A Decision Support Tool for Managing the Pipe Network of the Honolulu Board of Water Supply (Year 2)

A Decision Support Tool for Managing the Pipe Network of the Honolulu Board of Water Supply (Year 2)

National Institute for Water Resources, Water Resources Research Institute Program

3/1/2010 – 2/28/2011

Similar to numerous other cities, Honolulu's municipal water systems has many aging and unreliable components. The Board of Water Supply contends with a number of water main breaks and leaks, and recognizes the need to replace the aging pipelines. Associate Professor V. Amarjit Singh, with Professor Chittaranjan Ray, of the UH Civil and Environmental Engineering Department, continued their work to develop a model to forecast water main breaks and construct an asset management paradigm to rationalize the planning of the water infrastructure work.

The Honolulu Board of Water Supply (BWS) manages the drinking water supply and distribution system for the island of Oahu, Hawaii, serving approximately one million customers with 54 billion gallons of freshwater every year (Chung et al. 2008). In FY 2008–2009, the BWS had a total field operations budget of $19 million per year. The BWS maintains over 2,000 miles of pipes, and installs approximately 30 miles of pipe annually at an average cost of about $1.6 million per mile. Over the last 22 years the BWS Oahu water-distribution system has averaged 366 breaks per year. Given the scale of its operations, the BWS needed to develop the best management practices (BMPs) for pipe-utility management. Doing so would aid the BWS in deciding which pipes to replace and when, in a more scientific manner.

The following study objectives were established:

1. Develop a framework of BMPs for pipe-utility management at the BWS to aid in quality control and in prioritizing specific pipelines for replacement. The goal is to improve policymaking at the BWS so that decisions may be made in a more informed and scientific manner.

2. Develop a warning system using indicators; including the cause(s) of current/past pipe breaks, pipe age, pipe diameter, pipe type, and soil type to determine when and where pipes should be replaced.

3. Develop operating-characteristic curves for various pipes showing the number of breaks, the average cost per break per length in ground, and the average age of various pipes.

4. Calculate the reliability of the water-distribution system identifying various pipe ages, various pipe diameters, and various pipe types.

5. Undertake availability analysis, apply process-capability analysis to availability.

6. Undertake Bayesian analysis for the probability of failure of a given pipe age, pipe diameter, pipe type, and soil type.

7. Develop a pipe-replacement prioritization.

8. Develop a facility condition index.

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