Millstone Power Station, Unit 3, 2007 Annual Environmental

4-ADominion®Dominion Nuclear Connecticut, Inc.Millstone Power StationRope Ferry Road, Waterford, CT 06385

APR 2 5 2008U.S. Nuclear Regulatory CommissionAttention: Document Control DeskWashington, DC 20555-0001

Serial No.MPS Lic/GJCDocket Nos.License Nos.

08-0184RO50-423NPF-49

DOMINION NUCLEAR CONNECTICUT. INC.MILLSTONE POWER STATION UNIT 32007 ANNUAL ENVIRONMENTAL PROTECTIONPLAN OPERATING REPORT

In accordance with Section 5.4.1 of the Environmental Protection Plan (EPP), DominionNuclear Connecticut, Inc. hereby submits the Annual Environmental Protection PlanOperating Report (AEPPOR), describing implementation of the EPP for the previousyear. Enclosure 1 transmits information for the period of January 1, 2007 to December31, 2007.

Should you have any questions regarding this report, please contact Mr. William Bartron,at (860) 447-1791, extension 4301.

Sincerely,

J. Al1n PriceSice President - Millstone

zI72~9s

Serial No. 08-01842007 Annual Environmental Protection

Plan Operating ReportPage 2 of 2

Enclosures: 1

Commitments made in this letter: None.

cc: U.S. Nuclear Regulatory CommissionRegion I475 Allendale RoadKing of Prussia, PA 19406-1415

Mr. J. D. HugheyProject ManagerU.S. Nuclear Regulatory CommissionOne White Flint North11555 Rockville PikeMail Stop 8B3Rockville, MD 20852-2738

NRC Senior Resident InspectorMillstone Power Station

Annual Environmental Protection Plan Operating ReportJanuary 1 - December 31, 2007

Millstone Unit 3 Environmental Protection Plan

Dominion Nuclear Connecticut, Inc.Millstone Power Station

Rope Ferry RoadWaterford, Connecticut 06385

April 2008

2007 Arinual Environmental Protection Plan Operating Report (AEPPOR)

1. Introduction

This report covers the period January 1, 2007 through December 31, 2007. During2007, Millstone Power Station Unit 3 (MPS 3) completed refueling outage 3R1 1(04107107-05/19/07). Cycle 11 capacity factor was 98.4%; the current cycle 12(through 12/31/07) capacity factor was 98.5%.

As required by the MPS 3 Environmental Protection Plan (EPP), this AEPPORincludes:* summaries and analyses of the results of environmental protection activities,o a list of EPP noncompliances,

o a list of all changes in station design or operation which involved a potentiallysignificant unreviewed environmental question, and

o a list of non-routine reports, describing events that could have resulted insignificant environmental impact.

2. Environmental Protection Activities

2.1 Annual National Pollutant Discharge Elimination System (NPDES) Report ofEcological Monitoring (EPP Section 4.2)

Paragraph 5 of the Millstone Power Station (MPS) NPDES permit, issued toDominion Nuclear Connecticut, Inc. (DNC), requires continuation of biologicalstudies of supplying and receiving waters, entrainment, and intakeimpingement monitoring. These studies include analyses of intertidal andsubtidal benthic communities, finfish communities, entrained plankton, lobsterpopulations, and winter flounder populations. Paragraph 7 of the permitrequires an annual report of these studies to be sent to the Commissioner ofthe Connecticut Department of Environmental Protection (DEP). The reportthat fulfills these requirements for 2007, Annual Report 2007 - Monitoring theMarine Environment of Long Island Sound at Millstone Power Station,Waterford, Connecticut (Annual Report), presents results from studiesperformed during construction and operation of MPS, emphasizing those ofthe latest sampling year. Changes to the biological communities noted inthese studies are summarized in the Executive Summary section of theAnnual Report, which is attached as part of this report.

2007 AEPPOR Page 1 of 5

2.2 Effluent Water Quality Monitoring

Paragraph 3 of the MPS NPDES permit requires monitoring and recording ofmany water quality parameters at MPS intakes and at multiple monitoringpoints 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 permitrequires a monthly report of this monitoring to the Commissioner of theConnecticut DEP. The report that fulfills these requirements, the MonthlyDischarge Monitoring Report (DMR), includes data from all Millstone units.Consistent with prior annual AEPPOR submissions, water flow, temperature,pH, and chlorine data pertaining to MPS 3 are summarized in Table 1.

Each monthly DMR identifies NPDES permit exceedances (i.e., events wherea parameter value was beyond permitted limits) or exceptions (i.e., eventswhere permit conditions were not met) for the month. There were no NPDESexceedances or exceptions for MPS 3 circulating or service water dischargesreported in 2007.

Other events dealing with NPDES discharges are also included in the DMRsto provide the DEP with additional information. Information pertaining toevents that occurred in 2007 and were reported to the DEP in the monthlyDMRs, while unrelated to MPS 3's cooling water discharge but containingwastewater inputs from MPS 3, are extracted from the July and September2007 DMRs as follows. Both events described below relate to dischargesfrom DSN 006 (MPS 2 & 3 Non-Contaminated Floor Drains):

a) On July 6, 2007 at 1145, for approximately 22 minutes, the Plant ProcessComputer (PPC) data point associated with the inline pH instrumentation forDSN 006 recorded pH measurements greater than DNC's NPDES Permitlimit of 9.0 standard units (su). During the period, the highest pH recorded bythe PPC was 9.7 su. A confirmatory sample performed by chemistrypersonnel on July 6, 2007 at 1200 at DSN 006 observed pH at 9.2 su; thePPC recorded a pH of 9.3 su at the same time. Shortly after these resultswere observed, the major plant process inputs to DSN 006 were sampled andanalyzed: at 1215, the MPS 2 Oil/Water Separator #2 (6.7 su) and GeneralElectric Reverse Osmosis reject water (7.2.su); at 1217, the MPS 3 turbinebuilding sump (6.7 su); and at 1225, the MPS 3 Waste Test Tank berm (7.3su). The chemistry department conducted an ýevent review (including areview of all associated inline instrumentation tracked by the PPC). Giventhe drainage area for DSN 006 encompasses most of the area that surroundsboth MPS 2 and 3, the results were inconclusive regarding the cause of thepH excursion.

The following corrective actions associated with this event have beenimplemented:

pH devices with data loggers were purchased and installed within thethree main tributaries that contribute to DSN 006. Once a tributary is


identified with high pH, portable pH devices will then be used to furtheridentify specific up-stream sources.* The inline sampler at DSN 006 has been pre-programmed to immediatelydraw samples when a pH excursion exists so a larger array of analysescan be performed on the sample to aid in determining the source.Site personnel were reminded of the importance of controlling dischargesto the environment as per site proceduresý.

b) On September 19, 2007 between 1934 and 2136, the Plant ProcessComputer (PPC) data point associated with the inline pH instrumentation forDSN 006 (which samples at 60 second intervals) recorded pH measurementsgreater than DNC's NPDES Permit limit of 9.0 su on 19 occasions. Duringthis period, the highest pH recorded by the PPC was 9.36 su. On September20, 2007, while conducting an event review of this incident, chemistrydepartment personnel noted another increasing trend for DSN 006 pH on thePPC. At 1545, a confirmatory grab sample was obtained at the DSN 006sample point and the resulting pH was 9.47 su. Chemistry and environmentalcompliance personnel proceeded to the vendor makeup water system facilityto analyze this input to the DSN 006 catch basin for pH. The results indicatedthat the reject water was not the source of the elevated pH. At this time, itwas noted that areas adjacent to the catch basin near the vendor makeupwater system facility recently had footings excavated and concrete had beenpoured. Standing water from these evolutions had pooled around the catchbasin. The standing water was analyzed for pH with results of 12.04 and12.09 su, respectively. Indications are that the catch basin was installedwithout a seal between its components. As a result, standing water from thefooting excavation leaked into the DSN 006 drain system, causing the pH atDSN 006 to increase.

By way of corrective action, on September 21, 2007, prior to additionalexcavating, drilling, or pouring of cement, the remaining pooled wateradjacent to the catch basin was transferred to totes for off-site disposal by anauthorized vendor. To prevent further pH excursions resulting from pooledwaters associated with the described construction activity, the use ofadditional precautions (e.g., containing and reusing drilling water) for alldrilling and concrete pours in the area continued until the work wascompleted on September 28, 2007. Subsequently, the catch basin wasresealed to permanently preclude recurrence.

2.3 NPDES Permit Renewal Process

On December 10, 2007, the DEP issued a Tentative Determination to renewthe MPS NPDES permit. At the same time, a draft of the permit was issuedfor public comment.

3. Environmental Protection Plan Noncompliances


No EPP noncompliances were identified for MPS 3 in 2007.

4. Environmentally Significant Changes to Station Design or Operation

No MPS 3 Design Change Records or System Operating Procedure changes metthe criteria for inclusion in this report, i.e.,

* were initiated during the report year, and

* included a determination that a significant unreviewed environmental impactcould occur.

However, on July 13, 2007, DNC submitted a License Amendment Request for aStretch Power Uprate for MPS 3. Attachment 2 of this submittal provided aSupplemental Environmental Report, containing an assessment of potentialenvironmental impacts from the proposed increase in core power level.

5. Non-Routine Reports of Environmentally Significant Events

No MPS 3 events met the criteria for inclusion in this year's report, i.e.,* required the submittal of a Licensee Event Report (LER), and

* involved a situation that could result in a significant environmental impact.

Only two licensee events that constituted reportable occurrences at MPS 3 weresubmitted in 2007; they involved, respectively, the failure of two main steam safetyvalves to lift within the acceptance criteria, and the loss of offsite power caused bythe transmission system operator while defueled. Both were determined not tocause a significant environmental impact.


Table IMPS 3 NPDES Data Summary, Jan.parameters for MPS 3(1).

1 - Dec. 31, 2007 Selected water quality

Jan.

Feb.

Mar.

Apr.

May

June

July

Aug.

Sep.

Oct.

Nov.

Dec.

DischargeFlow(max)

(106 gpd)

1357.0

1357.5

1357.1

1356.5

1356.9

1356.5

1357.1

1358.6

1357.3

1359.6

1356.9

1357.1

DischargePH

Range

7.9-8.1

8.0-8.2

8.1-8.3

6.5-8.4

7.8-8.3

7.9-8.1

7.5-8.2

7.9-8.1

8.0-8.2

8.0-8.2

7.9-8.1

7.9-8.1

DischargeTemp.Range

(OF)

41.3-68.9

51.4-61.2

51.9-62.6

40.6-60.6

43.9-75.5

71.6-84.0

77.3-86.4

83.8-89.5

82.6-88.4

77.1-86.0

67.1-79.8

56.7-74.1

DischargeTemp.(avg),(OF)

61.4

55.0

55.7

47.9

57.2

76.8

82.1

85.8

84.8

81.6

72.4

63.6

AvgAT(OF)

15.8

17.1

16.6

4.3

5.8

15.6

15.5

15.9

15.9

16.2

16.4

17.4

MaxFAC

(ppm)

0.13

0.11

0.09

(2)

0.06

0.11

0.07

0.08

0.08

0.09

0.22

0.14

MaxTRC

(ppm)

<0.03

<0.03

<0.03

<0.03

0.04

0.03

<0.03

0.05

0.03

<0.03

<0.03

<0.03

MaxSWSFAC

(ppm)

0.22

0.21

0.24

0.25

0.22

0.17

0.22

0.20

0.18

0.22

0.18

0.20

Notes:

(1) Parameters are measured at MPS 3 discharge (DSN 001C), except for TRC, which is measured at MPSdischarge (quarry cuts; DSN 001-1), and SWS FAC (service water system; DSN 001C-5).

(2) Due to the refueling outage and reduced circulating water flows at MPS 3, sodium hypochlorite injection

of MPS 3 circulating water system was suspended for April 2007.

Abbreviations Used:Temp. = Water TemperatureAT = Delta-T (difference between discharge and intake water temperature)FAC = Free Available ChlorineTRC = Total Residual ChlorineSWS = Service Water System


Attachment to the2007 Annual Environmental Protection Plan Operating Report

January 1 - December 31, 2007

Executive Summary Section of"Annual Report 2007 - Monitoring the Marine Environment of Long Island Sound

at Millstone Power Station, Waterford, Connecticut"dated April 2008

Executive Summary

Winter Flounder Studies

The local Niantic River winter flounder populationis potentially affected by the operation of MillstonePower Station (MPS) primarily through entrainmentof larvae in the condenser cooling-water systems. Toassess possible effects, the abundance of adultspawners is measured within the Niantic River andlarvae are sampled at the plant discharges and in theNiantic River and Bay during late winter and earlyspring. Settled age-0 juveniles are collected in theriver in summer.

The relative abundance of adult spawners in 2007was 1.7 fish per trawl tow (catch-per-unit-effort;CPUE), which is similar to abundance in 2004 and2005 and higher than in 2006. Over the past decade,abundance of winter flounder spawners has remainedat a relatively low level, with CPUE fluctuatingaround 1-2 fish per tow. Winter flounder abundancein the Niantic River has been similar to levels foundthroughout Long Island Sound (LIS) by theConnecticut Department of Environmental Protection.Absolute abundance of the 2006 spawning popula-tion (the latest year for which an estimate could bemade) was about 11,500 fish, which was the largestvalue since 1999. However, this estimate isimprecise and had a large 95% confidence interval of0-41 thousand. Using another methodology, femalespawner abundance in 2007 was estimated at 2.1thousand. Other annual estimates ranged fromapproximately 1.6 thousand females in 2006 to 75thousand in 1982 and corresponding total eggproduction estimates were 1.1 to 44.8 billion. Duringthe past 26 years, Niantic River winter flounder abun-dance represented an estimated 0.4 to 3.3% of theentire LIS winter flounder resource.

In 2007, overall density of Stage 1 (newly hatched)larvae in the Niantic River fell into the lower one-third of the time-series of values since 1983. Incontrast, similar to the estimate in 2006, Stage 1abundance reached a record high in Niantic Bay.Since 1995, more Stage I larvae were found thanexpected from low adult spawner abundance,suggesting a density-dependent compensatory mech-anism during the egg stage enhancing their survival.This has been attributed to reduced predation on eggsby sevenspine bay shrimp, such that when eggdensities are low, higher egg survival produces moreStage 1 larvae. Density-dependent mortality is alsopresent throughout the larval period of life, as an

analysis suggested that mortality decreases withdecreasing egg production (a measure of early larvalabundance), which is further moderated by warmerspring water temperatures allowing for faster larvaldevelopment. This year, Stage 4 (pre-metamor-phosis) larvae in the Niantic River and Bay wererelatively abundant, ranking among the top five of allyears.

With the exception of a few years, densities of age-0 young in the Niantic River following larval meta-morphosis and settlement were linearly related toStage 4 larval abundance. However, at higher larvalabundance juvenile densities apparently reached anasymptote of about 250 young per 100 m2 of bottom,which could represent the carrying capacity of theriver habitat. Initial settled juvenile abundance wasrelatively modest this year, but despite a below-average mortality rate, late summer abundance fellinto the lower one-third of values since 1983.Abundance indices of age-0 fish were either notsignificantly correlated or were negatively correlatedwith the abundance of female adult spawners 3 to 5years later. Conversely, positive correlations werefound between age-i abundance indices and theseolder fish. However, there was much scatter in theserelationships and none of the early life stages wereconsidered to be reliable predictors of potential futureyear-class strength.

The number of larvae entrained is a measure ofpotential impact to winter flounder. In most years,Stage 3 larvae predominated in entrainment collec-tions. Annual estimates of entrainment are related toboth larval densities in Niantic Bay and MPSoperation. The 2007 entrainment estimate of about145 million reflected relatively, moderate larvaldensities and lowest cooling-water volume at Units 2and 3 since 1999. The low cooling-water usage thisyear and the 1996 retirement of Unit 1 reducedpotential MPS entrainment by an estimated 144million larvae.

Annual entrainment density (abundance indexdivided by total seawater volume) has varied withouttrend since 1976, indicating that larval productionand availability in Niantic Bay remained relativelystable despite increased water use during the 1986-95period of three-unit operation and reduced cooling-water demand in 1995-97. Correlations betweenentrainment estimates and abundance indices of post-entrainment age-0 juveniles were positive. Thisimplies no entrainment effect as the more larvae that

Executive Summary v

ii

were available to be entrained, the more larvae thatmetamorphosed and settled in Niantic River and Bay.This was also demonstrated by a comparison ofannual entrainment and juvenile year-class abun-dance, which suggested that entrainment estimateswere simply a measure of emerging year-classstrength. Thus, entrainment is not the most importantfactor in determining juvenile abundance.

The potential impact of larval entrainment on theNiantic River stock depends upon the fraction of theannual winter flounder reproduction entrained eachyear (termed production lo ss in this report), whichwas calculated as equivalent eggs removed byentrainment. Empirical mass-balance model calcu-lations showed that a large number of entrainedlarvae came from a number of sources in LIS besidesthe Niantic River. Based on the increase in eggsurvival noted in recent years, a factor that was notoriginally incorporated into the mass-balance model,most production loss estimates after 1994 areconservatively high. Correcting the estimates madesince 1995 by using a higher egg survival rateresulted in lower production loss estimates (revisedlong-term mean = 11.6%).

The small adult spawning stock in the rivercontinues to produce relatively large numbers oflarvae and young fish, which likely resulted frompopulation compensatory mechanisms. Despite rela-tively good abundance of age-0 winter flounder (a lifestage not entrained) in many recent years, significantrecruitment to the adult spawning population has notoccurred. Processes that are unrelated to MPSoperation and which occur after juvenile winterflounder leave shallow nursery waters during the fallof their first year of life seem to be operating toproduce fewer adults. A bottleneck, probably frompredation, appears to be occurring during the latejuvenile life stage (ages-I and 2). Environmentaleffects, including changes to the Niantic River habitat(e.g., increased eelgrass abundance), a warming watertemperature trend, and interactions with other species(e.g., predation), especially during early life history,are also important processes affecting winter flounderpopulation dynamics.

Fish Ecology Studies

Monitoring during 2007 indicated that no long-termabundance trends in various life stages of sevenselected taxa could be directly related to the operationof MPS. No significant long-term trends weredetected in populations of American sand lancelarvae collected in entrainment samples and juvenileor adult silversides collected by trawl or seine.

Similarly, no long-term trends were identified invarious life stages of grubby. Atlantic menhadenlarvae showed a significantly increasing trend inabundance, as did juveniles taken by seine and trawl.Densities of both anchovy eggs and larvae during2007 continued to show significant negative trends.The bay anchovy has experienced a regional declinein abundance. This species is important forage forpredatory fishes and birds. In particular, the stripedbass has recently increased in abundance along theAtlantic coast and may have contributed to reducednumbers of bay anchovy.

Data collected during 2007 continued to show nolong-term abundance trends in the numbers ofentrained cunner and tautog eggs and larvae.Juvenile and adult cunner and tautog havesignificantly decreased at the Intake trawl station, butthe decline was attributed to the 1983 removal of theUnit 3 intake cofferdam, a preferred habitat for thesespecies. Since that time, no significant abundancetrend was found from 1984 through 2007. Cunnerabundance significantly increased at the NianticRiver trawl station and continued to fluctuate withouttrend at Jordan Cove. The combined catches ofjuvenile and adult tautog collected at the three trawlstations increased, probably as a result of morerestrictive fishing regulations. Significant increasesin tautog abundance were found in Niantic Rivertrawl catches and in both Jordan Cove trawl andlobster pot catches.

Changes in the species composition and temporaland spatial abundance of fishes and shellfishescollected by trawl over the past 31 years appeared tobe unrelated to MPS operation. Shifts in thedominance of individual taxa were attributed tochanges in habitat, range extensions or contractions,and warmer ambient seawater temperatures occurringover the past 3 decades.

Cooling-water use at MPS was reduced 23% fromthe shutdown of Unit 1 in 1995, resulting in lessentrainment and impingement. Fish return systems atUnits 2 (2000) and 3 (1986) further reduce,impingement mortality at MPS. Based on the lack ofdecreasing trends for selected taxa except anchovies,for which there are other causes, MPS has hadminimal effect on local fish and shellfishassemblages.

Lobster Studies

Impacts associated with recent MPS operations onthe local lobster population were assessed bycomparing results of the 2007 study to data collectedfrom 1978 through 2006. Emphasis has been placed on

vi Monitoring Studies, 2007

'~ n:4~i

assessing long-term trends in the abundance andpopulation characteristics of lobsters collected in theMillstone Point area.

Throughout LIS, the lobster population was stable orincreasing from 1978 through 1999. The abundance oflobsters in LIS was lower from 2000 to 2007, butunrelated to MPS operations. Rather, the lobsterabundance declines were attributed to a significantmortality event in western LIS and to an outbreak ofshell disease affecting lobster populations from easternLIS to the Gulf of Maine. In the MPS area, nosignificant long-term trends were identified in theannual CPUE of lobsters (combined over all sizes andstations) collected either in pots or by trawl. The totalpot-CPUE of lobsters at the three monitoring stationshas varied without trend since 1978. However, annualCPUE of legal-size lobster has exhibited a significantdeclining trend at the Jordan Cove and Twotreestations, but not at the Intake station located nearbyMPS. Significant declines in the abundance of legal-size lobsters were due in part to shell disease and to a 3mm increase in the minimum legal size since 1978. Ofnote, the abundance of legal-size lobsters harvested bycommercial fishers in our area increased over the pastfew years, although lobster catches remained depressedin other areas of LIS.

Long-term trends observed in lobster populationcharacteristics over the past 30 years (growth, femalematurity and egg-bearing lobsters), were related towarmer ambient seawater temperature and/or therecent outbreak of shell disease, and not MPSoperation. Increased ambient water temperature maybe responsible for the increased susceptibility andtransmission of diseases affecting lobsters in LIS,which are near their southern range of distribution innearshore waters.

The number of lobster larvae entrained through theMPS cooling water systems was highly variable andhas not resulted in a decrease in local lobsterabundance. Impacts associated with entrainment andimpingement of lobsters at MPS have been greatlyreduced by the shutdown of Unit 1, which eliminated23% of the cooling water used, and the installation ofaquatic organism return systems at Units 2 and 3,which return impinged lobsters to Niantic Bay.

Rocky Intertidal Studies

Rocky intertidal monitoring studies during 2007continued to document ecological changes to theshore community near to, and associated with, theMPS thermal discharge. These changes are notwidespread, and remain restricted to approximately

150 m of shore-line on the east -side of the powerplant discharge to LIS.

Seasonal shifts in occurrence of annual algalspecies were noted at Fox .Island-Exposed (FE)during 2007. These shifts included abbreviatedseason for cold-water species (e.g., Monostromagrevillei, Spongomorpha arcta, and Dumontiacontorta) ,Yand extended season for warm-waterspecies (e.g., Grinnellia americana, Dasyabaillouviana, and Bryopsis hypnoides). Similar shiftshave been observed in most years since Unit 3 beganoperation (1986), with the exception of the extendedshutdown of all MPS reactors from March 1996 toJune 1998 when seasonality of these species at FEduring the recent' shutdown period was more typicalof other sites.

Thermal effects on dominant species abundance anddistribution patterns were also evident at FE in 2007and most apparent in the low intertidal zone.Seasonally high abundance of Hypnea musciformis, aspecies observed for the first time in 2001, andexpanded populations of Sargassum filipendula,Corallina officinalis, and Gelidium pusillum nowcharacterize the lower shore community at FE.Polysiphonia spp. maintained a perennial populationat FE in 2007, but occurred mainly as a summerannual at sites unaffected by MPS.

Ascophyllum nodosum growth during 2006-07continued to exhibit no clear relationships among ourmonitoring stations, nor correlation with plantoperating conditions, indicating that the thermal plumefrom MPS had little effect on local populations.Natural influences of other factors such as ambienttemperature conditions, storms and wave action,nutrients and light play the dominant role indetermining Ascophyllum growing conditions in theMillstone area.

The rocky intertidal monitoring program has alsodocumented regional patterns and modifications toshore communities unrelated to MPS operation.These include the introduction to the region of twoexotic red algae, Antithamnion pectinatum in 1986and Grateloupia turuturu in 2004, decreases inbarnacle abundance in recent years, and a long-termincrease in abundance of the common brownrockweed, Fucus vesiculosus. One phenomenonobserved in 2007 was the deposition of a largequantity of sand onto low intertidal areas of WhitePoint, resulting from spring storms, temporarilyburying algae and rock surfaces. The effect wastemporary, however, as subsequent redistribution ofthe sand permitted the more typical community to re-emerge.

Executive Summary vii

Eelgrass

Eelgrass (Zostera marina L.) population dynamicswere monitored during summer from 1985 to 2007 atthree locations near MPS. although some lofig-termdeclines in one or more eelgrass populationparameters (e.g., shoot density, shoot length, andstanding stock biomass) were observed at all threeareas monitored over the entire 22-year study period,monitoring results from 2007 indicate populationimprovement at all sites, continuing trends observedover the last 3 or more years. Eelgrass populations attwo monitoring sites to the east of MPS, near thefringes of the thermal plume (<1.5 km from the MPSdischarge to LIS), exhibited gradual declines since1985. These declines were not associated with MPSoperation, as thermal input from the cooling waterdischarge to these sites is at most minimal (<ICabove ambient conditions).

By comparison, heavy, often sudden, eelgrasslosses were documented on five separate occasionsprior to 2000 in the Niantic River. This estuary islocated well beyond (>2 km) waters influenced by theMPS thermal discharge. Since 2001, eelgrassdistribution in the Niantic River has expanded, andgradual, steady increases in shoot density, shootlength, and biomass were observed through 2007. Inprevious years, three short-term declines in eelgrassabundance have been directly associated with foulingand overgrowth of eelgrass; once by blue mussels(Mytilus edulis) at the Niantic River in 1992, andtwice by blooms of green algae (Cladophora spp.) atWhite Point in 1991 and 2004. Recent researchsuggests nutrient loading from land-based sources asthe cause of eelgrass disappearance in LIS to the westand elsewhere. Excess nutrients, coupled withincreases in regional water temperature and waterfowlgrazing, may factor strongly in declines ofpopulations near MPS. Eelgrass distribution onceextended over the entire Connecticut coastline, buthas constricted from west to east such thatpopulations around Millstone Point now represent thewestern range limit of eelgrass in LIS.

Benthic Infauna

Benthic infaunal monitoring during 2007 documentedsmall changes to sediment composition at the Effluent(EF) and Intake (IN) stations in the vicinity of MPS. Ingeneral, sediments at these stations were coarser (largermean grain size) and the silt/clay fraction was smaller.The sediments at EF and IN will continue to beaffected by the discharge of cooling water (EF) and theintake of cooling water (IN). Mean grain size and

silt/clay estimates at Jordan Cove (JC) have remainedrelatively consistent since the changes observed in1986, and sedimentary parameters at the referencestation Giants Neck (GN) were within the limits ofprevious observations and continue to exhibitvariability unrelated to MPS. Community abundanceand numbers of species at all sampling stations in 2007increased from the low values observed in 2006.Surface deposit-feeding oligochaetes and polychaeteswere the dominant organisms at all stations in 2007.Observed changes in abundance of infaunal taxaresulted in rank order changes among the dominanttaxa at all stations but overall, benthic communitiessampled in 2007 were comprised of fauna that hadbeen present in previous years. Multivariate analysesshowed higher community similarity among recentyears and changes in community composition from thesamples before the disturbances at IN and JC. Changesin community similarity from early sampling years tomore recent years were also observed at EF that iscontinuously affected by discharge of station coolingwater. The reference station GN where the effects ofMPS are not present has also exhibited temporalchanges in benthic community from earlier to morerecent years. Temporal and spatial variation in theMPS benthic communities observed 2007 are typical ofnear-shore marine environments. During 2007, therewere no unusual events that impacted benthic infaunalcommunities. Under current environmental conditionsthe infaunal communities appear relatively stable.

viii Monitoring Studies, 2007

Documents

Millstone Power Station, Unit 3, 2007 Annual Environmental