DRC-2025-000497

215 South State Street, Suite 500 Salt Lake City, Utah 84111 PH 801.618.0483 www.geosyntec.com

17 June 2024
DRAFT
Mr. Vern Rogers
EnergySolutions Director of Regulatory Affairs 299 South Main Street, Suite 1700 Salt Lake City, UT 84111 Subject: Radioactive Material License UT2300249
EPA ID Number UTD982598898
Class A West Embankment
Bulk Waste and CLSM Side Slope Settlement Evaluation
Dear Mr. Rogers,
Geosyntec Consultants (Geosyntec) has prepared this memorandum based on discussions with
EnergySolutions regarding the Utah Department of Environmental Quality (UDEQ) Division of
Waste Management and Radiation Control’s (DWMRC) direction in correspondence to
EnergySolutions dated 9 May 2024 to demonstrate and document that differential settlement
resulting from the placement of bulk waste abutting CLSM-encased waste is not anticipated to
cause damage to the future radon barrier and final cover system on the side slope of the Class A
West Embankment (CAW) at the EnergySolutions Clive Facility (Facility).
BACKGROUND
Waste placed in the area of the CAW relevant to this evaluation generally consists of two types,
including: (1) CLSM Bulk Waste Disposal consisting of compressible and incompressible waste
encased in CLSM lifts stacked with a maximum outer slope inclination of 3 Horizontal to 1
Vertical in “CLSM Pyramids;” and (2) Bulk Waste Disposal consisting of compressible and
incompressible waste disposed in compacted soil lifts at specific volume ratios of waste to soil.
DWMRC’s 9 May 2024 correspondence directs EnergySolutions to evaluate bulk waste abutting
the 8-foot thick CLSM lift under construction (lift AWB18240321FF) adjacent to completed
CLSM lift AWB18210225 in the northwest area of the CAW for the potential to cause differential
settlement that could adversely impact the future radon barrier and final cover system. A figure
with a plan view and representative cross-section of lifts AWB18240321FF and AWB18210225
with lift and waste thicknesses is presented along with a summary of waste disposal specifications
in correspondence from EnergySolutions to DWMRC dated 4 April 2024 (Attachment A). The
thickness of bulk waste abutting and overlying lifts AWB18240321FF and AWB18210225 is
Mr. Vern Rogers 17 June 2024
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similar to the configuration of previously-constructed CLSM lifts AWL01 and AWL02 in the
southwest area of the CAW which have had bulk waste placed to design grades (Figure 1).
EnergySolutions performs survey of settlement monuments on the areas of the CAW where waste
has been placed to design grades and temporary cover or the final cover system has been installed
as well as annual survey of the Facility using LiDAR technology to produce Facility topographic
maps.
The CAW final cover system consists of a 2-foot-thick clay radon barrier, two filter zones, a
protective soil layer, and a rip-rap cover. The main barrier component of the final cover system is
the low-permeability clay radon barrier which inhibits the vertical migration of water and radon
gas through the final cover system. If the clay radon barrier is subjected to excessive distortion
due to differential settlement of the waste mass beneath the final cover system, the material is
susceptible to cracking which would cause an unacceptable increase in the permeability of the
clay radon barrier to fluids and gases.
The purpose of this memorandum is to propose an approach for review and approval by DWMRC
to demonstrate and document that settlement of the CAW side slope is not expected to adversely
impact the future radon barrier and final cover system.
SETTLEMENT EVALUATION APPROACH
Geosyntec’s proposed approach for evaluating differential settlement is as follows:
• Evaluate actual observed settlement and differential settlement over previously-
constructed AWL01 and AWL02 CLSM lift areas where bulk waste placement over and
around the CLSM lifts on the CAW side slope and top deck has been completed
approximately 5 years ago. Facility topographic maps produced from annual LiDAR
survey of the Facility will be used to develop settlement isopach figures to compare the
maximum observed top deck settlement and differential settlement with the expected top
deck settlement from the settlement evaluation from the 1 June 2000 AGRA report titled
“Evaluation of Settlement of Compressible Debris Lifts” (Attachment B).
• Evaluate settlement and differential settlement of the CAW side slope based on the bulk
waste and CLSM lift geometry of AWB18210225 and AWB18240321FF using the
settlement evaluation approach described in the 1 June 2000 AGRA report titled
“Evaluation of Settlement of Compressible Debris Lifts” (Attachment B). Differential
settlement from the evaluation will be compared against differential settlement and
distortion limits established to prevent damage to the future radon barrier and final cover
system in the 4 October 2000 AMEC letter titled “Allowable Differential Settlement and
Distortion of Liner and Cover Materials” (Attachment C). Calculated settlement and
differential settlement will also be compared against actual observed settlement and
Mr. Vern Rogers 17 June 2024
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differential settlement over previously-constructed CLSM lifts AWL01 and AWL02
using the settlement isopach figures discussed above.
• Provide recommendations for modifications to waste lift placement methods and
settlement monitoring based on the results of the evaluation, as appropriate.
The results of our evaluation will be documented in a letter report with supporting figures and
attachments for DWMRC review. The letter report will be finalized after addressing DWMRC’s
comments. If you have any questions regarding this memorandum, please feel free to contact the
undersigned at [phone].
Sincerely,
Geosyntec Consultants

Royston Chan Brent C. Robinson, P.E. Professional Senior Principal Engineer
Attachments:
Figure 1 – Class A West Embankment Area of Interest
Attachment A – EnergySolutions Correspondence with DWRC
Attachment B – AGRA Evaluation of Settlement of Compressible Debris Lifts
Attachment C – AMEC Allowable Differential Settlement and Distortion of Liner and
Cover Materials