P.16 

TECHNICAL BACKGROUND SUPPLEMENT 

IN SUPPORT OF 

RULEMAKING ADJUSTMENT ACTIVITIES 

FOR REPORTABLE QUANTITIES (RQ) 

OF 

RADIONUCLIDES 

March 1989 

U.S. Environmental Protection Agency 

Office of Radiation Programs 

Washington, DC 
P.17 

i .r JEXECUTIVE SUMMARY 

The purpose of Chis sCudy was Co esCimaCe the poCenCial doses and risks 

associated wich environmencal releases of radionuclides from coal and coal ash 

piles ac utility and indusCrial facilicies wich coal-fired boilers. Such 

releases may occur during or following Che delivery of coal and Che disposal 

of coal ash. The dumping of coal and ash, as well as subsequenC releases of 

radionuclides from coal and ash piles, could be subjecc Co Che noCification 

requirements under Che Comprehensive Environmencal Response, CompensaCion, and 

LiabiliCy Act (CERCLA) of 1980, as amended, because such releases may equal or 

exceed the radionuclide reportable quantity (RQ). The RQ Is a reporting 

trigger for notifying Che Nacional Response Cencer of a release so that the 

need for a response can be evaluated in a timely manner. 

Conservative models were used to estimate the potential radiation doses 

and resulting health risks to nearby residents and to workers as a result of 

radionuclide releases from coal and coal ash piles. In particular for nearby 

residents assumed to reside 100 meters from the piles, doses and risks were 

.estimated via the following potential exposure pathways: (1) direct radiation; 

(2) various pathways of exposure to particulates released to the air, 

including inhalaCion, immersion in an airborne plume, direcc radiaCion from 

parciculaces deposited on the ground, and ingestion of crops contaminated by 

airborne deposition; (3) inhalation of radon; (4) ingestion of contaminated 

ground water, as well as ingestion of crops and livestock assumed Co be 

contaminated by the ground water; and (5) ingestion of contaminated surface 

water, as well: as ingestion of crops and livestock assumed to be contaminated 

by the surface water. The results of these risk analyses are presented in 

Table ES-1. As shown in the Table, the critical exposure pathway to nearby 

residents (i.e., the one yielding the highest dose and risk estimates) was 

found to be the inhalation of radon from ash piles, with the lifetime risk of 

fatal cancer caused by this exposure estimated to be 1.8 x IO"5. 

For workers, radiation doses and resulting health risks were estimated 

via four potential exposure pathways: (1) direct radiation when standing next 

to (i.e., 10 meters from) a coal or ash pile; (2) direct radiation when 

standing on a coal or ash pile; (3) various pathways of exposure to airborne 

particulaces, including inhalaCion, immersion in an airborne plume, and direcc 

radiaCion from parciculaces deposiCed on che ground; and (4) inhalaCion of 

radon. As shown in Table ES-2, Che cricical exposure paChway for workers was 

found Co be direcc radiaCion, especially when scanding on a coal or coal ash 

pile. The maximum lifecime risk of facal cancer caused by direct radiation . 

when standing on an ash pile for eight hours a day, five days per week, 50 

weeks per year for 47 years was estimated to be 4.3 x 10"*; the maximum 

lifetime risk caused by direct radiation from standing next to the ash pile 

during the same period was estimated to be 1.8 x 10"*. The lifetime cancer 

risks to workers due to exposures via the other pathways were estimated to be 

5 x IO"6 or less. 

The estimated health risks to nearby residents are well within the 

general range of health risks, 10"* to IO"7, routinely considered to be 

acceptable within the Superfund program. The estimated health risks to 

workers through all but the direct radiation pathways are also within this 

ill 
P.18 

• ,S 

accepCable range. The poCenCial risk from direcc radiaCion Co workers 

sCanding on or near a coal ash pile for eighc hours a day for 47 years is 

slighcly above che upper bound of generally accepted risks in the Superfund 

program. It is clear, however, that such potential exposures do not require 

an emergency response, but rather more appropriately should be evaluated in 

the contexC of general worker safecy and regulacory concrols. Furcher, in 

discussions wich induscry expercs and afCer a furcher evaluacion of worker 

praccices, ic became clear that workers generally are shielded more fully than 

is reflected in the model analyzed in Chis reporc. Taking inCo accounC chis 

addicional shielding, risks would be closer Co 2.6 x 10"* raCher Chan 4.3 x 

10"*. 

To puC Chese occupaCional risks inCo concexc, a lifecime risk of 4.3 x 

10"* corresponds Co an annual dose of 33 mrem and an annual risk of 9.2 x IO"6 

for facal cancers. This annual risk level is lower Chan Che observed annual 

risks of job-related accidental deaths for all other industries. For example, 

the U.S. average for all industries was 11 per 100,000 or 1.1 x 10'* in 1985. 

For industries with the safest record, wholesale and retail trades, the annual 

accidental death race averaged about 5 per 10,000 or 5.0 x 10"' from 1980 to 

1984. 

Finally, when comparing the yearly dose rate from an ash pile to 

naturally occurring background radiation levels, the dose to the worker falls 

on the lower end of the range of radiation exposures normally associated with 

naCural background radioactivity. The range of reported exposure races from 

natural background radiaCion varies from a low of 35 mrem/yr Co a high of 180 

mrem/yr. 

iv 
P.19 

TABLE ES-1 

ESTIMATED DOSES AND RISKS TO NEARBY RESIDENT 

Parameters* Coal Ash 

• Direct Radiation 

(at 100 meters) 

Dose (mrem/yr) 

Lifetime risk: 

1.7 x 10"1 

4.5 x IO"6 

6.1 x 10"1 

1.6 x IO"5 

• Particulate Emissions 

(at 100 meters) 

Dose (mrem/yr): 

Lifetime risk: 

3.4 x IO'2 

4.1 x IO"7 

2.7 x IO"2 

3.9 x IO"7 

• Radon Emissions 

(at 100 meters) 

Concentration (pCi/L): 

Lifetime risk: 

• Ground Waterb 

(at 30 meters) 

Concentration (pCi/L): 

Dose (mrem/y): 

Lifecime risk: 

9.0 x 10"* 

4.8 x IO"6 

0.0 

0.0 

0.0 

3.3 x IO"3 

1.8 x IO"5 

0.0 

0.0 

0.0 

• Surface WaCer 

(ac 600 meters) 

-- Concentration (pCi/L)c: 1.2 x IO"3 

Dose (mrem/y): 4.4 x IO"3 

-- Lifetime risk: 2.9 x IO"8 

2.0 x IO"1 

7.3 x IO"1 

4.6 x IO"6 

a Risks are for fatal cancers based on a 70 year life 

span. 

b There is no radionuclide migration to nearby well. 

c Water concentrations are reported only for Ra-226, but 

doses and risks reflect all radionuclides. 

v 
P.20 

TABLE ES-2 

ESTIMATED DOSES AND RISKS TO WORKER 

Parameters8 Coal Ash 

• Standing NexC Co Pile 

(aC 10 meters) 

Yearly dose (mrem): 1.5 14 

-- Lifetime risk: 2.0 x IO"5 1.8 x 10"* 

• Standing on Pile 

(1 meter height) 

- - Yearly dose (mrem): 

Lifetime risk: 

• Particulate Emissions 

(at 10 meters) 

- - Yearly dose (mrem): 

Lifetime risk: 

3.3 

4.3 x IO"5 

1.5 x IO"2 

1.9 x 10'7 

33 

4.3 x 10"* 

8.2 x IO"3 

1.3 x IO"7 

• Radon Emissions 

(at 10 meters) 

-- Concentration (pCi/L): 2.6 x IO"3 5.7 x IO"3 

-- Lifetime risk: 2.2 x IO"6 5.1 x IO"6 

" Risks are for fatal cancers based on exposures starting 

at age 18 and ending at 65 years of age. 

vi 
P.21 

. . 

TABLE OF CONTENTS 

Page 

1.0 Introduction 1 

2.0 Coal and Coal Quantities and Source Terms 1 

2.1 Coal 2 

2.2 Ash 6 

3.0 Direct Radiation 8 

3.1 Standing Near Coal and Ash piles 8 

3.1.1 Dose to Worker 10 

3.1.2 Dose to Resident 10 

3.2 Standing on Coal and Ash Piles 13 

3.2.1 Dose to Worker 13 

4.0 Fugitive Dust Emissions 13 

4.1 Radioactive Source Terms and Release Rates 14 

4.2 Particulate Doses and Risks 15 

4.2.1 Dose to Worker 15 

4.2.2 Dose to Resident 16 

5.0 Radon 17 

5.1 Radon Emanation and Release Rates 17 

5.2 Radon Concentrations and Risks 19 

5.2.1 Exposure to Worker 19 

5.2.2 Exposure to Nearby Resident 19 

6.0 Ground and Surface-Water 20 

6.1 Ground-Water Model 24 

6.2 Surface-Water Model 2 4 

6.3 Radioactive Source term 25 

6.4 Ingestion Model 2 6 

6.5 Water Concentrations and Doses 27 

7.0 Industrial Boilers 28 

7.1 Quantities of Coal and Ash 28 

7.2 Distance to Surface Stream 31 

7.3 Surface-Water Use 31 

7.4 Direct Radiation 31 

7.5 Conclusion 32 

Reference s 3 3 

Appendix 38 

V i l 
P.22 

LIST OF TABLES 

No. Page 

1 Coal and Coal Ash Pile Characteristics 

and Source Terms 3 

2 Major Assumptions and Parameters 4 

3 Doses and Risks to Worker 11 

4 Doses and Risks to Nearby Resident 12 

5 Qualitative and Comparative Evaluation 

of Utility and Industrial Boilers 29 

LIST OF FIGURES 

No. Page 

1 Hypothetical Coal and Coal Ash Site 21 

2 Coal Pile Configuration 22 

3 Ash Pile Configuration 2 3 

Vlll 
P.23 

1.0 INTRODUCTION 

The purpose of this study is to estimate the potential doses and 

risks associated with environmental releases from coal and coal 

ash piles at utility and industrial facilities with coal-fired 

boilers. Such releases may occur during or following the delivery 

of coal and the disposal of coal ash. The results of this study 

will be used to provide background information to consider 

exempting coal and coal ash piles from the CERCLA notification 

requirements. The dumping of coal and ash, as well as releases 

from coal and ash piles, could be subject to CERCLA notification 

requirements because such releases may equal or exceed the 

radionuclide reportable quantity (RQ). The RQ is a reporting 

trigger for notifying the National Response Center of a release 

so that government officials can evaluate the need for a 

response. 

The following exposure scenarios are evaluated in this report: 

(1) Direct radiation exposure, 

(2) Airborne releases of radon and fugitive dusts, 

(3) Pile leachate migration to ground-water, and 

(4) Pile surface-water runoff to a nearby stream. 

For direct radiation and airborne exposures, the potential doses 

and risks are evaluated for both an onsite worker and a nearby 

resident. Potential doses and risks from exposure to contaminated 

ground-water and surface-water runoff, however, are only analyzed 

for the nearby resident; workers are assumed drink water from 

other sources (bottled water or from a community supply system). 

2.0 COAL AND COAL ASH OUANTITIES AND SOURCE TERMS 

The quantities of coal held in storage and ash disposed by 

utility boilers are known to vary significantly. The actual size 

of such piles and their configurations vary, depending upon the 

type and size of the boiler at the facility. Section 7 addresses 

the applicability of this assessment to industrial boilers. The 

geometry of each pile and the total amount stored at any one site 

also change as a function of time since material is always being 

added, removed, and subjected to storage or waste management 

procedures. Because of this dynamic process, there is, in fact, 

no "model" pile that is truly representative of a specific site. 

Furthermore, storage and waste disposal management practices vary 

with each site. These practices could incorporate procedures or 

engineered features that provide greater confinement of the coal 

or coal ash. These practices, taken together, tend to minimize 

releases and exposures. 
P.24 

In view of these uncertainties, several simplifying assumptions 

were made in modeling each pile and exposure scenario. Within the 

context of this evaluation, the concept of the reference pile and 

exposure models is employed only to evaluate the magnitude of 

potential doses and risks, rather than to characterize industry 

practices. Table 1 presents the characteristics of the reference 

coal and coal ash piles used in this analysis. The assumptions 

and parameters used in this analysis are shown in Table 2. 

2.1 COAL 

Coal is typically stored in large piles. The practice is to 

stockpile a 60- to 90-day supply, which may represent as much as 

two million metric tons (Mt) of coal for a 1,000 megawatt (MW) 

power plant (EPR84, EPA88, EPA79). These large piles are kept 

inactive, with the coal maintained in open storage, while the 

daily plant requirements (up to about 7 days) are met by using 

smaller active piles. The amount of coal stored in active piles 

is typically a small fraction (less than 10 percent) of that 

stored in inactive piles (EPR84, EPA78). Depending upon 

environmental conditions, costs, climate, and geography, the 

active and inactive storage piles may both be enclosed in 

structures. Enclosed storage is not considered in this analysis 

since any associated releases from these facilities, other than 

radon and its decay products, would be negligible. In addition, 

the impact from radon and radon daughters at enclosed facilities 

is analogous to the potential effects estimated for open piles 

because radon is not retained by the storage facility. There is 

no need, therefore, to analyze coal storage facilities 

separately. 

Coal is stored primarily in two basic types of geometry; cone and 

rectangular. Coal piles are usually 25 to 45 feet high and can 

cover an area of up to 75 acres. Other types of configurations 

include kidney and wedge shapes (EPR84). For the purpose of this 

study, it is assumed that fifty percent of the piles are cone 

shaped and fifty percent are of rectangular configuration. Based 

on the results of a 1978 EPA study, it is also assumed that the 

typical inactive storage pile contains 95,000 Mt of coal (EPA78). 

This quantity is thought to be representative of overall 

practices of electric utility stations, coke plants, and 

industrial boilers; and may characterize about 70 percent of 

facilities with coal-fired plants. 

Although the demand for electricity has been increasing at 1.7 

percent per year for the last decade, the amount of coal stored 

at any one site has not necessarily increased at this rate 

(NER87) . For the purpose of this study, it is assumed that, as 

new facilities are built and operated, the distribution and size 
Table 1: Coal and coal ash pile characteristics and source terms 

PARAMETERS(a) COAL ASH 

o PHYSICAL/RADIOLOGICAL 

-Quantit y (Mt): 9.5(E+4)(b) 1.5(E+6) 

- Depth/Height (m): 11 5 

- Pile/Area Radius (m): 80 270 

- Total Area (m2): 2.0(E+4) 2.3(E+5) 

- Direct Radiation 

Effective Radius (m): 45 18 

- Edge of Pile to 

Receptor Distance (m) 

Worker: 10 10 

Public: 100 100 

- Concentration (pCi/g) 

U-238: 0.43 4.3 

Th-232: 0.35 3.5 

o SOURCE TERMS 

- Particulate Emission 

Rate (kg/yr): 610 340 

- Radionuclide 

Release Rate (Ci/yr) 

Radon: 2.3(E-1) 4.0(E+0) 

U-238: 6.6(E-7) 1.7(E-6) 

Th-232: 5.3(E-7) 1.4(E-6) 

- Ground/Surface-Water 

Total Inventory (Ci) 

U-238: 4.1(E-2) 6.3(E+0) 

Th-232: 3.3(E-2) 5.1(E+0) 

(

a

) See text for details, 

l) 

(

b

) Denotes exponential notation: 9.5(E+4) = 9.5 x 10+ 4 
P.26 

Table 2: Major assumptions and parameters 

(a) 

PARAMETERS 

o STANDING NEXT TO PILE 

WORKER RESIDENT 

- Distance (m): 

- Dose Rate (urem/h) 

Coal: 

Ash : 

- Occupancy 

Hours: 

Fraction (%): 

Indoor (%): 

Outdoors (%): 

- Shielding 

Factor (%): 

Fraction (%): 

10 

0.9 

8.1 

2,000 

100 

NA 

100 

70 

50 

100 

3.3(E-2)(b) 

1.2(E-1) 

8,766 

67 

67 

33 

80 

67 

o STANDING ON PILE 

- Height (m) : 

- Dose rate (urem/h) 

Coal : 

Ash : 

- Occupancy 

Hours: 

Fraction (%): 

Outdoors (%) : 

- Shielding 

Factor (%): 

Fraction (%): 

1.0 

2,0 

20 

2,000 

100 

100 

70 

50 

NA 

NA 

NA 

NA 

NA 

NA 

NA 

NA 

O AIRBORNE EMISSIONS 

Downwind 

distance (m): 10 100 

o GROUND/SURFACE-WATER 

- Distance to well (m): 

- Distance to stream (m) 

- Stream flow (cu.ft/s) 

NA 

NA 

NA 

(a) see text for details. 

(

b

) Denotes exponential notation: 3.3(E-2) 

30 

600 

10 

= 3.3 x 10 -2 
P.27 

of coal piles remain unchanged; only the total number of plants 

and total amount of coal consumed have increased. If in fact, 

there were a proportional relationship between rising electrical 

demand and coal storage, then the assumed amount (95,000 Mt) of 

coal would have to be increased by a factor of 1.18, to 112,000 

Mt. Within the context of this study, this uncertainty is assumed 

to be insignificant. 

The radioactivity content of coal is known to vary over two 

orders of magnitude (UNS82). The concentration of uranium-238 

(U-238) and thorium-232 (Th-232) in coal can range from 0.08 to 

14 pCi/g and 0.08 to 9 pCi/g, respectively (UNS82) . In a review 

of 800 coal samples characterizing U-238 concentrations, Wagner 

and Greiner noted that only 0.5 percent of the samples exceed an 

activity of 10 pCi/g (WAG82). Beck conducted an evaluation of 

nearly 1,000 U.S. coal samples and reported average (arithmetic) 

U-238 and Th-232 concentrations of 0.6 and 0.5 pCi/g, 

respectively (BEC80). The frequency distribution of measured U 

and Th contents in coal, however, indicates that concentrations 

(based on geometric mean) are in fact predominantly lower. For 

example, the reported mean geometric concentrations of U-238 and 

Th-232 are 0.34 pCi/g and 0.26 pCi/g, respectively (BEC80). 

In this analysis, the presence of uranium-235 (U-235) in coal is 

ignored because of its lower concentration when compared to 

U-238. Because of its shorter half-life, U-235 has decayed more 

rapidly than U-238. For each pCi of U-238 in coal there is less 

than 0.0073 pCi of U-235, or about less than 1 percent (NCR87). 

For the purpose of this analysis, the adopted coal concentrations 

are those used in support of the preparation of the 1989 

radionuclide National Emission Standards for Hazardous Air 

Pollutants (NESHAP) (EPA89). These concentrations are 0.43 and 

0.3 5 pCi/g for U-238 and. Th-232, respectively. As can be noted, 

the selected concentrations fall within the range bounded by the 

geometric mean (on the low end) and arithmetic average (on the 

upper end) as reported by Beck. In spite of the large variations 

noted in radionuclide concentrations, it is anticipated that over 

the operational life of most boilers, these variations would be 

expected to average out and fall within the range characterized 

by the arithmetic and geometric means. Finally, it is also very 

unlikely that a single mine producing coal with elevated 

radioactivity would be the sole supplier to any particular 

facility throughout its entire operational life. 
P.28 

2.2 ASH 

Coal ash is generated when coal is burned. The amount of ash 

produced depends upon the mineral content of the coal and type of 

boiler. During the combustion process, some of the ashes are 

entrained with hot flue gases to form fly ash while some, too 

large or heavy to be entrained, settle to the bottom of the 

boiler to form bottom ash. For example, pulverized coal boilers 

generate more fly ash than stoker boilers because the combustion 

process takes place in a state of suspension, rather than in a 

bed (EPA88, EPR88, EEI88). Liquid slag is formed when the ash 

melts under the intense heat and drains to the bottom of the 

boiler. 

In considering the total quantity of ash generated, the relative 

amounts of fly ash, bottom ash, and slag are dependent upon the 

type of coal used and the configuration of the boiler. In the 

aggregate, the distribution of fly ash may constitute about 70 to 

80 percent of the total ash produced, with the balance comprised 

of bottom ash and solidified slag material (EPA79). 

The mineral content of coal varies from 3 to 30 percent depending 

upon the mining region from which the coal originates (EPA88, 

ACA86). Utilities are also selecting coals with lower ash content 

to facilitate compliance with particulate emission standards. 

Coal is often washed to remove excess minerals. Washing can 

reduce the mineral content by as much as 50 to 70 percent. The 

average ash content of coal used in 1985 by electric utilities 

ranged from 5.9 to 29.4 percent, with a national average of 10.1 

percent. The average ash content of coal burned since 1975 has 

also decreased steadily, from about 14 percent to the current 

value of 10.1 percent (EPA88, ACA86). The ash content of coal is 

expected to remain at about 10 percent until the end of the 

century. For this analysis, it is assumed that the typical ash 

content is 10 percent. 

The majority (70 to 80 percent) of the coal ash produced is 

disposed in waste facilities (EPA88). The balance is being used 

or recycled in a variety of commercial applications, such as a 

cement substitute, structural fill, material filler or additive, 

land management, and soil conditioner (ACA86). 

Ashes are typically disposed into dry landfills or ash ponds. 

Sluiced ashes and flue gas desulfurization sludges are stored 

temporarily in ponds for dewatering and are later removed and 

transported to a dry landfill. Eventually, most of the ash is 

placed in a dry landfill. A typical ash disposal landfill may be 

anywhere from 75 to 150 acres in size (EEI88, EPA88). An ash pile 

of this size is presumed to support the disposal needs of a 
P.29 

modern power plant with a capacity that ranges from about 500 MW 

to 1,000 MW. Ash is disposed in landfills of varying dimensions. 

For example, the size of disposal areas can range anywhere from 

10 to 60 acres while some facilities use disposal areas as large 

as 200 acres. On the extreme, a site was reported to have a 

landfill facility of 438 acres (EPA88). In order to meet 

particulate emission standards, ashes generally are disposed in 

smaller areas or cells. Smaller active disposal areas may use as 

much as 20 acres and on the average comprise about 5 to 10 acres 

(N0V89). The depth of the ash bed upon closure may be as thick as 

30 feet (EPA88). 

For the purpose of estimating airborne and waterborne releases, 

it is assumed that the total area of the landfill is 60 acres, 

with an average depth of 15 feet. Given the disparity of 

information about such sites, 60 acres is assumed to be a 

conservative estimate and, therefore, will tend to overestimate 

releases. This acreage is also assumed to include all areas where 

ash is being handled as part of the overall waste management 

activities (including disposal, grading, capping, etc.) and where 

there exists the possibility for offsite releases. No credit is 

taken for features or practices which would tend to reduce such 

releases. For example, some utilities treat coal piles with a tar 

and water mixture to reduce fugitive dust emissions. Similarly, 

during ash disposal activities, the exposed disposal cells are 

periodically covered with soil caps to reduce wind erosion. 

The total quantity of ash is assumed to be 1.5 million Mt based 

on a disposal depth of 15 feet. Depending upon the size of a 

power plant and the ash content, this volume may in fact 

represent more than one year's worth of ash generation. 

The radionuclide distribution and concentrations in ash are also 

known to vary significantly. For example, U-238 and Th-2 32 

concentrations have been noted to range from 1.5 to 8.6 pCi/g and 

0.4 to 7.5 pCi/g, respectively (BEC89, BEC80). The average 

concentration of U-238 and Th-232 in fly ash are reported to be 

about 5.4 and 1.9 pCi/g, respectively (UNS82). The radioactivity 

of fly ash is typically higher than coal. This enrichment is 

dependent upon the type of coal used, its ash content, and the 

type of boiler (UNS82). The enrichment ratio also varies 

depending upon the elemental form of the radionuclide. For 

example, enrichment ratios of about 1.3 and 1.4 are reported for 

U-238 and Th-232, respectively (UNS82). The presence of U-235 in 

coal ash is not considered in this analysis because of the low 

concentration of U-235 in ash. For other radionuclides, much 

higher enrichment ratios have been observed; enrichment ratios of 

up to 2 have been observed for radium-226 and as high as 11 for 

polonium-210. 
P.30 

Because of the disparate information and data regarding the 

presence of radionuclides and their amounts in ash materials, a 

simplified approach is used here to estimate the "typical" U-238 

and Th-232 concentrations of fly ash, bottom ash, and slags. It 

is assumed that radionuclide mass balance is maintained between 

the coal that is introduced in the boiler and what is eventually 

recovered in the ash and slag contents. The small amount (less 

than 5 percent) which passes through particulate emission control 

systems and becomes airborne is ignored in this analysis. It is 

also assumed that the radioactivity typically contained in 

sludges is eventually taken to the landfill and combined with the 

ashes and slags for disposal. Finally, the uncertainty associated 

with the mechanisms of fly ash enrichment and radionuclide 

concentrations in fly ash, bottom ash, and slags is addressed by 

assuming that the concentrations of U-238 and Th-232 in the ash 

is an order of magnitude greater than their respective 

concentrations in coal. This approach yields U-238 and Th-232 

concentrations of 4.3 and 3.5 pCi/g, respectively. These values 

fall well within the observed range of concentrations. 

3.0 DIRECT RADIATION 

This section presents modeling assumptions to estimate doses and 

risks from direct radiation exposures to a worker near, or 

standing on, a coal or ash pile, and for a nearby resident 

situated just off the site boundary. The worker is assumed to be 

at a distance of 10 meters from either pile. Similarly, the 

exposure associated while standing directly on the coal or coal 

ash pile is estimated assuming an exposure height of 1 meter. The 

dose to the nearby resident is calculated for a distance of 100 

meters from the face of the coal and ash piles. The major 

assumptions and parameters are listed in Tables 1 and 2. This 

evaluation excludes the contribution from the ambient background 

exposure rate. The exposure rates are expressed in micro-Roentgen 

per hour (uR/h) and dose rates are noted as micro-rem per hour 

(urem/h). 

3.1 STANDING NEAR COAL AND ASH PILES 

Radiation exposures from the coal pile are estimated assuming 

that the individual is standing near the pile at a distance of 10 

meters (m). Given the volume and physical dimensions, the pile is 

modeled as a finite slab (SCH74, MOR73, CEM69). The effective 

area and radius of the coal pile, to which the worker or nearby 

resident are exposed, are assumed to be 6,400 m2 and 4 5 m, 

respectively. This surface area represents an average storage 

configuration between the rectangular and cone geometries. It is 

assumed that the radiation flux originates only from one side of 

the four-sided rectangular slab. For the cone configuration, the 
P.31 

flux is assumed to be due to half of the total lateral surface 

area. In either case, it is assumed that there are no 

obstructions that would shield or block exposures from the pile 

to the receptor. 

For the ash pile, the effective area and radius, from which the 

exposure originates, are assumed to be 1,000 m2 and 18 m, 

respectively. This area represents the frontal area of an active 

ash pile. It is assumed that the active face of the landfill is 

above grade and that there are no obstructions between the pile 

and the receptor. 

In estimating doses and risks, exposure duration is based on 

2,000 hours per year with 100 percent occupancy. Shielding may, 

however, reduce the exposure and dose. For example, if the 

individual were operating a vehicle or machinery while near the 

pile, the exposure could be reduced by a factor ranging anywhere 

from 0.15 to 0.7 (NCR85a) . For this analysis, it is assumed that 

the worker spends half of his time operating a vehicle or 

machinery which provides some shielding. A shielding protection 

factor of 0.7 is applied for 50 percent of the time (i.e., while 

operating equipment) and none for the balance of the time. In the 

aggregate, this model assumes that the worker is exposed 

effectively to a total of 1,700 hours per year (or 85 percent of 

the time) to either the coal or ash pile. 

Radiation exposure rates, for the U-238 decay chain, are 

calculated assuming equilibrium with its decay products (down to 

lead-210 and an effective gamma ray energy of 1.6 MeV per 

disintegration (NCR76). Similarly, an effective gamma ray energy 

of 2.3 MeV is used for the Th-232 decay series (down to 

thallium-201. Because the exposure is in part due to scattered 

gamma rays, a build up factor of 2.72 is applied because of the 

depth or thickness of the coal or coal ash piles. Typically about 

90 percent of the ambient radiation exposure rate is due to gamma 

rays originating only from the top 2 to 3 feet of materials 

(NCR87). 

The exposure rates for the worker, at 10 meters, are 0.9 and 8.1 

uR/h for coal and ash, respectively. In assessing the effect of 

varying distances on exposure rates, this calculation was 

repeated for two additional locations, 3 and 20 meters from the 

edge of the pile. These changes do not yield a significant 

reduction or increase, less than 15 percent, in the exposure 

rate. Within the context of this analysis, it is assumed that 

this variation is insignificant. 
3.1.1 Dose to Worker 

Using the assumptions listed above, estimated exposure rates, 

doses, and risks for coal and coal ash are shown for the worker 

in Table 3. The annual dose assuming 100 percent occupancy is 1.5 

and 14 mrem/yr for coal and coal ash, respectively. The risks 

associated with such exposures are estimated using a risk factor 

of 2.8 x 10~4 per rad for an adult. This individual is assumed to 

start working at age 18 and work until age 65. Combining these 

factors, the equivalent lifetime risk factor for fatal cancers is 

1.3 x 10~5 per mrem/yr, assuming a one-to-one relationship 

between absorbed dose and dose equivalent and a factor of 1.11 as 

the average ratio of tissue to air energy absorption 

coefficients. The lifetime risks due to direct radiation 

exposures are 2.0 x 10~5 for coal and 1.8 x IO"4 for coal ash. 

3.1.2 Dose to Resident 

The same methodology is applied to determine doses and fatal 

cancer risks to the nearby resident, however, the distance and 

occupancy factors were changed. For the nearby resident, the 

receptor point is assumed to be located at 100 meters. The 

occupancy factor assumes that two thirds of the individual's time 

is spent on the property. Of the time spent on the property, two 

thirds is spent indoors and one third is spent outdoors (NCR85a). 

For the time which is spent indoors, a factor of 0.8 is applied 

to account for the shielding afforded by the structure (NCR85a). 

In the aggregate, this model assumes that the nearby resident is 

effectively exposed to a total of 5,100 h/yr (or 58 percent of 

the time) to either the coal or ash pile. Other risk assessment 

studies have assumed similar exposure scenarios, durations, and 

shielding protection factors ranging from 58 to 67 percent 

(NRC80, NIE87, RAD88, NCR85a). 

The derived exposure rates are, respectively, 0.033 and 0.12 

urem/h for the coal and ash piles (see Table 2). The yearly doses 

and risks (for fatal cancers) are shown in Table 4 for the nearby 

resident. The dose due to the coal pile is estimated to be 

0.17 mrem/yr with a corresponding risk of 4.5 x IO""6. For the ash 

pile, the dose and risk are estimated to be 0.61 mrem/yr and 

1.6 x IO"5, respectively. 

It is instructive to place these doses in perspective by 

comparing them to exposures from naturally occurring 

radioactivity. NCRP Report No. 94 summarizes survey results 

which encompass varied geographical locations (NCR87). 

10 
P.33_ 

Table 3: Doses and risks to worker(a) 

PARAMETERS (b) 

o STANDING NEXT TO PILE 

(at 10 meters) 

-Yearly dose (mrem): 

-Lifetime risk: 

O STANDING ON PILE 

(l-meter height) 

-Yearly dose (mrem): 

, -Lifetime risk: 

o PARTICULATE EMISSIONS 

(at 10 meters) 

-Yearly dose (mrem): 

-Lifetime risk: 

o RADON EMISSIONS 

(at 10 meters) 

-Concentration (pCi/L) 

-Lifetime risk: 

COAL 

1.5 

2.0(E-5)(c) 

3.3 

4.3(E-5) 

1.3(E-2) 

1.6(E-7) 

2.2(E-3) 

1.8(E-6) 

ASH 

14 

1.8(E-4) 

33 

4.3(E-4) 

7.3(E-3) 

l.l(E-7) 

5.2(E-3) 

4.3(E-6) 

(a) See text for technical details and assumptions for each 

exposure pathway. 

(b) Risks are for fatal cancers based on exposures starting at 

age 18 and ending at 65 years of age. 

(

c

) Denotes exponential notation: 2.0(E-5) = 2.0 x IO"5. 

11 
P.34 

Table 4: Doses and risks to nearby resident(a) 

PARAMETERS (b) COAL ASH 

O DIRECT RADIATION 

(at 100 meters) 

- Dose (mrem/yr): 1.7(E-1)(«) 6.1(E-1) 

- Lifetime risk: 4.5(E-6) 1.6(E-5) 

o PARTICULATE EMISSIONS 

(at 100 meters) 

-Dose (mrem/yr): 2.7(E-2) 2.2(E-2) 

-Lifetime risk: 3.4(E-7) 3.4(E-7) 

O RADON EMISSIONS 

(at 100 meters) 

-Concentration (pCi/L): 7.0(E-4) 2.8(E-3) 

-Lifetime risk: 3.9(E-6) 1.6(E-5) 

o GROUND-WATER (c) 

(at 30 meters) 

-Concentration (pCi/L): 0.0 0.0 

-Dose (mrem/yr): 0.0 0.0 

-Lifetime risk: 0.0 0.0 

o SURFACE-WATER 

(at 600 meters) 

-Concentration (pCi/L) (<*) : 1.2(E-3) 2.0(E-1) 

-Dose (mrem/yr): 4.4(E-3) 7.3(E-1) 

-Lifetime risk: 2.9(E-8) 4.6(E-6) 

(a) see text for technical details for each exposure pathway. 

(b) Risks are for fatal cancers based on a 70 year life span. 

(

c

) There is no radionuclide migration to nearby well, see text. 

(

d

) Water concentrations are reported only for Ra-226, but doses 

and risks reflect all radionuclides. 

(

e

) Denotes exponential notation: 1.7(E-1) = 1.7 x 10"1 = 0.17. 

12 
P.35 

The range of reported exposure rates associated with natural 

background radiation vary from 35 to 180 mrem/yr. As can be 

noted, the incremental dose to the worker is still below the 

lower range of radiation exposures normally associated with 

natural background radioactivity. By comparison, the dose to the 

nearby resident is insignificant. 

3.2 STANDING ON COAL AND COAL ASH PILES 

Radiation doses attributed to standing on a coal or coal ash pile 

are modeled as an infinite slab source. Radiation exposure rates 

at one meter above the surface are calculated assuming that U and 

Th decay chains are in equilibrium with their decay products. The 

exposure rates are based on conversion factors of 1.8 and 2.8 

uR/h per pCi/g for U and Th, respectively. These conversion 

factors represent actual environmental exposure rates of typical 

soils, including gamma ray scatter, buildup, and self absorption 

(NCR76). 

3.2.1 Dose to Worker 

Using the assumptions noted earlier, the exposure rates, doses, 

and risks are estimated for a worker standing on a coal or ash 

pile (see Table 2) . The total yearly dose assuming 100 percent 

occupancy is estimated to be 3.3 and 33 mrem/yr for coal and coal 

ash, respectively (see Table 3) . The lifetime risks for fatal 

cancers due to such direct radiation exposures are estimated to 

be 4.3 x 10~5 for coal and 4.3 x 10~4 for coal ash. As stated 

earlier, only the incremental exposure due to coal ash approaches 

the lower range of radiation exposure rates normally associated 

with natural background radioactivity. (See Appendix for additional 

information reflecting industry practices.) 

When these risk estimates are put in perspective with other 

occupational hazards, they are comparable to the observed risk of 

job related accidental deaths for all industries. For example, 

the United States average for all industries was 11 per 100,000 

or 1.1 x 10~4 in 1984 and 1985 (EPA87a). For industries with the 

safest record, wholesale and retail trades, the annual accidental 

death rate averaged about 5 per 100,000 or 5.0 x 10~5 from 1980 

to 1984. For the worker standing on the ash pile for one year and 

receiving a dose of 3 3 mrem, the risk of fatal cancers is about 

9.2 x 10~6. This risk is in fact an incremental risk above the 

job related accidental death rate for this sector of the 

industry. 

4.0 FUGITIVE DUST EMISSIONS 

Airborne fugitive dust emissions can result in downwind exposures 

to a worker located onsite and to the general public. 

13 
P.36 

The exposure pathways of concern are inhalation of airborne 

particulates and direct radiation from plume deposition. In 

addition, ingestion of crops and vegetables contaminated from 

plume deposited radioactivity is also addressed as another 

potential exposure pathway. 

It should be noted that the particulate release rates do not take 

credit for the application of dust emission controls. For 

example, dust control measures which include the placement of top 

soil covers, application of water and chemical mixtures on 

exposed areas, and minimizing the active portion of the disposal 

area would tend to reduce such fugitive emissions. 

4.1 RADIOACTIVE SOURCE TERMS AND RELEASE RATES 

The •particulate emission rates presented in Table 1 were 

estimated using EPA and NRC models for resuspended particulates 

which are typically less than 100 micro-meter (um) (EPA89, 

NRC80). Larger particles which may be transported by surface 

creep and saltation processes do not contribute to airborne 

resuspension (HIN82, NRC80). These processes involve large 

particle sizes which are not resuspended or respirable. Surface 

creep involves particles (500 to 1,000 um in size) that are 

rolled along the surface and collide with other particles. 

Saltation involves particles (ranging from 100 to 500 um) which 

lurch into the air within a few centimeters of the surface and 

are rapidly brought back down by gravity. For this analysis, it 

is also assumed that smaller sized particles have elevated 

specific activities due to higher surface area-to-volume ratios 

(KAL85, NRC80). An activity enrichment factor (ratio of airborne 

particulate to nonresuspendable material) of 2.5 is applied to 

all dust emissions. 

The dust release rates depend upon each pile's exposed surface 

area. For the coal pile, the surface area is assumed to be 24,000 

m

2. The emission rate for coal dust is derived from data 

presented in a 1978 study which measured downwind dust emission 

rates near a 110,000-Mt coal pile (EPA78) . The study revealed 

that for particles within the respirable range (less than 7 um), 

the emission rate was 706 kg/yr. Assuming a proportional 

relationship for a 95,000-Mt coal pile, the revised yearly 

emission rate is 610 kg. The resulting U-238 and Th-232 yearly 

emission rates are 6.6 x IO"7 and 5.3 x IO"7 Ci/yr, respectively. 

For each decay chain, it is assumed that the following decay 

products are in equilibrium with their respective parent 

radionuclides: U-234, Th-230, Ra-226, lead-210 (Pb-210), 

polonium-210 (Po-210), Ra-228, Th-228, Ra-224, Pb-212, and 

bismuth-212 (Bi-212). 

14 
P.37 

As was noted earlier, the ash pile is much larger than the coal 

pile; it is assumed to have an exposed area of 60 acres or 

230.000 m2. The dust emission rates reflect erosion due to wind 

and vehicular traffic. The total estimated ash particulate 

emission rate is 340 kg/yr. The estimated fugitive emission rates 

and source terms are shown in Table 1. Because this particulate 

emission rate characterizes total wind blown material, the amount 

which is respirable is in fact less than the amount shown in 

Table 1. It is estimated that the respirable fraction is about 15 

percent of the total emission rate (TEK79, ACA86). The resulting 

U-238 and Th-232 yearly emission rates are 1.7 x 10~6 and 1.4 x 

10~6 Ci/yr, respectively. 

4.2 PARTICULATE DOSES AND RISKS 

Atmospheric dispersion to downwind locations is determined using 

the AIRDOS-EPA model. The model, as revised, is described 

elsewhere (EPA79, PAR89). Radionuclide concentrations are 

estimated for downwind locations of 10 and 100 meters from the 

edge of each pile. 

4.2.1 Dose to Worker 

In evaluating the dose and risk to the hypothetical worker, it is 

assumed that the worker is located 10 meters from the edge of 

either pile and is subjected to the following exposure pathways: 

inhalation, immersion, and ground deposition. The results reflect 

occupational exposures associated with 2,000 work hours per year. 

No other modifying factors (e.g., shielding, filtration, or 

additional dilution) are applied to the estimated concentrations 

or associated doses. 

The associated downwind doses and risks (for fatal cancers) are 

shown in Table 3. The dose and lifetime risk to the hypothetical 

worker are 7.3 x 10"3 mrem/yr and 1.1 x IO"7, respectively, for 

coal ash emissions. The corresponding dose and risk for the coal 

dust emissions are 1.3 x 10~2 mrem/yr and 1.6 x 10~7, 

respectively. 

It is interesting to note that the dose attributable to coal dusts 

is higher (just under a factor of 2) than that of fly ash 

emissions. As was noted earlier, the radionuclide concentrations 

for coal dusts were a factor of 10 lower than those for coal ash. 

Accordingly, lower radionuclide concentrations would tend to 

decrease the dose. The coal dust emission rate is, however, 

higher than the one derived for the ash pile. For the sake of 

comparison, the respective emission rates (in units of g/cm2-s) 

are as follows: coal dust, 8.1 x 10"1 1; coal ash due to wind 

15 
P.38 

erosion, 4.3 x 10~1 3; and coal ash due to vehicular traffic, 

1.8 x IO"12. Finally, the atmospheric dispersion factors are also 

slightly different between the coal and ash piles because the 

area of the ash pile is greater than that of the coal pile. 

4.2.2 Dose to Resident 

For the member of the general public, the dose and risk are 

estimated for a location near the site boundary. It is assumed 

that the resident is exposed to all possible pathways, including 

those described for the worker with the addition of ingestion of 

locally grown vegetables and crops that have become contaminated 

from plume deposited radioactivity. 

It is assumed that only a narrow strip of land and service road 

separate the edge of either pile to the property fence and that a 

narrow buffer zone exists beyond the fence line and the nearest 

residence. Given this configuration, the hypothetical resident is 

placed at about 100 meters from the edge of each pile. 

It should be noted that the selection of the 100 meter distance 

is not without basis. Based on the results of a review of U.S. 

Geological Survey maps for 99 utility sites located in 33 States, 

it was noted that, at the 94th percentile, occupiable structures 

were located at distances greater than 100 meters (EPA88, ICF89). 

At the 50th percentile, the nearest structures were noted at 

distances greater than 350 meters. The majority (60 percent) of 

this information is based on maps that are less than 10 years 

old. For the remaining maps, 3 6 percent of the data were obtained 

from maps dating from I960 to 1978. The balance, or 4 percent, of 

the maps are at least 28 years old. 

In order to supplement this information with more recent data, 

the EPA's Pollution Assessment Branch (Office of Air Quality 

Planning and Standards) was contacted. The Pollution Assessment 

Branch noted that it is not uncommon for residential or 

commercial structures to be located within 100 to 200 meters from 

utility sites (PET89, STE89). 

A review of Table 4 indicates that the dose to the nearby 

resident from ash emissions is estimated to be 2.2 x 10~2 mrem/yr 

and the lifetime risk for fatal cancers is estimated to be about 

3.4 x IO"7. The corresponding dose and risk from coal dust 

emissions are 2.7 x 10~2 mrem/yr and 3.4 x 10~7, respectively. 

The earlier discussion and comparison addressing the differences 

between coal and coal ash source terms and doses are also valid 

here. 

16 
5.0 RADON 

Radon emanation can result in downwind exposures to workers and 

members of the general public. The worker is assumed to be onsite 

at about 10 meters from either pile. Members of the general 

public are assumed to be located at 100 meters from the edge of 

each pile. Radon is released only from the exposed areas of the 

piles and no credit is taken for features or measures which may 

reduce the emanation rates. For example, coal ash may be disposed 

of in a dewatered form. The presence of residual water may 

significantly reduce radon emanation rates. Furthermore, when 

coal ash is disposed in landfills, each disposal cell is 

eventually capped with a soil cover. Such measures also reduce 

radon release rates. 

5.1 RADON EMANATION AND RELEASE RATES 

The estimated radon-222 (Rn-222) emanation rates are based on the 

relationship of Ra-226 concentrations in soils (pCi/g) to the 

areal exhalation rates (pCi/m2-s). Given the varied nature of 

coal and coal ash, some simplifying assumptions have been made. 

The assumed Ra-226 concentrations, release rates and exposed pile 

areas are listed in Tables 1 and 2 for both coal and ash piles. 

Several important factors govern the exhalation rate of radon, 

including mineral form, material density and porosity, particle 

size distribution, and moisture content. Changing meteorological 

conditions, such as atmospheric pressure, surface wind velocity, 

and differences between soil and air temperatures, are known to 

have pronounced effects on radon emanation rates (NCR85, NCR87). 

In this analysis, the radon source terms are estimated using a 

relationship (soil concentration to exhalation rate) which 

reflects empirical data. For example, the NCRP notes that for 

typical soils, an average radon emanation rate is about 0.5 

pCi/m2-s per pCi/g (NCR85). The U.S. Nuclear Regulatory 

Commission cites radon emanation rates for tailings and soils 

with varying moisture contents based on work conducted by Tanner 

and Schiager (NRC80). The reported rates for wet, moist, and dry 

materials are 0.35, 0.65, and 1.2 pCi/m2-s per pCi/g, 

respectively. Schiager suggests, for dry tailings, a radon 

emanation rate of 1.6 pCi/m^-s per pCi/g (SCH74). This conversion 

factor assumes an infinitely thick and dry tailings bed. 

Typically, about 90 percent of the radon source term originates 

from the first 7 feet of material. 

The emanation rates from coal is believed to be within the range 

of rates typically observed in soils. Beck, however, notes that 

for some types of coals, the emanation rate could be higher than 

17 
P.40 

that of soil (BEC89) . For example, bituminous coal was reported 

to be about 1.3 times higher and lignite coal was nearly 3 times 

higher. For this analysis, the coal radon exhalation rate is 

assumed to be 0.7 pCi/m2-s per pCi/g, a rate typically reported 

for soils. This average rate is based on the three values given 

above, excluding the rate for dry tailings. This rate is slightly 

higher (factor of 1.4) than the previously noted value for 

average soils. 

Given that coal ash disposal facilities may include such features 

as settling ponds or water saturated areas, the radon exhalation 

rate may in fact be much lower. In addition, coal ash is 

generally believed to have a lower exhalation rate than soils 

since the ash is vitrified. Radon is thought to be generated and 

to decay within the particle in which Ra-226 is trapped. Beck 

reports that fly ash typically has a lower exhalation rate than 

that of soil. For example, it is noted that the ratio of the 

production rate to that of the emanation rate is about 15 percent 

for soil and about 2 percent for fly and bottom ash (BEC89) . It 

is also noted that weathering may increase the exhalation rate. 

If the ash particles were subjected to weathering, conceivably 

the radon exhalation rate could increase over time and reach 

levels that may be typical to those observed from natural soils. 

Kalkwarf reports emanation coefficients ranging from 0.7 to 

9.8 percent for 3 sets of ash samples (15 measurements) and 1.8 

percent for an ash sample from the U.S. National Bureau of 

Standards (KAL85). The results reveal that smaller particles 

release radon at a greater rate than larger ones. For example, 

the emanation coefficient for particles less than 0.5 micro-meter 

(um) was about two times higher than that of particles within the 

range of 11-15 um. If the 11-15 um particle size were used as the 

cut off point for characterizing radon emanation rates between 

large and small particles, the radon emanation coefficient may be 

assumed to be about 3 percent for particles greater than il um 

and 4.3 percent for particles less than 11 um. Ratioing these 

values to the soil radon emanation coefficient rate of 15 percent 

and soil exhalation rate of 0.5 pCi/m2-s, an exhalation rate of 

0.13 pCi/m2-s per pCi/g is derived for coal ash. This exhalation 

rate is weighted to reflect the partitioning factor between fly 

ash (80 percent) and bottom ash and slag materials (20 percent) 

(EPA79) . 

The yearly radon release rate is calculated using the U-238 

concentration assuming secular equilibrium with Ra-226, surface 

area of each pile, and the derived radon exhalation rates of 0.7 

and 0.13 pCi/m2-s per pCi/g for coal and ash, respectively. The 

estimated radon release rates are 0.23 Ci/yr and 4.0 Ci/yr, 

respectively, for coal and ash piles. Radon-220 (Rn-220) 

18 
P.41 

emissions from the Th-232 decay chain are ignored because the 

dose associated with this noble gas is one order of magnitude 

less than the dose due to Rn-222 (PAR89). 

5.2 RADON CONCENTRATIONS AND RISKS 

Atmospheric dispersion to downwind locations were determined 

using the AIRDOS-EPA model. The model, as revised, is described 

elsewhere (EPA79). The downwind radon concentrations are 

estimated for two distances from the edge of the coal and ash 

piles. These distances are 10 meters for the worker and 100 

meters for the nearby resident. For the worker, the results 

reflect exposures associated with 2,000 work hours per year. For 

the general public, the risks are based on 100 percent occupancy 

(8,766 hours per year) and 70-year life span. 

5.2.1 Exposure to Worker 

The associated downwind concentrations and risks estimated for 

the worker are shown in Table 3. For the coal ash pile, the radon 

concentration is estimated to be 5.2 x 10"3 pCi/L with an 

associated lifetime risk (for fatal cancers) of 4.3 x IO"6. The 

corresponding radon concentration for the coal pile is estimated 

to be 2.2 x 10"3 pCi/L with an estimated risk of 1.8 x IO"6. As 

in the previous analysis for particulate emissions, no other 

modifying factors were applied to these results. 

5.2.2 Exposure to Nearby Resident 

For the general public, the downwind radon concentrations and 

risks are estimated for a location just outside the site 

boundary. It is assumed that only a narrow strip of land and 

service road separate the edge of either pile to the property 

fence and that a narrow buffer zone exists beyond the fence line 

and the residence. Given this configuration, the hypothetical 

resident is placed at about 100 meters from the edge of each 

pile. 

For the ash pile, the radon concentration is estimated to be 

2.8 x 10"3 pCi/L and the associated lifetime risk (for fatal 

cancers) is 1.6 x 10~5 (see Table 4). The corresponding radon 

concentration and risk for the coal pile are estimated to be 

7.0 x IO"4 pCi/L and 3.9 x IO"6, respectively. 

It is interesting to note that the radon concentration for the 

coal pile is somewhat lower (4 times) when compared to that of 

the fly ash. As was noted earlier, the radionuclide 

concentrations for coal were assumed to be 10 times lower than 

those for coal ash. Accordingly, lower radionuclide 

19 
P.42 

concentrations would tend to decrease the source term. On the 

other hand, the radon emanation rate is higher for coal when 

compared to coal ash, by a factor of about 5. Finally, the 

atmospheric dispersion and dilution factors are also slightly 

different between the coal and ash piles because the surface area 

of the ash pile is greater than that of the coal pile. 

6.0 GROUND AND SURFACE-WATER 

The ingestion exposure pathways evaluated in this report include 

the consumption of contaminated ground and surface-water and 

foodstuffs, such as vegetables, milk, and meat. The mechanisms 

whereby foodstuffs may become contaminated include the use of 

contaminated irrigation water, watering livestocks, and growing 

crops. The ingestion doses are estimated using the Environmental 

Protection Agency PRESTO-EPA-CPG model. The risks for fatal 

cancers are based on a lifetime exposure of 70 years. The PRESTO 

model, as revised, is described elsewhere (EPA87). 

Given the different types of facilities and varying site 

characteristics, the development of a typical or model coal-fired 

plant is beyond the scope of this evaluation. Because such 

facilities are located in several different geographical areas 

with different geochemical and geohydrological characteristics, 

it is not uncommon for many model parameters to vary by several 

orders of magnitude (FRE79, NCR85, NRC83, HEA84, EPR84). For 

example, ground-water velocity, surface stream flow rate, and 

hydraulic conductivity can vary over six orders of magnitude. 

With these considerations in mind, the ground and surface-water 

model parameters were selected to represent conservative 

conditions. 

The ground and surface-water model takes into account such 

parameters as the aquifer's bulk density, effective porosity, 

thickness, pore water velocity, dispersivities, radionuclide 

distribution coefficient, etc. See the PRESTO Code for more 

details on the required model input (EPA87). The selection of 

these parameters reflect the data provided in the PRESTO model 

and conservative assumptions for a humid site. Conceptually, the 

ground and surface-water models are illustrated in Figures 1, 2, 

and 3. 

20 
P.43 

Figure 1. Hypothetical coal and coal ash site 

21 
P.44 

HUMID PERMEABLE SITE - GROUNDWATER PATHWAY 

R = 1.11m/yr 

150m 

_____ _ 

30m — •<% 

,-l.t.m/yr 

HUMID IMPERMEABLE SITE - SURFACE WATER PATHWAY 

R = 1.11m/yr 

150m 

/ 

600m 

0.64 m/yr 

Figure 2. Coal pile configuration 

22 
P.45 

HUMID PERMEABLE SITE - GROUNDWATER PATHWAY 

R = 1.11m/yr 

- - r 

500m 

/ E 

• 

\ 

•• 

•

 30 m 

„ 

-^._fl_ 

-

HUMID IMPERMEABLE SITE - SURFACE WATER PATHWAY 

I R = 1.11 m/yr 

500m 

600m 

• 0.35 m/yr 

0.001 m/yr 

Hy 

Figure 3. Ash pile configuration 

23 
P.46 

6.1 GROUND-WATER MODEL 

The analysis is modeled for two cases: one for the coal pile and 

the other for the ash pile. The model assumes that ground-water 

contamination occurs when U-238 and Th-232, and their decay 

products, infiltrate an aquifer. Each pile is modeled as a volume 

source over an aquifer of constant depth (see Tables 1 and 2 and 

Figures 2 and 3). Ground water is then withdrawn from a 

down-gradient well located near each pile. All of the water needs 

are supplied from this well, including domestic supplies, crop 

and pasture irrigation, and watering of livestock. 

The ground-water model assumes that the unsaturated zone is 

permeable and is subjected to a high rainfall rate, 1.1 m/yr. The 

well is assumed to be located 30 m from the edge of the pile. The 

water table is assumed to be located 1 m below the bottom of 

either pile and the aquifer thickness is assumed to be 20 m. The 

ground-water velocity is assumed to be 2.0 m/yr and the 

permeability of the unsaturated zone below the piles is assumed 

to be 10 m/yr. ^ 

6.2 SURFACE-WATER MODEL 

In modeling the surface-water scenario, conservative assumptions 

are used to estimate drinking water concentrations. The 

surface-water model assumes that the site is located in a humid 

area with impermeable soils to maximize surface runoff. The 

surface-water runoff from the surrounding area is assumed to 

drain into the creek. The coal storage and ash disposal sites are 

located near the creek. The power plant and facility water needs, 

however, are assumed to be met from a river and not from the 

creek. The leachates from both piles are assumed to flow 

down-gradient and into the nearby creek (see Figures 1, 2, and 

3) . A farmer is assumed to draw all of his water needs from the 

creek for drinking and irrigation purposes. The creek is assumed 

to be also used to water livestocks. No ground or well water is 

available. The model assumes that the creek is located 600 meters 

away and that 30 percent of the rainfall becomes surface-water 

runoff. 

The selection of the creek's flow rate was based on a review of 

river and stream flow rates which are characteristic of utility 

coal-fired plants. The source of the data is an EPA study which 

identifies conditions and parameters needed to assess the 

potential human health and the environmental effects from coal 

combustion wastes. The report compiles flow rates for 100 

randomly selected coal power plant sites located in 33 States 

(EPA88). The reported flow rates were shown to vary 

significantly; in some cases, flow rates vary over six orders of 

24 
P.47 

magnitude. The overall average flow rate is about 18,000 ft3/s. 

Six sites reported flow rates lower than 10 ft3/s. In this 

analysis, a flow rate 10 ft3/s is used as a cut-off point to 

model a conservative scenario. 

It should be noted that if the average flow rate of 18,000 ft3/s 

were used instead, a higher degree of dilution would be obtained, 

consequently resulting in lower surface-water concentrations and 

doses. 

6.3 RADIOACTIVE SOURCE TERM 

The total radionuclide inventory of each pile is derived by 

multiplying the U-238 and Th-232 concentrations by the respective 

quantity of materials in each pile (see Table 1) . The coal pile 

radionuclide inventory is 0.041 Ci for U-238 and 0.033 Ci for 

Th-232. The radionuclide inventory for the ash pile is 6.3 Ci and 

5.1 Ci, respectively, for U-238 and Th-232. 

The radioactive source term is derived using the distribution 

coefficient (Kd; expressed in milliliter per gram, mL/g) and 

effective porosity to determine the amount of radioactivity 

assumed to be available for movement out of the coal and ash 

piles. 

The distribution coefficient (Kd) is also used to model the 

movement and retardation of U-238 and Th-232 in the aquifer and 

surface runoff. As with other ground-water parameters, the Kd 

values are also known to vary widely. Uranium and Thorium are 

ubiquitous in soils. The adsorption of U-238 and Th-232 and their 

decay products in soils and sediments is a reversible process. 

The range of Kd values is also dependent on the ion-exchange 

capacity of the soil as well as soil materials. For example, 

radium behaves like Sr2+ and Ba2+ (NCR85, EPR84) . The Ra-226 Kd 

has been reported to vary from low values (200-500 mL/g) to 

higher values (1,000-6,000 mL/g) for a variety of soils. In some 

instances, Kds as high as 20,000 to 30,000 mL/g have been 

observed or reported (NJD87). Generally, Kd values for soils of 

arid regions are lower than those observed in soil of humid 

regions. Similar cases can be made to illustrate the behavior of 

the other decay products considered in this analysis. 

In this analysis, two sets of Kd values are applied: one to 

characterize the leaching and movement of the radionuclides 

within the coal and ash materials and the other to model the 

natural.environment beyond the edge of either pile. The movement 

of these radionuclides is modeled using Kd values generally 

accepted by EPA for modeling similar situations (EPA87). 

25 
P.48 

For the coal and ash materials, the selected Kd values are 

assumed to be lower than those for soil because it is also 

assumed that coal or coal ash does not have the same ion-exchange 

capacity as that of natural soils (EPR84, EEI88, GIL83, NCR85a). 

The selected Kd values for the coal and ash, expressed in mL/g, 

are as follows: Po-210, 100; Pb-210, 100; Ra-226, 75; Th-228, 

3,000; Ra-228, 75; Th-230, 3,000; Th-232, 3,000; U-234, 50; and 

U-238, 50. In the context of ground and surface-water modeling, 

higher Kd values yield lower water concentrations. 

The areas beyond the edge of the pile include the unsaturated 

zone, aquifer, and surface soil. For these areas, the selected 

Kd values are as follows: Po-210, 220; Pb-210, 220; Ra-226, 220; 

Th-228, 60,000; Ra-228, 220; Th-230, 60,000; Th-232, 60,000; 

U-234, 750; and U-238, 750. As before, these units are expressed 

in mL/g. 

It should be pointed out that coal ash is generally believed to 

be insoluble because the activity is contained in a glass matrix. 

Weathering arid chemical action, however, may leach the activity 

held on the outer surface layer of the ash particle. In a study 

to assess the leaching properties of coal and coal ash samples, 

Wagner and Greiner indicated that radionuclides are not readily 

leached from coal or ash samples (WAG82). The study also supports 

the assumption that, in most cases, leachates do not appear to 

exceed the EPA guide (less than or equal to 5 pCi/L for Ra-226) 

for drinking water. Based on the Wagner and Greiner study, it was 

deduced that the Kd values used in this analysis are 

conservative. For example, the Ra-226 Kd derived from Wagner and 

Greiner data is, on the average, 500 mL/g for coal and 2,000 mL/g 

for ash. This analysis, on the other hand, uses a Ra-226 Kd of 75 

mL/g for both coal and coal ash. In varying degrees, this general 

relationship is also true for the other radionuclides. 

6.4 INGESTION MODEL 

The doses associated with the ingestion of contaminated water and 

foodstuffs are estimated using the PRESTO-EPA-CPG model (EPA87). 

The ingestion pathway addresses the consumption of contaminated 

water and foodstuffs, such as vegetables, milk, and meat. Water 

is assumed to be withdrawn from a down-gradient well or nearby 

creek. All of the water needs are supplied from this well or 

creek, including domestic uses, irrigation of crops and pastures, 

and watering of livestocks. The food and water consumption rates 

and environmental transport parameters reflect generally accepted 

assumptions and parameters used in the PRESTO model (EPA87). 

26 
P.49 

6.5 WATER CONCENTRATIONS AND DOSES 

The ground and surface-water concentrations, doses, and risks are 

given in Table 4. For the ground-water pathway, based on the 

results of the PRESTO code, the leachates are not expected to 

reach the well. Radionuclide migration, under the coal or ash 

pile and within the aquifer itself, is primarily dependent upon 

the distribution coefficients (Kds) and aquifer flow rate. For 

example, the movement of Ra-226 is typically on the order of 

about 0.2 cm per year based on a retardation factor of 900 and 

ground-water velocity of 2.0 m/yr. Given this rate of travel, 

Ra-226 does not reach the well within a 1,000-year time period. 

A similar set of examples can be made to illustrate this 

characteristic (immobility) for the remaining radionuclides. 

Accordingly, the dose and risks from this exposure pathway are 

assumed to be nil. 

Given the assumptions of the surface-water model, leachates are 

assumed to be released into the nearby creek. The Ra-226 

concentrations in the creek are estimated to be 0.0012 and 0.2 

pCi/L, respectively, for the coal and ash piles. Water 

concentrations are reported only for Ra-226. Doses and risks, 

however, reflect all radionuclides. The yearly doses are 

estimated to be 0.0044 mrem for the coal pile and 0.73 mrem for 

the coal ash. Typically, 80 percent of the dose is due to the 

drinking of contaminated water. The corresponding lifetime risks 

for fatal cancers are estimated to be 2.9 x 10~8 for the coal 

pile and 4.6 x 10~6 for the ash pile. 

In view of the presence of Ra-226, radon-222 (a decay product of 

Ra-226) may also be present in water. Radon-222 in surface-water 

is, however, not a problem because this noble gas is rapidly 

aerated out of the water (HES85, EPA89a). It has been shown that 

the presence of radon in surface-water supply systems is 

generally nondetectable and occurs only at very low 

concentrations, less than 100 pCi/L (HES85). The overall average 

for the United States is 1 pCi/L. Typically, such concentrations 

are well below the range of the proposed U.S. EPA drinking water 

radon concentration limit of 200 to 2,000 pCi/L (EPA89a). 

Comparing the ash pile Ra-226 concentration result to naturally 

occurring radium in surface-water reveals that its presence is 

within the range of natural environmental levels. For example, 

surface Ra-226 concentrations typically range from 0.1 to 0.5 

pCi/L (HES85, COT84). The Ra-226 concentration due to coal pile 

runoff is, however, significantly lower, by about two orders of 

magnitude. 

27 
P.50 

7.0 INDUSTRIAL BOILERS 

Industrial boilers are used mainly to produce process steam, 

generate electricity (typically, for the facility's own needs), 

and for space heating. Industrial boilers are used virtually in 

every industry from small manufacturing to large production 

facilities. As with utility coal-fired plants, the consumption of 

coal is proportional to the size or capacity of the industrial 

boiler. Typically, over 99 percent of the industrial boilers have 

a capacity of less than 75 MW (thermal) (EPA84). Given the varied 

distribution and application of industrial boilers, three 

industries typically dominate the consumption of coal. These are 

the chemical, paper, and metal fabrication industries (steel and 

aluminum). For example, these three industries consumed nearly 90 

percent of the total coal used by industrial boilers in 1974 

(EPA84). 

As was noted in Section 2 of this report, the quantity of 

stockpiled coal and ash disposed onsite were assumed to be 

representative of overall practices at utility coal-fired plants. 

It was also assumed that by evaluating utilities, the results 

would envelop industrial facilities which are typically much 

smaller in capacity or size. The use of coal within the 

industrial sector, to a certain extent, is also assumed to be 

implicitly addressed because the quantity of coal used in this 

analysis also reflects operating practices of industrial boilers. 

In order to assess whether there are other significant 

differences between utility and industrial boilers, a qualitative 

comparison was performed for these two types of facilities. The 

results of this comparative evaluation are shown in Table 5. 

Because there are some similarities between these two types of 

facilities, this discussion focuses only on parameters that are 

different. The relative likelihood of an assumption or a 

parameter applicable to utility or industrial boilers are also 

given in Table 5. The objective of this qualitative evaluation is 

to determine to what extent the utility risk assessment results 

also apply to industrial facilities. 

7.1 OUANTITIES OF COAL AND ASH 

Typically, industrial boilers use less coal and, consequently, 

generate smaller quantities of ash. The majority of industrial 

boilers also do not store large quantities of coal on site 

(STE89, EPA84). At industrial facilities, coal is also stored in 

silos rather than in exposed piles. Similarly, ashes are not 

always disposed on site; rather, they are often disposed 

elsewhere or shipped to cement or aggregate plants. Given these 

practices, it may be concluded that the amount of coal used and 

28 
TABLE 5 

QUALITATIVE ODMPARATIVE EVALUATION OF 

UTILITY AND INDUSTRIAL BOILEBS 

Key Input 

Parameter 

Assumption/ 

Value Used 

It of Cases 

Represented 

Utility Boilers a/ 

Rationale 

_ of Cases 

Represented 

Industrial Boilers b/ 

Rationale 

Quantity of Coal 9 . i. x 10 metric tons 70X Based on data in the 

literature 

<70X Based on data ln the 

literature and the fact 

that industrial boilers 

are of smaller capacity 

I.IJJ.II.I l I v -J! A_I I 1 . x 10 metric tons 501 Roughly an average figure 

based on literature and 

personal communications 

<1X Based on ash generation 

rates calculated using 

data in '84 NESHAPs BIO 

I.i.l.lt.lLtl l Ul AMI IJlSJ.-Sui Onsite -100* Based on literature, it 

appears that most utility 

boilers dispose of their 

ash onsite 

<100X Industrial boilers are 

probably located on 

smaller sites, which 

don't allow for onsite 

disposal 

Distance Lo Surface 

Water 

600 meters 50X An average figure based on 

data in 1988 Report to 

Congress 

<50X Industrial boilers less 

likely to be near 

surface water than 

utilities, which require 

surface water for 

cooling 

Stream flow Rate 10 CFS -5X Based on stream flow data 

in 1988 Report to Congress 

>5X Industrial boilers are 

probably more likely to 

be near smaller streams 

(again, they don't need 

to be near large bodies 

of water that serve Is a 

source of cooling water) 

Surface Water Use Individual uses stream 

as sole source of 

drinking water, water 

for watering livestock 

(which is his sole 

source of meat), and 

water for watering a 

garden (which is his 

sole source of 

vegetables) 

Unlikely to occur 

(-101) 

Based on the general 

recognition that it would 

be unlikely for a farmer to 

be located in such a 

position relative to a 

power plant, and to use 

such a small stream as a 

sole source of water 

Very unlikely to 

occur (0-1X) 

Based on data in '84 

NESHAPs BID, industrial 

boilers tend to belocated in generally 

urban/suburban areas; 

such a surface water use 

pattern in an urban/ 

suburban setting is very 

unlikely 

29 
TABLE 5 (continued) 

QUALITATIVE COMPARATIVE EVALUATION OF 

UTILITY AHD INDUSTRIAL BOILEBS 

Key Input 

Parameter 

Assumption/ 

Value Used 

II of Cases 

Represented 

Utility Boilers a/ 

Rationale 

t of Cases 

Represented 

Industrial Boilers b/ 

Rationale 

Distance to Nearest 

Resident 

100 meters -5X Based on a review of USGS 

topographical maps of 

almost 100 utility boiler 

sites 

~95X Industrial boilers are 

more likely to be 

located in generally 

urban/suburban setting, 

with closer nearby 

residents (on the order 

of 30-50 meters away) 

Overall conclusion: 1X-10X Overall conclusion: <1X 

a/ Based on the 1988 Report to Congress on Coal Combustion Wastes (EPA, Office of Solid Waste. EPA/530-SW-88-002, February 1988), there are approximately 1,378 utility 

boilers in the U.S. These boilers were located at roughly 500 different sites. 

b/ Based on data in the 1984 NESHAPs BID (EPA, Office of Radiation Programs, "Radionuclides: Background Information Document for Final Rules, Volume II," EPA 520/1-

8<J -022-2, October 1984), there were approximately 51,187 industrial boilers around 1981. 

30 
P.53 

ash generated by utility boilers represent an upper bound of the 

size of coal and ash piles at industrial sites. Accordingly, it 

is anticipated that the potential range of exposures and risks at 

industrial facilities is lower than those estimated for utility 

sites. 

7.2 DISTANCE TO SURFACE STREAM 

An average distance of 600 meters to the nearest surface-water 

body was used to characterize the utility site. Given that 

industrial boilers are smaller facilities, they are less likely 

to rely on a surface-water stream for cooling purposes. The 

presence of a small stream may, however, be sufficient to supply 

the needs of an industrial boiler, but would not be adequate for 

coal-fired power plants. On the other hand, industrial boilers 

may opt to use well water or depend on a community water supply 

system purely to be assured of a reliable source of water. 

Accordingly, industrial boilers are less likely than utility 

plants to rely solely on a surface stream. The risks associated 

with the surface-water exposure pathway is, therefore, assumed to 

be not much different than that of risks estimated for utility 

power plants. Given these considerations, it is assumed that the 

results obtained for utility sites represent an upper bound in 

terms of potential doses and risks associated with industrial 

facilities. 

7.3 SURFACE-WATER USE 

The exposure scenario assumes that a small farmer meets all of 

his water needs from a small surface stream. Surface water runoff 

and leachates from the coal and ash piles were assumed to flow 

into the stream. This water is used for drinking purposes as well 

as for crop irrigation and watering of livestocks. Industrial 

boilers are more likely to be located in urban or suburban areas. 

If an industrial boiler were located in an urban setting and next 

to a surface stream, the depicted pattern of water usage in such 

an urban setting would be an unlikely scenario. If the water were 

used to supply a community water system, the water would be 

treated (at least filtered) prior to being distributed. 

Accordingly, the potential risk of being exposed to leachate 

discharges in an urban setting is unlikely. In any case, the 

doses and risks estimated for utility boilers are expected to 

represent an upper bound for those at industrial facilities. 

7.4 DIRECT RADIATION 

The nearby resident was assumed to be located 100 meters away 

from the utility coal and ash piles. Recognizing that industrial 

boilers are more likely to be located in urban areas, there is a 

31 
P.54 

possibility that the nearby resident may in fact be closer to 

such piles. For industrial boilers, the distances may be on the 

order of 30 to 50 meters (STE89). Shorter distances between the 

source of radiation and receptor increase the dose. On the other 

hand, smaller coal and ash piles reduce the exposure rates 

because of the smaller source term and different physical 

configurations. Accordingly, these competing factors tend to 

negate each other. In view of these considerations, it is assumed 

that doses and risks for industrial boilers are bound by those 

estimated for utility boilers. Finally, given that the majority 

of industrial boilers are much smaller, the possibility of 

radiation exposure levels approaching those calculated for 

utility boilers is unlikely. 

7.5 CONCLUSION 

In overall terms, only a few set of parameters or assumptions 

differ between utility and industrial boilers (see Table 5) . 

Generally, it may be concluded that the doses and risks estimated 

for utility boilers may be applicable only to a small fraction of 

the total number of industrial boilers. In some instances, it was 

also noted that competing factors that tend to increase doses and 

risks are negated by others. In such instances, the net risks are 

no higher than those estimated for utility boilers and in some 

cases are possibly lower. Given the scope of this comparative 

evaluation, it is estimated that a small number (less than 1 

percent) of the industrial boilers may produce doses and risks of 

the same magnitude as those estimated for utility boilers. 

32 
P.55 

REFERENCES 

ACA86 Coal Ash Book - Technical Summary, American Coal Ash 

Association, Washington D.C, 1986. 

BEC89 Letter Transmittal - Paper titled: Some Radiological 

Aspects of Coal Combustion, Harold L. Beck and Kevin M. 

Miller, Jan. 13, 1989. 

BEC80 Beck, H.L., et al., Perturbations on the Natural Radiation 

Environment Due to the Utilization of Coal as an Energy 

Source, Natural Radiation Environment, CONF-780422, Vol. 

2, pp. 1521-1558, 1980. 

CEM69 Cember, H., Introduction to Health Physics, Pergamon 

Press, New York, 1969. 

CLI83 Cline, W., et.al., Radium and Uranium Concentrations in 

Georgia Community Water Systems, Health Physics, Vol. 44, 

Jan. 1983, pp. 1-12. 

COT84 Cothren, C.R., Lappenbusch, W.L., Compliance Data for the 

Occurrence of Radium and Gross Alpha-Particle Activity in 

Drinking Water Supplies in the United States, Health 

Physics, Vol. 46, Mar. 1984, pp. 503-510. 

EEI88 Edison Electric Institute, Ashes and Scrubber 

Sludges-Fossil Fuel Combustion By-Products: Origin, 

Properties, Use and Disposal, Publication No. 48-88-05, 

May 1988. 

EPA89 U.S. Environmental Protection Agency, Draft Environmental 

Impact Statement for Proposed NESHAPS for Radionuclides -

Background Information Document, Vol. II, EPA 

520/1-89-006, Feb. 1989. 

EPA89a U.S. Environmental Protection Agency, Draft Briefing 

Paper - Radon in Drinking Water - Options for the MCL, 

Office of Drinking Water, Feb. 1, 1989. 

EPA88 U.S. Environmental Protection Agency, Wastes from the 

Combustion of Coal by Electric Utility Power Plants, 

Report to Congress, EPA/530-SW-88-002, Feb. 1988. 

33 
P.56 

REFERENCES 

EPA87 Rogers, V. and Hung, C., Low-Level and NARM Radioactive 

Wastes - Model Documentation PRESTO-EPA-CPG - Methodology 

and Users Manual, U.S. Environmental Protection Agency, 

EPA 520/1-87-026, Dec. 1987, as revised. 

EPA87a Radiation Protection Guidance to Federal Agencies for 

Occupational Exposure, Federal Register Vol. 52, No. 17, 

pp. 2822-2834, Jan. 27, 1987. 

EPA84 U.S. Environmental Protection Agency, Radionuclides -

Background Information Document For Final Rules NESHAPS, 

Vol. II, EPA 520/1-84-022-2, Oct. 1984. 

EPA79 Moore, R.E., et al., AIRDOS-EPA: A Computerized 

Methodology for Estimating Environmental Concentrations 

and Dose to Man from Airborne Releases of Radionuclides, 

U.S. Environmental Protection Agency, EPA 520/1-79-009, 

Dec. 1979, as revised. 

EPA79a U.S. Environmental Protection Agency, Radiological Impact 

Caused by Emissions of Radionuclides into the Air in the 

United States, U.S. Environmental Protection Agency, 

EPA 520/7-79-006, Aug. 1979. 

EPA78 U.S. Environmental Protection Agency, Source Assessment: 

Coal Storage Piles, EPA-600/-78-0041, May 1978. 

EPR88 Electric Power Research Institute, Classification of Fly 

Ash for Use in Cement and Concrete, EPRI CS-5116, Final 

Report, Apr. 1987. 

EPR84 Kincaid, C.T., et al., Geohydrochemical Models for Solute 

Migration, Electric Power Research Institute, Battelle 

Pacific Northwest Laboratories, EPRI EA-3417, Vol.1, Final 

Report, Feb. 1984. 

FRE79 Freeze, R.A. and Cherry, J.A., Groundwater, Prentice-Hall, 

Inc., Englewoods Cliffs, NJ, 1979. 

GIL83 Gilbert, T.L., et al., Pathways Analysis and 

Radiation-Dose Estimates for Radioactive Residues at 

Formerly Utilized MED/AEC Sites, U.S. Department of 

Energy, ORO-83 2, Mar. 1983. 

34 
P.57_ 

REFERENCES 

HEA84 Heath, R.C, Basic Ground-Water Hydrology, U.S. Geological 

Survey Water - Supply Paper 2220, Third Printing, 1984. 

HES85 Hess, CT., et. al., The Occurrence of Radioactivity in 

Public Water Supplies in the United States, Health 

Physics, Vol.48, May 1985, pp. 553-586. 

HIN82 Hinds, W.C, Aerosol Technology, John Wiley & Sons 

Publications, 1982. 

ICF89 Telephone communication with Mr. Steve Wyngarden, ICF, 

Inc., Jan. 26, 1989. 

KAL85 Kalkwarf, D.R., Emanation Coefficient for Rn in Sized Coal 

Fly Ash, Health Physics, Vol. 48, Apr. 1985, pp. 429-436 

MOR73 Morgan, K.Z., Turner, J.E., Principles of Radiation 

Protection, R.E., Krieger Publishing Company, 1973. 

NER87 Electricity Supply and Demand for 1987-1996, North 

American Electric Reliability Council, Nov. 1987. 

NIE87 Niemczyk, S.J., et al., User's Manual for REUSIT: A 

Computer Code for Estimating the Risk from Residual 

Radioactivity, Draft Final Report, U.S. Environmental 

Protection Agency, Nov. 1987. 

NJD87 NJDEP, Technical Background Information Report for the 

Soil Blending Program, New Jersey Department of 

Environmental Protection, Baker/TSA, Inc., Jun. 1987. 

NCR87 NCRP, Exposure of the Population in the United States and 

Canada from Natural Background Radiation, National Council 

on Radiation Protection and Measurements, NCRP Report No. 

94, Dec. 1987. 

NCR85 NCRP, Evaluation of Occupational and Environmental 

Exposures to Radon and Radon Daughters in the United 

States, National Council on Radiation Protection and 

Measurements, NCRP Report No. 78, May 1985. 

NCR85a NCRP, Radiological Assessment: Predicting the Transport, 

Bioaccumulation, and Uptake by Man of Radionuclides 

Released to the Environment, National Council on Radiation 

Protection and Measurements, NCRP Report No. 76, May 1985. 

35 
P.58 

REFERENCES 

NCR76 NCRP, Environmental Radiation Measurements, National 

Council on Radiation Protection and Measurements, NCRP 

Report No. 50, Dec. 1976. 

NCR75 NCRP, Natural Background Radiation in the United States, 

National Council on Radiation Protection and Measurements, 

NCRP Report No. 45, Nov. 1975. 

NOV89 Telephone communication with Mr. John Novak, Edison 

Electric Institute, Washington, D.C, Jan. 25 ,1989. 

NRC83 Till, J.E., Meyer, H.R., Radiological Assessment - A 

Textbook on Environmental Dose Analysis, U.S. Nuclear 

Regulatory Commission, NUREG/CR-3332, Sept. 1983. 

NRC80 U.S. NRC, Final Generic Environmental Impact Statement on 

Uranium Milling (Project M-25), U.S. Nuclear Regulatory 

Commission, NUREG-0706, Vol. Ill, Sept. 1980. 

PAR89 Telephone communication with Mr. Barry Parks, U.S. EPA, 

ORP/Las Vegas, Jan. 20, 1989. 

PET89 Telephone communication with Mr. Warren Peters, U.S. EPA, 

Office of Air Quality Planning and Standards (08QPS) -

Pollution Assessment Branch, Research Triangle Park, N.C, 

Jan. 26, 1989. 

RAD88 Stricket, R.G., Lowe, J., Assessment of NORM 

Concentrations in Coal Ash and Exposure to Workers and 

Members of the Public, Radian Corporation Report to the 

Utility Waste Activities Group and Edison Electric 

Institute, Jun. 1988. 

SCH74 Schiager, K.J., Analysis of Radiation Exposures on or Near 

Uranium Mill Tailings Piles, U.S. Environmental Protection 

Agency, Radiation Data and Reports, Vol. 15, No. 7, pp. 

411-425, Jul. 1974. 

STE89 Telephone communication with Mr. Walt Stevenson, U.S. EPA, 

Office of Air Quality Planning and Standards (08QPS) -

Pollution Assessment Branch, Research Triangle Park, N.C, 

Feb. 2, 1989. 

36 
P.59 

REFERENCES 

TEK79 Information Base (Including Sources and Emission Rates) 

for the Evaluation and Control of Radioactive Materials to 

Ambient Air - Task 2, Report Prepared by Teknekron 

Research, Inc. for the U.S. EPA Office of Radiation 

Programs, Jul. 1979. 

UNS82 United Nations Scientific Committee on the Effects of 

Atomic Radiation,, Sources and Effects of Ionizing 

Radiation, Annex B and C, 1982. 

WAG82 Wagner, P., Greiner, N.,R., Third Annual Report -

Radioactive Emissions from Coal Production and 

Utilization, October 1, 1980 - September 30, 1981, Los 

Alamos National Laboratory, LA-9359-PR, Jun. 1982. 

37 
P.60 

Appendix 

ADDITIONAL INFORMATION ON WORKER EXPOSURE 

REFLECTING INDUSTRY PRACTICES 

The radiation exposure to a worker was calculated assuming that 

an individual is assigned to ash management activities with no 

other peripheral functions. These activities are assumed to occur 

on a full-time basis. The worker is assumed to spend 8 hours per 

day, 5 days per week, and 50 weeks per year performing such 

activities. The individual is assumed to be employed starting at 

age 18 and retiring at age 65, for a career spanning 47 years. 

The exposure model also contained the assumption that the worker 

spent 50% of his time seated one meter above the surface of the 

ash pile operating machinery or equipment to manage the pile. 

The equipment or machinery provides shielding and protection from 

ambient exposures. In the context of radiation protection, 

shielding protection factors can range from 0 to 1; with 1 

indicating no protection and 0 indicating maximum protection. 

Protection factors ranging from 0.15 to 0.7 have been cited in 

the literature for similar types of analyses (1, 2). In this 

analysis, a conservative protection factor of 0.7 was assumed. 

Given these assumptions, a yearly dose of 33 mrem was calculated 

for the hypothetical worker. The associated life-time risk for 

fatal cancers was estimated to be 4.3 x 10"4. 

Additional data and information which reflect industry practices 

were obtained from OSHA, trade organizations, and firms involved 

in the ash disposal business in order to assess the reasonableness of these assumptions. OSHA indicated that for the purpose of 

conducting risk assessment analyses, an occupational life span 

of 45 years is normally used (3). This value compares closely 

with the occupational life span of 47 years used in the risk 

assessment. 

The Edison Electric Institute and the American Coal Ash 

Association were contacted for information and both organizations 

referred us to companies which provide ash disposal management 

services to utilities (4, 5). These two firms are JTM industries, 

located in Atlanta, Georgia and the American Fly. Ash Company, 

located in Des Plaines, Illinois. 

Representatives from both organizations indicated that typically 

some individuals are fully assigned to ash disposal and management activities for as much as 8 hours per day, 5 days per week, 

and 50 weeks per year (6,7). However, it was noted that little 

time is spent in direct contact, i.e., walking or standing, on 

the ash pile itself. 

38 
P.61 

The ash is' disposed or emplaced using trucks or other vehicles. 

The ash is graded and compacted using bulldozers and graders. 

The worker rides or operates the equipment while seated 3-4 

meters above the ash pile. Some ash management personnel, other 

than equipment operators, perform QA and testing functions which 

require direct access to the ash pile. Typically, such 

individuals spend 8-10 hours per week on the ash pile without the 

benefit of any shielding that a vehicle may provide. The balance 

of the time is spent in a laboratory or on some related technical 

or administrative tasks. 

Comparing this information with the assumptions used in modeling 

the exposure, dose, and risks to the worker, indicates that the 

model is in agreement with OSHA and industry practices. The 

occupational duration is essentially identical and the assumption 

that such activities are conducted on a full-time basis by 

designated individuals is also realistic. 

In addition, while the risk assessment model took credit for 

shielding for half of the time, it appears from the above 

information that shielding is virtually always present and 

therefore the shielding protection factor could be applied for 

100 percent of the time. It was also noted that the vehicles 

being operated are heavy equipment, such as bulldozers, graders, 

and trucks. The size and mass of this type of heavy equipment 

provides more shielding, and therefore a more protective 

shielding factor, than was included in the risk assessment. The 

operator also rides or operates the equipment at a greater height 

or distance from the ash pile, which results in a lower dose from 

direct radiation. These factors provide additional protection 

that can be factored into the model. 

The shielding that the equipment provides may be reassessed to 

obtain a more realistic protection factor. Given the varying and 

complex physical configurations of such heavy equipment, it is 

beyond the scope of this analysis to provide a detailed model of 

such an exposure scenario. Such analyses are best performed using 

computer codes. Instead, a revised shielding protection factor 

has been obtained from a Nuclear Regulatory Commission (NRC) 

study which addressed the topic as part of a risk assessment 

study (2). 

Shielding protection factors ranging from 0.4 to about 0.7 are 

cited by the NRC for various types of equipment. The factors also 

inherently reflect varying distances above a plane since the 

height varies between different types of equipment. The factors 

also incorporate, to varying degrees, a range of physical 

configurations between the source of exposure and the receptor. 

For example, an operator located in the cab would benefit from 

little or no shielding, while an operator located above heavier 

39 
components (e.g., engine, transmission, chassis) would be exposed 

to a lesser radiation field. Given these considerations, a more 

protective shielding factor of 0.6 is assumed. 

Applying these revised distance, exposure duration, and shielding 

factors to the previous calculations, reveals that the dose and 

risks for the worker have been reduced by a factor of about 1.6. 

The revised annual exposure rate is estimated to be 21 mrem/yr 

versus 33 mrem/yr, as previously estimated. The corresponding 

life-time risks for fatal cancers is now 2.6 x 10"4 versus the 

previous estimate of 4.3 x 10'4. 

References/Sources 

1. NCRP, Radiological Assessment: Predicting the Transport, 

Bioaccumulation, and Uptake by Man of Radionuclides Released 

to the Environment, National Council on Radiation Protection 

and Measurements, NCRP Report No.76, May 1985. 

2. U.S. Nuclear Regulatory Commission, Reactor Safety Study: An 

Assessment of Accident Risks in U.S. Commercial Nuclear 

Power Plants, WASH-1400, Oct. 1975. 

3. Telecon with Ms. Sandra Lee, U.S. EPA, for OSHA data, Feb. 

24, and 28, 1989. 

4. Telecon with Mr. John Novak, Edison Electric Institute, 

Washington, DC, Feb. 21, 27, and Mar. 1, 1989. 

5. Telecon with Mr. Erast Borissoff, American Coal Ash 

Association, Washington, DC, Feb. 24 and 28, 1989. 

6. Telecon with Mr. Greg Cain, American Fly Ash Company, Des 

Plaines, IL, Mar. 1, 1989. 

7. Telecon with Mr. Gerry Heavilon, JTM Industries, Atlanta, 

GA, Mar. 1, 1989. 

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