonable, unlawful or based upon a technical judgment that is clearly invalid.

Appellants bear the burden of proof and the standard of proof on all issues in this matter is that of a preponderance of the evidence. Ariz. Admin. Code § R2-19-119.

A preponderance of the evidence is:

The greater weight of the evidence, not necessarily established by the greater number of witnesses testifying to a fact but by evidence that has the most convincing force; superior evidentiary weight that, though not sufficient to free the mind wholly from all reasonable doubt, is still sufficient to incline a fair and impartial mind to one side of the issue rather than the other.

Black’s Law Dictionary 1373 (10th ed. 2014).

5. ADEQ’s decision to modify the Renewed Permit, after the appropriate comment period, to allow stormwater to be discharged from Outfall 001 in the event of a 10-year, 24-hour storm event instead of a 100-year, 24-hour storm event was not arbitrary, unreasonable, unlawful, or based upon a technical judgment that was clearly invalid.

6. The revision does not violate the anti-backsliding prohibitions of Section 402(o) of the Clean Water Act, 33 U.S.C. § 1342(o). Section 402(o) applies only to “effluent limitations.” The statutory definition of that term requires a restriction “established by a State or the Administrator.” The phrase “established by a State or the Administrator” is controlling. It distinguishes generally applicable, formally adopted limits from other permit terms, negotiated conditions, or historical carryovers that may appear in a permit.

7. The 100-year, 24-hour Stormwater Discharge Trigger is not generally applicable or enforceable or required by any legal authority. It does not appear in any regulation promulgated by the U.S. Environmental Protection Agency (“EPA”) or ADEQ. Appellants only cited basis for the proposition that the restriction is generally enforceable is 40 C.F.R. § 440.131(b). The provisions of 40 C.F.R. Part 440 are not applicable to stormwater discharges but rather process water discharges from ore mining and dressing facilities. Nothing in 40 C.F.R. Part 440 regulates stormwater or the circumstances under which stormwater may be discharged. Even as to mine process water that is regulated by Part 440, there is no frequency restriction. Rather, 40 C.F.R. § 440.131(b) provides an exemption from discharge limitations if a facility:

is designed, constructed and maintained to contain the maximum volume of wastewater which would be generated by the facility during a 24-hour period without an increase in volume from precipitation and the maximum volume of wastewater resulting from a 10-year, 24-hour precipitation event.

This exemption is an affirmative defense to an enforcement action applicable only to a possible defense to (1) a discharger of mine process water; (2) who is subject to an independently specified volumetric discharge limitations under Part 440; and (3) cannot comply with the volumetric limitations because of a 10-year, 24-hour storm event. A defense to liability for a violation of an independently imposed volumetric limitation does not itself constitute such a limitation.

8. Outfall 001 is not permitted to discharge mine process water subject to Part 440. By contrast, Outfall 002, in the Renewed Permit, is allowed to discharge mine process water; but that outfall is governed by its own requirements with no storm event triggers and is not a subject of this challenge.

9. The 100-year, 24-hour Stormwater Discharge Trigger in RCM’s prior AZPDES permit was a negotiated permit term not formally promulgated as an “effluent limitation.” The numeric effluent discharge limitations in the Resolution permit—whose relaxation might be prohibited by Section 402(o)—have not been made less stringent, and Appellants do not challenge them.

10. Even if the 100-year, 24-hour Stormwater Discharge Trigger was considered an effluent limitation subject to Section 402(o), two exceptions to the anti-backsliding prohibition would justify ADEQ’s relaxation of the limitation. Section 402(o)(2)(A) allows relaxation of effluent discharge limitations when “material and substantial alterations or additions to the permitted facility occurred after permit issuance which justify the application of a less stringent effluent limitation.” Unrebutted testimony here demonstrates that prior to the issuance of the challenged permit, Resolution eliminated stormwater exposure to impacted material in 11 separate locations. That cleanup work constitutes the requisite “material and substantial alteration.”

11. Relaxation of an effluent limitation is also permissible under Section 402(o)(2)(B)(ii) if the prior effluent limitations were included in a permit based on a mistake of law. As noted above, the frequency restriction is not an enforceable limit. ADEQ offered unrebutted testimony that the inclusion of the 100-year, 24-hour Stormwater Discharge Trigger was not supported by law and absent Resolution’s consent could not be imposed.

12. The tribunal also concludes that this appeal is distinguishable from the Pinto Valley Mine. The two mines discharge into different water bodies. Pinto Valley Mine discharges into Pinto Creek, which has a completed TMDL. AZPDES permits must be consistent with the assumptions and requirements of an applicable TMDL. See Rio Hondo Land & Cattle Co. v. EPA, 995 F.3d 1124, 1129 (10th Cir. 2021) (citing 40 C.F.R. § 122.44(d)(1)(vii)(B)). The TMDL for Pinto Creek mandates that discharges from mine facilities cannot occur except for during a 100-year, 24-hour storm event. ADEQ is therefore authorized, and required, to include the 100-year, 24-hour storm event discharge conditions in the Pinto Valley Mine Permit. Absent authority in federal law, state law, or a TMDL, there is no legal basis for ADEQ to limit Resolution’s discharge from Outfall 001 based on a 100-year, 24-hour storm event.

ORDER

IT IS ORDERED that the San Carlos Apache Tribe and Arizona Mining Reform Coalition appeal be dismissed.

In the event of certification of the Administrative Law Judge Decision by the Director of the Office of Administrative Hearings, the effective date of the Order will be forty (40) days from the date of that certification.

-54864001

001

-137160-45720000Done this day, July 17, 2026.

/s/ Adam D. Stone

Administrative Law Judge

Transmitted by either mail, e-mail, or facsimile to:

Connie Castillo, Clerk

Water Quality Appeals Board

San Carlos Apache Tribe, Department of Justice

Alexander Ritchie, Attorney General

[email redacted]

Bern Velasco, Assistant Attorney General

[email redacted]

James N. Saul

Wild & Scenic Law Center

[email redacted]

Arizona Attorney General’s Office

James C. Olson, II, Assistant Attorney General

Taylor Parmenter, Assistant Attorney General

[email redacted]

Christopher D. Thomas

Janet M. Howe

HOLLAND & HART LLP

[email redacted]

By: OAH Staff