ML20236T631
| ML20236T631 | |
| Person / Time | |
|---|---|
| Issue date: | 11/16/1987 |
| From: | Derek Widmayer NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Bilhorn S NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| References | |
| REF-WM-54 NUDOCS 8712010409 | |
| Download: ML20236T631 (5) | |
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I NOV 161987 4
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MEMORANDUM FOR: Susan Bilhorn,-Project Manager I
I Operations Branch U L ii.
4 Division of Low-Level Waste ManipemehtT _
and Decommissioning, NMSS.
1._
FROM:
Derek A. Widmayer, Civil Engindsrh 'o GE GM _.._
j Technical Branch
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l Division of Low. Level Waste Management i
and Decommissioning, NMSS j
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SUBJECT:
GE0 TECHNICAL ENGINEERING REVIEW 0F GRAND' JUNCTION
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PHASE II DESIGN DOCUMENTS I have completed my review of the' subject documents and have enclosed my comments. Please contact me at X74263 if you have any questions.
I Original Signed By Derek A. Widmayer, Civil Engineer Technical Branch Division of Low-Level Waste Management and Decommissioning, NMSS
Enclosure:
As stated 1
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Comment GT/1 - General comment on parameter values used in Geotechnical l
Engineering Analyses
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1 NRC's review of the Grand Junction Preliminary Design'geotechnical engineering analyses was conducted on documents dated July, 1987. Generally, parameter values used in the analyses reviewed were not adequately justified. This is especially notable with respect to parameter values that are different from j
the value reported in the Grand Junction draf t Remedial Action Plan (dRAP).
1 NRC notes that " Additional Geotechnical Data" is being developed (page 1 of
" Subcontractor Documents"), and will be incorporated in reevaluations of the l
geotechnical engineering analyses. DOE should include all laboratory results l
that are the bases for parameter values in future design documents on the Grand 1
Junction UMTRAP site. Some of the following coments allude to the problem of insufficient justification, therefore, any new data developed should be incorporated into these analyses, or, if the parameter values will not be different as a result of the new data collection, then the values ured in these July documents should have improved justifications.
Comment: GT/2 - Low Permeability Layer On page 3 of " Subcontractor Documents," it is stated that, "The subgrade at I
the excavated disposal site will be scarified and compacted to 90% of Proctor Density (ASTM-D698). TAC agreed that a low permeability layer was not necessary."
NRC's concerns regarding the low permeability layer during our review of the dRAP included: (1) that it was unclear whether the materials used for the layer would come from Cheney foundation soils or from another borrow area, (2) that if the material contained a larger percentage of coarse materials, the required permeability would be hard to achieve, (3) that the RAP should identify the material type and characteristics and maintain control over the characteristics, and (4) give specifications to the soil should be placed and compacted to a minimum of 95% of the standard Proctor maximum dry density to achieve the required permeability.
NRC is concerned that, not only have the comments regarding the low permeability layer not been addressed, but that it has been determined that a low permeability layer is no longer necessary without adequate justification.
A complete demonstration that this low permeability layer is not necessary should be given including demonstrating that the permeability properties of the existing foundation soils will be adequate with scarification and the indicated recompaction.
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2 Comment GT/3 - Radon Barrier Thickness On page 7 of " Subcontractor Documents," it is stated that, "... Radon barrier materials shall be Contractor-furnished materials stockpiled on the disposal site by others."
l The dRAP indicated (on page 33) that the borrow for the radon barrier would be obtained by selective stockpiling of the foundation excavation material. The information found in " Calculations, Volume I" of the Preliminary Design j
Documents on availability of radon barrier material (Calculation No. 05-618-03-00) i shows that the intended source of radon barrier materials is excavated foundation materials. The calculations for the appropriate radon barrier thickness are also based on the use of excavated foundation.naterials (Calculation No. 05-670-01-00).
4 (a) NRC is concerned that the thickness calculated for the radon barrier is based on tests conducted on material th6t will not be used (contractor-furnished material rather than excavated foundation soils) for the radon barrier.
This discrepancy should be corrected, and appropriate test results on the appropriate borrow materials should be used to calculate the radon barrier thickness if excavated foundation soils are not going to be used for the radon barrier.
(b) Any effect on the availability of radon barrier materials, changes to the i
borrow areas for radon barrier materials, changes to the radon barrier thickness, or any other changes to the radon barrier calculations as a result of the l
consideration of comment GT/2 above should be incorporated into future design I
documents.
Comment GT/4 - Shear Strength Values for Geotechnical Engineering Analyses NRC continues to have concerns over some of the shear strength values used in the geotechnical engineering analyses in the Grand Junction Phase II Design Documents.
l (a) Main Pile Tailings - NRC expressed concerns over the shear strength values reported in the dRAP for the main pile tailings. Specifically, the NRC concerns were expressed regarding the values in Table E.6.7 and the value used in the slope stability analysis (37 ) in the dP.AP. The values for the main pile tailings new being used in the analyses in the preliminary design are conservative values within the range of values reported by the DOE reference in the dRAP (Vick, 1983), however, use of the values should be supported by laboratory testing results, or reasoning that the reference values can be used in this case. If the new geotechnical engineering data is appropriate, then it should be incorporated, as discussed in comment GT/1 above.
(b) Radon Barrier Materials - The value reported in the dRAP for phi for the long-term shear strength of the radon barrier materials was 33. NRC's concerns with this value as a result of the dRAP review were resolved. The value reported in Calculation No. 05-670-05-00, " Material Properties -
Summary," for the long-term shear strength of the radon barrier materials is 0. This value is used in both the settlement and cover cracking analysis
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(CalculationNo. 05-670-03-00) and slope stability analysis (Calculation No.
05-670-04-00). This change is not justified adequately, in fact, it appears that the value of 30 was originally intended to be used in the analyses, but was changed for some reason not detailed in the discussions. With either value, data and laboratory results that back up the parameter value, or assumptions that are relied upon to justify the value should be added.
(c) Foundation Soils Layer 2 - NRC expressed concerns following review of the l
dRAP about the shear strength parameter values of foundation soil layer 2 (called soil layer #5 in the dRAP) used in the geotechnical engineering analyses.
For both long-and short-term analyses of slope stability, values for this soil layer are different than the values reported in the dRAP.
Laboratory test results should be included to justify the new parameter values.
(d) Triaxial Testing - The NRC remains concerned that shear strength parameter values are being used that are a result of non-standard staged triaxial tests.
l Our comment on this matter from the review of the dRAP still holds with respect i
to values used in the Phase II Preliminary Design Documents. Data now being developed on contaminated materials and Cheney Reservoir Soils should include results from triaxial testing using standard engineering practice.
If staged triaxial tests are being conducted, then the results from them should be shown to be representative of values that would be obtained using the standard methods described in our comment on this subject from the Grand Junction dRAP review.
l If no additional triaxial tests are planned on at this time, then the results of the triaxial tests conducted at the time of dRAP preparation should be shown to be representative of results that would be obtained with standard techniques.
Comment GT/5 - Foundation Soil Layer 4 In the idealized cross sections of the Cheney Reservoir Disposal Site used for slope stability analysis in the dRAP, a layer of very weathered clay is included as soil layer #6. This same layer, now identified as foundation soil layer 4, is reported in the Preliminary Design Documents only to the extent that it is assumed absent, and the settlement and cover cracking (Calculation
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No. 05-670-03-00) and the slope stability (Calculation No. 05-670-04-00) analyses are performed without considering this layer. The assumption that foundation soil layer 4 is now absent has not been justified satisfactorily, j
especially when it is noted that on sheet #6 of Calculation No. 05-670-05-00, i
" Material Properties - Summary," this layer is present and the text identifies sheet #6 as a " typical cross section." Foundation soil layer 4 should be characterized more fully in order to assume it to be absent in the geotechnical engineering analyses. This characterization should include at least consideration of the extent and thickness of this layer.
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Comment GT/6 - Discrepancies in Parametric Values and Label References The values for the following parameters in Calculation No. 05-670-05-00, l
" Material Properties - Summary," do not have the same values used in Calculation l
No. 05-670-03-00, " Settlement and Cover Cracking":
l d) Main Pile Tailings, Shear Strength, Undrained, phi i
b) Radon Barrier, Material Type, Maximum Rock Size c) Radon Barrier, Material Type, Minimum Passing #200 sieve d Radon Barrier, Material Type, Percent finer than 1.002 mm e Radon Barrier, Permeability f Erosion Protection, Material Type, Type A g Erosion Protection, Material Type, Type B h Foundation Soil #2, Permeability i Foundation Soil #3, Permeability j) Foundation Soil, Bedrock, Permeability I
The cross section labeled D-D' in Calculation No. 05-670-04-00, " Slope Stability," and the cross section labeled E-E' in Calculation No. 05-670-05-00,
" Material Properties - Summary," are not indicated on any planar views of the Cheney Reservoir Disposal Site.
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