Bull Run Dam No. 2 Stilling Basin Right Bank Investigation (OR)
The City of Portland Water Bureau contracted WEST Consultants, Inc. to determine if the right (North) streambank at the Bull Run Dam No. 2 stilling basin is susceptible to failure or erosion under existing or alternative channel conditions. The downstream end of the stilling basin is currently formed by a rock weir that crosses the Bull Run River. This project examines the stability of the riprap with the rock weir, with a notched rock weir, and without the rock weir. Additionally, an analysis of Total Dissolved Gas (TDG) in the stilling basing was conducted for existing and removed weir project conditions.

An HEC-RAS model was used to obtain a baseline understanding of the hydraulics and to provide input to the TDG analysis. The HEC-RAS model was also used to provide boundary conditions to a 2-dimensional CCHE2D hydrodynamic model of the stilling basin and the Bull Run River in the vicinity of the project. The 2-dimensional model was used to assess hydraulic conditions along the right bank and on the rock weir to determine stability for a range of return interval floods.