Protecting any water distribution infrastructure from corrosion is essential to its performance. But the stakes are much higher when the habitability of an entire region depends on man-made infrastructure for a reliable water supply.

The Metropolitan Water District of Southern California’s (MWD) Etiwanda Pipeline is part of a complex network that helps bring water from the wetter parts of northern California to the parched basins and valleys of the south. It is 12-feet wide and stretches 10 miles beneath the communities of Fontana and Rancho Cucamonga north of Los Angeles.

Mortar linings must remain damp for optimal performance, and for most water pipelines, that’s not a problem. But more frequent and more severe droughts across California left the Etiwanda Pipeline dry at times. In periods of no water, the mortar dried out and began to crack. When water again filled the pipeline, the force of its motion caused chunks of weakened mortar to break free. The result: unimpeded corrosion of newly exposed steel.

During an initial phase of the rehab, MWD trialed various lining products from a host of manufacturers. For the new polyurethane lining to perform as intended, two coats were needed. Carboline’s Polyclad 767, a rigid polyurethane formula designed for water and wastewater pipelines and water tank linings, performed best and was chosen for the remainder of the work.

Polyclad 767’s cure time is short enough that the crew applying the second coat could safely guide the rotary spray equipment over the first coat after a very short wait. Its recoat window is long enough that the crew wouldn’t need to wipe down or abrade the first coat to ensure the second coat would adhere properly. Lining application wrapped up a staggering two months ahead of the initial schedule, saving crews time and money while restoring the pipeline’s integrity for years to come.