ML110050288

Investigation of Tritium Releases to Groundwater

ML110050288
Person / Time
Site:	Sequoyah
Issue date:	06/22/2010
From:	Julian H, Mike Williams GeoSyntec Consultants, Tennessee Valley Authority
To:	Office of Nuclear Reactor Regulation
References
FOIA/PA-2011-0001A FOIA/PA-2010-0209, FOIA/PA-2011-0001A
Download: ML110050288 (221)

Text

RECEIVED Chattanooga, TN JUN 2 2 Z010 TENNESSEE VALLEY AUTHORITY CNO & EVP Office River System Operations & Environment TVA Nuclear Research & Technology Applications Environmental Engineering Services - East SEQUOYAH NUCLEAR PLANT INVESTIGATION OF TRITIUM RELEASES TO GROUNDWATER Hank E. Julian, P.E., P.G.

Geosyntec'>

consultants and Matthew Williams Knoxville, Tennessee May 2007 Y

Q ** *,'  : TABLE OF CONTENTS Page No.

LIST OF FIG U RES ..................................................................................... .......................... iii A CRO NY M S A N D A BBREV IA TIO N S ................................................................................. v 1.0 INTR O D U CTION ..................................................................................... .......................... I 1.1 Purpose and Objectives ................................................................................................... i 1.2 Plant D escription ......................................................................................................... 2 1.3 H istorical Tritium M onitoring .................................................................................... 2

2.0 BACKGROUND

................................................. 6 2.1 Radiological Environmental Monitoring Program (REMP) ....................................... 6 2.1.1 REMP, G roundw ater .................................................................................................... 6 2.1.2 REMP Surface W ater .............................................................................................. 9 2.2 Radw aste System .................................................... J.................................................. 10 2.2.1 Liquid Radw aste System ....................................................................................... 10 2.2.1.1 System D escriptions ....................................................................................... 11 2.2.1.2 Shared Components ...................................................................................... 12 2.2.1.3 Separation of Tritiated and Nontritiated Liquids ......................................... 12 2.2.1.4 Tritiated W ater Processing ........................................................................... 12 2.2.1.5 N ontritiated W ater Processing ...................................................................... 13 2.2.1.6 Releases of Liquid Radw aste ........................................................................ 13 2.2.2 W aste Condensate Lines ........................................................................................... 16 2.2.3 G aseous Radw aste System .................................................................................... 17 2.3 Inadvertent Releases of Liquid Radw aste ................................................................. 18 3.0 HYD RO G EO LO G Y ....................................................................................................... 27 3.1 Site Location and Scope of Exploration .................................................................. 27 3.2 Physiography ............................................................................................................... 30 3.3 G eom orphology ....................................................................................................... 30 3.4 G eology ......................................................................................................................... 32 3.4.1 Stratigraphy ......................................................................................................... 32 3.4.2 Bedrock ..................................................................................................................... 32 3.4.3 Soil ............................................................................................................................ 37 3.4.4 Structure .................................................................................................................... 40 3.5 Hydrology .................................................. 41 3.6 G roundw ater ................................................................................................................. 43 3.7 O ffsite W ater Supplies .............................................................................................. 51 3.7.1 O ffsite G roundw ater Supplies ................................................................................ 51 3.7.2 O ffsite Surface W ater Supplies ............................................................................. 56 4.0 TR ITIUM INVESTIG A TION ...................................................................................... 58 4.1 Groundwater Sampling of Selected Existing Wells ................................................. 59 4.2 Manual Sampling of Storm Drain Catch Basin, Vaults, and Manholes .......... *.... 59 4.3 Groundwater Sampling using Geoprobe Methods ................................................... 62 4.4 W ater Level M onitoring ........................................................................................... 65 4.5 Interior Sam pling ....................................................................................................... 72 5.0 RESULTS AND RECOMMENDATIONS .................................................................... 75 i

5.1 Tritium D istribution .................................................................................................. 75 5.1.1 M anual Sam pling .................................................................................................. 75 5.1.2 Groundw ater Sam pling ............................................................................ ................. 76 5.2 Tritium Sources ......................................................................................................... 79 5.3 Tritium Transport and Fate ...................................................................................... 81 5.4 Recom m endations .................................................................................................... 82 6.0 REFEREN CES ................................................................................................................... 84 APPENDIX A ....................................................... 87 A PPEND IX B ............................................................................................................................. 114 ii

LIST OF FIGURES Page No.

1.1 Site M ap Showing.Key Plant Features .......................................................................... 3 1.2 Site Map Showing Historical Monitoring Wells ............................................................ 4 2.1 Onsite REMP Sampling Locations for Groundwater and Surface Water ....................... 7

.2.2 Offsite REMP Sampling Locations for Groundwater and Surface Water ..................... 8 2.3 Time-Series Tritium Concentrations from REMP Groundwater and Surface Water ........ 10 2.4 Site Map Showing Locations of Inadvertent Releases of Liquid RadWaste ................ 19 2.5 Photograph of Unit 2 Moat Drainage to Ground Surface .................................................. 20 2.6 Map Showing Extent of MFTDS Release to Railroad Bay (from Halter, 1997) .......... 21 2.7 Map Showing Extent of Sump Release at Unit 2 Additional Equipment Building (from H alter, 1998) ...................................................................................................... 23 2.8 Photographs of Sump Release Area at Unit 2 Additional Equipment Building (from H alter, 1998) ....................................................................................................................... 25 2.9 Schematic of Sampling Locations and Photograph of Unit I RWST Moat Drain ..... 26 3.1 Site Location M ap ......................................................................................................... 28 3.2 Locations of Exploratory Borings ............................................................................... 29 3.3 Site Topographic Map............................................ 31 3.4 Regional Map Showing Geologic Formations and Structure ................... 33 3.5 Surface of Conasauga Bedrock .................................................................................... 35 3.6 Pre-excavation Top of Bedrock Contours (ft-msl) at the Reactor, Auxiliary, Control, and Turbine Buildings (from TVA Drawing 10N21 1) ....................... 36 3.7 1971 Site Construction Photograph of the Reactor, Auxiliary, Control, and Turbine B u ild in gs ............................................................................................................................ 37 3.8 Operating Guide For Chickamauga Dam ..................................................................... 42 3.9 Mean 1995 - 1999 Discharge Channel Elevations ........................................................ 43 3.10 Site Bedrock M onitoring W ells .................................................................................... 44 3.11 Time-Series Groundwater Levels for Wells W 1, W2, L6, and L7 (1985-199 1) ...... 45 3.12 Time-Series Groundwater Levels for Wells W1, W4, W5 and L7 (1985-1991) .......... 46 3.13 Site-W ide Potentiom etric M ap ................................................................................... 47

3. 14 Potentiometric Surface at Diesel Fuel Oil Interceptor System on February 10, 2003 ....... 49 3.15 Schematic of Diesel Fuel Oil Interceptor Trench ....................................................... 50 3.16 Large Capacity Wells in the Vicinity of SQN from USGS GWIS Database ............... 53 3.17 Groundwater Supply Wells in the Vicinity of SQN from Bradfield (1992) ................. 55 4.1 Map Showing Manual Sampling Locations ................................................................. 61 4.2 Map Showing Geoprobe Sampling Locations and Monitoring Wells ......................... 63 4.3 Profile of G eoprobe Borings ......................................................................................... 64 4.4 Time-Series Water Levels at Wells W-21, 29, 30, 31 and the River ............................ 66 iii

4.5 Time-Series Water Levels at Wells 27, 32, 33, 34 and the River ................................ 67 4.6 Continuous Water Levels (top) and Temperatures (bottom) at Wells GP- 13, 14, W21, the Discharge Channel and the River ........................................................................... 68 4.7 Continuous.Water Levels (top) and Precipitation (bottom) at Wells 14, W21 and the D ischarge C hannel ........................................................................................................ 69 4.8 Local Potentiometric Surface from April 02, 2007 Water Level Measurements ...... 71 4.9 Groundwater Inleakage Locations at Auxiliary Building ............................................ 73 5.1 Time-Series Tritium Concentrations and Groundwater Levels at Well 31 .................. 76 5.2 Time-Series Tritium Concentrations and Groundwater Levels at Well W21 .............. 77 5.3 Time-Series Tritium Concentrations and Groundwater Levels at Wells 27 and 29 ......... 78 5.5 Time-Series Tritium Concentrations and Groundwater Levels at Well GP-13 ............ 79 5.6 Spatial Distribution of Tritium from Groundwater Sampling during January and F ebruary 2007 .......................................... .......................................................................... 80 0

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Acronyms and Abbreviations CBI Chicago Bridge & Iron CCW Condenser Circulating Water CDWE Condensate Demineralizor Waste Evaporator CVCS Chemical and Volume Control System EPA Environmental Protection Agency ERCW Essential Raw Cooling Water GIS Geographic Information System GWSI Ground-Water Site Inventory LLRWSF Low Level Radwaste Storage Facility MDC Minimum Detection Concentration MFTDS Modularized Transfer Demineralization System MWe Megawatt Electric MWt Megawatt Thermal NEI Nuclear Energy Institute NRC Nuclear Regulatory Commission 0 NRWT NT Nonreclaimable Waste Tank Neutralization Tank ODCM Offsite Dose Calculation Manual pCi/L Picocuries per liter PER Problem Evaluation. Report Rad DI Radwaste Demineralizer System RCA Radiation Control Area REMP Radiological Environmental Monitoring Program RWST Refueling Water Storage Tank SQN Sequoyah Nuclear Plant TRM Tennessee River Mile TVA Tennessee Valley Authority USGS United State Geological Survey WARL Western Area Radiological Laboratory WBN Watts Bar Nuclear Plant V

1.0 INTRODUCTION

1.1 Purpose and Objectives The Tennessee Valley Authority (TVA) is committed to controlling licensed material, minimizing potential unplanned, unmonitored releases to the environment from plant operations, and minimizing long-term, costs associated with potential groundwater and subsurface contamination. Although current public health standards and limits are deemed appropriate, they may not satisfy public trust issues when unplanned releases occur. In conjunction with the Nuclear Energy Institute (NEI), TVA has approved a voluntary policy to enhance detection, management and communication about inadvertent radiological releases in groundwater. The investigation described herein represents an initial step in policy implementation.

In August 2006, a team consisting of GeoSyntec Consultants, Sequoyah Nuclear Plant (SQN) staff, and corporate TVA personnel was establishedto locate potential source(s) of site tritium releases and to identify potential migration route(s) to groundwater. This report provides findings of the site subsurface investigation with recommendations for the path forward. The primary objectives of the investigation were to:

0 Identify potential radionuclide contaminant sources that account for observed measurements,

• Assess the nature and extent of subsurface tritium contamination, and 0 Characterize groundwater movement to evaluate potential contaminant migration routes.

Tasks associated with this investigation included:

0 Comprehensive review of historical radiological release information, 0 Review of site drawings and plant construction photographs, 0 Installation and sampling of soil borings and groundwater monitoring wells,

• Enhanced sampling of existing monitoring wells,

• Visual inspections and manual sampling of yard drains, sumps, manholes, and internal seeps, 0 Manual and continuous water level monitoring, and 0 Internal components investigations of both units using visual and boroscope methods.

I

1.2 Plant Description SQN is a two-unit nuclear power plant located approximately 7.5 miles northeast of Chattanooga at the Sequoyah site in Hamilton County, Tennessee. The plant has been designed, built, and is operated by TVA. Each of the two identical units (Units 1 and 2; Figure 1.1) employs a Pressurized Water Reactor Nuclear Steam Supply System with four coolant loops furnished by Westinghouse Electric Corporation. These units are similar to those of TVA's Watts Bar Nuclear Plant.

Each of the two reactor cores is rated at 3,455 MWt and, at this core'-power, each unit will operate at 3,467 MWt. The additional 12 MWt is due to the contribution of heat of the Primary Coolant System from nonreactor sources, primarily reactor coolant pump heat. The total generator output is 1,199 MWe. for the rated core power. The containment for each of the reactors consists of a freestanding steel vessel with an ice condenser and separate reinforced Concrete Shield Building. The ice condenser was designed by the Westinghouse Electric Corporation. The freestanding containment vessel was designed by Chicago Bridge & Iron (CBI). Unit I began commercial operation on July 1, 1981. Unit 2 began commercial operation on June 1, 1982.

1.3 Historical Tritium Monitoring As part of the SQN onsite Radiological Environmental Monitoring Program (REMP), quarterly groundwater monitoring for tritium began in 1971 at four bedrock monitoring wells (WI, W2, W4, and W5) located along the perimeter of the site (Figure 1.2). Onsite REMP groundwater monitoring was reduced to a single well (W5) in 1980. Tritium was initially observed in SQN groundwater at well W5 from 1989 sampling at a background concentration of 379 picocuries per liter (pCi/L). No other detection of tritium was observed at well W5 until 1998. From 1998 through 2001, tritium was consistently observed at concentrations ranging from 401 to 2,120 pCi/L at well W5. No further tritium detection has been observed at well W5 since 2001.

Evaluation of REMP data indicates no evidence of tritium or other radionuclides exceeding detection levels in offsite surface water or groundwater samples since 1992. Pre-1992 tritium concentrations in offsite surface water and groundwater samples reflect ambient concentrations resulting most probably from cosmogenic sources and nuclear weapons testing from the 1940s through the 1970s.

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SEQUOYAH NUCLEAR PLANT Key Plant Features

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SEQUOYAH NUCLEAR PLANT Historical Monitoring Wells Historical Groundwater Wells 0 Diesel 0 Diesel Extraction 0 LLRW 0 RadCon

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! 20 40 no am imA PREPARED BY.TVAGEOGRAPHIC INFORMATION MD ENG1NEERING bags Wa DWWa ftpholvgraO4 2004 Figure 1.2 Site Map Showing Historical Monitoring Wells 4

3 In February 2002, TVA expanded the REMP groundwater monitoring at SQN by installing five additional soil monitoring wells (wells 24 - 28) along 6- and 12-inch diameter condensate pipelines. These lines convey condensate and radwaste effluent from the Turbine and Auxiliary Buildings, respectively (Figure 1.1). The 6- and 12-inch lines discharge into the 72-inch cooling tower blow-down line and Low-Volume Waste Treatment Pond, respectively. Initial samples collected from these wells indicated no evidence of tritium (<220 pCi/L).

Monthly groundwater sampling for tritium was prescribed for well 27 beginning in August 2003.

Tritium was consistently observed slightly above the minimum detection concentration (MDC) of 220 pCi/L at this well beginning in September 2003. The consistency of observations prompted a sampling event in January and February 2004 that included other site wells (W14 and W21) in conjunction with manual sampling of vicinity sumps, moats, storm drain catch basins, and ponds. A relatively high tritium concentration of 9,080 pCi/L was observed at well 21. A subsequent set of seven monitoring wells (wells 29 - 35) were installed in April 2004, with routine sampling of selected wells beginning in May 2004. To date, tritium concentrations in these wells have ranged from MDC to 19,750 pCi/L. These concentrations have not exceeded the Environmental Protection Agency (EPA) Drinking Water Standard of 20,000 pCi/l for tritium (40 CFR 141.25). The Nuclear Regulatory Commission (NRC) Site Resident at SQN has been notified and is being kept informed as investigations continue.

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2.0 BACKGROUND

2.1 Radiological Environmental Monitoring Program (REMP)

The preoperational environmental monitoring program has established a baseline of data on the distribution of natural and manmade radioactivity in the environment near the plant site. The preoperational environmental monitoring program was initiated in the spring of 1971. The operational monitoring program initiated in the spring of 1980 reflects the current monitoring philosophy and regulatory guidelines.

REMP reports have been prepared by TVA's Western Area Radiological Laboratory (WARL) and SQN personnel since inception of the program in 1971. The SQN REMP has been modified over time to adjust for sampling locations, sampling methods, analytes, reporting frequency, and changes in laboratory methods/instruments and MDCs.

Currently, REMP reports catalog onsite direct radiation sampling, atmospheric radiation monitoring at eight sites located 10 to 20 miles from the plant, terrestrial radiation monitoring at area farms within six miles of the plant, and liquid pathway radiation monitoring along the Tennessee River and from area groundwater wells.

TVA participates in an Interlaboratory Comparison Program. This program provides periodic cross-check samples of the type and radionuclide composition normally analyzed in an environmental monitoring program. Results obtained in the monitoring and the cross-check programs are reported annually to the NRC.

Groundwater and surface water sampling have been a part of the program since it was instituted in 1971, and remain part of the current liquid pathway monitoring program. Onsite and offsite monitoring locations for groundwater and surface water are shown in Figures 2.1 and 2.2, respectively.

2.1.1 REMP Groundwater The monitoring well network at SQN (Figure 1.2) included six regional monitoring wells (wells WI, W2, W4, W5, and W8) that were installed before 1977. Quarterly groundwater monitoring for tritium began in 1977 at four bedrock monitoring wells (WI, W2, W4, and W5) located along the perimeter of the site (Figure 2.1). Onsite REMP groundwater monitoring was reduced to a single well (W5) in 1981. Offsite groundwater sampling also began in 1977 at seven area farms; but, since 1986 samples have been collected at just one location (Farm HW well; see Figure 2.2).

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SEQUOYAH NUCLEAR PLANT Onsite REMP Sampling Locations 0 Onsite Monitoring Wells

- - Feel 0 200 400 Goo00 1.000 PREPARED BY: TVA GEOGRAPHIC INFORMATIONAND ENGINEERING Image It a Oihal Ohtaphol grfta 2004 Figure 2.1 Onsite REMP Sampling Locations for Groundwater and Surface Water 7

G SEQUOYAH NUCLEAR PLANT Offsite REMP Sampling Locations REMP Monitoring Locations A Surface Water

• Groundwater Sequoyah Nuclear Plant A N 0 1 2 3 4 5 PREEPAREDBY TVAGEOGRAPHIC INFORMATION AND ENGINEERING Figure 2.2 Offsite REMP Sampling Locations for Groundwater and Surface Water 8

0 In the earlier years, groundwater was collected by grab sampling. Sometime in the late 1970s or early 1980s, well W5 was equipped with an automatic sampler. The automatic sampler transmits a daily sample aliquot to a composite container for monthly retrieval. Manual samples are collected quarterly from the offsite Farm HW well.

Quarterly samples are analyzed by gamma spectroscopy using a one pass method with an intrinsic germanium detector (Vortec and Canberra instruments). Samples are first distilled by centrifuging 50 ml of liquid, distilling that volume (if it is turbid), and then extracting 15m] to be analyzed. The composite sample is analyzed by gamma spectroscopy for gross beta activity (monthly) and tritium analysis is conducted on a quarterly basis. Tritium analysis is completed by liquid scintillation methods using a Packard scintillation unit. A total of five scintillation counts are performed for each test. Results are reported as the mean of the three highest counts.

Results of REMP groundwater monitoring are shown in Figure 2.3. From the period 1977 -

1998, both onsite and offsite groundwater monitoring indicates tritium concentrations that are

<MDC or are within the range of expected background concentrations. Tritium was initially observed in SQN groundwater at onsite well W5 from 1989 sampling at a background concentration of 379 pCi/L. No other detection of tritium was observed at well W5 until 1998.

However, from 1998 through 2001, tritium was consistently observed at concentrations ranging from 401 to 2,120 pCi/L at well W5. No further tritium detection has been observed at well W5 since 2001. During the period 1998 - 2001, tritium concentrations at the offsite Farm HW well and at all surface water monitoring locations were <MDC (Figure 2.3). Hence, tritium observations at well W5 during the 1998 - 2001 time interval exceed background concentrations and suggest an onsite source of contamination.

2.1.2 REMP Surface Water Surface water sampling locations have remained constant throughout the REMP program, including one upstream location and two downstream locations (Figure 2.2)* The upstream sampling location is the City of Dayton drinking water supply intake station at Tennessee River Mile (TRM) 497.0. The downstream samples are collected at Eastside Utility District water intake (TRM 473.0) and at a temperature station 0.3 mile downstream from the SQN discharge (TRM 483.4).

Samples are collected by automatic ISCO samplers at each of the three locations. The instruments are programmed to accumulate discreet samples every two hours and composite samples are collected monthly. The composite sample is analyzed for gross beta activity (monthly) and tritium (quarterly) using the methods described in Section 2. 1. 1.

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,-, - - r - N" N C'j Year Figure 2.3 Time-Series Tritium Concentrations from REMP Groundwater and Surface Water Monitoring Results of REMP surface water monitoring are shown in Figure 2.3. For comparison, USEPA RadNet surface water data (USEPA, 2007) for Soddy Daisy, Tennessee are depicted in the figure. The SQN REMP data indicate no evidence of tritium or other radionuclides exceeding detection levels in offsite surface water or groundwater samples since 1992. Pre-1992 tritium concentrations in surface water samples reflect ambient concentrations resulting most probably from cosmogenic sources and nuclear weapons testing from the 1940s through the 1970s.

2.2 Radwaste System 2.2.1 Liquid Radwaste System Liquid, gaseous, and solid radwaste disposal facilities at SQN are designed so that discharges of effluents are in accordance with 10 CFR Parts 20 and 50. The Liquid Waste Processing System is designed to receive, segregate, process, recycle for further processing, and discharge liquid wastes. Liquids entering the Liquid Waste Processing System are collected in sumps and tanks until determination of subsequent treatment can be made. They are sampled and analyzed to quantify radioactivity, with an isotopic accounting if necessary. Processed radioactive wastes not suitable for reuse and the liquid waste suitable for reuse, whose volume is not needed for 10

plant operations or not desired for reuse, are discharged from the plant or packaged for offsite disposal. Design and operation of the Radwaste System is characteristically directed toward minimizing releases to unrestricted areas. Under normal plant operation, the activity from radionuclides leaving the discharge canal is a small fraction of the limits in 10 CFR Parts 20 and 50.

2.2.1.1 System Descriptions The Liquid Waste Processing System was initially designed to collect and process potentially radioactive wastes for recycle to the Reactor Coolant System or for release to the environment.

The liquid waste processing system was, by original design, arranged to recycle as much reactor-grade water entering the system as practical. This was implemented by the segregation of equipment drains and waste streams, which prevents the intermixing of liquid wastes. The layout of the liquid waste processing system, therefore, consists of two main subsystems designed for collecting and processing reactor-grade (tritiated) and non-reactor-grade (non-tritiated) water, respectively. All liquids are now routinely processed as necessary for release to the environment instead of recycling, and are no longer maintained segregated based on tritium content during processing. This includes reprocessing the contents of tanks which accumulate waste water for discharge which may be unsuitable for direct release. Provisions are made to sample and analyze fluids before they are discharged. Based on the laboratory analysis, these wastes are either released under controlled conditions via the cooling water system or retained for further processing. A permanent record of liquid releases is provided by analyses of known volumes of waste. Actual radionuclide inventories of plant effluents are submitted to the NRC as a requirement of 10 CFR 50 by Nuclear Chemistry Offsite Dose Calculation Manual (ODCM).

In addition, a system is provided for handling laboratory samples which may be tritiated and may contain chemicals. Capability for handling and storage of spent demineralizer resins is also provided.

The plant system is controlled from a central panel in the Auxiliary Building and a panel in the main control room. All system equipment is located in or near the Auxiliary Building, except for the reactor coolant drain tank and drain tank pumps and the various Reactor Building floor and equipment drain sumps and pumps which are located in the Containment Building.

The Radwaste Demineralizer System (Rad DI) is located and operated in the Auxiliary Building railroad access bay when the vendor's service is requested.

At least two valves must be manually opened to permit discharge of liquid to the environment.

One of these valves is normally locked closed. A control valve trips closed on a high effluent radioactivity level signal. Controls are provided to prevent discharge without dilutions.

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2.2.1.2 Shared Components Parts of the Liquid Waste Processing System are shared by the two units. The Liquid Waste Processing System consists of one reactor coolant drain tank with two pumps, an Auxiliary Reactor Building floor and equipment drain sump with two pumps, a keyway sump with one pump, and a Reactor Building floor and equipment drain sump with two pumps inside the Containment Building of each unit. It also includes the following shared equipment located inside the Auxiliary Building: one sump tank and two pumps; one tritiated drain collector tank with two pumps and one filter; one floor drain collector tank with two pumps and one strainer; a monitor tank and two pumps; a chemical drain tank and pump; two hot shower tanks and pump; a spent resin storage tank; a cask decontamination tank with two pumps and two filters; the Auxiliary Building floor and equipment drain sump and two pumps; a passive sump; a Radwaste Demineralizer System; and the associated piping, valves, and instrumentation.

The following shared components are located in the Condensate Demineralizer Building for receiving, processing, and transferring wastes from the regeneration of condensate demineralizers: high crud, low conductivity tanks, pumps, and filters; a neutralizer tank and pumps; and a non-reclaimable waste tank and pumps.

2.2.1.3 Separation of Tritiated and Nontritiated Liquids GYN. Waste liquids that are high in tritium content are routed to the tritiated drain collector tank; while liquids low in tritium content are routed to the floor drain collector tank. All tritiated and nontritiated liquid waste are processed for discharge to the environment.

2.2.1.4 Tritiated Water Processing Tritiated reactor grade water is processed for discharge to the environment or for recycle to the primary water storage tank. The water enters the liquid waste disposal system from equipment leaks and drains, valve leakage, pump seal leakage, tank overflows, and other tritiated and aerated water sources including draining of the Chemical and Volume Control System (CVCS) holdup tanks, as desired.

The equipment provided in this channel consists of a tritiated drain collector tank, pumps, and filter and Radwaste Demineralizer System. The primary function of the. tritiated drain collector tank is to provide sufficient surge capacity for the radwaste processing equipment.

The liquid collected in the tritiated drain collector tank contains boric acid, and fission product activity. The liquid can be processed as necessary to remove fission products so that the water may be reused in the Reactor Coolant System or discharged to the environment.

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2.2.1.5 Nontritiated Water Processing Nontritiated water is sampled and processed as necessary for discharge to the river. The sources include floor drains, equipment drains containing nontritiated water, certain sample room and radiochemical laboratory drains, hot shower drains and other nontritiated sources. The equipment provided in this channel consists of a floor drain collector tank, pumps, and strainer, Radwaste Demineralizer System, hot shower tanks and pump, cask decontamination collector tank and pumps, and monitor tank and pumps.

Liquids entering the floor drain collector tank are from small volume, low activity sources. If the activity is below permissible discharge levels following analysis to confirm acceptably low level, then the tank contents may be discharged without further treatment other than filtration.

Otherwise, the tank contents are processed through the Radwaste Demineralizer System.

The hot shower drain tanks normally need no treatment for removal of radioactivity. The inventory of these tanks may be discharged directly to the cooling tower blowdown via the hot shower tank strainer or to other tanks in the liquid waste system.

The liquid waste system is also designed to process blowdown liquid from the steam generators of a unit having primary-to-secondary leak coincident with significant fuel rod clad defects. The blowdown from the steam generators is passed through the condensate demineralizer or directly P to the cooling tower blowdown line.

2.2.1.6 Releases of Liquid Radwaste The Tennessee River/Chickamauga Lake is the sole surface water pathway between SQN and surface water users along the river. Liquid effluent from SQN flows into the river from a diffuser pond through a system of diffuser pipes located at TRM 483.65. The contents of the diffuser pond enter the diffuser pipes and mix with the river flow upon discharge. The diffusers are designed to provide rapid mixing of the discharged effluent with the river flow. The flow through the diffusers is driven by the elevation head difference between the diffuser pond and the river. Flow into the diffuser pond occurs via the blowdown line, Essential Raw Cooling Water (ERCW) System, and Condenser Circulating Water (CCW) System. Two parallel pipelines comprise the diffuser system which is designed to provide mixing across nearly the entire width of the main channel.

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Release of radioactive liquid from the Liquid Waste Processing System can be from the cask decontamination collector tank, CVCS monitor tank, hot shower tanks, or chemical drain tank to the cooling towers blowdown line via the 6-inch diameter Waste Condensate Line (Figure 1.1).

The cooling tower blowdown line empties into the diffuser pond which discharges into the flyer through the diffuser pipes. Liquid wastes from the condensate Demineralizer system are released from the high crud low conductivity tanks, the non-reclaimable waste tank, and the neutralization tank.

The CCW system operates in three modes: open, closed, and helper. In the open mode, the cooling towers are not used. Cooling water is pumped from the intake and through the condenser, and is discharged into the diffuser pond. Dilution water for the radioactive liquid is provided by ERCW, which is in continuous operation and discharges to the cooling tower cold water canal. A weir at Gate Structure 1 ensures that under most river level conditions, the ERCW flow is diverted through the cooling tower blowdown line. The radioactive liquid is mixed with ERCW in the cooling tower blowdown line and flows into the diffuser pond.

In the closed mode, CCW is recirculated between the cooling towers and the condenser. In this mode of operation, the cooling towers blowdown flows at a minimum of 150,000 gpm into the diffuser pond in order to maintain the solids in the cooling water at an acceptable level.

In the helper mode, the CCW from the condenser goes through the cooling towers and is released to the diffuser pond through Gate Structure 1 and the cooling tower blowdown line.

Release of the radioactive liquids from the liquid waste system is made only after laboratory analysis of the tank contents. Once the fluids are sampled, they are pumped to the discharge pipe through a remotely operated control valve, interlocked with a radiation monitor and with instrumentation to ensure adequate dilution flow in the cooling tower blowdown line.

Minimum dilution flow can also be determined via ERCW flow instrumentation, or by periodic flow rate estimation. A similar arrangement is provided for wastes discharged from the condensate demineralizer waste system. The flow control valve is interlocked with a radiation monitor. Release of wastes will be automatically stopped by a high radiation signal.,

The steam generator blowdown system may discharge radioactive liquid. Liquid waste from this system is not collected in tanks for treatment, but is continuously monitored for radioactivity and may discharge to the cooling tower blowdown, or recirculate to the condensate system upstream of the condensate demineralizers. The flow control valve in the discharge line is interlocked with a radiation monitor and with instrumentation to ensure adequate dilution flow on the cooling tower blowdown. Minimum dilution flow can also be determined via ERCW flow instrumentation, or by periodic flow rate estimation.

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The Turbine Building sump collects liquid entering the Turbine Building floor drain system or from clean water sources. in the Auxiliary Building that are transferred to the Turbine Building sump. When the sump is nearly full (maximum capacity 30,000 gallons), the liquid is automatically discharged (level initiated) to the Low-Volume Waste Treatment Pond or the Yard Drainage Pond via the 12-inch diameter Waste Condensate Line (Figure 1.1). The Yard Drainage Pond drains by gravity to the Diffuser Pond which ultimately discharges to the river via the diffusers.

Means are provided for radiological monitoring during normal operations, including anticipated operational occurrences, and during accident condition various process streams and gaseous and liquid effluent discharge paths. Some of the monitors initiate automatic control actions.

Continuous radiological monitoring instruments for liquid processes and effluents include the following locations.

1. Station Sump Discharge Monitor (Turbine Building)

2. Waste Disposal System Discharge Monitor (Auxiliary Building)

3. ERCW Discharge Monitor (Headers A & B)

4. Condensate Liquid Demineralizer Monitor (Demineralizer Building)

5. Steam Generator Blowdown Liquid Discharge Monitor (Turbine Building)

6. Component Cooling System Monitor (Auxiliary Building)

The release locations are also subject to periodic sampling and include all liquid releases which could exceed the limits given in Appendix I, 10 CFR 50 and 10 CFR 20. The sampling and analysis requirements for these release points are defined in the SQN ODCM controls. The plant discharge meets Regulatory Guide 1.21 Revision 1, 10 CFR 20, and 10 CFR 50 guidelines.

The offsite dose calculations for drinking water are based on the assumption that the liquid effluent will be mixed with 60 percent of the river flow between the point of discharge and Chickamauga Dam. Although further mixing will occur, 60 percent dilution is assumed to be maintained for approximately 14 miles until Chickamauga Dam (TRM 471.0) is reached where 100 percent dilution is assumed to occur.

15

2.2.2 Waste Condensate Lines Figure 1.1 shows the locations of the 6- and 12-inch waste condensate lines at the site. The 12-inch waste condensate line receives water from the Turbine Building sump. Turbine Building drains are collected in the Turbine Building sump or discharged directly to various ponds or CCW discharge. Non-radioactive raw cooling water booster pump skid drains, SGB sample panel drains, and auxiliary feedwater pump leakoff drains are also collected in the Turbine Building sump. A temporary-use manifold allows RADCON-approval drainage (e.g., Cycle Outage Ice Melt) to be discharged to the Turbine Building sump. The header penetrates the Auxiliary/Turbine Building wall connecting to an existing drain (old titration room drain) and travels by gravity to the sump.

High conductivity chemical regenerate and rinse wastes that are produced during condensate demineralizer regeneration are routed to the neutralization tank (NT) or, alternately, to the nonreclaimable waste tank (NRWT) where they are collected and neutralized. If the contents of either tank (NT or NRWT) are not radioactive or if the radioactivity level is less than the discharge limit, it is transferred to the Turbine Building sump and subsequently discharged through the low volume waste treatment pond, or alternately it is discharged to the cooling tower blowdown via the 6-inch waste condensate line. If the contents of either the NT or NRWT are radioactive, they may be discharged to the cooling tower blowdown if the radioactivity level is within specification; otherwise, they are processed by the radwaste system.

The Turbine Building sump level is controlled by a high-low level switch that energizes the sump pumps. The sump effluents can be routed to the Yard Drainage Pond or the Low Volume Waste Treatment Pond.

The 6-inch waste condensate line receives routine (almost daily) radioactive effluent discharges from the Liquid Waste Processing System described in preceding sections. Potential leakage of this line was identified as a potential tritium source based on comparable tritium investigations completed at Watts Bar Nuclear Plant (WBN; ARCADIS, 2004), and similarity of SQN plant design to WBN.

The operating pressure of the 6-inch waste condensate line during a radwaste release varies from about 4 psig to negative pressure. Pressure testing of the 6-inch waste condensate line was performed under SQN work order no. 04-776838-004 on April 7, 2006. Service air was used to pressurize the line to 50 psig. After approximately 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, the pressure was measured at 49 psig. After 70 hours8.101852e-4 days <br />0.0194 hours <br />1.157407e-4 weeks <br />2.6635e-5 months <br /> the pressure was measured at 47 psig.

16

On July 10, 2006 a leakage test was performed by connecting a hose, from the Demineralizer Water System to the waste condensate line and filling the pipeline. Following the initial fill, a rotometer was installed (range 0 - 120 cc/min). Experimentation with the rotometer indicated that the lower detection limit of flow was about 1 drop per second which corresponds to approximately 1.3E-05 gpm.

Flow was allowed to stabilize for three weeks. After this period and on two separate occasions, the water supply was isolated (valve closure) from the condensate line. After four days of isolation, the water supply valve was reopened. On each occasion, the ball in the rotometer was observed to have zero movement as the water supply valve was opened. Pressure gauge readings were obtained to ensure that the rotometer results were not invalidated by temperature changes in the condensate line. Results indicated that rotometer testing was valid. The test pressure was approximately 40 psig. Therefore, a leak was not observed at the detection limit of the rotometer and conclusions by SQN staff were that the line does not leak.

2.2.3 Gaseous Radwaste System Controlled airborne releases from the plant ventilation system may result in measurable atmospheric deposition of plant-related radionuclides (including tritium) in the vicinity of the site. Some of this material may accumulate on plant roof surfaces and discharge into roof drains during precipitation events. Rain may also wash airborne releases onto facility soil and building surfaces.

The impact of this potential source of groundwater contamination may vary substantially with release periods and meteorological conditions. While this potential source is not likely to be a major contributor to groundwater contamination, operators of at least one nuclear power plant believe that measurable tritium concentrations in groundwater at their site are likely due to the deposition of tritium in airborne effluents (NRC, 2006). Recognition that atmospheric deposition may be a process actively contributing to observed wide-spread, low-level tritium concentrations in groundwater would allow explanation of the presence of these low-level concentrations when no other potential source can be identified.

The Gaseous Waste Processing System is designed to remove fission product gases from the reactor coolant and to permit operation with periodic discharges of small quantities of fission gases through the monitored plant vent. This is accomplished by internal recirculation of radioactive gases and holdup in the nine gas decay tanks to reduce the concentration of radioisotopes in the released gases. The offsite exposure to individuals from gaseous effluents released during normal operation of the plant is limited by Appendix I of 10 CFR 50 and by 40 CFR 190.

17

The Gaseous Waste Processing System consists of two waste-gas compressor packages, nine gas decay tanks, and the associated piping, valves and instrumentation. The equipment serves both units. Gaseous wastes can be received from the following: degassing of the reactor coolant and purging of the volume control tank prior to a cold shutdown, displacing of cover gases caused by liquid accumulation in the tanks connected to the vent header, purging of some equipment, sampling and gas analyzer operation, and boron recycle process operation (no longer in service).

Gaseous radioactive wastes are released to the atmosphere through vents located on the Shield Building, Auxiliary Building, Turbine Building, and Service Building.

2.3 Inadvertent Releases of Liquid Radwaste Design and operation of the Radwaste System is characteristically directed toward minimizing releases to unrestricted areas. However, accidental releases of radioactive effluents and unusual occurrences to outdoor environs at SQN have been documented by TVA (2006) for the period from July 1981 (Unit 1 startup) to July 2006. A comprehensive review of these data is important for this investigation since these historical releases may serve as sources of tritium identified within the site groundwater system. Records of releases by TVA (2006) are based on report documentation for most of the occurrences and via interviews conducted with SQN Radiation Protection staff for earlier events.

Eight accidental releases of radioactive effluents and unusual occurrences to outdoor environs at SQN have been documented to date. Figure 2.4 identifies the approximate locations of these events and descriptions are provided in the following paragraphs.

1. Condensate DemineralizorWaste Evaporator(CDWE) Building - mid-1980s Based on personnel interviews, radioactivity leached through a concrete wall of the CDWE Building to an outside concrete slab and soil. It is presumed that this was an aqueous release.

Contaminated soil was excavated and the building wall was painted with sealant. Quarterly surveys (RMD-FO-35) were subsequently performed by Radiation Protection.

2. Unit 2 Additional Equipment Building (Upper HeadInjection) - mid-i 980s Based on personnel interviews, a hose burst spraying water through a door to outside environs. An asphalt area was painted with sealant, and a vehicle and Porta-John toilet were decontaminated. Quarterly surveys (RMD-FO-35) were subsequently performed by Radiation Protection.

18

/

A 4 4

A 7 10 8 m

f

/ S

,, t

", II 5, 4 I Unit 1

1. CDWE Building

2. Unit 2 Additional Equipment Building /1

3. Auxiliary Building Exhaust

4. Unit 2 RWST Moat

5. MFTDS Release Unit 2

6. Unit 2 Additional Equipment Building 8.6 *

7. Unit 1 RWST Moat

8. Units 1 & 2 RWST Moats Figure 2.4 Site Map Showing Locations of Inadvertent Releases of Liquid RadWaste 19

3. Auxiliary Building Roof- early 1990s Based on personnel interviews, radioactive contamination was discovered on the Auxiliary Building roof. Origin of contamination was determined to be unfiltered fuel handling ventilation trains associated with Auxiliary Building ventilation stack discharge.

Remediation is cited as contamination being removed from the roof. Quarterly surveys (RMD-FO-35) were subsequently performed by Radiation Protection.

4. Unit 2 Refueling Water Storage Tank (RWST) Moat Drain - May 10, 1995 During performance of a routine environmental monitoring survey (RMD-FO-35),

radioactivity was identified in soil at the moat drainage outlet of the Unit 2 RWST (Figure 2.5). The drain outlet is located on the south side of the moat and discharges to gravel covered soil. Follow-up sampling was performed and Co-58, Co-60, Cs-134, and Cs-137 were identified in soil in excess of the MDC of 5.OE-07 gCi/g. Documentation includes survey number D-95-0558 with attached sample gamma analysis results from WARL.

Figure 2.5 Photograph of Unit 2 Moat Drainage to Ground Surface

5. ModularizedTransferDemineralizationSystem (MFTDS) Release to RailroadBay - May 19, 1997 Due to failure of the conductivity probe on the MFTDS, approximately 3,000 gallons of water was released to the 706 ft-msl elevation Railroad Bay (Figure 2.6). It was estimated that 600-1000 gallons of water was released to the RadWaste Yard immediately adjacent to the Railroad Bay door. Problem Evaluation Report (PER) No. SQ971429PER was initiated to investigate the release. A subsequent report (Smith, 1997) addresses cleanup at the site.

20

I EL. 706 RADWASTE YARD SAMPLING GRID 116 IGrid Point sample Iocation Sampling Asphalt Soil 1 sphalt and 1 soil form each pant Grid I 2.65-3 2.25-2 2 ND ND 3 ND ND 4 2.95-1 ND LI 5 6

7 6AE-2

.5E-3 t.6E-1 ND

.815-3 1.15-2 Iv t.

a 9

6.55-2 1.8E-3 D 5-1 ND ND 2.115.3 NO 18 I Edmated 12 3.522E-2 ND of water 13 10 0> 3 E-233..

E-2 3.05-3 le C14 k.J 3 E-2 2.M53 IE-2 6.71-3

.0E-2 .87E-3 17 1"5.6E-2 NO 1 ND NO 19 ND ND 16 Activitis not Quantative, they ara only for determining extent of contamination I

0 0 00 II rim*

Figure 2.6 Map Showing Extent of MFTDS Release to Railroad Bay (from Halter, 1997) 21

Smith (1997) indicates that the water spill was observed to spread over a 950 ft2 asphalted area. The initial response also noted a vortex near railroad ties within the release area.

Subsequent investigation revealed a French drain system parallel to both sides of the existing railroad track and extending outside of the Radiation Control Area (RCA). Soils samples were collected and select isotopes (Co-57, Co-58, Co-60, Cs-134, Cs-137, Nb-95, and Mn-54) were screened to 5.0E-07 gtCi/g. Results indicated radioactive contamination at and below the French drain system for several soil samples.

Asphalt and soil were excavated beginning June 6, 1997. Approximately 200 ft3 of uncontaminated asphalt and 2000 ft3 of uncontaminated soil were removed outside of the RCA. About 1000 ft3 of contaminated soil, sand, and gravel were also excavated outside of the RCA. Smith (1997) notes that there were no attempts to remove concrete containing electrical conduit banks that were observed to be contaminated. There were also culverts observed with inaccessible contaminated sand that were not removed. The excavated French drain outside of the RCA was backfilled with concrete.

Excavation of the affected are inside of the RCA resulted in about 5500 W of radioactive contaminated asphalt, soil, sand, and gravel. The excavation area was 18 x 54 ft with excavation depth being limited by a concrete pad about 3-ft below ground surface. This and other concrete supports within the RCA were not disturbed and residual radioactive is accounted for in Smith (1997). The excavated area within the RCA was backfilled with concrete.

Quarterly surveys (RMD-FO-35) were subsequently performed by Radiation Protection.

6. Unit 2 Additional Equipment Building (UpperHeadInjection) Sump Release - January 10, 1998 The Unit 2 Additional Equipment Building sump overflowed, exited the double-doors, and continued along a straight-line route (110 linear ft) to the nearest storm drain catch basin (Figure 2.7). The response team observed released water flowing into the catch basin.

Sampling confirmed radioactivity in asphalt and soil leading to the catch basin. Water samples collected at the catch basin and at the storm drain discharge to the Yard Drainage Pond did not identify the presence of radioactivity. A water sample collected inside the building indicated Xe-I133 to be the dominant radionuclide. A total of 32 soil samples were collected before and during excavation and sample analyses included a peak search for the Xe-133 energy peak. All results were negative. Select isotopes (Co-58, Co-60, Cs-134, and Cs- 137) were also used to screen soil samples to 5.OE-07 JtCi/g during excavation. Sediment samples from the release area catch basin contained CO-60 and Co-58 at 8.65E-07 and 5.99E-07 g.Ci/g, respectively.

22

Unit 2 Unit 2 Additional Equipment Building Sump Release Reactor January 1998 Building U2 Valve Vault A Unit 2 Equipment Building 68' CDWE Bldg.

Storm Drain 100' Storm Drain Catch Basin Posted Area Boundary Legend: RCA- ----------

Figure 2.7 Map Showing Extent of Sump Release at Unit 2 Additional Equipment Building (from Halter, 1998) 23

A recovery report by Halter (1998) described remediation associated with this release.

Decontamination of the Additional Equipment Building was initiated on January 10, 1998.

Three additional storm drain catch basins were identified for sampling no gamma energy peaks were identified from gamma spectroscopy analyses. The asphalt layer immediately outside of the door was removed. Excavation of gravel and soil along the release route 3

varied from 4 to 10 inches in depth and averaged about 19.5 ft in width. A total of 2070 ft of excavated material was removed and replaced with aggregate material. Figure 2.8 provides photographs of the recovery area. As shown in this figure, groundwater monitoring well W21 is located within the drainage route of the released water.

Quarterly surveys (RMD-FO-35) were subsequently performed by Radiation Protection.

7. Unit 1 Refueling Water Storage Tank (R WST) Moat Drain - April 3, 2002 Pre-excavation samples of the steam generator replacement crane foundation identified radioactivity in soil surrounding the Unit 1 RWST moat drain. The drain outlet is located on the west side of the moat, extending through a retaining wall and discharging to an asphalt parking area (Figure 2.9). Soil sampling was performed and radioactivity (Mn-54, CO-57, Co-58, Co-60, SB-125, Cs-134, and Cs-137) was identified in eleven shallow soil samples in excess of the MDCs. Seventeen additional soil samples were collected in August 2002 gamma scans indicated no activity for all samples. Documentation includes a drawing of sample locations with attached sample gamma analysis results from WARL.

Quarterly surveys (RMD-FO-35) were subsequently performed by Radiation Protection.

8. Tritium in Unit I and 2 R WST Moat CollectedRainwater - July 17, 2006 Each of the Unit 1 and 2 RWST moats is open to the collection of rainfall. This design differs from other plants such as WBN where permanent covers are installed to direct precipitation away from the moats. Per team discussions at the onset of this investigation, chemistry surveillance instruction 0-SI-CEM-040-421.0 was revised during the first quarter of 2006 to require tritium analysis of moat water. This revision also includes a requirement for discharge of Unit 2 moat water to either the Auxiliary Building RadWaste System or the Turbine Building Sump.

RWST moat water samples were collected July 11, 2006 and tritium concentrations of 517 and 19.5 pCi/mL were observed for Units 1 and 2, respectively. Documentation includes a memorandum by Halter (2006) describing operations, sampling, tritium results, and photographs.

24

Figure 2.8 Photographs of Sump Release Area at Unit 2 Additional Equipment Building (from Halter, 1998) 25

Numbered Sampling Locations q, ~

7 8

6 4 5 11 10 2 3 9 Retaining Unit I RWST

/

Plan View (NTS)

Figure 2.9 Schematic of Sampling Locations and Photograph of Unit 1 RWST Moat Drain

'I, -IT, 26

3.0 HYDROGEOLOGY 3.1 Site Location and Scope of Exploration The SQN site is situated on a peninsula extending from the western bank into Chickamauga Lake between TRM 484 and 485 (Figure 3.1).

Pre-operational subsurface investigations of the site began in 1953. Figure 3.2 depicts the locations of exploratory borings installed at the site during these investigations. Twenty-nine holes were drilled into rock while seventeen were fishtailed to the top of sound rock. From September 1968 to February 1969, additional holes were drilled to fill in a 100-foot grid in the Control and Auxiliary Building area, and in the reactor areas, with holes drilled at the intake structure and other locations in the general plant area. In addition to obtaining information on the foundation conditions, the holes in the reactor areas were used for dynamic seismic investigations. During September and October 1969, a third drilling program was carried out to further investigate the reactor, control, and auxiliary areas on a 50-foot spacing, and to examine the condition of the Kingston fault northwest of the plant site (TVA, 2005).

Post-operational subsurface investigations at the site have been conducted to resolve contaminant release issues and for siting of new facilities. Edwards et al. (1993) and Julian (1993) installed 21 soil borings and 9 groundwater monitoring wells to assess No. 2 Diesel Fuel Oil contamination from underground transfer lines. Julian (2000) conducted a groundwater supply study that included review of groundwater supply wells located in the vicinity of SQN. Siting for the Independent Spent Fuel Storage Installation (TVA, November 2001) involved the installation of three monitoring wells and numerous shallow borings to assess petroleum contamination (TVA, June and September 2001). From February 2002 - April 2004, 12 shallow groundwater monitoring wells were installed for evaluations of tritium releases from the 6- and 12-inch waste condensate lines.

Soil borings and wells installed as part of this tritium investigation are described in following paragraphs.

27

SEQUOYAH NUCLEAR PLANT Site Location

-Reservation Boundary AN Fe~

0 500 1,000 1.500 2W00 PREPARED BY:TVAGEOGRAPIHIC INFORMATIN ANDENGINEERING kmag is a [igka Rat&WGmphl 19701$

Figure 3.1 Site Location Map 28

SEQUOYAH NUCLEAR PLANT Exploratory Borngs BOREHOLE TYPE

• Corehole

• Borehole Reservation Boundary Feet 0 500 1,000 1,500 2.000 PREPARED BY: TVA GEOGRAPHIC INFORMATKIN AND ENGINEERING knap Is a Di&W Odhophowog.ah 2004 Figure 3.2 Locations of Exploratory Borings 29

• 3.2 Physiography The Valley and Ridge Province is a long narrow belt trending NE-SW that is bordered by the Appalachian Plateau on the west and by the Blue Ridge Province on the east.

Geochronologically, this province represents the eastern margin of the Paleozoic interior sea.

Structurally, it is part of an anticlinorium, the successor to a geosyncline that sank intermittently for ages as it received sediments from the concurrent rising land surface on the east. The topographic and geologic grain of this subregion is elongated NE-SW in conformity with the trend of the Appalachians region. Viewed empirically, the province is a lowland; an assemblage of long, narrow, fairly even-topped mountain ridges separated by somewhat broader valleys.

The ridges are developed in areas underlain by resistant sandstones and more siliceous limestones and dolomites. The valleys have been developed along structural lines in the areas underlain by easily weathered shales and more soluble limestones and dolomites.

Prior to the impoundment of Chickamauga Reservoir, the Tennessee River in the vicinity of SQN had entrenched its course to elevation 640. The small tributary valley floors slope from the river up to around elevation 800 ft-msl, while the crests of the intervening ridges range between 900 and 1000 ft-msl.

Figure 3.3 shows topography at SQN. The majority of the plant site resides at a grade elevation of 705 ft-msl. Elsewhere, terrain is rolling with the highest elevation of about 775 being encountered southeast of the plant site at the top of Locust Hill (LLRWSF site).

3.3 Geomorphology The SQN site resides near the western border of what was the active part of the Appalachian geosyncline during most of the Paleozoic era. During this time, the area was below sea level and more than 20,000 feet of sedimentary rocks were deposited. At the end of the Paleozoic era, some 250 million years ago, the area was uplifted and subjected to compressive forces acting from the southeast. Folds developed which were compressed tightly, overturned to the northwest, and finally broken by thrust faults along their axial planes. The resultant structure is characterized by a series of overlapping linear fault blocks which dip to the southeast. Since this period of uplift, the area has been subjected to numerous cycles of erosion. This erosion accentuated the underlying geologic structure by differential weathering of the less resistant strata resulting in the development of parallel ridges and valleys which are characteristic of the region.

30

I/

SEQUOYAII NUCLEAR PLANT NU 45

/ Site Topographic Map

/

~-' L~

/

r Emkp.

!uew*.

//

/ 2-ACrt 12-ftcIWas CwUonsuaw Lime Lot 1jERCV*'CW iuus i'~1

/

/ LM C.hoTwinsi

~ mkw 7

.7 / /

Risiewvtoni Bo..ndry 4

t sftw2

-I I L I Q7Q II C-" I K / Tennessee A

River I ~lh~ft qEAI~v WO~fIUBSNK Chickammauga

=

Vn.. Sd C~eU Reservoir U

/

Figure 3.3 Site Topographic Map 31

3.4 Geology 3.4.1 Stratigraphy Of the numerous sedimentary formations of Paleozoic age in the plant area, only the Conasauga Formation of Middle Cambrian age is directly involved in the foundation bedrock of the plant (Figure 3.4). Unconsolidated alluvial, terrace, and residual deposits mantle the Conasauga formation at the site. More recent alluvial deposits, that were associated with the floodplain of the Tennessee River, are now covered by the Chickamauga Reservoir.

3.4.2 Bedrock The Conasauga formation at the site is composed of several hundred feet of interbedded limestone and shale in varying proportions. The shale, where fresh and unweathered, is dark gray, banded, and somewhat fissile in character. The limestone is predominantly light gray, medium grained to coarse crystalline to oolitic, with many shaly partings. A statistical analysis of the cores obtained from the site area indicates a ratio of 56 percent shale to 44 percent limestone. Farther to the southeast and higher in the geologic section, the amount of limestone increases in exposures along the shore of the reservoir.

The general strike of the Conasauga is N30 0 E and the overall dip is to the southeast, normally steep, ranging from 600 to vertical; however, many small, tightly folded, steeply pitching anticlines and synclines result in local variations to the normal trend.

According to TVA (1979), cavities and solution openings are not a major problem in the site foundation. Most solution openings are restricted to the upper few feet of bedrock near the overburden/bedrock interface. The insolubility of interbedded shale in deeper bedrock functions as a lithologic control to the development of large solution openings. However, small solution openings and partings may exist at greater depths within the bedrock along faults and joints, especially along synclinal zones. Inspection of the walls of the exploratory holes with television disclosed thin, less than 0.05 foot, near-horizontal openings in some of the limestone beds. At the corresponding position, the drill cores showed unweathered breaks. These open partings are interpreted as "relief joints" developed by unloading either from erosion or excavation. The majority was found in the upper few feet of rock, but some were observed as deep as 131 feet below the rock surface.

32

Conasauga Formation Chickamauga Formation Knox Formation Formation Contact -

Major Thrust Fault Section A -A' (not to scale)

Figure 3.4 Regional Map Showing Geologic Formations and Structure 33

Figure 3.5 shows the Conasauga bedrock surface based on all available site boring data. As would be expected in a foundation composed of alternating strata of different composition and competency, the configuration of the bedrock surface is irregular (TVA, 1979). The strike of the rock strata is approximately parallel to the centerline of the reactors. Preliminary excavation for foundation investigations (down to 18 inches above design grade) exposed a series of alternating ridges of harder limestone separated by troughs underlain by the softer shale trending across the plant area. The last 18 inches were removed by careful and controlled means so as to limit breakage below the design grade to a minimum. Once foundation grade was reached, the area was carefully cleaned and then inspected jointly by engineers and geologists to determine what, if any, additional material needed to be removed because of weathering or shattering by blasting.

Figure 3.6 exemplifies top of rock exposed in the Reactor, Auxiliary, Control, and Turbine Buildings prior to excavation.

After the final excavation was approved, the area was covered either by a coating of thick grout or by a fill pour of concrete to prevent weathering of the shale interbeds due to prolonged exposure. Observation of rock exposed in the foundation areas, examination of cores, and investigations of the walls of exploratory holes with a borehole television camera all indicated that solution cavities or caves are not a major problem in the foundation. Verified cavities generally were limited to the upper few feet or rock where solution developed in limestone beds near the overburden-rock interface. Practically all of this zone was above design grade and was removed.

A consolidation grouting program was performed from February 18 through June 15, 1970 in the foundation areas for the Reactor, Auxiliary, and Control Buildings at the Sequoyah Nuclear Plant. The extent of the area treated is shown in TVA (2005; Figures 2.5.1-9 and 2.5.1-10). The purpose of this program was twofold. The first was to consolidate near-surface fractures predominantly caused by blasting and excavation. The second was to treat any localized open joints, bedding planes, fractures, or isolated small cavities that pre-construction exploratory drilling indicated might be present to a depth of 45 feet below the design foundation grade.

In the excavated area, the contact between the residual material and essentially unweathered rock occurs at an average elevation of 680 ft-msl. The highest design level for the plant foundation grade under the Class I structures is at elevation 665 ft-msl. As a result, the preliminary excavation averaged a minimum of 15 feet in rock. Over most of the area, the rock was suitable for foundation purposes at elevation 665 ft-msl.

34

SEQUOYAH NUCLEAR PLANT Top of Conasauga Bedrock Top of Bedrock Contour (ft-msl)

• Boring Reservation Boundary AN Fee 0 20 400 600 5W00 1 PREPARED BY:TVAGEOGRAPHIC INFORMATION ANDENGINEERING Imag. Is a DigiWOdhobogruphl 2004 Figure 3.5 Surface of Conasauga Bedrock 35

\1 VII r.,orofC~i 61 05!

(tOINZIO) roao ttC1tE70st-2 I7 M' 77'- _________- d Figure 3.6 Pre-excavation Top of Bedrock Contours (ft-msl) at the Reactor, Auxiliary, Control, and Turbine Buildings (from TVA Drawing 10N21 I) 36

In two areas, however, additional rock had to be excavated to remove localized pockets of deeper weathering. These zones were confined in two synclinal areas which crossed the excavation parallel with the north- south baseline. The axis of one lies approximately 70 feet plant east of the baseline and the axis of the other is approximately 140 feet plant west of the baseline. These trough-like synclines had channeled groundwater movement toward and along their axes with the result that weathering had progressed deeper in these areas. Generally, less than 10 feet of additional rock had to be removed from the synclinal zones to obtain a satisfactory foundation; however, in the vicinity of W140; S 220, on the south side of the Auxiliary Building, as much as 30 feet of weathered rock was removed.

3.4.3 Soil Unconsolidated alluvial, terrace, and residual deposits mantle the Conasauga formation at the site. More recent alluvial deposits that were associated with the floodplain of the Tennessee River are now covered by the Chickamauga Reservoir. Alluvium within the area of the main plant site was removed during construction and only residual soils remain. In the plant area'not mantled by terrace deposits, the Conasauga is overlain by varying thicknesses of residual silt and clay derived from weathering of the underlying shale and limestone. The residual soils are primarily silts and 'clays grading downward into saprolitic shale of the Conasauga. In a few localized areas weathered shale is exposed at the ground surface. However, in most exploratory drilling the residuum depths ranged from 3 to 34 ft.

A pre-construction soils exploration program was conducted at the plant site to determine the static physical characteristics of the soils. Standard split-spoon borings and undisturbed borings were made. Grain size analyses shows that soils across the site range from fat clay residual material to sand and gravel terrace deposits.

The age of unconsolidated material at SQN is in excess of 30,000 years. No carbonaceous soil was encountered in site excavation and no other dating criteria could be established (TVA, 1979). Carbon 14 dates from material found in high alluvial terrace deposits at the Watts Bar Nuclear Plant located about 38 miles northeast of Sequoyah placed the age of the material at 32,400 years.

Terrace deposits overlie residuum with varying thickness across the site., Terrace material consists predominantly of sandy clay with embedded rounded cobbles and pebbles of quartzite, quartz and chert. This material represents deposition at a time when the river was flowing at a higher elevation during an earlier erosion cycle. According to TVA (1979), a maximum thickness of 45 feet of terrace deposits was encountered in exploratory drilling in the topographically high areas southeast of the site, and it is quite probable that greater thicknesses exist under the highest portion of this area (i.e., Locust Hill). Evidence suggests that residual 37

material has essentially been eroded away under Locust Hill with terrace deposits directly overlying bedrock. This hill is the location of the LLRWSF.

Based upon more extensive borings, Boggs (1982) describes the Low Level Radwaste Storage Facility (LLRWSF) site as being underlain by residual and alluvial soils generally consisting of clay and silt with minor amounts of sand and gravel. According to Boggs (1982), soil thickness averages about 50 feet within the LLRWSF area, but varies radically over short distances due to a highly irregular bedrock surface configuration. Fill/spoil material was also used as foundation material beneath the LLRWSF.

In situ soil dynamic studies were made at the plant site to obtain data for computation of elastic moduli for earthquake design criteria. The areas investigated at the site were the Diesel Generator Building, the LLRWSFs, the ERCW pipeline, the Additional Diesel Generator Building, and the Primary Water Storage Tank.

Prior to and during construction, borrow investigations were made on an as-needed basis. The borrow samples were tested by the central materials laboratory according to ASTM D-698 to develop, compaction control curves. The compaction curves were divided into subclasses to control compaction of earthfill at the site. At SQN, Type A backfill (sandy to silty clay) was placed around all Category I structures. This material, which was selected earth placed in not more than 6-inch layers, has a minimum required compaction of 95 percent of the maximum dry density at optimum moisture content. The limits of excavation and the backfill around Category I structures can be visualized in Figure 3.7.

A free-draining granular fill material, consisting of crushed stone or sand and gravel, was placed below or next to Category I structures. This material was obtained commercially from off-site sources. The granular fill was suitable for compaction to a dense, stable mass and consisted of sound, durable particles which are graded within the following limits:

Percent by Weight Passing Minimum Maximum 11/4-inch 100 1-inch 95 100 33/4-inch 70 100

%-inch 50 85 No. 4 33 65 No. 10 20 45 No. 40 8 25 No. 200 0 10 0

38

" *,Discharge Conduits Figure 3.7 1971 Site Construction Photograph of the Reactor, Auxiliary, Control, and Turbine Buildings 39

• A crushed rock material that meets the gradation requirements shown below was used for remedial treatment in local areas. This was generally done where moisture caused the soil to be unsatisfactory as a base for earthfill placement. The material was used in a limited area at the RWST pipe tunnel. The material was placed in approximate 6-inch loose layers and rolled into the soil. If the required stiffness for the placement of earthfill was achieved, lifts of earth-fill or crushed stone fill were placed. If the required stiffness was not achieved, then additional lifts of the material were placed and rolled to obtain the desired stiffness. If shearing or pumping occurred in placement of the first lift, additional lifts of the material were placed as necessary.

Percent by Weight Passing Minimum Maximum 3-inch 95 100 2-inch 25 55 11/2-inch 0 15 1-inch 0 2 3.4.4 Structure The controlling features of the geologic structure at the Sequoyah plant site are the Kingston Thrust fault (Figure 3.4) and a major overturned anticline that resulted from the movement along the fault. This fault lies about a mile northwest of the plant site (Figure 2.5.1-2), and can be traced for 75 miles northeastward and 70 miles southwestward. The fault dips to the southeast, under the plant site, and along it steeply dipping beds of the Knox dolomite have been thrust over gently dipping strata of the Chickamauga limestone. The distance from the plant site, about one mile, and the dip of the fault, 30 degrees or more, will carry the plane of the fault at least 2000 feet below the surface at the plant site.

The major overturned anticline results in the Conasauga formation at the plant site resting upon the underlying Knox dolomite which normally overlies it. As a result of the ancient structural movement of the fault and major fold, the Conasauga formation at the plant site is highly folded, complexly contorted, and cut by many very small subsidiary faults and shears. The general strike of these beds are N 30'E and the overall dip is to the southeast, but the many small tightly folded, steeply pitching anticlines and synclines result in many local variations to the normal trend.

In some of the drill cores, small faults and shears were noted intersecting the bedding at various angles. These dislocations are the result of shearing along the limbs of the minor folds which developed contemporaneously with the major movement along the Kingston fault.

40

3.5 Hydrology The SQN site is in the eastern Tennessee portion of the Southern Appalachian region, which is dominated much of the year by the Azores-Bermuda anticyclonic circulation. This circulation over the southeastern United States is most pronounced in the fall and is accompanied by extended periods of fair weather and widespread atmospheric stagnation. In winter, the normal circulation pattern becomes diffuse as the eastward moving migratory high and low pressure systems, associated with the midlatitude westerly current, bring alternating cold and warm air masses into the area with resultant changes in wind direction, wind speed, atmospheric stability, precipitation, and other meteorological elements. In summer, the migratory systems are less frequent and less intense, and the area is under the dominance of the western edge of the Azores-Bermuda anticyclone with a warm moist air influx from the Atlantic Ocean and the Gulf of Mexico (TVA, 2005).

The climate of the watershed above SQN is humid temperate. All recharge to the groundwater system at the plant site is from local precipitation, which averages around 51 inches per year.

The Tennessee River above SQN site drains 20,650 mi 2. Chickamauga Dam, 13.5 miles downstream, and Watts Bar Dam upstream (TRM 529.9) affect water surface elevations at the Plant. Peaking hydropower operations of the dams cause short periods of zero and reverse flow near the plant. Based upon discharge records since closure of Chickamauga Dam in 1940, the average daily streamflow at the site is 32,600 cfs (TVA, 2005).

Chickamauga Reservoir water elevations vary seasonally according to operations for power production, navigation, and recreation. The operating guide for Chickamauga Dam is shown in Figure 3.8. As shown in Figure 3.9 elevations of the SQN Discharge Channel correlate with the operating guide. This is associated with plant operations during warmer months that are designed to comply with reservoir thermal release limits.

During high flow periods, the top of the normal operating zone may be exceeded for the regulation of flood flows. During the late spring and summer, TVA varies the elevation of Chickamauga Reservoir to aid in controlling mosquito populations. Elevations are lowered during the week and raised a foot on weekends, to strand mosquito eggs and larvae on the shoreline. Normal full pool elevation is 683.0 ft-msl. At this elevation, the reservoir is 58.9 miles long on the Tennessee River and 32 miles long on the Hiwassee River. The reservoir is approximately 3,000 feet wide at the site, with depths ranging from 12 feet to 50 feet at normal full pool elevation. Probable maximum flood elevation is 722.6 (TVA, 1979).

41

688 686 684 2007 Observed 682 Midnight Elevations (U

2006 Observed 680 Midnight Elevations 0~ 678 Normal Operating

-4 Zone 676 674 672 670 1_ , J L _ ___

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 2007 Figure 3.8 Operating Guide For Chickamauga Dam 42

690

--,-- Discharge Channel

-AM ~689Trn 688 o .0 S687

.686 A

j685 LU 684 683 682 681

-j) 0 Z a Figure 3.9 Mean 1995 - 1999 Discharge Channel Elevations 3.6 Groundwater The peninsula on which SQN is located is underlain by the Conasauga, a poor water-bearing formation. About 2,000 feet northwest of the plant site, the trace of the Kingston Fault separates the Conasauga Shale from a wide belt of Knox Dolomite (Figure 3.4). The Knox is a major water-bearing formation of eastern Tennessee. Based on a comprehensive examination of bedrock coreholes (TVA, 1979), groundwater in the Conasauga occurs in small openings along fractures and bedding planes; these rapidly decrease in size with depth, and few openings exist below a depth of 300 feet.

There is no groundwater use at SQN. The source of groundwater at SQN is derived from incipient infiltration of precipitation. Within overburden soils at the site, groundwater movement is generally downward. Local areas of natural lateral flow likely occur near some streams, topographic lows, and where extensive root systems exist. Anomalous groundwater movement might also occur in areas that have experienced soil unraveling and in the vicinities of pipelines (especially those with relatively permeable bedding and fill).

Groundwater movement is expected to occur mainly along strike of bedrock, to the northeast and southwest, into Chickamauga Reservoir. Groundwater also discharges from overburden soils into the reservoir, site drainage channels (i.e., Discharge Channel), and surface water impoundments (i.e., Diffuser Pond). Higher surface water levels of Chickamauga Reservoir (April - October) result in corresponding rises in the groundwater table and the lateral extent of this effect varies with groundwater hydraulic gradients. Lower levels of Chickamauga Reservoir (November - March) result in corresponding declines in the water table along the reservoir periphery.

43

Pre-construction boring logs collected by TVA (1979) suggest that groundwater transmissivity across the strike in the Conasauga formation is extremely low. Local variations in hydraulic conductivity within the shallow bedrock are primarily controlled by geologic structure and stratigraphy. Shale beds and clay seams provide lithologic restrictions to the vertical movement of groundwater. The Conasauga/Knox contact northwest of the plant has been described as a hydraulic boundary; however, no field testing has been conducted to verify this assumption.

Bedrock porosity is estimated to be about 3 percent based upon results of exploratory drilling.

Prior to the current study, a total of eight (8) long-term bedrock monitoring wells had been installed at the SQN site. Figure 3.10 indicates the depth of open borehole and/or screened interval for each well and wells are located as shown in Figure 1.2. Well construction details are provided in Appendix A.

800 WI 0I39 U o NS 65.2 W2 5431 N's N6r 70.5 W4 611.9 5.4 Nn 1150 WS 5441 107.0 None *00 750 LO 65*.9 94 45.1 095 L7 5.1 10.0 449 310 we 444.1 210.0 1No40 40-0 700 S650 i~i I 600 -1. - --- - --------- ----------

550 W1 W2 W4 W5 L6 L7 W8 Open Borehole Slotted Screen Blank Casing Figure 3.10 Site Bedrock Monitoring Wells Long-term groundwater level data have been collected to establish temporal trends for six wells at the SQN site. Since these monitoring wells are developed in bedrock and weathered bedrock, any deductions regarding groundwater movement is restricted to this flow regime. Figure 3.11 shows water level data obtained for wells WI, W2, L6, and L7. The plot indicates that groundwater levels measured for wells WI and L6 are strongly influenced by reservoir stage.

The fluctuation in groundwater levels at well L6 is almost completely correlated with the cyclic operation of the reservoir. Well W1 exhibits water levels that also correspond with the 44

periodicity of reservoir stage; however, reservoir effects are diminished for times around 1986 and 1988. This might be attributed to drought conditions and diminished precipitation at the site during these times. The hydrographs for wells W2 and L7 appear to be influenced by water retention basins on the south side of the plant and do not display reservoir stage effects. Well W2 is located near the Yard Drainage Pond and well L7 is in the vicinity of the Return Channel.

There is a large degree of correlation between water levels in the two wells and this may be related to plant discharges and pond operations. The free water surface in the Return Channel is maintained at a higher elevation than the reservoir by a discharge flume and weir. The minimum normal water surface elevation in the Return Channel is given as 689 ft-msl according to TVA drawing number 31W600-2. The average horizontal hydraulic gradient from well L7 to L6 is 0.01 ft/ft. The average horizontal hydraulic gradient from well W1 to W2 is about 0.003 ft/ft.

695 690

~685 -Wi W2 0

680 L6 L7 (4~ U.'

PRher 675 670 Year Figure 3.11 Time-Series Groundwater Levels for Wells WI, W2, L6, and L7 (1985-1991)

Figure 3.12 shows groundwater elevations for wells Wl, W4, W5 and L7. This plot also indicates that the Return Channel and the Discharge Channel influence groundwater elevations in the southeastern area of the SQN site. The average horizontal hydraulic gradient from well W4 to L7 is approximately 0.0071 ft/ft; from well W1 toward the Intake Channel it is about 0.007 ft/ft; and from well W4 to W5 it is approximately 0.004 ft/ft.

(P 45

695 690 685-W C W4 1680 ---- L7 10675 _______

670 Year Figure 3.12 Time-Series Groundwater Levels for Wells W1, W4, W5 and L7 (1985-1991)

The direction of regional groundwater movement is primarily towards the SQN Intake and Discharge Channels based on historical and recent (12/13/2006) potentiometric mapping (Figure 3.13). Exceptions to this directional flux have occurred locally due to leaking water lines serving the site; in areas of topographic highs/lows; and from dewatering operations of the Diesel Fuel Oil Interceptor Trench.

Extensive pre-construction characterization studies were conducted at the plant site to determine the static physical characteristics of the soils. However, few field tests or laboratory measurements were performed to assess the hydraulic properties of site soils and bedrock.

Laboratory permeameter testing of an undisturbed residual soil sample (boring US-53; TVA, 1979) indicates horizontal and vertical hydraulic conductivity values of 7.8E-07 and 1.3E-08 cm/s (a ratio of 1:60). A statistical summary of soil hydraulic properties at the LLRWSF (Table 3.1) suggests that residual soils and alluvium might be expected to exhibit saturated K values ranging from 5.8E-06 to 3.4E-09 cm/s.

Table 3.1 Statistical Summary of Soil Properties (from TVA, 1981)

Standard No. of Parameter Minimum Mean Maximum Deviation Samples Porosity 0.31 0.53 0.70 0.10 257 Density (Ib/ft3) 51.3 81.1 116.8 16.5 263 Saturated Hydraulic 3.4E-09 7.9E-07 5.8E-06 1.8E-06 19 Conductivity (cm/s)

Natural Saturation (%) 41.0 93.0 100.0 9.0 263 46

SEQUOYAH NUCLEAR PLANT Site-wide Potentiometic Surface Map December 13, 2006 Monitoring Wells

• Soil

" Bedrock

- Potentiometric Contours (ft-msl)

Reservation Boundary i ~Fel o 300 Goo 9W 1.200 1,500 PREPARED BY:TVAGEOGRAPHC INFORMATOIO ANDENGINEERING hrp is a OigW Oh og 2004 SiPututmsic_Swahe._skhWid. mpljnud- April17. 2007 Figure 3.13 Site-Wide Potentiometric Map 47

Sorptive characteristics of soils beneath the LLRWSF have been determined through laboratory testing of soil samples (Rogers, 1982). Batch techniques were used on composite samples to measure distribution coefficients (Kd) for radionuclides identified in Table 3.2. The sorptive capacity of the Conasauga was not measured at the time due to the lack of a recognized procedure for obtaining realistic Kd values for rock cores. Table 3.2 summarizes laboratory Kd results for LLRWSF soils.

Table 3.2 Soil Distribution Coefficients (Kd)

Radionuclide Kd (mLg Minimum Mean Maximum Co-58/60 1,740 4,820 8,000 Cs-134/137 850 2,390 >10,000 Sr-90 26 36 43 Mn-54 1,000 1,589 2,200 Zn-65 10,400 >10,400 >10,400 During investigations of the diesel fuel oil release, laboratory permeameter testing of undisturbed soil samples at well W14 (Edwards et al., 1993) provided vertical hydraulic conductivity values of 3.9E-07 and 1.6E-04 cm/s at depths of 8-10 and 23-25 ft, respectively. Both samples were characterized as clayey sands. The disparity in these hydraulic conductivity values prompted aquifer testing at the site by Julian (1993) to support final characterization and design of the Diesel Fuel Oil Interceptor System (Figures 3.14 and 3.15).

Single-well pump tests and Electromagnetic Borehole Flowmeter surveys (Young et al., 1997) were conducted by Julian (1993) at wells 22, 23, and EXT-4. The vertical distribution of horizontal hydraulic conductivity at each well is provided in Table 3.3. Incremental horizontal hydraulic conductivity ranged from 6.2E-07 to 1.9E-04 cm/s among all test wells.

48

• i l t**-. ... .

Figure 3.14 Potentiometric Surface at Diesel Fuel Oil Interceptor System on February 10, 2003 49

Avg. grade elev. 700 *-msl k-2,.5 t 4 t*_

Vertical Profile Not To Scale Groundwater alsoharge To Collec on Drums to CCW Channel EX(T-1 0 it*.

ke - 76 t.

Plan View Not To Scale Figure 3.15 Schematic of Diesel Fuel Oil Interceptor Trench 50

Table 3.3 Horizontal Hydraulic Conductivity Values from Single-Well Testing at Wells 22, 23, and EXT-4 Elevation Horizontal Hydraulic Conductivity (cm/s)

(ft-msl) Well 22 Well 23 Well EXT-4 676.4 5.4E-05 676.7 1.2E-04 677.7 1.8E-05 1.2E-04 678.7 4.6E-05 8.5E-05 679.7 3.7E-05 6.7E-05 680.7 4.OE-05 2.3E-05 1.4E-04 681.7 2.8E-05 1.5E-04 1.8E-05 682.7 3.ME-05 1.9E-04 8.2E-06 683.7 3.8E-05 1.4E-04 1.3E-04 684.7 7.3E-06 1.1 E-04 6.7E-05 685.7 1.1E-05 5.1E-05 1.8E-04 686.7 8.1E-07 2.6E-05 1.9E-05 687.7 4.8E-06 1.7E-05 1.2E-05 688.7 3.2E-06 9.9E-06 1.1E-05 689.7 8.9E-06 1.7E-05 1.4E-06 690.7 3.2E-06 1.1E-06 6.8E-06 691.7 4.8E-06 1.2E-06 692.7 6.2E-07 average = 2.5E-05 6.6E-05 5.7E-05 3.7 Offsite Water Supplies 3.7.1 Offsite Groundwater Supplies When SQN was initially evaluated in the early* 1970s, it was in a rural area, and only a, few houses within a tw0-mile radius of the plant site were supplied by individual wells in the Knox Dolomite (TVA; 1979). Because the average domestic use probably did not exceed 500 gallons per day per house, groundwater withdrawal within a two-mile radius of the plant site was less than 50,000 gallons per day. Such a small volume withdrawal over the area would have essentially no effect on area groundwater levels and gradients. Although development of the area has increased, public supplies are available and overall groundwater use is not expected to increase.

TVA (2005) provide tabulated data of wells and springs located within a 20-mile radius of the site from 1985 surveys. Julian (2000) provides results from a United State Geological Survey (USGS) Ground-Water Site Inventory (GWSI) database r'etrieval for wells in Hamilton County.

The data are a combination of domestic wells, wells installed for specific investigations, and other groundwater sites. Table 3.4 provides the results of this retrieval from the GWSI for 51

Hamilton County in the vicinity of SQN. Large capacity (i.e., discharge >100 gpm) well locations from the GWSI database are depicted in Figure 3.16.

Table 3.4 Wells in the Vicinity of SON from GWSI Database Hm:N-090 Well Number Hm:N-089 HIXSON NO.3 PUMP Latitude 351147 351148 I_

Longitude 851308 851353 Depth

.......(ft) 67 177 Disharge 2)_r 5,400 4,000 Aquifer Newman

_gpm Limestone Hm:0-018 350750 850458 148 2,000 Chepultepec Limestone Hm:O-030 SAVANNAH VALLEY 351114 850252 145 1,500 Hm:O-016 351424 850039 158 900 Hm:O-015 351428 850036 262 800 Knox Group Hm:O-008 351428 850039 120 760 Hm:J-016 EASTSIDE 350719 850509 400 Knox Group Hm:O-031 351115 850250 150 350 Hm:N-048 BINKLEY, S.DENT 351041 851237 180 300 Hm:N-056 THRASHER RR 351239 851250 103 300 Paleozoic Hm:N-075 FREEMAN WELL 351158 851117 202 270 Hm:N-083 USGS-TDOT 351150 851405 202 260 Hm:J-015 EASTSIDE +DUP 350720 850510 182 250 Knox Group Hm:O-003 351054 850238 250 250 Hm:N-060 OLDAKER 14 351.228 851010 144 250 Paleozoic 14m:N-059 WALKER 14A 351249 851101 223 245 Paleozoic Hm:N-086 USGS-REEVE 351407 851147 202 240 Hm:R-015 352038 850813 390 200 Hm:O-007 351437 850027 247 170 Hm:R-005 UNION-FORK/BAKE 352031 850819 193 160 Hm:R-073 NORRIS WELL 351525 850853 190 150 Hm:O-017 EASTSIDE 350735 850530 280 105 Knox Group Hm:J-013 EASTSIDE 350607 850510 251 100 Knox Group Hm:J-014 EASTSIDE 350655 850520 250 100 Knox Group Hm:N-084 USGS-CONARD 351320 851320 202 100 Hm:R-004 352031 850816 330 70 BOWMAN WELL AT SALE CR 352532 850848 1,310 40 Hm:O-041 351206 850307 112 20 Hm:S-008 351522 850417 75 20 Hm:N-054 FLOYD THRASHER 351223 851252 279 19 Urm:S-007 351943 850049 60 16 Hm:J-001 350614 850047 80 15 Hm:N-002 350953 850843 100 15 Hm:J-002 350504 850246 160 10 Um:N-046 HUD QUARRY 350937 851314 242 7 Paleozoic Hm:N-078 NOE 351320 850740 280 7 Hm:O-074 VINCENT WELL 351432 850637 342 7 I-m:S-006 351549 850516 269 5 1Hm:N-049 RAGAN HUD 351137 851341 270 2 52

SEQUOYAH NUCLEAR PLANT Large Capacity Wells in Vicinity of Site YEILD

• 600 - 5400 gpm

[ 260- 500 gpm A 150 - 250 gpm

• 100- 140 gpm Sequoyah Nuclear Plant 1

0 2 3 4 5 I PREPARED BY:TVAGEOGRAPHIICINFORMATION4 is a D1o Rosoremt I 97ws koaga Figure 3.16 Large Capacity Wells in the Vicinity of SQN from USGS GWIS Database ANDENGINEERING 53

Bradfield (1992) conducted a study of Cave Springs from 1987 to 989. This the second largest spring in East Tennessee and an important water supply. Cave spring is located approximately 8 miles southwest of SQN near state Highway 27. In addition to wells in the immediate vicinity of Cave Spring, Bradfield (1992) examined water groundwater quality/quantity for water supply wells in the region. Table 3.5 lists attributes of wells included in the study and Figure 3.17 shows the well locations relative to SQN.

Table 3.5 Wells in the Vicinity of SQN from Bradfield (1992)

Well Ground Well Casing Soil Estimatedl Depth Water-Bearing Number Elevation Depth Depth Thickness yield Zone(s) (ft)

(ft-msl) (ft) (ft) (ft) (gpm) 1 710 71 61 25 3,000 65-70 2 710 73 63 25 3,000 65-70 3 710 398 82 25 >300 160,190 260, 275, 320 4 710 177 140 25 >4,000 167-173 6 661 322 148 127 300 180,270 7 820 298 296 298 15 160-180, 270-290 8 880 231 226 231 5 200-231 9 685 103 93 37 400 59-71, 75-93,98-103 11 786 223 180 179 400 201-220 12 723 142 95 95 200 95-131 13 730 242 147 50 100 50-70, 177 14 850 302 130 124 <1 150-200 15 827 202 194 202 30 143-147, 197-202 16 770 251 135 126 40 200-250 17 750 190 188 174 200 175-90 18 703 342 88 85 100 299, 327 19 729 202 154 150 200 170-200 20 692 101 62 37 50 70-90 21 780 171 165 165 50 165-171 22 707 280 84 69 50 78 23 720 342 117 93 200 85-93 The majority of these wells are included in the GWSI database retrieval (Table 3.4). The relatively high well yields shown in Table 2 and Figure 3 (i.e. wells 1-6) are associated with the Cave Springs water supply. Other wells distributed across the region northeast of Cave Springs (Figure 3.17) are affiliated with productive carbonate aquifers.

54

Figure 3.17 Groundwater Supply Wells in the Vicinity of SQN from Bradfield (1992) 55

@ 3.7.2 Offsite Surface Water Supplies As listed in Table 3.6, there are 23 surface water users within the 98.6-mile reach of the Tennessee River between Dayton, Tennessee and Stevenson, Alabama. These include fifteen industrial water supplies and eight public water supplies (TVA, 200*).

The public surface water supply intake (Savannah Valley Utility District), originally located across Chickamauga Reservoir from the plant site at TRM 483.6, has been removed. Savannah Valley Utility District has been converted to a ground water supply. The nearest public downstream intake is the East Side Utility (formerly referred to as U.S. Army, Volunteer Army Ammunition Plant). This intake is located at TRM 473.0.

56

Table 3.6 Public and Industrial Surface Water Supplies Withdrawn from 98.6 Mile Reach Of Tennessee River Between

. Dayton, TN and Stevenson, AL Approximate Distance from Site Intake Name Use (MGD) Location (River Miles) Type Supply City of Dayton 1.78 TRM 503.8 R 19.1 (Upstream) Municipal Cleveland Utilities Board 5.03 TRM 499.4 L 37.6 (Upstream) Municipal Hiwassee RM 22.9 Bowaters Southern Paper 80.00 TRM 499.4 L 37.4 (Upstream) Industrial Hiwassee RM 22.7 & Potable Hiwassee Utilities 3.00 TRM 499.4 L 37.2 (Upstream) Municipal Hiwassee RM 22.5 Olin Corporation 5.00 TRM 499.4 L 37.0 (Upstream) Industrial Hiwassee RM 22.3 & Potable Soddy-Daisy Falling Water U.D. 0.93 TRM 487.2 R 7.1 (Upstream) Municipal Soddy Cr. 4.6 Plus 2 Wells Sequoyah Nuclear Plant 1615.70 TRM 484.7 R 0.0 Industrial East Side Utility 5.00 TRM 473.0 L 11.7 (Downstream) Municipal Chickamauga Dam not measured TRM 471.0 13.7 (Downstream) Industrial DuPont Company 7.20 TRM 469.9 R 14.8 (Downstream) Industrial Tennessee-American Water 40.90 TRM 465.3 L 19.4 (Downstream) Municipal Rock-Tennessee Mill 0.50 TRM 463.5 R 21.2 (Downstream) Industrial Dixie Sand and Gravel 0.04 TRM 463.2 R 21.5 (Downstream) Industrial Chattanooga Missouri Portland Cement 0.10 TRM 456.1 R 28.6 (Downstream) Industrial Signal Mountain Cement 2.80 TRM 454.2 R 30.5 (Downstream) Industrial Raccoon Mount. Pump Storage Project 0.56 TRM 444.7 L 40.0 (Downstream) Industrial Signal Mountain Cement 0.20 TRM 433.3 R 51.4 (Downstream) Industrial Nickajack Dam not measured TRM 424.7 60.0 (Downstream) Industrial South Pittsburg 0.90 TRM 418.0 R 66.7 (Downstream) Municipal Penn Dixie Cement 0.00001 TRM 417.1 R 67.6 (Downstream) Industrial Bridgeport 0.60 TRM 413.6 R 71.1 (Downstream) Municipal Widows Creek Stream Plant 397.40 TRM 407.7 R 77.0 (Downstream) Industrial Mead Corporation 4.40 TRM 405.2 R 79.5 (Downstream') Industrial R = Right River Bank, L = left River Bank 57

4.0 TRITIUM INVESTIGATION Field investigations during this study focused largely on areas north and south of Units 1 and 2.

Initial identification of areas for targeted investigations was based on information collected from the following sources:

• Preliminary site meetings with SQN staff;

" Previous tritium monitoring results associated with wells located along waste condensate lines;

• Historical tritium detection at other monitoring wells (e.g., W5 and W21);

" Preliminary assessments of inadvertent liquid radwaste releases;

• Relative locations of large/deep underground appurtenances;

" Potentially transmissive groundwater migration routes (e.g., pipeline bedding pathways).

The majority of tritium data collected from site groundwater monitoring prior to initiation of this investigation was available for review in spreadsheet format. Temporal and spatial examination of groundwater tritium concentrations data was conducted prior to field investigations. Reports documenting inadvertent liquid radwaste releases were made available by SQN staff. Hardcopy and electronic versions of essential site drawings were examined prior to and during field investigations. Key site features (e.g., underground lines and conduits) were electronically digitized and georeferenced imagery was developed using Geographic Information System (GIS)

(5 methods. Spatial data were incorporated into the GIS geodatabase with project progression.

Several thousand large format (8 x 10 inch) photograph negatives (prepared during plant construction) were also examined at the National Archives Southeast Region Facility.

Preliminary results suggested that tritium sources might be associated with inadvertent liquid releases from the MFTDS, Unit 1 and 2 RWST, CDWE Building, and/or the Unit 2 Additional Equipment Building. Based on comparable tritium investigations completed at WBN (ARCADIS, 2004), and similarity of SQN plant design to WBN, the Unit I and 2 Auxiliary and Shield Buildings were included as potential tritium sources during this investigation. Major tasks associated with the field investigation included:

1. Sampling of selected existing wells;

2. Manual sampling of storm drain catch basins, vaults, and manholes;

3. Groundwater sampling using Geoprobe methods;

4. Manual and continuous water level monitoring;

5. Interior sampling at select locations.

0 58

4.1 Groundwater Sampling of Selected Existing Wells Initial groundwater sampling for this study was targeted at site perimeter wells to confirm that offsite migration of tritium is not occurring. Fourteen existing wells were selected for sampling

.(Table 4.1). These wells are located along site boundaries and are not presently included in the routine groundwater monitoring network for tritium. Well locations are shown in Figure 1.2.

This sampling event included three bedrock wells (WI, W2, W4), soil/bedrock well L6 at the LLRWSF, eight soil wells south of Unit 2 (14, 16, 20, 22, 30, 32, 34, 35), and two diesel extraction wells (EXT-2, EXT-4) located near the discharge.

Table 4.1 Tritium Results from Selected Existing Wells Top of Top of Depth Bottom Tritium Diameter Casing Ground', from of Hole:, Sampling Concentratio-Location (In) (ft-msl) (ft-msl) TOC (ft) fft-msl) , Date n (pCi/L)

WI 6 708.9 705.6 155.0 553.9 10/04/2006 < 270 W2 6 700.9 700.1 157.8 543.1 10/05/2006 < 270 W4 6 742.3 732.3 130.4 611.9 10/05/2006 <'270 L6 3 734.8 733.8 79.7 655.1 10/04/2006 < 270 14 2 707.9 705.2 18.8 689.1 10/06/2006 < 270 16 2 707.6 706.1 23.6 684.0 10/06/2006 < 270 20 2 697.9 697.9 23.1 674.8 10/05/2006 < 270 22 2 700.9 698.4 21.4 679.5 10/05/2006 < 270 30 1 707.2 704.1 23.8 683.4 10/06/2006 < 270 32 1 706.3 704.1 22.7 683.7 10/06/2006 < 270 34 1 708.1 704.8 25.7 682.5 10/06/2006 < 270 35 1 708.9 705.8 23.6 685.3 10/06/2006 < 270 EXT-2 12 702.2 700.0 26.0 676.2 10/06/2006 < 270 EXT-4

• 12 704.4 700.0 26.0 678.4 10/06/2006 < 270 Wells were purged and sampled October 4-6, 2006, using a combination of submersible pumps and disposable Teflon bailers. Samples were collected in 100 mL wide-mouth plastic sample containers and transferred to plant personnel for shipment to WARL for tritium analysis.

Laboratory analysis indicated that tritium concentrations were less than the MDC of 270 pCi/L at all locations.

Perimeter well W5 has historically exhibited the presence. of tritium but was not included in this sampling scheme since it is routinely monitored by SQN and WARL personnel through REMP.

4.2 Manual Sampling of Storm Drain Catch Basin, Vaults, and Manholes, Storm drain catch basins, vaults, and manholes were sampled to detect potential in-leakage of tritiated water from groundwater or discharge from plant processes. Sampling locations were initially identified using the following criteria: availability of water, depth (i.e., deep storm drain catch basins), accessibility, and proximity to the waste condensate lines and historical releases.

59

Twenty sites were selected (Table 4.2), including eighteen catch basins, the Turbine Building 0

Sump Discharge, and a TV box sump. Sample locations are shown in Figure 4.1. All locations selected for sampling were within several hundred feet of the Reactor Buildings.

Table 4.2 Tritium Results from Manual Sampling Event Depth Depth to, .to. Tritium Invert: Water. Sampling', Concentratlo..

Location Typei  : Date -n (pCilL) sS-1 Catch Basin 4.96 4.69 10/13/2006 < 270 SS-2 Catch Basin 5.10 5.03 10/13/2006 < 270 SS-3 Catch Basin 2.70 2.59 10/13/2006 < 270 SS-4 Catch Basin 5.10 5.00 10/13/2006 < 270 SS-5 Catch Basin 3.77 3.74 10/13/2006 < 270 SS-6 Catch Basin 2.61 2.61 .10/13/2006 8,879 SS-7 Catch Basin 4.29 3.99 10/13/2006 < 270 SS-9 Catch Basin 5.03 4.99 10/13/2006 < 270 SS-10 Catch Basin 6.37 6.10 10/13/2006 < 270 SS-11 Catch Basin 8.31 8.07 10/13/2006 < 270 SS-12 Catch Basin 8.06 7.52 10/13/2006 < 270 SS-13 Catch Basin 2.05 2.04 10/13/2006 < 270 SS-14 Catch Basin 1.93 1.82 10/13/2006 425 Turbine Building SS-15 10/13/2006 < 270 Sump N/A SS-16 Catch Basin 3.46 3.39 10/13/2006 < 270 SS-17 Catch Basin 12.59 12.40 10/13/2006 < 270 ss-18 Catch Basin 10.18 9.84 10/13/2006 < 270 SS-19 Catch Basin 3.70 3.61 10/13/2006 < 270 SS-21 TV Box Sump 2.56 1.78 10/13/2006 284 SS-22 Catch Basin 7.80 7.59 10/13/2006 312 Samples were collected October 13 by dropping a sponge (on a string) through the catch basin grating to soak up water, retrieving it, and then wringing it into a 100 mL wide-mouth plastic sample container. Sponge and string were disposed of after each location sampled. The outside of the sampling containers were thoroughly rinsed to remove any trace of overflow. Depth-to-water and depth-to-invert were measured after sampling using an electronic water level meter, and the water level meter was decontaminated between locations. Sample containers were transferred to SQN personnel, then transported to WARL for tritium analysis.

Table 4.2 summarizes sampling results. Tritium was observed at catch basin locations SS-6 (8,879 pCi/L), SS-14 (425 pCi/L), SS-21 (284 pCi/L), and SS-22 (312 pCi/L). All other samples were less than the MDC. /

60

SEQUOYAH NUCLEAR PLANT Manual Sampling Locations

[n Catch Basin El Turbine Building Sump El TVBox Sump

---

Storm Drain AN Feet 0 100 20O 300 400 PREPARED BY:TVAGEOGRAPHIC INFORMATIONANDENGINEERING Imugeis a MOW Odhophotograph 2004 Figure 4.1 Map of Manual Sampling Locations 61

4.3 Groundwater Sampling using Geoprobe Methods Groundwater sampling using a Geoprobe allows sampling rods to be "pushed" into the ground without the use of drilling and produces minimal investigation-derived waste. The Geoprobe direct-push machine relies on a relatively small amount of static (vehicle) weight combined with percussion as the energy for advancement of a tool string. The Geoprobe offers a significant safety advantage since the probe tends to resist on concrete and steel pipelines, and downholes tools are easily decontaminated between borings.

Thirty-one (31) Geoprobe boring locations were initially identified at the site based on the existing knowledge of groundwater movement and the relative locations of major underground lines and appurtenances (e.g., ERCW lines and intake conduits). Bedding materials surrounding underground lines represent potential preferential pathways for subsurface movement of groundwater contaminants; therefore, these features were a consideration of the investigation.

Site design and as-built drawings of underground utilities were reviewed in relation to proposed boring locations to avoid potential drilling conflicts. For final verification of proposed boring locations, a radio frequency utility location investigation was conducted under contract with Underground Locators of Nashville, Inc, during November 2006. The utility location survey evaluated potential utilities and metallic obstructions around the areas of the field-staked boring locations. The boring locations were offset if direct obstructions were identified to provide a minimum horizontal clearance of the 2-ft locate variation in all directions.

Sampling of groundwater using Geoprobe methods was conducted during January and February 2007. Due to subsurface resistance at many locations (i.e., concrete), groundwater samples were ultimately collected at 23 locations (Figure 4.2; Table 4.3). When possible, groundwater samples were collected in situ (from within the Geoprobe push-rod at depth) using a 0.5-inch OD stainless steel bailer or were siphoned using Teflon tubing. Where groundwater recovery rates were slow, temporary 0.5-inch ID screen and casing were installed and samples were collected using a 0.5-inch OD stainless steel bailer or were siphoned using Teflon tubing. All temporary well materials were discarded after a single use; although, in some cases, Teflon tubing was reused after being decontaminated between samples. Groundwater samples were transferred to 100 mL wide-mouth plastic sample containers, and turned over to plant personnel to transmit to WARL for tritium analysis. Decontamination involved scrubbing downhole equipment with a distilled water/laboratory detergent mix and rinsing with distilled water.

62

SEQUOYAH NUCLEAR PLANT New Geoprobe Borings and Monftoning Wells Mofiltoing Wells a Diesed 2 oD Extrudcbm T, LLRW 0 Radcon x Radcvf(dnfted I Sbv Doyv A DryC~skSOV~

Ge~opbe Swings

• G"Mjb.8odkg

• GeoýWA.~

,uwrv~..Rw.Q.ENl

-*~- - A Figure 4.2 Map Showing Geoprobe Sampling Locations and Monitoring Wells 63

0 Figure 4.3 provides a profile of Geoprobe borings installed during the investigation. Five of the borings were completed as 1-inch monitoring wells to supplement groundwater level measurements in areas lacking groundwater level information. These wells include GP-7A, GP-7B, GP-10, GP-13, and GP-24 (Figure 4.2). Well diagrams are provided in Appendix A.

710 705 -

700 -

695 690 I V V

V V

, 685 -

V V

V V V V

680 V V

V 675 --

9 670 -

v Initial Groundwater Level 665 I I I I I I I 0 CD N 0

0. 0 0. CD I 0 !D CD

d. oL m. d. ma.CD . c. a.

CD C. CL 0.

CD 0. CD d CD d.

C. d. 0( CDC C C CD CL a. C) 0D 09 0 9 09 (9 a fD Figure 4.3 Profile of Geoprobe Borings Table 4.3 provides a summary of groundwater sampling locations and analytical results from Geoprobe investigations. As indicated, tritium was observed at low concentrations in borings (GP GP-7) near the Unit 1 RWST, in borings S-SE of Unit 2 (GP-21, GP-22, GP-25, GP-26),

and at GP-28. The highest tritium concentration observed in Geoprobe borings occurred at GP-13 (16, 211 pCiIL).

64

Table 4.3 Tritium Results from Geoprobe Sampling Top of Bottom TN NAD27 (ft) Tritium Ground Depth of Hole Sampling Concentratio Location (ft-msl) (ft) (ft-msl) Eastlng Northing Date n (pCIIL)

GP-1 704.1 36.0 668.1 2271360.0 305170.7 1/26/2007 274 GP-2 701.7 27.8 673.9 2271373.9 305226.7 1/29/2007 733 GP-3 702.4 32.5 669.9 2271401.2 305258.6 1/25/2007 623 GP-4 703.5 32.2 671.3 2271433.3 305221.2 1/30/2007 661 GP-5 704.9 30.0 674.9 2271510.6 305256.8 1/25/2007 420 GP-6 704.7 29.2 675.5 2271575.9 305218.7 1/25/2007 306 GP-7B 705.9 24.8 681.1 2271461.1 305425.8 2/12/2007 394 GP-9 705.7 31.2 674.5 2271708.1 305284.7 1/31/2007 < 270 GP-10 707.9 30.0 677.9 2271366.7 305237.9 2/01/2007 < 270 GP-13 705.3 26.5 678.8 2271543.4 305102.4 2/01/2007 16,211 GP-14 704.9 26.0 678.9 2271621.5 305069.1 2/05/2007 < 270 GP-16B 703.8 21.0 682.8 2271594.8 304938.8 2/15/2007 < 270 GP-17B 705.4 27.7 677.7 2271558.3 304862.1 2/16/2007 < 270 GP-18 704.9 28.0 676.9 2271476.6 304781.9 2/06/2007 < 270 GP-21 705.8 26.5 679.3 2271368.9 304750.0 2/06/2007 750 GP-22 706.7 30.0 676.7 2271304.2 304732.2 2/07/2007 2,700 GP-24 704.9 27.0 677.9 2271204.3 304744.0 2/07/2007 < 270 GP-25 703.8 21.8 682.0 2271230.4 304662.1 2/07/2007 874 GP-26 704.1 26.0 678.1 2271309.7 304630.9 2/07/2007 332 GP-27 705.3 25.0 680.3 2271425.5 304571.1 2/12/2007 < 270 GP-28 704.3 20.0 684.3 2271580.9 304774.2 2/13/2007 394 GP-29 704.2 24.0 680.2 2271629.2 304884.0 2/13/2007 < 270 GP-30 704.2 30.0 674.2 2271730.8 304953.5 2/13/2007 < 270 4.4 Water Level Monitoring Groundwater level monitoring at the site during this investigation included manual measurements at existing wells and new wells in close proximity to the plant site on approximately a monthly basis beginning December 13, 2006. Continuous water level and temperature monitoring was conducted at three selected wells (14, W2 1, and GP- 13) and at the head of the Discharge Channel. Solinst (Model 3001) downhole dataloggers were deployed (beginning 11/17/06) for continuous monitoring of water levels and temperatures. Continuous (hourly) surface water levels are collected for Chickamauga Reservoir on the southeast comer of the Intake Channel Skimmer Wall (Figure 1.1) at TRM 484.8.

65

1 Results from pre-investigation water level monitoring were coupled with recent data. Figure 4.4 depicts time-series groundwater levels for wells W21, 29, 30, and 31 in the vicinity of Unit 2.

As shown in the figure, groundwater gradients are consistent with time and all groundwater levels are influenced by operation of the Chickamauga Reservoir and the Discharge Channel (see Section 3.3). That is, under normal operations, water elevation begins to increase in April and recession begins in September. The maximum range of groundwater levels over this 3-year interval is 9.7 ft (wells W21 and 31). Groundwater levels at wells 29 and 30 fluctuated over

< 6.0 ft for this period. Apparent in Figure 4.4 is the excellent degree of correlation in groundwater levels at wells W21 and 31.

695

~690 ___

- W21 29~

c.685- 30

-31 Amk -River!

W 680 ___

675 . ....

Figure 4.4 Time-Series Water Levels at Wells W-21, 29, 30, 31 and the River Figure 4.5 shows time-series groundwater levels for RadCon wells in the vicinity of the 12-inch Waste Condensate Line. Although these wells are located at similar distances from the Discharge Channel, groundwater levels are not correlated with surface water elevations.

However, correlation in groundwater levels among these wells is evident. Compared to wells nearer Unit 2, the maximum range of groundwater levels over this 3-year interval was 13.1 ft (well 34). Groundwater levels at wells 27 and 33 fluctuated over <5.0 ft for this period.

66

705 700 1695 690

~ \t

• 685 7i 27-32

_- 33

.0 Q - 34 685 - River 680 675 Figure 4.5 Time-Series Water Levels at Wells 27, 32, 33, 34 and the River Continuous temperature and water level data collected for this investigation are presented in Figure 4.6. The most obvious feature in this figure is correspondence of water levels between well W21 and the Discharge Channel. Timing and magnitude of water level changes match exceedingly well. The continuous water level data are too coarse to allow exact time-matching between these two locations (i.e., measurements frequency was hourly at W2 1 and 20 minutes at the channel). However, data is sufficient to indicate that well W21 responds to changes in Discharge Channel water levels in less than two hours. Noting that well W21 is located 285 ft from the head of the Discharge Channel, hydraulic pressure changes via natural porous media at the site would not produce these types of responses. Results indicate the presence of a subsurface feature(s) residing at depth (<679 ft-msl) providing relatively direct connection between these two locations. Given the correlation in groundwater levels between wells W21 and 31 (Figure 4.4), this or another feature(s) also extends to the vicinity of well 31 (145 ft from the head of the channel).

Figure 4.7 presents continuous water level data at wells W21, 14, and the Discharge Channel for the interval 11/17/06 - 01/24/07. Of interest in this figure is the precipitous change in well W21 groundwater levels coincident with the beginning and ending of the plant outage from 11/26/06 -

12/24/06. Also noted is the anomalous departure of correlation between well W21 and the Discharge Channel from 12/05/06 - 12/15/06 during the outage interval. Daily operations log entries were examined in attempts to identify any major water transfers that might be associated with rapid changes in groundwater levels (e.g., RWST and Spent Fuel Pool transfers). There is no evidence of changes in groundwater levels associated with such transfers.

67

695 14

-- _ W21 0 GP-13 (manual)

____5 ___ _____ _________ q__ W21 (manual)

- ' o W14 (manual) d Discharge Channel 680 675 12/13/06 1/2/07 1/22/07 2/11/07 3/3/07 3/23/07 Date 30 25 ________

620-/1 AGP-13

14

....... Discharge Channel 115-10 "

5 12/13/06 1/2/07 1/22/07 2/11/07 3/3/07 3/23/07 Date Figure 4.6 Continuous Water Levels (Top) and Temperatures (Bottom) at Wells GP-13, 14, W21, the Discharge Channel, and the River 68

11 10 9

8 E 7 0 6 5

4 3

2 0

c..J (NI (Ni (NJ - -

- - - - - 0 0 0 0 Date 2.5 O o1.5 2

SQN Gage I L. I ____________________ GorgtownGag 0.5 C.

0

i. i _l .M 2.5 Georgetown Gage

• 2 o 1.5

• , 1 0.5 C. 0 I.-

0 0 I.-

0 F.-

0 (NJ Figure 4.7 Continuous Water Levels (Top) and Precipitation (Bottom) at Wells 14, W21, and the Discharge Channel 69

VWell 14 experiences abrupt weekly to biweekly groundwater level increases (Figures 4.6 and 4.7) over most of the monitoring period. The water level changes are correlated with pronounced water temperature decreases (Figure 4.6). Precipitation data from the plant meteorological station and from the Georgetown gage (9 miles NE of SQN) were obtained and are shown at the bottom of Figure 4.7. As shown, groundwater level and temperature changes at well 14 are clearly linked with rainfall events. It is highly probable that the well 14 wellhead seal has been damaged and that rainfall runoff is directly entering the well annulus at this location. Similar results are observed in temperature data at well W2 1. Again, data suggests that well W21 wellhead seal has been damaged.

Figure 4.8 depicts the potentiometric surface at the site based on April 02, 2007 groundwater level measurements. Groundwater movement is northerly over the Unit 1 portion of the site with the Intake Channel serving as a primary surface water control to hydraulic gradients. Over the Unit 2 side of the site, groundwater movement is primarily southerly with convergent flow toward the Discharge Channel.

C) 70

SEQUOYAH NUCLEAR PLANT Local Potentiometric Surface Map from Water Level Mesurements April 02, 2007 Monitoring Wells Diesel

• RadCon

• Geoprobe Potentiometric Contours (if-msl)

Nz Pe.*

0 10 200 300 400 6000 PREPARED BY:TVAGEOGRAPHIC INFORMATION ANDENGINEERING Impgeis a Di0oaOthcphooguph 2004 Figure 4.8 Local Potentiometric Surface from April 02, 2007 Water Level Measurements 71

t 4.5 Interior Sampling Groundwater inleakage occurs at SQN along concrete construction joints, poorly sealed pipe sleeves, concrete factures, and other locations. During this investigation, several areas were visually inspected and groundwater inleakage samples were collected for tritium analyses.

Inspection locations were selected based on historical observations of seepage, depth, and location (i.e., below groundwater table and in vicinity of observed tritium), and accessibility.

Locations identified for inspections and sampling included the Auxiliary Building, north wall of the Turbine Building, and RWST pipe tunnels for both units.

Groundwater inleakage has been documented at SQN since 1978 (TVA, 1978). At this time, groundwater inleakage was described in the Auxiliary Building. At the request of SQN, an inspection of the Auxiliary Building inleakage problem was performed by J. M. Boggs of TVA's Engineering Laboratory during May 1997. Inleakage locations were identified on plant drawings and catalogued with photographs (Figure 4.9).

As shown in Figure 4.9, twelve inleakage locations have been identified in the Auxiliary Building at floor elevations 653 and 669 ft-msl. Red symbols identified locations where inleakage rates were sufficiently high in 1997 to require collection. Blue symbols identified locations of low inleakage rates not requiring collection. These locations are listed in Table 4.4.

Two additional inleakage locations not identified in Figure 4.9 and Table 4.4 were documented (1997) at a leaking conduit in the Unit 1 UHI pit and at a 4-inch diameter pipe sleeve near elevation 655 ft-msl of the UHI pit.

Table 4.4 Auxiliary Building Groundwater Inleakage Locations Location Remarks 1 Elevation 653 ft-msl pipe chase, high inleakage rate 2 Seepage being collected, moderate inleakage rate Two inleakage locations, drip funnels being used for 3 collection 4 no comment 5 no comment 6 Leak at concrete construction joint 7 Leak above floor in wall 8 Patched 9 Leak at floor 10 no comment 11 no comment Sampling of groundwater inleakage from the north wall of the Turbine Building (near elevation 662 ft-msl) was conducted on 10/20/06. Analysis by WARL indicated that tritium was less than the MDC of 220 pCi/L.

72

f 11 p _

CI~ -. ~ ' .O K fl,.~f CC~ff~ maim..

-~~ ~ I ~ro.a~'saiP1c' t 4 .,,,,U:A D: iL 1 ~_ a lowi ~-T___

W1i~Fi

-4 LR 13 - .__ 10 ~

4+/-3

.'" IE.

99~o -

P1 AN fEL ý. 5A. 0

.5 Yi -

Li -d

,iiion i Ii

• Very Low Flowrate, No Collection Requ

• Flowrate Sufficiently High to Require C PLAN EL 5C.C9.0 Figure 4.9 Groundwater Inleakage Locations at Auxiliary Building

Inspection and sampling within the Unit 1 and 2 RWST pipe tunnels was performed by SQN staff under work orders 06-776301-000 and 06-776302-000 during 8/28/06 and 8/31/06.

Groundwater inleakage samples were collected from tunnel walls and water samples were collected from trough drains at each location. Analyses by WARL indicated that tritium was less than the MDC of 220 pCi/L for all samples.

Based on comparable tritium investigations completed at WBN, and similarity of SQN plant design to WBN, inspection of Unit I and 2 Annuli and transfer tube bellows are being performed by SQN staff. These inspections involve boroscope methods and removal of concrete block shield walls for access. Where possible, samples are being collected for analyses. These investigations are continuing and results are forthcoming.

74

5.0 RESULTS AND RECOMMENDATIONS 5.1 Tritium Distribution 5.1.1 Manual Sampling Manual sampling at 20 catch basins, vaults, and manholes (Figure 4.1; Table 4.2) during this study showed positive detection of tritium at four shallow locations. The sampling depths at these locations were >15 ft above the groundwater table. Tritium was observed at SS-6 (8,879 pCi/L), SS-14 (425 pCi/L), SS-21 (284 pCi/L), and SS-22 (312 pCi/L). All other samples were less than the MDC.

Observation of tritium in catch basin SS-6 (2.6 ft deep) near the Service Building is not completely explicable. The observed tritium concentration is an order of magnitude greater that tritium concentrations observed in groundwater from Geoprobe borings (GP GP-4) in the immediate vicinity. Results suggest that the observed tritium concentration might be associated with direct discharges to the single line entering this catch basin.

The low tritium concentration at catch basin SS-14 (1.9-ft deep), near the 12-inch waste condensate line, is similar to tritium concentrations observed for soil wells located along the condensate line. The 12-inch condensate line is located above ground at this location and leaks to ground surface could produce the observed concentration. Likewise, overflows from the Turbine Building sump could produce similar results.

The low tritium concentration observed at catch basin SS-22 (7.8 ft deep) may be the result of a release from the MFTDS (Section 2.3) that occurred in 1997. A correspondingly low tritium concentration at the SS-21 TV box sump (2.6-ft deep) may also be the results of the MFTDS release. However, this vault possesses an impermeable cover. It is conceivable that the source of tritiated water within the SS-21 sump is associated with contaminated groundwater some distance upgradient (west) of the electrical vaults. Electrical conduits (and their bedding materials) intersecting such vaults are probable avenues for shallow groundwater transport.

Manual sampling of several selected locations was performed during January 2004 to support siting of RadCon wells located along 12-inch waste condensate line. Water sampling results at all locations indicated tritium concentrations <MDC of 220 pCi/L. Sampling locations included:

• Diesel Fuel Oil Interceptor Trench discharge;

• Turbine Building sump;

• Low-Volume Waste Treatment Pond inlet;

• Condensate water discharge from Turbine Building roof to sump;

• CO 2 vault sump south of Turbine Building;

. Alum Sludge Ponds A (west) and B (east);

75

• Water Treatment Plant basement sump;

• Storm drain #45 north of High Pressure Fire Protection System tanks;

• Storm drain #44 east of Water Treatment Plant;

• Storm drain #46 south of Unit 2 Condensate Storage Tanks.

5.1.2 Groundwater Sampling From 1998 through 2001, tritium was consistently observed at concentrations ranging from 401 to 2,120 pCi/L at well W5 (Figure 1.2). No further tritium detection has been observed at well W5 since 2001. Beginning in February 2002, TVA expanded REMP groundwater monitoring at SQN (Section 1.3) with the addition of 12 soil monitoring wells and collection of groundwater samples from existing wells in proximity to known areas of tritium contamination.

Since August 2003, 206 groundwater sampling events have been conducted at one or more of these wells. Tritium concentrations observed from these sampling events are tabulated in Appendix B.

As shown in Appendix B, tritium concentrations measured at wells 24-28, 30, and 32-35 have been <MDC with only a few exceptions near the MDC. Relatively high tritium concentrations (2,576 - 19,750 pCi/L) have been continuously observed at well 31 since May 2004. As shown in Figure 5.1 tritium concentrations are generally correlated with groundwater levels at well 31.

25,000 692 690 20,000 688 15,000 686 684u o 10,000 E 682~

5,000 680 0 678 in I.-

00 0

- -- 00 0 Date Figure 5.1 Time-Series Tritium Concentrations and Groundwater Levels at Well 31 76

At well W2 1, tritium concentrations have ranged from 226 - 9080 pCi/L since sampling commenced in February 2004. As shown in Figure 5.2, there is no correlation between tritium concentrations and groundwater levels at well W21. Low tritium concentrations have also been consistently observed at well 27 (<500 pCi/L) and well 29 (<1800 pCi/L) with no relationships between tritium and groundwater levels at either location (Figure 5.3).

4,000 692 3,500 690 S3,000 688

. 2,500 686 C 2,000 w 684 16 o*1,500 E 682

• R 1,000 01 500 680 0 678 0

0 C'4 C,14 C4 N C40 Date Figure 5.2 Time-Series Tritium Concentrations and Groundwater Levels at Well W21 Groundwater sampling at 23 Geoprobe borings (Figure 4.2; Table 4.3) indicated low tritium concentrations (274 - 661 pCi/L) in borings (GP GP-7) surrounding the Unit 1 RWST.

Borings GP-21, GP-22, GP-25, and GP-26 exhibited low tritium concentrations (332 - 2700 pCi/L) in the area S-SE of Unit 2. Boring GP-28, just east of this area, provided a similarly low tritium concentration (394 pCi/L). The highest tritium concentration observed within all Geoprobe borings occurred at GP-13 (16, 211 pCi/L). Due to the relatively high groundwater tritium concentration at GP-13, a soil monitoring well was installed at this location and additional groundwater sampling was conducted. Figure 5.4 depicts sampling results to date.

77

600 696 500 694 .

V I*

-400 i~* ** *... . . . . . . . . . . ....... . . . ....

. . . . . 7

..... * ~ii~ i 692 0

S300 690 i

GrounwaterLe~.e E u 681

-a-Tritium Concentration 100 .....

• M. C (220 - 270 pC./L) 6860 GroundwO Level 0 684 Date 2,000 692 Tritium Concentration 1,800 ......... MDC (220 - 270 pCI/L) ... 29 Groundwater LeWei

-1 600 690~

.'A __I P 1,200 S1,000 P 688 1

Lu 686 o

-600 I- 400 0 682 0 ~c C0) 8 Date Figure 5.3 Time-Series Tritium Concentrations and Groundwater Levels at Wells 27 and 29 78

20,000 686.8 19.000 20 0686.8 0 686.6 686.4 0 18,000 C.

686.2 r- 17,000 686.

16,000 .2 30685.8 15,000 685.4 13,000 e 5 i Tritium Concentration 686.2 Groundwater Lessci Time-Serise foritium Coneeperations Fighure data regim (ire.,dweathere Ledrockand shallow1 bedrock), the extent of the tritium plume is reasonably bounded by sampling locations in the horizontal.

5.2 Tritium Sources Current results suggest that sources of tritiated groundwater are primarily associated with past inadvertent releases of liquids containing radioisotopes. Relatively high groundwater tritium concentrations have been observed at wells 31 and GP-13, noting that there have been no observations exceeding the EPA Drinking Water Standard of 20,000 pCi/L for tritium (40 CFR 141.25).

Historically, remediation procedures for inadvertent liquid releases have chiefly involved the collection and screening of soil samples and limited water samples for radionuclides. However, the radionuclide analytes exclude short-lived isotopes such as tritium (see Section 2.3).

Likewise, groundwater sampling associated with inadvertent liquid releases was not conducted during remediation. There is therefore a strong likelihood that tritium contamination from inadvertent liquid releases was not revealed due to the limitations of sampling and analytical protocols.

79

SEQUOYAII NUCLE-AR PLANT Tritium Plumes MonliodWi Locations

• REMP 0 D"MI

• Obo Exhatbnf

• LLRW

• RAflCON

• Sftlg

• Ceoprotie Be Tritiaum Concentration (pCiIL)

EMh20O- 400D

-2m040w l2WO.1W

=iMMOY VA*e*TWC*O F- 1W - an Figure 5.5 Spatial Distribution of Tritium from Groundwater Sampling During January and February 2007 80

An analog groundwater investigation of tritium releases at'WBN suggests that leaks through the fuel transfer tube and seismic gap (between Unit 2 Reactor and Auxiliary Buildings) contaminated groundwater at the WBN site. Tritium concentrations in these source areas are nearly 100 million pCi/L and the release of only a small volume of water is necessary to produce elevated tritium concentrations in site groundwater. Inspections of SQN Unit I and 2 fuiel transfer tubes, spent fuel pool, and associated components are currently being performed by SQN staff. These investigations are continuing and results are forthcoming.

Controlled airborne releases from the plant ventilation system may result in measurable atmospheric deposition of plant-related radionuclides (including tritium) in the vicinity of the site. Since this potential tritium source is not likely to be a major contributor to groundwater contamination, airborne release was not evaluated during this investigation.

Unit 1 - Elevated tritium concentrations in groundwater north of Unit I suggest that the inadvertent water release from the MFTDS in 1997 (see Section 2.3) is likely the primary source of shallow groundwater contamination in this vicinity. The estimated volume of water released by the MFT*DS is 600 - 1,000 gallons. A secondary source of tritium contamination in this vicinity is related to relatively small volumes of water that drain from the RWST moat and have discharged to ground surface for >25 years. Observation of tritium in catch basin SS-6 near the Service Building is not completely explicable, but results suggest that the observed tritium concentration might be associated with direct discharges to the single line entering this catch basin.

Unit 2 - Tritium concentrations in groundwater south of Unit 2 suggest that inadvertent'releases from the Unit 2 CDWE and additional Equipment Buildings (see Section 2.3) have contaminated shallow groundwater in this vicinity. A tertiary source of tritium contamination in this vicinity is related to the moat drain from the RWST that discharged to ground surface for >25 years.

Tritium concentrations at well 27 appear to be of an isolated nature and may be related to leakage of the 12-inch waste condensate line.

5.3 Tritium Transport and Fate Tritium is a conservative contaminant - it is not susceptible to attenuation via sorption or biochemical degradation. Reduction of tritium concentrations in the groundwater system at SQN will occur primarily by hydrodynamic dispersion and dilution. The dispersion process is related to variations in groundwater velocity that occur on a microscale by differences in media porosity and on a macroscale by variations in hydraulic conductivity. Dispersion will result in reductions of tritium concentrations with increasing distance from the source (e.g., the MFTDS railroad bay). Dispersion will be more pronounced in the soil horizon relative to the deeper and more transmissive weathered bedrock horizon. However, the fate and transport of tritium in the site groundwater system is also likely to be governed by avenues of relatively rapid groundwater 81

movement that exist within bedding material of larger pipelines and tunnels, and possibly along the weathered bedrock horizon.

Groundwater and surface water level measurements during the study confirm that the Intake and Discharge Channel will ultimately be recipient to tritiated groundwater discharge from the site.

Dilution ratios in the channels and subsequently the Tennessee River are dependent on plant operation and river flows.

• L4Recommendations o active remediation is recommended for the site due to the limited extent of tritium contamination, tritium concentrations in groundwater less than EPA Drinking Water Standard of 20,000 pCi/L (40 CFR 141.25), perceived low exposure and dose risks, and negligible potential for offsite groundwater migration. The following recommendations are submitted based on findings of this investigation.

Source Terms: Spatial data and anecdotal evidence suggest that tritium sources are primarily associated with past inadvertent releases of liquids containing radioisotopes.Additional groundwater sampling in the areas, of GP-13 would assist in bounding the tritium plume on the north (Unit 1) side of the site. Sampling would involve the installation of 6 - 8 shallow soil borings to confirm the extent of tritium contamination.1 There are no bedrock borings located in close proximity to Units 1 and 2 that can be used to examine fhe vertical distribution of tritium that might extend into the shallow Conasauga bedrocktwo bedrock borings extending into the upper 20 ft of bedrock are recommended for the zones exhibiting relatively high tritium concentrations (north and south of Units 1 and 2).

Results should be examined collectively to verify that higher tritium concentrations do not exist at excessive concentrations within the shallow bedrock flow system..-

It is likely that tritium contamination from inadvertent liquid releases was not revealed in past investigations due to the limitations of sampling and analytical protocols.',SQN procedures directed towards investigation and remediation of future releases should be developed or modified to identify short-lived isotopes such as tritium. Confirmatory sampling of environmental media following remediation of a spill should meet the MIDCs of applicable regulatory criteria. In most cases, a professional engineer with expertise in hydrogeology should be consulted to assist in remediation investigations./'

The components investigation currently being conducted by SQN staff should contnue to' substantiate that no releases to groundwater have occurred from internal source.Should problems be identified, their remedies should extend to external environs as necessary4 82

Routine Onsite Groundwater Monitoring:.-IJoutine groundwater quality and water levefl' monitoring should be continued at a quarterly frequency at wells 31, GP-13, and W21 for a minimum of two years. These data should be reviewed on an annual basis by a professional engineer with expertise in hydrogeology and groundwater science. In addition to tritium, boron should be considered as an analyte since it is typically added to primary, cooling water as a neutron moderatorkherefore, when detected at concentrations greater than background, boron can be an indicator of leaks from primary systems. -kesults of routine groundwater sampling should be reviewed annually by a professional engineer with expertise in hydrogeology..

Groundwater sampling protocols have been prepared by TVA and standard forms are available for use. In addition, the NRC (1979) and ASTM (2006) provide standard guidel-i-nes for groundwater sampling. The SQN staff should assure that acceptable groundwater sampling protocols are being utilized. In addition to groundwater collection methods, these practices also extend to: sample handling, labeling, storage, shipment and chain-of-custody procedures; qualification and training requirements for sampling personne[; applicable regulatory limits; analytical methods and MDCs, required analyti6al method uncertainties; quality control samples and acceptance criteria; required number of samples per analytical batch; and validation methods.

REMP Onsite Groundwater Monitoring: Bedrock well W5 is currently the only onsite well' A* being used for REMP groundwater monitoring purposes. The well location and type is poorly suited for rapid detection of groundwater contamination from primary plant systems. Well W5 resides too far from the plant, is situated adjacent to the Intake Channel, and is developed in bedrock tonsideration should be given to. an alternate well location(s) and type (e.g., well immediate to the site, along groundwater gradient, and appropriately screened).

Data Management and Quality: The current data management procedures result in significant difficulties related to groundwater data acquisition and authentication/VA and SQN should consider a programmatic evaluation of data management and quality practices to ensure that analytical results are documented, retained, and readily retrievable. At a minimum, documented analytical data shall contain the following information:

" Sample identification (e.g., location and well identification);

" Sample date and time;

• Measured concentration for all radionuclides where results have been reported (whether or not above the detection criteria, or positive or negative);

• Measurement uncertainty;

" Achieved MDCs;

" Records of data validation and verification;

" Identification of missing sample results;,'

11A 83

. Analytical method(s).

Development of a database should be considered that meets criteria described in American Nuclear Insurers Information Bulletin 80-1A. The database developed by TVA for the fossil fuel groundwater jonitoring program would serve as an ideal platform for groundwater data management.

Well Protection and Abandonment: Analytical results from repeated sampling at several site wells indicate that they can be abandoned. Wells that are deemed of no strategic importance have no, exhibited tritium concentrations >MDCs and are in close proximity to other monitoring wells. Wffells recommended for abandonment include: 30, 32, 34, 35, UNIW, UNW2, and UNW3..1 Wells installed for monitoring along the waste condensate lines and during this study do not possess well head protection.'-Lockable well head protective covers, balusters, and/or flush-mount covers should be installed at these wellsData suggest that jells 14 and W21 well head seals have Peen damaged, allowing direct entry of rainfall runoff.these well heads should be repaired.j1

6.0 REFERENCES

OARCADIS, Groundwater Investigation Report, Watts Bar Nuclear Plant, Spring City, Tennessee, June 2004 ASTM D5903-96(2006), "Standard Guide for Planning and Preparing for a Groundwater Sampling Event," ASTM International, 2006.

Edwards, M., H. E. Julian, C.D. Olson, J.L. Edge, and P. Rich, "Sequoyah Nuclear Plant, Fuel Oil Contamination Investigation and Corrective Action Plan," TVA Engineering Lab Report WR28-1-45-143, February 1993.

Halter, M., "Sequoyah Nuclear Plant - Unit 2 Additional Equipment Building Sump Spill, Final Recovery Report" Tennessee Valley Authority, January 22, 1998.

Halter, M., "RWST Moat Water as a Potential Tritium in Ground Water Source," Memorandum, Tennessee Valley Authority, July 17, 2006.

Julian, H. E., "Sequoyah Nuclear Plant Fuel Oil Contamination Investigation, Addendum to Report WR28-1-45-143," TVA Engineering Lab Report, December 1993.

Julian, H. E., "Sequoyah Nuclear Plant, Groundwater Supply Study," TVA Engineering Laboratory, Internal Report, April 2000.

84

NRC, "Liquid Radioactive Release Lessons Learned Task Force Final Report," Nuclear Regulatory Commission, September 1, 2006.

NRC Regulatory Guide 4.15, "Quality Assurance for Radiological, Monitoring Programs (Normal Operations) - Effluent Streams and the Environment," Revision 1, February 1979.

Rogers, W. J., "Distribution Coefficient Study for Sequoyah Nuclear Plant," .TVA Laboratory Services Branch Report No. 9., 1982.

Smith, W. E., "Sequoyah Nuclear Plant - RadWaste Yard Spill, Final Survey Report" Tennessee Valley Authority, July 31, 1997.

TVA, "Sequoyah Nuclear Plant - Records of Spills and Unusual Occurrences Important to Decommissioning," Memorandum from Michael F. Halter to Mark A. Palmer, Tennessee Valley Authority, Sequoyah Nuclear Plant, Soddy Daisy, Tennessee, July 11, 2006.

TVA, "Sequoyah Nuclear Plant, Final Safety Analysis Report, Amendment 19," Tennessee Valley Authority, October 13, 2005 TVA, "Supplemental Environmental Assessment, Independent Spent Fuel Storage Installation, Sequoyah Nuclear Plant," Tennessee Valley Authority, November 2001.

TVA, "Quantification of Total Petroleum Hydrocarbon in Soil at the Sequoyah Nuclear Dry Cask Storage Area," Tennessee Valley Authority, Environmental Engineering Services-East, June 2001.

TVA, "Dry Cask Storage Soil-Core Sampling Results - Supplement to Quantification Of Total Petroleum Hydrocarbons In Soil At The Sequoyah Nuclear Dry Cask Storage Area," Tennessee Valley Authority, Environmental Engineering Services-East, September, 2001.

TVA, "Sequoyah Nuclear Plant, Final Safety Analysis Report," Tennessee Valley Authority, 1979.

TVA, "Sequoyah Nuclear Plant - Ground Water Inleakage," April 4, 1978 Memorandum from R. M. Pierce to G. G. Stack, Tennessee Valley Authority, 1978.

TVA, "Sequoyah Nuclear Plant Low-Level Radwaste Storage Foundation Investigation,"

Tennessee Valley Authority, Engineering Design Soil Schedule 28.3, 1981.

USEPA, "USEPA RadNet Database Retrieval for Tritium in Surface Water at Soddy Daisy, Tennessee," http://oaspub.epa.gov/enviro/eramsquery.simple_output?Llocation=City&subloc=

DAISY%2CTN&media=SURFACE+WATER&radi=Tritium&Fromyear= I960&Toyear=-2006&

units=Traditional, April 2007.

85

J Young, S.C., H. E. Julian, H. S. Pearson, F. J. Molz, and J. K. Bowman, "User's Guide for Application of the Electromagnetic Borehole," U.S. EPA report, Robert S. Kerr Environmental Research Laboratory, Ada, OK, Report in Press, 1997.

(I 86

APPENDIX A WELL CONSTRUCTION LOGS 87

ROCK MONITORING WELL INSTALLATION RECORD PROJECT ocuw, T ,, N ,UM .PLAN I WELL NUMBER __ INSTALLATION DATE 600.1 ft PLANT COORDINATES EAST -1272.6 ft NORTH 708,67 ftmal GROUND SURFACE ELEVATION 705.6 ftmal TOP OF INNER CASING BACKFILL MATERIAL SAND & PEA GRAVEL CASING DIAMETER 6" CASING MATERIAL SOUD STEEL CASINO DRILLING TECHNIQUE IN ROCK PERCUSSION DRILLING TECHNIQUE IN SOIL AUGER DRILLING CONTRACTO R OUTER BOREHOLE DIAMETER OPEN BOREHOLE DIAMIIETER 6" LOCKABLE COVER ? NO COMMENTS PLASTIC PIPE ADDED TO RAISE THIS WELL 4.37 ft.

(NOT TO SCALE)

@0 GROUNDSm~Fcs TOO ROCK earoo7cAF 1.I 65.7 MEi ENO LAB 7MR1 88

MONITORING WELL INSTALLATION RECORD PROJECT SEQUOYAH NUCLEAR PLANT W2 INSTALLATION DATE PLANT COORDINATES EAST -1105.5 ft -1271.6 ft NORTH 7 700.1 flmal GROUND SURFACE ELEVATION TOP OF INNER CASING BACKFILL MATERIAL SAND & PEA GRAVEL CASING DIAMETER CASING MATERIAL SOUD STEEL CASING DRILLING TECHNIQUE IN ROCK PERCUSSION DRIMLNG TECHNIQUE IN SOIL AUGER DRILLING CONTRACTOR OUTER BOREHOLE DIAMETER OPEN BOREHOLE DIAMETER ("

LOCKABLE COVER ? NO COMMENTS NEAR GAS/DIESEL TANKS (NOT TO SCALE)

RbAKECAPP

____ fsoJ STID. CAffiN 70.5' 157' TOP OF ROCK

=1f=11 BOTTOMOF CASING OPEN4BOREHOLE GOflUT

.L ENW LAB7/25)01 Q

89

@ MONITORING WELL INSTALLATION RECORD PROJECT SEOUOYNA NUCLEAR PLANT W4 WELL NUMBER W4 INSTALLATION DATE PLANT COORDINATES EAST 948.1 It NORTH 39.6 ft GROUND SURFACE ELEVATION TOP OF INNER CASING 742.27 ftmal BACKFILL MATERIAL SAND & PEA GRAVEL CASING DIAMETER CASING MATERIAL SOLID STEEL CASING DRILLING TECHNIQUE IN ROCK PERCUSSION DRILLING TECHNIQUE IN SOIL AUGER DRILLING CONTRACTOR OUTER BOREHOLE DIAMETER OPEN BOREHOLE DIAMETER LOCKABLE COVER ?

%.AIv1mmr- 1 (NOT TO SCALE)

FAMMAE CAP GAWPN9VACi E TT LOPETO C&'JN APPROaM"TELY I I W r 5011 STEML CASINO 120.4' TOP OF ROCK

=1111 BOTTOM OFCA&MN j

-OPEN 80OD0L OROUTT I m ENOLAB 7/raff1 90

TENNESSEE VALLEY AUTHORITY River System Operations & Environment Research & Technology Applications Environmental Engineering Services - East SEQUOYAH NUCLEAR PLANT INVESTIGATION OF TRITIUM RELEASES TO GROUNDWATER 0

Hank E. Julian, P.E., P.G.

Geosyntec ,'

consultants and Matthew Williams Knoxville, Tennessee May 2007

TABLE OF CONTENTS Page No.

LIST OF FIGURES ....................................................................................................................... iii ACRONYM S AND ABBREVIATIONS .................................................................................. v

1.0 INTRODUCTION

........................................................................................................... I 1.1 Purpose and Objectives ................................................................................................ 1 1.2 Plant Description ......................................................................................................... 2 1.3 Historical Tritium M onitoring .................................................................................... 2

2.0 BACKGROUND

.......................................................................................................... 6 2.1 Radiological Environmental Monitoring Program (REMP) .................. 6 2.1.1 REMP Groundwater ............... *............................ 6 2.1.2 REMP Surface W ater .............................................................................................. 9 2.2 Radwaste System ...................................................................................................... 10 2.2.1 Liquid Radwaste System ....................................................................................... 10 2.2.1 .1 System Descriptions ....................................................................................... 11 2.2.1.2 Shared Components ....................................... 12 2.2.1.3 Separation of Tritiated and Nontritiated Liquids .......................................... 12 2.2.1.4 Tritiated W ater Processing ........................................................................... 12 2.2.1.5 Nontritiated W ater Processing ...................................................................... 13 2.2.1.6 Releases of Liquid Radwaste ........................................................................ 13 2.2.2 W aste Condensate Lines ...................................................................................... 16 2.2.3 Gaseous Radwaste System ..................................................................................... 17 2.3 Inadvertent Releases of Liquid Radwaste ..................................... ............................. 18 3.0 HYDROGEOLOGY ....................................................................................................... 27 3.1 Site Location and Scope of Exploration ................................................................... 27 3.2 Physiography ................................................................................................................. 30 3.3 Geomorphology ....................................................................................................... 30 3.4 Geology .......... I............................................................................................................... 32 3.4.1 Stratigraphy ............................................... 32

• 3.4.2 Bedrock ..................................................................................................................... 32 3 .4 .3 S o il ........................................................................................... ................................. 3 7 3.4.4 Structure .................................................................................................................... 40 3.5 Hydrology .................................................. 41 3.6 Groundwater ........................................................................................................... 43 3.7 Offsite W ater Supplies .............................................................................................. 51 3.7.1 Offsite Groundwater Supplies .............................................................................. 51 3.7.2 Offsite Surface W ater Supplies ............................................................................. 56 4.0 TRITIUM INVESTIGATION ....................................................................................... 58 4.1 Groundwater Sampling of Selected Existing W ells ................................................ 59 4.2 Manual Sampling of Storm Drain Catch Basin, Vaults, and Manholes ................... 59 4.3 Groundwater Sampling using Geoprobe M ethods ................................................... 62 4.4 W ater Level M onitoring ........................................................................................... 65 4.5 Interior Sampling ..................................................................................................... 72 5.0 RESULTS AND RECOM M ENDATIONS .................................................................... 75 i

5.1 Tritium Distribution ...................................................................................................... 75 5.1.1 M anual Sam pling .................................................................................................. 75 5.1.2 Groundw ater .Sampling ........................................................................................ 76 5.2 Tritium Sources ......................................................................................................... 79 5.3 Tritium Transport and Fate ...................................................................................... 81 5.4 Recom m endations ................................................................................................... 82

6.0 REFERENCES

.................................................. 84 A PPENDIX A ............................................................................................................................... 87 A PPENDIX B ............................................................................................................................. 114 ii

LIST OF FIGURES Pane No.

1.1 Site M ap Showing.Key Plant -Features ............................................................................ 3 1.2 Site Map Showing Historical Monitoring Wells ...................................... ................. 4 2.1 Onsite REMP Sampling Locations for Groundwater and Surface Water ....................... 7 2.2 Offsite REMP Sampling Locations for Groundwater and Surface Water ..................... 8 2.3 Time-Series Tritium Concentrations from REMP Groundwater and Surface Water ........ 10 2.4 Site Map Showing Locations of Inadvertent Releases of Liquid RadWaste ................ 19 2.5 Photograph of Unit 2 Moat Drainage to Ground Surface ............................................ 20 2.6 Map Showing Extent of MFTDS Release to Railroad Bay (from Halter, 1997) .......... 21 2.7 Map Showing Extent of Sump Release at Unit 2 Additional Equipment Building (from Halter, 1998) ...................................................................................................... 23 2.8 Photographs of Sump Release Area at Unit 2 Additional Equipment Building (from H alter, 199 8) ...................................................................................................................... 25 2.9 Schematic of Sampling Locations and Photograph of Unit I RWST Moat Drain ......... 26 3.1 Site Location M ap ........................................................................................... ............. .28 3.2 Locations of Exploratory Borings ............................................................................... 29 3.3 Site Topographic M ap ......................................... I........................................................ 31 3.4 Regional Map Showing Geologic Formations and Structure ....................................... 33 3.5 Surface of Conasauga Bedrock .................................................................................... 35 3.6 Pre-excavation Top of Bedrock Contours (ft-msl) at the Reactor, Auxiliary, Control, and Turbine Buildings (from TVA Drawing 10N211) ................................................ 36 3.7 1971 Site Construction Photograph of the Reactor, Auxiliary, Control, and Turbine Buildings ............................................................................................................................ 37 3.8 Operating Guide For Chickamauga Dam .............................. ....................................... 42 3.9 Mean 1995 - 1999 Discharge Channel Elevations ........................................................ 43 3.10 Site Bedrock M onitoring W ells .................................................................................... 44 3.11 Time-Series Groundwater Levels for Wells W1, W2, L6, and L7 (1985-1991) .......... 45 3.12 Time-Series Groundwater Levels for Wells W1, W4, W5 and L7 (1985-1991) .......... 46 3.13 Site-W ide Potentiom etric M ap ................................................................................... 47 3.14 Potentiometric Surface at Diesel Fuel Oil Interceptor System on February 10, 2003 ....... 49 3.15. Schematic of Diesel Fuel Oil Interceptor Trench ....................................................... 50 3.16 Large Capacity Wells in the Vicinity of SQN from USGS GWIS Database ............... 53 3.17 Groundwater Supply Wells in the Vicinity of SQN from Bradfield (1992) ................. 55 4.1 Map Showing Manual Sampling Locations ................................................................. 61 4.2 Map Showing Geoprobe Sampling Locations and Monitoring Wells.............. ...... 63 4.3 Profile of G eoprobe Borings ............................................................................................. 64 4.4 Time-Series Water Levels at Wells W-21, 29, 30, 31 and the River ............................ 66 iii

4.5 Time-Series Water Levels at Wells 27, 32, 33, 34 and the River ......................67 4.6 Continuous Water Levels (top) and Temperatures (bottom) at Wells GP-l 3, 14, W21, the Discharge Channel and the River ........................................................................... 68 4.7 Continuous Water Levels (top) and Precipitation (bottom) at Wells 14, W21 and the Discharge Channel ......................................................................................... ....... ..... 69 4.8 Local Potentiometric Surface from April 02, 2007 Water Level Measurements ...... 71 4.9 Groundwater Inleakage Locations at Auxiliary Building ............................................ 73 5.1 Time-Series Tritium Concentrations and Groundwater Levels at Well 31 ................. 76 5.2 Time-Series Tritium Concentrations and Groundwater Levels at Well W21 .............. 77 5.3 Time-Series Tritium Concentrations and Groundwater Levels at Wells 27 and 29 ......... 78 5.5 Time-Series Tritium Concentrations and Groundwater Levels at Well GP-13 ............ 79 5.6 Spatial Distribution of Tritium from Groundwater Sampling during January and February 2007 .................................................................................................................... 80 iv

Acronyms and Abbreviations CBI Chicago Bridge & Iron CCW Condenser Circulating Water CDWE Condensate Demineralizor Waste Evaporator CVCS Chemical and Volume Control System EPA Environmental Protection Agency ERCW Essential Raw Cooling Water GIS Geographic Information System GWSI Ground-Water Site Inventory LLRWSF Low Level Radwaste Storage Facility MDC Minimum Detection Concentration MFTDS Modularized Transfer Demineralization System MWe Megawatt Electric MWt Megawatt Thermal NEI Nuclear Energy Institute NRC Nuclear Regulatory Commission NRWT, Nonreclaimable Waste Tank NT Neutralization Tank ODCM Offsite Dose Calculation Manual pCi/L Picocuries per liter PER Problem Evaluation Report Rad DI Radwaste Demineralizer System RCA Radiation Control Area REMP Radiological Environmental Monitoring Program RWST Refueling Water Storage Tank SQN Sequoyah Nuclear Plant TRM Tennessee River Mile TVA Tennessee Valley Authority USGS United State Geological Survey WARL Western Area Radiological Laboratory WBN Watts Bar Nuclear Plant V

1.0 INTRODUCTION

1.1 Purpose and Objectives The Tennessee Valley Authority (TVA) is committed to controlling licensed material, minimizing potential unplanned, unmonitored releases to the environment from plant operations, and minimizing long-term costs associated with potential groundwater and subsurface contamination. Although current public health standards and limits are deemed appropriate, they may not satisfy public trust issues when unplanned releases occur. In conjunction with the Nuclear Energy Institute (NEI), TVA has approved a voluntary policy to enhance detection, management and communication about inadvertent radiological releases in groundwater. The investigation described herein represents an initial step in policy implementation.

In August 2006, a team consisting of GeoSyntec Consultants, Sequoyah Nuclear Plant (SQN) staff, and corporate TVA personnel was established to locate potential source(s) of site tritium releases and to identify potential migration route(s) to groundwater. This report provides findings of the site subsurface investigation with recommendations for the path forward. The primary objectives of the investigation were to:

0 Identify potential radionuclide contaminant sources .that account for observed measurements, 0 Assess the nature and extent of subsurface tritium contamination, and

• Characterize groundwater movement to evaluate potential contaminant migration routes.

Tasks associated with this investigation included:

0 Comprehensive review of historical radiological release information, 9 Review of site drawings and plant construction photographs, 0 Installation and sampling of soil borings and groundwater monitoring wells, 0 Enhanced sampling of existing monitoring wells, 0 Visual inspections and manual sampling of yard, drains, sumps, manholes, and internal seeps, 0 Manual and continuous water level monitoring, and 0 Internal components investigations of both units using visual and boroscope methods.

I

1.2 Plant Description SQN is a two-unit nuclear power plant located approximately 7.5 miles northeast of Chattanooga at the Sequoyah site in Hamilton County, Tennessee. The plant has been designed, built, and is operated by TVA. Each of the two identical units (Units I and 2; Figure 1.1) employs a Pressurized Water Reactor Nuclear Steam Supply System with four coolant loops furnished by Westinghouse Electric Corporation. These units are similar to those of TVA's Watts Bar Nuclear Plant.

Each of the two reactor cores is rated at 3,455 MWt and, at this core power, each unit will operate at 3,467 MWt. The additional 12 MWt is due to the contribution of heat of the Primary Coolant System from nonreactor sources, primarily reactor coolant pump heat. The total generator output is 1,199 MWe for the rated core power. The containment for each of the reactors consists of a freestanding steel vessel with an ice condenser and separate reinforced Concrete Shield Building. The ice condenser was designed by the Westinghouse Electric Corporation. The freestanding containment vessel was designed by Chicago Bridge & Iron (CBI). Unit I began commercial operation on July 1, 1981. Unit 2 began commercial operation on June 1, 1982.

1.3 Historical Tritium Monitoring As part of the SQN onsite Radiological Environmental Monitoring Program (REMP), quarterly groundwater monitoring for tritium began in 1971 at four bedrock monitoring wells (WI, W2, W4, and W5) located along the perimeter of the site (Figure 1.2). Onsite REMP groundwater monitoring was reduced to a single well (W5) in 1980. Tritium was initially observed in SQN groundwater at well W5 from 1989 sampling at a background concentration of 379 picocuries per liter (pCi/L). No other detection of tritium was observed at well W5 until 1998. From 1998 through 2001, tritium was consistently observed at concentrations ranging from 401 to 2,120 pCi/L at well W5. No further tritium detection has been observed at well W5 since 2001.

Evaluation of REMP data indicates no evidence of tritium or other radionuclides exceeding detection levels in offsite surface water or groundwater samples since 1992. Pre-1992 tritium concentrations in offsite surface water and groundwater samples reflect ambient concentrations resulting most probably from cosmogenic sources and nuclear weapons testing from the 1940s through the 1970s.

2

~' SEQUJOYAiI NUCLEAR PLANT ML; 4"Key Plant Features 64c O Cmidmmaft Une 124inch Wn% Condonmal Law

~4i ~ERMVWCW Lines B..i a.W AW Sio rainA

• A 4 W t~ ta Figure 1.1 Site Map Showing Key Plant Features

i SEQUOYAH NUCLEAR PLANT Historical Monitoring Wells Historical Groundwater Wells 0 Diesel 0 Diesel Extraction 0 LLRW sidin 0LLRW 0

Reservation Boundary PRoEPAREDBlYTVAGsorRApj INFORMAnIQANDENGINEERIN M&PgiS 2 Dfiai 00p-O 2004 storical Mon~itoring Wells 4

In February 2002, TVA expanded the REMP groundwater monitoring at SQN by installing five additional soil monitoring wells (wells 24 - 28) along 6- and 12-inch diameter condensate pipelines. These lines convey condensate and radwaste effluent from the Turbine and Auxiliary Buildings, respectively (Figure 1.1). The 6- and 12-inch lines discharge into the 72-inch cooling tower blow-down line and Low-Volume Waste Treatment Pond, respectively. Initial samples collected from these wells indicated no evidence of tritium (<220 pCi/L).

Monthly groundwater sampling for tritium was prescribed for well 27 beginning in August 2003.

Tritium was consistently observed slightly above the minimum detection concentration (MDC) of 220 pCi/L at this well beginning in September 2003. The consistency of observations prompted a sampling event in January and February 2004 that included other site wells (W14 and W21) in conjunction with manual sampling of vicinity sumps, moats, storm drain catch basins, and ponds. A relatively high tritium concentration of 9,080 pCi/L was observed at well 21. A subsequent set of seven monitoring wells (wells 29 - 35) were installed in April 2004, with routine sampling of selected wells beginning in May 2004. To date, tritium concentrations in these wells have ranged from MDC to 19,750 pCi/L. These concentrations have not exceeded the Environmental Protection Agency (EPA) Drinking Water Standard of 20,000 pCi/I for tritium (40 CFR 141.25). The Nuclear Regulatory Commission (NRC) Site Resident at SQN has been notified and is being kept informed as investigations continue.

(

5

2.0 BACKGROUND

2.1 Radiological Environmental Monitoring Program (REMP)

The preoperational environmental monitoring program has established a baseline of data on the distribution of natural and manmade radioactivity in the environment near the plant site. The preoperational environmental monitoring program was initiated in the spring of 1971. The operational monitoring program initiated in the spring of 1980 reflects the current monitoring philosophy and regulatory guidelines.

REMP reports have been prepared by TVA's Western Area Radiological Laboratory (WARL) and SQN personnel since inception of the program in 1971. The SQN REMP has been modified over time to adjust for sampling locations, sampling methods, analytes, reporting frequency, and changes in laboratory methods/instruments and MDCs.

Currently, REMP reports catalog onsite direct radiation sampling, atmospheric radiation monitoring at eight sites located 10 to 20 miles from the plant, terrestrial radiation monitoring at area farms within six miles of the plant, and liquid pathway radiation monitoring along the Tennessee River and from area groundwater wells.

TVA participates in an Interlaboratory Comparison Program. This program provides periodic cross-check samples of the type and radionuclide composition normally analyzed in an environmental monitoring program. Results obtained in the monitoring and the cross-check programs are reported annually to the NRC.

Groundwater and surface water sampling have been a part of the program since it was instituted in 1971, and remain part of the current liquid pathway monitoring program. Onsite and offsite monitoring locations for groundwater and surface water are shown in Figures 2.1 and 2.2, respectively.

2.1.1 REMP Groundwater The monitoring well network at SQN (Figure 1.2) included six regional monitoring wells (wells WI, W2, W4, W5, and W8) that were installed before 1977. Quarterly groundwater monitoring for tritium began in 1977 at four bedrock monitoring wells (WI, W2, W4, and W5) located along the perimeter of the site (Figure 2.1). Onsite REMP groundwater monitoring was reduced to a single well (W5) in 1981. Offsite groundwater sampling also began in 1977 at seven area farms; but, since 1986 samples have been collected at just one location (Farm HW well; see Figure 2.2).

6

NNIONNww"A" 47 Z SEQUOYAH NUCLEAR PLANT Onsite REMP Sampling Locations

, Onsite Monitoring Weiis

- Current REM

~7; A

PREPARED By. TVAGEOGRAPH.IC INFORMATIONAND EI4ONEERt4G hIMA9I 9 DOIgh00000bra 2004 Figure 2.1 Onsite REMP Sampling Locations for Groundwater and Surface Water 7

SEQUOYAH NUCLEAR PLANT Offsite REM P Sampling Locations REMP Monitoring Locations Ai Surface Water

• Groundwater Sequoyah Nuclear Plant N

• ' .. . Md..

O 1 2 3 4 5

REPAJ*EDBY TVAGEOGRAPHICNFORMATION AN40ENGINEERONG Figure 2.2 Offsite REMP Sampling Locations for Groundwater and Surface Water 8

In the earlier years, groundwater was collected by grab sampling. Sometime in the late 1970s or early 1980s, well W5 was equipped with an automatic sampler. The automatic sampler transmits a daily sample aliquot to a composite container for monthly retrieval. Manual samples are collected quarterly from the offsite Farm HW well.

Quarterly samples are analyzed by gamma spectroscopy using a one pass method with an intrinsic germanium detector (Vortec and Canberra instruments). Samples are first distilled by centrifuging 50 ml of liquid, distilling that volume (if it is turbid), and then extracting 15ml to be analyzed. The composite sample is analyzed by gamma spectroscopy for gross beta activity (monthly) and tritium analysis is conducted on a quarterly basis. Tritium analysis is completed by liquid scintillation methods using a Packard scintillation unit. A total of five scintillation counts are performed for each test. Results are reported as the mean of the three highest counts.

Results of REMP groundwater monitoring are shown in Figure 2.3. From the period 1977 -

1998, both onsite and offsite groundwater monitoring indicates tritium concentrations that are

<MDC or are within the range of expected background concentrations. Tritium was initially observed in SQN groundwater at onsite well W5 from 1989 sampling at a background concentration of 379 pCi/L. No other detection of tritium was observed at well W5 until 1998.

However, from 1998 through 2001, tritium was consistently observed at concentrations ranging from 401 to 2,120 pCi/L at well W5. No further tritium detection has been observed at well W5 since 2001. During the period 1998 - 2001, tritium concentrations at the offsite Farm HW well and at all surface water monitoring locations were <MDC (Figure 2.3). Hence, tritium observations at well W5 during the 1998 - 2001 time interval exceed background concentrations and suggest an onsite source of contamination.

2.1.2 REMP Surface Water Surface water sampling locations have remained constant throughout the REMP program, including one upstream location and two downstream locations (Figure 2.2). The upstream sampling location is the City of Dayton drinking water supply intake station at Tennessee River Mile (TRM) 497.0. The downstream samples are collected at Eastside Utility District water intake (TRM 473.0) and at a temperature station 0.3 mile downstream from the SQN discharge (TRM 483.4).

Samples are collected by automatic ISCO samplers at each of the three locations. The instruments are programmed to accumulate discreet samples every two hours and composite samples are collected monthly. The composite sample is analyzed for gross beta activity (monthly) and tritium (quarterly) using the methods described in Section 2.1 .1.

9

10,000 iVA MDC Upstream: Surface Water Downstream: Surface Water

......... Soddy Daisy: Surface Water (USEPA RadNet)

-- Onsite: Groundwater

-Offite: Groundwater 1,000 0

0 E

I1.

100 1 Year Figure 2.3 Time-Series Tritium Concentrations from REMP Groundwater and Surface Water Monitoring Results of REMP surface water monitoring are shown in Figure 2.3. For comparison, USEPA RadNet surface water data (USEPA, 2007) for Soddy Daisy, Tennessee are depicted in the figure. The SQN REMP data indicate no evidence of tritium or other radionuclides exceeding detection levels in offsite surface water or groundwater samples since 1992. Pre-1992 tritium concentrations in surface water samples reflect ambient concentrations resulting most probably from cosmogenic sources and nuclear weapons testing from the 1940s through the 1970s.

2.2 Radwaste System 2.2.1 Liquid Radwaste System Liquid, gaseous, and solid radwaste disposal facilities at SQN are designed so that discharges of effluents are in accordance with 10 CFR Parts 20 and 50. The Liquid Waste Processing System is designed to receive, segregate, process, recycle for further processing, and discharge liquid wastes. Liquids entering the Liquid Waste Processing System are collected in sumps and tanks until determination of subsequent treatment can be made. They are sampled and analyzed to quantify radioactivity, with an isotopic accounting if necessary. Processed radioactive wastes not suitable for reuse and the liquid waste suitable for reuse, whose volume is not needed for 10

plant operations or not desired for reuse, are discharged from the plant or packaged for offsite disposal. Design and operation of the Radwaste System is characteristically directed toward minimizing releases to unrestricted. areas. Under normal plant operation, the activity from radionuclides leaving the discharge canal is a small fraction of the limits in 10 CFR Parts 20 and 50.

2.2.1.1 System Descriptions The Liquid Waste Processing System was initially designed to collect and process potentially radioactive wastes for recycle to the Reactor Coolant System or for release to the environment.

The liquid waste processing system was, by original design, arranged to recycle as much reactor-grade water entering the system as practical. This was implemented by the segregation of equipment drains and waste streams, which prevents the intermixing of liquid wastes. The layout of the liquid waste processing system, therefore, consists of two main subsystems designed for collecting and processing reactor-grade (tritiated) and non-reactor-grade (non-tritiated) water, respectively. All liquids are now routinely processed as necessary for release to the environment instead of recycling, and are no longer maintained segregated based on tritium content during processing. This includes reprocessing the contents of tanks which accumulate waste water for discharge which may be unsuitable for direct release. Provisions are made to sample and analyze fluids before they are discharged. Based on the laboratory analysis, these wastes are either released under controlled conditions via the cooling water system or retained for further processing. A permanent record of liquid releases is provided by analyses of known volumes of waste. Actual radionuclide inventories of plant effluents are submitted to the NRC as a requirement of 10 CFR 50 by Nuclear Chemistry Offsite Dose Calculation Manual (ODCM).

In addition, a system is provided for handling laboratory samples which may be tritiated and may contain chemicals. Capability for handling and storage of spent demineralizer resins is also provided.

The plant system is controlled from a central panel in the Auxiliary Building and a panel in the main control room. All system equipment is located in or near the Auxiliary Building, except for the reactor coolant drain tank and drain tank pumps and the various Reactor Building floor and equipment drain sumps and pumps which are located in the Containment Building.

The Radwaste Demineralizer System (Rad DI) is located and operated in the Auxiliary Building railroad access bay when the vendor's service is requested.

At least two. valves must be manually opened to permit discharge of liquid to the environment.

One of these valves is normally locked closed. A control valve trips closed on a high effluent radioactivity level signal. Controls are provided to prevent discharge without dilutions.

11

2.2.1.2 Shared Components Parts of the Liquid Waste Processing System are shared by the two units. The Liquid Waste Processing System consists of one reactor coolant drain tank with two pumps, an Auxiliary Reactor Building floor and equipment drain sump with two pumps, a keyway sump with one pump, and a Reactor Building floor and equipment drain sump with two pumps inside the Containment Building of each unit. It also includes the following shared equipment located inside the Auxiliary Building: one sump tank and two pumps; one tritiated drain collector tank with two pumps and one filter; one floor drain collector tank with two pumps and one strainer; a monitor tank and two pumps; a chemical drain tank and pump; two hot shower tanks and pump; a spent resin storage tank; a cask decontamination tank with two pumps and two filters; the Auxiliary Building floor and equipment drain sump and two pumps; a passive sump; a Radwaste Demineralizer System; and the associated piping, valves, and instrumentation.

The following shared components are located in the Condensate Demineralizer Building for receiving, processing, and transferring wastes from the regeneration of condensate demineralizers: high crud, low conductivity tanks, pumps, and filters; a neutralizer tank and pumps; and a non-reclaimable waste tank and pumps.

2.2.1.3 Separation of Tritiated and Nontritiated Liquids Waste liquids that are high in tritium content are routed to the tritiated drain collector tank; while liquids low in tritium content are routed to the floor drain collector tank. All tritiated and nontritiated liquid waste are processed for discharge to the environment.

2.2.1.4 Tritiated Water Processing Tritiated reactor grade water is processed for discharge to the environment or for recycle to the primary water storage tank. The water enters the liquid waste disposal system from equipment leaks and drains, valve leakage, pump seal leakage, tank overflows, and other tritiated and aerated water sources including draining of the Chemical and Volume Control System (CVCS) holdup tanks, as desired.

The equipment provided in this channel consists of a tritiated drain collector tank, pumps, and filter and Radwaste Demineralizer System. The primary function of the tritiated drain collector tank is to provide sufficient surge capacity for the radwaste processing equipment.

The liquid collected in the tritiated drain collector tank contains boric acid, and fission product activity. The liquid can be processed as necessary to remove fission products so that the water may be reused in the Reactor Coolant System or discharged to the environment.

12

2.2.1.5 Nontritiated Water Processing Nontritiated water is sampled and processed as necessary for discharge to the river. The sources include floor drains, equipment drains containing nontritiated water, certain sample room and radiochemical laboratory drains, hot shower drains and other nontritiated sources. The equipment provided in this channel consists of a floor drain collector tank, pumps, and strainer, Radwaste Demineralizer System, hot shower tanks and pump, cask decontamination collector tank and pumps, and monitor tank and pumps.

Liquids entering the floor drain collector tank are from small volume, low activity sources. If the activity is below permissible discharge levels following analysis to confirm acceptably low level, then the tank contents may be discharged without further treatment other than filtration.

Otherwise, the tank contents are processed through the Radwaste Demineralizer System.

The hot shower drain tanks normally need no treatment for removal of radioactivity. The inventory of these tanks may be discharged directly to the cooling tower blowdown via the hot shower tank strainer or to other tanks in the liquid waste system.

The liquid waste system is also designed to process blowdown liquid from the steam generators of a unit having primary-to-secondary leak coincident with significant fuel rod clad defects. The blowdown from the steam generators is passed through the condensate demineralizer or directly to the cooling tower blowdown line.

2.2.1.6 Releases of Liquid Radwaste The Tennessee River/Chickamauga Lake is the sole surface water pathway between SQN and surface water users along the river. Liquid effluent from SQN flows into the river from a diffuser pond through a system of diffuser pipes located at TRM 483.65. The contents of the diffuser pond enter the diffuser pipes and mix with the river flow upon discharge. The diffusers are designed to provide rapid mixing of the discharged effluent with the river flow. The flow through the diffusers is driven by the elevation head difference between the diffuser pond and the river. Flow into the diffuser pond occurs via the blowdown line, Essential Raw Cooling Water (ERCW) System, and Condenser Circulating Water (CCW) System. Two parallel pipelines comprise the diffuser system which is designed to provide mixing across nearly the entire width of the main channel.

13

Release of radioactive liquid from the Liquid Waste Processing System can be from the cask decontamination collector tank, CVCS monitor tank, hot shower tanks, or-chemical drain tank to the cooling towers blowdown line via the 6-inch diameter Waste Condensate Line (Figure 1.1).

The cooling tower blowdown line empties into the diffuser pond which discharges into the river through the diffuser pipes. Liquid wastes from the condensate Demineralizer system are released from the high crud low conductivity tanks, the non-reclaimable waste tank, and the neutralization tank.

The CCW system- operates in three modes: open, closed, and helper. In the open mode, the cooling towers are not used. Cooling water is pumped from the intake and through the condenser, and is discharged into the diffuser pond. Dilution water for the radioactive liquid is provided by ERCW, which is in continuous operation and discharges to the cooling tower cold water canal. A weir at Gate Structure I ensures that under most river level conditions, the ERCW flow is diverted through the cooling tower blowdown line. The radioactive liquid is mixed with ERCW in the cooling tower blowdown line and flows into the diffuser pond.

In the closed mode, CCW is recirculated between the cooling towers and the condenser. In this mode of operation, the cooling towers blowdown flows at a minimum of 150,000 gpm into the diffuser pond in order to maintain the solids in the cooling water at an acceptable level.

In the helper mode, the CCW from the condenser goes through the cooling towers and is released to the diffuser pond through Gate Structure I and the cooling tower blowdown line.

Release of the radioactive liquids from the liquid waste system is made only after laboratory analysis of the tank contents. Once the fluids are sampled, they are pumped to the discharge pipe through a remotely operated control valve, interlocked with a radiation monitor and with instrumentation to ensure adequate dilution flow in the cooling tower blowdown line.

Minimum dilution flow can also be determined via ERCW flow instrumentation, or by periodic flow rate estimation. A similar arrangement is provided for wastes discharged from the condensate demineralizer waste system. The flow control valve is interlocked with a radiation monitor. Release of wastes will be automatically stopped by a high radiation signal.

The steam generator blowdown system may discharge radioactive liquid. Liquid waste from this system is not collected in tanks for treatment, but is continuously monitored for radioactivity and may discharge to the cooling tower blowdown, or recirculate to the condensate system upstream of the condensate demineralizers. The flow control valve in the discharge line is interlocked with a radiation monitor and with instrumentation to ensure adequate dilution flow on the cooling tower blowdown. Minimum dilution flow can also be determined via ERCW flow instrumentation, or by periodic flow rate estimation.

14

The Turbine Building sump collects liquid entering the Turbine Building floor drain system or from clean water sources in the Auxiliary Building that are transferred to the Turbine Building sump. When the sump is nearly full (maximum capacity 30,000 gallons), the liquid is automatically discharged (level initiated) to the Low-Volume Waste Treatment Pond or the Yard Drainage Pond via the 12-inch diameter Waste Condensate Line (Figure 1.1). The Yard Drainage Pond drains by gravity to the Diffuser Pond which ultimately discharges to the river via the diffusers.

Means are provided for radiological monitoring during normal operations, including anticipated operational occurrences, and during accident condition various process streams and gaseous and liquid effluent discharge paths. Some of the monitors initiate automatic' control actions.

Continuous radiological monitoring instruments for liquid processes and effluents include the following locations.

1. Station Sump Discharge Monitor (Turbine Building)

2. Waste Disposal System Discharge Monitor (Auxiliary Building)

3. ERCW Discharge Monitor (Headers A & B)

4. Condensate Liquid Demineralizer Monitor (Demineralizer Building)

5. Steam Generator Blowdown Liquid Discharge Monitor (Turbine Building)

6. Component Cooling System Monitor (Auxiliary Building)

OThe release locations are also subject to periodic sampling and include all liquid releases which could exceed the limits given in Appendix I, 10 CFR 50 and 10 CFR 20. The sampling and analysis requirements for these release points are defined in the SQN ODCM controls. The plant discharge meets Regulatory Guide 1.21 Revision 1, 10 CFR 20, and 10 CFR 50 guidelines.

The offsite dose calculations for drinking water are based on the assumption that the liquid effluent will be mixed with 60 percent of the river flow between the point of discharge and Chickamauga Dam. Although further mixing will occur, 60 percent dilution is assumed to be maintained for approximately 14 miles until Chickamauga Dam (TRM 471.0) is reached where 100 percent dilution is assumed to occur.

15

2.2.2 Waste Condensate Lines Figure 1.1 shows the locations of the 6- and 12-inch waste condensate lines at the site. The 12-inch waste condensate line receives water from the Turbine Building sump. Turbine Building drains are collected in the Turbine Building sump or discharged directly to various ponds or CCW discharge. Non-radioactive raw cooling water booster pump skid drains, SGB sample panel drains, and auxiliary feedwater pump leakoff drains are also collected in the Turbine Building sump. A temporary-use manifold allows RADCON-approval drainage (e.g., Cycle Outage Ice Melt) to be discharged to the Turbine Building sump. The header penetrates the Auxiliary/Turbine Building wall connecting to an existing drain (old titration room drain) and travels by gravity to the sump.

High conductivity chemical regenerate and rinse wastes that are produced during condensate demineralizer regeneration are routed to the neutralization tank (NT) or, alternately, to the nonreclaimable waste tank (NRWT) where they are collected and neutralized. If the contents of either tank (NT or NRWT) are not radioactive or if the radioactivity level is less than the discharge limit, it is transferred to the Turbine Building sump and subsequently discharged through the low volume waste treatment pond, or alternately it is discharged to the cooling tower blowdown via the 6-inch waste condensate line. If the contents of either the NT or NRWT are radioactive, they may be discharged to the cooling tower blowdown if the radioactivity level is within specification; otherwise, they are processed by the radwaste system.

The Turbine Building sump level is controlled by a high-low level switch that energizes the sump pumps. The sump effluents can be routed to the Yard Drainage Pond or the Low Volume Waste Treatment Pond.

The 6-inch waste condensate line receives routine (almost daily) radioactive effluent discharges from the Liquid Waste Processing System described in preceding sections. Potential leakage of this line was identified as a potential tritium source based on comparable tritium investigations completed at Watts Bar Nuclear Plant (WBN; ARCADIS, 2004), and similarity of SQN plant design to WBN.

The operating pressure of the 6-inch waste condensate line during a radwaste release varies from about 4 psig to negative pressure. Pressure testing of the 6-inch waste condensate line was performed under SQN work order no. 04-776838-004 on April 7, 2006. Service air was used to pressurize the line to 50 psig. After approximately 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, the pressure was measured at 49 psig. After 70 hours8.101852e-4 days <br />0.0194 hours <br />1.157407e-4 weeks <br />2.6635e-5 months <br /> the pressure was measured at 47 psig.

0 116

On July 10, 2006 a leakage test was performed by connecting a hose from the Demineralizer Water System to the waste condensate line and filling the pipeline. Following the initial fill, a rotometer was installed (range 0 - 120 cc/min). Experimentation with the rotometer indicated that the lower detection limit of flow was about 1 drop per second which corresponds to approximately 1.3E-05 gpm.

Flow was allowed to stabilize for three weeks. After this period and on two separate occasions, the water supply was isolated (valve closure) from the condensate line. After four days of isolation, the water supply valve was reopened. On each occasion, the ball in the'rotometer was observed to have zero movement as the water supply valve was opened. Pressure gauge readings were obtained to ensure that the rotometer results were not invalidated by temperature changes in the condensate line. Results indicated that rotometer testing was valid. The test pressure was approximately 40 psig. Therefore, a leak was not observed at the detection limit of the rotometer and conclusions by SQN staff were that the line does not leak.

2.2.3 Gaseous Radwaste System Controlled airborne releases from the plant ventilation system may result in measurable atmospheric deposition of plant-related radionuclides (including tritium) in the vicinity of the site. Some of this material may accumulate on plant roof surfaces and discharge into roof drains during precipitation events. Rain may also wash airborne releases onto facility soil and building surfaces.

The impact of this potential source of groundwater contamination may vary substantially with release periods and meteorological conditions. While this potential source is not likely to be a major contributor to groundwater contamination, operators of at least one nuclear power plant believe that measurable tritium concentrations in groundwater at their site are likely due to the deposition of tritium in airborne effluents (NRC, 2006). Recognition that atmospheric deposition may be a process actively contributing to observed wide-spread, low-level tritium concentrations in groundwater would allow explanation of the presence of these low-level concentrations when no other potential source can be identified.

The Gaseous Waste Processing System is designed to remove fission product gases from the reactor coolant and to permit operation with- periodic discharges of small quantities of fission gases through the monitored plant vent. This is accomplished by internal recirculation of radioactive gases and holdup in the nine gas decay tanks to reduce the concentration of radioisotopes in the released gases. The offsite exposure to individuals from gaseous effluents released during normal operation of the plant is limited by Appendix I of 10 CFR 50 and by 40 CFR 190.

0 17

The Gaseous Waste Processing System consists of two waste-gas compressor packages, nine gas decay tanks, and the associated piping, valves and instrumentation. The equipment serves both units. Gaseous wastes can be received from the following: degassing of the reactor coolant and purging of the volume control tank prior to a cold shutdown, displacing of cover gases caused by liquid accumulation in the tanks connected to the vent header, purging of some equipment, sampling and gas analyzer operation, and boron recycle process operation (no longer in service).

Gaseous radioactive wastes are released to the atmosphere through vents located on the Shield Building, Auxiliary Building, Turbine Building, and Service Building.

2.3 Inadvertent Releases of Liquid Radwaste Design and operation of the Radwaste System is characteristically directed toward minimizing releases to unrestricted areas. However, accidental releases of radioactive effluents and unusual occurrences to outdoor environs at SQN have been documented by TVA (2006) for the period from July 1981 (Unit 1 startup) to July 2006. A comprehensive review of these data is important for this investigation since these historical releases may serve as sources of tritium identified within the site groundwater system. Records of releases by TVA (2006) are based on report documentation for most of the occurrences and via interviews conducted with SQN Radiation Protection staff for earlier events.

OEight accidental releases of radioactive effluents and unusual occurrences to outdoor environs at SQN have been documented to date. Figure 2.4 identifies the approximate locations of these events and descriptions are provided in the following paragraphs.

1. CondensateDemineralizor Waste Evaporator(CD WE) Building - mid-1 980s Based on personnel interviews, radioactivity leached through a concrete wall of the CDWE Building to an outside concrete slab and soil. It is presumed that this was an aqueous release.

Contaminated soil was excavated and the building wall was painted with sealant. Quarterly surveys (RMD-FO-35) were subsequently performed by Radiation Protection.

2. Unit 2 Additional Equipment Building (UpperHead Injection) - mid-1980s Based on personnel interviews, a hose burst, spraying water through a door to outside environs. An asphalt area was painted with sealant, and a vehicle and Porta-John toilet were decontaminated. Quarterly surveys (RMD-FO-35) were subsequently performed by Radiation Protection.

18

Q Figure 2.4 Site Map Showing Locations of Inadvertent Releases of Liquid RadWaste 19

3. Auxiliary Building Roof- early 1990s Based on personnel interviews, radioactive contamination was discovered on the Auxiliary Building roof. Origin of contamination was determined to be unfiltered fuel handling ventilation trains associated with Auxiliary Building ventilation stack discharge.

Remediation is cited as contamination being removed from the roof. Quarterly surveys (RMD-FO-35) were subsequently performed by Radiation Protection.

4. Unit 2 Refueling Water Storage Tank (RWST) Moat Drain- May 10, 1995 During performance of a routine environmental monitoring survey (RMD-FO-35),

radioactivity was identified in soil at the moat drainage outlet of the Unit 2 RWST (Figure 2.5). The drain outlet is located on the south side of the moat and discharges to gravel covered soil. Follow-up sampling was performed and Co-58, Co-60, Cs-134, and Cs-137 were identified in soil in excess of the MDC of 5.OE-07 gtCi/g. Documentation includes survey number D-95-0558 with attached sample gamma analysis results from WARL.

Figure 2.5 Photograph of Unit 2 Moat Drainage to Ground Surface

5. ModularizedTransferDemineralizationSystem (MFTDS) Release to RailroadBay- May 19, 1997 Due to failure of the conductivity probe on the MFTDS, approximately 3,000 gallons of water was released to the 706 ft-msl elevation Railroad Bay (Figure 2.6). It was estimated that 600-1000 gallons of water was released to the RadWaste Yard immediately adjacent to the Railroad Bay door. Problem Evaluation Report (PER) No. SQ971429PER was initiated to investigate the release. A subsequent report (Smith, 1997) addresses cleanup at the site.

20

I EL. 706 RADWASTE YARD Concrete Sampling Grid 1

Asphalt 2.6E-3 SAMPLING GRID Soil 2.2E-2 10 Grid Point sample location I asphaft and I soil form "ch point 16 Buttress 2 ND ND D

3 ND ND 4 2.9E-1 ND 5 SAE-2 8.815-3 6

7 1.5E-3 1.6E-1 ND 1..E-2 19 1-2 8 6.SE-2 ND o*I 9 1.E-3 D 1 NO 2.

ND 15.3 .18 Estimated airea 12 3.51E-2E-2 NO of water 13 0 3E-2 2.7E-3 cmw, C10 6.7E-3 13E-2 1

Is 6

.0.-2 5.6E-2 ND 8.853 ND ND 17 I

19 ND ND Activities not Quantitative, they am only for determining extent of contamination 1 0 0 00 II "rck Figure 2.6 Map Showing Extent of MFTDS Release to Railroad Bay (from Halter, 1997) 21

Smith (1997) indicates that the water spill was observed to spread over a 950 ft2 asphalted area. The initial response also noted a vortex near railroad ties within the release area.

Subsequent investigation revealed a French drain system parallel to both sides of the existing railroad track and extending outside of the Radiation Control Area (RCA). Soils samples were collected and select isotopes (Co-57, Co-58, Co-60, Cs-134, Cs-137, Nb-95, and Mn-54) were screened to 5.OE-07 liCi/g. Results indicated radioactive contamination at and below the French drain system for several soil samples.

Asphalt and soil were excavated beginning June 6, 1997. Approximately 200 ft3 of uncontaminated asphalt and 2000 ft of uncontaminated soil were removed outside of the RCA. About 1000 ft of contaminated soil, sand, and gravel were also excavated outside of the RCA. Smith (1997) notes that there were no attempts to remove concrete containing electrical conduit banks that were observed to be contaminated. There were also culverts observed with inaccessible contaminated sand that were not removed. The excavated French drain outside of the RCA was backfilled with concrete.

Excavation of the affected are inside of the RCA resulted in about 5500 ft3 of radioactive contaminated asphalt, soil, sand, and gravel. The excavation area was 18 x 54 ft with excavation depth being limited by a concrete pad about 3-ft below ground surface. This and other concrete supports within the RCA were not disturbed and residual radioactive is accounted for in Smith (1997). The excavated area within the RCA was backfilled with concrete.

Quarterly surveys (RMD-FO-35) were subsequently performed by Radiation Protection.

6. Unit 2 Additional Equipment Building (UpperHead Injection) Sump Release - January10, 1998 The Unit 2 Additional Equipment Building sump overflowed, exited the double-doors, and continued along a straight-line route (110 linear ft) to the nearest storm drain catch basin (Figure 2.7). The response team observed released water flowing into the catch basin.

Sampling confirmed radioactivity in asphalt and soil leading to the catch basin. Water samples collected at the catch basin and at the storm drain discharge to the Yard Drainage Pond did not identify the presence of radioactivity. A water sample collected inside the building indicated Xe- 133 to be the dominant radionuclide. A total of 32 soil samples were collected before and during excavation and sample analyses included a peak search for the Xe-133 energy peak. All results were negative. Select isotopes (Co-58, Co-60, Cs-134, and Cs-137) were also used to screen soil samples to 5.OE-07 g.Ci/g during excavation. Sediment samples from the release area catch basin contained CO-60 and Co-58 at 8.65E-07 and 5.99E-07 gtCi/g, respectively.

22

Unit 2 Additional Equipment Building Sump Release Unit 2 Unit 2 Additional Equipment Building Sump Release Reactor Building January 1998 Unit 2 U2 Valve Vault A Additional Equipmenl Building 68' CDWE Bldg.

Storm Drain , 1 t00' Storm Drain Catch Basin Posted Area Boundary Legend: RCA Figure 2.7 Map Showing Extent of Sump Release at Unit 2 Additional Equipment Building (from Halter, 1998) 23

9 A recovery report by Halter (1998) described remediation associated with this release.

Decontamination of the Additional Equipment Building was initiated on January 10, 1998.

Three additional storm drain catch basins were identified for sampling no gamma energy peaks were identified from gamma spectroscopy analyses. The asphalt layer immediately outside of the door was removed. Excavation of gravel and soil along the release route varied from 4 to 10 inches in depth and averaged about 19.5 ft in width. A total of 2070 &

of excavated material was removed and replaced with aggregate material. Figure 2.8 provides photographs of the recovery area. As shown in this figure, groundwater monitoring well W21 is located within the drainage route of the released water.

Quarterly surveys (RMD-FO-35) were subsequently performed by Radiation Protection.

7. Unit 1 Refueling Water Storage Tank (R WST) Moat Drain- April 3, 2002 Pre-excavation samples of the steam generator replacement crane foundation identified radioactivity in soil surrounding the Unit I RWST moat drain. The drain outlet is located on the west side of the moat, extending through a retaining wall and discharging to an asphalt parking area (Figure 2.9). Soil sampling was performed and radioactivity (Mn-54, CO-57, Co-58, Co-60, SB-125, Cs-134, and Cs-137) was identified in eleven shallow soil samples in excess of the MDCs. Seventeen additional soil samples were collected in August 2002 gamma scans indicated no activity for all samples. Documentation includes a drawing of sample locations with attached sample gamma analysis results from WARL.

Quarterly surveys (RMD-FO-35) were subsequently performed by Radiation Protection.

8. Tritium in Unit 1 and 2 R WST Moat Collected Rainwater - July 17, 2006 Each of the Unit I and 2 RWST moats is open to the collection of rainfall. This design differs from other plants such as WBN where permanent covers are installed to direct precipitation away from the moats. Per team discussions at the onset of this investigation, chemistry surveillance instruction 0-SI-CEM-040-421.0 was revised during the first quarter of 2006 to require tritium analysis of moat water. This revision also includes a requirement for discharge of Unit 2 moat water to either the Auxiliary Building RadWaste System or the Turbine Building Sump.

RWST moat water samples were collected July 11, 2006 and tritium concentrations of 517 and 19.5 pCi/mL were observed for Units I and 2, respectively. Documentation includes a memorandum by Halter (2006) describing operations, sampling, tritium results, and photographs.

24

~W2t Release Area Covere wit Plast c Figure 2.8 Photographs of Sump Release Area at Unit 2 Additional Equipment Building (from Halter, 1998) 25

8 9 ra *1'Retaining Wall Moat Dri

~Unit 1

! RWST Figure 2.9 cemaic Sampling o Locations anPhtgphoUit1WT

\,\* /Plan View (NTS) 6 26 Figure 2.9 Schematic of Sampling Locations and Photograph of Unit 1 RWST Moat Drain 26

3.0 HYDROGEOLOGY 3.1 Site Location and Scope of Exploration The SQN site is situated on a peninsula extending from the western bank into Chickamauga Lake between TRM 484 and 485 (Figure 3.1).

Pre-operational subsurface investigations of the site began in 1953. Figure 3.2 depicts the locations of exploratory borings installed at the site during these investigations. Twenty-nine holes were drilled into rock while seventeen were fishtailed to the top of sound rock. From September 1968 to February 1969, additional holes were drilled to fill in a 100-foot grid in the Control and Auxiliary Building area, and in the reactor areas, with holes drilled at the intake structure and other locations in the general plant area. In addition to obtaining information on the foundation conditions, the holes in the reactor areas were used for dynamic seismic investigations. During September and October 1969, a third drilling program was carried out to further investigate the reactor, control, and auxiliary areas on a 50-foot spacing, and to examine the condition of the Kingston fault northwest of the plant site (TVA, 2005).

Post-operational subsurface investigations at the site have been conducted to resolve contaminant release issues and for siting of new facilities. Edwards et al. (1993) and Julian (1993) installed 21 soil borings and 9 groundwater monitoring wells to assess No. 2 Diesel Fuel Oil C> contamination from underground transfer lines. Julian (2000) conducted a groundwater supply study that included review of groundwater supply wells located in the vicinity of SQN. Siting for the Independent Spent Fuel Storage Installation (TVA, November 2001) involved the installation of three monitoring wells and numerous shallow borings to assess petroleum contamination (TVA, June and September 2001). From February 2002 - April 2004, 12 shallow groundwater monitoring wells were installed for evaluations of tritium releases from the 6- and 12-inch waste condensate lines.

Soil borings and wells installed as part of this tritium investigation are described in following paragraphs.

27

Figure 3.1 Site Location Map 28

SEQUOYAH NUCLEAR PLANT Exploratory Borings BOREHOLE TYPE

• Corehole

• Borehole Reservation Boundary Feet 0 1,000 100 1.000 2,000 PREPARED BY: TVAGEOGRAPHICK INFORMATIOANDENGIN4EERING knagelis aDigiaOrfthphowgiph 2004 Figure 3.2 Locations of Exploratory Borings 29

3.2 Physiography The Valley and Ridge Province is a long narrow belt trending NE-SW that is bordered by the Appalachian Plateau on the west and by the Blue Ridge Province on the east.

Geochronologically, this province represents the eastern margin of the Paleozoic interior sea.

Structurally, it is part of an anticlinorium, the successor to a geosyncline that sank intermittently for ages as it received sediments from the concurrent rising land surface on the east. The topographic and geologic grain of this subregion is elongated NE-SW in conformity with the trend of the Appalachians region. Viewed empirically, the province is a lowland; an assemblage of long, narrow, fairly even-topped mountain ridges separated by somewhat broader valleys.

The ridges are developed in areas underlain by resistant sandstones and more siliceous limestones and dolomites. The valleys have been developed along structural lines in the areas underlain by easily weathered shales and more soluble limestones and dolomites.

Prior to the impoundment of Chickamauga Reservoir, the Tennessee River in the vicinity of SQN had entrenched its course to elevation 640. The small tributary valley floors slope from the river up to around elevation 800 ft-msl, while the crests of the intervening ridges range between 900 and 1000 ft-msl.

Figure 3.3 shows topography at SQN. The majority of the plant site resides at a grade elevation of 705 ft-msl. Elsewhere, terrain is rolling with the highest elevation of about 775 being encountered southeast of the plant site at the top of Locust Hill (LLRWSF site).

3.3 Geomorphology The SQN site resides near the western border of what was the active part of the Appalachian geosyncline during most of the Paleozoic era. During this time, the area was below sea level and more than 20,000 feet of sedimentary rocks were deposited. At the end of the Paleozoic era, some 250 million years ago, the area was uplifted and subjected to compressive forces acting from the southeast. Folds developed which were compressed tightly, overturned to the northwest, and finally broken by thrust faults along their axial planes. The resultant structure is characterized by a series of overlapping linear fault blocks which dip to the southeast. Since this period of uplift, the area has been subjected to numerous cycles of erosion. This erosion accentuated the underlying geologic structure by differential weathering of the less resistant strata resulting in the development of parallel ridges and valleys which are characteristic of the region.

30

SEQUOYAH NUCLEAR PL IIIA 485 Site Topographic Map 24tCostm~

/

t tiGI Cortowx

/ - 4x *a Conde0mto Lim 7 / Cu~dmaft l 6

P-" U CobbTWeak c~.

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Tomes~*"

River I Chickamauga m __i i i i3i ca" / Reservoir Figure 3.3 Site Topographic Map 31

3.4 Geology 3.4.1 Stratigraphy Of the numerous sedimentary formations of Paleozoic age in the plant area, only the Conasauga Formation of Middle Cambrian age is directly involved in the foundation bedrock of the plant (Figure 3.4). Unconsolidated alluvial, terrace, and residual deposits mantle the Conasauga formation at the site. More recent alluvial deposits, that were associated with the floodplain of the Tennessee River, are now covered by the Chickamauga Reservoir.

3.4.2 Bedrock The Conasauga formation at the site is composed of several hundred feet of interbedded limestone and shale in varying proportions. The shale, where fresh and unweathered, is dark gray, banded, and somewhat fissile in character. The limestone is predominantly light gray, medium grained to coarse crystalline to oolitic, with many shaly partings. A statistical analysis of the cores obtained from the site area indicates a ratio of 56 percent shale to 44 percent limestone. Farther to the southeast and higher in the geologic section, the amount of limestone increases in exposures along the shore of the reservoir.

The general strike of the Conasauga is N30°E and the overall dip is to the southeast, normally steep, ranging from 600 to vertical; however, many small, tightly folded, steeply pitching anticlines and synclines result in local variations to the normal trend.

According to TVA (1979), cavities and solution openings are not a major problem in the site foundation. Most solution openings are restricted to the upper few feet of bedrock near the overburden/bedrock interface. The insolubility of interbedded shale in deeper bedrock functions as a lithologic control to the development of large solution openings. However, small solution openings and partings may exist at greater depths within the bedrock along faults and joints, especially along synclinal zones. Inspection of the walls of the exploratory holes with television disclosed thin, less than 0.05 foot, near-horizontal openings in some of the limestone beds. At the corresponding position, the drill cores showed unweathered breaks. These open partings are interpreted as "relief joints" developed by unloading either from erosion or excavation. The majority was found in the upper few feet of rock, but some were observed as deep as 131 feet below the rock surface.

32

S Conasauga Formation Chickamauga Formation Knox Formation Formation Contact Major Thrust Fault Approx. Scale 0 0.6

• *~X I JtJM 1 .1J %11 t '*

U IL.

Section A - A' (not to scale)

Figure 3.4 Regional Map Showing Geologic Formations and Structure 33

Figure 3.5 shows the Conasauga bedrock surface based on all available site boring data. As would be expected in a foundation composed of alternating strata of different composition and competency, the configuration of the bedrock surface is irregular (TVA, 1979). The strike of the rock strata is approximately parallel to the centerline of the reactors. Preliminary excavation for foundation investigations (down to 18 inches above design grade) exposed a series of alternating ridges of harder limestone separated by troughs underlain by the softer shale trending across the plant area. The last 18 inches were removed by careful and controlled means so as to limit breakage below the design grade to a minimum. Once foundation grade was reached, the area was carefully cleaned and then inspected jointly by engineers and geologists to determine what, if any, additional material needed to be removed because of weathering or shattering by blasting.

Figure 3.6 exemplifies top of rock exposed in the Reactor, Auxiliary, Control, and Turbine Buildings prior to excavation.

After the final excavation was approved, the area was covered either by a coating of thick grout or by a fill pour of concrete to prevent weathering of the shale interbeds due to prolonged exposure. Observation of rock exposed in the foundation areas, examination of cores, and investigations of the walls of exploratory holes with a borehole television camera all indicated that solution cavities or caves are not a major problem in the foundation. Verified cavities generally were limited to the upper few feet or rock where solution developed in limestone beds near the overburden-rock interface. Practically all of this zone was above design grade and was removed.

A consolidation grouting program was performed from February 18 through June 15, 1970 in the foundation areas for the Reactor, Auxiliary, and Control Buildings at the Sequoyah Nuclear Plant. The extent of the area treated is shown in TVA (2005; Figures 2.5.1-9 and 2.5.1-10). The purpose of this program was twofold. The first was to consolidate near-surface fractures predominantly caused by blasting and excavation. The second was to treat any localized open joints, bedding planes, fractures, or isolated small cavities that pre-construction exploratory drilling indicated might be present to a depth of 45 feet below the design foundation grade.

In the excavated area, the contact between the residual material and essentially unweathered rock occurs at an average elevation of 680 ft-msl. The highest design level for the plant foundation grade under the Class I structures is at elevation 665 ft-msl. As a result, the preliminary excavation averaged a minimum of 15 feet in rock. Over most of the area, the rock was suitable for foundation purposes at elevation 665 ft-msl.

34

ý5; SEQUOYAH NUCLEAR PLANT Top of Conasauga Bedrock

__ Top of Bedrock Contour (ft-msl

• Boring Reservation Boundary N

A Fedl 0 200 400 600 Sao IA PREPARED BY:TVAGEOGRAPHIC INFORMATION ANDENGINEERING bag. Isa DigW OvIIbqhoIOpaph 2004 Figure 3.5 Surface of Conasauga Bedrock 35

N0 0

Top of Cot fL 705.

3Ervice &Safi hv Ar I /It .. ..... f.......

Top of cut (.705t.

01 Figure 3.6 Pre-excavation Top of Bedrock Contours (ft-msl) at the Reactor, Auxiliary, Control, and Turbine Buildings (from TVA Drawing 10N211) 36

In two areas, however, additional rock had to be excavated to remove localized pockets of deeper weathering. These zones were confined in two synclinal areas which crossed the excavation parallel with the north- south baseline. The axis of one lies approximately 70 feet plant east of the baseline and the axis of the other is approximately 140 feet plant west of the baseline. These trough-like synclines had channeled groundwater movement toward and along their axes with the result that weathering had progressed deeper in these areas. Generally,. less than 10 feet of additional rock had to be removed from the synclinal zones to obtain a satisfactory foundation; however, in the vicinity of WI140; S 220, on the south side ofthe Auxiliary Building, as much as 30 feet of weathered rock was removed.

3.4.3 Soil Unconsolidated alluvial, terrace, and residual deposits mantle the Conasauga formation at the site. More recent alluvial deposits that were associated with the floodplain of the Tennessee River are now covered by the Chickamauga Reservoir. Alluvium within the area of the main plant site was removed during construction and only residual soils remain. In the plant area not mantled by terrace deposits, the Conasauga is overlain by varying thicknesses of residual silt and clay derived from weathering of the underlying shale and limestone. The residual soils are primarily silts and clays grading downward into saprolitic shale of the Conasauga. In a few localized areas weathered shale is exposed at the ground surface. However, in most exploratory drilling the residuum depths ranged from 3 to 34 ft.

A pre-construction soils exploration program was conducted at the plant site to determine the static physical characteristics of the soils. Standard split-spoon borings and undisturbed borings were made. Grain size analyses shows that soils across the site range from fat clay residual material to sand and gravel terrace deposits.

The age of unconsolidated material at SQN is in excess of 30,000 years. No carbonaceous soil was encountered in site excavation and no other dating criteria could be established (TVA, 1979). Carbon 14 dates from material found in high alluvial terrace deposits at the Watts Bar Nuclear Plant located about 38 miles northeast of Sequoyah placed the age of the material at 32,400 years.

Terrace deposits overlie residuum with varying thickness across the site. Terrace material consists predominantly of sandy clay with embedded rounded cobbles and pebbles of quartzite, quartz and chert. This material represents deposition at a time when the river was flowing at a higher elevation during an earlier erosion cycle. According to TVA (1979), a maximum thickness of 45 feet of terrace deposits was encountered in exploratory drilling in the topographically high areas southeast of the site, and it is quite probable that greater thicknesses exist under the highest portion of this area (i.e., Locust Hill). Evidence suggests that residual 37

material has essentially been eroded away under Locust Hill with terrace deposits directly overlying bedrock. This hill is the location of the LLRWSF.

Based upon more extensive borings, Boggs (1982) describes the Low Level Radwaste Storage Facility (LLRWSF) site as being underlain by residual and alluvial soils generally consisting of clay and silt with minor amounts of sand and gravel. According to Boggs (1982), soil thickness averages about 50 feet within the LLRWSF area, but varies radically over short distances due to a highly irregular bedrock surface configuration. Fill/spoil material was also used as foundation material beneath the LLRWSF.

In situ soil dynamic studies were made at the plant site to obtain data for computation of elastic moduli for earthquake design criteria. The areas investigated at the site were the Diesel Generator Building, the LLRWSFs, the ERCW pipeline, the Additional Diesel Generator Building, and the Primary Water Storage Tank.

Prior to and during construction, borrow investigations were made on an as-needed basis. The borrow samples were tested by the central materials laboratory according to ASTM D-698 to develop compaction control curves. The compaction curves were divided into subclasses to control compaction of earthfill at the site. At SQN, Type A backfill (sandy to silty clay) was placed around all Category I structures. This material, which was selected earth placed in not more than 6-inch layers, has a minimum required compaction of 95 percent of the maximum dry density at optimum moisture content. The limits of excavation and the backfill around Category I structures can be visualized in Figure 3.7.

A free-draining granular fill material, consisting of crushed stone or sand and gravel, was placed below or next to Category I structures. This material was obtained commercially from off-site sources. The granular fill was suitable for compaction to a dense, stable mass and consisted of sound, durable particles which are graded within the following limits:

Percent by Weight Passing Minimum Maximum 11/4-inch 100 1-inch 95 100 3/4-inch 70 100 3/4-inch 50 85 No. 4 33 65 No. 10 20 45 No. 40 8 25 No. 200 0 10 38

• , Discharge Conduits

• ll* B uild in g- o. ..

Figure 3.7 1971 Site Construction Photograph of the Reactor, Auxiliary, Control, and Turbine Buildings 39

• A crushed rock material that meets the gradation requirements shown below was used for remedial treatment in local areas. This was generally done where moisture caused the soil to be unsatisfactory as a base for earthfill placement. The material was used in a limited area at the RWST pipe tunnel. The material was placed in approximate 6-inch loose layers and rolled into the soil. If the required stiffness for the placement of earthfill was achieved, lifts of earth-fill or crushed stone fill were placed. If the required stiffness was not achieved, then additional lifts of the material were placed and rolled to obtain the desired stiffness. If shearing or pumping occurred in placement of the first lift, additional lifts of the material were placed as necessary.

Percent by Weight Passing Minimum Maximum 3-inch 95 100 2-inch 25 55 11/41/2-inch 0 15 1-inch 0 2 3.4.4 Structure The controlling features of the geologic structure at the Sequoyah plant site are the Kingston Thrust fault (Figure 3.4) and a major overturned anticline that resulted from the movement along the fault. This fault lies about a mile northwest of the plant site (Figure 2.5.1-2), and can be traced for 75 miles northeastward and 70 miles southwestward. The fault dips to the southeast, under the plant site, and along it steeply dipping beds of the Knox dolomite have been thrust over gently dipping strata of the Chickamauga limestone. The distance from the plant site, about one mile, and the dip of the fault, 30 degrees or more, will carry the plane of the fault at least 2000 feet below the surface at the plant site.

The major overturned anticline results in the Conasauga formation at the plant site resting upon the underlying Knox dolomite which normally overlies it. As a result of the ancient structural movement of the fault and major fold, the Conasauga formation at the plant site is highly folded, complexly contorted, and cut by many very small subsidiary faults and shears. The general strike of these beds are N 301E and the overall dip is to the southeast, but the many small tightly folded, steeply pitching anticlines and synclines result in many local variations to the normal trend.

In some of the drill cores, small faults and shears were noted intersecting the bedding at various angles. These dislocations are the result of shearing along the limbs of the minor folds which developed contemporaneously with the major movement along the Kingston fault.

40

3.5 Hydrology The SQN site is in the eastern Tennessee portion of the Southern Appalachian region, which is dominated much of the year by the Azores-Bermuda anticyclonic circulation. This circulation over the southeastern United States is most pronounced in the fall and is accompanied by extended periods of fair weather and widespread atmospheric stagnation. In winter, the normal circulation pattern becomes diffuse as the eastward moving migratory high and low pressure systems, associated with the midlatitude westerly current, bring alternating cold and warm air masses into the area with resultant changes in wind direction, wind speed, atmospheric stability, precipitation, and other meteorological elements. In summer, the migratory systems are less frequent and less intense, and the area is under the dominance of the western edge of the Azores-Bermuda anticyclone with a warm moist air influx from the Atlantic Ocean and the Gulf of Mexico (TVA, 2005).

The climate of the watershed above SQN is humid temperate. All recharge to the groundwater system at the plant site is from local precipitation, which averages around 51 inches per year.

The Tennessee River above SQN site drains 20,650 mi2 . Chickamauga Dam, 13.5 miles downstream, and Watts Bar Dam upstream (TRM 529.9) affect water surface elevations at the Plant. Peaking hydropower operations of the dams cause short periods of zero and reverse flow near the plant. Based upon discharge records since closure of Chickamauga Dam in 1940, the 4 average daily streamflow at the site is 32,600 cfs (TVA, 2005).

Chickamauga Reservoir water elevations vary seasonally according to operations for power production, navigation, and recreation. The operating guide for Chickamauga Dam is shown in Figure 3.8. As shown in Figure 3.9 elevations of the SQN Discharge Channel correlate with the operating guide. This is associated with plant operations during warmer months that are designed to comply with reservoir thermal release limits.

During high flow periods, the top of the normal operating zone may be exceeded for the regulation of flood flows. During the late spring and summer, TVA varies the elevation of Chickamauga Reservoir to aid in controlling mosquito populations. Elevations are lowered during the week and raised a foot on weekends, to strand mosquito eggs and larvae on the shoreline. Normal full pool elevation is 683.0 ft-msl. At this elevation, the reservoir is 58.9 miles long on the Tennessee River and 32 miles long on the Hiwassee River. The reservoir is approximately 3,000 feet wide at the site, with depths ranging from 12 feet to 50 feet at normal full pool elevation. Probable maximum flood elevation is 722.6 (TVA, 1979).

41

688 686 684 2007 Observed 682 Midnight Elevations 2006 Observed 680 Midnight Elevations 0

4-) 678 Normal Operating Zone

-LI 676 674 672 670 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 2007 Figure 3.8 Operating Guide For Chickamauga Dam 42

690 ARM 689 Trend 688 687 686 0

j685

- 684 683 682 681 Figure 3.9 Mean 1995 - 1999 Discharge Channel Elevations 3.6 Groundwater The peninsula on which SQN is located is underlain by the Conasauga, a poor water-bearing formation. About 2,000 feet northwest of the plant site, the trace of the Kingston Fault separates the Conasauga Shale from a wide belt of Knox Dolomite (Figure 3.4). The Knox is a major water-bearing formation of eastern Tennessee. Based on a comprehensive examination of bedrock coreholes (TVA, 1979), groundwater in the Conasauga occurs in small openings along fractures and bedding planes; these rapidly decrease in size with depth, and few openings exist below a depth of 300 feet.

There is no groundwater use at SQN. The source of groundwater at SQN is derived from incipient infiltration of precipitation. Within overburden soils at the site, groundwater movement is generally downward. Local areas of natural lateral flow likely occur near some streams, topographic lows, and where extensive root systems exist. Anomalous groundwater movement might also occur in areas that have experienced soil unraveling and in the vicinities of pipelines (especially those with relatively permeable bedding and fill).

Groundwater movement is expected to occur mainly along strike of bedrock, to the northeast and southwest, into Chickamauga Reservoir. Groundwater also discharges from overburden soils into the reservoir, site drainage channels (i.e., Discharge Channel), and surface water impoundments (i.e., Diffuser Pond). Higher surface water levels of Chickamauga Reservoir (April - October) result in corresponding rises in the groundwater table and the lateral extent of this effect varies with groundwater hydraulic gradients. Lower levels of Chickamauga Reservoir (November - March) result in corresponding declines in the water table along the reservoir periphery.

43

0 Pre-construction boring logs collected by TVA (1979) suggest that groundwater transmissivity across the strike in the Conasauga formation is extremely low. Local variations in hydraulic conductivity within the shallow bedrock are primarily controlled by geologic structure and stratigraphy. Shale beds and clay seams provide lithologic restrictions to the vertical movement of groundwater. The Conasauga/Knox contact northwest of the plant has been described as a hydraulic boundary; however, no field testing has been conducted to verify this assumption.

Bedrock porosity is estimated to be about 3 percent based upon results of exploratory drilling.

Prior to the current study, a total of eight (8) long-term bedrock monitoring wells had been installed at the SQN site. Figure 3.10 indicates the depth of open borehole and/or screened interval for each well and wells are located as shown in Figure 1.2. Well construction details are provided in Appendix A.

800 WI 553.9 86.5 N4 652 W2 543.1 580.5 0 755 W4 611.5 547 Ma.r. ¶150 750 Le 654. 9.4 45.1 so L 6".1 10.0 44.9 310 We 444.1 210.0 N-.. i 40.0 0 700 E

0 a,>'650

- -- --- H---

600 - -

-- ------- -w - - - - - - --- ----

550 Wl W2 W4 W5 L6 L7 W8 Open Borehole

• Slotted Screen Blank Casing Figure 3.10 Site Bedrock Monitoring Wells Long-term groundwater level data have been collected to establish temporal trends for six wells at the SQN site. Since these monitoring wells are developed in bedrock and weathered bedrock, any deductions regarding groundwater movement is restricted to this flow regime. Figure 3.11 shows water level data obtained for wells WI, W2, L6, and L7. The plot indicates that groundwater levels measured for wells WI and L6 are strongly influenced by reservoir stage.

The fluctuation in groundwater levels at well L6 is almost completely correlated with the cyclic operation of the reservoir. Well WI exhibits water levels that also correspond with the

(

44

periodicity of reservoir stage; however, reservoir effects are diminished for times around 1986 and 1988. This might be attributed to drought conditions and diminished precipitation at the site during these times. The hydrographs for wells W2 and L7 appear to be influenced by water retention basins on the south side of the plant and do not display reservoir stage effects. Well W2 is located near the Yard Drainage Pond and well L7 is in the vicinity of the Return Channel.

There is a large degree of correlation between water levels in the two wells and this may be related to plant discharges and pond operations. The free water surface in the Return Channel is maintained at a higher elevation than the reservoir by a discharge flume and weir. The minimum normal water surface elevation in the Return Channel is given as 689 ft-msl according to TVA drawing number 31 W600-2. The average horizontal hydraulic gradient from well L7 to L6 is 0.01 ft/ft. The average horizontal hydraulic gradient from well WI to W2 is about 0.003 ftift.

695 690 _

• -685 ". WW

_ _.. ,,- -W2 L6 1.7 675__ -R r 670 Year Figure 3.11] Time-Series Groundwater Levels for Wells WI, W2, L6, and L7 (1985-1991)

(68 Figure 3.12 shows groundwater elevations for wells WI, W4, W5 and L7. This plot also indicates that the Return Channel and the Discharge Channel influence groundwater elevations in the southeastern area of the SQN site. The average horizontal hydraulic gradient from well W4 to L7 is approximately 0.0071 ft/ft; from well W1 toward the Intake Channel it is about 0.007 ftift; and from well W4 to W5 it is approximately 0.004 ft/ft.

45

695 690 _

685 W4 680_ __ -W5 L7 675- ____ __ River 670 Year Figure 3.12 Time-Series Groundwater Levels for Wells Wl, W4, W5 and L7 (1985-1991)

The direction of regional groundwater movement is primarily towards the SQN Intake and Discharge Channels based on historical and recent (12/13/2006) potentiometric mapping (Figure 3.13). Exceptions to this directional flux have occurred locally due to leaking water lines serving the site; in areas of topographic highs/lows; and from dewatering operations of the Diesel Fuel Oil Interceptor Trench.

Extensive pre-construction characterization studies were conducted at the plant site to determine the static physical characteristics of the soils. However, few field tests or laboratory measurements were performed to assess the hydraulic properties of site soils and bedrock.

Laboratory permeameter testing of an undisturbed residual soil sample (boring US-53; TVA, 1979) indicates horizontal and vertical hydraulic conductivity values of 7.8E-07 and 1.3E-08 cm/s (a ratio of 1:60). A statistical summary of soil hydraulic properties at the LLRWSF (Table 3.1) suggests that residual soils and alluvium might be expected to exhibit saturated K values ranging from 5.8E-06 to 3.4E-09 cm/s.

Table 3.1 Statistical Summary of Soil Properties (from TVA, 1981)

Standard No. of Parameter Minimum Mean Maximum Deviation Samples Porosity 0.31 0.53 0.70 0.10 257 Density (Ib/ft3) 51.3 81.1 116.8 16.5 263 Saturated Hydraulic 3.4E-09 7.9E-07 5.8E-06 1.8E-06 19 Conductivity (cm/s)

Natural Saturation (%) 41.0 93.0 100.0 9.0 263 46

SEQUOYAH NUCLEAR PLANT Site-wide Potentiometrc Surface Map December 13, 2006 Monitoring Wells

• Soil

" Bedrock

-Potentiometric Contours (ft-msl)

Reservation Boundary 0 3W 1.200 1,5OO PREPARED BY:IVA GEOGRAPHIC INFORMATION ANDENGINEERING Ikage Is a DigitalOphoootoograpu2004 SQN-Poa4IuneOicSurbco.%*.ai4.mopl0.mxd - ApxII17.2007 Figure 3.13 Site-Wide Potentiometric Map 47

Sorptive characteristics of soils beneath the LLRWSF have been determined through laboratory testing of soil samples (Rogers, 1982). Batch techniques were used on composite samples to measure distribution coefficients (Kd) for radionuclides identified in Table 3.2. The sorptive capacity of the Conasauga was not measured at the time due to the lack of a recognized procedure for obtaining realistic Kd values for rock cores. Table 3.2 summarizes laboratory Kd results for LLRWSF soils.

Table 3.2 Soil Distribution Coefficients (Kd)

Radionuclide Kd (mUg)

Minimum Mean Maximum Co-58/60 1,740 4,820 8,000 Cs-134/137 850 2,390 >10,000 Sr-90 26 36 43 Mn-54 1,000 1,589 2,200 Zn-65 10,400 >10,400 >10,400 During investigations of the diesel fuel oil release, laboratory permeameter testing of undisturbed soil samples at well W14 (Edwards et al., 1993) provided vertical hydraulic conductivity values of 3.9E-07 and 1.6E-04 cm/s at depths of 8-10 and 23-25 ft, respectively. Both samples were characterized as clayey sands. The disparity in these hydraulic conductivity values prompted aquifer testing at the site by Julian (1993) to support final characterization and design of the Diesel Fuel Oil Interceptor System (Figures 3.14 and 3.15).

Single-well pump tests and Electromagnetic Borehole Flowmeter surveys (Young et al., 1997) were conducted by Julian (1993) at wells 22, 23, and EXT-4. The vertical distribution of horizontal hydraulic conductivity at each well is provided in Table 3.3. Incremental horizontal hydraulic conductivity ranged from 6.2E-07 to 1.9E-04 cm/s among all test wells.

48

Figure 3.14 Potentiometric Surface at Diesel Fuel Oil Interceptor System on February 10, 2003 49

0 romundw ater Disohurn.

to Channel grade elev. 700 it-mnsl Xflwg

ý-.oý4 t Vertical Profile Not To Scale Groundwater Discharge To Colleolon Drums to CCW Channel Extrection Wells A.ILA MdZEX(T.3 EXT-2 76 t.

Plan View Not To Scale Figure 3.15 Schematic of Diesel Fuel Oil Interceptor Trench 50

0 Table 3.3 Horizontal Hydraulic Conductivity Values from Single-Well Testing at Wells 22, 23, and EXT-4 Elevation Horizontal Hydraulic Conductivity (cm/s)

(ft-msl) Well 22 Well 23 Well EXT-4 676.4 5.4E-05 676.7 1.2E-04 677.7 1.8E-05 1.2E-04 678.7 4.6E-05 8.5E-05 679.7 3.7E-05 6.7E-05 680.7 4.OE-05 2.3E-05 1.4E-04 681.7 2.8E-05 1.5E-04 1.8E-05 682.7 3.OE-05 1.9E-04 8.2E-06 683.7 3.8E-05 1.4E-04 1.3E-04 684.7 7.3E-06 1.1E-04 6.7E-05 685.7 1.1E-05 5.1E-05 1.8E-04 686.7 8.1 E-07 2.6E-05 1.9E-05 687.7 4.8E-06 1.7E-05 1.2E-05 688.7 3.2E-06 9.9E-06 1.1E-05 689.7 8.9E-06 1.7E-05 1.4E-06 690.7 3.2E-06 1.1E-06 6.8E-06 691.7 4.8E-06 1.2E-06 692.7 6.2E-07 average = 2.5E-05 6.6E-05 5.7E-05 3.7 Offsite Water Supplies 3.7.1 Offsite Groundwater Supplies When SQN was initially evaluated in the early 1970s, it was in a rural area, and only a few houses within a two-mile radius of the plant site were supplied by individual wells in the Knox Dolomite (TVA; 1979). Because the average domestic use probably did not exceed 500 gallons per day per house, groundwater withdrawal within a two-mile radius of the plant site was less than 50,000 gallons per day. Such a small volume withdrawal over the area would have essentially no effect on area groundwater levels and gradients. Although development of the area has increased, public supplies are available and overall groundwater use is not expected to increase.

TVA (2005) provide tabulated data of wells and springs located within a 20-mile radius of the site from 1985 surveys. Julian (2000) provides results from a United State Geological Survey (USGS) Ground-Water Site Inventory (GWSI) database retrieval for wells in Hamilton County.

The data are a combination of domestic wells, wells installed for specific investigations, and other groundwater sites. Table 3.4 provides the results of this retrieval from the GWSI for 51

Hamilton County in the vicinity of SQN. Large capacity (i.e., discharge >100 gpm) well locations from the GWSI database are depicted in Figure 3.16.

Table 3.4 Wells in the Vicinity of SON from GWSI Database Weli Number " Latitude l Longitude I Depth Discharge* Aquifer

_ _ _ __- t (gpm),

Hm:N-090 351147 851308 67 5,400 Hm:N-089 HIXSON NO.3 PUMP 351148 851353 177 4,000 Newman Limestone Hm:0-018 350750 850458 148 2,000 Chepultepec Limestone Hm:O-030 SAVANNAH VALLEY 351114 850252 145 1,500 Hm:O-016 351424 850039 158 900 Hm:O-015 351428 850036 262 800 Knox Group Hm:O-008 351428 850039 120 760 Hm:J-016 EASTSIDE 350719 850509 400 Knox Group Hm:O-031 351115 850250 150 350 Hm:N-048 BINKLEY, S.DENT 351041 851237 180 300 Hm:N-056 THRASHER RR 351239 851250 103 300 Paleozoic Hm:N-075 FREEMAN WELL 351158 851117 202 270 Hm:N-083 USGS-TDOT 351150 851405 202 260 Hm:J-015 EASTSIDE +DUP 350720 850510 182 250 Knox Group Hm:O-003 351054 850238 250 250 Hm:N-060 OLDAKER 14 351228 851010 144 250 Paleozoic Hm:N-059 WALKER 14A 351249 851101 223 245 Paleozoic Hm:N-086 USGS-REEVE 351407 851147 202 240 Hm:R-015 352038 850813 390 200 Hm:O-007 351437 850027 247 170 Hm:R-005 UNION-FORK/BAKE 352031 850819 193 160 Hm:R-073 NORRIS WELL 351525 850853 190 150 Hm:O-017 EASTSIDE 350735 850530 280 105 Knox Group Hm:J-013 EASTSIDE 350607 850510 251 100 Knox Group Hm:J-014 EASTSIDE 350655 850520 250 100 Knox Group Hm:N-084 USGS-CONARD 351320 851320 202 100 Hm:R-004 352031 850816 330 70 BOWMAN WELL AT SALE CR 352532 850848 1,310 40 Hm:O-041 351206 850307 112 20 Hm:S-008 351522 850417 75 20 Hm:N-054 FLOYD THRASHER 351223 851252 279 19 Hm:S-007 351943 850049 60 16 Hm:J-001 350614 850047 80 15 Hm:N-002 350953 850843 100 15 Hm:J-002 350504 850246 160 10 Hm:N-046 HUD QUARRY 350937 851314 242 7 Paleozoic Hm:N-078 NOE 351320 850740 280 7 Hm:O-074 VINCENT WELL 351432 850637 342 7 Hm:S-006 351549 850516 269 5 Hm:N-049 RAGAN HUD 351137 851341 270 2 52

SEQUOYAH NUCLEAR PLANT Large Capacity Wells in Vicinity of Site YEILD 0 600 - 5400 gpm 0 26o- 50o gpm A 150 - 250 gpm 100- 140gpm Sequoyah Nuclear Plant N

0 1 2 3 4 5 PREPARED BY: TVA GEOGRAPHCI INFORMATION AND ENGINEERING kMogpIs a D0glalRauwr GmapIc I 970s Figure 3.16 Large Capacity Wells in the Vicinity of SQN from USGS GWIS Database 53

Bradfield (1992) conducted a study of Cave Springs from 1987 to 989. This the second largest spring in East Tennessee and an important water supply. Cave spring is located approximately 8 miles southwest of SQN near state Highway 27. In addition to wells in the immediate vicinity of Cave Spring, Bradfield (1992) examined water groundwater quality/quantity for water supply wells in the region. Table 3.5 lists attributes of wells included in the study and Figure 3.17 shows the well locations relative to SQN.

Table 3.5 Wells In the Vicinity of SON from Bradfleld (1992)

Well Ground Well Casing Soil Estimated Depth Water-Bearing Number Elevation Depth Depth Thickness yield Zone(s) (1i)

(ft-mW ) (ft) (ft) (ft) (gpm) 1 710 71 61 25 3,000 65-70 2 710 73 63 25 3,000 65-70 3 710 398 82 25 >300 160,190 260, 275, 320 4 710 177 140 25 >4,000 167-173 6 661 322 148 127 300 180,270 7 820 298 296 298 15 160-180, 270-290 8 880 231 226 231 5 200-231 9 685 103 93 37 400 59-71, 75-93,98-103 11 786 223 180 179 400 201-220 12 723 142 95 95 200 95-131 13 730 242 147 50 100 50-70, 177 14 850 302 130 124 <1 150-200 15 827 202 194 202 30 143-147, 197-202 16 770 251 135 126 40 200-250 17 750 190 188 174 200 175-90 18 703 342 88 85 100 299,327 19 729 202 154 150 200 170-200 20 692 101 62 37 50 70-90 21 780 171 165 165 50 165-171 22 707 280 84 69 50 78 23 720 342 117 93 200 85-93 The majority of these wells are included in the GWSI database retrieval (Table 3.4). The relatively high well yields shown in Table 2 and Figure 3 (i.e. wells 1-6) are associated with the Cave Springs water supply. Other wells distributed across the region northeast of Cave Springs (Figure 3.17) are affiliated with productive carbonate aquifers.

54

Figure 3.17 Groundwater Supply Wells in the Vicinity of SQN from Bradfield (1992) 55

W 3.7.2 Offsite Surface Water Supplies As listed in Table 3.6, there are 23 surface water users within the 98.6-mile reach of the Tennessee River between Dayton, Tennessee and Stevenson, Alabama. These include fifteen industrial water supplies and eight public water supplies (TVA, 200*).

The public surface water supply intake (Savannah Valley Utility District), originally located across Chickamauga Reservoir from the plant site at TRM 483.6, has been removed. Savannah Valley Utility District has been converted to a ground water supply. The nearest public downstream intake is the East Side Utility (formerly referred to as U.S. Army, Volunteer Army Ammunition Plant). This intake is located at TRM 473.0.

56

Table 3.6 Public and Industrial Surface Water Supplies Withdrawn from 98.6 Mile Reach Of Tennessee River Between Dayton, TN and Stevenson, AL Approximate Distance from Site Intake Name Use (MGD) Location (River Miles) Type Supply City of Dayton 1.78 TRM 503.8 R 19.1 (Upstream) Municipal Cleveland Utilities Board 5.03 TRM 499.4 L 37.6 (Upstream) Municipal Hiwassee RM 22.9 Bowaters Southern Paper 80.00 TRM 499.4 L 37.4 (Upstream) Industrial Hiwassee RM 22.7 & Potable Hiwassee Utilities 3.00 TRM 499.4 L 37.2 (Upstream) Municipal Hiwassee RM 22.5 Olin Corporation 5.00 TRM 499.4 L 37.0 (Upstream) Industrial Hiwassee RM 22.3 & Potable Soddy-Daisy Falling Water U.D. 0.93 TRM 487.2 R 7.1 (Upstream) Municipal Soddy Cr. 4.6 Plus 2 Wells Sequoyah Nuclear Plant 1615.70 TRM 484.7 R 0.0 Industrial East Side Utility 5.00 TRM 473.0 L 11.7 (Downstream) Municipal Chickamauga Dam not measured TRM 471.0 13.7 (Downstream) Industrial DuPont Company 7.20 TRM 469.9 R 14.8 (Downstream) Industrial Tennessee-American Water 40.90 TRM 465.3 L 19.4 (Downstream) Municipal Rock-Tennessee Mill 0.50 TRM 463.5 R 21.2 (Downstream) Industrial Dixie Sand and Gravel 0.04 TRM 463.2 R 21.5 (Downstream) Industrial Chattanooga Missouri Portland Cement 0.10 TRM 456.1 R 28.6 (Downstream) Industrial Signal Mountain Cement 2.80 TRM 454.2 R 30.5 (Downstream) Industrial Raccoon Mount. Pump Storage Project 0.56 TRM 444.7 L 40.0 (Downstream) Industrial Signal Mountain Cement 0.20 TRM 433.3 R 51.4 (Downstream) Industrial Nickajack Dam not measured TRM 424.7 60.0 (Downstream) Industrial South Pittsburg 0.90 TRM 418.0 R 66.7 (Downstream) Municipal Penn Dixie Cement 0.00001 TRM 417.1 R 67.6 (Downstream) Industrial Bridgeport 0.60 TRM 413.6 R 71.1 (Downstream) Municipal Widows Creek Stream Plant 397.40 TRM 407.7 R 77.0 (Downstream) Industrial Mead Corporation I

4.40 TRM 405.2 R 79.5 (Downstream) Industrial R = Right River Bank, L = left River Bank 57

4.0 TRITIUM INVESTIGATION Field investigations during this study focused largely on areas north and south of Units I and 2.

Initial identification of areas for targeted investigations was based on information collected from the following sources:

" Preliminary site meetings with SQN staff;

" Previous tritium monitoring results associated with wells located along waste condensate lines;

• Historical tritium detection at other monitoring wells (e.g., W5 and W21);

" Preliminary assessments of inadvertent liquid radwaste releases;

" Relative locations of large/deep underground appurtenances;

• Potentially transmissive groundwater migration routes (e.g., pipeline bedding pathways).

The majority of tritium data collected from site groundwater monitoring prior to initiation of this investigation was available for review in spreadsheet format. Temporal and spatial examination of groundwater tritium concentrations data was conducted prior to field investigations. Reports documenting inadvertent liquid radwaste releases were made available by SQN staff. Hardcopy and electronic versions of essential site drawings were examined prior to and during field investigations. Key site features (e.g., underground lines and conduits) were electronically digitized and georeferenced imagery was developed using Geographic Information System (GIS) methods. Spatial data were incorporated into the GIS geodatabase with project progression.

Several thousand large format (8 x 10 inch) photograph negatives (prepared during plant construction) were also examined at the National Archives Southeast Region Facility.

Preliminary results suggested that tritium sources might be associated with inadvertent liquid releases from the MFTDS, Unit I and 2 RWST, CDWE Building, and/or the Unit 2 Additional Equipment Building. Based on comparable tritium investigations completed at WBN (ARCADIS, 2004), and similarity of SQN plant design to WBN, the Unit I and 2 Auxiliary and Shield Buildings were included as potential tritium sources during this investigation. Major tasks associated with the field investigation included:

1. Sampling of selected existing wells;

2. Manual sampling of storm drain catch basins, vaults, and manholes;

3. Groundwater sampling using Geoprobe methods;

4. Manual and continuous water level monitoring;

5. Interior sampling at select locations.

58

4.1 Groundwater Sampling of Selected Existing Wells Initial groundwater sampling for this study was targeted at site perimeter wells to confirm that offsite migration of tritium is not occurring. Fourteen existing wells were selected for sampling (Table 4.1). These wells are located along site boundaries and are not presently included in the routine groundwater monitoring network for tritium. Well locations are shown in Figure 1.2.

This sampling event included three bedrock wells (W], W2, W4), soil/bedrock well L6 at the LLRWSF, eight soil wells south of Unit 2 (14, 16, 20, 22, 30, 32, 34, 35), and two diesel extraction wells (EXT-2, EXT-4) located near the discharge.

Table 4.1 Tritium Results from Selected Existing Wells Top of Top of., Depth Bottom Tritium Diameter Casing Ground from of Hole Sampling Concentratio.

Location. (in) (ft-msl) (ft-msl) TOC (ft) (ft-msl) Date n (pCi/L)

WI 6 708.9 705.6 155.0 553.9 10/04/2006 < 270 W2 6 700.9 700.1 157.8 543.1 10/05/2006 < 270 W4 6 742.3 732.3 130.4 611.9 10/05/2006 < 270 L6 3 734.8 733.8 79.7 655.1 10/04/2006 < 270 14 2 707.9 705.2 18.8 689.1 10/06/2006 < 270 16 2 707.6 706.1 23.6 684.0 10/06/2006 < 270 20 2 697.9 697.9 23.1 674.8 10/05/2006 < 270 22 2 700.9 698.4 21.4 679.5 10/05/2006 < 270 30 1 707.2 704.1 23.8 683.4 10/06/2006 < 270 32 1 706.3 704.1 22.7 683.7 10/06/2006 < 270 34 1 708.1 704.8 25.7 682.5 10/06/2006 < 270 35 1 708.9 705.8 23.6 685.3 10/06/2006 < 270 EXT-2 12 702.2 700.0 26.0 676.2 10/06/2006 < 270 EXT-4 12 704.4 700.0 26.0 678.4 10/06/2006 < 270 Wells were purged and sampled October 4-6, 2006, using a combination of submersible pumps and disposable Teflon bailers. Samples were collected in 100 mL wide-mouth plastic sample containers and transferred to plant personnel for shipment to WARL for tritium analysis.

Laboratory analysis indicated that tritium concentrations were less than the MDC of 270 pCi/L at all locations.

Perimeter well W5 has historically exhibited the presence of tritium but was not included in this sampling scheme since it is routinely monitored by SQN and WARL personnel through REMP.

4.2 Manual Sampling of Storm Drain Catch Basin, Vaults, and Manholes Storm drain catch basins, vaults, and manholes were sampled to detect potential in-leakage of tritiated water from groundwater or discharge from plant processes. Sampling locations were initially identified using the following criteria: availability of water, depth (i.e., deep storm drain catch basins), accessibility, and proximity to the waste condensate lines and historical releases.

59

Twenty sites were selected (Table 4.2), including eighteen catch basins, the Turbine Building Sump Discharge, and a TV box sump. Sample locations are shown in Figure 4.1. All locations selected for sampling were within several hundred feet of the Reactor Buildings.

Table 4.2 Tritium Results from Manual Sampling Event Depth; Depth to Wo Tritium, invert Water Sampling:: Concentratio.

Location Type (ft) (fty:) Date n (pCi/L)y SS-1 Catch Basin 4.96 4.69 10/13/2006 < 270 SS-2 Catch Basin 5.10 5.03 10/13/2006 < 270 SS-3 Catch Basin 2.70 2.59 10/13/2006 < 270 SS-4 Catch Basin 5.10 5.00 10/13/2006 < 270 SS-5 Catch Basin 3.77 3.74 10/13/2006 < 270 SS-6 Catch Basin 2.61 2.61 10/13/2006 8,879 SS-7 Catch Basin 4.29 3.99 10/13/2006 < 270 SS-9 Catch Basin 5.03 4.99 10/13/2006 < 270 SS-10 Catch Basin 6.37 6.10 10/13/2006 < 270 SS-11 Catch Basin 8.31 8.07 10/13/2006 < 270 SS-12 Catch Basin 8.06 7.52 10/13/2006 < 270 SS-13 Catch Basin 2.05 2.04 10/13/2006 < 270 SS-14 Catch Basin 1.93 1.82 10/13/2006 425 SS-15 Turbine Building 10/13/2006 < 270 Sump N/A 0 SS-16 SS-17 Catch Basin Catch Basin 3.46 12.59 3.39 12.40 10/13/2006 10/13/2006

< 270

< 270 SS-18 Catch Basin 10.18 9.84 10/13/2006 < 270 SS-19 Catch Basin 3.70 3.61 10/13/2006 < 270 SS-21 TV Box Sump 2.56 1.78 .10/13/2006 284 SS-22 Catch Basin 7.80 7.59 10/13/2006 312 Samples were collected October 13 by dropping, a sponge (on a string) through the catch basin grating to soak up water, retrieving it, and then wringing it into a 100 mL wide-mouth plastic sample container. Sponge and string were disposed of after each location sampled. The outside of the sampling containers were thoroughly rinsed to remove any trace of overflow. Depth-to-water and depth-to-invert were measured after sampling using an electronic water level meter, and the water level meter was decontaminated between locations. Sample containers were transferred to SQN personnel, then transported to WARL for tritium analysis.

Table 4.2 summarizes sampling results. Tritium was observed at catch basin locations SS-6 (8,879 pCi/L), SS-14 (425 pCi/L), SS-21 (284 pCi/L), and SS-22 (312 pCi/L). All other samples were less than the MDC.

0 60

SEQUOYAH NUCLEAR PLANT Manual Sampling Locations

[0 Catch Basin E] Turbine Building Sump El TVBoxSump

---

Storm Drain Feet 0 100 200 300 400 PREPARED BY:TVAGEOGRAPHIC INFORMATION ANDENGINEERING knage ia, DW Orthphcolgrah 2004 Figure 4.1 Map of Manual Sampling Locations 61

4.3 Groundwater Sampling using Geoprobe Methods Groundwater sampling using a Geoprobe allows sampling rods to be "pushed" into the ground without the use of drilling and produces minimal investigation-derived waste. The Geoprobe direct-push machine relies on a relatively small amount of static (vehicle) weight combined with percussion as the energy for advancement of a tool string. The Geoprobe offers a significant safety advantage since the probe tends to resist on concrete and steel pipelines, and downholes tools are easily decontaminated between borings.

Thirty-one (31) Geoprobe boring locations were initially identified at the site based on the existing knowledge of groundwater movement and the relative locations of major underground lines and appurtenances (e.g., ERCW lines and intake conduits). Bedding materials surrounding underground lines represent potential preferential pathways for subsurface movement of groundwater contaminants; therefore, these features were a consideration of the investigation.

Site design and as-built drawings of underground utilities were reviewed in relation to proposed boring locations to avoid potential drilling conflicts. For final verification of proposed boring locations, a radio frequency utility location investigation was conducted under contract with Underground Locators of Nashville, Inc, during November 2006. The utility location survey evaluated potential utilities and metallic obstructions around the areas of the field-staked boring locations. The boring locations were offset if direct obstructions were identified to provide a minimum horizontal clearance of the 2-ft locate variation in all directions.

Sampling of groundwater using Geoprobe methods was conducted during January and February 2007. Due to subsurface resistance at many locations (i.e., concrete), groundwater samples were ultimately collected at 23 locations (Figure 4.2; Table 4.3). When possible, groundwater samples were collected in situ (from within the Geoprobe push-rod at depth) using a 0.5-inch OD stainless steel bailer or were siphoned using Teflon tubing. Where groundwater recovery rates were slow, temporary 0.5-inch ID screen and casing were installed and samples were collected using a 0.5-inch OD stainless steel bailer or were siphoned using Teflon tubing. All temporary well materials were discarded after a single use; although, in some cases, Teflon tubing was reused after being decontaminated between samples. Groundwater samples were transferred to 100 mL wide-mouth plastic sample containers, and turned over to plant personnel to transmit to WARL for tritium analysis. Decontamination involved scrubbing downhole equipment with a distilled water/laboratory detergent mix and rinsing with distilled water.

62

SEQUOYAH NUCLEAR PLANT New Geoprobe Borings and Monitoring Wells Monitoring Wells e" LLRW 0 Oes&WExSUadm aRw NRod=a(&Aroyd)

NSbV (DVyeQk~yd A Dy CoskSki Geoprobe Borings

• G"Ibe BMWt

• G""obe V UAW UAW)V~~~tOMOCB.~N Figure 4.2 Map Showing Geoprobe Sampling Locations and Monitoring Wells 63

Figure 4.3 provides a profile of Geoprobe borings installed during the investigation. Five of the borings were completed as 1-inch monitoring wells to supplement groundwater level measurements in areas lacking groundwater level information. These wells include GP-7A, GP-7B, GP-10, GP-13, and GP-24 (Figure 4.2). Well diagrams are provided in Appendix A.

710 705 -

700 695 -

690 -

V

• 685 -

V V V V

V V 680 V

V 675 -

670 v Initial Groundwater Level I 665 N C. 1i in 91 - i0 0 "* CO

0. CD a.

03 d. 0. 0. 0. d.,

cD N N Ný NY a'.d~..o~~d~n N N C 0 0. a. o. o&

CD CD C)D0 Figure 4.3 Profile of Geoprobe Borings Table 4.3 provides a summary of groundwater sampling locations and analytical results from Geoprobe investigations. As indicated, tritium was observed at low concentrations in borings (GP GP-7) near the Unit 1 RWST, in borings S-SE of Unit 2 (GP-21, GP-22, GP-25, GP-26),

and at GP-28. The highest tritium concentration observed in Geoprobe borings occurred at GP-13 (16, 211 pCi/L).

64

Table 4.3 Tritium Results from Geoprobe Sampling Top of Bottom TN NAD27 (ft) Tritium Ground Depth of Hole Sampling Concentratlo Location (ft-msl) (ft) (ft-msl) Easting Northing Date n (pCI/L)

GP-1 704.1 36.0 668.1 2271360.0 305170.7 1/26/2007 274 GP-2 701.7 27.8 673.9 2271373.9 305226.7 1/29/2007 733 GP-3 702.4 32.5 669.9 2271401.2 305258.6 1/25/2007 623 GP-4 703.5 32.2 671.3 2271433.3 305221.2 1/30/2007 661 GP-5 704.9 30.0 674.9 2271510.6 305256.8 1/25/2007 420 GP-6 704.7 29.2 675.5 2271575.9 305218.7 1/25/2007 306 GP-7B 705.9 24.8 681.1 2271461.1 305425.8 2/12/2007 394 GP-9 705.7 31.2 674.5 2271708.1 305284.7 1/31/2007 < 270 GP-10 707.9 30.0 677.9 2271366.7 305237.9 2/01/2007 < 270 GP-13 705.3 26.5 678.8 2271543.4 305102.4 2/01/2007 16,211 GP-14 704.9 26.0 678.9 2271621.5 305069.1 2/05/2007 < 270 GP-16B 703.8 21.0 682.8 2271594.8 304938.8 2/15/2007 < 270 GP-17B 705.4 27.7 677.7 2271558.3 304862.1 2/16/2007 < 270 GP-18 704.9 28.0 676.9 2271476.6 304781.9 2/06/2007 < 270 GP-21 705.8 26.5 679.3 2271368.9 304750.0 2/06/2007 750 GP-22 706.7 30.0 676.7 2271304.2 304732.2 2/07/2007 2,700 GP-24 704.9 27.0 677.9 2271204.3 304744.0 2/07/2007 < 270 GP-25 703.8 21.8 682.0 2271230.4 304662.1 2/07/2007 874 GP-26 704.1 26.0 678.1 2271309.7 304630.9 2/07/2007 332 GP-27 705.3 25.0 680.3 2271425.5 304571.1 2/12/2007 < 270 GP-28 704.3 20.0 684.3 2271580.9 304774.2 2/13/2007 394 GP-29 704.2 24.0 680.2 2271629.2 304884.0 2/13/2007 < 270 GP-30 704.2 30.0 674.2 2271730.8 304953.5 2/13/2007 < 270 4.4 Water Level Monitoring Groundwater level monitoring at the site during this investigation included manual measurements at existing wells and new wells in close proximity to the plant site on approximately a monthly basis beginning December 13, 2006. Continuous water level and temperature monitoring was conducted at three selected wells (14, W2 1, and GP- 13) and at the head of the Discharge Channel. Solinst (Model 3001) downhole dataloggers were deployed (beginning 11/17/06) for continuous monitoring of water levels and temperatures. Continuous (hourly) surface water levels are collected for Chickamauga Reservoir on the southeast comer of the Intake Channel Skimmer Wall (Figure 1.1) at TRM 484.8.

65

• Results from pre-investigation water level monitoring were coupled with recent data. Figure 4.4 depicts time-series groundwater levels for wells W21, 29, 30, and 31 in the vicinity of Unit 2.

As shown in the figure, groundwater gradients are consistent with time and all groundwater levels are influenced by operation of the Chickamauga Reservoir and the Discharge Channel (see Section 3.3). That is, under normal operations, water elevation begins to increase in April and recession begins in September. The maximum range of groundwater levels over this 3-year interval is 9.7 ft (wells W21 and 31). Groundwater levels at wells 29 and 30 fluctuated over

< 6.0 ft for this period. Apparent in Figure 4.4 is the excellent degree of correlation in groundwater levels at wells W21 and 31.

695-A 690 w J

• W21 29 0 685 - 30 i 1-31

- 6 680 wu 8 -**RiverI 675 Figure 4.4 Time-Series Water Levels at Wells W-21, 29, 30, 31 and the River Figure 4.5 shows time-series groundwater levels for RadCon wells in the vicinity of the 12-inch Waste Condensate Line. Although these wells are located at similar distances from the Discharge Channel, groundwater levels are not correlated with surface water elevations.

However, correlation in groundwater levels among these wells is evident. Compared to wells nearer Unit 2, the maximum range of groundwater levels over this 3-year interval was 13.1 ft (well 34). Groundwater levels at wells 27 and 33 fluctuated over <5.0 ft for this period.

66

705 700 695 A/27 32 690 ---

685 __ River MU 680 675 0 u.L <1 .

1* 5 <: 0 U_

Figure 4.5 Time-Series Water Levels at Wells 27, 32, 33, 34 and the River Continuous temperature and water level data collected for this investigation are presented in Figure 4.6. The most obvious feature in this figure is correspondence of water levels between well W21 and the Discharge Channel. Timing and magnitude of water level changes match exceedingly well. The continuous water level data are too coarse to allow exact time-matching between these two locations (i.e., measurements frequency was hourly at W21 and 20 minutes at the channel). However, data is sufficient to indicate that well W21 responds to changes in Discharge Channel water levels in less than two hours. Noting that well W21 is located 285 ft from the head of the Discharge Channel, hydraulic pressure changes via natural porous media at the site would not produce these types of responses. Results indicate the presence of a subsurface feature(s) residing at depth (<679 ft-msl) providing relatively direct connection between these two locations. Given the correlation in groundwater levels between wells W21 and 31 (Figure 4.4), this or another feature(s) also extends to the vicinity of well 31 (145 ft from the head of the channel).

Figure 4.7 presents continuous water level data at wells W21, 14, and the Discharge Channel for the interval 11/17/06 - 01/24/07. Of interest in this figure is the precipitous change in well W21 groundwater levels coincident with the beginning and ending of the plant outage from 11/26/06 -

12/24/06. Also noted is the anomalous departure of correlation between well W21 and the Discharge Channel from 12/05/06 - 12/15/06 during the outage interval. Daily operations log entries were examined in attempts to identify any major water transfers that might be associated with rapid changes in groundwater levels (e.g., RWST and Spent Fuel Pool transfers). There is no evidence of changes in groundwater levels associated with such transfers.

67

695 690 It a It -, GP-13

-14

-_ W21

• GP-13 (manual)

• W21 (manual)

" W14 (manual)

...... Discharge Channel

-River 6802 -_ _

675 12/13/06 1/2107 1/22/0 7 2/11/07 3/3/07 3/23/07 Daft 30 25 - '

620- A Az GP-13 14

_- W21 15 ......... Discharge Channel 10 5 1 12/13/06 1/2/07 1(22/07 2/11/07 3/3/07 3/23/07 Date Figure 4.6 Continuous Water Levels (Top) and Temperatures (Bottom) at Wells GP-13, 14, W21, the Discharge Channel, and the River 68

11 10 9

8 E 7

.5 C.,

I- 6 0

'U 5

4 3

2 I.-

0 N

0 Date 2.5 SON Gage S

2 1.5 1

.2 0.5 0

2.5 Georgetown Gage 2

e.. 1.5 0l 1 0.5 0 ýT§ MU

-~-u---~F E*0 .

-U mI 8 0, Z 0 0,

(N N Figure 4.7 Continuous Water Levels (Top) and Precipitation (Bottom) at Wells 14, W21, and the Discharge Channel 69

VWell 14 experiences abrupt weekly to biweekly groundwater level increases (Figures 4.6 and 4.7) over most of the monitoring period. The water level changes are correlated with pronounced water temperature decreases (Figure 4.6). Precipitation data from the plant meteorological station and from the Georgetown gage (9 miles NE of SQN) were obtained and are shown at the bottom of Figure 4.7. As shown, groundwater level and temperature changes at well 14 are clearly linked with rainfall events. It is highly probable that the well 14 wellhead seal has been damaged and that rainfall runoff is directly entering the well annulus at this location. Similar results are observed in temperature data at well W21. Again, data suggests that well W21 wellhead seal has been damaged.

Figure 4.8 depicts the potentiometric surface at the site based on April 02, 2007 groundwater level measurements. Groundwater movement is northerly over the Unit I portion of the site with the Intake Channel serving as a primary surface water control to hydraulic gradients. Over the Unit 2 side of the site, groundwater movement is primarily southerly with convergent flow toward the Discharge Channel.

70

SEQUOYAH NUCLEAR PLANT Local Potentiometric Surface Map from Water Level Mesurements April 02, 2007 Monitoring Wells

• Diesel

• RadCon

• Geoprobe Potentiometric Contours (ft-msl) s -IFeet 0 100 200 300 400 500 IaPREPARED TVA BY:

knopis a Digia eN IFORNIATION GEOGRAsur dw~ograpIt20104 ANDENOINEERING Figure 4.8 Local Potentiometric Surface from April 02, 2007 Water Level Measurements 71

4.5 Interior Sampling Groundwater inleakage occurs at SQN along concrete construction joints, poorly sealed pipe sleeves, concrete factures, and other locations. During this investigation, several areas were visually inspected and groundwater inleakage samples were collected for tritium analyses.

Inspection locations were selected based on historical observations of seepage, depth, and location (i.e., below groundwater table and in vicinity of observed tritium), and accessibility.

Locations identified for inspections and sampling included the Auxiliary Building, north wall of the Turbine Building, and RWST pipe tunnels for both units.

Groundwater inleakage has been documented at SQN since 1978 (TVA, 1978). At this time, groundwater inleakage was described in the Auxiliary Building. At the request of SQN, an inspection of the Auxiliary Building inleakage problem was performed by J. M. Boggs of TVA's Engineering Laboratory during May 1997. Inleakage locations were identified on plant drawings and catalogued with photographs (Figure 4.9).

As shown in Figure 4.9, twelve inleakage locations have been identified in the Auxiliary Building at floor elevations 653 and 669 ft-msl. Red symbols identified locations where inleakage rates were sufficiently high in 1997 to require collection. Blue symbols identified locations of low inleakage rates not requiring collection. These locations are listed in Table 4.4.

Two additional inleakage locations not identified in Figure 4.9 and Table 4.4 were documented (1997) at a leaking conduit in the Unit 1 UHI pit and at a 4-inch diameter pipe sleeve near elevation 655 ft-msl of the UHI pit.

Table 4.4 Auxiliary Building Groundwater Inleakage Locations Location Remarks 1 Elevation 653 ft-msl pipe chase, high inleakage rate 2 Seepage being collected, moderate inleakage rate Two inleakage locations, drip funnels being used for 3 collection 4 no comment 5 no comment 6 Leak at concrete construction joint 7 Leak above floor in wall 8 Patched 9 Leak at floor 10 no comment 11 no comment Sampling of groundwater inleakage from the north wall of the Turbine Building (near elevation 662 ft-msl) was conducted on 10/20/06. Analysis by WARL indicated that tritium was less than the MDC of 220 pCi/L.

72

A 3 ý I f

F 4- ~ I1 1I

• -a,~I-Aro ". ( Tt.

N, ill 6 -Y 4

-o

~. 10 PL AN 4.L *5,. 0

- * ~ '~It:

I

• Very Low Flowrate, No Collection Required Flowrate Sufficiently High to Require Collec ~tion

,-~ . @-J -

PLAN CL 4r9.0 Figure 4.9 Groundwater Inleakage Locations at Auxiliary Building

Inspection and sampling within the Unit 1 and 2 RWST pipe tunnels was performed by SQN staff under work orders 06-776301-000 and 06-776302-000 during 8/28/06 and 8/31/06.

Groundwater inleakage samples were collected from tunnel walls and water samples were collected from trough drains at each location. Analyses by WARL indicated that tritium was less than the MDC of 220 pCi/L for all samples.

Based on comparable tritium investigations completed at WBN, and similarity of SQN plant design to WBN, inspection of Unit 1 and 2 Annuli and transfer tube bellows are being performed by SQN staff. These inspections involve boroscope methods and removal of concrete block shield walls for access. Where possible, samples are being collected for analyses. These investigations are continuing and results are forthcoming.

74

o 5.0 RESULTS AND RECOMMENDATIONS 5.1 Tritium Distribution 5.1.1 Manual Sampling Manual sampling at 20 catch basins, vaults, and manholes (Figure 4.1; Table 4.2) during this study showed positive detection of tritium at four shallow locations. The sampling depths at these locations were >15 ft above the groundwater table. Tritium was observed at SS-6 (8,879 pCi/L), SS-14 (425 pCi/L), SS-21 (284 pCi/L), and SS-22 (312 pCi/L). All other samples were less than the MDC.

Observation of tritium in catch basin SS-6 (2.6 ft deep) near the Service Building is not completely explicable. The observed tritium concentration is an order of magnitude greater that tritium concentrations observed in groundwater from Geoprobe borings (GP-I - GP-4) in the immediate vicinity. Results suggest that the observed tritium concentration might be associated with direct discharges to the single line entering this catch basin.

The low tritium concentration at catch basin SS-14 (1.9-ft deep), near the 12-inch waste condensate line, is similar to tritium concentrations observed for soil wells located along the condensate line. The 12-inch condensate line is located above ground at this location and leaks to ground surface could produce the observed concentration. Likewise, overflows from the Turbine Building sump could produce similar results.

The low tritium concentration observed at catch basin SS-22 (7.8 ft deep) may be the result of a release from the MFTDS (Section 2.3) that occurred in 1997. A correspondingly low tritium concentration at the SS-21 TV box sump (2.6-ft deep) may also be the results of the MFTDS release. However, this vault possesses an impermeable cover. It is conceivable that the source of tritiated water within the SS-21 sump is associated with contaminated groundwater some distance upgradient (west) of the electrical vaults. Electrical conduits (and their bedding materials) intersecting such vaults are probable avenues for shallow groundwater transport.

Manual sampling of several selected locations was performed during January 2004 to support siting of RadCon wells located along 12-inch waste condensate line. Water sampling results at all locations indicated tritium concentrations <MDC of 220 pCi/L. Sampling locations included:

• Diesel Fuel Oil Interceptor Trench discharge;

• Turbine Building sump;

• Low-Volume Waste Treatment Pond inlet;

• Condensate water discharge from Turbine Building roof to sump;

• CO 2 vault sump south of Turbine Building;

• Alum Sludge Ponds A (west) and B (east);

75

V

• Water Treatment Plant basement sump;

• Storm drain #45 north of High Pressure Fire Protection System tanks;

• Storm drain #44 east of Water Treatment Plant;

• Storm drain #46 south of Unit 2 Condensate Storage Tanks.

5.1.2 Groundwater Sampling From 1998 through 2001, tritium was consistently observed at concentrations ranging from 401 to 2,120 pCi/L at well W5 (Figure 1.2). No further tritium detection has been observed at well W5 since 2001. Beginning in February 2002, TVA expanded REMP groundwater monitoring at SQN (Section 1.3) with the addition of 12 soil monitoring wells and collection of groundwater samples from existing wells in proximity to known areas of tritium contamination.

Since August 2003, 206 groundwater sampling events have been conducted at one or more of these wells. Tritium concentrations observed from these sampling events are tabulated in Appendix B.

As shown in Appendix B, tritium concentrations measured at wells 24-28, 30, and 32-35 have been <MDC with only a few exceptions near the MDC. Relatively high tritium concentrations (2,576 - 19,750 pCi/L) have been continuously observed at well 31 since May 2004. As shown in Figure 5.1 tritium concentrations are generally correlated with groundwater levels at well 31.

25,000 692

......... MDC (220 - 270 pCI/L) won Groundwater Level 690 20,000 A 688 I684 C C

.215,000 a2 r

0 10,000 r 682k 0.......................................................... 678 0 05 Date Figure 5.1 Time-Series Tritium Concentrations and Groundwater Levels at Well 31 76

At well W2 1, tritium concentrations have ranged from 226 - 9080 pCi/L since sampling commenced in February 2004. As shown in Figure 5.2, there is no correlation between tritium concentrations and groundwater levels at well W21. Low tritium concentrations have also been consistently observed at well 27 (<500 pCi/L) and well 29 (<1800 pCi/L) with no relationships between tritium and groundwater levels at either location (Figure 5.3).

4,000 .692 Tintium Concentration MDC.. (220 -270 pClL) ________ W2__

3,500 Groundwater Level 690 U

S3,000 ___1_ i 688 C

.2 2,500

-686 8'S2,000 U C 684 E 682 a~1,000 _

500- 4 680 0 678 oir' 4 55 g as .S Date Figure 5.2 Time-Series Tritium Concentrations and Groundwater Levels at Well W21 Groundwater sampling at 23 Geoprobe borings (Figure 4.2; Table 4.3) indicated low tritium concentrations (274 - 661 pCi/L) in borings (GP GP-7) surrounding the Unit I RWST.

Borings GP-21, GP-22, GP-25, and GP-26 exhibited low tritium concentrations (332 - 2700 pCi/L) in the area S-SE of Unit 2. Boring GP-28, just east of this area, provided a similarly low tritium concentration (394 pCi/L). The highest tritium concentration observed within all Geoprobe borings occurred at GP-13 (16, 211 pCiIL). Due to the relatively high groundwater tritium concentration at GP-13, a soil monitoring well was installed at this location and additional groundwater sampling was conducted. Figure 5.4 depicts sampling results to date.

77

600 696 MU 27 500 694 692 690W I

E 2--

688 Tritium Concentration 100

.......... MDC (220 - 270 pCi/L)

-0 Groundwater Level 0 684 Date 2,000 692 1,800 -

1,600 690 Y. 1,400 o 1,200 68.2 1,000 w J800 686w E 600 e.

I- 400 684 200 0 682 Date Figure 5.3 Time-Series Tritium Concentrations and Groundwater Levels at Wells 27 and 29 78

20,000 686.8 19,000 66 18000686.4 17,000 I 686.0 16,000 685.8IL 15,000 - 1685_

2685.6 S14,000 I- ____685.4~ _ ___

13,000 13,00 Tritium 4 Concentration 6 685.2

- Groundwater Level i 12,000 685.0 Date Figure 5.4 Time-Series Tritium Concentrations and Groundwater Levels at Well GP-13 Figure 5.5 shows the distribution of tritium based on shallow (soil) groundwater sampling during January and February 2007. In general, the highest tritium concentrations in the shallow groundwater system are associated with two distinct areas north and south of Units I and 2.

Although data is sparse for the deeper flow regime (i.e., weathered bedrock and shallow bedrock), the extent of the tritium plume is reasonably bounded by sampling locations in the horizontal.

5.2 Tritium Sources Current results suggest that sources of tritiated groundwater are primarily associated with past inadvertent releases of liquids containing radioisotopes. Relatively high groundwater tritium concentrations have been observed at wells 31 and GP-13, noting that there have been no observations exceeding the EPA Drinking Water Standard of 20,000 pCi/L for tritium (40 CFR 141.25).

Historically, remediation procedures for inadvertent liquid releases have chiefly involved the collection and screening of soil samples and limited water samples for radionuclides. However, the radionuclide analytes exclude short-lived isotopes such as tritium (see Section 2.3).

Likewise, groundwater sampling associated with inadvertent liquid releases was not conducted during remediation. There is therefore a strong likelihood that tritium contamination from inadvertent liquid releases was not revealed due to the limitations of sampling and analytical protocols.

79

SEQUOYAH NUCLEAR PLANT Tritium Plumes Mkmioring Locations REMP Diesel Extuucllon LLRW 0 RADCON 0 Genen.

Tfr'm Ccomstooqw (pCiI)

O220 -2000 i20 8-0W

8

IIo-I~oM

~UEPAAEO*Y D1A0aCflMADbMOB#inSNG Figure 5.5 Spatial Distribution or Tritium from Groundwater Sampling During January and February 2007 80

An analog groundwater investigation of tritium releases at WBN suggests that leaks through the fuel transfer tube and seismic gap (between Unit 2 Reactor and Auxiliary Buildings) contaminated groundwater at the WBN site. Tritium concentrations in these source areas are nearly 100 million' pCi/L and the release of only a small volume of water is necessary to produce elevated tritium concentrations in site groundwater. Inspections of SQN Unit 1 and 2 fuel transfer tubes, spent fuel pool, and associated components are currently being performed by SQN staff. These investigations are continuing and results are forthcoming.

Controlled airborne releases from the plant ventilation system may result in measurable atmospheric deposition of plant-related radionuclides (including tritium) in the vicinity of the site. Since this potential tritium source is not likely to be a major contributor to groundwater contamination, airborne release was not evaluated during this investigation.

Unit 1 - Elevated tritium concentrations in groundwater north of Unit I suggest that the inadvertent water release from the MFTDS in 1997 (see Section 2.3) is likely the primary source of shallow groundwater contamination in this vicinity. The estimated volume of water released by the MFTDS is 600 - 1,000 gallons. A secondary source of tritium contamination in this vicinity isrelated to relatively small volumes of water that drain from the RWST moat and have discharged to ground surface for >25 years. Observation of tritium in catch basin SS-6 near the Service Building is not completely explicable, but results suggest that the observed tritium concentration might be associated with direct discharges to the single line entering this catch basin.

Unit 2 - Tritium concentrations in groundwater south of Unit 2 suggest that inadvertent releases from the Unit 2 CDWE and additional Equipment Buildings (see Section 2.3) have contaminated shallow groundwater in this vicinity. A tertiary source of tritium contamination in this vicinity is related to the moat drain from the RWST that discharged to ground surface for >25 years.

Tritium concentrations at well 27 appear to be of an isolated nature and may be related to leakage of the 12-inch waste condensate line.

5.3 Tritium Transport and Fate Tritium is a conservative contaminant - it is not susceptible to attenuation via sorption or biochemical degradation. Reduction of tritium concentrations in the groundwater system at SQN will occur primarily by hydrodynamic dispersion and dilution. The dispersion process is related to variations in groundwater velocity that occur on a microscale by differences in media porosity and on a macroscale by variations in hydraulic conductivity. Dispersion will result in reductions of tritium concentrations with increasing distance from the source (e.g., the MFTDS railroad bay). Dispersion will be more pronounced in the soil horizon relative to the deeper and more transmissiv*"weathered bedrock horizon. However, the fate and transport of tritium in the site groundwater system is also likely to be governed by avenues of relatively rapid groundwater 81

movement that exist within bedding material of larger pipelines and tunnels, and possibly along the weathered bedrock horizon.

Groundwater and surface water level measurements during the study confirm that the Intake and Discharge Channel will ultimately be recipient to tritiated groundwater discharge from the site.

Dilution ratios in the channels and subsequently the Tennessee River are dependent on plant operation and river flows.

5.4 Recommendations 6 o active remediation is recommended for the site due to the limited extent of tritium contamination, tritium concentrations in groundwater less than EPA Drinking Water Standard of 20,000 pCi!L (40 CFR 141.25), perceived low exposure and dose risks, and negligible potential for offsite groundwater migration)..The following recommendations are submitted based on findings of this investigation.

Source Terms: Spatial data and anecdotal evidence suggest that tritium sources are primarily associated with past inadvertent releases of liquids containing radioisotopes. "Idditional groundwater sampling in the areas of GP-13 would assist in bounding the tritium plume on the north (Unit 1) side of the site. Sampling would involve the installation of 6 - 8 shallow soil borings to confirm the extent of tritium contamination.j There are no bedrock borings located in close proximity to Units I and 2 that can be used to examine he vertical distribution of tritium that might extend into the shallow Conasauga bedrock.iTwo bedrock borings extending into the upper 20 ft of bedrock are recommended for the zones exhibiting relatively high tritium concentrations (north and south of Units I and 2).

Results should be examined collectively to verify that higher tritium concentrations do not exist at excessive concentrations within the shallow bedrock flow systemly It is likely that tritium contamination from inadvertent liquid releases was not revealed in past investigations due to the limitations of sampling and analytical protocols.cUQN procedures directed towards investigation and remediation of future releases should be developed or modified to identify short-lived isotopes such as tritium. Confirmatory sampling of environmental media following remediation of a spill should meet the MDCs of applicable regulatory criteria. In most cases, a professional engineer with expertise in hydrogeology should be consulted to assist in remediation investigations._

The components investigation currently being conducted by SQN staff should contnue to substantiate that no releases to groundwater have occurred from internal sources., Should problems be identified, their remedies should extend to external environs as necessary'..

82

Routine Onsite 01 Grounwaer Monitoring;>ioutine groundwater quality and water level$

dgroundwtrqaiyndwater monitoring should be continued at a quarterly frequency at wells 31, GP-13, and W21 for a minimum of two years. These data should be reviewed on an annual basis by a professional engineer with expertise in hydrogeology and groundwater science. In addition to tritium, boron should be considered as an analyte since it is typically added to primary cooling water as a neutron moderatorAcFlierefore, when detected at concentrations greater than background, boron can be an indicator of leaks from primary systems.'fesults of routine groundwater sampling should be reviewed annually by a professional engineer with expertise in hydrogeologyg.:

Groundwater sampling protocols have been prepared by TVA and standard forms are ayailable for use. In addition, the NRC (1979) and ASTM (2006) provide standard guidelifles for groundwater sampling. The SQN staff should assure that acceptable groundwater 'Sampling protocols are being utilized. In addition to groundwater collection methods, these practices also extend to: sample handling, labeling, storage, shipment and chain-of-custody procedures; qualification and training requirements for sampling personnel; applicable regulatory limits; analytical methods and MDCs, required analytical method uncertainties; quality control samples and acceptance criteria; required number of samples per analytical batch; and vialidation methods.

REMP Onsite GroundwaterMonitoring: Bedrock well W5 is currently the only onsite well O being used for REMP groundwater monitoring purposes. The well location and type is. poorly suited for rapid detection of groundwater contamination from primary plant systems. Well W5 resides too far from the plant, is situated adjacent to the Intake Channel, and is developed in bedrock..,Sonsideraiion should be given to an alternate well location(s) and type (e.g., well immediate to the site, along groundwater gradient, and appropriately screened ---

Data Management and Quality: The current data management procedures result in significant difficulties related to groundwater data acquisition and authentication.yVA and SQN should consider a programmatic evaluation of data management and quality ,practices to ensure that analytical results are documented, retained, and readily retrievable. At a minimum, documented analytical data shall contain the following information:

" Sample identification (e.g., location and well identification);

• Sample date and time;

• Measured concentration for all radionuclides where results have been reported (whether or not above the detection criteria, or positive or negative);

• Measurement uncertainty; 0 Achieved MDCs;

• Records of data validation and verification;.

" Identification of missing sample results3" 83

0 .- Analytical method(s).

Development of a database should be considered that meets criteria described in American Nuclear Insurers Information Bulletin 80-1 A. The database developed by TVA for the fossil fuel groundwater monitoring program would serve as an ideal platform for groundwater data management..

Well Protection and Abandonment: Analytical results from repeated sampling at several site wells indicate that they can be abandoned. Wells that are deemed of no strategic importance have not exhibited tritium concentrations >MDCs and are in close proximity to other monitoring wells."Wells recommended for abandonment include: 30, 32, 34, 35, UNIW, UNW2, and UNW3.J Wells installed for monitoring along the waste condensate lines and during this study do not possess well head protection. ,9ockable well h__ead protective covers, balusters, and/or flush-mount covers should be installed at these wellsjData suggest that wplls 14 and W21 well head seals have been damaged, allowing direct entry of rainfall runoff. b'hese well heads should be repaired:.j

6.0 REFERENCES

ARCADIS, Groundwater Investigation Report, Watts Bar Nuclear Plant, Spring City, Tennessee, June 2004 ASTM D5903-96(2006), "Standard Guide for Planning and Preparing for a Groundwater Sampling Event," ASTM International, 2006.

Edwards, M., H. E. Julian, C.D. Olson, J.L. Edge, and P. Rich, "Sequoyah Nuclear Plant, Fuel Oil Contamination Investigation and Corrective Action Plan," TVA Engineering Lab Report WR28-1-45-143, February 1993.

Halter, M., "Sequoyah Nuclear Plant - Unit 2 Additional Equipment Building Sump Spill, Final Recovery Report" Tennessee Valley Authority, January 22, 1998.

Halter, M., "RWST Moat Water as a Potential Tritium in Ground Water Source," Memorandum, Tennessee Valley Authority, July 17, 2006.

Julian, H. E., "Sequoyah Nuclear Plant Fuel Oil Contamination Investigation, Addendum to Report WR28-1-45-143," TVA Engineering Lab Report, December 1993.

Julian, H. E., "Sequoyah Nuclear Plant, Groundwater Supply Study," TVA Engineering

___ Laboratory, Internal Report, April 2000.

84

QNRC, "Liquid Radioactive Release Lessons Learned Task Force Final Report," Nuclear Regulatory Commission, September 1, 2006.

NRC Regulatory Guide 4.15, "Quality Assurance for Radiological Monitoring Programs (Normal Operations) - Effluent Streams and the Environment," Revision 1, February 1979.

Rogers, W. J., "Distribution Coefficient Study for Sequoyah Nuclear Plant," TVA Laboratory Services Branch Report No. 9., 1982.

Smith, W. E., "Sequoyah Nuclear Plant - RadWaste Yard Spill, Final Survey Report" Tennessee Valley Authority, July 31, 1997.

TVA, "Sequoyah Nuclear Plant - Records of Spills and Unusual Occurrences Important to Decommissioning," Memorandum from Michael F. Halter to Mark A. Palmer, Tennessee Valley Authority, Sequoyah Nuclear Plant, Soddy Daisy, Tennessee, July 11, 2006.

TVA, "Sequoyah Nuclear Plant, Final Safety Analysis Report, Amendment 19," Tennessee Valley Authority, October 13, 2005 TVA, "Supplemental Environmental Assessment, Independent Spent Fuel Storage Installation, Sequoyah Nuclear Plant," Tennessee Valley Authority, November 2001.

TVA, "Quantification of Total Petroleum Hydrocarbon in Soil at the Sequoyah Nuclear Dry Cask Storage Area," Tennessee Valley Authority, Environmental Engineering Services-East, June 2001.

TVA, "Dry Cask Storage Soil-Core Sampling Results - Supplement to Quantification Of Total Petroleum Hydrocarbons In Soil At The Sequoyah Nuclear Dry Cask Storage Area," Tennessee Valley Authority, Environmental Engineering Services-East, September, 2001.

TVA, "Sequoyah Nuclear Plant, Final Safety Analysis Report," Tennessee Valley Authority, 1979.

TVA, "Sequoyah Nuclear Plant - Ground Water Inleakage," April 4, 1978 Memorandum from R. M. Pierce to G. G. Stack, Tennessee Valley Authority, 1978.

TVA, "Sequoyah Nuclear Plant Low-Level, Radwaste Storage Foundation Investigation,"

Tennessee Valley Authority, Engineering Design Soil Schedule 28.3, 1981.

USEPA, "USEPA RadNet Database Retrieval for Tritium in Surface Water at Soddy Daisy, Tennessee," http://oaspub.epa.gov/enviro/eramsquery.simpleoutput?Llocation=City&subloc=

DAISY%2CTN&media=SURFACE+WATER&radi=Tritium&Fromyear= I960&Toyear=2006&

,Ci units=Traditional, April 2007.

85

Young, S. C., H. E. Julian, H. S. Pearson, F. J. Molz, and J. K. Bowman, "User's Guide for Application of the Electromagnetic Borehole," U.S. EPA report, Robert S. Kerr Environmental Research Laboratory, Ada, OK, Report in Press, 1997.

05 86

APPENDIX A WELL CONSTRUCTION LOGS Q

87

ROCK MONITORING WELL INSTALLATION RECORD PROJECT SEOUOYAH NUCLEAR PLANT WELL NUMBER __ INSTALLATION DATE PLANT COORDINATES EAST -1272.6 ft NORTH 800.1 ft TOP OF INNER CASING 7 GROUND SURFACE ELEVATION BACKFILL MATERIAL SAND & PEA GRAVEL CASING DIAMETER 6r CASING MATERIAL SOUD STEEL CASING DRILLING TECHNIQUE IN ROCK PERCUSSION DRILLING TECHNIQUE IN SOIL AUGER DRILLING CONTRACTOR OUTER BOREHOLE DIAMETER OPEN BOREHOLE DIAMETER _"

LOCKABLE COVER ? NO COMMENTS PLASTIC PIPE ADDED TO RAISE THIS WELL 4.37 ft (NOT TO SCALE)

EIOAL CAP*,, r.

0[

r SOLI9T CANG 151.7 TOP OF ROCK BOarOM OF cAmNe t 65.2" OPENBOREHOLE GROUT ]

ENOLAS7lZ1D1 88

MONITORING WELL INSTALLATION RECORD PROJECT SEOUOYAH NUCLEAR PLANT WELL NUMBER W2 INSTALLATION DATE NORTH -1271.6 ft PLANT COORDINATES EAST -1105.5 ft 70.91 GROUND SURFACE ELEVATION TOP OF INNER CASING BACKFILL MATERIAL SAND & PEA GRAVEL CASING DIAMETER CASING MATERIAL SOLID STEEL CASING DRILLING TECHNIQUE IN ROCK PERCUSSION DRILWNG TECHNIQUE IN SOIL AUGER DRILLING CONTRACTOR OUTER BOREHOLE DIAMETER OPEN BOREHOLE DIAMETER 6" LOCKABLE COVER ? NO COMMENTS NEAR GAS/DIESEL TANKS (NOT TO SCALE) 77 ROXAKE CA.?

UP0400 BFWACE

- rau M XE. ,,CA8IM 70.5' 157" MOPOFROCK WOTTMOFCA8M I OP!NBopm4OL ENO LAB 7,25A1 89

MONITORING WELL INSTALLATION RECORD PRO.JECT SEOUOVAH NUCL.EAR PLANT WELL NUMBER W4 INSTALLATION DATE PLANT COORDINATES EAST 948.1 ft NORTH 39.6 It GROUND SURFACE ELEVATION 723fv TOP OF INNER CASING 742.27 fMWal BACKFILL MATERIAL SAND &PEA GRAVEL CASING DIAMETER CASING MATERIAL: SOLID STEEL CASING DRILLING TECHNIQUE IN ROCK PERCUSSION DRILLING TECHNIQUE INSOIL AUGER DRILLING CONTRACTOR OUTER BOREHOLE DIAMETER________ OPEN BOREHOLE DIAMETER LOCKABLE COVER ? _____________

(NOT TO SCALE)

FOWAKECAP SLOPElD OPAIN GROUNDSUFWACE APPRO)"TELY IIV 120.4' TOP OF ROCK 8orTOM OF CAS4NO j OPENBOREOLE OROu; ENOLAB 7,2S/11 90

MONITORING WELL INSTALLATION RECORD PROJECT SEOUOYAH NUCLEAR PLANT WELL NUMBER INSTALLATION DATE PLANT COORDINATES EAST 146.0 ft 761.0 ft NORTH GROUND SURFACE ELEVATION 690.1 th TOP OF INNER CASING 8. ftm BACKFILL MATERIAL SAND & PEA GRAVEL _ "

CASING DIAMETER CASING MATERIAL SOUD STEEL CASING DRILLING TECHNIQUE IN ROCK PERCUSSION DRILLING TECHNIQUE IN SO4L AUGER DRILWNG CONTRACTOR OUTER BOREHOLE DIAMETER OPEN BOREHOLE DIAMETER _

LOCKABLE COVER 7 COMMENTS (NOT TO SCALE)

PJMMABW CAP SLDPUTO DMJN

/

w~wr UM.AS7d251UI

91

MONITORING WELL INSTALLATION RECORD PROJECT SEOUOYAH NUCLEAR PLANT WELL NUMBER Ls _ INSTALLATION DATE 8-11-81 PLANT COORDINATES EAST 1885.7 ft NORTH -M.4 ft GROUND SURFACE ELEVATION 733.8 ft-MSL TOP OF INNER CASING 734.8 ft-MSL BACKFILL MATERIAL SAND & PEA GRAVEL 3.

CASING DIAMETER CASING MATERIAL PVC DRILUNG TECHNIQUE IN I ROCK PERCUSSION DRILLING TECHNIQUE IN SOIL AUGER DRILUNG CONTRACTOR OUTER BOREHOLE DIAMETER 12" OPEN BOREHOLE DIAMIETER 5' LOCKABLE COVER ? NO LOCK COMAIMEN.TS .010" SLOT WRAPPED WITH FIBER GLASS CLOTH (NOT TO SCALE) j -RNAMELCAP PROTECTWE CASINO -

GROULDSURPAOE

/#-_--

'14

.. :! ~SCLID

~CASINO ~ .... .o.......iiii~iii*

3-PVC EL OO0' SCRE* N .......

_:?._:;*665.1 o tC 1 1- AIN 65 -*-- OFROCK(

.. ~.... F ASNO 65 . ......

EITIr SENTOWrEPELLETS~

PFJ ORAV!L ACOARSESAND K ENOLA13?7t2I 92

MONITORING WELL INSTALLATION RECORD PROJECT SEOUOYAH NUCLEAR PLANT WELL NUMBER L7 INSTALJATION DATE 8-11-81 PLANT COORDINATES EAST 1390.6 ft NORTH -6.0 ft GROUND SURFACE ELEVATION 731.0 ft-MSL TOP OF INNER CASING 733.1 ft-MSL BACKFILL MATERIAL SAND & PEA GRAVEL CASING DIAMETER CASING MATERIAL PVC DRILLING TECHNIQUE IN ROCK PERCUSSION DRILLING TECHNIQUE IN SOIL AUGER DRILLING CONTRACTOR OUTER BOREHOLE DIAMETER 12 OPEN BOREHOLE DIAMETER 5 LOCKABLE COVER? NO LOCK COMMENTS .0100 SLOT WRAPPED WITH FIBER GLASS CLOTH .

(NOT TO. SCALE)I

-- RMALE CAP SURFACE SOLID CASING r PVC EL700.0' SCREEN 664.3 Tm OP OROCi SENTOrgqrPEtLETSs PEAGRAVEL.&COARSE SAND ENOLAB7/213I1

()

93

IDESTROYED MONITORING WELL INSTALLATION RECORD PROJECT SEQUOYAH NUCLEAR PLANT WELL NUMBER W8 INSTALLATION DATE PLANT COORDINATES EAST 400.0 ft NORTH 680.0 ft GROUND SURFACE ELEVATION APPROX. 692.0 ft-MSL TOP OF INNER CASING 694.1 ft-MSL BACKFILL MATERIAL SAND & PEA GRAVEL CASING DIAMETER CASING MATERIAL SOLID STEEL CASING DRILLING TECHNIQUE IN ROCK PERCUSSION DRILLING TECHNIQUE IN SOIL AUGER DRILLING CONTRACTOR OUTER BOREHOLE DIAMETER OPEN BOREHOLE DIAMETER 8

• LOCKABLE COVER ?

COMMENTS AUTOMATIC SAMPLER (NOT OPERA TIONAL) AT THIS LOCATION.

(NOT TO SCALE)

GROUTL3 ENOLAB7/2"91

© 94

Sequoyah Nuclear Plant Boring ID: W14 Plezometer S 0 Description Construction D i Diagram UJ 0 7 705 '0 GRAVEL, (FILL)

Not Sampled Grout

,6::

700 .. GRAVEL, roots (FILL) 5 -_700 Not Sampled Bentonite M Crumbly, brown, sandy, SILTY CLAY, diesel odor (FILL?)

10 695

__ ~~Not Sampled ,,+E 15 690 Bentonite: IR Not Sampled:il-ii Crumbly, dark brown, sandy, SILTY CLAY, roots/twigs, diesel odor (FILL'?

20 685 Crumbly, dark brown, sandy, SILTY CLAY, roots/twigs, diesel odor (FILL?

25 680 Borinn Terminated at 25.6 ft BGS Project Name: Sequoyah Nuclear Plant. Drilling Date: 11/23/1992 Easting: 2271537 Company Name: TVA Drilling Company: MACTEC Northing: 304487 Location: South of Unit #2 Reactor Bldg Drilling Method: Hollow Stem Auger Top of Casing (ft): 707.88 Well Depth (ft): 18.75 Top of Ground (ft): 705.2 95

Tennessee Valley Authority LOG OF BORING 22 WELL CONSTRUCTION DETAIL MATERIALS DESCRIP.TION T.O.C.

_j W CL X M1 LL ZJIW nU-J 0 2.5 ft.

Light brown gravelly clay fill Yerlow-orange silty clay with roots 18 k 55 01"I.

Yellow-orange silty clay with light gray silt 40 mottelrng and root in silt stringers 62 810- Dark gray weathered silty shale 12_ _

12 Dark gray to yellow-orange weathered fissile shale with dark brown clay stringers 0 G5 reenish gray to dark brown weathered fissioe

• and silty shale 0

Olive gray to darkDrown weathered silty shale:

20 "

boring terminated 25 PROJECT Sequoyah Nuclear Plant DRILLING COMPANY Tri-State LOCATION Soddy Daisy, Tm DATE DRILLED DRILL RIG Hollow Stem Auger SURFACE ELEVATION 698.4 feet-msl LOGGER/ENGINEER Hank Julion T.O.C. ELEVATION 700.88 feet-.msl WATER LEVEL (INITIAL) WATER LEVEL (24-HOUR) 96

Sequoyah Nuclear Plant Boring ID: W21 C UPI Plezometer SDescription Construction

• - I Diagram 705 0

700 GRAVEL, with dark red-brown silty clay, (FILL) 5 Not Sampled Grut 695 Dark red-brown, SILTY CLAY, with rock fragments (FILL) 10 Not Sampled 690 Tan-brown and greenish gray weathered SILTY SHALE (FILL) 15 -- entonite il Il Not Sampled 685 Light tan-brown and red SILTY SHALE (FILL) 20-;

Not Sampled sen -

- _ ~ ~~~23.7 680 Red-brown, SILTY SHALE (FILL) 25 Not Sampled Bornn Terminated at 27.3 ft BGS Project Name: Sequoyah Nuclear Plant Drilling Date: 1/20/1993 Easting: 2271423.4 Company Name: "T'VA Drilling Company: MACTEC Northing: 304779.2 Location: South of Unit #2 Reactor Bldg Drilling Method: Hollow Stem Auger Top of Casing (ft): 706.23 Well Depth (ft): 27.3 Top of Ground (ft): 704.4 97

Sequoyah Nuclear Plant Boring ID: 24

- Plezometer 0 0

0. f  : Diagram 0

705 Grout 5

700 10 Bentonite Z3 695 15 690 Sand 20 685 Project Name: Secluoyah Nuclear Plant Drilling Date: 2/20/2002 Easting: 2271341.71 Company Name: TVA Drilling Company: TVA Northing: 304478.66 Location: East of Discharge Channel Drilling Method: 8" H.S.A. Top of Casing (ft): 705.7 Well Depth (ft): 23.2 Top of Ground (ft): 705.65 98

Sequoyah Nuclear Plant Boring ID: 25

- Plezometer

. Description Construction C, 0

> D Diagram Project Name: Sequoyah Nuclear Plant Drilling Date: 2/20/2002 Easting: 2271599.77 Company Name: TVA Drilling Company: TVA Northing: 304238.91 Location: East of Discharge Channel Drilling Method: 8" H.S.A. Top of Casing (ft): " 704.37 Well Depth (it): 19.8 Top of Ground (ft): 701.34 99

Sequoyah Nuclear Plant Boring ID: 27 co .2 m Plezometer

0. a 0 Description Cntuto Cntuto

> .- Diagram Lu 0 705 Grout 5 - 700 Bentonite 10- 10 695 15 Sand 690 20- 20 685 Project Name: Sequoyah Nuclear Plant Dnlling Date: 2/21/2002 Easting: 2270865.63 Company Name: TVA Drilling Company: TVA Northing: 304530.46 Location: South of Unit #2 Reactor Bldg Drilling Method: 8" H.S.A. Top of Casing (ft): 705.46 Well Depth (ft): 22 Top of Ground (ft): 705.34 100

Sequoyah Nuclear Plant Boring ID: 28

c. aPiezometer S. - 0 Description Construction

. Do r Diagram Iul 0

r 705 Grout 5- 700 Bentonite 695 10 690 15 Sand 685 20 Project Name: Sequoyah Nuclear Plant Drilling Date: 2/21/2002 Easting: 2270758.84 Company Name: TVA Drilling Company: TVA Northing: 304204.56 Location: South of Unit #2 Reactor Bldg Drilling Method: 6" Air Rotary Top of Casing (ft): 704.44 Well Depth (ft): 22 Top of Ground (ft): 704.6 0

101

f Sequoyah Nuclear Plant Boring ID: 29 AI C I* Plezometer 0

0 Description Construction SDiagram w

705 0

• -- -- Bentonite 700 5

695 10-- Sand 690 15 685 20-- Bentonite 680 Sand 25 Project Name: Sequoyah Nuclear Plant Drilling Date: 04/27/2004 Easting: 2271457.69 Company Name: TVA Drilling Company: TVA Northing: 304728.27 Location: South of Unit #2 Reactor Bldg Drilling Method: Geoprobe Top of Casing (ft): 706.06 Well Depth (ft);: 26.12 Top of Ground (ift): 702.97 102

Sequoyah Nuclear Plant Boring ID: 30 Plezometer 0 Description Constructionagram

> -Ea 705 0 - -

0- -- Bentonite 700 5

695 Sand 10

690 15 -

,15.8 Bentonite 685 20 Sand Project Name: Sequoyah Nuclear Plant Drilling Date: 04/27/2004 Easting:' 2271512.24 Company Name: TVA Drilling Company: TVA Northing: 304752.93 Location: South of Unit #2 Reactor Bldg Drilling Method: Geoprobe Top of Casing (ft): 707.15 Well Depth (ft): 23.75 Top of. Ground (ft): 704.13 103

jc@

U T Sequoyah Nuclear Plant Boring ID: 31 E.

c Plezometer 0 Description Construction 0 >. " Diagram LU 705 0 I Bentonite 700 5 - -

695 10 690 Sand 15

- 685 18.34 20 -

_680 25 -

_ -- Bentonite 675 30 - - Sand Project Name; Sequoyah Nuclear Plant Drilling Date: 04127/2004 Easting: 2271378.74 Company Name: TVA Drilling Company: TVA Northing: 304648.84 Location: South of Unit #2 Reactor Bldg . Drilling Method: Geoprobe Top of Casing (ft): 706.54 Well Depth (ft): 32,33 Top of Ground (ft): 703.78

© 104

Sequoyah Nuclear Plant Boring ID: 32

>Plezometer 01

.2 .oDConstruction to ;5 Diagram 00 ~2 J DescriptionDira 705 0 ..

Bentonite 700 5.

Sand 695 10 690 15 -- -

685 20 Sand 22.69 Project Name: Sequoyah Nuclear Plant Drilling Date: 04/2812004 Easting: 2270878.28 Company Name: TVA Drilling Company: TVA Northing: 304584.83 Location: South of Unit #2 Reactor Bldg Drilling Method: Geoprobe Top of Casing (ft): 706.33 Well Depth (ft): 22.66 Top of Ground (ft): 704.12 105

i1 Sequoyah Nuclear Plant Boring ID: 33 DESTROYED 9 Plezometer Description Construction

• >Diagram 705 0 --

0- Bentonite 700 5

695 10 Sand 15 -690 15---

C-,

685 20 21.6 680 25 Bentonite i

-675 Sand 30 Project Name: Sequoyah Nuclear Plant Drilling Date: 04/28/2004 Easting: 2270925.57 Company Name: TVA Drilling Company: TVA Northing: 304501.21 Location: South of Unit #2 Reactor Bldg Drilling Method: Geoprobe Top of Casing (ft): 708-69 Well Depth (ft): 31.58 Top of Ground (ft): 704.25 106

ET Sequoyah Nuclear Plant Boring ID: -34 DO Plezometer 0" Description Construction a > Di Diagram 0 705 Bentonite 700 10 695 Sand 15 6690

.- a.

20 685 20 B 19.5 Sand 25 - 680 Project Name: Sequoyah Nuclear Plant Drilling Date: 04/28/2004 Easting: 2270791.36 Company Name: TVA Drilling Company: TVA Northing: 304405.10 Location: South of Unit #2 Reactor Bldg Drilling Method: Geoprobe . Top of Casing (ft): 708.11 Well Depth (ft): 25.65 Top of Ground (if): 704.8 107

Sequoyah Nuclear Plant Boring ID: 35

-c = Piezometer 0 .2 Construction C. 0 CI -- >* DescriptionDirm *Diagram 0

705 Bentonite 5

700 Sand 10-Z 6895 Bentonite 15 V 690 15.12 Sand 20 685 Project Name: Sequoyah Nuclear Plant Drilling Date: 04/28/2004 Easting: 2270740.52 Company Name: TVA Drilling Company: TVA Northing: 304591.02 Location: South of Unit #2 Reactor Bldg Drilling Method: Geoprobe Top of Casing (ft): 708.87 Well Depth (ft) 7 23.57 Top of Ground (ft): 705.78 108

UT Sequoyah Nuclear Plant Boring ID: GP-7A Plezometer 0 .2 DConstruction

> E- Diagram 06a0 DescriptionDarm fLu

-- 705 Very soft to soft 5

700 i Cl Bentonite 10 695 0 CL Soft 15 - i-690 (I-20 685 Sand 25

-- 680:: Soft - Moderate  :

Moderate Soft - Moderate 30 675 KStopped Bodnn at 31 ft /

Project Name: SON Tritium Investigation Drilling Date: 2/16/2007 Easting: 2271466.20 Company Name: TVA Drilling Company: TVA Northing: 305423.58 Location: North of Unit #1 Reactor Bldg Drilling Method: Geoprobe Top of Casing (ft): 708.75 Driller/Engineer: Ray Duncan/Matt Williams Well Depth (ft): 27.3 Top of Ground (ft): 706.05 109

if Sequoyah Nuclear Plant Boring ID: GP-7B c-Plezometer 0 .2 Construction 0

Q _2 E0 Z. r Diagram Lu 0

705 Bentonite 5 -

700 Ia

-- 695 C.)::i(

15 -- 20, Soft

-- 690:

Sand  :::

680 695 24.4 690 30 15 Mope S1ft Borina:::

685 Project Name: SQN Tritium Investigation Drilling Date: 2/14/2007 Easting: 2271461.11 Company Name: TVA Drilling Company: TVA Northing: 305425.78 Location: North of Unit #1 Reactor Bldg Drilling Method: Geoprobe Top of Casing (ft): 708.93 Driller/Engineer Ray Duncan/Matt Williams Well Depth (ft): 24.8 Top of Ground (ft): 705.93 110

Sequoyah Nuclear Plant Boring ID: GP-10

¢m Plezometer 0 .00 o Description Construction

> Diagram jJ_ _

710 0

Very Soft

,Soft 705 5 Very Soft Bentonite 700 10 Soft- Moderate 695 15 Moderate 690 Moderate - Hard C:

Sand  : o 20 685 25 680  :

Moderate 27.94 30 675 35 670 KBodnq terminated 40 Project Name: SQN Tritium Investigation ' Drilling Date: 2/1/2007 Easting: 2271866.70 Company Name: TVA Drilling Company: TVA Northing: 305237.90 Location: North of Unit #1 Reactor Bldg Drilling Method: Geoprobe Top of Casing (ft): 710.43 Driller/Engineer: Ray Duncan/Mat Williams Well Depth (ft): 30 Top of Ground (ft): 707.93 III

Sequoyah Nuclear Plant Boring ID: GP-13 c

- or Plezometer

. Description Construction

• -. Diagram zu 0 705 Soft 700 Moderate Bentonite 4 1o0 10 695 W Ho I>

15- Soft 15 690 20 - 685 Unknown Obstruction Sand

\Borinn terminated - Unknown Obstruction v 22.93 25 680 Project Name: SON Tritium Investigation Drilling Date: 21212007 Easting: 2271543.43 Company Name: TVA Drilling Company: TVA Northing: 305102.45 Location: North of Unit #1 Reactor Bldg Drilling Method: Geoprobe Top of Casing (ft): 708.34 Driller/Engineer: Ray Duncan/Matt Williams Well Depth (ft): 26.5 Top of Ground (ft): 705.34 0

112

UT Sequoyah Nuclear Plant Boring ID: GP-24

,-) Plezometer 0 Description Construction a0 . D pDiagram

_=uJ ii__

E 0 705 Moderate Bentonite 5 700 Soft U) 10 695 03

• 0 15 690 Hard Sand 20 685 23.04 25 680 kBorinq terminated at 27 ft Project Name: SQN Tritium Investigation Drilling Date: 2/7/2007 Easting: 2271204.28 Company Name: TVA Drilling Company: TVA Northing: 304744.01 Location: South of Unit #2 Reactor Bldg Drilling Method: Geoprobe Top of Casing (ft): 707.94 Driller/Engineer: Ray Duncan/Matt Williams* Well Depth (ft): 27 Top of Ground (ft): 704.94 113

APPENDIX B TRITIUM CONCENTRATIONS (pCi/L) FOR WELLS WITH MULTIPLE SAMPLES 114

Tritium Concentration (pC IlL)

Date W21 24 25 26 27 28 29 30 31 32 33 34 35 GP-13 08/12/03 <220 09/09/03 297 10/07/03 339 11/04/03 446 12/02/03 407 12/30/03 299 01/27/04 371 02/13/04 9,080 02/24/04 9,000 285 03/23/04 322 03/31/04 1,524 04/20/04 429 05/18/04 1,116 277 1,006 <220 17,833 <220 <220 <220 <220 06/15/04 1,138 293 07/13/04 598 <220 <220 <220 257 <220 08/02/04 961 <220 <220 <220 455 <220 1,034 <220 5,547 <226 <220 <220 <220 09/07/04 1,050 <220 <220 <220 447 <220 10/05/04 1,169 <220 <220 <220 334 <220 10/12/04 1,261 791 3,768 10/18/04 1,557 834 3,465 10/26/04 1,633 914 10/29/04 3,619 11/01/04 2,270 819 2,646 11/02/04 2,000 <220 <220 <220 385 <220 11/08/04 2,492 1,191 3,094 11/15/04 1,384 703 2,627 11/22/04 1,712 753 2,576 11/30/04 1,555 687 3,293 11/30/04. 2,216 <220 <220 <220 349 <220 12/06/04 226 466 8,552 12/13/04 586 606 7,053 12/20/04 1,715 932 5,052 12/27/04 1,954 622 7,306 01/04/06 1,386 1,008 7,110 0 1/10/05 1,947 1,027 5,938 0 1/17/05 739 546 11,172 01/24/05 2,178 1,239 9,841 01/25/05 1,426 <220 <220 <220 303 <220 01/31/05 526 554 10,780 02/08/05 1,323 584 7,707 02/14/05 427 702 5,600 02/21/05 1,242 761 7,486 02/22/05 1,216 <220 <220 <220 426 332 02/28/05 739 953 8,589 03/07/05 1,242 993 9,714 03/14/05 652 9,354 115

Tritium Concentration (pCI/U)

Date W21 24 25 26 27 28 29 30 31 32 33 34 35 . GP-13 03/21/05 2,763 <220 <220 <220 <220 <220 890 9,407 03/28/05 492 948 8,898 04/04/05 674 1,019 13,445 04/11/05 562 742 12,824 04/18/05 731 1,202 15,535 04/25/05 967 1,326 17,011 04/29/05 809 9,745 05/02/05 1,796 1,465 9,532 05/10/05 1,226 1,218 10,831 05/16/05 974 1,050 11,604 05/23/05 956 865 12,069 05/30/05 2,773 881 12,372 06/06/05 761 497 15,144 06/14/05 404 555 19,750 06/14/05 1,072 312 140 120 403 273 06/21/05 985 771 19,545 06/28/05 1,325 1,117 17,423 07/05/05 1,038 1,390 15,900 07/12/05 732 279 199 178 327 118 791 11,760 07/18/05 372 514 11,593 07/25/05 690 -1,235 11,495 08/01/05 1,447 1,224 10,199 08/09/05 732 138 100 104 277 194 860 10,446 08/15/05 941 866 10,928 08/22/05 905 1,197 9,915 08/29/05 1,945 1,177 8,968 09/06/05 1,024 159 88 83 263 187 1,254 8,706 09/19/05 1,139 869 7,765 10/04/05 1,497 814 6,523 10/17/05 1,146, 819 5,936 11/07/05 1,903 1,410 4,123 11/29/05 1,118 205 112 80 478 168 12/05/05 699 1,127 5,063 12/12/05 850 1,007 5,609 01/02/06 959 929 4,796 01/16/06 841 1,029 6,081 01/24/06 610 218 0 107 321 0 02/06/06 662 987 5,613 02/20/06 527 1,236 7,495 02/21/06 531 148 51 18 177 67 03/06/06 811 797 7,171 03/21/06 1,069 118. 7 0 203 21 03/27/06 1,537 1,040 9,551 04/03/06 630 1,170 11,780 04/10/06 558 <270 1,228 17,544 04/17/06 1,474 <270 1,049 10,645 116

Tritfulm Concentration (pCIIL)

IDate w21 24 25 26 27 28 29 30 31 32 33 34 35 GP.13, 04/18/06 968 235 <220 <220 245 <220 04/24/06 1,644 <270 1,097 10,293 04/27/06 1,208 <270 1,014 12,036 05/01/06 1,536 <270 1,255 12,055 05/04/06 758 <270 1,321 11,341 05/08/06 1,780 1,377 10,380 05/11/06 989 1,313 10,689 05/15106 2,059 1,479 11,763 05/18/06 2,264 1,356 12,734 05/23/06 763 <270 1,400 14,147 05/25/06 1,097 968 16,191 05/29/06 1,017 417 1,184 17,068 06/01/06 1,134 1,274 15,708 06/06/06 1,298 <270 1,119 13,955 06/08/06 1,320 1,215 13,529 06/12/06 1,494 <270 1,272 14,910 06/13/06 1,193 <270 <270 <270 <270 <270 06/22/06 1,604 1,221 13,531 06/30/06 1,130 <270 973 <270 13,100 <270 <270 07/03/06 1,365 1,226 12,974 07/07/06 1,369 346 1,223 12,981 07/11/06 1,371 <270 <270 <270 352 <270 07/11/06 1,197 1,231 12,074 07/13/06 1,325 <270 983 11,911 07/18/06 1,534 1,262 11,509 07/20/06 1,383 373 1,268 12,261 07/24/06 784 <270 938 12,560 07/31/06 1,067 <270 1,011 13,024 08/07/06 1,000 <270 904 10,907 08/08/06 997 <270 <270 <270 341 <270 08/14/06 1,169 <270 932 9,838 08/21/06 934 310 1,248 9,499 08/28/06 2,188 <270 1,061 8,636 09/05/06 1,251 <270 981 9,303 09/05/06 1,570 <270 <270 <270 364 <270 09/11/06 1,806 <270 1,332 8,787 09/21/06 998 317 1,347 8,203 09/26/06 455 <270 1,126 7,942 10/02/06 704 <270 1,205 7,845 10/03/06 1,276 <270 <270 <270 371 <270 10/17/06 312 484 984 5,701 10/25/06 570 <270 683 6,530 10/30/06 649 <270 1,182 7,307 10/31/06 844 <270 <270 <270 434 <270 11/08/06 621 <270 1,174 7,087 11/13/06 842 <270 1,144 5,583 117

Tritium Concentration (pCIIL)

.Date* W21.24 25 26 27 28 29 30 31 32 33, 34 35 GP-13 11/22/06 794 <270 1,140 4,861 11/28/06 799 <270 <270 <270 <270 <270 11/29/06 985 301 1,433 4,026 12/03/06 4,109 12/04/06 4,373 12/05/06 1,366 <270 1,169 4,456 12/06/06 4,892 12/07/06 4,619 12/08/06 4,528 12/09/06 5,632 12/10/06 6,107 12/11/06 7,124 12112106 1,545 <270 1,067 6,017 12/13/06 5,231 12/14/06 4,071 12/15/06 4,577 12/16/06 4,135 12/17/06 3,654 12/18/06 3,702 12/191906 1,510 <270 806 3,718 12120/06 3,904 12/21/06 3,983 12122106 5,156 12123/06 8,214 12124/06 9,922 12125/06 11,497 12126/06 1,540 <270 <270 <270 369 <270 12,199 12/27/06 1,526 <270 949 13,161 12128/06 13.766 12129/06 13,334 12130/06 13,592 12131/06 12,850 01/01/07 12,620 01/02/07 12,513 0 1/03/07 908 <270 790 12,909 01/04/07 12,702 01/05/07 13,110 01/06/07 10,809 01/07/07 10,137 1/8/107 9,236 01/09/07 474 <270 739 9,336 01/10/07 9,384 01/11/07 8,748 01/12/07 8,604 01/13/04 9,083 01/14/07 8,286 118

Tritium Concentration (pCIIL)

Date W21 24 25 26 27 28 29 30 31 32 33 34 35 GP-13 01/15/07 8,148 01/16/07 869 <270 1,024 8,245 01/17/07 9,445 01/18/07 9,354 01/19/07 8,990 01/20/07 10,047 01/21/07 10,763 01/22/07 407 <270 885 7,736 01/23/07 596 <270 <270 <270 <270 <270 <270 8,136 01/24/07 8,032 01/29/07 978 <270 763 9,373 02/02/07 16,211 02/05/07 859 330 945 9,581 02/12/07 1,196 <270 906 8,483 02/16/07 17,604 02/19/07 1,359 299 828 7,309 02/20/07 961 <270 <270 <270 <270 <270 02/27/07 2,513 <270 611 7,549 18,395 03/06/07 1,386 <270 699 10,929 17,648 03/13/07 2,219 <270 839 10,855 17,584 03/19/07 1,343 <270 869 10,034 15,063 03/26/07 1,376 697 9,943 13,720 0

119