DSHW-2024-008455

[Date]
Mike Courouleau
Westinghouse Western Zirconium
10,000 West 900 South
Ogden, UT 84404-9760RE:Western Zirconium Fall 2023 Plant Area Groundwater Monitoring Report Response to CommentsUTD092024934
Dear Mr. Courouleau:
The Division of Waste Management and Radiation Control (Division) has reviewedthe Fall 2023 Plant Area Groundwater Monitoring Report(Report) Response to Comments (RTC), dated September
20, 2024, for the Westinghouse Western Zirconium (Western Zirconium) facility located in Weber County, Utah.
The RTCadequately addresses Comments #3and #4. However, based on the response, clarification of Comments #1 and #2are provided below.
Comment #1:
Comment #1 states: “Section 7.3, Background 95% UCL-BG-1 refers to the derivation of background threshold values (BTVs) for BG-1 based on 95 percent upper confidence limits (95UCLs).
However, the BTVs as provided in Appendix E are upper tolerance limits (UTLs). Please revise the report to correctly refer to the BTVs as UTLs and not UCLs.”
Western Zirconium’s response, “Section 7.3 correctly states that the background UCL is provided on Tables 4-6. The ProUCL output in Appendix D inadvertently included calculations of
background UTL. The ProUCL output for background UCLs will be updated into Appendix D to replace the background UTL output”, focuses on the ProUCL output included in Appendix D.
The issue is that the soil BTVs should be based on 95% UTLs rather than UCLs. As outlined in Utah Administrative Code R315-101-5(f) and Section 3.3.3.1 of the Division’s Technical Guide
to Risk Assessments (TGRA), BTVs should be based on 95UTLs. The only exception is on a case-by-case basis when the estimated 95UTL is greater than the maximum detected concentration.
In lieu of collection of additional data to resolve the elevated UTL issue, the maximum detected concentration should be used as the BTV. The Report, including all text and tables,should
be revised to reference the 95UTLs as BTVs. The ProUCL outputs arecontained within Appendix D (not Appendix E).
Comment #2:
Comment #2 from the February 20, 2024 comments on the Fall 2023 Plant Area Groundwater Monitoring Report suggested a conservative approach of marking an exceedance of the lower of the
screening levels to allow early detection of low levels of contamination. Comparison to the higher of the screening levels may not allow for early detection of low levels of contamination.
The narrative in the fourth paragraph of Section 4.0 in the Report (revised May 2024) continues to state, “results that exceeded the higher of the MCL RSL or background concentration
appear in bold font.”
Western Zirconium’s response to Comment #2 in the September 20, 2024, RTCstated that the tables were correctly updated however the subject sentence in Section 4.0 will be revised to
“Results exceeding the higher of the MCL/RSL are shaded; results exceeding the background concentration are bolded; and results exceeding the RBSL are marked with an asterisk.”
Bolding the results exceeding background concentrations and marking results exceeding the risk-based screening level (RBSL) with asterisk are acceptable and will help identify exceedances
of those two screening levels. The Division has suggested a conservative approach to marking exceedances. Shading the results that exceed the lower,rather than the higher,of the maximum
contaminant level/Regional Screening Level (MCL/RSL) would follow this conservative approach. While this approach has not been practiced in this Report, please ensure all future reports
address this issue.
Please provide a response to comments and a revised Report within 45 days of the date of this letter.
If you have any questions, please call Karen Wallner at [phone].
Sincerely,
Paige Walton,Manager Corrective Action Section
Division of Waste Management and Radiation Control
PW/KHW/[???]
c:Scott Braeden, Environmental Director, Weber-Morgan Health Department
Brian Cowen, Health Officer, Weber-Morgan Health Department
Michela Harris, Deputy Director, Weber-Morgan Health Department
Mike Courouleau, Westinghouse Western Zirconium (email and hardcopy)[[e-mail]]
Lawrence Cannon, AECOM (email)[[e-mail]]
Sean Moody, UDEQ, DWMRC (email)