AWWA DSS58694

AWWA DSS58694 Unidirectional Flushing: Operational Excellence at EPCOR Water Services
Conference Proceeding by American Water Works Association, 10/01/2003

Deagle, Gabrielle

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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 analyzedseven years of data records to determine the most advantageous flushing frequencies forthe City of Edmonton.The 2002 study looked at optimizing the existing UDF Maintenance Program to decreaseflushing frequencies while maintaining water quality and service. An abundant amount ofinformation related to the effectiveness of UDF existed so EWSI developed "AreaInformation Frequency Sheets". The sheets provided a systematic layout to compile allapplicable 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 morethan adequate to maintain service of high water quality to EWSI's customers. The firstconclusion of the study was encouraging as it indicated the flushing frequencies could bedecreased; however, it did not provide direction on how to divide the areas according toallowable time between flushing. From a literature review and the availability ofEdmonton data, five factors or "triggers" were determined to be influential in governingthe effect of unidirectional flushing.The outcome of the optimization study was the assignment of a one- to four-year flushingcycle 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 was2450; the actual number of runs was 1355. This reduced but effective flushing translatedto approximately $150,000 Canadian dollar saving in 2002. Over the next five years, thestudy projects 25% reduction in annual UDF costs. Through the resulting efficientflushing, large cost savings will be realized through reduced manpower, energyconsumption, and water use. Includes 2 references, tables, figures.