DRC-2025-002299

299 South Main Street, Suite 1700 ▪ Salt Lake City, Utah 84111 [phone] ▪ Fax: [phone] ▪ www.energysolutions.com
July 17, 2025 CD-2025-148 Mr. Doug Hansen, Director
Division of Waste Management and Radiation Control 195 North 1950 West Salt Lake City, UT 84114-4880 Subject: Federal Cell Facility Application: Responses to Round 2 Request for Information (per DRC-2025-001739)
Dear Mr. Hansen: EnergySolutions hereby responds to the Utah Division of Waste Management and Radiation Control’s June 5,
2025 (DRC-2025-001739) Requests for Information (RFI) on our Federal Cell Facility (FCF) Application. A response is provided for each request using the Director’s assigned reference number. Each RFI letter is addressed individually, with the text of the RFI quoted in bold italics followed by its response. Multiple follow-up RFI letters are addressed in this response, with each letter preceded by a solid line. The following attachments are also electronically provided to this response submission. 1. FILE: CD-2025-148, an electronic copy of these responses 2. FOLDER: Operational Period RESRAD Analysis July 2025, model input and output files 3. FOLDER: References
4. FILE: _README_SIBERIA_FILES, a guide to electronic files provided in support of this work; and the associated electronic files
SIBERIA was not re-run in response to the June 5, 2025 RFIs; but the README file and associated electronic files from the February 21, 2025 response (DRC-2025-000618) are re-attached for completeness.
No DU PA model changes result from these responses.
Appendix AB: Operational Period Modeling ▪ AB-3.a: (from DRC-2025-001739): Based on Table S-1 of the “Final Supplement Environmental Impact Statement for Disposition of Depleted Uranium oxide Conversion Product Generated from DOE’s Inventory of Depleted Uranium Hexafluoride,” which projects conversion activities at gaseous diffusion
plants continuing for over 40 years, the response to this RFI indicates that RESRAD was modeled for 50 years.
Please include both discussion and graphical representation covering the RESRAD modeled 50 year period in Appendix AB.
Graphical representation of the results from RESRAD has been extended to 50 years. The reports “Quarter Cell Summary Report.REP,” ”Half Cell Summary Report.REP,” “Full Cell Summary Report.REP,” and “10K ft2 Summary Report.REP” (located in FOLDER Operational Period RESRAD Analysis July 2025) has been modified to the extended results.
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▪ AB-10.a-1: (from DRC-2025-001739): The precise measurements of the 2000 stormwater retention pond, which were used in the RESRAD model, could not be located. While the model represents the surface water body as 100-meter by 105-meter, a review of Engineering Drawing 08081-G03 suggests the pond is
more rectangular in its physical form. Please provide the engineering drawing, with dimensional details, that informed the 100-meter by 105-
meter used in RESRAD. In DRC-2025-002177, the director determined that the information submitted in response to RFI
DRC-2025-000625 sufficiently addressed this question. EnergySolutions is discontinuing further pursuit of responses to request AB-10.a-1.
▪ AB-16.a: (from DRC-2025-001739): As discussed in RFI AB-3.a above, please include both discussion
and graphical representation covering the RESRAD modeled 50-year period in Appendix AB. Graphical representation of the results from RESRAD has been extended to 50 years. The model was
not re-run in response to these RFIs, but the report has been modified to the extended results (see the spreadsheet FILE “DU waste concs and RESRAD results-July 2025xlsx” in the FOLDER Operational Period RESRAD Analysis July 2025.

▪ AB-23.a-1: (from DRC-2025-001739): Completion of the RESRAD model rerun has been confirmed. However, additional adjustments may be required due to subsequent Requests for Information. These potential changes include modifying the stormwater retention pond dimensions, changes in hydraulic conductivity, and creating updated graphs for the operational period.
Please review and, if necessary, rerun the RESRAD model to ensure the responses to RFIs AB-3.a, AB-10.a, and AB-16.a are integrated, as they may impact the results.
Graphical representation of the results from RESRAD has been extended to 50 years. The modeled stormwater retention pond dimensions are supported by Engineering Drawing 0009-01 (FOLDER References). The report has been modified to the extended results.

Appendix B: Federal Cell Facility Engineering Drawings
▪ B-23.a: (from DRC-2025-001739): The leaders along the ditch centerline in the drawing seem to indicate the flow direction for the drainage ditch, based on a callout on the Federal Cell’s northeast side and the inverts at the cell corners. However, the proposed pitch of the drainage ditches is unclear, given the inconsistent dimension callouts addressed in RFI B-27.a.
Please clearly specify the pitch of the drainage ditches and provide accurate invert callouts.
The flow direction for the drainage ditch and leader along the ditch centerline in Engineering Drawing 14004-C01 has been clarified (located in FOLDER References). Additionally, the callouts are consistent, as described in the response to B-27.a. The proposed pitches of the drainage ditches in
Engineering Drawings 14004-C01 and 14004-C02 (located in FOLDER References) have been clarified and are internally consistent.
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▪ B-27.a: (from DRC-2025-001739): The revision of the dimension on Cross Section A (Sheet 14004 C02, pg. 380) has now created a low point in the invert between the northeast and southeast corners. Based on the current dimensions, surface drainage flowing due south will not be achieved.
Please revise or clarify the dimensions with consideration of RFI B-18 as requested in RFI B-23.a. The dimensions on Engineering Drawing 14004-C02 (located in FOLDER References) have been revised and clarified to demonstrate that surface drainage will be achieved. The reported ditch elevations do not create a low point along the east side of the cell. The cross sections represent elevations at the midpoints of the embankment and the ditches. ▪ B-34.a: (from DRC-2025-001739): The specified minimum distance of 3 feet from the Clay Liner
conflicts with the 5-foot minimum indicated by the dimensions. The original RFI requested minimum excavation dimensions, including the minimum cover from the “NATIVE SOIL” to the bottom of the
“FILTER ZONE” material in the Drainage Ditch. These details are necessary to ensure clear constructability of the “COMPACTED BORROW MATERIAL.” Please revise Note #3 on Sheet 14004 C03 (pg. 382) to clarify excavation limits. The excavation limits in Note #3 on Engineering Drawing 14004-C03 have been revised (located in FOLDER References). The details have been updated to reflect a minimum of 3 feet of excavation beyond the clay liner limits. The details also clearly show the minimum thickness of the compacted borrow material between the native soils and the bottom of the filter layer. ▪ B-46.a: (from DRC-2025-001739): Neither Note #2 of Sheet 14004 C05 nor Specification 155 of CQA/QC Manual in Appendix C details the “approved seed mixture to be used on the embankment.” This
information is necessary to confirm the intended seed mixture will not include plant species that could adversely affect the final cover’s performance.
Please provide specifications for the embankment seed mixture. Locally-adapted plant materials will be required to create a functioning vegetation community on the FCF top slope cover. The target vegetation community on the FCF top slope final cover consists of approximately 15% cover of small stature native shrub species (Atriplex confertifolia, Atriplex canescens, Bassia americana, Picrothamnus desertorum, and Suaeda torreyana), with additional cover
provided by sparse native forbs and grasses. Although several of these shrub species have been documented to root very deeply along waterways or under wetter climatic conditions elsewhere, the soil and climate conditions on and near the Clive site clearly limit the sizes and densities of native
shrubs. Greasewood will not be included in the target community due to its deep rooting habit, the affinity of badgers for larger stature shrub species, and the demonstrated affinity of small mammals for higher shrub densities.
The target vegetation community for the FCF top slope cover is based on documented species cover and densities as well as plant materials adapted to local climate and soil conditions. The native plant species that occur at Clive are well-adapted to the saline, high pH, and low-fertility soil conditions and low average annual precipitation of less than 10 inches (25 cm). Plant species on and near Clive occur in silty clay soils that possess a naturally occurring compacted clay layer at approximately 24 inches (60 cm) depth. As such, the native shrub species are not found to root deeply and appear to be able to take advantage of moisture perched above the compacted clay by extending root growth laterally instead of into the clay.
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The only non-native plant materials that will be included in the vegetation plan are non-invasive, fast-growing grasses used for initial soil stabilization (Quick Guard sterile Triticale). These grasses will be seeded in the fall or early winter to provide cover to stabilize soils and enhance soil development and
biological soil crust cover. The sterile rye (Quick Guard sterile Triticale) will not persist beyond the first 1–2 years of vegetation cover development. Only approved reclamation materials from reputable seed suppliers will be used. There are several invasive plant species that occur in the area: cheatgrass (Bromus tectorum), Halogeton (Halogeton glomeratus), and kochia (Bassia species) that are expected to invade early in the revegetation process. Early seeding of high densitites of sterile rye and native squirreltail, which are good competitors with cheatgrass and other annual weeds, will help to exclude invasives. Invasive weed species will be targeted for control, particularly during the first 1 to 2 years of vegetation development to allow native species to dominate the cover system.
Initial measures to be implemented during the Institutional Control Period to ensure successful long-term, steady-state vegetation establishment include biological soil crusts stockpiling, low profile surface recontouring, soil erosion control, seedbed preparation, application of appropriate seed mixes,
plant establishment, weed abatement, and monitoring. Borrow soils and biological soil crusts will be surveyed for noxious and invasive weeds prior to
removal from borrow sites to minimize the volume of noxious or invasive weed seeds and propagules in FCF top slope cover surface materials. Biological soil crusts will be salvaged from undisturbed, native soils associated with the target vegetation community. Soil crust salvage is usually from areas that are designated for clearing, though small areas of pristine crust could be salvaged to enhance the diversity of biological soil crusts organisms in the inoculation material. Certified weed-free erosion control blankets, straw bales, wood fiber, or straw wattles will be used as appropriate to limit erosion of soil and biological soil crust stockpiles. SEEDBED PREPARATION: The FCF final cover top slope soil surface will be left in a roughened
condition to enhance seed germination. All areas to be seeded will be scarified to a depth of 3–4 inches using rippers or disks spaced approximately 12 to 18 inches apart. Scarification will be perpendicular to slopes to prevent erosion rilling. Once scarification is completed, traffic on the
prepared area will be limited to prevent surface compaction. SEED MIXTURE: The target vegetation community for the cover system is Inter-Mountain Basins
Mixed Salt Desert Scrub consisting of saltbush species, gray molly, and other native shrub and grass species. Detailed seed mix for each area of cover construction will be documented prior to the start of construction. Re-establishing vegetation in this arid vegetation type is challenging because of
unpredictable precipitation and noxious or invasive weed competition. Proper seedbed preparation, mulching, locally adapted seed mixes, mycorrhizal fungi inoculation, seeding during late fall and early winter, and weed abatement will all improve plant establishment.
The approved seed mixture is presented in Table 1 and consists of Fourwing saltbush (Atriplex canescens), Shadscale saltbush (Atriplex confertifolia), Gray molly (Bassia americana), Bud sage (Picrothamnus desertorum), Sandberg bluegrass (Poa secunda), Mojave seablite (Suaeda torreyana), Bottlebrush squirreltail (Elymus elymoides), Thickspike wheatgrass (Elymus lanceolatus), Sterile rye (Quick Guard sterile Triticale), and Indian ricegrass (Achnatherum hymenoides).
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Table 1 Federal Cell Facility Top Slope Vegetation Density and Seeding Rates

SEED METHODS: Seeding will occur immediately following soil contouring and gravel mulching, and will be followed by the application of biodegradable mulch or other stabilizing materials. The main purpose of all seeding methods is to place the seed in direct contact with the soil at average depths of 0.5 inch, but not exceeding a depth of 1.0 inch, to cover the seed with soil, and to firm the soil around the seed to eliminate air pockets. Seeding will be used in all areas that have replaced
topsoil or surface fines, which will include all disturbed areas of the disposal cell including the 50% gravel admixture on side slopes. Direct (drill) seeding places seed into the soil at a uniform depth and will be used on slopes of less than 15%. However, because soil-gravel mixture on the FCF top slope
soil surface may limit the efficacy of drill seeding, broadcast seeding will also be used to provide effective seed placement where slope or soil composition does not permit drill seeding. Additionally, broadcast seeding followed by harrowing may also be employed, where necessary.
Broadcast seeding may be accomplished with 1) a hand-operated, cyclone-type seeder; 2) a mechanical broadcast seeder attached to the imprinting device; or 3) a seed blower that distributes the seed on top of the surface without mulch. The seeds must be covered by raking or dragging a chain or harrow over the seedbed. Imprinting with straw punch treatment also may be used to place seed in the soil. The cyclone type seeder can be used on any slope that can be reached by foot.
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Hydroseeding and hydro-mulching use water with a slurry of seed, mulch, and tackifier that is sprayed over the restored topsoil surface. Hydroseeding alone sprays only the seed on the soil surface. This method often does not allow good soil-to-seed contact, leaves seed exposed to desiccating wind
and temperatures, and increases seed loss by rodent and avian foraging. However, hydroseeding and hydro-mulching may be employed on side slopes as needed. SEEDING TIMING: In arid and semi-arid conditions, seeds must be planted in the appropriate time of the year. The seeding window for woody desert species is early to late fall. Container-grown seedlings can be planted in fall or early spring. Fall is generally the preferred planting time for desert
restoration, because it allows root establishment during cooler, often wetter, winter months, and allows for the establishment of healthy roots that result in greater above-ground biomass and growth the following growing season. VEGETATION MONITORING: Monitoring and maintenance will begin with implementation of the vegetation effort. The initial vegetation period from years one to two will require monitoring of
seeding success, weed invasion, and erosion on the FCF top slope cover. Vegetation inspections and monitoring will be conducted bi-annually in spring and fall during this period. The purpose of post-rehabilitation vegetative cover monitoring is to evaluate soil stability, vegetative cover and density, and noxious and invasive weed infestations. Bi-annual monitoring will continue for a minimum of five years. The objectives of monitoring are as follows:
• To quantify the effectiveness of temporary and permanent erosion-control structures.
• To ensure that the FCF top slop final cover and embankment are stable and that runoff is
naturally controlled in place, with no accelerated erosion or washouts. Any erosion issues should become apparent within the first 2 years or after the first significant runoff event.
• To quantify seeding success and transplant survival for 5 years. Establish permanent vegetation monitoring transects or plots to allow quantitative comparisons of plant cover and density, bare ground, and litter cover over time and to native analogues.
• To identify and treat noxious and invasive weed infestations. Except for noxious and invasive weed control, vegetation maintenance is not anticipated.
• To identify any other disturbances that may hinder reclamation success, such as soil compaction, excessive grazing, and diseases or pests. The long-term, steady-state vegetation community on the FCF top slope final cover will be considered viable when it consists of native shrub, forb, and graminoids species at the target cover
and densities required for a functioning cover system. Vegetation and erosion monitoring should continue for 5 years.
Where initial reclamation and plant establishment efforts fail to make progress toward meeting plant establishment standards after year two, reseeding or planting will take place. Areas will be reseeded where initial plant establishment efforts fail.
Revegetation will be considered successful when herbaceous and woody plant cover is 80 percent of the target cover, and there is no significant soil erosion and minimal (<10%) cover of noxious or invasive weeds. Negligible disturbance to soils and vegetation will occur during annual monitoring.
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ADAPTIVE MANAGEMENT: Adaptive management during the Institutional Control Period will be implemented to address unforeseen circumstances. Adaptive management is defined, for the purposes of this Plan, as a flexible, iterative approach to the successful development of a functional
vegetated cover. The management of the cover system will be directed by the results of annual monitoring activities and observations of factors that are inhibiting the development of vegetation on the cap. A review of Clive’s meteorological history reveals that seasonal drought is anticipated to occur periodically. The native vegetation is composed of drought-tolerant plant species that are capable of withstanding seasonal fluctuations in available moisture. However, an extended drought could potentially occur during part or all the 5-year vegetation development and monitoring period. Prolonged drought would entail low seasonal rainfall and high temperatures that reduce plant cover, increase plant mortality, increase pest infestations or herbivory, or otherwise limit the development and growth of vegetation on the cap. Remedial measures for prolonged drought would be limited to
reseeding and irrigation, and extension of the 5-year monitoring and reporting period. High-precipitation storm events can damage soils and vegetation. If qualitative and/or quantitative monitoring of the vegetated cover indicates that stochastic events have impeded soil stability or vegetation growth within the first 2 years post-installation, remedial actions such as mulch applications, erosion control materials, and reseeding will be required.
▪ B-50.a: (from DRC-2025-001739): The proposed orientation of the DU cylinders lacks clarity to achieve
structural integrity of the material, ensuring Controlled Low-Strength Material (CLSM) can be poured to adequately fill all voids, while maintaining the butter zone limitations.
Please provide clarification on the orientation, construction methods, and geometry of the DU cylinders and their relationship to the buffer zone and embankment as shown. Include structural details in the drawings or add explanatory text within the application to address these questions. As illustrated in Figure 1, the planned stacking arrangement is constrained by the available below-grade volume under the FCF’s top slope cover, as all depleted uranium wastes will be disposed of
below grade and under the top slope. The bottom layer of waste containers will be placed approximately 6 inches apart, considering handling and placement with heavy equipment, to minimize the need for Controlled Low-Strength Material (CLSM) fill. The placement configuration will be confirmed to comply with the maximum allowable embankment loading in accordance with Specification 58 of the FCF CQA/QC Manual prior to the start of waste placement. The number of gaseous diffusion plant (GDP) DU cylinders that could be disposed of at the Clive site is estimated from engineering specifications, packing dimensions, and SRS DU drum volume.
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Figure 1 - The Below-Grade Orientation of Cylinders (from Engineering Drawing 14004 – Sketch 1)
As is illustrated in Table 2, the number of 12-ft long, 4-ft diameter cylinders that could be disposed of is estimated to be 48,625 cylinders (based on the dimensions of the waste footprint and depth below
grade). Table 2 – Below Native Grade Cylinder Placement Configuration
Rows of Cylinders (1st Layer) DU Disposal Area Dimension (ft) 1,570
Cylinder Spacing (ft) 12.5
Rows of Cylinders 125
Columns of Cylinders (1st Layer)
DU Disposal Area Dimension (ft) 876.5
Cylinder Spacing (ft) 4.5
Columns of Cylinders 195
Rows of Cylinders (2nd Layer) 125
Columns of Cylinders (2nd Layer) 194

Total Number of Cylinders 1st Layer 24,375
Total Number of Cylinders 2nd Layer 24,250
TOTAL CYLINDERS 48,625
TOTAL VOLUME OF CYLINDERS (ft3) 7,332,477
TOTAL CLSM VOLME (ft3) 2,713,090

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▪ B-50.b: (from DRC-2025-001739): Appendix C, Specification #61 of the CQA/QC Manual requires DU cylinders to be punctured with a minimum of eight square inches or have their lids removed before
infilling. However, FCF-CW-PR-102 (Appendix I), concerning Federal Cell Facility Waste Void Remediation, lacks specifics on puncture methods or lid removal for CLSM inflow. It is unclear how this will be accomplished considering ALARA, uncertainty about container orientation, and potential CLSM
reactions with cylinder contents. Please provide methodologies and robust justification to confirm adequate CLSM infill for these
containers, satisfying NUREG sections 4.3.1 and 4.3.2, or demonstration of established professional industry practices and references to support the proposed approach. Depleted uranium will be disposed of in containers beneath the embankment top slope and below native grade in accordance with the FCF CQA/QC Manual. Containers to be disposed of in the FCF will be entombed in CLSM per the FCF CQA/QC Manual. Safe storage and disposal of depleted
uranium waste are essential for mitigating releases of radioactive materials and reducing exposures to humans and the environment. The FCF design features a hipped cap with relatively steeper sloping sides near the edges. The upper part, known as the top slope, has a moderate slope of 2.4%, while the side slope is markedly steeper at 20%. Depleted uranium will only be placed below native grade and beneath the embankment’s top slope. FCF waste containers will be placed using cranes, forklifts, and other industrial equipment, including electronic hooks, cameras, slings, and pallets. Engineering Drawing 14004-U03 (located in FOLDER References) depicts the waste zone limits to between 7.8 and 9.5 feet in height after CLSM placement is complete. Minimizing void spaces is critical to the long-term stability of the FCF. Procedure FCF-CW-PR-102, FCF Waste Void Remediation, provides guidance for the disposal of depleted uranium and is used to
move waste from the area of receipt to the FCF. The procedure delineates methods for filling voids in waste packages not meeting the criteria for direct burial set forth in the FCF Radioactive Material License. The engineering properties of the CLSM used to fill void spaces have been demonstrated to conform around variable shapes and sizes without bridging between containers. Once placed, depleted uranium containers will be further entombed within CLSM up to native grade.
Federal waste cover operations will be controlled in accordance with the FCF CQA/QC Manual. Fill placement and the ultimate designed cover have been modeled and found to be sufficiently impermeable to water, structurally sound, and erosion resistant. The liner will be protected from damage during operations by a minimum one-foot-thick layer of clean native material (referred to as liner protective cover). The entire FCF embankment above the disposed depleted uranium to the radon barrier will consist of clean native material (fill). The construction of both the liner protective cover and clean fill is specified in the FCF CQA/QC Manual.
The FCF design enables isolation of the facility after it has been filled and covered. Once closed, the FCF will not be disturbed by other ongoing operations at the site. The final FCF cover integrates long-term water and erosion control methods into the overall design, eliminating the need for active maintenance of the closed FCF. FCF CQA/QC Manual Work Elements – Waste Placement and Cover Construction describe the necessary processes and material specifications. Similarly, required engineering characteristics of materials supporting the construction of the FCF (including placement
procedures) are documented in the FCF CQA/QC Manual.
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The FCF CQA/QC Manual also includes locating, mapping, and marking of the FCF (including QC confirmation). Marking includes designation of horizontal and vertical field surveys by prequalified personnel. Document control of liner construction, waste placement, and cover construction records is
also specified.

Appendix O: Erosion Modeling ▪ O-5.a: (from DRC-2025-001739): The suitability of the Rangeland Hydrology and Erosion Model
(RHEM) to parameterize SIBERIA remains uncertain. Considering that limiting parameter space is acceptable in principle, please provide justification for
parameter culling given inherent uncertainties and parameter tradeoffs. The Rangeland Hydrology and Erosion Model (RHEM) simulations are designed to simulate a large
rainfall-runoff plot experimental campaign. Rainfall-runoff experiments or plot monitoring is standard practice for estimating SIBERIA parameters when data from existing landforms are not available (Evans et al. 2000; Willgoose and Riley 1998; Willgoose and Hancock 2011). When
obtaining sediment yield data from experimental plots is not possible, the use of “traditional” erosion models such as RHEM to estimate SIBERIA parameters is suggested (Al-Hamdan et al. 2012; Temme et al. 2009; Willgoose and Hancock 2011). The phrase “parameter culling” is taken to mean
checking whether the approach taken has made the input parameter ranges too narrow after trimming implausible values. In the case of the Federal Cell Facility (FCF) erosion model, the top slope of the cover exhibits low-gradient slopes constructed with an engineered material with no existing analogs available for collecting erosion data or geomorphological data. The RHEM simulations are designed to simulate a large rainfall-runoff plot experimental campaign to provide estimates of sediment yield from erosion from rills and inter-rill regions on hillslope profiles with a range of slopes and drainage areas, an approach suggested by Willgoose (2005) and Willgoose and Hancock (2011): “The similarity between LEMs and physically-based erosion models is that the underlying
physics is generally the same (although the details will depend on the LEM), so a considerable amount of knowledge can be transferred from our work with traditional models (e.g. cover factors).” (Willgoose and Hancock 2011)
The best reference set of sediment yields would be sourced from existing terrain with various hillslope and channel features. If this is not available, then a validated model predicting sediment
yield from various hillslope and channel features is considered an acceptable alternative (Willgoose, 2005, Willgoose and Hancock, 2011). RHEM predictions are based on a regression model for inter-rill processes and a stream power-based rill erosion formula with a conservative erodibility coefficient for rangeland (Al-Hamdan et al. 2012). Large channel formation is therefore extrapolated from the rill domain, but RHEM represents the best available source of sediment yield predictions for this problem.
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RHEM was used in conjunction with storm-based climate information from the Dugway, UT site to help identify plausible ranges of values for parameters. Specifically, RHEM was driven using information based on individual storm events from the USDA ARS climate file for Dugway, UT. The
climate information from the Dugway, UT site was used to generate estimates of the amount of material one would expect to be moved (i.e., sediment yield) by storm-induced erosion for slopes consistent with the Federal Cell Facility. When RHEM generates an estimate of the amount of material moved by storm-induced erosion, there are multiple sets of input parameters that can produce that result. A smaller value for one parameter can be offset by a different value in a different parameter (or parameters) to produce the same result. The existence of these tradeoffs is accommodated by using a range of values for the parameters. The use of a range of values also provides a quantitative way to accommodate and propagate uncertainty in the parameters out to uncertainty in the simulated erosion impacts.
The net effect is that RHEM has been used to generate sediment yields for 39 site-representative profiles, within which parameters were varied broadly based on the best available information and scientific understanding. These sediment yield profiles were then used in SIBERIA to model the
landscape evolution of the armored FCF disposal cell.
▪ O-5.b: (from DRC-2025-001739): Gully formation is of key interest and, according to the *RHEM Tutorial Guide, a limitation of the model is that “RHEM does not address channel, gulley, side-bank
sloughing, head cutting, rain-on-snow, and/or seep induced soil erosion processes.” Please provide information on how the limitation of the RHEM model has been addressed. *https://apps.tucson.ars.ag.gov/rhem/assets/docs/tutorials_and_fact_sheet/RHEM_Tutorial.pdf.
RHEM was used only to generate runoff, hillslope detachment, and the resulting sediment yield for the 39 site-representative profiles. The yields from these profiles then feed SIBERIA, which routes the sediment downslope and predicts when and where gullies initiate and evolve. RHEM is not used itself to model channel, gully, or head cut processes, however it provides input to SIBERIA which then models the initiation and development of gullies. In other words, RHEM supplies the initial hydrologic response (discharge as a function of area) and sediment yield from hillslope detachment rates from rain splash, sheet flow, and concentrated flow in rills. SIBERIA applies these RHEM outputs to predict where and when gullies form as convergent flow paths develop.
Application of RHEM to the Clive site can be compared to its application at a wetter site, where SIBERIA produces more and deeper channels. RHEM’s rill physics yields concavity indices θ ≈ 0.1-0.2 for the Dugway, UT storm set, indicating sheet-flow controls and shallow incision. At the wetter
Mena site in Arkansas, for example, θ is around 0.53 under the Mena storm set, which in SIBERIA produces deeper, more numerous channels. The Mena, AK result is consistent with Willgoose’s calibration guidance suggesting θ be in the range of 0.4–0.6 (Willgoose 2005). The low value of θ at
Clive compared to that for Mena, AR predictions indicates erosion from the lower precipitation amounts on low gradients is expected to be dominated by sheet flow rather than gullying, where the much larger precipitation amounts from Mena, AR predict channelization from these same slopes.
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When running SIBERIA using the current parameters at Clive for the unarmored version of the FCF, gully heads are generated because the storm runoff quickly exceeds the soil’s critical shear stress. The armoring substantially raises that threshold making it harder for gullies to form.
▪ O-5.c: (from DRC-2025-001739): REHM, an empirical model for estimating runoff and sediment yields in rangelands, differs structurally from SIBERIA, which uses physics-based, landform-specific calculations like advective channel formation and diffusive hillslope processes. Therefore, direct parameter mapping between the two does not appear to be suitable.
Please provide the method and justification used to address the disparity.
The RHEM simulations are designed to simulate a large rainfall-runoff plot experimental campaign to determine sediment yield. Rainfall-runoff experiments or plot monitoring is standard practice for estimating SIBERIA parameters when data from existing landforms are not available (Evans et al.
2000; Willgoose and Riley 1998; Willgoose and Hancock 2011). When data from experimental plots is not available, the use of “traditional” erosion models such as RHEM to estimate SIBERIA parameters is suggested, since:
The similarity between LEMs and physically-based erosion models is that the underlying physics is generally the same (although the details will depend on the LEM), so a
considerable amount of knowledge can be transferred from our work with traditional models (e.g. cover factors). (Willgoose and Hancock 2011) Corroborating discussion is also available in Al-Hamdan et al. (2012). RHEM has been used to provide results for how much soil a typical storm would move off 39 test slopes that match the FCF’s soil, cover, lengths, and 1–3% gradients (Figure 2). Then, four SIBERIA coefficients (b1, m1, n1, dZ) are adjusted until SIBERIA predicts the same soil-loss numbers on those slopes. That anchors SIBERIA to realistic hillslope erosion, yet SIBERIA still uses its own physics to grow channels across the full landform. Beyond 120 m (where no plot data exists), SIBERIA extrapolates using its own channel and diffusion equations, which is appropriate for evaluating
landform evolution over thousands of years.
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Figure 2 - Sediment yield predicted by RHEM for 15 different stochastic storm series applied to 39 experimental hillslope profiles with the same cover conditions. Results from the CLIGEN default random seed are plotted in black. Blue: slope 0.02; Green
▪ O-5.d: (from DRC-2025-001739): Previous submissions suggest a narrow interpretation of hillside diffusion being solely surface runoff driven. However, it is important to note that hillslope diffusion more broadly encompasses processes, notably soil creep. Soil creep involves gradual depth dependent
downslope movement, a characteristic not accounted for by RHEM. Please address this discrepancy and provide detail on the consideration of these factors.. SIBERIA represents soil creep through a linear diffusion term; RHEM provides only a rain-splash proxy. RHEM’s rain-splash component exhibits diffusive behavior at very small contributing areas, and the positive intercepts in the sediment-flux plots (Figure 2 and Figure 3) below 10m2 confirm this baseline signal. SIBERIA augments that baseline with a linear hillslope-diffusion term: 𝑞𝑞𝑠𝑠,𝐷𝐷=𝑑𝑑𝑑𝑑𝑑𝑑
where: dZ is the coefficient of diffusion — diffusivity per unit contour width (m1 y-1)
S is the local slope
Sensitivity tests covering dZ = 1 × 10-5 to 1 × 10-1 m1 y-1 show that maximum incision on the top slope of the armor-protected FCF remains within ±5 cm of the baseline until diffusivity exceeds roughly 1 × 10-3 m1 y-1. Above that threshold, both incision depth and average
annual sediment yield rise rapidly. Because the calibrated site-specific range (3.4 × 10-5 to
3.5 × 10-4 m1 y-1) lies well below this response threshold, creep-type diffusion is a secondary control relative to fluvial incision on the site’s 2–3% grades.
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Figure 3 - View of Figure 1 across smaller drainage areas; sediment yield projected by RHEM for 15
stochastic storm series on 39 experimental hillslope profiles with the same foliar and ground cover conditions. Results using the CLIGEN default random seed are plotted in black. Blue: slope 0.02; Green: slope 0.024; Orange: slope 0.03. Cover realization 305, units m3. ▪ O-5.e: (from DRC-2025-001739): Please provide rationale for the extremely low hillslope diffusivity
values selected. The adopted SIBERIA diffusive sediment flux (dZ) distribution is grounded in two lines of evidence.
First, it matches the calibrated range derived from the RHEM-SIBERIA curve fit. Second, it falls within published semi-arid rangeland values.
Sensitivity testing confirms that values of dZ below 1 × 10-3 m1 y-1 do not appreciably deepen incision into the armor-protected cover, whereas diffusivities ≥ 1 × 10-2 m1 y-1 more than double both sediment yield and maximum incision. Retaining a low central tendency while still sampling higher values in
uncertainty analyses is therefore both conservative and evidence based.
Appendix W: Surety
▪ W-1.a: (from DRC-2025-001739): The 2020 Federal Cell Facility Quantity Calculations and Assumptions do not include equipment hours.
Please revise to incorporate equipment hours where applicable.
In March 2021, EnergySolutions commissioned an independent evaluation by a facility decommissioning- and closure-experienced third-party entity to estimate the processes and activities associated with all premature closure activities for the Clive Disposal Facility (Geosyntec, 2021).
Decommissioning costs were developed under the assumption that select pieces of existing equipment
at the facility are operational and available for use in closure activities (Geosyntec, 2021, p. 5). The analysis included applicable rental costs for any necessary equipment that would be unavailable for
the required tasks. Furthermore, equipment costs were adjusted to include maintenance of equipment needed to dispose of the stored waste (shredder, train engine, compactor, CCS monitoring system)
Mr. Doug Hansen CD-2025-148 July 17, 2025
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and the cost of backup generator power for the shredder as a contingency if the on-site power station is unavailable (Geosyntec, 2021, p. 13).
Subsequent annual reviews after 2021 combine surety accounts for current site conditions and include annual inflation adjustments. EnergySolutions’ annual surety reviews conducted after this licensing action include evaluation of the premature closure of the FCF. The calculations and cost estimates included in the Director’s annual review and adjustment ensure that the amount remains appropriate to account for inflation, construction of new facilities, and other cost adjustments. Geosyntec developed effective unit rates from comprehensive costs for decontamination and decommissioning activities by combining the cost of labor required to perform each task (across broad worker classifications), time, maintenance, and acquisition costs of equipment needed (whether currently available or rented), raw material costs, material processing costs, employee per diem, subcontractor costs, mobilization, overhead, tools, and equipment. Unit rates were estimated by
dividing each comprehensive total cost by the appropriate physical dimension (e.g., mass, volume, length, area). An example of how equipment use is incorporated into the development of the unit rate for asphalt pad demolition is provided in Table 3. Table 3 – Example Development of a Unit Rate for Asphalt Pad Demolition

COST COMPONENT 2020 RATE
Example Project Labor $ 3,305.00
Example Project Equipment $ 350.00
Example Project Materials $ -
Example Project Per Diem $ 1,017.00
Example Project Subcontracting $ -
Example Project MTE $ 701.00
Total Example Project Cost $ 5,373.00
Example Project Volume (yd3) 428.83
Effective Example Project Unit Rate ($/yd3) $ 12.53

Unit Rate adjusted for 2021 Inflation (1.042) $ 13.06
Unit Rate adjusted for 2022 Inflation (1.07) $ 13.97
Unit Rate adjusted for 2023 Inflation (1.037) $ 14.49
Unit Rate adjusted for 2024 Inflation (1.025) $ 14.85
Unit Rate Referenced in EnergySolutions' Surety $ 14.85
Therefore, effective unit rates reflect comprehensive costs for decontamination and decommissioning activities, including labor, equipment time, equipment maintenance, acquisition costs of equipment
needed (whether currently available or rented), raw material costs, material processing costs, employee per diem, subcontractor costs, mobilization, overhead, tools, and equipment.

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▪ W-1.b: (from DRC-2025-001739): Line Item #31: DISPOSAL OF STORED FEDERAL WASTE is unclear on how the amount of Controlled Low Strength Material required to encapsulate the Cylinders has been determined because the application lacks clarity regarding the placement and encapsulation
construction methodology. Please provide further information to allow for verification of the calculation. EnergySolutions’ operators will use existing equipment to commence disposal of concentrated depleted uranium. The 5,408 drums of Savannah River Site (SRS) depleted uranium already in storage at the Clive Facility will be placed in the FCF within one year of license receipt (following construction of sufficient clay liner). As is illustrated in Engineering Drawings 2025 Fig 4D, 2025 Fig 7F, 2025 Fig 3C, 25001-C01, 25001-C02, 25001-L01, 25001-L02, and 25001-G01 (see FOLDER References), waste placement will be conducted in accordance with the specifications. Following acceptance and unloading, concentrated depleted uranium containers will be placed to minimize the
volume of void spaces between containers and to minimize entrapped air in the disposal lift. Quality control inspectors will visually inspect the placed waste for compliance with the specifications. After an acceptable quality control inspection, the lift will be backfilled by pouring CLSM over the waste
using standard concrete mixing and delivery equipment. The flowability of the CLSM will be controlled to ensure adequate filling of the voids. Quality control inspectors will test the CLSM against the specifications.

1. SITE OVERVIEW: Property outside Section 32 is governed by the Tooele County Conditional Use Permit #2700-87 (CUP). Reclamation costs are calculated in the Unrestricted Areas surety estimation.
Most of the Federal Cell area has been previously excavated for clay and fill borrow. The area has been covered through the 11e.(2) and LLRW sureties. Items such as the 2000 Evaporation Pond, power poles, revegetation, etc., remain covered under those sureties. This analysis and the corresponding surety account only for the elements described herein.
2. SITE RE-VEGETATION: Revegetation for the FCF parcel is covered within the LLRW Surety, Section 208. There has been no new construction of facilities, roads, or other activities within Section 32 that would increase the area requiring revegetation. Premature closure of the
FCF would decrease the revegetation area included in the surety.
3. CLOSURE FENCING AND INSPECTION ROADS: 2025 Fig 3C (see FOLDER References) identifies existing roads and fences and the roads and fencing changes required for
premature closure of the FCF. Closure roads and fencing changes around the adjacent LLRW and 11e.(2) cells are included in their respective sureties.
4. LINER PROTECTIVE COVER: There is no exposed FCF liner that requires a Liner
Protective Cover.
5. GRADE RESTORATION: 2025 Fig 4D (see FOLDER References) shows the two areas requiring restoration. The restoration fill quantities were calculated in the same manner as those for the LLRW and MW embankments. Table 4 summarizes the grade restoration quantities. These values are reflected in the FCF surety calculations.

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Table 4 - Grade Restoration Quantities
Area
(ft2)
Area
(yd2)
Average
Depth
(ft)
Volume
(yd3)
Area 1 267,548 29,728 5.5 54,501
Area 2 1,055,934 117,326 6.5 254,206
Totals 1,323,482 147,054 - 308,707

8. PREMATURE CLOSURE ANALYSIS: The design modification and construction for the
premature closure of the waste disposal embankments can be accomplished by following the current embankment and cover design principles. These principles would guide the redesign of each embankment as suggested in the following conceptual redesign plan:
a. Conduct an aerial survey of the embankment and develop current topographical data to be used as the base of the redesign.
b. Overlay on the aerial survey of the embankment the following areas: a. Limits of disposed waste, b. Extents of completed liner, and c. Additional areas of interest.
c. Determine the best areas for the placement of debris and soil waste generated (if any) from the decommissioning of the facilities.
d. Once step 3 is completed, redesign the embankments per the following criteria: a. Work within the criteria used for the modeling performed for the licensed embankment designs,
b. Side slopes cannot exceed 5:1, c. Top slopes should be 2.4% for the Federal Cell, d. Stormwater must freely drain off and away from the embankment, and e. Final contours (geometry) cannot concentrate stormwater flow that may lead to erosion of the cover
materials.
e. Design drainage ditches based on the approved closure ditch designs for each embankment. In general, the ditches slope from the northeast to the southwest, where they connect to the
southwest corner.
Once the aerial survey is completed and converted into an electronic file, a team of one engineer and one CAD designer (utilizing AutoCAD Civil3D, Land Desktop, or similar software) should be able to redesign, including reviews and revisions, the premature closure embankment designs within ten working weeks.
9. RESERVE CAPACITY ANALYSIS: The facilities and equipment used to manage and
dispose of DU are accounted for in the LLRW surety calculations. Therefore, the only reserve capacity is for DU in storage.
10. CLAY RESOURCE EVALUATION: Three work elements identified in the surety calculations require clay material. The calculated surety volumes for Radon Barrier, Evaporative Zone, and Top Surface Layer are 28,582 yd³, 2,258 yd³, and 2,258 yd³, respectively, for a total borrow volume of 33,098 yd³. Note that the current premature closure embankment designs do not require the construction of additional clay liner, since no waste will be placed within the side slopes of the premature closure cell.

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The proposed location for the clay borrow required for site closure is EnergySolutions’ property in the adjoining Section 31. No clay materials have been removed from the Section 31 property, which exceeds three-quarters of a square mile.
11. ROCK BORROW (COVER MATERIALS): In preparation for future final cover construction projects, EnergySolutions has maintained a contract with the United States BLM to purchase 200,000 yd³ of rock borrow material from the Grayback Hills Community Pit 24. The BLM has reserved a portion of the pit for EnergySolutions with a total reserve of approximately 800,000 yd³ of suitable material. During 2024, approximately 82,677 yd³ of material was removed from the designated area within BLM Community Pit 24, leaving a remaining reserve of at least 717,323 yd³.
The total amount of borrow for cover materials required to cover the premature FCF is approximately 112,448 yd³. The estimated total amount of rock borrow required for the Class A West, Mixed Waste, 11e.(2), and FCF embankments is 463,668 + 170,194 + 109,206 + 112,448 = 855,516 yd³. Accounting only for the unprocessed rock borrow stockpiled on Section
5, 855,516 – 82,677 = 772,839 yd³ of additional rock borrow would be required. The designated source of rock borrow material from Grayback Hills Community Pit 24 is not sufficient. However, additional areas of the pit are available for the purchase of materials, with more than 1 million cubic yards of borrow. Surety is provided to close the FCF if EnergySolutions cannot or will not after the first year of
operation. Dimensions of the prematurely closed cell and runoff ditches are summarized in Tables 5 and 6 (information illustrated on Engineering Drawings 2025 Fig-4D, 2025 Fig 7F, 2025 Fig 3C, 25001-C01, and 25001-C02 are located in FOLDER References). Table 5 – Premature Closure Dimensions – Waste and Fill
Cross Section Length (ft)
Elevation Change (ft) Slope (ft/ft)
Total Length (ft)
NE-SE 664.000 -0.00090 4263.95
NE-NW 544.125 -0.00178 4263.35
SE-SW 544.125 -0.00178 4262.98
NW-SW 664.000 -0.00090 4262.17
NE-SE 314.000 -0.00090 4298.32
NE-NW 194.125 -0.00178 4298.04
SE-SW 194.125 -0.00178 4297.98
NW-SW 314.000 -0.00090 4297.48
South Peak 4297.76 2.3295 4300.09
North Peak 4300.09 0.108056 4300.20
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Table 6 – Premature Closure Dimensions – Ditches
Ditch Length (ft)
Elevation
Change (ft) Slope (ft/ft)
Total
Length (ft)
NE-SE 704.000 -0.60 -0.000475718 4263.95
NE-NW 584.125 -0.95 -0.000483871 4263.35
SE-SW 584.125 -0.95 -0.000483871 4262.98
NW-SW 704.000 -0.60 -0.000475718 4262.17

Dimensions of the final cover for the prematurely closed cell are summarized in Table 7 (information see Engineering Drawings 2025 Fig-4D, 2025 Fig 7F, 2025 Fig 3C, 25001-C01, and 25001-C02 – see FOLDER References). Surety for premature closure is revised annually to reflect ongoing operations.
Table 7 – Premature Closure Cover Construction Volumes
Final Cover Layer
Area (ft2) Thickness (ft) Volume (yd3) Borrow (yd3) Material Classification
Radon Barrier 385,862 2.0 28,582 28,582 Clay
Frost Protection 411,224 1.5 22,846 22,846 BLM Rock Material
Filter Zone 464,349 1.0 17,198 35,841 BLM Rock Material
Side Rock 464,349 1.5 25,797 53,761 BLM Rock Material
Evaporation Zone 60,955 1.0 2,258 2,258 Clay
Top Surface Layer 60,955 1.0 2,258 2,258 Clay The amount of material that must be removed from borrow sources sufficient to complete premature
closure is reported in Table 8 (see Engineering Drawings 2025 Fig-4D, 2025 Fig 7F, 2025 Fig 3C,
25001-C01, and 25001-C02 see FOLDER References).

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Table 8 – Premature Closure Borrow Cover Volumes
Borrow Materials Volume
Clay 33,098 yd3
BLM Rock 112,448 yd3
Inspection Road
Length 2780 ft
Width 15 ft
Thickness 1 ft
Volume 1544 yd3
Fill
Waste Zone Volume 22,576 yd3
Cylinder Volumes 18,015 yd3
CLSM Volume 4,561 yd3
Clean Fill Volume 252,774 yd3
These volumes are applied to the 2024-escalated unit rates from the approved third-party estimate for
premature closure activities for the Clive Disposal Facility (see Table 9; Geosyntec, 2021). Subtotal
costs for each premature closure activity are summarized in Table 10.
Table 9 – Unit Rates for Premature Closure
Unit Rate Description
$300 / drum Overpack Damaged Drums (~10% of SRS Drums in Storage)
$35/ sack Supersack to house damaged drums in storage
3 FTE Labor to Overpack and bag damaged drums
0.33 hours/pallet Time to overpack and bag drums
1,352 man-hours Total Time required to overpack and bag drums
$30/man-hour Labor rate to Overpack and Bag
1 hour / trip Transport time from Storage to FCF
10 pallets/trip Amount of Pallets moved per Trip from Storage to FCF
$40/FTE Load, Transport, and Offload costs per manhour
$68.58 Unit cost for CLSM (material, labor to deliver and pump into
FCF) 2,000 yd3 Volume of CLSM necessary for premature closure

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Table 10 – Total Premature Closure Costs
Cost Description
$ 162,300.00 Total Cost to Overpack damaged drums
$ 40,560.00 Total Labor to Overpack and Bag ($30/man-hour x 1,352 man-hours)
$ 47,320.00 Cost to pack damaged drums in supersacks
$ 43,264.00 Cost to transport and offload pallets and sacks into the FCF
$ 137,160.00 Cost of CLSM for premature closure
$ 430,604.00 Total Premature Closure Cost
Surety for premature closure is revised annually to reflect ongoing operations.

▪ W-1.c: (from DRC-2025-001739): Line Item #211: SETTLEMENT MONITORING indicates 4
monuments are anticipated to close the cell. Please justify the limited number of settlement monuments included in post closure. In accordance with FCF construction requirements, a temporary cover is placed to specification over the waste, and settlement monuments are placed on a 140-to-150-foot grid over the top slope of the
embankment. The temporary cover is a one-foot-thick layer of native soil that must be monitored for settlement prior to final cover construction. The analysis for this item includes the cost of excavation and placement of the required volume of native soil (and overburden), along with the purchase and
placement of settlement monuments. The item also includes costs of monument surveys and engineering reviews for the required one year of settlement monitoring.
At volumes projected for the first year of operation, the premature FCF embankments require a large amount of fill material (beyond the volume of waste generated by site closure) to meet design grades. Based on an actual count by EnergySolutions, the number of monuments needed is four.

▪ W-1.d: (from DRC-2025-001739): Line Item #204: LINER CONSTRUCTION contains a 0.11 factor for excavating overburden, but the value of this indication is unclear. Additionally, it is unclear why the excavation volume for the liner matches exactly the volume of the liner being placed. This implies that the excavation costs begin from the Top of Liner and not from the Top of Native Grade. Please provide clarity on the calculation for these two items. In their 2021 independent evaluation of premature closure activities for the Clive Disposal Facilities, Geosyntec recommended the use of an overburden factor of 11% to account for the volume of mined clay lost during transport or that does not meet the FCF CQA/QC Manual specifications for clay liner and radon barrier construction. Geosyntec’s methodology is applied to FCF premature closure surety estimates.
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▪ W-1.e: (from DRC-2025-001739): Line Item 207: COVER CONSTRUCTION is unclear on which materials are being used in the calculation for volume.
Please revise the calculations to indicate consistent language throughout the application. The FCF will be progressively closed once depleted uranium has been placed below grade and infilled with CLSM. Interim fill will be placed and compacted in accordance with the specifications proposed in the FCF CQA/QC Manual. An interim cover system will be applied and allowed to settle, consolidate, and stabilize for at least one year. Once the interim cover is demonstrated to be stable
within acceptable limits, settlement monitors will be placed, and the final cover system constructed. The FCF’s cover design is engineered to reduce infiltration, prevent erosion, and protect from radionuclide exposure by limiting water flow to monitoring wells, increasing evapotranspiration from the top slope, and promoting runoff via steeply sloped sides. The general design of the FCF is a hipped cover with relatively steeper sloping sides near the edges. The upper part, known as the top
slope, has a moderate 2.4% grade, while the side slope is markedly steeper at 20%. The overall length of the FCF is 1,920 feet, and the overall width is 1,226.5 feet. As illustrated on Engineering Drawing 14004-C05, the layers used in the FCF top slope (constructed to 2.4%) cover consist of the following, from top to bottom:
• Surface layer: This layer is 12 inches thick and composed of native vegetated finer-grained, low-permeability silty clay and clay silt. The functions of this layer are to control runoff, minimize erosion, and maximize water loss from evapotranspiration. This layer of silty clay provides storage for water accumulating from precipitation events, enhances losses due to evaporation, and provides a rooting zone for plants that further decrease the water available for downward movement.
• Evaporative Zone layer: This layer is 12 inches thick and composed of finer-grained, low-permeability silty clay and clay silt material. The purpose of this layer is to provide additional storage for precipitation and additional depth for the plant rooting zone to maximize
evapotranspiration.
• Frost Protection Layer: This layer is 18 inches thick. The purpose of this layer is to protect layers
below from freeze/thaw cycles, wetting/drying cycles, and to inhibit plant, animal, or human intrusion. The Frost Protection Layer (also referred to as Type A Rip Rap) is a coarse, angular rock material used primarily for erosion control, slope stabilization, and scour protection. Its
material gradations, as determined by ASTM C-136 sieve analysis, are characterized by the following particle size distribution:
o D100: Maximum size ≤ 16 inches (100% of material passes a 16-inch sieve).
o D90: ≤ 12 inches (90% of material passes a 12-inch sieve).
o D50: ≥ 4.5 inches (50% of material is larger than a 4.5-inch sieve).
o D10: ≥ 2 inches (10% of material is larger than a 2-inch sieve).
o D5: ≥ No. 200 sieve (5% of material is larger than the No. 200 sieve, approximately 0.075 mm). This gradation ensures a well-graded mix of stone sizes, providing interlocking properties for stability while allowing sufficient voids for hydraulic permeability. Type A Rip Rap is typically composed of durable, hard, and non-friable rock such as granite, limestone, or other locally available stone meeting project-specific durability requirements.

Mr. Doug Hansen CD-2025-148 July 17, 2025
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• Upper Radon Barrier: This layer consists of 12 inches of compacted clay with low hydraulic conductivity and has the lowest conductivity of any layer in the cover system. This is a barrier layer that reduces the downward movement of water to the waste and the upward movement of gas out of the disposal cell. The as-built saturated hydraulic conductivity of this layer is 5x10⁻⁸
cm/s.
• Lower Radon Barrier: This layer consists of 12 inches of compacted clay with low hydraulic conductivity. This is a barrier layer placed directly above waste that reduces the downward movement of water. The as-built saturated hydraulic conductivity of this layer is 1x10⁻⁶ cm/s.

The layers used in the FCF side slope cover (constructed to 20%) consist of the following, from top to bottom:
• Rip Rap Cobbles: Approximately 18 inches of Type-A rip rap is placed on the side slopes above the Type-A filter zone. The Type-A rip rap ranges in size from 2 to 16 inches (equivalent to coarse gravel to boulders) with a nominal diameter of 12 inches (with 100% passing a 16-inch
screen and not more than 15% passing a 4½-inch screen).
• Filter Zone: The Type B filter in the side slope is 12 inches thick. The Type B filter material in
the side slope consists of granular material with a particle size ranging from 0.3125 to 3.0 inches in diameter (coarse sand to fine cobble) and a minimum hydraulic conductivity of 42 cm/sec. To promote drainage and avoid ponding, the filter zone is constructed with a specification that its
permeability exceeds 3.5 cm/sec.
• Frost Protection Layer (Sacrificial Soil): This layer is 18 inches thick, and the material ranges in size from 16 inches to clay-sized particles. The purpose of this layer is to protect layers below from freeze/thaw cycles, wetting/drying cycles, and to inhibit plant, animal, or human intrusion..
• Upper Radon Barrier: This layer consists of 12 inches of compacted clay with low hydraulic conductivity. This layer has the lowest conductivity of any layer in the cover system. It is a barrier layer that reduces the downward movement of water to waste and the upward movement
of gas out of the disposal cell. The as-built saturated hydraulic conductivity of this layer is 5x10⁻⁸ cm/s.
• Lower Radon Barrier: This layer consists of 12 inches of compacted clay with low hydraulic conductivity. This is a barrier layer placed directly above waste that reduces the downward movement of water. The as-built saturated hydraulic conductivity of this layer is 1x10⁻⁶ cm/s.
Dimensions of the final cover for the prematurely closed cell are summarized in Table 11 and illustrated in Engineering Drawings 2025 Fig 3C, 2025 Fig 4D, and 2025 Fig 7F (see FOLDER
References).
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Table 11 – Premature Closure Cover Construction Volumes
Final Cover Layer
Area (ft2) Thickness (ft) Volume (yd3) Borrow (yd3) Material Classification
Radon Barrier 385,862 2.0 28,582 28,582 Clay
Frost Protection 411,224 1.5 22,846 22,846 BLM Rock Material
Filter Zone 464,349 1.0 17,198 35,841 BLM Rock Material
Side Rock 464,349 1.5 25,797 53,761 BLM Rock Material
Evaporation Zone 60,955 1.0 2,258 2,258 Clay
Top Surface Layer 60,955 1.0 2,258 2,258 Clay
The amount of material that must be removed from borrow sources sufficient to complete premature
closure is reported in Table 12.

Table 12 – Premature Closure Borrow Cover Volumes
Borrow Materials Volume
Clay 33,098 yd3
BLM Rock 112,448 yd3
Inspection Road
Length 2780 ft
Width 15 ft
Thickness 1 ft
Volume 1544 yd3
Fill
Waste Zone Volume 22,576 yd3
Cylinder Volumes 18,015 yd3
CLSM Volume 4,561 yd3
Clean Fill Volume 252,774 yd3
These volumes are applied to the 2024-escalated unit rates from the approved third-party estimate for
premature closure activities for the Clive Disposal Facility (see Table 8; Geosyntec, 2021). Subtotal costs
for each premature closure activity are summarized in Table 10.

Mr. Doug Hansen CD-2025-148 July 17, 2025
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▪ References:
Al-Hamdan, O.Z., et al., 2012. Concentrated Flow Erodibility for Physically Based Erosion Models: Temporal Variability in Disturbed and Undisturbed Rangelands, Water Resources Research 48 (W07504) 1–15 doi: 10.1029/2011WR011464 Evans, K.G., et al., 2000. Post-Mining Landform Evolution Modelling: 1. Derivation of Sediment Transport Model and Rainfall-Runoff Model Parameters, Earth Surface Processes and Landforms 25
(2000) 743–763 Geosyntec Consultants. 2020 Annual Surety Review Narrative: Clive Combined Surety - EnergySolutions Clive Facility Clive, Utah (Project Number SLC1014). Report from Geosyntec Consultants to EnergySolutions. Salt Lake City. March 2021. SWCA. “Attachment A. Evapotranspirative Cover Revegetation and Maintenance Plan for the Clive Facility. Report from SWCA to EnergySolutions, 2015. Temme, A.J.A.M., et al., 2009. Can Uncertain Landscape Evolution Models Discriminate Between Landscape Responses to Stable and Changing Future Climate? A Millennial-Scale Test, Global and
Planetary Change 69 (2009) 48–58 Tollefson, Jennifer E. “Sphaeralcea coccinea.” Fire Effects Information System [online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory, 2006. Available: https://www.fs.usda.gov/database/feis/plants/forb/sphcoc/all.html. Accessed June 24, 2025.
Willgoose, G., 2005. User Manual for SIBERIA (Version 8.30), Telluric Research, Scone Australia Willgoose, G., and S.R. Riley, 1998. Application of a Catchment Evolution Model to the Prediction of Long-Term Erosion on the Spoil Heap at Ranger Uranium Mine Initial Analysis, Supervising Scientist Report 132, Supervising Scientist, Environment Australia, Canberra Australia, 1998 Willgoose, G.R., and G.R. Hancock, 2011. Applications of Long-Term Erosion and Landscape Evolution Models. In Handbook of Erosion Modelling, 1st edition, edited by R.P.C. Morgan and M.A. Nearing, pp. 339–359, Blackwell Publishing Ltd., Hoboken NJ

Mr. Doug Hansen CD-2025-148 July 17, 2025
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If you have further questions regarding these responses to the director’s request of DRC-2025-001739, please contact me at [phone]. Sincerely,

Vern C. Rogers
Director, Regulatory Affairs
Electronic enclosures
I certify under penalty of law that this document and all attachments were prepared under my direction or supervision in accordance with a system designed to assure that qualified personnel properly gather and evaluate the information submitted. Based on my inquiry of the person or persons who manage the system, or those persons directly responsible for gathering the information, the information submitted is, to the best of my knowledge and belief, true, accurate, and complete. I am aware that there are significant penalties for submitting false information, including the possibility of fine and imprisonment for knowing violations.

Vern C.
Rogers
Digitally signed by Vern C. Rogers DN: cn=Vern C. Rogers, o=EnergySolutions, ou=Waste Management Division, email=[e-mail], c=US Date: 2025.07.17 10:10:36 -06'00'