United States Solid Waste and EPA 542-R-99-006

Environmental Protection Emergency Response September 1999

Agency (5102G) clu-in.org

EPA Groundwater Cleanup:

Overview of Operating

Experience at 28 Sites
EPA 542-R-99-006

September 1999

Groundwater Cleanup:

Overview of Operating Experience

at 28 Sites

U.S. Environmental Protection Agency

Office of Solid Waste and Emergency Response

Technology Innovation Office

Washington, DC 20460
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

ii

NOTICE

This document was prepared for the U.S. Environmental Protection Agency (EPA) Technology Innovation Office

(TIO) by Tetra Tech EM Inc. under EPA Contract Number 68-W-99-003. Mention of trade names or commercial

products does not constitute endorsement or recommendation for use. For more information about this project,

please contact: Linda Fiedler, U.S. Environmental Protection Agency, Technology Innovation Office, 

401 M Street, S.W. (MC 5102G), Washington, D.C., 20460; telephone: (703) 603-7194; e-mail:

fiedler.linda@epa.gov.

This document may be obtained from EPA’s web site at <www.epa.gov or at clu-in.org>. A limited number of hard

copies of this document are available free of charge by mail from EPA’s National Service Center for Environmental

Publications (NSCEP), at <www.epa.gov/ncepihom/> or at the following address (please allow four to six weeks for

delivery): 

U.S. EPA/National Service Center for Environmental Publications

P.O. Box 42419 

Cincinnati, OH 45242

Telephone: (513) 489-8190 or (800) 490-9198 

Facsimile: (513) 489-8695 

ACKNOWLEDGMENTS

Special acknowledgment is given to the remedial project managers, potentially responsible parties, and vendors involved

at the case study sites for their thoughtful suggestions and support in preparing the individual case studies and in

contributing to this report.
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

iii

EXECUTIVE SUMMARY

This study examined operating experiences at 28 sites across the United States at which

completed or ongoing groundwater cleanup programs are in place. Although not a representative

sample, the sites present a range of the types of cleanups typically performed at sites with

contaminated groundwater. At 21 of the sites, pump-and-treat (P&T) systems were used alone as

the remediation technology; at two of the sites, permeable reactive barriers (PRBs), an in situ

technology, were used alone as the remediation technology. In addition, in situ technologies

were used in conjunction with P&T at five sites, including one site with P&T that was replaced

with a PRB. Individual reports have previously been published for each of the 28 sites by the

Federal Remediation Technology Roundtable and are available at <www.frtr.gov/cost>. 

Of the 28 case study sites, 24 are Superfund remedial actions, one is a Superfund removal action,

one is a state cleanup, and two are Resource Conservation and Recovery Act (RCRA) corrective

actions. Chlorinated solvents are the type of contaminant most frequently present, found at 21 of

the 28 sites. The sites are located throughout the U.S. and include a range of site types and

hydrogeological conditions. For example, nonaqueous phase liquids (NAPL) were observed or

suspected to be present at 18 of the 28 sites, and hydraulic conductivity varied among the sites by

more than six orders of magnitude.

This report summarizes information about the groundwater remediation systems at the 28 sites,

including: design, operation, and performance of the systems; capital, operating, and unit costs

of the systems; and factors that potentially affect the cost and performance of the systems. Data

from the case studies are compared and contrasted to assist those involved in evaluating and

selecting remedies for groundwater contamination at hazardous waste sites.

Data on performance through late 1997/early 1998 compiled for the report show that total

contaminant removal at the case study sites ranged from seven pounds to more than 510,000

pounds with a median contaminant mass removal of 2,000 pounds. The average annual volume

of groundwater treated ranged from 1.7 million to 550 million gallons (at P&T sites).

Although remediation has been completed at only two of the 28 sites, at the 26 sites with ongoing

remediation, progress has been made toward achieving cleanup goals, including: reducing the

size of a contaminated plume; reducing or eliminating a hot spot within a plume; reducing the

concentrations of contaminants within a plume; removing contaminant mass from a plume; and

achieving containment of a plume.

Capital and operating and maintenance (O&M) costs at the case study sites through late

1997/early 1998 also were compiled for this report. Although P&T and PRB systems may be

designed to accomplish similar remedial goals, the spatial area of groundwater they treat is

generally different; therefore, their costs are presented separately in this report. For the 26 P&T

systems, the approximate median capital cost was $1.9 million and the median average annual

operating cost was $190,000; with median unit costs of $96 of capital cost per average 1,000

gallons of groundwater treated per year and $18 of average annual operating cost per average

1,000 gallons of groundwater treated per year. For the three PRB systems, the approximate

median capital cost was $500,000 and the median average annual operating cost was $85,000;

with median unit costs of $520 of capital cost per average 1,000 gallons of groundwater treated
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

iv

per year and $84 of average annual operating cost per average 1,000 gallons of groundwater

treated per year. 

Since the sites summarized in this report were not selected as a representative sample of all

groundwater cleanup sites, the medians, averages, and ranges calculated in this report should not

be used to draw generalizations about cost and performance at other groundwater cleanup sites.

Results of analyses of the case studies showed that the factors affecting cost and performance and

the extent of the effect of those factors varied from site to site. However, based on the

information provided for the 28 case study sites and general observations of groundwater cleanup

as a whole, the following factors have a significant effect on the cost and performance of

groundwater remediation systems.

& Source control factors - Method, timing, and success of source controls to

mitigate contact of NAPLs or other contaminant sources, such as highly

contaminated soil, with groundwater

& Hydrogeologic factors - Aquifer properties that define contaminant transport and

groundwater extraction system design needs, including hydraulic connection of

aquifers that allows for multi-aquifer contamination, aquifer flow parameters,

influences from adjacent surface water bodies on the aquifer system, and

influences of adjacent groundwater production wells on the aquifer system

& Contaminant property factors - Contaminant properties that define the relative

ease that contaminants may be removed from the aquifer, the steps that are

required to treat the extracted groundwater, and the complexity of the contaminant

mixture

& Extent of contamination factors - The magnitude of the contaminated

groundwater plume, including the plume area and depth and the concentrations of

contaminants within the plume

& Remedial goal factors - Regulatory factors that affect the design of a remedial

system and/or the duration that it must be operated, including defining aquifer

restoration or treatment system performance goals and specific system design

requirements, such as disallowing reinjection of treated groundwater or specifying

the treatment technology to be used

& System design and operation factors - The adequacy of a system design to

remediate the site, system downtime, system optimization efforts, the amount and

type of monitoring performed, and the use of in situ technology to replace or

supplement a P&T system

Specific examples of how each of these factors affected the cost and performance of the

groundwater remediation systems at the case study sites are cited within this report.
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

v

TABLE OF CONTENTS

Section Page

EXECUTIVE SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii

LIST OF EXHIBITS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi

ACRONYMS AND ABBREVIATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii

1.0 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

2.0 OVERVIEW OF 28 CASE STUDY SITES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

3.0 DESIGN AND OPERATION OF REMEDIAL SYSTEMS 

AT 28 CASE STUDY SITES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

3.1 Technology Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

3.2 Remedial System Designs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3

3.3 System Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6

3.4 System Optimization and Modifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-8

4.0 PERFORMANCE OF REMEDIAL SYSTEMS AT 28 CASE STUDY SITES . . . . . . 4-1

4.1 Remedial Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

4.2 Progress Toward Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6

5.0 COST OF REMEDIAL SYSTEMS AT 28 CASE STUDY SITES . . . . . . . . . . . . . . . 5-1

6.0 FACTORS THAT AFFECTED COST AND PERFORMANCE OF REMEDIAL

SYSTEMS AT 28 CASE STUDY SITES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1

7.0 REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

vi

LIST OF EXHIBITS

Exhibit Title

2-1 Summary of 28 Case Study Sites

2-2 Remediation Systems - Years of Operation

2-3 Site Types and Locations

2-4 Categories of Contaminants Treated at 28 Sites

2-5 Specific Contaminants Treated at 28 Sites

2-6 Initial Volume of Contaminated Groundwater Plumes at 24 Sites

2-7 Presence of NAPLs at 28 Sites

2-8 Pertinent Hydrogeological Data at 28 Sites

3-1 Summary of Technologies Used at 28 Sites

3-2 Remedial Technologies Used at 28 Sites

3-3 Pump-and-Treat System Designs at 26 Sites

3-4 Designs of In Situ Treatment Systems at Seven Sites

3-5 Operation of Remedial Systems at 28 Sites

3-6 Types of Optimization and Modification Efforts at 28 Sites

3-7 System Optimization and Modification Efforts Conducted at 28 Sites

4-1 Summary of System Performance for 28 Sites

4-2 Unit Contaminant Mass Removed at 26 Sites

4-3 Summary of Average Contaminant Concentration Reduction at 17 Sites

4-4 System Performance Summary

5-1 Summary of Cost Data for 28 Sites

5-2 Summary of Remedial Cost and Unit Cost Data for 28 Sites

5-3 Average Operating Cost Per Year at 28 Sites

5-4 Capital Cost Per 1,000 Gallons of Groundwater Treated Per Year

5-5 Average Annual Operating Cost Per 1,000 Gallons of Groundwater

Treated Per Year

6-1 Factors Affecting Cost and Performance of Groundwater Remediation

Systems
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

vii

ACRONYMS AND ABBREVIATIONS

AS Air sparging

ACL Alternate concentration limit

BTEX Benzene, toluene, ethylbenzene, and xylene

DCE Dichloroethene

DNAPL Dense nonaqueous phase liquid

DoD U.S. Department of Defense

DOE U.S. Department of Energy

EPA U.S. Environmental Protection Agency

ISB In situ bioremediation

LNAPL Light nonaqueous phase liquid

MCL Maximum contaminant level

NAPL Nonaqueous phase liquid

NPV Net present value

OSWER Office of Solid Waste and Emergency Response

P&T Pump and treat 

PAH Polycyclic aromatic hydrocarbon

PCB Polychlorinated biphenyl

POTW Publicly-owned treatment works 

PRB Permeable reactive barrier

RCRA Resource Conservation and Recovery Act

ROD Record of Decision

SVOC Semivolatile organic compound

TCE Trichloroethene 

TIO Technology Innovation Office

USCG United States Coast Guard

VCB Vertical containment barrier

VOC Volatile organic compound
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

viii
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

 The Federal Remediation Technologies Roundtable consists of senior executives from eight agencies 1

with an interest in site remediation, including the U.S. Army, the U.S. Navy, the U.S. Air Force, the U.S.

Department of Energy (DOE), and EPA. The Roundtable, which was created to build a more collaborative

atmosphere among federal agencies involved in the remediation of hazardous waste sites, has on ongoing effort to

improve the type and availability of cost and performance information for site remediation technologies. This

information is being provided to assist those involved in evaluating and selecting remedies for hazardous waste

cleanups. 

1-1

1.0 INTRODUCTION

Groundwater contamination is present at the majority of Superfund and Resource Conservation

and Recovery Act (RCRA) corrective action sites. Groundwater remediation technologies

currently in use to clean up these sites include pump-and-treat (P&T) systems, and in situ

technologies such as bioremediation, permeable reactive barriers, and air sparging. As part of an

effort by the Federal Remediation Technologies Roundtable, the U.S. Environmental Protection 1

Agency (EPA) has prepared 28 case studies of ongoing and completed groundwater remediation

projects. The Roundtable has published these case studies, along with 112 other case studies

about a wide range of technologies, which are available through the Internet at

<www.frtr.gov/cost>, or in hard copy through the EPA National Service Center for

Environmental Publications (NSCEP). Case studies are about 10-20 pages in length and contain

information about site background, extent of contamination, technology design and operation,

performance, cost, observations and lessons learned, and points of contact for further

information.

The objective of this report is to provide a summary of information about the 28 groundwater

remediation case studies, including comparing results among sites, to further assist those

involved in evaluating and selecting remedies for groundwater contamination at hazardous waste

sites. The case studies present a range of the type of cleanups typically performed at

groundwater-contaminated sites, and include 21 sites with P&T systems alone, four sites with

P&T systems supplemented with in situ technologies, one site with P&T that was replaced by an

in situ technology, and two systems with only in situ technologies. The majority of the case

studies are ongoing projects, with remediation completed at two of the sites. 

The report presents an overview of each of the case study sites (Section 2); describes the design

and operation of the remediation systems, including efforts to optimize the systems (Section 3);

summarizes the performance of each of the systems at the sites, including final results for

completed remediations and progress towards goals for ongoing projects (Section 4); examines

the costs for these systems, including capital, operating, and unit costs (Section 5); and examines

the factors that potentially affect the cost or performance of the remediation systems (Section 6). 

References used to prepare this report are listed in Section 7 and are cited in parentheses.

As described in Section 2 of this report, the case study sites were selected in part on the basis of

availability of information. Therefore, it is important to note that the case studies are not

intended to be a representative sample of groundwater remediation projects; rather, they present a

range of the types of systems that are being used at Superfund and RCRA corrective action sites.

Further, this report is not intended to revise or update EPA policy or guidance on how to clean up

sites with contaminated groundwater. 
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

1-2
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

2-1

 Sites are located throughout the U.S.

and include a range of site types and

hydrogeological conditions

 At some sites, groundwater

remediation has been ongoing since

the late 1980s

 Chlorinated solvents are the most

common contaminant

2.0 OVERVIEW OF 28 CASE STUDY SITES

The 28 groundwater case study sites

included in this report were selected

from a list of candidate sites that was

developed using information from

previous work by EPA and

recommendations by EPA regional staff. 

The following criteria were used in

selecting the specific sites:

& Sites at which groundwater cleanup systems had been operated for a relatively

long period of time

& Sites for which aquifer cleanup goals (not only containment goals) had been

established

& Sites for which sufficient cost and performance data were available

Exhibit 2-1 summarizes general information about each of the 28 sites, such as duration and

status of remediation, categories of contaminants targeted for treatment, type of cleanup, project

lead, and highlights of the project. Of the 28 sites, 24 are Superfund remedial actions, one is a

Superfund removal action, one is a state cleanup, and two are Resource Conservation and

Recovery Act (RCRA) corrective actions. Of the 25 Superfund sites, four are EPA led, one is

U.S. Navy led, 11 are potentially responsible party (PRP) led, and nine are state led. The sites

have been grouped by the type of contamination that was targeted for cleanup at each (volatile

organic compounds [VOC], VOCs combined with other contaminants, or metals).

Exhibit 2-2 presents the years of operation at each site. Groundwater remediation at most of the

case study sites is ongoing, with systems operating over periods ranging from two years (USCG

Center and Moffett) to 11 years (Des Moines and Former Intersil). Cleanup has been completed

at two of the sites (Firestone and Gold Coast) and the remediation systems at three other sites

(French Ltd., Sol Lynn, and Sylvester/Gilson Road) have been shut down for various reasons,

although the cleanups at these sites are not considered complete. At one site (Western

Processing), the goal has been changed from restoration to containment. Nine of the 28 systems

have been operating since the late 1980s. For sites at which systems are ongoing, the information

presented in the report is current as of late 1997 or early 1998.

Exhibit 2-3 shows the type of site and the relative location of each site.
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

Notes: 

 Years of system operation as of end of June 1998

1

 SF indicates Superfund site; RCRA CA indicates RCRA corrective action site

2 2-2

Exhibit 2-1: Summary of 28 Case Study Sites

Site Name, Location, of System Remediation Categories Targeted Type of 

 CERCLIS ID no. Operation Status for Treatment Cleanup Lead(s)

Duration/Years Contaminant

1 2 Site Hig

VOCs CONTAMINATIONCity Industries SF Site, FL 4.0 Ongoing VOCs SF Remedial PRP Simple hydrogeology w(City Industries) hydraulic conductivityCERCLIS #FLD055945653 modeling usedDes Moines TCE SF Site, IA 10.5 Ongoing VOCs SF Remedial PRP Approximately 5 billio(Des Moines) date to contain and remCERCLIS #IAD98060687933 groundwater; dense no

(DNAPL) suspected

Former Firestone Facility SF 7.0 Complete VOCs SF Remedial PRP Groundwater cleanup cSite, CA years(Firestone)CERCLIS #CAD990793887Former Intersil Inc., CA 10.5 Ongoing VOCs State Cleanup PRP Used P&T for eight ye(Intersil) technology with perme

minimize cost of treatmeffectiveness of treatmeleasable or sellable con

French, Ltd. SF Site, TX 4.0 Monitored VOCs SF Remedial PRP Regulatory requiremen(French, Ltd.) Natural through modeling, that CERCLIS #TXD980514814 Attenuation be met at site boundary 

attenuation 10 years aft

Gold Coast SF Site, FL 3.5 Complete VOCs SF Remedial EPA Air sparging used to re(Gold Coast) area of contamination aCERCLIS #FLD071307680 cleanup, optimization mJMT Facility RCRA Site (formerly 10.0 Ongoing VOCs RCRA CA Owner/Operator Included use of an artifBlack & Decker), NY fracture zone in the bed(JMT)
Exhibit 2-1: Summary of 28 Case Study Sites

Groundwater Cleanup: Overview of Operating Experience at 28 Sites

Site Name, Location, of System Remediation Categories Targeted Type of 

 CERCLIS ID no. Operation Status for Treatment Cleanup Lead(s)

Duration/Years Contaminant

1 2 Site Hig

Notes: 

 Years of system operation as of end of June 1998 1 SF indicates Superfund site; RCRA CA indicates RCRA corrective action site 2 2-3

Keefe Environmental Services SF 5.5 Ongoing VOCs SF Remedial State Major modifications to Site, NH (Keefe) on optimization studyCERCLIS #NHD092059112Moffett Federal Airfield SF Site, 2.0 Pilot Scale VOCs SF Remedial U.S. Navy Permeable reactive barCA (Moffett) Ongoing reducing trichloroethen

concentrations; increasfor technology certifica

Mystery Bridge at Highway 20 SF 4.5 Ongoing VOCs SF Remedial EPA Monitored natural attenSite, WY (Mystery Bridge) remedy of the off-site pCERCLIS #WYD981546005Old Mill SF Site, OH 9.0 Ongoing VOCs SF Remedial EPA System of trenches use(Old Mill) groundwaterCERCLIS #OHD980510200SCRDI Dixiana SF Site, SC 6.0 Ongoing VOCs SF Remedial EPA '92-'94 Complex hydrogeology(SCRDI Dixiana) PRP '95-present made in system by PRPCERCLIS #SCD980711394Site A (Confidential SF Site), NY 3.0 Ongoing VOCs SF Remedial State Remedial system inclu(Site A) supplemented with air 

CERCLIS #Confidential bioremediationSol Lynn/Industrial Transformers 3.0 Shut Down VOCs SF Remedial State Multiaquifer contaminaSF Site, TX (Sol Lynn) Pending additional contaminatioCERCLIS #TXD980973327 Study remediation beganSolid State Circuits SF Site, MO 5.4 Ongoing VOCs SF Remedial State Complex hydrogeology (Solid State) in a Karst formation)CERCLIS #MOD9808854111U.S. Aviex SF Site, MI 5.0 Ongoing VOCs SF Remedial EPA '93-'96 Performance modeling (U.S. Aviex) State '96- optimizationCERCLIS #MID980794556 present
Exhibit 2-1: Summary of 28 Case Study Sites

Groundwater Cleanup: Overview of Operating Experience at 28 Sites

Site Name, Location, of System Remediation Categories Targeted Type of 

 CERCLIS ID no. Operation Status for Treatment Cleanup Lead(s)

Duration/Years Contaminant

1 2 Site Hig

Notes: 

 Years of system operation as of end of June 1998 1 SF indicates Superfund site; RCRA CA indicates RCRA corrective action site 2 2-4

VOCs COMBINED WITH OTHER CONTAMINANTSBaird and McGuire SF Site, MA 5.5 Ongoing VOCs, semivolatile SF Remedial EPA Complex mixture of co(Baird and McGuire) organic compounds extensive treatment traCERCLIS #MAD001041987 (SVOCs), pesticides,

metals

King of Prussia Technical 3.5 Ongoing VOCs, metals SF Remedial PRP Complex mixture of coCorporation SF Site, NJ extensive treatment tra(King of Prussia)CERCLIS #NJD980505341LaSalle Electrical SF Site, IL 5.5 Ongoing VOCs, SF Remedial State Relatively low groundw(LaSalle) polychlorinated presentCERCLIS #SCD980711394 biphenyls (PCBs)Libby Groundwater SF Site, MT 7.0 Ongoing VOCs, SVOCs SF Remedial PRP Light nonaqueous phas(Libby) and DNAPLs perpetuaCERCLIS #MTD980502736 contaminants in groundMid-South Wood Products SF 9.0 Ongoing VOCs, SVOCs SF Remedial PRP System optimization peSite, AR (MSWP) years of operation; conCERCLIS #ARD092916188 one localized area of coSolvent Recovery Services of New 3.0 Ongoing VOCs, metals Removal PRP Complex mixture of coEngland, Inc. SF Site, CT various properties led t(Solvent Recovery Service) train; DNAPLs presentCERCLIS #CTD009717604Sylvester/Gilson Road SF Site, NH 9.5 Shut Down VOCs, pesticides, SF Remedial State Modifications of the sy(Sylvester/Gilson Road) Pending metals system shut down since CERCLIS #NHD099363541 Explanation ESD to raise the altern

of Significant (ACL) for 1,1-dichloro

Difference method detection limit

(ESD)
Exhibit 2-1: Summary of 28 Case Study Sites

Groundwater Cleanup: Overview of Operating Experience at 28 Sites

Site Name, Location, of System Remediation Categories Targeted Type of 

 CERCLIS ID no. Operation Status for Treatment Cleanup Lead(s)

Duration/Years Contaminant

1 2 Site Hig

2-5

USCG Support Center, NC 2.0 Ongoing VOCs, metals RCRA CA Owner/Operator Use of PRB to treat gro(USCG Center) contaminated with TCE 

chromium; extensive saevaluate

Western Processing SF Site, WA 10.0 Ongoing VOCs, metals SF Remedial PRP Goals for off-site plum(Western Processing) modified to provide coCERCLIS #WAD009487514 contamination rather th

NAPL observed and suareas of the site

METALS CONTAMINATIONOdessa Chromium I SF Site, TX 4.5 Ongoing metals SF Remedial State Low groundwater prod(Odessa I) treatment for chromium CERCLIS #TXD980867279 Decision (ROD)Odessa Chromium IIS SF Site, TX 4.5 Ongoing metals SF Remedial State Relatively low groundw(Odessa IIS) multiaquifer contaminaCERCLIS #TXD980697114 treatment for chromium United Chrome SF Site, OR 10.0 Ongoing metals SF Remedial PRP Contaminant concentra(United Chrome) point at which extracteCERCLIS #ORD009043001 discharged to the publi

works (POTW) withoumajor modifications msystem

Notes:

 Years of system operation as of end of June 1998 1 SF indicates Superfund site; RCRA CA indicates RCRA corrective action site 2
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

2-6

Exhibit 2-2: Remediation Systems - Years of Operation
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

2-7

Exhibit 2-3: Site Types and Locations
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

2-8

Exhibit 2-4 summarizes the types of contaminants treated at the 28 sites. The contaminants fall

into the following categories. Multiple contaminant category groups have been targeted for

treatment at some sites.

& Volatile organic compounds (VOCs) 

 Chlorinated VOCs

 Benzene, toluene, ethylbenzene, and xylene (BTEX)

 Other VOCs

& Semivolatile organic compounds (SVOCs)

 Pesticides

 Polycyclic aromatic hydrocarbons (PAHs)

 Polychlorinated biphenyls (PCBs)

 Other SVOCs

& Metals

Chlorinated VOCs were the type of contaminant most frequently present, found at 21 of the 28

sites.

Exhibit 2-5 summarizes information about the specific contaminants addressed at the sites. Only

contaminants that were treated at more than one site are included in this exhibit. Six of the 10

most common contaminants treated were chlorinated VOCs, with trichloroethene (TCE), treated

at 18 sites, the most common. Benzene was the most commonly treated nonchlorinated VOC (at

five sites). Chromium was the most common metal, treated at seven of the sites. 

Exhibit 2-6 shows the volume of the contaminated groundwater plume at each site. For most of

the sites, the extent of contamination was quantified by the volume of contaminated groundwater. 

Plume volume presented for these sites generally represents one pore volume of the contaminated

plume prior to commencing groundwater cleanup activities at the site. The volume was

calculated by the site contractors or during the preparation of the cost and performance reports by

combining isoconcentration data for groundwater contaminants with reported or typical

hydrogeological data. The volume of contaminated groundwater at the sites ranged from 930,000

gallons (Intersil) to 5.6 billion gallons (Moffett). The average volume of the contaminated plume

was 440 million gallons, and the median volume was 29 million gallons.
20

11

3

2

3

2

2

9

0 5 10 15 20 25

Metals

Other SVOCs

PCBs

PAHs

Pesticides

Other VOCs

BTEX

Chlorinated VOCs

Number of Case Study Sites

18

15

9 9 8 7 7

5 4 3 3 2 2 2 2 2 2 2 2

0

2

4

6

8

10

12

14

16

18

20

Trichloroethene

DichloroethenesDichloroethanes

Vinyl Chloride

Trichloroethanes

Chromium

Tetrachloroethene

Benzene

Toluene

Ethylbenzene

Methylene Chloride

Benzo[a]anthracene

Cadmium

Methylethyl Ketone

Nickel

Tetrachloroethanes

PCBs

Pentachlorophenol

Xylenes

Number of Case 

Study Sites

Groundwater Cleanup: Overview of Operating Experience at 28 Sites

2-9

Exhibit 2-4: Categories of Contaminants Treated at 28 Sites

Exhibit 2-5: Specific Contaminants Treated at 28 Sites
Volume of Plume (Million Gallons)1

0.93

1.3

2.2

2.7

2.8

4.2

4.4

9.8

12.2

15

18.6

26.2

32.2

39

53

57.8

59.9

80

91

111

500

512

0.1 1 10 100 1000 

USCG Center Intersil Libby Old Mill Gold Coast Sol Lynn United Chrome SCRDI Dixiana Keefe Odessa I Mystery Bridge LaSalle City Industries JMT U.S. Aviex Solid State Sylvester/Gilson Road Odessa IIS French, Ltd. Baird and McGuire Western Processing Des Moines Firestone Moffett

Groundwater Cleanup: Overview of Operating Experience at 28 Sites

2-10

Exhibit 2-6: Initial Volume of Contaminated Groundwater Plumes at 24 Sites1

Note:

 Plume volume presented here generally represents one pore volume of the contaminated plume prior to commencing groundwater cleanup activit

1

plume was reported by contractors or estimated during the preparation of the case study reports from contaminant isoconcentration and hydrogeo
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

2-11

Exhibit 2-7 summarizes information on the observed and suspected presence of nonaqueous

phase liquid (NAPL) at the sites either as light nonaqueous phase liquid (LNAPL), which

generally floats on the water table, or dense nonaqueous phase liquid (DNAPL), which typically

sinks through permeable media (including saturated materials) to an impermeable barrier. Of the

28 sites: NAPLs were observed or suspected to be present at 18; DNAPL only was observed or

suspected at 12 sites; LNAPL only was observed or suspected at three sites; and both DNAPL

and LNAPL was observed or suspected at three sites. As described in Estimating Potential for

Occurrence of DNAPL at Superfund Sites [6], NAPL can be “suspected” at a site if its

components are present in groundwater at greater than one percent of either their pure-phase

solubility or effective solubility. For the case study sites, NAPL was considered “suspected” if at

lease one component was present at greater than one percent of its pure-phase solubility.

Exhibit 2-7: Presence of NAPLs at 28 Sites

Site Name and Location

NAPL Observed or Suspected

DNAPL LNAPL

Observed Suspected Observed Suspected 1 1

 Baird and McGuire, MA q

 City Industries, FL

 Des Moines, IA q

 Firestone, CA

 French, Ltd., TX q

 Gold Coast, FL q

 Intersil, CA

 JMT, NY q

 Keefe, NH

 King of Prussia, NJ q

 LaSalle, IL q

 Libby, MT q q

 Moffett, CA q

 MSWP, AR q q

 Mystery Bridge, WY

 Odessa I, TX

 Odessa IIS, TX

 Old Mill, OH

 SCRDI Dixiana, SC

 Site A, NY q

 Sol Lynn, TX q

 Solid State, MO q

 Solvent Recovery Service, CT q

 Sylvester/Gilson Road, NH q

 U.S. Aviex, MI q

 United Chrome, OR

 USCG Center, NC q

 Western Processing, WA q q

 Number of Sites 7 8 6 0

Note:

Suspected NAPL was identified in the case study reports when contaminants were present at more 1

than one percent of their either their pure-phase solubility or effective solubility.
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

2-12

Exhibit 2-8 presents information about the hydrogeologic conditions at the 28 sites. The average

hydraulic conductivity of the contaminated water-bearing layer(s) at the sites varied by more than

six orders of magnitude (0.023 feet per day (ft/day) to 1,200 ft/day). At more than half of the

sites, contamination was present in multiple water-bearing layers or aquifers. Seven of the sites

exhibited vertical groundwater flow between aquifers, 13 sites were influenced by adjacent

bodies of surface water, and eight sites were influenced by the presence of production wells (for

example, municipal). Reported depths to the top of contaminated aquifers ranged from zero (at

ground surface) to 45 ft below ground surface (bgs). Additional detail on the hydrogeologic

conditions, such as aquifer type, lithology, and degree of heterogeneity at the sites can be found

in the case studies.

Exhibit 2-8: Pertinent Hydrogeological Data at 28 Sites

Site Name and Location Range (ft/day) Contamination Flow Influence Area Aquifer (ft bgs)

Hydraulic Multiple Vertical Surface Production Depth to

Conductivity Aquifer GW Water Wells in Contaminated

Baird and McGuire, MA 3-45 Y N Y N 10 - 15

City Industries, FL 6.39 Y N N N NR

Des Moines, IA 535 N N Y Y 10 - 25

Firestone, CA 100-1200 Y N N Y NR

French, Ltd., TX 0.28-2.8 Y N Y N 10 - 12

Gold Coast, FL 40 Y N Y Y 5.0

Intersil, CA 370 N Y N N NR

JMT, NY 0.65-0.93 Y N N N 10.0

Keefe, NH 42.5 N N N N NR

King Of Prussia, NJ Variable N N Y N 15.0

LaSalle, IL 0.22 N Y N N 3 - 5

Libby, MT 100-1000 Y N Y Y 10 - 20

Moffett, CA 0.3-400 Y Y N N 5.0

MSWP, AR Variable Y N N N NR

Mystery Bridge, WY 340 N N N N 14 - 42

Odessa I, TX 1.6-5.1 Y N N Y 30 - 45

Odessa IIS, TX 1.6-5.1 Y N N Y 30 - 45

Old Mill, OH 0.22-1.25 N N Y N 5.0

SCRDI Dixiana, SC 10 Y N N N 14.0

Site A, NY 53.5 N Y Y N 15 - 18

Sol Lynn, TX 0.14-25.5 Y N N N 20 - 25

Solid State, MO 0.023-1.62 Y Y Y Y NR

Solvent Recovery 0.023-300 Y N Y N NR

Service, CT

Sylvester/Gilson Road, NH 30-50 Y Y Y N NR

U.S. Aviex, MI 9.1-45.4 N N N Y 20.0

United Chrome, OR 0.5-60 Y Y N N 0 - 10

USCG Center, NC 11.3-25.5 N N Y N 6.0

Western Processing, WA 1-100 Y N Y N 5 - 10

Notes:

GW = Groundwater

NR = Not recorded in case studies
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

3-1

 Most of the sites used P&T alone;

five of the sites used P&T in

combination with in situ technologies

 Eighteen of the P&T systems at the

sites used air stripping as

aboveground treatment; carbon

adsorption, metal removal, and

biological treatment also were used to

a lesser extent

 The volume of groundwater treated

per year of operation at the P&T sites

ranged from 1.7 million to 554

million gallons

 Optimization and modification efforts

have been made to some extent at all

of the sites

3.0 DESIGN AND OPERATION OF REMEDIAL SYSTEMS AT 28 CASE

STUDY SITES

The design of the groundwater remediation

systems at the 28 sites include: pump-and-treat

(P&T) systems used alone as the remediation

technology at 21 sites; in situ technologies

(permeable reactive barriers [PRB] in these

cases) used alone as the remediation technology

at two sites, and in situ technologies, such as in

situ bioremediation, air sparging, or PRBs, used

in conjunction with or to replace P&T systems at

five sites. Source controls were identified at 23

of the sites. Vertical containment barriers (VCB)

were used at five of the sites to provide hydraulic

control of contaminant plumes.

The technologies used at the 28 case study sites

are described briefly below, followed by a

detailed summary of the remedial system designs implemented at the case study sites.

3.1 Technology Descriptions

Pump-and-Treat

P&T involves extracting contaminated groundwater through recovery wells or trenches and

treating the extracted groundwater by ex situ (aboveground) processes, such as air stripping,

carbon adsorption, biological reactors, or chemical precipitation. Variables in the design of a 

typical P&T system include:

& The number and production rate of groundwater extraction points (determined by 

such factors as the extent of contamination and the productivity of the

contaminated aquifer)

& The ex situ treatment processes employed (determined by such factors as system

throughput and the contaminants that require remediation)

& The discharge location for treatment plant effluent (determined by such factors as

location of the site and regulatory requirements)

Additional information about the fundamentals of P&T technology can be found in Design

Guidelines for Conventional Pump-and-Treat Systems [1].
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

3-2

Air Sparging

Air sparging (AS) involves injecting a gas (usually air or oxygen) under pressure into the

saturated zone to volatilize contaminants in groundwater. Volatilized vapors migrate into the

vadose zone where they are extracted by vacuum, generally by a soil vapor extraction system. 

AS also is used to supplement P&T systems. For example, AS may be added to remediate

specific portions of a contaminated plume that are not treated effectively by P&T alone or to

accelerate cleanups. For the purpose of this report, the use of air to promote biodegradation

(sometimes referred to as “biosparging”) in saturated and unsaturated soils by increasing

subsurface concentrations of oxygen is referred to as in situ bioremediation. 

Permeable Reactive Barriers

A PRB, or treatment wall, consists of an in-ground trench that is backfilled with a reactive

medium. The selection of the reactive medium is based on the targeted contaminants and the

hydrogeologic setting of the site. Zero-valent iron is the most common medium used in PRBs to

date. Examples of other reactive media include, microorganisms, zeolite, activated carbon, peat,

phosphate, bentonite, limestone, and amorphous ferric oxide. The treatment processes that occur

within the tremch are degradation, sorption, or precipitation of the contaminant. PRB systems

may be configured as “funnel and gate” designs; in such configurations groundwater flow is

routed by two or more impermeable walls through a permeable reactive zone.

PRBs may or may not be similar to P&T systems in both purpose and function. Like a P&T

system, PRBs may be used to treat contaminated groundwater at the boundary of a site, or to

restore the groundwater throughout a site. However, the volume of groundwater treated by a

PRB at a site is typically much lower than it would be for a P&T system at the same site because

PRBs treat only the groundwater that passes through the barrier, while P&T systems actively

extract groundwater from an aquifer, usually at multiple locations throughout the plume. 

In Situ Bioremediation

In situ bioremediation (ISB) involves microbial degradation of organic constituents through

aerobic or anaerobic processes. In situ bioremediation includes processes by which nutrients

(such as nitrogen and phosphorus), electron donors (such as methane for aerobic processes or

methanol for anaerobic processes), or electron acceptors (such as oxygen for aerobic processes or

ferric iron for anaerobic processes) are added to the groundwater to enhance the natural

biodegradation processes. The addition of oxygen by biosparging is an example of such a

process. 

Source Controls

Source controls include such activities as excavation of soil at hot spots, in situ treatment of soil

(for example, by soil vapor extraction), and installation of VCBs for control of NAPLs. Source

controls are implemented to remove source materials or to isolate them from contact with

groundwater.
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

3-3

Vertical Containment Barriers for Hydraulic Control

VCBs, such as slurry or sheet pile walls, also are used to hinder the migration of contaminated

groundwater. VCBs are used in conjunction with groundwater extraction wells in an effort to

gain hydraulic control over a contaminated groundwater plume.

3.2 Remedial System Designs

Exhibit 3-1 lists the remedial technologies used at the 28 subject sites. At most of the sites (26 of

28), P&T systems were used for groundwater remediation. At five of the P&T sites, in situ

technologies were incorporated into the P&T approach. AS was incorporated at two sites, ISB at

three sites, and PRBs at one site. At two sites, PRBs were used alone as the remedial technology. 

Source controls were used at most (24) of the sites, and VCBs were used for hydraulic control 

five sites. 

Exhibit 3-1: Summary of Technologies Used at 28 Sites

Technology Sites

Number of

Total P&T Technologies 26

Total In Situ Technologies 7

P&T Only 21

P&T with In Situ Technology or Technologies 5

Air Sparging 1

In Situ Bioremediation 2

Air Sparging and In Situ Bioremediation 1

Permeable Reactive Barriers (replaced P&T) 1

In Situ Technology Only 2

Air Sparging 0

In Situ Bioremediation 0

Permeable Reactive Barriers 2

Vertical Containment Barriers for Hydraulic Control 5

Source Controls 24

Exhibit 3-2 identifies the specific remedial technology or technologies used at each of the sites. 

Extracted groundwater at the sites was treated using treatment systems varying from an

individual ex situ technology to a complex series of different technologies. The ex situ treatment

technologies included:

& Air stripping & Chemical or ultraviolet

& Carbon adsorption oxidation

& Filtration & Biological degradation

& Electrochemical removal of & Neutralization

metals & Equalization

& Oil/water separation
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

3-4

Vapor-phase treatment of off-gases from the ex situ technologies was employed at eight of the

sites. At those sites, vapor-phase incineration, carbon adsorption, filtration, or thermal oxidation

were used either individually or in series.

Exhibit 3-2: Remedial Technologies Used at 28 Sites

Site Name and Source Control(s)

Location Implemented

Remediation Technology

P&T (with ex situ treatment)

AS

ISB

PRB

VCB

OWSSTRIPGACMETALBIO

Other

 Baird and McGuire, qqq Filtration Concurrent excavation

 MA

 City Industries, FL q Equalization Prior excavation

 Des Moines, IA q Prior excavation

 Firestone, CA qqq Filtration Prior excavation

 French, Ltd., TX qq q Neutralization; q q Prior in situ

addition of nutrients bioremediation of soil and

and oxygen sludges

 Gold Coast, FL q q NA

 Intersil, CA q q Prior excavation

 JMT, NY q Prior excavation

 Keefe, NH qq q Prior excavation

 King of Prussia, NJ q q Equalization; Prior soil washing

clarification; filtration

 LaSalle, IL qqq Prior excavation

 Libby, MT qq q Prior excavation

 Moffett, CA q NA

 MSWP, AR q q Filtration Prior excavation

 Mystery Bridge, WY q Prior excavation/SVE

 Odessa I, TX q Filtration NA

 Odessa IIS, TX q Filtration Prior excavation

 Old Mill, OH q q Prior excavation

 SCRDI Dixiana, SC q q Prior excavation

 Site A, NY q Settling; filtration; q q Prior excavation

addition of nutrients;

pH adjustment of

effluent

 Sol Lynn, TX qqq pH adjustment Prior excavation

 Solid State, MO q Prior excavation

 Solvent Recovery q q Oxidation; filtration; q Prior excavation

 Service, CT pH adjustment

 Sylvester/Gilson Road, q qq q Prior and concurrent

 NH capping/slurry wall/

excavation/SVE

 U.S. Aviex, MI q NA

 United Chrome, OR q Prior excavation

 USCG Center, NC q Prior excavation

 Western Processing, q q Oxidation; filtration q NA

 WA

 Total Sites 4 18 10 11 3 2 3 3 5

Notes:

OWS = Oil/water separation AS = Air sparging

STRIP = Air stripping ISB = In Situ bioremediation

GAC = Granular activated carbon adsorption PRB = Permeable reactive barrier

METAL = Physical or chemical removal of metal VCB = Vertical containment barrier

BIO = Biological treatment NA = Not Available
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

3-5

Exhibit 3-3 identifies the extraction system design for each of the P&T sites. Groundwater

extraction designs at the 26 P&T sites varied in magnitude from one production well (JMT) to

several wells combined with trenches (MSWP and Old Mill) and to 210 vacuum wellpoints

(Western Processing). Pumping rates for the P&T systems ranged from 3 gallons per minute

(Old Mill) to more than 1,000 gallons per minute (Des Moines).

Exhibit 3-3: Pump-and-Treat System Designs at 26 Sites

Site Name, Location Extract Inject Extract Inject gpm On-site site

Number of Wells Trenches Rate (by Location) Discharge

Number of Pumping Wells/ Trenches Groundwater

Number Of Treated

Average OffReinjected

SurfaceWaterPOTW

Baird and McGuire, MA 6 0 0 0 60 6 0 q

City Industries, FL 13 0 0 0 105 13 0 q

Des Moines, IA 7 0 0 0 1041 7 0 q

Firestone, CA 25 0 0 0 484 15 10 q

French, Ltd., TX 109 59 0 0 189 NR NR q

Gold Coast, FL 5 3 0 0 44 5 0 q

Intersil, CA 3 0 0 0 8 4 0 q

JMT, NY 1 0 0 0 11.2 1 0 NR NR NR

Keefe, NH 5 0 1 0 23.4 1 5 q

King of Prussia, NJ 11 0 0 0 200 4 7 q

LaSalle, IL 0 0 3 0 17 3 0 q

Libby, MT 5 11 0 0 6.6 5 0 q q

MSWP, AR 15 0 8 0 24 10 5 q

Mystery Bridge, WY 3 0 0 0 103 3 0 q

Odessa I, TX 6 6 0 0 60 NR NR q

Odessa IIS, TX 10 9 0 0 58.5 NR NR q

Old Mill, OH 3 0 5 0 3.1 NR NR q

SCRDI Dixiana, SC 15 0 1 0 40 8 12 q

Site A, NY 5 0 0 1 18 5 0 q

Sol Lynn, TX 12 14 0 0 8 NR NR q q

Solid State, MO 7 0 0 0 34 4 3 q

Solvent Recovery Service, 12 0 0 0 20 6 6 q

CT

Sylvester/Gilson Road, NH 14 0 0 7 265 14 0 q

U.S. Aviex, MI 5 0 0 0 220 1 4 q

United Chrome, OR 30 0 0 0 242 NR NR q

Western Processing, WA 210 0 0 1 230 210 3 q

Minimum 0 0 0 0 3.1 1 0

Maximum 210 59 8 7 1041 210 12

Average 21 4 0.7 0.4 140 16 3

Median 7 0 0 0 51 5 0

Notes:

NR = Not reported
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

3-6

Exhibit 3-3 shows that treated groundwater was reinjected into the aquifer (11 sites), discharged

to an adjacent surface water by a permitted outfall (10 sites), discharged to a publicly owned

treatment works (POTW) (2 sites), or discharged using a combination of these methods (2 sites). 

Exhibit 3-4 describes the remedial systems at the seven case study sites where in situ

technologies were used.

Exhibit 3-4: Designs of In Situ Treatment Systems at Seven Sites

Site Name

and

Location Used Design of In Situ Treatment System

In Situ

Technology(ies)

French, ISB P&T system augmented with ISB. ISB system consisted of the reinjection of treated

Ltd., TX groundwater into the contaminated aquifer. The treated groundwater was oxygenated

and amended with nitrogen and phosphorus before reinjection.

Gold Coast, AS AS used only at end of cleanup to mitigate a small area of localized contamination.

FL

Intersil, CA PRB Original design was a P&T system, which was turned off in 1995 after PRB was

installed. PRB system consisted of two parallel slurry walls 300 and 235 feet long and

13 feet deep used to funnel groundwater through a 40-foot-wide, 4-foot-thick permeable

wall of granular iron.

Libby, MT ISB P&T system complemented with ISB. ISB system consisted of the reinjection of treated

groundwater into the contaminated aquifer. Treated groundwater was aerated and

amended with nitrogen and phosphorus in the treatment plant after removal of NAPL

and before it flowed through a series of fixed-film bioreactors.

Moffett, PRB PRB consisted of an impermeable “funnel” composed of two 20-foot-long sheet pile

CA walls. Reactive zone consisted of 6-foot-thick, 10-foot-wide, and 18-foot-high

(beginning 5 feet bgs) zone of granular iron. The reactive zone was located between two

zones of pea gravel, each two feet thick.

Site A, NY AS and ISB P&T system in conjunction with AS and ISB. AS system consisted of air injection

through 44 sparging wells at points approximately 10 feet below the water table, with

vapor collection through 20 soil vapor extraction wells (16 vertical and 4 horizontal). 

ISB system consisted of the reinjection of treated groundwater into the contaminated

aquifer. The treated groundwater was amended with nitrogen and phosphorus before it

was discharged to the reinjection trench.

USCG PRB PRB consisted of a 2-foot-thick and 152-foot-long zone of approximately 450 tons of

Center, NC granular zero-valent iron keyed into an underlying low conductivity layer at

approximately 22 feet bgs.

3.3 System Operation

Exhibit 3-5 presents data available on the operation of the remedial systems, including the

volume of groundwater treated and the percent of time the systems were operational. The

volume of groundwater treated per year of operation for the P&T systems ranged from 1.7

million gallons (Old Mill) to 554 million gallons (Des Moines). Estimated throughput per year

for the PRB sites ranged from 200,000 gallons (Moffett) to 2.6 million gallons (USCG Center).
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

3-7

Exhibit 3-5: Operation of Remedial Systems at 28 Sites

Site Name and Location Operational (%) Total Per Year

Volume of GW Extracted

 (million gallons)1

Percent of Time

 Baird and McGuire, MA 80 21 93

 City Industries, FL 151.7 50 90

 Des Moines, IA 4900 554 95

 Firestone, CA 1800 266 97

 French, Ltd., TX 306 76 90

 Gold Coast, FL 80 22 95

 Intersil (P&T), CA 36 5.0 98 3

 Intersil (PRB), CA 2 1.1 100 2,3

 JMT, NY 50.1 5.2 90

 Keefe, NH 46 11 97

 King of Prussia, NJ 151.5 57 76

 LaSalle, IL 23 5.2 75

 Libby, MT 15.1 2.9 89

 Moffett (PRB), CA 0.284 0.2 100 2

 MSWP, AR 100.6 12 NR

 Mystery Bridge, WY 192.8 54 100

 Odessa I, TX 125 30 95

 Odessa IIS, TX 121 30 95

 Old Mill, OH 13 1.7 99

 SCRDI Dixiana, SC 20.6 4.5 89

 Site A, NY 8.4 6.7 75

 Sol Lynn, TX 13 4.3 69

 Solid State, MO 257 62 95

 Solvent Recovery Service, CT 32.5 11 100

 Sylvester/Gilson Road, NH 1200 126 88

 U.S. Aviex, MI 329 96 95

 United Chrome, OR 62 7.2 99

 USCG Center (PRB), NC 2.6 2.6 100 2

 Western Processing, WA 974 119 97

 Minimum 0.284 0.2 69

 Maximum 4900 554 100

 Average 382.5 57 92

 Median 80 12 95

Notes:

At most of the sites, groundwater cleanups are in progress; therefore the values shown represent a portion 1

of the total volume treated. Data presented here generally are cumulative as of late 1997 or early 1998.

The volume of groundwater for PRB sites is equal to the volume of groundwater treated through the wall 2

at the site.

At the Intersil site, groundwater cleanup began with a P&T system; later a PRB was used. The two 3 

phases were treated above as separate sites.

NR = Not reported
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

3-8

The percent of time that the remedial systems were operational at the sites ranged from 69 to 100

percent. Downtime reportedly was required for routine maintenance (such as changing carbon,

cleaning air stripper media, and backwashing filters) and issues specific to particular sites, including:

& Iron corrosion and clogging of extraction wells (Baird and McGuire, Des Moines, Odessa I,

Odessa IIS, Mystery Bridge, and Solvent Recovery Services)

& Freezing or fouling of air stripper media (Solid State and City Industries)

& System modifications (Keefe, Solid State, Site A, MSWP, and Sylvester/Gilson Road)

& Equipment failures (Libby, French, Ltd., and King of Prussia)

& Brownouts (Keefe)

3.4 System Optimization and Modifications

Optimization and modification efforts that have been undertaken at the case study sites include

remedy refinement, pre-design modeling and testing, and system modifications. Exhibit 3-6

summarizes the types of optimization and modification efforts reported for the case study sites;

these are generally classified as pre-design and post-design efforts. Pre-design efforts at the case

study sites typically consisted of interim designs or systems (used at 13 sites) and groundwater

modeling (used at 11 sites). Post-design efforts consisted of optimization modeling (used at 13

sites), modifications of the groundwater extraction systems (used at twenty of the sites), and

modifications to the groundwater treatment systems (used at 15 sites). Exhibit 3-7 lists the

specific efforts made at each of the 28 sites.

At the time the case study reports were prepared, some of the sites at which remediation was

ongoing had identified plans for future system modifications. The following examples illustrate

these types of plans:

& At U.S. Aviex, further site characterization is needed and the remediation system may

require expansion.

& At City Industries, concentrations of contaminants in extracted groundwater may be low

enough to allow discharge directly to the POTW without prior treatment.

& At Sol Lynn, the system was shut down when extraction well pipes leaked and fouled, and

the extraction system had lost containment. Currently, the site is being reevaluated to

identify alternative remedial plans to address the issues with the extraction system.
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

3-9

Exhibit 3-6: Types of Optimization and Modification Efforts at 28 Sites1

Pre-Design Pre- or Post-Design Post-Design

Interim Design or Groundwater/

System Optimization Modeling Modifications Purpose/ Objective Modifications 

Optimization/Modifications of Extraction System Optimization/Modification

& Pilot-scale system & MODFLOW & Add extraction points & Increase extraction rate/ & Increase or reduce & 

& Demonstration & MT3D 

system & Abandon extraction points & Respond to reduction in

& Staged approach to enhancements to system 

construction & Randomwalk & Resize extraction pumps & Increase efficiency of 

& Treatability testing & Biotrans 

& Interim system to & (for most sites, the type system & Add or replace with in situ & 

contain plume while of modeling was not technologies full system is specified) & Change type of pump & Reduce shearing or 

designed aeration of extracted

& Quickflow extent of contamination & Add chemical & 

& Adjust pumping rates & Increase efficiency of && Modify extraction system & Increase efficiency of 

design system or respond to

& Use alternate remediation & Allow use of more cost- 

method effective method (for 

& Implement or expand & Respond to new source or

source controls increase efficiency in & Discontinue treatment & 

& Reduce performance & Reduce O&M costs & Reduce compliance & 

monitoring monitoring

contain plume equipment capacity system groundwater & Upgrade process & 

changes in remedial goals & Add process units to & 

example, AS or naturalattenuation) & Automate treatment & 

treating existing source areas 

equipment treatment train system operation 

Notes:

 Because the focus of the case studies was not on optimization, the types of optimization efforts listed in this table are not necessarily a comprehensive list of optimi

1

the case study sites. 
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

Notes:

 Because the focus of the case studies was not on optimization, the optimization efforts listed in this table are not necessarily a comprehensive list of optimization ef

1

sites. 

3-10

Exhibit 3-7: System Optimization and Modification Efforts Conducted at 28 Site

Site Name Design System Modeling Modification Reason Modification 

Pre-Design Post-Design

Interim Modeling Optimization

Groundwater Modifications to Extraction System Modificati

Baird and McGuire None identified Yes; provided Yes; provided Resized extraction Increase pumping rate to Enlarged sludge 

SF Site no details no details pumps meet design criteria thickener/replace

bioreactor with aistripper 

City Industries SF None identified None identified Examined Increased pumping Maximize pumping None identified Site varying from leading edge of zones of influence

pumping rates plume and decreased

pumping fromupgradient wells

Des Moines TCE None identified Two- None identified None identified Not applicable AS media changeSF Site dimensional from spherical to 

MODFLOW chandelier type/

anti-corrosion andbiofouling agentsadded to AS

Former Firestone None identified Yes; provided Yes; provided Installed 10 additional Prevent migration of None identified 

Facility SF Site no details no details wells off-site/ adjusted contaminated plume into

pumping rates/ intermediate zonesincreased overallpumping rate for a 2week period

Former Intersil, Inc. One extraction Yes; provided Yes; provided None identified Not applicable P&T system Site well w/air no details no details upgraded/switche

stripper to start from P&T to PRB 

in 1995
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

Exhibit 3-7: System Optimization and Modification Efforts Conducted at 28 Site

Site Name Design System Modeling Modification Reason Modification 

Pre-Design Post-Design

Interim Modeling Optimization

Groundwater Modifications to Extraction System Modificati

Notes:

 Because the focus of the case studies was not on optimization, the optimization efforts listed in this table are not necessarily a comprehensive list of optimization ef

1

sites. 

3-11

French, Ltd. SF Site Staged None identified MODFLOW None identified Not applicable Added second 

approach and Biotrans sheet-pile wall 

around DNAPL/ shut system down in 12/95

Gold Coast SF Site None identified None identified None identified Enlarged two Increase extraction rate/ None identified 

extraction wells/shut increase amount of TCEdown system for four and PCE desorbing frommonths/conducted air soilsparging in "source"areas/added peroxideto wells for a period,with no effect

JMT Facility RCRA Pilot test None identified None identified Conducted full-scale Unclog well/minimize Constructed Site (formerly Black rehabilitation of time to perform routine enclosure around & Decker) extraction well/ maintenance checks on the treatment

installed an electrical system systemand piping box atextraction well

Keefe None identified Yes; provided Yes; provided Constructed two Optimize system after None identified Environmental no details no details replacement extraction reevaluation becauseServices SF Site wells cleanup goals were not

being met

King of Prussia None identified MODFLOW Ongoing, using None identified Not applicable None identified Technical and MT3D MODFLOWCorporation SF Site and MT3DLaSalle Electrical None identified None identified None identified None - original design Not applicable None - original 

SF Site considered adequate design considered

adequate
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

Exhibit 3-7: System Optimization and Modification Efforts Conducted at 28 Site

Site Name Design System Modeling Modification Reason Modification 

Pre-Design Post-Design

Interim Modeling Optimization

Groundwater Modifications to Extraction System Modificati

Notes:

 Because the focus of the case studies was not on optimization, the optimization efforts listed in this table are not necessarily a comprehensive list of optimization ef

1

sites. 

3-12

Libby Groundwater Pilot test and None identified None identified Tested and converted Increase effectiveness of Peroxide system SF Site demonstration to lower-shear pumps/ OWS/address decrease in for aeration of IS

for in situ four extraction wells areal extent of source water

bioremediation abandoned, and one contamination replaced with

new well constructed bubbleless system

Mid-South Wood 1985-89 french None identified None identified Removed five No contaminants Added carbon Products SF Site drains extraction wells/ detected in the five wells/ treatment system 

continuously adjusted schedule adjusted for one year pumping schedule of according toextraction wells concentration results

Moffett Federal Currently in None identified None identified None identified Not applicable None identified Airfield pilot-test stageMystery Bridge at None identified Quickflow None identified None identified Not applicable None identified Highway 20 SFSite, Dow/DSIFacilityOdessa Chromium I 30-day pilot Randomwalk Yes; provided Added three injection Achieve higher injection Added chamber t

SF Site study and Geoflow no details wells/converted two rate/attempt to fully reaction tank/ 

monitoring wells to capture plume added backwashrecovery wells unit for filter

Odessa Chromium 30-day pilot Randomwalk Yes; provided Added two injection Achieve higher injection Added chamber tIIS SF Site study and Geoflow no details wells/installed rate/expedite cleaning of reaction tank/ 

recovery well source area added a backwash

unit

Old Mill SF Site None identified None identified None identified Added three collection Address new areas of Replaced two 

trenches contamination carbon canisters

discovered with one
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

Exhibit 3-7: System Optimization and Modification Efforts Conducted at 28 Site

Site Name Design System Modeling Modification Reason Modification 

Pre-Design Post-Design

Interim Modeling Optimization

Groundwater Modifications to Extraction System Modificati

Notes:

 Because the focus of the case studies was not on optimization, the optimization efforts listed in this table are not necessarily a comprehensive list of optimization ef

1

sites. 

3-13

SCRDI Dixiana SF 1992-4 EPA None identified Quickflow Added collection Collect contaminated Replaced tower aSite system/20 trench/ reduced groundwater from stripper with 

wells at 4 gpm extraction wells by shallow zone/achieve shallow-tray

five (15 remain in more efficient hydraulic stripperoperation) control

Site A (Confidential Bioremediation None identified None identified Expanded system by Address additional None identified 

SF Site) study adding more sparging contamination

wells discovered during

demolition activities

Sol Lynn/Industrial None identified MODFLOW MODFLOW Adjusted pumping Prevent cross- None identified Transformers SF strategy because of contamination of zonesSite additional and prevent further

contamination in the migration ofsilty aquifer identified contaminants

Solid State Circuits None identified None identified None identified Added three wells off Contain plume Electronically 

SF Site site linked air stripper 

blower to transferpumps so blowerwould shut offwhen not pumpin

Solvent Recovery None identified None identified None identified None identified Not applicable None identified Services of NewEngland, Inc. SFSiteSylvester/Gilson 4-well GW None identified MODFLOW Added six extraction Address hot spots None identified Road SF Site circulation wells
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

Exhibit 3-7: System Optimization and Modification Efforts Conducted at 28 Site

Site Name Design System Modeling Modification Reason Modification 

Pre-Design Post-Design

Interim Modeling Optimization

Groundwater Modifications to Extraction System Modificati

Notes:

 Because the focus of the case studies was not on optimization, the optimization efforts listed in this table are not necessarily a comprehensive list of optimization ef

1

sites. 

3-14

U.S. Aviex SF Site 1983-93 MODFLOW MODFLOW Adjusted pumping Optimize system on the Added pH 

interim and and rates for each well basis of concentration adjustment remedial Randomwalk Randomwalk continuously data for each well 

measure

U.S. Coast Guard 1994 pilot None identified None identified None identified Not applicable None identified Support Center studyUnited Chrome SF None identified None identified None identified Turned off some Stop treatment in areas Switched to 

Site extraction wells/ with contaminant sending untreated 

flushed some areas concentrations below water to POTW/ 

cleanup levels/solubilize injected deepcontaminants in areas of aquifer water intohigher contamination upper aquiferflushed

Western Processing None identified None identified None identified Discontinued Address change in Added metals 

SF Site operation of 210 remedial goal from precipitation to 

shallow well remediation to treatment system/ points/installed deep containment replaced carbon wells type
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

4-1

 Two of 28 sites have met all aquifer

restoration goals

 Most sites have made progress

toward meeting remedial goals,

including reducing or eliminating a

hot spot within a plume, reducing the

mass of contaminants within a plume,

and reducing concentrations of

contaminants within a plume

4.0 PERFORMANCE OF REMEDIAL SYSTEMS 

AT 28 CASE STUDY SITES

This section discusses the performance of the

remedial systems used at the 28 sites in terms of

the remedial goals set for the sites and progress

made toward achieving those goals.

4.1 Remedial Goals

Remedial goals for the containment and

mitigation of contamination have been

established at all the case study sites. The

remedial goals for the sites included the restoration of all groundwater beneath the site and any

off-site groundwater that may have been affected by the site, as well as the containment of on-site

contamination, allowing off-site contamination to attenuate naturally. It should be noted that all

of the sites selected for case studies were chosen because they had established aquifer cleanup

goals and not just containment only goals, although goals at one site (Western Processing) have

been changed to containment only since the case studies were prepared. In addition, performance

goals for the treatment systems, such as requirements related to water discharge of water and air

emissions, were established for a number of the sites. Exhibit 4-1 identifies the goals established

for each site and whether the goals have been achieved. 

Cleanup goals for the sites were established based on one or more of the following factors:

& Maximum contaminant levels (MCL)

& Primary drinking water standards

& Risk-based cleanup levels

& Approved alternative concentration limits (ACL)

& Optional cleanup levels for a non-time-constrained removal action

& Concentrations of contaminants in adjacent surface waters

For two-thirds of the sites, the aquifer goals established were based on MCLs.

Goals for the containment of contaminated groundwater were established for 25 of the 28 sites. 

The manner of containment required at each site varied but typically consisted of containment of

the contaminated groundwater on-site or halting of the continued migration of an existing off-site

plume.

Limits on air emissions were identified for three of the sites (JMT, LaSalle, and Libby). During

preparation of the case study reports, EPA did not focus on whether air emission limits were

established; therefore, it is possible that the reports did not identify limits at some of the other

sites.
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

4-2

Exhibit 4-1: Summary of System Performance for 28 Sites

Site Name and Location Technology Aquifer Plume Cleanup Level Basis Emission Discharge Total Pounds

Remedial Restore Contain Air Water

Remedial Goals Performance Goals Removed

Contaminant

Mass 1

 Baird and McGuire, MA P&T q q MCLs, surface water NR NR 2,100

 City Industries, FL P&T q N MCLs NR N 2,700

 Des Moines, IA P&T q N MCLs NR NR 30,000

 Firestone, CA P&T NR 500 2 NN N MCLs, drinking water

criteria, risk-based

 French, Ltd., TX P&T, ISB q N risk-based NR NR 510,000

 Gold Coast, FL P&T, AS NR 2,000 2 N N MCLs, drinking water N

 Intersil, CA q N MCLs NR N P&T, AS, 120 (P&T); 

PRB 15 (PRB) 

 JMT, NY P&T q N MCLs N N 840

 Keefe, NH P&T q N ACLs NR N 68

 King of Prussia, NJ P&T q N MCLs NR N 5,400

 LaSalle, IL P&T q NE drinking water N NR 130

 Libby, MT P&T, ISB q NE MCLs, risk-based N NR 37,000

 Moffett, CA PRB q N drinking water NR NE NR

 MSWP, AR P&T q N MCLs, risk-based NR q 800

 Mystery Bridge, WY P&T q NE MCLs NR N 21

 Odessa I, TX P&T q N MCLs NR N 1,100

 Odessa II, TX P&T q N MCLs NR N 130

 Old Mill, OH P&T q N risk-based NR N 120

 SCRDI Dixiana, SC P&T q N MCLs NR N 7

 Site A, NY P&T, AS, ISB q N MCLs NR NR 5,300

 Sol Lynn, TX P&T q q MCLs NR N 5,000

 Solid State, MO P&T q N MCLs NR NR 2,700

 Solvent Recovery

Service, CT P&T q N To be set NR N 4,300

 Sylvester/Gilson Road, 

 NH P&T q N ACLs NR N 430,000

 U.S. Aviex, MI P&T q q MCLs NR N 660

 United Chrome, OR P&T q N MCLs, risk-based NR N 31,000

 USCG Center, NC PRB q q drinking water NR NE NR

 Western Processing, WA P&T q N MCLs NR N 100,000

Notes: Minimum 7

q Goal established but not met Maximum 510,000

N Goal established and met Average 43,000

NR Goal established, but performance not reported Median 2,000

NE Goal not established

For sites at which groundwater cleanups are ongoing, the total mass of contaminant removed represents the performance 1

reported as of late 1997 or early 1998. Contaminant mass removals were calculated based on various types of mass balances

around the site treatment system, not based on groundwater monitoring data. Insufficient data were available to calculate a

removal of contaminant mass by in situ bioremediation; for those sites at which used in situ bioremediation was used, the

contaminant mass removed may be greater than shown here.

Firestone and Gold Coast - remediation has been completed at these two sites. 2
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

4-3

Contaminant Mass Removed

Exhibit 4-1 presents the contaminant mass removed for the case study sites. For 26 of the sites,

the mass of contaminant removed by the remediation systems was reported or could be calculated

from reported data. When concentration and throughput data for the treatment system were

available, these data were used to calculate the mass of the contaminant removed. Contaminant

mass removals calculated based on groundwater monitoring results were not available. Total

mass of contaminant removed ranged from seven pounds (SCRDI Dixiana) to 510,000 pounds

(French, Ltd.), with an average of approximately 43,000 pounds and a median of approximately

2,000 pounds. For almost one-third of the sites, contaminant mass removed ranged from 1,000

to 10,000 pounds per site. 

Because mass removal rates are dependent on many factors, including the extent and

concentration of the contamination, contaminant properties, and the volume of groundwater

treated, they generally are not used to evaluate the achievement of remedial goals. The

variability is demonstrated in Exhibit 4-2 which shows the average mass of contaminant removed

per year and per 1,000 gallons of water treated at each site. Contaminant mass removed per year

for the 26 sites varies from approximately two pounds to more than 100,000 pounds, and from

approximately 0.0001 pounds per 1,000 gallons treated to three pounds per 1,000 gallons treated. 

Sites with relatively higher mass removal rates per year do not consistently show relatively

higher mass removal rates per 1,000 gallons treated. This may be due in part to differences in the

concentration of contamination in the extracted groundwater. In addition, while not completed

for this report (due to a lack of available data), a comparison of mass removal rates at a site over

time can generally be useful in evaluating changes in system performance, for example, in

identifying when removal rates are approaching asymptotic values (see the case studies for

Western Processing and Firestone).

Reduction in Concentrations of Contaminants

Exhibit 4-3 presents the average reductions in concentrations of contaminants at the case study

sites, sorted by the number of years which the remediation system was in operation (for this

report, the number of years of performance data available). Average concentrations of

contaminants could be calculated on the basis of available data for 17 of the 28 case study sites. 

For several of the sites, average concentrations of contaminations were reported only for a group

of contaminants, and several others reported average concentrations of contaminants by

individual contaminant. In addition, three of the sites (United Chrome, Odessa II, and French

Ltd.) reported individual average concentrations of contaminants for more than one aquifer.
0.0001 0.001 0.01 0.1 1 10

Firestone

S ylvester/Gilson Road

Western Processing

Libby

S ite A

United Chrome

City Industries

King of Prussia

S ol Lynn

S olvent Recovery S ervice

Baird and McGuire

S olid S tate

French, Ltd.

Odessa I

U.S . Aviex

MS WP

JMT

Des Moines

Odessa II

LaS alle

Gold Coast

Keefe

Old Mill

Intersil

Mystery Bridge

S CRDI Dixiana

pounds per 1,000 gallons

1 10 100 1,000 10,000 100,000 1,000,000

pounds per year

Mass Removed per 1,000 Gallons Treated Mass Removed per Year

Groundwater Cleanup: Overview of Operating Experience at 28 Sites

4-4

Exhibit 4-2: Unit Contaminant Mass Removed at 26 Sites
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

4-5

Exhibit 4-3: Summary of Average Contaminant Concentration Reduction 

at 17 Sites

Site Name and Location Contaminant(s) Zone Start End Data Reduction

Basis1

Average Contaminant

Concentration (μg/L)2

Years

of Percent 1 3

Intersil, CA VOCs (4 contaminants) 1,609 31 11.1 98

Des Moines, IA VOCs (3 contaminants) 87 10 9 89

TCE 45 3 9 93

JMT, NY VOCs (4 contaminants) 950 30 8.6 97

TCE 450 7 8.6 98

United Chrome, OR Chromium Shallow Aquifer 1,923,000 18,000 8.6 99

Chromium Deep Aquifer 1,400 110 8.6 92

MSWP, AR Metals/VOCs (4 contaminants) 140 90 7.1 36 4

As 3 4 7.1 -33

PCP 22 11 7.1 50

Cr 30 5 7.1 83

Total PAHs 35 23 7.1 34

Odessa I, TX Chromium 980 540 5 45

Gold Coast, FL PCE 176 1 4.9 99

TCE 88 1 4.9 99

Odessa II, TX Chromium Perched Aquifer 180 190 4.8 -6 4

Chromium Trinity Aquifer 400 50 4.8 88

LaSalle, IL PCBs/ VOCs Shallow Aquifer 400 570 4.2 -43 4

French, Ltd., TX 1,2-DCA S1 Aquifer/INT Aquifer 256/ 917 0.8/ 1 3.9 >99

Vinyl chloride S1 Aquifer/INT Aquifer 129/ 420 1.2/ 1 3.9 >99

Benzene S1 Aquifer/INT Aquifer 516/ 640 0.6/ 2 3.9 >99

U.S. Aviex, MI 1,1,1-TCA 107 40 3.6 63

VOCs (10 contaminants) 158 67 3.6 58

Keefe, NH VOCs (5 contaminants) 80 18 3.5 78

LaSalle, IL PCBs/ VOCs Deep Aquifer 100 6 3.2 94

City Industries, FL VOCs and SVOCs (16 contaminants) 3,121 444 3 86

King of Prussia, NJ Metals (6 contaminants) 3,500 1,500 2.6 57

VOCs (9 contaminants) 4,500 4,000 2.6 11

Baird and McGuire, MA VOCs (specific contaminants not identified) 500 420 1 16

SVOCs (specific contaminants not identified) 1,000 520 1 48

Site A, NY BTEX 160 26 1 84

Notes:

Data on average concentrations were reported for 17 of the 28 case study sites; for those sites, data are shown here by contaminant(s) and 1 

zone; zones are noted only for those sites at which concentrations of contaminants were reported for more than one aquifer.

Average concentrations of contaminants are based on a reported geometric mean of all data, as presented in the case study reports; for sites 2 

with ongoing cleanups, average concentrations of contaminants shown at “end” time represent the concentrations reported as of the date

that data were available, typically late 1997 or early 1998.

 Percent reduction was calculated as the difference between average concentrations of contaminants at start and end points, divided by the 3

average concentration at the start.

Negative percent contaminant reductions were measured at three sites. These anomalies are discussed in the case studies for the sites. 4
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

4-6

4.2 Progress Toward Goals

Exhibit 4-4 lists the number of sites that have met specific remedial and system performance

goals.

Exhibit 4-4: System Performance Summary

Goal Specified Goals Specified Goals

Number of Sites with Number of Sites Meeting 1

Remedial Goals

Aquifer Restoration 28 2

Containment 25 22

System Performance Goals

Air emissions 3 3 2

Discharge of water 19 18

Notes:

Goals for each site are specified in the case study reports. 1

Air emission goals were specifically identified for only three of the case study sites. 2

Gold Coast and Firestone are the two case study sites for which all remedial goals have been

met, as described briefly below. 

& Gold Coast was a spent oil and solvent recovery facility that operated from 1970

to 1982. In the 1980s, groundwater was determined to be contaminated with

chlorinated and nonchlorinated VOCs at levels as high as 100 milligrams per liter. 

A P&T system consisting of five extraction wells (pumping at a total of

approximately 100 gpm) and two air stripping towers was put on line in 1990. By

the end of 1994, concentrations of groundwater contaminants were reduced to

levels lower than cleanup standards, with the exception of one source area. A

limited air sparging effort was able to reduce the contaminant levels in that area to

levels lower than cleanup standards by 1995. The site is located over a porous

limestone aquifer, which facilitated groundwater pumping, and the use of source

controls and in situ technology were identified as key factors in the success of the 

cleanup.

& The Firestone facility operated as a tire manufacturing plant from 1963 until

1980. In 1984, a 2.5-mile-long contaminated groundwater plume that contained

chlorinated solvents was identified. The primary target contaminant in the plume

was 1,1-DCE. A P&T system consisting of 35 extraction wells and ex situ air

stripping and carbon adsorption was put on line in 1986. By 1987, the

contaminated plume was contained and by 1992 the concentrations of 1,1-DCE in

the plume had been reduced to levels lower than the cleanup goals and the system

was shut down. During the operation of the groundwater extraction system, the

site operators frequently adjusted it to maintain maximum concentration of

contaminant at the treatment plant influent. That factor was identified as a key

one in the success of the cleanup.
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

4-7

In addition to the two sites listed above at which the specified aquifer cleanup goals have been

met, progress has been made toward meeting the specified remedial goals for most of the sites. 

Example successes include:

& Meeting aquifer cleanup goals in one or more zones at the site

At Des Moines, the cleanup goals for the off-site plume were achieved within two

years of startup of the remediation system. P&T continues to maintain an inward

hydraulic gradient and to remediate on-site groundwater. The aquifer at the site

is a relatively homogeneous formation of sand and gravel that has a relatively

high conductivity.

& Reducing the size of a contaminated plume

At Odessa I, the total plume area was reduced approximately 44 percent in two

years (from 1994 to 1996). On several occasions, the groundwater extraction

system was modified to improve efficiency.

& Reducing the concentrations of contaminants within a plume

At United Chrome, average concentrations of chromium were reduced in the

upper aquifer from more than 1,900 to 18 mg/L over nine years, and in the deep

aquifer from 1.4 to 0.11 mg/L over six years. On several occasions, the

groundwater extraction system was modified to target the more highly

contaminated areas of the plume.

& Removing contaminant mass from a plume

At French, Ltd., the P&T system removed approximately 517,000 pounds of

contaminant (measured as total organic carbon) from January 1992 through

December 1995. The mass was removed through aggressive pumping of

groundwater that contained relatively high concentrations of contaminants

(hundreds of mg/L) from more than 100 recovery wells.

& Achieving containment of a plume

At City Industries, the contaminated groundwater plume has been contained

hydraulically since the P&T system was put on line in 1994. 

It is important to note that groundwater cleanup is ongoing at most of the case study sites; 

therefore, the system performance presented in this report does not represent the final

performance to be achieved in remediating each of the sites. As discussed earlier, the data

presented in the case studies are generally available through late 1997 or early 1998.
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

4-8
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

5-1

 Capital and operating costs were

highly variable from site to site with

key cost drivers, including variable

monitoring requirements, significant

system modifications needed, and

size and complexity of the remedial

systems

 The following three types of unit

costs were calculated for each site:

& Average operating cost per year of

operation

& Capital cost per 1,000 gallons

treated per year

& Average annual operating cost per

1,000 gallons treated per year

5.0 COST OF REMEDIAL SYSTEMS AT 28 CASE STUDY SITES

This section discusses the costs of the remedial

systems at the 28 case study sites and unit costs

for the groundwater cleanups at these sites.

The costs for the sites typically were reported as

capital costs, operation and maintenance

(operating) costs, remedial design costs, and

other costs. For the purpose of this report,

calculated unit costs are provided as average

annual operating cost, capital cost per 1,000

gallons treated per year, and average annual

operating cost per 1,000 gallons treated per year. 

Average annual operating cost as a percentage of

capital cost is also presented. Assumptions used

in reporting cost data are summarized below.

& Cost data presented in the case study reports were based on data provided by EPA

remedial project managers, site owners, or vendors. The costs presented in this

report are based on the cost data in these case study reports. In addition, updated

cost data received in May 1999 for several of the sites (Baird and McGuire,

Libby, French Ltd., United Chrome, Sylvester/Gilson Road, Western Processing)

was included in this report. When actual cost data were not available, site

contacts provided estimates based on the best data available at the time.

& Groundwater cleanup is ongoing at most of the sites; therefore, the operating costs

(and in some cases the capital costs) do not represent the total to be spent to 

remediate a site. The data presented here generally are current as of late 1997 or

early 1998, with 1999 data available for the sites identified above.

& Because groundwater cleanup is ongoing at most of the sites and the total time

necessary to complete cleanup of a site was not known, a net present value (NPV)

of the remedial costs for the sites was not calculated for this report. The systems

in the 28 case studies had been operating for as few as 2 years and as long as 11

years. While many feasibility studies conducted under Superfund assume a 30-

year duration to estimate the cost of a P&T remedy, the use of this timeframe was

not considered to be applicable for this report because the two completed projects

were completed in 3.5 and 7 years.
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

5-2

& Capital and operating costs were extracted from cost data provided in the case

studies based on the Recommended Cost Format in Guide to Documenting and

Managing Cost and Performance Information for Remediation Projects [4]. 

Capital costs included: technology mobilization, setup, and demobilization;

planning and preparation; site work; equipment and appurtenances; startup and

testing; and other technology capital costs. Operating costs included: labor;

materials; utilities and fuel; equipment ownership, rental, or lease; performance

testing and analysis (although compliance testing was often not separated out);

and other technology operating costs. Source controls, RI/FS, and system design

costs were not included as capital or operating costs. However, VCBs used for

hydraulic control were included as capital costs.

& As previously discussed in Section 3.1, PRBs may differ in form and purpose

from P&T and PRB systems, and unit costs for sites at which PRBs were used are

shown separately from costs for sites at which P&T was used. PRBs treat only the

groundwater that passes through the barrier, while P&T actively extracts

groundwater from an aquifer. Therefore, the volume of groundwater treated by a

PRB will be relatively less than by a P&T system for the same size plume.

Cost Data

Exhibit 5-1 presents the cost data for cleanup of contaminated groundwater at each of the case

study sites. The table also identifies the major factors that influenced costs at each of the sites. 

Exhibit 5-2 summarizes overall remedial costs and unit costs for P&T and PRB sites,

respectively, including minimum, maximum, average, and median costs for each of the two

groups individually and combined. 

Capital costs per P&T site ranged from approximately $250,000 (Gold Coast) to $15 million

(Western Processing and French, Ltd.), and average annual operating costs ranged from

approximately $90,000 (MSWP) to $4.4 million (Western Processing). Average annual operating

costs ranged from 2.9 to 56 percent of the capital costs. The median capital cost was $1.9

million and the median average annual operating cost was $190,000; with median unit costs of

$96 of capital cost per average 1,000 gallons of groundwater treated per year and $18 of average

annual operating cost per average 1,000 gallons of groundwater treated per year.

Based on three sites, capital costs per PRB site ranged from approximately $370,000 (Moffett) to

$600,000 (Intersil [PRB]), and average annual operating costs per PRB site ranged from

approximately $26,000 (Moffett) to $95,000 (Intersil [PRB]). Average annual operating costs

ranged from 6.9 to 17 percent of the capital costs. For the PRB systems, the approximate median

capital cost was $500,000 and the median average annual operating cost was $85,000; with

median unit costs of $520 of capital cost per average 1,000 gallons of groundwater treated per

year and $84 of average annual operating cost per average 1,000 gallons of groundwater treated

per year.

The total remedial cost for each site was not projected, since the number of years in which each

system has been operating and the progress of each system toward meeting remedial restoration

goals vary from system to system. 
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

5-3

Exhibit 5-1: Summary of Cost Data for 28 Sites1,2,3

Site Name and (with data Treated per Capital Cost ($) as Fraction of Treated Per Year Treated Per Year

Location available) Year Cost ($) Per Year Capital Cost ($/1,000 Gallons) ($/1,000 Gallons) 

Years of 1,000 Average Average Volume of Volume of

Operation Gallons Operating Operating Cost Groundwater Groundwater

Average Capital Cost Per Operating Cost Per

Average Annual

P&T SITESBaird and 3.8 21,000 11,000,000 2,000,000 0.18 530 97 OpMcGuire, MA the 

wifor be 

City Industries, 3.0 50,000 1,200,000 170,000 0.14 23 3.3 OpFL bio

inc

Des Moines, IA 8.8 554,000 1,600,000 110,000 0.07 2.9 0.21 Un

sca

Firestone, CA 6.8 266,000 4,100,000 1,300,000 0.31 15 4.9 Fr

syanwe

French, Ltd. ,TX 4.0 76,000 15,000,000 3,400,000 0.21 200 43 La

anhig

Gold Coast, FL 3.7 22,000 250,000 120,000 0.49 11 5.6 Op

syye

Intersil (P&T), 7.3 5,000 330,000 140,000 0.43 65 28 GrCA wa

of op

JMT, NY 9.6 5,200 880,000 150,000 0.17 170 29 Mo

sypeex
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

Exhibit 5-1: Summary of Cost Data for 28 Sites1,2,3

Site Name and (with data Treated per Capital Cost ($) as Fraction of Treated Per Year Treated Per Year

Location available) Year Cost ($) Per Year Capital Cost ($/1,000 Gallons) ($/1,000 Gallons) 

Years of 1,000 Average Average Volume of Volume of

Operation Gallons Operating Operating Cost Groundwater Groundwater

Average Capital Cost Per Operating Cost Per

Average Annual

5-4

Keefe, NH 4.1 11,000 1,600,000 240,000 0.15 140 21 Op

purem

King of Prussia, 2.7 57,000 2,000,000 390,000 0.19 36 6.8 ElNJ incLaSalle, IL 4.4 5,200 5,300,000 190,000 0.03 1,000 36 Co

cococo

Libby, MT 5.3 2,900 3,000,000 500,000 0.17 1,000 170 Ch

pebiosamwepro

MSWP, AR 8.3 12,000 470,000 91,000 0.19 38 7.4 Us

op

Mystery Bridge, 3.6 54,000 310,000 170,000 0.56 5.7 3.2 LoWY groOdessa I ,TX 4.2 30,000 2,000,000 190,000 0.10 65 6.3 RO

be elenuan

Odessa II, TX 4.1 30,000 2,000,000 140,000 0.07 65 4.6 RO

be elenuan
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

Exhibit 5-1: Summary of Cost Data for 28 Sites1,2,3

Site Name and (with data Treated per Capital Cost ($) as Fraction of Treated Per Year Treated Per Year

Location available) Year Cost ($) Per Year Capital Cost ($/1,000 Gallons) ($/1,000 Gallons) 

Years of 1,000 Average Average Volume of Volume of

Operation Gallons Operating Operating Cost Groundwater Groundwater

Average Capital Cost Per Operating Cost Per

Average Annual

5-5

Old Mill, OH 7.8 1,700 1,600,000 210,000 0.13 960 130 M

incpe

SCRDI Dixiana, 4.6 4,500 1,800,000 94,000 0.05 410 21 PRSC to 

low 

Site A, NY 1.3 6,700 1,400,000 290,000 0.20 210 43 Us

eqtrespbio

Sol Lynn, TX 3.0 4,300 2,100,000 150,000 0.07 490 34 Co

inc

Solid State, MO 4.2 62,000 930,000 370,000 0.40 15 6 Ca

coexof 

Solvent 2.9 11,000 4,400,000 400,000 0.09 390 36 PrRecovery to Service, CT coSylvester/Gilson 9.5 126,000 7,200,000 1,900,000 0.27 57 15 SeRoad, NH on 

covaem

U.S. Aviex, MI 3.4 96,000 1,400,000 180,000 0.13 15 1.9 Op

syred
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

Exhibit 5-1: Summary of Cost Data for 28 Sites1,2,3

Site Name and (with data Treated per Capital Cost ($) as Fraction of Treated Per Year Treated Per Year

Location available) Year Cost ($) Per Year Capital Cost ($/1,000 Gallons) ($/1,000 Gallons) 

Years of 1,000 Average Average Volume of Volume of

Operation Gallons Operating Operating Cost Groundwater Groundwater

Average Capital Cost Per Operating Cost Per

Average Annual

5-6

United Chrome, 8.6 7,200 3,300,000 96,000 0.03 460 13 MOR iniWestern 8.2 119,000 15,000,000 4,400,000 0.30 130 37 IniProcessing, WA sy

(4) (4) (4)

wereqto bu

PRB SITESIntersil (PRB), 1.8 1,100 600,000 95,000 0.16 520 83 P&CA red

ab

Moffett, CA 1.2 200 370,000 26,000 0.07 1,600 110 De

incmotec

USCG Center, 1.0 2,600 500,000 85,000 0.17 190 33 UsNC sav

P&

Note:

Groundwater cleanups are ongoing at most sites; data presented here generally are current of late 1997 or early 1

1

Capital and operating costs were extracted from costs provided in the case studies based on the Recommended C

2

Documenting and Managing Cost and Performance Information for Remediation Projects [4]. Source controls, were not included as capital or operating costs.Cost data shown in the case study reports were based on data provided by EPA remedial project managers, site o

3

presented in this report are based on the total costs available at the time the case study report for the site was prepreceived in May 1999 for several of the sites (Baird and McGuire, Libby, French Ltd., United Chrome, Sylvester

Processing). When actual cost data were not available, site contacts provided estimates based on the best data avThe P&T system at Western processing was changed in response to a change in the remedial goals at the site from 

4

containment. The modified system pumped less than half of the water pumped by the original system. Howeveravailable to determine the cost implications of the system modification.
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

5-7

Exhibit 5-2: Summary of Remedial Cost and Unit Cost Data for 28 Sites1,2,3

 P&T Sites (26 sites) PRB Sites (3 sites) All Sit

Cost Category Range Average Range Average Range 

Median Median 

Years of System Operation (with 1.3 - 9.6 4.2 1.0 - 1.8 1.2 1.0 - data available) 5.3 1.3 Average Volume of Groundwater 1,700 - 550,000 21,000 230 - 2,600 1,100 230 - Treated Per Year (1,000 Gallons) 63,000 1,300 Total Capital Cost ($) 250,000 - 15,000,000 1,900,000 370,000 - 600,000 500,00 250,000 - 1

3,500,000 490,000 

Average Operating Cost Per 91,000 - 4,400,000 190,000 26,000 - 95,000 85,000 26,000 - 4Year ($) 670,000 69,000 Average Operating Cost Fraction 0.03 - 0.56 0.17 0.07 - 0.17 0.16 0.03 - of Capital Cost 0.20 0.13 Capital Cost Per Volume of 2.9 - 1,000 96 192 - 1,600 520 2.9 - Groundwater Treated Per Year 250 780 ($/1,000 Gallons)Average Annual Operating Cost 0.21 - 170 18 33 - 110 84 0.21 - Volume of Groundwater Treated 31 76 Per Year ($/1,000 Gallons)

Notes:

Groundwater cleanups are ongoing at most sites; data presented here generally are cumulative as of late 1997 or early 1998

1

Capital and operating costs were extracted from costs provided in the case studies based on the Recommended Cost Format 

2

Managing Cost and Performance Information for Remediation Projects [4]. Source controls, RI/FS, and system design costor operating costs.Cost data shown in the case study reports were based on data provided by EPA remedial project managers, site owners, or 

3

in this report are based on the total costs available at the time the case study report for the site was prepared and updated cofor several of the sites (Baird and McGuire, Libby, French Ltd., United Chrome, Sylvester/Gilson Road, Western Processing)

not available, site contacts provided estimates based on the best data available at the time.
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

5-8

Calculated Unit Costs

Calculated unit costs are used to compare and contrast remediation technologies. Although the

basis and methodology for calculation of unit costs for site cleanups are still a matter of some

debate, some unit costs can be used to compare costs and performance at ongoing and completed

cleanup efforts and in identifying cost-efficient remedial strategies for future cleanups. For this

report, the following three types of unit costs were calculated for each site:

& Average operating cost per year of operation

& Capital cost per 1,000 gallons of groundwater treated per year

& Average annual operating cost per 1,000 gallons of groundwater treated per year

Those unit costs, along with their ranges, averages, and medians are summarized in Exhibits 5-1

and 5-2 and depicted in Exhibits 5-3, 5-4, and 5-5, respectively. The three unit costs summarized

for the case study sites are described briefly below.

Average Operating Cost per Year of Operation

The average operating cost per year is determined by the throughput of the system and the

treatment processes required to treat the extracted groundwater, as well as the operating

efficiency of the system. Since a breakdown of annual operating costs by year was not available

for most of the sites, the change in operating costs over the life of a site’s remediation system

could not be evaluated for the purposes of this report. The average annual operating costs were

calculated by dividing the total operating cost to date by the number of years represented by that

cost. 

At SCRDI Dixiana, where approximately 40 gpm were pumped from 15 wells through a

relatively simple system and discharged to a POTW, the average annual operating cost

was $94,000 over 4.5 years. At French, Ltd., where approximately 190 gpm were

pumped from more than 100 wells through a more complex treatment system before being

reinjected into the aquifer, the average annual operating cost was more than $3.4 million

per year over 4 years. 

Capital Cost per 1,000 Gallons of Groundwater Treated Per Year

The capital cost per 1,000 gallons treated per year represents the relative costs of installing

remedial systems of varying capacity. This unit cost is influenced by factors such as the aquifer

complexity (which influences the size and complexity of the system needed to extract the

contaminated groundwater), the types of contaminants targeted for treatment at the site (which

influences the treatment plant components needed to remove the contaminants), the water and air

discharge limits for the particular site (which is also factor into the treatment plant components

needed), and restoration goals (which reflects the difference between sites where a large volume

of groundwater is treated over a relatively short time frame to clean up an aquifer versus

pumping at a lesser rate to prevent a contaminated plume from migrating from the site). 
26,000

85,000

91,000

94,000

95,000

96,000

110,000

120,000

140,000

140,000

150,000

150,000

170,000

170,000

180,000

190,000

190,000

210,000

240,000

290,000

370,000

390,000

400,000

500,000

1,300,000

1,900,000

2,000,000

3,400,000

4,400,000

10,000 100,000 1,000,000 10,000,000

M offett (P RB )

US C G C enter (P RB )

MSW P

SC RD I D ixiana

Intersil (P RB )

United C hrom e

Des Moines

Gold C oast

Odessa II

Intersil

S o l Ly nn

JMT

C ity Industries

M y stery B ridge

U.S. Aviex

LaS alle

Odessa I

Old M ill

Keefe

S ite A

S o lid S ta te

King of Prussia

S o lve nt Rec ove ry S e rvic e

Libby

Firestone

S y lve ste r/Gilson Ro ad

Baird and McGuire

Frenc h, Ltd.

W estern P roc essing

Average O perating C ost ($) P er Year

Groundwater Cleanup: Overview of Operating Experience at 28 Sites

5-9

Exhibit 5-3: Average Operating Cost Per Year at 28 Sites

The following example illustrates the effect of the aquifer complexity and treatment plant

requirements on the capital cost per 1,000 gallons of groundwater treated annually.

At the Gold Coast site, groundwater in a relatively shallow and homogeneous aquifer

contaminated with TCE was extracted and treated by an air stripper alone before it was

discharged to surface water. The capital cost was $11 per 1,000 gallons of water

treated. This compares with a cost of $1,020 per 1,000 gallons of water treated at the

LaSalle Site, where groundwater was extracted via a horizontal pumping regime and was

treated for a complex range of contaminants by a much more complex system. The

system consisted of two air strippers, both vapor and liquid-phase GAC, oil/water

separation, and pH adjustment.
11

15

15

15

23

36

38

57

65

65

65

130

140

170

190

200

210

390

410

460

490

520

530

960

1,000

1,000

1,600

3

6

1 10 100 1,000 10,000

Des Moines

Mystery Bridge 

Gold Coast

U.S. Aviex

Solid State

Firestone

City Industries

King of Prussia 

MSWP

Sylvester/Gilson Road

Odessa IIS

Odessa I 

Intersil (P&T)

W estern Processing

Keefe 

JMT 

USCG Center

French, Ltd.

Site A

Solvent Recovery Services

SCRDI Dixiana

United Chrome

Sol Lynn

Intersil (PRB)

Baird and McGuire

Old Mill

LaSalle 

Libby

Moffett (PRB)

Capital Cost Per Volum e of Groundw ater Treated Per Year ($/1,000 Gallons)

Groundwater Cleanup: Overview of Operating Experience at 28 Sites

5-10

Exhibit 5-4: Capital Cost Per 1,000 Gallons of Groundwater Treated 

Per Year
13

15

21

21

28

29

33

34

36

36

37

43

43

83

97

110

130

170

3

3

5

5

6

6

6

7

7

2

0.2

0.1 1.0 10.0 100.0 1,000.0

Baird and McGuire

U.S. Aviex

Mystery Bridge 

Des Moines

Odessa IIS

Firestone

Gold Coast

Solid State

Odessa I 

King of Prussia 

MSWP

United Chrome

Sylvester/Gilson Road

SCRDI Dixiana

Keefe 

Intersil (P&T)

JMT 

USCG Center

Sol Lynn

Solvent Recovery Services

LaSalle 

Western Processing

Site A

French, Ltd.

Intersil (PRB)

City Industries

Moffett (PRB)

Old Mill

Libby

Average Annual Operating Cost Per Volume of Groundwater Treated Per Year 

($/1,000 Gallons)

Groundwater Cleanup: Overview of Operating Experience at 28 Sites

5-11

Exhibit 5-5: Average Annual Operating Cost per 1,000 Gallons of

Groundwater Treated Per Year
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

5-12

Average Annual Operating Cost Per 1,000 Gallons of Groundwater Treated 

Per Year

The average annual operating cost per 1,000 gallons of groundwater treated per year represents

the relative costs to operate systems of various capacities and complexities. Similar to the capital

cost per 1,000 gallons of groundwater treated per year, this unit cost is highly dependent on sitespecific factors such as the aquifer complexity, the types of contaminants targeted for treatment,

the water and air discharge limits, and the restoration goals. 

The following example illustrates the effect of the complexity of a site treatment system on

average annual operating cost per 1,000 gallons of groundwater treated per year.

At Des Moines over 500 million gallons of groundwater were treated per year using a

relatively simple system consisting of an air stripper for an average annual operating

cost of $0.21 per 1,000 gallons of groundwater treated annually. Conversely, at Libby,

2.9 million gallons of groundwater were treated per year using a complex remediation

system consisting of oil/water separation, nutrient addition, and bioreactors for an

average annual operating cost of $173 per 1,000 gallons of groundwater treated

annually.

In general, systems that treat a relatively large volume of groundwater per year will cost less in

both capital and annual operating costs per 1,000 gallons of groundwater treated than a similar

system that treats a smaller volume of groundwater per year. While no specific correlation could

be derived based on the available information, the following example shows this trend.

The treatment systems at Des Moines, City Industries, and Mystery Bridge consisted of

P&T using air stripping as aboveground treatment. Des Moines treated a relatively

larger volume of groundwater annually. The following table summarizes some of the

data for these sites.

Site Name (1,000 Gallons) ($/1,000 Gallons)

Average Volume of Volume of

Groundwater Groundwater

Treated Annually Treated Per Year

Average Annual

Operating Cost Per

Des Moines, IA 554,000 0.21

City Industries, FL 50,000 3.3

Mystery Bridge, WY 54,000 3.2

The average annual operating cost per volume of groundwater treated annually

exemplifies the above trend.
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

6-1

 The factors that affected cost and

performance at the 28 case study sites

vary and are specific to each site

 No single factor was found to be the

most important factor in determining

cost and performance of groundwater

cleanup projects 

6.0 FACTORS THAT AFFECTED COST AND PERFORMANCE OF

REMEDIAL SYSTEMS AT 28 CASE STUDY SITES

The factors that affected cost and performance at

the 28 case study sites vary and are specific to

each site. This section discusses the key factors 

that affected cost and performance of the

groundwater cleanup at the case study sites

identified from the case studies and industry

knowledge about groundwater remediation. The

factors have been grouped into the categories

summarized in Exhibit 6-1.

Exhibit 6-1: Factors Affecting Cost and Performance 

of Groundwater Remediation Systems

Category Factors

Source control factors Presence of NAPL; application and timing of source controls

Hydrogeologic factors Properties of the aquifer; contamination of more than one aquifer;

influence of surface water on aquifer; influence of adjacent groundwater

production wells on aquifer

Contaminant property factors Treatability of the contaminant; fate and transport properties of the

contaminant

Extent of contamination factors Area and depth of contaminated plume; concentrations of contaminant

within the plume

Remedial goal factors Restoration of the aquifer rather than plume; MCL rather than lessstringent cleanup levels; cleanup of the entire aquifer rather than partial

cleanup; time allowed for cleanup

System design and operation System downtime; system optimization; amount and type of monitoring

factors performed; use of in situ technology

Each of the categories is discussed below; specific examples of how each factor affected cost or

performance of the groundwater cleanup systems at the case study sites are also presented.

Source Control Factors

Sources of groundwater contamination vary from surface discharges to buried wastes. When 

source material comes in contact with groundwater, contaminants begin to dissolve and move

into the groundwater by advection and dispersion mechanisms. In addition, contaminant sources

in the vadose zone may act as continuing sources of groundwater contamination via leaching of

contaminants onto storm water recharge that passes through the contaminated zone.

Biodegradation and volatilization also may contribute to the destruction or dispersion of

contaminants. However, in many cases, the mechanisms may have a negligible impact. 
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

6-2

The solubilities of many common contaminants (such as chlorinated solvents) are relatively low,

and sources of those contaminants may remain in the subsurface for extended periods of time. 

EPA has concluded that one of the most effective means of remediating a site at which

contaminated groundwater is present is to remove, or at least isolate, the source material from the

groundwater. The source controls implemented at the case study sites (see Exhibit 3-2) include

such methods as removal of hot spots (soil), soil vapor extraction, capping, and installation of

VCBs.

NAPL has been observed or suspected to be a source of groundwater contamination at a majority

of the case study sites (see Exhibit 2-7). Of the 28 sites, NAPLs were observed or suspected to

be present at 18. At twelve of the sites, only DNAPL was present; at three, only LNAPL was

present; and at another three both DNAPL and LNAPL were present.

At several sites (such as French Ltd., SRS, and Western Processing), efforts were made to

remove or isolate the NAPL from contact with the groundwater. Such efforts often involved

significant capital expenditures.

At Western Processing, both DNAPL and LNAPL were observed in the groundwater. A

slurry wall was constructed around the site to contain the plume and help achieve the

cleanup goals within a limited amount of time. The slurry wall required capital

expenditures of approximately $1.4 million.

If NAPL was not removed or isolated, the groundwater remediation efforts often were hindered. 

At Solvent Recovery Service, DNAPL is present in both the overburden and the bedrock

aquifers, and is a source from which a dissolved plume continually forms. Despite three

years of P&T operation, the complex hydrogeology and DNAPL present at this site have

resulted in fluctuating concentrations of total VOCs in the groundwater. Site

representatives indicated that they plan to apply for a technical impracticability (TI)

waiver because of the presence of the persistent source of DNAPL.

Hydrogeologic Factors

Hydrogeologic factors that influence the cost and performance of groundwater remediation

systems include the composition and hydraulic conductivity of a water-bearing layer; the depth to

groundwater; contamination of more than one aquifer; vertical groundwater flow; the influence

of surface water; and the influence of nearby groundwater production wells. These factors can

affect the complexity of the groundwater remediation system as well as the ability of the system

to meet the remedial goals at a site.

This report presents information about the hydrogeologic conditions at the 28 subject sites (see

Exhibit 2-8). The hydraulic conductivity of the contaminated water-bearing layer(s) at the sites

ranged from 0.023 ft/day to 1,200 ft/day, a range of more than six orders of magnitude. The

hydraulic conductivity also often varied within an individual site, such as United Chrome, where

the hydraulic conductivity in the upper aquifer was two orders of magnitude less than in the

lower aquifer. At more than one-half of the sites, contamination was present in more than one

water-bearing layer or aquifer. Seven of the sites exhibited vertical groundwater flow, 13 were

influenced by adjacent bodies of surface water, and production wells (municipal or otherwise)
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

6-3

were located in the vicinity of each of eight of the sites. Reported depths of the water table

ranged from zero (at ground surface) to 45 feet below ground surface.

The following examples illustrate specific cases hydrogeological factors affected the cost or

performance of the groundwater remediation technology implemented at a site.

Hydraulic Conductivity

At JMT, the hydraulic conductivity in the contaminated bedrock aquifer was relatively

low (0.65 ft/day). To increase hydraulic conductivity, controlled blasting was carried out

to create an artificial fracture zone, which served as an interceptor drain in the bedrock

around the extraction well. While that approach increased the capital cost of the system

(by an undetermined amount), it allowed effective extraction groundwater from the unit

by one well screened in the new fracture zone.

Contamination of More Than One Aquifer

At SCRDI Dixiana, eight distinct soil layers have been identified within the upper 100

feet of soils, including five water-bearing units. Early site characterization work at the

site misidentified the thicknesses and degrees of contamination of several of those units. 

Groundwater extraction wells were installed based on the results of that early work. The

wells were screened across two units, thereby presenting a pathway for contaminants to

migrate into a previously uncontaminated aquifer. In addition, the contaminated shallow

sand aquifer at the site was not identified until after the system had been installed,

resulting in the need to modify the remedial system to address multiple contaminated

aquifers.

Vertical Groundwater Flow

At Solid State, the groundwater system is a leaky artesian system in karst formations,

with shallow and deep bedrock zones separated by a semi-confining shale layer. 

Groundwater flow at the site is vertical as well as lateral, a condition that has resulted in

contamination of multiple aquifers and the need to extract groundwater at several depths.

Influence of Bodies of Surface Water 

At Site A, the groundwater flow is subject to tidal influence in the upper few feet of the

upper-most aquifer. Water levels at the site sometimes have risen, and SVE wells at the

site have been flooded.

Influence of Groundwater Production Wells

At Des Moines, groundwater flow is to the southeast; however, earlier high-volume

pumping from city wells may have affected the flow direction, facilitating the migration of

the contaminant plume. 
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

6-4

Contaminant Property Factors

The types and properties of the contaminants being treated at a site, such as whether the

contaminant has a tendency to be removed with extracted groundwater or to stay adsorbed to

subsurface soils, can affect the cost or performance of a remediation system. In addition, the

properties of the contaminants determine what treatment technologies are appropriate and the

complexity of the system required to treat contaminated groundwater ex situ or in situ. Examples

of sites where the contaminants (see Exhibits 2-4 and 2-5) and the contaminant properties

affected the cost or performance of the groundwater remediation are presented below.

Complex Mixture of Contaminants

At Sylvester/Gilson Road, contaminants included chlorinated solvents, such as methylene

chloride; nonchlorinated organics, such as toluene and phenols; and the metal selenium. 

The mix of contaminants was treated above ground by a long series of operations,

including pH adjustment, settling, neutralization, filtration, air stripping with vapor

incineration, and biological treatment.

Single Contaminant That was Relatively Easy to Treat

At JMT, groundwater was contaminated with chlorinated solvents. The groundwater

treatment system consisted of only an air stripper, which was capable of reducing

contaminant concentrations to a level where the treated groundwater could be

discharged to an adjacent surface water body.

Extent of Contamination Factors

Groundwater contamination concentrated in an isolated areal and vertical extent typically is

easier and cheaper to remediate than the same mass of contaminant when it extends deeper and

spreads out over a larger area. This factor affects the size of the extraction and treatment system

and the system complexity in terms of the quantity of groundwater to be extracted from the

aquifer and treated ex situ. The volumes of contaminant plumes at each of the sites are presented

in Exhibit 2-6. The following examples show the effects of a relatively small and relatively large

extent of contamination at which groundwater remediation has been completed.

At Gold Coast, the initial areal extent of the contaminant plume was estimated to be 0.87

acres, and the initial volume of the plume was estimated to be less than 3 million gallons. 

The site was remediated at a cost of less than $700,000.

At the Former Firestone facility, the initial areal extent of plume was estimated to be 100

acres (1,300 feet wide and 3,400 feet long), with an initial volume of as much as 2.9

billion gallons. The cost to remediate this site was nearly $13,000,000.
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

6-5

Remedial Goal Factors

Remedial goal factors that may affect the cost and performance of a site cleanup include the

stringency of the cleanup levels, the types of remedial goals, the types of performance

requirements that have been established for the remediation as well as the system complexity

required to meet these goals. The following remedial goal factors can influence the volume or

areal extent of groundwater that must be treated, the type of treatment train that may be used, or

the length of time that a system has to be operated.

& Stringency of the cleanup levels

 maximum contaminant levels 

 approved alternate concentration limits

 risk factors

 other criteria

& Types of remedial goals

 aquifer restoration

 aquifer restoration and containment

 other restoration goals

& Types of performance requirements

 treated wastewater discharge limits

 air emission limits

More stringent cleanup levels can require more complex systems, longer periods of operation,

and larger volumes of groundwater to be treated. The type or stringency of the performance

goals (treatment of extracted groundwater and/or air emissions) affect the manner and the extent

to which extracted groundwater or off-gas from the remediation system must be treated before

discharge. The following examples show the effects of various remedial goals on the cost and

performance of site cleanup.

Types of Remedial Goals

At Western Processing, an aggressive P&T system, consisting of more than 200

groundwater extraction points pumping approximately 265 gpm, was installed to pursue

aquifer restorations goals. After approximately seven years of operation, an ESD was

issued to change the focus of remediation from restoration to containment. As a result of

this change, the system was modified to a system pumping approximately 80 gpm. This

modification significantly reduced the operating cost for the system.

Performance Goals Established

At Solid State, the site engineer identified institutional constraints that restricted the

operator’s ability to reinject treated groundwater. Reinjection of groundwater may have

been a more cost efficient method for the disposal of treated groundwater, and could

have increased groundwater flow through the contaminated zone. This restriction is

believed to have increased the time required for site remediation more than any other

single factor.
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

6-6

In addition, as shown at the French, Ltd. site, different remedies specified in a site ROD can

impact cost and performance. 

Under the ROD for French Ltd., modeling was used as a basis to select natural

attenuation as a component of the site remedy. Modeling showed that concentrations at

the boundaries of the site would be acceptable after 10 years of natural attenuation, and

that P&T, which was costing more than $3 million annually, could be terminated.

System Design and Operation Factors

In addition to site characteristics and remedial goals, system design and operation can affect cost

and performance during remediation. System operation factors include the amount of time the

system is operational and the adequacy of the system design to handle the nature and extent of

the contaminants. For example, the long percentages of downtime for a system (see Exhibit 3-5)

or problems with system design can increase the cost of a site cleanup. Conversely, various

efforts in system optimization at a site (as detailed in Exhibit 3-7) can reduce the cost of a site

cleanup and/or improve the performance of a system. Described below are examples in which

system operation factors affected the cost or performance at case study sites.

System Downtime

At King of Prussia, the treatment system has been operational approximately 76 percent

of the time. Downtime has been caused by several factors, including the need to shut the

system down for two months to repair a crack in a filter, and has increased operating

costs.

System Optimization and Modification

After two years of operation, site engineers at Keefe performed an optimization study. As

a result, two new wells were installed at locations that would increase groundwater

extraction rates. Also, two existing wells were taken off line. Both extraction rates and

contaminant mass flux to the treatment system increased as a result of the modifications,

leading to more efficient capture of the plume.

When periodic groundwater monitoring results at MSWP indicated that aquifer cleanup

goals were met in five extraction wells, pumping from these wells was stopped and the

pumping rates from the other wells was adjusted to optimize system performance.
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

6-7

Additionally, the use of in situ technologies such as air sparging, ISB, and PRBs (see Exhibits 

3-2 and 3-4) can lower the cost and improve performance of a remedial system. Because only

seven of the case study sites used in situ technologies, and similar technologies were used at very

few of these sites, it is not possible to draw significant conclusions about the effect of using in

situ technologies on the cost and performance of groundwater cleanups. However, two specific

examples of the effects of using in situ technologies are described below.

At Intersil, the site owner replaced a P&T system that had been operating for eight years

with a PRB system. The PRB system continued to remove contaminant mass and reduce

concentrations of the contaminant in the aquifer, while minimizing the cost of treatment

and returning the site to sellable or leasable condition.

At Gold Coast, air sparging was used to mitigate elevated contaminant concentrations

around one well that was in a suspected source area. Once the contaminant levels in this

well were reduced, aquifer cleanup goals were able to be met, and the groundwater

remediation system at the site was able to be shut down.
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

6-8
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

7-1

7.0 REFERENCES

1. Cohen, R.M., J.W. Mercer, and R.M. Greenwald. 1998. EPA Ground Water Issue,

Design Guidelines for Conventional Pump-and-Treat Systems. EPA 540/S-97/504. 

<http://www.epa.gov/ada/issue.html>. September.

2. Federal Remediation Technologies Roundtable. 1998. Remediation Cost and

Performance Case Studies (28 total). <http://www.frtr.gov/cost/>. September.

3. Groundwater Remediation Technologies Analysis Center (GWRTAC). 1998. 

Remediation Technologies. <http://www.gwrtac.org/html/techs.html>. July.

4. EPA. 1998. Guide to Documenting and Managing Cost and Performance Information

for Remediation Projects, Revised Version. EPA 542-B-98-007. <http://www.frtr.gov> 

October.

5. EPA, Office of Emergency and Remedial Response (OERR). 1997. Cleaning Up the

Nation’s Waste Sites: Markets and Technology Trends. EPA 542-R-96-005. 

<http://www.clu-in.org>. April.*

6. U.S. Environmental Protection Agency (EPA), Office of Solid Waste and Emergency

Response (OSWER). 1997. Rules of Thumb for Superfund Remedy Selection. OSWER

Directive 9355.0-69, OSWER 9355.0-69, PB97-963301. EPA 540-R-97-013.

<http://www.epa.gov/superfund/resources/rules/index.htm>. August.*

7. EPA, OERR. 1996. Ground Water Cleanup at Superfund Sites. Directive 9283.1-11. 

EPA 540-K-96/008. <http://www.epa.gov/superfund/tools/gw/brochure.htm>. 

December.*

8. EPA, OERR. 1996. Presumptive Response Strategy and Ex Situ Treatment Technologies

for Contaminated Ground Water at CERCLA Sites: Final Guidance. Directive 9283.1-12. 

EPA 540/R-96/023. <http://www.epa.gov/superfund/resources/gwguide/gwfinal.pdf>. 

October.

9. EPA, OERR. 1993. Guidance for Evaluating the Technical Impracticability of

Groundwater Restoration. Directive 9234.2-25.

<http://www.epa.gov/swerffrr/doc/kjguide.htm>. September.

10. EPA, R.S. Kerr Environmental Research Laboratory and OSWER. 1992. Estimating

Potential for Occurrence of DNAPL at Superfund Sites. PB 92-963338. Publication

9355.4-07FS. <http://www.epa.gov/oerrpage/superfund/resources/gwdocs/estdnapl.pdf>. 

January.*

* Available from the U.S. Department of Commerce National Technical Information

Service, 5285 Port Royal Road, Springfield, Virginia 22151; 1(800)553-6847
Groundwater Cleanup: Overview of Operating Experience at 28 Sites

7-2