ML20206J516
| ML20206J516 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 12/31/1998 |
| From: | Foertch J, Keser M NORTHEAST NUCLEAR ENERGY CO. |
| To: | |
| Shared Package | |
| ML20206H932 | List: |
| References | |
| NUDOCS 9905120252 | |
| Download: ML20206J516 (14) | |
Text
Annual Environmental Protection Plan Operating Report January 1 - December 31,1998 -
Millstone Unit 3 Environmental Protection Plan 1
prepared by Northeast Utilities Service Company P.O. Box 270 Hartford, Connecticut 06141-0270 April 1999 9905120252 990430 2
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Annual Environmental Protection Plan Operating Report January 1 - December 31,1998 Millstone Unit 3 Environmental Protection Plan Prepared by:
Jim Foertch Reviewed by:
Milan Keser
Annual Environmental Protection Plan Operatine Report - 1998 1.
Introduction This report covers the period January 1 - December 31,1998. Unit 3 was placed on the NRC Watch List on January 29,1996 and had been ofr-line since March 30,1996 following the declared inoperability of the auxiliary feedwater containment isolation valves. Unit 3 returned to service on July 5,1998. Since restart, Unit 3 experienced occasional down-powers and shut-downs, e.g., a 9-day outage in mid-August to repair a leaking valve in the auxiliary feedwater -
system, a 2-day outage in mid-September and a 3-day outage in late-October resulting from high condensate conductivity, and a 2-day outage in mid-November resulting from storm-related intake conditions. Unit 3 shut down on December 11, in response to over-actuation of a main steam isolation valve during a surveillance, and returned to service on December 31.
During 1998, Unit 3 operated at a 33% capacity factor; since restart in July, the capacity factor for the cycle was 65%.
As required by the 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 result in significant environmental impact.
2.
Environmental Protection Activities 2.1 Annual National Pollutant Discharge Elimination System (NPDES) Report of Ecological Monitoring (EPP Section 4.2)
Paragraph 5 of the Station's NPDES permit requires continuation of biological studies of Millstone Nuclear Power Station (MNPS) supplying and receiving waters, entrainment studies, and intake impingement monitoring. These studies include analyses ofintertidal and subtidal benthic communities, finfish communities, entrained plankton, lobster populations, and winter flounder populations. Paragraph 7 of the permit requires an annual report of these studies to the Commissioner of Environmental Protection.
The report that fulfills these requirements for 1998, Monitorine the Marine Environment of Long Island Sound at Millstone Nuclear Power Station. Waterford. Connecticut - Annual Report.1998, (Annual Report) presents results from studies performed during 3-unit operation, and compares them to those from 2-unit operation. Past reports have indicated that the added cooling water flow for Unit 3 affects impingement and entrainment, causes sediment scouring near the MNPS discharges, and alters the characteristics of themial effluent plume. The extended shutdown of MNPS from 1996-1998 has also caused some changes to the 1998 AEPPOR 1
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physical environment in the vicinity of the station discharge, and additional changes were documented since restart of Unit 3 in July 1998. The biological effects of these changes are summarized in the Executive Summary section of the Annual Report (Attachment 1) and further discussed in the Annual Report itself(Attachment 2).
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 monitoring 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 the Commissioner of the Connecticut Department of Environmental Protection (DEP). The report that fulfills these requirements, Monthly Discharae Monitorina Report (DMR), inciades data from all three Millstone units. Those items that pertain to Unit 3 are summarized in Table 1.
During 1998, in support of Unit 3 restart activities and renewal of the Millstone Station NPDES Permit, the Station submitted much correspondence to the DEP (e.g., requests for Temporary and Emergency Authorization, additional information pertaining to the NPDES Permit renewal application). In compliance with the EPP (Section 3.2) and Station procedures, the NRC was sent concurrent copics of this correspondence.
Descriptions of events that pertain to Unit 3 discharges, or the Station as a whole, were summarized from the monthly DMRs, and included in Attachment 3. These events include any NPDES permit exceedances (i.e., events where the value of a parameter was beyond the permitted limit) or exceptions (i.e., events where a permit condition was not met) that were reported for discharges associated with Unit 3, as well as other environmentally-related events which did not necessarily involve NPDES permit exceedances or exceptions, but had been reported in Millstone DMRs for informational purposes. Submittals and letters are identified by unique "D-numbers" (e.g., D12063) to allow document and commitment tracking.
3.
Environmental Protection Plan Noncompliances During 1998, no EPP noncompliances were identified for Unit 3.
4.
Environmentally Significant Changes to Station Design or Operation As of December 31,1998, Unit 3 has 195 System Operating Procedures; of these,28 were added or revised during 1998. In addition, many procedures were modified to reflect small changes, ofinsufficient 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 was determined to have involved an unreviewed environmemal impact. Althoughjudged not to involve a significant impact, two operating practices-were detennined to require modification at each unit, including Unit 3. The original and modified operating practices are discussed below.
1998 AEPPOR 2
I Each unit has a separate Service Water System that provides cooling water to a number of plant components, including safety-related equipment that would be called upon to allow safe shut-down during an accident. To improve system reliability, sodium hypochlorite is injected as a biocide near the service water pump suctions; this methodology has proven very effective at minimizing biofouling of the service water system. However, it was recognized that the service wa.er strainers were periodically backflushed with redirected service water, to remove debris; therefore, the strainer blow-down represented a chlorinated wastewater discharge. To minimize this possibility, operating procedures were modified to secure service water chlorination during scheduled service water strainer backwashes.
There remained the possibility that automatic strainer blow-down, initiated during periods of high debris loading, could discharge chlorinated water. To preclude this, Unit 3 relocated the injection point for j
sodium hypochlorite, from the service water pump suction tojust downstream of the strainer.
j In a separate but similar issue, it was recognized that chlorinated water was also used as pump seal water, lubricating rotating pump shafts. The immediate change to operating procedure was to secure seal water flow to any pump expected to be off for an extended period.
During 1998, no Unit 3 Design Change Records (DCRs) met the acceptance 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. Although judged not to create a significant impact, the modification to the sodium hypochlorite injection point, mentioned above, is discussed in more detail below. In January 1998, Unit 3 received g
pennission from the DEP to relocate the injection point from the service water pump suction to
(
downstream of the strainer; the modification was installed in June. In September 1998, owing to material failures, Unit 3 had to temporarily relocate the injection point back to the original location; final repairs to the sodium hypochlorite injection system were completed in December.
5.
Non-Routine Reports of Environmentally Significant Events During 1998, 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 45 events that constituted reportable occurrences in 1998, none were determined to cause a significant environmental impact. Although judged not to require submittal of LERs, two events occurred at Millstone Station in 1998 that are included for yout information. On August 12,just prior to the shut-down to repair the aux feedwater valve, water temperature in the MNPS effluent quarry was about 87 F; following shut-down, temperature rapidly dropped to ambient levels of about 68 F.
After repairs were completed on August 21, and Unit 3 restarted, temperature rose to 95 F; shortly after this, NU personnel found 220 dead fish in the quarry (76% oyster toadfish,23% tautog). Apparently, the high temperatures, exacerbated by the rapid changes, exceeded the physiological limits of the fish resident in the quarry. Another fish kill (smaller; <30 fish) was noted in December, afler Unit 3 shut down to repair a MSIV (and inspect others). In this event, quarry water temperature dropped from about 68 F on December 10 to 48 F on December 12; apparently, this thermal change also was sufficient to cause some mortality to the resident populations. Since fish within the quarry are isolated from those outside, no impact to the region's fisheries occurred.
1998 AEPPOR 3
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Table 1. Millstone Unit 3 NPDES Data Summary, Jan.1 - Dec. 31,1998. Selected water quality parameters for Unit 3m, max
' 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.30-638 8.1-8.1 38.6-44.2 41.5 0.3 0.17
<0.03 0.18 Feb.30-486 8.0-8.2 38.2-41.3 39.3 0.0 0.05
<0.03 0.19 Mar.30-638 8.0-8.2 38.5-45.9 40.5 0.0 0.11 0.03
- 0.20 Apr. 486-638 7.3-8.2 42.1-50.1 45.0 0.0 0.13
<0.03 0.18 May 486-790 8.0-8.2 48.0-59.1-52.5 0.0 0.10 0.10 0.18 June 486-942 7.9-8.1 55.3-63.9 58.3 0.1 0.10 0.04 0.20 July 486 948 7.3-8.1 61.6-86.5-77.3 12.4 0.11 0.03 0.19 Aug. 486-948 7.7-8.7 67.1-97.0 81.0 12.6 0.07 0.04 0.23 Sep. 790-948 77-8.1 67.8-91.0 83.3 15.5 0.10 0.10 0.23 Oct. 638-954 7.7-8.1 56.5-85.0 76.3 15.1 0.21 0.05 0.21 Nov. 638-954 7.9-8.2 52.2-78.9 64.7 12.7 0.11
<0.03 0.23 Dec.30-942 7.9-8.2 40.8-70.2 53.4 6.2 0.19
<0.03 0.17 Notes:
(" Parameters are measured 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).
ATTACHMENT 1 to the Millstone Unit 3 Envircnmental Protection Plan Annual Environmental Protection Plan Operating Report January 1 - December 31,1998
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Executive Summary Lobster Studies oflobsters was to enhance recruitment and to sustain the lobster resource: larval production should increase as a Several aspects of MNPS operation could potentially larger pmponion of berried females will be able to spawn impact the local population of American lobster before reaching legal size. More than 90% of the berried (Homanes americanus). Upon hatching in early summer, females col lccted in our studies were of sublegal size and lobster larvac swim to the surface to begin the 6-to 8 the average size of berned females has become smaller week planktonic phase of their life cycle during which since 1989, when the legal size was first increased.
they are susceptible to entrainment through cooling water Additional evidence for the change in female systems. Juvenile and adult lobsters can be impmged on reproduction was observed in growth per molt estimates intake travelling screens or exposed to the heated effluent from our tag and recapture studies. Female growth per in the discharge area. Because of the regional ecenomic molt has significantly declined since 1979 and may be value of the Connecticut lobster fishery ($2-13 million related to carher maturation and increased reproductive annually) and the ecological importance of this species, activity. Females may saenfice somatic growth for lobsters have been monitored from May through October development of ovaries, and incubation and development smcc 1978 using wire lobster traps set at three stations of eggs. The fact that more females have become mature around MNPS. Since 1984, entrainment studies have and spawned at sizes well below the legal size is been conducted during the hatching season to estimate the important, since most nonberried females are removed by number oflobster larvac drawn through the cooling water the fishery shortly after reaching legal size. Spawning of system. He objective of the lobster momtoring program sublegal-sized bemed females provides a buffer against is to determine if operation of MNPS has caused changes recruitment failure and may help stabilize the LIS lobster in local lobster abundance and population characteristics fishery despite current high cxploitation rates, beyond those expected from changes in the fishery and The estimated total number oflarvae entrained at MNPS natural variability.
is highly dependent on the abundance of larvae and the Despite sustained high exploitation rates in nearshore v lume of cooling water used during summer when lobster larvae hatch. During the summer of 1996 and waters, landmgs made in the commercial fishery throughout New England have increased markedly over 1997, all MNPS Units were shut down and estimates of the last three decades. Results from our studies over the lobster larvae entrainment were the lowest reported in our studies. During 1998, only Unit 3 used appreciable past 21 years indicate an increasing trend in total catch, which is comprised mostly of recruit-sized lobsters (one amounts of cooling water, which is approximately equal molt below legal siic). The magnitude oflegal catches in to the volume required by Unit I and 2 combined. As a any year is highly dependent upon the abundance of result, the estimated number of larvac entrained during lobsters one molt smaller than legal size the year before 1998 was similar to estimates obtained when Units I and (i.e., the recrmts) and more than 90% of the lobsters larger 2 operated simultaneously during the summer. The than the mimmum legal size are removed by fishing each potential effect oflarval entrainment on subsequent legal year.
In contrast to the steady rise in commercial lobster abundance is difficult to assess due to the landings, the trend in our legal lobster CPUE has uncertainty conceming the source of entrained larvae, sigmficantly declined since lobster studies began in 1978.
their survival rate, and the relatively long period of time This decline is mostly due to the recent increases in between larval settlement and recruitment to the fishery minimum legal si/c in 1989 and 1990, although high (6-8 years). For the same reasons, the effects of the fishing effort, which has increased fourfold m LIS since prolonged shutdown of MNPS during 1996 and 1997 are the 1970s, may also contnbute to the decline. Recently, difficult to assess and not immediately observable, the abundance of recruits has increased each year since because the impact of reduced entrainment and its effect 1995; the 1998 catch was the second highest reported in on the local fishery may not be seen for several years after 21 years of lobster monitoring studies. These increases the impact occurs. Continued monitoring of lobsters will may lead to even higher landmgs as sublegal-size lobsters demonstrate the effects, if any, of MNPS operations on molt to legal si/c in 1999.
the locallobster population.
Several changes were observed in the population characteristics of local lebsters during 1998. These Rocky Intertidal Studies continue to be attributed to new fishery regulations implemented over the past to years rather than to power Rocky intertidal habitats, and the communitics of plant impacts. The most notable changes occurred in the algae and animals they support, form an important proportion of berried females and their size structure component of the Long Island Sound coastal ecosystem.
following mercases made to the legal size in 1989 and Monitoring studies of these habitats near MNPS during 1990. The objective ofincreasing the minimum legal size the last 20 years have documented ecological changes
I related to major operational changes.
While populations of bamacles and Chondrus, heavy mussel measurable, these impacts are not widespread, but sets) were related to the dominance of the Codium l
remain restricted to approximately 150 m of shoreline population.
This population remained dominant on the east side of the power plant discharge to Long through the shutdown period and after the restart of Unit Island Sound.
3.
Thermal impacts to the shore community near the Ascophyllum growth enhancement at the Fox island
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discharge at Fox Island were first observed in 1983, study site (FN), thought to be related to elevated i
after the opening of the second quarry cut. Thermal temperatures from the 3-unit MNPS discharge, was addition to this site was modified when Unit 3 began observed for the second consecutive year while all three commercial operation in 1986, and 3-unit operating units were shut down. Natural temperature increases conditions over the next ten years allowed for long-term related to tidal flushing of water from nearby shallow flats community development under a relatively consistent in Jordan Cove susceptible to solar warming may play a thermal regime. More recently, the shutdown of all more important role in determining temperature three reactors for more than 2 years (1996-98) returned conditions at FN than previously believed. Patterns of ambient temperature conditions to the discharge area.
Ascophyllum mortality, or tag loss. dunng 1997-98 were The restart of Unit 3 in July 1998 remtroduced elevated generally similar to previous years of MNPS operation, thermal regimes to this area. Relatively minor changes strengthening earlier conclusions that plant breakage is to the established shore biota were observed in response largely the result of natural disturbance from storm-driven to these events, but generally, the community that had
- waves, developed under 3-unit operating condition remained intact.
Eelgrass Quahtative algal samphng documented seasonal shins m annual species at Fox island-Exposed (FE)
Ecigrass is an ecologically important component of dunng 3-unit operation.
These shifts meluded shallow water coastal habitats. Eclgrass population abbreviated season for cold-water species (e.g.,
studies have been part of the MNPS ecological Monostroma grevil/ci. Spongomorpha arcta and m mtonng program since 1985.
Three eclgrass Dumontia contorta) and extended season for warm-Populations were monitored during 1998: Jordan Cove w ater species (e g.,
Grinnellia americana. Dasya (JC), White Point (WP), and Niantic River (NR). The JC baillouviana, and lirjopsis hypnoides). Seasonahty of and WP sites have been sampled since 1985, while the these species at FE dunng the recent shutdown period NR station has been changed several times since 1985 was more typical of other sites. Initial establishment of because of declines in the overall abundance of celgrass in perenmal populations of Graciliaria tikvahiac and the Niantic River.
Sargassumfilipendula at FE was also detected through Ecigrass shoot density and standing stock biomass quahtative studies during early 3-unit years. These estimates at all stations (JC, WP, NR) were lower in populations persisted and expanded during 3 unit 1998 relative to the previous high estimates of 1997.
operation, but were not observed dunng many While eclgrass beds near MNPS (JC and WP) exhibited collections at FE dunng the shutdown period. For the the most stability in population characteristics (standing most part, these responses to ambient temperature stock, shoot abundance and shoot length) over the long-conditions were, or are expected to be, reversed tenn Mu@ p ne
, thc Niantic River following (Jmt 3 restart m 1998, P Pulation (NR) has exhibited dramatic declines of the Thermal impacts on abundance and distnbution small, n n transient, beds within the estuary. The patterns of dominant species at FE were notable in the cunent c@ ass sh in & Mank h M % has low intertidal dunng 3-unit operation, due to tidal shown relatively little change in the past three years.
currents in the dischat;c area.
The low mtertidal Because the Niantic River is located well away from Chondrus population and associated seasonal epiphytes any influence f the MNPS thermal plume, previously at FE were replaced by a population of the opportunistic n ted declines at NR sites were related to other green alga Codium fragile supporting a perennia nvir nmental factors such as water quality, disease or Polysiphonia spp. population and periodically heavy waterfowl grahng.
sets of the blue mussel Mvtilus cdulis. Winter declines Smaller fluctuations in population parameters over m Polysiphonia abundance typical of other sites, higher the study period were noted at WP and JC, which are mid and low intertidal barnacle and Fucus abundance, I cated on the fringe of the predicted 3-unit thermal and small increases in Chondrus abundance were plum. Temperature momtonng showed no thermal observed at FE during the shutdown period, but incursi n at WP, but elevated temperatures were otherwise, little change occurred in low intertidal community composition, relative to recent years when bserved historically at JC, and thought to be possibly related to thermal plume incursion. Ilowever, recent i
MNPS was operatmg. Rather than direct thermal data collected since 1996, when MNPS was not efTects, many charactenstics of the impacted low perating, demonstrated that natural environmental intertidal community at FE (sparse, fluctuating factors were likely responsible for population
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fluctuations observed at JC as well. Elevated summer impacts related to past acute disturbance events were l
temperatures of up to 2-30C were observed at JC during noted earliest at IN, and were associated with dredging the shutdown period and in 1998, and were attributed to and cofferdam removal during Unit 3 construction from j
solar warming. These temperature increases were 1983-85. Since then, sediments (primarily silt / clay consistent with those observed in previous years when content levels) have stabilized and become more similar MNPS was operatmg, indicating that the MNPS thermal to sediments of pre-impact years. Ongoing community plume has little, if any, innuence on water temperatures recovery is evident. In particular, species richness at IN I
at the JC study site. Additionally, standing stock and increased in recent years, as have abundances of plant density at JC increased through the June-organisms that were common prior to 1983, such as September samphng period when Umt 3 was operating.
Aricidea catherinae.
These trends, along with The decline in population standing stock at JC is most concomitant decreases in abundance of opportunists likely related to site-specific natural factors such as such as the mollusc Nucula annulata and several waterfowl grating, and movement of nearby sandbars amphipod species, indicate that some degree of recovery into the study area.
is occurring at IN. Recovery at IN is not complete, however, as other organisms which have established Benthic Infauna post-impact community dominance, such as oligochaetes and Protodorvil/ca gaspecnsis, maintained llenthic infaunal community composition at three of the r increased their degree of dominance in recent years four sites monitored in the vicinity of MNPS has been and may persist indefinitely.
modified by construction and operation activities at Silt deposition at JC related to sediment scouring in M NPS. The effects of chronic disturbance from the the MNPS discharge area following Unit 3 start-up MNPS discharge were observed at one site (EF) resulted in increased sediment silt / clay content and throughout the 3-umt operating penod. Discharge effects rapid infaunal community change. Abundances of the were interrupted after station shutdown in March 1996, Previously dominant oligochaetes and the polychactes, and returned with Umt 3 restart in July 1998. Data Aricidea catherinae, Thaow spp. and Polycirrus collected from 1996 to 1998 showed minor changes to the eximius decreased. The long-term effects of this acute mfaunal commumty at EF. Acute disturbance events at disturbance have lessened since 1986. For example, A.
two sites occurred more than 10 years ago (dredging catherinac and Tharyx spp. abundances both rebounded activities at IN and siltation from discharge scourmg to record highs in 1998. However, other signs of a af er Umt 3 start-up at JC), and some impact-related p ssible trend towards recovery noted in previous years community changes were still observed during 1998.
(e.g., reduced siit/ clay content durbg 1994 and 1995, Data from the control site (GN) continued to provide a and rebounding abundances of oligochactes and P.
baschne for assessing natural variability in local ciiniius through 1993) have not materialized. Similarly, infaunal communities.
the opportunistic mollusc, Nucula annulata. which l
became an impacted community dominant, has
)
Sediment composition has been most stable at GN during the study period, which accounts for consistency maintained a population at JC through l998. Silt / clay of GN community composition.
Stability in c ntent of sediments at JC continued to be well above sedimentary characteristics continued through the 2-unit levels in 1998, and likely explains the limited shutdown period and the 1998 sampling year, with degree of community recovery noted at JC.
overall GN commumty composition also consistent with The suong influence of the MNPS discharge on the the carher study period.
GN was nu erically EF community became better understood with the dominated by the same three taxa (oligochactes, Tharyx extended shutdown period from March 1996 through spp., Aricidea catherinac) at similar relative abundance July 1998. During this period, sediment characteristics durmg both 2-umt and 3-umt operational periods. The at EF remained similar to those observed during 3-unit only noteworthy change in the GN infaunal community peration, but there were some shifts in the infaunal in 1998 w as low abundance of A.
catherinae, e mmunity at EF toward the community state observed continuation of a trend noted since 1994.
dunng 2-unit operation. These shifts included a decline Momtoring data from GN were also important for in oligochacte abundance, an increase in Aricidea documentation of regional trends in infaunal catherinae abundar ce and pulses in abundance of the communitics. In 1998, a large population pulse of the Opportunistic polychaetes Afediomastus ambiseta and polychuctes Alediomastus ambiseta and Pygospio Pygospio elegans and Tharyx spp. at EF in 1997-98 that c/cgans were noted at GN and all other stations. Similar wcre also observed at other sites.
During 3-unit regional pulses of Af. ambiscia and other organisms operation, similar regional pulses were observed at all (eg., the polychacte Prionospio stecnstrupi and the station except EF, where natural environmental cues amphipods Leptocheirus pinguis and Ampelisca spp.) in wcre apparently overridden by plant discharge effects.
the past have also been substantiated by GN community Therefore, absence of discharge effects (increased data.
water flow and heat) allowed for successful settlement and recruitment of these species in 1998. While these
changes at EF are ecologically significant on a small lived species, sand lance, anchovies and silversides or spatial scale, it is important to note that they are the the species that mature in one year, grubby and cunner.
result of cessation of disturbance to an impacted area Changes would not yet be readily discemible for the 100 m from the MNPS discharge.
longer-lived species maturing at older ages, Atlantic menhaden and tautog. Atlantic silversides taken by Fish Ecology Studies seine in JC, was the only selected species that increased in abundance during this outage period. However, it is difficult to relate this abundance increase to the MNPS Studies of fish assemblages in the vicinity of MNPS utage as silverside entrainment is very low and with were conducted to determine the effects of station nly a 0.80C water temperature increase occurring at the operation. These etfects have been dermed as station-JC seine site as a result of the MNPS discharge, thermal related changes in the occurrence, distnbution, and
'*8 "## "I' "I 'Y abundance of fishes which can alter commumty structure.
Potential effects include entrainment of early life history
\\Vinter Flounder Studies stages through the cooling-w ater system; impingement of juvenile and adult fish on the intake screens, which has been mitigated by the installation of fish retum The local Niantic River population of winter flounder sluiceways at Units 1 and 3; and changes in distnbution in (l'seudopleuronectes americanus) is potentially affected Jordan Cove as a result of the thermal discharge. Trawl, by the operation of MNPS, particularly by entrainment seine, and ichthyoplankton monitoring programs were oflarvae through the cooling-water systems of the three established in 1976 to provide the basis for identifying OPeratmg units. As a result, extensive studies of the life taxa potentially affected, as well as information on long-history and population dynamics of this valuable sport term abundance trends used to measure changes in the and commercial species have been undertaken since local populations.
1976.
This report summari/cs data collected m the Monthly mean seawater temperatures recorded at the momtoring programs from June 1997 through May MNPS intakes from January through May 1998 were 1998 (report year 1997-98) and in special tautog studies above average, particularly evident during February, conducted in June and July 1998. All MNPS umts were April, and May.
Summer temperatures were m an extended outage during this report period. Umts I approximately average and fall temperatures were and 2 have not operated since November 4,1995 and greater than the long-term 22-year mean.
February 20,1996, respectively. Unit 3 shut down on The A-mean trawl catch-per-unit-effort (CPUE) of March 30,1996 and resumed operation on July 5,1998.
fish larger than 15 cm during the adult winter flounder l
Durmg the shutdown period, no thermal discharge spawning season was 2.1, the second lowest of the series.
Larger females have made up a greater occurred and condenser cooling-water flow was mimmal compared to previous years of operation. The proportion of the spawning stock in recent years despite potential effects of MNPS, including this period of relatively large year-classes produced in 1988, 1992, reduced coolmg-water flow and no thermai plume, are and 1994, as winter flounder 20 to 30 cm in length were assessed below for cach selected fish taxon.
not common in survey catches. The Jolly stochastic Detailed analyses were conducted on seven taxa that model was applied to mark and recapture data to were most susceptible to MNPS operational impact due estimate the absolute abundance of the adult spawning to entrainment or effects of the thermal discharge.
population. The abundance estirnate for 1997 was Analyses of selected species generally focused on 6,829 winter flounder larger than 20 cm, which was comparmg temporal trends over the past two decades.
considerably less than estimated population sizes during Atlantic menhaden larvae had a significantly increasing 1984-91 that ranged between 33 and 80 thousand. One-trend in abundance during this time period. An increase third to almost two-thirds of the winter flounder found in Atlantic silverside taken by seine in JC occurred this in the Niantic River during the spawning period each year. Deciming abundance trends of larval American year were mature females. Female spawner abundance sand lance and juvenile and adult tautog and cunner estimates ranged from 2,349 (1996) to 68,210 (1982),
were probably related to regional declines, likely with corresponding total egg production from about 2.0 resulting from increased predation of sand lance and to 39.5 billion each year, overfishing in the case of tautog. Early life history The low abundance of newly-hatched larvae in stages of both tautog and cunner appear to be affected Niantic Bay compared to the Niantic River suggested similarly by environmental and biological processes, that most local spawning occurred within the river.
which seemed to have greater influence than MNPS Also, abundance indices of Stage i larvac in the river operation.
had been significantly conclated with independent The potential effects of MNPS, during this period of estimates of female spawner egg production through reduced coohng-w ater flow and no thermal plume, were 1994. Ilowever, in recent years when egg production assessed for the seven selected fish taxa. Outage has been the lowest, Stage I abundance was greater effects, if any, were expected to be evident for the short.
than expected, with apparent egg survival more than
four times greater than in previous years. This higher winter flounder population dynamics for impact egg survival could be a potentially important assessment. The value of no (i.e., for the unfished I
compensatory mechanism. Abundances of all stages of stock) in biomass units was estimated as 5.20. The larvae in the Niantic River and Bay during 1998 were estimate of b (the second SRR parameter), which about average for the 16-year time-series. Smaller size-describes the annual rate of compensatory mortality as a classes of larvae were dominant in the river and larger function of stock size, has shown little annual variation size-classes were more prevalent m the bay. Since since 1988. The third parameter in the SRR described a 1976, annual larval abundances in Niantic Bay appeared negative relationship between winter Counder recruit-to reDect region-wi6 trends, as they were highly ment and water temperatures in February, a month when correlated with abundance indices for Mount ilope Bay, considerable spawning, egg incubation, and hatching MA and RI.
occurs. Means of the latter two values were used in Larval growth and development were positively modeling.
correlated with water temperature, but other factors, The number of larvae entrained through the including density and prey abundance, also hkely condenser cooling-water system at MNPS is the most affected growth. Growth and development in 1998 direct measure of potential impact on v"nter flounder, were about average despite the warmer spring water Annual estimates of entrainment were related to both temperatures. Estimated mortality of larvae in the larval densities in Niantic Bay and plant operation. The Niantic River for 1984-98 ranged between 82 to 98%,
entrainment estimate in 1998 was about 8% thubcn with the value for 1998 about mid-range in rank, larvae, the fourth lowest since three-unit operation Density-dependence was examined by comparing began in 1986. His estimate was higher than expected mortahty and egg production estimates (a measure of as no units operated during the larval winter Counder early stage larval abundance) at various monthly and season and cooling-water volume was the second lowest seasonal water temperatures. Results of this analysis in 23 years; the estimate was a result of the high suggested that larval mortality decreased as egg densities of larvae present. As in previous years, Stage production decreased and April water temperatures 3 larvae predominated in entrainment collections.
increased.
The impact of larval entrainment on the Niantic River Despite relatively high larval production in 1998, stock depends upon the fraction of the winter flounder densities of newly metamorphosed demersal young production entrained each year. Empirical mass-balance were moderate. The seasonal 1998 median beam trawl calculations for 1984-98 showed that a large number of '
CPUE was about average for the data series since 1984.
entrained larvae come from areas of Long Island Sound The 1998 A-mean CPUE calculated for young winter other than the Niantic River, with an estimated 12 to Counder taken during the late fall and early winter at the 59% of entrained larvae originating from the Niantic trawl monitoring program stations was the smallest of River. The percentage of the total river production the 22-year time-senes. These annual trawl monitoring (calculated as equivalent eggs) entrained annually CPUEs were significantly correlated wi:h those of ranged between about 5 and 46% The value was-young fish taken in the Niantic River during the 21.2% in 1998 and the geometric mean was 12.6%.
j summer. These indices indicated that the 1988, 1992, A stochastic computer simulation model (SPDM) was and 1994 year-classes were relatively abundant, w hereas used for long-term assessments of MNPS impact over a the 1993 year-class was weak. Few juveniles, however, 100-year period (1960-2060). The winter flounder have been taken within the Niantic River during the stock simulated was female spawner biomass (ibs),
adult spawning population surveys in recent years.
which is more directly related to reproductive potential Young-of-the-year abundance indices were either not than numbers of fish. Conditional mortality rates significantly correlated or were negatively correlated corresponding to larval entrainment from mass-balance with their own abundance 3 to 5 years later as female calculations and juvenile and adult impingement at adult spawners.
However, the form of these MNPS were simulated according to historical relationships was unclear and they may be statistical information and projections; natural (M) and fishing artifacts. None of the early hfe stages was considered to mortality rates (F) were provided by CT DEP. For be a reliable index of potential future year-class simulation purposes, F was initially set at 0.40 in 1960
- strength, and reached a maximum of 1.33 in 1990. In this report, Egg production estimates from annual spawning the estimate of M was reduced to 0.2 at the suggestion surveys were scaled to numbers of spawnmg females of DEP Marine Fisheries staff, who also suggested und used as recruitment indices. These indices, together future model projections (i.e., for 1999 and beyond) be with adult female spawning stock estimates and mean made using three values of F that corresponded to annual February water temperatures, were the data to specific management levels. These were the fishing rate which a three parameter Ricker stock-recruitment to preserve 30% of the maximum spawning potential relationship (SRR) was fit. Additionally, an indirect (MSP; F30 = 0.3), the rate for the maximum sustainabic estimate of the winter Counder theoretical rate of yield to the fisheries (FMSY = 0.6), and the current increase (the SRR a parameter) was used for modeling estimated fishing mortality rate (Fcurrent = 0.8).
In the SPDM simulation, an initial stock size of To date, despite efforts of regulatory agencies to 114,732 lbs was used to represent the theoretical (no control fishing morrality, the Niantic River winter fishmg effects) MSP of the Niantic River female flounder r.ca nas not shown any evidence for a spawning stock. When fishing was added, the annual rebound in abundance. A lack of population build-up projections of the initially unfished stock become the has also been noted for other winter flounder stocks baseline time-series of annual spawning biomass in the throughout most of Southern New England. However, absence of any plant impact. Under the exploitation the local population has remained resilient and very rates simulated, the stochastic mean stock size of the small adult spawning stocks in recent years have baseline declined to 51,273 lbs by 1970 and to its produced relatively large numbers of larvae or young lowest point of 12,091 lbs in 1995. The latter value fish, which are likely the results of population was less than one-half of 25% of MSP (30,041 lbs, compensatory mechanisms. The announced retirement defined by the Atlantic States Marine Fisheries of Unit l will result in an immediate reduction of more Commission as a critical stock size). Similarly, the than 20% of the MNPS cooling-water flow and will impacted (including effects of MNPS entrainment and lessen future plant impact.
Continued efforts in impingement) stock size was reduced to 9,557 lbs in reducing fishing mortality are also necessary to ensure a 1995. Absolute differences between the baseline and quicker recovery of the Niantic River winter flounder impacted stock sizes reached a maximum of 4,900 lbs in population.
1998, but thereafter the effects of the shutdown of Unit I and decreased fishing rates beginning in 1999 began to take effect and stock sites increased. The strength of the effect varied according to the three rates of fishing used, and stock sizes were obviously ranked higher when lower fishmg rates were used. The simulation with the value of F = 0.3 did not appear to be realistic, because projected stock biomass was even greater than found during the 1960s and 1970s, when fishing rates were low and there were no plant effects. Generally, greater reductions in stock biomass resulted from Gshing than from larval entrainment, because fishing quickly reduces biomass by the selection of larger individuals throughout the lifetime of a year-class, whereas entrainment only occurs once, very early during larval life history. The simulated impacted spawning stocks began to return to baseline levels as operation of Units 2 and 3 ceased, with faster closure occumng at lower Gshing rates. Ultimately, all stocks became virtually identical to their corresponding baselines.
The probabihties that the Niantic River female spawning stock biomass would fall below selected reference sizes (25,30, and 40% of MSP) were deter-mined to help assess the long-term effects of MNPS operation. A stock smaller than 25% of MSP is considered overfished, whereas one that is at 40% of MSP can maximize yield to the fisheries while remaining stable. For both baseline and MNPS-impact simulations, stocks were likely greater than 40% of MSP in 1970. At the lowest point of all stock projections in the mid-1990s, stock projections were quite likely less than 25% of MSP.
Simulated reductions in fishing allowed for a rapid increase in spawner biomass, with the effect again relative to the rate of fishing that was chosen. Probabilities of achieving desirable biomass levels at F - 0.8 were less certain than those for F = 0.6 or 0.3, with only the latter rate assuring high probability of being greater than 40%
of MSP. This, however, may be a difficult management target to achieve.
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ATTACIIMENT 2 to the Millstone Unit 3 Environmental Protection Plan Annual Environmental Protection Plan Operating Report January 1 - December 31,1998
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