Impacts of entrainment and impingement on fish populations: A review of the scientific evidence

In 1972, the United States Congress enacted §316(b) the Clean Water Act, which mandates minimization of the adverse impacts of entrainment and impingement of fish and other aquatic life at cooling water intake structures. Since the Act was passed, there has been continuous controversy over the magnitude of any such impacts and over the need for mitigating measures to reduce these impacts. The objective of this paper is to examine the published scientific information relevant to this issue The review includes (1) peer-reviewed literature reporting results of studies of impacts of entrainment and impingement at power plants on fish populations, (2) peer-reviewed literature and “blue-ribbon” commission reports on aquatic resource degradation that evaluate causes of observed degradation of aquatic ecosystems, and (3) EPA's own assessments of causes of degradation in coastal environments. The clear conclusion from the review is that any impacts caused by impingement and entrainment are small compared to other impacts on fish populations and communities, including overfishing, habitat destruction, pollution, and invasive species. The available scientific evidence does not support a conclusion that reducing entrainment and impingement mortality via regulation of cooling water intakes will result in measurable improvements in recreational or commercial fish populations.