(d) Outlet Tunnel.--The last steel form placement was made to station 5+17.15 on March 8, 1954, and the form was then moved from the outlet tunnel to the power tunnel. For the remaining concrete lining in the outlet tunnel station 1+95 to station 5+17.15, including the raise and shaft sections, the contractor used wood panels.

Upstream of the tunnel adit portal, considerable work was performed to stabilize the left bank, the right rock cut, and the bottom approach. A concrete slab was placed over the bottom from station 1+49 to station 1+95, and on the left side a concrete retaining wall was built with its top varying from elevation 5394.14 at station 1+49 to elevation 5403.00 at station 1+95. The loose and shattered rock on the right side was made firm by placing a concrete wall against the questionable portions.

At the lower end of the tunnel the final concrete for backfill behind the steel liner, station 17+32 to station 17+44, was completed on May 1, 1954. Final concrete incident to the tunnel was placed October 1, 1954, in the inclined shaft section.

First concrete was placed in the floor slab November 2, 1954, followed by completion of the left wall panel November 14, 1954, and the right wall panel on November 15, 1954. Work was then expedited on the floor and vertical arch section, station 2+68.46 to station 2+02. This area was concreted December 3, 1954.

Concrete for the above four placements was all handled by the whirley crane erected on the rock dike between the outlet and power tunnels. Both a 2-cubic-yard and a 4-cubic-yard bucket were used by the contractor. The 2-cubic-yard bucket proved to be the most feasible and was used for the bulk of placing. The remaining concrete was completed October 25, 1956.

(e) Power Tunnel.--Concreting activity in the power tunnel and the intake structure was very similar to that outlined for the outlet tunnel and intake structure. Different carpenter crews worked in each, but the labor and concrete crews worked in first one and then the other.

Concrete placing by pumpcrete methods in the tunnel invert began on January 19, 1954, and finished March 11, 1954; this portion extended from station 2+14 to station 10+12. To take care of seepage water, a few gravel french drains were installed with pipe weep holes extending above the concrete line. These pipes were later used to grout backfill the drains. Soon after the invert was completed, the steel collapsible form was moved into the tunnel, set up at station 10+12, and concrete lining of the tunnel began at that point and advanced upstream. The first lining placement was made March 16, 1954, and the lining was completed to station 2+14 on April 29, 1954. Work on the raise section and inclined shaft continued but intermittently through the rest of the summer being delayed by unscheduled use of the tunnel in river diversion. The final concrete placement in the inclined shaft was not started until October 29, 1954. The power tunnel adit portal was concreted from station 1+95 to station 2+14 on June 8, 1954.

On November 11, 1954, concrete was placed in two floor slabs of the intake structure, and on November 26 concrete placement was completed in the lower sections of both the right and left walls. Concrete placement in the intake structure was completed with the placing of the control house roof slab September 14, 1956.

The penstock manifold lies between the right stilling-basin wall and the powerplant f-line and is bordered on the opposite two sides by the 3 and 12 lines. This area holds the concrete-encased penstock and butterfly valves. The first concrete was placed August 30, 1954, and the last concrete for encasement of the penstock was placed September 3, 1955.

When the penstock and bypass anchor block area became available, after being used for river diversion, the contractor commenced construction of concrete saddles for penstock supports. This work began with the first placement on July 23, 1955. The encasement of the penstock and bypass pipes was completed June 23, 1956. The air-valve house was completed May 11, 1956.

Placing of concrete around the steel penstock, from station 15+72 to station 17+44, was one of the first outdoor activities by the contractor in 1954. Following the

winter shutdown, the cut-and-cover section required considerable cleanup to remove material that sloughed in from both sides during the winter months. First concrete was placed by pumpcrete methods March 7, 1954, from station 15+72 to station 16+50.50. The remainder of the invert concrete was placed from that point to station 17+44 on March 29, 1954. The last placement around the steel penstock to station 17+44, including the headwall, was made June 17, 1954.

Concrete around the steel penstock was placed against rock below spring line. Curved, wooden form panels were used above spring line with an opening of about 20° across the top arch. Concrete in the arch was hand screeded to grade and given a wood trowel finish.

(f) Outlet Works Diversion Channel.--The first concrete placement in the outlet pipe channel was made for the left wall on April 15, 1954, and continued thereafter as wall forms or floor slab bulkheads were readied. The last concrete was placed in the floor on June 24, 1954, from station 17+44 to station 18+83.92. The air-valve house over the outlet pipe at about station 17+40 was completed May 17, 1954.

Concrete was placed in the footing for the left wall of the power pipe channel on July 8, 1954, and subsequent wall panels completed thereafter. A delay in work occurred when the channel was used as a part of the river diversion plan from August 5, 1954, through about September 23, 1954. Concrete placement for the remaining wall panels and floor slabs was pushed, and the last placement was made November 4, 1954, in the right wall.

Work on the division wall began at about the same time major work was done in the power pipe channel. First concrete was placed in a wall panel from station 18+83.92 to station 19+00.25 on May 21, 1954, and the last placement was made on July 10, 1954, closing the gap between the outlet and power pipe channels.

Outlet pipe manifold concrete placement in the schedule C area started May 1957. Saddles and rings were cast first, and the steel manifold was assembled. On September 26, 1957, during the pressure tests, the manifold failed, which altered the construction program (sec. 216). A portion of the second-stage concrete was placed from October 8, 1957, to the following December 18, completing the concrete backfill of the downstream portion of the branch of the manifold. The encasement of the upstream portion of the outlet manifold began April 28, 1958, and was completed June 2, 1958.

(g) Stilling Basin.--Forms for the exposed surfaces of the outlet works stilling basin were fabricated at the jobsite of 5/8-inch, 4- by 8-foot plywood sheets secured to 3- by 6-inch studs having a spacing of 12 inches. Forms were secured in place with she-bolts and 1/2-inch tie rods using walers of 3- by 6-inch dimension. Shiplap sheathing was used for walls covered by backfill. Prior to setting the forms in place, the surface was given a coat of plastic to prevent the concrete from sticking. Tie rods for the left wall were welded to the previously placed anchor bars, but this support proved to be inadequate as the anchor bars were placed on 5-foot centers. A double row of tie rods was then welded to the anchor bars and two sets of walers were used at each 5-foot elevation, which proved to be more adequate; however, in some instances the tie rod weld would break or the threaded end of the tie rod would strip. Forms were stripped as soon as the concrete had hardened sufficiently to prevent spalling of the concrete. After the forms were removed the plywood surface was cleaned, repaired where necessary, and set in place for the succeeding lift with a crane. Usually three placements could be obtained before a change of plywood sheets was required. The forms for the deflector walls were fabricated without a bottom plate, which permitted the plywood sheeting to bow between the studs at the construction joint on the floor slab. The forms bowing in this manner caused excessive loss of grout during concrete placing. Forms for the floor slabs were built in place of shiplap sheathing with 3- by 6-inch studs, the shiplap sheathing being placed vertically and fitted to the foundation contour. The studs were placed horizontally 12 to 15 inches apart depending on the slab thickness, and walers were 3 by 6 inches, placed vertically at approximately 3 feet apart. Forms were secured in place with she-bolts and 1/2-inch tie rods welded to the previously placed anchor bars. Additional rigidity was obtained by using 3- by 6-inch shoring, and horizontal keys were constructed in the transverse and longitudinal construction joints. Prior to placing of concrete a coat of plastic was applied to the interior surface of the forms. Forms were removed as soon as the concrete had hardened sufficiently to prevent spalling of the concrete.

Placing operations for the outlet works stilling basin were started on June 12, 1953. Concrete of 0.45 water-cement ratio design using 2-1/2-inch-maximum aggregate was placed with a 2- to 3-inch slump in the floor slabs. The concrete was delivered to the jobsite with 4-cubic-yard dumpcrete trucks and was deposited in place with a dragline using a 2-cubic-yard bucket. Concrete of 0.45 water-cement ratio design using 2-1/2- and 1-1/2-inch-maximum aggregate was placed in the stilling-basin walls with a 2-1/2- to 3-inch slump. Most of the concrete in the left wall was placed with a dragline which could handle only 1 cubic yard at a time causing placing of concrete to be slow. Concrete of 0.50 water-cement ratio design using 2-1/2-inch-maximum aggregate was placed with a slump of 2 to 3 inches in the left wall of the diversion channel lining. Consolidation of concrete was achieved by internal vibration with pneumatic operated vibrators, operating at a speed in excess of 7,000 revolutions per minute when immersed. Some trouble was experienced with the vibrators during the latter part of the construction season because of excessive moisture in the air lines. Frequent change of vibrators was necessary and caused delays in placing of concrete. Concrete placement was completed May 8, 1954.

Finishing of unformed concrete was performed by hand methods, except for use of a power float on a few of the floor slabs between stations 20+90.25 and 22+50.25. The concrete surfaces of the floor slabs were screeded with a 2- by 6-inch screed pulled by an air tugger. This method of screeding was very helpful to the finishers, especially on the parabolic floor slabs between stations 19+00.25 and 20+90.25. The horizontal construction joints of the walls were wood floated to eliminate high and low spots and to facilitate easier sandblasting at a later date. Tops of all walls were edged and sloped for drainage. Because of very few rock pockets and imperfections of construction joints, a minimum of repair work was required.

(h) Control House.--First concrete was placed in the control house substructure on September 17, 1955. The superstructure for outlet gates 7 and 8 was completed July 18, 1956, and for gates 1, 2, 3, 4, 5, and 6 was completed August 10, 1957.

(i) Spillway Tunnel.--Concrete placement in the tunnel invert began on August 11, 1954, and the last placement, to station 24+00, was finished September 14, 1954. All concrete was handled by pumpcrete methods using two pipelines, one on each side of the invert, and the finishing crews followed behind the placing operations. The first placement covered a distance of 160 feet, all others were of 200-foot length. There were no water-seepage problems, as the tunnel invert was comparatively dry.

Following completion of concrete placing in the tunnel invert, the contractor made preparations for placing concrete in the arch and sidewalls. The steel, collapsible form was taken into the tunnel and set up from station 7+72 to station 8+12. Extra bracing was built in and a working platform added on the downstream end about 4 feet below the crown of the forms arch; the platform also provided a footing anchorage to brace the upper portion of the arch wooden end bulkhead. To replace the old-style bulkhead used in the lining of the outlet and power tunnels, the contractor used a system of individual timber leaves. One end of each leaf was held to the form in a slot made by angle iron arranged to act as a clamp; each leaf could then be extended to rock and quickly shaped to contour with a minimum of time and effort. Leaves were replaced when they became broken or too short for use. Timber bracing was used to reinforce the bulkhead leaves against concrete and pumpcrete pressures.

Besides the form, the contractor used a timber jumbo in the tunnel to carry the pumpcrete pipe and a platform on which was mounted the pumpcrete machine. A conveyor belt fed the pumpcrete with concrete dumped directly from trucks. To speed up truck travel, a turntable platform was erected at the end of the conveyor eliminating the old time consuming method of trucks backing the full length of the tunnel. All units of the setup were mounted on wheels and track, coupled together, and moved as one unit.

Placing of concrete for the tunnel lining, behind the steel form, began on October 16, 1954, at station 7+72, and continued with good progress through November 17, 1954. One pipeline was used from the pump and over the steel form, and the sidewalls were filled by diverting the concrete from side to side. The arch was concreted by use of a slick line, and to all appearances a good tight filling was obtained. Troubles and delays were minor, as the pumpcreting operations were well organized and scheduled.

Following the tunnel lining placement to station 13+72, on November 17, 1954, the steel form was moved forward and revealed the rock section to be protruding too far inside the concrete line at numerous points. The contractor decided to stop concreting operations for the rest of the year and check and remove all protruding points. This program carried over into 1955, and concreting was completed July 12, 1955.

The first concrete in the spillway channel was placed in the floor slab and cutoff trench, station 27+60 to station 28+00, on July 7, 1954. This was the only floor placement of the year, work centering thereafter on both walls. Concrete placement in walls began on July 10, 1954, and continued throughout the remainder of the summer and early fall, with the completing wall placements being made on October 8, 1954. The floor was completed June 6, 1955.

The first concrete placements made in the inlet structure were the cutoff trench in the floor at station 4+35, which was concreted November 11, 1954, and the floor slab from station 4+35 to station 4+65, which was started November 26, 1954. Cold weather at the time of these two placements necessitated extra protection precautions. The inlet structure was completed April 13, 1956.

The contractor performed necessary preliminary work for and made one concrete placement in the inclined shaft invert section from station 5+50 to station 5+90.15. This placement involved considerable time and effort, putting in the reinforcing steel mats, laying the three runs of concrete sewer pipe, and erecting the form bulkheads. Time spent on preparing this placement was not continuous but extended from August 20, 1954, when the first dowels for reinforcing steel were placed, to November 19, 1954, when concrete placing began. To aid in holding the concrete on the slope of the shaft, the contractor placed a lid over the lower 20-foot section of the invert; the rest of the concrete was formed from screed strips. Sometime during the weekend of October 24, 1954, a large rock fell from the tunnel roof and crashed through both mats of reinforcing steel at station 5+55 and to the right of centerline, causing extra work in repairing, but no overall delay. Concrete was placed by pumpcrete methods, and the operation was very successful. The last placement of concrete for the inclined shaft was made May 2, 1957.

(j) Powerplant.--Specifications No. DC-3675 included construction of a powerplant with a substructure width of 80 feet 6 inches, a length of 246 feet, and a height extending from the subgrade to elevation 5368. The intermediate structure extended from elevation 5368 to elevation 5397.50. First-stage concrete in the substructure was completed during the 1953 construction season, except for portions of the b-, f-, and 3-line walls from elevations 5364.37 to 5368. The intermediate structure concrete placed during the 1953 construction season was only a few cubic yards in the b- and 1-line walls from elevation 5368 to elevation 5377.17 and in the 12-line wall from elevation 5368 to elevation 5371. Installation of the ground cables, forms, and reinforcing steel began on June 29, 1953.

Forms for the powerplant and training walls were fabricated at the jobsite, except the draft tube forms which were fabricated at the contractor's panel yard. Shiplap sheathing was used for forming concrete covered by backfill and for all foundation placements. The shiplap sheathing used for forming the foundation placements was placed vertically and fitted to the foundation contour. Studs of 3- by 6-inch dimension were placed horizontally 12 to 15 inches apart. Walers were placed vertically and secured in place with she-bolts and 1/2-inch tie rods which were welded to previously placed anchor pins grouted into the foundation. The forms for exposed concrete were fabricated of 5/8-inch, 4- by 8-foot plywood sheets secured to 3- by 6-inch studs. Walers were double 3- by 6-inch studs placed from 12 to 30 inches apart. Wall forms were secured in place with she-bolts and 1/2-inch tie rods, and were additionally braced to prevent displacement during placing of concrete. Prior to setting the forms in place, a coat of plastic was applied to prevent the concrete from sticking to the form surface. Usually two to three placements could be obtained before a change of plywood sheets was required. All exposed corners were chamfered. Draft tube forms which were fabricated at the contractor's panel yard were hauled to the jobsite in sections where they were set in place with a dragline and secured in place with she-bolts and 1/2-inch tie rods.

Concrete placing operations in the powerplant were started on July 9, 1953. Concrete was delivered to the jobsite from the contractor's mixing plant with 4-cubicyard dumpcrete trucks, and placing was accomplished with a dragline using a 2-cubicyard bucket. Surfaces of foundations and previously placed concrete were given a thin coating of mortar immediately prior to concrete placing. Concrete of 0.50-water-cement

ratio design using 2-1/2-inch-maximum aggregate was placed at 2- to 3-inch slump in foundation and wall placements of the powerplant. Concrete was placed in 18- to 20-inch lifts wherever possible.

Placing of concrete under the draft tube elbow sections was very difficult because of the distance under the forms. Concrete of 1-1/2-inch-maximum aggregate, with approximately a 4-inch slump, was used for sealing under the elbow sections. Vibrator holes were cut in the forms to aid in getting a good fill under the forms. A metal chute 18 inches in width was used for placing concrete under the last two elbow sections with good success. The metal chute was cut off and removed as placing progressed. Concrete in the training wall footings was 0.50-water-cement ratio design with 2-1/2-inch-maximum aggregate and a slump of 2-1/2 to 3 inches. The concrete placed in the training walls, which was below the fluctuating water level and not subjected to freezing and thawing, was 0.50-water-cement ratio design with 1-1/2-inch-maximum aggregate and a slump of 3 inches. Concrete placed above the fluctuating water level and subjected to freezing and thawing was a 0.45-water-cement ratio design. Concrete was placed to elevation 5380 in both training walls during the 1953 construction season. A hopper with a truck was used for depositing the concrete in place.

Concrete was placed in the voids between the large rock fragments in the dumped riprap to a depth of approximately 12 inches in the tailrace area between the training walls adjacent to the powerplant. The concrete placed in the voids had a slump of approximately 2 inches to prevent permeation of the concrete into the voids below. Concrete was placed in a manner to prevent points of rock fragments from protruding more than 6 inches above the surface of the concrete.

1954.

The last concrete placement for first-stage concrete was completed October 13,

G. Drilling and Grouting (Specifications No. DC-3675)

191. Drilling and Grouting Program--General. The drilling and grouting program for the Palisades project consisted of curtain drilling and grouting of the west abutment under cutoff walls No. 1 and 2; backfill grouting of the steel liner sections of the power and outlet tunnels; backfill grouting of the concrete-lined sections of the power, outlet, and spillway tunnels; radial hole drilling and grouting of the rock surrounding the tunnels; drilling and grouting the floor and walls of the intake structures; grouting the cooling coils in the thrust slabs and beams of the intake structures; grouting the joints around the plugs and in the cooling coils in the diversion adits of the power and outlet tunnels; grouting the joints between the first- and second-stage concrete in the outlet works anchor block, backfill grouting the arch of the right abutment exploratory tunnel, and other miscellaneous items, in accordance with the specifications.

192. West Abutment Drilling and Grouting. - (a) General.-- The purpose of the west abutment grouting was to reduce seepage through the foundation rock. To accomplish this, holes were drilled to a minimum depth of 30 feet and ranging to a maximum depth of 160 feet. Most of the holes were drilled to their final depth and grouted through a packer, which was set at the proper depths. In a few cases the holes were drilled and grouted in stages. Packer settings were generally determined by conditions encountered in the drilling. Pressures of from 50 to 250 pounds per square inch were used. Water-cement ratios of 7:1 to 1:1 were used. Thick grout was not used except where necessary to reduce leakage. A mix with a water-cement ratio of 5:1 was used for most of the holes.

The initial holes in the cutoff curtains were spaced at 80 feet. The intervening space was then equally subdivided consecutively to reach a 10-foot spacing on the closing holes.

(b) Drilling and Grouting.--The west abutment andesite was very easy to drill, many holes being drilled at the rate of approximately 30 feet an hour. Plug bits were used entirely, and the diamond cost per foot was very low. Each bit was generally used for drilling 600 to 800 linear feet of hole before being sent in for resetting. The diameter of the grout holes was 1-1/2 inches.