Role of Entrainment Survival in the BTA Selection Process

That some fish eggs, larvae, and early juveniles can survive passage through the cooling water systems of steam electric facilities has been known for more than 30 years.  The studies leading to this reveal that survival varies with species-, size, and temperature exposure, with survival estimates ranging from near zero for newly hatched delicate species to almost 100 percent for hardier species and life stages.  In this paper, we review key developments in the evolution of sampling gear, study designs, and analytical techniques that led to reliable estimates of entrainment survival.  Despite the past successes, some skepticism remains about the role of entrainment survival in the BTA selection process.  We demonstrate that failure to consider entrainment survival where it exists may 1) overestimate of the potential for adverse environmental impact and, hence, the benefits (both biological and economic) of alternative intake technologies designed to reduce entrainment losses, and 2) lead to the selection of intake alternatives that actually increase the impacts to individual fish populations.  This phenomenon will be illustrated for fine-mesh traveling screens, a technology gaining some interest as potential BTA.  Consideration of entrainment survival in the BTA selection process is receiving increasing acceptance within at least one regulatory agency (New York State Department of Environment Conservation) and necessitated site-specific confirmatory studies which were conducted this summer.  Preliminary results of this effort will be described.