SPRAY RIGS, PLOWS, AND MOWERS FOR WEED CONTROL Mechanical equipment for control of weeds, such as spray rigs, plows, and mowers, is readily available. Use on the terrain of irrigation projects often necessitates novel modifications or adaptations. Industry could provide worthwhile service by designing equipment for the special applications made by the Bureau. CONVEYANCE IMPROVEMENT Waterborne sealants A new development in canal seepage reduction during recent years has been the introduction of waterborne sealants. These are materials usually in emulsion form that can be mixed in small quantities with flowing or ponded canal water, and moved to areas of higher seepage. Laboratory and field research has been directed toward evaluating various chemical mixtures for ability to penetrate into canal soils to form a lasting seal. Continued industrial development of the waterborne sealant would provide irrigation projects with a tool long needed-materials and methods for sealing operating canals. Many Bureau canals are in service almost continuously, and to take them out of service for even short periods of time is frequently impossible. The necessity to treat a canal periodically could be accepted as an alternate to cessation of operations for more permanent linings. Asphaltic emulsion and portland cement grout as injected sealants A recent Bureau attempt to solve the inservice lining problem is yielding encouraging results. Equipment was designed and operated to inject liquid sealants such as asphalt emulsion below the surface of canal soils in operating canals Preliminary trials indicate the method is feasible An extension of this method is being considered with portland cement grout replacing the asphalt emulsion as the sealant. Cooperation with industry is desirable in perfecting the equipment, and wide application could be expected. Lower Cost Canal Lining Committee The Bureau of Reclamation formed the Lower Cost Canal Lining Committee in 1946 to become active in research to lower canal lining costs and to evaluate lining performance. Through very effective cooperation with industry, considerable achievements have been attained in this field. Miles of lined canals Approximately 3,000 miles of Bureau canals have been lined or treated to reduce seepage. Nearly 60 million square yards of lining have been installed with a variety of materials (table 1, p. 21). Obviously, considerable quantities of commercial materials were needed, and where soils were used much construction equipment was needed to accomplish the installation. Remaining unlined canals Along the 22,000 miles of unlined canals, much additional lining is desirable and would be installed, were costs of materials lowered. The advent of plastic films now coming into greater use may offer a partial solution to this problem. FIGURE 4.-Automatic dispenser utilizing melted long-chain fatty alcohols for forming and maintaining evaporation reduction monolayers is mounted on a raft in a reservoir. Dispensing rate is closely controlled by an anemometer and wind vane mounted on top of the dispenser and is proportional to wind velocity. Melted alcohol is forced out a spray nozzle, freezing immediately into a powder which settles to the water to form a monomolecular film. FIGURE 5.-Dense growth of aquatic weeds in canal can cause a reduction in carrying capacity and encourage overflow onto adjacent lands. Soil compacting equipment to place thinner earth lining For more effective and economical construction of linings, present equipment should be modified and possibly new items added. For example, soil compacting equipment capable of placing thinner earth linings on canal slopes is desirable. Also, new equipment for placing thinner linings of other materials is particularly needed for small canals and laterals. Research in soil additives Industry is now working on soil additives that can be mixed with soil to form a suitable lining. Equipment to apply the additives will be needed. The Bureau will cooperate in both laboratory and field tests of any such materials that appear economically feasible to use. Cement grout blanket placement Placement of cement grout blankets discussed in preceding sections would find ready acceptance in the lining of canals, especially the smaller canals and laterals. Anticorrosive coating on equipment Irrigation structures, such as gates and turnouts, are being more effectively protected against corrosion by improved protective coatings systems and techniques. Other exposed hard surface linings (concrete blocks, plastic, and rubber surface membranes, etc.) Buried membrane type linings: Asphalt (hot applied). Asphalt (prefabricated). Soil sealants (chemical, petro-chemical, and sediment). Miscellaneous: Includes resurfacing of existing lining, their undersealing and grouting, and the construction of cast-in-place concrete pipe in lieu of lining. Total.. Cast-in-place concrete pipe and plastic pipe Installation of pipe is expected to gain prominence in the future as the cost of right-of-way increases. Subsurface conveyance systems offer fewer maintenance difficulties than open canals and laterals. Prefabricated pipe has been used advantageously, and cast-in-place concrete pipe has been developed by industry for low-pressure installations. Further development may produce equipment for placement of larger sizes, possibly with reinforcement for higher pressures. The use of plastic pipe is limited to low-quantity deliveries for the individual farmer raising high-value crops. |