AWWA ACE68964

This powerpoint presentation begins by providing a brief overview of the City of Raleigh distribution system, water quality parameters affected by nitrification, the current Total Coliform Rule (TCR), and possible future regulatory compliance. The beginning of coliform studies by CDM in 2004 is presented, along with a water quality monitoring plan, and distribution system field studies. A 2005 CDM distribution system water quality field study is outlined, including sampling plan improvements, TCR sample site plan update, and study completion and summary of changes implemented. Results achieved include the following: dramatic decline in number of coliform positives; improved communication within the Water Plant Division, and between the Water Plant Division and other Public Utilities Divisions using GIS; tracking and trending of laboratory data; and, better prepared when drought hit in 2007-08. Summary of key past and future items that improve TCR compliance is presented, including the following: high residual chlorine concentrations; additional monitoring and enhanced operation of distribution system to keep tanks turned over and dead-ends flushed and to watch for nitrification; enhanced full-system flushing with elevated amounts of free chlorine flushed though sample sites, deadends; updated TCR Sampling Plan; improved model and identification of isolation zones; developed a Department Operating Procedure for coliform occurrence investigation and bridge department sharing of relevant information with GIS (spot flushing, main breaks, sample plans, new lines, backflow, plumbing), Response Team formed; expand cross-connection control program, site plumbing investigations; implement nitrification control procedures (lower ammonia, flushing, etc.); and, corrosion control and infrastructure upgrades and maintenance. Includes figures.