ML20138G985
| ML20138G985 | |
| Person / Time | |
|---|---|
| Issue date: | 10/07/1985 |
| From: | Higginbotham L NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Themelis J ENERGY, DEPT. OF |
| References | |
| REF-WM-41 NUDOCS 8510280152 | |
| Download: ML20138G985 (6) | |
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John G. Themelis, Project Manager UMTRA Project Office U.S. Department of Energy Post Office Box 5400 Albuquerque, New Mexico 87115
Dear Mr. Themelis:
Enclosed are the results of our technical reviews of two proposed modifications to the Remedial Action Plan for the Salt Lake City Project, transmitted to NRC by your letter of July 10, 1985. addresses the proposea elimination of the moisture requirement bounds for the compacted tailings. NRC staff have been in telephone contact with R. Rager of the TAC to provide early notification of the concerns detailed in this enclosure. As noted in the enclosure further analysis is necessary to justify this proposal in light of the effects of higher moisture content on strength, shrinkage, and compression properties of the soils. addresses deviations of the State of Utah rock durability specifications from those approved in the RAP review and specifically the proposed increase of the rock cover maximum absorption specification from 1.0%
to 2.0%.
Note that this review has been delayed while waiting for State of Utah personnel to provide gradation data from samples of the stockpiled rock.
The revie<t concludes that the proposed modification is acceptable, in part because the gradation test results have indicated that larger rock than approved in the RAP is to be used. This use of larger material, however, is also a change in the RAP specifications and requires reanalysis of filter design. DOE should contact State of Utah personnel and clarify this issue of rock gradation change and its effects on filter design.
If the design gradation is to be changed to the larger sized stockpiled material, a RAP modification including information on effects on filter design should be submitted for NRC review.
If the gradation given in the RAP stands, the NRC staff must be informed of this in order to reassess the proposed absorption modification.
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_2-OCT 7 - 1985 The NRC will complete this review upon receipt of the additional information requested pertinent to these two issues.
Should you have ar.y question regarding this transmittal, please contact me or Daniel Gillen of my staff.
Sincerely, 9Weinal situd! by b 13. llissiabou2a:n Leo B. Higginbotham, Chief Low-Level Waste and Uranium Recovery Projects Branch Division of Waste Management Office of Nuclear Material Safety and Safeguards
Enclosures:
As stated
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ENCLOSURE 1 REVIEW OF PROPOSED SALT LAKE CITY RAP MODIFICATIONS:
ELIMINATION OF M0ISTURE SPECIFICATIONS FOR COMPACTED TAILINGS by Engineering Branch, Division of Waste Management DISCUSSION The RAP specifies compacting the tailings and contaminated material to a minimum of 90 percent of the maximum dry density as determined by the ASTM D698 Method of Compaction at 0 to 3 percent below optimum moisture content.
By letter dated June 6,1985 (Michael W. Roshek, Utah Dept. of Transportation to Mark S. Day, State of Utah), Utah indicated that the restriction on the moisture content will increase the amount of required testing and will require additional compactive effort by the contractor, and that this additional work.
will result in an increased cost that was not initially considered in the estimated cost of the project.
By eliminating the moisture requirement, a greater degree of freedom is allowed for choosing the moisture content at which the soil may be compacted to achieve 90 percent of the maximum dry density.
However, compacting on the wet side of optimum rather than dry of optimum results in structural changes in the soil (dispersed vs. flocculated) which, in turn, may result in the following adverse conditions:
1.
The strength of soil compacted on the wet side of optimum will be generally less than that obtained from soil compacted dry of optimum and, as a result, the stability of the pile may be adversely affected [Ref 1.].
The DOE has neglected to address the effects on strength when the soil is compacted wet of optimum, i
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2.
The shrinkage of an expansive soil tends to increase with increases in the molding moisture content [Ref. 1].
In addition, a different compression behavior occurs for clays compacted wet of optimum rather than dry of optimum [Ref. 2].
Consecuently, compacting wet of optimum may result in significant consolidation of the pile.
Both phenomena, additional shrinkage and additional compressibility, may have an adverse effect on ii the integrity of the cover.
The DOE has failed to address the effects of shrinkage and compressibility of the soil because of excessive moisture i
when the contaminated tailings are compacted wet of optimum.
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CONCLUSIONS At this time, the staf f is unable to concur in this proposal.
The staff cannot be reasonably assured that the EPA standards will be met without justification for the modification, and analyses of possible consequences and measures to mitigate possible adverse effects resulting from the modification.
Therefore, these analyses must be presented before we can concur in this RAP change.
REFERENCES 1.
Banks, D. C., " Embankment - Design Concepts: Water Content - Density Relations and Effects on Design Parameters," from Notes for Construction of Earth and Rock-Fill Dams Course, U.S. Army Engineer Waterways Experiment Station, Corps of Engineers, Vicksburg, Mississippi, 1980.
2.
Winterkorn, H. F., and Fang, H.
Y., Foundation Engineering Handbook, Van Nostrand Reinhold Company, New York, 1975, pp. 253-256.
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OCT 7 - 1995 i
ENCLOSURE 2 J
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REVIEW OF PROPOSED SALT LAKE CITY RAP MODIFICATION:
4 ROCK DURABILITY SPECIFICATION CHANGES 4
by Geotechnical Branch, Division of Waste Management DISCUSSION The following changes to specifications established during the RAP review were proposed:
Test HAP Spec New Spec i;
Absorption
< 1%
< 2%
> 2.60
> 2.60 L.A. Abrasion
< 40%
< 25%
Na S0 Loss
< 10%
< 8%
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At NRC staff request, the State of Utah provided the results of gradation tests which were performed on the proposed rock.
Based on our review of this gradation information, the minimum D rock size is approximately 8 inches; 50 original specifications called for an average D size of approximately 41/2 50 inches, with a layer thickness of 18 inches.
Our review of the proposed new specifications indicates that the rock will meet the standards of at least fair quality rock (as established by the U.S. Bureau of Reclamation), with the exception of the absorption test.
However, in a letter to DOE dated February 13, 1985, the Utah Department of Transportation indicates that there are particles of calcium carbonate intermixed with the rock, which would probably cause the rock to absorb more moisture.
It can also be seen that the new specifications for LA abrasion and sodium sulfate loss are more stringent then the original specifications.
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- CONCLUSIONS Based on our review of the proposed riprap material, we conclude that the proposed changes in contract specifications are acceptable, because (1) the average rock size is approximately twice as large as needed, (2) the other durability specifications approved in the RAP review are either equaled or exceeded, and (3) there is calcium carbonate present which is probably influencing the absorption test results.
We consider that the proposed rock, with the increased 0 size, is preferable to the rock originally proposed.
50 RECOMMENDATIONS The change in rock size may necessitate a change in the filter layer underlying the riprap.
This should be reviewed by the Engineering Branch (WMEG).
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