ROOF RAISING AT PRWID
Inch-by-inch, a heavy crane begins hoisting the 34-ton, 65-foot diameter steel dome. Then degree-by-degree, it rotates to the cylindrical concrete building where it will sit.
The dome is the new roof for the digester at the Price River Water Improvement Distict Waste Water Treatment plant in Wellington. A digester is an all-you-can-eat buffet for bacteria that break down waste.
The old dome had corroded over the years to the point that it was unsafe. Bacteria are gassy little guys.
The steel lid had been assembled on site, designed and manufactured to fit precisely into the digester building, like a shell in a shotgun barrel.
Workers guide and manipulate the dome with guy lines, matching numbers on the lid with numbers on the building for alignment. But there's a problem: Once the crane cables take up the weight on the protruding beams, there's a slight distortion in the top. The distortion is magnified over the eight-foot wall. The bottom is three-inches out of round, no longer a perfect circle. Workers have to muscle it into shape, and once it's started past the concrete rim the rest slides into the building smoothly.
A second dome is scheduled for next spring.