Evening star. [volume] (Washington, D.C.) 1854-1972, 1904-09-28

street within the limits of the proposed
open-cut. They stated that the trench
would be from forty to sixty feet deep and
that the work would be done In the trench.
and they believed the noises from the WORK
would cause little or no annoyance to resi-
dents In the vicinity. 1t was pointed out
that for two-thirds of the distance of the
open trench there are no dweIlinghouSes on
either side of LIST street. and that conse-
quently the work on the larger portion OF
the tunnel would not annoy the citizens.
The Commissioners explained that the
whole trench would be screened from pub
lie view by a high board fence, so that
the operations would not be seen by per.
sons passing along the street. They also
declared that there would be no inter-
ference with the entrances to the Congress
Sional Library, and that bridges would be
constructed across the trench on the lines
of the drives through the Capitol grounds
and also across intersecting streets
Arrangements for Disposing of Dirt.
With reference to the suggestion that an
immense quantity of earth removed from
the excavations might be piled on the
Capitol plaza or in the vicinity of the tUn-
mel. the Commissioners explained that
tracks are laid in the tunnel as the OK
cavation progresses and trains of dirt cars
haul the dirt excavated back. through the
tunnel to point near Garfield Park, where
1t Is dumped. This course. 1t is stated,
cut through the Capitol grounds. Some
of the dirt, 1t was stated, is also used for
what is called the back f1ll." The Com
mlssioners gave assurance that no insight
ly piles of dirt would be permitted in the
vicinity of the trench.
1t has developed that in the event the
open cut Is made along list street the street
car tracks will probably be removed farther
east on the street, instead of carrying
them above the tunnel on a trestle, as was
formerly suggested. The Commissioners
believe that there would still be sufficient
room left on LIST street to accommodate
vemcuiar traffic even If the car tracks were
moved toward the east side of the street
The width of the street between east and
west building lines Is ITO feet. On the east
side of the street the curb extends about
ten feet from the building line. 1t is esti-
mated that the fence inclosing the tunnel
Will extend about sixty-five feet from the
west building line. Eliminating the space
occupied by the tunnel and that occupied
by the east sidewalk, a space thrty-fiye
feet wide would be left for the tracks of
the street railway and for vehicular traffic
from East Capitol street to B street.
Not Contemplated by Congress.
Col. Biddle was asked by the reporter if
he believed Congress contemplated the
building of the tunnel by the open-cut
method.
Il do not believe Congress contemplat ted
the open-cut method any more than did
the Commissioners" replied Col Biddle.
ut Is to be regretted that the change i'll
plan seems necessary. In making up my
decision with regard to this matter 1 have
been guided not only by my own engineer
ing experience but also by the consdera-
tons from the railroad companys stand.
point.
THE Pennsylvania Railroad Company
probably has the best, or one Of the best,
engineering forces in the world After
f,to
the work upon those plans, these engineers
find that 1t is best to make a change. They
are required to change all their plans and
to go to a large additional expense by rea-
son of the circumstances. The compa ny
will take care Of all damages to streets,
pavements. Capitol grounds, sewers, con-
Quits. street car tracks. and besides ether
possible damages and annoyances.
I'm view Of these considerations 1 feel
that the change would not be proposed I'M
less it was necessary and advisable In
immense engineering projects changes in
plan Of work are often found necessary,
by the railroad company and from other
considerations the change Is advisable in
the matter under consideration.
The open-cut method of tunnel construc-
ton may be observed on 1st street near
B street southeast and on 1st street be-
tween D and E streets northeast. The bot
tom of the tunnel at B street is about forty
feet below the surface of the street.
The "Twin Tunnel Plan.
The construction in this tunnel is what is
termed the ''twin-tunnel" style On each
side of the excavation. which is about fifty
feet wide. is wall of concrete about three
feet thick. Each of the two tracks is in
closed by an individual tunnel on either
side of the main excavation.
These individual tunnels are constructed
of brick and concrete, and they are sep
arated from each other by a substantial
masonry wall. On top of each of these
twin tunnels is laid thick layer of con-
crete and on top of the concrete is a layer
of waterproofing material about two inches
thick. Dirt is then filed in over the layer
of waterprooflng
g.. In order that the workmen may lay this
concrete and w-aterproofing under the tun-
melting process 1t would be necessary that
the excavation be made four or five feet
above the actual roof Of the tunnel. This
extra space above the roof of the tunnel
must be filled in with earth after the work.
men have finished laying the waterproofing
material. and it Is difficult. so it is stated
to fill this extra space solidly. On account
of the damp and soft nature of the earth 1t
IS feared that the earth above the tunnel
might settle and cause a sinking of the