Continuity Testing of the Rampart and Homestake Pipelines

Abstract

The Rampart Raw Water Pipelines deliver water from Aurora's Rampart Reservoir to the Griswold and Wemlinger Water Treatment Plants for treatment and distribution to the City of Aurora's customers. The Rampart Raw Water Pipeline Phase III (Sta. 617+81 to Sta. 841+50) consists primarily of 54-inch-diameter Prestressed Concrete Cylinder Pipe (PCCP) manufactured by the Concrete Pipe Division of United States Pipe and Foundry Company in 1980. In addition, Aurora jointly owns (with the City of Colorado Springs) the Homestake Pipeline, a 66-inch Prestressed Concrete Non-Cylinder pipeline, which is an intermountain water supply that is the primary source for the water transported through the Rampart Pipeline. Simpson Gumpertz & Heger (SGH) prepared a Preliminary Failure Risk Analysis and Repair Priorities report (dated February 13, 2008), which presents the results of the company's risk analysis and repair priorities for the distressed PCCP between Sta. 762+11 and Sta. 815+29. Based on review of available data and risk analysis, SGH evaluated the pipe sections with a high distress rate in the area indicated above. PPIC had identified 80 pipe sections with broken wires in 2006, compared to 38 pipes in the 2002 inspection. The number of pipes with broken wires more than doubled over a 3-year period, which equates to an increase of 28% per year. Because of the apparently high increase in wire breaks or wire break activity, SGH recommended performing wire continuity measurements on 8 pipes identified by PPIC in 2006 as having more than 50 wire breaks to develop a relationship between the REF/TC-predicted and the number of broken wires indicated by the continuity test. Additionally, Pure Technologies performed electromagnetic testing (P-wave) in 2002, and PPIC performed RFEC/TC testing in 2002 and 2006 on portions of the Homestake Pipeline. One pipe, Pipe 352, was identified with 5 to 20 wire breaks in 2002 by Pure; with 25 in 2002; and with 50 in 2006 by PPIC. This pipe was selected as a candidate for continuity testing and, ultimately, dissection, to verify the actual number and location of broken wires. Two separate continuity-testing programs were performed on Pipe 352. The pipe was then removed, dissected, and documented. This paper presents the results of the continuity tests performed on certain pipe sections of the Rampart and Homestake Pipelines to develop a relationship between the REF/TC-predicted number of broken wires and the number of broken wires indicated by the continuity test.