ML22060A244
| ML22060A244 | |
| Person / Time | |
|---|---|
| Site: | WM-00048 |
| Issue date: | 03/01/2022 |
| From: | Thomas Lancaster NRC/NMSS/DDUWP/URMDB |
| To: | Dayvault J US Dept of Energy, Office of Legacy Management |
| Lancaster T | |
| Shared Package | |
| ML22060A242 | List: |
| References | |
| Download: ML22060A244 (2) | |
Text
DATE U.S. Nuclear Regulatory Commission Attn: Document Control Desk Deputy Director Mail Stop T8-F5 Washington, DC 20555-0001
Subject:
U.S. Department of Energy (DOE) Office of Legacy Management Durango, Colorado, Disposal Site, Disposal Cell Cover Depression Maintenance To Whom It May Concern:
The U.S. Department of Energy (DOE), Office of Legacy Management (LM) is responsible for long-term surveillance and maintenance of the Durango, Colorado, Disposal Site (Site). The Site was licensed under a Nuclear Regulatory Commission general license in accordance with Title 10 Code of Federal Regulations Section 40.27 on September 16, 1996. The Sites Long-Term Surveillance Plan (LTSP) explains the requirements of that general license for custody and long-term care.
In accordance with Section 3.5 of the LTSP, Routine Site Maintenance and Emergency Measures, LM will be conducting a technical assessment and repair of the disposal cell depression under a priority level 4 maintenance action. Priority level 4 covers minor erosion, and establishes the response of evaluating erosion, assessing its impact, and responding as appropriate to address the problem. LM seeks NRC acceptance on the designation of this maintenance action as priority level 4 and the technical assessment and repair approach outlined in this letter.
The 2015 annual site inspection identified a linear depression approximately 18 feet long in a drainage channel along the north-northeast toe of the disposal cell. Engineering staff reviewed the as-built drawings for the disposal cell and determined that the depression is not located over tailings. In September 2016, a site visit was conducted so that engineering staff could conduct a field inspection of the surface depression. That field inspection found that the depression is located at the interface between two different sizes of riprap. The depth of the depression was estimated to be 12 to 18 inches.
In June 2020 a topographic survey of the depression was completed, and a floating pipe grid was installed. The floating pipe grid allows for qualitative assessments of the depression to be routinely performed. Any change in the floating pipe grid measuring two inches or more would trigger a new topographic survey. Qualitative monitoring of the pipe grid since its installation has not triggered a new topographic survey.
This technical assessment will remove rip rap and associated bedding layers, one layer at a time.
As layers are exposed, the materials and their conditions will be checked, with the goal of identifying the root cause of the depression. Tailings are estimated to be 30 to 50 yards from the depression and are not expected to be encountered during the technical assessment. The depression area will be repaired to its design specification and surveyed following the technical assessment. Depending on the findings of this technical assessment, additional repair work may
or may not be necessary. The depression area will continue to be observed during the annual site inspections.
The technical assessment and repair are tentatively scheduled for September 2022.
LM will continue to keep NRC informed of the status and results of the technical assessment and repair.
If you have any questions or comments regarding this letter, please contact me at (970) 248-6016 or Jalena.Dayvault@lm.doe.gov. Please address any correspondence to:
U.S. Department of Energy Office of Legacy Management 2597 Legacy Way Grand Junction, CO 81503 Sincerely, Jalena Dayvault Durango Site Manager cc via email:
Tom Lancaster, NRC Jalena Dayvault, DOE Jeff Carman, RSI Joel Doebele, RSI DOE Read File File: E/##/###, F/##/###