Alden’s engineers and biologists conducted extensive CFD modeling and biological evaluations to help the Holyoke Gas & Electric Department (HG&E) develop an effective downstream passage solution for endangered shortnose sturgeon at the Hadley Falls Station on the Connecticut River. The results of these studies produced engineering and hydraulic design criteria for an exclusion rack and downstream bypass.  The CFD modeling examined flow conditions for several alternative rack designs, as well as the bypass discharge to ensure safe downstream passage of fish and minimal interference of upstream migrants trying to locate the entrance to a fish lift.  Alden also developed conceptual designs and preliminary cost estimates for the preferred alternatives and conducted biological testing in a large laboratory flume with various configurations of bar racks and bypass entrance designs with juvenile shortnose sturgeon.  Agency acceptance of the final design was obtained by HG&E after Alden completed a desktop analysis of total downstream passage survival using the laboratory bypass efficiency data and theoretical estimates of turbine survival.