Front Cover
 Back Cover


Slides at the Panama canal
Full Citation
Permanent Link: http://ufdc.ufl.edu/AA00006085/00001
 Material Information
Title: Slides at the Panama canal
Physical Description: 16 p. : ; 23 cm.
Language: English
Creator: Goethals, George W ( George Washington ), 1858-1928
Publisher: U.S. Govt. Print. Office
Place of Publication: Washington, DC
Publication Date: 1916
Subjects / Keywords: Landslides -- Panama -- Panama Canal   ( lcsh )
Engineering -- Panama -- Canal Zone   ( lcsh )
Genre: federal government publication   ( marcgt )
non-fiction   ( marcgt )
Statement of Responsibility: by Major General George W. Goethals.
General Note: Caption title.
General Note: "Extract from the Annual report of Major General George W. Goethals. U.S. army, governor of the Panama Canal, for the fiscal year ended June 30, 1916."
General Note: Supplement to January 6, 1916, edition Canal record."
 Record Information
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 77299340
lccn - 16027396
sobekcm - AA00006085_00001
Classification: lcc - TC774 G73
System ID: AA00006085:00001

Table of Contents
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    Back Cover
        Back Cover 1
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Full Text



Extract from the Annual Report of Major General George
W. Goethals, U. S. Army, Governor of the Panama Canal,
for the fiscal year ended June 30, 1916.

Although the question of the slides has been dealt with in pre-
vious annual reports and official documents, there continues to exist
much ignorance on the subject. Also a great deal has been written
by those whose little knowledge makes them dangerous, and to
whose statements credence is given because of the position or prom-
inence of the writers. I have concluded, therefore, to report again
on the situation, even at the expense of repetition, notwithstand-
ing the general belief that anything published in annual reports is
buried in oblivion. Consideration will be given also to the various
theories that pave been advanced and to the remedies that have
been suggested.
For some unaccountable reason there seems to be a general belief
that the entire length of the Cut is affected. A report emanating
recently from English sources states that the bottom of the canal
through this section is found to be a bog, which is being constantly
pushed up, and through which the dredges have difficulty in main-
taining a channel; further, that it. is acknowledged on the part of
those in charge that the canal is a failure, and that American engi-
neers are seeking information in England relative to the Nicaragua
route. Such reports are false, and there is no foundation for them;
yet they seem to have gained credence probably because a pending
treaty between the United States and Nicaragua contemplates
securing from the latter all rights for building a canal on its territory.
As the Nicaragua route was at one time the one most generally
favored by the United States, investigations by commissions, boards,
and commercial bodies, covering a series of years, have been made
of the route, and data of all kinds collected: consequently every-
thing that is known about that route can be found at home, with-
out the necessity of seeking information in England. It makes a
A good news item, however; makes converts to the belief that the



entire 8.75 miles of the Cut is unstable, liable to collapse or upheaval,
completely closing the canal for all time, is useful in assisting ship-
ping companies to take advantage of present conditions to charter .
ships at excessive rates instead of complying with their obligations,
and permits an increase in insurance rates. -
Gaillard Cut extends from Pedro Miguel to Gamboa, a distance of :.
8.75 miles. The canal prism through this section averages 300 feet
bottom width, and has a depth of 45 feet. Every foot of the exist-
ing channel was excavated through rock, all of which, though of "
various kinds and densities, had to be drilled and blasted in order
to remove it.. It is possible that the water may have softened some
of the material, yet it is known that the softer varieties of rock
encountered in the excavation were protected from disintegration'
by contact with water. The bog theory is a myth. The Cut has
been stable with the exceptions of the portions in the vicinity of
Culebra and at Cucaracha. The slides at Culebra are on both sides
of the waterway, occupying a length of 2,800 feet, while the channel !
affected by the Cucaracha slide is less than 2,000 feet. long, so that
out of a total length of 8.75 miles only 0.88 mile is affected.
Another misconception that exists relates to the character of the
slides. They have not been, except in part at Cucaracha, a slipping
down of portions of a bank in order to reach the slope at which the
material will stand. Slides of this character have occurred, but
they were small in extent and easily handled. Those at Culebra
are breaks resulting from deformation or crushing of underlying
strata which, under changed conditions, could not bear the weight
of the superimposed mass, and caused a vertical settlement or drop
of the overlying material, which subsequently moved into the
prism. Final rest will be secured when all the material that is in
motion has been removed. As is shown by experience with smaller
breaks that have occurred from the same cause, when the end is
reached the final surface will be concave, or bowl shaped.
When water was turned into the Cut on October 10, 1913, the
channel was completed to full width and depth except at Cucaracha,
where the steam shovels were making but little headway against
the slide; three benches which had been left (one at La Pita Point,
one on the east side near Empire, and one on the west side oppo-
site Cucaracha); the inclines, one at either end of the Cut; and the
remains of two small slides, one on the east side, of the "break"
variety, and the other on the west side, a typical slide of clay which
occurred prior to the removal of the steam shovels, both of which,
between Empire and Culebra, were cleaned up by the dredges and
have remained quiescent since.
Cucaracha slide is on the east side of the canal south of Gold Hill.
It began to give trouble as early as 1884, during the operations of-


the French Canal Co., but all the indications pointed to a surface
movement only. The French built an elaborate system of drainage
to overcome the difficulty, and, while successful so long as work of
excavation was suspended, further deepening of the Cut in the vicin-
ity resulted in renewed activity, with complete destruction of the
drainage system; the remaining part of this system was carried
away by the slide in 1907. The slide gave trouble in 1906, when
excavation proceeded through this section. The difficulties increased
as the depth increased and in the autumn of 1907 became most for-
midable. From this time until 1910 the difficulties became less, and
it was believed that they had been overcome and that the clay re-
maining would be supported by a rock dike which was uncovered
and which apparently possessed ample strength to retain the mass
above and back of it. On January 20, 1913, the rock dike broke at
or below the bottom level of the canal and completely filled the
prism with clay and rock for a length of 1,600 feet, to a depth of 30
feet on the bank opposite from the slide, increasing toward the east
on a slope of about I on 4. Steps were taken, by means of sluicing,
to wash back as much of the top portions of the clay as possible into
the valley on the east side of the ridge. As steam shovels could not
cope with the situation economically and advantageously and as the
remainder of the Cut was ready for the admission of water, this was
allowed to enter and recourse had to dredges for the removal of the
balance. The time within which a passage through the slide was
cut, as well as the cost, is conclusive that this method was the most
efficient and economical way of handling the material.
In July, 1914, troubles in Mexico interfered with the handling of
cargoes by the Tehauntepec route, and shipping interests were
Clamoring for relief. The dredges had secured a channel through the
slide, and the Panama Railroad operated a line of barges through
the canal between the terminal ports, but these could noL handle
the traffic. While the full depth and width had not been secured
through the slide, the channel was sufficient for the passage of ship-
ping, and consequently the canal was opened to commerce in August,
Several movements have occurred since at Cucaracha, but they
were handled easily and did not delay commerce until the last of
August, 191Q, when a movement occurred, bringing down material
from the northeast corner of the slide area, and moved huge rock
bowlders across the center line of the channel, so constricting it as
to force a suspension of navigation on August 30, 1916. The larg-
est mass of rock occupied a length of 65 feet. The boulders required
drilling and blasting operations in order to remove them. Holes 20
feet deep in a flintlike substance were drilled at great expense of
time and drills before they could be broken up sufficiently for the


dredges to handle, and the closure of the canal lasted eight days,
although two small ships were passed through in the interval.
Gold Hill is of basalt, thrown up in a molten state through the
sedimentary deposits that already existed and poured over the
deposits on either side of the stem, giving to the vertical section the
general shape of a mushroom. The portions projecting beyond the
stem, being left unsupported, broke when the material moved from
under, and the rock thus detached came down with the rest of the
material at Cucaracha. This same action occurred on the opposite"
side of Gold Hill within a few months after the east Culebra slide
became active.
A slide developed during the excavation in 1906 north of Gold
Hill on the east side of the Cut. This was a typical slide, a surface
movement which flattens the slope, and slides of this character had
occurred in this locality during the French occupancy. The French
endeavored to overcome them by drainage tunnels, but the mate-
rial through which they were built was too fine grained to permit
the free passage of water, and the method was not continued.
In 1907, at, the village of Culebra, the type of slides designated
"breaks" first manifested itself. When the excavation had reached
a depth of 135 feet above the finished bottom level, a crack appeared
in the surface of the undisturbed ground, extending from one point
on the.prism slope to another. Subsequently there was a subsidence
of the surface on the side of the crack farthest from the prism, accom-
panied by an upward movement of a portion of the bottom of the
excavated area a little distance from the foot of the slope. This
was followed later by a settlement of the mass between the crack
and the Cut, which ultimately slid into the prism. The first break
affected but a few hundred feet, but as the depth of excavation
increased the breaks became more extensive both in length and
quantities of material involved; then they occurred on both the
east and west banks, the upward movement along the bottom of
the excavation continuing until the area affected extended for a
length of 2,000 feet north of Gold Hill. The borings of record failed
to disclose any weak underlying strata.
The cause undoubtedly was the unequal distribution of the pres-
sure exerted by the adjacent banks. Such being the case, it fol-
lowed that if the height of these banks were reduced the movement
would be lessened, and if reduced sufficiently would cease entirely.
Subsequent events proved this to be correct. The banks were light-
ened by taking material from the top, and there resulted final slopes
through this portion of the Cut of 1 on 1 to 1 on 61 for the east side
and from 1 on 2.46 to 1 on 4.35 for the west. side; the slopes con-
sisted of a series of steps. The upheaving of the bottom ceased


entirely, as already noted, and the canal prism was carried to full
depth and width throughout the entire 2,000 feet.
Toward the close of the dry season, in April, 1913, a crack ap-
peared on the east side opposite Culebra, about 1,300 feet from the
prism, in an old French dump. It was parallel to the canal, did
Snot join the banks, there was no breaking up of the banks between
it and the Cut, nor any subsidence-in short, there were none of the
indications that accompanied previous breaks. The geologist be-
lieved that it was due to the deformation of the underlying strata
and advocated lightening the banks by sluicing and steam shovels,
which was done. While this work was in progress the crack gradu-
ally closed, and though the surface between the crack and the Cut
was in places noticeably below the level of the surface to the east
of the crack, the closure was construed to mean that a condition of
equilibrium had been reached. The canal through this section was
completed, the water was turned in, and no further trouble was
anticipated in this section.
A crack had existed for some years at the foot of Zion Hill, south-
east, of Culebra. The hill was pronounced geologically secure against
any movement, and when the material was dug away from the
upper portions of this bank, and the slopes of the final bench reached
the crack, it did not increase and there was no movement.
Just prior to turning in the water a rock slide occurred north of
Gold Hill on the east side, increasing somewhat with the admission
of water, causing no change, however, in the crack on the top. A
similar slide occurred on the west side after the prism filled with
water. In both instances the movements were typical of the ordinary
slides-an adjustment of the slopes. The material was easily han-
dled by the dredges and the channel freed of all obstructions before
the canal was opened to navigation. This condition continued until
October 14, 1914, when, without any warning, a section of the east
bank north of Gold Hill settled vertically 20 feet. This section
measured 2,000 feet along the prism face, and extended back about
1,000 feet from the axis of the canal, generally along an irregular
curved line, but did not extend back to include the crack that had
developed in 1913. The top of the bank was from 300 to 350 feet
above sea level. After the settlement the upper surface of the
portion that broke away remained practically parallel to its original
. position, and the existing benches of the upper part of the slide had
not changed their relative positions, though they were badly broken
up, but the lower strata were squeezed out across the canal, reducing
the depth of water from 45 feet to 9 inches at one point within an
hour's time. Subsequently the broken mass moved into the Cut, as
was the case with other breaks. Navigation was suspended for a
week, but after this and until August, 1915, the dredges were able for


the most part to keep up with the material as it came down, and -j
would have been able to maintain such condition had not a movement
occurred on the west bank, necessitating work on this side to the
detriment of the east side. -.
A crack was found on the slope of Zion Hill in June, 1914, higher
up than the crack already mentioned, but observations made upon
it showed no movement, and the solidity df the hill was never
doubted. Subsequent to the break on the east side, a gradual but
general breaking up of the west bank followed. The crack on the
slope increased in size and new ones developed farther up the hill, .
until finally one extended to elevation 480 above sea level, the limit
of the present break. The movement into the Cut from the west
bank occurred early in August, 1915, when a section of Zion Hill
broke away and settled down. The edge of the break on this side is
also a curve.
The movements from the two sides were toward the central portion
of the inclosed area, and at this central portion the bottom was
forced up, at first forming an island, then a peninsula projecting from
the east bank, and finally an isthmus entirely across the channel.
The barrier increased until it had a length of 255 feet along the axis
of the canal and an elevation of 65 feet above the surface of the
water. The movements on the two sides are entirely different in
character. On the east side a settlement of a mass occurs, the top
generally tilting backward from the-prism, with a shoving out below.
On the west side, for the most part, rock masses become detached and
gradually settle down vertically, with very little lateral movement,
pushing out the material along the prism face.
When the break occurred on the east side it was realized that it
would extend eventually back to the limiting cracks, and that all the
material lying above some surface, concave in shape, unless removed,
would eventually enter the prism. It was impossible to handle any
of it by hydraulics away from the Cut, and the only other method
would be by steam shovels. These could only operate on firm
ground, and would necessitate the establishment of dumps. The
number of shovels that could be worked would be limited, and con-
sider-able excavation would be required before the sliding material
could be attacked. The dredges were capable of and were removing
over 1,000,000 cubic yards per month without any of the difficulties
attending steam-shovel operations, and what could be accomplished
by the latter would be relatively so small and the cost so high that.
the idea of introducing steam shovels was abandoned and the decision
reached that the material must be removed from the canal side by the
From experience with other breaks, it was known that the move-
ment would not be continuous. A settlement occurs, by which '


material is pushed into the prism; the movement is at first heavy and
rapid, gradually diminishes, and finally ceases. This condition of rest
is disturbed either by the rains or by the operations of the dredges
cutting into the banks. As all the material liable to move must be
taken out by the dredges from the Cut, there would come a time
when the machines would be idle, waiting for a movement to give
additional material for them to handle. The judicious application
of hydraulicking the bank would avoid such a condition, conse-
quently pumps for sluicing operations were installed on two barges.
SThese have been used for cutting and maintaining surface drainage
and for washing down material to the dredges, when the conditions
warranted it.
The finished section from Gold Hill north left an enormous mass of
hard rock on the east side and at the northwest corner of Gold Hill.
When the break occurred in 1914 this mass of rock was moved slowly
into the prism, but finally came to rest and seemed to hold the
material back of it, limiting the area of interference in the channel.
It stood up boldly'for nearly 100 feet and was designated by the
working force as "Gibraltar," which designation will be used when
referring to this mass of rock.
The slipping of the material into the Cut removed the support to
the mushroom portions of Gold Hill on its north side, which broke off
in large masses and followed down diagonally toward the prism, the
effect being similar to that described as having taken place at
Cucaracha, and the direction of the movement was due, no doubt, to
the retaining effect of "Gibraltar," though this took up slow move-
ments at times when the heavier masses back of it were disturbed by
subsequent settlements.
If the width of the prism through the slide section remained as
fixed for the project-300 feet bottom width-every movement, that
occurred on either the east or west bank would contract the channel,
and should a movement occur in both banks at the same time it
would probably result in closing the canal to navigation. The neces-
sity of restoring the channel to permit the passage of ships and the
maintenance of navigation were the main considerations. An addi-
tion to the width sufficient to take care of material pushed in by
subsequent movements, thereby increasing the chances of main-
taining a channel, was considered advisable until all the loosened
material had been removed. This led to a modification of the pro-
jected width, which was increased to 500 feet, 100 feet on either side
of the original prism lines.
SThe conditions as they existed then-in November, 1915-found
the canal closed to navigation indefinitely. There was across it an
isthmus 250 feet long in the direction of the axis of the canal, the top
of which was about 65 feet above water; the dredging operations


Were confined to the north of this isthmus, working toward the south,
with arrangements made for washing down the material in case it was
advisable to accelerate the motion of any part of the sliding area,
and with the project modified so as to give a completed width north
of Gold Hill of 500 feet.
In October, 1915, the President of the United States was advised
by a member of the National Academy of Sciences-which was
organized by an act of Congress to give expert advice to the President
and Congress on scientific matters-who stated that one of its mem-
bers had made an extensive study of earth slides in tropical countries,
and was convinced that there were relatively simple ways by which
they could be stopped, and suggested that a committee of mining
engineers and geologists of the academy be appointed to consider his
propositions. In consequence of this, the President of the United
States requested that a committee be appointed by the National
Academy of Sciences to "Consider and report upon the possibility
of controlling the slides, which are seriously interfering with the use
of The Panama Canal." From the correspondence it appears that
at a meeting held in New York, "* the hope was repeatedly
expressed that an effective solution may speedily be found."
The coming of the committee was welcomed on the Isthmus, .for
so much misinformation had been sent broadcast, doing more injury
to the canal than the closing of it by the slides; confidence had been
upset; and it was hoped not only that a remedy would be forthcoming
but that the report of the committee would be able to restore con-
fidence in the project, especially as those connected with the work
knew that the methods adopted would overcome the difficulties for
good and all, given the time and money, and that the waterway would
be all that had been expected.
Probably the greatest injury done the canal was through Prof.
Benjamin Le Roy Miller, Ph. D., who occupies the chair of geology
at Lehigh University. On returning to New York from Costa Rica
he stayed here a couple of days awaiting a steamer. He was given
every facility to examine the slides at Culebra, which were then at
their worst, and he is reported to have said for publication on his
arrival in the United States that he had made a thorough examina-
tion of the slides," and the conditions found were as follows-the
statement appearing in quotation marks in the press item:
At the Culebra Cut cracks have formed over 1,300 feet back from the
canal, and all of the ground intervening is moving toward the Cut. There is nodoubt
that much rock, now apparently stable, also will move, as its support is withdrawn by
the removal of loose earth and rock. Before the canal can be said to be completed
and permanently opened to traffic, the amount of material that must be taken out
will not fall far short of the amount already taken from the Culebra Cut.
Transportation companies planning to use the canal should realize that they must
not expect uninterrupted service for several years. During the dry season the canal


may be opened, but it is certain to be closed during the rainy season when the earth
is soaked with water and its movement toward the canal facilitated.
In view of the extent of the material that has now started toward the Cut, it seems
that steam shovels should again be employed. Practically all of Gold Hill and much
of Zion Hill must be removed, and to wait until the earth breaks loose and enters the
Cut where the dredges can attack it seems unwise, and unquestionably longer delays
I the completion of the project. If dredges alone are employed, as at present, the canal
S may be kept clear during the months when rainfall is lightened, but for many years
to come the rainy season is almost certain to cause such slides as to close the canal
for weeks or even months.
The "thorough examination" occupied ftuly three or four hours of
his time. The position that he occupied in one of the leading uni-
versities of the United States gave credence to his statements, which
were copied broadcast, and commented upon editorially to the detri-
ment of the canal. His dire predictions were naturally unsettling to
shipping interests, which were guided by them to some extent in
routing their commerce elsewhere.
It was anticipated that the committee from the National Academy
of Sciences would make a more thorough examination than Prof.
Miller had done, and it was hoped that, as a result, the statements
of Prof. Benjamin Le Roy Miller, Ph. D., would be found to be what
we considered them-erroneous, unwarranted, and unfair, and help
restore the confidence that he had helped to destroy.
The preliminary report by the committee of the National Academy
of Sciences was submitted to the President in January, 1916. At
that time they expected that their final report would be completed
in April, but up to date it has not been received. The preliminary
report will be found in Appendix N. It will be noted that the state-
ment made by Prof. Miller, that practically all Gold Hill and much of
Zion Hill must be removed, is not concurred in; and in this connection
it should be remembered that a committee of this character expresses
its opinions guardedly, for whatever happens they must be found on
the right side. They advocated, as a matter of scientific interest,
the making of an accurate triangulation of the hills in question-
Gold, Contractors, Culebra, and Zion-which has been done. By
checks made at frequent intervals the slightest movement on the
part of any of the four hills would be disclosed at once. No movement
of any kind has taken place.
The committee expressed the belief that every available and prac-
ticable device for controlling the water, both on the surface and under-
ground should be employed, and to this end advocated covering the
slopes with vegetation to prevent surface wash, closing peripheral
cracks, draining undisturbed and threatened areas, and draining by
For several years the expedient of covering the slopes with vegeta-
tion has been carried on, starting under the direction of Dr. Pittier,
of the Smithsonian Institution. Where the surface of the ground is


in motion, as in the case of active slides, the roots are disturbed, and
the steady growth of vegetation is impracticable. Trees and vege-
tation of all kinds growing on the surface of the ground which broke
in October, 1914, were carried down the slide and exercised no
deterring effect whatsoever. On sliding ground there is not sufficient
time to plant anything and no good would be accomplished. Where
the banks consist of the red clay of the country, it is only after con-
siderable difficulty that grass of any kind can be grown on them.
Vegetation stops erosion; on this account the work was undertaken
and is being carried on.
When peripheral cracks occur in rock with sufficient earth covering
they may be effectually closed by the use of a hydraulic grader, as
was clone in an incipient slide on the west bank of the canal hear
Las Cascadas. The sluicing down of the earth into a uniform slope
not only fills the cracks and prevents the access of surface water into
them, but facilitates the drainage by providing a ready means of
run-off into the canal. This method, while applied with good results
at the north end of the East Culebra slide, so long as the material is
at rest, a subsequent movement develops new cracks and irregu-
larities so that until all loose clay and rock is removed and the final
slope reached, the relief is temporary only. Where there is very
little earth covering, as is the case on Culebra Hill, and where the
cracks are wide and extend a great depth in rock, it is not practicable
to close them permanently without expense that is disproportionate
to the results obtained.
In compliance with the expressed wishes of the committee while
on the Isthmus; subsurface tile drains have been installed within an
area on Culebra Hill as an experiment. Also, as suggested by the
committee, the fault fissure under the hard Obispo tuff on the north
side of Contractors Hill has been sealed and a concrete-lined drain
constructed, draining the surface water into the canal, with a view
to the protection of the Cucaracha rock beds adjacent to this portion
of Contractors Hill.
It is admitted that if the water could be entirely excluded the
earth movements would cease, but unfortunately this is impossible.
With the heavy tropical downpours the best that can be done is by
drainage, to carry away what falls as rapidly as possible, but ground
water can not be eliminated. So far as concerns ground water, the
construction of the canal has created entirely new conditions. The
old tributaries of the Chagres River and those of the Rio Grande,
which formerly were natural' drains, are now well above the water
surface of the canal, and the canal has become the drainage channel
for the country for miles on either side. Even assuming that were it
possible to devise a system for getting rid of ground water, it must still.
exist below the surface of the water in the canal itself. The slides


in question affect the banks for a considerable distance down, prob-
ably below the bottom of the canal, and if ground water be primarily
the cause, then it can not be removed from the strata at which the
trouble starts.
Surface drainage was maintained throughout the period of dry
excavation. The adjacent country on either side of the canal was
drained-through the east and west diversions, which continued to
act as drains, discharging their accumulated waters into the Chagres.
In relieving the pressure, force pumps on barges have enabled the
washing down of part of the material, as already explained. The
hydraulic grader which was constructed in July, 1914, and put. in
commission in August, 1914, was built especially for opening chan-
nels to expedite surface drainage at various points along the line of
the canal, and to maintain them, and this work has been carried on,
although suspended south of the slide, due to the interruption and
shut-off of the channel last fall and winter.
So long as the slides are active and the configurations of their sur-
faces change as rapidly as they now do, it is impracticable to open
and maintain the permanent drains recommended in the moving
areas. When equilibrium is restored, and as a means of promoting
permanent stability, the drains of a permanent character should be
constructed and maintained.
Drainage by tunnels has been considered in connection with data
obtained since the committee's report was written, as the result of
experiments suggested by the chairman of the committee, Dr. Van
Hise, through whom the services of Prof. Warren J. Mead, of the
University of Wisconsin, were secured, and who was assisted by
Mr. Donald F. MacDonald in making tests of the rock formation in
which the east and west Culebra and Cucaracha slides have occurred.
I have received from Mr. MacDonald, the geologist, a brief report,
hereto appended, marked "Appendix O," which states the result of
the experiments, as follows:
Twenty-one average samples of the Cucaracha or sliding formation were taken
from below the water level of the canal. These samples, completely saturated, con-
tained 12.20 per cent of water by weight, or 27.8 per cent by volume. The 16 average
samples taken from well above the level of ground water, where the rocks were much
jointed and fractured and, therefore, perfectly drained, contained 10.60 per cent of
water by weight. As shown above, 12.2 per cent of water by weight fills all of the pore
spaces of the rock; therefore, 10.6 per cent by weight fills only 87 per cent of them,
leaving 13 per cent of the total pore space as having been emptied by drainage and by
drying. Now, 13 per cent of 27.8 per cent is 3.6 per cent of the total volume of the
rofk. This shows that natural drainage of the most perfect kind would not remove
more than 13 per cent of the water by weight, equivalent to 3.6 per cent of the volume
of the rock. However, most of the samples from the drained rock were taken very
close to the surface, so that very likely they lost some of their water through drying
out by the heat of the sun, for the dry season was more than a month old at the time
they were collected.

These facts show that while the sliding rocks have a high percentage of pore space,
the pores are mostly of capillary size and are filled with water which obeys the laws of
capillarity and which can not, therefore, be drained off. These experiments defi-
nitely established that all cures by drainage which had been offered to and urged on
the canal authorities were absolutely futile, and the money which might have been
wasted in worthless tunnels, wells, and acres of asphalt covering, was saved for the
only remedy that could bring permanent cure under the circumstances-redging.
Before considering the suggestions that have been made for con-
trolling or preventing the slides other than those already mentioned,
it may be well to state what was attempted by the canal forces in
this direction prior to the occurrence of the slides which- are now
During the excavation of the Cut 22 slides and breaks of various
extent occurred. The steps taken to protect exposed slopes by vege-
tation have been noted. It was believed that piles driven through
the loose material into firm ground below and tied at the tops might
check the movement, and this was tried at four of the slides, but
without success. In some instances the piles were carried bodily
down the slope; in others the underlying material, moving faster
than the upper portion, inclined the piles away from the Cut, and in
cases where the top surface moved faster than at the bottom, they
inclined in the opposite direction. The remains of these piles can
be seen at the present time in some of the areas so treated.
It was thought that in case of clay slides heavy riprap dumped on
the surface would find its way through the loosened material to firm
ground and check the movement, but this method was found as use-
less as the piling. Most of the riprap rock was taken out. at. the foot
of the slope as the excavation proceeded. Experiments were made
by concreting the face of the prism to prevent the disintegrating
effect of the air on some of the softer rocks; this was done by use of a
cement gun, by plastering the surface with cement mortar and by
reinforced concrete, anchored to the side of the prism with pieces of
rail. None of these methods was satisfactory or durable. The rem-
nants oT the French drains, which proved inadequate, were dug out at
the bottom of the prism. The conclusion was reached that the only
cure was the removal of all loosened material as it came into the Cut,
and in case of breaks to relieve the weight, where possible, from the
upper parts of the banks by steam shovels or sluicing operations.
In considering any method for stopping the slides some concep-
tion must be had of the enormous amount of material involved, as
well as the method in which it acts. The banks at present giving
trouble are from 300 feet to approximately 550 feet above sea level,
and extend back 1,300 to 1,800 feet from the faces of the prism, and
from these farthest points to the water surface the entire mass is
broken for a depth extending at least to the bottom of the canal.
As already explained, the movement is by fits and starts, sudden at


first and gradually subsiding, with renewed activity after a period
of quiescence. For instance, in August, 1916 a general movement
occurred at the east Culebra slide and consisted of a settlement from
20 to 25 feet vertically down at the rear portion of the area affected,
some 1,300 feet from the prism, by which a mass of material from
the lower part was projected into the Cut beyond the center line,
reducing the depth of water along this line an average of 5 feet.
Because of the width of the new channel, as well as the depth, navi-
gation was not interrupted, but some idea may be had of the enor-
mous amount of material that must be held back by any artificial
construction or device similar to those which have been proposed,
and the impossibility of their construction must be recognized.
Suggestions most frequently made have been along the line of
sowing vegetation and of properly draining the area. These have
already been considered. To sink a number of pipes and apply
steam for drying out the subsoil would be prohibitive on the score of
expense, even if it were practicable. It would be impossible to drive
and hold such pipes through the material in case of motion. Pipes
sunk for the purpose of pumping out the water are equally imprac-
ticable and impossible. From the experiments conducted by Prof.
Warren J. Mead and Mr. MacDonald all the water could not be ex-
tracted by this method. Piling the entire area at regular intervals
and tying the piles to anchors driven in the firm ground can not be
done, nor would it secure the result. anticipated by the proposers of
this scheme.
The construction of retaining walls would require the excavation
of material to secure the foundations, necessitating the removal of
all the material in motion, when the need for the retaining wall
would no longer exist. There is no form of construction that could
be designed that would hold back the superimposed mass while the
excavation for the foundations was in progress. The construction
of inverts to hold down the bottom of the prism is impracticable and
Wire netting rolled over the bank and held in place by stakes*
would not prevent the movement, but would seriously interfere with
the dredges in removing the material littered up with sections of
wire mesh, which would break loose with every movement of the
slide. Consolidating the mass by injecting grout would also be
impossible; the pipes could not be driven to firm ground below and
the earth and rock, as it now comes into the Cut, can be much more
easily handled than would be the case were this material solidified
by cement.
It was suggested that the slopes and the surface of the ground adja-
cent to the Cut be covered with asphalt, tar, or some preparation
which would exclude water from the ground. This was also pro-


posed by a member of the committee from the National Academy of
Sciences. That the committee did not include it among its recom-
mendations seems conclusive that in its opinion it was not practicable,
and no further comment seems necessary.
A number of theories have been advanced as to the cause of the
difficulties, among them that there exists a huge reservoir of water
within the earth and the pressure therefrom produces the slides. If
this be so, the pressure being sufficient to break the ground would
release the water and allow its escape. All the water that is drained
from the slide areas is accounted for by the rainfall and by the escape
of any ground water that the movement might liberate, and the
theory is untenable. The mutual attraction of the large masses on
either side of the Cut is assigned as the cause for bringing down the
material, and yet, another that. a huge magnet that previously existed
has been cut in two.
The latest theory advanced appears in an article published in the
New York Sun on June 18, 1916, by the Hon. Thomas Kearns,
ex United States Senator from Utah, and republished as Senate
Document No. 525, Sixty-fourth Congress, first session.
He believes, "* that the trouble is all caused by subter-
ranean gases formed in the earth which, when permitted to escape
through certain channels or breaks in the earth, carry with them
eruptive material, sometimes for a long distance, to the place of the
least, resistance." Coming from a man with such large practical
experience, it undoubtedly carried conviction to the minds of many
who-read it. Since Senator Kearns's examination was more thorough
than that made by Prof. Benjamin Le Roy Miller, Ph. D., it is com-
forting to note from his judgment also that Gold and Contractors
Hills are not likely to fall into the Cut.
Senator Kearns is in error when he states, "Since it (the canal) was
first opened to navigation on August 14, 1914, it has been closed and
out of commission virtually two-t.hirds of the time." The canal was
opened to traffic August 15, 1914, and up to June 18, the date of the
article, the canal was closed 232 days out of 656 days, or approx-
imately one-third of the time, instead of two-thirds, as stated.
Another error is that there was an upheaval in the bottom of the
Cut at some other point than the Culebra section. At no portion of
the canal has there been any upheaving except in the 2,000 feet north
of Gold Hill. This upward movement first occurred when the excava-
tion had reached elevation 175 feet above sea level, or 135 feet above
the finished bottom of the canal. The upheaval, as the result of the.
present slides, reached an elevation of 65 feet above the water surface,
or 110 feet above the bottom of the canal. In no case was there a
movement at. the bottom that was not preceded by a movement in
the adjacent bank. The movement in the bottom ceased entirely in


* 1913, when the side slopes were made sufficiently flat to reduce the
Pressure exerted by them to less than that required to accomplish
this upward movement. The upheaving in the bottom occurred
again subsequent to the break in October, 1914, when the huge
masses of the banks crowded toward the axis of the canal and dis-
Sturbed the condition of pressure that existed prior to the occurrence
S of the slides. Part of the shoaling in the canal is undoubtedly due
S to the resistance to the motion of the mass at some part of the bottom,
Which throws part of the slide itself upward with the effect shown.
According to Senator Kearns's theory, gases forming somewhere in
the interior of the earth in escaping carry with them eruptive material
to the place of least resistance, or in this instance through the bottom
of the canal. The breaks, which produced fissures several hundred
feet deep, liberated no gas. With a pressure sufficient to accomplish
such destruction of the structural formation of the rocks, apparently
the gases returned to their storage to attempt later a forced passage
through the bottom. We unconsciously endeavored to assist their
efforts by digging away 110 feet of their container, but even this did
not induce the gases to come forth; thus far there has been no evi-
dence of escape anywhere along the line of the canal, nor has there
been any upheaving movement anywhere except in the Culebra
district, where the slides occur. So long as there is no movement in
the banks we are able to reach bottom grade and keep it. Under the
circumstances, those on the work still adhere to their belief that
subterranean gases have nothing whatever to do with the movements
that have occurred.
The methods proposed for securing a channel through the slides
and to maintain it, adopted in October, 1915, were laid before the
committee of the National Academy of Sciences, including the sluicing
operations proposed on the west side, but no suggestions were made
which modified the plan in any way. The various propositions made
by a number of people seeking to help us in our troubles were care-
fully considered, as were also the theories advanced setting forth the
probable causes. There were a number of letters, the writers pro-
posing, for suitable monetary consideration, to cure the slides, but
these were filed. None of the suggestions or theories tended in any
way to change the plans adopted.
The dredges did their work so well that a channel was cut through
the Isthmus connecting the two banks, of sufficient size to pass the
small ships still tied up and awaiting transit. By April 15, 1916, a
sufficiently stable channel had been secured to warrant opening the
canal to navigation, and the transit, of shipping has continued to
date. Except at "Gibraltar" the waterway is 500 feet wide with 40-
foot depth over the greater part, this depending on the movements
That occur in the banks. So far as the Culebra slides are concerned,


the worst is over; the intervals between movements are becoming:.
greater and the quantities of material less; the only danger being at :
"Gibraltar," but it is hoped that the excavation continued along the
lines contemplated will enable the widening of this section to the I
adopted prism line Without interfering in any way with the transit..
of shipping. The reopening of the canal was at the beginning of the '
rainy season, and thus far the rainfall has been above the normal.
The recent movement at Cucaracha was, as usual, the unexpected, ;J
coming as it did from the high ground in the northeast corner of the
slide area. The difficulty attending this was not a question of amount
of material, for the dredges could cope easily with the movement on
this score; the hard flinty rock was difficult to break up, and caused
irritating and aggravating delays. 4
As predicted at the time the great Culebra movements occurred, ::
the slides will be overcome finally and for all time, notwithstanding
the calamity howlers and in spite of the disastrous predictions of the

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