Tiered Approach for the Condition Assessment of 50-year old Steel Waterline with History of Breaks

摘要

The City of Aurora, Colorado Water Department (Aurora Water) is implementing a condition assessment program for their aging waterlines. A critical part of this program is the evaluation of technology options and tiers of condition assessment approaches for buried waterlines to determine estimated remaining useful life and the best approach for rehabilitation/replacement planning.Aurora Water and CH2M partnered on a pilot project for this program by evaluating the condition of a 50-year-old 30-inch steel waterline. The waterline, located in a high traffic roadway, has frequently broken. A tiered approach for condition assessment was implemented to maximize information gain from lower-cost simple evaluations prior to evaluating technology options and investing in advanced pipeline tool inspections.The first tier of the evaluation reviews existing information to map the location of breaks, compile cathodic protection test data, and perform field inspection and cathodic protection system testing. In the initial evaluation, failures were identified in a condensed waterline reach that appeared to be less protected by the impressed current system. The next tier compared options for more advanced condition assessment and evaluated corrosion control strategies, including coatings, linings, joint bonding, and anode installation. Implementation of advanced pipe inspection technology then determines remaining pipe wall thickness in the affected area. This inspection technology was selected based on installation requirements and invasiveness of the tool, the quality and resolution of acquired data, and cost.This paper discusses the tiered approach in detail and the outcome of cathodic protection testing and advanced pipe inspection tool testing.