ML24275A049
| ML24275A049 | |
| 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: ML24275A049 (1) | |
Text
Bill Frazier, P.E., Site Manager U.S. Department of Energy Office of Legacy Management 2597 Legacy Way Grand Junction, CO 81503
SUBJECT:
U.S. NUCLEAR REGULATORY COMMISSIONS STAFF REVIEW OF THE JUNE 2020, DRAFT TUBA CITY, ARIZONA, DISPOSAL SITE, GROUNDWATER REMEDY PERFORMANCE REPORT 2002 THROUGH 2018
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 Report, 2002 Through 2018, dated June 2020 (Received September 29, 2023; Agencywide Documents Access and Management System [ADAMS] Package Accession No. ML23271A265).
NRC staff concurs with most of the conclusions and concerns voiced in the submittal, including the following:
Preferential flow paths are present within the aquifer which result in asymmetric drawdown patterns both horizontally and vertically during remedial system operation, The large, screened intervals of the existing extraction wells (approximately 150 feet of well screen on most wells) extend over 100 feet below the zones of highest groundwater contamination at the site, The operation of the remedial system during the 2002 to 2009 timeframe (extraction from 37 wells at an annual cumulative rate of 80 gallons per minute [GPM]) generally resulted in plume stabilization and a significant slowing of downgradient contaminant migration, although the contaminant plumes were not fully captured during this operational phase, The presence of solid phase uranium present in the subsurface appears to be likely based on the rebound of groundwater contaminant levels during periods of lesser or no pumping from the extraction well network, and The likelihood of a significantly longer cleanup duration than the 20 years proposed in the original remedial design (possibly many hundreds of years).
October 7, 2024
B. Frazier 2
NRC is aware of the Groundwater Compliance Action Plan (GCAP) Work Plan currently in preparation by DOE-LM to provide a better characterization of the subsurface contaminant distribution in both solid and dissolved phases and improve the conceptual model of groundwater flow and contaminant transport at the site. NRC provided comments on the November 2020, Draft GCAP Work Plan (ADAMS Package Accession No. ML23135A912) to DOE-LM in correspondence dated February 14, 2024 (ADAMS Accession No. ML24045A067).
The following questions and comments are provided on this submittal:
1.
Figure 9, Water Table Contours in August 2014 and June 2018, includes the well 0290 water level elevation of 4,977.78 feet on the June 28, 2018, contour map, which represents static conditions prior to startup of the groundwater extraction system. The wells water level elevation is erroneously contoured between the 4,990 and 5,000-foot groundwater elevation contours on the map. The 0290 well appears to represent a groundwater low along the eastern side of the site. Additionally, several other groundwater elevations shown on the June 2018 contour map, including wells 0940, 0271, NMW-8S, NMW-4A, NMW-2A, NMW-6S, are not properly contoured on the map. Please re-evaluate the contours and elevation data shown on the map and explain and/or correct, as appropriate. NRC also requests that depth to water/water level elevation data collected during the well gauging for each of the six contoured data sets in Figures 8, 9, and 10 be provided in tabular format.
2.
In Section 2.6.2.1, Nitrate Trends in Wells Inside the 2009 Capture Zone, the submittal states that well 0290, screened in Zone B and located at the eastern edge of the site, exhibited increasing nitrate concentrations during the 2009 to 2018 timeframe (also the timeframe of reduced pumping rates). Well 0290 is located approximately 125 feet east of Extraction Well 1124 and is included at the eastern edge of both the 2009 and 2017 capture zone areas. Does influent concentration data exist for the individual extraction wells in the vicinity of the 0290 well? If the capture of groundwater with highly elevated concentrations of nitrate is documented in the extraction wells nearest the 0290 well, the shutdown of the pumping in those wells would allow for downgradient migration to take place. The 0290 well, as mentioned in the previous comment, appears to represent a groundwater low on the June 2018 static water level contour map. No other Zone B monitoring wells are located on the eastern side of the disposal cell to evaluate system drawdown or provide groundwater analytical data.
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 10/07/24
ML24275A070; Ltr ML24275A049 OFFICE NMSS/DUWP/URMDB NMSS/DUWP/URMDB NAME RVonTill KHayes DATE Oct 7, 2024 Oct 7, 2024