Today's action amends the regulations that set forth the requirements for States to obtain and retain primary enforcement authority (primacy) for the Public Water System Supervision (PWSS) program under section 1413 of the Safe Drinking Water Act (SDWA) as amended by the 1996 Amendments. This rule adds the new administrative penalty authority requirement that States must meet in order to obtain or retain primacy, plus changes the timing for a State to adopt new or revised drinking water regulations. The rule also changes a State's primacy status while awaiting a final determination on its primacy application. Additionally, the rule's language provides examples of circumstances that require an emergency plan for the provision of safe drinking water. Lastly, this action expands the definition of a public water system (PWS). Since all of the above changes are merely a codification of the amended SDWA, the Agency is publishing this document as a final rule.