Evaluation of the effectiveness of intake wedgewire screens

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Abstract The Logan Generating Plant (LGP), owned and operated by US Generating Company, is located on the shore of the Delaware River in New Jersey. It withdraws make-up water from the river to replace evaporative water losses from its closed-cycle cooling tower system. The intake is equipped with two intake conduits that are situated perpendicularly to the current and terminate on the river bottom at depth of approximately 3 m. The intake terminuses are covered by cylinders constructed of 1-mm wedgewire screen. The LGPs intakes are located in an area of the river where striped bass spawn and rear. Previous studies determined that without screening, the plant would withdraw less than 0.03% of the study area’s striped bass. LGP was required to conduct an intake screen performance test to document the plant’s entrainment of striped bass eggs and larvae. Entrainment samples were collected from water filtered through the wedgewire screens. Source water body samples were collected from three transects in the river: one upriver, one down river, and one directly in front of the plant. Sampling at the transect in front of the intake was coordinated to occur at the same time as entrainment sampling. The densities of striped bass larvae in the source water body and in entrainment samples were used to estimate proportional withdrawal. The study found that the wedgewire screens performed better than expected. The average proportional withdrawal of striped bass larvae was 0.003%, an order of magnitude less than the estimate for an unscreened intake.