Unregulated Contaminant Monitoring Regulation for Public Water Systems; Analytical Methods for Perchlorate and Acetochlor; Announcement of Laboratory Approval and Performance Testing (PT) Program for the Analysis of Perchlorate

The Safe Drinking Water Act (SDWA), as amended in 1996, requires the U.S. Environmental Protection Agency to establish criteria for a program to monitor unregulated contaminants and to publish a list of contaminants to be monitored. In fulfillment of this requirement, EPA published the Revisions to the Unregulated Contaminant Monitoring Rule (UCMR) on September 17, 1999 (64 FR 50556), which included a list of contaminants to be monitored. Both perchlorate and acetochlor were placed on the UCMR (1999) List 1, Assessment Monitoring, with the method listed as "Reserved" pending imminent conclusion of EPA refinement and review of the analytical methods for perchlorate and acetochlor. EPA is taking direct final action on this rule. This rule specifies the approved analytical methods for measurement of perchlorate and acetochlor in drinking water and includes notice to all laboratories interested in supporting perchlorate monitoring of the laboratory approval requirements, including participation in a perchlorate Performance Testing (PT) Program. The rule also includes minor technical changes to correct or clarify the rule published on September 17, 1999.