ML20029C894

Annual Environ Protection Plan Operating Rept Jan-Dec 1993.

ML20029C894
Person / Time
Site:	Millstone
Issue date:	12/31/1993
From:	NORTHEAST UTILITIES SERVICE CO.
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ML20029C895	List: ML20029C894 ML20029C992 ML20029C993
References
B14833, NUDOCS 9405020317
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• Annual Environmental Protection Plan' Operating Report January 1 - December 31,1993 Millstone Unit 3 Environmental Protection Plan -

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A prepared by Northeast Utilities Service Company P.O. Ilox 270 IInrtfbrd, Connecticut 06141 0270 9

April 1994 9405020317 931231 PDR ADOCK 05000423 R .. PDR m

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Annual Environmental Protection Plan Operating Report ,

January 1 - December 31,1993 9

Millstone Unit 3 Environmental Protection Plan E

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Prepared by: it Reviewed 4/c by:i h // e sw

h Annual Environmental Protection Plan Report - 1993

1. Introduction This report cos rs the period January 1 - December 31,1993. During 1993, Unit 3 was shut down for about two weeks in early April, following a reactor trip caused by a low steam generator level alarm and subsequent repair of a steam generator safety valve, and from August to early November for a refueling outage. Unit 3 was at full power (nominal 1150 MWe) for most of the rest of the year. During 1993, Unit 3 operated at an annual capacity factor of 65.0%.

As required by Millstone Unit 3 EPP, this Annual Environmental Protection Plan Operating Report (AEPPOR) includes:

1) summaries and analyses of the results of environmental protection activities,

2) a list of EPP noncompliances,

3) a list of all changes in station design or operation which involved a potentially significant unreviewed environmental question, and

4) a list of non-routine reports, describing events that could roult in significant environmental impact.

2. Environmental Protection Activities 2.1 Annual NPDES Report of Ecological Monitoring (EPP Section 4.2)

Paragraph 5 of the referenced NPDES permit requires continuation of biological studies of MNPS supplying and receiving waters, entrainment studies, and intake impingement monitoring. These studies include analyses of intertidal and subtidal benthic communities, finfish communities, entrained .

plankton, lobster populations, and winter flounder populations. Paragraph 13 of the permit requires an annual report of these studies to the Commissioner of Environmental Protection. The report that fulfills these requirements for 1993, Monitoring the Marine Environment of Long Island Sound at Millstone Nuclear Power Station. Waterford Connecticut - Annual Report. 1993, presents results from studies performed during 3-unit operation, and compares them to those from 2-unit operation. The added cooling water flow for Unit .

3 affects impingement and entrainment, causes sediment scouring near the MNPS discharges, and alters the characteristics of thermal effluent plume.

The biological effects of these changes are summarized in the Executive Summary section of the above-named report (. Attachment 1) and further discussed in the report itself (Attachment 2).

1993 AEPPoR 1

2.2 - Effluent Water Quality Monitoring

, Paragraph 6 of the referenced NPDES permit requires monitoring and recording of many water quality parameters at MNPS intakes and at 37 discharge points within the plant, including outfalls of each unit to the effluent -

quarry, and outfall of the quarry to Long Island Sound. Paragraph 11 of the permit requires a monthly report of this monitoring to th Commissioner of Environmental Protection. The report that fulfills these cequirements, Monthly Discharge Monitoring Report, includes data from all three Millstone units. Those data that pertain to Unit 3 are summarized in Table la.-

During 1993, four NPDES exceptions were reported from discharges associated with Unit 3 (Table Ib). The first, on 12 February, was the report of total residual chlorine (TRC) concentration of 0.15 ppm (permit limit 0.10 ppm) at DSN 001, the common outfall of all three Units to Long Island Sound. Investigation concluded that the measurement was probably a-sampling anomaly, as only Unit I had performed circulating water chlorination (the procedure that uses sodium hypochlorite most rapidly) on that day; Unit 2 was only chlorinating service water (a procedure that uses hypochlorite at a much lower rate), and Unit 3 was not chlorinating even service water on that day, because the injection equipment was being relocated and modified.

The three other NPDES exceptions, free available chlorine ' (FAC) exceedances at Unit 3 service water discharge (DSN 001C-5), were associated -

with these modifications, and were attributed to. operator unfamiliarity and' '

procedural deficiency. The Unit 3 service water discharge is diluted approximately 30-fold by circulat.ing water before it enters the effluent quarry, and even the highest chlorine levels measured were well less than those of.

domestic city water; therefore, the environmental impacts associated with these NPDES exceptions are negligible. However, station management will take the appropriate steps to correct the deficiencies, to minimize the chance that the incidents will recur.

Sampling for hydrazine (N2H4), biological oxygen demand (BOD), and chemical oxygen demand (COD) is required only when discharging wastewater containing hydrazine. The major hydrazine discharges at Unit 3 me from ,

DSN 001C-la, releases following wet lay-up of steam generators during ,

extended outages; during 1993, these events occurred in August. Maximum  ;

hydrazine concentration was 61 ppm (permit limit '125 ppm); concurrent samples taken at the quarry cuts (DSN 001C) were all <0.1 ppm.

3. Environmental Protection Plan Noncompliances i

During 1993, no EPP noncompliances were identified for Unit 3. j l

1993 AEPPoR 2

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4. Environmentally Significarit Chi nges to Station Design or Operation l During 1993, no Unit 3 Plant Design Change Records (PDCRs) met the acceptance -i criteria for inclusion in this report, i.e., a) were initiated during the report year, and -

. b) included a determination that an unreviewed environmental impact could occur.

Of the 227 PDCRs initiated during 1993, none involved unreviewed environmental = r issues. .

f Unit 3 has 158 System Operating Procedures; of these,141 were added or revised  ;

during 1993. In addition, many procedures were modified to reflect small changes, s of insufficient magnitude to require the issuance of a new revision. However, each of these changes, as part of the review / approval process, included an environmental . -

evaluation; none were determined to involve an unreviewed environmental impact.  :

5. Non-Routine Reports of Environmentally Significant Events During 1993, no events occurred at Unit 3 that met the acceptance criteria for inclusion in this report, i.e., required submittal of a Licensee Event Report (LER)  :

from Unit 3, and involved a situation that could result 'in a significant environmental impact. Of the 23 events that constituted reportable occurrences in 1993, none were . ,

determined to cause a significant environmental impact.

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Table 1. Millstone Unit 3 NPDES Data Summary, Jan.1 - Dec. 31,1993. i

. a). Selected water quality parameters for Unit 3' (any exceptions are in imic ;ype).

discharge discharge discharge discharge avg max max SWS ,

flow range pH range temp. range temp. (avg) AT FAC TRC FAC (10' gpm) ("F) ' ("F) (*F) (ppm)- (ppm) (ppm)

Jan. 790-948 7.9-8.1 52.0-61.2 57.3 16.6 <0.05 <0.05 0.19 ,

Feb. 630-942' 7.8-8.1 51.1-59.9 55.3 18.1 <0.05 0.15 0.24 Mar. 638-942 6.0-8.1 38.1-59.9 54.9 17.8 <0.05 <0.05 0.15 Apr. 480-948 7.5-8.1 37.9-66.0 55.1 12.9 0.05 <0.05 0.17 May 790-948 7.5-8.0 61.5 73.8 68.5 17.1 0.07 0.10 0.16 '

June 790-942 7.1-7.9 71.2-81.9 76.4 17.4 0.08 <0.05 0.85 July 790-948 6.2-8.1 67.1-86.7 81.8 16.6 0.08 0.08 0.18 Aug.15-942 7.1-8.0 66.9-76.5 70.6 0.7 <0.05 <0.05 0.18 Sep.30-486 7.2-7.9 63.1-72.7 67.9 0.2 <0.05 <0.05 0.37 >

Oct.30-942 7.57.9 55.9-64.4 59.7 0.3 <0.05 <0.05 0.15 Nov. 486 948 7.4-8.0 50.0-74.8 64.3 11.5 <0.05 <0.05 0.12 Dec. 790-948 7.5-7.9 55.8-73.8 65.0 17.9 0.20 0.10 0.65 b). Number of NPDES cxceptions during year 2, Susp. Boric oit &

pil temp. FAC TRC Sol. BOD S COD3 hydrazmc 3

acid conduct hthium grease metals 0 0 3 1 0 0 0 0 0 0 0 0 0

' Parameters are measures at Unit 3 discharge (DSN 001C), except for TRC, which is measured at MNPS discharge (quarry cuts; DSN 001) and SWS FAC (service water system; DSN 001C-5).

2 Some parameters are measured at more than one point within Unit 3 or only under certain operating conditions. Values represent number of NDPES cxceptions for all discharge points. ,

3 Sampling for BOD, COD, and hydrazine is required only when discharging wastewater containing hydrazine; data for these events are presented in the text.

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Millstone Unit 3 Environmental Protection Plan Annual Environmental Protection Plan Operating Report ,

January 1 - December 31,1993 ]

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Executive Summary Lobster Studies values (69.5-70.2 mm), but within the range of values reported in 2-unit study years. Only 3.3% of The American lobster, Romarus americanus, is one the catch was oflegal-size during 1993, within the of the most valuable species in the Connecticut range of 3-unit years but below the range of 2-unit fishing industry. Between 0.8 and 2.7 million years (5.9-9.1%). Percentage of females carrying pounds have been landed annually since 1978 yielding external eggs (berried) during 1993 was 12.2% and between 2.4 and 8.4 million dollars to lobstermen higher than in any previous study year (3.1-12.1%).

employed in the fishery. Lobsters are highly Berried females were, however, smaller during 3-unit exploited throughout their range; in the Connecticut years (76.5 mm) than during 2-unit years (79.4 mm), -

lobster fishery, more than 90% oflegal-sized lobsters reflecting the high proportion (90%) of berried are harvested each year. New fishery regulations have females below the minimum legal size of 82.6 mm.

been implemented throughout the lobster range to The most important factor regulating molting and reduce the high fishing mortality rates and to increase growth of lobsters is water temperature. Water larval production and subsequent recruitment. Since temperatures during the 3-unit study years were, on 1984, Connecticut lobster nen have been required to average, slightly warmer than during 2-unit study install escape vents in traps; the escape vents allow years. As a result, the peak in catches of molting sublegal-sized lobsters to escape from traps and lobsters in 3-unit years occurred earlier (by 9 days) thereby reduce injury and mortality to this portion of than during 2 unit years. Imbster growth per molt, as the population. The minimum legal size (carapace determined by tag and recapture studies, averaged length) of lobster was gradually increased in 13.7% for both males and females in 3-unit studies, 3

Connecticut from 81.0 mm (3 /16 in) in 1988 to and was slightly higher than growth per molt 8'2.6 mm (3 % in) in 1990. Because of the regional observed during 2-unit studies (males 13.3% and economic importance of lobsters, the local population females 13.0%).  ;

of lobsters in the Millstone Point area have been Results from tag and recapture studies indicate that sampled annually from May through October since the overall percentage of recaptures in our traps was _ l 1978 to determine if operation of Millstone Nuclear similar during 2. and 3-unit years (19% vs. 20%), )'

Power Station (MNPS) has caused changes in local whereas the percentage of recaptures by commercial lobster abundance beyond those expected from natural lobstermen declined from 33% during 2-unit years to variability and high fishing mortality rates. Some 18% during 3-unit years. His decline of recaptures changes were observed in abundance and population in commercial traps was related to the 1984 escape characteristics of lobsters during 1993, but they were vent regulation and not to MNPS operation, most likely related to high fishing levels and changes Installation of escape vents, coupled with the fact that in fishery regulations (escape vents, minimum legal most of our tagged lobsters are sublegal, resulted in size increase) rather than to power plant impacts, fewer tagged lobsters retained in commercial traps.

The total number of lobsters caught and catch per Conversely, our traps did not have escape vents and unit effort (CPUE) of all sizes of lobster reached retained similar numbers of tagged sublegal lobsters.

record levels in 1992 and remained high during 1993. Lobster tagging also indicated that local individuals Total number caught (10,195) and CPUE (2.301) in are predominantly nonmigratory. Over 90% of the 1993 were the second highest reported (previous tagged lobsters recaptured in commercial traps were ranges were 6,376-11,438 and 0.904-2.457). While a caught within 5 km of Millstone Point. The average significant increasing trend was observed in total distance traveled by lobsters before they were caught CPUE from 1978 to the present, legal lobster catches in commercial pots was similar during 2 and 3 unit (those individuals 2 82.6 mm carapace length) have years (2.4 vs. 2.9 km). Although a predominance of significantly declined since the study began in 1978. localized movement was observed in our study, a The CPUE of legal-sized lobsters was 0.080 during number of lobsters (113) were reported caught 1993 and within the range reported in previous 3-unit outside LIS along the Rhode Island and Massachusetts studies, but lower than the range reported during 2- coasts, and in offshore deep water canyons on the edge

! unit studies (0.098-0.173). of the continental shelf, t

ne mean carapace length of lobsters caught during Since 1984, lobster larvae have been sampled from 1993 (70.8 mm) was larger than previous 3-unit May to August at the discharges of Units 1,2 or 3.

4 Executive Summary vii 1

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The average density of larvae collected during .1993 percentage) measured in 1993 were generally within was 1.081 per 1000 m3 of cooling water, which was the ranges of previous years; the only exceptions were the second highest value reported (previous ranges annual biomass at WP, which was the highest yet were 3-unit 0.525-1.334; 2-unit 0.409 and 0.504). reported, and percentage of reproductive shoots at JC Estimates of totallobster larvae entrained through the and NR, which were also maxima, plants cooling water system were based on sample The celgrass population at WP remains unaffected density of larvae and total MNPS cooling water by MNPS operation, as population parameters have demand during the May to August hatching period. been generally stable since 1985. At NR, wide During 1993 an estimated 389,767 larvae were fluctuations of abundance have occurred, including entrained, within the range of previous 3-unit years localized elimination of plants from NR #1 (1986-(296,173-615.285), but higher than the 2-unit 87), from NR #2 (1987), and from NR #3 (1987-93).

estimates of 77,458 and 128,550. Entrainment These abundance fluctuations, however, are related to numbers have been substantially higher since Unit 3 factors other than MNPS operation because the began operating because the cooling water demand of Niantic River is not impacted by the thermal effluent.

Unit 3 alone is about the same as that of Units 1 and Furthermore, in recent years NR #1 has been 2 combined. The potential impact of lobster larvae recolonized and the celgrass population has apparently entrainment is difficult to assess because of the recovered completely. At JC, changes in eclgrass uncertainty that exists concerning larval origin and abundance may be related to changes in water larval survival and recruitment rates to legal size. temperature, but, at least to date, these changes appear Since lobsters require 4-5 years of growth before they to be the result of natural variability rather than an are vulnerable to capture, and an additional 2 years of impact of 3-unit operation.

growth to reach legal size, a decline in local lobster abundance caused by larval entrainment would not be Rocky Intertidal Studies apparent for several years.

At present, fishery regulations implemented in Attached rocky shore communities, as described by 1984 (escape vents) and 1988 (increased minimum the NUSCO monitoring program, continue to serve ,

size) to preserve the LIS lobster resource appear to be as effective integrators of local environmental effective. The percentage of berried females has conditions in the vicinity of MNPS. Conditions increased each year since the minimum legal size was resulting in much of the variability among first increased and lower incidence of claw loss and communities at sampling sites outside the influence  !

reduced retention of sublegal sized lobsters in of MNPS were related to natural factors including site commercial traps were attributed to the use of escape orientation to prevailing wind-generated waves, the )

vents. However, fishing effort has more than doubled ability of available substratum (slope) to dissipate the since 1978 and further increases may offset some of horizontal force of those waves, and the character of l the benefits of the new regulations. that substratum (e.g., boulders, bedrock ledge, etc.). l Community differences beyond those attributed to Eelgrass natural factors occurred within the thermal plume area at sites located on Fox Island (FE and FN), and were -

Eelgrass is the predominant marine flowering plant directly attributed to MNPS operation. Various in estuaries and lagoons of tempemte and warm boreal aspects of the impact-related community changes at coasts in the Atlantic and Pacific Oceans. In the Fox Island were identified through separate studies vicinity of Millstone Point, celgrass populations can which included qualitative algal sampling, estimation exhibit wide temporal and spatial variability in shoot of intertidal organism abundance, and studies of local length, plant density, standing stock biomass and Ascophyllum nodosum populations.

other population parameters. During 1993, these Elevated temperature conditions caused by the 3-parameters were measured at three sites in the MNPS unit thermal plume allowed development of a unique i area: Jordan Cove (JC), White Point (WP) and flc.a at FE. The most notable shifts in species occur-Niantic River (NR). rence, revealed by qualitative algal sampling, were the Eelgrass population parameters (plant density, presence of warm water-tolerant species not typical of shoot length, standing stock biomass and percentage other sites (Agardhiella subulata, Gracilaria tikvahiae of reproductive shoots) and sedimentary charactcristics and Sargassumfilipendula), absence of common cold l (mean grain size, organic content and silt / clay water species (Mastocarpus stellatus, D;montia viii Monitoring Studies.1993

contorta and Polysiphonia lanosa) and extended or (GN), as the control site, continued to show little

- reduced periods of occurrence of seasonal species with temporal variation and no effect of MNPS operation.

warm or cold water affinities, respective y. 'Ihe dominant taxa collected during 1993 at subtidal During 1993, power plant impacts on dominant stations included the polychacte species Aricidea species abundance patterns, caused by 2-cut water catherinae, Tharyx spp., Prionospio steenstrupi, circulation pattems and by 3-unit operations, were Polycirrus eximius, Scoletema tenuis, Protodorvillea observed only at FE, and were most pronounced in gasprensis, Mediomastus ambiseta, Pygospio the low intertidal, where temperature conditions were elegans, the arthropods Ampelisca vadorum, A .

most severe The low intertidal community at FE, verrilli and Leptocheirus pinguis and representatives which prior to 1983 had been unimpacted and of the class Oligochaeta. The top four ranked taxa at

- characterized by perennial populations of Fucus, each station in 1993 accounted for 50% or more of all Chondrus and Ascophyllum and predictable seasonal individuals. In most cases, these organisms have' ,

peaks in barnacle abundance, has been replxed by a been the dominant subtidal taxa in both 2-unit and 3-persistent community dominated by Codium Ulva, unit operational periods. Most stations were Enteromorpha and Polysiphonia. Also, populations characterized by one or more clearly dominant taxon of species observed in undisturbed transects only at (oligochaetes at EF, GN and JC, Aricidea catherinae -

FE (Sargassum, Gracilaria) persisted during 1993. at GN and JC and Tharyx spp. at GN) during both Ascophyllum populations at three stations in the operational periods. There has been no single domin-vicinity of MNPS continued to be monitored in ant taxon at IN during either operational period, where 1993. Elevated temperatures (2-3 C above ambient) mean relative abundance of any single taxon rarely at our station nearest the discharge (FN) caused exceeded 10%. Analyses of local benthic commun- j

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Ascophyllum to grow longer and more rapidly at this ities have identified changes and long-term trends in site, relative to stations farther away. A moderate community parameters, and have permitted distinction level of growth enhancement was observed at FN between changes related to natural variability, and during 1992-93, when compared to previous years, those caused by power plant operation.

attributed to lessened thermal plume incursion resulting from an extended outage of Unit 2 for much Marine Woodborer Study of the peak growing season. As in previous years, Ascophyllum mortality, or loss of tagged plants and The Marine Woodborer Study report describes the tips, at our present sampling sites was not related to local distribution of Teredo bartschi, a semitropical proximity to the power plant but rather to degree of shipworm common from Texas to South Carolina, exposure to prevailing winds and waves, but capable of cstablishing isolated pop ilations near thermal discharges in more northern climates. T.

Benthic Infauna bartschi remains in MNPS discharge waters and, in 1993, it was collected for the first time in panels 500 .

During 1993, infaunal communities inhabiting m from the quarry cuts. Reduced currents around the soft-bottom subtidal habitats in the vicinity of rock outcroppings at this new site may trap discharge MNPS were sampled quarterly as part of a long-term water and increase the probability of collecting this monitoring program. These communities were charac- immigrant species. The absence of T. bartschi at EF terized in terms of species composition, abundance, in 1993 is probably related to unusual conditions and sedimentary parameters in order to identify spatial resulting from Unit 3 being off line from August to and temporal patterns in community structure and to November, during the peak recruitment period for this assess whether observed changes can be attributed to species. The distribution of T. bartschi remains construction or operation of the power plant. closely associated with the discharge waters of Changes in sediments resulting from Unit 3 MNPS, suggesting that the discharge population has construction and initial operation events have resuhed not adapted to ambient temperature conditions at in alterations to associated infaunal communities in White Point,1700 m from the quarry cuts. Even recent years. During l993, the effluent site (EF) con- though the current program represents a large tinued to show evidence of sediment scour, and Jordan reduction in sampling effort relative to previous study Cove (JC) sediment deposition. The intake site (IN) years, it continues to effectively monitor the exhibited continued recovery from dredging activities abundance of T. bartschi in the Millstone area.-

near the intakes in the early 1980s, and Giants Neck Executive Summary ix

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J Fish Ecology Studles grubby is unique because unlike the other potentially :

impacted fishes it experiences no fishing pressure. .

Studies of fish assemblages inhabiting the area Both larval and adult gmbby abundance indices have  !

around MNPS were conducted to determine the effects been stable throughout the 17 years of monitoring.  !

of station operations. These effects have been defined Tautog has been the second-most abundant egg taxon as power-plant related changes in the occurrence, entrained and has accounted for more than 30% of the f

distribution and abundance of fish species which total eggs collected since 1979. The tautog egg

- would affect the community structure. Fish entrainment estimate for this report year was the assemblages could be adversely affected by losses due lawest since three-unit operation began and the to impingement of juvenile and adu't fish on the average density of eggs at the entrainment site (EN)  ;

intake screens, entrainment of fish eggs and larvae was the second lowest since sampling began. Larval j through the cooling water system or by changes in tautog average densities at EN were within their '

thermal regime or physical habitats. historic range. The cunner egg entrainment estimate l Trawl, seine and ichthyoplankton monitoring also was the lowest since Unit 3 began operating.

programs were established in 1976 to determine the Cunner larval densities were within their historic j range. Prior to 1992-93, the trawl catch of cunner impact of MNPS on local fish assemblages. Of the 120 different fish taxa that have been collected since had been decreasing at all six stations. This year's i then in these programs, seven taxa (American sand trawl catches were below the two-unit operational l I

lance, anchovy, grubby, silversides, tautog, cunner catches at two inshore stations, but were at a historic and winter flounder) have been identified as having the high in Niantic Bay. Both tautog and cunner potential to be impacted by MNPS either by young-of-tha-year have accounted for a high  !

entrainment or because of their susceptibility to proportion N Se fish caught in the trawl since three- 'l thennal impacts. unit operation . an. ]

Abundance data were analyzed separately for two- Because over bd of the eggs entrained at MNPS .j unit (1976-1985) and three-unit (1986-1992) were tautog and cunner eggs, special studies were j operational periods and for the entire 17-year data conducted in 1993 to determine the entrainment i series (both periods combined) to determinc if changes mortality of these eggs. The average hatching rate in fish abundance have occurred. Larvae of sand lance was 4E To examine daily fluctuations of egg and anchovy have declined as have adult tautog and abundance, samples were collected every two hours cunner. Because so many factors affect the abundance during three 24-hour periods. Examination of the l of these taxa the reasons for these declines are difficult geometric mean for each 2-hour sampling period j to ascertain. American sand lance larvae has ranked showed that on the average, daily peak spawning for I i

third among fish larvae entrained and it has cunner and tautog occurred at about 1800 hours0.0208 days <br />0.5 hours <br />0.00298 weeks <br />6.849e-4 months <br /> and significantly decreased in abundance in the entrain- then declined rapidly. Estimated mortality rate ment and offshore samples. The bay anchovy is during this rapid decline was 44 % per hour for cunner typically the most abundant ichthyoplankton species and 47% per hour for tautog. These very high egg collected in estuaries within its range and it was the mortality rates may account for the low numbers of dominant larval taxa entrained at MNPS. Similar to cunner and tautog larvae collected compared to the the sand lance, this fish also exhibits large natural large number of eggs of these two fishes. j abundance fluctuations. Along the Connecticut coast, l

the Atlantic silverside and the inland silverside are Winter Flounder Studies among the most common shore-zone species. Typical of short-lived species, the catches of Atlantic ne local Niantic River population of the winter silverside by trawl and seine were highly variable and flounder (Pleuronectes americanus) is potentially annual catch indices ranged over two orders of affected by the operation of MNPS, particularly by -!

magnitude. De trawl CPUE of Atlantic silversides entrainment of larvae through the cooling-water was at a 17-year high at the two Niantic Bay Stations systems of the units. As a result, intensive studies of ~

(NB and IN), and all 1992-93 trawl catches were the life history and population dynamics of this above the two-unit annual averages. The catches of valuable sport and commercial species have been Atlantic and inland silversides in seines were all undertaken since 1976.

within historic ranges and above the two-unit period The median trawl catch-per-unit-effort (CPUE) of -

average, except for Atlantic silversides at JC. The fish larger than 15 cm collected in the Niantic River x Monitoring Studies,1993

1 during the February-April 1993 spawning season was collected during late spring and summer in the Niantic 1.9.- %!s value was only about 30% of'the CPUE of River since 1983 and in Niantic Bay since 1988. In .

6.2 for last yerr, and it was the smallest CPUE in the 1993, abundance of newly metamorphosed young was 18-year time series, ne Jolly stochastic model was relatively low, particularly in the Niantic River.

used with mark and recapture data to estimate the Mortality was once again apparently quite high in the absolute abundance of the adult spawning population bay, with no fish caught there by mid-summer.1. ate-(all winter flounder larger than 20 cm, which includes season median densities at two stations in the river some immature fish). The most recent abundance were among the lowest found since 1983.

estimate of 12,178 fish for 1992 was only 19% of the An index of abundance was calculated for young-of.

1991 estimate and further illustrated the severe decline the-year fish taken during the late fall and early winter -

of winter flounder abundance in recent years. at the trawl monitoring program stations. The 1992-Each year, about one-third to one-half of the winter 93 abundance index (1992 year-class) was 31.1, the flounder found in the Niantic River during the highest in the 17-year series. This was consistent spawning period have been mature females. Using with the high abundance of these fish found during available information on sex, age, and size the summer of 1992 and was indicative of the composition, the annual female winter flounder strength of the 1992 year-class. However, relatively parental stock sizes have been estimated for the past few of these fish were taken within the Niantic River 17 years. These estimates have ranged from 7,821 during the adult spawning population surveys in early (1993) to 78,629 (1982) fish, with corresponding 1993. Young-of-the-year abundance indices were not total egg deposition ranging from about 6.4 (1993) to significantly correlated with those for age-4 and 5 45.6 billion (1982). female adult spawners. Therefore, none of the early Estimates of larval winter flounder abundance at the life stages could be used as a reliable index of year-MNPS discharge (entrainment sampling) have been class strength for Niantic River winter flounder stock.

obtained since 1976, at a station in mid-Niantic Bay Egg production estimates from annual spawning since 1979, at three stations in the Niantic River surveys were scaled to numbers of spawning females since 1983, and at the mouth of the Niantic River and used as recruitment indices. These indices during 1991-93. The low abundance of newly-hatched together with adult female spawning stock estimates larvae in Niantic Bay compared to the Niantic River and mean annual February water temperatures were suggested that most local spawning occurred in the used to fit a three-parameter Ricker stock-recruitment river. Larval abundance in 1993 was the lowest in relationship (SRR). Additionally, the indirect esti- t both the Niantic Bay and River since sampling began mate of the winter flounder theoretical rate of increase in 1976 and 1983, respectively. Annual larval (the SRR a parameter) derived by the Connecticut abundances in the bay for 1976-93 appeared to reflect Department of Environmental Protection (DEP) was region-wide trends, because they were highly used for modeling the dynamics of the winter flounder -

correlated to abundance indices in Mount Hope Bay, population for impact assessment purposes. The MA and RI. value of a, re-scaled to units of fish numbers from Larval developmental stage and length were closely biomass units, was estimated as 5.42 and described related. Smaller larval size-classes predominated in the inherent potential for increase of the Niantic River the river and larger size-classes were more prevalent in winter flounder stock. The estimate of (the second the bay. In Niantic Bay, growth and development SRR parameter), which describes the annual rate of were correlated with water temperature, and in the compensatory mortality as a function of stock size, river growth appeared to be related to both water has shown little annual variation since 1988. The temperature (positively) and larval density third and last parameter in the SRR described a (negatively). Estimated mortality of larvae in the negative relationship between winter Bounder recruit-Niantic River for 1984-93 ranged from about 82 to ment and water temperatures in February, the month 98E Mortality was consistently highest during when most spawning, egg incubation, and hatching Stage 2 of development (3- to 4-mm size-classes), occur.

which is when feeding first occurs; larval abundance The number of larvae entrained through the declined about 90% during this stage in 1993. This condenser cooling-water system at MNPS is the most stage may include a " critical period" for winter direct measure of potential impact on winter flounder.

flounder as survival rates ger.erally improve Annual estimates of entrainment were related to larval progressively for larger size-classes. densities in Niantic Bay, as well as to plant opera-Young-of-the-year winter flounder have been tion. The entrainment estimate for 1993 of 41.1 Executive Summary xi

3 .-

. million was the lowest since three-unit oper tion An initial stock size of 97,075 lbs was used to began in 1986 and was one of the low'est in the 18- represent the theoretical (no fishing assumed)

. year series. Low entrainment was attributed to low maximum spawning potential (MSP) of the Niantic larval abundance, as all MNPS units operated River female spawning stock. When fishing effects throughout much of the larval winter flounder season were simulated, the annual projections of the initially during 1993. unfished stock become the baseline time series of

' The impact of larval entrainment on the Niantic annual spawning biomass for Niantic River winter River stock depends upon the fraction of its produc- flounder subjected to fishing, but in the absence of tion that is entrained each year. Empirical mass- any plant impact. Under the exploitation rates balance calculations for 1984-93 indicated that a large simulated, the stochastic mean stock size of the number of entrained larvae came from areas of Long baseline declined to about 48,300 lbs in 1971 and to Island Sound other than the Niantic River. An esti- 12,300 lbs in 1993. 'Ihe latter value was about one-mated 11 to 35% of the larvae entrained at MNPS half of a generally accepted critical stock size, defined appeared to have originated fmm the Niantic River dur- as 25% of MSP. Following simulated reductions in '

ing these years. Percentages of the river production fishing, however, the stock rapidly recovered. A new that were entrained annually ranged from about 4 to series of stock size projections were then simulated 21% and the estimated fraction of Niantic River by adding the effect of larval entrainment at MNPS.

winter flounder production that would be entrained The lowest. projected stock biomass under under full (100% caprity) three-unit operation ranged simultaneous fishing and effects of MNPS occurred in from about 5 to 24%. 1993 (10,600 lbs), whereas the greatest absolute A computer simulation model (SPDM) was used decline relative to the baseline occurred in 2001 (a for long-term assessments of MNPS impact. Input difference of 7,800 lbs). Generally, however, greater data used by the model included basic life-table reductions in stock biomass resulted from fishing parameters, the three-parameters of the SRR, than from larval entrainment, because fishing tends to February water temperature statistics, and simulation remove larger fish and reduce average weight of the parameters specific to each model run, including a remaining spawners. The simulated spawning stock random variability component. Conditional mortality retumed to near-baseline levels about 6 years after the rates corresponding to postulated larval entrainment scheduled termination of Unit 3 operation in 2025.

and juvenile and adult impingement at MNPS were The probabilities that the Niantic River female simulated according to historical information and spawning stock biomass would fall below selected projections. Fishing mortality rates (F) were pro- reference sizes (25,30, and 40% of MSP) were deter-vided by the DEP. Initially, F was set at 0.40 and mined to help assess the long-term effects of MNPS remained unchanged through the 1960s, increased grad- operation. A stock less than 25% of MSP is ually to 0.62 by 1988 and thereafter more rapidly to a considered overfished, whereas one that is at 40% of maximum of 1.30 in 1991. Based on proposed regula. MSP can maximize yield to the fisheries while -  ;

tory changes, F was projected to decrease substan- remaining stable. For both baseline and MNPS-

• Lially through the late 1990s, dropping to 0.50 by impact simulations, it was likely (p 2 0.87) that the 2001 and remaining unchanged through the rest of the stocks were greater than 40% of MSP in 1970. At simulated years. The winter flounder stock was the lowest point of both stock projections in 1993, simulated as female spawner biomass (lbs), which is all replicates were less than 25% of MSP Simulated more directly related to reproductive potential than reductions in fishing allowed for a rapid increase in fish numbers. Annual rates of Niantic River winter spawner biomass and it was likely greater than 30%

flounder larval entrainment were based on actual or of MSP by 2010 ( p 2 0.97) and had a better than estimated MNPS cooling-water flow and estimated or even (p = 0.56) chance of being greater than 40% of projected entrainment as derived from mass-balance MSP by 2020. These increases, however, assumed calculations. All SPDM runs were stochastic and con- that changes in fishing regulations would be ,

sisted of 100 Monte Carlo replicates for each yearly implemented as scheduled and that they would achieve -

stock pmjection over a 100-year period (19fo2060). the expected reductions in fishing mortality.

xii Monitoring Studies,1993

4

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A1TACIIMENT 2 to the Millstone Unit 3 Environmental Protection Plan

- Annual Environmental Protection Plan Operating Report January 1 - December 31,1993 i

i t