Hydrogeology students mapping a shallow hydraulic fracture exposed by excavation at theSimpson Station research facility, Clemson University, with the fracture rig in the background.The mapped fracture is shown on the inside cover.

1889

S O U T HC A R O L I N A

Eleventh Annual

David S. Snipes/Clemson

Hydrogeology SymposiumApril 3-4, 2003

Perspective of shallow fracture based on detailed field measurements.

11th Annual David S. Snipes/ClemsonHydrogeology Symposium

April 3-4, 2003

Time BellSouth Auditorium Ballroom A Meeting Rooms 1 and 2

9:00

RemediationModerator:Ron Falta

Induced FracturingModerator:

Larry Murdoch

Uranium/Arsenic/LawModerator:Rich Warner

9:15Implementation of a Full-Scale In Situ ChemcialOxidation (ISCO) Programin a Fractured BedrockAquiferJeremy S. Peacock

Use of Induced Fracturesas Enhancements to Soiland GroundwaterRemediation SystemsWilliam S. Slack

Uranium Minerals at MawBridge Pegmite near Cen-tral, SCRichard Warner

9:40 Field Test of DNAPL Re-moval by Alcohol FloodingRon Falta

The Form of HydraulicFractures at ShallowDepths in Piedmont SoilsJim Richardson

Measurements of Naturally-Occuring Radionuclides inDomestic Water SuppliesDebbie Falta &Lara Hughes

10:05Addressing Residual, MassTransfer Limited VOCContamination Using Sus-tainable Energy PoweredMicroblowersTM

Joe Rossabi

Measuring Changes InFracture Aperture In-SituDuring an Injection TestTodd Schweisinger

Distribution of Total Arsenicin Groundwater of the NorthCarolina Piedmont ProvinceCharles G. Pippin

10:30 Design, Permitting andConstruction of SC’s First-Ever RCRA CorrectiveAction Management UnitJames E. Furr

Air Sparging in Hydrau-lically Fractured Wells inLow Permeability Sedi-mentsRich Hall

Writing Technical Docu-ments from the Standpointof Advocacy and LegalProtectionJohn Charles Ormond, Jr.

10:55till

11:15BREAK

11:15till

12:00

Keynote Speaker: C.W. Fetter - Grand BallroomGround Water Remediation in the Globe - Miami Mining District

12:00till

1:00LUNCH - Grand Ballroom

OPENING REMARKS - Tom Keinath, Dean, College of Engineering & Science

Time BellSouth Auditorium Ballroom A Meeting Rooms 1 and 2

GeochemistryModerator:Brian Davies

HydrogeologyModerator:Fred Molz

CharacterizationModerator:Phil Reppert

1:00 Mineralogic, Geochemical,and GeomicrobiologicControl on Natural ArsenicContamination of Ground-waterJames A. Saunders

Georgia Coastal SoundScience Initiative - Evalua-tion of Ground-WaterFlow, Saltwater Contami-nation, and AlternativeWater SourcesJohn S. Clarke

Geology and Yield ofProductive CrystallineBedrock Wells in the Vicin-ity of Lawrenceville, Geor-giaLester J. Williams

1:25Development of ReactionZones during Passive Treat-ments of Low pH, FerricIron-Dominated Acid RockDrainageRobert C. Thomas

Tidal Fluctuation Im-pacts on GroundwaterElevations and VerticalGradientsJoseph A. Harrigan

Measurement of HydraulicGradients in the Slopes ofthe Panama CanalDave Mercer

1:50 Simulations of Metals At-tenuation Processes Relatedto Field Bioremediation ofAcidic GroundwaterMing-Kuo Lee

Solutions to a FlourideProblem in Some WaterSupply Wells in PittCounty, NCDavid P. Lawrence

The Self-Potential Methodin Applied Geophysics withApplications inHydrogeologyPhil Reppert

2:15 Movement of Trace Metalsin River Basins: the FloodPlain as a Reservoir forHeavy MetalsBeth Vanden Berg

A Numerical Investiga-tion of Hydraulic Con-ductivity Scale Depen-denceGeoffrey K. Chambers

2:40till

3:00BREAK

SPECIAL FORUM:The Education ofHydrogeologists

RemediationModerator:Ron Falta

Horizontal Wells/Fractures

Moderator:Larry Murdoch

CharacterizationModerator:Jim Castle

3:00 Affecting Subsurface FluidFlow to ImproveRemediation ProcessesMark Kluger

Including the Effects ofWellbore Hydraulics inAnalyses of the Perfor-mance of HorizontalWellsRobert Workman

Characterization of Strati-graphic Heterogeneity in theTemblor Formation (Mi-ocene), Coalinga, CaliforniaJamie L. Piver

Time BellSouth Auditorium Ballroom A Meeting Rooms 1 and 2

3:25 A Case Study where AirSparging and Soil VaporExtraction SuppressedAnaerobic Biodegradation ofChlorinated SolventsDavid B. Willis

Redevelopment andRehabilitation of a Hori-zontal Recovery WellJimmy Whitmer

Origin of Jamaican SoilCadmium: Possible Struc-tural ControlErik M. Goldman

3:50 In-Situ Remediation ofCarbon Tetrachloride usingEnhanced Reductive Dechlo-rination and HydraulicFracturing Elizabeth Rhine

Hydraulic FractureBranching and Segmen-tationR. Wu

Geological Influence on theOccurrence of Rare PlantSpecies in the JocasseeGorges Area of SouthCarolina Terry Ray

4:15 Effects of Production Pro-cesses and SubsurfaceCharacteristics on the Distri-bution of PesticidesRuss Miller &David Nichols

Hydraulic Fracturing inParticulate MaterialsHong Chang

Geologic Mapping in theAnderson South 7.5’ Quad-rangle, South Carolina andWADI SurveyAnthony Soricelli

4:50 MIXER AT GEOLOGY MUSEUM

POSTERS (Displayed in the Main Hall)

A Quantitative Method for Delineating Regional Stratigraphic Cycles on Gamma-Ray Logs from the CoastalPlain of South CarolinaPaul L. D’Annibale

Remediation of Dissolved-Phase Hydrocarbons in a Coastal Plain Aquifer by Monitored Natural AttenuationBenjamin R. Black

Methods for Determining Contaminant Migration Controls in the Transition Zone and Fractured Bedrock: ACase Study in the Piedmont of North CarolinaGrant Watkins

Electrofacies Characterization of the Upper Cretaceous McQueen Branch Aquifer of the South CarolinaCoastal PlainJen Cardran

Altering The Landscape - Random Fill And Effects On Recharge And Creation Of Contaminated Groundwaterin Piedmont Saprolites and Partially Weathered RocksDonald Privett

Profile of a 703-Foot Core from an Area of Elevated Uranium Levels in Groundwater Near the Reedy Thrust,Simpsonville/Fountain Inn, South CarolinaBruce Crawford

REMEDIATION OF DISSOLVED-PHASE HYDROCARBONS IN ACOASTAL PLAIN AQUIFER BYMONITORED NATURALATTENUATION

BLACK, BENJAMIN R.,bblack@pangeansolutions.com,Pangean Solutions, Inc., Woodstock, GA30188

A release of petroleum product at a Bulk StorageFacility in Fayetteville, North Carolina, resultedin the presence of free-phase, adsorbed-phase,and dissolved-phase hydrocarbons in the aquiferunderlying the facility. Several investigationshave been conducted at the facility to address hy-drocarbons in the subsurface. Free-phase andadsorbed-phase hydrocarbons have been re-moved. Delineation of the dissolved-phase hy-drocarbon plume appears to have been achieved,and an approach is now needed to remediate re-sidual hydrocarbons. The site is located in theAtlantic Coastal Plain Physiographic Province ofNorth Carolina. Only the surficial aquifer at thesite has been impacted by the release of hydro-carbons. The aquifer is unconfined, and is com-prised of fine to coarse-grained sands interbeddedwith plastic clay. The interbedded clays were firstencountered at depths of approximately 40 feet,and based on their absence in several boring lo-cations, appear to be laterally discontinuous.Bedrock was not encountered in any boring.Based on review of regional geologic maps, thepenetrated subsurface materials at the facilityappear to be surficial deposits of Quaternary ageand the Middendorf Formation of Cretaceous age.

Constituents detected in the groundwaterat the facility include, benzene, toluene,ethylbenzene, xylenes (BTEX), and methyltertiary-butyl ether (MTBE). BTEX and MTBEconcentrations are highest in the source area, withhistorical concentrations on the order of 12milligrams per liter (mg/L). Recent analyticaldata indicates an overall decrease in BTEX/MTBE concentrations. Based on the recentdecreasing trend and directives from the NorthCarolina Department of Environmental andNatural Resources (NCDENR) Division of WaterQuality (DWQ), an assessment was conductedto determine the applicability of using monitorednatural attenuation (MNA) to treat the dissolved-phase hydrocarbon plume at the facility.

The determination to use MNA was madebased on a baseline study that involved monitor-ing of several intrinsic parameters including dis-solved oxygen, pH, temperature, specific conduc-tivity, oxidation-reduction potential (ORP), ni-trate, sulfate, ferrous iron (Fe+2), carbon diox-ide, manganese, alkalinity, chloride, and meth-ane. The baseline study indicated that naturalattenuation of the dissolved-phase hydrocarbonswas possible via both aerobic and anaerobic res-piration. More specifically, several processes ap-pear to be taking place within the subsurface in-cluding denitrification, sulfanogenesis, iron-re-duction, and methanogenesis. Results of theMNA baseline study indicated that enough dis-solved oxygen, nitrate, sulfate, and ferric iron(Fe+3) were present in the subsurface to provideelectron receptors for natural attenuation to ef-fectively remediate the dissolved-phase hydro-

carbon plume.

Abstracts(Ordered by last name of first author)

1

ELECTROFACIESCHARACTERIZATION OF THEUPPER CRETACEOUS MCQUEENBRANCH AQUIFER OF THESOUTH CAROLINA COASTALPLAIN

CARDRAN, Jen, jencardran@yahoo.com,Geological Sciences, Clemson Univer-sity, Clemson, SC 29634

Interpreting the stratigraphy, lithology, andhydrogeology of subsurface units has historicallydepended, in large part, on core samples.However, cores may be prohibitively expensiveor difficult to access, whereas wireline logs canbe obtained for the entire interval of interest undervaried environmental conditions and at greatdetail. One approach for integrating log-derivedinformation on stratigraphy, lithology, andhydrogeology in a single study is throughelectrofacies analysis.

The McQueen Branch aquifer is ideal forelectrofacies studies because its lithologic andstratigraphic characteristics change vertically andlaterally, and it is present throughout the CoastalPlain of South Carolina. Considerable informa-tion on the aquifer has been derived from studiesof core taken at the Savannah River Site in AikenCounty, South Carolina, but few studies haveaddressed the regional aspects of the aquifer.Because wireline logs contain information forestimating porosity and permeability,electrofacies analysis may provide an efficientand cost-effective method for characterizing andmapping the regional distribution of these param-eters.

Eight wells throughout the Coastal Plain ofSouth Carolina were selected for the study, andfive geophysical logs from each well were ob-tained: gamma-ray, single point resistance, longand short normal resistivity, and spontaneouspotential. Each log was normalized to eliminatethe influence of scale, well casing, and units ofmeasure among the logs.

Because each log contains a large array ofnormalized log data, the data were compressedby blocking. Each well was blocked (or zoned)in such a way that dispersion of the data wasminimized within the blocks, and boundarieswere placed at those horizons where dispersionwas maximized. Electrofacies are delineatedfrom the blocked logs through cluster analysis,and each electrofacies is defined in terms of themedian grain size and sorting of the sedimentsrepresentative of each electrofacies. Such studiesmay be applied to porosity and permeabilitypredictions for aquifers and confining units in theCoastal Plain.

A NUMERICAL INVESTIGATIONOF HYDRAULIC CONDUCTIVITYSCALE DEPENDENCE

CHAMBERS, GEOFFREY K.,gchambe@clemson.edu, and MOLZ,FRED J. III, fredi@clemson.edu ,Environmental Engineering and Sci-ence, Clemson University, Clemson,South Carolina

In recent years there has been considerable con-troversy concerning the scale-dependence of hy-draulic conductivity (K) measurements. Typi-cally, this is shown by a plot of K values deter-mined at the core scale, the slug-test scale, thepumping test scale, and sometimes the cali-brated mathematical model scale, with appar -ent K values increasing with scale. Our studyhas shown that a great deal, but not all, of thisvariation may be explained in terms of the typeof average K that is produced by the measure-ment technique. It is well known that measure-ments based on steady flow parallel or perpen-dicular to layers of variable K will produce anapparent constant <K> that is the arithmetic andharmonic average, respectively, of the individualK values [McWhorter and Sunada, 1977]. For thetwo member case of uniform thickness, the arith-

2

metic average (parallel flow) and harmonic aver-age (perpendicular flow) are given as:

It may be shown that some type of mixture ofparallel and perpendicular flow will result in amean K value somewhere between these limit-ing cases [Cardwell and Parsons, 1945]. Thus inthe absence of other information, the geometricaverage is often used to estimate a workingmean value of K. This mean falls between thearithmetic and harmonic limits and is given forthe two layer case by:

All possible power -law averages between thearithmetic and harmonic limits for a heteroge-neous volume, V, may be represented conciselyby the formula [Journel et al., 1986]:

where p = -1, 0 and 1 yields the harmonic, geo-metric and arithmetic means, respectively. Thesemean values differ greatly when the medium ishighly heterogeneous. For example, for a givenset of units with K

1 = 0.1 and K

2 = 100, one has

<KH> ∪ 0.2, <K

G> ∪ 10 and <K

A> ∪ 50. Thus,

<KA> is 2.5 orders of magnitude larger than

<KH>.These observations explain why core-based

measurements of <K> would be expected, on av-erage, to be smaller than values derived from slug-tests or pumping tests. The more constrained flowthrough a core, that would tend to be closer to 1-D, would not be able to get around some low Kinclusions, and therefore would produce a meanK closer to the geometric or harmonic case, whilea pumping or slug test, with more unconstrained3-D flow would, tend toward the arithmetic case.Thus in a 3-D heterogeneous medium, one wouldbe surprised if core-based K values were not sig-nificantly lower than those derived from pump-

ing tests or slug tests, and this is what has beenobserved in numerous studies.

The fact that slug tests seem to produce <K>values that are lower than pumping tests couldoccur for a variety of reasons. As pointed outnumerous times [Butler and Healey, 1998], slugtest results often suffer from low K skin effects,which undoubtedly have lead to a systematic un-derestimation of <K>. Studies by Rovey andNieman [2001], however, have suggested thatskin effects are not the whole story. Our mean-based argument would also be expected to applyto a lesser extent to slug test versus pumping testgeometry, with the pumping test <K> being closerto (or perhaps greater than) the arithmetic meanthan the slug test <K>. Simulations in fracturedmedia have demonstrated a scale effect clearly,but there have been limited studies in typical po-rous media. Rayne [1993] performed simulatedslug and pumping tests in heterogeneous porousmedia based on an exponential variogram model.His simulations yielded slug test <K> values thatwere 3 to 7 times lower than pumping test val-ues. Rayne s simulations also showed that scaleeffect increased with increasing correlation lengthof K [Rayne, 1993].

The present study is devoted to thesimulation of pumping and slug tests in a mediumcontaining heterogeneous facies and K structurecharacteristic of an alluvial fan [Lu et al., 2002].Flow simulations were run on a three dimensionalmodel grid. Numerical simulations of pumpingtests and slug tests were compared to the volumeweighted harmonic, geometric, and arithmeticmean K of the medium. Data from this studysuggest that pumping tests and slug testsapproximate the arithmetic mean K rather thanthe geometric mean K. Data also suggest thatpumping test analysis may produce larger thanrealistic estimates of K due to observation wellsbeing shielded from drawdown response by lowK areas. Furthermore this shielding fromdrawdown response had a greater effect on theCooper-Jacob analysis method than the Theiscurve matching analysis method.

3

References:

Butler Jr., J. J., Healey, J. M., 1998. Relation-ship Between Pumping Test Parameters:Scale Effect or Artifact?. Ground Water,Vol. 36, no. 2, pp. 305-313.

Jacob, C. E., 1947. Drawdown test to determineeffective radius of artesian well. Trans.American Society of Civil Engineers. Vol112, pp. 1047-1064.

Cardwell, W. T., and Parsons, R. L., 1945.Averaging permeability of heterogeneousoil sands. Trans. Amer. Inst. of Mining,Metal., and Petro. Eng., Vol. 160, pp 34-42.

Journal, A. G., Deutsch, C. and Desbarats, A. J.,1986. Power averaging for block

effective permeability. SPE paper 15128.Lu, S., Molz, F. J., Fogg, G. E. and Castle, J.

W., 2002. Combining Stochastic Fractal andFacies Models for Representing NaturalHeterogeneity. Hydrogeology Journal.

McWhorter, D. B., and Sunada, D. K., 1977.Ground Water Hydrology and Hydraulics,Water Resources Publications, LLC, High-lands Ranch, Colorado.

Rayne, T. W., 1993. Variability of HydraulicConductivity in Sandy Till: The Effects ofScale and Method. PhD Dissertation,University of Wisconsin-Madison.

Rovey, C. W., and Nieman, W. L., 2001.Wellskins and Slug Tests: where s the bias?.Journal of Hydrology, Vol 243, pp 120-132.

HYDRAULIC FRACTURING INPARTICULATE MATERIALS

HONG CHANG,gte004k@prism.gatech.edu, L. N.GERMANOVICH, J. C.SANTAMARINA, and P. E. DIJK,Civil and Environmental Engineering,Georgia Institute of Technology, At-lanta, Georgia,

Experiments to investigate the mechanisms ofhydraulic fracture in particulate materials havebeen conducted. In these experiments, liquid isinjected into dry particulate materials, which arecompletely cohesionless. The liquid flow is lo-calized in thin self-propagating crack-like con-duits (Figure 1). By analogy we call themcracks or hydraulic fractures. When a frac-ture propagates in a solid, new surfaces are cre-ated by breaking material bonds. Consequently,the material is in tension at the fracture tip. Be-cause the particulate material is already frac-tured, no new surface is created and no fractureprocess per se is involved. Moreover, all mate-rial parts are in compression since it cannot bearany tension. Therefore the conventional fracturemechanics principles, such as fracture toughness,cannot be applied. This paper describes labora-tory experiments at both small and large scales.At the small scale, the experiments are performedon three dry particulate materials (Georgia RedClay, silica flour, and fine sand) to determine thecontrolling parameters of fracture behavior. Toreduce boundary effects and study scale effects,the experiments are also performed at the largescale.

(a) Front view (b) Edge View

Figure 1. Hydraulic fracture in particulatematerials. The liquid (joint compound) isinjected into the dry particulate material (Geor-gia Red Clay). After the liquid solidifies, theimprint of the fracture is recovered by remov-ing the surrounding material.

4

GEORGIA COASTAL SOUNDSCIENCE INITIATIVEEVALUATION OF GROUND-WATER FLOW, SALTWATERCONTAMINATION, ANDALTERNATIVE WATER SOURCES

CLARKE, JOHN S.,jsclarke@usgs.gov, U.S. GeologicalSurvey, Atlanta, GA. 30360

Saltwater contamination of supply wells at HiltonHead Island, South Carolina and Brunswick,Georgia has constrained further development ofthe Upper Floridan aquifer in coastal Georgia andcreated fierce competing demands for the limitedfreshwater supply. The Georgia EnvironmentalProtection Division (GaEPD) released an interimstrategy in April 1997 to manage saltwaterintrusion in the Upper Floridan aquifer. As partof this interim plan, GaEPD capped permittedwithdrawal from the Upper Floridan aquifer at1997 rates in the Savannah and Brunswick areas,and has funded a program of scientific andfeasibility studies (Coastal Sound ScienceInitiative) to support development of a final water-management strategy; implementation of the finalwater-management strategy is scheduled forJanuary 2006. In support of the Sound ScienceInitiative, the U.S. Geological Survey is workingwith GaEPD to evaluate ground-water flow,saltwater contamination, and alternative sourcesof ground water in the coastal area of Georgiaand adjacent parts of South Carolina and Florida.Project activities include:

• Evaluation of the hydrogeologic andwater-quality characteristics of the LowerFloridan aquifer;

• Evaluation of the fresh-saltwater interfaceoffshore of Tybee Island, Georgia andHilton Head Island, South Carolina;

• Evaluation of alternative water suppliesfrom excavated seepage ponds;

• Region-wide ground-water level and wa-ter-quality monitoring; and

• Simulation of saltwater intrusion usingdigital ground-water models.

To date (March 2003), the project has

completed an extensive deep-well drilling pro-

gram to assess the hydrogeologic and water-qual-

ity characteristics of the Lower Floridan aquifer,

with test wells installed in Camden, Glynn, McIn-

tosh, Bryan, and Effingham Counties. At each

drilling site, geologic, geophysical, and water-

chemistry data were collected, and monitoring

wells equipped with continuous water-level re-

corders were installed. Aquifer tests were con-

ducted at three of the deep-well sites. Offshore

borings were completed at 5 sites to characterize

the freshwater-saltwater interface. At each off-

shore site, geologic, geophysical, and water-

chemistry data were collected, and core samples

were analyzed for pore-water chemistry and hy-

draulic properties. Water-bearing potential of

seepage ponds was evaluated at sites in Glynn

and Bulloch Counties. The ground-water-level

monitoring network for coastal Georgia has been

expanded to include an additional 5 wells in the

Upper Floridan aquifer, 8 wells in the Lower

Floridan aquifer, 13 wells in the Brunswick aqui-

fer system, and 5 wells in the surficial aquifer

system. Two wells completed in the Lower

Floridan aquifer at St Marys and Tybee Island

have been added to the State’s “early warning”

network for saltwater contamination. Data are

being synthesized into a regional ground-water

flow model and solute-transport models for the

Savannah-Hilton Head Island and Brunswick ar-

eas. For more information see Web page: http://

ga2.er.usgs.gov/coastal/.

5

A QUANTITATIVE METHOD FORDELINEATING REGIONALSTRATIGRAPHIC CYCLES ONGAMMA-RAY LOGS FROM THECOASTAL PLAIN OF SOUTHCAROLINA

D ANNIBALE, PAUL L.,pldannibale@hotmail.com, GeologicalSciences, Clemson University,Clemson, SC 29633

The stratigraphic database for the Coastal Plainof South Carolina includes geophysical logs, core,and biostratigraphic data for more than forty wellsthat have been drilled to basement. In this study,an attempt was made to better understand thedepositional environments of the Coastal Plainsediments and their relationship to transgressive-regressive sequences by applying curve-smooth-ing algorithms to gamma-ray logs in order tominimize local perturbations and backgroundnoise while maintaining a significant regionalsignal. The resulting regional trends were quan-tified by means of an analysis of the derivativesof the smoothed logs, which provides consistencyin well log correlation and interpretation.

The gamma-ray log is analogous to a sto-chastic time series in that it is comprised of twocomponents: a long-term signal and short-termnoise. Local perturbations are, by nature, short-term; thus averaging several adjacent points tendsto converge on the long-term signal, or regionaltrend, which are therefore dependent on thecurve-smoothing algorithm used. The Savitzky-Golay moving-window average was applied atincreasing window sizes to the gamma-ray logsfrom more than twenty Coastal Plain wells, asthis algorithm is best suited for minimizing thelocal noise and maximizing the regional sig-nal, while preserving the peaks and troughs ofthe gamma-ray log. Once the size of the mov-ing-window was established so as to delineateregional trends, the sign of the first and secondderivatives of the smoothed logs was determined

at each measured depth. When combined, thesigns of the first and second derivatives yield fourdistinct outcomes (or curve shapes): bell-convex;bell-concave; funnel-convex; and funnel-concave.These four possible combinations are translatedinto a color series, and visual interpretation ofthe color series allows for the interpretation ofregional trends in terms of transgressive-regres-sive cycles and their constituent depositional en-vironments.

MEASUREMENTS OF NATU-RALLY-OCCURRING RADIONU-CLIDES IN DOMESTIC WATERSUPPLIES

FALTA, DEBORAH and HUGHES,LARA, Environmental Engineering andScience, Clemson University, Clemson,SC 29634

Occurrence information regarding naturalradioisotopes in drinking water is available withinthe literature from reviews of National UraniumResource Evaluation data, the National Inorganicsand Radionuclides Survey, and several analysesof drinking water standard violations reported bypublic water suppliers. The EnvironmentalProtection Agency and United States GeologicalSurvey have also conducted studies addressingspecific radionuclides and their distribution. Thegeochemical factors influencing the occurrenceof uranium, radium, radon and other radioisotopeswithin the United States is presented, along witha summary of average and maximum valuesreported within the literature. In response torecent concerns with elevated uranium inSimpsonville, South Carolina, students inClemson University’s Environmental Engineeringand Science department sampled and analyzedthe water supply for several of these homes forconcentrations of uranium, radium, radon, andlead, along with other water quality parameters.These values are compared to the publishedliterature.

6

FIELD TEST OF DNAPL REMOVALBY ALCOHOL FLOODING

FALTA, RON, CINDY LEE, SCOTTBRAME, JOHN COATES, and JIMMYERS, School of the Environment,Clemson University, Clemson, SC

A field test of multicomponent cosolvent floodingfor in-situ remediation of DNAPL source zoneswas conducted at the Groundwater RemediationField Laboratory (GRFL) at the Dover NationalTest Site (DNTS) at Dover Air Force Base,Delaware in July of 2001. The DNTS is one offour National Environmental Technology TestSites in the US. The GRFL at Dover consists oftwo sheet pile walled test cells located inside anouter containment wall. Each of the test cells isabout 15 feet by 10 feet in surface dimensions,and the sheet piles were driven down 45 feet, fivefeet into a confining clay layer. The sheet pilewalls have interlocking, grouted joints that forma water tight seal. The geology at the site consistsof unconsolidated Atlantic Coastal Plainsediments with interbedded sands, silts, and clays.The natural water table is located at a depth ofabout 29 feet. The test cell contained twelve 2-inch wells with 20 foot slotted screens, and a totalof 108 small fluid samplers located below thewater table.

A previous field test of air sparging in thistest cell had involved a controlled release of 66liters of pure tetrachloroethylene (PCE) into thetest cell by the EPA Project Officer and Staff.The air sparging experiment removed approxi-mately 58 liters of PCE, leaving about 8 liters ofPCE in the test cell [Gierke et al., 2002]. As partof the cosolvent flooding experiment, the EPAProject Officer and Staff performed a second PCErelease in the test cell, releasing up to 100 litersof PCE (the actual amount has not yet been dis-closed). This PCE was released at a depth of 35feet, so the experimental treatment zone extendsfrom 35 feet to the confining clay located at adepth of 40 feet.

The cosolvent flood used a mixture of 70%n-propanol and 30% saltwater containing calciumchloride dihydrate. Propanol is a common in-dustrial alcohol with relatively low toxicity andcost. Food grade calcium chloride dihydrate wasadded to water at 175 g/l to form a concentratedsaltwater solution that was mixed with the n-pro-panol. The purpose of the saltwater is twofold.The saltwater has a very high density comparedto water or propanol, so its addition increases thedensity of the cosolvent flooding solution, mak-ing it easier to deliver to the lower parts of anaquifer. The saltwater also increases the parti-tioning of propanol into PCE NAPL. In fact, athigh cosolvent concentrations, this mixture iscapable of converting PCE DNAPL into anLNAPL, thus reducing concerns about NAPLmobilization during the cosolvent flood.

Following the PCE release, an initialnonreactive tracer test was performed in the testcell, and it revealed a distinct and isolated highpermeability zone near the upper part of the satu-rated zone. Groundwater samples taken from theextraction wells during this tracer test showedconsistently high levels of dissolved PCE, withan average PCE concentration of about 80 mg/l.The individual multilevel samplers showed highlyvariable dissolved PCE concentrations, rangingfrom nearly zero, up to the PCE solubility in water(around 200 mg/l).

The cosolvent flood operated for a total of37 days with an average flow rate of about 3.2liters per minute. The initial volume of cosolventsolution on site was about 33,000 liters, and thecosolvent was recycled during the experiment bytreating it with an air stripper to remove the PCE,so it could be reinjected into the test cell. Maxi-mum extraction well PCE concentrations duringthe experiment were typically in the range 1000to 1500 mg/l, or nearly ten times the normal PCEsolubility. No DNAPL or LNAPL was producedfrom the extraction wells. Over the course of thefield experiment, a total of 45.4 liters of PCE wereremoved from the test cell.

Ground water sampling was conducted afterthe conclusion of the cosolvent flooding experi-

7

ment using the same flow field that was used inthe initial nonreactive tracer test. Groundwatersamples taken from the extraction wells showedlower dissolved PCE concentrations compared tothe earlier values, and the average PCE concen-tration was about 15 mg/l. Therefore, there wasapproximately an 80% reduction in the flowinggroundwater PCE concentrations measured afterthe cosolvent flood.

GROUND WATER REMEDIATIONIN THE GLOBE — MIAMI MININGDISTRICT

FETTER, C. W. Jr., Cwfetter@aol.com,C. W. Fetter, Jr. Associates, Suite 808,404 North Main Street, Oshkosh, WI54901

The Globe — Miami mining district is located 75mile east of Phoenix in the foothills between theSuperstition and Pinal Mountains. Nonferrousmetals have been mined there since 1878. Un-derground mining was used until the first openpit mine was opened in 1948. The principal metalextracted was copper, although lesser amountsof silver and gold were mined. The principal cop-per deposits were disseminated in the Precam-brian Pinal Schist during emplacement of theSchultze Granite pluton in Tertiary time. Bothoxide and sulfide copper minerals are present inthe district.

Copper ore was concentrated by several meth-ods including gravity separation, floation andleaching. One mining property developed amethod of concentration called vat leachingwhereby ore was first crushed and then placed ina vat where it was leached with an acidic solu-tion of ferric sulfate. The acidic leach plant tail-ings were then discarded in a nearby canyon,Webster Gulch, which drained into the PinalCreek watershed.

As early as 1939 wells in the Pinal Creek al-luvium downgradient of the leach plant tailingsdeposit began to yield sour water . As a result a

new well field 12 miles downstream was estab-lished. About 1940 the leach plant tailings com-pletely blocked Webster Gulch and formedWebster Lake. Webster Lake was used to storeprocess water, storm water and drainage frommining areas. When measured in 1986 the pH ofWebster Lake was about 2 — 3 with about 35,000mg/L TDS, 21,000 mg/L sulfate, 4400 mg/L iron,1200 mg/L aluminum, 650 mg/L magnesium, 300mg/L copper, 110 mg/L manganese and 35 mg/Lzinc.

In 1983 an investigation of the Pinal Creekaquifer system found that the alluvial aquifer hadacidic water with high sulfate, iron, copper alu-minum, zinc and manganese. The zone of acidwater extended a number of miles downstreamfrom the Globe-Miami mining district. The acidfront was moving downgradient at a rate of about2 to 3 feet per day. Ground water in the alluvialaquifer system is moving at an average linearvelocity in the range of 13 to 32 feet per day. Themovement of the acid front was retarded by re-action of the acidic water with calcite, which wascontained in the alluvium. Ground water froman uncontaminated part of the alluvial aquifer hada pH of 7.07 with TDS of 960 mg/L. Ahead ofthe acid front the ground water had a pH between6 and 7 and TDS of about 2500 mg/L. This wascaused by sulfate and calcium, sodium, magne-sium and sulfate, which were not retarded by theaquifer material. Behind the acid front the waterhad a pH of 3 to 4 with TDS of more than 10,000mg/L with high iron, copper, aluminum, sulfate,magnesium, manganese and chloride. The un-contaminated water had high bicarbonate andalkalinity, while the acid water had bicarbonateand alkalinity of zero.

The mining companies instituted groundwater remediation starting in 1987. Webster Lakewas drained in 1986 — 1988. Ground water wasalso pumped from the alluvium in Webster Gulchstarting in 1987. This water was placed inevaporation ponds for disposal. In 1989 a wellfield was established in Kiser Basin, to withdrawcontaminated ground water from the Pinal Creek

8

Alluvial Aquifer system. This water was alsoplaced in evaporation ponds.

In 2001 a permanent solution was imple-mented. A slurry wall was built across the PinalCreek alluvial aquifer immediately below the acidfront. All ground water is pumped from the aqui-fer behind the slurry wall and transported to atreatment plant. The water is treated to precipi-tate metals and the pH is adjusted to neutral. Thetreated water is transported back to the area ofthe slurry wall and discharged into Pinal Creekto replace the ground water that formerly had fedit. The sludge from the treatment plant is trans-ported for disposal in a mine pit located in im-permeable bedrock.

DESIGN, PERMITTING ANDCONSTRUCTION OF SC S FIRST-EVER RCRA CORRECTIVEACTION MANAGEMENT UNIT(CAMU)

FURR, JAMES E., jfurr@kubal-furr.com,Kubal-Furr & Associates, Inc.,Simpsonville, SC 29680

In December 2001, SCDHEC issued conditionalapproval of the first-ever permit for theconstruction of a Corrective Action ManagementUnit (CAMU) for long-term management ofRCRA remediation waste at Blackman-UhlerChemical Company of Spartanburg, SC. Kubal-Furr & Associates (KF&A) proposed the CAMUin their May 2000 Corrective Measures Study ofthe site as a cost-effective and reliable wastemanagement system to address the continuingreleases from nine solid waste management units(SWMUs) at the facility. The CAMU wasdesigned to consolidate the contaminatedwastewater sludge and associated soil, treatselected volatile and semi-volatile organiccompounds, and cap the waste to eliminate direct

exposure and continuing releases to groundwater.Approximately 14,000 cubic yards of remediationwaste will be managed and treated at the CAMU.Construction elements include a RCRA low-permeability composite cap and a horizontalpassive soil vapor extraction system. The CAMUwill be constructed in three phases or cells.CAMU Cell #1 was constructed in March 2003by Williams Environmental Services of StoneMountain, Georgia. Construction QualityAssurance (CQA) and construction certificationwas provided by KF&A and Carolina TechnicalServices, Inc. of Irmo. At the completion of Cell#3, the groundwater monitoring system willupgraded to incorporate additional saprolite andshallow bedrock CAMU monitoring wells for theRCRA post-closure period.

ORIGIN OF JAMAICAN SOILCADMIUM: POSSIBLESTRUCTURAL CONTROL

GOLDMAN, ERIK M.,egoldma@hotmail.com, Department ofGeological Sciences, Clemson Univer-sity , Clemson, SC 29634

Recent work has illustrated anomalously high Cdlevels in bauxitic terra rossa soils in the vicinityof St. Paul s, Manchester Parish, Jamaica. Insome cases these levels exceed those reported forcontaminated mine sites by orders of magnitude.These soils, of debatable origins but most likelythe result of a late Miocene ashfall (at least inpart), fill solution hollows in exceptionally purelimestone. As industry is not significantly estab-lished in the study area, the origin of the soil Cdmust be natural, rather than anthropogenic.

A field expedition undertaken inSeptember 2002 was designed to test thehypothesis that some structural control exists,resulting in the migration upwards of Cd fromdepth. Soil samples were taken in linear transectsacross both active and inactive faults, and tested

9

THE EFFECTS OF HYDRAULICFRACTURING ON AIR SPARGINGIN SAPROLITE

HALL, RICHARD, cherd_8@yahoo.com,and MURDOCH, LARRY, GeologicalSciences, Clemson University,Clemson, SC 29634-0919

During the past 10 years hydraulic fracturing hasbeen used to improve the performance of a vari-ety of types of environmental processes, but theeffect that fracturing has on air sparging is poorlyunderstood due to limited applications. The suc-cess of air sparging depends, in part, on the rateat which air can be injected into the contaminatedsaturated zone. This has limited the applicabil-ity of air sparging as a remediation technique infine-grained formations, such as clay-rich sapro-lites, where low permeability restricts flow rates.The purpose of this work is to investigate thepotential of using hydraulic fractures to increasethe realm of air sparging applications to includerelatively low permeability materials.

The field work for this project is being con-ducted at the Simpson Agriculture ExperimentalStation, which is approximately 8 km east ofPendleton S.C., on land owned by Clemson Uni-versity. Test wells have been installed in a clay-rich saprolite weathered from the Caesars HeadGranite, a discontinuously banded biotite grani-toid gneiss. The water table at the site is approxi-mately 8 m below ground surface. A total ofseven test wells screened at 13.7 m depth havebeen installed: four fractured wells, one conven-tional well, and two non-fractured wells, whichwere completed using techniques similar to thefractured wells. The volumes of sand in the frac-tures that have been created for initial testing are

for Cd using various geochemical methods.Preliminary results indicate that a fault-controlledsource of soil Cd cannot been ruled out at thistime.

relatively small (0.05-0.1 m3). Larger fractures(0.15-0.3 m3) will be created later to evaluate theeffects of fracture volume. Formation hydrologicconductivity of 10-5 to 10-4 cm/s were calculatedusing the Bower and Rice method on slug testdata. Preliminary sparge tests involved injectingair at constant pressure and monitoring transienteffects until flow equilibrated, then incrementallyincreasing pressure and repeating. The resultsfrom these tests provide and estimate of 31 KPaas the air entry pressure for the saprolite. Thespecific capacity of a conventional well and afractured well were found to be 0.25 m3 /(Mpamin) and 0.62m3 /(Mpa min) respectively. Theseresults suggest that the presence of a small hy-draulic fracture increases the specific capacity bya factor of 2.5.

The multi-phase flow simulator T2VOC isbeing used to evaluate the field tests. Parametervalues, such as formation permeability and entrypressure, are manipulated to predict the resultsof the field sparge tests. Preliminary results areencouraging. Future efforts will use the calibratedmodel to evaluate the effects of injection pres-sure, formation permeability, and fracture lengthand thickness on flow rates and volume of aqui-fer being influenced during sparging.

TIDAL FLUCTUATION IMPACTSON GROUNDWATER ELEVATIONSAND VERTICAL GRADIENTS

HARRIGAN, Joseph A., joe.harrigan@earthtech.com, Earth Tech,Greenville, SC 29615

Monitoring of tidal influence on groundwaterelevations was included in a basewide ground-water level measurement effort at an Air ForceBase in coastal central Florida. A comprehensiveset of basewide water level measurements wereneeded for the construction of a groundwater flowmodel. An earlier limited tidal influence studyindicated that groundwater levels were affectedby sea level fluctuations, but the magnitude and

10

AFFECTING SUBSURFACEFLUID FLOW TO IMPROVEREMEDIATION PROCESSES

KLUGER, MARK,mkluger@dajak.com, Dajak¤, LLC, 7Red Oak Road, Wilmington, DE19806

Virtually all subsurface remediation processesinvolve moving fluids (gas or liquid phase).

extent were not documented. Groundwater lev-els were continuously monitored for approxi-mately eight days in three three-well clusterslocated between 820 feet and 3,100 feet inlandfrom Hillsborough Bay. The three aquifers thatwere monitored were the Upper Surficial Aqui-fer (USA), the Basal Surficial Aquifer (BSA),and the Upper Floridan Aquifer (UFA). Sealevel and barometric pressure were also con-tinuously monitored for the same period. Therecorded data was plotted in three compositehydrographs, one for each well cluster, to evalu-ate trends. The recorded sea level data comparedvery well with the tide data recorded at the near-est NOAA tide gage station. A significant tidalabnormality occurred on the seventh day of re-cording resulting in very low tide levels. Thegroundwater levels tracked along with the tidefurther confirmed the tidal influence andgroundwater response. The water table in theUSA showed very little tidal influence. The twodeeper aquifers, the BSA and the UFA, showedsignificant tidal influence, with the influencediminishing inland. The tidal fluctuations alsoproduced at some locations temporary, cycli-cal head reversals between aquifers. These re-sults allowed the development of a tidal cor-rection procedure for the two deeper aquifers,showed some additional factors to account forwhen planning future groundwater level mea-surement events, and gave insight on possibleplume migration perturbations resulting fromdaily groundwater level and vertical gradientfluctuations.

These processes generally involve the extraction(e.g., pump and treat, soil vapor extraction, dualphase extraction, bio-slurping, etc.) or introduction(water floods, surfactant or co-solvent floods, insitu chemical oxidation or reduction, substrate ad-dition for enhanced bioremediation, etc.) of a fluidinto the geo-matrix. Unfortunately, the geo-matrixcan cause significant impediments to fluid flow andthus drastically reduce the efficacy of the chosenremedy.

Pressure pulsing technology can help overcomesome of the limitations imposed by subsurfaceconditions. It involves creating a porosity dilationwave by pulsing an injectate, such as water or othernon-compressible fluids (e.g., surfactants, colloi-dal iron, HRC, potassium permanganate, Fenton sreagent, etc.) into the saturated zone. The pulsedpressure wave, which has a high amplitude (typi-cally 10 to 100 psi) and low frequency (sub-Hertz),momentarily dilates pore volumes, reducing sur-face tension and capillary force effects in multi-phase fluids, and results in the movement of re-sidual liquids through pore throats at high veloci-ties. By applying dynamic energy to the geo-ma-trix, you increase system permeability. Porosity isno longer constant and, in fact, becomes variable.Furthermore, liquids disperse more uniformly.

Pressure pulsing can mobilize dense and/orhighly viscous liquids in all types of geo-matrices.Significantly, pressure pulsing will not mobilizeliquids through clay strata, as the porosity waveswill not efficiently propagate through the medium.Thus, confining units will continue to protect un-derlying zones. PPT has been used to:

• Improve NAPL recovery;• Enhance the performance of pump and treat

and dual phase extraction systems;• Place remedial amendments (e.g., surfac-

tants, oxidants, reductants, etc.) to contactcontaminants;

• Control source zones hydraulics;• Recover coal tar at manufactured gas

plants;• Recover creosote at wood production fa-

cilities;

11

SOLUTIONS TO A FLUORIDEPROBLEM IN SOME WATERSUPPLY WELLS IN PITT COUNTY,NORTH CAROLINA

LAWRENCE, DAVID P.,lawrenced@mail.ecu.edu, andSPRUILL, RICHARD K.,spruillr@mail.ecu.edu, Dept. of Geol-ogy, East Carolina University,Greenville, NC 27858; FOLDESI,CHRISTOPHER P., chris@gma-nc.com, and CAMPBELL, STEVENK., steve@gma-nc.com, GMA, Inc.,Greenville, NC, 27858

Two Cretaceous sand aquifers, the Black Creekand the Upper Cape Fear, are utilized for city andindustrial water supplies in the Coastal Plain ofNorth Carolina. Most of the water quality is high,but hydraulic conductivities (5 to 6 feet/day) arelow, and as a result of excessive withdrawals, thepotentiometric surfaces have been lowered tobelow the tops of aquifers in some localities.Reduction of pumping in the city of Greenville(central Pitt county) has reduced the rate of de-cline, but a long-term solution is needed. Fluo-ride contents remain a problem in some wells;fluoride contents of the aquifers range from lessthan 1 mg/L west of Greenville, to over 3 mg/Least of the city. The city utilities commission hasalways delivered water with less than 2 mg/Lfluoride, since E.P.A. regulations require suppli-ers to notify the public of health risks and fluo-ride levels, if concentrations are above 2 mg/L,and the maximum allowable is 4 mg/L. Exten-sive pumping of wells in eastern Greenville even-

tually leads to reversal of the natural eastwardgradient, and the drawing of higher fluoride wa-ter to the west into production wells. Currently,the only solution has been to severely limit thepumping of the easternmost wells. A future solu-tion that has been successfully modeled(MODFLOW 3-D finite difference program)could be to install from 2 to 5 injection wellsbetween the supply wells and the higher fluoridewaters, in order to maintain a pressure barrier,and reduce the excessive drawdown. The lowfluoride water for these injection wells wouldcome from the seasonal excess capacity of thecity water supply, derived from the Tar River.

• Increase aquifer effective transmissivityto facilitate the re-injection of treatedwater; and

• Rehabilitate wells.

SIMULATIONS OF METALSATTENUATION PROCESSESRELATED TO FIELDBIOREMEDIATION OF ACIDICGROUNDWATER

LEE, MING-KUO, leeming@auburn.edu,SAUNDERS, JAMES, A., WOLF,LORRAINE, W., and PARK,STEPHANIE, Department of Geologyand Geography, Auburn University,Auburn, AL 36849

At the Sanders Lead car-battery recycling plant,near Troy, Alabama, groundwater is highly acidic(pH varies from 3 to 3.5) and carries high con-centrations of Pb, Cd, Zn, Cu, and Fe. This in-dustrial site is analogous to natural acid minedrainage sites containing acidic, metals-ladengroundwaters that are toxic to natural life andhumans. A field pilot study began in December1999 as an alternative to an on-going pump-and-treat remediation that proved to be ineffective.Our field data demonstrate that the indigenoussulfate reducing bacteria (SRB) were capable ofanaerobically catalyzing sulfate reduction to forminsoluble metal sulfide solids.Thisbioremediation process diminishes and limits the

12

INTRODUCTION

A shallow unconfined aquifer below acar battery recycling plant in Troy, Alabama, isheavily contaminated with heavy metals andsulfate from sulfuric acid spills. To assess thefeasibility of bioremediation at this site, a fieldpilot study began in December 1999 as analternative to an on-going pump-and-treatremediation that proved to be ineffective. Theobjective of the field experiment was to injectrequired nutrients to stimulate the growth andmetabolic activity of SRB that we hypothesizedexisted in groundwater even under aerobic andlow-pH conditions (i.e., Elliott et al., 1998;

spreading of metals to near-by water resources.A reaction path model of sulfate reduction showsthe Eh effects on mineral precipitation and pHcontrols on the sorption of different metals. Leadstrongly adsorbs to hydrous ferric oxide (HFO)present in the aquifer over a wide pH range. Bothsorption (due to pH increase) and solid sulfideformation are important for removing lead. Al-though theoretical modeling shows that the sorp-tion of most cations is promoted as pH increases,HFO can only scavenge Zn, Cd, Co, and Ni atrelatively neutral pH conditions. Thus concen-trations of our primary contaminants Zn and Cdattenuate in acidic conditions primarily via pre-cipitation or co-precipitation of solid sulfidephase as Eh drops. The modeling result explainswhy the Pb plume is retarded in migration withrespect to the Cd plume under the low-pH condi-tions at the site. For As, arsenate sorbs stronglyonto the protonated weak sites of ferric hydrox-ide over the pH range of calculation. Arsenitesorption is also favored by increasing pH, how-ever, arsenite desorbs and becomes mobilized atvery low oxidation state as it reacts with dissolvedsulfide to form AsS complexes. Modeling re-sults have implications for remediating other siteswhere anthropogenic or natural geochemical pro-cesses release heavy metals and contaminatewater supplies.

Edwards et al., 2000). We further hypothesizedthat sulfate reduction could be stimulated to thepoint where amorphous solid sulfide phaseswould precipitate, leading to metal removals bycoprecipitation in solids. This study documentsthe principle biogeochemical processes thatoccur at the test site after injecting the bacteria-stimulating solutions. We tracked the changesin water chemistry (major and trace elements,sulfur isotope compositions, pH, Eh) andidentified solid mineral phases produced bybiochemical processes. Theoretical geochemi-cal modeling was conducted to predict how thewater chemistry evolves, which mineralsprecipitate, and how ferric hydroxides adsorbmetals over the bioremediation experiment.The modeling results were compared to fieldobservations of changes in water chemistry andprecipitations of solid materials after theinjection. Since the primary control on theprocess of metal attenuation is acid neutraliza-tion, our calculations aim at predicting the pHrange at which adsorption of metals onto ferrichydroxides minerals becomes significant. Inthis geologic setting, ferric hydroxides mayadsorb heavy metals and help limit or diminishtheir mobility downstream. A geochemicalmodel provides a powerful assessment of theeffects of bacteria sulfate reduction on mineralprecipitation and surface adsorption reactions.

METHODS

Injection Experiments: In the first test,performed on December 16, 1999, 100 poundsof sucrose (commercial grade), 5 pounds ofdiammonium phosphate [(NH

4)

2HPO

4], and 250

gallons of water were mixed in a plastic tank andadded by gravity injection into an existingmonitoring well NW3 screened in a shallow sandaquifer. The second test, performed on September19, 2000, mixture of 1000 gallons of water, 1000pounds of sucrose and 50 pounds of diammoniumphosphate were injected into the well NW12. Thefirst pilot experiment lasted only two months andthe second test lasted for almost one year to

13

monitor the long term changes of water chemistryduring bioremediation. The injection water forboth experiments was raw groundwater pumpedfrom the Cretaceous Tuscaloosa aquifer from aTroy s municipal well prior to chlorination.

Geochemical Analysis: Groundwatergeochemical changes (major ions, trace ele-ments, pH, Eh) were monitored in the injectionwells during the experiments. Temperature, pH,ORP, and electrical conductivity were mea-sured in the field using hand-held water qualityprobes. Raw and acidified water samples andtheir replicates were sent to ACTLABS andUniversity of Georgia for major ion and traceelement analysis using inductively coupledplasma mass spectrometry (ICP-MS). Samplesfor trace element and cation analyses werepassed through a 0.45 µm filter, acidified withconcentrated HNO

3, and stored in polyethylene

bottles.

FIELD SITE

Groundwater at the site near Troy, Alabamawas initially contaminated by lead, cadmium,zinc, and sulfuric acid released in 1980s from alarge car-battery recycling operation in south-eastern Alabama, USA, which accounts for~15% of the current US lead production.Concentrations of several metals greatly exceedmaximum contaminant levels suggested byUSEPA. Contaminated groundwater at the siteoccurs in a shallow, sandy water-table aquifercontaining abundant ferric oxyhydroxides.Depth to the water table is typically about 5 m,and an underlying clay-rich confining layeroccurs at a depth of about 12 m. Hydraulicconductivity of the aquifer ranges from 1.3 x10-

4 to 5.3 x10-4 cm/sec and the average ground-water water is on the order of 0.1 ft/day (3 cm/day). Contaminated groundwater dischargessoutheastward toward a natural wetland and hascaused extensive killing of natural vegetation atthe site. A large-scale conventional pump-and-treat remediation operation has been ongoing

for a decade with limited success in improvingwater quality. Our new bioremediation processinvolves the stimulation of naturally-occurringsulfate reducing bacteria to remediate themetals-contaminated groundwater in situ.

RESULTS

Groundwater Geochemistry Change: For bothinjection experiments, groundwater acidity de-creased with time from the initial injection.Groundwater in wells NW3 and NW12 had aninitial pH of 3.1 and 4.25, and had reached maxi-mum pH values of 4.2 and 5.2, respectively, af-ter the injection. Initial Eh values for groundwa-ter in NW3 and NW12 wells were +400 mV and+125 mV, respectively. The Eh value for NW3fell rapidly and dropped below -150 mV in onemonth after the nutrients injection. The Eh withinwell NW12 fell slowly by comparison, but alsofound to be dropping below -100 mV in just over120 days.

A dramatic reduction in the concentra-tions of lead and cadmium were observed at bothwell sites. Lead within wells NW3 and NW12fell from initial levels of 300 ppb and 85 ppb,respectively, to less than 5 ppb. Cadmium con-centrations fell from 450 ppb and 240 ppb forwells NW 3 and NW 12 respectively, to less than5 ppb. Similarly, other chalcophile ( sulfur -lov-ing ) elements (Cu, Zn) showed similar de-creases, consistent with all of these elementsforming or coprecipitating in relatively insolublesulfide phases. At both injection experiments thelarge reduction in lead and cadmium concentra-tions were accompanied by a lowering in sulfateconcentration and the development of a new rot-ten egg smell characteristic of hydrogen sulfideproduced by bacteria sulfate reduction. Redox-sensitive elements uranium and selenium concen-trations also decreased significantly as the Ehvalues dropped during the course of the experi-ments. Similarly, Al concentration also droppedduring the course of the experiments, apparentlydue to pH increase which probably caused pre-cipitation of an aluminum hydroxide phase.

14

Geochemical Modeling Results:Geochemist s Workbench (Bethke, 1996) wasused to investigate how bacteria sulfate reduc-tion induces the precipitation of metal sulfidesfrom the contaminated groundwater. Thecalculations also predict the sorption of metalsonto the surface the ferric oxide mineralspresent in the aquifer. The surface complex-ation reaction modeling was based on thedouble layer model presented by Dzombak andMorel (1990). To calculate the effect of SRBmetabolism processes, the fluid redox potentialEh decreases linearly from its initial values of+400 mV to -150 mV at the end of the reactionpath, as observed in the field duringbioremediation. The initial system contain 1kg of fluid (pH = 3.17) and a small amount offerric hydroxide. Ferric hydroxides used in thesimulation have high specific surface areas(600 m2/g) and thus provides a large number ofsites for sorption reactions.

The modeling results show how themobility of metals is affected by the geochemi-cal changes (a drop in Eh and an increase inpH) induced by bacteria sulfate reduction.Sulfide produced by sulfate reduction reactwith metals to form minerals including pyrite(FeS2), galena (PbS), sphalerite (ZnS),covellite (CuS), orpiment (As

2S

3) and others

precipitate at Eh below -50 mV. The precipita-tion of solid minerals significantly lowers theconcentrations of corresponding metals insolution. The calculation also shows thatvarious metals are sorbed over a wide range ofpH during sulfate reduction. Metal ions remainin solution as long as the pH is below 3.5. Asthe pH value increases over the reaction,sorption of metals on HFOs becomes signifi-cant in the reacting geochemical system.Dissolved Pb is strongly sorbed at relativelylow pH (< 4), which is consistent with itsremoval observed during the field remediation.The sorption of Zn, Cd, Co, and Ni takes placeonly at relatively neutral or high pH conditionsand has thus little effects in metal attenuation

in our acidic setting. The modeling resultexplains why the Pb plume is retarded inmigration with respect to the Cd plume underthe low-pH conditions. For As, arsenate sorbsstrongly onto the protonated weak sites offerric hydroxide over the entire range of calcu-lation. Arsenite dominates at lower oxidationand low pH conditions and its sorption is alsofavored by increasing pH. However, at very lowoxidation state as pH increases to about 5.8, Asdesorbs and becomes mobilized as its reactwith dissolved sulfide to form AsS complexes.

DISCUSSION

This study shows that primarygeochemical controls governing thebioremediation of metals-contaminatedgroundwater at the site include mineral precipi-tation or adsorption of metals on the surface ofHFOs. Redox potential (Eh) and pH are themost important factors controlling metalspeciation, precipitation, and sorption. Toxicmetals are soluble and mobile in aerobic, acidicgroundwater as those present at our study siteor similar acid mine drainage sites. Field datademonstrate that the indigenous SRB in ametal-contaminated aquifer were capable ofanaerobically catalyzing sulfate reduction toform insoluble metal sulfide solids. Thisbioremediation process diminishes and limitsthe spreading of metals to near-by water re-sources. Geochemical evolution of groundwa-ter during bioremediation is consistent withremoval of two principal metals (Pb and Cd)and other chalcophile elements as solid Zn, Pb,and Cu sulfide phases.

Geochemical modeling is used todemonstrate the relative importance of mineralprecipitation and sorption on the attenuation ofmetal contaminants. Modeling results showthat solid sulfide phase precipitation apparentlyremoves most aqueous Zn, Pb, and Cu,whereas both sorption (due to pH increase) andsulfide formation were important for removingPb. Ferric hydroxides in the aquifer have a

15

high affinity for aqueous metal species. Sorp-tion acts as an important metal scavenger forPb; however it does not play a significant rolefor removing Co, Ni, and Cd in acidic environ-ments such as our site. The plumes of Pb andCd observed in 1998 clearly show this chro-matographic ef fect of retardation. The cad-mium, which is not sorbed at low pH environ-ments, can be seen to have moved significantlydowngradient beyond the strongly sorbed lead.

Modeling results have implications forremediating other sites where naturalgeochemical processes release heavy metalsand contaminate water supplies. For example,the scope of the natural As contamination hadbeen recognized in alluvial aquifers worldwide(e.g., Bangladesh, west India) since early1990 s (Nickson et al., 1998). Our modelingresult is consistent with the hypothesis that Asis strongly sorbed by HFO under oxidizedcondition and the subsequent HFO (bacteria)reductive dissolution mechanism might be animportant process contributing to the problem.We hypothesize that deposition of streamsediments containing HFOs and organic matterin alluvial deposits ultimately triggers theactivity of dissimilatory Fe(III) reducingbacteria (DIRB), resulting in the release ofsorbed As to groundwater. Our modeling resultshows that arsenic is distinctive in being rela-tively mobile by desorption processes underreduced, neutral pH conditions. However, highAs concentrations are not expected in S-rich,acidic, reducing system since such geochemicalenvironments favor the precipitation of sulfideminerals that contain As.

REFERENCES

Bethke, C.M. 1996. Geochemical ReactionModeling. Oxford University Press, NewYork.

Dzombak, D.A., and F.M.M. Morel. 1990.Surface Complexation Modeling:Hydrousferric oxide. John Wiley & Son, New York.

Edwards, K.J, P.L. Bond, T.M. Gihring, andJ.F. Banfield. 2000. An archaeal iron-

oxidizing acidophile important in acid minedrainage. Science, 287: 1796-1798.

Elliott, P., S. Ragusa, and D. Catcheside. 1998.Growth of sulfate-reducing bacteria underacidic conditions in an upflow anaerobicbioreactor as a treatment system for acidmine drainage. Wat. Res. 32:3724-3730.

Nickson, R.T., J.M. McArthur, W.G. Burgess,K.M. Ahmed, P. Ravenscroft, and M.Rahman. 1998. Arsenic poisoning ofBangladesh groundwater. Nature 395:338.

MEASUREMENT OF HYDRAULICGRADIENTS IN THE SLOPES OFTHE PANAMA CANAL: HOW CANTHIS APPLY TO GROUNDWATERCHARACTERIZATION ANDREMEDIATION?

MERCER, DAVID G .,dmercer@slb.com, Westbay Instru-ments Inc., Vancouver, British Colum-bia, Canada

Potential landslides continue to be the greatestchallenge facing the engineers at the PanamaCanal Authority (ACP). A single landslide canimpede traffic through the canal for days, evenweeks. A thorough understanding of thegroundwater flow through the slopes adjacentto the canal is imperative for proper constructionof the engineering controls required to limit theoccurrence of landslides. To effectively modelthe hydraulic gradients in the slopes, the ACPuses Westbay s MP System to measure fluidpressures at multiple discrete zones in boreholesthroughout the length of the canal. The methodsused to accurately determine hydraulic gradientsin large engineering projects can also be utilizedfor groundwater characterization andremediation. A better understanding of the fluidpressure distribution on any site leads to a moreaccurate interpretation of the groundwater flowconditions that are essential to planning effectiveremediation.

16

EFFECTS OF PRODUCTIONPROCESSES AND SUBSURFACECHARACTERISTICS ON THEDISTRIBUTION OF PESTICIDES

MILLER, RUSSELL B.,rmiller@kestrelhorizons.com, andNICHOLS, DAVID G.,dnichols@kestrelhorizons.com, KestrelHorizons, LLC, Greenville, SC 29615

Determining the distribution of pesticides in thesubsurface is governed by the nature of the releaseand subsurface conditions. Understanding andquantifying the distribution of contaminants isof vital importance for any remediation projector risk assessment. In our investigation, weexamined the subsurface distribution oftoxaphene, DDT and its degradation products byintegrating production processes and summarycharacteristics of the waste with geologic andhydrogeologic data.

A Unilateral Administrative Order was issuedin April, 2000 by the U.S. EPA for the OldManning School Site located adjacent the LittlePee Dee River approximately two miles south ofDillon, South Carolina. The site was used as anelementary school for several decades and wassubsequently used as a pesticide formulationfacility from 1963 to 1978. During 1986,renovation activities (for an anticipated use as afood bank) were ceased and subsequent samplingevents identified the presence of toxaphene, DDT,DDD, DDE, methyl parathion and xylene.

At most pesticide formulating sites wheresimilar materials are involved, the extent ofcontamination is limited to the upper soil layers.In a few cases, ground water affects are noticeablebut are usually limited in area. This limitedmigration is due to the inherent properties of mostpesticides. In order for pesticides to be effective,they remain in the plant or in the root zone for anextended period of time and are relativelyimmobile. The presence of toxaphene, DDT andits degradation products extensively in soil and

below the water table indicates other factors wereoperating at this site. Toxaphene was found inground water as high as 120 ug/L as compared tothe MCL of 3 ug/L.

Results from soil analysis enumerated a Cshaped pattern when illustrating toxaphene versusdepth. The C shape indicates concentrationsare elevated at ground surface, decrease withdepth and increase again near the water table.Average toxaphene and DDT concentrations inthe surface soil samples were 4,040 and 1,150mg/kg as compared to the EPA cleanup standardof 52 and 170 mg/kg respectively.

Knowledge of production processes helpeddelineate affected materials. For example, sincethe pesticides were mixed into solutions withsolvents (primarily xylene) and cleaning agents,the mobility of the pesticides was enhanced. Insome areas, toxaphene-DDT ratios in the soilsare similar to that which was formulated in thesolutions distributed to the farmers. Knowledgeof the hydrogeology coupled with the chemicalcharacteristics is also useful in identifying thedistribution of the pesticides. For example,concentrations increased near the water table dueto changes in water levels and the hydrophobiccharacteristics of toxaphene and DDT.

Through better understanding of thedistribution of pesticides in the subsurface, projectobjectives were achieved that included reducingrisks associated at the site and minimizingunnecessary costs (such as removal of cleansoils).

WRITING TECHNICALDOCUMENTS FROM THESTANDPOINT OF ADVOCACY ANDLEGAL PROTECTION

ORMOND, JOHN CHARLES, JR.,COrmond@aol.com, Holler, Dennis,Corbett, Ormond, & Garner, 1777 BullStreet., Columbia SC 29201

The preparation of written materials, from geo-logical and/or engineering maps, diagrams, cal-

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culations or charts, to written summary s and re-ports are increasingly important for scientists inthe consulting and regulatory fields. Geologistsand other scientists and engineers do more andmore writing and are often asked to prepare adocument, once an opinion has been determined,to reflect the issue only from the standpoint ofthis position either for a private client or a regu-latory agency. This is true with most documentsprovided to a client or regulatory agency, whetheror not the documents are in anticipation of, orduring, litigation. As licensed professionals, ge-ologists and engineers should interpret geologi-cal and other data from an unbiased and neutralperspective. However, once that opinion has beenformed, a scientist is in no way precluded frompreparing documents which strongly support thatposition. Reports which are designed to recom-mend or take a scientific position or interpreta-tion can and should be written as an advocate ofthe position if the underlying work was diligentand supports the position. A neutral scientist canaccomplish this through the use of grammaticaltechniques, choice of words and many othermethods. Any professional scientist or engineerwho writes or creates written documents or ma-terials, will be better off is he or she can use lan-guage and grammar to support his or her posi-tion.

Documents created in anticipation of, orduring, litigation, whether it be judicial or ad-ministrative litigation, may be protected fromadversaries and other parties by the attorney workproduct doctrine. This doctrine has been ex-panded to include experts working with attorneysand technical professionals and scientists shouldbe knowledgeable enough about this doctrine tostay within its limits when a client or employeris dealing with a sensitive matter through an at-torney. The elements of the doctrine are simplebut its application is many times quite complexand misunderstood. If a matter may or has goneinto the litigation process, scientists and engineersmust consider the attorney work product doctrineprior to the creation or destruction of any docu-ment.

IMPLEMENTATION OF A FULL-SCALE IN SITU CHEMICAL OXI-DATION (ISCO) PROGRAM IN AFRACTURED BEDROCK AQUI-FER: PRACTICAL APPROACHESAND LESSONS LEARNED

PEACOCK, JEREMY S.,jpeacock@geosyntec.com, GeoSyntecConsultants, Inc., Atlanta, GA

A two-phased pilot test demonstrated that insitu chemical oxidation (ISCO) was effective indegrading trichloroethene (TCE) in a fracturedrock aquifer. This test involved the injection ofa dilute sodium permanganate solution underpumping and natural flow conditions. Basedon pilot test results, a full-scale ISCO programis being employed to remediate a TCE plumein a fractured rock aquifer beneath a residentialand commercial neighborhood.

After obtaining the necessary regulatoryapproval, a full-scale ISCO plan wasimplemented. Twelve new monitoring/injectionwells were installed to supplement the existingwell network. Upon completion, all new wellswere sampled to obtain baseline values forvolatile organic compounds (VOCs), metals, andwater quality parameters. Oxidant demandtesting was conducted on samples from each wellto provide information on total groundwateroxidant demand in the aquifer. Hydraulicconductivity was tested in the injection area byperforming slug tests in monitoring/injectionwells. Based on this data, eight wells wereselected to serve as injection wells. Baseline datacollected from new wells was also used to updatethe site hydrogeologic model, allowing anestimation of oxidant dispersion and mixing. Thisinformation was used to calculate injectionvolume and oxidant mass for each injection. Priorto beginning injections, thorough health andsafety and contingency plans were developed.Issues such as personnel protection, spill

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prevention, and response, and oxidanttransportation were addressed in these plans.

Injections are scheduled to occur semi-annually until successful remediation can bedemonstrated. The first round of oxidantinjections was completed in February 2003.Injections were accomplished through gravityfeed of a dilute sodium permanganate solutionto the screen zone of each injection well.Injection volumes ranged from 250 to 500 gallonswith sodium permanganate concentrationsbetween approximately 250 and 1800 ppm. Theoxidant solution was transported in a 500 gallontank attached to a dedicated sampling/injectiontrailer maintained at the site. A program ofsampling and monitoring will be instituted toensure that the ISCO program proceedseffectively and safely. This includes monitoringof a stream that serves as a local groundwaterdischarge point and detailed monitoring of aquifergroundwater for the presence of VOCs, metals,and sodium permanganate. Several unexpectedissues surfaced during the planning and initialinjection phase of the project. However throughproper analysis, planning, and testing, these issueswere adequately addressed.

DISTRIBUTION OF TOTALARSENIC IN GROUNDWATER OFTHE NORTH CAROLINAPIEDMONT PROVINCE

PIPPIN, CHARLES G.,chuck.pippin@ncmail.net,BUTCZYNSKI, MICHELE M. andCLAYTON, JONATHON H.,NCDENR — Groundwater Section,Mooresville, NC 28677

The North Carolina Department of Environmentand Natural Resources, Division of Water Quality,Groundwater Section (GWS), in cooperation with

the North Carolina Department of Health and

Human Services (NCDHHS) and four county

health departments have been assessing the extent

of total arsenic in the North Carolina Piedmont s

groundwater resource. Local health department

sampling over the past several years has identified

wells in three separate areas that have

concentrations of total arsenic above the former

EPA Drinking Water Standard of 0.05 mg/L. The

GWS completed water supply well sampling in

each area in an attempt to identify the source(s)

for the arsenic problems and to identify other

potentially affected wells. Early on, these efforts

suggested that the distribution of arsenic affected

wells is widespread. This work led to a

collaborative effort by several state and county

agencies as wells as the United States Geological

Survey to develop a plan to assess the distribution

of arsenic in NC. The plan consists of three

phases: (1) Reconnaissance Sampling and Hot

Spot identification; (2) Source Characterization;

and (3) Health Surveillance. This presentation

focuses on the results of Phase 1.

Data from the NCDHHS Laboratory and the

GWS has been combined to produce a geolocated

database of over 6,000 groundwater samples. The

combined data can generally be described as non-

parametric, positively skewed, highly censored

and having many different method detection

limits (MDLs). Several individual counties have

median values for arsenic that are greater than

current method detection limits. In order to

identify the hotspot areas, probability analysis

using indicator kriging was performed with

threshold values of 0.001 mg/L and the current

EPA Standard of 0.010 mg/L. Results of the

probability analysis indicate that analytical results

of groundwater samples collected from wells in

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most areas of the Piedmont should not have a

problem with elevated arsenic. Several areas,

however, do have a higher probability of

exceeding the threshold values. The figure below

indicates the areas where a 75% chance or greater

exist for wells to produce groundwater samples

that exceed the threshold values mentioned above.

In addition to the data used for indicator kriging,

a lot of data exist for individual counties that lack

sufficient location data to be geolocated. Based

on our analysis of both sets of data, wells in Stanly

and Union counties have the greatest probability

(~71% and ~53%, respectively) of hosting wells

that produce groundwater samples with elevated

arsenic concentrations. Analysis of census data,

municipal water records and other public water

supply records provides an estimate of well use

in Stanly and Union counties and suggests the

potential for thousands of wells to provide

groundwater with detectable concentrations of

arsenic. These and other high probability areas

are spatially correlative with the rocks of the

Carolina Slate Belt and other litho-tectonic belts

with volcanic rock members. Spatial density of

samples is not consistent across the Piedmont and

therefore, care must be taken when interpreting

the probability maps to ensure that sufficient

sample density is present to support the estimated

probability at a particular geographic area. To

assess this relationship a spatial index has been

created that indicates geographic areas where

both a high probability of arsenic and a minimum

sample density of 5 samples per 2.5 square miles

exist.

Threshold of 0.01 mg/L

FIGURE 1 — SHADED AREAS REPRESENTS A 75% OR GREATER CHANCE FORGROUNDWATER SAMPLES TO EXCEED THRESHOLD VALUES OF 0.001 MG/L AND 0.01MG/L FOR ARSENIC.

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CHARACTERIZATION OFSTRATIGRAPHICHETEROGENEITY IN THETEMBLOR FORMATION(MIOCENE), COALINGA AREA,CALIFORNIA: INTEGRATION OFGEOLOGIC MODELS ANDSEISMIC GEOPHYSICAL DATA

PIVER, JAIME L., JAMES W.CASTLE, MATTHEW T. POOLE,and REX A. HODGES, Dept. ofGeological Sciences, Clemson Univer-sity, Clemson, SC 29634-0919;IMHOF, MATTHIAS G., Dept. ofGeological Sciences, Virginia Tech,Blacksburg, VA 24061-0420

New methods of predicting interwellheterogeneity within the Miocene TemblorFormation near Coalinga, California are beingdeveloped and assessed through collaborationbetween the departments of Geological Sciencesat Clemson University and Virginia Tech. Usingwell-log data from a 5 sq-km area of the Coalingawell field, geologic computer models have beencreated at Clemson to provide realistic three-dimensional representations of lateral and verticalstratigraphic variation. The results are beingintegrated with models of subsurfaceheterogeneity produced from three-dimensionalseismic data by researchers at Virginia Tech.

Four stratigraphic bounding surfaces, whichare based on detailed stratigraphic study of theTemblor Formation, were identified and used incorrelating geophysical logs and as constraintsfor the geologic models. Deterministic andstochastic modeling techniques using density andgamma-ray logs have been used to represent thestratigraphy of three 0.5 sq-km study areas withinthe Coalinga well field. Similar modeling

techniques are now being applied to the entire 5sq-km study area to characterize heterogeneitybetween data points and to provide detailedrealizations of the stratigraphy and faciesdistributions within the Temblor Formation.Normalized density and sonic logs were used togenerate synthetic seismograms, which allows forintegration between the stratigraphicinterpretations and seismic data. The stratigraphicbounding surfaces and the reservoir heterogeneityfrom the geological modeling compare favorablywith amplitude variations on the seismic profiles.

ALTERING THE LANDSCAPE -RANDOM FILL AND EFFECTS ONRECHARGE AND CREATION OFCONTAMINATED GROUNDWATERIN PIEDMONT SAPROLITES ANDPARTIALLY WEATHERED ROCKS

PRIVETT, DONALD,dprivett@chestertel.com, STAREnvironmental, 1 Circle St.Great Falls, SC 29055

Areas of large random fill (such as broken con-crete, mixed with foreign saprolite and soil etc.)permit rapid infiltration and little run-off. Mostrandom fill consists of sequences of differentmaterials and/or material of different sizes, wherefill is used to raise an area too low for construc-tion (a old railroad cut ) or extend and enlarge asloping area to construction grade. Interfacesbetween different beds of various sizes anddifferent degrees of compaction may act as a baseto impede or enhance flow to the watertable.

Seepage flow paths through random filland into saprolite are quite different, becauseprimary and secondary structures, textures andgeometries, surface and soil properties are verydifferent. Water movement is determined bygravity, external pressure and internal molecularattraction (viscosity), the onset and extent ofrunoff depends on infiltration rates at specific

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GEOLOGICAL INFLUENCE ONTHE OCCURRENCE OF RAREPLANT SPECIES IN THEJOCASSEE GORGES AREA OFSOUTH CAROLINA

RAY, TERRY; tray@clemson.edu,CASTLE, JAMES W.; and BRAME,SCOTT; Department of GeologicalSciences, Clemson University , 340Brackett Hall, Clemson, SC 29634-0919

locations. Groundwater recharge in anycatchment area is determined by the volume ofsurface or overland flow and infiltration.

Preferred flow-paths through extremely het-erogeneous material may permit rapid infiltra-tion through the unsaturated zone to the base ofthe fill or gravitational runoff with little ground-water recharge. The volume of water within pref-erential paths is much larger and it may move tothe base or to the edge of the fill.

Dual porosity transport (determination ofwater movement through naturally fracturedrocks) is valid for most partly compacted fillmaterials where movement 1.) is along continu-ous fractures and along contacts of larger par-ticles i.e. connected porosity and 2.) is muchslower to stagnant through the surrounding finergrained porous matrix. Water moving throughboth the matrix of finer material and more rap-idly at and along large slabs and coarse fragmentsand through uncompacted macrovoids producean even more complex pattern. Slumping or gravi-tational flow of surface material over earlierdumped layers may form another semi gradedunit with still different transport properties.

Pollutants, deposited intentionally or uninten-tionally may migrate rapidly by advection, dif-fusion, dispersion, sorption and degradation to-wards the groundwater table. Preferential rapidflow and transport being directed by fractures,fissures, voids and cracks. Infiltration through andrecharge from any mixed in contaminates greatlyreduces the quality of groundwater.

Wadakoe Mountain, in the Jocassee Gorges areaof upstate South Carolina, is an area of uniqueplant diversity where many occurrences of rareplants have been documented recently (SouthCarolina Pulse, 2002). Two species are newlydiscovered, and several are new to South Caro-lina. The purpose of our study is to identify anddescribe geological factors that influence the oc-currence and distribution of these species.

Geologically, the study area is located on theSix-Mile thrust sheet within the Inner Piedmontgeologic province. Soils in this area, which isapproximately 5 miles east of the Brevard Faultzone, are typically acidic due to the weatheringof metamorphic rock. Abella (2002) associatedoccurrences of rare plant species in the JocasseeGorges area with an increased pH of the soil. Thecause of the greater soil pH in this area is of greatinterest to botanists, conservationists, and ecolo-gists. Geological factors that may influence soildevelopment in the Jocassee Gorges area includecomposition of the bedrock, site-specific slopes,geomorphology, and the topographic complex-ity.

Our recent field work in the study area hasrevealed an unmapped occurrence of carbonate-rich rock in the vicinity of the unusual plantspecies. The weathering of this rock type, andperhaps other related rock types, may beresponsible for producing soils of increased pH,which has a strong influence on the plantcommunities. Ongoing investigation of thegeology of Wadakoe Mountain includes moredetailed characterization of the rock types andtheir distribution, as well as other geologic factorsthat may influence the occurrence of rare plantspecies.

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THE SELF-POTENTIAL METHODIN APPLIED GEOPHYSICS WITHAPPLICATIONS INHYDROGEOLOGY

REPPERT, P., reppert@clemson.edu,Geological Sciences, Clemson Univer-sity, Clemson, SC 29634

The self-potential method is an economicalgeophysical method that can provide usefulinformation about subsurface fluid flow andsubsurface contamination. This talk will examinethe physical basis for self-potential measurementsand how the surface measurement relates back tothe underground anomaly. Specific case exampleswill be presented that demonstrate the ability ofthe self-potential method to detect DNAPL,LNAPL, as well as monitor groundwater flow.

IN-SITU REMEDIATION OF CAR-BON TETRACHLORIDE USINGENHANCED REDUCTIVEDECHLORINATION AND HY-DRAULIC FRACTURING

RHINE, ELIZABETH, erhine@arcadis-us.com, ARCADIS G&M, Inc., 420 E.Park Avenue, Greenville, SC 29601

A full-scale innovative, patented system using in-situ reactive zone (IRZ) technology was imple-mented at a former manufacturing facility to ac-complish enhanced reductive dechlorination(ERD) of carbon tetrachloride (CT). This pro-cess demonstrated the capability of reducing CTconcentrations without producing toxic levels ofdegradation products chloroform, methylenechloride, chloromethane, or vinyl chloride. A10% molasses reagent solution was injected intothe aquifer as a food source to promote prolif-eration of indigenous bacterial colonies. Onceadequate dissolved organic matter and essential

nutrients are supplied, the composition of micro-bial communities shifts so that bacteria that me-tabolize nitrogen, sulfate, dissolved metals andcarbon dioxide dominate. Once anaerobic con-ditions are established, as indicated by negativeredox potentials, the feed solution is reduced to5% molasses to maintain the population whileestablishing a need for additional carbon, whichin this case is carbon tetrachloride.

The injection field consists of 134 active in-jection wells over an area of approximately 4.1acres. CT concentrations at monitor well DD-37.8, located immediately downgradient of thesource area, were as high as 2,200 µg/L in 1991.Baseline analyses conducted on October 17, 2001just before start-up of the ERD system, indicatedCT concentrations were at 651 µg/L. By July23, 2002, CT concentrations had decreased tobelow the maximum contaminant level (MCL)of 5 µg/L in nine months. During the same pe-riod, CT concentrations in downgradient wellEW-4 declined from 2,080 µg/L at start-up to 95.8µg/L on November 20, 2002 (13 months). De-creased CT concentration at EW-4 is attributedto improved groundwater quality upgradient.

In one are of the IRZ injection well field, ahydraulic fracturing pilot study had been per-formed approximately one year earlier. Since theIRZ overlapped the hydraulic fractures, we wereable to observe the effects of fracturing in con-junction with ERD technology. Hydraulic frac-turing was performed to increase hydraulic con-ductivity in the saprolite section of the aquiferand further enhance reagent injection rates. Atotal of six fractures at depths ranging from 9 to44 feet below ground surface (bgs) were createdat a designated point within the source area. Theprimary monitor wells for this study, OW-HF1(screened from 52 to 57 bgs) and OW-HF1delta(multi-level well sampled from screened inter-val 41 to 43 bgs), were installed approximately6 feet downgradient of the 44 bgs fracture and 4feet sidegradient of the 23 bgs fracture, respec-tively.

The ERD injection wells were installedapproximately 45 feet upgradient of the

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monitoring wells and the hydraulically fracturedarea. The molasses reagent solution was injectedinto the aquifer to proliferate indigenous bacterialcolonies, creating anaerobic conditions neededto degrade the VOCs present in the groundwater.At OW-HF1, which is screened approximately10 feet below the fractured zones, a 58%reduction in VOCs was observed after one yearand degradation of all VOCs to below MaximumContaminant Levels (MCLs) occurred within 15months. At OW-HF1delta, which is screened ina zone between fractures, complete degradationof all VOCs was observed in less than 6 months.

The full-scale IRZ has show favorable reduc-tion of VOCs in most areas without hydraulicfracturing, meeting clean-up goals in over 70%of the treatment area within 15 months in boththe saprolite and bedrock aquifers. Injections inthese areas have been terminated. Due to the pro-cess of reductive dechlorination, no rebound ef-fects are anticipated. However, the southern por-tion of the treatment zone has shown a muchslower response to the traditional IRZ technol-ogy with the exception of OW-HF-1, which isscreened between fractures. Additional hydrau-lic fracturing will be utilized to enhance the ef-fectiveness of the current treatment system.

THE FORM OF HYDRAULICFRACTURES AT SHALLOWDEPTHS IN PIEDMONT SOILS

RICHARDSON , JIM,jrr0072002@yahoo.com, QINGFENGTAN, and LARRY MURDOCH,Department of Geological Sciences,Clemson University , Clemson, SC29634

The form, or geometry and thickness, of ahydraulic fracture plays a key role in theperformance of environmental remediationprojects. Fractures that are relatively thick andflat-lying are ideally suited to improve theperformance of wells, whereas fractures that aresteeply dipping may be better suited to the

creation of reactive barriers. Many hydraulicfractures have been created at shallow depths inthe Piedmont, but their forms are only knownapproximately from a few borings and indirectmeasurements. To sharpen the resolution of thedetails of fracture form, we excavated the vicinityof four hydraulic fractures and carefully mappedthe features on more than 65 m of trenchexposure. The data from these maps were usedto characterize fracture form, including geometry,sand thickness, distribution of sand within thefracture, and ground surface deformation.

The fractures were nearly elliptical in planview, and the center of the fractures were offsetfrom the injection casing (Fig.1). Most of eachfracture dipped toward the injection casing from12ß to 16ß, but dips locally ranged from horizon-tal to nearly 70ß. A peculiar aspect of the formwas observed in the vicinity of the injection cas-ing, where each fracture curved downward andthen back up to produce a gentle trough-like struc-ture around the casing. Hydraulic fractures inthick, silty clay glacial till are roughly flat-lyingnear the injection casing, according to previousstudies. The hydraulic fractures created at ourfield site were initiated slightly above the con-tact between stiff, B-horizon material and softer,underlying saprolite. Hydraulic fractures propa-gating in one material will grow toward a mate-rial with a lower elastic modulus. We expect thatthe peculiar tough-like aspect of fracture formwas produced when the incipient fracture grewdownward toward the nearby interface with rela-tively soft saprolite. As its length increased, how-ever, the fracture began to curve upward as it in-teracted with the ground surface.

Sand thickness was thickest near the centerof the fractures at a maximum of 2cm and ta-pered towards the edges. Approximately 2500measurements of sand thickness were made andthe average value is 0.6cm. Uplift surveys takenat the ground surface before and after the pump-

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ing event created maps which show gentle domesthat are good indicators of fracture extent andsand thickness.

The transport of sand in the fractures wastraced by sequentially injecting sand painted dif-ferent colors. The distribution of the differentcolors of sand was then mapped in the excava-tions, and the results used to develop a concep-tual transport model. The sand colors were dis-tributed in curvilinear features extending from theinjection casing towards the edges of the frac-tures. These features cut through previously in-jected sand and fan out at the leading edge. Thisresembles a river channel that fans out into aprogradational delta. The result is that the firstsand injected occurs near the injection casing andthe last sand injected occurs at the edges of thefractures. These findings cannot be explained bytraditional plug flow models. Instead, it appearsthat sand is transported in preferential pathwaysthat follow the axes of fracture lobes.

Figure 1. Perspective of a hydraulic fracture createdat a depth of 1.5 m in Piedmont soil.

ADDRESSING RESIDUAL, MASSTRANSFER LIMITED VOCCONTAMINATION USINGSUSTAINABLE ENERGYPOWERED MICROBLOWERS TM

ROSSABI, J., joseph.rossabi@srs.gov;DIXON, K.L.,Kenneth.dixon@srs,.gov; JACKSON,D. G., dennis.jackson@srs.gov; RIHA,B.D. brian.riha@srs.gov; HYDE. W.K.,Warren.Hyde@srs.gov; SRTC, Aiken,SC 29808; COSTANZA, J.,Jed64@bellsouth.net, Georgia Tech,Atlanta, GA.

It has been more than ten years since the first soilvapor extraction systems were installed toremediate volatile organic contaminants in thesubsurface. These high volume removal systemsincreased the effectiveness of remediation by anorder of magnitude over the baseline method ofthe time — ground water pump and treat. SVEwas so effective and broadly applicable it becamethe EPA s presumptive remedy for VOC sites(USEPA, 1996). Unfortunately, after 10 or moreyears of remediation, many of these early SVEsites still require cleanup. Although active SVEcan remove a large portion of the contaminantmass from a site very rapidly, removal of residualcontamination located in fine grain sediments islimited by the rate of diffusion. It has becomeapparent that the technology reaches a mass-transfer rate removal limit past which operationbecomes inefficient. This point often falls shortof the contaminant concentration cleanup goalsestablished for the site. Researchers have ad-dressed this mass transfer limitation in a varietyof ways — from more aggressive initial actionssuch as heating, to long term, low energy meth-ods of removal like barometric pumping. Heat-ing or advanced oxidation techniques require asubstantial amount of infrastructure, and opera-tion and maintenance costs. Barometric pump-ing requires sufficient pressure differential and

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subsurface permeability properties that can gen-erate environmentally relevant flow. Often theseconditions are not met at contaminated sites withshallow vadose zones or low permeability sub-surface materials. Between these endpoints, thereare opportunities for innovative sustainable meth-ods.

Targeting the recalcitrant contaminantcontained in fine grain sediments appears to bethe most direct way to remediate sites but it isdifficult to access contaminant trapped deepwithin the soil. Many environmentalprofessionals initially opt for the bigger hammerapproach and use large, energy consumingblowers to move more air through the subsurface,but this may not be the most efficient method. Toprevent downward migration of organics andcontamination of the water table, it may only benecessary to remove contaminants at a rate equalto the rate of mass transfer out of the fine grainzones (i.e., effective diffusion rate). If aremediation system can operate just ahead of thisrate, it is sufficient to protect the environment andwill often be economically efficient. We haverecently developed systems using small, lowpower electric vacuum blowers. Thesemicroblowers can draw a larger vacuum thenbarometric pumping (~10 H2O) and createlarger flow rates (>12 scfm). The blowers canbe powered by small solar panels and deployedat remote sites with minimal maintenance andno operation costs. The systems cost between$500 and $1500 depending on the siteconfiguration and operational needs and canoperate unattended for years. We have beensuccessfully operating these systems at SRS forapproximately one year and have found them tobe one of the most promising remediation toolsavailable for sustainable low cost remediation.

MINERALOGIC, GEOCHEMICAL,AND GEOMICROBIOLOGICCONTROLS ON NATURALARSENIC CONTAMINATION OFGROUNDWATER

SAUNDERS, James A.,saundja@auburn.edu, and LEE, Ming-Kuo, Dept. of Geology and Geography,Auburn University, AL, 36849.

Several water-rock reactions can lead to signifi-cant levels of dissolved arsenic in varyinghydrogeologic and geochemical environments.Distinction between natural and anthropogenicAs contamination is clearly important in estab-lishing liability as well as remediation goals andstrategies. However, we present data that showAs contamination can be a consequence of per-turbations of the ambient geochemical and mi-crobiologic conditions in aquifers without intro-duction of anthropogenic As sources. Natural Ascontamination of groundwater is a consequenceof the relative rates of two processes: groundwa-ter flow and As release from solid phases. Ifgroundwater flow is sluggish and arsenic releaserates are rapid, as in alluvial floodplains, thennatural As contamination can be an importanthealth issue as in Bangladesh, West Bengal, In-dia, Vietnam, etc. Natural arsenic can de derivedfrom a number of minerals or mineral(oid) sur-faces. Although arsenic forms two relativelycommon sulfide minerals (orpiment and realgar)it is most problematic from an environmentalstandpoint when it is present in minor amountsin reactive iron sulfides such as pyrite and mar-casite. This source of arsenic is very problem-atic in the Black Warrior Basin coal fields of Ala-bama, Appalachian coal fields in general, and alsohard rock base- and precious-metal mines ofthe western US, Canada, Ghana, etc. For ex-ample, the world-class Carlin-type gold depositsof northern Nevada contain hydrothermal iron-sulfides rich in both gold and arsenic. In anoxicmarine sediments, As coprecipitates in iron sul-fides and thus can be a source of arsenic wheresuch units react with groundwater as in Wiscon-sin. We have shown that biotite is a rapidly weath-ering mineral common to crystalline rocks of theSouthern Appalachians and it could provide a sig-nificant source of As to the hydrosphere. Per-haps some of As-contaminated groundwater innorthern Appalachian crystalline rocks may havea similar origin. Unstable, rapidly weathering,volcanic glass in young volcanic terrains of thewestern USA and elsewhere may also be a sig-nificant source of natural As contamination lo-

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cally. These are all distinct possibilities depend-ing on local geologic conditions. But our researchpoints to the young (post-Ice Ages) alluvial flood-plain environment as the most problematic siteworldwide where aquifer minerals, organic mat-ter, and anaerobic bacteria all are important inproducing natural arsenic contamination thatthreatens large human populations, particularlyin developing nations. Thus our presentation willfocus on the sources and causes of arsenic re-lease in this setting, including our new data onthe bacterial culprits responsible: iron-reducingbacteria.

MEASURING CHANGES INFRACTURE APERTURE IN-SITUDURING AN INJECTION TEST

SCHWEISINGER, TODD,todds@clemson.edu; and MURDOCH,LARRY, lmurdoch@clemson.edu,Geological Sciences, Clemson Univer-sity, Clemson, SC 29634

Fracture networks are critical to ground waterflow, but details of the geometry of networks inthe subsurface can be difficult to determine withcurrently available technology. Sheet fractures,or other flat-lying fractures, are an important com-ponent of fracture networks in crystalline rock.Using a televiewer, or other borehole geophysi-cal technique, it is possible to determine the deptha sheet fracture intersects a borehole, but it is moredifficult to determine the size of the fracture andits connectivity to other fractures in the network.The aperture of a sheet fracture will change inresponse to pressure changes during a hydraulicwell test, and the amount that the aperture changeswill depend on both the size of the crack and howit is connected to the network. We are develop-ing a field test that measures changes in apertureduring a well test to estimate fracture geometry.The test uses a borehole extensometer betweenstraddle packers to measure changes in aperture,

and transducers to measure pressure during andafter a hydraulic well test conducted by injectingat a constant flow rate. In general, the fractureopens as pressure increases during injection, andcloses as pressure decreases during recovery. Acoupled model of deformation and fluid flow isinverted to estimate fracture parameters that bestpredict the records of aperture and pressure.

Efforts toward developing this test havefocused on designing and fabricatinginstrumentation for acquiring the fieldmeasurements, and deriving theoretical analysesfor interpreting the results. The boreholeextensometer consists of two retractable anchorsseparated by connecting rods attached to asubmersible LVDT. The anchors are designed tolock themselves in place once actuated, thusminimizing creep over time. Another applicationfor this device is to measure long-term changesin fracture aperture due to Earth tide or othereffects, so it is important to reduce creep effects.The anchors are deployed on opposite sides of afracture and they are displaced as the fracturedilates. Lab tests show that the lower limit ofresolution is approximately 0.1 micron, andtemperature changes both downhole and aboveground appear to be a major threat to resolution.The connecting rods are configured to minimizeoverall length changes of the device owing todownhole temperature changes. Above ground,the data acquisition system is held at a nearconstant temperature in an insulated container toreduce spurious displacement measurementscaused by changing the temperature of theelectronics. Simple analytical models, and a morecomplete semi-analytical model are beingdeveloped to interpret the results of the field tests.The semi-analytical model determines thepressures and aperture changes during injectionof water into a flat-lying fracture intersecting aborehole. The solution is obtained by iteratingbetween one analysis for fluid-flow and anotherfor elastic displacements of the fracture usingmethods developed for modeling hydraulicfracture propagation.

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USE OF INDUCED FRACTURES ASENHANCEMENTS TO SOIL ANDGROUNDWATER REMEDIATIONSYSTEMS

SLACK, WILLIAM W., wslack@frx-inc.com, FRx, Inc., Cincinnati, Ohio

One cost modern society has placed upon theplanet earth has been the contamination of soiland groundwater by toxic or dangerouschemicals. Although practices that lead to suchproblems have by and large been discontinued,the remediation and restoration of contaminatedsites remain limited for the lack of sufficientlyrobust and efficacious techniques.

Hydraulic fracturing presents an opportunityto create regions with beneficial properties withincontaminated soil. The content of these regionscan either (1) enhance the delivery or recoveryof fluids from targeted soil or (2) directly effectthe in situ destruction or containment of selectedcontaminants. For example, sand-filled hydraulicfractures can increase the discharge of vaporrecovery wells by factors of 20 to 50 and extendthe radius of influence by commensurate ordersof magnitude in comparison to conventional wellsinstalled in low permeability soil or bedrock.Alternatively, fractures can be created withreactive material, such as granular iron, to formin situ permeable reactive barriers withouttremendous disruption or excavation from thesurface. In general, fractures enable the in situapplication of chemical or physical remedialprocesses – fracturing it self cannot accomplishremediation.

Fracturing technology has been used atdozens of sites in diverse geological settings. Ithas been coupled with pump-and- treat for bothgroundwater recovery and hydrological control,non-aqueous phase recovery, vapor recovery,dual-phase recovery, injection of oxidantsolutions, air sparging, delivery of biologicalsubstrates, etc. It has been used to create in situpermeable barriers that are reductive, oxidative,

or adsorptive. Fracturing techniques have createdelectrodes to support electro-osmotic inducedcontaminant transport. The targeted contaminantshave been as varied, although fuels and solventsdominate the list – in keeping with theirubiquitous use.

Examples of specific projects provide theopportunity to document the order-of-magnitudeeffects fractures can impose relative to theperformance of systems that rely uponconventional wells. Although few projects havea complete set of data, key pieces of informationfrom individual projects can be amalgamated toprovide a coherent representation of fracturingfor various purposes in different media. In thissense, several field-scale projects validateperformance estimates derived from moreexacting pilot studies and developmentexperiments. With confidence in the soundnessof underlying principals, project experience alsosuggests modifications to basic fracturingtechniques for further applications.

GEOLOGIC MAPPING AND WADISURVEY IN THE ANDERSONSOUTH 7.5-MINUTEQUADRANGLE, SOUTHCAROLINA

SORICELLI, ANTHONY,asorice@clemson.edu, and CASTLE,JAMES W., Geological Sciences,Clemson University, Clemson, SC29634-0919; CLENDENIN, C.W.,South Carolina Geological Survey,Columbia SC, 29212; andMITCHELL, H.L., South CarolinaDepartment of Natural Resources,Land, Water, & Conservation Division,Greenville, SC 29601

Mapping in the Anderson South 7.5-minutequadrangle, South Carolina, is leading to a betterunderstanding of the structural geology of thearea, which covers part of the Six Mile thrust

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DEVELOPMENT OF REACTIONZONES DURING PASSIVE TREAT-MENT OF LOW PH, FERRIC IRON-DOMINATED ACID ROCK DRAIN-AGE

THOMAS, Robert C.,thomas.bt@epa.gov, US EPA-ERD,Athens, GA 30605; ROMANEK,Christopher S., Dept. of Geology andSavannah River Ecology Laboratory,University of Georgia, Drawer E,Aiken, SC 29802; PADDOCK, LindaS; and COUGHLIN, Daniel P., Savan-nah River Ecology Laboratory, Univer-sity of Georgia, Drawer E, Aiken, SC29802

Passive alkalinity generating systems are a cur-rent option being used in the remediation of acidrock drainage (ARD). One particular design, thereducing and alkalinity producing system(RAPS), has gained popularity because it is theonly system capable of long-term treatment oflow pH ARD containing > 1 mg·L-1 ferric iron,aluminum, or oxygen. Although RAPS are notdesigned for metal retention, when they receivelow pH (<3), ferric iron-dominated ARD, bothferric iron and aluminum are precipitated in dis-tinct reaction zones.

In this study, a RAPS was simulated and themechanism of iron and aluminum removal wasinvestigated. Highly acidic (1304 mg·L-1 CaCO

3

equivalents), low pH (2.4), ferric iron-dominated(95 – 100 % ferric iron; 92 – 237 mg·L-1 totaliron) ARD was passed through the system for twoyears. Effluent pH was consistently near-neutral(6.4) and alkaline (619 mg·L-1 CaCO

3

equivalents) with >97% of the influent acidityremoved. Three distinct reaction zones wereidentified: 1) an orange “oxide zone” that isdevoid of limestone and contains mainly goethite

sheet of the Inner Piedmont. An interlayeredsequence of biotite gneiss, sillimanite mica schist,quartzo-feldspathic biotite gneiss, amphibolitegneiss, augen gneiss, and ironstone is recognized.Northwest-verging, recumbent isoclinal foldswith attenuated limbs deform the rock sequence.Isoclinal folds are refolded by northwest-verging,inclined closed folds and by northeast-southwest,doubly plunging antiforms. Two distinct bodiesof silicified cataclasite delimit northeast-southwest striking fault zones. One body formsa prominent ridge, which includes LittleMountain, and comprises left-stepping en echelonpods of silicified cataclasite. Un-silicified, inlinefaults (N72E/67NW) cut silicified cataclasitenortheast of the Little Mountain radio tower.Elliptical-shaped pods of left-stepping en echeloncataclasite are found along strike of the othersilicified cataclasite body, which is located to thenorth of Little Mountain. Zones of sub-parallelfractures with variable orientation are present tothe north and south of the two silicified cataclasitebodies. Geophysical VLF WADI survey linesconducted across the two silicified cataclasiteridges show anomalies that indicate the possiblepresence of water bearing, moderately to steeplydipping, sub-parallel fracture zones. Springlocations mapped as part of the study areconsistent with interpretations based on theWADI data.

A quarry in the southeastern portion ofthe study area contains a negative flower struc-ture and E-NE striking faults with left-lateralslickenlines. Arrangements of en echelon podsand other features found in the quarry indicatethat initial right-lateral movement was followedby left-lateral slip, which in turn was followedby right-lateral slip. Silicification did not occurduring the younger periods of left-lateral andright-lateral slip. This progression agrees with re-cently identified patterns of brittle faulting on PaxMountain, which is located north of the study area(Clendenin and Garihan, 2001).

29

and ferrihydrite; 2) a white “transitional zone”which contains partially dissolved limestone,gypsum, and amorphous aluminumhydroxysulfates; and 3) a black “sulfide zone”that contains ubiquitous framboidal pyrite andacid volatile monosulfides (AVS).

The three reaction zones developed througha series of mineral dissolution-precipitation re-actions that controlled pH and metal mobility.The oxide zone pH was maintained between 2.3and 3.8 by the precipitation of iron oxyhydroxidebalanced by the dissolution of aluminumhydroxysulfate. The transitional zone pH wasmaintained between 3.8 and 4.6 by a balancebetween aluminum hydroxysulfate precipitationand limestone dissolution. The pH of the sulfidezone was >6.5 due to carbonate buffering.

As the limestone content of the substrate wasconsumed at a limestone dissolution front, theboundaries between the three reaction zonesmigrated deeper into the substrate. The sulfidezone formed downstream of the limestonedissolution front. Over time, the transitional zonemigrated with the limestone dissolution front andoverprinted the sulfide zone. As limestone wascompletely removed from the trailing edge of thetransitional zone, the dissolution of aluminumhydroxysulfate was favored, resulting inoverprinting of the transitional zone by the oxidezone. Over time, an increasingly greater amountof the substrate will evolve into oxide zonematerial. If the limestone dissolution front isallowed to pass completely through the substrate,then ferrous iron and aluminum may be released.

MOVEMENT OF TRACE METALSIN RIVER BASINS AND THEFLOOD PLAIN AS A RESERVOIRFOR HEAVY METALS: THE NAHRIBRAHIM IN NORTHERN LEBA-NON AS A CASE STUDY

VANDEN BERG , BETH ,beth_vb@hotmail.com , B. DAVIES,Geological Sciences, Clemson Univer-sity; Clemson, SC 29634; and S.KORFALI , Lebanese American Uni-versity, Lebanon

The movement of pollutants, specifically metals,into or out of a surface stream is an importantenvironmental concern. The aim of this study isto determine the interaction between trace metalsin the flood plain soils and river bed sedimentsof a surface stream. The Nahr Ibrahim River islocated approximately 20 km north of Beirut andstretches 30 km inland from Mediterranean Sea.The river is constantly flowing due tocontributions from springs and groundwaterdischarge to the river. The majority of the basinis limestone and dolomite with periodic outcropsof sandstone and basalt. Sample sites werechosen based on the geomorphology of the basinto obtain a comprehensive representation of theriver as it flows from the spring heads in theMountain to the Mediterranean Sea. All sampleshave been analyzed using a modified Tessiersequential extraction method and XRD (x-raydiffraction). Based on previous work pertainingto the amount of metals in stream bed sediments,this study will incorporate information from soil,sediment and hydrogeological characterizationsof the Nahr Ibrahim River to determine themovement of pollutants into and out of the NahrIbrahim River system.

30

URANIUM MINERALS AT MAWBRIDGE PEGMATITE NEARCENTRAL, SC

WARNER, RICHARD ,wrichar@clemson.edu, Department ofGeological Sciences, Clemson Univer-sity, Clemson, SC 29634-0919, andCHRIS FLEISHER ,fleisher@gly.uga.edu, Department ofGeology, University of Georgia, Athens,GA 30602-2501

The Maw Bridge pegmatite is located on thenorthwestern side of Twelve Mile Creek, approxi-mately 2.8 km northwest of Central, South Caro-lina. The pegmatite is extremely coarse-grained,with feldspar and quartz crystals up to and ex-ceeding 20 cm in size. Of particular interest isthe occurrence of radioactive, uranium-bearingminerals at the site. The uranium minerals areblack with brownish black to black streak, haveglassy luster and conchoidal fracture, and aremetamict. Microprobe analysis reveals that theyare complex niobium-tantalum oxides belongingto both the samarskite and pyrochlore mineralgroups. Two distinct varieties of yttrium-richsamarskite, both containing appreciable rare earthelements but differing in their iron content, oc-cur. One of the two samarskite phases is distinc-tive in that it is unusually enriched in yttrium andis devoid of detectable iron, hence we have namedit Fe-free samarskite-(Y); it may represent achemistry not previously reported. Thepyrochlore mineral is the Ti-rich variety, betafite.Crystals are tantalum-rich, which is unusual (butnot unique) for betafite. Alteration along cracksis extensive, and is marked chiefly by loss of cal-cium and sodium. Betafite is the most uranium-rich (24-28 weight percent UO

2) of the niobium-

tantalum oxides and was in general the first tocrystallize. Fe-free samarskite-(Y) contains theleast uranium (6-8 weight percent UO

2) of the

three niobium-tantalum minerals, and is alwayslate in the paragenesis.

METHODS FOR DETERMININGCONTAMINANT MIGRATIONCONTROLS IN THE TRANSITIONZONE AND FRACTUREDBEDROCK: A CASE STUDY INTHE PIEDMONT OF NORTHCAROLINA

WATKINS, GRANT,gwatkins@ensr.com, ENSR Corpora-tion, Raleigh, NC; and NEDBILLINGTON, nbillington@schnabel-eng.com, Schnabel Engineering,Greensboro, NC

Numerous lithologic features influencemigration of contaminants released intoheterogeneous saprolite-fractured rock aquifersystems of the Piedmont region. In soil/saprolitematrices of the Piedmont, secondary permeabilityfeatures such as weathered mineral veins, beddingplanes, structural foliations, and micro-fracturesinfluence vertical migration of contaminants, bothin the unsaturated and saturated zones. On alarger scale, differential weathering in thepartially weathered rock (i.e., transition zone),the surface slope of competent bedrock, andfracture characteristics of the bedrock also controlmigration of contaminants that enter these deeperhydrostratigraphic zones. Identifying thesesubsurface geologic controls on both a local andregional scale is important to successfullydelineate and remediate the contaminant plume.A program of geophysical surveys, lineamentstudies, and aquifer tests were performed tosupport environmental investigations at a formermanufacturing facility in Guilford County, NorthCarolina. The site is impacted by chlorinatedaliphatic hydrocarbons (CAHs), which are denserthan water and have migrated into the saprolite-bedrock aquifer system to depths exceeding 140feet. Elevated concentrations of CAHs haveaccumulated in the transition zone and in shallowfractured bedrock because these lithologic zones

31

are less flow restrictive than the surroundingstrata. Objectives of the geophysical studies wereto characterize subsurface structural features thatcontrol bulk migration of non-aqueous phasecontaminants and to identify the location andorientation of preferential groundwater andcontaminant flow paths such as fractures andweathered areas in the transition zone andbedrock.

Surface geophysical techniques used at thesite include electromagnetic induction surveys,seismic refraction, 2D resistivity imaging, andsquare array resistivity soundings. Downholegeophysical methods included borehole caliperlogging, optical televiewer logging, temperaturelogging and fluid conductivity logging. Thesegeophysical surveys were supported further byborehole packer tests and aquifer pump tests.Results of these studies are being used to facilitatedevelopment of a conceptual site model to guidethe groundwater assessment and to optimizefuture remediation.

Resistivity surveys indicate that the dominantfracture orientation is NNE-SSW, a findingsupported by an aquifer pumping test, a streamlineament study and geometry of the bedrockplume. Groundwater flow and contaminanttransport shows strong control by fracture zonesfound in the transition zone and in the upperportion of fractured bedrock. Differentialbedrock weathering, possibly associated with thefracture network, was also identified by resistivityimaging and seismic surveys and appears tofurther influence contaminant migration. Caliperand optical televiewer logging indicate a low-density fracture network and relatively smallfracture apertures that decrease with depth.Hydraulic conductivity contrasts between theclayey saprolite, the highly weathered transitionzone, and the underlying, massive bedrock zoneshow significant control on contaminantmovement.

REDEVELOPMENT AND REHA-BILITATION OF A HORIZONTALRECOVERY WELL

WHITMER, JIMMY,jwhitmer@geosyntec.com, GeoSyntecConsultants, Atlanta, Georgia

In 1999, a horizontal recovery well was installedbeneath Building 645 at Robins Air Force Base,Georgia to recover groundwater impacted froma release of TCE. The well was also intended tolower the water table to enhance the effective-ness of a soil vapor extraction system. The hori-zontal well is 1300 feet long and 45 feet deepwith 400 feet of screen length. Groundwatermodeling of the site area predicted the well wouldproduce between 40 and 60 gallons per minute(gpm), and lower the water table by four feet.The horizontal well was only able to sustain aflow rate of approximately 8 gpm and had insig-nificant impact on the groundwater elevation inthe area of the well.

A review of the horizontal well design andinstallation procedure was conducted to identifythe cause of the lower than anticipated well yield.Geophysical logging, a video camera survey anda deviation survey of the well were also per-formed. A review of existing information andresults of the field surveys concluded that thedesign and installation method were the primarycause of the low well yield, and the well had notbeen properly developed by the installation con-tractor. The well was designed and installed withan interior filter fabric that partially collapsedallowing large volumes of sediment into the well.The fabric material was clogged with sedimentand drilling mud which resulted in restricted flow.Drilling mud still present in the well confirmedthat the well had not been adequately developed.

A work plan was prepared to outline the pro-cedures for removal of the filter fabric and reha-bilitation of the well.. Removal of filter fabricmaterial from the interior of an installed horizon-tal well had never been performed prior to this

32

project. New fabric extraction tools were de-signed and fabricated specifically for this task.Fabric removal was complicated by the largevolume of sediment within the well interior. Thebulk of the fabric material was successfully re-moved with the extraction tools, however smallfragments of fabric and HDPE shards remainedin the well causing pump clogging problems. Aninnovative well flushing technique was developedto remove the large amounts of sediment andsmall fabric pieces. Water was flushed throughthe well at a high volume (3000 gpm) and highvelocity (12 feet per second) to lift the sedimentand fabric material out. The flushing and fabricremoval activities removed approximately fivecubic yards of sediment from the well interior.

Flow rate data from the horizontal recoverywell indicates the well now has a pumping rateof 40 gpm and the water table has been loweredto levels below the SVE wells. The innovativeapproach to well rehabilitation has transformedan ineffective horizontal recovery well (installedat a cost of approximately $800,000) into a wellcapable of meeting the project objectives.

GEOLOGY AND YIELD OFPRODUCTIVE CRYSTALLINEBEDROCK WELLS IN THE VICINITYOF LAWRENCEVILLE, GEORGIA

WILLIAMS, L.J., lesterw@USGS.gov,U.S. Geological Survey, Atlanta, Georgia

Obtaining large quantities of ground waterneeded for industrial and municipal supply in thePiedmont and Blue Ridge physiographicprovinces is difficult because of the complexgeology and the typically low permeability ofcrystalline igneous and metamorphic rocks.Despite these complexities, areas of enhancedpermeability in the bedrock occur, and high-yielding wells are not uncommon. The U.S.Geological Survey, in cooperation with the Cityof Lawrenceville investigated a 44 square mile

area around the city to learn more about howsmall-scale structures in crystalline bedrock formweaknesses where increased chemical andphysical weathering occur. Studying small-scalestructures in boreholes and at land surface canbe a very effective means of identifying areashaving high ground-water production potential.

The wells studied penetrate a variety ofstructures and geologic settings, including areasthat generally represent (1) a highly foliated andlayered metamorphic rock setting, and (2) amassive (not layered) weakly foliatedmetamorphic rock setting. Rock and saprolitewere mapped at the land surface to determine thedistribution and relative position of rock types inthe area and to document small-scale structuralfeatures in the rocks. Small-scale features suchas joints, foliation, and compositional layeringwere studied in boreholes using geophysicalmethods to determine location, size, andcharacteristics of bedrock structures. Aquifertests, packer tests, and borehole flow-meter testswere conducted to identify water-bearing andnon-water bearing subsurface fractures and thehydraulic characteristics of these zones.

In the well-foliated and layered metamorphicrock setting, most of the ground water is derivedfrom high-yielding, water-bearing fracturesformed parallel to foliation and compositionallayering. These high-permeability features, alongwith high-angle joints seem to be the primaryreason for the unusually high-yields from wellsin the area — many of which yield between 100and 400 gallons per minute (gal/min). Individualfoliation fractures yield as much as severalhundred gal/min.

Low-yielding well sites, ranging from 1 to 25gal/min, penetrate massive and poorly foliatedrock and derive water from less productive jointsystems. Despite abundant jointing and apparentchemical weathering at one of the well sites, thenon-layered rocks lack the well-developed sub-horizontal fracturing related to foliation andcompositional layering that provide high wellyields elsewhere.

33

IT S HARD TO BEAT MOTHERNATURE: A CASE STUDY WHEREAIR SPARGING AND SOIL VAPOREXTRACTION SUPPRESSEDANAEROBIC BIODEGRADATIONOF CHLORINATED SOLVENTS

WILLIS, DAVID B., dwillis@arcadis-us.com, and MCKINSEY, TIM,tmckinsey@arcadis-us.com, ARCADISInc., Aiken, SC 29803

Natural anaerobic biodegradation has shown to bemore effective in reducing dissolved Trichloroethenein a shallow lower coastal plain aquifer than a com-bination air sparging and soil vapor extraction sys-tem.

A combination air sparging and soil vapor ex-traction (AS/SVE) system was installed in 1994 toremove dissolved trichoroethene (TCE) from im-pacted groundwater downgradient of a former sol-vent storage area at an industrial facility in Charles-ton, South Carolina. The impacted shallow aquiferis a complex series of thin-bedded clayey sands andsilts interbedded with thin clays that were impactedwith up to 10 mg/L of TCE and higher concentra-tions of degradation products (cis 1,2-dichloroethene up to 81 mg/L, and vinyl chlorideup to 16 mg/L). The complete dechlorination of

INCLUDING THE EFFECTS OFWELLBORE HYDRAULICS INANALYSES OF THEPERFORMANCE OFHORIZONTAL WELLS

WORKMAN, ROBERT,rworkman@crbgeo.net, GeologicalSciences, Clemson University and CRBGeological & Environmental Services,Greenville, SC, and LARRYMURDOCH , lmurdoch@clemson.edu,Geological Sciences, ClemsonUniversity, Clemson, SC

Horizontal wells have been used in ground waterand environmental projects for more than adecade, and these applications have motivatedavariety of techniques for predicting wellperformance. Most of the techniques used tosimulate horizontal wells are similar to those usedfor vertical wells. The wells typically are treatedeither as line sources characterized by uniformflux, or as highly conductive cells in a finitedifference grid. These techniques may provide

In favorable structural positions, sub-horizontal fractures at contact zones, betweenmajor rock types, and within layered rocks supplylarge quantities of water to wells inLawrenceville. Geologic mapping andgeophysical methods used during the study areimportant in characterizing the small-scalestructures that are necessary in locating andcharacterizing contributing water-bearing fracturezones. In addition to identifying structures, thecharacterization of rock type, topographicposition, depth of weathering, structural attitudeof the rocks, and recharge are required to assessground water availability in the Piedmont andBlue Ridge.

TCE through vinyl chloride suggested that anaero-bic biodegradaion was also removing the VOCs inaddition to air sparging and vapor extraction. TheTCE and degradation product concentrations re-mained stable during the AS/SVE system opera-tion.

The AS/SVE system was turned off in 2001 asa pilot test to determine if anaerobic biodegrada-tion would increase with less aeration. As expected,dissolved oxygen decreased. Other indicators weremore ambiguous. However, dissolved TCE andrelated degradation products in groundwater at theAS/SVE system decreased significantly when theAS/SVE system was turned off in 2001 and haveremained consistently lower. The decreased TCEand degradation products suggest that the naturalanaerobic biodegradation processes are more effec-tive in reducing TCE mass at this site than airsparging and soil vapor extraction.

34

meaningful results for some applications, but theyfall short of representing the flow processeswithin the well. In particular, current methodsare unable to represent head losses due toturbulent flow along the axis of the well, orturbulent flow through slots in well casing. Ofcourse, traditional methods of analyzing verticalwells do not include the effects of turbulenceeither, but the screens of most vertical wells arerelatively short and this oversight may have littleeffect. However, horizontal wells can be a 100m long or more, and the hydraulics within thewell bore can have an important effect on wellperformance. For example, consider anextremely long horizontal well in a clean sandwith a 40 gpm pump at one end. Clearly, theflow into the well screen will be highest near thepump and decrease along the length of the well.It seems reasonable to expect that at somedistance from the pump the cumulative inflowwill be 40 gpm and the rate of flow into theremainder of the screen will be negligible.Certainly the region over which this well willrecover contaminants is shorter than one wouldexpect by assuming uniform flux along thescreen.

We have developed a method for analyzingthe performance of horizontal wells by couplingthe non-linear equation governing turbulent flowalong a pipe with the linear equation governingflow through porous media. Turbulent flowthrough slots in the well screen are also included.The coupled system of equations is solved usinga Newton-Raphson type algorithm. Each of thecoupled equations is in analytical form, whichfacilitates the development of dimensionlessgroups that characterize well hydraulics.

Our initial example considers the steady stateflow to a horizontal well used for vaporextraction. Preliminary results indicate that wellbore hydraulics can have a significant effect onthe distribution of flow into a horizontal vaporextraction well, and we have confirmed that thehydraulics in the wellbore may limit theeffectiveness of some long wells. Furthermore,it appears to be straightforward to use thisapproach to evaluate the consequences of variousdesign parameters, such as the diameter of the

HYDRAULIC FRACTUREBRANCHING ANDSEGMENTATION

WU, R., gte755q@prism.gatech.edu, andL.N. GERMANOVICH, School ofCivil and Environmental Engineering,Georgia Institute of Technology, At-lanta, Georgia

Mixed mode mechanisms of fracture branchingand segmentation are critical issues in the under-standing of how geologic materials respond tostress. Laboratory experiments were conductedto find the relationship between the geometry ofbranched and segmented fractures and the appliedmixed mode loading. Hydraulic fractures werecreated in transparent polymethyl methacrylate(PMMA) samples. A dyed liquid is pumped intocylindrical PMMA samples to initiate the frac-tures. The direction of the initial planar fractureis controlled by applying thermal elastic stressesand/or a uniform confining pressure on the bound-ary (see Figure 1). After fracture initiation, thesamples are subjected to further hydraulic load-ing as well as torque at both ends. Under suchmixed mode loading, the fractures deviate fromtheir initial fracture plane which results inbranched and/or segmented fracture fronts (seeFigure 2).

screen and the distribution of slots along thelength of the screen. The analytical approach isstraightforward and flexible, so it appears thatthis method can be extended to a wide range ofproblems involving flow to wells.

Figure 1. Initial circular crack

35

PROFILE OF A 703-FOOT COREFROM AN AREA OF ELEVATEDURANIUM LEVELS INGROUNDWATER NEAR THEREEDY THRUST,SIMPSONVILLE /FOUNTAININN, SOUTH CAROLINA

CRAWFORD, BRUCE 1,crawfobd@dhec.sc.gov, CHADREIHM1, C.W. CLENDENIN2,SCOTT HOWARD2, and PETESTONE1;1SC DHEC, Columbia SC;2SC Geological Survey, Columbia, SC

A continuous rock core was recovered alongJenkins Bridge Road from a site adjacent to wa-ter wells that contain elevated uranium levels.Jenkins Bridge Road is located west of FountainInn and south of Simpsonville, SC. The core holewas collared in hanging wall rocks of the Reedythrust. The drill location was sited in line withthree water wells with uranium levels in excessof 2,000 :g/l in the groundwater. The three wellswere in line, of approximately the same depth(325 to 400 feet), and fairly evenly distributedover a distance of approximately 1,200 feet. Thecore was recovered 65 feet west of the centralwell, which had been logged previously withgamma and spectra-gamma tools. The purposeof recovering this core was to obtain informationon possible mineralogical sources of, and struc-tural controls on, the presence of uranium. Observations of the core show that the coun-try rock is a multilayered sequence of buff-white-

gray, coarse crystalline biotite granite; dark gray,fine-to-medium crystalline granodiorite; gray,fine-to-coarse crystalline granite-granite por-phyry; and dark gray, fine crystalline biotitegneiss. Pegmatite layers are present throughoutthe cored interval. Pyrite is the most abundantaccessory sulfide and may be associated withminor amounts of pyrrhotite and molybenite.Calcite also appears sporadically at differentdepths as vug —fill crystals along fractures or asbands in an alteration zone (skarn) associated withgarnet. Subvertical faults and fractures are rec-ognizable by thin mylonitic zones, rehealed epi-dote-coated planes, and juxtaposed lithologies.

Different intervals of the core have gradualincreases and decreases in gamma activity. Onefault plane with pronounced slickenlines at159.67 feet (159 feet 8 inches), however, has ap-preciably higher gamma activity. The slickenlinedsurface is coated with a presently unidentified,grayish-olive green mineral. Laboratory exami-nation by gamma-spectrometer of that material,revealed the presence of uranium-238 by theabundance of daughter products (e.g., radium-226, lead-214 and bismuth-214). The occurrenceof uranium is presently considered to be a singu-lar anomaly because similar occurrences were notidentified elsewhere in the recovered core. Acidtesting of the slickenlined surface produced ef-fervescence indicating the association of carbon-ate in conjunction with the uranium-bearing min-eral. Increased but not significant gamma activ-ity was noted in a biotite granite 170.75 feet (170feet 9 inches) and in a small pegmatite vein foundnear the bottom of the core at 675.5 feet (675feet 6 inches).

Presence of carbonate in the country rock andas vug-fill crystals supports groundwatergeochemistry findings from other wells contain-ing high uranium levels. In those wells, testedgroundwater had elevated alkalinity and dissolvedcalcium, higher pH, and diluted 14C (in dissolvedinorganic carbon). Those findings suggest a closeassociation between uranium and carbonate. Ourfindings also indicate an association with faults.Whether these relations are unique to the smallarea west of Fountain Inn or exemplify a morewidespread situation in the Piedmont is presentlyunder study.

Figure 2. Crack segmentation

37

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Clemson UniversitySchool of the EnvironmentDepartments of GeologicalSciences and Environmental

Engineering and Science