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Figure 18. --Sprinkler system for adding moisture to zone 1 material. On the sloping portion of the area, furrows were plowed on contours between pipe lines for more economical use of the water.

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Figure 19. --Moisture penetration on the face of a 12-foot cut in borrow area 2 after sprinklers had operated 72 hours. A cut from the bottom to top of the face resulted in a dry and moist earth mixture of near optimum moisture content. 4-16-48

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Figure 20. --View of borrow area 3 showing depth of cut and general type of material. The material shown here was considered excellent. In other parts of the area the material contained much less gravel, but it was still usable. 1804-4

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Figure 21. --View of east side of borrow area 3. The material was excavated in 12-foot lifts to a depth of 60 feet below original ground. 3-2-48

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The deepest point of excavation was 60 feet below the original ground surface (fig. 21).

(f) Areas 4, 5, and 6. --When the specifications for the spillway were changed (sec. 20), it became necessary to located an additional suitable rock source for surfacing the dam. The resident engineer and contractor's representatives located three sites of suitable rock and designated them as borrow areas 4, 5, and 6 (fig. 4). Area 4 was located 500 feet downstream from station 5+00, area 5 was located about 300 feet downstream from axis station 97+00, and area 6 about 200 feet downstream from axis station 163+00. All areas contained an overburden of soil and loose rock of varying depth up to a maximum of 4 feet, which the contractor was required to strip prior to any drilling or blasting. Areas 5 and 6 had a working face about 20 feet deep and all holes were drilled at 20-foot centers to this depth. Enough holes were drilled to produce an adequate volume of rock and only two rows in from the face were blasted at one time. Then the loosened rock was loaded and placed on the dam and the blasting process repeated. A similar drilling pattern was adopted in area 4, but holes were drilled to 24 feet and, in addition, coyote holes were put in along the bottom of the face and loaded and blasted. The contractor later tried drilling 2-foot holes and then blasting. This method was not satisfactory as it was slower and resulted in the loss of steel when drilling the second lift. The rock broken by the first blast would wedge in the hole while drilling the second lift.

34. Placement of Material. (a) Zone 3. --The contractor deviated from the normal procedure in constructing this zoned earth-fill dam because the cutoff trench excavation resulted in a considerable delay in grouting and embankment placement. Special permission was obtained to place zone 3 material prior to placing zones 1 and 2 materials. Zone 3 material was hauled from borrow area 3 in bottom-dump trucks and dumped into windrows spaced about 4 feet apart (fig. 22). Bulldozers were used to break the windrows down and spread the material in layers about 12 inches thick. The deposited material was incorporated into the fill by sluicing. By experimentation it was found that if a horizontal sprinkler pipe with numerous perforations so placed as to direct the flow downward was attached to the water wagon about 10 inches above ground, sufficient water could be applied by an average of four passes with the water wagon to properly sluice the gravel into place (fig. 23). When placing zone 3 material ahead of zones 1 and 2, the height to which it could be placed was limited. The outer slope of zone 3 material was made to conform to the required slope 4 to 1, 3 to 1, or 2 to 1 depending on the location. Because there was no material for the zone 3 material to lie against, the inside slope became a 1-1/2 to 1 reverse slope. As a result, the cross-sectional area of zone 3 material was trapezoidal.

Under normal placing conditions, placement of zone 3 material was permitted only when zone 1 and 2 material was higher than zone 3. This procedure prevented water which was used to sluice zone 3 material from draining into zones 1 and 2 and raising their water content above optimum.

(b) Zone 1. --Certain preliminary steps were carried out in the area on which zone 1 material was to be placed. When placement was on rock, the low spot in the area was dampened with water and the material deposited to a depth of approximately 10 inches with a moisture content at optimum or slightly more. The material was hand tamped. When material was placed upon earth, the surface was compacted by tamping rollers. After this preparatory treatment the surface was ready for fullscale placement operations.

The zone 1 material was hauled to the point of placement by bottom-dump trucks and discharged at wide-open position into windrows approximately 6 feet apart. The trucks moved at speeds of 20 miles per hour or less. A bulldozer was used to level the windrows to a layer about 10 inches thick. The newly placed 10-inch lift of material was compacted into a 6-inch layer by 12 passes of the sheepsfoot roller, as required by the specifications.

Near vertical walls or other places where a tamping roller could not be used, the contractor was required to compact the material by hand tamping. The commercial machine did not compact the material within specification limits unless operated over the area for so long a time that the cost of compaction was excessive. A more economical tamping machine (fig. 24) was made from a pneumatic jackhammer. This converted jackhammer, because of its greater weight, heavier pounding action, and

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Figure 22. --Placing embankment, zones 3, 2, and 1 materials.
The trucks on the extreme left are placing zone 3 materiál, the wa-
ter wagon is sluicing it into place, the two tractors pulling rollers
are compacting zone 2 material into place, and the trucks and bull-
dozers are placing zone 1 material.

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Figure 23. --Sluicing zone 3 material in place into the embankment. A bulldozer was used to level the material ahead of the water wagon. 364-4

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faster operation, was much more effective and economical than the commercial machine. The use of the commercial machine was discontinued after the first 3 weeks of use and the converted jackhammer was used exclusively for the remainder of the job.

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When elevation 922 was reached at station 170+00, the zone 1 material was sloped to form a ditch. When the other zones of material had also been placed to elevation 922, water was allowed to flow across the dam through the ditch in the zone 1 material. Placement operations were halted until the completion of the outlet works tunnel and installation of the 4- by 4-foot gate, after which the flow of water was diverted through the tunnel and normal construction activities were resumed.

(c) Zone 2. --Placement of zone 2 material followed the same general pattern as that of zone 1. It was found experimentally that a mixture of one part of silty material and four parts of pit-run gravel and sand resulted in a satisfactory zone 2 material. This material was processed and compacted in a manner identical to that used in zone 1. Because of the porosity of the outer edge of zone 1 material the contractor was required to make a one-blade-width cut. with a bulldozer at the line of contact of zones 1 and 2, so that when additional zone 2 material was placed, it would be bonded to zone 1 instead of lying against a porous layer of material.

(d) Modifications. --During construction of the dam embankment it became necessary to revise the location of the various zones above elevation 1047. According to the original plans the outside slope of each zone was to continue on its prescribed slope to elevation 1059.5. This resulted in such narrow working spaces between zones that proper placement and processing operations were not possible. At about elevation 1047 placement of zone 2 material was discontinued, zone 1 material was widened to cover zone 2, and the outside slopes of this widened zone were made 2-1/2 to 1 on the upstream and 2 to 1 on the downstream sides of the embankment. At elevation 1056 placement of zone 1 material was discontinued and only zone 3 material was placed from that point to elevation 1059.5 which was the subgrade for the roadway. Above elevation 1053 the outside slopes of the zone 3 material were changed to 1-1/2 to 1. This change in slope widened the top of the dam sufficiently to permit

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