Yeah. there is not much parking at Halcombs and does not look like you can park on the road above. Maybe they will have a shuttle so you can park below the dam. There is tons of parking down there.
I was there Sunday and put in at 2pm and was fortunate to get the last parking place. If there is not some sort of shuttle there later in the year, you might as well not even count Halcombs as a boat ramp as there is very very limited parking.