ML111250437

2010 Annual Environmental Protection Plan Operating Report

ML111250437
Person / Time
Site:	Millstone
Issue date:	04/28/2011
From:	Macmanus R Dominion, Dominion Nuclear Connecticut
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
11-225
Download: ML111250437 (13)

Text

Dominion Nuclear Connecticut, Inc.

Millstone Power Station Dominion-Rope Ferry Road Waterford, CT 06385 APR 2 8 2011 U.S. Nuclear Regulatory Commission Serial No.11-225 Attention: Document Control Desk MPS Lic/GJC RO Washington, DC 20555-0001 Docket Nos. 50-423 License Nos. NPF-49 DOMINION NUCLEAR CONNECTICUT, INC.

MILLSTONE POWER STATION UNIT 3 2010 ANNUAL ENVIRONMENTAL PROTECTION PLAN OPERATING REPORT In accordance with Section 5.4.1 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, 2010 to December 31, 2010.

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.11-225 2010 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 J. D. Hughey NRC Project Manager U.S. Nuclear Regulatory Commission One White Flint North, Mail Stop 08-BlA 11555 Rockville Pike Rockville, MD 20852-2738 NRC Senior Resident Inspector Millstone Power Station

Serial No.11-225 Docket No. 50-423 License No. NPF-49 Enclosure I MILLSTONE POWER STATION UNIT 3 2010 ANNUAL ENVIRONMENTAL PROTECTION PLAN OPERATING REPORT JANUARY 1 - DECEMBER 31, 2010 MILLSTONE POWER STATION UNIT 3 DOMINION NUCLEAR CONNECTICUT, INC. (DNC)

2010 Annual Environmental Protection Plan Operatinq Report (AEPPOR) 1.

Introduction:

This report covers the period January 1,2010 through December 31, 2010. During 2010, Millstone Power Station Unit 3 (MPS3) completed refueling outage 3R13 (April 10 - May 20). Since the refueling outage (through December 31, 2010), MPS3 has operated at a capacity factor of 98.6%; overall capacity for 2010 was 87.5%.

As required by the MPS3 Environmental Protection Plan (EPP), Appendix B to the MPS3 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 that 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).

Section 10(A) of Millstone Power Station's (MPS) NPDES permit, as issued to Dominion Nuclear Connecticut, Inc. (DNC) by the Connecticut Department of Environmental Protection (DEP) on September 1, 2010 (the Permit), 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.

Section 10(A)(2) of the Permit requires an annual report of these studies to be sent to the DEP Commissioner on or before July 3 1 st of each year. The latest report that fulfills these requirements, "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, which is attached as part of this report.

2.2 Effluent Water Quality Monitoring:

Sections 1 and 5 of the Permit require 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. Section 8 of the Permit requires that a monthly report of this monitoring be submitted to the DEP. The report that fulfills these requirements, the "Monthly Discharge Monitoring Report" (DMR),

includes discharge 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.

2010 AEPPOR Page 1 of 5

Each monthly DMR identifies NPDES permit exceedances (i.e., events where a parameter value was beyond permitted limits) or exceptions (i.e., events where Permit conditions were not met) for the month. During 2010, there were four MPS3 events that were reported as NPDES exceedances; the descriptions below are summarized from the monthly DMRs.

a) MPS3 Condensate PolishingFacility Discharge (DSN OOIC-6)

On July 22, 2010 at 1700 hours0.0197 days <br />0.472 hours <br />0.00281 weeks <br />6.4685e-4 months <br />, during a review of field data logs for the bench-top pH meter used for recording discharge serial number (DSN) 001C-6 hourly readings, several instances were identified where the sample temperature, recorded in conjunction with the NPDES permit in effect prior to reissuance on September 1, 2010, exceeded the 100IF permit limit.

Elevated temperatures are the result of exothermic acid-caustic reactions during the neutralization of waste from ion exchange resin bed regeneration.

The maximum temperature recorded was 120.41F on July 21, 2010.

Corrective actions included steps to assure that temperature is monitored before and during DSN 001C-6 discharges with a calibrated thermometer.

b) MPS2 and MPS3 Non-ContaminatedFloorDrains (DSN 006)

On August 5, 2010 at 1024 hours0.0119 days <br />0.284 hours <br />0.00169 weeks <br />3.89632e-4 months <br />, the MPS3 control room received an alarm indicating an impending out-of-range pH reading from the continuous monitor at DSN 006. The DSN 006 outfall at MPS discharges both process waters from the plant and surface water runoff from the yard drain system.

Station Chemistry was dispatched to the monitoring point and verified through the analysis of a grab sample that the pH had exceeded the NPDES allowed range of 6.0 to 9.0 s.u. The grab sample result was 9.45 s.u. The pH readings at DSN 006 were intermittently above 9.0 s.u. over a period of one hour from 1025 to 1125 and ranged from 9.01 to 9.45 s.u.

Samples were taken along the discharge flow path and the source of the high pH was traced back to residue from on-going concrete work which had entered the yard drain system after a heavy rain. The residue within the catch basin had a pH level of > 11.0 s.u. The remaining water and sediments in the catch basin which had the high pH were removed from the catch basin on August 10, 2010 and were properly disposed of off-site.

c) MPS3 Service Water Discharge (DSN 001 C-5)

On September 29, 2010 at 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br />, the flow proportioned DSN 001C-5 discharge free available chlorine (FAC) average concentration yielded a 0.33 mg/L result. The instantaneous Permit limit at this discharge for FAC is 0.25 mg/L. Upon discovery, Chemistry personnel reduced the sodium hypochlorite injection to the service water system from the metering pumps and the average concentration was reduced to 0.065 mg/I. A subsequent system walkdown and valve lineup check revealed no abnormalities.

d) Millstone Power Station (MPS) Quarty Cut Discharge (DSN 00 1-1)

On October 13, 2010 at 1455 hours0.0168 days <br />0.404 hours <br />0.00241 weeks <br />5.536275e-4 months <br />, MPS personnel sampled DSN 001-1 for total residual chlorine (TRC) during circulating water system chlorination as required by the NPDES permit. The result of the analysis was 0.15 mg/L TRC. The Permit limit at DSN 001-1 is 0.10 mg/L TRC. Subsequent samples were taken and the indicated TRC concentration peaked at 0.22 2010 AEPPOR Page 2 of 5

mg/L at 1550. At 1'555 hours0.00642 days <br />0.154 hours <br />9.176587e-4 weeks <br />2.111775e-4 months <br />, the TRC had returned to < 0.10 mg/L. As the TRC concentration was more than twice the Permit limit, a prompt notification was made to the DEP Water Bureau on October 14, 2010. A follow-up letter was forwarded to the DEP Water Bureau on October20, 2010 (D18161).

Efforts to better understand the factors that might have caused the chlorine exceedances included the following:

• On October 21, 2010, MPS personnel collected DSN 001-1 samples for TRC analysis during hydrolazing activities on the trash racks of the MPS3 intake. Circulating water chlorination was not in progress at the time, however, continuous service water chlorination was 0.10 mg/L FAC in the MPS3 service water discharge (DSN 001 C-5). Despite the absence of chlorination in the MPS3 circulating water system, TRC analyses at DSN 001-1 revealed a maximum TRC concentration of 0.14 mg/L during hydrolazing activities. A MPS3 intake sample (between the trash rack and traveling screens) analyzed after the DSN 001-1 discharge results of 0.14 mg/L was measured at 0.10 mg/L TRC.

Hydrolazing activities concluded at 1511 hours0.0175 days <br />0.42 hours <br />0.0025 weeks <br />5.749355e-4 months <br />. At 1747 hours0.0202 days <br />0.485 hours <br />0.00289 weeks <br />6.647335e-4 months <br />, samples analyzed at DSNO01 -1 for TRC were all < 0.02 mg/L.

• On November 3,2010, additional TRC analyses were performed using independent approved standard methods for TRC at the MPS3 Intake, MPS2 Discharge, MPS3 Discharge and DSN 001-1 discharge, as well as control samples approximately 1 km from MPS, during MPS3 intake hydrolazing. All results were undetectable for TRC.

• Plant procedures called for the operation of the screen wash pump whenever a diver is in the MPS3 intake for hydrolazing activities. Based on the review of plant conditions and sample results, the most likely cause for the October event was site activities which may have caused a reduction in the pressure of the domestic water used as dilution flow for service water chlorination. This may have resulted in increased service water chlorine concentration. When the screen wash pump operates, it also provides dilution flow to the service water chlorine supply header, with a pressure twice that of normal domestic water pressure. This higher pressure dilution flow and increased chlorine concentration would have combined with the organics generated by the hydrolazing at the MPS3 intake as the service water commingled with circulating water, and could generate false positives results for TRC when using the Hach Test Kit.

2.3 NPDES Permit Renewal Process:

As discussed above, the MPS NPDES permit was reissued by the DEP on September 1, 2010. DNC notified the NRC of the renewed permit via letter (10-554) dated September 23, 2010.

3. Environmental Protection Plan (EPP) Noncompliances:

No EPP noncompliances were identified for MPS3 in 2010.

2010 AEPPOR Page 3 of 5

4. Environmentally Significant Changes to Station Design or Operation:

During 2010, MPS3 installed, tested, and began operation of the variable frequency drives (VFDs) associated with the MPS3 circulating water pumps, consistent with NPDES Permit requirements. As of December 31, 2010, one of the six MPS3 VFDs continued to experience voltage oscillations that preclude acceptable operation of that VFD.

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 four licensee events that constituted a reportable occurrence at MPS3 occurred in 2010; none were determined to cause a significant environmental impact.

2010 AEPPOR Page 4 of 5

Table I MPS3 NPDES Data Summary, Jan. 1 - Dec. 31, 2010. Selected water quality parameters for MPS3(1 ). Values in bold represent reported exceedances, discussed in Section 2.2.

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. 1356.9 7.9-8.1 38.2-65.8 54.2 15.6 0.13 < 0.03 0.23 Feb. 1357.0 7.9-8.1 52.8-59.0 55.2 18.8 0.11 < 0.03 0.20 Mar. 1356.8 7.8-8.0 54.6-66.3 58.3 17.0 0.14 < 0.03 0.17 Apr. 1356.9 7.3-8.1 44.6-69.1 54.6 6.5 0.09 0.03 0.17 May 1356.9 7.9-8.1 49.7-80.5 61.1 6.9 0.13 0.03 0.18 June 1356.5 7.9-8.2 75.6-85.9 80.7 17.6 0.10 0.03 0.19 July 1357.0 8.0-8.2 81.3-90.5 85.8 17.2 0.09 0.03 0.19 Aug. 1357.3 7.9-8.2 68.8-91.6 85.8 15.5 0.09 0.06 0.22 Sep. 1362.2 8.0-8.2 84.0-95.0 87.8 19.1 0.08 0.05 0.33 Oct. 1361.4 7.9-8.1 74.9-89.7 80.5 18.1 0.10 0.22 0.16 Nov. 1360.6 7.8-8.0 65.1-80.3 71.8 19.0 0.06 0.03 0.15 Dec. 1360.6 7.8-8.0 54.5-74.2 63.0 19.8 0.09 0.03 0.18 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 2010 AEPPOR Page 5 of 5

Attachment to the 2010 Annual Environmental Protection Plan Operating Report January 1 - December 31, 2010 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 - 2009 Environmental Monitoring Annual Report Winter Flounder Studies of early larval abundance), which is further moderated by warmer spring water temperatures The local Niantic River winter flounder population allowing for faster larval development. This year, is potentially affected by the operation of Millstone Stage 2 larval abundance was particularly low, Power Station (MPS) primarily through entrainment indicating high mortality in that stage, perhaps of larvae in the condenser cooling-water systems. To exacerbated by high densities of jellyfish in the assess possible effects, the abundance of adult Niantic River. In each of the past 2 years, both egg spawners is measured within the Niantic River and production and Stage 1 larval abundance were low as larvae are sampled at the plant discharges and in the were the numbers of metamorphosing larvae.

Niantic River and Bay during late winter and early However, relative to the Niantic River, larval spring. Settled age-0 juveniles are collected in the abundance in Niantic Bay has increased in recent river in summer. Winter flounder are also collected years, suggesting higher production in LIS rather year-round in the trawl monitoring program. than in estuaries such as the Niantic River.

The relative abundance of adult spawners in 2009 With the exception of a few years, densities of age-was 0.3 fish per trawl tow (catch-per-unit-effort; 0 young in the Niantic River following larval meta-CPUE), which is the lowest value since these studies morphosis and 'settlement were linearly related to began in 1976. Over the past 15 years, CPUE of Stage 4 larval abundance. However, at higher larval winter flounder spawners in the Niantic River has abundance juvenile densities apparently reached an remained at a relatively low level, but similar to asymptote of about 250 young per 100 m 2 of bottom, levels found throughout Long Island Sound (LIS) by which could represent the carrying capacity of the the Connecticut Department of Environmental river habitat. As expected from low larval abundance Protection. During the past 28 years, annual Niantic in 2009, initial settled juvenile abundance was very River winter flounder abundance represented an low. Even with a lower than average mortality rate, estimated 0.4 to 3.3% of the entire LIS winter late summer abundance was the second lowest on flounder resource (mean = 1.34%). record, exceeding only 2006. CPUE indices of age-0 An absolute abundance of the 2008 spawning fish were either not significantly correlated or were population (the latest year for which an estimate negatively correlated with the abundance of female could be made) using the Jolly model could not be adult spawners 3 to 5 years later. Conversely, made due to a lack of recaptures of previously positive correlations were found between age-I marked fish. The last three absolute abundance abundance indices and older fish.

calculations made were imprecise, having large 95% The number of larvae entrained is a measure of confidence intervals, and are not considered reliable. potential impact to winter flounder. In most years, Using another methodology termed standardized Stage 3 larvae dominated entrainment collections.

catch, female spawner abundance in 2009 was esti- Annual estimates of entrainment are related to both mated at only 323 fish that produced about 238 larval densities in Niantic Bay and MPS operation.

million eggs. Other annual standardized catch With no spring refueling outage in 2009, the 2009 estimates ranged from approximately 987 females in entrainment estimate of about 152 million reflected 2008 to 75 thousand in 1982 and corresponding total moderate 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-I 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. This was attributed to reduced implies no entrainment effect, as the more larvae that predation on eggs by sevenspine bay shrimp, such were available to be entrained, the more larvae that that when egg densities are low, higher egg survival metamorphosed and settled in Niantic River and Bay.

produces more Stage I larvae. Density-dependent This was also demonstrated by a comparison of mortality is also present throughout the larval period annual entrainment and juvenile year-class abun-of life, as an analysis suggested that mortality dance, which suggested that entrainment estimates decreases with decreasing egg production (a measure were simply a measure of emerging year-class

strength. Thus, entrainment is not an important were detected in populations of juvenile or adult factor in determining juvenile abundance. silversides collected by trawl or seine. 'Similarly, no The potential impact of larval entrainment on the long-term trends were identified in various life stages Niantic River stock depends upon the fraction of the of grubby, cunner, and tautog. Atlantic menhaden annual winter flounder reproduction entrained each larvae showed a significantly increasing trend in year (termed production loss in this report), which abundance, as did juveniles taken by seine and trawl.

was calculated as equivalent eggs removed by Densities of both anchovy eggs and larvae and entrainment. Empirical mass-balance model calcu- American sand lance larvae continued to show lations showed that a large number of entrained significant negative trends. The bay anchovy has larvae came from a number of sources in LIS besides experienced a regional decline in abundance. This the Niantic River. In 2009, approximately 22% of species is important forage for predatory fishes and the entrained larvae were attributed to the river. birds. In particular, the striped bass has recently Based on the increase in egg survival noted in recent increased in abundance along the Atlantic coast and years, a factor that was not originally incorporated may have contributed to reduced numbers of bay into the mass-balance model, most production loss anchovy. Abundance of American sand lance larvae estimates made after 1994 were conservatively high. has been relatively stable over the past 25 years Correcting the post-1994 estimates by using a higher following a decline that occurred during the early egg survival rate resulted in lower production loss 1980s. These changes were most likely due to estimates (long-term mean = 10.7%). However, 2009 interactions with fishes that prey upon larval sand production loss estimates were implausibly large, lance.

suggesting an underestimate of egg production or an Data collected in 2009 continue to show no long-overestimate of the fraction of entrained larvae term abundance trends in the numbers of entrained attributed to the Niantic River due to the conservative cunner egg and larvae. Juvenile and adult cunner nature of the calculations. Increasing larval have 'significantly decreased at the Intake trawl production in LIS and importation into local waters station, but the decline was attributed to the 1983 could have accounted for much of this discrepancy. removal of the Unit 3 intake cofferdam, a preferred A small adult spawning stock in the river has reef-like habitat for this species. Since that time, no nonetheless resulted in relatively large numbers of significant abundance trend was found from 1984 larvae and young fish in several recent years, through 2009. Cunner abundance significantly probably from population compensatory mechanisms. increased at the Niantic River trawl station and Despite relatively good abundance of age-0 winter continued to fluctuate without trend at Jordan Cove.

flounder (a life stage not entrained) in some recent Tautog larvae showed a significant increasing trend years, significant recruitment to the adult spawning in abundance and a significant rise in the abundance population has not occurred. Processes that are of juveniles and adults was also noted in the trawl unrelated to MPS operation and which occur after and lobster pot catches.

juvenile winter flounder leave shallow nursery waters Changes in the species composition and temporal during the fall of their first year of life seem to be and spatial abundance of fishes and shellfishes operating to produce fewer adults. A bottleneck collected by trawl over the past 33 years were appears to be occurring during the late juvenile life unrelated to MPS operation. Shifts in the dominance stage (ages-I and 2), probably from predation. of individual taxa were attributed to changes in Environmental effects, including changes to the habitat, range extensions or contractions, and a Niantic River habitat (e.g., increased eelgrass warming trend in ambient seawater temperature that abundance), a warming trend in regional seawater has occurred over the past 3 decades.

temperature, and interactions with other species (e.g., Cooling-water use at MPS was reduced 23%

predation), especially during early life history, are because of the shutdown of Unit 1 in November also important processes affecting winter flounder 1995, resulting in less entrainment and impingement.

population dynamics. Weak year-classes produced in Fish return systems at Units 2 (2000) and 3 (1986) 2006-09 are indications of continued poor further reduce impingement mortality at MPS.

recruitment to the Niantic River spawning population Increasing trends in abundance or the lack of in forthcoming years. decreasing trends suggests that MPS has had minimal, if any, effect on local 'fish and shellfish Fish Ecology Studies assemblages.

Monitoring during 2009 indicated that no long-term Lobster Studies abundance trends in various life stages of seven selected taxa could be directly related to the Impacts associated with recent MPS operations on operation of MPS. No significant long-term trends the local lobster population were assessed by

comparing results of the 2009 study to data collected (e.g., Monostroma grevillei, Spongomorpha arcta, from 1978 through 2008. Emphasis has been placed and Dumontia contorta) and extended season for on assessing long-term trends in the abundance and warm-water species (e.g., Grinnellia americana, population characteristics of lobsters collected in the Dasya baillouviana, and Bryopsis hypnoides).

Millstone Point area. 'Similar shifts have been observed in most years since Throughout LIS, the lobster population was stable Unit 3 began operation (1986), with the exception of or increasing from 1978 through 1999. The the extended shutdown of all MPS reactors from abundance of lobsters in LIS was lower from 2000 to March 1996 to June 1998 when seasonality of these 2009, but unrelated to MPS operations. Rather, the species at FE during the recent shutdown period was lobster abundance declines were attributed to a more typical of other sites.

significant mortality event in western LIS and to an Thermal effects on dominant species abundance outbreak of shell disease affecting lobster populations and distribution patterns were also evident at FE in from eastern LIS to the Gulf of Maine. In the MPS 2009 and most apparent in the low intertidal zone.

area, no significant long-term trends were identified Seasonally high abundance of Hypnea musciformis, a in the annual CPUE of lobsters (combined over all species observed for the first time in 2001, and sizes and stations) collected either in pots or by trawl. expanded populations of Sargassum filipendula, The total pot-CPUE of lobsters at the three Corallina officinalis, and Gelidium pusillum now monitoring stations has varied without trend since characterize the lower -shore community at FE.

1978. However, annual CPUE of legal-size lobster Polysiphonia spp. maintained a perennial population has exhibited a significant declining trend at the at FE in 2009, but occurred mainly as a summer Jordan Cove and Twotree stations, but not at the annual at sites unaffected by MPS.

Intake station located nearby MPS. Significant Ascophyllum nodosum growth during 2008-09 declines in the abundance of legal-size lobsters were continued to exhibit no clear relationships among our attributed in part to shell disease and to a 3 mm monitoring stations, or correlation with MPS increase in the minimum legal size since 1978. operating conditions, indicating that the thermal Long-term trends observed in lobster population plume from MPS has had little effect on local characteristics over the past three decades (growth, populations. Natural influences of other factors, such female maturity and egg-bearing lobsters) appear as ambient temperature conditions, storms and wave related to warmer ambient seawater temperatures action, nutrients and light, play the dominant role in and/or the recent outbreak of shell disease, and not determining Ascophyllum growing conditions in the MPS operation. Increased ambient water temperature Millstone area.

may be responsible for the increased susceptibility The rocky intertidal monitoring program has also and transmission of diseases affecting lobsters in LIS, documented regional patterns and modifications to which are near their southern range of distribution in shore communities unrelated to MPS operation.

nearshore waters. These include the introduction to the region of two The number of lobster larvae entrained through the exotic red algae (Antithamnion pectinatum in 1986 MPS cooling water systems was highly variable and and Grateloupia turuturu in 2004), decreases in has not resulted in a decrease -in local lobster barnacle abundance in recent years, and long-term abundance. Impacts associated with entrainment and increases in abundance of the common seaweeds impingement of lobsters at MPS have been greatly Fucus vesiculosus and Chondrus crispus.

reduced by the shutdown of Unit I, which eliminated Eelgrass 23% of the cooling water used, and the installation of aquatic organism return systems at Units 2 and 3, which return impinged lobsters to Niantic Bay. Eelgrass (Zostera marina L.) population dynamics were monitored from 1985 to 2009 at three locations Rocky Intertidal Studies in the vicinity of MPS. Some long-term declines in one or more eelgrass population parameters (e.g.,

Rocky intertidal monitoring studies during 2009 shoot density, shoot length, and standing stock continued to document ecological changes to the biomass) were observed at all three areas monitored shore community near, and associated with, the MPS over the entire 25-year study period. Eelgrass thermal discharge. These changes are not populations at two monitoring sites to the east of widespread, and remain restricted to approximately MPS (JC and WP) near the fringes of the thermal 150 m of shore-line on the east side of the power plume (<15 km from the MPS discharge to LIS) station discharge to LIS. Seasonal shifts in have exhibited subtle declines in some population occurrence of annual algal species were noted at Fox parameters since 1985. These declines were not Island-Exposed (FE) during 2009. These shifts associated with MPS operation, as thermal input from included abbreviated season for cold-water species the cooling water discharge to these sites is at most

minimal (<i°C above ambient conditions). Results intermediate when compared to historical ranges.

from the 2009 mapping survey of Jordan Cove Surface deposit-feeding oligochaetes and polychaetes indicated extensive eelgrass beds have persisted in were the dominant organisms at all stations in 2009.

the vicinity of the JC and WP sampling sites since The suspension-feeders Mytilus edulis and 2002, with expansive high density areas since 2007. Spiochaetoperus oculatus were a notable feeding By comparison, complete and often sudden eelgrass type only at EF in 2009. Observed changes in bed losses were documented on five separate abundance of infaunal taxa resulted in rank order occasions prior to 2000 in the Niantic River. This changes among the dominant taxa at all stations, but estuary is located well beyond (>2 kin) waters overall, benthic communities sampled in 2009 were influenced by the MPS thermal discharge. Since generally comprised of fauna that had been present in 2001, eelgrass distribution in the Niantic River has previous years. Multivariate analyses showed higher expanded, with a gradual, steady increase in shoot community -similarity among recent years and density through 2009. Ongoing extensions of illustrated more abrupt changes in community municipal sewerage lines in the Niantic River composition in earlier study years related to sediment watershed, possibly coupled with depletion of disturbances related to MPS construction (dredging nutrient inputs from old septic systems, may be and cofferdam removal at IN) and operation (silt contributing to population recovery during the last 8 deposition from increased discharge flow at JC).

years. Steady temporal changes in community composition In previous years, three short-term declines in were observed at EF, a location that has been eelgrass abundance have been directly associated continuously affected by MPS cooling water with fouling and overgrowth of eelgrass: once by discharge flow since 1986. The GN reference blue mussels (Mytilus edulis) at the Niantic River in station, beyond any MPS influence, has also 1992 and twice by blooms of green algae exhibited temporal changes in benthic community (Cladophoraspp.) at White Point in 1991 and 2004. structure during the study period. These changes Recent research from New England and Mid-Atlantic were related to natural variability and other factors States suggests nutrient loading from land-based unrelated to MPS operation (e.g., ambient seawater sources as the cause of eelgrass disappearance in LIS temperature increase, storm events). Temporal and to the west and elsewhere. Excess nutrients, coupled spatial variation in the MPS benthic communities with increases in regional water temperatures and observed is typical of near-shore marine waterfowl grazing, may factor strongly in declines of environments. Local conditions in the MPS area populations near MPS. Eelgrass distribution once maintain a degree of environmental stability at all extended over the entire Connecticut coastline, but study sites, with only minor changes in benthic has constricted from west to east such that communities observed from year to year.

populations around Millstone Point now represent the western range limit of eelgrass in LIS.

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 these stations have become coarser (larger mean grain size) and the silt/clay fraction smaller. This coarsening of sediments was attributed to MPS-influenced water flow characteristic at each site:

intake of cooling water at IN and discharge of cooling water at EF. Mean grain size and silt/clay estimates at Jordan Cove (JC) have remained relatively consistent since the siltation event, related to sediment scouring near the MPS discharge, was observed in 1986. Sedimentary parameters at the reference station Giants Neck (GN) in 2009 were within the limits of previous observations, and have varied without trends since 1980.

Community abundance and numbers of species at all sampling stations in 2009 were generally