CY-07-052, Revised Groundwater Monitoring Plan to Support HNP License Termination

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Revised Groundwater Monitoring Plan to Support HNP License Termination
ML070860743
Person / Time
Site: Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png
Issue date: 03/21/2007
From: Gerard van Noordennen
Connecticut Yankee Atomic Power Co
To:
Document Control Desk, Office of Nuclear Material Safety and Safeguards
References
CY-07-052
Download: ML070860743 (24)
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Text

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CONNECTICUT YANKEE ATOMIC POWER COMPANY 17 362 INJUN HOLLOW ROAD

  • HADDAM NECK PLANT EAST HAMPTON, CT 06424-3099 MAR 2 1 2007 Docket No. 50-213 CY-07-052 Re: 10 CFR 50.82 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555-0001 Haddam Neck Plant Revised Groundwater Monitoring Plan to Support HNP License Termination In a letter dated January 9, 20071, Connecticut Yankee Atomic Power Company (CYAPCO) submitted Revision 2 to the Groundwater Monitoring Plan for the Haddam Neck Plant (HNP) site. The purpose of this submittal is to provide Revision 3 of the Plan, which was revised to address US NRC comments 2 . Only the revised text and Table 3-2 are provided (Attachment 1), as there are no proposed changes to remaining tables, figures and appendices provided in Revision 2.

There are no regulatory commitments contained in this submittal.

CYAPCO hereby requests the NRC review and concur with the revised Groundwater Monitoring Plan for the HNP site. If you should have any questions regarding this submittal, please contact me at (860) 267-3938.

Sincerely, G. P. van Noordennen Date Director of Regulatory Affairs and Quality Assurance 1 G.P. van Noordennen (CYAPCO) letter to US NRC, "Revised Groundwater Monitoring Plan to Support HNP License Termination and Radiological Groundwater Monitoring Procedures", dated January 9, 2007.

2 US NRC Memorandum from! Jon Peckenpaugh (System- Performance Analyst) to Ted Smith (Project Manager), Review and Recommendations. Pertaining to CYAPCO's Groundwater Monitoring Plan for the HNP, February 23, 2007.

NRC Document Control CY-07-052/Page 2 : Groundwater Monitoring Plan to Support HNP License Termination Plan, March 2007, Rev. 3 cc: S. J. Collins, Region I Administrator M. T. Miller, Branch Chief, Decommissioning Branch, Region I T. B. Smith, Project Manager, Haddam Neck Plant E. L. Wilds, Jr., Director, CT DEP Radiation Division P. Hill, CT DEP Remediation Division M. Firsick, CT DEP Radiation Division E. Waterman, USEPA, Region 1

CY-052 Attachment 1 Groundwater Monitoring Plan to Support HNP License Termination Plan, Rev. 3 (Text and Table 3-2, only)

March 2007

Groundwater Monitoring Plan to Support HNP License Termination Connecticut Yankee Atomic Power Company Haddam Neck Plant March 2007 Rev. 3 REV.3 18-MONTH GWMP

Table of Contents 1.0 Purpose ............................................................................................................................. 1 2.0 Scope and O bjectives ............................................................................................... 2 2.1 Scop e ......................................................................................................................... 2 2.2 Objectives ............................................................................................................ 3 3.0 Groundwater Monitoring Requirements ............................................................. 4 3.1 Summary Overview of HNP Hydrogeologic Conceptual Model ................ 5 3.1.1 Contaminant Distribution in Groundwater ......................................... 8 3.2 Groundwater Monitoring Well Network ........................................................ 9 3.2.1 Monitoring Well Locations and Rationale ........................................... 9 3.3 Groundwater Sampling and Analysis Requirements ................................. 11 3.3.1 Target A nalytes ........................................................................................ 12 3.3.2 Target Analyte Closure Criteria .......................................................... 12 3.4 Quality Assurance Requirements .................................................................. 13 3.5 Groundwater Monitoring Deliverables ........................................................ 13 4.0 Monitoring Plan Implementation Schedule ...................................................... 14 List of Tables Table 3-1 Monitoring Well Parameters Table 3-2 Monitoring Well Network and Well Characteristics Table 3-3 Target Radionuclides and Detection Limits Table 3-4 The Criteria and Performance Defined to meet Closure Requirement Acceptance at the end of the 18-month Clock for License Termination Table 4-1 18-Month License Termination Groundwater Monitoring Schedule List of Figures Figure 2-1 Haddam Neck Plant Property Map Figure 3-1 Inferred water elevation contours in shallow unconfined aquifer, Haddam Neck Plant, 17 August 2005.

Figure 3-2 Inferred water elevation contours in shallow unconfined aquifer, Haddam Neck Plant, 11 September 2005.

Figure 3-3 Inferred water elevation contours in shallow unconfined aquifer, Haddam Neck Plant, 5 December 2005 Figure 3-4 Areas of Significant Contaminant Releases and Soil Remediation Figure 3-5 Shallow Groundwater Flow Paths as Affected by Underground Structures Figure 3-6 Conceptual Groundwater Flow Patterns in Fractured Bedrock REV.318-MONTH GWMP

Figure 3-7 Aerial Photo of the Haddam Neck Plant Showing Exposed Bedrock Under the Former Primary Auxiliary Building, Waste Disposal Building and Tank Farm AreasFigure 3-8 Forward Particle Tracking from Two Rows of Arbitrary Points During Post-Demo Conditions Under Average Annual Recharge Figure 3-9 Reverse Particle Tracking from Major Monitoring Wells in Steady State Operational Mode Figure 3-10 Inferred Distribution of the Unfiltered Tritium (pCi/L) in the unconsolidated deposits hydrostratigraphic unit at the industrial area and upper peninsula area of the Haddam Neck Plant December 2003 Figure 3-11 Inferred Distribution of the filtered Tritium (pCi/L) in the shallow bedrock hydrostratigraphic unit at the industrial area and upper peninsula area of the Haddam Neck Plant December 2003 Figure 3-12 Inferred Distribution of Tritium (pCi/ L) in the unconfined aquifer at the industrial area and upper peninsula area of the Haddam Neck Plant June 2005 Figure 3-13 Inferred Distribution of Tritium (pCi/L) in the confined aquifer at the industrial area and upper peninsula area of the Haddam Neck Plant June 2005 Figure 3-14 Inferred Distribution of filtered Tritium (pCi/L) in the deep bedrock hydrostratigraphic unit at the industrial area and upper peninsula area of the Haddam Neck Plant December 2003 Figure 3-15 Inferred Distribution of Sr-90 (pCi/L) in the unconfined aquifer at the industrial area and upper peninsula area of the Haddam Neck Plant June 2005 Figure 3-16 Inferred Distribution of Sr-90 (pCi/L) in the confined aquifer at the industrial area and upper peninsula area of the Haddam Neck Plant June 2005 Figure 3-17 Monitoring Well Locations Figure 3-18 Cross Section Traces A-A' and B-B' Figure 3-19 Cross Section A-A' Inferred Vertical Tritium Plume Distribution Figure 3-20 Cross Section B-B' Inferred Vertical Tritium Plume Distribution List of Attachments Monitoring Well Construction Diagrams Monthly On-site Precipitation Totals for August 2002 through December 2005 REV. 3 18-MONTH GWMP 1I

1.0 Purpose The purpose of this groundwater monitoring plan is to define the requirements for verifying that groundwater contamination conditions at Connecticut Yankee Atomic Power Company's (CYAPCO) Haddam Neck Plant (HNP) meet the closure requirements as defined in the License Termination Plan (LTP) (Haddam Neck Plant License Termination Plan). The LTP specifies a minimum 18-month period of groundwater monitoring (to include two spring/high water seasons) to verify the efficacy of remedial actions at the facility. The monitoring period will begin following completion of remedial actions conducted with the use of groundwater depression systems. The groundwater monitoring program is required to demonstrate that groundwater contaminant conditions are below the established LTP closure criteria (a maximum dose rate of 25 mrem/yr for all exposure pathways, and conformance to the Derived Concentration Guideline Level, or DCGL) and exhibit either stable or decreasing trends.

This document describes the groundwater monitoring plan that will be implemented to support license termination at the HNP. The following sections describe the elements of the plan:

  • Scope and Objectives
  • Groundwater Monitoring Plan Requirements
  • Groundwater Monitoring Well Network
  • Groundwater Sampling and Analysis Requirements
  • Quality Assurance

" Groundwater Monitoring Plan Implementation Schedule and Deliverables A separate groundwater monitoring plan will be implemented to demonstrate compliance with the State of Connecticut Department of Environmental Protection (CTDEP)

Remediation Standards Regulation (RSR) Criteria in order to reach site closure under the Property Transfer Program.

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2.0 Scope and Objectives The scope and objectives of the groundwater monitoring plan for license termination are described in this section.

2.1 Scope The scope of this groundwater monitoring plan is confined to the portion of the Haddam Neck Plant site that either has historically exhibited plant-related groundwater contamination or may potentially exhibit plant-related groundwater contamination following decommissioning of plant facilities. The Haddam Neck Plant site is divided into the following functional areas (see Figure 2-1):

  • The Industrial Area and Upper Peninsula. This portion of the site includes the former power reactor and generating station facilities, cooling water facilities, related waste processing and treatment facilities, former spent and new fuel storage facilities, maintenance shops, warehouses, and administrative facilities. These facilities occupied the major portion of the developed part of the site, including the upper (i.e., plant northern) part of the peninsula that separates the cooling water discharge canal from the Connecticut River. This portion of the plant has historically exhibited plant-related groundwater contamination by radioactive constituents and is the primary focus of this groundwater monitoring plan.
  • The Parking Lot and Emergency Operations Facility. This portion of the site includes the primary parking area, former warehouses, the storm-water retention pond, and the former Emergency Operations Facility (EOF). No radioactive plant-related constituent release areas are located in this generally upgradient portion of the plant. Some selected wells in this area, however, will be monitored under this groundwater monitoring plan to ensure that contaminant plumes are bounded.
  • The Lower Peninsula. The lower (plant southern) part of the peninsula between the discharge canal and the Connecticut River. The lower peninsula has exhibited very low-level, discontinuous detections of plant-related radionuclides in the northern-most portion. One well, MW-117, will be monitored under this plan to ensure that closure criteria are not exceeded in this area.

The functional areas of HNP identified below are not subject to the 18-month license termination groundwater monitoring activity:

The Independent Spent Fuel Storage Installation (ISFSI). The ISFSI includes the spent fuel storage area and associated support facilities, and some former ancillary activity areas (i.e., the former shooting range and a bulky waste disposal area).

These areas have been approved for release from the license and are no longer part of the request for release.

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The Undeveloped Area of the Site ("Backlands"). The backlands include the balance of the HNP property not described above and is the majority of the total land area.

Although some surface effect from historical stack releases may have occurred, the backlands are located upgradient from the HNP and no apparent potential for groundwater contamination is identified. These areas have also been approved for release from the license.

2.2 Objectives The objectives of this plan are two-fold:

1) to define a process by which groundwater radiological contamination conditions at HNP will be measured and documented during the monitoring period required for license termination; and
2) to provide a structure for groundwater monitoring activities that will ensure that the process is implemented appropriately and that the information generated will verify that groundwater conditions satisfy LTP closure conditions.

REV. 318-MONTH GWMP 3

3.0 Groundwater Monitoring Requirements Several conditions are identified in the LTP as precursors to starting the 18-month groundwater monitoring activity. These conditions are identified below:

" Complete the development of a groundwater model and conduct particle tracking under a variety of scenarios,

  • Identify and finalize monitoring well locations and install monitoring wells,

" Allow areas on site where groundwater had been suppressed to recharge to seasonal norms,

  • Complete remediation, backfill, and radiologic assessment activities in the Tank Farm area, and any other radiological remediation areas requiring the use of a groundwater depression system.

As an additional enhancement in support of groundwater sampling, CYAPCO requires a minimum of five days between termination of monitoring well development activities and initiation of groundwater sampling for all newly installed monitoring wells.

These precursors have been completed and monitoring well locations have been finalized, all wells are installed, developed and the equilibration period expired prior to initiation of sampling the newly constructed monitoring wells. Remediation of the Tank Farm area is complete, final radiological assessment activities have been completed in December 2005, and the area has been backfilled.

The groundwater table in the soil and bedrock remediation areas has recharged to seasonal norms. Active dewatering to support deep soil remediation and structure demolition was discontinued in August 2005. This included termination of operation of the containment foundation mat dewatering sump, which had operated almost continually throughout the HNP operation. Nine monitoring wells were selected for weekly water level measurement to assess water level recovery and include:

  • MW-101S,
  • MW-102S,
  • MW-131S,
  • MW-130,
  • MW-508D,
  • MW-109S,
  • MW-106S,
  • MW-107S, and
  • MW-110S.

In addition, the water level in the mat sump was measured weekly to evaluate recovery.

The observed water levels in these wells were contoured using a commercial data contouring software (SurferTM) and the resulting water level elevation contours were plotted REV. 318-MONTH GWMP 4

over a site map indicating the well locations, location of remaining subsurface structures, and soil removal areas.

The contoured water elevations for 17 August 2005 revealed the expected groundwater depression in the central industrial area, immediately after stopping dewatering activities.

The water level recovered to seasonal norms within 30 days of termination of dewatering, as indicated by the water elevation contours for 11 September 2005, and continued to rise as rainfall increased during September and October (as shown in Attachment 2). Water level contour maps for the unconfined aquifer in August, September, and December are shown in Figures 3-1, 3-2, and 3-3, respectively. At this time, no residual effects of dewatering are observable on the groundwater levels at the site. Data-logging pressure transducers will be maintained in the nine monitoring wells used for this assessment during the 18-month monitoring period to evaluate long-term water level changes. The Connecticut River gage station is located in the discharge canal south of the HNP, and the location is shown on Figure 2-1. Should the river gage station become inoperable, the United States Geological Survey (USGS) River gage stations at Middletown, Connecticut, can be used to calculate the river stage at HNP. Synoptic water level measurements will be taken coincident with each groundwater sample event, as a minimum.

Following completion of the precursor activities, the 18-month groundwater monitoring has commenced. The requirements for groundwater monitoring in support of license termination are described in this section. The general categories of requirements are as follows:

  • Groundwater monitoring well network;

" Groundwater sampling and analysis requirements;

  • Quality Assurance Requirements; and
  • Data Reporting Requirements and Deliverables.

These topics are discussed in the following subsections.

In support of the 18-month Groundwater Monitoring Plan, a summary of the hydrogeologic conceptual model for the HNP site and the contaminant distribution in groundwater are provided in Section 3.1 below.

3.1 Summary Overview of HNP Hydrogeologic Conceptual Model A hydrogeologic Conceptual Site Model (CSM) was developed for the HNP based on both the regional geologic setting and hydrogeologic and chemical data collected at the site (CH2M HILL, 2005). The hydrogeologic CSM developed for the HNP describes a complex, leaky, multi-unit aquifer system exhibiting hydraulic interconnection between the perched, unconfined, and confined aquifers as delineated at the facility. Groundwater occurs under unconfined, semi-confined, and confined conditions in the subsurface at the HNP.

A localized perched aquifer consisting of wetland fluvial deposits and fill material is situated beneath the parking lot area (Figure 2-1). An organic silt layer that extends REV. 318-MONTH GWMP 5

throughout the outline of this former wetland exhibits aquitard properties and serves as an impermeable flow barrier, allowing the perched water table to exist. Plant-related radionuclides have not been detected in the perched aquifer.

The water table or unconfined aquifer beneath HNP consists of the unconsolidated sediments interconnected with shallow weathered and/or intensely fractured bedrock. This aquifer system exhibits porous media flow characteristics. Groundwater flow properties within the native sediments are essentially the same regardless of lithology and grain size.

The confined aquifer beneath HNP consists of a complex network of interconnected fractures in crystalline bedrock that were developed in response to local and tectonic stresses. The crystalline rock matrix has negligible effective porosity or permeability; therefore, groundwater flow in the bedrock is controlled by the secondary porosity and permeability developed within the fractures. The geometric distribution and openness, or aperture, of individual fractures controls groundwater flow and contaminant migration.

Bedrock characterization data indicate groundwater flows beneath the HNP mainly along sub- vertical fractures, which are generally along strike of the foliation trends, and along sub- horizontal fractures associated with glacial unloading.

Groundwater in both the unconfined and confined aquifers flows southerly across the site towards the Connecticut River (Figure 3-3). The Connecticut River is the discharge boundary for both surface water and groundwater for the entire watershed, acting as the definitive endpoint for groundwater flow paths in the hydrogeologic CSM for the HNP.

The distribution of groundwater contamination at the HNP site has been monitored over the last several years by means of a quarterly sampling program. As of June 2005, this monitoring program has shown that detectable concentrations of tritium and Sr-90 are present in site groundwater, but significant levels of Co-60 and Cs-137 have not been observed, especially in more recent years. This observation is consistent with the site-specific partition coefficients (Kds) determined for radionuclides at HNP. The partition coefficients control the distribution of the radionuclides in groundwater as compounds with low Kd values are strongly partitioned to groundwater relative to soil and geologic material, while compounds with higher Kd values are more readily partitioned to the solid phase.

Tritium has a Kd value of zero and Sr-90 has the lowest Kd (i.e. 8mL/g) of the remaining radionuclides at the site. Thus, the presence of tritium and Sr-90 in site groundwater is consistent with the site-specific Kds determined for Sr-90, Co-60, and Cs-137.

The lower Kd for tritium relative to Sr-90 has resulted in tritium migrating into the deeper, confined aquifer at the HNP site. Detection of Sr-90 in groundwater is generally limited to the shallow, unconfined aquifer.

Source areas at HNP are described by two types: 1) Primary Release Areas, where contaminants, consisting largely of dissolved radionuclides in aqueous coolant and other process solutions, were released to the ground under various circumstances; and 2)

Secondary Source Areas, consisting of surface and subsurface soil that was subsequently contaminated by the primary releases, either immediately on release, or due to downgradient migration of contaminants in groundwater. Secondary sources contained contaminants at concentrations above soil screening concentrations and could cause groundwater to exceed closure criteria in the future. The primary release and secondary REV. 318-MONTH GWMP 6

source areas were remediated during demolition activities. The primary release areas for significant releases of radioactive materials and secondary source areas are shown in Figure 3-4.

Groundwater at HNP flows from the inland areas toward the Connecticut River in a generally north to south direction (Figure 3-3). The Connecticut River forms the discharge boundary for surface water as well as shallow and deep groundwater at HNP.

Groundwater flow paths have been identified through observations of water elevation in multiple wells, and the flow paths have been simulated using the groundwater flow model for HNP (STRATEX LLC, 2005). Details of the hydrogeologic conceptual site model have been described previously (CH2M HILL, 2005). The general groundwater features are described below.

Within the near-surface portion of the unconfined aquifer, the groundwater flow is diverted by plant structures that intercept the bedrock/unconsolidated interface and extend to elevations above, or near to, the water table. These structures built onto/into bedrock include the following that will remain after demolition:

  • The reactor containment building (RCB) foundation and walls;
  • The spent fuel pool foundation;
  • The foundation walls beneath the plant-north portion of the former service building;
  • The discharge tunnels; and

" The B-switchgear building foundation.

Historically, other structures would have diverted shallow groundwater, creating preferential flow pathways; these include the Primary Auxiliary Building (PAB), the waste disposal building, the ion exchange building, and the spent resin facility. These structures were removed in their entirety during plant demolition. The diversion of shallow groundwater around these impediments to flow is illustrated in Figure 3-5.

Bedrock structural features (e.g., fracture sets and contacts between differing rock types) create preferential flow paths within the deeper bedrock. Of particular interest is a linear feature, believed to consist primarily of a near-vertical fracture set, in combination with intersecting near-horizontal fracture sets, that demonstrates connectivity (through hydraulic response during packer testing deep bedrock wells) extending from well MW-121A near the Connecticut River, to the MW-103 well cluster within the former wastewater tank farm area.

The general direction of groundwater flow in the deep bedrock (i.e., below structural interference) is illustrated in Figure 3-6. Figure 3-6 also illustrates the variability in flow patterns inherent to fractured rock systems. Areas of elevated hydraulic conductivity have been observed and inferred along structural features aligned with the rock foliation. These consist primarily of near-vertical fracture sets, rock foliation and contact zones. Secondary features exhibiting lower hydraulic conductivity include near-horizontal fracture sets at various elevations in the rock, as well as secondary mineral contacts (e.g., pegmatite dikes) that intersect the other features. Figure 3-7 is an aerial photograph of HNP that illustrates the exposed bedrock features in the former PAB footprint. Note the strong linear features REV. 318-MONTH GWMP 7

aligned with the general north-south trending foliation. Also apparent are discontinuous pegmatite dikes that cross and sometimes align with the foliation.

The characteristic groundwater flow beneath the plant with ultimate discharge into the Connecticut River is illustrated in Figure 3-8 which presents simulated particle track flow paths from releases in the inland portion of the industrial area under post-closure hydraulic conditions (i.e., no dewatering, no mat sump operation, demolition in final configuration).

Figure 3-9 illustrates a slightly different approach to flow path simulations. This figure shows reverse particle tracks (i.e., particles flowing backward from the river toward the inland portion of the industrial area) under historical operating conditions. In this scenario, the high conductivity preferential flow paths in bedrock appear to play a major role in groundwater flow direction.

3.1.1 Contaminant Distribution in Groundwater Based on the results of the quarterly groundwater monitoring conducted since 1999 and site-specific behavior of tritium and Sr-90, the dimensions of the groundwater contaminant plumes resulting from historical releases at HNP are best defined by tritium and Sr-90. The distribution of tritium at HNP has been monitored since 1999 and has changed over time.

Tritium in the unconfined aquifer has decreased over time due to source area remediation in the PAB area. Prior to remedial efforts, tritium was present across the site as summarized in Figures 3-10 and 3-11, which show the tritium distribution in the unconfined aquifer in December 2003. Prior to 2004, the unconfined aquifer was segregated into two separate geologic units: unconsolidated deposits and the shallow bedrock. Based on the refinement of the site conceptual model, these two hydrostratigraphic units have been combined into a single unconfined aquifer. In 2003, elevated tritium concentrations were observed across the site with distinct plumes mapped on both the east and west sides of the discharge tunnel (Figures 3-10 and 3-11) (CY, 2004). In June 2005, the tritium distribution was significantly diminished with elevated tritium only present in the vicinity of the RCB (Figure 3-12) (CY, 2005). The decrease in tritium activity in the unconfined aquifer is a function of the source remediation completed in the PAB area.

The tritium plume defined in the confined aquifer system indicates that the bulk of the plume has already moved downgradient and away from the initial release points. The tritium plume in December 2003 was focused in the source areas, while the tritium plume mapped in June 2005 had significant concentrations well downgradient of the source areas (Figures 3-13 and 3-14). The highest tritium concentration (16,500 pCi/L) at the beginning of the 18-month monitoring period was in bedrock well MW-118A at a depth of 75 feet bgs and distinctly downgradient from the source areas (Figure 3-13), while the highest tritium concentration in December 2003 was associated with MW-103D (9,060 pCi/L) adjacent to the RCB and tank farm area (Figure 3-14) (CY, 2004 and 2005).

Based on observations and measurements in deep bedrock boreholes at HNP as of June 2005, the maximum depth of tritium contaminant migration is approximately 175 feet below ground surface (bgs), with the highest concentrations observed around 75 feet bgs in MW-118A (CY, 2005). At depths below 175 feet bgs, the formation exhibits a persistent upward pressure differential, consistent with the Connecticut River's function as a regional discharge boundary for groundwater.

REV, 3 18-MONTH GWMP 8

In contrast to the widespread distribution of tritium at HNP, Sr-90 interacts with the aquifer matrix and is predominantly contained in the shallow, unconsolidated formation where it is retained. The observed Sr-90 concentrations generally diminish with distance from the source areas. Figures 3-15 and 3-16 illustrate the inferred distribution of Sr-90 in the unconfined and confined aquifers, respectively (CY, 2005).

3.2 Groundwater Monitoring Well Network The groundwater monitoring well network that will be used for the license-termination monitoring period includes wells in the perched, unconfined and confined aquifers located in the following general locations relative to historical contaminant releases and established plumes:

  • Upgradient wells in areas apparently un-impacted by plant-related groundwater contamination;
  • Wells located within contaminant release areas;

" Wells located downgradient of contaminant release areas; and

" Wells located along the downgradient site boundary.

A summary of the monitoring wells and associated parameters for each monitoring well is included in Table 3-1.

3.2.1 Monitoring Well Locations and Rationale The rationale for the monitoring well network and its relationship to the source and plume areas are summarized in Table 3-2 and monitoring well locations are shown in plan view on Figure 3-17 (encompassing the central industrial area of HNP). Well construction diagrams for the monitoring wells are presented in Attachment 1 to this plan. Figure 3-17 illustrates the relative position of monitoring wells in the central industrial area and in the peninsula area. Individual wells in the monitoring well network are identified by the primary purpose as upgradient wells, source area wells, or downgradient plume wells depending on their location (Table 3-2).

The proposed monitoring well network includes wells that characterize groundwater upgradient of the source areas, wells within and directly downgradient of the source areas, monitoring wells that characterize groundwater on the lateral portions of the defined plume, and wells in the downgradient plume areas. The monitoring well network also provides vertical profiling of the plume as wells are included in both the shallow, unconfined aquifer and deeper wells in the confined aquifer.

The wells established at HNP provide a functional network to monitor contaminants in groundwater and provide bounding observations at the lateral (i.e., between the inland hills; upriver and downriver of the industrial area) and vertical (i.e., between the ground surface and the lower extent of the plume) extent of contamination. In the event that additional wells are found to be necessary for LTP compliance, the data from those wells will be included in deliverables. However, the NRC will require six quarters of monitoring from these additional wells with two spring monitoring events, or after an evaluation of the REV. 318-MONTH GWMP 9

available radiological results and trends from these additional wells, the NRC may choose to waive the requirement of six quarters of sampling results with two spring sampling events as stated in the LTP.

The proposed monitoring well network includes wells that are located on both the east and west sides of the plume and include MW-123, MW-135, AT-i, and MW-508D on the west side of the plume, and MW-122S/D, MW-107S/D, MW-108, and MW-121A on the east side of the plume (Figure 3-17, Monitoring Well Location Map). These monitoring wells are screened in the unconsolidated material, shallow bedrock and deep bedrock and monitor both the unconfined and confined aquifers.

The four multi-level bedrock wells provide the bounding observations for vertical distribution of contamination in the confined aquifer system. Consistent with the horizontal plume definition, the vertical distribution of contaminants has also been assessed using tritium as the conservative indicator (i.e., tritium is non-retarded and is the most mobile of the plant-related contaminants). Groundwater sampling and analyses data from conventional monitoring wells and from the four multi-level bedrock wells were reduced and consolidated to prepare two vertical plume maps. The vertical plumes are plotted on two cross sections; one extending from the inland portion of the industrial area (near the containment building) to the Connecticut River, and the other extending parallel to the river from the parking lot area to the upper peninsula area (Figure 3-18, Cross Section Traces).

These cross sections integrate the June 2005 results from the multi-level well analysis and other wells along the section alignment (CY, 2005).

Section A-A' is the section extending toward the river and is shown in Figure 3-19. The highest tritium concentration (i.e., 16,500 pCi/L) was observed at a depth of approximately 50 feet bgs in MW-118A. MW-121A exhibited the deepest of the elevated concentrations (i.e., 8,560 pCi/L) at a depth of 175 feet bgs. This same depth is where vertical hydraulic equipotential conditions (i.e., at elevations above that depth, a downward pressure differential was observed; at elevations below that depth, upward pressure differential was observed) were observed during packer testing of MW-121A (CH2MHil1, 2004). This depth is inferred to be the approximate elevation at which groundwater discharges into the Connecticut River.

Section B-B' is the section parallel to the Connecticut River in Figure 3-18. This cross section, illustrated in Figure 3-20, indicates that the highest subsurface tritium concentrations were observed in MW-118A at 75 feet bgs (16,500 pCi/L), and in MW-119 at a depth of 85 feet bgs (14,300 pCi/L). The relationship between these two wells is inferred to be related to the presence of near-horizontal fractures at this elevation. However, the condition could also result from contamination migrating in near-parallel sub-vertical fracture sets that are transmitting the same water. The conservative inference (i.e., that a near-horizontal fracture set exists) is selected for this analysis. In this cross section, the deepest portion of the plume was found in MW-121A at 175 feet bgs.

Several of the sample zones completed in the multi-level wells are deemed to be non-representative due to extremely low levels of water production (i.e., as low as 0.0007 gallons per hour). These low-yielding zones, which include elevations 300 and 455 feet bgs in MW-119, and elevation 465 feet bgs in MW-121A did not produce sufficient water volume to REV. 3 18-MONTH GWMP 10

purge the multi-level packer assemblies and ensure that representative samples of formation water were collected.

The multi-level wells present sufficient observations in the deep bedrock to provide vertical bounding observations of contamination beneath HNP.

To maintain consistency and comparability in the monitoring activity, the same wells will be sampled during each sampling event. Monitoring wells will be inspected regularly and maintained and repaired as required over the course of the 18-month monitoring activity.

In the event a well becomes irreparably damaged, it will be replaced prior to the next scheduled sampling event with a well completed in the same hydrogeologic unit in approximately the same functional location as the damaged well.

Additional groundwater monitoring wells may be installed and/or sampled during the 18-month monitoring period at the request of CTDEP in order to reach Site closure under the Property Transfer Program. As of December 2006, two additional monitoring wells (MW-139 and -140) were installed within the former Tank Farm area and two wells (XR-500S and -

500D) were installed off-Site (outside NRC-licensed Site boundary), across the Connecticut River in Haddam Meadows State Park. Monitoring results for additional wells sampled during the 18-month monitoring period at the request of CTDEP will be reported, as appropriate, in the deliverables outlined in Section 3.5, but are not considered for LTP compliance.

Groundwater samples were collected from the two cross-River (XR) wells December 2006 and analyzed for the full complement of radiological substances of concern (SOCs) identified for HNP. Naturally-occurring constituents and indicator parameters (e.g., boron, total alpha, total beta) did not exceed expected background conditions. No SOCs were detected above minimum detectable concentrations. The non-presence of SOCs related to HNP groundwater contamination is completely consistent with the HNP hydrogeologic CSM that identifies the Connecticut River as a hydrologic boundary separating the surface drainages and groundwater systems on opposite sides of the river (CH2M Hill, 2005). The Connecticut River is identified as a discharge boundary for surface and groundwater on both sides of the river in the vicinity of HNP (CH2M Hill, 2004 and 2005, SRATEX LLC, 2005).

3.3 Groundwater Sampling and Analysis Requirements Groundwater sampling events will be planned and executed in the same manner as previous quarter groundwater monitoring events. A sample event plan will be prepared in accordance with Procedure RPM 5.3-3 (CY, 2006d). The sample event plan specifies the number and type of containers to be filled with sample groundwater from each well, preservation and handling requirements for samples, and analyses to be performed on samples from each well. The substances of concern identified as target analytes for this monitoring activity and the specification for analyses to be performed are described in the following subsections.

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3.3.1 Target Analytes Based on the CSM, the groundwater characterization program has identified the following radioactive constituents as target analytes for monitoring during the 18-month license termination monitoring activity:

" Strontium-90

  • Tritium In addition, boron, a non-radioactive constituent, will be monitored as a 'tracer' element.

However, for the purposes of site closure, the boron results will be evaluated under the RCRA program.

All samples from all of the monitoring wells identified in Table 3-2 will be analyzed for these constituents in each sampling event. In addition to the target analytes identified above, the following analyses was performed on the first spring event from all monitored wells.

  • Alpha Spectroscopic Analysis, and
  • Analyze for specific Hard-to-Detect Nuclides for the remaining 20 radionuclides identified in the LTP, which are not covered in the above analyses.

No constituents included in the gamma spectroscopic, alpha spectroscopic, or hard-to-detect-nuclides analyses were detected in these samples, which were collected April 2006 (CY, 2006a). A summary of the proposed analytical program including analytical methods, target analytes, and detection limits is summarized in Table 3-3 of the monitoring plan.

3.3.2 Target Analyte Criteria The LTP requirement for closure is 25 mrem/yr for all media and pathways. That is further refined to contributions from soil, existing groundwater, and potential future groundwater, based on the DCGLs. Table 3-3 provides the target analytes and the associated detection limits to meet those criteria. The actual calculated dose contribution from all pathways will be used to verify that CYAPCO meets the requirements for license termination for the site.

While the license termination criteria for the monitoring program are defined by the DCGL values, additional evaluations will be conducted. Time series plots will be generated for all constituents of concern. Trend analyses for each of the constituents will meet LTP termination requirements if they are stable or decreasing at the end of the 18 month monitoring period, and below the respective DCGL values. Trends will be evaluated using recognized industry standard statistical analyses, numerical modeling, or a combination of both to define plume migration in the terms of pulse movement to demonstrate license termination criteria will have been met. If license termination criteria have not been met, then the NRC will decide if additional monitoring is required. A summary of each license termination criteria and the path forward to meet the defined NRC acceptance is provided in Table 3-4.

REV. 3 18-MONTH GWMP 12

3.4 Quality Assurance Requirements The quality assurance requirements for the 18-month license termination monitoring activity require processing as LTP-Quality. The quality assurance requirements for the quarterly sampling events are identified in the procedures for groundwater sample event planning, implementation and reporting (Procedures RPM 5.3-0 (CY, 2006b), 5.3-1 (CY, 2006c), and 5.3-3 (CY, 2006d)); the programmatic quality assurance requirements, along with the requirements for data quality assessment, are described in the Groundwater Monitoring Program Quality Assurance Plan (CY, 2006e). All groundwater sample analyses will be performed by an off-site laboratory operating under a contractual scope of work consistent with the LTP-Quality requirements necessary for the 18 month groundwater monitoring plan sample events (CY, 2006e).

3.5 Groundwater Monitoring Deliverables The following deliverables will be produced during the 18-month license-termination groundwater monitoring period:

" Six quarterly groundwater monitoring summary letter reports. These brief letter reports will be submitted approximately 60 days following receipt of sample results for each sampling event and will summarize the following information:

o wells sampled in the previous quarterly monitoring event; o concentrations of substances of concern detected in monitoring well samples and any changes in concentration trends; o quarterly precipitation totals and groundwater elevations at the time of sampling.

  • Three semi-annual groundwater monitoring reports. The semi-annual reports will be submitted approximately 90 days following receipt of sample results from the second sampling event preceding each report. These reports will include detailed discussion of contaminant trend analysis, results of water level measurement and water level contouring, on site precipitation totals, and recommendations for subsequent monitoring rounds.
  • Supplemental monitoring reports as appropriate. In the event that an unplanned sample event is conducted for some reason or relevant data are generated from other sampling programs (e.g. RCRA), the results will be summarized, as appropriate, into the quarterly and/or semi-annual monitoring reports.
  • One final groundwater condition summary letter report. This report will summarize all previous monitoring results and support the confirmation that criteria for license termination have been met. The letter report will reference previously submitted semi-annual groundwater monitoring reports, and quarterly summary reports.

REV. 3 18-MONTH GWMP 13

4.0 Monitoring Plan Implementation Schedule The 18-month license termination groundwater monitoring activity schedule is shown in Table 4-1. This schedule is intended to meet the requirements of the HNP license termination plan (i.e., 18 months of monitoring following completion of remediation requiring the use of a groundwater depression system, and including two spring high water level periods).

Each round of sampling will involve one day collecting synoptic water levels for the wells included in this monitoring plan, and approximately two weeks to complete both the multiport and standard monitoring well sampling, documentation and shipping.

The schedule identifies six quarterly groundwater monitoring summary letter reports that will be submitted approximately 60 days after receipt of the quarterly sampling event sample results. Three semi-annual groundwater monitoring reports will be submitted approximately 90 days following the receipt of the second quarterly sampling event sample results included in each report. The final deliverable identified in the schedule is the final groundwater condition summary letter report summarizing the previous results and documenting that the criteria for license termination have been met.

REV. 3 18-MONTH GWMP 14

References CH2MHILL, 2004 Task 2 Supplemental Characterization Report, Prepared for Connecticut Yankee Atomic Power Company, November 2004 CH2MHILL, 2005 Hydrogeologic Conceptual Site Model for Haddam Neck Plant, Haddam Neck, Connecticut, Prepared for Connecticut Yankee Atomic Power Company, June 2005 CY, 2004 Semi-Annual Groundwater Monitoring Report, September and December 2003, May 2004 CY, 2005 Semi-Annual Groundwater Monitoring Report, First and Second Quarter Groundwater Sampling Events, October 2005 CY, 2006a Semi-Annual Groundwater Monitoring Report, January through June 2006, October 2006 CY, 2006b CY Procedure for Radiological Groundwater Monitoring Program (RPM 5.3-0), GGGR-R0053-000, November 2006 CY, 2006c CY Procedure for Groundwater Level Measurement and Sample Collection (RPM 5.3-1), GGGR-R5300-003, November 2006.

CY, 2006d CY Procedure for Groundwater Sample Event Planning and Data Management (RPM 5.3-3), GGGR-5303-000, November 2006 CY, 2006e Groundwater Monitoring Program Quality Assurance Plan for the Connecticut Yankee Decommissioning Project, ISC-GQP-00002-000, November 2006.

SRATEX LLC, 2005 Task 3 Groundwater Modeling Report, Prepared for Connecticut Yankee Atomic Power Company, December 2005.

REV. 318-MONTH GWMP 15

Table 3-2 Monitoring Well Network and Well Characteristics Screen Screen Well ID Monitoring Purpose Top Bottom Hydrostratigraphic Aquifer Monitored (ft bgs) (ft bgs)

Upgradient Wells (4 total)

MW-100D Upgradient 21 31 Deep Bedrock Confined MW-100S Upgradient 3.5 9 Unconsolidated Unconfined MW-101D Upgradient 39.8 49.8 Deep Bedrock Confined MW-101S Upgradient 8 18 Shallow Bedrock Unconfined Source Area Wells (19 total)

MW-102D Makeup water tanks source area 43 53 Deep Bedrock Confined MW-1 02S Makeup water tanks source area 12.8 22.5 Bedrock Unconfined MW-103A Wastewater Tank farm source area 30 40 Shallow Bedrock Confined MW-103B Wastewater Tank farm source area 60 70 Deep Bedrock Confined MWR-103D Wastewater Tank farm source area 48.5 58.5 Deep Bedrock Confined MWR-103S Wastewater Tank farm source area 15.5 25.5 Shallow Bedrock Confined MW-136D Wastewater Tank farm source area 20 30 Unconsolidated Unconfined MW-136S Wastewater Tank farm source area 10 20 Unconsolidated Unconfined Wastewater Tank farm source area/PAB soil remediation area 34 44 Unconsolidated Unconfined Wastewater Tank farm source area/PAB soil remediation area 12.5 22.5 Unconsolidated Unconfined PAB drumming room source area/soil remediation 47 57 Deep Bedrock Confined PAB drumming room source area/soil remediation 19 24 Unconsolidated Unconfined MW-130 PAB drumming room source areaiPAB soil Unconsolidated/shallow removal 20 30 bedrock interface Unconfined MW-112 Septic leach field source area 15 25 Unconsolidated Unconfined MW-113 Septic leach field source area 15 25 Unconsolidated Unconfined MW-132D Fuel building source area 26 29 Unconsolidated Unconfined MW-132S Fuel building source area 13 23 Unconsolidated Unconfined MW-137 Fuel building source area 23.5 33.5 Shallow Bedrock Unconfined MW-138 Zone 12 contaminated drain source area 10 20 Unconsolidated Unconfined Page 1of 3

Table 3-2 Monitoring Well Network and Well Characteristics Screen Screen Well ID Monitoring Purpose Top Bottom Hydrostratigraphic 1 Aquifer Monitored (ft bgs) (ft bgs)

Downgradient Plume Wells (25 total)

MWR-106D Downgradient plume 45 55 Deep Bedrock Confined MW-106S Downgradient plume 14.5 24.5 Shallow Bedrock Unconfined MW--107D Downgradient plume 90 100 Shallow Bedrock Confined MW-107S Downgradient plume 15 25 Unconsolidated Unconfined MW-1 08 Downgradient plume prior to discharge at discharge canal 15 25 Unconsolidated Unconfined MW-109D DowngradientRiver Connecticut plume prior to discharge at 45 55 Bedrock Confined MW--109S Downgradient plume prior to discharge at Connecticut River 15 25 Unconsolidated Unconfined MW-110D Downgradient plume prior to discharge at Connecticut River 70 80 Bedrock Confined MW-1 10S Downgradient plume prior to discharge at Connecticut River 15 25 Unconsolidated Unconfined MW-1 17 Isolated historic detection on peninsula 15 25 Unconsolidated Unconfined Downgradient plume near discharge to Multi-level well sample MW-1i18A Connecticut River - lower bound of plume in zones at: 30, 75, 125, bedrock 160 &235 Bedrock Confined Downgradient plume near discharge to Multi-level well sample MW-119 Connecticut River- lower bound of plume in zones at: 50, 85, 160, bedrock__________Bedrock 260, 300 &455 Confined Downgradient plume near discharge to Multi-level well sample MW-120 Connecticut River - lower bound of plume in zones at: 90, 105, 155, bedrock 210 &240 Bedrock Confined Downgradient plume near discharge to Multi-level well sample MW-121A Connecticut River - lower bound of plume in zones at: 105, 175, bedrock 285, 315 &465 Bedrock Confined MWR-122D Downgradient plume 185 195 Deep Bedrock Confined MW-122S Downgradient plume 9 19 Unconsolidated Unconfined MW--123 Downgradient plume 23.5 33.47 Shallow Bedrock Confined MW-124 Downgradient plume 11 21 Unconsolidated Unconfined MW-125 Downgradient plume along preferential flow pathway/Discharge tunnel soil remediation area 11 22 Unconsolidated Unconfined MW-133 Downgradient plume along preferential flow pathway 32 42 Deep Bedrock Confined Page 2 of 3

Table 3-2 Monitoring Well Network and Well Characteristics Screen 1 Screen - Hydrostratigraphic A Well ID Monitoring Purpose Top Bottom UnitAquifer Monitored (ft bgs) (ft bgs)

MW-134 Downgradient plume along preferential flow pathway/Discharge tunnel soil remediation area 18.72 28.72 Unconsolidated Unconfined MW-135 Downgradient plume 27.72 28.72 Unconsolidated Unconfined MW-508D Downgradient plume, defines plant north extent of plume 81.5 91.5 Shallow Bedrock Confined MW-508S Isolated perched plume under parking lot 14 24 Unconsolidated Perched MW-AT1 Downgradient plume 16 41 Unconsolidated Unconfined Notes:

bgs = feet below ground surface Page 3 of 3

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