APPENDIX D 

Human Health and Ecological Risk Assessment Analysis 
Appendix D 

Units of Measure 

1-MT 1-metric-ton 

3-L 3-liter 

°C degrees Celsius 

°F degrees Fahrenheit 

μg/L micrograms per liter 

cal/s calories per second 

K Kelvin 

kg/kg-mol kilograms per kilogram-mole 

kg/m2

 kilograms per square meter 

kg/m3

 kilograms per cubic meter 

kg/s kilograms per second 

kg-m/s2

 kilogram-meters per square second 

KW/m2

 kilowatts per square meter 

L/kg liters per kilogram 

m/s meters per second 

m2

 s-1 meters squared per second 

mg/kg milligrams per kilogram 

mg/kg BW/day milligrams per kilogram of body weight per day 

mg/m3

 milligrams per cubic meter 

mg/s milligrams per second 

mm/hr millimeters per hour 

ng/m3

 nanograms per cubic meter 
D–1

APPENDIX D 

HUMAN HEALTH AND ECOLOGICAL RISK ASSESSMENT ANALYSIS 

This appendix provides the detailed health and ecological risk assessments that support the 

Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement. 

D.1 INTRODUCTION 

As described elsewhere in this Long-Term Management and Storage of Elemental Mercury 

Environmental Impact Statement (Mercury Storage EIS), the Mercury Export Ban Act of 2008 

(P.L. 110-414) requires that, no later than January 1, 2010, the Secretary of Energy designate a facility or 

facilities of the U.S. Department of Energy (DOE) (which shall not include the Y–12 National Security 

Complex [Y–12] or any other portion or facility of DOE Oak Ridge Reservation) for the purpose of longterm management and storage of elemental mercury generated within the United States. The facility or 

facilities designated shall be operational and shall accept custody of elemental mercury for the purpose of 

long-term management and storage by January 1, 2013. 

The alternatives that are analyzed in this appendix are listed below. 

 No Action Alternative 

 New construction at the Grand Junction Disposal Site (GJDS) 

 New construction at the Hanford Site (Hanford) in the 200-West Area 

 Existing storage buildings at the Hawthorne Army Depot in the Central Magazine Area 

 New construction at Idaho National Laboratory’s (INL’s) Idaho Nuclear Technology and 

Engineering Center (INTEC) 

 Existing storage buildings at INL’s Radioactive Waste Management Complex (RWMC) 

 Existing building at the Bannister Federal Complex’s Kansas City Plant (KCP) 

 New construction at the Savannah River Site (SRS) E Area 

 New construction at Waste Control Specialists, LLC (WCS) (including interim storage in the 

existing Container Storage Building) 

For further description of these alternatives, see Chapter 2, Section 2.4, and Appendix C of this 

environmental impact statement (EIS). 

Mercury would be received as 99.5 percent or greater pure elemental mercury from a variety of sources, 

tabulated in Table D–1. 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–2

Table D–1. Dispatching Sites, Years, and Quantities of Elemental Mercury 

Site 

Years of 

Shipments 

Total Mass 

(metric tons) 

Y–12 National Security Complex 2013–2014 1,206 

Chlor-Alkali Facilities 

Ashta Chemical, Ashtabula, Ohio 2013–2019 108 

PPG, New Martinsville, West Virginia 2013–2019 244 

Olin, Charleston, Tennessee 2013–2019 478 

Olin, Augusta, Georgia 2013–2019 271 

Reclamation and Recycling Facilities, Mining, Shipments from Peru 

Mining (Carlin, Nevada) 2013–2052 3,687 

Mining (Peru, via Port of New York) 2013–2052 1,236 

Philadelphia region (Bethlehem Apparatus) 2013–2052 1,939 

Chicago region (D.F. Goldsmith) 2013–2052 831 

Total 2013–2052 10,000 

Note: To convert metric tons to tons, multiply by 1.1023. 

Key: Bethlehem Apparatus=Bethlehem Apparatus Company, Inc.; D.F. Goldsmith=D.F. Goldsmith 

Chemical and Metal Corporation. 

The starting point for Table D–1 is Chapter 1, Table 1–1, of this EIS, which provides an estimate of 

between 8,500 and 9,700 metric tons (8,000 and 10,700 tons) for the total amount of mercury that may be 

shipped to the chosen receiving site based on a 40-year period of analysis. For the purposes of this 

analysis, the amount was rounded up to 10,000 metric tons (11,000 tons). This is consistent with the U.S. 

Department of Energy Interim Guidance on Packaging, Transportation, Receipt, Management, and LongTerm Storage of Elemental Mercury (Interim Guidance) (DOE 2009a).1

 However, the data in Table D–1 

should not be interpreted as commitments on DOE’s part (e.g., to accept mercury from Peru via New 

York or to move mercury from Y–12 or to the exact dates of shipments from Y–12 and the chlor-alkali 

facilities). They are merely intended to be a reasonable set of numbers that can be used in a screening 

risk assessment. The data in Table 1–1 are not as detailed as those in Table D–1. The differences 

between the two tables are as follows: 

 1,206 metric tons at Y–12 (in Table D–1) vs. 1,200 metric tons (in Table 1–1): The amount is 

rounded down in Table 1–1. 

 Table 1–1 provides only the total amount of mercury available at chlor-alkali facilities 

(1,100 metric tons), whereas Table D–1 breaks the amounts down by individual sites, as follows: 

 The Chlorine Institute provided an estimate of a total of 1,950 metric tons of mercury in 

seven chlor-alkali facilities in 2007 (Chlorine Institute 2008). 

 The total inventory of 1,950 metric tons was allocated to the seven facilities based on the 

number of mercury cells at each facility. This is consistent with previously used methods 

(Brown 2009). For the three facilities for which the number of mercury cells was not 

reported, the balance of the mercury inventory was equally distributed. 

 Three of the facilities were scheduled to shut down chlor-alkali operations and disposition 

their mercury before the new storage facility begins operation. This leaves the four in 

Table D–1, which are also those for which data on the number of mercury cells were 

available in Brown (2009). 

 

1

 The analysis in this appendix is intended to be consistent with the Interim Guidance. 
Human Health and Ecological Risk Assessment Analysis 

D–3

 The amount of mercury produced as a byproduct of gold mining from 2013 to 2053 was predicted 

by extrapolating a linear regression analysis of gold production based on U.S. Geological Survey 

historical data and multiplying by a mercury byproduct ratio of 0.4. The byproduct ratio was 

obtained by averaging actual byproduct data from Nevada (Brooks and Matos 2006; Jones and 

Miller 2005; Nevada Bureau of Mines 2005). 

 Nevada accounts for greater than 80 percent of the gold production in the United States 

(NMA 2009). Therefore, as a simplifying assumption, Nevada was taken to be the source of all 

gold in the United States, with Carlin, Nevada being taken as the representative dispatching point. 

 On average, approximately 30 metric tons per year of elemental mercury has been exported to the 

United States via the Port of New York from U.S.-owned gold mines in Peru (Brooks et al. 2007). 

It was assumed that this activity would continue for the period of this analysis (40 years). 

 The balance of the mercury required to make up 10,000 metric tons, 2,770 metric tons, was 

assumed to come from reclamation and recycling (R&R) facilities. It was apportioned between 

Bethlehem Apparatus Company, Inc. (Bethlehem Apparatus) and D.F. Goldsmith Chemical and 

Metal Corporation (D.F. Goldsmith) according to the amount of mercury handled at each site per 

year, a ratio of 70:30, to give 1,939 and 831 metric tons, respectively. 

The rationale for this assumption is as follows. In 2008, six companies in the United States accounted 

for the majority of secondary mercury reclamation and production. The six R&R companies are as 

follows (USGS 2009): 

1. Bethlehem Apparatus in Hellerton, Pennsylvania 

2. D.F. Goldsmith in Evanston, Illinois 

3. Mercury Waste Solutions, Inc. in Union Grove, Wisconsin (headquartered in Mankato, 

Minnesota) 

4. AERC, Inc., in Allentown, Pennsylvania 

5. Onyx Environmental Services (a division of Veolia ES Technical Solutions, LLC) in 

Lombard, Illinois 

6. Clean Harbors Environmental Services, Inc., headquartered in Braintree, Massachusetts 

More than 50 smaller companies collect mercury-bearing products for recycling and ship them to the 

larger companies for retorting and purification, prior to reintroduction of the mercury back into the 

commercial market (USGS 2009). Bethlehem Apparatus is one of the world leaders in the recycling 

of a wide variety of solid- and liquid-mercury bearing wastes as it operates the world’s largest 

mercury recycling facility with 29 advanced high-vacuum mercury waste retorts, two continuous-feed 

fluorescent lamp retorts, eight quadruple-distillation systems, and a calomel processing plant 

(European Commission 2004). In addition to being the major purchaser of mercury byproduct from 

gold mining, Bethlehem Apparatus is estimated to control approximately 40 percent of the secondary 

recycling market share. Virtually all mercury used in the United States is supplied by Bethlehem 

Apparatus or D.F. Goldsmith. Bethlehem Apparatus is estimated to supply about 70 percent of the 

mercury demand, and D.F. Goldsmith accounts for almost all the remaining mercury sales to end 

users in the United States (EPA 2005). In conclusion, almost all retorting or purification of mercury 

occurs in the greater Philadelphia or Chicago regions. 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–4

Therefore, for the purpose of conducting a representative analysis for the transportation of surplus 

elemental mercury from R&R facilities to a long term storage facility, it is assumed that 70 percent 

would come from the Philadelphia region and 30 percent would come from the Chicago region. 

Mercury from Y–12 and the chlor-alkali facilities would be sent directly to the chosen storage facility. 

Mercury from domestic gold mines would also go directly to the chosen storage facility. For the purposes 

of simplification, all of the byproduct gold-mining mercury is assumed to originate from Nevada. In 

addition, approximately 30 metric tons (33 tons) per year of elemental mercury from U.S.-owned gold 

mines in Peru would continue to be shipped through New York City. Mercury from byproduct recycling 

and waste recovery would first go to one of the reclamation and recycling (R&R) facilities. The options 

for transporting the mercury include road or rail, with the mercury in either 3-liter (3-L) (0.8-gallon) 

(34.6-kilogram [76-pound]) or 1-metric-ton (1-MT) (1.1-ton) containers. The assumptions about how the 

mercury is assigned to the various transportation and container options are described in Section D.2.7. 

This risk assessment provides an evaluation of potential releases, exposures, and human and ecological 

consequences and risks related to activities involved in the transportation and storage of elemental 

mercury described above, including potential accidents associated with those activities. This information 

is used in this EIS to facilitate comparisons between several alternatives for storage of the surplus 

elemental mercury. 

For a discussion of the toxicological properties of various forms of mercury, see Sections D.3.1, D.3.2, 

and D.3.3. 

D.1.1 Risk Assessment Scope 

This appendix focuses on the human health and ecological risks that might arise under normal operating 

conditions and from storage- and transportation-related accidental releases. The work in this appendix 

draws upon the Final Mercury Management Environmental Impact Statement (MM EIS) that was 

prepared for the Defense National Stockpile Center (DNSC) of the Defense Logistics Agency 

(DLA 2004a). Where appropriate, the methodology of the 2004 report has been adopted as is. However, 

every calculation in that report has been reviewed skeptically, and modifications have been made to 

incorporate recent changes to input parameters, or where conservatisms can legitimately be removed or, 

occasionally, if the original analysis seems to be non-conservative. 

When considering accidental releases of mercury in this report, risk is expressed as a function of the 

frequency of occurrence of an accident and the magnitude of the consequences. Most of this risk 

assessment is concerned with how to estimate those frequencies and consequences for a variety of 

potential or hypothetical accident sequences that might occur anytime during the 40-year period of 

analysis considered in this EIS. 

In both the human health and ecological risk assessments, the approach to risk assessment is to use a risk 

matrix such as that shown in Figure D–1. 

In Figure D–1, the frequency has been assigned to four broad categories: frequency levels (FLs) IV 

(high), III (moderate), II (low), and I (negligible). The consequences have been assigned to four severity 

levels (SLs), I, II, III, and IV, with the presumption being that SL-I may be characterized as negligible to 

very low and that SL-IV is the most consequential. Unlike the frequency assignments, the SL 

assignments are different for different receptors: thus, the levels may be defined differently for workers or 

the public, for acute- or chronic-inhalation exposure, for human health effects resulting from deposition of 

mercury onto the ground, or for ecological receptors. Discussion of these assignments is provided in 

Section D.1.1.2. 
Human Health and Ecological Risk Assessment Analysis 

Figure D–1. Risk (Frequency and Consequence) Ranking Matrix 

This kind of semi-quantitative risk assessment is appropriate for high-level screening activities such as the 

current one of comparing potential storage sites for elemental mercury. Both industry and government 

make use of such semi-quantitative or similar qualitative schemes, as evident in the following 

publications: 

 The Preparation Guide for U.S. Department of Energy Nonreactor Nuclear Facility Documented 

Safety Analyses (DOE Standard 3009-94) presents a matrix that is very similar to that in 

Figure D–1. 

 In 1987, the U.S. Environmental Protection Agency (EPA) published Technical Guidance for 

Hazards Analysis: Emergency Planning for Extremely Hazardous Substances (EPA 1987) and 

presented a matrix very similar to that in Figure D–1 as appropriate for making judgments about 

the relative risks posed by chemicals that can have potentially lethal effects on humans. 

 The Center for Chemical Process Safety published Guidelines for Hazard Evaluation Procedures

(CCPS 1992), which provides examples of high, moderate, low, or negligible health effects; 

definitions of roughly equivalent frequency bands; and an illustrative risk matrix like that in 

Figure D–1. 

 In 2001, the Center for Chemical Process Safety published a book devoted to Layer of Protection 

Analysis (also known as LOPA, a simplified method of process risk assessment; CCPS 2001). 

This is an increasingly popular method of supplementing tried and tested methods of process 

hazards analysis with simple probabilistic analyses. The Center for Chemical Process Safety 

recommends the matrix method as one acceptable approach to using risk information as input to 

decisionmaking. 

D–5
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

Many other examples could be cited. The following sections define the meaning of the frequency and 

consequence assignments in Figure D–1. 

D.1.1.1 Frequency Assessment 

The assessment of frequencies in this report is not complex and is generally based on rate statistics from 

industry or professional judgment. Once the frequency (f) has been calculated, it is then assigned to a 

high, moderate, low, or negligible category as follows: 

 High – more than or equal to once in 100 years (f ≥ 10-2 per year) 

 Moderate – less than once in 100 years to once in 10,000 years (10-2 per year > f ≥ 10-4 per year) 

 Low – less than once in 10,000 years to once in 1 million years (10-4 per year > f ≥ 10-6 per year) 

 Negligible – less than once in 1 million years (f < 10-6 per year) 

The frequency bands are similar to those in Table 3–4 of DOE Standard 3009-94, the Preparation Guide 

for U.S. Department of Energy Nonreactor Nuclear Facility Documented Safety Analyses. This definition 

of frequency bands applies to all the risks considered in this EIS: human health risks by inhalation or 

ingestion and risks to ecological receptors. 

D.1.1.2 Consequence Assessment 

The assessment of consequences is considerably more complex. The source term is defined by various 

factors, such as the rate at which mercury vapor is released to the atmosphere, the height of release, or the 

heat content of the release. These characteristics are needed to calculate the atmospheric dispersion of 

mercury transported downwind. The predicted airborne concentrations encountered by workers and 

members of the public are then estimated and used as the consequence part of the estimate of health 

consequences via inhalation. In addition, the dispersion model is used to predict how much mercury 

would be deposited on the ground or on the surface of a body of water. Once this has been done, the 

concentration of mercury in soil, sediment, or water can be estimated and used as the basis for the 

calculation of the magnitude of the health effects incurred by humans and the magnitude of adverse 

consequences incurred by sensitive ecological receptors. 

The consequences of exposure to mercury depend on the chemical form of the mercury. For a primer on 

the forms of mercury found in environmental media, see GreenFacts (2009). 

For the purposes of this risk assessment, it is clearly important to consider exposure to elemental mercury, 

because that is the form of mercury in storage. Elemental mercury is sometimes written as Hg0

. The term 

“elemental mercury” is what is usually used in this report, but in some places elemental mercury and Hg0

are used interchangeably. 

It is next necessary to consider how elemental mercury can be converted into other forms. Mercury can 

exist in three oxidation states (EPA 1997b): Hg0

 (metallic), (mercurous), and Hg 2 Hg2

2+ 

(mercuric-Hg(II), otherwise known as divalent mercury; whenever the term “divalent mercury” appears in 

this risk assessment, it is synonymous with Hg2+). The properties and chemical behavior of mercury; 

strongly depend on the oxidation state. Mercurous and mercuric mercury can form numerous inorganic 

and organic chemical compounds; however, mercurous mercury is rarely stable under ordinary 

environmental conditions. In this risk assessment, use of the term “inorganic mercury” is used as 

shorthand for compounds of divalent and mercuric mercury. The mercuric salts most frequently found in 

all environmental media except the atmosphere are mercuric chloride (HgCl2), mercuric hydroxide 

(Hg [OH]2), and mercuric sulfide (HgS). 

Inorganic/divalent mercury can be formed from elemental mercury if the latter is involved in a fire. More 

discussion of this phenomenon is provided in Section D.7.3.3. This is important because, as is also 

D–6
Human Health and Ecological Risk Assessment Analysis 

D–7

discussed in Section D.7.3.3, divalent mercury has a much larger dry deposition velocity than elemental 

mercury. Therefore, in practice, the only accident scenarios considered in this risk assessment that can 

cause deposition of mercury are those involving fires, in which case inorganic mercury would be 

deposited on the ground or water bodies. 

Organomercuric compounds are the other form of mercury commonly formed in environmental media. 

Organomercuric compounds are defined by the presence of a covalent carbon-mercury (C-Hg) bond (that 

is, a bond in which pairs of electrons are shared between atoms). The organomercuric compounds most 

likely to be found under environmental conditions are the methylmercury compounds methylmercuric 

chloride (CH3HgCl) and methylmercuric hydroxide (CH3HgOH), and, in small fractions, other 

organomercuric compounds (i.e., dimethylmercury and phenylmercury). In this risk assessment, 

methylmercury is used a shorthand for “methylmercury compounds.” 

Methylmercury would not be present in the storage facilities, nor would it be formed in a fire. It would be 

formed subsequent to deposition on to the ground or into water and mixing with soil or sediment. In dry 

soil, it is assumed that 2 percent of the inorganic mercury would be converted to methylmercury. In wet 

soil or sediment, the assumed percentage is 15. See Section D.7.3.3 for further discussion. This 

conversion is taken account of in considerations of the effects of deposited mercury on humans and 

ecological receptors. 

In its Mercury Study Report to Congress, EPA largely confined its analysis of mercury in the environment 

and mercury’s health effects to consideration of three forms: elemental mercury, inorganic mercury, and 

methylmercury (EPA 1997d). In the case of inorganic mercury, many of the considerations are based on 

mercuric chloride, which is the most toxic of the mercuric salts found in environmental media. 

Methylmercury is taken as a surrogate for all organomercuric compounds, but in practice methylmercury 

compounds are by far the most prevalent. This practice—of limiting consideration to elemental mercury, 

inorganic mercury, and methylmercury—is followed in this risk assessment. 

Exposures can be either short term (i.e., “acute”) or long term (i.e., “chronic”). Exposures are classified 

as acute or chronic depending on the duration of the exposure. Although there is no precise consensus on 

the definitions of these terms, EPA defines acute exposures as those lasting up to or less than 24 hours, 

while exposures lasting a significant portion of a lifetime are defined as occurring on a chronic basis. 

This risk assessment includes acute exposures arising during accidents and chronic exposures resulting 

from residual environmental contamination after accidents. Other exposures that could arise from small, 

chronic releases during normal operating conditions are also discussed. 

D.1.1.2.1 Acute-Inhalation Exposure to Elemental Mercury, Consequences to Public Receptors 

This section focuses on the consequences of accidents in which elemental mercury becomes airborne and 

is subsequently inhaled over a short period of time. “Classical” risk assessments of hazardous materials 

often focus on the calculation of predicted fatalities—either as individual risk (expressed as the chance 

per year of fatality) or as societal risk (often presented as “f-n” or frequency-number lines). Examples 

include the Reactor Safety Study (NRC 1975), which also included a chlorine fatality risk assessment for 

comparison with the reactor risk, and an early but influential study of chemical facilities in the 

Netherlands (COVO 1976). In fact, it is in the Netherlands that possibly the most sophisticated riskbased approach to the regulation of hazardous chemicals has been adopted, making use of “locationbased” (individual) risk and societal risk (VROM 2006). 

Per VROM (an acronym for the Netherlands Ministry of Housing, Spatial Planning and the 

Environment), location-based risk is defined as the risk to individuals in a particular place, expressed as 

the annual probability of dying in the vicinity of an establishment where dangerous substances are 

(legally) present as a direct result of an onsite accident involving those substances. The Dutch External 

Safety Establishments decree sets environmental quality standards in the form of limit values for location-
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–8

based risk, e.g., 10-6 per annum for vulnerable objects and for sites in the process of remediation. Where 

the location-based risk to an existing vulnerable object is between 10-5 and 10-6 per annum, a “standstill” 

provision applies: i.e., the establishment concerned may not be modified in any way that will have the 

effect of increasing that risk. Societal risk takes account of population density in the vicinity of a highrisk activity and expresses the probability of a given minimum number of fatalities occurring as a result of 

a single accident involving dangerous substances. The focus is on large-scale mortality in case of an 

accident. 

Another regulatory body that focuses on the risk of fatality as input to decisionmaking is the United 

Kingdom Health and Safety Executive (HSE). In a safety report on chlorine (UKHSE 2009), for 

example, HSE states the following: 

“If quantitative arguments are used the methods, assumptions and the criteria adopted for 

decision making should be explained. For example in the case of fatality risks to people 

off-site it is common [HSE] practice for the maximum tolerable level of individual 

fatality risk to be set at 10-4 per year and for the broadly acceptable level to be set at 10-6

per year. The corresponding figures for workers are 10-3 and 10-6. There are no 

commonly agreed criteria for lower severity levels, however, HSE have published harm 

criteria for [Land Use Planning] purposes for a variety of substances, i.e., the ‘dangerous 

dose’ level, which is equivalent to a 1% chance of fatality when a healthy person receives 

the dose.” 

To judge mercury against these sorts of risk and fatality standards, it is necessary to have data on such 

health effects measures as the LC50, or a probit that expresses the probability of fatality as a function of 

airborne concentration and exposure time. For mercury, these data are simply not available. For 

example, in the Agency for Toxic Substances and Disease Registry’s 676-page Toxicological Profile for 

Mercury (ATSDR 1999), the LC50 is only mentioned in the glossary and acronym list, and probit is not 

mentioned at all. 

One can gain some understanding of where the LC01 might lie by considering EPA’s method for deriving 

Acute Exposure Guideline Levels (AEGLs). There are three AEGLs (see Table D–19). AEGLs represent 

threshold exposure limits for the general public and are applicable to emergency exposure periods ranging 

from 10 minutes to 8 hours. It is believed that the recommended exposure levels protect the general 

population, including infants and children and other individuals who may be susceptible. However, 

although the AEGL values represent threshold levels for the general public, it is recognized that 

individuals, subject to unique or idiosyncratic responses, could experience the effects described at 

concentrations below the corresponding AEGL. The three AEGLs have been defined as follows: 

AEGL-1 is the airborne concentration above which it is predicted that the general population, 

including susceptible individuals, could experience notable discomfort, irritation, or certain 

asymptomatic nonsensory effects. However, the effects are not disabling and are transient and 

reversible upon cessation of exposure. 

AEGL-2 is the airborne concentration above which it is predicted that the general population, 

including susceptible individuals, could experience irreversible or other serious, long-lasting adverse 

health effects or an impaired ability to escape. 

AEGL-3 is the airborne concentration above which it is predicted that the general population, 

including susceptible individuals, could experience life-threatening health effects or death. 

Airborne concentrations below AEGL-1 represent exposure levels that can produce mild and 

progressively increasing but transient and nondisabling odor, taste, and sensory irritation or certain 

asymptomatic, nonsensory effects. 
Human Health and Ecological Risk Assessment Analysis 

D–9

AEGLs are discussed in Table 2.15 of EPA’s Graphical Arrays of Chemical-Specific Health Effect 

Reference Values for Inhalation Exposures (EPA 2009a). The “point of departure” for AEGL-3 is an 

exposure of 26.7 milligrams per cubic meter (mg/m3

) for 1 hour, for which no fatalities were observed in 

rats, and 27.0 mg/m3

 for 2 hours, which caused lethality in 20 of 32 rats. The 1-hour AEGL-3 is 

8.9 mg/m3

 (i.e., one-third of the above-cited 1-hour experimental concentration). It is clear from the 

procedures that govern the derivation of AEGLs (NRC 2001) that AEGL-3 is intended to be a 

conservative threshold for the onset of fatalities. 

The observation that AEGL-3 is expected to be a threshold below which fatalities are not expected is 

pertinent to an assessment of the risks associated with elemental mercury transportation and storage. As 

shown in Table D–50 of this appendix (based on work published by the National Institute of Standards 

and Technology [NIST]), at the temperature assumed for accidental spillages of elemental liquid mercury 

(20 degrees Celsius [°C] or 68 degrees Fahrenheit [°F]), the saturated vapor density is 14 mg/m3

. This is 

less than twice AEGL-3 for a 1-hour release (8.9 mg/m3

). In practice, what this means is that the airborne 

concentration may already be below the LC01 and, even if it is not, it would very rapidly be diluted below 

that level by the action of atmospheric turbulence, either in the wake of the building adjacent to which it 

is released (as is the case for several of the scenarios in this EIS; see Section D.4) or by the action of the 

ambient atmospheric turbulence in the open. That is, for evaporating elemental mercury spills, it is highly 

unlikely that people would be exposed to airborne concentrations that exceed the LC01. 

The implications of this are that a risk assessment of the type discussed above, as utilized in the risk 

studies or by the regulatory agencies cited, in which individual and/or societal risks of fatality are used to 

judge the acceptability of some course of action involving a hazardous chemical, would lead to the 

prediction of essentially zero risk from elemental mercury storage and transportation because the 

frequency side of the risk equation (risk = (frequency) × (consequence)) is, for all intents and purposes, 

zero. This is an important insight that places the risks of mercury transportation in the context of the risks 

associated with other hazardous chemicals. That is, a priori one would expect that risks to individuals 

from spillages of elemental mercury should be negligible, measured on the kind of risk scale that is 

commonly used to assess the acceptability of activities involving hazardous chemicals (as described 

above). 

That having been said, one cannot conclude that the risk associated with acute human inhalation of 

elemental mercury is actually negligible or very small in the absolute sense, because there are severe 

effects at concentrations as low as a few tenths of a milligram per cubic meter (see Table D–19). A 

suggested way of binning acute-inhalation exposures, in a way similar to that done for frequencies, is 

summarized in Table D–2. 

The rationale for Table D–2 is as follows: AEGL-3 represents a threshold above which there is a distinct 

change in the expected nature of the consequences in that, as airborne concentrations increase above 

AEGL-3, there is increasing likelihood of fatality, whereas below AEGL-3 but above AEGL-2, there is 

potential for nonlethal, albeit potentially severe, health effects. Below AEGL-2, there is the potential for 

reversible health effects. 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–10

Table D–2. Definition of Consequence Severity Bands for 

Acute Inhalation of Elemental Mercury, Public Receptorsa

Acute-Inhalation Consequence 

Severity Level 

Corresponding Airborne 

Concentrations of 

Elemental Mercury Expected Health Effects 

Inhalation Severity Level IV ≥ AEGL-3 Potential for lethality as 

concentration increases above 

AEGL-3 

Inhalation Severity Level III < AEGL-3 and ≥ AEGL-2 Potential for severe, sublethal, 

irreversible health effects 

Inhalation Severity Level II < AEGL-2 and ≥ 0.1×AEGL-2b Potential for reversible health 

effects 

Inhalation Severity Level I < 0.1×AEGL-2b Potential for minor irritation, 

equated with negligible-to-verylow consequences a Exposure period up to 8 hours. 

b Ideally, this should be tied to some multiple or fraction of AEGL-1. However, AEGL-1 has not been defined for 

elemental mercury. 

Key: ≥=greater than or equal to; <=less than; AEGL=Acute Exposure Guideline Level. 

SL-I represents a range of concentrations in which there are negligible to at most minor health effects. 

This could, in principle, be bounded by AEGL-1 or some multiple or fraction of AEGL-1. However, 

there is no AEGL-1 for elemental mercury. DOE (2009b) has a Subcommittee on Consequence 

Assessment and Protective Actions that maintains a list of Protective Action Criteria for Chemicals –

Including AEGLs, ERPGs, & TEELs. Definitions of AEGLS have been provided previously. ERPGs, 

Emergency Response Planning Guidelines, are precursors of AEGLs and are approximately equivalent to 

the 1-hour AEGLs. TEELs, Temporary Emergency Exposure Limits, are intended as interim equivalents 

to ERPGs. TEEL-3, -2, and -1 for elemental mercury are 4.10 mg/m3

, 2.05 mg/m3, and 0.3 mg/m3, 

respectively. The first two of these have been superseded by AEGL-3 and AEGL-2, which, for a duration 

of exposure of 1 hour, are 8.9 mg/m3

 and 1.7 mg/m3, respectively. TEEL-1 for elemental mercury is 

somewhat more than 10 percent of the 1-hour AEGL-2, so setting the upper bound of SL-I in Table D–2 

equal to 0.1 × AEGL-2 seems to be a reasonable compromise. 

DOE also provides a TEEL-0, 0.025 mg/m3

, below which airborne concentrations are considered to be 

negligible. There is no ERPG or AEGL equivalent to this level. 

The definition of consequence bins in Table D–2 is consistent with the Preparation Guide for 

U.S. Department of Energy Nonreactor Nuclear Facility Documented Safety Analyses 

(DOE Standard 3009-94). Table 3–1 of that reference characterizes an offsite exposure to less than 

ERPG-2 as “low,” an exposure to ERPG-2 as “medium,” and an exposure to ERPG-3 as “high.” 

D.1.1.2.2 Acute-Inhalation Exposure to Elemental Mercury, Consequences to Workers 

Throughout the human health risk assessment, consideration is given to two classes of workers: “involved 

workers” and “noninvolved workers.” The involved workers are those actually working in the storage 

facility or on other mercury-related operations, such as unloading flasks or 1-MT containers and 

transferring them to storage. The noninvolved workers are those who are engaging in other activities on 

the site. For the purposes of this analysis, they are assumed to be within 50 meters (approximately 

160 feet) of the mercury storage facility. 

For workers, the National Institute for Occupational Safety and Health (NIOSH) has published a 

benchmark for acute exposures that are immediately dangerous to life or health (IDLH) (CDC 2002). For 

mercury, this is 10 mg/m3

; see Table D–18. The Occupational Safety and Health Administration (OSHA) 

defines an IDLH value in its hazardous waste operations and emergency response regulation as 

follows: “An atmospheric concentration of any toxic, corrosive or asphyxiant substance that poses an 
Human Health and Ecological Risk Assessment Analysis 

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immediate threat to life or would cause irreversible or delayed adverse health effects or would interfere 

with an individual’s ability to escape from a dangerous atmosphere” (29 CFR 1910.120). EPA, in its 

Technical Guidance for Hazards Analysis: Emergency Planning for Extremely Hazardous Substances

(EPA 1987), states that “The IDLH concentration represents the maximum concentration of a substance 

in air from which healthy workers can escape without loss of life or irreversible health effects under 

conditions of a maximum 30-minute exposure time.” 

In principle, it would be possible to develop an SL scheme tied to the IDLH, similar to that in Table D–2. 

Unfortunately, there are no IDLH equivalents of the three AEGLs. However, the IDLH approximately 

equals AEGL-3 for a 30-minute exposure (11 mg/m3

; see Table D–19). It therefore seems reasonable to 

adopt the same acute-inhalation SLs for workers as for members of the public. One could make a case 

that this is conservative because workers are generally expected to be healthy while the AEGLs are 

crafted to include susceptible members of the public. Therefore, Table D–2 applies to workers as well as 

to the public. 

D.1.1.2.3 Acute-Inhalation Exposure to Divalent Mercury, Consequences to Public Receptors 

In the event of a fire, airborne mercury would be converted into divalent mercury. Section D.7.3.3 

explains that, for the purposes of this analysis, it is conservatively assumed that 100 percent of the 

elemental mercury would be converted to divalent mercury. In the atmosphere, this is most likely to 

manifest itself as mercuric oxide, for which there are no AEGLs. 

For mercuric oxide, TEEL-3 is 10.8 mg/m3

, TEEL-2 is 1.08 mg/m3, TEEL-1 is 0.15 mg/m3, and TEEL-0 

is 0.027 mg/m3

. As noted above, the corresponding TEEL-3, -2, -1, and -0 for elemental mercury are 

4.10 mg/m3

, 2.05 mg/m3, 0.3 mg/m3, and 0.025 mg/m3. The first two of these have been superseded by 

AEGL-3 and AEGL-2, which, for a duration of exposure of 1 hour, are 8.9 mg/m3

 and 1.7 mg/m3, 

respectively. It would seem that, within the range of uncertainty in assigning values to AEGLs, ERPGs, 

and TEELs, it is reasonable to assume that AEGL-3 and -2 for mercuric oxide are, for all intents and 

purposes, the same as those for elemental mercury. Therefore, Table D–2 is taken to apply to divalent 

mercury as well as to elemental mercury. 

D.1.1.2.4 Chronic-Inhalation Exposures to Elemental Mercury, Consequences to Public 

Receptors and Noninvolved Workers 

This section is intended to address low-level exposures to elemental mercury that might take place over 

many years as a result of chronic releases during normal operations. In this case, the choice of benchmark 

is relatively simple. EPA has published a chronic-inhalation exposure reference concentration (RfC), 

valid for durations of exposure between 7 and 70 years, of 3.0 × 10-4 mg/m3

 (EPA 2009a; from IRIS 

[Integrated Risk Information System]). Concentrations below this level are considered to be negligible. 

The analysis in Section D.4.1 shows that all predicted concentrations outside the building during normal 

operations are below this reference level, so there is no need to build a range of severity categories 

analogous to that in Table D–2. 

D.1.1.2.5 Chronic-Inhalation Exposures to Elemental Mercury, Consequences to Involved 

Workers 

The general industry permissible exposure limit (PEL) for mercury vapor established by OSHA is 

0.1 mg/m3

 (29 CFR 1910.1000), the same as the 8-hour time-weighted average (TWA) (see Table D–21). 

The PEL is a ceiling limit not to be exceeded at any time. The NIOSH-recommended exposure limit is 

0.05 mg/m3

 on an 8-hour TWA basis, with a ceiling limit of 0.1 mg/m3. OSHA references the American 

Conference of Governmental Industrial Hygienists’ (ACGIH’s) 8-hour TWA/threshold limit value (TLV) 

for mercury vapor as being 0.025 mg/m3

 (OSHA 2009). Hence, the limit for chronic effects on workers is 

taken as the most conservative of these values, 0.025 mg/m3

. The analysis in Section D.4.1 shows that all 
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predicted concentrations inside the building during normal operations are below this reference level, so 

there is no need to build a range of severity categories analogous to that in Table D–2. 

D.1.1.2.6 Mercury Deposited on the Ground, Chronic Exposures Through Soil Pathway 

For evaluation of chronic effects related to exposures to residual contamination in soil after deposition via 

air, the starting point is the EPA soil screening levels (SSLs). These are health-based values for total 

organic or inorganic mercury in soil. They are considered to be protective of ingestion exposures to 

members of the public. See Section D.7.3.3 for an explanation of why it is expected that mercury 

deposited on the ground will be in the inorganic form. 

The generic SSL for inorganic mercury in soil, based on mercuric chloride, is 23 milligrams per kilogram 

(mg/kg). However, this generic value can be supplemented by an extensively studied real-life case, that 

of the remediation of East Fork Poplar Creek in Oak Ridge, Tennessee, and its floodplain 

(ATSDR 2009a, 2009b; ORNL 2009). Mercury was discharged into the creek from 1950-1963 as a result 

of separations of lithium isotopes at Y–12 in support of the hydrogen bomb project. Note that this 

discharge was not a result of elemental mercury storage at Y–12. The Agency for Toxic Substances and 

Disease Registry made a finding, based on mercuric chloride (with the same 23 mg/kg SSL), that a 

cleanup level of 180 mg/kg is protective of public health. This is based on a “worst-case” scenario 

involving young children who live close to East Fork Poplar Creek and play in the East Fork Poplar 

Creek floodplain. This case scenario is considered the worst case because it involves the most sensitive 

population (young children) exposed to the most highly absorbable forms of inorganic mercury (mercuric 

chloride and elemental mercury). The most probable route of exposure to inorganic mercury would be 

swallowing dust and dirt. 

Based on the foregoing, it is judged that the boundary between SL-I (negligible-to-very-low 

consequences) and -II (onset of adverse consequences due to ingestion of contaminated soil) is 180 mg/kg 

of inorganic mercury. Beyond that, no guidance has been found as to what level would cause irreversible 

health effects or fatalities. In practice, this does not matter because none of the scenarios analyzed in this 

EIS would lead to deposited concentrations of mercury at levels exceeding 180 mg/kg in soil. 

A mercury speciation study of the East Fork Poplar Creek floodplain soil showed that the distribution of 

mercury is 84–98 percent inorganic (mercuric sulfide), 3–8 percent elemental, and 0.003–0.01 percent 

organic (methylmercury) (ATSDR 2009b). As noted above, the initial deposit of mercury onto the 

ground is expected to contain at most a very small proportion of elemental mercury. In addition, the 

results quoted by the Agency for Toxic Substances and Disease Registry show that, at least in the specific 

environmental conditions that apply in the East Fork Poplar Creek floodplain, the conversion of inorganic 

mercury into elemental mercury is very small. Therefore, modifying the 180 mg/kg threshold for 

methylmercury content is not necessary. 

D.1.1.2.7 Ecological Receptors 

As discussed in Section D.5.4.1, the inhalation exposure route is generally insignificant for ecological 

receptors when compared with the ingestion exposure route. Section D.5 explains the selection of a short 

list of receptors that are considered representative of those found along the transportation routes, 

including plants and soil invertebrates, terrestrial animals, and aquatic and sediment-dwelling biota. 

These representative receptors are listed below: 

 Plants 

 Soil invertebrates 

 The short-tailed shrew 

 The American robin 

 The red-tailed hawk 
Human Health and Ecological Risk Assessment Analysis 

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 The great blue heron 

 The river otter 

 Aquatic biota 

 Sediment-dwelling (i.e., benthic) biota 

For each of the representative receptors, ecologically based benchmarks were derived; see Sections D.5.2 

and D.5.3. These are the toxicity reference values (TRVs) that, if exceeded in an environmental medium, 

may produce toxic effects in ecological receptors exposed to that medium. Therefore, by analogy with 

Table D–2, a TRV for a particular receptor is equivalent to the upper bound for SL-I. According to the 

2004 MM EIS (DLA 2004a), 10 times the TRV is the boundary between SL-II and -III, and SL-IV lies 

above 20 times the TRV. 

The TRVs are converted to ecological screening values, which are either in mg/kg, for soil or sediment, or 

micrograms per liter (μg/L) for water (taking due account of the likely chemical forms of mercury, such 

as inorganic compounds or methylmercury). The ecological screening values are then converted to 

equivalent deposited screening values (in kilograms per square meter [kg/m2

]), which can then be directly 

compared with the output of atmospheric dispersion models, (see Table D–35). 

D.1.1.2.8 Summary of Severity Levels 

Table D–3 summarizes the discussion of SLs for human and ecological receptors. 

D.1.2 Organization of This Appendix 

This appendix is organized as follows: Section D.2 describes the accident scenarios considered and the 

frequencies of each scenario. Any scenario for which the frequency is determined to be negligible is 

screened out at this stage. Section D.3 is an assessment of the toxicity of mercury exposure to humans. 

Section D.4 presents the exposure assessment and the human health consequences and risks per 

Figure D–1. 

Section D.5 presents the ecological risk assessment (ERA). It describes the general aspects of the toxicity 

of mercury exposure to ecological receptors and the derivation of benchmarks for each receptor, 

expressed as concentration in soil, sediment, or water. The consequences associated with the alternatives 

and the results of the frequency analysis are used to assess ecological risks. Section D.6 is the assessment 

of uncertainties. Section D.7 describes the technical details of the atmospheric dispersion and deposition 

models. 
D–14

Table D–3. Summary of Definitions of Consequence Severity Levels 

Acute-Inhalation Exposures – 

Involved and Noninvolved 

Workers and Public 

Receptorsa

Chronic-Inhalation 

Exposures – Involved 

Workersb

Chronic-Inhalation 

Exposures – Noninvolved 

Workers and Public 

Receptorsb

Exposure to Deposited 

Mercury – All Human 

Receptors 

Severity 

Level 

Level 

Definition Consequence 

Level 

Definition Consequence 

Level 

Definition Consequence 

Level 

Definition Consequence 

De

IV ≥ AEGL-3 Potential for 

lethality as concentration increases above AEGL-3 

N/A N/A N/A N/A N/A N/A ≥ 2

III < AEGL-3 

and ≥ AEGL-2 

Potential for severe, sublethal, irreversible health effects 

N/A N/A N/A N/A N/A N/A < 2

and ≥ 1

II < AEGL-2 

and ≥ 0.1 ×AEGL-2 

Potential for reversible health effects 

N/A N/A N/A N/A N/A N/A < 1

and 

I < 0.1 

×AEGL-2 

Potential for minor irritation, equated with negligible-tovery-low health consequences 

< ACGIH’s 8-hour TWA/TLV 0.025 mg/m3

Negligible < EPA RfC 

0.0003 mg/m3

Negligible < ATSDR 

-approved cleanup level (180 mg/kg) for East Fork Poplar Creek 

Negligible < S

a Applies to both elemental mercury vapor and inorganic mercury. b Elemental mercury vapor inhalation. c Ecological receptor screening value from Table D–35. 

Key: ≥ =greater than or equal to; < =less than; ACGIH=American Conference of Governmental Industrial Hygienists; AEGL=Acute Exposure Guidelin

Toxic Substances and Disease Registry; EPA=U.S. Environmental Protection Agency; kg=kilograms; mg=milligrams; mg/kg=milligrams per kilogram; 

meter; N/A=not applicable; RfC=reference concentration; SV=screening value; TLV=threshold limit value; TWA=time-weighted average. 
Human Health and Ecological Risk Assessment Analysis 

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D.2 ONSITE AND OFFSITE RELEASE EVENTS AND THEIR FREQUENCIES 

The purpose of this section is to describe the accident scenarios that were considered for this risk 

assessment and to provide estimates of their frequencies. The frequencies are then assigned to a high, 

moderate, low, or negligible category, as described in Table D–4. The event frequencies are used to 

determine whether a particular event scenario should be evaluated further in the risk assessment or 

dismissed as having negligible risk on the basis of frequency alone. The consequences and associated 

risks of those scenarios with non-negligible frequency are discussed in Section D.4 (“Exposure 

Assessment and Human Risk Analysis”) and Section D.5 (“Ecological Risk Assessment”). 

Table D–4. Frequency Categories for Accidental Events 

Frequency 

Category 

Estimated Annual 

Frequency (f) of 

Occurrence Description 

High f ≥ 1×10-2 Incidents that may occur several times during the design life of 

the facility. (Incidents that commonly occur.) Accidents of this 

frequency range are evaluated further. 

Moderate 1×10-2 > f ≥ 1×10-4 Accidents that are not anticipated to occur during the design life 

of the facility. Natural phenomena of this probability class 

include design-basis earthquake, 100-year flood, and maximum 

wind gust. Accidents of this frequency range are evaluated 

further. 

Low 1×10-4 > f ≥ 1×10-6 Accidents that would probably not occur during the design life of 

the facility. This class includes most design-basis accidents. 

Although unlikely, accidents of this frequency range are evaluated 

further. 

Negligible f < 1×10-6 Accidents that are not credible and are not evaluated further. 

The frequency category is used with the estimated human and ecological effect consequences to derive a 

subsequent estimate of the overall risk. 

Potential releases are divided into three types, as follows: 

 Releases that might take place on site at the storage locations during normal operations 

 Releases that might take place on site at the storage locations during accidents 

 Releases that might take place during offsite transportation accidents 

D.2.1 Assumption About the Mercury Storage Facility 

The Mercury Export Ban Act of 2008 does not indicate specific features required for the storage facility 

(or facilities) that would be used to store elemental mercury. Such buildings may be either newly 

constructed or existing structures. However, per Section 5, the Interim Guidance (DOE 2009a) 

establishes the basic requirements for safe storage of mercury, including preliminary design elements of a 

suitable new or existing facility. The analysis in this EIS assumes that all structures, existing or new, 

would be constructed or modified so as to be consistent with the Interim Guidance, which envisages that 

a storage facility would consist of the following four areas (not necessarily all in the same building): 

 Receiving and Shipping Area—This physical area would include dedicated space(s) for the 

receipt, inspection, acceptance, handling, and shipment of containers. 

 Handling Area—This physical area would include dedicated space(s) for work involving 

potential contamination, including (1) safely handling and cleaning palletized or individual flasks 

that have external mercury contamination and/or leaking mercury, (2) reflasking failed 3-L flasks 
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identified during the inspections for acceptance, and (3) safely managing leaking 

1-MT containers. This area is needed for non-routine and emergency response activities in the 

event of leaking flasks and containers. 

 Storage Area—This physical area would include dedicated space(s) for the storage and 

monitoring of mercury containers. 

 Office Administration Area—This physical area would include dedicated space(s) for the storage 

and maintenance of records, waste acceptance criteria, accountability criteria, shipping papers, 

and databases. 

The Interim Guidance further assumes that any DOE mercury storage facility (or facilities) would have 

the following characteristics: 

 Resource Conservation and Recovery Act–regulated and –permitted to receive discarded 

elemental mercury generated in the United States 

 Naturally ventilated (that is, not air conditioned) 

 Adaptable to a modular design 

 Operated for DOE by a contractor 

The Interim Guidance also provides the following: (1) a conceptual scale view of the overall operational 

area needed for storage of up to 10,000 metric tons (11,000 tons) of elemental mercury, based on a rough 

assessment of a 60:40 percent breakdown by approximately 6,000 1-MT and 116,000 3-L flasks, 

respectively, with 3-L flasks on pallets and racks and (2) an estimate of up to 14,000 square meters 

(150,000 square feet) for a “comfortably sized layout.” 

The storage facility would have features that would reduce the risk to the environment and maximize the 

efficiency of container inspection, including at least three boundaries between the mercury and the 

environment. These features would include the following: 

 The container: all containers accepted into the facility would meet DOE acceptance criteria to 

ensure structural integrity. 

 The spill containment tray that is under all the containers (see Section D.2.2 for details). If a 

container fails, the mercury would be contained and should be quickly discovered and cleaned up. 

 The solid concrete floor, which would be coated so as to be impermeable to mercury and water. 

Therefore, there is negligible risk that spillages inside the storage building would penetrate the 

floor and enter groundwater. 

 Perimeter curbing or other building design features that would prevent spilled mercury from 

flowing out of the building. 

D.2.2 Assumption About Mercury Containers 

Mercury received into the storage facility would be in elemental form with a purity of 99.5 volume 

percent or greater. The mercury would be free of any radiological components. The remaining 

0.5 percent content should not be capable of corroding carbon steel or stainless steel (elemental mercury 

has been proven not to corrode carbon steel or stainless steel) (DOE 2009a). 

The mercury is expected to arrive at the facility in either 3-L (0.8-gallon) (34.6-kilogram [76-pound]) or 

1-MT (1.1-ton) sizes. The following are assumptions about the storage containers: 

 After the containers are accepted, they would be separated in the facility by size (3-L or 1-MT). 
Human Health and Ecological Risk Assessment Analysis 

 The 3-L flasks would each contain 34.6 kilograms (76 pounds) of elemental mercury. 

 The 3-L flasks would not contain welds. 

 Although the Interim Guidance discusses several different types of 3-L flasks, varying in empty 

mass between 3.4 and 6.3 kilograms (7.5 and 13.9 pounds), a representative mass of 

4.1 kilograms (9.0 pounds) has been assumed for the present analysis. See Section D.6.1.3 for a 

discussion of the sensitivity of the results to this assumption. 

 The 3-L flasks would be both transported and stored in box pallets that contain an array of 

7 × 7 flasks, as shown in Figure D–2; the dimensions of each pallet would be 1.44 by 1.44 meters 

(56 by 56 inches). 

Figure D–2. 7 × 7 Array of 3-Liter Flasks 

 The Interim Guidance states, “The 3-L containers are preferred to be sent in box pallets that 

comply with the following: ...(4) the pallet may be constructed of painted steel, untreated 

hardwood with fire protective paint applied, treated hardwood, or other materials that have 

equivalent load capacity, fire resistance, degradation rate (e.g., expected life), and would not 

require disposal as hazardous waste.” The case chosen for study in this Mercury Storage EIS is 

use of wooden pallets because this case conservatively maximizes the amount of flammable 

material that would be available to vaporize elemental mercury in the event of a fire. 

 The 7 × 7 pallets of 3-L flasks would stand in a metal spill tray capable of holding the contents 

10 percent (approximately five) of the flasks in the pallet. 

 In the facility, the 3-L flasks in box pallets may be placed onto seismically rated storage racks and 

stacked two or three high. The height of the rack would not exceed 3.7 meters (12 feet). See 

Figure D–3. 

 The racks would require a 3-degree slope towards the aisle to allow leaked mercury to flow 

towards the edge of the spill tray to assist in quickly locating failed flasks. The walls of the spill 

tray would be sufficiently high to contain the contents of five flasks at the indicated angle. 

D–17
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

Figure D–3. 3-Liter Flasks in Box Pallets on a Seismically Rated Rack 

 The Interim Guidance states that overpacking the 3-L flasks into drums is not recommended for 

transportation or long-term storage. 

 The 1-MT container should not be filled with more than approximately 1.1 metric tons (1.2 tons) 

(1,090 kilograms [2,400 pounds]) of liquid mercury and must provide a minimum head space of 

15 percent after maximum fill. The gross weight of the full container should not exceed 

1.25 metric tons (1.4 tons) (1,250 kilograms [2,750 pounds]). For the purposes of this analysis, it 

is assumed that each 1-MT container contains exactly 1 metric ton (about 1.1 tons) (about 

1,000 kilograms [2,200 pounds]) of elemental mercury and weighs 1.16 metric tons (about 

1.3 tons) (1,160 kilograms [2,550 pounds]). A typical 1-MT container with Resource 

Conservation and Recovery Act labeling is shown in Figure D–4. 

 The 1-MT containers are expected to be sent on pallets, one container per pallet. The pallet 

should have a built-in spill tray capable of containing 1 metric ton of mercury. The spill tray side 

walls should be approximately 10 centimeters (4 inches) lower than the height of the container to 

allow for a forklift to remove the container. 

 Upon arrival at the storage facility, the 1-MT containers would be removed from their pallets and 

set into spill trays on the floor of the facility. 

 The 1-MT containers could be stored single or double stacked on the floor in spill trays; 

Figure D–5 shows a single-stack configuration with eight 1-MT containers. The spill tray would 

be designed to contain the full contents of one 1-MT container. The single-stack configuration 

was assumed for the purposes of analysis. 

D–18
Human Health and Ecological Risk Assessment Analysis 

Figure D–4. 1-Metric-Ton Container 

Figure D–5. 1-Metric-Ton Containers in a Spill Tray 

D.2.3 Releases During Normal Operations 

There is a long history of mercury storage at sites holding the DNSC inventory. Currently, 4,436 metric 

tons (4,890 tons) are held at three depots: New Haven, Indiana; Somerville, New Jersey; and Warren, 

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D–20

Ohio. Formerly, 699 metric tons (770 tons) of this inventory was held at Y–12, but this portion was 

moved to the Warren Depot in early 2005 (Munger 2005). 

Information made available by DNSC shows the most recent purchase of large quantities of mercury was 

in 1977 (approximately 2,000 3-L flasks); about 54,000 3-L flasks were purchased in 1964. No large 

purchases of mercury were made between 1964 and 1977, and there was no sale of mercury during that 

period. The DNSC inventory contained about 200,000 containers after the purchase in 1964; sales 

between 1977 and 1995 reduced the inventory to the present level of approximately 128,600 containers. 

Consequently, the containers in the DNSC inventory have been in static storage for at least 30 years, 

some for substantially longer. 

Oak Ridge National Laboratory examined 3-L flasks removed from the DNSC inventory (DOE 2009a). It 

is known that mercury does not react with steel containers at ambient temperatures; this was confirmed by 

metallurgical analysis of 3-L flasks from the DNSC inventory. Thus, containers in static storage in a 

well-maintained facility should have a long lifetime. 

In the course of preparation of the MM EIS (DLA 2004a, 2004b), information was gathered from site 

visits, phone calls, and various documents. The inspection reports for the mercury storage areas were 

reviewed for information about past releases of mercury. No mercury has reportedly escaped from any of 

the warehouses, and there is no known member of the public that has been affected at any of the existing 

storage locations. 

Decades of experience in maintaining the stockpile of mercury indicate that spills of mercury resulting in 

environmental contamination have not occurred, and that that normal (accident-free) operating conditions 

should be maintained at the storage facilities. The storage facilities are built to ensure containment of the 

mercury under most conditions. Spilled mercury is not known to penetrate the concrete floors and reach 

any surface-water or groundwater sources before cleanup occurs. 

During normal operations, the possibility that there could be small vapor releases from the stored mercury 

remains. The most obvious potential candidate is a leaking flask or 1-MT container. In 1996, 

16 kilograms (36 pounds) of mercury were found in a spill tray beneath flasks at the New Haven Depot. 

Subsequent analysis of the flask indicated an improperly constructed weld, rather than a degraded weld 

(as noted above, metallurgical analysis of flasks from the DNSC inventory showed that mercury does not 

degrade the containers). The Interim Guidance (DOE 2009a) provides a summary of more-recent 

investigations into the condition of the DNSC stockpile. From 1999 through the present, DNSC 

identified 3 3-L flasks out of approximately 128,000 that leaked a relatively large amount of mercury, 

0.5 kilograms (1 pound) or more (approximately 33 milliliters [1.1 fluid ounces]). This means that, over 

the last 10 years, there has been a historically observed leakage rate of 3-L flasks of 1 in 1.3 million 

flask-years (7.8 × 10-7 leaks per flask per year). This is probably a conservative estimate of what one 

might expect the leakage rate of new flasks sent to DOE’s new storage facility to be. 

The Interim Guidance envisages that 40 percent of the assumed 10,000 metric tons (11,000 tons) of 

elemental mercury would be flasked. Thus, at the end of the 40-year period assumed for analysis 

purposes, there would be approximately 120,000 flasks in storage, for which the frequency of occurrence 

of a leak would be 0.09 per year (once in approximately 11 years). Over the full 40 years, the average 

number of flasks in the facility any one year would be about 60,000, and the average frequency of a leak 

would be approximately 0.045 per year (once in approximately 22 years). This scenario is further 

discussed in Section D.4.1, where, for the purposes of bounding the effects of releases on the noninvolved 

worker and the public during normal operations, it is assumed that the entire contents of a flask leak into 

the spill tray beneath the pallet and remain undetected (a highly conservative assumption) for a long 

period. 

The risk to the involved worker is also considered in Section D.4.1, but not by analyzing the 

consequences of an undetected pool of mercury in a spill tray. Instead, it is shown that safety procedures, 
Human Health and Ecological Risk Assessment Analysis 

D–21

ventilation, and monitoring are expected to keep the airborne concentration below the ACGIH’s 8-hour 

TWA/TLV of 0.025 mg/m3

 while involved workers are in the building, thus reducing the involved 

workers’ risk to negligible proportions. 

D.2.4 Onsite Accidents and Release Scenarios 

These releases apply to all storage alternatives. No mercury has reportedly escaped from any of the 

warehouses currently used for elemental mercury storage by the Defense Logistics Agency or by DOE (at 

Y–12), and there is no known member of the public that has been affected at any existing storage 

location. 

As discussed in Section D.2.3, decades of experience in maintaining DNSC’s stockpile of mercury 

indicate that spills of mercury resulting in environmental contamination have not occurred and that 

normal (accident-free) operating conditions should be maintained at the storage facilities. The U.S. 

Department of Defense’s existing storage facilities are built to ensure containment of the mercury under 

most conditions. Spilled mercury has not been known to reach any surface-water or groundwater sources 

before cleanup occurs. For these reasons, the only pathway considered for potential accidental releases 

from the candidate storage buildings is via air, with the possible exception of the No Action Alternative: it 

is not known whether all facilities that are used to store mercury or commercial sites are designed and 

built to the same standards. 

D.2.4.1 Single-Flask Spill 

This scenario assumes that a single flask is dropped during handling, resulting in the breach of the flask, 

which is a highly conservative assumption for flasks of such robust construction. 

There are three plausible scenarios for handling flasks. One is that they are found to be leaking, in which 

case they would be moved individually to the Handling Area for remediation activities and then back to 

the Storage Area. In Section D.3 it is shown that the estimated frequency of leaking flasks in the storage 

facility is approximately 0.045 per year. With two movements associated with this leak, the estimated 

frequency of movement of individual flasks would be approximately 0.09 per year. 

The second scenario is that flasks are found to be leaking on arrival. According to the transportation 

analysis below, an average of 59 pallets, containing approximately 2,900 flasks would arrive each year. 

Conservatively assuming that 1 flask in 1,000 is leaking on arrival each year, 3 flasks per year may need 

to be moved to and from the handling area, a total of six movements per year, which far exceeds the 

predicted number in the previous paragraph. 

The third possibility is that partially full pallets would arrive and need to be consolidated. It is not known 

how many partially full pallets would arrive each year. For example, if 10 percent of the pallets (6) arrive 

half full and are consolidated, then approximately 25 flasks would be moved from each of 6 pallets into 6 

other pallets, a total of 150 individual flask movements per year. Thus, consolidation of pallets is likely 

to be the major source of individual flask movements. 

Some insight into how likely these flasks are to be dropped can be gleaned from the experience of 

overpacking flasks at DNSC depots in 2001 and 2002. As noted above, DNSC has approximately 

128,600 flasks, all of which were successfully overpacked without incident. Therefore the probability 

that an individual flasked will be dropped while being moved is less than 10-5. Thus, the estimated 

frequency of which a flask might be dropped would be less than 150 × 10-5 = 0.0015 per year. This is a 

moderate (FL-III) frequency. By the time it is multiplied by some probability (less than 1) of a rupture 

given a drop, it would likely be even lower. However, conservatively, the estimated frequency of a 

single-flask drop is taken to be 0.0015 per year (FL-III: moderate). 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–22

D.2.4.2 Single-Pallet Spill 

Pallets would be handled as they arrive. An average of 59 pallets per year (see Table D–9) would be 

moved from the truck or railcar to the storage racks, which are stacked three pallets high. At the proposed 

storage sites, a pallet could be dropped from a height as great as 3.7 meters (12 feet), the height of the top 

shelf of the rack. The predicted probability that a pallet would be dropped is 2.1 × 10-5 per handling 

event.2

 This would give a moderate (FL-III) frequency of approximately 0.001 per year. It is assumed 

that movement of pallets while in storage would at most add a small percentage to this frequency. 

Conservatively, it is assumed that all of the flasks in a pallet dropped from a height of 3.7 meters (12 feet) 

would be breached. At the storage sites, the flasks are in 7 × 7 arrays on the pallets. 

D.2.4.3 Triple-Pallet Spill 

As a conservative and hypothetical scenario, a portion of the racks holding the flask storage pallets is 

assumed to collapse (possibly as a result of a collision involving a forklift), resulting in the collapse of 

three pallets in a stack and the release of liquid mercury onto the floor. It is unlikely that the entire 

contents of three pallets would be spilled from a single stack onto the floor. This event is considered to 

be no more likely than a single-pallet drop and has a moderate (FL-III) frequency with the assumption 

that the full contents of the 147 3-L flasks in the three pallets would be spilled. 

D.2.4.4 1-Metric-Ton Container Spill 

The transportation analysis indicates that the facility would receive approximately 150 1-MT containers 

per year (see Table D–9). This means that the frequency of a drop from a forklift is 150 × 2.1 × 10-5, or 

approximately 0.003 per year (FL-III). There is no reason to lift the 1-MT containers more than a few 

feet from the ground—after passing initial inspection, the 1-MT containers would be lifted out of their 

crates and moved into the Handling Area for waste acceptance criteria testing. If a container is found to 

be leaking, it would be remediated there. The containers that pass the acceptance and verification process 

would be placed onto spill trays in the Storage Area. For the purposes of this analysis, it is assumed that 

1-MT containers are never lifted above the height of the drop test specified in Title 49 of the Code of 

Federal Regulations, Section 178.810, for containers required to meet Packaging Group III specifications, 

namely 1.55 meters (approximately 5 feet). Therefore, it is unlikely that a 1-MT container would be 

breached by a drop. Conservatively, it is assumed that no more than 1 in 100 dropped containers would 

be breached. This gives a predicted frequency of 3.0 × 10-5 per year, a low (FL-II) frequency. However, 

if the container is breached, it is conservatively assumed that 1 metric ton (about 1.1 tons) of mercury 

would spill onto the floor. 

It is assumed that only one 1-MT container would be moved at a time. In addition, since it is assumed 

that 1-MT containers would be single stacked, there is no equivalent of the triple-pallet collapse. 

D.2.4.5 Forklift Fire 

The Interim Guidance suggests an electric Yale ERC-055-VG as a nominal commercial forklift for 

consideration. It has power steering, a high-visibility mast that can be lifted to the 3.7-meter (12-foot) 

recommended maximum height of stacks, and cushioned tires (approximately 10- by 25-centimeter [4- by 

10-inch) wetted floor area on load). It has an approximately 2,490-kilogram (5,500-pound) capacity (at 

approximately 61-centimeter [24-inch] center), which is acceptable for the suggested 1.44- by 1.44-meter 

 

2

 As a point of reference, the Revised Draft Environmental Impact Statement for Decommissioning and/or Long-Term 

Stewardship at the West Valley Demonstration Project and Western New York Nuclear Service Center (DOE and 

NYSERDA 2008:I-32) identifies a waste package handling and drop accident frequency with a resultant puncture from the 

drop of 2.10 × 10 to 2.1 × 10 per package handling. For this Mercury Storage EIS, the upper range of 2.1 × 10 per waste 

package was multiplied by the number of packages handled annually. The accident frequency does not specify handling by a 

forklift, just handling, in general, but this is judged to be a viable source for a frequency value. 

-6 -5 -5
Human Health and Ecological Risk Assessment Analysis 

D–23

(56- by 56-inch) 3-L flask pallet or for moving 1-MT containers. The electric forklift would contain no 

fuel. Therefore, a forklift fire is not a credible scenario and has a negligible (FL-I) frequency. 

D.2.4.6 Building Fire 

This scenario assumes that a severe fire occurs involving combustible materials associated with mercury 

storage operations. These include wood storage pallets and miscellaneous materials, such as plastic 

sheeting, paper, cardboard, and flammable construction materials. Potential ignition sources include 

electrical control panels, distribution circuits, and fixtures. The amount of combustible material in the 

Storage Areas would be maintained at as low a level as feasible. 

The 2004 MM EIS (DLA 2004a) observed that loading materials at the Warren Depot are minimally 

combustible (other than wooden pallets), and there are limited ignition sources there. There is no wood in 

the structure of the warehouse itself. In addition, the EIS determined that, the installed fire suppression 

system would reduce the likelihood of building fires that could result in the breach of the flasks. 

Therefore, building fires over the course of time during storage were assigned to the negligible (FL-I) 

frequency category. 

It is assumed that the structure of the mercury storage building at DOE’s chosen storage site and other 

factors that might contribute to a fire would make the predicted frequency of a fire with mercury release 

no greater than that estimated for the Warren Depot in 2004. 

D.2.5 External Events 

Onsite accidents that are initiated by external events may occur at any of the candidate sites under 

consideration for the mercury storage facility. External events that are considered are listed below. 

 Wildfires 

 Earthquakes 

 High winds or tornadoes 

 Floods 

 Lightning 

 Snow loads 

 Aircraft crashes 

 Vehicle crashes 

 Nearby facility fires or explosions 

Each event is considered in terms of its likelihood of occurrence and its potential impact in terms of a 

mercury release from the flasks and 1-MT storage containers. The potential magnitude of these events 

varies significantly between the candidate sites due to the wide spectrum of climate, topography, 

seismology, and collocated site facilities that exist at each location. The structures proposed for mercury 

storage at the candidate sites vary from existing buildings with known designs to a hypothetical standard 

design for a new facility. The relevant building codes at each candidate site may also vary due to local or 

state requirements. These facility designs could potentially react differently to postulated external events; 

reactions would range from structural failure and concomitant mercury release to no damage and no 

mercury release. In this evaluation of external events, it is conservatively assumed that the storage 

facility at each candidate site would react to each external event with the largest postulated degree of 

damage and mercury release. For all external events, no credit is taken for emergency response actions of 

onsite personnel, which, in reality, could preclude or ameliorate mercury releases to the environment. 

Other than fires or explosions, the release of mercury to the environment from spills would occur over a 

relatively long time period, in which cleanup and confinement by onsite workers would significantly 

mitigate offsite releases. 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–24

D.2.5.1 Wildfires 

The propensity for wildfires at each site is a function of the climate, the presence of combustible 

vegetation, and the historic incidence of such events. A dry or hot climate or one that is subject to a high 

frequency of lightning has a greater potential for initiating wildfires, given the presence of combustibles. 

In addition, anthropogenic ignition sources, including cigarettes, fireworks, exhaust heat sources, and 

camp fires may cause such fires. Grasses, brush, shrubs, and trees all constitute potentially combustible 

material around each site. The initiation of a wildfire would be exacerbated by significant winds, which 

tend to spread the fire rapidly without mitigation measures by firefighters. Wildfires have occurred near 

some of the candidate sites (Albin, McBaugh, and May 2009; DLA 2004a:2-4, 2-5). With the exception 

of KCP, all the candidate sites are located in rural areas with the potential for wildfires. The KCP site is 

in an urban location surrounded by an area that consists of buildings and paved roads with little open 

natural combustible material. 

The expected frequency of a wildfire in the area around the mercury storage facility, coupled with the 

conditional probability that the wildfire would impinge on the facility and cause a significant mercury 

release, is considered to be negligible. A postulated wildfire event is bounded by the truck and railcar fire 

accident and intentional destructive act (IDA) fire scenarios; thus, a wildfire event is not evaluated 

further. 

D.2.5.2 Earthquakes 

Earthquake-produced ground motion is expressed in units of percent g (force of acceleration relative to 

that of Earth’s gravity). The latest probabilistic peak ground acceleration (PGA) data from the 

U.S. Geological Survey are used in this EIS to assess seismic hazard among the various mercury storage 

candidate sites. The PGA values cited are based on a 2 percent frequency of exceedance in 50 years. 

This corresponds to an annual frequency (chance) of occurrence of about 1 in 2,500 or 4 × 10-4 per year. 

A comparison of these PGA values for each site is presented in Table D–5. This FL is moderate (FL-III). 

Table D–5. Mercury Storage Site Peak Ground Acceleration 

Mercury Storage Site Peak Ground Acceleration (g)a

Grand Junction Disposal Site, Colorado 0.14 

Hanford Site, Washington 0.18 

Hawthorne Army Depot, Nevada 0.57 

Idaho National Laboratory, Idaho 0.12 

Kansas City Plant, Missouri 0.05 

Savannah River Site, South Carolina 0.17 

Waste Control Specialists, LLC, Texas 0.12 

Y–12 National Security Complex, Tennessee 0.22 

a This is the value that has a 1 in 2,500 (4 × 10-4 per year) annual frequency of exceedance, 

expressed in units of percent (g), or the force of acceleration relative to that of Earth’s gravity. 

This table shows that the Hawthorne Army Depot has the highest PGA, whereas KCP, INL, and WCS 

have the lowest. Structures at locations with higher PGAs would be designed, in accordance with the 

national and local building codes applicable at the time of construction, to withstand a larger-magnitude 

earthquake than those at locations with lower PGAs. However, since the structural design of each storage 

facility cannot be ascertained, an earthquake-initiated accident involving the release of mercury was 

postulated and analyzed. 

In the Final Site-Wide Environmental Impact Statement for Continued Operation of Los Alamos National 

Laboratory, Los Alamos, New Mexico, it was assumed that an earthquake would topple the top row of 

stored drums, which were stored in a configuration stacked three rows high (DOE 2008:D-31, D-32). 

This assumption was used in analyzing a seismic event for a radioactive waste storage facility. For an 

earthquake accident in this Mercury Storage EIS, it is conservatively assumed that all flasks would release 
Human Health and Ecological Risk Assessment Analysis 

D–25

their entire contents of mercury with no retention of any of the mercury within the flasks. In addition, it is 

conservatively assumed that the earthquake would cause the building roof to collapse and that the roof 

would then fall onto and breach all 1-MT mercury storage containers. As a result, a pool of mercury 

within the storage building would become the source of release to the environment. The following two 

alternative earthquake scenarios are considered in this EIS: 

 The building remains sufficiently intact so that the spill can still be regarded as occurring inside 

the building. 

 The building collapses and the spilled pool of mercury is, for all intents and purposes, in the open 

air. 

No attempt was made to assess the relative conditional probabilities of these two scenarios, i.e., they are 

both assigned a moderate (FL-III) frequency. 

The possibility that there could be a fire subsequent to the earthquake remains. In some EISs, a seismic 

event that then causes a fire is only considered when there a natural gas main, hydrogen, propane, or 

solvents in the building (DOE 1999:E-5.5, 2001A:D-82,D-83). In one EIS, the presence of a natural gas 

pipeline within a building that could be ruptured by an earthquake and cause a subsequent fire was not 

analyzed because the earthquake-induced damage to the building would result in a dilution of the released 

natural gas to below its flammability limit (DOE 2002a:C-11). Since none of the facilities evaluated in 

this EIS have fuel pipelines or stored fuels the frequency of an earthquake with subsequent fire would be 

negligible. 

The storage buildings could have small quantities of chemicals, such as flammable solvents. It is 

assumed that, if these should catch fire, there would be negligible effect on the stored mercury. 

D.2.5.3 High Winds or Tornadoes 

Data on tornado occurrence frequency and severity, using the Fujita or “F” scale, for the seven sites 

considered for mercury storage and Y–12, are presented in Table D–6 (NOAA 2009). Tornadoes of 

severity F1 and F0 are not expected to cause storage building damage sufficient to result in any 

significant mercury release to the environment. Many well-constructed buildings would survive an 

F2 tornado without serious damage to the roof or walls. Tornadoes have occurred most often and have 

been most severe in the county(ies) surrounding KCP, SRS, and WCS. Conversely, tornadoes have 

occurred least often and have been least severe in the count(ies) surrounding Hanford and the Hawthorne 

Army Depot. Severity F4 and F5 tornadoes have only occurred in the county(ies) surround KCP, and 

F3 tornadoes have only occurred in the county(ies) surrounding KCP, SRS, and WCS. 

Table D–6. Mercury Storage Candidate Site Tornado Frequency and Severity 

Mercury Storage Site 

Annual Tornado 

Occurrence Rate

Total (≥ F2)a

Tornado Severity 

Distribution 

(Fujita Scaleb) 

Predicted Annual Rate 

of Tornado (≥ F2) Strike 

on the Storage Facilityc

Grand Junction Disposal Site, 

Colorado 0.135 (0.0) 13% F1, 87% F0 0 

Hanford Site, Washington 0.0338 (0.0) 100% F0 0 

Hawthorne Army Depot, 

Nevada 0.0 (0.0) Not applicable 0 

Idaho National Laboratory, 

Idaho 0.118 (0.0) 29% F1, 71% F0 0 

Kansas City Plant, Missouri 0.523 (0.183) 2% F5, 3% F4, 8% F3, 18% 

F2, 27% F1, 42% F0 2.49×10-5

Savannah River Site, South 

Carolina 0.81 (0.19) 2% F3, 21% F2, 27% F1, 

50% F0 6.66×10-7
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–26

Table D–6. Mercury Storage Candidate Site Tornado Frequency and Severity (continued)

Mercury Storage Site Annual Tornado 

Occurrence Rate 

Total (≥ F2)a

Tornado Severity 

Distribution 

(Fujita Scaleb) 

Predicted Annual Rate 

of Tornado (≥ F2) Strike 

on the Storage Facilityc

Waste Control Specialists, 

LLC, Texas 0.388 (0.035) 9% F2, 24% F1, 66% F0 1.83×10-7

Y–12 National Security 

Complex, Tennessee 0.0506 (0.034) 8% F3, 23% F2, 46% F1, 23% F0 2.69×10-8

a Data collected from NCDC (2009) give tornado paths to within 4.0 kilometers (2.5.miles). The frequencies presented in 

column 2 of Table D–6 are for the annual rate of occurrence within a single county, if the facility is more than 4.0 kilometers

(2.5 miles) from the county boundary, or within more than one county otherwise. 

b Fujita Scale: F0, 40–72 mph; F1, 73–112 mph; F2, 113–157 mph; F3, 158–206 mph; F4, 207–260 mph; F5, 261–318 mph 

(NOAA 2009). 

c Obtained by multiplying the ≥ F2 annual occurrence rate in column 2 by the ratio of the building area to the area of the 

county(ies) from which data were collected. 

Key: mph=miles per hour. 

Source: NCDC 2009, tornado data from January 1, 1950, to April 1, 2009 (sum of tornadoes reported for county(ies) around 

each site). 

Table D–6 also provides an estimate of the frequency at which tornadoes of severity ≥ F2 would strike the 

storage building; F2 is conservatively assumed to be the lowest tornado severity level at which building 

damage could occur. Those frequencies are negligible (FL-I) except at KCP, where the result is driven by 

having conservatively used the footprint of the whole Bannister Federal Complex in the calculation of 

frequency (see footnote c to Table D–6). At KCP, the rate of building strikes is at FL-II. This is less than 

that for an earthquake, and the consequences would not be any more severe. Therefore, at KCP, the 

tornado risk is bounded by that of earthquakes. 

D.2.5.4 Floods 

All candidate sites may be subject to a flood, although the frequency of such an event would vary 

depending on the likelihood of floods at each location and the design and elevation relative to calculated 

floodplains of a specific storage facility. 

The Interim Guidance (DOE 2009a) states the following: 

“40 CFR 270.14(b)(11) also refers to the seismic/floodplain requirements. An elemental mercury 

storage facility should not, if possible, be located in a listed 100-year floodplain. If the chosen 

facility site is within a 100-year floodplain, then it must be shown that there is either no 

impoundment area “washout,” or the effect of “washout” is acceptable. The site should be 

examined and graded to avoid flooding. The upper lip of the facility’s slab should be well above 

grade, and the 60-ft apron area should be contoured and landscaped so runoff will move away 

from the facility with minimal erosion [see also 40 CFR 264.175(b)(4) for design requirements 

for run-on prevention]. Further, runoff from neighboring upland areas should be intercepted 

(e.g., by ditching) before the 60-ft apron and directed away from the facility.” 

For the purposes of this analysis, it is assumed that either the storage facility would not be located within 

the 100-year floodplain or that engineered features would ensure that the frequency at which floodwater 

would enter the building is less than once in 100 years—i.e., a moderate FL (FL-III)—the same as that for 

an earthquake. 

The magnitude of a flood event could range from water seepage into the building and exterior damage to 

large-scale water intrusion and high water levels inside the storage building. Flooding could compromise 

the water-resistant design of the building, cause a loss of electric power, and temporarily preclude access 

to the facility by normal ground transport vehicles. An extreme flood could cause toppling of stacked 

pallets and the failure of some storage flasks or containers. However, the number of flasks and containers 
Human Health and Ecological Risk Assessment Analysis 

D–27

assumed to fail and release mercury under the earthquake event would bound any such failures in an 

extreme flood event. The most likely impact of an extreme flood would be damage to the storage 

building and the deposition of soil and debris in the mercury storage area. 

Since the earthquake event frequency and consequences bound those for floods, the earthquake scenario 

is considered to be bounding for floods. 

D.2.5.5 Lightning 

Severe weather could cause the storage building to be struck by lightning. The combined frequency of a 

lightning strike on the building, failure of the building’s design to ground the lightning, initiation of a fire 

in the building from the lightning, and such a fire’s causing the release of mercury is expected to be low. 

A fire of sufficient magnitude to cause failure of mercury containers is not expected to occur as a result of 

a lightning strike. Although some candidate sites are more likely to be subject to lightning based on their 

meteorological history, the storage facility at each site would be designed to properly ground lightning 

strikes and mitigate any lightning-induced fires before the confinement integrity of mercury storage 

containers could be breached. The truck and railcar fire accident scenarios in this section and in the IDA 

analysis involve large quantities of mercury and bound any lightning-induced fire at the facility. 

Therefore, this event is not evaluated further. 

D.2.5.6 Snow Loads 

The possibility of a large accumulating snowfall resulting in large structural loads on the roof of the 

mercury storage facility would be considered in the design of the facility for each site. Although the 

likelihood of a large snowfall event is larger at some candidate sites, the structure at each site would be 

designed to withstand the appropriate design snow load without releasing mercury to the environment. In 

the event that severe snow loads cause the collapse of the roof, the collapsed structure could result in 

release of mercury from some storage containers. The mercury releases associated with an extreme snowload-induced roof collapse would be bounded by the earthquake accident scenario. Therefore, this event 

is not evaluated further. 

D.2.5.7 Aircraft Crashes 

Table D–7 presents a delineation of the relative location of all airports within the region of each of the 

candidate mercury storage sites, as well as the type of airport in terms of the aircraft that use these 

airports. This table shows that each site has a number of airports within a 50-mile (80-kilometer) 

distance. The Hawthorne Army Depot has the closest airport at 3 miles (5 kilometers) away, but this is a 

general aviation facility that accommodates small, private aircraft. Commercial airports that handle 

larger, jet aircraft are located 11 to 49 miles (18 to 79 kilometers) from the sites, with the closest near 

KCP and GJDS, followed by SRS E Area. 

Table D–7. Location and Type of Airports Near Candidate Mercury Storage Sites 

Mercury 

Storage Site Airport Type of Airport 

Distance From Site 

(miles) 

Grand Junction 

Disposal Site, 

Colorado 

Crawford 

Blake Field 

WestWinds 

Grand Junction Regional 

Mack Mesa 

Montrose Regional 

Hopkins Field 

North Fork Valley 

General Aviation 

General Aviation 

General Aviation 

Commercial 

General Aviation 

Commercial 

General Aviation 

General Aviation 

40 

18 

15 

17 

38 

37 

47 

38 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–28

Table D–7. Location and Type of Airports Near Candidate Mercury Storage Sites (continued)

Mercury 

Storage Site Airport Type of Airport 

Distance From Site 

(miles) 

Hanford Site 

200 Areas, 

Washington 

Vista Field 

Desert Aire 

Grant County International 

Moses Lake Municipal 

Othello Municipal 

Tri-Cities 

Prosser 

Quincy Municipal 

Richland 

Sunnyside Municipal 

Warden 

Yakima Air Terminal/ 

 McAllister Field 

General Aviation 

General Aviation 

Commercial 

General Aviation 

General Aviation 

Commercial 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

Commercial 

30 

16 

47 

45 

31 

31 

25 

47 

23 

22 

39 

43 

Hawthorne Army 

Depot, Nevada 

Gabbs 

Hawthorne Industrial 

Mina 

Rosaschi Air Park 

Yerington Municipal 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

42 

3 

30 

44 

43 

Idaho National 

Laboratory, 

Radioactive 

Waste 

Management 

Complex, Idaho 

Aberdeen Municipal 

American Falls 

Arco-Butte County 

Big Southern Butte 

Coxs Well 

Midway 

McCarley Field 

Carey 

Antelope Valley 

Howe 

Idaho Falls Regional 

Copper Basin 

Mackay 

Hollow Top 

Bear Trap 

Mud Lake/W. Jefferson County 

Pocatello Regional 

Rockford Municipal 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

Commercial 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

Commercial 

General Aviation 

41 

50 

16 

5 

22 

12 

40 

47 

31 

23 

48 

46 

40 

30 

39 

35 

46 

33 

Idaho National 

Laboratory, 

Idaho Nuclear 

Technology and 

Engineering 

Center, Idaho 

Aberdeen Municipal 

Arco-Butte County 

Big Southern Butte 

Coxs Well 

Midway 

McCarley Field 

Antelope Valley 

Howe 

Idaho Falls Regional 

Copper Basin 

Mackay 

Hollow Top 

Bear Trap 

Mud Lake/W. Jefferson County 

Pocatello Regional 

Rigby-Jefferson County 

Rockford Municipal 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

Commercial 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

Commercial 

General Aviation 

General Aviation 

45 

20 

11 

29 

10 

38 

35 

19 

43 

48 

41 

37 

46 

28 

49 

50 

33 
Human Health and Ecological Risk Assessment Analysis 

D–29

Table D–7. Location and Type of Airports Near Candidate Mercury Storage Sites (continued)

Mercury 

Storage Site Airport Type of Airport 

Distance From Site 

(miles) 

Kansas City 

Plant, Missouri 

Triple R 

Kansas City International 

Harry S. Truman Regional 

Butler Memorial 

Excelsior Spring Memorial 

East Kansas City 

Lawrence Smith Memorial 

Higginsville Industrial Municipal 

Charles B. Wheeler Downtown 

Lee’s Summit Municipal 

Lexington Municipal 

Roosterville 

Midwest National Air Center 

Plattsburg Airpark 

Vinland Valley Aerodrome 

Sherman AAF 

Gardner Municipal 

Lawrence Municipal 

Cedar Air Park 

Johnson County Executive 

New Century Aircenter 

Ottawa Municipal 

Miami County 

Hillside 

General Aviation 

Commercial 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

38 

24 

26 

48 

33 

20 

27 

49 

11 

11 

39 

24 

29 

44 

34 

34 

23 

35 

17 

12 

19 

47 

35 

10 

Savannah River 

Site E Area, 

South Carolina 

Augusta Regional at Bush Field 

Daniel Field 

Louisville Municipal 

Millen 

Plantation Airpark 

Burke County 

Wrens Memorial 

Aiken Municipal 

Allendale County 

Bamberg County 

Barnwell Regional 

Twin Lakes 

Hampton-Varnville 

Dry Swamp 

Orangeburg Municipal 

Lexington County at Pelion 

Edgefield County 

Commercial 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

18 

25 

47 

33 

44 

26 

42 

24 

30 

32 

15 

27 

44 

44 

48 

42 

32 

Waste Control 

Specialists, LLC, 

Texas 

Lea County Regional 

Lea County, Jal 

Lea County-Zip Franklin 

 Memorial 

Andrews County 

Denver City 

Seagraves 

Gaines County 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

19 

22 

40 

32 

38 

46 

29 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–30

Table D–7. Location and Type of Airports Near Candidate Mercury Storage Sites (continued)

Mercury 

Storage Site Airport Type of Airport 

Distance From Site 

(miles) 

Y–12 National 

Security 

Complex, 

Tennessee 

Crossville Memorial-Whitson 

 Field 

Mark Anton 

Campbell County 

Jamestown Municipal 

Knoxville Downtown Island 

McGhee Tyson 

Powell 

Monroe County 

Moore-Murrell 

Scott Municipal 

Rockwood Municipal 

Gatlinburg-Pigeon Forge 

McCreary County 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

Commercial 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

General Aviation 

46 

50 

24 

46 

22 

20 

15 

31 

50 

37 

25 

42 

49 

Note: Commercial airports handle a range of aircraft up to and including large passenger and cargo aircraft. General aviation 

airports, which include air taxis, handle small aircraft. To convert miles to kilometers, multiply by 1.60934. 

A number of evaluations have been made for aircraft crash accident frequency at the DOE Hanford, INL, 

SRS, and Y–12 sites. An assessment of aircraft crash frequency in the 200 Areas at Hanford 

(Chew 2003:16) used non-airport crash frequencies for five types of fixed-wing aircraft: general aviation, 

commercial air carrier, commercial air taxi, large military, and small military. These frequencies are in 

terms of the annual likelihood of occurrence per square mile of ground impact area. Although the generic 

mercury storage facility would have a building area of up to 14,703 square meters (158,256 square feet), 

an area of 18,581 square meters (200,000 square feet) was assumed to encompass proposed existing 

buildings at some of the sites. The frequency of a crash of a large commercial or military aircraft for this 

storage facility area would be 1.4 × 10-9 per year. If smaller commercial and military aircraft are 

included, the total aircraft crash frequency would increase to 7.3 × 10-7 per year. Over 98 percent of this 

total aircraft crash frequency is due to small general aviation aircraft. Thus, the total aircraft crash 

frequency in the Hanford 200 Areas would be less than 1 × 10-6 per year; this frequency is dominated by 

small aircraft that are not expected to cause significant damage to the storage building or mercury releases 

to the environment compared with accident scenarios that are analyzed in this section. 

Analysis of small- and large-aircraft-crash probabilities per square mile of area was previously performed 

for INL (DOE 2000:F-13). Using the bounding mercury storage facility area, the large- and 

small-aircraft-crash frequency is determined to be 6.5 × 10-7 per year. The small-aircraft-crash frequency 

accounts for over 99 percent of this frequency. 

Two previous EISs evaluated the annual frequency of an aircraft crash at SRS. The accident analysis of 

salt processing alternatives at the SRS S Area provided an aircraft impact frequency of 3.7 × 10-7 per year 

and a helicopter crash frequency of 4.8 × 10-7 per year (DOE 2001b:B-9). The sodium-bonded spent 

nuclear fuel aircraft crash analysis (DOE 2000:F-24) evaluated the SRS F Area and used data, in terms of 

frequency per square mile of impact area, for four types of aircraft: air carrier, air taxi, large military 

aircraft, and small military aircraft. Using the bounding storage facility area, the total aircraft crash 

frequency is calculated to be 2.4 × 10-8 per year. Small commercial and military aircraft account for 

78 percent of this frequency. 

An evaluation of an aircraft-crash-induced fire accident scenario was performed for the Y–12 site 

(DOE 2001a:D-73). Large-aircraft-crash accidents were not analyzed because their frequency was 

determined to be less than 1 × 10-7 per year, and small-aircraft-crash-induced fire scenarios were found to 

be bounded by other analyzed accidents. 
Human Health and Ecological Risk Assessment Analysis 

D–31

An accident analysis was performed for a generic DOE low-level radioactive waste storage facility to 

assess differences in risks between sites (Roglans-Ribas et al. 1995). This analysis determined frequency 

categories for a range of accident scenarios, including large-aircraft impact and small-aircraft impact, at 

Hanford, SRS, and INL. The four frequency categories were (1) greater than 10-2 per year, (2) 10-2 per 

year to 10-4 per year, (3) 10-4 per year to 10-6 per year, and (4) less than 10-6 per year. For all the sites, 

both small- and large-aircraft-impact accident scenarios were placed in the less than 10-6 per year category 

(Roglans-Ribas et al. 1995:Tables I and II). 

A summary of previously calculated aircraft crash frequencies at DOE sites is presented in Table D–8. 

Table D–8. Summary of Aircraft Crash Frequencies – Studies Performed for 

U.S. Department of Energy Sites 

Site 

Small-Aircraft-Crash 

Frequencya Large-Aircraft-Crash Frequencya Total-Aircraft-Crash Frequency 

Hanford Site 200 Areas 7.29×10-7 per year 1.4×10-9per year 7.3×10-7per year 

Idaho National 

Laboratory 

6.47×10-7 per year 3.0×10-9 per year 6.5×10-7 per year 

Savannah River Site 

S Area 

– – 3.7×10-7 per yearb

Savannah River Site 

F Area 

1.9×10-8 per year 5.0×10-9per year 2.4×10-8per year 

Y–12 National Security 

Complex 

– less than 10-7 per year – 

All sites less than 10-6 per year less than 10-6 per year less than 10-6 per year 

a Small aircraft are typically single- and twin-engine aircraft weighing less than 4,500 kilograms (10,000 pounds), 

whereas large aircraft have a greater weight and include jet, as well as propeller engines. 

b In addition, a helicopter crash frequency of 4.8 × 10-7 per year was calculated for SRS S Area. 

Source: Chew 2003:16; DOE 2000:F-13, F-24, 2001a:D-73, 2001b:B-9; Roglans-Ribas et al. 1995:Tables I and II. 

The consequences of a postulated small aircraft crash into a building storing hazardous and radioactive 

waste in drums on pallets, each holding 4 drums and stacked two pallets high, was calculated by DOE 

(DOE 2005). A general aviation aircraft was conservatively assumed to penetrate the structure. Based on 

aircraft and engine size, as well as aviation fuel tank capacity, this analysis determined that 4 drums 

would fail catastrophically due to engine impact; 25 would be engulfed in the fuel fire, causing 

catastrophic failure of 5 of these drums; and 22 would experience lid seal failure due to their juxtaposition 

to the fire. Thus, the release from this aircraft crash accident would consist of the entire contents of 

9 drums due to total failure and leakage from an additional 22 drums (DOE 2005). The drum and pallet 

geometry for this accident scenario is analogous to that of mercury flasks at the mercury storage facility. 

The seismic accident scenario analyzed for mercury storage assumes a much larger number of failed 

flasks than this aircraft crash event and also has a higher frequency. 

All the candidate sites could be subject to an aircraft crash, but none are closer than 17 miles 

(27 kilometers) from a commercial airport that handles large aircraft. The small area of the buildings, 

type of aircraft in the airspace, and associated flight vectors make the predicted frequency of such an 

accident negligible. Calculated frequencies of aircraft crashes from previous analyses have all shown that 

such an event has a likelihood of less than 10-6 per year and, in some cases, less than 10-7 per year for 

DOE sites. Moreover, large-aircraft-impact frequency was calculated to be a factor of 10 to 100 smaller 

than that for all aircraft. The mercury releases associated with an aircraft impact would be bounded by 

the earthquake and fire accident scenarios. Therefore, this event is not evaluated further. 

No mercury would be transported by air under the actions analyzed in this EIS. 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–32

D.2.5.8 Vehicle Crashes 

All candidate sites are expected to have a range of vehicles in use, from automobiles to trains. A vehicle 

crash into the storage facility would not cause any release of mercury because of the location of 3-L flasks 

and 1-MT containers inside the building relative to the exterior walls and because it is assumed that there 

are restrictions on vehicle speeds on site. Some exterior wall damage might result, requiring subsequent 

repair. Therefore, this event is not evaluated further. 

D.2.5.9 Nearby Facility Fires or Explosions 

All candidate sites include facilities with small quantities of combustible material in the form of wood, 

paper, or liquid hydrocarbon products. The only site with explosives is the Hawthorne Army Depot, but 

these explosives would be stored at a sufficient distance from the mercury storage facility in specially 

designed structures so as to preclude any damage from an accidental detonation that could release 

mercury to the environment. Facility design and operational procedures at the Hawthorne Army Depot 

are designed specifically to prevent accidental detonation of explosives. Any nearby facility fire is not 

expected to impinge on the mercury storage facility, but if there were damage, the consequences of the 

truck, railcar, and IDA fire analyzed in this EIS would bound the consequences of a nearby facility fire. 

The frequency of an explosion or fire at a nearby facility of sufficient magnitude to cause the release of 

mercury is estimated to be negligible. Therefore, this event is not evaluated further. 

D.2.6 Intentional Destructive Acts 

In accordance with 2006 DOE National Environmental Policy Act guidance (DOE 2006), this section was 

developed to explicitly consider the potential impacts of IDAs on long-term storage of elemental mercury. 

A wide range of IDA scenarios involving the release of mercury can be postulated for the sites being 

considered for mercury storage. Each involves an action by intruders or insiders that affects mercury 

inventories either at the storage facility or during transportation to the storage facility. The human health 

impacts of an IDA are directly related to the magnitude of mercury available for disposition, as well as 

the means of dispersing it to the environment. Other factors that affect impacts include population 

density, distance to the population, and meteorology. IDA scenarios were selected based on the 

magnitude of mercury at the storage facility or in a transport vehicle. Other factors that were considered 

include the nature of the IDA event that would result in the highest dispersion of mercury to the 

environment. The likelihood or frequency of the IDA scenarios analyzed in this section cannot be 

quantified because of the dependence on intruder actions and security measures that would be employed 

by DOE. Each IDA scenario assumes multiple actions by intruders with no successful mitigation or 

protection measures by DOE. Conservative analytical assumptions are also imposed on the calculations. 

The results are presented in terms of consequences, but not annual risks, because of the lack of an annual 

probability or frequency for these IDA events. 

The accident analyses in Section D.4 show that the largest airborne and ground mercury concentrations 

would result from scenarios in which a quantity of mercury in containers is exposed to a fire. The energy 

of a fire would exacerbate the mercury release rate and increase the plume release height. Since the 

accident analysis evaluates fire scenarios involving available fuel in a truck or railcar that contains 

mercury, the IDA scenarios were developed to incorporate larger quantities of flammable material in 

concert with mercury in containers on a truck or railcar. The largest easily accessible and mobile source 

of large quantities of flammable material is a gasoline tank truck, which may contain between 18,927 and 

34,069 liters (5,000 and 9,000 gallons) of gasoline (LAFD 2009). The IDA scenario postulates that a 

group of individuals hijack a fully loaded 34,069-liter (9,000-gallon) gasoline tank truck, which they then 

drive into either a truck or railcar loaded with mercury being carried in either 3-L flasks or 1-MT (1.1 ton) 

containers. Another postulated scenario would involve two groups of armed intruders: one hijacking the 

loaded tanker truck and the other disabling the train or truck carrying mercury. 
Human Health and Ecological Risk Assessment Analysis 

D–33

The postulated armed intruders would incapacitate any persons accompanying the shipment; release the 

gasoline in the tank truck on and around the mercury storage containers; and set the gasoline on fire, 

thereby engulfing the mercury cargo in an unmitigated fire. This IDA event may occur either in transit or 

at the unloading location at the mercury storage facility. The same quantity of gasoline and mercury are 

assumed to be available under both scenarios; these quantities would only be limited by the transport 

capacity of the truck or railcar. The most vulnerable large quantities of mercury were determined to be 

truck or railcar shipments either in transit or at the facility prior to unloading. 

IDA scenarios involving an attack on the storage facility other than during unloading of a truck or railcar 

are predicted to be less likely because of the distribution of mercury within the facility, presence of 

security, and facility design features that would ameliorate mercury releases to the environment. 

The above discussion does not apply to continued storage of DOE mercury at Y–12 because there would 

be no transportation of mercury to the site under the No Action Alternative. The mercury storage facility 

is located in a secure area with armed guards, a Perimeter Intrusion Detection and Alarm System, and 

daily patrols. This level of security and protection makes the mercury storage structure at 

Y–12 much less vulnerable to any postulated IDA scenario. The current mercury storage structure at 

Y–12 is composed of concrete block walls with steel I beams supporting a roof composed of gypsum and 

asphalt. Given the level of safety and security of this facility, as well as its construction and design, no 

additional IDAs that would result in human health consequences greater than those analyzed for accident 

events are postulated to occur. 

D.2.7 Offsite Transportation Accidents and Releases 

Offsite accidents could occur during transportation to the chosen storage site. The following are the 

assumptions governing the transportation analysis (some of these assumptions overlap those about the 

facility): 

 The following three transportation scenarios are considered: (a) Truck Scenario 1: full truck 

shipments; (b) Truck Scenario 2: truck shipments are at 50 percent capacity (doubling the number 

of truck shipments) from R&R and mining facilities and from Peru, but full truck loads from 

Y–12 and chlor-alkali facilities; and (c) shipments by rail-full railcars. Truck Scenario 2 also 

accommodates the possibility that there may be shipments of pallets containing less than 

49 flasks. 

 This analysis addresses up to 10,000 metric tons (11,000 tons) of mercury being transported and 

stored at a DOE facility. This total would include 1,206 metric tons (1,330 tons) from Y–12 

(11,000 tons), 1,101 metric tons (1,214 tons) from chlor-alkali facilities, 3,687 metric tons 

(4,064 tons) from domestic gold mining, 1,236 metric tons (1,362 tons) from U.S.-owned gold 

mines in Peru3

, and 2,770 metric tons (3,053 tons) from R&R facilities. The mercury from Y–12, 

chlor-alkali facilities, gold mining in the United States, and gold mining in Peru would be 

transported directly to the DOE facility without going to an R&R facility. 

 All mercury from Y–12 would be transported in 3-L (0.8-gallon) (34.6-kilogram [76-pound]) 

flasks. Mercury from chlor-alkali facilities would be transported in 1-MT containers. The overall 

proportion of mercury in 1-MT containers to that in 3-L flasks would be 60:40 (DOE 2009a). 

Mercury from mining or R&R facilities in the United States could be transported in either 3-L 

flasks or 1-MT containers. Mercury from mining in Peru would be transported in 3-L flasks 

(Brooks et al. 2007). 

 

3

 An estimate of this mercury was included in the quantity estimates as a conservative planning assumption regarding potential 

contributions to excess elemental mercury. However, the inclusion of an estimate of this mercury does not reflect or conclude 

that such mercury would be “generated in the United States” as that phrase is used in the Act. 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–34

 Packaging of the mercury at the point of origin, transportation to the R&R facilities or to a 

U.S. port, any processing and repackaging at the R&R facilities, and subsequent loading onto 

trucks or railcars are not analyzed in this Mercury Storage EIS on the grounds that all of these 

activities would be carried out anyway, irrespective of the final disposition of the elemental 

mercury. There is no direct rail access to GJDS, so transfer to trucks in the city of Grand 

Junction would be necessary. This is considered in Chapter 4, Section 4.3.9. 

 Elemental mercury would be transported either by road or rail. No other mode of transportation 

would be considered. 

 Y–12 shipments would occur in years 2013–2014. Chlor-alkali shipments would be spread 

across 7 years (2013–2019). R&R shipments would be spread across 40 years (2013–2052).4

 

Shipments from Peru would be imported through the Port of New York and would also be spread 

across 40 years. For the purposes of analysis, it is assumed that all mercury from mining in the 

United States would be shipped from Carlin, Nevada. Carlin is located near most of the major 

gold mines in northern Nevada; the state generates approximately 80 percent of U.S.-mined gold. 

 As stated above, mercury from Y–12 would be shipped to the DOE storage facility in 3-L 

(0.8-gallon) flasks containing 34.6 kilograms (76 pounds) of elemental mercury. In total, 

1,206,000 kilograms in 34,906 flasks would be shipped. 

 As noted above, each flask would contain 34.6 kilograms (76 pounds) of elemental mercury. In 

addition, the total mass of the empty flask could vary with flask type. The Interim Guidance, for 

example, lists flasks varying in weight from 3.4 to 6.3 kilograms (7.5 to 13.9 pounds). For the 

purposes of this analysis, container type T-13, with a mass of 4.1 kilograms (9.0 pounds), is taken 

to be representative. Therefore, the weight of a loaded flask would be 34.6 + 4.1, or 

38.7 kilograms (about 85 pounds). For a discussion of the sensitivity of the analysis to this 

assumption, see Section D.6.1.3. 

 Flasks would be transported in box pallets that each contain an array of 7 × 7 flasks. The 

dimensions of each pallet would be 1.44 by 1.44 meters (56 by 56 inches) (DOE 2009a). 

Therefore, one pallet would contain 34.6 × 49, or 1,695 kilograms (approximately 3,738 pounds), 

of elemental mercury. The total mass of the loaded flasks in a pallet would be 38.7 kilograms per 

flask × 49 flasks, or 1,896 kilograms (approximately 4,181 pounds). The mass of the pallet and a 

spill tray must be added to this figure. It is assumed that these would add 100 kilograms (about 

220 pounds) to the weight of the flasks, so the total weight of a loaded pallet would be 

1,996 kilograms, rounded up to 2,000 kilograms (4,400 pounds) or 2 metric tons (2.2 tons). 

 A 1-MT container should not weigh more than 1,250 kilograms (2,750 pounds) when loaded with 

1,100 kilograms (2,400 pounds) of mercury (DOE 2009a). Therefore, when loaded with 1 metric 

ton (about 1.1 tons) (about 1,000 kilograms [2,200 pounds]), it should not weigh more than 

1,160 kilograms (2,550 pounds). During transportation, it would be sitting in a spill tray that can 

contain the full 1 metric ton of mercury; this tray would be approximately 10 centimeters 

(4 inches) less than the height of the container so that a forklift would be able to remove the 

1-MT container using the lifts on top of it. The approximate dimensions of such a container are 

0.62 by 0.62 by 0.41 meters (24 by 24 by 16 inches). The assembly of 1-MT container, spill tray, 

and pallet is assumed to weigh 100 kilograms (about 220 pounds) more than the container itself, 

i.e., 1,260 kilograms (2,770 pounds). 

 

4

 The results of the risk analysis are not sensitive to the precise details of the temporal distribution of shipments. The analysis 

makes use of the annual average over 40 years only. 
Human Health and Ecological Risk Assessment Analysis 

D–35

 It is assumed that the capacity of a truck is 18,180 kilograms (40,000 pounds) 

(DLA 2004a:Section 2.3.1.1). Therefore, one truck could ship either (18,180 kilograms/ 

2,000 kilograms per pallet) = 9.09 (rounded down to 9) pallets of 49 flasks or (18,180 kilograms/ 

1,260 kilograms per 1-MT container) = 14.4 (rounded down to 14) 1-MT containers. The 

effective floor area of a truck is 2.4 meters (8 feet) wide by 15 meters (48 feet) long. A pallet’s 

dimensions (1.44 meters by 1.44 meters [56 by 56 inches or 4.67 by 4.67 feet]) would allow a 

row of pallets 1 wide and 10 long to be loaded into the truck, which is more than the weight limit 

of 9 pallets. The total of 14 1-MT containers that the truck would accommodate is also limited by 

weight rather than by area. 

 The capacity of a railcar is approximately 68 metric tons (75 tons) (DLA 2004b). Therefore, the 

railcar could, in principle, ship up to (68,000 kilograms/2,000 kilograms per pallet) = 34 pallets of 

49 flasks. However, the MM EIS (DLA 2004a:Section 2.3.1.1) shows that the effective usable 

floor area is 3 meters (10 feet) wide by 18 meters (59 feet) long, sufficient to accommodate two 

rows, each row with 12 pallets of 49 flasks, i.e., 24 pallets. Therefore, the railcar is limited by 

area to 24 pallets of 49 flasks. The railcar can accommodate (68,000 kilograms/1,260 kilograms 

per 1-MT container) = 54 1-MT containers; in this case, the total is not limited by available space. 

 There are four chlor-alkali facilities in the United States: Ashta Chemical (Ashtabula, Ohio, 

108 metric tons [about 120 tons]), PPG (New Martinsville, West Virginia, 244 metric tons [about 

270 tons]), Olin (Charleston, Tennessee, 478 metric tons [about 530 tons]), and Olin (Augusta, 

Georgia, 271 metric tons [about 300 tons]). The total mercury from chlor-alkali facilities would 

be 1,101 metric tons (1,214 tons). 

 It is assumed that 70 percent of R&R mercury would be shipped from the Philadelphia region 

(assuming geographic coordinates of Bethlehem Apparatus) and 30 percent from the Chicago 

region (assuming geographic coordinates for D.F. Goldsmith) to a DOE facility. See Section D.1 

for an explanation of these percentages. 

Table D–9 summarizes the amounts of mercury that would be transported from each of the locations 

listed in the assumptions above, with the corresponding total expected numbers of 7 × 7 pallets and 1-MT 

containers transported over 40 years. 

In general, the probability of a transportation accident or fatality during a specified operation (such as 

transportation from one site to another) is calculated by multiplying the number of miles traveled during 

the operation by a standard factor derived from empirical statistics, which is expressed in terms of the 

number of accidents per mile, the number of fatalities per mile, or the number of releases of hazardous 

material per mile. This transportation risk assessment considers a series of assumptions for three types of 

accidents: 

 Accidents that cause a spill of mercury that subsequently evaporates (no fire): The frequency of 

such accidents is derived from the above-mentioned empirical factor of releases per mile. 

 Accidents that cause a major fire that is sufficient to evaporate some of the mercury: The 

frequency of such accidents is derived from the above-mentioned empirical factor of accidents 

per mile, multiplied by the probability that, given an accident, a major fire would occur. 

 Accidents that cause fatalities due to mechanical impact (i.e., accidents that are unrelated to the 

fact that the cargo is mercury): The predicted frequency of such accidents is derived from the 

above-mentioned empirical factor of fatalities per mile. 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–36

Table D–9. Estimate of Amounts of Mercury to be Transported 

Site 

Years of 

Shipments 

Total Mass 

(metric tons)a

No. of 

Palletsb

No. of 

1-Metric-Ton 

Containersc No. of 

Trucks 

No. of 

Railcars 

Y–12 National Security Complex 2013–2014 1,206 713 0 80 30 

Chlor-Alkali Facilities 

Ashta Chemical, Ashtabula, Ohio 2013–2019 108 0 108 8 2 

PPG, New Martinsville, 

West Virginia 2013–2019 244 0 244 18 5 

Olin, Charleston, Tennessee 2013–2019 478 0 478 35 9 

Olin, Augusta, Georgia 2013–2019 271 0 271 20 6 

Reclamation and Recycling Facilities, Mining, Shipments from Peru – Truck Scenario 1 (full truck shipments) 

Mining (Carlin, Nevada) 2013–2052 3,687 526 2,798 259 74 

Peru (via Port of New York) 2013–2052 1,236 731 0 82 31 

Philadelphia region (Bethlehem 

Apparatus) 2013–2052 1,939 277 1,472 137 40 

Chicago region (D.F. Goldsmith) 2013–2052 831 119 631 60 17 

Reclamation and Recycling Facilities, Mining, Shipments from Peru – Truck Scenario 2 (50 percent capacity truck 

shipments), Railcar Scenario (full rail car shipments) 

Mining (Carlin, Nevada) 2013–2052 3,687 526 2,798 518 74 

Peru (via Port of New York) 2013–2052 1,236 731 0 164 31 

Philadelphia region (Bethlehem 

Apparatus) 2013–2052 1,939 277 1,472 274 40 

Chicago region (D.F. Goldsmith) 2013–2052 831 119 631 120 17 

a Average mass transported per year: 250 metric tons. 

b Number of pallets shipped per year: 59. 

c Number of 1-metric-ton containers shipped per year: 150. 

Note: To convert metric tons to tons, multiply by 1.1023. 

Key: Bethlehem Apparatus=Bethlehem Apparatus Company, Inc.; D.F. Goldsmith=D.G. Goldsmith Chemical and Metal 

Corporation. 

To calculate the frequency of occurrence of transportation accidents, certain input data are required. The 

input data include the definition of the transportation route, the estimation of the number of miles 

traveled, and the empirical accident factors and conditional probabilities discussed above. 

D.2.7.1 Data on Transportation Routes 

This subsection considers transportation by road or rail. The truck routes considered are conventional 

commercial routes that have no hazardous material restrictions. The domestic truck and rail routes 

considered and their associated mileage were obtained using DOE’s TRAGIS [Transportation Routing 

Analysis Geographic Information System] (Johnson and Michelhaugh 2003). Origination and destination 

points in TRAGIS are defined by nodes; therefore, the closest TRAGIS node to a given site was used for 

a particular origination or destination point. 

D.2.7.2 Input Accident Probabilities 

The basic probabilities applied in the transportation risk analysis for accident, fatality, and release rates 

for truck and rail were calculated using data obtained from the U.S. Department of Transportation Federal 

Motor Carrier Safety Administration and the Federal Railroad Administration, respectively. Both the 

truck and rail data are from the years 2004 to 2007. The rates calculated for rail are in terms of railcar 

miles. The conditional probability of a fire, given a truck accident, is less than 1 percent, and given a rail 

accident, is 1 percent; therefore, the bounding conditional probability for both of these cases is assumed to 

be 1 percent (NRC 1987). Table D–10 summarizes the basic probabilities used in the transportation 

analysis. 
Human Health and Ecological Risk Assessment Analysis 

D–37

Table D–10. Basic Probabilities Used in the Transportation Risk Analysis 

Description Value 

Truck accident with no mercury spill and no fire 6.510-7 per truck mile 

Truck accident with mercury spill (no fire) 8.510-8 per truck mile 

Probability of fire after truck accident 0.01a

Truck accident with fire and release of mercury 6.510-9 per truck mile 

Truck accident with mechanically induced fatality (no fire) 2.310-8 per truck mile 

Rail accident with no mercury spill and no fire 2.610-7 per railcar mile 

Rail accident with mercury spill (no fire) 1.210-9 per railcar mile 

Probability of fire after rail accident 0.01 

Rail accident with fire and release of mercury 2.610-9 per railcar mile 

Rail accident with mechanically induced fatality 1.610-8 per railcar mile 

a To obtain the probability per mile of a mercury spill with fire, this factor of 0.01 is applied to the probability per 

mile of a truck accident with no mercury spill and no fire, not to the probability per mile of a truck accident with 

mercury spill (no fire). This is likely conservative. 

Source: FMCSA 2006:39, 2007, 2008:49, 2009a, 2009b; FRA 2009; NRC 1987; Saricks and Tompkins 1999. 

D.2.7.3 Results of Probabilistic Transportation Accident Analysis 

The above data were used to calculate the predicted number of accidents per operation, as shown in 

Table D–11, for the specific example of truck transportation to GJDS in Colorado under Scenario 1. Data 

for other sites are similar. 

Table D–11. Probabilistic Analysis of Truck Accidents, Scenario 1, Grand Junction Disposal Site 

Dispatching 

Site Trucks 

Miles 

(one way) 

Truck 

Miles 

Mean No. of 

Accidents 

over 

40 Yearsa

Mean No. of 

Accidents 

with Spills 

over 

40 Yearsa

Mean No. of 

Accidents 

with Fires 

over 

40 Yearsa

Mean No. of 

Accidents 

with Death 

over 

40 Yearsa

Y–12 National 

Security Complex 80 1,570 125,560 8.2×10-2 1.1×10-2 8.2×10-4 2.9×10-3

Ashta Chemical, 

Ashta, Ohio 8 1,656 13,249 8.6×10-3 1.1×10-3 8.6×10-5 3.0×10-4

PPG, New 

Martinsville, 

West Virginia 

18 1,671 30,073 2.0×10-2 2.5×10-3 2.0×10-4 6.8×10-4

Olin, Charleston, 

Tennessee 35 1,569 54,915 3.6×10-2 4.6×10-3 3.6×10-4 1.2×10-3

Olin, Augusta, 

Georgia 20 1,811 36,218 2.4×10-2 3.1×10-3 2.4×10-4 8.2×10-4

Philadelphia 

region (Bethlehem 

Apparatus) 

137 1,957 268,150 1.7×10-1 2.3×10-2 1.7×10-3 6.1×10-3

Chicago region 

(D.F. Goldsmith) 60 1,256 75,372 4.9×10-2 6.4×10-3 4.9×10-4 1.7×10-3

Peru (via Port of 

New York) 82 2,034 166,788 1.1×10-1 1.4×10-2 1.1×10-3 3.8×10-3

Mining 

(Carlin, Nevada) 259 538 139,342 9.1×10-2 1.2×10-2 9.1×10-4 3.2×10-3

Total 909,667 5.9×10-1 7.7×10-2 5.9×10-3 2.1×10-2

Frequency 

(=Total/40) 1.1×10-2b 1.9×10-3 1.5×10-4b 5.1×10-4

a This heading applies to all entries below except the very last, which is the corresponding annual frequency. 

b The use of the Poisson distribution, as described below, means that the multiplicative factor of 0.01 between all crashes and crashes with fires, 

does not apply to the estimated frequencies. 

Note: To convert miles to kilometers, multiply by 1.60934. 

Key: Bethlehem Apparatus=Bethlehem Apparatus Company, Inc.; D.F. Goldsmith=D.F. Goldsmith Chemical and Metal Corporation. 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–38

Table D–11 shows that the total number of truck miles that would have to be traveled to complete the 

transfer of all the mercury listed in Table D–9 is approximately 910,000 miles (approximately 1.5 million 

kilometers). The probability of an accident with fire and mercury release per truck mile from Table D–10 

is 6.5 × 10-9 per mile. The product of this probability and the number of miles is 0.0059. This is the 

predicted mean number (Λ) of truck fires expected to occur during transportation of mercury to GJDS. 

The mean must be associated with a probability distribution; the most appropriate is the Poisson 

distribution, which is a discrete probability distribution that takes on the values n = 0, 1, 2, 3. It is often 

used as a model for the number of events (such as the number of telephone calls at a business or the 

number of accidents at an intersection) that would occur in a specific time period.5

 It has the following 

form: 

 P(n) = (Λn/n!)exp(-Λ) (n = 0,1,2,3... being the number of accidents) 

 P(0) = exp(-Λ) (the probability that there would be no accidents) 

 For Λ = 0.0059, P(0) = exp(-0.0059), approximately 0.994 

 P(n ≥ 1) the probability of one or more accidents is 1 exp(-Λ), approximately 0.0059 in this case. 

This is the probability of occurrence of one or more truck accidents with fires over a period of 

40 years. (When Λ is small, P(n ≥ 1) approximately equals Λ; this relationship breaks down as Λ

approaches unity or greater.) 

P(n ≥ 1) is the probability that one or more accidents would occur during the 40 years in which the 

assumed 10,000 metric tons (11,000 tons) of mercury would be transported to the receiving site. To 

convert the probability into a frequency, it is averaged over the period of operation of the storage facilities 

(40 years) to be consistent with the frequency definitions for the onsite accidents. 

In this case, dividing 0.0059 by 40 gives a frequency (f) of approximately 1.5 × 10-4 per year, which is in 

the moderate (FL-III) category—i.e., transportation of mercury to GJDS per 40 years would lead to truck 

accidents with fires (and associated releases of mercury) with a moderate frequency of 1.5 × 10-4 per year. 

Tables D–12 through D–14 summarize the results for each of the two truck scenarios and for the Railcar 

Scenario for all sites. 

 

5

 The Poisson distribution expresses the probability of a number of events occurring in a fixed period of time if these events 

occur with a known average rate and independently of the time since the last event (Engineering Statistics Handbook 2009). 
Human Health and Ecological Risk Assessment Analysis 

D–39

Table D–12. Frequency Analysis of Truck Accidents, Scenario 1, All Sites 

Mercury Storage Site 

Truck 

Miles 

Frequency of 

Accidents 

(per year) 

Frequency of 

Accidents with 

Spills 

(per year) 

Frequency of 

Accidents with 

Fires 

(per year) 

Frequency of 

Accidents with 

Death 

(per year) 

909,667 1.1×10-2 1.9×10-3 1.5×10-4 5.1×10-4 Grand Junction Disposal 

Site, Colorado – High (FL-IV) Moderate (FL-III) Moderate (FL-III) Moderate (FL-III)

1,251,164 1.4×10-2 2.5×10-3 2.0×10-4 7.0×10-4 Hanford Site, 

Washington – High (FL-IV) Moderate (FL-III) Moderate (FL-III) Moderate (FL-III)

1,161,577 1.3×10-2 2.3×10-3 1.9×10-4 6.5×10-4 Hawthorne Army Depot, 

Nevada – High (FL-IV) Moderate (FL-III) Moderate (FL-III) Moderate (FL-III)

984,288 1.2×10-2 2.0×10-3 1.6×10-4 5.5×10-4 Idaho National 

Laboratory, Idaho – High (FL-IV) Moderate (FL-III) Moderate (FL-III) Moderate (FL-III)

754,705 9.7×10-3 1.5×10-3 1.2×10-4 4.3×10-4 Kansas City Plant, 

Missouri – Moderate (FL-III) Moderate (FL-III) Moderate (FL-III) Moderate (FL-III)

869,314 1.1×10-2 1.8×10-3 1.4×10-4 4.9×10-4 Savannah River Site, 

South Carolina – High (FL-IV) Moderate (FL-III) Moderate (FL-III) Moderate (FL-III)

1,000,305 1.2×10-2 2.0×10-3 1.6×10-4 5.6×10 Waste Control -4

Specialists, LLC, Texas – High (FL-IV) Moderate (FL-III) Moderate (FL-III) Moderate (FL-III)

Note: To convert miles to kilometers, multiply by 1.60934. 

Key: FL=frequency level. 

Table D–13. Frequency Analysis of Truck Accidents, Scenario 2, All Sites 

Mercury Storage Site 

Truck 

Miles 

Frequency of 

Accidents 

(per year) 

Frequency of 

Accidents with 

Spills 

(per year) 

Frequency of 

Accidents with 

Fires 

(per year) 

Frequency of 

Accidents with 

Death 

(per year) 

1,559,319 1.6×10-2 3.1×10-3 2.5×10-4 8.7×10-4 Grand Junction Disposal 

Site, Colorado – High (FL-IV) Moderate (FL-III) Moderate (FL-III) Moderate (FL-III)

2,112,527 1.9×10-2 4.1×10-3 3.4×10-4 1.2×10-3 Hanford Site, 

Washington – High (FL-IV) Moderate (FL-III) Moderate (FL-III) Moderate (FL-III)

1,943,587 1.8×10-2 3.8×10-3 3.1×10-4 1.1×10-3 Hawthorne Army Depot, 

Nevada – High (FL-IV) Moderate (FL-III) Moderate (FL-III) Moderate (FL-III)

1,654,225 1.6×10-2 3.3×10-3 2.7×10-4 9.2×10-4 Idaho National 

Laboratory, Idaho – High (FL-IV) Moderate (FL-III) Moderate (FL-III) Moderate (FL-III)

1,385,734 1.5×10-2 2.8×10-3 2.2×10-4 7.8×10-4 Kansas City Plant, 

Missouri – High (FL-IV) Moderate (FL-III) Moderate (FL-III) Moderate (FL-III)

1,682,503 1.7×10-2 3.3×10-3 2.7×10-4 9.4×10-4 Savannah River Site, 

South Carolina – High (FL-IV) Moderate (FL-III) Moderate (FL-III) Moderate (FL-III)

1,806,502 1.7×10-2 3.5×10-3 2.9×10-4 1.0×10 Waste Control -3

Specialists, LLC, Texas – High (FL-IV) Moderate (FL-III) Moderate (FL-III) Moderate (FL-III)

Note: To convert miles to kilometers, multiply by 1.60934. 

Key: FL=frequency level. 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–40

Table D–14. Frequency Analysis of Rail Accidents, All Sites 

Mercury Storage Site 

Railcar 

Miles 

Frequency of 

Accidents 

(per year) 

Frequency of 

Accidents with 

Spills 

(per year) 

Frequency of 

Accidents with 

Fires 

(per year) 

Frequency of 

Accidents with 

Death 

(per year) 

317,260 2.0×10-3 9.2×10-6 2.1×10-5 1.3×10-4 Grand Junction Disposal 

Site, Colorado – Moderate (FL-III) Low (FL-II) Low (FL-II) Moderate (FL-III)

453,317 2.8×10-3 1.3×10-5 3.0×10-5 1.9×10-4 Hanford Site, 

Washington – Moderate (FL-III) Low (FL-II) Low (FL-II) Moderate (FL-III)

394,922 2.5×10-3 1.1×10-5 2.6×10-5 1.6×10-4 Hawthorne Army Depot, 

Nevada – Moderate (FL-III) Low (FL-II) Low (FL-II) Moderate (FL-III)

372,924 2.3×10-3 1.1×10-5 2.4×10-5 1.5×10-4 Idaho National 

Laboratory, Idaho – Moderate (FL-III) Low (FL-II) Low (FL-II) Moderate (FL-III)

250,966 1.6×10-3 7.2×10-6 1.6×10-5 1.0×10-4 Kansas City Plant, 

Missouri – Moderate (FL-III) Low (FL-II) Low (FL-II) Moderate (FL-III)

304,329 1.9×10-3 8.8×10-6 2.0×10-5 1.2×10-4 Savannah River Site, 

South Carolina – Moderate (FL-III) Low (FL-II) Low (FL-II) Moderate (FL-III)

394,112 2.5×10-3 1.1×10-5 2.6×10-5 1.6×10 Waste Control -4

Specialists, LLC, Texas – Moderate (FL-III) Low (FL-II) Low (FL-II) Moderate (FL-III)

Note: To convert miles to kilometers, multiply by 1.60934. 

Key: FL=frequency level. 

The following summarizes the above tables: 

 For both truck transportation scenarios: 

 The predicted frequency of an accident, regardless of the consequences, is high (FL-IV) for 

all receiving sites, with the exception of KCP under Scenario 1, for which the frequency is 

moderate (FL-III). 

 The frequency of an accident with specific consequences (spill, fire, or death due to 

mechanical impact) is moderate (FL-III) for all receiving sites. 

 The variation in predicted frequencies of truck accidents across the receiving sites, regardless 

of the consequences, is less than a factor of two, consistent with the difference between total 

truck miles, which is also less than a factor of two. 

 For rail transportation: 

 The predicted frequency of an accident, regardless of the consequences, is moderate (FL-III) 

for all receiving sites. 

 The predicted frequency of an accident with a consequence of a spill or fire is low (FL-II) for 

all receiving sites. 

 The predicted frequency of a fatality due to an accident is moderate (FL-III) for all receiving 

sites. 

 The variation in predicted frequencies of rail accidents across the receiving sites, regardless 

of the consequences, is less than a factor of two. 
Human Health and Ecological Risk Assessment Analysis 

D–41

D.2.7.4 Frequencies of Crashes with Fires During Rainfall 

As previously discussed, the only scenario that has the potential for mercury to be deposited on the 

ground or in water bodies is one involving a fire, which would cause the mercury to be converted from 

the elemental form, which has essentially zero potential for deposition or scavenging, to a form that can 

deposit. A fire would cause the released mercury to rise, so that the only possibility for high levels of 

mercury to be deposited on the ground near the source is if it is raining while the release is taking place.6

 

Five years’ worth of hourly meteorological data were obtained from the seven potential receiving sites or 

the nearest meteorological station (such as a nearby airport); from these data, the fraction of time during 

which it is expected to be raining at each site (or equivalently, the probability that it would be raining 

when a crash occurs7

) was estimated, as shown in Table D–15. 

Table D–15. Probability of Rainfall at Time of Crash 

Mercury Storage Site 

Probability 

of Rainfall Source of Data 

Averaged over 

(time period) 

Grand Junction Disposal 

Site, Colorado 

0.027 Grand Junction 

Airport 

2004–2008 

Hanford Site, 

Washington 

0.025 Hanford Site 2002–2006 

Hawthorne Army Depot, 

Nevada 

0.016 Reno Airport 2004–2008 

Idaho National 

Laboratory, Idaho 

0.027 Idaho National 

Laboratory 

2000–2004 

Kansas City Plant, 

Missouri 

0.054 Kansas City 

Airport 

2004–2008 

Savannah River Site, 

South Carolina 

0.056 Savannah River 

Site 

1997–2001 

Waste Control 

Specialists, LLC, Texas 

0.022 Odessa-Midland 

Airport 

2004–2008 

As can be seen, the difference between the driest site (Hawthorne Army Depot) and the wettest (SRS) is 

more than a factor of three. The various transportation routes would pass through regions of different 

rainfall characteristics. As a rough approximation, it is assumed that, on average, all of the transportation 

routes would run through areas with rainfall probabilities equal to the average of those in the above table, 

0.032. The results of the frequencies of crashes involving fires predicted to occur during rainfall are 

given in Table D–16. 

 

6

 See Section D.7.3.3 for a discussion about why scavenging by precipitation is represented by rainfall only, and snow is not 

explicitly included. 7

 In principal, the probability of a crash per mile might be a little higher in wet weather than in dry weather. However, it is

assumed that this is a counter balanced by caution on the part of drivers of trucks containing hazardous materials (e.g., not 

driving in adverse weather conditions). 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–42

Table D–16. Predicted Frequencies of Crashes with Fires During Rainfall 

Frequency of Accidents with Fires During Rainfall (per year) 

Mercury Storage Site Truck Scenario 1 Truck Scenario 2 Railcar Scenario 

4.7×10-6 8.1×10-6 6.6×10-7 Grand Junction Disposal Site, 

Colorado Low (FL-II) Low (FL-II) Negligible (FL-I) 

6.5×10-6 1.1×10-5 9.5×10-7

Hanford Site, Washington Low (FL-II) Low (FL-II) Negligible (FL-I) 

6.0×10-6 1.0×10-5 8.3×10-7

Hawthorne Army Depot, Nevada Low (FL-II) Low (FL-II) Negligible (FL-I) 

5.1×10-6 8.6×10-6 7.8×10-7 Idaho National Laboratory, 

Idaho Low (FL-II) Low (FL-II) Negligible (FL-I) 

3.9×10-6 7.2×10-6 5.3×10-7

Kansas City Plant, Missouri Low (FL-II) Low (FL-II) Negligible (FL-I) 

4.5×10-6 8.7×10-6 6.4×10-7 Savannah River Site, South 

Carolina Low (FL-II) Low (FL-II) Negligible (FL-I) 

5.2×10-6 9.4×10-6 8.3×10-7 Waste Control Specialists, LLC, 

Texas Low (FL-II) Low (FL-II) Negligible (FL-I) 

Key: FL=frequency level. 

As can be seen, all truck frequencies are now in the low (FL-II) category. All rail frequencies are in the 

negligible (FL-I) category. This means that any risk to any receptor from railcar fires with mercury spills 

during rain would be negligible (FL-I). 

D.2.8 Spills into Water Bodies 

Spills occurring during a transportation accident could result in leakage of the mercury cargo into the 

surrounding environment. This is the most problematic scenario in this EIS from the perspective of 

making solid, defensible estimates of risk because of large, inherent uncertainties. The most significant 

and challenging scenario (from a cleanup standpoint) would be a spill directly into a surface-water body 

such as a lake or river. This could occur if a truck or railcar crashes on a bridge, or if there is a crash 

where the truck or rail route is immediately adjacent to a river or a lake. 

With respect to crashes on a bridge, only a small proportion of any route is actually directly over water, so 

that one might expect that the frequency of a crash with subsequent spillage into water is in the low-tonegligible (FL-II to -I) range. However, at the time of writing, no good information was available on the 

actual probability of a crash per truck mile or railcar mile on a bridge. 

With respect to travel alongside rivers, there is a possibility that a truck or railcar might crash directly into 

a river, or release its contents near a river after which mercury might make its way into the river. See 

Section D.4.3.2 for discussion of the issues that might arise should such a spill occur. 

The various potential truck and rail routes form the dispatching sites to the storage sites were reviewed 

and numerous places found where routes were alongside or over rivers. However, in terms of length, two 

examples stand out. Truck shipments from the PPG facility in West Virginia would go north to 

Wheeling, following the Ohio river, for about 30 miles (50 kilometers). Rail shipments would go south, 

following the river, for about 40 miles (65 kilometers). However, since the total amount of mercury to be 

shipped from this site is only about 2 to 3 percent of the total, the frequency of spillage into the river 

would be negligible (FL-I). 
Human Health and Ecological Risk Assessment Analysis 

D–43

Interstate 70 in Colorado follows rivers and streams much of the distance in the state to get to GJDS. 

These include the Colorado River, Clear Creek, Eagle River, Straight Creek, and Gore Creek. The route 

to GJDS contains the greatest distance of any route where there might be a potential for spillage into a 

river. This issue is further discussed in Chapter 4, Section 4.3.9. 

It is difficult to calculate the frequency of crashes that would lead to spillage directly into water. 

Therefore, for the purposes of this analysis, it is very conservatively assumed that the frequency of such 

crashes is in the same range as the overall frequency of crashes with spills—moderate (FL-III) for both 

truck scenarios and low (FL-II) for the Railcar Scenario. 

D.2.9 Populations and Accident Scenarios 

The consequences of a mercury release are in principle related to the affected population within 

1.6 kilometers (1 mile) of the release. Urban and suburban areas may have populations exceeding 

3,226 people per square mile, whereas rural areas typically have a population density of 139 people or 

fewer per square mile. In general, an average of 30 percent of the miles traveled in the eastern United 

States would be within urban or suburban areas, with the remaining 70 percent in less-populated rural 

areas. For travel in the western United States, the rural road mileage would increase to 92 percent, with 

only 8 percent of the mileage in urban or suburban areas. 

Note, however, that this EIS does not account for population densities. The estimated risks to members 

of the public from inhalation of mercury are essentially individual risks, expressed as the predicted 

frequency at which an individual would be exposed to concentrations above AEGL-3, or, in some cases 

AEGL-2 or 0.1×AEGL-2. For all pathways via dry or wet deposition, the calculated risk is essentially the 

predicted frequency at which, somewhere along the transportation route, deposited levels of mercury 

exceed screening values tied to human or ecological receptor ingestion. Again, this measure of risk does 

not rely on knowledge of the population of human or ecological receptors within or near the contaminated 

areas. 

Note that although the traffic accident rate is higher in urban and suburban areas, the posted speed limits 

are lower, generally limiting the severity of vehicle accidents. In rural areas, the speed limits tend to be 

higher. Because the traffic density is lower in rural areas, the probability of collision decreases; however, 

it is reasonable to expect that the consequence of a collision that occurs could be more severe. In urban 

and suburban areas, the emergency response capability (i.e., mitigating reactions) is generally only 

minutes away whereas, in rural areas, initial emergency response could take up to an hour. 

D.2.10 Summary of Event Frequencies 

Table D–17 summarizes the analysis of event frequencies, which is an important precursor to the 

remaining portions of the risk assessment. 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–44

Table D–17. Summary of Onsite and Offsite Frequency of Hazardous Events 

Hazard Activity Postulated Scenario 

Frequency of 

Release 

Evaluated 

Further Comments 

Toxic Onsite storage Slow leak/release of 

liquid mercury. 

High 

(FL-IV) 

Yes Requires failure of container. 

Fire Onsite storage Building fire involving 

multiple flasks or 

1-metric-ton 

containers. 

Negligible 

(FL-I) 

No Limited ignition sources, reliable 

fire protection system, controls 

on combustible load, buildings 

constructed of nonflammable 

materials. 

Fire/explosion 

nearby 

All activities Fire/explosion at 

nearby building 

impacts mercury 

containers. 

Negligible 

(FL-I) 

No No facilities containing 

flammable or explosive materials 

located within 61 meters 

(200 feet). 

Wildfire All activities Wildfire consumes 

storage facility. 

Negligible 

(FL-I) 

No Although wildfires are common, 

fire monitoring, prevention and 

suppression systems greatly 

reduce likelihood of mercury 

release. 

Kinetic Onsite 

material 

handling 

Single flask is dropped 

during handling, 

resulting in breach. 

Moderate 

(FL-III) 

Yes Consolidation of partially filled 

pallets could lead to a large 

number of handling events per 

year. 

Kinetic Onsite 

material 

handling 

Single pallet is 

dropped during 

transfer to storage 

racks, resulting in 

breach. 

Moderate 

(FL-III) 

Yes Assumes pallet dropped from 

3.7 meters (12 feet) and all 49 

flasks breached. 

Kinetic Onsite 

material 

handling 

Triple-pallet collapse. Moderate 

(FL-III) 

Yes Requires failure of storage rack. 

Kinetic Onsite 

material 

handling 

Single 1-metric-ton 

container drop. 

Moderate 

(FL-III) 

Yes Assumes container dropped from 

a height of less than 1.5 meters 

(5 feet). 

Earthquake All activities Earthquake results in 

building damage and 

causes pallets and/or 

flasks to fall and spill. 

Moderate 

(FL-III)

Yes Requires an earthquake and 

failure of flasks or 1-metric-ton 

containers. 

Flood All activities Storage building 

floods, causing failure 

of 3-liter flasks or 1-

metric-ton containers. 

Moderate 

(FL-III) 

Yes Requires failure of flasks or 

1-metric-ton containers. 

Represented by earthquake 

scenario. 

Weather All activities High winds or 

tornadoes result in roof 

failure and cause 

pallets and/or flasks to 

fall. 

Low (FL-II) 

or 

negligible 

(FL-I) 

(tornadoes); 

negligible 

(FL-I) 

(high 

winds) 

Yes Requires failure of flasks or 

1-metric-ton containers. 

Bounded by earthquake scenario. 

Weather All activities Lightning strike causes 

small building fire 

involving limited 

number of mercury 

containers. 

Negligible 

(FL-I) 

No Lightning strike as initiator of 

building fire not considered 

credible. 

Weather All activities Snow load causes roof 

collapse, resulting in 

mercury containers’ 

falling. 

Negligible 

(FL-I) 

No Assumes building designed to 

requirements of building codes. 
Human Health and Ecological Risk Assessment Analysis 

D–45

Table D–17. Summary of Onsite and Offsite Frequency of Hazardous Events (continued)

Hazard Activity Postulated Scenario 

Frequency of 

Release 

Evaluated 

Further Comments 

Surface 

transportation 

Onsite storage Vehicle or train 

crashes into building, 

resulting in mercury 

container breach. 

Negligible 

(FL-I) 

No Assumed slow vehicle speeds on 

site. 

Surface 

transportation 

Offsite 

transport 

Truck or train crashes 

during transportation 

of mercury; fire breaks 

out. 

Moderate 

(FL-III) 

(truck) 

Low 

(FL-II) 

(rail) 

Yes Impact breaches flasks or 

1-metric-ton containers; spill and 

fire occur after crash. 

Surface 

transportation 

Offsite 

transport 

Truck or train crashes 

during transportation 

of mercury and fire 

breaks out in wet 

weather. 

Low (FL-II) 

(truck) 

Negligible 

(FL-I) (rail) 

Yes Impact breaches flasks or 

1-metric-ton containers; spill and 

fire occur after crash. 

Surface 

transportation 

Offsite 

transport 

Truck or train crashes 

and mercury spills (no 

fire). 

Moderate 

(FL-III) 

Yes Impact breaches flasks or 

1-metric-ton containers; 

subsequently evaporates. 

Surface 

transportation 

Offsite 

transport 

Truck or train crashes 

with mechanically 

induced fatality. 

Moderate 

(FL-III) 

Yes Impact causes fatality. 

Aircraft crash All activities Aircraft crashes into 

building, resulting in 

fire, mercury container 

breach. 

Negligible 

(FL-I) 

No Limited target area given type of 

aircraft, flight vectors, and size of 

storage area within building. 

Intentional 

destructive act 

Transport Full gasoline tanker 

driven into truck or 

railcar; fire breaks out. 

Not 

assessed 

Yes Gasoline fire causes release of 

mercury. 

D.3 HUMAN TOXICITY ASSESSMENT FOR MERCURY 

In 1997, EPA conducted a comprehensive assessment of mercury toxicity as part of its Mercury Study 

Report to Congress (EPA 1997a). The report assessed the toxicity of elemental mercury, inorganic 

mercury (or mercury salts), and methylmercury. Much of the information is also summarized on EPA’s 

IRIS (www.epa.gov/iris). In addition, the National Research Council completed a comprehensive 

assessment of the toxicity of methylmercury in 2000 (NRC 2000). EPA revised its assessment of 

methylmercury toxicity in July 2001, publishing revised oral reference doses (RfDs) (EPA 2002a). The 

following sections provide a brief overview of mercury toxicity in these three general forms. 

OSHA provides a convenient summary of exposure limits for various forms of mercury, reproduced in 

Table D–18 (OSHA 2009). These exposure limits were furnished by OSHA itself, NIOSH, and ACGIH. 

In addition, EPA has published proposed AEGLs for mercury vapor, as shown in Table D–19. 

AEGLs represent threshold exposure limits for the general public and are applicable to emergency 

exposure periods ranging from 10 minutes to 8 hours. It is believed that the recommended exposure 

levels are applicable to the general population, including infants and children and other individuals who 

may be susceptible. However, although the AEGL values represent threshold levels for the general 

public, it is recognized that individuals, subject to unique or idiosyncratic responses, could experience the 

effects described below at concentrations below the corresponding AEGL. 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–46

Table D–18. Exposure Limits for Mercury 

Mercury, Alkyl 

Compoundsa

Mercury, Aryl 

Compoundsb

Mercury, Inorganic 

Compoundsc

Occupational Safety and Health Administration 

8-hour TWA 0.01 mg/m3 0.1 mg/m3 0.1 mg/m3

Ceiling 0.04 mg/m3

National Institute for Occupational Safety and Health 

8-hour TWA 0.01 mg/m3, skin 0.05 mg/m3, skin 0.05 mg/m3, skin 

STEL/Ceiling 0.03 mg/m3 (STEL), skin 0.1 mg/m3 (ceiling), skin 0.1 mg/m3 (ceiling), skin 

IDLH 2 mg/m3 10 mg/m3 10 mg/m3

American Conference of Governmental Industrial Hygienists 

8-hour TWA 0.01 mg/m3, skin 0.1 mg/m3, skin 0.025 mg/m3, skin 

Short term 0.03 mg/m3, skin 

a Alkyl compounds are organic compounds generally resembling hydrocarbons with one hydrogen atom replaced by another 

atom. Thus, CH3Hg, methylmercury is an alkyl compound resembling methane. 

b Aryl compounds are organic compounds generally resembling an aromatic ring. Thus, phenylmercury is a cation C6H5Hg+

resembling a benzene ring that forms compounds such as phenylmercury acetate. As can be inferred from the exposure limits, 

aryl compounds are less toxic than alkyl compounds. 

c elemental mercury is included in the category of inorganic compounds. 

Key: IDLH=immediately dangerous to life or health; mg/m3

=milligrams per cubic meter; STEL=short-term exposure limit 

(15 minutes); TWA=time-weighted average. 

Source: OSHA 2007. 

Table D–19. Proposed EPA Values for Elemental Mercury Vapor AEGLs 

Exposure 10 minutes 30 minutes 60 minutes 4 hours 8 hours 

Guideline 

AEGL-1 NR NR NR NR NR 

AEGL-2 3.1 mg/m3 2.1 mg/m3 1.7 mg/m3 0.67 mg/m3 0.33 mg/m3

AEGL-3 16 mg/m3 11 mg/m3 8.9 mg/m3 2.2 mg/m3 2.2 mg/m3

Note: Reported values are in milligrams per cubic meter, NOT parts per million. See Section D.1.1.2.1 for definitions of 

AEGLs. AEGL-2 values for durations of exposure other than those explicitly listed in this table are obtained by linear 

interpolation. 

Key: AEGL=Acute Exposure Guideline Level; EPA=U.S. Environmental Protection Agency; mg/m3=milligrams per cubic 

meter; NR=not recommended (due to insufficient data). 

Source: EPA 2009a. 

D.3.1 Toxicity of Elemental Mercury 

The route of exposure (e.g., ingestion, dermal absorption, inhalation) is an important consideration in 

assessing elemental mercury toxicity. Elemental mercury is poorly absorbed in the human 

gastrointestinal tract and does not, consequently, exhibit significant oral toxicity. In contrast, elemental 

mercury is readily absorbed through the lungs (estimated absorption is 75 to 85 percent) and is expected 

to account for 97 percent of the total dose of elemental mercury vapor absorbed by an individual. The 

remaining 3 percent is expected to be absorbed through the skin. 

Once absorbed, elemental mercury is readily distributed throughout the body, crossing both the placental 

and blood–brain barriers. Subsequent oxidation by the hydrogen peroxidase catalase pathway may cause 

the mercury to become irreversibly retained in body compartments such as brain tissue. Unconverted 

elemental mercury is eliminated via urine, feces, and expired air. 
Human Health and Ecological Risk Assessment Analysis 

D–47

EPA (1997a) concluded that inhaled elemental mercury can cause a range of adverse neurological effects, 

including the following: 

 Tremors 

 Emotional liability (changeable mood, irritability, excessive shyness, loss of confidence, and 

nervousness) 

 Insomnia 

 Muscle weakness, twitching, and atrophy 

 Headaches 

 Polyneuropathy (a disease process involving a number of peripheral nerves) 

 Impairment of cognitive function 

Other severe sublethal consequences of inhaling elemental mercury include adverse renal effects and 

pulmonary dysfunction. Mercury exposure at concentrations consistent with those known to cause 

neurological effects were observed in one study to affect renal function. EPA also concluded that 

sufficient animal data are available to establish potential adverse reproductive and developmental effects. 

However, the data are insufficient to quantify the degree of the hazard. 

Regarding the potential carcinogenicity of elemental mercury, EPA concluded that the available data do 

not support a classification as to human carcinogenicity. The available human epidemiological studies 

have significant limitations, and the data from the only available animal study are considered inadequate. 

The limited available data from genotoxicity studies do not support the existence of a carcinogenic effect. 

D.3.2 Toxicity of Inorganic Mercury 

In keeping with EPA practice, the toxicity of inorganic mercury is assessed based on the toxicity of 

mercuric chloride. The absorption of inorganic mercury from the gastrointestinal tract has been estimated 

at 7 to 15 percent in human volunteers following oral administration of radio-labeled inorganic mercury 

(EPA 2002b). About 85 percent of inorganic mercury is eliminated in feces within a few days of 

ingestion. Dermal absorption of mercuric chloride was measured at 2 to 3 percent in guinea pigs. 

Mercury absorption from inhaled aerosols was measured at 40 percent in dogs. 

Inorganic mercury does not distribute as readily throughout the body as elemental mercury. Inorganic 

mercury has a limited capacity to cross the blood–brain and placental barriers. The principal adverse 

effect of low-level exposures to inorganic mercury is kidney disease consequent to autoimmune 

glomerulonephritis (EPA 2002b). At higher levels, inorganic mercury exposures are associated with 

peripheral and motor neurotoxicity in addition to renal impairment. There is limited evidence indicating 

that inorganic mercury exposures may have adverse developmental effects as well. 

EPA classifies mercuric chloride as a “possible human carcinogen” based on the absence of human data 

and limited evidence of carcinogenicity in rats and mice. 

D.3.3 Toxicity of Methylmercury 

Methylmercury is a highly toxic substance that is readily absorbed through the gastrointestinal tract 

(ATSDR 1999; EPA 2002a, 2002b). Once in the body, it readily passes into the adult and fetal brain, 

where it accumulates and is subsequently converted to inorganic mercury. Consequently, the nervous 

system is considered to be the critical target organ system for methylmercury toxicity. The nervous 

systems of developing organisms are considered of special concern. 

Chronic, low-dose exposures to methylmercury in fish have been associated with subtle, neurotoxic 

endpoints in children, including poor performance on neurobehavioral tests of attention, fine motor 

function, visual spatial abilities, and verbal memory. The effects of concern at high doses include mental 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–48

retardation, cerebral palsy, deafness, blindness, speech impairments, and sensory and motor impairments. 

There is also evidence indicating that methylmercury exposure can have adverse cardiovascular effects, 

possibly at exposure levels below those associated with neurological effects. There is additional evidence 

indicating that methylmercury exposure may have adverse effects on the immune and reproductive 

systems. Based on “inadequate” data in humans and limited data in animals, EPA classifies 

methylmercury as a “possible human carcinogen,” although there is no cancer slope factor available from 

EPA to assess cancer risks. 

D.3.4 Human Receptors and Benchmarks 

This section describes the receptors that were chosen for the human health analysis and the benchmarks 

applied to the exposure point concentrations. 

D.3.4.1 Receptors 

At each site, three human receptors are considered—involved workers, noninvolved workers, and 

members of the public. The involved worker is someone inside the storage facility or working on the 

truck or railcar unloading operation. The noninvolved worker is someone who does not specifically work 

on the mercury itself, but is nearby. The member of the public is the closest offsite individual. The 

locations of the nearest site boundary for each alternative site are shown in Table D–20. 

Table D–20. Distance to Closest Site Boundary at Mercury Storage Locations 

Site Distance Direction Notes 

Grand Junction Disposal Site

30 meters North and west Fence line 

Hanford Site (200 Areas)

3.5 kilometers West Washington State Route 240 

Hawthorne Army Depot

3.7 kilometers Southwest Site boundary 

Idaho National Laboratory (Idaho Nuclear Technology and Engineering Center)

13.4 kilometers South Site boundary 

U.S. Routes 20 and 26 

Idaho National Laboratory (Radioactive Waste Management Complex)

5.8 kilometers South Site boundary 

U.S. Routes 20 and 26 

Kansas City Plant 

100 meters South Site boundary 

Savannah River Site (E Area)

8 kilometers West South Carolina Highway 125 

Waste Control Specialists, LLC

67 meters East Fence line 

Note: To convert meters to feet, multiply by 3.281; kilometers to miles, by 0.6214. 

D.3.4.2 Benchmarks 

The following four benchmark quantities were used in the human health analysis: 

 Acute health effects among workers and members of the public exposed to concentrations of 

elemental mercury or inorganic mercury in air 

 Chronic health effects among workers exposed to concentrations of mercury in air 

 Chronic health effects among members of the public exposed to concentrations of mercury in air 

 Chronic health effects among members of the public exposed to mercury deposited on soil 
Human Health and Ecological Risk Assessment Analysis 

D–49

For a detailed discussion, see Section D.1.1.2. The benchmarks are summarized in Table D–3. 

D.4 EXPOSURE ASSESSMENT AND HUMAN RISK ANALYSIS 

This section describes the methods used to calculate the exposures to human receptors under each 

alternative and provides estimates of the magnitude of the consequences associated with each exposure 

scenario. Exposures are evaluated using modeled estimates of airborne concentration and deposited 

amounts per unit area at various receptor locations. These exposures are then compared with benchmarks 

to assess whether consequences are SL-I, -II, -III, or -IV. Finally, the frequency (FL-I, -II, -III, or -IV) of 

the exposure event is considered in conjunction with the consequences to reach a determination of risk 

(high, moderate, low, or negligible) to the receptor using Figure D–1. 

An important assumption in the following analysis is that elemental mercury would not be deposited on 

the ground either as a result of dry deposition or scavenging by rainfall (see Section D.7.3.3). 

However, in the event of a fire, it is conservatively assumed that all of the elemental mercury would be 

converted into divalent mercury. This material can deposit, (see Section D.7.3.3) thus dry and wet 

deposition calculations are included in the fire scenarios outlined below. 

D.4.1 Exposure During Normal Operating Conditions 

This pathway applies to any alternative or location in which the mercury is stored for an extended period 

of time. Exposures to involved workers could arise during normal operating conditions from small 

amounts of elemental mercury vapor escaping from storage containers or from residual contamination. 

Mercury vapor transported downwind could then be inhaled by noninvolved workers or members of the 

public. Because the mercury would escape as elemental mercury vapor, virtually no deposition of 

mercury would occur; therefore mercury inhalation is the only exposure route of concern. 

D.4.1.1 Involved Worker – Normal Operations 

It is assumed that, during normal operations, involved workers would never be exposed to airborne 

concentrations of mercury vapor above the ACGIH’s 8-hour TWA/TLV of 0.025 mg/m3

 of mercury 

vapor. This would be achieved by a combination of ventilation, inspection, monitoring, and use of 

personal protective equipment (PPE). The Interim Guidance explicitly states that the main requirement 

driving ventilation is to meet the ACGIH limit; in this context, for example, it recommends (but does not 

prescribe) a Storage Area ventilation system capable of 10 building air changes per hour, which would be 

run to ensure at least one building air change before workers enter the Storage Area. Similarly, the 

Interim Guidance describes the desirable features of ventilation systems in the Handling Area. 

In addition, the Interim Guidance provides advice about monitoring the air while workers are present in 

the mercury storage facility; it envisages the use of portable monitors, with due attention to calibration. 

Finally, if the airborne mercury concentration exceeds 0.025 mg/m3

, workers are to wear appropriate PPE 

with respiratory protection. 

Given the above assumptions about the operation of the facility, the concentrations to which the involved 

worker would be exposed would always be negligible during normal operations, and hence the associated 

human health risk would be negligible. 

It is pertinent to consider whether the historical record for DNSC sites has any information about airborne 

concentrations in the mercury storage buildings. One study of interest is that of mercury vapor 

monitoring at the Somerville, New Jersey, depot (Shim, Hsieh, and Watts 2002), where there has been 

mercury storage since 1957. These studies took place from September 17, 2001, through 

September 4, 2002, before, during, and after overpacking approximately 76,000 3-L flasks into drums. 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–50

Most flasks were stored in two cubicles in Warehouse 3E, while approximately 6,000 were stored in 

Warehouse 4E. The drums were subsequently stored partly in Warehouse 4E and partly in 

Warehouse 4D, which had not previously been used for mercury storage. 

The conditions in Warehouse 4D most closely approximate those that would likely be encountered in a 

new storage facility at one of the candidate sites. Prior to moving mercury into Warehouse 4D, measured 

concentrations were less than 2 × 10-6 mg/m3

 (less than 2 nanograms per cubic meter [ng/m3]). Once the 

drums had been moved into Warehouse 4D, monitoring over various periods from 2 days to a week 

produced an average concentration over all monitoring periods of 1.2 × 10-4 mg/m3

 and a peak of 

3.15 × 10-4 mg/m3

. The measurements were made with Lumex and Tekran mercury monitors. The 

Lumex records virtually instantaneous measurements of mercury concentration. The Tekran takes 

samples over periods that are typically a few minutes. 

By contrast, conditions in Warehouse 3E, Cubicle 1, were those pertaining to many decades of mercury 

storage. Before the overpacking operations, average measured concentrations over two periods of a few 

days each in August and September 2001 were 3.05 × 10-3 mg/m3

 and 1.90 × 10-3 mg/m3, respectively. 

During overpacking, concentrations reached approximately 0.01 mg/m3

 on January 10, 2002, and 

0.04 mg/m3

 on November 16, 2001. The latter figure exceeds the ACGIH’s 8-hour TWA/TLV of 

0.025 mg/m3

. However, this is not pertinent to the period of analysis at the proposed new storage facility 

because no large-scale overpacking is envisaged. Finally, after overpacking, the mercury was removed 

from Warehouse 3E, after which average mercury concentrations varied from approximately 

2.50 × 10-3 mg/m3

 to approximately 5.30 × 10-3 mg/m3 during four monitoring periods from February 

through May 2002. After this, average concentrations declined over a 2-month period to about 

2.00 × 10-3 mg/m3

, which appears to reflect a gradual venting of residual mercury. Sampling 

measurements as a function of height indicated that the residual contamination was on the floor. Similar 

results were obtained from monitoring in the other cubicle in Warehouse 3E, except that the peak postoverpacking concentrations were 2 to 3 times as high, up to approximately 0.013 mg/m3

, with a similar 

decline to about 2.00 × 10-3 mg/m3

 by the end of July 2002. Similar but considerably lower results were 

obtained in Warehouse 4E. 

In the proposed new storage facility, inspections on receipt for storage, and routine inspections during 

storage, would decrease the risk of residual contamination. Nevertheless, none of the measured 

concentrations from residual contamination (in contrast to those during overpacking) exceeded the 

ACGIH’s 8-hour TWA/TLV. 

Graney (2007) summarizes the measurements taken at the Somerville Depot and reports on other 

measurements taken at the Binghampton Depot (no longer used for mercury storage) and the Warren 

Depot. At the Warren Depot, for example, measurements taken with a Lumex monitor prior to 

overpacking in drums showed airborne concentrations inside the warehouse up to approximately 

9.00 × 10-5 mg/m3

. During overpacking, they rose to as much as 0.016 mg/m3. After overpacking, they 

remained as high as approximately 3.00–6.00 × 10-3 mg/m3

. However, floor cleaning reduced these 

concentrations by about a factor of 10. 

As noted above, the overall conclusion, based on measurements that are likely conservative for a new 

storage facility, is that there should be no difficulty in keeping both peak and average concentrations 

below the ACGIH’s TWA/TLV of 0.025 mg/m3

. In the context of the risk matrix, Figure D–1, this is 

considered a negligible concentration. Therefore the associated risk would be negligible. 

D.4.1.2 Noninvolved Worker and Public Receptor – Normal Operations 

Section D.2.3 explains that a leak of the full contents of a flask into a spill tray, which then remains 

undetected indefinitely, is taken as a surrogate scenario for the purposes of estimating impacts on 

noninvolved workers and the public during normal operations. Clearly, with the envisaged level of 
Human Health and Ecological Risk Assessment Analysis 

D–51

monitoring, it is virtually inconceivable that such a leak would go undetected, so this is a very 

conservative scenario. 

It is assumed that there is a steady state in which the evaporating mercury from the spill tray would leak 

from the storage building and mix into the turbulent building wake. The evaporation model for indoor 

spills of mercury is described in Section D.7.1.1, and the calculated evaporation rate is given in 

Table D–23. The building wake model is described in Section D.7.2.1. The building wake is a volume 

on the downwind side of a building in which turbulence generated by the building causes thorough 

mixing. Table D–23 shows that the predicted concentration in the wake of a newly constructed large 

building would be no more than approximately 2.0 × 10-5 mg/m3

, while Table D–24 shows that the 

building wake concentration would be no more than four times larger (i.e., 8.0 × 10-5 mg/m3

) in the wake 

of existing buildings at INL, Hawthorne Army Depot, KCP, or WCS. 

The appropriate concentration for comparison is EPA’s RfC of 3.0 × 10-4 mg/m3

, below which long-term 

concentrations are considered to be negligible. The noninvolved worker might actually be in the turbulent 

building wake. The public receptor would be further downwind, at which point even more dilution of the 

plume would have occurred. Therefore, for all sites, the predicted airborne concentrations encountered by 

the noninvolved worker and the public receptor would be negligible (SL-I), and the associated risks 

would be negligible. 

The above-referenced study by the New Jersey Institute of Technology (Shim, Hsieh, and Watts 2002) 

reports measurements of concentrations near the DNSC mercury storage warehouses. The average 

concentration observed prior to overpacking in drums was approximately 4.50 × 10-6 mg/m3

. The 

averages over successive periods of a few days during overpacking were 1.87 × 10-4 mg/m3

, 

2.65 × 10-5 mg/m3

, and 6.87 × 10-5 mg/m3, respectively. After overpacking, similar averages over three 

periods after the completion of overpacking were 9.67 × 10-6 mg/m3

, 5.10 × 10-6 mg/m3, and 

9.33 × 10-6 mg/m3

. These results are expected to be conservative for a new storage building and are 

generally consistent with the conservative predictions in the calculations reported above. 

Shim, Hsieh, and Watts also measured airborne concentrations of mercury at locations that are about a 

mile and a half (about 2.5 kilometers) from the DNSC mercury storage warehouses. These measurements 

were taken during nine separate periods of a few days to 3 weeks over a total period of about a year 

(September 2001 to September 2002). The average concentrations measured during these periods ranged 

from 1.48 to 3.74 × 10-6 mg/m3

, with an overall average of 2.59 × 10-6 mg/m3. Shim, Hsieh, and Watts

remarked that these readings are close to the global background level of 2.4 × 10-6 mg/m3, measured at a 

different site (the Perch River site) in upstate New York over a period of 2 years from July 1992 through 

July 1994. There were fluctuations, of course, depending on windspeed and wind direction, with a shortteam peak of 9.00 × 10-5 mg/m3

 measured during one episode of extremely low windspeed. However, 

this does not affect the conclusion that the average measured levels are well below EPA’s RfC of 

3.0 × 10-6 mg/m3

. 

Data on mercury concentrations are also available for Y–12 (Fortune 2007). The ambient air 

concentration downwind of the storage building has been continuously monitored since 1986 and 

averages 3.60 × 10-4 mg/m3

, again well below EPA’s RFC of 3.00 × 10-4 mg/m3. 

D.4.2 Onsite Accidents 

This section discusses the methods used to evaluate onsite accidents involving releases of mercury; it 

includes a simple spill and a spill occurring in conjunction with a fire. Concentrations are projected for a 

range of distances from the source of contamination and are thus applicable to any given storage location. 

Site-specific factors are provided when appropriate. 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–52

D.4.2.1 General Discussion of Types of Onsite Accidents 

For spills of elemental mercury with no fire, two physical phenomena act to mitigate the consequences. 

The vapor pressure of mercury at typical ambient temperatures is very low. According to NIST (Huber, 

Laesecke, and Friend 2006), the vapor pressure of mercury, converted to its saturated vapor density, is as 

shown in Table D–21. 

Table D–21. Saturated Vapor Density of Mercury as a 

Function of Temperature 

Temperature 

K oC oF 

Saturated Vapor 

Density (mg/m3

) 

273 0 32 2.38 

283 10 50 6.00 

293 20 68 14.09 

303 30 86 31.29 

313 40 104 65.88 

Key: K=Kelvin; °C=degrees Celsius; °F=degrees Fahrenheit; mg/m3=milligrams 

per cubic meter. 

For comparison, the benchmark for worker safety, the 1-hour AEGL-3 of 8.9 mg/m3 (see Table D–3), 

cannot be exceeded if the evaporating pool has a temperature of 289 Kelvin (K)/16 °C/61 °F or less. 

Even at a conservatively high temperature of 313 K/40 °C/104 °F, the mercury is already approximately 

five orders of magnitude more diluted than a pure elemental mercury vapor release. Hence, the further 

dilution required to bring the concentration down to the benchmarks such as the IDLH of 10 mg/m3

 or the 

60-minute AEGL-2 of 1.7 mg/m3

 considerably reduces predictions of distance beyond which the 

benchmarks are not exceeded (vis-à-vis point sources). 

With regard to conditions inside the storage building, the assumptions made for temperature of the 

evaporating pool are the same as those made in the MM EIS (DLA 2004a). Measurements taken at the 

Warren Depot from December 1999 through June 2000 showed that the highest temperature recorded 

inside the warehouse was 23 °C (74 °F). A more-limited set of readings from the New Haven Depot 

showed the highest recorded temperature of 24.5 °C (76 °F) during the period from September 1999 

through March 2000. The temperature assumed for the mercury evaporation model is 20 °C (68 °F), 

which is slightly lower than these readings for air temperature. Because mercury possesses a very large 

heat capacity, its temperature would lag behind that of the air in the warehouse. 

For releases of elemental mercury vapor, the dry deposition velocity and the rate of removal by rainfall 

are essentially zero (EPA 1997b). It is only during fire scenarios that elemental mercury is converted into 

forms that have non-zero dry deposition velocities or scavenging rates (see Section D.7.8.3). Therefore, 

for spills of elemental mercury, there is no need to be concerned about any pathways that result from 

deposition on the ground. Only predicted airborne concentrations are important. 

In Table D–22, there are five scenarios of more-than-negligible event frequency that involve the spill of 

mercury at ambient temperature inside the building—single-flask spill, single-pallet spill, triple-pallet 

spill, single 1-MT container spill, and earthquake spill (which also bounds other scenarios, such as high 

winds or tornadoes). 
Human Health and Ecological Risk Assessment Analysis 

D–53

Table D–22. Summary of Types of Accidents Considered in 

Onsite Spill Analysis 

Accident Scenario 

Could Occur 

Indoors? 

Could Occur 

Outdoors? 

Single-flask spill Yes No 

Single-pallet spill Yes Yes 

Triple-pallet spill Yes No 

1-metric-ton container spill Yes Yes 

Earthquake spill Yes Yes 

Evaporation inside the building is described in Section D.7.1.1 and is based on parameters such as vapor 

pressure and molecular weight, air velocity inside the building, pool temperature, and spill area. Spill 

area is estimated based on the amount of mercury spilled and physical constraints on how far the mercury 

can spread. As noted above, the representative scenarios inside the building are a single-flask spill, 

single-pallet spill, triple-pallet spill, 1-MT container spill, and earthquake spill. 

Some of these spills could potentially occur outside, but close to, the storage building. For example, a 

forklift could potentially drop a single pallet or 1-MT container on the loading dock. However, a triplepallet spill could only occur as a result of the collapse of a storage rack inside the building. Likewise, it is 

expected that single flasks would only be moved inside the building. 

Finally, if an earthquake occurs, the damage to the building could be such that the resulting spill of 

mercury remains essentially indoors, or the damage could be so severe that the spill could effectively be 

outside. The above discussion is summarized in Table D–23. 

D.4.2.2 Worker Inside Building (Involved Worker) – All Onsite Spill Scenarios, All Sites 

As described above, the saturated vapor density of mercury at the assumed release temperature of 20 °C 

(68 °F) is about 14 mg/m3

. This is only slightly above the assumed threshold for the worker, the SL-IV of 

8.9 mg/m3

 for an exposure of 1 hour.8 In practice, if there is a spill while a worker is present, that worker 

would leave the building rapidly. Therefore, in practice, the worker would be exposed to a toxic load 

much less than that accumulated in a half-hour’s exposure to SL-IV. If the worker moves rapidly, the 

equivalent toxic load could conceivably be in the SL-II (low) or even -I (very-low-to-negligible) 

frequencies range. 

Per Table D–17, the frequencies of all of the scenarios in Table D–22 are low (FL-II) or moderate 

(FL-III). Combining these frequencies with consequences in the SL-I to SL-II range gives a risk in the 

negligible-to-low range for the worker in the building at all sites. 

D.4.2.3 Predicted Concentrations in Building Wake – All Spill Scenarios 

New Construction 

Data for new facility construction at GJDS, Hanford’s 200-West Area, INL’s INTEC, SRS’s E Area, or 

WCS would be similar regardless of location. The generic storage building is expected to be 3 to 

6 meters (10 to 20 feet) high by 102 meters (336 feet) wide by 144 meters (471 feet) long. All nonbuoyant releases that occur inside the building or immediately adjacent to it would be mixed into the 

turbulent building wake. Table D–23 shows the predicted evaporation rates and concentrations in the 

building wake (where applicable) for the five scenarios listed in Table D–22. 

 

8

 See Section D.1.1.2.2 for the definitions of SLs for workers. 
Table D–23. New Construction, Predicted Evaporation Rates, and Concentrations in Building W

D–54

Scenario Mass Spilled (kg) Area (m2) Outdoors (O)/Stability Class or Indoors (I) Air Speed over Pool (m/s) Evaporation Rate (kg/s) Concen

in Bu

Wa

(kg/

I 0.1 6.66×10-9 9.96×

Single-flask spill 3.45×10 O/D 4.5 N/Aa N

1 7.11×10-1 O/F 1.5 N/Aa N

N/Ab 2.00 I 0.1 1.45×10-8 2.16×

O/D 4.5 N/Aa N

Full spill tray (slow release scenario) O/F 1.5 N/Aa N

I 0.1 1.23×10-7 1.85×

O/D 4.5 8.35×10-6 4.17

Single-pallet spill 1.69×103 3.48×101 O/F 1.5 2.93×10-6 4.39

I 0.1 2.81×10-7 4.21×

Triple-pallet spill 5.08×10 O/D 4.5 N/Aa N

3 1.04×102 O/F 1.5 N/Aa N

I 0.1 8.31×10-8 1.24×

O/D 4.5 1.74×10-6 8.68×

1-metric-ton container spill 1,000 2.06×101 O/F 1.5 4.86×10-7 7.28×

I 0.1c 2.76×10-5 4.13

O/D 4.5 7.98×10-4 N/

O/F 1.5 3.25×10-4 N/

N/A 4.5 N/Aa N

Earthquake – pool confined to building area N/Ab 1.50×104 N/A 1.5 N/Aa N

a These scenarios cannot occur outside the building. b Area limited, not mass limited. c Calculated with formula for evaporation in a turbulent flow because Reynolds number exceeds 320,000 (see Section D.8.1.1). d These scenarios assume that the building has collapsed, hence there is no building wake. 

Note: To convert kilograms to pounds, multiply by 2.2046; kg/m3 to mg/m3, by 106; square meters to square feet, by 10.7639; met

by 3.281. 

Key: kg=kilograms; m2=square meters; m/s=meters per second; kg/s=kilograms per second; kg/m3=kilograms per cub

mg/m3=milligrams per cubic meter; N/A=not available. 
Human Health and Ecological Risk Assessment Analysis 

D–55

Pertinent observations about Table D–23 are as follows: 

 A typical air speed over a spilled pool in a large building is about 0.1 meters per second (m/s) 

(see Section D.7.1.1), driven by natural convection. Generally, the flow is laminar, and the 

evaporation model (see Equation 7–1) is designed for laminar flow conditions. The exception is 

the earthquake scenario, where the evaporating pool is so large that the flow is turbulent and 

Equation 7–2, is used. 

 For all spills except the earthquake and the full spill tray, the pool is assumed to spread to the 

limit allowed by surface tension (the pool reaches the so-called “capillary depth,” which for 

mercury is 0.36 centimeters (0.14 inches); see Equation 7–4). 

 For the spill tray scenario, the surface area is limited by the dimensions of the spill tray itself, 

1.44 by 1.44 meters (56 by 56 inches); the area is approximately 2 square meters (22 square feet). 

 For the earthquake scenario in which the walls are still intact enough to confine the spill, the 

mercury would spread to occupy the floor area, in this case 15,000 square meters (approximately 

161,500 square feet). If the walls are not intact, then there is no building wake. See below for 

further discussion. 

 For indoor spills, the released mercury is assumed to leak from the storage building and be mixed 

into the building wake with a low windspeed of 1.5 m/s. This is low for almost all weather 

conditions and gives a conservative estimate of the concentration for most weather conditions 

(see Equation 7–9). 

 For outdoor spills, there are two calculations of building wake concentrations: in Atmospheric 

Stability Class D with a windspeed of 4.5 m/s and in Class F with a windspeed of 1.5 m/s. There 

are two countervailing tendencies here. The evaporation rate increases with increasing 

windspeed, whereas the building wake concentration is inversely proportional to windspeed. As 

can be seen in Table D–23, these effects tend to cancel out. 

For a noninvolved worker or a member of the public, the concentrations in Table D–23 should be 

compared with 0.1 × AEGL-2 (SL-II), which, for a duration of exposure of 1 hour, is 0.17 mg/m3

. All of 

the predicted concentrations in Table D–28 are below this benchmark, so the consequences to both onsite 

workers and members of the public would be in the SL-I (negligible-to-very-low) range. Hence, the 

corresponding risks would be negligible, per the risk matrix in Figure D–1. 

Implicit in the foregoing analysis is the assumption that the duration of release is no greater than 1 hour. 

It is assumed that emergency response to contain the release would be available in that time. It is also 

assumed that spills could and would be cleaned up sufficiently quickly to ensure that there are no chronic 

health effects from residual contamination or propagation into groundwater. 

Existing Buildings 

At some sites there are existing buildings with dimensions that differ from the proposed new construction. 

Data on these buildings are given in Table D–51. The different dimensions of these buildings primarily 

affect the floor area available for a spill to spread over (the area increases with increasing length and 

width) and the concentration in the building wake (inversely proportional to both width and height; see 

Equation 7–7). The dimensions of the existing buildings are repeated in Table D–24. As can be seen, the 

Hawthorne Army Depot and RWMC at INL would likely spread the storage among multiple buildings. 

The building at WCS is intended only to be an interim measure pending the construction of a new 

building. Y–12 is included because it is part of the No Action Alternative. 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–56 

Table D–24. Dimensions of Relevant Buildings 

Site 

Length 

(meters) 

Width 

(meters) 

Height 

(meters) 

Number of 

Buildings 

Floor Area 

(square 

meters) 

Building 

Wake 

Factor 

RWMC at Idaho National Laboratory 61 43 7 7 2,650×7 2.00 

Hawthorne Army Depot 61 15 11 29 947×29 3.84 

Kansas City Planta 154 154 32 1 24,000 0.42 

Container Storage Building at WCSb 58 51 8 1 3,000 1.41 

Y–12 National Security Complex 46 27 6 1 1,240 3.73 

New construction 145 103 6 1 15,000 1.00 

a The dimensions assumed for the existing building at Kansas City Plant are arbitrary and are much less than the actual dimensions of the 

building. The building wake factor is highly conservative. 

b This is for interim storage only. It is assumed that there would eventually be new construction at WCS. 

Note: To convert meters to feet, multiply by 3.281; square meters to square feet, by 10.7639. 

Key: RWMC=Radioactive Waste Management Complex; WCS=Waste Control Specialists, LLC. 

The last column shows by what factor the concentration in the building wake would change for existing 

buildings relative to the new construction. As can be seen, the greatest factor is just under 4 at Hawthorne 

Army Depot. Table D–25 explicitly displays the predicted concentrations in the building wake for the 

scenarios listed in Table D–23 (with the exception of the slow release from the spill tray). 

Table D–25. Building Wake Concentrations for New and Existing Buildings 

Concentration in Building Wake (kg/m3) 

Scenario 

Outdoors 

(O)/ 

Stability 

Class or 

Indoors 

(I) 

Air Speed 

over Pool 

(m/s) 

New 

Construction

Hawthorne 

Army Depot 

INL–

RWMC 

Kansas City 

Plant WCS–CSB 

Y–12 

National 

Security 

Complex 

Single-flask 

spill I only 0.1 9.96×10-12 3.83×10-11 1.99×10-

11 4.19×10-12 1.41×10-11 3.72×10-11

I 0.1 1.85×10-10 6.90×10-10 3.59×10-

10 7.54×10-11 2.54×10-10 6.71×10-10

O/D 4.5 4.17×10-9 1.60×10-8 8.33×10-

9 1.75×10-9 5.89×10-9

N/Aa Single-pallet 

spill 

O/F 1.5 4.39×10-9 1.68×10-8 8.77×10-

9 1.84×10-9 6.21×10-9

N/Aa

Triple-pallet 

spill I only 0.1 4.21×10-10 1.61×10-9 8.38×10-

10 1.76×10-10 5.93×10-10 1.56×10-9

I 0.1 1.24×10-10 4.77×10-10

2.48×10-

10 5.22×10-11 1.76×10-10 N/Ab

O/D 4.5 8.68×10-10 3.33×10-9 1.74×10-

9 3.65×10-10 1.23×10-9

N/Ab

1-metric-ton 

container spill 

O/F 1.5 7.28×10-10 2.79×10-9 1.46×10-

9 3.06×10-10 1.03×10-9

N/Ab

Earthquake – 

pool confined 

to building 

areac

I only 0.1 4.13×10-8 1.02×10-8d 1.48×10-

8d 2.82×10-8 8.75×10-9 5.57×10-9

a Under the No Action Alternative, no pallets would be moved outside the building at Y–12 National Security Complex. 

b There are no 1-metric-ton containers at Y–12 National Security Complex. 

c Earthquake spills “outside” occur when building collapses, hence there is no building wake. 

d For these multi-building sites, even though the earthquake is assumed to affect all of the buildings on the site, the concentration 

in the building wake cannot exceed that outside an individual building, where the rate of release of mercury is limited by the 

floor area of that building. 

Note: To convert meters to feet, multiply by 3.281; kg/m3

 to mg/m3, by 106. 

Key: CSB=Container Storage Building; INL=Idaho National Laboratory; kg/m3

=kilograms per cubic meter; m/s=meters per 

second; mg/m3

=milligrams per cubic meter; N/A=not applicable; RWMC=Radioactive Waste Management Complex; 

WCS=Waste Control Specialists, LLC. 
Human Health and Ecological Risk Assessment Analysis 

D–57

None of the predicted concentrations for existing buildings exceeds that for new construction by more 

than a factor of 4. All are lower than SL-II for noninvolved workers and the public. Therefore, the 

predicted concentrations would be negligible to very low and the risks from all onsite spills (with the 

exception of spills occurring during an earthquake with building collapse) would be negligible at all sites 

for both the noninvolved worker and the public. 

For outside spills, there is no difference between the involved worker and the noninvolved worker. 

D.4.2.4 Spill During an Earthquake with Building Collapse 

If the building collapses during an earthquake, the spilled mercury would evaporate as if in the open air. 

Section D.8.1.2 describes how the release rate is calculated in these circumstances. For a new building, 

that release rate in Atmospheric Stability Class D with a windspeed of 4.5 m/s is 7.98 × 10-4 kilograms 

per second (kg/s). This release rate (which is conservative for many of the weather conditions evaluated 

below) was input into a ground-level Gaussian dispersion model, which calculated downwind 

concentrations in a spectrum of weather conditions ranging from Classes A through F and in four discrete 

ranges of windspeed. The maximum predicted distances to consequence SLs II through IV (SL-II, -III, 

and -IV) are shown in Table D–26, which also displays the distances to the closest site boundary for each 

site, and, for those sites where the boundary is very close, the distance to the nearest public receptor. 

This calculation predicts that the maximum downwind distance from new construction to which a 

concentration could exceed SL-IV would be less than 100 meters (330 feet); SL-III could be exceeded to 

a distance of about 300 meters (980 feet); and SL-II could be exceeded to a distance of about 

1.1 kilometers (0.68 miles). There are similar results for existing buildings. These distances are shown in 

Table D–26. 

Consequences to the public would always be in the SL-I range for spills that occur during earthquakes at 

Hanford, Hawthorne Army Depot, INL, KCP, SRS, and Y–12 because concentrations above SL-I would 

not extend beyond the site boundary; the corresponding risks would be negligible. The same conclusion 

is valid for GJDS and WCS on the basis of the distance to the nearest residence. 

With respect to the involved and noninvolved worker, the reasoning here is much the same as it was for 

the involved worker inside the storage building (see Section D.4.2.2). The saturated vapor density of 

mercury at the assumed release temperature of 20 °C (68 °F) is approximately 14 mg/m3

. This is only 

slightly above the SL-IV of 8.9 mg/m3

. In practice, if there is a spill while a worker is present, that 

worker would be able to walk out of the cloud rapidly, in much less than the half-an-hour for which he or 

she could potentially be exposed to the SL-IV levels and still be able to escape. Therefore, in practice, 

the worker would be exposed to a toxic load much less than that accumulated in a half-hour’s exposure to 

concentrations above 8.9 mg/m3

 (AEGL-3) or 10 mg/m3 (IDLH). If the worker moves rapidly, the 

equivalent toxic load could conceivably be in the SL-II or even -I range. Therefore, combining these 

consequences with the moderate (FL-III) frequency of an earthquake gives a negligible-to-low risk to 

both involved workers and noninvolved workers. 

One also needs to consider the consequences to involved workers who are hit and injured by collapsing 

parts of the building. The worst case would be fatality. However, that is not a mercury-specific 

consequence and would be a widespread risk applying to all buildings on a site. From the perspective of 

mercury exposure, the worst case would be that of a worker who is injured or trapped and cannot walk 

away, as described in the previous paragraph. In the aftermath of an earthquake, such a worker may 

inhale mercury vapors for perhaps many hours before being rescued and thus may accumulate exposures 

in the SL-IV range. 

The frequency of a severe earthquake that could cause significant structural collapse of the storage 

building would be 4.0 × 10-4 per year. Based on projected personnel functions and time required to 

perform these activities, it is estimated that, on average, the equivalent of one worker would be in the 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–58 

Storage Area 8 hours per week for the purposes of inspections, monitoring, or movement of mercury that 

has been received. This correlates to 416 hours per year in which a worker could potentially be entrapped 

if a large earthquake were to occur. This is equivalent to a probability of 0.047 (416/8,760) that a worker 

would be in the building at a specific moment (e.g., when there is an earthquake). Data from an 

earthquake in Armenia show that the injury rate (as opposed to the death rate) for occupants in a one-story 

building is 4.2 percent (0.042) (Armenian et al. 1997). Conservatively assuming that all of these injuries 

coincide with being entrapped in debris within the building, the resulting probability would be 

7.9 × 10-7 per year (4.0 × 10-4 × 0.047 × 0.042), a frequency in the FL-I range. Thus, per Figure D–1, the 

risk of a worker being trapped in a collapsed building after an earthquake and being exposed to mercury 

in the SL-IV range would be negligible. 

Table D–26. Distances to the Closest Site Boundary or Public Receptor 

Compared with Calculated Distances – Outdoor Earthquake Scenario 

Predicted Distance (meters) 

Site Distance Direction Notes SL-II SL-III SL-IV 

GJDSa 30 meters North and west Fence line 1,140 290 <100 

Nearest resident to GJDS 4 kilometers away. 

Hanford Site 

(200 Areas)a

3.5 km West Site boundary 1,140 290 <100 

Hawthorne Army 

Depotb

3.7 km Southwest Site boundary 1,560 380 <100 

INL (INTEC)a 13.4 km South Site boundary 

U.S. Routes 20 and 26 1,140 290 <100 

INL (RWMC)b 5.8 km South Site boundary 

U.S. Routes 20 and 26 1,270 380 <100 

KCPc 350 meters South Site boundary 340 100 <100 

Nearest resident to KCP 350 meters away. 

SRS (E Area)a 8 km West South Carolina 

Highway 125 1,140 290 <100 

WCSa 67 meters East Fence line 1,140 290 <100 

Nearest resident to WCS 5.4 kilometers away. 

Y–12b 360 meters North Fence line 360 100 <100 

Nearest resident to Y–12 890 meters away. 

a New construction in predicted distances calculation. Rural site. 

b Existing building in predicted distances calculation. Rural site. 

c Existing building in predicted distances calculation. Urban site. 

Note: To convert meters to feet, multiply by 3.281; kilometers to miles, by 0.6214. 

Key: GJDS=Grand Junction Disposal Site; INL=Idaho National Laboratory; INTEC=Idaho Nuclear Technology and 

Engineering Center; KCP=Kansas City Plant; km=kilometers; RWMC=Radioactive Waste Management Complex; 

SL=severity level; SRS=Savannah River Site; WCS=Waste Control Specialists, LLC; Y–12=Y–12 National Security 

Complex. 

D.4.3 Offsite Accidental Transportation Spill of Mercury Without Fire 

There are two potential cases to be considered here: accidental spillage of mercury onto the ground and 

accidental spillage of mercury into a river or other water body. 
Human Health and Ecological Risk Assessment Analysis 

D–59

D.4.3.1 Spillage of Elemental Mercury Onto the Ground 

For exposures occurring via evaporation from a spill of elemental mercury with no fire during a 

transportation accident, the fraction of the mercury being carried by the truck or railcar that would be 

spilled is highly uncertain. It is extremely unlikely that all flasks or all 1-MT containers would be 

breached. However, to be conservative, it is assumed that such a catastrophic release could take place. 

The largest amount of mercury that can be carried in a truck or railcar is that contained in 54 1-MT 

containers. Assuming that all of this mercury is spilled and spreads until the pool is at its capillary depth 

(so conservative as to be essentially inconceivable in an outdoor spill), the predicted rate of evaporation 

given a windspeed of 4.5 m/s would be 7.35 × 10-5 kg/s. Running this through the Gaussian model and 

ranging over all possible combinations of atmospheric stability class and windspeed, the predicted 

maximum distances to the airborne toxic benchmarks for GJDS (for example) are as follows: SL-IV, less 

than 100 meters (330 feet); SL-III, about 100 meters (330 feet); and SL-II, about 340 meters (1,115 feet). 

As a result, a specific individual could not be exposed to concentrations that are greater than negligible if 

he or she lives more than about 340 meters (1,115 feet) from a crash. Conservatively, that specific 

individual could only be exposed above SL-I if the crash occurs along a 680-meter (2,230-foot) stretch of 

road, and then only if he or she lives by the roadside.9

 This is a small fraction of any of the routes. For 

GJDS, the average length of a truck trip is 2,000 kilometers (1,260 miles); 680 meters (2,230 feet) is 

approximately 0.00034 of this. The frequency of occurrence of a truck crash with spill on the routes to 

GJDS is 0.0031 per year; see Table D–13 (Scenario 2). The product of the function of the route and the 

frequency of the occurrence is approximately 1.1 × 10-6 per year, a low frequency. Under Truck 

Scenario 1 and the Railcar Scenario, the corresponding frequencies would be negligible. Therefore, the 

risk to an individual member of the public from transportation spills onto the ground en route to GJDS 

without a fire would be negligible under Truck Scenario 1 and the Railcar Scenario and low under Truck 

Scenario 2. The same results apply to all of the other sites. 

D.4.3.2 Spills of Elemental Mercury into Water Bodies 

It is conceivable that, during transportation, there could be a crash and a resulting spill of elemental 

mercury into a river or other body of water. The likelihood of this occurring is discussed in 

Section D.2.8. See Section D.5.4.2 for a discussion of how this might affect ecological receptors. 

Section D.5.4.2 makes the following conclusions regarding the consequences of the spillage of elemental 

mercury into a water body. In summary: 

 The available understanding of the behavior of elemental mercury spilled into a river or other 

water body is subject to great uncertainty so that an estimate of the consequences to humans (and 

ecological receptors) is not possible. 

 Should such a spillage occur, it appears that the processes that convert elemental mercury into 

forms that are potentially hazardous to humans (inorganic compounds of mercury and 

methylmercury) are slow and would allow ample time for cleanup. 

 If the spillage occurs onto the banks of a river or water body, but not directly into it, a study by 

Harris et al. (2007) appears to show that transportation to the water body would be slow, again 

allowing ample time for cleanup. 

The conclusion in the second bullet is questionable if the spill is into a fast-flowing river. 

The overall conclusion is that a direct spillage of mercury into a body of water could be of concern if it is 

not cleaned up, but that there is generally adequate time for such cleanup. Hence, the consequences to 

humans could be managed so that they would be negligible or low. Given this assumption and the fact 

 

9 The length of roadway on which a crash could occur and affect a specific individual is estimated by drawing a circle with a 340-meter 

(1,115-foot) radius centered on the individual. The relevant length of roadway is that which lies inside the circle. The maximum 

possible relevant length is two radii (i.e., 680 meters or 2,230 feet) if the individual lives immediately next to the roadway.
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–60 

that the frequency of crashes with spills on any of the transportation routes is no more than moderate (and 

this is an upper bound on the frequency of spills directly into water), the risk would be negligible or low 

for all transportation routes. However, this assessment should be tempered by nothing that there is a large 

range of uncertainty. 

D.4.4 Summary of Risks – All Mercury Spill Scenarios Without Fire 

Table D–27 summarizes the results of the foregoing analyses of spill scenarios. 

Table D–27. Summary of Risks of all Spill Scenarios Without Fire (Fixed Site and Transportation) 

Risk 

Scenario GJDS 

Hanfor

d Site 

Hawthorne 

Army Depot INL KCP SRS WCS 

No Action 

Alternative 

Spills Inside Buildinga

Involved worker N–L for all inside spills at all sites Y–12: N-L 

Other: Ub

Noninvolved Y–12: N 

worker 

N for all inside spills at all sites 

Other: Ub

Member of the Y–12: N 

public 

N for all inside spills at all sites 

Other: Ub

Spills Outside Building

Involved worker N–L for all outside spills at all sites Y–12: N 

Other: Ub

Noninvolved Y–12: N 

worker 

N–L for all outside spills at all sites 

Other: Ub

Member of the public 

1-metric-ton Y–12: N 

container spill N N N N N N N 

Other: Ub

Single-pallet spill Y–12: N 

N N N N N N N 

Other: Ub

Earthquake with Y–12: N 

building collapsec N N N N N N N 

Other: Ub

Spills During Transportation – Spills onto Ground 

Truck Scenario 1 N for members of the public for transportation to all sites by road or rail, both options Y–12: N/A 

(exposure of workers N/A for these scenarios). Other: Ub

Truck Scenario 2 L for members of the public for transportation to all sites by road or rail, both options Y–12: N/A 

(exposure of workers N/A for these scenarios). Other: Ub

Railcar Scenario N for members of the public for transportation to all sites by road or rail, both options Y–12: N/A 

(exposure of workers N/A for these scenarios). Other: Ub

Spills During Transportation – Spills into Water

Spills into water N–L for members of the public for transportation to all sites by road or rail, both options Y–12: N/A 

(exposure of workers N/A for this scenario). Dependent on the assumption that there is 

time for cleanup before significant conversion into forms (inorganic, methyl) to which 

receptors are more sensitive. Could be higher in circumstances in which cleanup may 

not be easy (e.g., a rapidly flowing river). 

Other: Ub

a The scenarios considered for inside spills are single flask, single pallet, triple pallet, 1-metric tons container (not applicable at Y–12 because there 

are no 1–MT containers at Y–12 under the No Action Alternative), full spill tray under a pallet, and earthquake with intact building walls. 

b “Other” means commercial sites that might be involved in the movement and storage of mercury under the No Action Alternative. For a 

qualitative discussion of the risks associated with these sites, see Section D.4.8.1. The risks depend on many unknown factors such as the 

standards of construction of storage buildings, the elemental mercury inventory, flammable materials in or near the storage building, distance 

to the nearest resident, and means of transportation to and from the site. Therefore, the risks are unknown and could be higher than those 

estimated for the proposed storage locations and Y–12. 

c This scenario bounds the risk from high winds and tornadoes. 

Key: GJDS=Grand Junction Disposal Site; INL=Idaho National Laboratory; KCP=Kansas City Plant; L=low; N=negligible; N/A=not applicable; 

SRS=Savannah River Site; U=unknown; WCS=Waste Control Specialists, LLC; Y–12=Y–12 National Security Complex. 
Human Health and Ecological Risk Assessment Analysis 

D–61

D.4.5 Accidental Offsite Transportation Fire 

Under the railcar or truck fire scenario, mercury is postulated to be released into the atmosphere and 

subsequently advection downwind. Table D–28 displays the parameters used as input to the atmospheric 

dispersion model for truck and railcar fires. Section D.7.4.1 explains how these parameters were chosen 

or calculated. 

The discussion of accidental offsite transportation fires only applies to the potential new storage locations 

and not to Y–12. 

Table D–28. Parameters for Estimating Emissions of Mercury 

During an Offsite Firea

Parameter Truck Fire Railcar Fire 

Windspeed (meters per second) (for conservatively 

calculating evaporation rate) 4.5 4.5 

Spill area (square meters) 35.7 41.6 

Fire area (square meters) 35.7 54.8 

Heat input (calories per second) 1.25×106 1.46×106

Duration of pallet fire/ 

mercury release (seconds) 762 1,308 

Release rate (milligrams per second), windspeed 

4.5 meters per second 1.3×106 1.6×106

Release rate (milligrams per second), windspeed 

1.5 meters per second 5.5×105 6.8×105

Plume rise (meters) 100 100 

0.1×AEGL-2 (kilograms per meter cubed) 2.44×10-7 2.51×10-7

AEGL-2 (kilograms per meter cubed) 2.94×10-6 2.51×10-6

AEGL-3 (kilograms per meter cubed) 1.52×10-5 1.3×10-5

a For further information on parameters, see Tables D–60, D–61 and D–62. 

Note: To convert meters to feet, multiply by 3.281, square meters to square feet, by 10.7639; cubic meters 

to cubic feet, by 35.3178; calories to joules, by 4.184; kilograms to pounds, by 2.2; and milligrams to 

ounces, by 0.00003527. 

The parameters presented in Table D–28 were used to calculate plume rise in a number of weather 

conditions, as shown in Table D–29. 

Table D–29. Predicted Plume Heights and Average Windspeeds for 

Truck and Railcar Crashes with Fires 

Atmospheric Truck Railcar 

Stability Class/ 

Windspeed 

(meters per 

second) 

Plume Height 

(meters) 

Average 

Windspeed 

(meters per second) 

Plume Height 

(meters) 

Average Windspeed

(meters per second) 

A/1.5 150 1.7 156 1.7 

B/3 322 3.6 345 3.6 

C/4.5 101 5.2 105 5.2 

D/4.5 99 5.5 103 5.5 

E/3 102 5.0 106 5.1 

F/1.5 271 5.9 287 6.1 

Note: See Section D.7.4 for a discussion of how these heights were calculated. To convert meters to feet, multiply by 3.281.
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–62 

Table D–29 shows that a plume rise of 100 meters (330 feet) is conservative for all weather conditions. 

To simplify the calculations, the plume rise is taken to be 100 meters for all weather conditions and for 

both truck and railcar fires. The foregoing assumptions also apply to the ecological risk analysis; see 

Section D.5. 

For the fire scenarios, for purposes of simplification, the Gaussian model calculations with dry and wet 

deposition were carried out in three weather conditions that are representative of the full range of weather 

conditions: 

 Atmospheric Stability Class A with a windspeed of 1.5 m/s, representative of conditions of low 

windspeed and high ambient thermally generated turbulence 

 Atmospheric Stability Class D with a windspeed of 4.5 m/s, representative of “average” weather 

conditions dominated by mechanically generated turbulence 

 Atmospheric Stability Class F with a windspeed of 1.5 m/s, representative of conditions with low 

ambient turbulence 

Human Exposure – Inhalation Pathway 

Calculations were performed in the three weather conditions to estimate how far downwind of the crash 

site concentrations in the severity bands SL-II, -III, and -IV might extend. The results are presented in 

Table D–30. 

Table D–30 shows that, to the extent that the three weather conditions are representative of all possible 

weather conditions, no individual along the transportation route could be exposed to a high airborne 

concentration of mercury. 

Table D–30. Predicted Range of Distances (meters) Downwind Within Which 

Acute Airborne Severity Levels Are Exceeded – Crashes with Fires 

Type of Accident 

Atmospheric 

Stability 

Class/Windspeed 

0.1×AEGL-2 

(SL-II) 

AEGL-2 

(SL-III) 

AEGL-3 

(SL-IV) 

A/1.5 m/s <100–2,600 160–700 Nowhere 

Truck crash D/4.5 m/s <100–16,000 Nowhere Nowhere 

F/1.5 m/s <100–40,000 600–1,300 Nowhere 

A/1.5 m/s <100–2,800 140–840 Nowhere 

Railcar crash D/4.5 m/s <100–20,000 700–2,300 Nowhere 

F/1.5 m/s <100–40,000 440–2,100 Nowhere 

Note: To convert meters to feet, multiply by 3.281. 

Key: <=less than; AEGL=Acute Exposure Guideline Level; m/s=meters per second; SL=severity level.

For truck or railcar scenarios (with pallet fires), a specific individual could not be exposed to 

concentrations that are above SL-III if he or she lives less than 2,300 meters (7,500 feet) from a crash 

(2,300 meters is taken as conservative for truck crashes). That specific individual could only be exposed 

above SL-II if the crash occurs along a 4,600-meter (15,000-foot) (4.6-kilometer [2.9-mile]) stretch of 

road, and then only if he or she lives by the roadside.10 This is a small fraction of any of the routes. The 

average length of a truck trip to GJDS, for example, is about 2,000 kilometers (1,260 miles), so 

4.6 kilometers (2.9 miles) is a very small fraction, 0.0023, of this. Under Truck Scenario 2, the frequency 

of occurrence of a truck crash with spill and fire in dry weather on the routes to GJDS would be 

 

10 The length of roadway on which a crash could occur and affect a specific individual is estimated by drawing a circle with a 

2,300-meter (7,500-foot) radius centered on the individual. The relevant length of roadway is that which lies inside the circle. 

The maximum possible relevant length is two radii (i.e., 4,600 meters [15,000 feet]) if the individual lives immediately 

adjacent to the roadway. 
Human Health and Ecological Risk Assessment Analysis 

D–63

0.00025 per year (see Table D–13). The product of the fraction of the route and the frequency of 

occurrence is about 5.8 × 10-7 per year, a negligible (FL-I) frequency. Thus, the risk of exposure above 

SL-III would also be negligible. This applies to Truck Scenarios 1 and 2, the Railcar Scenario, and 

transportation risks to all sites. 

For truck or railcar scenarios, a specific individual could be exposed to an SL-II airborne concentration of 

mercury over considerable distances. However, since no truck or rail route has more than a moderate 

frequency, the overall risk would be low for all transportation scenarios and all routes to all sites. Thus, 

by looking at the distances to which SL-III could be exceeded, the risks appear to be negligible. 

However, by looking at the distances to which SL-II could be exceeded, one sees that in fact the risks of 

all three transportation scenarios with wooden pallet fires would be low. 

The above discussion is summarized in Table D–31. 

Human Exposure—Inorganic Mercury Deposited on the Ground 

Humans can ingest mercury deposited on the ground (e.g., via plants). The chosen screening value is 

180 mg/kg (see Section D.1.1.2.6). The potential for exposure would be negligible if the level of 

deposited mercury is less than 180 mg/kg. The results of the analysis of all scenarios in all weather 

conditions show that these concentrations would never be exceeded, either by dry deposition or as a result 

of scavenging by rainfall. Therefore, the risks of exposure above the SL-II threshold would be negligible. 

Table D–31. Summary of Inhalation Risks to Human Receptors, 

Accidents with Fires in Dry Weather, All Sites 

Both Truck Scenarios Railcar Scenario 

Frequencya Moderate Low 

Consequenceb Low Low 

Risk Low Low 

a Frequencies of railcar or truck crashes with spills and fires from Tables D–12, D–13, and D–14.

b The highest consequence in any weather condition. 

D.4.6 Multiple Exposures 

The AEGLs are meant to be once-in-a-lifetime exposures since the health effects of mercury can be 

cumulative. The first question to be addressed is, how likely is it that there will be more than one 

accident of a specific type in the 40-year period of analysis that is assumed for this EIS. This is 

calculated by taking the mean number of accidents per year for a single accident (which essentially is the 

same as the frequency of the accident) and multiplying by 40 to get a mean number of accidents over 

40 years and inserting that product into a Poisson distribution.11 Using the Poisson distribution to 

calculate the probability of two accidents in 40 years gives the following: (a) annual frequency f = 10-2 per 

year – probability of two accidents in 40 years (P(2:40) = 5.36 × 10-2; (b) f = 10-3 per year – P(2:40) = 

7.69 × 10-4; (c) f = 10-4 per year – P(2:40) = 7.97 × 10-6; and (d) f = 10-5 per year – P(2:40) = 8.0 × 10-8. 

In addition, the frequency f for which the value of P(2:40) lies just below the FL-I/FL-II boundary of 10-6

per year is f = 3.5 × 10-5 per year. The following conclusions can be drawn from this analysis: 

 In the transportation analysis, no railcar accident with spill or with fire and spill has a predicted 

frequency greater than 3.0 × 10-5 per year; see Table D–14. Therefore, the probability of two 

spills in the 40-year period of analysis would be negligible and the associated risks arising from 

two spills would be negligible. 

 

11 For a more detailed discussion of the Poisson distribution, see Section D.2.7.2. 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–64 

 The frequency of truck accidents with spills is in the range 1.50 × 10-3 to 4.10 × 10-3; see 

Tables D–12 and D–13. Using the Poisson distribution, the corresponding values of P(2:40) are 

1.70 × 10-3 and 1.14 × 10-2 , respectively. Therefore, the question to be asked is, given that these 

two accidents occur, what is the probability that the same person will be affected by both? 

Referring to Table D–30: 

- No transportation accidents with fires can cause exposures to SL-IV concentrations 

- It is conceivable that two exposures in the SL-III range could add up to an exposure in the 

SL-IV range. Calculations similar to those reported in Table D–30 show that the 

concentrations greater than 0.5 × AEGL-3 do not extend more than 1,000 meters (3,300 feet) 

downwind. Using this information and factoring in the probability that the wind during the 

second crash would have to be blowing towards the specific human receptor brings the 

predicted frequencies into the FL-I (negligible range). 

- It is conceivable that two exposures in the SL-I range could add up to an exposure in the 

SL-II range. However, taking account of the fact that, even with the large ranges of up to 

40 kilometers (about 25 miles) shown in SL-II, the probability that the second crash will be 

close enough to a specific receptor to potentially expose that receptor, the frequency of two 

SL-I exposures would be no more than FL-II, which gives a low risk. 

 For onsite accident releases, all except those resulting from the earthquake with building collapse 

would mix into the building wake and produce concentrations that are less than half 

0.1 × AEGL-2; see Tables D–23 and D–25. Therefore, a double exposure would remain in the 

SL-I range and the corresponding risk would be negligible. 

 For the earthquake scenario with building collapse (f = 4 × 10-4 per year) the corresponding value 

of P(2:40) is 1.26 × 10-4 per year. A single earthquake exposure would never cause predicted 

concentrations to exceed the SL-II threshold. Conservatively assuming that two SL-I exposures 

would always exceed the SL-II threshold, in combination with the foregoing value of P(2:40), 

would lead to a low predicted risk. 

In conclusion, a conservative analysis shows that no risk to public receptors from two acute-inhalation 

exposures in 40 years would be greater than low. 

D.4.7 Fire – Intentional Destructive Act 

Section D.2.6 describes a fire caused by an IDA. The parameters needed for input into the atmospheric 

dispersion model are discussed in Section D.7.4.2, where it is explained that the railcar fire is a somewhat 

conservative bounding case for the truck fire. The results of the analyses have been calculated only for 

Atmospheric Stability Class D with a windspeed of 4.5 m/s and for Class F with a windspeed of 1.5 m/s, 

in accordance with DOE practice when meteorological data are not available for a site (actual 

meteorological data are available for some but not all sites). 

Human Exposure – Atmospheric Pathway 

Per Table D–63, the duration of release would be 10,660 seconds (approximately 3 hours). Interpolation 

in Table D–19 gives a corresponding AEGL-2 of 1 mg/m3

 (1.0 × 10-6 kg/m3) and an AEGL-3 of 

4.4 mg/m3

 (4.4 × 10-6 kg/m3). 

In Atmospheric Stability Class D conditions with a windspeed of 4.5 m/s, the thresholds for SL-IV 

(AEGL-3) and -III (AEGL-2) are not predicted to be exceeded anywhere. Concentrations in the SL-III 

range could occur out to about 34 kilometers (21 miles). 
Human Health and Ecological Risk Assessment Analysis 

D–65

In Atmospheric Stability Class F conditions with a windspeed of 1.5 m/s, SL-II concentrations exceeding 

0.1 × AEGL-2 could extend from less than 100 meters (330 feet) out to about 40 kilometers (25 miles). 

Concentrations exceeding AEGL-2 (SL-III) are predicted to extend from about 100 meters to about 

5.6 kilometers (3.5 miles) downwind of the point of release. Concentrations greater than the SL-IV 

threshold (AEGL-3) could occur in a “hot spot” extending from about 560 to 760 meters (1,800 to 

2,500 feet) downwind. 

Because frequencies are not assigned to IDA scenarios, it is not possible to match the above 

concentrations with corresponding estimates of risk. 

Human Exposure – Deposition Pathway 

The calculations predict that the threshold for SL-II (180 mg/kg) would not be exceeded anywhere. 

D.4.8 Risks Associated with the No Action Alternative 

The No Action Alternative would not provide a DOE-designated long-term storage facility for any excess 

elemental mercury. Excess mercury that could not be sold would be stored as a commodity to the extent 

allowed by law. Some mercury would likely be considered a waste and would be stored in accordance 

with law. Such storage would not necessarily occur at the sites identified as potential sources of excess 

mercury. This storage service might be provided by a commercial waste management company(ies). In 

addition, approximately 1,200 metric tons (1,330 tons) of DOE mercury would continue to be stored at 

Y–12. This DOE mercury is currently stored in approximately 35,000 3-L flasks. 

The analysis of risks associated with the No Action Alternative can be divided into two parts: 

 Risks associated with storage at commercial facilities, as outlined above. These risks are very 

hard to describe quantitatively because to do so would require a great deal of information that is 

not available at the time of writing. 

 Risks associated with the storage of DOE mercury at Y–12. These risks can be analyzed and 

characterized to the same level of detail as those for the candidate storage facilities. 

D.4.8.1 Risks Associated with Commercial Sites 

Many of the potential accident scenarios associated with the storage and movement of elemental mercury 

by commercial entities if DOE does not designate a long-term storage facility under the No Action 

Alternative would be the same as for transportation to and storage at one of the candidate sites. Thus, it is 

likely that mercury would be placed in 3-L flasks or 1-MT containers. Therefore, accidents involving the 

dropping of these or the dropping of pallets would be possible, both indoors and outdoors. Buildings 

would be vulnerable to external events, such as earthquakes, high winds, and aircraft crashes, among 

others. It is not known whether all buildings in which mercury would be stored or handled are designed 

to the same standards as the candidate storage facilities would be (for example, in their ability to resist 

earthquakes or high winds). The consequences of accidents involving severe damage to a building would 

depend on how much mercury is actually present in the building and where it is located relative to nearby 

populations; for example, it is conceivable that the distance to the fence line could be short and that there 

could be houses backing up to that fence line, in which case the risks could be higher than those predicted 

for the candidate storage buildings. 

Mercury would continue to be transported between various facilities. It seems likely that the total amount 

transported would be about the same as that used for analysis purposes in this EIS. However, what is not 

known is how much would be transported as full truck or railcar loads and how much as partial loads 

(e.g., one pallet or one 1-MT container on a truck). However, it would appear that the various 

transportation spills with fires that were analyzed for the candidate storage facilities would also be 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–66 

possible under the No Action Alternative, with concomitant, but currently unquantifiable, risks to human 

health and ecological receptors. 

The proposed action analyzed in this EIS is to implement the Mercury Export Ban Act by designating a 

Federal storage facility for elemental mercury. Based on Chapter 1, Table 1–1, the vast majority of 

mercury covered by this EIS would be generated by chlor-alkali facilities, R&R facilities and the goldmining industry. Under the No Action Alternative, this mercury would have to be stored indefinitely at 

multiple privately owned facilities. It could be argued that the biggest impact of No Action is widely 

dispersed storage. The potential benefit of the proposed action would be long-term DOE storage and 

management of this material as opposed to continued, dispersed storage by multiple private entities. 

D.4.8.2 Risks Associated with the Continuing Operation of Y–12 as an Elemental Mercury 

Storage Facility 

Some risks that pertain to candidate storage facilities do not apply to Y–12 under the No Action 

Alternative: 

 There would be no transportation to or from Y–12 under the No Action Alternative. Therefore, 

there would be no human health or ecological risks arising from transportation accidents. 

 There are no 1-MT containers at Y–12 and hence there would be no accidents involving such 

containers and no associated risks. 

 Flasks and pallets would not be handled outside the storage building. Hence, there could be no 

outside accidents involving these items, and no associated risk. 

Some risks at Y–12 are the same as or similar to those for the candidate storage facilities: 

 The analysis of the risk to the involved worker is the same as that in Section D.4.1.1 and shows 

that, given assumptions about ventilation, inspections, monitoring, and use of PPE, the 

concentrations to which the involved worker would be exposed would be less than the 8-hour 

ACGIH’s TWA/TLV of 0.025 mg/m3

. Hence, the associated risk would be negligible. 

 The analysis of a conservative scenario for leaks during normal operations (see Section D.4.1.2) 

shows that the predicted average long-term concentration in the building wake is approximately 

7.5 × 10-5 mg/m3

, less than EPA’s RfC of 3.0 × 10-4 mg/m3. Hence, predicted risks to 

noninvolved workers and public receptors at Y–12 would be negligible during normal operations. 

 The results of various indoor spillages at Y–12 are summarized in Table D–25, and show that 

predicted concentrations all lie in the SL-I range, which has negligible associated risk to 

noninvolved workers and members of the public, per Figure D–1. The analysis for involved 

workers shows that their risks would be in the low-to-negligible range. 

 The earthquake scenario at Y–12 with building collapse is analyzed in the same way as for the 

candidate storage facilities. Table D–26 shows that concentrations beyond the Y–12 fence line 

would lie in the SL-1 range with negligible associated risk. The risks to both involved and 

noninvolved workers would be low to negligible. 

In conclusion, continued operations of the mercury storage facility at Y–12 would pose negligible risk to 

members of the public and to ecological receptors, and at most low risk to involved and noninvolved 

workers. 
Human Health and Ecological Risk Assessment Analysis 

D–67

D.5 ECOLOGICAL RISK ASSESSMENT 

This ecological risk analysis focuses on a short list of receptors that are considered representative of those 

found along the transportation routes, including plants and soil invertebrates, terrestrial animals, and 

aquatic and sediment-dwelling biota. These representative receptors are listed below. 

 Plants 

 Soil invertebrates 

 The short-tailed shrew 

 The American robin 

 The red-tailed hawk 

 The great blue heron 

 The river otter 

 Aquatic biota 

 Sediment-dwelling (i.e., benthic) biota 

These ecological receptors are representative of species or communities that occur across a diversity of 

ecosystems present at alternative mercury storage sites and along routes to those sites. The representative 

ecological receptors exhibit sensitivity to mercury and other hazardous chemicals present in soil, 

sediment, surface water, or the food they eat (see Section D.5.1). Toxicological effects data 

(see Section D.5.2) and exposure information (see Section D.5.3) are available for the receptors, and 

individual receptor species or closely related and ecologically similar species are broadly distributed 

across the continent. Plants, earthworms, and sediment-dwelling invertebrates are an important 

component of the diets of many mammals, birds, and fish. Robins and shrews are mid-level predators 

exposed to contaminants in soil both directly by ingestion of soil and indirectly by ingestion of their 

mostly invertebrate soil-dwelling prey. Strictly herbivorous animals are not included as ecological 

receptors because bioaccumulation of mercury in plants is generally less than that in invertebrates; 

bioaccumulation of mercury and other hazardous chemicals in the food items of predators is a concern. 

Hawks and other birds of prey in terrestrial ecosystems are top predators that eat small mammals and 

birds. Herons and mustelids (e.g., mink, otter) are predators, feeding primarily on fish and other aquatic 

animals. These receptors represent the major exposure pathways for mercury in terrestrial and aquatic 

ecosystems and provide a common basis for comparing the potential adverse impacts of the alternatives 

being evaluated in this EIS.

Ecological consequences are evaluated using the same modeled concentrations as those presented in 

Section D.4. This section first provides a general description of potentially toxic effects on ecological 

receptors from exposure to mercury. Then, the TRVs for plants, earthworms, shrews, robins, hawks, 

aquatic biota, sediment-dwelling biota, river otters, and herons are derived for mercury. The derivation of 

the environmental-medium- and receptor-specific benchmarks based on the TRVs is discussed next. 

Finally, the results of the comparison of estimated concentrations of mercury in environmental media 

against the ecological benchmarks are presented. 

D.5.1 Mercury Ecotoxicity 

Soil and surface water may become contaminated by airborne releases of mercury. Because mercury 

deposited onto soil or into water bodies is persistent, chronic exposure to contaminated soil and water is 

assumed. This assumption is conservative for accidental releases because spills are likely to be mitigated 

by cleanup operations. Exposure to mercury by inhalation in air or suspended particles is assumed to be 

negligible, as explained in Section D.5.4.1. 

Elemental mercury released to the environment can be oxidized to divalent mercury through reactions 

with soil constituents. Elemental and divalent mercury under anaerobic conditions, such as in surface 

water and sediment, can be converted to methylmercury. Mercury that may be released to terrestrial 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–68 

systems is assumed to become divalent to some extent in the long term. Two percent of the mercury 

released to dry soil and 15 percent of the mercury released to wetland soil and sediment are assumed to 

convert to methylmercury (EPA 1999a). A partitioning equation was used to estimate the concentration 

of mercury leaching from sediment into the surface water. Any form of mercury released to aquatic 

systems is assumed to be a source of methylmercury, which is a conservative assumption because this is 

the most toxic form of mercury. Mercury investigations generally focus on aquatic rather than terrestrial 

ecosystems due to methylation and bioaccumulation of methylmercury in aquatic systems. Animals 

primarily associated with aquatic food chains accumulate more mercury than those associated with 

terrestrial food chains. Methylmercury biomagnifies in aquatic biota and, as a result, tends to occur at 

higher concentrations in higher trophic levels. Methylmercury is the most toxic form of mercury to birds, 

mammals, and aquatic organisms. 

Inorganic mercury accumulates to only a limited extent in plants and soil organisms and does not 

biomagnify in the organisms that feed on them. The effects of inorganic mercury on terrestrial receptors, 

according to EPA’s Mercury Study Report to Congress (EPA 1997a), are listed below. 

 In terrestrial plants, inorganic mercury can cause death as well as sublethal effects, such as 

decreased growth, root damage, hampered nutrient uptake, chlorophyll decline, and reduced 

photosynthesis. 

 Earthworms exhibit effects that range from toxicity to complete mortality when exposed to 

inorganic mercury. 

 In mammals, inorganic mercury is corrosive and may cause burning, irritation, salivation, 

vomiting, bloody diarrhea, upper gastrointestinal tract edema, abdominal pain, and hemorrhaging. 

Smaller animals are generally more susceptible to mercury poisoning than larger animals. 

 In birds, sublethal effects of inorganic mercury include liver damage, kidney damage, 

neurobehavioral effects, reduced food consumption, weight loss, spinal cord damage, effects on 

enzyme systems, reduced cardiovascular function, impaired immune response, reduced muscular 

coordination, impaired growth and development, altered blood and serum chemistry, and 

reproductive effects. 

The effects of methylmercury on aquatic receptors, according to EPA’s Mercury Study Report to

Congress (EPA 1997a), are listed below. 

 In aquatic plants, methylmercury can cause death, as well as sublethal effects such as premature 

aging, growth inhibition, decreased chlorophyll content, decreased protein and ribonucleic acid 

content, inhibited catalase and protease activities, inhibited and abnormal mitotic activity, 

increased free amino acid content, discoloration of floating leaves, and leaf and root necrosis. 

 The effects of methylmercury on fish include death, reduced reproduction, impaired growth and 

development, behavioral abnormalities, altered blood chemistry, impaired osmoregulation, 

reduced feeding rates and predatory success, and effects on oxygen exchange. The toxicity of 

methylmercury varies depending on the fish’s physiological and behavioral characteristics, and 

the methylmercury concentration tends to increase in aquatic organisms as the trophic level in 

aquatic food webs increases. 
Human Health and Ecological Risk Assessment Analysis 

D–69

D.5.2 Toxicity Reference Values 

The TRVs used to derive the environmental-medium- and receptor-specific benchmarks are discussed 

below. 

D.5.2.1 TRVs for Plants and Soil Invertebrates 

Published TRVs for plants and earthworms are predominantly lowest observed adverse effect level 

(LOAEL) values determined for soil amended with chemical solutions at different concentrations 

(Efroymson, Would, and Suter 1997; Efroymson et al. 1997). In most toxicity studies, no determination 

is made for the biological availability of the added constituents or of the total recoverable constituents 

(the type of information provided by the laboratory analysis of constituents in soil) in the test soil. 

Therefore, it is assumed that total recoverable constituents in soil found at the sites are 100 percent 

bioavailable and have the same toxicity as constituents added in laboratory toxicity tests. Mercury TRVs 

for plants and earthworms are presented in Table D–32. 

D.5.2.2 TRVs for Terrestrial Animals 

The methods for assessing the potentially toxic effects of mercury on terrestrial animals are based on the 

derivation of a TRV. The TRVs are derived to represent conservative estimates of the mercury doses (in 

milligrams per kilogram of body weight per day [mg/kg BW/day]) that, if exceeded when exposed to an 

environmental medium, may produce toxic effects in ecological receptors exposed to that medium. 

Literature toxicity data are used by establishing data selection criteria so that TRVs are as relevant to the 

unit assessment endpoints as possible. Furthermore, the conservatism of the TRVs is reinforced by using 

the lowest available, appropriate toxicity values and modifying them by uncertainty factors when 

necessary. Toxicity values used as the basis for the TRVs were selected as described below. The source 

for most toxicity values used as TRVs is Toxicological Benchmarks for Wildlife, 1996 Revision (Sample, 

Opresko, and Suter 1996). 

In an effort to address uncertainties up front in the ERA process, the preferred toxicity test endpoint is the 

lowest appropriate chronic observed adverse effect level (LOAEL) for nonlethal or reproductive effects. 

LOAELs are appropriate for evaluating the risk to nonthreatened and nonendangered receptor populations 

(Suter, Hall, and Sample 1994). When published LOAEL values are not available, LOAELs are 

estimated by multiplying published no observed adverse effects levels (NOAELs) by a factor of 10. If no 

NOAEL values are available, the next preferred form of toxicity data for use in deriving a TRV is an 

LD50 (median lethal dose) or an LC50 (median lethal concentration). Values based on chronic studies are 

preferred. Studies are considered to provide chronic toxicity data if conducted for a minimum duration of 

1 year in mammals, 10 weeks in birds (Sample, Opresko, and Suter 1996), or 7 days in fish or 

invertebrates. Studies shorter than 90 days in mammals, 18 days in birds, and 2 days in fish or 

invertebrates are considered acute. Studies longer than acute tests, but shorter than chronic tests, are 

considered subchronic. The derivation of mercury TRVs is shown for shrews, robins, hawks, river otters, 

and herons in Table D–32. 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–70 

Table D–32. Mercury Toxicity Reference Values for Ecological Receptors 

Receptor 

Form of 

Mercury 

Toxicity 

Reference Value 

Test 

Organism Toxic Endpoint Reference 

Inorganic 0.3 mg/kg soil Plants in soil Unspecified toxicity Efroymson, Would, and 

Suter 1997 

Plants 

Methyl None N/A N/A N/A 

Inorganic 0.1 mg/kg soil Octochaetus 

pattoni 

Survival and cocoon 

production 

Earthworms Efroymson et al. 1997 

Methyl 2.5 mg/kg soil Eisenia fetida Survival and regeneration of 

segments 

Efroymson et al. 1997 

Inorganic 27.7 mg/kg BW/day Mink Reproduction, estimated as 

NOAEL×10 

Sample, Opresko, and 

Suter 1996 

Short-tailed shrew 

Methyl 0.34 mg/kg BW/day Rat LOAEL for reproduction Sample, Opresko, and 

Suter 1996 

Inorganic 0.9 mg/kg BW/day Japanese quail LOAEL for reproduction Sample, Opresko, and 

Suter 1996 

American robin 

Methyl 0.064 mg/kg BW/day Mallard duck LOAEL for reproduction Sample, Opresko, and 

Suter 1996 

Inorganic 0.9 mg/kg BW/day Japanese quail LOAEL for reproduction Sample, Opresko, and 

Suter 1996 

Red-tailed hawk 

Methyl 0.064 mg/kg BW/day Mallard duck LOAEL for reproduction Sample, Opresko, and 

Suter 1996 

Inorganic 0.9 mg/kg BW/day Japanese quail LOAEL for reproduction Sample, Opresko, and 

Suter 1996 

Great blue heron 

Methyl 0.064 mg/kg BW/day Mallard duck LOAEL for reproduction Sample, Opresko, and 

Suter 1996 

Inorganic 5.8 mg/kg BW/day Mink Reproduction, estimated as 

NOAEL×10 

Sample, Opresko, and 

Suter 1996 River otter Methyl 0.015 mg/kg BW/day Mink LOAEL for mortality, weight 

loss, ataxia 

Sample, Opresko, and 

Suter 1996 

Inorganic 1.3 g/L Aquatic biota Tier II chronic value for 

inorganic mercury 

Aquatic biota Suter and Tsao 1996 

Methyl 0.0028 g/L Aquatic biota Tier II chronic value for 

methylmercury 

Suter and Tsao 1996 

Inorganic 0.15 mg/kg sediment Sedimentdwelling biota NOAA ER-L Jones, Suter, and 

Hull 1997 

Sediment-dwelling 

biota 

Methyl No toxicity reference 

value 

N/A N/A N/A 

Key: g/L=micrograms per liter; BW=body weight; LOAEL=lowest observed adverse effect level; mg/kg=milligrams per 

kilogram; N/A=not applicable; NOAA ER-L=National Oceanic and Atmospheric Administration Effects Range – Low; 

NOAEL=no observed adverse effects level. 

D.5.2.3 TRVs for Aquatic Biota 

For aquatic receptors, the preferred source of aquatic TRVs is Toxicological Benchmarks for Screening 

Potential Contaminants of Concern for Effects on Aquatic Biota: 1996 Revision (Suter and Tsao 1996). 

This document provides a compilation of aquatic toxicity values, including Federal ambient water quality 

criteria, derived Tier II values (secondary chronic and acute values), and chronic values from a variety of 

other governmental sources. Uncertainty factors (other than for use of a surrogate chemical) are not 

applied to TRVs from the above sources because the methods of their derivation already account for 

uncertainties. The preferred toxicity value for aquatic biota is the water quality criterion for mercury in 

freshwater. TRVs for inorganic and methylmercury are also presented in Table D–32. 

Sediment is also evaluated for potential toxicity to aquatic receptors. The preferred source of sediment 

TRVs is Toxicological Benchmarks for Screening Contaminants of Potential Concern for Effects on 

Sediment-Associated Biota: 1997 Revision (Jones, Suter, and Hull 1997). This document provides a 

compilation of sediment toxicity values, including EPA Sediment Quality Criteria for the Protection of 

Benthic Organisms, derived sediment quality benchmarks for nonionic organic chemicals based on 

equilibrium partitioning, Washington State sediment quality standards for some ionic organic compounds, 
Human Health and Ecological Risk Assessment Analysis 

D–71

National Oceanic and Atmospheric Administration values from Long and Morgan (1991) and Long et al. 

(1995), and values from other governmental sources. National Oceanic and Atmospheric Administration 

Effects Range – Low (NOAA ER-L) values were used as the preferred sediment TRV for mercury (Long 

and Morgan 1991). 

D.5.3 Ecologically Based Benchmarks for Mercury 

To expedite the evaluation of potential exposures, screening benchmarks for mercury in soil, surface 

water, and sediment were derived. For soil, the exposure dose was set equal to the TRV for each 

terrestrial receptor. Then the exposure equation was solved for the soil concentration, which became the 

soil screening value for each receptor. This procedure also was completed for exposure of river otters and 

great blue herons to mercury in surface water and sediment. 

As previously discussed, concentrations in environmental media were calculated to determine screening 

benchmarks resulting in a Hazard Quotient of 1 for each type of terrestrial receptor (lower trophic level 

and higher trophic level). The equations presented in the following sections were used to establish the 

screening benchmarks for the receptors exposed to soil, surface water, and sediment; these are presented 

in Tables D–33 (inorganic mercury) and D–34 (methylmercury). 
D–72

Table D–33. Ecological Screening Values for Inorganic Mercury 

Ecological Receptor, 

Pathway 

TRVa

(mg/kg BW/day) SPb

Ipc

(kg/day) 

BAFinv

d BCFe

Iaf

(kg/day) BAFmammg

Ish

(kg/day) 

Iwi

(L/day) 

BWj

(kg) 

Plants 0.3 N/A N/A N/A N/A N/A N/A N/A N/A N/A Soil invertebrates 0.1 N/A N/A N/A N/A N/A N/A N/A N/A N/A Short-tailed shrew 27.7 0.18 0.0012 0.34 N/A 0.008 13 0.0012 N/A 0.01

7 

American robin 0.9 0.04 0.061 0.34 N/A 0.061 13 0.013 N/A 0.08

0 

Red-tailed hawk 0.9 N/A 0 N/A N/A 0.124 13 0 N/A 1.13 Great blue heron, sediment 

0.9 0.18 0 0.34 N/A 0.009 N/A 0 N/A 2.39 

Great blue heron, water 0.9 N/A N/A N/A 3,530 0.422 N/A N/A 0.045 2.39 River otter, sediment 5.8 0.18 0 0.34 N/A 0.0278 N/A 0 N/A 8.55 River otter, water 5.8 N/A N/A N/A 3,530 1.360 N/A N/A 0.69 8.55 Aquatic biota 1.3 N/A N/A N/A N/A N/A N/A N/A N/A N/A Sediment-dwelling biota 0.15 N/A N/A N/A N/A N/A NA N/A N/A N/A 

a Toxicity reference value in milligrams per kilogram of body weight per day. b Soil-to-plant transfer factor: to vegetative parts for shrews and herons; to reproductive parts for robins (Baes et al. 1984).c Ingestion rate of plant tissue in kilograms per day (EPA 1993). d Soil-to-soil invertebrate transfer factor (HAZWRAP 1994). e Water-to-tissue bioconcentration factor (EPA 1999a). f Ingestion rate of animal tissue in kilograms per day (EPA 1993). River otter sediment value is rounded for display. g Food-to-tissue uptake factor for mammals and birds (HAZWRAP 1994). h Ingestion rate of soil in kilograms per day (EPA 1993). i Ingestion rate of water in liters per day (EPA 1993). j Body weight in kilograms (EPA 1993). k Calculated by solving exposure equations for predicted concentration in soil, sediment, or surface water when the exposure dose equals the toxicity re

milligrams per kilogram or micrograms per liter.

Key: N/A=not applicable; UFF=unit foraging factor. 
D–73

Table D–34. Ecological Screening Values for Methylmercury 

Ecological 

Receptor, Pathway 

TRVa

(mg/kg BW/day) SPb

Ipc

(kg/day) BAFinvd BCFe

Iaf

(kg/day) BAFmammg

Ish

(kg/day) 

Iwi

(L/day) 

BW j

(kg) 

Plants N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A Soil invertebrates 2.5 N/A N/A N/A N/A N/A N/A N/A N/A N/A Short-tailed shrew 0.34 0.137 0.0012 8.50 N/A 0.008 13 0.0012 N/A 0.017 American robin 0.064 0.137 0.061 8.50 N/A 0.061 13 0.013 N/A 0.08 Red-tailed hawk 0.064 N/A 0 N/A N/A 0.124 13 0 N/A 1.13 Great blue heron, sediment 

0.064 0.18 0 8.50 N/A 0.0086 N/A 0 N/A 2.39 

Great blue heron, water 

0.064 N/A N/A N/A 11,168 0.422 N/A N/A 0.045 2.39 

River otter, sediment 

0.015 0.137 0 8.5 N/A 0.0278 N/A 0 N/A 8.55 

River otter, water 0.015 N/A N/A N/A 11,168 1.360 N/A N/A 0.69 8.55 Aquatic biota 0.0028 N/A N/A N/A N/A N/A N/A N/A N/A N/A Sediment-dwelling biota 

N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A 

a Toxicity reference value in milligrams per kilogram of body weight per day. b Soil-to-plant transfer factor: to vegetative parts for shrews and herons; to reproductive parts for robins (EPA 1999a). c Ingestion rate of plant tissue in kilograms per day (EPA 1993). d Soil-to-soil invertebrate transfer factor (EPA 1999a). e Water-to-tissue bioconcentration factor (EPA 1999a). f Ingestion rate of animal tissue in kilograms per day (EPA 1993). River otter sediment value is rounded for display. g Food-to-tissue uptake factor for mammals and birds (EPA 1999a). h Ingestion rate of soil in kilograms per day (EPA 1993). i Ingestion rate of water in liters per day (EPA 1993). j Body weight in kilograms (EPA 1993). k Calculated by solving exposure equations for predicted concentration in soil, sediment, or surface water when the exposure dose equals the toxicity 

in milligrams per kilogram or micrograms per liter.

Key: NA=not applicable; UFF=unit foraging factor. 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–74

D.5.3.1 Lower-Trophic-Level Receptors (Short-Tailed Shrews and American Robins) 

The concentration of mercury in soil corresponding to the mercury soil screening benchmark for lowertrophic-level receptors (shrews, robins) is back-calculated from each receptor’s soil exposure dose 

(EDsoil), where EDsoil equals the TRV, i.e., Hazard Quotient = 1. The soil benchmark concentration 

(Csoi l) is calculated by dividing the benchmark daily dose (in milligrams of constituent per day) by the 

daily rate of ingestion of the constituent (mercury) for all types of material ingested, where the rate is 

given on the basis of per unit of the constituent in soil (in kilograms of soil per day). That is, 

(BW*EDsoil) Csoil = [(SP*Ip) + (BAFinv*Ia) + (Isoil*ST)] (5–1)

where: 

Csoil = Predicted concentration in soil (mg/kg) 

BW = Body weight (kg) 

EDsoil = Soil exposure dose for terrestrial receptor (mg/kg/day) 

SP = Soil-to-plant uptake factor (kg soil/kg plant); SPv for shrews and SPr for robins 

Ip = Receptor-specific ingestion rate of plant material (kg/day) 

BAFinv = Constituent-specific bioaccumulation factor for transfer from soil to invertebrate 

tissue (kg soil/kg tissue) 

Ia = Receptor-specific ingestion rate of animal material (kg/day) 

Isoil = Receptor-specific ingestion rate of soil (kg/day) 

ST = Bioavailability factor for constituents ingested in soil (assumed to be 1.0 for all 

constituents and receptors) 

Each component of the sum in the denominator of this ratio, when multiplied by the soil concentration, 

gives the daily dose of the constituent to the receptor (in milligrams per day) from ingesting that material 

type. This assumes that all of the constituent in the ingested material comes directly or indirectly from 

soil. The material types ingested by each receptor and the relevant bioaccumulation factors are defined 

by the parameters with non-zero values in Tables D–33 and D–34. 

D.5.3.2 Terrestrial Higher-Trophic-Level Receptors (Hawks) 

The concentration of mercury in soil corresponding to the mercury soil screening benchmark for 

terrestrial higher-trophic-level receptors (hawks) is back-calculated from the receptor’s soil exposure dose 

(EDsoil), where EDsoil equals the TRV, i.e., Hazard Quotient = 1. In the case of the higher-trophic-level 

receptor, all soil exposure is through the prey (shrew). The dose to the hawk is calculated by multiplying 

the hawk’s ingestion rate by the concentration of the constituent (mercury) in its prey, the shrew, and the 

unit foraging factor (UFF). The UFF is required for the hawk because its home range is larger than the 

areas assumed to be impacted by accidental releases of mercury. The concentration of the constituent in 

shrews is calculated from the animal-to-animal bioaccumulation factor (BAFmammal) and the 

concentrations in the diet of shrews weighted by the relevant fraction of the daily rate of ingestion of 

shrews, where the rates are given on the basis of per unit of the constituent in soil (in kilograms of soil per 

day). The concentration in each type of food ingested by shrews is the product of the appropriate transfer 

or bioaccumulation factor and the soil benchmark concentration. The dose equation for the hawk 

ingesting shrews is rearranged to calculate soil benchmark concentration (Csoil). 
Human Health and Ecological Risk Assessment Analysis 

That is, 

(EDsoil*IRshrew*BW) 

C (BAFmammal*Ia(hawk)*UFF) soil = 

[(SPv*Ip(shrew))+(BAFinv*Ia(shrew))+(Isoil*ST)] 

(5–2)

where: 

Csoil = Predicted concentration in soil (mg/kg) 

EDsoil = Soil exposure dose for terrestrial receptor (mg/kg/day) 

IRshrew = Total food and soil ingestion rate by the shrew (kg/day) 

BW = Body weight (kg) 

BAFmammal = Bioaccumulation factor of constituent ingested by the shrew (kg food/kg tissue)

13 for mercury 

, 

(BAFinv*Ia)+(Ised*ST)] 

Ia(hawk) = Ingestion rate of animal material by the hawk (kg/day) 

UFF = Unit foraging factor (unitless) 

SPv = Soil-to-plant uptake factor (kg soil/kg plant) 

Ip(shrew) = Ingestion rate of plant material by the shrew (kg/day) 

BAFinv = Constituent-specific bioaccumulation factor for transfer from soil to invertebrate 

tissue (kg soil/kg/tissue) 

Ia(shrew) = Ingestion rate of animal material by the shrew (kg/day) 

Isoil = Ingestion rate of soil (kg/day) by the shrew 

ST = Bioavailability factor for constituents ingested in soil (assumed to be 1.0 for all 

constituents and receptors) 

Each component of the sum in the denominator of this ratio, when multiplied by the soil concentration, 

gives the daily dose of the constituent to the prey and thus the receptor (in milligrams per day) from 

ingesting that material type. This assumes that all of the constituent in the ingested material comes 

directly or indirectly from soil. The material types ingested by each receptor and the relevant 

bioaccumulation factors are defined by the parameters with non-zero values in Tables D–33 and D–34. 

D.5.3.3 Terrestrial Semi-Aquatic Receptors (Great Blue Heron and River Otter) Exposed to 

Sediment 

The concentration of mercury in sediment corresponding to the mercury sediment screening benchmark 

for terrestrial semi-aquatic receptors (great blue heron and river otter) is back-calculated from each 

receptor’s sediment exposure dose (EDsed), where EDsed equals the TRV, i.e., Hazard Quotient = 1. The 

sediment benchmark concentration (Csed) is calculated by dividing the benchmark daily dose (in 

milligrams of constituent per day) by the daily rate of ingestion of the constituent (mercury) for all types 

of material ingested, where the rate is given on the basis of per unit of the constituent in sediment (in 

kilograms of sediment per day). That is, 

(BW*EDsed) 

Csed = [(SP*Ip) + (5–3)

where: 

 in sediment (mg/kg) 

r (mg/kg/day) 

ay) 

Csed = Predicted concentration

BW = Body weight (kg) 

EDsed = Sediment exposure dose for terrestrial recepto

SP = Soil-to-plant uptake factor (kg soil/kg plant) 

Ip = Receptor-specific ingestion rate of plant material (kg/d

D–75
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–76

BAFinv 

nimal material (kg/day) 

ST = r for constituents ingested in sediment (assumed to be 1.0 for all 

forms of mercury) 

nt 

bioaccumulation factors are defined by the parameters with non-zero values in Tables D–33 and D–34. 

D.5.3.4 i-Aquatic Receptors (Great Blue Heron and River Otter) Exposed to 

Surface Water 

 on the basis of per unit of the constituent in 

surface water (in liters of surface water per day). That is, 

Csw = [Isw+(BCF*Ia)] (5–4)

= Constituent-specific bioaccumulation factor (unitless) 

Ia = Receptor-specific ingestion rate of sediment-dwelling a

Ised = Receptor-specific ingestion rate of sediment (kg/day) 

Bioavailability facto

Each component of the sum in the denominator of this ratio, when multiplied by the sediment 

concentration, gives the daily dose of the constituent to the receptor (in milligrams per day) from 

ingesting that material type. This assumes that all of the constituent in the ingested material comes 

directly or indirectly from sediment. The material types ingested by each receptor and the releva

Terrestrial Sem

The concentration of mercury in surface water corresponding to the mercury surface-water screening 

benchmark for terrestrial semi-aquatic receptors (great blue heron and river otter) is back-calculated from 

each receptor’s surface-water exposure dose (EDsw), where EDsw equals the TRV, i.e., Hazard 

Quotient = 1. The surface-water benchmark concentration (Csw) is calculated by dividing the benchmark 

daily dose (in milligrams of constituent per day) by the daily rate of ingestion of the constituent (mercury) 

for all types of material ingested, where the rate is given

(BW*EDsw) 

where: 

 in surface water (milligrams/liter) 

ay) 

F or prey (liters/kilogram) 

I = Receptor-specific ingestion rate of animal material (kg/day) 

t 

bioaccumulation factors are defined by the parameters with non-zero values in Tables D–33 and D–34. 

D.5.3.5 Conversion of Ecological Screening Values to Equivalent Deposited Screening Values 

ides equivalent deposited screening values for the ecological screening values 

in Tables D–33 and D–34. 

Csw = Predicted concentration

BW = Body weight (kg) 

EDsw = Surface-water exposure dose for terrestrial receptor (mg/kg/d

Isw = Receptor-specific ingestion rate of surface water (liters/day) 

BC = Constituent-specific water-to-tissue bioconcentration factor f

a

Each component of the sum in the denominator of this ratio, when multiplied by the surface-water 

concentration, gives the daily dose of the constituent to the receptor (in milligrams per day) from 

ingesting that material type. This assumes that all of the constituent in the ingested material comes 

directly or indirectly from surface water. The material types ingested by each receptor and the relevan

The output of the atmospheric dispersion model provides airborne concentrations in kg/m3

 and amounts 

of deposited mercury in kg/m2

. For ease of comparison with these outputs, the ecological screening 

values can be converted into equivalent levels of deposited mercury (independent of the mercury release 

scenario). Table D–35 prov
Human Health and Ecological Risk Assessment Analysis 

D–77

Table D–35. Equivalent Deposited Screening Value 

Ecological Receptor, 

Pathway Form of Mercury 

Screening 

Value (mg/kg 

or μg/L) 

Equivalent 

Deposited 

Screening Value 

(kg/m2

) 

Plants Inorganic mercury 3.00×10-1 2.76×10-5

Soil invertebrates Inorganic mercury 1.00×10-1 9.18×10-6

Short-tailed shrew Inorganic mercury 1.10×102 1.01×10-2

River otter, sediment Inorganic mercury 2.00 2.23×10-1

River otter, water Inorganic mercury 1.62×103 2.67×10-1

American robin Inorganic mercury 7.36×102 1.84×10-4

Red-tailed hawk Inorganic mercury 1.40 1.49×10-1

Great blue heron, sediment Inorganic mercury 5.26×103 3.12×10-2

Great blue heron, water Inorganic mercury 1.03×101 3.61×10-2

Aquatic biota Inorganic mercury 1.30 3.36×10-2

Sediment-dwelling biota Inorganic mercury 1.50×10-1 6.35×10-6

Plants Methylmercury None None 

Soil invertebrates Methylmercury 2.50 1.13×10-2

Short-tailed shrew Methylmercury 8.00×10-2 3.60×10-4

River otter, sediment Methylmercury 1.00×10-2 1.31×10-4

River otter, water Methylmercury 6.86 7.78×10-4

American robin Methylmercury 2.09 4.50×10-5

Red-tailed hawk Methylmercury 3.20×10-2 3.09×10-2

Great blue heron, sediment Methylmercury 5.40×10-1 5.02×10-4

Great blue heron, water Methylmercury 8.00×10-3 3.11×10-3

Aquatic biota Methylmercury 2.80×10-3 2.72×10-4

Sediment-dwelling biota Methylmercury None None 

Key: mg/kg=milligrams per kilogram; μg/L=micrograms per liter; kg/m2=kilograms per square meter. 

D.5.4 Ecological Risk Analysis 

This section presents the estimated ecological health consequences associated with each of the release 

scenarios for the alternative sites. These consequences are characterized by comparing the screening 

values (or equivalent deposited screening values) with the output of the atmospheric dispersion 

calculations. 

Ecological consequences were also evaluated by considering the ratio of the exposure concentration to 

benchmarks for ecological receptors. A qualitative indication of the overall significance of the effect on 

an ecological receptor was taken from the MM EIS (DLA 2004a) to describe this ratio. If the calculated 

ratio is 20 or higher, a consequence level of SL-IV is assigned; between 10 and 20, SL-III; between 1 and 

10, SL-II; and below 1, SL-I (negligible); see Table D–3. These assignments are subsequently applied to 

the risk matrix presented in Figure D–1. 

D.5.4.1 Slow Leaks, Accidental Spills at Storage Sites, and Spills Without Fires During 

Transportation 

This section applies to all spills of elemental mercury except those directly into water 

(see Section D.5.4.2). The analysis applies to all sites because there are no site-specific differences in the 

way spilled mercury would behave. Ecological risks associated with slow leaks during normal operations 

and accidental spills arise from the escape of mercury vapors from the containers during storage and 

handling. Generally, the release of liquid mercury results in its subsequent volatilization into the 

atmosphere in the form of elemental mercury vapor. The ingestion of soil contaminated with mercury 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–78

represents the greatest inorganic plausible long-term threat from mercury releases. As discussed in 

Section D.7.3.3, deposition of airborne inorganic mercury is the primary mechanism of soil 

contamination. However, elemental mercury is not subject to significant atmospheric deposition, unlike 

compounds containing divalent mercury. Although mercury vapor transported downwind could then be 

inhaled by ecological receptors at the site or nearby, the inhalation exposure route is generally 

insignificant relative to the major exposure pathway (i.e., ingestion) for ecological receptors. 

Given the dispersion of mercury upon leaving the storage facility, exposures to ecological receptors 

would be minimal at most. As a result, risks to ecological receptors from slow leaks, accidental spills at 

storage sites, and spills without fires during transportation (other than spills directly into a water body) are 

considered to be negligible at all storage sites and along all transportation routes. 

D.5.4.2 Spills of Elemental Mercury into Water Bodies 

It is conceivable that, during transportation, there could be a crash and a resulting spill of elemental 

mercury into a river or other body of water. The likelihood of this occurring is discussed in 

Section D.2.7. For ecological receptors in the water bodies or underlying sediment, the severity of the 

consequences depends on how much of the elemental mercury is converted into inorganic or 

methylmercury. The following discussion of this topic relies heavily on a study by Pfister (1977). 

Oxidation of elemental mercury to divalent mercury ions can and has been shown experimentally to occur 

under conditions present at the bottoms of lakes and rivers. Despite the fact that most inorganic mercury 

is found in association with suspended solids or immobilized in the sediment and does not often exist in 

hazardous concentrations in solution, it serves as a ready reservoir for alteration by microorganisms (see 

also Holm and Cox 1975). Investigations have shown that inorganic mercury, whether discharged 

initially in this state or chemically oxidized from elemental mercury, is methylated in waters and natural 

sediments by bacteria under anaerobic conditions, be it enzymatically, as with the methanogenic bacteria, 

or non-enzymatically via the transfer of methyl groups from cobalt to mercury in biological systems. 

Methylation also occurs in the top layer of sediments if they are continuously oxygenated. From 

experimental data, it appears that all forms of mercury may be converted directly or indirectly to either 

mono- or dimethylmercury. Not surprisingly, the transformation rate varies as a function of pH, type of 

bacteria, initial concentration, amount of sunlight, organic sediment index, etc. Much inorganic mercury 

is sequestered in sediments but can then be transformed into methylmercury by bacteria. 

Holm and Cox (1975) found that no methylmercury (less than 0.6 μg/L) was formed over 48 hours in 

pure cultures of bacteria with elemental mercury added, although mercury was oxidized (but not 

recovered as mercuric ion) and did accumulate in bacterial cells. 

A study on fish (Harris et al. 2007) concluded that mercury spilled away from a lake had less than 

1 percent exported to the lake and that a steady state was not reached in 3 years. 

The following conclusions were made regarding spills into water bodies: 

 There is insufficient knowledge to perform a calculation of the risks arising from the direct 

spillage of elemental mercury into a water body. 

 Should such a spillage occur, it appears that the processes that convert elemental mercury into 

forms that are potentially hazardous to ecological receptors are slow and would allow ample time 

for cleanup. 

 If the spillage occurs onto the banks of a river or water body, but not directly into it, the study by 

Harris et al. (2007) appears to show that transportation to the water body would be slow, again 

allowing ample time for cleanup. 
Human Health and Ecological Risk Assessment Analysis 

D–79

However, the conclusion in the second bullet is questionable if the spill is into a fast-flowing river. 

D.5.4.3 Transportation Spills with Fire 

Ecological risks associated with transportation spills with fires arise from inhalation of airborne mercury 

or deposition of inorganic mercury on soil, on wetland sediments, or into water bodies. Some of this 

mercury subsequently is converted to methylmercury. As discussed previously, the inhalation exposure 

route is generally insignificant relative to the major exposure pathway (i.e., ingestion). 

As described in Sections D.2 and D.4, this analysis assumes that the pallets transporting the 3-L flasks or 

the 1-MT containers are made of wood. The analysis has been performed for truck and rail 

transportation. 

D.5.4.3.1 Pallet Fires – Truck Transportation 

This section considers truck crashes with pallet fires in both dry conditions and wet conditions. 

Dry Deposition 

Table D–36 presents the calculated amount of mercury deposited per unit area by dry deposition after a 

truck crash with fire as a function of distance downwind for Atmospheric Stability Class A with a 

windspeed of 1.5 m/s. These ground-level values are characteristic of those for elevated releases, 

showing an initial rise, a peak, and a subsequent decline. Interspersed between the results are the 

equivalent deposited screening values from Table D–38 (including the screening value itself and 10× and 

20× that value) to show the expected downwind extent of SL-IV, -III, and -II for the various ecological 

receptors. The extent of SL-I is not provided because exposures to ecological receptors at that SL are 

predicted to be negligible. 

The first column provides the distances downwind at which calculations were performed. The second 

column contains predicted quantities of mercury deposited per square meter, interspersed with the 

screening values for specific ecological receptors. The maximum predicted deposited amount is 

approximately 1.85 × 10-4 kg/m2

 at approximately 300 meters (980 feet) downwind. The fourth column 

provides the name of the ecological receptor, while the third column specifies the exposure pathway 

(i.e., whether by ingestion of inorganic mercury or methylmercury) and the SL that corresponds to the 

value in the second column. 

The table should be read as follows: the first row contains SL-II for sediment-dwelling biota exposed via 

the ingestion of inorganic mercury. This SL (6.35 × 10-6 kg/m2

) is below any calculated quantity of 

deposited mercury, so sediment-dwelling biota could potentially be exposed to SL-II concentrations at the 

source of the fire. The deposited quantities of mercury are expected to remain above this level out to a 

distance of between 2,000 and 3,000 meters (6,600 to 9,800 feet), so the downwind extent of the area 

within which sediment-dwelling biota could be exposed above SL-II as a consequence of ingestion via the 

inorganic pathway is from 0 to approximately 3,000 meters (9,800 feet). Similarly, sediment-dwelling 

biota could be exposed to concentrations above SL-III from between 100 and 200 meters (330 and 

6,600 feet) to just over 500 meters (1,640 feet) downwind, and above SL-IV from just under 200 meters 

(660 feet) to just under 500 meters (1,640 feet) downwind. 

Table D–36. Comparison of Predicted Ground-Level Centerline Airborne 

Concentrations with Equivalent Deposited Screening Values – Atmospheric Stability 

Class A, Windspeed 1.5 m/s, Truck Spill with Pallet Fire, No Rain 

Distance 

Downwind 

(meters) 

Deposited 

Material 

(kg/m2

) 

Form of Mercury and 

Screening Value 

Ecological 

Receptor, Pathway 

6.35×10-6 Inorganic Hg SV – SL-II Sediment-dwelling biota 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–80

Distance 

Downwind 

(meters) 

Deposited 

Material 

(kg/m2

) 

Form of Mercury and 

Screening Value 

Ecological 

Receptor, Pathway 

25 6.57×10-6

50 8.20×10-6

9.18×10-6 Inorganic Hg SV – SL-II Soil invertebrates 

100 1.32×10-6

2.76×10-5 Inorganic Hg SV – SL-II Plants 

4.50×10-5 Methyl Hg SV – SL II American robin 

6.35×10-5 Inorganic Hg SV×10 – SL-III Sediment-dwelling biota 

9.18×10-5 Inorganic Hg SV×10 – SL-III Soil invertebrates 

1.27×10-4 Inorganic Hg SV×20 – SL-IV Sediment-dwelling biota 

1.31×10-4 Methyl Hg SV – SL-II Otter, sediment 

200 1.42×10-4

1.84×10-4 Inorganic Hg SV – SL-II American robin 

1.84×10-4 Inorganic Hg SV×20 – SL-IV Soil invertebrates 

300 1.85×10-4

1.84×10-4 Inorganic Hg SV×20 – SL-IV Soil invertebrates 

1.83×10-4 Inorganic Hg SV – SL-II American robin 

500 1.34×10-4

1.31×10-4 Methyl Hg SV – SL-II Otter, sediment 

1.27×10-4 Inorganic Hg SV×20 – SL-IV Sediment-dwelling biota 

9.18×10-5 Inorganic Hg SV×10 – SL-III Soil invertebrates 

700 8.55×10-5

6.35×10-5 Inorganic Hg SV×10 – SL-III Sediment-dwelling biota 

1,000 4.70×10-5

4.50×10-5 Methyl Hg SV – SL-II American robin 

2.756×10-5 Inorganic Hg SV – SL-II Plants 

2,000 1.26×10-5

9.18×10-6 Inorganic Hg SV – SL-II Soil invertebrates 

6.35×10-6 Inorganic Hg SV – SL-II Sediment-dwelling biota 

3,000 5.79×10-6

4,000 2.12×10-6

5,000 1.10×10-6

10,000 5.57×10-7

20,000 1.57×10-7

30,000 8.25×10-6

40,000 5.60×10-6

Note: To convert meters to feet, multiply by 3.281. 

Key: Hg=mercury; kg/m2

=kilograms per square meter; SL=severity level; SV=screening value.

The affected ranges for other ecological receptors can be read off Table D–36 in the same way. Note that 

soil invertebrates are the only receptor in addition to sediment-dwelling biota that could potentially be 

exposed above SL-IV. 

Some receptors in Table D–36 show exposures through both the inorganic mercury pathway and the 

methylmercury pathway. An example is the American robin. In this case, the potential for exposure via 

the methylmercury pathway is greater than that via the inorganic mercury pathway. Both are included in 

Table D–36 for illustrative purposes, but from here on only the most sensitive pathway is included when 

presenting potential ranges over which exposures may occur. 
Human Health and Ecological Risk Assessment Analysis 

D–81

Finally, some receptors do not appear on Table D–36 because their associated SLs are greater than the 

maximum calculated level of deposited mercury, 1.85 × 10-4 kg/m2

. They are listed in Table D–37. 

Table D–37. Equivalent Deposited Screening Values Exceeding the 

Maximum Calculated Value in Table D–39 

Ecological Receptor, 

Pathway Form of Mercury 

Equivalent 

Deposited 

Screening Value 

(kg/m2

) 

Short-tailed shrew Inorganic mercury 1.01×10-2

River otter, sediment Inorganic mercury 2.23×10-1

River otter, water Inorganic mercury 2.67×10-1

Red-tailed hawk Inorganic mercury 1.49×10-1

Great blue heron, sediment Inorganic mercury 3.12×10-2

Great blue heron, water Inorganic mercury 3.61×10-2

Aquatic biota Inorganic mercury 3.36×10-2

Plants Methylmercury None 

Soil invertebrates Methylmercury 1.13×10-2

Short-tailed shrew Methylmercury 3.60×10-4

River otter, water Methylmercury 7.78×10-4

Red-tailed hawk Methylmercury 3.09×10-2

Great blue heron, sediment Methylmercury 5.02×10-4

Great blue heron, water Methylmercury 3.11×10-3

Aquatic biota Methylmercury 2.72×10-4

Sediment-dwelling biota Methylmercury None 

Key: kg/m2=kilograms per square meter. 

Table D–38 summarizes Table D–36 in such a way that it is easy to see which screening values are never 

exceeded and which are exceeded. 

Table D–38 shows that, for a truck spill with a pallet fire in Atmospheric Stability Class A conditions 

with no rain and a windspeed of 1.5 m/s, the following conclusions can be made: 

 There are only two ecological receptors that could potentially be exposed to SL-IV 

concentrations: sediment-dwelling biota and soil invertebrates (both via inorganic mercury). 

 There are only two ecological receptors that could potentially be exposed to SL-III 

concentrations: sediment-dwelling biota and soil invertebrates (both via inorganic mercury). 

 There are four ecological receptors that could potentially be exposed to SL-II concentrations: the 

two in the preceding bullets and plants (via inorganic mercury), American robins (via 

methylmercury), and river otters (via methylmercury); American robins could also be exposed to 

low concentrations of inorganic mercury in addition to their potential low exposure to 

methylmercury. 

 No other ecological receptors could be exposed to greater-than-negligible deposited levels of 

mercury. 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–82

Table D–38. Summary of Potential Exposure of Receptors to Deposited Mercury at 

Severity Levels II, III, and IV– Atmospheric Stability Class A, 

Windspeed 1.5 m/s, Truck Spill with Pallet Fire, No Rain 

Distance Downwind to Which the Lower Bound of Severity 

Ecological Receptor, Pathway (Form of Levels is Exceeded (meters) 

Mercury) SL-II SL-III SL-IV 

Sediment-dwelling biota (inorganic mercury) 2,000–3,000 700–1,000 500–700 

Soil invertebrates (inorganic mercury) 2,000–3,000 500–700 300–500 

Plants (inorganic mercury) 1,000–2,000 

American robin (methylmercury) 1,000–2,000 

River otter, sediment (methylmercury) 500–700 

American robin (inorganic mercury) 300–500 

Aquatic biota (methylmercury) 

Short-tailed shrew (methylmercury) 

Great blue heron, sediment (methylmercury) 

River otter, water (methylmercury) 

Great blue heron, water (methylmercury) 

Short-tailed shrew (inorganic mercury) 

Soil invertebrates (methylmercury) 

Red-tailed hawk (methylmercury) 

Great blue heron, sediment (inorganic mercury) 

Aquatic biota (inorganic mercury) 

Great blue heron, water (inorganic mercury) 

Red-tailed hawk (inorganic mercury) 

River otter, sediment (inorganic mercury) 

River otter, water (inorganic mercury) 

Note: Shaded cells denote no exceedance of the appropriate screening value. The ranges presented in this table represent the 

furthest point downwind at which the corresponding equivalent deposited screening values are exceeded. See the upper half of 

Table D–39 for the distances where the screening values are first exceeded. To convert meters to feet, multiply by 3.281. 

Key: SL=severity level. 

The calculations reported in Table D–38 for Atmospheric Stability Class A with a windspeed of 1.5 m/s 

were repeated for Class D with a windspeed of 4.5 m/s and Class F with a windspeed of 1.5 m/s. The 

results are summarized in Table D–39. 

Table D–39 shows characteristic behavior for elevated releases. In Atmospheric Stability Class A 

conditions, the associated high degree of atmospheric turbulence brings mercury down to ground level 

quickly, but also dilutes the plume quickly. More receptors are affected than in the other two stability 

classes, but not for great distances. The results for Class F are strongly affected by the fact that the dry 

deposition velocity is an order of magnitude lower than it is in the other two weather conditions 

(see Table D–59). If the dry deposition velocity had been of the same order, many more receptors would 

have been affected. This leaves Class D as the intermediate one that does not dilute the plume as quickly 

as Class A, but also does not bring mercury down to ground level as quickly near the source, so that no 

receptors are affected in the range of 100 to 1,000 meters (330 to 3,300 feet). 

Table D–39 shows that, for a truck crash with a pallet fire but no rain, ecological receptors could be 

exposed to deposited mercury in the SL-IV and SL-III range, but over distances of no more than 

700 meters (2,300 feet), and then only in Atmospheric Stability Class A conditions. Similarly, it is only 

in Class A conditions that the river otter could be exposed to SL-II concentrations of deposited mercury 

out to about 700 meters (2,300 feet). In Classes D and F, ecological receptors are predicted to be exposed 

to deposited mercury in the SL-II range or lower. 
Human Health and Ecological Risk Assessment Analysis 

D–83

Table D–39. Summary of Potential Exposure of Receptors to Deposited Mercury at 

Severity Levels II, III, and IV – Truck Spill with Pallet Fire, No Rain 

Distance (meters) to Which 

Benchmark is Exceeded 

(Aa

, 1.5 m/sb) 

Distance (meters) to Which 

Benchmark is Exceeded 

(Da

, 4.5 m/sb) 

Distance (meters) to Which 

Benchmark is Exceeded 

(Fa

, 1.5 m/sb Ecological ) 

Receptor SL-II SL-III SL-IV SL-II SL-III SL-IV SL-II SL-III SL-IV 

Sedimentdwelling biota 2,000–3,000 700–1,000 500–700 10,000–20,000 1,000–2,000 

Soil 

invertebrates 2,000–3,000 500–700 300–500 10,000–20,000 

Plants 1,000–2,000 5,000–7,000 

American 

robin 1,000–2,000 

2,000–3,000 

River otter 500–700 

Aquatic biota 

Short-tailed 

shrew 

Great blue 

heron 

Red-tailed 

hawk 

a Atmospheric Stability Class. 

b Windspeed measured at 10 meters. 

Note: Shaded cells denote no exceedance of the appropriate benchmark. The ranges in this table indicate that there is uncertainty in the predicted 

distances to which the various benchmarks are exceeded. The distances downwind at which the various concentrations are first encountered can 

conservatively be set to 0. To convert meters to feet, multiply by 3.281. 

Key: m/s=meters per second; SL=severity level. 

The consequences above can be combined with the predicted frequencies of crashes with fires from 

Tables D–12 and D–13 to provide risks. Tables D–12 and D–13 show that the predicted frequencies of 

spills with fires are in the FL-III range under both truck scenarios and for all of the candidate storage 

sites. Conservatively, these frequencies are associated with the highest SL predicted in any weather 

condition in Table D–39, a conservative assumption.12 Table D–40 summarizes the FL, consequence 

level, and risk to ecological receptors and applies to all candidate storage sites. 

Table D–40. Frequencies, Consequences, and Risks to Ecological Receptors from 

Truck Crashes with Pallet Fires and No Raina

Ecological Receptor 

Frequency Level of 

Crash with Fireb Consequence Levelc Riskd

Sediment-dwelling biota III (moderate) IV High 

Soil invertebrates III (moderate) IV High 

Plants III (moderate) II Low 

American robin III (moderate) II Low 

River otter III (moderate) II Low 

Aquatic biota III (moderate) I Negligible 

Short-tailed shrew III (moderate) I Negligible 

Great blue heron III (moderate) I Negligible 

Red-tailed hawk III (moderate) I Negligible 

a Applies equally to all seven candidate sites. 

b Frequencies of truck crashes with spills from Tables D–12 and D–13. 

c The highest consequence in any weather condition from Table D39. 

d Applies to both Truck Scenarios 1 and 2. 

 

12 In principle, one could calculate the probability, conditional on the occurrence of the crash with fire, that an SL-IV 

consequence for (say) sediment-dwelling biota could occur. This probability is less than unity, because it does not occur in all 

weather conditions. It might be small enough that, when multiplied by the FL-III frequencies in Table D–40, it would drop 

those frequencies into a lower frequency range. However, this is not possible because the calculations reported in Table D–39 

were only done for the three representative weather conditions, not all weather conditions. Nevertheless, omitting this step in 

the calculation of frequency does add considerable conservatism. 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–84

The following observations apply to the results represented in Table D–40: 

 As noted above, if a particular outcome occurs even in only one of the three representative 

weather conditions listed above, it is conservatively assumed to occur always (e.g., sedimentdwelling biota would only be exposed to potentially high concentrations in Atmospheric Stability 

Class A conditions). This introduces conservatism into the frequency portion of the risk equation. 

 The truck results apply to both Scenarios 1 and 2. 

 For all receiving sites, there is a high risk that, in the event of a truck crash with fire and no rain, 

somewhere along the truck routes, areas could contain deposited mercury in the SL-IV range for 

sediment-dwelling biota and soil invertebrates living in that area. Per Figure D–1, these indicate 

situations of major concern. 

 Furthermore, though not shown explicitly in Table D–40, there could be a moderate risk that, for 

the same event, areas along truck routes (in addition to the areas in the previous bullet) could 

contain deposited mercury in the SL-III range for sediment-dwelling biota and soil invertebrates. 

Per Figure D–1, these indicate situations of concern. 

 For all receiving sites, there is a low risk that, somewhere along the truck routes, for the same 

event, areas could contain deposited mercury in the SL-II range for nearby plants, American 

robins, and river otters. Per Figure D–1, these indicate situations of minimal concern. 

Furthermore, though not shown explicitly in Table D–40, there could be a low risk that areas 

along truck routes (in addition to the areas in the previous two bullets) contain deposited mercury 

in the SL-II range for sediment-dwelling biota and soil invertebrates. 

 For truck routes to all receiving sites, the risks to the short-tailed shrew, aquatic biota, the great 

blue heron, and the red-tailed hawk are negligible. 

Wet Deposition 

The wet deposition analysis proceeded exactly as for the dry deposition, except that the quantity against 

which equivalent deposited screening values were compared was the amount of mercury deposited on the 

ground by the action of rain instead of by dry deposition. Table D–41 is analogous to Table D–36 and 

presents the comparisons of calculated levels of deposited mercury with equivalent deposited screening 

values for Atmospheric Stability Class A with a windspeed of 1.5 m/s. 

The downwind distance to which a particular receptor could be exposed to greater than various deposited 

SLs can be read from Table D–41 in the same way as described in the text accompanying Table D–39, 

with the exception that, in this case, the predicted deposited levels of mercury do not rise to a peak but 

instead decline monotonically as a function of distance from the source of the release. Thus, for example, 

sediment-dwelling biota could potentially be exposed in the SL-II range out to between 30,000 and 

40,000 meters (18.6 and 24.8 miles). 
Human Health and Ecological Risk Assessment Analysis 

D–85

Table D–41. Comparison of Predicted Ground-Level Centerline Airborne Concentrations 

with Equivalent Deposited Screening Values – Atmospheric Stability Class A, 

Windspeed 1.5 m/s, Truck Spill with Pallet Fire and Rain 

Distance 

Downwind 

(meters) 

Deposited 

Material 

(kg/m2

) 

Form of Mercury and 

Screening Value 

Ecological 

Receptor, Pathway 

25 1.02×10-3

50 9.86×10-4

100 9.19×10-4

9.00×10-4 Methyl Hg SV×20 – SL-IV American robin 

7.78×10-4 Methyl Hg SV – SL-II Otter, water 

5.51×10-4 Inorganic Hg SV×20 – SL-IV Plants 

200 5.42×10-4

5.02×10-4 Methyl Hg SV – SL-II Great blue heron, sediment 

4.50×10-4 Methyl Hg SV×10 – SL-III American robin 

300 3.86×10-4

3.60×10-4 Methyl Hg SV – SL-II Short-tailed shrew 

2.76×10-4 Inorganic Hg SV×10 – SL-III Plants 

2.72×10-4 Methyl Hg SV – SL-II Aquatic biota 

500 2.70×10-4

700 2.23×10-4

1.84×10-4 Inorganic Hg SV×20 – SL-IV Soil invertebrates 

1.84×10-4 Inorganic Hg SV – SL-II American robin 

1,000 1.74×10-4 

1.31×10-4 Methyl Hg SV – SL-II Otter, sediment 

1.27×10-4 Inorganic Hg SV×20 – SL-IV Sediment-dwelling biota 

9.18×10-5 Inorganic Hg SV×10 – SL-III Soil invertebrates 

2,000 9.01×10-5 

6.35×10-5 Inorganic Hg SV×10 – SL-III Sediment-dwelling biota 

3,000 5.76×10-5 

4.50×10-5 Methyl Hg SV – SL-II American robin 

5,000 3.08×10-5 

2.76×10-5 Inorganic Hg SV – SL-II Plants 

7,000 1.97×10-5 

10,000 1.18×10-6 

9.18×10-6 Inorganic Hg SV – SL-II Soil invertebrates 

6.35×10-6 Inorganic Hg SV – SL-II Sediment-dwelling biota 

20,000 3.58×10-6

30,000 1.52×10-6

40,000 7.51×10-7

Note: To convert meters to feet, multiply by 3.281. 

Key: Hg=mercury; kg/m2

 kilograms per square meter; SL=severity level; SV=screening value. 

The calculations reported in Table D–41 for Atmospheric Stability Class A with a windspeed of 1.5 m/s 

were repeated for Class D with a windspeed of 4.5 m/s and Class F with a windspeed of 1.5 m/s. The 

results are summarized in Table D–42. 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–86

Table D–42. Summary of Potential Exposure of Receptors to Deposited Mercury at 

Severity Levels II, III, and IV – Truck Spill with Pallet Fire and Rain 

Distance (meters) to Which 

Benchmark is Exceeded 

(Aa, 1.5 m/sb) 

Distance (meters) to Which 

Benchmark is Exceeded 

(Da, 4.5 m/sb) 

Distance (meters) to Which 

Benchmark is Exceeded 

(Fa, 1.5 m/sb Ecological ) 

Receptor SL-II SL-III SL-IV SL-II SL-III SL-IV SL-II SL-III SL-IV 

Sedimentdwelling biota 10,000–

20,000 

2,000–

3,000 

1,000–

2,000 

30,000–

40,000 

3,000–

5,000 

20,000–

30,000 

7,000–

10,000 3,000–5,000 

Soil 

invertebrates 

10,000–

20,000 

1,000–

2,000 700–1,000 20,000–

30,000 

3,000–

5,000 

20,000–

30,000 

5,000–

7,000 2,000–3,000 

Plants 5,000–

7,000 300–500 300–500 7,000–

10,000 

10,000–

20,000 

1,000–

2,000 700–1,000 

American 

robin 

3,000–

5,000 200–300 7,000–

10,000 700–1,000 <100 

River otter 1,000–

2,000 3,000–5,000 

Aquatic biota 300–500 1,000–2,000 

Short-tailed 

shrew 300–500 1,000–2,000 

Great blue 

heron 200–300 700–1,000 

Red-tailed 

hawk 

a Atmospheric Stability Class. 

b Windspeed measured at 10 meters. 

Note: Shaded cells denote no exceedance of the appropriate benchmark. The ranges in this table indicate that there is uncertainty in the predicted 

distances to which the various benchmarks are exceeded. The distances downwind at which the various concentrations are first encountered can 

conservatively be set to 0. To convert meters to feet, multiply by 3.281. 

Key: <=less than; m/s=meters per second; SL=severity level. 

Table D–42 shows that, for a truck crash with a pallet fire and rain, some ecological receptors could be 

exposed to deposited mercury in the SL-IV range over distances of up to 5,000 meters 

(approximately 3.1 miles); in the SL-III range, up to 10,000 meters (approximately 6.2 miles); and in the 

SL-II range, up to about 30,000 meters (approximately 18.6 miles). The consequences above can be 

combined with the predicted frequencies of crashes with fires and rain from Table D–16 to provide risks. 

Table D–16 shows that the predicted frequencies of spills with fire and rain are in the low (FL-II) range 

for all of the candidate storage sites and under both truck scenarios. Conservatively, these frequencies are 

associated with the highest SL predicted in any weather condition in Table D–42. Table D–43 

summarizes the FL, consequence level, and risk to ecological receptors and applies to all candidate 

storage sites. 

Table D–43. Frequencies, Consequences, and Risks to Ecological Receptors from Truck Crashes 

with Pallet Fires and Raina

Ecological Receptor 

Frequency Level of 

Crash with Fireb Consequence Levelc Riskd

Sediment-dwelling biota II (low) IV Moderate 

Soil invertebrates II (low) IV Moderate 

Plants II (low) IV Moderate 

American robin II (low) IV Moderate 

River otter II (low) II Low 

Aquatic biota II (low) II Low 

Short-tailed shrew II (low) II Low 

Great blue heron II (low) II Low 

Red-tailed hawk II (low) I Negligible 

a Applies equally to all seven candidate sites. 

b Frequencies of truck crashes with fires and rain from Table D–16. 

c The highest consequence in any weather condition from Table D–45. 

d Applies to both Truck Scenarios 1 and 2. 
Human Health and Ecological Risk Assessment Analysis 

D–87

The following observations apply to the results represented in Table D–43: 

 As noted above, if a particular outcome occurs even in only one of the three representative 

weather conditions listed above, it is conservatively assumed to occur always. This introduces 

conservatism into the frequency portion of the risk equation. 

 The truck results apply to both Scenarios 1 and 2. 

 For all receiving sites, there is a moderate risk that, somewhere along the truck routes, for truck 

crashes with pallet fires and rain, areas could contain deposited mercury in the SL-IV range for 

sediment-dwelling biota, soil invertebrates, plants, and American robins. Per Figure D–1, these 

indicate situations of concern. Furthermore, though not shown explicitly in Table D–43, there 

could be a low risk that areas along truck routes (in addition to the areas in the previous bullet) 

could contain deposited mercury in the SL-III range for sediment-dwelling biota, soil 

invertebrates, plants, and American robins. 

 For all receiving sites, there is a low risk that, for the same event, somewhere along the truck 

routes, areas could contain deposited mercury in the SL-II range for nearby river otters, aquatic 

biota, short-tailed shrews, and great blue herons. Per Figure D–1, these indicate situations of 

minimal concern. Furthermore, though not shown explicitly in Table D–43, there is a low risk 

that areas along truck routes (in addition to the areas in the previous two bullets) could contain 

deposited mercury in the SL-II range for sediment-dwelling biota, soil invertebrates, plants, and 

American robins. 

 For all receiving sites, the risk to the red-tailed hawk is negligible. 

D.5.4.3.2 Pallet Fires – Rail Transportation 

This section considers railcar crashes with pallet fires in both dry conditions and wet conditions. 

Dry Deposition 

As was the case for truck pallet fires, calculations of deposited levels of mercury were carried out for 

Atmospheric Stability Class A with a windspeed of 1.5 m/s, Class D with a windspeed of 4.5 m/s, and 

Class F with a windspeed of 1.5 m/s. The results are summarized in Table D–44. 

Table D–44 shows that, for a railcar crash with fire but no rain, ecological receptors could be exposed to 

deposited mercury in the SL-IV range, but over distances of no more than 1,000 meters (3,300 feet), and 

then only in Atmospheric Stability Class A conditions. In Class A and D conditions, some receptors 

could be exposed to SL-III levels of deposited mercury out to about 5,000 meters (approximately 

3.1 miles). In Class A, D, and F conditions, several of the ecological receptors are predicted to be 

exposed to deposited mercury in the SL-II range for considerable distances downwind. Table D–44 is 

similar to Table D–39 except that predicted distances are somewhat greater. This is because the assumed 

rate of evaporation of mercury from a railcar fire, 1.6 kg/s, is greater than that assumed for a truck fire, 

1.3 kg/s; see Section D.8.4.1. 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–88

Table D–44. Summary of Potential Exposure of Receptors to Deposited Mercury at 

Severity Levels II, III, and IV – Railcar Spill with Pallet Fire, No Rain 

Distance (meters) to Which 

Benchmark is Exceeded 

(Aa, 1.5 m/sb) 

Distance (meters) to Which 

Benchmark is Exceeded 

(Da, 4.5 m/sb) 

Distance (meters) 

to Which Benchmark is Exceeded 

(Fa, 1.5 m/sb Ecological ) 

Receptor SL-II SL-III SL-IV SL-II SL-III SL-IV SL-II SL-III SL-IV 

Sedimentdwelling biota 3,000–

5,000 

1,000–

2,000 700–1,000 20,000–

30,000 

3,000–

5,000 3,000–5,000 

Soil 

invertebrates 

3,000–

5,000 700–1,000 500–700 10,000–

20,000 2,000–3,000 

Plants 1,000–

2,000 300–500 7,000–10,000 

American 

robin 

1,000–

2,000 

5,000–

7,000 

River otter 700–1,000 

Aquatic biota 300–500 

Short-tailed 

shrew 

Great blue 

heron 

Red-tailed 

hawk 

a Atmospheric Stability Class. 

b Windspeed measured at 10 meters. 

Note: Shaded cells denote no exceedance of the appropriate benchmark. The ranges in this table indicate that there is uncertainty in the predicted 

distances to which the various benchmarks are exceeded. The distances downwind at which the various concentrations are first encountered can 

conservatively be set to 0. To convert meters to feet, multiply by 3.281. 

Key: m/s=meters per second; SL=severity level. 

The consequences above can be combined with the predicted frequencies of crashes with fires from 

Table D–14 to provide risks. Table D–14 shows that the predicted frequencies of railcar spills with fires 

are in the FL-II range for all of the candidate storage sites. Conservatively, these frequencies are 

associated with the highest SL predicted in any weather condition in Table D–44. Table D–45 

summarizes the FL, consequence level, and risk to ecological receptors and applies to all candidate 

storage sites. 

Table D–45. Frequencies, Consequences, and Risks to Ecological Receptors from 

Railcar Crashes with Pallet Fires and No Raina

Ecological Receptor 

Frequency Level of 

Crash with Fireb Consequence Levelc Riskd

Sediment-dwelling biota II (low) IV Moderate 

Soil invertebrates II (low) IV Moderate 

Plants II (low) III Low 

American robin II (low) II Low 

River otter II (low) II Low 

Aquatic biota II (low) II Low 

Short-tailed shrew II (low) I Negligible 

Great blue heron II (low) I Negligible 

Red-tailed hawk II (low) I Negligible 

a Applies equally to all seven candidate sites. 

b Frequencies of railcar crashes with spills from Table D–14. 

c The highest consequence in any weather condition from Table D–44. 
Human Health and Ecological Risk Assessment Analysis 

D–89

The following observations apply to the results represented in Table D–45: 

 As noted above, if a particular outcome occurs even in only one of the three representative 

weather conditions listed above, it is conservatively assumed to occur always (e.g., sedimentdwelling biota are only exposed to SL-IV concentrations in Atmospheric Stability Class A 

conditions). This introduces conservatism into the frequency portion of the risk equation. 

 For all receiving sites, there is a moderate risk that, somewhere along the rail routes, areas could 

contain deposited mercury in the SL-IV range for sediment-dwelling biota and soil invertebrates 

living in that area. Per Figure D–1, these indicate situations of concern. 

 For all receiving sites, there is a low risk that, somewhere along the rail routes, areas could 

contain deposited mercury in the SL-III range for plants. Per Figure D–1, these indicate 

situations of minimal concern. Furthermore, though not shown explicitly in Table D–45, there is 

a low risk that areas along rail routes (in addition to the areas in the previous bullet) could contain 

deposited mercury in the SL-III range for sediment-dwelling biota and soil invertebrates. 

 For all receiving sites, there is a low risk that, somewhere along the rail routes, areas could 

contain deposited mercury in the SL-II range for nearby American robins, river otters, and aquatic 

biota. Per Figure D–1, these indicate situations of minimal concern. Furthermore, though not 

shown explicitly in Table D–45, there could be a low risk that areas along rail routes (in addition 

to the areas in the previous two bullets) could contain deposited mercury in the SL-II range for 

sediment-dwelling biota, soil invertebrates, and plants. 

 For all receiving sites, the risk to the short-tailed shrew, the river otter, and the red-tailed hawk is 

negligible. 

Wet Deposition 

Per Table D–16, the frequencies of railcar crashes with subsequent fire and rain would be negligible for 

the rail routes to every site. Therefore, all corresponding risks would be negligible. 

D.5.4.4 Intentional Destructive Acts 

Tables D46 through D49 summarize the results of calculations of the impact on ecological receptors 

consequent upon the intentionally initiated gasoline tanker fire described in Section D.2.6. These tables 

are similar to those above (see Section D.5.4.3.2) for the accidental railcar fire. As noted previously, the 

railcar fire is used as a conservatively bounding scenario for the truck fire (see also Section D.8.4.2). 

Tables D–46 and D–47 present the consequences of the IDA to ecological receptors via dry deposition 

(i.e., the accident is assumed to occur during dry conditions). 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–90

Table D–46. Summary of Potential Exposure of Receptors to Low, Moderate, or 

High Concentrations – Atmospheric Stability Class D, Windspeed 4.5 m/s, 

Intentionally Initiated Railcar Spill with Fires, No Rain 

Distance (meters) Downwind to Which Concentration Levels 

Are Exceeded 

Ecological Receptor (Form of Mercury) SL-II SL-III SL-IV 

Sediment-dwelling biota >40,000 10,000–20,000 5,000–7,000 

Soil invertebrates >40,000 10,000–20,000 2,000–3,000 

Plants >40,000 

American robin 20,000–30,000 

River otter 3,000–5,000 

Aquatic biota 

Short-tailed shrew 

Great blue heron 

Red-tailed hawk (methylmercury) 

Note: Shaded cells denote no exceedance of the appropriate screening value. The ranges presented in this table represent the 

furthest point downwind at which the corresponding equivalent deposited screening values are exceeded. To convert meters to 

feet, multiply by 3.281. 

Key: >=greater than; SL=severity level. 

Table D–47. Summary of Potential Exposure of Receptors to Low, Moderate, or 

High Concentrations – Atmospheric Stability Class F, Windspeed 1.5 m/s, 

Intentionally Initiated Railcar Spill with Fire, No Rain 

Distance (meters) Downwind to Which Concentration 

Levels Are Exceeded 

Ecological Receptor SL-II SL-III SL-IV 

Sediment-dwelling biota >40,000 2,000–3,000 700–1,000 

Soil invertebrates 30,000–40,000 1,000–2,000 

Plants 5,000–7,000 

American robin 3,000–5,000 

River otter 700–1,000 

Aquatic biota 

Short-tailed shrew 

Great blue heron 

Red-tailed hawk 

Note: Shaded cells denote no exceedance of the appropriate screening value. The ranges presented in this table represent the 

furthest point downwind at which the corresponding equivalent deposited screening values are exceeded. To convert meters to 

feet, multiply by 3.281. 

Key: >=greater than; SL=severity level. 

Tables D–48 and D–49 repeat the information in Tables D–46 and D–47, but in the following tables, the 

IDA is assumed to occur during rainfall (i.e., exposure via wet deposition). 
Human Health and Ecological Risk Assessment Analysis 

D–91

Table D–48. Summary of Potential Exposure of Receptors to Low, Moderate, or 

High Concentrations – Atmospheric Stability Class D, Windspeed 4.5 m/s, 

Intentionally Initiated Railcar Spill with Fire and Rain 

Distance (meters) Downwind to Which Concentration Levels 

Are Exceeded 

Ecological Receptor, Pathway SL-II SL-III SL-IV 

Sediment-dwelling biota >40,000 >40,000 20,000–30,000 

Soil invertebrates >40,000 30,000–40,000 20,000–30,000 

Plants >40,000 10,000–20,000 7,000–10,000 

American robin >40,000 7,000–10,000 5,000–7,000 

River otter, sediment 20,000–30,000 3,000–5,000 2,000–3,000 

Aquatic biota 10,000–20,000 2,000–3,000 500–700 

Short-tailed shrew 10,000–20,000 1,000–2,000 

Great blue heron 7,000–10,000 700–1,000 

Red-tailed hawk 

Note: Shaded cells denote no exceedance of the appropriate screening value. The ranges presented in this table represent the 

furthest point downwind at which the corresponding equivalent deposited screening values are exceeded. To convert meters to 

feet, multiply by 3.281. 

Key: >=greater than; SL=severity level. 

Table D–49. Summary of Potential Exposure of Receptors to Low, Moderate, or 

High Concentrations – Atmospheric Stability Class F, Windspeed 1.5 m/s, 

Intentionally Initiated Railcar Spill with Fire and Rain 

Distance (meters) Downwind to Which Concentration 

Levels Are Exceeded 

Ecological Receptor (Form of Mercury) SL-II SL-III SL-IV 

Sediment-dwelling biota >40,000 20,000–30,000 20,000–30,000 

Soil invertebrates >40,000 20,000–30,000 10,000–20,000 

Plants 30,000–40,000 10,000–20,000 10,000–20,000 

American robin 30,000–40,000 10,000–20,000 7,000–10,000 

River otter 20,000–30,000 5,000–7,000 3,000–5,000 

Aquatic biota 10,000–20,000 2,000–3,000 1,000–2,000 

Short-tailed shrew 10,000–20,000 2,000–3,000 700–1,000 

Great blue heron 10,000–20,000 1,000–2,000 300–500 

Red-tailed hawk (methylmercury) 

Note: Shaded cells denote no exceedance of the appropriate screening value. The ranges presented in this table represent the 

furthest point downwind at which the corresponding equivalent deposited screening values are exceeded. To convert meters to 

feet, multiply by 3.281. 

Key: >=greater than; SL=severity level. 

The above tables show that the IDA fire could lead to severe consequences to ecological receptors at 

considerable distances downwind. It is not possible to estimate the frequencies of IDAs, so the risks are 

not tabulated. 

D.6 UNCERTAINTY ASSESSMENT 

This section describes uncertainties in the risk estimates and an indication of the magnitude and 

predominant direction of the uncertainties (i.e., whether the stated risk estimates tend to understate or 

overstate the risks). 

D.6.1 Mercury Source 

The following discussion considers sources of mercury that might be expected under normal operating 

and accidental conditions. 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D.6.1.1 Normal Operating Conditions 

A principal assumption is the chemical form of mercury released. Mercury exists in three forms in the 

environment: elemental Hg0

 (metallic), Hg2 (mercurous), and Hg 2 2+ (mercuric) (see Section D.1.1.2). 

During normal storage, it is highly unlikely that mercury would be released in a form other than elemental 

mercury vapor. Specific types of chemical reactions must occur for elemental mercury to form a 

mercurous or mercuric compound. One example is oxidation of metallic mercury into mercuric mercury 

in water in the presence of an oxidizer such as hydrogen peroxide. However, it is highly unlikely that 

these conditions would occur within the storage facility during normal operating conditions. 

Consequently, the uncertainty in the assessment of releases of elemental mercury vapor is considered 

minimal. 

Exposure during normal operating conditions is extensively discussed in Section D.4.1. For the involved 

worker, the analysis of experiments, the historical record, and acknowledgment of the expected reliance 

on a combination of ventilation, inspection, monitoring, and use of personal protective equipment (PPE), 

indicate that it is so highly unlikely that the worker will be exposed to concentrations exceeding the 

ACGIH’s 8-hour TWA/TLV of 0.025 mg/m3

 of mercury vapor. 

In addition, highly conservative analysis of predicted concentrations in the turbulent building wake of 

storage buildings show that noninvolved workers and members of the public would be exposed to 

concentrations elemental mercury vapor that are far below EPA’s RFC of 0.003 mg/m3

. 

D.6.1.2 Accidental Spillages of Elemental Mercury 

The analysis considers a variety of spills of elemental mercury: inside the storage building, outside the 

storage building, and during transportation. For all such scenarios, the assessed human health and 

ecological risks are in the negligible-to-low range. This is in spite of conservative assumptions such as 

assuming a larger-than-expected spreading of the pool, thus providing a faster predicted rate of 

evaporation. Physical properties of mercury, such as its very low saturated vapor density at expected 

ambient temperatures, essentially ensure that consequences cannot be high. Thus uncertainties do not 

affect the conclusion that the risks associated with such spills are all in the negligible-to-low range. 

For direct spillage of elemental mercury into water, the biggest uncertainty is in how the elemental 

mercury would be transformed into those forms (inorganic and methyl) that, when ingested, are most 

significant in terms of their effects on humans and sensitive ecological receptors. The available 

information on such transformations is summarized in Section D.5.4.2. It appears that they are slow. In 

addition, if elemental mercury is spilled onto the banks of a river or other water body rather than directly 

into it, the available evidence suggests that the mercury would make its way into the water slowly. This 

would allow ample time for cleanup. 

In Section D.4.3.2, the human health risk of spillages into water is assessed as negligible to low. This 

almost entirely depends on the assumption that there would be time to clean up the spilled mercury before 

the deposited mercury could cause human health effects. The same conclusion follows for ecological 

receptors. This conclusion may not be valid for spillage into a fast-flowing river. Thus, uncertainties in 

this area are large. 

D.6.1.3 Transportation 

The transportation analysis assumes that empty 3-L flasks weigh 4.1 kilograms (9.0 pounds). It is 

possible that the flasks could weigh 6.1 kilograms (13.4 pounds). In that case, the mass of a 7 × 7 pallet 

would increase by 49 × 2.2 = 108 kilograms (238 pounds). This would increase the weight of a fully 

loaded pallet from about 2,000 kilograms (4,400 pounds) to about 2,100 kilograms (4,630 pounds). The 

weight limitation on trucks would then reduce the number of pallets per truck from 9.09 to 8.65, rounded 

D–92
Human Health and Ecological Risk Assessment Analysis 

D–93

down to 8. Under Truck Scenario 1, this would increase the frequency of crashes by a factor of 9/8 or 

1.125. The current analysis is therefore slightly non-conservative. Similar reasoning applies to the 

Railcar Scenario. Truck Scenario 2, in which the truck is only half full, is unaffected. 

D.6.1.4 Fires 

This EIS considers four fire scenarios: accidental truck fire, accidental railcar fire, deliberately initiated 

truck fire through collision with a gasoline tanker, and similarly initiated railcar fire. Although the 

mercury released into the atmosphere under a fire scenario would be partially in the form of elemental 

mercury and partially in the form of divalent mercury, this analysis implicitly assumes that all of the 

mercury is in the divalent form (see Section D.7.3.3). Under operating conditions that include stack 

emissions in the presence of environmental controls, EPA recommends phase allocations for mercury 

emissions of 20 percent vapor phase elemental mercury, 60 percent vapor phase divalent mercury, and 

20 percent particle phase mercury (EPA 1998). No information is available concerning the speciation of 

mercury resulting from sources involving combustion in the absence of emission controls. Because 

divalent mercury is assumed to be more susceptible to deposition processes than either elemental or 

particle mercury (EPA 1997b) and all forms of mercury are assumed to be equally as toxic as the most 

toxic form, the assumption that 100 percent of the mercury is released as divalent mercury represents a 

worst case when considering deposition. 

One potential conservatism in the analysis is the assumption that pallets would be made of wood. An 

alternative envisioned in the Interim Guidance (DOE 2009a) is the use of metal pallets. If these were 

used, there would be much less fuel to burn and a much shorter duration of release, and much less 

mercury would become airborne. 

Assumptions are used to address the mercury release rate, the duration of the fire (and correspondingly, 

the mercury release and deposition flux durations), the chemical type of mercury released, and the 

effective release height. As much as 2 kg/s of mercury would be released into the atmosphere in the case 

of the deliberately-initiated railcar fire. This release rate estimate was derived using the methods 

recommended in EPA guidance on conducting the offsite consequence analyses for Risk Management 

Programs required under the Clean Air Act (EPA 1999b). As noted in this guidance, these methods 

produce worst-case estimates. As such, the release rate used in this analysis is more likely to result in an 

overstatement of the risks from a railcar accident than an understatement. 

Consideration has been devoted to whether the method used for assessing the rate of evaporation of 

mercury is appropriate. For the accidental fires involving railcars and trucks, a search of many references 

and sources, including other EISs, turned up no method for calculating the evaporation rate from a pool of 

mercury (or any nonflammable substance) that is exposed to a fire. The kind of fire envisaged here is one 

in which the source of heat is the wood used to make the pallets containing the 7 × 7 array of 3-L flasks or 

the wood in which each 1-MT container is transported. Given the circumstances of the crash, it is 

extremely unlikely that the wood fire would be underneath the pool of mercury with the potential for 

directly boiling it. That is why the calculation envisages the mercury being raised to its boiling point and 

behaving as an evaporating pool. This process, if it occurs at all, would require radiative heat transfer 

from the burning wood to the pool. Given that the crash would damage the truck or railcar, the chances 

that any spilled mercury would necessarily remain in a pool collocated with the burning wood are 

small—it would be more likely to run away and spread across the ground such that radiative heat transfer 

would be very inefficient. 

The energy necessary to raise the entire mass of mercury on a railcar to its boiling point and to allow the 

evaporation of the amount of mercury predicted by Equation 7–19 represents 11.4 percent of the entire 

heat from the fire. The above considerations suggest that the configuration of the fire and pool would 

likely be such that this is a conservative estimate of the heat transferred to the pool, simply based on the 

qualitative observation that the resulting pool/fire configuration is unlikely to arrange itself into the 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–94

precise form required to maximize radiative heat transfer. On those grounds, the source term for 

accidental truck and railcar fires is likely to be conservative. 

In the case of the two IDAs, a fully loaded gasoline tanker is postulated to crash into the truck or railcar 

and its contents to spill and ignite. Some mercury flasks or 1-MT containers might be ruptured by the 

mechanical effects of the crash. Others might rupture as they are heated by the gasoline fire. Again, the 

resulting geometry of the burning fuel and the spilled mercury available for evaporation is very uncertain; 

thus there are very large uncertainties in the calculation of the fraction of heat from the fire that would 

actually heat the mercury and allow it to evaporate. It is assumed that the truck fire would consume 

0.2 percent of the fire’s energy to boil the predicted amount of mercury, while the railcar fire would use 

0.5 percent of the fire’s energy. Given this, the source terms for the IDA fires may not be conservative, 

and the consequences of such fires could be understated. 

The duration of the fire was estimated using the methods recommended by the U.S. Nuclear Regulatory 

Commission for conducting accident analysis of nuclear fuel cycle facilities (Ayer et al. 1988). As 

applied in this analysis, these equations tend to overestimate the rate of heat input into the rising 

contaminant plume (see above) and to underestimate the duration of the release. The overestimation of 

the rate of heat input into the rising contaminant plume tends to result in an overestimation of the 

effective release height, which tends to result in an underestimation of the dry deposition flux rate. The 

wet deposition flux rate is, however, largely insensitive to the effective release height. The noted 

underestimation of the release duration tends to result in an underestimation of the total mass of mercury 

deposited through both dry and wet deposition processes. Overall, the U.S. Nuclear Regulatory 

Commission methods, as applied in this analysis, would tend to result in an understatement rather than an 

overstatement of risk. 

The equation for estimating the effective release height (see Section D.7.4.1) is that recommended by the 

U.S. Army for use in chemical hazard prediction (Army 1980). Table D–60 shows the predicted height of 

plume rise for both the accidental truck and railcar fires in a variety of weather conditions. One hundred 

meters (330 feet) is a lower bound on the predicted plume rise in all cases; this height was chosen for all 

the weather conditions considered in this analysis. As a result, the assumptions about plume rise tend to 

overstate the results. 

For the IDA fires, the U.S. Army model predicts a height of plume rise of approximately 250 meters 

(820 feet) for both Atmospheric Stability Class D and F weather conditions. As discussed in 

Section D.8.4, the computer model actually used to perform the atmospheric dispersion calculations, 

SAPLUME, limits the height of plume rise in Class F conditions such that rise is terminated when the 

upper edge of the plume encounters an inversion lid at 260 meters (850 feet). In practice, the maximum 

plume rise allowed in Class F conditions is 120 meters (390 feet). Incorporating this assumption tends to 

overstate risk. 

While a plume is rising, the boundary is well defined and the concentration is essentially zero outside it. 

However, the model assumes that the radius of the plume defines the 10 percent concentration boundary 

of a Gaussian plume and that concentrations can extend beyond it. Thus, airborne concentrations and 

amounts deposited on the ground by dry deposition near the source tend to be overstated. 

Overall, the contaminant source assumptions are such that the analyses of accidental truck and railcar 

fires are more likely to overstate the risks than to understate them. 

For the IDA fires, no frequency estimates are possible, and hence no risk estimates are possible. 

However, the consequence results could be overstated or understated. 
Human Health and Ecological Risk Assessment Analysis 

D–95

D.6.2 Receptors 

This analysis estimates mercury concentrations in air, soil, surface water, and sediment that could occur 

as a result of onsite and offsite fires. Several receptor-related assumptions were made in the analysis. 

Explicit assumptions were made concerning receptor locations; implicit assumptions were also made. 

The analysis assumes that the mercury concentration estimated for each location represents the mercury 

exposure associated with a receptor nominally occupying that location. Over the short term, an 

individually identifiable location may be appropriate. Over the long term, an individual’s exposure 

represents an aggregate of the concentrations present in each of the numerous areas (or 

microenvironments) visited by the individual over time. EPA provides information on activity patterns, 

including information on the amount of time spent “at home” for men and women ages 18 to 64 years 

(EPA 1997c). According to EPA, men spend about 60 percent of their time at home, while women spend 

about 70 percent. 

The screening level for mercury deposited on the ground is based on exposure assumptions appropriate 

for a child (ATSDR 2009b). Thus, using the SSL in the derivation of the health-based benchmark results 

in the implicit assumption that the receptor of interest is a child. Moreover, because the assumed soil 

ingestion rate for children is higher than that of non-smoking adults, while the assumed body weight is 

lower, child-based screening levels are lower than those of adults. 

There is uncertainty about which organisms potentially exposed at the storage sites or in the environs of 

accidental releases are at most risk. If more-sensitive receptors are present, then they may not be 

adequately addressed by the assessment endpoints evaluated in the ERA. The receptor species listed as 

potentially present in the area are a limited subset of the species that may utilize the area to some extent 

for at least a portion of the year. However, the species evaluated in the ERA are considered to provide a 

conservative representation of the range of exposures that may be experienced by other species not 

evaluated. 

D.6.3 Environmental Pathways 

The modeling of atmospheric transport, transformation, and fate is a significant source of uncertainty in 

the risk estimates. In the case of elemental mercury, the uncertainties arise from the assumption that 

elemental mercury neither deposits nor transforms within the area addressed by this analysis. Also 

important is the assumption that the Pasquill Gifford Gaussian plume model is appropriate for this 

analysis (especially when applied close to the release sources). 

An important condition of the risk assessment is that releases of elemental mercury are not likely to 

deposit locally. The available information indicates that transformation of elemental mercury into other 

forms of mercury that are prone to deposition is unlikely. Discernible concentrations of the other forms 

of mercury locally (e.g., within 10 kilometers [6.2 miles] of the storage facility) are thus unlikely. This 

assumption is well supported by EPA’s Mercury Study Report to Congress (EPA 1997a). Homogeneous 

gas phase transformation of elemental mercury is considered to be of little consequence even on a 

regional scale. Regionally significant heterogeneous reactions are likely to occur very slowly as a result 

of the low water solubility of elemental mercury (Bloxam 1995; EPA 1997a). As concluded by 

EPA (1997c): 

Global atmospheric circulation systems can take Hg0

 emissions from their point of 

origin and carry them anywhere on the globe before transformation and deposition 

occur... .[Elemental] mercury vapor is not thought to be susceptible to any major 

process of direct deposition to the earth’s surface due to its relatively high vapor 

pressure and low water solubility. On non-assimilating surfaces elemental mercury 

deposition appears negligible...[and] this elemental mercury is expected to volatilize 

into the atmosphere. 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–96

Thus, even though some transformation and deposition of elemental mercury would inevitably occur, the 

available information indicates that on a local scale the magnitude of transformation and deposition of 

elemental mercury released as a result of normal operations is undoubtedly very small. Consequently, 

even though the transformation and fate assumptions may cause an understatement of the risks, the 

magnitude of the understatement would also be very small. The significance of any such understatement 

is tempered by the significant assumptions made in the risk assessment that tend to overstate risks. 

Numerous assumptions are implicitly made in employing a Gaussian plume model to estimate 

atmospheric pollutant concentrations and deposition rates. The implicit general assumptions are 

discussed in references addressing air pollution models such as Hanna, Briggs, and Hosker (1982) and 

Schulze (1991). Several specific assumptions of importance have been made in this analysis. These 

assumptions concern the selection of values or equations for windspeed, stability class, stability 

parameters, and deposition velocities. For ground-level releases, the computer model SACRUNCH was 

used to run dispersion models in a range of atmospheric stability classes and windspeeds that cover the 

whole range of data available from the sites. This approach essentially finesses any uncertainties that 

might arise if one chooses only one weather condition as a surrogate for all potential weather conditions. 

For the fire calculations, the computer model SAPLUME (SAIC 1994) was used with three weather 

conditions that, between them, span a range of conditions that are representative of the full spectrum of 

possible weather conditions: Atmospheric Stability Class A with a windspeed of 1.5 m/s, representing 

highly turbulent ambient atmospheric conditions; Class D with a windspeed of 4.5 m/s, representing 

“average” or “most likely” weather conditions; and Class F with a windspeed of 1.5 m/s, representing 

highly stable weather conditions. The analysis of human health risks and ecological receptor risks used 

the worst-case consequence, e.g., even if high inhaled levels of mercury relative to any specific 

benchmark were only predicted in one of the three weather conditions, the potential consequences were 

assumed to be high in all weather conditions. This adds an element of conservatism to the estimate of 

risks. 

The assumption that the Gaussian equations apply to distances close to the source area (distances less than 

100 meters [330 feet]) is problematic because there is no information to validate the model under the 

assumption. This uncertainty is to some extent addressed by considering that releases from within the 

storage building or just outside it are first diluted in the building wake. This is a more-realistic 

assumption than using the point source Gaussian model, which would overestimate peak centerline 

concentrations near the source. 

The analysis also explicitly assumes that the dry deposition velocity for divalent mercury is in the upper 

end of the range of available values. Thus, the dry deposition calculations in this EIS generally produce 

conservative results. 

Regarding the assumed rainfall scavenging rate of 1.5 × 10-4 s-1, Hanna, Briggs, and Hosker (1982) note 

that this is a median value from 20 field experiments conducted by McMahon and Dennison. They 

indicate a range of 0.4 × 10-4 s-1 to 3 × 10-3 s-1. They also state, “The use of scavenging coefficients for 

wet removal modeling is probably best regarded as an order-of-magnitude estimation procedure” (Hanna, 

Briggs, and Hosker 1982). Furthermore, windspeeds and stability classes are themselves uncertain due to 

changes in weather conditions. Taken as a group, the direction of any resulting bias is indeterminate. 

Intake from inhalation exposures is difficult to quantify for ecological receptors. Intake via this route is 

likely to be minimal relative to intake via ingestion. However, there is an increase in the uncertainty for 

the total risk encountered by leaving inhalation out and a likely but insignificant underestimate of total 

risk. 
Human Health and Ecological Risk Assessment Analysis 

D–97

D.6.4 Effects Due to Exposure to Mercury 

D.6.4.1 Human Health Effects 

The limitations in toxicological testing and extrapolation of results from toxicological study populations 

to the general population result in considerable uncertainty in determining the concentrations below 

which adverse effects are unlikely (e.g., Dourson, Felter, and Robinson 1996). However, the process of 

determining RfDs attempts to account for these uncertainties through the use of uncertainty and 

modifying factors. Consequently, it is unlikely that an RfC would understate toxicity. As noted by EPA, 

“the RfC is an estimate (with uncertainty spanning perhaps an order of magnitude) of a daily inhalation 

exposure of the human population (including sensitive subgroups) that is likely to be without an 

appreciable risk of deleterious effects during a lifetime.” The worker safety criteria are regulatory in 

nature and are thus considered appropriate for screening worker safety risks. 

Values of elemental mercury toxicity were used as the sole basis for evaluation of exposure to mercury 

vapor. The standard for mercury vapor is five times higher than the value for organic mercury alkyl 

compounds. However, use of the lower value would not change the results of the analysis because it is 

highly unlikely that any mercury vapor released under normal operating conditions would be transformed 

in a significant manner to any other form of mercury. EPA provides oral RfDs for mercuric chloride and 

methylmercury (3  10-4 mg/kg/day and 1  10-4 mg/kg/day, respectively), but not for elemental mercury 

(since it is primarily an inhalation hazard). Converting the inhalation RfC for elemental mercury to an 

equivalent oral RfD yields a value of 9  10-5 mg/kg/day. Although this conversion may not be 

appropriate from a toxicological standpoint, it does serve to illustrate that reliance on elemental mercury 

alone as the basis for toxicological comparison does not appear to bias the risk results away from 

protection of human health. 

Regarding the limitations in the toxicity data for mercury compounds, EPA classified its confidence in the 

elemental mercury RfC as “medium.” Inadequate quantification of exposure levels and lack of human or 

multi-species reproductive or developmental studies were cited by EPA as the reasons a rating of high 

could not be assigned (EPA 2002d). It is thus possible that the RfC understates (or overstates) the 

toxicity of elemental mercury. However, EPA’s use of a 30-fold uncertainty factor in the derivation of 

the RfC makes it unlikely that the RfC is insufficiently conservative. In contrast, EPA classified its 

confidence in the mercuric chloride and methylmercury RfDs as “high” in both cases. EPA identified the 

weight of evidence from the studies of the brown Norway rat and the overall quality of the mercuric 

chloride toxicity database as the reasons supporting its assessment of confidence. The quality of the three 

epidemiological studies used to derive the methylmercury RfD, together with consistent evidence from 

studies in monkeys, were cited by EPA as supporting its confidence assessment. In addition, the available 

information indicates that even if mercuric chloride or methylmercury is a carcinogen, they are unlikely to 

exhibit high carcinogenic potency. 

The toxicity values used to assess short-term health effects related to exposures to mercury present 

uncertainties. However, as a general statement, the methods used to derive IDLH and AEGL values from 

available human and animal data tend to be conservative and thus are likely, if anything, to introduce 

conservatism into the estimates of human health risks. 

D.6.4.2 Ecological Receptors 

In calculating constituent intakes, conservative exposure factors are assumed in order to be protective of 

all potential receptors. Low-end estimates of body weights and high-end estimates of ingestion rates are 

assumed in order to model the highest potential dose to the receptor. Conservatism is also employed in 

estimating bioavailability and the percent of contaminated plant and animal materials in the diet. The 

conservative exposure factors and exposure concentrations used provide confidence that calculated 

intakes are reasonably conservative estimates for receptor populations. Intakes from dermal and 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–98

inhalation exposures are not quantifiable for ecological receptors. However, this does not significantly 

increase the uncertainty of the estimated total intake because, for most receptors, intakes via these routes 

are likely to be minimal relative to intakes via ingestion. 

There is uncertainty associated with TRVs used in this ERA because the toxicity data are not site specific. 

Limitations in toxicity values include variations in physiological or biochemical factors that may exist 

among species, behavioral and ecological parameters that may make a species’ sensitivity to a 

contaminant different from that of the test organism, and limited information on long-term effects on 

natural populations. In addition, most laboratory studies use highly bioavailable forms of chemicals 

during toxicity-related derivations. Since most chemicals in nature are bounded or associated with 

inorganic matrices or organics, many are not as bioavailable as the forms used in the laboratory studies. 

The combination of maximum intakes and conservative TRVs provides confidence that the Hazard 

Quotients resulting from the evaluation are conservative. 

The TRVs for plants and earthworms are based on studies in which the receptors were maintained in soil 

to which the test compounds had been added. Because the concentration of biologically available 

mercury species is likely to be lower than the total concentration, the TRVs for plants and earthworms 

probably overstate the toxicity of inorganic mercury and methylmercury to these receptors. 

The TRV for mammals exposed to inorganic mercury is based on a study in which mink were fed 

mercuric chloride in the diet for 6 months, during which they had pups. An NOAEL of 1.0 mg/kg/day for 

reproductive success was reported. However, only one dose level was used in the study. Therefore, a 

higher dose might also have produced an NOAEL. The convention of multiplying the NOAEL by 10 to 

estimate an LOAEL is based on the observation that the LOAEL is 10-fold higher than the NOAEL in 

studies that use a series of 10-fold dilutions in the dose level. Therefore, 10 is an arbitrary conversion 

factor. However, since an LOAEL was not observed, the highest possible NOAEL is likely high enough 

that the toxicity of inorganic mercury is overstated by the assumptions used in this analysis. The TRV for 

mammals exposed to methylmercury is based on a study in which rats were fed methylmercury in the diet 

for 1 year, during which they had pups. An LOAEL of 0.16 mg/kg/day for viability of the pups was 

calculated by using an allometric (i.e., based on measurements of various body parts) equation for the 

food consumption rate. Therefore, there is some uncertainty in the actual dosage. Whether the LOAEL 

understates or overstates toxicity is indeterminate, but the effect on the analysis of risk is expected to be 

minor. 

TRVs for mammals were scaled from LOAELs for the test species by the body weight of each receptor. 

The scaling factor is based on the principle that uptake and retention of chemicals are determined by 

metabolic rate, which is in turn related to body weight. Therefore, the same dose is expected to have 

quantitatively different toxic effects in different receptors. There is uncertainty that the scaling factors 

used are strictly accurate for each combination of test species and ecological receptor. Also, whether the 

calculated TRV overstates or understates toxicity is indeterminate. However, the effect on the analysis of 

risk is expected to be minor. 

The TRV for birds exposed to inorganic mercury is based on a study in which Japanese quail were fed 

mercuric chloride in the diet for 1 year, during which they had offspring. An LOAEL of 0.9 mg/kg/day 

and an NOAEL of 0.45 mg/kg/day for reproductive success were calculated by using an allometric 

equation for the food consumption rate. Therefore, there is some uncertainty in the actual dosage. 

Whether the TRVs understate or overstate toxicity is indeterminate, but the effect on the analysis of risk is 

expected to be minor. The TRV for birds exposed to methylmercury is based on a study in which mallard 

ducks were fed methylmercury in the diet for three generations. An LOAEL of 0.064 mg/kg/day for 

reproductive success was observed. However, only one dose level was used in the study. Therefore, a 

lower dose might also have produced an LOAEL. As a result, the TRV for birds probably understates the 

toxicity of methylmercury. 
Human Health and Ecological Risk Assessment Analysis 

D–99

TRVs for aquatic biota are intended to protect most aquatic species and are therefore likely to overstate 

the toxicity of inorganic mercury and methylmercury. The TRV for sediment biota is based on a 

correlation of observed adverse effects on sediment biota with concentrations of mercury in sediments 

that were contaminated by other pollutants as well. Because the concentration of biologically available 

mercury is likely to be lower than the total concentration and because other contaminants may have 

contributed to the observed toxicity, the TRV for sediment biota probably overstates the toxicity of 

inorganic mercury in sediment. 

D.6.4.3 Summary 

The risk estimates are believed to provide an adequate basis for health-protective decisionmaking. Taken 

together, the simplifying assumptions cause significant uncertainty in the final risk estimates. However, 

the predominant conservatism of most of the assumptions likely outweighs the biases caused by other 

assumptions. Uncertainty in the human and ecological risk characterization is a direct result of the 

conservative methodology employed. The conservative methodology and assumptions used in the 

exposure pathway selection, exposure assessment, and toxicity assessment are expected to overestimate, 

rather than underestimate, the potential for mercury to pose risk to assessment endpoints. By 

overestimating risk, the actual risk of the alternatives considered is believed to be less than indicated by 

the numeric results presented in the risk assessment. 

D.7 TECHNICAL DETAILS AND ANALYSES – EVAPORATION, ATMOSPHERIC 

DISPERSION, AND DEPOSITION MODELING 

D.7.1 Evaporation 

This section describes the models used to calculate evaporation from spilled pools of mercury inside and 

outside buildings. 

D.7.1.1 Evaporation Inside Buildings 

The evaporation rate R (kg/s) for indoor spills is given by the following equation, derived from laminar 

boundary layer theory (Fauske and Associates 2007): 

 Re = 0.664 A.D(ρv(Tp)/L)(ν/D)

1/3(uL/ν)1/2 (7–1) 

where: 

Re = Evaporation rate (kg/s) 

A = Area of pool (square meters) 

D = Binary diffusion coefficient of mercury in air (approximately 1.0 × 10-5 meters squared 

per second [m2

 s-1]) (Perry and Chilton 1973) 

ρv(Tp) = Saturation vapor density of mercury at temperature Tp (kg/m3

) (see Figure D–6 and 

Table D–53) 

Tp = Pool temperature (K) 

L = Length of the liquid spill in the direction of the airflow (meters) 

ν = Kinematic viscosity of air (approximately 1.5 × 10-5 m2

 s-1) 

(Engineering Toolbox 2009a) 

u = Velocity of the airflow above the surface of the pool (m/s) 

The Fauske article indicates that natural-convection-driven air currents are more important than 

mechanical-ventilation-induced air currents, and a typical value for u is 0.1 m/s. At this velocity, the 

airflow over the pool is well within the laminar regime for all the indoor spills of interest in this EIS 

except for that caused by an earthquake—the transition from laminar to turbulent flow occurs when the 

Reynolds number uL/ν exceeds 320,000 (CCPS 1996). 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–100

D.7.1.2 Evaporation in the Open Air 

Spills could take place in the open air (e.g., in the aftermath of a transportation accident). In this case, 

formulas for evaporation are derived from turbulent boundary layer theory. The one used in this EIS is 

taken from guidance provided by the Center for Chemical Process Safety (CCPS 1996). 

The rate of evaporation from an outside pool of area A is given by: 

 Re = kg.A.Pvp(Tp).M)/(R.Tp) (7–2) 

where: 

Re = Evaporation rate (kg/s) 

kg = Mass transfer coefficient 

A = Area of pool (m2) 

Pvp = Vapor pressure of mercury (pascals) (see Table D–68) 

Tp = Pool temperature (K) 

R = Gas constant (8.31 joules per kilogram-mole [J/kg-mol]) 

M = Molecular weight (200.59 kilograms per kilogram-mole [kg/kg-mol]) 

kg = D. Nsh/L 

where: 

D = Binary diffusion coefficient of mercury in air (approximately 1.0 × 10-5 m2 s-1) 

(Perry and Chilton 1973) 

Nsh = Sherwood number 

L = Length of the liquid spill in the direction of the airflow (meters) 

 Nsh = 0.037 (ν/D)

1/3((uL/ν)0.8-15,200) (7–3) 

where: 

ν = Kinematic viscosity of air (approximately 1.5 × 10-5 m2 s-1) 

(Engineering Toolbox 2009a) 

u = Velocity of the airflow above the surface of the pool (m/s) 

D.7.1.3 Vapor Pressure and Saturated Vapor Density of Elemental Mercury 

Equations 7–1 and 7–2 require the saturated vapor pressure or saturated vapor density of mercury in 

pascals or kg/m3

, respectively. These data are available in a study of mercury vapor pressure from NIST 

(Huber, Laesecke, and Friend 2006). Figure D–6 provides a graphical representation of the vapor 

pressure of mercury as a function of temperature. Table D–50 provides a tabulation of the vapor pressure 

and the corresponding vapor density. As discussed in Section D.4.2.1, the default evaporation 

temperature assumed for this EIS is 20 °C (68 °F). 
Human Health and Ecological Risk Assessment Analysis 

Figure D–6. Mercury Vapor Pressure as a Function of Temperature 

D–101
Table D–50. Mercury Vapor Pressure and Vapor Density 

D–102

Key: T, K=temperature, Kelvin; t, °C=temperature, degrees Celsius; p, MPa=pressure, megapascals; mol/L=mole per liter; ng/mL=nanogram

Source: Huber et al. 2006. 
Human Health and Ecological Risk Assessment Analysis 

D–103

D.7.1.4 Area of Pool A and Linear Dimension L

When a spill occurs on a smooth surface, the elemental mercury would spread until it reaches a thickness 

defined by the “capillary length,” b, which is the minimum pool depth allowed by surface tension: 

 b = [2(σ (1-cosΘ)/ρLg)]1/2 (7–4) 

where: 

b = Capillary length 

σ = Surface tension of mercury 

Θ = Contact angle 

ρL = Density of liquid elemental mercury, approximately 13,580 kg/m3

 at 20 °C 

(Engineering Toolbox 2009b) 

g = Acceleration due to gravity (9.82 m/s2) 

The formula above is given by de Gennes, Brochart-Wyart, and Quéré (2002), who also give a calculated 

value for b, 0.36 centimeters (0.14 inches). 

If there is a spillage of m kilograms of liquid mercury, it would spread to an area A, where: 

 A = m/(bρL) = m/(0.0036×13,580) ~ 0.02m m2 (7–5) 

Equation 7–5 is used for indoor spills. For outdoor spills, the surface is highly unlikely to be smooth. 

And an effective value of b may be greater than 0.36 centimeters, or 0.0036 meters. However, for the 

sake of conservatism, Equation 7–5 is used for outdoor spills also unless explicitly stated otherwise. 

For the purposes of this EIS, it is assumed that the pool is circular and that the length of the spill in the 

direction of pool flow L equals the diameter: 

L = 2(0.02m/π)

1/2 (7–6) 

D.7.2 Atmospheric Dispersion 

This section describes the atmospheric dispersion models used for this EIS: mixing in the building wake, 

Gaussian dispersion, and plume rise. It also contains a discussion of dry and wet deposition. 

D.7.2.1 Mixing into the Building Wake 

Releases inside the building or outside but in the vicinity of the building would first mix into the building 

wake. The following discussion is divided into two parts: new construction and existing facilities. 

Table D51 provides details on the sizes of the buildings at the various sites, including the size of Y–12 

under the No Action Alternative. 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–104

New Construction 

The generic storage building is expected to be 3 to 6 meters (10 to 20 feet) high by 102 meters (336 feet) 

wide by 144 meters (471 feet) long. A simple model for the concentration C (kg/m3

) of effluent in the 

building wake is (Hanna, Briggs, and Hosker 1982): 

C = Re/(hWαU(h)) (7–7) 

where: 

C = Concentration of effluent in building value (kg/m3)

Re = Release rate (kg/s) 

h = Height of the building (meters) 

W = Width of the building (meters) 

α = Dimensionless constant, approximately 0.713

U(h) = Windspeed at height h (m/s) 

For the dimensions given above, using 102 meters for the width of the building, 

C = (1/0.7×6.2×103) R/U(h) ~ 0.0022 R/U(h) (7–8) 

For a windspeed of 1.5 m/s (typical of Atmospheric Stability Class F), Equation 7–8 becomes: 

C = 0.0015R (7–9) 

For a windspeed of 4.5 m/s (typical of Atmospheric Stability Class D), Equation 7–8 becomes: 

C = 0.0005R (7–10) 

Table D52 provides a summary table of the estimated release rate R and the concentrations in the wake 

of a newly constructed building under the various onsite spill scenarios discussed in Section D.4. 

Existing Buildings 

Similar calculations to those described in Equations 7–7 through 7–10 have been performed for existing 

buildings. Results are summarized in Table D53. 

 

13 Hanna, Briggs, and Hosker (1982) say that α lies between 0.5 and 2, with test results supporting values towards the lower end 

of the range. 
Table D–51. Physical Data for a Mercury Storage Facility – New Construction and Existing Build

D–105

Parameter New Facilitya INL – RWMC 

Hawthorne Army 

Depot KCP WCSb– CSB 

Facility footprint 205,536 sf Within existing DOE 

complex. 

Within existing DoD complex. 

Within existing DOE complex. 

Within existing commercial complex. 

Dimensions (length × width) 

471×336 sf 200×140 ft (each) 200×50 ft (each) Part of a large 

building of more 

than 3×106 sf 

190×166 ft; 

interim storage 

building only 

Building height 10–20 ft 24 ft 35 ft 32 ft 25 ft Number of buildings 1 7 29 1 1 Total storage space 146,496 sf 205,394 sf 290,000 sf 150,000 sf 28,500 sf Building construction Structural steel frame 

on reinforced-concrete slab and sheet metal shell; epoxy-sealed floor. 

Prefabricated modular buildings on curbedconcrete slab. Insulate and heated interior. Sealed floor. 

Concrete floor, walls, and support columns with steel roof trusses and transite roofing. 

– Enclosed, 

commercial-grade metal building erected on a reinforcedconcrete foundation with 24-inch-diameter piers. 

Percentage of storage space used 

85 percent 65 percent 50 percent 80 percent 100 percent 

Access/security Manned security 

24 hours per day, 7 days per week, with perimeter barbed-wire fence; remote interior and exterior surveillance. 

Exists within RWMC, a secure area. 

Exists within the Hawthorne Army Depot complex, a military secure area. 

Exists within Bannister Federal Complex. Perimeter fence and security gates. 

Exists within WCS; manned guardhouse at main complex entrance and perimeter fence. 

a Data for new facility construction would be similar regardless of location and would include the Grand Junction Disposal Site, the 200-West 

Idaho Nuclear Technology and Engineering Center at INL, E Area at the Savannah River Site, and WCS in Andrews County, Texas. 

b The CSB at WCS could store approximately 2,000 metric tons (2,200 tons), a fraction of the maximum of the 10,000 metric tons (11,000 

anticipated over a 40-year period of analysis. 

Note: To convert square feet to square meters, multiply by 0.092903; feet to meters, by 0.3048. 

Key: CSB=Container Storage Building; DoD=U.S. Department of Defense; DOE=U.S. Department of Energy; ft=feet; INL=Idaho National Labo

Plant; RWMC=Radioactive Waste Management Complex; sf=square feet; WCS=Waste Control Specialists, LLC. 

Source: See Appendix C for the provenance of Table D–51. 
D–106

Table D–52. Evaporation Rates and Building Wake Concentrations for Various Spill Scenarios – New C

Scenario 

Mass Spilled 

(kg) Area (m2) 

Outdoors 

(O)/Stability 

Class or Indoors 

(I) 

Air Speed over 

Pool (m/s) 

Evaporation 

Rate (kg/s) 

I 0.1 6.66×10-9 

Single-flask spill 3.45×10 O/D 4.5 N/Aa 

1 7.11×10-1

O/F 1.5 N/Aa 

I 0.1 1.23×10-7 

O/D 4.5 8.35×10-6 

Single-pallet spill 1.69×103 3.48×101

O/F 1.5 2.93×10-6 

I 0.1 2.81×10-7 

Triple-pallet spill 5.08×10 O/D 4.5 N/Aa 

3 1.04×102

O/F 1.5 N/Aa 

I 0.1 8.31×10-8 

O/D 4.5 1.74×10-6 

1-metric-ton container spill 1,000 2.06×101

O/F 1.5 4.86×10-7 

I 0.1c 2.76×10-5 

O/D 4.5 7.98×10-4 

Earthquake – pool confined to building area N/Ab 1.50×104

O/F 1.5 3.25×10-4 

I 0.1 1.45×10-8 

N/A 4.5 N/Aa 

Full spill tray (slow release scenario) N/Ab 2.00 N/A 1.5 N/Aa 

a These scenarios cannot occur outside the building. b Area limited, not mass limited. c Calculated with formula for evaporation in a turbulent flow because Reynolds number exceeds 320,000 (see Section D.7.1.1). d These scenarios assume that the building has collapsed, hence there is no building wake. 

Note: To convert kilograms to pounds, multiply by 2.2046; square meters to square feet, by 10.7639; meters to feet, by 3.281. 

Key: kg=kilograms; m2=square meters; m/s=meters per second; kg/s=kilograms per second; mg/m3=milligrams per cubic meter; N/A=not av
Human Health and Ecological Risk Assessment Analysis 

Table D–53. Building Wake Concentrations for Existing Buildings 

Concentration in Building Wake (kg/m3) 

Scenario 

Outdoors 

(O)/ 

Stability 

Class or 

Indoors (I) 

Air Speed 

over Pool 

(m/s) 

New 

Construction 

INL – 

RWMC 

Hawthorne 

Army Depot

Kansas City 

Plant WCS – CSB

Y–12 

National 

Security 

Complex 

Single-flask 

spill I only 0.1 9.96×10-12 1.99×10-11 3.83×10-11 4.19×10-12 1.41×10-11 3.72×10-11

I 0.1 1.85×10-10 3.59×10-10 6.90×10-10 7.54×10-11 2.54×10-10 6.71×10-10

O/D 4.5 4.17×10-9 8.33×10-9 1.60×10-8 1.75×10-9 5.89×10-9

N/Aa Singlepallet spill 

O/F 1.5 4.39×10-9 8.77×10-9 1.68×10-8 1.84×10-9 6.21×10-9

N/Aa

Triplepallet spill I only 0.1 4.21×10-10 8.38×10-10 1.61×10-9 1.76×10-10 5.93×10-10 1.56×10-9

I 0.1 1.24×10-10 2.48×10-10 4.77×10-10 5.22×10-11 1.76×10-10 N/Ab

O/D 4.5 8.68×10-10 1.74×10-9 3.33×10-9 3.65×10-10 1.23×10-9 N/Ab

1-metricton 

container 

spill O/F 1.5 7.28×10-10 1.46×10-9 2.79×10-9 3.06×10-10 1.03×10-9 N/Ab

Earthquake 

– pool 

confined to 

building 

areac

I only 0.1 4.13×10-8 1.48×10-8d 1.02×10-8d 2.82×10-8 8.75×10-9 5.57×10-9

a Under the No Action Alternative, no pallets would be moved outside the building at Y–12 National Security Complex. 

b There are no 1-metric-ton containers at Y–12 National Security Complex. 

c Earthquake spills “outside” occur when building collapses, hence there is no building wake. 

d For these multi-building sites, even though the earthquake is assumed to affect all of the buildings on the site, the concentration 

in the building wake cannot exceed that outside an individual building, where the rate of release of mercury is limited by the 

floor area of that building. 

Note: To convert meters to feet, multiply by 3.281; kg/m3

 to mg/m3, by 106. 

Key: CSB=Container Storage Building; INL=Idaho National Laboratory; kg/m3

=kilograms per cubic meter; mg/m3=milligrams 

per cubic meter; m/s=meters per second; N/A=not applicable; RWMC=Radioactive Waste Management Complex; WCS=Waste 

Control Specialists, LLC. 

D.7.3 The Gaussian Dispersion Model 

This section describes the Gaussian model (as modified to take into account dry and wet deposition). The 

most commonly used methods to estimate human exposure to airborne gases, vapors, and particles from 

individual sources are the Gaussian plume models. These models represent a steady state average 

solution to the transport of pollutants arising from wind, turbulence, and other atmospheric forces (for 

example, see Hanna, Briggs, and Hosker 1982). These models have been modified to estimate the flux of 

contaminants from the atmosphere to land, water, and other surfaces arising from atmospheric deposition 

processes. Such processes include particle impaction and settling, as well as scavenging during 

rainstorms. The following equation describes the model used for the evaluation of both short- and longterm effects in this analysis: 

    



















 



   



 



 















    2

2

2

2

2

2

)(2

)( exp )(2)( exp)( )(2 exp 2 ),,(

zy y z z

zh zh

xg y

U

Q zyxC

  

 (7–11) 

U

x dy

y

h

yU

v

xg

z z

s   



 



   

0

2 ))((2 exp

)(

12 )(

 

x 2

 (7–12) 





















 



    2

2

))((2 exp)(2)0,,()0,,(x

h vyxCyxF x

z

s z 

 (7–13) 

D–107
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

where: 

C(x,y,z) = Pollutant concentration at a location x meters downwind, y meters crosswind of 

the source, at a height of z meters (kg/m3

) 

Q = Pollutant release rate (kilograms per second [kg/s]) 

U = Windspeed in the x direction (m/s) 

y = Crosswind stability coefficient at location x meters downwind of the source 

(meters) 

z = Vertical stability coefficient at location x meters downwind of the source 

(meters) 

h = Effective release height of the source (including buoyant plume rise as 

appropriate) (meters) 

vs = Dry deposition velocity (m/s) 

Λ = Rainfall scavenging rate (liters per second) 

F(x,y,0) = Pollutant deposition flux rate at a location x meters downwind, y meters 

crosswind of the source, at ground level (kilograms per square meter per second) 

Focusing on rainfall only (i.e., neglecting dry deposition), Equations 7–11 and 7–13 become: 

    



















 



  



 



 

















   2

2

2

2

2

2

)(2

)( exp )(2)( exp/ )(2 exp 2 ),,(

zy y z z

zh zh Ux y

U

Q zyxC

   

 (7–14) 

and 

hyxCyxF x)(22),,()0,,(    z   (7–15) 

Equation 7–15 is used later in this section when discussing rainfall events. 

It may be objected that mercury vapor is very dense—after all, mercury has a molecular weight that is 

nearly an order of magnitude greater than that of air. However, as previously discussed, for spills at 

ambient temperature, the saturated vapor density is approximately 1.4 × 10-5 kg/m3

. This amount of 

mercury is mixed with approximately 1.2 kilograms of air in 1 cubic meter: the addition of mercury 

makes such a small difference to the density of the air that the resulting plume is essentially neutrally 

buoyant; thus it is appropriate to use the Gaussian model. The other kinds of releases considered here are 

those caused by fire, in which case the released mercury is part of a buoyant plume. The approach 

adopted below is to calculate a height of plume rise at which point the plume is neutrally buoyant; this 

height is appropriate to use as the starting point for Gaussian modeling. 

D.7.3.1 Stability Coefficients 

Formulas providing values for the dispersion parameters (y and z) as a function of distance (x) are 

available for each of the six Pasquill atmospheric stability classes. Briggs originally developed the most 

widely used equations in 1973 (Hanna, Briggs, and Hosker 1982) and provided formulas for y and z

under open-country and urban conditions for each of the six stability classes; see Table D–54. Briggs’ 

formulas were used in the Gaussian dispersion model. 

The Briggs’ formulas were developed for use between 100 meters and 10 kilometers (330 feet and 

6.2 miles) downwind of the source. 

D–108
Human Health and Ecological Risk Assessment Analysis 

D–109

Table D–54. Briggs’ Dispersion Coefficients 

Rural Terrain 

Atmospheric Stability Class σy (meters) σz (meters) 

A 0.22x (1+0.0001x)

-1/2 0.20x

B 0.16x (1+0.0001x)

-1/2 0.12x

C 0.11x (1+0.0001x)

-1/2 0.08x (1+0.0002x)-1/2

D 0.08x (1+0.0001x)

-1/2 0.06x (1+0.0015x)-1/2

E 0.06x (1+0.0001x)

-1/2 0.03x (1+0.0003x)-1

F 0.04x (1+0.0001x)

-1/2 0.016x (1+0.0003x)-1

Urban Terrain 

Atmospheric Stability Class σy (meters) σz (meters) 

A–B 0.32x (1+0.0004x)

-1/2 0.24x (1+0.001x)+1/2

C 0.22x (1+0.0004x)

-1/2 0.20x

D 0.16x (1+0.0004x)

-1/2 0.14x (1+0.0003x)-1/2

E–F 0.11x (1+0.0004x)

-1/2 0.08x (1+0.0015x)-1/2

D.7.3.2 Height of Release 

The height of release is dependent on the scenario being evaluated. For evaporation from pools, the 

release height is zero. For the fire scenarios, plume rise is discussed below. 

D.7.3.3 Wet and Dry Deposition 

This subsection describes the values of the dry deposition velocity and the rainfall scavenging rate that 

were used to determine how much mercury is deposited on the ground at any given location. The text 

below describes assumptions about how the mercury mixes with the soil. 

Deposition Parameters 

For releases of elemental mercury vapor, the dry deposition velocity and the scavenging rate are 

essentially zero (EPA 1997b). Under most of the scenarios identified in this risk assessment, mercury 

would in fact be released as elemental mercury, thus deposition pathways are not important. 

In the case of fire scenarios, such as the offsite truck or railcar fire, there is a possibility that mercury 

could be converted into a form with a significant dry deposition velocity. In practice, the mercury 

released into the atmosphere during a fire would partially be in the form of elemental mercury and 

partially in the form of divalent mercury. Under operating conditions that include stack emissions in the 

presence of environmental controls, EPA (1998) recommends phase allocations for mercury emissions of 

20 percent vapor phase elemental mercury, 60 percent vapor phase divalent mercury, and 20 percent 

particle phase mercury. No information is available concerning the speciation of mercury resulting from 

sources involving combustion in the absence of emission controls. Therefore, in this risk assessment, it is 

conservatively assumed that 100 percent of the mercury is released as divalent mercury because divalent 

mercury is more susceptible to deposition processes than either elemental or particle mercury 

(EPA 1997b). This is an important assumption in the assessment of ecological risks. 

EPA (1997b) has published estimates of dry deposition velocities for divalent mercury in all six 

atmospheric stability classes, in all four seasons, and for 11 different types of terrain (including urban)—a 

total of 264 values. Table D–55 shows an example for Atmospheric Stability Class A. 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–110

Table D–55. Deposition Velocities for Divalent Mercury (cm/s) 

 for Various Types of Land Areas in Atmospheric Stability Class A 

Season 

Type of Land Area Winter Spring Summer Fall 

Annual 

Average 

Water 1.09 0.98 0.92 1.00 1.00 

Barren land 1.16 1.05 0.98 1.07 1.07 

Range 1.89 1.49 1.67 1.78 1.71 

Mixed agricultural/range 1.62 1.60 1.90 1.93 1.76 

Agricultural 1.32 1.60 2.29 2.02 1.81 

Rocky open areas 1.98 1.84 1.95 1.97 1.94 

Nonforested wetland 2.02 1.85 1.91 1.88 1.92 

Mixed forest/wetland 3.49 3.28 3.17 3.32 3.32 

Coniferous forest 3.61 3.42 3.32 3.46 3.45 

Deciduous forest 3.61 3.42 3.32 3.46 3.45 

Urban 4.83 4.59 4.47 4.64 4.63 

Note: To convert centimeters to inches, multiply by 0.3937. 

Key: cm/s=centimeters per second. 

Source: EPA 1997b. 

In the analysis of fire scenarios described below, calculations are carried out in Atmospheric Stability 

Classes A, D, and F. Values of dry deposition velocity for each of these three classes were selected from 

Table 4–3 of EPA (1997b) on the following basis: 

 For rural sites, the highest deposition velocity associated with each of the Atmospheric Stability 

Classes A, D, and F, selected from those associated with any of 10 types of terrain (excluding 

urban) and all four seasons 

 For urban sites, the highest deposition velocity associated with each of the Atmospheric Stability 

Classes A, D, and F, selected from those associated with urban terrain and all four seasons 

The selected values are shown in Table D–56. 

Table D–56. Dry Deposition Velocities (cm/s) for Divalent Mercury 

Dry Deposition Velocity (cm/s) Atmospheric Stability Class Rural Urban 

A 3.6 4.8 

D 3.0 4.3 

F 0.29 0.36 

 Note: To convert centimeters to inches, multiply by 0.3937. 

Key: cm/s=centimeters per second. 

Regarding the scavenging rate Λ=1.5×10-4 s-1, Hanna, Briggs, and Hosker (1982) note that this is a 

median value from 20 field experiments conducted. They indicate a range of 0.4 × 10-4 s-1 to 3 × 10-3 s-1. 

They also state, “The use of scavenging coefficients for wet removal modeling is probably best regarded 

as an order-of-magnitude estimation procedure.” 
Human Health and Ecological Risk Assessment Analysis 

D–111

There is information in EPA (1997b) regarding the scavenging rate of mercury compounds in particulate 

form: 

Λ = α1.0×10-4×R s-1 (7–16) 

where R is the rainfall rate in millimeters per hour (mm/hr). Light, moderate, and heavy rainfall rates are 

1 mm/hr, 3 mm/hr, and 5 mm/hr (or more), respectively (CCPS 1996). The coefficient α depends on 

particle diameter and varies from a minimum of approximately 0.5 for particles with diameters in the 

range of 0.5 to 1 micron up to approximately 6.5 for particles with diameters in excess of approximately 

10 microns. 

It is assumed that the divalent mercury formed during the combustion process would be in particulate 

form for two reasons. First, the predominant divalent compound of mercury in the plume would be 

mercuric oxide, which is solid at the temperature of the plume after it has ceased rising and is at the 

temperature of the surrounding atmosphere. Second, particulate matter would be formed in the fire 

(e.g., soot), and it is assumed that divalent mercury would attach to these particles. 

EPA (1997b) discusses the particle size distribution and notes that it may differ from one combustion 

process to another, based on an analysis of flue gases. The distribution depends on the type of furnace 

and design of combustion chamber, composition of feed/fuel, particulate matter removal efficiency and 

design of air pollution control equipment, and amount of air in excess of stoichiometric amounts that is 

used to sustain the temperature of combustion. Data collected from measurements on flue gases indicate 

that there are two ranges of particle size. The first is governed by accumulation (i.e., the condensation of 

the mercury compound formed during combustion to form particles). The second range contains “coarse” 

particles, which would include soot and any particulate matter that may already be present in the air that 

mixes into the rising plume. The geometric mean diameter of several hundred measurements indicates 

that the accumulation mode dominates particle size, and a representative particle diameter for this mode is 

0.3 microns. A representative diameter for coarse particles is 5.7 microns. The fraction of particle 

emissions assigned to each particle class is approximated based on the determination of the density of the 

surface area of each representative particle size relative to the total surface area of the aerosol mass. 

Using this method, 93 percent and 7 percent of the total surface area are estimated to comprise 0.3- and 

5.7-micron-diameter particles, respectively. 

To simplify the calculation, it is assumed that all particles are in the range that has a 0.3-micron mean and 

that the corresponding value for α is approximately 0.8. 

The average rainfall rates at the seven candidate sites range from approximately 1 mm/hr (GJDS, 

Hawthorne Army Depot, Hanford, and INL), to approximately 2 mm/hr (KCP and WCS), to 

approximately 2.5 mm/hr (SRS). These rates correspond to values of Λ of 8.0 × 10-5 s

-1, 1.6 × 10-4 s-1, and 

2.0 × 10-4s

-1, respectively. For the purposes of this analysis, an intermediate value of 1.5 × 10-4 s-1 has 

been chosen. 

Note that this risk assessment does not explicitly consider precipitation scavenging by snowfall (it is 

included by implication in the rainfall scavenging rate). Slinn (1984) provides a comprehensive review of 

precipitation scavenging, including snow scavenging. He shows a figure (11.14) in which the snow 

scavenging rate for a given snowfall rate (rain equivalent) varies over four orders of magnitude depending 

on the shape and size of the snowflakes and on the size of the aerosol that is being scavenged. However, 

the scavenging rate for rain lies right in the middle of this range of uncertainty, so it was assumed that the 

rainfall scavenging rate in Equation 7–16 also applies to snow. 

Note that EPA’s study of the fate and transport of mercury in the environment (EPA 1997b, 

Section 4.3.2) used a precipitation scavenging rate that does not discriminate between the types of 

precipitation (rainfall or snowfall). This risk assessment adheres to that precedent. 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–112

Mercury Concentration in Soil 

In the 2004 MM EIS (DLA 2004a), the Gaussian model, modified for deposition and scavenging, was 

used to determine the location and magnitude of the highest mercury deposition (or flux) to soil in 

representative weather conditions of Atmospheric Stability Class D and a windspeed of 4.5 m/s. The total 

mass of mercury deposited per unit area at that location was calculated as the mercury flux (in units of 

milligrams per square meter per second) multiplied by the duration of plume passage. The mercury was 

assumed to mix completely within the top 5.1 centimeters (2 inches) of soil, which, when multiplied by 

the soil density (1.8 grams per cubic meter) and scaled accordingly, yields soil concentration estimates (in 

units of mg/kg). With the exception of the use of a single representative weather condition (discussed 

further below), these assumptions have been retained. 

In the case in which mercury is deposited on a water surface, the assumption was that the mercury would 

rapidly find its way into the sediment and mix into the top 2 centimeters (0.8 inches). It would then be 

partitioned into water using a sediment-water distribution coefficient Kd of 710,000 liters per kilogram 

(L/kg) for inorganic mercury and 27,000 L/kg for methylmercury. 

What is also needed is the percentage of the mercury in sediment or soil that would remain as inorganic 

mercury and the percentage that would transform into methylmercury. These assumptions are 

summarized in Table D57. 

Table D–57. Percentage of Inorganic and Methylmercury in 

Various Types of Soil 

Nature of Soil Inorganic Mercury Methylmercury 

Dry soil 98 percent 2 percent 

Wet soil 85 percent 15 percent 

Sediment 85 percent 15 percent 

D.7.3.4 Use of Gaussian Model in a Probabilistic Framework 

The outcome of calculations using the Gaussian model varies depending on the atmospheric stability 

class, the windspeed, and the roughness of the surface (e.g., a smooth, barren surface; a forest; or an urban 

environment). For the 2004 MM EIS (DLA 2004a), a simple screening analysis was performed using 

only Atmospheric Stability Class D with a windspeed of 4.5 m/s at a rural site (low surface roughness). 

In this EIS, the analysis is a little more sophisticated in that it includes calculations performed over the 

full range of weather conditions and weights results arising from the use of annualized joint frequency 

distributions (jfds). These give the probability of occurrence of weather conditions with a specific 

atmospheric stability class and a windspeed within a specified range and a specific direction (one of the 

usual 16 directions of the conventional wind rose). Table D58 shows the jfd for KCP.14 The data for the 

other sites are similar. In the jfd, there are four ranges of windspeed: 0–3 m/s, 3–5 m/s, 5–8 m/s, and 

greater than 8 m/s. In subsequent analyses, these are each represented by a single windspeed, 1.5 m/s, 

4.5 m/s, 6.5 m/s, and 8 m/s, respectively. 

 

14 The jfd for KCP is actually that for Kansas City International Airport. This is usual practice for running computer models for 

screening risk assessments such as the present one. For WCS, the data are from Midland-Odessa International Airport; for 

Hawthorne Army Depot, from Reno-Tahoe International Airport; for GJDS, from Grand Junction Regional Airport; and for 

Hanford, INL, and SRS, from measurements actually taken at the sites. In each case, 5 consecutive years of hourly weather 

data were analyzed and converted into the jfd format. 
Human Health and Ecological Risk Assessment Analysis 

D–113

It was necessary to choose a computer model that has the following capabilities: 

 Can model Gaussian dispersion for both ground-level and elevated releases 

 Can model dry deposition and possibly wet deposition15

 Can run a full spectrum of weather conditions 

 Can accept a jfd or equivalent 

 Can easily compare the calculated outcomes (airborne concentrations and deposited quantities per 

unit area) with numerous screening values (such as AEGL-2 and screening levels of deposited 

mercury for humans and all of the ecological receptors) and can calculate the probability that 

screening values would be exceeded as a function of distance downwind 

Initially, it was thought that MACCS2 [MELCOR Accident Consequences Code System] (NRC 1998) 

would fit the bill. However, in practice it becomes very cumbersome to use MACCS2 to satisfy the 

requirements of the fifth bullet above. Instead it was decided to use two Science Applications 

International Corporation computer models, SAPLUME (for elevated releases) and SACRUNCH (for 

ground-level releases), that have the ability to easily manipulate jfds and, in particular, to readily perform 

repetitive calculations for a host of screening values (SAIC 1994). These models have a considerable 

pedigree and have been used extensively for the modeling of accidental releases of hazardous chemicals. 

For example, they were used to model postulated hydrogen fluoride releases from refineries for regulatory 

purposes (Ultramar 1990) and were used extensively in helping EPA to prepare guidance on atmospheric 

dispersion modeling in support of the Risk Management Program (40 CFR 68; Kaiser 1999; Kaiser, Price, 

and Urdaneta 1999). Examples are EPA’s guidance on ammonia refrigeration facilities and wastewater 

treatment plants (EPA 2009a:Appendices E and F). However, to provide further support for the use of 

SAPLUME and SACRUNCH, Table D59 provides some sample comparisons with MACCS2. 

Table D59 mostly shows reasonable agreement between the predictions of MACCS2 and those of 

SACRUNCH or SAPLUME (within a factor of about 2) except close to the release under a rising plume, 

where concentrations are very small. Therefore, the use of SAPLUME and SACRUNCH instead of 

MACCS2 is judged to be acceptable. 

 

15 Wet deposition can be easily managed by postprocessing in an Excel spreadsheet. 
D–114

Table D–58. Joint Frequency Distribution for Kansas City Plant 

Percentage of Time Wind Blows from the Indicated Direction Atmospheric Stability 

Class 

Windspeed 

Range 

(m/s) NNE NE ENE E ESE SE SSE S SSW SW WSW W WNW 

0–3 0.00047 0.00025 0.00032 0.00025 0.00025 0.00010 0.00023 0.00057 0.00039 0.00043 0.00026 0.00022 0.00025 

A 

3–5 0.00021 0.00014 0.00019 0.00014 0.00014 0.00007 0.00016 0.00016 0.00023 0.00031 0.00019 0.00012 0.00014 0–3 0.00105 0.00055 0.00052 0.00056 0.00073 0.00047 0.00060 0.00059 0.00094 0.00064 0.00073 0.00072 0.00084 

B 3–5 0.00180 0.00108 0.00082 0.00098 0.00127 0.00098 0.00091 0.00127 0.00155 0.00134 0.00101 0.00096 0.00110 

5–8 0.00155 0.00105 0.00070 0.00068 0.00068 0.00098 0.00091 0.00115 0.00248 0.00171 0.00152 0.00084 0.00073 0–3 0.00046 0.00024 0.00029 0.00024 0.00031 0.00019 0.00046 0.00039 0.00058 0.00044 0.00030 0.00050 0.00052 3–5 0.00195 0.00120 0.00115 0.00098 0.00131 0.00077 0.00152 0.00136 0.00277 0.00225 0.00197 0.00159 0.00204 5–8 0.00574 0.00255 0.00267 0.00251 0.00380 0.00347 0.00438 0.00532 0.01050 0.00719 0.00537 0.00291 0.00335 

C 

>8 0.00094 0.00049 0.00038 0.00035 0.00080 0.00066 0.00108 0.00197 0.00516 0.00356 0.00171 0.00068 0.00077 

0–3 0.00095 0.00057 0.00046 0.00048 0.00061 0.00048 0.00053 0.00049 0.00075 0.00057 0.00055 0.00036 0.00060 3–5 0.00483 0.00241 0.00244 0.00169 0.00237 0.00192 0.00195 0.00220 0.00366 0.00284 0.00227 0.00164 0.00209 5–8 0.01811 0.01015 0.00747 0.00776 0.01396 0.01244 0.01371 0.01495 0.02249 0.01010 0.00511 0.00359 0.00590 

D 

>8 0.02418 0.01052 0.00656 0.00586 0.01518 0.01139 0.01326 0.02488 0.07615 0.03494 0.01010 0.00476 0.00972 

3–5 0.00518 0.00319 0.00352 0.00323 0.00295 0.00422 0.00471 0.00520 0.00708 0.00445 0.00295 0.00267 0.00356 

E 

5–8 0.00548 0.00185 0.00195 0.00267 0.00532 0.00565 0.00731 0.01188 0.02076 0.00996 0.00469 0.00262 0.00412 0–3 0.00369 0.00231 0.00237 0.00191 0.00212 0.00186 0.00305 0.00260 0.00448 0.00331 0.00220 0.00237 0.00396 

F 

3–5 0.00574 0.00445 0.00525 0.00403 0.00321 0.00462 0.00661 0.00738 0.01155 0.00848 0.00576 0.00525 0.00799 0–3 0.00661 0.00392 0.00397 0.00345 0.00403 0.00310 0.00487 0.00464 0.00713 0.00538 0.00405 0.00417 0.00618 3–5 0.01971 0.01247 0.01336 0.01106 0.01125 0.01258 0.01586 0.01757 0.02683 0.01966 0.01415 0.01223 0.01692 5–8 0.03088 0.01560 0.01279 0.01361 0.02376 0.02254 0.02631 0.03329 0.05623 0.02896 0.01668 0.00996 0.01411 

All stability 

classes 

>8 0.02512 0.01101 0.00694 0.00621 0.01598 0.01204 0.01434 0.02685 0.08130 0.03850 0.01181 0.00544 0.01050 

All 

windspeeds 

and classes 

– 0.08231 0.04300 0.03705 0.03432 0.05501 0.05026 0.06139 0.08236 0.17150 0.09250 0.04669 0.03179 0.04770 

Note: To convert meters to feet, multiply by 3.281. Key: >=greater than; m/s=meters per second. 
D–115

Table D–59. Comparisons of Outputs of MACCS2, SACRUNCH, and SAPLUME Runs 

D, 4.5 m/s, Ground Levela D, 4.5 m/s, 25 metersa D, 4.5 m/

Concentration 

kg/m3

Concentration 

kg/m3

Concentration 

kg/m3

Concentration 

kg/m3

Concentration 

kg/m3

Conc

k

Distance 

(meters) MACCS2 SACRUNCH Ratiob MACCS2 SAPLUME Ratiob MACCS2 SA

100 7.63×10-4 9.50×10-4 0.80 3.68×10-6 none N/A none 200 2.18×10-4 2.20×10-4 0.99 4.29×10-5 very small N/A none 500 4.29×10-5 3.50×10-5 1.23 2.97×10-5 3.50×10-5 0.85 1.17×10-7 1,000 1.33×10-5 1.00×10-5 1.33 1.16×10-5 1.40×10-5 0.83 1.58×10-6 4.2,000 4.42×10-6 3.10×10-6 1.42 4.17×10-6 5.00×10-6 0.83 1.88×10-6 1.5,000 1.15×10-6 7.40×10-7 1.56 1.13×10-6 1.30×10-6 0.87 8.63×10-7 8.10,000 4.58×10-7 2.80×10-7 1.64 4.54×10-7 4.50×10-7 1.01 3.99×10-7 3.

F, 1.5 m/s Ground Levela F, 1.5 m/s, 25 metersa F, 1.5 m

Concentration 

kg/m3

Concentration 

kg/m3

Concentration 

kg/m3

Concentration 

kg/m3

Concentration 

kg/m3

Conc

k

Distance 

(meters) MACCS2 SACRUNCH Ratiob MACCS2 SAPLUME Ratiob MACCS2 SA

100 4.79×10-2 2.27×10-2 2.11 1.48×10-21 none N/A none 200 7.29×10-3 5.30×10-3 1.38 7.79×10-10 none N/A none 500 3.77×10-4 8.20×10-4 0.46 2.25×10-5 7.00×10-5 0.32 1.32×10-28 1,000 2.44×10-4 2.10×10-4 1.16 7.13×10-5 8.00×10-5 0.89 9.04×10-13 2,000 8.63×10-5 6.20×10-5 1.39 4.88×10-5 5.00×10-5 0.98 4.00×10-8 1.5,000 2.18×10-5 1.50×10-5 1.46 1.84×10-5 1.80×10-5 1.02 1.10×10-6 2.10,000 1.21×10-5 6.90×10-6 1.75 9.13×10-6 8.40×10-6 1.09 1.49×10-6 1.

a Atmospheric stability class, windspeed, height of release.b Ratio = (MACCS2 concentration)/(SACRUNCH or SAPLUME concentration). Note: The assumed release rate is 1 kilogram per second of a passive (non-buoyant, non-heavy) chemical. Release approximates a point sourcemultiply by 3.281; kg/m3 to mg/m3, by 106. 

Key: kg/m3=kilograms per cubic meter; m/s=meters per second; mg/m3=milligrams per cubic meter; N/A=not applicable. 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–116

D.7.3.5 The Gaussian Model and Wet Deposition 

The approach described in Section D.7.3.4 applies only to dry deposition. A simplified approach was 

adopted to wet deposition. 

 From the 5-year data sets for each site, select only those hourly data that include rainfall. 

Calculate the fraction of time that it rains at each site (see Table D–15 for results). 

 Assume that the seven data sets, on the whole, are representative of the meteorology along all of 

the transportation routes. Calculate representative probabilities of rain for the routes to each of 

the seven candidate sites (see Section D.2.7.4). 

 Modify the predicted frequencies of crashes with fires by multiplying by the probability of rain 

during each trip (see Table D–16). 

 Perform runs of SAPLUME with a 100-meter (336-foot) release height (see below for why this is 

expected to be conservative for truck and railcar scenarios) for three representative conditions of 

atmospheric stability class and windspeed: A, 1.5 m/s; D, 4.5 m/s; and F, 1.5 m/s. 

 From the runs of SAPLUME, extract the plume centerline concentrations and vertical standard 

deviations as a function of distance in each of the three weather conditions. 

 Use Equation 7–15 to calculate the amount of mercury deposited per unit area under each release 

scenario. 

 Compare these to the equivalent deposited amounts per unit area for human and ecological 

receptors and make qualitative judgments about the severity of the consequences. 

 Combine these consequences with the aforementioned rainfall-modified frequencies of crashes 

with fires during rainfall to obtain estimates of risk. 

D.7.4 Modeling Fire Events 

As discussed above, it is only in the case of fire scenarios that deposition of mercury onto the ground is 

expected. Thus, the fire scenarios are important considerations with regard to chronic human health risk 

and ecological risk. The fires considered in this risk assessment include those caused by truck or railcar 

crashes off site. This section illustrates the fire modeling employed by focusing on a railroad accident 

that would result in the combustion of the pallets on a single railcar transporting 3-L flasks in a 

7 × 7 array. Pallets would not be stacked for transport. The accident is also assumed to cause a breach in 

a sufficient number of mercury containers to create an exposed area equal to the area of the railcar bed. 

This exposed mercury is assumed to reach its boiling point and to release mercury at the maximum rate 

consistent with the dynamics of boiling mercury. The analysis assumes that the mercury would boil as 

long as the pallets are on fire. 

The parameters of interest for long-term human health risk assessment are listed below. 

 Heat output, area, and duration of the pallet fire 

 Mercury release rate 

 Effective release height 

 Windspeed at the release height 
Human Health and Ecological Risk Assessment Analysis 

The heat output and area of the fire are used to estimate the effective release height. The mercury release 

rate, effective release height, and windspeed at the release height are used in conjunction with the 

Gaussian model to estimate atmospheric mercury concentrations and mercury deposition flux rates to soil. 

The duration of the pallet fire determines the duration of the mercury deposition, which is then used to 

determine the mercury concentrations in the soil, sediment, or surface water. The duration of the pallet 

fire and the mercury release rate determine the mass of mercury released into the atmosphere. 

D.7.4.1 Accidental Truck and Railcar Fires 

In this section, parameters of interest for truck and railcar fires are determined. The calculations included 

here are for the railcar fire. However, the calculations for the truck fire are similar. The dimensions of 

the railcar considered in this analysis are 18 by 3 meters (59 by 10 feet). As shown in Section D.2.7, the 

maximum number of pallets that can be loaded into the railcar is 24: 2 rows of 12 pallets each. Each 

unloaded pallet is assumed to weigh approximately 27 kilograms (60 pounds). Under these assumptions, 

the total mass of fuel available for combustion in the pallets is approximately 635 kilograms 

(1,400 pounds). The area occupied by the pallets, and consequently, the area of the fire is 48.7 square 

meters (530 square feet). Similar considerations show that the area of the truck fire is 35.7 square meters 

(380 square feet).

Pallet Fire Heat Output 

The heat output of the pallet fire (dHe /dt) for the railcar fire was estimated as follows. The rate of solids 

combusted in a fire was estimated as (Ayer et al. 1988): 

(Heat absorbed/m vapor fuel ass generated)

M Burned   flux (Heat generated)  A (7–17) 

The term A equals the area of the fire. The heat flux generated is the sum of the convective heat flux 

(18 kilowatts per square meter [kW/m2

] for wood) and the radiative heat flux (40 kW/m2 for wood) minus 

the surface radiation heat loss (16 kW/m2

 for wood), or 42 kW/m2 for wood. The heat absorbed/mass fuel 

vapor generated for wood is 3.6 kW-s/g. The area of the fire is about 41.6 square meters (448 square 

feet). Accordingly: 

M Burned



 = 42 kW/m2/3.6 kW-s/g = 11.667 g/s-m2 

 11.667 g/s-m2 × 41.6 m2 = 485.8 g/s 

At this rate of combustion, the pallet fire would last approximately 1,308 seconds, or about 21.8 minutes. 

The heat output is calculated as: 

dHe /dt = × THR × EFF × (1,000/4.186) M Burned



dHe /dt = 485.8 g/s × THR × EFF × (1,000/4.186) (7–18) 

where: 

dHe /dt = Heat output

M Burned = Rate of solids combusted in fire

THR = Theoretical heat release (18 kilojoules per gram for wood) 

EFF = Fraction of heat not lost to thermal radiation (0.7) 

D–117
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–118

Consequently: 

dHe /dt = 485.8 × 18 × 0.7 × (1,000/4.186) 

 = 1.4623 × 106

 calories per second (cal/s) 

Mercury Release Rate 

The equation used to estimate the mercury release rate is that specified by EPA for use in conducting the 

offsite consequence analyses for Risk Management Programs required under the Clean Air Act 

(EPA 1999b). The equation, originally published in EPA’s Technical Guidance for Hazards Analysis: 

Emergency Planning for Extremely Hazardous Substances (EPA 1987), estimates the worst-case release 

from a toxic liquid at elevated temperatures as follows: 

Re = (0.284 × u

0.78 × MW2/3 × A × VP × 453,600)/(82.05 × T × 60) (7–19) 

where: 

Re = Release rate (mg/s) 

u = Windspeed (m/s) 

MW = Molecular weight of mercury (200.59 kg/kg-mol) 

A = Surface area (approximately 54.8 square meters [590 square feet]) 

VP = Vapor pressure (760 millimeters of mercury at its boiling point) 

T = Temperature of released substance (630 K, the boiling point of mercury) 

The following are the assumptions for estimating evaporation from pools of mercury at the atmospheric 

boiling point: 

u = 1.5 m/s (Atmospheric Stability Class A or F weather conditions) or 4.5 m/s 

(Class D weather conditions) 

VP = 760 millimeters of mercury (the vapor pressure of any liquid at its boiling point) 

T = 630 K (357 °C or 673 °F) (the boiling point of mercury) 

Taken together, these assumptions yield a release rate (RR) for a railcar fire of about 1.56 × 106

 mg/s if 

the windspeed is 4.5 m/s. This equates to a total atmospheric mercury release of about 2,048 kilograms 

(4,514 pounds) for a 1,308-second (21.8-minute) duration. For different windspeeds u, this rate of release 

scales in proportion to (u/4.5)0.78; see Equation 7–19. 

Effective Release Height 

The effective release height was calculated using the following equations (U.S. Army 1980): 

 h = [6F/(U(h)γ

2 

s) + (r/γ)

3

]

1/3−r/γ (7–20) 

where 

F = g(dHe/dt)/(π ρa Ta Cp) (7–21) 
Human Health and Ecological Risk Assessment Analysis 

D–119

For air material properties, the equation for F becomes: 

F = 0.0000347 (dHe /dt) and the equation for h becomes: 

 h = [–5.2 (dHe /dt)/(U(h)) + (2r)

3

]

1/3−2r (7–22) 

For the truck plume radius, the equation becomes: 

 h = [–5.2 (dHe /dt)/(U(h)) + 313.3]1/3−6.8 (7–23) 

For the railcar fire plume radius, the equation becomes: 

 h = [–5.2 (dHe /dt)/(U(h)) + 582.6]1/3−8.4 (7–24)

For the plume specific heat input, these equations become: 

 h = [–6.5×106/(U(h)) + 313.3]1/3−6.8 (truck fire) (7–25) 

 h = [–7.28×106/(U(h)) + 582.6]1/3−8.4 (railcar fire) (7–26) 

where: 

h = Effective release height (meters) 

F = Buoyancy parameter 

U(h) = Average windspeed from ground to the plume rise elevation (m/s) 

γ = Entrainment coefficient (0.5 for uncontrolled fires) 

s = Stability parameter (technically, the square of the Brunt-Väisälä frequency) 

(–1.6 × 10-4 s-2) 

r = Initial plume radius 

 • Truck fire: 3.396 meters (11.14 feet) 

 • Railcar fire: 4.176 meters (13.70 feet) 

g = Gravitational acceleration (8.8 m/s2) 

dHe/dt = Rate of heat input to the plume 

 • Truck fire: 1.25 × 106 cal/s 

 • Railcar fire: 1.46 × 106

 cal/s 

ρa = Standard density of air (1.293 kg/m3

) 

Ta = Ambient air temperature (289 K [16 °C or 60 °F]) 

Cp = Specific heat of air (0.24 cal/g-K) 

Note that this equation does not explicitly relate the effective release height (h) to the other parameters 

because the average windspeed (an otherwise independent variable) is itself a function of h. 

Consequently, the equation was solved iteratively by successively calculating h and U(h) until successive 

estimates differed by less than 0.1 percent. 

The average windspeed (U) was estimated by integrating the assumed vertical windspeed profile (u(z)) 

over the height of the rising plume and dividing by the height, i.e., U = (1/h) ∫ u(z)dz.
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–120

The vertical windspeed profile was estimated using a power law equation for elevations up to 200 meters 

(660 feet). The power law equation relating the windspeed at an elevation to the windspeed at 10 meters 

(33 feet) is (Hanna, Briggs, and Hosker 1982): 

 u(z) = u(10) × (z/10)p (7–27)

where: 

u(z) = Windspeed at elevation z (m/s) 

u(10) = Windspeed at 10 meters (m/s) 

z = Elevation above ground (meters) 

p = A dimensionless exponent, dependent upon atmospheric stability class (see Hanna, 

Briggs, and Hosker 2002) 

The predicted height of plume rise and average windspeed for the six atmospheric stability classes with 

representative windspeeds are given in Table D60 for both the truck and railcar fires. 

Table D–60. Predicted Plume Heights and Average Windspeeds for Truck and 

Railcar Crashes with Fires 

Atmospheric Truck Fire Railcar Fire 

Stability 

Class/Windspeed 

Plume Height 

(meters) 

Average Windspeed 

(meters per second) 

Plume Height 

(meters) 

Average Windspeed 

(meters per second) 

A/1.5 150 1.7 156 1.7 

B/3 322 3.6 345 3.6 

C/4.5 101 5.2 105 5.2 

D/4.5 99 5.5 103 5.5 

E/3 102 5.0 106 5.1 

F/1.5 271 5.9 287 6.1 

Note: To convert meters to feet, multiply by 3.281. 

As can be seen, the lowest predicted height of rise is 99 meters (rounded to 100 meters [330 feet]), with 

only a small difference between the heights for the truck and railcar fire. Subsequent analyses are 

simplified by assuming that the height of plume rise is 100 meters in all conditions of atmospheric 

stability and windspeed for both truck and railcar fires. This is a conservative assumption for the 

purposes of this risk analysis. 

Parameters of Interest 

Table D61 presents the values for various parameters determined in this analysis. 

Note that the calculation of the fraction of the fire energy required to vaporize the mercury was performed 

to ensure that only a small fraction of the rate of release of heat used in the plume rise equations was 

consumed in evaporating the mercury. 
Human Health and Ecological Risk Assessment Analysis 

D–121

Table D–61. Estimated Values for Various Parameters of Interest in 

Truck and Railcar Fire Modeling–Wooden Pallet Fire 

Parameter Truck Fire Railcar Fire 

Molecular weight (MW) 200.6 200.6 

Boiling point (°F) 674 674 

T (boiling point) (K) 630 630 

Vapor pressure at T 760 760 

Windspeed (m/s) 4.5 4.5 

Spill area (ft2) 384 448 

Spill area (m2) 35.7 41.6 

Fire area (ft2) 384 590 

Fire area (m2) 35.7 54.8 

Heat input (cal/s) 1.25×106 1.46×106

Duration of pallet fire/mercury release(s) 762 1,308 

Release rate (mg/s) windspeed 4.5 m/sa 1.3×106 1.6×106

Plume rise (m)b 99 103 

Average windspeed (m/s) 5.52 5.55 

Specific heat (cal/gram K) 0.033 0.033 

Heat of vaporization (cal/mole) 13,599.1 13,599.1 

Heat of vaporization (cal/gram) 67.8 67.8 

Total heat input (cal) 9.52×108 1.91×109

Total mass released (grams) 9.91×105 2.09×106

Total energy to raise mass from 294 to 630 Kc (cal) 1.10×107 2.32×107

Total energy to boil the mass at 630 K (cal) 6.72×107 1.42×108

Sum of energy to raise temperature and boil mass (cal) 8.82×107 1.65×108

Percentage of fire energy needed to boil mass of mercury 9.3 8.6 

a The release rate at a different windspeed is so proportional to u0.78 (see equation 7-19). For u=1.5 m/s, the 

predicted evaporation rates for truck and railcar fires are 5.5×105

 and 6.8×105 mg/s, respectively. 

b Plume rise for Atmospheric Stability Class D and windspeed of 4.5 m/s. As noted above, 100 meters 

(330 feet) is used as the height of plume rise for all weather conditions; see Table D–60. 

c Equivalent to 17 to 357 °C or 61 to 673 °F. 

Key: °C=degrees Celsius; °F=degrees Fahrenheit; cal=calories; ft2=square feet; K=Kelvin; lbs=pounds; 

m=meters; m2

=square meters; mg=milligrams; min=minute; s=second. 

Observations on Plume Radius 

As described above, a height of 100 meters (330 feet) was used as the starting point for Gaussian 

dispersion modeling of truck and railcar fire scenarios using SAPLUME. Also needed is the plume 

radius. A simple model for the radius r of a buoyant plume is (Briggs 1984): 

dr/dt = β.dz/dt (7–28) 

Integrating this gives: 

 r(h)-r(0) = βΔh (7–29) 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–122

The symbols in Equations 7–28 and 7–29 have the following meanings: 

r = Plume radius (meters) 

h = Final plume height (meters) 

r(h) = Plume radius at height h (meters) 

r(0) = Radius immediately above the fire (meters) 

Δh = Height of plume rise (meters) 

z = Distance above ground (meters) 

t = Time (seconds) 

β = Entrainment coefficient (dimensionless) 

The coefficient β for a buoyant plume is typically 0.6.16 For Δh = 100 meters and neglecting r(0), the 

radius at a plume height of 100 meters (330 feet) is approximately 60 meters (197 feet). As the mercury 

rises, it entrains air. At 100 meters, the plume would be traveling horizontally through a circle of this 

radius at the average windspeed across that circle. For purposes of simplicity, that is assumed to be the 

windspeed at a height of 100 meters, u100 (m/s). In that case, the volume flux Vf of air through the circle 

of radius 60 meters is: 

 Vf = π (60)2u100 m3/s (7–30) 

The resultant mass flux through the 60-meter-radius circle is: 

 Mf = 1.205 Vf kg/s (7–31) 

where 1.205 kg/m3

 is the density of air at 293 K (20 °C). Another parameter needed for SAPLUME input 

is the momentum flux (MOMf) where: 

 MOMf = Mf. u100 kilogram-meters per square second (kg-m/s2) (7–32) 

Table D62 gives values of these parameters for three representative conditions of atmospheric stability 

class and windspeed: A, 1.5 m/s; D, 4.5 m/s; and F, 1.5 m/s; the windspeeds are measured at a height of 

10 meters (33 feet). 

Table D–62. Windspeed, Initial Airflow, and Momentum Flux at 

100-Meter Plume Height, Railcar Fire 

Weather Condition 

Stability Class, Windspeed 

Windspeed at 100 Meters

(u100) (m/s) 

Mass Flux 

(Mf)(kg/s) 

Momentum Flux 

(MOMf) (kg-m/s2) 

A, 1.5 m/s 2.1 28,600 60,000 

D, 4.5 m/s 6.2 84,500 120,000 

F, 1.5 m/s 2.2 30,000 66,000 

Note: To convert meters to feet, multiply by 3.281, kilograms to pounds, by 2.2046. 

Key: kg-m/s2

=kilogram-meters per square second; kg/s=kilograms per second; m/s=meters per second. 

As a final note, a rising plume is well defined and has a sharp boundary at the radius, so that the 

concentration under a rising plume at ground level is zero. This situation persists until the plume stops 

rising. However, to use the results of the plume rise calculations as input to SAPLUME calculations, it is 

assumed that the initial state at a height of 100 meters (330 feet) is a Gaussian plume with the 10 percent 

concentration at the radius. That being the case, the starting value of the standard deviation is r/2.14, and 

there would be some initially calculated concentration under the plume before SAPLUME moves it 

downwind. This is a conservatism in the calculation. 

 

16 This is only true if initial momentum jet effects can be neglected, as is true in this case. 
Human Health and Ecological Risk Assessment Analysis 

D–123

D.7.4.2 Intentional Destructive Acts – Truck Fire and Railcar Fire 

As described in Section D.2.6, the assumed IDA scenario is one in which a gasoline tanker is crashed into 

a truck or railcar containing mercury. Table D63 shows the parameters of interest for these scenarios in 

two weather conditions: Atmospheric Stability Class D with a windspeed of 4.5 m/s and Class F with a 

windspeed of 1.5 m/s. 

Table D–63. Parameters for Estimating Emissions of Mercury 

During an Intentional Destructive Act Gasoline Tank Truck Fire 

Parameter Mercury Truck 

Mercury 

Railcar 

Molecular weight (MW) 200.6 200.6 

Boiling point (°F) 674 674 

T (boiling point) (K) 630 630 

Vapor pressure at T 760 760 

Windspeed (m/s), 

stability class 4.5, D or 1.5, F 4.5, D or 1.5, F 

Spill area (ft2) 463 568 

Spill area (m2) 43 52.8 

Fire area (ft2) 463 568 

Fire area (m2) 43 52.8 

Heat input (cal/s) 2.47×107 3.03×107 

Duration of gasoline/mercury 

release(s) 8,682 10,660 

Quantity released (lbs/min) 

4.5 m/s, Da

1.5 m/s, Fa 

211.2 

97.7 

258.5 

117.1 

Release rate (mg/s) 

4.5 (m/s), Da

1.5 m/s, Fa

1.6×106 

6.9×105

2.0×106 

8.5×105

Minimum released quantity 

(lbs) 

4.5 m/s, Da

1.5 m/s, Fa

35,200 

16,280 

37,400 

16,940 

Plume rise (m) 

4.5 m/s, Da

1.5 m/s, Fa

235 

244.4 

251 

259 

a Windspeed, atmospheric stability class. 

Key: °F=degrees Fahrenheit; cal=calories; ft2

=square feet; K=Kelvin; lbs=pounds; 

m=meters; m2

=square meters; mg=milligrams; min=minute; s=second. 

As was the case for accidental fires, the predicted rate and duration of release are somewhat greater for 

the railcar fire than they are for the truck fire, so the Railcar Scenario is taken as bounding for the truck 

scenarios. 

Table D63 shows that the predicted plume rise in both weather conditions is about 250 meters (820 feet). 

However, for Atmospheric Stability Class F and a windspeed of 1.5 m/s, SAPLUME has an inversion lid 

hardwired into it at 260 meters (850 feet). This and other assumptions about windspeed as a function of 

height and quantities such as the Monin-Obukhov length, are the same as those used in SLAB, a widely 

used atmospheric dispersion model (Ermak 1990). SAPLUME assumes that the plume cannot rise 

through the inversion lid: rise is terminated when the upper edge of the plume reaches the inversion lid. 

In practice, in Class F conditions, SAPLUME does not accept a centerline plume rise of greater than 

about 120 meters (390 feet). This value is used as a conservative estimate of plume rise (i.e., leading to 
Draft Long-Term Management and Storage of Elemental Mercury Environmental Impact Statement 

D–124

increase estimates of ground-level concentrations) in Class F conditions. Table D64 provides initial data 

on airflow and momentum flux. 

Table D–64. Windspeed at Height of Plume Rise, Initial Airflow and Momentum Flux, IDA Fire 

Weather Condition 

Stability Class Windspeed 

Windspeed at Height of 

Plume Rise (Uh) (m/s) 

Mass Flux 

(Mf) (kg/s) 

Momentum Flux 

(MOMf) (kg-m/s2) 

D, 4.5 m/s U250 = 6.8 580,000 390,000 

F, 1.5 m/s U120 = 2.3 45,100 104,000 

Note: To convert meters to feet, multiply by 3.281; kilograms to pounds, by 2.2046. 

Key: IDA=intentional destructive act; kg-m/s2

=kilogram-meters per square second; kg/s=kilograms per second; m/s=meters per 

second. 

D.8 REFERENCES 

Albin, L., D. McBaugh, and S. May, 2009, Hanford Wildfire Response and Lessons Learned, Washington 

State Department of Health, accessed through http://www.crcpd.org/PDF/Debra_McBaugh.pdf. 

Armenian, H.K., A. Melkonian, E.K. Noji, and A.P. Hovanesian, 1997, “Deaths and Injuries Due to the 

Earthquake in Armenia: A Cohort Approach,” International Journal of Epidemiology, Vol. 26, No. 4. 

Army (U.S. Army), 1980, Handbook for Chemical Hazard Prediction, Handbook No. 385-2.1-80, 

U.S. Army Material Development and Readiness Command, Alexandria, Virginia, February. 

ATSDR (Agency for Toxic Substances and Disease Registry), 1999, Toxicological Profile For Mercury, 

U.S. Department of Health and Human Services, Public Health Service, Washington, D.C., March. 

ATSDR (Agency For Toxic Substances and Disease Registry), 2009a, Health Consultation Proposed 

Mercury Clean-Up Level For The East Fork Poplar Creek Flood Plain Soil, Oak Ridge, Tennessee, 

U.S. Department of Health and Human Services, Public Health Service, accessed through 

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