At Rivrguy's suggestion here's a thread on the currently hot issue of spending bundles of money for no fish.

Early in my career I spent a lot of time on some smaller streams that had all sorts of barriers. Most were somewhat intermittent for adult salmon but a bigger problem for juveniles and impossible for fish like sculpins. I found out, when I asked, that while the Hydraulics Code said "protect fish life" it meant salmon; sculpins were worthless.

And, WDFW does have (or should have) data on what happens when barriers are fixed. The culvert I mentioned on 101 had a smolt trap just upstream; just looking at numbers out versus known spawners above (the creek's entire anadromous zone was surveyed) would tell a lot. And having eliminated the exotics; that can be evaluated too.

Even more informative was a creek near PA. On Old Olympic Highway, which is north of 101, there was a fish ladder at a road crossing that was an intermittent barrier to adult coho. The creek originated in, and was Salmond accessible, into ONP. Anyway, they not only removed the ladder but also the dam that the roadbed made. That meant that all the accumulated sediment had to move down. There already were steelhead surveys up close to the Park and a smolt trap at the mouth. Knowledge should be power.