THE PANAMA CANAL
BY COLONEL GEORGE W. GOETHALS
CHIEF ENGINEER OF THE PANAMA CANAL
It is not possible in the time at our disposal to enter upon a description of the explorations and investigations which were made of various routes proposed for a canal joining the two oceans, nor can an account be taken of the considerations which resulted in the United States finally adopting the Panama route. Suffice it to say that under the Spooner Act, approved June 28, 1902, the President of the United States secured the necessary concession from the Republic of Panama, purchased the rights and property of the New French Canal Company, and undertook the construction of the canal on May 4, 1904.
The Isthmus of Panama runs nearly east and west, and the canal traverses it from Colon on the north to Panama on the south, in a general direction from northwest to southeast, the Pacific terminus being 22 miles east of the Atlantic entrance. (See map)
Torrential Floods of the Chagres River
The greatest difficulty of the Panama route is the control or disposition of the Chagres River and its tributaries. The Chagres River rises in the San Blas Mountains and drains a basin of 1,320 square miles, about half of which is above the mouth of the Obispo River. Its course is generally parallel to the Caribbean coast line so far as the mouth of the Obispo, where it turns almost at right angles to the westward pursuing this general course to Tabernilla, whence it traverses a tortuous channel in a general northwesterly direction and enters the Caribbean Sea to the west of Limon Bay.
The general elevation of the valley is but little above sea-level to Bohio, where the low-water surface of the Chagres is one foot above mean tide. At the mouth of the Obispo, 13 miles from Bohio, the low water surface is 48 feet above, and at Alhajuela, 11 miles farther, it is 95 feet above the same datum. Above Bohio the Chagres Valley is undulating, the hills becoming higher and steeper as the river is ascended, causing very rapid run-off of the rains, amounting to 100 inches and over in eight or nine months, the average duration of the wet season.
The maximum observed rainfall is 5.86 inches in one hour; the greatest recorded change in the river at Gamboa is a rise of 25.6 feet in 24 hours. Its discharge at the beginning of the rise was 8,200 cubic feet per second, increasing to 90,000 cubic feet per second at the peak of the flood. The excessive rainfall and precipitous character of the hills enclosing the valley make it a torrential stream. The bars formed during floods differ materially, and are of sand, gravel, pebbles, and rounded stones three inches to six inches in diameter. The sand and clay deposits are useful in giving suitable material for the impervious portion of the dams, while the gravel beds furnish ballast for the railroad and for other purposes.
The Chagres River has 26 tributaries between Bas Obispo and Gatun, the largest of which are the Gatun and Trinidad rivers, the former entering from the east with a drainage basin of about 160 square miles, and the latter from the west, draining an area of about 390 square miles. Each rises in the same character of country as the Chagres, and though with smaller drainage areas, they are of the same torrential character and must be reckoned with in the general question of the control of the Chagres and its tributaries.
Various methods for the disposition or control of the Chagres have received consideration. The first French company, in its attempt to cut a sea-level canal, found it necessary to provide diversion channels to care for the water of the rivers. The New Panama Canal Company adopted the plan of a dam across the river valley at Bohio, creating a lake above this point and discharging the flood waters to the level below by means of a spillway in the adjacent hills. The canal which the President was authorized to construct by the provisions of the Sponger Act was the lock type recommended by the First Isthmian Canal Commission in its report submitted November 16, 1901. This plan also provided a lake for controlling the Chagres by a dam at Bohio, following along the plans of the New Panama Canal Company, thereby utilizing to the fullest extent the work already accomplished.
Early in the progress of the work the construction of a sea-level canal was agitated; this is undoubtedly the ideal canal. It took such a hold on the public mind that, in consideration of the international importance of the work, the president convened a Board of Consulting Engineers to consider and report upon the type of canal which should be adopted. This Board consisted of 13 membersfive representatives of European countries and eight Americansand assembled in Washington in June, 1905. The minority of this Boardfive in numberreported in favor of the lock type for the reasons that such a canal would provide greater safety for ships and less danger of interruption to traffic by reason of its wider, straighter, and deeper channels, as well as quicker passage for large ships; the other considerations were that such a canal could be built in less time and for less money.
In forwarding the report of this Board to Congress, on February 19, 1906, the President stated: "The law now on our statue books seems to contemplate a lock canal. In my judgment a lock canal as herein recommended is advisable." On June 29, 1906, the Congress authorized the construction of the lock type of canal, in accordance with the genera plans of the minority of the Board, and the work has since been carried on along these lines.
This conclusion was not generally accepted as satisfactory; the plan was again vigorously attacked after the settlement and the slip in part of one of the toes of the Gatun Dam in the latter party of 1908, and the "Battle of the Levels" continued well into 1909, notwithstanding the fact that the then President-elect, with a party of eminent engineers, after a personal inspection of the work, advocated no change.
Wisdom of Choice of Lock
Since then, as the work has advanced,the wisdom of the choice is clearly shown and there is no doubt as to the ultimate success of the project. Developments within the last year in the form of slides have brought more prominently to the front the excellence of the judgement which accepted the minority plan in lieu of the sea-level plan as advocated by the majority, and show more clearly the greater difficulties that would be encountered in an attempt to construct a sea-level canal.
An English scientist, who has kept in close touch with the work since the Americans took charge, and who at first was skeptical as to the Gatun Dam, said, after a recent visit, that he was converted to the present plan because it is not a dam at all that is building, but a veritable hill. He also thought that the expressed opinion of the board of Consulting Engineers with reference to the Gatun Dam, namely, "that no such vast and boutful experiment should be indulged in," was now applicable to Culebra Cut. There are probably some who still believe a wrong choice was made, but a visit to the Isthmus is a sure cure for such cases, provided always that they are open to conviction.
In the present plan the control of the Chagres is also effected by a lake, but greater in extent, because the dam is located at Gatun instead of Bohio. This solution was first proposed by Godin de LÚpinay, a French engineer, who, in an exhaustive aper on the subject, prepared for the Congress of Engineers in Paris in 1879, advocated the construction of a lock canal with a dam at Gatun in lieu of a sea-level canal. The reasons which he advanced at that time were to the effect that such a canal could be built for less money, in less time, and with less sacrifice of life.
The Principal Features of the Canal
The canal which is now building consists of a sea-level entrance channel from the sea through Limon Bay to Gatun, about seven miles long, 500 feet bottom width, and 41 feet deep at mean tide. At Gatun the 85-foot lake level is obtained by a dam across the valley. The lake is confined on the Pacific side by a dam between the hills at Pedro Miguel, 32 miles away. The lake thus formed will have an area of 164 square miles and a channel depth of not less than 45 feet at normal stage.
At Gatun ships will pass from the sea to the lake level, and vice versa, by three locks in flight. On the Pacific side there will be one life of 30 feet at Pedro Miguel to a small lake held at 55 feet above sea-level by dams at Miraflores, whicher two lifts overcome the difference of level to the sea. The channel between the locks on the Pacific side will be 500 feet wide at the bottom and 45 feet deep, and below the Miraflores locks the sea-section, about eight miles in length, will be 500 feet wide at the bottom and 45 feet deep at mean tide. Through the lake the bottom widths are not less than 1,000 feet for about 16 miles, 800 feet for about four miles, 500 feet feet for about three miles, and through the continental divide, from Bas Obispo to Pedro Miguel, a distance of about nine miles, the bottom width is 300 feet.
The total length of the canal from deep water in the Caribbean, 41-foot depth at mean tide, to deep water in the Pacific, 45-foot depth at mean tide, is practically 50 miles, 15 miles of which are at sea-level. The variation in tide on the Atlantic side is 2.5 feet as a maximum, and on the Pacific it is 21.1 feet as a maximum.
Provisions are made to amply protect the entrances of the canal. During the winter months occasional storms occur on the Atlantic side of such violence that vessels cannot lie with safety in Colon Harbor, and during the progress of such storms entrance and egress from the canal would be unsafe. To overcome this condition, a breakwater will extend out about two miles from Toro Point in a northeasterly direction, which will not only protect the entrance, but will provide a safe harbor. Whether protection on the east side will be ultimately necessary is still an open question.
The Pacific entrance requires no protection from storms, but the set of the silt-bearing current from the east is at right angles to the channel and the silting made constant dredging necessary. To prevent this shoaling a dike is being constructed from the mainland at Balboa to Naos Island, a distance of about four miles; the benefits derived from it are already very marked.
The projected lakes will submerge the tracks of the Panama Railroad for the greater part of its length, and as this road is necessary for construction purposes, and ultimately for the operation and maintenance of the canal, it is being reconstructed throughout, with the exception of a few miles at either end. It was originally intended to pass the new railroad through Culebra Cut on a berm, 10 feet above the water surface, to be left for this purpose during the excavation of the channel through the cut, but the slides and the absolute necessity for keeping open railroad communication between the two ends of the line necessitated a change in the location, and a new line to the east of the cut has been selected.
In order to hold its concession the French company continued work on the canal up to the time that the United States assumed control, and after the transfer of rights and property was formally made the excavation was carried on by the United States with the various tools and appliances then in use.
Making The Isthmus Healthy
The first two and a half years of American control were given to preparation. All energies were devoted during that time to rid the Isthmus of disease by sanitation, to recruiting and organizing a working force, and providing for it suitable houses, hotels, messes, kitchens, and an adequate food supply; to assembling the plant to do the work; to increasing the capacity of the existing railway system, and to establishing a system of civil government for the Canal Zone, which is a strip of land 10 miles wide (five miles on either side of the center of the canal), extending across the Isthmus.
The work of sanitation included clearing lands, draining and filling pools and swamps for the extermination of the mosquito, the establishment of hospitals for the care of the sick and injured, and the quarantine. In addition, to secure and maintain better health conditions, municipal improvements were undertaken in the cities of Panama and Colon and the various settlements along the line of the canal, such as the construction of reservoirs, with mains and adjuncts, for furnishing wholesome and sufficient water, sewerage, pavements, and a system of roads.
Buildings to the number of 2,009 were constructed, including office buildings, hospitals, hotels, messes, kitchens, shops, storehouses, and living quarters. In addition to this, 1,536 buildings out of a total of 2,200 buildings turned over by the French were remodeled and repaired for use.
Recruiting agencies were established in the United States, Europe, and the West Indies.
An Immense Department Store
The Commissary Department of the Panama Railroad Company was enlarged until it is now a great department store supplying to the employees whatever may be necessary for their comfort and convenience. Manufacturing, cold storage, and laundry pants were established and turn out each day about 90 tons of ice, 14,000 loaves of bread, 2,400 rolls, 250 gallons of ice-cream, 1,000 pounds of roasted coffee, and 7,500 pieces of laundry. Four to five refrigerator cars, loaded with meats, vegetables, and such fruits as can be obtained, are sent out on the night freight to distant points, and every morning a supply train of about 16 cars, of which number six to eight are refrigerator cars, leaves Cristobal at 4:30 to distribute food-stuffs and laundry to the local commissaries along the line, where the employees make their purchases and where the hotels, messes, and kitchens secure their supplies for the day.
The construction plant, consisting of steam shovels, locomotives, cars, unloaders, spreaders, track-shifters, pile-drivers, cranes, dredges, steamboats, tugs, and barges, was purchased for the most part "knocked down," and shops for their erection and repair were constructed and enlarged. Some of the machinery was built from parts manufactured in the shops. The distance from the home market, with attendant vexatious delays in securing parts and material and the necessity for keeping the construction plant in the most efficient condition for economical operation, made it imperative that the shops be equipped to meet every possible contingency.
The capacity of the Panama Railroad, over a large part of which the spoil from Culebra Cut must be handled, was increased by double tracing it throughout, except from Cristobal to Gatun and from Culebra to Paraiso. Yards were enlarged and connections made to areas available for dumping grounds.
Laws were framed, and civil government was established with its necessary adjuncts of courts, police force, fire companies, customs and revenue service, post-offices, public works, and treasury.
A purchasing department was organized in the Untied States for the obtainment of supplies of all kinds and descriptions. Upon arrival on the Isthmus, the supplies are shipped to the various subdivisions of the canal-work for which they were purchased, or they are placed in storehouses along the line for issue when required.
It was only after these various yet necessary adjuncts had been provided and the forces for their operation were organized that the principal work in handthe building of the canalcould be pushed forward with any hope of success, and too much praise cannot be given to those who conceived and established them in a working condition.
The Department of Construction and Engineering is divided into three construction divisions. The Atlantic Division embraces the engineering construction from deep water in the Caribbean Sea to include the Gatun locks and dam; the Central Division extends from Gatun to Pedro Miguel, and the pacific Division from Pedro Miguel to deep water in the Pacific Ocean.
Keeping The Floods Out Of Culebra Cut
As already noted, the Americans continued the work in progress by the French in the cut through the continental divide, commonly known as the Culebra Cut, utilizing the French machinery until it could be replaced by more modern appliances. This is the most formidable part of the enterprise on account of the magnitude of the cutting, and also because of the difficulties attending it, due to the excessive rainfall and to the varying character of the materials encountered.
The efficient and economical working of the plant requires that provisions be made for the disposition of the large quantities of water that result from the rains. Whatever water is not carried off by the streams enters the cut, either through direct fall over the excavated area or by seepage into it. Proper drainage of the cut is therefore an ever existing problem, and two distinct phases are presented, viz:
1. To keep out the water of the surrounding country,
2. To rid the excavated area of the water that collects in it.
A system of diversion channels accomplishes the first, and gravity drains and pumps solve the second. The canal line follows the Obispo River, which drains the area from the divide to the Chagres River. It has four principal tributaries, two from the east, the Masambi and the Sardinilla, and two from the west, the Mandinga and the Comacho. These are cared for by two diversion channels.
On the east side of the cut the Obispo diversion has been constructed almost parallel to the canal and carried through a depression in the hills so as to discharge into the Chagres about one mile above the point at which the canal line crosses the river.
To the west of the cut the Comacho diversion carries the waters from Culebra to the Chagres River through the old channel of the Obisbo River. Through a hill between Haut Obispo and Bas Obispo, which sharply deflects the river, the French has build a tunnel for diverting the flood waters, and this forms a part of the new diversion.
The canal follows the Rio Grande on the southern slope of the divide, and its waters are cared for by a diversion channel constructed by the French. They also constructed a dam across the valley, impounding the waters, and the resulting reservoir supplies the settlements from Culebra to and including Panama. During the wet season the diversion channel carries the overflow from the reservoir.