The slip opinion is the first version of an opinion released by the Chief Clerk of the 

Supreme Court. Once an opinion is selected for publication by the Court, it is 

assigned a vendor-neutral citation by the Chief Clerk for compliance with Rule 23-

112 NMRA, authenticated and formally published. The slip opinion may contain 

deviations from the formal authenticated opinion.

IN THE COURT OF APPEALS OF THE STATE OF NEW MEXICO

Opinion Number: _____________

Filing Date: May 16, 2022

Nos. A-1-CA-38474 and A-1-CA-38478

(consolidated for purpose of opinion)

ELEPHANT BUTTE IRRIGATION

DISTRICT,

Petitioner-Appellant,

and

TURNER RANCH PROPERTIES, L.P.;

HILLSBORO PITCHFORK RANCH, LLC;

and GILA RESOURCES INFORMATION

PROJECT,

Petitioners-Appellants,

v.

NEW MEXICO WATER QUALITY

CONTROL COMMISSION,

Respondent-Appellee,

and

NEW MEXICO COPPER CORPORATION

and NEW MEXICO ENVIRONMENT

DEPARTMENT,
Intervenors-Appellees,

IN THE MATTER OF THE APPLICATION

FOR NEW MEXICO COPPER CORPORATION

FOR A GROUND WATER DISCHARGE

PERMIT FOR THE COPPER FLAT MINE, DP1840, DOCKETED AS GWB 18-06(P).

APPEAL FROM THE WATER QUALITY CONTROL COMMISSION

Jennifer J. Pruett, Chair

Barncastle Law Firm

Samantha R. Barncastle

Las Cruces, NM 

for Appellant Elephant Butte Irrigation District

New Mexico Environmental Law Center

Charles de Saillan

Santa Fe, NM

for Appellants Turner Ranch Properties, L.P., Hillsboro Pitchfork Ranch, LLC, and 

Gila Resources Information Project

Hector H. Balderas, Attorney General

Robert F. Sánchez, Assistant Attorney General

Santa Fe, NM

for Appellee New Mexico Water Quality Control Commission

Modrall, Sperling, Roehl, Harris & Sisk, P.A.

Stuart R. Butzier

Christina C. Sheehan

Albuquerque, NM

for Appellee New Mexico Copper Corporation

Andrew P. Knight, Special Assistant Attorney General

Albuquerque, NM
for Appellee New Mexico Environment Department
OPINION

HANISEE, Chief Judge.

{1} These appeals arise from an order of the New Mexico Water Quality Control 

Commission (the Commission) upholding the grant of New Mexico Copper 

Corporation’s (N.M. Copper) application for a discharge permit for the Copper Flat 

Mine (the Mine) in Sierra County, New Mexico issued by the New Mexico 

Environment Department (the Department) under the New Mexico Water Quality 

Act (the Act), NMSA 1978, §§ 74-6-1 to -17 (1967, as amended through 2019), and 

its implementing regulations, 20.6.2 NMAC and 20.6.7 NMAC.1 Determining that,

in upholding the grant of the discharge permit (DP-1840), the Commission did not 

act arbitrarily, capriciously, or otherwise not in accordance with the law, we affirm. 

BACKGROUND

A. The New Mexico Water Quality Act

{2} Before turning to the facts at hand, we first provide a brief overview of the 

statutory framework governing the issues before us. The Act was enacted by the 

New Mexico Legislature who sought “to abate and prevent water pollution.” Bokum 

Res. Corp. v. N.M. Water Quality Control Comm’n, 1979-NMSC-090, ¶ 59, 93 N.M. 

 

1This opinion resolves the parties’ challenges to the Commission’s Order in 

case numbers A-1-CA-38474 and A-1-CA-38478. Because these cases raise related 

issues arising from the same application for a discharge permit, we consolidate both 

for decision. See Rule 12-317(B) NMRA. 
2

546, 603 P.2d 285. The Act authorizes the Commission to “adopt water quality 

standards for surface and ground waters of the state,” which must “protect the public 

health or welfare, enhance the quality of water and serve the purposes of the . . . 

Act.” Section 74-6-4(C). The Act provides that, “the [C]ommission may require 

persons to obtain from a constituent agency designated by the [C]ommission a 

permit for the discharge of any water contaminant or for the disposal or reuse of 

septage or sludge.” Section 74-6-5(A). The Act further mandates that the constituent 

agency shall deny any application for a permit if: 

(1) the effluent would not meet applicable state or federal effluent 

regulations, standards of performance or limitations; 

(2) any provision of the . . . Act would be violated; 

(3) the discharge would cause or contribute to water contaminant 

levels in excess of any state or federal standard. 

Section 74-6-5(E).

{3} In 2009, the Act was amended to direct the Commission to adopt regulations 

particular to specific industries, including the copper mining industry, specifying 

“the measures to be taken to prevent water pollution and to monitor water quality.” 

Section 74-6-4(K); Gila Res. Info. Project v. N.M. Water Quality Control Comm’n, 

2018-NMSC-025, ¶ 3, 417 P.3d 369. The regulations were to be developed by the 

Department and proposed for adoption by the Commission. Section 74-6-4(K). 

Pursuant to these regulations, the Department proposed and the Commission adopted 
3

the Copper Rule. See Gila Res. Info. Project, 2018-NMSC-025, ¶ 1 (affirming the 

Commission’s adoption of the Copper Rule). The Copper Rule is a “supplement [to] 

the general permitting requirements . . . to control discharges of water contaminants 

specific to copper mine facilities.” 20.6.7.6 NMAC. The Copper Rule acknowledges 

that “open pit copper mining leads inevitably to some degree of contaminant 

discharge” and “operates from the premise that the most effective way to mitigate 

these inevitable discharges is through containment.” Gila Res. Info. Project, 2018-

NMSC-025, ¶ 43. Considering the inevitable discharges associated with open pit 

copper mining, the Copper Rule specifies that “[d]uring operation of an open pit,” 

the groundwater quality standards set forth by 20.6.2.3103 NMAC “do not apply 

within the area of open pit hydrologic containment.” 20.6.7.24(D) NMAC. 

B. DP-1840 and the Relevant Proceedings 

{4} We now describe the factual background leading to this appeal. N.M. Copper 

intends to reopen and operate the Mine, a historic open pit copper mine located 

approximately five miles northeast of Hillsboro in Sierra County, New Mexico. The 

Mine sits adjacent to and shares a border with both Hillsboro Ranch Properties and 

the Ladder Ranch (collectively, the Ranches). Several mining companies have 

attempted to operate the Mine over the past fifty years. See State ex. rel. Off. of State 

Eng’r v. Elephant Butte Irrigation Dist., 2021-NMCA-066, ¶¶ 6-31, 499 P.3d 690 

(explaining the complex history of the ownership and operation of the mine). In 
4

2009, N.M. Copper entered into an agreement to purchase the Mine and associated 

mineral claims, and did so in 2011.

{5} In March 2011, N.M. Copper submitted an application to the Department for 

a modification of the existing groundwater discharge permit for the Mine. In 

February 2018, the Department’s Groundwater Quality Bureau published a public 

notice of the Department’s proposal to issue DP-1840, stating that the Department 

would accept public comment on the proposed permit for thirty days, which was 

extended for an additional sixty days at the request of several parties. The 

Department held a public hearing on the proposed permit from September 24-28, 

2018, at which N.M. Copper, the Department, as well as the Ranches and the 

Elephant Butte Irrigation District (EBID) (collectively, Appellants) presented the 

testimony of technical witnesses. As well, forty-eight members of the general public 

made oral statements. In December 2018, the Administrative Hearing Officer (AHO) 

issued a report (the AHO Report) alongside proposed findings of fact and 

conclusions of law, determining that the discharge did not pose an “undue risk to 

property” and that the open pit water body will not be a water of the state, and 

therefore is not subject to surface water quality standards. That same month, the 

Secretary of the Department (the Secretary) issued its order (the NMED Order), in 

which the Secretary adopted the AHO’s Report of proposed findings of fact and 

conclusions of law and added thirteen additional findings and conclusions. Finally, 
5

in September 2019, the Commission adopted its final order (the Final Order), 

adopting the NMED Order with additional revisions, and granting N.M. Copper’s 

application for DP-1840. DP-1840 authorizes N.M. Copper to discharge a maximum 

25,264,000 gallons per day of tailings slurry, including “mine tailings, process water, 

impacted storm[]water, and domestic wastewater to a lined tailing impoundment,” 

known as the Tailings Storage Facility. Additionally, DP-1840 regulates “discharges 

from other mine units, including waste rock stockpiles, ore stockpiles, mineral 

processing units, process water impoundments, an open pit, sumps, tanks, pipelines, 

and other areas within the permit boundary of approximately 2,190 acres.”

C. The Final Order 

{6} In the Final Order, the Commission concluded that the opposing parties, 

including EBID and the Ranches, “did not prove that the discharges from DP-1840’s 

permitted mine operations will cause undue risk to [the Ranches’] property.” 

Although the Commission provided only limited insight into its reasoning, through 

the NMED Order the Secretary explained that “[t]he phrase ‘undue risk to property’ 

as used in the Copper Rule pertains to potential impacts to water quality from the 

permitted discharges, not to the depletion of groundwater.” Similarly, the Secretary

explained that its conclusion that “the discharges from permitted mine operations 

will not cause undue risk to the property of the Ranches, or [EBID], or anyone else” 

was based on a totality of expert witness testimony, specifically expert testimony
6

based on “site-specific modeling and analysis, and addressed scientific likelihoods 

rather than speculation.” And while the Final Order issued by the Commission did 

not articulate specific reasoning as it relates to the proposed pit lake, the Secretary 

explained, “The future pit lake at Copper Flat will not be a surface water of the state 

subject to the water quality standards in 20.6.4 NMAC.”

DISCUSSION

{7} EBID asserts that in granting N.M. Copper’s discharge permit the 

Commission “ignored its determination that the phrase ‘undue risk to property’ as 

used in the Copper Rule, 20.6.7 NMAC, may be broader than potential impacts to 

water quality from the permitted discharges.”

2 The Ranches similarly contend that

 

2EBID additionally contends that that the Commission “failed to consider that 

the Department had failed to engage in appropriate interagency coordination related 

to the [Mine], which itself, poses an undue risk to the Elephant Butte Irrigation 

District.” Specifically, EBID argues that “it would have assisted the [AHO] and the 

Secretary” when evaluating the risk to property presented by the Mine to “have 

access to items that are part of the [State Engineer’s] Dam Safety Bureau application 

process,” such as a design report, operation and maintenance manual, and emergency 

action plan. Similarly, EBID asserts that an emergency action plan developed in 

collaboration with EBID, the U.S. Bureau of Reclamation and all affected state 

agencies that addresses catastrophic events “should have been required as a permit 

condition” to ensure that the Mine does not pose an “undue risk to property.” While 

EBID emphasizes the importance of such coordinated efforts, it is not supported by 

statutory authority requiring such efforts. See In re Adoption of Doe, 1984-NMSC024, ¶ 2, 100 N.M. 764, 676 P.2d 1329 (“We assume where arguments in briefs are 

unsupported by cited authority, counsel after diligent search, was unable to find any 

supporting authority. . . . Issues raised in appellate briefs which are unsupported by 

cited authority will not be reviewed by us on appeal.” (citation omitted)). Our own 

research has revealed no such requirements, much less authority suggesting such an 

omission would be structurally fatal to a discharge permit. Because we have no 
7

the Commission failed to adequately explain its conclusion that DP-1840 will not

pose an “undue risk to property.” Additionally, the Ranches assert that DP-1840 

violates the Act, and the Commission did not adequately explain its conclusion that 

surface water standards will not apply to the pit lake. We first set forth the standard 

of review, then analyze Appellants’ arguments as they relate to the Commission’s 

interpretation of “undue risk to property,” and then turn to the Ranches’ remaining 

arguments. 

I. Standard of Review

{8} The Act provides that we “shall set aside the [C]ommission’s action only if it 

is found to be: (1) arbitrary, capricious, or an abuse of discretion; (2) not supported 

by substantial evidence in the record; or (3) otherwise not in accordance with law.” 

Section 74-6-7(B). “A ruling by an administrative agency is arbitrary and capricious 

if it is unreasonable or without a rational basis, when viewed in light of the whole 

record.” Colonias Dev. Council v. Rhino Env’t Servs., 2005-NMSC-024, ¶ 13, 138 

N.M. 133, 117 P.3d 939 (internal quotation marks and citation omitted).

Additionally, “[a]n agency’s action is arbitrary and capricious if it provides no 

rational connection between the facts found and the choices made, or entirely omits 

consideration of relevant factors or important aspects of the problem at hand.”

 

authority to apply conditions not within the Act, nor employ regulations not 

promulgated by the Commission, we reject these arguments. 
8

Albuquerque Cab Co. v. N.M. Pub. Regul. Comm’n, 2017-NMSC-028, ¶ 8, 404 P.3d

1 (internal quotation marks and citation omitted). An agency decision is not in 

accordance with the law “if the agency unreasonably or unlawfully misinterprets or 

misapplies the law.” Princeton Place v. N.M. Hum. Servs. Dep’t, 2018-NMCA-036, 

¶ 27, 419 P.3d 194 (internal quotation marks and citation omitted), rev’d on other 

grounds, 2022-NMSC-005, ¶ 3. 

{9} Although not bound by the agency’s interpretation, we “confer a heightened 

degree of deference to legal questions that implicate special agency expertise or the 

determination of fundamental policies within the scope of the agency’s statutory 

function.” Morningstar Water Users Ass’n v. N.M. Pub. Util. Comm’n, 1995-

NMSC-062, ¶ 11, 120 N.M. 579, 904 P.2d 28 (internal quotation marks and citation

omitted). However, “statutory construction itself is not a matter within the purview 

of the [agency]’s expertise,” so we “afford little, if any, deference to the [agency]” 

on questions of law not involving this expertise or policy determination. N.M. Indus. 

Energy Consumers v. N.M. Pub. Regul. Comm’n, 2007-NMSC-053, ¶ 19, 142 N.M. 

533, 168 P.3d 105 (internal quotation marks and citation omitted).

II. The Commission’s Order Determining That the Mine Did Not Pose an 

Undue Risk to Property Was Not Arbitrary, Capricious, or Otherwise 

Not in Accordance With the Law 

{10} The parties dispute the meaning and factors that must be considered in 

determining whether a discharge permit creates an “undue risk to property.” EBID 
9

and the Ranches contend that “undue risk” should encompass the Mine’s impact on 

both water quality and quantity. They also argue that they presented compelling 

evidence of an “undue risk” to their respective properties from both contamination 

and depletion. 

A. The Scope of “Undue Risk” 

{11} Appellants contend that the Commission erred in determining that the Mine 

did not present “an undue risk to property” because the Commission failed to 

consider the Mine’s inevitable depletion of surface water. EBID asserts that because 

the Commission did not provide a definition of the phrase, but instead explained that 

the consideration of undue risk “may be broader than potential impacts to water 

quality from the permitted discharges and shall be reviewed on a case[-]by[-]case 

basis,” the Commission rendered the phrase “superfluous in violation of the law.”3

 

3 EBID similarly contends that the meaning of “undue risk” requires a 

consideration of depletion because the Commission rejected the Secretary’s finding 

No. 4 which provided, “the phrase undue risk to property pertains to potential 

impacts to water quality from the permitted discharges, not to the depletion of 

groundwater” and instead explained that “the phrase . . . as used in the Copper Rule 

20.6.7 NMAC, may be broader than potential impacts to water quality from the 

proposed discharges and shall be reviewed on a case[-]by[-]case basis.” We 

disagree. Such modified language employed by the Commission does not mean that 

it considered, or must consider, potential depletion of groundwater in its discharge 

determination. Rather, in replacing the limiting language set forth by the Secretary, 

the Commission explained that in making a determination that a discharge permit 

poses an “undue risk,” it may broadly consider “potential impacts to water quality.” 

We simply do not view the Commission as having—by rejecting the Secretary’s 

wording in its order applicable only to this case—expanded the permit application 

process beyond the context of the discharge at issue on a case-by-case basis. Indeed, 
10

Similarly, the Ranches argue that because the Commission failed to consider the 

relevant factor of water depletion, its order is arbitrary, capricious, or an abuse of 

discretion. 

{12} We disagree with Appellants’ contention that a determination of whether a 

mine presents “an undue risk to property” requires consideration of potential 

depletion. This appeal arises from an order granting an application for a discharge 

permit, and the scope of the issues available for our review are neither broader nor 

narrower than that. Granting a discharge permit requires compliance with the Copper 

Rule and a determination that any discharge authorized under a permit creates no 

hazard to public health nor undue risk to property owners. 20.6.7.10(J) NMAC. 

Thus, any challenge asserting that the permit should not be granted must relate to 

“undue risk” attributed to the discharge authorized under DP-1840. As the NMED

Order provides, DP-1840 “only regulates discharges of water at the [M]ine site,” and 

“does not allocate water for use . . . or permit the pumping of groundwater.” Stated 

differently, DP-1840 has nothing to with and does not authorize or permit water from 

any source to be used at the Mine. Indeed, neither the Department nor the 

Commission has the authority to regulate the source from which a discharger 

 

to do so would require more than a vague declaration lacking regulatory specificity. 

In any event, the Commission did not expressly provide that depletion is a factor to 

be considered in making a determination that a discharge permit would create an 

“undue risk to property.” 
11

receives the water that is utilized in the processes resulting in the discharge. Rather, 

our Legislature has delegated such authority solely to the Office of the State 

Engineer. See NMSA 1978, § 72-2-9 (1907) (“The state engineer shall have the 

supervision of the apportionment of water in this state according to the licenses 

issued by him and his predecessors and the adjudications of the courts.”); see also

NMSA 1978, § 72-2-9.1(B)(2-3) (2003) (“The state engineer shall adopt rules for 

priority administration . . . so as to create no impairment of water rights . . . and . . . 

so as to create no increased depletions.”). 

{13} At oral argument for this appeal, when asked to define the phrase, the 

Department described “undue risk to property” to be “a larger than acceptable 

chance that these discharges permitted by this permit [would] cause harm to 

surrounding properties.” While we accept for purposes of this appeal—and given 

that there is no statutory, regulatory or jurisdictional direction pointing this Court to 

a broader or more inclusive inquiry in the context of a discharge permit—the 

Commission’s interpretation of the phrase “undue risk to property,” we decline to 

formally adopt the definition provided by the Department. The formal adoption of 

such an interpretation, or a different one altogether, requires agency rulemaking in 

our view. See New Energy Econ., Inc. v. Shoobridge, 2010-NMSC-049, ¶ 14, 149 

N.M. 42, 243 P.3d 746 (explaining that the Legislature “delegate[s] both 

adjudicative and rule-making power to administrative agencies”); see also 
12

Earthworks’ Oil & Gas Accountability Project v. N.M. Oil Conservation Comm’n, 

2016-NMCA-055, ¶ 8, 347 P.3d 710 (“A court may not intervene in administrative 

rule-making proceedings before the adoption of a rule or regulation.” (alteration, 

internal quotation marks, and citation omitted)). Although the phrase “undue risk to 

property” does not include technical language such that it would be beyond the 

understanding of those without expertise, the question of what constitutes an “undue 

risk” requires agency knowledge within the scope of the Commission’s statutory 

function. See Morningstar, 1995-NMSC-062, ¶ 11 (explaining that although not 

bound by the agency’s interpretation, “[t]he [C]ourt will confer a heightened degree 

of deference to legal questions that implicate special agency expertise or the 

determination of fundamental policies within the scope of the agency’s statutory 

function.” (internal quotation marks and citation omitted)); see also Gila Res. Info. 

Project, 2018-NMSC-025, ¶ 35 (“We will overturn the administrative construction 

of statutes by appropriate agencies only if they are clearly incorrect.” (internal 

quotation marks and citation omitted)).

{14} We therefore conclude that the Commission’s Final Order, as it relates to the 

scope of “undue risk to property” and its related decision not to consider potential 

depletion, was not arbitrary, capricious, or otherwise not in accordance with the law. 

Nothing the Commission said within the Final Order or adopted or modified from 

the wording employed by the Secretary convinces us otherwise. We now turn to 
13

Appellants’ contentions that the Commission failed to adequately address 

compelling evidence of “undue risk” to their respective properties.

B. The Sufficiency of the Commission’s Final Order 

{15} We review the Commission’s Final Order to determine if it is supported by 

substantial evidence. “For questions of fact, [the appellate court] looks to the whole 

record to determine whether substantial evidence supports the [agency]’s decision.” 

Pub. Serv. Co. of N.M. v. N.M. Pub. Regul. Comm’n, 2019-NMSC-012, ¶ 14, 444 

P.3d 460 (alteration, internal quotation marks, and citation omitted). “Substantial 

evidence requires that there is evidence that is credible in light of the whole record 

and that is sufficient for a reasonable mind to accept as adequate to support the 

conclusion reached by the agency.” Id. (internal quotation marks and citation 

omitted). “Substantial evidence on the record as a whole is evidence demonstrating 

the reasonableness of an agency’s decision, and we neither reweigh the evidence nor 

replace the fact[-]finder’s conclusions with our own.” Albuquerque Bernalillo Cnty. 

Water Util. Auth. v. N.M. Pub. Regul. Comm’n, 2010-NMSC-013, ¶ 18, 148 N.M. 

21, 229 P.3d 494 (internal quotation marks and citation omitted). 

{16} In applying whole record review, we consider the AHO’s Report, as well as 

the NMED Order and the Commission’s Final Order. Over the course of a five-day 

hearing in September 2018, the AHO considered an assortment of evidence, 

including expert testimony from N.M. Copper, EBID, and the Ranches, as well as 
14

public comment and nearly 18,000 pages of administrative record. Although the 

AHO recognized that “[t]he fears expressed by the Ranches, EBID, and many of the 

public commenters are understandable,” the AHO declared, “Migration of 

significant water contaminants over very long distances, or in directions contrary to

typical groundwater flow” to be unlikely. To best understand the AHO’s conclusion 

that such contamination is unlikely, we highlight selected findings of fact provided 

in the AHO’s Report, and emphasize that neither EBID nor the Ranches challenges 

the AHO’s findings of fact. 

{17} The AHO Report notes that N.M. Copper used “[forty] years of data from 

exploration drilling programs, monitoring wells, aquifer testing, including 

groundwater samples from the previous mining operations . . . to characterize the 

hydrologic settling of the [M]ine site.” The AHO Report also explains that the East 

Animas Fault—which sits adjacent to the Mine—“could not serve as a conduit for 

the migration of contaminants through groundwater flow” as the “general direction 

of the groundwater flow at the [M]ine site is west to east.” Regarding the waste rock 

stockpiles, the AHO concluded that “[n]o impacts to groundwater will occur should 

there be any seepage,” and if seepage did occur, “all parameters of predicted 

groundwater chemistry are below New Mexico’s groundwater standards.” Similarly, 

addressing the Tailings Storage Facility, the AHO determined that “[t]here will be 

no water quality impacts to groundwater or surface water from the [facility].” 
15

Because these uncontested findings of fact require the application and understanding 

of technical expertise, we accord them proper deference. See Pickett Ranch, LLC v. 

Curry, 2006-NMCA-082, ¶ 49, 140 N.M. 49, 139 P.3d 209 (“Particularly where 

specialized technical or scientific knowledge is involved, we will give great 

deference to an agency’s factual findings.”).

{18} The AHO Report underscored that “what constitutes ‘undue risk’ in 

connection with the issuance of a groundwater discharge permit has not been set out 

in a regulation or guidance document, statute or New Mexico case law,” and 

expressly declined to make a recommendation regarding undue risk. However, the 

AHO noted that “[a]part from this issue of undue risk, the recommended findings 

and conclusions support the issuance of . . . [DP-1840] as based on substantial 

evidence.” Although the AHO declined to make a conclusion regarding undue risk, 

we conclude that substantial evidence, including the evidence highlighted above, 

supports the Commission’s Final Order determining that the Mine does not present 

an “undue risk to property.” 

{19} In the Final Order, the Commission also noted that its “decision [to grant DP1840] is based on the totality of expert witness testimony . . . with more weight given 

to that from experts who based their conclusions on site-specific modeling and 

analysis and who addressed scientific likelihoods rather than speculation.” The 

Ranches contend that this “is hardly a sufficient explanation of the Commission’s 
16

decision,” and argues that the Commission should have identified which evidence it 

found to be speculative. In asking us to consider the evidence and expert testimony 

it presented, the Ranches effectively ask us to reweigh the evidence, which we 

cannot do. See Albuquerque Bernalillo Cnty. Water Util. Auth., 2010-NMSC-013, 

¶ 18. Moreover, at oral argument, the Ranches described the nature of the expert 

testimony of its hydrologists, explaining generally that one or more of them told the 

AHO that the East Animas Fault “could actually serve as a conduit and move the 

contamination in unpredictable ways.” We need not conclude that such evidence is 

or is not speculative, or whether it is persuasive or unpersuasive. Instead, we 

emphasize only that it appears to be reasonable for the AHO, and later the 

Commission, to give less weight to this evidence and hold that the factual findings 

of the AHO are supported by substantial evidence. See Montano v. N.M. Real Est.

Appraiser’s Bd., 2009-NMCA-009, ¶ 8, 145 N.M. 494, 200 P.3d 544 (“We will not 

disturb the agency’s factual findings [that are] supported by substantial evidence.”). 

{20} Because we decline to disturb the uncontested factual findings within the 

AHO Report, and determine that the Commission’s Final Order as it relies on such 

factual findings is supported by substantial evidence, we hold that the Commission’s 

determination that the Mine does not pose undue risk to property is not arbitrary, 

capricious, or otherwise not in accordance with the law. 
17

III. DP-1840 Does Not Violate the Act and the Commission’s Order 

Determining That the Pit Lake Is Not a Surface Water of the State Is Not 

Arbitrary, Capricious, or Otherwise Not in Accordance With the Law

{21} In addition to the arguments raised by both Appellants related to the 

Commission’s interpretation of “undue risk to property,” the Ranches additionally

assert that DP-1840 violates the Act because (1) the future pit lake will be a surface 

water of the state, and (2) DP-1840 will cause water contaminant levels in excess of 

state standards. In making these arguments, the Ranches contend that the 

Commission failed to adequately explain its conclusion that the pit lake is not a 

surface water of the state. The Department answers that the Commission correctly 

concluded that the water in the future open pit is eligible for the private waters 

exemption under the Act because there is no potential for outward migration from 

the pit such that water will contaminate other surface or groundwater. Agreeing with 

the Department that the pit lake is eligible for the private waters exemption of the 

Act, the Commission explains that the pit lake does not fall within the definition of 

“surface waters” of the State as it is not “naturally occurring,” a tributary, a 

“manmade bod[y] of water that [was] originally created in surface waters,” or a 

water of the United States. See 20.6.4.7(S)(5) NMAC. To address the Ranches’ 

arguments, we briefly discuss New Mexico’s surface waters of the state rule, then 

address the Commission’s Final Order as it relates to the pit lake. 

A. “Surface Waters of the State” 
18

{22} All surface waters of the state of New Mexico are subject to the water 

standards set forth by the Act. Pursuant to 20.6.4.7(S)(5)(a) NMAC, “surface waters 

of the state” are defined broadly as “all surface waters situated wholly or partly 

within or bordering upon the state,” including lakes, rivers, streams, wetlands, wet 

meadows, reservoirs and natural ponds and all tributaries of such waters, including 

“any manmade bodies of water that were originally created in surface waters of the 

state or resulted in the impoundment of surface waters of the state, and any ‘waters 

of the United States’ as defined under the Clean Water Act that are not included in 

the preceding description.” 20.6.4.7(S)(5)(b) NMAC. However, this expansive 

definition “does not include private waters that do not combine with other surface or 

subsurface water.” 20.6.4.7.S(5)(c) NMAC. The private waters exemption, which 

the Commission determined is applicable to the pit lake, derives from the statutory 

definition of “water” in the Act. Under the Act, “water” means “all water, including 

water situated wholly or partly within or bordering upon the state, whether surface 

or subsurface, public or private, except private waters that do not combine with other 

surface or subsurface water.” Section 74-6-2(H) (emphasis added). In other words, 

as the AHO correctly explained, “[t]o be exempt from the definition of a “[s]urface 

waters of the state” and therefore not subject to the requirements of the Act, “a water 

body[] (1) must not combine with other surface or subsurface waters, (2) must not 

be a water of the United States, and (3) must be located entirely on private lands.”
19

B. The Commission’s Order 

{23} The Ranches contend that the “Commission did not adequately explain its 

conclusion that surface water standards will not apply to the pit lake,” and argues 

that the pit lake is encompassed within the expansive definition of surface waters of 

the state because it will combine with surface waters—“act[ing] as a hydraulic sink, 

drawing in groundwater from the surrounding areas, and that water will combine 

with the water in the lake.” The Department, the Commission, and N.M. Copper 

respond that the Commission correctly upheld the Department’s conclusion because 

the pit lake does not meet the regulatory definition of surface waters of the state as 

it will be located entirely on private land, and will not combine with other surface 

water or ground water.

{24} In determining that the pit lake qualifies for the private waters exemption, the 

Commission adopted the AHO and Department’s reasoning that the pit lake will not 

combine with other surface waters, such to render it a surface water of the state. The 

AHO explained that the Department’s understanding of the phrase “combine with 

other surface or subsurface waters” as contemplated by the private waters exemption 

“refers only to water flowing out of a polluted water body into surrounding water, 

and not to surrounding water flowing into a polluted water body.” The Ranches are 

correct that 20.6.4.7.S(5)(c) NMAC, supplying the private waters exemption, does 

not include such a distinction. However, the application of the private waters 
20

exemption requires the application of highly technical agency expertise. See N.M. 

Indus. Energy Consumers, 2007-NMSC-053, ¶ 19 (stating that we “will confer a 

heightened degree of deference to legal questions that implicate special agency 

expertise or the determination of fundamental policies within the scope of the 

agency’s statutory function” (internal quotation marks and citation omitted)); see 

also Rio Grande Chapter of Sierra Club v. N.M. Mining Comm’n, 2003-NMSC-005, 

¶ 17, 133 N.M. 97, 61 P.3d 806 (providing that when resolving ambiguities in 

regulations, “which an agency is charged with administering, [we] generally will 

defer to the agency’s interpretation if it implicates agency expertise.” (internal 

quotation marks and citation omitted)). We are further persuaded by the evidence 

relied upon by the Commission in making its determination and adopted in the 

findings of fact in the AHO’s Report, including that the “pit lake will be a hydrologic 

sink,” and that “[t]here will be no outflow to groundwater or surface water,”—

meaning that only evaporation will cause water loss in the pit lake—and that “[t]here 

is no potential that the open pit water body could contaminate any other groundwater 

orsurface water of the [s]tate.” Although we decline to formally adopt the distinction 

set forth in the AHO’s Report—because it is not for the Court to establish definitions 

that are within the purview of our Legislature or appropriate regulatory entity—we 

conclude that its interpretation of the definition of surface waters of the state and the 

related private waters exemption is not arbitrary, capricious, or otherwise not in 
21

accordance with the law. See New Energy Econ., 2010-NMSC-049, ¶ 14; 

Albuquerque Cab Co., 2017-NMSC-028, ¶ 8.

C. Contaminant Levels in Excess of State Standards 

{25} The Ranches assert that DP-1840 violates Section 74-6-5(E)(3) of the Act, 

which provides that “[t]he constituent agency shall deny any application for a permit 

. . . if . . . the discharge would cause or contribute to water contaminant levels in 

excess of any state or federal standard.” The Ranches argue that “[d]ischarges from 

the disturbed mine areas into the future pit lake will cause [s]tate surface water 

standards to be exceeded,” and contends that N.M. Copper’s “own modeling shows 

that the future pit lake will exceed the applicable surface water standards” of 

mercury, selenium, and vanadium. Section 74-6-5(E)(3) generally requires the 

denial of a discharge permit if the anticipated discharge “would cause or contribute 

to water contaminant levels in excess of [20.6.2.3103 NMAC] standards.” Gila Res. 

Info. Project, 2018-NMSC-025, ¶ 22 (internal quotation marks and citation omitted). 

However, under the Copper Rule, the 20.6.2.3103 NMAC standards are inapplicable 

to an “area of open pit hydrologic containment.” 20.6.7.24(D) NMAC; see Gila Res. 

Info. Project, 2018-NMSC-025, ¶ 43 (acknowledging that under the Copper Rule 

the standards set forth by 20.6.2.3103 NMAC may be exceeded because the Rule 

“accepts that some discharge contamination is inevitable, seeks to contain that 

contamination, and relies on the hydrologic phenomenon produced by the open pit 
22

to contain it”). Because we uphold the Commission’s determination that the pit lake 

is not a surface water of the state, we necessarily conclude that the pit lake is not 

required to meet the contamination standards in 20.6.2.3103 NMAC.

CONCLUSION

{26} For the reasons articulated above, we conclude that Appellants have not 

established that the Commission’s Final Order upholding the grant of DP-1840—

including its interpretation of the phrase “undue risk to property” and its related 

determination that the Mine does not present an undue risk to their respective 

properties, as well its conclusion that the pit lake does not constitute a surface water 

of the state—was arbitrary, capricious, or unsupported by substantial evidence. We, 

therefore, affirm. 

{27} IT IS SO ORDERED.

_____________________________

J. MILES HANISEE, Chief Judge

WE CONCUR:

_____________________________

KRISTINA BOGARDUS, Judge

_____________________________

JACQUELINE R. MEDINA, Judge