The Use of a Porous Dike Structure for Reducing Fish Impingement at a Power Plant Employing Once-Through Cooling

In 2000, We Energies announced its intent to repower its Port Washington Power Plant site. The historic 380 MW coal-fueled plant was to be replaced with a two unit, natural gas-fueled combined cycle plant. Both the historic and new plant would have similar cooling water supply needs (814 MGD, or 565,000 gpm). Following a rigorous review of alternatives, the company selected, based on previous successful use at a now decommissioned station, a porous dike to enclose the existing intake channel to reduce impingement of trout and salmon. Engineering and hydraulic testing studies were conducted to assure that the proposed structure could both supply the required cooling water flow and withstand waves generated by storm events. Construction was initiated in May, 2008 and was completed by the end of September, 2008.  A two-year biological (impingement and entrainment monitoring) and operational performance evaluation study commenced in January, 2009 and was completed in December, 2010. Performance thus far, has been excellent. Initial operational / biological observations, to date, suggest that: (1) dislodged Cladophora, which caused forced outages in the past, has been substantially reduced; no forced outages have occurred since the dike was placed into service; (2) cooling water supply has not been impacted by winter icing conditions; (3) approach velocity measurements near the face of the dike confirm predictions (e.g., near ambient lake conditions; (4) winter impingement of gizzard shad has been virtually eliminated; summer impingement of alewife has also been substantially (e.g. greater than 90%) reduced; and (5) results of entrainment monitoring  have not yet been concluded.