119. Concrete in paving for upstream cofferdam.—The entire upstream slope of the upstream cofferdam shall be surfaced with a 6-inch thickness of continuous reinforced concrete paving, as shown on the drawings or as directed by the contracting officer. The paving shall terminate in the concrete cut-off wall, into which the top of the steel sheet-piling at the upstream toe of the cofferdam shall extend. The top of the sheet-piling shall be encased in the concrete at the bottom of the cut-off wall so as to form a continuous structure. The concrete paving shall be placed on the rock blanket which has previously been prepared for paving, as provided under paragraph 79 of these specifications. The concrete paving shall be laid in strips not over 16 feet in width running up and down the slope of the cofferdam, and construction joints, across which the reinforcement bars shall be continuous, shall be provided between the strips, as shown on the drawings or as directed by the contracting officer. When, for any reason, it is necessary to interrupt the placing of concrete in a strip for a sufficient length of time to permit the concrete taking a permanent set, thereby forming a definite construction joint, the contractor shall provide a suitable temporary form which will produce a clean, unbroken keyed surface normal to the slope of the cofferdam, which surface shall intersect the face of the paving in a horizontal line. The steel reinforcement shall be continuous across the construction joint. After the removal of the temporary form at the joint, and immediately before placing of the concrete in the strip is resumed, the contractor shall carefully clean and wet the surface of the joint to insure a good bond between the fresh concrete and the concrete previously placed. Feather-edged or irregular construction joints will not be permitted. The surface of the concrete paving shall be floated to a uniform and dense finish by means of wooden floats. Measurement of the concrete paving for payment will be made to the neat lines, as shown on the drawings or as prescribed by the contracting officer. No additional compensation will be paid for the slightly thicker paving necessary to fill such irregularities as may exist on the surface of the rock blanket. Payment for concrete in the cut-off wall and for the paving described in this paragraph will be made at the unit price per cubic yard bid in the schedule for concrete in paving for upstream cofferdam, which unit price shall include the cost of furnishing all labor, machinery, tools, and materials, except cement, required in the mixing, placing, curing, and protecting of the paving until acceptance. 120. Concrete in dam.-The item of the schedule, “Concrete in dam,” includes all concrete within the upstream cut-off trench and within the lines of the theoretical or regular sections of the dam above the foundations, as shown on the drawings, and does not include any attached Concrete above the roadway elevation or outside of the regular section of the dam. The placing of concrete in the dam shall begin in the panel having the lowest foundation. The concrete shall be placed in horizontal layers not exceeding 5 feet in thickness: Provided, That the placing of individual layers in alternate panels bounded by contraction joints, or contraction joints and outside faces of the dam, will be required: And provided further, That in placing the concrete the top of any two of these panels or columns outside of the slot on line of centers shall at no time differ in elevation more than 35 feet. The forms for surfaces between adjacent panels or Columns may be removed as soon as the concrete has sufficiently hardened, as determined by the contracting officer. The rate of placing concrete in any panel or column of the dam shall be such that not more than 5 feet in depth shall be placed in 72 hours, and not more than 35 feet in depth shall be placed in thirty (30) days unless otherwise specifically authorized in writing by the contracting officer. All concrete in the dam shall be permitted to set for a period of not less than 6 days before cooling is started, as provided in paragraph 121. After the concrete in any 190-foot grouting lift has been satisfactorily cooled, as determined by the contracting officer, all contraction joints in this grouting lift may be grouted, as provided in paragraph 91. The limitations on the placing of concrete, as stated in this paragraph, will be modified only when approved in writing by the contracting officer. In mixing concrete that is to be placed in the upstream 6-foot layer of concrete in the dam, the contractor shall, if directed by the contracting officer, add to the regular mix an additional one-half or full sack of cement for each cubic yard of concrete. The drawings do not show any reinforcement steel around the inspection and other galleries in the dam. However, the Government reserves the right at any time before these galleries have been formed to require that reinforcement steel be placed around them. The contractor shall be entitled to no additional allowance above the unit price bid in the schedule for concrete in dam by reason of such steel being required, but the placing of this steel, if required, will be paid for at the unit price bid in the schedule for placing reinforcement bars and rails. A curve showing the estimated volume of concrete in the dam for all elevations to the top of the roadway is shown for the convenience of the contractor. 121. Cooling concrete in dam.–After any portion of the concrete in the dam and tunnel plugs has set for a minimum period of 6 days, it shall be cooled by removing the excess heat above 72° F. The temperature of the concrete shall be reduced by running water of lower temperature through pipes placed in the concrete, as provided in paragraph 149. The contractor shall furnish, install, and operate a complete refrigeration plant for removing the excess heat. This plant shall have a capacity sufficient to reduce from 47°F. to 40°F. the temperature of a flow of 2,100 gallons of water per minute. Water may leave the embedded pipes at any temperature between 42°F. and 65° F., and the quantity of cooling water may vary from 350 to 2,100 gallons per minute, but the temperature of the cooling water entering the embedded pipes shall in no case be lower than 35° F. The capacity of the cooling water circulating water pump and the condensing water pumps shall be such that, with one unit out, the remaining units will deliver not less than 75 per cent of the total water required. If river water is used for condensing purposes the plant shall be designed for condensing water at a temperature of 82°F. The refrigeration plant shall have a capacity sufficient to provide for all transmission losses and to deliver the above-mentioned quantity of refrigeration to the cooling pipes embedded in the concrete. The refrigeration plant shall be divided into three units, each of which shall be complete in itself, but all units shall be interconnected so that they may be used in combination as well as separately. Installation of the plant shall include the excavation for and the building for housing the necessary machinery. The building shall be sufficiently large to accommodate the installation of an additional unit including auxiliaries, and the design of the 3-unit plant shall be such as to permit the furnishing and installing of an additional unit at minimum cost. In addition to the refrigeration plant the contractor shall furnish, install, and operate all piping, pumps, tanks, and equipment necessary for the satisfactory operation of the 3-unit refrigeration plant described in this paragraph and the circulation of the cooling water through the pipes placed in the dam. The average temperature rise due to setting of concrete is approximately 40°F, above placing temperatures. The amount of heat to be removed is approximately 700 B. T. U. per degree per cubic yard of concrete. The estimated amount of heat to be removed from a cubic yard of concrete and the time required are shown in the tabulation following, but the actual amounts may vary considerably from these estimates in any one year. Estimate of Temperatures, Heat to be Extracted, and Time to Cool Mean Maximum B. T. U, to Cooling Cooling of concrete, in which the necessary pipes for this purpose have been placed, shall begin as soon as the concrete has set for a period of 6 days and shall be completed as soon as possible and by using the full capacity of the refrigeration plant unless otherwise directed by the contracting officer. The velocity of water in the cooling pipes shall be not less than 2 feet per second. Arrangements shall be made by the contractor for reversing the direction of flow in the pipe loops in the concrete in order to equalize the temperatures if considered advisable as determined by the contracting officer. The method of applying the cooling water to the pipes placed in the dam shall be such that the pressures in the pipes are nowhere in excess of 100 pounds per square inch. Cooling water shall be applied until the mean temperature of the concrete around each embedded pipe is reduced to 72°F. or less. The refrigeration plant and all other cooling equipment required to be furnished by the contractor and the operation of the plant and method of applying the cooling water shall at all times be subject to the approval of the contracting officer. Payment for furnishing, installing, and operating the cooling plant will be made at the lump sum price bid therefor in the schedule, which price shall include the Cost of furnishing and installing the 3-unit plant with required auxiliaries as described in this paragraph, the cost of excavating for and providing a building sufficiently large to house the 3-unit plant and an additional unit, and the cost of operating the 3-unit plant and cooling all Concrete, as required by the provisions of this paragraph. The cooling plant and all cooling equipment shall be and remain the property of the contractor. 122. Concrete in parapets.-The item of the schedule, “Concrete in parapets,” covers all Concrete attached to the dam, except the power house and outlet tower bridges, which is above the roadway elevation or outside of the regular or theoretical section of the dam, as shown on the drawings, and includes, in addition to parapets, the elevator and special stairway houses, balconies, electroliers, curbs, and other architectural features on or attached to the dam, as shown on the drawings or as directed by the contracting officer. Casts, molds, or special forms to produce the intricate relief work of the architectural decorations will be furnished by the Government under the provisions of paragraph 27. Exceptional care shall be used in all concrete construction covered by this paragraph to insure high quality of workmanship, accurate dimensions, and strict adherence to alignment and grade, and no irregularities in alignment due to inaccurate finishing of top surfaces, bulging of forms, or other defects will be permitted. Excessive troweling of surfaces while concrete is yet plastic will not be permitted. All necessary precautions shall be taken to keep the concrete described in this paragraph thoroughly wet for at least 14 days after placing. * 123. Special finishing of walls in power house, parapets, and other concrete surfaces.—It is contemplated that it may be desirable to finish, by rubbing, the inside and top surfaces of the parapets, the surfaces of other architectural features on the dam, power house, and other buildings, possibly some of the walls of the power house, and portions of other concrete surfaces of the dam or appurtenant works. An item for this work has accordingly been placed in the schedule. This work shall be done only on the surfaces designated by the contracting officer, The Government does not guarantee that any concrete surfaces of the dam or appurtenant works will be required to be so finished by rubbing, and the contractor will not be entitled to any additional compensation by reason of no work being required under the item of the schedule covering the special finishing of concrete surfaces. Where and if this finishing is required the forms may be removed while the concrete is yet green but not earlier than 24 hours after the placing of the concrete. Immediately after stripping the forms, any required patching shall be done and major imperfections of finish removed or corrected. The entire surface shall then be thoroughly rubbed with a carborundum stone using plenty of clean water in the process. After this rubbing the surface shall be thoroughly cleaned by washing. A sand-cement wash of a mixture determined by the contracting officer shall be applied during the rubbing process if directed by the contracting officer. A perfect finish of smooth uniform surface and color will be required. The cost of all work described in this paragraph shall be included in the unit price bid in the schedule for special finishing of walls in power house, parapets, and other concrete surfaces. 124. Concrete in spillway structures.—The item of the schedule, “Concrete in spillway structures,” includes all concrete in the spillway crests and spillway channel linings, the latter terminating at the upstream face of the portals of the spillway tunnels and all concrete in the Stoney gate structures. Vertical joints in the concrete of the crest, normal to the axis of the crest, will be provided for convenience in construction and to provide for the expansion and contraction of the concrete. The contraction joints will divide the spillway crests into sections. The entire face of each vertical joint in the crests shall be painted with one thin coat of water-gas tar and allowed to dry before the adjacent concrete is placed againstit. The water-gas tar for this purpose Will be furnished by the Government under the provisions of paragraph 27. The provisions of Paragraph 114 shall apply in the placing of the concrete in the channel linings. No part of the concrete channel lining shall be placed until all grouting of the foundation of the adjacent spillWay crest within a radius of 100 feet has been completed. The contractor shall construct the drains through the lining, as shown on the drawings or as directed by the contracting officer. The Pipe for this purpose will be furnished by the Government in random lengths and shall be out and Placed by the contractor so that the mouth of the pipe is flush with the surface of the concrete lining. Payment for cutting and placing the pipe will be made at the unit price per Pound bid in the schedule for installing standard steel, cast-iron pipe, fittings, and valves. The coarse gravel at the head of the drains shall be furnished and placed by the contractor and the cost thereof shall be included in the unit price per cubic yard bid in the schedule for concrete in spillway structures. 125. Concrete in linings of inclined spillway tunnels.-The item of the schedule, “Concrete in linings of inclined spillway tunnels,” includes all concrete in each inclined spillway tunnel from the upstream face of the portal wall to a horizontal plane passing through the inclined spillway tunnel at an elevation 64 feet above the center line of the connecting outer diversion tunnel. 126. Concrete in diversion tunnel plugs.-The item of the schedule, “Concrete in diversion tunnel plugs,” includes all concrete required to be placed for the solid plugs in the outer diversion tunnels and for the upstream and downstream plugs and for the installation of gates and valves therein in the inner diversion tunnels. After the concrete linings in the diversion tunnels along the reaches of the plugs have been placed in the wedge-shaped steps or depressions, as shown on the drawings, the depressions shall be filled up with timber lining or a lean mixture of concrete to the normal circular section of the tunnel. At the option of the contractor the concrete surface on which this filled concrete is placed may be painted with a water-gas tar paint to prevent a bond between the old and new concrete, and to aid in the later removal of this filled concrete. The paint for this purpose will be furnished by the Government. After the filling of timber or concrete has been removed and the other necessary excavations have been made for the various plugs at the proper time in the construction program, the surfaces of the concrete tunnel linings against which the concrete in the plugs are placed shall be thoroughly cleaned and roughened by tooling or otherwise to the satisfaction of the contracting officer so as to insure an effective bond between the concrete of the linings and the plugs. The wedge-shaped depressions shall be carefully filled with concrete integral with the concrete in the plugs to key the plugs and linings together. A system of grout pipes shall be set, as directed by the contracting officer, in the surfaces of contact between the plugs and the tunnel lining or at other points, and after the concrete in the plugs has hardened and cooled, grout under high pressure, as provided in paragraph 153, shall be forced into the grout connections to insure a water-tight connection at all points between the plugs and the lining. If the character of the rock permits, as determined by the contracting officer, the diversion tunnel lining along the reaches of the tunnel plugs may be omitted and the excavated keyways built up to the normal circular section by timbering. The cost of filling the wedge-shaped keyways with timber or with lean concrete shall be included in the unit price per cubic yard bid in the schedule for concrete in diversion tunnel plugs: Provided, That cement for the concrete will be furnished by the Government. If timber is used for this purpose it shall be furnished by the contractor. The contractor shall furnish all drainpipe required for keeping the work unwatered while placing the tunnel plugs. 127. Concrete in outlet and penstock tunnels.-The item of the schedule, “Concrete in linings of outlet and penstock tunnels,” includes all concrete in the inclined tunnels between the bottom of the upstream intake towers and the inner diversion tunnels, as limited by the conCrete in these structures as provided in paragraphs 118 and 130, and all concrete in the penstock tunnels between the bottom of the downstream intake towers and the beginning of the metal lining plates in the 7-foot 7-inch diameter tunnel to the farthest downstream valve in the lower tier of the 'canyon wall outlet works, and further limited in the vicinity of the 15-foot 9-inch diameter riser}shaft and of the diverting power penstocks and the other three 7-foot 7-inch diameter diverting outlet tunnels by the theoretical excavation surfaces in the penstock tunnel, as determined by the specified average thicknesses of concrete. It also includes the concrete lining in the horizontal portions of this tunnel after it leaves the 15-foot 9-inch riser shaft, this Portion of the lining being limited by a vertical plane through the point of tangency with the |