Crews are laying the last layer of concrete on the Oroville Dam spillway with one day until the state Department of Water Resources’ deadline to have the structure ready to pass flows of 100,000 cubic-feet per second, or cfs. Over the last week, Kiewit Corp. construction workers connected the lower and upper chutes and erected the walls. Now all that is left is to place a coating of roller-compacted concrete in the middle chute “that will provide a stronger wearing surface,” said Erin Mellon, the department’s assistant director of public affairs.