Prior to Shimmick’s work on this project, adult salmon were able to enter the Colusa Basin Drain (CBD) through the Knights Landing Outfall Gates (KLOG) when certain flow velocities were met that attracted migrating salmon. Once salmon entered the CBD, there was no upstream route for salmon to return to the Sacramento River and, absent fish rescue operations, the fish perished and were lost from production. This project constructed a positive fish barrier (with new concrete wing walls and installation of a metal picket weir) on the downstream side of the existing KLOG in the CBD, as well as placed a small amount of riprap on the right bank of the CBD immediately downstream of the KLOG. This project served primarily as a fish passage improvement action that prevented salmon entry into the CBD while also maintaining outflows and appropriate water surface elevations. A secondary purpose of this project was to address an existing erosion site on the right bank of the CBD channel immediately downstream of the KLOG structure to enhance stability.
