Court Opinion

ID: 4423161
Source: CourtListenerOpinion
Date Created: 2019-08-06 18:06:59.509521+00
Date Added: 2024-06-11T14:51:17.768916
License: Public Domain

Maryland Department of the Environment v. County Commissioners of Carroll County,
Maryland
No. 5, September Term 2018

Frederick County, Maryland v. Maryland Department of the Environment
No. 7, September Term 2018

Environmental Law – Administrative Law – Clean Water Act – Stormwater
Discharge Permits – Impervious Surface Restoration. The Maryland Department of the
Environment may lawfully include an impervious surface restoration requirement in a
municipal separate storm sewer system (MS4) discharge permit without reference to the
“maximum extent practicable” standard in the federal Clean Water Act for certain pollution
controls. The Department was not arbitrary or capricious in deciding to include such a
provision in Frederick County’s most recent MS4 permit. 33 U.S.C. §1342(p)(3)(B)(iii);
Maryland Code, Environment Article, §9-322 et seq.

Environmental Law – Administrative Law – Clean Water Act – Stormwater
Discharge Permits – Scope of MS4 Permit. The Maryland Department of the
Environment may lawfully include an impervious surface restoration requirement in a
municipal separate storm sewer system (MS4) discharge permit when that requirement is
derived from commitments in the State Watershed Implementation Plan that were accepted
by the federal Environmental Protection Agency (EPA) when it adopted the Chesapeake
Bay TMDL, which in turn allocated pollutant reductions among various sources of
pollution for the purpose of achieving water quality standards in the Chesapeake Bay, in
compliance with the federal Clean Water Act. To the extent that other restoration
requirements in a permit are based on pollutant reduction allocation decisions made in other
EPA-approved TMDLs, any challenge to those decisions should have been made in
connection with the EPA’s approval of the TMDLs themselves and cannot be made as part
of judicial review in State court of a permit issued by the Department. 33 U.S.C. §1342(p);
Maryland Code, Environment Article, §§1-606, 9-322 et seq.

Environmental Law – Administrative Law – Clean Water Act – Stormwater
Discharge Permits – Classification of Phase I Jurisdictions. The Maryland Department
of the Environment had authority to treat Frederick County and Carroll County as Phase I
jurisdictions for purposes of their municipal separate storm sewer system (MS4) discharge
permits. It was not arbitrary or capricious for the Department to classify Carroll County
as a Phase I jurisdiction without also including Washington County in that category. 33
U.S.C. §1342(p)(1)-(2); Maryland Code, Environment Article, §9-322 et seq.
Environmental Law – Administrative Law – Clean Water Act – Stormwater
Discharge Permits – Water Quality Trading. A potential compliance method in a
municipal separate storm sewer system (MS4) discharge permit could authorize the
permittee to engage in water quality trading. Water quality trading occurs when a permittee
takes credit for a pollution reduction accomplished by another entity that the permittee
compensates. It was not arbitrary or capricious for the Maryland Department of the
Environment to omit water quality trading from an MS4 permit until it had finally adopted
regulations that it had proposed concerning that compliance method. 33 U.S.C. §1342(p);
Maryland Code, Environment Article, §9-322 et seq.

Environmental Law – Administrative Law – Clean Water Act – Stormwater
Discharge Permits – Permit Provision Related to Comprehensive Plan. The Maryland
Department of the Environment included a provision in municipal separate storm sewer
system (MS4) discharge permits requiring the permittees to cooperate with other agencies
during completion of the water resources element of the local comprehensive plan required
by a Maryland statute. The permit provision stated that such cooperation “shall not be
restricted by the responsibilities attributed to other entities by separate State statute,
including but not limited to reviewing and approving plans and appropriating funds.”
While the language of this provision is ambiguous, it does not, and could not, transfer the
responsibilities of other agencies to the permittee. 33 U.S.C. §1342(p); Maryland Code,
Environment Article, §9-322 et seq.; Land Use Article, §3-101 et seq.
     Circuit Court for Carroll County
     Case No. 06-C-15-068141
                                                                                          IN THE COURT OF APPEALS
     Circuit Court for Frederick County                                                        OF MARYLAND
     Case No. 10-C-15-000293
                                                                                                     Nos. 5 & 7
     Argued: September 13, 2018
                                                                                               September Term, 2018

                                                                                   MARYLAND DEPARTMENT OF THE ENVIRONMENT

                                                                                                          V.

                                                                                   COUNTY COMMISSIONERS OF CARROLL COUNTY,
                                                                                                 MARYLAND

                                                                                          FREDERICK COUNTY, MARYLAND

                                                                                                          V.

                                                                                   MARYLAND DEPARTMENT OF THE ENVIRONMENT

                                                                                                  Barbera, C.J.,
                                                                                                  *Greene
                                                                                                  *Adkins
                                                                                                  McDonald
                                                                                                  Watts
                                                                                                  Hotten
                                                                                                  Getty,

                                                                                                         JJ.

                                                                                             Opinion by McDonald, J.
                                                                                        Watts, Hotten, and Getty, JJ., dissent.

                                                                                                  Filed: August 6, 2019

                                                                                    *Greene and Adkins, JJ., now retired,
 Pursuant to Maryland Uniform Electronic Legal
Materials Act
                                                                                    participated in the hearing and conference of this
(§§ 10-1601 et seq. of the State Government Article) this document is authentic.
                                                                                    case while active members of this Court; after
                            2019-08-06 13:11-04:00                                  being recalled pursuant to the Maryland
                                                                                    Constitution, Article IV, Section 3A, they also
                                                                                    participated in the decision and adoption of this
Suzanne C. Johnson, Clerk                                                           opinion.
       In the quest to conserve a vital resource – the nation’s waters – Congress has enlisted

the federal, state, and local governments under the Clean Water Act (“the Act”)1 in a

regulatory approach sometimes called “cooperative federalism.” This effort involves a

type of regulation that takes the form of a “permit” issued by a federal agency (or a state

agency with federal oversight) at specified intervals to the regulated entity. Such permits

authorize discharges of pollution into waterways, which the Act otherwise prohibits. When

the targeted pollution is in stormwater, the permittee – i.e., the regulated entity – is often a

local government. Inevitably, as in any assignment of responsibility for solving a serious

problem, there is disagreement as to the solution and the allocation of that responsibility.

One way to resolve such disputes is through judicial review of the permit.

       This consolidated appeal concerns judicial review of the most recent permits issued

to Carroll County and Frederick County (“the Counties”) under the Act and a parallel

Maryland regulatory scheme. The permits regulate the discharge of polluted stormwater

into waterways in the Chesapeake Bay watershed. The permits were developed and issued

by the Maryland Department of the Environment (“Department”) under the supervision of

the United States Environmental Protection Agency (“EPA”), as part of an EPA-led, multi-

state effort to restore the Chesapeake Bay in compliance with the Act.

       1
           33 U.S.C. §1251 through §1388.
       Both Counties raise serious issues concerning the scope of the permits, the level of

effort required of each County, the classification of the Counties (which affects certain

conditions in the permits), and the absence or inclusion of certain terms in the permits.

Ultimately, we hold that the Department did not exceed its authority under State and federal

law when it issued the permits, nor did it act arbitrarily or capriciously in including the

challenged terms in the permits.

                                             I

                                       Background

A.     The Clean Water Act and Stormwater Controls for the Chesapeake Bay

       The Chesapeake Bay lies between the western and eastern shores of Maryland and

Virginia. As a recent federal court opinion has noted, its name derives from the Algonquin

word for “great shellfish bay.” Norfolk Southern Railway Co. v. City of Roanoke, 916 F.3d
315, 323 (4th Cir. 2019) (Wilkinson, J., concurring). While the Bay once hosted a quantity

of fish and shellfish described as “unbelievable, ... indescribable, and ...

incomprehensible,” that is no longer the case and “[i]nstead of fish, we quantify

phosphorus, nitrogen, sediment, and other pollutants” that threaten the health of the Bay’s

marine life. Id.

       The watershed of the Chesapeake Bay – the land from which water drains into it –

covers about 64,000 square miles in six states and the District of Columbia (“the Bay

States”), and extends from Cooperstown, New York, to Norfolk, Virginia. Pollution from

that region contaminates the waters that feed the Bay and ultimately the Bay itself.

“Restoring damaged waters like the Chesapeake Bay requires sustained effort, entailing

                                             2
cooperation and coordination among the federal government, state and local governments,

the enterprise of the private sector, and all the people who make this region their home.”

Norfolk Southern, 916 F.3d at 323 (internal quotation marks and citation omitted).

       Federal, state, and local governments have spent decades devising programs to

reduce the pollution that enters the Bay. This appeal concerns one such program. In any

effort to describe a complex regulatory regime, overseen by various government agencies,

one inevitably must become familiar with the concepts, jargon, and acronyms that define

that effort. We begin with an overview of the key elements pertinent to this appeal.

       Where Pollutants Come From – Point and Nonpoint Sources

       An important distinction for purposes of the Clean Water Act is the difference

between “point sources” and “nonpoint sources” of water pollution. Point sources are

discrete and localized, like a pipe carrying discharges from a factory or wastewater

treatment plant.2 Nonpoint source pollution, by contrast, comes from dispersed areas like

farms or fields where water runs off the land without being collected or channeled into a

point source.3 This distinction matters for purposes of the Act because the federal statute

regulates point sources of water pollution but does not directly regulate nonpoint sources.

       2
        A “point source” is defined as “any discernible, confined and discrete conveyance,
including but not limited to any pipe, ditch, channel, [or other types of conveyance], from
which pollutants are or may be discharged.” 33 U.S.C. §1362(14).
       3
         “Nonpoint source” is not defined in the Act. The EPA regards a “nonpoint source”
as “any source of water pollution that does not meet the legal definition of ‘point source’
in [the Act].” See EPA, Basic Information about Nonpoint Source (NPS) Pollution,
https://perma.cc/QPW5-LADC.

                                             3
      Discharge Permits

      The Act generally prohibits “any person”4 from discharging pollutants from a point

source into a waterway.5 33 U.S.C. §1311(a). Accordingly, the statute requires a permit

for the discharge of pollutants into a water body from a point source under specified

conditions. The Act establishes the National Pollution Discharge Elimination System

(“NPDES”) to govern such permits. 33 U.S.C. §1342. The EPA is authorized to issue and

enforce these permits. 33 U.S.C. §§1319, 1342(a)(1). The EPA may also delegate that

authority to a state so long as the state’s law establishes a parallel permitting program

consistent with the Act. 33 U.S.C. §1342(b). The EPA has delegated such authority to

most states, including Maryland.6

      Each discharge permit in Maryland is issued under the Act and under a parallel State

program. See Maryland Code, Environment Article (“EN”), §9-322 et seq.; COMAR

26.08.04.07. Under Maryland law, the Department is the agency designated to issue and

enforce these permits. EN §9-253; COMAR 26.08.04.01. Permits are generally issued for

fixed terms of five years or less, subject to renewal. See 33 U.S.C. §1342(b)(1)(B); EN

      4
          Under the Act, “person” includes “an individual, corporation, partnership,
association, State, municipality, commission, or political subdivision of a State, or any
interstate body.” 33 U.S.C. §1362(5).
      5
         “Discharge of a pollutant” means “any addition of any pollutant to navigable
waters from any point source [or] any addition of any pollutant to the waters of the
contiguous zone or the ocean from any point source other than a vessel or other floating
craft.” 33 U.S.C. §1362(12).
      6
          See EPA, NPDES Permits Around the Nation, https://perma.cc/2VF2-C7MK.

                                           4
§9-328(b). As a general rule, the Act prohibits subsequent permits from containing “less

stringent” conditions than the conditions in the previous permit – sometimes referred to as

the “anti-backsliding prohibition” in the Act. 33 U.S.C. §1342(o).

       The Act does not require permits for nonpoint sources or otherwise directly regulate

them. Accordingly, the EPA does not regulate those sources of water pollution. States

may do so through their own regulatory programs, as Maryland has done.7 The Act

authorizes federal grants to assist the states in such efforts. 33 U.S.C. §1288.

       Pollution Controls in Permits – Water Quality Standards and Effluent Limitations

       Under the Act, “water quality standards” are the benchmark for clean water. For

each water body covered by the Act, states submit water quality standards to the EPA for

review and approval.8 The standards are to be based on the water body’s “designated use”

(e.g., public water supply, fishing, recreational use) and include criteria necessary to

support that use (e.g., specific limits on certain pollutant concentrations). See 33 U.S.C.

§1313(c)(2)(A); 40 CFR §§130.3, 131.6; COMAR 26.08.02.01-.03.

       7
         The State relies on a “wide array of nonpoint source pollution control programs
[to combat] these varied pollution sources.” Maryland Department of the Environment,
Nonpoint Source Program (319) Management and Financial Assistance,
https://perma.cc/X6ZV-6T5E. Such programs include septic system upgrades, erosion and
sediment control on farms, fertilizer application management, and many others. See
Maryland Department of the Environment, Maryland’s 2015-2019 Nonpoint Source
Management Plan (updated August 4, 2016), available at https://perma.cc/RR5K-6EMB.
       8
         If the EPA does not approve a state-authored water quality standard, the EPA must
establish the standard itself. 33 U.S.C. §1313(c)(4).

                                             5
         To achieve water quality standards, the Act requires that discharge permits include

pollution controls for point sources. 33 U.S.C. §1311(b). The Act calls these controls

“effluent limitations” – “effluent” being the material discharged by a point source.9

Effluent limitations may be “technology based” or “water quality based.” See EPA,

NPDES Permit Limits, https://perma.cc/L4G6-24K9; Natural Resources Defense Council

v. EPA, 808 F.3d 556, 563 (2d Cir. 2015).

         Technology based effluent limitations are generally the first round of controls in the

effort to achieve water quality standards. See 33 U.S.C. §1311(b)(1)(A). They “represent

the minimum level of control that must be imposed in a permit[.]” 40 CFR §125.3(a). But

even the most stringent technology based effluent limitations have not achieved water

quality standards in thousands of the nation’s waterways.10 Congress anticipated this

possibility in 1972 by retaining water quality standards “as a supplementary basis for

effluent limitations … so that numerous point sources, despite individual compliance with

effluent limitations, may be further regulated to prevent water quality from falling below

acceptable levels.” EPA v. California ex rel. State Water Resources Control Board, 426
U.S. 200, 205 n.12 (1976). If technology based limitations do not achieve the water quality

         The term “effluent” is not defined in the Act. However, the Act defines “effluent
         9

limitation” as “any restriction established by a State or the [EPA] on quantities, rates, and
concentrations of chemical, physical, biological, and other constituents which are
discharged from point sources into navigable waters, the waters of the contiguous zone, or
the ocean, including schedules of compliance.” 33 U.S.C. §1362(11).
         10
              See American Farm Bureau Federation v. EPA, 792 F.3d 281, 289-91 (3d Cir.
2015).

                                               6
standards, permits may include “any more stringent limitation ... necessary to meet water

quality standards” – i.e., “water quality based effluent limitations.” 33 U.S.C.

§1311(b)(1)(C); 40 CFR §130.7(c).11 Thus, regardless of whether a waterway is over-

polluted due to point sources, nonpoint sources, or some mixture of both, the Act authorizes

the imposition of water quality based controls on point sources, in addition to the most

stringent technology based controls.12

       These two types of effluent limitations differ in their reference point and in their

strategies for reducing pollution.13 For technology based limitations, the reference point is

the source, and the strategy is to deploy pollutant-reducing technology at that source

regardless of its contribution of pollutants to the waterway. By contrast, for water quality

based effluent limitations, the reference point is the waterway, and the strategy is for the

       11
         Cf. COMAR 26.08.03.01C(2)(b) (“Best available technology shall be required as
the minimum for all permitted discharges. If it is determined that compliance with the
established water quality standards will not be achieved through [best available
technology], additional treatment shall be [required].”).
       12
         A core premise of water quality based effluent limitations in general is that
permitting agencies may require point sources to go beyond their existing capabilities to
achieve further pollution reductions. See Natural Resources Defense Council v. EPA, 915
F.2d 1314, 1316-17 (9th Cir. 1990).
       13
           See Michael P. Healy, Still Dirty After Twenty-Five Years: Water Quality
Standard Enforcement and the Availability of Citizen Suits, 24 Ecology L.Q. 393, 399
(1997) (“Technology-based standards are based on the source’s technological capacity to
control pollution, while water quality-based standards are based on the environmental
effect of the discharged pollution.”).

                                             7
point source to implement any additional actions (beyond the already required

technologies) necessary to achieve the applicable water quality standard.14

       The Point Sources Here – Municipal Separate Storm Sewer Systems (MS4s)

       This appeal concerns permits for a type of point source known as a “municipal

separate storm sewer system” (“MS4”).15 An MS4 is a network of conveyances (including

storm drains, gutters, and other drainage systems) designed to carry only stormwater (as

opposed to a “combined sewer system” that conveys both sanitary sewage and stormwater).

40 CFR §122.26(b)(8).

       MS4s differ from typical “end-of-pipe” point sources in certain respects.         A

common point source, such as a pipe that discharges waste from a factory, usually

discharges a known and finite set of pollutants from a specific location. By contrast,

stormwater picks up various pollutants as it flows across widely dispersed areas, including

paved (or “impervious”) surfaces, on its way to one of the many conveyances that make up

an MS4, and then into a waterway. The quantity of stormwater that flows through these

       14
           See EPA, NPDES Permit Writer’s Manual (September 2010) (“EPA Permit
Writer’s Manual”), available at https://perma.cc/P8BX-MNUY, at 5-1 (Technology based
effluent limitations “are developed independently of the potential impact of a discharge on
the receiving water, which is addressed through water quality standards and water quality-
based effluent limitations[.]”).
       15
          Shortly after the passage of the Clean Water Act in the 1970s, the question of
whether – and if so, how – to treat MS4s as point sources under the Act generated
regulations and litigation. The EPA initially adopted regulations exempting MS4s from
the Act’s permit requirement. That exemption was challenged and held invalid in Natural
Resources Defense Council v. Costle, 568 F.2d 1369, 1372-73 (D.C. Cir. 1977).
Ultimately, Congress enacted the Water Quality Act of 1987, which explicitly established
a discharge permit requirement for MS4s. See 33 U.S.C. §1342(p).

                                            8
conveyances into a waterway can vary unpredictably depending on the weather, any

development of the land (e.g., whether the land is paved), and other activities on the land

(e.g., litter, use of lawn fertilizers).

       Given these differences between an MS4 and a typical point source like a factory, a

discharge permit for an MS4 differs from that for a typical point source. A discharge permit

for a typical end-of-pipe point source usually sets numeric limits as effluent limitations for

the known set of pollutants discharged from that pipe.16 Using that same approach for an

MS4 would entail setting effluent limitations for each conveyance within the stormwater

drainage system, which would be administratively, technically, and financially

burdensome.17 Instead, an MS4 permit generally requires the permittee to implement

flexible management programs designed to reduce the pollution introduced into

       16
          EPA Permit Writer’s Manual, supra note 14, Ch. 5 (explaining in detail a
permitting agency’s process for developing technology based effluent limitations); Natural
Resources Defense Council v. EPA, 808 F.3d 556, 567 (2d Cir. 2015) (A discharge permit
imposes effluent limitations on a point source “based on how much technology is able to
reduce the amount of a pollutant at issue”).
       17
          See EPA, National Pollutant Discharge Elimination System Permit Application
Regulations for Storm Water Discharges, 55 Fed. Reg. 47990, 48037-38 (November 16,
1990) (“EPA Preamble to 1990 Phase I MS4 Rule”). The discussion of the background of
the regulations that appears together with the notice announcing the EPA’s final adoption
of the regulations is sometimes informally referred to as a “preamble” to the regulations.
However, it is not itself part of the regulations and does not appear in the Code of Federal
Regulations. See James T. O’Reilly, Administrative Rulemaking §10:1 (2019 ed.).

                                              9
stormwater, thereby limiting the amount of pollution discharged into the waterway.18 In

the language of the Act, an MS4 permit is to include “controls to reduce the discharge of

pollutants to the maximum extent practicable, including management practices, control

techniques and system, design and engineering methods, and such other provisions as the

[EPA] or the State determines appropriate for the control of such pollutants.” 33 U.S.C.

§1342(p)(3)(B)(iii).

       Implementation of the MS4 Permit Requirement – Phase I and Phase II

       The Act and related EPA regulations have applied the permit requirement to MS4s

in two phases. The first phase (“Phase I”) took effect during the period 1987-94 and

included stormwater systems that were serving more heavily populated areas – dubbed

“large” and “medium” MS4s – and those that were contributing to the failure of a water

body to meet water quality standards, irrespective of the size of the population served. See

33 U.S.C. §1342(p)(2); 40 CFR §122.26(b). Subsequently, a second phase (“Phase II”)

covered “small” MS4s. See 33 U.S.C. §1342(p)(5)-(6); 40 CFR §122.34. As a general

rule, permits for MS4s included in Phase I have been subject to an earlier timetable and

more stringent conditions than permits for MS4s included in Phase II.

       18
         See EPA Preamble to 1990 Phase I MS4 Rule, 55 Fed. Reg. at 48037-38; Natural
Resources Defense Council v. New York State Dep’t of Envtl. Conservation, 34 N.E.3d
782, 787 (N.Y. 2015).

                                            10
       Total Maximum Daily Load (TMDL)

       An important element in determining the conditions that appear in a discharge

permit is what is known as the “total maximum daily load” – or “TMDL.” The Clean

Water Act does not define this phrase, but describes it as the “level” of a pollutant that a

water body can tolerate without violating applicable water quality standards. 33 U.S.C.

§1313(d)(1)(C). In practice, the acronym “TMDL” has come to refer to more than just a

numeric measure of a pollutant. It has also come to refer to the process and calculations

used to determine that level of a pollutant and its allocation among sources of the pollutant.

The document in which an agency calculates the TMDL, in the sense of a numeric measure

of a pollutant, and allocates that level among various sources of pollution is also sometimes

referred to as a “TMDL.” A singularly complex example pertinent to this case is what is

referred to as the Chesapeake Bay TMDL (“Bay TMDL”),19 which is discussed in greater

detail below.

       The EPA has elaborated on the meaning of TMDL as a numeric measure of pollution

in its regulations. The term “load” refers to a measure of water pollution. See 40 CFR

§130.2(e) (defining “load” as “[a]n amount of matter or thermal energy that is introduced

into a receiving water”). The phrase “total maximum daily load” or “TMDL” is defined in

regulation as “the sum of” amounts of the relevant pollutant emanating from various point

and nonpoint sources together with a “natural background” amount of the pollutant and a

       19
        EPA, Chesapeake Bay Total Maximum Daily Load for Nitrogen, Phosphorus and
Sediment (December 29, 2010), available at https://perma.cc/RWM2-Y22N.

                                             11
“margin of safety.” 40 CFR §§130.2(i), 130.7(c)(1). A TMDL, in this sense, “can be

expressed in terms of either mass per time, toxicity, or other appropriate measure….” 40

CFR §130.2(i). To understand this definition of TMDL as a numeric measure requires an

understanding of the TMDL process.

       The TMDL process is based on the direction in the Act that each state identify

waterways for which technology based effluent limitations are not achieving water quality

standards.20 33 U.S.C. §1313(d)(1)(A). If water quality standards are not being met in a

waterway due to excess levels of a particular pollutant, the state is to determine the

maximum amount of that pollutant that the waterway can receive without violating water

quality standards – i.e., the TMDL for that pollutant as to that waterway. 33 U.S.C.

§1313(d)(1)(C). The resulting TMDL – as a cap on the pollutant – is sometimes referred

to as a “pollution budget” or “pollution diet.” E.g., Norfolk Southern, 916 F.3d at 324;

Conservation Law Foundation v. EPA, 964 F. Supp. 2d 175, 179 (D. Mass. 2013).

       The EPA’s regulations recognize that, in order for a state to calculate the maximum

level of a pollutant that a waterway can tolerate without violating water quality standards,

a state agency must conduct a complex scientific analysis. The state agency must consider,

among other things, the relationship between the water quality standards and the level of

the pollutant in the waterway, the various sources of the pollutant, and the extent to which

       20
          As indicated above, when technology based effluent limitations are inadequate to
achieve water quality standards, discharge permits may include water quality based
effluent limitations.

                                            12
each source contributes to the violation of water quality standards. See 40 CFR §130.7(c).

As indicated earlier, in developing the TMDL for that pollutant, the agency must also factor

in “seasonal variations and a margin of safety which takes into account any lack of

knowledge concerning the relationship between effluent limitations and water quality.” 33

U.S.C. §1313(d)(1)(C).

       Once the agency produces its best estimate of the maximum pollutant level

consistent with water quality standards – i.e., the TMDL in the sense of a numeric measure

of pollution – it must then apportion that amount to the relevant sources of that pollution

while allowing for the margin of safety required by the Act. See 40 CFR §§130.2(i),

130.7(c). The portion assigned to each relevant point source is called a “wasteload

allocation.” 40 CFR §130.2(h). The portion assigned to each nonpoint source is called a

“load allocation.” 40 CFR §130.2(g). In all, therefore, the TMDL – in the sense of a

numeric amount – for a given pollutant for a particular waterway is the sum of the

wasteload allocations, the load allocations, the natural background, and the margin of

safety. 40 CFR §§130.2(i), 130.7(c)(1). After a state has determined a TMDL for a

particular pollutant with respect to a particular waterway, it is to be submitted to the EPA

for approval. 33 U.S.C. §1313(d)(2).

       When a state submits a TMDL to the EPA, the state provides not only the maximum

pollutant amount, but also the various wasteload allocations and load allocations, together

with an explanation of the calculations that resulted in that maximum amount and the

allocations. EPA, Water Quality Planning and Management, 50 Fed. Reg. 1774, 1775

(January 11, 1985) (“it is impossible to evaluate whether a TMDL is technically sound and

                                            13
whether it will be able to achieve [water quality] standards without evaluating component

[wasteload and load allocations] and how these loads were calculated”). As indicated

earlier, an example of a document that contains the separate TMDLs (in the sense of

numeric amounts) for relevant pollutants, explains the reasoning and calculations

underlying those caps, and allocates those totals among the relevant sources of pollution is

the Bay TMDL.

       A TMDL such as the Bay TMDL is neither self-implementing nor directly

enforceable. Rather, it serves as an informational tool that the EPA and the states use in

seeking to achieve the specified pollutant levels – and the applicable water quality

standards – by means of discharge permits and other regulatory tools. See American Farm

Bureau Federation v. EPA, 984 F. Supp. 2d 289, 297-98 (M.D. Pa. 2013), aff’d, 792 F.3d
281 (3d Cir. 2015). To enforce the TMDL limits and corresponding water quality

standards, agencies that issue discharge permits seek to ensure that the total pollution

discharged by point sources does not exceed the wasteload allocations in the relevant

TMDLs. The combined pollution allotted to all of the point sources should equal the sum

of the wasteload allocations in a TMDL. Therefore, the discharge permit for each point

source is to contain water quality based effluent limitations consistent with the

“assumptions and requirements” of the wasteload allocation for that source in any

applicable TMDL. 40 CFR §122.44(d)(1)(vii)(B).

       A discharge permit may incorporate provisions related to several TMDLs. The

permits at issue in this case incorporate provisions not only from the Bay TMDL, but also

from TMDLs, developed by the Department and approved by the EPA, for certain

                                            14
waterways.21   Appendices to the Counties’ MS4 permits list the approved TMDLs

applicable to each County. One example, which will be discussed later in this opinion, is

the TMDL for fecal bacteria in Double Pipe Creek, whose watershed spans both Counties.

       Chesapeake Bay TMDL and Maryland Watershed Implementation Plan (WIP)

       In 2009, after decades of multilateral efforts aimed at restoring the Chesapeake

Bay,22 the EPA began the development of a Chesapeake Bay-wide TMDL.23 After

publishing a draft for a period of public review, the EPA adopted the Bay TMDL in late

2010.24 The Bay TMDL establishes limits for three pollutants – nitrogen, phosphorus, and

sediment – that threaten marine life by feeding large algae blooms that block sunlight and

       21
           See Maryland Department of the Environment,                 Approved TMDLs,
https://perma.cc/99S9-C7Q3.
       22
         For a summary of Bay clean-up efforts over the past several decades, see Farm
Bureau, 984 F. Supp. 2d at 298-303.
       23
          The EPA “established the Chesapeake Bay TMDL pursuant to a number of
existing authorities, including the [Clean Water Act] and its implementing regulations,
judicial consent decrees requiring EPA to address certain [waters in the Chesapeake Bay
watershed that were failing to meet water quality standards], a settlement agreement
resolving litigation brought by the Chesapeake Bay Foundation, the 2000 Chesapeake
Agreement [between certain Bay states], and Executive Order 13508.” See Bay TMDL at
1-16. That Executive Order directed the EPA to “mak[e] full use of its [Clean Water Act]
authorities to lead a collaborative and effective federal and state effort to meet the Bay’s
nutrient and sediment goals.” Id. at 1-17.
       24
          See EPA, Clean Water Act Section 303(d): Preliminary Notice of Total Maximum
Daily Load (TMDL) Development for the Chesapeake Bay, 74 Fed. Reg. 47792 (September
17, 2009); EPA, Clean Water Act Section 303(d): Notice for the Establishment of the Total
Maximum Daily Load (TMDL) for the Chesapeake Bay, 76 Fed. Reg. 549 (January 5, 2011)
(stating that the EPA established the Bay TMDL on December 29, 2010).

                                            15
reduce oxygen levels in the water.25 Bay TMDL at 2-6, 2-7. Specifically, the Bay TMDL

pollutant caps are designed to satisfy water quality standards involving “aquatic life uses”

and criteria such as water clarity and dissolved oxygen levels. Id. at 3-1, 3-2.

       Given the breadth and complexity of the Bay TMDL, the EPA established a unique

accountability framework to achieve its goals. Bay TMDL at ES-8. Although the Act

generally does not require an implementation plan for a TMDL, the EPA directed each Bay

State to create a “Watershed Implementation Plan” (“WIP”) to reduce pollution to the

levels set by the Bay TMDL. Each Bay State’s WIP serves two basic purposes – to break

down the EPA’s statewide Bay TMDL pollutant allocations among geographic areas and

among point and nonpoint sources within the state, and to identify the programs and

policies that the state will use to achieve those pollutant reductions. The Maryland WIP

was developed by the Department together with the Departments of Planning, Agriculture,

and Natural Resources. Maryland’s Final Phase I Watershed Implementation Plan (Dec.

3, 2010), available at https://perma.cc/8CMV-ENCB (“Maryland WIP”).26 Like the other

       25
          More precisely, the Bay TMDL divides waterways in the Chesapeake Bay
watershed into 92 “segments,” and establishes individual TMDLs – in the sense of numeric
amounts – for each segment for each of the three pollutants. Thus, the Bay TMDL is “an
assemblage of 276 TMDLs: individual TMDLs for each of the 3 pollutants – nitrogen,
phosphorus, and sediment – for each of the 92 segments (3 x 92 = 276).” Bay TMDL, at
xiii & 2-7.
       26
          The EPA anticipated that each state would write its WIP in three phases. The
State has published the first two iterations of its WIP and a draft version of the third
iteration. See Maryland Department of the Environment, Watershed Implementation
Plans, https://perma.cc/J985-WQ65. Citations in the text are to the first iteration of the
WIP, often referred to as the Phase I WIP. The “phases” of the WIP should not be confused

                                             16
Bay State WIPs, the Maryland WIP functions as a “roadmap” for how and when the State

will reach the pollution reduction goals set forth in the Bay TMDL. Maryland Department

of the Environment v. Anacostia Riverkeeper, 447 Md. 88, 109 (2016).

       Implementing the Maryland WIP in MS4 Permits

       The Maryland WIP listed several requirements to be included in the then-upcoming

round of Phase I MS4 permits in Maryland. Two of these requirements correspond to terms

in the Counties’ permits that are part of the dispute in this litigation.

       First, a commitment in the Maryland WIP involves restoration of impervious

surfaces – i.e., areas that have been paved or otherwise developed, as opposed to natural,

undeveloped areas. Natural areas allow stormwater to soak into the ground, where

pollutants are filtered to some extent. Impervious surfaces prevent that filtration process.

Instead, stormwater that encounters an impervious surface rushes over it, collecting

pollutants along the way. To “restore” an impervious surface is to make it function more

like a natural terrain that absorbs and filters rain water. Doing so accomplishes the same

end as a direct pollutant control, like a filter or other cleansing mechanism attached to a

conveyance. The less impervious surface that exists, the less polluted stormwater will run

across it and into the conveyances of the MS4. Thus, as is true in general for stormwater

management programs in MS4 permits, an impervious surface restoration requirement

serves as a surrogate for direct pollution controls. See Anacostia Riverkeeper, 447 Md. at

with the two phases of the MS4 permitting program, which will be discussed in some detail
in Part II.D. of this Opinion.

                                               17
122-23. The Maryland WIP called for “[c]ompletion of restoration efforts for twenty

percent of the [Phase I MS4] counties’ impervious surface area that is not already restored

to the maximum extent practicable.” Maryland WIP at 5-30.

       Second, another provision of the Maryland WIP refers to many applicable local

TMDLs with stormwater wasteload allocations. For example, for the Counties, the relevant

local TMDLs are compiled, as mentioned above, in appendices to their MS4 permits. The

Maryland WIP requires the creation of “[s]tormwater watershed implementation plans for

each EPA approved stormwater wasteload allocation” in the relevant local TMDLs.

Maryland WIP at 5-30. Such local watershed implementation plans are distinct from the

overall Maryland WIP.

       Maryland Stormwater Management Act

       In addition to the permitting program, the State Stormwater Management Act has,

since the mid-1980s, required local jurisdictions to implement stormwater management

programs “to reduce as nearly as possible the adverse effects of stormwater runoff.” EN

§4-201. Each county and municipality is to adopt ordinances necessary to implement such

a program consistent with State law. EN §4-202. The Legislature directed the Department

to adopt regulations governing such programs that would, among other things, indicate that

the primary goal is “to maintain after development, as nearly as possible, the

predevelopment runoff characteristics.” EN §4-203(b)(1); see also Anacostia Riverkeeper,
447 Md. at 110-13. The statute authorizes jurisdictions to impose and collect stormwater

remediation fees and other charges to carry out such programs. EN §§4-202.1, 4-204; see

also 96 Opinions of the Attorney General 61 (2011). Such fees provide “important revenue

                                            18
needed to offset the costs of building and maintaining municipal gutters and drains,

monitoring pollution levels, policing illegal discharges of polluted water, and educating the

public on proper environmental practices.” Norfolk Southern, 916 F.3d at 325 (referring

to similar local stormwater fee in Virginia).

       The Carroll County and Frederick County MS4 Permits

       The Department first issued MS4 permits to Carroll County and Frederick County

during the 1990s as part of Phase I of the MS4 permitting process, and has renewed those

permits several times since then. The permits that are the subject of this case are Carroll

County’s fourth and Frederick County’s third round of MS4 permits, which were both

issued in December 2014. In accordance with State law, the Department first issued draft

permits for public comment. See EN §1-604(a). In each case, the Department held a public

hearing and accepted comments on the draft permit. After considering those comments,

the Department made a Final Determination to issue each permit together with a document

entitled “Basis for Final Determination” that provided an explanation for its action. EN

§1-604(b).

       Pertinent to this case, the Maryland WIP commitment involving impervious surface

restoration is incorporated into Part IV.E.2.a of each permit. This provision has two

components. First, it requires each County to submit to the Department an “impervious

surface area assessment” consistent with guidelines provided by the Department. That

assessment, if approved by the Department, “shall serve as the baseline for the restoration

efforts” required by the permit. Second, by the end of the permit term, each County “shall

commence and complete the implementation of restoration efforts for twenty percent of

                                                19
the County’s impervious surface area consistent with the methodology described in [a

Department guidance document] that has not already been restored to the” maximum extent

practicable.

       Part IV.E.2.b of each permit includes a provision based on the commitment in the

Maryland WIP concerning local TMDLs. This provision requires each County to submit

to the Department for approval a plan to implement each stormwater wasteload allocation

in each relevant, EPA-approved local TMDL. Each plan must include a final date for

“meeting applicable [wasteload allocations] and a detailed schedule for implementing all

[necessary] structural and nonstructural water quality improvement projects, enhanced

stormwater management programs, and alternative stormwater control initiatives.” Upon

approval by the Department, the plans become enforceable conditions of the permits.

       Two other aspects of the permits are at issue here. The first is Part VI.B of each

permit, which requires the Counties to cooperate with other State agencies in the

development of elements of the Counties’ comprehensive growth plans that involve

stormwater management. The second contested aspect of the permits is the absence of an

authorization for “water quality trading.”27 As relevant here, such trading would allow the

Counties to earn credit for pollution reduction by paying others (whether point or nonpoint

sources) to take pollution-reducing actions. A County might consider water quality trading

       27
            “Water quality trading” is sometimes referred to as “nutrient trading.”

                                               20
in situations where paying another party to achieve a pollution reduction costs less than the

County’s own efforts to achieve a similar reduction.

B.        Procedural History

          In January 2015, Carroll County sought judicial review of its 2014 MS4 permit in

the Circuit Court for Carroll County. At the request of the parties, the matter was stayed

for more than a year while the parties pursued settlement and while challenges to similar

permits by environmental advocates were being litigated.28 After the stay expired, the

Circuit Court issued an opinion dated June 26, 2017, agreeing with the County on some of

its claims and with the Department on others. The court remanded the County’s permit to

the Department. The Department appealed that ruling and the County filed a cross-appeal.

          In January 2015, Frederick County sought judicial review of its 2014 permit in the

Circuit Court for Frederick County. As in the Carroll County case, the matter was stayed

pending settlement discussions and other litigation. After the stay expired, the Circuit

Court issued an opinion dated July 14, 2017, that largely rejected the County’s arguments,

but remanded the permit to the Department to address what the court believed were

ambiguities and inconsistencies in the permit’s wording. Frederick County appealed that

ruling.

          The Court of Special Appeals consolidated the two appeals for argument. Prior to

argument and decision in the Court of Special Appeals, the Counties asked this Court to

          28
         This Court resolved that litigation in Maryland Department of the Environment
v. Anacostia Riverkeeper, 447 Md. 88 (2016).

                                              21
grant a writ of certiorari in their respective cases. The Department agreed that the

Counties’ petitions should be granted.       This Court granted the two petitions and

consolidated the cases for argument.

                                             II

                                        Discussion

       Both Counties challenge conditions set forth in their most recent MS4 permits,

although some of the bases for their challenges differ.

       Two of the alleged flaws in the permits concern the impervious surface restoration

requirement. First, Frederick County argues that the Department exceeded its authority

under the Clean Water Act by failing to consider “practicability” when it included the

impervious surface restoration requirement in its permit. Frederick County bases this

argument on a provision of the Act that requires MS4 permits to include controls to reduce

pollution discharges “to the maximum extent practicable” – what is sometimes called the

MEP standard. Frederick County further argues that, even if the Act allows the Department

to set the restoration requirement without regard to the MEP standard, the Department

arbitrarily and capriciously failed to consider the County’s contention that compliance with

the degree of restoration required by the permit is impossible.

       Second, both Counties assert that the Department exceeded its authority under the

Act by including in the permit an impervious surface restoration requirement in which the

baseline for measuring compliance with the requirement relates to the unrestored

impervious surface throughout the entire County, rather than only the area served by the

County’s MS4.

                                            22
       Both Counties argue that the Department has unlawfully treated them as Phase I

jurisdictions for purposes of their MS4 permits – thereby subjecting them to more stringent

permit terms required of Phase I jurisdictions than those later required of Phase II

jurisdictions – because it incorrectly classified them in the early 1990s as “medium”

jurisdictions based on population. Carroll County also argues that its inclusion in Phase I

of the MS4 permitting program was arbitrary and capricious.

       Both Counties argue that the Department arbitrarily and capriciously failed to

include water quality trading as a compliance mechanism in their permits.

       Finally, Carroll County argues that a provision in its permit that requires the County

to cooperate with other State agencies in the development of stormwater-related aspects of

the County’s comprehensive growth plan unlawfully imposes new obligations on the

County.

       We first discuss the standards that govern our consideration of these arguments. We

then consider the substantive issues raised by the Counties.

A.     What and How We Review

       The General Assembly has provided for judicial review of permits issued by the

Department, such as the MS4 permits issued to the Counties. EN §1-601(a)(3), (c). Such

review is based on an administrative record that includes the various items set forth in EN

§1-606(c).29 Judicial review begins in the circuit court pursuant to the Maryland Rules.

       29
        Among other things, the record may include the permit application and any
accompanying data, documents contained in the supporting file for the draft permit,
comments submitted to the Department from the public, responses to those comments, the

                                             23
See Maryland Rule 7-201 et seq. (governing judicial review of administrative actions when

a statute provides for judicial review).

       In an appeal of the circuit court’s review of an agency action, an appellate court

reviews the agency’s action itself rather than the decision of the circuit court.

Hollingsworth v. Severstal Sparrows Point, LLC, 448 Md. 648, 654 (2016). Thus, while

the circuit court decisions here set the stage for our review and determined who would be

appellant and appellee in our Court, we are not assessing the merits of those court decisions.

Rather, we directly review the permits in light of the issues raised by the Counties.

       1.     Standards for Review of Discharge Permits

       a.   General Standards for Review of Agency Action

       The standards for judicial review of a discharge permit – and their corresponding

levels of deference to the agency – vary depending on whether the court is reviewing an

agency’s fact findings, discretionary decisions, or legal conclusions.        See Anacostia

Riverkeeper, 447 Md. at 118-21.

       Review of Fact Findings

       For fact findings, a reviewing court applies the “substantial evidence” standard,

under which the court defers to the facts found and inferences drawn by the agency when

the record supports those findings and inferences. Anacostia Riverkeeper, 447 Md. at 120.

tape or transcript of any public hearings, and the Department’s statement of the basis for
its determinations with respect to the permit.

                                             24
In particular, with respect to factual issues that involve scientific matters within an

agency’s area of technical expertise, the agency is entitled to “great deference.” Id.

       Review of Matters Committed to the Agency’s Discretion

       With respect to matters committed to agency discretion, a reviewing court applies

the “arbitrary and capricious” standard of review, which is “extremely deferential” to the

agency. Harvey v. Marshall, 389 Md. 243, 296-99 (2005); Spencer v. Md. State Bd. of

Pharmacy, 380 Md. 515, 529 (2004). This standard is highly contextual, but generally the

question is whether the agency exercised its discretion “unreasonably or without a rational

basis.” Harvey, 389 Md. at 297; Arnold Rochvarg, Maryland Administrative Law, §4.38

at 128 (2011).

       For guidance, a reviewing court may look to case law applying the similar standard

in federal administrative law. See Anacostia Riverkeeper, 447 Md. at 120-21; Office of

People’s Counsel v. Public Service Commission, 461 Md. 380, 399 (2018).30 Under this

standard, a reviewing court is not to substitute its own judgment for that of the agency and

should affirm decisions of “less than ideal clarity” so long as the court can reasonably

       30
          Under the federal standard, the reviewing court may consider whether: (1) the
agency’s choice was rationally connected to the facts found; (2) the agency considered the
relevant factors; (3) the agency made a clear error of judgment; (4) the agency relied on
factors the legislature did not intend for it to consider; (5) the agency failed to consider an
important aspect of the problem; (6) an explanation for the decision runs counter to the
evidence; and (7) the decision is so implausible that it could not be ascribed to a difference
in view or the product of agency expertise. Office of People’s Counsel, 461 Md. at 399
n.16.

                                              25
discern the agency’s reasoning. Bowman Transp., Inc. v. Arkansas-Best Freight System,

Inc., 419 U.S. 281, 285-86 (1974).

       Review of the Agency’s Legal Conclusions

       With respect to an agency’s legal conclusions, a reviewing court accords the agency

less deference than with respect to fact findings or discretionary decisions. Anacostia

Riverkeeper, 447 Md. at 122. In particular, a court will not uphold an agency action that

is based on an erroneous legal conclusion. Id. However, in construing a law that the agency

has been charged to administer, the reviewing court is to give careful consideration to the

agency’s interpretation.

       In construing a statute, a reviewing court applies the oft-stated approach to statutory

construction. That is, the court seeks to ascertain legislative intent – whether that of the

General Assembly or of Congress. That endeavor begins with the plain meaning of the

text, keeping in mind that the plainest language is controlled by the context in which it

appears. Kaczorowski v. Mayor & City Council of Baltimore, 309 Md. 505, 514 (1987).

The legislative history of the statute may then be reviewed to understand the purpose of

the legislation, resolve ambiguities, and confirm the apparent meaning of the text. Past

case law construing a provision is, of course, also helpful. Throughout, the court must be

mindful that the purpose is not to discern “purely judicial notions of public policy,” but

rather legislative intent. BAA, PLC v. Acacia Mutual Life Ins. Co., 400 Md. 136, 157

(2007).

       When a party challenges the agency’s interpretation of the statute the agency

administers, the court must assess how much weight to accord that interpretation, keeping

                                             26
in mind that it is “always within [the court’s] prerogative to determine whether an agency’s

conclusions of law are correct.” Schwartz v. Md. Dep’t of Nat. Res., 385 Md. 534, 554

(2005). The weight given an agency’s interpretation of a statute it administers depends on

several factors. Baltimore Gas & Electric Co. v. Public Service Commission, 305 Md. 145,

161 (1986). More weight is appropriate when the interpretation resulted from a process of

“reasoned elaboration” by the agency, when the agency has applied that interpretation

consistently over time, or when the interpretation is the product of contested adversarial

proceedings or formal rule making. Id. at 161-62.

       b.     Effect of the Clean Water Act’s Scheme of Cooperative Federalism

       In our consideration of the Department’s interpretation and application of the Clean

Water Act, we must take into account the extent to which the EPA’s administrative

interpretation and federal case law set parameters for the Department’s actions. The shared

implementation of a federal policy or program by federal and state agencies is sometimes

referred to as “cooperative federalism.” See Anacostia Riverkeeper, 447 Md. at 101. It

can affect how a state court reviews that implementation when the state agency’s actions

are limited by federal policies.     In general, a state agency that is delegated the

administration of the discharge permitting program under the Act is “bound to follow

EPA’s interpretation of the [Act].” Natural Resources Defense Council v. New York State

Dep’t of Envtl. Conservation, 34 N.E.3d 782, 794 n.16 (N.Y. 2015) (declining to entertain

                                            27
a challenge to an EPA regulation interpreting the Act and state agency’s compliance with

that interpretation).31

       Under the Act’s cooperative federalism scheme, the EPA has delegated the

administration of the Act’s discharge permitting program in Maryland to the Department.

Nonetheless, the EPA reviews and has the right to object to the Department’s draft

discharge permits. 40 CFR §123.44 (“EPA review of and objections to State permits”);

see also Memorandum of Agreement between EPA and Department (May 18, 1989),

available at https://perma.cc/3UNE-4CLN (explaining that the EPA will review all State-

prepared permits and may object to them). In addition, the EPA has overseen Maryland’s

efforts (as well as those of the other Bay States) to achieve the goals of the Bay TMDL –

i.e., efforts to develop and carry out the WIPs. See Farm Bureau, 984 F. Supp. 2d at 323-

24.

       31
          See also BellSouth Telecommunications, Inc. v. Sanford, 494 F.3d 439, 449 (4th
Cir. 2007) (state’s authority over telecommunications issue is part of deliberately
constructed model of “cooperative federalism” under which state agency applies expertise
and experience “subject to the boundaries set by Congress and federal regulators”); Perry
v. Dowling, 95 F.3d 231, 236-37 (2d Cir. 1996) (a state agency’s interpretation of the
federal Medicaid statute “warrants deference” when “the state has received prior federal-
agency approval to implement its plan, the federal agency expressly concurs in the state’s
interpretation of the statute, and the interpretation is a permissible construction of the
statute”); Aaron Saiger, Chevron and Deference in State Administrative Law, 83 Fordham
L. Rev. 555, 581 (2014) (“State officials who deal with the environment, education, or
antiterrorism are enmeshed in a system of regulatory federalism that often very
substantially deprives them of freedom of action.”).

                                           28
       c.     Deference Owed to the EPA’s Construction of the Clean Water Act

       In assessing the weight to be accorded the EPA’s construction of the Act, we look

to the deference that would be accorded such interpretations under federal case law. In

general, when an agency exercises authority to “make rules carrying the force of law” –

i.e., rulemaking, adjudications, or other actions involving similarly extensive

administrative procedures – the agency’s interpretation warrants deference under Chevron

U.S.A. v. Natural Resources Defense Council, 467 U.S. 837 (1984). Less formal agency

action may also merit Chevron deference depending on “the interstitial nature of the legal

question, the related expertise of the Agency, the importance of the question to

administration of the statute, the complexity of that administration, and the careful

consideration the Agency has given the question over a long period of time.” Barnhart v.

Walton, 535 U.S. 212, 222 (2002).

       Under Chevron, a federal court first determines “whether Congress has directly

spoken to the precise question at issue” in the pertinent statute – in this case, the Clean

Water Act. 467 U.S. at 842. If the Congressional intent is clear, the court “must give effect

to [that] unambiguously expressed intent.” Id. at 842-43. But “if the statute is silent or

ambiguous with respect to the specific issue,” the court must decide “whether the [EPA’s]

answer is based on a permissible [or reasonable] construction of the statute.” Id. at 843-

44.

       Even if the particular agency interpretation does not meet the criteria for Chevron

deference, a reviewing court may defer to that interpretation based on the persuasiveness

of the agency interpretation, considering factors such as “the thoroughness evident in its

                                             29
consideration, the validity of its reasoning, its consistency with earlier and later

pronouncements, and all those factors which give it power to persuade, if lacking power to

control.” Skidmore v. Swift & Co., 323 U.S. 134, 140 (1944) (Jackson, J.).32

       This Court has assessed the validity of State agency actions consistent with a federal

agency’s regulations or interpretations of a federal statute in light of these principles. See

Anacostia Riverkeeper, 447 Md. at 142 & n.61 (citing federal administrative deference case

law and finding an EPA policy memorandum “instructive” on interpretation of federal

regulation under the Clean Water Act); Sugarloaf Citizens’ Ass’n v. Department of the

Environment, 344 Md. 271, 313 (1996) (affirming Department action based in part on EPA

interpretation of the federal Clean Air Act, which was entitled to deference under

Chevron); Koons Ford of Baltimore, Inc. v. Lobach, 398 Md. 38, 54 (2007) (applying

Chevron and adopting the FTC’s interpretation of a federal statute that the FTC

administers); Montgomery Cty. v. Glenmont Hills Associates Privacy World at Glenmont

Metro Ctr., 402 Md. 250, 271-72 (2007) (citing Chevron in adopting HUD’s interpretation

that a federal statute did not preempt local agency action that the Court affirmed).

       32
          If those factors sound familiar, perhaps it is because Skidmore is a direct ancestor
of the leading case of this Court concerning the degree of judicial deference accorded to
state agency actions. See Baltimore Gas & Electric Co. v. Public Service Commission, 305
Md. 145, 161-62 (1986), citing and relying on Comptroller v. John C. Louis Co., 285 Md.
527, 544 (1978), which cites and relies upon Skidmore.

                                             30
       2.     Reviewability of Permit Terms Derived from TMDLs and WIP

       Incorporation of TMDLs and the Maryland WIP in the Counties’ MS4 Permits

       The MS4 permits at issue in this appeal incorporate or reference elements of the Bay

TMDL, the Maryland WIP, and certain local TMDLs. That raises the question whether

this litigation is the appropriate forum for what amounts to a challenge to those prior

administrative actions.

       The Appropriate Forum for Challenging Permit Provisions Derived from a TMDL

       Carroll County argues that provisions of a TMDL that are implemented in a permit

must be reviewable in the context of judicial review of that permit – i.e., in an action like

this one. The County reasons that, because Maryland statutory law does not provide for

judicial review of State-authored TMDLs and because the TMDLs themselves are not self-

executing, the only viable mode of judicial review is a challenge to a permit.

       The County is correct that the Maryland Code does not provide for judicial review

of a TMDL. The County is also correct that a TMDL is not self-executing. Farm Bureau,
792 F.3d at 291 n.4. However, the absence of a statutory mechanism for review of a TMDL

in State court does not mean it is not reviewable in any court. The EPA’s approval of a

state-submitted TMDL “is an act taken pursuant to the [Clean Water Act] and thus is

subject to challenge [in federal court] under the [federal Administrative Procedure Act.]”

Anacostia Riverkeeper, Inc. v. Jackson, 798 F. Supp. 2d 210, 222 (D.D.C. 2011). For

example, the major case challenging the validity of the Bay TMDL was held to be ripe for

judicial review in federal court because the “parties present[ed] a purely legal dispute on a

well-developed record about the EPA’s process of promulgating a TMDL.” Farm Bureau,

                                             31
792 F.3d at 293-94. Similarly, parties challenging other state-prepared, EPA-approved

TMDLs have obtained judicial review of the EPA’s approval of those TMDLs in federal

court. See, e.g., Friends of Earth, Inc. v. EPA, 446 F.3d 140 (D.C. Cir. 2006); Natural

Resources Defense Council v. Muszynski, 268 F.3d 91 (2d Cir. 2001); City of Kennett v.

EPA, 887 F.3d 424 (8th Cir. 2018).

       To the extent that the Counties are challenging decisions previously made or actions

taken in adopting an EPA-approved TMDL, judicial review of those decisions or actions

was available in federal court. Unsurprisingly, as this Court has previously indicated, an

action for judicial review of a discharge permit in State court is not the forum for raising

belated challenges to a TMDL that the challenger could have raised elsewhere. See

Anacostia Riverkeeper, 447 Md. at 129 n.46.33 Thus, in an action by a permittee under EN

       33
         In Anacostia Riverkeeper, this Court cited In re City of Moscow, Idaho, 10 E.A.D.
135, 2001 WL 988721 (EAB July 27, 2001) to illustrate this principle. Moscow was an
opinion of the Environmental Appeals Board (“Board”), the EPA’s final decisionmaker of
administrative appeals under the statutes that the EPA administers. In Moscow, a
municipality pursued an administrative appeal of a discharge permit for its sewage
treatment plant issued by the EPA. The municipality challenged, among other things, a
term in the permit that was derived from a state-prepared TMDL for the water body into
which the plant discharged pollutants. 2001 WL 988721 at *1, *16. The permit term
established a “seasonal constraint” on phosphorus discharges (between May and October,
the “normal growing season months” of algae blooms, which are fed in part by
phosphorus). Id. at *16 n.53.

       The municipality argued, among other things, that the EPA’s decision to adopt the
TMDL’s seasonal growth period as part of the permit was arbitrary and capricious, but the
Board disagreed. The Board observed that the TMDL clearly specified the growth period
and that federal regulations required that the municipality’s permit be consistent with the
“assumptions and requirements” of the treatment plant’s wasteload allocation established
by the TMDL. 2001 WL 988721 at *16.

                                            32
§1-601 challenging a permit term derived from a TMDL, the permittee may not base that

challenge on a decision that was previously made in the development of the TMDL.34

       Consistent with the principle recognized in Anacostia Riverkeeper, we conclude that

claims concerning a discharge permit that are essentially challenges to a governing TMDL

and that could have been raised in an action for judicial review of the EPA’s approval of

        The municipality also claimed that the TMDL’s seasonal growth period was
inaccurate. The Board also rejected that argument, holding that the administrative appeal
of the permit terms was not the appropriate forum for raising that claim. 2001 WL 988721
at *17. The Board reasoned that it was authorized to review “contested permit conditions”
but not the validity of “prior, predicate regulatory decisions that are reviewable in other
fora,” and that the TMDL was a prior predicate regulatory decision reviewable in a federal
district court under the federal Administrative Procedure Act. Id. at *18. The Board
concluded that the municipality’s claim was essentially a belated challenge to
determinations previously made in the TMDL and the EPA’s earlier decision to approve
the TMDL – which were reviewable elsewhere.

       As this Court indicated in Anacostia Riverkeeper, that reasoning applies in actions
to review discharge permits in Maryland courts. In Maryland, State courts are authorized
to review a discharge permit issued by the Department, but not a TMDL on which parts of
the permit may be predicated. Specifically, although the General Assembly has provided
for judicial review of discharge permits in EN §1-601(c), it has not authorized judicial
review of State-prepared TMDLs (which are not final until they receive EPA approval).
Instead, as noted in the text, the EPA’s approval of such a TMDL – necessary for it to be
effective – may be challenged in federal court.
       34
          Of course, just because something is mentioned in a TMDL does not mean that it
would be ripe for a challenge in federal court. For example, when an environmental group
challenged an alleged “authorization” of water quality trading in the Bay TMDL in federal
court, the court held that the claim was not ripe because the Bay TMDL only “expected”
or “encouraged” trading without making a final decision about it – let alone “authorizing”
it in a permit. See Food & Water Watch v. EPA, 5 F. Supp. 3d 62, 73-86 (D.D.C. 2013).
In other words, the challenger failed to identify a final, concrete decision in the TMDL that
was suitable for judicial review. That case illustrates that the principle identified in
Anacostia Riverkeeper applies only to provisions of a TMDL that reflect a reviewable final
action taken in the TMDL.

                                             33
that TMDL cannot be raised in a judicial review action under EN §1-601.35 Accordingly,

as explained further below, we will not entertain some of the Counties’ arguments that are

essentially challenges to provisions in EPA-approved TMDLs.36

B.     Whether the Impervious Surface Restoration Permit Term Unlawfully Exceeds
       the MEP Standard or is Arbitrary and Capricious

       The Clean Water Act, in describing provisions to be included in an MS4 permit,

refers to a standard of “maximum extent practicable” – often denominated by the acronym

“MEP.” 33 U.S.C. §1342(p)(3)(B)(iii). Whether the MEP standard governs all provisions

in an MS4 permit, or only certain provisions, is a matter of debate – a debate that we shall

wade into presently. Frederick County’s flagship argument in its appeal is that the

Department unlawfully disregarded the MEP standard and therefore exceeded its authority

when it included the impervious surface restoration requirement in the County’s permit.

       35
          We need not, and do not, address whether a State court would have authority to
directly review a TMDL prepared by the Department pursuant to an administrative
mandamus action, Maryland Rule 7-401 et seq., or otherwise.
       36
           Carroll County argues that the Department is “estopped” from arguing that the
County may not challenge a provision of a TMDL incorporated in its permit. The County’s
basis for this argument is that, in a 2003 case, the Department successfully argued that a
discharger cannot claim to have been aggrieved by a TMDL until the Department proposes
to issue a discharge permit that includes effluent limitations based on the TMDL. See In
re Wicomico River TMDL, No. 22-C-01-000623 (Wicomico Cty. Cir. Ct. June 13, 2003).
The County’s argument is not without some force as the Department’s position here
appears to contradict its argument in Wicomico River. However, the reviewability of a
permit term is a legal question, not subject to an estoppel argument. For the reasons set
forth in the text, it is our view that permit terms that directly implement a decision made in
an EPA-approved TMDL are not subject to review in an action in State court challenging
the permit.

                                             34
The County further argues that, even if the Act allows the Department to include provisions

in the permit without reference to the MEP standard, the impervious surface restoration

requirement is impossible to achieve and that the Department acted arbitrarily and

capriciously in including it in the permit. Carroll County does not join either of these

arguments, although its permit includes an identical impervious surface restoration

requirement.

       1.      The MEP Standard

       Congress did not define the MEP standard in the Act and the EPA has explicitly

declined to define it as well.37 The phrase “maximum extent practicable” suggests a

standard that is, or is close to, the most stringent standard in a hierarchy of possible

standards under the Act. However, in the context of the Act’s standards for pollution

controls, that is not the case.38 To understand why, it is helpful to review the dichotomy

between technology based and water quality based effluent limitations for point sources

and then consider how the MEP standard relates to those limitations.

       37
          The EPA has explained that it “intentionally [has] not provided a precise
[regulatory] definition of MEP to allow maximum flexibility in MS4 permitting.” EPA,
National Pollutant Discharge Elimination System – Regulations for Revision of Water
Pollution Control Program Addressing Storm Water Discharges, 64 Fed. Reg. 68722,
68754 (December 8, 1999).
       38
          See Jones Creek Investors, LLC v. Columbia County, Ga., 98 F. Supp.3d 1279,
1300 n.4 (S.D. Ga. 2015) (In the MS4 context, “[t]he phrase ‘maximum extent practicable’
is a term of art, and should not be attributed the ordinary meaning usually applied to those
words.”); National Research Council, Urban Stormwater Management in the United States
(The National Academies Press 2009) at 60 (“[T]he [MEP] standard for MS4s … [is] a
floor, not a ceiling, for permit requirements when receiving waters are impaired.”).

                                            35
       The Clean Water Act’s Hierarchy of Pollution Controls

       In principle, the most that a regulatory agency can require of a point source is to do

what is necessary to reduce pollutants to a level such that the waterway satisfies water

quality standards. Thus, the most stringent level of control – for any point source – is strict

compliance with water quality standards for the pertinent waterway. Given the difficulty

of calculating and enforcing such standards, Congress in the Act chose not to “make the

perfect the enemy of the good” and authorized the use of technology based effluent

limitations for typical, end-of-pipe point sources.      33 U.S.C. §1311(b)(1)(A).       Such

controls achieve some pollution reduction, although often not enough to achieve water

quality standards for the pertinent waterway. As explained above, technology based

effluent limitations are designed from the perspective of the discharger while controls

based on water quality standards – water quality based effluent limitations – are designed

from the perspective of the waterway.

       MEP Standard versus Water Quality Based Standard

       The MEP standard is analogous to a technology based effluent limitation in that its

reference point is the MS4 operator rather than the waterway.39        A water quality based

effluent limitation is more stringent than an MEP-level control just as such a limitation is

       39
          National Research Council, supra note 38, at 60 (grouping the MEP standard with
“other technology-based requirements” for stormwater permittees); see also Jones Creek
Investors, 98 F. Supp.3d at 1300 n.4 (MEP standard defined in the pertinent MS4 permits
as “the technology-based discharge standards and controls necessary for the reduction of
pollutants discharged from [an MS4]”).

                                              36
more stringent than a technology based control. Despite this analogy, water quality based

effluent limitations operate differently in end-of-pipe point source permits than they do in

MS4 permits. With an end-of-pipe point source, a technology based effluent limitation is

typically a numeric level of pollution and the point source must install technology to ensure

that the amount of pollution emitted from the pipe is below the specified level. A water

quality based effluent limitation may simply ratchet down that numeric level, requiring the

point source to come up with ways to reduce pollution further.

       With MS4s, however, there generally is no corresponding numeric cap on the

amount of pollution discharged by each conveyance within an MS4.40 Instead, the MS4

operator must implement the various MEP-level management programs required by its

permit. In that context, a water quality based control is a program in addition to the MEP-

level programs. To say that water quality based controls are “more stringent” than or

“beyond” MEP-level controls simply means that the MS4 operator must comply with the

water quality based control in addition to the MEP-level controls. For example, Frederick

County’s permit lists six management programs under the MEP standard. See Frederick

County Phase I MS4 Permit MD0068357, Part IV.D.1-6. In addition to those programs,

and under a separate section of the permit, the County is to comply with the impervious

surface restoration requirement. Id., Part IV.E.2.a.

       40
          See Upper Missouri Waterkeeper v. Montana Dep’t of Envtl. Quality, 438 P.3d
792, 799 (Mont. 2019) (noting that MS4 permits generally have included best management
practices rather than numeric limits).

                                             37
       The County and the Department appear to agree that the impervious surface

restoration requirement in the County’s permit is a water quality based control that is in

addition to those provisions included under the MEP standard. However, the County

asserts that the Department may not include such a term in the permit if it “goes beyond”

the MEP standard.

       2.       Whether an MS4 Permit Term May “Go Beyond” the MEP Standard

       At first blush, this Court’s decision in Anacostia Riverkeeper seems to resolve this

issue in the Department’s favor.41 In a background section of that opinion, the Court stated:

            MS4s are subject to the MEP standard[.] [They] are not, however,
            required to [achieve] effluent limitations necessary to meet water
            quality standards. [But the Act] still requires Maryland to set water
            quality standards and TMDLs – subject to the EPA’s approval.
            Flowing from this obligation is the requirement that MS4s are subject
            to effluent limitations that are consistent with [wasteload allocations]
            of EPA-approved TMDLs.

       41
          The Dissenting Opinion of Judge Watts contends that the Court’s holding in
Anacostia Riverkeeper is an “obstacle” to the Department’s position in this case and that
the permit term in question is “incompatible” with Anacostia Riverkeeper. Watts
Dissenting slip op. at 4-5. The Dissenting Opinion appears to have the mistaken belief that
Anacostia Riverkeeper somehow supports Frederick County’s challenge to this permit
term. In fact, in that case, the Court considered a permit term that appears in Phase I MS4
permits of five other jurisdictions and that is identical to the permit term that Frederick
County challenges here. The Court held that the term was valid and authorized by the
Clean Water Act. 447 Md. at 122-26. If we were simply to recite the holding of Anacostia
Riverkeeper and stop, Frederick County loses. But, in fairness to Frederick County and as
indicated in the text, the holding in Anacostia Riverkeeper was in response to a challenge
from a different perspective. Environmental groups argued that the permit term was
inadequate to comply with the MEP standard. Here, Frederick County argues, from the
opposite perspective, that the permit term unlawfully exceeds that standard. However, for
the reasons explicated in the text, we disagree and reach the same outcome that Anacostia
Riverkeeper did – that the permit term is valid and authorized by the Act.

                                              38
447 Md. at 104. In other words, an MS4 permit may include, as needed, effluent limitations

consistent with TMDL wasteload allocations, in compliance with the EPA regulation that

requires a discharge permit for a point source to contain such effluent limitations. See 40

CFR §122.44(d)(1)(vii)(B). Given that the impervious surface restoration requirement is

such an effluent limitation, Anacostia Riverkeeper seems to answer the question raised by

Frederick County – i.e., that the 20 percent impervious surface restoration requirement in

the permit is valid and authorized by the Clean Water Act. However, in Anacostia

Riverkeeper, the Court was addressing a question somewhat distinct from the one posed in

this case. In that case, the question was whether the impervious surface restoration

requirement satisfied the MEP standard whereas in this case the question is whether it

unlawfully exceeds it. The resolution of this question requires statutory construction of the

provision in which the MEP standard appears – 33 U.S.C. §1342(p)(3)(B)(iii) – which we

shall refer to as clause (B)(iii) for ease of reference.

       Construing Clause (B)(iii) – Statutory Language

       The Clean Water Act specifically addresses municipal and industrial stormwater

discharges in 33 U.S.C. §1342(p), which consists of six paragraphs. Paragraph 3 of that

subsection sets forth “permit requirements.”42 That paragraph reads as follows:

       42
          Paragraphs 1 and 2 concern the timing of the requirement to obtain certain
stormwater discharge permits. Paragraph 4 concerns the application requirements for those
permits. Paragraph 5 authorizes the EPA to conduct a study on other stormwater discharges
not covered by those permits. Paragraph 6 authorizes the EPA to adopt regulations based
on the study required by paragraph 5. 33 U.S.C. §1342(p)(1)-(2), (4)-(6).

                                               39
            (3) Permit requirements

               (A) Industrial discharges

               Permits for discharges associated with industrial activity shall meet
               all applicable provisions of [section 1342] and section 1311 of this
               title.

               (B) Municipal discharge

                  Permits for discharges from municipal storm sewers—

                  (i) may be issued on a system- or jurisdiction-wide basis;

                  (ii) shall include a requirement to effectively prohibit non-
              stormwater discharges into the storm sewers; and

                  (iii) shall require controls to reduce the discharge of pollutants
              to the maximum extent practicable, including management practices,
              control techniques and system, design and engineering methods, and
              such other provisions as the [EPA] Administrator or the State
              determines appropriate for the control of such pollutants.

33 U.S.C. §1342(p)(3). Subparagraph (A) relates to permit requirements for discharges by

industrial sources such as factories, landfills, construction sites, and power plants that have

operations exposed to rain water or snow melt. Subparagraph A does not directly relate to

the requirements in MS4 discharge permits.43

       Our focus is on Subparagraph (B) concerning the requirements for MS4 permits.

The first two clauses concern the geographic scope of an MS4 permit (clause (B)(i)) and

       43
          See 40 CFR §122.26(b)(14) (“Storm water discharge associated with industrial
activity means the discharge from any conveyance that is used for collecting and conveying
storm water and that is directly related to manufacturing, processing or raw materials
storage areas at an industrial plant.”).

                                              40
the separation of stormwater discharges from other discharges (clause (B)(ii)), but do not

include a reference to the MEP standard.

        Clause (B)(iii) concerns the controls and provisions required to reduce the discharge

of pollutants from MS4s. As is evident, the MEP standard appears in this clause. The

Department and the County disagree as to the role that the MEP standard plays in clause

(B)(iii).

        To construe clause (B)(iii) we begin, of course, with the plain language of the

statute. As this case illustrates, however, statutory language is not always “plain” in the

sense that it may take on different meanings, depending on how one parses a series of

words or clauses. The Department and Frederick County tabulate clause (B)(iii) in slightly

different ways to support their contrary interpretations. We apply an editorial pen below

to illustrate these different interpretations.

        Frederick County’s favored construction of clause (B)(iii) can be illustrated as

follows:

            Permits for discharges from municipal storm sewers –

            (iii) shall require controls to reduce the discharge of pollutants to the
            maximum extent practicable, including (1) management practices, (2)
            control techniques and systems, (3) design and engineering methods,
            and (4) such other provisions as the [EPA] Administrator or the State
            determines appropriate for the control of such pollutants.

Under the County’s construction, the “controls” subject to the MEP standard are listed in

a series following the word “including” – a series of four categories that includes (1)

management practices, (2) control techniques and systems, (3) design and engineering

methods, and (4) such other provisions as the permitting agency deems appropriate. In that

                                                 41
view, there are four categories of pollution controls that might be required by an MS4

permit, including a final catchall category, and all four fall under the MEP umbrella. As

indicated above, to support its preferred tabulation and avoid a phrase in the middle of the

series of clauses (“system methods”) that the County claims is nonsensical, the County

asserts that the word “system” is the result of a “typographical error” in the statute that

needs to be corrected to “systems.”44

       In contrast, the Department’s construction opts for a different tabulation, but does

not require revision of the language of the statute. That interpretation can be illustrated as

follows:

            Permits for discharges from municipal storm sewers –

            (iii) shall require (1) controls to reduce the discharge of pollutants to
            the maximum extent practicable, including (a) management practices,
            (b) control techniques and (c) system, design and engineering methods,
            and (2) such other provisions as the [EPA] Administrator or the State
            determines appropriate for the control of such pollutants.

Under this construction of the statute, the three categories of controls enumerated in the

initial series – i.e., certain “practices,” “techniques,” and “methods” – are subject to the

MEP standard while “other provisions” that the permitting agency deems appropriate under

the final clause are not limited by the MEP standard. The Department’s construction does

not require revision of the text itself, and groups items that could comfortably fit within the

       44
         In support of its contention that the statute contains a typographical error, the
County notes that the word “systems” appears in various documents related to stormwater
discharge permits, including two statements made while the legislation was debated in
Congress.

                                               42
category of “controls” separately from the final clause’s vaguer and seemingly broader

reference to “appropriate … provisions.”

       Confronted with similar competing grammatical arguments concerning the

application of the MEP standard in clause (B)(iii), a state appellate court in California

concluded that “[a]lthough it is not the clearest way of articulating the concept, the

language of [clause (B)(iii)] does communicate the basic principle that the EPA [or an

authorized state] retains the discretion to impose ‘appropriate’ water pollution controls in

addition to those that come within the definition of [MEP].” Bldg. Indus. Assn. of San

Diego Cty. v. State Water Res. Control Bd., 124 Cal. App. 4th 866, 882-83 (2004) (“BIA

case”).45 That court upheld requirements in an MS4 permit based on water quality

standards in the face of a contention, similar to that of Frederick County in this case, that

those provisions unlawfully exceeded the MEP standard.

       Thus, the statement in Anacostia Riverkeeper in a somewhat different context and

the assessment of the BIA court in a similar context both favor the Department’s

construction of clause (B)(iii). We also consider what legislative history exists and the

administrative construction of this federal statute by the federal agency charged with

administering it – the EPA.

       45
         See also John H. Minan, Municipal Separate Storm Sewer System (MS4)
Regulation Under the Federal Clean Water Act: The Role of Water Quality Standards?, 42
San Diego L. Rev. 1215, 1241-42 (2005) (discussion of grammatical argument in BIA case
by law professor who served on the permitting agency in that case).

                                             43
Legislative History of Clause (B)(iii)

       When Congress was considering the legislation that added the MS4 permit

requirements to the Act, legislators often spoke in general terms about achieving water

quality standards without elaborating on the MEP standard or addressing whether that

standard should apply to every pollutant control in an MS4 permit. Some statements

suggested that water quality based standards – i.e., standards other than MEP – would be

part of MS4 permits. For example, one senator stated that MS4 permit pollution control

“requirements are to contain control technology or other techniques to control these

discharges and should conform to water quality requirements.” 133 Cong. Rec. S733-02,

1987 WL 928615 (January 14, 1987) (statement of Senator Chafee). On the other hand,

another senator paraphrased clause (B)(iii) in language that mirrors the County’s

interpretation, including substituting the plural “systems” for “system.” Id. (statement of

Senator Durenberger). Yet another member of Congress both alluded to the goal of

controlling stormwater discharges “to protect the quality of the Nation’s waters” and in

paraphrasing the legislation, used the word “systems.” 133 Cong. Rec. H168-03, 1987 WL
928356 (January 8, 1987) (statement of Representative Roe). In the end, what legislative

history exists is “not especially illuminating” on the role of the MEP standard.46

       46
            Minan, supra, note 45, at 1243-44.

                                             44
       EPA’s Administrative Construction of Clause (B)(iii)

       The EPA’s position for many years was that an MS4 permit, like any discharge

permit, must achieve compliance with water quality standards.47 Indeed, when it adopted

regulations for Phase I MS4 permits, the agency described the controls that would be

required by such permits as follows: “[MS4] permits are to establish controls to the

maximum extent practicable[,] effectively prohibit non-storm water discharges to the

[MS4] and, where necessary, contain applicable water quality-based controls.” EPA,

National Pollutant Discharge Elimination System Permit Application Regulations for

Storm Water Discharges – Final Rule, 55 Fed. Reg. 47990, 47995 (November 16, 1990)

(“EPA Preamble to 1990 Phase I MS4 Rule”) (emphasis added).

       The EPA partially backed away from this view after the United States Court of

Appeals for the Ninth Circuit held that MS4 permits need not include water quality based

effluent limitations.   See EPA, National Pollutant Discharge Elimination System –

Regulations for the Water Pollution Control Program Addressing Storm Water Discharges

- Final Rule, 64 Fed. Reg. 68722, 68753 (December 8, 1999) (“EPA Preamble to 1999

       47
         EPA, Interim Permitting Approach for Water Quality-Based Effluent Limitations
in Storm Water Permits, 61 Fed. Reg. 43761 (August 26, 1996); EPA, Questions and
Answers Regarding Implementation of an Interim Permitting Approach for Water Quality-
Based Effluent Limitations in Storm Water Permits, 61 Fed. Reg. 57425 (November 6,
1996); EPA, Memorandum from E. Donald Elliott, Assistant Administrator and General
Counsel, EPA, re: Compliance with Water Quality Standards in NPDES Permits Issued to
Municipal Separate Storm Sewer Systems (January 9, 1991) at 1; see also Oliver A. Houck,
TMDLs III: A New Framework for the Clean Water Act’s Ambient Standards Program, 28
Envtl. L. Rep. (Envtl. Law Inst.) 10415, 10428 (1998) (discussing the EPA’s interpretation); Minan, supra,
note 45, at 1245-46 (same).

                                           45
Phase II MS4 Rule”) (recognizing that a Ninth Circuit decision “disagree[d] with EPA’s

interpretation of the relationship between” §1311 and §1342(p)).             Specifically, in

Defenders of Wildlife v. Browner, 191 F.3d 1159, 1164 (9th Cir. 1999), the Ninth Circuit

held that §1342(p)(3) “unambiguously demonstrates that Congress did not require [MS4s]

to comply strictly with” §1311(b)(1)(C), which requires that discharge permits contain

water quality based effluent limitations as needed.48 On the other hand, the court also stated

that the final provision of clause (B)(iii) gives the EPA (and thus a state permitting agency)

the discretion to “determine that ensuring strict compliance with state water-quality

standards is necessary to control pollutants [or] to require less than strict compliance with

state water quality standards.” 191 F.3d at 1166.49 Thus, while the Ninth Circuit did not

       48
         As noted earlier, while clause (A) of §1342(p)(3) requires industrial stormwater
dischargers to comply with all of §1311 (i.e., with both technology based and water quality
based effluent limitations), clause (B) lays out different requirements for MS4s without
mentioning §1311. The Ninth Circuit reasoned that, for MS4 permits, clause (B)(iii)
“replaces” both the technology and water quality based effluent limitation requirements in
§1311. 191 F.3d at 1165.
       49
          A related question – which is not raised here and which, therefore, we do not
address – is whether MS4 permits may require strict compliance with water quality
standards. That question is at issue in two cases in the United States Court of Appeals for
the District of Columbia Circuit that are currently in settlement proceedings. Center for
Regulatory Reasonableness v. EPA, Case Nos. 17-1060 & 16-1246 (D.C. Cir.). The
challengers in those cases argue that certain Phase II MS4 general permits issued by the
EPA violate clause (B)(iii) by requiring compliance with water quality standards. The
situation here is different in that no party claims that the Counties’ permits expressly
require compliance with water quality standards.

                                             46
agree with the EPA’s existing construction, it nevertheless recognized that a permitting

agency had discretion to include permit terms based on water quality standards.50

       In any event, after the Defenders of Wildlife decision, the EPA modified its

administrative interpretation of clause (B)(iii). Whereas the agency had taken the view that

MS4 permits, like all discharge permits, must contain water quality based effluent

limitations as needed, after the Ninth Circuit decision the EPA viewed such limitations as

permissible, but not mandatory, in MS4 permits. It cited Defenders of Wildlife as support

for the proposition that clause (B)(iii) “specifically preserves the authority for EPA or

[authorized states] to include other provisions determined appropriate to reduce pollutants

in order to protect water quality.” EPA Preamble to 1999 Phase II MS4 Rule, 64 Fed. Reg.

at 68788. Accordingly, the Phase II regulation provides that “[a]s appropriate, the permit

[for a small MS4] will include [m]ore stringent terms and conditions, including permit

requirements ... based on an approved [TMDL] or equivalent analysis, or where the [EPA

or state] determines such terms and conditions are needed to protect water quality.” 40

CFR §122.34(c)(1). Although the 1999 preamble and rule concern Phase II MS4 permits,

the EPA’s views on water quality based limitations generally apply to all MS4 permits.

       50
          Other courts have pointed to Defenders of Wildlife as setting forth the discretion
that the EPA (and state permitting agencies) have in drafting MS4 permit terms to require
pollution controls that satisfy the MEP standard or a more demanding water quality based
standard. See Natural Resources Defense Council v. New York State Dep’t Envtl
Conservation, 994 N.Y.S.2d 125, 135 (N.Y. App. 2014), aff’d, 34 N.E.3d 782 (N.Y. 2015);
Conservation Law Foundation, Inc. v. Boston Water and Sewer Commission, 2010 WL
5349854 at *5-6 (D. Mass. 2010); Tualatin Riverkeepers v. Oregon Dep’t Envtl Quality,
230 P.3d 559, 563-64 & n.10 (Ore. App. 2010); City of Arcadia v. State Water Resources
Control Board, 135 Cal. App. 4th 1392, 1429 (2006).

                                            47
For example, the Defenders of Wildlife decision upheld Phase I MS4 permits issued by the

EPA that included water quality based limitations.51

       The EPA has maintained that position through at least the time period relevant for

this litigation. In other words, since 1990, the EPA has held the view that the Act at least

authorizes water quality based effluent limitations in MS4 permits. 52 For example, in a

letter to the Department concerning Frederick County’s permit that appears in the

administrative record, the EPA made clear that permitting agencies may include water

quality based effluent limitations in MS4 permits: “Where the [permitting] authority

determines that MS4 discharges have the reasonable potential to cause or contribute to a

water quality standard excursion as [the Department] has done in this case, EPA

recommends that the … permitting authority exercise its discretion to include appropriate

narrative and/or numeric water quality-based effluent limitations … as necessary to meet

water quality standards.” EPA Letter to Maryland Department of the Environment re

       51
         See In re: Arizona Municipal Storm Water NPDES Permits for City of Tucson,
Pima County, City of Phoenix, City of Mesa, and City of Tempe, 1998 WL 284966, at *2
n.1 (EAB May 21, 1998) (stating, in the administrative decision that was reviewed in
Defenders of Wildlife, that the permittees were properly classified as operators of MS4s
requiring Phase I permits).
       52
         In its critique of the impervious surface restoration term of the Frederick County
MS4 permit, the Dissenting Opinion of Judge Watts discounts the EPA’s interpretation of
the Clean Water Act which, as indicated in the text, follows the interpretation of the Act
by the Ninth Circuit in Defenders of Wildlife. See Watts Dissenting slip op. at 11-12 &
n.7. Given the ambiguity in clause (B)(iii), the EPA’s interpretation – which is consistent
with the construction of the statute by the federal courts – is entitled to deference under
Chevron (and even if the Chevron did not apply, under Skidmore).

                                            48
Supplemental Comments on Frederick County Phase I MS4 Permit (September 23, 2014).

The EPA also stated that the requirement of consistency between TMDLs and permits

applies to MS4s as it does to all point sources: “Pursuant to 40 CFR 122.44(d)(1)(vii)(B),

where there is an applicable [TMDL] approved or established by EPA, a [discharge] permit

must include effluent limitations that are consistent with the wasteload allocation . . . in the

TMDL. This includes MS4 permits.” Id.

       Harmonizing MS4 Permit Terms with the TMDL Process

       Clause (B)(iii) is to be read harmoniously with the Act as a whole, including the

TMDL process. See King v. St. Vincent’s Hospital, 502 U.S. 215, 221 n.10 (1991) (when

construing statute, court should read statute as a whole and harmonize its provisions);

Condon v. State of Maryland-Univ. of Maryland, 332 Md. 481, 491 (1993) (same). In our

view, the EPA’s and Department’s interpretation of clause (B)(iii) is more consistent with

the Act as a whole than the alternative proposed by Frederick County.

       The EPA’s regulations require that a water quality based effluent limitation be

derived from the applicable water quality standard, without referring to a practicability test.

Permitting agencies “shall ensure that [t]he level of water quality to be achieved by [water

quality based effluent limitations] on point sources ... is derived from, and complies with,

all applicable water quality standards.” 40 CFR §122.44(d)(1)(vii)(A). The EPA’s

rationale is that “[d]eriving water quality-based effluent limits from water quality standards

is the only reliable method for developing water quality-based effluent limits that protect

aquatic life and human health.” EPA, National Pollutant Discharge Elimination System;

Surface Water Toxics Control Program – Final Rule, 54 Fed. Reg. 23868, 23879 (June 2,

                                              49
1989) (preamble to publication of the EPA’s rule that, in part, adopted 40 CFR

§122.44(d)(1)(vii)). Importantly, this rationale does not distinguish between types of point

sources, i.e., whether the discharger is a factory, a wastewater treatment plant, an MS4, or

any other kind of point source. The process of implementing TMDLs via discharge permits

“results in effluent limits that protect aquatic life and human health because the limits are

derived from water quality standards.” Id. In other words, when translating TMDL

wasteload allocations to effluent limitations in a permit, the pertinent water quality standard

remains the touchstone. Thus, when an entity discharges to a waterway subject to a TMDL,

its permit must contain effluent limitations consistent with the “assumptions and

requirements” of the corresponding wasteload allocation in the TMDL.                 40 CFR

§122.44(d)(1)(vii)(B).

       When the final provision of clause (B)(iii) is read to encompass water quality based

effluent limitations, MS4 permits are treated like any other discharge permit for purposes

of implementing TMDLs. This interpretation harmonizes clause (B)(iii) with the TMDL

provisions insofar as the latter likewise do not distinguish between types of point sources.

By contrast, if permitting agencies must constrain all TMDL based effluent limitations in

MS4 permits by some sort of practicability analysis, there would be tension with the basic

tenet that water quality based effluent limitations must derive from water quality standards.

       Summary

       In including the impervious surface restoration requirement in Frederick County’s

permit, the Department acted consistently with the EPA’s interpretation of clause (B)(iii)

– that is, that the Act authorizes permitting agencies to include water quality based effluent

                                              50
limitations in MS4 permits without reference to the MEP standard. As explained earlier,

clause (B)(iii) is ambiguous. A federal court reviewing the EPA’s interpretation of an

ambiguous federal statutory provision under Chevron would defer to the agency’s

reasonable construction of that language. In our view, the EPA’s interpretation of clause

(B)(iii) is a reasonable construction that is consistent with the rest of the Act and accords

with the Ninth Circuit decision in Defenders of Wildlife and other applicable court

decisions. Even under the less deferential Skidmore standard of review, a federal court

would likely defer to the agency’s interpretation in light of its consistent view that MS4

permits are subject to standards emanating from TMDLs. Moreover, the Department was

“bound to follow EPA’s interpretation” in light of the Clean Water Act’s scheme of

cooperative federalism. Natural Resources Defense Council v. New York State Dep’t of

Envtl Conservation, supra.      Accordingly, we hold that the Department did not act

unlawfully in including a water quality based effluent limitation (the impervious surface

restoration requirement) not subject to the MEP standard in the County’s permit.53

       3.     Whether the Inclusion of the Impervious Surface Restoration Requirement
              in Frederick County’s Permit was Arbitrary and Capricious

       Frederick County also argues that, regardless of whether the Act authorizes the

Department to include an impervious surface restoration requirement in MS4 permits

       53
          Because we hold that the Act authorizes the impervious surface restoration
requirement in the County’s permit, we need not address the Department’s alternative
argument that Maryland law allows such a condition as consistent with the federal Act’s
provision allowing for more stringent state-set permit conditions. See 33 U.S.C. §1370.

                                             51
without reference to the MEP standard, the Department acted arbitrarily and capriciously

when it included such a provision in the County’s permit. The County notes that, during

the comment period on the draft permit, it submitted to the Department a report that

purportedly demonstrated that compliance with the permit’s requirements within five years

was financially and logistically impossible.54

       As noted earlier, when agency action is challenged as arbitrary and capricious, the

question is whether there was a rational basis for that action. See Part II.A. of this Opinion.

In answering that question, a reviewing court is to be “extremely deferential” to the agency

and not to substitute its own judgment for that of the agency. To assess whether the

Department acted arbitrarily and capriciously in its consideration of Frederick County’s

objection to the permit term, we review both the procedure that the Department followed

and the substance of its action.

       Procedure

       Consistent with EN §1-604(a), the Department first issued a “tentative

determination” together with the draft permit on June 28, 2014. A public comment period

followed, during which the Department received many comments on the draft permit.

After consideration of those comments, the Department published a “final determination”

       54
          As described above, the General Assembly authorized counties to charge a
stormwater remediation fee to help finance stormwater management and restoration
required by MS4 permits. See EN §4-202.1. Frederick County adopted a fee of 1¢; at oral
argument before this Court, the County explained that it had elected to use general funds
to finance its obligations under the Clean Water Act.

                                              52
on December 10, 2014, along with the final permit, consistent with EN §1-604(b). See

Basis for Final Determination to Issue Frederick County’s NPDES MS4 Permit

MD0068357 (December 2014) (“Basis for Final Determination – Frederick County”).

      In general, the Environment Article gives the Department broad discretion in

replying to comments when the agency takes final action on a proposed permit. The

Department is not obliged to respond to all public comments, but rather may “pick and

choose” the comments it addresses. Kor-Ko Ltd. v. Maryland Dep’t of the Env’t, 451 Md.
401, 422 n.18 (2017). The fact that an agency does not change a proposed action or

regulation in light of comments requesting a change does not mean that the process lacked

a meaningful opportunity for comment or that the agency failed to consider those

comments. See Fogle v. H & G Rest., Inc., 337 Md. 441, 463 (1995).

      Substance

      In its comments on the draft permit, Frederick County voiced its concerns about the

feasibility of compliance with the impervious surface restoration requirement.         The

Department addressed Frederick County’s concerns about cost and feasibility, as well as a

number of other issues in the Basis for Final Determination that the Department published

with the final version of the permit.55 Basis for Final Determination – Frederick County at

18. The Department noted that the County believed that the 20 percent restoration

      55
         In the same document, the Department also addressed similar cost and feasibility
“estimates” submitted by Charles County and Harford County. Basis for Final
Determination – Frederick County at 18.

                                            53
requirement “exceeds an MEP level of effort and that compliance would be financially and

operationally infeasible.” Id. at 22. The Department responded to those concerns by

explaining that the restoration requirement was necessary for consistency with the Bay

TMDL and the Maryland WIP. Id. The Department also stated that the EPA had reviewed

the permit for such consistency and was “satisfied” that the permit achieved it based, in

part, on the impervious surface restoration requirement. Id. Although the Department’s

response may not have amounted to a point-by-point refutation of every detail of the

County’s comments, it did address the significant issues raised by the County. We cannot

say that the Department failed to respond in a reasoned manner.

       In particular, the Department had a rational basis for saying that the restoration

requirement is necessary for consistency with the Bay TMDL and the Maryland WIP. As

this Court recognized in Anacostia Riverkeeper, the EPA relied on the Maryland WIP,

which included the impervious surface restoration requirement, when developing the Bay

TMDL and the restoration requirement was a “key element” in securing EPA’s

endorsement of the Maryland WIP. 447 Md. at 128.

       It was reasonable for the Department to respond to the County’s claim of

impossibility by explaining that the restoration requirement derives from the Bay TMDL

and the Maryland WIP. The Bay TMDL and Maryland WIP were the result of significant

deliberation among various stakeholders together with the EPA and the Department. For

example, the record shows that Frederick County and the Department had been discussing

practicability and feasibility since at least 2012.

                                              54
      In our view, the Department was not arbitrary or capricious in including the

impervious surface restoration requirement in Frederick County’s MS4 permit.

C.    Whether the Permits Exceed the Appropriate Geographic Scope of an MS4 Permit

      Both Counties assert that their permits exceed the appropriate scope of an MS4

permit. The Counties focus on Part IV.E. of their permits. That section of the permit

requires the County to (1) conduct a detailed watershed assessment for the entire County;

(2) complete restoration of 20 percent of the impervious surface area in the County; (3)

develop and implement restoration plans for meeting applicable stormwater wasteload

allocations in EPA-approved TMDLs; (4) conduct public outreach and encourage public

participation in the watershed assessments, restoration plans, and achievement of the

TMDL limits and water quality standards; and (5) evaluate and document its progress in

meeting stormwater wasteload allocations in EPA-approved TMDLs.

      The Counties argue that the Department exceeded its authority under the Clean

Water Act in its specification of the impervious surface restoration condition and in

requiring compliance with stormwater wasteload allocations in applicable EPA-approved

TMDLs. To some extent, these arguments are based on making a distinction between the

permittee – in these cases, Frederick and Carroll Counties – and the activity that is

authorized by the permits – the discharge of pollutants by the MS4s operated in each

County.

      1.     Jurisdiction-Wide versus System-Wide Permits

      The Clean Water Act provides that “[p]ermits for discharges from municipal storm

sewers may be issued on a system- or jurisdiction-wide basis.”               33 U.S.C.

                                           55
§1342(p)(3)(B)(i). The EPA’s regulations reiterate that a permitting authority such as the

EPA or the Department may issue permits for Phase I MS4s on a system-wide or

jurisdiction-wide basis. See 40 CFR §122.26(a)(1)(v) (in exercising residual designation

authority to require Phase I permit, state or EPA may make designation on system-wide or

jurisdiction-wide basis), 40 CFR §122.26(a)(3)(ii) (permit for a large or medium MS4 may

be issued on system-wide basis or on a number of other bases, including with reference to

the “jurisdiction”). Neither the statute nor the regulations elaborate on what it means for

an MS4 permit to be issued on a “jurisdiction-wide” basis – as opposed to a “system-wide”

basis.56 The explanation offered by the EPA at the time it adopted these regulations

indicates that it was concerned with ensuring that permitting authorities had the necessary

flexibility to adapt permits to local conditions such as existing administrative systems,

police powers, and land use authority. EPA Preamble to 1990 Phase I MS4 Rule, 55 Fed.

Reg. at 48043.

      56
          The EPA regulations suggest that – at least with respect to a Phase I MS4 that is
classified as “large” or “medium” – a “jurisdiction-wide” permit may cover only a portion
of the corresponding system. See 40 CFR §122.26(a)(3)(ii) (authorizing the issuance of
either a system-wide permit “covering all discharges from [the MS4]” or “distinct permits
for appropriate categories of discharges within [the MS4] including, but not limited to …
discharges located within the same jurisdiction…”) (emphasis added). This provision does
not concern residually designated Phase I MS4s.

                                            56
       The permits that are the subject of this appeal are each issued to a County – a

jurisdiction – in its capacity as the operator of an MS4 – a system.57 But the challenges

raised by the Counties cannot be resolved by the descriptive label attached to their MS4

permits. The Counties contend that, regardless of whether a permit is issued on a system-

wide or jurisdiction-wide basis, the scope of the regulatory conditions in the permit must

relate to the discharges authorized by the permit. They argue that the baseline calculation

for the impervious surface restoration requirement effectively makes the Counties

responsible for pollutants carried by stormwater that does not flow into their MS4s. The

Counties further argue that permit provisions related to stormwater wasteload allocations

in local TMDLs also do so.

       2.     The Impervious Surface Restoration Requirement

       Impervious surface restoration requirements have been part of MS4 permits issued

by the Department since at least 1999. Maryland WIP at 2-26. The previous generation

of each County’s permit included an impervious surface restoration requirement of 10

percent of each County’s unrestored impervious surface.58

       57
        The Carroll County permit also includes, as co-permittees, all of the incorporated
municipalities in the County and thus pertains to several jurisdictions and several systems.
See 40 CFR §122.26(a)(3), (b)(1).
       58
         The general permit applicable to Phase II small MS4s also includes an impervious
surface restoration term, although it differs from the one included in the permits of Phase
I MS4s like the Counties. The current Phase II general permit requires restoration of 20
percent of the unrestored impervious surface in each permittee’s urbanized area by 2025.

                                            57
       The Impervious Surface Restoration Condition in the Current Permit

       With respect to impervious surface restoration, the current permit provides:

            Within one year of permit issuance, [the] County shall submit an
            impervious surface area assessment consistent with the methods
            described in the [Department] document “Accounting for Stormwater
            Wasteload Allocations and Impervious Acres Treated, Guidance for
            National Pollutant Discharge Elimination System Stormwater Permits”
            (MDE, June 2011 or subsequent versions). Upon approval by [the
            Department], this impervious surface area assessment shall serve as the
            baseline for the restoration efforts required in this permit.

            By the end of this permit term, [the] County shall commence and
            complete the implementation of restoration efforts for twenty percent
            of the County’s impervious surface area consistent with the
            methodology described in the [Department] document cited in [this
            section] that has not already been restored to the MEP. Equivalent
            acres restored of impervious surfaces, through new retrofits or the
            retrofit of pre-2002 structural [best management practices], shall be
            based upon the treatment of the WQv criteria and associated list of
            practices defined in the 2000 Maryland Stormwater Design Manual.
            For alternate [best management practices], the basis for calculation of
            equivalent impervious acres restored is based upon the pollutant loads
            from forested cover.

Carroll County Phase I MS4 Permit MD0068331, Part IV.E.2.a; Frederick County Phase I

MS4 Permit MD0068357, Part IV.E.2.a.

       On its face, this provision does not require the County to undertake impervious

surface restoration outside the geographic area that drains to the MS4, as it does not dictate

where such restoration must take place.59 But the permit provision uses unrestored

       59
          Some permit terms specify actions within the MS4 service area. For example,
Part IV.D. of the permit requires the County to implement certain management programs
in “areas served by [the] County’s MS4.” Some required programs involve actions that
are necessarily conducted on a county-wide basis, including outside the service area of the
MS4 – e.g., an “acceptable stormwater management program” under EN §4-201 et seq., an

                                              58
impervious surface throughout the entire County – not just within the MS4 service area –

as a starting point, or baseline, for calculating the required restoration.60 (In the case of

both Counties, the County’s MS4 serves only a portion of the County’s geographic area).

       The Counties do not contend that the inclusion of an impervious surface restoration

requirement itself is beyond the scope of an MS4 permit. Rather, they argue that the

reference to a county-wide measure of impervious surface as the baseline for the

requirement in the permit exceeds the Department’s authority. They assert that the

reference to that baseline in a permit has the effect of making the County responsible for

pollutants that never enter the County’s MS4.

       Anacostia Riverkeeper

       This Court considered the validity of an impervious surface restoration requirement

in Anacostia Riverkeeper. In that case, the Phase I MS4 permits in question included an

identical term requiring the permittee counties to restore 20 percent of the unrestored

“acceptable erosion and sediment control program” under EN §4-101 et seq. and a “public
education and outreach program to reduce stormwater pollutants.” MS4 Permits, Part
IV.D. 1, 2, 6. If the permits are modified (as sought by the Counties) to allow water quality
trading as a compliance method, the pollution reductions for which a County would receive
credit would not necessarily occur within the County, much less within its MS4 service
area. See Part II.E. of this Opinion.
       60
         In particular, the permit term refers to restoration of 20 percent of the County’s
impervious surface area consistent with the methodology in the Department’s guidance
document. That methodology involves a calculation of the impervious surface area
throughout the entire County (after excluding certain areas that are not directly at issue
here). See Accounting for Stormwater Wasteload Allocations and Impervious Acres
Treated (August 2014) at 1, 6-10.

                                             59
impervious surface over the five-year period covered by their permits. The requirement

was challenged by environmental advocacy groups as “too opaque” to satisfy the Act’s

direction that MS4 permits include provisions to reduce pollutants that satisfy the MEP

standard.61 They also argued that the Department had failed to adequately explain its use

of the 20 percent restoration condition or how that level of restoration would achieve the

Bay TMDL.

       This Court concluded that impervious surface restoration, as carried out in

accordance with the Department’s Stormwater Design Manual (incorporated by reference

in the permit term), is a stormwater management practice that functions as a “surrogate”

for direct reduction of pollutants in stormwater and that satisfies the MEP standard. 447
Md. at 122-23. Noting that the 20 percent restoration requirement was consistent with the

Maryland WIP, the Court further held that the Department’s decision to include that

requirement in the permits under review was supported by substantial evidence and was

not arbitrary and capricious. Id. at 128-29. The Court also upheld the temporal baseline

selected by the Department for measuring compliance with the 20 percent requirement. In

particular, it held that the Department had not erred in using the measure of unrestored

impervious surface in the counties in 2002 as the baseline. Id. at 132.

       In this case, the Counties also challenge the baseline used for the impervious surface

restoration requirement. However, in contrast to Anacostia Riverkeeper, the basis of that

       61
            The MEP standard is discussed in Part II.B. of this Opinion.

                                              60
challenge is geographic rather than temporal.62 It is rooted in the notion that MS4 permits

under the Act regulate discharges of pollutants only from an MS4 itself. See 33 U.S.C.

§1342(p)(3) (setting forth permit requirements for “permits for discharges from [MS4s]”).

In the Counties’ view, use of a county-wide baseline violates that principle because some

of the impervious surface included in that baseline is associated with pollution that never

enters the MS4.63 According to the Counties, to be consistent with the Clean Water Act,

an impervious surface restoration requirement must reference a baseline that includes only

the MS4 service area.64

       62
         The Counties point out that the use of 2002 as the baseline year for assessment of
the County’s impervious surface – instead of 1985, the baseline year in the Maryland WIP
– would effectively increase the target amount of restoration. Use of 2002 as the baseline
year would increase the baseline amount of impervious surface by including development
between 1985 and 2002. (In Anacostia Riverkeeper, environmental groups had argued that
a baseline year later than 2002 should have been used – i.e., that use of the 2002 baseline
was too lenient). However, in arguing that they are being held responsible for pollutant
discharges that do not emanate from their MS4s, the Counties focus on the geographical
element of the baseline calculation.
       63
          This is based on the following reasoning. Obviously, rain can fall anywhere in a
jurisdiction, such as a county, that operates an MS4. The rain will carry some pollutants
into conveyances within the county’s MS4 and, from there, into waterways. Other
pollutants, however, may never encounter the MS4. Instead, they will run into waterways
directly from fields, farms, parking lots, or other land uses in the county that are out of
reach of the MS4. Under the Act, the pollutants carried through the MS4 constitute a form
of point source pollution, and the pollutants not carried through the system are a form of
nonpoint source pollution (often called “stormwater runoff”). Since MS4 permits under
the Act authorize only discharges from point sources, such a permit may only include
conditions related to stormwater and the accompanying pollutants that enter (and are
discharged from) the MS4, not stormwater that never encounters the MS4. See Envtl Def.
Ctr., Inc. v. EPA, 344 F.3d 832, 841 n.8 (9th Cir. 2003).
       64
          Carroll County also invokes the doctrine of offensive non-mutual collateral
estoppel to argue that the Department is barred from using a county-wide baseline for

                                            61
       Origin of the 20 Percent Restoration Requirement

       There is no question that the pollutant discharges that the permit authorizes are those

from each County’s MS4. As this Court noted in Anacostia Riverkeeper and as discussed

in the previous section of this Opinion, the impervious surface restoration term is a water

quality based effluent limitation authorized by 33 U.S.C. §1342(p)(3)(B)(iii). In particular,

such a permit term is a numeric water quality based effluent limitation, as recognized by

the EPA.65

impervious surface. In particular, the County cites a 2003 administrative decision by the
Department’s final decisionmaker, which struck certain provisions of wastewater discharge
permits issued to three poultry processors. Tyson Foods, Inc., et al. v. MDE, OAH Case
No. MDE-WMA-063-200200001 (June 12, 2003). The final decisionmaker concluded
that, under State law, the permits could not include conditions that required the processors
to undertake certain activities relating to chicken manure at the farms of those who raised
chickens that were sold or otherwise provided to the processors, particularly when the
growers were not co-permittees.

        The Tyson Foods administrative decision did not involve an MS4 permit, much less
an issue identical to the one in this case, and did not discuss the Clean Water Act, EPA
regulations, or any other federal law, for that matter. Under those circumstances, the
doctrine of offensive non-mutual collateral estoppel does not apply to determine the
outcome of this case. See Garrity v. Maryland State Board of Plumbing, 447 Md. 359, 369
(2016) (among other things, issue decided in prior adjudication must be identical for
collateral estoppel to apply). The reasoning of the administrative decision in Tyson Foods
may be analogous in some respects to the argument advanced by the Counties in this case,
but it is not dispositive.
       65
         See EPA, Post-Construction Performance Standards & Water Quality-Based
Requirements: A Compendium of Permitting Approaches (June 2014) at 19 (including
impervious surface restoration terms in Maryland MS4 permits in a list of examples of
numeric water quality based effluent limitations); EPA, Revisions to the November 22,
2002 Memorandum “Establishing Total Maximum Daily Load (TMDL) Wasteload
Allocations (WLAs) for Storm Water Sources and NPDES Permit Requirements Based on
WLAs” (November 26, 2014) at 10 (identifying an identical 20% restoration term in the
Prince George’s County MS4 permit as a numeric water quality based effluent limitation).

                                             62
       Importantly, the amount of impervious surface to be restored is simply a surrogate

or proxy for an amount of pollution to be reduced. The Department’s guidance document

incorporated in the permit term explains how to calculate loads of pollution reduced, given

a certain kind and quantity of impervious surface restoration activity. Thus, when the

Department is determining how a county should calculate the number of impervious

surface acres to be restored, the Department is effectively determining a measure of

pollution reduction.

       As explained earlier, the EPA’s regulations require that a water quality based

effluent limitation be derived from applicable water quality standards, without reference to

a practicability test. See 40 CFR §122.44(d)(1)(vii)(A). This is because “[d]eriving water

quality-based effluent limits from water quality standards is the only reliable method for

developing water quality-based effluent limits that protect aquatic life and human health.”

EPA, National Pollution Discharge Elimination System: Surface Water Toxics Control

Program – Final Rule, 54 Fed. Reg. 23868, 23879 (June 2, 1989); see also Natural

Resources Defense Council v. Fox, 909 F. Supp. 153, 156 (S.D.N.Y. 1995).

       With respect to the baseline for the impervious surface restoration requirement,

those regulations require a permitting agency to craft the numeric component of a water

quality based effluent limitation by reference to “all applicable water quality standards.”

40 CFR §122.44(d)(1)(vii)(A). Thus, when establishing how each County is to calculate

the number of impervious surface acres to be restored – i.e., the proxy for an amount of

pollution to be reduced – the Act and EPA regulations direct the Department to focus on

what is necessary to achieve water quality standards in the Bay and the waters that feed it.

                                            63
       In our view, the Department’s use of a county-wide baseline as a reference point for

calculating the impervious surface restoration condition does not exceed the Department’s

authority under the Act because the impervious surface restoration condition implements a

stormwater wasteload allocation in a TMDL (specifically, the Bay TMDL) designed to

achieve water quality standards. Since at least 1991 the EPA has determined in various

contexts, including regulation, that permitting authorities may make trade-offs between

pollutant allocations for point and nonpoint sources. The EPA’s definition of TMDL

contemplates such trade-offs. See 40 CFR §130.2(i) (“If … nonpoint source pollution

controls make more stringent load allocations practicable, then wasteload allocations can

be made less stringent. Thus, the TMDL process provides for nonpoint source control

tradeoffs.”).

       Given that the possibility of such trade-offs is inherent in the definition of TMDL,

it is perhaps not surprising that the EPA has reiterated that concept when discussing how

states are to develop TMDLs. See EPA, Surface Water Toxics Control Program and Water

Quality Planning and Management Program, 57 Fed. Reg. 33040, 33048 (July 24, 1992)

(“States have the flexibility to consider the relative costs of point and nonpoint source

controls when preparing TMDLs, along with such other factors as reliability, relative

effectiveness, and degree of assurance that nonpoint source controls will actually be

implemented and maintained.”); EPA, Guidance for Water Quality-based Decisions: The

TMDL Process (1991) at 15 (“Under the [Act], the only federally enforceable controls are

those for point sources through the NPDES permitting process. In order to allocate loads

among both nonpoint and point sources, there must be reasonable assurances that nonpoint

                                            64
source reduction will in fact be achieved. Where there are not reasonable assurances, under

the [Act], the entire load reduction must be assigned to point sources.”).

       This long-established EPA policy is a reasonable interpretation of the Act and is

entitled to deference under Chevron. Even if the EPA policy were not entitled to Chevron

deference under federal law, we would defer to the agency under Skidmore and our own

standards of review. As explained at the outset of this opinion, the Act requires the

establishment of TMDLs when an existing regime of point source pollution controls is

inadequate to achieve water quality standards. TMDLs reflect pollutant levels necessary

to achieve those standards in compliance with the Act. The EPA has reasonably concluded

that permitting authorities must have the discretion to allocate pollutant loads between

point and nonpoint sources as needed to achieve the TMDL limits, including potentially

ratcheting up the requirements on point sources when necessary. See Farm Bureau, 984
F. Supp. 2d at 326 (in a case concerning the Bay TMDL, describing how a permit writer

may apportion pollutant amounts – “loads” – among point and nonpoint sources in

accordance with EPA guidance).66

       66
         In practice, the broad discretion to allocate TMDL-established pollutant amounts
between point and nonpoint sources means that permitting agencies may impose a level of
pollution reduction on point sources in part to help offset nonpoint source pollution. See
Michael M. Wenig, How “Total” Are “Total Maximum Daily Loads”? – Legal Issues
Regarding the Scope of Watershed-Based Pollution Control Under the Clean Water Act,
12 Tul. Envtl. L.J. 87, 117 & n.131 (1998) (recognizing that TMDL allocations can require
point sources to “bear the brunt of pollution reductions necessary to achieve” TMDLs);
Oliver A. Houck, TMDLs III: A New Framework for the Clean Water Act’s Ambient
Standards Program, 28 ELR 10415, 10420 (August 1998) (recognizing permitting
agencies’ option of “ratcheting down further on point sources” when setting wasteload
allocations).

                                             65
       Thus, nonpoint source pollution reduction may be assigned to point sources – i.e.,

through wasteload allocations in the development of TMDLs. At bottom, it is this

assignment of pollutant reductions to their wasteload allocations that is the essence of the

Counties’ objection to the impervious surface restoration requirement in their permits.67

The Department’s use of a county-wide baseline for the impervious surface restoration

condition is thus related to the broad discretion of the states and the EPA, in drafting a

TMDL, to assign an amount of nonpoint source pollution reduction to point sources.

       Moreover, federal regulations require that point source permits contain effluent

limitations consistent with the “assumptions and requirements” in wasteload allocations in

applicable TMDLs. See 40 CFR §122.44(d)(1)(vii)(B). As this Court noted in Anacostia

Riverkeeper, this standard is flexible. 447 Md. at 135. In this case, the impervious surface

restoration term in the Counties’ permits is consistent with the underlying premise of the

Bay TMDL (by way of the Maryland WIP) that Maryland’s Phase I MS4 permits will

include a corresponding impervious surface restoration requirement.

       That provision underwent significant development before reaching its final form in

the permits. For example, in accordance with the EPA regulations governing discharge

permits and a related memorandum of understanding with the Department, the EPA

       67
         The Maryland WIP states that the impervious surface restoration “strategy” (i.e.,
30% cumulative restoration for Phase I MS4s) is associated with a particular “load
reduction,” i.e., a certain quantity of pollution reduction. Maryland WIP at 5-30.

                                            66
formally objected to the Counties’ draft permits because, among other things, the

impervious surface restoration requirement was “not adequately expressed” and did not

achieve compliance with the Bay TMDL. See EPA, Specific Objection to Carroll County

Phase I MS4 Permit MD0068331 (September 20, 2012); EPA, Specific Objection to

Frederick County Phase I MS4 Permit MD0068357 (September 20, 2012). In response to

such objections and to comply with the requirement of consistency between TMDLs and

discharge permits, the Department adjusted the impervious surface term in the Counties’

permits to a form acceptable to the EPA. The EPA found the consistency requirement to

be satisfied in the final version of the permits and withdrew its objection.        EPA,

Supplemental Comments on Carroll County Phase I MS4 Permit (September 23, 2014);

EPA, Supplemental Comments on Frederick County Phase I MS4 Permit (September 23,

2014).

         Summary

         The impervious surface restoration term in the Counties’ MS4 permits is a numeric

water quality based effluent limitation corresponding to Maryland’s stormwater wasteload

allocation within the Bay TMDL. As such, when crafting that limitation, the Department

was authorized to focus on what would be necessary to achieve water quality standards,

and the Department determined that the baseline calculation method it chose was necessary

to achieve applicable water quality standards for the Bay. The Department did not exceed

                                            67
its authority under the Clean Water Act when it directed calculation of the impervious

surface using a county-wide baseline.68

          3.       Restoration Requirement Related to Local TMDLs

          Both Counties point to certain permit conditions that require the Counties to adopt

restoration plans and provide reports concerning compliance with stormwater wasteload

allocations set forth in EPA-approved TMDLs for waterways in the Counties. They argue

that these provisions unlawfully make the Counties responsible for discharges of third

parties. These provisions appear in Part IV.E. of each County’s permit and read as follows:

                     2. Restoration Plans

                                          *      *      *

    b.         Within one year of permit issuance, [the] County shall submit to [the
               Department] for approval a restoration plan for each stormwater
               [wasteload allocation] approved by EPA prior to the effective date of
               the permit. The County shall submit restoration plans for subsequent
               TMDL [wasteload allocations] within one year of EPA approval. Upon
               approval by [the Department], these restoration plans shall be
               enforceable under this permit. As part of the restoration plans, [the]
               County shall:

     i.        Include the final date for meeting applicable [wasteload allocations]
               and a detailed schedule for implementing all structural and
               nonstructural water quality improvement projects, enhanced
               stormwater management programs, and alternative stormwater control
               initiatives necessary for meeting applicable [wasteload allocations];

    ii.        Provide detailed cost estimates for individual projects, programs,
               controls, and plan implementation;

          68
          Given this conclusion, we need not address whether the impervious surface
restoration requirement is permissible as a State-determined effluent limitation that is
“more stringent” than what the Act requires.

                                                68
iii.   Evaluate and track the implementation of restoration plans through
       monitoring or modeling to document the progress toward meeting
       established benchmarks, deadlines, and stormwater [wasteload
       allocations]; and

 iv.   Develop an ongoing, iterative process that continuously implements
       structural and nonstructural restoration projects, program
       enhancements, new and additional programs, and alternative [best
       management practices] where EPA approved TMDL stormwater
       [wasteload allocations] are not being met according to the benchmarks
       and deadlines established as part of the County’s watershed
       assessments.

                                   *      *      *

       4. TMDL Compliance

       [The] County shall evaluate and document its progress toward meeting
       all applicable stormwater [wasteload allocations] included in EPA
       approved TMDLs. An annual TMDL assessment report with tables
       shall be submitted to [the Department]. This assessment shall include
       complete descriptions of the analytical methodology used to evaluate
       the effectiveness of the County’s restoration plans and how these plans
       are working toward achieving compliance with EPA approved TMDLs.
       [The] County shall further provide:

a.     Estimated net change in pollutant load reductions from all completed
       structural and nonstructural water quality improvement projects,
       enhanced stormwater management programs, and alternative
       stormwater control initiatives;

b.     A comparison of the net change in pollutant load reductions detailed
       above with the established benchmarks, deadlines, and applicable
       stormwater [wasteload allocations];

c.     Itemized costs for completed projects, programs, and initiatives to meet
       established pollutant reduction benchmarks and deadlines;

d.     Cost estimates for completing all projects, programs, and alternatives
       necessary for meeting applicable stormwater [wasteload allocations];
       and

                                         69
  e.        A description of a plan for implementing additional watershed
            restoration actions that can be enforced when benchmarks, deadlines,
            and applicable stormwater [wasteload allocations] are not being met or
            when projected funding is inadequate.

Carroll County Phase I MS4 Permit MD0068331, Part IV.E.2.b, IV.E.4; Frederick County

Phase I MS4 Permit MD0068357, Part IV.E.2.b, IV.E.4.

       The Counties assert that these permit terms are overbroad because some EPA-

approved local TMDLs assign nonpoint source pollution to the Counties’ MS4s, which are

point sources. Carroll County specifically cites the fecal bacteria TMDL for Double Pipe

Creek – one of the EPA-approved local TMDLs incorporated by reference in Attachment

B to the Carroll County permit.69

       The Double Pipe Creek TMDL assigns certain nonpoint source pollution – namely,

“contributions [of fecal bacteria] from domestic animal and [septic system] sources” – to a

stormwater wasteload allocation, which includes pollution budgeted to Carroll County’s

MS4.70 Because the permit requires the County to develop “restoration plans” to achieve

the stormwater wasteload allocations of relevant local TMDLs, the County argues that the

permit makes the County responsible for addressing nonpoint pollution from third parties

that never enters the County’s MS4. The County uses the Double Pipe Creek TMDL as an

       69
         The Double Pipe Creek watershed includes parts of both Counties and is also
incorporated in Frederick County’s permit.
       70
         The Double Pipe Creek TMDL distributes this nonpoint source pollution between
Carroll County’s and Frederick County’s MS4s.

                                             70
example, but this argument would apply to any EPA-approved local TMDL that assigns

nonpoint source pollution to stormwater wasteload allocations.71

       This dispute concerns not so much the incorporation of EPA-approved local TMDLs

in the permit, as the decisions that were made in the development of those TMDLs. In the

case of the Double Pipe Creek TMDL, Carroll County is questioning a decision made when

the EPA approved the Double Pipe Creek TMDL – namely, the decision to allocate

pollution from nonpoint sources to the Counties’ MS4s by way of a stormwater wasteload

allocation in the TMDL.

       Frederick County argues that, like the impervious surface restoration term, the

restoration planning requirement “unlawfully regulates stormwater beyond the scope” of

the Department’s authority. The County bases this argument on the assertion that the local

TMDLs “cover[] areas that do not drain to the County’s MS4.” The County provides little

explanation for this argument, but as far as we can tell, it derives from the same concern

raised by Carroll County – i.e., the decision made by the Department at the local TMDL

development stage to include nonpoint source pollution within the stormwater wasteload

allocation.

       71
          This issue is somewhat distinct from the issue discussed in the previous section
of this Opinion concerning impervious surface restoration in that the allocations at issue
there derived from the EPA’s reliance on the Maryland WIP in devising the Bay TMDL,
rather than directly from the EPA-approved TMDL itself.

                                           71
       For the reasons outlined earlier in this Opinion,72 the Counties should have raised

these arguments in a challenge to the EPA’s approval of the Double Pipe Creek TMDL and

other, similar local TMDLs. See, e.g., City of Kennett v. EPA, 887 F.3d 424 (8th Cir. 2018)

(municipal challenge to EPA-approved TMDL that would affect municipality’s wastewater

permit). Therefore, we will not entertain these arguments here. See Anacostia Riverkeeper,
447 Md. at 129 n.46.

D.     Whether the Counties are Appropriately Classified as Phase I Jurisdictions

       Frederick County first received an MS4 permit as a Phase I jurisdiction in 1994. It

subsequently applied for and received a Phase I permit in 2002. In 2006, it applied for the

Phase I permit at issue in this appeal. It first contested its status as a Phase I jurisdiction

during the public comment period following the Department’s publication of its draft

permit in 2014 and reiterated those arguments when it sought judicial review of the final

2014 permit.

       Carroll County first received an MS4 permit as a Phase I jurisdiction in 1995. It

subsequently applied for and received Phase I permits in 2000 and 2005. Unlike Frederick

County, it did not question its status as a Phase I jurisdiction during the administrative

process for its most recent permit, which was issued in 2014, but first contested its status

as a Phase I jurisdiction when it sought judicial review of that permit.73

       72
            See Part II.A.2 of this Opinion.
       73
          The Department argues that Carroll County may not now challenge its Phase I
classification because, unlike Frederick County, it failed to raise the issue during the public
comment period on its draft 2014 permit. However, given that Frederick County did

                                               72
       Both Counties argue that the Department has unlawfully treated them as Phase I

jurisdictions because it has incorrectly classified them as “medium” (and therefore Phase

I) – as opposed to “small” (and therefore Phase II) – MS4 jurisdictions since the time when

they first applied for and received their first MS4 permits in the early 1990s. This

distinction matters because, as indicated earlier, Phase I jurisdictions have generally been

subject to earlier and more stringent permit requirements than Phase II jurisdictions. In

particular, the Counties point to the impervious surface restoration requirement in their

Phase I permits.74 As relief, both Counties seek to be re-classified as Phase II jurisdictions

with their permit terms conformed to those that apply to Phase II MS4s.

       1.     Application of the MS4 Permit Requirement in Phases

       Phase I MS4 Permits

       In 1987, when Congress added the permit requirement for MS4s to the Clean Water

Act, it did not require permits for all MS4 discharges immediately. Instead, it adopted a

staggered approach.75 This approach started with applying the permit requirement first to

challenge the classification during the administrative process for its permit and that the
issue is essentially the same for both Counties, we will not avoid the issue on the basis of
lack of preservation.
       74
          The impervious surface restoration requirement is more stringent in Phase I MS4
permits than a similar term in Phase II MS4 permits, in three ways: larger baseline (county
wide vs. urbanized areas), earlier deadline (2019 vs. 2025), and higher percentage of area
to be restored (30% vs. 20%).
       75
          Congress created this staggered approach in the Water Quality Act of 1987 by
explicitly recognizing that all MS4 discharges were subject to the Act’s permit
requirement, establishing a moratorium on that requirement until 1994, and then exempting

                                             73
discharges from systems with the greatest potential to pollute waterways, which was

referred to as Phase I. These MS4s included those serving larger populations, because

areas with larger and denser populations tend to have more developed land with impervious

surface and, as a result, generate more stormwater pollution.76 Also included in the first

round were MS4s determined by the EPA or a state to be significant contributors of

pollutants, regardless of the size of the population served by those MS4s. This statutory

authority to issue permits based on water quality impact (as opposed to the proxy of

population served) is often referred to as the “residual designation authority” of the EPA

and the states.

       For our purposes, the relevant Phase I categories77 are the following:

            (1) Large MS4. A discharge from an MS4 serving a population of
                250,000 or more, referred to in the statute as a “large MS4.” 33
                U.S.C. §1342(p)(2)(C), (p)(4)(A).

            (2) Medium MS4. A discharge from an MS4 serving a population of
                100,000 or more but less than 250,000, referred to in the EPA’s

certain discharges from that moratorium at various intervals. See 33 U.S.C. §1342(p)(1)-
(2). As a result, the permit requirement was imposed on MS4s in stages.
       76
          Population served as a proxy for the amount of pollution in stormwater because
“discharges from [MS4s] serving larger populations are thought to present a higher
potential for contributing to adverse water quality impacts.... [P]ollutant loads from urban
runoff strongly depend on the total area and imperviousness of developed land, which in
turn is related to population.” EPA Preamble to 1990 Phase I MS4 Rule, 55 Fed. Reg. at
48038.
       77
         In all, Phase I covered five categories of MS4 stormwater discharges. See 33
U.S.C. §1342(p)(1)-(2). The other two Phase I categories are discharges for which a permit
had been issued before 1987 and discharges associated with industrial activity – neither of
which is at issue in this appeal. 33 U.S.C. §1342(p)(2)(A)-(B).

                                            74
               regulations as a “medium MS4.” 33 U.S.C. §1342(p)(2)(D); 40
               CFR §122.26(a)(1)(iv).

          (3) Residually Designated MS4. A discharge for which the EPA or a
              state “determines that the stormwater discharge contributes to a
              violation of a water quality standard or is a significant contributor
              of pollutants to waters of the United States.” 33 U.S.C.
              §1342(p)(2)(E).

The EPA adopted regulations in 1990 setting forth the permit requirements for Phase I

jurisdictions. EPA, National Pollutant Discharge Elimination System Permit Application

Regulations for Storm Water Discharges – Final Rule, 55 Fed. Reg. 47990 (November 16,

1990), codified in 40 CFR §122. Other than establishing different deadlines for the

submission of permit applications by large and medium jurisdictions, the regulations

generally did not distinguish among these three categories of Phase I MS4s. See 40 CFR

§122.26(d).

       Thus, in the early 1990s, an MS4 operated by a local government, like those of the

Counties, would be required to obtain a Phase I permit if: (1) the MS4 served 100,000 or

more people based on census figures, or (2) the EPA or the state had classified the MS4 as

a Phase I jurisdiction under the residual designation authority.

       Phase II MS4 Permits

       The Phase II round of MS4 permits covered stormwater discharges other than the

Phase I categories. 33 U.S.C. §1342(p)(6). Included in Phase II are MS4s serving fewer

than 100,000 people, referred to as “small” MS4s. In 1999, the EPA adopted regulations

setting forth permit requirements for small MS4s. See EPA Preamble to 1999 Phase II

                                             75
MS4 Rule; see also 40 CFR §122.34.78 Those regulations provided deadlines for initial

Phase II permit applications at various intervals during the early 2000s.

       2.       Population Classification for Purposes of Phase I

       As noted above, the Clean Water Act classifies MS4s according to the population

served by the MS4. The statute does not define what it means for an MS4 to “serve” a

population of a given size. In carrying out its statutory charge to adopt regulations on MS4

permit requirements,79 the EPA defined “medium” MS4s as falling into one of four

subcategories. The most relevant here included systems comprising storm sewers that are:

            (i) Located in an incorporated place with a population of 100,000 or
            more but less than 250,000, as determined by the latest Decennial
            Census by the Bureau of the Census (appendix G); or

            (ii) Located in the counties listed in appendix I, except municipal
            separate storm sewers that are located in the incorporated places,
            townships or towns within such counties;

40 CFR §122.26(b)(7)(i)-(ii) (as adopted in 1990). Like the statute, the regulations on their

face appear to use as a reference point the total population of the particular jurisdiction

without attempting to refine that number according to the portion of the population that

lives or works within the area “served” by the MS4.

       78
         For reasons not relevant here, the 1999 small MS4 regulations were remanded
and reissued in 2016. See Envtl. Def. Ctr., Inc. v. EPA, 344 F.3d 832 (9th Cir. 2003)
(remanding the 1999 regulations); EPA, National Pollutant Discharge Elimination System
(NPDES) Municipal Separate Storm Sewer System General Permit Remand Rule, 81 Fed.
Reg. 89320 (December 9, 2016).
       79
            33 U.S.C. §1342(p)(4).

                                             76
       Appendix I, referenced in the second subcategory of the regulation, listed 32

counties and was entitled “Counties With Unincorporated Urbanized Areas Greater Than

100,000, But Less Than 250,000 According to the Latest Decennial Census by the Bureau

of the Census” (emphasis added). As is evident, the title of Appendix I refers not only to

“unincorporated” areas, but also to “urbanized” areas – a term that does not appear in the

statute or otherwise in the EPA’s regulations.

       In explanatory material that accompanied the 1990 publication of the Phase I

regulations – what is sometimes referred to informally as a “preamble” to such a

publication80 – the agency elaborated on its conception of the second subcategory. It stated

that the second subcategory was meant to capture MS4s in “counties having areas that are

designated as urbanized areas by the latest decennial Bureau of Census estimates and where

the population of such areas exceeds 100,000 [but is less than 250,000], after the population

in the incorporated places, townships or towns within such counties is excluded.” EPA

Preamble to 1990 Phase I MS4 Rule, 55 Fed. Reg. at 48039.81 As defined by the Census

Bureau, the term “urbanized” generally refers to “high density development.” Id. at 48041

n.5.

       80
            See note 17 above.
       81
          An EPA guidance document issued shortly after adoption of the Phase I
regulations similarly stated the “medium” MS4 category included “Counties with census
designated urbanized areas that have a population greater than [or] equal to 100,000 but
less than 250,000 after incorporated areas, towns, and townships within such counties are
excluded.” EPA, Guidance Manual for the Preparation of Part 1 of MS4 Permit
Applications (April 1991) at 9 (emphasis added).

                                             77
       In its initial iteration in connection with the regulations adopted in 1990, Appendix

I listed jurisdictions in the second subcategory based on figures from the 1980 census – at

that time “the latest decennial census” – as did Appendix G with respect to jurisdictions in

the first subcategory. In 1999, at the same time that the EPA adopted regulations governing

Phase II MS4 permits, the agency also updated Appendix I (as well as Appendix G) based

on the 1990 census – which was then “the latest decennial census.” But the EPA also

amended the regulation concerning “medium” population jurisdictions to refer specifically

to the 1990 census and deleted the reference to the “latest” census. The agency stated that

it would not continue to update those appendices based on later decennial censuses. In the

preamble to the publication of those regulations and amendments, the EPA explained that

it was “freezing” the regulatory definition and listing based on the 1990 census because all

the covered MS4s had already applied for permits and “the deadlines from the existing

regulations have lapsed.”82 EPA Preamble to 1999 Phase II MS4 Rule, 64 Fed. Reg. at

68838, 68848-49. The EPA further explained that MS4s that later met the definition of a

“medium” jurisdiction could be made subject to the Phase I requirements by the permitting

agency, alluding to the agency’s residual designation authority under the Act. Id. at 68749

(“the permitting authority can always require more from operators of MS4s serving ‘newly

over 100,000’ populations”); see also EPA, National Pollutant Discharge Elimination

       82
         As noted earlier, at that time, Carroll and Frederick Counties were among those
operators of MS4s that, at the behest of the Department, had already applied for, and
received, Phase I permits, although they were not listed in Appendix I.

                                            78
System – Proposed Regulations for Revision of the Water Pollution Control Program

Addressing Storm Water Discharges, 63 Fed. Reg. 1536-01, 1567 (January 9, 1998).

       3.     Residual Designation Authority

       Factors for Designation and Procedural Requirements

       As indicated above, the Act authorizes the EPA, or the pertinent state agency, to

require that an MS4 obtain a Phase I permit if the agency “determines that the [MS4]

contributes to a violation of a water quality standard or is a significant contributor of

pollutants….” 33 U.S.C. §1342(p)(2)(E). In its Phase I permit regulations, the EPA

identified the following factors that could affect such a determination: the location of the

discharge, the size of the discharge, the nature and quality of the pollutants, and “other

relevant factors.” 40 CFR §122.26(a)(1)(v). Those regulations also specified certain

procedures that would be followed by the EPA when the EPA itself made such a

determination (as well as other types of case-by-case determinations). See 40 CFR

§124.52.83 No particular procedure was required of a state agency that made such a

determination.84 The parties have not presented – and we have not been able to identify –

       83
          In the context of a citizen petition to the EPA to exercise its residual designation
authority, the EPA may issue a formal document concerning the water quality impacts by
a stormwater discharger. See Conservation Law Foundation, Inc. v. Pruitt, 881 F.3d 24,
32 (1st Cir. 2018). However, the EPA’s practice in that context does not establish any
particular requirement for state agencies.
       84
         The regulation requires the EPA Regional Administrator to send written notice of
a designation by the Regional Administrator to the MS4, accompanied by an application
form for a Phase I permit. The regulations further provide that the propriety of the

                                             79
any further procedural or other requirements that a state must follow when designating an

MS4 as a Phase I permittee.85

      Use of Residual Designation Authority to Expand the Phase I Universe

      The vast majority of the MS4s subject to the Phase I permit requirements have been

brought into Phase I under the residual designation authority, rather than on the basis of

population. In a 2000 report to Congress, the EPA stated that, of the 1,017 MS4s that were

part of the Phase I program at that time (including Carroll and Frederick Counties), only

216 had been listed in the appendices to the 1990 and 1999 regulations, while 670 were co-

permittees with a larger MS4 or had been designated separately for inclusion in the

program. See EPA, Report to Congress on the Phase I Stormwater Regulations (2000), at

3-5, available at https://perma.cc/BJG3-TPWP. Thus, despite the fact that the listing of

large and medium MS4s required to obtain Phase I permits in the appendices to the Phase

designation remains open for consideration during the notice and comment period relating
to the permit.

        Prior to adoption of those regulations, a memorandum of the EPA’s Office of Water
Enforcement and Permits had appeared to indicate that state agencies would be expected
to follow the same procedure. Memorandum of the Director of the EPA Office of Water
Enforcement and Permits to Water Management Division Directors, et al. concerning
Designation of Storm Water Discharges for Immediate Permitting (August 8, 1990),
available at https://perma.cc/4NFA-NCXL, at 11. (Of note, that memorandum also
suggested that discharges from the area around Chesapeake Bay would be appropriate for
such a designation. Id. at 8-9). However, the regulations as adopted by the EPA set forth
procedures solely for a designation by the EPA itself.
      85
          As was the case with clause (B)(iii) concerning the application of the MEP
standard, see Part II.B. of this Opinion above, the legislative history of §1342(p)(2)(E),
which established the residual designation authority, is not particularly illuminating.

                                           80
I regulations was “frozen” based on the 1990 census, that universe has been significantly

expanded under the statutory designation authority. See id. at 3-2 n.7.86

       4.     Classification of Frederick County and Carroll County in the 1990s

       Neither Frederick County nor Carroll County was included in the listing of

jurisdictions deemed “medium” based on population in Appendix I to the EPA regulations

– either in the initial version of that listing based on the 1980 census or in the amended

version based on the 1990 census. Rather, the Department asked the Counties to apply for

Phase I MS4 permits in the early 1990s, and the Counties did so. It is inevitably difficult

to reconstruct events from the vantage point of 30 years later, but the parties have provided

some correspondence from that era that suggests how the Department and the Counties

came to accept the Counties’ status as Phase I jurisdictions.87

       After Congress added the MS4 permit requirement to the Act and the EPA first

adopted the Phase I regulations in 1990, the Department began corresponding with the

       86
          See also EPA, Stormwater Phase II Final Rule: Who’s Covered? Designation and
Waivers of Regulated Small MS4s (revised June 2012), at 2, available at
https://perma.cc/7WFA-VTYG (“Phase I MS4s were automatically designated nationwide
as medium MS4s ... or as large MS4s [based on population.] Many MS4s in areas below
100,000 in population, however, have been individually brought into the Phase I program
[by] permitting authorities.”) (emphasis added).
       87
          This correspondence appears in appendices to the parties’ briefs. There is no
documentation in the administrative record of these permits as to how either County came
to be treated as a Phase I jurisdiction in the 1990s. In the explanatory document that the
Department issued with the final version of the most recent Frederick County permit, it
indicated that it had not needed to exercise its residual designation authority to classify the
County as a Phase I jurisdiction in the 1990s because the County had agreed to apply for a
Phase I MS4 permit.

                                              81
Counties about whether they had to apply for a permit. At first, the Department told the

Counties it was “unclear” whether they would need to do so. Each County responded that

its unincorporated population was below the statutory threshold of 100,000. Carroll

County also emphasized its “primarily rural character.”88 Both Counties apparently asked

the Department to refrain from including them in Phase I, or at least to delay the application

of the Phase I requirements. The Department acceded to the latter request and postponed

the deadlines for both Counties to submit a Phase I permit application. Both Counties

eventually submitted applications for Phase I permits, apparently without further protest.

       As best we can tell from the available correspondence, neither the Department nor

the Counties focused on urbanized population in their correspondence when they discussed

the relevant population in the early 1990s. This is perhaps unsurprising because neither

the federal statutory nor regulatory text refers to “urbanized” areas.89 Instead, in their

correspondence, both the Counties and the Department discussed only total population and

the population in unincorporated areas with respect to whether the Counties were

“medium” MS4 jurisdictions that should apply for a Phase I permit.

       88
          The fact that a county may have a large rural area does not necessarily affect
whether it should be classified as a Phase I MS4 jurisdiction. See EPA Preamble to 1990
Phase I MS4 Rule, 55 Fed. Reg. at 48041 (“some of the counties addressed by [the Phase
I regulations] have, in addition to areas with high unincorporated urbanized populations,
areas that are essentially rural or uninhabited and may not be the subject of planned
development”).
       89
          As explained above, that criterion was explained in the preamble to the
publication of the 1990 Phase I regulations, but did not appear in the actual text of the
regulations.

                                             82
       In the correspondence available to us, the Department did not explicitly invoke the

statutory residual designation authority with respect to either County. However, the EPA

has at least twice included Carroll County and Frederick County in lists of permittees as

residually designated jurisdictions. EPA, Final National Pollutant Discharge Elimination

System Storm Water Multi-Sector General Permit for Industrial Activities, 60 Fed. Reg.

50804, 51272 (September 29, 1995); EPA, Storm Water Discharges Potentially Addressed

By Phase II of National Pollutant Discharge Elimination System Storm Water Program:

Report to Congress (March 1995) at A-14; see also EPA, Report to Congress on the Phase

I Storm Water Regulations (February 2000), at Apx. A (including Carroll County and

Frederick County in Table A-2 listing “Additional MS4s Participating in Phase I MS4

Program” – i.e., “additional” to Table A-1 listing the Phase I MS4 permittees named in the

population-based appendices to the regulations).90     There are also other indications,

outlined below, that the Counties were regarded as residually designated Phase I

jurisdictions in the 1990s.

       90
         Similarly, the version of the Maryland WIP issued in 2010 stated that Carroll
County had been designated by the Department as a Phase I MS4 under the residual
designation authority in the early 1990s. See Maryland WIP at 2-30.

                                           83
       5.     Analysis

       The Counties assert that they are not properly classified as Phase I MS4s because

they are not “medium” jurisdictions and were not otherwise designated as Phase I

jurisdictions by the Department in the early 1990s. They contend that they should not be

considered “medium” jurisdictions. In their view, the list of jurisdictions in Appendix I to

the Phase I regulations is the exclusive list of medium MS4 counties and neither County

appears on that list. Moreover, the Counties assert that their unincorporated, urbanized

populations never reached 100,000, either in the 1990s or recently.91 They argue the

Department did not exercise its residual designation authority in the 1990s, and Carroll

County argues it is unlikely the Department even could have done so. In addition, Carroll

County argues that the decision to include it as a Phase I jurisdiction was arbitrary and

capricious.

       So far as we can tell, the Counties’ challenge to their MS4 classification as Phase I

jurisdictions raises novel issues for this or any court. We have not found – nor have the

parties cited – any case that involves a county’s challenge to its classification as a Phase I

MS4.

       91
          Carroll County also claims that the Clean Water Act did not authorize the
Department’s use of population projections in the 1990s. We do not consider this argument
separately because we do not see it as materially distinct from the County’s other
population-based arguments.

                                             84
       Whether it is Unlawful for the Department to Treat the Counties as Phase I MS4s

       If the Counties had raised the question of their classification as Phase I jurisdictions

in the early 1990s, we might well have agreed that they should not have been brought into

Phase I as “medium” jurisdictions. However, the argument that Appendix I to the Phase I

regulations is the exclusive list of “medium” Phase I jurisdictions is without merit, as the

EPA itself has recognized that jurisdictions not listed could later qualify.92 However, given

the EPA’s interpretation of its own regulations expressed in the preamble to the publication

of the Phase I regulations in 1990, neither County likely met the EPA’s contemporaneous

interpretation of the medium category. In retrospect, it appears that neither County had a

population at that time above 100,000 in unincorporated, urbanized areas.93

       But we are not addressing this question in 1991.94 We decline to hold that today,

after nearly three decades as part of the Phase I permitting program, the Counties should

       92
         As discussed above, the EPA “froze” the list in Appendix I in 1999 based on the
1990 census because the deadlines set for Phase I permit applications had expired and the
pertinent jurisdictions had already applied (as had Carroll and Frederick Counties). The
agency recognized that jurisdictions that later qualified as medium jurisdictions could be
brought into the Phase I program through the residual designation authority. In any event,
the agency could not, by regulation, negate a legislative determination that MS4s serving
populations of a certain size were subject to the permit requirement.
       93
         In 1990, Frederick County’s “urbanized area” population was 58,393, and its total
“urban” population was 86,686; for Carroll County, the numbers were 0 and 38,418,
respectively. There is no need not explore the difference between “total urban” and
“urbanized area,” at least for 1990, since both figures were under 100,000 with respect to
each County.
       94
         Even if we could purport to be examining this issue from the perspective of the
early 1990s, it is not entirely clear that we have a complete record from that period.

                                              85
instead be relegated to a Phase II general permit with less stringent pollutant controls. We

reach this conclusion for several reasons:

            ● The approach taken by the Department in calculating the relevant
              population of the Counties in the early 1990s was arguably consistent
              with the statutory text and the text of the regulations, although it
              deviated from the EPA’s interpretation of those regulations, as
              articulated in the preamble to the publication of the regulations.95

            ● When the Counties were originally treated as Phase I jurisdictions in
              1991, neither County (nor apparently anyone else) questioned the
              method that the Department used to assess the relevant population.

            ● Both Counties stipulated, as recently as 2014, that they satisfy the
              statutory definition of a medium Phase I MS4 in consent orders that
              they entered into with the EPA concerning violations of earlier MS4
              permits.96

            ● In the case of the Carroll County permit, all of the incorporated
              municipalities in the County are included as co-permittees on the
              County’s Phase I permit, which thus regulates discharges of MS4s

       95
           The Dissenting Opinion of Judge Getty suggests that we have deferred
excessively to the EPA’s and the Department’s application of the Phase I classification, in
contravention of the “plain language” of the Clean Water Act and the EPA’s regulations
concerning the classification of MS4s. Getty Dissenting slip op. at 8. However, neither
the statutory nor regulatory text concerning Phase I jurisdictions refers to “urbanized”
populations – the key language on which the Dissenting Opinion relies. See 33 U.S.C.
§1342(p)(2); 40 CFR §122.26(a)(1)(iv). As explained in the text, that language appears
solely in the title of an appendix and in explanatory material prepared by the agency (the
preamble to the 1990 publication of the regulations).
       96
         In the Matter of Carroll County, Maryland, Consent Agreement and Final Order
(United States Environmental Protection Agency June 6, 2014) at ¶¶ 7, 14, 15; In the Matter
of the Board of County Commissioners of Frederick County, Maryland, Consent
Agreement and Final Order (United States Environmental Protection Agency November
25, 2014) at ¶¶ 8, 15, 16. Both orders recite that the pertinent County’s “MS4 serves a
population of at least 100,000,” which is verbatim the language of the Clean Water Act
defining medium Phase I jurisdictions. See 33 U.S.C. §1342(p)(2)(D).

                                              86
              serving those populations. See Carroll County Phase I MS4 Permit
              MD0068331, Part I.B.; see also 40 CFR §122.26(a)(3).

       ● The record before us does not include any document in which the
         Department explicitly exercised its residual designation authority to
         designate the Counties as Phase I jurisdictions independent of their
         status as medium jurisdictions. However, this is presumably because
         the Counties agreed to, or at least acquiesced in, their treatment as
         medium MS4s which may have foreclosed any need to invoke the
         Department’s residual designation authority.

       ● There are noteworthy indications that the Department and EPA believed
         that the Counties were appropriately designated as Phase I
         jurisdictions:97

               o The Maryland WIP refers to Carroll County as a residually
                 designated Phase I jurisdiction. Maryland WIP at 2-30.

               o The fact that the Department agreed to delay the Counties’
                 designation as Phase I jurisdictions suggests that it was acting,
                 at least in part, under the residual designation authority, as the
                 Phase I regulations refer to an agency authorizing a delay in the
                 submission of an application only in the case of a residually
                 designated Phase I jurisdiction.98

               o Given that TMDLs exist for waterways in both Counties – which
                 indicates that water quality standards are being violated – there
                 is a sound basis for concluding that discharges from each
                 County’s MS4 contribute to violations of water quality

       97
           Carroll County asserts that, if the Department had acted under its residual
designation authority, it was required to notify the County of its determination in writing
and send an application form with that notice under 40 CFR §124.52. However, as
discussed above, the cited regulation applies only to a Regional Administrator of the EPA,
not a state agency. Even if the notification requirement applied to the Department, Carroll
County does not explain why the Department’s correspondence with the County in 1991
would not satisfy the requirement. The regulation only requires that the permitting
authority shall notify the permittee of the decision to require a permit and “the reasons for
it.”
       98
            See 40 CFR §122.26(e)(5).

                                             87
                   standards, thus triggering the exercise of the residual designation
                   authority to include them as Phase I MS4 jurisdictions.

               o As indicated above, the EPA referred to the Counties as
                 residually designated Phase I jurisdictions in publications in
                 1995 and 2000. A contemporaneous guidance document issued
                 by the EPA identified jurisdictions in the Chesapeake Bay
                 watershed as examples of appropriate exercise of residual
                 designation authority. See note 84 above.

            ● Relegating the Counties from a Phase I permit to a Phase II permit
              with less stringent requirements at this juncture risks a violation of
              the anti-backsliding prohibition in the Clean Water Act.99 See 33
              U.S.C. §1342(o).

       The limited evidence of the Department’s decision-making process in classifying

these Counties as Phase I jurisdictions in 1991 may reflect the difficulty of responding to

challenges raised more than 20 years after the fact. The delay by the Counties in raising

this issue has also posed difficulties for this Court in evaluating the parties’ arguments and

the EPA’s views of the issue. There is not a clear picture of how the Department’s

population-based reasoning in 1991 translated into the EPA’s stated view in 1995 that the

Department had used its residual designation authority.

       What is clear, however, is that the Department had authority to classify the Counties

as Phase I jurisdictions and, at least in the EPA’s view, it did so. The Counties, in turn,

       99
         The EPA had objected to earlier drafts of both permits on the basis that simply
keeping the same terms of the Counties’ prior Phase I permits “would constitute
impermissible backsliding” in violation of the Act. See EPA, Specific Objection to Carroll
County Phase I MS4 Permit MD0068331 (September 20, 2012) at 3; EPA, Specific
Objection to Frederick County Phase I MS4 Permit MD0068357 (September 20, 2012) at
3.

                                               88
have at the very least acquiesced in that classification since the 1990s. There is thus no

question that the agencies charged with administering the Clean Water Act have

consistently regarded the Counties as Phase I MS4s and that there is a reasonable basis for

doing so. The Counties’ delay in challenging their Phase I designation perhaps means that

the Department did not exercise its designation authority more formally in the past, but that

does not require that we direct that they now be treated as Phase II jurisdictions.

       Whether Carroll County’s Classification is Arbitrary and Capricious

       As indicated in Part II.A. of this Opinion, the Department’s exercise of discretion

in crafting permit terms is subject to the “arbitrary and capricious” standard of review. The

Department’s decisions survive challenge under this standard so long as the Department

had a rational basis for its actions.

       Carroll County asserts that the Department acted arbitrarily and capriciously in

classifying it as a Phase I MS4 jurisdiction. Its argument is largely based on comparing

itself to other jurisdictions in Maryland that have been designated as Phase I and Phase II

MS4s. Carroll County claims its treatment as a Phase I MS4 subjects it to the same effluent

limitations as larger urban jurisdictions in Maryland, while other counties similar to it in

population size and land use are subject to less stringent regulation as Phase II jurisdictions.

In particular, it draws a comparison to Washington County, which has been designated as

a small (Phase II) MS4 jurisdiction. Carroll County asserts that it is not challenging the

                                              89
population categories in the Clean Water Act, but rather the different treatment of two

similarly situated counties.100

       In our view, the Department had a rational basis for making the impervious surface

restoration terms more stringent for Phase I MS4s than for Phase II MS4s, even accounting

for similarities between the smallest medium MS4s and the largest small MS4s. The

Department notes that the population of Carroll County exceeded that of Washington

County by a significant amount (when incorporated areas were excluded) at the time that

the Department began to treat the counties as Phase I or Phase II jurisdictions. In addition,

the Department’s discretion in crafting MS4 permit terms is bounded by the Bay TMDL,

the Maryland WIP, and the EPA.

       In the Maryland WIP, the Department committed to including impervious surface

restoration terms in MS4 permits similar to the ones the Department in fact included in the

permits it issued after the EPA incorporated the Maryland WIP into the Bay TMDL.

Moreover, the 30 percent restoration requirement for Phase I permittees inherently takes

account of differences in the population size of those permittees. As the Department

explained when it issued the Carroll County permit, “larger, more densely developed

jurisdictions will have more impervious area and medium jurisdictions will have less

impervious area that will require restoration.” Basis for Final Determination to Issue

       100
          In terms of the impervious surface restoration requirement, the Department
designed the Phase I MS4 permits to be more stringent than Phase II MS4 permits in three
ways: larger baseline (county-wide vs. urbanized areas), earlier deadline (2019 vs. 2025),
and higher percentage of area to be restored (30% vs. 20%).

                                             90
Carroll County’s NPDES MS4 Permit MD0068331 (December 2014) at 29. Finally, in an

objection to an earlier draft of the Carroll County permit, the EPA advised the Department

that the impervious surface restoration term in the Carroll County permit should align with

that in Prince George’s County’s permit, in order to comply with the Bay TMDL. EPA,

Specific Objection to Carroll County Phase I MS4 Permit MD0068331 (September 20,

2012) at 3. Thus, the Department had a rational basis for the differences in permit terms

between the Phase I and Phase II counties, even if some of them are close in population

size and share some similar characteristics.

E.     Whether the Permits Should Have Provided for Water Quality Trading

       “Water quality trading” is a method for complying with discharge permits that uses

market forces to reduce overall pollution at lower cost by shifting pollution reduction

activities from one entity to another. In particular, an entity subject to a pollution limit

may take credit for a pollution reduction accomplished by another entity that it

compensates for that privilege.101 Such trading presumably happens only if the other entity

is able to accomplish the pollution reduction at less cost than the entity subject to the

pollution limit. Thus, if water quality trading is available as a compliance method in a

permit, a permittee might satisfy part of its obligations under the permit by purchasing

pollutant reduction credits from other entities that take certain pollutant-reducing actions.

       101
           See EPA, Water Quality Trading Evaluation (October 2008), available at
https://perma.cc/KT3P-WXRS, at 1-1; EPA, Water Quality Trading Toolkit for Permit
Writers (updated June 2009), available at https://perma.cc/866S-M4V4, at 4.

                                               91
       The permits that are the subject of this appeal do not include water quality trading

as a compliance method. The Counties wanted their permits to include water quality

trading as a compliance option and contend that the Department’s decision not to allow for

water quality trading in the permits when they were issued in 2014 was arbitrary and

capricious.

       As the Counties point out, both the Department and the EPA support water quality

trading as an option in discharge permits. Over the past several years, the Department has

been developing a water quality trading program in Maryland. In December 2017, the

Department proposed regulations to establish such a program. See 44:25 Md. Reg. 1189-

95 (December 8, 2017).       Following the requisite notice and comment period, the

Department adopted those regulations, which became effective July 16, 2018. See 45:14

Md. Reg. 698-702 (July 6, 1018), codified at COMAR 26.08.11. In addition, on April 27,

2018, the Department issued a Phase II MS4 general permit,102 effective October 31, 2018,

which includes a term that conditionally allows water quality trading.103 The Department

       102
           While permits applicable to Phase I MS4s are usually customized for each
jurisdiction, the Department has developed a less rigorous general permit for Phase II
MS4s. See Maryland Department of the Environment, Maryland’s NPDES Municipal
Separate Storm Sewer System (MS4) Phase II General Permits, https://perma.cc/MLX2-
5NDU; EPA, Stormwater Discharges from Municipal Sources, https://perma.cc/UBS6-
NDK3.
       103
          In pertinent part, the Maryland Phase II MS4 general permit provides: “[The
Department] supports trading as a cost-effective means for achieving pollutant load
reductions[, and t]herefore, trading with other source sectors may be an option after formal
regulatory procedures are satisfied.” National Pollutant Discharge Elimination System

                                            92
did so because it anticipated that the final water quality trading regulations would be

adopted in 2018, as indeed they were. See Basis for Final Determination to Issue the

General Permit for Discharges from Small Municipal Separate Storm Sewer Systems

(April 27, 2018) at 25.

       The Counties argue that the Department also should have conditionally approved

water quality trading in their permits, and that the failure to do so was arbitrary and

capricious. We disagree. The Department issued these permits to the Counties in 2014,

just a year after it had convened a stakeholder group charged with examining several

fundamental issues about trading and making recommendations for a draft trading policy.

The Department explicitly mentioned that ongoing review when it explained in the Basis

for Determination as to each permit why the permit did not include water quality trading

as a compliance mechanism. By 2018, however, when the Department was completing the

Phase II MS4 general permit, it had already proposed trading regulations and reasonably

anticipated that those regulations would be adopted by the time that permit was effective.

The Department therefore had a rational basis for conditionally approving water quality

trading in the Phase II MS4 general permit but not in the permits issued four years earlier

to the Counties. See Harvey v. Marshall, 389 Md. at 297-99 (a “reasonable or rationally

motivated” administrative decision is not “arbitrary or capricious.”).

General Permit for Discharges from Small Municipal Separate Storm Sewer Systems (No.
13-IM-5500), at B-10.

                                            93
       Carroll County points out that, in order to add water quality trading to its permit

now, it must pursue a permit modification and undergo what it characterizes as “a lengthy

public participation process.” But the County has not shown that any burden associated

with the permit modification process would warrant a finding that the Department’s

decision in 2014 not to include water quality trading was arbitrary and capricious.104

F.     Effect of Permit Reference to Statutory Responsibilities of Other Entities

       One provision of the permits contains language that, in the view of Carroll County,

impermissibly transfers statutory obligations of other governmental entities to the

Counties. In particular, Part VI.B of each County’s permit provides as follows:

             [The] County shall cooperate with other agencies during the completion
             of the Water Resources Element (WRE) as required by the Maryland
             Economic Growth, Resource Protection and Planning Act of 1992
             (Article 66B, Annotated Code of Maryland). Such cooperation shall
             entail all reasonable actions authorized by law and shall not be
             restricted by the responsibilities attributed to other entities by separate
             State statute, including but not limited to reviewing and approving
             plans and appropriating funds.

(emphasis added).

       104
          At least six other counties – including Frederick County – have requested that
the Department modify their Phase I MS4 permits to incorporate the new water quality
trading program as an option for complying with an impervious surface restoration
requirement. We take judicial notice that the Department accepted those proposals and
issued final determinations in December 2018 modifying the permits for Anne Arundel,
Prince George’s, and Baltimore counties; in July, the Department issued tentative
modification determinations for Charles, Harford, and Frederick counties. See Maryland
Department of the Environment, Maryland’s NPDES Municipal Separate Storm Sewer
System (MS4) Permits, https://perma.cc/KFY9-VBDU.

                                                 94
       The law referenced in this part of the permits concerns how counties plan their future

development. Now codified in Title 3 of the Land Use Article (“LU”) of the Maryland

Code, the pertinent provisions of the Economic Growth, Resource Protection and Planning

Act, as amended, direct each county to develop a comprehensive plan that includes, among

other things, “a water resources element.” See LU §§3-101(a), 3-102(a)(1)(viii).105 As

part of the water resources element, a county must identify “suitable receiving waters and

land areas to meet stormwater management and wastewater treatment and disposal needs

of existing and future development.” LU §3-106(a)(2).

       Only Carroll County raises an issue on appeal concerning this provision of the

permits.106 In doing so, Carroll County contests only the language italicized in the

quotation above. The County concedes that the EPA allows states to coordinate federal

and state permitting requirements, as the Department attempts to do in requiring

       105
           The Economic Growth, Resource Protection and Planning Act of 1992 was
originally codified in Article 66B. Chapter 437, Laws of Maryland 1992. In 2006, the
General Assembly enacted the “water resources element” requirement in Article 66B,
§1.03(iii). Chapter 381, Laws of Maryland 2006. In 2012, the Legislature re-codified
various provisions of Article 66B, including those concerning the water resources element
requirement, as part of the new Land Use Article. Chapter 426, Laws of Maryland 2012.
       106
          Frederick County challenged the same provision in its permit in the Circuit Court.
The Circuit Court ruled that the Department could lawfully incorporate the cooperation
requirement of the Land Use Article into the permit. It also held that the language italicized
above seemed to require the County to disregard other State statutes, which would
impermissibly amend the Land Use Article. The Department did not contest that ruling.
For the reasons set forth in text, we agree that the permit term may not amend the Land
Use Article and may not be construed to do so or to require the Counties to disregard any
other laws.

                                             95
cooperation with other agencies in this permit term.107 The County argues, however, that

the italicized language “seems to purport that the comprehensive planning provision

overrides all other State statutes and relieves other entities of responsibilities attributed to

them by State statute, instead imposing those responsibilities on the County.”

       Although the Department admits that the language is opaque, it asserts that the

purpose of the final clause of this permit term “is to make clear that the County, when

formulating the water resources element of its comprehensive plan, may not decline to

cooperate with another agency because that agency, and not the County, has statutory

responsibility for a specific governmental activity, whether it be reviewing and approving

plans or appropriating funds.” In that view, this provision only precludes the County from

relying on other agencies’ specific responsibilities as a reason not to coordinate with those

agencies.

       In our view, the County’s interpretation is not a reasonable reading of the permit

provision. Some ambiguity arguably exists in the closing phrase of the permit provision:

“including but not limited to reviewing and approving plans and appropriating funds.” At

least in terms of grammar, what “including” modifies is not obvious. It could modify the

County’s “cooperation,” its “reasonable actions,” or the other entities’ “responsibilities.”

By the last antecedent rule, however, “including” would ordinarily be understood to modify

       107
         See EPA Preamble to 1999 Phase II MS4 Rule, 64 Fed. Reg. at 68739 (discharge
“permits may incorporate the requirements of existing State ... programs, thereby
accommodating State[s] ... seeking to coordinate the storm water program with other
programs”).

                                              96
“responsibilities.” See McCree v. State, 441 Md. 4, 21 (2014) (“Under the last antecedent

rule, a qualifying clause ordinarily is confined to the immediately preceding word or

phrase”) (internal quotations omitted). That reading makes the most sense here.

       The provision says only that other entities’ statutory requirements “shall not ...

restrict” the County’s obligation under State law to cooperate with those entities. This

permit term has no effect on statutory requirements pertaining to other entities, nor does it

transfer those obligations to the County. In other words, the permit term provides that the

responsibilities of other entities under State law to take such actions as “reviewing and

approving plans [or] appropriating funds” do not restrict the County’s obligation to

cooperate with those entities. Reasonably read, the permit term incorporates existing State

law without imposing new requirements on the County or relieving other entities of their

obligations under State law.

                                             III

                                        Conclusion

       For the reasons set forth above, we hold:

       (1)    The Department may lawfully include an impervious surface restoration

requirement in an MS4 permit without reference to the MEP standard. The Department’s

decision to do so in Frederick County’s most recent permit was not arbitrary or capricious.

       (2)    The Department may lawfully include an impervious surface restoration

requirement in an MS4 permit in which the required amount of restoration is based on the

amount of unrestored surface throughout the county that operates the MS4 when the

amount of restoration derives from commitments made in the Maryland WIP as part of the

                                             97
development of the Chesapeake Bay TMDL. To the extent that the Counties challenge

restoration provisions in their permits that derive from EPA-approved local TMDLs, such

challenges should have been made when the local TMDL was approved by the EPA and

are not appropriately part of judicial review of an MS4 permit in State court.

       (3)    The Department had authority to treat Frederick County and Carroll County

as Phase I jurisdictions for purposes of their MS4 permits. It was not arbitrary or capricious

for the Department to classify Carroll County as a Phase I jurisdiction without also

including Washington County in that category.

       (4)    Although the Department later elected to include “water quality trading” as

a compliance method for MS4 permittees, it was not arbitrary or capricious for the

Department to refrain from doing so in the Counties’ 2014 permits because it had not yet

finally adopted regulations it had proposed concerning that compliance method.

       (5)    A somewhat ambiguous provision in the Carroll County MS4 permit that

requires it to cooperate with other agencies in the development of the water resources

element of the County’s comprehensive plan under LU §3-101 et seq. did not – and could

not – transfer the responsibilities of those agencies to the County.

       After all the jargon, technical analysis, and regulatory provisions have been digested

and applied, it seems fitting to conclude with the words of Judge Wilkinson in a recent case

concerning the operation and financing of an MS4 in the Chesapeake Bay region:

       “No one is so naïve as to believe that the Chesapeake Bay [and its tributaries] can

be restored to the pristine condition … in which this country’s earliest inhabitants found

them. We would be fortunate to preserve a wholesome fraction of what once there was.

                                             98
This case is but a tiny chapter in the story of our nation’s effort to reconcile the just

demands of development with the imperative of preserving an environment that can help

make productive enterprise worth having.... We happily accepted the abundance that came

down from our forebears. How then can we impoverish the environment for those who

come after?”108

                             IN NO. 5, JUDGMENT OF THE CIRCUIT COURT FOR CARROLL
                             COUNTY AFFIRMED IN PART AND REVERSED IN PART.
                             COSTS TO BE SPLIT EVENLY BETWEEN THE PARTIES.

                             IN NO. 7, JUDGMENT OF THE CIRCUIT COURT FOR
                             FREDERICK COUNTY AFFIRMED IN PART AND REVERSED IN
                             PART. COSTS TO BE SPLIT EVENLY BETWEEN THE PARTIES.

      108
            Norfolk Southern, 916 F.3d at 325 (Wilkinson, J., concurring).

                                             99
Circuit Court for Carroll County
Case No. 06-C-15-068141
                                               IN THE COURT OF APPEALS
Circuit Court for Frederick County                  OF MARYLAND
Case No. 10-C-15-000293

Argued: September 13, 2018                                Nos. 5 & 7

                                                 September Term, 2018
                                       ______________________________________

                                          MARYLAND DEPARTMENT OF THE
                                                   ENVIRONMENT
                                                         v.
                                       COUNTY COMMISSIONERS OF CARROLL
                                                COUNTY, MARYLAND
                                       ______________________________________

                                          FREDERICK COUNTY, MARYLAND
                                                         v.
                                          MARYLAND DEPARTMENT OF THE
                                                   ENVIRONMENT
                                       ______________________________________

                                                    Barbera, C.J.
                                                    *Greene
                                                    *Adkins
                                                    McDonald
                                                    Watts
                                                    Hotten
                                                    Getty,

                                                       JJ.
                                       ______________________________________

                                     Dissenting Opinion by Watts, J., which Hotten and
                                                     Getty, JJ., joins.
                                      ______________________________________

                                                    Filed: August 6, 2019

                                     *Greene and Adkins, JJ., now retired, participated in
                                     the hearing and conference of this case while active
                                     members of this Court; after being recalled pursuant
                                     to the Maryland Constitution, Article IV, Section 3A,
                                     they also participated in the decision and adoption of
                                     this opinion.
       Respectfully, I dissent. Although I agree with the Majority that it was not arbitrary

and capricious for the Maryland Department of the Environment (“the MDE”) not to

include water quality trading as a compliance method in the municipal separate storm sewer

system (“MS4”) permits of Carroll County and Frederick County, I disagree with the

Majority as to the other issues. See Maj. Slip Op. at 97-98. I would hold that the MDE

was not authorized to set forth in Frederick County’s MS4 permit requirements that exceed

the “maximum extent practicable” standard, that the MDE lacked the authority to require

the Counties to restore 20% of the impervious surfaces1 throughout the entirety of each

county, and that the MDE misclassified the Counties’ MS4s as medium rather than small.2

       Under 33 U.S.C. § 1311(a)—part of the Clean Water Act, 33 U.S.C. §§ 1251-

1388—generally, it is illegal to discharge pollutants into navigable waters. That said, the

Environmental Protection Agency (“the EPA”)—or, under certain circumstances, a State

environmental agency, such as the MDE—may issue a permit for the discharge of

pollutants into navigable waters. See 33 U.S.C. § 1342(a)(1), (b). For example, the MDE

may issue to a county a permit for an MS4. See 33 U.S.C. § 1342(p)(3)(B). 33 U.S.C. §

1342(p)(3)(B) states:

       1
          “‘Impervious surface’ means a surface that does not allow stormwater to infiltrate
into the ground.” Md. Code Ann., Env’t (1987, 2013 Repl. Vol.) (“EN”) § 4-201.1(d)(1).
“‘Impervious surface’ includes rooftops, driveways, sidewalks, or pavement.” EN § 4-
201.1(d)(2).
        2
          Because I agree with Frederick County that the MDE was not authorized to set
forth in Frederick County’s MS4 permit requirements that exceed the “maximum extent
practicable” standard, there is no need to address Frederick County’s alternative argument
that its MS4 permit’s requirements are impossible to fulfill. Similarly, although I disagree
with the Majority as to the issue regarding Carroll County’s cooperation with other State
agencies, it is not necessary to go into detail in light of my positions on the other issues.
      Permits for discharges from municipal storm sewers--

             (i) may be issued on a system- or jurisdiction-wide basis;

             (ii) shall include a requirement to effectively prohibit non-stormwater
      discharges into the storm sewers; and

             (iii) shall require controls to reduce the discharge of pollutants to the
      maximum extent practicable, including management practices, control
      techniques and system, design and engineering methods, and such other
      provisions as the [EPA] or the State determines appropriate for the control of
      such pollutants.[3]

      On brief, the MDE does not deny that it set forth in Frederick County’s MS4 permit

requirements that exceed the “maximum extent practicable” standard. To the contrary, the

MDE contends that it was authorized to impose on Frederick County requirements that go

beyond the “maximum extent practicable” standard.

      I disagree, and would conclude that 33 U.S.C. § 1342(p)(3)(B)(iii)’s plain language

establishes that the MDE is authorized only to require Frederick County “to reduce the

discharge of pollutants to the maximum extent practicable[.]” In other words, in 33 U.S.C.

§ 1342(p)(3)(B)(iii), the “such other provisions” language does not authorize the MDE to

impose on Frederick County requirements that exceed the “maximum extent practicable”

standard. In 33 U.S.C. § 1342(p)(3)(B)(iii), every single item in question—namely,

“management practices, control techniques and system, design and engineering methods,

      3
        Consistent with 33 U.S.C. § 1342(p)(3)(B)(iii), 40 C.F.R. § 122.26(d)(2)(iv) states
that “[a] proposed management program” to control pollutants from an MS4 “shall include
a comprehensive planning process which involves public participation and where
necessary intergovernmental coordination, to reduce the discharge of pollutants to the
maximum extent practicable using management practices, control techniques and system,
design and engineering methods, and such other provisions which are appropriate.”

                                           -2-
and such other provisions as the [EPA] or the State determines appropriate for the control

of such pollutants”—is part of a list of “controls to reduce the discharge of pollutants to

the maximum extent practicable[.]” In short, in 33 U.S.C. § 1342(p)(3)(B)(iii), the “such

other provisions” language is subject to the “maximum extent practicable” standard.

Nothing in 33 U.S.C. § 1342(p)(3)(B)(iii) indicates that the “such other provisions”

language grants the MDE freewheeling authority to impose on the Counties whatever

requirements that it deems “appropriate[,]” no matter how onerous or costly.4

       This interpretation of 33 U.S.C. § 1342(p)(3)(B)(iii) is warranted not only by its

plain language, but also by our case law. Just three years ago, in Md. Dep’t of Env’t v.

Anacostia Riverkeeper, 447 Md. 88, 126, 134 A.3d 892, 915 (2016), this Court

unanimously held that the requirement to restore 20% of impervious surfaces in multiple

counties’ MS4 “[p]ermits complies with the [maximum extent practicable] standard” under

33 U.S.C. § 1342(p)(3)(B)(iii). In so holding, this Court rejected environmental groups’

contention “that the 20% restoration requirement is too opaque to comply with 33 U.S.C.

§ 1342(p)(3)(B)(iii), the [maximum extent practicable] standard.” Id. at 123, 134 A.3d at

913.   This Court pointed out “that MS4s are subject to the [maximum extent

practicable] standard under 33 U.S.C. § 1342[(p)(3)(B)(iii)].” Id. at 104, 134 A.3d at

901 (emphasis added). Similarly, this Court noted that 33 U.S.C. § 1342(p)(3)(B)(iii)

       4
        After an examination of a statute’s language, it is permissible to consider the
statute’s “legislative history as a confirmatory process.” Gomez v. Jackson Hewitt, Inc.,
427 Md. 128, 160, 46 A.3d 443, 462 (2012) (citation omitted). But, as the Majority notes,
“what legislative history exists is not especially illuminating on the role of the [maximum
extent practicable] standard.” Maj. Slip Op. at 44 (cleaned up).

                                           -3-
“requires ‘controls to reduce the discharge of pollutants’ to the [maximum extent

practicable.]” Id. at 177, 134 A.3d at 945 (emphasis added). And, this Court stated that

“stormwater management programs that are designed by regulated parties must, in every

instance, be subject to meaningful review by an appropriate regulating entity to ensure that

each such program reduces the discharge of pollutants to the maximum extent

practicable.” Id. at 157, 134 A.3d at 933 (cleaned up) (emphasis added).

       This Court’s holding in Anacostia Riverkeeper, id. at 126, 134 A.3d at 915, was

premised on the principle—expressed multiple times throughout the opinion—that MS4

permits are subject to the “maximum extent practicable” standard under 33 U.S.C. §

1342(p)(3)(B)(iii). Accordingly, Anacostia Riverkeeper forecloses the MDE’s contention

that 33 U.S.C. § 1342(p)(3)(B)(iii) allows it to impose on Frederick County requirements

that exceed the “maximum extent practicable” standard. If the MDE’s position were valid,

then this Court’s holding in Anacostia Riverkeeper, id. at 126, 134 A.3d at 915, would have

been completely meaningless; after all, if the MDE were free to ignore the “maximum

extent practicable” standard when issuing MS4 permits, why would this Court have

bothered to determine whether the MS4 permits complied with the “maximum extent

practicable” standard?

       Seeking to get around the obstacle that Anacostia Riverkeeper poses to its position,

the MDE sets forth a novel theory—namely, that the “maximum extent practicable”

standard is a “floor” rather than a “ceiling,” and that Anacostia Riverkeeper does not

indicate that the MDE may not impose requirements that go beyond the “maximum extent

practicable” standard. The Majority essentially goes along with the MDE’s interpretation

                                           -4-
of Anacostia Riverkeeper, reasoning that, in Anacostia Riverkeeper, “the question was

whether the impervious surface restoration requirement satisfied the [maximum extent

practicable] standard whereas in this case the question is whether it unlawfully exceeds it.”

Maj. Slip Op. at 39 (emphasis in original). The view of the Majority and the MDE is simply

incompatible with this Court’s holding in Anacostia Riverkeeper, 447 Md. at 126, 134 A.3d

at 915, which, to reiterate, was squarely based on the principle that MS4 permits must

comply with the “maximum extent practicable” standard. If MS4 permits did not need to

comply with the “maximum extent practicable” standard, this Court would have had no

reason to determine that the requirement to restore 20% of impervious surfaces in multiple

counties’ MS4 “[p]ermits complies with the [maximum extent practicable] standard” under

33 U.S.C. § 1342(p)(3)(B)(iii). Anacostia Riverkeeper, 447 Md. at 126, 134 A.3d at 915.5

       5
        Perplexingly, the majority opinion states that, in Anacostia Riverkeeper, 447 Md.
at 122-26, 134 A.3d at 912-15:

       [T]he Court considered a permit term that appears in Phase I MS4 permits of
       five other jurisdictions and that is identical to the permit term that Frederick
       County challenges here. The Court held that the term was valid and
       authorized by the Clean Water Act. If we were simply to recite the holding
       of Anacostia Riverkeeper and stop, Frederick County loses.

Maj. Slip Op. at 38 n.41 (cleaned up) (emphasis in original). Essentially, after asserting
that, in Anacostia Riverkeeper, this Court answered a question that is not at issue in this
case, oddly, the majority opinion asserts that, under the holding of Anacostia Riverkeeper,
Frederick County would “lose[.]” Maj. Slip Op. at 38 n.41. In actuality, the circumstance
that, in Anacostia Riverkeeper, this Court considered a permit term that is identical to a
term in the permit that Frederick County challenges informs the outcome of this case. In
Anacostia Riverkeeper, 447 Md. at 126, 134 A.3d at 914-15, this Court concluded that the
challenged permit term complied with the “maximum extent practicable” standard. In
Anacostia Riverkeeper, id. at 123-26, A.3d at 913-15, there was no allegation that the
permit term exceeded the “maximum extent practicable” standard. Frederick County

                                            -5-
       To be sure, as Frederick County acknowledges, its interpretation of 33 U.S.C. §

1342(p)(3)(B)(iii) indicates that the statute contains a typographical error—namely, the

word “system” should be “systems” so that it, like the immediately preceding noun

“techniques,” is plural. It is not unheard of for a statute to contain a typographical error.

Indeed, another sentence within 33 U.S.C. § 1342 contains three such errors; 33 U.S.C. §

1342(l)(3)(C) erroneously refers to “Section 1365(a) of this title” (in which “Section”

should be lowercase), and, in two instances, erroneously omits the word “section” before

referring to a certain provision “of this title[.]”

       Helpfully, the Majority sets forth illustrations of how each party parses the sentence

within 33 U.S.C. § 1342(p)(3)(B)(iii). See Maj. Slip Op. at 41-43. As the Majority notes,

Frederick County parses that sentence, in pertinent part, as follows: “shall require controls

to reduce the discharge of pollutants to the maximum extent practicable, including (1)

management practices, (2) control techniques and systems, (3) design and engineering

methods, and (4) such other provisions as the [EPA] Administrator or the State determines

appropriate for the control of such pollutants.”       Id. at 41 (alterations in original).

Meanwhile, the MDE parses the sentence, in pertinent part, as follows: “shall require (1)

controls to reduce the discharge of pollutants to the maximum extent practicable, including

(a) management practices, (b) control techniques and (c) system, design and engineering

methods, and (2) such other provisions as the [EPA] Administrator or the State determines

would not “lose[]” under this Court’s holding in Anacostia Riverkeeper, Maj. Slip Op. at
38 n.41; rather, this Court’s holding in that case clearly demonstrates that MDE has
exceeded its authority.

                                               -6-
appropriate for the control of such pollutants.” Id. at 42 (alterations in original). The

Majority adopts the MDE’s interpretation of 33 U.S.C. § 1342(p)(3)(B)(iii), reasoning that

it “does not require revision of the text itself, and groups items that could comfortably fit

within the category of ‘controls’ separately from the final clause’s vaguer and seemingly

broader reference to ‘appropriate … provisions.’” Maj. Slip Op. at 42-43 (ellipsis in

original).

       The Majority fails to address three matters that demonstrate that the MDE’s

interpretation of 33 U.S.C. § 1342(p)(3)(B)(iii) is incorrect. Specifically, the MDE’s

interpretation renders most of the sentence at issue nugatory, leads to an illogical result,

and indicates that the sentence has not one, but two glaring errors. These circumstances

violate the rules of statutory interpretation, under which a court must read a statute “as a

whole so that no word, clause, sentence or phrase is rendered surplusage, superfluous,

meaningless[,] or nugatory[,]” and must read the statute “to avoid an illogical result.”

Gomez v. Jackson Hewitt, Inc., 427 Md. 128, 143, 156, 46 A.3d 443, 452, 460 (2012)

(cleaned up).

       If, as the MDE asserts, 33 U.S.C. § 1342(p)(3)(B)(iii) directs it to “require . . . such

other provisions as [it] determines appropriate for the control of such pollutants[,]” then

the rest of the provision is nugatory. Under the MDE’s interpretation, the “such other

provisions” language allows it to impose on the Counties whatever provisions it

“determines appropriate[,]” without reference to the “maximum extent practicable”

standard. That begs the question: If the MDE may freely ignore it, what is the point of the

“maximum extent practicable” standard? In fact, what is the point of the list of items that

                                             -7-
begins with “management practices”? Simply put, there would be no reason for either the

“maximum extent practicable” standard or the list of items if 33 U.S.C. § 1342(p)(3)(B)(iii)

directs the MDE to impose whatever requirements it deems fit, whether “practicable” or

not.

       The MDE volunteers a possible reason for the “maximum extent practicable”

standard—but that reason reveals an internal inconsistency in the MDE’s contentions. The

MDE reasons that the “maximum extent practicable” standard is a “floor” rather than a

“ceiling.” In other words, according to the MDE, the “maximum extent practicable”

standard sets forth the minimum that the MDE must require of Frederick County, not the

maximum that it may require of Frederick County. That argument, however, is inconsistent

with the MDE’s assertion that the “such other provisions” language is not subject to the

“maximum extent practicable” standard. If, as the MDE maintains, the “such other

provisions” language is independent of the “maximum extent practicable” standard, then

the “maximum extent practicable” standard is neither a floor nor a ceiling—it is

meaningless, as the MDE is free to impose whatever requirements it deems fit, whether

practicable or not.

       The Majority refers to the “such other provisions” language as the “final clause[.]”

Maj. Slip Op. at 43. I agree with the Majority that the “such other provisions” language is

the final clause—and, moreover, it is clear that the final clause is a catchall clause that

supports Frederick County’s interpretation of 33 U.S.C. § 1342(p)(3)(B)(iii), not the

MDE’s. Under Frederick County’s position, there are four groups of controls that may be

included in an MS4 permit, including a final catchall category—the “such other provisions”

                                           -8-
clause—that are all governed by the “maximum extent practicable” standard. Under the

MDE’s position, the “such other provisions” language is an all-encompassing blank check

that sidesteps the “maximum extent practicable” standard and allows the MDE to impose

any requirement that it “determines appropriate[.]” Because the MDE’s interpretation of

33 U.S.C. § 1342(p)(3)(B)(iii) renders most of the statutory provision nugatory, I cannot

endorse it.

       Additionally, the MDE’s interpretation of 33 U.S.C. § 1342(p)(3)(B)(iii) leads to an

illogical result. As the Majority notes, under Frederick County’s interpretation of 33

U.S.C. § 1342(p)(3)(B)(iii), the list of items includes “control techniques and systems” and

“design and engineering methods[.]” Maj. Slip Op. at 41 (alteration in original). This

explanation is logical, as the term “control systems” makes as much sense as the term

“control techniques[.]” By contrast, under the MDE’s interpretation, the list of items

includes “control techniques” and “system, design and engineering methods[.]” Id. at 42.

I am unable to fathom what exactly “system methods” are. The Majority acknowledges

that Frederick County refers to the term “system methods” as “nonsensical[,]” id. at 42, yet

the Majority makes no effort to explain what the term means. Simply put, the term “system

methods” is indeed nonsensical, in sharp contrast to the terms “design methods” and

“engineering methods[.]” Adopting Frederick County’s interpretation of 33 U.S.C. §

1342(p)(3)(B)(iii) avoids the illogical result of construing the statute to refer to “system

methods”—an incomprehensible term.

       Finally, the MDE’s interpretation of 33 U.S.C. § 1342(p)(3)(B)(iii) indicates that

the sentence has not one, but two glaring errors. Specifically, under the MDE’s position,

                                           -9-
the sentence would be missing two serial commas:6 one after the word “techniques[,]” and

one after the word “design[.]” To be sure, as noted above, it is not unheard of for a statute

to contain a typographical error; and, the inclusion of serial commas is a matter of style

rather than a grammatical necessity.            Even so, independent of 33 U.S.C. §

1342(p)(3)(B)(iii), the rest of the statute includes fourteen serial commas in all. See 33

U.S.C. § 1342(a)(1), (a)(2), (b)(1)(A), (b)(2)(B), (b)(9), (f), (g) (twice, counting the title),

(k), (l)(2) (twice, counting the title), (q)(1) (title), (q)(3), (s)(3)(A)(ii). And, unlike the

practice of including the lowercase word “section” when drafting a statute that refers to

other statutes, see 33 U.S.C. § 1342(l)(3)(C), the practice of including a serial comma is

not unique to legal writing, and is often a habit that becomes ingrained as a result of years

of day-to-day writing.       Accordingly, it is difficult to believe that 33 U.S.C. §

1342(p)(3)(B)(iii)’s drafters simply forgot to include a serial comma in not one, but two

instances.

       Without meaningfully addressing the fatal flaws in the MDE’s interpretation of 33

U.S.C. § 1342(p)(3)(B)(iii) and its conflict with this Court’s holding in Anacostia

Riverkeeper, 447 Md. at 126, 134 A.3d at 915, the Majority quotes an opinion by one of

California’s six intermediate appellate courts. See Maj. Slip Op. at 43. In Bldg. Indus.

Ass’n of San Diego Cty. v. State Water Res. Control Bd., 124 Cal. App. 4th 866, 882-83

       6
         Also known as a Harvard comma or an Oxford comma, a serial comma is “a comma
[that is] used to separate the second-to-last item in a list from a final item [that is]
introduced by the conjunction and or or[.]” Serial Comma, Merriam-Webster, https://
www.merriam-webster.com/dictionary/serial%20comma [https://perma.cc/3KGX-2LJC]
(italics in original). For example, the phrase “red, white, and blue” includes a serial
comma. Id.

                                             - 10 -
(2004), the Fourth District Court of Appeal of California reasoned that the “such other

provisions” language in 33 U.S.C. § 1342(p)(3)(B)(iii) directs State environmental

agencies to impose whatever requirements they determine appropriate, without reference

to the “maximum extent practicable” standard. The California Court agreed with the

contention of State water boards and environmental organizations that, “given the absence

of a comma after the word ‘techniques,’” and “because the word ‘system’ [] is singular, it

necessarily follows from parallel-construction grammar principles that the word ‘system’

is part of the phrase ‘system, design and engineering methods’ rather than the phrase

‘control techniques and system.’” Id.

       The California Court’s logic is unpersuasive for several reasons. First and foremost,

the California Court treated the lack of a comma after the word “techniques” as an

indication that the words “techniques” and “system” do not go together—when, in fact, the

exact opposite is true; i.e., the lack of a comma between the words “techniques” and

“system” indicates that, indeed, the words go together. On a related note, for all its concern

about the lack of a comma after the word “techniques[,]” the California Court failed to

acknowledge that its interpretation of 33 U.S.C. § 1342(p)(3)(B)(iii) meant that there

should have been a serial comma after the word “techniques”—as well as a serial comma

after the word “design[.]” Also, the California Court did not mention the possibility that

the word “system” is singular due to a typographical error. Nor did the California Court

acknowledge that its interpretation of 33 U.S.C. § 1342(p)(3)(B)(iii) renders most of the

sentence, including the “maximum extent practicable” standard, nugatory. Nor did the

California Court mention that its interpretation of 33 U.S.C. § 1342(p)(3)(B)(iii) indicates

                                            - 11 -
that the statute includes the nonsensical term “system methods”—much less attempt to

explain what that term means.

       In addition to quoting Bldg. Indus. Ass’n of San Diego Cty., the Majority gives

deference to the EPA’s interpretation of 33 U.S.C. § 1342(p)(3)(B)(iii), under which the

MDE may impose on Frederick County requirements that exceed the “maximum extent

practicable” standard. See Maj. Slip Op. at 50-51. Although a court should give some

deference to an administrative agency’s interpretation of a statute that it administers, the

court is not obligated to adopt a statutory construction that renders most of the statute

meaningless and leads to an illogical result. In a nutshell, even after giving some deference,

I would decline to adopt the EPA’s strained interpretation of 33 U.S.C. §

1342(p)(3)(B)(iii).7

       7
        In a futile attempt to bootstrap deference to the EPA’s interpretation of the Clean
Water Act, the Majority relies on case law that does not apply—Chevron, U.S.A., Inc. v.
Nat. Res. Defense Council, Inc., 467 U.S. 837 (1984)—and an opinion from the United
States Court of Appeals for the Ninth Circuit—Defs. of Wildlife v. Browner, 191 F.3d
1159 (9th Cir. 1999)—that does not address the issue that is before this Court. See Maj.
Slip Op. at 48 n.52. As to Defs. of Wildlife, the Majority states: “[W]hile the Ninth Circuit
did not agree with the EPA’s existing construction, it nevertheless recognized that a
permitting agency had discretion to include permit terms based on water quality
standards.” Maj. Slip Op. at 46-47. As the Majority appears to recognize, the relevant
question before the Ninth Circuit was whether the Clean Water Act authorized the EPA to
“require strict compliance with [S]tate water-quality standards[.]” Defs. of Wildlife, 191
F.3d at 1166. The Ninth Circuit answered that question in the affirmative, explaining that
33 U.S.C. § 1342(p)(3)(B)(iii) “gives the EPA discretion to determine what pollution
controls are appropriate.” Id. Significantly, nowhere in Defs. of Wildlife did the Ninth
Circuit indicate that 33 U.S.C. § 1342(p)(3)(B)(iii) authorizes the EPA—or a State
environmental agency—to impose whatever requirements it determines appropriate,
without reference to the “maximum extent practicable” standard. Indeed, in two instances,
the Ninth Circuit recognized that, under 33 U.S.C. § 1342(p)(3)(B)(iii), local governments

                                            - 12 -
       In addition to wrongfully setting forth in Frederick County’s MS4 permit

requirements that exceed the “maximum extent practicable” standard, the MDE improperly

required the Counties to restore 20% of the impervious surfaces throughout the entirety of

each county, as opposed to 20% of the impervious surfaces in the Counties’ urbanized

that manage MS4s must “reduce the discharge of pollutants to the maximum extent
practicable[.]” Id. at 1165 (internal quotation marks omitted).
        As a matter of fact, contrary to the Majority’s assertion that “[o]ther courts have
pointed to Defenders of Wildlife as setting forth the discretion that the EPA (and state
permitting agencies) have in drafting MS4 permit terms to require pollution controls that
satisfy the [‘maximum extent practicable’] standard or a more demanding water quality
based standard[,]” that is not the case. See Maj. Slip Op. at 47 n.50. Although the Ninth
Circuit’s opinion in Defs. of Wildlife was mentioned in each of the cases that the Majority
identifies, none of those cases relied on Defs. of Wildlife as a basis for concluding that the
EPA or State environmental agencies have the discretion to issue MS4 permits that contain
requirements that exceed the “maximum extent practicable” standard. In actuality, in each
of those cases, the courts relied on Defs. of Wildlife for other propositions. See Nat. Res.
Def. Council v. New York State Dep’t of Envtl. Conservation, 994 N.Y.S.2d 125, 135
(N.Y. App. 2014) (The New York Supreme Court relied on Defs. of Wildlife for the
specific proposition that permits issued for “industrial dischargers” must comply with the
effluent limitations set forth in 33 U.S.C. § 1311.); Conservation Law Found., Inc. v.
Boston Water and Sewer Comm’n, 2010 WL 5349854, at *5-6 (D. Mass. 2010)
(unreported) (The U.S. District Court for the District of Massachusetts relied on Defs. of
Wildlife for the proposition that the EPA has the authority to “determine that ensuring strict
compliance with state water-quality standards is necessary to control pollutants” and the
proposition that the EPA has the authority to “require less than strict compliance with state
water-quality standards.”); Tualatin Riverkeepers v. Oregon Dep’t of Envtl. Quality, 230
P.3d 559, 562 n.8 (Ore. App. 2010) (The Court of Appeals of Oregon relied on Defs. of
Wildlife for the proposition that permits providing for discharges of municipal storm water
“need not require strict compliance with state water quality standards.”); City of Arcadia
v. State Water Res. Control Bd., 135 Cal. App. 4th 1392, 1429 (2006) (The Court of Appeal
for the Fourth District of California relied on Defs. of Wildlife for the proposition that the
EPA has the discretion to “‘determine that ensuring strict compliance with state water-
quality standards is necessary to control pollutants’” and that the EPA also has the authority
to “‘require less than strict compliance with state water-quality standards[.’]” (Quoting
Defs. of Wildlife, 191 F.3d at 1166-67)). Nowhere in any of these cases did the various
courts conclude that Defs. of Wildlife established the EPA’s—or State environmental
agencies’—authority to issue MS4 permits that contain requirements exceeding the
“maximum extent practicable” standard.

                                            - 13 -
areas—i.e., the areas that the Counties’ MS4s serve. As noted above, 33 U.S.C. §

1342(p)(3)(B)(iii) provides that MS4 permits “shall require controls to reduce the discharge

of pollutants to the maximum extent practicable, including management practices, control

techniques and system, design and engineering methods, and such other provisions as the

[EPA] or the State determines appropriate for the control of such pollutants.” Pursuant to

33 U.S.C. § 1342(p)(3)(B)(iii), see Anacostia Riverkeeper, 447 Md. at 151 n.71, 134 A.3d

at 930 n.71, on December 3, 2010, multiple State agencies, including the MDE, submitted

to the EPA “Maryland’s Phase I Watershed Implementation Plan for the Chesapeake Bay

Total Maximum Daily Load[.]” University of Maryland et al., Maryland’s Phase I

Watershed Implementation Plan for the Chesapeake Bay Total Maximum Daily Load at 1

(Dec.      3,   2010),    available   at   https://mde.maryland.gov/programs/Water/TMDL/

Documents/www.mde.state.md.us/assets/document/MD_Phase_I_Plan_12_03_2010_Sub

mitted_Final.pdf [https://perma.cc/XV7P-P3VT] (“the WIP”). In the WIP, under the

heading “Additional Program, Practices and Policies to Meet the 2017 Goal for Non-Point

Source Urban Stormwater[,]” and under the subheading “Increase [National Pollutant

Discharge Elimination System (‘NPDES’)] Watershed Restoration Requirements for MS4

Phase I County permits, including [State Highway Administration,]” the State agencies

stated:

          The following key elements of the strategy support reasonable assurance of
          the implementation of this element of the [WIP]: [] Establish impervious
          acreage treatment requirements in NPDES []MS4[] permits to achieve
          specific reductions in sediment, phosphorus and nitrogen consistent with this
          [WIP]. These permits will require the development of a detailed watershed
          restoration strategy that contains the following elements: . . . Completion of
          restoration efforts for twenty percent of the counties’ impervious surface area

                                              - 14 -
       that is not already restored to the maximum extent practicable[].

WIP at 5-30 (paragraph breaks omitted).

       Consistent with the WIP, in 2014, the MDE issued to the Counties MS4 permits

“requiring compliance with the Chesapeake Bay [total maximum daily load] through the

use of a strategy that calls for the restoration of twenty percent of previously developed

impervious land with little or no controls within this five[-]year permit term as described

in” the WIP. MDE, National Pollutant Discharge Elimination System Municipal Separate

Storm Sewer System Discharge Permit [for Carroll County] at 15, available at https://mde.

maryland.gov/programs/Water/StormwaterManagementProgram/Documents/Carroll%20

Final%20Permit%20with%20attachments.pdf             [https://perma.cc/FL5D-6UPU];    MDE,

National Pollutant Discharge Elimination System Municipal Separate Storm Sewer System

Discharge Permit [for Frederick County] at 15, available at https://mde.maryland.gov

/programs/Water/StormwaterManagementProgram/Documents/Signed%20Frederick%20

Permit%20with%20Attachments.pdf [https://perma.cc/XC4Y-8EMY].

       From my perspective, the MDE lacked the authority to require the Counties to

restore 20% of the impervious surfaces throughout the entirety of each county; in other

words, the Counties’ MS4 permits simply require the Counties to restore 20% of the

impervious surfaces in urbanized areas—i.e., the areas that the Counties’ MS4s serve. Just

as the urbanized areas of each county determined whether the county’s MS4 was small,

medium, or large, see 40 C.F.R. § 122.26(b)(4)(i), (b)(7)(i); 40 C.F.R. Pt. 122, App. I, so,

too, do the urbanized areas of each county determine the extent of the county’s

responsibility to restore 20% of impervious surfaces. It makes sense that each county

                                           - 15 -
should be responsible only for restoring 20% of impervious surfaces in urbanized areas; in

other words, the areas that each county’s MS4 serves should be the same as the areas in

which the county’s MS4 permit makes the county responsible for restoring 20% of

impervious surfaces.

       In addition to improperly requiring the Counties to restore 20% of the impervious

surfaces throughout the entirety of each county, the MDE misclassified the Counties’ MS4s

as medium rather than small. Generally, before October 1, 1994, the EPA and the MDE

could “not require a permit . . . for discharges [that were] composed entirely of

stormwater.” 33 U.S.C. § 1342(p)(1). But, this exception to the permit requirement did

not apply to “[a] discharge from a[n MS4] serving a population of 250,000 or more[,]” 33

U.S.C. § 1342(p)(2)(C), or “[a] discharge from a[n MS4] serving a population of 100,000

or more but [fewer] than 250,000[,]” 33 U.S.C. § 1342(p)(2)(D). An MS4 that serves a

population of at least 250,000 is known as a “large” MS4, 40 C.F.R. § 122.26(b)(4)(i); an

MS4 that serves a population of at least 100,000, but fewer than 250,000, is known as a

“medium” MS4, 40 C.F.R. § 122.26(b)(7)(i); and, generally, an MS4 that is neither large

nor medium is known as a “small” MS4, 40 C.F.R. § 122.26(b)(16)(ii). In short, “[p]ermits

must be obtained for all discharges from large and medium [MS4]s.” 40 C.F.R. §

122.26(a)(3)(i).

       Whether an MS4 is large, medium, or small depends on the population of the

incorporated place that the MS4 served according to the 1990 Decennial Census. See 40

C.F.R. § 122.26(b)(4)(i), (b)(7)(i). The EPA promulgated an appendix that listed the

counties that, according to the 1990 Decennial Census, had “[u]nincorporated urbanized

                                          - 16 -
population[s]” of at least 100,000, but less than 250,000. See 40 C.F.R. Pt. 122, App. I.

The only Maryland county that the appendix listed was Howard County. See id. In other

words, according to the EPA, Howard County’s MS4 was Maryland’s only medium MS4.

See id.

          The Majority correctly observes that, in 1990, neither Carroll County nor Frederick

County had a population of at least “100,000 in unincorporated, urbanized areas[,]” and

that, accordingly, neither Carroll County nor Frederick County “likely met the EPA’s

contemporaneous interpretation of the medium [MS4] category[.]” Maj. Slip Op. at 85

(cleaned up). Yet, the Majority “decline[s] to hold that[,] today, . . . the Counties should

instead be” considered to have had small MS4s. Id. at 85-86. I am unpersuaded by the

reasons that the Majority gives for declining to right the wrong that has evidently

occurred—namely, the misclassification of the Counties’ MS4s as medium rather than

small. See id. at 85-89. Nor would I find merit in the MDE’s contentions, such as its

argument that the Counties are equitably estopped from challenging the misclassification.

In my view, the Counties’ mere “acquiesce[nce]” to the misclassification, id. at 89, is

neither a reason to refrain from addressing the merits of their contention, nor a basis for

concluding that the MDE properly exercised its authority to classify the Counties’ MS4s

as medium. The MDE, not the Counties, has been in the driver’s seat when it comes to

classification and permitting. If there is any question as to whether a misclassification has

occurred, the fault lies with the MDE, not the Counties.

          Without a doubt, government protection of the environment has a sustaining and

welcome purpose. Indeed, protecting and fostering the health of the environment is an

                                             - 17 -
important goal in today’s society, now more than ever. But, the government must follow

the statutes and regulations that it establishes. Misapplication of environmental statutes

and regulations serves no purpose and will result in diminishment of regard for the law.

      For the above reasons, respectfully, I dissent.

      Judge Hotten and Judge Getty have authorized me to state that they join in this

opinion.

                                          - 18 -
Circuit Court for Carroll County
Case No. 06-C-15-068141
                                               IN THE COURT OF APPEALS
Circuit Court for Frederick County
Case No. 10-C-15-000293
                                                      OF MARYLAND
Argued: September 13, 2018
                                                          Nos. 5 & 7

                                                 September Term, 2018
                                       ______________________________________

                                          MARYLAND DEPARTMENT OF THE
                                                   ENVIRONMENT
                                                         v.
                                       COUNTY COMMISSIONERS OF CARROLL
                                                COUNTY, MARYLAND
                                       ______________________________________

                                          FREDERICK COUNTY, MARYLAND
                                                         v.
                                          MARYLAND DEPARTMENT OF THE
                                                   ENVIRONMENT
                                       ______________________________________

                                                    Barbera, C.J.
                                                    *Greene
                                                    *Adkins
                                                    McDonald
                                                    Watts
                                                    Hotten
                                                    Getty,

                                                       JJ.
                                       ______________________________________

                                             Dissenting Opinion by Getty, J.
                                       ______________________________________

                                                    Filed: August 6, 2019

                                     *Greene and Adkins, JJ., now retired, participated in
                                     the hearing and conference of this case while active
                                     members of this Court; after being recalled pursuant
                                     to the Maryland Constitution, Article IV, Section 3A,
                                     they also participated in the decision and adoption of
                                     this opinion.
       I join the dissent written by Judge Watts and agree with her analysis that the

Maryland Department of the Environment (“the Department”) exceeded its authority by

(1) issuing permit requirements that exceed the “maximum extent practicable” standard;

(2) requiring the Counties to restore 20% of all impervious surfaces county-wide; and (3)

classifying each County’s municipal separate storm sewer system (MS4) as medium rather

than small. Dis. Slip Op. at 1.

       I write separately to express my concern with this Court’s tradition of granting broad

deference to an agency’s interpretation of statutes and regulations. Under the facts of this

case, I would scale back the agency deference doctrine as recognized in Maryland.

       The Majority cites to Chevron U.S.A. v. Nat. Res. Def. Council, 467 U.S. 837 (1984),

for the broad principle that this Court must defer to an agency’s interpretation of its

controlling statutes. However, in Auer v. Robbins, 519 U.S. 452 (1997), the Supreme Court

held that deference is only owed to an agency’s reasonable interpretations of its ambiguous

regulations. At a minimum, I would adopt the constraints of Auer deference – that the

agency’s regulation be ambiguous and its interpretation reasonable to merit judicial

deference. Absent such determinations, this Court has a duty to exercise its best judgment

and resolve the issues at hand, else we “deny the people who come before us the neutral

forum for their disputes that they rightly expect and deserve.” Kisor v. Wilkie, 139 S. Ct.
2400, 2448 (2019) (Gorsuch, J., concurring).1

1
  In Kisor v. Wilkie, the Supreme Court clarified that Auer deference requires that (1) the
regulation is “genuinely ambiguous”; (2) the agency’s reading is “reasonable,” or within
the zone of ambiguity; and (3) the “character and context of the agency interpretation
       The pressing need for such constraints is best illustrated by the Majority’s deference

to the Department’s improper classification of each County’s MS4 as medium rather than

small. The Clean Water Act and its corresponding regulations are not ambiguous—in fact,

the Majority has already acknowledged that “neither County likely met the EPA’s

contemporaneous interpretation of the medium category,” under “the EPA’s interpretation

of its own regulations.” Maj. Slip Op. at 85. Rather than correct this error, the Majority

upholds a flawed agency decision that has subjected two rural counties to a burdensome

regulatory scheme intended for densely populated jurisdictions such as Montgomery

County and Baltimore City.2

       As described by the Majority, the Water Quality Act of 1987 extended the Clean

Water Act’s effluent permit requirements to encapsulate point-source pollution contained

in municipal stormwater. Nat’l Res. Def. Council, Inc. v. EPA, 966 F.2d 1292, 1296 (9th

Cir. 1992). The Act proscribed a timetable for the implementation of these requirements,

proceeding in two phases based on the size and perceived impact of each stormwater

system. 33 U.S.C. § 1342(p)(2)-(4). As relevant, between 1987 and 1994 (“Phase I” of

entitles it to controlling weight.” Id. at 2414-16 (2019). As Kisor was decided on July 26,
2019, it was not briefed or argued by either party. I include it in this dissent not as
controlling precedent, but to further illustrate the contours of Auer deference, and to
highlight the persuasive concurrence calling for a more constrained, moderated view of
agency deference.
2
  The EPA promulgated its Phase I implementing regulations in 1990 with the intent of
regulating MS4s servicing “urbanized” areas, characterized by the Census Bureau as “high-
density development . . . a central city (or cities) with a surrounding closely settled area.”
See EPA, National Pollutant Discharge Elimination System Permit Application
Regulations for Storm Water Discharges, Final Rule, 55 Fed. Reg. 47990, 48041, 48050
n.5 (Nov. 16, 1990).

                                            -2-
the permitting program) state agencies could only require permits for MS4s that (1) serve

a population of 250,000 or more (a “large MS4”); (2) serve a population of more than

100,000 but less than 250,000 (a “medium MS4”); or (3) are designated “a significant

contributor of pollutants to waters of the United States.” § 1342(p)(2)(C)-(E). The

substantive requirements contained in MS4 permits were left entirely to the discretion of

the EPA and state regulatory bodies. See § 1342(p)(3)(B) (“Permits for discharges from

municipal storm sewers . . . shall require controls to reduce the discharge of pollutants . . .

as the Administrator or the State determines appropriate”).

       The EPA has issued implementing regulations to further define its Phase I

classifications. Rules promulgated in 1990 governing Phase I permits establish that the

“medium” category encompasses (i) MS4s serving between 100,000 and 250,000 people

in an incorporated municipality; and (ii) a list of jurisdictions enumerated in Appendix I of

the regulatory text.3 40 CFR § 122.26(b)(7)(i)-(ii). In 1999, once all permitting deadlines

had passed, the EPA elected to freeze these classifications based on each jurisdiction’s

population as reported in the 1990 census. EPA, National Pollutant Discharge Elimination

System – Regulations for Revision of Water Pollution Control Program Addressing Storm

3
  Appendix I listed counties with at least 100,000 people in urbanized unincorporated
areas, a threshold satisfied by neither County. As of the 1990 census, Frederick County
had a total population of 150,208 with only 58,393 residing in urbanized areas – while
Carroll County was home to 123,372 people, with no urbanized population. See Maryland
Department of Planning, Urban and Rural Population in Maryland: 2000 and 1990 (May
2002),                                    available                                 at:
http://planning.maryland.gov/MSDC/Documents/Census/Cen2000/urban_rural/ua_rural2
k_cnty.pdf

                                             -3-
Water Discharges, Final Rule, 64 Fed. Reg. 68772, 68748-49 (Dec. 8, 1999).4 These

regulations contain “no minimum criteria or performance standards,” instead encouraging

the permitting agency to develop pollution controls for each permit on a case by case basis.

Nat’l Res. Def. Council, 966 F.2d at 1308.

       Under this statutory and regulatory framework, neither County satisfied the

requirements for a “medium MS4” during the Phase I permit period. As acknowledged by

the Majority, “neither County likely met the EPA’s contemporaneous definition of the

medium category,” as neither County had a population of 100,000 in an incorporated area,

and neither County was enumerated in Appendix I. Maj. Slip Op. at 85; See Nat. Res. Def.

Council, Inc. v. New York State Dep’t of Envtl. Conservation, 34 N.E.3d 782, 794 n.16

(N.Y. 2015) (holding that state agencies administering programs under the Clean Water

Act are “bound to follow [the] EPA’s interpretation”). Although the Department may,

notwithstanding population, designate jurisdictions as “significant contributor[s] of

pollutants to the waters of the United States,” contemporaneous reports and

correspondence by the Department demonstrate that the Counties were classified based

solely on their projected population growth.5 Therefore, by nonetheless requiring permits

4
  As the EPA suggested in the preamble to its 1999 regulations, state agencies may use
their residual designation authority to “require more from operators of MS4s serving
‘newly over 100,000’ populations.” Id. at 68749. This commentary does not expand the
scope of the residual authority, which remains predicated on the determination that “storm
water discharge from the source contributes to a violation of a water quality standard or is
a significant contributor of pollutants to the waters of the United States.” Id. at 68781.
5
  These reports and correspondence are detailed in appendices to the parties’ briefs. See,
e.g., MDE, Basis for Final Determination to Issue Frederick County’s NPDES MS4 Permit

                                             -4-
of both Counties during Phase I, the Department contravened the unambiguous

requirements of the Clean Water Act.

       No statutory, regulatory, or judicial authority requires we adhere to this result.

Contrary to the assertions of the Department and the conclusion of the Majority,

reclassification would not implicate the anti-backsliding provision of the Clean Water Act.

See 33 U.S.C. §1342(o)(1) (“[A] permit may not be renewed, reissued, or modified . . . to

contain effluent limitations which are less stringent than the comparable effluent

limitations in the previous permit”). This provision is inapplicable, as the Act contains an

explicit exception for permits issued on the basis of “technical mistakes or mistaken

interpretations of law.” 33 U.S.C. §1342(o)(2)(b)(ii). Absent the legally inaccurate

designation of Carroll and Frederick County stormwater systems as “medium MS4s,” the

Department would not have been authorized to require a permit of either County during

the Phase 1 period. See 33 U.S.C. §1342(p)(1) (providing that, beyond the MS4 categories

enumerated in §1342(p)(2), “the Administrator or the State . . . shall not require a permit

under this section for discharges composed entirely of stormwater”).

       Similarly, the Counties’ “acquiescence” to their MS4 classification is entirely

irrelevant to the question of reclassification. The Majority relies heavily on the notion that

the Counties have operated within the Phase I permitting program for three decades without

at 30 (Dec. 2014) (“MDE did not make a claim under its RDA [residual designation
authority] that Frederick County must apply as a Phase I. . . . MDE had no need to . . . make
a determination based on water quality violations or impairments”); MDE, Maryland’s
NPDES Municipal Stormwater Monitoring at 1 (1997) (“MDE used projections from the
Maryland Ofﬁce of Planning (MOP) to designate Carroll, Charles, Washington, and
Frederick counties when their populations surpassed 100,000”).

                                            -5-
protest. See Maj. Slip Op. at 88-9 (reasoning that the Counties “have at the very least

acquiesced [to Phase I] classification since the 1990s;” that “neither County (nor apparently

anyone else) questioned the method that the Department used to assess the relevant

population;” and that their acquiescence “may have foreclosed any need to invoke the

Department’s residual designation authority”). In the 1990s, the Counties dipped their toes

in the water, so to speak, with the altruistic goal of doing their fair and proportionate share

to achieve Maryland’s clean water objectives. Their agreement and voluntary participation

in the permitting program has no bearing on whether their classification was ever correct,

as the Clean Water Act outright prohibited states from requiring a Phase I permit of

jurisdictions that do not meet the requirements of §1342(p)(2). Moreover, no established

precedent suggests that historical acquiescence or administrative reliance have foreclosed

the Counties’ right to challenge their designation.6

       Lacking any legal justification for refusing the Counties’ request for reclassification,

the Majority nonetheless defers to the post hoc judgment of the EPA, concluding that “the

agencies charged with administering the Clean Water Act have consistently regarded the

6
  This argument appears to implicitly evoke the Department’s claim of equitable estoppel.
MDE insists that Maryland’s Watershed Improvement Plan (WIP) relies on the Counties’
Phase I commitments. Equitable estoppel results from (1) a party’s voluntary action, (2)
inducing good faith reliance, (3) resulting in a detrimental change in position. Permanent
Fin. Corp. v. Montgomery Cty., 308 Md. 239, 247 (1986). At a very minimum, the
Department has not suffered a detrimental change in position, as the Counties are on track
to meet their Phase I commitments during the current permit cycle. E.g. Carroll County,
2017 NPDES MS4 Permit Annual Report at 10 (Dec. 15, 2017), available at
http://ccgovernment.carr.org/ccg/npdes/2017_NPDES_Annual_Report.pdf.             Moreover,
any reliance was arguably in bad faith, as the Department, not the Counties, is responsible
for interpreting its governing regulations.

                                             -6-
Counties as Phase I MS4s and that there is a reasonable basis for doing so.” Maj. Slip Op.

at 89. Granting an agency controlling authority over the interpretation of its own governing

regulations amounts to an abdication of this Court’s essential duty to interpret and apply

the law. See Kisor, 139 S. Ct. at 2425 (Gorsuch, J., concurring) (arguing deference

“requires judges to accept an executive agency’s interpretation of its own regulations even

when that interpretation doesn’t represent the best and fairest reading”).

       Such absolute deference is improper even under the Majority’s stated standard of

review. Although an agency’s factual findings are entitled to deference when supported

by “substantial evidence,” Md. Dep’t of the Env’t v. Anacostia Riverkeeper, 447 Md. 88,

120 (2016), the Majority openly acknowledges that the record contains “limited evidence

of the Department’s decision-making process in classifying these Counties as Phase I

jurisdictions in 1991.” Moreover, “it is always within our prerogative to determine whether

an agency’s conclusions of law are correct.” Schwartz v. Md. Dep’t of Nat. Res., 385 Md.
534, 554 (2005); See also Auer, 519 U.S. at 461 (deference not warranted where agency

interpretation is “plainly erroneous or inconsistent with the regulation.”).       The legal

sufficiency of the Counties’ Phase I permits, governed entirely by the Clean Water Act and

its corresponding regulations, falls squarely within the purview of this Court.7

7
  The substantive terms of an MS4 permit are at the discretion of the Department, and
therefore subject to an “arbitrary and capricious” standard of review. See Harvey v.
Marshall, 389 Md. 243, 296-99 (2005). The Majority fails to identify any rational basis
for tying pollution controls categorically to the scheduling requirements of the Clean Water
Act—for example, requiring all Phase I counties to restore 30% of their total surface area
by 2019, while requiring Phase II counties to restore 20% of their urbanized area by 2025.
Rather, as discussed supra, the Clean Water Act and EPA regulations encourage states to

                                            -7-
       Applying Auer deference, an agency’s interpretation of its own regulations is only

entitled to deference “if [the] regulation is genuinely ambiguous . . . even after a court has

resorted to all the standard tools of interpretation.” Kisor, 139 S. Ct. at 2414. “[I]f the law

gives an answer—if there is only one reasonable construction of a regulation—then a court

has no business deferring to any other reading, no matter how much the agency insists it

would make more sense.” Id. at 2415. Nowhere does the Majority identify any ambiguity

in the plain language of the Clean Water Act or the implementing regulations promulgated

in 1990 and 1999. Rather, as the Majority acknowledges, the law provides a clear answer:

Neither County’s population, as reported in the 1990 Census, authorized their classification

as “medium” MS4s under established law.

       Allowing the Department to issue Phase I permits notwithstanding would “permit

the agency, under the guise of interpreting a regulation, to create de facto a new

regulation.” Id. (quoting Christensen v. Harris County, 529 U.S. 576, 588 (2000)).

Moreover,

       [w]hen we defer to an agency interpretation that differs from what we believe to be
       the best interpretation of the law, we compromise our judicial independence and
       deny the people who come before us the impartial judgment that the Constitution
       guarantees them. And we mislead those whom we serve by placing a judicial
       imprimatur on what is, in fact, no more than an exercise of raw political executive
       power.

Kisor, 139 S. Ct. at 2439 (Gorsuch, J. concurring).

       In the simplest terms, the Majority acknowledges that the Department’s construction

develop substantive permit terms on a case by case basis. See 33 U.S.C. § 1342(p)(3)(B);
Nat’l Res. Def. Council, 966 F.2d at 1308.

                                             -8-
of its unambiguous regulatory mandate was incorrect, finds little evidence on record to

support this interpretation, identifies no legal authority that bars judicial review, and yet

defers regardless. By nonetheless “affording ‘controlling weight’ to [the Department’s]

post-promulgation views” of its governing regulations, our ruling today perpetuates a

longstanding inequity, and risks foreclosing judicial review to litigants seeking to challenge

administrative overreach. Id. at 2446 (Gorsuch, J. concurring).

       For the foregoing reasons, I respectfully dissent.

                                            -9-