—-_—ssUCU 
THE RAISING OF THE DRY-DOCK DEWEY. 137 
About 1 A. M., on May 24, 1910, the valve man on watch noticed that the 
dock had taken a slight list to port. He accordingly corrected this list by 
admitting water which lowered the dock to a depth of 27 feet over the keel 
blocks. Shortly before 4 A. M., he noticed that the dock had again listed 
to port, and that the port side seemed to be rapidly going down. He called 
the dock-master, but before anything could be done, the port side was com- 
pletely under. This was about 4.30 A. M. ‘The starboard side also sank 
somewhat and was slowly filling with water. The dock’s position at 10.20 
A. M., on May 24, 1910, is shown on Fig. 1, Plate 71. No cause was known 
then for the sinking of the dock; in fact the cause was not definitely ascer- 
tained until the dock had been completely raised. It was known that much 
of the drainage piping had many small holes init. Repairs had been made 
from time to time, but no complete overhauling had been made, it being 
the intention to give the dock and all its piping a complete overhauling at 
its next self-docking, which was scheduled to take place in about seven 
months. It was not believed that any small holes that there might be in the 
drainage piping could possibly be sufficient to cause the sinking of the dock 
or to even appreciably interfere with its operation. It was thought possible 
that one of the main drainpipe connections between the central and end 
pontoons might have given way, thereby flooding one of the large compart- 
ments, No. 7, which would have been sufficient to sink the dock. Also 
one of the sea valves might possibly have given way. ‘This also would 
have been sufficient to sink the dock. But it was soon ascertained that 
neither of these things had happened, and that there was no material damage 
to the dock structure. ‘This was demonstrated to be the fact by opening 
the various compartments on the sunken side to communication with com- 
partments on the starboard side where the action of the water in the star- 
board compartments could be observed. ‘This will be described a little more 
fully later on in this paper. The work of raising the dock was therefore 
considerably complicated by the fact that the cause of its sinking was not 
known, and a great deal of investigation work was necessary in order to 
eliminate certain possible causes and to determine as far as possible the 
general condition of the structure, piping, etc. It may be well to state, in 
view of many misleading reports published at the time the dock sank, that 
there were no open valves, and no open manholes, that were the cause of 
the sinking of the dock. 
The work of raising the dock will now be taken up. Where the dock 
lay the depth of water over the bottom was about 65 feet at the inshore or 
forward end of the dock, and about 70 feet at the afterend. The character 
of the bottom was soft mud to a depth of about 3 feet, and under that com- 
