ABSTRACT 



The New Haven Harbor (Connecticut) Ecological Studies Summary Report 

 presents results from a seven-year monitoring program and analyzes possible im- 

 pacts of United Illuminating Company's 460 MW oil-fired electric generating sta- 

 tion on harbor biota. The report fulfulls an NPDES discharge permit requirement 

 and, in addition, is designed to maximize usefulness of the data base to other re- 

 searchers. Individual report sections are presented to characterize New Haven 

 Harbor and analyze plant impacts on: Hydrography , Plankton, Exposure Panels, Sub- 

 tidal Infauna, Epibenthic Invertebrates, Oyster Growth, Trace Metals, Ichthyofauna 

 and Avifauna. 



Hydrographic studies characterized in New Haven Harbor as a temperate 

 estuary defined by predictable seasonal changes in physical and chemical water 

 parameters that are primarily regulated by temperature and precipitation. The hy- 

 drographic regime in proximity to the plant is altered by operation of the plant's 

 condenser cooling system which draws in harbor water through a shoreline intake 

 structure at 625 cfs and discharges subaqueously near the shipping channel (700' 

 from shore) at a design AT of 8.3°C (15°F) . Effects of cooling system operation 

 on the current regime were restricted to small areas adjacent to intake and dis- 

 charge structures , and effects on heavy metal concentrations or dissolved gases 

 were inconsequential. As determined by mathematical modeling, the thermal plume 

 from the plant was buoyant for most salinity-temperature conditions. Aerial in- 

 frared imagery and thermal/dye studies showed the surface extent of the plume to 

 be limited - area bounded by the isotherm 2°F AT was less than 0.6% of the inner 

 harbor surface area . 



Biological parameters in New Haven Harbor, including species richness , 

 abundance and spatial distribution, fluctuated widely from year to year, but over- 

 all, most species assemblages could be characterized by somewhat predictable, 

 seasonal trends, similar to those observed in other Long Island Sound harbors. 

 Each biological assemblage was generally characterized by a group of numerically 

 and temporally dominant species over the duration of the study. Though abundances 

 and occurrence of these dominants varied substantially , most dominant species showed 

 predictable seasonal patterns in presence/ absence , abundances and spatial utili- 

 zation of the harbor. 



Mechanisms of plant impact on the harbor addressed in this report in- 

 clude impingement of epibenthic invertebrates and finfish, plankton entrainment 

 through the cooling water system, effects of altered current patterns associated 

 with the intake and discharge structures, possible changes in dissolved gases and 

 contact of organisms with the thermal plume. The small size buoyant nature, and 

 dynamics of the plume minimize its potential to impact the harbor biota, conse- 

 quently impingement on the traveling screens and entrainment through the cooling 

 system were determined to be the most important potential modes of plant effect on 

 the biota. Impacts were analyzed by comparing the two years of operational data 

 with the range of values observed during the five preoperational years. Several 

 species showed distributional or abundance changes, but were either 1) local changes 

 not in proximity to the plant; 2) harborwide and not restricted to the area of the 

 plant; or 3) not coincident with plant impact. 



The overall conclusion from comparison of preoperational and operational 

 periods for all assemblages monitored with respect to species composition, abundance, 

 diversity , and spatial and temporal distribution was that the plant had no dis- 

 cernible impact on the biota of New Haven Harbor. 



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