The camera with its lowering mechanism and power-supply are shown on figure 8. The camera proper is a stainless steel tube 2 inches in diameter and 311⁄2 inches long, containing a compass which supports a hollow truncated conical mirror, and a camera unit equipped with a 15-mm. lens. Illumination is provided by a high-voltage flash tube directly above the conical mirror. The lowering mechanism actuates picture exposures. One exposure is made for each threefourth inch of camera cable moving over the wheel h. The equipment is portable, and rapid color film developing services are available.

Since developing the very successful prototype, the corps has built two reproductions with minor modifications, and has procured two additional camera units from a private manufacturer licensed to construct these in accordance with the corps' drawings and specifications. Companion to the camera is an automatically driven picture projector which can be used for both plane and cylindrical image study of the interior surface of boreholes. The latter was constructed by the Eastman Kodak Co. in accordance with the corps' plans and specifications. Prices of the camera will depend on the number of complete units demanded and could range from $12,000 to $20,000 on that basis. Patent rights are held by the Corps of Engineers.

FOUNDATION EXPLORATIONS FOR EARTH DAMS

An investigation is now underway at the Waterways Experiment Station regarding the most reliable method of obtaining undisturbed samples of soft, weak clays suitable for producing reliable test data. Preliminary results indicate that the so-called Swedish Foil sampler has certain advantages in accomplishing this objective. This sampler contains movable steel ribbons which eliminate the friction between the sampler and the wall of the sampling tube. This equipment is supplied by Sprague and Henwood, U.S. distributors for the manufacturer.

Nuclear devices have been tested and are now in use to permit rapid determination of the density and water content of embankment samples for construction control and field research. Preliminary development and testing was carried out in cooperation with the Corps of Engineers.

FIGURE 8.-Bore-hole camera developed by the Corps of Engineers, U.S. Army. e, camera proper, stainless steel tube 24 inches in diameter with quartz window inclosing conical mirror near lower end; a, power supply; b, level-wind control for cable; c, cable wheel; d, leveling screws; g, hand crank for raising and lowering camera, geared into wheel c (Corps of Engineers, U.S. Army).

HYDRAULIC DESIGN

DAMS

Epoxy resin protective coating.-Laboratory and field tests are being conducted to develop epoxy resin protective coatings for concrete surfaces subject to high-velocity flow. Further discussion of this material is presented under "Epoxy Resins for Repair and Protection of Concrete."

The

Harza high-head outlet gate.-Reservoir outlet gates have been_designed and constructed to operate under heads up to 200 feet. Harza gate, developed initially by the late Mr. L. F. Harza, eminent consulting engineer, and later improved by his sons, R. D. Harza and A. C. Hoffman, is a new type of gate which is claimed to be less costly and may operate satisfactorily for higher heads than other gates presently in use. The gate, which is shown in figure 9, is constructed economically by welding structural steel beams and plates. Laboratory and field tests made for the Harza Engineering Co. have established that the Harza gate will operate satisfactorily for heads up to 150 feet. Although the corps has not used this type of gate, it is planned to design and test one such gate at a future dam to verify its hydraulic performance and to determine whether or not appreciable savings can be made over the use of other types of gates. The Harza gate would be subject to royalty charges, except for the initial experimental gate.

Fabridam.-The Fabridam is an inflatable rubberized fabric dam capable of installation on any stream, river, artificial channel, or waterway for varied purposes, such as flood control, water conservation, tidal control, lock systems, recreational facilities, etc. It might also be used in lieu of crest gates or flash boards on spillways of some dams. The fabric material is about one-eighth inch thick, consisting of four layers of extra strong fabric embedded in rubber. A system of pipes and valves are employed to inflate the dam with water, and the dam is deflated automatically by a siphon. A dam 6 feet high and 120 feet long has been installed by the Los Angeles City Water Department in the Los Angeles River. Operation of this installation has been completely satisfactory for about 5 years. It is understood that the cost of the installation was approximately $10,000. The material is available from the Firestone Rubber Co. There is some uncertainty regarding the life of the rubber and fabric material. If its life proves to exceed 25 years this product will be very valuable and its use should be widespread. Although the corps has not yet used the Fabridam, consideration is currently being given to making one installation in the near future to verify its hydraulic operation.

NAVIGATION LOCKS

Interlocking controls for miter gates.—An interlocking control system has been developed by the Corps of Engineers to prevent an operator from opening lock miter gates until the water levels on either side of

FIGURE 9.-Harza gate isometric view of gate and removable cover (partly open condition).

the gates become essentially coincident, thereby assuring that the strut arm will not be overloaded, which would result in damage and delays to navigation. The system operates from an air-purging differential pressure gage that controls a pneumatic booster-operated relay in the main control circuit. The system was installed in the control console in the upper control house of Eisenhower lock in April 1960 and was tested under actual operating conditions. The system was consistently accurate and would prevent operation of the gates until the water levels on either side of the gates were within 2 to 3 inches of being equalized. The system, as designed for the seaway locks, was limited to a maximum differential head of about 80 feet. However, this limitation can be overcome if necessary so that the sytem could be used on higher head locks. The cost of the components for the installation described above was about $500. Installation cost would probably be about $400. Since the system was fabricated

from commercially available components, no difficulty should be experienced in obtaining additional materials and components.

Television monitoring surveillance.-At many projects, visual observation of various elements of the dam and of entrances to the lock becomes slow and difficult because of the distances and heights involved. An alternative to keeping personnel on duty at each end of the lock at all times is to provide a television monitoring surveillance system. An experimental installation of a TV surveillance system has been made by the Corps of Engineers at The Dalles project on the Columbia River and has proven to be satisfactory. This system was designed and built from commercially available components. It utilizes cameras at four different locations situated so that an operator in the control house can view the downstream end of the lock and the downstream side of the spillway gates; the upstream lock entrance and the upstream area and upstream side of the spillway gates; the security areas at the entrance gates; and the storage and supply areas. Each of the four cameras are provided with close-up and general viewing lenses and can be rotated horizontally and elevated or depressed by the operator through a remote control system.

BREAKWATERS, JETTIES, AND GROINS

Concrete armor components.-A major problem in the design and construction of coastal structures is producing a structure that will not be significantly damaged or destroyed by the huge forces of storm waves. The most desirable protection for the structures is a flexible armor layer composed of large stone. In many areas, however, suitable quality stone is not available or the stone is of a composition such that sufficient large pieces cannot be obtained. Under such conditions stone may have to be transported from other areas and the unit cost becomes quite high. As a substitute for stone variously shaped concrete components have been devised to be used in the armor layer. Through a test program on small-scale hydraulic models at the U.S. Army Engineer Waterways Experiment Station at Vicksburg, Miss., it was determined that three of these shapes, the tribar, tetrapod, and quadripod, indicated the greatest potential for use. These are shown in figures 10, 11, and 12.

The tribar is composed of three vertical bars connected by a trunk section. From the center point of the trunk the bars are spaced 120° apart, and the horizontal distance between bars is equal to the length of the bar. This unit was developed and patented by Tribars, Inc., of Honolulu, Hawaii. The tetrapod is composed of four legs or pods projecting from a common point with each pod spaced 120° from that adjacent. This unit was developed and patented by Neyrpic Laboratories in Grenoble, France. The quadripod is composed of four pods, projecting from a common point with three pods in the same plane and the fourth extending vertically, making an angle of 90° with the plane of the other pods. This unit was developed by the Corps of Engineers.

In the United States, tetrapods have been used by the Corps of Engineers at Crescent City Harbor, Calif., Kahalui Harbor, Hawaii, and by Richfield Oil Corp. at Rincon Island, Calif.; tribars were used by the Corps of Engineers at Nawiliwili Harbor, Hawaii; and quadripods will be used at Santa Cruz Harbor, Calif., construction of