New-York tribune., 1920-02-16
che cast-iron tube designed, construct
ed by the shield-boring method. In

che cast-iron tube designed, construct
ed by the shield-boring method. In
this connection the report states:
"The shield method of tunneling is
recognized as standing out preami-
nently as the method which has been
used successfully in constructing all
the railroad tunnels under the East and
Hudson rivers. To date twenty two
tubes have been built under these
rivers by this method, so that there is
very complete detailed information
available in regard to this method Of
construction under conditions which
would be met during the driving of
the vehitular tunnel.
Mn this method Of construction the
tunnel lining is built under the pro-
lection Of q circular shield which is
pushed ahead of the portion of the tun-
mel already built and serves as a pro-
lection for the men carrying on the
work Of excavation and building the
tunnel lining. Th. lining has been
constructed Of cast iron, consisting of
successive rings bolted together to form
the completed tunnel structure. Inside
lining has generally been placed in or
der to serve as protection for the
cast Iron and provide finished struc-
ture. This method of construction, in
addition to the fact that it is we'll
known and has been successfully used,
has the great advantage that all the
operations are conducted under the bed
OF the river without obstructing the
waterway"
Proper Ventilation Provided
The plans recommended, the report
continues. follow closely those adopted
IN constructing subaqeous tunnels un-
der the North River, and the experience
gained in driving these tunnels is ap-
plicable to this tunnel. 1t is consid-
cred certain tliat the methods hereto
1ore used in previous work insure the
successful completion of this tunnel"
Considerable research work has been
done in connection with the ventilation
problems presented by the new bore.
The principal danger in this direction
comes through the distribution of car
bon monoXide gases from exhausts of
motor driven vehicles.
In order to provide proper ventila-
ton the plans call for two ducts, one
underneath the roadbcd, through which
the fresh air will be drawn into the
tube, and the other overhead, through
which the foul air will be drawn off
one at each end inside the pierhead
! lines and one at each end on shore
The problem of providing sufficient
fresh air" the report says, "has been
investigated in detail by testing auto
mobiles to determine the amount and
composition Of the exhaust gases given
OF by cars under operating conditions
and by determining the amount of dilu-
tion required to render these exhaust
done under contract with the Bureau
OF Mines at it's experimental station al
pittsburgh and New Haven, Conn
There is absolutely no question as te
the feasibility or practicablity OF
vcntilating the vehicular iunnei at g
reasonable COST"
Mr.. Holland stated on Saturday the
tests already made had convinced hin
q proportion Of carbon monoxide Of
three parts In 10000 was we'll within
the safety none. and hts ventilation
ties., he said, put the safety line at E
higher proportion, and he thought the
figure aimed at by the commission
would be so much inside the safe ares
Is to involve absolutely no risk.
In order to determine the necessary
space required 70 permit the passag,
Of heavy traffic, the report says, We
hicles crossing on Hudson River ferrie.
were measured. "It was found,' thu
| tV1VA SOAIAAUSo, tiidC tHc lIiItlClIP III
nensions of ordinary and unusua
>raffc was IL feet 2 inches in heigh
md feet in width. The vehicle.
axcceding these dimensions reprcsen
bout 3h per cent of the total, with
My per cent exceeding the height a!
ixed above. The average speed O.
.ohration as observed over the Eas
stvtr bridges on the up grades wa
ound not to exceed twelve miles al
hour. In accordance Herewith, tn,
lear headroom of the tunnel has bee,
ixed 1T IS feet 6 inches, and the widtl
{ roadway for two lines IF traffic
lowing clearances for safe and con
,snient operation, was fixed at q
'eet, which corresponds very closel,
18th the width of the roadways owe
he Williamsburg Bridge"
TIE report estimates that approx
asr's 10000 tons Of freight is light
-, erroas the Hudson over the var
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