It is proposed to allot $15,000 of the Anzalduas Dam funds to the Nogales flood-control project to modify existing works.

The amount officially set aside for the acquisition of the Andrade properties from the Imperial Irrigation District is $600,000. However, due to the flood on the Rio Grande in June 1954, congressional concurrence was obtained to divert temporarily $200,000 of these funds for the purpose of completing the investigative phase of the upper dam by June 30, 1955.

RIO GRANDE INTERNATIONAL DAMS PROGRAM

In article 5 of the 1944 treaty, the two Governments agreed to construct jointly through their respective sections of the Commission, the dams required on the main channel of the Rio Grande, for the optimum regulation and use of the annual flow of the river. The article further provides that 1 of the storage dams shall be constructed in the section between Santa Helena Canyon and the Pecos River; 1 in the section between Eagle Pass and Laredo, Tex.; and a third in the section between Laredo and Roma, Tex.; and states that one or more of the stipulated dams may be omitted and others than those enumerated may be built subject to the approval of the two Governments. It further provides that construction of the international storage dams shall start with the lowest major dam which shall be completed within 8 years of the date of entry into force of the treaty.

Falcon Dam

Construction of the lowermost of the international storage dams, Falcon Dam, was completed in fiscal year 1954, and storage and regulation of the international waters began in August 1953. The dam was dedicated by President Eisenhower and President Cortines of Mexico in October 1953. Generation of hydroelectric power at Falcon Dam began in October 1954, with deliveries of the United States share being made to the Secretary of the Interior for transmission and disposition pursuant to the terms of Public Law 406, 83d Congress.

The benefits which have already accrued from the Falcon Dam and Reservoir project in its first year of operation are noteworthy. Before its completion, the dam, by installation of expedient and provisional works, impounded floodwaters in August 1953 which, together with smaller flood inflows in the months immediately following, provided a full supply of domestic and irrigation waters for the lower Rio Grande Valley in both the United States and Mexico during the year ending June 1954. The gross value of crops produced in that period in the portion of the valley in Texas is estimated to exceed $100 million. If the dam had not been built, the natural flow of the river would have permitted diversion on only about half of the total irrigation requirements and the remainder would have wasted to the Gulf of Mexico.

In the last days of June 1954, when the reservoir was nearly depleted, a recordbreaking flood poured into the Rio Grande from the Pecos and Devils Rivers, having a peak discharge of about 1,100,000 second-feet at Del Rio, Tex., nearly twice that of the previously recorded peak, and including more than 2,500,000 acre-feet of water. This flood, while it took a disastrous toll of lives as well as property in the border cities of Del Rio-Ciudad Acuna, Eagle Pass-Piedras Negras, and Laredo Nuevo Laredo, it was entirely contained in Falcon Reservoir,

saving the Lower Rio Grande Valley in Texas, where about 350,000 people reside and properties are valued at about $0.5 billion, from damages which it is estimated would have been at least $55 million. The flood magnitude would have far exceeded that for which the Lower Rio Grande Valley flood-control project was designed. Thus, in the first year of operation of the Falcon project its accrued benefits to the United States, from flood control alone, amounted to more than the total cost of the project to the United States-estimated to be $37,650,000. These flood-control benefits are in addition to those attending the full regulated supply of irrigation waters provided during the first year of operation, which are estimated by residents of the lower valley to have enabled the production of crops worth at least $40 million more than would have been produced without Falcon Dam.

Moreover, storage of the June 1954 flood waters which would have otherwise wasted to the gulf, reasonably assures an adequate supply of domestic and irrigation waters for the existing developments in the valley during 1955. Further, incidental to releases at the dam for those purposes, generation of hydroelectric power during the coming year is reasonably assured. An additional benefit already accruing from the dam is the improvement of the quality of the irrigation water attending the use of stored floodwaters of appreciably lower mineral content than that of the ordinary river flows.

From prior year funds appropriated for the Falcon project $3,524,861 are available, of which $2,300,292 will be required during the current fiscal year.

It is anticipated that the balance of $1,224,569 will be required in fiscal year 1956 for payment of claims of the construction contractor and unforeseen contingencies. The contractor has advised that he will file a claim which, from information available, will amount to about $1 million. The balance is unforeseen contingencies.

Upper dams

The proposed upper dams are a major part of the Rio Grande international storage dams project which the two Governments agreed in article 5 of the water treaty of 1944 to construct jointly for the optimum regulation and use of the greatest annual quantity of the annual flow of the river. The main features and present status of work in connection with the upper dams project are briefly described as follows:

In September 1948 the Commission began comprehensive investigations of the dam site possibilities in the entire reach of the Rio Grande from Fresno Creek, in the upper section of the Big Bend country, downstream to Del Rio, Tex., a distance of 345 river-miles. The principal elements of these investigations consisted of topographic, geological, and hydrological surveys and engineering economic studies. During the course of these investigations a total of 45 prospective dam sites were studied, 31 of which were eliminated from further consideration because of unfavorable features, such as hazardous geological conditions, prohibitive construction costs, inadequate reservoir capacity, or because they are not strategically located for the most advantageous control and utilization of the river flow.

Results of the preliminary studies were reviewed by a Board of Engineers and technical advisors of the Commission during a conference in July of 1953. Following analyses and comparison of the relative merits of the 14 sites still under consideration, it was concluded that the Diablo site, by virtue of its location below the Pecos and Devils Rivers, would afford the greatest conservation and flood control benefits and the Board therefore recommended that this site should be the first to be subjected to detailed investigations.

In combination with the Falcon Dam now in operation, a dam at the Diablo site, of the impounding capacity under consideration, would not only provide urgently needed additional conservation of the available water supply of the Rio Grande for irrigation and domestic uses, but it would also regulate to channel capacity such disastrous floods as originated on the Pecos and Devils Rivers in June of 1954. The many lives lost and the multimillion dollar property damage in both countries as a result of this flood have tragically emphasized the urgent need for the Diablo Dam for flood-control purposes alone. Incidental to these purposes the Diablo Dam would develop a large block of hydroelectric energy. Late in September 1954, a joint conference of geological consultants for the Commission convened to study the findings of the first phase of the field investigations of the Diablo Dam sites. These field explorations, largely completed at that time, had revealed no seriously adverse geologic aspects with respect to any of the four alternate sites and, following careful field inspections and a review of the results of the investigations, the panel of consultants recommended that site No. 1,

the farthest upstream and the most favorable from the standpoint of economy of construction, be selected as the most suitable. Immediately thereafter the Commission entered into a program of specific site explorations and initiated office engineering studies to determine the most appropriate basic designs for a dam at the Diablo No. 1 site and the determination of the respective reservoir capacities required at this site for optimum regulation of the river's flow from the standpoints of conservation, flood control, and power development. It is anticipated that by March of 1955 the specific site and related studies will have been sufficiently advanced to enable development of agreements with Mexico as to the general design of the dam, the total construction cost and division thereof between the 2 countries and recommendations by minute to the 2 Governments that the second of the major international storage dams contemplated by the treaty be constructed at the Diablo site.

Anzalduas Dam

LOWER RIO GRANDE FLOOD-CONTROL PROJECT

(Authorized by the act of August 19, 1935, and Public Law 495, 82d Cong., approved July 10, 1952.)

The proposed Anzalduas Diversion Dam is an integral part of the lower Rio Grande flood-control project, developed by the International Boundary and Water Commission in 1932, approved by the Governments of the United States and Mexico through a formal exchange of notes in October 1932, and authorized on behalf of the United States by the congressional acts referred to above.

Anzalduas Dam, recommended by the Commission in Minute 196, and approved by the two governments, is essential to both the United States and Mexico in order to effect, in accordance with the design of the flood-control project, diversion into the constructed floodways of flood waters in the river in excess of the capacity of the river channel downstream from the site of the diversion structure. Floods of a magnitude requiring diversion into the floodways originate in the watershed below Falcon Dam, and infrequently spills from Falcon may result in appreciable floods in the valley. Each government has completed its financial arrangements to begin construction of the diversion structure. However, in the case of the United States, the act of August 19, 1935, requires that all rights-of-way located in Hidalgo and Cameron Counties, Tex., are to be donated gratuitously to the United States. Following the failure in 1953 of Hidalgo County to approve a bond issue to acquire the needed rights-of-way within its boundaries, Cameron County, undertook to finance the entire estimated cost of the rights-of-way, amounting to $500,000. In August 1954, the Hidalgo County court at law ruled that Cameron County had the right to condemn lands in Hidalgo County for the project, opening the way for the former county to proceed with the acquisition. Although the primary purpose of the dam is as a flood-control structure, it may be used to effect irrigation or other diversions, in which event, in the case of the United States, provision is made in Public Law 495, 82d Congress, for reimbursement to the Government of the costs of the dam attributable to irrigation or other water supply purposes, when and if the structure is so used.

Anzalduas Dam will be a concrete structure located in the channel of the Rio Grande about 5 river miles above the Hidalgo-Reynosa Bridge and approximately midway between the Mission and Hackney Lake Inlets to the main floodway of the lower Rio Grande flood control project. It will be about 525 feet wide between end walls and will have a length of 165 feet, including the spillway apron. It will be founded on rock and the crest of the gate seats would be set at the level of the present river bottom. Control and diversion of floodwaters will be effected by operation of 6 large roller-type gates, each of which will be 75 feet long, 14 feet in diameter, with 7-foot lip, making the overall height 21 feet. In addition to the concrete gated section, a low earth dike some 4,600 feet long will be required on the United States side of the river.

Total estimated cost of the United States share of the dam, including related works, located wholly within the United States, is $4,319,416, divided by features, as follows:

Upon conveyance by Cameron County of all necessary rights-of-way to the United States, the conditions imposed on the expenditure of current appropriations will have been met and construction can be initiated within 60 days on the related features located wholly within the United States and within 90 days on the joint construction of the dam structure. In addition to the $1,500,000 appropriated in 1953 for Anzalduas Dam, there are available from construction funds of the lower Rio Grande flood-control project $411,264 for the related works of the dam. It is felt that this $1,911,264 will be sufficient for 1955 and 1956 to assure full participation by the United States in this joint activity.

NOGALES FLOOD PROJECT

(Authorized by act of August 19, 1935; exchange of notes between the governments for original project.)

In 1936, pursuant to the above authorization, the Commission completed construction of a concrete lined flood-control channel extending through the main parts of the adjoining border cities of Nogales, Sonora, and Nogales, Ariz., to correct an international flood problem. At the termination of the lined channel, a stilling basin was provided to check the velocity of flow prior to its entering the natural channel below. In 1948, due to the expansion of Nogales, Ariz., the lined channel was extended beyond the stilling basin to the northerly limit of that city.

The proposed work consists of backfilling and placing concrete floor at channel grade over the stilling basin. This work was included in the plans when the lined channel was extended but was postponed in order to determine if it was actually needed. Experience has shown that the gravel and sand carried by arroyo flows will not naturally fill the basin, that each rainstorm leaves in the basin stagnant pools of water in which organic matter decays and mosquitoes. breed, creating an unsanitary condition adversely affecting the nearby residential area of Nogales, Ariz. Correction of this condition, urged by the citizens of Nogales, is therefore now indicated.

CALEXICO-MEXICALI SANITATION

In the water treaty of 1944, the two Governments agreed to give preferential attention to the solution of all border sanitation prok lems and each Government authorized its respective section of the Commission to join in an in estigation of the sanitation problem at the adjoining border cities of Calexico, Calif.-Mexicali, Baja Calif. By Public Law 786, 81st Congress (64 Stat. 486), the Secretary of State is authorized, subject to certain conditions, to enter into an agreement with the appropriate officials of Mexico for the construction, operation, and maintenance by the International Boundary and Water Commission of a sanitation -project for the two cities.

The city of Calexico (population about 6,500) and the city of Mexicali (population about 70,000) are separated only by the boundary line. Neither has any sewage treatment works. Raw sewage from Mexicali discharges into an open ditch which passes through the center of that city, thence into the channel of New River which generally contains little or no dilution waters. In this channel the sewage flows north to cross the international boundary into the United States within 1,500 feet of the business district of Calexico, and at a point about 2,000 feet farther north, the raw sewage of that city empties into the same channel. The result is a seriously threatening health hazard to the populations of both border communities, an extremely obnoxious stench in both communities, and unsanitary conditions in the stream farther north, in the United States, where it passes through the Imperial Valley to the Salton Sea. Federal, State, and local health authorities as well as the local residents in both countries, are urging immediate remedial action.

The Commission began study of the problem in 1947 and 1948, but development of remedial measures was delayed by (1) investigations by Mexico of the feasibility of construction of a plant in Mexicali for treatment of its sewage, and (2) lack in Mexicali of sewage collection facilities. Mexico now concurs that an international sewage treatment plant is the most feasible means of solving the problem, and in April 1954 Mexico began as a domestic project, the construction of sewage collection facilities in Mexicali.

Preliminary surveys have been made and negotiations are in process by the Commission with the view to reaching an agreement and submitting to the two Governments recommendations for the construction of the international sewage treatment works required, and the division of cost thereof between the two

Governments. Concurrently, negotiations are in process between the United states section and the city of Calexico with the view to reaching an agreement with that city as regards its payment of an equitable share of the cost allocable to the United States, as stipulated in Public Law 786, 81st Congress.

OPERATION AND MAINTENANCE, INTERNATIONAL BOUNDARY AND WATER COMMISSION, UNITED STATES AND MEXICO

Operation and maintenance of completed projects, or of completed integral segments of a project under construction, as authorized by existing treaties and/or public laws, are wholly financed from this appropriation.

The objectives of the program of operation and maintenance are:

(1) To assure, insofar as possible, maximum efficiency and usefulness of the projects in achieving the purposes of original construction; (2) to safeguard, insofar as possible, the capital investment already made by the United States Government; and (3) to continue the joint program of international cooperation with Mexico in the operation of international works. The following table indicates total requirements for operation and maintenance for fiscal years 1954, 1955, and 1956.

1 Includes estimated contributions from Willacy and Hidalgo Counties, Tex. (pursuant to the act ap proved April 25, 1945 (59 Stat. 89)).

EL PASO PROJECTS

These projects located above and below El Paso, Tex., consist of: (a) The Rio Grande canalization project, (b) American Dam and Canal project, and (c) Rio Grande rectification project.