ML091320561

Annual Environmental Protection Plan Operating Report

ML091320561
Person / Time
Site:	Millstone
Issue date:	04/27/2009
From:	Griffin R Dominion Nuclear Connecticut
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
09-201-02, FOIA/PA-2011-0115
Download: ML091320561 (13)

Text

Dominion Nuclear Connecticut, Inc.

Millstone Power Station Dominion-Rope Ferry Road Waterford, CT 06385 APR 2 7 2009 U.S. Nuclear Regulatory Commission Serial No.09-201 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 2008 ANNUAL ENVIRONMENTAL PROTECTION PLAN OPERATING REPORT In accordance with Section 5.4.1 of the Environmental Protection Plan (EPP), Dominion Nuclear Connecticut, Inc. hereby submits the Annual Environmental Protection Plan Operating Report (AEPPOR), describing implementation of the EPP for the previous year. Enclosure 1 transmits information for the period of January 1, 2008 to December 31, 2008.

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

Sincerely, Station Safety and Licensing Jz-~

Serial No.09-201 2008 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.09-201 Docket No. 50-423 License No. NPF-49 Enclosure 1 MILLSTONE POWER STATION UNIT 3 2008 ANNUAL ENVIRONMENTAL PROTECTION PLAN OPERATING REPORT JANUARY 1 - DECEMBER 31, 2008 MILLSTONE POWER STATION UNIT 3 DOMINION NUCLEAR CONNECTICUT, INC. (DNC)

Annual Environmental Protection Plan Operating Report January 1 - December 31, 2008 Millstone Power Station Unit 3 Environmental Protection Plan Dominion Nuclear Connecticut, Inc.

Millstone Power Station Rope Ferry Road Waterford, Cohnecticut 06385 April 2009

2008 Annual Environmental Protection Plan Operating Report (AEPPOR)

1. Introduction This report covers the period January 1, 2008 through December 31, 2008. During 2008, Millstone Power Station Unit 3 (MPS3) completed refueling outage 3R12 (October 11, 2008 - November 24, 2008). Cycle 12 capacity factor was 98.8%; the current cycle 13 (through 12/31/08) capacity factor was 102.2%.

As required by the MPS3 Environmental Protection Plan (EPP), 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)

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 that fulfills these requirements for 2008, "Annual Report 2008 - 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 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 that 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.

2008 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 exceptions for MPS3 circulating or service water discharges reported in 2008.

Information pertaining to events that'occurred in 2008 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 July and October 2008 DMR (as revised by the March 2009 DMR) as follows. Both events described below relate to discharges from DSN 006 (MPS2 & 3 non-contaminated floor drains):

a) On July 7, 2008 at 2:04 PM, the city water (domestic) line which supplies water to the General Electric (GE) Makeup Water Facility Building was identified by operations personnel to have failed. Domestic water entered the nearby storm drain system associated with discharge serial number (DSN) 006. Upon discovery, the leak was immediately isolated. Analysis results of a grab sample taken at DSN 006 on July 7, 2008 at 2:25 PM was 0.30 mg/L Total Residual Chlorine (TRC). The NPDES permit's instantaneous limit at DSN 006 is 0.24 mg/L TRC. Subsequent samples collected by chemistry personnel at 3:05 and 4:00 PM were within permit limits, reading 0.14 mg/L and 0.07 mg/I TRC, respectively. Water flow data recorded on the MPS Plant Process Computer (PPC) for DSN 006 indicated the pipe failure occurred just prior to 2:00 PM with DSN 006 water flow data peaking at approximately 345 gallons per minute (gpm) at 2:14 PM, and then slowly returning to normal flow (approximately 40 gpm) at 3:30 PM. Total daily flow was calculated using the MPS PPC for DSN 006 on July 7, 2008 at approximately 72,400 gallons per day (gpd), well within the NPDES permit limit of 432,000 gpd. The GE Makeup Water Facility was restored to full capacity following the successful repair of the water line on July 8, 2008 at 4:45 PM.

b) On October 14, 2008 at 4:11 PM while analyzing a DSN 006 weekly grab sample for Total Residual Chlorine (TRC), chemistry personnel received a result of'0.25 mg/L TRC. The NPDES permit instantaneous limit at DSN 006 for TRC is 0.24 mg/L. Samples at 4:15, 4:25, and 4:50 PM were 0.29 mg/L, 0.46 mg/L, and 0.35 mg/L, respectively. Subsequently, sampling confirmed TRC concentrations were within NPDES permit limits; at 6:18 PM, the TRC analysis was 0.13 mg/L at DSN 006. Earlier in the day, main condenser tube cleaning commenced at MPS3 as part of the refueling outage. Consistent with protocols previously established with the DEP for this type of maintenance, both the influent and effluent sides of the waterbox are pumped to a collection container adjacent to the MPS3 Turbine Building. This water is held for a period of time, which allows for settling of the debris; a pH analysis is performed on the collection container to ensure compliance with the NPDES permit, and then the water is discharged via DSN 006. When notified of the increasing TRC results from DSN 006 at 2:30 PM, the city water discharges (i.e., waterbox influent) to DSN 006 were stopped. The domestic water that had been 2008 AEPPOR Page 2 of 4

flowing to DSN 006 was directed to the grassy area adjacent to the work area. The normal drainage from this grassy area is to a Stormwater Discharge (DSN 027). For the remainder of the cleaning, the influent discharge line was redirected to DSN 027, where sampling for TRC was performed daily. Additionally, after settling and prior to discharge to DSN 006, both pH and TRC analyses were performed on the collection container to ensure compliance with DSN 006 NPDES permit parameters.

2.3 NPDES Permit Renewal Process The MPS NPDES permit renewal process is continuing. Hearings on the revised draft NPDES permit commenced on December 4, 2008 and concluded on February 26, 2009. Post hearing submittals as requested by the DEP hearing officer are due May 8, 2009.

3. Environmental Protection Plan Noncompliances No EPP noncompliances were identified for MPS3 in 2008.

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.

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 eight licensee events that constituted reportable occurrences at MPS3 were submitted in 2008; they all were determined not to cause a significant environmental impact.

2008 AEPPOR Page 3 of 4

Table 1 MPS3 NPDES Data Summary, Jan. 1 - Dec. 31, 2008. 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. 1357.2 7.9-8.1 56.0-65.3 60.1 16.9 0.15 <0.03 0.20 Feb. 1356.7 7.9-8.0 55.3-69.1 58.6 19.0 0.20 <0.03 0.17 Mar. 1357.2 7.9-8.1 55.3-68.2 59.1 17.1 0.18 <0.03 0.19 Apr. 1357.2 7.9-8.1 59.0-70.0 64.3 17.9 0.09 0.03 0.17 May 1356.5 7.9-8.1 66.3-76.2 70.0 17.3 0.12 <0.03 0.19 June 1357.4 7.9-8.1 70.9-83.0 76.8 15.4 0.10 0.03 0.20 July 1357.2 8.0-8.1 80.3-88.1 84.0 15.1 0.07 0.04 0.23 Aug. 1357.2 7.9-8.1 83.2-89.3 85.6 15.6 0.06 0.04 0.17 Sep. 1357.3 7.8-8.1 81.8-93.6 84.7 15.9 0.08 0.04 0.17 Oct. 1357.2 7.6-8.1 55.1-86.2 69.5 7.0 0.12 0.05 0.20 Nov. 1356.5 7.8-8.1 45.2-70.0 57.5 3.6 0.10 <0.03 0.17 Dec. 1357.0 7.8-8.1 58.4-72.7 64.6 18.0 0.10 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 2008 AEPPOR Page 4 of 4

Attachment to the 2008 Annual Environmental Protection Plan Operating Report January 1 - December 31, 2008 Executive Summary Section of "Annual Report 2008 - Monitoring the Marine Environment of Long Island Sound at Millstone Power Station, Waterford, Connecticut" dated April 2009

Executive Summary Winter Flounder Studies such that when egg densities are low, higher egg survival produces more Stage 1 larvae. Density-The local Niantic River winter flounder population dependent mortality is also present throughout the is potentially affected by the operation of Millstone larval period of life, as an analysis suggested that Power Station (MPS) primarily through entrainment mortality decreases with decreasing egg production of larvae in the condenser cooling water systems. To (a measure of early larval abundance), which is assess possible effects, the abundance of adult further moderated by warmer spring water spawners is measured within the Niantic River and temperatures allowing for faster larval development.

larvae are sampled at the plant discharges and in the However, in 2008, Stage 4 (pre-metamorphosis)

Niantic River and Bay during late winter and early larvae in the Niantic River and Bay were in low spring. Settled age-0 juveniles are collected in the abundance. One factor likely contributing to reduced river in summer. Winter flounder are also collected larval abundance this year was unprecedented high year-round in the trawl monitoring program. densities of jellyfish in the Niantic River.

The relative abundance of adult spawners in 2008 With the exception of a few years, densities of age-was 0.5 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 14 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 27 years, annual Niantic in 2008, initial settled juvenile abundance was River winter flounder abundance represented an relatively low. Coupled with an above-average estimated 0.4 to 3.3% of the entire LIS winter mortality rate, late summer abundance was the flounder resource (mean = 1.32%). second lowest on record, exceeding only 2006.

Absolute abundance of the 2007 spawning popula- CPUE indices of age-0 fish were either not tion (the latest year for which an estimate could be significantly correlated or were negatively correlated made) was estimated at approximately 53,000 fish. with the abundance of female adult spawners 3 to 5 However, this estimate and those of the previous 2 years later. Conversely, positive correlations were years are imprecise, having large 95% confidence found between age-i abundance indices and older intervals. The three most recent absolute abundance fish.

estimates are not considered reliable, given that The number of larvae entrained is a measure of previous estimates were highly correlated with CPUE potential impact to winter flounder. In most years, values and the latter remain low. Using another Stage 3 larvae dominated entrainment collections.

methodology termed standardized catch,, female Annual estimates of entrainment are related to both spawner abundance in 2008 was estimated at only larval densities in Niantic Bay and MPS operation.

987 fish, which produced about 700 million eggs. The 2008 entrainment estimate of about 39 million Other annual standardized catch estimates ranged reflected low larval densities and a spring refueling from approximately 1.6 thousand females in 2006 to outage at Unit 2. The refueling outage and the 1996 75 thousand in 1982 and corresponding total egg retirement of Unit 1 reduced potential MPS entrain-production estimates were 1.1 to 44.8 billion. ment in 2008 by an estimated 22 million larvae.

In 2008, overall abundance of winter flounder Annual entrainment density (abundance index larvae in the Niantic River was the lowest found over divided by total seawater volume) has varied without the time-series going back to 1983 and was second trend since 1976, indicating that larval production lowest in Niantic Bay. In most years since 1995, and availability in Niantic Bay remained relatively more Stage 1 larvae were found than expected from stable despite increased water use during the 1986-95 low adult spawner abundance, suggesting a density period of three-unit operation and reduced cooling-dependent compensatory mechanism during the egg water demand in 1995-97. Correlations between stage that enhanced survival. This was attributed to entrainment estimates and abundance indices of post-reduced predation on eggs by sevenspine bay shrimp, entrainment age-0 juveniles were positive. This Executive Summary v

implies no entrainment effect as the more larvae that Fish Ecology Studies were available to be entrained, the more larvae that metamorphosed and settled in Niantic River and Bay. Monitoring during 2008 indicated that no long-This was also demonstrated by a comparison of term abundance trends in various life stages of seven annual entrainment and juvenile year-class abun- selected taxa could be directly related to the dance, which suggested that entrainment estimates operation of MPS. No significant long-term trends were simply a measure of emerging year-class were detected in populations of juvenile or adult strength. Thus, entrainment is not the most important silversides collected by trawl or seine. Similarly, no factor in determining juvenile abundance. long-term trends were identified in various life stages of grubby, cunner, and tautog. Atlantic menhaden The potential impact of larval entrainment on the larvae showed a significantly increasing trend in Niantic River stock depends upon the fraction of the abundance, as did juveniles taken by seine and trawl.

annual winter flounder reproduction entrained each Densities of both anchovy eggs and larvae and year (termed production loss in this report), which American sand lance larvae continued to show was calculated as equivalent eggs removed by significant negative trends. The bay anchovy has entrainment. Empirical mass-balance model calcu- experienced a regional decline in abundance. This lations showed that a large number of entrained species is important forage for predatory fishes and larvae came from a number of sources in LIS besides birds. In particular, the striped bass has recently the Niantic River. In 2008, approximately 10% of increased in abundance along the Atlantic coast and the entrained larvae were attributed to the river. may have contributed to reduced numbers of bay Based on the increase in egg survival noted in recent anchovy. Abundance of American sand lance larvae years, a factor that was not originally incorporated has been relatively stable over the past 25 years into the mass-balance model, most production loss following a decline that occurred during the early estimates made after 1994 were conservatively high. 1980s. These changes were likely due to interactions Correcting the post-1994 estimates by using a higher with fishes that prey upon larval sand lance.

egg survival rate resulted in lower production loss estimates, with 2008 estimate of 8.4% (long-term Data collected in 2008 continue to show no long-mean = 10.7%). term abundance trends in the numbers of entrained cunner eggs and larvae. Juvenile and adult cunner The small adult spawning stock in the river have significantly decreased at the Intake trawl continued to produce relatively large numbers of station, but the decline was attributed to the 1983 larvae and young fish in recent years, which likely removal of the Unit 3 intake cofferdam, a preferred resulted from population compensatory mechanisms. habitat for this species. Since that time, no Despite relatively good abundance of age-0 winter significant abundance trend was found from 1984 flounder (a life stage not entrained) in several recent through 2008. Cunner abundance significantly years, significant recruitment to the adult spawning increased at the Niantic River trawl station and population has not occurred. Processes that are unre- continued to fluctuate without trend at Jordan Cove.

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

appears to be occurring during the late juvenile life stage (ages-1 and 2), probably from predation. Changes in the species composition and temporal Environmental effects, including changes to the and spatial abundance of fishes and shellfishes Niantic River habitat (e.g., increased eelgrass collected by trawl over the past 32 years appeared to abundance), a warming trend in regional sea water be unrelated to MPS operation. Shifts in the temperature, and interactions with other species (e.g., dominance of individual taxa were attributed to predation), especially during early life history, are changes in habitat, range extensions or contractions, also important processes affecting winter flounder and warmer ambient seawater temperatures occurring population dynamics. Relatively weak year-classes over the past 3 decades.

produced in 2006-08 are indications of likely Cooling-water use at MPS was reduced 23% from continued poor recruitment to the Niantic River the shutdown of Unit I in 1995, resulting in less spawning population in forthcoming years. entrainment and impingement. Fish return systems at Units 2 (2000) and 3 (1986) further reduce impingement mortality at MPS. Based on increasing vi Monitoring Studies, 2008

trends in abundance or the lack of decreasing trends, Rocky Intertidal Studies it appears that MPS has had minimal effect on local fish and shellfish assemblages. Rocky intertidal monitoring studies during 2008 continued to document ecological changes to the shore community near, and associated with, the MPS Lobster Studies thermal discharge. These changes are not wide-Impacts associated with recent MPS operations on spread, and remain restricted to approximately 150 m the local lobster population were assessed by of shore-line on the east side of the power station comparing results of the 2008 study to data collected discharge to LIS.

from 1978 through 2007. Emphasis has been placed Seasonal shifts in occurrence of annual algal on assessing long-term trends in the abundance and species were noted at Fox Island-Exposed (FE) population characteristics of lobsters collected in the during 2008. These shifts included abbreviated Millstone Point area.

season for cold-water species (e.g., Monostroma Throughout LIS, the lobster population was stable or grevillei, Spongomorpha arcta, and Dumontia increasing from 1978 through 1999. The abundance of contorta) and extended season for warm-water lobsters in LIS was lower from 2000 to 2008, but species (e.g., Grinnellia americana, Dasya unrelated to MPS operations. Rather, the lobster baillouviana,and Bryopsis hypnoides). Similar shifts abundance declines were attributed to a significant have been observed in most years since Unit 3 began mortality event in western LIS and to an outbreak of operation (1986), with the exception of the extended shell disease affecting lobster populations from eastern shutdown of all MPS reactors from March 1996 to LIS to the Gulf of Maine. In the MPS area, no June 1998 when seasonality of these species at FE significant long-term trends were identified in the during the recent shutdown period was more typical annual CPUE of lobsters (combined over all sizes and of other sites.

stations) collected either in pots or by trawl. The total Thermal effects on dominant species abundance pot-CPUE of lobsters at the three monitoring stations and distribution patterns were also evident at FE in has varied without trend since 1978. However, annual 2008 and most apparent in the low intertidal zone.

CPUE of legal-size lobster has exhibited a significant Seasonally high abundance of Hypnea musciformis, a declining trend at the Jordan Cove and Twotree species observed for the first time in 2001, and stations, but not at the Intake station located nearby expanded populations of Sargassum filipendula, MPS. Significant declines in the abundance of legal-Corallina officinalis, and Gelidium pusillum now size lobsters were due in part to shell disease and to a 3 characterize the lower shore community at FE.

mm increase in the minimum legal size since 1978.

Polysiphonia spp. maintained a perennial population Long-term trends observed in lobster population at FE in 2008, but occurred mainly as a summer characteristics over the past three decades (growth, annual at sites unaffected by MPS.

female maturity and egg-bearing lobsters) appear Ascophyllum nodosum growth during 2007-08 related to warmer ambient seawater temperature continued to exhibit no clear relationships among our and/or the recent outbreak of shell disease, and not monitoring stations, or correlation with plant operating MPS operation. Increased ambient water conditions, indicating that the thermal plume from temperature may be responsible for the increased MPS has had little effect on local populations. Natural susceptibility and transmission of diseases affecting influences of other factors, such as ambient lobsters in LIS, which are near their southern range temperature conditions, storms and wave action, of distribution in nearshore waters.

nutrients and light, play the dominant role in The number of lobster larvae entrained through the determining Ascophyllum growing conditions in the MPS cooling water systems was highly variable and Millstone area.

has not resulted in a decrease in local lobster The rocky intertidal monitoring program has also abundance. Impacts associated with entrainment and documented regional patterns and modifications to impingement of lobsters at MPS have been greatly shore communities unrelated to MPS operation.

reduced by the shutdown of Unit 1, which eliminated These include the introduction to the region of two 23% of the cooling water used, and the installation of exotic red algae (Antithamnion pectinatum in 1986 aquatic organism return systems at Units 2 and 3, and Grateloupia turuturu in 2004), decreases in which return impinged lobsters to Niantic Bay.

barnacle abundance in recent years, and a long-term Executive Summary vii

increase in abundance of the common brown rockweed, Fucus vesiculosus.

I IBenthic Infauna Eeigrass Benthic infaunal monitoring during 2008 Eelgrass (Zostera marina L.) population dynamics documented continuation of long-term trends in were monitored from 1985 to 2008 at three locations sediment composition at the Effluent (EF) and Intake in the vicinity of MPS. Some long-term declines in (IN) stations in the vicinity of MPS. In general, one or more eelgrass population parameters (e.g., sediments at these stations have become coarser (larger shoot density, shoot length, and standing stock bio- mean grain size) and the silt/clay fraction smaller.

mass) were observed at all three areas monitored This coarsening of sediments was attributed to MPS-over the entire 24-year study period. Eelgrass influenced water flow characteristic at each site: intake populations at two monitoring sites to the east of of cooling water at IN and discharge of cooling water MPS near the fringes of the thermal plume (<1.5 km at EF. Mean grain size and silt/clay estimates at Jordan from the MPS discharge to LIS) have exhibited Cove (JC) have remained relatively consistent since gradual declines since 1985. These declines were not the siltation event related to sediment scouring near the associated with MPS operation, as thermal input from MPS discharge observed in 1986. Sedimentary the cooling water discharge to these sites is at most parameters at the reference station Giants Neck (GN) minimal (<10 C above ambient conditions). in 2008 were within the limits of previous observations Monitoring results from 2008 indicate population and continued to exhibit variability unrelated to MPS.

improvement at all sites, which continued trends Community abundance and numbers of species at all observed over the last 3 or more years. sampling stations in 2008 were generally intermediate By comparison, complete and often sudden when compared to historical ranges. Surface deposit-eelgrass bed losses were documented on five separate feeding oligochaetes and polychaetes were the occasions prior to 2000 in the Niantic River. This dominant organisms at all stations in 2008. Observed estuary is located well beyond (>2 km) waters changes in abundance of infaunal taxa resulted in rank influenced by the MPS thermal discharge. Since order changes among the dominant taxa at all stations, 2001, eelgrass distribution in the Niantic River has but overall, benthic communities sampled in 2008 expanded, with gradual, steady increases in shoot were comprised of fauna that had been present in density, shoot length, and biomass observed through previous years. Multivariate analyses showed higher 2008. Ongoing extensions of municipal sewerage community similarity among recent years and lines in the Niantic River watershed, possibly illustrated changes in community composition in coupled with depletion of nutrient inputs from old earlier study years related to sediment disturbances at septic systems, may be contributing to population IN and JC. Changes in community composition from recovery during the last 7 years. early sampling years to more recent years were also observed at EF, a location continuously affected by In previous years, three short-term declines in MPS cooling water discharge flow. The GN reference eelgrass abundance have been directly associated station, beyond any MPS influence, has also exhibited with fouling and overgrowth of eelgrass: once by temporal c!*anges in benthic community structure blue mussels (Mytilus edulis) at the Niantic River in during the study period. Temporal and spatial 1992 and twice by blooms of green algae variation in the MPS benthic communities observed in (Cladophoraspp.) at White Point in 1991 and 2004. 2008 is typical of near-shore marine environments.

Recent research from New England and mid-Atlantic There were no unusual events, either natural or MPS-states suggests nutrient loading from land-based related, that caused any large-scale shifts in benthic sources as the cause of eelgrass disappearance in LIS infaunal communities monitored in 2008, and under to the west and elsewhere. Excess nutrients, coupled current environmental conditions, these infaunal with increases in regional water temperature and communities appeared relatively stable.

waterfowl grazing, may factor strongly in declines of populations near MPS. Eelgrass distribution once extended over the entire Connecticut coastline, but has constricted from west to east such that populations around Millstone Point now represent the western range limit of eelgrass in LIS.

viii Monitoring Studies, 2008