The resort at the N end of Sprague has a decent dock. you have to pay a few bucks to fish but for the last year or so it has always paid off. I think the resorts at Williams has one although I'm not sure. Good luck
Check out Fish Trap lake - 20 miles West of Spokane on I-90, can't miss the signs (Fish Trap Lake exit - road goes south for a couple of miles to the lake). There are several docks to fish from, or you can rent a little motor boat for cheap. Lots of trout and a few catfish.