The repair job at the battered Oroville Dam spillway lacks a price tag and a finalized design. But it has drawn the interest of four leading construction contractors, all with experience in big dam projects. The four contenders for the project are Kiewit Corp. of Omaha, Neb.; Granite Construction of Watsonville; Barnard Construction Co. of Bozeman, Mont.; and ASI Constructors Inc. of Pueblo West, Colo., according to the Department of Water Resources. DWR released its repair plan Thursday, acknowledging the work won’t be finished until 2018 and will leave the fractured spillway partially undone when the next rainy season begins this fall.