Great question? I walked down there a couple of weeks ago and it looked like another 10 feet or so for water just to touch the 'lip' of the abyss...3,540? So, I think close to >3,550' would be a minimum usable lake level taking into account trying not to back the average trailer off the edge. That's also assuming they would allow drive axles to be on the soil (say, "slippery and poor traction"). Since the ramp has been high-and-dry, they did move the walkway/dock access to the north and did a lovely job of grooming the exposed ramp at a fairly consistent grade down to the drop-off. That was undoable while it was covered with water, as you know. (I do not think you will see the ramp utilized for anything that cannot be hand-launched for at least a couple of years.) Right now, it seems to be a popular spot for dogs...lol.
Incidentally, I heard rumor the Nation has a lobbying effort/proposal to modify the public ramp so it could be used and is being met with resistance from NPS. Not sure...rumor. If that comes to fruition, probably a $10-12 million-dollar (pure guess) excavation job, minimum.
It will take another 5ft or so to make the valet ramp usable. Which is unlikely in my opinion.
They had a plan to cut a new launch ramp and cart path by the main cart ramp but by the time they got approval the construction cost had gone way up. So now they are looking at another plan to make it to the other side of the old main cart ramp and make it larger. Basically putting Launch ramp right into the old wake board park.
I heard the public ramp budget got approved with outside funds. but the problem is if any money gets put into the park the money could be used on any NPS project. So they are working with another group that can take outside donations and apply to specific projects within the Rec area. So it sounds like there is a plan to not only get the public ramp to operate at lower levels but make a new ramp at APM. But nothing will happen fast. Time moves slow down there.