How to Protect Your Pipeline from Corrosion in a Pipeline Spaghetti Bowl

The ground is full of all kinds of pipelines of different sizes, materials, pressures and cathodic protection (CP) systems. Most metallic or concrete pipes installed these days utilize a cathodic protection system of some kind. How do you ensure that the cathodic protection system of your new pipeline will not be compromised by existing cathodic protection systems nearby? Freese and Nichols, Inc. (FNI) recently designed 27,200 feet of 48-inch and 47,400 feet of 42-inch treated water pipeline for the North Texas Municipal Water District in rural North Texas. Paralleling existing utility corridors was favored during pipeline alignment selection to avoid severing properties and reduce overall land acquisition costs, but this also posed challenges during design. The route selected for this pipeline included paralleling an existing natural gas transmission line continuously for approximately 22,000 feet. The existing gas line, configured with an impressed current cathodic protection system, could have significant impacts on corrosion protection systems and life-span of parallel pipelines. Reducing the chance of interference between the two pipelines' cathodic protection systems and ensuring measures were taken to monitor any potential interference in order to extend the life of this asset was a driving factor for the cathodic protection design of this pipeline. This paper discusses the pipe materials considered including bar-wrapped pipe and polyurethane coated steel pipe, as well as the cathodic protection systems considered including impressed current, magnesium ribbon and magnesium groundbeds. Other cathodic protection considerations for a rural pipeline including test station details, rectifier details and placement and pipeline crossing details are discussed in this paper.