DRC-2018-004073 - 0901a06880801d3b

Page 1 of 47 DRC-2018-004073
RADIOACTIVE MATERIAL LICENSE NO. UT 2300249
STATEMENT OF BASIS
for
AMENDMENT 23
Low Level Radioactive Waste Disposal Facility
EnergySolutions, LLC
299 South Main Street, Suite 1700
Salt Lake City, UT 84111
April 27, 2018
Purpose
This statement of basis establishes the foundation on which Radioactive Material License No. UT
2300249 (RML) was recommended for amendment. The revised license is designated as Amendment 23.
The proposed revisions were submitted by EnergySolutions, LLC (ES) within seven separate requests.
The revisions reviewed by staff for Amendment 23 are listed chronologically below with several brief
details:
On June 8, 2016 (CD16-0119), ES submitted a request as a part of the RML License Renewal Application
(Revision 3) to the Director of the Division of Waste Management and Radiation Control (Director) to
amend License Condition 41 of the RML addressing the Clay Distortion Study.
On April 6, 2017 (CD17-0092), ES submitted a request to the Director to modify the Environmental
Monitoring Plan (EMP) which is included with the approved RML Application as Appendix M. The
EMP is a requirement of License Condition 26 of the RML.
On November 10, 2017 and May 9, 2017 (CD17-0252 / CD17-0112), respectively, ES submitted requests
to the Director to amend License Conditions 73 and 76 of the RML addressing several aspects of surety.
On January 24, 2018 (CD18-0015 / CD18-0020), ES submitted requests to the Director to amend License
Conditions 28 and 42 of the RML addressing the Cover Test Cell and the use of the Evaporative Zone
Depth in cover design modeling, respectively.
On February 21, 2018 (CD18-0028), ES submitted a request to the Director to amend License Condition
16.F.i of the RML addressing non-aqueous waste.
The Division has reviewed the submitted information and each revision proposed for Amendment 23 was
deemed appropriate and necessary. The changes requested are considered minor, administrative in nature
and do not include monitoring, sampling or health and safety issues. Therefore, the Director has
Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 2 of 47 DRC-2018-004073
determined that in accordance with UAC R313-17-2 a public comment period is not required for these
requests.
Additionally, several minor administrative changes were made to clarify and improve the License text.
The changes considered below succeed the previous license and will be incorporated into Amendment 23
of the License.
License Change Summary
License
Condition
Minor/Major
Change
Description of Changes and Basis for Changes
16.F.i Minor Change conditions for treatment of Non-aqueous Waste.
26 Minor No text changes were made to License Condition 26; however,
revisions to the EMP were made to correct outdated equipment
models for radon detection equipment, inaccurate references, and
grammatical errors.
28 Minor Updating objectives of License Condition for the destructive
testing and analysis of the Cover Test Cell.
41 Minor ES submitted the results of the Clay Distortion Study and
therefore requested that the condition be removed
42 Minor In response to the condition requirements ES submitted
alternative cover designs addressing Division’s concerns with the
Evaporative Zone Depth parameter and therefore requested that
the condition be removed.
73 Minor Commensurate with passage of Utah Senate bills 2015-173 and
2017-79, ES is allowed to submit surety calculations for the
combined licensed facilities. The revision aligns the submittal
with the 11e.(2) license and changes the date for the Clive
Facility annual surety update to March 1 each year.
76. Minor Text changes were required to align the condition with Utah
House Bill 296 with regards to the State’s Radioactive Perpetual
Care and Maintenance Account.
90 Minor Text add to the RML requiring the Licensee to provide a
reasonably accessible area of land for a stand-alone, state-owned
modular building located on the Licensee Controlled Area for as
long as the License is in effect.

Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 3 of 47 DRC-2018-004073
Additional details regarding the changes to the license are contained in the following Appendices:
Appendix License Condition Number Subject / Topic
A 16.F.i Non-Aqueous Waste
B 26 Environmental Monitoring Plan Revisions
C 28 Cover Test Cell
D 41 Clay Distortion Study
E 42 Evaporative Zone Depth
F 73 & 76 Surety Submittal Date & Perpetual Care
G 90 State Office

Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 4 of 47 DRC-2018-004073
Blank Page
Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 5 of 47 DRC-2018-004073
Appendix A
License Condition 16.F.i – Non-Aqueous Waste
Statement of Basis to Amend License Condition 16.F.i
On February 21, 2018 (CD18-0028), EnergySolutions, LLC (ES) submitted a request to the Director of
the Division of Waste Management and Radiation Control (Director) to amend License Condition 16.F.i
of the RML.
The License Section and current License Condition are as follows:
PROHIBITIONS AND WASTE ACCEPTANCE REQUIREMENTS
16.F. Liquid Waste Restrictions
i. Except for liquid mercury and minimal quantities as described in License Condition 17 and in
the current Waste Characterization Plan, receipt of non-aqueous liquid waste is prohibited
unless specifically approved by the Director.
The amended License Condition:
16.F. Liquid Waste Restrictions
i. Except for liquid mercury and non-aqueous liquids less than 1% of the volume of the
waste in a container, the Licensee shall notify the Director in writing and provide the
Waste Profile Record of any new, not previously approved, non-aqueous liquid waste
streams. This notification shall be provided at least seven calendar days prior to
management of the waste at the Clive Facility. Unless the Director has unresolved issues
that have been communicated to the Licensee within seven days of the notification, the
waste shall be deemed acceptable for management. If issues remain unresolved seven
days from the date of notification, written Director approval will be required before the
waste may be managed. minimal quantities as described in License Condition 17 and in the
current Waste Characterization Plan, receipt of non-aqueous liquid waste is prohibited unless
specifically approved by the Director.

This amendment to Condition 16.F.i. is based on many years of experience by the facility treating non-
aqueous waste. Under the current Condition, the facility is required to receive Director approval to treat
each non-aqueous waste stream. During the years that this Condition has been in place, none of the waste
stream treatment processes have been denied based on technical issues.
Under the amended Condition the facility will still submit the Waste Profile and treatment plan to the
Director. The Director shall then have seven calendar days to review the request and bring questions to
the facility. If the Director doesn’t have issues with the submittal, the facility may continue with
treatment. If there are questions that take more than the seven days to resolve, the facility may only treat
the non-aqueous waste following written approval by the Director.

Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 6 of 47 DRC-2018-004073
Blank Page

Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 7 of 47 DRC-2018-004073
Appendix B
License Condition 26 – Environmental Monitoring Plan Revisions
Statement of Basis to Modify Environmental Monitoring Plan
On April 6, 2017 (CD17-0092), ES submitted a request to the Director to modify the Environmental
Monitoring Plan which is included with the approved License Application submittal as Appendix M and
is a requirement of License Condition 26 of the RML.
Purpose
On April 6, 2017, ES submitted a request to the Director to amend License Condition 26 of the RML. A
revised request was received on February 9, 2018 and a substitute revision was received on March 1,
2018. An email discussion between Otis Willoughby and Robert Sobocinski added additional language to
the March 1 submission and was included in the final revision.
The requests were reviewed by the Division and were deemed appropriate.
The Division has reviewed all the submitted information. The changes requested are considered minor,
administrative in nature and do not include monitoring, sampling or health and safety issues. Therefore,
the Director has determined that in accordance with UAC R313-17-2 a public comment period is not
required for these requests.
EMP Change Summary
EMP Section Minor/Major
Change
Description of Changes and Basis for Changes
3.0 Definitions –
“Glass Fiber
Filter”
Minor Changed “ASMT” to “ASTM” to correct typographical error.
3.0 Definitions –
“Soil Reporting
Levels” and other
references to the
Division
throughout the
document.
Minor Changed “the Utah Division of Radiation Control” to reflect the
organizational change that occurred July 1, 2015 and to designate
the Division Director as the legal authority. The section now reads:
“the Director of the Utah Division of Waste Management and
Radiation Control (Director)(Division)”
5.1.1 Airborne
Particulates
And other
locations
throughout
document.
Minor Changed drawing number from 10014-U03 to 07007-J01 to update
facility changes since last revision.
Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 8 of 47 DRC-2018-004073
EMP Section Minor/Major
Change
Description of Changes and Basis for Changes
5.1.1 Radon - Minor Removed reference to a specific model of radon detector and
replaced it with a detector specification. The modified sentence
now reads: “Radon concentrations are monitored using dosimeters
with a radon minimum detectable activity (MDA) of ≤ 0.4 pCi/L.”
5.2 VTD Effluent Minor Added the word “campaign” in front of the word “startup” to clarify
when filters had to be changed. The revised sentence reads “A new
filter is used prior to each VTD campaign startup.”
5.4.2 Annual Soil
Samples
Minor The sentence, “Radial surface soil samples will be collected from
the soil stations in Tables 1 through 3.” was removed because it was
inaccurate. The next sentence provides the sample locations. The
radial locations were never actually listed in the tables.
5.4.2 Annual Soil
Samples
Minor The phrase, “as shown on Drawing 2008 G05.”, was added to the
end of the sentence, “Radial surface soil samples will be collected
at 300 meter intervals along the 8 compass directions centered near
the center of Section 32”, to clarify sampling locations.
5.4.2 Annual Soil
Samples
Minor The phrase,” from the site boundary”, was added to the end of the
sentence, “The first sample will be taken just outside the site
boundary and additional samples will be taken at 300 meter
intervals extending out to 1,500 meters.” to clarify sampling
locations.
5.4.2 Annual Soil
Samples
Minor The word, “radial”, was added to the sentence, “All 48 samples will
be analyzed by gamma spectroscopy.” to clarify which soil samples
is being referred to .
5.4.3 PCB Soil
Samples
Minor Soil sample handling requirements changed to reflect requirements.
6.1 Laboratory
Qualifications
Minor Removed statement that implies the ES Lab is certified by the State
and added information regarding the lab’s quality assurance
program.
6.2.2 Particulate
Air Sample Alpha
Beta screening
Minor Replaced “the Environmental Monitoring Plan” with “this plan”

Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 9 of 47 DRC-2018-004073
Appendix C
License Condition 28 – Cover Test Cell
Statement of Basis to Amend License Condition 16.F.i
On January 24, 2018 (CD18-0015), ES submitted a request to the Director to amend License Condition
28 of the RML. The following provides a basis for amending License Condition 28 of RML 2300249.
The License Section and current text of License Condition 28 are as follows:
ROUTINE MONITORING AND CONTAMINATION SURVEYS FOR NEW LICENSEES:
28. The Licensee shall submit the following to the Director for review and approval pending resolution of
all issues as judged by the Director:
A. The Licensee shall submit a corrective action plan for the Cover Test Cell for Director approval
by no later than July 23, 2008. The corrective action plan shall identify all means necessary to
collect valid data to verify actual performance of the cover system. Said plan shall include Cover
Test Cell design, construction, instrumentation, monitoring, reporting, and comparison of actual
performance to projected performance. The Cover Test Cell corrective action plan shall include:
i. Performance goals to meet the objective of verifying modeled cover system performance.
ii. Methodologies and plans that provide quantitative and qualitative results capable of satisfying
the objective.
iii. Design, construction, and operational plans to implement the methodologies and plans.
iv. Quality control and quality assurance requirements of work to be performed. Quality control
and quality assurance specifications and procedures shall state specific actions and processes
the Licensee will use to ensure compliance with designs and specifications, monitoring,
reporting, ensure data validity, timely detect data deficiencies, enhance accuracy of data
interpretation, and ensure correctness of results prior to being submitted to the Division.
v. In the event that the plan results in new instrumentation or construction, the Licensee shall
complete all such activities within 30-days of Director approval. Within 30-days of
completion of said construction, the Licensee shall submit an As-Built report for Director
approval.
B. The Licensee shall submit an annual report for Director approval by March 1 of each calendar
year. This annual report shall detail the Licensee’s progress in implementing the corrective
action plan, provide the data collected in the past year, analyze the data, and interpret the meaning
of the data relative to the overall objective of the corrective action plan.
The entirely amended License Condition:
28. Within 60 days of issuance of License Amendment 23, the Licensee shall submit for Director’s review and
approval a Study Plan evaluating relevant strategies for the destructive testing and analysis of the
earthen components in the Cover Test Cell. The objectives of this study shall be (1) to acquire, to the
extent practicable, representative, site-specific parameter data for validating the existing model for
infiltration through the LARW cover system as well as for the support of future modeling of
unsaturated flow through rock-cover systems used at the Clive facility, and (2) to examine the in-
Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 10 of 47 DRC-2018-004073
service physical properties of the Cover Test Cell earthen materials from the time of the Cover Test
Cell’s initial construction until the present and to document any changes.
A. The Study Plan shall address in-situ and laboratory sampling and testing for determination of
the Cover Test Cell’s physical properties. Sampling and testing shall be conducted using,
whenever possible, ASTM methods, or if not possible, alternative methods approved by the
Director. Exploratory borings, trenching and/or block sampling shall be used to obtain
relatively undisturbed representative samples. Sampling and testing shall occur at several
locations randomly selected across the surface of the Cover Test Cell and within each earthen
layer of the cover system. The Study Plan shall include a description of how the following
data will, to the extent feasible, be collected:
i. Collection of data for in-service moisture content and dry bulk density of each soil
sample.
ii. Characterization of grain-size distribution, porosity, and residual and saturated moisture
content (theta(r), and theta(s)) for each soil layer in the vertical profile.
iii. Estimation of soil-water potential (e.g., matric potential, or matric suction) as a function
of moisture content for each soil layer in each vertical profile. Data shall be sufficient so
that laboratory test results represent the full range of suction head vs. moisture content
values potentially existing at the Clive Site. The laboratory data shall be used to create
standard laboratory Soil-Water Characteristic Curves (SWCCs) or Soil Water Retention
Curves (SWRCs) representing potential conditions at the facility from very wet to very
dry.
iv. Collection of data to assess saturated hydraulic conductivity and unsaturated hydraulic
conductivity (as a function of moisture content) for each soil layer in each vertical
profile.
v. Observation and characterization of changes, if any, from as-built conditions in physical
properties of earthen materials.
vi. Estimation of the amount of heterogeneity (based on soil classification, relative
compaction, etc.) within each earthen layer.
vii. Collection of moisture content data for the pan-lysimeter sand and gravel material located
below the point of sampling in the base of the lower clay radon barrier.
viii. A schedule based on calendar days following plan approval for when the field and
laboratory work will take place.
B. Following Director approval of the study plan, the Licensee shall conduct the study as
outlined.
C. Within 60 days of completion of the Study, the Licensee shall submit a Report documenting
and evaluating the results of the Study. The Report shall contain the following elements:
i. A description of the study report contents including all data collected such as exploration
logs, field and laboratory test results, analysis and technical interpretation of data by a
qualified independent expert.
Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 11 of 47 DRC-2018-004073
ii. The report shall include an evaluation of the field and laboratory data compared with the
previous HELP model inputs. Based on this evaluation, the Licensee shall recommend
and justify:
a. Acceptance of the previous HELP model and the cover design used for the LARW
embankment, or
b. Potential changes to HELP-model inputs and/or other model inputs for future
modeling, and/or
c. An outline of enhanced waste management procedures, or
d. A reevaluation of Embankment Cover design.
D. If the Director determines that additional information or revaluation is required, the Licensee
shall provide all requested information and resolve all issues identified within a timeframe
agreed upon by the Director and the Licensee.
Introduction
The purpose of this license amendment is to provide an alternative CAP for making use of the CTC
wherein ES might satisfy the original intent, which includes securing sufficient high-quality, near-surface
rock, soil and water data to validate and audit existing infiltration and transport models and to allow for
development of functional infiltration and transport models for waste embankments at Clive in the future.
This amendment should help clarify parameters to be used in modeling and help hasten acceptable site-
related work. The ultimate objective of making this amendment is to provide better assurance of
radiological protection for the public.
Instrumentation Failures at the CTC
DRC (2012) describes how most of the instrumentation in the Cover Test Cell ceased to function early on
during the Cover Test Cell testing period. This was thought to be associated with a number of factors,
including corrosion of metal components due to excessive soil salinity, a lightning strike which affected
electrical circuits, and mechanical failure. Also, during 2016, the tipping gauge intended for measuring
drainage through the cover rock and soil appeared to fail mechanically, creating anomalous readings. As a
result of failures of this type, it became clear to the Division that the majority of the data intended to be
obtained from the original instruments placed in the CTC rock and soil layers could no longer be
obtained. That, in turn, resulted in general failure to fulfill the primary purpose of the CTC, namely to
validate, confirm, and/or provide an audit of, prior existing infiltration and transport model assumptions,
model parameter values and model results, and to provide acceptable parameter estimates for future use.
License Condition 28A
As a consequence, in part, of instrumentation failures at the CTC, the Division prepared Condition 28A
and included it in ES’ Radioactive Material License No. UT2300249. License Condition 28A included a
requirement that ES develop a corrective action plan (CAP) for the CTC. The CAP was deemed necessary
for ensuring validation and auditing of both previous and future contaminant transport models used at the
site so that the Division can have confidence in the model results. Important objectives for the CAP were
to include development and description of i) performance goals to meet the objective of verifying
modeled cover system performance, and ii) methodologies and plans that provide quantitative and
qualitative results capable of satisfying the objective. While the Division encouraged action on this
Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 12 of 47 DRC-2018-004073
License Condition, ES expressed its opinion that the main functions of the CTC were still being served,
including measurement of subsurface temperatures and drainage. The Division, however, disagreed, since
soil moisture content, matric potential and hydraulic conductivity were not being evaluated (see, for
example, DRC, 2012).
An Alternative CAP
An alternative to the previously described CAP has now been negotiated between the Division and ES
and is included here as an amendment for License Condition 28 (including both parts A & B). This
amendment requires ES to develop an alternative CAP for the CTC and conduct in-situ testing and
sampling, using either trenching or large-diameter boring, followed by laboratory analysis, to gain as
much useful information as possible in connection with destructively testing the CTC. The plan
developed based on this amendment will describe how sampling and testing will be performed to gather
information about soil in-service moisture content, dry bulk density, grain-size distribution, porosity,
residual moisture content, saturated moisture content, suction vs. moisture content for each soil layer in
multiple vertical profiles, saturated and unsaturated hydraulic conductivity, changes from as-built
conditions in physical properties of earthen materials, amount of heterogeneity present, and lysimeter
boundary conditions. The anticipated results should satisfy the original intent of testing at the CTC and
remedy the current need for site-specific data. Sampling will be conducted using, whenever possible,
ASTM methods. Exploratory borings, trenching and/or block sampling will be used to obtain relatively
undisturbed representative samples. Sampling and testing will occur at several locations randomly
selected across the surface of the Cover Test Cell and within each layer of the cover system.

Following Director approval of this alternative CAP, the Licensee will be required to conduct the
activities as outlined within an agreed upon schedule, and submit a report. The report will indicate how
field and laboratory data compare with previous HELP model inputs, including those for the LARW
cover model. Based on this evaluation, the Licensee will either demonstrate that the data support previous
model assumptions, or the License will provide potential changes to future modeling inputs, or describe
how it will design and/or manage its future embankments and waste in ways that, if needed, will meet
those design requirements.

Although this sampling and testing program will collect measurements taken at only a single point-in-
time, this CAP (in light of the previous in-situ instrumentation damage, and likely future damage) appears
to represent the best course of action that could be undertaken at this point to validate and audit existing
and future flow and transport models. The results from the CAP should help to confirm through site-
specific data what the models (with their assumptions about, or estimates of, their various parameter
values) have predicted or will predict. And these results should help provide confidence in future
modeling that will take advantage of this data.

The judicious application of CTC data to the evaluation of modeling of radioactive materials disposed of
in onsite embankments is warranted since the upper part of the CTC (overlying the lower radon barrier)
has earthen materials each having the same order of placement and thickness as the corresponding layers
present in a large part of the LARW cover system and which are similar to (although with some
differences from) the earthen layers proposed for the Class A West cover system.

Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 13 of 47 DRC-2018-004073
Reference
DRC (Utah Department of Environmental Quality, Division of Radiation Control), 2012, Review and
Audit of EnergySolutions’ Cover Test Cell Corrective Action Plan and Related Documents, Letter to Sean
McCandless, EnergySolutions’ Director of Compliance and Permitting, from Rusty Lundberg, DRC
Executive Secretary, January 31, 2012, DRC-2012-003421.

Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 14 of 47 DRC-2018-004073
Blank Page
Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 15 of 47 DRC-2018-004073
Appendix D
License Condition 41 – Clay Distortion Study
Statement of Basis for Removal of License Condition 41
On June 8, 2016 (CD16-0119), ES submitted a request as a part of the RML LRA (Revision 3) to the
Director to amend License Condition 41 of the RML. The following provides a basis for removing
License Condition 41 from Radioactive Material License No. 2300249.
The License Section and current License Condition are as follows:
CONSTRUCTION ACTIVITIES
41. On or before August 1, 2012, the Licensee shall submit, for Director’s review and approval, a detailed
plan for a study of the clayey soils to be used in the radon barrier of the CAW embankment cover.
The objective of this study is to determine the amount of strain that the soils can withstand without
cracking when subjected to both axial lengthening and bending as would be experienced when the
clay settles differentially as part of the cover system. Within nine months of Director’s approval of
the study plan, the Licensee shall execute the study and submit a report with results of the study.
Based on results of the study and the Director’s review, the Director may require the Licensee to
modify the embankment and cover design.
The entirely amended License Condition:
41. Reserved On or before August 1, 2012, the Licensee shall submit, for Director’s review and approval,
a detailed plan for a study of the clayey soils to be used in the radon barrier of the CAW embankment
cover. The objective of this study is to determine the amount of strain that the soils can withstand
without cracking when subjected to both axial lengthening and bending as would be experienced
when the clay settles differentially as part of the cover system. Within nine months of Director’s
approval of the study plan, the Licensee shall execute the study and submit a report with results of the
study. Based on results of the study and the Director’s review, the Director may require the Licensee
to modify the embankment and cover design.
Background
License Condition 41 became a part of Radioactive Material License No. 2300249 (RML) when the
Division of Radiation Control (DRC) issued Amendment 14 to the RML on November 26, 2012 (DRC,
2012a). Amendment 14 addressed changes to the RML needed to incorporate EnergySolutions’ (ES)
request (ES, 2011b) to construct and operate the Class A West (CAW) embankment, a low level
radioactive waste embankment located at the Clive Facility in Utah. License Condition 41 addresses an
unresolved concern for the clayey soil to be used in the radon barrier portion of the CAW embankment
cover.
Importance of Cover
Among the many design features associated with the CAW embankment, the final cover has been
identified by ES as one of several principal design features for the embankment. The cover encourages
Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 16 of 47 DRC-2018-004073
run-off of precipitation, limits dose rates, and endures natural forces through time. The cover is required
to minimize infiltration, maintain structural stability and integrity. One mechanism recognized to
potentially impact cover performance is localized settlements, in the form of depressions, which can lead
to excessive tensile strains in the fine-grained components of the cover system.
Addressing Localized Settlement
As summarized by the EPA publication Draft Technical Guidance for RCRA/CERCLA Final Covers
(pg 267, EPA, 2004), ‘…, compacted clays tested under unconfined or low confinement conditions exhibit
relatively brittle behavior and reach failure at axial extensional strains of 0.02 to 4%, with most
compacted clays exhibiting failure at extensional strains of 0.5% or less.’ This mechanism of localized
settlement, as described in Gilbert et al, (pg 40, Gilbert, 1987), can be analyzed using a simple beam
model. The model assumes a portion of the cover will lose support over a length, L (ft) and as a result
undergo differential settlement, Δ (ft). The analysis determines that the average tensile strain developed
within a cover section can be computed from a relationship between distortion, Δ / L (ft/ft) and tensile
strain ∈, (%). A mathematical solution of this relationship is depicted in the following Figure 1 as the
lower red line. Similar graphical representations are included in Gourc et al. (pg 288, Gourc, 2010), EPA
(pg 2-63, EPA, 2004), LaGatta et al. (pg. 403, LaGatta, 1997); and Gilbert (pg. 41, Gilbert, 1987). The
upper blue line in Figure 1 was included in a report prepared by AMEC Earth & Environmental, Inc.
(AMEC, 2000) and formally submitted to the DRC by ES in support of final rock armor covers at the
Clive facility long before the CAW embankment was proposed. It has been previously pointed out that
this upper blue line was derived from coordinate points visually picked from a figure included in the
LaGatta et al. 1997 publication.

With an understanding of the relationship shown on Figure 1, if one has knowledge of the maximum
tensile strain, ∈ by which a clay soil can sustain without failure, then the maximum distortion, Δ / L that
the soil can tolerate may be estimated from this relationship shown in Figure 1. So with that in mind,
researchers such as LaGatta et al. 1997; and Gilbert 1987 found that maximum tensile strain, ∈ (%) can
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10
Te
n
s
i
l
e

S
t
r
a
i
n
,

∈
(%)
Distortion, ∆/ L
Figure 1, Tensile Strain, ∈t vs. Distortion, Δ / L
Tensile Strain, Ît
∈%=1+∆𝐿𝐿2 −1 ×100%
Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 17 of 47 DRC-2018-004073
be correlated to the fine-grained soil property of Plasticity Index, PI (%). The following Figure 2 depicts
the relationship between the soil testing data of tensile strain and soil plasticity index from more than 16
projects (for data see LaGatta, 1997). Similar versions of this graph or tabulations have been published
with each of the above references as well as DOE-UMTRA 1989.

This analytical rationale was presented in the AMEC 2000 report for embankment cover designs at the
LARW and the Class A embankments. And the methodology had been previously approved by the DRC
for both the LARW and Class A embankments. In ES 2011b, ES relied once again on the AMEC 2000
report to support the CAW embankment cover design without augmenting the data set with site-specific
extensional soil testing data of the potential cover soil. Throughout the review process for the CAW
embankment no supplemental extensional soil testing data of the proposed on-site clayey soil at the
facility was included on a figure similar to Figure 2. In these and past instances, ES and their consultants
have subjectively selected a conservatively lower bound, horizontal line relationship that is not dependent
of the cover soil’s PI values, for the value of maximum tensile strain that clayey soil can sustain. The
value of ∈ = 0.2% was chosen (see red line in Figure 2). Later and after approval of the Amendment 14
request, which approved the CAW embankment, a previously existing publication with an interpretation
of the data for Figure 2, prepared by the U.S. Department of Energy (DOE) Uranium Mill Tailings
Remedial Action project (UMTRA, 1989) was discovered and included in the forthcoming clay distortion
study evaluation. The DOE-UMTRA relationship of a lower bounding regression of the data is similar to
that derived by AMEC 2000 yet has a slight slope resulting in a relationship of ∈ (%) = 0.003(PI) + 0.05
(see black line) and therefore is dependent on actual site specific soil plasticity testing.
Using the analytical rationale just described, starting with the upper blue line on Figure 1, the selected
maximum tensile strain, ∈= 0.2% results in an approximate maximum distortion, Δ / L = 0.06 ft/ft. Based
on this value the consultant recommended an allowable distortion, Δ / L = 0.02 ft/ft. This represented a
y = 0.003x + 0.05
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
4.50
5.00
0 10 20 30 40 50 60
Ma
x
.

T
e
n
s
i
l
e

S
t
r
a
i
n
,

∈
(%
)
PI, %
Figure 2, Plasticity Index vs. Max. Tensile Strain
AMEC 2000 selected tensile strain of 0.2% as a lower bound (y = 0.2%).DOE-UMTRAChap 14
Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 18 of 47 DRC-2018-004073
factor of safety of approximately 3.0. Previously, ES provided information indicating that, based on
information available at the time a maximum allowable distortion value of 0.02 ft/ft for the cover
represented a reasonably conservative design criterion (AMEC, 2000). This conclusion was based on the
published laboratory testing data on tensile strains versus soil plasticity as shown in Figure 2 that
generally supported a finding that higher tensile strains in clayey soil, similar in plasticity to those
proposed for use in the proposed CAW embankment cover would be required to cause failure or cracking.
CAW Review insists on On-site Testing
As part of the initial review process for the CAW embankment and License amendment request the DRC
requested ES (DRC, 2011) to confirm that the allowable distortion, Δ / L of 0.02 ft/ft was still relevant
based on a review of available publications since the AMEC 2000 report. In response ES provided
additional information (ES 2011a, 2012a, 2012b, 2012c) including field and laboratory testing from
projects other than the Clive project supporting the previously approved allowable distortion value of 0.02
ft/ft. However, at the time of the approval of the Amendment 14 request, including the CAW
embankment, in 2012 (DRC, 2012a) the DRC determined that there remained sufficient uncertainty
associated with the selection of the appropriate distortion criteria and included the License Condition 41
with License Amendment 14 because ES had not demonstrated using site-specific soil testing for the
maximum tensile properties of soil material proposed for the CAW embankment cover.
It was DRC’s expectation that the inclusion of License Condition 41 would result in ES conducting
laboratory testing within the framework of an approved study plan to assess the tensile strain and
distortion induced crack resistance properties of representative clayey soil that would be used in
constructing the final cover. And that the DRC expected ES to integrate existing tensile strain data with
site-specific tensile strain data and as the condition states “the objective of this study is to determine the
amount of strain that the soils can withstand without cracking…” Also, during review the DRC invited
ES to consider alternate methodology from that which is discussed above and in AMEC 2000.
In response to the anticipated License Condition 41, ES (ES, 2012b) indicated they would develop a clay
study plan to perform site-specific tensile testing to assess properties of the proposed Clive cover soil and
that the testing would be completed prior to CAW embankment cover construction. Also, in the interim
and prior to completion of the clay study, ES further reduced the project specification (SP #133) for the
allowable distortion value observed prior to commencement of final cover construction from 0.02 ft/ft to
0.007 ft/ft as specified in Specification 133 of the LLRW and 11e.(2) CQA/QC Manual Work Element –
Temporary Cover Placement and Monitoring. Following the AMEC 2000 methodology, this reduction
resulted in a factor of safety of approximately 8.0.
To Address LC 41 - Study Plan Proposed, Reviewed, and Approved
ES submitted an initial Study Plan (SP) on August 9, 2012, several months before the RML Amendment
14 was issued. The SP underwent revision following several reviews and was ultimately approved by the
DRC on July 3, 2013 (DRC, 2013). Among many items described in the approved plan the following
items are highlighted:
• that the allowable 0.02 ft/ft distortion was a result of literature research
• it was reasonable that the proposed Clive cover soil could survive higher strains than predicted by
published data
Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 19 of 47 DRC-2018-004073
• the SP will assess the cracking resistance of on-site cover soil from Section 5 and 29
• clayey soil from Section 5 borrow pits will be statistically compared to the clayey soil obtained
from Section 29 borrow pits. The statistical analysis will compare the means and standard
deviations of values of Atterberg Limits, % fines, and optimum moisture contents using F & T
tests with a 95% confidence they belong to the same population
• results will be studied to assess a margin of safety between tensile strain at crack initiation and
the allowable design criteria
• that a derived equation correlating distortion with tensile strains will be provided
• temporal changes in strain will be accounted for during testing, and
• that the specimen soil sample in a triaxial tension apparatus will represent a soil element entirely
in tension, replacing the need for bending and digital photography
On a supportive note, the SP review process introduced the DOE-UMTRA Chapter 14, Figure 14.1 and
the UMTRA equation for tensile strain as a function of soil plasticity index (as referred to earlier above).
ES emphasized the mechanics for a plain-strain model that is still used today by the DOE for closure
design of uranium mill facilities. However, within the DRC review comments of the study plan the DRC
encouraged ES to consider alternate methods to evaluating potential differential settlement.
Study Completed and Submitted
The study report entitled EnergySolutions Clive Facility Clay Distortion Study (ES, 2014) was
submitted to the DRC on April 7, 2014 (report dated March 3, 2014). The study results provided an
assessment of the proposed clayey soil’s resistance to tensile strains. The scope of the study included
geotechnical characterization of the clayey soil from Section 5 that had been amended and stockpiled
onsite. The testing results characterized the clayey soil as low plasticity (CL) clay with a mean Plasticity
Index of 15%, a percent passing the #200 screen of 95%, and a clay activity of 0.45. The study concluded
these geotechnical classification results suggest a clayey soil with low hydraulic conductivity and with
little swell or shrinkage potential. The study also concluded, based on statistical analyses, that the Section
5 samples are from the same clayey material as those tested from Section 29.
Representative samples of the on-site clayey soil were prepared for a series of triaxial extension tests
meant to simulate a range of conditions that have a high probability of bracketing the conditions the radon
barrier layer may experience. The bracketing conditions were described by degrees of average saturation:
"dried" saturation (Save = 32.6%), "as compacted" saturation (Save = 89.5%), and 100% saturated
(saturated by back pressure). As discussed in the report, “as-compacted” samples were placed in a
desiccator for three or more weeks until they achieved a uniform interior relative humidity prior to the
”dried” triaxial testing.
Triaxial tension testing was performed to generate effective stresses that simulate cover tensile stresses
and strains. The initial triaxial extension test on a “dried” specimen was done at a chamber (or cell)
pressure of 5 psi to approximate field loading (overburden) conditions at the bottom of the upper radon
barrier layer. “The theory behind this test was that the upper radon barrier layer may dry out and
become brittle in the dry climate at the Clive site, and the strain required for crack formation would likely
be reduced from the "as compacted" condition.” (AMEC, 2014). Triaxial testing on the “dried” sample
achieved extensional strain of 1.0%, within the constraints of the testing apparatus, with no signs of
failure. Triaxial testing continued on an “as-compacted” sample that achieved extensional strain of 2.0%
Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 20 of 47 DRC-2018-004073
with no signs of failure. Triaxial testing on a “saturated” sample achieved extensional strain of 2.0% with
likely failure.
Various additional loading and saturation conditions were studied and the results for each test are
summarized in the following table. As indicated in the study report, the higher chamber (cell) pressures
of 70 and 120 psi were intended for extreme conditions and to exceed sample strength.
Representative Condition (Degree of Saturation) Chamber (cell) Pressure, (psi) Maximum Tensile
Strain, ∈ (%)
Dried 5 (field overburden loading) > 1.0
As-Compacted 5 > 2.0
Saturated 5 2.0
As-Compacted 10 (above overburden loading) 0.7 As-Compacted 10 > 1.9
Saturated 10 0.9
As-Compacted 15 1.8 Dried 70 > 1.9 As-Compacted 120 > 3.1
Triaxial extension testing performed within expected site overburden loading conditions of 5 psi with
“dried” and “as-compacted” saturation conditions achieved extensional strains from 1.0% to 2.0% with no
signs of failure, at 100% saturation the specimen likely failed at an extensional strain of 2.0%. Other
testing results listed in the table above generally support these findings. The AMEC 2014 report
concludes based on the testing results that, “If the compacted radon barrier clay layer's moisture content
and saturation stays at or somewhat above it’s "as compacted" condition it will likely maintain ductility
and resist failure and cracking at low to moderate strains. If the compacted radon barrier clay layer
dries out quickly before settlement is essentially completed (which is unlikely), the dry radon barrier
material will gain a significant amount of dry strength and maybe too strong to fail or crack under
imposed tensile stresses.” (AMEC, 2014).
In summary, depending on the testing conditions (excluding the results from unrealistic extreme
conditions), the maximum tensile strain demonstrated by the clay soil intended to be used for the Clive
radon barrier ranged between 0.7% and 2.0%. This range is depicted on Figure 2, using the mean
Plasticity Index of 15%. The lowest value of 0.7% is three times more than the value of 0.2% assumed by
AMEC 2000. The on-site testing results appear to confirm the assumptions for AMEC 2000 were indeed
reasonable and conservative.
As encouraged by the DRC review process the clay study report introduced and went to considerable
effort to describe an alternate design methodology for localized differential settlement of the CAW
embankment cover. The authors of the study propose an integration of soil strength properties, as
understood, using unsaturated soil mechanics with the concepts of plate modeling as proposed by
Timoshenko et al. (Timoshenko, 1959). The methodology has a new set of assumptions and uncertainties
that would require appropriate peer review and independent confirmation. At this time the introduction of
an entirely new methodology is beyond the intent and scope of the license condition and study plan.
Conclusions
The DRC reviewed the results of the study and issued an acknowledgement letter with an RFI to ES on
Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 21 of 47 DRC-2018-004073
April 8, 2014 (DRC, 2014) requesting clarification if the study results are applicable to the
evapotranspiration (ET) cover profile being considered at that time. A response was received from ES on
May 8, 2014 stating that the ES SP was designed to support the Rock Armor cover design. ES’s
consultant developed a favorable analysis that the study results were applicably to an ET Cover, however,
the ET cover design was too preliminary to be certain.
These results indicate that the clayey soil proposed for the radon barrier portion of the cover can sustain
elongation strains from 0.7% to more than 2.0%. Including this data on Figure 2 with PI of 15% and the
lowest reported tensile strain of ∈ = 0.7% indicates that the previous AMEC 2000 selection of ∈ = 0.2%
was conservative and reasonable. The standard methodology presented by industry as described in Gourc
2010, EPA 2004, LaGatta 1997; and Gilbert 1987, including the Department of Energy (DOE-UMTRA,
1989), suggest an analysis using a simple beam model is appropriate provided an adequate factor of safety
is applied to address uncertainties.
Using the analytical rationale described earlier, starting with the lower red line (the mathematical
solution) line on Figure 1, the results of a maximum tensile strain, ∈= 0.7% from on-site soil testing,
results in an approximate maximum distortion, Δ / L = 0.119 ft/ft. Based on the consultant’s
recommended allowable distortion, Δ / L = 0.02 ft/ft this represents a factor of safety of approximately
5.93. Based on the LLRW and 11e.(2) CQA/QC Manual recommended allowable distortion, Δ / L =
0.007 ft/ft this represents a factor of safety of approximately 16.93.
This is consistent with the DRC review comment which indicated: “if the tensile strain at crack initiation
is known by experiment than that tensile strain at crack initiation value can be associated with the value
of distortion at which failure occurs using the derived correlation. One can divide or multiply the result
by a factor of safety to decrease the value of distortion at failure to maximum allowable distortion
criterion useful for field application.” (DRC, 2012b).
There may appear to be excess in the Division’s analysis with the resulting factors of safety, however, the
Division strongly believes it is necessary to maintain the allowable distortion, Δ / L = 0.007 ft/ft until ES
adequately demonstrates to the Director’s satisfaction, through the utilization of contemporary
methodology how the theory of bending strains contribute to the total tensile strains effecting the cover
performance, as well as how an alternate proposed methodology is relevant and applicable to the existing
design and performance of waste embankments at the Clive facility.
References:
AMEC Environmental and Infrastructure, Inc., 2014, EnergySolutions Clive Facility Clay Distortion
Study, Clive, Utah. AMEC Job No. 10-817-05290, dated March 3, 2014.
AMEC Earth and Environmental, Inc., 2005, Geotechnical Report, Combined Embankment Study,
Envirocare, Clive, Utah. AMEC Job No. 4-817-004769, dated December 13, 2005
AMEC Earth and Environmental, Inc., 2000, Letter, Allowable Differential Settlement and Distortion of
Liner and Cover Materials, New LARW and Proposed LLRW Embankments, Clive , Utah. AMEC Job
No. 0-817-003091A, dated October 4, 2000.
DOE (U.S. Department of Energy), 1989. “Technical Approach Document, Revision II,” Uranium Mill
Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 22 of 47 DRC-2018-004073
Tailings Remedial Action Project UMTRA-DOE/AL 050425.0002, dated December, 1989, Albuquerque,
NM, 309 p.
DOE, MKE UMTRA Design Procedures, Chapter 14, Manual, January, 1989
EPA (U.S. Environmental Protection Agency), 2004. “(DRAFT) Technical Guidance for of
RCRA/CERCLA Final Covers,” Seminar Publication, EPA 540-R-04-007, U.S. Environmental Protection
Agency, Office of Solid Waste and Emergency Response, Washington, D.C., 421 p. April, 2004
EnergySolutions, Inc., 2017, Radioactive Material License UT2300249: Class A West Embankment Clay
Distortion Study Plan; Results. ES No. CD14-0067, Dated April 7, 2014. DRC-2014-002721.
EnergySolutions, LLC, 2012a. Radioactive Material License #UT 2300249 and Ground Water Quality
Discharge Permit No. UGW450005. Amendment and Modification Request – Class A West
Embankment: Liquefaction Addendum and Response to DRC Comments and Suggestions. ES No. CD12-
0114, dated May 7, 2012. DRC-2012-001429.
EnergySolutions, LLC, 2012b. Radioactive Material License #UT2300249 and Ground Water Quality
Discharge Permit No. UGW450005. Amendment and Modification Request – Class A West
Embankment: Response to Round 3 Interrogatory R313-25-7(3)-04. ES No. CD12-0075, dated March 20,
2012. DRC-2012-001250.
EnergySolutions, LLC, 2012c. Radioactive Material License #UT2300249 and Ground Water Quality
Discharge Permit No. UGW450005. Amendment and Modification Request – Class A West
Embankment: Response to Round 2 Interrogatory. ES No. CD12-0008, dated January 12, 2012. DRC-
2012-001023.
EnergySolutions, LLC. 2011a. Radioactive Material License #UT 2300249 and Ground Water Quality
Discharge Permit No. UGW450005. Amendment and Modification Request – Class A West
Embankment: Round 1 Interrogatory Response. ES No. CD11-0295, Dated October 31, 2011. DRC-
2011-007541.
EnergySolutions, LLC. 2011b, Radioactive Material License #UT 2300249 and Ground Water Quality
Discharge Permit No. UGW450005. Amendment and Modification Request – Class A West
Embankment; Retraction of the Class A South/11e.(2) Embankment Design Change Request. ES No.:
CD11-0123, dated May 2, 2011. DRC-2011-004689.
Gilbert, P.A. and Murphy, W.L., 1987. “Prediction/Mitigation of Subsidence Damage to Hazardous
Waste Landfill Covers,” EPA/600/2-87/025, U.S. Environmental Protection Agency, Hazardous Waste
Engineering Research Laboratory, 81 p. March, 1987.
Gourc, J.P., Camp, S., Viswanadham, B.V.S., and Rajesh, S. (2010), Deformation behavior of clay cap
barriers of hazardous waste containment systems: Full-scale and centrifuge tests. Geotextiles and
Geomembranes, Journal of the International Geosynthetic Society, Vol. 28, Issue 3, June 2010, p. 281-
291.
LaGatta, M.D., Boardman, B.T., Cooley, B.H., and Daniel, D.E., 1997, “Geosynthetic Clay Liners
Subjected to Differential Settlement,” Journal of Geotechnical and Geoenvironmental Engineering, Vol.
123, No. 5, pp. 402-410.
Lee, K.L., and Shen, C.K., 1969, Horizontal Movements Related to Subsidence" , Journal of the Soil
Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 23 of 47 DRC-2018-004073
Mechanics and Foundations Division, ASCE, Vol. 94, No. SM 1, pp. 139-166.
Leonards, G.A., and Narain, J., 1963, Flexibility of Clay and Cracking of Earth Dams, Journal of Soil
Mechanics and Foundations Division ASCE, Vol. 89, No. SM 2, pp. 47-98.
DRC (Utah Department of Environmental Quality, Division of Radiation Control), 2014, Class A West
Embankment Clay Distortion Study Plan; Results: Request for Information, dated April 8, 2014. DRC-
2014-002804.
DRC, 2013, Class A West, Clay Distortion Study: Radioactive Material License (RML) UT 2300249,
(Study Plan Approval Letter), dated July 3, 2012. DRC-2013-002724.
DRC, 2012a, Class A West Amendment Request: Radioactive Material License UT 2300249,
Amendment 14, GWQDP UGW450005 Modification; Final Agency Action. dated November 26, 2012.
DRC, 2012b, Class A West Embankment: Clay Distortion Study Plan; DRC Request for Information.
dated September 13, 2012. DRC-2012-003361
DRC, 2011 Class A West Embankment – License Amendment Request dated May 2, 2011: Radioactive
Material License (RML) Number UT 2300249 and Ground Water Quality Discharge Permit No.
UGW450005. (Round 1 Interrogatory), Dated August 29, 2011. DRC-2011-007320.
Timoshenko, S. and Woinowsky-Krieger, S. 1959, Theory of plates and Shells, McGraw-Hill Book
Company, Inc. 1959.

Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 24 of 47 DRC-2018-004073
Blank Page

Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 25 of 47 DRC-2018-004073
Appendix E
License Condition 42 – Evaporative Zone Depth
Statement of Basis to Remove License Condition 42
On January 24, 2018 (CD18-0015) ES submitted a request to the Director to replace the requirements in
License Condition 42 with “Reserved”. The following provides a basis for removing License Condition
42 from Radioactive Material License No. 2300249.
The License Section and current License Condition are as follows:
CONSTRUCTION ACTIVITIES 42. On or before December 21, 2012, the Licensee shall submit a revised cover design (including at least
descriptions, design calculations, drawings, and specifications) and an assessment addressing
performance of the revised Class A West cover design and transport of potential releases from the
proposed Class A West disposal unit.
The entirely amended License Condition:
42. Reserved On or before December 21, 2012, the Licensee shall submit a revised cover design
(including at least descriptions, design calculations, drawings, and specifications) and an assessment
addressing performance of the revised Class A West cover design and transport of potential releases
from the proposed Class A West disposal unit.

Background
License Condition 42 became part of Radioactive Material License no. 2300249 (RML) when the
Division of Radiation Control (DRC) issued License Amendment 14 on November 26, 2012 (DRC,
2012). Amendment 14 addressed changes to the RML needed to incorporate a Licensee request to
construct and operate a new waste disposal embankment, the Class A West (CAW) embankment, at its
low-level radioactive waste facility at Clive, Utah. License Condition 42 requires the Licensee to provide
a cover design and submit an analysis of embankment and subsurface radionuclide transport,
demonstrating that this modified cover design will provide equal or better performance than predicted by
previous cover designs. This revised CAW cover design was not specified by the DRC, but at the time
was anticipated to be related to the cover design already submitted for the CAW embankment, which
incorporated some cover design changes. License Condition 42 instigated an evaluation of the CAW
embankment cover system, with either analytical, or numerical models and verification of the
effectiveness of the designs.
Cover System Concerns
The final cover of the CAW embankment is regarded as a principal design feature of the embankment that
will control the amount of water entering the waste-containment system and therefore the potential long-
term flux of radionuclides in groundwater. Infiltration through the final cover is assessed with models to
make long term predictions of the behavior of water within the embankment. The license amendment
request for the CAW embankment provided a new cover design that was supported by a variety of
Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 26 of 47 DRC-2018-004073
software packages (computer codes) to determine water movement through the embankment and to
compliance points. During the subsequent regulatory review the DRC found there was a reliance on
modeling to predict the performance of the embankment and at the time of submission of the CAW
embankment request the Division was aware of some limitation of the modeling. Additionally, in
evaluating a cover system the Division conveyed concerns relating to the hydraulic barrier being
susceptible to failure due to such things as water accumulating on the barrier, freeze thaw action, and
plant and animal interaction. The final cover system is intended to allow very little infiltration of water
into waste for a very long time, and the hydraulic barrier of the final cover is essential to achieving low
infiltration rates, whereas the other layers of the cover system protect the hydraulic barrier layers.
Performance Assessments
Performance assessments for low-level radioactive waste (LLRW) disposal facilities are a quantitative
analysis used to demonstrate compliance with performance objectives governing radiological protection
to the general public. Performance requirements stipulate that the cover for an embankment employ
earthen (natural) material, including a hydraulic barrier to limit radon releases and minimize water
infiltration. Also, that the cover design provide mechanisms to move water away from the waste, and
provide protection from erosion, frost damage, and biointrusion; and limit radionuclide exposure to
effectively isolate and stabilize the waste, and maintain overall site stability. To assess the risks from the
infiltration of water through a disposal embankment and the subsequent transport of constituents to
compliance wells, the Division requires an infiltration and transport performance assessment to determine
water infiltration, and transport of hazardous and radioactive constituents for a period of 200 and 500
years, respectively, through the cover system and waste disposal unit, and into groundwater to a
compliance point. Simulating the processes of surface runoff, infiltration, and lateral flow through the
engineered cover of the CAW embankment are fundamental to the performance assessment of the CAW
embankment.
The impact of infiltration and transport through an embankment is assessed by means of models that
approximate the movement of water and the transfer of radionuclides. Modeling of the cover system uses
computer codes to generate models that simulate cover hydrology and water-balances. A water balance
study is a standard tool for the analysis of the performance of an embankment in relation to infiltration
and transport, and is a fast, robust, and a rigorous method for the prediction of flow rates in, and through
an embankment. These models are used as tools to evaluate the impact of releases in the future; therefore,
decisions are made with the aid of the water balance models. Questions concerning the computer codes
used to create these models results from limitations of the software to represent complex system geometry
and behavior, including engineered covers, and changing site conditions over time. Also included in
these concerns are uncertainties about interpretation and use of data, parameter variability in space, and
assumptions about system dimensionality, initial, and boundary conditions.
The Licensee evaluated and submitted performance assessments of infiltration and transport for three
cover designs for the CAW embankment. An infiltration and transport modeling report for rock armored
cover on the CAW embankment was submitted in April 2011, using methodologies established
previously and refinements developed over time (Whetstone, 2011a), and two new site-specific
performance assessment of evapotranspiration cover systems (ET cover) for the CAW embankment were
submitted in October of 2012 (Neptune and Company, Inc., 2012).
Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 27 of 47 DRC-2018-004073
The Licensee considered the site specific performance assessment for the two ET cover systems, ET
Cover System 1 and ET Cover System 2, to be consistent with and support earlier assessments. Although
the CAW embankment is larger than the existing Class A and Class A North embankments, the approach
and methodology for the modeling were similar, because the designs are similar. The Division
considered it reasonable that the same methodology be applied. The approach used in infiltration and
transport performance assessments of the alternative ET cover designs and the rock armor cover includes
long-term climate record, representative of the Clive site; representation of near-surface processes that
affect infiltration; infiltration of water through the covers; analysis of subsurface contaminant transport,
and potential migration of contaminants in groundwater to a compliance well for a period of 500 years
following embankment closure, and for the ET cover systems projected peak concentrations in a well for
a period up to 10,000 years following embankment closure.
Proposed CAW Cover Systems
Components of the proposed cover for the CAW embankment can be categorized as infiltration layers, or
evapotranspiration layers, which provide protection and drainage; and layers of low hydraulic
conductivity materials (hydraulic barrier) to resist the movement of water into the underlying waste.
Protective layers provide the mechanisms to remove water and protect underlying layers from degradation
from erosion, intrusion, and freeze/thaw cycles. Evapotranspiration layers store and release water,
reducing further infiltration. Drainage layers collect water that has entered the cover system and
encourage lateral movement to reduce the accumulation of water on the hydraulic barrier layer (radon
barrier), this limits vertical infiltration of water through the hydraulic barrier into the waste. The radon
barrier limits infiltration; i.e. it is a hydraulic barrier in the proposed CAW embankment covers.
The proposed CAW embankment ET cover designs included top slope and side slope that have the same
configuration. The earthen layers in the ET covers were sloped to promote surface runoff and lateral
drainage to a surface drainage system, and vegetated to increases evapotranspiration. The arrangements
of the layers used in both, ET Cover System 1 and ET Cover System 2, are shown in Figure 1, and are
described below. Beginning at the top of the cover the layers used are:
Surface and evaporative zone layer - 6 inches thick layer of native vegetated soil material with a
minimum 15% gravel admixture, above an evaporative zone layer of native soil material. Native
vegetation is applied to the top layer to enhance evapotranspiration and erosion control. This
layer controls runoff, minimizes erosion, and maximizes water loss. The silty clay of the
evaporative zone provides additional storage for water from precipitation events, and provides a
rooting zone for plants to enhance losses due to evapotranspiration, and further decrease the water
available for further infiltration. The evaporative zone is the same material as the surface layer
without gravel added. The evaporative zone layer thickness was set to 6 inches, 12 inches, and 18
inches in various simulations to evaluate the influence of additional storage on the water flow into
the waste layer.
Frost Protection Layer - 18 inch thick layer of material ranging in size from clay size particles to
16 inches rock placed below the evaporative zone layer. This layer protects layers below from
freeze/thaw and wetting/drying cycles, and inhibits plant, animal, or human intrusion.
Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 28 of 47 DRC-2018-004073
Filter zone – 6-inch thick Type-B filter material, with particles ranging in size from 0.2 to 1.5
inches (with 100% passing a 1.5 inch sieve, 24.5% passing a 0.75 inch sieve, and 0.4% passing a
no. 4 sieve (0.187 inch). This layer corresponds to a coarse sand to fine gravel mix interface to
collect water that has drained vertically from the layers above and direct it laterally to a surface
drainage system. Six inches of Type-B filter material is placed below the frost protection layer in
one of the proposed ET cover designs.
Upper Radon Barrier - 12 inch thick compacted clay with a low hydraulic conductivity of 5 x 10-
8 cm/sec. A barrier layer that reduces the downward movement of water to waste and the upward
movement of gas. Has the lowest conductivity of any layer in the cover system.
Lower Radon Barrier - 12 inch thick compacted clay with a low hydraulic conductivity of 1 x 10-
6 cm/sec. A barrier layer placed directly above the waste that reduces the downward movement
of water.
Temporary cover - native soil material that is free of debris, and is placed within 60 days of
surveying the design top of waste elevation. This layer help prevent the movement of waste
before the cover is built, and holds settlement monuments. It is not part of the engineered cover
system.
The two ET cover systems differed in the placement of a filter zone, between the frost protection layer and the upper radon barrier in ET Cover System 2.

Figure 1. Schematic of the two CAW embankment engineered ET cover systems, ET Cover System 1 and ET Cover
System 2, showing the arrangement and thickness of the layers of the various components of the cover system.
Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 29 of 47 DRC-2018-004073
The thickness of the evaporative zone layer was examined in the modeling by using three discrete
thicknesses: 6 inches, 12 inches, and 18 inches. The thickness and arrangement of the other layers were
maintained. Neptune and Company reported the flow out of the bottom of the radon barrier was small,
even for the 6 inch thick evaporative zone. There was a small additional reduction in flow out the bottom
of the radon barrier with the addition of another 6 inches of evaporative zone. Further increases in the
thickness of the evaporative zone provided no net increases of flow out the bottom of the radon barrier
(Neptune and Company, Inc., 2012). The ET cover systems performances were influenced by the water
retention characteristics of the evaporative zone layer soil materials that is required to retain water that
accumulates during cooler months, when evaporation and evapotranspiration is limited.
The CAW embankment rock armor cover design is the same as that proposed for the previously
considered Class A Combined embankment (Whetstone Associates, Inc., 2005 and 2006), and is
primarily the same as was previously approved for the Class A and Class A North embankments
(Whetstone Associates, Inc., 2000a, 2000b, and 2000c). The CAW embankment cover differed from the
Class A and Class A North embankments covers in that the rip rap cover layer has been increased to 24
inches in thickness, from the previous 20 inches, and the proposed Type-B filter zone thickness in the
CAW embankment is 18 inches on the side slopes, but remains 6 inches on the top slope. Also, filter
design criteria for the Type-B filter zone layers was updated to reflect additional filter criteria (increased
permeability); with increased thickness and permeability the Type-B filter zone has been designed to
drain more water laterally away from the disposed waste.
The earthen layers in the rock armor cover were selected and arranged such that lateral flow is maximized
and infiltration is minimized. The CAW embankment rock armor cover design includes both a low-
angled top slope and steeper side slope. The design of the cover for the side slope is similar to the top
slope, except for the material used in the rip rap layer (larger materials to stabilize the steeper slope), and
the thickness of the lower Type-B filter. Figure 2 illustrates the arrangement of the CAW embankment
rock armor cover system components in the top slope and in the side slope, which consist of the following
layers, from top to bottom:
Rip Rap - 24 inches of Type-B rip rap placed on the top slopes. This is designed to resist
degradation by surface geologic processes and biotic activity. The Type-B rip rap used on the top
slopes ranges in size from 0.75 to 4.5 inches with a nominal diameter of approximately 1.25 to 2
inches. Engineering specifications for the rip rap are that not more than 50% of the Type-B rip
rap passes a 1.25-inch sieve. The side slopes use a Type-A rip rap that is also 24 inches thick
with particles that range in size from 2 to 16 inches (equivalent to coarse gravel to boulders) with
a nominal diameter of 4-1/2 inches. Engineering specifications for the Type-A rip rap are that
100% of the Type-A rip rap passes a 16-inch screen and not more than 50% pass a 4 1/2-inch
screen.
Upper Filter Zone - 6 inches of Type-A filter material, will be placed below rip rap and above the
sacrificial soil. The Type-A filter gradation corresponds to a poorly sorted mixture of coarse sand
to coarse gravel and cobble. Engineering specifications for the Type-A filter material require a
range in size from 0.08 to 6.0 inches, with 100% passing a 6-inch sieve, 70% passing a 3-inch
sieve, and not more than 10% passing a no. 10 sieve (0.08 inch).
Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 30 of 47 DRC-2018-004073
Sacrificial Soil - 12-inch layer consisting of a mixture of silty sand and gravel, placed between
the upper and lower filter zone to protect the lower layers of the cover from freeze/thaw effects,
i.e. frost protection layer. Engineering specifications indicate the sacrificial soil material will be
determined by the following specifications: D15 filter / D85 sac soil must be < 5; D50 soil / D50 sac
soil must be ≤ 25; and D15 filter / D15 sac soil must be ≥ 4.
Lower Filter Zone - 6 inches of Type-B filter material for the top slope, and 18 inches of the
Type-B filter for the side slope will be placed above the radon barrier. The Type-B size gradation
corresponds to a coarse sand and fine gravel mix. Engineering specifications indicate this filter
material will be determined by the following specifications: D15 filter / D85 sac soil must be < 5;
D50 soil / D50 sac soil must be ≤ 25; and D15 filter / D15 sac soil must be ≥ 4. And the Type B filter
will have a minimum hydraulic conductivity of 3.5 cm/sec. The Type-B filter material in the side
slope will have the same engineering specifications as the top slope.
Radon Barrier - Upper radon barrier consisting of 12 inches of compacted clay with a maximum
hydraulic conductivity of 5x10-8 cm/sec, and the lower radon barrier consisting of 12 inches of
compacted clay with a hydraulic conductivity of 1x10-6 cm/sec or less.
Water Balances
At the Clive site drainage through a proposed cover can be related to natural water balance mechanisms.
The proposed rock armor and ET cover systems make use of resistive principles, i.e. they have a
hydraulic barrier, which are layers of low hydraulic conductivity that minimize infiltration. The hydraulic
barrier is overlaid by layers of native material, and/or rock, with storage and drainage layers that remove
water. Performance assessments of the cover using a water balance need to realistically represent
precipitation, occurring as either rain or snow at the Clive site and the only source of cover system water,
infiltration, evaporation/transpiration, lateral movement, changes in storage, and drainage of water within
the cover systems. Conceptually, the Division’s perceived water budgets of the CAW embankment cover
systems embodies a water balance for ET Cover System 1, ET Cover System 2, and the rock armored
cover system (both top and side slopes) that is related to precipitation falling directly on the various cover
systems, infiltration into the upper cover or surface runoff, and evaporation, transpiration, lateral flow,
and changes in storage within the upper cover; and finally infiltration through and drainage out of the
barrier layers. Infiltration is defined as the precipitation that moves into the cover system. Water
movement within the cover system is controlled by variables such as the amount of infiltrating water
moving into, storage within, hydraulic conductivity of drainage layers, and evaporation losses of the
cover; and gradient across the radon barrier. Evapotranspiration or infiltrations layers of the cover
systems accumulate precipitation until it can evaporate or transpirate back to the atmosphere, or is moved
lateral off the embankment to drainage ditches. Drainage through the cover occurs when water
accumulation rates exceed evapotranspiration or lateral drainage and water accumulates on the hydraulic
barrier, creating a hydraulic gradient through the barrier that can drive water into and through the barrier.
Since, a major function of the final cover is to minimize infiltration into the underlying waste; the
hydraulic barrier is a critical component in limiting infiltration to the small values necessary to meet the
performance requirements.
Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 31 of 47 DRC-2018-004073

Figure 2. Schematic of the CAW engineered rock armor cover system, showing the arrangement and thickness of the various components of the cover system.
ET cover’s exploits the water storage capacity of finer textured soil materials and the water removal
capability of vegetation. In general, ET covers consist of a surface layer that can be vegetated, designed
to enhance evapotranspiration during the growing season, and layers below that provide storage during
seasons of low evapotranspiration, and protect the lower hydraulic barrier layers from frost actions.
Under natural conditions, plants remove water from the upper cover material through root uptake and
evapotranspiration, reducing the water available for further infiltration deeper into the profile. By
maximizing water removal by evaporation and evapotranspiration, and storage of water in the cover
materials, ET covers reduce infiltration. Figure 3 illustrates the components of a conceptual water
balance for the proposed CAW embankment ET cover systems.
The traditional rock armor cover at Clive employed materials to protect lower layers and move water
away from the hydraulic barrier that impedes the vertical movement of water. The rock armor upper
surface (rip rap) has limited ability to hold water at the surface; any precipitation readily enters the rip rap
layer and moves through, with no surface runoff. Evaporation is limited, because the large spaces in the
rip rap inhibit any capillarity action to return water from underlying materials to the rip rap for
evaporation. Therefore, the rip rap surface layer restrains evaporation of moisture from underlying
materials, so more water is available for further infiltration. Because, the rock armor cover is not
vegetated, only evaporation will occur. Evaporation may extend to the bottom of the rip rap layer and
Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 32 of 47 DRC-2018-004073
into the upper portion of the upper filter zone. Water that adheres to the surface of rip rap materials or in
the upper filter zone will evaporate when the vapor pressure of air in the rip rap is less than the saturated

Figure 3. Conceptual water balances for the CAW embankment’s two ET covers. See Figure 1 for a description of the individual layers.
vapor pressure. This condition would be enhanced when wind is blowing over and interacting with the
rip rap surface. The high evaporation rate at the Clive site limits the amount of natural groundwater
recharge due to precipitation, except during high intensity precipitation events (Adrian Brown
Consultants, Inc., 1997). This phenomenon would probably apply to the rock armor cover also. Water
infiltrating the cover moves vertically downward through the rip rap and upon encountering the upper or
lower drainage layers in the cover, once saturated, continue laterally due to gravity drainage, depending
on the location in the vertical sequence. Water in the rock armor cover is removed by lateral movement
off the cover, some evaporation occurring within the sequence, or moves downward through the cover.
Drainage layers, when saturated, allow water to move laterally out of the system. Water that has moved
through the infiltration layers accumulates on the hydraulic barrier layer, a portion of the accumulated
Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 33 of 47 DRC-2018-004073
water will flow laterally in the lower drainage layer, but a portion will infiltrate vertically downward into
and through the barrier. The barrier layer allows vertical flow when enough water has accumulated and
there is a positive head on it. Water that eventually moves through the cover can contact the waste. Figure 4
illustrates the components of a conceptual water balance for the CAW embankment rock armor cover system.

Figure 4. Conceptual water balances for the CAW embankment rock armor cover. See Figure 2 for a description of
the individual layers.
Modeling
Performance assessments evaluating the infiltration of water through embankments and the subsequent
transport of constituent from an embankment to compliance wells have been performed for all Clive
embankments. A similar methodology has been used in all of these models to ensure consistency in
embankment performance. These performance assessments include groundwater flow and contaminant
transport models generated by Rogers and Associates Engineering Corporation (1990), Bingham
Environmental (1991, 1993a. 1993b, 1994, 1995a, 1995b), Utah Department of Environmental Quality
(DEQ) Division of Water Quality (1994), Adrian Brown Consultants, Inc. (ABC) (1997, 1998),
Whetstone Associates, Inc. (2000a, 2000b, 2000c, 2000d, 2001, 2003, 2005, 2007, 2011a, and 2011b),
and Neptune and Company, Inc. (2012). The DRC, with assistance from Dr. David Stevens, Utah State
University, performed contaminant transport modeling for pathways below the LARW and 11e.(2)
embankments to verify the results of earlier modeling (DEQ, 1994). The DEQ modeling included
extensive sensitivity analyses on modeling input parameters. The methodology used in rock armor
modeling was initially described in detail in the comprehensive modeling reports for the LARW
embankment, prepared by Adrian Brown Consultants, Inc. (ABC) in 1997 and 1998, and initially for the
ET cover in modeling performed by Neptune and Company, Inc. in 2012.
The ET cover systems infiltration and transport performance assessment of radioactive constituents from
the CAW embankment utilized the software packages: U.S. Department of Agriculture’s HYDRUS
program (Simunek and van Genuchten, 1998), and Argonne National Laboratory’s RESRAD program
(C. Yu, et al, 2001). The HYDRUS program is a two dimensional finite element code that simulates the
movement of water in variably-saturated media to estimates infiltration, overland flow, soil water storage,
lateral flow, and evapotranspiration The RESRAD program analyzes potential human and biota radiation
exposures. Improvements in the radionuclide inventory, half-lives, and distribution coefficient values for
Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 34 of 47 DRC-2018-004073
Class A radionuclides that had improved over time were updated in the modeling. Modeling of the CAW
embankment with an ET cover involved a number of steps (Neptune and Company, Inc., 2012). These
are:
Infiltration through closed CAW embankment covers (final cover), waste, and time of travel from
the bottom of the waste to the top of the aquifer was predicted using HYDRUS models;
HYDRUS models were used to estimate long-term annual infiltration of water into waste for
RESRAD transport and dose models.
In the HYDRUS models the profile and geometry of the simulated domain was discretized into a finite
elements grid for both ET covers. The grids were refined at and near the surface of the domain to
minimize mass balance errors. Water flow was chosen as the HYDRUS simulation process and the
vertical distribution of hydraulic and other parameters characterizing the cover profile, and boundary
condition were specified. Atmospheric boundary conditions were applied as part of the upper boundary
condition. In the atmospheric boundary, weather data is used to determine evaporation based on available
energy in the system, according to temperature, solar radiation, and wind speed. No-flow boundary
conditions were applied at the sides and part of the top. A seepage face boundary condition was applied in
the simulations in the case when a material can become saturated and lateral flow can occur. A free-
drainage boundary condition was assigned at the bottom of the hydraulic barrier layer. Figure 5 shows
the configuration of both ET Cover Systems for HYDRUS modeling.
The infiltration and transport performance assessment for the ET cover systems provided infiltration rates,
and concentrations over time; the estimate of a steady-state infiltration rate applied in the transport model;
and comparison of groundwater concentrations within 500 years of site closure to groundwater protection
limits; evaluation of dose for hypothetical inadvertent intruder scenarios within 1,000 years of
embankment closure; and identification of groundwater concentrations at the time of highest
concentrations within 10,000 years. The Division believes an ET cover system, with adequate storage
capacity and protection could hold water in the near surface until it can move back into the atmosphere
through evaporation and transpiration. However, the Division could not realistically replicate their
conceptual understanding of the ET cover systems and the HYDRUS models, or accept that the proposed
ET covers provided enough erosion and biointrusion protection for the anticipated life of the hydraulic
barrier in relation to the required design life of the cover system. Therefore, the Division never reached a
determination where the ET cover infiltration and transport models could be approved.
Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 35 of 47 DRC-2018-004073

Figure 5. Model domain and boundary conditions applied to ET Cover System 1, and ET Cover System 2.
Rock armor performance assessment of water infiltration and ultimately the migration of hazardous and
radioactive constituents from the CAW embankment were investigated using EPA’s Hydrologic
Evaluation of Landfill Performance (HELP) code (Schroeder, et al, 1994a and 1994b), the Pacific
Northwest Laboratories’ Unsaturated Soil Water and Heat Flow (UNSAT-H) code (Fayer and Jones,
1990), and the PATHRAE-RAD code (Merrell, et al, 1995). The HELP code is a quasi-two dimensional
program that estimates infiltration, overland flow, soil water storage, lateral flow, and evapotranspiration.
The UNSAT-H code is a one-dimensional, finite-difference program that simulates the water balance as
well as soil heat flow. The PATHRAE-RAD code is a one dimensional transport program that calculates
maximum annual effective dose, or concentration in saturated or unsaturated media.
Infiltration and transport modeling for the CAW embankment rock armor cover was prepared and
submitted in April 2011, using the methodologies established previously and refinements developed over
time (Whetstone Associates, Inc., 2011a). Refinements in radionuclide inventory, half-lives, and
distribution coefficient values for Class A radionuclides that developed over time in the course of
modeling and in response to Division comments were incorporated into the modeling. Modeling of the
Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 36 of 47 DRC-2018-004073
CAW embankment with rock armor cover involved a number of steps (Whetstone Associates, Inc. 2011a,
and 2011b). These are:
Infiltration through a closed CAW embankment cover (final cover) was predicted using a HELP
model;
Infiltration/drainage rates predicted by the HELP model were input into a UNSAT-H model to
predict moisture content and time of travel from the bottom of the waste to the top of the aquifer;
A dispersive solution for vertical contaminant transport from the base of the cell through the
vadose zone to the top of the water table; followed by horizontal transport of constituents
through the shallow aquifer to a compliance well using PATHRAE models.
As previously stated, infiltration through the CAW embankment rock armor cover was modeled using a
HELP model (Whetstone Associate, Inc., 2011a). The HELP program is the most commonly used
program for the prediction of infiltration through a cover and into an embankment. The model divides
precipitation into overland flow, surface storage, snowmelt, infiltration, lateral drainage within the cover,
evapotranspiration, soil moisture, and unsaturated surface drainage. If the air temperature is ≤0°C,
precipitation is stored as a snowpack on the surface; the snowpack melts when the air temperature rises
above 0°C. In the rock armor model, water that infiltrates downward more than 20 inches within the
cover is constrained in the model so it cannot be removed by evaporation. Therefore, water will not
evaporate from the entire rip rap layer, which is 24 inches thick. Water is removed due to evaporation
only from a depth called the evaporation zone depth (EZD) of the cover. Because the cover is not
vegetated, the EZD represent the maximum depth of evaporation and any water that infiltrates below the
EZD can only be routed laterally, via a drainage layer or vertical downward as infiltration. The EZD used
in the CAW model influences the storage of water near the surface of the cover and therefore directly
affects the computation of evaporation and run off. Because the EZD is limited to the upper 20 inches of
the rip-rap layer, it is not likely that significant water is held to the EZD depth, to be evaporated from the
cover system. Figure 6 shows the configuration of the rock armor cover used in the HELP modeling.

Figure 6. Water balance for the HELP model of the CAW embankment cover.
The Licensee provided information to support a 20-inch EZD input value, from a number of data sources,
indicating it is environmentally conservative, because it allows efficient evaporation from nearly all rip
Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 37 of 47 DRC-2018-004073
rap interstices, but not from all of the rip rap (Whetstone Associates Inc, 2011b). The choice of a value
for EZD has been the object of much discussion between the Licensee and the Division. The Division has
been working with the Licensee to resolve this problem.
A model developed with the HELP program is limited to certain idealized conditions and spatial or
temporal variation of properties cannot be handled, i.e. the assumption that embankment conditions
remain uniformly constant throughout a simulation. Other limitations in HELP models, which lead to
Division concerns, include overestimates of net infiltration, or under predicted runoff in water balance
calculations, precipitation data being handled on a daily average basis, and no runoff during winter
months (when average temperatures are below freezing) since the model assumes that precipitation is
stored on the surface as snow. Another phenomenon not captured by HELP is the frequently very dry
condition of the upper portion of the cover surface. The surface materials will dry to a point where the
vapor pressure of water in the material pores is in equilibrium with the atmospheric vapor pressure. This
additional drying increases the storage capacity of the upper portion of the cover profile leading to
overestimates of net infiltration by HELP. This underestimation of available water becomes more
significant for materials composed of clays and silts.
Modeling using the HELP program is based on simplifying assumptions, which give conservative
representation of evaporation, runoff, and infiltration of precipitation into a waste profile. The HELP
program is a useful tool for the hydraulic evaluation of an embankment; however, the results should be
properly interpreted and carefully considered. Because of the inherent limitations of an analytical
solution from a HELP model, some aspects of the model, particularly the way evaporation is
implemented, may not realistically duplicate actual conditions; however, because of the abundant
uncertainties, these solutions can be valuable tools for understanding and estimating the movement of
water through an embankment.
Results of HELP infiltration modeling, conducted for the CAW embankment rock armor cover, indicate
an average precipitation infiltration rate of 0.036 inches/year for the top slope area and an average
infiltration rate of 0.066 inches/year for the side slope (Whetstone Associates 2011b). These infiltration
values are comparable to the results of modeling for the Class A and Class A North embankments. The
Division notes in the assessment of the infiltration of water in the CAW cover the Licensee demonstrated
the cover design of the CAW satisfied groundwater protection criteria, with some radionuclides
concentration limits.
As part of the review process the Division reviewed the submission and prepared comments, and in 2012
determined the infiltration and transport modeling simulations provided for the CAW Embankment
support finding that groundwater protection criteria for Class A Waste will be met, provided that
inventories of radionuclides do not exceed limitations determined through the modeling (Whetstone
Associates 2011b; DRC, 2012). The Division also reviewed the two ET covers and prepared numerous
comments that the Licensee responded to, but could never reach a determination where the Division could
approve either of the ET Cover Systems.
Conclusions
The objective of License condition 42 was to investigate covers for the CAW embankment and
demonstrate the efficiency of the designs; to fulfill this objective three covers were evaluated. Infiltration
Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 38 of 47 DRC-2018-004073
into and through the cover is a significant factor affecting embankment performance, and directly affects
radionuclide leach rates and vadose zone and aquifer velocities. Because, models are used to predict
groundwater concentrations in compliance wells for a period of 500 years or greater after closure,
accurate prediction of infiltration through the closed CAW embankment engineered cover is critical part
of the performance assessment. The HELP and HYDRUS computer codes were applied to the various
covers for the CAW embankment, to represent infiltration through the cover systems. The HELP model
was not particular data intensive; but was able to obtain reasonable (conservative) estimates of
infiltration. In contrast, HYDRUS models may provide more accurate prediction of infiltration and
represent the covers more realistic, but the selection of model inputs and boundary conditions is more
complex. It is the Division’s position that the Licensee should develop and use defensible methodology
to demonstrate the effectiveness of cover design in relation to compliance with performance objectives.
Because the Division had concerns with the modeling of the ET cover systems, even with a more realistic
representation of the processes, the HYDRUS models were still found to be more uncertain. In this
regard, an acceptable approach was determined to be the HELP model, with a reasonably good
(conservative) approximation of all parameter combinations considered. Based on the information
summarized above, the Division concludes that the projected performance of the currently proposed
CAW embankment cover design (with an EZD value of 20 inches) would be adequate to minimize water
infiltration and resist degradation.
REFERENCES
Adrian Brown Consultants, Inc. (ABC), 1997. Volume I. LARW Infiltration Modeling Input Parameters and Results, prepared for Envirocare of Utah, Inc. 41 pp plus tables, figures, and attachments. May 15, 1997. Adrian Brown Consultants, Inc. (ABC), 1998. Volume II. LARW Groundwater Fate and Transport
Modeling Input Parameters and Results, prepared for Envirocare of Utah, Inc. 44 pp. plus tables, figures and attachments. February 12, 1998.
Bingham Environmental, 1993a. Report on Technical Demonstration Study, Envirocare Waste Disposal Facility, South Clive, Utah. (May 6, 1993).
Bingham Environmental, 1993b. Report on Contaminant Transport Modeling at Envirocare of Utah Waste Disposal Facility, South Clive, Utah. August 3. Bingham Environmental, 1994. Containment Justification Study of Additional Contaminants in 11e.(2) Waste, 11e.(2) Waste Disposal Facility, Envirocare of Utah, South Clive, Utah, South Clive, Utah. 29 pp. plus figures and appendices. June 30, 1994. Bingham Environmental, 1995a. Memorandum to George Hellstrom, Envirocare of Utah, Inc. from David Cline and David Waite, Regarding Hydrologic Evaluation of Active Cell LARW Mobile Waste Disposal Cell Clive, Utah. August 15, 1995.
Bingham Environmental, 1995b. Memorandum to Vern Andrews, Envirocare of Utah, Inc. from David Cline and David Waite, Regarding PATHRAE Modeling [of] Additional LARW Radionuclides, 4 pp plus appendices. June 1, 1995.
Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 39 of 47 DRC-2018-004073
C. Yu, A.J. Zielen, J.-J. Cheng, D.J. LePoire, E. Gnanapragasam, S. Kamboj, J. Arnish, A. Wallo III, W.A. Williams, and H. Peterson, 2001, User’s Manual for RESRAD Version 6: Environmental Assessment Division, Argonne National Laboratory.
Department of Environmental Quality (DEQ), Division of Water Quality, 1994. Memorandum from Loren Morton (DWQ) to Dane Finerfrock (DRC) regarding DWQ/USU PATHRAE Contaminant
Modeling: Evaluation of Envirocare of Utah’s August 30, 1993 Proposed Changes to Embankment Cover Design, February 25, 1994 EnergySolutions – CAW Cell Infiltration and Transport Modeling 70. Division of Radiation Control (DRC), 2011. Interrogatory CAW R313-25-8(1)-08/1: Technical Analyses; Releases of Radioactivity, October 5, 2011. Division of Radiation Control (DRC), 2012, Class A West Amendment Request; Radioactive Material License UT 23000249, Amendment 14, GWQDP UGW 450005 Modification; Final Agency Action, dated November 26, 2012.
Fayer, M.J., and Jones, T.L., 1990 (April). UNSAT-H version 2.0: Unsaturated Soil Water and Heat Flow Model, PNL-6779, Battelle Memorial Institute. Merrell, G.B., Rogers, V.C., and Chau, T.K., 1995. The PATHRAE-RAD Performance Assessment Code for the Land Disposal of Radioactive Wastes, Rogers & Associates Engineering Corporation, RAE- 9500/2-1. March 1995.
Neptune and Company, Inc., October 5, 2012, Modeling Report: Fate and Transport of Contaminants from the Class A West Embankment and Exposure to a Post-Closure Traditional inadvertent Human Intruder at EnergySolutions Clive, Utah Facility. Rogers and Associates Engineering Corporation, 1990. Evaluation of the Potential Public Health Impacts Associated With Radioactive waste Disposal at a Site Near Clive, Utah, Rogers and Associates Engineering Corporation, RAE-9004/2-1, June 1990. Schroeder, P.R., and Peyton, R.L., 1995. HELP Modeling Workshop, IGWMC Ground-Water Modeling Short Courses, Colorado School of Mines, Golden, CO.
Schroeder, P.R., Aziz, N.M., Lloyd, C.M., and Zappi, P.A., 1994a. The Hydrologic Evaluation of Landfill Performance (HELP) Model: User’s Guide for Version 3, EPA/600/R-94/168A; US EPA Office of Research and Development, Washington, D.C. Schroeder, P.R., Dozier, T.S., Zappi, P.A., McEnroe, B.M., Sjostrom, J.W., and Peyton, R.L., 1994b. The
Hydrologic Evaluation of Landfill Performance (HELP) Model: Engineering Guide for Version 3, EPA/600/R-94/168B; US EPA Office of Research and Development, Washington, D.C. Simunek, J.M Sejnal, and van Genuchten, M. Th., 1998, the HYDRUS 1D software Package for Simulating One-Dimensional Movement of Water, Heat, and Multiple Solutes in Variably-Saturated
Media. Version 2.0, US Salinity Laboratory, ARS/USDA, Riverside California. Utah Department of Environmental Quality (DEQ) Division of Water Quality, 1994. Memorandum from
Loren Morton (DWQ) to Dane Finerfrock (DRC) regarding DWQ/USU PATHRAE Contaminant
Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 40 of 47 DRC-2018-004073
Modeling: Evaluation of Envirocare of Utah’s August 30, 1993 Proposed Changes to Embankment Cover Design, February 25, 1994.
Whetstone Associates, Inc, 2000a. Envirocare Of Utah Western LARW Cell Infiltration and Transport Modeling, consultants report dated March 2, 2000a. Document Number 4104M.000302.
Whetstone Associates, Inc, 2000b. Envirocare of Utah Revised Western LARW Cell Infiltration and Transport Modeling, consultants report dated June 12, 2000b. Document Number 4104M.000612. Whetstone Associates, Inc, 2000c. Envirocare of Utah Revised Western LARW Cell Infiltration and Transport Modeling, consultants report dated July 19, 2000c. Document Number 4104M.000719. Whetstone Associates, Inc, 2000d. Envirocare of Utah Class A, B, & C Cell Infiltration and Transport Modeling, consultants report dated August 1, 2000d. Document Number 4104O.000801 Whetstone Associates, Inc, 2001. “Results of Cf-251 Modeling for the Class A Cell, Using the 898-Year Half Life”, technical memorandum to Dan Shrum, Envirocare of Utah from Susan Wyman,
Whetstone Associates, Inc, 2003. “Technical memorandum on 11(e).2 Cell Transport Modeling Using New Zn Kd and Higher Radionuclide Concentrations”, technical memorandum to Dan Shrum, Envirocare of Utah from Susan Wyman, Whetstone Associates, dated November 10, 2003, Document Number 4101L.031110, 2 pp.
Whetstone Associates, Inc, 2005. Envirocare of Utah Class A Combined (CAC) Cell Infiltration and Transport Modeling Report, dated November 18, 2005. Document Number 4101W.051118. Whetstone Associates, Inc, 2007. Envirocare of Utah Class A South Cell Infiltration and Transport Modeling Report, dated December 7, 2007. Document Number 4101L.071207. Whetstone Associates, Inc. 2011a. EnergySolutions Class A West Disposal Cell Infiltration and Transport Modeling Report, dated April 19, 2011, Document Number 4101K.110419. Whetstone Associates, Inc. 2011b. EnergySolutions Class A West Disposal Cell Infiltration and Transport Modeling Report, dated November 28, 2011, Document Number 4104K.120223.
Whetstone Associates, Inc. 2012. EnergySolutions Class A West Disposal Cell Infiltration and Transport Modeling Report, dated February 23, 2012 Document Number 4104K.111128.

Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 41 of 47 DRC-2018-004073
Appendix F
License Conditions 73 and 76 – Surety Submittal Date & Perpetual Care
Statement of Basis to Amend License Conditions 73 and 76
On November 10, 2017 and May 9, 2017 (CD17-0252 / CD17-0112), respectively, ES submitted requests
to the Director to amend License Conditions 73 and 76 of the RML. The amendment to Condition 73, in
accordance with the passage of Senate bills 2015-173 and 2017-79, will bring this condition in agreement
with the 11e.(2) license and with the state-issued Part B Permit. Condition 76 has been modified to
comply with changes to the Utah Code as directed by House Bill 296 which was approved during the
2017 general session.
The License Section and current License Condition 73 are as follows:
FINANCIAL ASSURANCE/CLOSURE
73. The Licensee shall at all times maintain a Surety that satisfies the requirements of Utah Admin.
Code R313-25-31 in an amount adequate to fund the decommissioning and reclamation of
Licensees’ grounds, equipment and facilities by an independent contractor. The Licensee shall
annually review the amount and basis of the surety and submit a written report of its findings by
December 1 each year for Director approval. At a minimum, this annual report shall meet the
following requirements:
A. Summary of Changes – the annual report shall include a written summary of any change in
the cost estimate previously approved by the Director, including, but not limited to:
i. A description of any modification, addition, or deletion of any direct cost or post-closure
monitoring and maintenance (PCMM) cost line item, including supporting justification,
calculations and basis;
ii. Any change to the unique reference number (cost line item) assigned approved by the
Director for any direct or PCMM cost line item;
iii. Updates to the cost estimate for decommissioning the CAW embankment to ensure the
cost estimate remains current in the event that the Director determines the CA and CAN
embankments must be closed as a single embankment using the approved design of the
CAW embankment. The cost estimate must meet the requirements of License Condition
73; and,
iv. Updates to the cost estimates for closing and decommissioning the CA and CAN
embankments as separate embankments using the approved designs for each
embankment. The surety shall be based on the approved cost estimate for the CA and
CAN embankments until the Director determines it is no longer feasible for the CA and
CAN embankments to be closed separately. At that time, the surety shall be based on the
Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 42 of 47 DRC-2018-004073
approved cost estimate provided for License Condition 73.A.iii. The update to the cost
estimate for the CA and CAN embankments must include funding to move excess
materials that have been placed outside of the approved CA design to the CAN
embankment, as well as all other costs associated with closing the CA and CAN
embankments separately. The cost estimate must meet the requirements of License
Condition 73.
B. Indirect Costs shall be based on the sum of all direct costs in accordance with the following values:
Surety Reference No. Description Percentage
300 Working Conditions 5.5%
301 Mobilization/ Demobilization 4.0%
302 Contingency 15.0%
303 Engineering and Redesign 2.25%
304 Overhead and Profit 19.0%
305 Management Fee and Legal Expenses 4.0%
306 DEQ Oversight 4.0%
C. RS Means Guide estimates of direct construction costs provided in the annual report shall be
derived from or based on the most recent edition of the RS Means Guide for Heavy
Construction.
D. Report Certification – the annual report shall be prepared under the direct supervision of and
certified by a Professional Engineer or Professional Geologist currently licensed by the State
of Utah with at least five (5) years of construction cost estimation experience. The annual
report shall be developed in accordance with the standards of professional care.
E. Electronic Format – the Licensee shall provide the report in both paper and electronic
formats, as directed by the Director.
F. Within 60-days of Director approval of said annual report, the Licensee shall submit written
evidence that the surety has been adequately funded.
G. The Licensee shall prepare and maintain current a gravel resource evaluation report on-site
that quantifies the gravel reserves remaining in the Grayback Hills Gravel Pit located in
Section 24 of T. 1 N., R. 12 W (SLBM). Such report shall be prepared and certified on or
before December 1 of each year by a professional engineer or professional geologist currently
registered in the State of Utah.
Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 43 of 47 DRC-2018-004073

The amended License Condition 73:
73. The Licensee shall at all times maintain a Surety that satisfies the requirements of Utah Admin.
Code R313-25-31 in an amount adequate to fund the decommissioning and reclamation of
Licensees’ grounds, equipment and facilities by an independent contractor. The Licensee shall
annually review the amount and basis of the surety and submit a written report of its findings by
December 1 each year for Director approval. At a minimum, this annual report shall meet the
following requirements:
A. At its election, the Licensee’s annual proposed closure and post-closure costs shall be based
on either Summary of Changes – the annual report shall include a written summary of any
change in the cost estimate previously approved by the Director, including, but not limited to:
i. an annual cost estimate using unit rates from the current edition of RS Means Facilities
Construction Cost Data and other site-specific processes, indirect costs based on the sum
of applicable direct costs in accordance with the indirect cost multipliers in Table 73 or
others mutually agreed to by the Licensee and the Director; or A description of any
modification, addition, or deletion of any direct cost or post-closure monitoring and
maintenance (PCMM) cost line item, including supporting justification, calculations and
basis;
Table 73
Surety Reference No. Description Percentage
300 Working Conditions 5.5%
301 Mobilization/ Demobilization 4.0%
302 Contingency 15.0%
303 Engineering and Redesign 2.25%
304 Overhead and Profit 19.0%
305 Management Fee and Legal Expenses 4.0%
306 DEQ Oversight 4.0%
ii. an initial financial assurance determination and for each financial assurance
determination every five years thereafter, a competitive site-specific estimate using a
third party contractor for closure and postclosure care of the licensed facility. Any
change to the unique reference number (cost line item) assigned approved by the
Director for any direct or PCMM cost line item;
iii. Either the method in Condition 73.A.i or in Condition 73.A.ii shall be updated
annually as required by Condition 73.B. Updates to the cost estimate for
Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 44 of 47 DRC-2018-004073
decommissioning the CAW embankment to ensure the cost estimate remains current
in the event that the Director determines the CA and CAN embankments must be
closed as a single embankment using the approved design of the CAW embankment.
The cost estimate must meet the requirements of License Condition 73; and,
iv. Updates to the cost estimates for closing and decommissioning the CA and CAN
embankments as separate embankments using the approved designs for each
embankment. The surety shall be based on the approved cost estimate for the CA
and CAN embankments until the Director determines it is no longer feasible for the
CA and CAN embankments to be closed separately. At that time, the surety shall be
based on the approved cost estimate provided for License Condition 73.A.iii. The
update to the cost estimate for the CA and CAN embankments must include funding
to move excess materials that have been placed outside of the approved CA design to
the CAN embankment, as well as all other costs associated with closing the CA and
CAN embankments separately. The cost estimate must meet the requirements of
License Condition 73.
B. Indirect Costs shall be based on the sum of all direct costs in accordance with the following
values:
Surety Reference No. Description Percentage
300 Working Conditions 5.5%
301 Mobilization/ Demobilization 4.0%
302 Contingency 15.0%
303 Engineering and Redesign 2.25%
304 Overhead and Profit 19.0%
305 Management Fee and Legal Expenses 4.0%
306 DEQ Oversight 4.0%
B. The Licensee shall annually review the surety amount and basis of the surety and submit a
written report of its findings by March 1 each year for Director approval. At a minimum, this
annual report shall include an accounting for current site conditions and that includes an
annual inflation adjustment to the financial assurance determination using the Gross
Domestic Product Implicit Price Deflator of the Bureau of Economic Analysis, United States
Department of Commerce. RS Means Guide estimates of direct construction costs provided
in the annual report shall be derived from or based on the most recent edition of the RS
Means Guide for Heavy Construction.
Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 45 of 47 DRC-2018-004073
C. The combined annual surety is $76,690,920.92with the LLRW subtotal of $50,005,828.16 as
approved in the Director’s letter dated April 26, 2018. Report Certification – the annual
report shall be prepared under the direct supervision of and certified by a Professional
Engineer or Professional Geologist currently licensed by the State of Utah with at least five
(5) years of construction cost estimation experience. The annual report shall be developed in
accordance with the standards of professional care.
D. Electronic Format – the Licensee shall provide the report in both paper and electronic
formats, as directed by the Director.
E. Within 60-days of Director approval of said annual report, the Licensee shall submit written
evidence that the surety has been adequately funded.
F. The Licensee shall prepare and maintain current a gravel resource evaluation report on-site
that quantifies the gravel reserves remaining in the Grayback Hills Gravel Pit located in
Section 24 of T. 1 N., R. 12 W (SLBM). Such report shall be prepared and certified on or
before December 1 of each year by a professional engineer or professional geologist currently
registered in the State of Utah.
The current License Condition 76 is as follows:
76. The Licensee shall at all times maintain a Surety for perpetual care, using an instrument that
satisfies the requirements of Utah Admin. Code R313-22 and R313-25. The Surety for perpetual
care shall be in the amount last approved by the Waste Management and Radiation Control
Board, as provided in Utah Code Ann. 19-1-307(2), less the amount contributed to the
Radioactive Waste Perpetual Care and Maintenance Account created under Utah Code Ann. 19-
3-106.2.
The amended License Condition 76:
76. The Licensee shall at all times maintain a Surety for perpetual care, using an instrument that
satisfies the requirements comply with Utah Admin. Code § 19-3-106.2 Perpetual care and
maintenance of commercial radioactive waste disposal facilities. The Surety for perpetual care
shall be in the amount last approved by the Waste Management and Radiation Control Board, as
provided in Utah Code Ann. 19-1-307(2), less the amount contributed to the Radioactive Waste
Perpetual Care and Maintenance Account created under Utah Code Ann. 19-3-106.2.
A. The Licensee shall pay any fee imposed by the Legislative Management Committee on an owner
or operator of a commercial radioactive waste treatment or disposal facility for the perpetual
care and maintenance of the facility within 60 days of receipt of such notice.

Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 46 of 47 DRC-2018-004073
Blank Page

Statement of Basis RML No. UT 2300249 – Amendment 23 April 27, 2018
Page 47 of 47 DRC-2018-004073
Appendix G
License Conditions 90 – State Office
Statement of Basis to Add License Condition 90
See the following license condition text for the basis of adding License Condition 90 to Radioactive
Material License No. 2300249.
The New License Section and License Condition 90 are as follows:
STATE OFFICE
90. In order to facilitate the fulfillment of the Division’s oversight, inspection, and administrative
responsibilities under the Utah Radiation Control Act, the Utah Administrative Code, and this
License, the Licensee shall provide a reasonably accessible area of land, including utility
hookups, for a stand-alone, state-owned modular building located on the Licensee Controlled
Area in Section 29 of Township 1 South and Range 11 West, Tooele County, Utah for as long as
the License is in effect. The Director shall be responsible and pay for the upkeep, maintenance
and repair of the state-owned modular building. The Director shall pay Licensee just
compensation for the value of the land occupied by the state-owned modular building on
Licensee’s property pursuant to this condition. If the Licensee and Director cannot agree on the
reasonable value of the compensation, the value of the just compensation shall be determined by
an independent appraisal. The Licensee and Director shall use reasonable efforts to agree on the
terms of a lease agreement relating to the cost and other terms and conditions related to the
Director’s use the Licensee’s property. Once a location for the modular building is established,
the Licensee may, for just cause, change the location if the Licensee pays for all reasonable costs
of relocation.