UNITED STATES ENVIRONMENTAL PROTECTION AGENCY GUIDANCE FROM HOTLINE COMPENDIUM WSGH46 SUBJECT: Monitoring for Unregulated Contaminants SOURCE: Jeff Sexton, OGWDW (202) 260-7276 In the Phase H Rule that was promulgated on January 30, 1991, (56 FR 3526) Section 141.40 requires all Community Water Systems (CWS) and Non-Transient Non-Community Water Systems (NTNCWS) to monitor for 24 unregulated contaminants. The codified language does not dictate the exact reporting requirements for analytical results that are below the Method Detection Limits (MDLs). In a separate rule making, the Lead and Copper Rule promulgated on June 7, 1991 (56 FR 26460), EPA mandated in Section 141.89 that contaminant levels below the MDL be reported as zero. By analogy to the Lead and Copper Rule, should zero be reported to the state when a value less than the MDL is obtained for a Phase II unregulated contaminant? Response: No. The requirement for reporting of contaminant levels below the MDL as zero applies to the calculation of a running annual average of quarterly analytical results for the determination of compliance with an MCL. An example would be the determination of compliance with the VOC MCLs (a guidance document on reporting violations of the VOC [Phase I] requirements to FRDS was prepared by the Drinking Water Branch in 1990.) The only violation that can be incurred relative to the unregulated contaminants, however, is a monitoring violation. In the Phase I VOC Rule (52 FR 25715), Section 141.35 states that the State "shall furnish to the Administrator for each sample analyzed under Section 141.40: (1) Results of all analytical methods, including negatives; ..." The analytical results for the unregulated contaminants that are below the Method Detection Limit (MDL) should be reported as less than the specified MDL. For example, if an unregulated contaminant could not be quantified at, or above, the MDL of say 0.5 ug/1, it should be reported as "< 0.5 ug/1" and not as zero or "ND" (not detected). In this way, the users of the data have a better "handle" on the actual value. Less-than values also give one an indication of the quality of the laboratory data; i.e., how low their MDLs are. If statistical calculations then need to be made, the less than value can be assigned a value such as zero or one-half of the MDL. OGWDW is developing reporting guidance for Phase U unregulated contaminants and expects it to be available late spring 1992. ------- |