ML20058H708
| ML20058H708 | |
| Person / Time | |
|---|---|
| Site: | 07000925 |
| Issue date: | 02/24/2020 |
| From: | Lux J Environmental Properties Management |
| To: | Davis P, Robert Evans, Kenneth Kalman Document Control Desk, Office of Nuclear Material Safety and Safeguards, State of OK, Dept of Environmental Quality (DEQ) |
| Shared Package | |
| ML20059K920 | List: |
| References | |
| Download: ML20058H708 (3) | |
Text
February 24, 2020 Mr. Ken Kalman U.S. Nuclear Regulatory Commission 11555 Rockville Pike Rockville, MD 20852-2738 Mr. Paul Davis Oklahoma Department of Environmental Quality 707 North Robinson Oklahoma City, OK 73101 Mr. Robert Evans U.S. Nuclear Regulatory Commission 1600 East Lamar Blvd; Suite 400 Arlington, TX 76011-4511 Re: Docket No.70-925; License No. SNM-928 Groundwater Flow Model Report
Dear Sirs:
Solely as Trustee for the Cimarron Environmental Response Trust (CERT), Environmental Properties Management LLC (EPM) submits herein a report on the revision of groundwater flow models for the Cimarron Site.
The December 31, 2015 Facility Decommissioning Plan1 proposed the installation of groundwater extraction wells in the alluvial material of the Cimarron River floodplain. The extraction wells were to be constructed with well screens that extended through the entire saturated thickness of the alluvial deposits.
After completing the detailed technical review of the 2015 decommissioning plan, the US Nuclear Regulatory Commission (NRC) issued requests for additional information (RAIs) on February 9, 2017. One of the RAIs requested an assessment of the likelihood that dissolved uranium varies vertically in different aquifers or portions of an aquifer at the site. The NRC recommended, analysis of a pump and treat system with a combination of partially and fully penetrating wells, if the dissolved uranium is believed to be stratified at the site. A preliminary evaluation of the vertical distribution of uranium in groundwater in alluvial material had been initiated in December 2016, and the report Vertical Distribution of Uranium in Groundwater2 demonstrated that uranium was stratified at the site.
1 Environmental Properties Management LLC, December 2015 2 Environmental Properties Management LLC, May 2017
During meetings conducted in September 2017, the NRC requested that EPM consider installing extraction wells with well screen located in the zone in which uranium exceeds the decommissioning criteria. This would maximize the mass of uranium removed per unit volume of groundwater, optimizing the efficiency of groundwater treatment systems.
Consequently, the November 2, 2018 Facility Decommissioning Plan - Rev 13 proposed to advance direct push borings using a hydraulic profiling tool at the proposed location of each extraction well, collecting samples at two-foot intervals to assess the vertical distribution of contaminants in the groundwater. The screened interval for each well would then be determined by the results of the vertical profiling investigation.
The method of advancing borings and specifying screened intervals was discussed during meetings conducted in April 2019. During meetings conducted on August 29, 2019, the NRC expressed concern that the groundwater flow models for the Cimarron site assumed that well screens would extend through the entire saturated zone (those models showed complete capture of groundwater within the remediation areas). If the well screen were shortened, the results from the model output may change. In addition, the vertical profiling effort showed that the alluvial material may not be as homogeneous and isotropic as were assumed in the groundwater flow models.
The NRC requested that the flow models be revised to assign a layer of higher permeability and a layer of lower permeability to the alluvial aquifer, and that the effect of a shorter well screen within the more permeable zone on the capture zone be evaluated.
Enclosed please find a report on the revision of the groundwater flow models. To summarize, when the models were modified to provide for zones of higher and lower permeability, and shorter well screens, particle tracking model runs still showed anticipated recovery of groundwater throughout the remediation areas.
The vertical profiling of uranium and nitrate concentrations at proposed extraction well locations has been completed, and a report on the work will be submitted by the end of March 2020. We believe it is reasonable to maintain the course that was presented in the 2018 decommissioning plan, providing for well screens to extend throughout the zone in which uranium or nitrate concentrations exceed State Criteria, and designate the locations of pump intakes at the zone of maximum contaminant concentration.
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3 Environmental Properties Management LLC, November 2018
If you have questions or comments, please contact me at 405-641-5152 or at jlux@envpm.com.
Sincerely, Jeff Lux, P.E.
Trustee Project Manager Enclosure cc: NRC Public Document Room (electronic copy only)