ML20217H067

Forwards Draft Comments on Drafts of Environ Assessment, Remedial Action Plan & Processing Site Characterization Rept for Remedial Actions at Gunnison Site

ML20217H067
Person / Time
Issue date:	02/26/1985
From:	Hawkins E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
To:	Themelis J ENERGY, DEPT. OF
References
REF-WM-61, TASK-TF, TASK-URFO NUDOCS 9710150021
Download: ML20217H067 (16)

Text

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040WMtM 101E 040WMHf102E 61 John Thenalis, Project Manager Uranium Mill Tailings Project Office U.S. Department of Energy

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x Post Office Cox 5400 Albuquerque, New Mexico 87115

Dear Mr. Themelis:

Enclosed are our draft consnents on the drafts of the Environmental Assessment, Remedial Action Plan, and Processing Site Characteri7ation Report for remedial actions at the Gunnison UMTRAP site in Gunnison, Colorado. The consnents are being forwarded to you in draf t form in order to meet your request for receipt of the Gunnison consnents by March 1, 1985. The final comments will be sent to you directly from NRC Headquarters by Mr. Mark Haisfield as soon as possible.

Should you require clarification or wish to further discuss these draft comments, we are prepared to discuss them in more detail. If we can be of further assistance, please contact Sandra L. Wastler on FTS 776 2811 or Mark Haisfield on FTS 427-4722.

Sincerely,Ack

.S44) ,

ad Edwa7dF.Hawkins, Chief '

Licensing Branch 1 Uranium Recovery Field Office Region IV Cases Closed: 040WM177101E 040WM177102E

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NRC Coments - Gunnison Site Surface Water Hydrology and Erosion DRAP

1. Appendix E , PM,F,,Dg,emin,a,t,ig Based letter fromon aM.review Bone to of T. theJohnson DOE flood analyses dated (provided August 17, by) cover 1984 , we conclude that the Probable Maximum Flood (PMF) for the Gunnison River may not have been adequately or conservatively estimated. Our review of the analyses indicates that teveral important input O, parameters to the HEC-1 model have not been properly estimated.

Because the PMF on the Gunnison River determines the riprap size that will be provided to protect the toe of the tailings pile, it is important that an adequate estimate of the flow velocity be detemined. Further, because the design must remain functional for a 1000-year period witbout routine maintenance, it becomes very important to conservatively estimate the flow velocities and shear forces associated with the PMF.

The 00f. PMF estimcte of 205,000 cfs for the Gunnison River was compared to regional maximum flood (RMF) estimates as presented in Crippen and Bue (1977). Based on this comparison, the RMF value of about 210,000 cfs exceeds the DOE PMF estimate. The NRC staff has concluded that RMF data, in most cases, do not represent conservetive PMF values and that any PMF which does not exceed these O RMr velues has Prnbebir been ueeerestimeted.

The DOE estimate for the Gunnison River was also compared to the DOE PMF estir. ate for the Animas River (Durango EIA). The PMF for the Animas River, with a drainage area of 770 square miles was computed to be 271,800 cfs, it is doubtful that the Animas River basin is drastically different from the Gunnison River basin, in terms of flood prcducing characteristics.

Further exar.ination of the HEC-! analyses indicate that several param*ters in the PMF anelyses have not been properly estimated.

1)

Areal drainage reduction basWTibbViii of Pt'F.2)The was reducedPMF for thefor the Gunnison combined drainege River 1

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2 area (2000 mi ) of the Gunnison River and Tomichi Creek. This reduction should not be applied when dealing with only the peak PMF flow in the Gunnison River. >

2) Rainfall Infiltration Rates. The SCS curve numbers that were seTe~c't'e'd'Tn"tWe'liEC-1 model are not considered to be conservative, since little in'tial saturation of soils is assumed to be present, using these values. For these values to L be acceptable, the 24-hour PMF should be preceded by a significant- amount of rb fall (e.g., the rearrangement of the last two 24-hour segments of the 72-hour PMP to the first two 24-hour segments), to minimize later infiltration.

Alternately, more conservative estimates of the curve numbers O- (e.g., AMC-ll!) or saturation of the soils should be used in the analyses.

3) Times of Concentration. The formula used to calculate times of concentratToEltc's), and resulting lag times, may not be appropriately reasonable or conservative when dealing with extremely steep mountain streams with very high flow velocities. Based on our exanination of topographic maps and portions of the Gunnison River basin, the staff recomends use of the stream hydraulics method (Ref. Design of Small Dams) to estimate tc's and resulting lag times, for streams IhTsTteep.

4) Stom Centering. It is nou d that the HEC-1 analyses were performed using several sub-basins of the Gunnison River, but using a uniform PMF rainfall amount over the entire basin. A nore appropriate nethod of analysis is to use the procedures O outiinee in sydrometeorolo9 1cei aePort No. 49 where varyiec rairfall depths are centered according to an actual isohyetal pattern over the sub-basins to produce the peek PMF in the entire basin.

Taking the above factors into consideration, a revised PMF analysis should be performed to conservatively determine the upper litrit of flooding potential for this site. An acceptable method for addressing th6 above input paranters and computing the PMF may be found in ANSI N-170, " Standard for Determining Design Basis flooding of Power Reactor Sites".

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2. Appendix E ,,R,jp, rap _To,e,, Protection

. A. Calculational Basis for Rock Size Provide the basis for the determination of Dg n riprap size of 6 inches for the rock to be placed at the toe of the pile to prevent erosion during a PMr. Based on our review of the HEC-2 analyses, it is difficult to determine what methods were used to compute the required D rock size. Our independent analyses for e flow velocity of015 fps and depth of 7 feet indicate th.g a D size of approximately 15" will required for an assumed 1 onIOfailureslope,usingCorpsofEngineers i forvulae (Ref. " Hydraulic Design of Flood Control Channels").

t However, DOE calculations indicate a required Dcn of only 6" (page E-33). The basis for the 6" rock size sh501d be further i

discussed and/or evaluated.

B. Effect of Revised PMF Analyses

' Using)the above , therevised PMF riprap for tneestimates (as arolicable toe of the pile should be - See Questior. 1 re-evaluated, based on the velocities computed using the

.evised DMF.

C. Effects of Pptential thannel Heanderino and Movement The geomorphic evaluation proviaed in Appendix B indicates that a potential for chanael movement exists at the site. Because g of the recognizid uncert. Inty regarding channel stability, and y the potential fcr migration (of unpredictable extent) of the Gunnison River channel toward the pile, we conclude that an additional margin of safety should be applied to the design of the rock toe. This would provide additional protection in the event of a flood which channelizes flow and produces high velocities at the pile, similar to those velecities produced in h'e the exist 19 Gunnison River e.hannel under PMF conditions.

recomend that redesign of the - ock be performed, using an additional margin of safety to acco nt for this phenomena.

i Taking into consideratior the above concerns, the rock toe protecticm should be re-evaluated.

, 3, Appendi x E, - Erosion Prote,c,tj o,n_,f,o,r, Top,, a,nd SJ,de, o,f,,,Pil,e The NRC staff has concluded that the design for long-term erosion protection for the top slopes of the reclaimed pile may not be adequate to meet EPA long-terr' stability criteria. We believe that the currently-proposed erosion protection could be damaged by

, rainfall much less intense than the PHP.

The erosion protection for the pile has been designed to resist only the effects of unconcentrated sheet flow, which may not be an accurate representation cf conditions which are likely to exist in the future. We conclude that areas of flow concentration will form due to differential settlement, random flow spreading, and/or uneven O grading. We conclude that erosive volocities may be produced by precipitation much less severe than the PMP, if such phenomena occur.

Ba,ed on independent analyses performed by the NRC staff, we l conclude that rock with a D of about 1-1/2 inches should be placed i on the top at a thickness o'f Otwo feet. We conclude that the proposed rock with a D 40 of about 3-1/2 inches is acceptable for the i

sides of at a thicknes5 of one foot).

Accordingly, either revise the design of the rock for the top of the pile, or provide additional analyses to document that the design adequately accounts for flow concentration due to different settler.ent and uneven grading.

4 Appendia E ~~~- Dam Failures 4

O Identify any upstream dams whose failure could affect the site. If it is determined that there are upstream dams that are not desdgned for an occurrence of a PMF, provide analyses to determine the effects cf failures of such dams on the various site design features. Identify any future efforts that will be undertaken by the dar ovners to upgrade the dams or spillways to pass a PMF.

secognizing that dam failure calculations are difficult to perform and are sensitive to certain assumptions such as time-of-failure,

fadlure r. ode, etc. , you tray provide the results of conservative (t'ut less rigerous) calculations used to estir, ate peak water levels ar.d velocities at the site. Corps of Engineers and U.S. Weather Bureau 4

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unsteady flow models may be used for such predictions, if a more rigorous approach is taken.

Hy d r o g e o Qqy_,( G r,o,u,n,d -Wa,t e,r, ,C h a r a c t e r i z a t igd l

DEA

5. The Gunnison UMTRAP site has contaminated ground water hydraulically

> downgradient from the site in the alluvial aquifer of the Gunnison Valley. Our review concentrates on the seven criteria provided by EPA in Subpart C cf 40 CFR Part 19?. These seven criteria are used by NRC staff to review the adequacy of hydrogeologic assessments.

Of the seven criteria, the hydrogeologic assessment in the Gunnison DEA and DRAP satisfies criterion 1, establishment of background Q ground-water quality, and criterion 2,-identification of ground-water cottamination. The other five criteria, however, have

not been adequately satisfied.

Additional field characterization presently underway should satisfy criterion 3, characterization of the extent of ground-water contamination, including relative concentrations of contaminants within contaminant plumes, and criterion 4, characterization of the rate and direction of contaminated ground-water migration. Gnce these assessments are completed, DOE should be able to satisfy criteria 5, 6 and 7 and select appropriate actions for the Gunnison

UMTRAP site. The NRC would recommend that new data and analysis i

derived from on-going investigations be submitted prior to issuance

of a final EA to allow the NRC to review the data to assure EPA's

! seven criteria have been satified and to avoid schedule delays

. The fo11 ewing paragraphs reiterate the NRC's concerns as originally expressed in our comments on the PDEA. Ground-water quality information in the DEA, DRAP, and SCR indicates that shallow ground water hydraulically downgradient from the site is contaminated, and that water from this same aquifer is being consumed by residents of the Gurrison Valley. As reported in these documents, concentrations of uraniun, arsenic, and selenium in ground water consumed by the ,

residents are below maxirum allowable concentrations for drinking water (e.o., MCL's under 40 CFR Part 141). Additional characterization of the extent of ground-water contanination is warranted, however, because these concentrations may increase c, the contarinated ground water beneath the site migrates downgradient toward the domestic users of the shallow aquifer. We recomended 5

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that DOE characterize the variation of ground-water quality with depth, the lateral extent of ground-water contamination, and the fate of contaminated ground water near the confluence of the Gunnison River and Tomichi Creek (i.e., does the contaminated ground water completely discharge into the surface water or does it migrate beyond the confluence).

Under criterion 4, the DEA, DRAP, and SCR should characterize the stratigraph.i of sediments that conduct the contaminated ground water because stratigraphic heterogeneities may significantly affect rates and directions of contaminant migration. In addition, the documents should characterize the distribution of hydttulic head in the g alluvial equifer in the valley by measuring water levels in shallow v monitoring and domestic welle in this aquifer. This information ;s necessary to (1) predict the rates and directions of contaminent migration, and (2) characterize recharge-discharge relationships of the alluvial aquifer with the Gunnison River. Tomichi Creek, and other surface water bodies in the valley (e.g., gravel pits, irrigationcanals, ponds,etc.). This information will also aid in characterizing the potential for migration of contaminated ground water toward a municipal well in the alluvial aquifer, which is located several thousand feet north of the site.

Once this information is developed, we recommend that you pursue the strategy for selecting appropriate remedial actions for ground water as described in the DEA and DRAP, which includes characterization of the extert of contamination, identification of remedial action alternatives, and evaluation and optimization of these alternative actions. By pursuing this strategy and satisfying the EPA cuiderce O Providee for such decisioas $a subPart c of 4o cra eart 197', oot should be able to support its decisions.

6. More explanation is needed to adequately justify that the proposed stabilized embankment and liner system will protect ground water after reredial actions are completed at the site. As presently described and evaluated, the proposed design does not demonstrate adequate protection of ground water beneath the site. Future versions of the RAP should include conservative predictions of post-reredial action performance to demonstrate compliance with the EPA starterds in 40 CFR Part 192.

7 The hydrologic characterization of the Gunnison site alluvial aquifer provided in Appendix D of the DEA is inadtquate. Me Theis 6

l method used to analyze the test data is not valid because many of  ;

the assurptions made by Theis in developing the method are violated.

. Additionally, neither the early or late time / drawdown plots provided as Figures D.2.6 and D.2.7 fit the Theis type curve. Until a more detailed lithologic description of this unit is provided, one must assume that the acuifer is unconfined, poorly sorted, very course-grained anc poorly compacted. Use of the Jacob straight line method on the late til t drawdown data or the Theis method as i modified for thick unconfined aquifers would have resulted in more i

representive hydraulic properties. Taking the above facts into '

consideration, a revised analysis of the pump test data should be ,

perfonned to provide representative hyaraulic properties of the '

alluvial aquifer.

8. Page D-55; It is stated that the difference in hydraulic head ,

between the shallow and deep observation wells indicates that '

confining layers or lenses are present within the aquifer making it

" semi-confined." This observation by itself does not prove or disprove the existance of sitt and clay lenses within the aquifer.

4 All it says is that there is vertical flow within the aquifer.

Unless additional geologic evidence proves the existance of

confining layers, this paragraph should be deleted.

9. Page D-55; it is stated that there are higher concentrations of 4

uranium and iron present in the shallow wells than in the deep wells. The authors attribute this to sorption by clay layers present between the shallow and deep wells. It should be noted that

uranium is a fairly mobile species and would not be expected to be significently sorbed by clay fractions. It is possi5iy more reasonatle to attribute this to a redox phenomeus, pH change or the Q fact that the shallow wells are closer to the contaminant source (bottom of the pile) than are the deep wells. Alsu, according to the authers, high concentrations of Fe are present in the natural ground water anyway. The text should be modified to reflect the

! oossibility that other natural mechanisms may be responsible for 1.his phenomenon, i

! 10. Page D-51; it is stated that the pump test data indicate the 3

presence of a layer or zone which acts like a confining layer. The

! data presented in Figure D.2.6 may indicate a boundary condition.

l However, this may also represent a no-flow boundary similar to the bedrock / channel boundaries depicted in Figure D.T.S. Unless a

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i additional geologic evaluation proves the presence of co 'ining layers, this inference should not be used as proof of t finement.

11. Page D-67; Accoroing to DOE's plan for implemeting EPA standards for i UMTRAP sites, ground water and contaminant modeling will use existing data from each site to explain historic contaminant transport and predict post-remedial action concentrations and rates of migration. The DOE modeling olen is predicated on two invalid q

assumptions sites, and *{2)thatthemodelcanbeusedasapredictiontool.(1) that sufficient In the case of Gunnison, we recommend that chemical and transport models not be used in a predictive manner because there is not O enou9h eeta coacerain9:

a) Dispersivity and scale dependence of dispersivity. Also, TRUMP uses finite-difference approximation to advection-dispersion i equations. The validity of this equation is questionable at the travel distances involved in this problem.

! b) Uranium and heavy metals are the only contaminants of concern (50g does not appear to be a health hazard at the site). The reduction in concentrations of these species is governed by corelex adsorption-coprecipitation reactions that are not adequately understood. No kinetic or thermodynamic data exist on these reactions. A source term for trace elements computed by PHREE 0E would be meaningless, c) The nethod of computing the source term via PHREE 0E and the O ea'atioa on Pa9e o-7o 4$ over simp 14riee-One alternative might ee to model moisture flow and possibly mass 2 transport in one dimension through two hypothetical columns of tailings: 1) existing profile, and 2) remedial action profile.

Solute flux into the water table for the proposed remedial action would be conpared to that of the original profile. In this way, the effectiseness of the remedial action in isolating contaninants from the grmd water system could be evaluated. The flux of l contenirants into the ground water would be lowered by a factor equal tc the ratio of the two fluxes. Due to the existence of retardet on and renovel processes associated with uranium and other d

heavy retals, this evaluation could be considered conservative.

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12. Page D-67, 68; FEMFLO, TRUST, and TRUMP are extrenely expensive models to utilire. DOE does not have sufficient data to adequately describe the site complexities that would justiiy the use of such models. We recommend that DOE use any ana1 3 .ical models which may provide valuable information at a fraction of the cost.

DRAP

13. Pages D D-55; The authors attempt to present a case to justify

" semi-confinement of th? alluvial aquifer underlying the Gunnison site." However, on page 14 of the draft RAP, the authors are calling the aquifer unconfined. This inconsistency should be clarified.

O 14 Pane 17; (DRAP) The alluvial aquifer is being defined as unconfined, which is inconsistent with data presented in the draft EA. Also, it is unclear as to the basis for determining that the depth of the aquifer is 130 feet. Data presented in the DEA _ indicated that the aquifer may be 200 feet thick under the site and cited literature sources as saying it could be as much as 400 feet thick, Geology DEA

15. More regional information is needed to adequately evaluate the geology of the site. Supporting regional physiographic, geomorphological, sedimentological, stratigraphic, and structural infornetion is needed. Evaluation of site-s when adequate local information is provided)pecific data in alone a (even Q cannot result proper assessment of the long-term suitability of a site in relation s to the EPA requirements (40 CFR 192). Given the nature of geological processes, past, present and future geologic conditions at any given localized site are inextricably linked to the geologic character of the larger region (geologic province) in which it is located.

Standard professional nethods and procedures require that adequate geologic investigations of a site include complementary infornation to describe:

1. The genmorphic conditions at the site and their relation to the recional geonorphic setting.

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?. The site stratigraphy and its relationship and om tation with the regional stratigraphy.

1 3. The structural geology of the site and the relationship of site i

structure to regional tectenics.

4 The geologic history of the site as it relates to the regional geologic history.

5. The hydrocarbon, metallic and non-metallic mineral resources c'

, the site as they relate to regional or analogous trends.

The regional information required usually can be derived primarily

,O trom a review or the existia9 pertiae"t 9eo'o9'c 'iterature- the information should be documented by references to all relevant published and unpublished material. The UMTRAP document review process will be expedited if the DOE submittals contain sufficient inforr.ation for the re 'iewer to make an independent assessment of the conclusions regardirig the geologic suitability of the site.

16. With regard to the terrace at the level of the site, the location of the terrace scarps and the projected duration of the terrace relative to the 200- to 1,000-year stability requirement for the i pile should be identified.

Geotechnical DEA O 17. Parje 20; Reference is made to a ' foot thick

• clay filter" layer.

V

. This term is anbiguous as to whether the layer is to function as a l liner or as a filter for the capillary break layer. Please clarify the tern and indicate the purpose of the clay.

18. Pages 21 and 37; The construction activities listed for the two alternative sites include placement of " clay filter" and capillary break layers. We are not convinced that it is appropirate to assure that these design espects are necessary without further characterization of the ground-weter regime at the sites. In additier , there is insufficient data to support conclusions related to the availability of site soils for use in liner or cover layers.

Some basic site characterization work at the two alternative sites is needed to enabit a r. ore representative cost conparison.

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19. Page 24; The discussion on cover construction indicatts that long-tem moisture contents of 5 percent (top 1 foot) and 10 percent (bottom 4 feet) were assumed for radon barrier calculations.

However, the test data on the silty-clay borrow material (DSCR) indicates in-situ moisture contents ranging from 4 to 9 percent (5.8 percent average). Justify your use of 10 percent. In addition, Item 4 of E-17 states that.long-term moisture contents are based on calculations u ing site-specific data. The method used for estimating long-term moisture contents should be clarified.

20. Page E-35; The rock durability criterion of less than 10 percent loss after 12 cycles of freeze / thaw appears to be too low. In addition the criterion for the Schmidt Hamer test appears to be in O error- laefereace: Nuatc/ca-2642. Tebie 5 2-) erovide the basis used to determine the rock durability criteria and verify the criteria for the Schmidt Hammer test.

~21. Page E-39; The determination of the need for a waste water treatrent plant could significantly impact the cost comparisons presented in the DEA. The determinaM ct, should be included in future versions of the EA and RAP.

SCR

22. The DSCR does not Mevntely characterize the subsurface materials at the site. Provie *c.e esults of the 22 borings performed by Fcrd, Bacon and Davis (GC :eries) and any other new or historical data to characterize these naterials. This information is necessary to evalcete the liquefaction potential of underlying foundation Q soils.

Radiologica1 _

DEA

26. Page 77; Because of seasonal fluctuations in radon concentrations, the average outdoor background should be an annual average radon concentration. The average outdoor background radon concentration provided in the DEA may not be representative of actual background.

In order to provide a representative overage outdoor background radon ccncentration an arr.ual average should be determined by taking three or four 24-hour sar'ples at the five sampling locations in differer.t seasons of the year.

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m 24 Page 79; Uranium, Pb-210, Th-232 and Th-230 concentrations in the tailings should be provided along with a discussion on why these radionuclides are or are not included for health effect considerations. A comparison of these values with natural background should also be made. The DEA should be modified accordingly in order to provide a complete analysis of the radiological health effects from radioactive particulates.

25. Page 97; Ra226 is a bone seeker and whole body risk estimates should include this fact rather than assigning a whole body risk factor on the basis of a dose to the bronchi only.

26. _Page 101. Paragraph one refers to " airborne radioactive particulate concentrations yet the DEA only addresses Ra-226.

Q' Therefore the analysis as presented in the DEA is incomplete. The effects cf airborne Th-230 and Pb-210 should also be addressed.

This lack of information affects the assumptions in the second pcragraph as well.

27, h:ce H-E;

a. The risk factor f this DEA is 100 X 10'grdeaths excessper fatal lung -cancer, person WLM, iswhich in the used for general population and for the remedial action worker. The Evans et al (1981) reference, which gives the primary justification for using this risk factor, states that workers are a higher risk than the general population for equal exposures to radon daughters. A higher risk factor conparable to those recorrnended by UNSCEAR and used by -

the NRC should-be applied to the remedial action worker,

b. LorTering total organ doses over 50 and 100 years for both workers .d the general population would help to clarify the difference when compared to expected background exposures rather than' cor;>aring only relative risk.

28. Page H ; Second paragraph. The dose conversion factor for 1 WLM in BEIR Ill has been superceded by NCRP #77 (1984) which lists 14 REM /Wu'.

'29. Page H-9; The average wind speed of 2.1 meters per second from the Isbill Associates source should be used rather than the average 2.7 nete s per second from the Fercheau reference. The 1sbill wind data was collected over a 5-year period, whereas the Fercheau data

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DRAFT was collected over a 2-year period. Also, because the Isbill data is a product of NOAA's Environmental Data Service, it is probably a better data source. With the isbill average wiad speed, a 30 percent greater on-pile radon concentration remedial action worker health effect is obtained.

30. Page H15; Equation at top should fist 730 hours0.00845 days <br />0.203 hours <br />0.00121 weeks <br />2.77765e-4 months <br /> /WLit for a member of the public.

DRAP

31. Page 8, Section 2.5 and Page A9; states that, when working levels are between 0.02 WL and 0.03 WL, the government will have the P3 flexibility to decide if measures should be taken to reduce working V levels. This is inconsistent with the EPA standard in 40CFR192.12(b)(1). The standard requires that a reasonable effort be made to reduce working levels to below 0.02 WL. A decision to take no action would constitute the application of supplemental standards. The DRAP should be modified to reflect compliance with the EPA standards.

32. Page 36; It appears that dust control will depend exclusively on spraying The DRAP should recognize the possibility of extreme dust conditions and require more restrictive controls when warranted.

Controls such as reduction or stoppage of work should be considered.

The DRAP should be modidied acc.ordingly.

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