ML081270204

Annual Environmental Protection Plan Operating Report, January - December 2007

ML081270204
Person / Time
Site:	Millstone
Issue date:	04/25/2008
From:	Price J Dominion Nuclear Connecticut
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
08-0184
Download: ML081270204 (13)

Text

Dominion Nuclear Connecticut, Inc.

Millstone Power Station 4-ADominion Rope Ferry Road, Waterford, CT 06385 APR 2 5 2008 U.S. Nuclear Regulatory Commission Serial No. 08-0184 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 2007 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, 2007 to December 31, 2007.

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

Sincerely, J. Al1n Price Sice President - Millstone zI72~9s

Serial No. 08-0184 2007 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 Mr. J. D. Hughey Project Manager U.S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Mail Stop 8B3 Rockville, MD 20852-2738 NRC Senior Resident Inspector Millstone Power Station

Annual Environmental Protection Plan Operating Report January 1 - December 31, 2007 Millstone Unit 3 Environmental Protection Plan Dominion Nuclear Connecticut, Inc.

Millstone Power Station Rope Ferry Road Waterford, Connecticut 06385 April 2008

2007 Arinual Environmental Protection Plan Operating Report (AEPPOR)

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

As required by the MPS 3 Environmental Protection Plan (EPP), this AEPPOR includes:

• summaries and analyses of the results of environmental protection activities, o a list of EPP noncompliances, o a list of all changes in station design or operation which involved a potentially significant unreviewed environmental question, and o 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 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 2007, Annual Report 2007 - 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.

2007 AEPPOR Page 1 of 5

2.2 Effluent Water Quality Monitoring Paragraph 3 of the MPS NPDES permit requires monitoring and recording of many 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 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 Millstone units.

Consistent with prior annual AEPPOR submissions, water flow, temperature, pH, and chlorine data pertaining to MPS 3 are summarized in Table 1.

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

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

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

The following corrective actions associated with this event have been implemented:

pH devices with data loggers were purchased and installed within the three main tributaries that contribute to DSN 006. Once a tributary is 2007 AEPPOR Page 2 of 5

identified with high pH, portable pH devices will then be used to further identify specific up-stream sources.

• The inline sampler at DSN 006 has been pre-programmed to immediately draw samples when a pH excursion exists so a larger array of analyses can be performed on the sample to aid in determining the source.

Site personnel were reminded of the importance of controlling discharges to the environment as per site proceduresý.

b) On September 19, 2007 between 1934 and 2136, the Plant Process Computer (PPC) data point associated with the inline pH instrumentation for DSN 006 (which samples at 60 second intervals) recorded pH measurements greater than DNC's NPDES Permit limit of 9.0 su on 19 occasions. During this period, the highest pH recorded by the PPC was 9.36 su. On September 20, 2007, while conducting an event review of this incident, chemistry department personnel noted another increasing trend for DSN 006 pH on the PPC. At 1545, a confirmatory grab sample was obtained at the DSN 006 sample point and the resulting pH was 9.47 su. Chemistry and environmental compliance personnel proceeded to the vendor makeup water system facility to analyze this input to the DSN 006 catch basin for pH. The results indicated that the reject water was not the source of the elevated pH. At this time, it was noted that areas adjacent to the catch basin near the vendor makeup water system facility recently had footings excavated and concrete had been poured. Standing water from these evolutions had pooled around the catch basin. The standing water was analyzed for pH with results of 12.04 and 12.09 su, respectively. Indications are that the catch basin was installed without a seal between its components. As a result, standing water from the footing excavation leaked into the DSN 006 drain system, causing the pH at DSN 006 to increase.

By way of corrective action, on September 21, 2007, prior to additional excavating, drilling, or pouring of cement, the remaining pooled water adjacent to the catch basin was transferred to totes for off-site disposal by an authorized vendor. To prevent further pH excursions resulting from pooled waters associated with the described construction activity, the use of additional precautions (e.g., containing and reusing drilling water) for all drilling and concrete pours in the area continued until the work was completed on September 28, 2007. Subsequently, the catch basin was resealed to permanently preclude recurrence.

2.3 NPDES Permit Renewal Process On December 10, 2007, the DEP issued a Tentative Determination to renew the MPS NPDES permit. At the same time, a draft of the permit was issued for public comment.

3. Environmental Protection Plan Noncompliances 2007 AEPPOR Page 3 of 5

No EPP noncompliances were identified for MPS 3 in 2007.

4. Environmentally Significant Changes to Station Design or Operation No MPS 3 Design Change Records or System Operating Procedure changes 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.

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

5. Non-Routine Reports of Environmentally Significant Events No MPS 3 events met the criteria for inclusion in this year's report, i.e.,

• required the submittal of a Licensee Event Report (LER), and

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

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

2007 AEPPOR Page 4 of 5

Table I MPS 3 NPDES Data Summary, Jan. 1 - Dec. 31, 2007 Selected water quality parameters for MPS 3(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 41.3-68.9 61.4 15.8 0.13 <0.03 0.22 Feb. 1357.5 8.0-8.2 51.4-61.2 55.0 17.1 0.11 <0.03 0.21 Mar. 1357.1 8.1-8.3 51.9-62.6 55.7 16.6 0.09 <0.03 0.24 (2)

Apr. 1356.5 6.5-8.4 40.6-60.6 47.9 4.3 <0.03 0.25 May 1356.9 7.8-8.3 43.9-75.5 57.2 5.8 0.06 0.04 0.22 June 1356.5 7.9-8.1 71.6-84.0 76.8 15.6 0.11 0.03 0.17 July 1357.1 7.5-8.2 77.3-86.4 82.1 15.5 0.07 <0.03 0.22 Aug. 1358.6 7.9-8.1 83.8-89.5 85.8 15.9 0.08 0.05 0.20 Sep. 1357.3 8.0-8.2 82.6-88.4 84.8 15.9 0.08 0.03 0.18 Oct. 1359.6 8.0-8.2 77.1-86.0 81.6 16.2 0.09 <0.03 0.22 Nov. 1356.9 7.9-8.1 67.1-79.8 72.4 16.4 0.22 <0.03 0.18 Dec. 1357.1 7.9-8.1 56.7-74.1 63.6 17.4 0.14 <0.03 0.20 Notes:

(1) Parameters are measured at MPS 3 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).

(2) Due to the refueling outage and reduced circulating water flows at MPS 3, sodium hypochlorite injection of MPS 3 circulating water system was suspended for April 2007.

Abbreviations Used:

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

FAC = Free Available Chlorine TRC = Total Residual Chlorine SWS = Service Water System 2007 AEPPOR Page 5 of 5

Attachment to the 2007 Annual Environmental Protection Plan Operating Report January 1 - December 31, 2007 Executive Summary Section of "Annual Report 2007 - Monitoring the Marine Environment of Long Island Sound at Millstone Power Station, Waterford, Connecticut" dated April 2008

Executive Summary Winter Flounder Studies analysis suggested that mortality decreases with decreasing egg production (a measure of early larval The local Niantic River winter flounder population abundance), which is further moderated by warmer is potentially affected by the operation of Millstone spring water temperatures allowing for faster larval Power Station (MPS) primarily through entrainment development. This year, Stage 4 (pre-metamor-of larvae in the condenser cooling-water systems. To phosis) larvae in the Niantic River and Bay were assess possible effects, the abundance of adult relatively abundant, ranking among the top five of all spawners is measured within the Niantic River and years.

larvae are sampled at the plant discharges and in the With the exception of a few years, densities of age-Niantic River and Bay during late winter and early 0 young in the Niantic River following larval meta-spring. Settled age-0 juveniles are collected in the morphosis and settlement were linearly related to river in summer. Stage 4 larval abundance. However, at higher larval The relative abundance of adult spawners in 2007 abundance juvenile densities apparently reached an was 1.7 fish per trawl tow (catch-per-unit-effort; asymptote of about 250 young per 100 m2 of bottom, CPUE), which is similar to abundance in 2004 and which could represent the carrying capacity of the 2005 and higher than in 2006. Over the past decade, river habitat. Initial settled juvenile abundance was abundance of winter flounder spawners has remained relatively modest this year, but despite a below-at a relatively low level, with CPUE fluctuating average mortality rate, late summer abundance fell around 1-2 fish per tow. Winter flounder abundance into the lower one-third of values since 1983.

in the Niantic River has been similar to levels found Abundance indices of age-0 fish were either not throughout Long Island Sound (LIS) by the significantly correlated or were negatively correlated Connecticut Department of Environmental Protection. with the abundance of female adult spawners 3 to 5 Absolute abundance of the 2006 spawning popula- years later. Conversely, positive correlations were tion (the latest year for which an estimate could be found between age-i abundance indices and these made) was about 11,500 fish, which was the largest older fish. However, there was much scatter in these value since 1999. However, this estimate is relationships and none of the early life stages were imprecise and had a large 95% confidence interval of considered to be reliable predictors of potential future 0-41 thousand. Using another methodology, female year-class strength.

spawner abundance in 2007 was estimated at 2.1 The number of larvae entrained is a measure of thousand. Other annual estimates ranged from potential impact to winter flounder. In most years, approximately 1.6 thousand females in 2006 to 75 Stage 3 larvae predominated in entrainment collec-thousand in 1982 and corresponding total egg tions. Annual estimates of entrainment are related to production estimates were 1.1 to 44.8 billion. During both larval densities in Niantic Bay and MPS the past 26 years, Niantic River winter flounder abun- operation. The 2007 entrainment estimate of about dance represented an estimated 0.4 to 3.3% of the 145 million reflected relatively, moderate larval entire LIS winter flounder resource. densities and lowest cooling-water volume at Units 2 In 2007, overall density of Stage 1 (newly hatched) and 3 since 1999. The low cooling-water usage this larvae in the Niantic River fell into the lower one- year and the 1996 retirement of Unit 1 reduced third of the time-series of values since 1983. In potential MPS entrainment by an estimated 144 contrast, similar to the estimate in 2006, Stage 1 million larvae.

abundance reached a record high in Niantic Bay. Annual entrainment density (abundance index Since 1995, more Stage I larvae were found than divided by total seawater volume) has varied without expected from low adult spawner abundance, trend since 1976, indicating that larval production suggesting a density-dependent compensatory mech- and availability in Niantic Bay remained relatively anism during the egg stage enhancing their survival. stable despite increased water use during the 1986-95 This has been attributed to reduced predation on eggs period of three-unit operation and reduced cooling-by sevenspine bay shrimp, such that when egg water demand in 1995-97. Correlations between densities are low, higher egg survival produces more entrainment estimates and abundance indices of post-Stage 1 larvae. Density-dependent mortality is also entrainment age-0 juveniles were positive. This present throughout the larval period of life, as an implies no entrainment effect as the more larvae that Executive Summary v

ii were available to be entrained, the more larvae that Similarly, no long-term trends were identified in metamorphosed and settled in Niantic River and Bay. various life stages of grubby. Atlantic menhaden This was also demonstrated by a comparison of larvae showed a significantly increasing trend in annual entrainment and juvenile year-class abun- abundance, as did juveniles taken by seine and trawl.

dance, which suggested that entrainment estimates Densities of both anchovy eggs and larvae during were simply a measure of emerging year-class 2007 continued to show significant negative trends.

strength. Thus, entrainment is not the most important The bay anchovy has experienced a regional decline factor in determining juvenile abundance. in abundance. This species is important forage for The potential impact of larval entrainment on the predatory fishes and birds. In particular, the striped Niantic River stock depends upon the fraction of the bass has recently increased in abundance along the annual winter flounder reproduction entrained each Atlantic coast and may have contributed to reduced year (termed production lo ss in this report), which numbers of bay anchovy.

was calculated as equivalent eggs removed by Data collected during 2007 continued to show no entrainment. Empirical mass-balance model calcu- long-term abundance trends in the numbers of lations showed that a large number of entrained entrained cunner and tautog eggs and larvae.

larvae came from a number of sources in LIS besides Juvenile and adult cunner and tautog have the Niantic River. Based on the increase in egg significantly decreased at the Intake trawl station, but survival noted in recent years, a factor that was not the decline was attributed to the 1983 removal of the originally incorporated into the mass-balance model, Unit 3 intake cofferdam, a preferred habitat for these most production loss estimates after 1994 are species. Since that time, no significant abundance conservatively high. Correcting the estimates made trend was found from 1984 through 2007. Cunner since 1995 by using a higher egg survival rate abundance significantly increased at the Niantic resulted in lower production loss estimates (revised River trawl station and continued to fluctuate without long-term mean = 11.6%). trend at Jordan Cove. The combined catches of The small adult spawning stock in the river juvenile and adult tautog collected at the three trawl continues to produce relatively large numbers of stations increased, probably as a result of more larvae and young fish, which likely resulted from restrictive fishing regulations. Significant increases population compensatory mechanisms. Despite rela- in tautog abundance were found in Niantic River tively good abundance of age-0 winter flounder (a life trawl catches and in both Jordan Cove trawl and stage not entrained) in many recent years, significant lobster pot catches.

recruitment to the adult spawning population has not Changes in the species composition and temporal occurred. Processes that are unrelated to MPS and spatial abundance of fishes and shellfishes operation and which occur after juvenile winter collected by trawl over the past 31 years appeared to flounder leave shallow nursery waters during the fall be unrelated to MPS operation. Shifts in the of their first year of life seem to be operating to dominance of individual taxa were attributed to produce fewer adults. A bottleneck, probably from changes in habitat, range extensions or contractions, predation, appears to be occurring during the late and warmer ambient seawater temperatures occurring juvenile life stage (ages-I and 2). Environmental over the past 3 decades.

effects, including changes to the Niantic River habitat Cooling-water use at MPS was reduced 23% from (e.g., increased eelgrass abundance), a warming water the shutdown of Unit 1 in 1995, resulting in less temperature trend, and interactions with other species entrainment and impingement. Fish return systems at (e.g., predation), especially during early life history, Units 2 (2000) and 3 (1986) further reduce are also important processes affecting winter flounder ,impingement mortality at MPS. Based on the lack of population dynamics. decreasing trends for selected taxa except anchovies, for which there are other causes, MPS has had Fish Ecology Studies minimal effect on local fish and shellfish assemblages.

Monitoring during 2007 indicated that no long-term abundance trends in various life stages of seven Lobster Studies selected taxa could be directly related to the operation of MPS. No significant long-term trends were Impacts associated with recent MPS operations on detected in populations of American sand lance the local lobster population were assessed by larvae collected in entrainment samples and juvenile comparing results of the 2007 study to data collected or adult silversides collected by trawl or seine. from 1978 through 2006. Emphasis has been placed on vi Monitoring Studies, 2007

'~ n:4~i assessing long-term trends in the abundance and 150 m of shore-line on the east -side of the power population characteristics of lobsters collected in the plant discharge to LIS.

Millstone Point area. Seasonal shifts in occurrence of annual algal Throughout LIS, the lobster population was stable or species were noted at Fox .Island-Exposed (FE) increasing from 1978 through 1999. The abundance of during 2007. These shifts included abbreviated lobsters in LIS was lower from 2000 to 2007, but season for cold-water species (e.g., Monostroma unrelated to MPS operations. Rather, the lobster grevillei, Spongomorpha arcta, and Dumontia abundance declines were attributed to a significant contorta),Yand extended season for warm-water mortality event in western LIS and to an outbreak of species (e.g., Grinnellia americana, Dasya shell disease affecting lobster populations from eastern baillouviana,and Bryopsis hypnoides). Similar shifts LIS to the Gulf of Maine. In the MPS area, no have been observed in most years since Unit 3 began significant long-term trends were identified in the operation (1986), with the exception of the extended annual CPUE of lobsters (combined over all sizes and shutdown of all MPS reactors from March 1996 to stations) collected either in pots or by trawl. The total June 1998 when seasonality of these species at FE pot-CPUE of lobsters at the three monitoring stations during the recent' shutdown period was more typical has varied without trend since 1978. However, annual of other sites.

CPUE of legal-size lobster has exhibited a significant Thermal effects on dominant species abundance and declining trend at the Jordan Cove and Twotree distribution patterns were also evident at FE in 2007 stations, but not at the Intake station located nearby and most apparent in the low intertidal zone.

MPS. Significant declines in the abundance of legal- Seasonally high abundance of Hypnea musciformis, a size lobsters were due in part to shell disease and to a 3 species observed for the first time in 2001, and mm increase in the minimum legal size since 1978. Of expanded populations of Sargassum filipendula, note, the abundance of legal-size lobsters harvested by Corallina officinalis, and Gelidium pusillum now commercial fishers in our area increased over the past characterize the lower shore community at FE.

few years, although lobster catches remained depressed Polysiphonia spp. maintained a perennial population in other areas of LIS. at FE in 2007, but occurred mainly as a summer Long-term trends observed in lobster population annual at sites unaffected by MPS.

characteristics over the past 30 years (growth, female Ascophyllum nodosum growth during 2006-07 maturity and egg-bearing lobsters), were related to continued to exhibit no clear relationships among our warmer ambient seawater temperature and/or the monitoring stations, nor correlation with plant recent outbreak of shell disease, and not MPS operating conditions, indicating that the thermal plume operation. Increased ambient water temperature may from MPS had little effect on local populations.

be responsible for the increased susceptibility and Natural influences of other factors such as ambient transmission of diseases affecting lobsters in LIS, temperature conditions, storms and wave action, which are near their southern range of distribution in nutrients and light play the dominant role in nearshore waters. determining Ascophyllum growing conditions in the The number of lobster larvae entrained through the Millstone area.

MPS cooling water systems was highly variable and The rocky intertidal monitoring program has also has not resulted in a decrease in local lobster documented regional patterns and modifications to abundance. Impacts associated with entrainment and shore communities unrelated to MPS operation.

impingement of lobsters at MPS have been greatly These include the introduction to the region of two reduced by the shutdown of Unit 1, which eliminated exotic red algae, Antithamnion pectinatum in 1986 23% of the cooling water used, and the installation of and Grateloupia turuturu in 2004, decreases in aquatic organism return systems at Units 2 and 3, barnacle abundance in recent years, and a long-term which return impinged lobsters to Niantic Bay. increase in abundance of the common brown rockweed, Fucus vesiculosus. One phenomenon Rocky Intertidal Studies observed in 2007 was the deposition of a large quantity of sand onto low intertidal areas of White Rocky intertidal monitoring studies during 2007 Point, resulting from spring storms, temporarily continued to document ecological changes to the burying algae and rock surfaces. The effect was shore community near to, and associated with, the temporary, however, as subsequent redistribution of MPS thermal discharge. These changes are not the sand permitted the more typical community to re-widespread, and remain restricted to approximately emerge.

Executive Summary vii

Eelgrass silt/clay estimates at Jordan Cove (JC) have remained relatively consistent since the changes observed in Eelgrass (Zostera marina L.) population dynamics 1986, and sedimentary parameters at the reference were monitored during summer from 1985 to 2007 at station Giants Neck (GN) were within the limits of three locations near MPS. although some lofig-term previous observations and continue to exhibit declines in one or more eelgrass population variability unrelated to MPS. Community abundance parameters (e.g., shoot density, shoot length, and and numbers of species at all sampling stations in 2007 standing stock biomass) were observed at all three increased from the low values observed in 2006.

areas monitored over the entire 22-year study period, Surface deposit-feeding oligochaetes and polychaetes monitoring results from 2007 indicate population were the dominant organisms at all stations in 2007.

improvement at all sites, continuing trends observed Observed changes in abundance of infaunal taxa over the last 3 or more years. Eelgrass populations at resulted in rank order changes among the dominant two monitoring sites to the east of MPS, near the taxa at all stations but overall, benthic communities fringes of the thermal plume (<1.5 km from the MPS sampled in 2007 were comprised of fauna that had discharge to LIS), exhibited gradual declines since been present in previous years. Multivariate analyses 1985. These declines were not associated with MPS showed higher community similarity among recent operation, as thermal input from the cooling water years and changes in community composition from the discharge to these sites is at most minimal (<IC samples before the disturbances at IN and JC. Changes above ambient conditions). in community similarity from early sampling years to By comparison, heavy, often sudden, eelgrass more recent years were also observed at EF that is losses were documented on five separate occasions continuously affected by discharge of station cooling prior to 2000 in the Niantic River. This estuary is water. The reference station GN where the effects of located well beyond (>2 km) waters influenced by the MPS are not present has also exhibited temporal MPS thermal discharge. Since 2001, eelgrass changes in benthic community from earlier to more distribution in the Niantic River has expanded, and recent years. Temporal and spatial variation in the gradual, steady increases in shoot density, shoot MPS benthic communities observed 2007 are typical of length, and biomass were observed through 2007. In near-shore marine environments. During 2007, there previous years, three short-term declines in eelgrass were no unusual events that impacted benthic infaunal abundance have been directly associated with fouling communities. Under current environmental conditions and overgrowth of eelgrass; once by blue mussels the infaunal communities appear relatively stable.

(Mytilus edulis) at the Niantic River in 1992, and twice by blooms of green algae (Cladophoraspp.) at White Point in 1991 and 2004. Recent research suggests nutrient loading from land-based sources as the cause of eelgrass disappearance in LIS to the west and elsewhere. Excess nutrients, coupled with increases in regional water temperature and 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.

Benthic Infauna Benthic infaunal monitoring during 2007 documented small changes to sediment composition at the Effluent (EF) and Intake (IN) stations in the vicinity of MPS. In general, sediments at these stations were coarser (larger mean grain size) and the silt/clay fraction was smaller.

The sediments at EF and IN will continue to be affected by the discharge of cooling water (EF) and the intake of cooling water (IN). Mean grain size and viii Monitoring Studies, 2007