A Tale of Two Utilities: How Portland Water (Oregon) and WaterOne (Kansas) Justify and Apply Condition Assessment for Pipe Risk Management

Abstract

Two utilities, the Portland Water Bureau of Oregon, and WaterOne of Kansas, provide water supply to over 400,000 customers. Both utilities have over 2,000 miles of pipe. Portland Water has more cast iron pipe and low break rates, due to a relatively non-corrosive environment. WaterOne has more ductile iron and cast iron pipe, with a corrosive soil environment. WaterOne has much higher break rates. Most pipes in the Portland Water system are run to failure; a pipe replacement program is focused primarily on those pipe segments with a history of low consequence leaks and breaks. WaterOne also has a pipe replacement program but break history is only one of eight criteria. Both utilities use condition assessment for the management of high consequence pipes. Portland Water uses primarily leak detection. WaterOne uses methods to detect pipe wall thickness lost. A business case methodology has been used to justify condition assessment. Portland Water has justified a major condition assessment effort by considering the risk cost of catastrophic failure. WaterOne has justified a major condition assessment by considering the value of selective replacement of the most corroded sections of a pipe only and deferral of the remainder of the pipe.