War Department

Corps of Engineers, US Army.

War Department

Corps of Engineers, US Army

Deficiency.

1895 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905

1906 1907 1908 1909 1910 1911 1912

Diagram No.7. San Carlos Irrigation Project.

122. Referring to "Comments on Mr. Olberg's report" in that appendix, the board believes that the damage to the agency will not exceed $200,000.

123. In the brief submitted by the Arizona Eastern Railroad Co. to the Secretary of the Interior in 1909, in the matter of their application for renewal of right of way through the reservoir and dam sites, the damage to their property that would result from the building of a dam at San Carlos was described as follows:

The actual cost of building a new line to avoid the water line of the proposed reservoir involves the construction of 12.6329 miles of main line and 1.7045 miles of siding, which, after allowing full credit for the value of the material recovered from the present track and full value of material recovered from the two steel bridges, will amount to $680,190.94.

The estimated increased cost of operating the new line after it has been completed, due to increase of maximum grades, rise and fall, curvature, etc., will amount to $67,649.55 yearly, which annual outlay capitalized at 5 per cent gives an equivalent money investment of $1,352,991, to which add cost of construction, $680,190.94, gives a total of the damage which will be suffered by the railroad company of $2,033,181.94. The estimate of the cost of reconstruction of this line was made upon an actual survey and is extremely conservative; and the estimate of increased cost of operation was calculated by well-recognized formula.

124. The relocated line referred to as then surveyed is not high enough at all points to clear the maximum flow line at elevation 190 feet, but the change required to put it above the flow line will not increase the cost. Only the actual cost to the railroad of reconstructing the line should be paid; and the board believes that this cost will not exceed $680,191. The board doubts whether the cost of operation of the new line will exceed that for the present line; nor is it convinced of the correctness of the method employed by the railroad in computing this increased cost. According to the company's figures, the present line has an equivalent straight level length of 14.5762 miles, while the new line has an equivalent straight level length of 14.3881. On the same basis of operating cost the new line would be slightly less expensive to operate than the present line. But the railroad calls the new line "mountain line" and the present line "valley line," and uses a greater operating cost per mile in the former than in the latter case. There is no such difference in the character of the country traversed as to warrant the distinction implied by the words. "valley" and "mountain." The board has, accordingly, allowed nothing for increased cost of operation.

125. The act (vol. 28, Stat. L., p. 668) under which the railroad line was constructed across this reservation contains the clause that Congress shall have at all times power to alter, amend, or repeal this act and revoke all rights thereunder. Whether or not, under strict legal construction, this would release the United States from payment of the cost of relocating the line, the board believes that, as a matter of equity, the railroad ought to be reimbursed for the necessary outlay involved therein; but it also believes that if the United States finds it advisable to establish a reservoir at this site, such as to require a relocation of the railroad, the railroad would have no just claim for compensation because of increased cost of operation, even if there actually is such an increase.

DESILTING.

(Appendix I.)

126. While the observations and studies of the board indicate that the quantity of silt carried by the Gila River is considerably less than was formerly thought, it is nevertheless sufficiently great to necessitate, sooner or later, some desilting method in order to retain sufficient water storage capacity in the San Carlos Reservoir. Even though it were possible to construct a dam sufficiently high to permit the indefinite postponement of desilting, it would nevertheless be inadvisable to permanently deprive the irrigated lands of the fertilizing value of the silt. Since no lands are of inexhaustible fertility, either the river silt or some other fertilizer must eventually be applied to the land to be included in the project.

127. The desilting method suggested by Mr. Davis (First Annual Report of the Reclamation Service, p. 83), and later discussed for the Engle Dam (Third Annual Report of the Reclamation Service, p. 417, Engle Reservoir), is that of providing large gates in the dam at about stream-bed level or slightly above, through which with the reservoir empty or nearly so the flow of the stream would sluice deposits. It is elsewhere pointed out that at San Carlos provision against a series of low-flow years must be made by storage. The sluicing method is not applicable except when the reservoir is empty or nearly so. If the San Carlos Reservoir should become nearly empty and the remaining water in the reservoir, together with the flow of the stream, should be used for sluicing, the next year might begin with an empty reservoir, and if a year of low-river discharge, crops would suffer. The sluicing method is evidently better adapted for use in a country where the run-off is more uniform than it is in Arizona.

128. The board agrees with the 1905 reclamation board that "the topography of the country around the proposed reservoir is of such a nature that it will not be financially feasible to construct canals around the reservoir for flushing purposes." The impracticability of constructing such a canal eliminates from consideration a suggested plan based on a canal around the reservoir to carry all water past the dam except at such times as the quantity of water flowing in the river was greater than the amount needed for irrigation or greater than the capacity of the canal.

129. A modification of this plan would be to construct a conduit on the floor of the valley, having its upper end at a diversion dam constructed across the stream at a point just above the highest flow line of the reservoir, its lower end extending through the impounding dam. Water would be discharged into the reservoir when the flow of the stream exceeded the requirements of irrigation or the capacity of the conduit. Neither this nor the preceding method would take care of all the silt carried by the stream; the canal would care for a greater quantity than would the conduit. Either method, however, would add to the life of the reservoir. The conduit would be shorter than the canal because more nearly straight and because it would not have to extend beyond the upper end of the reservoir. The board rejects the plan for a conduit because of the danger that the conduit might become choked, because of the impossibility of

repairing damages to it without draining the reservoir, and because it would add largely to the immediate first cost. It could not be added in after years without putting the reservoir out of use for quite a period.

130. The method suggested by Mr. J. H. Quinton in his report of September 11, 1909, contemplates an excavating plant operated by siphonage, and one or more permanent conduits built on the floor of the valley, with outlet through the dam, and with manholes or standpipes at intervals rising above the surface of the water in the reservoir. The excavating plant would consist of a barge bearing a suction pipe extending to the bed of the reservoir (surface of silt deposited in reservoir), a tug to tow this barge, and a discharge pipe leading to the standpipe. The connection with the standpipe would be made through a 90° elbow, the vertical leg of which would be supported in a bearing in which the leg could turn through 360°, and this leg would extend down the standpipe a sufficient distance to cause discharge pipe and elbow to constitute a siphon. Certain of the details of this system present grave difficulties, but they need not be discussed since the system is open to the insuperable objection that even with a perfect vacuum the power exerted would be insufficient to raise and transport material through any considerable distance. The conduits would be open to the objection stated in the preceding paragraph, and to the additional one that interest on their cost would run for a long period before they were called upon to render any service.

131. The board believes that the most promising method, indeed the only practicable method, is dredging. A number of methods of conveying the dredged material from the dredge to the dam were considered: The pumping of the material through long floating pipe lines by use of relay pumps, or through shorter floating pipe lines into a permanent conduit; the transportation of the material in self-propelled barges; and the dredging and transportation of the material by self-propelled hopper dredges. In view of the average length of haul, about 4 miles, transportation of the material in bulk will probably be cheaper than the method by pumping through pipe lines. The objection to the conduit on the bed of the reservoir has previously been stated. Whether suction or ladder dredges would be the more efficient and economical is a question which it is now not thought necessary to answer. Should a suction dredge be used it is believed that the Fruhling head can be used to advantage in this material.

132. Careful consideration of the actual cost of dredging under many different conditions leads the board to the conclusion that the cost of removing the material from the San Carlos Reservoir will be approximately 3 cents per cubic yard, or including interest and depreciation about 5 cents. Not all of the 7,260,000 cubic yards carried into the reservoir on the average per year will have to be removed (see par. 93), and it is believed that only about 6,000,000 will have to be dredged. The cost of the dredging at 5 cents per cubic yard will therefore be $300,000 per year, or on the basis of 90,000 acres irrigated (par. 153) $3.33 per acre per year.

133. Schuyler, in his report of 1900 (S. Doc. No. 152, 56th Cong., 1st sess.), laid stress on power development at the San Carlos Dam. The dam contemplated by the board includes a means of taking