effect on the quality of water reaching the consumer. Also, the report focuses on traditional distribution system design, in which water originates from a centralized treatment plant or well and is then distributed through one pipe network to consumers. Non-conventional distribution system designs including decentralized treatment and dual distribution systems are only briefly considered. Such designs, which would be potentially much more complicated than traditional systems, require considerably more study regarding their economic feasibility, their maintenance and monitoring requirements, and how to transition from an existing conventional system to a non-conventional system. Nonetheless, many of the report recommendations are relevant even if an alternative distribution system design is used.
The federal regulatory framework that targets degradation of distribution system water quality is comprised of several rules under the Safe Drinking Water Act, including the Lead and Copper Rule (LCR), the Surface Water Treatment Rule (SWTR), the Total Coliform Rule (TCR), and the Disinfectants/Disinfection By-Products Rule (D/DBPR). The LCR establishes monitoring requirements for lead and copper within tap water samples, given concern over their leaching from premise plumbing and fixtures. The SWTR establishes the minimum required detectable disinfectant residual and the maximum allowed heterotrophic bacterial plate count, both measured within the distribution system. The TCR calls for distribution system monitoring of total coliforms, fecal coliforms, and/or E. coli. Finally, the D/DBPR addresses the maximum disinfectant residual and concentration of disinfection byproducts like total trihalomethanes and haloacetic acids allowed in distribution systems. A plethora of state regulations and plumbing codes also affect distribution system water quality, from requirements for design, construction, operation, and maintenance of distribution systems to cross-connection control programs.
Despite the existence of these rules, programs, and codes, current regulatory programs have not removed the potential for outbreaks attributable to distribution system-related factors. Part of this can be attributed to the fact that existing federal regulations are intended to address only certain aspects of distribution system water quality and not the integrity of the distribution system in its totality. Most contaminants that have the potential to degrade distribution system water quality are not monitored for compliance purposes, or the sampling requirements are too sparse and infrequent to detect contamination events. For example, TCR monitoring encompasses only microbiological indicators and not in real time. With the exception of monitoring for disinfectant residuals and DBPs within the distribution system and lead and copper at the customer’s tap, existing federal regulations do not address other chemical contaminants.
Although it is hoped that state regulations and local ordinances would contribute to public safety from drinking water contamination in areas where federal