Opposition Brief — California Sportfishing Protection Alliance, et al., Petitioners v. Adam Nickels, Acting Regional Director, United States Bureau of Reclamation, et al.

No. 25-989

In the Supreme Court of the United States

CALIFORNIA SPORTFISHING PROTECTION ALLIANCE,

ET AL., PETITIONERS

v.

ADAM NICKELS, ACTING REGIONAL DIRECTOR, UNITED

STATES BUREAU OF RECLAMATION, ET AL.

ON PETITION FOR A WRIT OF CERTIORARI

TO THE UNITED STATES COURT OF APPEALS

FOR THE NINTH CIRCUIT

BRIEF FOR THE FEDERAL RESPONDENTS

IN OPPOSITION

D. JOHN SAUER

Solicitor General

Counsel of Record

ADAM R.F. GUSTAFSON

Principal Deputy Assistant

Attorney General

ROBERT N. STANDER

Deputy Assistant

Attorney General

ROBERT P. STOCKMAN

ANGELA N. ELLIS

Attorneys

Department of Justice

Washington, D.C. 20530-0001

SupremeCtBriefs@usdoj.gov

(202) 514-2217

QUESTION PRESENTED

The Department of the Interior, together with California’s San Luis & Delta Mendota Water Authority,

operates the Grassland Bypass Project in California’s

Central Valley. The project funnels irrigation water

from the San Joaquin Valley through a bypass channel

to a canal known as the San Luis Drain that empties into

a tributary of the San Joaquin River. Since 1997, Interior has operated the project without a National Pollutant Discharge Elimination System permit under a statutory exemption for the return flows of irrigated agriculture. Petitioners contend that the project does not

meet the statutory requirements for that exemption.

The question presented is as follows:

Whether the Grassland Bypass Project falls within

the Clean Water Act’s exemption for “discharges composed entirely of return flows from irrigated agriculture,” 33 U.S.C. 1342(l)(1), where the irrigation return

flows mix only with dispersed, nonpoint source pollution

such as that transported by groundwater that leaches

into the project’s drain.

(I)

PARTIES TO THE PROCEEDING

Petitioners are the California Sportfishing Protection Alliance, Friends of the River, the San Francisco

Crab Boat Owners Association, Inc., and Felix Smith.

Respondents are Adam Nickels, Acting Regional Director of the United States Bureau of Reclamation; the

United States Bureau of Reclamation; the San Luis &

Delta-Mendota Water Authority; and the Grassland

Water District.

(II)

TABLE OF CONTENTS

Page

Opinions below ................................................................................ 1

Jurisdiction ...................................................................................... 1

Statement ......................................................................................... 2

Argument ....................................................................................... 10

Conclusion ...................................................................................... 22

TABLE OF AUTHORITIES

Cases:

City and Cnty. of San Francisco v. EPA,

604 U.S. 334 (2025) ......................................................... 15, 16

Committee to Save Mokelumne River v. East Bay

Mun. Util. Dist., 13 F.3d 305 (9th Cir. 1993),

cert. denied, 513 U.S. 873 (1994)......................................... 21

County of Maui v. Hawaii Wildlife Fund,

590 U.S. 165 (2020) .....................................3, 4, 13, 17, 19, 20

Decker v. Northwest Envtl. Def. Ctr.,

568 U.S. 597 (2013) ................................................................. 4

Fishermen Against the Destruction of the Env’t,

Inc. v. Closter Farms, Inc., 300 F.3d 1294

(11th Cir. 2002) ...................................................................... 20

League of Wilderness Defenders/Blue Mountain

Biodiversity Project v. Forsgren, 309 F.3d 1181

(9th Cir. 2002) .......................................................................... 3

Natural Res. Def. Council, Inv. v. Costle,

568 F.2d 1369 (D.C. Cir. 1977) .............................................. 4

Oregon Natural Desert Ass’n v. Dombeck,

172 F.3d 1092 (9th Cir. 1998), cert. denied,

528 U.S. 964 (1999) ........................................................... 3, 11

Oregon Natural. Desert Ass’n v. United States

Forest Serv., 550 F.3d 778 (9th Cir. 2008) ................... 12, 15

(III)

IV

Cases—Continued:

Page

Sierra Club v. El Paso Gold Mines, Inc.,

421 F.3d 1133 (10th Cir. 2005), cert. denied,

547 U.S. 1065 (2006) ............................................................. 21

South Florida Water Mgmt. Dist. v. Miccosukee

Tribe of Indians, 541 U.S. 95 (2004) ............................ 18, 19

Utility Air Regulatory Grp. v. EPA,

573 U.S. 302 (2014) ............................................................... 16

Ysleta del Sur Pueblo v. Texas,

596 U.S. 685 (2022) ............................................................... 16

Statutes and regulations:

Clean Water Act,

33 U.S.C. 1251 et seq. ...............................2-4, 8-11, 13-17, 20

§ 101(a), 33 U.S.C. 1251(a) ................................................. 2

§ 208, 33 U.S.C. 1288 et seq. ............................................. 18

33 U.S.C. 1288(a) ......................................................... 18

§ 301, 33 U.S.C. 1311 et seq.:

33 U.S.C. 1311(a) ........................................................... 3

§ 402, 33 U.S.C. 1342 et seq.:

33 U.S.C. 1342(a) ........................................................... 3

33 U.S.C. 1342(a)(1) ...................................................... 2

33 U.S.C. 1342(l)(1) ............................. 2, 5, 8-12, 17, 19

§ 502, 33 U.S.C. 1362 et seq.:

33 U.S.C. 1362(12) ................................................. 12, 15

33 U.S.C. 1362(12)(A).............................................. 3, 12

33 U.S.C. 1362(14) ......................................................... 3

33 U.S.C. 1362(16) ....................................................... 12

Clean Water Act of 1977, Pub. L. No. 95-217,

§ 33(b), 91 Stat. 1577 (33 U.S.C. 1362(14)) .......................... 4

§ 33(c), 91 Stat. 1577 (33 U.S.C. 1342(l)(1)) ................. 5, 7

V

Regulations—Continued:

Page

40 C.F.R.:

Section 122.2 ...................................................................... 14

Section 122.3(i)................................................................... 21

Section 122.41 ...................................................................... 2

Miscellaneous:

123 Cong. Rec. (1977):

p. 26,682 ................................................................................ 5

p. 38,924 ................................................................................ 5

p. 39,115 ................................................................................ 5

S. Rep. No. 370, 95th Cong., 1st Sess. (1977)......... 5, 9, 17, 18

Webster’s Third New International Dictionary

(2002) ...................................................................................... 13

In the Supreme Court of the United States

No. 25-989

CALIFORNIA SPORTFISHING PROTECTION ALLIANCE,

ET AL., PETITIONERS

v.

ADAM NICKELS, ACTING REGIONAL DIRECTOR, UNITED

STATES BUREAU OF RECLAMATION, ET AL.

ON PETITION FOR A WRIT OF CERTIORARI

TO THE UNITED STATES COURT OF APPEALS

FOR THE NINTH CIRCUIT

BRIEF FOR THE FEDERAL RESPONDENTS

IN OPPOSITION

OPINIONS BELOW

The opinion of the court of appeals (Pet. App. 1a-30a)

is reported at 150 F.4th 1260. The opinion of the district

court (Pet. App. 32a-80a) is reported at 657 F. Supp. 3d

1341.

JURISDICTION

The judgment of the court of appeals was entered on

September 5, 2025. A petition for rehearing was denied

on November 18, 2025 (Pet App. 81a-82a). The petition

for a writ of certiorari was filed on February 17, 2026.

The jurisdiction of this Court is invoked under 28 U.S.C.

1254(1).

(1)

2

STATEMENT

The Clean Water Act (CWA or Act), 33 U.S.C. 1251

et seq., generally prohibits the unauthorized discharge

of pollutants to waters of the United States. 33 U.S.C.

1311(a). Of particular relevance here, one means by

which a discharge may be authorized is through a permit under the National Pollutant Discharge Elimination

System (NPDES) program. Ibid., 33 U.S.C. 1342(a)(1).

The NPDES program generally imposes certain conditions on permitholders who are responsible for pointsource discharges of pollutants to waters of the United

States. See 40 C.F.R. 122.41. But the CWA exempts

from the permit requirement “discharges composed entirely of return flows from irrigated agriculture.” 33

U.S.C. 1342(l)(1).

This case concerns the Grassland Bypass Project in

California’s Central Valley. Since 1997 the Grassland

Bypass Project has operated without an NPDES permit

under the CWA’s exemption for irrigation return flows.

Pet. App. 14a. Petitioners contend that the irrigatedagriculture exemption does not apply here, and that the

Grassland Bypass Project therefore needs an NPDES

permit, because the Project’s irrigation return flows

commingle with diffuse, nonpoint source pollution before they are discharged to waters of the United States.

Pet. 3. The United States District Court for the Eastern District of California rejected that contention, Pet.

App. 77a-78a, and the court of appeals affirmed, id. at

3a.

1. Congress enacted the CWA “to restore and maintain the chemical, physical, and biological integrity of

the Nation’s waters.” 33 U.S.C. 1251(a). To that end,

the Act generally prohibits “the discharge of any pollu-

3

tant by any person.” 33 U.S.C. 1311(a). The Act defines

the term “ ‘discharge of a pollutant’ ” to include “any addition of any pollutant to navigable waters from any

point source.” 33 U.S.C. 1362(12)(A).

The Act establishes permitting programs through

which designated federal or state officials may authorize discharges of pollutants from point sources to waters of the United States. Under the NPDES program,

the Environmental Protection Agency (EPA) or an authorized State may permit the discharge of pollutants.

33 U.S.C. 1342(a).

a. The CWA distinguishes between point sources

and nonpoint sources. The Act defines the term “ ‘point

source’ ” as “any discernible, confined and discrete conveyance,” such as a “pipe, ditch, channel, [or] tunnel.”

33 U.S.C. 1362(14). The Act “does not define ‘nonpoint

source pollution,’ but ‘it is widely understood to be the

type of pollution that arises from many dispersed activities over large areas, and is not traceable to any single

discrete source.’ ” Pet. App. 5a (quoting League of Wilderness Defenders/Blue Mountain Biodiversity Project v. Forsgren, 309 F.3d 1181, 1184 (9th Cir. 2002)).

Nonpoint sources include, for example, “unconfined

rainwater runoff or groundwater.” County of Maui v.

Hawaii Wildlife Fund, 590 U.S. 165, 173 (2020) (citation

omitted).

Although the Act generally prohibits unpermitted

discharges of pollutants to navigable waters “from any

point source,” 33 U.S.C. 1362(12)(A), it does not directly

regulate pollution from nonpoint sources, see Oregon

Natural Desert Ass’n v. Dombeck, 172 F.3d 1092, 1096

(9th Cir. 1998), cert. denied, 528 U.S. 964 (1999). Instead, Congress vested the States with primary responsibility to develop plans for identifying nonpoint sources

4

and establishing best management practices to improve

water quality. See Maui, 590 U.S. at 174 (“[A]s to

groundwater pollution and nonpoint source pollution,

Congress intended to leave substantial responsibility

and autonomy to the States.”). The CWA “envisions

EPA’s role in managing nonpoint source pollution and

groundwater pollution as limited to studying the issue,

sharing information with and collecting information

from the States, and issuing monetary grants.” Id. at

175.

b. When Congress enacted the CWA in 1972, it did

not include any special provisions related to irrigated

agriculture. EPA quickly determined that application

of the Act’s permitting requirements to irrigation activities would require the agency to issue potentially “millions” of permits and thereby pose “unmanageable administrative burdens.” Natural Res. Def. Council, Inc.

v. Costle, 568 F.2d 1369, 1374, 1377 (D.C. Cir. 1977).

One year after Congress enacted the CWA, EPA therefore promulgated regulations to exempt several kinds

of point-source discharges from the NPDES permit

program. See Decker v. Northwest Envtl. Def. Ctr., 568

U.S. 597, 602 (2013). But in 1977, the D.C. Circuit held

that EPA’s regulations were invalid because EPA

lacked statutory authority to exempt categories of

point-source discharges from the permit requirements.

Costle, 568 F.2d at 1377.

Congress quickly stepped in to “accomplish[]

through legislation” “[w]hat the EPA could not do by

regulation.” Pet. App. 7a. Congress amended the

CWA’s definition of the term “point source” to exclude

“ ‘return flows from irrigated agriculture.’ ” Clean Water Act of 1977, Pub. L. No. 95-217, § 33(b), 91 Stat. 1577

(33 U.S.C. 1362(14)). Congress also amended the Act to

5

exempt return flows from irrigated agriculture from the

NPDES permit requirements. Id. § 33(c), 91 Stat. 1577

(33 U.S.C. 1342(l)(1)). The exemption provides as follows:

(1) Agriculture return flows

The Administrator shall not require a permit under this section for discharges composed entirely of return flows from irrigated agriculture, nor shall the Administrator directly or indirectly, require any

State to require such a permit.

33 U.S.C. 1342(l)(1).

In enacting the irrigated-agriculture exemption,

Congress sought to ease EPA’s administrative burden.

Pet. App. 8a (quoting 123 Cong. Rec. 38,924, 38,956

(1977)). Congress also sought to alleviate the disparity

between farmers who depended on surface irrigation

(and therefore required NPDES permits) and those

who did not. Id. at 8a-9a (quoting 123 Cong. Rec. 26,682,

26,702 (1977), and 123 Cong. Rec. 39,115, 39,210 (1977)).

Congress also considered the difficulty in determining

whether pollutants in return flows from irrigated agriculture originated from a point or nonpoint source. Id.

at 9a-10a (quoting S. Rep. No. 370, 95th Cong., 1st Sess.

35 (1977) (Senate Report)).

2. a. The Secretary of the Interior, through the Bureau of Reclamation, operates the Central Valley Project, the largest and one of the most important federal

water-management projects in the United States. The

Central Valley Project draws water from the Sacramento River in the north to the drier San Joaquin Valley in the south, which “typically receives less rainfall

than necessary to cultivate the crops” and thus requires

irrigation. 945 F.3d 1076, 1079. The Central Valley

6

Project requires drainage to remove irrigation water

that otherwise would raise the water table and salinity

level, harming agricultural fields and damaging crops.

C.A. Supp. E.R. 769; id. at 953.

b. This case involves the tile-drain system for removing irrigation water that has been delivered by the

Central Valley Project and used for agriculture on a

97,400-acre swath of farmland on the west side of the

San Joaquin Valley known as the Grassland Drainage

Area. Pet. App. 35a-36a. The land in the drainage area

includes active, fallow, and retired farmland, as well as

non-irrigable land used for public infrastructure, residences, and businesses. Id. at 36a. All the land in the

drainage area has been irrigated at some point. Ibid.

Studies in the 1980s revealed that drainage water

from parts of the Central Valley had been leaching selenium—a naturally occurring element that is toxic at

higher levels—into wetland ecosystems. C.A. Supp.

E.R. 953. The Department of the Interior (Interior) and

the San Luis & Delta Mendota Water Authority (Water

Authority) subsequently developed the Grassland Bypass Project, an effort to mitigate potential toxicity

from drainage. Pet. App. 11a-13a. Interior and the Water Authority have jointly implemented the Grassland

Bypass Project since 1996. Id. at 11a.

The Grassland Bypass Project funnels irrigation return flows from the Grassland Drainage Area into the

Grassland Bypass Channel, which conveys the return

flows further into a canal known as the San Luis Drain.

Pet. App. 13a. The water then flows through the drain

for 28 miles before emptying into Mud Slough, a tributary of the San Joaquin River. C.A. Supp. E.R. 771-772.

Over time, surrounding groundwater has seeped into

the drain. Pet. App. 13a. Sediments containing pollu-

7

tants like selenium have also accumulated in the drain.

Ibid.

Since 1997, Interior and the Water Authority have

operated the Grassland Bypass Project without an

NPDES permit under the statutory exemption for irrigated agriculture, 33 U.S.C. 1342(l)(1). Pet. App. 14a.

The Project is regulated under California’s nonpointsource-pollution program. Ibid.

3. a. In 2011, petitioners filed suit, alleging that the

Grassland Bypass Project was unlawfully discharging

pollutants without an NPDES permit. C.A. Supp. E.R.

1940, 1999-2000, 2008. In 2016, the district court initially granted summary judgment for defendants, and

petitioners appealed. Pet. 12.

b. The court of appeals reversed. 945 F.3d 1076.

The court agreed with the district court’s interpretation

of the term “irrigated agriculture” as encompassing “all

activities related to crop production,” id. at 1084-1085,

but it identified three aspects of the district court’s decision that it viewed as erroneous. First, the Ninth Circuit held that the district court had erred in assigning

to petitioners the burden to disprove that the statutory

exemption for irrigated agriculture applied. Id. at 1083.

Second, the court of appeals concluded that the district

court had erred in reading “entirely” to mean “mostly”

in the phrase “ ‘discharges composed entirely of return

flows from irrigated agriculture.’ ” Id. at 1085 (citation

and emphasis omitted). Third, the Ninth Circuit concluded that the district court had erred in striking certain theories of liability on pleading grounds. Id. at

1086-1087.

c. On remand, the district court again granted summary judgment for the defendants. Pet. App. 32a-80a.

The court noted that petitioners had identified “four al-

8

leged sources of pollutants that are commingling with

the return flows from irrigated agriculture” within the

Grassland Bypass Project: (i) “groundwater originating from beneath ‘non-irrigated’ land adjacent to the

Drain which seeps into the Drain through cracks and

weep holes”; (ii) “sediment that has settled out over

time in the Drain from the waters it carries”; (iii) “water

transported into tile drains” underneath retired agricultural land now occupied by a solar project; and (iv)

water from “ ‘highways, residences and other

non-irrigated lands’ ” that allegedly enters the drain.

Id. at 62a-63a (citation omitted).

The district court began by interpreting the CWA

exemption for irrigated agriculture return flows,

33 U.S.C. 1342(l)(1). Pet. App. 54a-62a. Applying the

Ninth Circuit’s reasoning in Glaser, the court construed

the statutory phrase “discharges composed entirely of

return flows from irrigated agriculture” as limited to

discharges that “do not contain additional discharges

from activities unrelated to crop production.” Id. at

56a-57a (citation omitted). Observing that the CWA defines the term “discharge” to exclude nonpoint-source

flows, id. at 57a, the court held that the exemption generally covers discharges of pollutants from irrigated agriculture, but that a permit is required if a return flow

contains pollutants “from an extra or supplementary

point source,” id. at 58a.

The district court next construed the term “irrigated

agriculture” to include any activity that “is related to

the function and operation of the overall drainage plan.”

Pet. App. 60a-61a. The court concluded on that basis

that the exemption from the NPDES permitting requirement would apply to the Grassland Bypass Project, which manages the overall drainage plan for the

9

Grassland Drainage Area’s agricultural activities, unless the court could identify a point source of nonagricultural pollutants that commingle with the Project’s irrigation return flows. Id. at 62a.

The district court then examined each source of additional pollutants that petitioners had identified. Pet.

App. 62a-77a. The court concluded that each alleged

pollutant either came from a nonpoint source or was attributable to activities related to crop production. Id. at

77a. The court held on that basis that the CWA exemption for irrigated agriculture applies and that the Grassland Bypass Project does not require an NPDES permit. Ibid.

d. The court of appeals affirmed. Pet. App. 1a-30a.

The court began its analysis by examining the text of

the statute, which exempts from the NPDES program

“discharges composed entirely of return flows from irrigated agriculture.” Id. at 18a (quoting 33 U.S.C.

1342(l)(1)). Referencing its prior decision in Glaser, the

court of appeals reaffirmed that the term “irrigated agriculture” includes “all activities related to crop production,” and that the term “entirely” means “ ‘wholly, completely, fully.’ ” Ibid. (citations omitted).

The court of appeals concluded, however, that the

text did “not dictate” whether the term “ ‘entirely’ ” “requires every pollutant within a return flow to be from

irrigated agriculture or every discharge within a return

flow to be from irrigated agriculture.” Pet. App. 18a19a (emphases added). The court viewed the Senate Report as shedding light on this issue. Id. at 19a. That

report stated that “[t]he word ‘entirely’ was intended to

limit the exception to only those flows which do not contain additional discharges from activities unrelated to

crop production.” Ibid. (quoting Senate Report 35)

10

(brackets in original). The court concluded that, because “the term ‘discharge’ necessarily presumes a

point source” under the CWA, “the exemption applies

to irrigation return flows that do not contain additional

point source discharges from activities unrelated to

crop production.” Id. at 20a (emphasis added).

The court of appeals then turned to the four sources

of pollutants (see pp. 7-8, supra) that are alleged to commingle with the Grassland Bypass Project’s return

flows. The court determined that each of those alleged

sources was either a nonpoint source or a point source

related to agriculture. Pet. App. 26a-27a. The court

held that three of the four sources—groundwater seepage from adjacent non-irrigated land, groundwater

seepage and runoff from “highways, residences, and

other non-irrigated lands,” and runoff and groundwater

from the land occupied by the solar project—are nonpoint sources. Id. at 27a. The court further concluded

that the fourth source—“accumulated and remobilized

sediment in the Drain”—either “originates from nonpoint sources or from a point source related to crop production.” Id. at 28a. The court of appeals therefore held

that, because petitioners had not identified any addition

of pollutants from a point source unrelated to crop production, the defendants had met their burden to establish that the Grassland Bypass Project was exempted

from the NPDES program under Section 1342(l)(1)’s

exemption for return flows from irrigated agriculture.

Id. at 29a-30a.

ARGUMENT

For nearly three decades, the Department of the Interior and the Water Authority have operated the

Grassland Bypass Project without an NPDES permit

11

under the CWA’s exemption for irrigated agriculture,

even though some nonpoint source pollution commingles with the irrigation return flows. Although petitioners concede that commingling is inevitable, they contend that this circumstance renders the irrigatedagriculture exemption unavailable. The court of appeals correctly rejected that argument, see Pet. App.

18a, and its decision does not conflict with any decision

of this Court or another court of appeals. The petition

for a writ of certiorari should be denied.

1. The court of appeals correctly held that the presence of diffuse nonpoint-source pollution does not disqualify the Grassland Bypass Project from the CWA’s

exemption for irrigated agriculture. The court was also

correct (and petitioners do not appear to dispute) that

none of the alleged sources of pollutants that petitioners

identify involve non-exempt point-source discharges.

a. The court of appeals concluded that “the exemption [for irrigated agriculture] applies to irrigation return flows that do not contain additional point source

discharges from activities unrelated to crop production.” Pet. App. 20a. That analysis reflects the best

reading of the statutory text.

The exemption states that “[t]he [EPA] Administrator shall not require a permit under this section for discharges composed entirely of return flows from irrigated agriculture, nor shall the Administrator directly

or indirectly, require any State to require such a permit.” 33 U.S.C. 1342(l)(1). Under the CWA, “the word

‘discharge’ is used consistently to refer to the release of

effluent from a point source.” Oregon Natural Desert

Ass’n v. Dombeck, 172 F.3d 1092, 1098 (9th Cir. 1998),

cert. denied, 528 U.S. 964 (1999). The Act states that

“[t]he term ‘discharge’ when used without qualification

12

includes a discharge of a pollutant.” 33 U.S.C. 1362(16).

“ ‘[D]ischarge of a pollutant,’ ” in turn, is defined as “any

addition of any pollutant to navigable waters from any

point source.” 33 U.S.C. 1362(12) (emphasis added); accord Oregon Natural Desert Ass’n v. United States Forest Serv., 550 F.3d 778, 782, 784 (9th Cir. 2008) (reaffirming that the term “discharge” is limited to “ ‘releases from point sources’ ”) (citation omitted).

It follows, then, that the irrigated-agriculture exemption applies where (as here) irrigation return flows

do not mix with any point-source discharge unrelated to

irrigated agriculture. Because the only pollutant “discharges” (i.e., point-source releases) attributable to the

Grassland Bypass Project pertain to irrigation return

flows, the Project’s discharges are “composed entirely

of return flows from irrigated agriculture,” 33 U.S.C.

1342(l)(1), and therefore qualify for the statutory exemption. Under this reading of the exemption’s text,

the exemption would not apply to any irrigation return

flow that commingles with pollutants discharged from a

point source that would otherwise require an NPDES

permit. That is so because those “discharges” are no

longer “composed entirely of return flows from irrigated agriculture,” ibid., but additionally include the

“discharge” from the other point source. The irrigatedagriculture exemption would generally cover irrigation

return flows that mix with releases from nonpoint

sources, however, since those releases are not “discharges” as defined by the statute. See 33 U.S.C.

1362(12), (16).

This interpretation, adopted by the court of appeals,

best effectuates the irrigated-agriculture exemption’s

text, including by giving the term “discharge” its statutorily defined meaning. 33 U.S.C. 1362(12)(A). Con-

13

trary to petitioners’ argument that the court’s reading

“negate[s]” the adverb “ ‘entirely,’ ” Pet. 27 (citation

omitted), the court’s reading gives full effect to that

term, which the court of appeals interpreted to mean

“wholly, completely, fully.” Pet. App. 18a (quoting Webster’s Third New International Dictionary 758 (2002)).

The court determined that, in the context of the exemption, the word “ ‘entirely’ ” means that “every discharge

within a return flow” must “be from irrigated agriculture.” Id. at 19a (emphasis added). Thus, the court correctly concluded, the “exemption applies to irrigation

return flows that do not contain additional point source

discharges from activities unrelated to crop production.” Id. at 20a.

The court of appeals’ interpretation of the irrigatedagriculture exemption also respects the statutory structure. Unlike petitioners’ proposed reading, the court’s

interpretation would not expand EPA’s permitting authority to cover nonpoint sources that otherwise fall

outside the NPDES framework. But it would require a

permit if an irrigation return flow mixes with pollutants

discharged from an unpermitted point source that otherwise would require an NPDES permit, such as outflow from an industrial site or municipal waste treatment facility. The court’s interpretation therefore

would not enable a polluter to evade responsibility under the CWA by laundering unpermitted pollutants

from NPDES-covered point sources through the

irrigated-agriculture exemption. Cf. County of Maui v.

Hawaii Wildlife Fund, 590 U.S. 165, 178-179 (2020) (rejecting interpretation that would have created “a large

and obvious loophole”).

The court of appeals’ reading also respects the balance that Congress struck in enacting the exemption.

14

Pet. App. 21a. If petitioners’ proposed interpretation

were correct, “all three of Congress’s aims” in enacting

the irrigated-agriculture exemption “would be

thwarted.” Id. at 22a. First, EPA would be tasked with

“issuing permits for an inordinate amount of irrigation

return flows.” Ibid. Second, “[f]armers reliant on surface irrigation for their crops would be disproportionately burdened with NPDES permit requirements relative to farmers blessed with abundant rainfall for their

crops.” Ibid. And third, EPA, the States, farmers, and

the courts would face the “ ‘virtually impossible’ task of

disentangling commingled pollutants.” Ibid. (citation

omitted). The court’s interpretation, by contrast, adheres to the plain text of the statute and is consistent

with the CWA’s overall structure. 1

The court of appeals correctly rejected petitioners’

contrary reading of the irrigated-agriculture exemption. Under that reading, an NPDES permit would be

required so long as any pollutant from a nonContrary to petitioners’ assertion (Pet. 25, 29-30), the decision

below is also consistent with relevant EPA regulations. Petitioners

cite (Pet. 28) 40 C.F.R. 122.2, which defines the term “ ‘discharge of

a pollutant’ ” to include “surface runoff which is collected or channeled by man.” That regulation, which relates to EPA’s municipal

and industrial stormwater program, merely means that where (for

example) an industrial site collects runoff and channels it into waters of the United States, that point-source discharge will generally

require an NPDES permit. The regulation does not alter the meaning of the irrigated-agriculture exemption, which requires a court to

identify the sources from which pollution originated to determine

whether particular releases are “discharges.” Petitioners have not

shown that EPA has any practice, let alone a longstanding one, of

interpreting that regulation to require an NPDES permit under the

circumstances presented here, where an irrigation return flow allegedly mixes with diffuse nonpoint-source pollution.

1

15

agricultural source—even pollution from nonpoint

sources that are not otherwise subject to NPDES permitting requirements—commingles with project flows.

Petitioners’ arguments in support of that approach are

unavailing.

Petitioners contend (Pet. 19) that the discharges

here are not made up “entirely” of “discharges * * * of

return flows from irrigated agriculture” because those

return flows commingle with nonpoint-source pollution

before being released to Mud Slough. Petitioners’ argument ignores the remainder of the statutory text, and

particularly the CWA’s definition of the term “discharge.” See 33 U.S.C. 1362(12). Although not all of the

pollutants released to Mud Slough result from irrigation return flows, all of the discharges (i.e., point-source

releases) attributable to the Grassland Bypass Project

fall within the Section 1342(l)(1) exemption.

Petitioners’ approach would also undermine the

broader structure of the CWA. Irrigation return flows

are exempt from CWA permitting requirements under

Section 1342(l)(1), while nonpoint-source releases are

not subject to those requirements in the first place because they are not “discharge[s] of a pollutant” as the

CWA defines that term. See Pet. App. 4a (explaining

that the CWA’s distinction between point and nonpoint

sources “is an organizational paradigm of the [Act]”)

(quoting Oregon Natural Desert Ass’n., 550 F.3d at

780). Under petitioners’ reading of the statute, commingling the two types of releases triggers the CWA’s

permitting requirements, even though neither type of

release standing alone is subject to those requirements.

That interpretation would contravene the Act’s structure and purpose. See, e.g., City and Cnty. of San Francisco v. EPA, 604 U.S. 334, 350 (2025) (“It is a ‘funda-

16

mental canon of statutory construction that the words

of a statute must be read in their context and with a view

to their place in the overall statutory scheme.’ ”) (quoting Utility Air Regulatory Grp. v. EPA, 573 U.S. 302,

320 (2014)).

Indeed, if petitioners’ reading were correct, the inevitable presence of nonpoint-source pollutants would

effectively negate the exemption for irrigated agriculture, even though the non-point source pollutants themselves fall outside the NPDES permitting program. Petitioners conceded below that “some amount of nonpoint

source pollution unrelated to irrigated agriculture will

inevitably commingle with irrigation return flows.” Pet.

App. 22a. That concession logically implies that petitioners’ own interpretation would “sap the interpreted

provision of all practical significance.” Id. at 23a; see

id. at 22a-23a (explaining that, under petitioners’ interpretation, commingling with “windblown dust” would

render an irrigation return flow ineligible for the irrigated-agriculture exemption).2 Because “the benefit of

[the irrigated-agriculture exemption] would be eviscerated” if petitioners’ reading were correct, it is “exceedingly hard to reconcile” that reading with the statutory

design. San Francisco, 604 U.S. at 351; see Ysleta del

Sur Pueblo v. Texas, 596 U.S. 685, 698-699 (2022) (reiterating the “longstanding canon[] of statutory construction” that courts “must normally seek to construe ConPetitioners dismiss the Ninth Circuit’s discussion of windblown

dust as “invent[ing] a ‘straw man,’ ” arguing that petitioners have

not cited windblown dust “as a basis for requiring an NPDES permit.” Pet. 38 (capitalization omitted). But petitioners do not dispute

that their proposed interpretation of the CWA’s text would logically

extend to pollution from sources as diffuse as windblown dust,

where that pollution commingles with agricultural return flows.

2

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gress’s work ‘so that effect is given to all provisions, so

that no part will be inoperative or superfluous, void or

insignificant’ ”) (citation omitted).

In addition to rendering the irrigated-agriculture exemption a practical nullity, petitioners’ interpretation

would expand EPA’s permitting authority beyond what

Congress has authorized. EPA lacks regulatory authority over irrigation return flows because 33 U.S.C.

1342(l)(1) exempts those flows from CWA permitting

requirements, and it lacks regulatory authority over

nonpoint-source pollution because such pollution does

not involve a CWA “discharge.” See Maui, 590 U.S. at

175. There is no sound reason to construe the Act as

giving the agency regulatory authority when the two

types of releases are commingled.

b. The legislative history of the irrigatedagriculture exemption also supports the Ninth Circuit’s

interpretation. The Senate Report states that “[t]he

word ‘entirely’ was intended to limit the exception to

only those flows which do not contain additional discharges from activities unrelated to crop production.”

Pet. App. 19a (quoting Senate Report 35) (brackets in

original). Because “the [CWA] term ‘discharge’ necessarily presumes a point source,” the court of appeals

read that language to indicate that “the exemption applies to irrigation return flows that do not contain additional point source discharges from activities unrelated

to crop production.” Id. at 20a. That description covers

the circumstances here, since the only “point source discharges” in the pollutant releases were the agricultural

discharges that are exempt from CWA permitting requirements.

Petitioners criticize (Pet. 32-35) the court of appeals

for “selectively constru[ing] a phrase in the committee

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report in isolation,” but their invocation of additional

snippets of legislative history does little to advance

their argument. The first paragraph they quote explains that all agricultural runoff sources, “regardless

of the manner in which the flow was applied to the agricultural lands, * * * are more appropriately treated under” Section 208 of the Act. Pet. App. 9a (quoting Senate Report 35). Section 208 covers “areawide waste

treatment management plans”—not NPDES permitting. 33 U.S.C. 1288(a). Nor do petitioners offer any

persuasive argument as to the second paragraph, which

specifies that the irrigation exception is limited to

“those flows which do not contain additional discharges

from activities unrelated to crop production,” and that

“the committee did not intend to differentiate among return flows based upon their content.” Pet. 33 (citing

Pet. App. 11a-12a, 21a). Rather, those statements underscore that Congress did not mean for return flows to

lose their exemption simply because their “content” includes some commingled, nonpoint source pollutants—

instead, the exemption is crafted to ensure it cannot be

used as a vehicle for “additional discharges.” And while

petitioners contend that the Senate Report uses “the

term ‘discharge’ in its ‘every day meaning,’ ” Pet. 36 (citation omitted) the Court may properly assume that the

report’s drafters “used key statutory terms as they

were defined by the statute,” Pet. App. 20a.

2. Petitioners contend (Pet. 23-30, 31-32) that review

is warranted because the decision below conflicts with

decisions of this Court and other courts of appeals. That

argument is incorrect.

a. Petitioners assert (Pet. 23-27) that the decision

below conflicts with this Court’s decision in South Florida Water Management District v. Miccosukee Tribe of

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Indians, 541 U.S. 95 (2004). That is incorrect. Miccosukee involved a Florida facility that pumped polluted

water from a canal to navigable water. Id. at 100-101.

The defendants argued that the pump did not require

an NPDES permit because the pump itself did not generate the discharged pollutants, which instead came to

the canal from other sources. Id. at 104. This Court

disagreed, holding that “a point source need not be the

original source of the pollutant; it need only convey the

pollutant to ‘navigable waters.’ ” Id. at 105.

Petitioners read (Pet. 24-26) Miccosukee to mean

that an NPDES permit is required whenever a pollutant is discharged through a point source, no matter its

origin. But as the court below recognized, Miccosukee

did not involve the irrigated-agriculture exemption in

Section 1342(l)(1). Pet. App. 25a. Rather, Miccosukee

makes clear that generally, “a point source that conveys

a pollutant—even if it does not generate that

pollutant—is subject to the NPDES permitting

scheme.” Ibid. (citing Miccosukee, 541 U.S. at 105).

The irrigated-agriculture exemption, however, creates

a carveout from that general rule.

Petitioners are likewise wrong in contending (Pet.

27-28) that the decision below conflicts with Maui. In

Maui, this Court held that an addition of a pollutant

“from” a point source “to” navigable waters may require an NPDES permit if that addition is “the functional equivalent of a direct discharge,” even if the pollutant passes through groundwater en route from the

point source to navigable waters. 590 U.S. at 183 (emphasis omitted).

Maui does not address, let alone answer, the question presented here. Petitioners suggest (Pet. 28) that

the court of appeals’ decision conflicts with “longstand-

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ing EPA regulation” and “invites evasion of the

NPDES” permitting requirements, contrary to the

Maui Court’s interpretive choice not to “open a loophole allowing easy evasion of the statutory provision’s

basic purposes,” 590 U.S. at 180. But as explained

above, the court of appeals’ decision is consistent with

EPA regulations, and with the purposes of both the

CWA as a whole and the irrigated-agriculture exemption in particular. See pp. 13-16 & n.1, supra.

b. Petitioners assert (Pet. 30-31) that the decision

below conflicts with two decisions of other courts of appeals. But petitioners do not identify any decision that

has adopted their proposed interpretation, and they do

not explain how either of the decisions they cite would

have led to a different result here. In fact, both decisions are entirely consistent with the decision below.

Petitioners rely in part (Pet. 30) on the Eleventh Circuit’s decision in Fishermen Against the Destruction of

the Environment, Inc. v. Closter Farms, Inc., 300 F.3d

1294 (2002). Consistent with the decision below, Closter

Farms held that irrigation return flows do not require

an NPDES permit merely because they mix with pollutants, like those from nonpoint sources, that are independently excluded from the NPDES program. Id. at

1298. The Eleventh Circuit observed (with respect to a

neighboring waste-treatment plant) that “[a]ny pollutants that originated in the non-agricultural properties

adjacent to Closter Farms obviously do not fall within

the agricultural exemptions.” Ibid. But the court had

no occasion to define the circumstances in which nonagricultural contributions might defeat the exemption,

since the court “conclude[d] that there [wa]s insufficient

evidence in the record that Closter Farms discharged

any non-agricultural pollutants.” Ibid.

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Petitioners’ reliance (Pet. 31) on the Tenth Circuit’s

decision in Sierra Club v. El Paso Gold Mines, Inc., 421

F.3d 1133 (2005), cert. denied, 547 U.S. 1065 (2006), is

also misplaced. The disputed question in El Paso Gold

Mines concerned “whether Congress intended successor owners of a point source to be subject to Section

402’s NPDES permitting requirements.” Id. at 1142.

Petitioners’ sole citation to El Paso Gold Mines is to an

explanatory parenthetical that describes the Ninth Circuit’s holding in Committee to Save Mokelumne River

v. East Bay Municipal Utility District, 13 F.3d 305 (9th

Cir. 1993), cert. denied, 513 U.S. 873 (1994)—a case

that, like El Paso Gold Mines, did not involve the

irrigated-agriculture exemption.

3. Even if the Court granted a writ of certiorari and

reversed the court of appeals’ judgment on the question

presented here, the Grassland Bypass Project would

not require an NPDES permit. Petitioners assert (Pet.

19) that “all parties agree” that the San Luis Drain is a

point source and that discharges from the Drain to Mud

Slough are discharges of pollutants to a navigable water

that would require an NPDES permit if they are not

“ ‘composed entirely of return flows from irrigated agriculture.’ ” But in fact, although the courts below did

not reach the question, see Pet. App. 16a n.2, the government argued below that NPDES permitting is not

required here for an additional reason: flows from the

San Luis Drain into Mud Slough are “[d]ischarges from

a water transfer” that “conveys or connects waters of

the United States,” 40 C.F.R. 122.3(i), and are thus exempt from the permitting requirement. See Gov’t C.A.

Br. 46-47. That independent ground on which the decision below could ultimately be upheld provides an additional reason to deny review here.

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CONCLUSION

The petition for a writ of certiorari should be denied.

Respectfully submitted.

D. JOHN SAUER

Solicitor General

ADAM R.F. GUSTAFSON

Principal Deputy Assistant

Attorney General

ROBERT N. STANDER

Deputy Assistant

Attorney General

ROBERT P. STOCKMAN

ANGELA N. ELLIS

Attorneys

MAY 2026