ML20214L757
| ML20214L757 | |
| Person / Time | |
|---|---|
| Issue date: | 08/01/1986 |
| From: | Nataraja M NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Martin D NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| References | |
| REF-WM-86 NUDOCS 8609100359 | |
| Download: ML20214L757 (4) | |
Text
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i 1996 SS/7/31/MEM0.
MEMORANDUM FOR:
Daniel E. Martin, Section Leader Low-Level Waste and Uranium Recovery Projects Branch, WM FROM:
Mysore. S. Nataraja, Section Leader Engineering Branch, WM
SUBJECT:
WMEG REVIEW 0F THE DRAFT " COMPARATIVE ANALYSIS OF DISPOSAL SITE ALTERNATIVE REPORT" (CADSAR) FOR THE SLICK ROCK, NEW MEXIC0, UMTRA SITE In accordance with Technical Assistance Request No. WM-86629, we have reviewed the geotechnical engineering aspects of the subject document. Our review comments are attached.
The draft CADSAR document indicates that the scopes of work for geotechnical and hydrological evaluations for the Slick Rock site were sent to the NRC for review, apparently to our URF0 office.
In response to our request, Mark Haisfield of your staff is obtaining these documents from URF0.
It is our recommendation that WMEG have the opportunity to review these documents and provide comments to DOE as part of our CADSAR review prior to the beginning of site characterization activities. A staff review of the scopes of work should help to assure that all relevant data required for remedial action will be obtained through the proposed field characterization program.
This review was performed by Steve Smykovski and coordinated with Mark Haisfield of WMLU. Any questions that you may have on the enclosure may be directed to S. Smykowski on x74109.
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DATE : 8/l/86
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SS/7/31/ ENCL ATTACHMENT GE0 TECHNICAL ENGINEERING REVIEW 0F THE DRAFT COMPARATIVE ANALYSIS OF DISPOSAL SITE ALTERNATIVE REPORT (CADSAR)
FOR THE SLICK ROCK, NEW MEXICO, UMTRAP SITE prepared by:
Engineering Branch, WM 1.
The draft CADSAR indicates that the foundation soils at the stabilization-in-place (SIP) site are permeable silty sands and gravels. The foundation soils for the stabilization-on-site (S0S) alternative are identified as " alluvial gravel, cobbles, and an occasional boulder in a matrix of silty sand" (page 19). The foundation soils at Burro Canyon are silty sands overlying bedrock (page 13).
These specific soils at each site, if saturated, may be susceptible to liquefaction or significant loss in shear strength under the vibratory motion of the specified design earthquake (0.29, page 12) and special design considerations may be required. Has the potential for liquefaction been addressed for each of the alternative sites and has this potential been factored into the cost comparative evaluation shown in Table 6.1?
2.
The draft CADSAR does not provide a discussion on slope stability which would allow the staff to conclude that the EPA standards will be met for each alternative site.
It would likely be possible to provide an engineered slope design which would ensure the necessary stability in order to meet the EPA standards. However, specific but different design considerations may be required which would significantly impact the construction costs for each alternative site. What specific design considerations for slope stability are required for each alternative site and have these specific design considerations been factored into the comparative evaluation shown in Table 6.1?
3.
Table 3.2, page 12, indicates that the foundations soils are a concern for the Slick Rock site which may impact the costs for meeting the EPA standards. However, the CADSAR does not discuss the basis for the concern nor does it indicate how this concern is reflected in the cost comparative evaluation in Table 6.1.
The foundation soils at the Burro Canyon site are indicated not to be a concern (Table 3.3), however, information has not been provided which would support this conclusion.
Since the purpose of the CADSAR is to identify and discuss the technical aspects of each alternative site for remedial action, this CADSAR document should identify and address these concerns. Supporting information should be provided which would indicate l
SS/7/31/ ENCL.
-whether these concerns for. foundation stability would adversely impact the design meeting the EPA standards.
4.
The draft CADSAR indicates that relocation of the tailings material to L
the_ Pioneer Uravan site was identified as an option for reclamation during the alternative site selection process (page 4). However, the CADSAR indicates that the site has not been evaluated in this document, but that it is physically comparable to the Burro Canyon site.
Potential radon barrier t
sources were ider.tified in Disappointment Valley at the Pioneer Uravan site (Section'3.3.2, page 15). Has a cost comparison been performed for relocating
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the tailings-to the Pioneer Uravan site and using the material at that site for the radon barrier?
5.
Section B.2, Page B-1, indicates that since data were not available on the radon diffusion coefficient, a common cover thickness of 5 feet was chosen for each alternative on the basis of prior experience. Since the ability of the remediated site to meet the EPA standard for the release of radon depends heavily upon the effectiveness of the radon barrier, it is extremely important that this barrier be of adequate thickness.
If SOS or relocation to Burro Canyon are selected for remedial action, segregated layering of tailings would j'
be possible and coulo reduce the required cover thickness. This could significantly affect-the costs and accordingly, it should be factored into the draft CADSAR. Past experiences have indicated that the costs for remedial I
action can be significantly impacted by increasing the radon barrier thickness.
A meaningful cost comparative analysis would need to address these cost differences. At the CADSAR stage, a reasonable estimate of the required radon barrier thickness should be made.
- 6. According to the draft CADSAR, the SIP alternative will require an estimated 190,000 cubic yards of radon barrier material. The SOS and Burro i
l
_ Canyon alternatives, however, will require an estimated 90,000 and 100,000 cubic yards of radon barrier material, respectively. The CADSAR should explain why the-SIP alternative requires almost twice the volume of radon barrier material to cover the same volume of tailings with the same five foot thickness.
Does this reflect the need for special design conditions?
7.
The effects of total and differential settlements for each alternative to meet the EPA standards have not been discussed.
If the SIP alternative is l
chosen for remedial action, the tailings may be susceptible to larger differential settlements if zones of soft material exist.
If placement of the tailings is controlled, as would be the case with the SOS and relocation alternative, differential settlements may not be a problem and would likely be j.
less than those expected with the SIP alternative. What special design l
considerations are required to reduce the amount of differential settlement at 9
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SS/7/31/EhCb i each site and have these effects been factored into the comparative analysis shown in Table 6.1?
8.
The draft CADSAR mentions the size and quantity of large size rock required for flood and erosion protection. However, it does not identify specific design criteria that are required for the rock. Wiiat is the basis for the indicated rock sizes and is there assurance that the proposed borrow sources can provide the size, quantity, and quality of rock required for each of the alternative sites?
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