Proceedings: Second International Conference on Case Histories In Geotechnical Engineering, June 1-5, 1988,St. Louis, Mo., Paper No. 1.09

Geotechnical and Groundwater Site Characterization,on the UMTRAProjectJ.A. CaldwellTechnical Assistance Contractor, Albuquerque, New Mexico

R.E. RagerTechnical Assistance Contractor, Albuquerque, New Mexico

L.CoonsTechnical Assistance Contractor, Albuquerque, New Mexico

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SYNOPSIS: Reclamation of 24 inactive uranium mill tailngs piles involves remedial work to stabilize the piles forlOUD years. Site characteri zat ion of geotechnica1 and groundwater condit ions at each site is undertaken prior toremedial action design. This paper describes the approach to UMTRAProject site characterization. A case history,Green River, is described. Details of site characterization costs for most sites are provided.

INTRODUCTION

The Uranium Mill Tailings Remedial Action(UMTRA) Project involves the construction ofremedial action to stabilize and reclaim 24inactive uranium mill tailings piles in 10states. An important part of the planning anddesign of remedial action is sitecharacterization. This paper describes theUMTRA Project site characterization program.Details of site characterization at the GreenRiver, Utah, site are discussed in order toprovide a complete overview and a specific casehistory of UMTRA Project approaches andmethods, as well as the end product.

Site characterization work at UMTRA Projectsites, discussed in this paper, includes thefollowing: geological investigations; fielddrilling and test pitting; collection oftailings, soil, rock, and surface-water andgroundwater samples; laboratory testing oftailings, soils, rocks, and water; and thecompilation of site characterization reportsdescribing the site stratigraphy, groundwaterregime, and the properties of the in-place andconstruction materials. Site characterizationwork performed at UMTRA Project sites, but notdiscussed in this paper, includes:archaeological surveys; plant and animalsurveys; radiological and other wastecharacterization work; and climatological andsurface-water characterization.

THE UMTRA PROJECT

The UMTRA Project is managed by the U.S.Department of Energy (DOE) in terms of the theUranium Mill Tailings Remedial Control Act(UMTRCA) of 1983. Site characterization,design, and construction are performed bycontractors to the DOE.

In terms of UMTRCA, the U.S. EnvironmentalProtection Agency (EPA) sets the standards forthe remedial action. The U.S. NuclearRegulatory Commission (NRC) and affected statesand tribes review and concur in the design ofthe remedial action works.

The EPA standards require, among other things,that the remedial action be effective for atleast 1000 years, to the extent practical, andat least for 200 years. Remedial action must bedesigned and constructed to prevent dispersalof the tailings and other contaminatedmaterials, and must prevent inadvertent use oftailings by man. Remedial actions should notrely for their efficacy on maintenance,although in practice, maintenance andsurveillance programs are planned at all sites.

To date, construction is complete at:Canonsburg, Pennsylvania; Shiprock, New Mexico;and Salt Lake city, Utah. Construction work isin progress at: Durango, Colorado; MexicanHat, Utah; and Lakeview, Oregon. sitecharacterization is complete, or significantlyadvanced at the remaining sites, with theexceptions of Gunnison and Naturita, Colorado,where alternate site selection studies are inprogress. In terms of Federal legislation, theProject is scheduled to be complete by 1993.

THE TECHNICAL APPROACH DOCUMENT AND CONTRACTUALPROCEDURES

Technical Approach

The technical approach to site characterizationat UMTRA Project sites is described in aTechnical Approach Document (TAD). The TAD,which was compiled in close discussion with theEPA, NRC, and affected states and tribes, setsout in detail the methods and approachesemployed to characterize the following aspectsof tailings piles and new disposal sites:geology; groundwater; site and regionalseismicity; subsurface soils and rocks andtheir geotechnical and hydrogeochemicalproperties; tailings and their geotechnical andradiological properties; and the geotechnicaland radon attenuation properties of potentialconstruction materials (soils and rocks thatwill be used to construct and cover thereshaped or relocated tailings pile andassociated contaminated materials). A latersection of this paper discusses some of thetechnical approaches in detail.

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Detailed site characterization procedures aredocumented in the Standard Operating Proceduresof the various contractors to the DOE on theUMTRA Project.

Performance of Site Characterization Work

The UMTRA Project is managed from the DOEAlbuquerque Operations Office in Albuquerque,New Mexico. The Technical Assistance Contractor(TAC) is located with the DOE. The TAC iscontracted to the DOE to provide, among otherservices: site characterization work:conceptual designs: and the compilation ofEnvironmental Impact Statements/EnvironmentalAssessments (EIS/EAs) and Remedial Action Plans(RAPs). TAC staff perform geological sitecharacterization work as well as planning,control, interpretation, and compilation offield programs and their results forgeotechnical and groundwater characterizationwork.

Due to the fact that the 24 sites are scatteredacross a wide geographic area, TACsubcontractors are employed to perform sitecharacterization work. This work involvesdrilling, geotechnical sampling, and in-situtesting (i.e., with a piezocone). Laboratorytesting of soils, rocks, and water is done incommercial facilities subcontracted to the TAC.

Because of the technical expertise required,groundwater sampling is done by a team of TACstaff who travel from site to site withspecially-equipped vehicles.

Scopes Of Work

When subcontract work is required at a site,the usual procedure is for the TAC to call forbids from qualified subcontractors. The numberof bidders varies significantly depending onthe site location and the nature of the workrequired. Once bids have been issued, there isusually a site meeting at which salient aspectsof the terrain as well as the work required arediscussed with prospective subcontractors. Bidsare reviewed upon receipt in Albuquerque inaccordance with standard government contractprocedures. Normally, the contract is awardedto the lowest bidder. (This has, unfortunately,not always led to the employment of the better,more competent contractors.)

The technical work to be performed by thesubcontractor is described in the bid in theScope of Work. This is the only part of the bidand contract compiled by the TAC technicalstaff. A typical Scope of Work incorporates adescription of the site, a detailed listing ofthe work to be done,and technicalspecifications.

Site control

During subcontractor performance of sitecharacterization work, technical staff from theTAC are present. A full-time site person, the

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Field Technical Representative (FTR), isempowered to: monitor the contractor: observethat proper work is performed: confirm thatrequired operating procedures are observed: andrequest that specific work (e.g., in-situtesting) be done at appropriate times. The FTRis not empowered to control or direct thesubcontractor's work. The FTR keeps a dailydiary that is used as the basis for agreeing toand paying bills submitted by thesubcontractor.

GEOTECHNICAL SITE CHARACTERIZATION - TECHNICALAPPROACH

Geotechnical site characterization includesgeologic, geomorphic, subsurfaceinvestigations, and seismic studies.

Geologic site characterization of UMTRA Projectsites is an integral part of the overall designeffort. This characterization consists of asummary of the regional geologic setting, localsite geology, regional and local structures,Quaternary geology of the site region, and thelocal distribution of surficial units. The in-depth geologic studies are presented in theSite Characterization Report section of theRemedial Action Plan (RAP).

The purpose of the geomorphic hazard assessmentis to identify the geomorphic processes thataffect the site, to estimate the probability oftheir occurrence, and to evaluate the possiblemagnitude of their effects during the life ofthe reclamation. The general approach used toaccomplish these goals involves three steps:(1) identify past geomorphic processes andestimate their rates from the geomorphic andstratigraphic records (post-glacial time,roughly 10,000 years): (2) identify presentgeomorphic processes and estimate their ratesfrom historic records and field observations

(typically less than 80 years): and (3) predictfuture geomorphic processes and rates.

The purpose of subsurface characterization ofUMTRA Project sites is to define thegeotechnical conditions of existing tailingspiles, foundation soils, and proposed borrowsources. The stratigraphy and physicalproperties of materials composing thestratigraphic units are characterized.Stratigraphy is determined by using informationlogged in boreholes and test pits. Piezoconeprobings or seismic field studies may also beused to define stratigraphy. Materialproperties are determined by laboratory andfield tests.

The nature and material properties of thetailings piles must be determined in order todecide if stabilization in place can beaccomplished without recompacting or otherwiseconsolidating the pile. In addition, thebehavior and stratigraphy of the foundationsoils must be determined in order to assess the

stability of the pile. An initial exploratoryprogram consisting of a series of piezoconepenetration tests similar to the static conepenetration test described in the ASTM D3441are performed at a minimum density of one per

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acre to cover the tailings pile. Each testpenetrates the entire depth of the pile andextends into the foundation soils until stiffor dense soils are encountered. Data fromthese probes are used to: (1) define thestratigraphy of the pile (e.g., locatesignificant layers, zones, and pockets ofslimes within the embankment), (2) determinethe rat~ of dissipation of induced porepressures (the rate of pore water pressuredissipation is used to estimate the tailingshydraulic conductivity and consolidationparameters), (3) obtain the penetrationresistance of the tailings and their strengthand bearing capacity, and (4) determine thegroundwater level.

The stratigraphy interpreted from the piezoconedata is considered in determining the locationof additional boreholes conducted in the secondphase of field work. These borings areperformed to obtain undisturbed and disturbedsamples for laboratory testing and to verifythe stratigraphy defined by the piezocone data.Sufficient borings are conducted to verify theinformation from the piezocone. At least oneof the borings is taken 20 feet into bedrock orup to 250 feet below the tailings-soilinterface if foundation stratigraphy andmaterial properties permit.

Borings with sampling are also conductedadjacent to the piles in order to identifyvariability of the near-pile foundation soils.Test pits are excavated on the pile to obtainrepresentative sand, sand-slime, and slimetailings samples for laboratory testing. Testdata are used to determine the geotechnicalproperties of the tailings when placed asfills.

For separate disposal areas, borings arerequired in order to determine the foundationsoil and bedrock characteristics at a disposalsite. The density of borings is approximatelyone for every three acres. A sufficient areais covered to allow repositioning of the pilewithin the general area of interest. Theseborings extend at least 20 feet below grade, atleast two borings extend up to 50 feet belowgrade, or to a minimum of 20 feet, intobedrock. One of the borings may extend as deepas 250 feet if the soil at the site is deep.

Borrow areas are identified by performing aborrow assessment. For radon cover material, alimited number of areas are investigated byexcavating eight to 12 test pits at each area.Both large and small bulk samples are obtainedin order to perform classification and materialproperties tests.

For rock armoring material, one or more areasare investigated in order to define the limitsand quality of rock armor borrow material. Forgravel sites, six to eight test pits areconducted at each area. Both large and smallbulk samples are obtained. For bedrock sites,samples are obtained from rock outcrop areas.

Laboratory tests are performed on tailings,foundation, fill, and soil borrow sources inorder to determine appropriate materialproperties needed for design. These includestrength, compressibility, compaction,permeability, capillary moisture, radon

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diffusion coefficient, and correlative propertytests. Rock samples are tested for durabilityusing petrographic, LA abrasion, absorption,sodium sulfate soundness, and specific gravitytests. Other types of soil and rock tests areperformed if needed.

As part of the design of reclamation work atUMTRA Project sites, studies are conducted todefine the seismic hazard. These evaluationsresult in a seismotectonic characterization ofeach site and provide a set of earthquakedesign parameters. These parameters include:the design earthquake magnitude, on-site peakhorizontal ground acceleration, the distancesto, and lengths of, capable faults, and thetypes of capable fault displacement. Duringthe seismic investigation, the potential foron-site fault rupture is analyzed.

Once the acceleration has been determined for asite using methods outlined in the previoussections of this chapter, the impact ofstratigraphy upon the acceleration isevaluated. The site is classified as havingshallow or deep soils. Based upon thisclassification, modification to the siteacceleration is as follows:

o For shallow soil sites having less than 30feet of overburden above bedrock, the sitesurface acceleration used in liquefactionand slope stability analyses is consideredto be the same as the acceleration derivedfrom the seismic study.

o Deep soil sites require adjustment to theon-site acceleration derived from theseismotectonic site characterization. Theacceleration must be modified forattenuation to amplification through thesoil in order to derive the surfaceacceleration used as input intoliquefaction and stability analyses.

In order to assess the long-term stability ofthe tailings piles, the long-term static andearthquake loading conditions are determined.Natural slopes, which may affect the long-termperformance of the embankment, are alsoanalyzed for static and earthquake loadingconditions. In addition, short-term static andseismic loading of the embankment andconstruction slopes must be analyzed to assessthe suitability of the proposed designs.

Settlement of the reconstructed tailings pilesat UMTRA Project sites is assessed in order toevaluate long-term stability. Settlement canoccur within the reclaimed tailings embankmentand in the foundation soils upon which theembankment is constructed. The absolute anddifferential settlement depend on thedistribution of different types of materials,the compressibility of each soil type, and thestresses on specific soil layers. Settlement,especially differential settlement, can lead tosurface-water runoff flow concentrations whichcould erode the pile cover and/or lead tocracking of the radon cover.

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In order to evaluate the long-term stability oftailings piles at UMTRA Project sites, theliquefaction potential of the pile andfoundation soils under design earthquakeconditions is assessed. The liquefactionpotential of a site is determined by the soilproperties, depositional history, depth togroundwater, and characteristics of theearthquake motion to which it is subjected.

GROUNDWATER SITE CHARACTERIZATION

Subsurface investigations are performed at eachformer mill processing site and potentialtailings disposal site to define the presenceand extent of groundwater-bearing(hydrostratigraphic) units. The ultimateobjective of these investigations is to developthe appropriate remedial action plan for waterresources protection and a cost-effectiveremedial action plan for cleanup of theinactive mill sites. Aquifer hydraulic andgeochemical characteristics are defined foreach hydrostratigraphic unit to aid indetermining the amount and extent of presentand potential contamination by the milltailings operations.

Groundwater site characterization begins withan inventory and review of existinghydrogeologic literature and water well recordsin the vicinity of the site. An earlyassessment is made to: (1) identify water userswithin a two-mile radius of the site: (2)estimate the extent of contamination: (3)identify possible sources of contamination nearthe mill site other than mill tailings: and (4)to identify potential disposal sites. Fieldtesting, drilling and monitor wellinstallation, water sampling, soil sampling,and aquifer-hydraulic testing are completed inphases.

Key elements in the groundwatercharacterization for each site include thefollowing:

o Definition of the contaminant source.o Characterization of representative

background water quality for eachhydrostratigraphic unit of concern and forsurface water.

o Definition of presence and extent ofcontaminant plumes, as well as dischargeof plumes to surface water.

The contaminant source term is characterized bycollecting and analyzing tailings solids andpore water samples. Saturated and unsaturatedhydraulic conductivities of undisturbedtailings samples may be determined. Toestimate the rate of movement of leachatethrough the tailings at the disposal site, thehydraulic conductivity of one or more remoldedand compacted tailings samples is determined.Contaminant sources other than mill tailingsare identified and may be characterized if itis determined that contamination from thatsource may affect, or in any way bias, thecharacterization of the tailings pile or thedisposal site hydrogeology.

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Background groundwater quality is determined byestablishing representative values forconstituents from water samples obtained fromwells upgradient of the tailings pile. Thesebackground wells must be sufficientlyupgradient so that the groundwater isunaffected by tailings seepage. Existingsprings and wells may be used, or it may benecessary to install monitor wells specificallyto determine background water quality. Wheresix or more sample analyses are available, thebackground concentration range is assumed to bethe arithmetic mean (or possibly the geometricmean, depending upon the distribution of thedata) plus or minus two standard deviations.For less than six samples, the backgroundconcentration range is assumed to be equal tothe observed range of data. Obvious outliersin the data set are eliminated and anexplanation for doing so is provided forreviewers.

The vertical extent of contamination in thegroundwater system is determined by installinga group or "nest" of monitor wells at specificlocations on the site, and downgradient andcrossgradient from the site. Each well in thisnest is screened within a discrete intervalwhich is different in depth below the surfacefrom all other wells in the nest. The deepestwell showing no impact from tailings seepagedefines the lower limit of contamination. Thelateral extent of contamination is determinedby installing monitor wells progressively awayfrom the contaminant source(s) until water-quality analyses from the outermost wells showthat there is little or no contamination. Atmany of the UMTRA Project sites, the lateralextent of contamination is defined by one ormore groundwater discharge points such assprings, intermittent drainages, or rivers.

As solvents and other chemicals were used at

some of the UMTRA Project sites during themilling processes, an EPA Priority Pollutantscan is conducted at one or more of the monitorwells, usually on the site or immediatelydowngradient from the site. Then, at severalof the other wells at each site, organiccontamination is screened by analyzing fortotal organic carbon (TOC) and total organichalogens (TOX).

CASE HISTORY: GREEN RIVER

Green River, utah, is one of the 24 UMTRAProject sites at which remedial action workwill be undertaken. The following sectionsdescribe the site characterization workcompleted at the Green River site. Finaldesigns have been prepared for the remedialaction work: and construction is scheduled tobegin in the summer of 1988.

Green River Site Description

The Green River inactive uranium mill site isin Grand County, Utah, approximately one milesoutheast of the city of Green River and 0.5mile south of u.S. Highway 6 & 50. The 48-acresite is in Sections 15 and 22, Township 21South, Range 16 East, Salt Lake Meridian, andis bordered by the mainline track of the Denverand Rio Grande Western (D&RGW) Railroad on thenorth and the recently completed Interstate 70on the south.

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The 48-acre designated site consists of thetailings pile (eight acres), the mill yard andore storage areas (23 acres), four mainbuildings, a water tower, and several smallbuildings. The buildings are all structurallysound and marginally contaminated.

Dispersion of tailings by wind and watererosion has contaminated approximately 30acres. The total volume of contaminatedmaterials, including the tailings andunderlying soils, is estimated to be 185,000cubic yards (cy).

In order to stabilize the tailings and meet theEPA standards, the tailings and othercontaminated materials will be consolidatedinto a disposal cell out of Brown's Washapproximately 500 feet south and 50 feet higherin elevation than the existing mill site. Thesite occupies a level area that is disected bya shallow, ephemeral stream. This streamdrains to the northwest around the mill site.Bedrock is exposed in the bottom of drainagenear the mill site. The site surface is formedof pediment sand and gravel and is covered bysagebrush and wild forbs. A power line crossesthe site area.

TO GREEN RIVER ~

o"WAG' OOON' 0 .

-TO THE

GREEN RIVER.

.200 0 200 400

P"""'"- .

SCALE IN FEET

Geotechnical site Characterization

The Green River site is in the northern part ofthe Canyon Lands section of the ColoradoPlateau Physiographic Province, an area of lowhistoric seismicity. The site region isdrained by the Green River which passes 0.5mile west of the site. The tailings pile restson the bank of Brown's Wash, intermittenttributary with a watershed of 85 square miles.The peak horizontal acceleration at the site is0.21g.

Subsurface Investigation

The Green River tailings pile was characterizedby drilling five borings and excavating threetest pits on the pile. The locations of theseboreholes and test pits are presented in Figure1.

Tailings are divided into three categoriesaccording to the size of the particles. Thethree designations are: sand; sand-slime; andslime. At Green River, the slimes were removedfor upgrading at Rifle, Colorado, leaving only

#/L.....,';;:;-"

LEGEND

. MONITOR WELL

\MUNITIONBUNKER

o TEST PIT

A SURFACE WATER.

( <> > . SAMPLING SITELOCATIONS OF MONITOR WELLS, V _ STREAM FLOW DIRECTIONABANDONED BOREHOLES, TEST PITS, AND -x- FENCESURFACE-WATER SAMPLING SITES, GREEN RIVER, UTAH, TAILINGS SITE

FIGURE 1

o TEST BOREHOLE

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the sand tailings. Sand tailings, as usedhere, refers to those tailings with up to 30percent passing the No. 200 sieve. Most of theGreen River pile contains less than 20 percentpassing the No. 200 sieve. The Unified SoilClassification System (USCS) classifies thematerial as silty or clayey sand: SP-SM, SP-SC,SM, and SC.

Moisture contents within the tailings pilerange from 1.2 to 6.4 percent. Blow countsfrom SPT tests range from four to 16, whichcorrelates with a loose to medium-denseconsistency. Groundwater was not encounteredwithin the tailings.

The Green River disposal area was characterizedby drilling eight borings and excavating seventest pits as shown on Figure 1. In addition,information obtained from many of the 34monitor well drill holes was used to definesubsurface stratigraphy.

The soils underlying the site consist ofbetween five and 16 feet of loose to densesilty or clayey sand alluvium. Large lenses ofclay are contained within the layer. Dense to

4150

4100

LOWER-MIDDLEHYDROSTRATIGRAPHIC UNIT

3950

3900

250 125 0 250, .. IHORIZONTAL SCALE IN FEET

DATUM IS MEAN SEA LEVEL

sz STATICWATER LEVEL,9/86

I CASIN.GPERFORATIONS

TD - TOTAL DEPTH

very dense sand and gravel alluvium underliesthese near-surface soils. The soils in turnoverlie bedrock of coarse conglomeratesandstone of the Dakota Sandstone and shales ofthe Cedar Mountain Formation. These near-surface soils lie within the area of windblowncontamination and are considered representativeof this material. Groundwater was notencountered within the soils at the site.

Geologic cross sections were developed fromoutcrop and borehole information. A typicalcross section is shown on Figure 2. Theconditions at the site reflect the regionalbedrock configuration of shallow dipping bedsof Mancos Shale overlying a thin anddiscontinuous layer of Dakota Sandstone whichin turn overlies the Cedar Mountain Formation.

Geotechnical testing of the site soils andtailings included standard penetration tests,moisture content and dry densities, gradationtests, Atterberg Limits, compaction tests,remolded and undisturbed consolidation,triaxial shear, permeability, and capillarymoisture tests.

PROPOSED DISPOSAL SITE

BOTTOM HYDROSTRATIGRAPHIC UNIT

LEGEND

Opg - PEDIMENT GRAVELS

Oal - BROWN'S WASHALLUVIUM

SANDSTONE

CONGLOMERATE

SHALE/MUDSTONE

LIMESTONE

RECENT ALLUVIUM

Km - MANCOS SHALE

Kd - DAKOTA SANDSTONE

Kcm - CEDAR MOUNTAIN FORMATION

Kcmb - CEDAR MOUNTAIN FORMATIONBUCKHORN CONGLOMERATEMEMBER

FIGURE 2__ UNCONFORMITY

HYDROGEOLOGICCROSS SECTIONGREEN RIVER. UTAH.TAILINGSITE

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4050I-WWU.

Z0

4000>w...w

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Groundwater Site Characterization

Thirty four monitor wells, three well points,and six surface-water sampling sites (Figure 1)were used to characterize the shallowgroundwater system at the Green River site.Eight of the wells were installed by previousinvestigators in 1982 to characterize thetailings pile and the alluvium beneath andperipheral to the pile. The remaining wells,well points, and surface-water sites wereinstalled by the TAC and were used tocharacterize three distinct Cretaceous-agebedrock units.

Depth to groundwater in the alluvium beneaththe tailings surface ranges from 11 to 16 feet;the base of the tailings is above the watertable. At the proposed disposal site south ofthe present pile (see Figure 2), groundwater isfirst encountered at an approximate depth of 60feet below the surface. The general directionof groundwater flow in the alluvium and bedrockaquifers is west toward the Green River.

Background water-quality analyses indicate thatthe total dissolved solids (TDS) contents ofthe alluvial aquifer and the two shallow-mostbedrock aquifers range from 4000 milligrams perliter (mg/l) to 7000 mg/l; the bottom bedrockunit contains groundwater of significantlybetter quality (TDS near 1900 mg/1). The EPAand State of Utah Secondary Drinking WaterStandard for TDS is 500 mg/l. Contaminationfrom tailings seepage was detected in thealluvium beneath the pile and in the shale andsiltstone bedrock unit immediatelybeneath the

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alluvium. The lateral contamination (nitrate,ammonium, uranium, and manganese) is restrictedto the area beneath the pile. Downgradientfrom the pile, some contamination dischargesfrom the alluvial aquifer into Browns Wash, asmall intermittent tributary of the GreenRiver. Contamination in the underlying bedrockaquifer disperses downgradient and flowspreferentially in some areas throughinterconnected fractures visible in outcropsand core samples. The bottom sandstone unit isprotected from tailings seepage by strongupward vertical hydraulic gradients. Three ofthe wells completed in this unit flow at theland surface during certain times of the year.

Preliminary estimates of contaminant migrationand future contamination were made for the twocontaminated aquifers beneath the presenttailings pile. These estimates assumedispersion (non-point discharge) in the bedrockunit and discharge of contaminated water fromthe alluvium into Brown's Wash 400 feet west(downgradient)of the tailings. To reducenitrate concentrations as N03 to 44 mg/l, theEPA primary drinking water standard fornitrate, calculations show a natural flushingtime of 90 years is needed for the alluvium; 30years is needed for the bedrock aquifer.uranium concentrations will be reduced to theEPA health advisory level of 0.015 mg/l (10picocuries per liter (pci/1» in 160 years inthe alluvium, and in 260 years in the bedrockaquifer. These two contaminants represent themost mobile and one of the most retardedcontaminants at the Green River site,respectively.

TABLE 1 COMPARISON OF SITE CHARACTERIZATION COSTS FOR THREE UMTRA SITES

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SITE ID: AMBROSIA LAKE GREEN RIVERREMEDIAL ACTION COST: 21. 2 7.1TOTAL SITE COST: 29.5 16.8

ITEM NUMBER FOOTAGE COST/ITEM NUMBER FOOTAGE COST/ITEM------- --------- ------ ------- ---------GEOTECHNICAL BOREHOLES 42 1192 28550 12 277 20955TEST PITS 25 250 1527 24 240 1365

MONITOR WELLS,LYSIMETERS& STANDPIPES 23 4050 76942 35 1047 (W/GEOT)GEOPHYSICAL LOGGING 23 4050 10998 35 1047 (W/GEOT)PIEZOCONE 126 3668 33652 N/A N/A N/AWATER ANALYSIS N/A N/A 14883 N/A N/A 11202SOIL ANALYSIS N/A N/A 23314 N/A N/A 22482

TOTAL 189866 56004

SITE ID: RIFLE (PROCESSING SITE) RIFLE (DISPOSAL SITE)REMEDIAL ACTION COST: 48.1TOTAL SITE COST: 73.7

ITEM NUMBER FOOTAGE COST/ITEM NUMBER FOOTAGE COST/ITEM------- --------- ------ ------- ---------

GEOTECHNICAL BOREHOLES 29 N/A (OTHERS) 11 755 150777

TEST PITS 5 N/A (OTHERS) 16 170 4061MONITOR WELLS 85 4830 299731 10 1180 (W/GEOT)LYSIMETERS & TENSIOMETER N/A N/A N/A 12 228 (W/GEOT)GEOPHYSICAL LOGGING 85 4830 23715 10 1180 8783

WATER ANALYSIS N/A N/A 8568 N/A N/A 0

SOIL ANALYSIS N/A N/A 5609 N/A N/A 18950

SITE CHARACTERIZATION COSTS

Table 1 lists details of the costs ofgeotechnical and groundwater sitecharacterization work at three UMTRA Projectsites. In particular, the costs of workinvolved in the Green River case history areprovided. Table 2 gives a summary of sitecharacterization costs at the remaining UMTRAProject sites.

Also shown on Table 1 are the remedial actioncosts and the total site costs. The remedialaction cost is the cost of constructingremedial works at the site. It includes thecosts of site preparation, decontamination,relocation, cover, erosion protection,restoration, and construction management. Thetotal site cost includes the costs of: planningand design development; engineering; siteacquisition, surveillance and maintenance; andtechnical and management support. The cost forthe Rifle processing and disposal sites isgiven as a single combined cost as all tailingswill be consolidated at one facility.

CONCLUSION

This paper has described the work to beperformed in order to characterize geotechnicaland groundwater conditions at the 24 sites that

constitute the UMTRA Project. The case historyof the Green River site characterization hasbeen discussed in detail. Costs for the sitecharacterization work have been provided.

Complete site characterization is an essentialfirst step in preparing cost-effective remedialaction plans for engineering works that mustremain stable for 200 to 1000 years. As shownin both the project and site case historiesdecribed in this paper, complete sitecharacterization is a multifaceted undertakingthat involves skill, cost, and site-specificapproaches.

ACKNOWLEDGEMENTS

The Technical Assistance Contractor to the U.S.Department of Energy is a joint venture of:Jacobs Engineering Group Inc.; Roy F. Weston;and Sergent, Hauskins and Beckwith. Theauthors acknowledge the work and contributionsof all their colleagues on the UMTRA Project:in particular Marie Lucero who compiled thecost data is to be especially thanked. Theauthors also wish to thank DOE for permissionto publish this paper.

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TABLE 2 SITE CHARACTERIZATION SUMMARY

SITE 10: OUR (PROC & DISP SITE) MEXICAN HAT TUBA CITY GRJ (PROC & DISP SITE)REMEDIAL ACTION COST: 36.5 25.0 12.1 67.5TOTAL SITE COST: 61.2 34.6 20.3 169.5

ITEM NUMBER COST/ITEM NUMBER COST/ITEM NUMBER COST/ITEM NUMBER COST/ITEM--------- ------ --------- ------ --------- ------ ---------GEOTECHNICAL BOREHOLES 25 38130 39 289535 17 32610 48 214533TEST PITS 28 1425 14 930 18 2000 80 5314MONITOR WELLS 25 (W/GEOT) 11 (W/GEOT) 19 174928 42 19770LYSIMETERS N/A N/A N/A N/A N/A N/A N/A N/AGEOPHYSICAL LOGGING N/A N/A N/A N/A N/A N/A N/A N/APIEZOCONE N/A N/A 40 12015 26 (I'I/GEOT) N/A N/AWATER ANALYSIS N/A 15347 N/A 8787 N/A 29263 N/A 1170SOIL ANALYSIS N/A 15449 N/A 17309 N/A 15998 N/A 24911----TOTAL 70351 328576 254799 265698

SITE 10: BELFIELD/BOWMAN FALLS CITY MONUMENT VALLEY LKV (PROC & DISP SITE)REMEDIAL ACTION COST: 5.4 18.6 9.8TOTAL SITE COST: 19.8 32.2 18.0

ITEM NUMBER COST/ITEM NUMBER COST/ITEM NUMBER COST/ITEM NUMBER COST/ITEM--------- ------ --------- ------ --------- ------ ---------GEOTECHNICAL BOREHOLES 72 (OTHERS) 138 (OTHERS) 0 N/A 36 82570TEST PITS 30 (OTHERS) 20 2845 5 800 16 2940MONITOR WELLS 18 36690 40 93062 23 145830 28 (1'1/GEOT.LYSIMETERS 11 (W/MON) N/A N/A N/A N/A N/A N/AGEOPHYSICAL LOGGING 11 4798 40 14000 N/A N/A N/A N/APIEZOCONE N/A N/A 222 26750 N/A N/A N/A N/AWATER ANALYSIS N/A 12840 N/A 10800 N/A 30234SOIL ANALYSIS N/A 15079 N/A 26750 N/A 13200

TOTAL 69407 174207 190064 85510

SITE 10: RIVERTON SHIPROCK SLICK ROCK MAYBELLREMEDIAL ACTION COST: 15.8 11.8 16.0 16.1TOTAL SITE COST: 27.3 20.0 26.7 26.0

ITEM NUMBER COST/ITEM NUMBER COST/ITEM NUMBER COST/ITEM NUMBER COST/ITEM--------- ------ --------- ------ --------- ------ ---------GEOTECHNICAL BOREHOLES 47 80134 69 (OTHERS) 11 5985 33 9396TEST PITS 19 3000 24 1282 23 1173 10 1050MONITOR WELLS 32 (W/GEOT.) 34 14365 22 44172 15 107975LYSIMETERS N/A N/A N/A N/A N/A N/A N/A N/AGEOPHYSICAL LOGGING N/A N/A N/A N/A 5 1000 15 5900PIEZOCONE N/A N/A N/A N/A 12 1929 40 14779WATER ANALYSIS N/A 5330 N/A 4882 N/A 9590 N/A 28794SOIL ANALYSIS N/A 3184 N/A 11590 N/A 19466 N/A 18285

TOTAL 91648 32119 83315 186179

SITE 10: SLC (PROC & DISP SITE) SPOOK LOWMANREMEDIAL ACTION COST: 44.9 2.8 4.4TOTAL SITE COST: 67.1 9.9 12.7

ITEM NUMBER COST/ITEM NUMBER COST/ITEM NUMBER COST/ITEM--------- ------ --------- ------ ---------GEOTECHNICAL BOREHOLES 97 (OTHERS) 1 890 21 26000TEST PITS 6 600 20 2165 16 2187MONITOR WELLS 36 97000 10 28686 12 983LYSIMETERS N/A N/A N/A N/A 6 36598GEOPHYSICAL LOGGING N/A N/A 10 10302 N/A N/APIEZOCONE N/A N/A N/A N/A N/A N/AWATER ANALYSIS N/A 4882 N/A 5817 N/A 2126SOIL ANALYSIS N/A 11597 N/A 6945 N/A 15675

TOTAL 114079 54805 83569