Congress designed the Clean Water Act (CWA or the
Act) to ensure that anyone holding a discharge permit
issued under the Act has notice of how much they must
control their discharges to comply with the law. The
CWA requires that the U.S. Environmental Protection
Agency (EPA) and authorized states provide this notice
by prescribing specific pollutant limitations in the National Pollutant Discharge Elimination System (NPDES)
permits they issue. Consistent with its text, this Court
and the Second Circuit have read the Act to require EPA
and states to develop specific limits to achieve goals for
surface waters, called water quality standards.

Parting with these decisions, the Ninth Circuit
held here that EPA may issue permits that contain
generic prohibitions against violating water quality
standards. Rather than specify pollutant limits that
tell the permitholder how much they need to control
their discharges as required by the CWA, these prohibitions effectively tell permitholders nothing more
than not to cause "too much" pollution. These generic
water quality terms expose San Francisco and numerous permitholders nationwide to enforcement actions
while failing to tell them how much they need to limit
or treat their discharges to comply with the Act.

The question presented is:

Whether the Clean Water Act allows EPA (or an authorized state) to impose generic prohibitions in NPDES
permits that subject permitholders to enforcement for
exceedances of water quality standards without identifying specific limits to which their discharges must conform.

Whether the Clean Water Act allows EPA (or an authorized state) to impose generic prohibitions in NPDES permits that subject permitholders to enforcement for exceedances of water quality standards without identifying specific limits to which their discharges must conform