Evening star. [volume] (Washington, D.C.) 1854-1972, 1956-11-25
Continued From First Page

to be the only Office. where Sec
retarieS can ask to go home
early because of seasickness.
/ During the spray -splattered
harbor tour, two guides ex-
planned what was going on. They
were William Jordan, an engi-
neer with the Maryland State
Roads Commission, and Fred
ChaimSon. an inspector with
Singstad & Baillie. the engineer
ing firm which designed the tun-
mel. Mr.. Chaimson. a 26-year-
| old Washington native, lives al
434l First street NE. and COM
mutes to the project every day
He explained that the first
step in the actual construction
was the preparation Of the 81
tube sections. Three Sfipyards
did the work. Each section is
made of two 300-foot-long steel
tubes laid side by side and con-
nected by steel ribs.
The end of each tube is sealed
with a sheet, steel diaphragm
Ibraced with m a ssive steel
II-beams on the inside. After
launching, each section is towed
to a 'shape-up dock near the
tunnel site.
Like Icing a Cake
There the interior is covered
with concrete to a thickness of
20 inches ga inches in the tubes
which will lie beneath the deep
est water.) The roadway is not
laid on the bottom of the tube
but on a deck built above the
bottom.
AS the concreting proceeds, the
tube sections float lower and
lower in the water. The outside
of each section is protected by a
thin layer of pneumatic con-
crete shattered on like cake icing
The bottom is coated before the
launching and the coating is
carried up the sides of the shell
as it sinks lower.
When the sections are just
barely floating. they are towed
into position above the trench
dug in the bottom of the harbor
They weigh about 10000 tons by
then. They are moved under the
supporting framework of the
twin lowering barges and more
concrete is poured into pockets
between the two tubes, causing
the section to sink.
Surveyors transits are sighted
on poles fastened to the tubes
and projecting above the water
to align the sections exactly
Divers under the water direct the
placing of the tubes against the
ends of the tubes already in
place. When the position is just
right, they slip steel pins into
the locking Tugs. .
Then steel collars are clampeC
over the junction. more concretC
is poured underwater to com.
Iplete the seal and hold the tubt
in place and 10 feet of mud ant
clay is dredged into the trench
on top Of the tubes. Norma
sitting will fill the trench the
rest Of the way.
Half Of Sections Placed
There are 81 sections Of tubing
altogether. The eleventh one wa,
sunk into place last Wednesday
The remaining 10 are all afloal
in various stages of concreting
They will be sunk at about two
week intervals, until the last u
in place about next June.
The steel diaphragms are cut
out after the tubes are in place
and covered. The IL tubes al
ready in place extend out under
the harbor from the southern
shore. but only the first -four
have been cut open.
That's where the inspection
party went. to the end Of the
fourth tube-1.200 feet into the
water and 70 feet down. The
tunnel slopes down on q ga per
cent grade for that distance
Afr that, the grade eases to a
per cent before starting the
gradual rise toward the other
shore.
At its lowest point, the road
way will be 30 feet below the
surface Of the water.
The final iuneture Of tubes
will be made at 9 shalloWer
depth near The northern shore.
The engineers have allowed two