ML24046A197
| ML24046A197 | |
| Person / Time | |
|---|---|
| Site: | 07000925 |
| Issue date: | 01/30/2024 |
| From: | Hayes K NRC/NMSS/DDUWP/URMDB |
| To: | Lux J Cimarron Environmental Response Trust |
| Shared Package | |
| ML24046A190 | List: |
| References | |
| Download: ML24046A197 (3) | |
Text
From: Kevin Hayes Sent: Tuesday, January 30, 2024 9:55 AM To: Lux, Jeff J Cc: Lifeng Guo; James Smith; Bill Von Till
Subject:
Follow up to Friday, January 26th Teams Mtg - Cimarron DP Rev 3 RAI Responses Attachments: NRC Review Cimarron RAI Responses Figs-Tables 30Jan24.pdf
GoodMorningJe,
AsafollowuptoourrecentTeamsmee ngontheCimarronDecommissioningPlanRevision3,RAIResponses, NRChassummarizedourtechnicalreviewofthesubmi alinthisemail.
Asdiscussedatthemee ng,theRAIresponsesareacceptabletotheNRC.Thatbeingsaid,NRCstadoes havedieringopinionsrelatedtosomeaspectsofthesitedatainterpreta onbytheLicensee.
Thiscommunica onisdesignedtoputtheseissuesonyourradarandprovidesuppor ngdocumenta onto NRCsrequestforvisualobserva onofthehillslopeandstreamchanneltotheeastofthesiteduringthe ini algroundwaterinjec onac vi es.Thea achedpdfincludessuppor ngdocumenta onforNRCsreview, includingtablesand"gureswithNRCnota ons.
Ifyouhaveanyques ons,pleasefeelfreetocontactus.
U.S. Nuclear Regulatory Commission (NRC) staff have reviewed the December 8, 2023, Cimarron Environmental Response Trust (Licensee) submittal of responses to the October 2, 2023, Request for Additional Information (RAI) related to site groundwater remediation (ML23346A262 and ML23251A212, respectively). The submittal included responses to several groundwater remediation-related topics at the Cimarron site including groundwater flow model calibration, groundwater flow direction evaluation and monitoring well locations, and the potential for vertical migration associated with injection, and remedial action reporting to the NRC.
The Licensees RAI responses related to groundwater are acceptable to the NRC. However, NRC staff does have differing technical opinions related to some aspects of the site data interpretation by the Licensee. The following technical data interpretations proposed by the Licensee are not shared by NRC staff:
Groundwater contamination is essentially restricted to permeable zones within the Transition Zone area of BA-1.
The characterization of Sandstone B monitoring well 02W51 as a perched zone monitoring well located upgradient of Injection Trench GWI-BA1-01.
Historical groundwater elevation data within the Sandstone B monitoring wells in the BA-1 remediation area does not indicate a northeasterly to easterly flow component, in addition to the northerly groundwater flow component.
The monitoring of Transition Zone monitoring wells 02W20 and 02W26 during active injection into Sandstone B at the GWI-BA1-01 trench will adequately evaluate the potential for short-circuiting of the injected water to the topographic slope to the east.
1 The following sections provide additional details regarding NRCs technical review of the previously listed issues. Supporting documentation for NRCs technical evaluation is attached.
- 1. Groundwater Contamination within the Transition Zone
The Licensees position that groundwater contamination within the Transition Zone is primarily restricted to the more permeable zones, summarized in Section 1.2.1 of the Licensees RAI response to NRC, cited the prevalence of elevated uranium soil sample concentrations within depth intervals characterized as higher permeability zones (coarse grained soils, shown in Table GWRM-1-1 in the response). Although higher uranium concentrations within coarse grained soils are present within the Transition Zone, the highly interbedded nature of the soils in this area make permeability characterizations based on field logging descriptions and/or grain size distributions very challenging. The Transition Zone soils vary lithologically from sands to silts or clays (and various combinations of these soil textures) over vertical intervals of 1 foot or less. A review of historical geologic logs and subsequent comparison to the Table GWRM-1-1 entries may indicate fine grained soils (silts and clays) in very close proximity to or, in some cases, within zones described as high permeability by the Licensee.
These observations tend to support the NRC staff opinion that the estimated cleanup time for the BA-1 Transition Zone and the upland of former burial trenches area may be underestimated. The persistently elevated uranium concentrations in the Transition Zone monitoring wells in the recent 2023 sampling event may support the presence of higher uranium concentrations within the lower permeability soils. Significantly lower uranium concentrations were observed in the Sandstone B and Alluvial monitoring wells in the most recent sampling event. No response from the Licensee is requested for this issue.
- 2. Sandstone B Monitoring Well 02W51 and Groundwater Flow
The characterization of the 02W51 monitoring well as a perched zone well and the groundwater flow direction within the Sandstone B monitoring wells in the BA-1 remediation area were presented in Section 3.2.2 of the Licensees RAI response to the NRC. The Licensees interpretation of the 02W51 Sandstone B well as a perched zone well and the subsequent description of the water level data from the well as anomalous resulted in the data being dropped from groundwater flow interpretations and a more northerly flow direction documented in the submittal. NRC staff is of the opinion that existing site data, well construction details, and documented subsurface responses to the pilot testing activities in 2017 tend to support characterization of the 02W51 monitoring well as a water table monitoring well within Sandstone B rather than a perched zone monitoring well. The elevated water level elevation in the 02W51 well results in an easterly to northeasterly component in the groundwater flow field for Sandstone B. No response from the Licensee is requested for this issue. The supporting documentation for NRCs review is provided in the attachment.
- 3. Injection Monitoring of Topographic Slope to the East of Injection Trench GWI-BA1-01
The RAI response provided in Section 3.2.3 by the Licensee indicated that Transition Zone monitoring wells 02W20 and 02W26 will be included in the in-process monitoring wells for evaluation of uranium plume migration within groundwater and possibly to the vicinity of the ephemeral stream east of the site. The location of these wells approximately 80 to 135 feet northeast of the Sandstone
2 B GWI-BA1-01 injection trench are not well situated to evaluate the topographic slope due east of the trench. With no Sandstone B monitoring wells located east of the trench for water level monitoring and mounded groundwater approximately 14 to 15 feet above the typical static water table elevation during active injection, NRC staff is concerned about potential seepage on the eastern slope or in the stream channel resulting from the injection. Supporting documentation for NRCs review is attached.
NRC requests that the Licensee visually observe the topographic slope and ephemeral stream channel located east of the injection area of BA-1 at appropriately scheduled timeframes during the initial phase of active injection. The observations of the slope and channel are intended to ensure that the water injected into Sandstone B trench GWI-BA1-01 does not short-circuit the subsurface system and emerge as seeps, surface water flow or other similar types of discharges in the area.
KevinR.Hayes,P.G.,CPG,GISP Hydrogeologist UraniumRecoveryandMaterialsDecommissioningBranch DivisionofDecommissioning,UraniumRecovery,andWastePrograms OfficeofNuclearMaterialSafetyandSafeguards Phone:3014150549 Email:Kevin.Hayes@nrc.gov
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