Introduction 



In accordance with Section 221-430 of Chapter 

 446k of the Connecticut General Statutes and 

 Section 402b of the Federal Water Pollution Con- 

 trol Act, Northeast Nuclear Energy Company 

 (NNECO) was issued a National Pollution Dis- 

 charge Elimination System (NPDES 

 CT0003263) permit regulating the discharge of 

 cooling water to Long Island Sound (LIS) from 

 Millstone Nuclear Power Station (MNPS). Para- 

 graph 5 of this permit, issued by the Connecticut 

 Department of Environmental Protection (C"T 

 DEP) states that 



The permittee shall conduct or continue to 

 conduct biological studies of the supplying and 

 receiving waters, entrainment studies, and in- 

 take impingement monitoring. The studies 

 shall include studies of intertidal and subtidal 

 benthic communities, fmfish communities and 

 entrained plankton and shall include detailed 

 studies of lobster population's and winter floun- 

 der populations. 



Further, paragraph 13 of the permit requires that 



On or before April 30, 1986 and annually there- 

 after, submit for the review and approval of 

 the Commissioner a detailed report of the on- 

 going biological studies required by paragraph 

 5 and as approved under paragraph 12. 



The present report satisfies this NPDES reporting 

 requirement, and provides summaries of the on- 

 going biological monitoring studies conducted by 

 Northeast Utilities Service Company (NUSCO) 

 and contractor personnel on behalf of NNECO 

 at MNPS during calendar years 1986 and 1987. 

 During this period combined three-unit operations 

 occurred for the fu^st time. Referenced frequently 

 throughout this report are data collected prior to 

 1986 (see NUSCO 1987), which serve as the base- 



line against which potential effects of three-unit 

 operation can be compared. 



The goal of the MNPS monitoring program, 

 established in 1968, has been to characterize the 

 various estuarine communities in the vicinity of 

 MNPS and determine if station construction and 

 operation have resulted in changes beyond those 

 that would be expected to occur naturally. To 

 accomplish this goal, various investigations have 

 been conducted. Early biological investigations 

 included exposure panel monitoring of fouling 

 communities and surveys of intertidal sand and 

 rocky shore communities and shore-zone fish as- 

 semblages. The scope was expanded between 

 1970 and 1973 to include impingement and en- 

 trainment monitoring, surveys of pelagic and 

 demersal fish assemblages, plankton and subtidal 

 benthic communities and studies of lobster and 

 Niantic River winter flounder population dynam- 

 ics (NUSCO 1987). In addition, numerous 

 hydrographic studies have been conducted for the 

 purpose of thermal plume mapping and predictive 

 modeling. Tidal circulation models were also de- 

 veloped to refme thermal plume predictions and 

 to model dispersal of larval winter flounder. A 

 detailed discussion of early studies was provided 

 by NUSCO (1987). 



The Study Area 



The MNPS is located on the southeastern 

 coast of Connecticut in the Town of Waterford, 

 approximately 8 km west southwest of New I^n- 

 don (Fig. 1). The approximately 500-acre site is 

 situated on Millstone Point, a peninsula in the 

 eastern part of LIS that is bounded on the west 

 by Niantic Bay, on the east by Jordan Cove and 

 on the south by Twotree Island Channel. The 

 I IS estuary is approximately 82 km long and 40 

 km wide with an average depth of 19 m (Nixon 

 1983). Because the average tidal excursion in LIS 



Introduction 



