ML20197D258
| ML20197D258 | |
| Person / Time | |
|---|---|
| Issue date: | 01/31/1989 |
| From: | NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | |
| Shared Package | |
| ML20197D252 | List: |
| References | |
| REF-WM-72, TASK-TF, TASK-URFO NUDOCS 9712290019 | |
| Download: ML20197D258 (51) | |
Text
-
e 1LR/SP00K1/89 DRAFT O
TECHNICAL EVALUATION REPORT FOR TF.E PROPOSED REMEDIAL ACTION AT THE SP0OK TAILINGS SITE SPOOK, WYOMlHG TABLE OF CONTENTS January,1989 O
Division of Low-Level Waste llanagement and Decomissioning Office of Nuclear Materials Safety and Safeguards U.S. Nuclear Regulatory Comission
[M22 g g 890127 WM-72 pg
i TER/ SPOOK 1/89 Section Page
1.0 INTRODUCTION
........................... 4 1.1 EPA Standards........................ 4 1.2 Site and Proposed Action.................. 5 1.3 Review Process....................... 8 1.4 TER Organization...................... 9 1.5 Susanary of Open Issues and Confirmatory items........ 9 2.0 GEOLOGIC STABILITY.......................
11 2.1' IntroJJction.......................
11 2.2 Location.........................
11 0
2.3 Geology..........................
11 2.3.1 Stratigraphic Setting...............
11 2.3.2 Structural Setting.................
12 2.3.3 Geomorphic Setting................,, 14 2.3.4 Seismicity.....................
15 2.4 G eo log i c S ta b i l i ty....................
15 2.4.1 Geomorphic Stabili ty................
15 2.4.2 seismotectonic Stability..............
19 2.5 Conclusions........................
20 3.0 GE0TEr.HNICAL STABILITY.....................
21 3.1 Introduction.......................
21 3.2 Site Characterization Evaluation.............
22 3.2.1 Site Description..................
22 3.2.2 Site Investigattor.s................
22 0
3.2.3 Site Stratigraphy.................
23 3.2.4 Testing Program..................
24 3.3 Geotechnical Engineering Evaluation............
24 3.3.1 Stability Evaluation................
24 3.3.2 Liquefaction....................
25 3.3.3 Settlement.....................
25 3.3.4 Cover Design....................
26 3.4 Geotechnical Construction Criteria............
27 3.4.1 Construction of the low-Permeability Layer....
27 3.4.2 Placement of AML Backfill Above Disposal Cell...
27 3.5 Conclusions........................
28 4.0 SURFACE WATER HYDROLOGY AND EROSION PROTECTION.........
29 4.1 Introduction.......................
29 4.2 Hydrologic Description..................
29 4.3 Flooding and Water Surf ace Profiles............
29 4.4 Con clu s i ons........................
30
TER/SP00K 1/89 5.0 WATER RESOURCES PROTECTION...................
31 5.1 Introduction.......................
31 5.2 Hydrogeologic Characterization..............
31 5.2.1 Hydrostratigraphy and Groundwater Occurrence....
31 5.2.2 Geochemical Conditions and Water Use........
33 5.2.3 r.xtent of Lor.tamination..............
34 5.2.4 Tailings Characterization.............
34 5.3 Conceptual Design Features for Water Resources Protection.
35 5.4 Disposal and Control of Residual Radioactive Material...
35 5.4.1 Groundwater Protection Stsndard..........
35 5.4.1.1 App 1tcability of Supplemental Standards...
36 5.4.1.2 Proposed Supplemental Standards.......
37 5.4.1.3 Compliance Demonstration..........
38 0;
5.4.2 Closure Performance Standard............
39 5.4.3 Groundwater Monitoring and Corrective Action..
39 5.5 Demonstration of "As Close as is Reasonable........
40 5.6 Cleanup and Control of Existing Contamination.......
41 5.7 Conclu sions........................
42 6.0 RADON ATTEhUATION AND SITE CLEAN-UP,.............
43 6.1 Introduction.......................
43 6.2 Radon Attenuation.....................
43 6.1.1 Evaluation of Parameters..............
43 6.2.2 Evaluation of Radon Barrier.
..........45 6.3 Site Cleanup.......................
46 6.4 Conclusions........................
47 7.0
SUMMARY
48
8.0 REFERENCES
AND BIBLIOGRAPHY..................
49
l TER/ SPOOK 1/89
1.0 INTRODUCTION
The Spouk, Wyoming site was designated as one of the 24 abandoned uranium mill tailings piles to receive remedial action by the U.S. Department of Energy (DOE) under the Us anium Hill Tailings Radiation Control Act of 1978 (UMTRCA). UMTRCA requires, in part, that the U.S. Nuclear Regulatory Cc'aission (NRC) cont.ur with DOE's selection of remedial action, such that the remedial action meets standards promulgated by the U.S. Environmental Protection Agency (EPA). This draft Technical Evaluation Report (TER) documents HRC staff's review of the DOE preliminary final remedial action plan and outlines the conclusions and outstanding issues / items resulting from this review.
1.1 EPA Standards As required by UMTRCA, remedial action at the Spook site must comply with standords established by the EPA in 40 CFR Part 192, Subparts A-C.
These standards may be sumarized es follows:
1.
The disposal site shall be designed to control the tailings and other residual radioactive material for 1000 years to the extent reasonably achievable and, in any case, for at least 200 years [40 CFR 192.02(a)].
2.
The disposal site design shall prevent radon-222 fluxes from residual radioactive materials to the atmosphere from exceeding 20 picocuries/ square meter /second or from increasing the annual average concentration of radon-222 in air by more than 0.5 picocuries/ liter
[40CFR192.02(b)].
The remedial action shall ensure that, radium-226 concentrations in 3.
O inne that is not Part of the disPoia site averased over aar 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 of soil more than 15 centimeters below the land surface
[40CFR192.12(a)].
On September 3, 1985, the U.S. Tenth Circuit Court of Appeals remanded the groundwaterstandards(40CFRPart192.2(a)(2)-(3))andstipulatedthatEPA promulgate new groundwater standards. EPA proposed these standards in the form of revisions to Subparts A-C of 40 CFR Part 192 in September 1987. The 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 cleanup of contamination that occurred before the remedial action of the tailings.
l TER/ SPOOK 1/89 1.2 Site and Proposed Action The Spook mill and tailings site is in Converse County; 48 miles northeast of Casper, Wyoming; and 36 miles northwest of Douglas Wyoming (Figure 1.1) The site is currently part of a remote, active sheep cattle ranch.
The Spook site consists of an abandoned open pit uranium mine, a mill site area at the edge of the pit, and several miscellsneous contaminated areas (Figure 1.2). Tailings are along the southeast pit wall and on the ground surface adjacent to the pit. Several small ore reserve piles and a depleted acid pond are nurth and south, respectively, of the pit.
The designated site, which includes thu tailings and former mill area O-enc mpasses ab ut five acres. The windblown contamination and ore reserve piles are outside of the designated site but will be included in the remedial action. Also, while the depleted acid pond south-west of the designated Spook site will be remediated as a vicinity pro)erty, a significant amount of its contaminated material will be placed in tie UMTRA Project tailings disposal cell. The total volume of contaminated r.aterials is estimated to be 243,000 cubic yards (cy).
Adjacent to the site are 9 piles of overburden material removed from the pit during mining. These piles contain an estimated 1.6 million cy of material.
The remedial action plan for the Spook site consists of a joint effort between the DOE Uranium Mill Tailings Remedial Action (UMTRA) Project and the State of Wyoming Abando..ed Mined Lands (AML) Program. The AML Program is authorized under the Surface Mining Control and Reclamation Act of 1977, Public Law 95-87, and administered by the participating state. The DOE portion of this joht remedial action will cone,ist of the cleanup, consolidation, and stabilization of all " residual radioactive materials" in the Spook pit. The AML Program
(
responsibilities will consist of backfilling the pit with overburden material, recontouring the disturbed area, and revegetating the final cover.
Both portions of the design will be constructed by a single contractor.
NRC staff's review focuses on the UMTRA Project portion of the site remediati'>n and those portions of the AML Program work which may affect the UMTRA Project design
! Reference 16).
The concurrent UMTRA Project /AML Program design is comprised of the following major phases:
o DOE (UMTRA Project) preparation of the esbanbnent foundation at EL 5020 in the bottom of the Spook pit (approximately 15 feet above the groundwater level).
o State (AHL Program) placement and compaction of a 3-foot thick leachate reduction layer over the botton of the pit.
T J OH NS TON CAMP BELL WESTON J
3sf e
N C
l i
SPOOK ROSS SITE NATRONA RD.
NIO B R A R A g
I i
es I
Casper g
olenrock P'3
~
~
g 3
4sr I
as 2! PLATTE GO6H 1
, as CARBON I
ALBANY Wheatland
\\)
10 0
10 20 30
-m S CALE IN MILES WYOMING cheyenne FIGURE 1.1 (SOURCEt REFERENCE 2)
LOCATION OF THE SPOOK SITE IN CONVERSE COUNTY, WYOMING
~ _. _ _.
.I lii'!!!iiliiiiiiii!!
.I AREA D l
- +g
.n.
- N.8 l
!l!
, ] j.,
50 7 t
- q.,
j;;;
P
'k,*.,, [
I.-
I I
' a..:,
i:!8i! '
'l,v.,,,
',, :548 g.
l l
(!!fpi!
s$,,
- ~
kREA '
!I'*5 433Xf T: ?.t.'-
%',s......
.p!!.
.jy:'
9:
'/y 5
. ss:
gg,,y I.'
s,,
1 jiji; sis!
Wi**....,
!!i*
s, AREA B
a ARGA C
- m:::
o gg..
e(
\\
4 t.EGEND
- 'e AREA A : TAILINGS PILES
^
g4 ds! !::N,
,'if 1
AREA B : MILL YARD AREA C: Wil SLOWN TAILINGS l
h q-pi:,
.}
$b AREA D : LITTLE ORE PlLES
~
<*i;i \\
pse
,,.. r>:'
AREA E: ACID POND
,f
,.,. QW sys::s '..
- ?ili
- ii::
l.
- .:...s..
PIT SOUNDARY e
i APPROXIMATE LOCATION
.l g
x O', [
g.;
OF MINE TUNNELS
' *i iii:
OVERBURDEN PILES
- AREA E
/
s c
1 E
CONTOUR INTERVAL:
20' 400 o
400 5 AL IN FEET FIGURE 1.2 (SOURCE: RETERENCE 2)
LIMITS OF YAILINGS CONTAMINATION AND TUNNEL LOCATIONS, SPOOK SITE - CONVERSE COUNTY, WYOMING
l TER/ SPOOK 1/89 0 00E stabilization of the tsilings, millyard, windblown and demolition debris in an embankment at the bottom of the Spook pit; the base of which will be approximately hexagonal and cover five acres in area. The average depth of the embankment will be about 32 feet (with a maximum depth of 53 feet). The sides will be constructed at a 1 verticle to 2 horizontal slope, with the top slopes three to eight percent grade, o
DOE placement and compaction of a 1.5-foot thick, low-penneability layer over the tailings embankment to minimize infiltratioii.
o State 11acement of a h foot thick layer of selected granular material over tie low-permeability layer to promote lateral drainage around the tailings embankment.
o State backfill of the it with compacted overburden material. The average depth of overb rden above the tailings will be 56 feet, with the least contaminated portion near the finished surface and the most contaminated at the bottom of the pit.
State completion of site reclamation by recontouring the disturbed area and revegetating the final cover to provide a stable topograhic condition similar to the pre-mining ground surface.
The final UMTRA site area will cover 13 acres. This area arresponds to the surface area of the pit plus a 100-foot wide perimeter buffer zone.
After completion of the joint remedial action, DOE will implement the surveillance and maintenance responsibilities for the final UMTRA site area in accordance with an NRC license, to be issued following adequate completion of the remedial action.
O 1.3 Review erocess NRC staff's review was performed in accordance with the Standard Review Plan forUMTRCATitle1 Mill.TailingsRemedialActionPlans("SRP"; Reference 1)and consisted of comprahensive assessments of DOE's proposed preliminary final design and remedial action plan.
The information, assessed by NRC staff during this review was primarily provided in the following documents, submitted by DOE for review (References 2through6).
1.
Remedial At. tion Plan and Site Design for Stabilization of the Inactive Uranium Mill Tailings at Spook, Wyoming; preliminary final, cated December 1988 (including text and appendices A, B, C, D, and E). - " RAP" 2.
Uranium Mill Tailings Remedial Action Project (UMTRAP-AML), Spook, Wyoming; Informa', ion for Reviewers, dated November 19aa.
I
TER/ SPOOK 1/89 3.
Uranium Mill Tailings Remedial Action Project (UMTRAP-AML), Spook, Wyoming; Subcontract Documents, dated November 1988.
4.
UraniumMillTailingsRemedialActionProject(UMTRAP-AML), Spook, Wyoming;InformationforBidders,datedNovember1988(2 volumes).
5.
UraniumMillTailingsRemedialActionProject(UMTRAP-AML), Spook, Wyoming; Calculations,datedNovember1988(2 volumes).
These documents were stibm ted by DOE for NRC staff's review on Decerber 12, 1988. Also enclosed with > ~ ese documents was DOE Responses to NRC comments on the Spook, Wyoming draf t RxP, submitted to DOE on October 15, 1987; and on the April 22, 1988 (gn and draft Environmental Assessment, submitted to DOE on preliminary Desi Reference 7).
1.4 TER Organization The purpose of this draft TER is to document NRC staff's review of DOE's preliminary final remedial action plan and design for the Spook site and to address the open issues resulting from this review. The follow' sections of this report have been organized oy technical discipline relatit. to the EPA Sections i 3, and 4 provide the standards in 40 CTR Part 192, Subparts A-C.
technical basis for NRC staff's conclusions and identification of any remaining open items with respect to the long-term stability standard in 192.02(a). Section 5, Water Resources Protection, sumarizes NRC staff's conclusions and any remaining o>en items regarding the adequacy of DOE's demonstration of corp 11ance witi respect to EPA's groundwater protection requirements in 40 CFR Part 192. Section 6 provides the basis for the staff conclusions and identification of any open items with respect to the radon control standards in 192.02(b).
O 1.5 Sumary of Open Issues and Confirmatery Items NRC staff's review of DOE's preliminary final remedial action plan and design has identified only one open issue, which is addressed in section 5.5 of this TER. The issue relates to DOE's deferral of groundwater cleanup until after promulgation of EPA's final groundwater protection standards. While NRC staff considers DOE's deferral to be acce) table for conditional concurrence at this time, this issue must be addressed aefore NRC will provide final concurrence on the remedial action at this site.
In addition to the one open issue, NRC staff has identified two confirmatory items, which are sumarized in Table 1.1 below. These are items, referencing either information or comitments, that DOE must confirm in writing to support NRC conclusions relating to the EPA standards. This documentation needs to be provided in the final RAP submitted to NRC for conditional concurrence.
l TER/ SPOOK 1/89 TABLE 1.1
SUMMARY
OF CONFIRMATORY ISSULS TER Explanation Subsection 1.
DOE needs to document a commitmelit to comply with 6.3 40 CFR 192.21(f), if significant uranium or thorium contamination is found after the radium-226 limits O
3re met during excavation of the residual radioactive materials.
2.
DOE needs to document the derivation of the radium-226 6.3 to uranium-238 ratio of 4.8 and its intended use for delineating the areal extent of tailings, and state that the EPA standards will be met in cleanup of the residual radioactive matericis.
l O
-_.-.---.__._.m_
TER/ SPOOK 1/89 2.0 GEOLOGIC STABILITY 2.1 Introduction This section of the TER documents NRC staff's review of geological information for the proposed remedial action at the Spook uranium mill tailings disposal site. Backgrouiid information for this section of the TER is derived priniarily from DOE's RAP (Peference 2), DOE's Final Desi n for Review, subcontract docurnents and calculations LReferences 4 and 6, the State of Wyoming's Abandoned Mine Lands Report of Investigations Reference 8), staff's observations during the site visits, and independent sources, as cited.
O 22 ' ' "
The Spook site is located along an unnamed tributary of the Dry Fork, a heaubter tributary to the Cheyenne River in the western Great Plaing, Wyoming.
The tributary, called Spook Wash in this report, drains about 1.3 km. About 40 percent of the basin has been disturbed by mining activity. The cl.annel is blocked by the open pit which extends southward (Figure 2.1) to the basin divide. The channel is also blocked by three of nine overburden piles, and by an older refilled open pit mine (the Loma pits). The next watershed to the south is )artially disturbed by the Spook pit and three overburden piles, one of which blocks its channel.
Site characterization was conducted for an area including an abandoned open-pit mine, a mill area and tailings pile, as well as overburden piles and other mine areas to be reclaimed by the State of Wyotring.
2.3 Geology g
EPA standards in 40 CFR 192 do not include generic or site-specific requirements i
for characterization of geological conditions at UMTRA Project sites. Rather, 40CFR192.02(a)requirescontrolshallbedesignedtobeeffectiveforupto 1,000 years, to the extent achievable, and in any case for at least 200 years.
NRC staff has interpreted this standard to mean that certain geological conditions must be mat in order to have reasonable assurance that long-term performnce objectives will be achieved. Guidatice regarding these conditions is spcctfied in NRC's SRP (Reference 1).
2.3.1 Stratigraphic Setting DOE characterized regional and site stratigraphy, referencing publishea work and original field investigations as reconnended in SRP section 2.2.0.1 (Reference 1). The Spook site is situated on broad rolling plains developed in Eocene Wasatch Formation rocks. The Wasatch is one of a thick sequence of continental strata in the Powder River Basin. The Wasatch underlies the site to a depth of approximately 340 feet.
In the central basin, it is composed of thick lenticular sandstones interbedded with siltstone, shale, and coal. The Wasatch apparently was derived from the Laramie Range, uplifted to the south
. * ' '..h
/ N
- f 7.00!!.
s.
\\
...%)
,; 800 8
. S?ii .
\\
fh.1 Y
()
'l
' 7orm* er - '$$,,,,,. @....., Y.
~~
North Ramp
,i,"*
' gg;..
..,, eig;gg,: ':ye:.g,jfj:t,;ib!
/ g [,;. Spook;,g;.N;!!
l ; 800i h
- . ; 7:tir;4;9 - ~
+.
/ J / $
e s;!j!!
Dre1nage
/
+
{g
/ 'o ; N X
m.:ys. -
Q Mill
- g:
("N
()
O Scale t
O 500 T
s i
i.!@},ii:
\\
Feet
)
so r
, --.,).
k
.4
.yt ez '9l}.;hfi[....
/
7;
?!k. :...j..200!$9 Explanation
- i.300'2 6
j
'Wie. ';.<///. * :.:.
e ii20G;i Overburden Pi;es o-l
- f:;.:!:.,!!.
'!!100 Tallings Ac1d l ':;
(3 Pond
- !l$7.jf...g:i.: j:ijg:!l(!ll(!.!:S'Ig:lljl-ll$llklll9
,\\
..jf w/
Strosm Channels
).
s, / (dotted where dkturbod)
.:x l
/
Hortronta) Mine Drifts
- )ouglas, Wyoming 30 Miles FIGURE 2.1 Index map of spook pit, tallings, overburden, and mill.
~. _ _
}
TER/ SPOOK 1/89 I
13 -
I during Laramide time. The Wasatch grades to clayey and silty facies laterally andnorthwardacrossthebasin(Reference 9). Uranium deposits in the Powder River Basin are found in sandstones of the Wasatch.
(
The Wasatch is underlain by the Paleocene Fort Union Formation. The two units
'j are similar in appearance and conformable through most of the basin. However, i
they are separated due to unconformab?e relations observed on the flanks of the basin (Reference 9). The Fort Union exceeds 3,000 feet of thickness in the Spook area. Fort Union rocks are in turn underlain by Cretneous and older 4
j rocks, which are not of importance to the remedial action. NRC staff finds reasonable assurance that detailed subsurface stratigraphic conditions at Spook will not affect the site's ability to meet remedial action standards.
/7 The abandoned will tailings are piled on Wasatch Formation rocks along the r
U eastern face of Spook pit.
Locally, the unit-is coarse-grained arkosic yellow and red sandstone. The sandstone has a fluvial origin is mainly cross-bedded, i
l and is poorly cemented. Comentsintherockincludeclayandironoxides.
l Thin ano discontinuous stringers of coal, petrified wood, sparse interbeds of dark mudstone and yellow uranium mineralization are observed in the pit.
Quaternary deposits occur at the top edge of the pit, but were extensively disturbed by mining. Alluvium adjacent to the disposal area is as-thin as two feet, and bedrock occurs very near the surface.
However, it thickens to 40 feet along the north end of the pit. The State's drilling data and shallow reflection seismic surveys suggest the thickest alluvium occurs along paleochannels. The alluviu:n-bedrock contact north of the disposal area occurs at an elevation slightly lower than the top of the proposed tailings pile.
Surficial deposits are mainly sandy loam and prcbably consist of fluvial sediment derived from local bedrock and reworked eclian sediment.
' h Details of the area's stratigraphy, as it influences hydrogeological and geotechnical conditions of the site and ability of the remedial action to meet UMTRA Project groundwater standards, are discussed in other sections of this TER. The staff find reasonable assurance that stratigraphic conditions at Spook will not directly affect the site's ability to meet long-term stability standards.
2.3.2 Structtiral Setting DOE characterized the region's structural setting referencing published regional geological maps and their field observations of features critical to assuring long-term stability of the remedial action. These studies were recommendedinSRPsection2.2.2.3(Reference 1). The Spook area lies near the axis of the Powder River Basin. The area occurs as both a structural and physiographic basin and is surrounded by structural highlands. The basin lacks major structural features in the Wasatch and Fort Union formations, and appears i
to have been stable since Eocene time. Wasatch beds near the site are nearly
..__y y..%-.
,,m.
m
_.,,,_,,Z_,.,_.6_.____
.m,,
i TER/SP0OK 1/8g L
flat lyin, and dip only one d ree to 24 degrees in most of the basin. The j
structura axis on basement roc s does not coincide with the surficial axis, suggesting the basin has experienced deformation since early Tertiary time.
l i
Fractures are mapped in Wasatch rocks east of the site, and are interpreted as
- tension fractures associated with incipient anticlinal warping of the Powder RiverBasin(Reference 9). Differential movement along the fractures is not-i
- observed in the field. Similar fractures were also observed in the site area.
On serial photographs they appear in bedrock exposures, but can also be l
observed in a few areas even though overlain by shallow surficial deposits.
i
- Their appearance through soil results from concentration of vegetation, and suggests the fractures help maintain higher soil moisture. The features are i
difficult to recognize in the field and are not observed in the walls of Spook
~
' n pit. Like their regional ccunterparts, they do not exhibit fault displacement.
V The staff finds reasonable assurance that structural conditions at Spook will t
not affect the site's ability to meet remedial action standards.
2.3.3 Geomorphic Setting 1
l D0E characterized regionJ1 physiography referring to published literature and topogra > hic maps, as recommended in SRP section 2.2.2.2 (Reference 1). Site
- geomorpite conditions were characterized by aerial photographic interpretation j
and field observations. The area is located in the Cheyenne River basin in the i
westernGreatPlains>hysiographicprovince(Reference 10). The Big Horn i
i Mountains to the nortiwert and Laramie Mountains to the south form the I
bordering Rocky Hountain province.
L The Spook site occurs along the southern slope of a small drainage basin, called Spook Wash in this TER. The drainage channel is intersected by the pit-and blocked by several overburden piles, and,,much of the basin has been
- - O disturbed. Runofffroma6out20 acres (1.0skm')oncedraiaedthrov9hthe area affected by mining. Surficial d6 posits are mainly 2 to 10 feet thick, but 4
I go as deep as 40 feet ' n paleochannels exposed in Spook pit.- Quaternary
{-
deposits form a relatively continuous mantle in the area.
Bedrock outcrops typically occur along h111 slopes and drainage divides. Outcrops occur preferentially on ridge crests oriented perpendicular to prevailing wind 4
direction.- AML Program site investigators concluded that these outcrops resulted from eclian deflation because the ridge crests provide surficial deposits with minimal protection from wind.
- Under ordinary conditions,1a major remedial action: concern is protection of-
+
tailings from catastrophic flood erosion. At-Spock, however, placement of the 4
tailings below grade in.the abandoned pit lessens this concern. The Spock site is at greater risk from long-term erosion,- channel changes, and drainage basin development..-Therefore, staff analyzed the potential depth of channel erosion-
~
during the perforsunce period of the remedial ~ action. Three, aspects of the site's characteristics and design have been emphasized by DOE for protection of L
1
,,w-.,-
,y 4.-
-.w..
.. e,- 4
,,,,.,,..,v~,
,.m.,,
.~-..m
..e,.,.,_-4-4..
- ,-_.+-.#
e
TfR/ SPOOK 1/89 the tailings from deep erosion:
bedrock (2) deep burial of the tailings, (3) surface recontouring by the(1)
State.
These aspects are reviewed in the Geomorphic Stability section of this report.
2.3.4 Seismicity 00E chart.cterized regional seismicity by obtaining data bases provided by the National Oceanographic and Atmospheric Administration (NOAA), ay applying accepted techniques to determine earthquake magnitudes and by employing methods suggested in SRP section 2.2.2.3 (Reference 1),for calculating peak horizontal ground accelerations generated by a design-basis event.
The Spook site is located in a relatively stat,le border area between the middle Rocky Mountain and Black Hills seisrotectonic provinces.
O Historical and instrumental seismic activity has been sparse, and is concentrated at distances greater than 80 bn away in tl:e Laramie Range, the Black Hills, and beyond (Reference 2?. DOE characterized regional seismicity and faults in adjacent seismotectonic provinces, and determined that the design seismic ground acceleration for the site is 0.019 (Reference 2).
However, because the tailings will be buried below grade, they are susceptible to minimal risk of failure due to seismic shaking. The staff concludes that only on-site fault rupture intersecting the tailings would result in a potential failure to meet thestandards(Reference 2).
of seismic risk for this site is not necessary.Therefore, the staff find that detailed analys 2.4 Geologic Stability Geological conditions and processes at the site are characterized to detertaine the ability to meet 40 CFR 192.02 andstructuralconditionsarecon(a),
in general, site lithologic, stratigraphic, sidered for their suitability as a disposal (V3 foundation and their potential interaction with tailings leacheate and ground wcter.
The effer.t of the s;te's bedrock geology on hydrogeological and geotechnical conditions is discussed in other sections of this TER.
NRC staff considered geomorphic processes for their potential impact upon long-term tailings stabilization and isolation. Our geomorphic review was based on the proposed AHL Program design (References 4, 6 and 8).
Potential geologic hazards, including seismic shaking, liquefaction, on-site fault rupture, ground collapsc, and volcanism were reviewed for the purpose of assuring the lon,-term stability of the disposal cell and success of the renedial action.
2.4.1 Geomorphic Stability Stabilization of mill tailings in their present location or in an above-grade pile would require constant maintenance and repair of erosion control features, and would impede the State's efforts to reclaim the abandoned nine.
The proposed 1
I TER/ SPOOK 1/89 burial of S >ook's tailings will result in elimination of the site's major geomorphic 1azard -- erosion of tailings during a catastrophic flood event in the Spook Wash basin. Burial of the tailings will also eliminate hazards resulting from eolian deflation of contaminated materials.
The staff has carefully reviewed the State's pro)osed mine reclamation plan, its relationship to DOE's remedial action and tie proposed restoration of geomorphic features at the site. OurrevIewwasaimedtoensurethatproposed burial of the tailings will provide protection from long-term geomorphic processes At the site.
Dased upon our review, we conclude that DOE places reliance f or meeting long-term geomorphic stability requirements on the following three aspects of the site and design (Reference 2).
Protectioni of the tailings by bedrock DOE asserts that bedrock occurs higher than the proposed tailings pile, and will provide a stable base level to prevent future downcutting and erosion of pit fill. The RAP and design provides an east-west cross-section toshowtherelations(Figure 2.2). The staff's review indicates that a more likely orientation of eroding channels would be frcm Spook Wash southwardthroughthepitbackfill(Figure 2.3).
In this orientation, no bedrock occurs higher than the elevation of the proposed tailings pile.
In addition, the staff observed (trip report, J. Grissn and L. Deering to J. Starmer, November 29,1988) that the Wasatch sandstone rock appears to be poorly cemented and probably lacks the induration needed to provide a stable base level for long time periods. The staff concludes that the bedrock may not provide significant erosion protection, and that reasonable assurance of long-term stability of the tailings pile should be based on other aspects of the site and design.
O aiae reciamation: surface contourino and 8 sia stabiiitr The State's mine reclamation plan includes two design features intended to increase tha site's long-term geomorphic stabilit The first feature is topographic mounding of backfill over Spook pit (y. Drawing No.
SPK-AML-PS-10-0203; Reference 4). The design should result in runoff away from the pile. Preferential erosion will occur in areas away from the pile. Gullies forming near the pile will not have enough basin area to support headward erosion to the area overlying tailings.
Second, the State will reconstruct Spook Wash and a small tributary to the north with channel patterns and hydraulic geometry designed to minimize erosion. The constructed channel pattern will be meandering to increase channel length, and therefore decreace channel gradient.
IIRC staff compared an arbitrary drainage basin, whose mouth lies at the downstream end of the area affected by mining and mine reclamation, with
O O
WEST-EAST seeo<
alluvium
.seeo w
g N
S:20 "N~---------.
[Ensises e.oue sueFact g
s:20 N rtc m y ;,. g.e. u
.x, -- - - --
see
/
~ - - - - -
A M L fill
,,,,,o,,,,,g
.;Io vlu *
,(
g f
7- -
- sooo-
/
xxisTwes
=
gt,on o
/
N888**TED sooo
- n_ soeso N /
..a,.0, W
d T.8L98sGS
/
I" nedrock f
so.a.
,/
.,o.o s(
EfEN sazo.
7to =res
%ee w
so2o rou ro cese:oo i
sooo.
sooo CROSS-SECTION M
- /
\\
90 _ _o 90 soo M.L SG.LE FEEi i
FIGURE 2.2 East-west topographic profile and geologic cross-section of Spook pit showing location of tailings and the elevation of the alluvium-bedrock contact. Note the contact occurs above the peak of the tailings pile. Profile is parallel to Spook Wash.
(Simplified from DOE design drawing SPK-FS-10-0109.)
.u_.
Y i
T SOUTH EAST NORTH A
A*
' *
- D **I',e.
cise e
***e..,
,,Q,.
f '
- '** % m n
~,v'**""*"
..~~ e e
'. A l
. :,;.. ~ T -.
- - :,,.. - ~.e..e.
atee ee N'-'
.enseeee seem fm3ese se**e.een Aast fel C
..r.
- e -e. e
^
sees PROPOcto TAILante LOCAfsee
.aovese
~ ""
Aast MIB
~ ' I ' - ~ - ' e eee,e seees wr ptime**ted.a r
PFT FLefs4 ee,.
was.tenFe
= e@ee FIGURE 2.3 Topeyraphic profile and geologic cross-secties along Speet pit and $ poet Ilesh. Even though tallings t
will lie helse heersch esposures to the pit ualls, se bedrock stil octor heteese Spoot IIesh and tse taillegs felleetag remed6el acties. Secrect e111 met Supede erestem of $peet 16esh, thrwegh reclassed fl11, to the tattlegs. Sta6 titty of the tattlegs rettes spee stablitty and greetent of reeletard Speet unst, and the depth of fill overlyleg the plie. (Tattlegs layent is based upon BOE dessge dreetag
[
5Ft-p5-10 4 08. Topograply of the pit, reclaaettee elevettons, and geological relations are tates frun J
Ahl emps I
l 1
[
i TER/ SPOOK 1/89 others in the western united states for which gully threshold conditions havebeenestablished(Reference 11; Figure 3.9). Our analysis shows that the Spook basin is similar to other semiarid basins which have not experienced gully formation. The basin's area and gradient also lie belcw e statistically derived threshold for gullying determined from those semiarid basins. The staff conclude that while hillslope and chann11 erosion are likely to occur over the long term, widespread gully growth is unlikely. Therefore, the design provides reasonable assurance that drainage channels will not affect the long-term stabilization of the tailings pile.
Depth of burial of the Spook tailings pile O
According to the UMTRA Project /AHL Program design for pile location and surface reclamation, the Spook tailings will lie beneath 50 feet of fill where they approach closest to Spook Wash. The tailings pile peak will lie 48 feet beneath the surface. Regardless of the mode of erosion, this depth of fill should exceed any depth of downcutting which could occur over the next 1,000 years. Gullies elsewhere in the western united states ate known to exist to depths of about 30 feet, These gullies, however, drain larger basins and required hundreds or thousands of years to develop.
Based on these criteria, NRC staff has reasonable assurance that ciannels at Spook wil' not erode through pit backfill and expose tailings during the performance period of the remedial action.
In conclusion, NRC staff finds that site characteristics and the proposed surface rechstion plan should result in the long-term stability required by UMTRCA standards.
2.4.2 Seismotectonic Stability DOE must provide reasonable assurance that the remedial action design will not be affected by seismicity. Proposed remedial action at Spook provides assurance that the tailings will not be affected by seismic shaking, liquefaction, or ground collapse during seismic events. On-site fault rupture, however, could potentially 'ntersect the tailings pile, and affect the backfill and the surface of the site.
No faults are mapped in the vicinity of the site, and DOE's site characterization did not result in discovery of unkncwn structures. Bedrock fractures observed near the disposal site, and in the region (Reference 9), appear to result from regional tectonic stress, but are not associated with crustal faults.
Differential movement along the fractures is not observed. Furthermore, the fractures are not observed intersecting Spook pit. Therefore, NRC staff finds there is reasonable assurance that seismic activity in the Spook region will not affect the remedial action.
TER/ SPOOK 1/89
- to -
2.5 Conclusions Based upon review of the preliminary final RAP, and supporting information for the Spook, Wyoming site, NRC staff has reasonable assurance that regional and site geological conditions have been characterized adequately to meet 40 CFR 192. While long-term arosion is likely to occur at the site, lar;dscape restoration and depth of burial will provide adequate erosion protection during the performance period of the remedial action.
O O
i TEft/ SPOOK 1/89 3.0 GE0 TECHNICAL STABILITY 3.1 Introduction 1his section presents llRC staff's review of the geotechnical engineering aspects of the proposed remedial actions at the Spook site. The review consists primarily of evaluations of site characterization and slope stability aspects of the stabilized tailings embankment and the cover design. The object of this review was to determine whether the proposed remedial actions would result in the stabilized embankment complying with the long-term stability requirementsoftheEPAstandardin40CFRPart192.02(a),SubpartA,fromthe perspective of slope stability, liquefaction and settlement.
The proposed remedial actions at the S)ook site involves two programs: (1)the DOE portion, dealing with cleanup of tie residual radioactive materials under the UMTRA Project; and (2) the State of Wyoming portion, dealing with reclamation of the abandoned mine wastes under tie AHL Program. Both DOE and State work will be performed concurrently, by a single subcontractor as both UMTRA and AML Program materials will be dispt, sed in the Spook pit.
In summary, to stabilize the tailings and the EPA standards, DOE's proposed remedial action involves placement and compaction of all contaminated materia's in a single pile within the south end of the Spook pit. This stabilized tailings pile will have a side slope of 50 percent and top slope of three to eight percent. The base of the stabilized pile will be nearly hexagonal and cover five acres inside the pit. The pile will have an average depth of about 32 feet with a maximum depth of 53 feet.
The tailings and contaminated materials will be covered with a 1.5-foot thick O
iow-Permeabiiity iaver to iahibit ief 41tratioa of water ia to aad throush the contaminated materials. The upper surface of the material will be crowned to promote positive drainage, thereby reducing infiltration. This tailings pile embankment with its cover is also referred to as a " disposal cell" in this TER, Prior to placing the tailings materials, the State will cover the entire bottom of the S)ook pit with a 3-foot thick leschhte reduction layer of sandy material (undert1eAMLProgram). Then the State will proceed with the reclamation of the pit, concurrent with the construction of t1e stabilized tailings pile. The reclamation / restoration will involve placing and com) acting stock)iled overburden material in the pit, filling the backfilled pit to tie level of t1e original surrounding ground surf ace. The backfill will average about 56 feet thick above the top of the tailings and will serve as a radon barrier for the tallings as well as eliminate the need for erosion protection rock. The pit, former mill yard, and windblown areas will be restored to original ground surface contours and revegetated under the AHL Program.
I TER/ SPOOK 1/89 NRC staff's review of the geotechnical aspects of the proposed remedial actions at the Spook pit focused on the DOE /UMTRA portion of the project and only relevant portions of the proposed AHL Program work that may affect the UMTRA program design.
3.2 Site Characterization Evaluation 3.2.1 Site Description 48 miles The Spook mill site and tailings pile are in Converse CountyIon 1 of this TER),
northeast of Casper, Wyoming. Figures 1.1 and 1.2 (see sect present the location and limits of the areas designated for remedial action under UNTRCA and reclamation under the AHL Program.
The tailings, which were originally dumped near the edge of the Spook pit have numerous erosion gullies. The eroding water has transported some of the tailings down along the east wall and into a portion of the pit bottom. The bottom of the pit is approximately 100 feet below the eastern edge of the pit.
The former mill area and the windblown contaminated area are relatively flat and are sparsely vegetated.
3.2.2 Site Investigations subsurface explorations at the site were performed by the following investigators.
1.
Mountain States Research and Development (11SRD) Program -- These investigations were conducted by Sergent, Hauskins & Beckwith in 1981.
They consisted of drilling 62 shallow borings in the tailings found on the edge of the pit and in the windblown contaminated area to determine the volume and radioactivity of the materials to be stabilized under the 0,t UMTRA Project.
2.
Jacobs Engineering Group, Inc., the Technical Assistance Contractor (TAC) for DOE -- This investigation, conducted in 1987, consisted of digging 20 test pits to determine the extent and volume of tailings and contaminated materials present on the eastern edge of the pit and at the bottom of the Spook pit, the proposed disposal site. Bulk samples of soil were obtained to perform the laboratory tests to determine their geotechnical properties.
3.
Morrison-KnudsenEngineers,Inc.,theRemedialActionContractor(RAC)for DOE -- This investigation, conducted in 1988, consisted of drilling 37 borings and digging 12 test pits to obtain additional confirmatory data on the site conditions and additional samples of various materials for laboratory tests to determine their geotechnical design parameters.
TER/ SPOOK 1/89 Information for Bidders, Volume I, (Leference 5) presents information on the geotechnical investigations such as '.ecation of borings and test pits, logs of borings and test pits, and laboratory test data on the soil samples obtained from the above investigations.
3.2.3 Site Stratigraphy
=
The general stratigraphy within the project limits consists of tailings occurring over insitu overburden material which in turn is underlain by bedrock. The tailings at this site are sandy tailings with of less than 20 percent passing the No. 200 sieve and can be classified as predominantly silty sands.
Q The stratigraphy adjoining the easter rim of the pit consists of tailings uederlain by a six-to nine-foot thic. iayer of sandy clays or clayey sands, which in turn overlies the sandstone bedrock. During the proposed remedial action, the tailings will 'e removed from this area and placed at the bottom of u
the pit. This area will be backfilled and graded to the original contours of the general area, under the AML Oroject. Water was not encountered either in the tailings or in the bedrock, within the depths of investigations.
The stratigraphy at the bottom of the pit, the proposed disposal sit, consi of residuals of milling and mining operations of the sandstone ore i j
occurring as overburden over the sandstone bedrock. This residual t erburden soil is a fine to medium sand witt. some silt and gravel. The depth of this residual soil is highly variable, ranging from five feet to more than 30 feet.
In some areas, cobbles to large boulder-sized rocks are ched with the sands.
Tne elevation of the sandstone bedrock surface within the Spook pit is irregular and varies more than 25 feet, due to the manner in which the pit was n.i nN.
The top of tne bf.drock varies from elevation 5C25 feet to 5000 feet, O
the lowest,,oint being at the northern end of the pit. The groundwater was encountered at an estimated elevation of 5005 feet, which is generally in the bedrock throughout most of the mine pit. This is approximately 15 feet below the proposed bottom elevation of the stabilized tailings plie. Section 5 of this report presents the groundwater conditions at the site. Figure 3.7 of the preliminary final rap (Refarence 2), presents the generalized stratigraphy and cross section of the Spook pit disposal site.
The.)w-permeability material proposed for the radon / infiltration barrier over the tailings pile is clayey silt cr silty clay from the nyerburden pile No.
700. This overburden pile also contains sand, material, and the stestig aphy is not simple and uniform. Therefore, the low permeability material to be used as the low-permeability material should be selectively ren:oved from this pile, as DOE nas indicated.
NRC staff has revietted the logs of the oorings ar.d test pits, as well as the scope of the geotechnical exploration progrw. The staff concludes that the execution of the geotechnical investigations, as documented on these logs,
TER/ SPOOK-1/89 are in keeping with accepted standards in the geotechnical engineering profession.
Further, the scope of the investigations, including tha number of borings and test pits, conducted at the Spook mill site is adequate to establish the stratigraphy and soil conditions as required to assess the geotechnical design aspects of the proposed stabilization of the tailings and i
contaminated material: in the Spook pit. The geotechnical explorations, conducted in connection with the characterization of the site, are in accordance with the applicable provisions of Chapter 2 of the SRP (Reference 1).
3.2.4 Testing Program
)
NRC staff reviewed the geotechnical engineering testing program for the Spook site. The testing program included physical properties tests, compaction tests, triaxial shear strength tests, and permeability tests on samples of O
ta414a93 other coata=$aated =ateriais aad==teriai iateaded for the radon / infiltration barrier.
The staff finds that the tests were conducted in accordance with the American Society for Testing Materials (ASTM) test procedures and that the design parameters were established using procedure 3 1
acceptable in the geotechnical engineering profe:sion. The staff finds that the testing program engloyed to define the material properties was appropriate for supporting the engineering analyses descrioed in the following sections.
I Furthermore, the scope of the testing program and utilization of the resulting data to define the material properties are consistent with the applicable provisions of the SRP (Reference 1).
3.3 Geotechnical Engineering Evaluation 3.3.1 Stability Evaluation The remedial action invcives the following activities:
1.
Preparing the subgrade at the bottou of the pit by removing and replacing unsuitable or low-density material not readily capable of in-place compaction, atj proof rolling the subgrade to ensure a minimum density of 90 percent standard proctor density (ASTM D698). The groundwater table will be a minimum of 15 feet below the bottom of this foundation; therefore, the tailings and the backfill material will be in an unsaturated condition.
2.
Placing a 3-foot thick leachate reduction layer of sandy material, compacted to a minimun density of 90 percent standard proctor density.
3.
Placing tailings and other contaminated materials in the proposed disposal cell area N a minimum density of 90 percent standard proctor density.
The AML Program opcration to backfill the pit will be carried out by the same subcontractor, so that the placement of the tailings, low-permeability cover over the tailings disposal cell, and backfill will be carried out rs
l l
TER/ SPOOK 1/89 concurrently (see section 3.4.1 for discussion on concurrent construction).
The backfill will result in an average overburden thickness of 56 feet above the torstopes of the tailings pile.
Thisconstructionsequence(placingthetailings,covermaterial,andAHL Program fill material concurrently in 12 inch liftc) will result in a minimal difference in height between the tailings and adjoining materials during construction (approximately a foot or so); therefore, the stability of the slopes of the tailings pile should not be a problem. NRC staff conclude that the tailings pile slopes will be stable during construction and a more detailed evaluation of the slope stability is not warranted.
In the long term, the
.taWngs pile will be buried within the AML Program backfill and, therefore, will not pose any slope stability problem. HRC staff concurs with DOE that bcth "he snort-term and long-term stability of the slopes cf the buried tail gs pile will not be a problem at this site, and does not warrant further
~
evaluation.
3.3.2 Liquefaction The tailings, contaminated material, and the backfill material will all be placed at a mininim of 90 percent standard proctor density and will be in an unsaturated condition. The groundwater table is at a minimum depth of 15 feet below the bottom of the tailings material. The disposal cell containing the tailings and contaminated material will be covered by the Am. Program backfill within the Spook pit. Because of the placement density, unsaturated condition, and physical confinement within the Spooh pit, the tailings and contaminated materials will not be susceptible to liquefaction during a seu mic event.
NRC staff concludes that the stabilized tailings and contaminated materials will not be susceptible to liquef action.
3.3.3 Settlement Lung-term settlement of the tailings and backfill materials, whic!. could result in either local depressions on top of the cover or cracks in the cover, is of concern. Depressions in the cover would initiate erosion gully psthways, and severe deep erosion of the cover might result in exposing tha tailings material.
A crack in the cover might open up a pathway for surface weter to infiltrate into or thrcugh the tailings material.
Since the tailings and most of the contaminated materials in the disposal cell are sandy materials, a major portion of the settlement will be instantaneous, taking place during const a ction, and can be cvmpensated for before completion of the construction. Therefore, instantaneous settlement should not have any deleterious affect on the performance of compacted fills-However, time dependent or delayed settlement may occur due to compression of the low-permcability cover layer and any virgin compression of the sandy materis1, as a result of a higher overburden pressure that preconsolidation stress. Because
l TER/ SPOOK 1/69 of this potential delayed aff,
the staff considered DOE's evaluation of the impact of time dependent settlem..t on the performance of the compacted fill.
DOE estimates that the total settlencnt may range between 14 to 16 inches, out of which eight inches of instantaneous settlement would take place during construction and only six to eight inches would show up as time dependent or delayed settlement.
NRC staff used conservative assumptions and independently evaluated the total settlement to be approximately 20 inches, out of which 12 inches of instantaneous settlement would take place during construction and eight inches would show up as time dependent or delayed settlement. The difference in the settlement valces that were calculated by EDE and NRC are within the normally acceptable range for two independent evaluations.
The parameters used in DOE's evaluations were determined by appropriate O
laboratory tests, and the method of evaluation used is accepted in the geotechnical engineering )rofession.
Because of the large areal extent and engineered placement of t1e tailings pile and cover, a delayed settlement of approximately six to eight inches would not be expected to result in a crack (caused by differential settlement in the cover), but would likely show up as a gradual depression in the cover. The surface of the cover will be graded to promote quick runoff of the surface water, and therefore, this minor depression would not be expected to significantly affect the surface water runoff pattern and initiate any significant erosion gullies. This aspect is addressed in detail in section 4 of this TER.
NRC staff concludes that the long-term or delayed settlement of the tailings pile will not result in any adverse effects on the ability of the tailings pile, stabilized under the UMTRCA program, to meet the EPA standards.
3.3.4 Cover Design The proposed cover for the tailings pile is a 1.5 feet thick layer of low-permeability.raterial, selectively taken from one of the overburden piles (pileNo.700). The cover material is a silty clay or clayey silt, which when compacted to a density of 95 percent standard proctor (ASTM D698) is expected to have a saturated hydraulic conductivity of 10E-6 cm/sec.
00E has performed laboratory tests on representative samples to demonstrate the achievability of the hydraulic conductivity assumed in the design.
In addition to the low-permeability material cover, the AHL Program will backfill the pit, placing overburden material on top of the tailings disposal cell. The average thickness of the AHL Program material on top of the tailings disposal cell will be approximately 56 feet. The AHL Program design calls for placing an approximately 10-foot thick layer of relatively more permeable material imediately above the low-permeability r.over on top of the tailings disposal cell. This is intended to promote a quick drainage of any infiltration, away from and down the slope of the cover. The AML Program esi for placing a 10-foot thick layer of relatively clean material (gn also ce'1s regarding the l
TER/ SPOOK 1/89 level of radioactive contamination) at the very top of the AML Program backfill. This cover is designed to limit the release of Radon-222 to the ettnosphere from the residual radioactive materials to within the EPA standards. The evaluation of the radon attenuation aspects of the cover is addressed in sucion 6.2, and the evaluation of the infiltration barrier aspects of the cover is addressed in section 4 of this TER.
3.4 Geotechnical Construction Criteria 3.4.1 v.structing the Low-Permeability Layer The low-permeability cover layer will be 1.5 feet thick and will be placed on the tailings disposal cell which will have a side slope of 50 percent (two O
horizontal to one vertical) and a top slope of four to eight percent. The disposal cell will be surrounded by end buried in the AML Prograc backfill.
The contract documents state that both the UMTRA Project and AHL Program work will be constructed by a single subcontractor. The compaction requirement for the cover is 35 percent standard proctor, whereas the recuirements for the tailings and AML Program backfill are 90 percent standarc proctor.
Placing a thin layer (cover layer) between two different materials and maintaining a 50 percent vertical slope for the thin layer will require special care during construction. The NRC considers this low-permeability layer to be a critical component of the cover and emphasizes the need for DOE /RAC to take appropriate measures to ensure compliance with the minimum thickness assumed in Me design and compaction requirements specified in the contract. The suggesteo construction sequence on Drawing SPK-PS-10-0109 (Reference 4) is acceptable to the staff, provided the required minimum thickness o
% low-permeability cover layer is maintained.
NRC staff notes that the e ave suggested construction detail wculd require more low-permeability material than that calculated for a unifcrmly thick (1.5 feet) layer covering the disposal O
cell. While this is not a concurrence issue for NRC, the aifect this may have on the pay.nent quantity in the cuntract should be considered b.y DOE.
3.4.2 Placement of AHL Bcckfill Above the Tailings Disposai Cell The backfill above the tailings disposal cell will be placed under the AML Program by the same subcontrartor working on the UMTRA Project portion of.
the work. Since DOE is responsible for assuring that the UMTRA Project portion of the project complit; with the EPA standards, DOE should also assure that the material placed above the tailings disposal cell will not adversely affect the ability of the disposal cell to meet the EPA standards.
In response to a question (question No. 26; Reference 7) on this item posed by HRC staff, DOE agreed to ensure that the backfill would be placed according to specifications that are similar to that of DOE's.
The specifications in the preliminary final RAP regarding the placemen~ of c
backfill material appear to be adequate.
However, while the frequency of testing to be performed during placement is specified in the Quality Assurance 4
TER/ SPOOK 1/89 3 discussion (section 1.6.B.5) of the AML Program Specification on Earthwork (Section 2200A), the staff consider that it should also be included or referenced in the discussion on Field Quality Assurance (section 3.6). The frequency of testing and other provisions needed to ensure that the backfill is placed according to the specifications should also be provided in the RemedialActionInspectionPlan(RAIP)forthissite.
3.5 Conclusions Based on review af the design for the Spook site project, as presented in the remedial action plan documents (References 2, 4, 5 and 6), NRC staff concludes that the geatechnical engineering aspects of site characterization and design are consistent with the applicable provisions of the SRP, and that the design O
. should result in the stabilized disposal cell complying with the geotechnical aspects of the long-term stability requirements of the EPA standard (40 CFR Part192.02(a)). Our conclusion is predicated on the expectation that DOE will take appropriate measures (including necessary inspectior: and testing during construction) to ensure that the low-permeability cover will be constructed with a minimum thickness of 1.5 feet, and that the backfill will be placed unoer the AML Program according to specificaticns similar to those of DOE's.
O
L i
+
- TER/SP0OK 1/89 e
29'-
I 1
i 3
4.0 i
SURFACE WATER HYDROLOGY AND EROSION PROTECTION-l i
4 4.1 _ Introduction This section_ presents HRC. staff's review of the surface water hydrology and erosion protection aspects of the proposed remedial _ actions for the Spook,-
Wyoming UMTRA Project site. -These aspects of the review were minimal, due to i-the unique below grade design proposed for stabilization of the residual radioactive' material at this site. Any below grade design, where-the tailings i
.are stabilized well below the natural ground surface, would generally result j
in an extremely stable configuration.
t 4.2
&drologic Description and Site Conceptual Design
!:O:
The site is iocated near the head of an unnamed draina9 chennai which dr
~ to'the Dry Fork of the Cheyenne River.
s Surface runoff in the inmediate.
i vicinity of-the pit is either intercepted by the pit itself or by-several i
adjacent ephemeral: stream channels. The channels of-three such streams are blocked by-stockpiled materials, and one of the streams flowed through the northeast portion of the pit area before disturbed by mining. The land surface adjacent-to the Spook pit is moderately sloped.
In order to stabilize the tailings in-accc. dance with EPA standards, all of the contaminated materials will be.placed in a single pile in the south end of the Spook pit.
The pile will then be covered with backfill material in accordance with the AML Program which provides an average of 56 feet of overburden b
material directly ove,r the tailings in the pit. 'The channel.of the-ephemeral
- stream in the northeast area of the pit will be restored to flow directly over
-the backfilled material in the northeast portion of.the pit.
This channel will be located a sufficient distance away from the tailings, in the southeta
_ Q end of the pit the stability of-the tailings pile., so that any erosion in the channel should have no 4.3 Flooding'and Water Surface Profiles n
I. order to determine site impacts fror flooding the State evaluated peak-r flows and velocities, including the need for eros, ion protection designs.
Since the decign events were developed in accordance with the AML Program, they do not_ necessarily conform to previously-approved criteria at other UMTRA e
-Program sites.
However, for reasons explained below, site-stability should be assured due to the placement cf the tailings in' a pit with 56 feet of overburden placed:over the tailings; therefore, site stability is not dependent on the.use e
}
of? specific erosion protection designs..
! Flooding estimates, based on a frequency of occurrence of the oesign rai f ll of once in 1000 years, were used by the State to design various erosion na
{
protection 1 features _ at the site. Based on our review of the _ rainfall 4
)
p-
=
1 TER/ SPOOK 1/P9 estimates, infiltration losses, times of concentration, rainfall distributions, and flood computations, we conclude that the flood estimates may not be reasonable estimates of the 1000 year flood event. The rainfall estimate was developed by extrapolation of limited rainfall data, and we conclude such extrapolations are generally not appropriate to estimate such rare events.
For the purposes of this tailings configuration (which is below grade), the magnitude of the rainfall or flood event should not affect the stability of the tailings.
NRC staff emphasizes that there are no credible flood events or series of flood events at this site which should effect the physical stability of the tailings in a 1000-year period. First, the tailings will be stabilized below grade in the Spook pit and covered with an average of 56 feet of overburden.
(^)
As indicated in the staff's review of geomorphic stability (see section 2.4.2 of this TER), it is not reasonable for 56 feat of erosion to occur in 1000 v
years or less. Second, even if erosion were to occur directly over the tailings, the tallings would continue to remain in the pit, due to the physical configuration of the pit. Under such conditions where erosion of the overburden material occurs, it is likely that the eroded area would eventually become a depositional area (low point).
With the above factors in mind, HRC staff did not perform a detailed review of the design as relates to erosion protection. Even if proper consideration has not been given by DOE to expected flood events and erosional processes in a 1000-year period, the stability of the tailings is assured by their location in the pit. Some erosion at the ground surface is to be expacted and could even occur h ectly over the tailings or in adjacent channels and watercourses.
However, such erosion will be minimai and should not c; tend to e depth of 56 feet.
O 4.4 Conclusions Based on our review of the information submitted by DOE, NRC staff concludes that the site design will meet EPA requirements as stated in 40 CFR Part 192 wit'.; regard to long term erosion protection and stability. An adequate design has been provided to reasonably assure stability of the tailings at Spook for a period of up to 1000 years.
L TER/ SPOOK 1/89 5.0 Water Resources Protection 5.1 Introduction The NRC staff has reviewed the preliminary final Renedial Action Plan and Site Conceptual Design (KAP) for the Spook, Wyoming UMTRA site for compliance with EPA's proposed groundwater protection standards in 40 CFR Part 192, Subparts A-C (?? FR 36000). The NRC staff used the NRC Draft Technical Position on Information Needs to Demonstrate Compliance with EPA's Groundwater Protection Standards in 40 CFR Part 192 Subparts A-C (Reference 12) as guidance for the review.
CQ The renedial action plan for the Spook site consists of a joint effort between the DOE and the State of Wyoming AML Program to stabilize all residua' radioactive material on site and reclaim the abandoned open pit uranium mine.
The DOE portion of the joint remedial action consists of stabilization of approximately 243,385 cubic yards of residual radioactive material in a single pile in the bottom of the pit, and placement of a low permeability cover over G6 feet (1.6 million cubic yards) gram will backfill the pit with approximately the stabilized pile. The AML Pro of overburcea material excavated from the pit during mining, and will recontour the land sucface and revegetate the final Cover.
DOE has proposed application of supplemental standards under the provisions of 40 CFR Part 192 Subpart C for groundwater protection because the aquifer contains Class III ground water. Based on our review, NRC staff considers that COE has provided adequate information to demonstrate that supplemental startards are apnlicable at the Spook site, and that the proposed remedial action Complies dith the site-specific supplemental standards. We also mU consider that DOE has adequately justified that the proposed supplemental standards are protective of human health and the environment and demonstrated that the proposed remedial action comes as close to meeting the otherwise applicable standards as is reasonable under the circumstances.
The findings and conclusions documented by NRC staff in the following paragraahs apply only to the Spook UMTRA site and should not be construed as applicable for any other UMTRA site.
5.2 Hydrogeologic Characterization 5.2.1 Hydrostratigraphy and Groundwater Occurrence NRC considers that DOE has charact(rized the hydrogeologic characteristics in the vicinity of the disposal site using acceptable techniques, methods and approaches, and the assessment of hydrogeologic characteristics is aiecuate to support DOE's performance assessment to denonstrate compliance with the proposed supplemental standards.
l l
TER/SP0OK 1/89 Based on DOE's hydrogeologic characterization activities, DOE determined that ground water below the Spook site occurs in two sandstone units within the Tertiary Wasatch Formation. Ground water is unconfined in the uppermost unit and confined in the lower sandstone unit. The sandstone aquifers are separated by a thick, intera11y extensive, silty shale unit. Based on inspection of cores frem lithologic logs, results of water quality analysis, ar.d inferred gradients, the shale unit appears to serve as an aquitard, effectively precluding hydraulic connunication between the two sandstone units.
Uppermost Aquifer Based on lithologic logs from borings and monitor wells, the uppermost aquifer unit consists of fine to coarse-grained sandstone containing silty shale lenses.
O The average thickness of the uppermost unit is approximately 110 feet. Depths to the water table range from 40 to 120 feet from the land surface, and approxit.ately 20 feet below the excavated pit.
DOE observed seasonal fluctuations in ground water elevations of less than one foot in wells measured over a 1.5 year period. The observed saturated thickness of the aquifer is approximately 20 feet in the vicinity of the site.
Based on measured ground water elevations in 27 wells screened in the uppec sandstone unit DOE constructed potentiometric surface maps to determine the direction and rate of flow. Examination of the potentiometric surface indicates that the predominant direction of groundwater flow is to the northeast under an average hydraulic gradient of 0.005. The gradient steepens to the northeast of the site, and a southeast compor.ent of flow under a very steep gradient is observed to the south of the site, based on data from two wells.
DOE conducted pump tests in two wells located in the bottom of the pit and east of the pit to determine aquifer properties and evaluate hydre gic boundary s
conditions. DOE estinated the average hydraulic conductivit,r to be approximately 15 ft/ day. Using Darcy's Law, and assuming an average effective porosity of 0.20 for a porous medium, DOE calculated an average linear groundwater velocity of 0.38 ft/ day. This velocity is consistent with the observed migration rate of the contaminant plume emanating from the tailings pile over the past 25 years.
DOE indicates that ground water in the uppermost aquifer is recharged by groundwater underflow, infiltration, and seepage from intermittent streams, and groundwater discharge occurs as groundwater underflow. DOE indicates that groundwater discharge to the land surface or nearby surface water bodies has not been observed within a two mile radius of the site, which was the extent of IDOE'ssurvey.
This contention is based on DOE's field observations, and conversations with local ranchers. Although NRC staff visited the Spook site during the cry season in October,1988, no groundwater discharge was observed at the surface or along stream channels of the Dry Fork of the Cheyenne River.
DOE also indicates that projection of the potentiometric surface of the upper
TER/SP0OK 1/89 sandstone unit would indicate that the elevation of the water table is below the surface elevation of drainages in the site vicinity.
FRC staff considers that the lack of evidence of groundwater discharge in the site vicinity supports D0t's contention that there is a low probability that humans or the environment will be exposed to hazardous constituents from the disposal unit.
Middle Shale Unit DOE has determined that the eiddle shale unit is composed of well consolidated silty shale and shale, and ranges in thickness from 40 feet in the site vicinity to greater than 150 feet thick in the downgradient direction of the site. DOE indicates that this unit is saturated and functions as an aquitard.
Q l.ower Sandstone Aquifer Based on lithologic logs, DOE has determined that the lower sandstone unit consists of moderately cemented fine to coarse grained sandstone. Based on borings and hydraulic head measurements from six monitor wells, DOE has characterized the lower sandstone unit as a confined aquifar, occurring in excess of 160 feet below the surface near the site. The potentiometric surface ranges between 60 to 140 feet below the unexcavated land surface.
DOE constructed potentiometric maps based on water level measurements from the six wells screened in the lower unit to determine groundwater flow directions and gradients. Exainination of the maps reveals a groundwater flow direction predominately to the southeast, under a hydraulic gradient of 0.01.
5.2.2 Geochemical Conditions and Water Use n
Uppermost Aquifer y
Band on results of water quality analyses from up-and down-gradient wells in the uppermost aquifer, DOE has determined that ambient concentrations of selenium and uranium are highly variable, and tend to incresce downgradient of the Spook pit. DOE contends that the observed variability in ambient ground water is due to the presence of a zone of uranium mineralization underlying the Spook site. COE concludes that downgradient concentrations of uranium and selenium are elevated because ground water has passed through the zone of highest grade ore, and uranium and selenium have become mobilized due to the presence of oxidizing conditions. 1he observed oxidizing conditions downgracient of the site are likely due to the introduction of water during closely spaced exploration drilling done adjacent to the pit, and mining act'.vities within the Spook pit and Loma pit to the northeast.
A total of six downgradient monitor wells and two upgradient wells were used to exmine the variability of ambient water quality. Downgradient background wells were selected using the extent of observed nitrate cont. amination as a tracer to define the extent of tailings related contamination. Representative background wells located outside the contaminant plume include wells 931, 933,
TER/ SPOOK 1/89 934, 943, 944, 922 and 939. Downgradient uranium concertrations range from 0.97 to 2.9 mg/1, which is 22 to 06 times the proposed EPA Maximum Concentration Level (MCL) of 0.044 mg/1, and the downgradient selenium concentrations range from 0.05 to 0.83 mg/1, which is from 5 to 83 times the EPA MCL of 3.01 mg/1.
Upgradient ambient uranium concentrations range from 0.11 to 0.15 mg/1, which is 3 times the EPA proposed MCL, and upgradient selenium concentrations range from 0.03 to 0.18 mg/1, or 3 to 18 times the EPA Mr.L.
Based on an inventory of groundwater use within a two mile radius of the Spook site, groundwater in the uppermost aquifer is not used as a ource of drinking water or for any other purpose due the natural poor water quality.
Middle Shale Unit O
sased on a sie,le downgraoient,eli screened 3a feet beiow tne base of the uppersandstone unit, observed background concentrations are below the EPA MCLs for all constituents.
Lower Sandstone Aquifer 00E selected two upgradient wells to determine background rater quality.
Analyses of the samples showed that the average background concentrations for all con;tituents were below the proposed EPA MCLs.
In general, water quality isgood,withonaverageTotalDisolvedSolids(TDs)concentrationof450mg/1.
The lower aquifer does not appear to have been affected by the uranium roll front deposit or by the existing contaminant plume.
Based on the well inventory conducted withi a two mile racius of the site, as many as eleven wells exist in the site vic'....ty which obtain water from the 1swer sandstone aquifer or deeper units. The wells are used for both stock O
water'ng and domestic purposes. Several of these weils are flowing artesian wells. Based on a conversation between DOE and the Converse County Planning Commissioner, future demand for water supplies are not expected to increase because of the lack of anticinated development (Reference 2).
5.2.3 Extent of Contamination Based on existing characterization information, the extent of downgradient contamination caused by seepage of leachate is confined to the uppermost aquifer. The contaminant plume extends approximately 4000 feet downgradient and is approximately 2500 feet wide. Elevated concentrations of selenium, uranium, nitrate, chromium, and radium-226/228 have been observed in the plume.
5.2.4 Tailings Characterization DOE estimated existing source concentrations in tailings materials from a pore water sample and a batch leach test run on a composite tailings solid sample.
l
i
'l TER/ SPOOK 1/89 L
Measured source concentrations for hazardous constituents for each method are-presented-in Table 5.1.
Table 5.1 Constituent Pore Water Sample Leach Test Concentrations (mg/1)
Results(mg/1)
- 3. 5t.
6.3 Nitrate 470.0 64.0 a -
-Based on NRC staff review, DOE's characterization of the source term is incompiete because it did nct attempt to characterize the solid phases of the tailings, or the source concentrations in the tallings for radium-226/228 and chromium, concentrations for which are elevated in the contaminant plume.
i However, because there is a low probability that humans or the eavironment wouldbeexposedtocontaminatedgroundwater(seesections5.4.1.1and5.5)
NRC staff considers that DOE's characterization of source concentrations in
.L the tailings is adequate.
5.3 Conceptual Design Features For Water Resources Protection i-In accordance with draft 40 CFR Part 192.01(a)(3), DOE has specified the features of the disposal unit design needed for groundwater protection, which r
include:
a) placement of a contoured cover to promote sheet flow off the pile; b) revegetating the p4le surface to promote evapotranspiration; c' placement of a leachate reduction layer over the pit bottom to enhance retardation of tailings constituents, d) placement of the tailings at zero to three percent
.O dry of optimum conditions and limiting amount of water used for dust control; e) placement of a 1.5 foot clay cap over tailings having a hydraulic conductivity of 1 E-6 to 1 E.7 cm/s; f) placement of 56 feet of compacted overburden material over the tailings. 00E has also demonstrated that the b
design does not rely on active maintenance to assure acceptable performance, as discussed in section 5.4.2 of the draft TER, closure Performance Standard.
5.4 Disposal and Control of Residual Radioactive Material-5. 4.1-Groundwater Protection Standard Under Title'I of the Uranium Mill Tailin'gs Radiation Control Act of 1978, as amended, EPA's proposed groundwater protection standards in. 40 CFR Part 192
~
Subparts A and C requires that-disposal units be designed to control residuel radioactive material'in conformance with site-specific groundwater protectica standards. EPA's proposed strndards in Subpart C of 40 CFR Part 192 include provisions for supplemental. standards as an exemption from the primary standards in.Subpart A in special cases where compliance with the primary standard is not necessary to protect human health and the environment.
e
&e,-m m
-.--- s-e
1 7
h TER/SP0OK 1/89,
DOE may propose implementation of applemental standards for groundwater i
protection if it determines that any of the criteria in 40 CFR Part 192.21 a> ply.
In order to propose supplemental standards, DOE should: 1) demonstrate t1at supplemental standards are applicable using the criteria in 40 CFR Part 192.21;2) specify the supplemental standards that it proposes in lieu of the primary standard in Subpart A; 3) demonstrate that the proposed remedial action complies with the proposed supplemental standards; and 4) demonstrate that the proposed remedial action comes as close to oceting(Reference 12).the otherwise applic F
standard as is reasonable under the circumstances 5.4.1.1.
Applicability of Supplemental Standards C
DOE has proposed application of supplemental standards for the Spook, Wyoming i
-UMTRA site in lieu of the primary standard based on the " Class III"
~
applicability criterion in EPA's proposed standards in 40 CFk Part 192.21(g).
]
As defined in the standards, Class III ground water is not a current or potential-source of drinking water because of any of three reasons, including widespread, ambient contamination not due to activities involving residual radioactive materials from a designated processing site that cannot be cleaned up using treatment methods reasonably employed in public water supply systems 1
(40-CFR Part 192.11(e)). DOE determined that the upper sandstora of the Wasatch Formation beneath the site contains Class III ground water because of widespread i
contamination associated with naturally-occurring uranium mineralization and extensive uranium miM ng activities.
DOE's determination is based on the following:
1)
Representative background concentrations of selenium and urenium range s)aticily from 0.05 to 0.83 mg/l and 0.97 to 2.90 mg/1, respectively.
- n T1ese background levels exceed their respective MCLs by as much as 5 to 83
(.) -
tires and 22 to 66 times, respectively.
2)
The elevated level: of selenium and uranium were caused by natural water-rock intaractions and mining activities, rather than activi involving residual radioactive matericls at the Spock site. The et ted
+
concentrations exist upgradient from the Spook site and in other areas of the uppermost aquifer that have not been impacted by seepage from the Spock uranium tailings.
3)
Background concentrations of selenium and uranium in groundwater in the upper sandstone of the Wasatch Formation cannot be cleanad ro using treatment methods reasonably employed in public water-suppt systems.
' 4)~
Groun:1 water in-the uppermost aquifer satisfies the Class VI definition in the, Wyoming State Groundwater Quality Regulations (Reference 13) based on the elevated corcentration of selenium.-
J '
4 4
TER/ SPOOK 1/89 -
NRL staff independently verified the Class III groundater designation using the-EPA classification methodology in Reference 14 and the proposed definition in 40 CFR Part 192. The staff determined that the upper sandstone unit of the Wasatch Fovmatics contains Class IIIB ground water based on the following conclusions:
1)-
Background concentrations of selanium and uranium in ground water in the uppermost aquifer exceed EPA's hJ for selenium in 40 CFR Part 141 and proposed concentr6 tion limit for uianium in 40 CFR Part 192. Treatment of the ground water would be necessary prior to distribution to public consumers.
2)
Ground water in the uppermost aquifer cannot be cleaned up using treatment h
methods reasonably employed in public water-supply systems. Treatment methods such as desalination, ozonation, ion exchange, and chemical precipitation and filtration are used to some extent in EPA's Region VIII, whichincludesWyoming(Reference 14). However, use of these treatment methods in public water supply systems near the Spook site would not be economically viable because it would cost consumers more than the
$300/ household / year ($1986) economic viability threshold estimated by EPA in Reference 14.
3)
The uppermost aquifer is boundLd below by a Type 2 boundary beneath because it is underlain by a laterally-extensive, low-permeability, thick, silty shale unit. The hydraulic gradient across this confining unit is directed upwards towards the uppermost 3quifer.
In addition, the aquifer does not discharge to surface water within the 2-mile classification review-area-arouna the Spock site. Therefore, the uppermost aquifer has a low degree of-interconnection with adjacent ground water and surface water ~
units.
4)
Elevated background concentrations of selenium and uranium have been caused by natural leaching of mineralized deposits in the aquifer and by induced leaching caused by mining exploration and excavation, rather than activities involving the residua ra9aactive materials at the Spook site.
Therefore, the NRC staff concludes that DOE is eligible to apply for supplemental standards in-lieu of the primary standards in Subpart A of 40 CFR Part 192 because~the upper sandstone of the Wasatch Formation at the Spook, Wyoming, UMTRA site;contains Class IIIB ground water.
5.4.1.2 Proposed Supplemental Standards In lieu of'the otherwise applicable standards for the Spook site, 00E indicates that for the proposed supplemental standards, the remedial action will ensure that concentrations of hazardous constituents released downgradient from the
- disposal facility will;not exceed concentrations which would adversely affect
= human health or the environment.
i TER/SP0OK 1/89 NRC staff considers DOE's prnposed supplemental standards for the Spook site to be acceptable and adequate to protect public health and the environment.
' 4.1.3 Compliance Demonstration in accordance with 40 CFR Part 192 Subparts A and C, DOE is required to demonstrate thtt the overall performance nf the proposed disposal unit and disposal unit cesign is adequate to comply with the site-specific groundwater protection standard discussed in section 5.4.1.2, above. The demonstration should consist of an integrated analysis of the performance of the natural and engineered features of the disposal site, and include the following components:
1)anassessmentofthehydrogeologiccharacteristicsofthedisposalsite sufficient to supp rt analysis of the disposal unit designs and disposal
_O performance (sectkn 5.2); 2) a design analysis of the disposal unit (section U
5.3); and 3) a periormance assessment of the disposal unit (Reference 13).
Performance Assessment In support of demonstrating that the proposed remedial action complies with the proposed site-specific supplemental stendards, DOE estimated concentrations of h zardous constituents in ground water for various rates of infiltration through the low permeability layer above the tailings. The P.0C groundwater tr*.nsport uudel developed by Konikow and Bredehoeft was used to estimate the effects of dilution and dispersion on source concentrations leaching from the stabilized pile at.various rates of infiltration ranging from 1 E-8 cm/s to 6 E-8 cm/s.
Regional values of infiltration estimated from climatological data and water budget studies are on the order of 6 E-8 cm/s. Based on the regional estimate of infiltration, and the contoured cover designed to enhance surface runoff, DOE assumed a site-specific infiltration rate of 3 E-8 cm/s to be realistic in O
its Performaace anaissis, and a va1ue of 6 E-8 cm/s to be a worst-ca:e situation. Assuming these values are representative of site-specific conditions at the Spook design, seepage from the stabilized tailings would not significantly increase concentrations of uranium and selenium above observed background levels. The predicted concentration for nitrate for the lower rate is below the MCL of 44 mg/l at the base of the pile, and below the MCL at an arbitrary distance of 4000 feet downgradient of the pile for the higher rate of 6 E-8 cm/s. These results indicate that concentrations contributad from the disposal cell cc.iply with the proposed supplemental standard.
However, NRC staff considers that DOE has not provided adequate justification for use of regional estimates (6 E-8 cm/s) and even lower values (3 E-8 cm/s) of infiltration in its analysis because the disposal cell represents a disturbed environment relative to regional conditions. NRC staff considers that worst-case value for infiltration would be on the order of 1 E-6 cm/s, which is the higher value of saturated hydraulic conductivity of the clay cover over the tailings under a unit gradient, rather than the regional recharge value of 6 E-8 cm/s. Because DOE's estimates of infiltration are not supported by site specific data or a quantitative analysis, a justifiably conservative value to assume for infiltration would be more on the order of 1 E-7 cm/s.
i TER/ SPOOK 1/89 While HRC staff considers that DOE did not use defensible infiitration values to demonstrate compliance with the proposed supplemental standards, results of independent sthff calculations based on an Infiltration rate of '. E-7 cm/s indicate that aredicted concentrations of selenium and uranium are still within the range of o) served background values, and concentrations for nitrate are less than 2.5 times the MCL at the pile base.
Because the probability of exposure of contaminated water to human: or the environment is low, these concentrations are ac:eptable and protective of human health and the environment. Thus NRC staff considers that DOE's proposed reinedial action for groundwater protection complies with the proposed supplemental standards.
5.4.2 Closure Performance Standard In accordance with the closure performance standard of 40 CFR Part
\\
192.02(a)(4), 00E is required to demonstrate that the proposed disposal design:
- 1) minimizes the need for further maintenance as required in 40 CFR Part 264.111(a); and 2) controls, minimizes, or eliminates releases of hazardous constituents to ground water as required in 40 CFR Part 264.111(b).
Relative to 40 CFR Part 264.111(a), DOE has adequately demonstrated compliance with the long term stability standards in 40 CFR Part 192.02(a), as described in sections 2.0, 3.0, and 4.0 of this draft TER. Further, DOE has demonstrated that the design features needed to comply with the site-specific groundwater protection standard do not rely on active maintenance tn ensure satisfactory performance. The barriers are composed of earthern materials that are likely to remain stable and maintain their integrity during the 1000 year design life see section 4).
In addition, if an increase in available infiltration occurs, the potential increase in seepage f rc:a the disposal unit would not adversely affect human health or the environment because the probability of human or environmental exposure to ground water is low. NRC considers that DOE has O
demoastrated that the aeed for further maiateaance of the disPosa1 site has been minimized.
Relative to 40 CFR Part 264.111(b), DOE has adequately demonstrateo com)11ance with the proposed supplemental standards (section 5.4.1.3).
Thus, DOE 1as demonstrated that the proposed design controls and minimizes release of hazarrious constituents to groundwater to the extent necessary to protect human health and the environment.
5.4.3 Groundwater Monitoring and Corrective Action DOE is required to describe an integrated monitoring program to be conducted before during and after completion of the dis]osal action to demonstrate that the initial disposal performance coinplies wit 1 the groundwater protection and closure performance standards under 40 CFR Parts 192.02(a)(3) and (4).
NRC staff considers that DOE has adequately fulfilled the preoperational monitoring requirements of the proposed EPA groundwater protection standards.
s i
TER/SP0OK_1/89-40 -
l 4
Houevep,-DOE has proposed not to monitor the performance of the disposal unit st the Spook sitt due to unique s.le and situation specific characteristics.
DOE' contends that monitoring the ground water would be pointless because of the the low probability of human and environmental exposure to contaminated ground water, and because contaminant leachate. concentrations approximate background concentrations. NRC staff finds that DOE's proposal to not monitor ground water at the Spock site is acceptable given the unique t
[
site conditions at the Spook site.
2 Because of the low probability of exposure, credible failure scenarios of the dis p sal unit have little significance with respect to protection of human
-health and the environment. Therefore, NRC considers no corrective actions L
_need to be planned at this time. However,-if conditions at the site change
!-~
significantly such that exposure becomes significantly more likely, then
. monitoring and corrective actions may be needed. The need for such action will be evaluated from time to time under the NRC custodial license, i
5.5 Demonstration of "As Close as is Reasonable" DOE has proposed supplemental standards in lieu of the primary groundwater protectionstandardinSubpartAin40CFR192.02(a)(3).
Based on information-provided in the preliminary final RAP and a telephone conversation between L. Deering, NRC, and R. Heidenberg, DOE / TAC on January 4,1989, DOE has indicated that the otherwise applicable standard would be the site-specific grounowater protection standard in 40 CFR 192.02(a)(3), which would identify
-uranium,' selenium, and nitrate as hazardous' constituents. The concentration limits would be downgradient background concentratirn limits for uranium and selenium, and an MCL for nitrate.
Appropriate background concentrations would 7
be selected from the range of observed downgradient background concentrations for uranium and selenium, which range from C.97 to 2.9 mg/1, 0.05 to 0.83 mg/1,respectively. The proposed point of compliance would be the downgradient
{
edge of the disposal cell.-
NRC staff considers that:for the otherwise applicable stand.ards, DOE sh~
include as hazardou'. constituents the fif teen constituents that were de.. 6ed 1
-in seventeen tailings ponds. sampled by the NRC URF0 staff, which are listed in Table 5.2.
These constituents are reasonably expected to be in the tailings and are listed in Appendix VIII of 40.CFR part 264.
, Table 5.2 Arsenic Cadmium-Fluoride Molybdenum Selenium BariumL Chromium Lead Nickel-Thorium-Berylliur Cyanide Mercury Radium Uranium a
l TER/ SPOOK 1/89 00E indicates that the proposed remedial action at the site comes reasonably close to meeting the otherwise applicable standard because:
1)
Predicted concentrations of bazardous constituents approximate observed background concentrations for uranium and selenium, and are less than 2.5 times higher than the Nitrate MCL at the base of the pile. The pradicted nitrate concentration is justifiably higher than the MCL considering that a) predicted nitrate concentrations are conservative, b) the ambient water quality is unfit for use, and 3) the probability of exposure is very low because there are no known discharge locations in the site vicinity.
2)
Alternative supplies of good quality water are readily available from deeper aquifers.
O 3)
Irrigation of crops as a potential exposure pathway is not likely because the land surrour. ding the Spook sito vicinity is used for Range land.
4)
Considering that the probability of exposure of contaminated groundwater to humans or the environment is low, DOE's low permeability cover placed over the tailings is a conservative design feature to ensure that concentrations are as low as is achievable under the circumstances.
5)
Hitrate concentrations in groundwater iN1d be reduced further by employing more costly, alternative designs, such as the use of a CLAYMAX cover aver the tailings; however, considering the low probability of exposure to contaminated groundwater, alternative designs such as a CLAYMAX cover would increase project costs without contributing any significant additional benefits.
q Based o1 the information arovided by DOE, KRC staff considers that DOE hcs V
adequately demonstrated tiat the proposed design comes as close to meeting the otherwise applicable standard under the circumstances.
5.6 Cleanup and Control of Existing Contamination DOE is required to demonstrate complier.ce with proposed EPA standards in+40 CFR Part 192, Subparts B and C for cleanup and control of existing contaminaticn.
DOE's cleanup evaluation should consist of a 1) groundwater cleanup standaru,
- 2) cleanup demonstration, and 3) cleanup monitoring program (Reference 12).
NRC may allow deferral of cleanup if DOE demonstrates that the disposal may proceed independently of cleanup.
DOE has not addressed in the RAF how groundwater cleanup will comply with EPA requirements in Subparts B and C of 40 CFR Part 192 because the present level of site characterization is not sufficient to address groundwater cleanup. DOE indicates that aquifer restoration will be addressed under the next task of the UMTRA Project as part of a separate National Environmenti.i Policy Act (?! EPA) process because of additional characterization needs.
i TER/ SPOOK 1/89 00E indicates in the RAP that construction of the proposed disposal unit will not preclude or preempt future evaluation and implementation of groundwater cleanup or control activities because the limited size of the pile footprint.
Perimeter drilling for restoration will allow for a radius of influence to exceed the pile's radius, thereby allowing pumping of the aquiftr under the pile, without causing significant disturbance of the pile.
NRC staff considers that DOE's deferral of groundwater cleanup is acceptable until after EPA promulgates final groundwater protection standards. This finding is based on the fact that the existing contaminant plume is slow moving; there is a low probability of exposure to existing contaminated watcr because the water in the affected aquifer is not used for any purpose, there are no known nearby ground *:ater discharge locations, and the area is sparsely D
populated; exposure to contaminated water would present a chronic rather than an acute hazard; and DOE and the state of Wyoming could implement temporary institutional controls of the affected portion of the =quifer.
NRC staff considers that DOE's deferral o' corrective action for existing contamination is an open issue until DOE addresses cleanup after promulgation of EPA's finh1 groundwater prntectica standards.
5.7 Conclusions In conclusion, DOE has proposed application of supplemental standards under the provisions of 40 CFR Part 192 Subpart C for groundwater protection because the aquifer contains Class III groundwater. Based on our review, NRC staff considers that DOE has provided adequate information to demonstrate that supplemental standards are a pplicable at the Spook site, and that the proposed remedial action cosplies wit 1 the site-specific supplemental standards. We also consider that DOE has edequately justified that the proposed supplemental y
standards are protective of human health and the environment, and demonstrated that the proposed remeial action comes as close to meeting the otherwise applicable standard as is reasonable under the circumstances.
t i=
' TER/ SPOOK 1/89'
_. 43 -
i 4
6.0 RADON ATTENUATION AND S011 CLEANUP l
6.1 Introduction l
This section of tha TER documents the staff evaluation of the radon attenuation 1
design and the radittion survey plan for. tho >1anned remedial actions at the
- Spooh, Wyoming UMTRAP site. The results of tiis review consist primarily of
'a evalut.tions of the material characterization, radon barrier design, and soil cleanup aspects of the proposed remedial action, to assure compliance with the applicable EPA standards.
[
6.2 Radon Attenuation U
The. staff's review of the cover design for radon attenuation included
.O evaiuation of the Pertinent desisn Parameters for both the taiiinss and the radon barrier soils, and the calculations of the radon barrier (earth cover)
{
thickness:(References 2,5,6,and15).
The design parameters of the tailings and earth materials that were evaluated for acceptability included: long-term moisture content, material layer thickness, bulk density, specific gravity, porosity, and radon diffusion i
coefficient.
In addition, radium content and radon emanation coefficient j
parameters were evalcated for the tailings materials only. These parameters were used in calcuht %g the radon barrier thickness using the' RAECOM computer code.
6.1.1 Evaluation of Parameters i
To meet the EPA standards-for limiting release of Radon-222 from residual radioactive materials to the atmosphere, the disposal cell containing tailings and contaminated materials will be covered with an earthen material
, radon barrier). The radon barrier reduces the effluence of Ra-222 by reducing the 4
diffusion rate to acceptable quantitias, as per the-EPA standards. The
};
required thickness of the barrier depends on the properties of the barrier and tailings. At the Spock site the radon barrier consists of a 1.5 feet thick low-permeability material layer covering the disposal cell and an average of 56 feet thick overburden material _ placed above it.~ The-low-3ermeability layer will be placed by DOE under the UMTRCA program, whereas tie overburden-material will be placed by the Wyoming State under-the-AML program; both the materials will be:placed by a single subcontractor. NRC staff reviewed-4
'both tne physical and radiological parameters of the tailings and radon barrier materials, used as input for-the' RAECQ1 code for their representativeness and validity.
.The design assumes-allong-term moisture content of 7.6 percent for the AML overburden material,10.9 percent for low-permeability matetial,11.4. percent for windblown material, 4.9 percent for. contaminated material (mill yard, acid
\\
E w
TER/ SPOOK 1/89 pond and ore pile), and 6.3 percent for tailings. These values were selected consIdering the optimum moisture content, as determined in ASTM D698 test; 15-bar capillary coisture content, as determined in laboratory tests on mpresentative samples;' an' moisture content as determined by an empirical athod. Generally, the long-term moisture content value selected was the lowest of those obtained using the above three methods. This is a conservative approach. The selection of the long-term moisture content was performed in accordance with the guidance provided in the SRP (Reference 1) and is thus acceptable to staff.
The material thicknesses (layers) used in DOE's analyses are baset on the volume of the tailings and other contaminated materials to be placed in the oisposal cell, the configuration of the disposal cell, and the final ground surface contours of the Spook pit as reclaimed in the AHL Program. These volumes were determined based on data obtained from field investigations (geotechnical, radiological and survey) and appear to be reasonable estimations of the. volumes of-the materials to be handled. There is no specific e
requirement for arny selective placement of highly contaminated raterial at the bottom of the disposal cel? because it will be buried in the pit under about 57.5 feet of earthen material, and the design is conservative. The design calculations use an average thickness of 56 feet for the AML Program cover material,1.5 feet for low-permeability material cover,18 feet for windblown material, six feet for other contaminated material, and 24 feet for tailings material. The material thicknesses used by DOE in their analyses are a reasonable representation of the expected field conditions.
Material properties such as bulk density and specific gravity were determined by field and laboratory tests, and the corresponding porosity was calculated.
The average dry bulk density-and porosity were 1.68 ge/cc and 0.360 for the AHL 4
Program overburden material,1.684 ga/cc and 0.329 for low-permeability material, 1.627 gn/cc and 0.319 for windblown raterial, 1.675 ga/cc and 0.376
~
for contaminated materials, and 1.691 gm/cc and 0.370 for tailings. NRC staff has reviewed the geotechnical data and concludes that the above values of the parameters are a reasonable representation of the average conditions that should be used.in the design computations.
Radon diffusion coefficients for the cover materials and tailings were derived from a correlation curve of moisture saturation versus radon diffusion coefficients for the estimated long-term moisture content of the materials.
This curve was based on diffusion coefficient and moisture saturation data from laboratory measurements on samples of soil and tailings that are representative 4 -
of the conditions in the disposal-cell and Spook pit. The average values of the diffusion coefficient parameter used in the design were 0.0325 sq.cm/sec
- for AML Program cover material, 0.016 sq.cm /sec for-low-permeability cover material, 0.004 sq.ca/sec for windblown material 0.029sq.cm/see for contaminated materials, and 0.0285 sq.cm/sec for tailings material. NRC :;taff has reviewed the-information used in determining the. diffusion coefficient values for these materials and judge them to be reasonable.
-~
TER/ SPOOK 1/89.
The radium content (Ra-226) of several materials at the site were measured (References 5 and 6).
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. The weighted average value of the radi.:m content was 39 pci/gm for windblown material, 243 pci/gm for contaminated uaterial, and 408 pei/gm for tailings material. These are average values for large volumes of materials, and the staff considers them to be reasonable and acceptable.
DOE's General Counsel has determined that the overburden material to be placed in the pit does not constitute " residual radioactive materials," as definedinUMTRCA(Reference 15).
NRC's legal counsel has concurred with this finding ind therefore, the radioactive contamination or radium content of q
the AML Progiam overburden materials was not considered in calculating the v
radon effluence from the disposal cell, using the RAECOM code.
The radon emanation coefficients were measured in the laboratory on samples rg resentative of field conditions. An emanating coefficient of 0.6 for the windblown material and 0.32 for the contaminated and tailings materials were used in the design calculations. Based on the values of this parameter determined for similar materials at other UMTRAP sites, staff considers these values to be reasonable and acceptable.
The ambient air radon concentration was measured to be 1.1 ci/ liter. The locations of these measurements were away from the tailing. and are expected to reflect the background conditions for the area. The technique used to measure this parameter has been previously approved by HRC. This is one of the input parameters for the RAECOM modeling calculation. The value of the measured ambient air radon concentration is reasonable and acceptable to NRC staff.
6.2.2 Evaluation of Radon Barrier For a given assumed thickness of the radon barrier, the RAECOM code calculates the radon gas release rate. DOE used a radon barrier consisting of a 1.5 feet thick low-permeability cover layer and 56-foot thick AML Program overburden layer in their calculation and determined a radon effluence rate of 0.0059 picocurie per square meter per second potentially emitted from the top of the AML Program fill.
The EPA standard requires that the release rate of radon-222 from the residual radioactive materials to the atmosphere not exceed an cverage release rate of 20 picocuries per square meter per second. The calculated radon release rate is a small fraction of that permitted in the EPA standards. DOE' has performed parametric calculations to demonstrate thH even unde" the most conservative and worst combination of critical parameters, the radon release rate is significantly-less than that required under the EPA
. standards. The reason for this is the 56-foot thick overburden material cover, placed over the disposal cell, under the AML Program.
m,_
a TER/ SPOOK 1/89
. The detere' nation of various-parameters needed for the radon barrier tiesign, and the method of analysis is in accordance with the guidelines in the SRP (Reference 1). MRC staff concurs with DOE that the radon release rate at the top of the reclaimed Spook pit, within which the residual radioactive materials will be buried, will be well below the limits allowed under the EPA standards.
6.3 Site Cleanup Site characterization surveys have been conducted at the site to identify the
~
subsurface boundary of the tailings pile, as well as the depth and area of the mill yard, ore storage, and windblown contaminated areas. The results of these site characterization surveys are used to plan-the control monitoring for n
excavation of the residual radioactive material DOE is responsible for
\\/
stabilizing.
DOE has cosmitted to " satisfy the EPA standards in 40 CFR 192 Subpart B and other applicable laws and regulations" (Reference 2, section 1.2). However, DOE noted that there may be areas of the site with cranium or thorium concentrations that are elevated above their normal relationship to radium-226 (section C.3, Reference 2).- DOE will tieed to comply with 40 CFR 192.21(f) if significant uranium or thorium contamination is found after the radium-226 limite, have been met. Dn ing a telecon on January 19, 1989, DOE staff (R.Richey) agreed to document DOE's cosmitment to apply-the supplemental standards provision if this situation were to be encountered during excavation, i1RC staff considers this commitment a confirmatory item for DOE to document in the final RAP.
In addition DOE proposed use of a radium-226 to uranium-238 ratio of 4.8 to distinguish tailings from unprocessed material (section 4.3.7, Reference 2).
O anc =t << roaad ao sustific tioa for 1 ction of tais ratio a4 could aat distinguish the purpose for which the ratio was to be uced. During the telecon referenced above, DOE / TAC explained that the ratio had been selected as
.a midpoint between-data-values derived from samples.of the overburden material ar.d the tailings pile. The purpose of this ratio was to delineate the areal extent of materials for'which DOE is responsible for versus those the State
-will cleanup under the AML Program. DOE stated that the areas for which they
- are: responsible.will be cleaned up to meet the EPA standards'. NRC staff finds
- this approach acceptable, but-considers that it needs to be clearly documented in the final RIS. Therefore, NRC staff has identified this as a confirmatory ites;.
Finally, NRC staff's review of the procedures identified in the RAP for the final radiological verification: survey finds them consistent with generic procedures-(RAC-015)-that have~been reviewed and approved of by:HRC' staff.
.Therefore, other than the confirmatory items identified above NRC staff-concurs with the site cleanup' aspects of the proposed remedial action.
4 Q-
TER/ SPOOK 1/89 4 i
6.4 Conclusions The radon barrier proposed for covering the residual radioactive materials at the Spook,ite will reduce the radon release rate from the surface of the Spook pit to-less than that permitted under the 40 CFR Part 192.02(b), and therefore, con. plies with the EPA standards. It is, therefore, acceptable to l
NRC staff.
NRC staff generally concurs with the site cleanup aspects of DOE's proposed remecial action for the S)ook site. However, two items are identified in section 6.3 of this TER t1at need DOE confirmation in the final RAP. As the first item, DOE needs to document a commitment to comply with 40 CFR 192.21(f) if significant uranium or thorium contamination is found after the radium-226 Os limits are met during excavation of the residual radioactive materials. For the second item. DOE needs to document the derivation of the 4.8 radium-226 to uranium-238 ratio and its intended use for delineating the areal extent of tailings, and state that the EPA standards will be met in cleanup of these residual radioactive materials.
O.
v 1
Y e
+& &
4,
\\b [t$%7h
/f/,'" %/e'#[4, p4
/
p IMAGE EVALUATION
- /// (
\\/gM TEST TARGET (MT-3)
\\
3
////+
'44 I.0 5 83 Bla 5E E i,l la:m HE r I.8 l m*=
l.25 l
I.4 I,'=i.6 1
=
4 150inm 4
6"
+
%#)'exzzz
+ a,. 4%
PHOTOGRAPHIC SCIENCES CORPORATION 4p V
WEBSTER NE YOR ',14580 (71M 2451600
as o
3
////p d2 tt IMAGE EVALUATION 4
NM j %
- 4
////
%f/
0 1
TEST TARGET (MT-3) kz7 f
2 1.0 5En H2 y l_ Els f
1.1
[" EE 114 i.25 jg jg 4
150mm 4
6" d#%
/#
- $ b////
'% O PHOTOGR APHIC SCIENCES CORPOR ATION f.
P.O. BOX 338 pg 4
WEBSTER, NEW YORK 14580 D/11M 265-1600
1 sr
+? $9 0 d
"* >h IMAGE EVALUATION
/// /
[,([o, 4)gy>p gg%
e ff TEST TARGET (MT-3)
- 4y l.0 lf 82 Eu y @ ll!E i.i s i= LE l.8
_5_""
I.25 1.4
-l 1.6
~
4 150mm 6"
/<$
4
- I (4 %,
$A,,,4 4%
3,,$//77
_ _, = _ _
7 WEBSTER NE\\V YORK 14580 (7161 MS1600
g TER/ SPOOK 1/89 i;!
7.0
SUMMARY
i.
This Technical Evaluation Report (TER) susanarizes NRC staff's review of the proposed remedial action for the inactive uranium niill tailings site at Spook,
[.
f Based on this review, NRC staff is prepared to provide conditional Wyoming.
concurrence on the remedial action plen and site conceptual design. However, Ji 4
0
~ !
two items have been it'entified that should be addressed in the f;nal documents provided for conditional concurrence. Complete concurrence will be provided h!
when DOE has adequately addressed cleanup of the existing groundwater
^
contamination in accordance with the final EPA standards yet to be promulgated.
~
!O M.
q) s l
N
~
Y
!!l 1
)
(
1 j
Y l
a f\\
=
=0 a
g
=
j E
j m
)
TER/ SPOOK 1/89 8.0 REFEREllCES AND BICLIOGRAPHY 1.
U.S. Nuclear Regulatory Comission,1985. Standard Review Plan for UMTRCA Title ! Mill Tailings Remedial Action Plans; HRC, Division of Waste Manageraent, October,1985.
2.
U.S. Departnent of Energy, 1988. Remedial Action Plan and Site Conceptual Design for Stabilization of the Inactive Uranium Mill Tailings Site at Spook, Wyoming; Preliminary Final, Text and Appendices A through E, UMTRA-00E/AL 050515.0000, December, 1988.
3.
U.S. Department of Energy, 1988. Uranium Mill Tailings Remedial Action
/~3 Project (UMTRAP-AML), Spook, Wyoming -- Information for Reviewers; Final V
Design for Review, November, 1986.
4.
U.S. Department of Enengy,1988. Uranium Mill Tailings Remedial Action Project (UMTRAP-AML), Spook, Wyoming -- Subcontract Documents; Final Design for Revfew, November, 1988.
5.
U.S. Department of Energy,1988. Uranium Hill Tailings Remedial Aution Project (UMTRAP-AML), Spook, Wyoming -- Information for Bidders, Volume 1 and II, November 1988.
6.
U.S. Department of Energy,1988.
Uranium Mill Tailings Remedial Action Project (UMTRAP-AML), Spook, Wyoming -- Calculations, Volume I and II, November, 1900.
7.
Letter dated December 12, 1988, from W. J. Arthur of DOE to P. H. Lohaus
,r 3 of NRC enclosing DOE responses to NRC coments on the draft RAP, U
preliniinary Des'.gn, and draft Environmental Assessment for tne L'MTRA Site at Spook, Wyoming.
8.
Hydro-Engineering,1987. Report of Investigation for Abandoned Mined Lands Program 15-3, Spook Site; prepared by Hydro-Engineering Inc., Casper, Wyoming for the State of Wyoming, Department of EnvirF mental Quality.
9.
Sharp, W,N. and Gibbons, A.B., 1964. Geology and Uranium Deposits of the Southern Part of the Powder River Basin, Wyoming: U.S. Geological Survey Bulletin 1146-D, 60 pp.
10, Hunt, C.B., 1974. Natural Regions of the United States anc Canada: San Francisco, W. H. Freeman and Company, 725 pp.
- 11. Wells, S.G. and Gardner, T.W.,1985. Geomorphic Criteria for Seles ing Stable Uranium Tailings Disposal Site in New Mexico; New Mexico Energy Research and Development Institute, Technical Report HMERDI 2-69-1112, 353 pp.
l l
TER/ SPOOK 1/89 12.
U.S. Nuc. lear Regulatory Connitsion,1988, Information Needs to Demonstrate Compliance With EPA's Proposed Groundwater Protectio' Standards in 40 CFR Part 192, Subparts A-C.
- 13. Wyoning Departnent of Environmental Quality,1980. Water Quality Rules and Regulations, Chapter Ill, Quality Standards for Wyoming Groundwaters; WDEQ, Cheyenne, Wyoming.
14 U.S. Environnantal Protection Agency,1986. Guidelines for Ground-Water Classification under the EPA Groundwater Protection Strategy (Final Draft).
- 15. Letter dated December 12, 1988, from W. J. Arthur of DOE to P. H. Lohaus of flRC transsiitting DOE determinatinn on what constitutes residual radinactive material for the UMTRA site at Spook, Wyoming.
- 16. Letter dated January 17, 1989, fro:n P. H. Lohaus of NRC to W. J. Arthur of DOE responsind to DOE's determination on what constitutes residual 3
radioactive material for the UMTRA site at Spook, Wyoming.
17.
U.S. Bureau of Reclamation, U.S. Department of the Interior,1873. Design of Small Dams.
- 18. Chow, V. T.,1959. Open Channel Hydraulics; McGraw-Hill Book Company, tiew York.
19.
U.S. Army Corps of Engineers, 1970. Hydraulic Design of Flood Control Channels; Eli 1110-2-1601.
20.
U.S. Arrty Corps of Engineers,1970. Additional Guidance for Riprap Channel Protection; EM 1110-2-1601.
O 21.
U.S. Department of Commerce, U.S. Army Corps of Engineers, 1964. Probable Maximum Precipitation Estimates, United States Between the Continental Livide and the 103rd Meridian; Hydrometeorological Report No. 55, March
- 1984,
- 22. Nelson, J. D. et al.,1986. Methodologies for Evaluating Long-Term Stabilization Designs of Uranium Hill Tailings impouncments; NUREG/CR-4620 June 1986.
23.
U.S. Environmental Protection Agency,1983. Final Environmental Impact Statement for Standaros for the Control of Byproduct Materials from Uranium Ore Processing (40 CFR 192), Volume I.
24.
U.S. Environmental Protection Agency, 1984. Ground-Water Protection Strategy.
TER/ SPOOK 1/89 LIST OF CONTRIBUTORS Susan Bilhorn Project Manager Lynn Deering Groundwater hdrologist Joel Grim Geologist Banad Jagannath Geotechnical Engineer Ted Johnson Surface Water Hydrologist Dennis Sollenberger Health Physicist O
,