Is There a Relationship Between Cooling Water Intake Flow and Impingement at Vermont Yankee Nuclear Power Plant?

One 24-hour impingement sample was collected from the intake traveling screens each week between 29 March 2005 and 28 November 2006 at Vermont Yankee located on Vernon Pool of the Connecticut River near Vernon, Vermont. Twenty-seven species of fish represented by 12 families were collected in the impingement samples, with Yellow Perch (64.6%) , Bluegill (10.5%), Rock Bass (6.8%), Black Crappie (5.4%) and Pumpkinseed (4.2%) comprising 91.5% of the total impingement abundance. Seasonal peaks in impingement abundance were observed during the spring and early-summer months of April - June, and also during the fall to early-winter months of October - December of both 2005 and 2006. Vermont Yankee withdraws varying amounts of ambient non-contact cooling water by operating the condensed cooling system in open, hybrid, or closed cycle modes to insure compliance with hourly thermal discharge limits, thus providing the opportunity to compare impingement rates with water withdrawal rates. We evaluated the relationship between the volume of cooling water withdrawn and daily impingement rates (fish per million cubic meters) after adjustment for seasonal variability in fish abundance based on coincident bi-weekly fish surveys in the source water body withdrawal zone.