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- 7 - duplicate, on a larger scale, the constant-flow effect of the carburetor float- chamber, experiments were run with a 3~4 inch float valve in a three gallon bucket. With this system it was ,possible to maintain a relatively constant rate of flow regardless of any static pressure changes resulting from the liquid level changes in the rotenone barrels. The next problem was the development of a satisfactory system for maximum rotenone dispersal across the stream channels. The major channels, included in the Green River Project, range from 200 to 300 feet in width. In general, water depths are sufficiently great to eliminate any possibility of locating drip barrels in the channels proper. The best alternative appeared to be a plan to mount barrels on the highest available river banks and attach them to a hose line stretched across the stream. Numerous experiments were made with such systems under "laboratory" conditions, to determine the most efficient arrangement. $y using 5p-foot sections of 3~~- inch, plastic garden hose, it was possible to construct an extremely versatile dispersal line. Valves were coupled between hose sections so as to release liquid at two or three points along the line (Figure 2). Rotenone flow was controlled at the barrels, by a main valve. No attempt was made to control flow measurement from the comparatively inaccessible dispersal valves coupled into the hose line. These were simply adjusted so that all emitted approximately equal flows at intervals along the hose line span. All preliminary testing of dispersal equipment was done with water, which, having a lower viscosity than emulsifiable rotenone, flows much more rapidly. In order to determine the actual efficiency of the proposed dispersal system as well as rotenone flow rates, rates of rotenone decay, stream current effects, dispersion rates and station spacing, it was felt that a field test with rotenone was necessary. For this pilot study section on the Green River propere aboutstdwentyemilessbelop a Green River, Wyoming. (Eiserman, 1961)(Stone, 1961_). The sites selected were representative of the most difficult river sections from the standpoints of both access and stream conditions. The trial was planned for late August, 19b1, when river flow was in excess of 700 cfs. At each station, a wire was sloped from the maximum height of the barrel location to the water's edge at the opposite bank. The wire was stretched taut and supported, at intervals, by steel fenceposts driven into the river bottom. The hose and valve dispersal line was then hung from the wire and bound at close intervals so as to prevent excessive sagging, (Figure 2). The upper treatment station was placed in operation and it soon became apparent that at 700 cfs flow the dispersal system could not apply rotenone at a rate faster than that which. would provide a maximum concentration of 3.5 ppm. In order to gain the other information desired from the pilot study the dispersal time was increased to nine hours. The lower station, approximately fourteen miles downstream, was activated six hours after the upper station. In order to check treatment efficiency, live cages containing various sized carp were distributed throughout the 24 miles of the test area. These were placed in locations where it was felt that rotenone might have difficulty reaching. Careful observations were made on these and the general fish kill relative to thoroughness of rotenone dispersion and velocity of rotenone movements. In general, the dispersal systems worked very satisfactorily and produced relatively rapid chemical diffusion. A thorough check of the entire test area including the test fish indicated that the fish kill was nearly complete. This initial indication of success was later substantiated by investigations during the second week of September. The pilot study demonstrated that a practical treatment technique was possible. . _~.d.... -~ 7l~l+f~'llwa4 ~ t: 1xuF<1,~:.4,r,K~..~ -., ~_._a ..