ML101310232

2009 Annual Environmental Protection Plan Operating Report

ML101310232
Person / Time
Site:	Millstone
Issue date:	04/27/2010
From:	Macmanus R Dominion, Dominion Nuclear Connecticut
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
10-195, FOIA/PA-2011-0115
Download: ML101310232 (13)

Text

Dominion Nuclear Connecticut, Inc.

Millstone Power Station S1Dominion Rope Ferry Road Waterford, CT 06385 APR 2 ' 2.010 U.S. Nuclear Regulatory Commission Serial No.10-195 Attention: Document Control Desk MPS Lic/GJC R0 Washington, DC 20555-0001 Docket Nos. 50-423 License Nos. NPF-49 DOMINION NUCLEAR CONNECTICUT. INC.

MILLSTONE ;POWER STATION UNIT 3 2009 ANNUAL ENVIRONMENTAL PROTECTION PLAN OPERATING REPORT In accordance with Section 5.41 'of the Environmental Protection Plan (EPP), Appendix B to the Millstone Power.Station Unit 3 Operating License, Dominion Nuclear Connecticut, Inc. hereby submits-the Annual:Environmental Protection. Plan Operating Report (AEPPOR), describing implementation of the EPP for the previous year. transmits information for the period of January 1, 2009 to December 31, 2009.

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

Sincerely, R. K. MacManus Director, Nuclear Station Safety and Licensing

Serial No.10-195 2009 Annual Environmental Protection Plan Operating 'Report Page 2 of 2

Enclosures:

1 Commitments made in this letter: None.

cc: U.S. Nuclear Regulatory Commission Region I 475 Allendale Road King of Prussia, PA 19406-1415 Ms. C. J. Sanders NRC Project Manager U.S. Nuclear Regulatory Commission One White Flint North, Mail Stop 8B3 11555 Rockville Pike Rockville, MD 20852-2738 NRC Senior Resident Inspector Millstone Power Station

Serial No.10-194 Docket Nos. 50-245 50-336 50-423 License Nos. DPR-21 DPR-65 NPF-49 ATTACHMENT 1 2009 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT.

MILLSTONE POWER STATION UNITS 1, 2, AND 3 DOMINION NUCLEAR CONNECTICUT, INC. (DNC)

Annual Environmental Protection Plan Operating Report January I - December 31, 2009 Millstone Power Station Unit 3 Environmental Protection Plan Dominion Nuclear Connecticut, Inc.

Millstone Power Station Rope Ferry Road Waterford, Connecticut 06385 April 2010

.2009 Annual Environmental Protection Plan Operating Report (AEPPOR) 1.

Introduction:

This report covers the period January 1, 2009 through December 31, 2009. During 2009, Millstone Power Station Unit 3 (MPS3) operated at a capacity factor of 97.6%;

the current cycle 13 (from'the end of the latest refueling outage (11/24/08) through 12/31/09) capacity factor was 98.5%.

As required by the MPS3 Environmental Protection Plan (EPP), Appendix B to the Millstone Power Station Unit 3 Operating License, this AEPPOR includes:

• summaries and analyses of the results of environmental protection activities,

-a list of EPP noncompliances,

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

• a list of non-routine reports, describing events which could have resulted 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 Millstone Power Station (MPS) NPDES permit, issued to Dominion Nuclear Connecticut, Inc. (DNC), requires continuation of biological

.studies of supplying and receiving waters, entrainment, 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 7 of the NPDES permit requires an annual report of these studies to be sent to the Commissioner of the Connecticut Department of Environmental Protection (DEP). The report which fulfills these requirements for 2009, "Annual Report 2009 - Monitoring the Marine Environment of Long Island Sound at Millstone Power Station,

.Waterford, Connecticut" (Annual Report), presents results from studies performed during construction and operation of MPS, emphasizing those of the latest sampling year. Changes to the biological communities noted in these studies are summarized in the Executive Summary section of the Annual Report, submitted in April 2010, which is attached as part of this report.

2.2 Effluent Water Quality Monitoring:

Paragraph 3 of the MPS NPDES permit requires monitoring and recording of various water quality parameters at MPS intakes and at multiple 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 NPDES permit requires a monthly report of this monitoring to the Commissioner of the Connecticut DEP. The report which fulfills these requirements, the "Monthly Discharge Monitoring Report" (DMR), includes data from all MPS units.

Consistent with prior annual AEPPOR submissions, water flow, temperature, pH, and chlorine data pertaining to MPS3 are summarized in Table 1.

2009 AEPPOR Page 1 of 4

Each monthly DMR identifies NPDES permit exceedances (i.e., events where a parameter value was beyond permitted limits) or exceptions (i.e., events where NPDES permit conditions were not met) for the month. There were no NPDES exceedances or exceptionsfor MPS3 circulating or service water discharges reported in 2009.

Information pertaining to events which occurred in 2009 and were reported to the DEP in the monthly DMRs, while unrelated to MPS3's cooling water

'discharge but containing wastewater inputs from MPS3, are summarized from the February and March 2009 DMRs as follows. Both events described below relate to discharges from discharge serial number (DSN) 006 (MPS2 & MPS3 non-contaminated floor drains):

a) On February 4, 2009 at 1119, during fire water sprinkler header flow testing in the"MPS3 turbine building (TB), a sprinkler head was found to be spraying water in the east side of the TB. Operations personnel isolated and drained-the firewater system to the TB floor drains. As part of the response to the sprinkler head leak, chemistry personnel performed total residual chlorine (TRC) sampling of the TB sump (drains to DSN 006) to ensure compliance with the Permit. Results of the sump were < 0.03 mg/L TRC.

Later that day, at 1907 through 2042, the inline pH instrumentation associated with the plant process computer (PPC) and the environmental data acquisition network (EDAN) recorded DSN 006 discharge pH results greater than the Permit limit of 9.0 standard units (su). At 1910, MPS3 chemistry personnel performed confirmatory grab sampling for discharge pH at DSN 006. The result of confirmatory sampling was 9.51 su. The MPS3 TB sump was immediately isolated from discharging to DSN 006. The MPS3 condenser pit and TB sump pits were analyzed and pH was determined. to be 9.5 su and 10.0 su, respectively. To maintain the level in the TB sump, the MPS3 operations department aligned the sump to the MPS3 liquid radioactive waste system for processing as authorized by the NPDES Permit CT0003263. Additionally, some of the contents of the TB sump were pumped to totes for future disposition.

As part of the initial corrective actions and investigation, the MPS2 chemistry department was contacted to perform confirmatory sampling of the MPS2 east and west TB sumps (both drain to DSN 006 via an inline granular activated carbon filter and oil water separator). The results of the sampling at 2050 were 7.70 su and 9.12 su, respectively, and are based on incidental leakage of MPS2 secondary side and closed cooling water systems, along with groundwater in-leakage. The General Electric (GE) makeup water facility discharge (drains to DSN 006) was verified to be operating within limits.

After verifying all inputs to DSN 006 to be within NPDES Permit limits, on February 5, 2009 at 1815, the TB sump was aligned to DSN 006.

2009 AEPPOR Page 2 of 4

I¸I$

b) On March 16, 2009 at 1315, draining the "A" MPS3 generator step-up (GSU) transformer pit was initiated for the first time to discharge accumulated rain water and/or snow melt. MPS had received authorization from the DEP on September 25, 2008 to tie the three MPS3 GSU transformer pits into the existing yard drain system via the oil water separator associated with the MPS2 GSU transformers, which ultimately drains to DSN 006. The steps for performing this draining evolution were incorporated into the appropriate MPS3 operations department procedure.

While draining the "A" pit, the continuous inline pH monitor at DSN 006 started rapidly increasing from a pH of 7.09 su to a peak pH of 9.66 su at 1352. At 1331, draining of the "A" GSU. pit was halted. At 1343, a confirmatory grab sample at DSN 006 was 9.95 su. An additional confirmatory pH analysis was performed on the "A" pit contents at 1400.

The resulting pH was 10.35 su. At approximately 1428, with the "A" GSU transformer pit discharge isolated, the inline pH at DSN 006 trended below 9.0 su. As corrective actions, all valves associated with the three MPS3 GSU transformer pits were safety tagged closed and all water located in the three MPS3 GSU transformer pits was pumped to tanker trucks-for offsite disposal as Connecticut regulated waste.

2.3 NPDES Permit Renewal Process:

The MPS NPDES permit renewal process is continuing. Significant events during 2009 included 18 days of testimony during the evidentiary hearing held in January and February, and the post-hearing briefs and memoranda submitted in May.

3. Environmental Protection Plan (EPP) Noncompliances:

No EPP noncompliances were identified for MPS3 in 2009.

4. Environmentally Significant Changes to Station Design or Operation:

No MPS3 design change records or system operating procedure changes met the criteria for inclusion in this report, i.e.,

" were initiated during the report year, and

• included a determination that a significant unreviewed environmental impact could occur.

Environmental reviews performed in 2009 included assessment of the variable frequency drives (VFDs) for MPS3 circulating water pumps; installation and operation of these VFDs will be in accordance with all appropriate permits.

5. Non-Routine Reports of Environmentally Significant Events:

No MPS3 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 a reportable event at MPS3 occurred in 2009; one involved a security issue, and the other involved the MPS3 reactor trip on December 19. Both events were determined not to cause a significant environmental impact.

2009 AEPPOR Page 3 of 4

Table I MPS3 NPDES Data Summary, Jan. 1 - Dec. 31, 2009. Selected water quality parameters for MPS3(1 ).

Discharge Discharge Discharge Discharge Avg Max Max Max Flow -PH Temp. Temp. AT FAC TRC SWS (max) 'Range Range (avg) (OF) (ppm) (ppm) FAC (106 gpd) (OF) (OF) (ppm)

Jan. 1357.0 7.9-8.1 55.3-63.4 58.5 19.0 0.15 < 0.03 0.23 Feb. 1356.6 7.9-8.1 54.0-61.5 57.3 18.9 0.14 < 0.03 0.19 Mar. 1357.4 7.9-8.2 53.6-62.9 58.3 18.3 0.10 < 0.03 0.19 Apr. 1356.8 7.9-8.1 58.8-69.0 63.6 18.2 0.13 0.04 0.20 May 1357.5 7.9-8.1 66.5-77.1 70.4 17.9 0.17 0.04 0.17 June 1357.3 7.8-8.1 71.7-83.8 76.6 16.9 0.12 0.03 0.17 July 1357.2 7.9-8.1 79.5-89.1 83.1 17.2 0.06 0.04 0.22 Aug. 1357.1 8.0-8.2 84.2-94.4 87.6 17.9 0.07 0.04 0.17 Sep. 1357.4 8.0-8.2 83.9-88.3 86.0 18.1 0.10 0.04 0.19 Oct. 1356.9 7.9-8.1 72.4-85.4 78.9 18.3 0.10 0.03 0.17 Nov. 1357.0 7.7-8.0 69.2-80.3 73.8 19.3 0.13 < 0.03 0.19 Dec. 1356.8 7.9-8.0 40.1-77.1 58.7 12.7 0.14 < 0.03 0.20 Notes:

(1) Parameters are measured at MPS3 discharge (DSN 001C), except for TRC, which is measured at MPS discharge (quarry cuts; DSN 001-1), and SWS FAC (service water system; DSN 001C-5).

Abbreviations Used:

Temp. = Water Temperature AT = Delta-T (difference between discharge and intake water temperature)

FAC = Free Available Chlorine TRC = Total Residual Chlorine SWS = Service Water System 2009 AEPPOR Page 4 of 4

Attachment to the 2009 Annual Environmental Protection Plan Operating Report January 1 - December 31, 2009 Executive Summary Section-of "Annual Report 2009 - Monitoring the Marine Environment of Long Island Sound

.at Millstone Power Station, Waterford, Connecticut" dated April 2010

Executive Summary Winter Flounder Studies larval abundance were low as were the numbers of metamorphosing larvae. However, relative to the Various life history stages of winter flounder have 'Niantic River, 'larval abundance in Niantic Bay has been monitored since 1976 as the local Niantic River increased 'in recent years, suggesting higher

,population may be affected by the operation' of ' .production in LIS rather than in estuaries such as the Millstone Power Station (MPS), particularly through Niantic River.

the entrainment of larvae. During the past 28 years, Densities of age-0 young. in the Niantic River annual Niantic River adult winter flounder abundance .following larval metamorphosis and settlement were represented an estimated 0.4 to 3.3% of the total LIS *'linearly related to Stage 4 larval abundance at low to winter flounder resource (mean = .1.34%). Over the moderate levels. However, at higher larval abun-past 15 years, low abundance levels have been found- dance juvenile densities apparently reached an throughout Long Island Sound (LIS) by the -asymptote of about 250 young per 100 m 2 of bottom,

'Connecticut Department of Environmental Protection which could represent the carrying capacity of the (CTDEP). During the same'time' period, adult winter' river habitat. As expected from low larval abundance flounder abundance -in the Niantic River has in 2009, initial settled juvenile abundance was very S.remained low. Reflecting these trends, catch-per- low. Even with a lower than average mortality rate, unit-effort (CPUE)"in 2009 was 0.3 fish per trawl .late summer abundance was the second lowest on

-tow, the smallest value of the time-series. record, exceeding 'only 2006. There were non-An absolute abundance estimate of the 2008 significant or negative correlations between CPUE

-spawning population (the latest year for which an 'indices of age-0--fish and the abundance of female estimate could be made) using-the Jolly model was' adult spawners 3 to 5 years later. Conversely, not calculated due to a lack of *recaptures of positive correlations were found between age-I previously marked fish. The last three absolute abundance indices and older fish.

abundance estimates were imprecise, having large The number of larvae entrained at MPS is a 95% confidence intervals, and are not considered measure of potential impact- to winter flounder. In reliable. most years, Stage 3 larvae 'dominated entrainment Using another methodology termed' standardized collections. Annual estimates of entrainment are catch, female spawner abundance in 2009 was esti- related-to both larval densities in Niantic Bay and

-mated at only '323 fish that produced about 238 .MPS cooling-water volume. With no spring million eggs. 'Previous annual standardized catch refueling outage in 2009, the 2009 entrainment estimates ranged from approximately 987 females in estimate of about 152 million reflected moderate 2008 to 75 thousand in 1982 and corresponding total Niantic Bay larval densities.

egg production estimates were 0.7 to 44.8 billion. Annual entrainment density (abundance index In 2009, overall abundance of winter flounder divided by total seawater volume) has varied without larvae in -the Niantic River was the second lowest trend since 1976, indicating that larval production since 1983, exceeding only 2008. The Niantic Bay and availability in Niantic Bay remained relatively abundance index ranked within the lower one-third of *stable despite increased water use during the 1986-95 its time-series. In most years since 1995, more Stage period of three-unit operation and reduced cooling-1 larvae were found than expected from 'low adult water demand in 1995-97. Correlations between spawner abundance, suggesting a density-dependent entrainment estimates and abundance indices of post-compensatory mechanism during the egg stage that entrainment age-0 juveniles -were positive. This enhanced survival. Density-dependent mortality implies no entrainment effect, as the more larvae that

!occurs throughout the larval period of life. An were available for entrainment, the more larvae analysis suggested that mortality decreases with metamorphosed and settled in Niantic River and Bay.

decreasing egg production (a measure'of early larval This was also demonstrated by a comparison of abundance). Larval mortality is also influenced by annual entrainment and juvenile year-class abun-prevailing water temperatures, with warmer springs dance, which suggested that entrainment estimates allowing for faster development and lower mortality. were simply a measure of emerging year-class In 2009, Stage 2 larval abundance was particularly strength. Thus, entrainment is not an important low, indicating high mortality in that stage. In each factor in determining juvenile abundance.

of the past 2 years, both egg production and Stage 1 Executive Summary v

.1~

The potential, impact of larval entrainment on the operation of MPS. No significant long-term trends Niantic River stock depends upon the fraction of the were detected in populations of juvenile or adult

.annual winter flounder, reproduction entrained each silversides collected by trawl or seine. Similarly, no

--yeaf (termed production loss in this report), which long-term trends were identified in various life stages was calculated as equivalent eggs removed by of grubby, cunner, and tautog. Atlantic menhaden

• entrainment. Empirical mass-balance model calcu- larvae showed a significantly increasing trend in lations showed that a large number, of entrained. abundance, as did juveniles taken by seine and trawl.

larvae came. from a number of sources ,in LIS besides Densities of both anchovy eggs and larvae and the Niantic River. In 2009, -approximately 22% of American sand lance larvae continued to show the entrained larvae were attributed to the -river. significant negative trends. The bay anchovy has Based on the increase in egg survival noted in recent. experienced a regional decline in abundance. This

• years, production loss estimates, after 1994 were, species is important forage for predatory fishes and conservatively high. Correcting the post-1994 *birds. In particular, the striped bass has recently estimates using a higher egg survival rate resulted in. increased in abundance along the Atlantic coast and lower production loss estimates (long-term mean = may have contributed to reduced numbers of bay 10.7%). However the production loss. estimate in 'anchovy. Abundance of American sand lance larvae 2009 was implausibly large, suggesting an.* has been relatively stable over the past 25 years underestimate of egg production or an overestimate. .following a decline -that occurred during the early of larvae entrained

• from*- the Niantic River. 1980s. These changes were most likely due to Increasing larval production in LIS and importation interactions with fishes that prey upon larval sand into local waters could have accounted for much of lance.

the discrepancy between the 2009 .and long-term Data collected in 2009 continue to show no long-average production losses. term abundance trends in the numbers of entrained Despite a small adult spawning stock in the river, cunner eggs and larvae. Juvenile and adult cunner

-there have nonetheless been relatively large numbers- have significantly decreased at the Intake trawl of larvae and- young fish in several recent years, .station, but the decline was attributed to the 1983 probably from population compensatory mechanisms removal of the Unit 3- intake cofferdam, a preferred and possibly greater contributions from spawners reef-like habitat for this species. Since that time, no*

outside of the Niantic River. Relatively good abun- significant abundance trend was found from 1984

.dance .of age-0 winter flounder (a life stage not through 2009. Cunner abundance significantly entrained) occurred in some recent years, yet -.increased at the Niantic River trawl station and significant recruitment to - the adult spawning, ,continued to fluctuate without trend at Jordan Cove.

population did not occur. Processes that are unre- *Tautog larvae showed a significant increasing trend

.lated to MPS operation and which occur after in abundance and a significant rise in the abundance juvenile winter flounder leave shallow nursery waters of juveniles and adults was also noted in the trawl during the fall of their first year of life seem to be and lobster pot catches.

operating to account for fewer adults. A bottleneck Changes in the species composition and temporal appears to be occurring during the late juvenile life and spatial abundance of fishes and shellfishes stage (ages-i and 2), ,probably from predation. collected by trawl over the past 33 years were Environmental effects, including changes to the unrelated to MPS operation.. Shifts in the dominance Niantic River habitat (e.g., increased eelgrass of individual taxa were attributed to changes in abundance), a warming trend in regional seawater -habitat, range extensions or contractions, and a temperature, and interactions with other species (e.g., warming trend in ambient seawater temperature that predation), especially during early life history, are has occurred over the past 3 decades.

also important processes affecting winter flounder Cooling-water use at MPS was reduced 23%

population dynamics. Weak year-classes produced in because of the shutdown of Unit 1 in November 2006-09 are indications of likely continued low 1995, resulting in less entrainment and impingement.

recruitment to the Niantic River spawning population Fish return systems at Units 2 (2000) and 3 (1986) in forthcoming years. further reduce impingement mortality at MPS.

Increasing trends in abundance or the lack of Fish Ecology Studies decreasing trends suggests that MPS has had minimal, if any, effect on local fish and shellfish Monitoring during 2009 indicated that no long-term assemblages.

abundance trends in various life stages of seven selected taxa could be directly related to the vi Monitoring Studies, 2009

LobsterStudies widespread, and remain restricted to approximately 150 m of shore-line on the east side of the power Impacts associated with recent MPS operations on station discharge to LIS.

the local lobster population were' assessed by Seasonal shifts in occurrence of annual algal comparing results of the 2009 study to data collected species were noted at Fox Island-Exposed (FE) from 1978 through 2008. Emphasis'has been placed 'during 2009. These shifts included abbreviated on assessing long-term trends-in the abundance and season for cold-water species (e.g., Monostroma population characteristics of lobsters collected in the ,grevillei, Spongomorpha arcta, and Dumontia Millstone Point area. contorta) and extended season for warm-water Throughout LIS, the lobster population was stable or species (e.g., Grinnellia americana, Dasya increasing from 1978 through 1999. The abundance of 'baillouviana, and Bryopsis hypnoides). Similar shifts

-lobsters in LIS was -lower from 2000 to 2009, but have been observed in most years since Unit 3 began unrelated to MPS operations' Rather, the' lobster operation (1986), with the exception of the extended

-abundance -declines -were attributed- to a significant . shutdown of all MPS reactors from March 1996 to mortality event in Western LIS and -to an outbreak of June 1998 when seasonality of these species at FE

• shell disease affecting lobster populations from eastern during the recent shutdown period was more typical LIS to the Gulf of Maine. In the MPS area, no . of other sites.

Thermal effects on dominant species abundance

-significant long-term trends were identified in :the annual CPUE of lobsters (combined over all sizes and -and distribution patterns were also evident at FE in stations) collected either in pots or by trawl. The total 2009 and most apparent in the low intertidal zone.

-pot-CPUE-'of lobsters at the three monitoring stations Seasonally high abundance of Hypnea musciformis, a has varied without trend since 1978. However, annual species observed for the first time in 2001, and CPUE of legal-size lobster has exhibited a significant expanded populations of Sargassum filipendula, declining trend at the Jordan Cove and Twotree Corallina officinalis, and Gelidium pusillum now stations, but not at -the Intake *station located nearby characterize the lower shore community at FE.

'MPS. Significant declines in the abundance of legal- 'Neosiphonia (formerly Polysiphonia) harveyi

.-size lobsters were attributed in part to shell disease and -maintained a perennial population at FE in 2009, but to a 3 mm increase in the minimum legal size since occurred mainly -as a summer annual at sites 1978. unaffected bylMPS.

Long-term trends observed in lobster population Ascophyllum nodosum growth during 2008-09 characteristics over the past three decades (growth, continued to exhibit -no clear relationships among our female maturity and egg-bearing lobsters) appear monitoring stations, or correlation with plant operating related to warmer ambient seawater temperatures .conditions, indicating that the thermal, plume from and/or the recent outbreak of shell disease, and not MPS has had little effect on local populations. Natural MPS operation. Increased ambient water temperature influences of -other 'factors, such as ambient

-,may be responsible for the increased susceptibility temperature conditions, storms and wave action, and transmission of diseases affecting lobsters in LIS, nutrients and light, play the dominant role in which are near their southern range of distribution in determining Ascophyllum growing conditions in the nearshore waters. Millstone area.

The rocky intertidal monitoring program has also The number of lobster larvae entrained through the MPS cooling water systems was highly variable and documented regional patterns and modifications to has not resulted in a decrease in local lobster shore communities unrelated to MPS operation.

abundance. Impacts associated with entrainment and These include the introduction to the region of two impingement of lobsters at MPS have been greatly exotic red algae (Antithamnion pectinatum in 1986 reduced by the shutdown of Unit 1, which eliminated' and Grateloupia turuturu in 2004), decreases in 23% of the cooling water used, and'the installation of barnacle abundance in recent years, and long-term aquatic organism return systems at Units 2 and 3, increases in abundance of the common seaweeds which return impinged lobsters to Niantic Bay. Fucus vesiculosus and Chondrus crispus.

Rocky Intertidal Studies Eelgrass Rocky intertidal monitoring studies during 2009 Eelgrass (Zostera marina L.) populations were continued to document ecological changes to the monitored from 1985 to 2009 at three locations in the shore community near, and associated with, the MPS vicinity of MPS. Data from 2009 surveys indicated thermal discharge. These changes are not that at all three study sites supported healthy and Executive Summary vii

expansive eelgrass populations, consistent with these stations have become coarser (larger mean grain results from the past 6-7 years. These populations size) and the silt/clay fraction smaller. This coarsening have also exhibited variability in 'population of sediments was attributed to MPS-influenced water parameters (e~g., shoot density, shoot length, and flow characteristic at each site: intake of cooling water standing stock biomass) and distribution over the at IN and discharge of cooling water at EF. Mean entire 25-year study period, but this variability was grain size and silt/clay estimates at Jordan Cove (JC) not related to MPS operation. Eelgrass populations at -have remained relatively consistent since the siltation

.two monitoring sites to the east of MPS (Jordan Cove event, related to sediment scouring near the MPS I- JC and White.Point - WP) near. the fringes of the discharge, was observed in 1986. Sedimentary

-thermal plume (< 1.5 km from the MPS discharge to parameters at the reference station Giants Neck (GN)

LIS) have exhibited moderate variability and- subtle ,in 2009 were within the limits of previous declines in some population parameters since 1985. observations, and have varied without trends since However, both predicted and measured thermal input 1980.

from the cooling water discharge to these sites is at Community abundance and numbers of species at all most minimal (< IVC above ambient conditions) and sampling stations in 2009 were generally intermediate well below levels considered stressful to eelgrass. , when compared to historical ranges. Surface deposit-By comparison, high eelgrass population variability feeding oligochaetes and polychaetes were the

-.has been observed inthe Niantic River, (NR), where dominant organisms at all stations in 2009. The complete and often sudden eelgrass bed losses were suspension-feeders Mytilus edulis and Spiochaetoperus

-documented on five separate occasions prior to 2000. oculatus were a notable feeding type only at EF in

.This estuary is located well beyond (> 2 km) waters '2009. Observed changes in abundance of infaunal

• influenced by the MPS thermal discharge. . Since taxa resulted 'in .rank order changes among the

• 2001, eelgrass distribution in the Niantic River has dominant taxa at all stations, but overall, benthic expanded, with a gradual, steady increase in shoot communities sampled in 2009 were generally

,density through 2009. Ongoing extensions of comprised of fauna that had been present in previous

,municipal sewerage lines in the Niantic River years. Multivariate analyses showed higher watershed, possibly coupled with depletion of community, similarity among recent years and

.nutrient inputs from old septic systems, may be illustrated more abrupt changes in community contributing to population recovery during the last 8 composition in earlier study years related to sediment years. disturbances related to MPS construction (dredging In previous years, three short-term declines in .and cofferdam removal at IN) and operation (silt

- eelgrass abundance have been directly associated deposition from increased discharge flow at JC).

,-with fouling and overgrowth of eelgrass: once by *Steady temporal changes in community composition

-blue mussels (Mytilus edulis) at the NR site in 1992 were observed at EF, a location that has been and -twice by blooms of green algae (Cladophora continuously affected by MPS cooling water discharge spp.) at the WP site in 1991 and 2004. Recent. flow since 1986. The GN reference station, beyond

.research from New England and mid-Atlantic states any MPS influence, has also exhibited temporal

'suggests nutrient loading from land-based sources as changes in benthic community structure during the the cause of eelgrass disappearance in LIS to the west study period. These changes were related to natural and elsewhere. Excess nutrients, coupled with variability and other factors unrelated to MPS increases in regional water temperatures and operation (e.g., ambient seawater temperature increase, waterfowl grazing, may factor strongly in declines of storm events). Temporal and spatial variation in the populations near MPS. Eelgrass distribution once MPS benthic communities observed is typical of near-extended over the entire Connecticut coastline, but shore marine environments. Local conditions in the has constricted from west to east such that MPS area maintain a degree of environmental stability populations around Millstone Point now represent the at all study sites, with only minor changes in benthic western range limit of eelgrass in LIS. communities observed from year to year.

Benthic Infauna Benthic infaunal monitoring during 2009 documented continuation of long-term trends in sediment composition at the Effluent (EF) and Intake (IN) stations in- the vicinity of MPS. Sediments at viii Monitoring Studies, 2009