ML20214K195
| ML20214K195 | |
| Person / Time | |
|---|---|
| Issue date: | 09/08/1986 |
| From: | Knapp M NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Themelis J ENERGY, DEPT. OF |
| References | |
| REF-WM-69 NUDOCS 8612020213 | |
| Download: ML20214K195 (9) | |
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John G. Themelis, Project Manager DISTRIB ION:
Uranium Mill Tailings Project Office WM sf RD Smith, URF0 U.S. Department of Energy WMLU rf MKnapp Albuquerque Operations Office NMSS rf DGillen P.O. Box 5400 RBrowning JKane DMartin Albuquerque, NM 87115 MBell MFliegel JBunting MHaisfield
Dear Mr. Themelis:
BFord MNataraja The Nuclear Regulatory Connission (NRC) has completed its review of the Draft CADSAR for the Maybell, Colorado site. Our review consisted of a broad overview looking for fatal flaws, potential issue areas, and omissions. The Draft CADSAR is a very preliminary document, which is produced before much environmental data has been collected and before detailed engineering data is available. With this in mind, we did not see any fatal flaws at this time which would preclude use of the two proposed alternatives. However, NRC concurrence that either alternative will meet Environmental Protection Agency standards cannot be provided until the detailed information discussed above has been reviewed.
The enclosed conarents, which identify potential issue areas and omissions, would be useful in improving the quality of the Final CADSAR and should be incorporated where possible. These comments also provide requirements which will be necessary when developing remedial action plans.
It is in this spirit that our corrments are provided.
If you have any questions regarding these comments, please contact Mark Haisfield at FTS 427.-4722.
Sincerely, C.
1 Malcolm R. Knapp, Chief Low-Level Waste and Uranium Recovery Projects Branch Division of Waste Managertent Office of Nuclear Material Safety and Safeguards
Enclosure:
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REVIEW 0F MAYBELL DRAFI LKudAR SITING AND HYDR 0GE0 LOGIC COMMENTS 1.
Section 3.0, Characterization of Sites, Page 5 Characterization of each alternate site has not considered the neighboring mines and heap-leach facilities. Stabilization of the tailings may be jeopardized by future mining at the site.
2.
Section 3.1.3, Table 3.2, Page 9 Table 3.2 indicates that ground water conditions are not a concern at the t
Maybell site. This conclusion is supported by the statements that "The water table is approximately 150 feet below the site in the Browns Park Formation" and "There is evidence to show that a neutralization zone exists three to four feet below the tailings with no significant movement of radienuclides or other contaminants beyond this zone." However, the i
draf t CADSAR does not appear to contain sufficient ground water quality or geochemical data to conclude that ground water contamination is not a concern. Some ground water concerns that may need to be addressed during characterization are:
d.
The present and future water use in the area may need to be addressed. This is important, because the Browns Park Formation appears to be a significant aquifer composed largely of sandstone, is up to 900 feet in thickness, and may have 750 feet of saturation (Ford Bacon and Davis Utah,1981, pages 2-4 and 2-13).
Furthermore, future water use in the area may increase as a result of energy development (uranium, oil and gas, coal, and oil : hale). This may be especially true at this site, since a uranium mine and milling area is immediately adjacent to the site.
b.
The sandstones of the Browns Park Formation may not offer much attenuative capacity either in the unsaturated or saturated zones.
c.
Radiological contaminants may be much more mobile in the ground water after having been processed.
r d.
Local ground water flow directions may not reflect regional ground water flow due to the existence of open pits around the tailings site.
e.
It may be difficult to determine background water quality due to past milling and mining activities in the area.
4 1
b 5
2-f.
It may be difficult to determine if any ground-water pollution associated with the pile is from the pile or from adjacent mining, milling, and heap leaching operations,'or both.
g.
In order to identify ground-water pollution from the pile, post remedial-action monitoring may need more detail than planned, because of adjacent mining, milling, and heap leaching operations.
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3.
Section 3.1.3, Table 3.2, Page 9
{
Table 3.2 of the Maybell draft CADSAR states that the DOE does not i
consider ground water conditions to be a " concern" for the stabilization-in-place alternative. The table states that there is a
" neutralization zone" three to four feet below the tailings pile which prevents "significant movement" of radionuclides or other contaminants.
DOE does not define " neutralization zone", nor does it include any details concerning this zone in the draft CADSAR. DOE apparently feels that the
" neutralization zone" will protect the ground water of the Browns Park Fonnation, an aquifer approximately 900 feet thick consisting p(rimarily of j
sandstones interspersed with "some shale and mudstone layers" Ford Bacon and Davis Utah,1981), which underlies the tailings. However, without.
additional information concerning the " neutralization zone", the NRC staff j
i cannot assess whether the potential exists for contaminants to move from the reclaimed tailings pile and into the ground water.
In the final CADSAR, 00E should define " neutralization zone", describe the zone in more i
detail (e.g., thickness, areal extent, ir.ineralogy, grain size, permeability, etc.) and identify the properties responsible for isolating l
j radionuclides and other contaminants. Since incorporating engineered ground water protection (i.e., an impermeable liner) into the remedial action could seriously impact the final cost, DOE should demonstrate early in the evaluation process that the " neutralization zone" will adequately protect the ground water.
4.
Section 3.0, Table 3.3_, Page 11 This table is inconsistent in stating that geomorphology (erosion in Johnson Wash) is a concern while surface waters in the area are not.
l These two issues are one in the same and cannot be treated separately.
5.
Section 3.0, Table 3.3, Page 11 Table 3.3 states that surface water is not a concern for the Johnson Pit disposal alternative. However, we consider this conclusion to be premature because in section 4.2, page 15, it is stated that the pit would l
be " filled with the tailings and other contaminated materials to above the elevation of the surrounding terrain to provide external drainage away from the stabilized tailings." A conceptual design which calls for i
4 i
O V overfilling of the Johnson Pit to provide drainage away from the tailings may also subject them to the erosional forces of surface water flow.
Therefore, surface water is a concern for the Johnson Pit alternative unless further information indicates otherwise.
6.
Section 3.0, Table 3.3, Page 11 Table 3.3 states that " prior to backfilling" the ground water table in the Browns Park Formation intersected the bottom of Johnson Pit. This is a potential problem, as ground water may infiltrate the tailings pile from below, providing a mechanism for leaching and transporting contaminants.
To mitigate this problem, DOE will leave "at least 10 feet" of fill in the bottom of the pit to separate the tailings from the groundwater. The concern remains, however, and Table 7.2 (page 23) identifies that the proximity of ground water to the tailings, particularly during wet periods, is a risk associated with selecting the Johnson Pit alternative.
The cost impact of mitigating this problem is not examined in the draft CADSAR. The final CADSAR should recognize the potential impacts of mitigating the ground water infiltration problem for the Johnson Pit alternative and explore whether using methods such as allowing more than 10 feet of backfill to remain in the pit (which will reduce the volume of tailings the pit can hold) or constructing a liner are feasible methods of eliminating water infiltration from below.
7.
Section 4.1, Stabilization in Place (SIP), Page 14 Regrading of the tailings pile and the erosion protection required for the SIP alternative will need to be discussed in the final CADSAR. Review of the draft CADSAR and the FBDU (1981) report indicate that extensive regrading of the tailings pile and considerable erosion protection may be required for several reasons:
The topographic map and Cross rection of the tailings pile in a.
the FBDU report (Figs. 2-2, 2-5A) reveal slopes on the E and SE sides of the tailings that are rather steep.
Rough calculations indicate slopes as steep as Sh:1v at the SE corner. Erosion on the eastern side of the pile (FBDU, p. 2-4) is probably directly attributable to the steepness of the slope.
It therefere appears that significant regrading of the pile will be necessary to make these slopes less steep.
b.
Figure 3.1 of the draft CADSAR and Figures 2-2, 2-4, 2-5A, and 2-5B of the FBDU report depict a channel (or gully) on the tailings pile. Construction of a drainage channel directly on the stabilized pile is generally undesirable, because erosion could occur in the middle of the pile rather than along the edges. Therefore, extensive regrading of the tailings pile
. appears to be necessary to alter the present system of surface drainage.
c.
Examination of aertal photographs and topographic maps indicates the presence of nearby gullies and erosion features which could potentially impact the site design.
Provisions for protection of the stabilized pile against lateral erosion and headcutting need to be examined to estimate the erosion protection requirements associated with the phenomena.
The extent of tailings regrading and erosion protection considered in the draft CADSAR for the SIP alternative needs to be clarified and expanded in the final CADSAR.
8.
Section 5.0, SIGNIFICANT ISSUES, Page 16 The draft CADSAR is a preliminary document with no technical information on seismology and geophysics. Therefore, before making any preliminary technical evaluation, the following points should be addressed:
a.
The report cites the existence of faults within 0.25 miles of the tailings. These faults should be characterized fully and the risk associated with the faults impact on the site should be discussed.
b.
Seismic activities within the vicinity of the site should be addressed and a map showing the locations of the earthquakes should be provided, c.
The report should identify the design acceleration.
d.
Table 7.2 should include faults as a risk item.
9.
Section 5.1, Flood Studies, Page 16 This section leaves the impression that flood studies are required only if the SIP option is chosen, and then only to define the rock size required to armor Johnson's Wash. We conclude that flood studies (PMP and PMF) are required for both the SIP and Johnson Pit alternatives for two reasons:
a.
Tables 3.2 and 3.3 list erosion of Johnson's Wash into the tailings as a concern for both options. Therefore, the size of rock required to armor the piles and/or Johnson's Wash should be determinea from flood studies for both options.
b.
The size of rock required to armor the diversion system which protects the tailings from surface runoff should be determined from flood studies. This is obviously important for the SIP 1
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. option since the present diversion system has been breached on the western side (FBDU, p. 2-4).
The need for such a diversion system for the Johnson Pit option is not addressed in the draft CADSAR, but aerial photographs indicate one may be required.
- 10. Section 6.0, Table 6.2, Page 19 The table shows erosion-protection costs for the Johnson Pit alternative are 50% higher than for the SIP alternative (page 18). This appears to contradict sections 4.1 and 4.2, Site Conceptual Designs, which specify similar volumes of erosion-protection materials for each alternative. The final CADSAR should justify erosion protection costs in more detail.
- 11. Section 7.1, Table 7.1, Page 21 This table states, that for the Johnson Pit alternative, "headcutting of Johnson's Wash would not affect the site." This appears to be in direct conflict with Table 3.3 on page 11, which lists erosion of Johnson's Wash into the pit as a concern.
Based on our review, headcutting and lateral erosion appear to be potential problems at the Johnson Pit; therefore, Table 7.1 should be amended for consistency.
- 12. Section 7.1 Table 7.1, Page 21 In the comparison of disposal alternatives, isolation from the bed rock aquifer by Mancos Shale is cited as a positive technical factor for the Stabilization-in-Place alternative. However, the draft CADSAR does not seem to recognize the Browns Park Formation which directly underlies the site and may be a significant bedrock aquifer. Credit for this aspect of the site should rot be taken until additional ground water information is obtained.
- 13. Section 7.2, Table 7.2, Page 23_
The table assigns 25". risk to the SIP option t'ased on a potential of erosion-protection needs above those anticipated, and no such risk for the Johnson Pit alternate site. The comparison directly contradicts Tables 3.2 and 3.3, which icentify Johnson Wash as a threat to geomorphic stability at both sites. This inconsistency should be resolved.
14.
Section 7.2. Table 7.2, Page 23 This table contains risk values associated with each alternative.
However, the table contains no reference to methods for the risk dssessments.
This information should be supplied.
O
- 15. Section 8.0, Recommendations, Page 24 We conclude that a surface water quality investigation should be included as part of the field characterization program. Such an investigation should be made to determine the quality of water upstream from the site, downstream, and draining directly off the tailings pile. This data is necessary to establish background surface water quality and any current contamination of surface water caused by the tailings.
It will later be used to assess the effects of the chosen stabilization option on surface Water quality as part of the monitoring program. Of particular importance is the effect of runoff from Johnson's Wash on the water quality of Lay Creek and especially the Yampa River, from which at least one farmhouse is known to obtain drinking water (FBDU, p. 2-5). The potential for future surface water use in the downstream areas affected by the tailings should also be addressed.
i
. ENGINEERING COMMENTS
- 16. Section 3.0, Chara_cterization of Sites, Page 5 Section 3.0 provides very little factual information on actual site conditions. Basic information needs to be presented (site stratigraphy, exploration data, description of static and dynamic engineering properties of foundation, embankment and borrow materials, soil and rock characteristics that would prevent migration of contaminants) on the processing site, Johnson Pit and proposed borrow areas.
The two references cited in Tables 3.2 and 3.3 should be provided to understand the basis for D0E's conclusions on concerns for site characteristics that are identified in these tables.
The areal extent and thickness of pockets of slimes at the south end of the tailings pile and the condition of the partially backfilled Johnson Pit (material types, construction method for placement and any compaction effort, etc.) need to be described and understood in order to make a reasonable estimate of their impact and costs on remedial action work.
It would appear from Table 8.1 that the results of site investigations that would cover geotechnical drilling, borrow areas and groundwater would be available for incorporation into the Final CADSAR. After having established preliminary site conditions, an engineering assessment would need to be made on potential slope stability and settlement or subsidence problems, on stability under earthquake loading and any specific feature that might adversely impact safe construction and operation. The impact of these specific site features on remedial action costs would then need to be estimated.
- 17. Section 4.0 Site Conceptual Design, Page 14 The staff agrees with DOE that the designs of possible alternative disposal options in this section are preconceptual only, and will change as site characterization is completed. As an example, the proposed alternative for stabilization of Johnson Pit needs to establish the engineering properties and condition of the existing pit materials and slopes and backfilled portion (material types, densities) in order to identify required remedial action work (cutting back or sealing of pit walls and bottom, etc.). The staff would anticipate major revisions and updating of Section 4.0 in the Final CADSAR along with sectional views that illustrate the conceptual scope and extent of proposed remedial action work.
O
. 18. Section 6.0, Cost Estimates, Page 17 Section 6.0 and the work items in the cost estimate summaries of Tables 6.1 and 6.2 are not sufficiently described which raises questions as to whether the cost estimates appropriately reflect the remedial work to be performed. As an example, it is unclear for the proposed stabilization in place alternative, what work effort and costs have been considered for either removing or stabilizing the soft slime materials at the south end of the existing tailings pile.
In the Final CADSAR, Section 6.0 should be expanded to describe the major design features and construction operations with sufficient information on remedial action quantities and cost presented to demonstrate that the significant design and construction features have been adequately addressed.
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