Laboratory and Field Evaluations of Wedgewire Screens for Protecting Early Life Stages of Fish at Cooling Water Intake Structures
Stephen V. Amaral1, Douglas A. Dixon2, Elgin S. Perry3
1Alden Research Laboratory, Inc., Holden, MA, United States; 2Electric Power Research Institute, Palo Alto, CA, United States; 3Statsitical Consultant, Huntingtown, MD, United States

Cylindrical wedgewire screens are a technology that has potential for effectively reducing the entrainment and impingement of ichthyoplankton at power plant cooling water intakes; however, performance data were lacking. The Electric Power Research Institute (EPRI), with funding from the U.S. Environmental Protection Agency, began a multi-year laboratory and field evaluation of pilot screens with the objective of determining their biological performance. Following a laboratory study in which optimum design and operational criteria were identified, a field evaluation of the screens was conducted from 2004-2006. A specially test facility was constructed, and entrainment sampling took place at three representative field sites. Paired entrainment samples were collected through an open (control) port and a test screen and densities were compared to estimate the ability of test screens to reduce entrainment. Sampling was conducted with two screen slot widths and two intake velocities. The statistical approach for data analysis was based on a repeated measures design where the subject was the ambient population of ichthyoplankton and the repeated measures were the samples collected from the test and control intakes. The response variable was sample density. This design is analogous to a randomized block design where each trial would be the blocking factor, but it allowed for more flexibility in incorporating additional variables and offered an intuitive means of identifying the effect of different variables on the difference between test and control densities. The resulting model was a repeated measures three-factor ANCOVA with two covariates, implemented using a general linear model in SAS. Additional experimental design and analysis procedures, problems encountered, and approaches used to overcome the problems will be presented. The study results will also be reviewed, particularly with respect to variable sample density, variable environmental perturbations, and application of results to full scale technology applications.

Keywords: Fish protection; Power plants; Fish screen; Repeated measures

Biography: Mr. Amaral is a Senior Fisheries Biologist with Alden Research Laboratory, Inc., located in Holden, Massachusetts, USA. He has B.S. and M.S. degrees in fisheries biology, both from the University of Massachusetts. For the past 20 years, Mr. Amaral has been extensively involved in the design, evaluation, and application of fish passage and protection technologies at water intakes. His research has included lab and field studies with several types of behavioral deterrents and various screening technologies.