materials for calking grout pipes; brazing and soldering materials for copper expansion and seal. ing strips; muriatic acid for use in the construction of hollow-tile walls; and also all other required materials not specifically mentioned in this paragraph or in Paragraph 27, that will not become a part of the completed construction work. The contractor shall haul all these materials as well as all materials delivered to the contractor by the Government from the point of delivery to the site of the work. The cost of hauling, storing, and handling all the materials described above and of furnishing all the materials required to be furnished by the contractor shall be included in the unit prices bid for the work for which the materials are required. - 29. Preference for domestic articles or materials.-Preference will be given to articles or materials of domestic production, conditions of quality and price, including duty, being equal. Unless otherwise stated in the bid, it will be understood that domestic articles or materials only will be used, and the use of foreign articles or materials will not be permitted unless (1) they are of better quality, or (2) being equal in quality, will be furnished at lower cost to the Government, or (3) domestic articles or materials are not available. The term “domestic articles of materials” in this connection means articles or materials manufactured or assembled in the United States or its possessions. 30. Foundation and other test drilling records,-The drawings included in these specifications show the available records of test drilling done at the dam site during 1922 and 1923. The Government does not guarantee any interpretation of these records. Additional drilling is in progress at the date of the issuance of these specifications and available information, including logs of holes and drill cores, for all of the drilling done, will be available for the information of bidders and the contractor at the office of the Bureau of Reclamation at Las Vegas, Nev. The contractor must assume all responsibility for deductions and conclusions as to the nature of the rock or other materials to be excavated, for the difficulties of making and maintaining the required excavations and doing other work affected by the geology at the site of the work, and for the final preparation of the foundations for the dam, power plant, and other structures. 31, Report on geology.-A report on the geology of the Boulder Canyon and Black Canyon dam sites and reservoir sites on the Colorado River was prepared in 1923 by Geologist F. L. Ransome, then with the United States Geological Survey. A copy of this report is available at the office of the Bureau of Reclamation at Denver, Colo., and another copy at the office of the Bureau of Reclamation at Las Vegas, Nev., where prospective bidders and the contractor may consult it, but permission will not be given to remove the copies from the respective offices. The Government assumes no responsibility for the interpretation of this report and the prospective bidders and the contractor must assume all responsibility for deductions and conclusions as to geologic formations and conditions which might affect the required operations under these specifications. 32. River discharge records,-Hydrographs of the Colorado River at different points are shown on the drawings. Except for hydrographs after October 1, 1929, the data used in preparing the hydrographs were taken from water supply papers published by the United States Geological Survey. Estimated discharge curves for the Colorado River at Black Canyon dam site above and below the dam have also been prepared and are included with the drawings. The hydrographs and the discharge curves are included in the drawings for the convenience of bidders and the contractor, but the Government does not guarantee their reliability or the accuracy of any of the figures on these drawings, - - . .

33. Approval of plans by Colorado River Board.—Public Resolution No. 65 adopted by the Seventieth Congress and approved by the President on May 29, 1928 (45 Stat. 1011), authorized and directed the Secretary of the Interior to appoint a board of engineers and geologists, designated the Colorado River Board, to examine the proposed site of the dam and to review and approve the plans therefor. The drawings included with these specifications are those which have been submitted to the Colorado River Board for approval. Final approval has been given to the designs for the diversion works and other features which must be completed during the early stages of construction. Final approval of plans for the section of the dam and for the spillways is deferred awaiting the results of further analysis and of tests on models of these features. These tests are being conducted at the time of issuing these specifications and the final design drawings, for these features, as approved by the Colorado River Board, will be made available to the contractor early in the construction period and in advance of the requirements therefor. Construction of the dam and spillways shall not be commenced until these final approved drawings are furnished to the contractor. Required changes in all features will be handled under the provisions of articles 3 and 4 of the contract. The contractor's plant shall be laid out and his operations shall be conducted in a manner to accommodate any reasonable change in the location and design of the dam, power plant, and appurtenant works, or any part thereof, without additional cost to the Government.

34. Use of Boulder City as camp site.—Owing to the inaccessibility of the work, the magnitude of the operations, and the severe weather conditions during a large part of the year on account of extreme heat, and having in mind the health, comfort, and general welfare of those engaged on the work, it has been decided to establish the Government town of Boulder City, Nev., located approximately 23 miles southeast of Las Vegas, Nev., as shown on the drawings. A general plan of the town has been made, including provision for water supply and sewerage disposal and a layout of streets, sidewalks, city lighting, and other municipal improvements. Construction of these improvements will be in progress at the time award is made for the work under these specifications and it is expected that the water supply and sewerage systems for the town will be completed ready for use within six months thereafter. The town will be for the joint use of the Government, the contractor, and the employees of both, and for others who may be permitted, through leases or otherwise, to engage in business therein or to follow their trades or practice their professions. Certain areas as determined by the contracting officer will be set aside in Boulder City for the use of the contractor as sites for office and headquarters buildings, warehouses, garages, commissary, hospital, dormitories, boarding houses, homes for the contractor's employees, and other incidental purposes. The plans and type of Construction of the buildings to be erected by the contractor and his employees in Boulder City shall be subject to the approval of the contracting officer and all such buildings shall be connected with the water supply and sewerage systems of the town. Expensive or permanent types of construction will not be required, but the buildings erected by the contractor or his employees shall have a reasonably attractive appearance and no unpainted shanties or tar paper shacks will be permitted. When the water supply system is completed and in operation, the contractor and his employees may obtain water from it for domestic and other purposes, as required for use in those portions of Boulder City set aside for the use of the contractor and his employees. The contractor shall furnish and install at his own expense all necessary piping for obtaining the water from the city mains, such installations to be in accordance with plans and specifications approved by the contracting officer. For the use of the land set aside for the 90ntractor and for the municipal services and facilities made available for the benefit of the °ontractor and his employees, the contractor will be charged at the rate of five thousand dollars ($5,000) per month for and during the entire period from the date when the water system for the town is first put in operation to the date of final acceptance of the work under these speci. fications by the Government, such charge to also cover the contractor's proportionate part of the cost and expense of operation and administration of the town. In addition to such charge the contractor will be charged monthly for all water used at the rates to be established for water service, not to exceed fifty cents ($0.50) per thousand gallons. Electricity for domestic purposes will be made available to the contractor upon request, from the electrical distribution system to be provided by the Government in Boulder City, for which the contractor will be charged at the rates to be established. The contractor will be permitted to sublease to his employees for home sites any part of the land set aside for his use, but such land shall not be used or subleased for business or professional enterprises or concessions, except commissary, hospital, dormitories, boarding houses, and clubhouses equipped with barber shops and other facilities for the use of the contractor's employees. After the date of final acceptance of the work the contractor shall have the right to lease the land at the regular established rates and to pay for water and electricity or other conveniences at the regular established rates: Provided That should the contractor not elect to exercise the right to lease the land, the improvements placed thereon shall be removed by the contractor within six months from the date of final acceptance of the work, subject to the supervision and approval of the contracting officer: And provided further, That if such improvements are not so removed by the contractor they shall become the property of the Government. It is contemplated that Boulder City will be under the exclusive administration and control of the Government through the instrumentality of a commission to be appointed by the Secretary of the Interior. The contractor will be afforded the privilege of nominating one member of such commission. Nothing contained in this paragraph shall be construed as in any wise obligating the Government to continue to operate the town of Boulder City beyond such date as may be determined by the Secretary of the Interior, or to preclude the Secretary of the Interior from transferring the control and operation of such town to any instrumentality other than the Government after the date of final acceptance of the work under these specifications. The main camp of the contractor and homes for not less than eighty (80) per cent of the contractor's employees shall be established and maintained in Boulder City, and except as may be permitted in writing by the contracting officer for small isolated camps, such as at the Arizona gravel deposits, and for necessary boarding and lodging facilities at the dam site, the contractor and those operating or associated with the contractor will not be permitted during the period of the contract to establish camps at other sites. The contractor may, with the consent of the contracting officer, use for plant, storage, and incidental purposes any land which is the property of the Government in the vicinity of the work but outside the area to be flooded by the reservoir, except such reservations as are made by the Government for its use or the use of other contractors: Provided, That if private land is 80 used by the contractor, the contractor shall make all necessary arrangements with the owner and pay all rentals or other costs connected therewith: Provided further, That such use shall not interfere with any part of the work or with the work of other contractors or the Government: And provided further, That the Government will assume no responsibility for damage to or interference with the contractor's use of such land due to any operations under the contract or to floods due to construction of the dam or otherwise. 35. Drinking water at site of works,—During the construction period the contractor shall provide an adequate supply of pure cool water for drinking purposes at the site of all works. This water shall meet all local or State requirements for domestic water, and the quality and adequao of the supply of water shall be subject to the approval of the contracting officer. The entire cost of furnishing drinking water as required by the provisions of this paragraph shall be included in the unit prices bid for the various items of work in the schedule. The contractor shall furnish water for use by the Government in the testing laboratory and for other purposes at the site of the work and payment therefor will be made at the price per thousand gallons established for use of water by the contractor in Boulder City. to 36, Electric power for construction purposes.—A contract has been entered into with the Southern Sierras Power Co. and the Nevada-California Power Co. to furnish power for construction purposes. This power will be delivered at 2,300 volts, 3-phase, 60 cycles, at a substation near the dam'site in such amounts as desired up to a maximum of 15,000 kilowatts. The power will be transmitted from San Bernardino or Victorville, Calif., over a single transmission line about 240 miles in length and the power service will be subject to such interruptions as may be expected in the normal operation of a line of this length. The contractor shall provide, at his own expense, whatever amount of stand-by power he may consider necessary to supplement the delivery of power over a single transmission line, to insure continuity of operation of the essential part of his construction plant. The contract with the Southern Sierras Power Co. and the Nevada-California Power Co. requires that power shall be available for use not later than June 25, 1931, and the power may be available thirty days or more previous to that date, but the Government does not guarantee that power will be available for use by the contractor by June 25, 1931. Beginning with the date when power is first used, but in no event later than June 25, 1931, unless power is not available on that date, in which event beginning on the date when power is available, the contractor will be charged monthly for such power as is used by the contractor at the following rates:

(a) Power furnished by power companies.—A readiness to serve charge of seventeen thousand onehundred six dollars ($17,106) per month plus an energy charge of six mills ($0.006) perkilowatthour. For fractional months at the beginning or end of the period, the readiness to serve charge shall be computed in accordance with the actual number of days that power is so obtained. Should suspensions occur in the delivery of power exceeding twenty-four (24) hours in duration, the total elapsed time during which the delivery of power is suspended in any calendar month in excess of twenty-four (24) hours will be ascertained and a deduction of twenty-five dollars ($25) will be made from the monthly bill to the contractor for each one quarter (%) hour of such suspension in excess of twenty-four (24) hours. Suspensions of less than twenty-four (24) hours or prearranged suspensions of longer duration which are approved in writing in advance by the contractor will not be considered in determining the total elapsed time during which delivery is suspended in any one calendar month.

(b) Powerfurnished from Hoover power plant.—When power becomes available from the power plant at the Hoover Dam the Government will terminate the contract with the Southern Sierras Power Co. and the Nevada-California Power Co. and will thereafter serve power to the contractor from the Hoover power plant. The contractor will be charged monthly for such energy *S is received from the Hoover power plant at the rate of six mills ($0.006) per kilowatt-hour *nd no readiness-to-serve charge will be required. After termination by the Government of the contract with the Southern Sierras Power Co. and the Nevada-California Power Co., no

oductions will be made for suspensions in the delivery of power. The contractor shall furnish,

onstruct, and maintain at his own expense the necessary circuits, equipment, and material for distributing the power from the substation and from the Hoover power plant, and all equip*nt, material, and work in connection with the contractor's electrical installation shall conform to specifications and plans acceptable to the contracting officer and shall be maintained ** safe and satisfactory operating condition. On each circuit leaving the substation or the Hoover power plant, the contractor shall furnish and install an automatic oil circuit breaker, having an interrupting capacity of not less than 26,000 amperes at 2,500 volts, so that troubles on one circuit will not interfere with the operation of other parts of the distribution system, and a watt-hour meter for measuring the energy used on the circuit. Meters shall be subject to test by the Government at any reasonable time at the option of the Government and will also be tested upon the request of the contractor. If test discloses that the error of a meter exceeds two per cent (2%) it shall be adjusted so that the error shall not exceed one per Cent (1%) and proper correction shall be made in the amount of energy recorded by said meter as used in the thirty (30) day period immediately preceding the test and such correction shall constitute full adjustment of any claims arising out of such inaccuracy. The energy delivered will be determined from the readings of these meters: Provided, That should the meters fail to register, the energy delivered will be estimated from the best information available. Power furnished to the contractor at the substation near the dam site and from the Hoover power plant is for use in the contractor's operations in that vicinity only and power will be made available from the Boulder City electric distribution system for the contractor's camp and other requirements in Boulder City at rates to be established for the sale of power in Boulder City. 37. Sand and gravel deposits.-Sand, gravel, and cobbles for concrete and Sand for mortar, grout, and gunite shall be obtained by the contractor from natural deposits on the Arizona side of the Colorado River about 8 miles upstream from the dam site. These deposits will be referred to in these specifications as the Arizona gravel deposits and are so designated on the drawings which show their approximate location. The deposits are the property of the Government and will be turned over to the contractor at the #'s. contractor commences operations, for the purpose of furnishing the aggregates require toe specifications. No charge will be made to the contractor for sand, gravel, and cobbles $n from these deposits. The fact that sfosfom which the aggregates are to be obtained shall not be construed as constituting the 6fterol of all materials taken from the deposits of, São ed quality of all such materials used *IUlo site of the deposits, or so much thereof as is required, of top soil, vegetatio so P brusosód, loam, unsuitable sand, gravel and cobbles, and other objectionable matter o d §5? and maintain the deposits in a suitable condition for the excavation and 6. O o material in a manner satisfactory to the contracting officer and so lo o at all times in the most economical and practicable

manner the entire yielderoa.bl rials in the portion of the deposits being worked. Combustible materials to oom theoeposits shall be burned and other rejected materials shall be disposed of by théontrâctor in a manner satisfactory to the contracting officer. Since the provisions of these specifications, as stated in other paragraphs, require that water be stored in the reservoir prior to the completion of the work and as such storage will flood the gravel deposits, it will be necessary for the contractor to remove and store sufficient material from these deposits to complete the work after the deposits have been flooded. The storage of this material may be above the water surface of the required storage at any location which may be selected by the contractor and approved by the contracting officer. The contractor shall assume all risk of damage to his plant and equipment at the gravel deposits, by reason of seasonal floods in the river adjacent to the gravel deposits which possibly may, after construction of the cofferdams, reach an elevation of 720 or higher. The cost of all work required by this paragraph shall be included in the unit prices bid in the schedule for the items of work in which the materials obtained are used, which unit prices shall also include all expenses of the 000"

****reening, Washing, furnishing, hauling, storing, mixing, and other operations necessary on the aggregates,