The new CP for 91.5 at Capitol Peak is actually a help for KGHI and adjacent channel NCE stations north of Oly.
The antenna they have specified has a fish-shaped pattern. It puts a deep null toward co-channel KGHI and should eliminate the ongoing interference to them. The opposite null is vaguely toward the new KXOT site.
In their filing, they note that they are making the application because of complaints by KGHI. As far as I know, it's actually KGHI listeners and not KGHI itself who contacted the FCC about the mess. But it's apparent that the FCC told them to get legal or get lost.
The upshot is less a little interference to KVTI and mostly KXOT listeners in Oly from the 91.5 translator. And a BIG help to KGHI listeners anywhere west of Capitol Peak and as far west as Montesano and Central Park.
The full 10 Watts is directed south easterly. So the only place the K218CU translator is going to be stronger is Rochester, Grand Mound and Centralia. But at least they get to keep it if the FCC approves it.
I didn't go over the application in great detail, but it looks grantable on first pass.