ML20195B786
| ML20195B786 | |
| Person / Time | |
|---|---|
| Issue date: | 04/30/1999 |
| From: | NRC |
| To: | |
| Shared Package | |
| ML20195B783 | List: |
| References | |
| REF-WM-66 NUDOCS 9906030026 | |
| Download: ML20195B786 (7) | |
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TECHNICAL EVALUATION REPORT b j
FOR THE PROPOSED REMEDIAL ACTION AT THE NATURITA URANIUM MILL TAILINGS SITE j NATLKITA COLORADO l
I Enclosure 9906030026 990521 PDR WASTE WM-66 PDR 4s
1 ABSTRACT This Technical Evaluation Report (TER) summarizes the U.S. Nuclear Regulatory Commission (NRC) staffs review of the proposed remedial action for the Naturita Uranium Mill Tailings 4 Disposal Site (Naturita site). The sections of the TER are arranged by technical discipline to correspond to the Environmental Protection Agency's (EPA's) standards in Title 40 of the Code of Federal Regulations (CFR), Part 192, Subpads A through C (EPA,1995). The NRC staff review of the U.S. Department of Energy final Remedial Action Plan (RAP; DOE,1994), MK Ferguson Remedial Action inspection Plan (MK,1998), final draft Remedial Action Plan and Site Design for the Upper Burbank Repository (RAP; DOE,1995) and associated documents identified open issues in geologic stability, geotechnical stability, erosion protection, groundwater hydrology, and radon attenuation and site cleanup as presented in Table 1.1 (Summary of Open Issues). The final Remedial Action Plan and Site Design for the Upper Burbank Repository (RAP: DOE,1998) has been reviewed by NRC staff for finalization of this TER. Previously open issues have been adequately addressed or deferred as noted in Table 1.1 of this final TER.
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p;s j e-TABLE OF CONTENTS
. Section L Paae
1.0 INTRODUCTION
'. . . . .. ....,... .. .. . .. . 1-1
' 1.1 EPA Standards . . . . . . . . . . ... . . . . .1-1 1.2 ~ Site and Proposed Action . . . .. .. ... . . . . 1-1 1.3 Review Process . . . . . . . . . . .. .. .. . . .. . 1-2 1.4 - . TER Organization . . . . . . . . . .. . .... .. . . .. . 1-3 1.5 - Summary of Open issues . . . .. . .. . ,. . ... ..... 1-3
- 2.0 ' GEOLOGIC STABILITY . . . . . . . . . . . . . . .. . . . .... ..... ... . 2-1
.2.1L Introduction .... ..... . .. . . . . . . . - . . 2-1 2.2 Location' ... ... ,. . ...... . .. . . . . ......... ... . 2-1 2.3 Geology ... ..... .. .... ... .. . . .. . . 2-1 2.3.1 Physiographic Setting .. . . . . .. . . . . . . 2-1 2.3.2_ Stratigraphic Setting . . . . ... . . ... . ..... . 2-2 2.3.3 Structural Setting .. , , , . . .2 2.3.4 Geomorphic Setting . ... .. . . . . . . .. 2-5
- 2.3.5 Seismicity . . . . . . . ... .. . . .. . .. 2-5 2.3.6 Natural Resources . . ... . ., . . .2-7 2.4 Geologic Suitability ~ . . . ... . , . .... .2-7 2.4.1 Bedrock Suitability . . . . . . .. ..... 2-7
'2.4.2 Geomorphic Stability . .. ..,. . ... 2-8 2.4.3- Seismotectonic Stability . .. . . ...... . .. ..... ... ... 2-9 2.5 Conclusions . .. .. .. ... ... ., .. . .. ....... . ...... 2-9
- 3.0 .GEOTECHNICAL STABILITY L , . . . . .. . .. .. . . . . . , . 3-1
. 3.1 Introduction . . . . . ... . . . .... .. . . . ........ 3-1 3.2 Site and Material Characterization . . . . ., , . . . . . . . . 3-1 3.2.1 Site Descriptions . .. . . .. . ... .. .... . . . 3-1
. 3.2.1.1 Processing Site . . .. . . . .. . . 3-1 3.2.1.2 Disposal Site at Uravan . .. .. , . . . 3-2 3.2.1.3 Borrow Materials Site . .... . . . ..... . . 3-2 3.2.2 Site investigations . ..... , . . . .. 3-2 3.2.3 Upper Burbank Disposal Site Stratigraphy . . . .. .3-3 3.2.4 Testing Program . . ,... .... . . . . 3-3
- 3.3 - ' Geotechnical Engineering Evaluation . .... . ... .. . ... . . . 3-3 3.3.1 Slope Stability Evaluation .. ..... .. .. ..... . .3-3 3.3.2 Settlement and Cover Cracking. . . . . , ,. . . . 3-4 3.3.3 Liquefaction . . . . . . . . , . . . . . .. . . 3-5 3.3.4 Cover Design . . . .. . .. . ...... . ,.. . . . . 3 3.4 - Geotechnical Construction Details . .. . . . .. . . .3-6 3.4.'1 Construction Methods and Features . , , . .. . , .. ..... . 3-6 3.4.2 Testing and Inspection . , . . . . . . . . . . . . . . . .
. ........... 3-6 3.5 Conclusions . . . . . . . . . 1. . . . . . ....... ..... .... .. . . .... 3-6
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l 4.0 SURFACE WATER HYDROLOGY AND EROSION PROTECTION .4-1 4.1 Hydrologic Description and Site Conceptual Design . . . .4-1 4.2 Flooding Determinations . 4-1 4.2.1 Selection of Design Rainfall Event .4-1 4.2.2 Infiltration Losses . .42 4.2.3 Times of Concentration . .4-2 4.2.4 Rainfall Distributions . .4-3 4.2.5 Computation of PMF. . .4-3 4.2.5.1 Top and Side Slopes .4-3 4.2.5.2 Aprons . . . . .4-4 4.2.5.3 Diversion Channels . 4-4 4.3 Water Surface Profiles and Channel Velocities .4-4 4.3.1 Top and Side Slopes .4-4 4.3.2 Upstream Aprons .
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4.3.3 Diversion Channels . .4-5 l 4.4 Erosion Protection . .4-5 ;
4.4.1 Sizing of Erosion Protection . .4-5 l 4.4.1.1 Top and Side Slopes .4-6 I 4.4.1.2 Upstream Aprons . .4-6 4.4.1.3 Diversion Channels . . .4-6 4.4.1.3.1 Channel Side Slopes .4-6 ,
4.4.1.3.2 Channels (Main Section) . . .4-7 !
4.4.1.3.3 Channel Outlets . .4-7 :
4.4.1.3.4 Sediment Considerations . . .4-7 4.4.2 Rock Durability . . .. . ... . .. 4-8 4.4.3 Testing and Inspection of Erosion Protection . . , . 4-9 4.5 Upstream Dam Failures . . . .. . . 4-10 4.6 Conclusions . . . . .4-10 5.0 WATER RESOURCES PROTECTION . . .. .5-1 5.1 Introduction . . . 5-1 52 Hydrogeologic Characterization . . . 5-1 5.2.1 Identification of Hydrogeologic Units . . .5-1 5.2.1 A Processing Site . .5-1 5.2.1 B Disposal Site . 5-2 5.2.2 Hydraulic and Transport Properties . . 5-2 5.2.2 A Processing Site . .. . 5-2 5.2.2 B Disposal Site .. . . 5-3 5.2.3 Extent of Contamination. . . . .5-3 5.2.3 A Processing Site . .. . .5-3 5.2.3 B Disposal Site . . . .5-3 5.2.4 Water Use . . . .. .. 5-4 5.2.4 A Processing Site ... . .5-4 5.2.4 B Disposal Site .. .. . .5-4 5.3 Conceptual Design Features to Protect Water Resources . ... ... 5-5 5.3 A Processing Site . .. .. . .. . .5-5 NATURITA TER ii APRIL 1999
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1, i -. 5.3 8 Disposal Site - .. .. .. .. .
.5-5 5.4 Disposal and Control of Residual Radioactive Materials .. . .5-5 5.4.1 Water Resources Protection Standards For the Disposal Site . . . .. 5-5 5.4.2 . Performance Assessment for the Disposal Site .. . ......... .5-6 1
1 5.4.3 Closure Performance Demonstration for the Disposal Site ... .. 5-7 5.4.4 Groundwater Monitoring and Corrective Action Plan at the Disposal Site . . .. . .. .. ... .. . .5-7 5.5 Clean-up and Control of Existing Contamination at the Processing Site , , . 5-7 5.6 . Conclusions . . . . . . . . . . .. . . . .. . . . .... 5-8 6.0 RADON ATTENUATION AND SITE CLEANUP . . . . . .. .... .. .6-1 6.1 Introduction . . . . . . . . . . . , . . .. .. . . . ..... ... .. . 6-1 6.2 Radon Attenuation . .. . . . . . . . . . . . . . . ... . . .6-1 6.2.1 Evaluation of Parameter Values . . . ..,. .. . 6-1 6.2.1.1 Contaminated Materials. . .... .. 6-2 6 2.1.2 Radon Barrier. . . . .. . .. .. ,. .. 6-4 6.2.2 Evaluation of Radon Attenuation Model .. . ... . .. 6-5 6.2.3 Durability of the Radon Barrier .. . . . . .... . .6-5 6.3 Site Cleanup . . .. . . . . . . . .. . .6-6 6.3.1 Radiological Site Characterization. . , .6-6 6.3.2 Cleanup Standards , , . ..,... .. . .. 6-6 6.3.3 Supplemental Standards , ... . . .. . . 6-7 6.3.4 Verification . . . . , , . . ..., ,
. . .... ... 6-9 6.4 Conclusions . . .. .. .. . . . ,,... .. . . 6-9
7.0 REFERENCES
. .. ... ,. .. . ... .... ..... .. . . ... ... 7-1 1
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LIST OF FIGURES Fiaure Paae FIGURE 1.1 - LOCATION MAP OF THE NATURITA SITE. COLORADO .. . 1-3 FIGURE 1.2 ' MAP OF THE NATURITA PROCESSING SITE . . . . . . . . . . . . . . . 1 -4 FIGURE 1.3 NATURITA PROCESSING SITE. . ... . .. . . ... .. . .. .1-5 FIGURE 1.4 LOCATION OF THE UPPER BURBANK DISPOSAL SITE . . . . . . . , . . . . 1 -6 FIGURE 1.5 DIAGRAM OF THE UPPER BURBANK DISPOSAL CELL . ............. 1-7 FIGURE 1.6 CROSS SECTION VIEWS OF THE UPPER BURBANK DISPOSAL CELL , 1-8 FIGURE 2.1. STRATIGRAPHY OF THE UPPER BURBANK SITE , . . . . . . . . . . . . . . 2-3 LIST OF TABLES Table Paae TABLE 1.1
SUMMARY
OF OPEN ISSUES . ... .. . .... . . . . . . .1-9 TABLE 5.1 HAZARDOUS CONSTITUENTS ANC CONCENTRATION LIMITS FOR THE DISPOSAL SITE . . . . . . . . . .. . .. . . .. .5-9 i
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LIST OF ACRONYMS AND ABBREVihTIONS E.
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..Apronym or Definition
' Abbreviation
! -ALARA- As low As Reasonably Achievable L ,
/CFR Co' de of Federal Regulations -
COE U.S. Army Corps of Engineers
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DOE U.S. Department of Energy '
EPA . U.S. Environmental Protection Agency i HMR. Hydrometeorological Report l
L LTSP Long-Term Surveillance Plan MCL- Maximum Concentration Limit, or Maximum Contaminant Level
.NEPA- National Environmental Policy Act .
NOAA National Oceanographic and Atmospheric Administration -
NRC: .U.S. Nuclear Regulatory Commission j
PMF Probable Maximum Flood
.PMP Probable Maximum Precipitation
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4 POC Point of Compliance-RAIP Remedial Action Inspection Plan CRAP Remedial Action Plan 1
SRPl Standard Review Plan TER <
Technical Evaluation Report i I
UMTRA Uranium Mill Tailings Remedial Action - <
UMTRCA~ Uranium Mill Tailings Radiation Control Act of 1978 1
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1.0 INTRODUCTION
. The Naturita site was designated as one of 24 abandoned uranium mill ta :ings piles to receive remedial action by the U.S. Department of Energy (DOE) under the Uranium Mill Tailings Radiation Control Act of 1978 (UMTRCA). UMTRCA requires, in part, that the U.S. Nuclear i Regulatory Commission (NRC) concur with DOE's selection of remedial action, such that the I remedial action meets appropriate standards promulgated by the U.S. Environmental Protection Agency (EPA). This Technical Evaluation Report (TER) documents the NRC staffs review of the DOE Remedial Action Plan (RAP) (DOE, 1994,1995, and 1998), Remedial Action inspection Plan (RAIP) (MK,1998) and all associated documentation pertinent to the proposed remedial action.
1.1 EPA Standards
' As required by UMTRCA, remedial action at the Naturita site must comply with regulations established by the EPA in 40 CFR Part 192. Subparts A through C (EPA,1995). These regulations may be summarized as follows:
- 1. The disposal site shall be designed tc control the tailings and other residual >
radioactive material for 1000 years to tt.e extent reasonably achievable and, in any case, for at least 200 years (40 CFR 192.02(a)(1)].
' 2. The disposal site design shall provide reasonable assurance that releases of radon-222 from residual radioactive materials (RRMs) to the atmosphere will not exceed 20 picocuries/ square meter /second or increase the annual average ,
concentration of radon-222 in air at any location outside of the disposal site by l
more than 0.5 picoeurie/ liter (40 CFR 192.02(b)(1) and (2)J.
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- 3. The remedial action shall ensure that radium-226 concentrations, in land that is q not part of the disposal site, averaged over any area of 100 square meters, do not exceed the background level by more than 5 picocuries/ gram (pCi/g) . j averaged over the first 15 centimeters of soil below the surface and 15 pCi/g averaged over any 15-centimeter-thick layer of soil more than 15 centimeters below the land surface (40 CFR 192.12(a)].
- On January 11,1995, EPA published a' final rule for groundwater standards for remedial actions at inactive uranium processing sites (40 CFR 192, Subparts A through C). The standards consist of two parts; a first part, governing the control of any future groundwater contamination ,
that may occur from tailings piles after remedial action, and a second part, governing the !
cleanup of contamination that occurred before the remedial action of the tailings. In accordance with UMTRCA Section 108(a)(3), the remedial action shall comply with the EPA standards.
1.2 Site and Proposed Action !
'The Naturita uranium mill processing site is located in Montrose County Colorado approximately two miles northwest of the town of Naturita along Colorado State Highway 141
- (Figure 1.1). The site encompasses approximately 53 acres and includes the former tailings NATURITA TER - 1-1 APRIL 1999 4
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area, the mill facility and ore buying station, and the adjacent ore storage area (Figure 1.2). No f
tailings pile remains at the site due to the removal and transport of tailings to the Durita facility at Vancorum, Colorado, for reprocessing by the Ranchers Exploration and Development Corporation. The approximately 547,000 cubic yards (yd3) of contaminated material remaining l
at the Naturita processing site (Figure 1.3) includes 115,000 yd3 from 14 acres of mill yard, !
12,000 yd from 12 acres of former ore storage area,295,000 yd' from 196 acres of windblown and/or other material (areas A through G), 117,000 yd from 27 acres of former tailings area, ,
and 8,000 yd of demolition debris. Radium-226 concentration for the contaminated material ranges from 15 to 143 pCi/l. l i
The proposed remedial action for the disposal and stabilization of the contaminated materials is to relocate them to the Upper Burbank disposal site at Uravan, Colorado. The Upper Burbank disposal site is located cpproximately 13 road miles (21 kilometers) northwest of the Naturita !
processing site (Figure 1.1). The disposal cell will be configured as shown in Figures 1.4 and 1.5.
1.3 Review Process The NRC staff review was performed in accordance with the Standard Review Plan (SRP) for UMTRCA Title i Mill Tailings Remedial Action Plans (NRC,1993) and consisted of comprehensive assessments of DOE's RAPS for the Natunta processir.g and disposal sites l (DOE,1994,1995 and 1998)
The 1996 staff review of the RAPS submitted by DOE indicated that there were open issues as presented in Section 1.5 and discussed in further detail in Chapters 2 through 6 of the draft TER. The NRC staff reviewed sii revisions to the RAP submitted by DOE in this regard. All the open issues (with the exception of several groundwater issues) were resolved, and the NRC staff can now concur with the proposed remedial action. The NRC staff revised the TER into final form, presented here, to include evaluations and conclusions with respect to the additional information submitted by DOE.
The remedial action informaiion assessed by the NRC staff was provided primarily in the following documents (DOE, 1994,1995, ano 1998; MK 1994 and 1998).
- 1. DOE,1994, Remedial Action Plan and Site Design for Stabilization of the inactive Uranium Mill Tailings Site at Naturita, Colorado, Final, UMTRA-DOE /AL/62350-40PF, March 1994 (NAT-RAP), Remedial Action Selection Report, including Attachments 1,3, and 4.
- 2. MK Ferguson Company,1998, UMTRA Project, Naturita Remedial Action Inspection Plan, Rev.1 (Apnl 17,1998).
- 3. DOE,1995, Remedial Action Plan and Site Design for Stabilization of the Naturita Title l Residual Radioactive Materials at the Upper Burbank Repository, Uravan, Colorado, final draft, with Appendices A - G (November 1995).
l NATURITA TER 1-2 APRll 1999
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- 4. DOE,1998, Remedial Action Plan and Site Design for Stabilization of the Naturita Title i Residual Radioactive Materials at the Upper Burbank Repository, Uravan, Colorado, page changes (June,1998).
- 5. . DOE,1998, Remedial Action Plan and Site Design for Stabilization of the Naturita Title I Residual Radioactive Materials at the Upper Burbank Repository, Uravan, Colorado, final draft, with Appendices A - G (1998).
- 6. MK Ferguson Company,1994, Proposed supplemental standards areas for Naturita processing site and surrounding vicinity properties,3885-NAT-R-01-01232-00, January 10,1994, 1.4 ' TER Organization '
The purpose of this TER is to document the NRC staff review of DOE's RAPS and RAIP for the Naturita disposal and processing sites. The following sections of this report have been organized by technical discipline relative to the EPA standards in 40 CFR Part 192, Subparts A-C. Sections 2,3, and 4 provide the technical basis for the NRC staff's conclusions with respect -
to the long-term stability standard in 192.02(a). Section 5, Water Resources Protection, summarizes the NRC staff's conclusions and remaining open issues regarding the adequacy of DOE's compliance demonstration with respect to EPA's groundwater protection requirements in 40 CFR Part 192. Section 6 provides the basis for the staff conclusions and identifies open issues with respect to the radon control standards in 192,02(b) and soil cleanup standards in .
192.12.
~ 1.5 - Summary of Open Issues in its review of the preliminary final RAP for the Naturita processing and disposal sites, the NRC staff identified 26 open issues. Those issues have been satisfactorily addressed by DOE in the Final RAP with the exception of several groundwater issues that have been deferred until a later
. phase of the Uranium Mill Tailings Remedial Action (UMTRA) Project.
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i NATURITA TER 18 4pRll 1999
TABLE 1.1
SUMMARY
OF OPEN ISSUES OPEN ITEMS TER STATUS Subsection FINAL TER
- 1. DOE needs to provide additional information to 2.3.5 and CLOSED demonstrate that Fault 90 is a salt tectonic feature 2.4.3 and capable of no more than a magnitude 3 event.
The staff will consider this an open issue pending receipt of information relating to Fault 90 to show that the maximum earthquake determined for the site, magnitude 6.9 at 14.9 km, is a conservative conclusion.-
DOE needs to provide information to justify that the mean value from the 1994 model of Campbell and Bozorgnia (1994) will be adequate for the design acceleration.
- 2. Until DOE completes testing of Upper ClJb Mesa 3.2.4 CLOSED soils, those analyses remain an open isste.
- 3. The PHA value willimpact the stability analysis. 3.3.1 CLOSED For a PHA higher than 0.3g, a dynamic or deformation analysis will be required. 1 Determination of a satisfactory PHA with respect to slope stability remains an open issue.
- 4. DOE needs to address the discrepancy betw .7 3.4.1 CLOSED specified radon barrier compaction (100 peresnt of maximum dry density) versus calculated values (95 percent of maximum dry density).
- 5. ~ The RAP and specification do not address the 3.4.2 CLOSED problems associated with compacting a Fat Clay (CH) soil at the 100 percent of Standard Proctor maximum dry density. Since the CH soil must presumably be compacted wet of optimum, and desiccation cannot be tolerated, additional
-discussion is needed in the RAP.
- 6. The staff is unable to comment on the 3.4.2 and CLOSED geotechnical/ earthworks aspects of the Remedial 4.4.3 '
Action inspection Plan (RAIP) or the testing and inspection quality control requirements for the erosion protection materials as an up-to-date version of the RAIP was not available during this review.
NATURITA TER 1-9 APRIL 1999
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l OPEN ITEMS TER STATUS Subsection FINAL TER
- 7. DOE has not adequately addressed the design of 4.2.5.2, CLOSED the upstream apron. DOE needs to: (1) redesign 4.3.2, and the apron; (2) provide adequate riprap sizes; 4.4.1.2 (3) compute peak Probable Maximum Flood flow rates for the upstream apron using concentrated
- flood flows; and (4) consider natural gullies in the analysis of the flow rates.
- 8. The location of the diversion channel outlet near 4.4.1.3.3 CLOSED the Uravan Title 11 cellis not considered to be acceptable. Flows discharging from the dWersion channel could adversely affect the toe of the Title ll cell. DOE should either relocate the outlet of the channel or provide a revised design to account for flows potentially impacting the Title 11 cell.
- 9. A considerable amount of sediment frorr the 4.4.1.3.4 CLOSED upland drainage areas can be expected to enter the diversion channels. To document the acceptability of the channel design. DOE should demonstrate that: (1) the channels will have sediment carrying capacity; (2) potential sediment deposition in the channel will not significantly affect the flow capacity; (3) any blockage in the channels l
will not have an adverse effect on the stability of the contaminated tailings; and (4) the riprap in the {
channel provides adequate protection.
- 10. The RAP should be revised to provide conclusive 5.2.3 CLOSED 1 evidence as to whether or not the following constituents represent site-specific contaminants in the alluvium at the processing site: lead, nitrate, and silver. These constituents were excluded from I the statistical analysis for a variety of reasons.
- 11. The RAP should provide analyses of the San 5,2.3 CLOSED Miguel River during low flow periods, in order to substantiate that the river has not been contaminated from the processing site.
NATURITA TER 1-10 APRIL 1999
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- 12. The RAP should provide specific information about 5.2.4 CLOS 5D
' the existing wells, including their locations and water quality, in order to substantiate that existing wells and water uses have not been impacted by l the processing site.
- 13. A clear strategy and/or short-term measures for 5.0 DEFERRED
. groundwater remediation at the processing site should be included in the RAP, Short-term
, measures are needed for protection of human ,
health and the environment until a compliance strategy is developed and implemented. In the absence of short-term measures,' DOE should estabhsh, and include in the RAP. site-specific comphance standards for the processing site as required by the regulations. In addition, DOE -
needs to designate a point of compliance for the processing site, which will be used to dem_ onstrate compliance with the site-specific standards as required by the regulations. If groundwater remediation at the processing site is planned to .
rely on natural flushing, the RAP needs to substantiate that the processing site conditions justify such reliance to achieve compliance with the standards.
- 14. DOE needs to provide a satisfactory justification 5.4.1 and CLOSED for applying supplemental standards consistent Table 5-1 with the regulations or apply the primary standards, including establishment of concentration limits and a Point of Compliance
._(POC) in the uppermost aquifer as required by the regulations.
.15. DOE needs to identify site-specific hazardous 5.4.1 and CLOSED constituents based on procedures outlined in the Table 5-1 EPA standards. All constituents that have been identified in the residual radioactive material and that are also included in Appendix I of 40 CFR Part 192 must be included.
I NATURITA TER.' 1-11 APRIL 1999 I
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l OPEN ITEMS TER STATUS Subsection FINAL TER 3 1
- 16. The Background Water Quality Section of the RAP 5.2.3 CLOSED should be revised to include all of the site-specific constituents, including organic and other constituents or provide adequate justification for their exclusion. Also, justification shoula be provided for the use of data from Well 768 to establish background, or additional information should be provided to support the position that this !
well has not been contaminated by the existing l
tailings located at the site. i
- 17. The RAP should be revised to include 5.4.4 CLOSED performance monitoring at the POC, or by indirect l methods, such as recommended in 40 CFR 192.20(a)(4).
- 18. The RAP should include a commitment to 5.6 DEFERRED i undertake corrective action within 18 months to restore system performance to the concentration limits originally established for the disposal site, in the event that such limits are found or projected to be exceeded.
18A DOE should explain how the concentration limits 5.4.1 CLOSED for strontium and tin at the Upper Burbank i Disposal site were derived.
- 19. DOE should provide the additional Th-230 and U- 6.3.1 CLOSED 236 data obtained with the cobbly soil study to substantiate that adequate characterization of these radionuclides has been performed.
- 20. DOE should provide more soil background Ra-226 6.3.1 CLOSED data and correct the soil Ra-226 data in Table 6.1.
- 21. DOE needs to address how partial remediation of 6.3.3 CLOSED the areas proposed for no remediation would cause " environmental harm that is clearly excessive compared to the health benefits to persons living on or near the site, now or in the future" as required by 40 CFR 192.21(b).
- 22. DOE should remove the former ore storage area 6.3.3 CLOSED .
from consideration of supplemental standards under Part 192.21(c).
NATURITA TER 1-12 APRIL 1999
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l OPEN ITEMS TER STATUS L Subsection FINAL TER
- 23. DOE should discuss possible future uses of all the 6.3.3 CLOSED supplemental standard areas in the section on potential health risks to persons that might occupy the areas.-
- 24. DOE should provide guidance (possibly a 6.3.3 CLOSED reminder on the extent of excavation) indicating that the remediation will come as close to meeting the otherwise applicable standards as is reasonable under the circumstances. __
- 25. DOE needs to reconsider how much removal can 6.3.3 CLOSED be performed around the gas line without increased unit cost. Also, DOE needs to discuss what entity has the future responsibility for any .
contaminated material excavated from along the gas line and show that the designated enti'y has knowledge ofits responsibility. In addition, Ra-226 data for the area along the gas line should be provided,
- 26. As required by 40 CFR 192.22(c), DOE should 6.3.3 CLOSED provide copies of any comments from land owners regarding the proposed application of supplemental standards to portions of their -
property.
i l
l I NATURITA TER 1-13 APRIL 1999
fi, .
2.0' GEOLOGIC STABILITY h .- 2.1 Introduction -
This section of the TER documents the staff's review of geologic and seismologic information for
- the Upper Burbank disposal cell, slated for disposal of the remaining Title i material from the Naturita site'. The EPA standards listed in 40 CFR 192 do not include generic or site-specific
. requirements for the characterization of geologic conditions at UMTRA Project sites. Rather,40 CFR 192.02(a) requires control shall be designed to be effective for up to 1000 years, to the extent achievable, and,- in any case, for at least 200 years. NRC staff have interpreted this standard to mean that certain geologic conditions must be met in order to have reasonable assurance that this long-term performance objective will be achieved, This review follows the guidance in 40 CFR 192.02, ar. specified in NRC's SRP for Title i UMTRA sites (NRC,1993). The review is based on information provided in the Naturita RAP for the disposal site (DOE,1998), references cited in the RAP, additional references available in the geologic literature, and associated documentation p9rtinent to the proposed remedial action.
2.2 Location The Upper Burbank cell is located on Club Mesa, an erosional remnant bounded by the San Miguel and Dolores River valleys, as well as Hieroglyphic Canyon. The mesa lies immediately west of Uravan in western Colorado. TER Section 1.2 contains additionallocation information.
- 2.3 Geoloav The RAP contains a description of the site geology, which is compiled from a variety of maps, books, and journal articles available in the open literature.
2.3.1 Physiographic Setting The site lies in the eastern portion of the Colorado Plateau physiographic province, a region
- covering much of eastern Utah, northern Arizona, northwestern New Mexico, and western Colorado. The Plateau is characterized by semi-arid climate, elevations mostly over 1500 meters, and, with the notable exception of the Paradox Basin, bedrock of generally flat-lying j sedimentary units. The site is in the Canyonlands section of the Plateau, an area characterized l
by deeply incised drainages and isolated remnant mesas. The major land forms near the site are the Uncompahgre Plateau to the northeast and the Paradox Basin to the southwest (Figure 2.1, Page A2-2; DOE,1998). Club Mesa is one of several mesas between the' San
,, Miguel and Dolores Rivers.. Tributaries of these streams have incised the upland between them i to define these mesas, which are characterized by bedrock dipping at low angles to the .
' northeast.
" The Uncompahgre Plateau is a northwest-trending upland about 160 km long and 50 km wide. l
. The southwest border is marked geomorphically by the San Miguel and Dolores River valleys, and the northeast border by the Gunnison and Uncompahgre River valleys. The Plateau was ;
uplifted during the Late Cretaceous-Early Cenozoic Laramide orogeny, presumably due to_
l NATURITA TER 2-1 APRIL 1999
=:
r reactivation of high-angle faults in the Precambrian basement rocks (Ely and others,1986). As the Precambrian basement was uplifted, Mesozoic sediments were faulted and folded into monoclinal structures that presently drape the margins of ths P!mau. The Upper Burbank disposal site lies approximately 10 km southwest of the hinge line marking the base of the southwest monocline. l The Paradox Basin is a northwest-trending, elliptically shaped region of relatively low relief j within the Colorado Plateau. Its long axis extends over 200 km from near Green River, Utah, to ;
Cortez, Colorado. The Paradox Basin is a paleostratigraphic basin that accumulated evaporite i deposits 1-2 km thick in the Pennsylvanian Period. An overburden of clastic sediments shed in I a southwesterly direction from the ancestral Uncompahgre uplift, in combination with basement fault blocks trending toward the northwest, caused the salt beds to deform into a series of northwest-trending anticlines and synclines from the Pennsylvanian through Jurassic Penods.
Overlying Mesozoic sediments were folded during this episode of salt diapirism. Subsequent dissolution of salt has caused some subsidence of the Mesozoic units, and deformation during the Laramide Orogeny may have further folded Paradox Basin sediments. The northeastern-most anticline of the Paradox Basin underlies the Paradox Valley, approximately 5 km southwest of the site. Club Mesa lies between the Uncompahgre Plateau and Paradox Basin.
Based on a review of the RAP (DOE,1998) and other references, the staff finds the physiographic setting to be adequately characterized.
2.3.2 Stratigraphic Setting The Upper Burbank site is underlain by a sequence of Mesozoic and Paleozoic marine and continental sedimentary rocks (Figure 2.1). A thin sequence of pre Pennsylvanian limestones and shales may overlie Precambrian basement at considerable depth, but these rocks are not exposed in the site area. The Pennsylvanian Hermosa Group comprises the evaporites that have experienced ductile deformation throughout the Paradox Basin. This unit is interpreted to ,
be thin and deep beneath the site, although it thickens rapidly where it crops out at the core of I an anticline 6 km southwest in the Paradox Valley. The Permian Cutler Formation, a sequence of continental clastics derived from the ancestral Uncompahgre highlands, is several kilometers thick beneath the site. The Triassic Moenkopi and Chinle Formations, both shallow water clastics with minor limestone, are separated from the Cutler Formation, and from each other, by !
unconformities. The Moenkopi and overlying Chinle are relatively thin in the site area (approximately 30 and 60 m, respectively), and only the Chinle has minor exposure. The Triassic Wingate Sandstone and Kayenta Formation (sandstone and siltstone) are conformable :
over the Chinle, are each about 60 m thick near Uravan, and likewise exposed only in deeply incised channels. The water table is near the Wingate-Kayenta boundary beneath the Upper Burbank cell. The Jurassic Navajo Sandstone conformably overlies the Kayenta Formation.
RAP Table 2.1 (Page A2-10; DOE,1998) states that this formation is not found at the site area, .
but is found in the western part of the site region. However, RAP Figure 3.2 (Site Area Geologic Map; DOE,1998), shows Navajo Sandstone exposed in the bottom of Hieroglyphic Canyon near the confluence with the San Miguel River, less than 2 km northeast of the Upper Burbank disposal cell l
NATURITA TER 2-2 APRIL 1999 i
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m FIGURE 2.1. STRATIGRAPHY OF THE UPPER BURBANK SITE.
NATURITA TER 2-3 APRIL 1999
7 Approximately 40 m of Jurassic Entrada Sandstone unconformably overlies the Navajo Sandstone. The Entrada forms steep slopes in the lower portions of Club Mesa. The Summerville Formation, a marine shale with siltstone, is conformable over the Entrada. This unit is about 30 m thick near the site, and it serves as an aquitard inhibiting vertical fluid transport. The Jurassic Morrison Formation, which serves as the cap rock of Club Mesa, overlies the Summerville Formation. The lower Salt Wash Member of the Morrison Formation is the host rock for the tailings cell. This highly competent, fluvial sandstone and siltstone unit is more than 100 m thick at Club Mesa. Immediately up-slope of the cell (southwest)is the base of the Brushy Basin Member of the Morrison Formation. Over 100 m of variegated shale, mudstone and sandstone of the Brushy Basin are present on Club Mesa. A remnant of the Cretaceous Burro Canyon Formation remains at the highest elevations of the rnesa, approximately 1.5 km west of the Upper Burbank cell. This remnant consists of approximately 50 m of fluvial sandstone overlain by shale-mudstone. Any Tertiar) units that may have been present in the site area have been removed by erosion.
NRC finds that DOE has sufficiently described the stratigraphy of the site area.
2.3.3 Structural Setting The site lies within the eastern portion of the Colorado Plateau, a relatively stable, intracontinental subpiate with greater crustal thickness than adjacent provinces. Two major shear zones were established in Precambrian time, and these features appear to exert some control on the Plateau features present today. The northwest-trending Olympic-Wichita Lineament extends from Washington to Oklahoma; the Uncompahgre uplift and Paradox Rasin lie within this trend. The northeast-trending Colorado Lineament extends from Arizona to Minnesota and may have some relation to localized northeast-trending areas of seismic activity in the Colorado Plateau (Bernreuter and others,1995). These broad lineaments intersect within the site region. The Colorado Lineament apparently served as a preferred pathway for Tertiary magmas as they intruded Mesozoic sediments. The Miocene faccolithic intrusions of the La Sal Mountains are in the junction zone of the Colorado and Olympic-Wichita lineaments. In addition, Abajo Mountain, a similar intrusion. is within the Colorado Lineament farther to the southwest.
Club Mesa exhibits two orthogonal fracture sets, northeast and northwest trending, but these are regional sets that are probably not related to the lineaments.
The site lies several kilometers northeast of the Paradox Valley anticline, which contains strata faulted and folded from salt diapirism and, perhaps, Leramide deformation. Some northwest-trending faults are associated with this anticline. Several kilometers northeast of the site is the Uncompahgre Plateau, which was uplifted along basement-rooted, steeply dipping, curved reverse faults (Ely and others,1986) during the Laramide Orogeny (Late Cretaceous to Eocene ,
time). These faults may be associated with shallow-rooted normal faults that compensate for curvature in the reverse faults as they plunge beneath the Precambrian core of the uplift. Some structures bounding the Plateau remain seismically active today, though possibly from reactivation as extensional structures. The bounding fault, labeled Fault 81 by Kirkham and Rogers (1981), has no historical seismicity, but was determined to be capable. This fault is responsible for the design earthquake of the Upper Burbank site (see TER Section 2.4.3).
NATURITA TER 2-4 APRIL 1999 l
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- I Club Mesa lies on the southwest limb of the northwest-trending Nucia syncline. This broad, shallow syncline lies between the salt-cored Paradox Valley anticline, the northeastern-most anticline of the Paradox Basin, and the faults and monoclinal folds marking the southwest margin of the Uncompahgre Plateau. The strata of Club Mesa dip homoclinally to the northeast at 1 to 3 degrees.
The staff finds that the structural setting has been adequately described.
2.3.4 Geomorphic Setting There is considerable topographic relief near the Upper Burbank site due to both tectonic up and erosional denudation processes. Between Uravan in the San Miguel Valley (about 1525 m elevation) and the crest of the Uncompahgre Plateau 20 km northeast (3000 m), there is n
' 1500 m of relief. The Upper Burbank cellis approximately 200 m above Uravan on the eastern
~
margin of Club Mesa, in a quarry into the Salt Wash Member of the Morrison Formation. Club Mesa is bounded on the north by the San Miguel River valley, the east by Hieroglyphic Can and the west by the Dolores River valley. The southwest margin of the mesa is marked by a tributary of the Dolores River. The mesa is approximately 4 km east to west and 5 km north to south. The mesa edges are generally steep, supported by the resistant Salt Wash Member and
. Entrada Sandstone. The site is drained by side drainages of Hieroglyphic Canyon.
Both the San Miguel and Dolores Rivers are undersized for their valleys, indicative of greater runoff during Pleistocene deglaciation. The braided channel patterns and wide valleys of these rivers contrast with the steep, narrow valleys of their tributaries and the dendritic drainages of tributary headwaters. Since Miocene time, the major geomorphic processes in the area have been incision and widening of major stream valleys. Valley widening occurs largely through scarp retreat. Mesa cliffs consist of resistant sandstones, and retreat occurs primarily by mass wasting of more erodible underlying units.
NRC considers that the RAP adequately describes the geomorphic setting.
2.3.5 Seismicity The Naturita site lies within the interior of the Colorado Plateau physiographic province. The site is subject to seismic events in the Colorado Plateau, the Plateau's more seismically active
' border zones, and the surrounding tectonic provinces The border zones are defined by Kirkham and Rogers (1981) based on structural boundaries and trends in seismicity. The Colorado Plateau is bounded on the south and west by the Basin and Range Province, the east by the Western Mountains Province, and the north by the Uinta-Eikhead and Wyoming Basin Provinces.
There is some debate about the precise geographic boundaries of the provinces and Plateau border zones, but there is little question that seismicity overall is greater around the margins than within in the Plateau (Kirkham and Rogers,1981). The interior of the Colorado Plateau is a region of relatively low seismicity; The closest areas of moderate seismicity are located at the boundaries of the Colorado Plateau with surrounding provinces. The largest historical event in j the Colorado Plateau west of the site was a 1988 magnitude 5.5 event near the Wasatch fault NATURITA TER 2-5 APRIL 1999
zone. At the northeast edge of the Colorado Plateau, the largest events were magnitude 5.3 {
and 5.4 earthquakes in 1969 and 1973. At the southeast edge of the Colorado Plateau, the largest events were two magnitude 5.1 earthquakes in 1966 and 1967, and at the southwest edge, the largest event was a 1959 magnitude 5-1/2 to 5-3/4 earthquake in northern Arizona.
Any characteristic seismic event in the Plateau boundaries or adjoining provinces would be too far away (>50 km) to adversely impact the site. Historical seismic records show less than a
. dozen earthquakes of magnitude 5 or greater within the Colorado Plateau, and all of these were proximal to the margins. An 1882 earthquake with magnitude estimated at 6.5 or greater may have been centered on the northeast margin of the Plateau (McGuire and others,1986), l although more recent evidence places the epicenter in the Colorado Front Range (Kirkham and Rogers,1986).
There are several regional structural features within the Colorado Plateau that contribute to the site's seismic hazard: the Colorado Lineament, the Paradox Valley fault system, and the j Uncompahgre uplift. Many small seismic events have c curred along specific segments of the Colorado Lineament in the past. However, these spatially limited earthquake swarms have differing characteristics, and, overall, the lineament does not appear to be a major seismogenic structure (Brill and Nuttli,1983). Bernreuter and others (1995) believe that a 50 km long basement fault ber,eath the Colorado River south of Moab, Utah, may be capable of an event as large as magnitude 7, but with very low probability. This section of the Colorado Lineament is more than 100 km west of the site. The staff notes that Section 2.10.2 of the RAP (DOE,1998) m:sinterprets Bernreuter and others, (1995) regarding the name of this seismic zone.
Bernreuter and others (1995) do not label this northeast-trending zone the Moab fault. Those authors recognize the Moab fault to be a northwest-trending structure most likely due to salt tectonics.
Ten to fifteen kilometers southwest of the site, the northeastern limb of the Paradox Valley anticline hosts several structures, one of which is a 62 km long fault labeled as Fault 90 by Kirkham and Rogers (1981). The RAP states that this and parallel faults of Paradox Valley are almost certainly underlain by structures related to evaporite flow or dissolution. Hunt (1969) and Cater (1970) are cited as support for this interpretation. The RAP states that, because of this relationship, the normal fault length-magnitude relationships do not apply; therefore, Fault 90 is interpreted to be capable of no more than a magnitude 3 event.
NRC requested additionalinformation to demonstrate that Fault 90 is rooted in the salt stratigraphy, and, thus, is capable of no more than a magnitude 3 event and exempt from standard fault length-magnitude relationships. The 1998 update to the RAP (pages A4-5 to A4-7) provided additionalinformation on faults associated with collapse of salt anticlines in the Paradox Basin and similar faults in other parts of the Colorado Plateau. The faults related to salt anticlines are not associated with the underlying tectonic system and the ages of movement on faults related to salt flow is pre-Quaternary. Thus, these faults are not capable. Similar faults associated with salt structures in the Paradox Basin were investigated for the Stick Rock UMTRCA Title I site (NRC,1996). In their review of the Slick Rock site, the NRC staff concluded that these collapse-induced faults are considered non-tectonic since they result from down-dropping sedimentary rocks that overlie areas of salt removed by flow and dissolution. The observed seismicity associated with salt flowage is magnitude 3 or less and, thus, not significant NATURITA TER 2-6 APRIL 1999
4 compared to the' design earthquake at the Naturita site (magnitude 6.9 at a distance of 15 km from the site). The tectonic character of Fault 90 is now a closed issue.
Steeply dipping faults associated with the Uncompahgre uplift approach the site as close as 15 km, and at least one of these faults appears to be historically seismogenic. In 1985, an event of magnitude 2.9 centered 55 km north-northwest of the site may have occurred along the steeply northeast-dipping Granite Creek fault (Ely and othere,1986). There is some question whether
= movement of the Uncompahgre uplift is continuing to occur or whether this seismicity results from reactivation of reverse faults as extensional features. Cater (1966) states that the uplift continues today; however, Ely and others (1986) believe that the 1985 event was extensional.
The Uncompahgre-related structure that passes 15 km from the site is called Fault 81 by Kirkham and Rogers (1981). Cater (1970) found this fault to have Quaternary offset, so it is '!
Lconsidered to be capable. With a length of 34 km and possibly capable of a magnitude 6.9 event, this is the design fault for the site.
NRC concludes that DOE presents adequate information on the historical seismic events of the Colorado Plateau and surrounding areas of interest.
2.3.6 Natural Resources
' The site region contains natural resources of oil, natural gas, uranium, vanadium, coal, and potash; the immediate area features abundant uranium and vanadium. Deposits of these minerals are concentrated in the Salt Wash Mcmber of the Morrison Formation, which is the disposal cell host rock. However, boreholes surrounding the site indicate no economic deposits !
beneath the tailings cell (Umetco and Peel,1994). Economic deposits of oil or gas are very unlikely, as the site lies near the axis of a low, broad syncline. No faults that may serve as hydrocarbon traps are close to the site. Large oil and gas deposits in the area are generally associated with the salt anticlines of the Paradox Basin to the southwest. Potash is mined from the Paradox Salt Member of the Pennsylvanian Hermosa Formation; although, the only current production is more than 100 km from the site. Any deposits near the site are likely too deep to be. economically viable. The Dakota Sandstone contains coal deposits in the region, but this unit has been eroded from Club Mesa. Mining occurs in the San Juan Mountains to the southeast, but mining in that area is in igneous units that are not present in the site area. NRC finds the RAP adequately describes natural resources in the area, 2.4 Geolooic Suitability in an effort to provide reasonable assurance that radiological barriers will remain intact for at least 200 years,' and up to 1000 years to the extent achievable, the RAP provides information on the bedrock, geomorphic, and seismic stability of the site.
{
2.4.1 Bedrock Stability
- The Upper Burbank cell is an excavation entirely within the Salt Wash Member of the Morrison Formation, a competent sandstone and siltstone unit. Thirty-five meters of the Salt Wash unit lies between the base of the cell and the underlying Summerville Formation; no soillies beneath !
the cell. Rock durability studies (Umetco,1995) suggest that portions of the Salt Wash Member l
)
- NATURITA TER - 2-7 APRIL 1999 l
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f I are the most erosionally resistant horizons in the local stratigraphic column, one indication of l stability. The Salt Wash is moderately fractured in vertical, orthogonal northeast- and northwest-trending sets, with average spacing approximately 1 meter. The Summerville Formation is an effective aquitard beneath the Salt Wash Member. Water originally within the tailings cells northeast of the Upper Burbank cell has caused a zone of perched raffinate to form on top of the Summerville, but this is down-dip and down-gradient of the Upper Burbank cell. The low dip of the contact, the thickness of the overlying Salt Wash Member, and the coherent elastic strength l
of layers and their interfaces indicate that slip along the Salt Wash-Summerville contact plane is virtually impossible, even with the addition of a perched water table. The closest mapped faults related to the salt anticline and collapse structures of the Paradox Valley are 4 km from the site.
Therefore, the cell is not at risk of displacement due to fault offset.
The staff considers that the RAP adequately addresses the topic of bedrock stability.
2.4.2 Geomorphic Stability Given~the location of the Upper Burbank cell on Club Mesa, the cell has potential for destabilization by mesa scarp retreat. Scarps at the edge of Hieroglyphic Canyon and San Miguel River valley will continue to retreat, but long-term erosion rates are low. The San Miguel )
River appears to be presently incising its channel from Jravan several miles downstream, and, ;
at the same time, it is either aggrading or migrating across its flood plain upstream of Uravan. l The channelincision is not expected to exceed the maximum average rate of 0.4 m per thousand years (Hunt,1956; Yeend,1969; Larson and others,1975) for the Colorado River system in the Colorado Plateau. The San Miguel River tributaries, such as Hieroglyphic Canyon, are also unlikely to exceed this rate. Canyon widening (scarp retreat) may occur at a !
rate 3 times that of incision, or up to 1.2 m/1000 years. Mass wasting of large fracture-bounded blocks can lead to high rates of scarp retreat, but the absence of large block accumulations or conical colluvium mounds at scarp bases in the area, as well as the smoothness of canyon walls, indicates that this is not a concern. Moreover, scarp retreat rates on the order of 1 m/1000 years in the site area have been documented by dating packrat middens and applying other geochronologic methods (Smith,1980). NRO concludes that scarp retreat of San Miguel River valley and Hieroglyphic Canyon does not pose a threat to the site during cell fife.
Headward erosion by Hieroglyphic Canyon tributaries that drain the site will not affect the cell, because it will sit 230 m from the canyon rim. Runoff from the mesa surface up-slope of the cell will be redirected to avoid the cell This is discussed further in TER Section 4.4.
The site is not at nsk from debris flows, soil creep, rock falls, or eolian processes. No large eolian features, such as dunes or sand ramps, are apparent in the area; although, such features are not specifically addressed in the RAP. Subsidence from salt dissolution is not a hazard in the immediate vicinity, as any evaporites that may underlie the site are interpreted to be 2-3 km deep and relatively thin. The area has extensive uranium and vanadium deposits, but boreholes indicate no economic deposits beneath the Upper Burbank site. None of the many mine adits on Club Mesa pass beneath the cell. The site is subject to ash fall from very large volcanic eruptions in the Western United States, but the probability of such an event occurring over the lifetime of the cellis negligible.
NATURITA TER 2-8 APRIL 1999 e
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I The RAP presents sufficient evidence that Club Mesa and the tailings cell will be geomorphically ]
stable far beyond the 1000-year performance period.
2.4.3 Seismotectonic Stability The Club Mesa site is subject to ground motion from seismicity on faults associated with the Uncompahgre uplift, as well as floating earthquakes in the Colorado Plateau, and seismicity loc'ated within the Colorado Lineament. Seismicity along the southwest margin of the i Uncompahgre uplift appears to present the greatest hazard to the site.
The RAP identifies Fault 81 of Kirkham and Rogers (1981) along the Uncompahgre margin as the controlling fault for seismic hazard at the Upper Burbank site. Although this fault shows no historical seismicity, it has Quaternary offset based on geomorphic relationships observed in Unaweep Canyon (Cater,1970). The fault is 34 km Icng, passing within 14.9 km of the cell.
The RAP states that this fault is capable of a magnitude 6.9 earthquake based on the fault length-mgnituue relationship of Bonilla and others (1984). The precise dip is unknown, but the fault is suspected to be steeply dipping. Section 4.2.7 of the RAP states that a magnitude 6.9 event from Fault 81 at 14.9 km would produce a peak horizontal ground acceleration (PHA) of 0.28 g at the site using the attenuation' relationship of Campbell and Bozorgnia (1994). DOE stated in the RAP that 0.28g is the median vane from ttis 1994 attenuation model.
The SRP for Title I sites (NRC,1993) states that the 84th percentile ground motion value from ,
the Campbell (1981) model could be adopted as the design value. This level of ground motion l
was chosen because of the limited number of accelerograms available at that time to develop attenuation relationships. Since 1981, updated ground motion attenuation relationships have been published based on more accelerograms, thus, providing confidence that the 50*
percentile (median) value of ground motion is acceptable. In addition, a recent staff analysis of the risk associated with uranium recovery facilities led the staff to conclude that because of the relatively low risk posed by tailings piles, the choice of ground motion level at the 84th percentile is too conservative. For these reasons, the recent draft SRP for Title 11 sites (NRC,1999) found that an acceptable level of design for UMTRCA sites is the 50* percentile (median) value of ground motion. Thus, the RAP value of 0.28g is adequate for the design acceleration. !
The RAP uses 6.2 as the maximum magnitude for a floating earthquake in the site area.
Magnitude 6.2 has been used at other UMTRCA Title i sites within the Colorado Plateau, such as Slick Rock and Mexican Hat This maximum magnitude is conservative because it is larger than the historical earthquakes associated with the Colorado Plateau province. PHA calculations for a floating earthquake assume an epicentral distance of 15 km, so the site ground motions from the floating earthquake PHA are below the design ground motion from Fault 81.
Seismic zones within the Colorado Lineament may be capable of generating events as large as magnitude 7 with low probability (Bernreuter and others,1995), but the distance of such zones from the site exceed 100 km. Therefore, site ground motions resulting from such events are also well below the design ground motion for the site.
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The staff concludes that a magnitude 6.9 earthquake associated with Fault 81and at a distance of 14.9 km from the site is a conservative maximum earthquake for the site.
2.5 Conclusions Based on a review of the RAP (DOE,1998) and additional material, NRC finds that the geology and geologic stability of the Upper Burbank disposal cell have been adequately characterized.
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NATURITA TER -- 2-10 APRIL 1999
3.0 GEOTECHNICAL STABILITY 3.1 Ir.coduction This section presents the results of the NRC staff review of the geotechnical engineering aspects of the proposed remedial actions at the Naturita, Colorado, UMTRA Project site, as detailed in DOE's RAP (DOE,1998a and 1998b) and Remedial Action inspection Plan (RAIP, l MK-F,1998). . The remedial action consists of the removal of all remaining contaminated i materials from the processing site to the Upper Burbank disposal cell 13 road miles northwest of the Naturita processing site.
1 The disposal cell will be below-grade and will provide for the segregation of the Title I material from other radioactive material at Uravan. Contaminated material will be consolidated and ;
encapsulated in the cell and will be covered by a 3-foot-thick compacted earth radon / infiltration barrier, a 5.5-foot-thick compacted carth frost barrier, a 0.5-foot-thick bedding layer, and a 1-foot-thick rock riprap layer. TI,a geotechnical engineering aspects reviewed include: l (1) information related to the processing, disposal, and borrow sites; (2) materials associated with the remedial action, including the foundation and excavation materials, building debris, and other contaminated materials; and (3) design and construction details related to the disposal site, disposal cell, and its cover. The staff review of related geologic aspects such as l stratigraphic, structural, geomorphic, and seismic characterization of the site is presented in Section 2.0 of this report.
3.2 Site and Material Characterization !
3.2.1 Site Descriptio.ns !
l 3.2.1.1 Processing Site 4
The processing site (Figure 1.2) is located in Montrose County, Colorado, on Highway 141, two miles northeast of the town of Naturita. The Natunta processing site includes the following features: (1) the abandoned Naturita mill yard; (2) the former tailings pile area that is located on the floodplain of the San Miguel River between Highway 141 to the west and the San Miguel River to the east; and (3) the former ore storage area located to the west of Highway 141.
During 1976-77, the tailings at the Naturita processing site were transported for further processing to the Durita Facility heap leach plant. Although the Naturita processing site no longer has a tailings pile, the site has 400,000+ cubic yards (cy) of residual contamination that is distributed approximately as follows:
Contaminated soil (389,000 cy)
Stockpiled demolition debris (8,300 cy)
Stockpiled vicinity property (VP) materials (3,000 cy)
- Stockpiled drums (55 gal) containing processing waste petroleum products (72 cy)
Stockpiled bags (approx 18 cu ft ea) with asbestos-containing materials (665 cy)
NATURITA TER 3-1 APRIL 1999
s DOE reports that actual quantities could vary from those tabulated above.
3.2.1.2 Disposal Site at Uravan The Upper Burbank disposal site at Uravan is about 13 road miles northwest of the Naturita i processing site (Figure 1.1). The embankment will be located slightly to the south of a drainage I divide, and it will be necessary to accommodate only minor amounts of offsite runon plus the runoff from the surface of the disposal cell. The disposal cell will cover approximately 10 acres !
and will be designed to contain from 500,000 to 800,000 cy of contaminated materials. The actual cell size will depend on the extent of contaminated materials excavated during construction. The top slopes of the embankment will range from 2 to 4 percent, and the i
sideslopes will be SH:1V. The disposal cell configuration is shown in Figure 1.4 and cross '
sections through the cell are shown in Figure 1.5.
The Upper Burbank Repository is located in the northwestern part of the Upper Burbank Quarry, and is entirely underlain by sandstone and shale of the Salt Wash Member of the Morrison Formation. See Section 2.3.2 of this TER for a more detailed description of the stratigraphic setting.
3.2.1.3 Borrow Materials Site The borrow material for the radon barrier and frost protection layer will be obtained from the Upper Club Mesa borrow site, which is approximately 1500 feet northwest of the Upper Burbank disposal site.
3.2.2 Site Investigations Geotechnical investigation and site characterization programs were performed at the mill site, the disposal site, and the borrow site. Data obtained during the characterization programs were reported in Appendix D to the RAP (DOE,1998b).
The scope of the geotechnicalinvestigations included excavating test pits and drilling boreholes.
Information from several monitor well installations was also utilized. Borings and test pits were logged by a field engineer or geologist. The locations of test pits, boreholes, and monitor wells were given in the RAPS. Subsurface investigations for material properties of the underlying soil at the processing site were carried out in conjunction with the investigation to define the limits of contamination. The resulting samples of site materials were tested and analyzed in the laboratory to evaluate the engineering characteristics of the materials.
Test pits were excavated with a backhoe. Bulk soil samples were collected from the pits.
Individual borehole logs provide detailed information about the drilling methods used. Generally, hollow-stem augers (6.5-inch) were used until refusal; thereafter, a rotary bit (4.0 inches) and casing were used to bedrock. Three sampling methods were used: (1) the Standard Penetration test; (2) a 2.42-inch inside diameter, ring-lined, split-barrel sampler; and (3) a 3.0-inch diameter, thin-walled Shelby tube.
NATURITA TER 3-2 APRIL 1999
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The available data obtained from the field investigations and laboratory tests were used to construct stratigraphic sections and to define the engineering parameters of the soils to be incorporated into the cell.
3.2.3 Upper Burbank Disposal Site Stratigraphy The Upper Burbank disposal cellis on a bedrock bench approximately 600 feet above the San Miguel River. The bedrock beneath the disposal cell consists of sandstone of the Salt Wash Member. The bedrock at the site is reported to be stable, and the sandstones at the contact between the Salt Wash Member and the Summerville Formation are reported to be dry.
Additional stratigraphic information and a column are found in Section 2.3.2 of the TER.
The staff has reviewed the details of the test pits and borings, as well as the scope of the overall geotechnical exploration program discussed in Section 3.2.2 above. The staff concludes that the geotechnicalinvestigations conducted at the Naturita processing and Upper Burbank disposal sites, and at the Upper Club Mesa borrow site, adequately establish the stratigraphy I and the soil conditions, generally conform with applicable provisions of Chapter 2 of the SRP (NRC,1993), and adequately support the assessment of geotechnical stability of the stabilized contaminated materialin the disposal cell.
3.2.4 Testing Program l The materials at the three sites were classified according to the Unified Soil Classification {
system (ASTM D-2487). Atterberg limits (ASTM D-4318) and gradation tests (ASTM D-422) I were performed on selected samples to classify the soils. In addition, the following tests were conducted; specific gravity (ASTM D-854), compaction (ASTM D-698), saturated and I unsaturated hydraulic conductivity, consolidation (ASTM D-2435), shear strength (EM 1110 1906), radon barrier erodibility (Crumb test, STP 623; dispersion, ASTM D-4221; and pinhnle, STP 623), capillary-moisture relations (ASTM D-3152), and erosion barrier durability. The results of the individual tests completed to date are included in the RAP.
The testing program for the processing, disposal, and borrow sites was consistent with the needs of the proposed remedial action; representative samples of construction materials and samples of geotechnical materials that may affect or be affected by the remedial action were tested. The number of samples tested is considered sufficient to support the necessary geotechnical analyses desenbed in subsequent sections. In particular, the testing approach is consistent with the NRC SRP and the DOE Technical Approach Document (DOE,1989).
Samples were tested in accordance with standard procedures, and quality assurance and quality control were performed in accordance with standard UMTRA Project procedures.
Therefore, Open item No. 2, regarding testing of the Club Mesa soils, is closed.
3.3 Geotechnical Enoineerina Evaluation 3.3.1 Slope Stability Evaluation The staff has reviewed the exploration data, test results, critical slope characteristics, and methods of analyses pertinent to the slope stability aspects of the remedial action plan for the NATURITA TER 3-3 APRIL 1999
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Naturita UMTRA Project disposal embankment. The analyzed cross-section with the longest 5 horizontal to 1 vertical sideslope has been compared with the exploration records and the design details. .The staff finds that the most critical slope wcti: has been considered for the stability ana!ysis.
l Soil parameters for the various materials in the stabilized embankment slope have been adequately established by appropriate testing of representative material. Values of parameters for other earthen materials have been assigned on the basis of data obtained from geotechnical explorations at the site and data published in the literature.
DOE has proposed applying a peak horizontal ground acceleration (PHA) of 0.289 as discussed in Section 2.4.3. For a PHA of less than 0.39, staff finds that the DOE evaluation has employed the appropriate methods of stability analysis (Bishop's Simplified Method, Ordinary Fellenius Method, Janbu's Simplified Method, and Spencer's Method) and has addressed the likely adverse conditions to which the slope may be subjected.
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Factors of safety against failure of the slope for seismic loading conditions and static loading conditions were evaluated conservatively for both the short-term (end-of-construction) and long-term state on the basis of a PHA equal to 0.3g. The values of the seismic coefficients used in the pseudo-static analysis are 0.20g for the long-term condition and 0.15 9 for the short-term condition. The staff finds that the use of the pseudo-static method of analysis for seismic stability of the slopes is acceptable considering the flatness of the slopes and the conservatism in the soil parameter values, if the PHA is less than or equal to 0.3g. The minimum factors of safety against failure of the slope were 2.19 and 1.22 for the short-term static and pseudo-static conditions, respectively, compared to required minimums of 1.3 and 1.0, respectively. The minimum factors of safety against failure of the slope were 3.58 and 1.73 for the long-term static and pseudo-static conditions, respectively, compared to accepted minimums of 1.5 and 1.0, respectively. The analyses appear to have been made in a manner consistent with Chapter 2 of the NRC SRP. Open issue No. 3 is closed with the satisfactory selection of the design PHA.
3.3.2 Settlement and Cover Cracking The staff has reviewed the analysis of total and differential settlement of the disposal cell and foundation materials and the resulting potential for cracking of the radon barrier. Calculations indicate that all settlement due to placement of the relocated contaminated materials, radon barrier, frost protection layer, and erosion protection will include immediate (elastic) and secondary (creep) components. The foundation is assumed to be incompressible, because it will consist of competent bedrock.
Fifteen point locations on section A-A' and 13 point locations on section B B' (Figures 1B and 28, Appendix D, DOE,1995) were selected for settlement analysis for both 500,000 and 800,000 cu yd cover options. The staff agrees that appropriate sec+ ions have been chosen to assess the most critical conditions for differential settlement. Calculated settlements along the profiles varied from 3 inches to 9.5 inches (section A-A') and 7.5 inches to 10.5 inches (section B B') for the 500,000 cy cover, with resulting maximum local slopes of 0.005 and 0.0075, respectively, Calculated settlements along the profiles varied from 4 inches to 21 inches NATURITA TER. 3-4 APRIL 1999
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, o-(section A-A') and 3 inches to 21 inches (section B-B') for the 800.000 cy cover, with resulting maximum local slopes of 0.007 and 0.014, respectively.
The maximum tensile strain was determined to be 0.00054 (section A-A') and 0.00020 (section B-B') for the 500,000 cy cover option, and 0.000068 (section A-A') and 2.3 x 10-2 (section B-B')
for the 800,000 cy cover option. The calculated tensile failure strain for the proposed radon barrier material (Pl=30) was 0.14 percent.
DOE has concluded that total and differential settlement of the materials comprising the proposed disposal cell will not have an adverse effect on the ability of the cell to meet the stability standards. The staff agrees that settlement generally will be small due to the compaction of the materials in the cell and the granular nature of much of the material. In addition, differential settlement should not cause ponding concerns due to the sloping configuration of the cell, and cracking of the cover due to settlement should not occur because the resulting maximum strain is well below the calculated tensile failure strain.
3.3.3 Liquefaction The staff has reviewed the information presented on the potential for liquefaction at the site based on the results of geotechnicalinvestigationt., including boring and test pit togs, test data, soil profiles, and other information. ' The soils in the disposal cell will be compacted to a minimum of 90 percent of maximum Standard Proctor density (ASTM D-698) and will be in an unsaturated condition; therefore, the disposal cell is not considered susceptible to liquefaction.
The groundwater table at the site is substantially below the base of the disposal embankment.
The foundation beneath the disposal cell is stable bedrock and, thus, not susceptible to
- liquefaction. Because of the absence of water and liquehable soil, there is no potential for liquefaction of material within or beneath the disposal cell and, therefore, applicable provisions of Chapter 2 of the NRC SRP have been mot.
3.3.4 Cover Design The cover system will provide a total of 10 feet of protection over the contaminated material and collectively is designed to limit infiltration of precipitation, protect the pile from erosion, and control the release of radon from the cell. In addition to the discussion of the cover presented in this section of t!)e TER, details of the staff review of the cover's performance related to erosion protection features are presented in Section 4.0 of this document; the review of the cover's performance related to limiting infiltration is presented in Section 5.0; and the review of the radon attenuation aspects of the cover is presented in Section 6.0.
The RAP (DOE,1998a and 1998b) indicates that the radon / infiltration barrier will consist of compacted, silty-to-clayey soil that will limit infiltration and inhibit radon emanation. The gradation requirements call for a minimum of 50 percent by weight passing the No. 200 sieve.
Testing has indicated that the borrow soil should generally meet the requirements, and that inspection procedures will verify gradation. Test results indicate that radon / infiltration barrier material, when compacted to at least 95 percent of maximum dry density (ASTM D-698), will produce a laboratory-saturated permeability on the order of 104 cm/sec.
NATURITA TER 3-5 APRIL 1999
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The frost protection layer will consist of materials excavated from the Club Mesa borrow area.
DOE has evaluated the frost depth using the BERGGREN. BAS computer code developed at the U.S. Army Corps of Engineers (COE,1968). This code has been used fc' cther UMTRA sites.
The total worst-case 200-year frost penetration depth at the disposal site is calculated to be 44.1
' inches. The cover design provides for the appropriate depth by the total thickness of riprap (12 inches), bedding (6 inches),'and frost protection layer (60 inches) above the radon barrier. The staff has reviewed the input data used in determining the total frost penetration dept _h, and concluded that these values are a reasonable representation of the extreme site conditions to be 3 expected in a period of 200 years. Because DOE's calculation was based on the 200-year rather than the 1000-ycar frost depth, actual frost penetration is likely to be somewhat in excess of the stated values. NRC staff accepts this approach for the Naturita site because the additional frost penetration, if it were to occur, would not adversely affect the stability of the cell.
The RAP indicates that the layer immediately above the frost protection layer is to be a 6-inch-thick bedding / drain layer, intended to drain water laterally off the cell and protect the radon barrier from the riprap. Details of the review of the erosion protection design are found in Section 4.0 of this report. '
The cover design has been evaluated by NRC staff for geotechnical long-term stability, and, for these aspects, the design is acceptable. ;
i 3.4 Geotechnical Construction Details )
3.4.1 Construction Methods and Features The staff has reviewed and evaluated the geotechnical construction criteria provided in Appendices D and G to the RAP (DOE,1998b). Design calculations and construction requirements were based on achieving 95 percent of standard compaction for the radon barrier soils. The staff concludes that the plans and drawings clearly convey the proposed remedial action design features. In addition, the excavation and placement methods and specifications represent accepted standard practice. Therefore, the staff concludes that Open issue No. 4 was satisfactorily addressed in the final specifications.
' 3.4.2 Testing and inspection
. An up-to-date version of the RAIP and specifications were reviewed for consistency, and found to be satisfactory; therefore, Open Issue No. 6 is closed. Potential problems in the compaction of Fat CLAY (CH) soils were also addressed in the specifications, thus, Open issue No. 5 is
' closed.
3.5 Conclusions Based on the review of the design and the geotechnical engineering aspects of the proposed remedial action as presented in the Naturita preliminary final RAP and supporting documents, NRC staff has been provided with reasonable assurance that the long-term stability aspects of
. the EPA standards will be met.
NATURITA TER . 3-6 APRIL 1999
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4.0 SURFACE WATER HYDROLOGY AND EROSION PROTECTION j 4.1 Hydroloaic Description and Site Conceptual Desian DOE proposes to move. contaminated material from the Natunta, Colorado, processing site to ,
the Upper Burbank disposal area at the Uravan site. Small localized drainage areas exist !
upland of the Upper Burbank site and will contribute flood flows that must be diverted around the i disposal cell. Several gullies exist in the immediate site area upstream and downstream of the site.
In order to comply with EPA standards that require stability of the tallings for 1000 years to the ;
extent reasonably achievable and, in any case, for at least 200 years, DOE proposes to stabilize
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the contaminated materials in an engineered disposal cell to protect them from flooding and erosion. The design basis events for design of the erosion protection included the Probable Maximum Precipitation (PMP) and the Probable Maximum Flood (PMF) events, both of which are considered to have low probabilities of occurrence during the 1000-year stabilization period.
As proposed by DOE, the tailings will be consolidated into a below-grade disposal cell that will )
' be protected by a rock cover. The rock cover will have a maximum slope of 2-4% on the top ;
slopes and 20% on the side slopes. The disposal cell will be surrounded by channeb that will 1 safely convey flood runoff away from the cell. In addition, an interceptor channel, north of the ce!I, will be constructed to divert flood flows from the upland drainage area away from the disposal cell. l The upland drainage areas around the cell have short, steep slopes and scattered, steep gullies.
Some of these slopes have competent rock exposed on the surface. These slopes and gullies will discharge flows directly into the diversion channels surrounding the cell and will require the use of upstream rock aprons to protect against erosion.
4.2 Floodina Determinations The computation of peak flood discharges for various design features at the site was performed by DOE in several steps. These steps included: (1) selection of a design rainfall event;
'2) determination of infiltration losses; (3) determination of times of concentration; and (4) determination of appropriate rainfall distributions corresponding to the computed times of concentration. Input parameters were derived from each of these steps and were then used to determine the peak flood discharges to be used in water surface profile modeling and in the final determination of rock sizes for erosion protection. !
4.2.1 Selection of Design Rainfall Event One of the most disruptive phenomena affecting long-term stability is surface water erosion.
DOE has recognized that it is very important to select an appropriately conservative rainfall event on which to base the flood protection designs. DOE has concluded and the NRC staff concurs (NRC,1990) that the selection of a design flood event should not be based on the extrapolation of limited historical flood data, due to the unknown level of accuracy associated_
with such extrapolations. Rather, DOE utilized the PMP, which is computed by deterministic NATURITA TER 4-1 APRIL 1999
methods (rather than statistical methods), and is based on site-specific hydrometeorological characteristics. The PMP has been defined as the most severe reasonably possible rainfall event that could occur as a result of a combination of the most severe meteorological conditions
, occurring over a watershed. No recurrence intervalis normally assigned to the PMP; however,
- DOE and NRC staff have concluded that the probability of such an event being equaled or exceeded during the 1000-year stability period is small. Therefore, the PMP is considered by NRC staff to provide an acceptable design basis.
Prior to determining the runoff from the drainage basin, the flooding analysis requires the determination of PMP amounts for the specific site location. Techniques for determining the PMP have been developed for the entire United States primarily by the National Oceanic and Atmospheric Administration (NOAA) in the form of hydrometeorological reports for specific regions. These techniques are widely used and provide straightforward procedures with j minimal variability. The staff, therefore, concludes that use of these reports to derive PMP ;
estimates is acceptable. I A PMP rainfall depth of approximately 8.2 inches in 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> was used by DOE to compute the ;
PMF discharges for the small drainage areas at the disposal site. This rainfall estimate was j developed by DOE using Hydrometeorological Report (HMR) 49 (NOAA,1977). The staff j
.~ performed an inoependent check of the PMP value based on the procedures given in HMR 49. i Based on this check of the rainfall computations, the staff concludes that the PMP was i acceptably derived for this site.
4.2.2 Infiltration Losses l Determination of the peak runoff rate is dependent on the amount of precipitation that infiltrates into the ground during the occurrence of the rainfall. If the ground is saturated from previous rains, very little of the rainfall will infiltrate, and most of it will become surface runoff. The loss rate is highly variable, depending on the vegetation and soil characteristics of the watershed.
Typically, all runoff models incorporate a variable runoff coefficient or variable runoff rates.
Commonly-used models, such as the U.S. Bureau of Reclamation Rational Formula (USBR, 1977), incorporate a runoff coefficient (C), where a C value of 1 represents 100% runoff and no infiltration. Other models, such as the COE Flood Hydrograph Package HEC-1, separately l compute infiltration losses within a certain period of time to arrive at a runoff amount during that time period.
- In computing the peak flow rate for the design of the rock riprap erosion protection at the disposal site, DOE used the Rational Formula (USBR,1977). In this formula, the runoff coefficient was assumed by DOE to be unity; that is, DOE assumed that no infiltration would occur. Based on a review of the' computations, the staff concludes that this is a very conservative assumption and is, therefore, acceptable.
4.2.3 Times of Concentration The time of concentration is the amount of time required for runoff to reach the outlet of a drainage basin from the most remete point in that basin. The peak runoff for a given drainage basin is inversely proportional to the time of concentration. If the time of concentration is NATURITA TER 4-2 APRIL 1999 p
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computed to be small, the peak discharge will be conservatively large. Times of concentration and/or lag times are typically computed using empirical relationships such as those developed by Federal agencies (USBR,1977). Velocity-based approaches are also used when accurate estimates are needed. ' Such approaches rely on estimates of actual flow velocities to determine the time of concentration of a drainage basin.
Various timee,'of concentration for the riprap design were estimated by DOE using the Kirpich Method (USBR,1977). This velocity-based method is considered by the staff to be appropriate l
. for estimating times of concentration. , Based on the precision and conservatism associated with this method, the staff concludes that the times of concentration have been acceptably derived.
The staff further concludes that the procedures used for computing the times of concentration are representative of the small, steep drainage areas present at the site.
4.2.4 Rainfall Distributions I
After the PMP is determined, it is necessary to determine the rainfall intensities corresponding'to shofter rainfall durations and times of concentration. A typical PMP value is derived for periods of about 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />. If the time of concentration is less than 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, it is necessary to extrapolate the data presented in the various hydrometeorological reports to shorter time periods. DOE utilized a procedure recommended in HMR 49 and by the NRC staff (NRC,1990). This procedure involves the determination of rainfall amounts as a percentage of the 1-hour PMP and computes rainfall amounts and intensities for very short periods of time. DOE and NRC staff have concluded that this procedure is conservative.
in the determination of peak flood flows, approximate PMP rainfall intensities were derived by DOE as follows:
1 1
Rainfall Duration Rainfall intensity l (minutes) - (inches /hr) 2.5 54.0 5.0 44.0 l 15.0 24.0 l 60.0 8.2 1
The staff checked the rainfall intensities for the short durations associated with small drainage ;
basins. Based on a review of this aspect of the flooding determination, the staff concludes that the. computed peak rainfall intensities are conservative. '
. - l 4.2.5 Computation of PMF l l
4.2.5.1 Top and Side Slopes The PMF was estimated for the top and side slopes using the Rational Formula (USBR,1977),
which provides a standard method for estimating flood discharges for small drainage areas. For i a maximum top slope length of 600 feet, DOE estimated the peak flow rate to be about 0.66 '
cubic feet per second per foot of width (cfs/ft). For an additional side slope length of 80 feet and ;
NATURITA TER 4-3 APRIL 1999 i
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a flow concentration factor of 2, DOE estimated tne peak flow rate to be 1.1 cfs/ft. Although other slope lengths and configurations produce lower peak discharges, DOE adopted the most conservative flow rates for design purposes. Based on staff review of the calculations, the estimates are considered to be acceptable.
4.2.5.2 Aprons The side slopes of the cell discharge directly into diversion channels. Therefore, no aprons are required downstream of the side slopes. However, aprons are required at severallocations upstream of the cell and channels to prevent erosion. The aprons are needed where steep, natural side slopes discharge concentrated flows into the diversion channels.
DOE compuied peak PMF flow rates for the upstream aprons using assumptions of concentrated flow, based on the topography immediately upstream of the cell. Several natural gullies exist and will further concentrate flood flows. Because the shear stresses produced in a gully are !ikely to exceed the flow depths produced by uniform flow spreading across a plane surface, DOE considered such flow concentrations in the analysis. Staff review of these flow computations indicate that the analyses are acceptable, and Open issue No. 7 is closed. 1 4.2.5.3 Diversion Channels Diversion channels are provided to intercept and divert runoff from the upland drainage areas on all sides of the cell. Channels 1,2, and 3 will be constructed in a horseshoe shape around the !
cell. An interceptor channel will be constructed north of the cell to intercept runoff before it reaches the other diversion channels or the cell area.
In the PMF analysis, HEC-1 was used to compute peak flow rates at different locations in the i channels. Based on a check of the calculations of drainage area, time of concentration, and i rainfallintensity, the staff concludes that the PMF estimates are acceptable. ;
4.3 Mfater Surface Profiles and Channel Velocities Following the determination of the peak flood discharge, it is necessary to determine the resulting water levels, velocities, and shear stresses associated with that discharge. These parameters then provide the basis for the determination of the required riprap size and layer thickness needed to ensure stability during the occurrence of the design event.
4.3.1 Top and Side Slopes in determining riprap requirements for the top and side slopes, DOE utilized the Safety Factors Method (Stevens, and others,1976) and the Ctephenson Method (Stephenson,1979),
respectively. The Safety Factors Method is used for relatively flat slopes of less than 10 percent, the Stephenson Method is used for slopes greater than 10 percent. The validity of these design approaches has been verified by the NRC staff through the use of fiume tests at Colorado State University. It was determined that the selection of an appropriate design procedure depends on the magnitude of the slope (Abt and others,1987). The staff, therefore, NATURITA TER 4-4 APRIL 1999
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concludes that the procedures and design approaches used by DOE are acceptable and reflect state-of-the art methods for designing riprap erosion protection 4.3.2 Upstream Aprons DOE has adequately addressed the design of the upstream apron by:
- 1. providing riprap of adequate size to be stable against concentrated flows associated with the design storm (PMP);
I 2.~ . providing uniform and/or gentle grades along the apron and the adjacent ground surface such that runoff into the diversion channels is distributed uniformly at a relatively low velocity, minimizing the potential for flow concentration and erosion; and
- 3. providing an adequate apron thic'tness and depth to prevent undercutting.
The rock for the aprons will consist of oversized sandstone blocks. DOE provided a design that incorporated the concepts discussed above. The rock was sized (actually oversized) based on the occurrence of concentrated flows, using shear stress methods, as recommended by the staff. Additional discussion of the riprap design of the upstream apron can be found in Section 4.4.1.2, below.
4.3.3 Diversion Channe!s The COE HEC-2 and normal depth computations were used to estimate depths and velocities under the estimated discharge conditions in the channels. The Safety Factors Method was used to determine riprap sizes for the ditch. Based on staff review of the calculations, the analysis is
- acceptable. Additional, detailed information related to the design of erosion protection for the I
ditches may be found in Section 4.4, below.
4.4 Erosion Protection 4.4.1 Sizing of Erosion Protection Riprap layers of various sizes and thicknesses are proposed for use at the site. The design of each layer is dependent on its location and purpose. Riprap of the following types, sizes, and layer thicknesses are proposed for use at the site:
Type- Average Size Layer Thickness (inches) (inches)
Type A 1.5 12 Type B 5.6 12 Type B1 - 7.0 15 Sandstone 21-36 Varies NATURITA TER 4-5 APRIL 1999 i
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! J-l 4.4.1.1 Top and Side Slopes l
The riprap on the top slope has been sized to withstand the erosive velocities resulting from an i l on-cell PMP, as discussed above. DOE proposes to use a 1.0-foot-thick layer of Type A rock with a minimum D50 of 1.5 inches. The riprap will be placed on a 0.5-foot-thick bedding layer, j The Safety Factors Method was used to determine the rock size.
The rock layer on the side slopes is also designed for an occurrence of the local PMP. DOE proposes to use a 1.0-foot-thick layer of Type B rock with a minimum D50 of approximately 5.6 l I
inches.1 The rock layer will be placed on a 0.5-foot-thick bedding layer. Stephenson's Method was used to determine the required rock size. Conservative values were used for the specific gravity of the rock, the rock angle of internal friction, and porosity.
Based on staff review of the DOE analyses and the acceptability of using design methods recommended by the NRC staff, as discussed in Section 4.3 of this report, the staff concludes '
that the proposed rock sizes are adequate.
4.4.1.2. Upstream Aprons Riprap sizes for the aprons were computed using acceptable assumptions of concentrated sheet flow and gully flows _ DOE cc rectly evaluated the potential for high velocity flows from upstream drainage areas to impact the apron and will place oversized sandstone rocks to dissipate the energy. The required size of the rock varies from 21 to 36 inches, and DOE will use sizes that are even larger than the required size. Staff review indicates that the rock sizes are conservative, and, therefore, acceptable.
4'4.1.3 Diversion Channels The design of the diversion channels was analyzed by DOE in the following areas:
- 1. design of the side slopes for concentrated flows entering the channel from the upland drainage area; 2f design for runoff directly through the channel;
- 3. design of channel outlets; and 4.' ' sediment considerations. l 4.4.1.3.1 Channel Side Slopes Type B and Type B1 riprap layers are proposed for a substantiallength of the ditch. The design g
of the ditch side slopes considered the effe'cts of PMF sheet flows directly down the proposed ;
L 'sid_e slopes from the upland drainage areas. Using the Stephenson Method for the 1V on 5H i ditch side slope, the required D50 was found to be less than the size proposed. The staff concludes that the proposed rip-rap is conservative and isc therefore, acceptable.
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.4.4.1.3.2 Channels (Main Section)
For flows directly through the channels, the Safety Factors Method was used to determine the
! rock sizes. Based on a review of the calculations, the proposed riprap layers are considered to be adequate.
4.4.1.3.3 Channel Outlets The channel outlets generally will be constructed in competent rock, in several areas, DOE will provide oversized sandstone blocks to form the outlet of the channels where discharge to natural ground occurs. .Therefore, no erosion or headcutting is expected to occur. Based on direct site observations and review of the construction drawings, the staff concludes that flows discharging from the diversion channels will not adversely affect the Title ll cell and will be safely discharged from the site. DOE has acceptably located the outlets of the channel and has
' provided an acceptable design to account for. flows that could potentially impact the Title il cell.
Therefore, the staff concludes that Open issue No. 8 is closed.
4.4.1.3.4 Sediment Censiderations In general, sediment deposition can be a problem in diversion ditches when the slope of the diversion ditch is less than the slope of the natural ground where flows enter the ditch. It is
. usually necessary to ptovide sufficient slope and capacity in the diversion ditch to flush or store any sediments that will enter the ditch.: In particular, significant design. features may be !
necessary in areas where natural gullies are intercepted by the diversion ditchc Concentrated flows and high velocities could transport large quantities of sediment, and the size of the particles transported by the natural gully may be larger than the man-made diversion ditch can effectively flush.
For this site, a considerable amount of sediment from the upland draiasge area can be expected to enter the diversion ditch, for the following reasons:
- 1. The upland drainage areas have steep slopes, whereas, the diversion channels have been designed with relatively flat slopes. Flow velocities in the ditches may not be as high as those occumng on the natural ground. Therefore, sediment, cobbles, and boulders may be transported to the ditch and may not be easily flushed by the lower velocities in the ditch.
2.- The potential for gully development (and resulting high flow velocities) in the upland drainage area and subsequent transport of bed-load materialinto the diversion channels is high. Based on review of topographic maps of the area and a staff site visit to the area, gullies and areas of flow concentration are evident upstream of the diversion channels.
Flows moving toward the diversion channels will tend to concentrate in these gullies, increasing the potential for gully incision and transport of sediment.
To document the acceptability of the channel design, DOE demonstrated that: (1) the channels
. will have some sediment-carrying capacityL(2) potential sediment deposition in the channels will
- NATURITA TER _4-7 APRll1999 l
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l not significantly affect the flow capacity; (3) any blockages in the channels will not have an adverse effect on the stability of the contaminated tailings; and (4) the riprap in the channels provides adequate protection.
First, DOE provided analyses that indicated that the channels wil! be able to flush out much of the sediment. Using storm events of various magnitudes, DOE calculated the velocities needed l
to transport materials of various sizes. DOE determined that the slopes of the channels are sufficient to transport much of the deposited materials during most flood events.
Second, DOE estimated the amount of sediment that will be deposited. DOE determined that the channels will have adequate flow capacity, even if a significant amount of blockage occurs.
Based on review of the sediment analyses provided by DOE, the staff considers that sediment accumulations in the diversion channels have been adequately addressed. As discussed above, acceptable analyses of the effects of sediment buildup in the channels have been provided. Therefore, the staff concludes that Open issue No. 9 is closed.
4.4.2 Rock Durability EPA standards require that control of residual radioact.ve materials be effective for up to 1000 j years, to the extent reasonably achievable, and, in any case. for at least 200 years. The previous sections of this report examined the ability of the erosion protection to withstand flooding events reasonably expected to occur in 1000 years. In this section, rock durability is considered to determine if there is reasonable assurance that the rock itself will survive and remain effective for 1000 years.
Rock durability is defined as the ability of a material to withstand the forces of weathering.
Factors that affect rock durability are: (1) chemical reactions with water; (2) saturation time; (3) temperature of the water; (4) scour by sediments; (5) windblown scour; (6) wetting and drying; and (7) freezing and thawing.
DOE identified several sources of rock in the immediate site vicinity. The suitability of these rocks as a protective cover was then assessed by laboratory tests to determine the physical characteristics. DOE conducted the tests and used the results of these tests to classify the !
rock's quality and to assess the expected long-term performance of the rock. In accordance 1 with past DOE rock-testing practice, the tests included:
- 1. Petrographic Examination (ASTM C295). Petrographic examination of rock is used to determine its physical and chemical properties. The examination establishes if the rock l contains chemically unstable minerals or volumetrically unstable materials.
- 2. Bulk Specific Gravity (ASTM C127). The specific gravity of a rock is an indicator of its j strength or durability. In general, the higher the specific gravity is, the better the quality of l the rock. -
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- 3. Absorption (ASTM C127). A low absorption is a desirable property and indicates slow I disintegration of the rock by salt action and mineral hydration. !
NATURITA TER 4-8 APRIL 1999
- 4. Suifate Soundness (ASTM C88). In locations subject to fmezing or exposure to salt water, a low percentage is desirable.
- 5. Schmidt Rebound Hammer. This test measures the hardness of a rock and can be used l in either the field or the laboratory.
- 6. Los Angeles Abrasion (ASTM C131 or C535). This test is a measure of rock's resistance l to abrasion. I
- 7. Tensile Strength (ASTM D3967 or ISRM Method). This test is an indirect test of a rock's tensile strength.
DOE then used a step-by-step procedure for evaluating durability of the rock, in accordance with procedures recomrnended by the NRC staff (NRC.1990), as follows:
i Step 1. Test results from representative samples are scored on a scale of 0 to 10. I Results of 8 to 10 are considered " good"; results of 5 to 8 are considered " fair", ;
and results of 0 to 5 are considered " poor." !
Step 2. The score is multiplied by a weighting factor. The effect of the weighting factor is l to focus the scoring on those tests that are the most applicable for the particular i rock type being tested. I 1
Step 3. The weighted scores are totaled, divided by the maximum possible score, and multiplied by 100 to determine the rating. l Step 4. .The rock quality scores are then compared to the criteria that determines its I acceptability, as defined in the NRC scoring procedures. j in accordance with the procedures suggested by the staff, DOE determined from preliminary testing that the rock proposed for the disposal site scored above 80. The staff concludes that the rock will be of sufficient quality to meet EPA standards.
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4.4.3 Testing and inspection of Erosion Protection DOE provided a detailed inspection and testing program for the selection and placement of rock in the RAIP. The staff evaluated these testing and inspection quality control requirements for the erosion protection materials and concludes that the proposed testing program is acceptable.
For the large blocks of sandstone to be used, DOE applied additional testing and inspection procedures to ensure the quality of each large rock. Each piece was inspected by a trained geologist, who verified that:
- 1. The sandstones were fine-grained and cemented with quartz. ,
NATURITA TER 4-9 APRIL 1999
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.'2l -)The rock porosity was low with few fractures that would increase the potential for freeze-thaw processes to affect the rock.
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- 3. There were no significant joints, fractures, partings, or seams that would induce ice wedging.
- 4. The sandstone was derived from massive, bedded formations, reducing the potential for significant bedding planes.
' Based on staff review of the over$11 testing and inspection plan for all types of rocks that were
- produced and placed, the staff concludes that the program is acceptable.
4.5' Uostream Dam Failures
. There are no impoundments near the site whose failure could potentially affect the site.
4.6 Conclusions Based on review of the information submitted by DOE NRC staff concludes that the site design
( :.:will meet EPA requirements as stated in 40 CFR 192 with regard to flood design measures and erosion protection. The staff concludes that an adequate hydraulic design has been provided to reasonably assure stability of the contaminated material at the disposal site for a period of 1000
. years, or in any case, at least 200 years.
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L 5.0 WATER RESOURCES PROTECTION 5.1 Introductio_D !
I The Natunta processing site is located in the San Miguel River Valley and is underlain by unconsolidated alluvial floodplain deposits and fill material. The alluvium is the upper-most ,
aquifer at the processing site and is contaminated from former processing-site activities. The (
alluvium is underlain by the Brushy Basin and the Salt Wash Members of the Morrison Formation. The Brushy Basin consists of interbedded shale, sandstone, and conglomerate lenses. The Salt Wash consists predominantly of sandstone with some shale. The Brushy
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Basin and the Salt Wash have not been affected by uranium processing activities. Existing groundwater contamination does not presently represent a risk to human health or the environment.
However, DOE is required to demonstrate that cleanup or control of existing processing-related groundwater contamination at the Naturita site will comply with the EPA groundwater protection standards in Subpart B of 40 CFR Part 192. Groundwater cleanup at the fermer processing site will be addressed under a separate DOE program and a National Environmental Policy Act process, using strategies and options outlined in a programmatic environmentalimpact statement that has been developed for the.UMTRA Project. The need for and extent of groundwater cleanup at the Naturita site will be evaluated based on the extent of existing contamination, the potential for current or future groundwater use from the uppermost aquifer, and protection of human health and the environment.
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At the Upper Burbank Disposal site, DOE must comply with the final standards (40 CFR 192.20) issued by the EPA on January 11,1995. From a review of the information submitted; it appears that the site will comply with the requirements of Subpart A of the EPA groundwater protection ;
standards. However, the NRC staff has yet to reach a determination on the long-term !
surveillance plan, which the DOE has not yet submitted to the NRC.
I 5.2 Hydrooeoloaic Characterization-5.2.1 Identification of Hydrogeologic Units !
l A. Processing Site At the Naturita processing site; unconfined groundwater occurs within the alluvial flood plain deposits from 3 to 18 ft (0.9 to 5.5 m) below the land surface. The saturated thickness is approximately 15 ft (4.6 m) in the vicinity of the site. The next deepest aquifer at the site is the ,
Salt Wash Member of the Morrison formation, which consists predominantly of sandstone with 2 some shale. The Salt Wash aquifer is separated from the alluvial aquifer by the Brushy Basin
- l. Member of the Morrison formation. Under the site, the Brushy Basin Member is considered an aquitard and consists of thick, laterally extensive, interbedded shales with some sandstones. It ,
ranges in thickness from 110 to 165 ft (33.5 to 50.3 m). The top of the Salt Wash aquifer is '
i approximately 130 to 165 ft (39.6 to 50.3 m) below land surface near the site. The total i thickness of the Sait !Nash aquifer has not been determined, but is at least 80 ft (24.4 m) thick in i the vicinity of the processing site.
1 NATURITA TER 5-1 APRIL 1999 u
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B. Disposal Site Five principal hydrostratigraphic units occur within the upper 800 ft (240 m) of sediments beneath the disposal site From the land surface down, these are: (1) sandstones and shales l of the Salt Wash Munber of the Morrison Formation; (2) shales and siltstones of the l Summerville Formation; (3) sandstone of the Entrada; (4) sandstones of the Kayenta; and (5) sandstones of the Wingate Formation.
l The Salt Wash Member directly underlies the disposa# site and has a thickness of about 120 ft (37 m). This unit is predominantly comprised of sandstone with some interbedded shale layers.
The Summerville Formation underlies the Salt Wash Member. This unit is considered an aquitard and is 90 ft (27 m) thick. It is composed of massive clayey muastones, silty shales, clayey siltstones, and minor, interbedded sandstones. The Entrada Formation underlies the ;
Summerville Formation and has a thickness of approximately 160 ft (49 m). The Summerville Formation is a sandstone. Underneath the Summerville formation is the Kayenta Formation, which has a thickness of approximately 180 ft (95 m). This formation consists of interbedded layers of sandstone, siltstone, shale, and some conglomerate. Below the Kayenta Formation is the Wingate Formation. This formation is about 250 ft (76 m) thick and is a sandstone. The Kayenta Formation together with the 'Ningate Formatic n form the first saturated aquifer beneath the disposal site.
l Below the Wingate Formation is the Chinle Formation. The Chinle Formation is about 400 ft ;
(120 m) thick and is predominantly a siltstone. Because of it's low permeability, the Chinle '
Formation acts as an aquitard to vertical groundwater movement.
5.2.2 Hydraulic and Transport Properties A. Processing Site The occurrence of shallow groundwater in the alluvial aquifer is limited by the lateral extent of the alluvium in the vicinity of the Natunta processing site. The average hydraulic conductivity for the alluvial aquifer is 3.0 ft/ day (0.001 cm/sec) and the average linear groundwater velocity is 0.06 ft per day (2x10'5 cm/sec). The groundwater flow direction in the alluvium is subparallel (northwest) to the San Miguel River. Groundwater from the alluvial aquifer discharges into the San Miguel River northwest of the site.
The Salt Wash aquifer is a major regional groundwater system in the area. The potential area of natural discharge from the Salt Wash aquifer is the San Miguel River northwest of the processing site. For the Salt Wash aquifer, hydraulic conductivities averaged 0.06 ft/ day (2x10-5 cm/sec) and the average linear groundwater velocity is estimated to be 0.002 ft/ day (7x104 cm/sec). The Salt Wash aquifer is separated from the alluvial aquifer by the Brushy Basin Member, which locally is considered an aquitard. Groundwater in the Salt Wash aquifer is confined, and has a potentiometric surface that is higher in elevation than the water table in the alluvial aquifer. Therefore, if any significant flow were to occur between the Salt Wash aquifer and the alluvial aquifer, water movement would be upwards from the Salt Wash aquifer through the Brushy Basin Member and into the alluvial aquifer.
NATURITA TER 5-2 APRIL 1999
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'B. Disposal Site
= The disposal site is underlain by approximately 600 ft (180 m) of unsaturated sandstone.
l siltstone, and shale. The Summerville Formation, composed of shale and siltstone, is about 120 ft (37 m) below the site and has a hydraulic conductivity of less than 0.01 ft/yr
, , (1.0x104 cm/sec). This 90 ft (27m) thick layer functions as an aquitard and should prevent any i potential groundwater contamination from the disposal site from reaching the Kayenta/Wingate l - aquifer. '
The Kayenja/Wingate Formation is the uppermost aquifer beneath the disposal site. Only the Kayenta/Wingate aquifer is saturated beneath the disposal site. The aquifer is unconfined and at a depth of approximately 600 ft (180 m). Average hydraulic conductivity of the Wingate formation is 0.12 ft/ day (4.2x104 cm/sec). Groundwater flow beneath the repository is toward
. the north at velocity of about 8 ftlyr. Primary recharge to the Kayenta/Wingate aquifer is -
l northeast of the San Miguel River along the Uncompahgre Plateau. Secondary recharge to the ,
Wingate portion of the aquifer is from the Paradox Valley south of the site. Discharge from the !
aquifer is to the San Miguel River. -
l 5.2.3 Extent of Contamination A. Processing Site '
To determine whether uranium processing activities at the Naturita processing site have i influenced groundwater quality in the alluvial aquifer, DOE collected samples from on-site and ;
down gradient monitor wells and analyzed these samples for the constituents (including lead, nitrate, and silver) listed in Table 1 to Subpart A and Appendix I of 40 CFR Part 192. Based on this analysis, arsenic, cadmium, chromium, fluoride, methylene chloride, molybdenum, selenium, strontium, thallium, tin, toluene, uranium and vanadium, radium-226 and -228, and gross alpha may be contaminants in the alluvial aquifer groundwater. Of these constituents; arsenic,
' cadmium, molybdenum, selenium, uranium, radium-226 and -228, and gross alpha were found to exceed the EPA maximum concentration limits. Based on uranium concentrations, a contaminant plume extends at least 1500 ft (460 m) down gradient from the former mill yard and has a maximum width of approximately 900 ft (275 m). Contaminated groundwater from the j alluvial aquifer discharges into the San Miguel River, where no impacts on the river water quality
, have been observed to date.
Groundwater in the Salt Wash aquifer was found to not be contaminated as a result of milling operations at the processing site..
l B. Disposal Site Groundwater at the disposal site is presently uncontaminated by the disposal of contaminated i l material.'
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i 5.2.4 Water Use 1
A. Processing Site Eight wells are located within 2 miles (3.2 kilometers) of the processing site. Water from these wells are used for domestic purposes. Five of these wells are located up gradient from the processing site (four obtain water from the alluvial aquifer and one from the Salt Wash aquifer).
. The two remaining wells are located down gradient of the site, but are located on the opposite side of the river. There should be no threat to up gradient wells from contaminated groundwater from the processing site in the alluvial aquifer as groundwater flow is in the opposite direction from these wells Groundwater pollution in the alluvial aquifer should not be a threat to down gradient wells because the river represents a discharge point for the alluvial aquifer. Since l these wells are located on the other side of the river, groundwater contamination in the alluvial aquifer should not reach them. Therefore, the staff concludes that Open issue No.12 is closed.
No impacts to groundwater have been observed or are expected in the Salt Wash aquifer from the processing site. No impacts to surface water quality have been observed from contaminated alluvial groundwater at the site.
Future use of groundwater in the alluvium for domestic consumption is not expected. This is because the alluvial aquifer has a very low potential for use as a source of water, since it is limited to the small area of alluvium in and adjacent to the San Miguel River. Alternative supplies of reliable, good-quality water are available frorn +'e town of Naturita, from surface water, and from c.eeper groundwater aquifers.
B. Disposal Site Four wells produce groundwater within two miles (3.2 kilometers) of the disposal site. All of l these wells are owned by Umetco Minerals Corporation. These wells are no longer being used and will be piugged prior to deeding the land in and around Uravan to the federal government.
Five additional wells are within a radius of five miles from the site. All of these wells are l up gradient of the disposal site and, therefore, cannot be impacted by the site. Future use of groundwater beneath the Upper Burbank site is timited by the poor water quality and low permeability of the Wingate Formation and significant depth [600 ft (180 m)] to groundwater. In the future, land will be deeded to the federal government, which will limit the development of groundwater resources by the general public.
4 There are no agricultural or domestic surface-water users within a 2-mile (3.2-kilometer) radius of the site. Umetco Minerals Corporation does have water rights on the San Miguel River for industrial uses. Within a 5-mile (8-kilometer) radius of the site, water use is limited to springs used for stock water. The closest spring used for stock watering is located about 4 miles (6 kilometers) northeast of the site.
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5.3 Conceptual Qgsian Features to Protect Water Resources A. Processing Site I
- Groundwater contamination does not represent a risk to human health or the environment l
because there is currently no consumption of the contaminated groundwater in the alluvial aquifer. The distribution of hazardous constituents in groundwater will decrease with time, l
' because contaminated materialis being moved off site to another location and because the l
alluvial aquifer discharges to the San Miguel River. This means that existing contamination in i alluvial aquifer groundwater will eventually be flushed out of the aquifer and diluted by the water in the San Miguel River. Groundwater cleanup at the former processing site will be addressed under a separate DOE program and a National Environmental Policy Act process, using !
strategies and options outlined in a programmatic environmental impact statement that has been l developed for the UMTRA Project B. Disposal Site l l
The climate in the vicinity of the disposal site is semiarid. Under natural conditions deep percolation at the disposal site is less than 0.01 ft eft2 /yr and may for all practicable purposes be zero The lack of a perched zone under the disposal site and the lack of springs and seeps along the canyon walls further indicate that the site has a very low infiltration rate. The disposal '
site was modeled by DOE to determine possible infiltration rates after cover construction.
Modeling results suggest a very low infiltration rate of about 0.028 ft /ft2 /yr through the cover.
This infiltration rate equates to a flow of approximately 0.1 gpm (9660 ft'/yr) through the base of ;
the 8-acre disposal cell. This indicates that very little deep percolation should occur underneath the disposal cell. Travel time for liquid from the base of the disposal cell through the Summerville Formation was calculated to be in excess of 1,000 years.
The residual radioactive materials that will be disposed of at the site are principally contaminated ;
soils. The contamination of these soils should be relatively low due to the mixing of the original tailings materials with surficial soils. Batch tests performed on this soil material confirm that this material has relatively low concentrations of radionuclides and heavy metals. Geochemical attenuation of any leachate from the disposal site would occur as contaminated water flows through the bedrock formation.
5.4 pisposa! and Control of Residual Radioactive Materials 5.4.1 Water Resources Protection Standards For the Disposal Site The EPA groundwater standards (40 CFR 192.02) require three basic elements for setting the groundwater protection standards. These are: (1) determination of hazardous constituents; (2) proposal of a concentration limit for each hazardous constituent found to exist in the tailings or leachate; and (3) specification o' the point of compliance. The DOE analyzed groundwater samples from the alluvial aquifer beneath the Naturita processing site and conducted laboratory batch leach tests of contaminated soil material from the Naturita processing site. Based on these tests, DOE identified 25 hazardous water quality parameters that are reasonably expected NATURITA TER 5-5 APRIL 1999
to be in or derived from residual radioactive matenal to be disposed of at the site. These
. parameters were selected to be monitored at the point of compliance and are presented in Table 5-1. For these parameters, the DOE has established concentration limits (Table 5-1). The proposed concentration limits are either the maximum concentration limit or, for those hazardous constituents without maximum concentration limits, the statistical maximum of background groundwater quality derived from water samples collected from Wingate wells CM93-1 and CM93-2. Concentration limits for strontium and tin will be determined by routine sampling of CM 93-1 and CM 93-2 during long-term site surveillance activities. Since DOE will sample for many other parameters other than tin and strontium, the ground-water protection program should detect any potential contamination in tne ground water from the disposal site, during the period when tin and strontium concentration limits are being established.
Wingate well CM93-2 is designated as the point of compliance for the disposal site. This wellis i
immediately down gradient of the disposal cell. !
l 5.4.2 Performance Assessment for the Disposal Site DOE must demonstrate that the performance of the disposal unit will comply with EPA's groundwater protection standards in 40 CFR 192 Subparts A and C. The disposal cell design should minimize and control releases of hazardous constituents to groundwater and surface water to the extent necessary to protect human health. The following are important to performance of the disposal site: ;
- 1. The uppermost aquifer, the Wingate Formation, lies approximately 600 ft (180 m) below the base of the disposal cell and is hydrogeologically isolated from surface l recharge or initial transient drainage from the dicposal cell by low permeability shales and mudstones overlying the aquifer.
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- 2. The Summerville Formation, the principal aquitard beneath the site, is approximately 90 ft (27 m) thick and effectively isolates groundwater in the underlying Kayenta/Wingate aquifer from potential contaminants in the disposal cell.
- 3. Geochemical properties of the bedrock materials attenuate hazardous constituents possibly associated with leaching of the residual radioactivo materials.
- 4. The multi-layered cover reduces the infiltration rate and minimizes long-term seepage from the cell.
- 5. The disposal cell will be contoured to provide efficient drainage of precipitation away from the disposal cell and to minimize excess moisture in the cover and associated infiltration.
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5.4.3 Closure Performance Demonstration for the Disposal Si'a DOE must demonstrate that the proposed disposal design will: (1) minimize and control groundwater contamination; (2) minimize the need for further maintenance; and (3) meet initial performance standards of the design, in accordance with the closure performance standards of 40 CFR 192.02. The disposal cell design uses a multi-layered cover to reduce the infiltration rate and minimize long-term seepage from the cell. The disposal cell will be contoured to provide efficient drainage of precipitation away from the disposal cell and to minimize excess moisture in the cover and associated infiltration. In addition, natural stable material will be used in constructing the disposal cell to minimize the need for further maintenance.
5.4.4 Groundwater Monitoring and Corrective Action Plan at the Disposal Site The DOE is required by 40 CFR 192.03 to implement groundwater monitoring during the
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post-disposal period for the purpose of demonstrating that the disposal cell will perform in l accordance with the design. The regulation 40 CFR 192.04 requires the implementation of a corrective action program if the monitoring shows an exceedance of concentration limits. The ;
monitoring plan required under 40 CFR 192.03 should be designed to include verification of the !
' site-specific assumptions used to project the disposal system performance. Prevention of groundwater contamination may be assessed by indirect methods, such as measuring the moisture migration within various components of the cover, tailings, or beneath the tailings, as well as direct groundwater monitoring.
At the disposal site, DOE will monitor potential repository seepage using wells at the contact of the Salt Wash and Summerville Formations near the disposal cell for a period of time following completion of remedial action. Monitoring any perched groundwater on the top of the Summerville from the disposal cellincludes well BR951, BR95-2, and BR95-3. If seepage is detected in these monitor wells, performance monitoring of wells CM93-1 and CM93-2 will be conducted.
5.5 Clean-uo and Control of Existino Contamination at the Processina Site The DOE is required to demonstrate that cleanup or control of existing processing-related groundwater contamination at the Naturita site will comply with the EPA grouldwater protection standards in Subpart 8 of 40 CFR Part 192. Groundwater cleanup at the former processing site will be addressed under a separate DOE program and a National Environmental Policy Act process, using strategies and options outlined in a programmatic environmental impact statement that has been developed for the UMTRA Project. The need for and extent of groundwater cleanup at the Naturita site will be evaluated based on the extent of existing contamination, the potential for current or future use of groundwater from the uppermost aquifer, and protection of human health and the environment.
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The staff concludes that the proposed semedial action for the Naturita sites will acceptably comply with the EPA groundwater standards;with the exception of the following open issues (Nos 13 and 18) that may be deferred until the groundwater cleanup phase of the project.
-40 CFR 192, Subparts B and C at the Naturita processing site (deferral provided by the UMTRCA amendment of 1982).
2.- DOE must provide the details of its groundwater monitoring program (sampling frequency, etc.) for the disposal site to demonstrate compliance with 40 CFR 192.03.
This information can be included when DOE submits the long-term surveillance plan i to the NRC for review.
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[ , e Tablo 5-1 Hazardous Constituents and Concentration Limits for the Disposal Site Constituent Concentration Limit Aluminum 0.1 mg/L (background)
~ Antimony . 0.1 mg/L (background)
Arsenic 0.05 mg/L (maximum concentration limit)
' Barium - 1.0 mg/L (maximum concentration limit)
Beryllium 0.05 mg/L (background)
Cadmium 0.01 mg/L (maximum concentration limit)
Chromium 0.05 mg/L (maximum concentration limit)
Copper 0.02 mg/L (background)
Cyanide - 0.01 mg/L (background)
Fluoride 5.9 mg/L (background)
Gross alpha (excluding uranium and radon) 44.7 pCi/L (background)
Lead 0.05 mg/L (maximum concentration limit)
Mercury 0.002 mg/L (maximum concentration limit)
Molybdenum 0.1 mg/L (maximum concentration limit) ,
Nickel 0.05 mg!L (background)
Nitrate (as N) - 10 mg/L (maximum concentration limit) 1 Radium 226 and -228 5.0 pCi/L (maximum concentration limit)
Selenium .
0.01 mg/L (maximum concentration limit)
Silver 0.05 mg/L (maximum concentration limit)
Strontium 0.1 mg/L (background)
Thallium 0.01 mg/L (background) l Tin 0.005 mg/L (background)
Uranium 0.044 mg/L (maximum concentration limit)
Vanadium 0.05 mg/L (background) l Zinc 15.5 mg/L (background) l NATURITA TER 5-9 APRIL 1999 l
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6.0 RADON ATTENUATION AND SITE CLEANUP 6.1 Introduction This section of the TER documents the staff evaluation of the radon attenuation design for the disposal cell and the processing site cleanup plan for the remedial action at the Natunta, Colorado, UMTRA Project site (DOE,1998a and 1998b). The evaluation includes review of the material characterization, radon barrier design, site radiological characterization, proposed remedial actions, and site cleanup verification plan to ensure compliance with the applicable EPA standards. The review followed the NRC SRP for UMTRCA Title i sites (NRC,1993).
6.2 Radon Attenuation To meet the EPA standards for long-term control of radiation and limiting release of radon from residual radioactive materials to the atmosphere, the contaminated material will be relocated to the Upper Burbank disposal site at Uravan, Colorado, and covered with the following layers:
3-foot radon barrier, 5.5-foot frost protection, 6-inch bedding, and 12-inch riprap. The radon barrier layer of the cover has been designed to limit the long-term average release of radon from the disposal cell to meet the EPA flux standard of 20 pCi/m 2/s and to attain released radon levels as low as reasonably achievable (ALARA).
Because radon (Rn-222) is a gas with a short half-life (3.8 days), the amount of radon from uranium mill tailings reaching the atmosphere is reduced by restricting the gas movement long enough so that radon decays to a solid daughter that remains within the disposal cell. The physical and radiological parameters influencing the amount of radon available to the soil pore spaces and its movement are incorporated into a computer code. The staff evaluated the estimation of the long-term (at least 200 years) average (over the entire cell surface, over at least 1 year) radon flux from the disposal cell cover by utilizing the RADON computer code.
Most of the code input values are parameter values derived during characterization of the various materials that will make up the cell and/or based on conservative estimates. The combination of input parameter values and underlying assumptions comprise the radon flux model. Staff also reviewed the construction specifications for materials placement for consistency with the radon flux model assumptions (material sequence and compaction) and evaluated the other layers of the cover for their ability to protect the radon barrier layer from drying, natural weathering, and biointrusion.
An' additional aspect of the staff review considered that the radon barrier layer is also designed to satisfy criteria for construction and infiltration of surface water. In addition, the potential for cracking of the barrier layer due to settlement or heaving within the cell and the potential for freeze-thaw and erosional damage to the cover were evaluated. These aspects of the cell .
design are evaluated in Sections 3 and 4 of this TER. '
6.2.1 Evaluation of Parameter Values The staff's review addressed the adequacy of the parameter values (i.e., code input) by evaluating the justification or assumptions made for each value to confirm that each value was representative of the material or a conservative estimate, consistent with site construction NATURITA TER 6-1 APRIL 1999
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l specifications, and based on long-term conditions. Design parameters of the contaminated and barrier materials that were evaluated include: material placeme sequence; layer thickness; bulk density; specific gravity; porosity; long-term moisture content; and radon diffusion coefficient. In addition, the radium concentration and radon emanation fraction of the contaminated materials were evaluated. The sampling and testing methods for the materials were also reviewed to determine their appropriateness and to ensure that the data were adequate.
6.2.1.1 Contaminated Materials Although the Naturita processing site no longer held a tailings pile, areas of the site contain residual contamination. These areas are:
- 1. former tailings pile area (27 acres, at the lowest elevation)
- 2. mill yard and ore buying station (14 acres, on higher terrace)
- 3. ore storage area (12 acro, west of Highway 141)
- 4. windblown / waterborne materials (196 acres)
The volume of contaminated material is esRnated 'o be 548,000 cubic yards (cy), including approximately 8000 cy of processing site det.r;s to be placed in the disposal cell. Approval of the application of supplemental standards (no remedial action) associated with the processing site proposed by DOE will reduce the volume of disposed material by approximately 147,000 cy of mainly windblown material. The proposed application of supplemental standards is discussed in Section 6.3.3 and the impact of its approval and implementation on the radon barrier analysis is discussed in Section 6.2.2.
The disposal cell design indicates that contaminated material from the mill yard (includes retention basin and ditch soils, vicinity property materials, demolition debris, and ore buying station) and cre storage area will be placed at the bottom of the cell and covered by soil from the former tailings pile area. Windblown material will be placed last (DOE,1995; Figure 1.6, Page 1-10). The windblown material comprises approximately 39 percent of the material to be disposed, if the supplemental standards application for the processing site is approved, and 55 percent, if the application is not approved (DOE calculation 17-737-01-02).
Radon model parameter values for the contaminated material were derived from DOE (1995)
RAP calculation 17-741-02. Most of these values were determined from laboratory testing performed on material compacted to 90 percent (Standard Proctor), as the material is to be placed in the cell at this level of compaction. Staff is concerned that some of the contaminated material parameter values are based on limited testing or non-conservative estimates.
However, staff's concern is mitigated by the proposed thickness of the radon barrier and frost protection layers of the cell cover, so that the contaminated material parameter values are not an issue (see Section 6.2.2 of this TER). For documentation purposes, the evaluation of each parameter value follows.
Average maximum dry density and specific gravity measurements for each material type was used to calculate porosity. The values for mill yard and ore storage area materials were NATURITA TER 6-2 APRIL 1999
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1 combined (volume weighted), because these materials will be combined during placement in the cell. The resulting parameter values (below) are acceptable to staff.
Material Densitv* # Tests Spec. Gravity # Tests Porosity i i
mill yard / -
ore storage 1.60 11 2.69 10 .40
. tailings area 1.61- 9- 2.63 7 .39 windblown 1.51 11 2.58 6 .42
- g/cc
_ at 90 percent compaction The long-term moisture content parameter value of each material was based on the average of minus 15-bar capillary moisture test ret ults. The tailings pile area (five samples) averaged 5.1 percent by weight moisture, mill yarJ material averaged (five samples) 10.8 percent, one ore 4 storage sample yielded 11.1 percen'., and windblown material (four samples) averaged 13.0 percent. The high moisture value (cr windblown soilis considered reasonable because of the high clay content (3 samples averaged 26 percent) of the material. To be conservative, staff used a windblown material moisture value of 9.0 percent in its radon model.
A single soil sample each from the mill yard, ore storage, and windblown contaminated material was measured for radon diffJsion coefficient. Each sample was tested at five different moisture contents and a best fit curve prepared. The diffusion coefficient value corresponding to the-estimated long-term moisture 'of the material was selected. An average radon diffusion coefficient of 0.0188 cm 2/s represents the mill yard / ore storage layer in the cell and 0.0136 cm2/s was derived for the windblown material. A value of 0.025 cm 2/s was estimated for the tailings ]
pile area.- Because of the limited data, staff used the more conservative code-calculated diffusion coefficient value for windblown material (0.031 cm'/s) in its modeling.
Twelve radon emanation fraction measurements on contaminated material ranged from 0.06 to
. 0.35. The volume weighted average emanation fraction for the mill yard / ore storage soils (four samples each) was 0.33, and for windblown material (four samples) the value was 0.22. No tests were performed on former pile area soil, so the mill yard / ore storage value was assumed to l be representative of this material. These_ values appear reasonable, but staff utilized more conservative values in its model.
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' DOE determined the Ra-226 content of the contaminated materials primarily by gamma spectroscopyo incremental Ra-226 depth profiles were constructed for each measurement grid
- point. :The average Ra-226 concentration was determined for each subarea by integrating the profiles over the. volume, based on the excavation depth. Based on these data, volume-weighted average Ra-226 concentrations were calculated for each layer in the disposal cell as i follows!
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Area Ra 221(pCi/a) # Samolej Volume (x1000 cv) Thickness (cm)
Mill Ys $ debris / 78 Ore Storage 133 27 134.6 119',122 tailings pile 90 56 116.1 113
. Windblown 38 281 294.1 171',402
('if supplemental standards applied)
Higher Ra-226 values than the average measured values were modeled. A value of 59.5 pCi/g was used for windblown material and 94.1 pCi/g for former tailings pile soil. This approach is conservative and, therefore, is acceptable to staff.
6.2.1.2 Radon Barrier The parameter values for the radon barrier matenal were selected based on the results of laboratory testing of samples from the Club Mesa borrow site.
The summary table of geotechnical design parameters in the RAP (DOE,1998) calculation 010 (sheet 8), indicates that radon barrier material has an average of 50 percent fines. However, the construction specifications do not contain a requirernent for a minimum percent fines (material passing the No. 200 sieve) for radon barrier soil, although calculation 006 (sheet 107) indicates that the radon barrier soil will have a minimum of 50 percent fines. In addition, the actual material tested contained an average of 86 percent and a minimum of 80 percent fines (calculation 006 sheet 108).
Barrier material was tested at 95 percent compaction, but will be placed at 100 percent ,
according to the design and construction specifications. The moisture test value derived from material at the lower compaction may not be conservative for the radon flux model moisture parameter, because the looser soil would hold more water. Therefore, staff modified the value :
for this parameter in its flux model.
The density and porosity parameter values for the radon barrier material appear to be based on the average measurements of two samples (calculation 010 sheet 6). However, the RAP (DOE, 1995; Section 6.3.4) indicates that 10 samples were tested, although the summary of soil test results (calculation 006 sheet 108) indicates that 5 samples tested for maximum density averaged 1.60 g/cc (39.64 pcf) and 4 samples tested for specific gravity averaged 2.70, resulting in a calculated porosity of 0.41, Calculation 010 sheet 6 states that the density value for design is 1.50 g/ce, but the radon flux analysis uses the less conservative 1.60 g/cc value. Staff utilized the conservative values of 1.5 g/cc and 0.44 for density and porosity in its model.
The long-term moisture content parameter value was based on two minus-15-bar capillary
- moisture tests that averaged 19.4 percent. At this moisture value, a radon diffusion coefficient of 0.0063 cm2/s was derived. However, a code-calculated value of 0.0021 cm 2/s was used in the flux analysis, which is not conservative. Staff normally would use the Rawls and Brakensiek equation to estimate the long-term moisture content, but data on the organic content of the barrier soil were not available. The material tested had a high fines content that may produce unreliable or unrepresentative capillary moisture test results. Therefore, staff used a moisture NATURITA TER 6-4 APRIL 1999
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value of 16 percent, deemed reasonable for clayey soil. and a calculated diffusion coefficient value of 0.0097 cm 2/s in its model. In addition, DOE provided as budt calculations which showed sufficient protection.
The thickness of the radon barrier layer is set by the design at 3 feet to satisfy ALARA considerations. This is acceptable to NRC staff because this thickness provides reasonable assurance that the long-term radon flux standard can be met, as discussed below.
6.2.2 Evaluation of Radon Attenuation Model DOE provided two radon flux models and utilized the RADON computer code to evaluate the radon attenuation capacity of the barrier. One model assumed that the upper 16 feet (500 cm) of contaminated material was composed of windblown material, and the other assume ! 'his layer was composed of material from the former tailings pile area. Both models assume that the side slopes of the cell have the same layer sequence and thickness To be conservative, neither model considers the radon attenuation ability of the frost protection layer. Each model was run first to estimate the average long-term radon flux from a 3-foot-thick barrier and second to determine the required barrier thickness to achieve a flux of 20 pCi/m2 s. The resulting values are:
Contaminated Laver Flux (oCi/m:s) Reauired Barrier Thickness Windblown Material 1.3 2.4 inches (6 cm)
Tailings Pile Area 9.1 8.5 inches (21 cm)
Staff modeled the more conservative parameter values discussed in previous sections and used a conservative, but realistic layer sequence and thickness. The layers modeled were:
(1) 4.5 feet (138 cm) mill yard / ore storage material; (2) 3.5 feet (106 cm) tailings pile area soil; (3) 4 feet (122 cm) windblown material; and (4) 3 feet (90 cm) of radon barrier. This model reflects a minimal amount of material with low-levels of Ra-226 (assumes that supplemental standards are approved) and, therefore, there is a higher total Ra-226 concentration than is expected to be present. The staffs modeling resulted :n an estimated long-term radon flux of 11.8 pCi/m /s. This provides reasonable assurance that the radon barrier design meets the EPA radon flux standard.
6.2.3 Durability of the Radon Barrier One aspect of barrier durabihty that can be evaluated by radon flux'modeling is freeze-thaw damage. DOE calculated that the frost penetration into the cover would extend 44 inches (conservatively modeling the frost protection layer at its long-term moisture content). With the proposed 66-inch-thick frost protection layer and the 18-inch-thick bedding and riprap cover, the radon barrier soil would not be affected by freeze-thaw events (see further discussion in TER Section 3.3.4). Therefore, flux modeling with parameter values altered to reflect a frost damaged radon barrier was not necessary. Evaluation of the potential for cracking of the radon barrier due to desiccation or cell instability is addressed in Section 3.4.
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Another aspect of the evaluation of the long-term integrity of the radon barrier is estimating the likelihood of intrusion by burrowing animals or deep-rooted plants This aspect of cell design was not addressed, but staff considers that biointrusion of the radon barrier will be restricted by l the unfavorable environment of the rock layer in the final cover. Although it is recognized that some volunteer plant growth will occur on the cover, significant root penetration 7 feet deep to the radon barrier, is not anticipated. !
l 6.3 Site Cleanuo 6.3.1 Radiological Site Characterization Field sampling and radiological surveys at the Naturita processing site and adjacent areas resulted in the identification of contaminated matenals covering 133 acres. In Section 6.5.1 of l the DOE RAP for the processing site (DOE,1998) the discussion of site characterization I mentions that data have not indicated a potential for preferential mobilization of Th-230 at the site. Staff considered that characterization of soil Th-230 and U-238, as described in the RAP, !
is inadequate. NRC staff estimated from the coordinates given in Table B-3 of Calculation 17-730-01-01 that only one sample each from the former tailings pile and ore storage areas were analyzed for Th-230. However, DOE states (DOE,1994; Section 6.5.1) that further characterization of Th-230 and uranium will be performed in conjunction with test pitting of the cobbly soil. DOE subsequently provided additional Th-230 and U-238 data obtained with the cot.'bly soil study to substantiate that adequate characterization of these radionuclides was performed.
Soil background levels of Ra-226 were measured in the Naturita area and DOE stated that the average value is 2.3 pCi/g. The value is based on four samples ranging from 1.1 to 3.4 pCi/g.
Since little was known about the location of the site and the various processes, the Remedial Action Contractor randomly located test pits across the mill site and adjacent vicinity properties for soil extraction and radioactive characterization, in order to provide adequate characterization of uranium and radium at the processing site, a sampling protocol was established prior to remediation. DOE provided additional soil background data and established the Ra-226 background to be 1.5 pCi/G in the final report and vicinity property reports.
6.3.2 Cleanup Standards DOE committed to excavate contaminated soil to meet the EPA standard of 5 pCi/g (surface) and 15 pCilg (subsurface) plus background for Ra-226 in soil and to place the contaminated materials in an engineered disposal cell. Excavation will be monitored to ensure that cleanup efforts are complete. The cleanup plan is to stockpile the debris and vicinity property materialin the mill yard and begin site excavation at the higher elevations.
All buildings on the site will be demolished, and all contaminated debris will be placed 'in the disposal cell. Therefore, cleanup of buildings is not required.
DOE stated that subsoi! conditions in the tailings pile area generally consist of a high percentage of cobbles and gravels greater that a Number 4 sieve. Therefore, DOE proposes use of the generic procedure for determining the bulk Ra-226 and Th-230 content of cobbly soil for NATURITA TER 6-6 APRIL 1999
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excavation control and verification. NRC concurred on the generic procedure, but stipulated that a report detailing the site-specific procedures used should be provided for NRC review in a separate report or in the Completion Report. DOE provided corrected and updated cobbles-to-fines information in the update to the RAP, and the staff finds this additional information
' acceptable.
6.3.3 SupplementalStandards DOE submitted (DOE,1994; Appendix A, includirig calculation 17-730-02-02) an application for supplemental standards to exclude remediation of some windblown tailings areas and tailings
- buried around a gas line. DOE also provided the same information by letter dated October 7, 1994, and NRC staff responded on April 19,1995, with two general and six specific comments -
resulting from its review of the application. DOE provided a response to those comments on j December 21,1995. At the time of completion of this TER, those responses were treated and ;
resolved as Vicinity Properties.
The Vicinity Properties under consideration for supplemental standards total approximately l 142 acres and contain approximately 119,600 cubic yards of contaminated soil. The general justification for not excavating these Vicinity Properties is that cleanup would be difficult and i costly land the material does not pose a significant health risk. The application of the l supplemental standard of "no remedial action" for these Vicinity Properties is based on meeting j 40 CFR 192.21 (a-f) criteria that represent circumstances that would result due to remedial !
action. The Part 192 criteria applied by DOP, are: l
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- a. clear and present risk of injury to workers or the public; j
- b. environmental harm that is excessive (long-term, manifest) compared to the health benefits; and ,
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- c. high' cost relative to long-term benefits at a vicinity property, and the residual radioactive materials do not pose a clear present or future hazard.
l The type of Vicinity Properties and the above criteria that DOE applied to each Vicinity Properties are: River Front Wetlands (Former P!!s Area and Area E)- Criterion b; Former Ore l Storage Area Steep Slopes - Criteria a, b, and c; Steep Slopes with Windblown Radioactive Material (Areas B, C, D, E, F, G1, and G2)- Criteria a, b, and c; and High-Pressure Gas Line -
Criteria a, b, c.
NRC staff provided specific comments on each Vicinity Property type, as well as the general comment that all Vicinity Properties proposed by DOE for the application of supplemental standards include'the criterion of environmental harm without adequate justification. DOE ,
addressed how partial remediation of the areas proposed for "no remediation" would cause
" environmental harm that is clearly excessive compared to the health benefits to persons living on or near the site, now or in the future" as required by 40 CFR 192.21(b). DOE provided individual assessments and applied the appropriate criteria for supplemental standards in each
' vicinity property completion report.
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l DOE indicates that the river front wetlands (3.8 acres) are under the jurisdiction of the COE, and areas with cottonwood and willow seedlings that occur next to the river are to be protected.
However, the UMTRA Project has replaced wetlands vegetation at other sites. DOE also indicates that spillage of contaminated material during excavation could contaminate the river, but some of this material probably enters the river with each flood. As indicated above, DOE addressed how remediation of the river front wetlands "would, notwithstanding reasonable ,
measures to limit damage, directly produce environmental harm that is clearly excessive I
' compared to the health benefits to people living on or near the site, now or in the future," as I required by 40 CFR 192.21(b). i For Vicinity Properties with steep slopes, DOE indicated that there are relatively flat portions, but that the extra cost to gain access with equipment would exceed the long-term benefits. DOE- i provided detailed discussion of the cost to benefit information and limited health risk for each l individual vicinity property completion report for justification and use of the supplemental standards. I l
The steep slopes of Areas B, C, and E border the east side of the highway. RAP Figure 3 indicates that, typically, a 50-foot-wide strip beside the highway will not be excavated. Area D covers 114.5 acres on the west side of the highway. It appears that some portions of these areas could be remediated without excessive cost or risk, assuming that the elevated radon readings are not due to natural (in situ) deposits. Because final excavation limits for all areas are determined by the DOE contractor in the field, DOE should provide guidance (possibly a reminder on the extent of excavation map) indicating that the remediation will come as close to meeting the otherwise applicable standards as is reasonable under the circumstances. DOE provided discussion of the cost to benefit information in the individual vicinity property i completion report for justification and use of the supplemental standards.
In addition, the construction of a golf course on the east side of the highway at the Naturita site (Area E) and a recreational vehicle park on the west side of the highway (Area D) has been suggested (February 22,1995, letter from D. Crane, Chairman, Naturita Citizens Group to W. Woodworth, DOE, Project Site Manager for Naturita). There was no consideration of these possible future uses of the areas in the original information provided by DOE. DOE was asked to provide a discussion of possible future uses of all the supplemental standard areas in the discussion of potential health risks to persons that might occupy the areas. DOE provided this information and discussed the potential health risk in each individual vicinity property completion report.
One steep windblown area, labeled G2, has an average Ra-226 concentration of 53 pCi/g (10 samples) and the highest value was 206 pCilg. DOE provided discussion of the health risk and of the cost to benefit information in the individual vicinity property completion reports for justification and use of the supplemental standards.
For the gas line, DOE proposes that a 5-foot-wide area on either side of the line remain unexcavated. Notes of a conversation with an employee of the Natural Gas Company indicate that excavation must be by hand for 3 feet on either side of the line. DOE indicates that the cost and time for hiring specialized workers or providing workers extra training and special equipment for work near the gas line may not be warranted because of the low risk of public l
NATURITA TER 6-8 APRIL 1999
radiation exposure, but specialized workers or training may not be necessary for work several feet away from the line. Also, DOE has not provided information to indicate what entity (the State of Colorado, City of Naturita, or Natural Gas Company) would have the responsibility of disposing of the contaminated material should the gas line be dug up. In addition, Ra-226 data were not provided for the assessment of potential health risk, because DOE assumed the remote location would prevent public exposure. DOE treated the gas line area as a vicinity property and provided justification for the use of supplemental standards in the completion report for this area, A record of a conversation with a representative of the Natural Gas Company was the only land owner comment originally provided by DOE DOE's submittal stated that a record of negotiations with the other owners is documented in the Remedial Action Agreement, but no copies of these agreements or discussions were provided. As required by 40 CFR 192.22(c),
DOE provided NRC with copies of comments from land owners regarding the proposed application of supplemental standards to portions of their property. DOE provided copies of the discussions and agreements in the vicinity property completion report, which was reviewed by the staff and found acceptable.
6.3.4 Verification The final radiological verification survey for land cleanup will be based on 100-square-meter areas. The standard method for Ra-226 verification is analysis of composite soil samples by gamma spectrometry, but DOE may use several other measurement techniques, depending on particular circumstances. DOE indicates that the nine-point composite gamma measurement technique or the RTRAK detection unit may be used in the windblown areas. NRC has previously agreed to the use of these procedures with adequate quality controlin specific cases.
DOE stated that verification for Th-230 will follow the generic thorium policy. Also, any uranium cleanup verification will be derived as part of a supplemental standard.
No on site structures at the processing site will require radiological verification, because all structures will be demolished and the debris will be buried at the disposal cell.
6.4 Conclusions Based on review of the design and analyses presented in the RAP (DOE,1998) and associated documents, NRC staff concludes that the radon attenuation model has some short-comings, but l modeling by the staff demonstrates that the radon barrier design is conservative. Radon l attenuation provided by the frost protection layer was, conservatively, not considered in either model. In addition, DOE has committed to do further testing of materials and will perform a final radon flux analysis with as-built parameter values to verify the design. This final analysis will be provided for NRC review as part of the Completion Report. Therefore, assuming all cell stability issues will be resolved, staff is assured that the average surface radon flux will be below the EPA standard.
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4 The staff finac that the radiological characterization program, the proposed processing site l cleanup, and verification plans have been addressed in the che"~es to the Remedial Action l Plan and the Vicinity Property Completion Reports.
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7.0 REFERENCES
Abt, S.R., et al., " Development of Riprap Design Cnteria by Rip p Testing in Flumes. Phase 1,"
NUREG/CR-4651,1987. q l
Bernreuter, D., McDermott, E. and J. Wagoner, " Seismic Hazard Analysis of Title 11 Reclamation i Plans," Lawrence Livermore National Laboratory, Livermore, CA,1995.
)
Bonilla, M.G., Mark, R.K., and Lienkaemper, J.J., " Statistical Relations Among Earthquake Magnitude, Surface Rupture, Length, and Surface Fault Displacement," Bulletin of the Seismological Society of America, v. 74, p. 2379-2411,1984. )
i Brill, K. G., Jr. and 0.W. Nuttli,
- Seismicity of the Colorado Lineament," in Geology, Vol.11, pp.
20-24, ' Boulder, Colorado,1983 Campbell, K.W.,"Near-Source Attenuation of Peak Horizontal Ground Acceleration," Bulletin of the Seismological Society of America, v. 71, pp. 2039-2070,1981.
Campoell, K.W. and Y. Bozorgnia, "Near-Source Attenuation of Peak Horizontal Acceleration ,
from Worldwide Accelogram Records from 1957 to 1993," Proceedings, Fifth U.S International I Conference on Earthquake Engineering, Chicago, Illinois, pp. 283-292,1994. l Cater, F.W., Jr., " Age of the Uncompahgre Uplift and Unaweep Canyon, West-Central Colorado," U.S. Geological Survey, Professional Paper 550-C, Washington, DC, pp. C86-C92, I 1966.
Cater, F.W. Jr., " Geology of the Salt Anticlines Region in Southwestern Colorado," Professiona' Paper 637, map scale 1:62,500, U.S. Geological Survey, Washington, D.C.,1970.
DOE," Remedial Action Plan and Site Design for Stabilization of the inactive Uranium Mill Tailings Site at Naturita," Colorado, Final, UMTRA-DOE /AL/62350-40PF, March 1994 (NAT-FAP), Remedial Action Selection Report, including Attachments 1,3, and 4,1994.
DOE," Remedial Action Plan and Site Design for Stabilization of the Naturita Title i Residual Radioactive Materials at the Upper Burbank Repository," Uravan, Colorado, final draft, wdh Appendices A - G (November 1995),1995.
DOE, " Remedial Action Plan and Site Design for Stabilization of the Naturita Title i Residual Radioactive Materials at the Upper Burbank Repository," Uravan, Colorado, page changes (June,1998),1998a.
DOE," Remedial Action Plan and Site Design for Stabilization of the Naturita Title i Residual Radioactive Materials at the Upper Burbank Repository," Uravan, Colorado, final draft, with Appendices A - 0 (1998),1998b.
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Ely, R.W., Wong, l.G., and Chang, P.S.,"Neotectonics of the Uncompahgre Uplift, Eastern Utah and Western Colorado,"j_n Contributions to Colorado Seismicity and Tectonics, W.P. Rogers ed., C :!crado Geological Survey, Denver, Colorado, p. 75-92, 1986.
EPA (U.S. Environmental Protection Agency),40 CFR Part 192, Groundwater standards for remedial actions at inactive uranium processing sites, Final Rule: U.S. Environmental Protection
. Agency, January 11,1995.
Hunt, C.B., " Cenozoic Geology of the Colorado Plateau," U.S. Geological Survey Professional Paper 279, Washington, DC,1956.
Hunt, C.B., " Geological History of the Colorado Plateau," U.S. Geological Survey Professional Paper 669-C, pp.59-130,1969.
Kirkham, R.M., and Rogers, W.P.,
- Earthquake Potentialin Colorado, a Preliminary Evaluation,"
Colorado Geological Survey Bulletin, no. 43, Denver, Colorado,1981.
Kirkham, R.M., and Rogers, W.P., " Interpretation of November 7,1882, Colorado Earthquake,"
Colorado Geological Survey Open File Report 86,1986.
Larson, E.E., Ozima, M., and Bradley, W.C., " Late Cenozoic basin volcanism in northwestern Colorado and its implications concerning tectonism and the origin of the Colorado River system,"
in Cenozoic History of the Rocky Mountains: Geological Society of America Memoir 144, p.155-178,1975.
McGuire, R.K., Krusi, A., and Oaks, S.D., "The Colorado Earthquake of November 7,1882: Size, Epicentral Location, Intensities, and Possible Causative Fault," The Mountain Geologist, v.19, p.
11-23, 1986.
MK Ferguson Company, " Proposed supplemental standards areas for Naturita processing site and surrounding vicinity properties," 3885-NAT-R-01-01232-00, January 10,1994.
MK Ferguson Company, UMTRA Project "Naturita Remedial Action inspection Plan,"
Revision-1 (April 17,1998),1998.
NOAA (National Oceanic and Atmospheric Administration), " Probable maximum precipitation estimates, Colorodo River and Great Basin drainages " U.S. Department of Commerce, Hydrometeorological Report No. 49,1977.
NRC,1990. Final Staff Technical Position Design of Erosion Protection Covers for Stabilization of Uranium Mill Tailings Sites," NMSS/LLWM, August 1990.
NRC,.1993. " Final Standard Review Plan for the Review and Remedial Action of Inactive Mill Tailings Sites under Title i of the Uranium Mill Tailings Radiation Control Act," NMSS/LLWM, June 1993.
i NATURITA TER 7-2 APRIL 1999
n , -
. ,e -
I NRC,1996. Letter from D. Gillen, NRC to R. Sena, DOE, " Final Technical Evaluation Report for the Stick Rock, Colorado, Uranium Mill Tailings Site," September 30,1996.
. NRC,1998a. Letter to Mr. George Rael, Director, U.S. Department of Energy, Albuquerque Operations Office, ERD /UMTRA, P.O. Box 6400, Albuquerque, NM, dated Novernber 27,1998, with comments on Naturita Colorado, Vicinity Properties NT-058S and NT-065S, from Joseph J.
Holonich, Chief, Uranium Recovery Branch, Division of Waste Management, Office of Nuclear Materials Safety and Safeguards.
NRC,1998b. Letter to Mr. George Rael, Director, U.S. Department of Energy, Albuquerque Operations Office, ERD /UMTRA, P.O. Box 5400, Albuquerque, NM, dated December 9,1998, with Acceptance of Completion Report For Naturita Colorado, Vicinity Property NT-059S, from N. King Stablein, Acting Chief, Uranium Recovery Branch, Division of Waste Management, Office of Nuclear Materials Safety and Safeguards.
NRC,1998b. Letter to Mr. George Rael, Director, U.S. Department of Energy, Albuquerque ,
Operations Office, ERD /UMTRA, P.O. Box 5400, Albuquerque, NM, dated December 9,1998, l with Acceptance of Completion Report For Naturita Colorado, Vicinity Property NT-069S, from N. King Stablein, Acting Chief, Uranium Recovery Brarch, Division of Waste Management, Office of Nuclear Materials Safety and Safeguards.
NRC,1999a. Letter to Mr. George Rael, Director, U.S. Department of Energy, Albuquerque Operations Office, ERD /UMTRA, P.O. Box 5400, Albuquerque, NM, dated January 6,1999, with Acceptance of Completion Report For Naturita Colorado, Vicinity Property NT-067S, from N.
King Stablein, Acting Chief, Uranium Recovery Branch, Division of Waste Management, Office of Nuclear Materials Safety and Safeguards.
NRC,1999b. Draft Standard Review Plan for the Review of a Reclamation Plan for Mill Tailings Under Title ll of the Uranium Mill Tailings Radiation Control Act, Draft Report for Comment, NUREG-1620, January 1999.
Smith, R.S.U., "Long Term Stability of Union Carbide's Tailings Piles at Uravan, Colorado," l University of Houston Geology Department. Houston, Texas,1980.
Stephenson, D, "Rockfill in Hydraulic Engineering," Elsevier Scientific Publishing Co., New York, 1979.
Stevens, M.A., Simons, D.B., and Lewis, G.L.,
- Safety Factors for Riprap Protection," ASCE Jouinal cithe Hydraulics Division, Vol.102, No. HYS, May 1976.
Umetco Minerals Corporation and Peel Environmental Services, "Hydrogeology of Club Mesa, Uravan, Colorado," unpublished report,1994.
Umetco Minerals Corporation, " Calendar Year 1994 Environmental Monitory Data, Performance Evaluation Report, ALARA Report," prepared by Umeteo Minerals Corporation for Uravan Radioactive Materials License CO-660-02S,1995.
j NATURITA TER 7-3 APRIL 1999 1'
United State Bureau of Reclamation, " Design of Small Dams,' U.S. Department of the Interior, U.S. Bureau of Reclamation,1977.
Yeend, Warren, E., " Quaternary Geology of the Grand and Ba*tlement Mesas Area, Colorado,"
U.S. Geological Survey, Professional Paper No. 617, 50 p.,19ti9.
(
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