Fish Passage Effectiveness Study

The primary goal of this study was to access the biological performance of the downstream passage facilities installed at Ball Mountain and Townshend Hydroelectric Projects located on the West River in Vermont. To achieve this goal, fish passage efficiency was estimated using radio telemetry techniques and bypass survival was estimated using mark recapture techniques at the Townshend Dam site. Due to the similarity in design between the two sites, The Flow Labs team was able to convince the resource agencies that the study results from Townshend would be applicable to the performance of the bypass system at Ball Mountain, preventing the need for conducting studies at both sites. Bypass survival was estimated by determining the survival and injury rates offish passing through the bypass pipe and outlet tunnel at the Townshend dam. Marked trout were released into the bypass and discharge and recaptured using a full-flow collection net with a live car installed downstream of the discharge. All recaptured fish were accessed for injury, scale loss, and mortality, which were used to calculate total bypass survival and injury rates. 

Bypass efficiency was determined by releasing radio-tagged trout upstream of the turbine intakes and tracking their movements as they approached the intakes and passed downstream into the tailrace either through the turbines or bypass system. The radio telemetry data were used to determine the percentage of fish using both the turbine and bypass routes. The results of the study demonstrated 100% bypass survival and an acceptable level of bypass efficiency. The Flow Labs team was able to obtain agency and FERC acceptance of the study results, which alleviated the need for additional testing and any modifications to the bypass system or turbine operation to improve downstream passage.