DSHW-2024-004345

[Date]
Eric Dodson
Westinghouse Western Zirconium
10,000 West 900 South
Ogden, UT 84404-9760RE:Western Zirconium Remediation Work Plan – AOC 15 and SWMU 18UTD092024934
Dear Mr. Dodson:
The Division of Waste Management and Radiation Control has completed its review of the Western Zirconium Remediation Work Plan – AOC 15 and SWMU 18 (Work Plan), dated December 2023,
for the Western Zirconium Facility located in Weber County. The Work Plan proposes revisions to the original work plan that was approved by the Division in December 2014 and updated
in January 2019.
This Work Plan proposes to excavate soil within AOC 15, install a HDPE geomembrane and stormwater pipe, and place engineered fill material to improve drainage collection of surface water.
The objective of this project is to limit the risk of exposure to site contaminants within AOC 15 and SWMU 18.
Based on the review, the Division is providing the following comments:
Section 2.3, Confirmation Sampling. The text indicates that confirmation samples will only be collected for the two risk drivers (radium-226 and zirconium). However, Table 1 of Appendix
A presents the Area of Concern (AOC) 15 risk summary which shows the human health drivers for soil corrective action include arsenic, hexachlorobenzene, lead-210, radium-226, radium-228,
thorium-228, thorium-230, and zirconium. The footnote indicates that radium-226 and zirconium each contribute around 30% of the total risk. While based on investigation data radium-226
and zirconium may contribute 50% or more to total risk, Utah Administrative Code (UAC) R315-101-5 requires evaluation of cumulative risk. Cumulative risk includes all potential contributors
to risk. Further, Section 4 of the Division’s Technical Guide for Risk Assessments (August 2, 2005 (utah.gov)) clearly stats that reduction of contaminants of potential concern (COPCs)
may not be conducted through a simple comparison to a screening level or based on frequency of detection. The confirmation sampling and subsequent confirmation risk assessment must
include all the contaminants listed in Table 1 of Appendix A to include arsenic, hexachlorobenzene, lead-210, radium-226, radium-228, thorium-228, thorium-230, and zirconium. Also,
revise Table 2, AOC Cleanup Levels, to include appropriate screening levels for all COPCs.
Section 2.3, Confirmation Sampling. This section only indicates that confirmation will be compared to cleanup levels and regional screening levels. Please clarify to indicate that
a post remedial risk assessment will be conducted to confirm residual levels of contamination are protective of all identified receptors.
Section 2.3, Confirmation Sampling. This section does not address ecological risk. The CMS in Appendix A indicates that ecological risks were within acceptable risk levels. However,
a demonstration that post corrective measures result in concentration protective of ecological receptors must also be demonstrated, in accordance with UAC R315-101. In lieu of conducting
a final ecological risk assessment, the Work Plan should clearly discuss that a goal of the remedial actions is to remove available habitat and that an ecological waiver is requested.
Section 2.3, Confirmation Sampling. The Work Plan states that confirmation samples will be collected from locations outlined in the Corrective Measures Study (CMS) and include five
locations. As the above comments discuss the evaluation of risk, the number of sample locations must be adequate to provide the required data for derivation of the exposure point concentration
(EPC) for the risk assessment analysis. Please propose a minimum number of eight sample locations.
Sections 2.3 and 2.4, Confirmation Sampling and Analytes and Analytical Methods. The Work Plan references risk-based clean up levels that were developed for the chemicals. Theclean
up levels were developed in 2012 and will need to be revised based on current toxicity information.
Section 2.4, Analytes and Analytical Methods. Revise Table 2 to include the laboratory methods for all COPCs. In addition, please include the method detection limits (MDLs) for each
COPC demonstrating the levels are below the cleanup levels. Note that hexachlorobenzene is best analyzed using Method 8270 for semi-volatile organics, therefore, trip blanks are not
required.
Section 2.5, Results. The Work Plan states that if concentrations exceed the lowest cleanup levels, further assessment will be conducted when the facility is decommissioned. In accordance
with UAC R315-101, use of engineering controls, such as the HPDE liner and clean fill, may only be used if risks are within the acceptable risk range. The confirmation data must be
evaluated and a risk assessment conducted to demonstrate that the residual contamination, prior to implementing the engineering controls, is protective of the on-site and construction
worker. If results are within the acceptable limits (equal to below 1E-04 for cancer risk and equal to or below 1 for noncancer), then any excess risk may be assessed at decommissioning.

Further, the Work Plan does not discuss controls that will be used to ensure the corrective actions will be maintained to ensure protection of human health and ecological risk. For
example, discuss inspection, periodic vegetation removal, etc.
Section 2.8, Reporting. Please include the analytical data package in the Corrective Measures Implementation (CMI) Report in addition to the summary of the excavation grading, pipe
installation, results of confirmation sampling, as-built documentation, photographs, and field notes.
General. In order to ensure protection of birds protected by the Migratory Bird Treaty Act, corrective measures should occur outside prior to nesting and before fledge (spring to early
summer).
As noted in the CMS for Solid Waste Management Unit (SWMU) 18, risks to soil were not evaluated due to the presence of surface water. It is noted that contamination of surface water
was noted. As part of the corrective measures for SWMU 18, surface water is to be mitigated using measures to prevent or minimize the daylighting of groundwater. As both the surface
water and groundwater have associated contamination, it is reasonable to assume that the soil that has come into contact with water is likely contaminated. Soil data are needed to ensure
that risk to exposure to soil post corrective measures is within acceptable levels and protective of both human health and the environment.
Please provide a response to comments and a revised Work Plan to address these comments within 45 days of the date of this letter.
If you have any questions, please call Karen Wallner at [phone].
Sincerely,
Douglas J. Hansen,Director
Division of Waste Management and Radiation Control
DJH/[???/[???]
c:Scott Braeden, Environmental Director, Weber County Health Department
Brian Cowen, Health Officer, Weber County Health Department
Michela Harris, Deputy Director, Weber County Health Department
Kent Bradford, Westinghouse Western Zirconium [email][[e-mail]]
Lawrence Cannon, AECOM [email]
[[e-mail]]