Integrating GIS, Hydraulic Modeling, Failure Forecasting, and Planning Software to Build a Better R&R Mousetrap

As far back as the 1950s, many of the mature urban water systems in the US started experiencing higher numbers of failures, dirty water complaints and other age-related distribution problems. A handful of proactive utilities responded by developing aggressive pipe rehabilitation and replacement (R&R) programs that targeted the most obvious “culprit” mains. After decades conducting successful R&R programs, the number of failures and the frequency of water quality complaints declined. These proactive utilities are now asking themselves, “What do we do now? ”Modeling software is increasingly required to simultaneously weigh all the factors that determine which pipes to address and in what order. The analysis often starts with a statistical assessment of failure probabilities by pipe characteristic (age, material, diameter, etc.). One of the most advanced tools for failure forecasting is LEYP, developed by CEMAGREF, France. LEYP helps determine predicted break rates for various cohorts (groups) of pipe and correlations between pipe characteristics and environmental factors (location, soils, materials, etc.). Following failure forecasting, a multi-criteria decision making tool is employed to examine a range of probabilistic and consequential factors influencing R&R. These factors include, for example, impact on sensitive users, water quality and effects of rail and roadway vibration. One tool that is gaining popularity for this type of analysis is Annual Rehabilitation Planning (ARP), a computer model developed for the European research program CARE-W based on Electre Tri. ARP provides a rigorous definition of criteria and a robust analytical approach that uses reference profiles which take uncertainty into account, as opposed to simply adding ranking scores of various criteria. A model that works well in combination with ARP is KANEW, an Awwa Research Foundation (AwwaRF - now the Water Research Foundation) funded planning tool, which has been expanded and further developed in Europe. KANEW can generate macro-level planning models to help determine R&R needs over a long time horizon.This paper will review a process using a combination of advanced modeling to make R&R decisions; explain how these models are used in collaboration with Geographic Information Systems (GIS), field and hydraulic modeling data to make R&R decisions; and show an example of how values for the criteria have can be derived using a wide array of sources including:GIS and pipe inventory data;Work orders, capital planning documents, complaint records, etc.;Planning overlays available from other city departments and other agencies and utilities;Hydraulic models;Field data (pipe coupons, soil samples, visual observations, etc.).This information will provide utilities with a road map for improving the process by which R&R decisions are made leading to an answer for the question, “What do I do now? ”