We'll hear argument now in case 23-753, the City and County of San Francisco versus the

Environmental Protection Agency. Ms. Steeley?

Mr. Chief Justice, and may it please the Court, Section 301B1C of the Clean Water Act

assigns EPA the job of setting the effluent limitations necessary to meet and implement water quality standards.

The water quality standards are not the limitations themselves.

Instead, they set the goals for the water body.

EPA must translate those goals into discharge limitations.

The generic prohibitions fail this task.

As Judge Collins explained below, the generic prohibitions erase the distinction between

water quality standards and discharge limitations, making them one and the same.

The generic prohibitions revive the very cause or contribute standard Congress repealed,

and they do not function as discharge

limitations. As the Second Circuit recognized, they add nothing that tells a permit holder

how to control its discharges. EPA claims it uses the generic prohibitions as a backstop,

an insurance policy against changing circumstances.

But the Clean Water Act already gives EPA all the tools it needs to address uncertainty.

EPA can reopen, modify, or terminate a permit when conditions change, and it can exercise its statutory authority to protect public welfare in emergencies.

What EPA cannot do is expose permit holders to liability based on receiving water conditions. It cannot control. The generic

prohibitions are also inconsistent with the Act's permit shield. The shield protects

permit holders from liability as long as they comply with their

permit terms. But by imposing indeterminate requirements, the generic prohibitions prevent

permit holders from relying on the shield's protections. San Francisco is therefore exposed to

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