ML20236T948
| ML20236T948 | |
| Person / Time | |
|---|---|
| Issue date: | 10/30/1987 |
| From: | Starmer R NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Fliegel M NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| References | |
| REF-WM-68 NUDOCS 8712020187 | |
| Download: ML20236T948 (6) | |
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MEMORANDUM FOR: Myron Fliegel, Section Leader
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Operations Branch Division of Low-Level Waste Management and Decommissioning, NMSS FROM:
R. John Starmer, Section Leader Technical Branch Division of Low-Level Waste Management and Decommissioning, NMSS
SUBJECT:
GREEN RIVER PRELIMINARY DESIGN REVIEW Enclosed are the Siting Section, LLTB, comments on the Green River Preliminary design. Some of the comments are in the nature of observations while others detail apparent errors in the calculations.
Finally, other comments concern design problems, such as those on erosion protection / rock specifications, and tailings embankment design, that are of such importance that the NRC's concurrence on the design could be affected.
This review was performed by Ted Johnson (Surface Water Hydrology) Joel Grimm (Geology) and Mike Young (Ground-water hydrologist).
Please contact Kristin Westbrook of my staff on X74543 if you have any questions.
Ori6 nal Signed B7 1
1 R. John Starmer, Section Leader l
Technical Branch Division of Low-level Waste Management and Decommissioning, NMSS
Enclosure:
As stated DISTRIBUTION:
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, l NRC/ GROUND WATER COMMENTS ON GREEN RIVER, UTAH UMTRA PROJECT SITE PRELIMINARY DESIGN DOCUMENT
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1.
Tailings Amendments - General comment DOE is proposing to stabilize the Green River tailings on top of a fractured bedrock unit. Random dispersal of leachate into the substrate is possible, which could pose significant problems to DOE when demonstrating compliance with EPA's ground-water protection standards. Chemical amendment of the tailings to l
improve Icachate quality, as discussed during the recent on-board review i
meeting, could provide assurances to NRC staff that leachate migrating from the embankment will not significantly impact the underlying ground water. DOE did not discuss the possibility of amending the tailings in the design document.
Therefore, NRC staff suggests that DOE consider amending the tailings, and estimate !eachate quality with and without amendments.
2.
Material Excavation, Subcontract Documents, Drawing No. GRN-PS-10-0512 l
DOE's embankment design is based on the assumption that all the contaminated l
material will be stabilized in the excavated area. However, DOE has not fully determined the level of contamination in the impoundment structures west of the l
mill yard, or from the area west of the mill buildings within the mill yarc, as discussed during the on-board review meeting on 15 September 1987. Therefore, p
!y additional unaccounted contaminated material may exist. Because these areas could provide significant additional volumes for disposal, NRC staff suggests that DOE survey these areas radiologically and determine the extent of l
contamination prior to finalizing the embankment design.
3.
Cover design, Subcontract Documents Drawing No. GRN-PS-10-0517 A major attribute of the current Green River embankment design is that below-grade disposal of the tailings lowers the exposed surface area and the level of infiltration. However, as discussed during the S0lLM0lST technical review meeting in February 1987, the flanks of the' tailings embankment will likely be the zone where infiltration is greatest. This is due to surface water that drains from the crest of the pile towards the flanks, increasing the amount of time that water can infiltrate the pile. This appears especially applicable to the Green River design, because most of the armored drainage channels will be covered with backfill material, thus eliminating evaporation as a significant process for removing water. Therefore, NRC staff suggests that DOE increase the thickness of the cover along the flanks of the tailings embankment, especially beneath the buried drainage channels, to lower infiltration into the tailings.
4.
Monitor Well Abandonment, Subcontract Documents, Drawing No. GRN-PS-01-0518 The drawing included in the preliminary design is unclear with respect to which monitor wells / borings will be abandoned, and which wells will be maintained during the remedial action.
It appears that almost all wells and borings are
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.S 9 4 gc WM-68/MHY/GRN PRE DES /GW/10 87 2-to be abandoned as part of the remedial action. DOE has not provided justification for abandoning the devices indicated in the drawing.
NRC staff considers monitoring ground water during remedial action necessary to evaluate the impacts of tailings disposal on ground-water resources. Not monitoring ground water during remedial action will create data gaps in DOE's database and make demonstration of compliance with EPA's ground-water i
protection standards more difficult.
Therefore, the staff suggests that DOE clarify their plans and provide justification for abandoning wells and well I
points at the Green River site.
5.
Permeability of Cover Material, Volume I, Calculation 10-536-01, Sheet 45/63 l
NRC staff has identified a possible discrepancy between the permeability value l
used in the design and measured values.
DOE used a conservative value of i
1 E-07 cm/s for the proposed cover material (Sheet 45/63), but test results on Sheet 44/63 indicate the permeability of the disposal site soils range from 1
2.8 E-05 to 5.2 E-06 cm/s depending on the clay content. These results are significantly higher than DOE's conservative value. Because DOE is not proposing to separate the clay material from the site soils, the permeability 4
of the untreated soil material may be too high to be used in the cover.
I Therefore, NRC staff requests that DOE resolve this apparent discrepancy and, if necessary, describe how the site soils can be used successfully as cover material without separating the clay component.
I 6.
Clean-up Inconsistency, Volume I, Calculation #10-535-01, Sheet 1 and Calculation #10-536-01, Sheet 1/63 DOE has presented inconsistent clean-up criterion for the removal of tailings i
along the banks of Brown's Wash. On Sheet 1 of Calculation 10-535-01, DOE states that " excavation is carried out to the 15 pCi/g limit...", whereas on Sheet 1/63 of Calculation 10-536-01, DOE states that the " depth of excavation is based on the level of contamination to 5 pCi/g of Ra-226." NRC staff l
request that DOE address this inconsistency and reevaluate, if necessary, the volume of tailings to be removed along Brown's Wash.
7.
Tailings Embankment Design, Subcontractor Documents, Drawing No. GRN-PS-10-0517 The drawing and detail indicate that precipitation falling on the pile is designed to be discharged via percolation into the alluvial material and bedrock along the flanks of the embankment.
No surface discharge structures are proposed to quickly convey water away from three sides of the embankment.
NRC staff considers this to be a flaw in the current design because the performance of the disposal cell will be affected by:
1.
Water collecting in the riprap lens beneath overlying backfill, leading to
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h WM-68/MHY/GRN' PRE DES /GW/10 87 increased flux through the infiltration barrier and possible saturation of the tailings.
2.
Saturation of the riprap lens by severe or prolonged precipitation, and overtopping onto the backfill material causing' unanticipated erosion.
3.
Possible saturation of the overlying backfill material and decreased landscape stability, a concern of future occupants of the decommissioned mill buildings 300 feet NW of the embankment.
4.
Allowing perolation of water from the alluvium and bedrock back into the tailings material.
3 Jt DOE has not characterized the properties of the alluvium adequately for its integral use in the design. Therefore, NRC staff suggests that DOE either fully characterize the transmissive properties of the alluvium and bedrock adjacent to the embankment, or alter the current design to quickly convey precipitation and surface runoff away from the pile, i
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GE0 LOGY /GE0 MORPHOLOGY COMMENT GREEN RIVER PHASE II PRELIMINARY DESIGN Calculation 10-536-08-00: Tailings Embankment; layout, quantities, and capacity Sheet 4 states that excavation is planned to proceed to elevation 4,115 feet and is not expected to encounter Cedar Mountain Formation rocks. Based on drawings and core data provided to the staff during'a September 15, 1987 on-board review meeting, this condition appears unrealistic.
In a telephone conversation (J. Grimm,NRC, October 23,1987) R. Rager (DOE / TAC) acknowledged l
that the design specification is incorrect and should be disregarded. The-tailings embankment will indeed be founded on Cedar Mountain Formation rocks, barring any future alterations in the design. The staff consider that future drafts of the design require revision to attain accuracy and consistency _in the
.i design specifications as they are related to the site's geology.
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s MEMO GREEN RIVER DESIGN REVIEW GREEN RIVER SURFACE WATER HYDROLOGY AND EROSION PROTECTION QUESTION AND COMMENTS 1.
Staff review of the rock riprap durability specifications (Spec.. 02278-3) indicates that the rock will have to meet only the following durability requirements:
i Not less than 2.45 Specific Gravity Not greater than 4.00 Absorption Not greater than 30% loss (5 cycles)
NASO 4 Soundness In general, we conclude that these requirements will not be acceptable to-guarantee the placement of rock which will meet EPA long-term stability requirements. Based on research performed for the NRC staff (NUREG/CR-2642, Table 6.7), rock meeting only these minimum specifications is likely to-weather severely and thus may not meet EPA longevity standards.
1 kg While we fully recognize that the selected rock will likely exceed minimum
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l requirements, it is nevertheless possible that rock approaching-the minimum limits could be utilized, if these specifications are used. The minimum-limits should be raised, or a specific quarry should be selected. The source selected should be one where, based on testing, the specifications limits are l
known to exceed the absolute minimums and the rock quality is actually much
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better. As proposed, the rock is not considered to be acceptable'for placement, even if oversized.
I DOE should provide the basis for the selection of the rock durability l
l specifications and should provide additional information regarding the 1
durability of the selected rock, including any information and evaluations i
related to oversizing.
Additionally, DOE should document the efforts that were made to locate sources 4
of good-quality rock.
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