The times. [volume] (Richmond, Va.) 1890-1903, 1902-07-05
TUbNELL|NG UNDER
HARLEM RIVER
New Work Excites Wonder and
Admiration Of the Age.
SUBMARINE TUBES TO BEL LAID
And Without the Use of Compressed
Air-How an Engineering Difficulty
Has Been Met in
Novel Way.

since the New York subway was be-
with many new engineering problems.
The work has been SO productive os me-
chaDical novelties that not a technical
periodical in the country has failed TO
show an interest in the undertaking. and
one part of the tunnelinE is regarded as
so extraordinary that the London En-
cheering News has sent a special repre-
sentative across the Atlantic TO write
about it.
This especially distinctive problem is
the Harlem River tunnel. It IS now pro-
posed TO complete the river stretch with
ont the use of compressed sir and WITH
ous caissons-a proposition winch "oui"
have been regarded few years ago as
nearly impossible and certainly aInpTec-
ucablc. The originator Of the new plan
is Duncand y. McBenn. Is WAS Only after
ns had considered all tho recognized
methods Of tunneiog under water that
he finally devised this one
The Harlem River has a- UNUSUAL sort
OF bottom. Under the top stratum OF
rnuG Is y clay soil containing much sand.
This combination. when subjected 10
water PRESSURE does what the engineers
kl:cw rs ''blowiTIg. which means that
it rises. or puts up. when the water
generates underneath 1t. In river
bCitCIn that DiOWS IL IS obviously
i,arosstblo to do open-work tunneling.
To- you can't hold the bottom Gown. II
was after the nature OF tho clay-and-
sand soil was discovered tina: the idea
OF going under the river by the open
work process had TO De abandoned.
A SIMPLE EXPLANATION.
IF tho bottom had been OF blue clay.
"a In the Chicago River" explains Mr..
Mclean, we could have tunneled IN
49,. IN, ri .
"a Sale Street tunnel of Chicago. but 1t
was evident os soon rs VIC became famil-
lar with the Harlem that such a method
would be impra ctic2ble.
The open-wcrl process having been
laid aside. Mr. Mclean began to plan
so,ae method by which 1t would he pos
sillo. If The necessity should arise, to
hold down the blowing bottom by
means of compressed air. Engineers had
discussed many times the feasibility Of
making river tunnels by means Of
series of caissons. but no one had Yet
solved the problem of establishing con-
ncctioRs between the different separate
caissons. The plan finally hit upon by
the subcontra ctCT involved the making
req hing one-half way across the stream
Its roof and sides protecting the work
men from the water. This box, with no
bottom but the soil beneath the water,
is not being built into position all at
once, but piece by piece.
II was required of the subcontrac tors
that they should use only half the river
at 4 time Tor their operations. leaving
the other half free for traffic and en-
1irely finishing the first half before
the remainder of the stream.
The first thing to do was TO dredge
charrel, the final total depth of the
charnel to be about fifty-three feet below
the ordinary high water level Already
the dredging has been done to a depth
of nearly forty feet. The channel has
sloring sides, and on each side is
working platform for dredging aud other
machinery. one platform being fifty feet
feet
ONE DANGER AVOIDED.
In preparing for the building of the