40 CFR 93.164 — Inter-precursor mitigation measures and offsets.

Federal agencies must reduce the same type of pollutant as being increased by the Federal action except the State or Tribe may approve offsets or mitigation measures of different precursors of the same criteria pollutant, if such trades are allowed by a State or Tribe in a SIP or TIP approved NSR regulation, is technically justified, and has a demonstrated environmental benefit.