ML24275A086
| ML24275A086 | |
| Person / Time | |
|---|---|
| Site: | WM-00073 |
| Issue date: | 10/07/2024 |
| From: | Hayes K NRC/NMSS/DDUWP/URMDB |
| To: | Frazier B US Dept of Energy, Office of Legacy Management |
| Shared Package | |
| ML24275A070 | List: |
| References | |
| Download: ML24275A086 (1) | |
Text
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Bill Frazier, P.E., Site Manager U.S. Department of Energy Office of Legacy Management 2597 Legacy Way Grand Junction, CO 81503
SUBJECT:
UNITED STATES NUCLEAR REGULATORY COMMISSIONS STAFF REVIEW OF THE FEBRUARY 2022, DRAFT TUBA CITY, ARIZONA, DISPOSAL SITE, GROUNDWATER REMEDY PERFORMANCE UPDATE 2019-2021
Dear Mr. Frazier:
The U.S. Nuclear Regulatory Commission (NRC) staff is writing in response to the U.S.
Department of Energy, Office of Legacy Management (DOE-LM) document entitled, Draft Tuba City, Arizona, Disposal Site, Groundwater Remedy Performance Update 2019 Through 2021, dated February 2022 (Received April 20, 2023; Agencywide Documents Access and Management System [ADAMS] Package Accession No. ML23110A544). The following comments are provided:
1.
Table 5, Extraction Volume and Contaminant Mass Removed During Interim Active Treatment 2014-2021, lists the total pounds of nitrate, sulfate, and uranium mass removed during the active pumping conducted during 2019, 2020, and 2021. The submittal indicates that water quality samples were collected monthly from the extraction wells in 2019 during 99 days of active pumping and that no water quality samples were collected during the 2020 pumping event. The submittal does not specify what extraction well sampling was conducted during the 2021 pumping event. Please provide the extraction well sample laboratory analytical data collected during the 2019-2021 pumping events and any specifics regarding sample locations, procedures, and use of the analytical data to calculate the dissolved mass captured by the extraction system.
2.
In Section 2.3, Plume Geometry and Concentrations, the submittal lists several new wells added to the groundwater sampling events starting in 2019, including several 1400-series wells (1400 through 1424). No well construction information for these wells was provided in the submittal. I was also unable to access geologic logs or pertinent well construction information for these wells via the DOE-LM GEMS website. Please provide top of casing/surface elevations, top and bottom of screen interval elevations, total depth/base of borehole elevations, and other pertinent lithologic and well construction data for the wells added to the sampling program in 2019. Water level depth and October 7, 2024
B. Frazier elevation data from the 2019 to 2021 evaluation period for all gauged wells, including the 1400-series wells, is also requested.
3.
In Section 2.3.1, Uranium, the submittal indicates that wells 1408 and 1409, constructed on the lower terrace, upgradient from the sentinel wells and added to the sampling events in 2019, were below the standard for uranium while downgradient wells 0691 and 1003 exceeded the uranium threshold. Given the layout of the monitoring well locations, it appears likely that the uranium present in the downgradient wells is due to some type of preferential flow path(s) which were not intersected by the screened intervals of the 1408 and 1409 upgradient wells. NRC anticipates that DOE-LM will address these unresolved mechanisms controlling contaminant migration processes at the site in the Groundwater Compliance Action Plan (GCAP) Work Plan formulation which is in progress.
4.
In Section 2.3.2, Nitrate, the submittal indicates that newly sampled wells 1405 and 1406 (located near the historical center of the interpolated nitrate plume) were below the nitrate groundwater standard. As mentioned in Comment 2., construction information for the 1400-series wells is requested.
These analytical data points resulted in an apparent hole in the nitrate plume footprints shown in Figure 10. This plume geometry, with highly contaminated monitoring wells to north, west, and east of the 1405 and 1406 wells, lends additional credence to the assertion that contaminants are migrating along discrete preferential flow paths. As mentioned in Comment 3, evaluation and understanding of the contaminant migration processes are of critical importance to a successful groundwater remedy at the site. NRC recommends a thorough evaluation of potential lithologic, bedding plane, and fracture controls on groundwater flow to include review of geologic logs, geologic/hydrogeologic cross sections, aquifer testing, remedial system operations, water level elevation inconsistencies, geophysical data (Nuclear Magnetic Resonance, etc.), and potential field data gaps, as the GCAP Work Plan preparation continues.
5.
The plume maps presented in the submittal do not allow for the evaluation of contaminant concentrations between wells of different screened intervals and depths. The newly sampled 1400-series wells have no historical analytical data for comparison. Please provide the laboratory analytical data and any field parameter-related/purging data sheets for all the wells sampled during the review period.
B. Frazier If you have any questions concerning the NRC review of the report, please contact me at 301-415-0549 or by email at Kevin.Hayes@nrc.gov.
Sincerely, Kevin R. Hayes, P.G., CPG, Hydrogeologist Uranium Recovery and Materials Decommissioning Branch Division of Decommissioning, Uranium Recovery, and Waste Programs Office of Nuclear Material Safety and Safeguards Docket Numbers: WM-00073 cc: Tuba City, AZ ListServ List Signed by Hayes, Kevin on 10/07/24
ML24275A070; Ltr ML24275A086 OFFICE NMSS/DUWP/URMDB NMSS/DUWP/URMDB NAME RVonTill KHayes DATE Oct 7, 2024 Oct 7, 2024