          United States Court of Appeals
                       For the First Circuit

No. 00-2028

                           UNITED STATES,

                       Plaintiff, Appellant,

                                 v.

              MASSACHUSETTS WATER RESOURCES AUTHORITY;
                  METROPOLITAN DISTRICT COMMISSION,

                       Defendants, Appellees.


         APPEAL FROM THE UNITED STATES DISTRICT COURT

                 FOR THE DISTRICT OF MASSACHUSETTS

        [Hon. Richard G. Stearns, U.S. District Judge]


                               Before

                         Boudin, Chief Judge,
                      Torruella, Circuit Judge,
                  and Stahl, Senior Circuit Judge.



     Robert H. Oakley, Attorney, with whom Greer S. Goldman,
Attorney, Brian Donohue, Attorney, Steve Keller, Attorney, Scott
Bauer, Attorney, Lois J. Schiffer, Assistant Attorney General,
George B. Henderson, II, Assistant United States Attorney, and
Donald K. Stern, United States Attorney, were on brief, for
appellee.
     John M. Stevens, Jonathan M. Ettinger, Jack W. Pirozzolo,
Foley, Hoag & Eliot LLP, and Nancy C. Kurtz, were on brief, for
appellant.
     Alexandra D. Dawson on brief for Nashua River Watershed
Association, Inc., Massachusetts Audubon Society, Inc., Friends
of Quabbin, Inc., Water Supply Citizens Advisory Committee, and
Rutherford H. Platt, amici curiae.
                                 July 16, 2001




           STAHL, Senior Circuit Judge.             The federal Safe Water

Drinking    Act    (SDWA    or    Act)   authorizes     the   Environmental

Protection Agency (EPA) to prescribe criteria specifying when

public water systems are "required" to install a filtration

system.    The Act also provides, however, that courts asked to

issue an injunction enforcing the EPA's filtration standards

"may enter . . . such judgment as protection of public health

may require . . . ."         This appeal requires us to resolve the

apparent tension between these two provisions.            Specifically, we

must   decide     whether   the   SDWA   requires    courts   to    order   the

statutorily prescribed remedy of filtration for violations of

its    substantive    provisions     and    the   regulations      promulgated

thereunder, or, alternatively, whether courts have the authority

in SDWA cases not to order such remedies in those instances

where the equities are found to counsel forbearance.                Suffice it

to say, we are not faced with an imminent threat to the public

health in this case; none has been alleged by the United States

on appeal.        Rather, this dispute mainly has to do with the

operation of an EPA rule that purports to oblige public water

systems to install a filtration system if they fail to meet

certain regulatory standards by a prescribed deadline -- an

                                      -2-
obligation that extends into the future indefinitely, and that

does not account for the present and future safety of the

system's drinking water.

          Based on our reading of the Act, we find that the

district court acted within its discretion by declining to order

that the Massachusetts Water Resources Authority (MWRA) install

a filtration system.     We therefore affirm its judgment.

                            I. Background

          The facts surrounding this controversy are laid out in

extensive detail in the district court's two written opinions,

United States v. Mass. Water Res. Auth., 48 F. Supp. 2d 65 (D.

Mass. 1999) (MWRA I) (holding that district court had equitable

discretion not to order filtration remedy for SDWA violation);

United States v. Mass. Water Res. Auth., 97 F. Supp. 2d 155 (D.

Mass. 2000) (MWRA II) (declining to order filtration remedy

based on equities of the case), and so we confine our recitation

to those facts bearing specifically upon this appeal.

A.        Regulatory Regime

          In 1974, Congress, legislating in an area that had

previously received scant attention under federal law, passed

the Safe Drinking Water Act, Pub. L. No. 93-523, 88 Stat. 1660

(codified as amended at 42 U.S.C. §§ 300f to 300j-8 (1991 &

Supp. 2000)), with the basic goal of protecting the purity of

the   drinking   water   provided    by   the   nation's   public   water


                                    -3-
systems.1      To this end, the Act vests authority in the EPA to

promulgate and enforce two types of water-purity standards:

maximum contaminant levels (MCLs) and treatment techniques.

Under    the    Act,    the   EPA   is    to     regulate    the   majority   of

contaminants in drinking water by formulating MCLs -- numerical

standards that represent the agency's expert determination as to

"the level at which no known or anticipated adverse effects on

the health of persons occur and which allows an adequate margin

of safety."      Id. § 300g-1(b)(4)(A).              By contrast, the EPA only

may require the implementation of specific treatment techniques,

consisting of engineering or design standards, in instances

where the Administrator deems it infeasible, for technological

or economic reasons, to ascertain an acceptable concentration

level    for    the    contaminant.            Id.   §   300g-1(b)(7)(A).     As

originally written, the SDWA did not specifically require that

the EPA develop either MCLs or treatment techniques with respect

to any particular contaminant.                 As a result, between 1974 and

1986 the EPA promulgated regulations concerning only twenty-

three drinking water contaminants, and of these pollutants, all

but one had previously been subject to regulations issued by the



     1Under the SDWA, the term "public water system" encompasses
any "system for the provision to the public of piped water for
human   consumption   through   pipes   or   other   constructed
conveyances, if such system has at least fifteen service
connections   or   regularly   serves   at   least   twenty-five
individuals." 42 U.S.C. § 300f(4)(A).

                                         -4-
Public Health Service.          James Kavanaugh, Comment, To Filter or

Not to Filter: A Discussion and Analysis of the Massachusetts

Filtration Conflict in the Context of the Safe Drinking Water

Act, 26 B.C. Envtl. Aff. L. Rev. 809, 814 (1999).

            In 1986, however, Congress amended the Act so as to

require (rather than merely to authorize) the EPA to develop

treatment    regimes      with       respect      to   scores       of    additional

contaminants,      and   to    require     that    violations       of    the   Act's

substantive provisions and the rules promulgated thereunder be

prosecuted by either the states or the EPA.                      Id. at 814-15.

These amendments were prompted by the EPA's perceived laxity in

issuing rules under and enforcing the SDWA, see 2 William H.

Rodgers, Jr., Environmental Law, § 4.20A, at 152 (Supp. 2001)

("In making these changes Congress [was] convinced that it

[could]    control   prosecutorial         options      [under      the    SDWA]   by

replacing     'mays'          with     'shalls'        in     its        enforcement

instructions."), and by anecdotal evidence suggesting a rise in

biological and chemical contamination of public water supplies

throughout the United States.

            Through these amendments, Congress also expressed a

growing preference for the employment of specific treatment

techniques, as opposed to the promulgation of MCLs, to solve the

problem of contaminated drinking water.                      This policy shift

occurred      as   the    result      of   mounting         scientific      evidence


                                        -5-
demonstrating      the   efficacy   of    filtration    and    disinfection

techniques    in     reducing   waterborne      viral        and   bacterial

contamination.      Id., § 4.20A, at 151.        Reflecting this view,

Congress specifically required that disinfection be employed by

all public water systems to reduce the live quantities of those

pathogens, except for systems specifically eligible to receive

a variance from the EPA.        42 U.S.C. § 300g-1(b)(8).           Congress

also changed the SDWA to provide for filtration of public water

systems.   Id. § 300g-1(b)(7)(C)(i).        But unlike the disinfection

mandate, filtration was not directly imposed upon all public

water systems; rather, Congress provided that the EPA "shall

propose and promulgate . . . criteria under which filtration .

. . is required as a treatment technique for public water

systems supplied by surface water sources."             Id.

           On June 29, 1989, pursuant to this statutory command,

the EPA promulgated the Surface Water Treatment Rule (SWTR or

Rule), 40 C.F.R. §§ 141.70-.73.            The SWTR focuses on public

systems that draw their water in some measure from above-ground

sources.   It seeks to reduce the risk of illness from waterborne

pathogens to one yearly occurrence per 10,000 consumers of water

from covered public systems.        Drinking Water; National Primary

Drinking Water Regulations; Filtration, Disinfection; Turbidity,

Giardia    lamblia,      Viruses,   Legionella,        and    Heterotrophic

Bacteria, 54 Fed. Reg. 27,486, 27,490 (June 29, 1989) (codified


                                    -6-
at 40 C.F.R. pts. 141 and 142).     Specifically, the Rule requires

that all public systems achieve a three-log (99.9 percent)

reduction in the Giardia lamblia parasite and a four-log (99.99

percent)   reduction   in   viral     contamination,    40   C.F.R.   §

141.70(a); establishes a mandatory disinfection requirement for

all systems, subject to the granting of variances by the EPA,

id. § 141.72; specifies the standards according to which all

filtration systems must be constructed, id. § 141.73; and sets

out eleven "avoidance criteria" for levels of certain waterborne

contaminants that all public water systems hoping to forego

filtration must satisfy, id. §§ 141.71(a)-(b).2        On December 16,

1998, in response to an additional amendment to the SDWA passed

in 1996, see 42 U.S.C. § 300g-1(b)(2)(C) (Supp. 2000), the EPA

promulgated the Interim Enhanced Surface Water Treatment Rule

(IESWTR), 40 C.F.R. §§ 141.170-.173, which requires that public

water systems implement treatment techniques with respect to the

protozoan Cryptosporidium larvum, whose presence in public water

systems has risen in the past two decades and which has been

demonstrated to cause significant health problems, particularly

for those individuals with weakened immune systems.          This Rule,

whose requirements must be met by public water systems by the



    2 Of the eleven "avoidance criteria," two relate to source
water quality, four concern minimum levels of disinfection, and
five involve system-specific watershed protection and operations
requirements. 40 C.F.R. §§ 141.71(a)-(b).

                                -7-
end   of    2001,   requires     a    two-log       (99    percent)    reduction     in

Cryptosporidium by all water systems that employ filtration, and

an extension of watershed controls to cover Cryptosporidium for

all unfiltered water systems.             Id. § 141.173(b).

              The   filtration       mandate       in   the   SWTR    is   written   in

unequivocal -- and, in the context of federal regulations,

unusually broad -- terms.               Tracking the pertinent deadlines

embodied in the Act, the Rule requires that public water systems

not meeting all of the avoidance criteria by December 30, 1991,

"must provide treatment consisting of both disinfection . . .

and filtration" by June 29, 1993, or, if the violation occurs

after December 30, 1991, within eighteen months of the date that

the violation has been established.                       Id. § 141.73 (emphasis

added).       Moreover, filtration decisions under the Rule are

final, in that the Rule provides no mechanism by which a public

water      system   may   petition     for     a    reopening    of    a   filtration

determination.       See id.     The upshot of this regulatory scheme is

that once a public water system has been found to have violated

one of the avoidance criteria, it forever remains subject to an

enforcement suit requesting the installation of a filtration

system.3      This result obtains no matter how safe the system's


      3
     The SDWA contains no statute of limitations, and "an action
on behalf of the United States in its governmental capacity . .
. is subject to no time limitation, in the absence of
congressional enactment clearly imposing it." E.I. Dupont de
Nemours & Co. v. Davis, 264 U.S. 456, 462 (1924); cf. United

                                        -8-
drinking water is following the violation, and regardless of how

diligent the water system is in remedying the problems that

caused the avoidance-criteria failures in the first place.

             Despite the mandatory nature of the Rule regarding the

need for filtration, the EPA cannot compel a violator to comply

with its provisions merely by issuing its own enforcement order.4

Rather, the agency must bring suit in federal district court to

request that a remedy provided for elsewhere in the Act, such as

the construction of a filtration facility, be ordered.                See 42

U.S.C. § 300g-3(b) ("The [EPA] Administrator may bring a civil

action   .    .   .     to    require   compliance   with   any   applicable

requirement . . . .").            And the Act provides that in deciding

such suits, courts "may enter . . . such judgment as protection

of public health may require, taking into consideration the time

necessary to comply and the availability of alternative water

supplies."        Id.        The language of this judicial-enforcement




States v. Telluride Co., 146 F.3d 1241 (10th Cir. 1998)
(refusing to apply general five-year statute of limitations for
civil actions by the United States to enforcement suits under
Clean Water Act because statute of limitations does not cover
claims for equitable relief).
     4
     Without resort to judicial process, however, the EPA may
impose a civil penalty not exceeding $25,000 per day for
violations of administrative orders.      42 U.S.C. § 300g-
3(g)(3)(A).

                                        -9-
provision has remained untouched, in pertinent part, since the

Act's original passage in 1974.5

               As a practical matter, much of the burden of enforcing

the     SDWA    falls    on    the    shoulders         of   state    environmental

authorities,        such       as     the     Massachusetts          Department    of

Environmental Protection (DEP).                    This is so because, under the

Act, state agencies that adopt drinking water regulations deemed

by the EPA to be at least as stringent as its own may assume

primary responsibility for identifying violations of the EPA's

regulations and for enforcing the filtration requirement against

the violators.       Id. § 300g-2(a).              The Act provides that within

thirty months of the promulgation of the SWTR, those state

agencies that participate in SDWA enforcement must identify the

water     systems       that    are     required        to   install     filtration

facilities.6        Id.    §    300g-1(b)(7)(C)(iii).                Although   state


      5
      In 1986, Congress amended § 300g-3(b) by increasing the
maximum available civil penalties under the Act from $5,000 per
day to $25,000 per day, and by eliminating the requirement that
an SDWA violation must be "willful" in order to be the basis for
civil penalties.   And in 1996, Congress substituted the term
"any applicable requirement" for "a national primary drinking
water regulation" to reflect the semantic changes effected by
the 1986 amendments to the Act.
      6
     In 1996 Congress once again amended the SDWA to permit the
EPA to excuse from filtration certain public water systems that
draw water from uninhabited, undeveloped watersheds over which
the public water system has "consolidated" (i.e., sole)
ownership of the surrounding lands.         42 U.S.C. § 300g-
1(b)(7)(C)(v).   The MWRA, however, does not qualify to take
advantage of the exception because it does not have consolidated
ownership of the land surrounding its reservoirs.

                                            -10-
authorities are afforded the first opportunity under this system

to make formal determinations regarding the need for filtration,

the EPA must bring its own enforcement action in the absence of

such a state determination, provided the state agency and the

violating water system are given thirty days' notice and an

opportunity      for     consultation       with    the     EPA.        Id.    §   300g-

3(a)(1)(B).

              On June 28, 1993, after the DEP adopted drinking water

regulations requiring filtration whenever a public water system

fails to satisfy the SWTR's avoidance criteria, see Mass. Regs.

Code   tit.    310,    §§     22.20A(2),    (4),     the    EPA    granted       primary

enforcement      responsibility         to     the     DEP.             Public     Water

Supervision: Program Revision for Commonwealth of Massachusetts,

58 Fed. Reg. 34,583 (June 28, 1993).

B.            The MWRA

              Established in 1984, the MWRA owns and operates the

public water system that provides most of the drinking water for

the city of Boston and surrounding communities.                               Its water

system serves approximately two million customers in over forty

Massachusetts         cities    and    towns.         The     MWRA       has     primary

responsibility for treating its drinking water and transporting

that water from its reservoirs to the distribution systems of

the local communities it serves.                   In providing water to its

customers,      the    MWRA    works   in    tandem    with       the    Metropolitan


                                       -11-
District    Commission    (MDC),   an   organization      responsible   for

monitoring the quality of water in the MWRA system and managing

the watersheds surrounding the principal sources of the MWRA's

water supply.7

           The MWRA's water system, which was originally designed

by the Massachusetts Board of Health in the late nineteenth

century, consists of three large reservoirs connected by a

network of 265 miles of water mains and 130 miles of aqueducts.

Feeding into the system are two above-ground bodies of water in

central Massachusetts, the Quabbin and Wachusett Reservoirs,

which collectively contain approximately 475 billion gallons of

water.     The Quabbin Reservoir, by far the larger of the two

bodies of water, empties into the Wachusett Reservoir.             The MWRA

draws water from the eastern edge of the Wachusett Reservoir at

the Cosgrove Intake, and transports the water through a series

of   tunnels   and    aqueducts    until   it   reaches    the    Norumbega

Reservoir,     an     intermediate      storage    basin     in     Weston,

Massachusetts.       From there the water travels in all directions,

through a complex, 6,700-mile web of additional tunnels, pipes,



     7Even though the MDC was named as a defendant in this
lawsuit by virtue of its ownership and control of many of the
water-treatment facilities in question, the United States did
not allege in the district court, nor does it allege before this
court, that the MDC violated any laws with respect to this
controversy.   We therefore refer to the appellees throughout
this opinion as "the MWRA," except where it is necessary to
distinguish between the two entities.

                                   -12-
and aqueducts, ultimately connecting to the local distribution

centers in the various communities that the MWRA serves.

           For    some   time,     the   MWRA    has   employed     two    basic

techniques to treat its drinking water: disinfection, used to

kill live contaminants, and corrosion control, used to minimize

the leaching of metals (such as lead) into the water from the

antiquated pipes through which the water travels before reaching

the taps of consumers.        The water supply undergoes disinfection

as it enters the distribution system through the Cosgrove Intake

and again as it departs the primary distribution system at the

Norumbega Reservoir.         In the mid-1990s, the MWRA replaced the

chloramine disinfection treatment it used at the Cosgrove Intake

with an alternative disinfection treatment of ozonation, which

consists   of    the   injection    of   ozone    bubbles   into    the    water

supply.8   According to the MWRA, ozonation kills a wider range

of pathogens than do the traditional disinfection techniques,

and the process        provides the added benefit of improving the

taste    and    coloration    of    treated      water.     While    the     EPA

acknowledges the general effectiveness of ozonation, the agency

has taken the position that it is not, by itself, an effective

substitute for filtration.




     8
     The MWRA continues to use chloramine disinfection at the
Norumbega Reservoir site.

                                     -13-
         In the months following the EPA's formulation of the

SWTR, the MWRA determined that it would not be able to fulfill

all of the avoidance criteria by the December 30, 1991 deadline.

In particular, the MWRA concluded that occasional spikes in

fecal coliform bacteria that had been measured in the Wachusett

Reservoir in the late 1980s and early 1990s, a phenomenon later

attributed to the seasonal roosting habits of gulls, could not

be controlled by that date.   Consequently, the MWRA did not seek

a formal avoidance determination from the DEP.     On January 24,

1992, the DEP notified the MWRA that, according to the terms of

the SDWA, it would be required to install a filtration system by

June 30, 1993.

         By early 1993, after it became clear that the MWRA

could not design and install a filtration system before June

1993, the MWRA, the MDC, and the DEP entered into negotiations

on an administrative consent order (ACO) to govern the MWRA's

compliance with the SWTR.     Rather than requiring the immediate

installation of a filtration system, the ACO established a

"dual-track" approach for compliance.     Under this scheme, the

MWRA was permitted in the short term to employ a treatment

regime consisting of disinfection, ozonation, and covered water

storage facilities, while at the same time embarking upon an

aggressive   watershed   protection   plan   for   the   Wachusett

Reservoir.   The MWRA also was expected to continue its campaign


                               -14-
of "gull harassment," a policy meant to scare away birds so as

to prevent them from defecating in the reservoir.                 If the MWRA

properly   pursued    these    endeavors,     it    would    be    given   the

opportunity under the ACO to petition, on or before August 3,

1998, for a "reopener" establishing that the avoidance criteria

had been met and that filtration was not required.9               At the same

time as it pursued the watershed protection strategy, however,

the MWRA also was obligated to plan the siting and design of the

filtration facility that it would be required to install in the

event that it could not establish its eligibility for filtration

avoidance by August 1998.      The MWRA, the MDC, and the DEP signed

the ACO on June 11, 1993.

           Given that the ACO essentially excused the MWRA from

complying with a key component of the SWTR, it seems rather

surprising at first blush that the EPA, while aware of the

negotiations   over    the    ACO,    did   not    attempt   to    block   its

implementation.       In fact, despite having written the Rule's

filtration requirement in mandatory terms (and despite the Act's

mandate that there be filtration when the Rule's standards were

not met), the EPA's actual practice has been to enforce the

filtration mandate with less than the unswerving rigor that the

statutory and regulatory language would seem to require.                   For


    9A subsequent amendment to the ACO pushed back to October
31, 1998, the MWRA's target date for demonstrating compliance
with the avoidance criteria.

                                     -15-
instance, notwithstanding the filtration command in the SWTR, in

1992 the EPA issued an internal guidance memorandum that gave

state enforcement authorities the discretion to postpone final

filtration determinations if a water system is able to prove

that    it     could    later   meet     the   avoidance       criteria      through

intermediate      measures.       And     while    the   EPA    never      expressly

acquiesced       in    the   provision    in     the   ACO    that    created    the

potential for the MWRA to eventually avoid filtration (in fact,

it stated in a letter to the parties to the ACO that it reserved

the right to bring an enforcement action at a later date), it

did promise the DEP and the MWRA that it would abstain, at least

in the short term, from filing its own enforcement suit once the

ACO was executed.

             Consistent with this approach, the EPA worked closely

with the MWRA in its implementation of both compliance tracks in

the    three    years     following     the    signing   of     the   ACO.      This

assistance included the agency's advice on steps to be taken by

the MWRA to satisfy the avoidance criteria.                    In November 1996,

John DeVillars, the EPA Regional Administrator, wrote a letter

to the MWRA in which he generally commended the MWRA on its

progress but cautioned that "in order to avoid filtration, more

still needs to be done"         (emphasis added).          At least through the

end of 1996, this statement epitomized the EPA's deliberately

ambiguous       posture      vis-à-vis     the    MWRA's       need   to     install


                                        -16-
filtration: the agency generally supported the MWRA's efforts to

achieve compliance with the avoidance criteria by alternative

means, even as it held out the threat of suing to require

filtration if it later found itself unsatisfied with the MWRA's

performance.

          In early 1997, after the MWRA acknowledged that it

could not meet several interim deadlines contained in the ACO,

the EPA began to lose patience, and the working relationship

between the MWRA and the EPA quickly deteriorated.           In two

letters to the MWRA dated January 8, 1997, and May 15, 1997, the

EPA Regional Administrator expressed "extreme concern" for the

MWRA's failure to produce adequate design plans for a Wachusett

Reservoir filtration facility, and reminded the MWRA that it was

still in technical violation of the SWTR for its failure to

install a filtration system back in 1993.     The EPA's displeasure

with the MWRA's approach was only exacerbated by a September 18,

1997 agreement between the DEP and the MWRA that amended the ACO

to delay the completion of the design of the filtration plant

until January 31, 2002.

          On October 1, 1997, over a year before the MWRA was to

have   submitted   its    petition    to   reopen   the   filtration

determination, the MWRA and the MDC filed with the DEP an early

"Request for Review and Revision of DEP Determination that

Filtration is Required for Wachusett Reservoir."      This document


                               -17-
requested that the MWRA be excused from further pursuing the

filtration track by the end of 1997 if it could establish

prospective compliance with the SWTR's avoidance criteria.              The

EPA, which was not consulted by the MWRA prior to the filing of

this request, responded critically upon learning of it.               In a

December 9, 1997 letter to the MWRA, the MDC, and the DEP, the

EPA Regional Administrator revealed that he had asked the U.S.

Department of Justice to bring an SDWA enforcement action to

require "filtration . . . [and] measures to enhance protection

of the Wachusett reservoirs . . . according to a clear, binding

and expeditious schedule."       Such legal action was necessary, in

his   opinion,   because   the   MWRA   "did   not   meet   the   avoidance

criteria in 1991, has not met them to this day, and will not

meet them by next summer, either."

           Three days after the EPA Regional Administrator sent

this letter, the DEP issued a noncommittal response to the

MWRA's request to forego filtration.           While refusing to allow

work on the filtration track to be terminated in light of the

MWRA's acknowledgment that it could not meet the avoidance

criteria regarding Giardia, viruses, and total coliform counts

by the end of 1997, the DEP did grant the MWRA until October 31,

1998, or nearly three months later than allowed by the ACO, to

reapply for a filtration waiver.        Accepting that invitation, the

MWRA submitted a follow-up request to the DEP on October 30,


                                  -18-
1998.    In that request, the MWRA sought permission to treat its

water using ozonation and chloramine disinfection only.                          The

MWRA also proposed that the savings realized from not installing

a filtration facility be spent on a pipeline replacement plan

and stepped-up monitoring program.                On November 13, 1998, the

DEP formally approved the request, finding that the MWRA had

come into compliance with all of the SWTR's avoidance criteria

and concluding that the MWRA had developed satisfactory plans

for improving the quality of its water.                      The DEP's action

effectively excused the MWRA from having to install a filtration

system for the time being; however, the approval made clear that

any future violation of any of the avoidance criteria would

result in revocation of the waiver and reimposition of the

filtration requirement.

C.          The Proceedings Below

            Meanwhile, on February 12, 1998, the United States had

filed the instant SDWA lawsuit on behalf of the EPA.                             The

lawsuit sought an injunction ordering the MWRA to comply with

the filtration requirement set out in the Act and the Rule.                      The

district     court,        while    permitting    some     initial      discovery,

effectively        stayed     the    case   for   nearly     a   full     year    in

anticipation of the DEP's disposition of the MWRA's filtration-

waiver request.        Once the DEP approved the request, the United

States     moved     for     summary    judgment,    citing      uncontradicted


                                        -19-
evidence of the MWRA's past failures to meet the avoidance

criteria and its continued refusal to install a filtration

system.          Its position was augmented by the MWRA's acknowledgment

that,       in    January   1999,    it   had    failed   to   meet   one    of   the

avoidance criteria at the Wachusett Reservoir -- in this case,

the standard relating to fecal coliform concentration.10                     The EPA

subsequently asked the DEP to revoke the MWRA's filtration

waiver based on this violation, but the DEP declined to do so.

Since the January 1999 avoidance-criteria failure, the MWRA's

record of providing safe drinking water has been unblemished.

                 On May 3, 1999, the district court ruled on the United

States's motion for summary judgment.                 While noting the DEP's

November 1998 finding that the MWRA had come into compliance

with     all       the   avoidance    criteria      and   opining     that    "this

conclusion might have been conclusive of the litigation," the

court found that the           MWRA's January 1999 violation "entitles

the EPA to a judicial declaration that the MWRA is liable under



       10
      The MWRA asserts that the January 1999 fecal coliform
failure was illusory, in that the relevant water samples barely
missed meeting the acceptable levels of bacterial colonies and
that the testing during that period was conducted at tolerance
levels and frequencies far more rigorous than those required by
the SWTR and other EPA guidelines. The district court noted,
however, that the MWRA failed to raise the testing-technique
issue in opposition to the United States's motion for partial
summary judgment.      MWRA II, 97 F. Supp. 2d at 176.
Consequently, it found the testing method used by the MWRA in
January 1999 to be "a fact of no legal significance." Id. at
189.

                                          -20-
the SDWA for injunctive relief and civil penalties."               MWRA I, 48

F. Supp. 2d at 70.

           The district court went on to hold, however, that,

based on the principle that the discretion of courts to fashion

equitable remedies as appropriate may only be circumvented by a

"clear legislative command," the court retained the discretion

to determine the type of relief that should be granted.                  Id. at

71 (citing Weinberger v. Romero-Barcelo, 456 U.S. 305, 313

(1982)).        While   acknowledging        a   statement   in    the    Act's

legislative history to the effect that courts shall not use

"traditional balancing principles used by equity courts" in

ruling on SDWA suits, id. (quoting H.R. Rep. No. 93-1185 (1974),

reprinted in 1974 U.S.C.C.A.N. 6454, 6476), the court determined

that the judicial-enforcement provision of the Act contained

language "descriptive of the traditional powers of a court of

chancery" and that the statute did not "impos[e] the same narrow

mandate" on courts to enforce violations of its substantive

provisions that it placed on the EPA to promulgate rules.                   Id.

at 71.     In the final analysis, the court discerned no clear

command    that     courts     "limit       [themselves]     to    mechanical

enforcement of EPA compliance orders," id., although it did find

a "presumption expressed by Congress in the SDWA that filtration

will   almost    always   be   the   preferred      remedy   for   a[n]    SWTR

violation."     Id. at 72.


                                     -21-
            Having   determined       that    it   possessed    the    equitable

discretion to withhold the filtration remedy, the district court

ordered a bench trial to determine whether, in fact, it was

appropriate to exercise such discretion with respect to the

MWRA.   As the court saw it, the issue to be tried was whether

"the MWRA's alternative strategy of ozonation, chlorination, and

pipe replacement [will] better serve Congress's objective of

providing 'maximum feasible protection of the public health'

than will the EPA's insistence on filtration."                  Id.

            Between December 1999 and February 2000, the district

court presided over a twenty-four day bench trial in which it

heard from twenty-three witnesses and entered 524 exhibits into

evidence.     At trial, the United States sought to establish that

filtration combined with disinfection is much more effective

against highly treatment-resistant pathogens, such as Giardia

and Cryptosporidium, than the ozonation alternative favored by

the   MWRA.     It   also    sought    to    prove      that   the    process    of

ozonation, while generally effective in combating most forms of

live waterborne pathogens, may produce microbes that nourish

certain types of bacteria, thereby creating the potential for

"regrowth" of certain pathogens in the water supply.                     For its

part,   the   MWRA   noted    that    it     was   in   compliance      with    the

avoidance criteria at the time of trial, thereby removing the

urgency of installing a filtration system.               It further attempted


                                      -22-
to     demonstrate     that   its    proposed     approach     of    pipeline

rehabilitation, watershed protection, and ozone and chloramine

disinfection treatments would provide more comprehensive water

purification than filtration alone.

              The district court issued its findings of fact and

conclusions of law on May 5, 2000, holding, for the first time,

that the MWRA would not be required to install a filtration

system under present circumstances.             MWRA II, 97 F. Supp. 2d at

188.       While finding that filtration combined with disinfection

was    a    superior   treatment    technique    to   the   MWRA's   proposed

"ozonation-only" strategy, the court determined that, given the

lack of an actual health issue in light of the MWRA's compliance

with the avoidance criteria at the time of trial, "[a]ny risk to

public health entailed by selection of the 'ozone-only' option

is within acceptable levels." Id.           In making this determination,

the court relied heavily on studies introduced at trial by the

MWRA indicating that the ozonation technique could successfully

keep the concentrations of pathogens in the water supply at or

below      the   safety   levels    specified    by   the   SWTR     avoidance

criteria.        Id.   It further found that, while the threat of

bacterial "regrowth" posed by ozonation was real, that threat

could more effectively be addressed through pipe rehabilitation,




                                     -23-
flushing, and corrosion control than through filtration.11                       Id.

Moreover, the court, noting the tremendous sums that the MWRA

was spending and had pledged to spend in subsequent years on

health-related       system    improvements, 12           accepted    the     MWRA's

argument that the installation of a $180 million filtration

system would severely complicate the MWRA's efforts to take on

other water purification projects, such as pipe replacement,

that    would   be   needed    with    or     without      the     presence    of   a

filtration      system.       Id.      As     to    the    issue     of   watershed

protection, the court agreed with the MWRA that the plan of

acquiring lands close to the Wachusett Reservoir had proven

successful in creating an effective barrier against manmade

contamination, and that the implementation of a filtration plan

would       reduce   popular        support        for     maintaining        strict

environmental protection of the protected areas.                   Id. at 187-88.




       11
      The district court noted that the possibility of
"regrowth,"   without actual evidence of heightened levels of
bacteria, was not     a component of the SWTR's filtration-
avoidance criteria. Id. at 189.
       12
      In particular, the court found that the MWRA had budgeted
approximately $1.7 billion for four major (and needed) capital
improvement projects: a new water supply tunnel; a covered-
storage facility for treated water; a new disinfection facility;
and an ongoing water-main rehabilitation project. Id. at 169.
Additionally, the district court found that the MWRA had
instituted a successful grant program in which it was providing
$25 million per year to its constituent cities and towns to
improve the safety of their local water delivery systems. Id.


                                      -24-
          In sum, the district court found the MWRA's proposed

treatment plan to be a "sound alternative to . . . filtration

when competing demands for limited resources and the level of

risk from all potential threats to the safety of MWRA water are

considered."     Id. at 189.   The court determined that, in light

of the ACO, only one avoidance criteria violation remained

relevant -- the fecal coliform violation in January 1999 -- and

that, based on that single SWTR violation and the myriad efforts

undertaken by the MWRA to improve the quality of its water, the

United States had not demonstrated that reallocating funds from

the   MWRA's    planned   health-related   system   improvements   to

filtration was warranted.      Id.   Consequently, the court denied

the United States's request for injunctive relief.          Id.    It

retained jurisdiction, however, to facilitate reexamination of

the decision in the event that future circumstances warrant it.

Id.   This appeal followed.

               II. Equitable Discretion under the SDWA

          On appeal, the United States does not challenge any of

the district court's factual findings, including the court's

determination that the MWRA's "ozonation-only" approach is an

acceptable alternative to filtration.         Nor does the United

States assert that the district court        abused its equitable

discretion by declining to order filtration in light of the




                                 -25-
MWRA's history of avoidance-criteria noncompliance.13                            Instead,

its appeal essentially is confined to one argument: that under

the SDWA, courts have no discretion to withhold indefinitely a

provided-for     remedy,       such       as    filtration,        if     it   has   been

demonstrated     that    a     public          water    system      has    violated     a

substantive     requirement         of    the    Act.        The    district     court's

determination regarding the scope of its equitable discretion

presents    a   pure     issue       of    law,        and   so     we    review     that

determination de novo.           Fergiste v. INS, 138 F.3d 14, 17 (1st

Cir. 1998).

            In this case, the United States seeks to bring the MWRA

into compliance with the filtration requirement by resort to the

SDWA's statutory injunction provision, 42 U.S.C. § 300g-3(b).

The role a court plays in deciding whether to grant a statutory

injunction is different than the one it plays when it weighs the

equitable    claims     of    two    private      parties      in    a    suit    seeking

injunctive relief.           Yakus v. United States, 321 U.S. 414, 441



    13The United States does suggest that the district court
erred by discounting the MWRA's pre-1999 avoidance-criteria
violations in its decision not to order filtration.      It also
contends that it has not been estopped from pointing out the
MWRA's pre-1999 violations by its failure to block the ACO.
However, as the United States states in its brief, under its
theory of the case -- that a district court does not have the
discretion to excuse SWTR violations -- the additional
violations are essentially irrelevant, as even one failure to
meet the avoidance criteria after the December 30, 1991 deadline
creates an ongoing violation that triggers the filtration
obligation under the Rule.

                                          -26-
(1944).   This is so because a court asked to order a statutory

injunction     must   reconcile     two    sets    of    competing      concerns.

Courts asked to issue an injunction must ordinarily assume the

role of a court of chancery -- a role that requires them to

determine whether the equities of the case favor, and whether

the   public    interest    would    be    served       by,   the   granting   of

injunctive     relief.      See   United    States       v.   Oakland    Cannabis

Buyers' Coop., ___ U.S. ___, 121 S. Ct. 1711, 1720 (2001) ("In

exercising their sound discretion, courts of equity should pay

particular regard for the public consequences in employing the

extraordinary remedy of injunction.") (quoting Romero-Barcelo,

456 U.S. at 312).        But in the context of statutory injunctions,

the court's freedom to make an independent assessment of the

equities and the public interest is circumscribed to the extent

that Congress has already made such assessments with respect to

the type of case before the court.              Burlington N. R.R. v. Bair,

957 F.2d 599, 601-02 (8th Cir. 1992) (citing Atchison, Topeka &

Santa Fe Ry. v. Lennen, 640 F.2d 255, 259 (10th Cir. 1981) (per

curiam)); cf. Clark v. Smith, 38 U.S. (13 Pet.) 195, 203 (1839)

(finding "inherent in the Courts of Equity a jurisdiction to .

. . give effect to the policy of the legislature").

          In its decisions addressing this complicated area of

law, the Supreme Court has held repeatedly that the retention of

a   court's    discretion    to   shape    an    injunction     authorized     by


                                    -27-
statute to the equities of the case -- or not to issue an

injunction    at       all   --   is   to    be   presumed,    but     that   this

presumption may be overcome by a proper showing of congressional

intent.     "The grant of jurisdiction to ensure compliance with a

statute hardly suggests an absolute duty to do so under any and

all circumstances, and a federal judge sitting as chancellor is

not mechanically obligated to grant an injunction for every

violation of law."           Romero-Barcelo, 456 U.S. at 313; see also

id.   at    322    (Stevens,       J.,      dissenting)     ("Unless    Congress

specifically commands a particular form of relief, the question

of remedy remains subject to a court's equitable discretion.");

Town of Huntington v. Marsh, 884 F.2d 648, 651 (2d Cir. 1989)

("[I]n the area of environmental statutes, the Supreme Court has

explicitly rejected the notion that an injunction follows as a

matter of course upon a finding of a statutory violation.").

And while Congress certainly may intervene and guide or control

the exercise of the courts' discretion, or even extinguish it

entirely, courts measuring the quantum of equitable discretion

preserved    in    a    statute    are    "not    lightly   [to]     assume   that

Congress has intended to depart from established principles."

Romero-Barcelo, 456 U.S. at 313 (citing Hecht Co. v. Bowles, 321

U.S. 321, 329 (1944)).            This default rule can be justified, at

least in part, by the fact that "[w]hen Congress entrusts to an

equity court the enforcement of prohibitions contained in a


                                         -28-
regulatory enactment, it must be taken to have acted cognizant

of the historic power of equity to provide complete relief in

light of the statutory purposes."                Mitchell v. Robert DeMario

Jewelry, Inc., 361 U.S. 288, 291-92 (1960).                   In this vein, the

Supreme Court has held that if Congress wishes to circumscribe

these equitable powers, it must do so with clarity: "Unless a

statute in so many words, or by a                 necessary and inescapable

inference, restricts the court's jurisdiction in equity, the

full   scope     of    that       jurisdiction    is    to   be    recognized      and

applied."        Porter v.        Warner Holding Co., 328 U.S. 395, 398

(1946) (emphasis added).

            In    order      to    ascertain     whether     Congress      meant    to

constrain    the      equitable      discretion    afforded       courts    in   SDWA

cases, our examination begins -- and, for the most part, ends --

with the SDWA itself.              This is so because the discretion that

inheres in a statutory injunction provision is, by definition,

a product of the statute, and accordingly must be cabined by the

purposes for which the statute was created.                       United States v.

Monsanto,    491      U.S.    600,    613   (1989).       Where,    as   here,     the

statutory injunction provision does not explicitly delimit the

court's equitable authority, it is necessary to "look to the

[statute's] remedial framework as a whole."                  Williams v. Jones,

11 F.3d 247, 256 (1st Cir. 1993).                      This task requires that

courts not only consider the "language, history and structure"


                                        -29-
of the legislation, TVA v. Hill, 437 U.S. 153, 174 (1978), but

also the "underlying substantive policy" that the statutory

procedures are designed to further, Amoco Prod. Co. v. Village

of Gambell, 480 U.S. 531, 544 (1987).               Under this analysis, the

language     and    structure   of   the   Rule     regarding   the    need    for

filtration     reflect    policy     judgments      made   by   the    EPA,    not

Congress, and as such, are not relevant indicia of legislative

intent.    Cf. Chevron U.S.A., Inc. v. Natural Res. Def. Council,

467   U.S.    837,    842-43    &    n.9   (1984)    (directing       courts    to

distinguish between agency policy and congressional intent and

to reject administrative constructions that do not give effect

to the intent of Congress).

             The United States does not quibble with this analytical

framework.         Rather, it argues that the judicial-enforcement

provision of the SDWA, 42 U.S.C. § 300g-3(b), when read along

with the rest of the Act, admits of only one appropriate outcome

in cases where a water system fails an avoidance criterion: the

delinquent water system must be directed to install a filtration

system.    Accordingly, in the United States's view, the SDWA does

create a "necessary and inescapable inference" that courts may

not decline to order filtration whenever a violation of the Act

or the rules promulgated thereunder has been established.




                                      -30-
            In reaching this conclusion, the United States focuses

on the SDWA's judicial-enforcement provision, 42 U.S.C. § 300g-

3(b), which states, in relevant part:

            The [EPA] Administrator may bring a civil
            action in the appropriate United States
            district court to require compliance with
            any applicable requirement [of the Act] . .
            . . The court may enter, in an action
            brought under this subsection, such judgment
            as protection of public health may require,
            taking into consideration the time necessary
            to   comply   and    the   availability   of
            alternative water supplies . . . .

            As the United States sees it, the key words in this

passage are "compliance" and "comply."          Based on their presence,

as   well   as    on   the    Act's   command    that   the   EPA    delimit

circumstances under which filtration is "required," id. § 300g-

1(b)(7)(C)(i), the United States contends that, while § 300g-

3(b) may not have abrogated courts' equitable powers to specify

when ("the time necessary to comply") and how ("the availability

of alternative water supplies") a violator is to comply with the

filtration requirement, the provision does deprive courts of the

authority    to   allow      SDWA   violators   to   remain   in    permanent

noncompliance.     In this respect, the United States contends that

the case at bar is most akin to Hill, a decision in which the

Supreme Court found that the district court did not have the

equitable discretion under the Endangered Species Act to decline

the issuance of an injunction if it found that a violation of



                                      -31-
the statute's substantive provisions had occurred.               437 U.S. at

193-95.

          To bolster this argument, the United States adverts to

a   passage    from   §    300g-3(b)'s    legislative      history    that,   it

argues,   evinces         congressional     intent   to    diminish    courts'

equitable discretion under the SDWA.           This passage, appearing in

the   report    of    the    House   Interstate      and   Foreign    Commerce

Committee (which authored the version of the Act that ultimately

became law in 1974), states:

          [T]he Committee intends that courts which
          are considering remedies in enforcement
          actions under [§ 300g-3] are not to apply
          traditional balancing principles used by
          equity courts. Rather, they are directed to
          give utmost weight to the Committee's
          paramount objective of providing maximum
          feasible protection of the public health at
          the times specified in the bill.

H.R. Rep. No. 93-1185 (1974), reprinted in 1974 U.S.C.C.A.N.

6454, 6476.

          The Second Circuit has accepted this analysis, albeit

in dicta, and concluded that, for largely the same reasons

advanced by the United States, courts may not consider the

propriety vel non of filtration in individual SDWA cases.                     In

United States v. City of New York, 198 F.3d 360 (2d Cir. 1999),

a case in which a citizens' group sued to undo a consent

agreement between New York City and the EPA that required the

installation of a filtration system, the court in dicta stated:


                                     -32-
          [T]he decision to filtrate or not is a
          policy choice that Congress seems to have
          made and that, in any event, is beyond our
          judicial function.    Our conclusion is not
          altered by appellants' interesting, but
          ultimately   unpersuasive,  argument   that,
          since the SDWA authorizes a court to enter
          "such judgment as protection of public
          health may require," 42 U.S.C. § 300g-3(b),
          the district court has the power to refuse
          to order filtration in this action . . . .
          We think that the equitable power vested in
          the district court is more circumscribed
          than intervenors propose; it is available to
          ensure compliance with the statute and the
          regulations promulgated thereunder, not to
          rework or reject these legislative and
          regulatory determinations.

Id. at 366.14

          While we agree that the SDWA's text and legislative

history provide evidence of Congress's intent not to allow

courts in SDWA cases to apply the traditional test for issuing

injunctions,15 we are not convinced that such evidence gives rise


     14
      This passage was dicta because the court disposed of the
proposed intervenors' appeal on the alternative ground that the
district court did not abuse its discretion by denying the
organization's requests for intervention as a matter of right
and for permissive intervention. See id. at 367-68.
     15
      In order to issue a permanent injunction, a district court
typically must find that (1) the plaintiff has demonstrated
actual success on the merits of its claims; (2) the plaintiff
would be irreparably injured in the absence of injunctive
relief; (3) the harm to the plaintiff from defendant's conduct
would exceed the harm to the defendant accruing from the
issuance of an injunction; and (4) the public interest would not
be adversely affected by an injunction. E.g., A.W. Chesterton
Co. v. Chesterton, 128 F.3d 1, 5 (1st Cir. 1997). At least with
respect to some statutory injunction provisions, however, courts
have found that when Congress decides to make available the
remedy of injunction for violations of a statute's substantive

                              -33-
to a "necessary and inescapable inference" that the substantive

remedies made available under the Act must always be ordered

whenever   a   regulation   promulgated   under   the   Act   has   been

violated.16 Rather, we believe that as long as a court issues a

"judgment as public health may require," 42 U.S.C. § 300g-3(b),

thereby ensuring that the public system provides water that is

safe according to standards identified by the EPA, the court

retains a measure of flexibility under the Act to tailor the

specifics of an equitable remedy that will help bring about that

goal.    Our determination on this point is bolstered by several




provisions, irreparable injury is presumed to flow from such
violations.   E.g., United States v. City of Painesville, 644
F.2d 1186, 1194 (6th Cir. 1981).
     We note that, in spite of the legislative history indicating
Congress's intent to narrow the scope of equitable discretion
under the SDWA, at least one court has applied traditional
principles of equitable balancing to determine the propriety of
an injunction for violations of the Act's substantive
provisions. See United States v. Midway Heights County Water
Dist., 695 F. Supp. 1072 (E.D. Cal. 1988) (denying public water
system's motion for stay of preliminary injunction requiring it
to comply with national drinking water regulations).
    16We note that in City of New York, the proposed intervenors
did not argue that the equities of the case favored withholding
filtration in that particular case; rather, they sought to
effect a "head-on challenge to filtration" per se. 198 F.3d at
366. The proposed intervenors' challenge principally was based
on their assertion that "filtration . . . is [both] dangerous to
consumers [and] fiscally wasteful." Id. at 363; see also id. at
364 ("[Appellants] do[] not seek to enforce administratively
established    criteria;   [they]    seek[]   to    block   such
enforcement."). Moreover, in City of New York (unlike in the
present case) the public water system conceded that it would not
be able to meet the avoidance criteria in the future. Id. at
362-63.

                                -34-
factors relating to the Act's "language, history and structure,"

Hill, 437 U.S. at 174, and its "underlying substantive policy,"

Village of Gambell, 480 U.S. at 544.

          First, the critical passage of the SDWA's judicial-

enforcement subsection states that, following a violation of the

Act's substantive provisions, the court "may enter . . . such

judgment as protection of public health may require . . . ."            42

U.S.C. § 300g-3(b) (emphasis added).          When Congress uses the

permissive   "may"   in    settings   such   as   §   300g-3(b),   it   is

"eminently reasonable" to presume that the choice of verbiage is

a deliberate one, and that, in the context of that statute,

"'may' means may."17      McCreary v. Offner, 172 F.3d 76, 83 (D.C.

Cir. 1999); see also United States v. Rodgers, 461 U.S. 677, 706

(1983) ("The word 'may,' when used in a statute, usually implies

some degree of discretion."); Flynn v. United States, 786 F.2d

586, 591 (3d Cir. 1986) (finding that where statute states that

court "may" grant injunctive relief, the statute's use of the

conditional "suggests that such relief is not mandatory in every

case").   This tenet of statutory construction should obtain



     17
      Conversely, when Congress employs the word "shall" in like
contexts, it often means that "Congress has imposed a mandatory
duty upon the subject of the command."      Forest Guardians v.
Babbitt, 174 F.3d 1178, 1187 (10th Cir. 1999) (citing Monsanto,
491 U.S. at 607).   However, even the use of the word "shall"
does not necessarily eliminate all equitable discretion if
Congress's purpose not to eliminate such discretion is manifest.
Hecht Co., 321 U.S. at 329.

                                 -35-
unless "obvious inferences from the structure and purpose of the

statute [indicate] that 'may' was intended to have something

other than its ordinary meaning."                    Reynolds v. Spears, 93 F.3d

428, 434-35 (8th Cir. 1996) (citing United States v. Rodgers,

461 U.S. at 706) (internal quotation marks omitted).

            If anything, the strongest inference that may be drawn

from the SDWA is that Congress did intend for "may" in § 300g-

3(b) to track its everyday meaning.                       As mentioned in Part I,

supra, Congress amended the Act in 1986 to enhance the level of

enforcement under the SDWA.                  See 42 U.S.C. § 300g-3(a)(1)(B)

(providing that if the responsible state enforcement authority

does not commence enforcement action within thirty days of being

notified    by     the     EPA     of        existence       of       violation,       "the

Administrator shall issue an [administrative] order . . . or the

Administrator shall commence a civil action . . . .") (emphases

added);    Rodgers,      supra,    §    4.20A,       at    152    ("In   making       these

changes    Congress       [was]    convinced          that       it   [could]    control

prosecutorial options by replacing 'mays' with 'shalls' in its

enforcement      instructions.").              But    in   so     amending      the   Act,

Congress    left      untouched    the       "mays"       contained      in   the     Act's

neighboring judicial-enforcement provision, thereby making only

prosecution      of     substantive          SDWA     violations         an   expressly

mandatory     undertaking.             It     presumably          did    so   with      the

understanding      that    under       the    Act,    enforcement        requires       the


                                         -36-
actions of two entities -- the state enforcement authority or

the U.S. Attorney's office, who must sue to require compliance,

and the district court, which must issue an injunction -- to

bring about a substantive remedy under the Act.                        "[W]hen the

same   [provision]      uses    both    'may'     and   'shall,'       the     normal

inference is that each is used in its usual sense -- the one act

being permissive, the other mandatory."                 Anderson v. Yungkau,

329 U.S. 482, 485 (1947); see also Barbieri v. RAJ Acquisition

Corp. (In re Barbieri), 199 F.3d 616, 619-20 (2d Cir. 1999)

(distinguishing     neighboring         subsections     of     same    section     of

Bankruptcy Code based on presence of "may" in one provision and

"shall" in the other provision).

           Additional evidence of the preservation of equitable

discretion      comes   from    the     fact    that,     in     the    1986    SDWA

amendments,      Congress      vested     power    in    the     EPA     to    issue

administrative orders for minor SDWA violations, and to collect

fines for those violations, without first seeking authorization

from the courts.        See 42 U.S.C. § 300g-3(g).             In the report of

the    Senate   Environment      and     Public    Works       Committee       (which

generated the version of the bill that ultimately became law) on

the enactment of these amendments, the Committee stated that

"[t]he purpose of adding administrative order authority is not

to replace judicial enforcement, but to add a complementary

enforcement     mechanism."       S.     Rep.   No.     99-56,    at    9     (1986),


                                       -37-
reprinted in 1986 U.S.C.C.A.N. 1566, 1574.       By affording the

EPA an intermediate remedy for SDWA violations that does not

require court action, Congress explicitly contemplated a system

in which substantive violations of the Act (particularly minor

ones) would not always result in the issuance of an injunction.

See Romero-Barcelo, 456 U.S. at 317-18.

          In sum, there is substantial evidence in the SDWA's

text and legislative history to suggest that "may" really does

mean "may" in § 300g-3(b).     While these clues alone might not

suffice to eliminate all doubt that Congress intended for "may"

to have a permissive meaning, at a minimum, they do eliminate

the possibility that the SDWA's structure and purpose generate

an "obvious inference" that the word "may" in § 300g-3(b) really

means "shall."18   Rodgers, 461 U.S. at 706; see also Russ Winner,

The Chancellor's Foot and Environmental Law: A Call for Better

Reasoned Decisions on Environmental Injunctions, 9 Envtl. L.


     18
      The United States asserts that by creating a filtration
exemption under the SDWA in 1996 for water systems with
uninhabited and undeveloped watersheds in consolidated control,
42 U.S.C. § 300g-1(b)(7)(C)(v), Congress demonstrated its belief
that such an amendment was needed to circumvent the mandatory
command of the Act's filtration requirement. We disagree. This
provision merely authorizes state enforcement agencies, who
would otherwise be obliged to bring an enforcement action for
avoidance-criteria violations, see id. § 300g-3(a)(1)(B)
(requiring the EPA to bring suit for substantive SDWA violation
if state enforcement agency fails timely to do so), to permit
compliance with the Act by means other than filtration for
certain types of water systems. The amendment does not touch
upon the power of the court to issue -- or not issue -- an
injunction.

                               -38-
477, 506 (1979) ("If . . . the legislation explicitly requires

that 'an injunction must issue,' a court . . . has no choice but

to comply.    Most of the time, however, the legislature is silent

as to injunctive remedy or merely says that an injunction 'may'

issue.   In this case, courts usually retain their full equitable

discretion.").

          Our conclusion on the SDWA's preservation of equitable

discretion also is reinforced by other portions of the Act's

judicial-enforcement provision.      While the United States relies

heavily on language in § 300g-3(b) referring to compliance with

the Act, and specifically on statements to the effect that the

EPA Administrator is authorized to "bring a civil action . . .

to require compliance" and that a court hearing an SDWA suit

"may enter . . . such judgment as protection of public health

may require, taking into consideration the time necessary to

comply," we find that such language, when compared to similar

language in other federal enforcement statutes, does not compel

the conclusion that the court must issue an injunction.

          Take, for example, the provision empowering the EPA to

bring a civil action "to require compliance."        Similar language

appears in a number of other statutes' judicial-enforcement

provisions, and generally has been construed as leaving intact

the judiciary's equitable discretion to deny the issuance of an

injunction.      The   courts   reaching   this   interpretation   have


                                  -39-
reasoned that the language simply represents Congress's grant of

authority to an agency to bring a suit to require compliance --

in other words, that the agency can seek to require compliance

through legal process.

            For instance, under the judicial-enforcement provision

of   the   Securities   and    Exchange   Act   of   1934,    15   U.S.C.    §

78u(d)(1), the SEC "may, in its discretion, bring an action . .

. to enjoin . . . acts or practices" violating the statute's

substantive provisions.        In SEC v. Frank, 388 F.2d 486, 491 (2d

Cir. 1968), Judge Friendly, writing for the panel, found such

language not susceptible of the interpretation that equitable

discretion had been stripped from the district court: "Such

bland language affords no sufficient basis for concluding that

Congress meant special weight to be given the Commission's

decision to allow its staff to institute suit.                 If Congress

wishes to go further, it should say so in language all can

understand."    Likewise, in Federal Power Commission v. Arizona

Edison Co., 194 F.2d 679, 684-86 (9th Cir. 1952), the Ninth

Circuit,    reaching    an    analogous   conclusion   with    respect      to

identical language in the judicial-enforcement provision of the

Federal Power Commission Act, 16 U.S.C. § 825m(a), held that the

courts' traditional powers of equity had not been eviscerated by

the agency's power to bring suit to require compliance.             Another

example of this usage, albeit in a slightly different context,


                                   -40-
appears in the citizen-suit provision of the Clean Water Act;

under this statute, suits may not be instituted by individuals

or organizations if the EPA or the appropriate state enforcement

authority "has commenced and is diligently pursuing a civil or

criminal action . . . to require compliance" with the Act's

substantive provisions.             33 U.S.C. § 1365(b)(1)(B) (emphasis

added).       Despite this reference to "requir[ing] compliance" in

the statutory language, the Supreme Court held in Romero-Barcelo

that the Clean Water Act does not require the issuance of an

injunction in all cases where a statutory violation has been

identified.         456 U.S. at 313 (holding that "[t]he grant of

jurisdiction to ensure compliance with a statute hardly suggests

a duty to do so under any and all circumstances").                   These

examples demonstrate that a statutory provision that gives an

agency the power to litigate "to require compliance," without

more, does not necessarily obligate the court asked to rule on

such a suit to issue any particular remedy.19

               The other passage in § 300g-3(b) referred to by the

United States -- the one stating that courts are to consider

"the        time   necessary   to    comply   and   the   availability   of

alternative water supplies" in fashioning equitable relief -- is

better construed to mean that, to the extent a court issues a



       19
      As we note infra, we believe that the district court did
require compliance with the SDWA in this case.

                                       -41-
"judgment as public health may require" that does include the

filtration remedy (which, as the district court noted, will

usually be the case), it must allow the public water system

reasonable   time   to   comply   in   light   of   the   availability   of

alternative water sources.        From the command that a court must

consider the time necessary to comply when it does order a

"judgment as public health may require," however, it does not

necessarily follow that the court must always exact the type of

compliance sought by the agency whenever a violation of the Act

has been identified.     This construction is supported by the fact

that, in spite of the ubiquitousness of the term "compliance" in

§ 300g-3(b), courts are not expressly limited by the statute to

entering judgments that "require compliance," but instead have

been granted the leeway to issue "judgment[s] as protection of

public health may require."        Cf. Natural Res. Def. Council v.

Southwest Marine, Inc., 236 F.3d 985, 1000 (9th Cir. 2000)

(holding that, with respect to judicial-enforcement provision in

Clean Water Act limiting courts to "enforce[ment]" of existing

standards and orders, "the authority to 'enforce' an existing

requirement is more than the authority to declare that the

requirement exists and repeat that it must be followed"), cert.

denied, 121 S. Ct. 2242 (2001).

         In sum, while the United States's position certainly

is not implausible, the fact that the MWRA's interpretation of


                                   -42-
the SDWA is at least as plausible effectively forecloses the

possibility that a "necessary and inescapable inference" exists

in the Act as to the necessity for filtration upon a finding of

a regulatory violation.   Porter, 328 U.S. at 398.

          The United States insists that, in terms of breadth of

equitable discretion, the SDWA bears an uncanny resemblance to

the Endangered Species Act (ESA) -- a statute found by the

Supreme Court to have removed courts' authority to withhold

injunctive relief.   Hill, 437 U.S. at 193-95.       In Hill, the

Supreme Court found that the ESA had flatly banned federal

agencies from carrying out activities which threaten to destroy

or modify the habitat of endangered species.         Id. at 194.

Through an examination of the statute's voluminous text and

legislative history, the Court found that Congress "ha[d] spoken

in the plainest of words, making it abundantly clear that the

balance had been struck in favor of affording endangered species

the highest of priorities . . . ."         Id.   In so finding,

moreover, the Court essentially ignored the statute's judicial-

enforcement provision, 16 U.S.C. § 1540(g), which, far from

expressly requiring the issuance of an injunction upon the

finding of a statutory violation, merely gives district courts

"jurisdiction . . . to enforce any . . . provision" of the Act.20


     20
      This apparent omission was noted in a dissent by then-
Justice Rehnquist, who, after taking note of the provision,
determined that it was not strong enough to eliminate the

                              -43-
Attempting to tether this case to that precedent, the United

States flags what it sees as analogous indicia of legislative

intent with respect to the filtration mandate in the SDWA, and

urges us to overlook the similarly permissive nature of the

SDWA's judicial-enforcement provision.

           While there is force to this argument, in the final

analysis we do not believe that it holds water.                      The principal

problem with the United States's effort to juxtapose the ESA and

the SDWA is that, for reasons discussed above, the overwhelming

evidence of congressional intent that the Supreme Court found in

Hill   simply   does    not    exist     with   respect    to     the     filtration

mandate in the SDWA.       The United States points us to no specific

evidence that the narrow goal of filtration (as opposed to the

broader   aim   of     safe    drinking       water)   was      to    receive    the

overarching priority that endangered-species protection garnered

under the ESA.       As the district court noted, by imposing the

disinfection mandate directly even as it imposed the filtration

remedy    indirectly,         Congress     "stopped       short      of     ordering

filtration as an all-encompassing preventive."                    MWRA II, 97 F.

Supp. 2d at 165.       As for the Supreme Court's failure to consider

the language of the ESA's judicial-enforcement provision in

Hill, we note that in subsequent cases, such as United States v.



presumption of retained equitable discretion.                Hill, 437 U.S. at
211-13 (Rehnquist, J., dissenting).

                                       -44-
Oakland Cannabis Buyers' Cooperative, the Court has found that

piece of legislative evidence to be particularly relevant in

ascertaining the extent to which equitable discretion had been

retained.      See ___ U.S. ___, 121 S. Ct. 1711, 1721 (2001)

(analyzing     judicial-enforcement            provision      of      Controlled

Substances Act, 21 U.S.C. § 882(a), and concluding that the

district court "is not textually required by any clear and valid

legislative command" in that provision to issue an injunction)

(internal quotation marks omitted).            Whether or not the approach

taken in Hill with respect to the ESA is still "good law," we

are not persuaded that a similar approach is appropriate here.

            Apart from its arguments concerning the text of the

SDWA, the United States also pursues a broader line of attack in

this appeal: that the district court's decision excuses an

ongoing statutory violation, and therefore exceeds the scope of

equitable discretion that may be exercised under any statute.

While    acknowledging     the    Supreme    Court's      statement     that   "a

federal     judge   sitting      as   chancellor     is    not     mechanically

obligated to grant an injunction for every violation of law,"

Romero-Barcelo, 456 U.S. at 313, the United States contends that

the Court has never authorized courts to do what it claims the

district court did in this case -- namely, to permit a water

system    in   violation    of    the   SDWA    to   remain      in   violation

indefinitely.       In pressing this argument, the United States


                                      -45-
points to three of the Court's seminal cases in this area from

the last century:      Hecht Co., Romero-Barcelo, and          Village of

Gambell. Even though the Supreme Court endorsed the district

court's   exercise    of   equitable   discretion   in    each   of   those

decisions,   the     United   States   correctly    observes     that   the

district court's order in all three cases was designed to lead

to compliance with the relevant statute.21               By declining to

order the MWRA to install a filtration system, the United States

contends, the district court was unfaithful to these precedents

by "allow[ing] the MWRA to remain out of compliance with the

SDWA and the SWTR permanently."

          We agree that in all three of these cases -- and,

indeed, in all cases in which the Supreme Court has spoken in

this area -- the violating party was not permitted to evade the

substantive requirements of the statute.       We disagree, however,


    21In Hecht Co., the defendant had remedied its past
violations of the Emergency Price Control Act, and the district
court had found that those transgressions were not likely to
recur. 321 U.S. at 325-26. In Romero-Barcelo, the Court noted
that the violator (the Navy) was likely in the near future to
receive the permit it needed to comply with the Federal Water
Pollution Control Act amendments to the Clean Water Act, and
found that the statute's judicial-enforcement provision "permits
the district court to order that relief it considers necessary
to secure prompt compliance with the Act."      456 U.S. at 320
(emphasis added). And in Village of Gambell, the Court found
that because oil companies needed to receive further approval
from the Secretary of the Interior before engaging in drilling
off the coast of Alaska, the district court was not required,
under the Alaska National Interest Lands Conservation Act, to
enjoin the companies' activities based on their past failures to
meet the Act's procedural requirements. 480 U.S. at 544.

                                  -46-
with the United States's argument that the court is permitting

noncompliance in this case.                "[W]hen a court of equity exercises

its   discretion,        it       may    not      consider      the    advantages       and

disadvantages of nonenforcement of the statute, but only the

advantages and disadvantages of employing the extraordinary

remedy    of    injunction         over     the     other      available      methods    of

enforcement."          Oakland Cannabis Buyers' Coop., 121 S. Ct. at

1722 (internal citations and quotation marks omitted).                           Because

the court's order is designed to ensure that the Act's paramount

objective      of    safe       drinking       water    remains      fulfilled    in    the

future, the district court did not, as the United States argues,

sanction perpetual noncompliance with the Act.                          See Village of

Gambell, 480 U.S. at 544 (directing courts charged with ensuring

compliance      with        a    statute       to      focus    on    "the    underlying

substantive         policy      the     process        was   designed    to    effect").

Contrary to the situation in Hill, this is not a case where

"Congress' order of priorities, as expressed in the statute,

would be deprived of effect if the District Court could choose

to deny injunctive relief."                Oakland Cannabis Buyers' Coop., 121

S. Ct. at 1721 (internal quotation marks omitted) (citing Hill,

437 U.S. at 194).

            Although the EPA is correct that filtration is an

absolute requirement under the SDWA/SWTR regime for those water

systems     that      fail       to     meet     the     avoidance      criteria,       the


                                            -47-
preeminence of filtration in bringing about the goal of safe

drinking water is primarily a function of the Rule, not the Act.

The purpose of the Act, in the words of its drafters, is to

"assure    that   water     supply   systems      serving    the       public   meet

minimum national standards for protection of public health."

H.R. Rep. No. 93-1185,         reprinted in 1974 U.S.C.C.A.N. 6454,

6454.     In other words, the framers of the Act were concerned

with ensuring that consumers of public water systems have access

to safe drinking water, with the safety of the water to be

judged according to objective criteria developed by the EPA.

Filtration, while serving an important role in furtherance of

the objective of safe water, is merely a prophylactic remedy

made available to help bring about that objective.                        One fact

underscores this point particularly well, and demonstrates why

the exercise of equitable discretion is especially appropriate

with respect to this particular regulatory scheme: under the

Act, if a water system never violates any of the avoidance

criteria, its water is presumptively "safe" according to the

SDWA,   regardless     of    whether    it     ever   installs     a    filtration

system.     In essence, the water system's compliance with the

avoidance    criteria       makes    the      water   safe   from       the     EPA's

perspective -- a point conceded by the United States at trial.

We fail to see how accomplishment of the Act's substantive goals

is   undermined   by   overlooking         past   violations     of     regulatory


                                       -48-
deadlines that have no bearing on the current or future purity

of the water delivered to consumers.            See Romero-Barcelo, 456

U.S. at 310 (noting that purpose of injunctive relief is to

deter future violations, not to punish past ones) (citing Hecht

Co., 321 U.S. at 329-30); cf. Friends of the Earth v. Laidlaw

Envtl. Servs. (TOC), Inc., 528 U.S. 167, 192 (2000) (holding

that district court had discretion under Clean Water Act "to

determine which form of relief is best suited, in the particular

case,   to    abate   current    violations    and    deter   future   ones")

(emphasis added).       Moreover, given that the district court has

retained jurisdiction in this case for the purpose of policing

any    future    violation,     thereby    allowing    it   to   revisit   the

validity of its earlier decision not to order filtration, the

United States has a ready forum in which to seek relief for any

future avoidance-criteria violations.            See Romero-Barcelo, 456

U.S. at 320 ("Should it become clear that . . . compliance with

the [statute] will not be forthcoming, the statutory scheme and

purpose would require the court to reconsider the balance it has

struck.").

              Besides the issue of ongoing supervision to ensure

compliance, the case at bar bears a close similarity to Romero-

Barcelo in at least one other respect: the district court's

focus on the relevant statute's substantive purposes, rather

than    its     technical   requirements.       In    Romero-Barcelo,      the


                                    -49-
plaintiffs   claimed   that,   by    allowing   the   Navy    to   continue

bombing   exercises    on   Vieques    Island   without      first      having

obtained a discharge permit, the court was countenancing an

ongoing statutory violation -- namely, the unpermitted discharge

of   ordnance   into   navigable      waters.     456     U.S.     at    314.

Disagreeing with this characterization, the Supreme Court found

that, by tying future Navy activities to its procurement of a

discharge permit, the district court had "neither ignored the

statutory violation nor undercut the purpose and function of the

permit system."    Id. at 315.        This was the case, according to

the Court, because "[t]he integrity of the Nation's waters, . .

. not the permit process, is the purpose of the [statute]."                Id.

at 314.   So it is here: the manifest purpose of the SDWA is safe

drinking water, not filtration.

          Of course, we are aware that the filtration mandate is,

in some meaningful way, more "substantive" than the FWPCA's

permit requirement, and that, through the 1986 amendments to the

SDWA, Congress expressed its intent that filtration should be

used by water systems that fail to meet the standards for

avoidance established by the EPA.          But in the end, we believe

that we would do far greater violence to both the text and the

purpose of the SDWA were we to strip courts of the flexibility

to shape equitable decrees in appropriate situations.              For as we

noted infra, under § 300g-3(b), courts are authorized to issue


                                    -50-
"judgments   as    protection   of   public   health   may   require."

Moreover, by retaining jurisdiction in this case, the district

court has assumed the responsibility of ensuring that, through

continued oversight of the MWRA's avoidance-criteria compliance,

the MWRA's water supply will remain "safe" according to the

EPA's standards.

         The United States's final contention -- in reality, it

is nothing more than a variation on the basic theme of its

appeal -- is that the district court, by holding a trial on the

propriety of applying the filtration requirement to the MWRA,

arrogated to itself powers that had been placed by Congress in

the hands of the EPA.     In its view, the district court's trial

amounted to little more than an improper reconsideration of the

determinations that the EPA made in promulgating the Rule.

Under the SDWA, the United States argues, such considerations

are the exclusive province of experts in the EPA, not the

courts, and if the district court's decision is left to stand,

every water system that finds itself displeased with the SWTR's

rigid requirements will have the opportunity to challenge the

wisdom of the Rule as applied to it.

         This line of reasoning only is valid as far as it goes

-- and it does not go as far as the United States suggests.         It

is certainly true that, in delegating authority to the EPA to

ascertain circumstances in which "filtration . . . is required"


                                 -51-
of    public    water     systems,        42    U.S.C.    §    300g-1(b)(7)(C)(i),

Congress      entrusted     the     EPA    with    the    power    to   make     policy

judgments with respect to the factors that would make filtration

mandatory.      It is also true that, as a general matter, those

judgments are not to be second-guessed by courts.                            But policy

determinations in statutes and regulations that Congress chooses

to have enforced through suits in equity are always subject to

courts' equitable discretion -- that is, at least to the extent

that Congress has preserved discretion in the statute and has

not proscribed, through its expressions of policy, the type of

equitable remedy that a court seeks to implement.                        If Congress

has    left    the   door    open    to     a    court   to    exercise       equitable

discretion respecting enforcement of a statute such as the SDWA,

and the court senses that the equities of the case may favor

alternative means of exacting compliance with the statute ( i.e.,

other than the issuance of an injunction), the court does not

exceed the boundaries of its authority by conducting fact-

finding for the purpose of determining how best to wield its

discretion      in   light    of     the       priorities      established      in    the

statute.      The district court did not hold a trial to revisit the

underlying wisdom of the SWTR; rather, it held a trial to

ascertain whether, based on both the particular facts of this

case    and    the   substantive          goals    of    the    Act,    it    was    more

appropriate to order filtration or to permit the MWRA to pursue


                                           -52-
its alternative approach to the extent that it could satisfy the

Rule's avoidance criteria and ultimately provide a safer water

supply.

            In sum, with respect to the SDWA, a court must "take

as given the value choices embodied in the statutes and policies

administered      by   the   [agency],   but   is   entitled   and   in   fact

required to consider whether the enforcement of the [agency's]

order would violate equitable principles that are neutral with

regard to those value choices."          NLRB v. P*I*E Nationwide, Inc.,

894 F.2d 887, 893 (7th Cir. 1990).                  In our view, this is

precisely what the district court did in this case.

                                 Conclusion

            Under the SDWA, it should be a rare case in which a

violation of regulatory standards does not lead to an injunction

if the responsible enforcement agency requests one.              This is so

because, as the district court in this case properly found, the

SDWA contains a "presumption expressed by Congress . . . that

filtration will almost always be the preferred remedy for a[n]

SWTR violation."       MWRA I, 48 F. Supp. 2d at 72.       Expressions by

Congress of this sort, once identified, must be respected by

courts,    lest    equitable     discretion     become   the    judiciary's

preferred method of reshaping policy determinations made by

other branches of government that are better equipped to make

them.     But the district court, after carefully considering the


                                    -53-
facts,    found    that    this    was    indeed     such   a    rare    case,   and

accordingly declined to issue an injunction.                    In rendering this

judgment, the court was careful to shape its decision so as to

ensure that the MWRA's drinking water will meet the avoidance-

criteria standards that are the EPA's benchmarks for safety.                       It

exercised the flexibility left to it by Congress in the statute,

and    assumed     the    responsibility        of   monitoring         the   MWRA's

compliance    in    the    event    that    future     violations        require    a

reexamination of the decision not to order filtration.                             In

short, the district court used its equitable discretion to

appropriate ends: furthering the substantive purposes of the

Act.     In so doing, it did not act outside the scope of its

authority with respect to the specific statute at issue in

declining to issue an injunction.                  Accordingly, the district

court's judgment is

           Affirmed.       No costs.




                                         -54-
