21
Triumph
Everything is on a colossal scale.
–Scientific American
March 18, 1911
I
“It is hard for me to transmit to you the feeling we all possessed toward the work,” Robert Wood said. “Rarely can man see his own work, but we saw it physically . . . year by year . . .”
They saw it in the deepening of Culebra Cut; in the rise of docks and warehouses; in the new railroad; in the fortifications being built at Toro Point and Margarita Island in Limon Bay and on the islands of Perico, Flamenco, and Naos in the Bay of Panama. (The giant 16-inch guns being installed were the largest, heaviest weapons in the possession of the United States and had a range of twenty miles.) They saw it in the hydroelectric plant built adjacent to the spillway of Gatun Dam, and in the dam itself, which in its final stage looked as if it had been there always, more like a huge glacial moraine than anything else. It was all measurable progress.
And there was the lake. It had begun its rise with the closing of the West Diversion channel in 1910, when the dam was still incomplete. In the time since, as the water inched steadily up the long, sloped inner face of the dam, as the Chagres gathered and spread inland mile by mile, the realization of what a very different kind of canal it was to be, the conception of a long arm of fresh water suspended in the jungle, began to take hold and with good effect.
Popular interest at home mounted proportionately, the nearer the dream seemed to fulfillment. In the last years of construction, hundreds of articles appeared in magazines and Sunday supplements under such titles as “The Spirit of the Big Job” or “Realizing the Dream of Panama,” “Great Work Nobly Done,” “The Greatest Engineering Work of All Time,” “Our Canal.” In 1913, in anticipation of the projected grand opening, close to a dozen different books were published about Panama and the canal.
But it was also in the closing years of the task that the great locks took form for all to see and they were the most interesting and important construction feats of the entire effort. They were the structural triumphs at Panama. In their overall dimensions, mass, weight, in the mechanisms and ingenious control apparatus incorporated in their design, they surpassed any similar structures in the world. They were, as was often said, the mighty portals of the Panama Gateway. Yet they were something much more than monumental; they did not, like a bridge or a cathedral, simply stand there; they worked. They were made of concrete and they were made of literally thousands of moving parts. Large essential elements were not built, but were manufactured, made in Pittsburgh, Wheeling, Schenectady, and other cities. In a very real sense they were colossal machines, the largest yet conceived, and in their final, finished form they would function quite as smoothly as a Swiss watch. They were truly one of the engineering triumphs of all time, but for reasons most people failed to comprehend.
To build all the locks took four years, from the time the first concrete was laid in the floor at Gatun, August 24, 1909. Most impressive of all was their size, and especially if seen during the last stages of construction before the water was turned in. Visitors who stood on the dry floor of a single lock chamber when all of it was still open to the light felt as though they had suddenly lost their sense of scale. Each individual chamber was a tremendous concrete basin closed at both ends with steel gates. The walls, one thousand feet long, rose to eighty-one feet, or higher than a six-story building. The impression was of looking down a broad, level street nearly five blocks long with a solid wall of six-story buildings on either side; only here there were no windows or doorways, nothing to give human scale. The gates at the ends, standing partly open to the sky, were like something in a dream.
Greatest of the “ocean leviathans” in the year 1913, a ship larger than the Titanic had been, was the proud new 52,000-ton Imperator, of the Hamburg-American Line. The Imperator accommodated 5,500 people (for whom there were no less than eighty-three lifeboats); she had a “Pompeian Bath,” a “social hall” that could accommodate seven hundred passengers traveling first class; and the Imperator could have been contained within a lock chamber with ample room to spare (six feet on each side, nearly sixty feet at either end). A single lock if stood on end would have been the tallest structure in the world, taller even than the Eiffel Tower.*
The artist Joseph Pennell, having climbed down to the floor of an empty lock chamber at Pedro Miguel, found the shapes of gates and walls towering above him so “stupendous” that he was almost unable to draw. Walter Bernard, editor of Scientific American, returned from a visit to the Isthmus to write an article on “The Mammoth Locks” in which he conceded that it is impossible even to consider the subject “without drifting into the superlative mood.” Another visitor would recall “the feeling that follows a service in a great cathedral.”
To build the Great Pyramid or the Wall of China or the cathedrals of France, blocks of stone were set one on top of the other in the ageold fashion. But the walls of the Panama locks were poured from overhead, bucket by bucket, into gigantic forms. And within those forms there had to be still other forms to create the different culverts and tunnels, the special chambers and passageways, required inside the walls. Everything had to be created first in the negative, in order to achieve the positive structure wanted.
Moreover, the creation of the building material itself was a “science” requiring specific, controlled measurements and a streamlined system of delivery from mixing plant to construction site. Timing was vital.
Concrete–a combination of sand, gravel, and portland cement (itself a mixture of limestone and clay)–had been known since the time of the Romans, but was used very little as a building material until the late nineteenth century and then mainly for subbasements and floors. Dry docks and breakwaters were built of reinforced (or ferro) concrete–concrete in which metal rods are added–and in the early 1900’s several major buildings were built of the same material in Europe and the United States, as well as silos, some small bridges, and a Montgomery Ward warehouse in Chicago. George Morison drew up plans for his concrete bridge over Rock Creek Park in Washington, and by 1912 a tremendous concrete railroad bridge, the Tunkhannock Viaduct, was under way near Scranton, Pennsylvania. Nothing even approaching the size of the Panama locks had yet been attempted, however, and not until the building of Boulder Dam in the 1930’s would any concrete structure equal their total volume. The largest amount of concrete ever poured in a day anywhere else was about 1,700 cubic yards. At Gatun alone the daily average was nearly double that.
“No structure in the world contains as large an amount of material,” William Sibert wrote proudly of the great flight of locks at Gatun. With their approach walls, they measured nearly a mile from end to end. The volume of concrete poured was more than 2,000,000 cubic yards–enough, somebody figured, to build a solid wall 8 feet thick, 12 feet high, and 133 miles long. Taken together, the locks at the other end of the canal, at Pedro Miguel and Miraflores, were larger still, with a volume of some 2,400,000 cubic yards.
The lock chambers all had the same dimensions (110 by 1,000 feet) and they were built in pairs, two chambers running side by side in order to accommodate two lanes of traffic. The single flight at Gatun consisted of three such pairs. There was one pair at Pedro Miguel and two at Miraflores, making six pairs (twelve chambers) in all.
The chambers in each pair shared a center wall that was sixty feet wide from bottom to top. The width of the side walls was forty-five to fifty feet at the floor level, but on the outside they were constructed as a series of steps, each step six feet high, starting from a point twenty-four feet from the base level. So at the top, the side walls were only eight feet wide.
The floors of the chambers were solid concrete, anywhere from thirteen to twenty feet thick.
Once completed, the stepped backs of the side walls would be filled in, covered entirely with dirt and rock. And the locks, once they were in use, would never be less than half full of water. So their size would appear nowhere ne
ar so overwhelming.
Seen during construction they were a fantasy of huge, raw-looking concrete monoliths, of forms of sheet steel that looked like colossal, blank theatrical flats, of monstrous cranes and soaring cableways– aerial bucket brigades, as somebody said–and of little automatic railroads shunting here and there. The swarms of workers at the lock sites appeared lost beside the rising shapes and the incredible array of mechanical contrivances. The noise was shattering.
At Gatun big square buckets of concrete, nearly six tons to a bucket, were swung through the air high above the locks, dropped to position, and dumped, all by means of a spectacular cableway. Eighty-five-foot steel towers stood on either side of the locks (four on each side) and the cables stretched across a span of some eight hundred feet. The towers were on tracks, so they could be moved forward as the work progressed.
Sand and gravel were brought up the old French canal in barges and were stockpiled near a mixing plant. Then sand, gravel, and portland cement were fed into the plant (a battery of eight concrete mixers) By a little automatic railroad, the cars running in and out on a circular track. Another small railroad carried the buckets of wet concrete from plant to cableway, Two buckets on Two flatcars pushed by one of the French locomotives. At the cableway Two empty buckets would descend from overhead, the Two full buckets would be snatched up, delivered through the air at a speed of about twenty miles per hour, then returned to repeat the cycle.
The advantage of such an overhead delivery system was that the work area could be kept free of everything except the essential forms Within which the concrete was poured. As fast as a bucketload was deposited, men knee-deep in wet concrete would spread it out.
All the locks were constructed in thirty-six-foot sections, each a single monolith that took about a week to build to its full height. The big steel forms, also on tracks, would then be moved ahead to the next position.
At Pedro Miguel and Miraflores, where the terrain was not so open or spacious as at Gatun, division head Williamson and his civilian engineers decided to use cantilever cranes rather than cableways, cranes so enormous in size that they could be seen rising above the jungle from miles distant. Some of these were in the shape of a gigantic T. Others looked like Two gigantic T’s joined together and were known as “chamber cranes,” because they stood within the lock chambers, their long cantilever arms reaching out over the center and side walls. All the cranes moved on tracks and were self-propelling.
The T-shaped variety were the “mixing cranes.” One arm of the T hoisted sand and gravel and cement from stockpiles to mixing plants located in the base of the T. The other arm transferred buckets of fresh concrete to the chamber cranes that in turn swung the buckets to the desired position. The complete operation was about as mechanized as it could possibly have been and to the average onlooker a very weird, unearthly sight to behold. The operator of a chamber crane, the man who guided the concrete to its destination, sat alone in a tiny box hanging from the delivery arm of the crane, nearly a hundred feet off the ground.
Five million sacks and barrels of cement were shipped to Panama to build the locks, dams, and spillways, all of it from New York on the Ancon and the Cristobal, and an idea of what such quantities amounted to is imparted by a single budgetary statistic: an estimated $50,000 was saved in recovered cement after Goethals issued a directive requiring the men to shake each sack after it was emptied.
Gravel and sand for those structures closest to the Atlantic– Gatun Locks, the Gatun spillway–came by water from points twenty to forty miles east of Colón, the gravel from Porto Bello, where a big crushing plant was built, the sand from Nombre de Dios.* On the Pacific side, the rock (basalt, or traprock) was quarried and crushed right at Ancon Hill, while the sand came from Chamé Point, in the Bay of Panama.
By latter-day standards the engineers were novices in the use of concrete. Numerous discoveries had still to be made about the critical water-cement ratio in the “mix design” and the susceptibility of the material to environmental attack. To build anything so large as the concrete locks at Panama was an unprecedented challenge, but what was built had also to hold up in a climate wherein almost everything, concrete included, could go to pieces rapidly. Yet, however comparatively crude the level of theoretical technology may have been regarding the material, the results were extraordinary. After sixty years of service the concrete of the locks and spillways would be in near-perfect condition, which to present-day engineers is among the most exceptional aspects of the entire canal.
The design and engineering of the locks, the results of years of advance planning, can be attributed largely to three men: Lieutenant Colonel Hodges and two exceptionally able civilians, Edward Schildhauer and Henry Goldmark. Schildhauer, slight of build, clean-shaven, very businesslike, was an electrical engineer and still in his thirties. Goldmark, who with his starched collars and thin, well-brushed hair looked like a corporation lawyer, had responsibility for designing the lock gates.
The fundamental element to be reckoned with and utilized in the locks– the vital factor in the whole plan and all its structural, mechanical, and electrical components–was water. Water would lift and lower the ships. The buoyancy of water would make the tremendous lock gates, gates Two to three times heavier than any ever built before, virtually weightless. The power of falling water at the Gatun spillway would generate the electrical current to run all the motors to operate the system, as well as the towing locomotives or “electric mules.” The canal, in other words, would supply its own energy needs.
No force would be required to raise or lower the level of water in the locks (and thus to raise or lower a ship in transit) other than the force of gravity. The water would simply flow into the locks from above–from Gatun Lake or Miraflores Lake–or flow out into the sealevel channels. The water would be admitted or released Through giant tunnels, or culverts, running lengthwise within the center and side walls of the locks, culverts eighteen feet in diameter, as large nearly as the Pennsylvania Railroad tubes under the Hudson River. At right angles to these main culverts, built into the floor of each lock chamber, were smaller cross culverts, fourteen to a chamber, these about large enough to admit a two-horse wagon. Every cross culvert had five well like openings into the floor, which meant there were all together seventy such holes in each chamber, and it was from these that the water would surge or drain, depending on which valves were opened or shut.
The valves in the large culverts were immense sliding steel gates that moved On roller bearings up and down in frames in the manner of a window. There were Two gates to each valve and they weighed ten tons apiece. To fill a lock, the valves at the lower end of the chamber would be closed, those at the upper end opened. The water would pour from the lake through the large culverts into the cross culverts and up through the holes in the chamber floor. To release the water from the lock, the valves at the upper end would be shut, those at the lower end opened.
The reason for having as many as seventy wellholes in the chamber floor was to distribute the turbulence of the incoming water evenly over the full area and thereby subject chamber and ships to a minimum of disturbance. It was the engineers’ intention to be able to raise or lower a ship in a chamber in about fifteen minutes. Of all the moving parts in the system, the largest and most conspicuous were, of course, the lock gates, or “miter gates,” as they were known, which swung open like double doors and closed in the form of a flattened V. The leaves of the gates weighed many hundreds of tons apiece and were the largest ever erected. Their construction was begun at Gatun in May 1911. As structures they were relatively simple and posed no special challenge, except, again, for their magnitude. A skin of plate steel was riveted to a grid of steel girders in exactly the manner of a steel ship’s hull–or of a modern airplane wing, which they much resembled in vastly enlarged form. And being both hollow and watertight, they would actually float, once there was water in the locks, and thus the working load on their hinges would be comparatively little.
The leaves were all a standard sixty-five feet wide and seven feet thick. They varied in height, however, from forty-seven to eighty-two feet, depending on their position. The highest and heaviest (745 tons) were those of the lower locks at Miraflores, because of the extreme variation in the Pacific tides.
During construction, inspectors went down inside the gates through a system of manholes to check every rivet, an extremely uncomfortable task with the sun beating on the outer steel shell. All imperfect rivets were cut out and replaced and the watertightness of the shell was tested by filling the gate leaves with water.
As a safety precaution there were also to be duplicate gates throughout. One set of double doors was backed by another, in the event that the first set failed to function properly or was rammed by a ship. And since each lock chamber (except the lower locks at Miraflores) had its own set of intermediate gates, the complete system consisted of 46 gates (92 leaves), the total tonnage of which (sixty thousand tons) was almost half again greater than that of a ship such as the Titanic.
The purpose of the intermediate gates was to conserve water. While the locks were built to accommodate ships as large as the Titanic or the Imperator, or larger, each lock chamber could be reduced in size, by closing the intermediate gates, if the ship in transit was not one of the giants and could be accommodated by a chamber of six hundred feet or less. And of all the oceangoing ships in the world at that time, approximately 95 percent were less than six hundred feet long.
To lift a great merchant liner, or any ship of more than six hundred feet, to the level of Gatun Lake would require an expenditure from the lake of 26,000,000 gallons of water, the equivalent of a day’s water supply for a major city. For a complete lockage through the canal, for one ocean-to-ocean transit, the expenditure would be double that amount, all of it fresh water and all washed out to sea.
David McCullough Library E-book Box Set Page 397