The sun., 1903-06-14
TUNNEL CAlSSON, new STYLE.
ENGINEER M'EEiN UiS ONE
HALF ACROSS THE HARLEM.
II Is 22G Feet Long, 81 Feet Across, with
PaliSadOcd Sides and Tight Roof,
and Half the Harlem River Tunnel
VIII Be Euilt In the One HON.

D. D Mclean Of the engineering and con-
tracing firm Of Mclean & McNlullen has put
into practice in the Rapid Transit tunnel
under the Harlem River at Hath street
plan Of underwater tunnelIing which he
believes is entirely new The system
has been working for a week with thor
oughly satisfactory results
When Mr.. Mclean first made his plan
other engineers scofred at it. As he says.
he bet the capital of his firm that he was
right and now he knows that he has won
the bet Mr. McBean believes that his
plan is applicable to Hudson River and
Detroit RIVER tunnelling and .!..t it is much
simpler, safer and cheaper than any other
plan which has been suggested for tunnel
ing through muddy river bottoms
The McBean plan. as nearly as a layman
can grasp it, is to drive two parallel rows
of timber sheathing, tongued and grooved
together, far enough apart to include be-
tween them the completed tunnel. They
are driven much deeper than the bottom
of the tunnel is to be. Some excavating is
done between them with dredges as though
in an open cut. Then the shea;hing is
trimmed of along the top to true level,
under water. A dam of sheathing is built
across the end and a watertight timber
roof lis laid on top. The sheathing. the
dam at one end and the shore at the other,
and the roof thus form the top and sides
of box under water of which the bottom
is the river-bed mud. There are valves in
the roof, through which men. machinery
aid materials can be introduced, through
manhole which piotrudes above the
&C : bo E,1,,uh nj, is
into the box to keep up pressure which
eulalizes the pressure of the water on the
outside of the box.
In the Harlem River the top of a calsson
thus built was sunl. on June C. Work
has been going on in the big box ever SINCE
There were twenty-three feet Of mud and
water to be- taken out. Part Of this was
taken out before the roof was put on
the box, and now only seven and a
half feet mains A cent ntrfugal pump is
used for e, ,ting the thick mud out. There
has been very little leakage of water into
the caisson six inch centrifugal pump
handles all the leakage
The casson is 226 feet long and 81 feet
wide. 1t reaches from the west shore
of the Harlem almost half way across
the river. When the caiFson is emptied
of mud and earth and water, the masonry
tunnel will be built inside OF it just as
though it were house being built in open
air All the materials will be lowered
through the protruding tubes and under
water valves When the tunnel in the
caisson is finished the caisson will be lifted
and the west half of the river will be opened
to navigation--there are temporary piers
and docks built on both sides of the caisson
now-and a new caisson will be built from
the middle of the river to the east side.
The old way Of building the tunnel would
have been to construct cotferrlams above
and below the line of the tunnel and do the
work in an open dry cut -chidren-of-
1srael-crossing- the -Red-Sea fashion. In
channel like that OF the Harlem this was
not only worry difficult to plan, but very
expensive to execute. Mr. Mclean did
not see it at all. Another way of making
the tunnel would have been to drive tube
forward by sections from one side of the
river to the other. under the mud. Then
all materials would have had to be taken in
through a shaft on shore and carried out
into the tunnel on a submarine railroad,
greatly increasing the inconvenience and
danger of working.
Mr.. McBean is preparing an article for
one of the scientific publications in which
he intends to have somo fun with the engi-
neers who said that under-mud work
couldn't be done that way. He will also call
the attention Of the contrac tors for the
Pennsylvania tunnel to his plan. 1t isn't
natanta n