Kettle Park is a small park, with some picnic benches, fire pits, and a boat launch. I am not sure of the regulations on boating on the river here, but it looks like a good place to put a boat in the water.
You get a great view of the Kettle Dam here, and if they're spilling it's quite a sight. Be aware of changing water levels, although the cache should be at a point that it will be findable without getting wet.
You're looking for a camouflaged flat sandwich lock and lock container, with a logbook and pencil. There is room for small trading items or trackables.