EXPEDITED SITE CHARACTERIZATION: A RAPID,COST-EFFECTIVE PROCESS FOR PREREMEDIAL

SITE CHARACTERIZATION

Jacqueline C. Burton, Ph.D.John L. Walker, Ph.D.Ted V. Jennings, Ph.D.

Pradeep K. Aggarwal, Ph.D.Bruce Hastings, B.S.

William T. Meyer, Ph.D.Candace M. Rose, B.S.

Carol L. Rosignolo, M.S.

Argonne National LaboratoryArgonne, Illinois

iSTi

ABSTRACTArgonne National Laboratory has developed a unique, cost-

and time-effective, technically innovative process forpreremedial site characterization, referred to as Expedited SiteCharacterization (ESC). The cost of the ESC field samplingprocess ranges from 1/10 to 1/5 of the cost of traditional sitecharacterization. The time required for this ESC field activityis approximately 1/30 of that for current methods. Argonne'sprsremediai site investigations based on this approach havebeen accepted by the appropriate regulatory agencies.

The ESC process is flexible and neither site norcontaminant dependent. The process has been successfullytested and applied in site investigations of multiplycontaminated landfills in New Mexico (for the U.S. Depart-ment of the Interior's Bureau of Land Management [BLM]) andat former srain storage facilities in Nebraska and Kansas,contaminated with carbon tetrachloride (for the Department ofAgriculture's Commodity Credit Corporation [CCC/USDA]). Aworking demonstration of this process was sponsored by theU.S. Department of Energy (DOE) Office of TechnologyDevelopment as a model of the methodology needed toaccelerate site characterizations at DOE facilities.

Basic features of the ESC process are as follows: (1) Atechnical manager with a broad base of expertise and a team ofscientists with diverse expertise and strong field experienceare essenti-!. (2) Participation of the same technical teamthroughout the processes of planning, field implementation,data integration, and report writing is required. (3) Thetechnical team first critically reviews and maximizes use ofexisting data to form working hypotheses that guidedevelopment of the ESC program. (4) The entire technicalteam visits a site to identify site characteristics that prohibitor promote any hypothesis or technological approach.(S) After the site visit, a suite of noninvasive and minimallyinvasive technologies is selected, to give greater confidenceand overlapping evidence for conclusions about site features.Significant technical advances have been made in the use andintegration of surface vegetation sampling, aquifer chemistryand isotopes, deep sampling with an electronic conepenetrometer. sample preservation methodologies, and surfacegeophysics to delineate and corroborate site details. (6) In nocase is the traditional approach of installing a large number ofmonitoring wells followed. (7) A dynamic work plan that

outlines the program is produced for the sponsoring andregulatory agencies. This plan is viewed as a guide, subject tomodification, rather than an absolute, unchangeabledocument. (8) The manager and the entire team participate inthe technical field program, with technical activities occurringsimultaneously. (9) Data from the various activities arereduced and interpreted each day by the technical staff.Although computer programs are used to visualize andintegrate the data, people, not computers, do the datainterpretation arid integration. (10) Each day the team andmanager meet, review results, and modify the program tooptimize activities that are generating overlapping orconfirming site details.

The result of this process is the optimization of the fieldactivity to produce a high-quality technical product that isboth cost and time effective. Argonne has achievedtechnically sound site characterizations that are acceptable toregulatory agencies and have provided extensive cost and timesavings in both the BLM and CCC/USDA programs.

INTRODUCTIONGovernmental agencies are under increasing pressure to

remediate hazardous waste sites in a cost-efficient and timelymanner. One of the major stumbling blocks in initiating thecleanup process is lengthy and costly site characterizationactivities that do not produce adequate technical data for properselection and design of a remedial action. Most often thesecharacterization activities rely on the traditional approach ofrandom grid sampling and/or installation of a massive numberof monitoring wells in hopes of generating sufficient data tosatisfy a regulatory body. The end result of these activities ismost often a constant reiteration of sampling, which leads tocost and time overruns with no definitive conclusions oncorrect remedial actions.

One of the major goals of the Environmental ResearchDivision of Argonne National Laboratory is to develop andprovide governmental agencies with technically sound, cost-and time-effective frameworks for preremedial sitecharacterization. The process developed and proven workableby Argonne for several diverse sites and different agencies isreferred to as Expedited Site Characterization (ESC). The ESCprocess, as presented in this paper and half-day course, isflexible and neither site nor contaminant dependent.

The first portion of this paper and lecture discusses thebasic features of the ESC process. The process relies heavilyon the use of a scientific approach to problem solving andrequires both a technical manager and l^am members withdiverse and considerable scientific capabilities. Both themanager and team members are involved in all phases of theprogram from planning to field implementation to datareduction and report writing. The ESC emphasizes use ofmultiple technologies for delineating and corroborating sitefeatures rather than random, statistical approaches.Noninvasive or minimally invasive technologies are usedrather than the traditional approach of monitoring wellinstallation.

Three examples of the successful implementation of theESC approach are presented here. The examples are taken frompreremedial site characterization studies conducted by Argonnefor the Department of Interior, Bureau of Land Management(BLM), in New Mexico, and for the Commodity CreditCorporation, United States Department of Agriculture(CCC/USDA). The BLM program involved design andimplementation of the ESC approach for New Mexico landfillsthought to contain hazardous waste. The problem faced by theCCC/USDA is soil and groundwater contamination fromformer CCC grain storage facilities in the Midwest.Specifically, carbon letrachioride was used to fumigate thesegrain storage facilities in the 1950s and 1960s. Subsequently,the carbon letrachioride has leached into the soil andgroundwater of several Midwest communities.

The BLM Flora Vista Landfill and the CCC/USDA Waverly.Nebraska, site will be discussed to illustrate the importance ofmaximizing use of existing data and multiple technologies toprovide technically sound data and expedite the preremedialsite characterization process. The CCC/USDA Murdock,Nebraska, site investigation illustrates the technical, cost,and time benefits of the ESC's minimally invasivetechnologies for sampling versus random installation ofmonitoring wells.

The ESC investigations at all of these sites have beensuccessful in producing high-quality studies that are acceptableto regulators, with significant cost and lime savings to thegovernment agencies.

Technicalmanager

plus team ofscientists

Criticalevaluation anduse of existing

data

THE ESC PROCESSThe ESC process emphasizes the use of the scientific

method to solve sile investigation problems with technicallydefensible data. The bcsic features and steps of the ESCprocess are discussed below and outlined in Figure I.

An experienced technical manager with a broad base ofexpertise and a team of scientists with diverse expertise andstrong field experience are required to make the process work.The Argonne team is composed of geologists, geochemists,geophysicists. hydrogeologists, chemists, biologists,computer scientists, health and safety personnel, andregulatory staff, as well as technical support staff. Of thegeoscience staff, seven scientists are at the Ph.D. level, twoare at the master's level, and one is at the bachelor leveL Theyhave a combined total of 170 years of experience in variousaspects of the geosciences. Other disciplines within the teamfollow approximately the same distribution in terms of degreelevel and experience. The technical team works togetherthroughout the process. In other words, the team that plansthe program also implements the program in the field andwrites the reports. Individuals with lesser degrees orexperience do not carry out the field work while the moreexperienced scientist remains in the office.

The lechnical team first critically reviews and interpretsexisting data for the site and contaminants to determine whichdata sets are technically valid and can be used in initiallydesigning the field program. One of the most basic mistakesin the site characterization process is failure to use technicallysound available data to form working hypotheses onhydrogeology, contaminant distribution, etc. for initialtesting.

After assembling and interpreting existing data for thesite, the entire technical team visits the site to identify as agroup the site characteristics that may prohibit or enhance anyparticular technological approach. Logistic and communityconstraints are also identified at this point

After the field visit, the team selects a suite oftechnologies appropriate to the problem and completes thedesign of the field program. No one technique works well atall sites, and a suite of techniques is necessary to fully

Site visitas a team

Selection ofappropriatetechnologies

- Multiple- Non-invasive

Dynamicwork plan

Managerand team

to field

Daily datareduction

andintegration

Modificationof program

asnecessary

Optimizationof

field program

Figure I. Process for Implementing Expedited Site Characterization

delineate site features. In addition, multiple technologies areemployed to give greater confidence in conclusions about sitefeatures. Noninvasive and minimally invasive technologiesare emphasized to minimize risk to the environment, thecommunity, and the staff. In no case is the traditionalapproach of installation of a missive number of monitoringwells followed.

A dynamic work plan that outlines the program is producedfor the sponsoring and regulatory agencies. The word dynamicis emphasized because the work plan is viewed as a guide,subject to modification, for the site characterization activityrather than a document that is absolute and unchangeable.Therefore, the health and safety plan and qualityassurance/quality control plan must be broad and encompassall possible alterations to the work plan. The cooperation ofthe regulating agency is essential in successfulimplementation of this process.

The entire team participates in the technical field program.Several technical activities are undertaken simultaneously.These may range from different surface geophysicsinvestigations to vegetation sampling. Data from the variousactivities are reduced and interpreted each day by the technicalstaff. Various computer programs are used to visualize andintegrate the data. However, people do the data interpretationand integration, not computers. The computers are just onemore tool in use at the site.

At the end of the day, the staff members meet, reviewresults, and modify the next day's program as necessary tooptimize activities that are generating overlapping orconfirming site details. Data are not arbitrarily discarded —each finding must be explained and understood. Anomalousreadings may be due to equipment malfunctions, laboratoryerror, and/or the inability of a technique to work in a givensetting even though theoretically it should.

The end result of this process is the optimization of thefield activity to produce a high-quality technical product thatis cost and time effective.

EXAMPLES OF ESC PROCESSIMPLEMENTATION

Three examples of the successful implementation of theESC methodology are discussed below. The BLM Flora VistaLandfill program in New Mexico is an example of the use ofnoninvasive, multiple geophysical technologies to delineateimportant site features for site characterization and todetermine whether remediation is needed. The CCC/USDAWaverly, Nebraska, site illustrates the importance of criticallyevaluating existing data in forming working hypotheses forsite characterization. In addition, the Waverly programdemonstrates the benefits of multiple technologies in the ESCmethodology in interpreting site hydrogeology andcontaminant movement. The third example, the CCC/LfSDAMurdock, Nebraska, site, illustrates the technical, cost, andtime benefits gained by the ESC process in its emphasis onminimally invasive sampling methodologies rather thanmonitoring well installation for groundwater and soilsampling during the characterization process.

Flora Vista LandfillGeologic Setting and Site History

The BLiM's Flora Vista Landfill is an inactive landfilllocated approximately 5 mi west of Aztec and approximately6 mi northeast of Farmington in San Juan County, NewMexico (Figure 2). The landfill covers 13 acres and is a

#A Flora VistaFarmington

• Gallup• Santa Fe

Albuquerque

Roswell

• Alamogofdo

Las Cruces* A Mesilla Dam

La Union-X

Figure 2. Location of Flora Vista Landfill in New Mexico

modified sanitary (not covered daily) landfill that was leasedand used by San Juan County from July 1978 through 1989.The State of New Mexico Environmental ImprovementDivision alleged in 1986 that large quantities of petroleum,industrial, or other hazardous waste had been deposited at theFlora Vista Landfill between the 1970s and August 1985.These wastes were supposedly deposited in septage waste pitsat the site without the BLM's authorization. Written disposalrecords were not maintained by the county or BLM during thelife of the landfill. Therefore, allegations of hazardous wastedisposal could not be confirmed or denied on the basis of anywritten records.

The BLM authorized both a preliminary assessment (PA) in1986 (AEPCO. Inc., 1986) and a site investigation (SI) in1987 by a private contractor (Roy F. Weston, 1988). Bothcontractors generated maps of previously covered trenches andpits. However, these maps yielded conflicting results thatArgonne could not readily explain because of the paucity ofwritten records for the landfill. Surface and subsurface soilsamples were collected during the PA and SI programs.Analytical results from both the PA and SI samples indicatedthe presence of some hazardous compounds (tetrachloro-ethylene, toluene, benzene, acetone. 4-methylphenol,1,1,1-trichloroethane, etc.) in one septage pit area of thelandfill. In addition, the SI results were interpreted by thecontractor as indicating possible lateral and vertical migrationfrom this pit Recommendations of the SI included the drillingof five monitoring wells at the site. On the basis of the resultsof the PA and SI, operation of the landfill was suspended, andthe landfill was covered with approximately 2 ft of sandysoil. Argonne was then asked to initiate an expeditedpreremedial SI to determine if remediation of the landfill wasrequired.

ESC Program for Flora VistaThe ESC was designed as a two-phase program. The first

phase consisted of geological and geophysical investigationsto identify source areas (previously unmapped trench and pitareas; contaminant plumes) and migration pathways (in the

.subsurface, bedrock and ^roundwater levels and aquiiards; onthe surface, arroyos and topographic relief). This informationwas then used to select sampling locations for [he secondphase of the program, testing for migration from source areas.If necessary, a third phase incorporating data from the firsttwo phases would be initiated to locate monitoring wells.

Only the results of the first phase of the program for FloraVista are presented here. All available geological and sitehistory data were used for reconstructions, and four surfacegeophysical investigations were conducted. The featurestargeted for location by the four techniques were thefollowing: for seismic refraction, subsurface lithologies andthe water table; for electromagnetics (frequency and timedomain), buried trench and pit boundaries, conductive plumes,subsurface lithoiogic features, and the water table; formagnetics, buried trenches; and for resistivity, lithoiogiccharacteristics and the water table.

The existing data on the disposal history of the Flora VistaLandfill were extremely sparse at the beginning of theArgonne program, as discussed above. Before the site visit byArgonne staff, the landfill had been covered with 2 ft of sandysoil, fenced, and closed. In addition to the exterior fence, thecounty had fenced one interior area in the southwest corner ofthe landfill, where a septage pit was supposedly located.Except for this area, no records indicated the locations ofadditional pits or trenches (the principal source areas forcontaminants at the landfill). Therefore, the initial programwas iesigned with two major objectives: (1) mapping now-buried source areas (trenches and pits) and (2) definingmigration pathways for contaminant movement from thesesource areas (bedrock surfaces, clay lenses, surface drainagepatterns, etc.). When the source and migration routes weredelineated, an optimal sampling program could be designed tofully test migration from these sources.

Source Areas. The geophysical techniques for mappingtrenches and pits included magnetometer and electromagnetic(EM) surveys. The EM31 and EM34 surveys were used formapping pits because one of the chief fears was that oil fieldwastes might have been placed in the landfill trenches andpits. These materials are frequently conductive and should bedelected by the EM equipment. The chief emphasis was on theEM31 for pit and trench mapping because of the shallow depthand because no shallow clay layers had previously beenobserved in the immediate vicinity of the landfill. The depthof exploration for the EM34 (about 50 ft) is much deeper thanfor the EM31 (about 15 ft). Regional geologic data indicatedthat clays could lie at this depth (30-50 ft). Therefore, theEM34 measurements might indicate clay units rather thanconductive fluids associated with landfilling activities. Forour purposes, however, in the early stages of this program, weincluded anomalies from the EM34 data in the trench mappingbecause we felt that in either case, clay versus fluid, we wouldwant to test that particular area.

The results of the magnetometer, EM31. and EM34 surveys(Figures 3-5, respectively) show that several areas repeatedlyappeared as anomalies with the different techniques. However,some areas yielded a response to only one technique, such asthe fenced area in Figure 4 for the EM31 survey. Thislocation is of particular interest because it is the supposedseptage pit area fenced by the county just before the landfillwas closed. The fact that this area was responsive to the EM31and not the magnetometer or EM34 indicates that it may wellbe a near-surface pit containing conductive materials. Onefeature to note is that the boundaries of the anomaly appear toextend well beyond the county's fence line.

Figure 3. Geophysical Magnetic Survey Identified Portions ofSome Solid Waste Trenches

Figure 4. Anomalous Values from EM31 Survey LocatedConductive Fluids and Solids at the Landfill

Figure 5. Anomalous Results of EM34 Survey Indicative ofSolid Waste Trenches a! the Flora Vista Landfill

The anomalous areas identified by each survey were nextoverlain to generate a map of potential source areas (both pitsand trenches) for the landfill (Figure 6). This process will bedescribed after the migration pathways have been identified inthe next section.

Migration Pathways. The next step in the program was todetermine if any technique was generating data that would beuseful in delineating information on migration pathways.After two days in the field, it was evident that the seismicrefraction survey was mapping a bedrock surface at fairlyshallow levels (15-45 ft) beneath the landfill surface. Thisrelatively shallow bedrock surface had not been predicted bythe regional geologic data (Baltz et al., 1966; Stone et al.,1983; Welder et al.. 1986). However, inspection of several

Magnetic Contours MM EM31 Contours HH EM34 Contours

Figure 6. Magnetic and Electromagnetic Data Were Combined to Establish Probable Locations of Shallow and Deep WasteMaterials

nearby outcrops indicated that the Tertiary NacimientoFormation could be present as an erosional bedrock surface atthe landfill site. The Nacimienlo is a hard, lithified, fairlyimpermeable sandstone. Because it was believed that thissurface might play an important role in unsaturated flow fromthe trenches and pits, the field program was altered to include amore comprehensive seismic refraction survey within andimmediately around the landfill. Thirty-eight profiles withshort spreads of 130 ft were acquired inside the fence(Figure 7). These data provided 76 depths to bedrock beneathshot points that were used to construct a bedrock topographymap (Figure 7).

As Figure 7 shows, the bedrock surface is an erosionalsurface with valleys, depressions, and definite drainagepatterns. In addition to defining polenlial subsurface flowdirections, a topographic map was constructed in the field forthe landfill itself (Figure 8). This surface map was then usedto define surface migration pathways from the landfill.

Integration of Data and Selection of Sampling Sites. Thedata on source areas and potential migration pathways werecombined to prioritize sample locations for the site(Figure 9). Source areas were represented by integrating themagnetic, EM31, and EM34 contours taken from Figures 3-5.Principal subsurface migration pathways were represented bythe thin lines from the bedrock mapping (Figure 7) andprincipal surface migration pathways by the thick lines fromthe surface topographic mapping (Figure 8) Sampling andsoil boring locations could now be chosen to test formovement or leaching of materials from these source areaswithout drilling into a trench or pit in the first phase of iheprogram. This restriction eliminated the possibility ofintroducing contamination into the subsurface by arbitrary

drilling through potentially contaminated pits and trenches.Inspection of the sampling and soil boring locations inFigure 9 reveals that all major migration pathways weretested.

Results of Field Testing of Source and Migration PathwayPredictions

When soil borings were installed, the trench areas trendingnorth-south in the landfill were found to be real. The accuracyof predictions of trench boundaries was within 5 ft Predicteddepths to bedrock were accurate within 10 ft, and the soilborings substantiated the general nature of the bedrocksurface.

The only pit area actually drilled was the fenced areamapped by EM31 (Figure 9). During the SI, the contractorhad drilled two soil borings in this pit area, one inside ihefenced area and one just south of the southern interior fenceboundary. On the basis of the analytical results from thisdrilling, the contractor had proposed that lateral and verticalmigration of contaminants had occurred from the pit area. Thelocation of the contractor's two soil borings (WB1 and WB2)are shown in cross-sectional view in Figure 10 withArgonne's soil borings in this pit area, with the results of theEM3I study superimposed. Argonne's soil borings, coupledwilh a reexamination of the contractor data and the EM 31response, proved that this is actually one large septage pit andthat no lateral or vertical migration has occurred from it. Theinterior fence is just an artificial boundary that is not at allrepresentative of the extent of the pit. Without the EM31data, outlining the possible boundaries of the pit. and theseismic data, giving an idea of the location of the base of thepit, considerable lime and money could have been wasted indrilling and ailempiing to understand this one area.

Figure 7. Seismic Refraction Survey Identified a ConsolidatedBedrock Surface beneath the Landfill that Controls SubsurfaceFlow

Figure 8. Surface Topographic Map Shows Direction ofSurface Drainage at the Landfill

Surface Drainage Subsurface Drainage Subsurface Drainage Divide

Magnetic Contours %M EM31 Contours EM34 Contours

SamplingPoints

Figure 9. Integration of All Data Established a Framework for Sampling and Drilling at the Landfill

Hydrogeology and Depth to Water TableSurface geophysical programs were also integrated with

geological data to define the depth to the water table at FloraVista and the nature of the geologic units from the surfacethrough the water table. Significant results of that portion ofthe program are as follows: (1) Seismic refraction,resistivity, and time-domain electromagnetic (TDEM) studiesall predicted that the water table was 150 ft beneath thesurface. These predictions were confirmed when two existingwells were located near the site and the depth to water wasmeasured at 150 ft. (2) Seismic refraction predicted that

consolidated bedrock extended from 40 ft beneath the surfacethrough the water table interface. (3) TDEM and frequency-domain electromagnetic studies identified clay layers(aquitards) in the subsurface. (4) The existence of both theclay layers and the bedrock was confirmed by drilling.

DiscussionResults from the ESC program demonstrated that

groundwater is not threatened by the migration of materialsfrom the Flora Vista Landfill. Only low levels of volatile andscmivolatile organic compounds and metals (e.g.. acetone,

EM31 Response

NorthFenced Area

la

o

1

5850 - i

5 8 4 0 -

5830 -

5820 -

5810 - 1

[:••:•:••] S a n d C o v e r

[/>] Sand

• Clay

K - | Sand/Clay

BOH Bottom of Hole

Figure 10. Drilling Confirmed the Position of the Waste Pit Predicted by the Electromagnetic Survey

South

PresentLandfillSurface

Topsoil

| Silt

Nacimiento Bedrock

Original Seplage PitBOH' Nadmiento

ErosionSurface

benzene, chlorobenzene, ethylbenzene, naphthalene, toluene,xylene, lead, chromium, and zinc) were found in isolatedlocations in the septage pit of the landfili and nowhere else onthe site. No evidence exists for either lateral or verticalmovement these contaminants from the waste pit or landfill-Future movement is unlikely because the area receives < 8 in.of rainfall annually.

Groundwater occurs at depth of approximately 150 ftbeneath the landfill. The groundwaier is protected frommigration of potential contaminants by 85-100 ft ofNacimiento consolidated bedrock and 10-20 ft of clay in thealluvium.

Argonne recommended closure of the landfill with noinstallation of monitoring wells or remediation required by theBLM. These recommendations were accepted by theappropriate regulatory agencies.

Waverly, Nebraska, SiteSite Setting and History

At the CCC/VSDA Waverly site in southeastern Nebraska,carbon tetrachloride was found in a public supply well (1.100ppb and 710 ppb) in 1986. Site investigations in 1987 by theRegion VII U.S.

Environmental Protection Agency (EPA) established thatcarbon tetrachloride soil contamination at the formerCCC/VSDA grain storage facility was responsible for thegroundwater contamination (Woodward-Clyde. 19881. Site

characterization studies conducted by a private contractorconcluded that the groundwater regime at the Waverly siteconsisted of a single aquifer in a sand unit with an intermittentclay layer. Groundwaier flow was estimated to be toward thenorth-northwest (Figure 11). The contaminated public anddomestic wells were located northeast of the formerCCC/L'SDA sue. Pumpage from the public well was thought tobe responsible for drawing the contamination to thenortheast.

On the basis of this site characterization study (Woodward-Clyde. 1988), a groundwater extraction well (GWEX) and avapor extraction system (VES) were installed by the EPA atWaverly as part of an emergency removal action in1987-1988. In 1988, operation of the GWEX and the VESsystem was turned over to the CCC/USDA. The remedialsystems have significantly decreased the carbon tetrachlorideconcentrations in the soil vapor and groundwater at the formerCCC/'USDA me. In addition, groundwaier contamination in apublic supply well and monitoring wells located on andnortheast of the site has fallen below detectable levels.However, a domestic well located farther northeast of the siteand estimated to be within the capture zone of the GWEXcontinued to show carbon tetrachloride contamination(Figure 11). Because the groundwater flow direction wasthought to be to the northwest from the site, continuedcontamination in the domestic well was difficult to understand,especially because contaminant levels in monitoring wellslocated between this domestic well and the site had fallenbelow the deiection limit.

A1

PresumedGroundwater Flowin Designing System

\

\

UncontaminatedDomestic Well

ContaminatedDomestic Well

1400 ft

Monitoring Wells O(no CCI4)

• Public WaterSupply Wells

A Domestic Wells

O Monitoring Wells

A-A' Cross Section forFuture Diagrams

PWS-3

Former CCC/USDA GrainFacility at Waverly

0I

800I

Feet

TreatmentSystem

A

PWS-2

PWS-1

Figure 11. Waverly, Nebraska, Site, with Direction of Groundwater Flow Presumed from Previous Investigations

A Record of Decision (ROD) for Waverly was issued by theEPA in 1990. Among other items, the ROD required anexplanation of the contamination in the domestic wellnortheast of the site and reevaluation of the are? of influenceof the existing GWEX. At this point, the CCC/USDArequested Argonne's assistance in addressing these two issues.

The ESC ProcessEvaluation of Existing Data. The first step in the ESC

process for Waverly was critical review and evaluation ofexisting data. Although the private contractor performing theinitial SI had compiled ail existing well data, no effort hadbeen made to use these data to understand the geology andhydrogeology of the site (Woodward-Clyde, 1988). A reviewof the available geologic logs of monitoring wells, irrigationwells, and public supply wells, coupled with geologicreconstructions based on these well data, indicated that twosand aquifer units separated by a continuous clay layer werepresent immediately beneath the Waverly site (Figure 12).This concept is directly opposed to the conclusions reached inthe previous SI, in which one aquifer was postulated for theWaverly site. In addition, evaluation of major ion chemistryin groundwater samples from monitoring wells installed at thesite indicated significant differences between the upper andlower sand units (Figure 13).

Use of these existing data led to the conclusion that thegroundwater flow direction for the upper aquifer was mostlikely to the north-northeast and not the north-northwest(Figure 14). The mistake in determining the flow directionoccurred because the previous contractor assumed that oneaquifer was present and mixed water level measurements fromthe upper and lower aquifers. (Only the upper aquifer iscontaminated at the Waverly site.)

To substantiate the northeasterly flow direction of theupper aquifer, groundwater levels were recorded before the fieldinvestigations began by using monitoring wells installed inthe upper and lower aquifers during the previous sitecharacterization efforts at Waverly. These measurementsindicated that the groundwater flow in the upper aquifer was tothe northeast, not to the northwest as determined in (heprevious study (Figure 14). The water level elevation in thelower aquifer was about 1 ft lower than that in the upperaquifer. Nevertheless, water levels in the lower aquifer werenot influenced by pumpage in the upper aquifer, indicating alack of hydraulic connection between the two aquifers.

However, as Figure 12 shows, the behavior of the aquifersystems about 3.000 ft north of the former grain storagefacility could not be stated with any degree of certainty

Mixed Sand, Silt, and Clay

TwoAquifers

Figure 12. Revised Concept of Aquifer System at Waverly. Produced by ANL with a Review of Existing Data

(line A-A'. Figures 11 and l-l). Well logs in this areaindicated a one-aquifer system. Whether the two aquifersbeneath the former grain storage sue merged or one waspinched out was unknown.

The ESC field program was designed to answer specificquestions in light of this new mode! for the aquifer systems.The major objectives wer* > 1) to verify the presence of twoaquifers north of the sue and determine if they merge or if oneaquifer is pinched out and '2) to determine the extent of anypreviously unmapped contamination in the upper aquifer.

As a refcrzncs point for the field studies, a type geologicsection with data from immediately beneath the former grainstorage site was establ ished for comparison with andinterpretation or" field Jala from north-northeast of the siteiFigure 15;. Geologic data along line A-A 'f igure 14) weregathered from soil borings -made with a hnilow-sicm auser ora mud-n;tary dr.lll. Gr-ninJ'*iie. ' >j/nnles were obtained with aHydrjp' jnch :• r analysis >f major ions, is Mopes, and carbontetrachlor.de. f'.-r comparison with known aquifer chemistriesimmediately beneath the former CCO/t 'SDA site. A surfacetime-domain geophysics investigation was conducted alongline A-A' :n an attempt to help map and substantiate ordisprove the continuous nature af !he clay layer separating thetwo aquifers. The J-.e •>!' data from these three differentmethodologies to reach, conclus ions on hydrogeologicfeatures at Waverly increased the credibility of the resultsgenerated by the ESC process without installing a largenumber ot' m.inii.'nng wells

Use itf C:'OIIIII\ i.x soil Honngs u-.ve drilled lo inenorthwest, north, .ind rv••rthea-.t >( the sue ro evaluate theunhnui r . -f ;ne " M -.and units and the intervening clav

Figure 1?. Major Element Chemistry of the Two Aquifers atWaverly

clayer. Geologic Ings of the soil horings indicated :hepresence of clay and »and uniLs away from the site (Figure 16!.However, the geologic Ja.'a could be interpreted to indicateei'.her that both of the sand units and the intervening clay werecontinuous across the area of investigation or that the upperaqaifer was pinched out to the north. Therefore, the geologicdaia could not be used alone to delineate the exacth\drogeolr.gic relationships north of the site.

L'sc1 of GrounJ^awr Geochemistry. Groundwater sampleswere collected with a HydroPunch from the six soil bonngsdrilled for the geology study along line A-A'. Comparison ofthe major ion and tritium isolopic compos i t ions ofgroundwater samples collected from these soil borings to thereference geocheraical data (Figure 17) provided strongevidence iiut the upper aquifer is absent away from theWaverly sue (Figure IKI. The ionic tritium concentrations ofgt 'unjwater samples L illecicd jbove and below the clay layerintersected in soil '>• nr.gs ar«-ut 2.(100 ft north northca.st of

A'

UncontaminatedDomestic Well

Contaminated £Domestic Well

1400 ft

CorrectGroundwater

Flow

Monitoring Wells O(no CCI4)

• Public WaterSupply Wells

A Domestic Wells

O Monitoring Wells

A-A' Cross Section forFuture Diagrams

PWS-3

Former CCC/USDA GrainFacility at Waverly

800I

Feet

TreatmentSystem

A

PWS-2

PWS-1

Figure 14. Direction of Groundwater Flow in the Upper Aquifer at Waverly, Determined by ANL from a Review of Existing Data

the site were low and less variable, similar to those of samplesfrom the lower aquifer at the site (Figure 17). This resultindicates that the upper aquifer is absent north of the site. Thegeochemical data further indicate that the hydraulic separationbetween the two aquifers is maintained away from the site andthat contamination is not migrating to the lower aquifer. Thegeochemical data, therefore, allowed questions left from thegeologic interpretation to be answered and the interpretationof the aquifer system to be further refined.

Use of Surface Geophysics. Additional evidence for theabsence of the upper aquifer north of the Waverly site wasobtained from surface geophysical surveys. A TDEM surveywas performed along line A-A' (Figure 14) in the areas of soilboring investigations. Data reduction using traditionaltechniques produced a subsurface profile (Figure 19) that wasinconsistent with the known geologic relationships at the site(Figure 15). Consequently, the data were reprocessed with themore sophisticated technique of image inversion. Thistechnique does not require a priori constraints on the numberof lithologic layers, as do the traditional methods; therefore,it provides a more unbiased means of interpreting thegeophysical data. Results of the image inversion processingof TDEM data are shown in Figure 20. The disappearance ofthe upper aquifer sand unit is indicated to the north, consistentwith the geochemical data.

Use of an Integrated Model. Figure 21 shows theintegrated model of the geologic and hydrogeologicrelationships at Waverly, based on the geological,geochemical, and geophysical data. As this diagram shows,the upper aquifer is pinched out the north-northeast of the site,and only the lower aquifer is present. No merging of the twoaquifers occurs.

On the basis of this hydrogeologic model, carbontetrachloride values obtained from the HydroPunch sampling,and the history of contamination and pumpage from adjoiningwells, the configuration of the contaminant plume wasreconstructed. This reconstruction indicated that the capturezone of the GWEX installed at Waverly was insufficient tocapture the entire plume. The portion of the plume notcaptured by the GWEX continued to migrate to the northeast,along the natural direction of groundwater flow. This portionof the plume is the cause of the continued contamination in thedomestic well northeast of the Waverly site. The predictedplume configuration was confirmed by additional drilling andgroundwater sampling (Figure 22).

DiscussionAt the CCC/USDA Waverly site, improper use of existing

data prevented full understanding of the hydrogeologic systembefore remedial construction began. The end result was

10

A1

Feel AboveMean

Sea Level

1130-

1120 -

1110-

1100-

10PC -

1080-

1070-

1060-

1050-

1040 -

1030 -

1020-

1010-

Sile

3000 2500 2000I

1500

Feet

1000 500

Figure 15. Type Geologic Section Directly Beneath Former CCC/USDA She at Waverly

A'1130-

1120-

1110-

1100-

1090-

Feet AboveMean 1070-

S e a L e v e l 1060-

1050-

1040-

1030-

1020-

1010-

3000 2500 2000 1500

Feet

1000 500

Figure 16. Geologic Log Data at Waverly AJlowcd More than One Possible Inierpretation for Aquifer Sand Units

A1

1130

1120

1110

1100

1090

Feet AboveMean 1070

1060

1050

1040

1030

1020

1010

High, variablecomposition

High 3 H(>20 TU)

3000 2500 2000 1500

Feet

I1000

f500

Figure 17. Geochemical Data for the Waverly Aquifers Directly Beneath the Former CCC/O'S DA Site

1130-

1120-

1110-

1100-

1090-

_ ,.. 1080-Feet Above

Mean 1070-

1060-

1050-

1040-

1030-

1020-

1010-

A1

High, variablecomposition

High 3H(>20 TU)

Low, lessvariable

composition

3000 2500 2000I

1500Feet

1000 500

Figure 18. Geochemical Data Were Crucial in Correctly Defining the Hydrogeological Regime at Waverly

12

A'

O—i

20 —

g 40 —

Q.

g 6 0 -

8 0 -

1 0 0 -

W24 W25 W26 W27 W28 W29 W30 W31 W32 W33 W34 W35 W36 W37 W38I I I I I I I I I I I I I I I

6 7 7

Figure 19. Conventional TDEM Profile (ohm-meters) at Waverly (Section A-A1)

A A1

W24 W25 W26 W27 W28 W29 W30 W31 W32 W33 W34 W35 W36 W37 W38

20-

£ 40 —

i.60 H

80 —

100 —

i- \ <20Upper Aquifer

Sand

VP7A 15-20Lower Aquifer

Sand

Figure 20. Image Inversion TDEM Profile (ohm-meters) at Waverly (Section A-A1)

significant additional cost to the CCC/USDA, «:<!.ich wasrequired to install modifications to the present system (anadditional GWEX, piping back to the treatment plant,additions to the treatment plant, etc.), that should not havebeen incurred. In addition, wells to the northeast of the sitewould eventually have been contaminated by migration of theplume, resulting in potential health threats to individuals.

The Argonne field program for the additional SI was brief(approximately two months including report writing) and didnot necessitate the installation of permanent monitoringwells. The use of multiple methodologies allowed the aquifersystem northeast of the site to be understood with onlytemporary intrusion into residential and agricultural areas.

Murdock, Nebraska, SiteSite Setting and History

The CCC/USDA operated another grain storage facility atMurdock, Nebraska, approximately 22 mi north-northeast ofLincoln and the Waverly, Nebraska, site discussed above.Carbon tetrachloride was found in the public water supply at

Murdock in 19SS (636 ppb), and an Immediate RemovalAction was initiated by the EPA. The CCC/USDA acceptedresponsibility for the groundwater contamination and signedan Order on Consent Agreement in 1991, in which the agencyagreed to evaluate remedial actions for the Murdock site. Thegeneral location of Murdock and the former CCC/USDA siteare shown in Figure 23. As part of an ongoing program forthe CCC/USDA, Argonne was asked to evaluate previous SIdata for the Murdock site to determine if additional sitecharacterization was required for correct evaluation of remedialalternatives.

The ESC ProcessEvaluation of Existing Data. Various Sis of the Murdock

area were carried out after the initial identification of theproblem in 1985 and the Immediate Removal Action in 1986and early 1987 (Ecology and Environment, 1986; Woodward-Clyde, 1987; CH2MHHI, 1988a, 1988b). The primaryobjectives of these studies were to outline the contaminantgroundwater plume, to determine the flow direction of theaquifer, and to ascertain whether a soil source was present at

13

A1

1130-

1120-

1110-

1100-

1090-

Feet Above 1080-Mean

Sea Level 1070-

1060-

1050-

1040-

1030-

1020-

1010-

3000 2500 20001

1500

Feet

1000I

500

Figure 21. Pinchout of the Upper Aquifer at Waverly, as Interpreted from TDEM Data, Geochemistry, and Geology

the former CCC/USDA site, all for the purpose of evaluatingand selecting remedial options. No soil source was found atthe former CCC/USDA site. Major results from previousinvestigations of the •• mndwatcr plume are given below.

The first investigation used soil gas measurements toindicate the direction of movement of the groundwatcr plumeand to guide the installation of monitoring wells. However,the assumption that surface soil gas measurements can be usedto indicate the behavior of contaminants in groundwater atdepth is flawed. The many factors affecting soil gas values(soil moisture, soil type, geologic features, temperature,Henry's law) invalidate their use as indicators of plumemovement at depth. In addition, review by Argonne of thesoil gas procedures used at Murdock demonstrated that the boththe data collection and analytical procedures were performedincorrectly. Unfortunately, monitoring wells were installedon the basis of a northeasterly flow direction for the plume andaquifer, based on the results of the soil 2as investigation(Figure 24).

Four pairs of monitoring wells (one well in each pairshallow at about 30-55 ft and one deep at about 80 ft) wereinstalled, and one set of groundwater samples was collectedfrom each. Samples from only one pair of wells testedpositive for carbon tetrachloride; samples from the other threepairs of wells were negative. On the basis of these results, atheoretical model was derived for the plume at Murdock with aflow direction to the west-northwest (Figure 25), muchdifferent from the direction deduced from the soil gas survey.

Given these conflicting and questionable results from theprevious Sis at Murdock, the CCC/USDA requested Argonnc todesign an ESC program for the site that would generate dataadequate for evaluation and possible design of a remedial

system. Although this ESC study encompassed severaltechnologies, much like the Waverly ESC study discussedabove, only one aspect of the Murdock ESC program will bediscussed here.

Plume Delineation. One of the major objectives ofArgonnes ESC program is to advance the use of subsurfacegroundwater sampling techniques that do not requireinstallation of monitoring wells. Normally, numeroussamples are required to completely and accurately define thelateral and vertical extent of nonconductive contaminationwithin an aquifer. Generating shese data with the monitoringwell approach requires a massive number of wells. Amonitoring well under CERCLA guidelines is limited to a !O-ftscreen. Therefore, a 50-ft-thick aquifer requires five wells toaccurately sample the vertical distribution of contaminants atone location. The average cost of monitoring wellinstallation is S120/ft. and each well requires approximatelythree days to complete. Attempts to accurately mapgroundwater contamination during site characterization withthis approach are prohibitively expensive and timeconsuming. Hence, Argonne sought to use a more cost- andJime-effective approach to oblaining groundwater sampleswithout monitoring well installation.

Argonne used geologic reconstructions, geophysics, andgeochemistry in the first phase of the ESC program atMurdock to constrain and prioritize the sampling program.The results of these studies indicated only one aquifer flowingto the north-northwest at Murdock. The aquifer issemiconfined beneath the former CCC/L'SDA site but becomesunconfined to the north.

The aquifer was sampled both laterally and vertically forcontamination during the second phase of the ESC. Two

14

SBR-01 , SBA-07

Domestic Well

0 £H 800l i t

Feet

Domestic Well

S B A " 1 0 * SBA-11*

,SBA-04,

• SBA-13

Former FederalGrain Facility

AreaofGWEXInfluence

SBA-15

>SBA-14

PlumeConfiguration

Figure 22. Configuration of the Contaminant Plume at Waverly

400 800i l

400 800

Foimst CCCUSOAGmn Sloiag*

FaaMy

Figure 23. General Location of the Former CCC/USDA Site atMurdoclc, Nebraska

• groundwaMr new auctionbasad on « H I yds suivsy

Figure 24. Presumed Direction of Groundwater Flow atMurdock, as Determined by Soil Gas Studies, and SubsequentLocations of Monitoring Wells

15

sampling techniques (hollow-stem auger with an attachedHydroPunch and an electronic cone penetrometer [ECPT] witheither the HydroPunch or bailer) allowed the rapid delineationof both the vertical and lateral extent of the plume withoutinstallation of monitoring wells. Argonne appreciates thecooperation of EPA Region VII in accepting thesegroundwater samples as equivalent to monitoring wellsamples.

Figures 26 and 27. respectively, show the lateral andvertical extent of the carbon tetrachloride plume at Murdock.The plume outlined by the Argonne ESC studies was confirmedby positive carbon tetrachloride results in water samplescollected where the plume exits into a creek at the northernedge of the town. The plume distribution and flow directionpredicted by the ESC are much different from those predictedby the earlier studies. The ESC program generated sufficientcontrol data on the distribution of carbon tetrachloride in theaquifer to allow the CCC/USDA to make accurate evaluationsof remedial alternatives.

Cost and Time Comparisons for the ESC Aquifer SamplingMethodology versus Monitoring Well Installation. A costand time analysis comparing the subsurface samplingapproach of the Murdoclc ESC to the traditional approach ofmonitoring well sampling was made to illustrate theadvantages of the ESC. The following data were used inconstructing the cost comparison: (1) During the ESCprogram. 84 aquifer samples were obtained. (2) The depth tothe aquifer at Murdock is approximately 55 ft, and the aquifer

/N\

400

200 pc© cartxxi tttncNortda

800 ppD cirtnn wncModo*

• " ^ ^ • grournjw8!»r flow direction

Figure 25. Theoretical Plume Model and Groundwater FlowDirection for Murdock, Based on Monitoring Well Data

is approximately 30 ft thick. An average depth of 70 ft wasused in determining monitoring well costs. (3) The averagecost for monitoring well installation is SI20/ft, and the timeis approximately three days including development (4) Onesample per monitoring well is assumed for equivalence withECPT and hollow-stem auger sampling. (5) No costs forprofessional staff were included in the comparisons. Costswere limited to drilling contractor estimates and the actual

>500 ppb carbon tetrachloride

5-500 ppb carbon tetrachloride

= HydroPunch andcone penetrometer

=well= groundwater flow direction

A-A' = cross section

400 800i i

Former CCC/USDAGrain StorageFacility

Figure 26. Lateral Extent of the Contaminant Plume at Murdock, as Measured by Argonne with the HydroPunch and ConePenetrometer

1,300-j

s.2toCDCOCO

CD

« 1,200-

Aquiferunconfined

Former CCC facility

Watertable

i— Piezometricsurface

Clay

5-500 ppb carbon tetrachloride

>500 ppb carbon tetrachlorideAquifer confined

0A

1,000 2,000ft

3,000 4,000

Figure 27. Venical Extent of the Contaminant Plume at Murdock, as Determined by Argonne with the Hydropunch andCone Penetrometer

costs of the ECPT and hollow-stern auger contractors plusequipment. (6) Comparisons include costs for sampleanalysis by a Contract Laboratory Program laboratory atLevel IV quality.

The actual cost of the ESC groundwater sampling andanalysis program was $200,000, and 16 field days wererequired. The estimated cost and time for the monitoring wellapproach for sampling and analysis of the same number ofaquifer samples at Murdock are $1,000,000 and 252 days.Therefore, the cost of the ESC method is approximately 1/5that of the monitoring well approach, while the time isapproximately 1/15. At sites where the aquifer is thicker, costdifferences would be even more pronounced.

At another CCC/USDA site in Utica, Nebraska, the aquiferis 60 ft thick. For this site, the actual cost of the first phaseof the ESC was $175,000, and the time for completion was10 days. The guidelines above were used to estimate themonitoring well costs at $1,750,000 for an equivalent numberof groundwater samples. Thus, the cost of the ESC approach is1/10 that of the standard monitoring well approach for Utica.The time required for installation of monitoring wells wasestimated at 288 days, for a time differential of 1/28 in favorof the ESC approach.

More importantly, in addition to efficiency of cost andtime, the ESC approach produces a better technical product.Monitoring wells are usually placed sporadically within theaquifer during site characterization. Therefore, completesampling of the aquifer is seldom achieved because of costconstraints. The ESC approach allows for complete samplingand achieves the needed cost and time savings.

DiscussionPrevious site investigations at Murdock were unsuccessful

in accurately delineating the carbon tetrachloride plume. TheESC methodology allowed for rapid and accurate delineation of

both the vertical and lateral extent of the plume without theinstallation of monitoring wells. The ESC approach not onlygenerated better technical data but resulted in significant costand time savings for the CCC/USDA.

SUMMARY AND CONCLUSIONSThe ESC methodology has been demonstrated to be a time-

and cost-efficient process for producing high-qualitypreremedial site characterizations. The ESC methodology isbased on a scientific approach to problem solving that allowsregulatory guidance to be easily incorporated. In other words,science drives the program within a regulatory framework.This methodology differs from attempts to follow a regulatoryguidance document without incorporating a scientificapproach. Such attempts have too often been made inenvironmental site investigations; they have probably beenthe major reason for the technical failure of many previousprograms.

The ESC process is flexible and neither site norcontaminant dependent. The process has been successfullytested and applied in Sis of multiply contaminated landfills inNew Mexico (for the BLM) and at former grain storagefacilities in Nebraska and Kansas, contaminated with carbontetrachloride (for the CCC/USDA). Argonne's preremedial siteinvestigations based on the ESC approach have been acceptedby the appropriate regulatory agencies.

The ESC is a process and not a specific technology.Technologies are incorporated as required by the problem to besolved. Whenever possible, existing available technologiesand methodologies are used for the program. However.Argonne has used the ESC process as a platform foradaptation, development, and testing of new technologies,because the program incorporates a multiple-technologyapproach that allows rapid verification and testing of newconcepts.

17

ACKNOWLEDGMENTThis work was supported by the New Mexico Bureau of

Land Management through interagency agreement YA651-1A9-340002 with the U.S. Department of Energy (DOE), bythe U.S. Department of Agriculture through interagencyagreement 04 P2-92-USDA-CCC with DOE, and by DOE'sOffice of Technology Development under contractW-3MO9-Eng-38.

REFERENCESAEPCO, Inc., Preliminary Assessment CP\) Report for Flora

Vista Site. Farmington. San Juan County. New Mexico.Final report prepared for the Bureau of Land Managementunder contract AA852-CT5-26, 1986.

Baltz, E.H., S.R. Ash, and R.Y. Anderson, History ofNomenclature and Stratigraphy of Rocks Adjacent to theCretaceous-Tertiarv Boundary. Western San Juan Basin-New Mexico. U.S. Geological Survey Professional Paper524-D, 1966.

CH2MHill, Draft EE/CA Work Plan. Murdock. Nebraska.WA 196-716Y, U.S. EPA REM IV, Contract 68-01-7251,March 1988a.

CH2MHU1, Agency Review Draft: Engineering Evaluation/Cost Analysis. Volume I-Report. Volume 11-Appcndices.Murdock. Nebraska. WA 196-716Y, December 1988b.

Ecology and Environment, Inc.. Site Investigation. MurdockGroundwater Contamination. Murdock. Nebraska.Technical Directive Document R-07-8601-029, U.S. EPARegion VII REM/FIT, September 1986.

Roy F. Weston, Inc., Final Site Investigation Report: FloraVista Site. San Juan County. Final report prepared for theBureau of Land Management under contract AA852-CT-4,1988.

Stone, W.J., et al., Hvdrogeoloqv and Water Resources of SanJuan Basin. New Mexico. New Mexico Institute of Miningand Technology, Hydrogeologic Report 6, 1983.

Welder, G.E., Plan for Study for the Regional Aquit'er SystemAnalysis of the San Juan Structural Basin. New Mexico.Colorado. Arizona, and Utah. U.S. Geological SurveyWater Resources Investigations Report 85-4294, 1986

Woodward-Clyde Consultants, Initial Site Evaluation.Murdock Bin Site. Murdock. Nebraska. Document 379-ESI-RT-ENVP-1, U.S. EPA Region VII REM/FIT. June1987.

Woodward-Clyde Consultants, Site Characterization Reportand Description of Expedited Response Action System.Waverlv Groundwater Contamination Site. Waverly.Nebraska. Vol. I, EPA Contract 68-01-6939. REM II,Document 264-ER1-RT-FPNB-1, February 1988.

DISCLAIMER

process disclosed, or represents that Us use would not inence herein to any specific ^merc.a. pr^u . P ^ i t t endorsement , recom-

United Stales Government or any agency thereof.

13