iii CONTENTS

NOTATION ...................................................................................................................... ........ xi

ENGLISH/METRIC AND METRIC /ENGLISH EQUIVALENTS ........................................ xiv

SUMMARY ....................................................................................................................... ....... 1

1 INTRODUCTION .............................................................................................................. 5

2 TENORM WASTE STREAMS ......................................................................................... 7

2.1 Produced Water .......................................................................................................... 9

2.2 Scale ..................................................................................................................... ...... 10 2.3 Sludge and Filter Cake ............................................................................................... 10

2.4 Filter Socks .............................................................................................................. ... 10 2.5 Lead-210 Deposits in Gas Equipment ........................................................................ 10 2.6 TENORM-Contaminated Equipment ......................................................................... 11

2.7 TENORM-Contaminated Soils .................................................................................. 11 2.8 Synthetic Fracturing Proppant .................................................................................... 11

3 LANDFILL DISPOSAL AND POTENT IAL EXPOSURE SCENARIOS ....................... 13

3.1 Landfill Disposal ........................................................................................................ 13 3.2 Exposure Scenarios and Analysis ............................................................................... 16 3.2.1 Operational Phase Scenarios ............................................................................ 17 3.2.1.1 Well Site Operations Scenarios ......................................................... 17 3.2.1.2 Transportation Scenarios ................................................................... 19 3.2.1.3 Landfill Operations Scenarios ........................................................... 19

3.2.2 Future-Use Scenarios ....................................................................................... 20 3.2.3 Sensitivity Analysis ......................................................................................... 22

4 MODELING METHODOLOGIES .................................................................................... 23

4.1 Pathway Analysis Overview ....................................................................................... 23 4.2 Description of Risk Assessment Methodology .......................................................... 25 4.2.1 Methodology for Operational Phase Scenarios ............................................... 25 4.2.1.1 Well Site Operations ......................................................................... 25 4.2.1.2 Transportation ................................................................................... 25 4.2.1.3 Landfill Operations ........................................................................... 26 4.2.2 Methodology for Future-Use Scenarios ........................................................... 26 4.2.3 Calculating Maximum Allowable TE NORM Concentrations for Landfill Disposal ........................................................................................................... 27 4.3 Hydrologic Modeling ................................................................................................. 27 4.3.1 Landfill Hydrologic Modeling ......................................................................... 28iv CONTENTS (Cont.)

4.3.2 Hydrogeological Setting of a Ge neric Landfill and Model Parameter

Values .............................................................................................................. 29 4.3.3 Unsaturated Zone Modeling ............................................................................ 30 4.3.4 Groundwater Transport Modeling ................................................................... 30

4.3.4.1 The Distribution Coefficient and Retardation ................................... 30 4.3.4.2 Dispersivity ....................................................................................... 32

4.3.4.3 Groundwater Flow and Contaminan t Transport Code Selection ...... 32

5 HYDROLOGICAL MODELING RESULTS .................................................................... 35

5.1 Landfill Hydrologic Modeling ................................................................................... 35 5.2 Unsaturated Zone Flow and Transport ....................................................................... 41 5.3 Saturated Zone Flow and Transport ........................................................................... 41

5.4 Discussion of Results ................................................................................................. 44

6 DOSE AND RISK ASSESSMENT RESULTS ................................................................. 47

6.1 Well Site Operational Phase Scenarios ...................................................................... 47 6.1.1 Radiological Doses for Well Site Workers ...................................................... 47 6.1.2 Parameter Sensitivity Analyses fo r Well Site Operation Scenarios ................ 49 6.2 Radiological Dose from Accidental Public Exposure Scenarios ............................... 52

6.3 Future-Use Scenarios .................................................................................................. 54 6.3.1 Calculated Radiological Dose to Source Ratio for Future-Use Scenarios ...... 54 6.3.2 Results of Analysis for Different Radionuclides ............................................. 56

6.3.3 Estimated Allowable Concentr ations in the Landfill ....................................... 56 6.3.4 Parameter Sensitivity Analyses for Future-Use Scenarios .............................. 56 6.4 Radiological Dose and Risk from Transportation ...................................................... 58 6.4.1 Cargo-Related Doses and Risks ....................................................................... 58

6.4.2 Vehicle-Related Risks ..................................................................................... 60 6.5 Radiological Dose and Risk from Landfill Operations .............................................. 61 6.5.1 Waste Handling and Placement Operators ...................................................... 62 6.5.2 General Public Exposures Due to Landfill Operations .................................... 63 6.5.3 Leachate Management Workers ...................................................................... 63 6.5.4 Parameter Sensitivity Analyses for Landfill Operation Scenarios .................. 64 6.6 Summary of Dose and Risk Assessment Results ....................................................... 65 6.7 Calculating the Maximum Allowabl e Radium Concentration for TENORM Disposal in Landfills in North Dakota ........................................................................ 67

7 CONCLUSIONS AND RECOMMENDATIONS ............................................................. 71

7.1 Conclusions ............................................................................................................... . 71

7.2 Recommendations ...................................................................................................... 73v CONTENTS (Cont.)

8 REFERENCES .................................................................................................................. . 75

APPENDIX A: Radionuclide Analysis Data for TENORM Waste Samples Collected

in North Dakota ............................................................................................. A-1

APPENDIX B: Risk Assessment Data Tables ....................................................................... B-1

APPENDIX C: Landfill Designs Tested with the HELP Model ............................................ C-1

APPENDIX D: Literature Review of the Distribution Coefficient K d ................................... D-1

APPENDIX E: Groundwater Calculations ............................................................................. E-1

FIGURES

2.1 Histogram Illustrating the Distribution of the Ratio of Th-232 to Total Radium Activity Concentrations from All Samples Where Th-232 Was Measured ................. 9

3.1 Special Waste Landfills Permitted in North Dakota ..................................................... 16

4.1 Typical Radiation Exposure Leve ls for Common Activities ........................................ 24

5.1 HELP Model Results for the Closed I ndustrial Waste Landfill for Precipitation, Evapotranspiration, and R unoff over 100 Years ........................................................... 36

5.2 HELP Model Results for the Closed I ndustrial Waste Landfill for Percolation through the Compacted Soil of the Cap and through the Upper Geomembrane

Liner over 100 Years .................................................................................................... 37

5.3 HELP Model Results for the Closed I ndustrial Waste Landfill for Percolation through the Recompacted Liner Soil and th e Deep Natural Soil over 100 Years ........ 38

5.4 HELP Model Results for the Closed I ndustrial Waste Landfill with Decomposed

Geomembranes and an Inactive LCS for Percolation through the Cover’s Barrier Soil, the Recompacted Liner Soil, and th e Deep Natural Soil over 100 Years ............ 39

5.5 Hydraulic Heads, Landfill Location, and Receptor Locations at the Upgradient End of the Modeling Domain ....................................................................................... 42

5.6 Base Case Results for C/Co at 100 m over 10,000 Years for Each of the

ROCs Modeled.............................................................................................................. 45vi FIGURES (Cont.)

6.1 Steps Involved in Estimating the Allowa ble Concentration in the Landfill from

Future-Use Scenarios .................................................................................................... 55

6.2 Worker Dose for Receiving and Handli ng TENORM Wastes at the Landfill ............. 65

6.3 Worker Dose for Waste-Placement Activities at the Landfill ...................................... 66

D.1 Relationship between K d and Leached Fraction of Ra-226 Samples ........................... D-5

TABLES

2.1 North Dakota TENORM Waste Ch aracterization Data ................................................ 8

3.1 Large Volume Industrial Waste Landfill and Special Waste Landfills Permitted in

North Dakota in 2013 .................................................................................................... 15

4.1 Values Used To Model Radionuclide Concentrations in the Groundwater Downgradient of a Landfill ........................................................................................... 33

5.1 Summary of HELP-Model-Derived Percola tion Results for Industrial and Special

Waste Landfill Scenarios .............................................................................................. 40

5.2 Half-life and Rate Constant Values for Radionuclides of Concern .............................. 43

5.3 Maximum Ratio of Downgradient Gr oundwater Concentration to Leachate Recharge Concentration over 10,000 Years ................................................................. 46

6.1 Waste Streams Used in Evaluating Radi ation Dose in Different Worker and

Public Scenarios from We ll Site Operations ................................................................ 48

6.2 Estimated Maximum Dose Rate for Di fferent Well Site Operations Using Average Radionuclide Concentration ........................................................................... 48

6.3 Estimated Maximum Dose Rate for Di fferent Well Site Operations Using

Maximum Radionuclide Concentration ........................................................................ 49

6.4 Sensitivity Analyses for Well Site Operations Assuming Average Radionuclide

Concentrations in the TENORM Wastes ...................................................................... 50

6.5 PPE Sensitivity Analysis Results for We ll Site Operation Worker Scenarios ............. 51vii TABLES (Cont.)

6.6 Estimated Dose Rates for Maximum and Average Concentrations at Different Times for a Child Using Filter Socks as a Toy ............................................................. 52

6.7 Estimated Dose Rates for Maximum and Average Concentrations at Different Times for a City Dweller Exposed to Filter Socks in a Dumpster ................................ 53

6.8 Estimated Dose Rate for Maximum and Average Concentrations at Different Times for Proppant Used at a Playground .................................................................... 54

6.9 Summary Results for Dose to Source Ratio ................................................................. 56

6.10 Limiting Average Concentration Based on Future-Use Scenarios and Allowable

TENORM Concentrations at the 10 0-mrem/yr Dose Limit Assuming a

Two Meter-Thick Cover ............................................................................................... 57

6.11 Limiting Average Landfill Concentration and Limiting Scenario with Maximum DSR by Radionuclide ................................................................................................... 57

6.12 Cargo-Related Transportation Doses and Risks for Base Case and Maximum Case Conditions, Assuming a Transporta tion Distance of 250 km ....................................... 60

6.13 Vehicle-Related Transp ortation Risks for Base Case and Maximum Case Conditions, Assuming a Round-Trip Tran sportation Distance of 500 km ................... 61

6.14 Radiological Dose Associated with Landfill Disposal of TENORM under the

Base Case Scenario ....................................................................................................... 62

6.15 Allowable Total Radionuclide Activity and the Resultant Allowable TENORM Concentration at the 100-mrem/yr Dose Limit ............................................................. 63

6.16 Estimated Dose Rate from Evaporation Pond Operations ............................................ 64

6.17 Estimated Allowable TENORM Concentra tions Based on Future-Use Scenarios

and Landfill Worker Scenarios ..................................................................................... 67

6.18 Allowable Radionuclide Concentrations in the Waste Stream Disposed of at the

Landfill Based on Different Radionuclide Concentration Fractions in the Waste

Stream ........................................................................................................................ ... 69

A.1 Radionuclide Analysis Data for TENORM Waste Samples Collected in

North Dakota ................................................................................................................. A-3

B.1 RESRAD-BUILD Input Parameters Desc ribing Well Site Operations ........................ B-3viii TABLES (Cont.)

B.2 Input Parameters Describing Public E xposures to the Unauthorized Release of Filter Socks and Proppants ............................................................................................ B-6

B.3 TSD-DOSE Input Parame ters Describing Landfill Worker Operations for Disposing of Containerized Waste ................................................................................ B-7

B.4 TSD-DOSE Input Parameters Desc ribing Landfill Worker Operations for Disposing of Bulk Waste ......................................................................................... B-8

B.5 RESRAD-BUILD Input Parameters Describing Evaporation Pond Worker Operations .................................................................................................................... . B-9

B.6 Parameters Describing the Landfill Future-Use Scenarios ........................................... B-10

B.7 Parameters Used for the Tran sportation Risk Assessment ........................................... B-13

B.8 Conditional Accident Probabilities and Associ ated Release Fraction by Accident Severity Category .......................................................................................... B-14

C.1 Special Waste Landfill Design...................................................................................... C-3

C.2 Industrial Waste Landfill Design .................................................................................. C-4

D.1 Ra-226 Leached Fraction and K d of Samples Containing Ra-226 ............................... D-4

E.1 Calculations Relating Disposal Concen tration of Unity, Appropriate Range of

In-Landfill K d Values, Leachate Concentration Reaching Water Table, Downgradient Proportion of Leachat e Recharge, and Concentration in Groundwater for 100-m Downgradient Receptor and 20-m Thick Unsaturated

Zone .......................................................................................................................... .... E-3

E.2 Calculations Relating Disposal Concen tration of Unity, Appropriate Range of

In-Landfill K d Values, Leachate Concentration Reaching Water Table, Downgradient Proportion of Leachat e Recharge, and Concentration in Groundwater for 100-m Downgradient Receptor and 5-m Thick Unsaturated Zone ... E-4

E.3 Calculations Relating Disposal Concen tration of Unity, Appropriate Range of

In-Landfill K d Values, Leachate Concentration Reaching Water Table, Downgradient Proportion of Leachat e Recharge, and Concentration in Groundwater for 300-m Downgradient Receptor and 20-m Thick Unsaturated

Zone .......................................................................................................................... .... E-5ix TABLES (Cont.)

E.4 Calculations Relating Disposal Concen tration of Unity, Appropriate Range of

In-Landfill K d Values, Leachate Concentration Reaching Water Table, Downgradient Proportion of Leachat e Recharge and Concentration in Groundwater for 300-m Downgradient Receptor and 5-m Thick Unsaturated Zone ... E-6x This page intentionally left blank.xi NOTATION

The following is a list of the acronyms, initialisms, and abbreviations (including units of measure) used in this document.

ACRONYMS, INITIALISMS, AND ABBREVIATIONS

A&A Auxier and Associates, Inc.

Barr Barr Engineering

CEDE committed effective dose equivalent

DOE U.S. Department of Energy

DSR dose to source ratio

EDE effective dose equivalent EPA U.S. Environmental Protection Agency

Golder Golder Associates

HDPE high-density polyethylene HELP Hydrologic Evaluation of Landfill Performance

ICRP International Commissi on on Radiological Protection

K hydraulic conductivity

K d distribution coefficient

LCF latent cancer fatality LCS leachate collection system

LF leached fraction

LLW low-level radioactive waste

MEI maximally exposed individual

MODFLOW Modular Three-Dimensional Fini te-Difference Groundwater Flow Model MT3DMS Modular 3-D Multi-Species Transport Model

NCRP National Council on Radiation Protection and Measurements

NDAC North Dakota Administrative Code NDDH North Dakota Department of Health NDDOT North Dakota Department of Transportation NORM naturally occurring radioactive material(s)

NRC U.S. Nuclear Re gulatory Commissionxii PPE personal protective equipment

ROC radionuclide of concern

SD standard deviation

TCLP toxicity character istic leaching procedure TEDE total effective dose equivalent TENORM technologically e nhanced naturally occurri ng radioactive material TSD treatment, storage, and disposal

Wenck Wenck Associates, Inc.

RADIONUCLIDES

Pb-210 lead-210

Ra-226 radium-226

Ra-228 radium-228

Rn-222 radon-222

Th-232 thorium-232

U-238 uranium-238

UNITS OF MEASURE

cm centimeter(s)

cm 2 square centimeter(s)

cm 3 cubic centimeter(s)

d day(s)

ft foot (feet)

ft 2 square foot (feet)

ft 3 cubic foot (feet)

g gram(s) gal gallon(s)

h hour(s) ha hectare(s)

in. inch(es)xiii kg kilogram(s) km kilometer(s)

km 2 square kilometer(s)

L liter(s)

L 3 cubic liter(s) lb pound(s)

m meter(s)

M mass

m 2 square meter(s)

m 3 cubic meter(s) mg milligram(s) mi mile(s)

mi 2 square mile(s) mil one thousandth of an inch (0.0254 millimeter) mL milliliter(s) mm millimeter(s) mph mile(s) per hour mrem millirem(s)

pCi picocurie(s)

rem roentgen equivalent man

 R micro-roentgen

s second(s)

yd 3 cubic yard(s) yr year(s)xiv ENGLISH/METRIC AND METRIC /ENGLISH EQUIVALENTS

The following table lists the appropriate equivalents for English and metric units.

Multiply By To Obtain

English/Metric Equivalents

acres 0.4047 hectares (ha) cubic feet (ft 3 ) 0.02832 cubic meters (m 3 ) cubic yards (yd 3 ) 0.7646 cubic meters (m 3 ) degrees Fahrenheit (oF) –32 0.5555 degrees Celsius (oC) feet (ft) 0.3048 meters (m) gallons (gal) 3.785 liters (L) gallons (gal) 0.003785 cubic meters (m 3 ) inches (in.) 2.540 centimeters (cm) miles (mi) 1.609 kilometers (km) miles per hour (mph) 1.609 kilometers per hour (kph) pounds (lb) 0.4536 kilograms (kg) short tons (tons) 907.2 kilograms (kg) short tons (tons) 0.9072 metric tons (t) square feet (ft 2 ) 0.09290 square meters (m 2 ) square yards (yd 2 ) 0.8361 square meters (m 2 ) square miles (mi 2 ) 2.590 square kilometers (km 2 ) yards (yd) 0.9144 meters (m)

Metric/English Equivalents centimeters (cm) 0.3937 inches (in.) cubic meters (m 3 ) 35.31 cubic feet (ft 3 ) cubic meters (m 3 ) 1.308 cubic yards (yd 3 ) cubic meters (m 3 ) 264.2 gallons (gal) degrees Celsius (oC) +17.78 1.8 degrees Fahrenheit (oF) hectares (ha) 2.471 acres kilograms (kg) 2.205 pounds (lb) kilograms (kg) 0.001102 short tons (tons) kilometers (km) 0.6214 miles (mi) kilometers per hour (kph) 0.6214 miles per hour (mph) liters (L) 0.2642 gallons (gal) meters (m) 3.281 feet (ft) meters (m) 1.094 yards (yd) metric tons (t) 1.102 short tons (tons) square kilometers (km 2 ) 0.3861 square miles (mi 2 ) square meters (m 2 ) 10.76 square feet (ft 2 ) square meters (m 2 ) 1.196 square yards (yd 2 )1 RADIOLOGICAL DOSE AND RISK ASSESSMENT OF LANDFILL DISPOSAL

OF TECHNOLOGICALLY ENH ANCED NATURALLY OCCURRING RADIOACTIVE MATERIALS (TEN ORM) IN NORTH DAKOTA

by

Christopher B. Harto, Karen P. Smith, Sunita Kamboj, and John J. Quinn

SUMMARY

Some of the waste streams generated by the oil and gas sector in North Dakota contain naturally occurring radi oactive materials (NORM) in con centrations above background. In North Dakota, these materials are referred to as technologically enhan ced NORM (TENORM). If these wastes are not properly managed, they can potentially present unacceptably high human

health risks. The North Dakota De partment of Health (NDDH) is considering possible changes to North Dakota Radiologic Health Rules and Solid Waste Management Rules regarding TENORM. The NDDH is taking steps to ensure that any possible ru le changes regarding handling and disposal of TENORM are protective of human health and the environment. Argonne National Laboratory (Argo nne) has conducted a radiological dose and risk assessment of the disposal of TENORM wastes in permitted Industrial Waste and Special Waste Landfills in

North Dakota.

The risk assessment evaluated the radiologi cal doses associated with a number of scenarios associated with oil and gas well site operations, improperly managed wastes, transportation of TENORM, and disposal of TENORM in Industrial Waste and Special Waste Landfills permitted in North Dakota. Limited characterization data are available for most of the TENORM waste streams generated in North Da kota by oil and gas operations. The study was designed to minimize its reliance upon specific wa ste characterization data. For the well site worker and public accidental expos ure scenarios, potential doses we re calculated on the basis of both the average and maximum radionuclide concentr ations for specific waste types relevant to the scenario, the latter providing conservatively high dose estimates. For th e landfill worker and future use-scenarios, the study was designed to calculate the maximum allowable radionuclide concentrations that could be pr esent in landfilled wastes such that potential doses would not exceed the 100-mrem/yr dose limit recommended fo r members of the general public by the

International Commission on Ra diological Protection (ICRP).

The primary TENORM waste streams of concern from oil and gas wells in North Dakota include scale accumulated within pipe and other oilfield equipment, sludge accumulated in produced water storage tanks and vessels, filter cake from filtration of water, disposable filter socks, and some synthetic fract uring proppants that have been found to contain low levels of

TENORM. These wastes were found to contain el evated levels of the radionuclides radium-226 (Ra-226), radium-228 (Ra-228), lead-210 (Pb-2 10), and thorium-232 (Th-232). A total of 119 waste samples were analyzed by the NDDH, although not all radionuclides were measured for all samples (more details on the waste ch aracterization can be found in Section 2 and2 Appendix A). Many previous TENORM risk assessm ent studies did not in clude thorium because of the lack of data. In addition, state regul ations for TENORM and NORM disposal typically impose limits based upon total radium (Ra-226 plus Ra-228) activity con centrations. This study recommends similar limits, taking into consideration the presence of Th-232 and the relative

concentrations of Th-232 and total radi um in the waste samples measured.

Pathway analysis computer codes were used to estimate doses for both workers and members of the general public. These code s included the RESRAD-BUILD, RADTRAN, TSD-DOSE, and RESRAD. A wide range of exposure scenario s were evaluated. The risks associated with a number of specific well si te operations were estimated, including mixing hydraulic fracturing fluid, produ ced water filtration, pipe cl eaning, storage tank cleaning, equipment cleaning at a gas processing plant, an d sludge treatment. In all scenarios except the produced water filtration scenario, it was assu med that workers were equipped with personal protective equipment (PPE) (e.g., respirators, eye protection, and gloves). The maximum dose calculated, assuming average waste activity conc entrations, was 20 mrem/yr for the worker involved in mixing hydraulic fracturing fluid. However, when maximum radionuclide concentrations were assumed, the dose for work ers engaged in pipe cl eaning was 130 mrem/yr, and the dose for storage tank cleaners was 70 mrem/y r. When the sensitivit y analyses were run, assuming workers were not equipped with PPE, the estimated dose for a number of the scenarios approached or exceeded the 100 mrem/yr level. Thes e results suggest that it may be important to monitor and limit the duration of exposure fo r workers involved in pipe and storage tank cleaning activities and that the use of proper PPE is important to protect workers with regular exposure to TENORM.

Risk to the public from improper waste disp osal was estimated for three scenarios. The first involved a child playing with a used filte r sock, the second involved a load of filter socks being disposed of in an urban dumpster, and the third involved a child playing in a pile of spilled synthetic proppants. The maximum dose calculated, assuming maximum radionuclide concentrations, was 4.9 mrem/yr for the individual e xposed to the filter socks disposed of in an urban dumpster. When average concentrations were assumed, the estimated dose dropped below 1 mrem/yr. Assuming maximum concentrations, th e dose for a child playing with a used filter sock was less than 1 mrem/yr, while the dose for a child playing in a field where proppants were illegally dumped was less than 2 mrem/yr. While these few scenarios seem to indicate that the risks to the public are likely relatively low from short-term exposure to waste that is improperly disposed of, they are not repres entative of all possible exposures . Extra care should be taken to ensure that such exposures do not occur.

The routine cargo-related doses and risks from transportation were estimated for a truck

driver and an individual livi ng near the landfill. The maximu m doses to drivers and to any member of the public were found to be about 20 mrem/yr and 3.2 × 10 -6 mrem/yr, respectively. Since these doses are quite small compared with the 100-mrem/yr recommended dose limit, the transportation of TENORM does not appear to be a major consideration in possible rule changes regarding TENORM disposal. Moreover , the maximum collective doses to persons living along and sharing the tran sportation corridor for routine and accident conditions were

1.3 × 10 -4 person-rem/yr and 7.2 person-rem/yr, respectiv ely. It should be noted that the risk of3 getting involved in a fatal transportation accident is at least 100 times grea ter than that of the driver contracting a latent fatal cancer associated with the TENORM shipment.

Landfill disposal scenarios considered both worker and public exposures during operation of the landfill, as well as possibl e exposures to future users of the land post-closure. Exposure to landfill workers involved with receiving and handling waste, transporting waste within the landfill, and waste placement were all analyzed. Fi ve future-use scenarios were also evaluated: (1) a residential-use scen ario, in which a resident is assume d to construct a house on top of the landfill, use the surrounding area for growing cr ops, and obtain drinking and irrigation water from an on-site well; (2) an industrial-use scen ario, in which the land encompassing the landfill is used for industrial purposes; (3 ) a recreational-use scenario, in wh ich the landfill is turned into a recreational area; (4) an intruder scenario, in which a resident on the landfill site accidentally uncovers the buried wastes and disperses the mate rial around his or her pr operty; and (5) an offsite groundwater-use scenario, in which an off-s ite resident obtains wa ter from a well drilled downgradient of the landfill. For the groundwater-use scenario, inf iltration and percolation rates were modeled using the Hydrologic Evalua tion of Landfill Performance (HELP) model.

Groundwater flow and contaminant trans port were modeled using the Modular

Three-Dimensional Finite-Di fference Groundwater Flow Mode l (MODFLOW) and the Modular 3-D Multi-Species Transport Model (MT3DMS).

For landfill disposal, the analyses were r un to calculate the maximum average waste activity concentration for each radionuclide that could be disposed of in the landfill while ensuring that potential doses to all receptors did not exceed 100 mrem/yr during either landfill operations or during future use of the landfill property. The results showed that potential exposures to landfill workers are more restrictive than potential expos ures related to future use of the landfill, in terms of the maximum TENORM con centrations that can be disposed of in the landfill safely. The workers involved in receiv ing and handling or waste placement activities received the highest estimated dose. Decreasi ng the volume of TENORM wastes that can be disposed of per year in a single landfill could effectively reduce doses to all landfill workers. Alternatively, potential doses could be reduced by limiting the number of hours that workers are exposed to the TENORM wastes.

On the basis of the hydrologic modeling and the dose assessment results, disposal of

TENORM wastes in both Industrial Landfills an d Special Waste Landfills is appropriate provided restrictions are placed on the averag e waste activity concentration, waste volumes disposed per year, and the dept h of the TENORM wastes within the landfill. North Dakota regulations may be modified to allow TENORM wastes containing an average concentration of less than or equal to 50 pCi/g of total radium (independent of background radium levels) to be disposed of in either Industrial Landfills or Special Wastes Landfills, provided the following

conditions are met:

• No more than 25,000 tons of TENORM wa stes are disposed of in a single landfill per year.4 • The average thorium activity concentration in the waste does not exceed 24 pCi/g. (This concentration assumes a thorium to radium ratio of 49% at 50 pCi/g total radium.)

• TENORM wastes must be covered by at least 2 m (6 ft) of a combination of

the landfill cover materials and clean wa stes that do not c ontain radionuclides.5 1 INTRODUCTION

Some of the waste streams generated by the oil and gas sector in North Dakota contain naturally occurring radio active materials (NORM) in concen trations above natural background levels of radionuclides. In North Dakota, thes e materials are referred to as technologically enhanced NORM (TENORM). If these wastes ar e not properly managed, they can potentially present unacceptably high human health risks. The international petroleum industry uses a variety of methods to ensure the safe management and disposal of these wastes. The North Dakota Department of H ealth (NDDH) is considering po ssible changes to North Dakota Radiologic Health Rules and Solid Waste Ma nagement Rules regarding TENORM. The NDDH is taking steps to ensure that any possible ru le changes regarding ha ndling and disposal of TENORM are protective of human health and the e nvironment. As part of this effort, the NDDH requested that Argonne National Laboratory (Argonne) conduct a ra diological dose and risk assessment of the disposal of TENORM wastes in permitted Industrial Waste and Special Waste

Landfills in North Dakota.

This report presents the results of Argonne ’s radiological dose a nd risk assessment. Specifically, it presents results associated with the following:

• Worker exposures to TENORM wastes associated with well site operations,

• Accidental public exposu res associated with improperly managed well site operation wastes (e.g., filter socks) and materials (e.g., proppants),

• Worker and public exposures associat ed with transportation of TENORM wastes to landfills, and

• Worker and public exposures associat ed with TENORM disposal Industrial and Special Waste Landfills permitted in North Dakota.

In addition, this report presents informati on supporting these dose and risk assessments. The document is organized as follows:

• Section 2 presents information de scribing the TENORM waste streams generated by the petroleum industry in North Dakota;

• Section 3 presents information about landfill disposal , including design criteria for permitted Industrial Waste and Special Waste Landfills in North Dakota and assumptions used to define the well site and landfill exposure scenarios;

• Section 4 presents the models and met hods used to assess (1) the fate and transport of TENORM, including m odeling of the subsurface hydrologic regime, and (2) radiological dose and risk;6 • Section 5 presents the results of the hydrologic modeling;

• Section 6 presents the results of the ra diological dose and risk assessments;

• Section 7 presents conclusions and recommendations;

• Appendix A presents the radionuclide analysis data for TENORM waste samples collected in North Dakota;

• Appendix B presents parameter values used in the dose and risk assessment models; and

• Appendices C through E present various groundwater-related data and results.7 2 TENORM WASTE STREAMS

Some oil and gas production and development activities can cause NORM to accumulate

in certain waste streams in concen trations above background. This ma terial is often referred to as TENORM to distinguish it from ot her forms of NORM that are not by-products of some form of processing. The State of North Da kota uses the term TENORM in its regulations. This section describes the TENORM waste generated by oi l and gas operations in North Dakota.

In the United States, the sources for elev ated TENORM levels are uranium-238 (U-238) and thorium-232 (Th-232), which are naturally pr esent in underground formations from which oil and gas are produced. The primary radioisotopes of concern in petrol eum industry wastes are radium-226 (Ra-226) and radium-228 (Ra-228), wh ich result from the radioactive decay of U-238 and Th-232, respectively, and their associ ated decay products. The primary radionuclide of concern (ROC) for the gas industry is lead-210 (Pb-210), which forms a scale inside the pipes and equipment containing natural gas. Pb-210 is a decay product of gaseous radon-222 (Rn-222), which comes from the radioactive decay of Ra-226.

The oil and gas waste streams known to potentially contain elevated TENORM

concentrations include:

1. Produced water, which is formation wa ter that is brought to the surface along with the produced oil and gas;

2. Scale, which is a hard, insoluble de posit that accumulates on the inside surfaces of the equipment used at produc tion facilities, and solid debris that comes in contact with produced water;

3. Sludge, which is a slightly granular , usually hydrocarbon- rich deposit that accumulates in the bottom of some storage and process vessels;

4. Filter cake, which is material collected inside filters used to remove particulates from produced water and fl owback water or from treating other oilfield wastes to remove liquids for sale or disposal; and

5. Disposable filter socks, which are used to filter particulates out of produced water prior to transport and disposal.

Production and processing equipment that contai n residual quantities of theses wastes and soils that have been impacted by theses wastes also create a TENORM waste management issue if radionuclide concentrations are high enough to present a human health risk. In addition, some synthetic proppants used during we ll fracturing activities are know n to contain low levels of activity, thus presenting another source of potential exposure. The following sections provide more detailed descriptions of each of these TENORM waste streams. Waste streams explicitly included in the scope of the worker and public ex posure risk analysis include scales, sludges and filter cake, filter socks, natural gas processing equipment, and proppants.8 For this study, the NDDH worked with indus try partners to collect data on activity concentrations from typical TENORM waste streams generated in the state. Table 2.1 summarizes the average, median, minimum, and maximum activity concentr ations for the four radionuclides evaluated (Ra-226, Ra-228, Pb-210, and Th-232), along with the number of samples for each waste type. The analytical resu lts supporting the summary data in Table 2.1 are presented in Appendix A. The number of samp les varied by radionuclide for a given waste stream, since not all radionuclides were measured for all samples. While all samples included Ra-226 and Ra-228, other radionuclides, such as Th-232 and Pb-210, were only measured for a subset of the samples.

Previous TENORM risk assessment studies ha ve not typically incl uded thorium because

of a lack of data. In addi tion, state regulations on TENORM and NORM disposal generally impose limits based upon total radium (Ra-226 + Ra-228) activity concentrations. However, given that the data provided showed the presence of Th-232 in a large number of waste samples,

it was included in this analysis. Figure 2.1 shows the distribution of the ratio of Th-232 activity concentration measured in each sample to the to tal radium concentration. The average value for

TABLE 2.1 North Dakota TENORM Waste

Characterization Data

Type of Waste Scale Sludge a Filter Sock Proppant

Average Ra-226 (pCi/g) 548 58.3 32.8 8.2 Median Ra-226 (pCi/g) 134 24.5 6.9 8 Minimum Ra-226 (pCi/g) 9.4 2 0.9 1.8 Maximum Ra-226 (pCi/g) 4,710 1,230 374 9.1 Number of samples 38 57 18 6

Average Ra-228 (pCi/g) 332 15.4 13.8 9.9 Median Ra-228 (pCi/g) 66.2 9.7 5.6 9.8 Minimum Ra-228 (pCi/g) 2.6 0.5 2.4 3.1 Maximum Ra-228 (pCi/g) 3,590 66.3 130 11.2 Number of samples 38 57 18 6

Average Pb-210 (pCi/g) 5,270 67.2 36.9 8.5 Median Pb-210 (pCi/g) 5,270 31.1 5 8.6 Minimum Pb-210 (pCi/g) 5,270 2.1 3.5 6.2 Maximum Pb-210 (pCi/g) 5,270 318 70 9.74 Number of samples 1 7 17 6

Average Th-232 (pCi/g) 71.7 17.2 12.7 9.1 Median Th-232 (pCi/g) 40.3 9.4 12.7 9.2 Minimum Th-232 (pCi/g) 6.5 2.1 6.5 8.1 Maximum Th-232 (pCi/g) 460 97.5 18.9 10.2 Number of samples 27 50 2 6

a Filter cake is assumed to have a similar composition to sludge.

Sources: Radig (2013a, 2014a–c); Poppke (2014).9 FIGURE 2.1 Histogram Illustrating the Distribut ion of the Ratio of Th-232 to Total Radium Activity Concentrations from All Samples Where Th-232 Was Measured

this ratio was 0.31, with a standard deviation (SD) of 0.18 and a maximum value of 0.94. This ratio was used to help estimate acceptable wa ste acceptance criteria based upon total radium

concentrations.

2.1 PRODUCED WATER

The production of formation water is one of the primary mechanisms for bringing TENORM radionuclides to the surface where they can become waste management and worker protection issues. The radionucli des found in produced water gene rally include Ra-226, Ra-228 and their decay products; elemen tal uranium and thorium typically have not been found in produced water in the United States. Radium, whic h is more soluble than either uranium or thorium, can be mobilized in formation water and transported to the surface in the produced water stream. As the produced wa ter is brought to the surface, some of th e dissolved radium precipitates out in solid form, either in scales or sludges. Some portion of the radium, however, remains in solution in the produced water stream . The majority of produced water generated in the United States is disposed of in saltwater disp osal wells. This waste stream was excluded from 0 5 10 15 20 25 30

0.100 0.200 0.300 0.400 0.500 0.600 0.700 More#ofSamples

Ratio of Th 232 to Total Radium Activity Concentration10 this risk assessment, except for activities associated with produced water filtration at the well site. Throughout this report, the term produced water is used to encompass all water that is produced from the well, including flowback wate r which is produced in the first few days following well treatment (e.g., hydrofracturing).

2.2 SCALE

In the United States, scale deposits that accumulate inside production and processing equipment and on solid debris (e.g., sand grains) that comes in contact with produced water typically take the form of hard and relatively insoluble deposits of barium sulfate (BaSO 4 ) or strontium sulfate (SrSO 4 ). When in solution in the produced wa ter, the radium can co-precipitate with the sulfate scales. These radium-bearing scales become a waste management issue when they are removed when equipment is serviced and cleaned.

2.3 SLUDGE AND FILTER CAKE

TENORM-contaminated sludges can accumulate in the bottom of vessels that are used to store or otherwise manage produced water, incl uding water storage tanks, oil/water separators, and heater treaters. Sludges typically are composed of solid debris, such as sand, scale, or rust particles, that settle out of the production stream. The primary ROCs in sludges in the United States are Ra-226, Ra-228, and their decay products, although data obtained from

North Dakota indicate that Th-232 may be present as well. Typica lly, the radium takes the form of a co-precipitate with sulfate or carbonate deposits. In addition, f ilters that are used to separate particulates from produced water ge nerate a solid waste referred to as filter cake. This material is likely to have a similar composition to the sludg e that is removed from produced water storage and handling equipment.

2.4 FILTER SOCKS

Disposable filter socks are used to filter pa rticulates out of pro duced water prior to transport and disposal. These filters accumulate sludges and scales over time and must be changed and disposed of on a regular basis. In the past year, the improper di sposal of these filter socks has become a major problem in the State of North Dakota (Donovan 2014a,b). This assessment evaluated potential risks to workers th at handle filter socks and to the general public resulting from accidental exposures to filter so cks that have been improperly disposed of.

2.5 LEAD-210 DEPOSITS IN GAS EQUIPMENT

Thin films of Pb-210 may accumulate on th e inside surfaces of gas production and processing equipment. The source of the Pb-210 is considered to be gaseous Rn-222, which is a component of natural gas from many formations . The Pb-210 may be present in elemental form, as a chemical precipitate, or as an integrated constituent of the equipment metal. When compared11 with published information on radium-bearing TENOR M wastes, very little information has been published characterizing petroleum industry wastes containing Pb -210. The NDDH did not collect data describing Pb-210 cont amination at gas facilities in North Dakota. For this waste stream, data collected for a pr evious Argonne analysis were us ed. That study found an average concentration of 260 pCi/g and a maximum c oncentration of 10,000 pCi/g for Pb-210 in gas processing equipment (Smith et al. 1999).

2.6 TENORM-CONTAMINATED EQUIPMENT

Production and processing equipment thatcontain residual quantities of TENORMcontaminated water, scales, sludges, or film s can present a waste management problem if radionuclide concentrations are high enough. TENOR M-contaminated equipment that cannot be easily cleaned (e.g., wellhead filters, valves, or screens), or is otherwise ready for disposal at an approved disposal facility (e.g., equipment that is no longer functional), must be managed appropriately. Data describing the potential volume of this waste stream have not been collected

in North Dakota. This waste stream was not in cluded in the scope of this risk assessment.

2.7 TENORM-CONTAMINATED SOILS

Soils that have been impacted by TENORM- contaminated wastes, such as produced water, scales, or sludges, can present a waste management problem if radionuclide concentrations are high enough. Soils may become contaminat ed through the intentional application or accidental release of contaminated wastes. For exam ple, the practice of disposing of oily wastes by landspreading can inadvertently result in the distri bution of TENORM wastes across the affected soils. Similarly, soils in unlined or leaking dis posal pits can become contaminated with TENORM. Overall, contaminat ed soils will likely represent only a small portion of the total TENORM waste stream (Radig 2013a). As a result, this waste stream was not included in the scope of this risk assessment.

2.8 SYNTHETIC FRACT URING PROPPANT

A proppant is a solid material, treated sand, or man-made ceramic material designed to keep an induced hydraulic fract ure open during or following a fracturing treatment. Some synthetic fracturing proppants, which consist of small, ceramic beads made from bauxite, have

been shown to contain low levels of radioac tivity. While these materials are not currently regulated as radioactive material , proppant that has been spille d or becomes unusable is a solid waste and may need to be disposed of as radioactive waste. The total quantity of proppant that might need to be disposed of is not currently known but is thought to be a small fraction of the total TENORM waste stream. The disposal of this waste stream in landfills was not included in the scope of this risk assessment; however, acci dental general public e xposures to improperly managed proppants were included.12 This page intentionally left blank.13 3 LANDFILL DISPOSAL AND POTENTIAL EXPOSURE SCENARIOS

This section provides a general description of the two differe nt landfill designs evaluated in this risk assessment, as well as the well site and landfill exposure pathways that were

evaluated.

3.1 LANDFILL DISPOSAL

Landfills are used to dispose of a wide vari ety of wastes, and, typically, the degree of engineering control increases with the hazard leve l of the wastes. Landfills are categorized by the types of waste streams that can be accepted for disposal; regulatory requirements vary by landfill category. In general, waste disposal in properl y constructed landfills that are equipped with liners, a leachate collection system (LCS), a nd other active and passive institutional controls provides a high degree of isolation from humans and the environment. In the United States, a variety of petroleum industry wastes are disposed of in landfills, usually in landfills designed and regulated for industrial wastes, or specifically for petroleum industry wastes. These wastes include scales, sludges, contaminated soils, ex cess equipment, and other solid debris. TENORMcontaminated wastes also are disposed of in landfills; however, this practice is typically limited to disposal in landfills specifically license d for either TENORM or regulated low-level radioactive wastes (LLW). The costs associated with disposal in these types of landfills are generally quite high, because the higher costs in curred in the United State for constructing and operating licensed TENORM or LL W disposal facilities are passed on to the customers. One state (Michigan) allows the disposal of soli d waste and debris contai ning an average Ra-226 concentration less than or equal to 50 pCi/g in landfills permitted to accept nonhazardous municipal wastes, which translates into lower costs (Michigan Department of Environmental Quality 2007).

In North Dakota, the landfill types evaluated in this study included Small Volume Industrial Waste Landfills and Special Waste Landfills (“Special Waste Landfills”) and Large Volume Industrial Waste and Municipal Soli d Waste Ash Landfills (“Industrial Waste Landfills”), which differ in design requirements specified by the North Dakota Administrative

Code (NDAC) (2014). North Dakota regulations do not currently allow the disposal of radioactive wastes in either of these two landfill types.

The rules for Small Volume Industrial Waste Landfills and Special Waste Landfills (NDAC; Chapter 33-20-07.1) (“Special Waste Landf ills”) pertain to oilfield special waste (Radig 2013a). These landfills require a composite liner consisting of at least 1 m (3 ft) of recompacted clay with a hydrauli c conductivity (K) less than 1 × 10 -7 cm/s (3 × 10 -9 ft/s) overlain

with a flexible membrane liner with a thickness of at least 1.5 × 10 -3 m (60 mil). A drainage layer above the liner must have a K exceeding 1 × 10 -3 cm/s (3.3 × 10 -5 ft/s) and a sufficient thickness to provide a transmissiv ity of at least 3 × 10 -2 cm 2 /s (3.2 × 10 -5 ft 2 /s). The liner and the LCS must maintain their integrity during the operational period and the pos t-closure period. The final cover of the landfill must include a bottom layer of compacted soil with a K less than 1 × 10 -7 cm/s (3.3 × 10 -9 ft/s), at least 0.5 m (1.5 ft) th ick; a clay-rich soil, suitable as a plant root zone, at least14 0.3 m (1 ft) thick, and at least 0.15 m (0.5 ft) of topsoil. During the operational phase, the liners and LCS must collect at least 90% of the precip itation that falls on the landfill and must be capable of removing leachate to limit the hydraulic head above the upper liner to 0.3 m (1 ft) or less. At closure, landfills must be revegetated with a mixture of adapted native grasses to minimize erosion and promote evapotranspiratio n of rain and snowmelt, thus helping to minimize infiltration. During post-closure, the final cover and liner system must collect or reject 98.5% of the precipitation. The post-closur e period is a minimum of 30 years (NDAC; Chapter 33-20-04.1-09(5)(b)).

Large Volume Industrial Waste and Municipal Solid Waste Ash Landfills (NDAC; Chapter 33-20-10) (“Industrial Waste Landfills”) require a double liner and LCS. The bottom composite liner must be at least 1 m (3 ft ) of recompacted clay with a K less than

1 × 10 -7 cm/s (3.3 × 10 -9 ft/s) overlain with a flexible membrane liner with a thickness of at least

1.5 × 10 -3 m (60 mil). Above this is the lower dr ainage layer with a K exceeding 1 × 10 -3 cm/s (3.3 × 10 -5 ft/s) and a sufficient thickness to prov ide a transmissivity of at least 3 × 10 -2 cm 2 /s (3.2 × 10 -5 ft 2 /s). Above the lower drainage layer, the second liner is a flexible membrane liner

with a thickness of at least 2.0 × 10 -3 m (80 mil), above which is th e upper drainage layer with a K exceeding 1 × 10 -3 cm/s (3.3 × 10 5 ft/s) and a sufficient thickness to provide for a transmissivity of at least 3 × 10 -2 cm 2 /s (3.2 × 10 -5 ft 2 /s). A leachate detection and removal system must be included, and an impoundment to contain leachate may be required by the state. The final cover of the landfill must be at least 2.4 m (8 ft) thick, including a composite cover consisting of a bottom layer of comp acted soil with a K less than 1 × 10 -7 cm/s (3.3 × 10 -9 ft/s) at least 0.6 m (2 ft) thick overlain with a flexible membrane liner with a thickness of at least

1.5 × 10 -3 m (60 mil). Above this is a drai nage layer with a K exceeding 1 × 10 -3 cm/s (3.3 × 10 -5 ft/s) and a sufficient thickness to provide for a transmissivity of at least 3 × 10 -2 cm 2 /s (3.2 × 10 -5 ft 2 /s). Above the drainage layer is a soil layer at least 1 m (3 ft) thick to protect the bottom barrier from freezing. The upper 0.3 m (1 ft) of this layer must be suitable as a plant root zone. The top layer must be at least 0.15 m (0.5 ft ) of topsoil. During the operational phase, the

liners and LCS must collect at leas t 97% of the precipitation that fa lls on the landfill and must be capable of removing leachate to limit the hydraulic head above the upper liner to 0.3 m (1 ft) or less within 36 hours of a precipita tion event. During post-closure, the final cover, liner system, and LCS must collect or reject 99.9% of the precipitation th at falls on the landfill. The post-closure period is a minimum of 30 years (NDAC; Chapter 33-20-04.1-09(5)(b)).

Table 3.1 describes the six landfills permitted in 2013 in North Dakota holding permits as Large Volume Industrial Waste or Special Wast e Landfills. The locations of these and other Special Waste Landfills are shown in Figure 3.1. On e landfill, Chimney Butte , has an alternative final cover system consisting of an evapotranspi rative cover of 1.5 m (5 ft) of uncompacted soil (Radig 2013b). Average dimensions of these land fills are used to define the generic landfill evaluated in this study. These average values in clude a total size of 19 ha (46 acres), a waste thickness of 38 m (125 ft), a total volume of 3,600,000 m 3 (4,700,000 yd 3 ), and a life expectancy of 18.8 years. Per Radig (2013c), the total volume of TENORM wastes that would be shipped to a single landfill per year was assumed to be 25,000 tons.

Rules for Surface Impoundment Provisions (NDAC; Chapter 33-20-08.1) would be in effect for landfill LCSs that manage leachate on- site. New impoundments are required to have a15 TABLE 3.1 Large Volume Industrial Waste Landfill and Special Waste Landfills Permitted in

North Dakota in 2013

Total Size Maximum Waste Thickness Total Volume Expected Life

Landfill Name Landfill Type (ha) (acre) (m) (ft) (m 3 ) (yd 3 ) of Facility (yr)

Clean Harbors –

Cell D Large volume

industrial waste 19 47 32 ~105 2,973,000 3,889,000 13.0

Marquis Alliance

– 13 Mile Special waste 19 48 51 ~ 168 3,742,000 4,895,000 22.0

Nuverra – Ideal Special waste 7.6 18.9 30 ~100 1,332,000 1,741,840 8.7

Section 18 – Chimney Butte Special waste 31 76.2 38 ~ 126 7,397,000 9,674,891 30.0

Tervita – Blue

Buttes Special waste 24 59 26 ~ 85 3,809,000 4,981,450 23.2

WISCO Special waste 10 25.5 50 ~165 2,447,000 3,200,000 16.0

Source: Radig (2013c).

liner of at least 1.2 m (4 ft) of compacted soil with a K less than 1 × 10 -7 cm/s (3.3 × 10 -9 ft/s), or

a combination of a soil liner and/or flexible li ner to control the migra tion of waste during the impoundment’s operational period and, for impound ments closed with solid waste in place, during the post-closure period. At closure, two options are available for an impoundment. One is to remove standing liquids, waste, waste residu es, liners, any leak de tection system, and any underlying or surrounding contaminated soil. This would be followed by regrading and restoration. The other option is to treat liquids, residues, and so ils by removal of liquids, drying, or other means and then provide post-closur e care under Industrial Waste Landfill rules.

At several landfills in North Dakota, leachate is managed w ithin evaporation ponds that typically have a composite liner. Any TENORM that mobilizes into the leachate will accumulate within these evaporation ponds over time a nd will either result in increasing TENORM concentrations within the aqueous phase or fo rm precipitates or scal e at the bottom of the evaporation ponds. Furthermore, the use of fans or spray systems to enhance the evaporation rate from the ponds may result in the formation of aerosols containing TENORM, which may travel downwind of the ponds. Radig (2014d) describe d impoundments used as leachate evaporation ponds. They range in size from 0.3 to 2 ha (0.8 to 5 acres) (most are 0.6 to 1 ha, or 1.5 to 2.5 acres) and in capac ity from 5,160 to 65,100 m 3 (1,363,000 to 17,200,000 gal (most 7,600 to 13,000 m 3 , or 2 to 3.5 million gal). They have a liner of 0.6 m (2 ft) of compacted clay and

1.5 × 10 -3 m (60 mil) high-density polyethylene (HDPE), or a liner of double HDPE (usually

2.0 × 10 -3 m or 80 mil upper and 1.5 × 10 -3 m or 60 mil lower) with a geo-net drainage layer in between. Some oilfield special waste facilities dispose of some of their leachate at injection wells

in accordance with state or federal rules.16 FIGURE 3.1 Special Waste Landfills Permitted in North Dakota

3.2 EXPOSURE SCENARIOS AND ANALYSIS

The potential exposure scenario s related to landfill disposal of TENORM can be grouped into two major categories: operational phase scen arios and future-use scenarios. Operational phase scenarios were evaluated to estimate the potential exposur es resulting from well site operations, transportation of TENORM from production facilities to generi c landfill sites, and landfill operations. Future-use scenarios evaluated potential risks to receptors at points of time in the future after the operational phase has been comp leted (i.e., after the landfill is closed). While the exposure scenarios strive to be as complete as possible, in general, the scenarios model the maximally exposed individual (MEI); that is, the individual who is most likely to receive the largest dose and incur the greatest risk. This type of analysis is performed in order to estimate an upper-bound risk for a particular operation.

Specific information about the exposure scenar ios is provided in the following sections.17 3.2.1 Operational Phase Scenarios

Operational phase scenarios were evaluated to estimate poten tial exposures resulting from well site operations, transportation, and landfill op erations. They evaluate the dose to both the workers (e.g., workers at the well sites, truck dr ivers during transportation, and landfill workers) and members of the public (e.g., potential expos ure to improperly managed filter socks and proppants, persons living along the transportation corridors, and pers ons living in the vicinity of the landfill during operations). The public exposures related to well site operations were not evaluated because the majority of the material s produced at well sites are wet and produce very little airborne emissions, and because the general public is not typically pr esent at the well site, such that external exposure woul d be significantly less than for the on-site workers evaluated. In general, exposure pathways considered for th e operational phase incl uded external radiation, inhalation of contaminated dust, and incidental ingestion of contamin ated soil or sand.

3.2.1.1 Well Site Operations Scenarios

The doses were estimated for well pad work ers involved in mixing hydraulic fracturing fluid and filtering produced water; equipmen t cleaning workers involved in pipe cleaning, storage tank cleaning, and gas pro cessing equipment cleaning; disposal well workers involved in filtration and connecting/disconnecting trucks; a nd sludge treatment plant workers involved with treating and managing sludge. 1 Assumptions for these worker scenarios are presented in Table B.1 of Appendix B and include the following:

• Hydraulic Fracturing Fluid Mixing Worker. It was assumed that exposure is from the blending operations in the sa nd blender and that only the direct external exposure is an applicable pathway. The inhalation and ingestion pathways were excluded because of the assumed use of personal protective equipment (PPE) (e.g., respirators, eye protection, and gloves).

• Produced Water Filtration Worker. Most of the dose is from incidental ingestion. The inhalation pathway was excl uded because of the wet nature of the process. It was assumed that this worker does not wear PPE.

• Equipment Cleaning Worker Scenarios. It was assumed that equipment cleaning workers are involved in re moving scale and sl udge or Pb-210 film from equipment taken out of service. Th e types of equipment that are cleaned for reuse include piping and storage tanks. Three types of workers were modeled: pipe cleaners a nd storage tank cleaners work ing in the oil industry,

1 For the purposes of estimating doses associated with each task, it was assumed that a single worker would perform only one task. For each scenario, a conservatively high number of hours per year was assumed. In reality, a worker may perform multiple tasks, some of which could also involve exposure to TENORM, and others that might not involve any exposure. Potential doses of individual workers should be assessed on the basis

of their actual wo rk assignments.18 and equipment cleaners working at a gas industry processing facility. Only the

individual who would come in direct c ontact with the contaminated equipment was modeled (this individual is likely to have greater exposure). It was assumed that respiratory protection wa s used and that the receptor was exposed only by the direct external exposure due to the use of PPE.

• Sludge Treatment Worker Scenario. It was assumed that sludge treatment workers are involved in treating the sludge generated during the well site operations (e.g., dewatering wastes to meet landfill acceptance criteria). Parameters for sludge treatment workers were assumed to be similar to the parameters for storage tank cleaning workers. However, sludge treatment workers would be shielded by water in the tanks and the exposure duration would be higher. No exposure from i nhalation and ingestion pathways was assumed for sludge treatment workers because it was assumed that workers

use PPE.

Doses also were estimated for the public resulting from improperly managed filter socks and proppants. Filter socks are used to filter wast ewater at drilling sites. They look like small

nets and could be mistaken for an item that chil dren could use for play or for fishing. A proppant is a solid material, treated sand, or man-made ceramic material, designed to keep an induced hydraulic fracture open during or foll owing a fracturing treatment. It is added to a fracking fluid.

Three accidental exposure scenar ios were evaluated: two filt er sock exposure scenarios and one proppant exposure scenario . Assumptions for these accident al public exposure scenarios are presented in Table B.2 of Appe ndix B and include the following:

• Filter Socks Used as a Toy. It was assumed that a number of filter socks are collected by a child and used as a toy for play, with an assumed exposure of

24 hours over the course of a year; the exposure pathways considered included direct external exposure and ina dvertent ingestion of radionuclides.

• Filter Socks Disposed of in a Dumpster. It was assumed that a number of used filter socks were dumped in a city du mpster and that a city dweller was exposed to the dumpster for 8 hours ever y day for 5 days (total exposure of 40 hours over the course of a year). The exposure pathway considered was direct external exposure.

• Proppant Used at a Playground. It was assumed that a truckload of proppant material was illegally dumped in an ope n field. Children used that area as their playground and spent 2 hours every day for 50 days (total exposure of 100 hours over the course of a year). Ch ildren were exposed by direct external exposure, inhalation, and ingestion pathways.19 3.2.1.2 Transportation Scenarios

The transportation operations evaluated in this assessment included loading the cargo onboard, transport of the material to its final destination, and any stops for maintenance or refueling along the way. The potential receptors in cluded the driver of th e transportation vehicle (truck transport only), persons living along the transportation corridor, persons sharing the transportation corridor, persons at stops for refu eling or maintenance, as well as persons living

near the entrance of the landfill site. Paramete rs used for the transportation scenarios are presented in Table B.7 of Appendix B.

3.2.1.3 Landfill Operations Scenarios

Two types of landfill operators were evaluated: a waste-placement operator, and a leachate management worker. The waste-placement operator was assumed to be involved with activities related to receiving and sampling the waste (e.g., review ing the manifest, weighing the truck, and inspecting the shipment), as well as di recting placement of the waste while standing in the vicinity of the truck and also moving and compacting waste in the disposal cell. It was assumed that all wastes have been dewatered prio r to shipment to the landfill in accordance with North Dakota landfill waste accepta nce criteria (NDAC; Chapter 33- 20-01.1). Potential routes of exposure for the waste-placement operator incl uded external irradiation, inhalation of contaminated particulates, and inadvertent ingestion of contaminated part iculates. Inhalation of particulates were not considered a potential pathway of exposu re for instances in which the wastes are disposed of in containers. Exposur e times were estimated based on the volume of material disposed of and typical handling procedures at the landfill. 2 Parameters used for the landfill operations scenarios for containerized and bulk waste are presented in Tables B.3 and B.4 of Appendix B, respectively.

It was assumed that the leachate worker is responsible for managing the leachate generated at the landfill, and th at the leachate generated will be collected in an evaporation pond. Depending on the evaporation pond operation, pote ntial routes of exposure for the pond management worker included external irradiatio n, inhalation of contaminated particulates, and inadvertent ingestion of contaminated particul ates. Parameters used for the evaporation pond operations scenarios are presente d in Table B.5 of Appendix B.

Doses and health risks resulting from potential airborne emissions generated during waste placement of bulk wastes also were evaluate d for the population living near the landfill.

2 For each landfill operations scenario, the dose is estimate d on the basis of the duration of the operation, source geometry, and total activity and mass of the waste disposed of in 1 year at the landfill. The number of times an operation is performed and the mass i nvolved in each operation are calcula ted internally in the code. For example, in the TSD-DOSE code, the only input parame ters required for receiving and handling operation are waste density (required to estimate th e mass in each shipment), the time required to inspect one shipment, and the average distance the operator is from the waste. The code internally estimates the amount of waste and activity in one truckload of shipment and the number of shipments involved, and, from that, calculates the total yearly dose for the receivi ng and handling scenario.20 Exposures were estimated for the maximally expos ed member of the public (i.e., an individual living adjacent to the landfill) and the collective population dose (i.e., the population living within an 80-km [50-mi] radius of the landfill). The primary path way of exposure is inhalation of contaminated particulates. External irradiation, in cidental ingestion of contaminated particulates, and ingestion of contaminated foodstuff also we re evaluated for completeness. The residents

were assumed to remain at the residences 24 hours a day, 365 days a year. Parameters used for the public exposures regulating from landfill ar e presented in Table B.4 of Appendix B.

3.2.2 Future-Use Scenarios

Future-use scenarios were evaluated to estim ate the potential radi ation doses and risks associated with activities after the operational phase has been completed. For all pathways, the

associated doses and risks were evaluated over a 1,000-year time horizon and considered the fate and transport of the radionuclides through th e environment. The only exception is the groundwater pathway. As discussed in Section 4. 2, the groundwater pathwa y was evaluated over 10,000 years to make sure that the maximum dose to a receptor off-site who makes use of the groundwater was captured. The analysis evalua ted the disposal of containerized TENORM wastes, as well as bulk wastes. Four future-use scenarios evaluated poten tial doses to on-site receptors, including an on-site resident, industria l worker, recreational visitor, and intruder. A fifth future-use scenario evaluated potential doses to an individual living adjacent to the landfill after closure who consumes groundwater. In gene ral, the exposure pathways for the future-use scenarios included external radiation; inhalati on of contaminated dust; inhalation of radon; and, depending on the particular exposure scenario eval uated, ingestion of contaminated particulates, water, plants, meat, and milk. The parameters ut ilized for the evaluation of these scenarios are presented in Table B.6 of Appendix B.

North Dakota Solid Waste law and rules emphasize that landfills must combine suitable locations and engineered improvements to minimize impacts on groundwater and surface water. The law and rules stipulate that a perpetual r ecord must be placed on the deed to notify any person conducting a title search that the land has been used as a so lid waste disposal facility. The recording must describe the amount and type of wa ste disposed of and must state that the landfill may not be used for cultivated crops, heavy gr azing, buildings, or any other use which might disturb the protective vegetative and soil cover. Given this, the following scenarios are intended to be conservative and do not necessarily represen t the most likely uses of the land post landfill

closure.

The on-site residential scenario was designed to evaluate a very conservative scenario. Under this scenario, it was assumed that an indivi dual lives on the site; produces most of his or her food on-site, including vegetables, milk, meat, and fish; and uses groundwater derived from the site for both household and agricultural purpose s. This scenario may not represent a realistic future use of a landfill property; however, these assumptions are commonly used by risk assessors in evaluating the potential dose to a MEI. The resident was assumed to spend 18 hours each day on-site (12 hours spent indoors), 365 days per year. The likely exposure pathways for

the on-site resident included external irradiation and inhala tion of indoor and outdoor radon. The following pathways of exposure also were evaluate d: inhalation of contaminated particulates;21 inadvertent ingestion of contaminated soil; and ingestion of crops, milk, and meat grown or hunted on the contaminated property.

The industrial land-use scenario considered potential exposures to an individual working inside a building constructed over the landfill. The receptor was assumed to work on-site 8 hours per day, 5 days per week. Exposure time was assu med to consist of 6 hours spent indoors and 2 hours spent outdoors. The exposure pathways evaluated included external irradiation,

inhalation of indoor and outdoor ra don, inhalation of contaminated particulates, and inadvertent ingestion of soil.

The recreational land-use scenario evaluated potential doses to an individual who visits

the former landfill site for recreational use. It was assumed that the recreational visitor makes twenty 1-hour visits to the site each year. Th e exposure pathways evaluated for the recreational

visitor included external irra diation, inhalation of outdoor rad on, inhalation of contaminated particulates, inadvertent ingestion of soil, and consumption of meat hunted on the property. Any water used by recreational visitors was assume d to come from an unaffected, off-site supply.

The intruder scenario evaluated potential doses to an individual who accidentally

encounters the wastes buried in the landfill after a peri od of 100 years, at a point in time where the land use and institutional controls are no longer in place to prevent such encounters. It was assumed that an intruder digs a 3-m (9-ft) deep foundation hole for the house. The foundation

hole was assumed to be 20 m by 10 m (200 m 2 ) (66 ft by 33 ft [239 yd 2 ]) at the bottom and 26 m by 16 m (416 m 2 ) (85 ft by 52 ft [498 yd 2 ]) at the top (giving a 1:1 slope for the sides of the hole.) The top 2 m (6 ft) of material removed in digging the foundation was assumed to be clean cover material and the bottom 1 m (3 ft) of material was assumed to be waste. For this scenario, it was assumed that a portion of the so il excavated during the digging (680 m 3 [890 yd 3 ] of cover

material and 232 m 3 [303 yd 3 ] of waste) would be distributed in a 10,000-m 2 area (12,000 yd 2 ). The intruder was assumed to spend 18 hours each day on-site (12 hours spent indoors), 365 days per year. The likely exposure pathways for th e intruder included exte rnal irradiation and

inhalation of indoor and outdoor radon. The fo llowing pathways of exposure also were evaluated: inhalation of contaminated particulat es; inadvertent ingestion of contaminated soil; and ingestion of crops, milk, and meat grow n or hunted on the contaminated property.

The off-site resident scenario was analyzed to evaluate potentia l doses resulting from future impacts on the underlying aquifer associ ated with disposal of TENORM waste in the

landfill. It was assumed that the resident lives ad jacent to the former landf ill property and that all

of his or her water is retrieved from a residential well located 100 m (330 ft) from the edge of the landfill containing the TENORM waste. It was assu med that the individual produces most of his or her food on-site, including vegetables, milk, and meat, and uses groundwater derived from the site for both household and agri cultural purposes. The off-site resident was assumed to drink 510 L (135 gal) of water per year. The exposure pa thways for this receptor included ingestion of groundwater and ingestion of crops, milk, and meat produced using th e groundwater. Inhalation

of radon via volatili zation during showering also was cons idered as a potential pathway of exposure; however, this pathway probabl y is not a major c ontributor to dose.22 3.2.3 Sensitivity Analysis

Sensitivity analyses were conducted on the parameters for which data are limited or highly variable and for parameters that have a significant impact on estimated doses. Some examples of the parameters selected for sensit ivity analysis include the distance between the radiological source and the receptor, location of the MEI, and cover thickness above the TENORM-containing waste (from here on referred to as the depth to TENORM). Sensitivity analysis was conducted by multiplying the base parameter value by a constant and calculating the dose with the new parameter value. This procedure was then repe ated; however, rather than multiplying by a constant, the parameter was divided by the same constant value. The sensitivity of a parameter is related to the ch ange in the dose produced by the change in the parameter value.23 4 MODELING METHODOLOGIES

This section presents the general modeling ap proaches that were us ed to assess (1) fate and transport of TENORM within waste stream s, including modeling of the subsurface hydrologic regime, and (2) the human health risk associated with the exposure scenarios

described in Section 3.2.

4.1 PATHWAY ANALYSIS OVERVIEW

Radiation exposure pathways can be separated into external and internal components. External exposure, which occurs when the radi oactive material is ou tside of the body, is a concern primarily only for gamma radiation beca use it can easily penetrate tissue and reach internal organs. Internal exposur e occurs when the ra dioactive material is taken into the body through inhalation or ingestion. For internal exposu res, alpha and beta par ticles are the dominant concern because their energy is almost completely absorbed in adjacent cells, potentially causing biological harm.

Exposure to internally deposite d radioactive contaminants is expressed in terms of the 50-year committed effective dose equivalent (CEDE). This concept, developed by the

International Commission on Radi ological Protection (ICRP 1977), re presents the weighted sum of the dose equivalent in various organs. The CEDE considers the radiosensitivity of bodily organs, the biological effectiveness of different types of radiation, and variable retention times in the body for different radionuclides. For extern al pathways, no long-term residence of radionuclides in the body occurs, and the measure of dose is the effective dose equivalent (EDE). Both CEDE and EDE are expressed in units of rem.

The major radiological health concern fr om exposure to TENORM is the potential induction of cancer. The development of radiation-induced cancer is a stochastic process and is considered to have no threshold dose (i.e., the pr obability of occurrence, not the severity of effect, increases with dose, and there is no dos e level below which the risk is zero). The relationship between radiation dos e and the development of cancer is well characterized for high doses of most types of radiation; for low doses, however, it is not well defined and is subject to a large degree of uncertainty. Low levels of radia tion exposure may present a health risk, but it is

difficult to establish a direct cause-and-effect re lationship because of the lack of data and the presence of compounding environmental stresses. In the absence of defi nitive data, the risks from low levels of radiological exposure are es timated by extrapolating from data available for increased rates of cancers observed at higher doses . For this assessment, radiation doses were converted to carcinogenic risks by using risk factors identified in ICRP Publication 103 (ICRP 2007). The ICRP risk factor fo r both workers and the public is 5.7  10 –7 per mrem (i.e., 5.7 additional cancer cases in 10 million pe ople for each additional mrem of exposure). Risks are expressed as the increased probability of fatal cancer, nonfatal cancer, and severe hereditary effects over a lifetime.24 As a point of reference, radia tion exposures from natural sources of radiation result in an annual dose of about 311 mrem/yr. About 210 mrem /yr is from exposures to Rn-222 and its short-lived decay progeny, and the rest is from exposures to other natura l sources of radiation (NCRP 2009). By applying the ICRP risk factor for the public, th e risk of cancer over a lifetime from background radiation is 2  10 –4 per year. In addition, the ICRP recommends that exposures to members of the general public from non- background sources of radiation not exceed 100 mrem/yr (ICRP 1991). Figure 4.1 shows this limit in relation to other common radiation exposures. This level of exposure was used in the risk assessment for comparison purposes.

The primary health concern from TENORM is related to increased cancer risk from exposure to elevated radiation levels. There is al so the possibility of adverse systemic effects due to chemical effects of exposure to the radionu clides. However, based on previous TENORM risk assessments conducted by Argonne (Smith et al. 2005) and due to relatively low concentrations of chemically effective radionuclides (e.g., uranium) , the chemical health risks from exposure to radionuclides were not evaluated for this study.

FIGURE 4.1 Typical Radiation Exposure Le vels for Common Activities (Source: NRC 2014) 1000

620

310

70 40 30 30 10 100

0 200 400 600 800 1000 1200

Whole Body Cat

Scan US Average Annual Background Dose Pelvic X

‐ Ray Food Chest X

‐ RayDoseinmrem25 4.2 DESCRIPTION OF RISK ASSESSMENT METHODOLOGY

Pathway analysis computer codes were used to estimate the dose to both workers and members of the general public. These code s included RESRAD-BUILD, RADTRAN, TSDDOSE, and RESRAD. References for each of these codes are provided in the following sections.

4.2.1 Methodology for Operational Phase Scenarios

The methodology for operational phase scenar ios is discussed in Section 4.2.1.1 for well site operations, in Section 4.2.1.2 for transportation, and in Section 4.2.1.3 for landfills. As discussed in Section 3.2.1, the ra diological impacts on both the work ers who participate in these operations and members of the ge neral public were considered.

4.2.1.1 Well Site Operations

Worker and public doses from well site ope rations were estimated using the RESRADBUILD computer code developed at Argonne (Yu et al. 2003). For more information about the RESRAD-BUILD code and access to the code, see https://web.evs.anl.gov/resrad/

home2/Build.cfm.

The RESRAD-BUILD computer code is a pa thway analysis model to evaluate the potential radiation dose incurred by an individual who works or liv es in a building contaminated with radioactive material. The code can model point, line, area, and volume source geometries. The contamination could be (1) on the surface; (2) with in the material, such as pipes, or wires; or (3) accumulated inside the object or on objects, such as filter cake and filter socks. The volume source can be composed of up to five layers of different materials. A shielding material between the source and receptor can be specified for external gamma dose calculations. Seven exposure pathways are included in the code: (1) direct ex ternal exposure, (2) external exposure from the deposited material on the floor, (3) air submer sion, (4) inhalation of airborne radioactive particulates, (5) inhala tion of indoor radon progeny, (6) direct ingestion, and (7) ingestion of deposited material.

4.2.1.2 Transportation

The transportation risk assessment considered human health risks from routine transport (normal, incident-free conditions ) of TENORM and from potential accidents. In both cases, risks associated with the nature of the cargo itself and those related to th e transportation vehicle (regardless of type of cargo) were considered. For routine trans portation, the cargo-related risk results from the potential exposure to low levels of external radiation near a loaded shipment of TENORM, and vehicle-related risks are from potential exposure to increased vehicular emissions. For accidents, the car go-related risk lies in the potential release and dispersal of TENORM into the environment during an accident and the subsequent exposure to the nearby population through multiple exposure pathways, such as exposure to contaminated soil,26 inhalation, or the ingestion of contaminated foo d. Vehicle-related accidents result in fatalities caused by physical trauma unrelated to the cargo.

The RADTRAN computer code, developed by Sandia National Laboratories, was used for the transportation risk assessment (Weiner et al. 2013). The code has been used extensively for transportation risk assessments since it was or iginally issued in the late 1970s as RADTRAN (RADTRAN 1) and has been reviewed and update d periodically. The co de calculates the MEI doses as well as population doses. For more information about the RADTRAN code, see https://rsicc.ornl.gov/c odes/ccc/ccc5/ccc-508.html.

4.2.1.3 Landfill Operations

The TSD-DOSE computer code, deve loped by Argonne with support from the U.S. Department of Energy (DOE), estimates ra diological doses to workers and members of the public from operations at a treatment, storage, an d disposal (TSD) facility (Pfingston et al. 1998). The estimated radiological doses address seven distinct reference operations, and the default parameters used in TSD-DOSE for the referen ce operations were deve loped based on data collected from detailed dose assessments for eight different TSD facilities. Each of the reference operations can be toggled on or off, and the para meter values defining the reference operations can be modified to model specific activities at different TSD faciliti es. The seven reference operations modeled wi th TSD-DOSE include:

1. Transport to a TSD facility,

2. Receiving and sampling,

3. Storage,

4. Incineration,

5. Disposal at an on-site landfill,

6. Transport to an off-site landfill, and

7. Incinerator maintenance.

4.2.2 Methodology for Future-Use Scenarios

The RESRAD computer code, developed by Argonne under DOE sponsorship, is used to evaluate radioactively contamin ated sites (Yu et al. 2001). For more information about the RESRAD code and access to the code, see ht tps://web.evs.anl.gov/resrad/home2/resrad.cfm. RESRAD implements the methodology described in DOE’s manual for developing residual radioactive material guidelines. The code esti mates the time-integrated annual dose and excess lifetime cancer risk to a chronically exposed indi vidual at a site with radiological contamination27 (DOE 1990). The calculated total dose, referred to as the total effective do se equivalent (TEDE),

is the sum of the EDE from external radiation plus the 50-year CEDE from internal radiation.

The RESRAD code focuses on radioactive contamin ants initially in soil and their subsequent transport in air, water, and bi ological media to indi vidual on-site receptors. Nine exposure pathways are considered in RESRAD: direct ex posure, inhalation of particulates and radon, and ingestion of plant foods, meat, m ilk, aquatic foods, water, and soil. The RESRAD computer code was used in conjunction with the hydrologic mo dels described in Section 4.2 to estimate radiological doses associated w ith the ingestion a nd general use of groundwater potentially

contaminated with TENORM.

4.2.3 Calculating Maximum Allowable TENORM Concentrations for Landfill Disposal

Previous analyses demonstrated that the hi ghest potential doses a ssociated with landfill disposal are associated with future-use scen arios such as those discussed in Section 3.2.2 (Smith et al. 1999). In those analyses, the futu re-use scenarios imposed the most stringent constraints (i.e., the lowest radionuclide concentr ations) in terms of th e amount of TENORM that could be safely disposed of in the landfill. As a result, in this study, initia lly the risk assessments

for future-use scenarios were conducted firs t to back-calculate the maximum average concentration of TENORM that could be accepte d at a landfill without exceeding the regulatory dose limit of 100 mrem/yr for any one of th e future-use receptors. These maximum concentrations were then used to evaluate pot ential doses to worker s and the general public during the landfill operations phase and to receptors associated with transportation of the TENORM wastes to the landfill. However, estimat es of potential doses associated with some landfill operations scenarios (the waste handl ing and placement workers) using the maximum

concentrations from the future-use scenario an alyses resulted in unacceptably high doses. As a result, additional calculations were run for t hose scenarios to derive the maximum allowable TENORM concentrations for landfill disposal required to limit dose to these workers to 100 mrem/yr.

4.3 HYDROLOGIC MODELING

The objective of the hydrological analyses was to provide information on the

concentrations of TENORM radioi sotopes of concern in groundwater as functions of time and

location. This information was then used to assess human health risk. Future-use scenarios were considered by using appropriate time frames fo r the analyses. Because the operational phase is short compared with likely transport times for ra dionuclides to reach the location of potential onand off-site receptor wells, operational impacts from groundwater resources are not expected to

occur. Future-use scenarios were evaluated to a time horizon of 10,000 years for both on- and off-site receptors.28 4.3.1 Landfill Hydrologic Modeling

Infiltration and percolation for two landfill types were analyzed with the Hydrologic Evaluation of Landfill Performance (HELP) model (Schroeder et al. 1994a,b). The HELP model is considered quasi-two-dimensional because it c ouples one-dimensional vertical percolation and one-dimensional lateral drainage and surface runo ff. HELP can be used to model the various layers of a landfill system, including vertical pe rcolation through soil, compacted barrier soil, or waste; lateral drainage through sa ndy drainage layers with or w ithout leachate collection; and vertical percolation through geomembranes of diffe rent materials and qual ity. It is a generally accepted tool for estimating leachate rates and volu mes. Management of data input and analyses of the model’s output were facilitated using Visual HELP (Waterloo Hydrologic, Inc. 2000).

The HELP model has the capability to gene rate statistically supported weather data (monthly precipitation, monthly te mperature, quarterly relative humidity, evaporative zone depth, growing season span, and average wind speed ) for a user-defined duration of years. For this study, data from Bismarck, North Dakota, were used. Bismarck is located roughly 100 to 300 km (60 to 200 mi) southeast of the main oil a nd gas activity (Figure 3.1) and is assumed to have similar weather to the study area. To be co nservative, the evapora tive depth was set to a small value (25 cm or 10 in.); the completed la ndfill was assumed to be treeless (leaf area index of zero); and the grass cover of the completed land fill was set to a status of a fair condition. The synthetic weather generator was run for 100 years to provide a large amount of information on the variability of the input to the modeled landfill.

As detailed in Section 3.1, two landfill types were considered in the analyses. The model layers of the Special Waste Landfill and Indus trial Waste Landfill are defined in Appendix C (Tables C.1 and C.2, respectively).

The slope assigned to LCS piping and sloped layers was 1.5%, while the maximum length of a slope was set to 30 m (98 ft), which represents the length of a surf ace sloped toward an LCS pipe. This slope value is considered a conserva tive assumption because it a llows for larger head buildup in drainage layers.

Porosity, field capacity, wilting point, and saturated hydraulic conductivity of various layers in the HELP model were assumed to be th e default values for each specific material type in the HELP model, with the following excepti ons. The porosity of sand drainage layers was

reduced from the default value to 0.22 to be conservative. The saturated hydraulic conductivity of the sand drainage layers was set to 1 × 10 -3 cm/s (3.3 × 10 -5 ft/s), while the saturated hydraulic conductivity of barrier layers wa s set to a maximum of 1 × 10 -7 cm/s (3 × 10 -9 ft/s), per North Dakota regulatory requirements (NDAC; Chapter 33-20-07.1 and Chapter 33-20-10) (see Appendix C).

Synthetic liner material is required by No rth Dakota regulations. In this study, the geomembrane material was assumed to be HDPE, which is included in the HELP material options. The number of pinholes was set to 25 pe r ha (10 per acre), the number of material defects was set to 4 per ha (1.6 per acre), and the installation placement quality was conservatively set to HELP’s default “poor” condition.29 The landfill in the HELP model was set to be 19 ha (46 acres), the average size of the landfills permitted in North Dakota in 2013 (Table 3.1). Based on the waste areas and total waste volumes of the landfills permitted in 2013, the average waste thickness, including daily and intermediate soil cover, was 38 m (125 ft). This value was used in the HELP assessment of closed landfills, while half of this thickness was used as input to assess the open, operating

landfill condition.

In each case, an additional HELP model layer was included at the bottom of the model— a natural soil representing a thic kness of unsaturated soil above the water table. This material was set to a thickness of 20 m (66 ft) and was conservatively assumed to be loamy sand. The purpose of this extra layer was to evaluate th e rate of movement of leachate through this

unsaturated zone.

For each of the two landfills, five cases were evaluated with the HELP model:

• Operational phase . To assess the operational ph ase with an open (active) landfill cell, the waste, including daily and intermediate soil cover, was

assumed to be half of the total th ickness, or 19 m (62.5 ft). Daily or intermediate cover exposed at the surface was assumed to have similar infiltration characteristics as the underlying waste. The LCS is functional.

• Post-closure phase . In this case, the landfill cap is completed. The geomembrane liners and the LCS are functional.

• Post-closure phase—no geomembranes . The geomembrane of the Special Waste Landfill’s synthetic liner and the geomembrane of the Industrial Waste Landfill’s cap and synthetic liners are assumed to have decomposed and are

absent from the HELP mode l. The LCS is functional.

• Post-closure phase—no geomembranes or LCS . The synthetic liners are assumed to have decomposed, and the LCS no longer functions.

• Sensitivity of post-closure phase . In this variation of the post-closure phase, the LCS continues to operate and th e HDPE liners are present; however, the quality of the synthetic liner material is worse. The number of pinholes is increased to 125 per ha (51 per acre), the number of material defects is doubled to 8 per ha (3.3 per acre), an d the installation pl acement quality is

reduced to HELP’s “bad” condition.

4.3.2 Hydrogeological Setting of a Generi c Landfill and Model Parameter Values

North Dakota’s surficial geology is dominate d by glacial depositional processes, which have resulted in thick sequences of glacial drift in mo st areas. The drift is predominantly finegrained glacial till of low perm eability. Relatively thin, discontinuous sand units may be present

within the drift also. Review of hydrogeologic reports for six la ndfills in western North Dakota30 permitted in 2013 indicated consistency with this overall description. Fine-grained glacial tills dominate, with hydraulic conductivity values of 1 × 10 -6 to 1 × 10 -8 cm/s (3 × 10 -8 to

3 × 10 -10 ft/s) (Golder 2013; Wenck 2012a; Carlso n McCain 2012; Barr 2013). Sandy zones are possible within the glacial drift sequence with hydraulic conductiv ity values ranging from

1 × 10 -3 to 1 × 10 -5 cm/s (3 × 10 -5 to 3 × 10 -7 ft/s) (Golder 2013; Wenck 2012a; Carlson McCain 2012; MWH 2012); however, these sa ndy units represent discontinuous, perched aquifers rather than important resources (Golder 2013; Wenck 2012b; Barr 2013). Barr (2013) described a conceptual site model consisting of perched groundwater that likely seeps slowly downward rather than spreading laterally. Some s ite investigations docum ented a deep confining clay with an upper surface at a depth of 18 m (60 ft) (Wenck 2012a). One study documented a regional bedrock aquifer groundwater flow syst em at a depth of 140 m (460 ft) or more (Barr 2013). Measured hydraulic gradient s at the sites range from 0.003 to 0.03.

Although geologic and hydrogeologic conditions vary spatially, based on review of the site-specific information, the hydrogeologic settin g for a generic North Dakota landfill location is expected to include thick, fine-grained glac ial till with minor sand and gravel units, and a regional bedrock aquifer at a si gnificant depth. For the purpose of modeling to support decisionmaking regarding TENORM disposal in North Da kota, parameter values were assumed for a base case and for sensitivity cases, to evaluate the outcome from parameter values that would promote contaminant transport and concentrations.

4.3.3 Unsaturated Zone Modeling

Flow through the thick, unsaturated, natural soil beneath the landfill was evaluated using the HELP model. For the depth to groundwater below the landfilled waste, 20 m (66 ft) was assumed for the base case, although much larger de pths to a practical aquifer are possible. To evaluate sensitivity, a depth to groundwater of onl y 5 m (16 ft) was also considered. In both of these cases, a localized sandy unit within the glacial dr ift was assumed to convey groundwater in an amount suitable for use by a nearby receptor. HELP modeling was used to estimate the rate of travel through this material. Based on the time of travel through the unsat urated zone, radioactive decay of ROCs was calculated. In a conservativ e aspect of the calculation, sorption during unsaturated zone transport was ignored.

4.3.4 Groundwater Transport Modeling

4.3.4.1 The Distribution Coefficient and Retardation

Sorption of a contaminant can occur on the so lid portion of an aquifer. The distribution coefficient (K d ) is the slope of the linear sorption isotherm, relating th e ratio of the amount of a

solute sorbed onto a solid to the concentration of the solute.

K

d = C*/C solute

, (4.1)31 where

K d = distribution coefficient (L 3 /M),

C*= sorbed concentration (M/M), and

C

solute = solute concentration (M/L 3 ).

A higher K d value produces greater re tardation in the moveme nt of a contaminant.

Retardation is the ratio of the ra te of bulk groundwater flow to the rate of contaminant transport.

The K d value affects the retardation, R , of the contaminant by the relationship

R = 1 + ( K

d

)( B d )/ n , (4.2)

where

R = retardation (unitless),

B d = bulk density (M/L 3 ), and

n = porosity (unitless).

The contaminant transport approach relying on the use of the distri bution coefficient, K d , to model retardation is easily incorporated in to equations supporting groundwater models. In reality, the K d approach works best for contaminants that sorb weakly to soil and aquifer materials, are present in low concentrations, do not precipitate, and where the ambient conditions such as pH and chemical concentrations do not vary significantly (B rady and Bethke 2000). However, for cationic heavy metals and radionuclides, the approach has shortcomings because of sorption and precipitation processe s. Alternative approaches coul d rely on surface complexation theory (Bethke and Brady 2000) or non-linear isotherms.

In this study, the relatively simple K d approach was followed because of the following

factors:

• TENORM radionuclide concentrations are expected to be low in the aquifer underlying the landfill;

• Calculated downgradient concentrations will be conservatively high given the typical K d results, compared with surface co mplexation results or laboratory or field observations;

• Additional conservatism can be incorporated when choosing a K d value; and

• Simplicity in implementation.

An analysis of literature values for K d is presented in Appendix D. The available information demonstrates a wide range of K d values for each ROC. For radium and thorium, K d values of 100, 1,000, and 10,000 mL/g are appropriate to evaluate the sensitivity of calculations to this parameter. For lead, K d values of 10, 100, and 1,000 mL/g should be examined.32 4.3.4.2 Dispersivity

In contaminant transport modeling, the dispersi vity parameter controls the spread of a plume. Longitudinal dispersivity has been shown to increase with increasing scale of observation (Gelhar et al. 1992). Analysis of data suggests a great deal of noise in the relationship and a dependence on the reliabili ty of the estimate; however, a lo ngitudinal dispersivity of roughly 1/10th the scale of the study area is suggested (Zheng and Bennett 1995 ). Transverse and vertical dispersivity are generally much lower than longitudinal and can be approximated as 1/10th and 1/100th, respectively, of the longitudina l dispersivity (Zheng and Bennett 1995).

4.3.4.3 Groundwater Flow and Contam inant Transport Code Selection

The Modular Three-Dimensional Finite -Difference Groundwater Flow Model (MODFLOW) (Harbaugh et al. 2000), the numerical model used the most by the U.S. Geological Survey for groundwater flow problems, was used in this study to estimate the flow of groundwater away from the water table directly beneath a landfill. MODFLOW (Harbaugh et al. 2000) simulates the steady-stat e or transient flow of groundwater in an irregularly shaped flow system in which aqui fer layers can be confined, unconfined, or both

confined and unconfined. Flow from external stresses, such as flow to wells, areal recharge, evapotranspiration, flow to drains, and flow through river beds, can be modeled. Hydraulic

conductivities or transmissivities for any layer may vary spatially and be anisotropic, and the storage coefficient may be heterogeneous. Various boundary conditions may be simulated, including specified head, specified flux, and head-dependent flux.

The Modular 3-D Multi-Species Transpor t Model (MT3DMS) (Zheng and Wang 1999), a companion code of MODFLOW, was used to calculate the movement of dissolved constituents. MT3DMS (Zheng and Wang 1999) is a three-dimensi onal finite-difference computer model that can be used to simulate changes in concentra tions of miscible contam inants in groundwater, considering such processes as advection, di spersion, diffusion, and some basic chemical reactions, with various types of boundary conditions and external sources or sinks. The chemical

reactions included in MT3DMS include linear so rption and first-order decay. MT3DMS is used

to calculate the concentrations of the contaminants of concer n as functions of time at the locations of on- and off-site receptors. In this study, the leachate from the landfill was assumed

to act as a continuous source of contamination to the aquifer. Th is is a reasonable assumption for Ra-226. A method by Baird et al. (1990), when a pplied with parameter estimates for this North Dakota study, suggested an annual leach ed fraction (LF) on the order of 1 × 10 -8 , which supports a very long source. Concentrations of ROCs predicted by MT3DMS were used to analyze risk at receptor loca tions 100 m and 300 m (328 ft and 984 ft) downgradient of the landfill for the on- and off-site receptors, respectively. Concentrations of the ROCs at the two receptor locations were calculated for a period of 10,000 years. These concentrations were used as input for risk assessment calculations. The parameters used for these calculations are

summarized in Table 4.1.33 TABLE 4.1 Values Used To Model Radio nuclide Concentrations in the Groundwater Downgradient of a Landfill

Parameter Base Case Value Sensitivity Analysis Value(s)

Distance to receptor 300 m (984 ft) 100 m (328 ft)

K d 10,000 mL/g (Ra-226, Ra-228, or Th-232) 1,000 mL/g (Pb-210) 1.000 and 100 mL/g (Ra-226, Ra-228, or Th-232) 100 and 10 mL/g (Pb-210)

Hydraulic conductivity of shallow groundwater flow system (K) 1  10 -4 cm/s (3.3× 10 -6 ft/s) 1  10 -3 cm/s (3.3 × 10 -5 ft/s)

Longitudinal dispersivity 30 m (98 ft) 300 m (980 ft)

Hydraulic gradient 0.015 0.0334 This page intentionally left blank.35 5 HYDROLOGICAL MODELING RESULTS

This section presents the results of th e hydrological modeling for transport of radionuclides through the landfill and below the la ndfill in both the unsat urated and saturated

zones.

5.1 LANDFILL HYDROLOGIC MODELING

The HELP database’s average annual pr ecipitation data for Bismarck was 39 cm (15.4 in.). Figure 5.1 shows the synthetic weather generator’s results for 100 years. The annual amount of evapotranspiration from model runs was slightly less than the precipitation amount,

with much lower runoff a nd even lower infiltration.

The HELP model results for the various landf ill scenarios show va riability of annual percolation rates throughout the modeled 100-year time frame, but these results fluctuate around an annual average. Figures 5.1 through 5.3 illustrate, for example, the closed Industrial Waste

Landfill results from the HELP model over a 100-year period for (1) precipitation, evapotranspiration, and runoff; (2) percolati on through the cap’s comp acted soil and the upper geomembrane liner; and (3) percolation through th e recompacted liner soil and the deep natural soil. The results show about 0.0013 cm (0.0005 in.) of leachate per year escaping from the

bottom of the landfill. In a cont rasting example, Figure 5.4 shows the percolation for a point in the future of an Industrial Waste Landfill when the geomembranes have decomposed and the LCS is inactive. In this case, 2 cm (0.8 in.) pe r year is passing through both the cap and the soil liner. The leachate percolating through the bottom of the deep natural soil begins to mimic the rate through the upper units after about 60 years, in dynamic equilibrium.

Table 5.1 presents the percolation rates associ ated with all tested scenarios. Closed landfills with operating LCSs reject almost all precipitation as a combination of evapotranspiration, runoff, and collected leachate, which allows very small amounts to percolate through the landfill liner system for both the Industrial and the Special Waste cases. North Dakota’s rejection requirement is met for each case with an operating LCS except for the Industrial Waste Landfill sensitivity run (geomemb ranes with more pinholes, more defects, and worst placement quality), which fell slightly be hind the required rejection rate due to the additional conservatism of the input paramete rs. For both the Industrial and Special Waste Landfills, the sensitivity analysis of the opera ting landfill (geomembranes with more pinholes, more defects, and worst placement quality) indicate s percolation rates that are similar to those without any liner, thus demonstrating the importance of the geomembrane quality.

This study did not estimate the length of tim e for partial or complete decomposition of the landfill geomembranes to occu r. The percolation ra te calculated by the HELP model without geomembranes is a rate that is relevant to long-term analysis for groundwater modeling and, therefore, was used in this assessment.36FIGURE 5.1 HELP Model Results for the Closed Industrial Waste Landfill for Precipitation, Evapotranspiration, and Runoff over100 Years37FIGURE 5.2 HELP Model Results for the Closed Industrial Waste Landfill for Percolation through the Compacted Soil of the Cap andthrough the Upper Geomembrane Liner over 100 Years38FIGURE 5.3 HELP Model Results for the Closed Industrial Waste Landfill for Percolation throughthe Recompacted Liner Soil andtheDeep Natural Soil over 100 Years39FIGURE 5.4 HELP Model Results for the Closed Industrial Waste Landfill with Decomposed Geomembranes and an Inactive LCSfor Percolation through the Cover’s Barrier Soil, the Recompacted Liner Soil, andthe Deep Natural Soil over 100 Years40 TABLE 5.1 Summary of HELP-Model-Derived Perco lation Results for Industrial and Special

Waste Landfill Scenarios

Case Layer Average

Percolation

(in./yr) % Rejected a % Required for

Post-Closure

With LCS Operating Average

Collected

Leachate (gal/yr) b Notes c

Operating Industrial Landfill, half the waste

thickness Upper geomembrane liner 0.5 96.75 624,505 Clay liner 0.01 99.94 97.00 12,490 Thick natural soil 0.01 99.94 12,490

Closed Industrial Landfill, good

membranes and LCS Cap geomembrane 0.025 99.84 31,225 Upper geomembrane liner 0.015 99.90 18,735 Clay liner 0.0005 100.00 99.99 625

Thick natural soil 0.0005 100.00 625

Closed Industrial Landfill, membranes decomposed Clay cap 0.8 94.81 999,208 Clay liner 0.8 94.81 999,208

Thick natural soil 0.4 97.40 499,604 A

Closed Industrial Landfill, membranes decomposed and LCS no longer functioning Clay cap 0.8 94.81 999,208 Clay liner 0.8 94.81 999,208

Thick natural soil 0.8 94.81 999,208 B

Operating Industrial Landfill, sensitivity of post-closure (worse pinholes, defects, placement quality) Cap geomembrane 0.7 95.45 874,307 Upper geomembrane liner 0.6 96.10 749,406 Clay liner 0.6 96.10 97.00 749,406 Thick natural soil 0.4 97.40 499,604 B

Operating Special Landfill, half the waste

thickness Clay liner 0.025 99.84 90.00 31,225

Thick natural soil 0.012 99.92 14,988

Closed Special Landfill, good membranes and

LCS Cap barrier soil 0.9 94.16 1,124,109 Clay liner 0.022 99.86 98.50 27,478

Thick natural soil 0.01 99.94 12,490 Closed Special Landfill,

membranes decomposed Cap barrier soil 0.8 94.81 999,208 Clay liner 0.8 94.81 999,208

Thick natural soil 0.8 94.81 999,208 B Closed Special Landfill,

membranes decomposed and LCS no longer functioning Cap barrier soil 0.8 94.81 999,208 Clay liner 0.8 94.81 999,208

Thick natural soil 0.8 94.81 999,208 B

Operating Special Landfill, sensitivity of post-closure (worse pinholes, defects, placement quality) Cap barrier soil 0.9 94.16 90.00 1,124,109 Clay liner 0.8 94.81 999,208

Thick natural soil 0.8 94.81 999,208

a Percentage rejected is in comparison to 15.4 in. of annual precipitation.

b Average collected leachate per year assumes an average landf ill size of 46 acres.

c Note A: This percolation rate is still climbing after 100 years to reach a dynamic equilibrium of 0.8 in./yr.

Note B: Dynamic equilibrium achieved at about 60 years.41 A key finding of the HELP model analysis was the future leach rate when the geomembranes have decomposed and the LCS is inactive. For both the Industrial and Special Waste cases, the percolation rate through the clay liner below the waste was 2 cm (0.8 in.) per year. This same percolation rate is partially due to similarities in cap materials but mainly is a result of having the same requirements for r ecompacted clay below the waste. This is a significant finding for two reasons. First, it indica tes the long-term future rate that leachate would pass through to the underlying natural soils and to the underlying aquifer. Second, despite differences in the requirements for landfill layers and their thicknesses and properties, both the Industrial and the Special Wast e Landfills perform the same in terms of long-term future percolation.

5.2 UNSATURATED ZONE FLOW AND TRANSPORT

Transport in the unsaturated zone was appr oximated by incorporati ng an additional layer in the HELP model, as described in Section 4.3.1. This layer was a natural soil below the landfill liner system. It was conservatively assumed to be loamy sand so that it would have a moderately high permeability. Its thickness was assumed to be 20 m (66 ft).

The HELP modeling relied on default values for porosity, field capacity, wilting point, and saturated hydraulic conductivity for this natural soil ; these values were considered suitable for the purpose of a generic estimate. Results su ggested a breakthrough of landfill leachate at the bottom of the thick loamy sand at approximately 60 years. The HELP-model-derived unsaturated zone flow rate was therefore on the order of 0.34 m (1.1 ft) per year. Of the ROCs, only those with a short half-life (Pb-210 and Ra-228) coul d experience a significant loss of contaminant mass during this unsaturated zone transport. This is also the case if the unsaturated zone is

assumed to be conservative ly thin at 5 m (16 ft).

Transport through the un saturated zone would allow ROCs to be subject to sorption and dispersion. As a conservative a ssumption, these processes were ignored in determining the

concentration at the water table beneath the landfill. Only the Pb-210 and Ra-228 concentrations required adjustment due to decay. The activity con centration lost during unsaturated transport is

related to the landfill concentration as:

water table concentration = landfill concentration * e decay constant * transport time (5.1)

5.3 SATURATED ZONE FLOW AND TRANSPORT

Calculation of lateral groundwater flow and transport begi ns with numerical modeling of groundwater flow. A MODFLOW model was creat ed covering a domain of 5,000 m (3 mi) by 1,000 m (0.6 mi) by 7 m (23 ft) in thickness. Fi gure 5.5 shows the upgradient end of the modeling domain, the landfill location, and the base case hydraulic heads. Grid cells were 10 m (33 ft) by 10 m (33 ft) by 1 m (3 ft). Constant head boundaries were assigned to the two ends of the domain in order to impose a uniform hydrau lic gradient of 0.015. Th e overall hydrogeologic setting of the recently permitted landfills described in Section 4.3.2 is a surficial42FIGURE 5.5 Hydraulic Heads, Landfill Location, and Receptor Locations at the Upgradient End of the Modeling Domain43 low-permeability glacial till above a confined aquifer. The modeled aquifer was therefore assumed to be a confined aquifer rather than an unconfined, surficial aquifer, as unconfined aquifers are less prevalent in western North Dakota, and landfills would be much less likely to be proposed or permitted in such a location. The hydr aulic conductivity for the modeled aquifer was

set to 1 × 10 -4 cm/s (3 × 10 -6 ft/s). The ratio of hor izontal to vertical hyd raulic conductivity was set to 10 for all layers’ cells. The generic landf ill of 19 ha (46 acres) was modeled near the upgradient end of the domain, and recharge in this landfill footprint was 2 cm/yr (0.8 in./yr), as discussed in Section 5.1. The hydraulic heads in the resulting flow fiel d are illustrated in Figure 5.5, which also shows the landfill location and receptors located 100 m (328 ft) and 300 m (984 ft) downgradient of the landfill. A sli ght bowing of the equipotentials near the landfill is due to the recharge in the landfill footprint.

MT3DMS relies on the flow field calcula ted by MODFLOW. For this study, MT3DMS modeled the following transport processes: advection, dispersion, source/sink mixing, and chemical reaction, including sorption and first-or der decay. Input to these packages included an effective porosity of 0.25, a longit udinal dispersivity of 30 m (98 ft), a horizontal transverse dispersivity of 3 m (10 ft), a ve rtical transverse dispersivity of 0.3 m (1 ft), and bulk density of 1.8 g/cm 3 (112 lb/ft 3 ). For the modeling of sorption, the optio n selected was the linear isotherm.

The K d for the ROCs was set to mid-range values based on the literature to serve in base case scenarios, along with values one order of magn itude higher or lower to evaluate sensitivity (Table 4.1).

Rather than a half-life value, MT3DMS requires the first-orde r decay rate constant. These are presented in Table 5.2.

In MT3DMS, the contaminated flux to the aquifer was modeled as recharge, with a rate of 2 cm (0.8 in.) per year as discussed in Section 5.1. This ra te assumes that the liners are decomposed, and is therefore a pr actical consideration for a long-term scenario. This recharge flux was modeled as entering the aquifer throug hout the landfill footprint. Recharge was not modeled elsewhere; rather, the gr oundwater flow field was simply maintained at the prescribed gradient except for a slight perturbati on at the landfill due to the recharge.

The concentration of each ROC in the recharge flux was given a valu e of unity (1), and the proportion of the concentrati on of unity was modeled at recep tor locations 100 m (328 ft) and 300 m (984 ft) downgradient of the landfill footprint and along the centerline of the flow model.

TABLE 5.2 Half-life and Rate Constant Values for Radionuclides

of Concern

Radionuclide Half-life (y r ) Rate Constant (1/s) Rate Constant (1/yr)

Pb-210 22.2 9.90 × 10 -10 3.12 × 10 -2

Ra-226 1,600 1.40 × 10 -11 4.33 × 10 -4

Ra-228 5.75 3.82 × 10 -9 1.21 × 10 -1

Th-232 1.40 × 10 10 1.57 × 10 -18 4.95 × 10 -1144 The base case scenario was tested for each ROC. In addition, the follwing cases were explored to evaluate the sensit ivity of the calculation to reasonable changes in input parameter

values:

• K d lower by a factor of 10 (more conservative),

• K d higher by a factor of 10 (less conservative),

• Dispersivities increased by a fact or of 10 (more conservative),

• Hydraulic gradient increased by a fa ctor of 2 (more conservative), and

• Hydraulic conductivity incr eased by a factor of 10 (more conservative).

A total of six MT3DMS runs were made to evaluate base case results and the five sensitivity scenarios listed above. Figure 5.6 show s the results for the base case values for the 100-m (328-ft) downgradient location. For all m odel runs, the C/Co (ratio of downgradient groundwater concentration to leachate recharge concentration) was determined for 10,000 years to obtain information on the long-range behavior of the transport proce sses. The maximum C/Co in each case was at the 10,000-year point; the valu es associated with each distance and scenario are presented in Table 5.3. Results for C/Co of the ROCs at the downgradient receptor locations showed tremendous reduction from the input c oncentration due to re tardation and decay processes, especially at the 300-m (984 ft) distance. These maximum C/Co values were used as input in a spreadsheet of groundw ater calculations. This spreadsh eet was a means of calculating the full process from disposal concentrati on of TENORM in the landfill to downgradient groundwater concentrations for each ROC. The pro cess included an initial assumption of unity for the disposal concentration of NORM (assu med to be the sorbed concentration), an appropriate three-order-of-magnitude range of in-landfill K d values as discussed in Section 4.3.4.1, decay in the unsaturated zone, determination of the landfill leachate concentration recharging the underlying aquifer, the MT3DMS-derived proportion of the concentrations of this leachate recharge reach ing the receptors, and the concentration at the receptors. The receptor concentrations are thereby tied to the disposal concentrations of unity; changes in disposal concentration produced rapid results for the downgradient groundwater concentration. These results are presented in Appendix E for the 100-m (328 ft) and 300-m (984-ft) downgradient receptor locations, and for the base case 20-m (66-ft) thick unsaturated zone above the aquifer as well as the 5-m (16- ft) thick unsaturated zone. For each ROC, the maximum concentration among all tested sensitivity scenarios, including the most conservative

in-landfill K d values, was used as input in risk assessm ent for future-use scen arios in Section 6.3.

5.4 DISCUSSION OF RESULTS

The literature-based K d values were a key item in this analysis. These values, which were

selected based on available information from example sites, produced a large amount of retardation in the transport of dissolved-phase ROCs. The slow rate of tr ansport, combined with radioactive decay, reduced the downgradient concen trations significantly. In the case of each45 FIGURE 5.6 Base Case Results for C/Co at 100 m ( 328 ft) (ratio of downgradient concentration to leachate recharge concentration) over 10,00 0 Years for Each of the ROCs Modeled

ROC, the risk to a receptor is dependent on inhe rent properties of the ROC and concentration at the receptor, which is in turn dependent on the starting concentration determined for the landfill leachate reaching the water table.

The C/Co concentrations calculated by MT3D MS at the two downgradient distances are conservative for use in risk assessment in that they do not provide estimates of activity concentrations that would occur in pumped groundwater. That is, a pumping well at these downgradient locations would crea te a cone of depression and have the possibility of drawing cleaner groundwater from both cros s-gradient areas and from deep er portions of the aquifer. Thus, the activity concentrations of pumped groundw ater could be lower than those calculated by

MT3DMS.46 TABLE 5.3 Maximum Ratio of Downgradient Groundwater Concentration to Leachate Recharge Concentration over 10,000 Years

C/Co

ROC Base Case Decreased K d Increased K d Increased Dispersivity Increased

Gradient Increased Hydraulic Conductivity

Downgradient Distance of 100 m

Pb-210 7.88 × 10 -13 2.89 × 10 -7 6.14 × 10 -19 1.05 × 10 -9 1.27 × 10 -11 1.34 × 10 -7

Ra-226 1.45 × 10 -08 3.69 × 10 -7 9.64 × 10 -14 6.53 × 10 -6 2.05 × 10 -7 1.30 × 10 -4

Ra-228 3.06 × 10 -22 1.92 × 10 -16 4.57 × 10 -30 1.61 × 10 -20 4.68 × 10 -21 1.59 × 10 -16

Th-232 5.59 × 10 -7 5.59 × 10 -7 5.59 × 10 -7 1.81 × 10 -4 6.65 × 10 -6 1.97 × 10 -3

Downgradient Distance of 300 m

Pb-210 3.47 × 10 -32 5.26 × 10 -17 0 2.92 × 10 -22 3.09 × 10 -28 1.96 × 10 -15

Ra-226 3.53 × 10 -25 3.64 × 10 -23 5.66 × 10 -35 1.01 × 10 -13 2.60 × 10 -20 2.09 × 10 -8

Ra-228 0 0 0 0 0 0

Th-232 6.50 × 10 -23 6.50 × 10 -23 6.50 × 10 -23 3.88 × 10 -11 2.40 × 10 -18 9.75 × 10 -7

The downgradient C/Co values of most ROCs s howed little sensitivity to the thickness of

the unsaturated natural soil betw een the landfill and the water table. For the 100-m (328-ft) downgradient receptor location, the thin (5 m or 16 ft) unsaturated zone resulted in a C/Co 4 times greater for Pb-210 and more than 200 times greater for Ra-228. This effect is due to the relatively short half-lives for these ROCs. The ot her ROCs at 100 m (328 ft), and all four ROCs at 300 m (984 ft), had no difference in the C/Co values when the thin unsaturated zone was

assumed.47 6 DOSE AND RISK ASSESSMENT RESULTS

This section presents the re sults of the radiological dose and risk assessments. The assessment considered the potential doses and risk s from latent fatal cancers associated with the several operational phase scenarios and several futu re-use scenarios that considered the potential doses and cancer risks to different hypothetical receptors after the landfill operations were completed. Descriptions of each scenario are presented in Section 3.2, and information about values defining each scenario is presented in Appendix B.

For the well site operations scenarios and the public expos ures to improperly managed filter socks and proppants, potential doses and risks were presented for wastes assuming the average and maximum radionuclide concen trations as presented in Table 2.1.

As discussed in Section 4.2.3, the future-use s cenario analyses were used to initially

estimate the allowable radionuclide concentrations that could be sa fely disposed of in landfills on the basis that previous analyses of landfill disposal had indicated that future-use scenarios were the constraining scenarios. These concentrations we re further adjusted to ensure that all workers and the general public did not receive unaccepta bly high doses during the operational phase of

the landfill.

The results of the dose and risk assessments are presented in the fo llowing sequence: well site operational scenarios, including accidental public exposure to improperly managed filter socks and proppants; future-use landfill scenar ios; transportation sc enarios; and landfill operational scenarios.

6.1 WELL SITE OPERATIO NAL PHASE SCENARIOS

For the well site operations and public expos ure scenarios, doses were calculated using the average and maximum concentrations dete cted in each waste stream in North Dakota (see Table 2.1). Table 6.1 lists the waste stre am used in different exposure scenarios.

6.1.1 Radiological Doses for Well Site Workers

It was assumed that well site workers ar e involved in mixing hydr aulic fracturing fluid and produced water filtration activities. The assu mptions and input parameters used to model

well site worker scenarios ar e discussed in Section 3.2.1.1 and are listed in Table B.1 in Appendix B, respectively. Because of the large degree of uncertainty re lated to the radionuclide source term concentrations, two sets of dose assessments were performed. One set of dose assessment used the average concentration a nd the other set used the maximum radionuclide

concentrations. Tables 6.2 and 6.3 list the estimat ed maximum dose rate for different well site operations using average and maximum waste st ream concentrations, respectively, for the exposure pathways consid ered to be viable.48 TABLE 6.1 Waste Streams Used in Evaluating Radiation

Dose in Different Worker and Public Scenarios from Well Site Operations

Scenario Waste Stream

Well pad workers

Mixing hydraulic fracturing fluid Proppant

Produced water filtration F ilter cake and filter socks

Equipment cleaning workers

Pipe cleaning Scale Storage tank cleaning Sludge Gas processing Pb-210 film

Sludge treatment workers

Sludge treatment Sludge

General public

Filter socks used a toy Filter socks Filter socks dumped in a dumpster Filter socks Illegal dumping of proppant on a field Proppant

TABLE 6.2 Estimated Maximum Dose Rate (mrem/yr) for Different Well Site Operations Using Average Radionuclide Concentration

Operations Exposure Source Direct External Exposure Ingestion Total Dose Rate (mrem/yr)

Mixing hydraulic fracturing fluid Proppant 20 NA a 20

Produced water filtration Filter socks

Filter cake 0.031 0.44 0.47

Pipe cleaning Scale 14 NA 14 Storage tank cleaning Sludge 3.8 NA 3.8 Equipment cleaning at gas processing Pb-210 film 0.0003 NA 0.0003 Sludge treatment workers Sludge 1.6 NA 1.6

a NA = not applicable.49 TABLE 6.3 Estimated Maximum Dose Rate (mrem/yr) for Different Well Site Operations Using Maximum Radionuclide Concentration

Operations Exposure

Source Direct

External Exposure Ingestion Total Dose

Rate (mrem/yr)

Mixing hydraulic fracturing fluid Proppant 23 NA a 23

Produced water filtration Filter socks

Filter cake 0.36 1.8 2.2

Pipe cleaning Scale 130 NA 130 Storage tank cleaning Sludge 70 NA 70 Equipment cleaning at gas processing Pb-210 film 0.012 NA 0.012 Sludge treatment workers Sludge 30 NA 30

a NA = not applicable.

For all well site worker exposures, except the produce water filtration worker, it was assumed that PPE (respirators, eye protection, and gloves) would be worn. Assuming the average

radionuclide concentrations in the TENORM wa ste streams, the highest potential dose, calculated for the mixing hydraulic fracturing flui d worker is 20 mrem/yr; all other doses are well below this level. The 20-mrem/yr dose is below the recommended 100-mrem/yr dose limit (ICRP 1991). Assuming the maximum radionuclide c oncentration, the dose for the pipe cleaning worker is 130 mrem/yr, and the dose for the st orage tank cleaning worker is 70 mrem/yr; other doses are considerably lower. These potentially high doses to the pipe and storage tank cleaning workers are based on the assumption that th e workers perform this activity for 2,000 and 100 h/yr, respectively. Doses to these individu als could be reduced by limiting the annual exposures and splitting the task among multiple work ers, if needed. The main contributors to

dose for the well site worker sc enarios are Ra-226 and Ra-228; the exception is for the worker cleaning equipment at a gas processing f acility for whom only Pb-210 is a ROC.

6.1.2 Parameter Sensitivity Analyses for Well Site Operation Scenarios

For the well site operation s cenarios, dose was mostly from direct external exposure, and for the produced water filtration worker, from the ingestion pathways. For external exposure pathways, the sensitive parameters are exposure distance, source thickness, and shield thickness. For conducting sensitivity analysis, the parameter values were reduced (low end) and increased (high end) by a factor of 2 from the base case. For the worker using PPE while cleaning equipment at the gas processing fa cility, sensitivity analysis wa s not performed because the dose at the base case is very small. Table 6.4 lists the results of the sensi tivity analysis, based on average radionuclide concentra tions in the TENORM wastes.

For the hydraulic fracturing fluid mixing worker scenario, the sensitivity analyses were conducted on exposure distance using values of 0.5, 1, and 2 m (1.6, 3.3, and 6.6 ft) and on50TABLE 6.4 Sensitivity Analyses for Well Site Operations Assuming Average Radionuclide Concentrations in theTENORM WastesaSensitivity forReceptor DistanceSensitivity forShielding ThicknessSensitivity for SourceThicknessOperationsBase CaseDose(mrem/yr)Low End(mrem/yr)High End(mrem/yr)Low End(mrem/yr)High End(mrem/yr)Low End(mrem/yr)High End(mrem/yr)Mixing hydraulic fracturing fluid—with PPE 20 26 13 25 12 No change No changeProduced water filtration 0.47 0.55 0.45 NAbNAb0.46 0.50Pipe cleaning—with PPE 14 23 7.8 16 8.7 7.1 26Storage tank cleaning—with PPE 3.8 5.4 2.2 NA NA 2.5 4.5Sludge treatment workers—with PPE 1.6 1.9 1.2 14 0.02 1.2 1.9aFor conducting the sensitivity analyses, parameter values were reduced (low end) and increased (high end) by a factor of 2 from the base valuefor the parameter. For the worker involved in equipment cleaning at the gas processing facility, sensitivity analysis was not performed becausethe dose is very small.bNA = The scenario doesnot include any shielding.51 shield thickness using values of 0.5, 1, and 2 cm (0.2, 0.4, and 0.8 in.). Changing the source thickness by a factor of 2 was found to have no effect on the dose values.

For the workers involved in produced water filtration, most of the dose was from incidental ingestion. The sensit ivity analyses were conducted on exposure distance using values of 0.15, 0.3, and 0.6 m (0.5, 1, and 2 ft) and on sour ce thickness using values of 0.5, 1, and 2 cm (0.2, 0.4, and 0.8 in.). No shielding was involved.

For the pipe cleaning worker scenario, th e sensitivity analyses were conducted on exposure distance using values of 0.15, 0.3, and 0.6 m (0.5, 1, and 2 ft), on shield thickness using values of 0.5, 1, and 2 cm (0.2, 0.4, and 0.8 in.), and on source thickne ss using values of 0.325, 0.65, and 1.3 cm (0.1, 0.2, and 0.5 in.). For the st orage tank cleaning scenario, sensitivity analyses were conducted on exposure distance using values of 0.15, 0.3, and 0.6 m (0.5, 1, and 2 ft) and on source thickness using values of 7.5, 15, and 30 cm (3, 6, and 12 in.). No shielding

was involved.

For the sludge treatment worker, the sens itivity analyses were conducted on exposure distance using values of 0.5, 1, and 2 m (1.6, 3.3, a nd 6.6 ft), on shield thic kness using values of 25, 50, and 100 cm (10, 20, and 39 in.), and on s ource thickness using values of 7.5, 15, and 30 cm (3, 6, and 12 in.).

An additional set of sensitivity runs was perf ormed for each scenario in which the worker was assumed to be wearing PPE to test the risk if PPE were not worn. Th ese results are shown in

Table 6.5. If well site workers do not wear PPE, potential doses canbe considerably higher in some scenarios. For the pipe cleaning worker, the dose could range from 390 to 650 mrem/yr for the average and maximum radionuclide concentr ations, respectively. For the gas processing equipment cleaner, the doses could be as high as 670 mrem/yr assuming maximum concentrations. However, for the hydraulic fr acturing fluid mixing a nd storage tank cleaner

TABLE 6.5 PPE Sensitivity Analysis Results for Well Site Operation Worker Scenarios

Maximum Concentration Average Concentration

With PPE Without PPE With PPE b Without PPE

Mixing hydraulic fracturing fluid 23 30 20 26 Pipe cleaning 127 650 14 390 Storage tank cleaning 70 73 3.8 7.4 Equipment cleaning at gas processing facility 0.012 670 0.0003 18 Sludge treatment 30 85.8 1.6 15.4

a The produced water filtration scenario was not includ ed because it was assumed that these workers do not need to wear respirators, given the wet nature of the activity.

b PPE includes respirators, eye protection, and gloves.52 scenarios, the increase in dose is much smaller. This difference is due to the lower concentration

of Pb-210 in the wastes encounter ed during these activities, as Pb -210 is a strong driver of the dose received through the ingestion pathway whic h increases without th e proper use of PPE.

6.2 RADIOLOGICAL DOSE FROM ACCIDENT AL PUBLIC EXPOSURE SCENARIOS

The doses from accidental public exposures associated with improperly managed filter socks and proppants were estimated for three ex posure scenarios: two filter sock exposure scenarios and one proppant exposure scenario. Th e assumptions and input parameters used to model the accidental public expo sure scenarios are discussed in Section 3.2.1.1 and listed in Table B.2 in Appendix B, respectively. For each s cenario, one set of dose assessments used the average concentration and the ot her set used the maximum radi onuclide concentrations. Doses

were calculated for different times in the future ranging from 0 to 1,000 years.

Tables 6.6 and 6.7 list the time-dependent dose rates using the average and maximum

filter socks concentrations for th e two respective filter socks expos ure scenarios. The doses to an individual child playing with used filter so cks as a toy range from 0.036 to 0.052 mrem/yr (using average filter socks concentr ations) and 0.21 to 0.42 mrem/yr (using maximum filter socks concentrations) at different times. Most of the dose is from the ingestion pathway because the

child is assumed to come into direct contact with the filter socks. The doses to a city dweller exposed to filter socks in a city dumpster range from 0.39 to 0.51 mrem/yr (using average filter socks concentrations) to 2.7 to 4.9 mrem/yr (usi ng maximum filter sock s concentrations) at

different times. The dose is from the external ex posure pathway, only because the city dweller

TABLE 6.6 Estimated Dose Rates for Maximum and Average Concentrations at Different Times for a Child Using Filter Socks as a Toy

Dose Rate (mrem/yr) at

Maximum Concentrations Dose Rate (mrem/yr) at Average Concentrations

Time (yr) External Ingestion Total External Ingestion Total

0 0.022 0.19 0.21 0.0020 0.049 0.051

3 0.024 0.21 0.23 0.0023 0.050 0.052

10 0.022 0.25 0.27 0.0024 0.049 0.052

30 0.019 0.32 0.34 0.0024 0.048 0.050

100 0.019 0.40 0.42 0.0024 0.046 0.048

120 0.018 0.40 0.42 0.0024 0.045 0.047

150 0.018 0.40 0.42 0.0023 0.045 0.047

300 0.017 0.38 0.40 0.0022 0.042 0.045

500 0.016 0.35 0.37 0.0021 0.040 0.042 1,000 0.013 0.29 0.30 0.0019 0.034 0.03653 TABLE 6.7 Estimated Dose Rates for Maximum and Average Concentrations at Different Times for a City Dweller Exposed to Filter Socks in a Dumpster

Dose Rate (mrem/yr) at

Maximum Concentration Dose Rate (mrem/yr) at Average Concentration

Time (yr) External Ingestion a Total External Ingestion a Total

0 4.4 0 4.4 0.40 0 0.40

3 4.9 0 4.9 0.48 0 0.48

10 4.5 0 4.5 0.51 0 0.51

30 4.0 0 4.0 0.50 0 0.50

100 3.8 0 3.8 0.49 0 0.49

120 3.8 0 3.8 0.49 0 0.49

150 3.7 0 3.7 0.48 0 0.48

300 3.5 0 3.5 0.46 0 0.46

500 3.3 0 3.3 0.44 0 0.44 1,000 2.7 0 2.7 0.39 0 0.39

a Because there is no direct contact w ith filter socks, there is no ingestionrelated dose.

does not come in direct contact with the filter socks. The poten tial dose to the city dweller is much higher compared with the potential total dose received by a child that uses filter socks as toy because of the difference in the assumed geometry of the source (i.e., the city dumpster is much bigger than the filter sock) and assumed ex posure duration (i.e., the city dweller is exposed to the dumpster 40 h/yr, whereas the child is e xposed to the toy 24 h/y r). For both scenarios, these doses are quite small compared with the 100-mrem/yr recommended dose limit to members of the general public (ICRP 1991).

For the proppant exposure scenario, it was assu med that a truckload of proppant material was illegally dumped in an open field. It was furt her assumed that children used that area as their playground and spent 2 hours every day there for 50 days (total exposure duration of 100 hours over the course of 1 year). Children were expos ed by direct external exposure and ingestion pathways. Table 6.8 lists the time-dependent dose rates using the maximum and average proppant concentrations for the proppant exposur e scenario. The doses to a child exposed to proppant at the playground range from 1.3 to 1.9 mrem/yr at different times (using maximum proppant concentrations) and from 1.2 to 1.7 mrem/yr (using average proppant concentrations). These doses are quite small compared with the 1 00-mrem per year dose limit to members of the general public (ICRP 1991).54 TABLE 6.8 Estimated Dose Rate for Maximum and Average Concentrations at Different Times for Proppant Used at a Playground

Dose Rate (mrem/yr) at

Maximum Concentration Dose Rate (mrem/yr) at Average Concentration

Time (yr) External Ingestion Total External Ingestion Total

0 1.3 0.071 1.3 1.1 0.063 1.2

3 1.6 0.074 1.7 1.5 0.065 1.5

10 1.8 0.074 1.9 1.6 0.066 1.7

30 1.8 0.073 1.8 1.6 0.065 1.7

100 1.7 0.071 1.8 1.6 0.064 1.6

120 1.7 0.071 1.8 1.6 0.064 1.6

150 1.7 0.071 1.8 1.6 0.063 1.6

300 1.7 0.068 1.8 1.5 0.061 1.6

500 1.6 0.065 1.7 1.5 0.059 1.5 1,000 1.5 0.059 1.6 1.4 0.053 1.4

6.3 FUTURE-USE SCENARIOS

6.3.1 Calculated Radiological Dose to Source Ratio for Future-Use Scenarios

An assessment was performed to estimate th e potential radiological doses and related risks to hypothetical receptors fo r several future-use scenarios. In these analyses, it was assumed that once all landfill operations were completed, the landfill would be re leased to the public without restrictions. The radiological assessm ent was conducted for a landfill in which the TENORM is placed at 2 m (6 ft) below the top of the landfill. It was assumed that the landfill encompasses an area of 186,000 m 2 (222,400 yd 2 ), with the waste layer being 38 m (125 ft) thick (an adequate size for a Large Industrial Waste Landfill).

Five future-use scenarios were considered : (1) a residential-use scenario, in which a

resident is assumed to construct a house on t op of the landfill, use the surrounding area for growing crops, and obtain drinking and irrigation water from an on-site well; (2) an industrialuse scenario, in which the land encompassing the landfill is used for industrial purposes; (3) a recreational-use scenario, in which the landfill is turned into a recreationa l area; (4) an intruder scenario, in which an intruder digs through the waste and spreads the ex cavated soil outside and constructs a house on top of the contaminated ar ea, uses the surrounding ar ea for growing crops, and obtains the irrigation water from an on-si te well; and (5) an off-site groundwater-use scenario, in which an off-site resident obtains water from a well drille d downgradient of the landfill. A detailed description of the future -use scenarios and receptors is provided in

Section 3.2.2.55 As discussed in Section 4.2.3, this analysis was structured to firs t estimate the maximum

allowable radionuclide concentration that could be disposed of without exceeding the dose limit of 100 mrem/yr (ICRP 1991) for future users, gi ven multiple scenarios. It was assumed that Ra-226, Ra-228, Th-232, and Pb-210 would be dispos ed of at the landfill. Therefore, the allowable concentrations of Ra-226, Ra-228, Th-232, and Pb-210 were estimated. It was assumed that the short-lived progeny with half-liv es less than 6 months ar e in secular equilibrium with the parent radionuclide (i.e ., the radionuclide concentrations of the progeny are equal to the radionuclide concentration of the parent). Figure 6.1 shows the steps invol ved in estimating the allowable concentration at a specific landfill usin g future-use scenarios, which would result in

the most conservative values.

Radionuclide concentrations in groundwater associated with the la ndfill operations were taken from the results of the hydrologic mode ling conducted for this study (Section 5.3). The groundwater concentrations associat ed with a water table depth of 20 m (66 ft) were used; this depth corresponds to a conservatively shallow depth to water in the study area (Section 4.3.2). For the off-site groundwater-use scenario, the estimated groundwater co ncentrations at 100 m (330 ft) downgradient of the landfill were used.

FIGURE 6.1 Steps Involved in Estimating the

Allowable Concentration in the Landfill from

Future-Use Scenarios56 6.3.2 Results of Analysis for Different Radionuclides

Dose to source ratios (DSRs) were estimat ed for individual ra dionuclides. Table 6.9

summarizes the maximum DSR for each scenario a nd identifies the limiting future-use scenario

that results in maxi mum DSR among different scenarios for each radionuclide analyzed.

6.3.3 Estimated Allowable Concentrations in the Landfill

The limiting scenario DSR was used in estima ting the average allowable concentration in the landfill based on a 100-mrem/yr public dose li mit. It was assumed that TENORM is mixed

with waste at the landfill and that TENORM waste is less than 10% of the to tal waste disposed of

at the landfill. The allowable TENORM concentrat ion can be 10 times higher compared with the average concentration at the landfill. Total ac tivity that can be brought to the landfill was calculated by assuming that 25,000 tons of the TENORM waste is brought to the landfill every year. Table 6.10 lists the limiting average concentr ation in the landfill, allowable radionuclide concentration in the TENORM, and the total activity that can be brought to the landfill. In these calculations, it is assumed that only one radionu clide is present; if multiple radionuclides are disposed at a landfill, the sum of fractions should be used.

6.3.4 Parameter Sensitivity Analyses for Future-Use Scenarios

Depth to TENORM was found to be a very sens itive parameter. It represents the total depth to TENORM material in the landfill cell following landfill closure. The analysis is not sensitive to the specific type of cover. The total thickness may include only engineered cap material or may also include some thickness of clean fill material. The dose was estimated in five future-use scenarios considering a 1-m (3-ft) cover and 3-m (10-ft) depth to TENORM on the waste material disposed of at the landfill and the allowable landfill concentration that can result in the maximum dose of 100 mrem/yr. Table 6.11 lists the limiting landfill concentration and the limiting scenario that establishes the minimum allowable concentrations at the landfill.

TABLE 6.9 Summary Results for Dose to Source Ratio

Maximum DSR (mrem/yr per pCi/g) for Each Scenario

Radionuclide Resident Intruder Industrial

Worker Recreational

Visitor Off-site

Resident a Limiting

Scenario

Pb-210 9.0 × 10 -18 9.2 × 10 -2 2.6 × 10 -18 3.4 × 10 -20 1.80 × 10 -5 Intruder

Ra-226 7.7 4.4 2.6 2.6 × 10 -5 6.0 × 10 -3 Resident

Ra-228 4.8 × 10 -9 1.4 1.4 × 10 -9 1.8 × 10 -11 1.8 × 10 -18 Intruder

Th-232 2.0 × 10 -4 2.4 5.8 × 10 -5 7.4 × 10 -7 5.5 × 10 -2 Intruder

a Doses were estimated using groundwater concentration.57TABLE 6.10 Limiting Average Concentration Based on FutureUse Scenarios and Allowable TENORM Concentrations at the 100-mrem/yr Dose Limit Assuming a Two Meter-Thick Cover

Radionuclide Limiting Average

Concentration

in the Landfill (pCi/g) Allowable

Concentration in

the TENORM (pCi/g) Total Activity (Ci) That Can Be Brought

to the Landfill in

1 Year

Pb-210 1,100 11,000 270

Ra-226 13 130 3.3

Ra-228 70 700 18

Th-232 41 410 10

TABLE 6.11 Limiting Average Landfill Concentr ation (pCi/g) and Limiting Scenario with Maximum DSR by Radionuclide

1-m Depth to TENORM 2-m Depth to TENORM 3-m Depth to TENORM

Radionuclide Allowable

Concentration (pCi/g) Limiting

Scenario Allowable

Concentration (pCi/g) Limiting

Scenario Allowable

Concentration (pCi/g) Limiting

Scenario

Pb-210 470 Intruder 1,100 Intruder 5.6 × 10 6 Groundwater,

Off-site

Ra-226 8 Resident 13 Resident 36 Resident

Ra-228 30 Intruder 70 Intruder 5.0 × 10 14 Resident Th-232 18 Intruder 41 Intruder 1,800 Groundwater,

Off-site

The groundwater concentration calculated by the hydrologic mode ling was used to

estimate the DSR for the off-site resident scen ario; however, the groundwat er concentration did not include the buildup of progeny. To evaluate the impact of progeny buildup on the analysis, the RESRAD-OFFSITE code (Yu et al. 2007) was used, because it includes buildup of progeny during the transport of contamina tion from the waste layer to th e groundwater. In the analysis with the RESRAD-OFFSITE code, the most conser vative parameters for groundwater transport were used, and the DSR for the off-site residentscenario was estimated. It was noted that the DSRs for Pb-210, Ra-226, and Th-232 for the off-s ite resident scenario were higher than those estimated using the groundwater concentration from the hydrologi c modeling, but they did not change the limiting scenario for any case, and th ey did not result in more restrictive allowable concentrations, overall.58 6.4 RADIOLOGICAL DOSE AND RI SK FROM TRANSPORTATION

A transportation risk assessment was perf ormed for the transp ortation of TENORM wastes from the generation sites to a disposal site. In this an alysis, only overla nd transportation using combined tractor-trailer trucks was eval uated. The transportation assessment consisted of evaluating the risks from both routine transp ort and transportation under accident conditions. Two major components of transportation risks we re analyzed: cargo-related risks and vehiclerelated risks. The assumptions a nd input parameters used to m odel the transportation scenarios

are discussed in Section 3.2.1.2 and listed in Ta bles B.7 and B.8 in Appendix B, respectively

Because the exact location of the disposal facility is unknown, the transportation risks to persons sharing and living along the transportati on corridor were calculated on a per-kilometer basis. A base case value of 250 km (155 mi) was sele cted as a reasonable di stance to the disposal facility. Transportation risks wi ll be proportional to the distance to the disposal facility.

It was assumed that 25,000 tons of the TENORM waste is brought to the landfill in 1 year, and radionuclide concen trations in the TENORM are based upon the maximum allowed inventory at the landfill derive d on the basis of the future-u se scenarios. The allowable TENORM concentration values are presented in Table 6.9 and discussed in Section 6.3.3.

6.4.1 Cargo-Related Doses and Risks

Cargo-related risks were evaluated for bot h routine conditions and accident conditions. Under routine conditions, the cargo-related ri sks are associated with the external gamma radiation emanating from the TENORM shipment . The potential receptors include the driver, persons living along the transportation corridor, pe rsons sharing the trans portation corridor, and persons living near the entrance of a disposal site. Cargo-rela ted risks are evaluated only for “one-way” distances, as the returning tr ucks would not contain any TENORM cargo.

Cargo-related risks under accid ental conditions result from the dispersal of radioactive material following a transportation accident. These risks consider the probab ility of the accident occurring, the probability of the accident causi ng a release of radioac tive material, and the consequence of the accident. The exposure pa thways evaluated for cargo-related risks under accident conditions include external gamma radiation, inhalation of radioactive dust, and ingestion of contaminated material in food pr oducts. The radiological transportation risk is a function of the probability of the accident occu rring, the release fraction of a given severity category, the probability of the accident severity category, and the dose associated with that accident severity category. Therefore, the transportation risk considers all types of accidents, ranging from minor collisions that do not release radioactive material, to major accidents that

result in the release of the entire cargo of radioactive material. Although the units for cargorelated risks under accidents are the units of dose equivalent (mrem), it should be emphasized that the estimated dose is a pr oduct of the consequence of the accident, expressed in units of mrem, and the probability of the radioactive materi al being released to the environment, which is

dimensionless.59 Radiological doses to an individual living near the dis posal facility from routine transportation activities were estimated by assumi ng the individual would be present during each shipment; therefore, the total dos e to this receptor is a product of the total number of shipments and the “per event” dose for a TENORM shipment passing near the disposal facility.

For the base case, an annual TENORM disposal rate of 25,000 tons per year was assumed. This number, which represents the expected annual waste disposal rate, translates into 1,000 shipments per year of TENORM wastes to th e disposal facility. For the maximum case, assuming the maximum waste disposal rate of 50,000 tons per year (double the base case), the total number of shipments would be approximate ly 2,000 per year. The actual shipment could carry any radionuclide mix as long as the to tal dose at the landf ill did not exceed the 100-mrem/yr dose limit. The allowable TENORM c oncentration values based on the future-use scenarios are presented in Table 6.9 and discus sed in Section 6.3.3. The estimated dose rate at 1 m (3 ft) from the cargo depends on the radi onuclide actually present in the shipment. For example, the external dose from a shipment that contains only Ra-226 w ould be higher compared with the dose from a shipment that contai ns only Pb-210. Therefore, for the routine transportation assessment, the dos e rate value of 0.025 mrem/h at 1 m (3 ft) was estimated from the radionuclide shipment that re sulted in the maximum dose.

Table 6.12 provides the resultant doses and risks from the transportation of TENORM from the generation sites to the hypothetical la ndfill under both routine and accident conditions

for the base case and maximum case number of sh ipments. The routine cargo-related doses to an individual living near the landfill range from 1.6 × 10 -6 mrem/yr (base case) to

3.2 × 10 -6 mrem/yr (maximum case). These doses are quite small compared with the 100-mrem/yr public dose limit and correspond to a risk of developing a radi ation-induced latent

fatal cancer of 9 × 10 -13 and 2 × 10 -12 for the base case and maximum case, respectively. Similarly, the collective doses to persons living along and shar ing the transpor tation corridor range from 6.5 × 10 -5 person-rem/yr to 1.3 × 10 -4 person-rem/yr, based on a shipping distance of 250 km (155 mi). These doses correspond to developing 4 × 10 -8 to 7 × 10 -8 latent fatal cancers within the exposed collective population.

The annual dose to the driver was estimated to be approximately 20 mrem/yr, with an

annual cancer risk of 1 × 10 -5 for both the base case and maximum case. This dose estimate is based on the external dose rate at 2 m (0.01 mrem /h) and assumes that no individual driver will exceed 2,000 hours. The radionuclide shipment that resulted in the maximum dose at allowable

concentration at the landfill was used in estima ting the dose to the driver. This dose estimate is

conservative because the dose rate in the cab of the truck would be reduced due to shielding between the source and the driver, and it is unlikely that the same driver would be used for all TENORM shipments. Even with these conservative assumptions, the 20-mrem/yr dose to the driver is well below the 100-mrem/yr dose li mit to the members of the general public (ICRP 1991).

The cargo-related transportation risks under accident conditions ar e also provided in Table 6.12. The transportation risks range from 3.6 person-rem/yr (base case) to 7.2 personrem/yr (maximum case) for a shipping distan ce of 250 km (155 mi). These doses correspond to contracting 2 × 10 -3 to 4 × 10 -3 cancers each year in the exposed collective population.60 TABLE 6.12 Cargo-Related Transportation Doses and Risks for Base Case and Maximum Case Conditions, Assuming a Transportation Distance of 250 km (155 mi)

Base Case (1,000 Shipments/yr) Maximum Case (2,000 Shipments/yr)

Receptor Dose (mrem/yr) Risk Dose (mrem/yr) Risk

Routine Conditions

Driver a 20 1  10 -5 20 1  10 -5

Individual b 1.6  10 -6 9  10 -13 3.2  10 -6 2  10 -12
General population c 6.5  10 -5 4  10 -8 1.3  10 -4 7  10 -8

Accident Conditions

General population c 3.6 2  10 -3 7.2 4  10 -3

a Based on 0.01 mrem/h, 2,000 h/yr.

b Estimated dose and risk are very conservative because an individual may not be present for all shipments.

c Doses to the collective general population are expressed in units of person-rem/yr. Risks to these same receptors are expressed in terms of latent cancer fatality.

6.4.2 Vehicle-Related Risks

Vehicle-related risks are inde pendent of the cargo being tran sported. These ri sks result in potential latent cancer fatalities (LCFs) from vehicular emissions and traffic fatalities due to transportation accidents. Vehicle -related risks are calculated base d on round-trip distances, since these risks are independent of the cargo being transported. In other words, the same vehiclerelated risks are expected to occur when the tr ansport vehicle is hauli ng a full load of TENORM waste from the generation site to the disposal facility as when the empty truck returns to the generation site from the disposal facility.

For risks associated with vehicular emissi ons, unit risk factors (LCF/km per person/km 2 ) were obtained from Biwer and Butler (1999). Ve hicle-related risks from vehicular emissions consider the size of the vehicle, diesel emissions from the vehicle, fugiti ve dust, and tire/brake particulates. For large tractor trailers (greater th an 15 metric tons), the LCF unit risk factor was

estimated at 8.36  10 -10 fatalities/km per person/km 2 (Biwer and Butler 1999). A population density of 3.7 persons/km 2 was used in the transportati on risk assessment (U.S. Census Bureau 2014).

Vehicle-related fatalities from truck tran sportation accidents have been estimated for transport in North Dakota (NDDOT 2012). It has been reported that the North Dakota average61 fatality rate associated with combination tr actor-trailer trucks on in terstate highways is

9.3  10 -9 fatalities per kilometer (NDDOT 2012).

Table 6.13 provides the results for the vehi cle-related transportation risks based on a disposal facility located 250 km (155 mi) from the generation site. The risks themselves are based on a round-trip distance of 500 km (311 mi). For routine shipments, the risks range from

8  10 -7 fatalities/yr (base case) to 2  10 -6 fatalities per year (maximum case). Fatalities associated with vehicular accidents are larger than the estimated fatalities from latent fatal cancers and range from 5  10 -3 fatalities (base case) to 1  10 -2 fatalities per year (maximum case). The risk of getting involved in a fatal tran sportation accident is at least 100 times greater than that of the driver contracting a latent fatal cancer associated with the TENORM shipment.

6.5 RADIOLOGICAL DOSE AND RISK FROM LANDFILL OPERATIONS

Radiological doses and cancer risks were calculated for wo rkers and the general public associated with the operational phase of the landfill. Two types of landfill operators were evaluated: waste handling and placement operators, and leachate management workers. Two sets of analyses were conducted for waste handling and placement operators. One set of analyses considered the bulk transport and disposal of TENORM wastes, while the other set of analyses considered shipment and disposal of th e wastes in 200-L (55- gal) containers.

The operational phase receptors evaluated in this assessment included (1) workers involved in receiving and handling wastes, on-site transport, and disposal (i.e., waste placement in the landfill), (2) members of the general public, and (3) evaporat ion pond operators. The assumptions and input parameters used to model the landfill operational phase scenarios are

discussed in Section 3.2.1.3 and lis ted in Tables B.3 through B.5 in Appendix B, respectively.

As discussed in Section 4.2.3, maximum allo wable average TENORM concentrations in

the landfilled wastes were back -calculated on the basis of the landfill future-use scenarios (see Section 6.3). These maximum allowable concentr ations were then used to estimate potential doses to workers and the general public during the landfill operations. However, estimates of potential doses for the waste handling and placement operators using the maximum

TABLE 6.13 Vehicle-Related Transportation Risks for Base Case and Maximum Case Conditions, Assuming a Round-Trip Transportation Distance of 500 km (311 mi)

Fatalities per Year

Receptor Base Case (1,000 Shipments/yr) Maximum Case (2,000 Shipments/yr)

Routine conditions 8  10 -7 2  10 -6

Accident conditions 5  10 -3 1  10 -262 concentrations from the future-use scenario analyses exceeded the 100-mrem/yr general public dose limit. One way to reduce these doses to accept able levels would be to reduce the volume of TENORM wastes disposed of at the landfill. Altern atively, the radionuclide concentrations in the

TENORM wastes sent to the landfill also could be restricted to lower levels. In this assessment,

additional calculations were r un to derive lower maximum a llowable TENORM concentrations for landfill disposal that would be protective of these workers.

6.5.1 Waste Handling and Placement Operators

The doses to these workers were first a ssessed on the basis of the maximum allowable

TENORM concentrations calculated on the basis of the future-use scenarios presented in Table 6.10. The doses associated with the disposal of bulk or containerized TENORM wastes for the base case (25,000 ton/yr) to th e waste handling and placement operators and members of the general public are summarized in Table 6.14. As shown in Table 6.14, the doses associated with the disposal of containerized TENORM are less than the doses associated with the disposal of

TENORM in bulk because direct contact with the waste would be minimized. Doses to workers in many scenarios are above the 100-mrem/yr public dose limit (ICRP 1991). The workers associated with bulk waste receiving and handling or waste placement activities have the highest

calculated doses overall.

TABLE 6.14 Radiological Dose Associated with Landfill Disposal of TENORM under the Base

Case Scenario

Bulk Waste Disposal C ontainerized Waste Disposal a

Operations Pb-210 Ra-226 Ra-228 Th-232 Pb-210 Ra-226 Ra-228 Th-232

Receiving and handling (mrem/yr) 4.9  10 -1 130 390 1.1  10 -2 2.5  10 -1 75 210 1.1  10 -2

On-site transport of

bulk/containerized waste to landfill (mrem/yr) 2.1  10 -1 110 320 9.4  10 -3 2.1  10 -1 59 170 7.5  10 -3

Waste placement (mrem/yr) 260 120 350 850 1 120 350 3.9  10 -3

MEI (mrem/yr) 2.1  10 -1 3.9  10 -3 3.3  10 -3 2.5  10 -1 2.1  10 -1 3.9  10 -3 3.3  10 -3 2.4  10 -1

Collective population dose (person-mrem) b 6.8  10 -1 1.2  10 -2 1.1  10 -2 830 6.8  10 -1 1.2  10 -2 1.1  10 -2 810

a TENORM wastes are not expected to be released from the c ontainer during disposal operati ons, resulting in a smaller dose or risk to the general public.

b Doses to the collective general population ar e expressed in units of person-mrem/yr.63 Table 6.15 provides the total allowable activ ity of each radionuclide that could be disposed of at the landfill in order to limit the maximum dose to these workers to 100 mrem/yr or

less. The resultant TENORM concentration base d on worker scenarios is more restrictive compared with those derived for the future-use s cenarios. The concentrations calculated for the worker involved in receiving and handling or waste placement activities are the limiting values.

6.5.2 General Public Exposures Due to Landfill Operations

Potential doses to the MEI of the genera l public are estimated to be low (0.0033 to 0.25 mrem/yr) for the bulk disposal alternative. Colle ctive population doses to persons living within 80 km (50 mi) of the di sposal facility are estimated to range from 0.011 to 830 personmrem/yr for the base case. Th ese doses correspond to 6.3 × 10 -9 to 4.7 × 10 -4 per year LCFs, respectively, for the sa me collective population.

6.5.3 Leachate Management Workers

Table 6.16 summarizes the estimated worker dos es associated with the operations of the evaporation pond based on the maximum allowabl e TENORM concentrations derived for the

future-use scenarios. The radionuclide concentr ation at the evaporati on pond is equal to the concentration in the leachate generated at the landfill.

The maximum estimated doses received by the leachate sampling worker range from 0.044 to 0.0096 mrem/yr from individual radionuc lide activity in the evaporation pond. The maximum estimated doses received by the evaporation pond cleani ng worker range from 0.0015 to 0.0070 mrem/yr from individual radionuclid e activity in the evaporation pond. It was assumed that the evaporation pond is operationa l for 25 years. For Pb-210 and Ra-226, the maximum dose occurred at time zero, and for Ra-228 and Th-232, the maximum dose occurred

at a later time due to the buildup of progeny.

TABLE 6.15 Allowable Total Radionuclide Activity (Ci) and the Resultant Allowable TENORM Concentration at the 100-mrem/yr Dose Limit

Allowable Activity (Ci) That Results in 100-mrem/yr Dose Resultant Allowable TENORM Concentration (pCi/g)

Operations Pb-210 Ra-226 Ra-228 Th-232 Pb-210 Ra-226 Ra-228 Th-232

Receiving and handling 56,000 2.4 4.5 90,000 2,200,000 98 180 3,600,000

On-site transport of

dewatered/containerized

waste to landfill 130,000 3.0 5.5 110,000 5,100,000 120 220 4,400,000

Waste placement 110 2.6 5.0 1.2 4,200 110 200 4864 TABLE 6.16 Estimated Dose Rate (mrem/yr) from Evaporation Pond Operations

Leachate Sampling Worker Dose (mrem/yr) Evaporation Pond Cleaning Worker Dose (mrem/yr)

Time (yr) Pb-210 Ra-226 Ra-228 Th-232 Pb-210 Ra-226 Ra-228 Th-232

0 1.8  10 -2 9.6  10 -3 3.3  10 -2 1.1  10 -2 2.9  10 -3 1.5  10 -3 5.3  10 -3 1.8  10 -4

1 1.8  10 -2 9.6  10 -3 4.1  10 -2 3.8  10 -3 2.8  10 -3 1.5  10 -3 6.5  10 -3 6.0  10 -4

3 1.7  10 -2 9.6  10 -3 4.4  10 -2 9.9  10 -2 2.7  10 -3 1.5  10 -3 7.0  10 -3 1.6  10 -3

5 1.6  10 -2 9.6  10 -3 4.1  10 -2 1.6  10 -2 2.5  10 -3 1.5  10 -3 6.5  10 -3 2.5  10 -3

7 1.5  10 -2 9.6  10 -3 3.5  10 -2 2.1  10 -2 2.3  10 -3 1.5  10 -3 5.5  10 -3 3.4  10 -3

9 1.4  10 -2 9.6  10 -3 2.9  10 -2 2.6  10 -2 2.2  10 -3 1.5  10 -3 4.6  10 -3 4.1  10 -3

10 1.3  10 -2 9.6  10 -3 2.6  10 -2 2.8  10 -2 2.1  10 -3 1.5  10 -3 4.1  10 -3 4.4  10 -3

15 1.1  10 -2 9.6  10 -3 1.5  10 -2 3.5  10 -2 1.8  10 -2 1.5  10 -3 2.4  10 -3 5.5  10 -3

20 9.8  10 -3 9.5  10 -3 8.2  10 -2 3.9  10 -2 1.6  10 -2 1.5  10 -3 1.3  10 -3 6.1  10 -3

25 8.4  10 -3 9.5  10 -3 4.5  10 -3 4.1  10 -2 1.3  10 -2 1.5  10 -3 7.2  10 -4 6.5  10 -3

The radionuclide concentration at the eva poration pond could be much higher compared

with the leachate concentration due to evaporation. Even if the evaporation pond concentrations were 100 times higher, the leachate sampling wo rker and evaporation pond cleaning worker doses would be much lower than 100 mrem/yr.

6.5.4 Parameter Sensitivity Analyses for Landfill Operation Scenarios

As stated previously, the estimated doses fo r all the initial analyses were based on the

maximum allowable concentration at the landfi ll derived from the future-use scenarios. However, because there is some uncertainty regarding the concentration of the TENORM radioisotopes, a sensitivity analysis on the TENORM concentration was conducted for the various disposal activities. The results for tw o worker scenarios for the maximum case are displayed on two-dimensional plots of dose (mrem) versus radionuclide concentration (pCi/g) (Figures 6.2 and 6.3). Because any radionuclide mixture is possible, multiple isotopes are presented on the graphs; the total dose would be the sum of the estimated dose for each radionuclide present at any given concentration. As the plots indicate, dose is most sensitive to increasing concentrations of Th-232, and least se nsitive to increasing concentrations of Pb-210.

As stated earlier, the receiving and handling or waste placement worker for the bulk waste disposal alternative yielded the largest doses . A plot of potential dose to the receiving and handling worker versus TENOR M concentration is provided in Figure 6.2. As shown in Figure 6.2, when concentrations of Ra-226 approach 100 pCi/g, the dose to the worker is near 100 mrem/yr. For the waste-placement worker, a si milar plot of dose versus concentration is provided in Figure 6.3. In this ca se, the Ra-226 concentration can approach 105 pCi/g before the dose reaches 100 mrem/yr.65 FIGURE 6.2 Worker Dose for Receiving and Handling TENORM Wastes at the Landfill

6.6 SUMMARY OF DOSE AND RI SK ASSESSMENT RESULTS

As discussed in Section 6.1, potential doses to all of the well site workers are well below the 100-mrem/yr public dose limit assuming aver age radionuclides for TENORM wastes in North Dakota (see Table 6.2). Potential doses to the pipe cleaning worker (130 mrem/yr) and storage tank cleaning worker (70 mrem/yr) are of potential concern if the maximum radionuclide concentrations are assumed (see Table 6.3). Steps to reduce the exposures of these workers may be appropriate, including limiting th eir annual exposures. Most of the well site worker scenarios assumed the workers would be using PPE, including respirators. If PPE is not worn, potential doses to these workers would be unacceptably high (see Table 6.5).

As discussed in Section 6.2, based on the e xposure scenarios modele d, potential doses to the general public related to accidental exposure to improperl y managed filter socks and proppants are generally very low, even wh en maximum radionuclide concentrations are assumed. For the child exposed by playing with filter socks, the dose is below 0.5 mrem/yr for all calculations (Table 6.6). For the individual exposed to filter sock s improperly disposed of in a 1.00E

‐ 05 1.00E

‐ 04 1.00E

‐ 03 1.00E

‐ 02 1.00E

‐ 01 1.00E+00 1.00E+01 1.00E+02

1 10 100 1000 10000Dose(mrem/yr)

TENORM Concentration (pCi/g) Pb

‐ 210

Ra

‐ 226

Ra

‐ 228

Th

‐ 23266 FIGURE 6.3 Worker Dose for Waste- Placement Activities at the Landfill

dumpster, the dose is below 1 mrem/yr, assuming average concentrations, and below 5 mrem/yr, assuming maximum concentrations (Table 6.7). Finally, for the child exposed by playing in spilled proppants, the doses ar e all below 2 mrem/yr for all calculations (Table 6.8). The

scenarios evaluated in this st udy are not representative of a ll possible exposures related to improperly managed filter socks and proppants. Different exposure scenarios would result in different doses, some of which could be higher.

In Section 6.3, radionuclide-specific results were presented for the limiting average

radionuclide concentration for wastes that coul d be disposed of in landfills, the maximum

allowable concentration in the TEN ORM wastes, and the total activity level that could be safely disposed of in a single year, based on the evaluation of multiple future-use scenarios (Table 6.10). If multiple radionuclides are disposed of in a single landfill, the sum of fractions

should be used to determine the appropriate limits. Sensitivity an alyses indicate that Depth to TENORM waste is an important parameter. The limiting average radionuclide concentration for each individual radionuclide increases significant ly as the Depth to TENORM increases from 1 to 2 to 3 m thick (Table 6.11).

As discussed in Section 6.5.1, landfill worker doses in many scenarios were above the 100-mrem/yr public dose limit using the allowable TENORM concentration (f or a landfill with a 2-m [6-ft]-thick cover) based on future-use s cenarios (see Table 6.14). The worker involved in receiving and handling or waste-placement activi ties received the highest dose. As a result, 1.00E

‐ 02 1.00E

‐ 01 1.00E+00 1.00E+01 1.00E+02

1 10 100 1000 10000Dose(mrem/yr)

TENORM Concentration (pCi/g) Pb

‐ 210

Ra

‐ 226

Ra

‐ 228

Th

‐ 23267 allowable TENORM concentrations based on the 100-mrem/yr limit for landfill workers were also derived (see Table 6.15). Table 6.17 compar es the limiting TENORM concentrations based on the future-use scenarios (for a landfill with a 2-m [6-ft] depth of TENORM) and landfill

worker scenarios.

The dose results presented for transportati on (Section 6.4) and the leachate management worker scenarios (Section 6.5.3) are conserva tive because the results are based on the

TENORM-allowed concentrations derived from the future-use scenarios. The actual doses received would be smaller, if the TENORM-allowed concentrations derived from the landfill operation phase worker scenarios were used.

6.7 CALCULATING THE MAXIMUM AL LOWABLE RADIUM CONCENTRATION

FOR TENORM DISPOSAL IN LANDFILLS IN NORTH DAKOTA

Most state-level TENORM regulations establish limits specific to total radium concentration (i.e., Ra-226 plus Ra-228) in the waste stream. In the case of waste disposal criteria, such as the maximum allowable total radi um concentration that can be disposed of in a landfill, these limits are indepe ndent of background levels of radium. For example, if the

maximum allowable concentration is 50 pCi/g total radium, that is the total concentration allowable regardless of the background leve l at the landfill or point of generation.

Table 6.17 presents the results of estima ted allowable TENORM concentrations for

individual radionuclides. Data for TENORM wastes generated in North Dakota show that Pb-210 and Th-232 also may be present in the waste streams along with radium isotopes. As shown in Table 6.17, Th-232 has the minimum estim ated allowable TENORM concentration that can be disposed of at the landfill without ex ceeding the 100-mrem/yr dose limit for any worker or member of the public. Additional analyses ar e needed in order to calculate the maximum

allowable total radium concentration that can be present in landfilled wastes, taking into account that Th-232 also may be present. This analysis entailed using the sum of fractions method for an assumed concentration of Th-232 per total radium concentration. As discussed in Section 2,

TABLE 6.17 Estimated Allowable TENORM

Concentrations Based on Future-Use Scenarios and

Landfill Worker Scenarios

Allowable TENORM Concentration (pCi/g)

Radionuclide Based on Landfill

Worker Scenarios Based on Future-Use

Scenarios

Pb-210 4,200 11,000

Ra-226 98 130

Ra-228 180 700

Th-232 48 41068 radionuclide concentration fractions were calcu lated using waste char acterization data for North Dakota TENORM wastes (see Figure 2.1).

Mathematically, the sum of fractions is represented as shown in Equation 6.1.



# 

 

###  n

i

i i 

### AC Con

1 

### 1 , (6.1)

where

Con i = concentration of radionuclide i in the source,

AC i = allowable concentration of individual radionuclide i at the dose limit, and

n = total number of radionuclides above background present in the source.

When the activity fractions of radionuclides in the source are know n, the total allowable

concentration in the source at the dose limit can be estimated from the allowable concentration of

individual radionuclide i at the dose limit as presented in Equation 6.2.



# 

 

###  n

i

i i

total 

### AC W

ACS 1 

### 1

, (6.2)

where

W i = the activity fraction of radionuclide i , and

ACS total = total allowable activity co ncentration in the source.

The total allowable concentration in the source was used to estimate the individual

radionuclide allowable concentration in th e source as presented in Equation 6.3.

itotal i 

### WACSACS   (6.3)

Table 6.18 presents the activity fractions of radionuclides and th e resulting allowable

concentration of individual radionuclides calculated using Eq uations 6.2 and 6.3. The calculation was performed utilizing average activity fr actions and various assumed radionuclide

concentration fractions to acc ount for uncertainty. The maxi mum allowable total radium concentration that could be safely disposed of in a landfill without exceeding the 100-mrem/yr dose limit for any receptor, while also taking in to account the additional activity from thorium that may be present, varied from 51.6 pCi/g to 66.6 pCi/g. The lower concen tration could be used to establish a limit of 50 pCi/g total radium for TENORM wastes disposed of in landfills. This value corresponds to the assumpti on that the ratios of Th-232 to total radium and of Ra-226 to total radium are both average, plus 1 SD (i.e ., Th-232/total radium at 49% and Ra-226/total radium at 80%). While many individual waste sa mples may have activity fractions that would result in higher concentrations of Ra-226 a nd/or Th-232 compared with the 50 pCi/g total

allowable radium concentrati on, the dose from cumulative e xposure over time to a varying stream of waste would approach the averag e activity fractions over the 1-year time period modeled.69 TABLE 6.18 Allowable Radionuc lide Concentrations in the Waste Stream Disposed of at the

Landfill Based on Different Radionuclide Con centration Fractions in the Waste Stream

Allowable Concentrations (pCi/g)

in the Waste Activity Fraction in the Waste

Radionuclide Concentration

Fractions in the Waste Ra-226 Ra-228 Th-232 Total Ra-226 Ra-228 Th-232 Total

Radium

Average a 0.49 0.27 0.24 87.2 43.0 23.6 20.6 66.6

Average Th-232/total radium and

Ra-226/total radium at 1 SD b 0.61 0.15 0.24 83.3 50.8 12.8 19.7 63.6

Average Ra-226/total radium +

1 SD Th-232/total radium c 0.44 0.24 0.33 79.6 34.6 19.0 26.0 53.6

Average + 1 SD for both

Ra-226/total radium and

Th-232/total radium d 0.54 0.14 0.33 76.7 41.2 10.4 25.0 51.6

a All radionuclides in the waste are presen t at average concentration (i.e., Th- 232/total radium at 31% and Ra-226/total radium at 65%).

b Th-232/total radium is present at average concentration, and Ra-226/total radium is at average + 1 SD (i.e., Th-232/total

radium at 31% and Ra-226/ total radium at 80%).

c Th-232/total radium is present at average concentration, and Ra-226/total radium is at average + 1 SD (i.e., Th-232/total

radium at 31% and Ra-226/ total radium at 80%).

d Th-232/total radium and Ra-226/total radium both are at average + 1 SD (i .e., Th-232/total ra dium at 49% and Ra-226/total radium at 80%).70 This page intentionally left blank.71 7 CONCLUSIONS AND RECOMMENDATIONS

This section presents conclusions drawn from the analyses presented in this report and

recommendations for decisions and actions the NDDH may consider related to regulation of

TENORM wastes.

7.1 CONCLUSIONS

The NDDH can use the results of this study to make decisions about the disposal of TENORM wastes in North Dakota Special Wast e and Industrial Waste Landfills, even though waste characterization data are limited, and specif ic landfill locations have not been evaluated. Throughout the analyses, conservative assumptions have been made in the absence of definitive information. Although this approach could overes timate potential doses to receptors, it is a commonly used and prudent approach to ensure public health protection. Sensitivity analyses have been conducted on many parameters that might have a substantial bearing on the dose

calculations in order to furthe r support decisions about TENORM waste management at the well site, as well as TENOR M landfill disposal.

The following general conclusions about we ll site operations, landfill disposal, and potential exposures to specific receptors are sup ported by the analyses a nd results presented in

Sections 5 and 6.

• Potential doses to well site work ers appear to be acceptable based upon average activity concentrations and th e appropriate use of PPE. However, these doses can increase significantly and potentially even exceed

recommended doses if concentrations a pproach the maximum of the range of

activities shown in Table 2.1. The use of appropriate PPE is important to help minimize exposure, especially for workers performing cleani ng tasks that may involve encountering scale.

• For well site operational scenarios, the pipe cleaning and storage tank cleaning workers received the highest doses. If maximum radionuclide concentrations are assumed, their doses are of poten tial concern (i.e., exceeding or approaching the ICRP’s recommended public exposure limit of 100 mrem/yr). These doses may be reduced to accep table levels by limiting the workers’ duration of exposure.

• The estimated doses from accidental public exposure to improperly managed filter socks and proppant were a small fraction of the public dose limit of 100 mrem/yr under all scenarios modeled. However, the scenarios evaluated in this study are not representative of all possible exposures related to improperly managed filter socks and proppants.72 • The estimated annual dose to the driv er involved in transporting TENORM

waste to the landfill was a small fract ion of the public dose limit of 100 mrem/yr. The transpor tation of the TENORM waste should not be a major component in deciding on the possi ble changes to th e rules regarding TENORM disposal.

• Potential exposures to landfill workers are more restrictive than potential exposures related to future use of the landfill, in terms of the maximum

TENORM concentrations that can be dis posed of in the landfill safely. The workers involved in receiving and handling or waste placement activities received the highest dose.

• Increasing the depth of the TENORM wast es in the landfill can effectively

reduce doses to future-use scenario s. Decreasing the volume of TENORM wastes that can be disposed of per ye ar in a single landfill could effectively reduce doses to both landfill workers and future-use scenarios. Alternatively, potential doses could be reduced by limiti ng the number of hours that workers are exposed to the TENORM wastes.

• On the basis of the hydrologic mode ling and the dose assessment results, disposal of TENORM wastes in both I ndustrial and Special Wastes Landfills is appropriate, provided certain rest rictions are met. From a groundwater contamination perspective, TENORM wastes, therefore, may be appropriately disposed of in either landfill type. Th e thicker cover required for Industrial Waste Landfills (2 m [6 ft] as opposed to 1 m [3 ft]) results in lower potential doses to the receptors in all of the fu ture-use scenarios modeled, except the off-site resident whose potential dose is independent of the landfill depth to

TENORM.

• Further refinement of data paramete rs for the hydrologic modeling (e.g., sitespecific K d values, site-specific hydrogeological data) is not warranted given that the groundwater exposure pathway is not a significant co ntributor to dose, except for scenarios assuming the thicke st landfill cover (which limits other pathways) and very high concentrations of Pb-210 and Th-232.

• Initial waste characterization data for TENORM waste streams generated by oil and gas production in North Dakota i ndicate that thorium may be present in the wastes in addition to radium. Establishing a total radium limit that takes

into account the levels of thorium th at may be present is a conservative approach that ensures potential exposu res to workers and the general public

are maintained below the recommended annual dose limit.73 7.2 RECOMMENDATIONS

The following recommendations are supported by the analyses and results presented in this report.

• For the maximum TENORM concentrati ons presented in Table 2.1, in order to keep exposures to acceptable levels , it may be necessary for workers to wear PPE (particularly resp irators). This could be a ppropriate for all workers with inhalation exposure risks, includ ing workers involved in pipe cleaning, storage tank cleaning, equipment cleani ng at gas processi ng facilities, and sludge treatment.

• For the pipe cleaning and storage tank cleaning workers, additional analyses may be warranted to ensure that their exposures do not exceed or approach the ICRP’s recommended public exposure limit of 100 mrem/yr. It may be appropriate to limit the work ers’ duration of exposure.

• North Dakota solid waste regulations may be safely modified so that the maximum exposure to any landfill worker does not exceed 100 mrem/yr, to allow TENORM wastes containing an aver age concentration of less than or equal to 50 pCi/g of total radium (i ndependent of background radium levels) to be disposed of in either Special Waste or Industrial Waste Landfills, based on the following conditions:

 No more than 25,000 tons of TENORM wa stes are disposed of in a single landfill per year.

 The average thorium activity concentration in the waste does not exceed 24 pCi/g. (This concentration assumes a thorium to radium ratio of 49% at 50 pCi/g total radium, based on the c onservative assumption that the ratios

of Th-232 to total radium and of Ra- 226 to total radium are both average, plus one SD greater than those in all samples observed for this report.)

 TENORM wastes must be covered by at least 2 m (6 ft) of a combination

of the landfill cover materials and clean wastes that do not contain

radionuclides.74 This page intentionally left blank.75 8 REFERENCES

Baird, R.D., G.B. Merrell, R.B. Klein, V.C. Rogers, and K.K. Nielson, 1990, Management and Disposal Alternatives for NORM Wastes in Oil Production and Gas Plant Equipment , RAE8837/2-1, prepared for American Petroleum Instit ute, Dallas, TX, by Ro gers and Associates Engineering Corp., Sa lt Lake City, NV.

Barr Engineering, 2013, Site Characterization Inves tigation Report and Environmental Monitoring System Plan, WISCO Oilfield Speci al Waste Landfill, Williston, North Dakota

, prepared for WISCO, Inc., Feb.

Bethke, C.M., and P.V. Brady, 2000, “How the K d Approach Undermines Ground Water Cleanup,” Ground Water 38(3):435–443.

Biwer, B., and J.P. Butler, 1999, “Vehicle Emi ssion Unit Risk Factors for Transportation Risk Assessments,” Risk Analysis 19(6):1157–1171.

Brady, P.V., and C.M. Bethke, 2000, “Beyond the K d Approach,” Ground Water 38(3):321–322.

Carlson McCain, Inc., 2012, Site Characterization Report, Ch imney Butte Disposal Facility, Billings County, ND , prepared for Section 18, LLC, Mayer, MN, July 13.

DOE (U.S. Department of Energy), 1990, Radiation Protection of the Public and the

Environment , DOE Order 5400.5, Feb.

Donovan, L., 2014a, “Potentially Radioactive Materi al Spilling Out of Tr ailers near Watford City,” Bismarck Tribune , Feb 22.

Donovan, L., 2014b, “Radioactive Dump Site Found in Remote North Dakota Town,” Bismarck

Tribune , March 11.

Gelhar, L.W., C. Welty, and K.W. Rehfeldt, 1992, “A Critical Review of Data on Field-Scale Dispersion in Aquifers,” Water Resources Research 28(7):1955–1974.

Golder (Golder Associates), 2013, Sawyer Landfill Cell D Design Report, Sawyer,

North Dakota , prepared for Sawyer Disposal Services, LLC, May 23.

Harbaugh, A.W., E.R. Banta, M.C. Hill, and M.G. McDonald, 2000, MODFLOW-2000, The U.S. Geological Survey Modular Ground-water Model— User Guide to Modularization Concepts

and the Ground-Water Flow Process , U.S. Geological Survey Op en-File Report 00-92, Reston,

VA.76 ICRP (International Commission on Radiological Protection), 1977, Recommendation of the International Commission on Radiological Protection , Publication 26, Pergamon Press, New York, NY.

ICRP, 1991, 1990 Recommendations of the Inter national Commission on Radiological

Protection , Publication 60, Pergamon Pr ess, Oxford, United Kingdom.

ICRP, 2007, The 2007 Recommendations of the International Commission on Radiological

Protection , ICRP Publication 103, Annals of the ICRP 37(2–4):1–332.

Michigan Department of Environmental Quality, 2007, Cleanup and Disposal Guidelines for

Sites Contaminated with Radium-226 , Waste and Hazardous Mate rials Division, Lansing, MI. Available at http://www.michigan.gov/doc uments/deq/whm-rps-EQC-1602-200703-cleanupdisposal-guidelines-radiu m-226_192499_7.pdf. Accessed Feb. 6, 2014.

MWH, 2012, Application for a Solid Waste Management Facility Permit, Tervita, LLC Proposed Special Waste Landfill, Tervita Blue Buttes Fa cility, McKenzie County, North Dakota, Nov.

NCRP (National Council on Radiati on Protection and Measurements), 2009, Ionizing Radiation Exposure of the Population of the United States, Report No. 160.

NDAC ( North Dakota Administrative Code ), 2014, Article 33-20, “Solid Waste Management and Land Protection.” Available at http:// www.legis.nd.gov/information/acdata/html/33-20.html. Accessed Jan. 10, 2014.

NDDOT (North Dakota Departme nt of Transportation), 2012, North Dakota Highway Safety Plan, 2013 , prepared by the Safety Division, Traffi c Safety Office, Sept. Available at http://www.dot.nd.gov/divisions/safe ty/docs/2013-HSP-Final.pdf.

NRC (U.S. Nuclear Regulatory Commission), 2014, “Doses in Our Daily Lives.” Available at http://www.nrc.gov/about-nrc/radiation/ar ound-us/doses-daily-lives.html. Accessed Oct. 17, 2014.

Pfingston, M., et al., 1998, TSD-DOSE: A Radiological Dose A ssessment Model for Treatment, Storage, and Disposal Facilities , ANL/EAD/LD-4 (Rev. 1), Argonne National Laboratory, Argonne, IL.

Poppke, T., 2014, personal communication by e-mail from Poppke (Division of Waste Management, North Dakota Department of Heal th) to C. Harto and others (Argonne National Laboratory), May 7.

Radig, S., 2013a, personal communication by e-mail from Radig (D ivision of Waste Management, North Dakota Depart ment of Health) to K.P. Smith and others (Argonne National Laboratory), Dec. 9.77 Radig, S., 2013b, personal communication by e-mail from Radig (D ivision of Waste Management, North Dakota Depart ment of Health) to K.P. Smith and others (Argonne National Laboratory), Dec. 19

Radig, S., 2013c, personal communication by e-mail from Radig (D ivision of Waste Management, North Dakota Depart ment of Health) to K.P. Smith and others (Argonne National Laboratory), Dec. 17.

Radig, S., 2014a, personal communication by e-mail from Radig (D ivision of Waste Management, North Dakota Depart ment of Health) to K.P. Smith and others (Argonne National Laboratory), Feb. 26.

Radig, S., 2014b, personal communication by e-mail from Radig (D ivision of Waste Management, North Dakota Depart ment of Health) to K.P. Smith and others (Argonne National Laboratory), March 5.

Radig, S., 2014c, personal communication by e-mail from Radig (D ivision of Waste Management, North Dakota Department of Heal th) to C. Harto and others (Argonne National Laboratory), March 17.

Radig, S., 2014d, personal communication by e-mail from Radig (D ivision of Waste Management, North Dakota Department of Heal th) to C. Harto and others (Argonne National Laboratory), Jan. 14.

Schroeder, P.R., N.M. Aziz, C.M. Lloyd, and P.A. Zappi, 1994a, The Hydrologic Evaluation of Landfill Performance (HELP) Model: User’s Guide for Version 3 , EPA/600/R-94/168a, U.S. Environmental Protection Agency, Office of Research and Development, Washington, DC, Sept.

Schroeder, P.R., T.S. Dozier, P.A. Zappi, B. M. McEnroe, J.W. Sjostrom, and R.L. Peyton, 1994b, The Hydrologic Evaluation of Landfill Pe rformance (HELP) Model: Engineering Documentation for Version 3 , EPA/600/R-94/168b, U.S. Envir onmental Protection Agency,

Office of Research and Devel opment, Washington, DC, Sept.

Smith, K.P., D.L. Blunt, G.P. Williams, J.J. Arni sh, M. Pfingston, J. Herbert, and R. Haffenden, 1999, An Assessment of the Dispos al of Petroleum Industry NO RM in Nonhazardous Landfills

, DOE/BC/W-31-109-ENG-38-8 (OSTI ID: 13061), prep ared for U.S. Department of Energy, National Petroleum Technology Office, Tulsa, OK.

Smith, K.P., H.I. Avci, J.J. Arnish, a nd J. Quinn, 2005, unpublished information, Argonne National Laboratory, Argonne, IL.

U.S. Census Bureau, 2014, 2010 Census Urba n Lists Record Layouts. Available at http://www.census.gov/geo/reference/ua/u alists_layout.html. Accessed May 21, 2014.78 Waterloo Hydrologic, Inc., 2000, Visual HELP Version 2.2.0.2.

Weiner, R.F., et al., 2013, RADTRAN 6/RadCat 6 User Guide, SAND2013-8095, Sandia National Laboratories, Albuquerque, NM, and Livermore, CA, Sept.

Wenck Associates, Inc., 2012a, Detailed Site Hydrogeologic Char acterization & Investigation Report, Ideal Oilfield Disposal, LLC, Special Waste Landfill, McKenzie County, North Dakota

, prepared for Ideal Oilfield Disposal, Inc., Fargo, ND, Aug.

Wenck Associates, Inc., 2012b, Permit Application Design Re port, Williston Landfill , prepared for Marquis Alliance Energy, Williston, ND, Nov.

Yu, C., et al., 2001, User’s Manual for RESRAD, Version 6 , ANL/EAD-4, Argonne National Laboratory, Argonne, IL.

Yu, C., et al., 2003, User’s Manual for RESRAD-BUILD Version 3 , ANL/EAD/03-1, Argonne National Laboratory, Argonne, IL.

Yu, C., et al., 2007, User’s Manual for RESRAD-OFFSITE Version 2 , ANL/EVS/TM-07-1, Argonne National Laboratory, Argonne, IL.

Zheng, C., and G.D. Bennett, 1995, Applied Contaminant Transport Modeling: Theory and

Practice , Van Nostrand Reinhold, New York.

Zheng, C., and P.P. Wang, 1999, MT3DMS, A Modular Three-Dimensional Multi-Species Transport Model for Simulation of Advection, Dispersion, and Chemical Reactions of Contaminants in Groundwater Systems; Documentation and User’s Guide, U.S. Army Engineer Research and Development Center Cont ract Report SERDP-99-1, Vicksburg, MS.A-1 APPENDIX A:

RADIONUCLIDE ANALYSIS DATA FOR TENORM WASTE SAMPLES

COLLECTED IN NORTH DAKOTAA-2 This page intentionally left blank.A-3TABLE A.1 Radionuclide Analysis Data for TENORM Waste Samples Collected in North DakotaType of Waste Equipment Type Sample Date Ra-226 (pCi/g) Ra-228 (pCi/g) Pb-210 (pCi/g) Th-232 (pCi/g) SourceFilter sockNAa12/6/2011 25.8 19.3 4.49 18.9 Radig(2014b)Filtersock NA 12/6/2011 10.8 6.47 7.64 6.51 Radig(2014b)Filter sock NA Not reported 374 130 60 Radig (2013)Filter sockNA Not reported 47.211.110Radig (2013)Filter sockNA Not reported 41.41147.7Radig (2013)Filter sockNA Not reported 24.610.670Radig (2013)Filter sockNA Not reported 28.80.27Radig (2013)Filter sockNA Not reported 178.731.8Radig (2013)Filter sockNA Not reported 15.27.9Radig (2013)Filter sockNA Not reported 3.044.95Radig (2013)Filter sockNA Not reported 44.80.99Radig (2013)Filter sockNA Not reported 3.164.64.7Radig (2013)Filter sockNA Not reported 7.44.31.83Radig (2013)Filter sockNA Not reported 0.913.70.71Radig (2013)Filter sockNA Not reported 43.21.02Radig (2013)Filter sockNA Not reported 1.713.12.43Radig (2013)Filter sockNA Not reported 6.42.6570Radig (2013)Filter sockNA Not reported 1.072.446.1Radig (2013)Pipe NA 10/8/2013 352 251 340Radig(2014a)Pipe NA 10/8/2013 248 173 233Radig(2014a)ProppantNA 12/3/2013 1.763.1Radig (2014b)Proppant NA 12/6/2011 9.1 11.2 9.67 10.2 Radig(2014b)Proppant NA 12/6/2011 8 9.98 8.61 9.08 Radig(2014b)Proppant NA 12/6/2011 7.95 9.94 6.15 9.27 Radig(2014b)Proppant NA 12/6/2011 8.07 9.83 8.65 9.35 Radig(2014b)Proppant NA 12/6/2011 8.84 9.21 9.74 8.76 Radig(2014b)Proppant NA 12/6/2011 7.25 8.99 7.96 8.08 Radig(2014b)ScaleFiretube 11/18/2001 15480.0Radig (2014c)ScaleFiretube 11/18/2001 10671.6Radig (2014c)ScaleFiretube 11/18/2001 94.960.6Radig (2014c)ScaleFiretube 11/18/2001 27.817.2Radig (2014c)ScaleFiretube 7/7/2010309261Radig (2014c)ScaleFiretube 7/9/2010427339Radig (2014c)A-4TABLE A.1 (Cont.)Type of Waste Equipment Type Sample Date Ra-226 (pCi/g) Ra-228 (pCi/g) Pb-210 (pCi/g) Th-232 (pCi/g) SourceScaleFiretube 7/13/2010 141122Radig (2014c)ScaleFiretube 7/13/2010 4,700 3,590Radig (2014c)ScaleFiretube 12/7/2010 12686.6Radig (2014c)Scale Firetube 4/26/2011 <77.7 <8.1<80.3 Radig(2014c)Scale Firetube 4/26/2011 1,867.5 971.4 460.3 Radig (2014c)Scale Firetube 4/26/2011 1,386.1 865.2 247.2 Radig (2014c)Scale Firetube 4/26/2011 940.8 569.5 109.9 Radig (2014c)Scale Firetube 4/26/2011 192.5 132.1<19.3 Radig(2014c)Scale Firetube 5/5/2011 201.8 187.383.2 Radig(2014c)Scale Firetube 5/5/2011 24.9 10.330.3 Radig(2014c)Scale Firetube 8/26/2011 90.4 59.828.6 Radig(2014c)Scale Firetube 9/14/2011 1,960.6 <24.974.8 Radig(2014c)Scale Treater 9/14/2011 57.0 <2.613.4 Radig(2014c)Scale Firetube 9/14/2011 56.6 38.413.7 Radig(2014c)Scale Firetube 9/14/2011 25.7 18.416.3 Radig(2014c)Scale Firetube 9/14/2011 9.4 7.57.7 Radig(2014c)ScaleFilter sock 10/5/2011 42.924.5Radig (2014c)Scale Tubing 10/6/2011 <115.2 <23.6 <88.4 Radig (2014c)Scale Firetube 10/18/2011 180.0 131.651.4 Radig(2014c)Scale Firetube 10/18/2011 167.8 48.136.5 Radig(2014c)ScaleFilter sock 10/18/2011 63.539.5<23.6 Radig (2014c)Scale Firetube 10/18/2011 31.5 19.06.5 Radig(2014c)Scale Firetube 10/18/2011 14.0 9.07.4 Radig(2014c)Scale Firetube 12/9/2011 247.9 167.893.3 Radig(2014c)Scale Firetube 12/9/2011 63.3 24.823.8 Radig(2014c)Scale Firetube 1/20/2012 271.5 155.649.7 Radig(2014c)Scale Firetube 1/20/2012 266.5 125.2<106.8 Radig(2014c)Scale Firetube 1/20/2012 160.3 107.435.1 Radig(2014c)Scale Firetube 1/20/2012 123.8 60.855.4 Radig(2014c)Scale Firetube 2/17/2012 392.6 271.560.4 Radig(2014c)Scale Firetube 2/17/2012 98.5 51.0<40.3 Radig(2014c)Scale Pipe 10/8/2013 4,710 2,550 5,270Radig(2014a)Scoria Soil 2/17/2012 2.6 2.2<2.9 Radig(2014c)A-5TABLE A.1 (Cont.)Type of Waste Equipment Type Sample Date Ra-226 (pCi/g) Ra-228 (pCi/g) Pb-210 (pCi/g) Th-232 (pCi/g) SourceSludgeTreater 10/14/2010 64.52.7Radig (2014c)SludgeTank 10/14/2010 26.72.2Radig (2014c)SludgeTank 10/25/2010 5.52.5Radig (2014c)Sludge Tank 7/22/2011 122.4 62.534.4 Radig(2014c)SludgeTank 7/22/2011 1,231.162.2Radig (2014c)Sludge Tank 7/22/2011 6.3 3.5<3.4 Radig(2014c)Sludge Tank 7/25/2011 18.2 9.7<6.1 Radig(2014c)Sludge Tank 7/26/2011 3.7 3.1<3 Radig(2014c)Sludge Tank 7/26/2011 4.2 1.4<3.1 Radig(2014c)Sludge Tank 7/26/2011 2.0 1.0<2.3 Radig(2014c)Sludge Tank 7/27/2011 16.6 14.88.6 Radig(2014c)Sludge Tank 7/27/2011 13.0 7.75.1 Radig(2014c)Sludge Tank 7/27/2011 12.6 6.56 Radig(2014c)Sludge Tank 8/2/2011 3.8 <0.52.1 Radig(2014c)Sludge Tank 8/2/2011 16.2 11.86.5 Radig(2014c)Sludge Tank 8/3/2011 13.7 8.1<5.1 Radig(2014c)Sludge Tank 8/3/2011 12.5 6.34.4 Radig(2014c)Sludge Tank 8/4/2011 29.2 21.87.4 Radig(2014c)Sludge Tank 8/4/2011 30.0 17.49.4 Radig(2014c)Sludge Tank 8/4/2011 25.5 15.013.2 Radig(2014c)Sludge Tank 8/4/2011 5.3 2.9<3.4 Radig(2014c)Sludge Tank 8/5/2011 3.2 1.6<2.5 Radig(2014c)Sludge Tank 8/5/2011 5.6 1.5<2.9 Radig(2014c)Sludge Tank 8/8/2011 65.4 38.321.5 Radig(2014c)Sludge Tank 8/8/2011 21.4 14.4<7 Radig(2014c)Sludge Tank 8/8/2011 13.7 13.86.5 Radig(2014c)Sludge Tank 8/8/2011 18.3 12.3<6.7 Radig(2014c)Sludge Treater 8/26/2011 16.6 21.416.3 Radig(2014c)Sludge Treater 9/14/2011 81.0 <4.218.3 Radig(2014c)Sludge Treater 9/14/2011 31.0 20.114.6 Radig(2014c)Sludge Treater 10/6/2011 79.6 52.922.4 Radig(2014c)Sludge Treater 10/6/2011 42.2 23.715.9 Radig(2014c)Sludge Treater 10/6/2011 24.1 16.99.1 Radig(2014c)A-6TABLE A.1 (Cont.)Type of Waste Equipment Type Sample Date Ra-226 (pCi/g) Ra-228 (pCi/g) Pb-210 (pCi/g) Th-232 (pCi/g) SourceSludge Treater 12/9/2011 59.2 36.915.4 Radig(2014c)Sludge Treater 12/9/2011 24.5 11.8<6.2 Radig(2014c)Sludge Treater 1/20/2012 58.7 39.719.8 Radig(2014c)Sludge Tank 9/9/2013 17.4 <1.6<9.4 Radig(2014c)Sludge Treater 9/9/2013 123.7 66.397.5 Radig(2014c)Sludge Treater 9/9/2013 45.6 23.2<11.5 Radig(2014c)Sludge Treater 9/9/2013 264.7 21.833.9 Radig(2014c)Sludge Tank & treater 9/9/2013 36.821.012.8 Radig (2014c)Sludge Tank 9/9/2013 33.6 18.218.7 Radig(2014c)Sludge Tank & treater 9/9/2013 34.716.2<11.7 Radig (2014c)Sludge Tank & treater 9/9/2013 31.612.3<11.2 Radig (2014c)Sludge Tank 9/9/2013 16.0 10.4<10.8 Radig(2014c)Sludge Tank 9/9/2013 25.9 8.3<12 Radig(2014c)Sludge Tank & treater 9/9/2013 24.68.3<10 Radig (2014c)Sludge Tank & treater 9/9/2013 17.18.39.3 Radig (2014c)Sludge Tank & treater 9/9/2013 25.58.2<9.5 Radig (2014c)Sludge Treater 9/9/2013 19.7 7.7<7.1 Radig(2014c)SludgeFlare pit Not reported 16916.964Radig (2013)SludgeFlare pit Not reported 1236.936.7Radig (2013)SludgeTank Not reported 5.14.55.5Radig (2013)SludgeFlare pit Not reported 27.32.931.1Radig (2013)SludgeFlare pit Not reported 15.31.3112.9Radig (2013)SludgeFlare pit Not reported 49.40.65318Radig (2013)SludgeFlare pit Not reported 90.52.13Radig (2013)aNA = not applicable.A-7 Appendix A References

Radig, S., 2013, personal communication by e- mail from Radig (Division of Waste Management, North Dakota Depart ment of Health) to K.P. Smith and others (Argonne National Laboratory), Dec. 9.

Radig, S., 2014a, personal communication by e-mail from Radig (D ivision of Waste Management, North Dakota Depart ment of Health) to K.P. Smith and others (Argonne National Laboratory), Feb. 26.

Radig, S., 2014b, personal communication by e-mail from Radig (D ivision of Waste Management, North Dakota Depart ment of Health) to K.P. Smith and others (Argonne National Laboratory), March 5.

Radig, S., 2014c, personal communication by e-mail from Radig (D ivision of Waste Management, North Dakota Department of Heal th) to C. Harto and others (Argonne National Laboratory), March 17.A-8 This page intentionally left blank.B-1 APPENDIX B:

RISK ASSESSMEN T DATA TABLESB-2 This page intentionally left blank.B-3 APPENDIX B:

RISK ASSESSMEN T DATA TABLES

TABLE B.1 RESRAD-BUILD Input Parame ters Describing Well Site Operations

Parameter Value Remark a

Well Pad Workers

Mixing hydraulic fracturing fluid (exposed to proppant)

Exposure time (h/yr) 2,000 The inhalation and ingestion pathways are excluded because of the use of personal protective equipment (PPE) (respirators, eye protection, and gloves). Direct external exposure is the only applicable pathway. Exposure is from the blending operations in the

sand blender. Exposure distance (m) 1

Source material Concrete Source density (g/cm 3 ) 1.6 Exposure source geometry Source length (m) 13.2 Source height (m) 1.9 Source width (m) 2.5

Shield material Steel Shield thickness (cm) 1 Shield density (g/cm 3 ) 7.86 Produced water filtration (exposed to filter cake and filter socks)

Exposure time (h/yr) 250 The inhalation pathway is

excluded because of the wet nature of the process. It is

assumed that this worker does

not wear PPE somewhat infrequently on well sites. May have service workers

who do this most of the time. May be similar to disposal well worker exposures. Exposure distance (m) 0.3

Source material Concrete Source density (g/cm 3 ) 2.6 Exposure source geometry Source diameter (m) 0.152 Source height (m) 0.01 Shield thickness (cm) 0 Shield density (g/cm 3 ) NR b

Equipment Cleaners

Pipe cleaning (exposed to scale) c

Exposure time (h/yr) 2,000 The inhalation and ingestion pathways are excluded

because of the use of PPE. Direct external exposure is the only applicable pathway. Distance (m) 0.3 Scale thickness (cm) 0.65 Scale density (g/cm 3 ) 2.6 Pipe length (m) 9.15 Pipe diameter (m) 0.15

Shield material Steel Shield thickness (cm) 1 Shield density (g/cm 3 ) 7.86B-4 TABLE B.1 (Cont.)

Parameter Value Remark

Storage tank cleaning (exposed to scale and sludge) d

Exposure time (h/yr) 100 The inhalation and ingestion pathways are excluded

because of the use of PPE. Direct external exposure is the only applicable pathway. Distance (m) 1

Scale material Concrete Scale/sludge thickness (cm) 15 Scale/sludge density (g/cm 3 ) 1.6 Tank length (m) 13.7 Tank width (m) 2.6 Shield thickness (cm) 0 Shield density (g/cm 3 ) NR

Gas processing (exposed to Pb-210 film) e

Exposure time (h/yr) 2,000 The inhalation and ingestion pathways are excluded

because of the use of PPE. Direct external exposure is the only applicable pathway. Cleaning is done indoors. Exposure distance (m) 0.3

Source material Concrete Pb-210 film thickness (cm) 0.65 Pb-210 film density (g/cm 3 ) 2.6 Gas pipe length (m) 9.15 Gas pipe diameter (m) 0.15

Shield material Steel Shield thickness (cm) 1 Shield density (g/cm 3 ) 7.86

Disposal Well Worker

Filtration (exposed to filter cake and filter socks)

Exposure time (h/yr) 2,000 Exposure pathways and parameter values are the same as for well pad workers except for the exposure time. Exposure distance (m) 0.3

Source material Concrete Source density (g/cm 3 ) 2.6 Exposure source geometry Source diameter (m) 0.152 Source height (m) 0.01 Shield thickness (cm) 0 Shield density (g/cm 3 ) NR

Sludge Treatment Plant Workers (exposed to sludge)

Exposure time (h/yr) 2,000 The parameters are assumed to be similar as for storage tank cleaning. However workers would be shielded by water in the tanks and the exposure duration would be higher. No exposure from the inhalation and ingestion pathways. Exposure distance (m) 1.0

Source material Concrete Sludge thickness (cm) 15 Sludge density (g/cm 3 ) 1.6 Sludge tank length (m) 13.7 Sludge tank width (m) 2.6

Shield material Water Shield thickness (cm) 50 Shield density (g/cm 3 ) 1.0

Footnotes on next page.B-5 TABLE B.1 (Cont.)

a If the inhalation and ingestion pathways are included, airborne dust loading of 1 × 10 -4 g/m 3 , a worker

inhalation rate of 1.2 m 3 /h, and an ingestion rate of 6.25 × 10 -3 g/h would be used from Smith et al.(1996).

b NR = not required.

c Parameters for pipe cleaning activity are based on Smith et al. (1996).

d Sludge thickness, density, exposure duration, and distance are based on Smith et al. (1996).

e Pathways and parameters for equipment cleaning in gas processi ng activity are assumed to be the same as for pipe cleaning activity. It is assumed that th e pipe is contaminated in gas processing.B-6 TABLE B.2 Input Parameters Describing Public Exposures to the Unauthorized Release of Filter Socks and Proppants

Parameter Value Remark

Filter Sock Exposure Scenario 1

Filter socks used as a toy Ingestion and direct external exposure pathways are included. Inadvertent ingestion rate (g/h) 6.25 × 10 -3
Exposure time (h/yr) 24 Distance (m) 0.5

Source material Concrete Source material density (g/cm 3 ) 1 Toy geometry a

Area (cm 2 ) 90 Length (cm) 10

Filter Sock Exposure Scenario 2

Filter socks dumped in a dumpster b Only direct external exposure pathway is included because no

direct contact with the filter socks. Exposure time (h/yr) 40 Exposure distance (m) 1 Shielding thickness (cm) 0.32 Shielding density (g/cm 3 ) 7.86

Source material Concrete Source material density (g/cm 3 ) 1 Dumpster geometry (m)

Length 1.83

Width 1.52 Height 1.1

Proppant Exposure Scenario

Illegal dumping of proppant material on a field Ingestion and direct external exposure pathways are included. Inadvertent ingestion rate (g/h) 6.25 × 10 -3
Exposure time (h/yr) 100 Exposure distance (m) 1

Source material Concrete Source material density (g/cm 3 ) 1.6 Source geometry

Area (m 2 ) 10,000 Thickness (m) 0.15

a The toy is assumed to be in the shape of a cylindrical ball constructed with multiple filter socks such that the total weight of the toy does not exceed 1 kg (length = 10 cm, area = 90 cm 2

, density = 1 g/cm 3 ).

b The dumpster is assumed to be constructed of 1/8-in. thick steel walls and has the dimensions of a 4-yd 3 dumpster (6 ft length, 5 ft width, and 3.6 ft height).B-7 TABLE B.3 TSD-DOSE Input Parameters Describing Landfill Worker Operations for Disposing of Containerized Waste

Parameter Value Remark

Receiving and Handling

Density (g/cm 3 ) 1.4 Used “Receiving and Sampling” operation in TSD-DOSE code (Step A). Inspect manifest: exposure time (h) 1 Inspect manifest: distance (m) 1

On-site Transport of Containerized Waste

Density (g/cm 3 ) 1.4 Used “Transport to TSD Facility” operation in TSD-DOSE code (Step A and Step B). Load and secure shipment: exposure time (h) 0.75 Distance to truck (m) 1 Drive time to landfill (h) 0.25 Shielding thickness (cm) 0.16 Distance to truck (m) 2 Truck bed/tank size (m)

Length 6

Width 2 Height 1

Containerized Waste Placement

Density (g/cm 3 ) 1.4 Used “On-site Landfill” operation in TSD-DOSE code (Step B and Step D). Unload containers: exposure time (h) 0.75 Unload containers: distance (m) 1 Mix waste: exposure time (h) 0.75 Mix waste: distance (m) 1 Shielding thickness (cm) 5 Exposure geometry (m)

Length 8

Width 2 Height 2

Source: Pfingston et al. (1998).B-8 TABLE B.4 TSD-DOSE Input Parameters Describing Landfill Worker Operations for Disposing of Bulk Waste

Parameter Value Remark

Receiving and Handling Used “Receiving and Sampling” operation in TSD-DOSE code (Step A). Density (g/cm 3 ) 0.7 Inspect manifest: exposure time (h) 1 Inspect manifest: distance (m) 1

On-site Transport of Bulk Waste to Landfill Area Used “Transport to TSDFacility” operation in TSDDOSE code (Step A and Step B). Density (g/cm 3 ) 0.7 Secure shipment: exposure time (h) 0.75 Distance to truck (m) 1 Drive time to landfill (h) 0.25 Shielding thickness (cm) 0.16 Distance to truck (m) 2 Truck bed/tank size (m)

Length 6

Width 2 Height 1

Disposal at the Landfill and Waste Placement Used “On-site Landfill” operation in TSD-DOSE code (Step A and Step B). Density (g/cm 3 ) 1.4 Unload waste: exposure time (h) 0.75 Unload waste: distance (m) 1 Airborne respirable dust concentration (g/m 3 ) 1.0 × 10 -3 Used “On-site Landfill” operation in TSD-DOSE code (Step A and Step B). Mix waste at the landfill: exposure time (h) 0.75 Mix waste at the landfill: exposure distance (m) 1 Shielding thickness (cm) 5 Exposure geometry (m)

Length 8

Width 2 Height 2

Maximally Exposed Indivi dual (MEI)/Collective Population Bulk Disposal Bulk disposal results in general public exposure. Exposure time (h) 24 Exposure frequency (d/yr) 365 MEI distance to source (km) 0.3 Wind speed (m/s) 4 Percentage of time wind blows in direction (%) 50 Population density: 0–20 mi (persons/mi 2 ) 9.7 Average from 2010 Census

data for North Dakota. Population density: 20–50 mi (persons/mi 2 ) 9.7 Average from 2010 Census

data for North Dakota.

Sources: Pfingston et al. (1998); U.S. Census Bureau (2014).B-9 TABLE B.5 RESRAD-BUILD Input Parame ters Describing Evaporation Pond Worker Operations

Parameter Value Remark/Assumption

Evaporation Pond Worker Activities Water concentration calculated from the leachate

concentration. Leachate Sampling

Exposure time (h) 60 Sample is collected every day and sampling time is

10 minutes. Distance to pond (m) 0.5

Source material Water Source material density (g/cm 3 ) 1 Exposure geometry (m)

Length 100 Pond size is 100 m by 100 m and water depth is 2 m.

Width 100 Height 2 Evaporation Pond Cleaning

Exposure time (h) 10 Cleaning is performed 60 times/yr, and it takes 10 minutes to remove debris collected at the pond. Distance to pond (m) 1

Source material Water Source material density (g/cm 3 ) 1 Exposure geometry (m)

Length 100 Pond size is 100 m by 100 m and water depth is 2 m.

Width 100 Height 2B-10 TABLE B.6 Parameters Describing the Landfill Future-Use Scenarios a

Parameter Value Remark

Average radionuclide concentration (pCi/g) 1 No t applicable for off-site resident scenario.

Dilution factor 1 Calculated for intruder scenario from area, intruded depth, and landfill cover depth.

Groundwater concentration (pCi/L) 0 Value will be calculated for off-site resident

scenario.

Area (m 2 ) 10,000 Assumed value for intruder scenario. Will be

estimated from the size of the landfill for on-site resident, recreational, and industrial scenarios. Not applicable for off-site resident

scenario.

Density of waste layer (g/cm 3 ) 2 Mixture of soil/TENORM (EPA 1993).

Waste layer thickness 0.92 Assumed value for intruder scenario and will be

estimated from the total volume of TENORM waste disposed of for on-site resident, recreational, and indust rial scenarios. Not applicable for off-site resident scenario.

Cover depth (cm) 0 Assumed value for intruder scenario. Will be

estimated from the landfill characteristics for on-site resident, recreational, and industrial scenarios. Not applicable for off-site resident

scenario.

Density of cap material (g/cm 3 ) 1.6

Plant/soil transfer factor

Radium 6.8 × 10 -5 A&A (1996)

Lead 3.3 × 10 -5 A&A (1996)

Thorium 1.7 × 10 -6 A&A (1996)

Uranium 0.025 RESRAD code default Exposure time (h/d)

Residential

Indoor 12 Scenario assumption Outdoor 6 Scenario assumption

Industrial

Indoor 6 Scenario assumption Outdoor 2 Scenario assumption

Recreational

Indoor 0 Scenario assumption Outdoor 1 Scenario assumption Inhalation rate (m 3 /yr)

On-site resident 8,400 Table 2.3 in RESRAD Manual

On-site industrial worker 11,400 Table 2.3 in RESRAD ManualB-11 TABLE B.6 (Cont.)

Parameter Value Remark

Recreational visitor 14,000 Table 2.3 in RESRAD Manual

Off-site resident 8,400 Table 2.3 in RESRAD Manual Soil ingestion rates (mg/d)

On-site resident 100 Table 2.3 in RESRAD Manual

On-site industrial worker 100 Table 2.3 in RESRAD Manual

Recreational visitor 100 Table 2.3 in RESRAD Manual

Off-site resident NA b
Erosion rate (mm/yr) 1 RESRAD code default Non-leafy vegetable productivity (kg/m 2 ) 0.7 RESRAD code default Leafy vegetable productivity (kg/m 2 ) 1.5 RESRAD code default Fodder productivity (kg/m 2 ) 1.1 RESRAD code default Milk intake (L/yr) 92 RESRAD code default Fruit, vegetable, and grain consumption (kg/yr) 160 RESRAD code default Leafy vegetable consumption (kg/yr) 14 RESRAD code default Meat intake (kg/yr) 63 RESRAD code default Water intake (L/yr) 510 RESRAD code default Type of home construction Slab Scenario assumption Type of office construction Slab Scenario assumption Precipitation rate (m/yr) 0.39 Site specific Evapotranspiration coefficient 0.62 Site specific

Runoff coefficient 0.06 Site specific Wind speed (m/s) 5.2 Site specific Irrigation rate (m/yr) 0.2 RESRAD code default Livestock fodder intake for meat (kg/d) 68 RESRAD code default Livestock fodder intake for milk (kg/d) 55 RESRAD code default Livestock water intake for meat (L/d) 50 RESRAD code default Livestock water intake for milk (L/d) 160 RESRAD code default Livestock intake of soil (kg/d) 0.5 RESRAD code default Depth of soil mixing layer (m) 0.15 RESRAD code default Depth of roots (m) 0.9 RESRAD code default

Storage Times (d)

Fruits, non-leafy vegetables, and grains 14 RESRAD code default Leafy vegetables 1 RESRAD code default

Milk 1 RESRAD code default

Meat 20 RESRAD code default

Livestock fodder 45 RESRAD code default

Well water 1 RESRAD code default

Radon-Specific Parameters

Cap total porosity (%) 40 RESRAD code default Cap volumetric water content (%) 5 RESRAD code default Cap radon diffusion coefficient (m 2 /s) 2 × 10 -6 RESRAD code default Foundation thickness (m) 0.15 RESRAD code default Foundation density (g/cm 3 ) 2.4 RESRAD code default Foundation total porosity 0.1 RESRAD code default

Foundation volumetric water content 0.3 RESRAD code default Foundation radon diffusion coefficient (m 2 /s) 3 × 10 -7 RESRAD code defaultB-12 TABLE B.6 (Cont.)

Parameter Value Remark

Waste diffusion coefficient (m 2 /s) 2 × 10 -6 RESRAD code default Vertical mixing thickness (m) 2 RESRAD code default Building air exchange rate (h -1 ) 0.5 RESRAD code default Building room height (m) 2.5 RESRAD code default Foundation depth below ground surf ace(m) -1 RESRAD code default Rn-222 emanation coefficient (%) 4 Rood and Kendrick 1996 Rn-220 emanation coefficient (%) 15 RESRAD code default

a For the intruder scenario, the contamination configurati on is different, but the exposure pathways and other parameters are the same as for the on-site resident scenario. Many parameters values listed are RESRAD defaults, more representative values were used, if available.

b NA = not applicable.

Sources: A&A (1996); Rood and Kendrick (1996); EPA (1993; Yu et al. (2001).B-13 TABLE B.7 Parameters Used for th e Transportation Risk Assessment

Parameter Value Source

Number of shipments per year 1,000 From the assumption that 25,000 tons/year waste disposed of in Special Waste Landfill divided by the maximum truck capacity of

25 tons

Distance to landfill (km) 250 Assumed distance

Travel fraction rural 0.865 Estimated from values in Table D-3 of Weiner et al. (2013)

Travel fraction suburban 0.104

Travel fraction urban 0.031

Closest distance to nearby roads for a receptor living near the waste disposal facility (m) 300 Default in the code

Population density (persons/km 2 ) From 2010 Census data for North Dakota

Rural 1.5

Suburban 846 Traffic density (vehicles per hour) From value in Table D-3 of Weiner et al. (2013) Rural 293

Suburban 575 Urban 1,063

Dose-rate 1 m from vehicle (rem/h) 2.5 × 10 -5 Based on information from the state (if available), otherwise value be estimated

Trailer size (m) 8

Truck velocity (km/h) 88.49 a Based on average speed (55 mph) in rural areas and freeways from Table 6.11 in DOE (2002)

Accident rate (acci dents/km) 3.4 × 10 -7 For North Dakota from Table 6.20 in DOE (2002)

Accident fatality rate (fatalities/km)

Rural 1.1 × 10 -8 5-year average (2007–2011)

Suburban 4.4 × 10 -9 NDDOT (2012)

Vehicular emission fatality rate (fatalities/km) 8.36 × 10 -10 Assuming Truck Class VIIB from Table 6.41 in DOE (2002)

Sources: DOE (2002); NDDOT (2012); Weiner et al. (2013); U.S. Census Bureau (2014).B-14 TABLE B.8 Conditional Accident

Probabilities and Associated Release Fraction by Accident Severity Category

Accident Severity Category Conditional Probability Release

Fraction a

I 0.55 0

II 0.36 0.01

III 0.07 0.1

IV 0.02 1

a Values are for the total material release fraction (the fraction of the material in a package released to the environment during an accident).

Source: NRC (1977).

Appendix B References

A&A (Auxier and Asso ciates, Inc.), 1996, Leachate Analysis of Martha Oil Field Wastes

, Martha, KY, prepared for Ashland Exploration, Inc., Houston, TX.

DOE (U.S. Department of Energy), 2002, A Resource Handbook on DOE Transportation Risk

Assessment , DOE/EM/NTP/HB-01, July.

EPA (U.S. Environmental Protection Agency), 1993, DRAFT Diffuse NORM Wastes—Waste Characterization and Preliminary Risk Assessment , RAE-9232/1-2, Vol. 1, prepared by S. Cohen and Associates, Inc., and Rogers & As sociates Engineering Corp. for the Office of Radiation and Indoor Air, Washington, DC.

NDDOT (North Dakota Departme nt of Transportation), 2012, North Dakota Highway Safety Plan, 2013 , prepared by the Safety Division, Traffi c Safety Office, Sept. Available at http://www.dot.nd.gov/divisions/safe ty/docs/2013-HSP-Final.pdf.

NRC (U.S. Nuclear Regulatory Commission), 1977, Final Environmental Statement on the Transportation of Radioactive Mate rial by Air and Other Modes , NUREG-0170, Dec.

Pfingston, M., et al., 1998, TSD-DOSE: A Radiological Dose A ssessment Model for Treatment, Storage, and Disposal Facilities , ANL/EAD/LD-4 (Rev. 1), Argonne National Laboratory, Argonne, IL.

Rood, A.S., and D.T. Kendrick, 1996, “Measur ement of 222Rn Flux, 222Rn Emanation, and 226Ra Concentration from Inj ection Well Pipe Scale,” in NORM/NARM: Regulations and Risk

Assessment , Proceedings of the 29th Midyear Topical Meeting of the Hea lth Physics Society, Scottsdale, AZ, Jan. 7–10, pp. 139–144.B-15 Smith, K.P., D.L. Blunt, G.P. Williams, and C.L. Tebes, 1996, Radiological Dose Assessment Related to Management of Naturally Occurri ng Radioactive Materials Generated by the Petroleum Industry , ANL/EAD-2, Argonne National Laboratory, Argonne, IL.

U.S. Census Bureau, 2014, 2010 Census Urba n Lists Record Layouts. Available at http://www.census.gov/geo/reference/ua/u alists_layout.html. Accessed May 21, 2014.

Weiner, R.F., et al., 2013, RADTRAN 6/RadCat 6 User Guide, SAND2013-8095, Sandia National Laboratories, Albuquerque, NM, and Livermore, CA, Sept.

Yu, C., et al., 2001, User’s Manual for RESRAD, Version 6 , ANL/EAD-4, Argonne National Laboratory, Argonne, IL.B-16 This page intentionally left blank.C-1 APPENDIX C:

LANDFILL DESIGNS TESTED WITH THE HELP MODELC-2 This page intentionally left blank.C-3TABLE C.1 Special Waste Landfill DesignSpecial Waste Landfill Open Cell(Operational Phase)Special Waste Landfill Capped Cell(Post-Closure Phase and Sensitivity Test)Special Waste Landfill Capped Cell (Degraded)Layer ThicknessMaterial andRequirementHELPModelLayer TypeHELPModelMaterial Layer ThicknessMaterial andRequirementHELPModelLayer TypeHELPModelMaterial Layer ThicknessMaterial andRequirementHELPModelLayer TypeHELPModelMaterial1 0.5 ft Topsoil Verticalpercolation9. Siltyloam1 0.5 ft Topsoil Verticalpercolation9. Siltyloam2 1 ft Clayey soil Verticalpercolation8. Loam 2 1 ft Clayey soil Verticalpercolation8. Loam3 1.5 ft Recompacted soil,K<1e-7 cm/sBarrier soil 16.Barriersoil3 1.5 ft Recompactedsoil,K<1e-7 cm/sBarrier soil 16. Barriersoil1 62.5 ft Waste Verticalpercolation18.Municipalwaste4 125 ft Waste Verticalpercolation18.Municipalwaste4 125 ft Waste Verticalpercolation18.Municipalwaste2 1 ft Drainage layer,K≥1e-3 cm/s,T≥3e-2 cm2/s.Presumed LCS.Lateraldrainage2. Sand 5 1 ft Drainage layer,K≥1e-3 cm/s,T≥3e-2 cm2/s.Presumed LCS.Lateraldrainage2. Sand 5 1 ft Drainage layer,K≥1e-3 cm/s,T≥3e-2 cm2/s.Presumed LCS.Lateraldrainage(no LCS inone case)2. Sand3 60 mil Geomembrane Geomembrane35. HDPE 6 60 mil Geomembrane Geomem-brane35. HDPE4 3 ft Recompactedclay,K<1e-7 cm/sBarrier soil 16. Barriersoil7 3 ft Recompacted clay,K<1e-7 cm/sBarrier soil 16.Barriersoil6 3 ft Recompactedclay,K<1e-7 cm/sBarrier soil 16. Barriersoil5 66 ft Native soilunsaturated zoneVerticalpercolation4. Loamysand8 66 ft Native soilunsaturated zoneVerticalpercolation4. Loamysand7 66 ft Native soilunsaturated zoneVerticalpercolation4. LoamysandAbbreviations: HDPE = high-density polyethylene; LCS = leachate collection system.C-4TABLE C.2 Industrial Waste Landfill DesignaIndustrial Waste Landfill Open Cell(Operational Phase)Industrial Waste Landfill Capped Cell(Post-Closure Phase and Sensitivity Test)Industrial Waste Landfill Capped Cell(Degraded)Layer ThicknessMaterial andRequirementHELPModelLayer TypeHELPModelMaterial Layer ThicknessMaterial andRequirementHELPModelLayer TypeHELPModelMaterial Layer ThicknessMaterial andRequirementHELPModelLayer TypeHELPModelMaterial1 3.5 ft Topsoil and soil Verticalpercolation9. Siltyloam1 3.5 ft Topsoil and soil Verticalpercolation9. Siltyloam2 1 ft Drainage layer,K≥1e-3 cm/s,T≥3e-2 cm2/s.Presumed LCS.Lateraldrainage2. Sand 2 1 ft Drainage layer,K≥1e-3 cm/s,T≥3e-2 cm2/s.Presumed LCS.Lateraldrainage(no LCS inone case)2. Sand3 60 mil Geomembrane Geomembrane35. HDPE4 2 ft Compacted soil,K<1e-7 cm/sBarrier soil 14. Siltyclay3 2 ft Compactedsoil,K<1e-7 cm/sBarrier soil 14. Siltyclay1 62.5 ft Waste Verticalpercolation18.Municipalwaste5 125 ft Waste Verticalpercolation18.Municipalwaste4 125 ft Waste Verticalpercolation18.Municipalwaste2 1 ft Drainage layer,K≥1e-3 cm/s,T≥3e-2 cm2/s,therefore b =32 cm = 1 ft.Presumed LCS.Lateraldrainage2. Sand 6 1 ft Drainage layer,K≥1e-3 cm/s,T≥3e-2 cm2/s,therefore b = 32 cm= 1 ft.Presumed LCS.Lateraldrainage2. Sand 5 1 ft Drainage layer,K≥1e-3 cm/s,T≥3e-2 cm2/s,therefore b =32 cm = 1 ft.Presumed LCS.Lateraldrainage(no LCS inone case)2. Sand3 80 mil Geomembrane Geomembrane35. HDPE 7 80 mil Geomembrane Geomem-brane35. HDPE4 1 ft Drainage layer,K≥1e-3 cm/s,T≥3e-2 cm2/sLateraldrainage2. Sand 8 1 ft Drainage layer,K≥1e-3 cm/s,T≥3e-2 cm2/sLateraldrainage2. Sand 6 1 ft Drainage layer,K≥1e-3 cm/s,T≥3e-2 cm2/sLateraldrainage(no LCS inone case)2. Sand5 60 mil Geomembrane Geomembrane35. HDPE 9 60 mil Geomembrane Geomem-brane35. HDPEC-5TABLE C.2 (Cont.)Industrial Waste Landfill Open Cell(Operational phase)Industrial Waste Landfill Capped Cell(Post-closure phase and Sensitivity test)Industrial Waste Landfill Capped Cell(degraded)Layer ThicknessMaterial andRequirementHELPModelLayer TypeHELPModelMaterial Layer ThicknessMaterial andRequirementHELPModelLayer TypeHELPModelMaterial Layer ThicknessMaterial andRequirementHELPModelLayer TypeHELPModelMaterial6 3 ft Recompactedclay,K<1e-7 cm/sBarrier soil 16. Barriersoil10 3 ft Recompacted clay,K<1e-7 cm/sBarrier soil 16. Barriersoil7 3 ft Recompactedclay,K<1e-7 cm/sBarrier soil 16. Barriersoil7 66 ft Native soilunsaturated zoneVerticalpercolation4. Loamysand11 66 ft Native soilunsaturated zoneVerticalpercolation4. Loamysand8 66 ft Native soilunsaturated zoneVerticalpercolation4. LoamysandAbbreviations: HDPE = high-density polyethylene; LCS=leachate collection system.aEach drainage layer’s thickness is calculated as the required transmissivity (T) divided by the required hydraulic conductivity (K) and is approximately 1 ft.C-6 This page intentionally left blank.D-1 APPENDIX D:

LITERATURE REVIEW OF THE DI STRIBUTION COEFFICIENT K DD-2 This page intentionally left blank.D-3 APPENDIX D:

LITERATURE REVIEW OF THE DI STRIBUTION COEFFICIENT K D

D.1 K d of Radium

Auxier & Associates (A&A) (1996) performed leaching analyses on radium-226 (Ra-226)-containing materials using the toxicity characteristic leaching procedure (TCLP). Samples included naturally occu rring radioactive material (NORM) pipe scale and NORMcontaminated soil associated with oil field wast es in Kentucky. The scale samples were crushed to promote a worst-case leaching scenario. Tabl e C.1 shows the results for the scale and soil samples. The activity leached fraction (LF) wa s calculated by A&A (1996) as the amount of Ra-226 in the leachate divided by the total amount of Ra-226 in the leachate plus Ra-226 residual on the solid sample. The LF ranges from 2.5 × 10 -4 to 4.1 × 10 -3 (Table D.1).

A&A (1996) used the TCLP results to es timate the distribution coefficient, K d, by equating it to the ratio of the re sidue activity concentr ation to the leachate activity concentration.

Because of the differences in the TCLP method co mpared with the traditional batch test method

for K d , the TCLP method differs in terms of the so lution-to-solid ratio and the acidity of the liquid phase, and the K d is expected to be underestimated (A&A 1996). This K d :LF relationship is illustrated in Figure D.1.

A report by Swann et al. (2004) includes anal ysis of leaching of radium from NORM scale and sludge samples. In this case, the maximum LF was 1.1 × 10 -3 for NORM-containing tank sludge, while the LF from a mixture of NORM and soil was 3.6 × 10 -3 . These are in the same range of the LFs determined by A&A (1996). Swann et al. (2004) note that soils have the ability to complex soluble radium, which results in higher LFs for scale-soil mixtures than for pure scale. This is supported by the data from both A&A ( 1996) and Swann et al. (2004).

The U.S. Environmental Protection Agency (EPA) (2004) has summarized the work of numerous publications on the K d values of radium. Limited data are available, and very high apparent adsorption may be due to the precipitati on of (Ba,Ra)SO 4 during experiments. The EPA recommends site-specific conditions for K d testing. Radium sorption may depend on the pH of the system. Summarized findings from the literature about radium sorption on soils include the following:

• K d values of 6.7, 12.6, 26.3, and 26.3 mL/g on sandy material at pH values of 6, 7, 8, and 9, respectively, and desorption Kd values of 10.9, 31, 38, and 29 mL/g at the same pH levels, indica ting that adsorption and desorption of radium increase with increasing pH, and that radium essentially undergoes complete reversible adsorption.

• K d values of 214 to 467 mL/g on sandy soil samples with a pH of 7.6 to 8.0.D-4TABLE D.1 Ra-226 Leached Fraction and Kdof Samples Containing Ra-226A B C = B*2 D E = D*100 C/(C+E) 1,000* B/DSample DescriptionSample’sRa-226*(pCi/g)TCLP Ra-226Concentrationin 2 L ofLeachate*(pCi/L)Amount ofRa-226 inLeachate(pCi)TCLPResidue in100 gSample*(pCi/g)Amount ofRa-226 inResidue(pCi) LF Kd(mL/g)AverageKd(mL/g)SCHS004 Soil near tanks75 917 62 6,200 2.73 × 10-37,2946,102SCHS002 Soil near tanks 110 11 22 54 5,400 4.06 × 10-34,909SCHS003 Soil downgradient of tanks 920 71 142 1,000 100,000 1.42 × 10-314,08525,561SCHS001 Soil downgradient of tanks 1,100 27 54 1,000 100,000 5.4 × 10-437,037SCHC001 Scale of 1 pipe 1,600 15 30 1,200 120,000 2.5 × 10-480,00079,286SCHC002 Scale of 7 pipes 1,500 14 28 1,100 110,000 2.54 × 10-478,571SCHC003 Scale of 3 pipes 1,700 <0.6 Ignored 2,000 200,000 Ignored Ignored* Uncertainty estimates not shown.Source: Data from A&A (1996).D-5 • K d values at one site of 10 to 1,000, 000 mL/g, with a recommended value of 100 mL/g.

• A cited compilation of multiple studies listed K d values for various soil types (but geochemical conditions were not documented):

 Sand: 57 to 21,000 mL/g, geometri c mean 500 mL/g, 3 observations

 Silt: 1,262 to 530,000 mL/g, geometric mean 36,000 mL/g, 3 observations

 Clay: 696 to 56,000 mL/g, geometric mean 9,100 mL/g, 8 observations

 Organic soil: 2,400 mL/g, 1 observation.

Vandenhove et al. (2009) also provided a co mpilation of literature values, including many of those included by the EPA (2004). They determined a geometric mean K d of Ra-226 of 2,500 mL/g based on 51 samples from various soil types. The variability among different soil types was large and ranges were overlapping. No other parameter (pH, cation exchange capacity, or organic matter) was found to be useful in refining K d values for Ra-226.

The assumed K d of a landfilled waste-soil mixture and the assumed activity concentration

of the mixture can be used to estimate a so lute concentration. Knowing the presumed North Dakota landfill disposal concentration (and rounding up to be conservative) and assuming a conservatively high LF with an associated conservatively low K d (see Figure D.1), the

dissolved concentration of Ra-226 can be esti mated. Note that although some literature K d values

for radium have been in the tens to hundreds of mL/g, most are in the thousands or higher. The A&A data (Figure D.1) suggest that the K d of Ra-226 is fairly stable with assumed higher LF

levels.

FIGURE D.1 Relationship between K d and Leached Fraction of Ra-226 Samples (Source: A&A 1996)D-6 D.2 K d of Thorium

Vandenhove et al. (2009) compiled da ta on 46 measurements of the K d of thorium in various soils. The overall geometric mean wa s 1,900 mL/g with a range of 19 to 250,000 mL/g. They note that the high values may be due to precipitation of thorium compounds. Following an EPA method that incorporates pH in the categorizing of K d values, they proposed values of 1,000 mL/g for pH less than 5, 3,000 for pH from 5 to 8, and 300 for pH gr eater than 8. The EPA (2004) reported a similar range and pH bins.

D.3 K d of Lead

Vandenhove et al. (2009) compiled da ta on 23 measurements of the K d of lead in various soils. Very little information was found to be available on the K d of lead radioisotopes. The overall geometric mean was 2,100 mL/g with a range of 25 to 127,000 mL/g. The values of pH

were determined to influence the K d values. Data in the range of 3 to 6.4 pH units had a geometric mean of 570 mL/g, while data in the ra nge of 6.4 to 8.3 mL/g had a geometric mean of 7,900 mL/g.

D.4 K d Summary

The studies described here provide a wide range of K d values for Ra-226, ranging from approximately 10 to 500,000 mL/g, with similar la rge ranges for the other radioisotopes. The results may depend on methods, pH (mainly in the case of thorium), other geochemical conditions, and soil type (or whethe r the sample is pure scale). In the absence of site-specific K d or leaching studies, conservative estimates (i.e., promoting high concentrations) may be made. The dissolved concentration value (C solute ) leaking from a landfill should be estimated for radium and thorium using a rounded-up value for the di sposal activity concentr ation (assumed C*) and

K d values of 100, 1,000, and 10,000 mL/g so that the sensitivity of the source concentration can be explored. For lead, K d values of 10, 100, and 1,000 mL/g should be examined.

Appendix D References

A&A (Auxier and Asso ciates, Inc.), 1996, Leachate Analysis of Martha Oil Field Wastes

, Martha, KY, prepared for Ashland Exploration, Inc., Houston, TX.

EPA (U.S. Environmental Protection Agency ), 2004, “Understanding Variation in Partition Coefficient, K d , Values,” in Volume III: Review of Geochemistry and Available K d Values for Americium, Arsenic, Curium, Iodi ne, Neptunium, Radium, and Technetium , EPA 402-R-04- 002C, Washington, DC, July.D-7 Swann, C., J. Matthews, R. Ericksen, and J. Kuszmaul, 2004, Evaluations of Radionuclides of Uranium, Thorium, and Radium Associated with Produced Fluids, Precipitates, and Sludges from Oil, Gas, and Oilfield Brine Injec tions Wells in Mississippi, Final Report , U.S. Department of Energy Award Number DE-FG26-02NT 15227, March.

Vandenhove, H., G. Gil-Garcia, A. Rigol, and M. Vidal, 2009, “New Best Estimates for Radionuclide Solid–Liquid Distribut ion Coefficients in Soils. Part 2. Naturally Occurring Radionuclides,” Journal of Environmental Radioactivity 100:697–703.D-8 This page intentionally left blank.E-1 APPENDIX E:

GROUNDWATER CALCULATIONSE-2 This page intentionally left blank.E-3TABLE E.1 Calculations Relating Disposal Concentration of Unity, Appropriate Range of In-Landfill KdValues, LeachateConcentration Reaching Water Table, Downgradient Proportion of Leachate Recharge, and Concentration in Groundwaterfor 100-m (328-ft) Downgradient Receptor and 20-m (66-ft) Thick Unsaturated ZoneNote A Note BNote C Note DMax. C/Co and Max. Conc. in10,000 Years at 100-m Downgradient ReceptorLF leachate Conc. atIncreased Increased HydraulicDecay Water Base Case Decreased KdIncreased KdDispersivity Increased Gradient ConductivityKd(mL/g)CsolutepCi/mLCsolutepCi/LConst.1/yrTablepCi/LC/Co pCi/L C/Co pCi/L C/Co pCi/LC/Co pCi/L C/Co pCi/L C/Co pCi/LPb-210 1,000 0.001 10.0310.157.88E-13 1.21E-13 2.89E-07 4.44E-08 6.14E-19 9.44E-20 1.05E-09 1.61E-10 1.27E-11 1.96E-12 1.34E-07 2.06E-08100 0.01 100.0311.57.88E-13 1.21E-12 2.89E-07 4.44E-07 6.14E-19 9.44E-19 1.05E-09 1.61E-09 1.27E-11 1.96E-11 1.34E-07 2.06E-0710 0.1 1000.031157.88E-13 1.21E-11 2.89E-07 4.44E-06 6.14E-19 9.44E-18 1.05E-09 1.61E-08 1.27E-11 1.96E-10 1.34E-07 2.06E-06Ra-226 10,000 0.0001 0.10.000430.0971.45E-08 1.42E-09 3.69E-07 3.60E-08 9.64E-14 9.39E-15 6.53E-06 6.36E-07 2.05E-07 1.99E-08 1.30E-04 1.26E-051,000 0.001 10.000430.971.45E-08 1.42E-08 3.69E-07 3.60E-07 9.64E-14 9.39E-14 6.53E-06 6.36E-06 2.05E-07 1.99E-07 1.30E-04 1.26E-04100 0.01 100.000439.71.45E-08 1.42E-07 3.69E-07 3.60E-06 9.64E-14 9.39E-13 6.53E-06 6.36E-05 2.05E-07 1.99E-06 1.30E-04 1.26E-03Ra-228 10,000 0.0001 0.10.127.2E-053.06E-22 2.21E-26 1.92E-16 1.39E-20 4.57E-30 3.30E-34 1.61E-20 1.16E-24 4.68E-21 3.38E-25 1.59E-16 1.15E-201,000 0.001 10.120.000723.06E-22 2.21E-25 1.92E-16 1.39E-19 4.57E-30 3.30E-33 1.61E-20 1.16E-23 4.68E-21 3.38E-24 1.59E-16 1.15E-19100 0.01 100.120.00723.06E-22 2.21E-24 1.92E-16 1.39E-18 4.57E-30 3.30E-32 1.61E-20 1.16E-22 4.68E-21 3.38E-23 1.59E-16 1.15E-18Th-232 10,000 0.0001 0.15E-110.15.59E-07 5.59E-08 5.59E-07 5.59E-08 5.59E-07 5.59E-08 1.81E-04 1.81E-05 6.65E-06 6.65E-07 1.97E-03 1.97E-041,000 0.001 15E-1115.59E-07 5.59E-07 5.59E-07 5.59E-07 5.59E-07 5.59E-07 1.81E-04 1.81E-04 6.65E-06 6.65E-06 1.97E-03 1.97E-03100 0.01 105E-11105.59E-07 5.59E-06 5.59E-07 5.59E-06 5.59E-07 5.59E-06 1.81E-04 1.81E-03 6.65E-06 6.65E-05 1.97E-03 1.97E-02Note A. Concentration of unity (1 pCi/g) assigned to disposal concentration, to be scaled to downgradient groundwater concentration at receptor well. The disposalconcentration is assumed to bethe sorbed concentration, and through the assumption of a linearisotherm and an appropriaterange of concentrations of Kdvalues, the solute in landfill leachate is calculated.Note B. See Kddiscussion in Appendix D. The largest Kdvalues correspond to the less conservative case, the mid-range Kdvalues are the base case, and the smallest Kdvalues are moreconservative.Note C. Conc. at water table = conc. of landfill leachate * e^(time * decay constant). Time is a 60-year transport time for water in the unsaturated zone.Note D. Each column of proportions is the result of MT3DMS analysis scaled from a starting recharge flux to the aquifer of unity for each radionuclide of concern(ROC). Each adjacent column ofconcentrations is the concentration at the water table multiplied by the proportion.E-4TABLE E.2 Calculations Relating Disposal Concentration of Unity, Appropriate Range of In-Landfill KdValues, LeachateConcentration Reaching Water Table, Downgradient Proportion of Leachate Recharge, and Concentration in Groundwaterfor 100-m (328-ft) Downgradient Receptor and 5-m (16-ft) Thick Unsaturated ZoneNote A Note BNote C Note DMax. C/Co and Max. Conc. in10,000 Years at 100-m Downgradient ReceptorLF leachate Conc. atIncreased Increased HydraulicDecay Water Base Case Decreased KdIncreased KdDispersivity Increased Gradient ConductivityKd(mL/g)CsolutepCi/mLCsolutepCi/LConst.1/yrTablepCi/LC/Co pCi/L C/Co pCi/L C/Co pCi/L C/Co pCi/L C/Co pCi/L C/Co pCi/LPb-210 1,000 0.001 10.0310.627.88E-13 4.94E-13 2.89E-07 1.81E-07 6.14E-19 3.85E-19 1.05E-09 6.58E-10 1.27E-11 7.97E-12 1.34E-07 8.41E-08100 0.01 100.0316.27.88E-13 4.94E-12 2.89E-07 1.81E-06 6.14E-19 3.85E-18 1.05E-09 6.58E-09 1.27E-11 7.97E-11 1.34E-07 8.41E-0710 0.1 1000.031627.88E-13 4.94E-11 2.89E-07 1.81E-05 6.14E-19 3.85E-17 1.05E-09 6.58E-08 1.27E-11 7.97E-10 1.34E-07 8.41E-06Ra-226 10,000 0.0001 0.10.000430.0991.45E-08 1.44E-09 3.69E-07 3.67E-08 9.64E-14 9.57E-15 6.53E-06 6.49E-07 2.05E-07 2.03E-08 1.30E-04 1.29E-051,000 0.001 10.000430.991.45E-08 1.44E-08 3.69E-07 3.67E-07 9.64E-14 9.57E-14 6.53E-06 6.49E-06 2.05E-07 2.03E-07 1.30E-04 1.29E-04100 0.01 100.000439.91.45E-08 1.44E-07 3.69E-07 3.67E-06 9.64E-14 9.57E-13 6.53E-06 6.49E-05 2.05E-07 2.03E-06 1.30E-04 1.29E-03Ra-228 10,000 0.0001 0.10.120.0163.06E-22 5.02E-24 1.92E-16 3.15E-18 4.57E-30 7.49E-32 1.61E-20 2.63E-22 4.68E-21 7.67E-23 1.59E-16 2.61E-181,000 0.001 10.120.163.06E-22 5.02E-23 1.92E-16 3.15E-17 4.57E-30 7.49E-31 1.61E-20 2.63E-21 4.68E-21 7.67E-22 1.59E-16 2.61E-17100 0.01 100.121.63.06E-22 5.02E-22 1.92E-16 3.15E-16 4.57E-30 7.49E-30 1.61E-20 2.63E-20 4.68E-21 7.67E-21 1.59E-16 2.61E-16Th-232 10,000 0.0001 0.15E-110.15.59E-07 5.59E-08 5.59E-07 5.59E-08 5.59E-07 5.59E-08 1.81E-04 1.81E-05 6.65E-06 6.65E-07 1.97E-03 1.97E-041,000 0.001 15E-1115.59E-07 5.59E-07 5.59E-07 5.59E-07 5.59E-07 5.59E-07 1.81E-04 1.81E-04 6.65E-06 6.65E-06 1.97E-03 1.97E-03100 0.01 105E-11105.59E-07 5.59E-06 5.59E-07 5.59E-06 5.59E-07 5.59E-06 1.81E-04 1.81E-03 6.65E-06 6.65E-05 1.97E-03 1.97E-02Note A. Concentration of unity (1 pCi/g) assigned to disposal concentration, to be scaled to downgradient groundwater concentration at receptor well. The disposalconcentration is assumed to bethe sorbed concentration, and through the assumption of a linearisotherm and an appropriaterange of concentrations of Kdvalues, the solute in landfill leachate is calculated.Note B. See Kddiscussion in Appendix D. The largest Kdvalues correspond to the less conservative case, the mid-range Kdvalues are the base case, and the smallest Kdvalues are moreconservative.Note C. Conc. at water table = conc. of landfill leachate * e^(time * decay constant). Time is a 15-year transport time for water in the unsaturated zone.Note D. Each column of proportions is the result of MT3DMS analysis scaled from a starting recharge flux to the aquifer of unity for each ROC. Each adjacent column of concentrations is theconcentration at the water table multiplied by the proportion.E-5TABLE E.3 Calculations Relating Disposal Concentration of Unity, Appropriate Range of In-Landfill KdValues, LeachateConcentration Reaching Water Table, Downgradient Proportion of Leachate Recharge, and Concentration in Groundwaterfor 300-m (984-ft) Downgradient Receptor and 20-m (66-ft) Thick Unsaturated ZoneNote A Note BNote C Note DMax. C/Co and Max. Conc. in 10,000 years at 300-mDowngradient ReceptorLF Leachate Conc. atIncreasedIncreasedHydraulicDecay Water Base Case Decreased KdIncreased KdDispersivity Increased Gradient ConductivityKd(mL/g)CsolutepCi/mLCsolutepCi/LConst.1/yrTablepCi/L C/Co pCi/L C/Co pCi/L C/Co pCi/LC/Co pCi/L C/Co pCi/L C/Co pCi/LPb-210 1,000 0.001 1 0.031 0.15 3.47E-32 5.33E-33 5.26E-17 8.08E-18 0.00E+00 0.00E+00 2.92E-22 4.49E-23 3.09E-28 4.75E-29 1.96E-15 3.00E-16100 0.01 10 0.031 1.5 3.47E-32 5.33E-32 5.26E-17 8.08E-17 0.00E+00 0.00E+00 2.92E-22 4.49E-22 3.09E-28 4.75E-28 1.96E-15 3.00E-1510 0.1 100 0.031 15 3.47E-32 5.33E-31 5.26E-17 8.08E-16 0.00E+00 0.00E+00 2.92E-22 4.49E-21 3.09E-28 4.75E-27 1.96E-15 3.00E-14Ra-226 10,000 0.0001 0.1 0.00043 0.097 3.53E-25 3.44E-26 3.64E-23 3.54E-24 5.66E-35 5.52E-36 1.01E-13 9.80E-15 2.60E-20 2.54E-21 2.09E-08 2.04E-091,000 0.001 1 0.00043 0.97 3.53E-25 3.44E-25 3.64E-23 3.54E-23 5.66E-35 5.52E-35 1.01E-13 9.80E-14 2.60E-20 2.54E-20 2.09E-08 2.04E-08100 0.01 10 0.00043 9.7 3.53E-25 3.44E-24 3.64E-23 3.54E-22 5.66E-35 5.52E-34 1.01E-13 9.80E-13 2.60E-20 2.54E-19 2.09E-08 2.04E-07Ra-228 10,000 0.0001 0.1 0.12 7.2E-05 0.00E+00 0.0E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.0E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+001,000 0.001 1 0.12 0.00072 0.00E+00 0.0E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.0E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00100 0.01 10 0.12 0.0072 0.00E+00 0.0E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.0E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00Th-232 10,000 0.0001 0.1 5E-11 0.1 6.50E-23 6.50E-24 6.50E-23 6.50E-24 6.50E-23 6.50E-24 3.88E-11 3.88E-12 2.40E-18 2.40E-19 9.75E-07 9.75E-081,000 0.001 1 5E-11 1 6.50E-23 6.50E-23 6.50E-23 6.50E-23 6.50E-23 6.50E-23 3.88E-11 3.88E-11 2.40E-18 2.40E-18 9.75E-07 9.75E-07100 0.01 10 5E-11 10 6.50E-23 6.50E-22 6.50E-23 6.50E-22 6.50E-23 6.50E-22 3.88E-11 3.88E-10 2.40E-18 2.40E-17 9.75E-07 9.75E-06Note A. Concentration of unity (1 pCi/g) assigned to disposal concentration, to be scaled to downgradient groundwater concentration at receptor well. The disposalconcentration is assumed tobe the sorbed concentration, and through the assumption of a linearisotherm and an appropriaterange of concentrations of Kdvalues, the solute in landfill leachate is calculated.Note B. See Kddiscussion in Appendix D. The largest Kdvalues correspond to the less conservative case, the mid-range Kdvalues are the base case, and the smallest Kdvalues are moreconservative.Note C. Conc. at water table = conc. of landfill leachate * e^(time * decay constant). Time is a 60-year transport time for water in the unsaturated zone.Note D. Each column of proportions is the result of MT3DMS analysis scaled from a starting recharge flux to the aquifer of unity for each ROC. Each adjacent column of concentrations is theconcentration at the water table multiplied by the proportion.E-6TABLE E.4 Calculations Relating Disposal Concentration of Unity, Appropriate Range of In-Landfill KdValues, LeachateConcentration Reaching Water Table, Downgradient Proportion of Leachate Recharge and Concentration in Groundwaterfor 300-m (984-ft) Downgradient Receptor and 5-m (16-ft) Thick Unsaturated ZoneNote A Note B Note C Note DMax. C/Co and Max. Conc. in 10,000 years at 300-mDowngradient ReceptorLF Leachate Conc. atIncreased Increased HydraulicDecay Water Base Case Decreased KdIncreased KdDispersivity Increased Gradient ConductivityKd(mL/g)CsolutepCi/mLCsolutepCi/LConst.1/yrTablepCi/L C/Co pCi/L C/Co pCi/LC/Co pCi/LC/Co pCi/L C/Co pCi/L C/Co pCi/LPb-210 1,000 0.001 1 0.031 0.62 3.47E-32 2.17E-32 5.26E-17 3.29E-17 0.00E+00 0.00E+00 2.92E-22 1.83E-22 3.09E-28 1.94E-28 1.96E-15 1.22E-15100 0.01 10 0.031 6.2 3.47E-32 2.17E-31 5.26E-17 3.29E-16 0.00E+00 0.00E+00 2.92E-22 1.83E-21 3.09E-28 1.94E-27 1.96E-15 1.22E-1410 0.1 100 0.031 62 3.47E-32 2.17E-30 5.26E-17 3.29E-15 0.00E+00 0.00E+00 2.92E-22 1.83E-20 3.09E-28 1.94E-26 1.96E-15 1.22E-13Ra-226 10,000 0.0001 0.1 0.00043 0.099 3.53E-25 3.51E-26 3.64E-23 3.61E-24 5.66E-35 5.62E-36 1.01E-13 1.00E-14 2.60E-20 2.59E-21 2.09E-08 2.08E-091,000 0.001 1 0.00043 0.99 3.53E-25 3.51E-25 3.64E-23 3.61E-23 5.66E-35 5.62E-35 1.01E-13 1.00E-13 2.60E-20 2.59E-20 2.09E-08 2.08E-08100 0.01 10 0.00043 9.9 3.53E-25 3.51E-24 3.64E-23 3.61E-22 5.66E-35 5.62E-34 1.01E-13 1.00E-12 2.60E-20 2.59E-19 2.09E-08 2.08E-07Ra-228 10,000 0.0001 0.1 0.12 0.016 0.00E+00 0.00E+00 0.0E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+001,000 0.001 1 0.12 0.16 0.00E+00 0.00E+00 0.0E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00100 0.01 10 0.12 1.6 0.00E+00 0.00E+00 0.0E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00Th-232 10,000 0.0001 0.1 5E-11 0.1 6.50E-23 6.50E-24 6.50E-23 6.50E-24 6.50E-23 6.50E-24 3.88E-11 3.88E-12 2.40E-18 2.40E-19 9.75E-07 9.75E-081,000 0.001 1 5E-11 1 6.50E-23 6.50E-23 6.50E-23 6.50E-23 6.50E-23 6.50E-23 3.88E-11 3.88E-11 2.40E-18 2.40E-18 9.75E-07 9.75E-07100 0.01 10 5E-11 10 6.50E-23 6.50E-22 6.50E-23 6.50E-22 6.50E-23 6.50E-22 3.88E-11 3.88E-10 2.40E-18 2.40E-17 9.75E-07 9.75E-06Note A. Concentration of unity (1 pCi/g) assigned to disposal concentration, to be scaled to downgradient groundwater concentration at receptor well. The disposal concentration is assumed to be thesorbed concentration, and through the assumption of a linear isotherm and an appropriate range of concentrations of Kdvalues, the solute in landfill leachate is calculated.Note B. See Kddiscussion in Appendix D. The largest Kdvalues correspond to the less conservative case, the mid-range Kdvalues are the base case, and the smallest Kdvalues are moreconservative.Note C. Conc. at water table = conc. of landfill leachate * e^(time * decay constant). Time is a 15-year transport time for water in the unsaturated zone.Note D. Each column of proportions is the result of MT3DMS analysis scaled from a starting recharge flux to the aquifer of unity for each ROC. Each adjacent column of concentrations is theconcentration at the water table multiplied by the proportion.