ML081270204
| 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
4-ADominion Dominion Nuclear Connecticut, Inc.
Millstone Power Station Rope Ferry Road, Waterford, CT 06385 APR 2 5 2008 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555-0001 Serial No.
MPS Lic/GJC Docket Nos.
License Nos.
08-0184 RO 50-423 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. 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.
parameters for MPS 3(1).
1 - Dec. 31, 2007 Selected water quality Jan.
Feb.
Mar.
Apr.
May June July Aug.
Sep.
Oct.
Nov.
Dec.
Discharge Flow (max)
(106 gpd) 1357.0 1357.5 1357.1 1356.5 1356.9 1356.5 1357.1 1358.6 1357.3 1359.6 1356.9 1357.1 Discharge PH Range 7.9-8.1 8.0-8.2 8.1-8.3 6.5-8.4 7.8-8.3 7.9-8.1 7.5-8.2 7.9-8.1 8.0-8.2 8.0-8.2 7.9-8.1 7.9-8.1 Discharge Temp.
Range (OF) 41.3-68.9 51.4-61.2 51.9-62.6 40.6-60.6 43.9-75.5 71.6-84.0 77.3-86.4 83.8-89.5 82.6-88.4 77.1-86.0 67.1-79.8 56.7-74.1 Discharge Temp.
(avg),
(OF) 61.4 55.0 55.7 47.9 57.2 76.8 82.1 85.8 84.8 81.6 72.4 63.6 Avg AT (OF) 15.8 17.1 16.6 4.3 5.8 15.6 15.5 15.9 15.9 16.2 16.4 17.4 Max FAC (ppm) 0.13 0.11 0.09 (2) 0.06 0.11 0.07 0.08 0.08 0.09 0.22 0.14 Max TRC (ppm)
<0.03
<0.03
<0.03
<0.03 0.04 0.03
<0.03 0.05 0.03
<0.03
<0.03
<0.03 Max SWS FAC (ppm) 0.22 0.21 0.24 0.25 0.22 0.17 0.22 0.20 0.18 0.22 0.18 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 =
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 The local Niantic River winter flounder population is potentially affected by the operation of Millstone Power Station (MPS) primarily through entrainment of larvae in the condenser cooling-water systems. To assess possible effects, the abundance of adult spawners is measured within the Niantic River and larvae are sampled at the plant discharges and in the Niantic River and Bay during late winter and early spring.
Settled age-0 juveniles are collected in the river in summer.
The relative abundance of adult spawners in 2007 was 1.7 fish per trawl tow (catch-per-unit-effort; CPUE), which is similar to abundance in 2004 and 2005 and higher than in 2006. Over the past decade, abundance of winter flounder spawners has remained at a relatively low level, with CPUE fluctuating around 1-2 fish per tow. Winter flounder abundance in the Niantic River has been similar to levels found throughout Long Island Sound (LIS) by the Connecticut Department of Environmental Protection.
Absolute abundance of the 2006 spawning popula-tion (the latest year for which an estimate could be made) was about 11,500 fish, which was the largest value since 1999.
- However, this estimate is imprecise and had a large 95% confidence interval of 0-41 thousand. Using another methodology, female spawner abundance in 2007 was estimated at 2.1 thousand.
Other annual estimates ranged from approximately 1.6 thousand females in 2006 to 75 thousand in 1982 and corresponding total egg production estimates were 1.1 to 44.8 billion. During the past 26 years, Niantic River winter flounder abun-dance represented an estimated 0.4 to 3.3% of the entire LIS winter flounder resource.
In 2007, overall density of Stage 1 (newly hatched) larvae in the Niantic River fell into the lower one-third of the time-series of values since 1983.
In contrast, similar to the estimate in 2006, Stage 1 abundance reached a record high in Niantic Bay.
Since 1995, more Stage I larvae were found than expected from low adult spawner abundance, suggesting a density-dependent compensatory mech-anism during the egg stage enhancing their survival.
This has been attributed to reduced predation on eggs by sevenspine bay shrimp, such that when egg densities are low, higher egg survival produces more Stage 1 larvae. Density-dependent mortality is also present throughout the larval period of life, as an analysis suggested that mortality decreases with decreasing egg production (a measure of early larval abundance), which is further moderated by warmer spring water temperatures allowing for faster larval development.
This year, Stage 4 (pre-metamor-phosis) larvae in the Niantic River and Bay were relatively abundant, ranking among the top five of all years.
With the exception of a few years, densities of age-0 young in the Niantic River following larval meta-morphosis and settlement were linearly related to Stage 4 larval abundance. However, at higher larval abundance juvenile densities apparently reached an asymptote of about 250 young per 100 m2 of bottom, which could represent the carrying capacity of the river habitat. Initial settled juvenile abundance was relatively modest this year, but despite a below-average mortality rate, late summer abundance fell into the lower one-third of values since 1983.
Abundance indices of age-0 fish were either not significantly correlated or were negatively correlated with the abundance of female adult spawners 3 to 5 years later.
Conversely, positive correlations were found between age-i abundance indices and these older fish. However, there was much scatter in these relationships and none of the early life stages were considered to be reliable predictors of potential future year-class strength.
The number of larvae entrained is a measure of potential impact to winter flounder. In most years, Stage 3 larvae predominated in entrainment collec-tions. Annual estimates of entrainment are related to both larval densities in Niantic Bay and MPS operation. The 2007 entrainment estimate of about 145 million reflected relatively, moderate larval densities and lowest cooling-water volume at Units 2 and 3 since 1999. The low cooling-water usage this year and the 1996 retirement of Unit 1 reduced potential MPS entrainment by an estimated 144 million larvae.
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 Executive Summary v
ii were available to be entrained, the more larvae that 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 the most important factor in determining juvenile abundance.
The potential impact of larval entrainment on the Niantic River stock depends upon the fraction of the annual winter flounder reproduction entrained each year (termed production lo ss 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.
Based on the increase in egg survival noted in recent years, a factor that was not originally incorporated into the mass-balance model, most production loss estimates after 1994 are conservatively high. Correcting the estimates made since 1995 by using a higher egg survival rate resulted in lower production loss estimates (revised long-term mean = 11.6%).
The small adult spawning stock in the river continues to produce relatively large numbers of larvae and young fish, which likely resulted from population compensatory mechanisms. Despite rela-tively good abundance of age-0 winter flounder (a life stage not entrained) in many recent years, significant recruitment to the adult spawning population has not occurred.
Processes that are unrelated 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 produce fewer adults. A bottleneck, probably from predation, appears to be occurring during the late juvenile life stage (ages-I and 2).
Environmental effects, including changes to the Niantic River habitat (e.g., increased eelgrass abundance), a warming water temperature trend, and interactions with other species (e.g., predation), especially during early life history, are also important processes affecting winter flounder population dynamics.
Fish Ecology Studies Monitoring during 2007 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 American sand lance larvae collected in entrainment samples and juvenile or adult silversides collected by trawl or seine.
Similarly, no long-term trends were identified in various life stages of grubby.
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 during 2007 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.
Data collected during 2007 continued to show no long-term abundance trends in the numbers of entrained cunner and tautog eggs and larvae.
Juvenile and adult cunner and tautog 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 habitat for these species.
Since that time, no significant abundance trend was found from 1984 through 2007.
Cunner abundance significantly increased at the Niantic River trawl station and continued to fluctuate without trend at Jordan Cove.
The combined catches of juvenile and adult tautog collected at the three trawl stations increased, probably as a result of more restrictive fishing regulations.
Significant increases in tautog abundance were found in Niantic River trawl catches and in both Jordan Cove 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 31 years appeared to be unrelated to MPS operation.
Shifts in the dominance of individual taxa were attributed to changes in habitat, range extensions or contractions, and warmer ambient seawater temperatures occurring over the past 3 decades.
Cooling-water use at MPS was reduced 23% from the shutdown of Unit 1 in 1995, resulting in less entrainment and impingement. Fish return systems at Units 2 (2000) and 3 (1986) further reduce
,impingement mortality at MPS. Based on the lack of decreasing trends for selected taxa except anchovies, for which there are other causes, MPS has had minimal effect on local fish and shellfish assemblages.
Lobster Studies Impacts associated with recent MPS operations on the local lobster population were assessed by comparing results of the 2007 study to data collected from 1978 through 2006. Emphasis has been placed on vi Monitoring Studies, 2007
'~
n:4~i 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 2007, 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 shell disease affecting lobster populations from eastern LIS to the Gulf of Maine.
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 due in part to shell disease and to a 3 mm increase in the minimum legal size since 1978. Of note, the abundance of legal-size lobsters harvested by commercial fishers in our area increased over the past few years, although lobster catches remained depressed in other areas of LIS.
Long-term trends observed in lobster population characteristics over the past 30 years (growth, female maturity and egg-bearing lobsters), were related to warmer ambient seawater temperature 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 2007 continued to document ecological changes to the shore community near to, 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 plant discharge to LIS.
Seasonal shifts in occurrence of annual algal species were noted at Fox.Island-Exposed (FE) during 2007.
These shifts included abbreviated season for cold-water species (e.g., Monostroma grevillei, Spongomorpha arcta, and Dumontia contorta),Yand 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 2007 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.
Polysiphonia spp. maintained a perennial population at FE in 2007, but occurred mainly as a summer annual at sites unaffected by MPS.
Ascophyllum nodosum growth during 2006-07 continued to exhibit no clear relationships among our monitoring
- stations, nor correlation with plant operating conditions, indicating that the thermal plume from MPS 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 a long-term increase in abundance of the common brown rockweed, Fucus vesiculosus.
One phenomenon observed in 2007 was the deposition of a large quantity of sand onto low intertidal areas of White Point, resulting from spring storms, temporarily burying algae and rock surfaces.
The effect was temporary, however, as subsequent redistribution of the sand permitted the more typical community to re-emerge.
Executive Summary vii
Eelgrass Eelgrass (Zostera marina L.) population dynamics were monitored during summer from 1985 to 2007 at three locations near MPS. although some lofig-term declines in one or more eelgrass population parameters (e.g., shoot density, shoot length, and standing stock biomass) were observed at all three areas monitored over the entire 22-year study period, monitoring results from 2007 indicate population improvement at all sites, continuing trends observed over the last 3 or more years. Eelgrass populations at two monitoring sites to the east of MPS, near the fringes of the thermal plume (<1.5 km from the MPS discharge to LIS), exhibited gradual declines since 1985. These declines were not associated with MPS operation, as thermal input from the cooling water discharge to these sites is at most minimal (<IC above ambient conditions).
By comparison, heavy, often sudden, eelgrass losses were documented on five separate occasions prior to 2000 in the Niantic River. 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, and gradual, steady increases in shoot density, shoot length, and biomass were observed through 2007. 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 Niantic River in 1992, and twice by blooms of green algae (Cladophora spp.) 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 silt/clay estimates at Jordan Cove (JC) have remained relatively consistent since the changes observed in 1986, and sedimentary parameters at the reference station Giants Neck (GN) were within the limits of previous observations and continue to exhibit variability unrelated to MPS. Community abundance and numbers of species at all sampling stations in 2007 increased from the low values observed in 2006.
Surface deposit-feeding oligochaetes and polychaetes were the dominant organisms at all stations in 2007.
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 2007 were comprised of fauna that had been present in previous years. Multivariate analyses showed higher community similarity among recent years and changes in community composition from the samples before the disturbances at IN and JC. Changes in community similarity from early sampling years to more recent years were also observed at EF that is continuously affected by discharge of station cooling water. The reference station GN where the effects of MPS are not present has also exhibited temporal changes in benthic community from earlier to more recent years.
Temporal and spatial variation in the MPS benthic communities observed 2007 are typical of near-shore marine environments. During 2007, there were no unusual events that impacted benthic infaunal communities. Under current environmental conditions the infaunal communities appear relatively stable.
viii Monitoring Studies, 2007