and Drinking Water

This document contains direction developed solely to provide internal guidance to U.S. Environmental Protection Agency (EPA) personnel. EPA retains the discretion to adopt approaches that differ from this guidance on a case-by-case basis. The guidance set forth in this document does not create any rights, substantive or procedural, enforceable at law by a party to litigation with EPA or the United States. The use of mandatory language such as "must " and "require " in this guidance document reflects sound scientific practice and should not be construed to create any legal rights or requirements. The use of non-mandatory language such as "may, " "can, " or "should " in this guidance does not connote a requirement but does indicate EPA’s strongly preferred approach for validating and peer reviewing EPA methods prior to publication for general use