mostly of a general character, and give but little consideration to
the engineering features of the canal construction. In considering
the canal as a carrier of ocean traffic probably the first inquiry
will be that relating to harbors. In reality there is no natural
harbor at either end of the Nicaragua route. Fifty years ago there
was an excellent harbor at Greytown into which ships drawing as much
as 30 feet found ready entrance, and within which was afforded a
well-protected anchorage. As early as that date, however, a point of
land or sand-pit was already pushing its way northward in consequence
of the movement of the sand along the beach in that direction, and
in 1865 it had nearly closed the entrance to the harbor. For many
years that entrance has been entirely closed, and now what was
once the protected harbor of Greytown is a shallow body of water,
completely closed, and known as the Greytown Lagoon. There is a narrow,
circuitous, and shallow channel leading from it out to an opening in
the sand-bar, which may be navigated by boats drawing not more than 2
or 3 feet, and by means of which freight and passengers are taken from
steamers, which are obliged to anchor in the offing. Occasionally heavy
storms break through this strip of sand between Greytown Lagoon and
the ocean, and for a short time form a shallow entrance to the former.
The sand movement in that vicinity northward or westward is so active
that it is but a short time before such openings are again closed.
The deepest water in the lagoon probably does not exceed 8 or 10 feet
at the present time, and the most of it is much shallower. The tidal
action at Greytown is almost nothing, as the range of tide between high
and low is less than 1 foot. The mean level of the Caribbean Sea is the
same as that of the Pacific Ocean.
Under these circumstances it is necessary to create what is practically
a new harbor at Greytown, and that work is contemplated in the plans
of the Isthmian Canal Commission. The canal line is found entering the
lagoon about 1 mile northwest of Greytown, where a harbor is planned
having a length of 2500 feet and a width of 500 feet, increased at
the inner end to 800 feet to provide a turning-basin. The entrance to
this harbor from the ocean will be dredged to a width of 500 feet at
the bottom, and it will be protected outside of the beach-line by two
jetties, the easterly about 3000 feet long, and the westerly somewhat
shorter. These jetties would “be built of loose stone of irregular
shape and size, resting on a suitable foundation,” the largest,
constituting the covering, weighing not less than 10 to 15 tons each.
These jetties would be carried 6 feet above high water and have a top
width of 20 feet. The trade winds, which blow from the easterly and
northeasterly, would have a direction approximately at right angles to
that of the easterly jetty, and ships making the entrance of the canal
would consequently be protected against them while between the jetties.
The easterly of these jetties would act as an obstruction against the
westerly movement of the sand, but it is practically certain that a
considerable amount of the latter would be swept into the channel,
and possibly to some extent into the harbor, necessitating dredging
a considerable portion of the time. The commission estimates that
the maintenance of the entrance and harbor would require an annual
expenditure of $100,000.
=331. Artificial Harbor at Brito.=—The harbor at Brito presents a
problem of a different kind. There is absolutely no semblance of a
harbor there at the present time (1902); it is simply a location on the
sandy beach of the ocean protected against swells from the west by a
projecting rocky point called Brito Head, the Rio Grande River emptying
into the ocean just at the foot of Brito Head, between it and the canal
terminus. The entire harbor and its entrance would be excavated in
the low ground of that vicinity, composed mostly of sand and silt,
although there would be a little rock excavation. The entrance to the
harbor would be dredged 500 feet wide at the bottom, and be protected
by a single jetty on the southeasterly side. The harbor itself would
be excavated back of the present beach; it would have a length of 2200
feet and a width of 800 feet. As the depth of water increases rather
rapidly off shore, the 10-fathom curve is found at about 2200 feet from
low-water mark, hence the jetty would not need to be more than probably
1800 to 2000 feet long. In this vicinity the water is usually smooth;
indeed but few storms annually visit this part of the coast. The
conditions are quite similar to those found on the coast of Southern
California. There is little sand movement in this vicinity, and the
annual expenditures for maintenance of the harbor and entrance would be
relatively small; the commission has estimated them at $50,000.
=332. From Greytown Harbor to Lock No. 2.=—The canal line, on leaving
the harbor at Greytown, is found in low marshy ground for a distance of
about 7 miles, the excavation being mainly through the sand, silt, mud,
and vegetable matter characteristic of that location. Throughout almost
this entire distance the natural surface is but little above sea-level.
The first ground elevated much above this marshy country is known as
the Misterioso Hills, in which Lock No. 1 is founded, having a lift
of 36½ feet and raising the water surface in the canal by that amount
above sea-level. Another stretch of marshy country, but not quite so
wet as the preceding, follows for a distance of about 11 miles, when
the Rio Negro Hills rise abruptly to an elevation of a little over 150
feet above sea-level. At this point is located Lock No. 2, with a lift
of 18½ feet. This lock is about 21 miles from the 6-fathom line off
Greytown. The canal line here practically reaches the San Juan River,
the latter lying a considerable distance easterly of the canal, between
this point and the ocean. Between Greytown and Lock No. 2 embankments,
never reaching a greater height than 10 to 15 feet, are required to
keep the water in the canal at various locations along the low ground.
These embankments do not necessarily follow parallel to the centre
line of the canal route, but are planned to connect hills, or rather
high ground, so as to reduce their length and give them a more stable
character than if they were located close to the canal excavation.
While some embankments will still be found above Lock No. 2, they are
few, and even lower than those already noticed. From Lock No. 2 to Lake
Nicaragua the route of the canal lies practically along the San Juan
River, the chief exception to that statement being the cut-off in the
vicinity of the Conchuda dam.
[Illustration: Lock No. 1, Nicaragua Route, about Seven Miles from
Greytown.]
[Illustration: Telegraph Office at Ochoa on the San Juan River.]
=333. From Lock No. 2 to the Lake.=—Inasmuch as both the Serapiqui and
San Carlos rivers flow from Costa Rican territory into the San Juan,
that is, from its right bank, the canal line necessarily is located
along the northerly or left bank of that river. At a distance of 23
miles from the ocean the canal line cuts through what are called the
Serapiqui Hills opposite the mouth of the river of that name, and at
a distance of a little over 26 miles from the ocean it pierces the
Tamborcito Ridge, where is found the deepest cutting on the entire
route. The total length of cut through this ridge is about 3000 feet,
but its greatest depth is 297 feet, and it consists largely of hard,
basaltic rock. The next lock, or Lock No. 3, is found about 17 miles
from Lock No. 2, or 38 miles from the sea, and it has, like Lock No. 2,
a lift of 18½ feet, raising the surface of the water in the canal to an
elevation of 73½ feet above the sea. Continuous heavy cutting through
what are called the Machado Hills brings the line to Lock No. 4, at
a distance of a little less than 41 miles from the ocean. This lock
has a lift varying from 30.5 to 36.5 feet, inasmuch as it raises the
surface of the water in the canal to the summit level in the lake. The
maximum lift of 36.5 feet would be required when the lake level stands
at an elevation of 110 feet above the sea, and 30.5 feet when the same
surface stands at an elevation of 104 feet above the sea. Although the
water surface in the canal level above this lock is identical with the
summit level in the lake, the canal line again runs through continuous
heavy cutting for a distance of 5 miles before it reaches the canalized
San Juan. This portion of the line between Lock No. 4 and the San Juan
River is called the Conchuda cut-off, for the reason that the point
called Conchuda, where the great dam is located, is but 3 miles down
the river from the point where the canal enters it. From Conchuda
to the lake, as has already been stated, the canal line follows the
course of the San Juan River, which must be canalized by considerable
excavation of earth and rock, both along the bed and in cut-offs. The
greater part of this cutting must obviously be on that portion of the
river toward the lake, as that is the highest part of the river-bed in
its natural condition.
=334. Fort San Carlos to Brito.=—The distance from the point of
entrance of the canal into the San Juan River near Conchuda to Fort
San Carlos on the shore of Lake Nicaragua is about 50 miles, while the
distance across the lake on the canal line is 70.5 miles, which brings
the line to Las Lajas on the southwesterly shore of the lake.
There is considerable heavy cutting through the continental divide
between the lake and the first lock westerly of it, i.e., Lock No. 5.
The maximum cutting is but 76 feet in depth, and the average is but
little less than that for nearly 3 miles. This lock is located a little
less than 10 miles from the lake and nearly 176 miles from the 6-fathom
line off Greytown. The place at which this lock is located is known as
Buen Retiro. The lift of Lock No. 5 varies from 28½ feet as a maximum
to the minimum of 22½ feet, bringing the water surface in the canal
down to 81½ feet above mean ocean level. Lock No. 6 is located but
about 2 miles west of Lock No. 5, and also has a lift of 28½ feet. The
line now runs along the course of the Rio Grande to the ocean, Lock No.
7 being also 2 miles west of Lock No. 6, again with a lift of 28½ feet.
The last lock on the line, or Lock No. 8, but a mile from the Pacific
Ocean, and about 182 miles from the Caribbean Sea, has a maximum lift
of 28½ feet, and a minimum lift of 20½ feet, the range of tide in the
Pacific Ocean being but 8 feet at Brito. There are thus four locks
between the lake and the Pacific Ocean, each having a possible lift of
28½ feet.
[Illustration: Surveying Party of the Isthmian Canal Commission on the
San Juan River.]
The entire distance between the 6-fathom lines in the two oceans is
183.66 miles.
=335. Examinations by Borings.=—Obviously it is of the greatest
importance that such structures as the locks and dams required in
connection with this canal route should be founded on bed-rock. In
order to determine not only such questions, but the character of all
materials to be excavated from one end of the route to the other, a
great number of borings were made along the canal line, not only by the
water-jet process, but also with the diamond drill. By means of the
latter, whenever it was so desired, cores or circular pieces could be
taken out of the bed-rock so as to show precisely its character at all
depths. These borings, both through earthy material by the jet and into
bed-rock by the diamond drill, were made at suitable distances apart
along the centre line of the canal, and in considerable numbers, closer
together at proposed lock and dam sites. By these means every lock on
the line has certainly been located on bed-rock, as well as the great
dam at Conchuda. In addition to this the commission has been able to
classify the material to be excavated, so that if the canal should be
built every contractor would know precisely the character and quantity
of the various materials which he would have to deal with.
=336. Classification and Estimate of Quantities.=—The following table
is arranged to exhibit a few only of the principal items of excavation,
so as to give an approximate idea at least of the magnitude of the work
to be done:
Dredging 130,920,905 cu. yds.
Dry earth 47,440,316 ”
Soft rock 14,029,170 ”
Hard rock 24,151,214 ”
Rock under water 2,780,040 ”
Embankment and back-filling 8,389,960 ”
Clearing 6,831 acres.
Stone-pitching 250,089 sq. yds.
Concrete, excluding retaining-walls 3,400,840 cu. yds.
Concrete in retaining-walls 424,321 ”
Cut-stone 22,272 ”
Steel and iron,
excluding cast-iron culvert lining 61,735,230 lbs.
Cast-iron culvert lining 19,286,000 ”
Brick culvert lining 34,542 cu. yds.
Cost of lock machinery $1,600,000
Excavation in coffer-dam 9,907 cu. yds.
Pneumatic work 145,557 ”
Piling 415,600 lin. ft.
Rock fill in jetties 451,500 cu. yds.
Clay puddle, bottom and side 936,800 ”
=337. Classification and Unit Prices.=—The classification of the
material to be excavated, both on the Nicaragua and Panama routes, was
one to which the commission gave very thoughtful study no less than to
the prices to be used in making the estimates. The following table,
taken from pages 67 and 68 of the commission’s report, exhibits the
classification and the prices adopted by the commission for purposes of
its estimates:
Removal of hard rock, per cu. yd. $1.15
Removal of soft rock, per cu. yd. .80
Removal of earth, not handled by dredge, per cu. yd. .45
Removal of dredgable material, per cu. yd. .20
Removal of rock, under water, per cu. yd. 4.75
Embankments and back-filling, per cu. yd. .60
Rock in jetty construction, per cu. yd. 2.50
Stone-pitching, including necessary backing, per sq. yd. 2.00
Clearing and grubbing in swamp sections of Nicaragua,
per acre 200.00
Other clearing and grubbing on both routes, per acre 100.00
Concrete, in place, per cu. yd. 8.00
Finished granite, per cu. yd. 60.00
Brick in culvert lining, per cu. yd. 15.00
All metal in locks, exclusive of machinery and culvert
linings, per lb. .075
All metal in sluices, per lb. .075
Cast-iron in culvert lining, per lb. .04
Allowance for each lock-chamber for operating machinery 50,000.00
Additional allowance for each group of locks
for power-plant 100,000.00
Price of timber in locks, per M B. M 100.00
Sheet-piling in spillways, per M B. M 75.00
Bearing piles in spillways, per lin. ft. .50
Average price of pneumatic work for the Bohio dam, below
elevation—30, per cu. yd. 29.50
Caisson work for the Conchuda dam, in place, per cu. yd. 20.00
Single-track railroad complete with switches, stations,
and rolling stock, per mile of main line 75,000.00
There are evidently other more or less uncertain expenditures,
depending upon all possible conditions affecting the cost of such work,
including those of climate, police, and sanitation. In order to cover
such expenditure the commission determined to add 20 per cent to all
its estimates of cost on both routes, and that percentage was so added
in all cases.
=338. Curvature of the Route.=—Among the engineering features of
a ship-canal line it is evident that curvature is one of great
importance. Small steam-vessels may easily navigate almost any
tortuous channel, but it is not so with great ocean steamships. On the
other hand, it may require very deep and expensive cutting to reduce
the curvature of the route, as curves are usually introduced to carry
the line around some high ground. It is necessary, therefore, to make
a careful and judicious balance between these opposing considerations.
The commission wisely decided to incur even heavy cutting at some
points for the purpose of avoiding troublesome curvature on the
Nicaragua route. The table on page 415, taken from page 135 of the
commission’s report, gives all the elements of curvature for the entire
line.
[Illustration: Boring Party of the Isthmian Canal Commission on a Raft
in the San Juan River.]
From the description of the line as given, it is evident that much
curvature must be found in spite of the most judicious efforts to avoid
it, and the table indicates that condition. Yet the amount of curvature
may be considered moderate for a location through such a country as
Nicaragua. The smallest radius is seen to be a little over 4000 feet.
The result may be considered satisfactory for such a difficult canal
country, although the total amount of curvature is rather formidable.
+-----------+---------+---------+------------------+
| Number of | Radius. | Length. | Total Degrees of |
| Curves. | | | Curve. |
+-----------+---------+---------+------------------+
| | Feet. | Miles. | ° ′ ″ |
| 2 | 17,189 | 1.53 | 26 51 10 |
| 8 | 11,459 | 6.80 | 179 31 50 |
| 4 | 8,594 | 4.31 | 151 40 50 |
| 1 | 8,385 | 1.43 | 51 44 30 |
| 2 | 7,814 | 1.90 | 73 28 30 |
| 1 | 7,759 | 1.73 | 67 16 50 |
| 5 | 6,876 | 4.64 | 204 34 40 |
| 2 | 5,927 | 2.40 | 122 41 20 |
| 16 | 5,730 | 11.08 | 584 47 40 |
| 2 | 5,289 | 2.27 | 129 45 50 |
| 1 | 5,209 | 1.15 | 66 38 30 |
| 2 | 5,056 | 1.22 | 73 17 40 |
| 1 | 4,982 | .82 | 49 49 00 |
| 3 | 4,911 | 2.75 | 169 36 00 |
| 1 | 4,297 | .63 | 44 19 50 |
| 1 | 4,175 | .81 | 58 20 40 |
| 4 | 4,045 | 3.82 | 285 25 40 |
+-----------+---------+---------+------------------+
| 56 | | 49.29 | 2,339 50 30 |
+-----------+---------+---------+------------------+
=339. The Conchuda Dam and Wasteway.=—The most important single
engineering feature of the whole plan is the dam at Conchuda. The
ordinary low-water elevation in the river at the dam site may be taken
at about 55 feet above the sea. Inasmuch as the greatest elevation of
the water in the lake is supposed to be about 110 feet, it will be
seen that its surface will be but 55 feet above the present elevation,
making its maximum depth at that point about 105 feet if there should
be no fill on the up-stream side of the dam, inasmuch as the present
depth of water in the river at the stage assumed is about 50 feet.
This dam would be a structure of concrete masonry with cut-stone facing
only at a few points where it would be advisable to use that material.
A large part of the flood discharge, or the discharge of other surplus
water, would be made over a properly designed crest of the dam; hence
its outline would be that shown in the accompanying figure, shaped
so as to prevent the overflowing sheet of water from damaging the
structure. This dam will be founded upon pneumatic caissons, and the
borings made by the commission show that the deepest of them would
reach satisfactory bed-rock at no greater depth than 25 feet below
sea-level, or about 80 feet below the ordinary stage of water in the
river. The construction of this dam therefore would involve no unusual
operations, but it would all be performed within the more usual and
easy limits of the pneumatic process of constructing foundations. The
masonry crest of this dam would be finished at the elevation of 97
feet above sea-level, or about 13 feet below the highest elevation of
water in the lake. The length of that part of this masonry dam, located
on pneumatic caissons, would be 731 feet, but the total length of the
entire masonry structure would be 1310 feet. The total length of crest,
including the masonry piers on it, over which the surplus waters would
flow, would be 810 feet, but there are twenty piers 9 feet thick, so
that the net length of crest available for overflow of waste-waters
would be about 630 feet. The piers to which reference is made are those
required for the support of the movable gates of the Stoney type which
would be employed to regulate the discharge over the dam. The maximum
elevation of the tops of these piers required for the support and
operation of the Stoney gates is 132 feet above sea-level. The masonry
dam thus furnished with movable gates can be used in times of flood
to prevent the water of the lake rising above about 110 feet above
sea-level. In times of low rainfall or during the dry season the gates
would prevent the escape of water needed for storage.
[Illustration: Castillo Viejo, on the San Juan River, about
thirty-seven miles from the lake and at the Castillo Rapids. The old
fort is shown on the right at the summit of the hill.]
The total available length of crest on this masonry dam is not
sufficient to exercise all the control that is needed to keep the lake
within desired limits, and the commission was obliged to avail itself
of a low depression or saddle between the hills less than a half-mile
easterly of the dam site. The depression affords an additional total
length of crest of 1239 feet, or, taking out thirty-one piers, each 9
feet wide, a net available length of 960 feet, making in combination
with the crest of the main dam a total net available length of 1590
feet. The total wastage over these two structures, i.e., the main dam
at Conchuda and the Conchuda wasteway on the Costa Rican side of the
river, may be at the rate of 100,000 cubic feet per second, with a
maximum depth over the crest of 7 feet, which is sufficient to meet the
demands of the heaviest rainfall in the lake basin.
The plans and elevations on pages 421, 423, and 424 show all the main
features of both the Conchuda dam and wasteway as designed by the
commission.
=340. Regulation of the Lake Level.=—One of the most important
engineering questions connected with the consideration of the Nicaragua
route is that of the regulation or control of the surface of the water
in Lake Nicaragua constituting the summit level of the canal.
As has already been stated, the drainage-basin of the lake, about
12,000 square miles in area, is subjected to an annual wet season
extending from about the middle of May to the middle of December,
the dry season extending over the remaining portion of the year. The
average annual rainfall over the entire lake basin is not accurately
known, although the Isthmian Canal Commission maintained rainfall
records at several points on the lake shore and at other points in the
basin during periods of 1½ to 2 years, and records running back over
periods of perhaps 12 to 15 years are available from Rivas, Granada,
and Masaya. Fortunately, also, both the Nicaragua and the Isthmian
Canal Commissions maintained gauging-stations at various points on the
San Juan throughout the periods of service of these commissions, so
that the discharges of the river could be known from accurate measures
at various seasons for at least two or three years. These observations,
although not as extended as could be desired, yield sufficient data
for a comparatively thorough treatment of the subject of lake-surface
control.
Obviously throughout the rainy season of the year, except during years
of low rainfall, some water would necessarily be wasted from the lake
because its retention would raise the surface of the lake too high,
causing damage, floods, or injurious overflows at various places around
the lake shore. On the other hand, unless some water were stored from
the rainy periods or wet seasons there would not be sufficient in
the lake to supply during the dry period of the year, or during low
rainfall years, the requisite quantity for the wastage of evaporation
from its surface and for the operation of the canal, and at the same
time maintain the minimum depth of water of 35 feet required in the
canal. It was necessary, therefore, to design at least the general
features of such regulating-works as would prevent the lake from rising
too high in wet periods, and from falling too low in dry periods or low
rainfall years.
[Illustration: Village of Fort San Carlos at Entrance to the San Juan
River. Lake Nicaragua is on the right and San Juan River in the middle
ground.]
=341. Evaporation and Lockage.=—The observations of both commissions
show conclusively that the average evaporation from the surface of Lake
Nicaragua is about 60 inches or 5 feet per year, varying from perhaps a
maximum of 6 inches per month to a minimum of possibly about 4 inches
per month. Furthermore, careful estimates of the quantity of water
required for the purposes of the canal, on the supposition that about
10,000,000 tons of traffic would pass through it annually, including
lockage, leakage through the gates of the locks, evaporation, power
purposes, and other incidentals, show that about 1000 cubic feet of
water per second must be provided. Whatever may be the character of the
season, therefore, there must be at least sufficient water stored in
the lake to provide for the wastage of evaporation from the lake and
canal surfaces and for the proper operation of all the locks throughout
the length of the canal. The superficial area of Lake Nicaragua is but
little less than 3000 square miles. The quantity of water required for
the operation of the canal, amounting to 1000 cubic feet per second,
would, for the entire year, make a layer of water over the lake surface
of less than 5 inches in thickness. In other words, the operation of
the canal, for a traffic of about 10,000,000 tons annually, requires an
amount of water less than one twelfth of that which would be evaporated
from the lake surface during the same period.
=342. The Required Slope of the Canalized River Surface.=—The dam
located at Conchuda and fitted with suitable movable gates affords
means of accomplishing the entire lake-surface control. That dam is
located, however, nearly 53 miles from the lake, and in order that the
requisite discharge may take place over it during the rainy season
there must be considerable slope of the water surface in the canalized
river from the lake down to the dam. It was necessary, therefore, to
compute that slope, from data secured by the commission, with the
lake surface at various elevations between the minimum and maximum
permitted. These slopes were found to be such that the difference in
elevations of the surface of the water at the dam and in the lake might
vary from about 6 to 9 feet, those figures representing the total fall
for the distance of 53 miles.
=343. All Surplus Water to be Discharged over the Conchuda Dam.=—The
Nicaragua Commission contemplated the construction of dams not only on
the San Juan River at Boca San Carlos, about 6 miles below Conchuda,
but also another a few miles west of the lake at La Flor, so as to
discharge the surplus waters at both points, but by far the largest
part over the dam at Boca San Carlos. The Isthmian Canal Commission,
however, decided to build no dam on the west side of the lake, but to
discharge all the surplus waters over the dam at Conchuda.
[Illustration: The Active Volcano Ometepe in Lake Nicaragua, showing
Clouds on Leeward Side of the Summit. The crater is nearly eleven miles
from the canal line.]
=344. Control of the Surface Elevation of the Lake.=—The rainfall
records in the lake basin have shown that a dry season beginning
as early as November may be followed by an extremely low rainfall
period, which in turn would be followed by a dry season in natural
sequence, lasting as late as June. It may happen, therefore, that
from November until a year from the succeeding June, constituting a
period of nineteen months, there will be a very meagre rainfall in the
lake basin, during which the precipitation of the seven low rainfall
wet months may not be sufficient even to make good the depletion of
evaporation alone during the same period. It would be necessary, then,
at the end of any wet season whatever, i.e., during the first half of
any December, or in November, to make sure of sufficient storage in the
lake to meet the requirements of the driest nineteen months that can
be anticipated. That condition was assumed by the commission, and the
elements of control of the lake surface, in its plans, are such as to
afford resources to meet precisely those low-water conditions.
[Illustration: Plan of Conchuda Dam Site, showing Location of Boring.]
The commission’s study of these features of the Nicaragua Canal problem
resulted in plans of works to prevent the surface of the lake ever
falling below 104 feet above sea-level, or rarely if ever rising higher
than the elevation of 110 feet above the same level, thus making the
possible range of the lake surface about 6 feet between its lowest and
its highest position.
Obviously at the end of a dry season the gates at the dam will always
be found closed, and there will be no water escaping from the lake
except by evaporation and to supply the needs of canal operation. It
is equally evident that the gates will also remain closed so as to
permit no wastage during the early part of the wet season. As the wet
season proceeds the surface of the lake will rise toward, and generally
quite to its maximum elevation; the operation of wasting over the
weirs will then commence. The time of beginning of this wastage will
depend upon the amount and distribution of the rainfall during the
wet period. Indeed no wastage whatever would be permitted during such
a low-water wet season as that shown by the records of 1890, which
was almost phenomenal in its low precipitation. The rainfall for the
entire drainage-basin would be impounded in the lake in that case, and
it would then fall short of restoring the depletion resulting from
evaporation and requirements of the canal. On the other hand, during
such a wet season as that of 1897 wastage would begin at an early date.
In general it may be said that neither the rate nor the law of the rise
of water surface in the lake can be predicted. There will be years when
no wastage will be permitted, but generally considerable wastage will
be necessary in order to prevent the lake rising above the permissible
highest stage.
[Illustration: Profile of Site of Conchuda Dam showing Borings.]
Detailed computations based upon the statistics of actual rainfall
records in the basin of Lake Nicaragua may be found by referring to
pages 147 to 152 of the Report of the Isthmian Canal Commission, and
they need not be repeated here. Those computations show among other
things that October is often a month of excessive rainfall, and that
the greatest elevation of the lake surface is likely to follow the
precipitation of that month. Hence the greatest discharge of surplus
waters over the Conchuda dam may be expected in consequence of the
resulting run-off or inflow into the lake. Those computations also
show that at long intervals of time the lake surface might reach an
elevation of nearly 112 feet above sea-level for short periods, causing
the discharge in the canalized river or over the Conchuda dam to reach
possibly 76,000 cubic feet per second, the elevation of the water at
the dam being 104 feet above sea-level. Furthermore, the Sabalos River
and one or two other small streams, emptying into the San Juan above
the dam, might concurrently be in flood for at least a few hours and
augment the discharge over the dam to 100,000 cubic feet per second.
The regulating-works at the dam, consisting of the movable (Stoney)
gates, were devised by the commission to afford that rate of discharge,
an aggregate net or available length of overflow crest at the dam and
wasteway of 1590 feet being necessary for that purpose with a depth of
water on the crest not exceeding 7 feet.
[Illustration: CONCHUDA DAM. SECTION SHOWING CAISSONS]
[Illustration: CONCHUDA DAM. DIAGRAM SHOWING ARRANGEMENT OF SLUICE GATE]
The commission states on page 156 of its report:
“While, therefore, no detailed instructions can be set
forth regarding the condition of the sluices at the
wasteway on specified dates, the general lines of their
operation should be stated below, viz.:
“1. A full lake with surface probably a little above
110 feet on December 1.
“2. Wasteway sluices closed at least from about
December 1 to some date in the early portion of the
succeeding rainy season, or throughout that season if
it be one of unusually low precipitation.
“3. A variable opening of wasteway sluices, if
necessary, during the intermediate portion of the rainy
season, so as to maintain the lake surface elevation
but little, if any, below 110 at the beginning of
October.
“4. The operation of wasteway sluices during October
and November so as to reach the 1st of December with a
full lake, or lake elevation probably a little above
110 feet.”
It is thus seen that while the measures for control and regulation are
entirely feasible, they are not sharply defined, nor so simple that
some experience in their operation might not be needful for the most
satisfactory results.
=345. Greatest Velocities in Canalized River.=—It is necessary to
ascertain whether the velocities induced in the canalized portions
of the San Juan River would not be too high for the convenience of
traffic during the highest rainfall season. The following table and the
succeeding paragraph, taken from the commission’s report, show that no
sensible difficulty of this kind would exist.
--------------+-------------------------+----------------------
| Elevation of Water at Dam.
Elevation of +-------------------------+----------------------
Lake. | 103 Feet. | 104 Feet.
--------------+------------+------------+-----------+-----------
| Feet per | Miles per | Feet per | Miles per
Feet. | Second. | Hour. | Second. | Hour.
110 | 4.16 | 2.8 | 3.9 | 2.7
111 | 4.51 | 3.1 | 4.2 | 2.9
112 | 4.85 | 3.3 | 4.5 | 3.1
--------------+------------+------------+-----------+----------
“The discharge of the river corresponding to the velocity of 2.7 miles
per hour is 63,200 cubic feet per second; while that corresponding to
3.3 miles per hour is 77,000 cubic feet per second. These estimated
high velocities will occur but rarely, and they will not sensibly
inconvenience navigation. In reality they are too high, for the reason
that while the overflow at the minimum river section materially
increases the areas of those sections, it has been neglected in this
discussion.”
[Illustration]
[Illustration: Brito, at the Pacific Terminus of the Nicaragua Route,
showing the mouth of the Rio Grande on the left and the easterly side
of Brito Head.]
=346. Wasteways or Overflows.=—At a number of places on the route
there are some small streams which must be taken into the canal, and
which when in flood require that certain wasteways or overflows from
the canal prism should be provided at or near where such streams are
received. These wasteways are simply overfall-weirs with the crests
at the elevation of the lowest water surface in the canal prism. The
principal works of this kind are on the east side of the lake and
involve a total drainage area or area of watershed of about 107 square
miles. Ample provision has been made by the commission for all such
structural features.
=347. Temporary Harbors and Service Railroad.=—Before actual work
could be begun at either end of the Nicaragua route temporary harbors
would have to be constructed both at Greytown and at Brito to enable
contractors to land plant and supplies or other material. These
temporary harbors would probably require no greater depth of water
than 18 feet, but they would be works of considerable magnitude, and
provision was made for them in the commission’s estimate of cost.
Again, a service railroad of substantial character would have to be
built from Greytown up to Sabalos, approximately half-way between the
Conchuda dam and Fort San Carlos, as well as from the west shore of the
lake to Brito, making a total line of about 100 miles. The commission
estimated the cost of this railroad and its rolling stock at $75,000
per mile.
=348. Itemized Statement of Length and Cost.=—The following table gives
the lengths of the various portions of the canal and the principal
items of its cost, so arranged as to show the classification of the
various items of the total sum to be expended for all purposes during
the construction of the entire work.
The commission estimated the total time required in preparing for and
performing the actual construction of the work at eight years, but the
writer believes that at least two years more should be allowed for the
work.
------------------------------------------------+------+------------
|Miles.| Cost.
------------------------------------------------+------+------------
Greytown harbor and entrance | 2.15| $2,198,860
Section from Greytown harbor to lock No. 1, | |
including approach-wall to lock | 7.44| 4,899,887
Diversion of Lower San Juan | | 40,100
Diversion of San Juanillo | | 116,760
Lock No. 1, including excavation | .20| 5,719,689
Section from lock No. 1 to lock No. 2, including| |
approach-walls, embankments, and wasteway | 10.96| 6,296,632
Lock No. 2, including excavation | .20| 4,050,270
Section from lock No. 2 to lock No. 3, including| |
approach-walls, embankments, and wasteway | 16.75| 19,330,654
Lock No. 3, including excavation | .20| 3,832,745
Section from lock No. 3 to lock No. 4, including| |
approach-walls, embankments, and wasteway | 2.77| 4,310,580
Lock No. 4, including excavation | .20| 5,655,871
Section from lock No. 4 to San Juan River, | |
including approach-wall and embankments | 5.30| 8,579,431
Conchuda dam, including sluices and machinery | | 4,017,650
Auxiliary wasteway, including sluices, | |
machinery, and approach-channels | | 2,045,322
San Juan River section | 49.64| 23,155,670
Lake Nicaragua section | 70.51| 7,877,611
Lake Nicaragua to lock No. 5, including | |
approach-wall to lock and receiving-basins for| |
the Rio Grande and Chocolata | 9.09| 19,566,575
Diversion of the Las Lajas | | 199,382
Lock No. 5, including excavation | .20| 4,913,512
Dam near Buen Retiro | | 125,591
Section from lock No. 5 to lock No. 6, including| |
approach-walls and wasteway | 2.04| 3,259,283
Lock No. 6, including excavation | .20| 4,368,667
Section from lock No. 6 to lock No. 7, including| |
approach-walls, embankments, and wasteway | 1.83| 2,309,710
Diversion of Rio Grande | | 176,180
Lock No. 7, including excavation | .20| 4,709,502
Section from lock No. 7 to lock No. 8, including| |
approach-walls, embankments, and wasteway | 2.43| 1,787,496
Diversion of Rio Grande | | 117,580
Lock No. 8, including excavation | .20| 4,920,899
Section from lock No. 8 to Brito harbor, | |
including approach-wall | .23| 553,476
Brito harbor and entrance, including jetty | .92| 1,509,470
Railroad, including branch line to Conchuda | |
dam site, at $75,000 per mile | | 7,575,000
Engineering, police, sanitation, and general | |
contingencies, 20 per cent. | | 1,644,010
+------+------------
Aggregate |183.66|$189,864,062
------------------------------------------------+------+------------
PART VI.
_THE PANAMA ROUTE FOR A SHIP-CANAL._
=349. The First Panama Transit Line.=—The Panama route as a line
of transit across the isthmus was established, as near as can be
determined, between 1517 and 1520. The first settlement, at the site
of the town of old Panama, 6 or 7 miles easterly of the present city
of that name, was begun in August, 1517. This was the Pacific end of
the line. The Atlantic end was finally established in 1519 at Nombre
de Dios, the more easterly port of Acla, where Balboa was tried and
executed, having first been selected but subsequently rejected.
The old town of Panama was made a city by royal decree from the throne
of Spain in September, 1521. At the same time it was given a coat of
arms and special privileges were conferred upon it. The course of
travel then established ran by a road well known at the present time
through a small place called Cruces on the river Chagres, about 17
miles distant from Panama. It must have been an excellent road for
those days. Bridges were even laid across streams and the surface was
paved, although probably rather crudely. According to some accounts it
was only wide enough for use by beasts of burden, but some have stated
that it was wide enough to enable two carts to pass each other.
=350. Harbor of Porto Bello Established in 1597.=—The harbor of
the Atlantic terminus at Nombre de Dios did not prove entirely
satisfactory, and Porto Bello, westerly of the former point, was made
the Atlantic port in 1597 for this isthmian line of transit. The harbor
of Porto Bello is excellent, and the location was more healthful,
although Porto Bello itself was subsequently abandoned, largely on
account of its unhealthfulness.
[Illustration: PROFILE OF PANAMA ROUTE]
[Illustration: PROFILE OF NICARAGUA ROUTE
Profiles of the two Canal Routes. The horizontal scales are different,
but the vertical scales are the same.]
=351. First Traffic along the Chagres River, and the Importance of the
Isthmian Commerce.=—As early as 1534, or soon after that date, boats
began to pass up and down the Chagres River between Cruces and its
mouth on the Caribbean shore, and thence along the coast to Nombre de
Dios and subsequently to Porto Bello. The importance of the commerce
which sprang up across the isthmus and in connection with this isthmian
route is well set forth in the last paragraph on page 28 of the report
of the Isthmian Canal Commission:
“The commerce of the isthmus increased during the century and Panama
became a place of great mercantile importance, with a profitable trade
extending to the Spice Islands and the Asiatic coast. It was at the
height of its prosperity in 1585, and was called with good reason
the toll-gate between western Europe and eastern Asia. Meanwhile the
commerce whose tolls only brought such benefits to Panama enriched
Spain, and her people were generously rewarded for the aid given by
Ferdinand and Isabella in the effort to open a direct route westward to
Cathay, notwithstanding the disadvantages of the isthmian transit.”
=352. First Survey for Isthmian Canal Ordered in 1520.=—This commercial
prosperity suggested to those interested in it, and soon after its
beginning, the possibility of a ship-canal to connect the waters of the
two oceans. It is stated even that Charles V. directed that a survey
should be made for the purpose of determining the feasibility of such
a work as early as 1520. “The governor, Pascual Andagoya, reported
that such a work was impracticable and that no king, however powerful
he might be, was capable of forming a junction of the two seas or of
furnishing the means of carrying out such an undertaking.”
=353. Old Panama Sacked by Morgan and the Present City Founded.=—From
that time on the city of Panama increased in wealth and population in
consequence of its commercial importance. Trade was established with
the west coast of South America and with the ports on the Pacific
coast of Central America. In spite of the fact that it was made by
the Spaniards a fortress second in strength in America only to old
Cartagena, it was sacked and burned by Morgan’s buccaneers in February,
1671. The new city, that is the present city, was founded in 1673, it
not being considered advisable to rebuild on the old site.
[Illustration: View of the Harbor of Colon.]
=354. The Beginnings of the French Enterprise.=—The project of a
canal on this route was kept alive for more than three centuries by
agitation sometimes active and sometimes apparently dying out for
long periods, until there was organized in Paris, in 1876, a company
entitled “Société Civile Internationale du Canal Interocéanique,” with
Gen. Etienne Türr as president, for the purpose of making surveys and
explorations for a ship-canal between the two oceans on this route.
=355. The Wyse Concession and International Congress of 1879.=—The work
on the isthmus for this company was prosecuted under the direction
of Lieut. L. N. B. Wyse, a French naval officer, and he obtained for
his company in 1878 a concession from the Colombian Government,
conferring the requisite rights and privileges for the construction of
a ship-canal on the Panama route and the authority to do such other
things as might be necessary or advisable in connection with that
project. This concession is ordinarily known as the Wyse concession.
A general plan for this transisthmian canal was the subject of
consideration at an international scientific congress convened in Paris
in May, 1879, and composed of 135 delegates from France, Germany, Great
Britain, the United States, and other countries, but the majority of
whom were French. This congress was convened under the auspices of
Ferdinand de Lesseps, and after remaining in session for two weeks a
decision, not unanimous, was reached that an international canal ought
to be located on the Panama route, and that it should be a sea-level
canal without locks. The fact was apparently overlooked that the range
between high and low tides in the Bay of Panama, about 20 feet, was so
great as to require a tidal lock at that terminus.
=356. The Plan without Locks of the Old Panama Canal Company.=—A
company entitled “Compagnie Universelle du Canal Interocéanique”
was organized, with Ferdinand de Lesseps as president, immediately
after the adjournment of the international congress. The purpose of
this company was the construction and operation of the canal, and it
purchased the Wyse concession from the original company for the sum
of 10,000,000 francs. An immediate but unsuccessful attempt was made
to finance the company in August, 1879. This necessitated a second
attempt, which was made in December, 1880, with success, as the entire
issue of 600,000 shares of 500 francs each was sold. Two years were
then devoted to examinations and surveys and preliminary work upon the
canal, but it was 1883 before operations upon a large scale were begun.
The plan adopted and followed by this company was that of a sea-level
canal, affording a depth of 29.5 feet and a bottom width of 72 feet. It
was estimated that the necessary excavation would amount to 157,000,000
cubic yards.
The Atlantic terminus of this canal route was located at Colon,
and at Panama on the Pacific side. The line passed through the low
grounds just north of Monkey Hill to Gatun, 6 miles from the Atlantic
terminus, and where it first met the Chagres River. For a distance
of 21 miles it followed the general course of the Chagres to Obispo,
but left it at the latter point and passing up the valley of a small
tributary cut through the continental divide at Culebra, and descended
thence by the valley of the Rio Grande to the mouth of that river where
it enters Panama Bay. The total length of this line from 30 feet depth
in the Atlantic to the same depth in the Pacific was about 47 miles.
The maximum height of the continental divide on the centre line of the
canal in the Culebra cut was about 333 feet above the sea, which is a
little higher than the lowest point of the divide in that vicinity.
Important considerations in connection with the adjacent alignment made
it advisable to cut the divide at a point not its lowest.
[Illustration: Old Dredges near Colon.]
=357. The Control of the Floods in the Chagres.=—Various schemes were
proposed for the purpose of controlling the floods of the Chagres
River, the suddenness and magnitude of which were at once recognized as
among the greatest difficulties to be encountered in the construction
of the work. Although it was seriously proposed at one time to control
this difficulty by building a dam across the Chagres at Gamboa, that
plan was never adopted, and the problem of control of the Chagres
floods remained unsolved for a long period.
=358. Estimate of Time and Cost—Appointment of Liquidators.=—It was
estimated by de Lesseps in 1880 that eight years would be required for
the completion of the canal, and that its cost would be $127,600,000.
The company prosecuted its work with activity until the latter part of
1887, when it became evident that the sea-level plan of canal was not
feasible with the resources at its command. Changes were soon made in
the plans, and it was concluded to expedite the completion of the canal
by the introduction of locks, deferring the change to a sea-level canal
until some period when conditions would be sufficiently favorable to
enable the company to attain that end. Work was prosecuted under this
modified plan until 1889, when the company became bankrupt and was
dissolved by judgment of the French court called the Tribunal Civil
de la Seine, on February 4, 1889. An officer, called the liquidator,
corresponding quite closely to a receiver in this country, was
appointed by the court to take charge of the company’s affairs. At
no time was the project of completing the canal abandoned, but the
liquidator gradually curtailed operations and finally suspended the
work on May 15, 1889.
=359. The “Commission d’Etude.”=—He determined to take into careful
consideration the feasibility of the project, and to that end appointed
a “commission d’études,” composed of eleven French and foreign
engineers, headed by Inspector-General Guillemain, director of the
_Ecole Nationale des Ponts et Chaussées_. This commission visited
the isthmus and made a careful study of the entire enterprise, and
subsequently submitted a plan for the canal involving locks. The cost
of completing the entire work was estimated to be $112,500,000, but
the sum of $62,100,000 more was added to cover administration and
financing, making a total of $174,600,000. This commission also gave
an approximate estimate of the value of the work done and of the plant
at $87,300,000, to which some have attached much more importance than
did the commission itself. The latter appears simply to have made the
“estimate” one half of the total cost of completing the work added to
that of financing and administration, as a loose approximation, calling
it an “intuitive estimate”; in other words, it was simply a guess
based upon such information as had been gained in connection with the
work done on the isthmus.
[Illustration: The Partially Completed Panama Canal, about eight miles
from Colon.]
=360. Extensions of Time for Completion.=—By this time the period
specified for completion under the original Wyse concession had nearly
expired. The liquidator then sought from the Colombian Government an
extension of ten years, which was granted under the Colombian law dated
December 26, 1890. This extension was based upon the provision that a
new company should be formed and work on the canal resumed not later
than February 28, 1893. The latter condition was not fulfilled, and a
second extension was obtained on April 4, 1893, which provided that the
ten-year extension of time granted in 1890 might begin to run at any
time prior to October 31, 1894, but not later than that date. When it
became apparent that the provisions of this last extension would not
be carried out an agreement between the Colombian Government and the
new Panama Company was entered into on April 26, 1900, which extended
the time of completion to October 31, 1910. The validity of this last
extension of time has been questioned.
=361. Organization of the New Panama Canal Company, 1894.=—A new
company, commonly known as the new Panama Canal Company, was organized
on the 20th of October, 1894, with a capital stock of 650,000 shares
of 100 francs each. Under the provisions of the agreement of December
26, 1890, authorizing an extension of time for the construction of
the canal, 50,000 shares passed as full-paid stock to the Colombian
Government, leaving the actual working capital of the new Panama
Company at 60,000,000 francs, that amount having been subscribed in
cash. The most of this capital stock was subscribed for by certain
loan associations, administrator, contractors, and others against whom
suits had been brought in consequence of the financial difficulties
of the old company, it having been charged in the scandals attending
bankruptcy proceedings that they had profited illegally. Those suits
were discontinued under agreements to subscribe by the parties
interested to the capital stock of the new company. The sums thus
obtained constituted more than two thirds of the 60,000,000 francs
remaining of the share capital of the new company after the Colombian
Government received its 50,000 shares. The old company had raised by
the sale of stock and bond not far from $246,000,000, and the number
of persons holding the securities thus sold has been estimated at over
200,000.
=362. Priority of the Panama Railroad Concession.=—The Panama Railroad
Company holds a concession from the Colombian Government giving it
rights prior to those of the Wyse concession, so that the latter could
not become effective without the concurrence of the Panama Railroad
Company. This is shown by the language of Article III of the Wyse
concession, which reads as follows:
“If the line of the canal to be constructed from sea to sea should
pass to the west and to the north of the imaginary straight line which
joins Cape Tiburon with Garachine Point, the grantees must enter into
some amicable arrangement with the Panama Railroad Company or pay an
indemnity, which shall be established in accordance with the provisions
of Law 46 of August 16, 1867, ‘approving the contract celebration on
July 5, 1867, reformatory of the contract of April 15, 1850, for the
construction of an iron railroad from one ocean to the other through
the Isthmus of Panama.’” It became necessary, therefore, in order to
control this feature of the situation, for the old Panama Company
to secure at least a majority of the stock of the Panama Railroad
Company. As a matter of fact the old Panama Canal Company purchased
nearly 69,000 out of the 70,000 shares of the Panama Railroad Company,
each such share having a par value of $100. These shares of Panama
railroad stock are now held in trust for the benefit of the new Panama
Canal Company. A part of the expenditures of the old company therefore
covered the cost of the Panama Railroad Company’s shares, now held in
trust for the benefit of the new company.
=363. Resumption of Work by the New Company—The Engineering Commission
and the Comité Technique.=—Immediately after its organization the new
Panama Canal Company resumed the work of excavation in the Emperador
and Culebra cuts with a force of men which has been reported as
varying between 1900 and 3600. It also gave thorough consideration
to the subject of the best plan for the completion of the canal. The
company’s charter provided for the appointment of a special engineering
commission of five members by the company and the liquidator to report
upon the work done and the conclusions to be drawn from its study. This
report was to be rendered when the amount expended by the new company
should reach about one half of its capital. At the same time the
company also appointed a “Comité Technique,” constituted of fourteen
eminent European and American engineers, to make a study of the entire
project, which was to avail itself of existing data and the results of
such other additional surveys and examinations as it might consider
necessary. The report rendered by this committee was elaborate, and it
was made November 16, 1898. It was referred to the statutory commission
of five to which reference has already been made, which commission
reported in 1899 that the canal could be constructed within the limits
of time and money estimated. On December 30, 1899, a special meeting
of the stockholders of the new company was called, but the liquidator,
who was one of the largest stockholders, declined to take part in it,
and the report consequently has not received the required statutory
consideration.
[Illustration: The Excavation at the Bohio Lock Site.]
=364. Plan of the New Company.=—The plan adopted by the company placed
the minimum elevation of the summit level of the canal at 97½ feet
above the sea, and a maximum at 102½ feet above the same datum. It
provided for a depth of 29½ feet of water and a bottom width of canal
prism of about 98 feet, except at special places where this width was
increased. A dam was to be built near Bohio, which would thus form an
artificial lake with its surface varying from 52.5 to 65.6 feet above
the sea. Under this plan there would be a flight of two locks at
Bohio, about 16 miles from the Atlantic end of the canal, and another
flight of two locks at Obispo about 14 miles from Bohio, thus reaching
the summit level, a single lock at Paraiso, between 6 and 7 miles from
Obispo, a flight of two locks at Pedro Miguel about 1.25 miles from
Paraiso, and finally a single lock at Miraflores, a mile and a quarter
from Pedro Miguel, bringing the canal down to the ocean elevation.
The location of this line was practically the same as that of the
old company. The available length of each lock-chamber was 738 feet,
while the available width was 82 feet, the depth in the clear being
32 feet 10 inches. The lifts were to vary from 26 to 33 feet. It was
estimated that the cost of finishing the canal on this plan would be
$101,850,000, exclusive of administration and financing.
In order to control the floods of the Chagres River, and to furnish a
supply of water for the summit level of the canal, a dam was planned to
be built at a point called Alhajuela, about 12 miles from Obispo, from
which a feeder about 10 miles long, partly an open canal and partly in
tunnels or pipe, would conduct the water from the reservoir thus formed
to the summit level.
=365. Alternative Plan of the New Panama Canal Company.=—Although
the plan as described was adopted, the “Comité Technique” apparently
favored a modification by which a much deeper excavation through
Culebra Hill would be made, thus omitting the locks at both Obispo and
Paraiso, and making the level of the artificial Lake Bohio the summit
level of the canal. In this modified plan the bottom of the summit
level would be about 32 feet above the sea, and the minimum elevation
of the summit level 61.5 feet above the sea. This modification of plan
had the material advantage of eliminating both the Obispo and Paraiso
locks. The total estimated cost of completing the canal under this plan
was about $105,500,000. Although the Alhajuela feeder would be omitted,
the Alhajuela reservoir would be retained as an agent for controlling
the Chagres floods and to form a reserve water-supply. The difference
in cost of these two plans was comparatively small, but the additional
time required to complete that with the lower summit level was probably
one of the main considerations in its rejection by the committee having
it under consideration.
=366. The Isthmian Canal Commission and its Work.=—This brings
the project up to the time when the Isthmian Canal Commission was
created in 1899 and when the forces of the new Panama Canal Company
were employed either in taking care of the enormous amount of plant
bequeathed to it by the old company or in the great excavation at
Emperador and Culebra. The total excavation of all classes, made up to
the time when that commission rendered its report, amounted to about
77,000,000 cubic yards.
The work of the commission consisted of a comprehensive and detailed
examination of the entire project and all its accessories, as
contemplated by the new Panama Canal Company, and any modifications of
its plans, either as to alignment, elevations, or subsidiary works,
which it might determine advisable to recommend. In the execution of
this work it was necessary, among other things, to send engineering
parties on the line of the Panama route for the purpose of making
surveys and examinations necessary to confirm estimates of the new
Panama Canal Company as to quantities, elevations, or other physical
features of the line selected, or required in modifications of
alignment or plans. In order to accomplish this portion of its work the
commission placed five working parties on the Panama route with twenty
engineers and other assistants and forty-one laborers.
[Illustration: The French Location for the Bohio Dam.]
=367. The Route of the Isthmian Canal Commission that of the New
Panama Canal Company.=—The commission adopted for the purposes of
its plans and estimates the route selected by the new Panama Canal
Company, which is essentially that of the old company. Starting from
the 6-fathom contour in the harbor of Colon, the line follows the low
marshy ground adjoining the Bay of Limon to its intersection with the
Mindi River; thence through the low ground continuing to Gatun, about
6 miles from Colon, where it first meets the Chagres River. From this
point to Obispo the canal line follows practically the general course
of the Chagres River, although at one point in the marshes below Bohio
it is nearly 2 miles from the farthest bend in the river, at a small
place called Ahorca Lagarto. Bohio is about 17 miles from the Atlantic
terminus, and Obispo about 30 miles. At the latter point the course of
the Chagres River, passing up-stream, lies to the northeast, while the
general direction of the canal line is southeast toward Panama, the
latter leaving the former at this location. The canal route follows up
the general course of a small stream called the Camacho for a distance
of nearly 5 miles where the continental divide is found, and in which
the great Culebra cut is located, about 36 miles from Colon and 13
miles from the Panama terminus. After passing through the Culebra cut
the canal route follows the course of the Rio Grande River to its mouth
at Panama Bay. The mouth of the Rio Grande, where the canal line is
located, is about a mile and a half westerly of the city of Panama. The
Rio Grande is a small, sluggish stream throughout the last 6 miles of
its course, and for that distance the canal excavation would be made
mostly in soft silt or mud.
Although the line selected by the French company is that adopted by the
Isthmian Canal Company for its purposes, a number of most important
features of the general plan have been materially modified by the
commission, as will be easily understood from what has already been
stated in connection with the French plans.
=368. Plan for a Sea-level Canal.=—The feasibility of a sea-level
canal, but with a tidal lock at the Panama end, was carefully
considered by the commission, and an approximate estimate of the
cost of completing the work on that plan was made. In round numbers
this estimated cost was about $250,000,000, and the time required to
complete the work would probably be nearly or quite twice that needed
for the construction of a canal with locks. The commission therefore
adopted a project for the canal with locks. Both plans and estimates
were carefully developed in accordance therewith.
=369. Colon Harbor and Canal Entrance.=—The harbor of Colon has been
fairly satisfactory for the commerce of that port, but it is open to
the north, and there are probably two or three days in every year
during which northers blow into the harbor with such intensity that
ships anchored there must put to sea in order to escape damage.
The western limit of this harbor is an artificial point of land
formed by material deposited by the old Panama Canal Company; it
is called Christoph Colon, and near its extreme end are two large
frame residences built for de Lesseps. The entrance to the canal is
immediately south of this artificial point. The commission projected a
canal entrance from the 6-fathom contour in the Bay of Limon, in which
the harbor of Colon is found, swinging on a gentle curve, 6560 feet
radius, to the left around behind the artificial point just mentioned
and then across the shore line to the right into the lowland southerly
of Colon. This channel has a width of 500 feet at the bottom, with
side slopes of 1 on 3, except on the second curve, which is somewhat
sharper than the first, where the bottom width is made 800 feet for a
length of 800 feet for the purpose of a turning-basin. This brings the
line into the canal proper, forming a well-protected harbor for nearly
a mile inside of the shore line. The distance from the 6-fathom line to
this interior harbor is about 2 miles. The total cost of constructing
the channel into the harbor and the harbor itself is $8,057,707, and
the annual cost of maintenance is placed at $30,000. The harbor would
be perfectly protected from the northers which occasionally blow with
such intensity in the Bay of Limon, and it could readily be made in all
weathers by vessels seeking it.
=370. Panama Harbor and Entrance to Canal.=—The harbor at the Pacific
end of the channel where it joins Panama Bay is of an entirely
different character in some respects. The Bay of Panama is a place
of light winds. Indeed it has been asserted that the difficulties
sometimes experienced by sailing-vessels in finding wind enough to
take them out of Panama Bay are so serious as to constitute a material
objection to the location for a ship-canal on the Panama route. This
difficulty undoubtedly exists at times, but the simple fact is to be
remembered that Panama was a port for sailing-ships for more than two
hundred years before a steamship was known. The harbor of Panama, as
it now exists, is a large area of water at the extreme northern limit
of the bay, immediately adjacent to the city of Panama, protected from
the south by the three islands of Perico, Naos, and Culebra. It has
been called a roadstead. There is good anchorage for heavy-draft ships,
but for the most part the water is shallow. With the commission’s
requirement of a minimum depth of water of 35 feet, a channel about 4
miles long from the mouth of the Rio Grande to the 6-fathom line in
Panama Bay must be excavated. This channel would have a bottom width
of 200 feet with side slopes of 1 on 3 where the material is soft.
Considerable rock would have to be excavated in this channel. At 4.41
miles from the 6-fathom line is located a wharf at the point called La
Boca. A branch of the Panama Railroad Company runs to this wharf, and
at the present time deep-draft ships lie up alongside of it to take on
and discharge cargo. The wharf is a steel frame structure, founded upon
steel cylinders, carried down to bed-rock by the pneumatic process.
Its cost was about $1,284,000. The total cost of the excavated channel
leading from Panama harbor to the pier at La Boca is estimated by the
commission at $1,464,513. As the harbor at Panama is considered an open
roadstead, it requires no estimate for annual cost of maintenance.
[Illustration: The Bohio Dam Site.]
=371. The Route from Colon to Bohio.=—Starting from the harbor of
Colon, the prism of the canal is excavated through the low and for the
most part marshy ground to the little village called Bohio. The prism
would cut the Chagres River at a number of points, and would require a
diversion-channel for that river for a distance of about 5 miles on the
westerly side of the canal. Levees, or protective embankments, would
also be required on the same side of the canal between Bohio and Gatun,
the Chagres River leaving the canal line at the latter point on its way
to the sea.
=372. The Bohio Dam.=—The principal engineering feature of the entire
route is found at Bohio; it is the great dam across the Chagres River
at that point, forming Lake Bohio, the summit level of the canal. The
new Panama Canal Company located this dam at a point about 17 miles
from Colon, and designed to make it an earth structure suitably paved
on its faces, but without any other masonry feature. Some borings had
been made along the site, and test-pits were also dug by the French
engineers. It was the conviction of the Isthmian Canal Commission,
however, that the character of the proposed dam might be affected
by a further examination of the subsurface material at the site.
Consequently the boring parties of the Commission sunk a large number
of bore-holes at six different sections or possible sites along the
river in the vicinity of the French location. These borings revealed
great irregularity in the character and disposition of the material
below the bed and banks of the river. In some places the upper stratum
of material was almost clear clay, and in other places clear sand,
while all degrees of admixture of clay and sand were also found. At
the French site the bed-rock at the deepest point is 143 feet below
sea-level, with large masses of pervious and semi-pervious sand,
gravel, and mixtures of those materials with clay. Apparently there is
a geological valley in the rock along the general course of the Chagres
River in this vicinity filled with sand, gravel, and clay, irregularly
distributed and with all degrees of admixture, large masses in all
cases being of open texture and pervious to water. The site adopted by
the commission for the purposes of its plans and estimates is located
nearly half a mile down the course of the river from that selected by
the new Panama Canal Company. The geological valley is nearly 2000 feet
wide at this location, but the deepest rock disclosed by the borings
of the commission is but 128 feet below sea-level. The actual channel
of the river is not more than 150 feet wide and lies on the extreme
easterly side of the valley. The easterly or right bank of the river at
this place is clean rock and rises abruptly to an elevation of about 40
feet above the river surface at ordinary stages. The left or westerly
bank of the river is compacted clay and sand, and rises equally as
abruptly as the rocky bank of the other side, and to about the same
elevation. From the top of the abrupt sandy clay bank a plateau of
rather remarkable uniformity of elevation extends for about 1200 feet
in a southwesterly direction to the rocky hill in which the Bohio
locks would be located. The rock slope on the easterly or northerly
bank of the river runs down under the sandy river-bed, but at such an
inclination that within the limits of the channel the deepest rock is
less than 100 feet below sea-level.
[Illustration]
[Illustration]
[Illustration: Profile of Bohio Dam Site, selected for Plans and
Estimate, with section of Dam.]
After the completion of all its examinations and after a careful study
of the data disclosed by them, the commission deemed it advisable to
plan such a dam as would cut off absolutely all possible subsurface
flow or seepage through the sand and gravel below the river surface.
It is to be observed that such a subsurface flow might either disturb
the stability of an earth dam or endanger the water-supply of the
summit level of the canal or both. The plan of dam finally adopted
by the commission for the purposes of its estimates is shown by the
accompanying plans and sections. A heavy core-wall of concrete masonry
extends from bed-rock across the entire geological valley to the top
of the structure, or to an elevation of 100 feet above sea-level, thus
absolutely closing the entire valley against any possible flow. The
thickness of this wall at the bottom is 30 feet, but at an elevation
of 30 feet below sea-level its sides begin to batter at such a rate as
to make the thickness of the wall 8 feet at its top. On either side of
this wall are heavy masses of earth embankment of selected material
properly deposited in layers with surface slopes of 1 on 3. As shown
by the plans, the lower portions of the core-wall of this dam would
be sunk to bed-rock by the pneumatic process, the joints between the
caissons being closed and sealed by cylinders sunk in recesses or
wells, also as shown by the plans.
=373. Variation in Surface Elevation of Lake.=—The profile of this
route shows that the summit level would have an ordinary elevation of
85 feet above the sea, but it may be drawn down for uses of the canal
to a minimum elevation of 82 feet above the same datum. On the other
hand, under circumstances to be discussed later, it may rise during
the floods of the Chagres to an elevation of 90 or possibly 91 or 92
feet above the level of the sea. The top of the dam therefore would be
from 8 to 10 feet above the highest possible water surface in the lake,
which is sufficient to guard against wash or overtopping of the dam by
waves. The total width of the dam at its top would be 20 feet, and the
entire inner slope would be paved with heavy riprap suitably placed and
bedded.
=374. Extent of Lake Bohio and the Canal Line in It.=—This dam would
create an artificial lake having a superficial area during high water
of about 40 square miles. The water would be backed up to a point
called Alhajuela, about 25 miles up the river from Bohio. For a
distance of nearly 14 miles, i.e., from Bohio to Obispo, the route of
the canal would lie in this lake. Although the water would be from 80
to 90 feet deep at the dam for several miles below Obispo, it would
be necessary to make some excavation along the general course of
the Chagres in order to secure the minimum depth of 35 feet for the
navigable channel.
[Illustration: Location of the Proposed Alhajuela Dam on the Upper
Chagres.]
=375. The Floods of the Chagres.=—The feature of Lake Bohio of the
greatest importance to the safe and convenient operation of the canal
is that by which the floods of the river Chagres are controlled or
regulated. That river is but little less than 150 miles long, and its
drainage area as nearly as can be estimated, contains about 875 square
miles. Above Bohio its current moves some sand and a little silt in
times of flood, but usually it is a clear-water stream. In low water
its discharge may fall to 350 cubic feet per second.
As is well known, the floods of the Chagres have at times been regarded
as almost if not quite insurmountable obstacles to the construction
of a canal on this line. The greatest flood of which there is any
semblance of a reliable record is one which occurred in 1879. No direct
measurements were made, but it is stated with apparent authority that
the flood elevation at Bohio was 39.3 feet above low water. If the
total channel through which the flood flowed at that time had been as
large as at present, actual gaugings or measurements of subsequent
floods show that the maximum discharge in 1879 might have been at the
rate of 136,000 cubic feet per second. As a matter of fact the total
channel section in that year was less than it is at the present time.
Hence if it be assumed that a flood of 140,000 cubic feet per second
must be controlled, an error on the safe side will be committed. Other
great floods of which there are reliable records are as follows:
1885 Height at Bohio 33.8 feet above low water.
1888: ” ” ” 34.7 ” ” ” ”
1890: ” ” ” 32.1 ” ” ” ”
1893: ” ” ” 28.5 ” ” ” ”
The maximum measured rate of the 1890 flood was 74,998 cubic feet per
second, and that of 1893, 48,975 cubic feet per second. It is clear,
therefore, that a flood-flow of 75,000 cubic feet per second is very
rare, and that a flood of 140,000 cubic feet per second exceeds that of
which we have any record for practically forty years.
=376. The Gigante Spillway or Waste-weir.=—It is obvious that the dam,
as designed by the commission, is of such character that no water must
be permitted to flow over its crest, or even in immediate proximity to
the down-stream embankment. Indeed it is not intended by the commission
that there shall be any wasteway or discharge anywhere near the dam. At
a point about 3 miles southwest of the site of the dam at Bohio is a
low saddle or notch in the hills near the head-waters of a small stream
called the Gigante River. The elevation of this saddle or notch is such
that a solid masonry weir with a crest 2000 feet long may readily be
constructed with its foundations on bed-rock without deep excavation.
This structure is called the Gigante spillway, and all surplus
flood-waters from the Chagres would flow over it. The waters discharged
would flow down to and through some large marshes, one called Peña
Blanca and another Agua Clara, before rejoining the Chagres. Inasmuch
as the canal line runs just easterly of those marshes, it would be
necessary to protect it with the levees or embankments to which
allusion has already been made. These embankments are neither much
extended nor very costly for such a project. The protection of the
canal would be further aided by a short artificial channel between the
two marshes, Peña Blanca and Agua Clara, for which provision is made
in the estimates of the commission. After the surplus waters from the
Gigante spillway pass these marshes they again enter the Chagres River
or flow over the low, half-submerged country along its borders, and
thence through its mouth to the sea near the town of Chagres, about 6
miles northwest of Gatun.
=377. Storage in Lake Bohio for Driest Dry Season.=—The masonry crest
of the Gigante spillway would be placed at an elevation of 85 feet
above the sea, identically the same as that which may be called the
normal summit level of the canal. It is estimated that the total uses
of water in the canal added to the loss by evaporation, taken at six
inches in depth per month, from the surface of the lake will amount
to about 1070 cubic feet per second if the traffic through the canal
should amount to 10,000,000 tons per annum in ships of ordinary size.
This draft per second is the sum of 406 cubic feet per second for
lockage, 207 for evaporation, 250 for leakage at lock-gates, and 200
for power and other purposes, making a total of 1063, which has been
taken as 1070 cubic feet per second. The amount of storage in Lake
Bohio between the elevations of 85 and 82 feet above sea-level, as
designed, is sufficient to supply the needs of that traffic in excess
of the smallest recorded low-water flow of the Chagres River during the
dry season of a low rainfall year. The lowest monthly average flow of
the Chagres on record at Bohio is 600 cubic feet per second for March,
1891, and for the purposes of this computation that minimum flow has
been supposed to continue for three months. This includes a sensible
margin of safety. In not even the driest year, therefore, can it be
reasonably expected that the summit level of the canal would fall below
the elevation of 82 feet until the total traffic of the canal carried
in ships of the present ordinary size shall exceed 10,000,000 tons.
If the average size of ships continues to increase, as will probably
be the case, less water in proportion to tonnage will be required for
the purposes of lockage. This follows from the fact that with a given
tonnage the greater the capacity of the ships the less the number
required, and consequently the less will be the number of lockages made.
[Illustration: The Eastern Face of the Culebra Cut.]
=378. Lake Bohio as a Flood controller.=—On the other hand it can be
shown that with a depth of 5 feet of water on the crest of the Gigante
spillway the discharge of that weir 2000 feet long will be at the rate
of 78,260 cubic feet per second. If the flood-waters of the Chagres
should flow into Lake Bohio until the head of water on the crest of
the Gigante weir rises to 7½ feet, the rate of discharge over that
weir would be 140,000 cubic feet per second, which, as already shown,
exceeds at least by a little the highest flood-rate on record. The
operation of Lake Bohio as a flood controller or regulator is therefore
exceedingly simple. The flood-waters of the Chagres would pour into the
lake and immediately begin to flow over the Gigante weir, and continue
to do so at an increasing rate as the flood continues. The discharge
of the weir is augmented by the increasing flood, and decreases only
after the passage of the crest of the flood-wave. No flood even as
great as the greatest supposable flood on record can increase the
elevation of the lake more than 92 to 92½ feet above sea-level, and
it will only be at long intervals of time when floods will raise that
elevation more than about 90 feet above sea-level. The control is
automatic and unfailingly certain. It prevents absolutely any damage
from the highest supposable floods of the Chagres, and reserves in
Lake Bohio all that is required for the purposes of the canal and
for wastage by evaporation through the lowest rainfall season. The
floods of the Chagres, therefore, instead of constituting the obstacle
to construction and convenient maintenance of the canal heretofore
supposed, are deprived of all their prejudicial effects and transformed
into beneficial agents for the operation of the waterway.
=379. Effect of Highest Floods on Current in Channel in Lake
Bohio.=—The highest floods are of short duration, and it can be stated
as a general law that the higher the flood the shorter its duration.
The great floods which it is necessary to consider in connection
with the maintenance and operation of this canal would last but a
comparatively few hours only. The great flood-flow of 140,000 cubic
feet per second would increase the current in the narrowest part of
the canal below Obispo to possibly 5 feet per second for a few hours
only, but that is the only inconvenience which would result from
such a flood discharge. That velocity could be reduced by additional
excavation.
=380. Alhajuela Reservoir not Needed at Opening of Canal.=—Inasmuch
as this system of control, devised and adopted by the Isthmian Canal
Commission, is completely effective in regulating the Chagres floods;
the reservoir proposed to be constructed by the new Panama Canal
Company at Alhajuela on the Chagres about 11 miles above Obispo is not
required, and the cost of its construction would be avoided. It could,
however, as a project be held in reserve. If the traffic of the canal
should increase to such an extent that more water would be needed for
feeding the summit level, the dam could be built at Alhajuela so as to
impound enough additional water to accommodate, with that stored in
Lake Bohio, at least five times the 10,000,000 annual traffic already
considered. Its existence would at the same time act with substantial
effect in controlling the Chagres floods and relieve the Gigante
spillway of a corresponding amount of duty.
=381. Locks on Panama Route.=—The locks on the Panama route are
designed to have the same dimensions as those in Nicaragua, as was
stated in the lecture on that route. The usable length is 740 feet
and the clear width 84 feet. They would be built chiefly of concrete
masonry, while the gates would be of steel and of the mitre type.
=382. The Bohio Locks.=—The great dam at Bohio raises the water
surface in the canal from sea-level in the Atlantic maritime section
to an ordinary maximum of 90 feet above sea-level; in other words,
the maximum ordinary total lift would be 90 feet. This total lift is
divided into two parts of 45 feet each. There is therefore a flight
of two locks at Bohio; indeed there are two flights side by side, as
the twin arrangement is designed to be used at all lock sites on both
routes. The typical dimensions and arrangements of these locks, with
the requisite culverts and other features, are shown in the plans and
sections between pages 396 and 397, Part V. They are not essentially
different from other great modern ship-canal locks. The excavation for
the Bohio locks is made in a rocky hill against which the southwesterly
end of the proposed Bohio dam rests, and they are less than 1000 feet
from it.
=383. The Pedro Miguel and Miraflores Locks.=—After leaving Bohio
Lake at Obispo a flight of two locks is found at Pedro Miguel, about
7.9 miles from the former or 21½ miles from Bohio. These locks have a
total ordinary maximum lift of 60 feet, divided into two lifts of 30
feet each. The fifth and last lock on the route is at Miraflores. The
average elevation of water between Pedro Miguel and Miraflores is 30
feet above mean sea-level. Inasmuch as the range of tide between high
and low in Panama Bay is about 20 feet, the maximum lift at Miraflores
is 40 feet and the minimum about 20. The twin locks at Miraflores bring
the canal surface down to the Pacific Ocean level, the distance from
those locks to the 6-fathom curve in Panama Bay being 8.54 miles. There
are therefore five locks on the Panama route, all arranged on the twin
plan, and, as on the Nicaragua route, all are founded on rock.
=384. Guard-gates near Obispo.=—Near Obispo a pair of guard-gates are
arranged “so that if it should become necessary to draw off the water
from the summit cut the level of Lake Bohio would not be affected.”
=385. Character and Stability of the Culebra Cut.=—An unprecedented
concentration of heavy cutting is found between Obispo and Pedro
Miguel. This is practically one cut, although the northwesterly end
toward Obispo is called the Emperador, while the deepest part at the
other end, about 3 miles from Pedro Miguel, is the great Culebra cut
with a maximum depth on the centre line of the canal of 286 ft. On page
93 of the Isthmian Canal Commission’s report is the following reference
to the material in this cut: “There is a little very hard rock at the
eastern end of this section, and the western 2 miles are in ordinary
materials. The remainder consists of a hard indurated clay, with some
softer material at the top and some strata and dikes of hard rock. In
fixing the price it has been rated as soft rock, but it must be given
slopes equivalent to those in earth. This cut has been estimated on
the basis of a bottom width of 150 feet, with side slopes of 1 on 1.”
When the old Panama Canal Company began its excavation in this cut
considerable difficulty was experienced by the slipping of the material
outside of the limits of the cut into the excavation, and the marks of
that action can be seen plainly at the present time. This experience
has given an impression that much of the material in this cut is
unstable, but that impression is erroneous. The clay which slipped
in the early days of the work was not drained, and like wet clay in
numerous places in this country it slipped down into the excavation.
This material is now drained and is perfectly stable. There is no
reason to anticipate any future difficulty if reasonable conditions
of drainage are maintained. The high faces of the cut will probably
weather to some extent, although experience with such clay faces on the
isthmus indicates that the amount of such action will be small. As a
matter of fact the material in which the Culebra cut is made is stable
and will give no sensible difficulty in maintenance.
[Illustration: The Culebra Cut.]
=386. Small Diversion-channels.=—Throughout the most of the distance
between Colon and Bohio on the easterly side of the canal the French
plan contemplated an excavated channel to receive a portion of the
waters of the Chagres as well as the flow of two smaller rivers,
the Gatuncillo and the Mindi, so as to conduct them into the Bay
of Manzanillo, immediately to the east of Colon. That so-called
diversion-channel was nearly completed. Under the plan of the
commission it would receive none of the Chagres flow, but it would be
available for intercepting the drainage of the high ground easterly
of the canal line and the flow of the two small rivers named, so that
these waters would not find their way into the canal. There are a few
other small works of similar character in different portions of the
line, all of which were recognized and provided for by the commission.
=387. Length and Curvature.=—The total length of the Panama route from
the 6-fathom curve at Colon to the same curve in Panama Bay is 49.09
miles. The general direction of the route in passing from Colon to
Panama is from northwest to southeast, the latter point being about
22 miles east of the Atlantic terminus. The depression through which
the line is laid is one of easy topography except at the continental
divide in the Culebra cut. As a consequence there is little heavy
work of excavation, as such matters go except in that cut. A further
consequence of such topography is a comparatively easy alignment, that
is, one in which the amount of curvature is not high. The smallest
radius of curvature is 3281 feet at the entrance to the inner harbor at
the Colon end of the route, and where the width is 800 feet. The radii
of the remaining curves range from 6234 feet to 19,629 feet.
The following table gives all the elements of curvature on the route
and indicates that it is not excessive:
+-----------------+-------+-------+----------------+
|Number of Curves.|Length.|Radius.|Total Curvature.|
+-----------------+-------+-------+----------------+
| | Miles | Feet. | ° ′ |
| 1 | 0.88 |19,629 | 14 17 |
| 1 | .48 |13,123 | 11 04 |
| 4 | 4.22 |11,483 | 111 32 |
| 15 | 11.61 | 9,842 | 355 50 |
| 4 | 2.44 | 8,202 | 90 20 |
| 2 | 1.67 | 6,562 | 77 00 |
| 1 | .73 | 6,234 | 35 45 |
| 1 | .82 | 3,281 | 75 51 |
| +-------+-------+----------------+
| | 22.85 | | 771 39 |
+-----------------+-------+-------+----------------+
=388. Principal Items of Work to be Performed.=—The principal items
of the total amount of work to be performed in completing the Panama
Canal, under the plan of the commission, can be classified as shown in
the following table:
Dredging 27,659,540 cu. yds.
Dry earth 14,386,954 ”
Soft rock 39,893,235 ”
Hard rock 8,806,340 ”
Rock under water 4,891,667 ”
Embankment and back-filling 1,802,753 ”
----------
Total 97,440,489 ”
Concrete 3,762,175 cu. yds.
Granite 13,820 ”
Iron and steel 65,248,900 lbs.
Excavation in coffer-dam 7,260 cu. yds.
Pneumatic work 108,410 ”
=389. Lengths of Sections and Elements of Total Cost.=—The lengths of
the various sections of this route and the costs of completing the work
upon them are fully set forth in the following table, taken from the
commission’s report, as were the two preceding:
TOTAL ESTIMATED COST.
--------------------------------------------+---------+------------
| Miles. | Cost.
--------------------------------------------+---------+------------
Colon entrance and harbor | 2.39 | $8,057,707
Harbor to Bohio locks, including levees | 14.42 | 11,099,839
Bohio locks, including excavation | .35 | 11,567,275
Lake Bohio | 13.61 | 2,952,154
Obispo gates | | 295,434
Culebra section | 7.91 | 44,414,460
Pedro Miguel locks, including excavation | |
and dam | .35 | 9,081,321
Pedro Miguel level | 1.33 | 1,192,286
Miraflores locks, including excavation | |
and spillway | .20 | 5,781,401
Pacific level | 8.53 | 12,427,971
Bohio dam | | 6,369,640
Gigante spillway | | 1,209,419
Peña Blanca outlet | | 2,448,076
Chagres diversion | | 1,929,982
Gatun diversion | | 100,000
Panama Railroad diversion | | 1,267,500
+---------+------------
Total | 49.09 | 120,194,465
Engineering, police, sanitation, and general| |
contingencies, 20 per cent. | | 24,038,893
+---------+------------
Aggregate | |$144,233,358
--------------------------------------------+---------+------------
The item in this table called Panama Railroad diversion affords
provision for the reconstruction of the railroad necessitated by the
formation of Lake Bohio. That lake would submerge the present location
of the railroad for 14 or 15 miles.
[Illustration: The Culebra Cut with Steamer Deutschland in it.]
=390. The Twenty Per Cent Allowances for Exigencies.=—It will
be observed that in the estimates of cost of the canal on both
the Nicaragua and the Panama routes, 20 per cent is allowed for
“engineering, police, sanitation, and general contingencies.” For the
purposes of comparison the same percentage to cover these items was
used on both routes. As a matter of fact the large amount of work
which has already been performed on the Panama route removes many
uncertainties as to the character of material and other features of
difficulty which would be disclosed only after the beginning of the
work in Nicaragua. It has therefore been contended with considerable
basis of reason that a less percentage to cover these uncertainties
should be employed in connection with the Panama estimates than in
connection with those for the Nicaragua route. Indeed it might be
maintained that the exigencies which increase cost should be made
proportional to the length of route and the untried features. On the
other hand, both Panama and Colon are comparatively large centres
of population, and, furthermore, there is a considerable population
stretched along the line of the Panama Railroad between those points.
The climate and the unsanitary condition of practically every centre
of population in Central America and on the isthmus contribute to the
continual presence of tropical fevers, and other diseases contingent
upon the existing conditions of life. It is probable, among other
things, that yellow fever is always present on the isthmus. Inasmuch as
the Nicaragua route is practically without population, the amount of
disease existing along it is exceedingly small, there being practically
no people to be sick. The initial expenditure for the sanitation of
the cities at the extremities of the Panama route, as well as for
the country between, would be far greater for that route than on the
Nicaragua. This fact compensates, to a substantial extent at least,
for the physical uncertainties on the Nicaragua line. Indeed a careful
examination of all the conditions existing on both routes indicates the
reasonableness of applying the same 20 per cent to both total estimates
of cost.
=391. Value of Plant, Property, and Rights on the Isthmus.=—The
preceding estimated cost of $144,233,358 for completing the Panama
Canal must be increased by the amount necessary to be paid for all the
property and rights of the new Panama Canal Company on the isthmus. A
large amount of excavation has been performed, amounting to 77,000,000
cubic yards of all classes of materials, and nearly all the right of
way has been purchased. The new Panama Canal Company furnished the
commission with a detailed inventory of its entire properties, which
the latter classified as follows:
1. Lands not built on.
2. Buildings, 2431 in number, divided among 47
subclassifications.
3. Furniture and stable outfit, with 17 subclassifications.
4. Floating plant and spare parts, with 24
subclassifications.
5. Rolling plant and spare parts, with 17 subclassifications.
6. Plant, stationary and semi-stationary, and spare parts,
with 25 subclassifications.
7. Small material and spare parts, with 4 subclassifications.
8. Surgical and medical outfit.
9. Medical stores.
10. Office supplies, stationery.
11. Miscellaneous supplies, with 740 subclassifications.
The commission did not estimate any value for the vast amount of plant
along the line of the canal, as its condition in relation to actual use
is uncertain, and the most of it would not be available for efficient
and economical execution of the work by modern American methods.
Again, a considerable amount of excavated material along some portions
of the line has been deposited in spoil-banks immediately adjacent to
the excavation from which it was taken, and would have to be rehandled
in forming the increased size of prism contemplated in the commission’s
plan.
In view of all the conditions affecting it, the commission made the
following estimate of the value of the property of the new Panama Canal
Company, as it is now found on the Panama route:
Canal excavation $21,020,386
Chagres diversion 178,186
Gatun diversion 1,396,456
Railroad diversion (4 miles) 300,000
-----------
22,895,028
Contingencies, 20 per cent 4,579,005
-----------
Aggregate 27,474,033
Panama Railroad stock at par 6,850,000
Maps, drawings, and records 2,000,000
-----------
$36,324,033
The commission added 10 per cent to this total “to cover omissions,
making the total valuation of the” property and rights as now existing,
$40,000,000.
In computing the value of the channel excavation in the above
tabulation it was estimated that “the total quantity of excavation
which will be of value in the new plan is 39,586,332 cubic yards.”
=392. Offer of New Panama Canal Company to Sell for $40,000,000.=—In
January, 1902, the new Panama Canal Company offered to sell and
transfer to the United States Government all its property and rights on
the isthmus of every description for the estimate of the commission,
viz., $40,000,000. In order to make a proper comparison between the
total costs of constructing the canal on the two routes it is necessary
to add this $40,000,000 to the preceding aggregate of $144,233,358,
making the total cost of the Panama Canal $184,233,358. It will be
remembered that the corresponding total cost of the Nicaragua Canal
would be $189,864,062.
[Illustration: The Railroad Pier at La Boca, the Panama end of the
Canal.]
=393. Annual Costs of Operation and Maintenance.=—It is obvious that
the cost of operating and maintaining a ship-canal across the American
isthmus would be an annual charge of large amount. A large organized
force would be requisite, and no small amount of material and work
of various kinds and grades would be needed to maintain the works in
suitable condition. The commission made very careful and thorough
studies to ascertain as nearly as practicable what these comparative
costs would be. In doing this it gave careful consideration to the
annual expenditures made in maintaining the various ship-canals of
the world, including the Suez, Manchester, Kiel, and St. Mary’s Falls
canals. The conclusion reached was that the estimated annual costs of
maintenance and operation could reasonably be taken as follows:
For the Nicaragua Canal $3,300,000
For the Panama Canal 2,000,000
----------
Difference in favor of Panama $1,300,000
=394. Volcanoes and Earthquakes.=—Much has been written regarding the
comparative liability to damage of canal works along these two routes
by volcanic or seismic agencies. As is well known, the entire Central
American isthmus is a volcanic region, and in the past a considerable
number of destructive volcanic eruptions have taken place at a number
of points. There is a line of live volcanoes extending southeasterly
through Nicaragua and Costa Rica. Many earthquake shocks have occurred
throughout Nicaragua, Costa Rica, and the State of Panama, some
of which have done more or less damage in large portions of those
districts. At the same time many buildings which have been injured have
not been substantially built. In fact that has generally been the case.
Both routes lie in districts that are doubtless subject to earthquake
shocks, but there is little probability that the substantial structures
of a canal along either line would be essentially injured by them. The
conclusions of the commission as to this feature of the matter are
concisely stated in three paragraphs at the top of page 170 of its
report:
“It is possible and even probable that the more accurately fitting
portions of the canal, such as the lock-gates, may at times be
distorted by earthquakes, and some inconvenience may result therefrom.
That contingency may be classed with the accidental collision of ships
with the gates, and is to be provided for in the same way, by duplicate
gates.
“It is possible also that a fissure might open which would drain the
canal, and, if it remained open, might destroy it. This possibility
should not be erected by the fancy into a threatening danger. If
a timorous imagination is to be the guide, no great work can be
undertaken anywhere. This risk may be classed with that of a great
conflagration in a city like that of Chicago in 1871, or Boston in 1872.
“It is the opinion of the commission that such danger as exists from
earthquakes is essentially the same for both the Nicaragua and Panama
routes, and that in neither case is it sufficient to prevent the
construction of the canal.”
The Nicaragua route crosses the line of live volcanoes running from
northwest to southeast through Central America, and the crater of
Ometepe in Lake Nicaragua is about 11 miles only from the line. The
eruptions of Pelée and Soufriere show that such proximity of possible
volcanic action may be a source of great danger, although even the
destruction by them does not certainly indicate damage either to
navigation or to canal structures at the distance of 11 miles. Whatever
volcanic danger may exist lies on the Nicaragua route, for there is no
volcano nearer than 175 miles to the Panama route.
=395. Hygienic Conditions on the Two Routes.=—The relative
healthfulness of the two routes has already been touched upon. There
is undoubtedly at the present time a vast amount of unhealthfulness
on the Panama route, and practically none on the Nicaragua route, but
this is accounted for when it is remembered, as has also been stated,
that there is practically no population on the Nicaragua route and
a comparatively large population along the Panama line. There is a
wide-spread, popular impression that the Central American countries
are necessarily intensely unhealthful. This is an error, in spite of
the facts that the construction of the Panama Railroad was attended
with an appalling amount of sickness and loss of life, and that records
of many epidemics at other times and in other places exist in nearly
all of these countries. There are the best of good reasons to believe
that with the enforcement of sanitary regulations, which are now well
understood and completely available, the Central American countries
would be as healthful as our Southern States. A proper recognition of
hygienic conditions of life suitable to a tropical climate would work
wonders in Central America in reducing the death-rate. At the present
time the domestic administration of most of the cities and towns of
Nicaragua and Panama, as well as the generality of Central American
cities, is characterized by the absence of practically everything which
makes for public health, and by the presence of nearly every agency
working for the diseases which flourish in tropical climates. When
the United States Government reaches the point of actual construction
of an isthmian canal the sanitary features of that work should be
administered and enforced in every detail with the rigor of the
most exacting military discipline. Under such conditions, epidemics
could either be avoided or reduced to manageable dimensions, but
not otherwise. The commission concluded that “Existing conditions
indicate hygienic advantages for the Nicaragua route, although it is
probable that no less effective sanitary measures must be taken during
construction in the one case than in the other.”
=396. Time of Passage through the Canal.=—The time required for
passing through a transisthmian canal is affected by the length, by
the number of locks, by the number of curves, and by the sharpness
of curvature. The speed of a ship, and consequently the time of
passage, is also affected by the depth of water under its keel. It
is well known that the same power applied to a ship in deep water
of unlimited width will produce a much higher rate of movement than
the same power applied to the same ship in a restricted waterway,
especially when the draft of the ship is but little less than the
depth of water. These considerations have important bearings both upon
the dimensions of a ship-canal and upon the time required to pass
through it. They were most carefully considered by the commission, as
were also such other matters as the delay incurred in passing through
the locks on each line, the latter including the delay of slowing or
approaching the lock and of increasing speed after passing it, the
time of opening and closing the gates, and the time of emptying and
filling the locks. It is also evident that ships of various sizes will
require different times for their passage. After giving due weight
to all these considerations it was found that what may be called an
average ship would require twelve hours for passing through the Panama
Canal and thirty-three hours for passing through the Nicaragua Canal.
Approximately speaking, therefore, it may be stated that an average
passage through the former waterway will require but one third the time
needed for the latter.
[Illustration: A Street in Panama.]
=397. Time for Completion on the Two Routes.=—The time in which an
isthmian canal may be completed and ready for traffic is an element of
the problem of much importance. There are two features of the work to
be done at Panama, each of which is of sufficient magnitude to affect
to a controlling extent the time required for the construction of the
canal, viz., the Bohio dam and the Culebra cut. Both of these portions
of the work may, however, be prosecuted concurrently and with entire
independence of each other. There are no such features on the Nicaragua
route, although the cut through the divide west of the lake is probably
the largest single work on that route. In considering this feature of
the matter it is well to observe that the total amount of excavation
and embankment of all grades on the Nicaragua route is practically
228,000,000 cubic yards, while that remaining to be done on the Panama
route is but little more than 97,000,000 cubic yards, or 43 per cent
of the former. The accompanying figures show the relative quantities of
total excavation, concrete, iron, and steel required in construction
along the two routes, as well also as the total amounts and radii of
curvature.
[Illustration: Diagrams comparing some of the main Elements of the two
Routes.]
The commission has estimated ten years for the completion of the
canal on the Panama route and eight years for the Nicaragua route,
including in both cases the time required for preparation and that
consumed by unforeseen delays. The writer believes that the actual
circumstances attending work on the two routes would justify an
exchange of these time relations. There is great concentration of
work in the Culebra-Emperador cut on the Panama route, covering about
45 per cent of the total excavation of all grades (43,000,000 cubic
yards), which is distributed over a distance of about 7 miles, with
the location of greatest intensity at Culebra. This demands efficient
organization and special plant so administered as to reduce the
working force to an absolute minimum by the employment of machinery
to the greatest possible extent. A judicious, effective organization
and plant would transform the execution of this work into what may be
called a manufactory of excavation with all the intensity of direction
and efficiency of well designed and administered machinery which
characterizes the concentration of labor and mechanical appliances in
great manufacturing establishments. Such a successful installation
would involve scarcely more advance in contract operations than was
exhibited, in its day, in the execution of the work on the Chicago
Drainage-canal. By such means only can the peculiar difficulties
attendant upon the execution of great works in the tropics be reduced
to controllable dimensions. The same general observations may be
applied to the construction of the Bohio dam, even should a no more
favorable site be found.
The greatest concentration of excavation on the Nicaragua route is
between the lake and the Pacific, but it constitutes only 10 per cent
of the total excavation of all grades, and it can be completed in far
less time than the great cut on the Panama route. If this were the
only great feature of work besides the dam, the time for completion
of work on this route would be materially less than that required for
the Panama crossing. As a matter of fact, there are a succession of
features of equivalent magnitude, or very nearly so, from Greytown
nearly to Brito, extending over a distance of at least 175 miles,
requiring the construction of a substantial service railroad over a
considerable portion of the distance prior to the beginning of work.
This attenuation of work requires the larger features to be executed in
succession to a considerable extent, or much duplication of plant and
the employment of a great force of laborers, practically all of whom
must be foreigners, housed, organized, and maintained in a practically
uninhabited tropical country where many serious difficulties reach a
maximum. It is not within the experience of civil engineers to execute
by any practicable means that kind of a programme on schedule time.
The weight of this observation is much increased when it is remembered
that the total volume of work may be taken nearly twice as great in
Nicaragua as at Panama, and that large portions between Lake Nicaragua
and the Caribbean Sea must be executed in a region of continual and
enormous rainfall. It would seem more reasonable to the writer to
estimate eight years for the completion of the Panama Canal and ten
years for the completion of the Nicaragua Canal.
=398. Industrial and Commercial Value of the Canal.=—The prospective
industrial and commercial value of the canal also occupied the
attention of the commission in a broad and careful study of the
elements which enter that part of the problem. It is difficult if not
impossible to predict just what the effect of a transisthmian canal
would be either upon the ocean commerce of the United States or of
other parts of the world, but it seems reasonable to suppose from the
result of the commission’s examinations that had the canal been in
existence in 1899 at least 5,000,000 tons of the actual traffic of
that year would have been accommodated by it. The opening of such a
waterway, like the opening of all other traffic routes, induces the
creation of new traffic to an extent that cannot be estimated, but it
would appear to be reasonable to suppose that within ten years from the
date of its opening the vessel tonnage using it would not be less than
10,000,000 tons.
[Illustration: View of Panama.]
The Nicaragua route would favor in distance the traffic between our
Atlantic (including Gulf) and Pacific ports. The distances between
our Atlantic ports and San Francisco would be about 378 nautical
miles less than by Panama. Between New Orleans and San Francisco
this difference in favor of the route by Greytown and Brito would be
580 nautical miles. It must be remembered, however, that the greater
time by at least twenty-four hours required for passage through the
Nicaragua Canal practically obliterates this advantage, and in some
cases would throw the advantage in favor of the Panama waterway. This
last observation would hold with particular force if for any reason
a vessel should not continue her passage, or should continue it at a
reduced speed during hours of darkness, which could not be escaped on
the Nicaragua Canal, but might be avoided at Panama. For all traffic
between the Atlantic (including Gulf) ports and the west coast of
South America the Panama crossing would be the most advantageous. As a
matter of fact, while there may be some small advantage in miles by one
route or the other for the traffic between some particular points, on
the whole neither route would have any very great advantage over the
other in point of distance or time; either would serve efficiently the
purposes of all ocean traffic in which the ports of the United States
are directly interested.
The effect of this ship waterway upon the well-being of the United
States is not altogether of a commercial character. As indicated by
the commission, this additional bond between the two portions of the
country will have a beneficial effect upon the unity of the political
interests as well as upon the commercial welfare of the country. Indeed
it is the judgment of many well-informed people that the commercial
advantages resulting from a closer touch between the Atlantic and
Pacific coasts of the country are of less consequence than the unifying
of political interests.
In a final comparison between the two routes it is to be remembered
that the concession under which the new Panama Company has been and
is now prosecuting its work is practically valueless for the purposes
of this country. It will therefore be necessary to secure from the
republic of Colombia, for the Panama route, as well as from the
republics of Nicaragua and Costa Rica, for the Nicaragua route, such
new concessions as may be adequate for all the purposes of the United
States in the construction of this transisthmian canal. The cost of
those concessions in either case must be added to the estimated total
cost of the work, as set forth, in order to reach the total cost of the
canal along either route.
=399. Comparison of Routes.=—Concisely stating the situation, its main
features may be expressed somewhat as follows:
Both routes are entirely “practicable and feasible.”
Neither route has any material commercial advantage over the other as
to time, although the distance between our Atlantic (including Gulf)
and Pacific ports is less by the Nicaragua route.
The Panama route has about one fourth the length of that in Nicaragua;
it has less locks, less elevation of summit level, and far less
curvature, all contributing to correspondingly decreased risks peculiar
to the passage through a canal. The estimated annual cost of operation
and maintenance of the Panama route is but six tenths that for the
Nicaragua route.
The harbor features may be made adequate for all the needs of a canal
by either route, with such little preponderance of advantage as may
exist in favor of the Panama crossing.
The commission estimated ten years for the completion of the Panama
Canal and eight years for the Nicaragua waterway, but the writer
believes that these relations should be exchanged, or at least that the
time of completion for the Panama route should not be estimated greater
than for the Nicaragua.
The water-supply is practically unlimited on both routes, but the
controlling or regulating works, being automatic, are much simpler and
more easily operated and maintained on the Panama route.
The Nicaragua route is practically uninhabited, and consequently
practically no sickness exists there. On the Panama route, on the
contrary, there is a considerable population extending along the entire
line, among which yellow fever and other tropical diseases are probably
always found. Initial sanitary works of much larger magnitude would be
required on the Panama route than on the Nicaragua, although probably
as rigorous sanitary measures would be required during the construction
of the canal on one route as on the other.
The railroad on the Panama route and other facilities offered by a
considerable existing population render the beginning of work and the
housing and organization of the requisite labor force less difficult
and more prompt than on the Nicaragua route.
The greater amount of work on the Nicaragua route, and its distribution
over a far greater length of line, involve the employment of a
correspondingly greater force of laborers, with greater attendant
difficulties, for an equally prompt completion of the work.
The relative seismic conditions of the two routes cannot be
quantitatively stated with accuracy, but in neither case are they of
sufficient gravity to cause anxiety as to the effects upon completed
canal structures.
Concessions and treaties require to be secured and negotiated for the
construction of the canal on either route, and under the conditions
created by the $40,000,000 offer of the new Panama Canal Company
this feature of both routes appears to possess about the same
characteristics, although the Nicaragua route is, perhaps, freer from
the complicating shadows of prior rights and concessions.