Figure 50.--Cleanup in flow breccia material on the left abutment. A triple-action air tamper is shown near the center of the photograph. P113-129-398, May 2, 1960. Figure 51. --Columnar basalt on the right abutment. P113129-401, May 2, 1960. All embankment material used during August, September, and October was excavated from borrow area A. During the latter part of September and until October 2, the contractor pumped the flow of the river through a 48-inch-diameter pipeline on the right bank of the river. The flow of the river increased until four pumps were unable to take care of it, and as a result water backed up and over the portion of borrow area A adjacent to the river, saturating the material over the entire bottom area. During October, November, and December it was impossible to excavate to the proper depth of cut in the bottom portion of the pit where most of the fine material lay. As a result of this, the contractor elected to do some mixing, excavating in a horizontal cut in the bottom as the material dried and also from the drier gravels near the surface. This method of mixing gave a very satisfactory material, but it proved costly. The amount of fine material which could be obtained from the lower portions of the pit was limited due to moisture content. On November 2 the contractor requested permission to extend borrow area A to a dry area lying across the river from the east portion of the original area. This request was granted by letter of November 19 with the stipulation that all fine material in excess of 550, 000 cubic yards must be obtained from borrow area B rather than from borrow area A or its extension. The extension to borrow area A was used as a source of fine material during the latter part of November and until December 3, when an excess amount of pumice was encountered and the extension area had to be abandoned. During December the contractor excavated the majority of the required material from borrow area B (fig. 52). After placing operations were discontinued on the fill because of freezing weather, the contractor continued to operate the separation plant until December 30, 1959, stockpiling zone 1 material. Excavation operations were resumed on March 25, and material was obtained from borrow area B during April and most of May. From the latter part of May until August 9, the contractor alternated between borrow areas A and B to obtain maximum utilization of available equipment. By August 9, 1960, an estimated 550, 000 cubic yards of material had been excavated from borrow area A and the contractor was instructed to take all remaining material from borrow area B. Excellent material was obtained from both borrow areas A and B and far better densities and percolation factors than expected were obtained. Original test pits were dug about 15 feet deep in borrow area A; however, as excavation progressed good material was encountered below these test pit depths. This deeper excavation proceeded into the hill until cuts up to 40 feet deep were obtained. Additional silt layers were encountered at the lower depths, which blended with the upper gravels to produce excellent material. Although both borrow areas A and B produced excellent zone 1 embankment material, in borrow area A there was a pumice deposit which was not used. Also, in the eastern end of this borrow area considerable large rock was encountered. Borrow area B also had pumice deposits located mostly in the eastern portion. This area had more large rocks than borrow area A most of which were used for the zone 4 embankment. Practically all excavation in both areas was made by 25-cubic-yard two-wheel motorized scrapers that were pushed by 191-horsepower crawler tractors when being loaded. Cuts were usually made on a 1-1/2 to 1 to a 4 to 1 slope in such a manner as to cut through the various strata of silts, sands, and coarser rock. A 3-cubic-yard shovel was used in both pits for a short period; but this did not prove as efficient as scrapers, so it was discontinued. (c) Rock Quarries. --All suitable rock from the required excavations, such as the tunnel, dam foundation, spillway, and access road, was stockpiled both upstream and downstream of the dam. This stockpiled rock was used for the dam faces at the lower elevations. When the majority of this stockpiled rock was gone, the contractor chose several other locations from which to borrow rock; they were as follows: A talus slide rock area approximately 1 mile downstream on the right side of the river. A talus slide rock area approximately one-half mile downstream from the dam on the left side of the river. A rock quarry along the relocated State Highway No. 27 approximately one-half mile above the dam on the south side of the river. This required blasting; and since most of the rock was hackly basalt, it was used only for the inside portions of zone 4 (fig. 53). A quarry at the mouth of Bear Creek (fig. 54) approximately 2-1/2 miles upstream from the dam. All the upper portions of zone 4 material were obtained from this source. This proved to be excellent rock but all of it had to be blasted. All zone 4 material was excavated with a 3-cubic-yard shovel, loaded on rock wagons, hauled directly to the dam, and dumped in place. Rock rakes were used to work the larger rocks to the outside face of the dam (fig. 55). 49. Separation Plant. The specifications required that all rock over 3 inches be removed from zone 1 material and used in the zone 3 portion of the embankment. The contractor purchased a wobbler classifier which was 48 inches wide, contained 18 bars, and had a total length of 15 feet. It was powered by a 15-horsepower variable-speed electric motor. Material was excavated and hauled from the borrow pits in 25-cubic-yard motorized rubber-tired scrapers and was dumped at a point above the plant. The material was then pushed by dozer into a hopper with an uncontrolled feed onto the wobbler. An endless rubber belt ran under and parallel to the wobbler and carried the zone 1 material on an approximately 20° incline to a bin equipped with an air-operated gate. The bin discharged into 25-cubic-yard motorized rubber-tired scrapers which hauled the material to the zone 1 embankment. The setup is shown in figure 56. Moisture, when required, was added to the zone 1 material as it left the belt and fell into the zone 1 bin. From two to four spray bars, fed from a pump, were used to supply the water. This method proved very satisfactory and a very close moisture control was obtained. Cobbles larger than 3 inches were discharged from the end of the wobbler onto a short endless belt running at right angles to the wobbler, which in turn discharged onto an inclined endless belt that carried the zone 3 material to a stockpile. From this stockpile it was loaded by shovel and hauled to the embankment. The contractor started installing the plant on the southwest end of borrow area A approximately one-fourth mile upstream from the dam in March 1959 and completed the installation in July 1959. The plant was not completely satisfactory. Although it was rated at 350 to 400 cubic yards per hour, its maximum output was approximately 275 cubic yards per hour under ideal conditions. If the material was too dry as it came onto the wobbler, it fed too fast and the fines were not removed, so a flap gate was installed controlling the feed onto the wobbler. This flap was adjustable and with material having proper moisture content it was raised. If the material was too wet, clay and silt lumps were not removed and consequently were deposited in the zone 3 stockpile. Both of these conditions could have been eliminated with a longer wobbler. The separation was expensive because the material had to be handled too many times. The zone 1 storage bin was too small and the contractor could not coordinate his hauling to keep the plant in continuous operation. B. Embankment Construction 50. General. Embankment placing operations extended over two construction seasons. Placing started on September 13, 1959, in the bottom of the cutoff trench approximately 55 feet below the river level and continued until December 22, 1959, when operations were discontinued because of freezing weather. Placing was resumed on March 25, 1960, and continued until September 22, 1960, when the dam embankment was virtually complete. Figure 52. -- Fifteen-foot vertical cut in borrow area B showing gradation of sands, silts, and gravels. P113-129-297, November 7, 1959. Figure 53. --Zone 4 material from the rock quarry adjacent to station 13+00 of the relocated highway, as it was placed in the embankment. This material was a hackly basalt which broke into small pieces and had to be held back from the face of the dam to allow for larger face rock. P113-129-501, July 28, 1960. |