AWWA DSS58694

Unidirectional flushing (UDF) is an important program EPCOR Water Services Inc. (EWSI) implements to ensure the distribution of high quality water to their customers. The following paper describes the recent optimization study that compiled and analyzed seven years of data records to determine the most advantageous flushing frequencies for the City of Edmonton. The 2002 study looked at optimizing the existing UDF Maintenance Program to decrease flushing frequencies while maintaining water quality and service. An abundant amount of information related to the effectiveness of UDF existed so EWSI developed "Area Information Frequency Sheets". The sheets provided a systematic layout to compile all applicable data recorded since 1995. The area information includes: basic statistics; flushing history; water quality; and, customer complaints. Initial conclusions indicated Edmonton's existing two-year flushing frequency was more than adequate to maintain service of high water quality to EWSI's customers. The first conclusion of the study was encouraging as it indicated the flushing frequencies could be decreased; however, it did not provide direction on how to divide the areas according to allowable time between flushing. From a literature review and the availability of Edmonton data, five factors or "triggers" were determined to be influential in governing the effect of unidirectional flushing. The outcome of the optimization study was the assignment of a one- to four-year flushing cycle and the selection of either 2002 or 2003 as the next year to flush for each UDF area. This optimization study was a success. The budgeted number of UDF runs for 2002 was 2450; the actual number of runs was 1355. This reduced but effective flushing translated to approximately $150,000 Canadian dollar saving in 2002. Over the next five years, the study projects 25% reduction in annual UDF costs. Through the resulting efficient flushing, large cost savings will be realized through reduced manpower, energy consumption, and water use. Includes 2 references, tables, figures.