ML22105A041

2021 Annual Environmental Operating Report

ML22105A041
Person / Time
Site:	Millstone
Issue date:	04/15/2022
From:	Armstrong L Dominion Energy Nuclear Connecticut
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
22-046
Download: ML22105A041 (11)

Text

Dominion Energy Nuclear Connecticut, Inc.

Millstone Power Station ~ Donlinion 314 Rope Ferry Road, Waterford, CT 06385 ~ Energy DominionEnergy.com

• APR 1 5 2022 U.S. Nuclear Regulatory Commission Serial No.22-046 Attention: Document Control Desk MPS Lie/LO RO Washington, DC 20555-0001 Docket No. 50-423 License No. NPF-49 DOMINION ENERGY NUCLEAR CONNECTICUT, INC.

MILLSTONE POWER STATION UNIT 3 2021 ANNUAL ENVIRONMENTAL OPERATING REPORT In accordance with Section 5.4.1 of the Environmental Protection Plan (EPP), Appendix B to the Millstone Power Station Unit 3 Operating License, Dominion Energy Nuclear Connecticut, Inc.

hereby submits the Annual Environmental Operating Report (AEOR), describing implementation of the EPP for the previous year. Enclosure 1 transmits information for the period of January 1, 2021, to December 31, 2021.

Should you have any questions regarding this report, please contact Mr. Dean E. Rowe at (860) 444-5292.

Sincerely,

~UV-<Picr L. J. Armstrong Director, Nuclear Station Safety and Licensing

Serial No.22-046 2021 Annual Environmental Operating Report Page 2 of 2

Enclosures:

1 Commitments made in this letter: None.

cc: U.S. Nuclear Regulatory Commission Region I 2100 Renaissance Blvd, Suite 100 King of Prussia, PA 19406-2713 R. V. Guzman NRG Project Manager Millstone Units 2 and 3 U.S. Nuclear Regulatory Commission One White Flint North, Mail Stop 08 C2 11555 Rockville Pike Rockville, MD 20852-2738 NRG Senior Resident Inspector Millstone Power Station

Serial No.22-046 2021 Annual Environmental Operating Report Enclosure 1 MILLSTONE POWER STATION UNIT 3 2021 ANNUAL ENVIRONMENTAL OPERATING REPORT JANUARY 1, 2021 - DECEMBER 31, 2021 MILLSTONE POWER STATION UNIT 3 DOMINION ENERGY NUCLEAR CONNECTICUT, INC. (DENC)

2021 Annual Environmental Operating Report (AEOR) 1.

Introduction:

This report covers the period January 1, 2021 through December 31, 2021 . During 2021, Millstone Power Station Unit 3 (MPS3) operated within fuel cycle 21, which began in November 2020, and is scheduled to end in April 2022.

As required by the MPS3 Environmental Protection Plan (EPP), Appendix B to the MPS3 Operating License, this AEOR includes:

• summaries and analyses of the results of environmental protection activities,

• a list of EPP non-compliances and the corrective actions taken to remedy them,

• a list of all changes in station design or operation , tests, and experiments which involved a potentially significant unreviewed environmental question, and

• a list of non-routine reports submitted in accordance with subsection 5.4.2.

2. Environmental Monitoring Activities:

2.1 Annual National Pollutant Discharge Elimination System (NPDES) Report of Ecological Monitoring (EPP Section 4.2).

Section 10(A) of Millstone Power Station's (MPS) NPDES permit (the Permit), as issued to Dominion Nuclear Connecticut, Inc. (DNC; now Dominion Energy Nuclear Connecticut, DENC) by the Connecticut Department of Environmental Protection (DEP; now the Department of Energy and Environmental Protection ,

or DEEP) on September 1, 2010, requires, among other things, continuation of biological studies of supplying and receiving waters. These studies include analyses of intertidal and subtidal benthic communities, finfish communities, entrained plankton, lobster populations, and winter flounder populations. Section 10(A)(2) of the Permit requires an annual report of these studies to be sent to the DEEP Commissioner on or before July 31 of each year. The latest report that fulfills these requirements, "Annual Report 2020 - Monitoring the Marine Environment of Long Island Sound at Millstone Power Station, Waterford, Connecticut" (Annual Report), dated July 2021, presents results from long-term studies, emphasizing those of the latest sampling year. Characteristics of and changes to the biological communities noted in these studies are summarized in the Executive Summary section of the Annual Report, which is attached as part of this report.

2.2 Effluent Water Quality Monitoring:

Several sections of the Permit require monitoring and recording of various water quality parameters at MPS intakes and at multiple monitoring points within the plant, including outfalls of each unit to the effluent quarry, and outfall of the quarry to Long Island Sound. Section 8 of the Permit requires that a monthly report of this monitoring be submitted to the DEEP. The report that fulfills these requirements, the "Monthly Discharge Monitoring Report" (DMR), includes discharge data from all MPS units. Consistent with prior annual AEOR submissions, water flow, temperature, pH, and chlorine data pertaining to MPS3 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 2021 AEOR Page 1 of 3

Permit conditions were not met) for the month. During 2021, there were no exceedances or exceptions at a discharge associated with MPS3.

2.3 NPDES Permit Renewal By way of background, in 2014 MPS established a team, and scheduled milestones, to ensure that a completed permit renewal application was submitted to the DEEP, in accordance with general requirements, prior to the permit's expiration in August 2015. The permit renewal application was submitted on February 6, 2015, and the DEEP issued a Notice of Sufficiency on March 6, 2015; therefore, the permit is administratively continued and in effect until its reissuance.

3. Environmental Protection Plan (EPP) Non-compliances:

No EPP non-compliances were identified for MPS3 in 2021.

4. Environmentally Significant Changes to Station Design or Operation, Tests, and Experiments:

No MPS3 design change records or system operating procedure changes initiated during 2021 included a determination that a significant unreviewed environmental question existed.

5. Non-Routine Reports of Environmentally Significant Events:

No non-routine reports were submitted in accordance with subsection 5.4.2 of the EPP.

2021 AEOR Page 2 of 3

Table 1. MPS3 NPDES data summary, Jan 1-Dec 31, 2021. Selected water quality parameters for MPS3(1).

Discharge 2021 I Discharge Maximum Discharge pH Average Maximum Temp. Range Average 1::,. Maximum Maximum Flow Range(SU) Discharge SWS FAC (OF) Temp. (°F) FAC (ppm) TRC (ppm)

(10 6 gpd) Temp . (°F) (ppm)

Min Max Min Max January 1361.0 7.7 8.1 44.1 71.5 59.1 14.7 0.09 0.04 0.19 Februar 1360.5 8.1 54.1 67.2 58.9 17.2 0.10 0.03 0.18 March 1215.5 8.1 54.9 68.5 61.1 18.5 0.08 0.05 0.18 April 1170.5 7.7 8.1 60.4 80.5 72.7 27.4 0.07 0.04 0.18 May 1360.3 7.7 8.0 66.7 82.7 75 .5 20.9 0.09 0.03 0.20 June 1360.3 7.7 8 .1 58.5 84.7 72.6 10.4 0.10 0.04 0.17 Jul 1356.2 7.5 7.9 79.9 89.2 84.3 15.4 0.07 0.03 0 .17 August 1361.8 7.5 7.9 83.4 92.5 86.6 15.0 0.07 0.04 0.17 September 1356.0 7.7 8.0 86.1 93.3 88.3 16.8 0.06 0.04 0.18 October 1360.5 6.8 8.1 78.4 90.9 84.2 17.8 0.08 0.06 0 .20 November 1360.8 8.0 8.1 67.5 85.8 76.1 18.0 0.08 0 .05 0.18 December 1360.5 8 .0 8.2 65.3 79.2 70.0 20.5 0.11 0 .04 0.20 Notes:

(l} Parameters are measured at MPS3 discharge (DSN 00lC), except for TRC (total residual chlorine), which is measured at MPS discharge (quarry cuts; DSN 001-1), and SWS FAC (service water system free available chlorine; DSN 00lC-5).

2021 AEOR Page 3 of 3

Attachment to the 2021 Annual Environmental Operating Report January 1 - December 31, 2021 Executive Summary Section of "Annual Report 2020 - Monitoring the Marine Environment of Long Island Sound at Millstone Power Station, Waterford, Connecticut" dated July 2021

Executive Summary This report summarizes results of ongoing pectinatum and Grate/oupia turuturu) . Similar environmental monitoring programs conducted in shifts have been observed in most years included relation to the operation of Millstone Power Station in this time-series. However, some species with (MPS). MPS can affect local marine biota in the cold-water affinity (e.g., Protomonospora, following ways: large organisms may be impinged Dumontia) occurred less regularly at Millstone on the traveling screens that protect the condenser Point (MP) and White Point (WP) as well, cooling and service water systems; smaller ones reflecting regional temperature increases may be entrained through the condenser cooling- compared to earlier study years .

water system, which subjects them to various Thermal effects on dominant species' mechanical, thermal, and chemical effects; and abundance and distribution patterns were also marine communities in the discharge area may also evident at Fl in 2020, and most apparent in the low be subjected to mechanical, thermal, and chemical intertidal zone. Seasonally high abundance of effects resulting from the outflow of the cooling Hypnea musciformis, a species observed for the water. first time in 2001, and expanded populations of This report contains a separate section for each Coral/ina officinalis and Gelidium pusil/um now major biological monitoring program, some of which characterize the lower shore community at Fl.

have been conducted without interruption since Melanothamnus (previously Neosiphonia) harveyi 1976. These long-term studies have provided the maintained a perennial population at all three sites representative data and scientific bases necessary in 2020 .

to assess potential biological impacts as a result of Ascophy/lum nodosum growth, represented as MPS construction and operation. the most recent internodal length, was greatest at In addition to sections related to the biological MP in 2020, higher than Fl and significantly higher monitoring program, this report includes a section than WP. With all sites combined, growth in 2020 providing a complete and thorough description of all was lower than 2019, and was the fourth lowest National Pollutant Discharge Elimination System mean growth since this methodology began in (NPDES) permit compliance work undertaken for 2011 . This continues to demonstrate no clear the implementation of flow reduction and/or relationships among monitoring sites, or correlation entrainment mitigation technologies, operational with station operating conditions, indicating that the methods or other measures undertaken in 2020, thermal plume from MPS has had little effect on and a section which provides a comprehensive local populations. Natural influences of other summary of activities and accomplishments of factors, such as ambient temperature conditions, Dominion Energy Nuclear Connecticut (DENG) in storms and wave action, nutrients and light, play the the Niantic River Nitrogen Work Group effort. dominant role in determining Ascophyllum growing conditions in the Millstone area.

Rocky Intertidal Studies The rocky intertidal monitoring program has also documented regional patterns and modifications Rocky intertidal habitats are extensive in the to shore communities unrelated to MPS operation.

Millstone area, and support rich and diverse These include the introduction to the region of communities of attached algae and animals. Rocky three exotic red algae (Antithamnion pectinatum in intertidal studies at MPS are designed and 1986, Grateloupia turuturu in 2004, and implemented to characterize these communities. Dasysiphonia japonica in 2010), decreases in Analyses of rocky shore data to date indicate that barnacle abundance in more recent years, and changes attributed to MPS operation are minor, long-term increases in abundance of the common transient, and restricted to a small area along 150 seaweeds Fucus vesicu/osus and Chondrus meters of shoreline in the immediate vicinity of the crispus.

discharge.

As in previous years, seasonal shifts in Eelgrass occurrence of annual algal species were noted at Fox Island (Fl) during 2020. These shifts included Eelgrass (Zostera marina L.) was monitored at absence or abbreviated season for cold-water three locations in the vicinity of MPS. Data from species (e .g., Protomonostroma undulatum, 2020 surveys indicated that the two study sites Spongomorpha arcta) and extended season for nearest to the MPS thermal plume (Jordan Cove warm-water species (e.g ., Antithamnion (JC) and White Point (WP)) supported healthy and Executive Summary

expansive eelgrass populations, consistent with MPS3, but also illustrated regional temporal results since the study began in 1985. While there community shifts unrelated to MPS operation.

has been moderate variability in abundance and Changes in community structure and functional distribution over the entire study period at these group dominance at EF, JC, and IN during the two sites, this variability was not related to MPS 1980-2020 time series reflect not only effects operation. Both predicted and measured thermal related to construction and initial operation of input to these sites from the cooling water MPS3, but other regional and/or local biotic and discharge is at most minimal (< 1°C above abiotic factors. Community changes at GN from ambient conditions) and well below levels 1980-2020 were attributed solely to these latter considered stressful to eelgrass. factors, and not to MPS operation.

By comparison, high eelgrass population variability has been observed in the Niantic River, Lobster Studies where complete and often sudden eelgrass bed losses were documented on six separate Impacts associated with recent MPS operations occasions prior to 2020. Data from the 2020 on the local lobster population were assessed by survey show continued recovery of some eelgrass comparing results of the 2020 study year to data beds in the Niantic River. Because the Niantic collected from 1978 through 2019. Emphasis has River is located well away from any influence of been placed on assessing long-term trends in the the MPS thermal plume, eelgrass population abundance and population characteristics of fluctuations there must be related to lobsters collected in the Millstone Point area.

environmental factors such as increasing ambient Throughout LIS, the lobster population was stable seawater temperatures, disease, increased or increasing from 1978 through 1999. Commercial turbidity, and waterfowl grazing. Results from this lobster catches in LIS precipitously declined from monitoring therefore suggest that fluctuations in 2000 to 2013, and experienced a record low in eelgrass populations observed at sites in the 2017. Although the past three years (2018-2020)

Niantic River are due to changes in local and show increases in commercial catches, they remain regional environmental conditions and not to MPS low in comparison to historical records. In this operation. study, lobsters in the MPS area have shown a similar trend, with abundance indices (total catch Benthic Infauna and catch per unit effort (CPUE)) approximately 75% lower in research pots and 99.7% lower in Benthic infauna! monitoring during 2020 trawls during the past eight years (2013-2020),

documented continuation of long-term trends in compared to highest levels in the 1990s. Declines sediment characteristics at subtidal sites in the in pot and in trawl catches were unrelated to MPS vicinity of MPS. The effluent sampling site (EF) operations and attributed to an increase in mortality sedimentary environment remained coarse, with associated with ambient seawater temperature rise low silt/clay which is related to discharge of cooling and temperature mediated stressors that include a water into Long Island Sound (LIS) at the quarry shell disease affecting lobster populations from cuts. Sediments at the intake site (IN) have been eastern LIS to the Gulf of Maine. Egg-bearing generally consistent with sediment characteristics females have been disproportionately and prior to dredging during MPS Unit 3 (MPS3) negatively impacted by shell disease in comparison construction. Sediments at Jordan Cove (JC) to other lobsters. In addition, predation by the high continued to have the smallest mean grain size number of Tautog caught in traps contributed to and highest silt/clay content of all four stations, record high lobster mortality during 2015 - 2020.

attributed to the discharge area scouring and fine Declines in the abundance of legal-size lobsters sediment deposition in the vicinity of the JC site. were attributed in part to the outbreak of shell Sedimentary characteristics at the reference site disease and to a nearly 5 mm increase in the at Giants Neck (GN) were similar to previous minimum legal-size since 1978. Recent reductions years' observations and continued to reflect in landings of legal-size lobsters harvested by natural variability unrelated to MPS. commercial lobster fishers in eastern LIS coincided Dominant taxa at all sites were reflective of with declines observed in this study, and lobster climax communities that have undergone long- catches remained severely depressed in other term successional development in response to areas of LIS since the lobster die-off observed in their sedimentary environments. Multidimensional 1999.

scaling showed distinct separation of communities Long-term trends observed in lobster population affected by construction and initial operation of characteristics during the past four decades Executive Summary ii

(molting, female size at maturity, abundance and 1986, impingement impacts were further reduced size characteristics of egg-bearing females) at MPS with the installation of a fish return at Unit appear related to warmer ambient seawater 2 in early 2000. The implementation of these temperatures and/or the recent outbreak of shell mitigation measures serves to mInimIze disease, and not MPS operation. Increased entrainment and impingement impacts at MPS.

ambient water temperature may be responsible for Annual variations in ichthyoplankton the increased susceptibility and transmission of entrainment likely reflected differences in diseases affecting lobsters in LIS, which is at the spawning and transport of eggs and larvae within southern boundary of their range of distribution in LIS . Other factors, such as extremes in seasonal nearshore waters. water temperature, may also affect larval growth The number of lobster larvae entrained through and development. A number of temporal and the MPS cooling water systems was highly variable spatial changes were identified in the community and very low in recent years, due to low adult of fishes and macroinvertebrates collected in the lobster abundance and low larval densities MPS trawl monitoring program. These changes throughout LIS. Impacts associated with were unrelated to the operations of MPS, but impingement of lobsters at MPS have been greatly rather were associated with shifts in the reduced by the use of aquatic organism return dominance of individual taxa from changes in systems at both units, which return impinged habitat, range extensions or contractions related lobsters to Niantic Bay with documented very high to a warming trend in ambient seawater survival rates. temperature, and changes in fishing rates and fishing regulations .

Fish Ecology Studies Winter Flounder Studies Results from the Fish Ecology monitoring program suggest MPS operation has not had a Various life history stages of Winter Flounder discernible effect on local fish assemblages based have been monitored since 1976 to determine on analysis of changes in community composition what effect, if any, MPS may have on the local and long-term abundance trends . No significant Niantic River population, particularly through the long-term trends in abundance were identified for entrainment of larvae. Over the past two decades ,

Anchovy, Gunner and Tautog eggs, Grubby low Winter Flounder abundance levels have been larvae, or juvenile and adult Silversides. Atlantic found throughout LIS by the Connecticut Menhaden larvae showed a significantly Department of Energy and Environmental increasing trend in abundance, as did juveniles Protection (CTDEEP). During the same time collected in seines and trawls. A significant period, adult Winter Flounder abundance in the decreasing trend was exhibited for American Sand Niantic River has remained low. Reflecting the Lance larvae and Grubby collected in trawls . Over continued trend of low abundance, the l'.-mean the past 45 years, Gunner and Tautog larval Catch Per Unit Effort (CPUE) for adult fish abundances have significantly increased. (>15cm) captured in the year-round Trawl Juvenile and adult trawl catches of Gunner Monitoring Program (TMP) in 2020 was the lowest increased at the Niantic River (NR) station and (0.2) value since 1976.

decreased at the Jordan Cove (JC) trawl stations. In 2020, overall combined larval abundances in Trawl catches of juvenile and adult Tautog have Niantic Bay (sampling sites EN and NB) and significantly increased at the NR station. No Niantic River (sites A, B, and C) were below trends in the abundance of juvenile and adult average for their respective time-series. All Gunner and Tautog were observed at the Intake abundances of larval stages (Stages 1 - 4) in the (IN) trawl station following the removal of the River and Bay stations were below time-series MPS3 intake cofferdam in 1983. means . Relative to the Niantic River, larval The magnitude of entrainment is dependent abundance in Niantic Bay has slightly increased in upon egg and larval densities and condenser recent years, suggesting higher production in LIS cooling water flows during their periods of rather than in estuaries such as the Niantic River.

occurrence. Reductions in cooling-water flows Summer juvenile abundance from the 2020 have been implemented at MPS with the use of Niantic River beam trawl survey was low for the variable frequency drives and timed refueling time-series and reflected low larval abundance.

outages during the peak period of Winter Flounder The number of larvae entrained at MPS is a annual spawning . In addition to the Unit 3 fish measure of potential impact to Winter Flounder.

return, which was in operation at unit start-up in Annual estimates of entrainment are related to Executive Summary iii

both larval densities in Niantic Bay and MPS cooling-water volume. The 2020 entrainment estimate of 79 .3 million reflected lower than average Niantic Bay larval densities. Reduced entrainment in spring 2020 can be attributed to low larval density and reduced cooling water volumes from the use of the variable frequency drives (VFD) during the "Interval" from April 4 - May 18 (see NPDES Permit Compliance section) and pump shutdowns during the Unit 2 spring refueling outage from April 23 to June 6.

As a result of VFD use during the "Interval", Winter Flounder larval entrainment was reduced 42.6%

when compared to that expected under baseline total permitted flow.

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 account for fewer adults. A bottleneck in recru itment may occur during the late juvenile life stage (ages-1 and 2), probably from predation. Environmental effects , including changes to the Niantic River habitat (e.g., widely fluctuating 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.

Results from Winter Flounder studies through 2020 suggest that MPS operations have had minimal effects on Winter Flounder biomass in the Niantic River. Declines in stock size have been greatly evident on a regional basis, including LIS ,

Rhode Island and all other Southern New England waters. Entrainment during the larval life stages of Winter Flounder occurs, however there has been large variation in the amount of larval mortality and recruitment in recent years, both occurring independently of MPS operations.

Executive Summary iv