(3) All material would be excavated at the unit price bid for borrow area N material.

The deficiency of suitable zone 1 material in borrow area K (sec. 149(a)) led to the development of an extension to borrow area N, at the north end of the pit, along with the opening up of the supplemental K borrow areas, K1 through K7. Order for changes No. 9, dated August 3, 1955, directed the contractor to obtain additional zone 1 material from borrow area N, as well as the supplemental K borrow areas; and, in addition, provided for the excavation and transportation to the dam embankment of zone 2 material from borrow area N. The approximate limits of the extension to borrow area N are shown on drawing 456-108-1544.* Prior to full development of the extension as a source of zone 1 material, it was thoroughly investigated. This work was performed during 1954, when representative material was removed from test holes and checked for moisture content, gradation, compaction and permeability. Approximately 20 auger holes were excavated and the material tested by Government forces.

In excavating borrow area N and its extension for zone 1 and zone 2 materials, the contractor used, for the most part, a 6-cubic-yard power shovel and a 7-cubic-yard dragline (fig. 138). A pneumatic-tired earth loader was also used but on an intermittent basis, as it was frequently moved from pit to pit depending on the moisture conditions. The quantities for materials obtained from borrow area N, in cubic yards, were approximately as follows:

150. General. Palisades Dam is a rock-faced, earth fill structure, 270 feet high, 2, 100 feet long between abutments at the crest, 2, 100 feet wide at the base (from upstream to downstream extremities) and composed of approximately 13, 500,000 cubic yards of material. The crest is 5, 630 feet above sea level. Initial construction of the dam embankment started in August 1952 with the first placement of zone 3 type material. By August 1957 the embankment was virtually complete. See specifications drawings 456D-117 and 456-D-118, included as figures 6 and 139, for general plan and sections of the embankment.

151. Preparation of Foundation. After stripping humus, boulders, and undesirable materials, the foundation for zones 1, 2, and 3 was roughly leveled, sprinkled, and rolled. Gravelly materials were compacted with crawler-type tractors, and finegrained materials with standard sheepsfoot rollers. The clay-silt series in the cutoff trenches was treated like rock, with all loose material being removed by hand methods and air jets. For more detailed information, see sections 143 and 148.

152. Zone 1 Material. - (a) Construction Methods.-- The final cleanup of the claysilt series in the main and upstream cutoff trenches was accomplished by removing all loose material with hand tools and/or air jets. Drainage ditches were excavated along the upstream and downstream edges of the trenches to intercept any water flowing through the sand and gravel overburden. Pumping stations were located in low spots to remove the inflowing water sufficiently to keep the clay-silt contact dry. Zone 1 material was placed to a depth of 3 or 4 feet, and then the drainage ditches were partially backfilled with zone 3 material. Both types of material were adequately compacted in accordance with specifications requirements. This process was repeated, keeping the ditches about 3 feet below the top of the zone 1, until the fill was above the water table, at which point the ditches were fully backfilled with zone 3 material and abandoned. In several areas within the cutoff trenches, irregular depressions were encountered in the foundation requiring special compaction. These were filled with zone 1 material, placed in approximately 4-inch layers, and compacted with pneumatic hand tampers.

*Not included.

Figure 138. --A 7-cubic-yard dragline bucket getting its teeth changed during construc

tion operations at Palisades Dam. During tough excavation work, the dragline needed a change of teeth about every 3 days. PL-789.

DETAILS OF CONCRETE GUARD POST

GENERAL PLAN AND SECTIONS

Final cleanup of the abutments progressed upward with and slightly ahead of the zone 1 fill. Right-abutment work, for the most part, was similar to that in the cutoff trenches wherever the clay-silt series was encountered, loose material being removed with hand tools and/or air jets. By comparison, final cleanup of the left abutment was relatively minor, as most of the overburden was removed down to andesite during the stripping work of the 1952 and 1953 construction seasons. The unsuitable material that remained was in isolated pockets and its final removal was accomplished by hand methods.

Prior to placement of any new zone 1 material, the contractor removed all pockets of excessively wet zone 1 material found on the fill after the spring thaws and prolonged periods of rain. The unsuitable material was either wasted or stockpiled for future use upon sufficient drying.

Zone 1 material was hauled primarily with bottom-dump trucks and then spread to the required thickness with 200-horsepower crawler-tractor dozers. Compaction was accomplished with 12 passes of 11-foot-wide sheepsfoot rollers. Some of the zone 1 material hauled contained an undesirable amount of roots, rocks, etc., which was handpicked and removed from the embankment. Water was added, as required, with sprinkler wagons consisting of 150-horsepower rubber-tired tractors mounted with 4, 500-galloncapacity tanks. The water was processed into the fill with double-disk plows drawn by 200-horsepower crawler tractors. The depth of the lifts was held well under the 6-inch maximum allowed in the specifications, as daily profiles showed an average for all zone 1 lifts to be approximately 0.4 of a foot.

The zone 1 material adjacent to the concrete cutoff walls and along the leftabutment rock contact was compacted with pneumatic hand tampers or rolled with a special narrow-drum roller consisting of a single 5-foot drum, cut in half, and mounted on a central tongue. Omission of the conventional frame permitted the special roller to work closer to the walls and left-abutment rock than would be possible with standard equipment.

Extensive water-washed depressions were encountered in several areas of the left-abutment contact with the impervious material. The contractor requested and was granted permission to fill these holes with lean concrete in lieu of zone 1 material at no increase in price to the Government. This work was usually performed in conjunction with the placement of concrete in the cutoff walls and aided materially in keeping construction of the specially compacted areas from falling behind that of the rest of the zone 1 embankment. Approximately 1,510 cubic yards of lean concrete were placed in these depressions.

(b) Moisture Control.--The different moisture contents of the material from the various zone 1 borrow areas made moisture control some what of a problem. Borrow area N zone 1 material was consistently dry, but by adding water with fire hoses at the pit and by means of a sprinkler wagon on the fill, good moisture control was achieved for borrow area N material. Borrow area K zone 1 material, on the other hand, was consistently wet. The excavation and placement operations for this material, as a result, had to be limited to facilitate as much drying as possible. Selective excavatioh in the pit and the long cuts opened for the earth loader aided materially in the drying work. (See also sec. 149.) On the embankment, material from borrow area K was spread over as large an area as possible, using relatively thin lifts which were disked frequently until a satisfactory moisture content was reached. Warm weather in July, August, and early September also aided in the drying effort. When moisture conditions in borrow area K were too unfavorable, operations were switched to the other K pits, K1 through K7. Although this switching to the other K pits permitted a continuation in the placement of zone 1, the problem of variation in moisture content was somewhat increased, with the material from K1, K2, and K4 pits usually being very dry and the material from K3, K5, K6, and K7 pits usually excessively wet.

To expedite zone 1 placement, in 1954, the placing limits were relaxed partially in the impervious blanket area from 500 feet upstream of the dam axis to and within the upstream cutoff trench. The zone 1 material was considered dry enough to cover with another lift of borrow area K material if the penetration-resistance needle reading was greater than 500 pounds per square inch, and dry enough to cover with a lift of dry

material from another borrow pit if the needle reading was greater than 300 pounds per square inch. With this control it was possible to use a larger amount of borrow area K material.

For other data on moisture, compaction, etc., refer to the "Summary of Field and Laboratory Tests of Compacted Fill--Fine Grained Materials" contained in the "Final Report of Test Apparatus Installation--Palisades Dam, " February 1958.

(c) Progress.--Final computations showed that approximately 4, 850, 800 cubic yards of zone 1 material were placed in the dam embankment. A breakdown of this final quantity showing the progress of zone 1 placement on a yearly basis is indicated below:

1/ The above dates are for the first and last placement only of zone 1 each
year. In between these dates actual placement of zone 1 may have been
negligible for several days or more at a time because of bad weather,
contractor's diversion of the river, etc. This also applies to the place-
ment dates given elsewhere for zones 2, 3, and 4.

153. Zone 2 Material. - (a) Screening Plant.--Palisades Contractors' initial efforts at processing zone 2 material started on September 17, 1952, with use of a portable grizzly. This method removed oversize rocks but provided no facilities for adding moisture. A 2-1/2-cubic-yard dragline was used to feed the grizzly from a zone 2 stockpile with the entire unit moving as the excavation progressed. The unit was shut down from September 24 to October 3 while the grizzly was being modified so that it could be fed directly from trucks. The new operation, although more efficient, was still slow. During the latter part of 1952, construction was started on the permanent screening plant which was to contain facilities for adding moisture to the zone 2 material.

The contractor started using his permanent screening plant in 1953, and the plant, with several subsequent modifications, served throughout the construction period. A discussion of the plant, including certain difficulties that developed, the efforts at their solution, and the results obtained, is given in the final construction report (see bibliography).

(b) Construction Methods.--Zone 2 material was hauled to the dam embankment, primarily in bottom-dump trucks, where it was dumped and spread in 7-inch loose lifts with 200-horsepower crawler-tractor dozers. Compaction was accomplished with sheepsfoot rollers pulled by 200-horsepower crawler tractors. Occasionally the contractor was permitted to haul zone 2 material directly to the embankment, bypassing the screening plant. This occurred only when the zone 2 material from a borrow area or foundation excavation was determined to be near a processed condition and to contain only a small percentage of oversize rock. The oversize rock that was present was handpicked and hauled from the fill by truck. On June 2, 1954, a mechanical rock picker was tried by Palisades Contractors for this work but proved inadequate. In 1955 a rock rake was used to pull the oversize rock to the surface of the fill for subsequent hand picking. As the results were considered to be satisfactory, its use was continued. The rock rake was found also to be beneficial for mixing when water was added to the material on the fill.

(c) Moisture Control.--Water was added to zone 2 material at the screening plant, on the fill, and occasionally in the borrow pit. As adding water and then processing the