AWWA JAW68261

This study investigated 16 repair sites of drinking water mains to monitor the effect of main repairs on water quality. Samples were collected from the distribution system and from the soil and groundwater surrounding the mains. Changes in water quality outside the isolated repair area were also monitored. A total of 424 water samples collected from consumers' homes and flushed hydrants were assayed for total coliforms, Escherichia coli, and aerobic endospores. Total coliforms were detected in 4.0% of these samples and E. coli in only a single sample. Almost all of the positive samples (16 of 17) were collected during the flushing step of the repair process. Water quality changes, including losses of chlorine residuals and peaks in turbidity, were also observed outside the repair area. Repairs of water mains are routinely conducted by water utilities, and, moreover, the frequency of repairs in some systems can be quite high because of the system's age and resulting deterioration. Water utilities should have measures in place to ensure that their operational practices are adequate for public health protection as well as for regulatory compliance. Includes 36 references, tables, figures.