El Dorado Chemical Company v. EPA , 763 F.3d 950 ( 2014 )


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  •                 United States Court of Appeals
    For the Eighth Circuit
    ___________________________
    No. 13-1936
    ___________________________
    El Dorado Chemical Company
    lllllllllllllllllllll Plaintiff - Appellant
    v.
    United States Environmental Protection Agency; Gina McCarthy,1 Administrator,
    United States Environmental Protection Agency; Ron Curry,2 Regional
    Administrator, United States Environmental Protection Agency Region 6
    lllllllllllllllllllll Defendants - Appellees
    ____________
    Appeal from United States District Court
    for the Western District of Arkansas - El Dorado
    ____________
    Submitted: January 13, 2014
    Filed: August 15, 2014
    ____________
    Before GRUENDER, BRIGHT, and KELLY, Circuit Judges.
    1
    Gina McCarthy is substituted for her predecessor, Lisa P. Jackson, as
    Administrator of the U.S. Environmental Protection Agency. Fed. R. App. P.
    43(c)(2).
    2
    Ron Curry, Region 6 Administrator of the U.S. Environmental Protection
    Agency, is substituted for his predecessor, Sam Coleman, Acting Region 6
    Administrator of the U.S. Environmental Protection Agency. Fed. R. App. P.
    43(c)(2).
    ____________
    KELLY, Circuit Judge.
    El Dorado Chemical Company (EDCC) operates a chemical manufacturing
    plant in El Dorado, Arkansas. As a byproduct of its operation, the plant discharges
    dissolved minerals, including sulfate and chloride, into two unnamed tributaries (UTA
    and UTB); these tributaries reach downstream to Flat Creek and Haynes Creek. In
    2004, Arkansas imposed more stringent limits on the dissolved minerals EDCC could
    discharge into these bodies of water, and granted EDCC three years to comply. In
    response, EDCC initiated a Third Party Rulemaking to increase the levels of dissolved
    minerals permitted in both UTA and UTB. Arkansas adopted these revisions and
    submitted them to the U.S. Environmental Protection Agency (EPA) for approval.
    The EPA rejected the changes, citing concerns that the revisions did not adequately
    protect the aquatic life in Flat Creek and Haynes Creek. EDCC moved for judicial
    review, and the district court3 upheld the EPA’s decision, granting summary judgment
    in favor of the EPA. EDCC now appeals, arguing the EPA overstepped its authority
    in considering the effects on aquatic life in the two creeks. Because we find the EPA
    had the authority to look at downstream effects, and because EDCC failed to
    adequately demonstrate the affected waters would be protected, we affirm.
    I. Background
    A. Statutory and Regulatory Framework
    Since 1972, the states and the federal government have worked together “to
    restore and maintain the chemical, physical, and biological integrity of the Nation’s
    3
    The Honorable Susan O. Hickey, United States District Court Judge for the
    Western District of Arkansas.
    -2-
    waters,” in a partnership governed by the Clean Water Act (CWA).4 33 U.S.C.
    § 1251(a). With this goal in mind, the CWA authorizes states to establish water
    quality standards for bodies of water within its borders. 33 U.S.C. § 1313(a)–(c).
    Water quality standards “define[] the water quality goals of a water body, or portion
    thereof, by designating the use or uses to be made of the water and by setting criteria
    necessary to protect the uses.” 40 C.F.R. § 131.2. They comprise (1) the designated
    use(s) of the waters (e.g., water supply, propagation of fish, or recreation), 40
    C.F.R. § 131.10; (2) the water quality criteria necessary to safely permit those
    designated uses, 40 C.F.R. § 131.11; and (3) antidegradation requirements to protect
    waters whose quality is better than required, 40 C.F.R. § 131.12. 40 C.F.R. § 131.6.
    States must review their water quality standards at least every three years. 33
    U.S.C. § 1313(c)(1). And under the CWA, each state must create a “continuing
    planning process” (CPP) to, among other things, govern the process for revising its
    water quality standards. 40 C.F.R. § 130.5(a). “In designating uses of a water body
    and the appropriate criteria for those uses, the State shall take into consideration the
    water quality standards of downstream waters and shall ensure that its water quality
    standards provide for the attainment and maintenance of the water quality standards
    of downstream waters.” 40 C.F.R. § 131.10(b).
    Although states assume the primary role in determining water quality
    standards, 40 C.F.R. § 131.4, states must submit proposed standards and revisions to
    the EPA for approval. 33 U.S.C. § 1313(c)(2); 40 C.F.R. §§ 131.5, 131.21. The EPA
    must ensure proposed water quality standards meet the requirements of the CWA. 33
    U.S.C. § 1313(c)(3). Designated uses must be “consistent with the requirements of
    the [CWA],” and water quality criteria must “protect the designated water uses.” 40
    C.F.R. § 131.5(a)(1)–(2). The EPA is empowered to issue its own water quality
    standards if a state does not make appropriate adjustments to its proposed standards,
    4
    The statute is also known as the Federal Water Pollution Control Act.
    -3-
    and the EPA may also promulgate revised or new standards “when necessary to meet
    the requirements of the [CWA].” 33 U.S.C. § 1313(c)(3)–(4).
    Water quality standards in Arkansas are developed by the Arkansas Pollution
    Control and Ecology Commission (the Commission). Ark. Code Ann. § 8-4-201(b).
    The Arkansas Department of Environmental Quality administers and enforces the
    state’s water quality standards.5 Ark. Code Ann. § 8-4-203(a). It does so through a
    permitting program, the National Pollutant Discharge Elimination System (NPDES).6
    See 33 U.S.C. § 1342. Under the NPDES program, a point source7 cannot discharge
    a pollutant unless the discharge is authorized by an NPDES permit. See id.; see also
    33 U.S.C. § 1311. These permits contain, inter alia, numerical discharge limits. Like
    water quality standards, NPDES permits must first be submitted to the EPA for
    approval, unless the EPA waives this requirement. 33 U.S.C. § 1342(d)–(e); Arkansas
    v. Oklahoma, 
    503 U.S. 91
    , 102 (1992) (“[The EPA] retains authority to block the
    issuance of any state-issued permit that is outside the guidelines and requirements of
    the [CWA].”).
    5
    We refer to these two entities collectively as “Arkansas.”
    6
    NPDES permits are issued by the EPA or, in those jurisdictions in which the
    EPA has authorized the state to issue permits, by a state agency subject to EPA
    approval. 33 U.S.C. § 1342(a)–(d); see also Approval of Arkansas’ NPDES Program,
    51 Fed. Reg. 44518-01 (Dec. 10, 1986).
    7
    The CWA defines “point source” as “any discernible, confined and discrete
    conveyance, including but not limited to any pipe, ditch, channel, tunnel, conduit,
    well, discrete fissure, container, rolling stock, concentrated animal feeding operation,
    or vessel or other floating craft, from which pollutants are or may be discharged.” 33
    U.S.C. § 1362(14).
    -4-
    B. EDCC’s Third Party Rulemaking
    EDCC’s chemical manufacturing facility discharges its wastewater into UTB,
    which flows into UTA. UTA, in turn, reaches downstream to Flat Creek. Flat Creek
    then flows into Haynes Creek. Arkansas has designated UTA, Flat Creek, and Haynes
    Creek for use as, among other things, perennial gulf coastal fisheries, and UTB as a
    seasonal gulf coastal fishery. This case involves Arkansas’ attempt to revise the water
    quality criteria for UTA and UTB in response to EDCC’s Third Party Rulemaking.
    In June 2004, EDCC renewed its NPDES permit. This new permit contained
    more stringent limits on the dissolved minerals EDCC could discharge than the
    previous permit. EDCC had until June 1, 2007, to comply with the new limits. On
    August 31, 2006, before the new limits became effective, EDCC filed a petition for
    a Third Party Rulemaking with Arkansas, seeking to modify Arkansas’ water quality
    standards.8 Specifically, EDCC sought to make two changes. First, EDCC wanted
    to remove the “domestic water supply” designated uses of UTA, UTB, and parts of
    Flat Creek and Haynes Creek. Second, EDCC wanted to increase the maximum
    permissible concentrations of chloride, sulfate, and total dissolved solids (“TDS”) for
    those same bodies of water.
    Arkansas approved both of EDCC’s proposed changes on June 22, 2007, and
    submitted them to the EPA for approval. Because these four bodies of water were not
    currently used as sources for the domestic water supply, in November 2007 the EPA
    8
    Arkansas permits site-specific modifications to its water quality standards “to
    accommodate important economic or social development in a local area,” Ark. Admin.
    Code 014.04.2-3 Reg. 2.306, and permits third parties to petition for such an
    amendment, Ark. Code Ann. § 8-4-202(c)(1). See also 33 U.S.C. § 1313(e)(3)(F)
    (authorizing states to establish a “continuing planning process” that includes
    procedures for revising water quality standards).
    -5-
    approved the removal of the domestic water supply designated uses for all four bodies
    of water.
    The EPA did not, however, approve the revised water quality criteria—i.e., the
    proposed sulfate, chloride, and TDS limits. In January 2008, the EPA informed
    Arkansas that it lacked adequate supporting evidence, so Arkansas supplemented its
    documentation. Again in April 2009, the EPA rejected the proposed rule regarding
    the higher mineral concentrations and identified additional information necessary to
    make a determination. In response, EDCC conducted another study and submitted
    further documentation, which it argued was substantially more comprehensive than
    what the EPA had accepted and approved in a prior Third Party Rulemaking.
    Nevertheless, the EPA emphasized its concern that the proposed revisions would have
    negative effects on aquatic life in Flat Creek and Haynes Creek. Toxicity testing
    submitted by EDCC had indicated reproductive problems to the water flea in the
    creeks when exposed to the maximum proposed mineral concentrations.
    After receiving the EPA’s latest concerns, EDCC did not run any additional
    tests or commission further studies on the impact to aquatic life in Flat and Haynes
    Creek. Instead, EDCC petitioned Arkansas to re-open the Third Party Rulemaking.
    This time, EDCC rescinded its proposed changes to the water quality criteria for Flat
    Creek and Haynes Creek; the sulfate, chloride, and TDS limits would thus revert back
    to the more strict levels. However, EDCC sought to re-adopt its proposed—and less
    strict—sulfate, chloride, and TDS limits for UTA and UTB. Arkansas agreed. As a
    result, on December 3, 2010, Arkansas rescinded the previously approved changes to
    the sulfate, chloride, and TDS limits in Flat and Haynes Creeks, and re-adopted the
    proposed criteria for UTA and UTB.
    Arkansas submitted this new rule to the EPA for approval. The EPA again
    requested more information before making a determination, particularly with regard
    to the potential effects of the revised criteria for UTA and UTB on Flat and Haynes
    -6-
    Creeks. EDCC, communicating through and to Arkansas, responded by explaining
    that because it removed Flat and Haynes Creeks from the Rulemaking, it would not
    address questions concerning those two bodies of water. EDCC no longer wanted to
    change the sulfate, chloride, and TDS concentrations for the creeks. On August 31,
    2011, the EPA issued a final decision letter disapproving the revised water quality
    criteria. As the EPA explained, it “determined that supporting documentation remains
    insufficient to demonstrate that the site-specific minerals criteria for the waterbodies
    associated with EDCC are appropriately protective of aquatic life.” The EPA
    highlighted its concerns that EDCC failed to consider how the revised criteria for
    UTA and UTB would affect the downstream water quality in Haynes and Flat Creeks
    and that its supporting evidence was scientifically flawed.
    In October 2011, EDCC filed a complaint in the Western District of Arkansas
    seeking judicial review of the EPA’s decision to disapprove the proposed water
    quality criteria. EDCC claimed it provided the EPA with the necessary documentary
    support and the EPA based its disapproval on inappropriate factors. Both EDCC and
    the EPA filed cross motions for summary judgment, and the district court granted
    summary judgment to the EPA. EDCC now appeals, arguing the EPA usurped the
    role that Congress delegated to Arkansas to develop water quality standards and the
    EPA’s decision is contrary to EDCC’s scientific evidence.
    II. Discussion
    A. Standard of Review
    “We review de novo a district court’s decision whether an agency’s action
    violates the A[dministrative Procedure Act (APA)].” Thomas v. Jackson, 
    581 F.3d 658
    , 664 (8th Cir. 2009) (quotation omitted).
    -7-
    As an initial matter, EDCC argues that the district court applied the incorrect
    standard of review in upholding the EPA’s decision. According to EDCC, the EPA
    had to present “compelling evidence, based on strong science,” in order to reject
    Arkansas’ proposed water quality standards. The burden is, in EDCC’s view, on the
    EPA. EDCC acknowledges, nonetheless, that judicial review of administrative
    decisions is governed by the APA. 5 U.S.C. § 706. Section 706 provides, inter alia,
    that the reviewing court shall uphold agency actions, findings, and conclusions unless
    they are “arbitrary, capricious, an abuse of discretion, or otherwise not in accordance
    with law.” 5 U.S.C. § 706(2)(A). An agency decision is arbitrary or capricious if:
    the agency has relied on factors which Congress has not intended it to
    consider, entirely failed to consider an important aspect of the problem,
    offered an explanation for its decision that runs counter to the evidence
    before the agency, or is so implausible that it could not be ascribed to a
    difference in view or the product of agency expertise.
    Cent. S.D. Co-op Grazing Dist. v. Sec’y of U.S. Dep’t of Agric., 
    266 F.3d 889
    , 895
    (8th Cir. 2001) (quoting Motor Vehicle Mfrs. Ass’n of U.S., Inc. v. State Farm Mut.
    Auto. Ins. Co., 
    463 U.S. 29
    , 43 (1983)). Thus, “[t]he scope of our review is narrow
    and we are not to substitute our judgment for that of the agency.” 
    Id. (citing Motor
    Vehicle 
    Mfrs., 463 U.S. at 43
    ). “If an agency’s determination is supportable on any
    rational basis, we must uphold it.” Voyageurs Nat’l Park Ass’n v. Norton, 
    381 F.3d 759
    , 763 (8th Cir. 2004).
    EDCC fails to harmonize the APA’s general “arbitrary and capricious” standard
    with its proposed “compelling evidence” standard. Rather, EDCC suggests the
    arbitrary and capricious standard—and the district court’s order by extension—
    undermines the primacy of states under the CWA. See 33 U.S.C. § 1251(b) (“It is the
    policy of the Congress to recognize, preserve, and protect the primary responsibilities
    and rights of States to prevent, reduce, and eliminate pollution, to plan the
    development and use (including restoration, preservation, and enhancement) of land
    -8-
    and water resources, and to consult with the Administrator in the exercise of his
    authority under this chapter.”). This suggestion ignores the statutory reality that states
    do not have unfettered discretion under the CWA. States may establish and revise
    water quality standards, yet all new and revised water quality standards must be
    submitted to the EPA. 33 U.S.C. § 1313(c)(2)(A). The EPA has the power to reject
    a state’s proposed water quality standard, and even promulgate its own standards in
    some circumstances. 
    Id. § 1313(c)(3)
    (“If the Administrator determines that any such
    revised or new standard is not consistent with the applicable requirements of this
    chapter, he shall . . . notify the State and specify the changes to meet such
    requirements. If such changes are not adopted by the State . . . the Administrator shall
    promulgate such standard . . . .”).
    Despite EDCC’s insistence, the EPA is permitted—and in fact statutorily
    required—to scrutinize a state’s water quality standards. Under the CWA, the EPA
    must determine whether a state’s water quality standard is “consistent with the
    [CWA’s] requirements.” 33 U.S.C. § 1313(a)(3)(C), (c)(2)(A). As the Fifth Circuit
    has noted, “[n]othing indicates a congressional intent to restrict EPA’s review of state
    standards” or require deference to the states’ determinations. Miss. Comm’n on
    Natural Res. v. Costle, 
    625 F.2d 1269
    , 1275–76 (5th Cir. 1980) (rejecting the state’s
    argument that the EPA could only disapprove of a state standard if it is “arbitrary,
    capricious, or totally unreasonable”). And the APA, in turn, indicates that we should
    uphold the EPA’s decision unless it is arbitrary or capricious. 5 U.S.C. § 706(2)(A);
    accord 
    Costle, 625 F.3d at 1276
    . Similarly, we have held that when reviewing agency
    action we grant deference to the agency’s “high level of technical expertise.” Cent.
    S.D. 
    Co-op, 266 F.3d at 894
    (quotation omitted).
    EDCC points to an EPA administrative decision that suggests when the EPA
    interprets state water quality standards for purposes of issuing NPDES permits, it
    ought to uphold the state’s interpretation of that standard absent a state’s “clear error.”
    In re Ina Road Water Pollution Control Facility, 2 E.A.D. 99, 100 (EAB 1985). In a
    -9-
    footnote, the administrator noted the EPA could substitute its own interpretation if it
    had compelling reasons, such as “strong scientific or technological support.” 
    Id. at 101
    & n.7.
    EDCC’s reliance on this case and its progeny is misplaced. Even if this case
    somehow altered our application of the APA’s arbitrary and capricious standard, Ina
    Road Water Pollution involves a different step in the regulatory structure. In Ina Road
    Water Pollution, the EPA had already approved the state’s water quality standards and
    was interpreting those standards in issuing NPDES permits.9 By contrast, the EPA in
    this case is deciding in the first instance whether to approve Arkansas’ water quality
    standards. And water quality standards serve as guidelines for setting applicable
    limitations in individual NPDES permits. Contrary to EDCC’s urging, even if Ina
    Road Water Pollution set out a general standard for NPDES permits, it is not
    inconsistent for the EPA to give greater deference to states when interpreting and
    applying standards that the EPA has already found comply with the CWA.
    B. Scope of the EPA’s Authority
    That said, we may still find the EPA’s decision was arbitrary and capricious if
    it acted outside the scope of its authority by “rel[ying] on factors which Congress has
    not intended it to consider.” Cent. S.D. 
    Co-op, 266 F.3d at 894
    (quotation omitted).
    EDCC’s main argument is that the EPA usurped Arkansas’ role in setting water
    9
    Before the EPA can issue an NPDES permit, the state must certify, or waive
    its right to certify, that the discharge authorized by the permit will comply with the
    state’s water quality standards. 33 U.S.C. § 1341(a); 40 C.F.R. §§ 122.4(b), 124.53.
    In Ina Road Water Pollution, Arizona certified that a permit’s effluent limitations
    complied with its water quality standards, but the EPA disagreed and imposed more
    strict limits. Ina Road Water Pollution, 2 E.A.D. at 100.
    -10-
    quality standards. More specifically, EDCC contends the EPA exceeded its authority
    by looking at the downstream effects on Flat Creek and Haynes Creek. The EPA cited
    concern that changing the mineral concentrations in UTA and UTB would negatively
    impact the aquatic life in Flat and Haynes Creeks, and rejected Arkansas’ revised
    water quality criteria. One test in particular indicated “sub-lethal reproductive effects
    to the water flea . . . for Flat and Haynes Creeks.” Even if this test result was
    valid—which EDCC disputes—EDCC argues the EPA should have cabined its
    inquiry to the impact of the revised water quality criteria on UTA and UTB.
    According to EDCC, only states—not the EPA—may consider downstream effects in
    establishing water quality criteria.
    EDCC cites two regulations in support of its position. The first regulation
    describes a state’s duty when establishing water quality standards:
    In designating uses of a water body and the appropriate criteria for those
    uses, the State shall take into consideration the water quality standards
    of downstream waters and shall ensure that its water quality standards
    provide for the attainment and maintenance of the water quality
    standards of downstream waters.
    40 C.F.R. § 131.10(b). This regulation prescribes the factors states must consider
    when setting water quality standards, but says nothing about the EPA’s role in this
    process. A second regulation describes the EPA’s review process for states’ proposed
    water quality standards:
    [The] EPA is to review and to approve or disapprove of State-adopted
    water quality standards. The review involves a determination of:
    (1) Whether the State has adopted water uses which are consistent with
    the requirements of the Clean Water Act;
    (2) Whether the State has adopted criteria that protect the designated
    water uses;
    -11-
    (3) Whether the State has followed its legal procedures for revising or
    adopting standards;
    (4) Whether the State standards which do not include the uses specified
    in section 101(a)(2) of the Act are based upon appropriate technical and
    scientific data and analyses, and;
    (5) Whether the State submission meets the requirements included in
    § 131.6 of this part.
    40 C.F.R. § 131.5; see also 40 C.F.R. § 131.6 (outlining the “[m]inimum requirements
    for water quality standards submission”). EDCC argues that because § 131.5, the
    regulation outlining the EPA’s review process, does not explicitly mention effects on
    downstream waters, the EPA may not disapprove water quality criteria on that basis.
    Instead, according to EDCC, § 131.5 only reserves authority for the EPA to look at
    in-stream effects.
    According to the EPA, however, it has the statutory and regulatory authority to
    ensure water quality standards are maintained downstream when a state revises
    upstream water quality standards. In its brief on appeal, the EPA pointed to both the
    state’s requirements under § 131.10(b) and the EPA’s review under § 131.5, reading
    them in harmony: “In determining whether state-adopted criteria are sufficiently
    protective of designated water uses per 40 C.F.R. § 131.5(a)(2), EPA reviews the
    criteria to ensure all requirements are met, including those imposed in § 131.10(b).”
    Despite EDCC’s alternative reading, “[i]t is well established that an agency’s
    interpretation need not be the only possible reading of a regulation—or even the best
    one—to prevail.” Decker v. Nw. Envtl. Def. Ctr., 
    133 S. Ct. 1326
    , 1337 (2013).
    When evaluating competing interpretations, “we defer to [the] agency’s interpretations
    . . . unless we find that a regulation is contrary to unambiguous statutory language,
    that the agency’s interpretation of its own regulation is plainly erroneous or
    inconsistent with the regulation, or that application of the regulation [is] arbitrary or
    capricious.” Nack v. Walburg, 
    715 F.3d 680
    , 684 (8th Cir. 2013) (quotation omitted).
    This is true, “even if the agency’s interpretation of its own regulation is expressed
    -12-
    merely in a brief to the court rather than through other means.” 
    Id. at 685
    (citing Talk
    Am., Inc. v. Mich. Bell Tel. Co., 
    131 S. Ct. 2254
    , 2261 (2011)). We cannot say the
    EPA’s reading of its own regulations—that it may look at downstream waters when
    evaluating a state’s water quality standards—is plainly erroneous.
    First, § 131.5 does not state the EPA is limited to looking at in-stream effects
    when approving or disapproving water quality standards. Rather, it directs the EPA
    to review the state’s water quality standards—that its designated uses comply with the
    CWA and that the criteria protect those uses. Section 131.5 does not, by its terms,
    prohibit the EPA from considering “[w]hether the State has adopted criteria that
    protect the designated uses” of downstream, as well as in-stream, waters.
    Section 131.6 further indicates the EPA has authority to review downstream waters;
    it outlines what information a state must submit to the EPA when seeking review of
    water quality standards. In addition to including the designated water uses and water
    quality criteria, the state must also supply the “[m]ethods used and analyses conducted
    to support water quality standards revisions.” 40 C.F.R. § 131.6(b). As § 131.10(b)
    directs, part of a state’s analysis for its water quality standards must be the
    maintenance of downstream waters. It follows that the EPA may not only receive, but
    may also review this methodology.
    Second, the CWA itself supports the EPA’s interpretation. The EPA has both
    the authority and obligation to ensure that revisions to a state’s water quality standards
    “meet[] the requirements of [the CWA].” 33 U.S.C. § 1313(c)(3). The CWA
    endorses a holistic approach to the nation’s waterways. See, e.g., 33 U.S.C.
    § 1315(b)(1)(B) (“Each State shall prepare and submit to the [EPA] . . . an analysis
    of the extent to which all navigable waters of such State provide for the protection and
    propagation of a balanced population of shellfish, fish, and wildlife, and allow
    recreational activities in and on the water.”) (emphasis added); 33 U.S.C. § 1341(a)(2)
    (when issuing NPDES permits, “[w]henever such a discharge may affect, as
    determined by the [EPA], the quality of the waters of any other State, the [EPA] . . .
    -13-
    shall so notify such other State, the licensing or permitting agency, and the [permit]
    applicant”). Congress passed the CWA to “restore and maintain the chemical,
    physical, and biological integrity of the Nation’s waters.” 33 U.S.C. § 1251(a);
    
    Arkansas, 503 U.S. at 105
    –07 (citing the CWA’s “broad purpose” as one justification
    for the EPA’s authority, in the NPDES context, to regulate upstream pollution sources
    in order to achieve downstream water quality standards). EDCC’s myopic reading of
    the CWA would run roughshod over its purpose.
    Finally, EDCC argues that the NPDES permitting program provides sufficient
    protection for downstream waters, which would then preserve the purpose of the
    CWA. Under NPDES, “no permit shall issue . . . if the [EPA] objects in writing to the
    issuance of such permit as being outside the guidelines and requirements of [the
    CWA].” 33 U.S.C. § 1342(d)(2). And “[n]o permit may be issued . . . [w]hen the
    conditions of the permit do not provide for compliance with the applicable
    requirements of CWA, or regulations promulgated under CWA,” or “[w]hen the
    imposition of conditions cannot ensure compliance with the applicable water quality
    requirements of all affected States.” 40 C.F.R. § 122.4(a), (d). Nevertheless, the
    EPA’s interpretation of its own regulations is not rendered plainly erroneous simply
    because the EPA may preserve downstream water quality standards at a later step in
    the regulatory process. The NPDES program provides EPA with the opportunity to
    ensure downstream waters are protected from point source pollution. Yet EDCC does
    not explain why NPDES must be the exclusive means for protecting downstream
    waters. Neither the CWA nor the related regulations compel this reading. EDCC’s
    contention is further weakened by the fact that under NPDES, the EPA may waive
    objections to a particular permit application, and may even waive notice of a permit
    application entirely for specific categories of point source pollution. 33 U.S.C.
    § 1342(d)(3), (e). Consequently, we find the EPA did not act arbitrarily or
    capriciously by denying Arkansas’ revised water quality standards based, in part, on
    possible downstream effects.
    -14-
    C. Evidentiary Support
    Arkansas, not the EPA, bears the burden of adducing evidence the proposed
    water quality criteria meet the requirements of the CWA. See, e.g., 40 C.F.R.
    §§ 131.6, 131.21. Here, the EPA determined that Arkansas’ supporting
    documentation was insufficient to demonstrate that the proposed water quality criteria
    are “appropriately protective of aquatic life” in UTA, UTB, and Flat and Haynes
    Creeks. The EPA must have a rational basis for its determination. 
    Voyageurs, 381 F.3d at 763
    (“If an agency’s determination is supportable on any rational basis, we
    must uphold it.”). On appeal, EDCC argues the EPA lacked a rational basis. In doing
    so, EDCC emphasizes the limited nature of its proposed changes and questions the
    EPA’s reliance on purportedly unreliable and otherwise deficient evidence. We
    address each argument in turn.
    EDCC first points out its proposed changes are relatively moderate. EDCC
    sought, with Arkansas’ approval, to raise the chloride criteria for UTA and UTB from
    14 mg/L to 16 mg/L and 23 mg/L respectively. The revised criteria, EDCC
    emphasizes, are still more restrictive than the EPA’s own recommendations or those
    approved in other rulemakings for other sites. Under the CWA, the EPA publishes
    water quality criteria guidelines “reflecting the latest scientific knowledge.” 33 U.S.C.
    § 1314(a)(1). And in 1988, the EPA published national guidance criteria for chloride,
    setting limitations at 230 mg/L for chronic toxicity. Water Quality Criteria, 53 Fed.
    Reg. 19028-01 (May 26, 1988). The proposed criteria in this case are substantially
    lower than the guideline criteria; yet adherence to the guidelines is not sufficient, on
    its own, to warrant EPA approval. The EPA must still determine whether the
    proposed criteria otherwise comply with the CWA. And state water quality criteria
    must “protect the designated water uses.” 40 C.F.R. § 131.5(a)(2). We cannot agree
    that the moderate nature of the proposed changes, standing alone, is sufficient to find
    the EPA’s decision lacked a “rational basis.”
    -15-
    EDCC also questions the EPA’s interpretation of and reliance on the scientific
    evidence in the record. To assess this argument, we must consider two comprehensive
    studies that EDCC commissioned through GBMC & Associates (GBMC): one in
    2006 and—in response to the EPA’s request for more support—another in 2009. The
    goal of these studies was to demonstrate EDCC’s proposed water quality criteria
    would protect the designated uses of UTA, UTB, and the two creeks. Despite these
    studies, the EPA found insufficient evidence that these bodies of water would remain
    protected given the proposed increased mineral concentrations. EDCC contends that
    the EPA ignored the extensive scientific evidence and that EPA’s conclusions—drawn
    from specific tests in the record—about the in-stream and downstream effects of the
    revised criteria are simply incorrect.
    The first study was conducted in 2006 when EDCC, through GBMC, prepared
    a “Site Specific Water Quality Study for Chloride, Sulfate, and TDS.” EDCC,
    through Arkansas, then submitted this study to the EPA as the requisite documentation
    that the revised water quality criteria still adequately protected designated uses. See
    40 C.F.R. § 131.6(b). As part of this 2006 study, GMBC conducted an “Aquatic Life
    Field Study” to “document whether the designated aquatic life use was being
    maintained” in UTA and UTB and to determine whether “the permitted discharges
    from EDCC are beneficial or detrimental to the maintenance of those uses.”
    According to the Aquatic Life Field Study, the revised water quality criteria maintain
    UTA and UTB’s designated use as seasonal fisheries, including preserving the
    supporting biotic communities necessary for fishery use. EDCC asserts the EPA
    failed to acknowledge these findings when disapproving the proposed mineral
    concentrations.
    The EPA did not ignore the study’s conclusion, but it did question whether the
    study was helpful in determining whether the designated uses were being maintained.
    In this Aquatic Life Field Study, GMBC sampled the aquatic life in UTA and UTB,
    in part, by comparing downstream waters (impacted by EDCC’s current discharge)
    -16-
    to other bodies of water, called “reference reaches” (not impacted by EDCC’s current
    discharge). In its disapproval, the EPA questioned EDCC’s reliance on reference
    reaches that were already impacted by significant dissolved mineral pollution.
    Regardless, even if EDCC and the EPA could agree on the choice of proper reference
    reaches, and assuming the study’s conclusions were sound, the study did not analyze
    any effects on Flat and Haynes Creeks. At best then, the 2006 study was incomplete.
    As a result, the EPA informed Arkansas (which in turn informed EDCC) that the
    evidence was inadequate; more information was needed, particularly about Flat and
    Haynes Creeks. The EPA identified information still needed and additional tests that
    could be run.
    In response to this request for additional documentation, EDCC asked GMBC
    in 2009 to prepare the “Aquatic Life Supplemental Report.” As part of this study,
    whole effluent toxicity testing (WET testing) was conducted on spiked water samples
    created to simulate the mineral concentrations proposed in the initial Rulemaking for
    all four bodies of water. These spiked water samples were then compared to current
    water samples, “control samples,” from UTA, UTB, and Flat and Haynes Creeks.
    GMBC analyzed the effects on the fathead minnow and water flea. EPA had
    requested such a test “to demonstrate the ability of the approved criteria to support the
    aquatic life . . . .” GMBC concluded that the proposed criteria were adequately
    protective of aquatic life in all four bodies of water. Yet despite this conclusion, the
    study also acknowledged negative reproductive effects on the water flea in Flat and
    Haynes Creeks: the water fleas did not die more rapidly, but had fewer offspring when
    exposed to the proposed chloride, sulfate, and TDS concentrations than the water fleas
    in the control samples. GMBC explained this result “may or may not be directly
    related to the dissolved minerals.” It suggested historic oil and gas activities in the
    area could be responsible.
    After receiving the 2009 study, the EPA remained critical of the proposed
    criteria. The EPA acknowledged “that non-point sources and other factors out of
    -17-
    EDCC’s control are possible contributors to the increased mineral loads in Flat and
    Haynes Creeks.” However, the EPA would not rely on the study’s mere speculation
    as to the cause of the negative test results. The existence of other contributing factors
    “does not . . . relieve the 3rd party of the burden to propose criteria that will be
    protective of the aquatic life uses for these waters.” The EPA suggested changing the
    criteria to protective levels and analyzing the test results more thoroughly. EDCC
    declined to do so. Instead, EDCC petitioned Arkansas to re-open the Third Party
    Rulemaking with the specific goal of rescinding the revisions to the criteria for the
    two creeks. EDCC does not abandon its argument that the EPA erred, therefore, in
    looking downstream at the effects of the proposed criteria on these two creeks (which
    were no longer subject to the revised criteria); but its primary argument is that the
    WET test results are not sufficiently valid to support the EPA’s action.
    EDCC first argues the WET test’s methodology was unsound. Though it
    followed the EPA’s instructions to use synthetic water, EDCC asserts that use of
    synthetic water for this test was both inappropriate and unreliable. EDCC points to
    an EPA manual regarding how to conduct WET tests for the NPDES program. See
    40 C.F.R. § 136.3, Table IA (referencing the EPA manual). The manual indicates that
    when determining the effects of the discharge on already contaminated water, WET
    testing should be conducted using water collected from the point of discharge (i.e., not
    synthetic water). The objective of the test in the NPDES context, however, is to
    determine whether a point source, and its existing discharge, is complying with its
    permit. Here, the EPA sought to evaluate the effects on aquatic life if the state revised
    water quality criteria by increasing specific dissolved mineral limits.
    EDCC also contends the EPA could consider only those WET tests that were
    conducted pursuant to the NPDES requirements due to Arkansas’ EPA-approved
    procedures for modifying water quality criteria as detailed in Arkansas’ CPP.
    Arkansas’ CPP requires third parties seeking to revise water quality standards to
    “demonstrat[e] that existing aquatic life uses will be maintained.” The CPP permits
    -18-
    parties to submit recent WET tests, conducted pursuant to NPDES requirements, as
    evidence. Notably, however, the Arkansas’ CPP does not preclude the EPA from
    requesting or considering other evidence.
    Finally, EDCC argues the “anomalous” test results for the water flea from the
    2009 study are not relevant: they were based on synthetic waters created to reflect
    proposed revised criteria for Haynes and Flat Creeks—i.e., these studies were
    conducted before EDCC moved to reopen the Rulemaking to rescind any proposed
    changes for the creeks. However, the EPA did not rely on the 2009 study to
    definitively state the revised criteria for UTA and UTB did not protect aquatic life.
    Instead, the EPA explained the study was a red flag requiring further explanation. The
    test results suggest that altering the mineral levels in the creeks could lead to problems
    for their aquatic life. And changing the mineral levels upstream could alter mineral
    levels downstream. The EPA had the authority to consider the downstream effects of
    revisions to UTA’s and UTB’s water quality standards, and could deny revisions if
    not adequately assured of downstream waters’ protection. The EPA’s continued
    reference to this test was thus not irrational.
    Rather than addressing the EPA’s concerns about the 2009 study and the
    potential effects on the creeks, EDCC rescinded the Arkansas-approved water quality
    criteria revisions to Flat and Haynes Creeks. EDCC then insisted that, as a result, the
    EPA could no longer look at potential effects in those two bodies of water. In turn,
    according to EDCC, the WET test results were irrelevant: EDCC asserted “[s]ince
    these waterbodies are no longer part of the 2011 Rulemaking approved by the
    Commission, specific questions regarding the status of those water bodies will not be
    addressed . . . .” In short, EDCC refused to supply more information about possible
    effects on Flat and Haynes Creeks. While EDCC now criticizes the EPA’s decision
    to disapprove the revisions for UTA and UTB based on the 2009 study’s “isolated”
    and “anomalous” test, the EPA looked to this test because Arkansas and EDCC
    presented little other information regarding effects on Haynes and Flat Creeks. We
    -19-
    cannot say the EPA’s refusal to approve the proposed water quality criteria on the
    basis of incomplete information was arbitrary or capricious. Particularly in light of
    the deference we grant to the EPA on review, we find there was a rational basis for the
    EPA’s disapproval. See Lockhart v. Kenops, 
    927 F.2d 1028
    , 1034 (8th Cir. 1991)
    (“[O]ur deference to the agency is greatest when reviewing technical matters within
    its area of expertise, particularly its choice of scientific data and statistical
    methodology . . . .”) (quotation omitted).
    D. Mass Balance Approach
    The EPA also found the method Arkansas used to derive the water quality
    criteria—the “mass balance approach”—was “scientifically indefensible.” The mass
    balance approach does not, standing alone, derive criteria adequately protective of the
    existing designated uses. The EPA explained in its letter that Arkansas should have
    considered, inter alia, stream flow conditions; results from properly conducted toxicity
    tests; the downstream water quality standards; facility design flow capacity; and inputs
    from other point sources in the watershed. The mass balance approach determined the
    dissolved mineral limits necessary to account for EDCC’s discharge. That does not,
    however, indicate that the criteria, and EDCC’s discharge, are protective of aquatic
    life. The EPA’s disapproval of the mass balance approach in this context was not
    arbitrary or capricious.
    III. Conclusion
    We cannot find the EPA was arbitrary or capricious in rejecting Arkansas’
    -20-
    proposed water quality standards. Accordingly, we affirm the district court.10
    ______________________________
    10
    We note that nothing precludes Arkansas from resubmitting proposed water
    quality standards with more adequate documentation. The EPA explained in its
    decision that in the event the evidence does not support EDCC’s proposed revision,
    Arkansas could “conduct a full use attainability analysis (UAA) to determine an
    appropriate level of aquatic life use for an area that has been historically impacted by
    industry.” In other words, Arkansas could attempt to further revise the designated
    uses, as well as the water quality criteria. During oral argument the parties also
    acknowledged the construction of a wastewater pipeline, which could diminish
    EDCC’s discharge and thus its need for these specific water quality criteria revisions.
    -21-