The U.S. Environmental Protection Agency (EPA) is proposing minor amendments to its Clean Water Act (CWA) regulations to codify that under the National Pollutant Discharge Elimination System (NPDES) program, only “sufficiently sensitive” analytical test methods, i.e., those that are capable of detecting and measuring the pollutants at, or below, the respective water quality criteria or permit limits, can be used when completing an NPDES permit application and when performing sampling and analysis pursuant to monitoring requirements in an NPDES permit.
This proposal is based on requirements in the CWA and existing EPA regulations. It also would codify existing EPA guidance on the use of “sufficiently sensitive” analytical methods with respect to measurement of mercury and extend the approach outlined in that guidance to the NPDES program more generally. Specifically, EPA is proposing to clarify the existing NPDES application, compliance monitoring, and analytical methods regulations. The amendments in this proposed rulemaking affect only chemical-specific methods; they do not apply to the Whole Effluent Toxicity methods or their use.
EPA and state permitting authorities use data from the permit application to determine whether pollutants are present in an applicant’s discharge and to quantify the levels of all detected pollutants. The pollutant data enables the director of the permitting authority to make a sound reasonable potential determination and, if necessary, establish appropriate permit limits. It is critical, therefore, that applicants provide data that are measured with a precision and accuracy that will be meaningful to the decision making process. The same holds true for monitoring and reporting relative to permit limits established for regulated parameters.
The public will have 45 days to comment on the proposed rulemaking after publication in the Federal Register.