The Bridgeport evening farmer. [volume] (Bridgeport, Conn.) 1866-1917, 1916-03-17

not only destroy the tunnel but would
also disturb the everything material.
From the main tunnel smaller bran
ches may be extended into the ma
teria1 to be drained and frequent Dor
ings made from the surface to con-
duct drainage water to the tunnels
from the everything strata. Such a
system would be expensive, but
might be effective in draining the
are tapped by it.
6. Sluicing.-It is suggested also
that a cut be made by sluicing in the
East Culebra, slide, starting at an APP
propriated point on the canal and di-
verging from it diagonaHy in a gem
eraI south easterly direction, in the,
zone of gentle slopes and in such a
position as to reach the large pond
which now exists on the slide. This
cut would partly separate the roughly
rectangular slide into two approx
mately triangular parts, and the adj
joining ground could be sluiced along
it into the canal. 1t would provide
a main drainage line for the ground
on both sides of it, would empty the
surface ponds and would lower the
ground water in adjacent sliding ma
teriaL The pressure of the triangle
of ground ia the rear of the cut
against the triangle in front of it
would be Iessened; and it is probable
that movement in the forward part
of the slide would cease sooner than
it would otherwise. When the cut
is once esta blished it offers a second
line of defense against the slide by
making it possible to work along two
fronts.
In addition to the Immediate rene
dial measures suggested above, there
are certain observations and protec-
tive measures which should be under
taken with a view to the future. A
few slides are now in mott H.. but
many more are quiescent. A slide is
not necessarily dead because it has
not moved notably for a few years. Its
stability may hang on a delicate bal
ance which may be disturbed by some
developing weakness. There is
also a bare possibility that Gold and
Contractors hills are not so firmly
supported as they are believed to be.
Repeated surveys of properly placed
signals for a number of years to come
should be made in order,
(a) To indicate i'll good time when
additional work of prevention is
needed; to indicate how large a
dredging fleet must be kept in readi-
ness, and to furnish to the engineer of
advance indications of
conditions.
(b) To test the effectiveness of
remedial measures which may be taxi
en- to control lor prevent slides. These |
tests would be more sensitive and
definite than the mere occurrence or
non-occurrence of slides. 1
Y (c) To furnish a reliable basis for |
when, in the course of time |
it appears that the earth and ROCK
have so decreased that a |
may be inferred.
Two of three core borings should |
be made on each side of the canal, the
thinks, to study the nature
of the high hills. 1t recommends a
Investigation of the 1ocali-
ties, percentage of porosity of the sew
eraI formations, the effect Of tropical !
the nature of the disinte-
grafton which accompanies the wealth
ering of these rocks, the chemical
changes which cause the so-called hot
areas. A mechanical testing of the /
strength of various rocks is suggested
since the future of the slides is large
" dependent upon the strength of
The rocks. Greater facility for the
study of earthquake shocks in this
region are also recommended.
In summing up the history of the
present slides, the committee con-
e1udes that since the three great
slides are all in the Culebra district,
his is the chief area of danger. This
s the natural consequence of the fact
hat by far the deepest part of the
hat the weakest of the geological
formations, the Cucaracha, is strongly
developed here.
i Slides may occur in other parts of
he canal, but they will be relatively
small, and infreQuent; for the banks
ire not high and the unstable ground Il