Phased and Focused Approach for Water Pipeline Corrosion Assessment

The Southern Nevada Water Authority (SNWA), Las Vegas, Nevada, experienced a corrosion failure on the Las Vegas Valley Lateral in 2007 and retained the services of HDR Engineering, Inc. (HDR) to provide a critical condition assessment of this large-diameter potable water pipeline in Las Vegas, Nevada. Consisting of approximately 58,000 linear feet (17,678.4m) of predominantly 66-, 72-, and 90-inch-diameter (1676.4, 1828.8, and 2286 mm) cement-mortar-lined-and-coated (CML&C) steel pipe and some 96-inch-diameter (2438.4 mm) pre-stressed concrete cylinder pipe (PCCP), the Las Vegas Valley Lateral (LVVL) and the North Las Vegas Lateral (NLVL) pipelines were constructed during the late 1960s with no cathodic protection and only a few corrosion test stations installed. The project team included various specialized subconsultants (Schiff Associates, Kleinfelder, TRC Solutions, Rafael Civil, and the RockSolid Group) for corrosion testing and evaluation, geotechnical investigation, surveying, test station installation and excavations, and broadband electromagnetic testing. Buried pipelines often operate in a state of anonymity with respect to internal or external corrosion until the deterioration is severe enough to cause failure. Corrosion is the deterioration of a substance or its properties because of a reaction with its environment. External environments (around the outside surface of the pipe) more commonly promote water pipe corrosion. Condition assessment of the pipeline provides useful information to determine the current pipe condition to make recommendations for repair, renewal, or monitoring. The focus of this paper is the application of specialized inspection technologies for water pipeline condition assessment and the development of the strategic phases of field work to deploy these technologies only when needed. The progression to the next phase of work required an evaluation of the data and results obtained from the previous phase.