REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.


three of these could be used at the same time, leaving one out of the four for workable adjustments, and working three steam shovels to each mile of length, and terracing each side of the excavation, such a plan would permit of the use of 18 steam shovels on each mile of excavation for each 100 feet of depth of cutting. On the assumption that the larger portion of the excavation of the eight miles is concentrated in five miles, this would permit of the simultaneous operation of 90 steam shovels on this five-mile section for each 100 feet of depth of excavation.
 Considering the fact that the scheme outlined above will require three years for the installation of the maximum number of 82 constantly working steam shovels, this should be sufficient time to shape up the general work of excavation in such a manner as to permit of the use of the full number of machines, and as they would be engaged on the attack of the excavation at the point of greatest depth at the end of three years, when the full number is established, the conditions should be such as to admit of uniform operations.
 It is understood that steam shovels in excess of 24 a year would be installed on other portions of the work on other sections outside of the central section under consideration, this number of 24 being used as it is considered an ample number of machines to install in the central eight-mile heavy section in view of the various difficulties surrounding the work and the fact that each steam shovel will require for loading, switching, main running, and dumping tracks approximately three miles of track, two locomotives, and a sufficient number of cars, unloading apparatus, bank spreaders, and other auxiliary appliances, together with the necessary personnel constituting the general organization, all of which, however, should easily be provided at the rate of progress required to install the excavating units.
 In connection with this rate of progress there are various elements of flexibility which can be considered. First, the adoption of two or three eight-hour shifts will materially increase the output for twenty-four hours. More shovels than those enumerated in the above schedule could be installed and operated. Efficient management, such as a contractor would give the work, should and would materially increase the efficiency of the entire organization and consequently of the excavating units, increasing output.
 These remarks and conclusions are all based on the assumption that the men and material necessary for this work will be promptly furnished as required and the work conducted in accordance with ordinary business methods; in other words, as by a contractor having ample means and full facilities at his command.
 At Culebra proper and at Emperador, and possibly at other points along the canal where the basaltic rock exists, slopes much steeper than 1 to 1 could be adopted, and consequently a large saving made in the most expensive-and hardest class of material to be removed and at the point where the greatest number of yards to be excavated is now concentrated.
 At other points along the excavation shales and other material will be found which will stand, at least temporarily, at much steeper slopes than 1 to 1, and it crtainly would not be necessary to remove the entire cross section back to a I to 1 slope prior to the opening of the canal for navigation. This process could be spread over several years after the opening of the canal.
 Herewith is submitted a sketch marked "Exhibit A," showing some typical cross sections on the terrace plan.
 This attached sketch is of course simply a tentative cross section. It has not been considered necessary for this purpose to go into the full details of the readjustment of these slopes which may be necessary at various points along the line, to be determined by the character of the material in each separate locality. At some points a heavy retaining wall may be necessary; at others it may be sufficient to break the submerged slope with an intermediate berm at, say, 10 feet below low water, or at such a point as would be sufficiently below the surface as not to be affected by wave action, and to riprap'this bench and slope above it; or it may be necessary to carry this paving to the extreme depth of section where the material is liable to be washed by current action. With the use of the 50-foot berm to serve the purpose so that a retaining wall would not have to support a surcharged embankment, an economical method of slope protection might be the covering of the slope with a moderate layer of concrete. At other places it might


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