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Mr. WEYMOUTH. Of course, if a dam were built at Spencer Canyon, it would ruin Boulder Canyon as a reservoir for any large storage on the river, and that would make it highly objectionable for that reason. There is not a large reservoir above Spencer Canyon site. It is comparatively small, but I do not remember the exact size.
For Bridge Canyon, Spencer Canyon, and Devil's Slide dam sites the topography was obtained in 1923 by the United States Geological Survey, but in most cases in insufficient amount to cover the sites for power houses as well. No data are available on the foundations of these sites. The estimates of cost are based on assumed depths to rock of 60, 90, and 120 feet, the middle depth being used for a general comparison of plans. The accessibility of the sites has been assumed without actual knowledge of this condition.
As to the Boulder Canyon Reservoir site, detailed topography of the reservoir area and dam sites has been obtained; surveys made for connecting railroads indicate a readily accessible site. The two most favorable dam sites indicated by detailed geological investigations have been thoroughly drilled. Concrete materials have been located and subjected to practical tests to determine their suitability with gratifying results. This work was carried on from 1918 to 1923.
With respect to Bulls Head Reservoir site, the topography for this site was obtained in 1902 and 1903. The location was diamond drilled in 1903 by the Reclamation Service as reported in the second annual report of that service.
As to the Mohave Valley Reservoir site, the general topography of this reservoir site was made by the Reclamation Service in 1902 and 1903 and that of the dam site by the United States Geological Survey in 1923. No drilling has been done. Estimates of the depth to rock are based on conditions existing at the railroad bridge a few miles above and at other dam sites on the river. And I might say in that connection that the east abutment of the bridge at that point rests on poles. It was reported by the engineers for the Sante Fe Railroad that at a depth of 100 feet they had not reached bedrock.
Senator ASHURST. And at 100 feet they had not struck bedrock!
Mr. WEYMOUTH. On the Arizona side. Our experience has been in our investigations of the Colorado River that wherever the river is deep and narrow the distance to bedrock is very deep but where the river was narrow the distance to bedrock is much less. That proved to be the case not only in the Boulder Canyon where we drilled several different distances, but in Black Canyon, and it is likely to be the case at Mohave. No one can say definitely that that is true, but it stands to reason that such would be the case because there is a certain amount of water passing that point, so my judgment is that the rock at Topock is likely to be 150 feet or more.
Senator ASHURST. Is that prohibitive?
Senator ASHURST. What would be the size of a proposed dam near Topock, near Needles?
Mr. WEYMOUTH. That, of course, would depend upon the height. We made estimates for some storage. The Mohave site has been considered seriously for flood control only and not for storage. It is not a favorable site to store. I will touch upon that later.
The fact of necessary changes in railroad trackage and facilities is computed from information furnished by the railroad company. That is for the Mohave site.
The general topography of Parker dam site was taken in 1902–3. Additional topography was furnished by Fred A. Noetzli, Associate Member American Society Civil Engineers. The site has not been tested for foundations.
Designs and estimates for the Black Canyon dam have been worked out in great detail for various heights, based on complete field data.
Information on the Diamond Creek, Bullshead, and Parker sites is in such shape that the designs and estimates can be considered little better than preliminary.
The foundation conditions and right of way difficulties at the Mohave Valley site are unknown.
The Bridge Canyon, Spencer Canyon, and Devil's Slide sites have only incomplete topography from which estimates can be made.
A reservoir at Boulder Canyon with dam constructed at the lower site in Black Canyon would have the following advantages:
(a) It is readily accessible.
(c) Construction materials of demonstrated suitability are available near the dam site in sufficient quantity for the construction of any dam considered.
(d) In contrast with a reservoir at Mohave Valley it would not interfere with any proposed irrigation project.
(e) Within the limits considered estimates indicate that storage can be created in Boulder Canyon Reservoir at less cost than at any other known site on the lower river, with the possible exception of a flood control reservoir only at Mohave which could probably be built at about the same cost.
(f) It is a better power site than the Diamond Creek site developed to utilize the full drop in the river below greater reservoir capacity for the same raise in water surface which increases the potential power; and secondly, to the shorter distance to the principal power market which makes power developed of greater unit value.
(9) It is better adapted to development of power in connection with a flood-control dam than is the Mohave Reservoir on account of the greater head available.
(h) In case of the larger reservoirs the area of water surface exposed to loss through evaporation is less than at other sites.
(i) It is so located as to control discharge from all important tributaries with the exception of the Williams and Gila Rivers.
(j) It is the nearest to the lands to be benefited of any point on the river where it is feasible to construct a reservoir adequately providing for ultimate requirements of flood control, silt storage and irrigation storage combined.
(k) It is the most advantageous site at which the entire cost of construction can be repaid through the marketing of power developed incidentally at the dam site.
(1) The dam site is adapted to raising a dam built originally for flood control alone to the height necessary to provide the required ultimate irrigation storage-or possibly to the height necessary to utilize the entire drop in the river between Diamond Creek and the dam site.
If a dam is built at the Mohave site it will inundate a large irrigable area of about 35,000 acres in a valuable portion of an Indian reservation; submerge a town which is the division point of a transcontinental railroad, and make necessary the reconstruction of 22 miles of main line double track of railroad, involving additional length of line. It will make necessary the reconstruction of a portion of a transcontinental highway. It is not a good power site. The site is not adapted for raising a dam to provide for ultimate storage requirements as economically as another site.
In order to properly consider the best method of controlling the river from the west boundary of the Grand Canyon National Park to Parker I have made several estimates of the various sites and have grouped them under various plans listed as plan A, B, C. D, E, F, G, and H. The principal matters of interest in connection with each of these plans is shown in the two tables attached and is indicated diagrammatically on the blue prints.
Now, I have some prints for the members of the committee, and if the members would look at them they could understand me a little better perhaps.
The CHAIRMAN. I think you have made it very clear. Just pass them around.
Mr. WEYMOUTH. I have also made some tables which illustrates the cost of the different schemes.
The CHAIRMAN. Are they the tables in the House hearings?
Senator JOHNSON of California. I assume that these will be put in the record.
The CHAIRMAN. Yes.
100 150 200 250 300 350 400 450 500 550
Miles above Yuma FIG. 22. DEVELGPMENT OF COLORADO RIVBR BELOW GRAND CANYON, PLANB A TO D, INCLUSIVE. FOOD STORAGB INDICATED 18
THAT REQUIRED UNDER PRESENT CONDITIONS.