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 Posted: 06/11/2008
New philosophy drives approach to revised TCR
Carrie Lewis, superintendent of the Milwaukee (Wis.) Water Works and AWWA's representative on the TCR revision advisory committee, described a fundamental shift in approach to microbiological regulation of drinking water: The federal advisory committee on a new TCR has agreed in principle to a regulation using total coliforms as an “indicator of system health, not public health.” The advisory committee, backed by a technical workgroup, recommends keeping the maximum contaminant level (MCL) and the maximum contaminant level goal for E. coli. However, a positive test for total coliforms or E. coli would prompt a distribution system assessment and corrective action. “The presumption is that the utility would take responsibility,” said Lewis, speaking at a session at the AWWA annual conference. David Visintainer, St. Louis Public Utilities director, discussed the implications of the new rule for utilities, but stressed that nothing is final. The proposals include more flexible site selection for repeat sampling after a positive sample, “so that repeat sampling can become an opportunity to collect useful data” and try to pinpoint any deficiency. In a regular monitoring regimen, two or more positive total coliform samples in systems with fewer than 40 samples a month, or 5 percent or more positive TC samples for systems with more than 40 samples a month, would trigger a level 1 assessment, estimated to take from one-half to two person-days to conduct. The level 1 assessment would be utility-directed, Visintainer said, and would seek to identify possible contributing events, such as treatment interruptions, pressure loss, vandalism, cross connections or main repairs. Any sanitary defects found, whether associated with the positive sample or not, would need to be corrected. However, Visintainer noted, many positive TC samples are never attributed to a cause. Not conducting an assessment and correcting any deficiency is termed a treatment technique violation under the rule, though a treatment is not prescribed. A level 2 assessment would be triggered by exceeding the acute MCL—two positive E. coli samples or a positive E. coli and a positive total coliform sample from a routine or repeated sampling. Public notice would only be required for MCL or treatment technique violations or for monitoring and reporting violations. The new rule is not scheduled for proposal until 2010 and promulgation in 2011; however, that schedule may be affected by a new administration next year, said Sean Conley from the US Environmental Protection Agency. Mary Parmelee, MainStream Editor
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