Evening star. [volume] (Washington, D.C.) 1854-1972, 1956-11-25
Newsnon TunneI-StroIIs
Under Baltimore Horbor

feet as a margin for error. If
there is no error, the final
sealing collar will be two feet
wider than the others.
First Twin Tube Project
The longest twin-tube tunnel
anywhere in the United States
outside of New York. the Balti-
more project is the first in the
world to use prefabricated tubes
in double sections. The sunken-
tube method has been used in
tunnels under Hampton Roads
lat Norfolk. Va. which is longer
and at Detroit, but in each case,
only a single tube was used.
The older method Of construc-
ton, and still necessary where
the harbor bottom is too hard to
dredge easily, is the driven"
method. in which the tunnel is
drilled out from one side to the
other.
Returning from the icy boat
ride, the party entered the
framework of the south and
lventilating shaft. The massive
ducts inside are aereodynamic-
ally-shaped concrete to handle
the enormous air flow.
Clambering down through
IwalkwayS in the concrete, the
party came out in the first tube.
Forms were in place near the
top of the tube to receive con-
crete for the ceiling.
Motorists will see a nearly
square opening when they drive
through fiat roadway, a fiat
ceiling and a fiat wall on the
exposed" side. The inner side,
which is up against the other
tube, is curved. Fresh air will
be pumped into the tunnel
through the hollow space be-
meath the roadway. 1t will
emerge from fiues in the curbing
Dry As a Bone
The wasted air will be sucked
up through ceiling vents and
carried to the ends Of the tubes
through the hollow space above
the ceiling.
The northbound tube was dry
as a bone. despite the weight of
water above it, except for one
trickle. That trickle didn't come
from a leak, however, but from
a faucet someone had let drip.
Walking down to the end OF
the fourth tube, one gradually
lost the sense of grade. It was
only on the return that the up
grade made itself felt.
Electric bulbs we're strung
along the walls. When they were
turned off for a moment. the
darkness closed in With breath
taking intensity. The blackness
was made more complete, II
seemed. by the tiny square OF
daylight at the open end 1900
feet away. You couldn't see a
thing.
Motorists will have no such
trouble. Fluorescent tubes over
head will make two continuous
/ lines Of light through each sec
ton. The lights are graded in
intensity with the brightest at
the open ends. preventing sud-
den blindness when one plunges
underground from the daylight.
The walls and ceiling will be
tiled and the roadway paved
with brick.
/ Begun in April, 1855, the con-
struction is slightly behind
schedule. But engineers hope to
make up the lag.
Three-fOurths Completed
The tunnel itself is considered
rs per cent finished. The access
roadways are not so far along.
In addition TO the tunnel and
roads, there are As bridges in
the expressway interchanges and
crossings. The whole system Is
so arranged that any driver VINO
gets on one Of the expressways
cannot get Of again untu he
has gone through the tunnel
and come out the other side.
A toll gate at the southern end
will have IA collection booths
The toll is expected 70 be IS
cents for private cars and As 70
rs cents for trucks.
Financed entirely with revenue
bonds based on the tolls charged.
the tunnel project is part Of the
same financial package that in
eludes the toll bridges across