Hydraulic Model Study of the Blue River Dam Power Plant, Penstock, and Outlet Works

Abstract

The Stone and Webster Engineering Corporation (S&W) contracted with St. Anthony Falls Hydraulic Laboratory (SAFHL) to construct and test a physical hydraulic model of a modified stilling basin for the Blue River Dam Power Plant Project outlet works. This project was designed by Stone and Webster for the Eugene Water and Electric Board. Modification to the stilling basin was necessary to accommodate changes in the design of the outlet structure necessitated by the installation of hydroelectric power generating turbines. The basin is presently owned and operated as a flood control structure by the U.S. Army Corps of Engineers (COE). The facility is operated according to COE procedures within the general constraints of a reservoir water surface level of maximum 1357 ft MSL and minimum 1180 ft MSL, and between the minimum and maximum flows of 50 cis to 8400 cfs, respectively. Flow exiting the reservoir is controlled through gates located at the upstream end of a 2000 it long 18.5 diameter conduit. The downstream end of the conduit concludes in an open channel outfall into the existing stilling basin. The design scheme for the hydro facility involved modifying the outlet works to incorporate a multiple bay gated outlet structure and a bifurcation leading to the powerhouse. Modifications included pressurization of the penstock and outlet works necessitated by the combined usage of the flow conduit for both hydropower and flood discharge. The objective of the study was to perform comparative testing of the existing outlet works stilling basin and the proposed design. In this effort, the study evolved into five distinct phases of testing. The test results are summarized according to phases with the reason for and objectives of the next phase outlined in the conclusion of each existing phase. A summary of the various phases is as follows: