EPA is approving the use of updated versions of previously approved American Society for Testing and Materials (ASTM), Standard Methods for Examination of Water and Wastewater (Standard Methods or SM) and Environmental Protection Agency (EPA) analytical methods for compliance determinations of chemical and microbiological contaminants in drinking water. At the same time, the Agency is withdrawing approval of the previous versions of the 14 EPA methods. Previous versions of the SM and ASTM methods will continue to be approved. The Agency is promulgating these methods as a direct final rule because the Agency does not expect adverse comments and wants to ensure prompt availability of the methods for compliance monitoring. In addition, the Agency is making minor technical corrections or clarifications to the regulations, amending the regulation to change the composition of Performance Evaluation (PE) samples and require successful analysis of PE samples once each year.