AWWA JAW69707

Total coliform monitoring in the distribution system is perhaps the most expensive and intensive sampling mandated by law, with the national cost of sampling required by the Total Coliform Rule (TCR) calculated as being in excess of $100 million annually. For all but the largest utilities, however, the sampling mandated under the TCR is inadequate to measure with any confidence the real differences in total coliform occurrence between months. Because of the low number of samples taken by all but a few large facilities, most sample sizes are too small for systems to be able to verify the effectiveness of any mitigative action following a TCR violation. This article explains the statistical limitations of current TCR practices and argues that current monitoring of total coliform does not meet the stated objectives of the rule. In addition, the authors suggest strategies to enhance information recovery from total coliform observations. Includes 7 references, tables, figures.