American water resource agencies are increasingly turning to risk analysis to prioritize replacement and rehabilitation (R&R) activities, especially for distribution and collection system piping. Risk is commonly evaluated using a two-dimensional matrix, and pipes scoring highest in both dimensions (failure likelihood and failure consequence) are scheduled for attention first. This approach is an improvement over traditional methods but still has two shortcomings: It ignores the cost of the rehabilitation as compared with its benefits, and it does not help utilities identify those activities that are worth undertaking from a community value point of view―and those that are not. A number of agencies, including the Orange County Sanitation District (OCSD), are developing more comprehensive approaches to address both of these shortcomings and to identify wOCSD is a large regional treatment agency in Orange County, California.
It serves 22 cities, two special districts, and the portions of the County of Orange with a total population of 2.4 million
within a 470-square-mile area. It treats an average daily flow of 243 million gallons and produces over ten million gallons daily of reclaimed water. Among its major assets are:
- Two large treatment plants
- 17 pumping stations of various capacities
- 620 miles of both large- and small-diameter pipe
- Two ocean outfalls, one of which is five miles long.
OCSD has been developing an asset management program for several years. The work described in this paper was influenced by that program and by OCSD’s continuing efforts to provide the best value for the communities it serves.