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- 14 - On September 9, because observations indicated some live fish were still present, particularly in off-channel slough areas, the uppermost ten miles of the New Fork River treatment area were retreated. No unforeseen or unmanageable problems developed relative to operational techniques; and personnel and equipment functioned more efficiently that anticipated. During treatment, the Utah Department was prepared to carry out a detoxification program to protect native fish species in the river reaches below the Flaming Gorge Dam. While the detoxification, per se, was effective, the available supply of rotenone neutralizer was insufficient to meet total ~ neutralizing requirements. As the L rotenone concentrations, probable causativerfactordsdshouldybeoreviewedm It has been pointed out that final water-flow readings were taken just prior to the start of treatment. These readings were made directly from the U.S. Geological Survey gauges. At almost all these stations there is a percentage of error between the gauge reading and the actual measured flow as periodically determined by Survey personnel. This error may vary considerably according to water conditions and may be either plus or minus. When the final flows were read for the Green River Project an estimated error, based on past data, was applied to the gauge readings. Subsequent comparison, however, has revealed that these estimated final flows were still greater than the actual river volume (Table 1). In addition, the mainstream volumes dropped considerably during the treatment period with the result that stream flows on the third day, September 6, were actually 19 to 24 percent lower than originally calculated. Both of these variations were complementary and the increased rotenone concentrations complicated detoxification. It is suggested that where a detoxification program is planned, relatively exact flow figures must be calculated during each day of rotenone treatment. One additional suggestion for better rotenone control would be a maximum refinement of aerial application systems. With the helicopter employed on the Green River Project, rotenone release control was inadequate resulting in excessive concentrations for-such waters as the Blacks Fork River-and an additional possible source of complication for detoxification facilities. A total of 21,495 gallons of-Chem Fish Regular was. used on the project. This material was purchased from the Chemical Insecticide Corpora- tion, Metuchen, New Jer$:ey, at a total cost of $76,307.25.