ML101310232
| ML101310232 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 04/27/2010 |
| From: | Macmanus R Dominion, Dominion Nuclear Connecticut |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 10-195, FOIA/PA-2011-0115 | |
| Download: ML101310232 (13) | |
Text
S1Dominion Dominion Nuclear Connecticut, Inc.
Millstone Power Station Rope Ferry Road Waterford, CT 06385 APR 2 ' 2.010 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555-0001 Serial No.
MPS Lic/GJC Docket Nos.
License Nos.10-195 R0 50-423 NPF-49 DOMINION NUCLEAR CONNECTICUT. INC.
MILLSTONE ;POWER STATION UNIT 3 2009 ANNUAL ENVIRONMENTAL PROTECTION PLAN OPERATING REPORT In accordance with Section 5.41 'of the Environmental Protection Plan (EPP), Appendix B to the Millstone Power.Station Unit 3 Operating License, Dominion Nuclear Connecticut, Inc. hereby submits-the Annual:Environmental Protection. Plan Operating Report (AEPPOR), describing implementation of the EPP for the previous year. transmits information for the period of January 1, 2009 to December 31, 2009.
Should you have any questions regarding this report, please contact Mr. William -Bartron, at (860) 447-1791, extension 4301.
Sincerely, R. K. MacManus Director, Nuclear Station Safety and Licensing
Serial No.10-195 2009 Annual Environmental Protection Plan Operating 'Report Page 2 of 2
Enclosures:
1 Commitments made in this letter: None.
cc:
U.S. Nuclear Regulatory Commission Region I 475 Allendale Road King of Prussia, PA 19406-1415 Ms. C. J. Sanders NRC Project Manager U.S. Nuclear Regulatory Commission One White Flint North, Mail Stop 8B3 11555 Rockville Pike Rockville, MD 20852-2738 NRC Senior Resident Inspector Millstone Power Station
Serial No.10-194 Docket Nos. 50-245 50-336 50-423 License Nos. DPR-21 DPR-65 NPF-49 ATTACHMENT 1 2009 ANNUAL RADIOLOGICAL ENVIRONMENTAL OPERATING REPORT.
MILLSTONE POWER STATION UNITS 1, 2, AND 3 DOMINION NUCLEAR CONNECTICUT, INC. (DNC)
Annual Environmental Protection Plan Operating Report January I - December 31, 2009 Millstone Power Station Unit 3 Environmental Protection Plan Dominion Nuclear Connecticut, Inc.
Millstone Power Station Rope Ferry Road Waterford, Connecticut 06385 April 2010
.2009 Annual Environmental Protection Plan Operating Report (AEPPOR) 1.
Introduction:
This report covers the period January 1, 2009 through December 31, 2009. During 2009, Millstone Power Station Unit 3 (MPS3) operated at a capacity factor of 97.6%;
the current cycle 13 (from'the end of the latest refueling outage (11/24/08) through 12/31/09) capacity factor was 98.5%.
As required by the MPS3 Environmental Protection Plan (EPP), Appendix B to the Millstone Power Station Unit 3 Operating License, this AEPPOR includes:
summaries and analyses of the results of environmental protection activities,
-a list of EPP noncompliances, a-list of all changes in station design or operation which involved a potentially significant unreviewed environmental question, and
- a list of non-routine reports, describing events which could have resulted in significant environmental impact.
- 2. Environmental Protection Activities:
2.1 Annual National Pollutant Discharge Elimination System (NPDES) Report of Ecological Monitoring (EPP Section 4.2).
Paragraph 5 of the Millstone Power Station (MPS) NPDES permit, issued to Dominion Nuclear Connecticut, Inc. (DNC), requires continuation of biological
.studies of supplying and receiving waters, entrainment, and intake impingement monitoring. These studies include analyses of intertidal and subtidal benthic communities, finfish communities, entrained plankton, lobster populations, and winter flounder populations. Paragraph 7 of the NPDES permit requires an annual report of these studies to be sent to the Commissioner of the Connecticut Department of Environmental Protection (DEP). The report which fulfills these requirements for 2009, "Annual Report 2009 - Monitoring the Marine Environment of Long Island Sound at Millstone Power Station,
.Waterford, Connecticut" (Annual Report), presents results from studies performed during construction and operation of MPS, emphasizing those of the latest sampling year. Changes to the biological communities noted in these studies are summarized in the Executive Summary section of the Annual Report, submitted in April 2010, which is attached as part of this report.
2.2 Effluent Water Quality Monitoring:
Paragraph 3 of the MPS NPDES permit requires monitoring and recording of various water quality parameters at MPS intakes and at multiple monitoring points within the plant, including outfalls of each unit to the effluent quarry, and outfall of the quarry to Long Island Sound. Paragraph 11 of the NPDES permit requires a monthly report of this monitoring to the Commissioner of the Connecticut DEP. The report which fulfills these requirements, the "Monthly Discharge Monitoring Report" (DMR), includes data from all MPS units.
Consistent with prior annual AEPPOR submissions, water flow, temperature, pH, and chlorine data pertaining to MPS3 are summarized in Table 1.
2009 AEPPOR Page 1 of 4
Each monthly DMR identifies NPDES permit exceedances (i.e., events where a parameter value was beyond permitted limits) or exceptions (i.e., events where NPDES permit conditions were not met) for the month. There were no NPDES exceedances or exceptionsfor MPS3 circulating or service water discharges reported in 2009.
Information pertaining to events which occurred in 2009 and were reported to the DEP in the monthly DMRs, while unrelated to MPS3's cooling water
'discharge but containing wastewater inputs from MPS3, are summarized from the February and March 2009 DMRs as follows. Both events described below relate to discharges from discharge serial number (DSN) 006 (MPS2 & MPS3 non-contaminated floor drains):
a) On February 4, 2009 at 1119, during fire water sprinkler header flow testing in the"MPS3 turbine building (TB), a sprinkler head was found to be spraying water in the east side of the TB. Operations personnel isolated and drained-the firewater system to the TB floor drains. As part of the response to the sprinkler head leak, chemistry personnel performed total residual chlorine (TRC) sampling of the TB sump (drains to DSN 006) to ensure compliance with the Permit. Results of the sump were < 0.03 mg/L TRC.
Later that day, at 1907 through 2042, the inline pH instrumentation associated with the plant process computer (PPC) and the environmental data acquisition network (EDAN) recorded DSN 006 discharge pH results greater than the Permit limit of 9.0 standard units (su). At 1910, MPS3 chemistry personnel performed confirmatory grab sampling for discharge pH at DSN 006. The result of confirmatory sampling was 9.51 su. The MPS3 TB sump was immediately isolated from discharging to DSN 006. The MPS3 condenser pit and TB sump pits were analyzed and pH was determined. to be 9.5 su and 10.0 su, respectively. To maintain the level in the TB sump, the MPS3 operations department aligned the sump to the MPS3 liquid radioactive waste system for processing as authorized by the NPDES Permit CT0003263. Additionally, some of the contents of the TB sump were pumped to totes for future disposition.
As part of the initial corrective actions and investigation, the MPS2 chemistry department was contacted to perform confirmatory sampling of the MPS2 east and west TB sumps (both drain to DSN 006 via an inline granular activated carbon filter and oil water separator). The results of the sampling at 2050 were 7.70 su and 9.12 su, respectively, and are based on incidental leakage of MPS2 secondary side and closed cooling water systems, along with groundwater in-leakage. The General Electric (GE) makeup water facility discharge (drains to DSN 006) was verified to be operating within limits.
After verifying all inputs to DSN 006 to be within NPDES Permit limits, on February 5, 2009 at 1815, the TB sump was aligned to DSN 006.
2009 AEPPOR Page 2 of 4
I¸I$
b) On March 16, 2009 at 1315, draining the "A" MPS3 generator step-up (GSU) transformer pit was initiated for the first time to discharge accumulated rain water and/or snow melt. MPS had received authorization from the DEP on September 25, 2008 to tie the three MPS3 GSU transformer pits into the existing yard drain system via the oil water separator associated with the MPS2 GSU transformers, which ultimately drains to DSN 006. The steps for performing this draining evolution were incorporated into the appropriate MPS3 operations department procedure.
While draining the "A" pit, the continuous inline pH monitor at DSN 006 started rapidly increasing from a pH of 7.09 su to a peak pH of 9.66 su at 1352. At 1331, draining of the "A" GSU. pit was halted. At 1343, a confirmatory grab sample at DSN 006 was 9.95 su. An additional confirmatory pH analysis was performed on the "A" pit contents at 1400.
The resulting pH was 10.35 su. At approximately 1428, with the "A" GSU transformer pit discharge isolated, the inline pH at DSN 006 trended below 9.0 su. As corrective actions, all valves associated with the three MPS3 GSU transformer pits were safety tagged closed and all water located in the three MPS3 GSU transformer pits was pumped to tanker trucks-for offsite disposal as Connecticut regulated waste.
2.3 NPDES Permit Renewal Process:
The MPS NPDES permit renewal process is continuing. Significant events during 2009 included 18 days of testimony during the evidentiary hearing held in January and February, and the post-hearing briefs and memoranda submitted in May.
- 3. Environmental Protection Plan (EPP) Noncompliances:
No EPP noncompliances were identified for MPS3 in 2009.
- 4. Environmentally Significant Changes to Station Design or Operation:
No MPS3 design change records or system operating procedure changes met the criteria for inclusion in this report, i.e.,
" were initiated during the report year, and included a determination that a significant unreviewed environmental impact could occur.
Environmental reviews performed in 2009 included assessment of the variable frequency drives (VFDs) for MPS3 circulating water pumps; installation and operation of these VFDs will be in accordance with all appropriate permits.
- 5. Non-Routine Reports of Environmentally Significant Events:
No MPS3 events met the criteria for inclusion in this year's report, i.e.,
required the submittal of a Licensee Event Report (LER), and involved a situation that could result in a significant environmental impact.
Only two licensee events that constituted a reportable event at MPS3 occurred in 2009; one involved a security issue, and the other involved the MPS3 reactor trip on December 19. Both events were determined not to cause a significant environmental impact.
2009 AEPPOR Page 3 of 4
Table I Summary, Jan. 1 - Dec. 31, 2009. Selected water quality parameters MPS3 NPDES Data for MPS3(1).
Jan.
Feb.
Mar.
Apr.
May June July Aug.
Sep.
Oct.
Nov.
Dec.
Discharge Flow (max)
(106 gpd) 1357.0 1356.6 1357.4 1356.8 1357.5 1357.3 1357.2 1357.1 1357.4 1356.9 1357.0 1356.8 Discharge
-PH
'Range 7.9-8.1 7.9-8.1 7.9-8.2 7.9-8.1 7.9-8.1 7.8-8.1 7.9-8.1 8.0-8.2 8.0-8.2 7.9-8.1 7.7-8.0 7.9-8.0 Discharge Temp.
Range (OF) 55.3-63.4 54.0-61.5 53.6-62.9 58.8-69.0 66.5-77.1 71.7-83.8 79.5-89.1 84.2-94.4 83.9-88.3 72.4-85.4 69.2-80.3 40.1-77.1 Discharge Temp.
(avg)
(OF) 58.5 57.3 58.3 63.6 70.4 76.6 83.1 87.6 86.0 78.9 73.8 58.7 Avg AT (OF)
Max FAC (ppm)
Max TRC (ppm) 19.0 18.9 18.3 18.2 17.9 16.9 17.2 17.9 18.1 18.3 19.3 12.7 0.15 0.14 0.10 0.13 0.17 0.12 0.06 0.07 0.10 0.10 0.13 0.14
< 0.03
< 0.03
< 0.03 0.04 0.04 0.03 0.04 0.04 0.04 0.03
< 0.03
< 0.03 Max SWS FAC (ppm) 0.23 0.19 0.19 0.20 0.17 0.17 0.22 0.17 0.19 0.17 0.19 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 =
Service Water System 2009 AEPPOR Page 4 of 4
Attachment to the 2009 Annual Environmental Protection Plan Operating Report January 1 - December 31, 2009 Executive Summary Section-of "Annual Report 2009 - Monitoring the Marine Environment of Long Island Sound
.at Millstone Power Station, Waterford, Connecticut" dated April 2010
Executive Summary Winter Flounder Studies Various life history stages of winter flounder have been monitored since 1976 as the local Niantic River
,population may be affected by the operation' of Millstone Power Station (MPS), particularly through the entrainment of larvae. During the past 28 years, annual Niantic River adult winter flounder abundance represented an estimated 0.4 to 3.3% of the total LIS winter flounder resource (mean =.1.34%). Over the past 15 years, low abundance levels have been found-throughout Long Island Sound (LIS) by the
'Connecticut Department of Environmental Protection (CTDEP). During the same'time' period, adult winter' flounder abundance -in the Niantic River has S.remained low.
Reflecting these trends, catch-per-unit-effort (CPUE)"in 2009 was 0.3 fish per trawl
-tow, the smallest value of the time-series.
An absolute abundance estimate of the 2008
-spawning population (the latest year for which an estimate could be made) using-the Jolly model was' not calculated due to a lack of *recaptures of previously marked fish.
The last three absolute
- abundance estimates were imprecise, having large 95% confidence intervals, and are not considered reliable.
Using another methodology termed' standardized catch, female spawner abundance in 2009 was esti-
-mated at only '323 fish that produced about 238 million eggs. 'Previous annual standardized catch estimates ranged from approximately 987 females in 2008 to 75 thousand in 1982 and corresponding total egg production estimates were 0.7 to 44.8 billion.
In 2009, overall abundance of winter flounder larvae in -the Niantic River was the second lowest since 1983, exceeding only 2008. The Niantic Bay abundance index ranked within the lower one-third of its time-series. In most years since 1995, more Stage 1 larvae were found than expected from 'low adult spawner abundance, suggesting a density-dependent compensatory mechanism during the egg stage that enhanced survival.
Density-dependent mortality
!occurs throughout the larval period of life.
An analysis suggested that mortality decreases with decreasing egg production (a measure'of early larval abundance). Larval mortality is also influenced by prevailing water temperatures, with warmer springs allowing for faster development and lower mortality.
In 2009, Stage 2 larval abundance was particularly low, indicating high mortality in that stage. In each of the past 2 years, both egg production and Stage 1 larval abundance were low as were the numbers of metamorphosing larvae.
However, relative to the
'Niantic River, 'larval abundance in Niantic Bay has increased 'in recent
- years, suggesting higher
'.production in LIS rather than in estuaries such as the Niantic River.
Densities of age-0 young. in the Niantic River
.following larval metamorphosis and settlement were
- 'linearly related to Stage 4 larval abundance at low to moderate levels.
However, at higher larval abun-dance juvenile densities apparently reached an
-asymptote of about 250 young per 100 m 2 of bottom, which could represent the carrying capacity of the river habitat. As expected from low larval abundance in 2009, initial settled juvenile abundance was very low. Even with a lower than average mortality rate,
.late summer abundance was the second lowest on record, exceeding 'only 2006.
There were non-significant or negative correlations between CPUE
'indices of age-0--fish and the abundance of female adult spawners 3 to 5 years later.
Conversely, positive correlations were found between age-I abundance indices and older fish.
The number of larvae entrained at MPS is a measure of potential impact-to winter flounder. In most years, Stage 3 larvae 'dominated entrainment collections. Annual estimates of entrainment are related-to both larval densities in Niantic Bay and
.MPS cooling-water volume.
With no spring refueling outage in 2009, the 2009 entrainment estimate of about 152 million reflected moderate Niantic Bay larval densities.
Annual entrainment density (abundance index divided by total seawater volume) has varied without trend since 1976, indicating that larval production and availability in Niantic Bay remained relatively
- stable despite increased water use during the 1986-95 period of three-unit operation and reduced cooling-water demand in 1995-97.
Correlations between entrainment estimates and abundance indices of post-entrainment age-0 juveniles -were positive.
This implies no entrainment effect, as the more larvae that were available for entrainment, the more larvae metamorphosed and settled in Niantic River and Bay.
This was also demonstrated by a comparison of annual entrainment and juvenile year-class abun-dance, which suggested that entrainment estimates were simply a measure of emerging year-class strength.
Thus, entrainment is not an important factor in determining juvenile abundance.
Executive Summary v
.1~
The potential, impact of larval entrainment on the Niantic River stock depends upon the fraction of the
.annual winter flounder, reproduction entrained each
--yeaf (termed production loss in this report), which was calculated as equivalent eggs removed by
- entrainment. Empirical mass-balance model calcu-lations showed that a large number, of entrained.
larvae came. from a number of sources,in LIS besides the Niantic River. In 2009, -approximately 22% of the entrained larvae were attributed to the -river.
Based on the increase in egg survival noted in recent.
- years, production loss estimates, after 1994 were, conservatively high.
Correcting the post-1994 estimates using a higher egg survival rate resulted in.
lower production loss estimates (long-term mean =
10.7%).
However the production loss. estimate in 2009 was implausibly
- large, suggesting an.*
underestimate of egg production or an overestimate.
of larvae entrained
- from* - the Niantic River.
Increasing larval production in LIS and importation into local waters could have accounted for much of the discrepancy between the 2009.and long-term average production losses.
Despite a small adult spawning stock in the river,
-there have nonetheless been relatively large numbers-of larvae and-young fish in several recent years, probably from population compensatory mechanisms and possibly greater contributions from spawners outside of the Niantic River. Relatively good abun-
.dance.of age-0 winter flounder (a life stage not entrained) occurred in some recent years, yet significant recruitment to - the adult
- spawning, population did not occur. Processes that are unre-
.lated to MPS operation and which occur after juvenile winter flounder leave shallow nursery waters during the fall of their first year of life seem to be operating to account for fewer adults. A bottleneck appears to be occurring during the late juvenile life stage (ages-i and 2),,probably from predation.
Environmental effects, including changes to the Niantic River habitat (e.g.,
increased eelgrass abundance), a warming trend in regional seawater temperature, and interactions with other species (e.g.,
predation), especially during early life history, are also important processes affecting winter flounder population dynamics. Weak year-classes produced in 2006-09 are indications of likely continued low recruitment to the Niantic River spawning population in forthcoming years.
Fish Ecology Studies Monitoring during 2009 indicated that no long-term abundance trends in various life stages of seven selected taxa could be directly related to the operation of MPS. No significant long-term trends were detected in populations of juvenile or adult silversides collected by trawl or seine. Similarly, no long-term trends were identified in various life stages of grubby, cunner, and tautog. Atlantic menhaden larvae showed a significantly increasing trend in abundance, as did juveniles taken by seine and trawl.
Densities of both anchovy eggs and larvae and American sand lance larvae continued to show significant negative trends.
The bay anchovy has experienced a regional decline in abundance.
This species is important forage for predatory fishes and
- birds.
In particular, the striped bass has recently increased in abundance along the Atlantic coast and may have contributed to reduced numbers of bay
'anchovy. Abundance of American sand lance larvae has been relatively stable over the past 25 years
.following a decline -that occurred during the early 1980s.
These changes were most likely due to interactions with fishes that prey upon larval sand lance.
Data collected in 2009 continue to show no long-term abundance trends in the numbers of entrained cunner eggs and larvae. Juvenile and adult cunner have significantly decreased at the Intake trawl
.station, but the decline was attributed to the 1983 removal of the Unit 3-intake cofferdam, a preferred reef-like habitat for this species. Since that time, no*
significant abundance trend was found from 1984 through 2009.
Cunner abundance significantly
-.increased at the Niantic River trawl station and
,continued to fluctuate without trend at Jordan Cove.
- Tautog larvae showed a significant increasing trend in abundance and a significant rise in the abundance of juveniles and adults was also noted in the trawl and lobster pot catches.
Changes in the species composition and temporal and spatial abundance of fishes and shellfishes collected by trawl over the past 33 years were unrelated to MPS operation.. Shifts in the dominance of individual taxa were attributed to changes in
-habitat, range extensions or contractions, and a warming trend in ambient seawater temperature that has occurred over the past 3 decades.
Cooling-water use at MPS was reduced 23%
because of the shutdown of Unit 1 in November 1995, resulting in less entrainment and impingement.
Fish return systems at Units 2 (2000) and 3 (1986) further reduce impingement mortality at MPS.
Increasing trends in abundance or the lack of decreasing trends suggests that MPS has had minimal, if any, effect on local fish and shellfish assemblages.
vi Monitoring Studies, 2009
LobsterStudies Impacts associated with recent MPS operations on the local lobster population were' assessed by comparing results of the 2009 study to data collected from 1978 through 2008. Emphasis'has been placed on assessing long-term trends-in the abundance and population characteristics of lobsters collected in the Millstone Point area.
Throughout LIS, the lobster population was stable or increasing from 1978 through 1999. The abundance of
-lobsters in LIS was -lower from 2000 to 2009, but unrelated to MPS operations' Rather, the' lobster
-abundance -declines -were attributed-to a significant mortality event in Western LIS and -to an outbreak of
In the MPS area, no
-significant long-term trends were identified in :the annual CPUE of lobsters (combined over all sizes and stations) collected either in pots or by trawl. The total
-pot-CPUE-'of lobsters at the three monitoring stations has varied without trend since 1978. However, annual CPUE of legal-size lobster has exhibited a significant declining trend at the Jordan Cove and Twotree stations, but not at -the Intake *station located nearby
'MPS. Significant declines in the abundance of legal-
.-size lobsters were attributed in part to shell disease and to a 3 mm increase in the minimum legal size since 1978.
Long-term trends observed in lobster population characteristics over the past three decades (growth, female maturity and egg-bearing lobsters) appear related to warmer ambient seawater temperatures and/or the recent outbreak of shell disease, and not MPS operation. Increased ambient water temperature
-,may be responsible for the increased susceptibility and transmission of diseases affecting lobsters in LIS, which are near their southern range of distribution in nearshore waters.
The number of lobster larvae entrained through the MPS cooling water systems was highly variable and has not resulted in a decrease in local lobster abundance. Impacts associated with entrainment and impingement of lobsters at MPS have been greatly reduced by the shutdown of Unit 1, which eliminated' 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.
Rocky Intertidal Studies Rocky intertidal monitoring studies during 2009 continued to document ecological changes to the shore community near, and associated with, the MPS thermal discharge.
These changes are not widespread, and remain restricted to approximately 150 m of shore-line on the east side of the power station discharge to LIS.
Seasonal shifts in occurrence of annual algal species were noted at Fox Island-Exposed (FE)
'during 2009.
These shifts included abbreviated season for cold-water species (e.g., Monostroma
,grevillei, Spongomorpha arcta, and Dumontia contorta) and extended season for warm-water species (e.g.,
Grinnellia americana, Dasya
'baillouviana, and Bryopsis hypnoides). Similar shifts have been observed in most years since Unit 3 began operation (1986), with the exception of the extended
. shutdown of all MPS reactors from March 1996 to June 1998 when seasonality of these species at FE during the recent shutdown period was more typical
.of other sites.
Thermal effects on dominant species abundance
-and distribution patterns were also evident at FE in 2009 and most apparent in the low intertidal zone.
Seasonally high abundance of Hypnea musciformis, a species observed for the first time in 2001, and expanded populations of Sargassum filipendula, Corallina officinalis, and Gelidium pusillum now characterize the lower shore community at FE.
'Neosiphonia (formerly Polysiphonia) harveyi
-maintained a perennial population at FE in 2009, but occurred mainly -as a summer annual at sites unaffected bylMPS.
Ascophyllum nodosum growth during 2008-09 continued to exhibit -no clear relationships among our monitoring stations, or correlation with plant operating
.conditions, indicating that the thermal, plume from MPS has had little effect on local populations. Natural influences of -other 'factors, such as ambient temperature conditions, storms and wave action, nutrients and light, play the dominant role in determining Ascophyllum growing conditions in the Millstone area.
The rocky intertidal monitoring program has also documented regional patterns and modifications to shore communities unrelated to MPS operation.
These include the introduction to the region of two exotic red algae (Antithamnion pectinatum in 1986 and Grateloupia turuturu in 2004), decreases in barnacle abundance in recent years, and long-term increases in abundance of the common seaweeds Fucus vesiculosus and Chondrus crispus.
Eelgrass Eelgrass (Zostera marina L.) populations were monitored from 1985 to 2009 at three locations in the vicinity of MPS. Data from 2009 surveys indicated that at all three study sites supported healthy and Executive Summary vii
expansive eelgrass populations, consistent with results from the past 6-7 years. These populations have also exhibited variability in 'population parameters (e~g., shoot density, shoot length, and standing stock biomass) and distribution over the entire 25-year study period, but this variability was not related to MPS operation. Eelgrass populations at
.two monitoring sites to the east of MPS (Jordan Cove I-JC and White.Point - WP) near. the fringes of the
-thermal plume (< 1.5 km from the MPS discharge to LIS) have exhibited moderate variability and-subtle declines in some population parameters since 1985.
However, both predicted and measured thermal input from the cooling water discharge to these sites is at most minimal (< IVC above ambient conditions) and well below levels considered stressful to eelgrass.
By comparison, high eelgrass population variability
-.has been observed inthe Niantic River, (NR), where complete and often sudden eelgrass bed losses were
-documented on five separate occasions prior to 2000.
.This estuary is located well beyond (> 2 km) waters
- influenced by the MPS thermal discharge.. Since
- 2001, eelgrass distribution in the Niantic River has expanded, with a gradual, steady increase in shoot
,density through 2009.
Ongoing extensions of
,municipal sewerage lines in the Niantic River watershed, possibly coupled with depletion of
.nutrient inputs from old septic systems, may be contributing to population recovery during the last 8 years.
In previous years, three short-term declines in
- eelgrass abundance have been directly associated
,-with fouling and overgrowth of eelgrass: once by
-blue mussels (Mytilus edulis) at the NR site in 1992 and -twice by blooms of green algae (Cladophora spp.) at the WP site in 1991 and 2004.
Recent.
.research from New England and mid-Atlantic states
'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 temperatures 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 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 intermediate when compared to historical ranges. Surface deposit-feeding oligochaetes and polychaetes were the dominant organisms at all stations in 2009.
The suspension-feeders Mytilus edulis and Spiochaetoperus oculatus were a notable feeding type only at EF in
'2009.
Observed changes in abundance of infaunal taxa resulted 'in.rank order changes among the dominant taxa at all stations, but overall, benthic communities sampled in 2009 were generally comprised of fauna that had been present in previous years.
Multivariate analyses showed higher community, similarity among recent years and illustrated more abrupt changes in community composition in earlier study years related to sediment disturbances related to MPS construction (dredging
.and cofferdam removal at IN) and operation (silt deposition from increased discharge flow at JC).
- Steady temporal changes in community composition were observed at EF, a location that has been continuously affected by MPS cooling water discharge flow since 1986. The GN reference station, beyond any MPS influence, has also exhibited temporal changes in benthic community structure during the study period. These changes were related to natural variability and other factors unrelated to MPS operation (e.g., ambient seawater temperature increase, storm events). Temporal and spatial variation in the MPS benthic communities observed is typical of near-shore marine environments. Local conditions in the MPS area maintain a degree of environmental stability at all study sites, with only minor changes in benthic communities observed from year to year.
viii Monitoring Studies, 2009