ML20197E015
| ML20197E015 | |
| Person / Time | |
|---|---|
| Issue date: | 04/20/1988 |
| From: | NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | |
| Shared Package | |
| ML20197E002 | List: |
| References | |
| REF-WM-68, TASK-TF, TASK-URFO NUDOCS 9712290177 | |
| Download: ML20197E015 (64) | |
Text
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TECHNICAL EVALUATION REPORT FOR THE PROPOSED R MEDIAL ACTION O
AT THE GREEN RIVER TAILINGS SITE GREEN RIVER, UTAH a,
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9712290177 860420 PDR WASTE WPt-68 PDR
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4 thole OF CONTENT
'Section P_ ale -
1.0 INTR 000CTION...................................................
5 i
1.1 EPA Standards........................................
'1.2 : Site and Proposed Action.................................. 5 Rev i ew P ro ce s s......................................
1.3
..... 9 1.4 TER Organization..........................................
10 1.5-Summary of Open Issues....................................
10 i
2.0 GEOLOGIC STABILITY.............................................
13 2.1 Introduction..............................................
13 1
2.2 L o c a t i o n.................................................. 13 2.3 Geology...................................................
13 2.3.1 Stra tigraphi c Setting.............................. 13
- 2. 3. 2 ; Stru ctu ra l Setti ng................................. 14 2.3.3 Geomorphi c Setti ng................................. 15 (l
2.3.4 Seismicity.........................................
16 4
- 2. 4 Geo l og i c Sta bi l i ty........................................ 17 v-l
- 2. 4.1 ' Bedroc k Su i tabi l i ty................................ 17 2.4.2 Geomorphic Stabi11ty............................... 18-
-2.4.3 Seismotectonic Stabilit
- 2. 5 - Con cl u s i on s...................y........................... 20
- 2 3.0 GEOTECHNICAL STABILITY.........................................
24 3.1 I n t r od u c t i on............................................... 2 4 3.2 Site Characterization.............................l.......
25 1
3.2.1 Site Description........................................ 25
-3.2.2 Site Investigation................................. 25 i
- 3.2.3 S i te S trati g raphy................................. 26 3.2.4 Testing _ Program.................................... 28 3.3 Geotechnical Engineering Evaluation....................... 28.
-3.3.1 Slope Evaluation................................... 28
' - 1hg 3.3.3 Cover Design........................................W
-3.3.2 Liquefaction.........................................d l
3.4 Geotechnical Construction-Criteria.........................aa 3.5 S i t e D e s i g n............................................... 31 3. 6 Co n c l u s i o n................................................. 3 2 4.0 ~ SURFACE WATER HYDROLOGY AND EROSION PROTECTION................. 33 4.1 Hydrologic' Description and Conceptual Design.............. 33 4.2 Flooding Determination....................................
33 7
4.2.1l Probable Maximum Percipitation..................e.. 34 i
4.2.2 Inf11tration Loss.................................. 34 4.2.3 Time of Concentration..............................
34 i
4.2.4'. PMP Rainfall Distribution.......................... 35 4.2.5 Computation of PMF................................. 35 4.2.5.1 On -si te Drainage............................ 35 L
4.2.5.2 ' Green River................................. 35 4.2.5.3 B rown ' s Wa s h................................ 35 1
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4.3 Water Surface Profiles and Channel Velocities............. 36 4.3.1 On-Site Drainage...................................
36 4.3.21 Green River........................................ 36 4.3.3 Brown's Wash....................................... 36 4.4 Erosion Protection........................................ 36 4.4.1 Green River........................................ 36 4.4.2 On-site Drainage................................... 37 i
4.4.3 Top and Sides of Pi1e..............................
37 o
4.4.4 Ro c k D u r a b i l i ty.................................... 38
-4.5 Upstream Dam Failures.....................................
38 4.6 f ic n 1 u s i o n s............................................... 38 5.0 WATE R KLs0VRCES PROTECT ION..'................................... 39 5.1 Introduction..............................................
39 5.2 Site Chara cterization P rogram............................. 39 5.2.1 Geometry of Hydrostratigraphic Units............... 39 4
5.2.2 Hydrolog i c Condi ti ons.............................. 40 5.2.3 Hydraulic Characteristics.......................... 4) 5.2.4 Groundwater Quality Monitoring.....................
42 O_
5.2.5 Geochemical Conditions............................. 43 l-j.
5.3 Conceptual Design Features to Protect Water Resources..... 43 5.3.1 Infiltration Limiting Covers.......................
44 5.3.2 O ther Cover L ayers................................ 44 l
5.3.3 Tailings Amendments................................
45 5.3.4 Hydrogeochemical Liner.............................
46 5.4 Disposal and Control of Residual Radioactive Material..... 46 5.4.1 Groundwater Protection Standards for Disposal...... 46 5.4.1.1 Hazardous Constituents...................... 47 l
5.4.1.2 Concentration Limits........................
47 5.4.1.3 Point of Conp11ance......................... 48 l
5.4.1.4 Assessment of Impacts From Non-Listed l
Constituents............................... 48 L
5.4.2 Water. Resources Protection Performance Assessment.. 48 5.4.3 Closure Performance Assessment.....................
50 l
5.4.4 Groundwater Performance Monitoring Program......... 50 l Q 5.4.5 Corrective Action P1an.............................
51 L
5.5 Cleanup and Control of Existing Contamination............. 51 5.5.1 Groundwater Protection Standards for Restoration... 52 5.5.1.1 Hazardous Constituents......................
52 5.5.1.2 Concentration Limits........................
52 5.5.2 Restoration Demonstration..........................
52 5.5.3 Groundwater Monitoring Program..................... 53 5. 6 Co n c l u s i o n s............................................... 54 6.0 RADON ATTENUATION AND SITE CLEAN-UP............................ 55 6.1 I n t rodu c t i o n.............................................. 5 5 6.2 Radon Attenuation.........................................
55 l
6.2.1 Evaluation of_ Parameters...........................
55 6.2.2 Evaluation of Radon Barrier........................
57 6.3 Site C1eanup..............................................
58 4
j 6.4 Conclusions...............................................59 a
7.0 SUKHARY...............................,,,,,,,,,,,,,,,,,,,,,,,,,,gg
8.0 REFERENCES
/ BIBLIOGRAPHY........................................
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1.0 INTRODUCTION
The; Green River site was designated'as one of 24 abandoned-uranium mill tailings piles to be remediated by the U.S. Department of Energy-(DOE) under the Uran..a Mill Tailings: Radiation' Control ~Act of 1978 (UMTRCA).- UMTRCA requires, in part, that NRC concur with DOE's selection of remedial action.
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such that 'the remedial _ action meets appropriate standards promulgated by the U.S. Environmental Protection Ai,ency (EPA).- This draft Technical Evaluation
[:
1 Report (TER) documents the NRC staff's review of the DOE preliminary final-design and remedial action plan and outlines:the-resulting outstanding issues.
s-1.1 EPA Standards 1;o I
- As required by-UMTRCA, remedial cction at the Green River site must comply with regulations established by the EPA in 40 CFR Part 192, Subparts A-C. -These-3 L
regulations may be sunnarized as follows:
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- 1.
Thel disposal-siteshall'bedesignedtocontrolthetailingsandother I
. residual radioactive material for 1000 years to the ext ~ent~ reasonably l
. achievable and, in any case, for at least 200 years [40 CFR 192.02(a)].
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2.
The disposal site design-shall prevent radon-222 fluxes from residual ~
radiactive materials'to the atmosphere from exceeding 20.pococuries/ square
[
meter /second or from' increasing the annual average concentration of radon-222 in air by more than 0.5.picoeuries/ liter [40 CFE 192.02(b)].
I 3.
The remedial action shall ensure that radium-226 concentrations in i
land that is not part of the disposal site averaged over any area of 100 square meters do not exceed the background level by more than 5 picoeuries/ gram averaged over the first 15 centimeters of soil below the surface and 15 picocuries/ gram averaged over any 15-centimeter thick layer
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of soil more than 15 centimeters below the land surface [40 CFR 192.12(a)].
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!On September 3, 1985, the U.S. Tenth Circuit Court of Appeals remanded the j
groundwater standards (40 CFR Part 192.2(a)(2)-(3)) and stipulated that EPA 4
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-promulgate new groundwater standards. EPA proposed these standards in the form of revisions t.o Subparts A-C of 40 CFR Part 192 in September, 1987. The 4
proposed standards consist of two parts; a first part governing the control of any future groundwater contamination that may occur' from tailings piles after remedial action, and a second part that. applies to the clean _up of
. contamination that occurred before the remedial action of the tailings.
1.2 Site and Proposed Action The Green River uranium mill-site is located in Grand Couety, Utah, approximately one mile' southwest of the city of Green River (see Figure 1.1).
The 48 acre site consists of the tailings pile (8 acres), the mill yard and ore storagearea(23 acres),fourmainbuildings,awatertowerandseveralsmall
' buildings. The designated site contains an estimated 144,200 cubic yards (cy) of uranium mill tailings produced from 1958 to 1961. Windblown and waterborne contamination constitutes an additional 45,700 cy of contaminated material.
Figure 1.2 depicts the general features of the Green River tailings site prior to initiation of remedial action.
The remedial action proposed by DOE consists of the following major activities:
1.
Movement of all contaminated materials-(uranium mill tailings windblown and waterborne contaminants and demolition debris from the mill building addition, office building' addition, and roaster building)toadisposal.embankmentonaterracelocatedaboveBrown's Wash.
2.
Stabilization of contaminated material in the embankment which is constructed primarily below the existing ground surface.
3.
Coverage of the embankment with a one foot thick infiltration / radon barrier of compacted sitly clay and a four and one half foot erosion protection layer consisting of selected fill, bedding material, Type A and Type B riprap to ensure long-term stability, reduce radon emissions and protect groundwater and surface water, r
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V FIGURE 1.2 PRESENT CONDITIONS, GREEN RIVER TAILINGS SITE (From Reference 8) i h
g After completion of remedial action, the disposal site will be fenced and posted with appropriate warning signs to discourage human intrusion.
In addition, the site will be surveyed and monitored periodically by a custodial agency under a NRC license.
1.3 Review Process
,l The NRC staff resiew was performed in accordance with the Standard Review Plan for UMTRCA Title I Mill Tailings Remedial Action Plans (Reference 5) and consisted of comprehensive assessments of DOE's proposed preliminary final design and remedial action plan.
Staff review of preliminary final data and cesigns submitted by DOE indicate that there are still outstanding items as outlined in Section 1.5 and discussed in furthur detail in Chapters 2 through 7 O
of this TER. Aii oPen icems of concern must be addressed before concurrence with the proposed remedial action can be granted by NRC. The NRC will review all appropriate data submitted by DOE in this regard. Upon resolution of the open items, the NRC staff will revise this TER into final form to include evaluations and conclusions with respect to the additional information submitted by D0E.
The remedial action information assessed by the NRC staff was provided primarily in the following documents:
1.
Remedial Action Plan and Final Design for Stabilization of the O
inactive uranium Miii Taiiin9s at Gree, River, uteh, rinai, volumes I,II, and III, February,1988,UMTRA-DOE /AL 05010.GRNO 2.
UraniumMillTailingsRemedialActionPlan(UMTRAP),GreenRiver; Design Calculations, Volumes I,II,III, and Addendum 1, November, 1987.
3.
UraniumMillTailingsRemedialActionPlan(UMTRAP),GreenRiver, Utah, Information for Bidders, Volumes I,II,III, Dectsnber,1987.
4.
UraniumMillTailingsRemedialActionPlan(UMTRAP),GreenRiver; Design Calculations, Addendum 1, February,1988.
10 5.
Supplemental Geotechnical Data in support of the Remedial Action Plan, Letter from J. Arthur, DOE to P. Lohaus NRC, March 11, 1988.
6.
Environmental Assessment of Remedial Action, Green River Uranium Mill Tailings Site, Green River, Utah, December, 1987.
l 7.
cesponses to NRC comments by DOE dated September, 1987 and December, I
1987.
1.4 3ROrganization The purpose of this draft Technical Evaluation Report is to document the NRC staff review of DOE's preliminary final remedial action plan for the Green 7
River Site and discuss the open items resulting from this review. The following sections of this report have been organized by technical discipline relative to the EPA standards in 40 CFR Part 192, Subparts A-C.
Sectior 2, 3, and 4 provide the technical basis for-the NRC staff's conclusions and identification of remaining cpen items with respect to the long-term stability h
standardin192.02(a). Section 5 Water Resources Protection, sumarizes the NRC staff's conclusions and remaining open items regarding the adequacy of DOE's compliance demonstration with respect to EPA's groundwater protection requirements in 40 CFR Part 192. Section 6 provides the basis for the staff conclusions and identification of open items with respect to the radon control standardsin192.02(b).
1.5 Sumary of Open Items The NRC staff review of the proposed DOE preliminary final design and remedial action plan has identified open items, which are discussed in more detail in the following chapters. A brief sumary of these open items is provided in Table 1.1
11-TABLE 1.1 SUtEARY OF OPEN ITEMS Explanation and Staff Finding TER Regulatory Subsection Citation 1.
DOE has not submitted all the test data 3.3.3 192.02(a) 1 for the amended soil used in the in-filtration / radon barrier and the demon-stration of achieving the hydraulic conductivity assumed in the design; finding on the infiltration / radon barrier portion of the pile cover is deferred 2.
DOE has not established the geochemical 5.2.5 192.20(a)(2) conditions beneath the current or pro-posed disposal areas; finding deferred; 3.
DOE has not determined whether a tailings 5.3.3 192.02(a)(4) amendment is necessary; finding defert.3d; 264.111(b) 4.
DOE has not determined whether a geo-5.3.4 192.01(a)(4) l chemical liner is necessary; finding 264.111(b)
I deferred; L
5.
DOE has not determined the source of 5.4.1.1 192.02(a)(3 l
the organics in the leachate; not in 264 93 compliance 3 t 6.
DOE has not specified cr proposed con-5.4.1.2 192.02(a)(3)(ii) centration limit for all constituents 264.94 found in groundwater and the tailings under Subpart A; not in compliance; l
12
............a...........................m..........................
Explanation and Staff Finding TER Regulatory Subsection Citation
................................................cs...........................
7.
DOE has not specified a POC; not-in 5.4.1.3 192.02(a)(3) compliance; 264.95 8.
DOE has not estimated potent'ial down-5.4.2 192.20(b)(4)
. gradient concentrations for all listed constituents; not in compliance 9.
DOE has not proposed a groundwater 5.4.4 192.02(a)(4)(b) performance monitoring program; not in compliance;
- 10. DOE has not proposed a corrective 5.4.5 192.02(a)(4)(c) action plan; finding deferred;
- 11. DOE has not specified or proposed con-5.5.1.2 192.02(a)(3)(11) centration limit for all constituents 192.02(a)(3)(v) found in groundwater and the tailings 262.94 under Subpart B; not in compliance;
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- 12. DOE has not included a restoration plan 5.5.2 192.12(b)(4) to cleanup relict ground-water coraam; 192.20(c)(4) ination; not in compliance pending legal finding;
- 13. DOE has not proposed a ground-water 5.5.3 192.20(B)(4) monitoring program to verify plume movements; not in compliance pending a DOE decision to extend the remedial period.
a 13 k.0 -Geologic-Stability 2.! -Introduction This-section of the TER documents-the staff's review of geological.information for the-proposed remedial action'at_the Green River uranium mill tailings:
disposal site.
Background geologic-information for this TER is derived from DOE'sRemedialActionPlan(Reference 8), DOC's-FinelDesignforReview
- (Reference 9,10, and 11), supplementary information provided during the review
_ pro ass,; staff's site visits, and independent sources 'as cited.
2.2 Location O
The uranium mill tailings site is located along Browns Wash, one quarter mile l
- east of-the Green River, and one mile southeast of the town of Green River.
Utah. Green River is located along Interstate 70 in east-central Utah, 210 miles southeast of-Salt Lake City and 60 miles west of the Colorado state lir,a.
The' site is found on the USGS Green River.15-minute and Salina'2-degree-
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1 topographic maps.
2.3 Ceolony
' EPA standards-listed in 40 CFR 192 do not include generic or site-specific requirements for the characterization of geological conditions at'UMTRA Project-
, sites.: Rather, 40 CFR 192.02(a); requires control'shall be designed to be
~ ffective for up to 1,000 years, to the extent achievable, and in any case for-e
~
' at least 200 years. NRC staff have interpreted this standard to mean that certain-geological: conditions must-be met in order to have reasonable assurance that the long-term performance objective will-be achieved. Guidance with regard to these conditions is specified in NRC's UMTRCA Standard Review Plan-
-(SRP)2(Reference 5).
2.3.1 Stratigraphic Setting DOE characterized regional and site stratigraphy by reference to published work and original field investigations as recomended in SRP section 2.2.2.1
14 (Reference 5). The Green River UMTRAP site consists of'two principal areas of focus:(1)theabandonedtailingspile,and(2)theinactivemillandproposed tailings-disposal area. The abandoned mill tailings are located on the Browns k.tsh flood plain atop 12 to 20 feet of sandy and gravelly-alluvium. The mill buildings and proposed disposal area occur on a terrace or pedimerst formed at the confluence of Browns Wash and the Green' River. Deposits beneath the terrace consist of sandy alluvium with undifferentiated amounts of mud and gravel. The alluvium's thicknessivaries from zero -in gully exposures, to
-approximately 20 feet. Both areas of interest are und elain by Cretaceous-
< strata in excess of 200 feet thickness, Bedrock strata beneath the area include-(1) Mancos Shale, ',2) Dakota Sandstone, and (3) the Cedar Mountain
- Formation. The Mancos crops out in the scarp formed by Browns Wash, and thins O
and pinches out-in the subsurface southward across the mill site. The Dakota Sandstone occurs below the Mancos, cropping out along the tailings pile at the base of the scarp. - Grey to yellow Sandstone and conglomerate of the Dakota also crop out along Browns Wash's flood plain, along Brown Wash's banks wesi, of the site, and in gullies across the mill yard and proposed disposal area. The Dakota's northward dip causes it to subcrop south of the mill yard where it is
~
buried by Quaternary deposits. The exact extent and continuity of the Dakota has'not been established by remedial action investigations. However, it
-appears to be discontinuous beneath the terrace due to erosion and original stratigraphic-thinning. ' South of the terrace and near Interstate 70, it rises again to the surface in eroded exposures and roadcuts. Underlying the DSkota, h the Cedar Mountain Formation forms the region's basal Cretaceous unit.
The Cedar Mountain consists mostly of varigated bentonitic mudstone and shale with abundant interbeds of sandstone, siliceous limestone nodules, and has a distinctivebasalconglomerate(Reference 7). The Cedar Mountain is considered equivalent to the Burre, lyon Fm. of northwestern Colorado and southeastern TUtah(Reference 6). Thc Cretaceous strata are underlain next by Jurassic and older strata which are not of significance to the remedial action.
2.3.2 Structural Setting DOE characterized the region's structural setting by reference to published regional geologic maps, aerial reconnaissance, and field observation and mapping of features critical to assuring the long-term stability of the
15 remedial action. These studies were recommended in SRP section 2.2.2.3 (Reference 5). The Green River site is situated on the axis of a broad anticline having a northward plunge of approximately 31 degrees (Reference 4 and6). Strata underlying the site dip variabiy between 2 and 10 degrees northward. A series of broad arcuste normal faults are found in the area. The Little Grand Wash fault cuts the anticline 2.5 miles south of the site. Faults associated with the Salt Wash Graben lie 7 miles scuth of the site. Two normal faults associated with extension and collapse alor.g the anticline's axial plane are found between the Little Grand Wash Fault and Salt Wash Graben between 3 and 6 miles southeast of the site. Each of these faults trends directly toward the site but er. Mar to end northward at Little Grand Wash fault.
9 2.3.3 Geomorphic Setting DOE characterized the region's physiography by reference to published W
i literature and topographic maps, as recomended in SRP section 2.2.2.2-(Reference 5). Site geomorphic conditions were charat.terized by aerial photographic interpretation and field observatiorts. Green River is located in the Canyonlands Section of the north central Colorado Plateau' physiographic province (Reference 33). The region's striking physiogrcphy 'results-from erosion in strata of varying resistance previously deformed by broad structural uplifts and crustal compression. The book Cliffs, a few miles to tht: north, form the northern boundary of the Canyonland's Section and the southern edge of the Uinta basin. The Colorado and Green rivers occur along broad strike valleys in the Mancos Shale.
Browns Wash drains 85 square miles and has approximately 3,000 feet relief.
The tailings pile, containing 200,000 cubic yards of contaminated material, occupieseightacresoftheBrown'sWashfloodplain(DOE,1988). Tailings are up to 10 feet thick and occur less than 10 feet above the unconfined alluvial aquifer as measured in October 1987. The pile has minimal erosion protection consisting of a thin soil cover and a low berm along a portion of the wash.
Floods in Browns Wash eroded an estimated 14,000 tons of tailings during 1959 and 1968.
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The mill yard and propose! disposa1' area occur on a fluvial terrace 50-60 feet r
'above the flood plain, iThe terrace is eroded on Mancos
- Dakota.:and Cedar
. Mountain bedrock ard is covered by up to 20' feet of alluvium. The_ proposed
- disposal area is dissected by several gullies exposing bedrock. The terrace surface has also been extensively disturbed by construction, borrow, and fill
' activities.-Upstreamdrainageisapproximately110 acres (0.45ka')with
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runoff occurring as sheetflow to a number of gullies, all of which drain north
'or northwestward to Browns Wash.- hterstate 70 presently _ serves as the approximate drainage divide'above.the site.
- 2.3.4.' Seismicity DOE characterized regional-satsaicity by obtaining earthquake data bases Q'
providedbytheNationalOceanographicandAtmospheric' Administration (NOAA),
lby applying accep_ted. techniques to cetermine earthquake magnitudes, and by employingmethodssuggestedinSRPsection2.2.2.3(Reference 5)for calculating' peak horizontal ground accelerations generated by a design-basis
, event..
~
Green River is located in a relatively stable interior area of the Colorado'
. Plateau. Historical:and instrumental seismic events have been concentrated talong the margins of.the' Plateau, where it meets the Basin and' Range province, including the intermountain seismic belt 100 miles wett of' Green River L(Reference 8). Most-of the major structural and tectonic features of the-site Q' Lregion date to Laramide time and are considered inactive'in.the present fseismotectonic. regime.
A majority of events whose epicenters occur in the site region are known to be generated by controlled blasting,- rockbursts and coal bumps (accidental
- mine-gas explosions) in the Book Cliffs coal mining area (Reference 8). These
-events have generated Richter magnitudes up to 4.2.
. DOE's analysis of potential earthquake ragnitude for the interior Colorado Plateau. included determincion of both the Maximum Earthquake (ME) and Floating EarthquakeL(FE)fortheregion. A paucity of seismic records for the Colorado
' Plateau suggests the ME value could be between 6.2 and 6.8 (Reference 8). The
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average,6.5,isthevalueadoptedbypreviousauthors(Reference 32)and appears very conservative considering that everis of magnitude 5.0 or greater
.-have been_ scarce _on the plateau and its border zones.
An'FE magnitude, resulting from an earthquake enassociated with known tectonic
- structures, is generally less than an ME magnitude for a given seismotectonic i
_prov nce. DOE suggests a range of 5.5 to 5.8 may represent reasonable values of FE magnitude, based on=the historical record for the Colorado Plateau.
Because the~ range of ME magnitudes are higher, DOE adopted 6.2 as a conservative design event. Resulting calculations, therefore, assume an FE l
event of magnitude 6.2-occurring 15 km from the site.- This event would result inhorizontal-groundaccelerationof0.21g(Reference 8)baseduponCampbell
.(Reference 1).
(See Seismotectonic Stability Section).
2.41LGeologic Stability
-Geologic conditions and processes at the site are characterized to detemine
-theirabilitytomeet40CFRIg2.02(a).
In general, site lithologic, _
' stratigraphic,'and structural conditions are considered for their suitability as a disposal foundation and their potential interaction with tailings leachate and ground water..Geomorphic processes are considered for-their potential impact upon long-term tailings stabilization and isolation.
Potential geolo,1c
- O. hazards,includingseismicshaking, liquefaction,on-sitefaultrupture, ground co us,se.and voicanism are identified for the purpose of assuring the
?long-term stability of the= disposal cell and success of the remedial action
' design.'-
'2.4.1 Bedrock Suitability LEven though surficial deposits and bedrock : nits beneath the tailings pile and proposed disposal site appear suitable for meeting EPA st.endards, adequate characterization of the site presented a major concern early in NRC's review
. process. Precise characterization of site stratigraphy was hampered because Cretaceous strata, particularly the Dakota Sandstone, exhibit considerable
- thinning and pinch outs in the area. All the units are also considerably 1
18 variableintheirlithologyandgrainsize,andeachexhibitsgradational contacts or interbedding with adjacent units. Bedrock exposures are poor and
. data collection relied on well-bore methods,, Finally, design. changes and inconsistencies in portrayal of site geology resulted in uncertainty which geologic units would form the disposal foundation.
C&reful reviews of the Remedial Action Plan, reference to geologic literature.-
. requests for additional information, additional drilling by DOE, and staff site visits resulted-in a better understanding of the site stratigraphy.and structure.- Precise details regarding the exact extent of the Dakota Sandstone, its contact with the underlying Cedar Mountain, and the relationships of these strata to the proposed disposal design remain unclear at this time.
It is the O staff s opinion, however,.that DOE's level of characterization effort was t.
L suited to the information required. Small-scale complexities of the site's underlying bedrock cannot be better characterized by well-bore methods. The staff has reasonable assurance the drilling program to date adequately characterizes underlying lithologies. More detailed stratigraphic relations will be made apparent by site excavation.-
2.4.2 Geomorphic Stability DOE concluded that attempts to stabilize the tailings in place could be-l
_ accomplished only by drastic measures and with uncertain assurance of achieving O iong-term stabiiity. ermsed r-val of Green River's taiiings fr-Br-ns Wash flood plain to the' site's fluvial terrace will result in elimination of the site's major geomorphic hazard: erosion of tailings during a catastrophic
= flood event in the Browns Wash drainage basin. DOE analysts show that placing the tailings at an-elevation of 4,130 ft places them above the PMF' elevation of
.4,092ft(Reference 8). See section 4.4 of this TER for reviews of flooding potential and elevations.
DOE considers-that all other geomorphic hazards at the site occur with frequency or extent such that remedial actions can be designed to minimize
.their effects and meet long-term stability standards. However, even the alternate disposal-site is subject to long-term geomorphic changes as site gullies continue to erode, and as the banks of Browns Wash recede. DOE
4
-39 proposes to protect the site:from continued gully growth, headcutting, and down-cuttingby(1)contouringtheproposedpileandenv'ironstominimize
= runoff concentrations into existing gullies and winimize formation of new qullies,-(2)creatingariprapapronatthebaseofthepiletohaltfuture gully encroachment, and.(3) keying the base of erosion-resistant covers-and aprons.into the Dakota and Cedar Mountain formations so a resistant foundation
-is~ maintained.
No critical structures are planned to be founded upon surficial depositsorMancosShale(Reference 8).
To achieve the above site-stability criteria, DOE adopted the following design features:
(1) DOE d eigned a tailings embankment totalling 6 acres with top
()
slopes of 5% and side slopes of 20%, each covered by erosion-resistant riprap.
Runoff is to be directed in four separate directions leaving the' embankment and crossing the recontoured environs under sheet-flow conditions (DOE,1987; calculation 10-555-01-00). The embankment's environs will have its gullies filled in and will be recontoured to slopes approximately 25 to 8%
and extending 100 to 400 feet outward from the entiankment. These design-elements should eliminate gully formation atop the tailings and minimize potential continued gully enlargement immediately.
surrounding the disposal.
h
.(2); DOE's design provides riprap toe protection consisting of an apron of l
'18-inch diameter rocks for a width of 20-feet around the embankment.
This feature is designed to protect the tailings embankment from encroachment of relatively shallow gullies which develop during the
' design life period.
l(3) Riprap forming an apron will descend to bedrock on the three sides of the esbankment, northeast, northwest and southwest, which will be subjected to potential gully headcutting and deepening during the design life. The riprap wall will preserve the embankment cover in the event that all surficial deposits and fill are eroded during the site's performance period. Stability will be attained because the t
.. n
.. - - - - +,
'20 riprap, descending and keyed to bedrock, cannot be undercut by gullies deepening and headcutting through the surficial materials.
Primary and secondary geomorphic hazards identified by DOE (1988) and the intended remedial actions are sumarized in Table 2.1.
The staff has reasonable assurance that geomorphic conditions of the site have been adequately characterized and that the remedial actions listed above will mitigate the effects of long-term geomorphic changes. For a discussion of rock-size requirements, rock gradations, quantitles, durability and other aspects of erosion protection design details, see Section 4.5 of this TER.
2.4.3 Seismotectonic Stability O Studies by DOE to analyze seismic hazards included search for a design-basis fault, selection of a design earthquake, calculation of estimated peak horizontal ground acceleration, recognition of potential for on-site fault rupture, and recognition of potential for earthquake-induced geologic failures at the site. The study to delineate faults with recent movement in the site region consisted of low-sun angle aerial reconnaissance, interpretation of aerial photographs in black-and-white, color, false-color infrared, and LANDSAT imagery, and field reconnaissance of mapped faults within 65 km of the site.
In addition, the DOE obtained and analyzed NOAA's list of instrumentally and historically recorded earthquake data for the Colorado Plateau and an area of 200 km radius around Green River. Epicenter locations within a 65 km radius of O
the site were plotted oa >a fau1t aae sei uicity base man (aefereace si 9 ate 1
obeledD.4.1).
Supplementary in'armation (Reference 3) provided at NRC's request included (a) NOAA earthquake epicenter data files, and (b) notes and discussion of observations made during aerial reconnaissance, field work, and photogeologic interpretation.
DOE's site characterization effort did not result in discovery of unknown faults. Therefore, examination of regional faults for design purposes relied
f,_
21 x
iupon faults already mapped and discussed in-the geologic literature. Staff site' visits. included inspection of three fault groups nearest the site, groups 1,2,and5(Reference 34) All three faults _ exhibit topographic scarps where I
differing lithologies occur in each fault block.- Such scarps can be attributed
- to differing resistance to erosion. Where similar lithologies are juxtaposed in-each block of a fault no topographic offset is observed. At the observation (points, the faults do.not display signs of recent movement or truncation of Ouaternary deposits. Based on thsse observations, DOE concludes the potential designfaultsarenotcapable(Reference 8).
Given a lack of capable faults within 65 km of the site, DOE based its evaluation.of site seismic hazards on a general appraisal of Colorado Plateau
-seismotectonics and the available earthquake records. Because an earthquake of magnitude 6.2canbeexpecteutooccurinthe'ColoradoPlateau(seeSection c
2.3.4),_andbecauseacapabledesign-basisfaultisnotidentifiedinthe site's region, DOE adopted a Floating Earthquake of magnitude 6.2 occurring-15 km from the site as the design _ earthquake. NRC staft consider this a justified value because:
(a) Tablel'ofAlgermissenandothers-(1982)indicatesthatthemaximum magnitudeearthquakefortheColoradoPlateau(Algermissen'ssource zone no.16) is 6~.1. ' Using Algermissen's relt.tionship for magnitude as 6 function of intensity, M = 1.3 + 0.6(I), a magnitude 6.1 would be the equivalent of Modified Mercalli Intensity of I,= 8.
This value.is near or slightly-above the maximum intensity observed in the Cclorado-Plateau in its brief historical record.- It is not overly conservative to assume a somewhat higher magnitude value since the period of performance is significantly longer than the historical period; (b)
In its assessment of seismic hazards at potential sites for high-level radioactive waste repositories in the Paradox Basin, DOE (1984) identified structures capable of generating earthquakes with magnitudes as high_as 6.5.
The presence of such structures within the plateau, and evidence that fault-scarp expression can be reduced by only a few decades or centuries of erosion, indicates that such an
2'l earthquake may have occurred despite a lack of any existing surficial deformations. Despite such structures, the staff consider that this magnitude is unjustifiably conservative for a design event at the Green River location.
(c) DOF's calculations of the Maximum Credible Earthquake for other UMTRA Project sites in the Colorado Plateau are given as 6.2.
t NRC staff concur that peak horizcatal acceleration at Green River resulting from a 6.2 magnitude earthquake at a distance of 15 km, using Campbell (Reference 1)84thpercentilevalues,is0.219 Staff find data inputs and these results to be reasonable and conservative for DOE's calculation of the seismic coefficient for the site. See section 3.3 of this TER for calculations O
and aPeiications of the seismic coenicient and the geotechni:ai stasi,ity of the remedial action design.
2.5 Conclusions Based upon review of the Final Remedial Action Plan, Final Design for Review, and DOE's response to NRC connents on drafts of these documents, Staff has reasonable assurance that regional and site geologic conditions have been--
characterized adequately to meet 40 CFR Part 192. Conditions hindering long-term stability of the site have been identified and either avoided by alternative site selection or mitigated by features in the remecial action O
design.
23 TABLE 2.1 PRIMARY AND SECONDARY GEOMORPHIC HAZARDS ASSOCIATED WITH THE GREEN RIVER UMTRA PROJECT SITE, AND THEIR PROPOSED REMEDIAL ACTION Primary Hazardf-Proposed Remedial Action Catastrophic. flooding in Removal of tailings above flood plain Browns Wash PMF runoff from embankment, Erosion-resistant riprap cover erosion of tailings Gully headcutting into Ripraptoeprotection(spron) embankment i
. p.,
Gully deepening and under-Buried riprap wall Jescending and o cutting of e:aankment keyed to competent <tdrock Secondary Hazards Proposed Remedial Action Rain splash erosion, sheet-
. Riprap erosion protec. tion-wash, and eolian erosion of tailings Chemical weathering of erosion-Useofnoncalcareou[lithologies resistant materials for riprap Shrink-swell-of bentoc.itic Elimination of Mancos Shale as a
'lithologies foundation for the embankment Frost heave and solufluctio6 Burial of radon attenuation layers Y of embankment covers below frost zone and inhibition of (d
surface-water infiltration
'24 i
i i
3.0 GE0TECHNICTL STABILITY 3'.1 - Introduetion--
~This section presents the NRC staff review of-the:geotechnical engineering.
aspects'of the. remedial' actions attthe Green River site and consists primarily-of evaluations of the site characterization.and stability aspe ts of the stabilized tailings embankment, and cover design. The staff review of-the related geological aspects such as geologic, geomorphic, and seismic
. characterization of the site is presented in Section'2 of this. report. The
. staff review of the groundwater conditions at this site is presented in Section n
5.of this report.
-.V.
g
- At the Green River Uranium Mill site.(presently an inactive site) the ore.
-concentrate was: shipped to a processing plant in Rifle, Colorado and thereby the tailings left at this site were predominantly sandy tailings with no slime.
The 48-acre area designated for remedial action consists of the tailings pile,
. former ore storage area, v.dTba' ndoned strectures and facilitles associated with-the uranium mil'..during~.its operation.
In' addition, tailings dispersed by-wind and water erosion have contaminated approximately 30 acres of adjoining
~
area. The prerosed remedialsacticn of stabilization-on-site consists of
. placing all the contaminated material at the site (approximately 200,000 cyds)
.in to a single pile, which is calle'd the disposal cell. The location of=this 2;
~dispossi cell is approximately 500 ft south and about 50 ft.. higher in elevation than the existing. tailings pile-location..The bottom portion of.the disposal cell is designed to be excavated partly below the existing ground surface and rests on bedrock. The. top of:the disposal cell is'about 25 ft.
above the adjoining ground surface.. The gently contoured embankment (side-
. slopes of 5 horizontal to I vertical)Lof the above existing ground portion of thsicell.will then be covered with an infiltration / radon-barrier consisting of compacted earth cover, gravel bedding and a rock-layer (riprap) to ensure the following:L(1) long-term stability of embankment and reduced radon emissions;
-(2)= reduced infiltration; (3) protection of surface water quality; (4) protection against animal intrusion; (5) minimized plant root intrusion; (6) i f
-~.
~
25 prevention of inadvertent human intrusion; and ',') prevention of material dispersion.
(Reference 8).
3.2 Site Characterization 3.2.1 Site Description The Green River inactive uranium mill site is in Grand County, Utah, approximately one mile southeast bf the city of Green River and 0.5 mile south of U.S Highways 6 & 50. The project site is 0.5 mile east of the Green River.
Brown's Wash, an intermittent tributory to the Green River, drains the immediate area around the site and flows along the north side of the existing tailings pile.
Figures 3.1and3.2offinalRAP(Reference 8)showthe O
iocation and present conditions of the Green River project site.
A 48-acre l
area around the inactive mill and existing tailings pile is designated for i
remedial actions under UMTRCA Title 1.
The existing tailings pile is in the f.
flood plain of Brown's Wash and is subject to erosion by flood flows in Brown's Wash and runoff from the site vicinity. The existing teilings pile is covered with a thin layer of earthen material averaging six-inches thick, and this cover has been eroded in places. Also, riprap and ditches ar'e placed around the pile to control water runoff into Brown's Wash, which parallels the site on the norts. The proposed locetion for the stabilized tailings embankment (disposalcell)isalevelareaabout500ft,southoftheexistingtailings pile and b about 50 to 60 ft, higher in elevation than the present location.
O The disposai site is eissected by a shaiiow ephemerai stream.
The disposai site surface is covered by sagebrush and wild forbet.
3.2.2 Site Investigations Subsu ' ace explorations at the site were performed by the following i'
-tigators:
(1) Bendix Field Engineering Corporation to determine the extent of contamination. The investigations resulted in data from 105 bore-holes, 184 in situ Ra-226 measurements, and 139 soil samples.
Addendum D1 to Appendix 0 in Reference 1 presents detailed information on this investigation. The results of this investigation were useu in establishing the volume of contaminated mate ial to be removed to comply with the EPA standards. This contaminated material is to be placed in the disposal cell.
(2) JacobsEngineeringGroup,Inc.(1986-1987) and Morrisor.-Knudson Engineers,Inc.(1986-1987). The scope of the geotechnical investigations included borings from which soil samples and rock cores were obtained, test pits from which bulk samples were obtained, and installation of monitoring wells. These investigations were performed to determine geotechnical characteristics of the site and to obtain samples of the soil and rock material to perform laboratory
[
O tests to determine their properties, information to Bidders, volumes 1, II, and III of Reference 9, present detailed information on site conditions and logs of these field investigations.
3.2.3 Site Stratigraphy The elevation of the Green River project site varies from about 4050 to 4200 feet above mean sea level.
Borings were obtained using standard geotechnical crilling and sampling techniques. These methoos included drilling with hollow stem augers, and sampling at near continuous intervals with Standard O
penetration 1ests (Sp1) and, on occasioo, a 2.s. inch inside. diameter ring lined split-barrell sampier. The SPT tests were conducted according to ASTM D 1586 procedures.
Figure 3.7ofRAP(Reference 8)showslocationsoftheboringsand test pits. Section 2 of this report presents an an evaluation of the geologic, geomorphic, and seismic characteristics of the site.
The overburden materials at the site consist of c alluvium deposit underlaid by a_ thin layer _of gravel which in turn overlies the bedrock. The alluvium deposit consists of silty to clayey sand, with dense sand and gravel occurring at the bottom of this deposit. The alluvium dcposit is in a loose to dense condition with the Standard Penetration Test resistance values ranging from 3 to 43, with an average of 18 blows /ft.. The sedimentary bedrock units at the 1
=- <
__j
site consist of a shale mem6er of the Mancos shale, the Dakota sandstone, and the Cedar Mountain Formation. The upper portion of the bedrock is weathered.
and fractured. Refer to-Section 2 of_this report for detailed evaluation of the bedrock conditions at the site.
At the exitting tailings pile area, the site stratigraphy consists of sand tailings overlying the alluvium deposit (silty sand-clayey sand) which in
-turn overlies the bedrock. Tailings and contaminated alluvium will be excavated for disposal in the disposal cell.
At the proposed disposal cell site, the bedrock units are the Dakota sandstone underlaid by the Cedar Mountain Formation consisting of shale and mudstone.
. The overburden soils at the proposed cell location consist of from 5 to 16 ft.
-of loose to dense alluvium (silty sand - clayey sand). Large lenses of clay are contained within this layer. Dense to very dense sand and gravel occur at the bottom of this deposit. Since the disposal cell is proposed to be founded on the bedrock, the overburden material will be excavated. This material will be used as Select Fill Type-A material for the disposal cell cover at this site.
.The groundwater table at the proposed disposal cell location is estimated to be
'at-elevation 4085 ft, approximately 55 ft. below the ground surface and 30 ft, below the bottom of the disposal cell, Refer to Section 5 for detailed evaluation of the groundwater conditions at this site.
Soil for the' radon barrier cover and gravel for.the bedding layer are proposed to be taken from Borrow Site 1.
Figures 3.15 through 3.24 of the final rap (Reference 8)showthelocationandstratigraphyoftheproposedborrowarea.
A' total.of 24 test pits were dug to investigate the availability and
-suitability of the' soils for the intended use. The stratigraphy at the borrow sita consists of alluvial deposit with a surficial layer of silty-clayey sand,
-underlaid by low-plasticity clay. The clay layer is underlaid by a alluvial sand and gravel stratum. The test pits were terminated in the sand-gravel stratum. The low-plasticity clay is proposed to be used for the infil-tration/ radon barrier cover and the alluvial sand-gravel material will be
. processed to obtain the gravel needed for the bedding layer.
The staff has reviewed-the-details.of the borings and test pits as well as the scope of the overall geotechnical exploration program. The staff concludes
-that the geotechnical investigations conducted at the Green River site have adequately established the stratigraphy and soil conditions to support assessment of the geotechnical stability of_the stabilized tailings and contaminated material in the disposal cell. Further, the geotechnical explorations are in general conformance with applicable provisions of Chapter 2 of the NRC Standard Review Plan (SRP) for UMTRCA Title ! Mill Tailings Remedial ActionPlans(Reference 5).
3.2.4 Testing Program O
The staff. has reviewed the geotechnical engineering testing program for the steen River site. The testing program inciuded physicai properties tests, compaction tests, triaxial shear strength tests, permeability tests, and dispersion tests on samples of tailings and borrow materials intended for use in the disposal cell. The staff finds that the testing program employed to define the material properties was appropriate for the support of necessary-engineering analyses described in the following sections. F.drther,'thescope of the testing program and the utilization of the resulting data to define the material properties are in general agreement with_ applicable provisions of the SRP. However,.the 00E has notLsubmitted all the test data for the infiltra-tion / radon barrier soil,-which is the' clay from the borrow site amended with 3-percent by weight of Sodium Bentonite. The evaluation of the radon barrier
~
> - O materini can not be compieted untii the stafr reviews aii the test data on the amended soil.
-3,3 Geotechnical Engineering Evaluation 3.3.1. Stability' Evaluation The evaluation _of the geotechnical-stability of-the slopes of_the proposed stabilized tailings: pile.is presented in this section. The staff has reviewed the exploration data, test results, critical slope' characteristics and methods of ' analyses _ pertinent to the slope stability aspects of the remedial action
dh 29 plan (References 10&11). The analyzed cross section with the 5 horizontal to 1 vertical slope has been compared with the exploratory records and design details. The staft finds that the characteristics of the slope have been properly represented and that the most critical slope section has been considered for the stability analysis.
Soil parameters for the various materials in the stabilized embankment slope have been adequately established by appropriate testing of representative material. Values of soil parameters have been assigned to other layers (riprap, gravel bedding, bedrock etc.) on the basis of data obtained from geotechnical explorations at the site and data published in the literature.
The staff finds that the determination of these parameters for slope stability O follow conventional geotechnical engineering practice, and are also in compliance with the applicable provisions of Chapter 2 of the SRP. The staff also finds that an appropriate method of stability analysis (Bishop method) has been employed and has addressed the likely adverse conditions to which the slope might be subjected.
Factors of safety against failure,of the slope for seismic loading conditions have been evaluated for both the short term
~
(end-of-construction)stateandlong-termstate.
Factors of safety for the static loading conditions were not evaluated because thc seismic loading condition is more critical and results in lower factors of safety than those for the static loading condition. The seismic stability of the slope was investigated by the pseudo-static method of analysis using horizontal seismic O
coefficients of 0.1 for the end-of-construction case and 0.14 for the long-term case. The value of the seismic coefficients were calculated as per the guidance in the SRP and are acceptable to the staff. The staff finds the pseudo-static method of analysis to be acceptable considering the degree of conservatism in the soil parameter values and the flatness of the slopes (5H:1V). The minimum factors of safety against failure of the slope were 2.3 and 1.67 for the end-of-construction and long-term conditions, compared to a required minimum of 1.1 for both conditions. The details of the radon tarrier cover design have not been reviewed and concurred in by the NRC. But, the strength parameters for the cover materials used in the stability analysis are conservative, and any change in the thickness of the radon barrier cover will not have significant impact on the stability of the slopes of the disposal cell. Therefore, the staff concludes that the proposed stabilized slopes would j
30 be stable under short-term and long-term conditions and thus, for this design aspect, would comply with the EPA standard (40 CFR part 192.02(a)) for long-term stability.
3.3.2 Liquefaction Base on review of results of the geotechnical investigations, including boring logs, test data, and soil profiles, the NRC staff concludes that the DOE has adequately assessed the potential'for liquefaction at the Green River site.
Because the compacted dry density of the stabilized pile will be equal to a minimum of 90 percent of maximum dry density as determined by the ASTM D-698 test, and the tailings pile embankment design provides for the tailings materials to be in an unsaturated condition, the tailings pile itself is not considered to be susceptible to liquefaction.
The disposal cell is founded on bedrock, which is not susceptible to liquefaction. The groundwater table at the site is estimated to be approximately 30 f t. below the bottom or foundation of the disposal cell.
~
The staff concludes that the stabilized tailings pile is not susceptible to liquefaction.
3.3.3 Cover Design The proposed design for the tailings embankment cover consists of the following, in descending order from the top: (1) one foot thick, Type-A riprap.
(2) 6 in. thick gravel bedding, (3) three feet thick Select Type-A fill, (4) 6 in, thick gravel bedding and (5) one foot thick radon / infiltration barrier material. Theradonbarrier,aspresentedintheRAP(References 8&10),
assumes a hydraulic conductivity of 10E-7 cm/sec. for the radon barrier
-material. This degree of impermeability has to be demonstrated in a field test.
In addition, the staff is concerned with the practicality of successfully constructing the thin, one foot thick, infiltration / radon barrier layer to fulfill its design function for the long-term life of the UMTRCA project. The staff has transmitted their concerns to DOE on this item as review comments, and they provide a detailed explanation for.the staff's position. At this time the staff has not concurred with the DOE's design for
31 theinfiltration/radonbarrierportionofthecover. The tailings pile cover design is an open-ites, yet to be resolved.
3.4 Geotechnical Construction Criteria The radon barrier material is proposed to be mixed with 3 percent by weight of.
Sodium Bentonite. Before finalizing an evaluation of the redon/ infiltration barrier design, the NRC staff intpnds to review the DOE's procedure for mixing the soil and placing the mixture to achieve the desired hydraulic conductivity.
The NRC staff also intends to request the DOE to demonstrate, by a full scale field test, the practicality of placing a one foot thick infiltration / radon barrier clay layer as per the design proposed in the RAP, and to perform field
- O
"ductivity value can be achieved for the full depth of the compacted "d"" " '
d'**""""'d'""'""'
con layer. -Details of the proposal-for geotechnical inspection and testing during construction will be evaluated at the tir.3 the Remedial Action Inspection Plan (RAIP)isreviewed.
The RAIP will be submitted by the DOE at a later date for NRC's concurrence.
3.5 Site Design The-area at the toe of the disposal cell slope is filled with riprap. This O
ion reaches the toe of the slope.
'"'""'""'"""'"'"*d'd'"'"""'
-eros Type B riprap with a D50 size of 1.5 ft.
is used in this area.
See Drawing No.GRN-PS-10-0517 Typical Riprap Toe ProtectionDetail(Reference 8). The Select Fill Type B soil, proposed to be filled above the riprap is excavated from the disposal cell foundation area, and the specifications for this material have no special gradation requirements. The staff is concerned that the fine particles of this overlying fill will'gradu11y migrate with time into the large voids in the riprap. A combination of gravity and infiltrating water could initiate this particle movement, and will _become noticeble in the long-tenn when this migration results.in surficial subsidence. This could require maintenance.in the long-term. The DOE should address this concern in the design.- This is not
32 expected to e)7ect the stability of the dispoal cell slope, but will require maintenance.
3.6 Conclusion Based on review of the design for the Green River site as presented in the remedialactionplan(Reference 8),theNRCstaffconcludesthatthedesign complies with the long-tem stability aspects of the EPA standards ( 40 CFR Part192.02(a)). For reasons provided in Sections 3.3.4 and 3.4 above, the NkC does not concur with the present design for protection against radon emission from the stabilized tailings pile.
O O
\\
,e 33 4.0 SURFACE WATER HYDROLOGY AND EROSION PROTECTION 4.1 Hydrologic Description and Site Conceptual Design The Green River site is located near Green River, Utah and is situated on a plateau approximately 50 feet above the Green River channel. The Green River has a drainage area of approximately 40,590 square miles and is located approximately 2000 feet east of the site.
Brown's Wash is located insnediately north of the site and has a drainage area of approximately 85 square miles. Overland flows north of the site are i
diverted from Brown's Wash by a railroad embankment; surface flows south of the g
site are diverted by a highway embankment. Significant flooding has occurred U
in Brown's Wash, and tailings have been eroded in the past.
In order to comply with EPA standards, which require stability of the tailings for a 1,000-year (or minimum 200-year) period, 00E proposes to stabilize the tailings and contaniinated materials in an engineered embankment to protect them from flooding and erosion. The existing tailings will be soved from their present location in the floodplain of Brown's Wash to a locat' ion on a plateau about 40 feet above the maximum level of flooding in Brown's Wash. The design basis events for protection of the embankment slopes included the Probable Maximum Precipitation (PMP) and the Probable Maximum Flood (PMF) events, both of which are considered to have very low probabilities of occurrence during the O'
1,000-year stabilization period.
The tailings will be consolidated into a single pile, which will be protected by soil and rock covers. The covers will have maximum slopes of 5% on the top and 20% on the sides. The square-shaped pile will be surrounded by aprons which will safely convey flood runoff away from the tailings and prevent gully erosion into the stabilized pile.
4.2 Flooding Determinations In order to determine site impacts from flooding, DOE analyzed peak flows and velocities and evaluated the need for erosion protection features. DOE 1
I
34 estimated the PMF peaks resulting from an occurrence of the PHP over the various small drainage areas. These design events meet the criteria outlined intheStandardReviewPlan_(Reference 5)andare,therefore, acceptable, j
The details of DOE's flood computations were analyzed by the NRC staff as
-follows:-
4.2.1 ProbableMaximumPrecip,itation(PMP)
A PMP rainfall depth of approximately 8.5 inches in one hour was used by DOE to r
compute the PMF for the small drainage areas at the site. This rainfall 4
estimatewasdevelopedbyDOEusingHydrometeorologicalReport(HMR)49 (Reference 25). Based on a check of the rainfall computations, the staff concludes that the PHP was acceptably derived for this site.
4.2.2 Infiltration Losses In computing the peak flow rate for the design of the rock eposion protection, DOE used_the rational formula, Q 3 C i A.
In this formula,'the runoff coefficient (C)wasassumedbyDOEtobeunity;thatis.DOEassumedthatno infiltration losses would occur.
Based on a revie; of the computa tions, the staff concludes that this is a very conservative assumption when using the rational formula and is therefore acceptable.
- O 4.2.3 Time of Concentration The time of concentration is the amount of time required for runoft to reach the outlet of a drainage. basin from the most remote point in that basin. The peak runoff for a given drainage basin is inversely proportional to the time of concentration for that basin.
If the time of concentration is conservatively computed to be small, the peak oischarge will therefore be conservatively L
large.
Verioustimesofconcentration(tc)fortheapronsandembankmentswereesti-mated by DOE using the Kirpich Method, as discussed in Reference 14. The staff concludes that the procedures used for computing tc are representative of the
)
w-
.,n-e
,,-,..e
,,,..n.,
.n.,-,
4
35 small steep drainage areas present at the site. For very small drainage areas with very short times of concentration, DOE utilized tc's as low as 2.5 minutes _which is considered to be conservative.
4.2.4 PMP Rainfall Distributions DOEderivedrainfalldistributionsandintensitiesfromHMR49(Reference 25),
which is acceptable.
In the determination of peak flood flows in ditches and aprons, rainfall intensities for durations as short as 2.5 minutes were used.
-Based on a review of this aspect of the flooding determination, the staff concludes that the computed peak rainfall intensity of about 56 inches / hour (correspondingtoa-tcof2.5 minutes)isconservative,andtherefore,
]
acceptable.
(
4.2.5 -
Computation of PMF 4.2.5.1 Onsite Drainage DOEutilizedtherationalformula(Reference 14)tocompute he peak sheet flows down the slopes and PMF flows on the aprons, given the input parameters discussed above. Based on our review of the calculations presented, the staff concludes that this method of computation has been conservatively applied.
l 4.2.5.2 Green River The PMF for the Green River was not estimated by D0E. However, the Green River is located well below the lowest site elevation, and by inspection, it can be seen that flooding on the Green River will not affect the site.
4.2.5.3 Brown's Wash iThe PMF for Brown's Wash was estimated by DOE using Reference 12, which is a standard computational method for estimating peak flood discharges. Our review of the computations _ indicates that DOE has used conservative and/or reasonable methods for estimating input parameters such as lag times, infiltration losses, and rainfall distributions. Based on that review and on a comparison with
36 other peak flood discharge data such as that found in Reference 11, we conclude that the estimated peak PMF discharge of 100,000 cfs is acceptable.
4.3 Water Surface Profiles and Channel Velocities 4.3.1 Onsite Drainage Water surface profiles, velocities, and shear stresses used in designing onsite features were computed using Manning's formula. The NRC staff checked the e
water level and velocity computat' ions in accordsnce with standard procedures, such as those given in Reference 17, to determine their accuracy. Based on this check, the staff concludes that the estimates are appropriate.
4.3.2 Green River Water surface profiles for the Green River were not developed by DOE. However, the elevation of Green River below the site is such that flooding will not pose a threat to the encapsulated cell.
S 4
4.3.3 Brown's Wash Water surface profiles in Brown's Wash were developed by DOE using Reference 5, a standard computational procedure used nationwide. The NRC staff checked the results of several computations to determine the adequacy of the stream j -
profiles.- Based on these checks, we agree with DOE that the computed maximum PMF water level in Brown's Wash will be approximately 40 feet below the stabilized pile. We therefore conclude that Brown's Wash poses no flooding threat to the stabilized site.
A 4.4 Erosion Protection 4.4.1.
-Green River The elevation and location of the site are such that flooding on the Green River poses no threat to the integrity of the tailings pile.
1 J
i-4.4.2 Onsite Drainage Aprons are proposed along the perimeter of the pile at the toe of the stalilized es6ankment slopes; these. perimeter aprons are desinged to prevent gully l erosion into the stabilized pile. DOE proposes that the erosion protection for_the aprons will be designed for an occurrence of a local PMP.
This design basis meets the criteria outlined in-the SRP and is, therefore, acceptable.
Additionally,'the staft concludes that the computational models used by DOE are conservative and that the proposed riprep design meets-the c.*iteria outlined in References 18 and 19. At those locations where the aprons are keyed irito natural ground, the riprap protection will be designed so that (1) erosive
.Q: velocities at the end of the protected areas do not affect the tailings, and (2) headeutting from existing natural gullies will not advance into the-stabilized pile.-
4.4.3 Top and Sides of Piles
~
The rock covers, which will be used to protect the soil cover from wind and water erosion, are designed for an_ occurrence of the local PHP.
For the top of the. pile (maximum 51 slopes)andforthesidesofthepile(205 slopes). DOE proposes a 12-inch layer of rock with a minimum D of about 3+3) inches. The.
50 rock layers will 6>e placed on bedding layers. The Safety Factors Method
- O (Refer ac 23) **$ #$'d to d't raia r#9uired rock 51285 for the top s10P 5 of
.the pile. TheStephensonMethod(Reference 26)wasusedforthesteeperside slopes.
.The rock to be placed in the apron. areas was designed using the Safety Factors Method.. The riprap will have an minimum everage size of approximately 18 inches _and will be placed on a_ bedding layer. Based on our review of the calculations of the rock size and thickness, we conclude that.the proposed riprap for the apron areas is acceptable. Based on its review, the staff finds these designs acceptable, since they have been_conservati_vely developed _in accordance with documented, referenced methods.
~
l n
i 4.4.4 Rock Durability For the rock to be placed in the ditches and on the pile, gradation and rock durability criteria were presented. DOE has also identified a quarry at Fresent Junction where rock of acceptable quality can be found. Based on a-comparison of the data with the criteria provided in Reference 27, we conclude that the rock durability criteria proposed and the rock quarry at fremont Junction are adequate to assure that rock of acceptable quality has been provided.
4.5 Upstream Dam failures, There are no impoundments on the Green River whose failure could potentially affect the site.
4.6 Conclusions Based on its review of the information submitted by DOE, the staff concludes that the site design will meet EPA requirements as steted in 40 CFR 192 with regard to flood design measures and erosion protection. An adequate hydraulic design has been provided to. reasonably assure stability of the contaminated material at Green River for a period of-up to 1,000 years.
O
______~________
39 5.0 WATER RESOURCES PROTECTION 5.1 Introduction TheNRChasreviewedtheRemedialActionPlan(Reference 8)andtheFinal DesignforReview(Reference 9)fortheGreenRiver,UtahUMTRAProjectsite.
These documents were reviewed against the EPA standards listed in 40 CFR 192, 4
related to ground-water protectio.n. The standards, proposed on September 24, 1987, are considered by NRC staff to be binding upon DOE until the final standards are promulgated. The standards are structured to address control of futurecontanination(SubpartA),cleanupofrelictcontaminatedgroundwater (SubpartB)andimplementationofthestandards(SubpartC).
- O 5.2 Site Characterization Program Pursuantto40CFR192.20(a)(2),DOEisrequiredto" consider [ ground-water protection]onacase-specificbasis,drawingonhydrologicalandgeochemical surveys and all other relevant data." This subsection of the TER discusses DOE site characterization activities, considered to be equivalent to the site survey required by 40 CFR Part 192.20(a)(2), for defining the geometry of the hydrostratigraphic units (Subsection 5.2.1), the hydrologic conditions (Subsection 5.2.2),thehydrauliccharacteristics(Subsection 5.2.3),the ground-waterquality(Subsection 5.2.4),andthegeochemicalconditions
,]
(Subsection 5.2.5).
5.2.1 Geometry of Hydrostratigraphic Units DOE characterized the geometry of the hydrostratigraphic units at the Green River site in three drilling phases. A total of 36 wells and we11 points were installed to characterize the site. The site stratigraphy is reviewed, evaluated and discusseo in Section 2.3.1 of this TER. The site hydrostratigraphy, as interpreted by DOE and Fresented in the RAP, is composert of an eiluvial unit (including the Brown's Wash alluvium, an upper pediment gravel, and small portions of the Mancos shale and the Dakota Sandstone), the UpperCedarMountainFormation(Kcmutinterbedsofshaleandlimestone),the
40 4
(
Lower Cedar Mountain formation (Keels saridstones, siltstones and l
conglomerates),andtheBuckhornConglomerateUnitoftheCedarMountain Formation (Kcab). More information on the stratigraphy of the Green River site is presented Section 2.3.1 of this TER.
Based on review of information and interpretations presented the RAP and the draft Environmental Assessment (DEA), the staff finds that DOE has adequately characterized the geometry of the hydrostratigraphic units at the Green River site and that DOE's interpretationsarereasonableinaccordancewith40CFRPart192.20(a)(2).
5.2.2 Hydrologic Conditions DOE characterized the hydrologic conditicEs (hydraulic gradients, flow directions) at the Green River site by collecting water level information from O the installed wells for approximately 1.5 years. The wells were sampled in Jurie 1986, September 1986, March 1987, and October 1987. Based on water level sampling, the hydraulic gradients and directions of the hydrostratigraphic units are as follows:
Unit Hydraulic Gradient Direction Alluvial 0.0029 - 0.0125 W-NW Kcmu 0.0063 - 0.0083 NW Kcm1 0.0083 - 0.025 N-NW(highlyvariable)
Buckhorn Cong.
0.040 - 0.044 N
O Vertical hydraulic gradients between each unit are generally upward for the units beneath the tailings and leachate plumes, except for a downward gradient trom the alluvium to the Kcau at the current location of the tailings. Based on a review of water level measurements made by DOE, and independent staff calculations,- the staff finds that the hydrologic conditions of the hydrostratigraphic units chars.cterized by DOE at the Green River site, including seasonal variations, are reasonable and are in accordance with 40 CFR 192.20(a)(2).
41 5.2.3 Hydraulic Characteristics DOE characterized the hydraulic characteristics conditions (hydraulic conductivity, porosity) of the hydrostratigraphic units by perfoming slug and pump tests on 21 monitor wells installed at the Green River site. The porosity values were taken from established hydrogeologic texts and are reasonable for the material characterized at the site. The raw data collected during the tests were analyzed using five methods cosmonly accepted in the hydrologic community. Based on the tests and analyses, the hydraulic conductivities and velocities, using information from subsection 5.2.2, are as follows:
Hydraulic Unit Conductivity (ft/ day)
Velocity (ft/ day)
Alluvial 3.30 - 54.6 1.14 Kcmu-0.0068 - 17.0 0.01 - 0.71 Kcal-0.0055 - 21.6 0.02 - 2.7 Kcmb 0.076 - 7.6 0.072 - 0.17 DOE explained the wide range of hydraulic conductivities for the Kcau and Kcm) as being. caused by extensive vertical and horizontal fracturing. These fractures were observed in cores collected during well drilling. DOE has not characterized the aperture, direction or length of the fractures, despite the predominance of fracture flow expected in the aquifer systems. NRC staff
. concludes that DOE need not' address the fracture characteristics for the staff to concur on the disposal plan.. However, the presence of these fractures may increase the difficulty in implementire a post-closure monitoring program if the' fracture characteristics are not well understood. DOE will have to consider this uncertainty when proposing the performance monitoring program to be implemented following remedial action as required under 40 CFR 192.02(a)(4)(b). Based upon review of.the pump test data'and the calculations used to derive hydraulic conductivity, the staff finds that DOE has characterized the hydraulic conditions of the hydrostratigraphic units at _ Green Riveradequatelytodemonstratecompliancewith40CFR192.20(a)(2).
i 42 6.2.4 Ground-Water Quality Monitoring Program DOE has implemented a sampling program to characterize ground-water quality at the Green River site. Several EPA standards must be addressed under this broad category of water quality characterization. The applicable requirements, standards and staff findings are:
(1) DOE sust establish an upgradient monitoring program to characterize background levels of listed constituents. These constituents are itsted and referenced in 40 CFR 264.93, with the addition of molybdenum, radium, uraniumandnitrate(40CFR192.02(a)(3)(1)). DOE established a monitoring program to define upgradient concentrations of the listed constituent, that are reasonably expected to be present in the tailings O
or ground water. DOE has sampled and anaiyzed upgradient grouod water for the four hydrostratigraphic units present at the Green River site. Based on NRC staff review of the monitoring program established for the site, the staff finds it is sufficient to characterize background levels of listedconstituentsandcomplieswith40CFR192.02(a)(3)(iv).
(2) FortheconstituentswhicharelistedinSubsection5.2.4(1),DOEmust establish a monitoring program adequate to define the extent of ground-water contamination. The monitoring program consists of eight wells for the alluvial aquifer and five wells for the Kcmu aquifer. After monitoring ground-water quality at the current location of the tailings, U
DOE concluded that contamination of ground water occurred only in the alluvial and the Kca.u units; ground water in the Kcal has no significant increase of uranium or nitrate concentrations above background levels, and the upward hydraulic gradient inhibits downward movement of contaminants.
The staft finds that the monitoring program established to define the ext e of ground-water contamination by listed constituents from the tailingscomplieswith40CFR192.12(c)(1).
(3) DOE must implement a hydrologic monitoring program sufficient to establish background ground water quality through one or more upgradient wells.
Water samples were taken and analyzed at least four times for the alluvium, one time for the Kcmu, four times for the Kcml, and and three
l 43
]
times for.the Kes6.
Because DOE has adequately characterited the dissolved constituent concentrations of background ' ground water with at l
1 east one upgradient well tor each unit, the staff finds that the i
monitoring program implemented at the Green River site cceplies with 40 CFR192.20(a)(2).
i i
+
5.2.5 Geochemical Conditions Pursuantto40CFR192.20(a)(2),.00Eistequiredtoperformageochemical survey of the site and base ground-water protection activities on the results of this survey. The important goal of this geochemical survey is to define the conditions that influence the mobility of radionuclides and other listed t
constituents. DOE considers the most important condition to be the
[
Q oxidation-reduction potential (Eh), or redox conditions, because.many of the listed constituents found at the site are redox sensitive, and becme DOE based their assessment of compliance or noncompliance on the assumed redox T
conditions.
DOE has not yet measured or established by analysis the Eh conditions for the ground water of either the current or proposed final disposal area for the tailings.
In DOE's response to NRC staff commente on the
~
Final Design for Review, dated March 2, 1988, DOE stattd that g,round-water
^
samples will be taken and analyzed for redox couples to establish the Eh conditions.
Currently, DOE asserts. hat the Eh conditions are reducing. thus promoting attentuation of uranium.
If the Eh conditions are found to be oxidizing, then DOE must provide more complete analysis of ground-water impacts Q
and propose appropriate actions,-if necessary, to meet the standards. Until-00E can demonstrate that the geochemical conditions are defined. NRC-staff considers this to be an_open item and thus cannot issue a finding on compliance with40CFRPart192.20(a)(2).
1 5.3 Conceptual Design Features To Protect Water Re curces Pursuant to 40 CFR Part 192, Subparts A and C, specifically, 40 CFR Parts 192.02(a)(4),192.20(a)(3)(iii),and 264'111(a and b), DOE must specify the design featuras necessary to protect ground water resources. The features must
- be designed to manage the migration of liquids through'the stabilized material, minimize the need for further maintenance, and control, minimize or eliminate i
l'
'n.w--,.v--y,. - -,
y
,,3
-+y y
y 7,,.w, 3,,y,---,4-y-w,-,
e n.,
,-w,w-,-,,ym.nm.,-,y
,e rr -w--w w
wu--w e we es v o e--
v ww rr= w e w ec e i= w tr m,-
. ~ - -..
n
--..-.._.s-
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44 the releases of hazardous constituents to ground water, These design features, if determined to be necessary, incibde the infiltration limiting cover
)
-(Subsection 5.3.1, other cover layers designed to protect ground water (subsection 5.3.2),tailingsamendments(Subsection 5.3.3),andthe hydrogeochemical liner (Subsection 5.3.4).
5.3.1 Infiltration Limiting Cover DOE prLosed a low-hydraulic conductivity infiltration limiting cover for the Green River site, also called the radon barrier. The radon barrier is designed to be one-foot thick, amended with 31 sodium bentonite, by weight (RAP, Page B-1). DOE performed laboratory hydraulic conductivity tests of the amended radon barrier material. The laboratory test results indicate that the material has a hydrauisc conductivity value of less than 1.0 E-07 cm/s, which is the accepted criterion for raden barrier conductivity. Field measurements of the amended radon barrier material are not proposed. Without verification of the field hydraulic conductivity values with in-site field tests, the staff does not have confidence that field hydraulic conductivity values will be comparable to the laboratory values after placement.
However, DOE did' describe the design and construction of the radon barrier in the RAP and has complied with 40 CFR i
Part192.20(a)(3)(111).
With respect to compliance with 40 CFR Part 264.111(b),DOEhasnot demonstrated that a one foot thick radon barrier can be constructed such that the hydraulic conductivity is minimized for the 200
',000 year time-frame.
7 i
DOE needs to demnstrate that the cover, no matter how thick, can be constructed using commonly accepted engineering practices to comply with 40 CFR Part264.111(b). Field testing of a test plot is the only method that will verify the design hydraulic conductivity value. For more information on this open issue, the reader is referred to Section 6.2.2 Evaluation of Radon Barrier of this TER.
5.3.2 Other Cover Layers In order to protect the radon barrier from damaging freeze-thaw action, and to comply with 40 CFR 264.111(c). DOE has proposed to cover the radon barrier with
45 i
three fest of select fill which will be excavated from the site.
l The staff finds that this additional cover will inhibit infiltration by (1) l allowing-downward percolating precipitation to be absorbed by the material, and l
(2) by setting uF aLwick effect with the underlying bedding layer further j
reducing the effects of capillary tension on infiltration rate. Though the f
l select fill material will probably become saturated during the 200 - 1000 year U
[
L ime-frame for the life of the facility, the layer will be an factor inhibiting t
infiltration. The staff finds that D0E's description of the additional cover 1
layers.which are designed to prot'ect ground water complies with 40 CFR Parts l
192.20(a)(3)(iii)and 264.111(aandb),butrefersthereadertoSubsection3.0 i
'Geotechnical Stability for more information on the analysis'of the freeze-thaw h
action on the cover integrity.
O
.3.3 Tailings Amendments 5
j L
i n
. DOE-proposes not to amend the tailings with any material that could further L
protect ground-water resources. DOE stated (Reference 30: December 17, 1987 F
responsetoNRCcopmentiGW/1onthePreliminaryDesign(60%))thatan i
j.
amendment "probably will not. be needed" to lower contaminant levels in the L
Cedar Mountain ground water, because of the likelihood tiat solid mineral assemblages in the Kcau will react with leachate and lower contaminant concentrations. To further their argument. DOE also' indicated a potential
}
L problem with pile stability if large volumes of the amendments were leached
. from the base of the embankment. This issue is addressed in Subsection 3.0 i-
- - Geotechnical Stability of the TER.
Because geochemical information is yet to be collected and submitted for review, and because'the DOE assertions of compliance rely on geochemical 4rguments, the staff finds that DOE has not demonstrated that natural attenuation will decrease contaminant concentrations to acceptable levels at the'pointofcompliance(seesubsection5.2.5). The need to amend the tailings cannot be' fully resolved until DOE determines the geochemical conditions of the Kcmu. Therefore the staff cannot issue a finding on compliance with 40 CFR Parts 192.02(a)(4)and264.111(b).
4 f
~
46 DOE will have to further address this issue if they propose ACLs, because of a i
requirement that the water quality standard be as low as' reasonably achievable (ALARA;40CFRPart192.02(a)(3)(v)).
5.3.4 Hydrogeochemical Liner DOE has also suggested that a hydrogeochemical liner is not needed beneath,the
^
tailings because the dissolved constituents will be attenuated onto the solid mineral assemblages in the Kcmu., Because DOE has not shown, based on field data, that attenuation will lower constituent concentrations to acceptable levels, the staff cannot issue a finding on whether a hydrogeochemical liner is necessary to meet the standards or whether the proposed action complies with 40 CFRParts192.02(a)(4)and264.111(b).
O 5.4 Disposal And Control Of Residual Radioactive Material DOE must demonstrate compliance with the EPA standards listed in 40 CFR Parts 192, Subparts A and C for disposal and control of residual radioactive material. This section of the TER describes the staff findings with respect to DOE compliance with applicable portions of Subparts A and C,~ and discusses the Ground-waterProtectionStandardforDisposal(Subsection 5.4.1),theWater ResourcesProtectionPerformanceAssessment(Subsection 5.4.2),theClosure PerformanceAssesseunt(Subsection 5.4.3),theGround-WaterPerformance MonitoringProgram(Subsection 5.4.4),andtheCorrectiveActionPlan O
(5"' " 5
- 5)-
5.4.1 Ground-Water Protection Standard for Disposal For any site, 40 CFR Part 192.02 requires the results of three basic analyses for proposing the ground-water protection standard. These case-specific analyses include the determination of hazardous constituents, proposal of concentration limits for each hazardous constituent found to exist in the tailingsorleachate,andthespecificationofthepointofcompliance(POC).
47 5.4.1.1 Hazardous Constituents Pursuantto40CFRParts192.02(a)(3)(i)and264.93,DOEisrequiredtoselect the hazardous constituents based on the characterization of the presence of listed constituents which are found and referenced in 40 CFR Part 264.93 including radium, uranium, molybdenum, nitrate and gross-alpha activity.
In the alluvial ground water DOE characterized the constituents found above background to be gross-alpha activity, molybdenum, nitrate, asmonium, selenium anduranium(Reference 8. Paged-422). 00E also indicated the possible presence of organic contamination in the form of methylene chloride, and two additional semi-volatile organic contaminants. DOE has not discussed whether these organics are reasonably expected to be in the waste (40 CFR Part 264.93(a)), or the impacts of their presence on remedial action. 'In the Kcau ground water DOE characterized the-constituents found above background to be gross-alpha, molybdenum, nitrate, assor.ium, selenium and uranium. DOE also characterized listed constituents found in tailings pore water sampled from-lysimeters which include cadmium, chromium, nitrate, selenium, uranium and -
ammonium. After reviewing the results of water quality analyses presented by DOE, and with the exception of the organics issue, NRC staff finds that DOE's salection of the hazardous constituents found in the leachate and residual radioactivematerialcomplieswith40CFRParts192.02(a)(3)(1)and264.93.
DOE should' indicate whether the three organics suspected of being in the leachate resulted from laboratory error or whether the organic constituents-should bo listed as constituents suspected of being present in the waste.
5.4.1.2 Concentration Limits Pursuant'to40CFRParts192.02(a)(3)(11andv)and264.94,DOEisrequiredto specify:or propose concentration limits for all hazardous constituents listed in40CFRParts192.02(a)(3)(i)and264.93,andidentifiedinSubsection 5.4.1.1, which are not to be exceeded past the P00. The proposed limits may be eitherbackground-concentrations,MaximumConcentrationLimits(HCLstaslisted in40CFRParts192.02(a)(3)_and263.94(a),orAlternateConcentrationLimits (ACLs).L DOE has specified MCLs for. cadmium (0.01 mg/1), chromium (0.05 mg/1)
" and~ selenium (0.05 mg/1), but did not specify a concentration limit for -
nitrate, uranium, gross-alpha activity, molybdenum, or asunonium. Proposing l
48 limits for nitrate, uranium, gross-alpha activity and mo.lybdenum is required by the standards. A limit should also be discussed for amonium which was detectedinhighlevels,butisnotincludedin40CFR192.02(a)(3)(1)or 264.94(a). DOE must specify concentrations for these constituents which cannot beexceededpastthePOCinordertocomplywith40CFRParts192.02(a)(3)(ii andv)and264.94 5.4.1.3 Point of Compliance Pursuantto40CFRParts192.02(a)(3)and264.95,DOEisrequiredtoproposea POC at the Green River disposal site. The POC is a vertical surface that extends downward into the uppemost aquifer along the hydraulically cowngredient limit of the disposal area. DOE should state or propose a POC for U
the Green River disposal site. DOE has not complied with the requirerents of 40CFRParts192.02(a)(3)and264.95 5.4.1.4 Assessment of Impacts from Hon-Listed Constituents DOE indicated a aluminum, iron, magnesium and sulfate are present in the pore water at higher levels than background. Consumption of these constituents
-at the level found in the tailings could harm consumers of ground water or the environment when the constituents drain to surface water bodies, as may be the case with alluvial ground water draining to Brown's Wash. Because NEFA of 1969 requires that environmental impacts be assessed, DOE should assess the impact O
of reieases of these non-,isted constituents on the pusiic heaith an,i safety and the environment. The staft finds that DOE should discuss what actions should be taken, if any, to limit environmental impacts from these non-listed constituents.
5.4.2 Water Resources Protection Performance Assessment To demonstrate compliance with EPA standards in 40 CFR Part 192, DOE needs to perform an integrated analysis of all pertinent aspects o) the proposed remedial actions which predicts potential impacts to ground water caused by disposal ef the tailings. -This analysis, a Water Resources Protection Perfomance Assessment, is discussed in Section 2.2 of the NRC staff draft
1 49 technical position entitled "Information Needs to Demons,trate Compliance with
' EPA's Pr posed Groundwater Protection Standards in 40 CFR Parts 192, Subparts l
A-C.
DOE performed an analysis which predicts downgradient concentrations of nitrate
- usingamethodology-thatconsidered(1)theinfiltrationrateintothecell, (2)themassfluxofnitratemigrationfromthebaseofthecell,(3)the mixing of the mass flux of nitrate with underlying ground water in the Cedar Mountain Formation, and (4) the prediction of a steady-state plume. NRC staff considers this approach and methodology to be appropriate, and finds that the parametersusedbyDOEintheanalysisareconservative(e.g., saturated hydraulic conductivity of 1.0 E-07 cm/s, minimum gradient of unity, i
concentrations of contaminants in the tailings pore water). DOE did not
- O coasider in their approach whether the oxidation of ausnonium to nitrate will l
constitute a significant additional source of nitrate. This' consideration
[
should be added to the approach in order to fully evaluate downgradient
-concentrations of nitrate. Also, DOE did not perform analyses for uranium.
1
[
gross-alpha activity, molybdenum, or ammonium even though they were selected as l
. listed constituents. Therefore, DOE should conduct a performance assessment-analysis, predict steady-state downgradient concentrations for these additional listed constituents, in order to fully demonstrate compliance with 40 CFR Part j
192.20(b)(a).
i.
Finally some confusion exists regarding the conditions assumed for the impacts O assessme,nt. The RAP (Page D-434) indicated that the impact assessment for nitrate was based on a flux rate of 1.0 E-08 cm/s, whereas DOE's transmittal dated March 11, 1988 included analyses with fluxes of 1.0 E-07 cm/s and 1.0 l.
E-08 cm/s. _The staff is unsure whether the transmittal ~ calculations supersede
[
the RAP calculations or whether any conclusions are based on the higher, more
-conservative flux rate. The analytical approach presented in the documents sent to NRC' staff is acceptable. However, the analyses which used 1.0 E-08 cm/s as the saturated hydraulic conductivity is not acceptable to the staff.
because of the strong possibility that the -laboratory values listed in the RAP will not-be representative of hydraulic conductivities that are expected in the field. DOE should continue.to use the upper benchmark hydraulic conductivity value in their assessments of ground-water impacts. The staff considers the u_
60 ground water impacts question an open issue until DOE clarifies which steady-state conditions will be used for final impacts analysis.
5.4.3 Closure Performance Assessment Pursuant to 40 CFR Parts 264.111(aandb),DOEisrequiredtodemonstratethat the closure disposal design minimizes the need for active maintenance, and that the disposal unit controls, minim 12es, or eliminates releases of hazardous constituents to groundwater.
By demonstrating that closure of the disposal unit is adequate to meet long-term stability requirements in 40 CFR Part 192.02(a) DOE has complied with 40 CFR Part 264.111(a).
To address 40 CFR Part 264.111(b), DOE has perfonned an analysis of the cover (i.e., a performance assessaent) with a 1-D computer simulation using the SOILMOIST code. SOILHOIST, has not been validated using any field data, but appears, based on expert judgement by the NRC staff, to have provided sonservative results on infiltration rates when the saturated hydraulic conductivity of 1.0 E-07 cm/s was used as imput. These results indicate an infiltration rate slightly higher than the saturated hydraul-ic conductivity and a 30-year time-frame for the system to reach steady-state. The staff finds that DOE adequately analyzed the cover and has complied with 40 CFR Parts 192.02(a)(4)and264.111(b).
5.4.4 Ground-Water Performance Monitoring Program p) u Pursuant to 40 CFR Part 192.02(a)(4)(b) DOE is required to implement a monitoring plan to be carried out during the post-disposal period. DOE stated intheRAP(Page92)thattheneedforlong-term, post-remedial-action monitoring of shallow ground-water zones will be decided at a later date. NRC staff considers the EPA standards clear in this case. The plan must be contained in the RAP, and be adequate to demonstrate that initial performance of the disposal is in accordance with the design requirements and comply with the groundwater protection and closure performance standards. As mentioned in Subsection 5.2.4 Ground-Water Quality Monitoring Program of this TER, the proposed monitoring network should account for the fracture network found _
beneath the site and be capable of detecting contamination leaving from the
51 cell before migrating past the POC, At this time, DOE can provide a conceptual monitoring program for the post-disposal period, that uses to the extent possible, monitoring wells c'errently constructed hydraulically downgradient from the proposed cell. The statement made by DOE that a decision to monitor is pending should be revised. NRC staff finds that DOE has not complied with 40CFRPart192.02(a)(4)(b),becauseDOEhasnotsubmittedaground-water monitoring plan for review.
5.4.5 Corrective Action Plan Pursuantto40CFR192.02(a)(4)(c),DOEisrequiredtoimplementacorrcctive action program to bring the disposal site into compliance if the ground-water standards are found or projected to be exceeded. DOE did not propose ACL's for bq nitrate, uranium or gross-alpha activity, thus the staff assumes that the background concentrations will be used to determine compliance. Using these assumed standards, and DOE's analysis, the Green River site will be out of compliance for nitrate and possibly uranium and gross alpha activity. A corrective action plan would have to be implemented, and thus DOE should submit a plan for review. Proposing specific actions to cleanup ground water at this time may not possible, however, DOE should consider reasonable failure scenarios of the disposal unit and demonstrate that corrective actions could be implemented no later thaa 18 months after a finding of exceedance of the ground-water standards. NRC staff finds that DOE has not complied with 40 CFR 192.02(a)(4)(c),becauseDOEhasnotsubmittedacorrectiveactionplanfor review.
5.5 Cleanup And Control Of Existing Contamination DOE needs to demonstrate compliance with the EPA standards listed in 40 CFR Part 192, Subparts B and C for cleanup and control of existing contamination.
This section of the TER describes the staff findings with respect to DOE compliance with applicable portions of Subparts A and B, and discusses the Ground-WaterProtectionStandardforRestoration(Subsection 5.5.1),
RestorationDemonstration(Subsection 5.5.2),andtheGround-WaterMonitoring Program (Subsection 5.5.3).
~
52 5.5.1 Ground-Water Protection Standard for Restoration The NRC staft interprets 40 CFR 192.12 as requiring two basic items for adequately proposing the ground-water protection standard for restoration.
These items, n ich are case-specific, include the determination of hazardous constituents, and the proposal of concentration limits for each hazardous constituents found to exist in the tailings or ground water.
5.5.1.1 Hazardous Constituents Pursuantto40CFRParts192.02(a)(3)(1)andk64.93,DOEisrequiredto implement a moni oring program adequate to define the extent of ground-water Q
contamination by listed constituents and to monitor compliance with this subpart. AtdiscussedinSubsections5.2.A(2)and5.4.1.1,DOEhas implemer.ced a ground-water monitoring program and selected the constituents found or reasonably expected to be found in the ground water and tailings. The stafffindsthatDOEhascompliedwith40CFRParts192.02(a)(3)(i)and264.93.
~
5.5.1.2 Concentration Limits Pursuantto40CFRParts192.12(a)(3)(iiandv),192.12(c)(2)and264.94, DOE is required to specify or propose concentration limits for all listed hazardous constituentslistedin40CFRParts192.02(a)(3)(i)and264.93,andidentified Q
in Subsection 5.4.1.1 of this TER. As discussed in Subsection 5.4.1.2 of this TER, DOE has specified McLs for cadmium (0.01 mg/1), chromium (0.05 mg/1) and selenium (0.05mg/1),butdidnotspecifyaconcentrationlimitfornitrate, uranium, gross-alpha activity, molybdenum, or discuss a limit for armonium,
.alaminum, iron, magnesium or sulfate. DOE must specify concentrations for these constituents which are not to be exceeded following groundwater cleanup, in order to fully comply with the EPA standards listed above for this subsection.
5.5.2 Restoration Demonstration Pursuantto40CFR192.20(b)(4),DOEisrequiredtoinclude,intheRAP,aplan to cleanup ground-water contamination at the site caused by releases of
53-hazardous' constituents-to the ground-water system. -DOE has proposed to defer any decision on ground-water rastoration until EPA promulgates final
_ ground-water protection ~ standards. AspertheletterfromP.Lohaus(NRC)to J. Arthur (DOE).. dated Fubruary 9,1988,= NRC indicated that DOE may postpone -
restoration of relict contaminated ground water if DOE demonstrates that lisposal can proceed independently of restoration. DOE has not provided a demonstration _in the RAP' allowing NRC to conditionally concur on the remedial action. DOE should demonstrate tl)at control of the tailings'can proceed independently of restoration so that NRC staff can issue a finding on postponement of restorat;on. ~Until a demonstration is issued by DOE, NRC staff findsthatDOE-hasnotcompliedwiththerequirementsin40CFR192.20(b)(4).
Related to this subsection, DOE may be required to extend the remedial period
- :past that necessary to stabilize the tailings.
If this occurs, then DOE will have;to-invoke 40CFR192.12(c)(4),anddemonstratethattherequirements.of.
this subpart are met during'the extended remedial period.
5.5.3 Ground-Water Monitoring Program a
Pursuantto40CFRPart192.20(b)(4). DOE-is.requiredtoproposeandimplement a' ground-water monitoring program,:if 40 CFR 192.12(c)(4) is invoked, in order to verify; projections of plume. movement and attenuation during remedial action..
DOE has not proposed a. restoration plan or determined whether the remedial
-period is to be extended, thus the need for a groundwater monitoring program
-cannot be established-at this time. As' discussed in Subsection 5.4.4 of this
,TER.; DOE'is proposing to defer decisions on long-term monitoring at the disposal site until a later date. The staff assumes that decisions on monitoring the relict plume falls under this category of deferment. DOE must decide whether to extend the remedial period to address relict contamination.
-and propose a monitoring program to be implemented in the interim. NRC staft defers decisions on compliance with 40 CFR Part 192.20(b)(4), until DOE de: ides whether to extend the-remedial period.
54
5.6 CONCLUSION
S Based upon the review of.the Final Remedial Action Plan, the Final Design for Review, the draf t Environmental Assessment, and DOE's response to NRC comunents on draft versions of these document, NRC staff finds that open items exist with respect to meeting 40 CFR Part 192. As discussed NRC staff deferred decisions on the need to place geochemicci layers beneath the tailings, until the geochemical conditions are characterized. For other items listed below, DOE needs to demonstrate compliance with the applicable standards:
O O
55 6.0 RADON ATTEhUATION AND SOIL CLEANUP 6.1 Introduction This section of the TER documents the.staft evaluation of the radon attenuation design and the radiation survey plan to assure compliance with the EPA standard.
' 6.2 Rador Attenuation The review of the cover design for the radon attenuation included evaluation of the pertinent design parameters for both the tailings and the radon barrier soils,andthecalculationsofthe'radonbarrier(earthcover) thickness O
(References 1. 2, 3 a 4).
The design parameters for the tailings and earth cover materials evaluated
.for acceptability include: long-term moisture content, material thickness, bulk density, specific gravity, porosity, and radon diffusion coefficient.
In addition,-radium content and radon emanation coefficient parameters were evaluated for the tailings materials only. The computer code' RAECOM was used
.to calculate the radon barrier cover thickness, and the input included the
.above parameters.
6.2.1' Evaluation of Parameters 10 In order to meet-the EPA standards for limiting release of Raden-222 from residual radioactive material to the atmosphere, the tailings pile will be
.'coveredwithanearther, cover.(radonbarrier). The radon barrier reduces the effluence of Ra-222 by reducing the diffusion rate to acceptable quantities.
- The thickness of the barrier depends on the properties of the barrier and tailings. For the earthen cover for radon attenuation, the DOE proposed to use silty clay from a borrow site and mix it with 3 percent by weight of Sodium Bentonite.
The material properties and radiological parameters used in the design of the radon barrier for the stabilized tailings pile at the Green River site have been reviewed.
1
.c 56 1The design assumes a long-term moisture content of 13.75 for the radon barrier soil (Reference 10). Optimum moisture content from the Standard Proctor Compaction tests for this material varied from 12.9% to 17.95. The average in
' situ moisture content for this material, based on tests performed on samples from the borrow site pits, is approximately 5.55. The laboratory tests performed at 15 bar capillary pressure indicates a moisture saturation lower than that calculated for the long-term moisture content used in the DOE calculations. -The long-term moisture content for the tailings materials is assumed to be 115. The final design does not provide any justification'for the value of long-term moisture content used in the calculations for the radon barrier material, but seem to relay on parametric analyses to fustify the design. Although parametric analyses is a useful tool to demonstrate the
_O sensiivity of certain parameters and conservatism in the design, it shouid not be used in lieu of determining critical parameters by appropriate methods. The DOE should provide proper-justification and documentation for the long-term moisture content for the amended soil that is proposed for the radon barrier.
The material thickness (layers) used in DOE's analysis are based on the conceptual design of the remedial action plan and data available from field investigations. The tailings and the contaminated wind blown materials will be placed in the disposal cell,-and there is no layering or preferred placement of these materials within the disposal cell. The design assumes uniform, average properties for these materials. The material thicknesses used by the DOE in O the analysis are a reasonab,e representation of the fieid conditions.
Material properties such as bulk density and specific gravity were determined by field and laboratory tests, and the corresponding porosity was calculated.
The bulk density and porosity for the tailings material are 1.57 gm/c.c and
'0.425 respectively. The corresponding properties for the radon barrier soil (virginsoil,notmixedwithbentonite)were1.8gm/c.cand0.33respectively.
However, the DOE has not provided these parameters for the amended soil. The bulk density and specific gravity parameters for the tailings material are acceptable to the staff.
Radon diffusion coefficients for the cover material and tailings were derived from a correlation curve of moisture saturation versus radon diffusion
57 coefficients based on the estimated moisture for the long-term for the materials. This curve was developed using diffusion coefficient and moisture saturation data from both field and laboratory measurements of soil samples that are representative of the condition in the stabilized pile. The staff review of the values of diffusion coefficients will be perfonned after the DOE provides adequate justification for the values of the long-term moisture contents _used in the design.
Theradiumcontent(Ra-226)ofseveralmaterialsatthesitewasmeasured. The average radium content to be used in the analysis was determined by weighted averaging with depth in a measurement hole and then averaging over an area at any given depth. Th, weighted average value of the radium content for the entire pile was calculated to be 88 pei/gm. However, the average radium content will be verified by field nieasurements on the stabilized tailings pile before placing the radon barrier earth cover. The staft concurs with the value and methodology used in design for establishing-the average radium content.
The radon emanation coefficient was measured in the laboratory on samples representative of field conditions. An emanating coefficien't of 0.21 was conservatively used in design for the tailings material. The NRC staff concludes that the emanation coefficient of the contaminated material has been acceptably characterized for the Green River site based on testing of representative samples.
O -The ambient air radon concentration was measured to be 2 pci/1. The technique used to neasure the radon concentration and the result is acceptable to the NRC staff. This parameter is an input for the RAECOM modeling calculation used in designing the thickness of the radon barrier cover.
6.2.2 Evaluation of Radon Barrier The radon barrier (earth cover) thickness necessary to comply with the radon efflux limit was calculated using the RAECOM computer code. For a given assumed thickness of the radon barrier, the RAECOM code calculates the radon gas release rate. The EPA standard requires that the release of raden-222 from residual radioactive material to the atmosphere not exceed an average release d
58 rate of 20 picocuries per square meter per second. The DOE has assumed a cover thickness of 1 foot and shows the calculated radon release rate to comply with the EPA standards.
But as discussed above, the DOE has not adequately justified all the parameters used in the calculations and the NRC will review the radon barrier design after DOE submits all the information identified in the previous section.
In addition, the NRC is concerned about the practicality of constructing a one foot thick clay layer to achieve a hydraulic conductivity of 10E-7 cm/sec for its entire thickness, and be able to fulfill its design function for the long-term life of the UMTRCA project. The staff concerns are mentioned in section 3.3.3 of this report, and in the review comments on this topic based on the previous staff review of the final RAP.
6.3 Site Cleanup
- Site characterization surveys have been conducted at the site to indentify the subsurface boundary of the tailings pile, as well as, the depth and area of the former mill yards, ore storage, and windblown contaminated areas. Radiometric surveys.and sampling were also conducted in the buildings at the site. The results of the site characterization survey are being used to plan the control monitoring for the excavation and the building decontamination, as well as the final radiological verification survey for the land and the buildings. DOE has committed to the clean-up of the processing site and mill buildings in accordance with the EPA standard (40 CFR 192 Subpart B).
In addition to the EPA standards for the buildings DOE proposes that removeable 2
surface alpha contamination shall not exceed 1000 dpm/100 cm, and the average over one square meter total non-removeable alpha contamination shall not exceed 2
5000 dpm/100 cm. DOE proposes an absolute maximum limit for total alpha 2
contamination of 15,000 dpm/100 cm. These limits are in compliance with NRC Regulatory Guide 8.30 " Health Physics Surveys in Uranium Mills".
As a result of DOE's compliance with the EPA standard and NRC Regulatory Guide 8.30 with regard to removeable alpha contamination, the NRC is prepared to concur with the DOE's radiological survey plan. Although it should be pointed out that while NRC has no objection to DOE's utilization of the NRC proposed limits for removable alpha contamination, the DOE should comply with their own
59 more stringent standards as provided in the UMTRA Project Environmental, Health andSafetyPlan(UMTRA-DOE /AL-150224).
6.4 Conclusions As previously discussed-in section 3.3.3, the infiltration / radon barrier design for the proposed Green River remedial action is an open item. With regard to the site clean-up, the DOE has cosmitted to clean-up the processing site and mill buildings in accordance with the EPA standards and NRC Regulatory Guide 8.30. Therefore, the NRC finds the proposed site clean-up to be acceptable.
G
_ rg et 4
60 7.0
SUMMARY
This Technical Evaluation Report (TER) sumarizes the NRC staff review of the proposed remedial action for the Green River Tailings site. Additional information is needed prior to unconditional concurrence by NRC. The deficient areas have been noted in the text and additional information is requested from DOE. Staff review of the additional information will be presented as a supplement to this report and wil.1 include the NRC concurrence position on the proposed remedial action.
O
61
8.0 REFERENCES
/ BIBLIOGRAPHY 1.
Campbell, K.W.,1981, Hear-source attenuation of peak horizontal ground acceleration: Bulletin of the Seismological Society of America, v. 71, p.
2039-2070.
2.
DOE,1984, Draf t Environmental Assessment, Davis Canyon site, Utah: DOE Document Number DOE /RW-0010.
3.
DOE, 1987b, Green River draft Remedial Action Plan site conceptual design; geology, seismicity, and geomorphology: supplements submitted as enclosures to letter J.R. Anderson, DOE, to D.E. Martin, NRC, 3/13/87.
4.
McKnight, E.T., 1940, Geology of area between Green and Colorado rivers, Grand and San Juan counties, Utah: U.S. Geological Survey Bulletin 908, 147 p.
5.
NRC, 1985, Standard review plan for UMTRCA Title I mill. tailings Remedial Action Plans: U.S. NRC, Division of Waste Management, October, 1985.
6.
Williams, P.E. and Hackman, R.J., 1971, Geology of the Salina quadrangle, Utah: U.S. Geological Survey Miscellaneous Investigations Series Map I-591-A.
h 7.
Young, R.G., Million, I., and Hausen, D.M., 1960, Geology of the Green River mining district, Emery and Grand counties, Utah: U.S. Atomic Energy Connission Report RME-98 (revised), 89 p.
8.
Remedial Action Plan and Final Design for Stabilization of the Inactive Uranium Mill Tailings at Green River, Utah, Final, Vol. 1,11 and III, February,1988; UMTRA-DOE /AL 050510.GRNO.
9.
Uranium Mill Tailings Remedial Action Project (UMTRAP), Green River, Utah; Information to Bidders, Volumes I, II & III, December 1987.
l I
62
- 10. Uranium Mill Tailings Remedial Action Project (UMTRAP), Green River, Utah; Design Calculations, Volumes I,Il & III dated November 1987.
-11.
UraniumMillTailingsRemedialActionProject(UMTRAP),GreenRiver, Utah; Design Calculations - Addendum 1, February 1988.
l 12.
U.S. Arg Corps of Engineers, Hydrologic Engineering Center," Flood Hydrograph Package, HEC-1, continuously updated and revised.
13.
U.S. Nuclear Regulatory Commission, Regulatory Guide 1.59, " Design Basis Floods for Nuclear Power Plants," January 1983.
14.
U.S. Bureau of Reclamation, U.S. Department of the Interior, Desian of
(]
Small Dams, 1973.
v
- 15. Staft Technical Position WM-8201, " Hydrologic Design Criteria for Tailings Retention Systems," January 1983.
16.
U.S. Arg Corps of Engineers, Hydrologic Engineering Center, " Water Surface Profiles, HEC-2." continuously updated and rev(sed.
- 17. Chow, V. T.,
"Open Channel Hydraulics," McGraw-Hill Book Company, New York, 1959.
O 18.
U.S. Arg Corps of Engineers, " Hydraulic Design of Flood Control Channels," EM 1110-2-1601, 1970.
19.
U.S. Arg Corps of Engineers, " Additional Guidance for Riprap Channel Protection " EM 1110-2-1601, 1970.
20.
U.S. Department of Commerce, U.S. Arg Corps of Engineers, Hydrometeoro-logical Report No. 43, " Probable Maximum Precipitation, Northwest States,"
1966.
21.
U.S. Arg Corps of Engineers, " Engineering and Design - Standard Project riood Determinations," EM 1110-2-1411, 1965.
l
63
- 22. Crippen, J. R. and Bue, C. D., " Maximum Floodflows in the Conterminous United States," USGS Water Supply Paper 1887 (1977),
- 23. Simons, D. 8., and Senturk, F., Sediment Transport Technology, Fort Collins, Colorado, 1976.
- 24. Codell, R.
B., " Design of Rock Armor for Uranium Mill Tailings Enbankments," U.S. Nuclear Regulatory Commission, Unpublished Draft Report, February 1985.
25.
U.S. Department of Commerce, U.S. Army Corps of Engineers, Hydrometeoro-logical Report No. 49, " Probable Maximum Precipitation Estimates Colorado O
River and Great Basin Drainages," 1977.
26.- Stephenson, D., Rockfill Hydraulic Engineering Developments in Geotechnical Engineering f27, Elsevier Scientific Publishing Company, 1979.
~
- 27. Nelson, J. D. et al., " Methodologies for Evaluating Long-Term Stabilization Designs of Uranium Mill Tailings Impoundments,"
NUREG/CR-4620 June 1986.
- 28. Supplemental Geotechnical Data in support of the Remedial Action Plan, Letter from J. Arthur, DOE to P. Lohaus NRC, March 11, 1988.
- 29. Environmental Assessment of Remedial Action, Uranium Mill Tailings Site, Green River, Utah, December, 1987
- 30. DOE's Response to NRC Comments, Letters form J. Arthur, DOE to P. Lohaus, NRC, September and December, 1987
- 31. Letter to J. Arthur, DOE from P. Lohaus, NRC, March 14, 1988
- 32. Kirkham R. M. and W.P. Rogers,1981. Earthquake Potential in Colorado:
A Preliminary Evaluation; Colorado Geological Survey Bulliten No. 43
,-...-v-
64
\\
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- 34. Trip Report, Memorandum from J. Grisen to R. J. Starmer, June 17, 1987 O
-