This is the 460 building
where the boats are assembled so that the hull is all together before it rolls out on the pier. The boat you see on the right has the hull
close to complete.(all major equipment installed) The boat on the left is just the missile compartment and you can see the end is covered
by a green cover (that is so you can not see the thickness of the hull). It looks like all the missile tubes are in on it and the blue machine
you see about half way down is the automatic welder that was use to weld them in. The blue rig in back of the boat is used for standing the missile
tubes up when they are getting ready to load them, it takes two overhead cranes to load one missile tube, because of the weight.
The 5 blue towers you see next to the boat on the right are where the hull butts are and they are used to protect the auto
welder that does them. You can see that the shaft is not in the boat on the right as well as the sternplanes. Some things to remember
is that almost all things are end loaded on these boats. The floor has tracks in them so that when you move the boats on the strong backs you go in
straight lines. 
This is a cutaway view of a Trident
and you can see that there are only 4 watertight compartments(Forward compt, missile compt, Rector comp and Engine room.)To get to the Engine room from the missile room
you go over the Rector compartment. (It does not show that good in the cutaway.) Someone sent me this so I don't know were I got it. I try to give credit for all pictures I use, if they are not mine.
The first picture is the barge that brings sections down from QP, RI and the other picture
is part of the fwd section. There are two(2) 96 wheeled transporters under it and they can carry about 700 tons of hull. The way this works is the barge is put to a special section of the pier stern first, then it puts the legs down to hold it steady. With the hull setting on strong backs and blocks. the transporters drive under and with Hyd lift the hull section up
and drive it off the barge onto the pier then using blocks under the strong backs the transporter lowers the section down on the floor. This something to see them move a section.
I found the pictures on the web.
This is the Virginia while in the
260 building just before it was moved out on the Land Level Pier. To give you some idea on how big the building is
the offices that you see in the left upper are 4 stories high. You can see the black tarp over the sonar dome and just aft of that
is the Cruise Missile tubes. Just under them (if you follow the staging is the bow planes opening. You can see how small the people look.
on the floor of the building, this building is about as high as a 8 to 10 story building. The build is not a fully enclosed it just protects
the workers and boats from the weather. Again you see the blue staging just aft of the sail I think that must have been a hull butt
that was welded last. You can see the number of blue strong backs under the ship each one has three trucks that move the ship and a very slow
speed. The area where the people are walking is the transit lane and normally a ship will not be in it
for any length of time. There are a total of 5 bays in the building 4 that are used for building ships and one
that is used for transit. 
The first picture was taken from the pontoon for the dry dock. The pontoon is the bottom of the Dry Dock but it has tanks so that it can be floated or stay on the bottom of the dry dock. When it is floated it is raised up and locked into place by moving it forward to set on pilings. When it is in place the pontoon is at the same height as the land level when the submarine sits. The second picture is the sub moving toward the dry dock. (Note the America Flag on top of the sail) The third picture shows the tracks and the carts that are used to move the sub. I can't remember how many they use but it is 3 under each strong back All the carts move at the same time and speed (I think the total is around 90 carts). The each have a hydraulic lift so that they and pick up the ship, also they can set the ship down and pick themselves up so that they can be turned 90 degrees. When the ship gets on the pontoon the dry dock is super flooded again and it raises the ship and pontoon up so it can be move aft. The dry dock is then pumped down and the pontoon is set on the bottom of it. Then when you want to get the sub afloat you open the tanks in the pontoon and it will stay on the bottom and the ship will float off when the dry dock is flooded. If you have a question about how this works e-mail me and I will try and answer it.