I'm in the planning stage of a cross Washington trip. The plan is to cross the Columbia river somewhere around where the John Wayne trail meets the Iron Horse trail. I can't find anything that looks like a reasonable option. The trail is gated off and it does not look like you can cross the near by dam (at least not since 911). The I90 appears to be the option I've seen mentioned the most often, but doing that on a bike takes more courage than I think I have.
Has anyone around here succeeded in getting across in this area?