Improving the Selection of Sewer Main Replacement, Repair and Rehabilitation Treatments Using GIS and Asset Management Systems

The selection of sewer mains for replacement, rehabilitation or repair requires prioritization of scarce capital funds. Historically, many sewer utilities have either unabashedly based their selection on number and vehemence of customer complaints (the “squeaky wheel” approach) or by using various “rules of thumb” (say, “after three dig repairs”) that lack quantitative rigor. The City of Calgary had been using video scores based on the WRc recommendations, and found that many mains exceeding WRc video scores of 165 did not require replacement, indicating that this was not reliable as a sole criterion. A system has been developed to predict the “money worth spending” on a sewer to deliver desired service levels, and use a number of criteria as proxies to calculate a best-estimate of that value.