rapids was more economical than a location further up-stream. Going further downstream would have necessitated excavating through loose material below the rapids to get a favorable foundation on ledge rock. While each channel had rapids, the south channel was deeper and the C. St. P. M. & O. Ry., ran along the south bank at this point. The bank is 85 feet above the river bed and made depositing of concrete in the powerhouse comparatively easy.

The site presented other natural advantages when it came to locating the spillway. Placing it next to the powerhouse, which is in the old channel, would have caused the north end to come in the north or new channel, necessitating a high, costly concrete spillway with the disadvantages accompanying a long fall of the spilling water. Accordingly the cheaper earth embankment was built adjoining the powerhouse and the spillway located on the plateau further north, where ledge rock rose to elevation 872.0 or 37 feet above the north channel river bed.

The embankment material between the powerhouse and the south bank was obtained from the south bank. That between the powerhouse and spillway section was handled by steam shovels and trains. It was transported over a timber trestle and dumped, after which it was sluiced in place.

The water in the south channel of the river was coffered off above and below the proposed site. Ordinary timber crib coffers filled with rock and "A" frames sheeted upstream and backed up with rock were used. The first coffers crossed the south channel above and below the site and extended across to the island. This left open the channel north of the island. Upon closing the north channel the water was allowed to pass through twelve sluices in the hollow dams on either side of the generator house and through the sluices in the draft tubes.

CONSTRUCTION CAMP

The construction camp was located on the south bank and 85 feet above the river, at the south end of the base line of the powerhouse. The buildings are laid out along regular streets, and in general are of standard take-down patterns of Fargo En

gineering Co. There is a frame house for the Superintendent in charge of the work, which will be used for the operators, private "shacks" for the remaining engineers and foremen, and bunk houses for the men. The bunk houses were well lighted, ventilated, steam heated, with running water and electric lights. There were two bath houses with shower baths, hot and cold water and sufficient toilets. The wash rooms, bath houses, toilets and mess hall are all connected with a sewer which empties into the river below the camp and dam site.

The water supply is from springs above the camp. The water was collected in two reservoirs which are emptied alternately. The water shed was fenced off to protect the supply from contamination.

Dr. I. F. Thompson, reporting for the Wisconsin State Board of Health, said: "When one takes into consideration the fact that this work is to be completed in one year, I consider the camp to be a model for the care and protection of the health of the men."

DESIGN

Careful estimates of cost and efficiency, of vertical and horizontal installations were made, with the decision in favor of the vertical.

For the six units decided upon, each with 92-inch diameter wheels, it was necessary to make the generator house 193 feet long. Adjoining the generator house on the south is the switch. room. The floor level of the generator house and switch room is at elevation 873.00 or 25 feet below headwater. On either side of the generator house the impounded waters are taken care of by hollow dams resting on rock at about elevation 835.0 and about 73 feet high.

concrete and steel Water was taken

In general the allowable stresses on the were 600 to 16,000 pounds per square inch. at 62.5 pounds per cubic foot and earth at 102.5 pounds per cubic foot, or 40 pounds per cubic foot immersed. The sloping deck slabs on the hollow dam sections were figured as simple beams, although in fact they were continuous and were reinforced for negative moment over the piers.

View from downstream coffer dam, showing draft tube openings and tail race excavation nearly completed.

In the design no uplift pressures were assumed. In that portion of the dam upstream from the generator house where uplift might occur, due to the solid floor surrounding the sluices or spillway tubes, it was thought that any water underneath the dam would escape upward into the spillway tubes, through openings left for that purpose.

All piers were saw-toothed into the rock to make sliding impossible.

Each draft tube has two sluices or spillway tubes which will be used only in case it is necessary to lower the pond below the level of the penstock sill. These tubes will spill the entire flow of the river for ordinary flows.

The pond will be held at elevation 898.0 by the 13 automatic Stauwerke gates, whose combined lengths are 832 feet. As previously stated, the concrete structure supporting these gates is located on the rock plateau north of the north river channel.

STAUWERKE GATES

In addition to the usual determinations of first cost and flood capacity, various other considerations determined that the Stauwerke Gates would give the best operation for the Wissota spillway.

Wissota is in a cold country, where heavy ice formations occur. Furthermore the possibility of a dam failure above, of interference with back water, and the attempt at elimination of the personal equation and operating troubles, by reason of requiring power for hoisting mechanism, etc., were all considerations which established the automatic spillway as an ideal one for Wissota.

The Fargo Engineering Company, investigated thoroughly operating conditions and questions of reliability in connection with various installations in Europe. Subsequently Fargo Engineering Co. became representatives for the Stauwerke Company, Zurich, Switzerland, for the Central and Northern United States. In this way preliminaries, details and rights incident to the use of these gates in this country can be expedited.

The automatic spillway which is proposed for the Wissota Dam consists of thirteen steel gates 64 feet wide by 10% feet