ML20245C274

Final Technical Evaluation Rept for Proposed Remedial Action at Riverton Tailings Site,Riverton,Wy

ML20245C274
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Issue date:	04/30/1989
From:	NRC
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ML20245C253	List: ML20245C251 ML20245C274
References
REF-WM-60 NUDOCS 8904270087
Download: ML20245C274 (15)

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FINAL TECHNICAL EVALUATION REPORT FOR THE PROPOSED REMEDIAL ACTION AT THE RIVERTON TAILINGS SITE RIVERTON, WYOMING April, 1989 l

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l TABLE OF CONTENTS Page 1.0 Introduction..................................................... I 1.1 EPA Standard................................................ I 1.2 Site and Proposed Action................................... 2 1.3 R e v i ew P ro c e s s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.4 T E R O rg a n i z a t i o n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.5 Summary of Open Issues and C o n fi rma to ry I t ems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.0 Tailings Reclamation............................................ 7 2.1 Introduction............................................... 7 2.2 Tailings Reclamation....................................... 7 3.0 S i t e Re c l ama t i o n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.1 Introduction............................................... 8 3.2 Cieanup and Control of Existing Groundwater Contamination............................. 8 3.3 Site Cleanup............................................... 9 4.0 S u mma ry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 5.0 Refe rence/ B ib l i o g ra p hy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 SUPPLEMENT 1 - Remedial Action Plan Modification No.1 1

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1.0 INTRODUCTION

The Riverton, Wyoming site was designated as one of 24 abandoned uranium mill tailings piles to be remediated by the U.S. Department of Energy (DOE) under I the Uranium Mill Tailings Radiation Control act of 1978 (UMTRCA). UMTRCA requires, in part, that NRC concur with DOE's selection of remedial action, such that the remedial action meets appropriate standards promulgated by the

~ U.S. Environmental Protection Agency (EPA). ' This final Technical Evaluation Report (1ER) documents the NRC staff's review and concurrence with the DOE's final Design and Remedial Action Plan (RAP) for Riverton issued July 9,1987.

In addition, a supplement is appended to this TER which documents the staffs review and concurrence with DOE's RAP Modification No.1, dated January 23, 1989, 1.1 EPA Standards As required by UMTRCA, remedial action at.the Riverton site must comply with regulations established by the EPA in 40 CFR Part 192, Subparts A-C. These regulations may be summarized as follows:

1. The disposal site shall be designed to control the tailings and other residual radioactive material for 1000 years to the extent reasonably achievable and, in any case, for at least 200 years [40 CFR 192.02(a)]. 3

2. The disposal site design shall prevent radon-222 fluxes from residual radioactive materials to the atmosphere from exceeding 20 picocuries/

square meter /second or from increasing the annual average concentration of radon-222 in air by more than 0.5 picocuries/ liter [40 CFE 192.02(b)].

3. The remedial action shall ensure that radium-226 concentrations in land that is 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 averaged over the first 15 centimeters of soil below the surface and 15 picocuries/ gram averaged over any 15-centimeter thick layer of soil more than 15 centimeters below the land' surface [40CFR192.12(a)].

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l-p e 4 The remedial action shall ensure in any occupied or habitable building an annual average radon decay product concentration (including background) not to exceed .02 WL, or, in any case, a radon decay product concentration (including background) not to exceed .03 WL. In addition, the level of gamma radiation shall not

- exceed background by more than 20 microroentgens per hour.

On September 3,1985, the U.S. Tenth Circuit Court of Appeals remanded the groundwater standards (40 CFR Part 192.2(a)(2)-(3)) and stipulated that EPA promulgate new groundwater standards. EPA proposed these standards in the form of revisions to Subparts A-C of 40 CFR Part 192 on September, 1987. The proposed standards consist of two parts; a first part governing the control of any future groundwater contamination that may occur from tailings piles efter remedial action, and a second part that applies to the cleanup of

. contamination that occurred before the remedial action of the tailings.

1.2 Site and Proposed Action The Riverton uranium mill is located approximately 2.5 miles southwest of the center of Riverton, in fremont County, Wyoming (see Figure 1.1). The 173 acre processing site consists of the tailings site (approximately 70 acres),

portions of the mill structure and foundations, and other associated buildings including a pump house, scale house and wash house. The site also has several piles of rubble and some buried process tanks and debris. The tailings pile at the processing site contains an estin.ated 1,500,000 cubic yards (cy) of uranium mill tailings produced by Fremont Minerals, Inc. from 1958 to 1963. The remedial action at the Riverton processing site consists of the relocation of the tailings and contaminated materials from the existing tailings pile, mill yard, windblown contaminated areas, and vicinity properties to the UMETCO Gas Hills site (an NRC licensed UMTRCA Title II facility) and reclamation of the processing site in accordance with the EPA standards.

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Long-term surveillance and maintenance is not anticipated at the processing site upon completion of the remedial action. However, when EPA issues the final groundwater protection standards, DOE will re-evaluate the need for institutional or other controls and will take appropriate action so as to comply with the re-issued standards. Any controls necessary at the processing site is the responsibility of DOE or other designated federal agency. The UNETCO Title II site licenste is responsible for the disposal and reclamation of the commingled tailings.

1.3 p view Process The NRC staff review was parformed in accordance with the Standard Review Plan for UMTRCA Title I Mill Tailings Remedial Action' Plans (Reference 7)

~and consisted of comprehensive assessments of DOE's final Design and Remedial Action Plan (RAP). . Staff review of final data and designs submitted by DOE resulted in NRC's conditional concurrence in the Riverton RAP on October 15, 1987.

The remedial action information assessed by the NRC staff in this TER is contained _in the following documents (Reference I to 6):

1. Remedial Action Plan and Site Design for Stabilization of the Inactive Uranium Mill Tailings at Riverton, Wyoming, Final, October, 1987, UMTRA-DOE /AL 050507.0000.

2. Environmental Assessment of Remedial Action at Riverton Uranium Mill Tailings Site, Riverton, Wyoming, June,1987, UMTRA-DOE /AL-051507.000.

3. Processing Site Characterization Report for the Uranium Mill Tailings Sites at Riverton, Wyoming, October 1985, UMTRA-D0E/AL-050107.0000

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4. Modification No. I to the Uranium Mill Tailings Remedial Action Plan (UMTRAP), Riverton, Wyoming, October 13, 1988.

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5. Uranium Mill Tailings Remedial Action Design Calculations, Riverton, Wyoming, May 1987.

- 6. Uranium Mill Tailings Remedial Action Subcontractor Documents, Riverton, . Wyoming, May 1987.

1.4 TER Organization

- The purpose of this' Technical Evaluation Report (TER) is to document the NRC staff review of DOE's final remedial action plan (RAP) for the Riverton Site.

The proposed remedias action at the Riverton, Wyoming UNTRA site is unique, since it involves shipping the tailings and other waste to the UMETCO Gas Hills Title II:Itcensee for disposal. This Title II licensee has accepted responsibility under their license for disposal and eventual reclamation of this waste. DOE's responsibility at the Riverton site is limited to reclamation of the processing site, which consists of cleanup of the existing groundwater and U soil contamination. TER Section 2 provides the basis for the staff's conclusions and identification of any open issues with respect to tailings reclamation.

TER Section 3 provides the NRC staffs conclusions'and any remaining open issues regarding site' reclamation activities relative to the EPA standards in 40 CFR Part'192, subparts A-C.

1.5 Summary of Open Issues and Confirmatory Items The NRC staff's review of the DOE's final remedial action plan and design has identified only one open issue, which is discussed in TER Section 3.2, and no confirmatory items. The open issue relates to DOE's deferral of groundwater cleanup until after promulgation of EPA's final groundwater protection standards. While the staff considered DOE's deferral to be acceptable for conditional concurrence, the issue must be addressed before NRC will provide final concurrence on the remedial action at this site.

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g TABLE 1.1 RIVERTON UMTRAP SITE CONCURRENCE CONDITIONS CONCURRENCE CONDITION

1. Upon promulgation of EPA groundwater standards for Title I sites,

DOE will review data on groundwater conditions at the Riverton processing site'and will make an assessment of the need for further remedial action to come into compliance with those standards in a timely manner. DOE's proposed course of' action will be submitted to NRC for review and Concurrence.

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2.0 TAILINGS RECLAMATION

- 2.1 Introduction This'section of the TER documents the staff's evaluation of DOE's proposal to relocate the tailings and contaminated materials from the Riverton processing site to the UMETCO Gas ' Hills facility (an NRC licensed UMTRCA Title II facility).

2.2 Tailings Reclamation In accordance with Section 108'(a)(1) of UMTRCA, DOE proposed a remedial action plan which consisted of the relocation of the tailings and contaminated 1 materials from the existing tailings pile, mill yard, windblown contaminated areas, and vicinity properties to the UMETCO Gas Hills site. Upon delivery of o the Title I tailings and contaminated materials from Riverton,.the Title II

- facility' licensee would assume responsibility for the disposal and reclamation of the commingled tailings. In accordance with the requirements of-10 CFR 40 Appendix A, the Title II licensee, UNETCO, provided a revised reclamation plan for the commiingled tailings to the NRC for concurrence, including information on the bonding / surety arrangements to assure completion of the reclamation of the commingled tallings. Upon review of this information, the NRC staff found the reclamation plan to be in compliance with the Title II EPA standards. The staff concurred with the reclamation plan on October 7, 1987 and the financial surety arrangements on December 29, 1987. Since the Riverton remedial action site is a UMTRCA Title I site, the NRC also reviewed the UNETCO reclamation L plan in light of the requirements of the EPA Title I standards. Based on this review, the NRC concluded that the reclamation of the Riverton tailings and contaminated material-as proposed by UNETCO in accordance with the Title II EPA

. standards, also meets the requirements of the Title I EPA standards.

- Therefore, the NRC found the proposed tailings reclamation plan as described in the remedial action plan to be in compliance with the EPA Title I standard.

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3.0 SITE RECLAMATION 3.1 Introduction This section of the TER documents the staff evaluation of DOE's plans relative to the existing groundwater and radiological contamination at the Riverton processing site to assure compliance with the EPA standard.

3.2 Cleanup and Control of Existing Contamination DOE needs to demonstrate compliance with the EPA standards listed in 40 CFR Part 192, Subpart B and C for cleanup and control of existing contamination.

As addressed in the Environmental Assessment and the Remedial Action Plan, DOE ,

proposed deferring aquifer restoration until EPA issues final groundwater protection standards. NRC has taken the position that DOE may postpone restoration of relic contaminated groundwater if DOE demonstrates that disposal can proceed independently of restoration. DOE has determined and the NRC staff agrees that performing remedial action to relocate the tailings prior to EPA issuing new standards will not affect the measures that will ultimately be required to meet the cleanup aspects of the final EPA groundwater protection standards. In fact removal of the tailings at the processing site removes the source of groundwater contamination. The site groundwater conditions have been adequately characterized and DOE does not anticipate that any substantial changes to the remedial action will be required. After EPA issues the final groundwater protection standards, DOE has committed to take whatever action appropriate to comply with the reissued standards. Therefore, based on the information provided in the Environmental Assessment and the Remedial Action Plan, the NRC staff agrees to defer review of DOE's compliance with EPA groundwater standards for restoration, restoration demonstration and groundwater monitoring program at the processing site.

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3.3 Site Cleanup Site characterization surveys have been conducted at the site to identify the subsurface boundary of the tailings pile, as well as the depth and area af the windblown contaminated areas. Subsurface evaluations were performed using gama well logging techniques and by analyzing cores from bore holes. In addition, radiometric surveys and sampling were also conducted in the buildings at the site. The results of the site characterization survey were used to plan the control monitoring for the contaminated soil excavation and the building decontamination, as well as the final radiological verification survey for the land and the buildings. DOE has comitted to the cleanup of the processing site and mill buildings in accordance with the EPA standard (40 CFR 192 Subpart B). As a result of DOE's proposed compliance with the EPA standard, the NRC has concurred with the DOE's radiological survey plan. In addition, the DOE committed to comply with standards as provided in the UMTRA Project Environmental, Health and Safety Plan (UMTRA-DOE /AL-150224). This plan contains the standards to be used with regard to removeable surface alpha contamination.

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SUMMARY

This Technical Evaluation Report (TER) sumarizes the NRC staff review of the remedial action for the Riverton UMTRAP site. On July 9,1987 the NRC issued a conditional concurrence with DOE's remedial action. The condition remaining on the NRC's concurrence states:

"Upon promulgation of EPA groundwater standards for Title I sites, DOE will review data on groundwater conditions at the Riverton processing site and will make an assessment of the need for further remedial action to come into compliance with those standards in a timely manner. DOE's proposed course of action will be submitted to NRC for review and concurrence."

Staff review of this additional information will be presented as an supplement to this report and upon compliance with the EPA groundwater standards the NRC can issue full concurrence on the remedial action plan.

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5.0 References /81bliography

1. Remedial Action Plan and Site Design for Stabilization of the Inactive Uranium Mill Tailings site at Riverton, Wyoming, Final, October, 1987, UMTRA-DOE /AL 050507.0000,

2. Environmental Assessment of Remedial Action at Riverton Uranium Mill Tailings Site, Riverton, Wyoming, June,1987, UMTRA-D0E/AL-051507.000.

3. Processing Site Characterization Report for the Uranium Mill Tailings sites at Riverton, Wyoming, October 1985, UMTRA-DOE /AL-050107.0000

4. Modification No. I to the Uranium Mill Tailings Remedial Action Plan (UMTRAP), Riverton, Wyoming, October 13, 1988.

5. Uranium Mill Tallings Remedial Action Design Calculations, Riverton, Wyoming, May 1987.

6. Uranium Mill Tailings Remedial Action Subcontractor, Documents, Riverton, Wyoming, May 1987.

7. NRC,1985, Standard Review Plan for UMTRCA Title I Mill Tailings Remedial Action Plans: U.S. NRC, Division of Waste Management, October, 1985.

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SUPPLENENT 1 MODIFICATION NO. 1 TO THE REMEDIAL ACTION PLAN FOR THE RIVERTON, WYOMING SITE

_ Background By'1etter dated September 6, 1988, DOE submitted for NRC review a proposed protocol to be used to guide excavation of thorium-230 (Th-230) contaminated material' at the' Riverton, Wyoming uranium mill tailings site. The NRC comments on the protocol were discussed with DOE via several telephone calls. Using

.the protocol as a basis, ' DOE submitted Modification No. I to the Remedial Action Plan (RAP) for NRC concurrence by letter dated October 13, 1988. The NRC reviewed the October 13, 1988 submittal and as a result requested several clarifications be made to the RAP modification prior to NRC concurrence.

Based on the proposed changes to the RAP telefaxed by DOE on November 2,1988, the NRC by letter dated November 3, 1988 indicated their intention of concurring in Modification No. I to the RAP. Formal concurrence, indicated by NRC signature on final RAP, was completed January 23, 1989. Concurrence in this modification did not change the overall conditional concurrence on the RAP itself. The NRC's concurrence in the remedial action is conditional upon promulgation of the final EPA groundwater standards and resulting DOE restoration analysis.

Proposed Modification to the Remedial Action Plan The purpose of the proposed change to the remedial action plan is to establish an excavation protocol for thorium-230 contamination in the absence of excess radium-226 at the Riverton, Wyoming, mill tailings site. In accordance with l 40 CFR Part 192.21 and 192.21 (h) DOE applied supplemental standards under l 192.22 in lieu of Subpart A or B standards because radionuclides other than l

! radium 226 and its decay products were present in sufficient quantities and concentrations to constitute a significant radiation bezard from residual radioactive materials. In addition, DOE proposed that in accordance with 40 CFR 192.22 (b), Th-230 be excavated to levels that are as low as is reasonably achievable (ALARA). ALARA conditions proposed by DOE for Th-230

k :k o consists of excavating all material above the saturated zone that exceeds 35 pC1/g Th-230 and leaving in place Th-230 contaminated soils within the saturated zone. Sections B.1 and 8.3.3 of the RAP were modified to

-incorporate into protocol as described above.

0verall Impact of the Proposed Modification The proposed protocol. avoids difficult construction measures and resulting expenditures which would be unreasonably high relative to the long-term

. benefits.; The protocol does result in low-level contaminated material remaining in portions of the saturated zone in the subsurface. However, the contaminated material does not cover the entire area of the processing site, and the actual flux from the site will. remain below the 20 pC1/m2 -sec criterion for the entire 1000 year control period. In addition,'the material is in a location where construction of homes is not likely and any future excavation will mix the contamination with clean materials and further dilute the concentration.

Groundwater impacts are expected to be negligible since the thorium appears to be in the insoluable hydroxide forin which is not mobile. In addition, the shallow aquifer is not the primary source of domestic, municipal, or industrial water supplies in the Riverton area because of insufficient quantity and poor chemical quality. Available water quality analyses also indicates that Th-230 and chemical-contaminant concentrations do not exceed proposed EPA groundwater standards. DOE proposes to re-evaluate groundwater conditions at the Riverton site when the final EPA standards are re-issued.

Compliance With the EPA Standard The proposed revision to the Remedici Action Plan for Riverton based on the proposed Thorium 230 protocol has been reviewed by the NRC staff and found to be in compliance with the EPA standards. Therefore, the NRC formally concurred with the proposed Remedial Action Plan Modification No. I on January 23, 1989.

The NRC's concurrence on this RAP Mod does not alter the existing conditional concurrence on the overall remedial action plan, j

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