A video released Friday by the state Department of Water Resources shows construction crews at Oroville Dam, the nation’s tallest, continuing to rebuild the severely damaged main spillway and emergency spillway. Hundreds of construction workers are racing on a $500 million project to rebuild enough of the main spillway by Nov. 1 so that it can be ready for heavy rains this winter. The job is scheduled to be finished in 2018. Crews this week are filling in crevices with concrete, in preparation of laying roller compacted concrete on top of that.