an integrated framework for evaluating subsurface contamination remediation technologies

© 1999,

AAPG/DEG

, 1075-9565/99/$14.00/0Environmental Geosciences, Volume 6, Number 2, 1999 82–89

82

E N V I R O N M E N T A L G E O S C I E N C E S

An Integrated Framework for Evaluating Subsurface ContaminationRemediation Technologies

JAMES L. REGENS,* DONALD G. HODGES,* PATRICK L. WILKEY,

‡

ERIC ZIMMERMAN,

‡

ANTHONY Q. ARMSTRONG,

§

LINDA KELLEY,

i

TIMOTHY A. HALL,

¶

AND EUGENE A. HUGHES**

*

Tulane University Medical Center, New Orleans, LA 70112

‡

Argonne National Laboratory, Argonne, IL 60439

§

Oak Ridge National Laboratory, Oak Ridge, TN 37830

i

CB Consulting, Inc., Lafayette, CA 94549

¶

ManTech Environmental Corporation, Houston, TX 77027

**

Erin Engineering and Research, Inc., Walnut Creek, CA 94596

ABSTRACT

Reliable tools are needed to ensure efficient selection and deploy-

ment of conventional and innovative technologies to remediate

trichloroethylene-contaminated soils and groundwater. This ar-

ticle describes a Technology Evaluation Framework (TEF) that

integrates eight criteria (technical performance, life cycle cost,

process residuals, regulatory feasibility, risk, future use, natural

resource damages, and stakeholder concerns) relevant to site-

specific technology selection and deployment for voluntary or

regulatory agency–mandated cleanups. The TEF provides a ba-

sis for systematically comparing innovative and conventional

technologies in terms of meeting remediation goals. The com-

pleted TEF provides a documented, reproducible evaluation

summarized on a rollup sheet, which can be updated as new in-

formation becomes available. The results of a pilot application

of the TEF at the 317 Area of Argonne National Laboratory in

Illinois are reported.

Key Words:

remediation technologies, subsurface contamina-

tion, groundwater, soil, trichloroethylene.

INTRODUCTION

Remediating subsurface contamination today often in-volves balancing technology performance and risk reduc-tion with fixed or limited budgetary resources, stakeholders’concerns, and regulatory constraints (MacDonald and Ka-vanaugh, 1994; National Research Council, 1994; Begley,1996). In response to these information needs, an integratedapproach for systematically comparing conventional and in-novative remediation technologies to assess site-specific re-mediation options has been designed. The TechnologyEvaluation Framework (TEF) integrates eight criteria rele-

•

•

vant to technology selection and deployment for voluntaryor regulatory agency–mandated cleanups of soil or ground-water. A pilot application of the TEF was conducted usingdata from three U.S. Department of Energy sites and oneU.S. Department of Defense site (Regens et al. 1998).Trichloroethylene (TCE) was used for the benchmarkingexercise because TCE contamination of soil and groundwa-ter is a pervasive problem at U.S. Department of Defenseinstallations, across the U.S. Department of Energy nuclearweapons complex, and private sector sites (McCarty, 1997;National Research Council, 1997). This article reports theresults of the TEF’s application to the 317 Area at ArgonneNational Laboratory (ANL) in Illinois.

OVERVIEW OF THE TECHNOLOGY EVALUATION FRAMEWORK

The TEF provides a standardized methodology to inte-grate diverse factors influencing the deployment of environ-mental technologies. The TEF encompasses an array of fac-tors ranging from technical performance, life cycle costs,and risk to future use. Eight criteria with measurable indica-tors (technical performance, life cycle cost, process residu-als, regulatory feasibility, risk, future use, natural resourcedamages, and stakeholder concerns) are employed to assessthe capability of a technology or suite of technologies to ad-dress environmental restoration problems on a site-specificbasis (Figure 1).

The TEF provides a basis for systematically comparinginnovative and conventional technologies in terms of meet-ing remediation goals. Because the TEF does not employ aseries of a- priori weights for each criterion, it facilitatestradeoffs among the eight criteria based on site-specificneeds, such as temporal or physical constraints, scheduledemands, and funding profiles.

R E G E N S E T A L . : E V A L U A T I N G R E M E D I A T I O N T E C H N O L O G I E S

83

To complete the TEF, the user needs to assemble sitebackground data and define working assumptions, includingdeployment scenarios for each of the technologies beingevaluated, to produce the information required to generateratings on each indicator for the various criteria. The com-pleted TEF provides a documented, reproducible evaluationsummarized on a rollup sheet, which can be updated as newinformation becomes available.

ENVIRONMENTAL SETTING

Argonne National Laboratory, located

z

40 km southwestof Chicago, Illinois, has been in operation since the late1940s and comprises

z

800 hectares. For the foreseeable fu-ture, land use will remain industrial. Located in suburbanChicago, the area surrounding ANL has undergone majorresidential development.

At

z

183 m above sea level, ANL overlays a shallow, len-ticular, confined aquifer and a major river valley that is

z

24m lower in elevation immediately to the south of the site.The regional topography in the vicinity of ANL is flat; to-pography at the site is slightly rolling. Surface drainagefrom Argonne flows via small streams to the river valley.The region has a generally moderate climate. Winters arecold, with an average of 112 days per year when the mini-mum temperature is at or below 0

8

C and 3 days per yearwhen the minimum temperature is below

2

17

8

C. Summersare moderately warm and humid, with an average of 27 daysper year when the maximum temperature is at or above32

8

C. Annual precipitation averages 101 cm. Precipitationis usually well distributed, although on average fall is thedriest season. Average annual snowfall is 102 cm.

The pilot application of the TEF focused on remediatingTCE contamination in ANL’s 317 Area that resulted fromcleaning and degreasing related to the manufacturing, re-search, and laboratory efforts at the site. Downstreamgroundwater monitoring indicates no off-site migration of

the TCE-bearing plume, although stakeholders have ex-pressed concerns regarding potential natural resource dam-ages to the forest located adjacent to Argonne because ofcontamination at the site.

Site Geology

ANL is located within the Morainal Country of the GreatLakes Section of the Central Lowland Physiographic Prov-ince. Glacial till deposits are the primary shallow subsurfacematerial. Native deposits have been modified in areas of ex-cavation and fill activities. ANL is in an area of recessional,glacial moraine deposits of varying thickness overlying Sil-urian bedrock formations. These moraines consist primarilyof northwestward- to southeastward-trending reworked tillscomposed primarily of sand, pebbles, and cobbles, whichhave a silt and clay matrix. Discontinuous, lenticular sandand gravel deposits are also locally present within these tilldeposits. Soils are primarily low-permeability silts andclays of glacial origin. Glacial overburden thickness rangesfrom 15–20 m. Vertical permeability of these predomi-nantly silty clay deposits ranges from 3.8

3

10

2

6

to 7.0

3

10

2

8

cm/sec. Cation-exchange capacity ranges from 0.03–0.10 milliequivalent/g, indicating relatively good attenua-tion characteristics.

Analysis of grain size distribution indicates a gradual in-crease in silt content with increasing depth (Figure 2).Within the predominantly silt- and clay-bearing till overbur-den are scattered lenticular deposits of silt and sand rangingin thickness from 0.3–3.7 m. In general, these lenses are dis-continuous. Bedrock underling the glacial overburden mate-rials is predominantly gray dolomite. The upper 3 m of thedolomite is highly fractured and oxidized, indicating that itis or was a typical shallow weathered zone.

Hydrogeology

Perched groundwater occurs beneath ANL’s 317 Areawithin the silt and sand layers under confined conditions asperched groundwater. Static water levels within these unitsrange from

z

1.2–13.4 m below ground surface. Shallowmonitoring well data indicate that the groundwater flow issouth–southeastward, with relatively steep horizontal hydrau-lic gradients ranging from 0.01–0.04. Groundwater also wasencountered within the dolomite. Static water levels withinthis unit range from

z

20.7–23.8 m below ground surface.These depths indicate that groundwater is present under un-confined water table conditions in this unit and flows south-westward with an average horizontal gradient of

z

0.02.Single-well permeability testing performed in newly in-

stalled monitoring wells indicates that hydraulic conductiv-ity values within the silt and sand lenses ranged from 2.6

3

10

2

3

to 1.4

3

10

2

6

cm/sec. Bedrock aquifer hydraulic con-ductivities ranged from 8.5

3

10

2

3

to 2.8

3

10

2

6

cm/sec.By using horizontal gradient data and estimated effective

FIGURE 1: Criteria for the TEF.

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porosity values, lateral groundwater seepage velocities werecalculated; these range from 0.6–8.8 m/yr in the silt andsand layers and from

z

0.6–5.8 m/yr in the dolomite aquifer.The geologic and hydrogeologic data indicate that the scat-tered silt and sand layers and the upper weathered zone ofthe dolomite aquifer act as the primary groundwater con-taminant migration pathway. The majority of the TCE con-

centrations detected in subsurface soil and groundwater arepresent in these zones (Figure 3).

TECHNOLOGY DEPLOYMENT SCENARIOS

To test the TEF, a set of remediation scenarios was developedfor the 317 Area. Actual remediation might include deploying

FIGURE 2: Schematic of geologic crosssection. horiz., horizontal; VOC, volatile or-ganic compounds.

FIGURE 3: Schematic of TCE plume inANL 317 Area.


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the technologies described below alone or in combination. Fiveconventional technologies (slurry wall, pump-to-contain, pump-and-treat, capping, and dig-and-haul) and five innovative tech-nologies (in situ groundwater management, funnel-and-gatewith an iron filings wall, LASAGNA, low-temperature thermaldesorption, and soil vapor extraction) are considered. In addi-tion to containment or treatment, long-term monitoring typi-cally would be part of remedial actions. However, to compareindividual soil and groundwater remediation technologies, long-term monitoring activities that are not specifically associatedwith the deployment of a particular technology are not consid-ered as part of the scenarios summarized below.

Groundwater Containment

Three technologies for groundwater containment wereevaluated: slurry wall, in situ groundwater management, andpump-to-contain. Construction of a slurry wall along theleading edge of the TCE-bearing groundwater plume wouldrequire approximately one month (assuming a three-operatorcrew). The slurry wall would be 30.5 m long, 12.2 m deep,and 0.6 m wide. It would be constructed through silty clayand silty sands, with on-site soils mixed with 6% bentonite(on a dry-unit-weight basis) used as backfill. The depth togroundwater is 7.6 m, and conventional slurry trenchingwould be used. No residuals would be generated from thisprocess.

Alternatively, a system for in situ groundwater manage-ment could be constructed at the leading edge of the TCE-bearing groundwater plume and measure 30.5 m long, 12.2 mdeep, and 1.8 m wide. A crew of five operators would con-struct the system in three months. It would be constructedthrough silty clay and silty sands. Sand would be imported forbackfill and would be mixed in Frac tanks before placementin the trench. Conventional slurry trenching methods wouldbe used. The depth to groundwater is 7.6 m. The excavationspoils would be hauled for disposal to a site 32 km away.

Groundwater containment also could be pursued usingpump-to-contain with six extraction wells, each with a 1.5-m-long stainless screen. Four operators working 10 days wouldconstruct these wells, each 12.2 m deep with a 10.2-cm diam-eter. The wells would be located at the leading edge of thegroundwater TCE plume. Wells would pump 13.6 L/min to-tal, and the influent TCE concentration would be 10 mg/L.Double-contained conveyance piping would extend 91.4 m,and the contaminated groundwater would be treated by usinga skid-mounted, liquid-phase granular activated carbon sys-tem. The wells would operate for 10 years and remove TCEuniformly over time. An operator would remain on site one-fourth of the time to maintain and monitor the system.

Groundwater Treatment

Funnel-and-gate with an iron filings wall, LASAGNA(Monsanto Corp., St. Louis, MO), and pump-and-treat were

compared. On the basis of hydrogeologic conditions, no lat-eral containment would be needed to install a funnel-and-gate system. In approximately three months, a crew of fiveoperators would construct a gate across the leading edge ofthe TCE plume. The iron filings wall, which includes thegate, would be 30.5 m long, 12.2 m deep, and 1.5 m wide. Itwould be constructed through silty clay and silty sands. Thedepth to the groundwater is 7.6 m. The on-site soils wouldbe mixed with bentonite and used as backfill. Conventionalslurry trenching methods would be used, and disposal ofgate excavation spoils would be at a site 32 km away. Theiron filings would not be replaced.

The LASAGNA system could be constructed across theleading edge of the TCE plume to a length of 30.5 m and adepth of 12.2 m. It would be constructed through silty clayand silty sands; groundwater occurs at a depth of 7.6 m.Construction would be completed in approximately onemonth, and the system would operate for five years with acrew of five operators. The electrical requirements of thissystem would be 2,000,000 kWhr/yr.

A pump-and-treat system using 15 extraction wells couldbe constructed within the TCE plume in one month with acrew of four operators. These 10.2-cm diameter wellswould each have a 1.5-m-long stainless screen and be in-stalled to a depth of 12.2 m. The wells would pump 36.4 L/min total, and the influent TCE concentration would be 50mg/L. Double-contained conveyance piping would extend152.4 m, and the contaminated groundwater would betreated by using a skid-mounted, liquid-phase granular acti-vated carbon system. This system would be set to operatefor 10 years with uniform TCE removal over time. An oper-ator would remain on site half-time to monitor and maintainthe system.

Soil Containment

A slurry wall and capping were evaluated as soil contain-ment options. The slurry wall would be constructed aroundthe TCE source and measure 140.2 m long, 12.2 m deep,and 0.6 m wide. The wall would be constructed throughsilty clay and silty sands. On-site soils would be used asbackfill and mixed with bentonite. The depth to groundwa-ter is 7.6 m. Conventional slurry trenching methods wouldbe used; no residuals would be generated. Constructionwould require approximately two months with a crew ofthree operators. For the capping alternative, a ResourceConservation and Recovery Act (RCRA) cap covering 0.10hectares would be constructed with surface vegetation tocover the source term area. Construction would require onemonth, and the crew would consist of eight laborers.

Soil Treatment

Three technologies initially were considered (dig-and-haul, low-temperature thermal desorption, and soil vapor

86


extraction), but soil vapor extraction was eliminated fromconsideration because the fine-grained soil composition ofthe 317 Area make it inapplicable for that site. By using dig-and-haul, the excavation volume would be 3440.5 m

3

. Thetransportation distance would be 32 km, and the digging andhauling duration would be two weeks. The excavating andloading crew would consist of four laborers, and the trans-portation crew would use 25 20-ton trucks. To install a low-temperature thermal desorption (LTTD) system, excavationand loading in the treatment unit would require four labor-ers. There would be a low-temperature thermal treatmentunit with an off-gas treatment unit, and treatment would re-quire three weeks. A volume of 3440.5 m

3

would be treated,and the treated soils would be backfilled on site.

RESULTS

All three of the technologies evaluated for groundwatercontainment were rated as high on the Technical Performanceindicators (Figure 4). At $188,000, the total life-cycle costsfor the slurry wall are less than one-half that of the twoother technologies, and in situ groundwater management

•

was almost 40% less expensive than is pump-to-contain. Inlarge part, this stems from the fact that is pump-to-containoperations and maintenance (O&M) costs extend over a 10-yr period while there are no O&M costs for the slurry wallor in situ groundwater management. Permitting experiencewas rated high for the slurry wall and pump-to-contain, butin situ groundwater management received a low rating forregulatory feasibility because it has been used only for fielddemonstration projects. Process residuals for each technol-ogy were rated as high because existing systems can easilyaccommodate residuals from these systems. Risk ratings forthe three technologies were identical, with all implementa-tion risks being categorized as low. All three technologieswere rated as medium for relative risk reduction because notall of the potential exposure pathways are mitigated. Allthree technologies were rated as low for future use becausefuture land uses are likely to be limited due to remainingcontamination.

The three groundwater treatment technologies were ratedas high for all four indicators of Technical Performance,with two exceptions (Figure 5). Pump-and-treat was rated asmedium for effectiveness because it probably will not

FIGURE 4: TEF summary for groundwater containment. approx., approximately; IGM, in situ groundwater management; w/, with; M&I, management and integation.


87

achieve remedial action objectives. LASAGNA was ratedas medium on reliability because this technology has beenused only in demonstrations. Although their technical per-formance was roughly comparable, life-cycle costs differedsignificantly among the three technologies. At a cost of ap-proximately $1.5 million, LASAGNA was the most expen-sive technology evaluated for groundwater treatment due todifferentials in the cost of O&M. Risk ratings for the threetechnologies considered were identical except for the sitesafety risk for LASAGNA, which was rated as medium be-cause of the potential worker exposure to high voltage in anonroutine application. Regulatory feasibility ratings differamong the three technologies. Permitting experience forpump-and-treat was rated as high, because it is a conven-tional technology that has been implemented frequently.Permitting experience with funnel-and-gate has been lim-ited; thus, so it was rated as medium. LASAGNA was ratedas low because its use has been limited to demonstrations.Stakeholder concerns for groundwater treatment were per-formance, cost, and risk associated with LASAGNA andnatural resource damages for all technologies considered.

Soil Containment

The only differences in the ratings for the two soil con-tainment technologies were for life-cycle costs and futureuse. The total costs for the slurry wall were more than dou-ble those identified for the RCRA cap. Capping was consid-ered to severely limit future land use because of the perma-nence of the cap and restrictions on access. No stakeholderconcerns related to implementation of these technologieswere identified.

Soil Treatment

Only dig-and-haul and LTTD were identified as being ap-plicable for remediation of ANL’s 317 Area. Both technolo-gies were rated high in terms of technical performance. To-tal costs for dig-and-haul were almost $1 million greaterthan those of LTTD because of the large difference in capi-tal costs between the two. Another key difference betweenthe two technologies was risk. Relative risk reduction wasrated high for dig-and-haul and medium for LTTD. Expo-sure risk was rated low for dig-and-haul and medium forLTTD because of the potential exposure to contaminants

FIGURE 5: TEF summary for groundwater treatment. H, hour.

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during the treatment process. Transportation risk was ratedmedium for dig-and-haul due to the relatively large volumeof soil that would be transported on public roads.

CONCLUSIONS

Decision support tools can aid significantly efforts by en-vironmental managers to select and deploy technologies toremediate subsurface contamination. Reliance on such toolsmakes it possible to screen multiple technologies rapidly toidentify the most promising alternatives. This pilot applica-tion of the TEF provides significant insights into the abilityof the TEF to support decision-making about site remedia-tion options.

The results of the ANL case study reveal that the TEF pro-vides a standardized approach for documenting and visuallydisplaying information about the technology alternatives con-sidered and the expectations for the decision. Documentationsupports future requirements to evaluate progress, incorpo-rate new data, and assess overall performance. Use of theTEF encourages careful consideration of a broad mix of tech-nology options and alternatives before making a final deci-sion. The TEF also can incorporate differences in weightingplaced on particular criteria by site-specific decision contextsand makes trade-offs apparent.

In addition, because the underlying assumptions relativeto a technology’s scoring are documented, the TEF is suit-able for incorporating information gained through early andcontinuous involvement of stakeholders. Such a dialoguepotentially can increase the accuracy and completeness ofthe information on which the evaluation is based. In es-

•

sence, use of the TEF can help ensure that the full range ofrelevant factors is taken into account in selecting and de-ploying technologies to remediate soil and groundwatercontamination.

ACKNOWLEDGMENTS

This research was supported by the U.S. Department ofEnergy (DOE), Cooperative Agreement No. DE-FC01-94EW54102. The views and opinions expressed do not nec-essarily represent the official position of the U.S. Govern-ment or DOE.

REFERENCES

Begley, R. (1996). Risk-based remediation guidelines take hold.

Environ Sci Technol, 30

,438A–441A.

MacDonald, J. A., and Kavanaugh, M. C. (1994). Restoring con-

taminated groundwater: An achievable goal?

Environ Sci Tech-

nol, 28

, 362A–368A.

McCarty, P. L. (1997). Breathing with chlorinated solvents.

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ence, 276

, 1521–1522.

National Research Council. (1994).

Alternatives for groundwater

cleanup.

Washington, DC: National Academy Press.

National Research Council. (1997)

Innovations in ground water

and soil cleanup.

Washington, DC: National Academy Press.

Regens, J. L., Hodges, D. G., Wilkey, P. L., Kelley, L., Armstrong,

A. W., Zimmerman, R. E., Hall, T. A., and Hughes, E. A.

(1998).

An integrated framework for environmental technology

evaluation.

Prepared for the U.S. Department of Energy, Office

of Environmental Management. New Orleans: Consortium for

Environmental Risk Evaluation.

•

•

ABOUT THE AUTHORS•

James L. Regens, Ph.D,

James L. Regens, Ph.D., is Freeport-

McMoRan Professor of Environmental

Policy and Director of the Entergy Spa-

tial Analysis Research Laboratory at Tu-

lane University Medical Center. Dr. Re-

gens has an endowed chair with tenure in

the Department of Environmental Health

Sciences, School of Public Health and

Tropical Medicine, Tulane University Medical Center. He is respon-

sible for developing and managing a multidisciplinary research pro-

gram focusing on health and ecological risk assessment, environmen-

tal restoration, public health, and natural resources. Dr. Regens

specializes in health and ecological risk assessment, environmental

remediation, and strategic planning.

Donald G. Hodges, Ph.D.,

Donald G. Hodges, Ph.D., is an Asso-

ciate Professor and Assistant Director of

the Entergy Spatial Analysis Research

Laboratory at Tulane University Medical

Center. Dr. Hodges is a tenured faculty

member in the Department of Environ-

mental Health Sciences, School of Pub-

lic Health and Tropical Medicine, Tu-

lane University Medical Center. His research program focuses on

environmental economics and policy, environmental and natural re-

source management, and environmental restoration.


89

Patrick L. Wilkey, P.E.,

Patrick L. Wilkey, P.E., is Director of

the Center for Environmental Restoration

systems, Argonne National Laboratory.

He has 20 years of experience in design,

construction, consulting, and research,

including projects on brownfields; nu-

clear, hydroelectric, and coal-fired power

plants; conventional and high-rise struc-

tures; nuclear waste repositories; sanitary, hazardous, low-level and

mixed-waste remediation and disposal; and gas pipelines. Mr.

Wilkey has designed and executed plans for geotechnical exploration

across the United States. He has performed and managed research

into the characterization and remediation of soil and groundwater

contaminated by hazardous, urban, and military wastes.

Linda Kelley, P.E., P.M.P.,

Linda Kelley, P.E., P.M.P., is a civil/

geotechnical engineer from UC Berkeley

with 14 years of experience planning and

executing remedial cleanups in Califor-

nia. Ms. Kelley is a principal with CB

Consulting, Inc. in San Luis Obispo, CA

and specializes in closure-related remedi-

ation of hazardous waste disposal sites

and CERCLA and RCRA cleanups at industrial facilities.

Anthony Armstrong

Anthony Armstrong is the leader of

the Risk and Regulatory Analysis Group

of the Life Sciences Division of Oak

Ridge National Laboratory. His research

interests are development and imple-

mentation of probabilitistic risk assess-

ment methods and software, performing

cost/risk/benefit analysis to support envi-

ronmental decisions and conducting performance assessments of en-

vironmental remediation technologies.

Eric Zimmerman, Ph.D.,

Eric Zimmerman, Ph.D. is a Civil En-

gineer at the Center for Environmental

Restoration Systems, Argonne National

Laboratory. Dr. Zimmerman received

his Ph.D. is Geotechnical/Environmental

Engineering from Northwestern Univer-

sity in 1972. He is his responsible for en-

gineering and geophysics areas in the Center for Environmental

Restoration Systems, Argonne National Laboratory.

Timothy A. Hall, Ph.D.,

Timothy A. Hall, Ph.D., is President

of ManTech Environmental Corpora-

tion. Dr. Hall has 22 years of consulting

experience in environmental and energy

technical services and regulatory analy-

sis, involving management of large,

complex programs for industrial clients,

federal and state agencies, and research

institutes. Dr. Hall’s technical areas of primary interest are hazard-

ous waste management, site investigation and remediation, envi-

ronmental laws and regulations, cost/risk/benefit analysis of en-

ergy and environmental compliance strategies, energy resource

development and utilization, and strategic planning.

Eugene Hughes

Eugene Hughes is President and

founder of Erin Engineering and Research

and has 30 years of experience evaluating

safety, reliability, and economic perfor-

mance of large industrial facilities. He has

participated in and led major elements of

risk-assessment and refinement. He has

established a corporation, which provides

both application software to support evaluation and enhancement of

industrial facilities and services necessary to implement innovative

technological solutions to problems facing plant management, opera-

tions, and maintenance.

an integrated framework for evaluating subsurface contamination remediation technologies

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