REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL


 Does that mean dry earth? Should the word "earth" be added after "dry?"
 Mr. BATES. It means dry earth, such as we had in the drainage canal of Chicago, where it cost about 18 cents. It is quite true that a correction making the text to read "two to eight," etc., might be advisedly made when the phrase is understood to refer to rock in the dry. As a matter of fact, the actual cost of rock to the contractor may be stated to run about 45 or 50 cents in the dry, if it be all limestone rock. The average contractor's price for submerged-rock excavation runs about four or five dollars, and from that standpoint the statement is perfectly correct as it stands.
 Mr. Stearns then asked about the construction of the Gamboa dam with reference to the retention of silt.
 Mr. BATES. I would raise the level of the floor of .the sluices so that the water would be backed up for a mile and a half, catching as much of the silt as would deposit.
 In the silt pond above the dam I would place an ordinary hydraulic dredge which would excavate accumulations of silt and pipe them through the dam into a steam hopper barge in the Obispo basin. This self-discharging barge would have capacity of three or four thousand tons and could steam to any convenient depositing area.
 I might say that at Galveston, Tex., we are excavating material (about 10 million yards) and making a round trip of about 9 miles and distributing it from stations on the shore of a canal run into the city, over the site of the city, at an average cost last month of about 7 cents.
 Mr. STEARNS. How is the distribution effected from the dredge?
 Mr. BATES. Inside the hull is a trunk, and on either side of this trunk are two parallel waterways, the suction pipe being connected with these trunks so that the same apparatus which loads the vessels unloads it.
 Mr. HUNTER. Going back to the point which I raised, it appears -to me to be of some importance as to the succession of two floods. Did I understand you to say that in such case it will be necessary to discharge all the flood water into the canal, sending part to the Atlantic and part to the Pacific? Would it be necessary to discharge it with such velocity as to interfere with navigation?
 Mr. BATES. I think I will have to ask one question. What is the volume of the succession of the floods that you assume?
 Mr. HUNTER. I am not assuming anything, except that before you are able to discharge the first flood which has filled your basins you have a second flood upon you, and it is absolutely necessary for you to discharge the water of the first flood, and therefore you would have to discharge such a quantity that you would turn out water into your canal at such a rate that the velocity would be four or five miles per hour.
 Mr. BATES. If you assume a double flood at the height of 1879-in any such event, then it would be wise and prudent, for perhaps twenty-four hours once in a generation, to let a current of 6 feet a second pass through, but such an event has never transpired, and there is no evidence in the records that it ever will transpire.
 Mr. HUNTER. With reference to the Mindi dam, are there borings on that site?
 Mr. BATES. Yes; they were taken by the Commission.
 Mr. HUNTER. Have you any records on the site of the damn on the Pacific side? I was unable to follow your plan very closely, and perhaps it would be of interest to tell us a tittle more about that dam.
 Mr. BATES. You will find this on Plate VII. On the east side you have at Sosa Hill one abutment, and on the west side you have what I call West Rio Grande Hill. It has no name that I know. The distance across here is about 4,300 or 4,400 feet; not quite a mile. Borings have been taken particularly in the vicinity of La Boca. An excavation was made westward for a distance of about 400 feet and the evidence shows rock bottom nowhere far from the surface. The rock line varies from 35 to 68 feet.
 The Chairman then mentioned as a matter of personal observation, that at the head of La Boca pier the rock was covered by 17 feet of water at low tide before it was excavated, and that it comes to the surface about 400 yards east of that.


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