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structure. Eleven months after completion of concreting work, the joints were washed out, tested with water, and the leaks calked with lead wool. About 42 sacks of cement were forced into the joints, which opened a maximum of 0. 002 inch during grouting operations. Low grouting pressures were used because of the low sliding resistance of the shale foundation.

D. Gate Installations

58. High- Pressure Gates. - Six high-pressure gates were installed at Trenton Dam. Four gates, 6 feet wide by 7 feet 6 inches high, were installed in the river outlet structure and two gates, 4 by 4 feet, were installed in the canal outlet conduit. All the gates were received from the contractor in good condition in advance of requirements. After installation, the gates and operating systems were pressure tested and trial operating runs were made.

59. Radial Gates. - Three radial gates, 30 feet high and 42 feet wide, were installed in the Trenton Dam spillway. The gates were fabricated by Johnson Machine Works, Inc., Chariton, Iowa, under specifications No. 3321. The last gate was delivered to the site in July 1953, and erection of the gates was begun immediately and completed during October of the same year. During installation, the gate parts were handled by two cranes, one of 10-ton capacity and the other of 60-ton capacity. After the bridge over the spillway was completed, the lighter gate members were handled and placed from the bridge deck by the 10-ton crane. As limited by the bridge capacity, heavy gate members were placed by the 60-ton crane from the spillway floor. After installation of the gates, including the gate hoists, counterweights, floats, and control mechanisms had been completed, water was pumped into the gate float wells and the gate operation was tested.

(a) Palnting-— Prior to painting, the radial gates were sandblasted then covered with a rust-inhibitive wash solution and a wetting agent. A coat of zinc-chromate priming paint was next applied. A second coat of priming paint was applied to the upstream side of the gate and, while the paint was still wet, a coat of sand was applied by using low air pressure. After the sand coating was dry, two coats of aluminum-finish paint were applied. The remainder of the gate, including the interior surfaces, was also covered with two coats of aluminum-finish paint, but without a second priming or sand coat.

CHAPTER VI--TEST INSTALLATIONS

60. Purpose. - In addition to making tests on the fill to control embankment construction, test apparatus is installed in most dams built by the Bureau to determine the behavior of the earth embankment and appurtenant structures during construction and later reservoir operation. The apparatus permits measurements of pore fluid pressures in the embankment and foundation, consolidation of the embankment, and vertical settlement and horizontal alinement changes on the surface of the dam.

61. Piezometer Installation. - A total of 25 piezometer tips were installed in the compacted impervious embankment, foundation gravel and sand, and in the shale bedrock. The installation included 12 foundation-type tips and 13 embankment-type tips. The tips were installed in shallow holes excavated in the compacted embankment (fig. 37).

[graphic]

Figure 37.--Laboratory technician preparing plastic tubing for installation of piezometer in the embankment. P328-701-4711, April 4, 1953.

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