AWWA JAW70392

Soil intrusion during water main repairs can render a distribution system vulnerable to contamination. Because fecal indicators are not always present in soil and groundwater near water mains, they cannot be used to monitor intrusion into the distribution system. This study provides data to support the use of aerobic endospores to monitor intrusion and evaluate distribution system maintenance practices. Aerobic endospores are naturally found in soil, easy to measure, and more resistant to chlorine than bacterial indicators. In the case of suspected low or negative pressure in a part of the distribution system, aerobic-endospore measurement could be useful in assessing the possibility that the lack of pressure was associated with potential contamination. Aerobic endospores also meet the criteria for an ideal microbial indicator of intrusion, namely the ability to confirm both the pathway by which potentially contaminated water entered the distribution system and the extent of the intrusion. Includes 52 references, tables, figures.