If you put in around tunnel one it's class II. The last IV is screaming 1/4 mile, which ends just above the diversion dam. You can put in just above tunnel one (and just below the dam), but it's a little scary crossing US 6 with boat on your shoulder. You can also park on the downstream side of the tunnel and walk as far up as you like. This is a fairly common beginner run.
At current flows I wouldn't do it though. We need another 100 cfs if you want any plastic left after your run. Also, stay right when the river splits. Otherwise you'll end up in the Golden water supply.
"A witty saying proves nothing."
- Voltaire (1694-1778)