ML20195E320
| ML20195E320 | |
| Person / Time | |
|---|---|
| Issue date: | 06/17/1988 |
| From: | Tokar M NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Fliegel M NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| References | |
| REF-WM-74, REF-WM-75 NUDOCS 8806240010 | |
| Download: ML20195E320 (6) | |
Text
herrffttI YLb FAN 171988 MEMORANDUM FOR: Myron Fliegel, Section Leader Operations Branch Division of Low-Level Waste Management and Decomissioning, NHSS FROM:
Michael Tokar, Section Leader Technical Branch Division of Lc5-Level Waste Management and Decomissioning, HMSS
SUBJECT:
REVIEW COMMENTS OF ENGINEERlHG SECTION ON BEL / BOW DRAFT EA AND DRAFT RAP The Engineering Section has completed our review of the Belf'ield and Bowman Draft Environmental Assessment and tbs Draft Remedial Action Plan. Based on our review w? have enclosed our coments on the conceptual design provided in the draft RAP.
In our review we have noticed a wide variation in the level of design details that are provided for the different geotechnical engineering issues. Some issues such as slope stability and settlement are barely addressed and only concluding design statements are provided. Although the Appendices that were submitted provide substantial information and test results, there is very little in the draft RAP to correlate or use these results with specific design features. This approach is not consistent with the SRP guidelines where a logical and reasonable evaluation of the available data is recomended to orovide the supporting bases for selection of design parameters. This lack of correlation between furnished test results and important design considerations significantly reduces the benefits that can be derived from a draft' RAP review.
DOE and its consultants should be encouraged to correlate and describe the significance of the test results with specific selected design parameters and methods in the draft RAP.
Based on our review we conclude that the design features addressed by enclosed coment nos. 2, 3, 4, 5, 7, 9, 10 and 12 would reasonably be expected to have been covered in a draft RAP. The other coments cover design aspects that would be expected to be covered in the final RAP.
Wli 8806240010 880617 h/
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PDR WASTE
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Myron Fliegel There are design and construction features unique to the Belfield and Bowman project sites that would be better understood if a site visit could be arranged to visually evaluate their importance. These features would include the specific erbankment, foundation and borrow materials that are proposed for use in the construction of the disposal site and the existing site topography and drainage features that could influence long-tera stability. We request that arrangements for a site visit with DOE and its consultants be arranged for the Engineering Section reviewer.
If you have any questions regarding this review, please contact Joseph Kane of sqy staff (2-3449).
(0d@03I D Michael Tokar, Section Leader Technical Branch Division of Low-Level Waste Management and Decomissioning, HMSS cc: w/o encl.
J. Surmeier H. Tokar DISTRIBUTION:
Central File HMSS r/f LLTB r/f RLBangart JGreeves w/ene,1.
D. Gillen L. Deering T. Johnson K. Westbrook J. Kane JFG LLlu
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- 06// 7/88 OFFICIAL RECORD COPY
ENCLOSURE REVIEW COMMENTS OF ENGINEERING SECTION OF BEL /B0W DRAFT EA AND DRAFT RAP Prepared by Joseph D. Kane, LLTB, LLWM 1.
Draft RAP, Page 17, 3.2.2 - Radiation Levels and Concentrations -
Belfield Processing Site.
The description of the excavatior operations to remove contaminated soils from the Belfield site should be expanded to cover:
(1) the anticipated configuration (plan with top and cottoh. of slopes, bottom elevations) of the excavation when completed; (2) the measurements (type, equipment to be used, frequency of readings) to be made to ensure that all contaminated materials are removed; and (3) the specific grading plan for restoring the excavated area after removal of the contaminated soils.
2.
h ft RAP, Page 29, 3.4.1 - Processing Sites.
Copies of the logs for the test pit explorations in the Griffin Borrow site (Fig. 3.11) have not been provided. The logs should be available to evaluate this potential borrow source for rado, barrier materials, particularly to understand ths problems with avoiding the lignite layers.
The borrow excavation operations should be described to cover (1) the fieldmethodtobeusedtoidentifyacceptableradonbarriermaterials}
(2) the method of excavation (will the soils over depth be mixed?), (3 the anticipated configuration of the excavated borrow area, and (4) the specific grading plan for restoring the excavated area.
3.
Draft RAP, Page 37, 3.4.2 - Infiltration / Radon Barrier and Random Fill.
Provide the support for the statement that the Griffin borrow soils exhibit good properties for radon barrier material by specifically l
identifying all the laboratory test data upon which this statement is l
based.
It would be helpful if all the pertinent data were graphically summarized for each important engineering characteristic (e.g. low l
l permeability, good radon diffusion properties) and the selected design I
parameter was shown in relation to the available data.
With respect to Table 0.4.7, is back pressuring the sample in the triaxial cell the cause of the change in density from the initial to the final condition? Because the final densities are significantly higher than the densities to be required in compaction control, the resulting hydraulic conductivity values provided on Table D.4.7 may not be conservative.
Please discuss this potential non-conservative effect with specifics on radon barrier design.
In addition, on Table D.4.7 it is indicated that samples were taken from a depth interval of 2.0 to 8.0 feet. Will actual excavation operations duplicate this mixing of materials with depth?
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Draf t RAF, Page 37, 3.4.2 - Erosion Protection Materials.
The description of the sand and gravel materials from the Bowman borrow site needs to be expanded to describe (1) the subsurface conditions (areal extent, soil layering, depths of available borrow quantities), (2) the anticipated method of borrow excavation, (3) the method of sampling used and the test results on gradation and material quality and durability (referenced to specific test data) and (4).he design details demonstrating how the appropriate filter criteria has been met.
5.
Draft RAP, P?.ge 37, 3.4.2 - Erosion Protection Materials.
Description of the p(lans for borrowing at the Rhame site should include (1) the rock source areal extent and deaths), (2) the anticipated ran and distribution of rock sizes and how t11s range was determined, (3) ge potential problems with excluding deleterious materials or in obtaining the required volume, and (4) the specific criteria and test results that demonstrate suitable material quality and durability.
6.
Draft RAP, Page 42, 3.5.2 - Groundwater Movement.
Provide the location of the spring on Fig. 0.5.16, 7.
Draft RAP, Page 63, 4.3.9 - Conceptual Design.
There is very little factual information provided on the stability analyses of the disposal embankment slopes. As suggested in the Standard Review Plan, the information to be provided should include: (1) cross-sections and profiles with representative engineering properties (density, shear strengths) for the embankment and in situ materials; (2) discussion of the procedures used to select the conservative soil properties and profiles for analyses from tae available field and laboratory data; (3) a description of the ground water conditions assumed in the stability analyses (including any effects from flooding or ponding assumed to occur f rom design bases events); (4) stability calculations for both static and dynamic loading conditions including the design assumptions (e.g. boundaries of the various types of embankment and foundation soils, dynamic and water pressures acting within the slope);
dnd (6) failure surfaces corresponding to the lowest factors of safety.
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Draft RAP, Page 63, 4.3.9 - Conceptual Design.
Soils that are compacted to only 90 percent of Standard Proctor are not so dense to be unquestionably safe against liquefaction ty)e failure.
Also, the level of compactive effort to be required for cotesionless filter and be<Ying materials has not been provided and therefore, the ability of these materials to resist liquefaction needs to be addressed with supporting information. The discussion on the site's soil for resisting liquefaction should be expanded in the final RAP to address concerns with 90 percent compacted soils and the cohesionless soils, along with a clear description of the water conditions that could coiservatively be assumed to develop in the long-term for both the e'abankment and foundation soils.
9.
Dcaft RAP, Page 64, 4.3.9 - Conceptual Design.
Only concluding statements on the effects of settlement are provided. A discussion on settlement needs to provide essential information (Refer to SRP for guidance on type of information) and should include calculations with the supporting technical basis for concluding that differential settlement will not be a problem (e.g. cracking of the radon barrier coverlayer). The discussion should also address the anticipated non-uniform placement of organics and debris in the embankment and how the presence of these materials has been cor.sidered in the slope stability and settlement analyses. What controls in construction on the placeaient of organics and debris othar than on maximum percent will be required that will ensure conditions more severe than those assumed in design will not occur?. It would be worthwhile when describing the results-of the settlement study to tie in the settlement and displacement monitoring that is planned for the surveillance and maintenance program that is intended to verify that the completed disposal site is functioning as designed.
- 10. Draft RAP, Page 65, 4.3.9 - Design Criteria.
What compactive effort and moisture control is to be required for the filter and bedding layers? Are the windblown materials (Fig. 4.3) to be compacted the same as the contaminated materials? What laboratory test results are available for the windblown materials to understand their engineering characteristics? Recognizing that cohesive soils when compacted dry of optimum may, upon wetting, exhibit significant compressibility, are there valid design considerations for compacting the contaminated materials as dry as five percent below optimum as proposed?
What construction controls other than on compaction and moisture (e.g.
maximum size, maximum or minimum percent fines, soil classification, lift thickness, plasticity, quality and durability) are to be required for the radon barrier materials, random fill and filter and bedding layers? Have the practical considerations for construction placement of an approximately 30-inch wide layer been considered? (This results from a 6-inch thick layer on a 5H to IV slope).
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Draft RAP, Page 65, 4.3.10 - Design Criteria.
This paragraph notes that the radon cover thickness needs to be determined during final design. The final RAP should discuss the specific test results used in final design, the technical bases for selecting the final design parameters and also provide the pertinent calculations supporting the final design thickness.
Draft RAP, Page 67, 4.3.11 - Toe Protection Rock Sizing: Conceptual 12.. Design.
Excavating to a depth of seven feet below ground surface for the rock apron could at some locations result in extending the excavation below the upper water surface. What provisions are planned to permit performing this work in the dry? The design of the rock toe apron should address protection measures (filter criteria) needed to prevent the migration of fines from the natural soils into the rock apron.
In addition, what design profisions have been considered to prevent ponding in the rock apron from adversely affecting the stability of the final embankment. What specific drainage measures are planned to remove water that is collected in the rock toe apron?
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