A helicopter lowers a load of rocks to fill in a hole near the Oroville Dam's emergency spillway, Tuesday, Feb. 14, 2017, in Oroville, Calif. The barrier, at the nation's tallest dam, is being repaired after authorities ordered mass evacuations for everyone living below the lake out of concerns the spillway could fail and send a 30-foot wall of water roaring downstream. (AP Photo/Rich Pedroncelli)