81. Earth fill in cofferdams.-The earth fill portions of, the cofferdams shall consist of a mixture similar to the natural mixture of silt, sand, and gravel in Hemenway Wash and may be obtained from borrow pits in Hemenway Wash or other places in the vicinity of the work or from required common excavation in the river channel: Provided, That only the gravelly material from the river channel excavation, which will form a stable and compact embankment when placed and rolled in 12-inch layers as provided elsewhere in this paragraph, will be acceptable, as determined by the contracting officer after actual excavation is in progress. No separation, sorting, blending or segragation of the materials will be required: Provided further, That material from different parts of the borrow pits or required excavation shall be placed on certain parts of the embankments as designated by the contracting officer: And provided further, That no stones having maximum dimensions of more than nine (9) inches shall be placed in the earth-fill embankments. Should stones of such size be found in the otherwise approved embankment materials, they shall be removed by the contractor either at the site of the excavation or after transporting to the embankments but prior to rolling and compacting the materials in the embankment. Such stones may be used in the rock-fill portions of the embankments or in the rock blankets on and above the upstream cofferdam if their maximum dimensions are not in excess of the requirements for these features. The mixture of silt, sand, and gravel shall be placed in the embankment in approximately horizontal layers not more than twelve (12) inches in thickness after rolling. All materials shall be uniformly moistened by sprinkling on the embankment. The full thickness of each 12-inch layer shall be moistened to such degree that, in the opinion of the contracting officer, the maximum compactness of embankment will be assured after rolling as specified. The roller used for compacting the embankment shall be of the “Rohl” type, having cast-iron ball feet equally spaced over its cylindrical surface and its weight shall be not less than 1,000 pounds per linear foot of width of tread. The entire surface of each layer of embankment rolled shall have the roller pass over it at least three times. If, in the opinion of the contracting officer, the rolled surface of any layer of material is too smooth to bond properly with the succeeding layer it shall be roughened or loosened by harrowing or otherwise to the satisfaction of the contracting officer before the succeeding layer is placed thereon. Measurement, for payment, of the materials placed in the earth-fill portions of the cofferdams will be made in embankment after compacting by moistening and rolling as specified, and payment will be made at the unit prices per cubic yard bid in the schedule for earth fill in Cofferdams, which unit prices shall include the cost of clearing, grubbing, and stripping the approved borrow pits, if required, and the entire cost of all excavating in the borrow pits, loading, hauling, spreading, moistening, harrowing, and other operations required in placing the materials, as described in these specifications, in the finished embankments.

82, Rubble masonry walls.-The contractor shall construct rubble masonry walls along the Canyon rim above the power plant and intake towers and below the highway on both sides of the Canyon, as directed by the contracting officer, wherever necessary for protection of the permament works from injury by falling rocks, as determined by the contracting officer. Rubble masonry parapets and retaining walls, where and if required as determined by the contracting officer, shall also be constructed by the contractor, as shown on the drawings or as directed by the contracting officer. The rock used for the rubble masonry shall be clean, hard, dense, and durable. Either bowlders or broken rock from excavation may be used if fulfilling the *quirements as to quality and dimensions. If broken rock is used, excessive projections and *ute angles shall be removed, and the stones used as headers shall have a roughly squared and *sonably flat exposed face. At least one-fourth of the total volume of masonry shall consist "headers of a length equal to the thickness of the wall for walls less than 18 inches in thickness, and headers at least 18 inches in length for walls over 18 inches in thickness. The headers shall be distributed uniformly throughout the wall. The stones in the wall shall be placed as closely as practicable to the lines and grades established by the contracting officer. The largest stones shall be used in the foundation and lower part of the wall, and all stones shall be laid upon their broadest face. Cement mortar of a mix and consistency approved by the contracting officer shall be used for filling the joints between stones. The surfaces of all stones used in the wall shall be thoroughly cleaned and wetted before being firmly embedded in the layer of mortar previously spread over the preceding layer of stones. The contractor shall not use mortar that has taken an initial set before being placed in the wall, and shall place all stones before the mortar in which they are embedded has taken an initial set. The headers and other large masses of stone shall be brought to an even bearing on the layer immediately below, and the interstices between the larger masses of stone shall be filled by thrusting rock fragments or spalls into the mortar. No unfilled spaces will be permitted in the wall. In order to provide sufficient lateral bond in the wall, the stones in any layer shall break joints with the stones of the preceding layer. Transverse bond shall be provided by the use of headers. If it is necessary to move a stone after it has been placed upon the mortar bed, it shall be lifted clear without sliding and reset, so that no injury will result to the mortar bond of stones already laid. After the stone has been laid as above specified, the joints of all exposed faces shall be thoroughly cleaned and pointed in a workmanlike manner satisfactory to the contracting officer. Measurement for payment for constructing rubble masonry walls will be made in place on the basis of the sectional area specified by the contracting officer. Payment for rubble masonry walls will be made at the unit price per cubic yard bid therefor in the schedule, which unit price shall include the cost of procuring, handling, hauling, and placing the broken rock or bowlders, and materials, except cement, required for constructing the rubble masonry walls.

83. Disposal of excavated materials. As provided elsewhere in these specifications, portions of the excavated materials may be used in required embankments, but the remainder of the excavated materials must be wasted. The disposal of all excavated materials that are wasted shall be subject to the approval of the contracting officer. All spoil banks or waste piles shall be located where, in the opinion of the contracting officer, they will not harmfully interfere with the natural flow of the river, with the operation of the future power plant, or with the discharge of water through the diversion tunnels and the outlet works. No materials shall be wasted in the river channel, either above or below the dam site, below the maximum high-water surface except by written permission of the contracting officer. Spoil banks shall be located where they will not detract from the appearance of the completed structure, or interfere with the accessibility of the structure for operation. Where required by the contracting officer, spoil banks which are visible from the dam or highway shall be roughly leveled and trimmed to reasonably regular lines, and the contractor shall not be entitled to any additional compensation on account of such work. The cost of disposal of all excavated materials that are wasted shall be included in the unit prices bid in the schedule for excavation. Materials excavated from the dam and power house foundations and from other required work may be used in the construction of cofferdams and other embankments: Provided, That such materials shall fulfill the requirements for these structures, as specified in paragraphs 77 to 81, inclusive. As provided elsewhere in these specifications payment for placing materials from required excavation, in embank ments, except temporary embankments that are to be constructed at the expense of the contractor and except fills required in the construction of the highway and for the elevator Spur track, will be made at the unit prices per cubic yard bid in the schedule for the items of embank ment construction, which payment will be in addition to the payment for excavation of the material.

GROUT AND DRAINAGE SYSTEMS

84. Drilling grout holes in tunnels, adits, and shafts.-Except for considerable portions of the diversion tunnels upstream from the tunnel plugs in the outer diversion tunnels and upstream from the upstream plugs in the inner diversion tunnels, holes for high-pressure grouting shall be drilled through the concrete linings of the tunnels, adits, and shafts and into the surrounding rock as shown on the drawings or as directed by the contracting officer. At the option of the contractor, pipe connections for high-pressure grouting may be placed prior to placing concrete by attaching one end of the pipe to the forms and cutting the pipe so that the other end will be not less than 6 inches from the rock, or the pipe connections may be set after the holes have been drilled through the concrete. In the first case drilling will be through the portions of concrete lining only beyond the end of the pipes and into the rock, and in the second case will be continuous through the entire thickness of the lining and into the rock. The location, direction, order of drilling, and depth of each hole shall be as ordered by the contracting officer. The diameter of each hole at the bottom shall be not less than 1 inch. Each hole shall be protected from becoming clogged or obstructed by a grout connection grouted into the grout hole and suitably capped or otherwise protected until the hole is grouted, and any hole becoming obstructed before it is grouted shall be opened up to the satisfaction of the contracting officer by and at the expense of the contractor. Plate-steel liner plates furnished by the contractor shall be provided with properly located holes through which grout holes may be drilled, or, at the option of the contractor, holes may be drilled through the steel lining after it is placed. The grout holes will be measured for payment after the holés are drilled and only the length of holes actually drilled by direction of the contracting officer will be considered in making the measurements. Payment for drilling grout holes in tunnels, adits, and shafts will be made at the unit price per linear foot bid therefor in the schedule: Provided, That any hole required to be drilled to a greater depth than 25 feet will be ordered in writing and the drilling of the entire hole will be paid for as extra work under the provisions of article 5 of the contract and paragraph 10 of these specifications.

85. Drilling grout holes in foundations for dam and spillway crests.-Grout holes shall be drilled in the foundations of the dam, spillway crests, inlet structures for the outer diversion tunnels, and elsewhere if required, as shown on the drawings or directed by the contracting officer. It is intended that grout holes shall be drilled in the bottom of the upstream cut-off trench of the dam at about 5-foot intervals. It is expected that in general these grout holes will be required to be drilled to varying depths up to a maximum of 150 feet. The direction, order of drilling, and depth of each hole shall be as ordered by the contracting officer. The diameter of each hole at the bottom shall be not less than 1 inch. It may be found necessary to drill grout holes in other parts of the foundations than as shown on the drawings, or it may be found necessary, after all the holes in a given region have been drilled and grouted, to drill additional holes. No additional allowance over the unit prices bid in the schedule will be made to the contractor for drilling such holes nor for the expense of moving equipment or other Operations incidental to returning to an old area or moving to a new area. Each hole shall be Protected from becoming clogged or obstructed by being suitably capped or otherwise protected until it is grouted and any hole becoming obstructed before it is grouted shall be opened up to the satisfaction of the contracting officer by and at the expense of the contractor. The grout - holes will be measured for payment after the holes are drilled and only the length of holes actually drilled by direction of the contracting officer will be considered in making the measurements. Payment for the drilling as described in this paragraph will be made at the unit prices per linear foot bid in the schedule for drilling grout holes in foundations for dam and spillway crests, which unit prices shall include the cost of all labor, materials, plant, and operations required in drilling the holes and maintaining them free from obstruction until grouted.

86. Drilling drainage holes in foundation for dam.—Drainage holes shall be drilled in the foundation for the dam, and elsewhere if required, as shown on the drawings or as directed by the contracting officer. In general, the elevation of the bottom of drainage holes shall be higher than the bottom of adjacent grout holes, and drainage holes will not be required to be drilled to a greater depth than 150 feet beyond the surface of contact between the concrete of the dam and the foundation rock. The depth of each hole shall be as ordered by the contracting officer. Drainage holes shall not be drilled until all adjacent grout holes within a minimum distance of 150 feet have been drilled and grouted. The diameter of each drainage hole at the bottom shall be not less than 2 inches. If after a given area is grouted and drilled for drainage it is found desirable to drill and grout additional grout holes, the contractor may be required to open up previously drilled drain holes by redrilling to secure perfect drainage. Such redrilling of old holes will be ordered by the contracting officer in writing and will be paid for as extra work under the provisions of article 5 of the contract and paragraph 10 of these specifications. Drainage holes will be measured for payment after the holes are drilled and only the length of holes actually drilled by direction of the contracting officer will be considered in making the measurements. Except as otherwise provided for redrilling, payment for the drilling as described in this paragraph will be made at the unit prices per linear foot bid in the schedule for drilling drainage holes in foundation for dam, which unit prices shall include the cost of all labor, materials, plant, and operations required in drilling the holes and maintaining them free from obstruction until the work is completed.

87. Pressure grouting, general,—Sand for pressure grouting shall be furnished by the contractor and shall be clean and of such fineness that 100 per cent will pass a No. 8 standard sieve, and 30 per cent will pass a No. 50 standard sieve. Cement for grouting will be furnished by the Government under the provisions of paragraph 27. When required by the contracting officer, the cement shall be screened before it is used in grout for pressure grouting. All high-pressure grouting shall be done with a neat cement mixture and by the pumping method. Before pressure grouting is begun, all holes and contraction joints shall be thoroughly washed out with water of a quality provided in paragraph 102, under continuous pressure, as required by the contracting officer, up to the required grouting pressure. Grouting shall not be stopped in any hole until the hole takes grout at the rate of not more than one cubic foot in ten minutes when the required grouting pressure is applied. After the grouting of the hole is finished, the pressure shall be maintained by means of a stop-cock or other suitable device until the grout has set sufficiently so that it will be retained in the hole. The apparatus for mixing and placing grout shall be of a type approved by the contracting officer and capable of effectively mixing and stirring the grout and forcing it into the holes at any desired pressure up to the maximum required. Measurement for payment for pressure grouting will be made on the basis of the number of sacks of cement and cubic feet of sand, counted separately, actually forced into the holes or grout connections at the direction of the contracting officer. In measuring the grout for payment the volume of one sack of cement will be considered as 1 cubic foot and the volume of the sand will be taken as that of the sand in its loose dry state. Pressure grouting will be paid for at the unit prices per cubic foot bid therefor in the schedule, which unit prices shall include the cost of all labor, materials except cement, plant, and operations required for the grouting. No payment will be made for grout lost due to improper anchorage of grout pipes, or for grout rejected by the contracting officer on account of improper mixing, and the contractor will be charged for cement used in such wasted or rejected grout the same amount that the cement cost the Government at the point of delivery to the contractor.

88. Pressure grouting in tunnels, adits, and shafts.-After the concrete lining in the tunnels, adits, and shafts and in the tunnel plugs is in place and the required holes have been drilled and grout connections, including vent pipes, provided for, the material surrounding the linings and tunnel plugs shall be pressure grouted as directed by the contracting officer. No grout hole or grout connection shall be grouted until the adjacent concrete is placed and has set a sufficient length of time up to a maximum of 60 days, as determined by the contracting officer. Each drilled grout hole, grout connection, and vent pipe where required shall have forced into it under a pressure of not less than 50 pounds and not more than 500 pounds per square inch, as directed by the contracting officer, a grout composed of cement and water, or cement, sand, and water in proportions to be determined by the contracting officer. In describing grouting operations in these specifications for tunnels, adits, and shafts, pressure grouting is referred to under two general divisions; viz, low-pressure grouting and high-pressure grouting. It is contemplated that the pressure ordinarily used in low-pressure grouting will vary from 50 to 100 pounds per square inch and in high-pressure grouting from 100 to 500 pounds per square inch. Low-pressure grouting shall usually precede high-pressure grouting, and will be used principally to fill the voids between the lining and the rock, particularly above the arches. If, during the grouting of any hole, grout be found to flow from adjacent grout connections in sufficient quantity to seriously interfere with the grouting operation, or to cause appreciable loss of grout, such connections may be temporarily capped. Where such capping is not essential, ungrouted holes shall be Jeft open to facilitate the escape of air and water as the grout is pumped in. Where necessary, vent pipes shall be set, as shown on the drawings and provided in paragraph 145, to permit the excape of air and water from pockets in the material surrounding the concrete linings. Plate steel conduit linings for outlet works and power penstocks will be furnished with tapped holes for making grout connections. The contractor shall pressure grout around all metal conduits, gate frames, and transitions, where directed by the contracting officer, and payment for this work will be made at the unit price per cubic foot bid in the schedule for pressure grouting in tunnels, adits, and shafts.

89. Pressure grouting in foundations for dam and spillway crests.-Each drilled grout hole and grout connection for pressure grouting the foundations for the dam, spillway crests, and inlet structures for the outer diversion tunnels shall have forced into it under a pressure of not less than 100 pounds and not more than 300 pounds per square inch, as directed by the contracting officer, a grout composed of cement and water, or cement, sand, and water in proportions to be determined by the contracting officer. In general, the unit grout pressure required for all pressures above the minimum of 100 pounds per square inch will be determined by the contracting officer on the basis of the full reservoir hydrostatic head at the elevation of the grouting connection and an addition of 50 pounds per square inch. No grout hole or grout connection for grouting the foundations for the dam and spillway crests shall be grouted until all concrete required within a radius of 50 feet and to a thickness of 10 feet is placed and has set a sufficient length of time, as determined by the contracting officer. No grout hole or grout connection for grouting the foundations for the inlet structures of the outer diversion tunnels shall be grouted until all concrete within a radius of 50 feet is placed and has set a sufficient length of time, as determined by the contracting officer. If, during the grouting of any hole, grout be found to flow from adjacent grout connections in sufficient quantity to seriously interfere with the grouting Operation or to cause appreciable loss of grout, such connections may be temporarily capped. Where such capping is not essential, ungrouted holes shall be left open to facilitate the escape of or and water as the grout is forced in. Measurement of and payment for pressure grouting as . described in this paragraph will be made as provided in paragraph;87.