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 POTENTIAL 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 TENORM Concentrations for Landfill 

Disposal ........................................................................................................... 27

4.3 Hydrologic Modeling ................................................................................................. 27

4.3.1 Landfill Hydrologic Modeling ......................................................................... 28
iv

CONTENTS (Cont.) 

4.3.2 Hydrogeological Setting of a Generic 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 Contaminant 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 for 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 Concentrations 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 Allowable Radium Concentration for TENORM 

Disposal in Landfills in North Dakota ........................................................................ 67

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

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

7.2 Recommendations ...................................................................................................... 73
v

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 Kd ................................... 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 Levels for Common Activities ........................................ 24

5.1 HELP Model Results for the Closed Industrial Waste Landfill for Precipitation, 

Evapotranspiration, and Runoff over 100 Years ........................................................... 36

5.2 HELP Model Results for the Closed Industrial 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 Industrial Waste Landfill for Percolation 

through the Recompacted Liner Soil and the Deep Natural Soil over 100 Years ........ 38

5.4 HELP Model Results for the Closed Industrial Waste Landfill with Decomposed 

Geomembranes and an Inactive LCS for Percolation through the Cover’s Barrier 

Soil, the Recompacted Liner Soil, and the 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.............................................................................................................. 45
vi

FIGURES (Cont.) 

6.1 Steps Involved in Estimating the Allowable Concentration in the Landfill from 

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

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

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

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

TABLES 

2.1 North Dakota TENORM Waste Characterization 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 Percolation 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 Groundwater Concentration to Leachate 

Recharge Concentration over 10,000 Years ................................................................. 46 

6.1 Waste Streams Used in Evaluating Radiation Dose in Different Worker and 

Public Scenarios from Well Site Operations ................................................................ 48 

6.2 Estimated Maximum Dose Rate for Different Well Site Operations Using 

Average Radionuclide Concentration ........................................................................... 48 

6.3 Estimated Maximum Dose Rate for Different 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 Well Site Operation Worker Scenarios ............. 51 
vii

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 100-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 Transportation Distance of 250 km ....................................... 60 

6.13 Vehicle-Related Transportation Risks for Base Case and Maximum Case 

Conditions, Assuming a Round-Trip Transportation 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 Concentrations 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 Describing Well Site Operations ........................ B-3 
viii

TABLES (Cont.) 

B.2 Input Parameters Describing Public Exposures to the Unauthorized Release of 

Filter Socks and Proppants ............................................................................................ B-6 

B.3 TSD-DOSE Input Parameters Describing Landfill Worker Operations for 

Disposing of Containerized Waste ................................................................................ B-7 

B.4 TSD-DOSE Input Parameters Describing 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 Transportation Risk Assessment ........................................... B-13 

B.8 Conditional Accident Probabilities and Associated 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 Kd of Samples Containing Ra-226 ............................... D-4 

E.1 Calculations Relating Disposal Concentration of Unity, Appropriate Range of 

In-Landfill Kd Values, Leachate Concentration Reaching Water Table, 

Downgradient Proportion of Leachate Recharge, and Concentration in 

Groundwater for 100-m Downgradient Receptor and 20-m Thick Unsaturated 

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

E.2 Calculations Relating Disposal Concentration of Unity, Appropriate Range of 

In-Landfill Kd Values, Leachate Concentration Reaching Water Table, 

Downgradient Proportion of Leachate Recharge, and Concentration in 

Groundwater for 100-m Downgradient Receptor and 5-m Thick Unsaturated Zone ... E-4 

E.3 Calculations Relating Disposal Concentration of Unity, Appropriate Range of 

In-Landfill Kd Values, Leachate Concentration Reaching Water Table, 

Downgradient Proportion of Leachate Recharge, and Concentration in 

Groundwater for 300-m Downgradient Receptor and 20-m Thick Unsaturated 

Zone .............................................................................................................................. E-5 

 
ix

TABLES (Cont.) 

E.4 Calculations Relating Disposal Concentration of Unity, Appropriate Range of 

In-Landfill Kd Values, Leachate Concentration Reaching Water Table, 

Downgradient Proportion of Leachate Recharge and Concentration in 

Groundwater for 300-m Downgradient Receptor and 5-m Thick Unsaturated Zone ... E-6 

 
x

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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 Commission on Radiological Protection 

K hydraulic conductivity 

Kd 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 Finite-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 Regulatory Commission 
xii

PPE personal protective equipment 

ROC radionuclide of concern 

SD standard deviation 

TCLP toxicity characteristic leaching procedure 

TEDE total effective dose equivalent 

TENORM technologically enhanced naturally occurring 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) 

cm2

 square centimeter(s) 

cm3

 cubic centimeter(s) 

d day(s) 

ft foot (feet) 

ft2

 square foot (feet) 

ft3 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) 

km2 square kilometer(s) 

L liter(s) 

L3 cubic liter(s) 

lb pound(s) 

m meter(s) 

M mass 

m

2

 square meter(s) 

m3 cubic meter(s) 

mg milligram(s) 

mi mile(s) 

mi2 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) 

yd3 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 (ft3) 0.02832 cubic meters (m3)

 cubic yards (yd3) 0.7646 cubic meters (m3)

 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 (m3)

 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 (ft2) 0.09290 square meters (m2)

 square yards (yd2) 0.8361 square meters (m2)

 square miles (mi2) 2.590 square kilometers (km2)

 yards (yd) 0.9144 meters (m)

Metric/English Equivalents

 centimeters (cm) 0.3937 inches (in.)

 cubic meters (m3) 35.31 cubic feet (ft3)

 cubic meters (m3) 1.308 cubic yards (yd3)

 cubic meters (m3) 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 (km2) 0.3861 square miles (mi2)

 square meters (m2) 10.76 square feet (ft2)

 square meters (m2) 1.196 square yards (yd2)
1 

RADIOLOGICAL DOSE AND RISK ASSESSMENT OF LANDFILL DISPOSAL 

OF TECHNOLOGICALLY ENHANCED NATURALLY OCCURRING 

RADIOACTIVE MATERIALS (TENORM) 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 radioactive materials (NORM) in concentrations above background. In 

North Dakota, these materials are referred to as technologically enhanced NORM (TENORM). If 

these wastes are not properly managed, they can potentially present unacceptably high human 

health risks. The North Dakota Department 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 rule changes regarding 

handling and disposal of TENORM are protective of human health and the environment. 

Argonne National Laboratory (Argonne) 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 radiological 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 Dakota by oil and gas operations. The study was 

designed to minimize its reliance upon specific waste characterization data. For the well site 

worker and public accidental exposure scenarios, potential doses were calculated on the basis of 

both the average and maximum radionuclide concentrations for specific waste types relevant to 

the scenario, the latter providing conservatively high dose estimates. For the landfill worker and 

future use-scenarios, the study was designed to calculate the maximum allowable radionuclide 

concentrations that could be present in landfilled wastes such that potential doses would not 

exceed the 100-mrem/yr dose limit recommended for members of the general public by the 

International Commission on Radiological 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 fracturing proppants that have been found to contain low levels of 

TENORM. These wastes were found to contain elevated levels of the radionuclides radium-226 

(Ra-226), radium-228 (Ra-228), lead-210 (Pb-210), 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 characterization can be found in Section 2 and 
2 

Appendix A). Many previous TENORM risk assessment studies did not include thorium because 

of the lack of data. In addition, state regulations for TENORM and NORM disposal typically 

impose limits based upon total radium (Ra-226 plus Ra-228) activity concentrations. This study 

recommends similar limits, taking into consideration the presence of Th-232 and the relative 

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

Pathway analysis computer codes were used to estimate doses for both workers and 

members of the general public. These codes included the RESRAD-BUILD, RADTRAN, 

TSD-DOSE, and RESRAD. A wide range of exposure scenarios were evaluated. The risks 

associated with a number of specific well site operations were estimated, including mixing 

hydraulic fracturing fluid, produced water filtration, pipe cleaning, storage tank cleaning, 

equipment cleaning at a gas processing plant, and sludge treatment. In all scenarios except the 

produced water filtration scenario, it was assumed that workers were equipped with personal 

protective equipment (PPE) (e.g., respirators, eye protection, and gloves). The maximum dose 

calculated, assuming average waste activity concentrations, was 20 mrem/yr for the worker 

involved in mixing hydraulic fracturing fluid. However, when maximum radionuclide 

concentrations were assumed, the dose for workers engaged in pipe cleaning was 130 mrem/yr, 

and the dose for storage tank cleaners was 70 mrem/yr. When the sensitivity 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. These results suggest that it may be important to 

monitor and limit the duration of exposure for 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 disposal was estimated for three scenarios. The 

first involved a child playing with a used filter 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 exposed 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, the 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 representative 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 living near the landfill. The maximum 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 transportation corridor for routine and accident conditions were 

1.3 × 10-4 person-rem/yr and 7.2 person-rem/yr, respectively. It should be noted that the risk of 
3 

getting involved in a fatal transportation accident is at least 100 times greater 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 possible 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. Five future-use scenarios were also evaluated: 

(1) a residential-use scenario, in which a resident is assumed to construct a house on top of the 

landfill, use the surrounding area for growing crops, and obtain drinking and irrigation water 

from an on-site well; (2) an industrial-use 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 recreational area; (4) an intruder scenario, in which a resident on the landfill site accidentally 

uncovers the buried wastes and disperses the material around his or her property; and (5) an offsite groundwater-use scenario, in which an off-site resident obtains water from a well drilled 

downgradient of the landfill. For the groundwater-use scenario, infiltration and percolation rates 

were modeled using the Hydrologic Evaluation of Landfill Performance (HELP) model. 

Groundwater flow and contaminant transport were modeled using the Modular 

Three-Dimensional Finite-Difference Groundwater Flow Model (MODFLOW) and the Modular 

3-D Multi-Species Transport Model (MT3DMS). 

For landfill disposal, the analyses were run 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 exposures related to future use of 

the landfill, in terms of the maximum TENORM concentrations that can be disposed of in the 

landfill safely. The workers involved in receiving and handling or waste placement activities 

received the highest estimated dose. Decreasing 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 and Special Waste Landfills is appropriate 

provided restrictions are placed on the average waste activity concentration, waste volumes 

disposed per year, and the depth 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 wastes 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 wastes that do not contain radionuclides. 

 
5 

1 INTRODUCTION 

Some of the waste streams generated by the oil and gas sector in North Dakota contain 

naturally occurring radioactive materials (NORM) in concentrations above natural background 

levels of radionuclides. In North Dakota, these materials are referred to as technologically 

enhanced NORM (TENORM). If these wastes are 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 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 rule changes regarding handling and disposal of 

TENORM are protective of human health and the environment. As part of this effort, the NDDH 

requested that Argonne National Laboratory (Argonne) conduct a radiological 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 and risk assessment. 

Specifically, it presents results associated with the following: 

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

• Accidental public exposures associated with improperly managed well site 

operation wastes (e.g., filter socks) and materials (e.g., proppants), 

• Worker and public exposures associated with transportation of TENORM 

wastes to landfills, and 

• Worker and public exposures associated with TENORM disposal Industrial 

and Special Waste Landfills permitted in North Dakota. 

In addition, this report presents information supporting these dose and risk assessments. 

The document is organized as follows: 

• Section 2 presents information describing 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 methods used to assess (1) the fate and 

transport of TENORM, including modeling 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 radiological 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 concentrations above background. This material is often referred to as 

TENORM to distinguish it from other forms of NORM that are not by-products of some form of 

processing. The State of North Dakota uses the term TENORM in its regulations. This section 

describes the TENORM waste generated by oil and gas operations in North Dakota. 

In the United States, the sources for elevated TENORM levels are uranium-238 (U-238) 

and thorium-232 (Th-232), which are naturally present in underground formations from which 

oil and gas are produced. The primary radioisotopes of concern in petroleum industry wastes are 

radium-226 (Ra-226) and radium-228 (Ra-228), which result from the radioactive decay of 

U-238 and Th-232, respectively, and their associated 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 water that is brought to the surface along 

with the produced oil and gas; 

2. Scale, which is a hard, insoluble deposit that accumulates on the inside 

surfaces of the equipment used at production 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 flowback 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 contain 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 well fracturing activities are known 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 exposure risk analysis include scales, sludges and 

filter cake, filter socks, natural gas processing equipment, and proppants. 
8 

 For this study, the NDDH worked with industry 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 concentrations 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 results supporting the summary data in Table 2.1 are 

presented in Appendix A. The number of samples 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 have not typically included thorium because 

of a lack of data. In addition, 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 total radium concentration. The average value for 

TABLE 2.1 North Dakota TENORM Waste 

Characterization Data 

Type of Waste Scale Sludgea

 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 Distribution 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 waste 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 radionuclides found in produced water generally include Ra-226, Ra-228 

and their decay products; elemental uranium and thorium typically have not been found in 

produced water in the United States. Radium, which 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 water is brought to the surface, some of the 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 disposal 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

# of Samples

Ratio of Th 232 to Total Radium Activity Concentration
10 

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 water 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 (BaSO4) or 

strontium sulfate (SrSO4). When in solution in the produced water, 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, including 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. Typically, the radium takes the form 

of a co-precipitate with sulfate or carbonate deposits. In addition, filters that are used to separate 

particulates from produced water generate a solid waste referred to as filter cake. This material is 

likely to have a similar composition to the sludge that is removed from produced water storage 

and handling equipment. 

2.4 FILTER SOCKS 

Disposable filter socks are used to filter particulates out of produced 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 disposal 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 that handle filter socks and to the general public 

resulting from accidental exposures to filter socks that have been improperly disposed of. 

2.5 LEAD-210 DEPOSITS IN GAS EQUIPMENT 

Thin films of Pb-210 may accumulate on the 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 compared 
11 

with published information on radium-bearing TENORM wastes, very little information has been 

published characterizing petroleum industry wastes containing Pb-210. The NDDH did not 

collect data describing Pb-210 contamination at gas facilities in North Dakota. For this waste 

stream, data collected for a previous Argonne analysis were used. That study found an average 

concentration of 260 pCi/g and a maximum concentration 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 that contain residual quantities of TENORMcontaminated water, scales, sludges, or films can present a waste management problem if 

radionuclide concentrations are high enough. TENORM-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 included 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 contaminated through the intentional 

application or accidental release of contaminated wastes. For example, the practice of disposing 

of oily wastes by landspreading can inadvertently result in the distribution of TENORM wastes 

across the affected soils. Similarly, soils in unlined or leaking disposal pits can become 

contaminated with TENORM. Overall, contaminated 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 FRACTURING PROPPANT 

A proppant is a solid material, treated sand, or man-made ceramic material designed to 

keep an induced hydraulic fracture 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 radioactivity. While these materials are not currently 

regulated as radioactive material, proppant that has been spilled 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, accidental general public exposures to improperly 

managed proppants were included. 

 
12 

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13 

3 LANDFILL DISPOSAL AND POTENTIAL EXPOSURE SCENARIOS 

This section provides a general description of the two different 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 variety of wastes, and, typically, the degree of 

engineering control increases with the hazard level 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 properly constructed landfills that are equipped with 

liners, a leachate collection system (LCS), and 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, excess equipment, and other solid debris. TENORMcontaminated wastes also are disposed of in landfills; however, this practice is typically limited 

to disposal in landfills specifically licensed 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 incurred in the United State for constructing and 

operating licensed TENORM or LLW disposal facilities are passed on to the customers. 

One state (Michigan) allows the disposal of solid waste and debris containing 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 Solid 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 Landfills”) 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 hydraulic 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 transmissivity of at least 3 × 10-2 cm2

/s (3.2 × 10-5 ft2/s). The liner and the LCS must 

maintain their integrity during the operational period and the post-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) thick; a clay-rich soil, suitable as a plant root zone, at least 
14 

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 precipitation 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 evapotranspiration 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-closure 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 drainage layer with a K exceeding 1 × 10-3 cm/s 

(3.3 × 10-5 ft/s) and a sufficient thickness to provide a transmissivity of at least 3 × 10-2 cm

2

/s 

(3.2 × 10-5 ft2/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 the upper drainage layer with a 

K exceeding 1 × 10-3 cm/s (3.3 × 105 ft/s) and a sufficient thickness to provide for a 

transmissivity of at least 3 × 10-2 cm

2

/s (3.2 × 10-5 ft2/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 compacted 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 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 ft2/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 least 97% of the precipitation 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 within 36 hours of a precipitation event. During post-closure, the final cover, liner system, 

and LCS must collect or reject 99.9% of the precipitation that 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 Waste Landfills. The locations of these and other 

Special Waste Landfills are shown in Figure 3.1. One landfill, Chimney Butte, has an alternative 

final cover system consisting of an evapotranspirative cover of 1.5 m (5 ft) of uncompacted soil 

(Radig 2013b). Average dimensions of these landfills are used to define the generic landfill 

evaluated in this study. These average values include a total size of 19 ha (46 acres), a waste 

thickness of 38 m (125 ft), a total volume of 3,600,000 m3

 (4,700,000 yd3), 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 a 
15 

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) (m3) (yd3) 

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 liner to control the migration of waste during the 

impoundment’s operational period and, for impoundments 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 residues, liners, any leak detection 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 soils by removal of liquids, drying, 

or other means and then provide post-closure care under Industrial Waste Landfill rules. 

At several landfills in North Dakota, leachate is managed within evaporation ponds that 

typically have a composite liner. Any TENORM that mobilizes into the leachate will accumulate 

within these evaporation ponds over time and will either result in increasing TENORM 

concentrations within the aqueous phase or form precipitates or scale 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) described 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 capacity from 5,160 to 65,100 m3

 (1,363,000 to 17,200,000 gal (most 7,600 to 

13,000 m3

, 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 scenarios related to landfill disposal of TENORM can be grouped 

into two major categories: operational phase scenarios and future-use scenarios. Operational 

phase scenarios were evaluated to estimate the potential exposures resulting from well site 

operations, transportation of TENORM from production facilities to generic 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 completed (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 scenarios is provided in the following sections. 
17 

3.2.1 Operational Phase Scenarios 

Operational phase scenarios were evaluated to estimate potential exposures resulting from 

well site operations, transportation, and landfill operations. They evaluate the dose to both the 

workers (e.g., workers at the well sites, truck drivers during transportation, and landfill workers) 

and members of the public (e.g., potential exposure to improperly managed filter socks and 

proppants, persons living along the transportation corridors, and persons 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 materials produced at well sites are wet and produce very 

little airborne emissions, and because the general public is not typically present at the well site, 

such that external exposure would be significantly less than for the on-site workers evaluated. In 

general, exposure pathways considered for the operational phase included external radiation, 

inhalation of contaminated dust, and incidental ingestion of contaminated soil or sand. 

3.2.1.1 Well Site Operations Scenarios 

The doses were estimated for well pad workers involved in mixing hydraulic fracturing 

fluid and filtering produced water; equipment cleaning workers involved in pipe cleaning, 

storage tank cleaning, and gas processing equipment cleaning; disposal well workers involved in 

filtration and connecting/disconnecting trucks; and 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 sand 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 excluded 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 removing scale and sludge or Pb-210 film 

from equipment taken out of service. The types of equipment that are cleaned 

for reuse include piping and storage tanks. Three types of workers were 

modeled: pipe cleaners and storage tank cleaners working 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 work assignments. 
18 

and equipment cleaners working at a gas industry processing facility. Only the 

individual who would come in direct contact with the contaminated equipment 

was modeled (this individual is likely to have greater exposure). It was 

assumed that respiratory protection was 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 inhalation 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 wastewater at drilling sites. They look like small 

nets and could be mistaken for an item that children 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 following a fracturing treatment. It is added to a fracking fluid. 

Three accidental exposure scenarios were evaluated: two filter sock exposure scenarios 

and one proppant exposure scenario. Assumptions for these accidental public exposure scenarios 

are presented in Table B.2 of Appendix 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 inadvertent 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 dumpster and that a city dweller was 

exposed to the dumpster for 8 hours every 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 open 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). Children 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 included the driver of the transportation vehicle 

(truck transport only), persons living along the transportation corridor, persons sharing the 

transportation corridor, persons at stops for refueling or maintenance, as well as persons living 

near the entrance of the landfill site. Parameters 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., reviewing the manifest, weighing the 

truck, and inspecting the shipment), as well as directing 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 prior to shipment to the landfill in accordance with 

North Dakota landfill waste acceptance criteria (NDAC; Chapter 33-20-01.1). Potential routes of 

exposure for the waste-placement operator included external irradiation, inhalation of 

contaminated particulates, and inadvertent ingestion of contaminated particulates. Inhalation of 

particulates were not considered a potential pathway of exposure for instances in which the 

wastes are disposed of in containers. Exposure 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 that the leachate generated will be collected in an evaporation pond. 

Depending on the evaporation pond operation, potential routes of exposure for the pond 

management worker included external irradiation, inhalation of contaminated particulates, and 

inadvertent ingestion of contaminated particulates. Parameters used for the evaporation pond 

operations scenarios are presented 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 evaluated for the population living near the landfill. 

 

2 For each landfill operations scenario, the dose is estimated 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 involved in each operation are calculated internally in the code. For 

example, in the TSD-DOSE code, the only input parameters required for receiving and handling operation are 

waste density (required to estimate the 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 receiving and handling scenario. 
20 

Exposures were estimated for the maximally exposed 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 pathway of exposure is inhalation of 

contaminated particulates. External irradiation, incidental ingestion of contaminated particulates, 

and ingestion of contaminated foodstuff also were 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 are presented in Table B.4 of Appendix B. 

3.2.2 Future-Use Scenarios 

Future-use scenarios were evaluated to estimate the potential radiation 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 the environment. The only exception is the 

groundwater pathway. As discussed in Section 4.2, the groundwater pathway 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 evaluated the disposal of containerized TENORM 

wastes, as well as bulk wastes. Four future-use scenarios evaluated potential doses to on-site 

receptors, including an on-site resident, industrial 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 general, the exposure pathways for the future-use 

scenarios included external radiation; inhalation of contaminated dust; inhalation of radon; and, 

depending on the particular exposure scenario evaluated, ingestion of contaminated particulates, 

water, plants, meat, and milk. The parameters utilized 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 record must be placed on the deed to notify any 

person conducting a title search that the land has been used as a solid waste disposal facility. The 

recording must describe the amount and type of waste disposed of and must state that the landfill 

may not be used for cultivated crops, heavy grazing, 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 represent 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 individual 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 purposes. 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 inhalation of indoor and outdoor radon. The 

following pathways of exposure also were evaluated: 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 assumed to consist of 6 hours spent indoors and 

2 hours spent outdoors. The exposure pathways evaluated included external irradiation, 

inhalation of indoor and outdoor radon, 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. The exposure pathways evaluated for the recreational 

visitor included external irradiation, inhalation of outdoor radon, inhalation of contaminated 

particulates, inadvertent ingestion of soil, and consumption of meat hunted on the property. Any 

water used by recreational visitors was assumed 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 period 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 m2

) (66 ft by 33 ft [239 yd2]) at the bottom and 26 m 

by 16 m (416 m2) (85 ft by 52 ft [498 yd2]) 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 soil excavated during the digging (680 m3 [890 yd3] of cover 

material and 232 m3

 [303 yd3] of waste) would be distributed in a 10,000-m2 area (12,000 yd2). 

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 the intruder included external irradiation and 

inhalation of indoor and outdoor radon. The following pathways of exposure also were 

evaluated: inhalation of contaminated particulates; inadvertent ingestion of contaminated soil; 

and ingestion of crops, milk, and meat grown or hunted on the contaminated property. 

The off-site resident scenario was analyzed to evaluate potential doses resulting from 

future impacts on the underlying aquifer associated with disposal of TENORM waste in the 

landfill. It was assumed that the resident lives adjacent to the former landfill 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 assumed 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 agricultural purposes. The off-site resident was assumed to drink 

510 L (135 gal) of water per year. The exposure pathways for this receptor included ingestion of 

groundwater and ingestion of crops, milk, and meat produced using the groundwater. Inhalation 

of radon via volatilization during showering also was considered as a potential pathway of 

exposure; however, this pathway probably is not a major contributor 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 sensitivity 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 repeated; 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 change in the dose produced by the change in the 

parameter value. 

 
23 

4 MODELING METHODOLOGIES 

 This section presents the general modeling approaches that were used to assess (1) fate 

and transport of TENORM within waste streams, 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 radioactive material is outside of the body, is a 

concern primarily only for gamma radiation because it can easily penetrate tissue and reach 

internal organs. Internal exposure occurs when the radioactive material is taken into the body 

through inhalation or ingestion. For internal exposures, alpha and beta particles are the dominant 

concern because their energy is almost completely absorbed in adjacent cells, potentially causing 

biological harm. 

Exposure to internally deposited radioactive contaminants is expressed in terms of the 

50-year committed effective dose equivalent (CEDE). This concept, developed by the 

International Commission on Radiological Protection (ICRP 1977), represents 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 external 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 from 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 probability of occurrence, not the severity of 

effect, increases with dose, and there is no dose level below which the risk is zero). The 

relationship between radiation dose 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 radiation exposure may present a health risk, but it is 

difficult to establish a direct cause-and-effect relationship because of the lack of data and the 

presence of compounding environmental stresses. In the absence of definitive data, the risks 

from low levels of radiological exposure are estimated 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 for both workers and the public is 5.7  10–7 per mrem 

(i.e., 5.7 additional cancer cases in 10 million people 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, radiation 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 natural sources of radiation 

(NCRP 2009). By applying the ICRP risk factor for the public, the 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 also the possibility of adverse systemic effects due 

to chemical effects of exposure to the radionuclides. 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 Levels 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‐Ray

Dose in mrem
25 

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 codes 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 scenarios 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 radiological impacts on both the workers who participate in these 

operations and members of the general public were considered. 

4.2.1.1 Well Site Operations 

Worker and public doses from well site operations 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 pathway analysis model to evaluate the 

potential radiation dose incurred by an individual who works or lives 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) within 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 external exposure, (2) external exposure from the 

deposited material on the floor, (3) air submersion, (4) inhalation of airborne radioactive 

particulates, (5) inhalation 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 the transportation vehicle 

(regardless of type of cargo) were considered. For routine transportation, 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 cargo-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 food. 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 originally issued in the late 1970s as RADTRAN 

(RADTRAN 1) and has been reviewed and updated periodically. The code calculates the MEI 

doses as well as population doses. For more information about the RADTRAN code, 

see https://rsicc.ornl.gov/codes/ccc/ccc5/ccc-508.html. 

4.2.1.3 Landfill Operations 

The TSD-DOSE computer code, developed by Argonne with support from the 

U.S. Department of Energy (DOE), estimates radiological doses to workers and members of the 

public from operations at a treatment, storage, and 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 reference operations were developed 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 parameter values defining the reference operations 

can be modified to model specific activities at different TSD facilities. The seven reference 

operations modeled with 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 contaminated sites (Yu et al. 2001). For more information about the 

RESRAD code and access to the code, see https://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 estimates the time-integrated annual dose and excess 

lifetime cancer risk to a chronically exposed individual at a site with radiological contamination 
27 

(DOE 1990). The calculated total dose, referred to as the total effective dose 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 contaminants initially in soil and their subsequent 

transport in air, water, and biological media to individual on-site receptors. Nine exposure 

pathways are considered in RESRAD: direct exposure, inhalation of particulates and radon, and 

ingestion of plant foods, meat, milk, aquatic foods, water, and soil. The RESRAD computer code 

was used in conjunction with the hydrologic models described in Section 4.2 to estimate 

radiological doses associated with the ingestion and general use of groundwater potentially 

contaminated with TENORM. 

4.2.3 Calculating Maximum Allowable TENORM Concentrations for Landfill Disposal 

 Previous analyses demonstrated that the highest potential doses associated with landfill 

disposal are associated with future-use scenarios such as those discussed in Section 3.2.2 

(Smith et al. 1999). In those analyses, the future-use scenarios imposed the most stringent 

constraints (i.e., the lowest radionuclide concentrations) in terms of the amount of TENORM that 

could be safely disposed of in the landfill. As a result, in this study, initially the risk assessments 

for future-use scenarios were conducted first to back-calculate the maximum average 

concentration of TENORM that could be accepted at a landfill without exceeding the regulatory 

dose limit of 100 mrem/yr for any one of the future-use receptors. These maximum 

concentrations were then used to evaluate potential doses to workers and the general public 

during the landfill operations phase and to receptors associated with transportation of the 

TENORM wastes to the landfill. However, estimates of potential doses associated with some 

landfill operations scenarios (the waste handling and placement workers) using the maximum 

concentrations from the future-use scenario analyses resulted in unacceptably high doses. As a 

result, additional calculations were run for those 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 radioisotopes 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 for the analyses. Because the operational phase is 

short compared with likely transport times for radionuclides 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 couples one-dimensional vertical percolation and 

one-dimensional lateral drainage and surface runoff. HELP can be used to model the various 

layers of a landfill system, including vertical percolation through soil, compacted barrier soil, or 

waste; lateral drainage through sandy drainage layers with or without leachate collection; and 

vertical percolation through geomembranes of different materials and quality. It is a generally 

accepted tool for estimating leachate rates and volumes. 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 generate statistically supported weather data 

(monthly precipitation, monthly temperature, 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 and gas activity (Figure 3.1) and is assumed to 

have similar weather to the study area. To be conservative, the evaporative depth was set to a 

small value (25 cm or 10 in.); the completed landfill was assumed to be treeless (leaf area index 

of zero); and the grass cover of the completed landfill 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 Industrial 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 surface sloped toward an LCS 

pipe. This slope value is considered a conservative assumption because it allows 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 the default values for each specific material type 

in the HELP model, with the following exceptions. 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 was 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 North 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 per 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 thickness 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 the 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 phase with an open (active) 

landfill cell, the waste, including daily and intermediate soil cover, was 

assumed to be half of the total thickness, 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 model. 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 the 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), and the installation placement quality is 

reduced to HELP’s “bad” condition. 

4.3.2 Hydrogeological Setting of a Generic Landfill and Model Parameter Values 

 North Dakota’s surficial geology is dominated by glacial depositional processes, which 

have resulted in thick sequences of glacial drift in most areas. The drift is predominantly finegrained glacial till of low permeability. Relatively thin, discontinuous sand units may be present 

within the drift also. Review of hydrogeologic reports for six landfills in western North Dakota 
30 

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; Carlson McCain 2012; Barr 2013). Sandy zones are 

possible within the glacial drift sequence with hydraulic conductivity 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 sandy 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 site investigations documented 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 system at a depth of 140 m (460 ft) or more 

(Barr 2013). Measured hydraulic gradients 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 setting for a generic North Dakota landfill location 

is expected to include thick, fine-grained glacial till with minor sand and gravel units, and a 

regional bedrock aquifer at a significant depth. For the purpose of modeling to support decisionmaking regarding TENORM disposal in North Dakota, 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 depths to a practical aquifer are possible. To 

evaluate sensitivity, a depth to groundwater of only 5 m (16 ft) was also considered. In both of 

these cases, a localized sandy unit within the glacial drift 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 unsaturated zone, radioactive 

decay of ROCs was calculated. In a conservative 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 solid portion of an aquifer. The distribution 

coefficient (Kd) is the slope of the linear sorption isotherm, relating the ratio of the amount of a 

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

Kd = C*/Csolute, (4.1) 
31 

where 

Kd = distribution coefficient (L3/M), 

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

Csolute = solute concentration (M/L3). 

A higher Kd value produces greater retardation in the movement of a contaminant. 

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

The Kd value affects the retardation, R, of the contaminant by the relationship 

R = 1 + (Kd)(Bd)/n, (4.2) 

where 

R = retardation (unitless), 

Bd = bulk density (M/L3

), and 

n = porosity (unitless). 

The contaminant transport approach relying on the use of the distribution coefficient, Kd, 

to model retardation is easily incorporated into equations supporting groundwater models. In 

reality, the Kd 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 (Brady and Bethke 2000). 

However, for cationic heavy metals and radionuclides, the approach has shortcomings because of 

sorption and precipitation processes. Alternative approaches could rely on surface complexation 

theory (Bethke and Brady 2000) or non-linear isotherms. 

In this study, the relatively simple Kd 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 Kd results, compared with surface complexation results or laboratory 

or field observations; 

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

• Simplicity in implementation. 

An analysis of literature values for Kd is presented in Appendix D. The available 

information demonstrates a wide range of Kd values for each ROC. For radium and thorium, Kd

values of 100, 1,000, and 10,000 mL/g are appropriate to evaluate the sensitivity of calculations 

to this parameter. For lead, Kd values of 10, 100, and 1,000 mL/g should be examined. 

 
32 

4.3.4.2 Dispersivity 

In contaminant transport modeling, the dispersivity 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 reliability of the estimate; however, a longitudinal 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 longitudinal dispersivity (Zheng and Bennett 1995). 

4.3.4.3 Groundwater Flow and Contaminant 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-state or transient flow of groundwater in an 

irregularly shaped flow system in which aquifer 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 Transport 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-dimensional finite-difference computer model that 

can be used to simulate changes in concentrations of miscible contaminants in groundwater, 

considering such processes as advection, dispersion, 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 sorption and first-order decay. MT3DMS is used 

to calculate the concentrations of the contaminants of concern 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. This is a reasonable assumption for 

Ra-226. A method by Baird et al. (1990), when applied with parameter estimates for this 

North Dakota study, suggested an annual leached 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 locations 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 Radionuclide 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) 

 

Kd 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 0.03 

 
34 

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35 

5 HYDROLOGICAL MODELING RESULTS 

This section presents the results of the hydrological modeling for transport of 

radionuclides through the landfill and below the landfill in both the unsaturated and saturated 

zones. 

5.1 LANDFILL HYDROLOGIC MODELING 

The HELP database’s average annual precipitation 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 and even lower infiltration. 

The HELP model results for the various landfill scenarios show variability 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) percolation through the cap’s compacted soil and the upper 

geomembrane liner; and (3) percolation through the 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 contrasting 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.) per 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 associated 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 (geomembranes with more pinholes, more defects, and 

worst placement quality), which fell slightly behind the required rejection rate due to the 

additional conservatism of the input parameters. For both the Industrial and Special Waste 

Landfills, the sensitivity analysis of the operating landfill (geomembranes with more pinholes, 

more defects, and worst placement quality) indicates 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 time for partial or complete decomposition of 

the landfill geomembranes to occur. The percolation rate 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. 
36 

FIGURE 5.1 HELP Model Results for the Closed Industrial Waste Landfill for Precipitation, Evapotranspiration, 100 Years 
37 

FIGURE 5.2 HELP Model Results for the Closed Industrial Waste Landfill for Percolation through the Compacted 

through the Upper Geomembrane Liner over 100 Years 
38 

FIGURE 5.3 HELP Model Results for the Closed Industrial Waste Landfill for Percolation through the RecompactDeep Natural Soil over 100 Years 
39 

FIGURE 5.4 HELP Model Results for the Closed Industrial Waste Landfill with Decomposed Geomembranes anfor Percolation through the Cover’s Barrier Soil, the Recompacted Liner Soil, and the Deep Natural Soil over 100 
40 

TABLE 5.1 Summary of HELP-Model-Derived Percolation Results for Industrial and Special 

Waste Landfill Scenarios 

Case Layer 

Average 

Percolation 

(in./yr) 

% 

Rejecteda

% Required for 

Post-Closure 

With LCS 

Operating 

Average 

Collected 

Leachate 

(gal/yr)b

 Notesc

 

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 landfill 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 recompacted clay below the waste. This is a 

significant finding for two reasons. First, it indicates 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 Waste Landfills perform the same in terms of long-term future 

percolation. 

5.2 UNSATURATED ZONE FLOW AND TRANSPORT 

Transport in the unsaturated zone was approximated by incorporating 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 suggested 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) could 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 conservatively thin at 5 m (16 ft). 

Transport through the unsaturated zone would allow ROCs to be subject to sorption and 

dispersion. As a conservative assumption, 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 concentration lost during unsaturated transport is 

related to the landfill concentration as: 

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

5.3 SATURATED ZONE FLOW AND TRANSPORT 

Calculation of lateral groundwater flow and transport begins with numerical modeling of 

groundwater flow. A MODFLOW model was created covering a domain of 5,000 m (3 mi) by 

1,000 m (0.6 mi) by 7 m (23 ft) in thickness. Figure 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 hydraulic gradient of 0.015. The overall hydrogeologic 

setting of the recently permitted landfills described in Section 4.3.2 is a surficial 
42 

FIGURE 5.5 Hydraulic Heads, Landfill Location, and Receptor Locations at the Upgradient End of the Modeling D
43 

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 hydraulic conductivity for the modeled aquifer was 

set to 1 × 10-4 cm/s (3 × 10-6 ft/s). The ratio of horizontal to vertical hydraulic conductivity was 

set to 10 for all layers’ cells. The generic landfill 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 field 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 slight bowing of the equipotentials near the 

landfill is due to the recharge in the landfill footprint. 

MT3DMS relies on the flow field calculated by MODFLOW. For this study, MT3DMS 

modeled the following transport processes: advection, dispersion, source/sink mixing, and 

chemical reaction, including sorption and first-order decay. Input to these packages included an 

effective porosity of 0.25, a longitudinal dispersivity of 30 m (98 ft), a horizontal transverse 

dispersivity of 3 m (10 ft), a vertical transverse dispersivity of 0.3 m (1 ft), and bulk density of 

1.8 g/cm3

 (112 lb/ft3). For the modeling of sorption, the option selected was the linear isotherm. 

The Kd 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 magnitude higher or lower to evaluate sensitivity 

(Table 4.1). 

Rather than a half-life value, MT3DMS requires the first-order 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 rate assumes that the liners are 

decomposed, and is therefore a practical consideration for a long-term scenario. This recharge 

flux was modeled as entering the aquifer throughout the landfill footprint. Recharge was not 

modeled elsewhere; rather, the groundwater flow field was simply maintained at the prescribed 

gradient except for a slight perturbation at the landfill due to the recharge. 

The concentration of each ROC in the recharge flux was given a value of unity (1), and 

the proportion of the concentration of unity was modeled at receptor 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 (yr) 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 × 1010 1.57 × 10-18 4.95 × 10-11
44 

The base case scenario was tested for each ROC. In addition, the follwing cases were 

explored to evaluate the sensitivity of the calculation to reasonable changes in input parameter 

values: 

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

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

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

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

• Hydraulic conductivity increased 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 shows the results for the base case values for the 

100-m (328-ft) downgradient location. For all model 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 processes. The maximum C/Co 

in each case was at the 10,000-year point; the values 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 concentration due to retardation and decay 

processes, especially at the 300-m (984 ft) distance. These maximum C/Co values were used as 

input in a spreadsheet of groundwater calculations. This spreadsheet was a means of calculating 

the full process from disposal concentration of TENORM in the landfill to downgradient 

groundwater concentrations for each ROC. The process included an initial assumption of unity 

for the disposal concentration of NORM (assumed to be the sorbed concentration), an 

appropriate three-order-of-magnitude range of in-landfill Kd 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 reaching 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 Kd values, was used as input in risk assessment for future-use scenarios in Section 6.3. 

5.4 DISCUSSION OF RESULTS 

The literature-based Kd 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 transport, combined with 

radioactive decay, reduced the downgradient concentrations significantly. In the case of each 
45 

FIGURE 5.6 Base Case Results for C/Co at 100 m (328 ft) (ratio of downgradient concentration to 

leachate recharge concentration) over 10,000 Years for Each of the ROCs Modeled 

ROC, the risk to a receptor is dependent on inherent 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 MT3DMS 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 create a cone of depression and have the possibility of drawing 

cleaner groundwater from both cross-gradient areas and from deeper portions of the aquifer. 

Thus, the activity concentrations of pumped groundwater 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 Kd Increased Kd

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 showed little sensitivity to the thickness of 

the unsaturated natural soil between 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 other 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 results of the radiological dose and risk assessments. The 

assessment considered the potential doses and risks from latent fatal cancers associated with the 

several operational phase scenarios and several future-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 exposures to improperly managed 

filter socks and proppants, potential doses and risks were presented for wastes assuming the 

average and maximum radionuclide concentrations as presented in Table 2.1. 

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

estimate the allowable radionuclide concentrations that could be safely 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 were further adjusted to ensure that all workers 

and the general public did not receive unacceptably high doses during the operational phase of 

the landfill. 

The results of the dose and risk assessments are presented in the following sequence: well 

site operational scenarios, including accidental public exposure to improperly managed filter 

socks and proppants; future-use landfill scenarios; transportation scenarios; and landfill 

operational scenarios. 

6.1 WELL SITE OPERATIONAL PHASE SCENARIOS 

 For the well site operations and public exposure scenarios, doses were calculated using 

the average and maximum concentrations detected in each waste stream in North Dakota 

(see Table 2.1). Table 6.1 lists the waste stream used in different exposure scenarios. 

6.1.1 Radiological Doses for Well Site Workers 

 It was assumed that well site workers are involved in mixing hydraulic fracturing fluid 

and produced water filtration activities. The assumptions and input parameters used to model 

well site worker scenarios are 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 related to the radionuclide 

source term concentrations, two sets of dose assessments were performed. One set of dose 

assessment used the average concentration and the other set used the maximum radionuclide 

concentrations. Tables 6.2 and 6.3 list the estimated maximum dose rate for different well site 

operations using average and maximum waste stream concentrations, respectively, for the 

exposure pathways considered 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 Filter 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 NAa 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 NAa 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 waste streams, the highest potential dose, 

calculated for the mixing hydraulic fracturing fluid 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 concentration, the dose for the pipe cleaning 

worker is 130 mrem/yr, and the dose for the storage 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 the workers perform this activity for 2,000 and 

100 h/yr, respectively. Doses to these individuals could be reduced by limiting the annual 

exposures and splitting the task among multiple workers, if needed. The main contributors to 

dose for the well site worker scenarios are Ra-226 and Ra-228; the exception is for the worker 

cleaning equipment at a gas processing facility for whom only Pb-210 is a ROC. 

6.1.2 Parameter Sensitivity Analyses for Well Site Operation Scenarios 

 For the well site operation scenarios, 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 facility, sensitivity analysis was not performed because the dose 

at the base case is very small. Table 6.4 lists the results of the sensitivity analysis, based on 

average radionuclide concentrations 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 on 
50 

TABLE 6.4 Sensitivity Analyses for Well Site Operations Assuming Average Radionuclide Concentrations in tTENORM Wastesa

Sensitivity for 

Receptor Distance 

Sensitivity for 

Shielding Thickness 

Sen

Operations 

Base Case 

Dose 

(mrem/yr)

Low End 

(mrem/yr) 

High End 

(mrem/yr) 

Low End 

(mrem/yr) 

High End 

(mrem/yr) 

Low 

(mrem

Mixing hydraulic fracturing fluid—with PPE 20 26 13 25 12 No chProduced water filtration 0.47 0.55 0.45 NAb NAb 0.

Pipe cleaning—with PPE 14 23 7.8 16 8.7 7Storage tank cleaning—with PPE 3.8 5.4 2.2 NA NA 2Sludge treatment workers—with PPE 1.6 1.9 1.2 14 0.02 1

a For conducting the sensitivity analyses, parameter values were reduced (low end) and increased (high end) by a factor of 2 fr

for the parameter. For the worker involved in equipment cleaning at the gas processing facility, sensitivity analysis was not pthe dose is very small. 

b NA = The scenario does not 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 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 0.5, 1, and 2 cm 

(0.2, 0.4, and 0.8 in.). No shielding was involved. 

For the pipe cleaning worker scenario, the 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 thickness using values of 0.325, 

0.65, and 1.3 cm (0.1, 0.2, and 0.5 in.). For the storage 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 sensitivity analyses were conducted on exposure 

distance using values of 0.5, 1, and 2 m (1.6, 3.3, and 6.6 ft), on shield thickness using values of 

25, 50, and 100 cm (10, 20, and 39 in.), and on source thickness using values of 7.5, 15, and 

30 cm (3, 6, and 12 in.). 

An additional set of sensitivity runs was performed for each scenario in which the worker 

was assumed to be wearing PPE to test the risk if PPE were not worn. These results are shown in 

Table 6.5. If well site workers do not wear PPE, potential doses can be 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 concentrations, respectively. For the gas processing 

equipment cleaner, the doses could be as high as 670 mrem/yr assuming maximum 

concentrations. However, for the hydraulic fracturing fluid mixing and 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 PPEb 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 included 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 encountered during these activities, as Pb-210 is a strong driver of the 

dose received through the ingestion pathway which increases without the proper use of PPE. 

6.2 RADIOLOGICAL DOSE FROM ACCIDENTAL PUBLIC EXPOSURE SCENARIOS 

The doses from accidental public exposures associated with improperly managed filter 

socks and proppants were estimated for three exposure scenarios: two filter sock exposure 

scenarios and one proppant exposure scenario. The assumptions and input parameters used to 

model the accidental public exposure scenarios are discussed in Section 3.2.1.1 and listed in 

Table B.2 in Appendix B, respectively. For each scenario, one set of dose assessments used the 

average concentration and the other set used the maximum radionuclide 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 the two respective filter socks exposure scenarios. The doses to an 

individual child playing with used filter socks as a toy range from 0.036 to 0.052 mrem/yr (using 

average filter socks concentrations) 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 (using maximum filter socks concentrations) at 

different times. The dose is from the external exposure 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 0.036 
53 

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 Ingestiona Total External Ingestiona 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 with filter socks, there is no ingestionrelated dose. 

does not come in direct contact with the filter socks. The potential 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 exposure duration (i.e., the city dweller is exposed 

to the dumpster 40 h/yr, whereas the child is exposed to the toy 24 h/yr). 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 assumed that a truckload of proppant material 

was illegally dumped in an open field. It was further 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 exposed 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 exposure 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 100-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 the potential radiological doses and related 

risks to hypothetical receptors for several future-use scenarios. In these analyses, it was assumed 

that once all landfill operations were completed, the landfill would be released to the public 

without restrictions. The radiological assessment 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 m2

 (222,400 yd2), 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 top 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 recreational area; (4) an intruder 

scenario, in which an intruder digs through the waste and spreads the excavated soil outside and 

constructs a house on top of the contaminated area, uses the surrounding area for growing crops, 

and obtains the irrigation water from an on-site well; and (5) an off-site groundwater-use 

scenario, in which an off-site resident obtains water from a well drilled 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 first 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, given multiple scenarios. It was assumed that 

Ra-226, Ra-228, Th-232, and Pb-210 would be disposed 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-lives less than 6 months are 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 involved in estimating the 

allowable concentration at a specific landfill using future-use scenarios, which would result in 

the most conservative values. 

 Radionuclide concentrations in groundwater associated with the landfill operations were 

taken from the results of the hydrologic modeling conducted for this study (Section 5.3). The 

groundwater concentrations associated 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 concentrations 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 Scenarios 
56 

6.3.2 Results of Analysis for Different Radionuclides 

 Dose to source ratios (DSRs) were estimated for individual radionuclides. Table 6.9 

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

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

6.3.3 Estimated Allowable Concentrations in the Landfill 

 The limiting scenario DSR was used in estimating the average allowable concentration in 

the landfill based on a 100-mrem/yr public dose limit. It was assumed that TENORM is mixed 

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

at the landfill. The allowable TENORM concentration can be 10 times higher compared with the 

average concentration at the landfill. Total activity 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 concentration 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 radionuclide 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 sensitive 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 

Residenta

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. 
57 

TABLE 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 Concentration (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 × 106 Groundwater, 

Off-site 

Ra-226 8 Resident 13 Resident 36 Resident 

Ra-228 30 Intruder 70 Intruder 5.0 × 1014 Resident 

Th-232 18 Intruder 41 Intruder 1,800 Groundwater, 

Off-site 

The groundwater concentration calculated by the hydrologic modeling was used to 

estimate the DSR for the off-site resident scenario; however, the groundwater 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 contamination from the waste layer to the groundwater. In the analysis 

with the RESRAD-OFFSITE code, the most conservative parameters for groundwater transport 

were used, and the DSR for the off-site resident scenario was estimated. It was noted that the 

DSRs for Pb-210, Ra-226, and Th-232 for the off-site resident scenario were higher than those 

estimated using the groundwater concentration from the hydrologic modeling, but they did not 

change the limiting scenario for any case, and they did not result in more restrictive allowable 

concentrations, overall. 
58 

6.4 RADIOLOGICAL DOSE AND RISK FROM TRANSPORTATION 

A transportation risk assessment was performed for the transportation of TENORM 

wastes from the generation sites to a disposal site. In this analysis, only overland transportation 

using combined tractor-trailer trucks was evaluated. The transportation assessment consisted of 

evaluating the risks from both routine transport and transportation under accident conditions. 

Two major components of transportation risks were analyzed: cargo-related risks and vehiclerelated risks. The assumptions and input parameters used to model the transportation scenarios 

are discussed in Section 3.2.1.2 and listed in Tables 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 transportation corridor were calculated on a per-kilometer 

basis. A base case value of 250 km (155 mi) was selected as a reasonable distance to the disposal 

facility. Transportation risks will 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 concentrations in the TENORM are based upon the maximum allowed 

inventory at the landfill derived on the basis of the future-use 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 both routine conditions and accident conditions. 

Under routine conditions, the cargo-related risks are associated with the external gamma 

radiation emanating from the TENORM shipment. The potential receptors include the driver, 

persons living along the transportation corridor, persons sharing the transportation corridor, and 

persons living near the entrance of a disposal site. Cargo-related risks are evaluated only for 

“one-way” distances, as the returning trucks would not contain any TENORM cargo. 

 Cargo-related risks under accidental conditions result from the dispersal of radioactive 

material following a transportation accident. These risks consider the probability of the accident 

occurring, the probability of the accident causing a release of radioactive material, and the 

consequence of the accident. The exposure pathways evaluated for cargo-related risks under 

accident conditions include external gamma radiation, inhalation of radioactive dust, and 

ingestion of contaminated material in food products. The radiological transportation risk is a 

function of the probability of the accident occurring, 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 product of the consequence of the accident, expressed in units of 

mrem, and the probability of the radioactive material being released to the environment, which is 

dimensionless. 
59 

 Radiological doses to an individual living near the disposal facility from routine 

transportation activities were estimated by assuming the individual would be present during each 

shipment; therefore, the total dose 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 the 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 approximately 2,000 per year. The actual shipment could 

carry any radionuclide mix as long as the total dose at the landfill did not exceed the 

100-mrem/yr dose limit. The allowable TENORM concentration values based on the future-use 

scenarios are presented in Table 6.9 and discussed in Section 6.3.3. The estimated dose rate at 

1 m (3 ft) from the cargo depends on the radionuclide actually present in the shipment. For 

example, the external dose from a shipment that contains only Ra-226 would be higher compared 

with the dose from a shipment that contains only Pb-210. Therefore, for the routine 

transportation assessment, the dose rate value of 0.025 mrem/h at 1 m (3 ft) was estimated from 

the radionuclide shipment that resulted 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 landfill under both routine and accident conditions 

for the base case and maximum case number of shipments. 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 radiation-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 sharing the transportation 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 estimating 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 limit to the members of the general public 

(ICRP 1991). 

 The cargo-related transportation risks under accident conditions are 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 distance 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 

Drivera

 20 1  10-5 20 1  10-5

Individualb 1.6  10-6 9  10-13 3.2  10-6 2  10-12

General populationc

 6.5  10-5 4  10-8 1.3  10-4 7  10-8

 

Accident Conditions 

General populationc 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 independent of the cargo being transported. These risks result in 

potential latent cancer fatalities (LCFs) from vehicular emissions and traffic fatalities due to 

transportation accidents. Vehicle-related risks are calculated based 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 transport vehicle is hauling 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 emissions, unit risk factors (LCF/km per person/km2

) 

were obtained from Biwer and Butler (1999). Vehicle-related risks from vehicular emissions 

consider the size of the vehicle, diesel emissions from the vehicle, fugitive dust, and tire/brake 

particulates. For large tractor trailers (greater than 15 metric tons), the LCF unit risk factor was 

estimated at 8.36  10-10 fatalities/km per person/km2

 (Biwer and Butler 1999). A population 

density of 3.7 persons/km2

 was used in the transportation risk assessment (U.S. Census 

Bureau 2014). 

 Vehicle-related fatalities from truck transportation accidents have been estimated for 

transport in North Dakota (NDDOT 2012). It has been reported that the North Dakota average 
61 

fatality rate associated with combination tractor-trailer trucks on interstate highways is 

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

 Table 6.13 provides the results for the vehicle-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 transportation 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 workers 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 the 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) evaporation pond operators. The 

assumptions and input parameters used to model the landfill operational phase scenarios are 

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

 As discussed in Section 4.2.3, maximum allowable 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 concentrations 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  10-2
62 

concentrations from the future-use scenario analyses exceeded the 100-mrem/yr general public 

dose limit. One way to reduce these doses to acceptable levels would be to reduce the volume of 

TENORM wastes disposed of at the landfill. Alternatively, the radionuclide concentrations in the 

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

additional calculations were run to derive lower maximum allowable 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 assessed 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 the 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 Containerized Waste Disposala

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 container during disposal operations, resulting in a smaller dose 

or risk to the general public. 

b Doses to the collective general population are expressed in units of person-mrem/yr. 

 
63 

 Table 6.15 provides the total allowable activity 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 based on worker scenarios is more restrictive 

compared with those derived for the future-use scenarios. 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 general public are estimated to be low (0.0033 to 

0.25 mrem/yr) for the bulk disposal alternative. Collective population doses to persons living 

within 80 km (50 mi) of the disposal facility are estimated to range from 0.011 to 830 personmrem/yr for the base case. These doses correspond to 6.3 × 10-9 to 4.7 × 10-4 per year LCFs, 

respectively, for the same collective population. 

6.5.3 Leachate Management Workers 

 Table 6.16 summarizes the estimated worker doses associated with the operations of the 

evaporation pond based on the maximum allowable TENORM concentrations derived for the 

future-use scenarios. The radionuclide concentration at the evaporation 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 radionuclide activity in the evaporation pond. The 

maximum estimated doses received by the evaporation pond cleaning worker range from 

0.0015 to 0.0070 mrem/yr from individual radionuclide activity in the evaporation pond. It was 

assumed that the evaporation pond is operational 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 48 
64 

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 evaporation 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 worker 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 for all the initial analyses were based on the 

maximum allowable concentration at the landfill 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 two 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 sensitive 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 TENORM 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 similar plot of dose versus concentration is 

provided in Figure 6.3. In this case, 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 RISK 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 average 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 their 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 exposure scenarios modeled, potential doses to 

the general public related to accidental exposure to improperly managed filter socks and 

proppants are generally very low, even when 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 socks 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 10000

Dose (mrem/yr)

TENORM Concentration (pCi/g)

Pb‐210

Ra‐226

Ra‐228

Th‐232
66 

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 are all below 2 mrem/yr for all calculations (Table 6.8). The 

scenarios evaluated in this study are not representative of all 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 could be disposed of in landfills, the maximum 

allowable concentration in the TENORM 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 analyses indicate that Depth to 

TENORM waste is an important parameter. The limiting average radionuclide concentration for 

each individual radionuclide increases significantly 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 (for a landfill with a 

2-m [6-ft]-thick cover) based on future-use scenarios (see Table 6.14). The worker involved in 

receiving and handling or waste-placement activities 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 10000

Dose (mrem/yr)

TENORM Concentration (pCi/g)

Pb‐210

Ra‐226

Ra‐228

Th‐232
67 

allowable TENORM concentrations based on the 100-mrem/yr limit for landfill workers were 

also derived (see Table 6.15). Table 6.17 compares 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 transportation (Section 6.4) and the leachate management 

worker scenarios (Section 6.5.3) are conservative 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 ALLOWABLE 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 radium concentration that can be disposed of in a 

landfill, these limits are independent 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 level at the landfill or point of generation. 

 Table 6.17 presents the results of estimated 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 estimated allowable TENORM concentration that 

can be disposed of at the landfill without exceeding the 100-mrem/yr dose limit for any worker 

or member of the public. Additional analyses are 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 48 410 
68 

radionuclide concentration fractions were calculated using waste characterization 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 

Coni = concentration of radionuclide i in the source, 

ACi = 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 known, 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 

Wi = the activity fraction of radionuclide i, and 

ACStotal = total allowable activity concentration in the source. 

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

radionuclide allowable concentration in the source as presented in Equation 6.3. 

i  WACSACS itotal (6.3) 

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

concentration of individual radionuclides calculated using Equations 6.2 and 6.3. The calculation 

was performed utilizing average activity fractions and various assumed radionuclide 

concentration fractions to account for uncertainty. The maximum 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 into account the additional activity from thorium 

that may be present, varied from 51.6 pCi/g to 66.6 pCi/g. The lower concentration 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 assumption 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 samples may have activity fractions that would 

result in higher concentrations of Ra-226 and/or Th-232 compared with the 50 pCi/g total 

allowable radium concentration, the dose from cumulative exposure over time to a varying 

stream of waste would approach the average activity fractions over the 1-year time 

period modeled. 
69 

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

Landfill Based on Different Radionuclide Concentration 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 

 

Averagea 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 SDb

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 radiumc

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 radiumd

0.54 0.14 0.33 76.7 41.2 10.4 25.0 51.6 

a All radionuclides in the waste are present 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 radium at 49% and 

Ra-226/total radium at 80%). 

 
70 

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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 Waste and Industrial Waste Landfills, even though 

waste characterization data are limited, and specific landfill locations have not been evaluated. 

Throughout the analyses, conservative assumptions have been made in the absence of definitive 

information. Although this approach could overestimate 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 further support decisions about TENORM waste management at the well 

site, as well as TENORM landfill disposal. 

The following general conclusions about well site operations, landfill disposal, and 

potential exposures to specific receptors are supported by the analyses and results presented in 

Sections 5 and 6. 

• Potential doses to well site workers appear to be acceptable based upon 

average activity concentrations and the appropriate use of PPE. However, 

these doses can increase significantly and potentially even exceed 

recommended doses if concentrations approach 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 cleaning 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 potential concern (i.e., exceeding or 

approaching the ICRP’s recommended public exposure limit of 100 mrem/yr). 

These doses may be reduced to acceptable 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 driver involved in transporting TENORM 

waste to the landfill was a small fraction of the public dose limit of 

100 mrem/yr. The transportation of the TENORM waste should not be a 

major component in deciding on the possible changes to the 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 disposed 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 wastes in the landfill can effectively 

reduce doses to future-use scenarios. Decreasing the volume of TENORM 

wastes that can be disposed of per year in a single landfill could effectively 

reduce doses to both landfill workers and future-use scenarios. 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 and Special Wastes Landfills 

is appropriate, provided certain restrictions are met. From a groundwater 

contamination perspective, TENORM wastes, therefore, may be appropriately 

disposed of in either landfill type. The 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 future-use scenarios modeled, except the 

off-site resident whose potential dose is independent of the landfill depth to 

TENORM. 

• Further refinement of data parameters for the hydrologic modeling (e.g., sitespecific Kd values, site-specific hydrogeological data) is not warranted given 

that the groundwater exposure pathway is not a significant contributor to dose, 

except for scenarios assuming the thickest 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 indicate 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 that may be present is a conservative 

approach that ensures potential exposures 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 concentrations presented in Table 2.1, in order 

to keep exposures to acceptable levels, it may be necessary for workers to 

wear PPE (particularly respirators). This could be appropriate for all workers 

with inhalation exposure risks, including workers involved in pipe cleaning, 

storage tank cleaning, equipment cleaning at gas processing 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 workers’ 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 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 Special Waste or Industrial Waste Landfills, based 

on the following conditions: 

 No more than 25,000 tons of TENORM wastes 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 conservative 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 

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75 

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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 Contract Report SERDP-99-1, Vicksburg, MS. 
A-1 

APPENDIX A: 

RADIONUCLIDE ANALYSIS DATA FOR TENORM WASTE SAMPLES 

COLLECTED IN NORTH DAKOTA 

 
A-2 

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A-3 

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

Type of Waste Equipment Type Sample Date Ra-226 (pCi/g) Ra-228 (pCi/g) Pb-210 (pCi/g) Th-232 (pCi/g) 

Filter sock NAa 12/6/2011 25.8 19.3 4.49 18.9 

Filter sock NA 12/6/2011 10.8 6.47 7.64 6.51 

Filter sock NA Not reported 374 130 60 Filter sock NA Not reported 47.2 11.1 10 

Filter sock NA Not reported 41.4 11 47.7 

Filter sock NA Not reported 24.6 10.6 70 Filter sock NA Not reported 2 8.8 0.27 Filter sock NA Not reported 17 8.7 31.8 Filter sock NA Not reported 15.2 7.9 

Filter sock NA Not reported 3.04 4.9 5 

Filter sock NA Not reported 4 4.8 0.99 Filter sock NA Not reported 3.16 4.6 4.7 Filter sock NA Not reported 7.4 4.3 1.83 Filter sock NA Not reported 0.91 3.7 0.71 Filter sock NA Not reported 4 3.2 1.02 Filter sock NA Not reported 1.71 3.1 2.43 Filter sock NA Not reported 6.4 2.65 70 Filter sock NA Not reported 1.07 2.44 6.1 Pipe NA 10/8/2013 352 251 340 

Pipe NA 10/8/2013 248 173 233 

Proppant NA 12/3/2013 1.76 3.1 

Proppant NA 12/6/2011 9.1 11.2 9.67 10.2 Proppant NA 12/6/2011 8 9.98 8.61 9.08 Proppant NA 12/6/2011 7.95 9.94 6.15 9.27 Proppant NA 12/6/2011 8.07 9.83 8.65 9.35 Proppant NA 12/6/2011 8.84 9.21 9.74 8.76 Proppant NA 12/6/2011 7.25 8.99 7.96 8.08 Scale Firetube 11/18/2001 154 80.0 

Scale Firetube 11/18/2001 106 71.6 

Scale Firetube 11/18/2001 94.9 60.6 

Scale Firetube 11/18/2001 27.8 17.2 

Scale Firetube 7/7/2010 309 261 

Scale Firetube 7/9/2010 427 339 
A-4 

TABLE 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) 

Scale Firetube 7/13/2010 141 122 

Scale Firetube 7/13/2010 4,700 3,590 

Scale Firetube 12/7/2010 126 86.6 

Scale Firetube 4/26/2011 <77.7 <8.1 <80.3 Scale Firetube 4/26/2011 1,867.5 971.4 460.3 Scale Firetube 4/26/2011 1,386.1 865.2 247.2 Scale Firetube 4/26/2011 940.8 569.5 109.9 Scale Firetube 4/26/2011 192.5 132.1 <19.3 

Scale Firetube 5/5/2011 201.8 187.3 83.2 

Scale Firetube 5/5/2011 24.9 10.3 30.3 Scale Firetube 8/26/2011 90.4 59.8 28.6 Scale Firetube 9/14/2011 1,960.6 <24.9 74.8 

Scale Treater 9/14/2011 57.0 <2.6 13.4 

Scale Firetube 9/14/2011 56.6 38.4 13.7 Scale Firetube 9/14/2011 25.7 18.4 16.3 Scale Firetube 9/14/2011 9.4 7.5 7.7 Scale Filter sock 10/5/2011 42.9 24.5 

Scale Tubing 10/6/2011 <115.2 <23.6 <88.4 Scale Firetube 10/18/2011 180.0 131.6 51.4 

Scale Firetube 10/18/2011 167.8 48.1 36.5 Scale Filter sock 10/18/2011 63.5 39.5 <23.6 

Scale Firetube 10/18/2011 31.5 19.0 6.5 

Scale Firetube 10/18/2011 14.0 9.0 7.4 Scale Firetube 12/9/2011 247.9 167.8 93.3 

Scale Firetube 12/9/2011 63.3 24.8 23.8 Scale Firetube 1/20/2012 271.5 155.6 49.7 Scale Firetube 1/20/2012 266.5 125.2 <106.8 

Scale Firetube 1/20/2012 160.3 107.4 35.1 Scale Firetube 1/20/2012 123.8 60.8 55.4 Scale Firetube 2/17/2012 392.6 271.5 60.4 Scale Firetube 2/17/2012 98.5 51.0 <40.3 Scale Pipe 10/8/2013 4,710 2,550 5,270 

Scoria Soil 2/17/2012 2.6 2.2 <2.9 
A-5 

TABLE 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) 

Sludge Treater 10/14/2010 64.5 2.7 

Sludge Tank 10/14/2010 26.7 2.2 

Sludge Tank 10/25/2010 5.5 2.5 

Sludge Tank 7/22/2011 122.4 62.5 34.4 

Sludge Tank 7/22/2011 1,231.1 62.2 

Sludge Tank 7/22/2011 6.3 3.5 <3.4 

Sludge Tank 7/25/2011 18.2 9.7 <6.1 

Sludge Tank 7/26/2011 3.7 3.1 <3 Sludge Tank 7/26/2011 4.2 1.4 <3.1 Sludge Tank 7/26/2011 2.0 1.0 <2.3 Sludge Tank 7/27/2011 16.6 14.8 8.6 

Sludge Tank 7/27/2011 13.0 7.7 5.1 

Sludge Tank 7/27/2011 12.6 6.5 6 

Sludge Tank 8/2/2011 3.8 <0.5 2.1 

Sludge Tank 8/2/2011 16.2 11.8 6.5 Sludge Tank 8/3/2011 13.7 8.1 <5.1 

Sludge Tank 8/3/2011 12.5 6.3 4.4 

Sludge Tank 8/4/2011 29.2 21.8 7.4 Sludge Tank 8/4/2011 30.0 17.4 9.4 Sludge Tank 8/4/2011 25.5 15.0 13.2 

Sludge Tank 8/4/2011 5.3 2.9 <3.4 Sludge Tank 8/5/2011 3.2 1.6 <2.5 Sludge Tank 8/5/2011 5.6 1.5 <2.9 Sludge Tank 8/8/2011 65.4 38.3 21.5 

Sludge Tank 8/8/2011 21.4 14.4 <7 

Sludge Tank 8/8/2011 13.7 13.8 6.5 Sludge Tank 8/8/2011 18.3 12.3 <6.7 

Sludge Treater 8/26/2011 16.6 21.4 16.3 Sludge Treater 9/14/2011 81.0 <4.2 18.3 Sludge Treater 9/14/2011 31.0 20.1 14.6 Sludge Treater 10/6/2011 79.6 52.9 22.4 Sludge Treater 10/6/2011 42.2 23.7 15.9 Sludge Treater 10/6/2011 24.1 16.9 9.1 
A-6 

TABLE 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) 

Sludge Treater 12/9/2011 59.2 36.9 15.4 Sludge Treater 12/9/2011 24.5 11.8 <6.2 

Sludge Treater 1/20/2012 58.7 39.7 19.8 Sludge Tank 9/9/2013 17.4 <1.6 <9.4 

Sludge Treater 9/9/2013 123.7 66.3 97.5 

Sludge Treater 9/9/2013 45.6 23.2 <11.5 

Sludge Treater 9/9/2013 264.7 21.8 33.9 Sludge Tank & treater 9/9/2013 36.8 21.0 12.8 

Sludge Tank 9/9/2013 33.6 18.2 18.7 

Sludge Tank & treater 9/9/2013 34.7 16.2 <11.7 

Sludge Tank & treater 9/9/2013 31.6 12.3 <11.2 Sludge Tank 9/9/2013 16.0 10.4 <10.8 

Sludge Tank 9/9/2013 25.9 8.3 <12 

Sludge Tank & treater 9/9/2013 24.6 8.3 <10 

Sludge Tank & treater 9/9/2013 17.1 8.3 9.3 

Sludge Tank & treater 9/9/2013 25.5 8.2 <9.5 

Sludge Treater 9/9/2013 19.7 7.7 <7.1 Sludge Flare pit Not reported 169 16.9 64 

Sludge Flare pit Not reported 123 6.9 36.7 Sludge Tank Not reported 5.1 4.5 5.5 Sludge Flare pit Not reported 27.3 2.9 31.1 Sludge Flare pit Not reported 15.3 1.31 12.9 Sludge Flare pit Not reported 49.4 0.65 318 

Sludge Flare pit Not reported 9 0.5 2.13 

a NA = not applicable. 
A-7 

Appendix A References 

Radig, S., 2013, personal communication by e-mail from Radig (Division of Waste 

Management, North Dakota Department of Health) to K.P. Smith and others (Argonne National 

Laboratory), Dec. 9. 

Radig, S., 2014a, personal communication by e-mail from Radig (Division of Waste 

Management, North Dakota Department of Health) to K.P. Smith and others (Argonne National 

Laboratory), Feb. 26. 

Radig, S., 2014b, personal communication by e-mail from Radig (Division of Waste 

Management, North Dakota Department of Health) to K.P. Smith and others (Argonne National 

Laboratory), March 5. 

Radig, S., 2014c, personal communication by e-mail from Radig (Division of Waste 

Management, North Dakota Department of Health) to C. Harto and others (Argonne National 

Laboratory), March 17. 

 
A-8 

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B-1 

APPENDIX B: 

RISK ASSESSMENT DATA TABLES 

 
B-2 

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B-3 

APPENDIX B: 

RISK ASSESSMENT DATA TABLES 

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

Parameter Value Remarka

 

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/cm3

) 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/cm3

) 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/cm3

) 2.6 

Exposure source geometry 

Source diameter (m) 0.152 

Source height (m) 0.01 

Shield thickness (cm) 0 

Shield density (g/cm3

) NRb

 

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/cm3

) 2.6 

Pipe length (m) 9.15 

Pipe diameter (m) 0.15 

Shield material Steel 

Shield thickness (cm) 1 

Shield density (g/cm3

) 7.86 

 
B-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/cm3

) 1.6 

Tank length (m) 13.7 

Tank width (m) 2.6 

Shield thickness (cm) 0 

Shield density (g/cm3

) 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/cm3

) 2.6 

Gas pipe length (m) 9.15 

Gas pipe diameter (m) 0.15 

Shield material Steel 

Shield thickness (cm) 1 

Shield density (g/cm3

) 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/cm3

) 2.6 

Exposure source geometry 

Source diameter (m) 0.152 

Source height (m) 0.01 

Shield thickness (cm) 0 

Shield density (g/cm3

) 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/cm3

) 1.6 

Sludge tank length (m) 13.7 

Sludge tank width (m) 2.6 

Shield material Water 

Shield thickness (cm) 50 

Shield density (g/cm3

) 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/m3, a worker 

inhalation rate of 1.2 m3

/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 processing activity are assumed to be the same as for 

pipe cleaning activity. It is assumed that the 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 

Inadvertent ingestion rate (g/h) 6.25 × 10 exposure pathways are included. -3

Exposure time (h/yr) 24 

Distance (m) 0.5 

Source material Concrete 

Source material density (g/cm3

) 1 

Toy geometrya

 

Area (cm2

) 90 

Length (cm) 10 

 

Filter Sock Exposure Scenario 2 

Filter socks dumped in a dumpsterb 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/cm3

) 7.86 

Source material Concrete 

Source material density (g/cm3

) 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 

Inadvertent ingestion rate (g/h) 6.25 × 10 exposure pathways are included. -3

Exposure time (h/yr) 100 

Exposure distance (m) 1 

Source material Concrete 

Source material density (g/cm3

) 1.6 

Source geometry 

Area (m2

) 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 cm2

, 

density = 1 g/cm3

).

b

 The dumpster is assumed to be constructed of 1/8-in. thick steel walls and has the dimensions of a 

4-yd3

 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/cm3

) 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/cm3

) 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/cm3

) 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/cm3

) 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 TSD 

Facility” operation in TSDDOSE code (Step A and 

Step B). 

Density (g/cm3

) 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/cm3

) 1.4 

Unload waste: exposure time (h) 0.75 

Unload waste: distance (m) 1 

Airborne respirable dust concentration (g/m3

) 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 Individual (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/mi2

) 9.7 Average from 2010 Census 

data for North Dakota. 

Population density: 20–50 mi (persons/mi2

) 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 Parameters 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 

Distance to pond (m) 0.5 10 minutes. 

Source material Water 

Source material density (g/cm3

) 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 

Distance to pond (m) 1 10 minutes to remove debris collected at the pond. 

Source material Water 

Source material density (g/cm3

) 1 

Exposure geometry (m) 

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

Width 100 

Height 2 
B-10 

TABLE B.6 Parameters Describing the Landfill Future-Use Scenariosa

Parameter Value Remark 

 

Average radionuclide concentration (pCi/g) 1 Not 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 (m2

) 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/cm3

) 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 industrial 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/cm3

) 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 (m3

/yr) 

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

On-site industrial worker 11,400 Table 2.3 in RESRAD Manual 
B-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 NAb

 

Erosion rate (mm/yr) 1 RESRAD code default 

Non-leafy vegetable productivity (kg/m2

) 0.7 RESRAD code default 

Leafy vegetable productivity (kg/m2

) 1.5 RESRAD code default 

Fodder productivity (kg/m2

) 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 (m2

/s) 2 × 10-6 RESRAD code default 

Foundation thickness (m) 0.15 RESRAD code default 

Foundation density (g/cm3

) 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 (m2

/s) 3 × 10-7 RESRAD code default 
B-12 

TABLE B.6 (Cont.) 

Parameter Value Remark 

 

Waste diffusion coefficient (m2/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 surface(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 configuration 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 the 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/km2

) 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. 

Rural 293 (2013) 

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) 88.49a

 Based on average speed (55 mph) in rural 

areas and freeways from Table 6.11 in DOE 

(2002) 

 

Accident rate (accidents/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 

Fractiona

 

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 Associates, 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 & Associates Engineering Corp. for the Office of 

Radiation and Indoor Air, Washington, DC. 

NDDOT (North Dakota Department of Transportation), 2012, North Dakota Highway Safety 

Plan, 2013, prepared by the Safety Division, Traffic Safety Office, Sept. Available at 

http://www.dot.nd.gov/divisions/safety/docs/2013-HSP-Final.pdf. 

NRC (U.S. Nuclear Regulatory Commission), 1977, Final Environmental Statement on the 

Transportation of Radioactive Material by Air and Other Modes, NUREG-0170, Dec. 

Pfingston, M., et al., 1998, TSD-DOSE: A Radiological Dose Assessment 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, “Measurement of 222Rn Flux, 222Rn Emanation, and 

226Ra Concentration from Injection Well Pipe Scale,” in NORM/NARM: Regulations and Risk 

Assessment, Proceedings of the 29th Midyear Topical Meeting of the Health 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 Occurring Radioactive Materials Generated by the 

Petroleum Industry, ANL/EAD-2, Argonne National Laboratory, Argonne, IL. 

U.S. Census Bureau, 2014, 2010 Census Urban Lists Record Layouts. Available at 

http://www.census.gov/geo/reference/ua/ualists_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 

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C-1 

APPENDIX C: 

LANDFILL DESIGNS TESTED WITH THE HELP MODEL 

 
C-2 

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C-3 

TABLE C.1 Special Waste Landfill Design 

Special Waste Landfill Open Cell 

(Operational Phase) 

Special Waste Landfill Capped Cell 

(Post-Closure Phase and Sensitivity Test) Special Waste Land

Layer Thickness 

Material and 

Requirement 

HELP 

Model 

Layer Type 

HELP 

Model 

Material Layer Thickness

Material and 

Requirement 

HELP 

Model 

Layer Type 

HELP 

Model 

Material Layer Thickness

Material 

Requirem

 1 0.5 ft Topsoil Vertical 

percolation 

9. Silty loam 

1 0.5 ft Topsoil 

2 1 ft Clayey soil Vertical 

percolation 

8. Loam 2 1 ft Clayey soil 

3 1.5 ft Recompacted soil, 

K<1e-7 cm/s 

Barrier soil 16. 

Barrier soil 

3 1.5 ft Recompacte

soil, K<1e-7 cm/

1 62.5 ft Waste Vertical 

percolation 

18. Municipal waste 

4 125 ft Waste Vertical 

percolation 

18. Municipal waste 

4 125 ft Waste 

2 1 ft Drainage layer, 

K≥1e-3 cm/s, T≥3e-2 cm2/s. 

Presumed LCS. 

Lateral drainage 

2. Sand 5 1 ft Drainage layer, 

K≥1e-3 cm/s, T≥3e-2 cm2/s. 

Presumed LCS. 

Lateral drainage 

2. Sand 5 1 ft Drainage la

K≥1e-3 cm/T≥3e-2 cm2

Presumed L

3 60 mil Geomembrane Geomembrane 35. HDPE 6 60 mil Geomembrane Geomem- brane 35. HDPE 

4 3 ft Recompacted 

clay, K<1e-7 cm/s 

Barrier soil 16. Barrier 

soil 

7 3 ft Recompacted clay, 

K<1e-7 cm/s 

Barrier soil 16. 

Barrier soil 

6 3 ft Recompacte

clay, K<1e-7 cm/

5 66 ft Native soil 

unsaturated zone 

Vertical percolation 

4. Loamy sand 

8 66 ft Native soil 

unsaturated zone 

Vertical percolation 

4. Loamy sand 

7 66 ft Native soil 

unsaturated 

Abbreviations: HDPE = high-density polyethylene; LCS = leachate collection system. 
C-4 

TABLE C.2 Industrial Waste Landfill Designa

Industrial Waste Landfill Open Cell 

(Operational Phase) 

Industrial Waste Landfill Capped Cell 

(Post-Closure Phase and Sensitivity Test) 

Industrial Waste L

(Deg

Layer Thickness 

Material and 

Requirement 

HELP 

Model 

Layer Type 

HELP 

Model 

Material Layer Thickness

Material and 

Requirement 

HELP 

Model 

Layer Type 

HELP 

Model 

Material Layer Thickness

Material a

Requirem

1 3.5 ft Topsoil and soil Vertical 

percolation 

9. Silty loam 

1 3.5 ft Topsoil and 

2 1 ft Drainage layer, 

K≥1e-3 cm/s, T≥3e-2 cm2/s. 

Presumed LCS. 

Lateral drainage 

2. Sand 2 1 ft Drainage la

K≥1e-3 cm/T≥3e-2 cm2

Presumed L

 3 60 mil Geomembrane Geomembrane 35. HDPE  4 2 ft Compacted soil, 

K<1e-7 cm/s 

Barrier soil 14. Silty 

clay 

3 2 ft Compacted 

soil, K<1e-7 cm

1 62.5 ft Waste Vertical 

percolation 

18. Municipal waste 

5 125 ft Waste Vertical 

percolation 

18. Municipal waste 

4 125 ft Waste 

2 1 ft Drainage layer, 

K≥1e-3 cm/s, T≥3e-2 cm2/s, 

therefore b = 32 cm = 1 ft. Presumed LCS. 

Lateral drainage 

2. Sand 6 1 ft Drainage layer, 

K≥1e-3 cm/s, T≥3e-2 cm2/s, 

therefore b = 32 cm = 1 ft. Presumed LCS. 

Lateral drainage 

2. Sand 5 1 ft Drainage la

K≥1e-3 cm/T≥3e-2 cm2

therefore b 32 cm = 1 fPresumed L

3 80 mil Geomembrane Geomembrane 35. HDPE 7 80 mil Geomembrane Geomem- brane 35. HDPE 4 1 ft Drainage layer, 

K≥1e-3 cm/s, T≥3e-2 cm2/s 

Lateral drainage 

2. Sand 8 1 ft Drainage layer, 

K≥1e-3 cm/s, T≥3e-2 cm2/s 

Lateral drainage 

2. Sand 6 1 ft Drainage la

K≥1e-3 cm/T≥3e-2 cm2

5 60 mil Geomembrane Geomembrane 35. HDPE 9 60 mil Geomembrane Geomem- brane 35. HDPE 
C-5 

TABLE C.2 (Cont.) 

Industrial Waste Landfill Open Cell 

(Operational phase) 

Industrial Waste Landfill Capped Cell 

(Post-closure phase and Sensitivity test) 

Industrial Waste L

(deg

Layer Thickness 

Material and 

Requirement 

HELP 

Model 

Layer Type 

HELP 

Model 

Material Layer Thickness 

Material and 

Requirement 

HELP 

Model 

Layer Type 

HELP 

Model 

Material Layer Thickness 

Material 

Requirem

6 3 ft Recompacted 

clay, K<1e-7 cm/s 

Barrier soil 16. Barrier 

soil 

10 3 ft Recompacted clay, 

K<1e-7 cm/s 

Barrier soil 16. Barrier 

soil 

7 3 ft Recompact

clay, K<1e-7 cm

7 66 ft Native soil 

unsaturated zone 

Vertical percolation 

4. Loamy sand 

11 66 ft Native soil 

unsaturated zone 

Vertical percolation 

4. Loamy sand 

8 66 ft Native soil 

unsaturated 

Abbreviations: HDPE = high-density polyethylene; LCS=leachate collection system. 

a Each 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 

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D-1 

APPENDIX D: 

LITERATURE REVIEW OF THE DISTRIBUTION COEFFICIENT KD

 
D-2 

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D-3 

APPENDIX D: 

LITERATURE REVIEW OF THE DISTRIBUTION COEFFICIENT KD

D.1 Kd 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 occurring radioactive material (NORM) pipe scale and NORMcontaminated soil associated with oil field wastes in Kentucky. The scale samples were crushed 

to promote a worst-case leaching scenario. Table C.1 shows the results for the scale and soil 

samples. The activity leached fraction (LF) was 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 estimate the distribution coefficient, Kd, by 

equating it to the ratio of the residue activity concentration to the leachate activity concentration. 

Because of the differences in the TCLP method compared with the traditional batch test method 

for Kd, the TCLP method differs in terms of the solution-to-solid ratio and the acidity of the 

liquid phase, and the Kd is expected to be underestimated (A&A 1996). This Kd:LF relationship 

is illustrated in Figure D.1. 

A report by Swann et al. (2004) includes analysis 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 Kd values of radium. Limited data are available, and very high 

apparent adsorption may be due to the precipitation of (Ba,Ra)SO4 during experiments. The EPA 

recommends site-specific conditions for Kd testing. Radium sorption may depend on the pH of 

the system. Summarized findings from the literature about radium sorption on soils include the 

following: 

• Kd 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, indicating that adsorption and desorption of 

radium increase with increasing pH, and that radium essentially undergoes 

complete reversible adsorption. 

• Kd values of 214 to 467 mL/g on sandy soil samples with a pH of 7.6 to 8.0. 
D-4 

TABLE D.1 Ra-226 Leached Fraction and Kd of Samples Containing Ra-226 

A B C = B*2 D E = D*100 C/(C+E) 1

Sample Description 

Sample’s 

Ra-226* 

(pCi/g) 

TCLP Ra-226 

Concentration 

in 2 L of 

Leachate* 

(pCi/L) 

Amount of 

Ra-226 in 

Leachate 

(pCi) 

TCLP 

Residue in 

100 g 

Sample* 

(pCi/g) 

Amount of 

Ra-226 in 

Residue 

(pCi) LF 

SCHS004 Soil near tanks 75 9 17 62 6,200 2.73 × 10-3 

SCHS002 Soil near tanks 110 11 22 54 5,400 4.06 × 10-3 SCHS003 Soil downgradient of tanks 920 71 142 1,000 100,000 1.42 × 10-3 SCHS001 Soil downgradient of tanks 1,100 27 54 1,000 100,000 5.4 × 10-4 SCHC001 Scale of 1 pipe 1,600 15 30 1,200 120,000 2.5 × 10-4 SCHC002 Scale of 7 pipes 1,500 14 28 1,100 110,000 2.54 × 10-4 SCHC003 Scale of 3 pipes 1,700 <0.6 Ignored 2,000 200,000 Ignored * Uncertainty estimates not shown. Source: Data from A&A (1996). 
D-5 

• Kd 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 Kd values for various soil types 

(but geochemical conditions were not documented): 

 Sand: 57 to 21,000 mL/g, geometric 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 compilation of literature values, including 

many of those included by the EPA (2004). They determined a geometric mean Kd 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 Kd values for Ra-226. 

The assumed Kd of a landfilled waste-soil mixture and the assumed activity concentration 

of the mixture can be used to estimate a solute 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 Kd (see Figure D.1), the 

dissolved concentration of Ra-226 can be estimated. Note that although some literature Kd 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 Kd of Ra-226 is fairly stable with assumed higher LF 

levels. 

FIGURE D.1 Relationship between Kd and Leached Fraction of Ra-226 

Samples (Source: A&A 1996) 

 
D-6 

D.2 Kd of Thorium 

Vandenhove et al. (2009) compiled data on 46 measurements of the Kd of thorium in 

various soils. The overall geometric mean was 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 Kd 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 greater than 8. The EPA 

(2004) reported a similar range and pH bins. 

D.3 Kd of Lead 

Vandenhove et al. (2009) compiled data on 23 measurements of the Kd of lead in various 

soils. Very little information was found to be available on the Kd 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 Kd values. Data in the range of 3 to 6.4 pH units had a 

geometric mean of 570 mL/g, while data in the range of 6.4 to 8.3 mL/g had a geometric mean of 

7,900 mL/g. 

D.4 Kd Summary 

The studies described here provide a wide range of Kd values for Ra-226, ranging from 

approximately 10 to 500,000 mL/g, with similar large 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 whether the sample is pure scale). In the absence of site-specific Kd

or leaching studies, conservative estimates (i.e., promoting high concentrations) may be made. 

The dissolved concentration value (Csolute) leaking from a landfill should be estimated for radium 

and thorium using a rounded-up value for the disposal activity concentration (assumed C*) and 

Kd values of 100, 1,000, and 10,000 mL/g so that the sensitivity of the source concentration can 

be explored. For lead, Kd values of 10, 100, and 1,000 mL/g should be examined. 

Appendix D References 

A&A (Auxier and Associates, 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, Kd, Values,” in Volume III: Review of Geochemistry and Available Kd Values for 

Americium, Arsenic, Curium, Iodine, 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 Injections 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 Distribution Coefficients in Soils. Part 2. Naturally Occurring 

Radionuclides,” Journal of Environmental Radioactivity 100:697–703. 

 
D-8 

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E-1 

APPENDIX E: 

GROUNDWATER CALCULATIONS 

 
E-2 

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E-3 

TABLE E.1 Calculations Relating Disposal Concentration of Unity, Appropriate Range of In-Landfill Kd Values, 

Concentration Reaching Water Table, Downgradient Proportion of Leachate Recharge, and Concentration in Grofor 100-m (328-ft) Downgradient Receptor and 20-m (66-ft) Thick Unsaturated Zone

Note A Note B Note C Note D 

Max. C/Co and Max. Conc. in 10,000 Years at 100-m Downgradient Receptor 

 LF leachate Conc. at Increased  Decay Water Base Case Decreased Kd Increased Kd Dispersivity Increased Gra

Kd

(mL/g) 

Csolute

pCi/mL 

Csolute

pCi/L 

 Const. 

1/yr 

Table 

pCi/L C/Co pCi/L C/Co pCi/L C/Co pCi/L C/Co pCi/L C/Co pC

Pb-210 1,000 0.001 1 0.031 0.15 7.88E-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 1.96

 100 0.01 10 0.031 1.5 7.88E-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 1.96 10 0.1 100 0.031 15 7.88E-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 1.96Ra-226 10,000 0.0001 0.1 0.00043 0.097 1.45E-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 1.99 1,000 0.001 1 0.00043 0.97 1.45E-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 1.99 100 0.01 10 0.00043 9.7 1.45E-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 1.99Ra-228 10,000 0.0001 0.1 0.12 7.2E-05 3.06E-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 3.38 1,000 0.001 1 0.12 0.00072 3.06E-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 3.38 100 0.01 10 0.12 0.0072 3.06E-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 3.38Th-232 10,000 0.0001 0.1 5E-11 0.1 5.59E-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 6.65 1,000 0.001 1 5E-11 1 5.59E-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 6.65 100 0.01 10 5E-11 10 5.59E-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 6.65Note A. Concentration of unity (1 pCi/g) assigned to disposal concentration, to be scaled to downgradient groundwater concentration at receptor well. The disposal con

the sorbed concentration, and through the assumption of a linear isotherm and an appropriate range of concentrations of Kd values, the solute in landfill leachate is calc

Note B. See Kd discussion in Appendix D. The largest Kd values correspond to the less conservative case, the mid-range Kd values are the base case, and the smallest K

conservative. 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 (RO

concentrations is the concentration at the water table multiplied by the proportion. 
E-4 

TABLE E.2 Calculations Relating Disposal Concentration of Unity, Appropriate Range of In-Landfill Kd Values, 

Concentration Reaching Water Table, Downgradient Proportion of Leachate Recharge, and Concentration in Grofor 100-m (328-ft) Downgradient Receptor and 5-m (16-ft) Thick Unsaturated Zone

Note A Note B Note C Note D 

Max. C/Co and Max. Conc. in 10,000 Years at 100-m Downgradient Receptor 

 LF leachate Conc. at Increased  Decay Water Base Case Decreased Kd Increased Kd Dispersivity Increased Gra

Kd

(mL/g) 

Csolute

pCi/mL 

Csolute

pCi/L 

 Const. 

1/yr 

Table 

pCi/L C/Co pCi/L C/Co pCi/L C/Co pCi/L C/Co pCi/L C/Co p

Pb-210 1,000 0.001 1 0.031 0.62 7.88E-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 7.9

 100 0.01 10 0.031 6.2 7.88E-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 7.9 10 0.1 100 0.031 62 7.88E-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 7.9Ra-226 10,000 0.0001 0.1 0.00043 0.099 1.45E-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 2.0 1,000 0.001 1 0.00043 0.99 1.45E-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 2.0 100 0.01 10 0.00043 9.9 1.45E-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 2.0Ra-228 10,000 0.0001 0.1 0.12 0.016 3.06E-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 7.6 1,000 0.001 1 0.12 0.16 3.06E-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 7.6 100 0.01 10 0.12 1.6 3.06E-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 7.6Th-232 10,000 0.0001 0.1 5E-11 0.1 5.59E-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 6.6 1,000 0.001 1 5E-11 1 5.59E-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 6.6 100 0.01 10 5E-11 10 5.59E-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 6.6Note A. Concentration of unity (1 pCi/g) assigned to disposal concentration, to be scaled to downgradient groundwater concentration at receptor well. The disposal co

the sorbed concentration, and through the assumption of a linear isotherm and an appropriate range of concentrations of Kd values, the solute in landfill leachate is cal

Note B. See Kd discussion in Appendix D. The largest Kd values correspond to the less conservative case, the mid-range Kd values are the base case, and the smallest K

conservative. 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 columconcentration at the water table multiplied by the proportion. 
E-5 

TABLE E.3 Calculations Relating Disposal Concentration of Unity, Appropriate Range of In-Landfill Kd Values, L

Concentration Reaching Water Table, Downgradient Proportion of Leachate Recharge, and Concentration in Groufor 300-m (984-ft) Downgradient Receptor and 20-m (66-ft) Thick Unsaturated Zone

Note A Note B Note C Note D 

Max. C/Co and Max. Conc. in 10,000 years at 300-m Downgradient Receptor

 LF Leachate Conc. at Increased 

 Decay Water Base Case Decreased Kd Increased Kd Dispersivity Increased Grad

Kd

(mL/g) 

Csolute

pCi/mL 

Csolute

pCi/L 

Const. 

1/yr 

Table 

pCi/L C/Co pCi/L C/Co pCi/L C/Co pCi/L C/Co pCi/L C/Co pC

Pb-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 4.75 100 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 4.75 10 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 4.75Ra-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 2.54 1,000 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 2.54 100 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 2.54Ra-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 1,000 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 100 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 0.00ETh-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 2.40 1,000 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 2.40 100 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 2.40Note A. Concentration of unity (1 pCi/g) assigned to disposal concentration, to be scaled to downgradient groundwater concentration at receptor well. The disposal conc

be the sorbed concentration, and through the assumption of a linear isotherm and an appropriate range of concentrations of Kd values, the solute in landfill leachate is cal

Note B. See Kd discussion in Appendix D. The largest Kd values correspond to the less conservative case, the mid-range Kd values are the base case, and the smallest Kd 

conservative. 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 oconcentration at the water table multiplied by the proportion. 
E-6 

TABLE E.4 Calculations Relating Disposal Concentration of Unity, Appropriate Range of In-Landfill Kd Values, L

Concentration Reaching Water Table, Downgradient Proportion of Leachate Recharge and Concentration in Groufor 300-m (984-ft) Downgradient Receptor and 5-m (16-ft) Thick Unsaturated Zone 

Note A Note B Note C Note D 

Max. C/Co and Max. Conc. in 10,000 years at 300-m Downgradient Receptor 

 LF Leachate Conc. at Increased 

Decay Water Base Case Decreased Kd Increased Kd Dispersivity Increased Gr

Kd

(mL/g) 

Csolute

pCi/mL 

Csolute

pCi/L 

Const. 

1/yr 

Table 

pCi/L C/Co pCi/L C/Co pCi/L C/Co pCi/L C/Co pCi/L C/Co 

Pb-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. 100 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. 10 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.Ra-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. 1,000 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. 100 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.Ra-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. 1,000 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. 100 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.Th-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. 1,000 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. 100 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.Note A. Concentration of unity (1 pCi/g) assigned to disposal concentration, to be scaled to downgradient groundwater concentration at receptor well. The disposal concsorbed concentration, and through the assumption of a linear isotherm and an appropriate range of concentrations of Kd values, the solute in landfill leachate is calculate

Note B. See Kd discussion in Appendix D. The largest Kd values correspond to the less conservative case, the mid-range Kd values are the base case, and the smallest Kd 

conservative. 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 concentration at the water table multiplied by the proportion.