The Lolo Creek Permanent Weir Design and Construction Project (Lolo Permanent Weir) is being implemented by NPT and BPA to replace the current adult trapping system located on Lolo Creek, near Weippe, Idaho.  As a part of the required collection and monitoring program, NPT has been operating a manually placed picket weir, supported by tripods placed in the stream bed. The existing system does not currently meet NPT’s needs with regard to effectiveness, durability, and safety.  In many cases, NPT is unable to trap fish when flows are greater than 500 cfs due to an inability to deploy the pickets at higher flows. When already in place, an increase of flows above 500 cfs has resulted in significant damage and loss of trapping effectiveness. Personnel safety has been at risk during these conditions when attempting to deploy the system too early or when trying to salvage the trap after high flow events.

The new collection system will be designed to overcome the challenges currently identified at the site in addition to improving overall collection efficiency and trap and transfer operations. The new weir will be a permanent system and will eliminate the need for annual construction efforts. When the weir is not in operation, it will remain in the river in the down position.  Fish collection and monitoring provisions will be facilitated by a landside holding area. With the holding area placed near the shoreline, access and durability of the system will be markedly improved and will allow operations personnel greater efficiency and safety.