1980 | Bill Martin inside Shasta Dam
Though Shasta Dam is designed as a gravity structure, an enormous chunk of concrete holding back the three arms of the Sacramento River in an engineering-advantageous site, the dam flexes about five inches over its designed range of full-pool and draw-down levels.
Of the various means of tracking the dam’s response to the seven trillion tons of water impounded upstream, this one is most reliable — a plumb-bob on a five-hundred-foot wire passing through the heart of the dam, with reference cross-hairs in several interior galleries.