of the pit was logged and four samples taken. A second deposit with similar material was found about 12 miles west.

If the data obtained may be taken as representative, the Hartline deposit, although similar in many respects, is much less favorable than the Adrian deposit by reason of the very high proportion of sand, the exceptionally high fineness modulus of the sand, and the lower fineness modulus of the gravel.

Results of tests on aggregate.-Sieve analyses, silt determinations, and calorimetric tests were made in the Denver laboratory on all of the above-mentioned samples. Some concrete tests are contemplated. The principal results of the completed tests are tabulated below:

NOTE.-Depth of layers and proportions of sand and gravel were taken into account in determining "weighted averages" values.

Foundation conditions.-Knowledge of foundation conditions at the dam site is limited to the information secured by a geological examination and the drilling of 16 diamond-drill holes. On the basis of information it is believed that the surface of bedrock lies at approximately elevation 880 across the valley and rises with side slopes of about 112 to 1 to the elevation of the crest of the dam. The foundation rock over the whole area is described as a medium gray, fine grained, hard, dense granite, with joints at intervals of 2 to 6 feet. There is no shattering or crushing at joints and the presence of the joints will facilitate quarrying and excavating the rock. Open joints were found to depths of 35 feet but it is believed that these joints can be successfully sealed by grouting. The cores indicated that 5 to 10 feet of rock was unsound and should be removed from the valley floor and that 10 to 15 feet should be removed from the rock surfaces on the slopes. From 20 to 70 feet of fine-grained

clay lies above the bedrock. This is believed to be impervious and it should afford a watertight connection between the sheet piling of the cofferdams and the bedrock. A mixture of clay, sand, and gravel is found above this clay stratum, varying from a few feet up to one hundred feet. The presence of the clay just above the granite will undoubtedly simplify the foundation work and aid in keeping water out of the excavation but at the same time the clay may tend to squeeze out under the weight of the overburden and this condition will affect the design of the cofferdams from the standpoint of stability.

Two depressions in the surface of the bedrock were disclosed in the drilling, one at elevation 790 and another at elevation 780. Sufficient drilling has not yet been done to determine the shape and extent of these depressions but they are believed to be potholes in an old stream bed or else depressions eroded by glacial action. There are no surface indications of faults within the area of the site. The large amount of river deposit over the valley floor necessitates enormous quantities of foundation excavation.

Diversion of river during construction.-The care of the Columbia River during construction of the dam presents a difficult problem owing to the large discharges that must be passed. During the period in which there are records giving the flow at the dam site, the maximum daily average flow is found to be 496,000 cubic feet per second. In the period of record 17.83 years, the mean daily maximum flow exceeded 450,000 cubic feet per second during three different periods and these aggregate only 42 days.

The diversion works will be carried out in two main stages. The first stage includes the excavating of a diversion channel along the east bank of the river; the driving of a cellular sheet pile cofferdam to rock, parallel to and adjacent to the east bank of the river; and the turning of the river into the diversion channel by means of timber cribs sunk in the main channel between the west bank of the river and the ends of the cellular cofferdam. The upstream cribs will be built to elevation 795 which is estimated to pass 600,000 cubic feet per second without overtopping the cofferdam. After completing the excavation within this first cofferdam the concrete will be brought up to elevation 1,025, except the alternate blocks across the spillway section which will be left at elevation 950 for the passage of flood water. In addition to these low blocks thirty-one 12-foot diameter temporary openings will be left through the dam for the passage of flood water.

The cofferdams of the second stage of the diversion plan will extend from the east bank of the river to the ends of the sheet pile cellular cofferdam. These will be raised to elevation 1005 which is estimated to divert 450,000 cubic feet per second through the openings left in the west portion of the dam. After the excavation is completed the concrete in the east section of the dam will be poured to elevation 1,025. Fourteen additional temporary 12-foot diameter holes will be placed in this section which, together with the 20 permanent 5 foot 8 inch by 10 foot outlets, will provide enough spillway capacity to pass 50,000 cubic feet per second after the 15 holes through the power-house section of the dam have been closed, without overtopping the low blocks at elevation 950. This will give

two months time at least in the low-water season for raising the low blocks. A number of the low blocks will be kept low at all times until the drum gates are installed.

The temporary 12-inch diameter openings will be utilized until the spillway crest is completed after which they will be plugged with concrete. A steel bulkhead will be provided for closing each of these openings to facilitate the pouring of the concrete plug.

Description of dam and appurtenances.-The Columbia River Dam is located on the Columbia River near the head of Grand Coulee in section 1, T. 28 N., R. 30 E., and section 6, T. 28 N., R. 31 E. It is a straight concrete gravity dam 450 feet high and 4,100 feet long at the elevation of the roadway on top of the dam.

The spillway consists of an overflow section of the dam, across the river channel, with an overall length of 1,918 feet. The spillway discharge assumed to be a maximum of 1,000,000 second-feet, is controlled by fourteen 124 by 28 foot structural-steel drum gates. The drum gates will be designed for automatic control, handoperation, or remote control from the power plant. With 1,000,000 second-feet discharge over the spillway, the water surface in the reservoir will be at elevation 1,289.6, causing a 30-foot depth on the crest of the spillway. The energy of the spillway water will be dissipated on a sloping concrete apron. This apron will be designed to create a hydraulic jump at all stages of the tailwater. The final design of this apron will be determined by hydraulic model tests. The spillway will be bridged by 14 concrete arches, providing a 24-foot roadway, these arches being supported on concrete piers 14 feet thick carried up from the overflow crest structure.

Sluiceway openings are placed through the dam on the right side of the spillway at elevations 935, 1,050, and 1,165 for emergency and diversion purposes. Twenty 5 foot 8 inch by 10 foot conduits are shown on the drawing at elevation 935. These conduits have a discharge capacity of 30,000 second-feet with water surface in the reservoir at elevation 965. The drawings also show eight 5 foot 8 inch by 10 foot conduits at elevation 1,050 and likewise at elevation 1,165. All of these sluiceway conduits are controlled by tandem 5 foot 8 inch by 10 foot hydraulically operated slide gates.

The Columbia River is the main artery for fish migrations between the tributaries and the Pacific Ocean and for this reason the problem of passing fish through or over the dam is of utmost importance. A mechanical fish elevator, somewhat similar to that used on the Baker Dam has been tentatively selected as the most practicable type for fish traveling in an upstream direction. This elevator will raise the fish from the head end of a flume, located adjacent to the draft tubes, up to the crest elevation of the dam and will then lower them into the reservoir. The fish elevator consists principally of a flume extending the full width of the tailrace along the downstream side of the power plant, together with a fish elevator operating from the head of the flume upward through an inclined shaft to the crest of the dam and downward through a second inclined shaft to the reservoir.

As the possibility of navigation of the Columbia River is very remote, due to the great expense involved in improving the river below the dam, no design or cost for locks has been included in this report.

The meager information available relative to property damage within the reservoir basin does not warrant the preparation of a detailed estimate at this time. This item of cost is included in a general estimate for reservoir right-of-way.

POWER PLANT

Buildings and structures.-The power house is located on the downstream toe of the dam to the left of the spillway section. The building is a concrete and steel structure 1,028 feet long and 78 feet wide with the 220,000-volt transformer equipment located between the power-house superstructure and the dam. The generator-room floor has been placed at an elevation just above the maximum recorded tailwater elevation, but the entire building is made watertight to an elevation several feet above an assumed maximum flood water condition.

All low voltage switching equipment, governor oil pumping equipment, and the passages for carrying water, oil, and air piping and power busses and cables are located in the substructure of the building. Two house generators are located at the extreme left-hand end of the plant at which point there is also dismantling space for the units and a machine shop for handling repair work. The building contains two cranes having a combined capacity sufficient to lift the heaviest part of any generating unit.

A control house containing the control equipment for both power house and pumping plant is located apart from the power house adjacent to the left end of the building.

Water is supplied to the turbines through a concrete and steel trash rack structure on the upstream side of the dam. An individual penstock controlled by a stoney gate at the upper end is provided for each main generating unit. The penstock openings have their center lines at elevation 1180. The steel penstocks pass through the dam at this elevation and then follow the downstream face of the dam to the turbines in the power house. A Gantry crane is provided on the top of the dam` for handling penstock gates and other equipment.

Hydraulic and electrical machinery.-Fifteen main generating units of 105,000 kilowatt-capacity each are proposed for the power plant. The turbines are rated at 147,000 horsepower each at 330 feet head and the generators are rated at 120,000 kilovolt-amperes each at 120 revolutions per minute, 22,000 volts, 60 cycles, 87.5 per cent power factor. An individual governing system including actuator, oil pump, and oil tank is provided for each turbine and each generator has a direct-connected exciter.

Each generating unit has its own transformer bank for raising th voltage to 220,000 and switching and protection equipment has been included for one outgoing transmission line per generating unit. In addition, five of the generators are equipped with oil circuit breakers, cables and control equipment for supplying power to the twenty pumps which are proposed for the ultimate installation in the pumping plant.

Annual costs. The annual cost of operation and maintenance of the power plant has been taken at 50 cents per kilowatt of installed capacity for the ultimate development or $785,000. For the purpose

of financial studies it has been assumed that the annual operation and maintenance cost of the initial development consisting of three units will be one-third of the cost of the complete development and will increase uniformly as additional units are installed. The annual operation and maintenance cost for the dam has been taken as $150,000.

Depreciation for both dam and power plant has been taken on an assumed average 30-year life for all items considered depreciable. An annuity has then been set up which when invested at 4 per cent will accumulate the required amount for replacement at the end of a 30-year period. On this basis the required annuity is 1.78301 per cent of the original cost of the depreciable items.

These annual costs are summarized in the following tabulations:

Cost of depreciable items for three units in power plant‒‒‒‒

9, 563, 176

Columbia River pumping plant. The pumping plant building is located along the reservoir shore line just upstream from the left abutment of the dam. It is a reinforced concrete structure about 640 feet long by 100 feet wide with practically all the building below water when the reservoir is at maximum elevation. A Gantry crane will travel the entire length on top of the building and will give access to the machinery through removable hatchways placed over the pumping units. Drainage for the interior of the structure is secured by means of a drainage tunnel leading to a gravity outlet in the tailrace below the power plant. This tunnel will also carry the power cables from the power plant to the pumping plant for the operation of the pump motors. A concrete and steel trash-rack structure occupies the entire reservoir side of the building.

Twenty pumping units are proposed for the ultimate installation, each unit consisting of a single stage pump, having a capacity of 800 second-feet when operating under a total head of 370 feet, direct