C HEADQUARTERS, DEPARTMENT OF THE ARMY, Hon. R. R. RUBOTTOM, Jr., DEAR MR. RUBOTTOM: Further reference is made to your letter of October 30, 1958, to the Secertary of the Army, transmitting for review and comment a report entitled "Proposed Diablo Dam and Reservoir," dated September 1958 as prepared by the U.S. section of the International Boundary and Water Commission, United States and Mexico. We have reviewed the report and find that the proposed works are fully compatible with the responsibilities of the Corps of Engineers. Your courtesy in furnishing the report for review is appreciated. Sincerely yours, E. C. ITSCHNER, Major General, U.S. Army, Chief of Engineers. D The Honorable the SECRETARY OF STATE. DEPARTMENT OF AGRICULTURE, Washington, D.C., December 18, 1958. DEAR MR. SECRETARY: This is in reply to the letter of October 30, 1958, from Mr. R. R. Rubottom, Jr., Assistant Secretary, transmitting two copies of a report entitled "Proposed Diablo Dam and Reservoir" for review and comment by this Department. The report outlines a plan for the joint construction by the United States and Mexico sections of the International Boundary and Water Commission, in conformity with the 1944 Water Treaty, of Diablo Dam on the Rio Grande River about 1 mile below the confluence of the Devils River tributary and 12 miles upstream from Del Rio, Texas. The total reservoir capacity would be 5,660,000 acre-feet. Flood control capacity, including substorage, in which each country would have an undivided interest, would be 2,110,000 acre-feet; conservation storage capacity would be 3 million acre-feet, of which 1,686,000 acre-feet would be the U.S. share; and silt retention storage capacity would be 550,000 acre-feet, of which 309,000 acre-feet would be the U.S. share. The estimated U.S. share of the first cost and of the annual cost of the dam, respectively, including minimum recreation facilities recommended by the National Park Service, would be approximately $49,750,000 and $1,845,000. The benefit-cost ratio is estimated at 1.96 to 1 for a 50-year period of analysis and 2.48 to 1 for a 100-year analysis basis. A staff member of the Agricultural Research Service assisted in the determination of benefits expected from increased water supplies for irrigation, and the International Boundary and Water Commission submitted a preliminary draft of the report to field personnel of the Soil Conservation Service and Agricultural Research Service of this Department for review and comment. Consideration was given to their comments in preparation of the final draft of the report. The report is clearly written and presents in a well-organized manner adequate information pertinent to a determination of its economic justification. Its usefulness would be enhanced by the presentation of more detailed economic data, particularly those used in the evaluation of benefits, appendixes. We feel that the benefits from increased water supply for irrigation as included in the report were properly determined and can be considered a satisfactory estimate. The proposed project does not affect the interests of the Department of Agriculture in national forests or forested lands. The effect of the stabilization provided by the proposed dam and reservoir on the agricultural interests of the irrigated lands of the 548 mile reach of the Rio Grande River below Del Rio would be beneficial through increase and flow regulation of irrigation water supplies and in reduction of recurring flood and sediment damages to high producing croplands. We appreciate the opportunity to review the report. Sincerely yours, E. L. PETERSON, Assistant Secretary. E DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE, Hon. ROY R. RUBOTTOM, Jr., Assistant Secretary for Inter-American Affairs, DEAR MR. RUBOTTOM: In response to your suggestion, I am pleased to submit for your consideration our comments on the proposed Diablo Dam and Reservoir project. This is in accordance with your letter of October 30, 1958, transmitting copies of the report on this subject dated September 1958. The report has been reviewed in accordance with this Department's interest and responsibilities in the general health and sanitation; municipal and industrial water supply; water pollution control, and insect vector control aspects of the water resources programs. The opportunity to review this report is appreciated. EDWARD FOSS WILSON, COMMENTS ON THE "REPORT ON PROPOSED DIABLO DAM AND RESERVOIR," RIO GRANDE INTERNATIONAL STORAGE DAMS PROJECT (INTERNATIONAL BOUNDARY AND WATER COMMISSION, UNITED STATES AND MEXICO, U.S. SECTION, DEPARTMENT OF STATE) The 1944 water treaty between the United States and Mexico, contemplated the construction of three storage dams in the main channel of the Rio Grande below Fort Quitman, Tex. Diablo Dam located near Del Rio, Tex., and approximately 290 river miles upstream from Falcon Dam would be the second in this series. Falcon Dam, the first in the series, is located near Laredo, Tex., and was completed in 1953. The purpose of Diablo Dam and Reservoir is to provide, in conjunction with Falcon Dam and Reservoir, optimum feasible conservation, regulation, and flood control of the river. Releases of U.S. waters from Diablo Reservoir would be made to (1) satisfy domestic and irrigation requirements between Diablo and Falcon Reservoirs; and (2) maintain sufficient storage of U.S. water in Falcon Reservoir to supply domestic and irrigation requirements downstream therefrom. Releases of U.S. waters together with Mexican waters will be made as necessary at the minimum practical rates. If power facilities are provided at Diablo Dam, releases of U.S. water for other purposes will be utilized incidentally for the generation of power; and to an extent not inconsistent with the use of water for domestic and irrigation purposes, additional releases may be made for power generation. As proposed, Diablo Reservoir would have a total capacity of 5,660,000 acrefeet consisting of 2,110,000 acre-feet of flood control storage, 3 million acre-feet of conservation storage, and 550,000 acre-feet of silt-retention storage. The U.S. share would be as follows: (1) flood control, 1,055,000 acre-feet; (2) conservation, 1,686,000 acre-feet; and (3) silt retention, 309,000 acre-feet. Total first cost of the project is estimated at $71,160,000, of which $46,521,000 would be provided by the United States. The benefit-cost ratio for the United States is estimated to be 1.96 to 1 for a 50-year period of analysis and 2.48 to 1 for a 100-year period. The report states that one of the benefits to be derived from the proposed Diablo Dam and Reservoir is the betterment of the chemical quality of the water for downstream municipal use, and a decrease of the dangers of stream pollution which has occurred in the past during periods of low flow. The chemical and organic pollution of the Rio Grande is of major concern to both public and private groups and any project which would improve the quality of the water by the maintenance of minimum adequate flows would be extremely beneficial to the health and welfare of the residents of this area. The report, however, does not indicate a minimum flow to be maintained in the river. This suggests the possibility that while river water quality may be substantially improved at times, no improvement or even deterioration from present conditions may occur at other times. It is, therefore, strongly recommended that a minimum flow be maintained in all sections of the river and that no reductions from present minimum flows be permitted. It is further recom mended that agreement be reached with parties concerned relative to desired river water quality criteria and to the amount of minimum flow that should be maintained to meet those criteria. With regard to water requirements for municipal and industrial uses, the Public Health Service concurs with the estimates presented in the report. The Public Health Service also concurs with the material presented in the report covering the mosquito control aspects of the proposed project. However, on page 102 under paragraph 67 of the report it is suggested that the words "Public Health Service" be deleted and further that the sentence read, "corrective measures for mosquito control on the U.S. side should be coordinated with the Texas State Department of Health." F U.S. DEPARTMENT OF THE INTERIOR, Hon. R. R. RUBOTTOM, Jr., DEAR MR. RUBOTTOM: This is in reply to your letter of October 30 transmitting for our views a report entitled "Proposed Diablo Dam and Reservoir," September 1958, prepared by the U.S. section of the International Boundary and Water Commission, United States and Mexico. At various times during the past 4 years, the U.S. section of the IBWC consulted the Assistant Commissioner and Chief Engineer, Bureau of Reclamation, in connection with the investigation of Diablo Dam and Reservoir, particularly in respect to design problems. That office finds that its suggestions for clarification of some of the hydrologic aspects of development and changes in designs and cost estimates were considered in the September 1958 report. The Assistant Commissioner and Chief Engineer suggests, however, that when final designs for the dam are prepared, further consideration be given to modification of floodrouting criteria and design of the section of the dam at the U.S. penstocks. He advises that any changes as a result of such modification would not affect significantly the overall estimated cost of the proposed development. We assume that the U.S. section will consult further with the Bureau relative to the final plans and designs for construction and operation of the dam as provided by the interdepartmental agreement of February 3, 1944. The Bureau of Reclamation is authorized to rehabilitate the Mercedes division, Lower Rio Grande rehabilitation project, and a loan has been granted to Cameron County Water Control and Improvement District No. 1 for rehabilitation of its irrigation system in the lower valley under the Small Reclamation Projects Act. The Bureau is also studying other potential water resource improvements in the lower valley. The Texas Board of Water Engineers after review of the report of the U.S. section of the IBWC approved the proposal, subject to the following qualifications: "(a) The proposed Diablo Dam must be integrated with other water conservation activities on the Rio Grande below Fort Quitman, Tex., and operated in such manner that the amount of water allocated to the U.S. section and available for release from and through Falcon Dam, which would otherwise be available for use by existing lawful diverters and appropriators of the U.S. section below Falcon Dam, will not be impaired or diminished; and "(b) All releases of conservation storage water allocated to the U.S. section from the proposed Diablo Dam for hydroelectric power purposes shall be subordinated to higher priority or preference uses of lawful diverters and appropriators of the U.S. section below Diablo Dam and in accordance with State law." Among other things, we understand the qualifications of the Texas Board of Water Engineers to mean that existing lawful diverters and appropriators of water below Falcon Dam will continue to have available for beneficial consumptive use at least the same amount of water, including that provided through regulation by storage, as would be available to such users without Diablo on the river. On the basis of this understanding we concur. The Department of the Interior has a further vital interest in the construction and operation of the proposed Diablo Dam and Reservoir. This interest stems from the Secretary's statutory responsibilities (act of June 18, 1954, 68 Stat. 255) for allocation of capital investment to power and marketing of electric energy generated at the downstream Falcon Dam. The law provides that the energy must be marketed at rates to recover costs of producing and transmitting the energy and amortizing the allocated capital costs. Although an interim power rate schedule is in effect, it has been the Bureau of Reclamation's position that a final allocation of costs to power cannot be made until the upstream Diablo Dam and Reservoir are planned in detail or constructed, so that the firming effect of such storage on generating capacity at Falcon can be reflected in the power benefits. Several years of operating experience at Falcon may be required to form a basis for agreement in this matter. On May 1, 1957, we advised the Secretary of State that we expect to use data and power system experience in the determination of a proper allocation of costs. The report of the U.S. section of the IBWC concludes that construction of a Federal powerplant would not be economically justified on the basis of costs estimated by the U.S. section and energy values or benefits assigned by the regional office of the Federal Power Commission. That office concluded that dependable capacity could not be assigned with the proposed type of operation and that all energy generated at Diablo would be classified only as fuel-replacement energy with an at-site value of 1.7 mills per kilowatt-hour. The regional office of the Federal Power Commission concedes, however, that this value does not necessarily determine the rates at which energy could be sold either at the site or at the market. Our present contracts for the sale of power from Falcon Dam, which are based on capacity being available a percentage of time, indicate that higher revenues than 1.7 mills can be anticipated at the Diablo project. Revenues from the sale of power generated at the Falcon Dam hydroplant during 1958 averaged 3.2 mills per kilowatt-hour. The report of the Bureau of Sport Fisheries and Wildlife, U.S. Fish and Wildlife Service, dated September 1958 and included as appendix A to the report of the U.S. section of the IBWC, is a review draft and was circulated for the comments of interested agencies. We are attaching a copy of the report approved by the Bureau of Sport Fisheries and Wildlife, U.S. Fish and Wildlife Service. It is requested that this report, dated November 1958, be substituted as appendix A for the preliminary report dated September 1958, and that the discussion on page 113 of the report of the U.S. section beginning on line 5 and ending on line 18, "A survey of sports fishing benefits * * * would therefore be approximately $176,000 annually" be deleted and the following paragraphs substituted. “Although this project will create an impoundment type of fishing and increase total fisherman use in the project area, it will also destroy, through inundation of part of the Devils River, one of the most valuable reaches of stream fishing in Texas. Mitigation of this stream fishing loss, as separably identifiable from reservoir fishery gains, could be achieved through the development described in paragraph 89 of the November 1958 report of the Bureau of Sport Fisheries and Wildlife at a cost of $544,000. In the judgment of that Bureau, the value of the fishery losses to be mitigated would justify this expenditure. The unique nature of this type fishery in this part of Texas merits adoption of the mitigation measures. "The Bureau of Sport Fisheries and Wildlife is of the opinion that, if this mitigation measure is not included in the project plan, the reservoir fishery benefits should be reduced by this amount which would represent an annual equivalent of $19,200 over a 50-year period or $14,900 over a 100-year period when amortized at 21⁄2-percent interest. "The Bureau of Sport Fisheries and Wildlife has evaluated the fish and wildlife benefits of the project, exclusive of the Devils River fishery losses, in terms of the lowest cost alternative justifiable single-purpose project which would provide comparable benefits. The capital cost of this alternative project and the corresponding measure of the benefits, which in the judgment of that Bureau justify it, would be $4,672,600. This would represent an annual equivalent of $164,900 over a 50-year period or $127,600 over a 100-year period when amortized at 22 percent. These benefits are dependent upon adoption of the recommendations in paragraph 99 of the appended report." By mutual agreement with water resource construction agencies of the Federal Government, it has become customary for the reporting officers to incorporate in their reports specific references to the recommendations made by the U.S. Fish and Wildlife Service and to the actions thereon proposed by the reporting agency. We believe it would be helpful if the U.S. section of the Commission were to include in its report specific references to the recommendations of the U.S. Fish and Wildlife Service for preservation and enhancement of fish and wildlife resources and a statement of the U.S. section's proposed action. The National Park Service will be pleased to cooperate with project sponsors in further studies on recreational potentials, development, and use. We appreciate the opportunity of reviewing your proposal. Sincerely yours, FRED G. AANDAHL, Assistant Secretary of the Interior. |