AWWA JAW58672

The performance-based measurement system (PBMS) is a new approach developed by the US Environmental Protection Agency (USEPA) to modify analytical methods. Method modifications are made to improve performance, increase laboratory efficiency, or reduce costs, outcomes that should ultimately lead to better quality water data. USEPA methods 1622 and 1623 are the first of the agency's microbiological methods to be modified by PBMS. Laboratories and manufacturers have two avenues for introducing method modifications to improve performance or efficiency. Tier 1 validation is used when an individual laboratory wants to alter a component or step in the method for in-house use. Tier 2 validation is used when a manufacturer or other organization wants to demonstrate acceptable performance of a modified version of the method for nationwide use. The PBMS approach to method flexibility is straightforward in principle, but the actual "how-to" of applying the approach can be confusing, even for those laboratories conducting tier 1 studies. This article details how to use PBMS, including conducting modified method acceptability studies, and offers case studies of successful and unsuccessful modification outcomes. Includes 20 references, tables.