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Figure 22. --Embankment placing operations during early stages of construction. 5-SL-686, June 29, 1950

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Figure 23. --Completed embankment viewed from same point as preceding photograph. 5-SL-1114, September 18, 1951

Placing was resumed in June 1950, with the first zone 1 material being tamped in the dike section June 20. Operations were extremely slow during July as the material was at or above optimum moisture content and there were continual rainstorms. Conditions improved, however, and progress was satisfactory until operations were terminated for the season. Satisfactory progress was made throughout the unusually dry season of 1951 and the dam and dike embankments were completed August 25, 1951. Figures 22, 24, and 25 show embankment placing operations.

Placing of the four classes of material used in construction of the dam is discussed in the following sections.

58. Earth Fill (Zone 1). Material for zone 1 was obtained from two borrow areas, No. 6 and the extension of No. 6 (sec. 28). Excavation of these areas is discussed in section 53. These areas are a morainal deposit, the material consisting largely of gravel with sand-clay binder which proved to be an excellent impervious material. Borrow area 6, the initial source, proved to contain far more moisture than was either evidenced or reported in preconstruction investigations. Moisture in place varied from optimum to, more frequently, 1 or 2 percent above optimum. This moisture condition made placing operations costly. Little drying effect was obtained through air jetting at the separation plant and by other means attempted in the pit. The best method of drying was to scarify and disc-harrow the material on the fill before rolling. Frequent rainstorms forced suspension of operations and heavy dews were sufficient to delay starting in the early morning hours.

On August 25, 1950, permission was granted the contractor to increase the maximum size of rock allowable in zone 1 from 3 to 5 inches and to change the downstream slope of zone 1 in the main dam from 1 to 1 to 1/2 to 1 (sec. 28). Addition of the 5-inch rock lessened the difficulties caused by excessive moisture and reduced somewhat the tendency of the screens in the separation plant to plug. It is interesting to note that this change in slope reduced the cross section of the zone 1 to the least section of any rolled-earth dam yet constructed by the Bureau.

The second borrow area, the extension of area 6, was opened on September 11, 1950, when it was determined that the material, although more thoroughly consolidated and difficult to excavate, was considerably drier.

Material was excavated and loaded in the pit by a power shovel and transported to the separation plant in bottom-dump trailers. After separation, the material was reloaded in bottom-dump trailers and/or end-dump trucks for transporting to the dam and dike. Spreading was accomplished by bulldozers and, depending upon moisture content, the material was either sprinkled or scarified to increase or reduce the moisture content prior to rolling with dual-drum sheepsfoot rollers. Upon being granted permission to include up to 5-inch rock in the impervious section of the dam, the contractor agreed to increase the number of roller passes from 12 to 14 at no additional cost to the Government.

59. Sand and Gravel Fill (Zones 2 and 4). Materials for use in zone 2 and a major portion of zone 4 were obtained from borrow areas located in the streambed and flood plain upstream from the dam. The material consisted of clean well-graded river sand and gravel having a maximum size of 3 inches. The material was ideal for the purpose intended, being easily placed and well suited to the compaction specified.

The material was placed in approximately 12-inch lifts and was required to be thoroughly wetted prior to compacting with four passes of a heavy crawler tractor (fig. 24).

Field densities of the material indicate that the material was compacted to an average of 80 percent of relative density (sec. 16). Seventy percent had been proposed as adequate.

Placing methods in the zone 4 section were the same as outlined above. The material type just discussed was used, along with suitable dam foundation excavation and oversize screenings from the separation plant, to make up the total yardage requirements.

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Figure 24. --Placing zone 2 and zone 4 material in the upstream part of the river section. Material in the foreground is being compacted with a large crawler tractor and sheepsfoot roller. 5-SL-890, November 2, 1950

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Rolling zone 1 material in a pothole downstream from station 14+00. 5-SL-682, June 29, 1950

60. Tamped-Earth Fill (Special Compaction). - The extremely irregular foundation and abutments resulting from the blocky characteristics of the exposed andesite rock surfaces required a great amount of special compaction or tamped-earth fill. Areas along abutments were tamped with small pneumatic hand tampers and one large trailermounted pneumatic tamper to a thickness of 2 feet measured in a horizontal direction from the contacted surface. On the foundation it was necessary to use the same procedure in filling small depressions to obtain a cushion and a reasonably level floor before employing sheepsfoot rollers. Material used was from the same source as the remainder of zone 1. After dumping, the material was shoveled into place by hand and larger rocks removed so that mechanical tampers could obtain the desired results. A total of 1,643 cubic yards of material was placed in the dam and dike in this manner.

61. Rock and Cobble Fill (Zone 3). A major portion of this material was originally intended to be obtained from designated slide rock borrow areas adjacent to the dam site. Preliminary estimates of yardages contained in these areas were higher than actually existed, and the supply was augmented by rock spalls and smaller weathered, but sound, rock fragments from the riprap quarry. The remainder of the material was oversize cobbles recovered from the separation plant. The quantity of this material was reduced approximately 7 percent when the maximum size of rock allowable in zone 1 was changed from 3 to 5 inches.

Material was placed in approximately 3-foot lifts with no special compactive effort, the larger rock being bulldozed to the outer slope. Because of the high moisture content of material in zone 1 borrow areas, it was necessary to stockpile some cobble screenings and reprocess them after drying in order to remove objectional amounts of sand and clayey material before placing.

62. Riprap on Upstream Slope. - Riprap material was quarried from designated areas as previously described (sec. 56). The rock was quarried within the gradation requirements and was hauled in end-dump trucks and dumped and bulldozed into place. Some barring and hand placing was necessary to fill voids and maintain a reasonably regular slope. Riprap placement was maintained as close as possible to the average fill elevation during construction.

63. Special Zones at the Top of the Dam. Slopes on zone 1 material were altered to provide for a 12-foot horizontal width of material where it was discontinued at elevation 10,044. Zone 3 material on the upstream slope of the dam was discontinued at elevation 10,038, 10 feet below the crest elevation. Downstream zone 3, zone 2, and riprap materials were continued to elevation 10,047 plus camber, or 1 foot below the crest. A maximum camber of 1.5 feet was placed in the main dam section; and 0.7 foot was placed in the dike section. The remainder of the fill consisted of 12 inches of selected gravelly material. The upstream slope of the dike section was varied at the left abutment to provide for an access road to the dam. (See order for changes No. 5 in section 28.)

D. Foundation Drilling and Grouting

64. General. Drilling and grouting operations were initiated on the dam and dike foundation August 27, 1949, and all foundation drilling and grouting were completed November 8, 1950, work being discontinued during the winter months. Filling of voids behind the tunnel lining, which was performed by grouting methods at the contractor's expense, was initiated November 25, 1949, and completed May 25, 1950. Pressure grouting of the tunnel was not initiated until May 23, 1950, since all void filling back of the concrete lining was required to be substantially complete prior to pressure grouting operations. Pressure grouting of the tunnel was completed June 30, 1950.

65. Drilling Grout Holes.

(a) Foundation. --Foundation drilling throughout the the grout cap was performed on 10-foot centers and generally to stage depths of 35 and 60 feet in alternate holes, and to stage depths of 55 and 110 feet in alternate holes.

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Figure 26. --Large pneumatic tamping machine being used to compact zone 1 material on right abutment of main dam. 5-SL-1050, June 21, 1951

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