A Remarkable California Concrete Water Tower the Highest in the World.
The accompanying illustrations show an interesting reinforced concrete water tower and the methods employed in its unique construction, as recently completed. It is located 10 miles north of San Bernardino, Cal., near the summit of the San Bernardino range, in Little Bear valley, at an elevation of 5,100 ft. above sea level. It stands in the 880-acre reservoir of the Arrowhead Reservoir and Power company, and is connected with the portal tunnel No. I, which is the outlet of the reservoir.
This structure is IBS ft. high and measures Li ft. outside diameter, with an inside diameter of ti ft. to the 124-ft. level, at which point it is enlarged to 10 ft. U in., thus giving a shell thickness of 2 ft. and 1 ft. 0 in. It has an ornamental 8-story superstructure carrying the valve stands and winch mechanism for raising and lowering valves and screens. The design of the superstructure necessitated the cutting and fitting of 2,800 pieces of lumber to measure. The first floor of the superstructure projected beyond the cylinder of the tower 14 in., was 14 in. thick, and acted as a cantilever carrying the entire weight of the second floor and roof upon a projection by means of 10 columns spaced equal distance apart.
It is of interest to note that the foundation block, 30 ft. square and 6J4 ft. thick, is heavily reinforced with i in. twisted steel, and rests upon a solid rock bed. Upon this foundation block arc two blocks, each 4 in. thick and of smaller size, one irregular in shape and one circular. Reinforcement of tower cylinder is deeply imbedded in these three blocks, mak ing a very rigid structure that, when completed. was found to sway but 1 in. in a high wind; and so accurately was the work carried up that when completed there was found to be at the top a variation from true vertical of less than ¼-in.
This is an outlet water tower and designed to control the water supply of the completed system which is to lead through a series of tunnels and conduits to the valley below, and it is held that the impounding dam and the lake tilled, the water will stand about 100 ft. deep round the tower. To withstand this pressure at the bottom, special attention was paitl to grading and cleaning the aggregate, the sand being thoroughly washed and freed of mica and loam and the crushed stone being carefully selected. A very dense mixture was secured. In addition to this, the lower 30 ft. of the tower was given a coat of 1 in. mortar trowelled to a smooth finish and upon this a coat of waterproof paint.
On the inside of the tower there are ten balanced 20 in. valves, each weighing about one ton—three of them sluice valves at the bottom on one level, and the other seven being spaced spirally at intervals of 20 ft. up the tower. These valves are each fastened by 20 bronze stud bolts to a 22 in. cast iron nipple, which passes through the wall of the tower, and are controlled from the first floor of the superstructure by means of steel rods 1,’4-in. in diameter, covered with brass tubing.
Elbows of cast iron are bolted to the nipples, and on each elbow rests an iron screen 6 ft. high and 3 ft. in diameter, composed of vertical bars on the outside of the tower. These screens are raised and lowered by means of a chain operated from the second floor of the superstructure. The connections between the fittings are made watertight by the use of white lead and corrugated copper gaskets.
In case a screen becomes choked with debris, the operator at the top closes that valve, relieving the water-pressure, raises the screen to the surface of the water, removes the debris, resets the screen and opens the valve again.
It will thus be noted that this process indicates the necessity which resulted in the devising of this tower. It was designed to control the water by a gate in the tunnel operated through a shaft, a grizzly screen over the portal being provided to keep out debris. But as the water rose in the lake the decreasing pressure made it difficult and finally impossible to keep the screen clear and, because of this, and the advantage of being able to let in any stratum of water desired for domestic use, a tower was suggested.
In order to obtain a smooth and impervious face on the outside a steel form was used and great care taken in tamping and spading. This form was raised by means of four 1-ton differential pulleys, which were fastened to channel iron heads supported by a scaffold carried up on the inside of the tower. This scaffold was kept 30 ft. in advance of the concrete and was built with 6×6 posts and 2×6 ledgers to carry the heavy valves and fittings as they were hoisted into place.
As it was not possible to make a continuous run of concrete great care was taken to prevent percolation between joints of old and new work. The surface of the old concrete being roughed up with picks and a groove 2 in. deep by 3 in. width made. Upon this was laced a mortar composed of 1 part cement to 2 of sand before the regular mixture was placed.
It may be stated that cold, snow and windy weather were encountered, which at times made progress difficult. The thermometer sometimes registering 8 degrees above, made recourse to steam necessary, to keep the con Crete from freezing a steam line was carried up the inside of the tower and connected by means of a steam hose to a coil of perforated pipe upon the outside of the steel form. A canvas hood over all confined the steam and temperature was kept at 60 to 70 on the coldest nights.
This interesting structure is said to be the highest concrete water tower in the world.