Does Section 1311(b)(1)(C) of the Clean Water Act authorize the EPA to include "end-result" provisions in National Pollutant Discharge Elimination System (NPDES) permits? These provisions make a permittee responsible for the quality of the receiving water rather than specifying required actions. The Court must determine if such requirements constitute "limitations" under the statute.

• All "limitations" imposed under § 1311 must qualify as "effluent limitations," which restrict quantities, rates, and concentrations of pollutants.
• Even if other limitations are allowed, § 1311(b)(1)(C) does not authorize requirements that condition compliance on whether receiving waters meet water quality standards.
• End-result requirements exceed the EPA's statutory authority because they do not provide specific rules for permittees to follow.
• Such provisions eviscerate the "permit shield" protection provided by 33 U. S. C. § 1342(k).

• The phrase "any more stringent limitation" in § 1311(b)(1)(C) is broad enough to encompass end-result requirements.
• End-result limitations are necessary when the EPA lacks sufficient information to develop specific effluent limitations for a particular facility.
• Such provisions are supported by the EPA's Combined Sewer Overflow (CSO) Control Policy and related administrative guidance.
• Prohibiting these requirements would disrupt the issuance of "general permits" used by various businesses and agricultural enterprises.

• The Court held that § 1311(b)(1)(C) does not authorize "end-result" provisions in NPDES permits.
• While rejecting the argument that all limitations must be "effluent limitations," the Court noted that Congress's omission of the word "effluent" from § 1311(b)(1)(C)—contrasted with its inclusion in § 1311(b)(1)(A) and (B)—indicates an intentional choice, citing *Russello v. United States*.
• Applying *Webster's Third New International Dictionary*, the Court reasoned that a "limitation" is a restriction imposed "from without"; end-result requirements are restrictions from within because the permittee determines the necessary steps to avoid liability.
• The Court found that the terms "implement" and "meet" in § 1311(b)(1)(C) require "concrete measures" rather than simply mandating a result.
• Historically, the pre-1972 Water Pollution Control Act (WPCA) used a backward-looking enforcement model; the Court reasoned that the CWA's 1972 overhaul deliberately scrapped this approach in favor of "direct restrictions," citing *EPA v. California ex rel. State Water Resources Control Bd.*
• The Court concluded that end-result requirements would negate the "permit shield" under 33 U. S. C. § 1342(k), which deems a permittee compliant if they adhere to permit terms.
• The Court noted the statutory silence on how to allocate responsibility among multiple dischargers contributing to water quality violations as evidence that Congress did not intend for end-result requirements.
• The Court determined the EPA has other tools, such as emergency powers under 33 U. S. C. § 1364 or refusing permits until information is provided, to ensure water quality without using end-result provisions.