Under the National Marine Fisheries Service (NMFS) recovery plan for Snake River Sockeye Salmon, recovery goals are set forth for Alturas Lake, Pettit Lake, and Redfish Lake. Estimating emigrant juveniles and returning adults are a key component to recovery efforts.  A feasibility study conducted by Montgomery and Watson (1994) indicated a summer discharge of 2.5 cfs and peak discharge in Pettit Lake Creek of 57 cfs. Subsequently, the weir was constructed in 1995 utilizing information from this study. However, discharges exceeding 100 cfs have been realized annually. That said, the existing weir was designed for flows significantly lower than the maximum experienced.

Pettit Lake Creek is currently equipped with a removable juvenile weir that is affixed to a channel-spanning concrete sill. The structure is a vertical flat plate barrier with perforated panels that relies on sweeping flow to clean the attached panels. Disadvantages to such structure, especially highlighted as undersized for flow, include weir overtopping, backwater flooding, and debris accumulation. Increases in flow, but primarily debris accumulation from small slotted screens (issue not accounted for in original feasibility study), are the drivers for difficult weir management during spring trapping. However, under NMFS criteria, slotted screen openings on the Pettit Lake weir cannot be enlarged.

Tribal concern is two-fold: safety of personnel and proper operation of the weir to collect accurate and precise data. Under current conditions, neither of these are being conducted appropriately. As water and debris increase, staff is on weir maintenance 24 hours a day, operating primarily on limited 1-2 hour napping windows. This is a concern for employee safety, especially during night hours commuting to and from the trap. In addition, the weir was not fitted with hand rails or a proper walkway (constructed with wood boards that freeze over); both of which are large safety issues. Concurrently, there are issues trapping emigrating juveniles if debris is not maintained: 1.) juveniles will overtop the weir; 2.) juveniles become impounded in backwater flooding; and, 3.) juveniles become impinged on the weir face. All three have and will continue to result in significantly elevated mortality rates.

Thus, improvements and modifications are a priority for the structure in Pettit Lake Creek. The Tribes have identified a specific weir type that will be the conceptual basis for this design, engineering, and construction contract. Due to NMFS criteria and the resulting change to overall length of the weir, a final design will need to utilize the current footprint to allow for safe collection of juveniles.  At the same time, the Tribes would seek to modify the weir to include an adult trap box in preparation for increased returns from current and future propagation techniques.