ML24358A017
| ML24358A017 | |
| Person / Time | |
|---|---|
| Site: | WM-00073 |
| Issue date: | 01/07/2025 |
| From: | Hayes K NRC/NMSS/DDUWP/URMDB |
| To: | Frazier B US Dept of Energy, Office of Legacy Management |
| References | |
| Download: ML24358A017 (1) | |
Text
Bill Frazier, P.E., LM Site Manager U.S. Department of Energy Office of Legacy Management 2597 Legacy Way Grand Junction, CO 81503
SUBJECT:
U.S. NUCLEAR REGULATORY COMMISSION STAFF REVIEW OF THE JULY 2024, DRAFT TUBA CITY, ARIZONA, DISPOSAL SITE, GROUNDWATER REMEDY PERFORMANCE UPDATE 2023
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 2023, dated July 2024 (Received November 13, 2024; Agencywide Documents Access and Management System [ADAMS] Package Accession No. ML24319A122). The following comments are provided:
1.
Table 6, Extraction Volume and Contaminant Mass Removed During Interim Active Treatment, 2014-2023, lists the total pounds of nitrate, sulfate, and uranium mass removed during the active pumping during 2023 by eight extraction wells (Wells 1101 through 1103, 1105, 1108, 1110, 1120, and 1121 per Table 7). The text on page 16 of the submittal indicates that water quality samples collected in August 2023 were used to estimate the mass removal volumes for each of the listed contaminants. Were these analytical results, which were not provided in the submittal, the result of samples collected at each individual extraction wellhead during pumping or were one or more blended samples of the influent groundwater from the extraction wells collected from the piping downstream of the wells prior to discharge to the evaporation pond? If analytical results are available from each extraction wellhead, are the concentrations exhibited by each extraction well representative of the dissolved plume concentrations shown in the vicinity of each extraction well on Figures 7, 8, and 9? NRC would appreciate additional details on the sampling conducted, including the analytical results from the laboratory and the addition of identification labels to the extraction wells shown on Figure 10.
2.
Section 2.2, Water Table Elevations and Estimated Extent of 2019 Capture Zone, states that the water level elevations were measured at the site in February 2023, prior to the onset of pumping, and in August 2023 approximately four months after the pumps were turned on. The submittal indicates that the water levels remained relatively constant between February January 7, 2025
B. Frazier 2
and August, except for the estimated capture zone area where water levels decreased by nearly 6 feet in Well 0290 immediately east of the site boundary. However, a review of Figure 6 indicates the same water level in the 0290 well in both the February and August maps (5000.39 feet). Most of the water levels for wells on both maps are identical, although the contours are slightly different between the two maps. Why are newly installed nested wells 1428/1457 and 1429/1458 not included in the August 2023 water table contour map on eastern side of the site boundary? Please correct the elevation data and contours shown on the Figure 6 maps and explain why the newly installed wells were not accounted for in the August 2023 contour map.
NRC also requests that all depth to water and water level elevation data collected during February and August 2023 be provided in tabular format.
3.
Section 2.3.1, Uranium, states that the uranium concentration in Well 0290 is above the standard, but the contamination is isolated to the area surrounding the well. The August 2023 plume shown on Figure 7, Uranium Plume, depicts the Well 0290 groundwater contamination area as a detached plume, isolated from the main dissolved uranium plume. As mentioned in the first comment, any available analytical data from the extraction wells immediately west of the 0290 well (west of the evaporation pond), could provide valuable insight into the spatial distribution of the dissolved uranium plume. Recent extraction well influent concentrations, as well as historical influent concentrations from the formerly active extraction well in close proximity to Well 0290 (east of the evaporation pond), could be a useful guide in the evaluation of the dissolved uranium plume.
4.
Section 2.3.2, Nitrate, states that the nitrate concentrations exceeding standards in newly installed Well 1431, located approximately 4,000 feet south-southwest of the southern site boundary, appear isolated south of the contiguous plume as delineated by 1433/1462 to the north. NRC does not concur with the premise that the Well 1431 contamination is detached from the source area plume. With monitoring well network gaps of 800 to 1,200 feet in the area between Well 1431 and the source area plume, connection of the dissolved contamination areas appears likely. Contaminant migration along distinct, potentially narrow, preferential pathways is a likely explanation for the 1431 nitrate levels. The transport of contaminants to areas not anticipated by the water table elevation contours/flow maps, such as the nitrate contamination in Well 1431 and in the 1428/1457 wells east-northeast of off-site Well 0290, strongly support a preferential pathway mechanism operating in the site subsurface.
5.
Please provide water elevation data, laboratory analytical results, and any field parameter-related/purging data sheets for well gauging and well sampling activities conducted during 2023. Additionally, geologic logs for the newly installed monitoring wells (Wells 1428-1434; 1457-1463) are also requested.
B. Frazier 3
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 01/07/25
ML24358A017; Ltr ML24358A017 OFFICE NMSS/DUWP
/URMDB NMSS/DUWP
/URMDB NMSS/DUWP
/URMDB NAME KHayes RVonTill KHayes DATE Dec 30, 2024 Jan 7, 2025 Jan 7, 2025