the hetch hetchy reservoir near yosemite. tonight a look at an innovative project to keep water moving in the event of a big earthquake. >> from the ground like any other hole in the ground m a construction site. go below, and you'll see why this is special. >> hayward fault runs below and through this area. >> keeping this pipe working in a major earthquake for people in the bay area. >> it shows it survived the earth kwa >> allen overseas the commission showed us around. it's like a giant room surrounding the pipe. and the engineers designed two of the larnlest trains ever manufactured to make sure it stays intact. this animation shows how two work together whchlt a quake