ML20141P041
| ML20141P041 | |
| Person / Time | |
|---|---|
| Issue date: | 02/26/1986 |
| From: | Higginbotham L NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Themelis J ENERGY, DEPT. OF |
| References | |
| REF-WM-39 NUDOCS 8603180479 | |
| Download: ML20141P041 (12) | |
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DISTR 8BUTION JM 39 s/f M Nataraja WMLU r/f EF Hawkins, URF0 NMSS s/f ffb I6 686 JO Bunting k~._____
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DM faillen CE Martin S Smykowski 0 da annath Mr. John G. The:nelis, Project Manager F d Uraniusn Mill Tailings Prcject Office D Br Albuquerque Operations Office P.O. Box 5400 M Eli M *I Albuquerque, New Mexico 87115
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Dear Mr. Themelis:
We have completed our review of the draft Technical Approach Doccment (TAO) for the UMTRA project transfaitted to us by your letter of December 19, 1985.
Comments prepared by our f.echnical staff are enclosed for your consideration.
Please note that although the goal of our review is to achieve compatibility i
between the LAD and our Standard Review Plan (SRP) where possible, it should 1
not be assumed that following the TAD will saticfy all inforn.ation needs end requirements of a review perforn'ed in accordance with the SRP. Althcugh the SRP presents general a::ceptance criteria, it does not in roost cases repres6nt l
a detailed checklist of acceptable procedures and methods for characterization i
and design. Site specific conditions prevent this.
Should you have any questions regarding this review, please contact ri.e or Daniel Gillen of my staff.
I Sincerely, Ceiginal Got(! lif Aw 11, lhggithham i.eo B. Higginbotham, Chief tow _ Level Waste and Uranium Recovery I'rojects Branch Division of Waste Management Office of Nuclear Material and Safety and Safeguards
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Enclosures:
WM Encord fue WM Preiectdt., L.
As stated
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ENCLOSURE 1 f
COMMENTS ON UMTRAP TECHNICAL APPROACH DOCUMENT I
(Gectechnical Engineering, Radon Barrier Design)
Section 1.2.4, Page 50, Paragraph 4 The TAD cites a reference by Sherard et al (1985). A complete listing of this reference should be provided in the bibliography.
Section 1.2.4 - Fage 51, Table 1-3 I
The recommended design criteria for Soil Group 4 needs to be clarified.
Section 1.2.4 - Page 52, Paragraph 3:
The TAD states that when a rock blanket is used over filter, the maximum size of the rock shculd be equal to one-tenth of the blanket thickness. This statement should be corrected to read " minimum" size.
Section 2.3.3 Page 79, Paragraph 1:
Piidslines should be added on the type and size of borings to be drilled at each of the alternate sites during this initial site selection phase.
Section 2.3.4, Page 80, Paragraph 1:
The first paragraph presents the scope of the first phase of the field study consisting of only piezocone tests, and the second paragraph presents the scooe
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of the second phase of the field study consisting of borings and sampling.
Statements should be added to indicate that the field investigations will be conducted in two phases, and the scope of the investigations may be expanded to suit data r.eeds of the individual site.
Sectice 2.3.5, Page 84:
l A section needs to be added on Laboratory Testing for this option of stabilizirig the tailings.
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. Section 2.5.2, Page 98, Paragraph 2:
The proposed criterion for seismic stability evaluation for the end-of-construction condition is not in conformance with the decisions made in the technical discussion group meetings between DOE (TAC /RAC) and NRC.
The consensus of the group was that the seismic coefficient (k) to be used in the pseudo-static analysis for the end-of construction condition should be the higher of either 0.1 or 50 percent of the value of the peak acceleration at the site. This paragraph should be revised to reflect the agreement reached by the DOE (TAC /RAC) and NRC group.
1 Section 2.5.3, Page 100, Table 2.2:
For Situation 3 under Preferred Method column, it chould read as "Either method:
C ' 'u from UU test or E. I plus estimated pcre pressures.
u Section 2.7.1 Page 107, Paragraph 1:
The paragraph should be revised to state that liquefaction potential of both the foundation sotl and tailings pilo should be assessed.
Section 3.1.2, Pace 115, Paragraph 2:
It is unclear what " anticipated characteristic sixe" is intended to mean.
Clarification of this term is recommended.
Section 3.1.2, Page 116, Sentence 1; The TAD indicates that "an attempt would be made to define the extent and volume of off pile contaminated materials to be excavated to within roughly 20 percent." Statements shoole be added to clarify what this 20% indicates, and what implications this will have on the ability of the cleaa-up process to adequately d@ fine and remove contaminated materials.
_Section 3.1.3, Page 127, Approach to Designing the Radon Barrier:
This section of the TAD dcas not fully discuss or reference the methods that will be used for estimating values for several radiological parameters, such as radon emanation and diffusion coefficient. 00E may not want to limit itself
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to only measurement of such parameters.
The NRC's Standard Review Plan references acceptable calculational alternatives for estimation of these parameters.
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. Section 3.1.3, Page 129, Radon Emanation:
We understand that the diffusion coefficient testing is to be performed on samples at the long-term moisture content as described in paragraph 1 on page 135.
The description of radon emanation on page 129 is not in agreement with this.
Section 3.1.3, Page 130, Radon Diffusion Coefficients:
Measurements of the radon diffusion coefficients should be made on samples with the density (in addition to the long-term moisture content) at or near the predicted long-term value.
Section 3.1.3, Page 131, Cover Sampling:
The TAD should clarify the meaning and implications of the word residual in the term "overall residual uncertainty".
Section 3.1.3, Page 133. Paragraphs 1 and 2 In order to perform the somewhat lengthy testing and analyses described in these paragraphs, impacts to construction schedules may occur.
The TAD should consider this and describe what procedures whould be implemented to allow for modifications to the cover thickness resulting from these analyses.
Test results may indicate required cover thickness varying around the pile due to heterogeneity of the radon barrier material.
The TAD should indicate that the cover thickness will be determined by an area weighted average or more conservative method.
The TAD should address what procedures would be used to adjust the moisture content of undistrubed soil samples to the predicted long-term moisture content such that uniform moisture is assured throughout the sampla.
Section 3.1.3, Page 134, Sentence 1:
The TAD states that "the mean value of the design parameter for each layer of pile or cover is of interest..." When mean values are used, the method for averaging the values should be defined (i.e. area-weighted, volume-weighted, arithmetic mean, etc.).
It is also unclear which design parameters are being i
referenced by this statement.
. Section 3 1.3, Page 135, Inherent safety factors in the design approach This section should be modified to a discussion of how DOE's design of radon barriers provides reasonable assurance that radon emissions will be below the EPA limit.
In light of the fact that some of the positive factors such as snow cover may be offset by negative factors such as cover cracking from extended dry periods, this section should stress the conservatism applied to the selection of the most influential design parameters, i.e., diffusion coeeficient and long-term moisture content.
Section 3.2, Page 139, Radon Barrier Moisture Content:
This section discusses several methods for determining moisture contents of soils at various bar suctions.
However, no criteria are identified for selecting which value for the long-term moisture content will be used.
Section 3.2.2, Page 142, Paragraph 2:
Before the staff is able to form a position on any of these conclusions, we would need to review the "real data" that has been mentioned and compare it with the results of the correlations.
It is recommended that this data be referenced in the TAD.
I Section 3.2.3, Page 144, Paragraph 4:
What is the definition of " stable moisture content?" Does this term refer to the same concept as the "long-term moisture content?" It is also unclear how the discussion of the data gathered at the Gennison, Tuba City, and Riverton sites are to applied to your proposed procedures for estimating the long-term moisture content.
Clarification of these items should be included in the TAD.
b Section 3.2.4, Page 145, Paragraph 1:
This paragraph is confusing and should be reworded.
In addition, unless an acceptable technical justification is provided, erosion protection layers should not be assumed to generically increase the long-term moisture content of soil covers.
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. Section 3.2.4, Page 145, Paragraph 2:
The TAD states that many factors will be considered when estimating the long-term moisture content.
In addition to these factors, the TAC will be running the computer program "DSUFW" to simulate the long-term moisture content of the cover and tailings.
The staff is unfamiliar with this program and has not had the opportunity to review it.
If DOE is planning on using this program for designing the radon barrier, documentation of the program should be sent to the staff for review.
Attachment A to Section 3.0, Pages 148-159 In light of correspondence between DOE and EPA regarding this paper's confusing statements on the use of average design parameters, DOE should rethink the necessity of including this attact. ment in the TAD.
Section 5.7.2, Page 234, Bullet 3:
J The sentence should read " Minimizing the overall pile area to effectively reduce overall cover requirements (without adversly affecting pile stability)."
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ENCLOSURE 2 COMMENTS ON UMTRAP TECHNICAL APPROACH DOCUMENT (Geology, Hydrology, Geochemistry)
Section 2.2.3, Standard Methods for Assessing Common Hazards, Page 73 It is stated in the description of river hazard field investigations that aerial reconnaissance will extend at least 10 miles upstream and downstream from the site. However, it is stated earlier in the document (page 68) that the summaries and procedures described in the Technical Approach Document for assessing common critical geomorphic hazards are adapted from Nelson et al.
(NUREG/CR-3397,1983) anp Schumm and Chorley (NUREG/CR-3276). Nelson et al.
(ibid, Appendix D, page 109) recommend that reconnaissance flights " cover an area at least 20 miles upstream and downstream from the site."
It is suggested that DOE revise the upstream-downstream aerial reconnaissance distance from 10 to 20 miles.
Section 2.4, Seismic, Page 88 Our comments on the previous draft version of Section 2.4 (letter from B.Jagannath, NRC, to R. Rager, DOE / TAC, November 21, 1985, Attachment 1) are not addressed in the present Technical Approach Document (TAD). Mr. Rager has indicated that the present TAD pre-dates the ar: ival of our previous comments and that they will be addressed in future versions. Therefore, we have not repeated our November 21, 1985, comments in this review.
Section 4.1.1, Unsaturated Zone Movement, Pages 195 to 197 In Section 4.1, the Technical Approach Document describes a number of methods that might be used to calculate water infiltration into and through the tailings pile. The Technical Approach Document does not describe how the data for these calculations will be obtained; particularly the hydraulic conductivity values. The hydraulic conductivity values will be of particular importance should credit for the pile cover be taken in calculating the infiltration rate for the remedial action of choice. Therefore, the determination of appropriate hydraulic conductivity values should be incorporated into Section 2.3.6 (Borrow Area Site) in both the general section and field and laboratory programs. Further, Section 4.1 (Unsaturated Zone Movement) should reference this intent.
Section 4.1.1, Contaminant Source, Pages 194-195 l
This section of the Technical Approach Document describes three approaches for characterizing the contaminant source. The problem is that each of these t
approaches used by itself could underestimate the magnitude of the contaminant l
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The " preferred" method involves measuring the "... groundwater quality directly below the tailings, yet directly above the water table, and assume the concentrations of chemical constituents in the pore water at this point are representative of the contaminant source." The second approaco suggested is to characterize "...either the solid phase or the pore water within the tailings
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as the contaminant source". The third method suggested is to calculate what the apparent source would be based on concentrations and distributions of contaminants in the downgradient groundwater. Each of these suggestions, used by itself, could underestimate the magnitude of the contaminant source.
For example, the " preferred" method does not account for contamination that could be leached from the solid phase, and assumes that the chemistry going on in the pile is fixed. However, even if leaching were considered, the measurements below the pile could be at a point where contamination has been depleted (directly below the pile) or has yet to arrive (directly above the water table). The second suggestion considers only the contaminants in "...either the solid phase or the pore water within the tailings". This approach ignores either the contamination (leachate) from the solid phase or the contamination in the pore water. The last method looks only at contamination in the 4
groundwater downgradient from the pile and calculates a source term. This method has the same drawbacks as the " preferred" method.
Further, in order to 5
calculate back to a " source", numerous assumptions must be made about contaminant transport and the chemistry going on between the pile and the i
downgradient measurement locations. A more straightforward and practical approach would be to combine aspects of all three suggestions. This composite approach would consist of (1) the analyses of contaminants from both pore water I
and solid phase leachates from the tailings, from below the tailings and j
downgradient from the tailings and (2) use of geochemical codes to gain an understanding of the geochemical system (rather than for prediction of 3
contaminantattenuation). The use of such a composite approach should provide l
a conservative and/or defensible analysis of the amount of contamination available for transport.
3 Section 4.4.1, Movement of Contaminated Ground Water Page 193, Lines 15-18 The Technical Approach Document refers to "... employing..." "... simplifying assumptions which result in conservative, defensible analysis...as much as i
l possible." However, there is no guidance as to when simplifying assumptions / conservative analysis will or will not be used. For example, will i
they be used in cases when sufficient data are not available (see page 202, i
lines 3-5)? The document needs to be more specific concerning the employment of this strategy.
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Section 4.1.1, Attenuation of Contaminants, Page 199, Lines 1-14 8
The Technical Approach Document indicates that in the evaluations of contaminant movement "... mechanical dispersion, dilution, filtering of suspended or colloidal solids, biological decomposition of organic compounds, f-denitrification of nitrate, ion exchange, other surface sorption reactions, i
precipitation of dissolved chemicals, ion sieving by dense clay layers t
(ultrafiltration), and decay of radioactive elements" will be considered at
..each UMTRA project site." The following discussion then describes the guidelines to be followed. However, this discussion does not provide guidelines for systematic consideration of each of the above attenuation 4
processes. The effect is that it is not clear (1) whether all of the processes I
will be considered for each site and (2) what data will be collected to support i
each consideration. The Technical Approach Document needs to present systematic guidelines for the consideration of each of the processes.
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Section 4.1.1, Attenuation of contaminants, Page 200, Lines 1-8 i
a The Technical Approach Document suggests that "...even a small fraction of one i
percent carbonate minerals is sufficient to provide considerable neutralization capacity." However, all of the carbonate contents of the solid phase may not i
be available for buffering if the carbonate minerals are coated with iron oxides. Thus, an additional approach that should be considered is to titrate the solid with leachate to determine the neutralization capacity of the soil empirically.
4 Section 4.1.1, Attenuation of Contaminants, Page 200, Line 20 l
On page 199, lines 21 and 22 state that "... neutralization produces a condition in which the solubility of Fe and A1... decreases." Further, it is stated that l
as they precipitate, they scavenge other contaminant metals such as Mn.
However the Technical Approach Document (on page 200, line 20) suggests that both Fe and Mn persist "... at elevated levels in the aquifer downgradient from the zone of neutralization." While Fe and contaminants such as Mn may persist l
at levels above background, these two statements do not appear to be l
consistent. This inconsistency should be clarified.
In addition, the TAD l
should include the systematic approach that will be followed to evaluate geochemical attenuation.
Section 4.1.1, Attenuation of Contaminants, Page 201, Lines 1-12 l
The Technical Approach Document suggests that in cases in which the aquifer 3
affected by the tailings is oxidizing, several types of analysis can be used to produce a qualitative estimate of attenuation, and that more than one type of
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k analysis should be used in order to provide a check on the reliability of the other measurements. However, there is no indication what the DOE will do. The Technical Approach Document needs to lay out the systematic approach to be taken.
Section 4.1.1, Attenuation of Contaminants, Page 201, Lines 23-25 The Technical Approach Document states that "...a qualitative estimate of the affect of adsorption / desorption on contaminant migration can be made by comparing the current distribution of a contaminant near a tailings pile with that of a non-sorbing tracer..."
It is not clear whether " distribution" means (1) spatial distribution in solution of the contaminant versus that of the non-sorbing tracer, or (2) the distribution of the contaminant in solution and in the solid phase versus that of the non-sorbing tracer.
In the first case either the contaminant needs to be compared to the quantity at the source (in which case there is no use in sampling the tracer). Or, both the contaminant and the tracer need to be sampled downgradient from the pile until each approaches background.
In the second case there would be little need to sample the tracer because the distribution of the contaminant in solution versus that in the solid phase would by itself be a measure of attenuation. The most straightforward method is contained in case one. The Technical Approach Document needs to more clearly state how qualitative estimates of the effects of adsorption / desorption on contaminant migration vill be determined.
l Section 4.1.1, Attenuation of Contaminants, Pages 202, Lines 3-5 The Technical Approach Document states that qualitative estimates of contaminant migration will be used for contaminants for which sufficient data are available. The Technical Approach Document does not, however, indicate what will be done if sufficient data are not available. Thus, the document needs to provide guidance concerning alternative methods if data are not available for the qualitative approach (e.g., collection of more data).
Section 4.1.1, Attenuation of Contaminants, Page 202, Lines 6-25 The Technical Approach Document suggests that reducing conditions will maintain redox sensitive contaminants in low solubility and high sorption states.
Therefore, in order to determine if mineral precipitation under reducing conditions is a reasonable attenuation mechanism, the presence of reducing l
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It cannot be assumed, however, that all redox l
sensitive contaminants will be in chemical equilibrium within the system (Stumm,1966, Lindberg and Runnels,1984, Hostettler,1984, among others). The effect of such an assumption could be to overestimate attenuation. This is
4 especially true in modeling geochemical attenuation. The Technical Approach Document should acknowledge the limitations of the redox concept and discuss how this information will be used.
Section 4.1.1, Attenuation of Contaminants, Page 203, Lines 1-14 The Technical /groach Document states that the precipitation of gypsum tends to reduce local permeability. However, as gypsum precipitates, calcium carbonate goes into solution, which could result in an increase in permeability. The Technical Approach Document does not describe an analysis to verify the reduction of local permeability. The Technical Approach Document needs to clarify how this fits into the technical approach.
Section 4.1.2, Predicted Concentrations, Page 205 Lines 9-10 The Technical Approach Document states that " Geochemical models will be used only if necessary to define bounding conditions, i.e., to establish limits."
This statement is too restrictive. Models can also be used to suggest worst case /best case and can be used to gain an understanding of both laboratory and field data. The Technical Approach Document should consider these additional applications.
l Section 4.1.3, Impact on Beneficial Use, Page 213 The section on " Impact on Beneficial Use" of ground water states that predicted land use data is difficult to obtain from s.lanning agencies beyond 30 years.
From this it is concluded that "although the rules and regulations guiding the UMTRAP Project regt, ire stabilization of the contaminated materials for 1000 years, or at least 200 years, it is felt that water use and resource value projections beyond 30 years are of limited usefulness". However, these projections are used in the determination of the impact on beneficial use which in turn must be used in the cost-benefit analysis. The cost-benefit analysis then helps in the determination of what type of ground water restoration technique will be required or if ground water restoration will be done at all.
However, if no attempt is made to estimate beneficial use beyond 30 years, the benefit of restoration will be assigned a zero value for any impacts due to ground water contamination beyond 30 years.
For example, if it is determined that the water use at a particular site for the next 30 years is agricultural and that the water contamination will be a problem for 25 years; the cost benefit analysis will determine a value based on 25 years of impacts. However, if it is determined that water contamination will be a problem for 60 years, the text implies that since impact on beneficial use can only be projected for 30 years, the cost-benefit analysis will only determine a value based on 30 l
b 4 years. This would be unacceptable, since the cost-benefit analysis would underestimate the benefit of restoration, which in this case should have a value based on 60 years of impact and not 30 years.
In this example it would be better to make a reasonable guess at future land and water use beyond 30 years, rather than unrealistically assign a zero value to ground water impacts beyond 30 years. The Technical Approach Document should be modified to make a best guess at land uses beyond 30 years or to make a conservative assumption in the cost-benefit analysis such as assuming the water will be used for its highest possible use beyond 30 years.
Section 4.3, Risk Analysis, pages 218-220 Section 4.2 indicates that a cost-benefit analysis will be used to help determine if restoration will be implemented and if so, what type of restoration will be carried out. However, the next section (Section 4.3) describes a risk assessment that will be done at each site for ground water contamination, but does not describe how the risk assessment will be used. If the decision of whether to implement a ground water restoration program is based on the cost-benefit analysis, it does not seem appropriate to do a risk assessment after ground water restoration decisions have been made. However, if a risk assessment is important in making ground water restoration decisions, then it is suggested that the risk assessment be incorporated in Section 4.1.3 (Impact on Beneficial Use) or the cost-benefit analysis.
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