Antibacksliding: Reissued NPDES permits cannot be less stringent except in limited conditions. Which statement best reflects this concept?

• A. Reissued NPDES permit cannot be less stringent except in limited conditions
• B. Antibacksliding allows backsliding freely in special cases
• C. Antibacksliding applies to water quality standards only
• D. NPDES permits are always more stringent than old ones

Answer: (A)

Antibacksliding is the rule that when an NPDES permit is renewed, the new permit’s effluent limits for the same pollutants must be at least as stringent as the current permit, with only narrow, legally defined exceptions. This protects pollution controls from weakening just because a permit is reissued.

The statement reflects that idea directly: a reissued NPDES permit cannot be less stringent except in limited conditions. That summarizes the standard approach—limits are kept or strengthened at renewal, not casually loosened.

The other ideas don’t fit as well. Saying backsliding is allowed freely in special cases contradicts the fundamental purpose of antibacksliding, which is to prevent weakening protections. Claiming it applies only to water quality standards narrows the concept incorrectly to one aspect, whereas the rule governs permit limits overall (including technology-based limits). And stating that NPDES permits are always more stringent is too absolute because there are narrowly defined exceptions where a relaxation is permitted under the statute or regulations.