Design and Implementation of Studies to Characterize Entrainment at Cooling Water Intake Structures

Under the new §316(b) rule, generating facilities will conduct an Entrainment Characterization Study.  For some facilities it will be the first entrainment study, and others the first in many years.  The study design, which must be pre-approved by the permitting agency after undergoing a peer review, should address diel, seasonal, and annual variations in entrainment.  Information on density in the source water, species and life stage composition, and sizes will be required.  Studies must be robust to confounding issues, such as gear avoidance, extrusion through nets, destruction of organisms, and incomplete or erroneous identification, through the careful selection of sampling gear, sampling locations, analytical methods, and a rigorous quality control plan.  Newly developed technologies, such as DNA barcoding, may also be incorporated to ensure that quality objectives are met.

In some cases additional study components will be desirable.  Where entrainment-reducing technologies are already in place, the study could be expanded to provide site-specific estimates of their efficacy.  If hardy species of fish or shellfish are entrained, an estimate of their survival following cooling system passage could replace the default assumption of complete mortality.  In some instances, identification of previously dead or moribund specimens could reduce concern over entrainment.