The Environmental Protection Agency ("EPA") is granting the California Air Resources Board ("CARB") its request for an authorization of its amendments to its Commercial Harbor Craft regulations ("CHC Amendments") . EPA is also confirming that certain CHC amendments are within the scope of a prior EPA authorization. CARB's CHC Amendments primarily subject diesel-fueled engines on crew and supply, barge and dredge vessels to the in-use engine emission requirements of the original CHC regulations; allow CARB or EPA Tier 2 or higher tier certified off-road ("nonroad") engines to be used as auxiliary or propulsion engines in both new and in-use CHC vessels; and clarify requirements and address certain issues that have arisen during CARB's implementation of the original CHC regulations. This decision is issued under the authority of the Clean Air Act ("CAA" or "Act") .