There has been much criticism of the lock sites, but the engineers now in charge seem to have perfect confidence in their work.
During the fiscal year 1908–’09 the work of excavating for the Gatun locks was continued by steam shovels and one 20-inch suction dredge. Material excavated in the dry amounted to 933,546 cubic yards, and that in the wet to 479,950 cubic yards. It was decided to construct curtain walls to stop any underflow; these will extend across the lock under the sill of the emergency dam and downstream outside the walls to the intermediate gates. As an additional precaution to making the concrete floor 13 feet thick as before mentioned a system of sumps under the floor with telltales in the walls will be built.
The plant for the construction of the locks is practically installed and ready for work, it being operated entirely by electricity.
At the Pedro Miguel locks 715,726 cubic yards were removed in 1908–’09. One lock chamber was completed to grade, but 45,000 cubic yards remain for removal in the other one.
At Miraflores work was done the past year with steam shovels and one suction dredge. The total amount excavated was 1,147,527 cubic yards which is one-half of the total estimated quantity.
IX. CONSTRUCTION OF THE DAMS
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.