ML20211G826
| ML20211G826 | |
| Person / Time | |
|---|---|
| Issue date: | 05/29/1986 |
| From: | Hawkins E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Themelis J ENERGY, DEPT. OF |
| References | |
| REF-WM-63 NUDOCS 8606200204 | |
| Download: ML20211G826 (6) | |
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I DISTRIBUTION Docket file WM-063 PDR/DCS WM-063/HDR/86/05/28/0 ngart, RIV
-I-PGarcia T01sen MAY 2 91986 RBrich EHawkins LLW Branch, WMLU TJohnson, NMSS 0 r/f URF0:HDR Docket No. WM-063 Mr. John Themelis U.S. Department of Energy Albuquerque Operations Office P.O. Box 5400 Albuquerque, New Mexico 87115
Dear Mr. Themelis:
3 We have completed our review of the Draft Remedial Action Plan and Site Conceptual Design for Stabilization of the Mexican Hat site. As we
_ -,..,_... agreed...our_ rev.iew.. consisted of. a broad overview..of..the. document. looking
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for.." fatal flaws,". unaddressed areas,-andisufficiency of~ basic data and.
information. To sumarize the enclosed comments, there appears to be no major problems with the proposed remedial action. The coments tend to
- - address more-specific technical questions and-issues-that should not-~ ~
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drastically affect the overall plan. At this point, there does not seem to be much value in meeting to go over these comments.
If you feel that a meeting would be beneficial, please let us know. However, we should plan to meet when more detailed designs are submitted for review.
Should you have any questions regarding our review or the items discussed in the enclosure, please contact me at FTS 776-2805 or Howard Rose on FTS 776-2816 Sincerely, Edward F. Hawkins, Chief Licensing Branch 2 Uranium Recovery Field Office Region IV
Enclosure:
As stated 1
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NRC Comments on Mexican Hat Draft Remedial Action Plan and Site Conceptual Design Radon Barrier 1.
Page 14, Section 3.2.1 Once annual average RN-222 levels are obtained from the current monitoring program, provide the results to the NRC, URF0.
2.-- Page 58, Design Rationale Item No. 2 - Provide substantiation that using average values of the radon emanating fraction from both the upper and lower piles is adequate to describe the emanating fraction for the materials j
._.., _......m..._..inc.luded. min..the ore storage, mill-yard and -windblown areas and.i s-
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.. reasonably. conservative.. The NRC's.SRP-directs-usage of-a -
0.35 emanating fraction for materials not specifically measured.
The emanating fractions from Ra-226 activities for the upper pile
- material ranges from-120-330 pCi/g and averages-0.20 - -0.06.
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Accordingly, an E of at least 0.26 is required for these unmeasured materials.
3.
Page 59, Design Criteria, paragraph 3 Review of the reported climatological data indicates that harsh winters and periods of snow cover are infrequent for this region.
For example, according to the DEA, for about a 20 year period, Mexican Hat received an annual average snowfall of 3.3 inches.
In addition, all normal maximum monthly temperatures were above freezing, while only 4 monthly normal minimum temperatures were below freezing.
Thus, it is extremely unlikely that frost will penetrate the rock and bedding material and impact the radon barrier material. Therefore, the statements in the DRAP that " harsh" winter conditions add an additional degree of safety to the design are not warranted for this climate.
4 Page 60 Provide the bar suction values corresponding to 5, 11 and 15 percent moisture contents for the TZ material, and discuss how these values correspond to the NRC SRP requirements.
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2 5.
Page B-11, bottom paragraph Discuss the quality control field procedures that will be utilized to assure that the assumed volume-weighted average Ra-226 concentration is accurate.
If field QC procedures will not be used, then a substantiated conservative Ra-226 concentration must be used.
6.
Page B-14, Section B.4.3, last paragraph Although the material which comprises the three distinct areas of offsite contamination only accounts for about 7 percent of the total volume of contaminated material, it is important to note that this
- material is the uppermost layer of contaminated materialc Please refer to coment No. 5 for specific required information.
7.
Page B-17, Windblown material Describe the.1ower permeability-materials 'that-this Iayer.will be..
tandwiched between, and provide the respective long-term
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permeabilities and the basis for the assumed value.
- 8. -- Page B-17,- Radon Barrier (unamended)- - -
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Since only)one sample was used from the windblown, radon barrier (unamended and radon barrier (amended) materials to determine the respective long-term moisture content, it seems reasonable to assume a more conservative long-term moisture content number for the unamended radon barrier cover layer. The NRC's SRP requires a value that correlates to the -15 Bar suction value should be used for the long-term moisture content of the radon barrier material. The value proposed in the DRAP (6%) corresponds more closely to the -2 bar value, while 2.5% corresponds to the -15 bar value. Accordingly, revise the design to consider the proper moisture content.
9.
Page B-19, Section B.S.2, first sentence Please clarify and explain the nature of the material referred to in the first sentence.
10.
Page B-21, second paragraph Although we agree that the standard is 20 pCi/m2s, the design should be based on reasonably conservative assumptions and not necessarily on mean values of a few measurements.
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3 11.
Page B 21, third paragraph, first sentence The NRC does not agree with the statement that the long-term moisture conter.t is a conservative estimate of the moisture content of the lower unamended TZ layer of cover material (see comment No. 8 above).
12.
Page B-23, Radon diffusion coefficients State whether any site specific "D" measurements intended for the off-pile material (layer 3).
If not, demonstrate that assumed values will be reasonably conservative.
13.
Page B-30, Section B.S.6 s
No information-is provided on a sensitivity (analysis for thei.e., 2.5% D = 2.6E-2).
unamended TZ material at the -15 bar value
.,,.Rev.ise..this_section to provide.the necessary analysis ~.....
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14.
Page B-33, Section B.S.7, sixth paragraph, second sentence
_. -... _ _ _ _ _ _ _... -A qualification -should be added to this' statement that 11 percent---
corresponds to TZ material amended with 7 percenf bentonite.
If amendation of TZ material is utilized, appropriate diffusion 6
coefficient measurements will be required.
Geotechnical 15.
Page 53, Conceptual design A detailed analysis of differential settlement will be required before final concurrence in the proposed design.
16.
Page 59, first sentence Provide a quality assurance plan that will assure uniform mixing of the top 1 foot of radon barrier soils with bentonite.
17.
Page 50, Design Rationale The discussion of Remedial Action Alternatives for ground water is deficient.
It lacks an explanation of the basis and/or supportive data to properly define a particular position on ground-water restoration.
There is no basis shown for not implementing physical or mechanical restoration procedures for the site.
If the position on restoration
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4 is for natural flushing of the hydrostratigraphic units impacted, more explicit information is necessary to explain the geochemical basis for why natural flushing will be adequate. This must include geochemical mechanisms specific to the site as well as a thorough description of estimated time frames for natural flushing and how estimates were derived.
Also, more explicit informaticn is needed to properly describe dilution, natural buffering and estimates of concentration with time.
- 18. Page D-58, Site Geology Discuss in explicit detail how the bedrock base existing beneath the
_pjje.wijj..effect-integrity and stabilization: The effect of" thermal' contraction and expansion due to se6sonal conditions needs further explanation with regard to creep and heaving of pile contents and cap.
..........._.19...mPage.D-58,. Impact of Natural Resource. Development-
- e It is stated that the top of the lower hydrostatic unit contains hydrocarbons. Discuss in detail economic aspects of the local area, with regard to mineral rights, possible~ petroleum withdrawal -
(present and future), subsidence and associated aquifer impacts.
- 20. Page D-97, Strength A new test or tests will have to be conducted on siltstone existing at the site. Valid results for strength test (s) must be submitted.
It is not sufficient to relate the properties of other materials, only valid tests conducted on rock material from the site will be accceptable.
- 21. Page B-49, Settlement Effects on Cover Integrity and D-98, Data Needs Geophysical survey (s) must be conducted at the site to establish extent and geometry of the bedrock base existing beneath the site.
It is possible that the rock geometry beneath the pile could jeopardize integrity and stabilization of the tailings and cover.
Surface Water Hydrology and Erosion Protection
- 22. Page 51 Provide additional information regarding the erosion protection designs that are proposed to prevent headcutting and erosion of the numerous gullies and arroyos at the site. At the present time, it D'
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5 is not clear what types of designs will be used and how these designs will be implemented.
Provide preliminary designs that show depth _to bedrock and the general configuration of the erosion protection as it is keyed into the rock. These preliminary designs are needed in order to detennine the overall feasibility of the remedial action, particularly for the gullies and arroyos that have large drainage areas and/or have very steep slopes.
Include the following information:
a.
gully configuration and cross-section b.
drainage area c.
riprap design-to be used
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depths to bedrock at each gully.
- 23. Page 51
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.s. Provide. preliminary designs regarding the -proposed diversion -
channels and other natural channels at the-site. 'Information is
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needed for each channel, as follows:
a.
channel width, shape, and/or cross-section
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b.
channel slope c.
drainage area d.
PMF peak flow estimate e.
PMF velocities f.
riprap requirements g.
riprap toe requirements h.
exit velocity, exit design, and depth to bedrock at exit point.
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- 24. Page 61, Design Criteria The NRC staff does not necessarily agree with the rock durability criteria outlined in DOE's Technical Approach Document (TAD), and does not agree that these criteria are acceptable.
In general, the criteria in the RAD are much less stringent than other normally acceptable criteria, such as the USBR criteria for good-quality rock. However, we do agree that oversizing may be a viable alternative and can only be evaluated after additional durability tests are performed.
Based on the preliminary data provided, it does not appear that the rock will meet USBR criteria for even poor-quality rock. We suggest that additional efforts be performed to locate rock of better quality.
If such rock cannot be found, DOE should indicate the methods and criteria that will be used to oversize the poor-quality rock that is available.
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