The Gatun dam has aroused more adverse criticism than any other canal feature. Most startling statements have been made concerning it. Its history is worthy of notice. The first study of the Panama route under United States authority was made by an Isthmian Canal Commission of which Admiral Walker was chairman and Generals Hains and Ernst and Mr. Noble were members. With respect to the location of locks, the report of this commission said: “No location suitable for a dam exists in the Chagres River below Bohio”. Hains and Ernst signed this report. In a paper read before the American Society of Civil Engineers on March 5, 1902, Mr. George S. Morison, a very distinguished American engineer, said: “All engineers who have examined the route of the Panama Canal agree that the neighborhood of Bohio is the only available location for a dam by which the summit level must be maintained”.

Under authority of the President, by executive order dated June 24, 1905, a board of consulting engineers was appointed to consider the various plans proposed for the construction of a canal across the Isthmus. The minority of the board, as has been stated before, recommended a lock canal with a dam at Gatun. The majority of the board, 8 to 5, opposed the idea of a dam and locks at Gatun on two grounds: first, that the introduction of locks in a treatment of the question was objectionable from many points of view; and, second, that the maintenance of a summit by means of an earth dam of immense magnitude to control the flood waters of this river introduced an element of great danger since the dam, without sheet piling, was proposed to be founded on the alluvial-filled gorges of the Chagres River, where the depth at one point extended 258 feet below the level of the sea.

Of the minority above mentioned one member, Mr. Noble, was a member of the former Commission who had reported that Bohio was the lowest point on the Chagres where a dam was practicable.

The report was reviewed by the Isthmian Canal Commission which included among its members Major Harrod and Generals Hains and Ernst. They all indorsed the minority report, notwithstanding the fact that in March, 1905, Major Harrod was opposed to any lock plan, and that his two associates had said in 1901 that no proper site for a dam existed below Bohio.

It is true that every consideration of the Panama Canal type by any unauthorized body rejected the idea of a dam at Gatun, and its indorsement is confined to a minority of the board of consulting engineers and to three members of the canal commission who had previously either been in favor of a sea-level canal or who had said, in effect, that Gatun was not a proper site for the dam.

The attitude of the majority of the board of consulting engineers upon this most important question is best shown by an extract from its report. “The United States Government is proposing to expend many millions of dollars for the construction of this great waterway which is to serve the commerce of the world for all time and the very existence of which would depend upon the permanent stability and unquestioned safety of all dams. The board is therefore of the opinion that the existence of such costly facilities for the world’s commerce should not depend upon great reservoirs held by earth embankments resting literally upon mud foundations or those of even sand and gravel. The board is unqualifiedly of opinion that no such vast and doubtful experiment should be indulged in, but, on the contrary, that every work of whatever nature should be so designed and built as to include only those features which experience has demonstrated to be positively safe and efficient”.

The remarkable diversity of statement in regard to this dam is shown by the following quotations.

Mr. Teller in a speech in the last session of Congress said in part, “Let me say a word or two about the great dam to be built at Gatun. We were told in the beginning that the engineers would find a foundation upon which they could build a safe dam. The French Government declared they had found such a foundation; our own engineers declared they had found it. It turned out that they had struck some floating pieces of rock in the mud, and when they had gone down 287 feet they found the same conditions practically that they found in the first 50 feet. The place where it is proposed to construct this dirt dam, which will be half a mile wide and 135 feet high (now 115 feet), is a great swamp. No such dam has ever been built in the history of the world, and the engineers of the world, with few exceptions, have declared it cannot be built. The dam at Gatun is to be built upon a foundation of doubtful safety, and there is not an engineer in the country who does not know that it is doubtful”.

Lindon W. Bates, in his “Retrieval at Panama”, says, “The utter indifference to real information as to existing conditions at Panama has been astounding. Despite, for instance, the private knowledge of the Commission in 1906 through their last 15 months that the bores in these Gatun gorges were flowing bores, not one additional test had been undertaken in them. In summary of foundation conditions one thing is certain. First and foremost and indispensibly there must be at the Isthmus, since the underground conditions have been revealed, the safe barring off of permeable strata under the crucial dam. This cannot be done at Gatun for the high dam”.

On the other hand an editorial in the Engineering News of February 25, 1909, says, “We can testify from actual personal observation and study of the dam site and of the borings and pits that the Gatun dam will be as safe and permanent as any structure ever reared by man”.

In the President’s message of February 17, 1909 there is this statement, “As to the Gatun dam itself, they (the board of engineers) show that not only is the dam safe, but that on the whole the plan already adopted would make it needlessly high and strong, and accordingly they recommend that its height be reduced by 20 feet, which change I have accordingly directed”.

In the Engineering News of April 1, 1909 is the following statement, “If a private corporation, not subject to the clamor of public criticism were confronted with the task of throwing a dam across the Chagres Valley at Gatun, they would build a structure which would be not more than one-fifth the size of that which is now being built there”. Farther on in the same article a comparison of the Gatun dam with alluvial dams of India and the levees along the Mississippi is summed up with these words, “Compared with any and all of these the conditions for safe and permanent dam construction at Gatun may be considered ideal”. Is it any wonder that people are confused and disgusted when they attempt to obtain the truth?

The length of the dam is to be 7,700 feet, but the natural surface reaches or exceeds the dam elevation in three places for about 700 feet in all. At the level of 21 feet above the sea it will be about 2,600 feet long in two sections, separated by Spillway Hill. According to the engineer’s report the dam will rest upon brown or blue clay and silt. Under the dam there are two geologic gorges, one 185 feet deep (below sea level) and the other 255 feet deep. These are filled with river alluvium and other deposits, consisting, according to official reports, of silt, soil, brown and blue clay, rotten wood, sand, and gravel — the most, if not all of it water bearing. The cross-sectional area of the shallower gorge is 205,000 square feet and of the deeper one 120,000 square feet.

(For profile, cross-section, and plan see the following page.)

The dam is to consist of two piles of rock 1,200 feet apart and carried up to 60 feet above mean tide with the space between them and up to 115 feet above sea-level filled by selected material deposited in place by the hydraulic process. A slip occurred at one of these rock toes during November, 1908, and caused considerable alarm throughout the country, so much, in fact, that the President sent W.H. Taft with a group of 7 noted engineers to investigate. They reported that “A full study of all the data and of the material, and of the plans that are proposed leaves no doubt in our minds as to the safe, tight, and durable character of the Gatun dam”.

At the close of the fiscal year 1908–’09 three 20-inch suction dredges were depositing material over the area between the rock piles, and the fill had reached an average elevation of 16 feet above sea-level. A total of 2,501,372 cubic yards was placed in the dam during the year.

Excavation through the Spillway Hill was practically completed and 30,464 cubic yards of concrete laid. During the year 359,821 cubic yards of material were removed from Spillway hill by steam shovels and placed on the dam.

The original canal plans provided for a flight of two locks at La Boca, near the Pacific, and one at Pedro Miguel. Steps were taken to construct the former and trestles were built along the toes from which to dump material from Culebra Cut. The trestles failed after dumping began and material overlying the rock moved laterally, the movement continuing for two weeks in some places. After this result these dams were abandoned so that instead of locks at La Boca they will be built at Miraflores. Another reason for the change besides poor foundations is the military advantages of the latter over the former position.

Both the dams at Pedro Miguel and Miraflores will be constructed of two rock piles, the portion between being filled by hydraulic methods. Very little work has been done upon them.