Summertime has ended and so has one of the biggest jobs at CAP: relining the discharge lines and manifolds at Mark Wilmer Pumping Plant.
The discharge lines are massive, measuring 12 feet in diameter and nearly 2,500 feet long, making the job long and arduous. The work involved removing the old lining system and replacing it with a new epoxy coating. First, crews removed the existing coal tar enamel coating utilizing an ultra-high pressure (UHP) water blast that operated at 34,000 pounds per square inch (psi). Large vacuums were brought in to remove the coal tar debris which was up to a half-inch thick in the bottom of the pipe before removal.
Next, abrasive blasting was done with copper ore slag to roughen and clean the steel surface of the inside of the pipe in preparation for painting. More than a million pounds of blast media was used to achieve the 3-4 mil profile on the steel surface, which is comparable to the roughness of 150-grit sandpaper.
Finally, 50 mil, roughly 1/20-inch of new coating was applied to the roughened steel using a plural component, 100% solids epoxy. Quality control testing was done to help ensure that the coating will last for 25-30 years. Mark Wilmer Pumping Plant has two discharge lines; the first one was relined last summer.
This process took 85 days, with crews working two shifts, seven days a week and was completed seven days ahead of schedule. Early delivery of the project allows CAP to begin pumping at Mark Wilmer Pumping Plant a week sooner, a benefit to all Arizonans.