ML23094A078

Annual Environmental Operating Report

ML23094A078
Person / Time
Site:	Millstone
Issue date:	04/04/2023
From:	Armstrong L Dominion Energy Nuclear Connecticut
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
23-082
Download: ML23094A078 (1)

Text

Dominion Energy Nuclear Connecticut, Inc.

Millstone Power Station 314 Rope Ferry Road, Waterford, CT 06385 A#

j Dominion Energy DominionEnergy.com U.S. Nuclear Regulatory Commission APR OJt 2023 Serial No.23-082 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 2022 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, 2022, to December 31, 2022.

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

Sincerely, Jri evQ/44 {4r/l- , //

L.J. Armstrong 0 Director, Nuclear Station Safety and Licensing

Serial No.23-082 2022 Annual Environmental Operating Report Page 2 of 2

Enclosures:

1 Commitments made in this letter: None.

cc: U. S. Nuclear Regulatory Commission Region I 475 Allendale Rd., Suite 102 King of Prussia, PA 19406-1415 R. V. Guzman NRC 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 NRC Senior Resident Inspector Millstone Power Station

Serial No.23-082 2022 Annual Environmental Operating Report Enclosure 1 MILLSTONE POWER STATION UNIT 3 2022 ANNUAL ENVIRONMENTAL OPERATING REPORT JANUARY 1, 2022 - DECEMBER 31, 2022 MILLSTONE POWER STATION UNIT 3 DOMINION ENERGY NUCLEAR CONNECTICUT, INC. (DENC)

2022 Annual Environmental Operating Report (AEOR) 1.

Introduction:

This report covers the period January 1, 2022, through December 31, 2022. During 2022, Millstone Power Station Unit 3 (MPS3) concluded fuel cycle 21 in April 2022:

MPS3 underwent a refueling outage from April 7, 2022, to June 4, 2022. Fuel cycle 22 began in June 2022 and is expected to continue until Fall 2023.

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 Stations (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 2021 - Monitoring the Marine Environment of Long Island Sound at Millstone Power Station, Waterford, Connecticut (Annual Report), dated July 2022, 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.

2022 AEOR Page 1 of 3

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. During 2022, there was one exceedance at a discharge associated with MPS3. A description of the event, and of corrective actions, is excerpted from the July DMR (D19208).

MPS3 Condensate Polishing Facility Discharge (DSN 001C-6)

On July 2, 2022, a quarterly Total Suspended Solids (TSS) sample was collected from DSN 001C-6. On July 5, 2022, sample analysis was completed and indicated a measured TSS concentration of 43.5 milligrams per liter (mg/L) for the quarterly sample which exceeded the maximum daily limit for TSS of 30 mg/L. At 1622 hours0.0188 days <br />0.451 hours <br />0.00268 weeks <br />6.17171e-4 months <br /> on July 5, 2022, Brian Conte of DENC provided immediate verbal notification to the CT Department of Energy and Environmental Protection (CT DEEP) of the permit exceedance. Following this notification, a 5-day written report was provided on July 8, 2022, in accordance with Regulations of Connecticut State Agency (RCSA) Section 22a-430-3(j)(11)(D). Additional TSS samples were taken during the month and can be found electronically attached in the NetDMR for July 2022 (DSN001C-6).

All subsequent samples contained TSS concentrations within permit limits. This event was entered into Millstones corrective action program and an evaluation identifying potential cause was conducted. The evaluation measured multiple TSS concentration removal efficiencies based on filter media, tank recirculation, and acid cleaning and peroxide additions to the tank. Procedure updates are in progress, based on the results of this evaluation, to ensure future TSS concentration exceedances do not occur during similar system alignments.

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 permits 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 2022.

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

No MPS3 design change records or system operating procedure changes initiated during 2022 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.

2022 AEOR Page 2 of 3

Table 1. MPS3 NPDES data summary, Jan 1-Dec 31, 2022. Selected water quality parameters for MPS3(1).

Discharge Discharge Average Maximum Average Maximum Maximum Maximum 2022 Discharge Flow pH Range Temp. Discharge Temp. FAC TRC SWS FAC (SU) Range (oF) Temp.

(106 gpd) ( oF) (ppm) (ppm) (ppm)

Min Max Min Max ( oF)

January 1346.1 8.1 8.2 56.8 71.4 65.0 22.8 0.10 0.05 0.17 February 1233.2 8.1 8.3 58.9 78.9 63.7 19.5 0.06 0.06 0.15 March 1235.0 8.1 8.3 59.7 72.2 65.8 23.5 0.09 0.05 0.14 April 1268.0 6.8 8.3 43.6 70.8 54.2 5.9 0.08 0.06 0.17 May 961.5 7.8 8.3 53.3 61.2 57.2 2.3 0.06 0.05 0.15 June 1360.4 8.0 8.3 54.2 82.0 74.9 9.9 0.03 0.07 0.16 July 1360.8 7.7 8.2 77.5 88.0 82.8 12.0 0.05 0.08 0.16 August 1360.6 7.9 8.3 82.2 89.9 85.9 12.2 0.06 0.06 0.16 September 1360.3 8.0 8.3 82.6 89.0 86.3 13.3 0.08 0.09 0.18 October 1361.0 7.9 8.3 75.7 87.8 80.3 15.8 0.07 0.04 0.19 November 1361.5 7.9 8.1 65.5 83.0 73.8 15.0 0.06 0.05 0.18 December 1360.7 7.9 8.1 57.8 76.0 65.0 17.0 0.07 0.03 0.17 Notes:

(1) Parameters are measured at MPS3 discharge (DSN 001C), 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 001C-5).

2022 AEOR Page 3 of 3

Attachment to the 2022 Annual Environmental Operating Report January 1 - December 31, 2022 Executive Summary Section of Annual Report 2021 - Monitoring the Marine Environment of Long Island Sound at Millstone Power Station, Waterford, Connecticut dated July 2022

Executive Summary This report summarizes results of ongoing Similar shifts have been observed in most years environmental monitoring programs conducted in included in this time-series. However, some relation to the operation of Millstone Power Station species with cold-water affinity (e.g.,

(MPS). MPS can affect local marine biota in the Protomonospora, Dumontia) occurred less following ways: large organisms may be impinged regularly at Millstone Point (MP) and White Point on the traveling screens that protect the condenser (WP) as well, reflecting regional temperature cooling and service water systems; smaller ones increases compared to earlier study years.

may be entrained through the condenser cooling- Thermal effects on dominant species water system, which subjects them to various abundance and distribution patterns were also mechanical, thermal, and chemical effects; and evident at FI in 2021, and most apparent in the low marine communities in the discharge area may also intertidal zone. Seasonally high abundance of be subjected to mechanical, thermal, and chemical Hypnea musciformis, a species observed for the effects resulting from the outflow of the cooling first time in 2001, and expanded populations of water. Corallina officinalis now characterize the lower This report contains a separate section for each shore community at FI. Melanothamnus major biological monitoring program, some of which (previously Neosiphonia) harveyi maintained a have been conducted without interruption since perennial population at all three sites in 2021.

1976. These long-term studies have provided the Ascophyllum nodosum growth, represented as representative data and scientific bases necessary the most recent internodal length, was greatest at to assess potential biological impacts as a result of WP in 2021, followed by MP then FI. With all sites MPS construction and operation. combined, growth in 2021 was lower than 2020, In addition to sections related to the biological and was the third lowest mean growth since this monitoring program, this report includes a section methodology began in 2011. This continues to providing a complete and thorough description of all demonstrate no clear relationships among National Pollutant Discharge Elimination System monitoring sites, or correlation with station (NPDES) permit compliance work undertaken for operating conditions, indicating that the thermal the implementation of flow reduction and/or plume from MPS has had little effect on local entrainment mitigation technologies, operational populations. Natural influences of other factors, methods or other measures undertaken in 2021, such as ambient temperature conditions, storms and a section which provides a comprehensive and wave action, nutrients, and light, play the summary of activities and accomplishments of dominant role in determining Ascophyllum growing Dominion Energy Nuclear Connecticut (DENC) in conditions in the Millstone area.

the Niantic River Nitrogen Work Group effort. The rocky intertidal monitoring program has also documented regional patterns and modifications Rocky Intertidal Studies to shore communities unrelated to MPS operation.

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

transient, and restricted to a small area along 150 meters of shoreline in the immediate vicinity of the Eelgrass discharge.

As in previous years, seasonal shifts in Eelgrass (Zostera marina L.) was monitored at occurrence of annual algal species were noted at three locations in the vicinity of MPS. Data from Fox Island (FI) during 2021. These shifts included 2021 surveys indicated that the two study sites absence or abbreviated season for cold-water nearest to the MPS thermal plume (Jordan Cove species (e.g., Protomonostroma undulatum, (JC) and White Point (WP)) supported healthy and Spongomorpha arcta) and extended season for expansive eelgrass populations, consistent with warm-water species (e.g., Grateloupia turuturu). results since the study began in 1985. While there Executive Summary i

has been moderate variability in abundance and MPS3, but also illustrated regional temporal distribution over the entire study period at these community shifts unrelated to MPS operation.

two sites, this variability was not related to MPS Changes in community structure and functional operation. Both predicted and measured thermal group dominance at EF, JC, and IN during the input to these sites from the cooling water 1980-2021 time series reflect not only effects discharge is at most minimal (< 1oC above related to construction and initial operation of ambient conditions) and well below levels MPS3, but other regional and/or local biotic and considered stressful to eelgrass. abiotic factors. Community changes at GN from By comparison, high eelgrass population 1980-2021 were attributed solely to these latter variability has been observed in the Niantic River, factors, and not to MPS operation.

where complete and often sudden eelgrass bed losses were documented on six separate Lobster Studies occasions prior to 2021. Data from the 2021 survey show continued recovery of some eelgrass Impacts associated with recent MPS operations beds in the Niantic River. Because the Niantic on the local lobster population were assessed by River is located well away from any influence of comparing results of the 2021 study year to data the MPS thermal plume, eelgrass population collected from 1978 through 2020. Emphasis has fluctuations there must be related to been placed on assessing long-term trends in the environmental factors such as increasing ambient relative abundance and population characteristics seawater temperatures, disease, increased of lobsters collected in the Millstone Point area.

turbidity, and waterfowl grazing. Results from this Throughout LIS, the lobster population was stable monitoring therefore suggest that fluctuations in or increasing from 1978 through 1999. Commercial eelgrass populations observed at sites in the lobster catches in LIS precipitously declined from Niantic River are due to changes in local and 2000 to 2013 and experienced a record low in regional environmental conditions and not to MPS 2021. In this study, lobsters in the MPS area have operation. shown a similar trend, with abundance indices (total catch and catch per unit effort (CPUE))

Benthic Infauna approximately 75% lower in research pots and 99.7% lower in trawls during the past nine years Benthic infaunal monitoring during 2021 (2013-2021), compared to highest levels in the documented continuation of long-term trends in 1990s. Declines in pot and in trawl catches were sediment characteristics at subtidal sites in the unrelated to MPS operations and attributed to an vicinity of MPS. The effluent sampling site (EF) increase in mortality associated with ambient sedimentary environment remained coarse, with seawater temperature rise and temperature low silt/clay which is related to discharge of cooling mediated stressors that include a shell disease water into Long Island Sound (LIS) at the quarry affecting lobster populations from eastern LIS to the cuts. Sediments at the intake site (IN) have been Gulf of Maine. Egg-bearing females have been generally consistent with sediment characteristics disproportionately and negatively impacted by shell prior to dredging during MPS Unit 3 (MPS3) disease in comparison to other lobsters. In addition, construction, although the presence of pebbles predation by the high number of Tautog caught in and shell fragments resulted in higher mean grain traps contributed to record high lobster mortality sizes in the last two years. Sediments at Jordan during 2015 - 2021. Declines in the relative Cove (JC) typically have the smallest mean grain abundance of legal-size lobsters were attributed in size and highest silt/clay content of all four part to the outbreak of shell disease and to a nearly stations, attributed to the discharge area scouring 5 mm increase in the minimum legal-size since and fine sediment deposition in the vicinity of the 1978. Recent reductions in landings of legal-size JC site. Sedimentary characteristics at the lobsters harvested by commercial lobster fishers in reference site at Giants Neck (GN) were similar to eastern LIS coincided with declines observed in this previous years observations and continued to study, and lobster catches remained severely reflect natural variability unrelated to MPS. depressed in other areas of LIS since the lobster Dominant taxa at all sites were reflective of die-off observed in 1999.

climax communities that have undergone long- Long-term trends observed in lobster population term successional development in response to characteristics during the past four decades their sedimentary environments. Multidimensional (molting, female size at maturity, relative scaling showed distinct separation of communities abundance, and size characteristics of egg-affected by construction and initial operation of bearing females) appear related to warmer Executive Summary ii

ambient seawater temperatures and/or the recent mitigation measures serves to minimize outbreak of shell disease, and not MPS entrainment and impingement impacts at MPS.

operations. Increased ambient water temperature Annual variations in ichthyoplankton may be responsible for the increased susceptibility entrainment likely reflected differences in and transmission of diseases affecting lobsters in spawning and transport of eggs and larvae within LIS, which is at the southern boundary of their LIS. Other factors, such as extremes in seasonal range of distribution in 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 during suggest MPS operation has not Various life history stages of Winter Flounder had a discernible effect on local fish assemblages have been monitored since 1976 to determine based on analysis of changes in community what effect, if any, MPS may have on the local composition and long-term abundance trends. No Niantic River population, particularly through the significant long-term trends in abundance were entrainment of larvae. Over the past two decades, identified for Anchovy, Cunner and Tautog eggs, low Winter Flounder abundance levels have been Grubby larvae, or juvenile and adult Silversides. found throughout LIS by the Connecticut Atlantic 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 -mean the past 46 years, Cunner and Tautog larval Catch Per Unit Effort (CPUE) for both adult abundances have significantly increased. Juvenile (>15cm) and juvenile (<15cm) fish captured in the and adult trawl catches of Cunner increased at the year-round Trawl Monitoring Program (TMP) in Niantic River (NR) station and decreased at the 2021 were low (1.1 and 0.1, respectively).

Jordan Cove (JC) trawl stations. Trawl catches of In 2021, larval abundances in Niantic Bay juvenile and adult Tautog have significantly (sampling sites EN and NB) were above average increased at the JC and NR stations. No trends in for Stages 1 and 4 and below average for Stages the abundance of juvenile and adult Cunner and 2 and 3. Niantic River (sites A, B, and C) larval Tautog were observed at the Intake (IN) trawl abundances were above average for Stages 1, 3 station following the removal of the MPS3 intake and 4, and near average for stage 2. Relative to cofferdam in 1983. the Niantic River, larval abundance in Niantic Bay The magnitude of entrainment is dependent has slightly increased in recent years, suggesting upon egg and larval densities and condenser higher production in LIS rather than in estuaries cooling water flows during their periods of such as the Niantic River. Summer juvenile occurrence. Reductions in cooling-water flows abundance from the 2021 Niantic River beam have been implemented at MPS with the use of trawl survey was low for the time-series and variable frequency drives and timed refueling 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 1986, impingement impacts were further reduced both larval densities in Niantic Bay and MPS at MPS with the installation of a fish return at Unit cooling-water volume. The 2021 entrainment 2 in early 2000. The implementation of these estimate was 145.4 million larvae. Reduced Executive Summary iii

entrainment in spring 2021 can be attributed to reduced cooling water volumes from the use of the variable frequency drives (VFD) during the Interval from April 4 - May 14 (see NPDES Permit Compliance section). As a result of VFD use during the Interval, Winter Flounder larval entrainment was reduced 32.5% 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 recruitment 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 2021 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