ML20237D458
| ML20237D458 | |
| Person / Time | |
|---|---|
| Issue date: | 08/31/1998 |
| From: | NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | |
| Shared Package | |
| ML20237D457 | List: |
| References | |
| REF-WM-86 NUDOCS 9808260198 | |
| Download: ML20237D458 (36) | |
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COMPLETION REVIEW REPORT FOR THE REMEDIAL ACTION AT THE SLICK ROCK, COLORADO t
URANIUM MILL TAILINGS
- REMEDIAL ACTION PROJECT SITES August 1998 I
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I DIVISION OF WASTE MANAGEMENT U.S. NUCLEAR REGULATORY COMMISSION l
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PDR WASTE l
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TABLE OF CONTENTS Section Page INTRODUCTION.................
,1 1.0. BACKGROUND...
1 1.1 UMTRCA..........
... 1 1.2 CONCURRENCE PROCESS FOR THE SELECTION OF DOE'S REMEDIAL ACTIONS...................
..... 1 1.3 CONCURRENCE PROCESS FOR THE PERFORMANCE OF DOE'S REMEDIAL ACTIONS.....................
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1.4 SLICK ROCK, COLORADO SITE.....
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1.5 COMPLETION REVIEW REPORT ORGANIZATION.....
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i 2.0 ANALYSIS OF DOE REMEDIAL ACTION PERFORMANCE
................. 6 2.1 PREVIOUS ACTIONS..
.6 2.2 REVIEW OF REMEDIAL ACTION PERFORMANCE.
...... 7 2.2.1 Geotechnical Engineering Review Results..........
... 7 2.2.2 Surface Water Hydrology and Erosion Protection Review Results........
.8 2.2.3 Radioactivity Cleanup and Control Review Results................... 9 2.2.4 Groundwater Protection Review Results....
......... 27 3.0
SUMMARY
. 28
4.0 REFERENCES
.29 APPENDIX A - NRC SITE VISITS TO THE SLICK ROCK UMTRA PROJECT SITE....... A-1 APPENDIX B - UMTRCA, THE EPA STANDARDS, AND THE PHASED UMTRA PROJECT. B-1 i
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LIST OF FIGURES
' FIGURE,
pg 1.1 Locations of the Union Carbide and North Continent UMTRA Sites near Slick Rock, Colorado.................................... 3 1.2 Locations of Burro Canyon Disposal Site and Processing Sites near Slick Rock, Colorado.....................................
... 4 LIST OF TABLES Table 1. Summary of Slick Rock Site OCS QC Measurements........................... 17.
' Table 2. Layer Specific Parameter Values 'Used by DOE in l
Calculation of Radon Flux from Burro Canyon Disposal Cell.................... 22 Table 3. NRC's Revised Estimate of Diffusion Coefficients............................ 26 i
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SLICK ROCK, COLORADO UMTRA PROJECT SITES COMPLETION REVIEW REPORT INTRODUCTION i
The Slick Rock sites are part of the abandoned uranium mill tailings sites to be remediated by the U.S. Department of Energy (DOE) under the Uranium Mill Tailii.gs Radiation Control Act of 1978 (UMTRCA). UMTRCA requires, pursuant to Section 104(f)(1), that the U.S. Nuclear Regulatory Commission (NRC) concur with the DOE's determination that the remedial action has been properly completed. This Completion Review Report (CRR) documents the NRC staff's basis for its concurrence decision with respect to DOE's Certification Summary for the completion of surface remediation at the Slick Rock sites.
1.0 BACKGROUND
1 1.1 UMTRCA Title I of UMTRCA provides for remedial action at abandoned uranium mill tailings sites and associated vicinity properties. The purpose of this legislation is to protect the public health and safety and the environment from radiological and non-radiological hazards associated with the process related materials at these sites.
UMTRCA directs DOE to select and perform remedial actions at 24 abandoned uranium mill tailings sites to ensure compliance with the general environmental standards promulgated by the Environmental Protection Agency (EPA) under Section 275(a) of the Atomic Energy Act of 1954, as amended by UMTRCA. UMTRCA also requires DOE to obtain NRC's concurrence with DOE's selection and pe.1ormance of the remedial actions. Following completion of the remedial actions, UMTRCA authorizes NRC to license the long-term custody, maintenance, and monitonng of the disposal sites to ensure continued protection of the public health and safety and the environment.
Appendix B includes a more detailed discussion of this legislation.
1.2 CONCURRENCE PROCESS FOR THE SELECTION OF DOE'S REMEDIAL ACTIONS To document its selection of the remedial action to be implemented at a particular site, DOE develops and issues a Remedial Action Plan (RAP). The RAP describes the series of activities l
and presents the design proposed by DOE to provide for the long term protection of the public and the environment. Usually this involves cleanup of the processing site, adjacent windblown areas, and vicinity properties, in addition to stabilization of the residual radioactive materints in addition, DOE issues a Remedial Action Inspection Plan (RAIP), which establishes the quality control program of testing and inspection that will be employed for the remedial action. In accordance with UMTRCA Section 108(a)(1), the NRC staff reviews and concurs with the RAP i
and the RAlP, and any subsequent modifications. By its concurrence in the remedial action selection, the NRC staff concludes that the planned remedial actions will comply with EPA's applicable standards in 40 CFR 192, Subparts A, B, and C. The basis for the concurrence in l
DOE's selection of remedial action is documented in a Technical Evaluation Report (TER).
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l 1.3 CONCURRENCE PROCESS FOR THE PERFORMANCE OF DOE'S REMEDIAL ACTIONS The remedial action work is performed by DOE contractors under Federal procurement regulations. During construction, DOE inspects and documents activities in accordance with the UMTRA Project Quality Assurance Plan, the Remedial Action Inspection Plan (RAIP), and the RAP. In addition, the NRC staff conducts independent inspections during construction, as determined necessary.
Upon completion of the remedial action, DOE compiles construction records and prepares a completion report to document that remedial actions were performed in accordance with the RAP or RAP modifications, and the RAIP Based on this information, DOE certifies that all provisions of the RAP have been satisfied and, therefore, that the remedial actions comply with the applicable EPA standards in 40 CFR 192.
Based on its review of DOE's documentation, and on its site visits and observations, NRC makes a concurrence decision with regard to DOE's remedial action completion determination for each site, and then documents the basis for this concurrence decision in the CRR. By its concurrence in the remedial action performance, the NRC staff concludes that the remedial action has been completed in accordance with the NRC approved design. NRC's concurrence with DOE's completion determination fulfills the Commission's responsibility under UMTRCA Section 104(f)(1).
1.4 SLICK ROCK, COLORADO SITES The Slick Rock uranium mill tailings sites are located near the town of Slick Rock, in San Miguel County, Colorado (Figure 1.1). There are two designated UMTRA Project sites at Slick Rock: (1) the Union Carbide (UC) site, which began operating in 1C57, and (2) the North Continent (NC) site, which dates back to 1931. Both sites are owned by Union Carbide Corporation and are adjacent to the Dolores River. The UC site is located approximately two kilometers (one mile) i downstream from the NC site. Contaminated materials covered an estimated 22 hectares (55 acres) at the UC site and approximately 4.9 ha (12 acres) at the NC site. All mill buildings from both sites were removed prior to the commencement of remedial actions.
The sites contained concrete foundations, demolition debris, tailings piles, and areas contaminated by windblown and waterbome radioactive materials, with the total estimated I
volume of contaminated materials comprising approximately 594,900 cubic meters (778,100 cubic yards). Contamination associated with both sites has leached into the groundwater.
Finally, in addition to the on-site contamination, four vicinity properties were also contaminated.
DOE conducted on-site remedial action at the Slick Rock UMTRA Project sites between February 23,1995, and December 4,1996, and transferred the contaminated materials from these sites to the Burro Canyon (BC) disposal site. BC is located on a small mesa, isolated from
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upland drainages, approximately 4.0 km (2.5 mi) east of the processing sites (Figure 1.2).
I Remedial action included the following:
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MAP LOCATION FIGURE 1.1 LOCATIONS OFTHE NORTH CONTINENT AND UNION CARBIDE SITES NEAR SLICK ROCK, COLORADO l
mc saessivsamzumuoc Figure 1.1 Locations of the Union Carbide and North Continent UMTRA Sites near Slick Rock, Colorado DRAFT / December 1997 3
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Construction and removal of the retention basin, collection ditches, and decontamination pad; o
- Installation and monitoring of displacement monuments; o
o Excavation, hauling, and placement of the contaminated tailings, windblown /waterbome and vicinity property materials in the tailings disposal cell; o Construction of a tailings cell cover system, which included: radon barrier, drainage, frost protection, and erosion protection layers; o Construction of toe ditches at the tailings disposal cell; Restoration of the processing sites via backfill, grading for drainage, and revegetation; and o
Installation of perimeter signs, survey and boundary monuments, and granite site markers.
o The NRC was not involved with the actual remedial action activities which were performed by the DOE contractors. However, DOE obtained NRC concurrence with the site construction design and a few significant modifications thereof as Project interface Documents (PIDs). NRC also visited the site during construction to monitor the progress of the remedial action activity (see Appendix A).
1.5 COMPLETION REVIEW REPORT ORGANIZATION The purpose of this CRR is to document the NRC staff review of DOE's Slick Rock Completion Report (CR). Section 2 of this report presents the analysis of remedial action construction. This section is organized by technical discipline and addresses engineering and radiation protection aspects of the remedial action. Appendix A provides a listing of NRC staff visits to the Slick Rock site. Appendix B provides a detailed description of the requirements of UMTRCA and the I
resulting phased process of the UMTRA project. In some CRRs, NRC provided a table cross-checking the requirements of the approved RAP and RAIP with DOE's CR documentation, in a
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subsequent effort to streamline the documentation process, NRC eliminated that table from this 1
and other recent CRRs, but continues to address its conclusions and issues in the text of the I
technical discussions in Section 2.
l 2.0 ANALYSIS OF DOE REMEDIAL ACTION PERFORMANCE 2.1 PREVIOUS ACTIONS' l
NRC staff, based on its review of the RAP (DOE,1996) and the RAIP (MK-Ferguson,1996),
concurred that the remedial action, as designed, would meet the applicable EPA standards. This concurrence was based on technical findings that there is reasonable assurance that the selection of the remedial action would' meet the standards for long-term stability, radon attenuation, water resources protection, and cleanup of contaminated land and buildings.
Staff reviews included assessments in the areas of geology, geotechnical engineering, ground-water hydrology, surface water hydrology, and health physics. The NRC concurred on the final RAP and the RAIP on September 30,1996. The basis for the NRC staff's concurrence in DOE's ~
selection of remedial action at the Slick Rock sites is documented in the TER issued in Septembe.r 1996 (NRC,1996).
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2.2 REVIEW OF REMEDIAL ACTION PERFORMANCE NRC staff's primary objective in reviewing DOE's certification of remedial action completipn is to.
determine whether the remedial actions have been performed in a manner consistent with specifications provided in the RAP, RAP modifications or PIDs, and the RAIP, and if not, that deviations to these specifications still result in compliance with the EPA standards. In support of this action, the NRC staff participated in site reviews and field observations (See Appendix A).
During remedial action construction activities, there were conditions encountered which required modifications of the original remedial action plan. These conditions and the associated design changes were submitted by DOE as four Class i PIDs (i.e. those related to meeting the EPA standards) and were concurred in by the NRC staff. These PIDs are listed in Section 11 of Volume I of the CR and are reflected in the as-built conditions presented in the CR.
The following sections present the results of the review of remedial action performance by individual technical discipline. Note that for the Slick Rock remedial action completion review, the pertinent technical disciplines are: (1) geotechnical er:gineering; (2) surface water hydrology and erosion protection; (3) radiation protection; and (4) groundwater resources protection.
2.2.1 Geotechnical Engineering Review Results The NRC staff reviewed the Slick Rock, Colorado, CR to determine whether the geotechnical engineering aspects of the remedial action were completed in accordance with: (1) the applicable construction specifications in the RAP; (2) all RAP modifications; (3) the RAIP; and (4) the final design. Items reviewed included descriptions of construct:on operations, as-built drawings, laboratory and field testing data, Remedial Action Contractor (RAC) inspection reports, and DOE and RAC Quality Assurance Audits.
During its review, the NRC staff noted the following:
- 1. Appropriate tests (gradation and moisture content) and inspections were performed by DOE or its agents to ensure that the proper material type was placed in each phase of construction. Placement and compaction of construction materials were routinely inspected by DOE or its agents to ensure that the moisture and density requirements were met, and that the soil moisture was uniform throughout the compacted lifts. The loose thickness of the lifts was verified periodically by DOE or its agents to ensure compliance with the specification requirements for each particular type of material.
- 2. Laboratory and field testing by DOE or its agents was conducted in accordance with acceptable test procedures and by trained and qualified personnel. Records indicating acceptable calibration of measuring and testing equipment are provided in the CR.
- 3. The CR shows that frequencies of material testing and insoection comply with the frequencies specified in the RAIP and in the NRC Staff Technical Position on Testing and inspection Plans (NRC,1989).
- 4. Continuous inspections by DOE or its agents confirmed that the volume of organics included in the construction materials was limited to the range specified in the RAP.
- 5. The radon barrier 1ayer was continually inspected by DOE or its agents to ensure that the specified lift thicknesses and compaction levels were achieved.
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- 6. The material type, placement, and compaction methods specified for the radon barrier layer
,resulted in the desired moisture and density of the barrier.
- 7. As-built drawings adequately document that the completed remedial action is consistent with the NRC-approved design.
8.
Final slope, elevation, and compaction operations were adequately inspected to ensure that the final conditions were consistent with those stated in the RAP and final design.
Based on the above observMions as a result of reviewing the Slick Rock CR, the NRC staff concludes that the geotechnical engineering aspects of construction were performed in accordance with the specifications identified in the RAP and RAIP.
2.2.2 Surface Water Hydrology and Erosion Protection Review Results The NRC staff reviewed the surface water hydrology and erosion protection aspects of remedial
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actions at Slick Rock to ensure that they were constructed in accordance with the applicable construction specifications as stipulated in the RAP, RAP modifications, RAIP, and the final design. Areas of review included construction operations, laboratory and field testing, and quality assurance audits. In addition, the review was also based on NRC observation of the remedial action.
l The remedial action design included erosion protection in several specific areas, including:
(1) riprapped top and side slopes; and (2) a buried riprap toe adjacent to the side slope. The top and side slopes of the cell were designed to prevent long-term erosion and gullying of the disposal cell. The buried riprap toe was placed to prevent erosion and migration of gullies towaru the cell.
The NRC staff reviewed each of these features and determined that testing, placement, and configuration complied with specifications in the RAP, RAP modifications, and the RAIP. The review was partially based on NRC staff observation during the remedial actions, as well as assessment of the verification results presented in the CR. In addition, the NRC staff reviewed the placement of riprap on the top and side slopes of the cell and in the toe.
1 During the review, the NRC staff noted the following:
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- 1. Tests (gradation and durability) and inspections were performed by DOE or its agents to ensure that erosion protection materials were properly selected. The review of the documentation indicated that placement of materials was routinely inspected by DOE or its 1
agents to ensure that the rock size and gradation specifications were met. Likewise, the j
thickness of the rock layers were verified periodically by DOE or its agents to ensure compliance with the specifications for the particular type of material.
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- 2. Laborato4y and field testing was conducted by DOE or its agents in accordance with specified test procedures.
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- 3. Testing and inspection frequencies for materials used at the site for erosion protection were l
documented by DOE as complying with the frequencies specified in the RAIP.
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Based on its observations and review of the CR, the NRC staff concludes that the required durability and gradation tests were performed during the remedial action. The riprap isof adequate quality and has been placed acceptably. The NRC staff concurs that the reme. dial
- action has been adequately completed at Slick Rock, with respect to erosion protection.
2.2.3 Radioactivity Cleanup and Cor: trol Review Results The NRC staff reviewed radioactivity cleanup and control aspects of remedial actions at the Slick Rock sites to ensure that residual radioactive materials were cleaned up in accordance with -
specifications in the RAP and final design. Areas of radioactivity cleanup review included contaminated material excavation, cleanup verification procedures and data, and application of supplemental standards. For radioactivity control, the as-built details of the disposal cell cover and the final radon attenuation calculation were reviewed to ensure compliance with the RAP design for. limiting radon releases and with the long-term radon flux standard in 40 CFR 192.02.
The review was based primarily on the staff's assessment of information presented in the Slick Rock CR.
The criteria for site cleanup and radon attenuation were established in the RAP and concurred in by NRC staff in the TER as providing assurance that the processing sites and disposal cell would meet the EPA requirements of 40 CFR Part 192. For soil cleanup, the criterion for radium-226 in soil requires cleanup at the processing sites and on adjacent lands to levels complying with the applicable EPA standards (40 CFR 192.12), such that the average radium-226 concentrations 2
above background in each 100 m area (grid) do not exceed 5 pCi/g in the top 15 cm of soil or 15 pCi/g in any underlying 15-cm layer.
For contaminated buildings and structures, the RAP indicated that there were no plans to release contaminated materials or buildings for unrestricted use. The TER indicated that contaminated demolition debris on the sites would be buried in the disposal cell. Therefore, cleanup criteria were not specified in the RAP and verification of buildings and structures was not required.
In places on the processing site where significant concentrations of Th-230 would remain in soils after the excavation and cleanup that was necessary to reduce the Ra-226 to the required levels, the RAP indicated that the UMTRA Project generic protocol for Th-230 cleanup and verification (Chemoff 1993) would be followed to establish supplemental standards for the Th-230 under criterion (h) of the standards of 40 CFR 192.21. The generic protocol, which was generally approved by the NRC (Holonich 1994), provided DOE three cleanup criteria for establishing supplemental standardsi The most restrictive of these criteria could be generally applied to any part of the site and at any depth, wherever Th-230 remained. In using the criterion for this generic application, a supplemental standard would be imposed for Th-230 such that the Ra-226 concentration 1000 years in the future (the 1000-year Ra-226 concentration), from ingrowth from Th-230 decay plus residual Ra-226, would not exceed the cleanup standards for Ra-226 ^
. (concentrations above background to be less than 5 pCi/g for the top 15 cm of soil and less than 15 pCilg for successive 15-cm layers). Thus, using the generically applicable criterion means the Th-230 cleanup standard could vary over the site based on variations in residual Ra-226 at different locations. The other criteria in the protocol were for more specific circumstances involving deep deposits of Th-230, or for contaminat on extending into the saturated zone. For I
- Th-230 in material buried deeper than eight ft below grade, allowable concentrations would be i
developed based on the calculated concentration of radon progeny that might exist in a house l
built above the contaminated material.
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The above use of a supplemental standard for Th-230 represents the only planned use of supplemental standards at the Slick Rock designated sites (not including vicinity properties) that wa's specified in the RAP and TER.
I For verification of soil cleanup, a number of criteria were approved for the Slick Rock sites. The RAP indicated that the final radiological verification survey would be based on 100 m areas. Per 2
the RAP, for verification for Ra-226 in soil, one method to be used would be the standard verification method, which consists of having composite soil samples analyzed by gamma spectrometry (DOE 1996). Other methods could be used if approved. In addition, the RAP indicated that two in situ methods could be used for areas of windblown contamination: (1) nine-l
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point composite gamma measurements made using hand-held instruments and (2) the RTRAK mobile gamma detection unit (for areas that are too large to sample using hand methods).
The RAP and TER also discussed the verification of cleanup for soils with significant cobbles.
When the subsoil consists of a percentage of cobbles sufficient to affect the measurement of the total radionuclides concentration, excavation control and verification were to be based on bulk radionuclides concentrations calculated from measurements on the finer soil fraction.
The RAP and TER indicated that verification for Th-230 contamination (here Th-230 contamination means Th-230 in excess of Ra-226 contamination) would be performed using the UMTRA Project generic Th-230 protocol. This protocol provides the following scheme for establishing the frequency of verification sampling for Th-230. In areas on the processing sites that are suspected, based on process knowledge or other sources such as previous sampling data, of preferential thorium contamination mobilization, as compared to radium mobilization, 2
100% of the (100 m ) grids are to be sampled and analyzed for Th-230. In subpile areas,10% of I
the grids are to be sampled. In areas where process knowiedge and characterization data '
j indicate no potential for preferential mobilization, grids do not have to be sampled for Th-230.
To ensure that the radon emissions from the disposal cell weutd be controlled appropriately, the i
criterion to be met was the radon flux standard from 40 CFR 192.02(b)(1):
(b) Provide reasonable assurance that releases of radon-222 from residual radioactive i
j material to the atmosphere will not:
(1) Exceed an average release rate of 20 picocuries per square meter per second.
The radon attenuation design provided in the RAP was conditionally approved by the NRC in the TER. The design was revised slightly, for a different borrow source for the radon barrier material, with the submittal of Project Interface Document (PID) 11-S-14 (Pape 1996). The revised design was conditionally approved by the NRC in April 1997 (Cain 1997). An earlier PID,11-S-03, also affected the radon attenuation design, but the impact of the design change of this PID was evaluated in the TER (Holonich 1996). The radon attenuation design, from the RAP and PID 11-S-14, included placement of contaminated materials with the lowest Ra-226 concentration on the top of the relocated contaminated materials, followed by a 1% ft layer of radon barrier material, and a 2 ft layer of frost barrier material. The conditions imposed by the NRC in approving the RAP and PID 11-S-14 designs are (NRC 1996 and Holonich 1996): (1) DOE was
. to perform testing to determine and justify the long-term moisture content of the UC (Union Carbide site) offpile and subpile material, (2) DOE was to measure, during construction, the Ra-226 concentration, emanation fraction, and radon diffusion coefficient for the UC offpile and subpile materials, (3) DOE was to measure the Ra-226 concentrations in the radon barrier and 9
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frost barrier materials, to assure that concentrations are at background levels as was assumed in prior modeling, and (4) DOE was to measure the radon diffusion coefficient of the radorj barrier material and justify the diffusion coefficient at the long-term moisture content.
During the review, with respect to the above criteria and commitments, NRC staff noted the following:
- 1. Site Cleanup:
a) Extent of excavation:
It appears that the excavation of the contaminated areas of the designated processing sites has been performed by DOE as set out in the RAP. Two drawings in calculation 11-212 03, in Volume 1 of the Final Design for Construction (DOE 1995) (sheets 42G and 13E of the calculation for the UC and NC processn.g sites, respectively), show estimated boundaries of the extent of contamination. In the CR, two drawings show the approximate boundaries of the extent of excavation: SRK-SV-0001 (page 2 of Table J.6 of Appendix J to the CR) for the UC site, and SRK-SV-0008 (page 2 of Table J.7 of Appendix J) for the NC site. Based on comparisons of these drawings, the boundaries of estimated contamination and actual excavation agree. Thus, it appears that the contaminated areas of the designated sites have been excavated.
b) Cleanup of buildings:
The CR indicates that at the time of remedial action there were no buildings on site which required decontamination and that all of the contaminated structures at the Slick Rock sites were demolished and placed in the Burro Canyon disposal cell. This action meets the requirements of the RAP and TER for buildings.
c) Routine application of supplemental standards for Th-230 contamination:
Appendix J (Section 2.5) of the CR (DOE 1997) indicates that for excavation control and for verification, Th-230 measurements were made and the 1000-year concentration of Ra-226 I
was determined for comparison with the EPA standards for Ra 226. ',~his conforms to one of the requirements of the generic Th-230 protocol to be followed (cited in the RAP and TER) for use of supplemental standards for areas of Th-230 contamination near the surface of the final grade, described above.
In its approval of the generic Th-230 protocol, the NRC imposed additional conditions, one of which is applicable to the Slick Rock sites. The NRC indicated (Holonich 1994) that because the generic Th-230 protocol does not consider the volume of Th-230 contamination, or the additional health risk from any residual uranium, implementation of the protocol for each site should include a site-specific analysis of the health risk, and should emphasize reducing the Th-230 to ALARA levels. The NRC (Holonich 1994) noted that the DOE's dose assessment included some assumptions that the NRC staff thought may not be conservative for all sites, 2
one of which was the assumption that the contaminated area involved only one 100 m grid.
The CR did not originally contain a site-specific dose assessment of the residuallevels of Th-230. Thus, the NRC staff reviewed the Th-233 verification data to determine how many verification grids were involved in the use of the Th-230 criteria of the generic Th-230 protocol. For this tally, the staff counted grids for which the Th-230 concentration exceeded either 5 pCi/g above background for surface samples or 15 pCi/g above background for subsurface (deeper than 15 cm) samples. Concentration levels less than these values would 10
__ 7 be reasonably expected to occur with Ra-226 concentrations at the EPA cleanup standards
- (with the assumption that Th-230 is roughly in equilibrium with Ra-226 in material of tailings
' origin).' The NRC staff identified 3 grids at the Slick Rock UC site and 6 grids at the NC site which involved the use of the generic Th 230 criteria. These grids were relatively scattered, with at most 3 of the grids next to each other at the NC site. The staff concludes that the grids involved are relatively isolated; therefore the dose assessment used in supporting the generic Th-230 protocol should be applicable to the Slick Rock sites. The staff concludes that the requirement for a site-specific. dose assessment is satisfied by the generic analysis performed to support the generic Th-230 protocol. The staff notes, that Section 3.3 of Appendix J of the CR was revised to describe a site-specific dose assessment for the Th-230, with a calculated dose to a resident farmer of 9 mrem / year.
Section 3.3 of Appendix J of the CR also provides an ALARA analysis for the Th-230 contamination. The CR indicates that Th-230 concentrations decrease slowly with depth, so that removing 1 or 2 feet of material would not significantly decrease the risk (from radiation doses). However, the costs of excavating, transporting, and disposing of the excavated material would be significant, and the additional remediation activities would pose health and safety risks to workers. ~ In the CR DOE concluded that it would not be reasonable to j
excavate Th 230 to levels below 43 pCi/g. The NRC staff agrees that the excavation performed appears to be ALARA.
- 2. Soil Cleanup Verification:
a) Areal extent of verification:
in the Slick Rock CR, two drawings show the approximate boundaries of the extent of excavation: SRK-SV-0001 (page 2 of Table J.6 of Appendix J to the CR) for the UC site, and i
SRK-SV-0008 (page 2 of Table J.7 of Appendix J) for the NC site. Based on spot checks of l.
the data presented in Tables J.6 (for the UC site) and J.7 (for the NC site) of Appendix J of l
the CR, it appears that results have generally been presented for excavated areas within the boundaries of the designated sites. There were a few grids for which verification results were not presented in these tables; these exceptions are described in subsection c) below.
b) Routine verification methods and results:
The CR indicates, in Appendix J (Section 2.2) that approved procedures were used for soil verification measurements (DOE 1997).The method used for the majority of the verification grids was composite soil sampling. The Remedia! Action Contractor (RAC) procedure for verification soil sampling, procedure OP-003-1, is included as part of Exhibit J.1 to Appendix J of the CR. The grids for verification sampling at the Slick Rock processing sites were 10 m 2
by 10 m (100 m area). From each verification grid, a composite sample.was taken, formed from nine relatively uniformly spaced plugs taken to a depth of 15 cm. The plugs were mixed to form the composite, from which an aliquot is taken for analysisi The aliquot is placed in a sample can and counted with the Opposed Crystal System (OCS), which is a gamma spectromet;/ system, to measure the Ra-226 concentration. The initial count is corrected (for the disequilibrium of Rn-222 and prugeny and for moisture content) to estimate the final result. The' sample is then dried and the sample cans are then sealed and stored for 20 days to allow ingrowth of Rn-222 and progeny, after which a final count is made to obtain the
- verification concentration.
As indicated above, the RAP indicated that two in situ meihods could be used for areas of windblown contamination: (1) nine-point composite gamma measurements made using hand-11
J
\\
i held instruments and (2) the RTRAK mobile gamma detection unit (for areas that are too large to sample by hand methods). As described in Section 6.2.1.3 of the Remedial Action Assessment section of Volume 1 of the CR, the RTRAK system was not used for ven;ficatio'n,
~
at the Slick Rock sites.
The composite gamma measurement technique, referred to as the Hand-held Gamma Verification System (HGVS), was used for verification, and its use is described in Section 2.4 of Appendix J of the CR and in Section 6.2.1.2 of the Remedial Action Assessment section of Volume 1 of the CR. The HGVS was used at some locations at the UC and NC processing sites where soil samples were difficult to collect, including locations of exposed rock. The procedure for verification using the HGVS, procedure OP-003-9, is included as part of Exhibit J.1 to Appendix J of the CR. The method is based on a correlation of average gamma radiation count rate (with a shielded instrument) to soil Ra-226 concentration (measured by soil sampling and analysis). For the HGVS, gamma count rates are measured at nine locations above the soil within a verification grid (100 m area). The average gamma count 2
rate is calculated, and this average is used to estimate the Ra-226 concentration in the so:1.
An initial correlation between the average gamma count rate and the measured soil concentration of Ra-226 was developed, prior to use for verification measurements, using paired measurements from 40 grid areas. During verification, additional soil samples were obtained from at least 5% of the grid locations (38 additional locations), to add data points to the correlation. From the 78 data points, a linear regression was calculated, along with the upper bounds of one-sided 95% confidence intervals on the predicted Ra-226 concentrations.
To simplify, a straight line was then fit to these upper bounds, to provide a linear estimator of
.the upper bounds. The linear estimator of the upper bounds was then used during verification to "... conservatively predict Ra-226..." concentrations based on the average gamma count rate. Thus, for verification measurements, the measured gamma count rate is used to estimate an upper bound (95% confidence) on the Ra-226 concentration in the soil.
The final data, regression analysis, and plot of the data and regression curves for the HGVS measurements are provided in Exhibit J.2 to Appendix J of the CR. These items were reviewed by the NRC staff. Tables J.6b and J.7b of Appendix J to the CR provide results of the HGVS measurements, including results for the " quality control" soil sample i
measurements. From a review of these tables, it was verified that soil sample results were available for 38 verification grids, which was greater than 10% of all the HGVS verification grids. Thus, the requirement for soil samples to be obtained from at least 5% of the verification grids was met. From the data shown in Exhibit J.2, the staff verified that the data from these 38 additional soil samples were included in the development of the regression and the linear estimator of the upper bound curve. The NRC staff also concludes that the approved procedure was adequately implemented.
From the NRC staff's brief review of the data, plot, and regression for the HGVS method, including a comparison of the data obtained during verification activities (the 38 additional soil sample data points) to the data obtained prior to verification (the 40 initial data points), it appears that the data obtained during verification activities exhibit significantly greater
. variability than do the initial data. This could be an indication that the initial data points were not properly representative of the areas for which the HGVS procedure was to be used. By grouping the additional data and the initial data together for the regression analysis, as described in the CR, the greater variability in the data obtained from verification sampling (which would seem to be the most representative)is effectively diluted (reduced) by the lesser variability in the initial data. Thus, the regression developed in the CR may 12
underestimate the actual variability in verification sampling results for the HGVS technique, and thus may underestimate the value of the upper bound (95% confidence) on Ra-226
'conoeritrations at particular gamma count rates. The result may be that the upper bound values are associated with a lower (lower than 95%) confidence level than was intended.
This could result in a higher than planned probability that the Ra-226 concentration has been i
underestimated at some verification grids, and that the actual Ra-226 concentration exceeds the EPA standard. The NRC staff acknowledge
- that the confidence level for the calculated
{
upper bound values may be less than the inter.ed 95%, but the confidence level is still expected to be reasonably high. Thus, the NRC staff concludes that the HGVS verification method, as used, is an appropriate and acceptable method for verification in those areas for which soil sampling was difficult at the Slick Rock processing sites There were a few grids for which verification measurements did not use the methods f
described here; these exceptions are described in subsection c) below, i
The background concentration of Ra-226 in soil was determined to be 1.4 pCi/g, as described in both the CR (Section 2.3 of Appendix J) and in Table 6.1 of the Remedial Action Selection Report of the RAP (DOE 1996). Section 3 of Appendix J of the CR discusses the soil
. verification measurements and results. From the two Slick Rock processing sites, a total of about 4500 soil samples were taken and analyzed for Ra-226, with about 240 of these also analyzed for Th-230. About 350 grids were verified using the HGVS.
For the two sites, the gross Ra-226 concentrations from surface (less than 15 cm of backfill) soil samples were an average of 2.0 pCi/g and a maximum of 6.4 pCi/g. Gross Ra-226 concentrations for deeper soil samples (at least 15 cm of backfill) were an average of 5.0 pCi/g and a maximum of 15.8 pCi/g. For surface soil samples analyzed for Th-230, the gross 1
1000-year Ra-226 concentrations were an average of 2.0 pCi/g and a maximum of 6.4 pCi/g.
For deeper soil samples analyzed for Th-230, the gross 1000-year Ra-226 concentrations were an average of 2.3 pCi/g and a maximum of 15.4 pCi/g. The NRC staff performed spot checks of the verification results in Table J.6 and J.7 of the CR, and found no data to contradict the summary values from Section 3 of Appendix J described here. Thus, from the
' values of the Ra-226 concentrations and 1000-year Ra-226 concentrations, the verification measurements indicate that the EPA standards were generally met for soil cleanup of Ra-226 and that the Th-230 standards, from the generic Th-230 protocol for routine application of supplemental standards to Th-230 contamination, were also met.
For the HGVS measurements, the predicted upper bounds (95% confidence) on the Ra-226 concentrations were up to 6.5 pCi/g (the average was not provided). Five of the HGVS upper l
bound results were greater than 6.4 pCilg (5 pCi/g lirrit plus background of 1.4 pCi/g). Four l
of these five locations (D-26-25, D-34-10, E-24-02, and E-24-03) also had_ soil samples taken for quality controls, and the results of the analyses of the soil samples were less than 6.4 pCi/g. The fifth location (D-34-05) was a location with greater than 15 cm of backfill, so the limiting value is 16.4 pCilg (15 pCi/g limit plus background of 1.4 pCi/g). The NRC staff concludes that the available information for these five grid locations provides a high degree of
. confidence that the EPA standard for Ra-226 has been met.
c) Verification grids with nonstandard verification methods:
At the Slick Rock UC site, there were some verification grids for which standard verification l
measurements were not performed or no verification measurements were performed. These locations are described in Section 3.7 of Appendix J to the CR.
13
P There is no verification measurement for location F-01-10, because this grid was on a natural rock cliff side and could not be sampled due to safety hazards. The CR also indicates that this grid has no soil, and so is unlikely to be significantly contaminated, if contaminated at all.
The NRC staff. concludes that there is an acceptable level of confidence that the EPA standard for Ra-226 has been met for this grid.
{
Six other grids (D-28-06, D 28-11, D-28-12, D-28-17, D-28-18, and D-28-24) could not be l
sampled using standard verification methods due to safety concems associated with their locations on the steep banks of a roadside. Instead,~ the locations were sampled at the top of the slope, the toe of the slope, and 6 ft up from the toe of the slope. From these samples, the maximum Ra-226 concentration was 7.4 pCi/g, from a location that was backfilled with greater than 15 cm of backfill. The next highest Ra-226 concentration was 6.0 pCi/g. The NRC staff agrees that the results obtained provide an acceptable level of confidence that the EPA standard for Ra-226 has been met.
There also were a few grid locations in Areas C and D, in the area of supplemental standards application for the high pressure gas line, for which standard verification was not performed.
A few of these grids did not have any verification results. For grid locations bordering the supplemental standards area shown in Area C (drawing SRK-SV-0004, page 30 of 91 of Table J.6 of Appendix J of the CR), partial grid samples were collected. Because these grids are in areas proposed for supplemental standards application, standard verification samples are not necessary. As indicated in Section 3.7 of Appendix J to the CR, information on the resideal levels of Ra-226 at these supplemental standards locations is provided in Appendix K to the CR.
d) Quality assurance measurements by outside laboratories:
Quality assurance measurements performed by outside laboratories for measurements of Ra-226 and Th-230 in soils are described in Sections 6.2.3.3 and 6.2.3.4 of the Remedial Action Assessment section of Volume 1 of the CR and Section 4 of Appendix J to the CR.
These sections of the CR indicate that the quality assurance (QA) measurements for Ra-226 and Th-230 in soil changed during the course of work at the Slick Rock sites. Initially,4% of all verification samples were independently analyzed by an offsite laboratory (Barringer), as a check on the measurements from the onsite laboratory (which was run by the RAC). In the later stages of the work at the Slick Rock sites, this offsite laboratory program was replaced by a blind sample testing program. From NRC staff discussions with DOE and its contractor, it ap;..ars that the blind sample program was implemented to provide QA data that would be more useful than data from the previous program. For this blind sample program, test soil samples were prepared from material collected at several UMTRA Project sites, and samples were sent to the Yankee Atomic Environmental Laboratory (YAEL) and to the Slick Rock site laboratory for analyses of Ra-226 and Th-230.
The QA measurements from Barringer for the early part of the project are presented in Appendix J of the CR. However, in Section 6.2.3.3 of the Remedial Action Assessment section of Volume 1 of the CR, it is stated that it was difficult to compare the results of the Barringer data to the onsite OCS data. This difficulty was due to differences in analytical techniques, and because of the possibility that bcth the Barringer and OCS data could be biased low or high. Because of this difficulty, a comparison of the Barringer data to the OCS data was not presented in the final CR The NRC staff agrees that the direct comparison of the Barringer data to the OCS data may be inappropriate. This means that the primary quality assurance for the onsite OCS analyses must come from the analyses performed at 14 i
i the onsite laboratory, including the quality control measurements for the OCS, described below.
Results of the blind sample testing program are discussed in Appendix J of the CR. Table J.2 of Appendix J shows the results of the quaderly Ra-226 and Th-230 blind analyses by the onsite laboratories, Barringer, and the YAEL. This table also shows the 2-standard deviation ranges for the results. Section 4,1 of Appendix J indicates that the results of blind analyses l
were acceptable if the 2-standard deviation ranges for the sample and the known analyses l
overlapped. Such overlap occurred for most of the blind analyses by the onsite laboratories.
Results not meeting the criterion for Ra-226 analyses included those for Naturita OCS '
' number 1 (NAT-1) for the fourth quarter of 1995 and the first and second quaders of 1996; I
NAT-2 and NAT 3 for the second quarter of 1996; and NAT-3 for the third quarter of 1996.
However, in all these cases the sample results were higher than the known results. The CR concluded that since the bias was conservative (tending to overestimate concentrations), the i
results for the onsite laboratories were acceptable. Section 4.2 of Appendix J of the CR also indicates that the Slick Rock site laboratory blind analysis for Th-230 for the fourth quarter of 1995 was invalid, due to a batch failure in processing. The sample was not reanalyzed, but it was noted that the results for the following quarter were acceptable. The NRC staff concludes that the quality assurance results are acceptable.
e) Quality control measurements for the OCS.
The CR (Section 6.2.2.2 of the Remedial Action Assessment section of Volume 1 and Section 2.3 of Appendix J) indicated that a performance criterion for operation of the gamma spectrometry system (the OCS) used for Ra-226 verification measurements was that, at the concentrations of the standards (5 pCi/g), the Ra-226 verification must be performed such that the analytical results are within plus or minus 30 percent of true concentrations, at the 95 percent confidence level. Appendix J of the CR briefly describes the measurements made and the results used to show compliance with this criterion. The error limits were empirically determined, using a National Institute of Standards and Technology traceable reference material, with a Ra-226 concentration of 5.12 pCi/g, that was routinely analyzed during the verification process. It appears that these measurements were performed multiple times per day, as more than 2000 of these OCS quality control (QC) checke were performed.
Table J.1 of Appendix J of the CR provides a summary of the OCS QC measurements,-
including the mean and two standard deviation value of the OCS measurements for each OCS instrument used for the Slick Rock verification analyses. This summary is repeated in Table 1 below. As indicated by the mean value plus and minus two standard deviations, the 95% confidence intervals of the OCS measurements were within 30% of the true value.
Thus the NRC agrees that the performance criterion for the operation of the OCSs was met for the systems used at the Slick Rock sites.
i i
15 l
1 l
Table 1. Summary of Slick Rock Site OCS QC Measurements Average
~
OCS number result i 2s
- Number of checks
- SRK-2 4.7 i 0.9 1012
. SRK-4 4.7 i 0.9 1002 NAT-1 *
~5.1 i 0.7 169 NAT-2 * -
5.4 i 1.0.
95 NAT-3
- 5.2 i 0.8 118
. Here
- 2s means plus or minus 2 standard deviations (though the CR used the term sigma). Note that the true concentration of the standard used for the QC checks was 5.12 pCi/g.
' * ' These are Naturita site OCS instruments, that were used for some of the Slick Rock verification analyses.
From the data shown in Table J.1 of the CR (see Table 1 above), the NRC staff has evaluated the significance of the differences between *.he mean QC measurements for OCSs SRK-2 and SRK-4 and the true mean concentration of the reference material. Using a Student's t test, the mean concentrations measured by these two OCSs are significantly different from the true mean concentration (p<0.05). Since the measurernents were apparently performed as quality controlmeasurements, the NRC staff concludes that the performances of OCSs SRK-2 and SRK-4 may not have been within reasonable bounds.
The CR has not provided any analysis of these means of the QC measurements and has not provided any analysis of potential corrections that could be performed to account for the apparent low bias in results from OCSs SRK-2 and SRK-4.
The NRC staff estimated the impacts of such potential corrections, as follows. The results for OCSs SRK-2 and SRK-4 appear to be biased low by approximately-8.2%, and a correction factor would be 1.09 (5.12 oCi/g + 4.7 pCi/g). From the CR it cannot be determined which verification measurements for Ra-226 were made using OCSs SRK-2 and SRK-4; therefore the staff looked at all verification results (a worst case). From this review, the staff determined that there could be about 27 verification grids (25 of which were surface samples, with less than 15 cm of backfill) for which the corrected results would exceed the EPA standards for Ra-226 in soil. Of these, the highest corrected concentrations are 17.2 pCi/g for subsurface samples and 7.0 pCi/g for surface samples. Therefore, the EPA standard for Ra-226 may not have been met for all verification grids (about 27 grids might exceed the standard),' although the standard would only be exceeded by a small amount.
' The staff notes that the affected grids are generally isolated from each other, and that results from most immediately adjacent verification grids would be within the standards. Also, the average concentration of Ra-226 remaining on the site is significantly below (within) the standards. _The staff considers it likely that future inhabitants of the site would be exposed to the residual radioactivity from many verification grids, so the impact (on potential dose) from isolated grids would be lessened. For these reasons, the NRC staff concludes that the intent of the FPA standards has been met and the residual concentrations are considered acceptable.
The NRC staff also concludes that the quality control measurements do not appear to indicate any problems in the way that verification measurements were made.
16
f) Corrections for cobbles in soil:
- for soils with significant cobbles. Section 6.2.1.3 of the Remedial Action Assessment section of Volume 1 of the CR indicates that there were no appreciable amounts of cobbly material in the subpile areas, so the cobbles-to-fines soil verification protocol was not used at the Slick Rock UC and NC sites.
g) Frequency of Th-230 measurements:
As discussed earlier, the RAP and TER indicated that verification for Th-230 contamination l
(here Th-230 contamination means Th-230 in excess of Ra-226 contamination) would be performed using the UMTRA Project generic Th-230 protocol. This protocol (Chemoff 1993) provides the following scheme for verification sampling for Th-230. In areas on the processing sites that are suspected of preferentially mobilizing thorium contamination over radium contamination, based on process knowledge or other sources such as previous 2
sampling data,100% of the (100 m ) grids are to be sampled and analyzed for Th-230. In subpile areas,10% of the grids are to be sampled. And, in areas where process knowledge and characterization data indicate no potential for preferential mobilization, sampling for Th-230 is not required. Also, if any verification samples exceed the generic Th-230 criteria of the protocol, the surrounding eight grids will be examined to determine if these also exceed the criteria.
(
Sections 2.5,3.12, and 3.13 of Appendix J of the CR (DOE 1997) describe the Th-230 l
verification sampling performed at the Slick Rock processing sites. Section 2.5 indicates that Th-230 sampling was conducted on a minimum of 10% of the subpile grids at both of the Slick Rock processing sites. Sections 3.12 and 3.13 describe the three areas on the Slick i
Rock sites where previous sampling indicated the presence of levels of Th-230 elevated i
above the Ra-226 concentrations. In two of these locations, Th-230 sampling was performed at 100% of the verification grids. In the other location, the excavation was deeper than the depth where Th-230 was expected to be in excess of Ra-226 levels. In this general area, more than 5% of the grids received Th-230 sampling, to provide an indication that Th-230 was not migrating more than the Ra-226.' One verification grid required additional excavation and resampling because the initial sampling indicated a Th-230 concentration greater than the generic Th-230 protocol value.' Verification samples from all of the surrounding grids -
were sampled for Th-230. The NRC staff concludes that Th-230 verification measurements l
were performed at the frequencies required.
- 3. Nonroutine Application of Supplemental Standards:
Three areas within the gas pipeline right of way through the Slick Rock UC sit? are under consideration for application of supplemental standards. These areas are referred to as the Gas Plant Area. S8 Road Area, and Madame Curie Area. Drawings provided in Appendix K of the CR show that the pipeline generally lies 2--4 ft below the ground surface, and that the contamination in these three areas is thought to remain generally above the pipeline,
- although it appears that only limited characterization of the remaining contamination has been performed. At one point contamination around the pipeline actually Does under the public road. In performing remedial actions within the pipeline right of way, contaminated materials were excavated no closer than 10 ft from the pipeline location. ~ Because of standard precautions about allowable slopes for excavations, contaminated material was left in the slopes away from the pipeline at distances greater than 10 ft. In addition, six inches of I
L 17 L
contaminated material were removed from the surface above the pipeline (in a 20-ft band,10 ft to either side of the pipeline). Because of standard precautions that had to be taken to,
assure that the slopes were no steeper than allowable and because the county road,was.
required to remain open, an area underlying the county road is also included in the supplemental standards area. DOE proposed leaving the remaining contaminated material in place near the pipeline and under the county road based on risks of injury to workers and the public if the material were excavated.
The EPA cleanup standards in 40 CFR 192.21 specify criteria that may be used to determine applicability of supplemental standards. Section K.1 of Appendix K of the CR indicates that criterion (a) of the EPA Standards at 40 CFR 192.21 is applicable to the pipeline right of way.
This criterion (hereinafter, criterion (a)) states:
(a) Remedial actions required to satisfy Subparts A or B would pose a clear and present risk of injury to workers or to members of the public, notwithstanding reasonable measures to avoid or reduce risk.
The NRC staff was originally concemed (Holonich 1998) that the CR did not contain sufficient justification for the applicability of criterion (a). Specifically, the staff noted that the CR described measures that could be used to mitigate the risks associated with working around the gas pipeline, but did not provide justification for why such mitigative measures would not be reasonable to apply. In addition, the staff was concemed that the arguments about the high cost for implementing risk-reducing measures and the reluctance of the owner of the gas pipeline right of way easement to allow full access to the area were not appropriate to demonstrating the applicability of criterion (a). In response to those concerns, the DOE provided additional discussion and clarification, in Appendix K to the CR, to support a i
justification for the applicability of criterion (a).
Section K.4.1.2 of Appendix K describes the risks associated with working performing remedial activities around the high-pressure gas pipeline. The revised section indicates that the risks of working around the pipeline are prohibitively high when the pipeline is pressurized. It also states that even if the pipeline is depressurized and purged, there remains an extreme degree of risk for anyone in the general vicinity of the line. The risks are directly linked to the in-ground age of the pipeline, because internal and extemal deterioration begin to affect the physical integrity of the components. The deterioration, coupled with the constant pressure on the pipeline, can, over time, produce weak points that are not readily identifiable. The risks include the possibility of physically rupturing or puncturing the line as a direct result of remedial action activities. It is also conceivable the activity associated with the removal of contaminated material from around the line could exacerbate a weak 6 pot and cause a rupture even with the most cautious of operations. Such a breech, coupled with the almost certain combustion of any gas remaining in pockets in the pipeline present a direct health risk both to the workers conducting the remedial action as well as any personnel in the immediate area. After the remediated line has been reburied and the pressure returned the possibility of a blow out still exists and this possibility would extend along the entire length of line that had been depressurized. A failure at that time would place workers, local residents, and visitors ut risk. The CR also acknowledged that an important reason that remedial action of all the contaminated material around the pipeline was not pursued is that the gas company, which owns a right-of-way for its pipeline, refused to allow more remedial action than what was performed.
18 l
The NRC staff concludes that reasonable mitigative measures would not sufficiently reduce 1
- the risks associated with excavations around the high-pressure gas pipeline The staff also 1
' ackno' ledges that the refusal of the pipeline owner to allow complete remedial action w
contributed to the DOE's decision not to pursue further remedial action. The staff thus concurs that criterion (a) is applicable to the material around the gas pipeline, and the use of a supplemental standard is appropriate.
Because of its location, the residual contamination is unlikely to present any significant risk to people in the future, and if repairs to the pipeline are necessary, the land owner and pipeline owner are aware that contamination exists around the pipeline. Thus, the NRC staff concludes that the cleanup of contamination around the pipeline has come as close to meeting the Ra-226 standards as is reasonable under the existing circumstances.
Section K.4.1.2 of Appendix K to the CR also indicates that for cleanup to proceed in the S8 Road Area, the County road would have to be closed. This road is the only access to a large area west of the site for public and emergency vehicles. Relative to the applicability of Criterion (a), the NRC staff concludes that closing the County road would be an unreasonable mitigative measure to reduce risks to workers. This provides additionaljustification for the applicability of Criterion (a) for the S8 Road Area.
- 4. Radon Attenuation:
The cover system that was installed at the Burro Canyon disposal cell to meet th' e radon flux standard was generally built as designed in the RAP and PID 11-S-14. The contaminated materials with the lowest Ra-226 concentration were placed on the top of the relocated tailings materials followed by a 1% ft layer of radon barrier material and a 2 ft layer of frost barrier material. However, the actual characteristics of the disposal cell and cover materials,
^ which were measured and calculated during construction of the cell, were different than those assumed for the design in the RAP. Because of these differences, for the CR review, the NRC staff has performed a complete review and analysis of the radon flux from the as built disposal cell. Both DOE's analysis of the radon flux and NRC's analysis are discussed below.
The DOE used the RAECOM computer code to calculate the radon flux through the cover system of the as built Burro Canyon disposal cell. The CR includes the most recent calculation for the radon barrier, calculation number 11-535-03-00. The calculations to support the CR were performed for a baseline case, which used mean values of parameters, and for a " worst case," which used the mean values adjusted by plus or minus the standard error of the value, where the adjustment was always in the direction to produce higher exit flux. The NRC staff review focused on the worst case analysis, because acceptable results for this analysis would provide reasonable assurance that the radon flux limit would not be exceeded. Table 2 shows the layer-specific parameter values that DOE used for its worst case radon flux analysis (DOE 1997). Other parameter values used by DOE were an I
l ambient (above ground) radon concentration in air of 1.5 pCi/L and a radon flux into the 2
bottom layer of 0 pCi/m -s.
l l
19
- Table 2. Layer-Specific Parameter Values Used By DOE in Calculation of Radon Flux from Burro Canyon Disposal Cell Bulk, Ra-226 Radon Moisture Rakioh diffusion Thickness
. density concentration emanation content coefficient 2
Layer (cm)
Poros;ty (g/cm')
(pCi/g).
fraction (weight percent)'
(cm /s)
Frost barrier (top) 61 0.43 1.62 0
0 9.2 0.023 Radon barrier ;
43-0.39 1.70 0'
O 11.2 0.015 Clean fill 61 0.39 1.62 1.06 0.42 9.2 0.018 UC subpile/offpile 61 0.40 1.62 6.57 0.47 7.7 0.023 UC subpile/offpile 61 0.40 1.62 12.32 0.46 7.7 0.023 UC subpile/offpile 61 0.40 1.62 32.09 0.39 7.7 0.023 UC subpile/offpile 61 0.40 1.62 33.59 0.32 7.7 0.023 UC subpile/offpile 61 0.40 1.62 30.42 0.36 7.7 0.023 UC subpile/offpile 61 0.40 1.62 53.03 0.34 7.7 0.023 UC subpile/offpile 61 0.40 1.62 52.97 0.33 7.7 0.023 The NRC staff's review addressed the adequacy of the parameter values used in the DOE calculations, by evaluating the justifications and assumptions for each parameter value to confirm that selected values were representative of the material, or were conservative estimates; were consistent with the as built construction; and were based on long-term conditions. The calculation number 11-535-03-00, in Volume 3 of the CR, contains most of the information related to the radon barrier design. The NRC staff then performed an independent calculation of the radon flux from the Burro Canyon disposal cell using the RADON code (NRC 1989), waich implements the same model as the RAECOM code. The following discussions provide NRC's evaluation of the parameter values and of DOE's justifications and assumptions, and discuss NRC staff's calculation of radon flux.
a) Evaluation of layer thicknesses:
The DOE calculations evaluate radon emissions from the top 16 ft of material in the disposal cell (not including cover materials). This approsch is considered adequate, because deeper materials would contribute negliglbly to the radon flux from the top of the disposal cell. ' The layer thicknesses for the UC subpile and offpile material and the clean fill material are the thicknesses from which the Ra-226 concentrations and radon emanation fractions were measured during placement of these materials i'n the disposal cell. The 2-ft layers provide for adequately detailed characterization of the radon source term in the cell.
The layer thicknesses for the radon barrier and frost barrier materials are the values from the cover design specifications provided in the RAP. The as-built average thicknesses of these
' layers are slightly thicker than these design values, at 1.58 ft for the radon barrier and 2.04 ft for the frost barrier, based on the data provided in a Disposal Cell Layer Thickness chart in Section ll of Volume 1 of the CR (DOE 1997). NRC staff considers that the thicknesses in Table 2 are considered conservative (in that they tend to overestimate the calculated radon flux) and are thus adequate for the radon flux calculation.
b)' Evaluation of bulk density and porosity:
The determinations of bulk density and porosity are described in calculation number 11-535-03-00, in Volume 3 of the CR. The results from a series of maximum dry density tests and specific gravity measurements were averaged to determine representative values of maximum density and specific gravity for each different material. The compacted dry densities were then calculated based on the compaction specifications and the maximum dry l
20
density. Representative porosities were then calculated from the specific gravities and
- compacted dry densities. These methods are generally acceptable to the NRC staff.
For the frost barrier material, an adjustment to the porosity (at the compacted density) was made to account for the degrading effects of freeze-thaw cycles. The porosity was increased by 11.5%, from 0.39 to 0.43 (calculation number 11-535-03-00, in Volume 3 of the CR), which was stated to be a conservative adjustment for freeze-thaw degradation. The NRC staff agrees that such an adjustment is conservative. The staff notes, however, that the bulk density for the frost barrier should also have been adjusted, to correspond to the adjusted porosity. The adjusted density would be 1.50 g/cm, instead of the value of 1.62 g/cm.
3 Although this adjustment would have a very small impact on the radon flux calculation, NRC staff used the adjusted value in its calculation.
c) Evaluation of Ra-226 concentration and radon emanation fraction:
The determinations of Ra-226 concentrations and radon emanation fraction are described in calculation number 11-535-03-00, in Volume 3 of the CR. During placement and compaction of contaminated materials at the disposal cell, measurements were made of Ra-226 concentration, Th-230 concentration, and the radon emanation fraction.
The Th-230 and Ra-226 concentrations were used to determine the Ra-226 concentrations to be used in the radon barrier calculations. In cases where the Th-230 concentration exceeded the Ra-226 concentration, decay of the original Ra-226 plus ingrowth from the Th-230 decay were considered in calculating the 1000-year Ra-226, which was then used for the radon barrier calculations. In cases where Th-230 concentration is less than the Ra-226 concentration, the present concentration of Ra-226 was used. This method results in the use of the higher of the present and the 1000-year Ra-226 concentrations, and so is considered a
conservative. The NRC staff agrees that this method is adequate.
These Th-230, Ra-226, and emanation fraction measurements were made at 27 locations on the disposal cell, as shown in a figure on page 89 of 108 of the calculation (in Volume 3 of the CR). The Ra-226 concentrations and emanation fractions were tabulated for each 2-ft interval in depth below the radon bsrrier layer (Table 2 of Appendix D to calculation number 11-535-03-00), These summaries also included mean values and standard errors of the mean values. The mean values (of the highest Ra-226 concentration over 1000 years and the emanation fraction) were used in the baseline radon flux calculation, while values of the mean plus the standard error of the mean were used in the worst case calculation. In general, this approach is acceptable to the NRC staff.
However, the staff noted that none of the sampling locations were on the side slopes of the disposal cell, even though i+ appears that roughly 30% of the total surface area of the disposal cell is on the side slopes. Although the. staff acknowledges that it appears extremely unlikely that Ra-226 concentrations in materials on the side slopes of the disposal cell are i
l high encugh that the radon flux standard would be exceeded, the CR did not contain additional information that might indicate that the Ra-226 concentrations from locations on the top slopes would be representative of the con entrations on the side slopes as well.
Thus, in comments to DOE on the draft CR (Holonich 1998), the NRC staff expressed concem that insufficient information on the representativeness of the Ra-226 measurements had been provided. In its responses to the NRC comments (Woodworth 1998), DOE provided additional clarification on this issue. The DOE indicated that the disposal cell was reconfigure when it was found, toward the end of construction, that the total quantity of 21-l
contaminated material was less than original estimates. The as-built disposal cell now has a larger top-slope and smaller side slopes, and as a result, all the sampling locations, which were originally on the side-slopes are now located on the top-slopes. The DOE abo.
indicated that the sampling locations are still distributed such that all areas of the cell were
~
l' sampled. The NRC staff concludes that the sampling locations used are adequate to represent the entire surface of the disposal cell.
In'the NRC's TER approving the RAP radon barrier design, one of the conditions imposed, to which the DOE committed, was that the DOE was to measure the Ra-226 concentrations in l
the radon barrier and frost barrier materials, to assure that concentrations are at background levels as was assumed in the modeling. Section 1.0 of the Frost Protection Material section of Appendix E of the CR indicates that the frost protection material was taken from the excavation of the disposal cell. Thus, the frost protection material is the same material as the " clean fill" material that was put in the disposal cell above the contaminated materials.
Measurements of the clean fill material (from calculation 11-535-03-00, in Appendix B of the CR) indicate an average Ra-226 concentration of 1.32 pCi/g, with a standard deviation of 1.23. Thus, the frost protection material has Ra-226 concentrations essentially at.
background levels, in its responses to comments (Woodworth 1998), DOE provided additionalinformation regarding the radon barrier material. The DOE indicated that the radon barrier material came from the Suckla borrow source. Based on 12 measurements, the Ra-226 concentrations ranged from 1.2 to 3.3 pCi/g, and had an average of 2.4 pCi/g, which is slightly higher than the background level of 1.4 pCilg. The NRC staff concludes that the Ra-226 concentrations in the radon barrier and frost protection materials are adequately close to background levels for the radon flux analyses performed.
d) Evaluation of long-term moisture content:
The selection of long-term moisture content values for the radon flux calculations is described in calculation number 11-535-03-00 (Volume 3 of the CR. For the radon barrier material and the UC offpile and subpile material, data were available for 15-bar moisture content, in situ moisture content, and optimum moisture content. For these materials, whichever of the three was the lowest was used to represent the long-term moisture content in the radon flux calculations. This method of selecting the representative value is considered generally acceptable by the NRC staff. However, the NRC staff disagrees with one detail of the implementation. The calculation in the CR has used the same moisture content for the baseline analysis as for the worst case analysis. For the radon barrier and UC offpile and subpile materials, the in situ moisture content was used, since these values were lower than the optimum moisture contents and 15-bar moisture contents. In developing the in situ moisture content, measurements were made at a number of locations, and the average value was used for the radon flux calculation. From the same sets of measurements, worst case in situ moisture contents could be calculated as the mean value minus the standard error of the mean. For the NRC's analysis, the NRC staff have used such revised worst case values of moisture content, which are 7.1% (by weight) for the UC offpile and subpile material and 10.5% fer the radon barrier material (from a table of in situ moisture content in Appendix A of the calculation, page 28 of 108).
For the clean fill material and the frost barrier material,15-bar moisture measurements were not available, so the analysis in the CR used the lower of the in situ and optimum moistures.
l Since the 15-bar moisture values were not available, there is less assurance that DOE's chosen moisture content is representative of the long-term moisture content. Thus, for the l
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NRC analysis, the NRC staff have chosen to use a moisture content of 6%, that is thought to I
t be very conservative.
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e) Evaluation of radon diffusion coefficients:
The selection of radon diffusion coefficient values for the radon flux calculations is described in calculation number 11-535-03-00 (Volume 3 of the CR (DOE 1997)). For the radon barrier and UC offpile and subpile materials, the radon diffusion coefficient was determined based on tests of samples of the materials.1 For the radon barrier material, four samples were
' taken, and measurements were made at five moisture saturation fractions for each sample.
For the UC offpile and subpile materials, six samples were taken, with measurements made at four to five moisture saturation fractions for each sample. For each sample, values were plotted and a best fit of the diffusion coefficient as a function of moisture saturation was obtained using a least squares method. The diffusion coefficient for each sample was determined from the long-term moisture content and the best-fit function. The diffusion coefficient to be used in the radon flux calculations was then determined as the mean of the individual sample values (for the baseline analysis) or the mean plus the standard error of the mean (for the worst-case analysis). This method for determining the radon diffusion coefficients is considered acceptable by the NRC staff.
For the frost barrier and clean fillinaterials, the radon diffusion coefficient was estimated using an empirical correlation function:
2 2
D = (0 07 cm /r) exp [-4(S-Sp,3s)),
2 where D is the diffusion coefficient (cm /s), S is the moisture saturation fraction, and p is the porosity. The use of this correlation function is described in Regulatory Guide 3.46 (NRC 1989), and is considered acceptable by the NRC staff.
j The general methods used to determine the diffusion coefficients are acceptable. However, l
for the worst-case analysis, the diffusion coefficients were based on the same moisture content used for the baseline analysis. Thus, for the NRC's analysis of the radon flux, the i
diffusion coefficients have been recalculated based on the revised worst-case moisture contents as described above. These revised values are shown in Table 3.
Table 3. NRC's Revised Estimates of Diffusion Coefficients Moisture content Diffusion Bulk density (weight (saturation coefficient Material (g/cm')
Porosity percent) fraction)
(cm /s) 2 l
Frost barrier 1.50 0.43 6
0.21 0.036
- f Radon barrier 1.70 0.39 10.5 0.46 0.016
- l
. Clean fill 1.62 0.39 6
0.25 0.030
- l.
UC offpile and subpile 1.62 0.40 7.1 0.29 0.026
- Diffusion coefficient calculated from correlation equation at indicated porosity and saturation fraction b
Diffusion Coefficient Calculated as mean plus standard error of the mean from individual sample values at saturation fraction (individual values based on fitted function).
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f) Evaluation of generalinput parameters:
In addition to the layer-specific parameters, the radon flux calculation requires the arnbient, j
radon concentration in air and the initial radon flux (into the bottom layer of the disposal cell).
As discussed in the TER, the radon concentration in air was measured in 1977 to be 1.5 pCi/L, which is the value used in the CR calculation. The TER also indicates that more
. recent monitoring, in 1990 and 1991, yielded a concentration of 0.5 pCi/L. As concluded earlier, this latter value is more appropriate, but the difference in the calculated radon flux is negligible, f
i
. The CR indicates that the initial radon flux was assumed to be zero, though no supporting documentation was given (page 6 of 108 of calculation 11-535-03-00 in the CR). Because the layers of material that are deeper than those explicitly modeled generally have higher concentrations of Ra-226, the initial radon flux would be expected to be greater than zero.
2
- For the NRC's analysis of the radon flux, the staff has chosen to use a value of 100 pCi/m s.
The impact of this change on the calculated radon flux would be fairly small, because the c
depth of the materials that are considered is great (16 ft).
I' g) Evaluation of calculated radon flux:
The analyses of radon flux in the CR used the RAECOM software, which is acceptable to the NRC staff. The results of the analyses in the CR were calculated radon fluxes on top of the 2
2 frost barrier of the disposal cell of 2.53 pCi/m -s for the baseline case and 3.95 pCi/m -s for the worst case. The NRC staff used the RADON software, which implements the same calculational models as does the RAECOM software, to reanalyze the radon flux. The NRC staff used the parameter values that DOE used for its calculations as shown in Table 2 of this report, with the changes to the diffusion coefficients, moisture contents,- dry density of the frost barrier material, ambient radon concentration, and initial radon flux, as noted above.
Based on these changes, the NRC staff estimated a worst case long-term radon flux of 6.9 pCi/m -s for the as-built disposal cell. These estimates of the radon flux are significantly 2
2 below the standard of 20 pCi/m -s.
Based on this review, the NRC staff concludes that there is adequate assurance that the 2
long-term radon flux standard of 20 pCi/m s will be met.
b) Radon flux measurements:
it is noted that radon flux measurements on the radon barrier were taken to meet a Clean Air Act requirement (in 40 CFR 61, Subpart T), and are provided in Appendix J of the CR (DOE 1997). However, since the EPA Clean Air Act requirement is not applicable to the NRC's involvement in the UMTRA Project, these data were not reviewed.
i) Other DOE commitments:
As discussed earlier, the NRC's approvals of the radon barrier designs of the RAP and PID 11-S-14 imposed the following conditions: (1) DOE was to perform testing to de;crmine and justify the long-term moisture content of the UC (Union Carbide site) offpile and subpile material, (2) DOE was to measure, during construction, the Ra-226 concentration, emanation fraction, and radon diffusion coefficient for the UC offpile and subpile materials, (3) DOE was to measure the Ra 226 concentrations in the raden barrier and frost barrier materials, to assure that concentrations are at background levels as was assumed in prior modeling, and (4) DOE was to measure the radon diffusion coefficient of the radori barrier material and justify the diffusion coefficient at the long-term moisture content.
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i Regarding commitment (1), as discussed in subsection d) above, additional measurements
- were performed. Regarding (2), as discussed in subsections c) and e), these
- characterization measurements for the UC offpile and subpile material have been made.
c Regarding (3), the discussion at the end of subsection c) indicates that the Ra-226
-l concentrations in the radon barrier and frost barrier materials have still rnt been provided.
Regarding (4), as discussed in subsection e), measurements of the rador, diffusion coefficient in the radon barrier material have been performed. Thus, all of these additional DOE commitments have been met, with the exception of measuring and providing information on the Ra-226 concentrations in the radon barrier and frost barrier materials (and this was discussed in subsection c), above).
Based on the above evaluations, the NRC staff concludes that commitments and requirements I
l stated in the RAP and TER have generally been fulfilled and that the data in the CR and other 4
documents provide reasonable assurance that the standards (or the intent of the standards) for soil cleanup and for disposal cell radon control have been met at the Slick Rock processing sites and the Burro Canyon disposal site.
2.2.4 Groundwater Protection Review Results The NRC staff reviewed the groundwater hydrology and the groundwater resources protection aspects of the remedial actions conducted by DOE at the Slick Rock sites during construction and as documented in the CR, to ensure that they were in compliance with EPA's groundwater protection standards in 40 CFR Part 192, Subparts A-C, and are consistent with the commitments made in the RAP. Areas of review included water resources protection standards l
for disposal, performance assessment, closure performance standards, and groundwater monitoring and corrective action. DOE committed to several Water Resources Protection I
l activities identified in its RAP documents and in the NRC TER. Briefly these commitments were:
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- 1. Construction of four standpipe wells within the disposal cell at the low point of the bottom t
subgrade. (TER section 5.4.4) l
- 2. Actively pump the standpipe wells if water levels approach the top of the sanri layer L
exposed in the disposal cell side wall. (TER section 5.4.4) i
' 3. Install a piezometer downslope of the disposal cell, interacting the sand layer exposed in the disposal cell side wall. (TER section 5.4.4)
- 4. ' Plug and abandon certain monitoring wells used for characterization at the former processing sites, and the disposal site. (DOE construction specification 02090-1)
During its review, of the CR and related documents, the NRC staff noted that DOE provided
. confirmation of completing the following commitments:
1; Standpipe wells: Section ll Design Assessment
'2. - Pump if water approaches top of sandstone Isyer: Section 11 Design Assessment
- 3. Piezometer in sandstone layer: Calculation SRK-06-97-24-12-06-00 submitted and approved after remedial action plan concurrence showed the piezometer was not needed.
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- 4. Well Abandonment: Drawings SRK-PS-10-0713, SRK-PS-10-0723,and SRK-PS 0732, and ir,dividual abandonment records.
Based on the above observations, the NRC staff concludes that the groundwater protection aspects of the remed,al action were completed in accordance with the design and procedures identified in the RAP, and the RAIP.
3.0
SUMMARY
NRC staff reviewed geotechnical engineering, surface water hydrology and erosion protection, radiation cleanup and cot: trol, and groundwater protection aspects of the remedial action performed at the Slick Rock uranium mill tailings sites. The purpose of this review was to determine whether DOE hed performed remedial actions at the sites in accordance with specifications in the RAP, RAP modifications, and other supporting project documents, and thus with the EPA standards in 40 CFR Part 192, Subparts A-C. Based on its review of the CR and on observations made during periodic on-site construction visits, the NRC staff concludes that DOE performed remedial action at the S!ick Rock sites in accordance with the EPA standards.
Therefore, NRC concurs with DOE's certification that DOE has completed the remedial actions specified for these sites.
4.0 REFERENCES
Cain C.L. 1997. Review of Project Interface Document No.11-S-14 for the Stick Rock Disposal Site. Letter to G. Rael, Albuquerque Operations Office, U.S. Department of Energy, dated April 11,1997. U.S. Nuclear Regulatory Commission, Office of Nuclear Material Safety and Safeguards, Division of Waste Management, Uranium Recovery Branch, Washington, D.C.
Chemoff A.1993. Letter to J.J. Sumleier, Uranium Recovery Branch, Division of Low-Level Waste Management & Decommissioning, Office of Nuclear Material Safety and Safeguards, U.S.
Nuclear Regulatory Commission, dated December 22,1993. U.S. Department of Energy, Albuquerque Field Office, Uranium Mill Tailings Remedial Action Project Office, Albuquerque, New Mexico.
DOE (U.S. Department of Energy).1995. Uranium Mill Tailings Remedial Action Project (UMTRAP), Slick Rock, Colorado, Calculations, Final Design for Construction. Dated September 1995.
DOE (U.S. Department of Energy).1996. Remedial Action Plan and Site Design for Stabilization of the inactive Uranium Mill Tailings Sites at Glick Rock, Colorado. Final report, dated May 1996.
Report DOEIAL/62350-21F, REV. 2, DOE, Albuquerque, New Mexico.
DOE (U.S. Department of Energy).1998. Slick Rock, Colorado, NRC Copy, Final Completion Report. Volumes 1-3, dated June 1997, with page changes through August 1998.
Holonich J.J.1994. Review of UMTRA Project Thonam-230 Generic Protocol. Letter to A.R.
Chemoff, Uranium Mill Tailings Remedial Action Project Office, U.S. Department of Energy, dated July 5,1994. U.S. Nuclear Regulatory Commission, Office of Nuclear Material Safety and Safeguards, Division of Waste Management, High-Level Waste and Uranium Recovery Projects Branch, Washington, D.C.
26
Holonich J.J. 1996. Review of Project Interface Document No.11-S-03 for the Slick Rock DisposarSite. Letter to R. Sena, Environmental Restoration Division, U.S. Department of Energy,* dated November 4,1996. U.S. Nuclear Regulatory Cor.. mission, Office of Nuclear Material Safety and Safeguards, Division of Waste Management, Uranium Recovery Branch, Washington, D.C.
Holonich J.J. 1998. Review of Completion Report for the S!!ck Rock, Colorado, Uranium Mill Tailings Remedial Action Project Sites. Letter to G. Rael, ERDIUMTRA, Albuquere,ue Operations office, U.S. Department of Energy, dated January 26,1998. U.S. Nuclear Regulatory Commission, Office of Nuclear Material Safety and Safeguards, Division of Waste Management, Uranium Recovery Branch, Washington, D.C.
MK-Ferguson Company,1996, Remedial Action Inspection Plan, Slick Rock, CO, MK-F-UMTRA-57, Rev. O, August 1996.
NRC (U.S. Nuclear Regulatory Commission).1989. Calculation of Radon Flux Attenuation by Earthen Uranium Mill Tailings Covers. Regulatory Guide 3.64, NRC, Office of Nuclear Regulatory Research, Washington, DC.
NRC (U.S. Nuclear Regulatory Commission). 1996. Final Technical Evaluation Report for the Remedial Action at the Slick Rock, Colorado, Uranium Mill Tailings Processing and Disposal Sites. Dated September 1996. NRC, Division of Waste Management, Washington, D.C.
NRC (Nuclear Regulatory Commission),1989, Staff Technical Position on Testing and Inspection Plans during Construction of DOE's Remedial Action at Inactive Umnium Mill Tailings Sites, Rev.
2, January 1989.
I Pape J.M.1996. Letter to J.J. Holonich, High-Level Waste and Uranium Recovery Projects Branch, Division of Waste Management, Office of Nuclear Material Safety and Safeguards, U.S.
Nuclear regulatory Commission, dated September 5,1996, with attached Project Interface j
Document 11-S-14. U.S. Department of Energy, Albuquerque Operations Office, Environmental Restoration Division, Albuquerque, New Mexico.
I Woodworth L.A.1998. Letter to J.J. Holonich, Uranium Recovery Branch, Office of Nuclear l
Material Safety and Safeguards, U.S. Nuclear Regulatory Commission, dated May 28,1998.
U.S. Department of Energy, Albuquerque Operations Office, Environmental Restoration Division, Albuquerque, New Mexico.
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APPENDIX A NRC SITE VISITS TO THE SLICK ROCK UMTRA PROJECT SITES DATE STAFF, DISCIPLINE PURPOSE June 9,1987 R. J. Starmer, Acting Branch Chief Review site characteristics K.B. Westbrook, Hydrologist to support staff review of I
M. Young, Geologist (?)
dRAP l
August 4,1988 S.L. Wastler, Project Manager Site familiarization for RAP J.P. Grimm, Geologist review L. Deering, Hydrologist l
September 22,1993 M.W. Haque, Project Manager Site familiarization for RAP E.S. Brummett, Health Physic lst review T.L. Johnson, Surface Water Hydrologist M.C. Layton, Hydrologist D.S. Rom, Geotechnical Engineer December 5,1995 D.M. Gillen, Section Leader Site tour C.E. Abrams, Project Manager l
May 23,1996 C.E. Abrams, Project Manager issue resolution concerning S.M. McDuffie, Geologist regional and site-specific j
geological features.
l June 4,1998 T.L Johnson, Surface Water Hydrologist Construction site visit J
B. Jagannath,Jeotechnical Engineer l
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APPENDIX B i ' UMTRCA, THE EPA STANDARDS, AND THE PHASED UMTRA PROJECT Title I of the Uranium Mill Tailings Radiation Control Act (UMT.RCA) defines the statutory authority and roles of the DOE, the NRC, and the EPA with regard to the remedial action program for inactive uranium mill tailings sites.
The Standards l
UMTRCA charged the EPA with the responsibility for promulgating remedial action standards for l
inactive uranium mill sites. The purpose of these standards is to protect the public health and
(
safety and the environment from radiological and non-radiological hazards associated with radioactive materials at the sites. UMTRCA required that EPA promulgate these standards by no later than October 1,1982. After October 1,1982, if the EPA had not promulgated standards in final form, DOE was to comply with the standards proposed by EPA under Title I of UMTRCA until such time as the EPA had promulgated its star' hrds in final form.
The final EPA standards were promulgated with an effective date of March 7,1983 (48 FR 602; January 5,1983); see 40 CFR Part 192 - Standards for Remedial Actions at inactive Uranium Processing Sites, Subparts A, B, and C. These regulations may be summarized as follows:
- 1. - The disposal site shall be designed to control the tailings and other residual radioactive materials for up to 1000 years, to the extent reasonably achievable, and, in any case, for at least 200 years (40 CFR 192.02(a)].
- 2. The disposal site design shall provide reasonable assurance that radon-222 from residual radioactive material to the atmosphere will not exceed an average release rate of 20 picocuries per square meter per second, or will not increase the annual average concentration of radon-222 in air, at or above any location outside the disposal site, by more i
than one-half picocurie per liter [40 CFR 192.02(b)].
- 3. ' The remedial action shall be conducted so as to provide reasonable assurance that, as a result of residual radioactive materials from any designated processing site, the concentrations of radium-226 in land averaged over any area of 100 square meters shall not l
exceed the background level by more than 5 picocuries/ gram averaged over the first 15 centimeters of soil below the surface and 15 picoeuries/ gram averaged over 15 centimeter thick layers of soil more than 15 centimeters below the surface [40 CFR 192.12(a)].
l
. 4. The objective of remedial action involving buildings shall be, and reasonable effort shall be l
made to achie e, an annual average (or equivalent) radon decay product concentration (including bacground) not t'o exceed 0.02 WL, and the level of gamma radiation shall not exceed the background level by more than 20 microroentgens per hour [40 CFR 192.12(b)].
- 5. The portion of the EPA standards dealing with grc andwater requirements, l
_40 CFR 192.20(a)(2)-(3) were remanded by the Tenth Circuit Court of Appeals on September j
3,1985. Based on this court decision, EPA was directed to promulgate new groundwater l-standards. EPA proposed these standards in the form of revisions to Subparts A-C of 40 CFR Part 192 in September 1987, and the final groundwater standards were promulgated January 11,1995.
B-1 l
o Before the groundwater standards were final, as mandated by Section 108(a)(3) of UMTRCA, the remedial action at the inactive uranium processing sites were to comply with EPA's proposed.
standards until such time as the final standards are promulgated. DOE performed remeqlial action at the inactive processing sites in accordance with NRC's concurrence with the remedial action approach based on the proposed EPA groundwater standards (52 FJ 36000; September 24,1987). Delaying implementation of the remedial action program would be inconsistent with Congress' intent of timely completion of the program. Modifications of disposal sites after completion of the remedial action to comply with EPA's final groundwater protection standards may be unnecessarily complicated and expensive and may not yield commensurate benefits in terms of human and environmental protection. Therefore, the Commission believes that sites where remedial action has been essentially completed prior to EPA's promulgation of final 1
groundwater standards, will not be impacted by the final groundwater standards. Although j
additional effort may be appropriate to assess and clean up contaminated groundwater at these sites, the existing designs of the disposal sites should be considered sufficient to provide long-term protection against future groundwater contamination. NRC does not view UMTRCA as requiring the reopening of those sites that have been substantially completed when NRC concurred with the selection of remedial action in accordance with applicable EPA standards, proposed or otherwise in place at the time such NRC concurrence was given.
DOE Selection (Desian) Phase For each site, UMTRCA requires that DOE select a plan of remedial action that will satisfy the EPA standards and other applicable laws and regulations, and with which the NRC wil! concur.
For each site, this phase includes preparation by DOE of an Environmental Assessment or an Environmental Impact Statement, and a Remedial Action Plan (RAP). The RAP is structured to provide a comprehensive understanding of the remedial actions proposed at that site and contains specific design and construction requirements. To complete the first phase, NRC and the appropriate State or Indian tribe will review the RAP and then concur that the RAP will meet the EPA standards.
The Performance (Construction) Phase in this phase the actual remedial action (which includes decontamination, decommissioning, and reclamation) at the site is done in accordance with the RAP. The NRC and the State / Indian tribe, as applicable, must concur in any changes to the concurred-in plan that arise during construction. At the completion of remedial action activities at the site, NRC concurs in DOE's determination that the activities at the site have been completed in accordance with the approved plan.' Prior to licensing (the next phase), title to the disposed tailings and contaminated materials must be transferred to the United States and the land upon which they are disposed of must be in Federal custody to provide for long-term Federal control. Disposal sites on Indian land will remain in the beneficial ownership of the Indian tribe.
NRC concurrence in the DOE determination that remedial action at a processing site has been accomplished in accordance with the approved plan may be accomplished in two steps where residual radioactive material is not being moved from the processing site to a different disposal site. The Uranium Mill Tailings Remedial Action Amendments Act of 1988 allows for a two-step approach for Title I disposal sites. The Amendments Act will allow DOE to do all remedial actions, other than groundwater restoration, for the first step of closure and licensing. The second step, which can go on for many years, will deal with existing groundwater restoration.
When groundwater restoration is completed, the Long-Term Surveillance Plan required under the B-2
r licensing phase will be appropriately amended. For sites that are being moved, licensing will occur irrone step. There is no groundwater restoration at the disposal site and the processing sit' will nbt be licensed after completion of remedial action.
e The Licensino Phase Title I of UMTRCA further requires that, upon completion of the remedial action program by DOE, the permanent disposal sites be cared for by the DOE or other Federal agency designated by the President, under a license issued by the Commission. DOE will receive a general license under 10 CFR Part 40.27 following: (1) NRC concurrence in the DOE determination that the disposal
'l site has been properly reclaimed, and (2) the formal receipt by NRC of an ucceptable Long-Term Surveillance Plan (LTSP). NRC concurrence with DOE's performance of the remedial action
~ indicates that DOE has demonstrated that the remedial action complies with the provisions of the EPA standards in 40 CFR part 192, Subparts A, B, and C. This NRC concurrence may be i
completed in two steps as discussed above. There is no termination date for the general license.
l Public involvement has been and will continue to be provided through DOE's overall remedial l
action program for Title I sites. The local public will have an opportunity to comment on the 1
remedial action or closure plans proposed and implemented by DOE and to raise concems regarding final stabilization and the degree of protection achieved. NRC fully endorses State / Indian tribe and public input in all stages of the program. At the time the LTSP is submitted, the NRC will consider the need for a public meeting in response to requests and public concems.
The Surveillance and Monitorina Phase L
in this phase, DOE and NRC periodically inspect the disposal site to ensure its integrity. The l
LTSP will require the DOE to make repairs, if needed.
One of the requirements in the EPA standards is that control cf the tailings should 'be designed to be effective for up to 1000 years without active maintenance. Although the design of the stabilized pile is such that reliance on active maintenance should be minimized or eliminated, the NRC license will require emergency repairs as necessary. In the event that significant repairs are necessary, a determination will be made on a site specific basis regarding the need for additional National Environmental Policy Act actions, and health and safety considerations based l
on 10 CFR Parts 19,20, and 21. Title I of UMTRCA defines the statutory authority and roles of l
the DOE, the NRC, and the EPA, with regard to the remedial action program for inactive uranium l
mill tailings sites.
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Mr. George Rael, Director Environmental Restoration Division Albuquerque Operations Office ERD /UMTRA P.O. Box 5400 Albuquerque, NM 87185-5400 B-3 1
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U.S. DEPARTMENT OF ENERGY CERTIFICATION
SUMMARY
FOR THE BURRO CANYON UMTRA DISPOSAL SITE SLICK ROCK, COLORADO The Director of the Environmental Restoration Division and the Contracting Officer for the U.S. Department of Energy certify the Burro Canyon (Slick Rock), Colorado disposal site is complete and meets all design criteria and technical specifications of the surface Remedial Action Plan required under Public Law 95-604. The undersigned request that the U.S. Nuclear Regulatory Commission concur ' th certification.
- f. 9 0
.em illiams Geor J. Rael C ntracting Officer Direct r
/rograms and R&D Branch Environmental Restoration Division Contracts and Procurement Division DATE:
6-
-7b DATE:
N4V 27 E390
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The Chief, Uranium Recovery Branch, Division of Waste Management, Office of Nuclear Materials Safety and Safeguards, U.S. Nuclear Regulatory Commission hereby concurs with the U.S. Department of Energy's completion of surface remedial action at the Burro Canyon (Slick Rock), Colorado disposal site.
OM t1, /d@O~ 4 l
Joseph J. Holonich, Chief i
Uranium Recovery Branch Division of Waste Management Office of Nuclear Material Safety l-and Safeguards U.S. Nuclear Regulatory Commission DATE:
8 u 96 i
L_____________.
_