The could build a replica death star if they really wanted to.
Let's say we want to do this and I assume you want this tunnel to be ADA compliant?
- What is the level difference between TBA and the bottom of the river? 6'? 8'?
- What is the thickness of the ceiling of your tunnel going under a river? 2'? (I have no idea how thick the concrete is for ROA and or what utilities are under it if any)
- What is the height of the tunnel? 8'?
So to go from TBA and down below the tunnel we need to go maybe 16'? An ADA compliant ramp is a max of 30" rise per run. So we would need 6 runs where you are allowed 1 foot of elevation change per 12 foot of linear distance. A single 30" rise would need to be 30' long. In order to get down you would need 180' ramp not including landing space etc.
The distance between TBA area and the island is around 150' depending on where you measure.
So we just got down, but we didn't even get back up yet.
I guess we can build an elevator shaft with some switch back stairs that's 2-3 stories tall going straight down somewhere. I wouldn't want to have to design the drainage system for this tunnel.
Maybe it's late and I didn't do my math right.
Oh wait, the island itself isn't ADA compliant anyway so who cares.