New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1903-12-27
IMPROVED METHOD OF TUNNEL BUILDING
TIE nohh TUBES NEW-FORKERS BUILD THE MORE
EXPERTS FIND OUT ABOUT THEM

Duncan - 1cisSan. whose novel methods OF car
ryins the subway beneath the Harlem River have
attracted much attention recently. talked freely 10
1ElDNne reporter about his plans, going into the
ninutest Details concerning them. In the course
OF the conversation. Mr. Mclean made this start
ling announcement:
I can start to buie tunnel under the East
River or under the North River by my method
Eve years after work was begun on the first and
after Il shall have been begun by the Pennsylvania
Railroad on the second. and finish my tunnel before
the other is completed. Besides. by ry method,
can provide 4 system OF outside drainage for
tunnel impossible in the shield method OF con-
struction. that would go far toward preventing
possible accidents. and 7 coulL supply a FONDA
ton FAR more secure than any contemplated in
the plans for any OF the tunnels now under con-
struction TO be begun, and could insure
perfectly true grades and perfectly aligned walls
where they cannot be secured by any OF the older
methods 7 could raise the level OF the East River
tunnel thirty-ave feet above that contemplated IN
Tie present plans. eliminating a 3 SO per cent
grade from pier line 20 pier line and making the
length OF the lowest level great that possible
disaster from a comparatively small quantity of
water settling 10 the low point, as the present
plans Ak the grade. co1ld lot happen The elm
ration OF this grade alone would save annually in
ske cost Of the operation OF The tunnel railroad 3z
per cent on z permanent investment OF 81. 5o0Ooo.
Ny plan would allow me 70 start a. the pier line
grade Of The Est River tunnel now planned.
and carry IL across 1he river a level whereas
pier line 10 the or the stream OF $40 feet in
every hundred
= IS apparent by the accompanying diagram that
a quantity Of water that would entirely I'll the Ia
foot 6 inch tunnel FOR train length at the centre
would. i distributed over the distance from pier
line 10 pier llne MI only about one-tenth Of its
space. atoTding a possibility q escape to those
on 9 trala running into such an accumulation by
NJ AcBean's plaza provided the electric conduc-
tors above The level Of such a flood. whereas
-s- he
would far 10 the low point al the centre and cause
certain disaster. Mr.. McBean's plan. also. he as
Ferts would allow the drawing Of Of such an acct
GENITAL food through outside drains impossible TO
te built IN q tunnel constructed by present meth
ods III Mclean also asserts that. IN addition to
the saving and safety resulting from this change
OF grade sra gain IN time Of construction, the
cost If fuilcirS the tunnels would be greatly
Guced bog mis- plan.
In building the west half OF the tunnel under the
Harlem M Mclean departed from ell previous
runne.iug methods under water. Briefly put IN
plain English. dredged his tunnel and walled Il
with heavy tiwbeIs under water, and then, having
cut Of the top q the wall evenly TO grade, let
down upon il timber roof OF sufficient strength TO
resist the weight Of the water above, pumped out
the water within the chamber thus formed, and let
IN air at pressure Just sufficient 20 counterbaance
the water pressure, IS IS required in all sub
aqueous workings, laid his concrete foundations
and built the permanent tubes OF cast steel and
encssed them in concrete. the specifications
required
In building the east half the same plan viii be
pursued except that the expensive temporary roof
Of timber vii be dispensed with, and the upper
halves Of the permanent steel tubes, with their
concrete castings, viii be substituted for it. These
half tubes viii be built pontoons, the concrete
castings viii be added. they viii be hoated into
place over the dredged and timber sheathed chan
nel and sunk upon these walls, so that hanges az
their edges rest on steel covered timber ends These
hanges viii De bolted into place by divers and the
naturally compressed sir IN the sunken arches VIII
form a working chamber for cleaning out the lower
half % the ditch for laying the concrete founda-
tons and for casing and boiling into place the
remaining seyrneuts 20 complete the tubes or
course. the depth OF the working is increased
additional air pressure 10 keep out the water and
mud viii have TO be supplied by cornpressors. but
the original working chamber viii be the air space
within the arches Of steel when they sunken,
less the slight encroachrnent OF water AZ the bot
tom, due 10 compression the arches weighted
down.
Several knotty problems presented themselves in
making a practical application OF this plan. Any
gas under pressure is prone TO shift its position
freely result OF the slightest change IN eqiAo-
rum Of the mass. One who has tried TO sink
inverted basin II water knows how difficult it is 10
prevent fitting OF the vessel which will allow the
air 10 escape at one side. The longitudinal pard-
tion between the two half tubes VIII serve as a
bulkhead 10 keep equal quantities Of air on each
side but 10 prevent a possible endwlse tilt.
transverse bulkhead viii also be built into each
also the temporary sinking weights can be hung
beneath the longitudinal partition, throwing the
centre OF gravity below the base OF the double
arch and thus keeping the sinking roof On an even
keel The partition itself might be built below the
sortng line OF the arch for that purpose. and add
that much 10 the work OF construction above va
ter but gaps corresponding 10 the transverse wall
nes anc braces would have 10 be left
The roof is 70 be built IN three sections. the end
rext the east shore being placed in position first.
This viii be s. feet long, and has grade
throughout the entire length. The remainder Of
the 300 feet. which will have vertically curved
gradient. VIII be built IN TWO equal parts. These
three sections must be Joined under water after
they are sunk and the manner OF Joining them is
interesting. The end bulkhead OF each section will
be six feet back from the end OF the wall OF the
tube. Out OF the top OF the roof in these end
lions viii be left three pieces. forming hole large
enough TO admit q diver He Will bolt the
sections together and leaving the little chamber
thus formed viii replace the pieces, the last OF
which viii serve a keystone the arch. HAY
ing covered this keystone with concrete dumped on
from the pals IN which II viii be lowered 10 him
he viii be drawn Up, and sfterward the temporary
bulkhead VIII be removed. the compressed air will