Probably a main-lined plug would work....that's what people do when they target stocked, surplus steelhead in places such as Cape Meares Lake and others.
Your problem will be getting your plug in front of a steelie in there. It's deep and slow at the lower end and those fish will be shooting through that kind of water.
You chances will go way up if you can get to the current at the upper end, but that's a long row. I used to put a skiff in at the dam and power up to the faster water and do quite well on plugs.