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Permeable Reactive Barriers, Permeable Treatment Zones, and Application of Zero-Valent Iron

Application

Application of Zero-Valent Iron

A-Zone Aquifer ZVI Permeable Reactive Barrier Project, Hookston Station Site, Pleasant Hill, California: Final Construction Report
GeoSierra Environmental, Inc.
California Regional Water Quality Control Board, San Francisco Bay Region. 45 pp, Sep 2009

An iron PRB was installed in 2009 at an off-site location near the Hookston Station site to degrade TCE, cis-1,2-DCE, VC, and 1,1-DCE in site groundwater and limit their migration downgradient. Constructed using azimuth-controlled vertical hydrofracturing technology, the PRB consists of one continuous reactive zone of ZVI ~480 feet in length and ~32 feet in vertical height.

Case Studies: Closing Solvent Sites Using Activated Carbon Impregnated with Iron
Harp, T.A., LT Environmental, Inc, Arvada, CO.
Proceedings of the Annual International Conference on Soils, Sediments, Water and Energy 14(18):217-228(2009)

BOS 100(r), an innovative remediation product, is an activated carbon impregnated with an iron salt and pyrolized into nano-sized deposits of porous, metallic iron. The carbon catalyst adsorbs chlorinated contaminants, and the iron provides treatment via reductive dechlorination. This paper presents three case studies of application to sites with dissolved-phase CVOCs to document the effectiveness of the technology. (1) Full-scale treatment of TCE in 2005 with staggered injections of the product. (2) Full-scale cleanup of PCE at a former drycleaner in 2008 with staggered injections of the product. (3) Injection of the carbon slurry in 2007 as a PRB to intercept a PCE plume at an active drycleaner.

Cost and Performance Report: Nanoscale Zero-Valent Iron Technologies for Source Remediation
A. Gavaskar, L. Tatar, and W. Condit
Environmental Security Technology Certification Program, CR-05-007-ENV, 54 pp, 2005.

Emulsified Zero-Valent Nano-Scale Iron Treatment of Chlorinated Solvent DNAPL Source Areas
T. Krug, S. O'Hara, M. Watling, and J. Quinn.
ESTCP Project ER-0431, 763 pp, 2010

A field demonstration/validation of EZVI injections to remediate chlorinated solvent DNAPL (PCE and daughter products) source zones was conducted in 2006 at Site 45, a former drycleaning facility at Marine Corps Recruit Depot, Parris Island, SC. EZVI promotes both abiotic and biotic degradation of contaminants. The demonstration also compared the efficacy of pneumatic injection versus direct injection for EZVI delivery. ESTCP Cost & Performance Report

Evaluation of the Propagation of Secondary Fractures from Hydraulic Fracture and Injection to Create a Treatment Zone in Low Permeability Fractured Clay Soils
Peace, C. and L.M. Austrins.
REMTECH 2010: The Remediation Technologies Symposium, Banff, AB, Canada, 20-22 Oct 2010. Environmental Services Association of Alberta, Edmonton, AB (Canada), 29 slides, 2010

At the site of a chemical production plant in operation since the 1950s, the subsurface was contaminated with a variety of chlorinated VOCs (unspecified). A soil fracturing and injection pilot study was carried out in a low-permeability, fractured silty clay till to introduce slow-release amendment into secondary fractures and create a remedial diffusion halo into the surrounding low-permeability clay till. Quantifying the propagation and relative location of secondary fractures, as well as determining the effective treatment zone, was a primary metric for successful application. A total of six locations at three depths, 12, 15, and 18 ft bgs were fractured, and a mixture of guar, ZVI, glycol, and breaker solution was injected. Effective emplacement in the treatment area occurred and was quantified spatially. This successful pilot allowed for the optimization of fracture geometry before implementation at a larger scale, and the technique has been applied to several other areas of the site.

In Situ Chemical Reduction (ISCR) Technology for Complete and Efficient Treatment of Freon and Chlorinated Solvents in Groundwater
J. Mueller.
NICOLE Technical Meeting, 4 November 2010, Brussels, Belgium. 12 pp with tables + 37 slides, 2010

The unique attributes of EHC ISCR technology for effective treatment of Freon and other chlorinated solvents were documented at a U.S. site affected by PCE, TCE, cis-1,2-DCE, 1,1-DCE, 1,1,1-TCA, 1,1-DCA, and various Freon compounds. After 84 days of treatment, the EHC systems showed excellent removal (>99%) of all the contaminants of interest, including all Freon compounds. This presentation provides details from this project as well as an overview of a large-scale EHC PRB configuration for treatment of carbon tetrachloride.

In Situ Remediation of PCE at a Site with Clayey Lithology and a Significant Smear Zone
Molin, J., J. Mueller, D. Hanson, T. Fowler, and T. Skrotzki.
Remediation Journal, Vol 20 No 3, p 51-62, 2010

This paper describes the pilot-scale demonstration of in situ chemical reduction (ISCR) technology using EHC(r) at the former Serry's Dry Cleaning site in Corvallis, OR. The groundwater was affected by chlorinated VOCs, primarily PCE, TCE, DCE, and vinyl chloride, at concentrations up to 22,000, 1,700, 3,100, and 7 ug/L, respectively, prior to treatment. EHC(r) combines a slow, controlled-release carbon source and ZVI for the anaerobic chemical reduction of CVOCs. Performance data are available for the 3-year period following the injections.

Jet-Assisted Injection of Nano-Scale, Zero-Valent Iron to Treat TCE in a Deep Alluvial Aquifer
Chang, P.R., A.D. Pantaleoni, and D.J. Shenk.
Proceedings of the Seventh International Conference on Remediation of Chlorinated and Recalcitrant Compounds (Monterey, CA; May 2010). Battelle Press, ISBN: 978-0-9819730-2-9, Paper & presentation D-098, 6 pp & 15 slides, 2010

An innovative injection approach was field-tested at a former aerospace manufacturing facility (Unidynamics, Goodyear, Arizona) to overcome significant challenges posed by the low permeability of the soil and depth of the contaminated groundwater. A 10,000-pound psi fracture lance injection tool was used to distribute nano-scale ZVI in a targeted injection interval between 108 to 118 ft bgs. Injection of 1,400 pounds of PolyMetallix(tm) was completed at two injection points spaced 15 ft apart over 3 days. Each injection point had a radius of 30 ft. Groundwater data showed a TCE mass removal efficiency of 82 to 96% within 2 weeks after completion of the injections.

Successful ISCR-Enhanced Bioremediation of a TCE DNAPL Source Utilizing EHC� and KB-1�
Peale, J.G.D., J. Mueller, and J. Molin.
Remediation Journal, Vol 20 No 3, p 63-81, 2010

Successful full-scale implementation of in situ chemical reduction (ISCR)-enhanced bioremediation of a TCE DNAPL source zone was conducted at an operating facility in Portland, OR. In the demonstration, concentrations of TCE were reduced rapidly to below the maximum contaminant level in less than 6 months following ISCR implementation using EHC® and bioaugmentation with the KB-1® consortium. EHC is a hydrophilic carbon/ZVI blend that promotes degradation of aliphatic hydrocarbons via microbial and abiotic pathways. The remedial action objective for the source area--TCE concentrations below 1% of the solubility limit, or 11,000 µg/L—was achieved in less than 12 months.

USA Defense Depot Memphis
U.S. EPA Region 4 Web site.

The most consistently detected VOC group of chemicals at concentrations above comparison criteria in the site media are CVOCs, such as TCE, PCE, 1,1,2,2-PCA, carbon tetrachloride, and chloroform. The final ROD (2004) for Dunn Field calls for excavation and off-site disposal of the contents of pits and burial trenches, SVE of principal-threat waste in the unsaturated subsurface soils, treatment of the groundwater CVOCs via injection of ZVI, and installation of a ZVI PRB to address high groundwater concentrations downgradient of Dunn Field. SVE operation began in the VOC-contaminated sand and gravel layer beneath source areas in July 2007. In situ thermal desorption (ISTD) began in the VOC-contaminated silty clay zone (top 30 ft) in May 2008. VOC removals for all remedies to date (soil and groundwater) totals ~9,000 pounds. A revised proposed plan and ROD amendment are planned for 2009 to document changes undertaken to achieve the remedial action objectives of the original ROD.

In Situ Reduction

Field Assessment of Carboxymethyl Cellulose Stabilized Iron Nanoparticles for In Situ Destruction of Chlorinated Solvents in Source Zones
He, F., D. Zhao, and C. Paul.
Water Research 44(7):2360-2370(2010)

CMC-stabilized ZVI nanoparticles (with trace Pd catalyst) were pilot tested for in situ destruction of CVOCs (PCE, TCE, and PCBs) that had been in groundwater for decades. The pilot site was located in a well-characterized secondary source zone of PCBs and CVOCs. The stabilized nanoparticle suspension was prepared on site. Rapid degradation of PCE and TCE was observed in both downgradient monitoring wells following each injection. Although CVOC concentrations gradually returned to their pre-injection levels after ~2 weeks, the injection of CMC-stabilized nanoparticles and the abiotic reductive dechlorination process appeared to boost subsequent long-term bio-dechlorination as PCE and TCE concentrations continued to decline after 2 weeks. Longer abstract Additional information: Field Report (2006), EPA Grant GR832373, Slide Presentation (2011)

Permeable Reactive Barriers

Cost and Performance Case Studies from the Federal Remediation Technologies Roundtable

An Assessment of Zero Valence Iron Permeable Reactive Barrier Projects in California
J. Muegge, California Department of Toxic Substances Control, Document 1219, 154 pp, 2008

A review of the performance of 10 PRBs installed primarily to address chlorinated contaminants indicates that a ZVI PRB should not be expected to provide near-term improvement of water quality very far below its installation. The same levels observed downgradient of a PRB before its installation can persist for extended periods (often decades) despite the presence of a PRB. The PRBs were installed at Alameda Naval Air Station, BP-Hitco, DuPont Oakley, Fairchild/Applied Materials, Intersil, Moffett Field, Mohawk Laboratory, Sierra Army Depot (2 separate PRBs), and Travis Air Force Base. Additional information: This report is summarized by J.P. Muegge and P.W. Hadley in a paper in Remediation Journal 20(1):41-57(2009).

Capstone Report on the Application, Monitoring, and Performance of Permeable Reactive Barriers for Ground-Water Remediation, Volume 1: Performance Evaluations at Two Sites
2003. R.T. Wilkin and R.W. Puls, U.S. EPA, National Risk Management Research Lab., Ada, OK. EPA 600-R-03-045a, 156 pp.

Capstone Report on the Application, Monitoring, and Performance of Permeable Reactive Barriers for Ground-Water Remediation, Volume 2: Long-Term Monitoring of PRBs � Soil and Ground Water Sampling
2003. C.J. Paul; M.S. McNeil; F.P. Beck, Jr.; P.J. Clark; R.T. Wilkin; R.W. Puls. EPA 600-R-03-045b, 145 pp.

Contamination Movement around a Permeable Reactive Barrier at Solid Waste Management Unit 12, Naval Weapons Station Charleston, North Charleston, South Carolina, 2009
Vroblesky, D.A., M.D. Petkewich, and K.J. Conlon.
U.S. Geological Survey Scientific Investigations Report 2010-5086, 84 pp, 2010

Chlorinated VOC (PCE, 1,1,1-TCA, TCE, cDCE, VC, 1,1-DCE, 1,2-DCA, and 1,1-DCA) groundwater contamination at SWMU 12 at the Naval Weapons Station Charleston, SC, is being addressed in part by a ZVI PRB 130 ft long and 3 ft wide installed in December 2002. In early 2004, groundwater contaminants began moving around the southern end of the PRB. USGS is monitoring and documenting the interaction of PRB and groundwater. Additional information: 2004-2006 Report 2006-2007 Report 2008 Report

DNAPL Remediation: Selected Projects Where Regulatory Closure Goals Have Been Achieved
EPA 542-R-09-008, 2009

The purpose of this paper is to highlight sites where dense nonaqueous phase liquid (DNAPL) source reduction has been demonstrated as an aid in meeting regulatory cleanup goals. The presence of DNAPL in the subsurface can serve as a long-term source of dissolved contaminant plumes in groundwater, making it more difficult to reach regulatory closure. However, once the DNAPL source is addressed, residual groundwater plumes may be more amenable to treatment, including less aggressive techniques such as monitored natural attenuation (MNA) or bioremediation. This paper updates the document, DNAPL Remediation: Selected Projects Approaching Regulatory Closure, prepared in 2004 by providing more recent information on technologies and on five additional selected sites at which DNAPL source reduction technologies were applied.

Demonstration of a Multifunctional Permeable Reactive Barrier for the Treatment of Landfill Leachate Contamination
T. Van Nooten, H. Sterckx, W. Boenne, L. Bastiaens, D. Dirickx, and P. Verkaeren.
In Situ and On-Site Bioremediation 2009: Proceedings of the 10th International In Situ and On-Site Bioremediation Symposium, 5-8 May, Baltimore, Maryland. Battelle Press, ISBN: 9780981973012, 2009

A pilot-scale multifunctional PRB (multibarrier) was designed and demonstrated at the Belgian landfill site Hooge Maey for semipassive treatment of landfill leachate containing ammonium and adsorbable organic halogens (AOX). The pilot-scale implementation employed a steel container 9 m in length containing different treatment compartments. AOX and COD were removed efficiently in a compartment filled with active carbon. Nitrification compartments equipped with diffusive oxygen emitters were present to effect microbial conversion of ammonium to nitrite, which in turn was converted to N2 in a downgradient denitrification compartment supplied with an external carbon source. Despite an efficient diffusive oxygen supply, ammonium removal in the nitrification compartments was low due to exceptionally cold winter temperatures that inhibited microbial activity. Nitrification and denitrification processes are expected to improve with increasing temperatures in spring. Remaining ammonium concentrations were removed mainly by ion exchange in a compartment filled with clinoptilolite until the material reached saturation. Potential in situ bioregeneration of the saturated clinoptilolite is being investigated. The multibarrier project has its own Web site with a project bibliography.

Design, Construction and Monitoring of a Permeable Reactive Barrier Technology for Use at Rocky Flats Environmental Technology Site (RFETS)
2000. Dwyer, Brian P., Sandia National Labs., Albuquerque, NM, Report No: SAND2000-2702. NTIS: DE00767720. 65 pp.

Design, Construction, and Monitoring of the Permeable Reactive Barrier in Area 5 at Dover Air Force Base
2000. Gavaskar, Arun; Neeraj Gupta; Bruce Sass; Woong-Sang Yoon; Robert Janosy, Battelle, Columbus, OH. Report No: AFRL-ML-WP-TR-2000-4546. NTIS: ADA380005. 399 pp.

Enhancements to Natural Attenuation: Selected Case Studies
T.O. Early (ed.).
WSRC-STI-2007-00250, 132 pp, 2007

Presents case studies of engineered covers; biostimulation and bioaugmentation to address trichloroethene (TCE) contamination at Cape Canaveral, FL; a ZVI PRB for TCE and chromate at the U.S. Coast Guard Support Center, Elizabeth City, NC; a full-scale mulch biowall for TCE at Offutt Air Force Base, NE; and a wetland enhancement/reactive mat for TCE, carbon tetrachloride, chloroform, and 1,1,2,2-tetrachloroethane at Aberdeen Proving Ground.

Evaluation of Permeable Reactive Barrier Performance
EPA 542-R-04-004, 2004

This report on the performance of permeable reactive barriers (PRB) for groundwater remediation was prepared under the auspices of the Federal Remediation Technologies Roundtable, a collaborative effort among federal agencies involved in hazardous waste site cleanup. Three United States (U.S.) government agencies, the Department of Defense (DoD), Department of Energy (DOE), and United States Environmental Protection Agency (EPA), as well as the Interstate Technologies and Regulatory Council (ITRC) contributed to the report, which is a concise summary of the conclusions and recommendations of the three agencies' individual studies at different sites.

Field Application of a Permeable Reactive Barrier for Treatment of Arsenic in Ground Water
R.T. Wilkin, S.D. Acree, D.G. Beak, R.R. Ross, T.R. Lee, and C.J. Paul.
EPA 600-R-08-093, 81 pp, 2008

In June 2005, a pilot-scale PRB containing granular iron was installed at a former metal smelting facility near Helena, MT, to treat ground water contaminated with concentrations (>25 mg/L) of arsenite and arsenate. The barrier is 9.1 m long, 14 m deep, and 1.8 to 2.4 m wide (in the direction of ground-water flow). Within the PRB, As concentrations are 2 to <0.01 mg/L. After 2 years of operation, significant decreases in As concentrations are evident. This report covers site characterization, remedial design and implementation, and monitoring results for this pilot-scale PRB. Additional information: (Wilkin et al. 2009, Abstract)

Field Applications of In Situ Remediation Technologies: Permeable Reactive Barriers
2002

This document summarizes technical data and lessons learned from profiles of more than 40 installations of permeable reactive barriers (PRBs) for ground-water remediation in the United States, Canada, and selected locations abroad. Included are data from ongoing and completed pilot- and full-scale PRB demonstrations and full-scale cleanups. More in-depth information about each of the sites included in this summary document is available on the RTDF web site.

Fry Canyon, UT, USGS Project Home Page

Three different PRBs were installed at the demonstration site in 1997, respectively containing Cercona Bone Char Phosphate, Cercona foamed ZVI pellets, and amorphous ferric oxide. The project will utilize geochemical and hydrologic approaches to assess the performance of the PRBs toward the long-term remediation of the Fry Canyon upgrade tailings site.

Field Demonstration of Permeable Reactive Barriers to Remove Dissolved Uranium from Groundwater, Fry Canyon, Utah, September 1997 through September 1998: Interim Report
Selected Hydrologic Data for the Field Demonstration of Three Permeable Reactive Barriers near Fry Canyon, Utah, 1996-2000

Handbook of Groundwater Remediation Using Permeable Reactive Barriers: Applications to Radionuclides, Trace Metals, and Nutrients
2002. David Naftz, et al. (eds.). Academic Press, San Diego, CA. ISBN: 0125135637, 550 pp.

This handbook offers numerous case studies to introduce the reader to current applications, innovations, and methods for using PRBs in the removal of inorganic contaminants from ground water.

In Situ Chemical Reduction (ISCR) Technologies: Significance of Low eH Reactions
J. Dolfing, M. Van Eekert, A. Seech, J. Vogan, and J. Muellers.
Soil & Sediment Contamination, Vol 17 No 1, p 63-74, Jan 2008

In March 2005, 22,000 kg of ISCR reagent was injected to form an 82-m PRB across a plume of dissolved-phase carbon tetrachloride (CT) about 150 m downgradient of the suspected source area. The ISCR reagent slurry was injected at 126 injection points advanced via direct push. By August 2006, CT concentrations had decreased from > 1,600 ppb to < 5 ppb, achieving > 99% removal.

An In Situ Permeable Reactive Barrier for the Treatment of Hexavalent Chromium and Trichloroethylene in Ground Water
D.W. Blowes, et al.
EPA 600-R-99-095a, EPA 600-R-99-095b, and EPA 600-R-99-095c, 1999.

In Situ Remediation Technology Status Report: Research and Application of Permeable Barriers
1998

This document is an attempt to compile worldwide research efforts and applications in the field of permeable reactive barriers (PRB). Research projects are organized by the type of contamination treated (organics or inorganics) and by the type of reaction process (sorption, precipitation, substitution, or degradation), and then by the specific material. Field projects are organized by state, province, or country.

In Situ Remediation Technology Status Report: Treatment Walls
EPA 542-K-94-004, 1994

Describes field demonstrations or full-scale applications of in situ abiotic technologies for nonaqueous phase liquids and ground water treatment.

Innovative Technology Evaluation Report: EnviroMetal Technologies, Inc., Metal-Enhanced Dechlorination of Volatile Organic Compounds Using an In-Situ Reactive Iron Wall
EPA 540-R-98-501, 1998. 110 pp.

Long-Term Groundwater Monitoring Optimization, Clare Water Supply Superfund Site, Permeable Reactive Barrier and Soil Remedy Areas, Clare, Michigan
EPA 542-R-07-010, 2007

This report contains a review of the long-term groundwater monitoring network for the Permeable Reactive Barrier (PRB) and Soil Remedy Areas at the Clare Water Supply Superfund Site in Clare, Michigan. The current monitoring network in each area was evaluated using a formal qualitative approach and statistical tools found in the Monitoring and Remediation Optimization System software (MAROS). The report also contains recommendations for the groundwater monitoring networks based the results of these qualitative and quantitative evaluations.

Long-Term Performance Assessment of a Permeable Reactive Barrier at Former Naval Air Station Moffett Field
A. Gavaskar, W.S. Yoon, J. Sminchak, B. Sass, N. Gupta, J. Hicks, and V. Lal.
Naval Facilities Engineering Service Center, Port Hueneme, CA. CR-05-006-ENV, 37 pp, 2005.

A pilot-scale PRB filled with zero-valent iron was installed at former Naval Air Station Moffett Field in April 1996 to address chlorinated organics in the ground water. It was monitored periodically for the next 8 years. This report describes the results of the last round of monitoring conducted in July 2004, the relationship of the recent results to those of previous rounds, and implications for the longevity and hydraulic performance of the PRB.

Long-Term Performance of Permeable Reactive Barriers Using Zero-Valent Iron: An Evaluation at Two Sites. Environmental Research Brief
2002. R.T. Wilkin, R.W. Puls, G.W. Sewell, U.S. EPA, Ada, OK. EPA 600-S-02-001, 19 pp.

Mine Waste Technology Program: Permeable Treatment Wall Effectiveness Monitoring Project, Nevada Stewart Mine
A.L. McCloskey.
EPA 600-R-06-153, 100 pp (plus appendices A-F, 282 pp), 2007

This project demonstrates the effectiveness of Apatite II™ (cleaned fishbone) to remove metals (zinc, iron, manganese, lead, and cadmium) from water flowing from a mining site.

Passive Reactive Barrier. Innovative Technology Summary Report
2002. U.S. DOE, Office of Environmental Management. DOE/EM-0623, 37 pp.

This report describes the performance of two PRBs installed at DOE's Oak Ridge Reservation in Tennessee.

Performance Assessment and Recommendations for Rejuvenation of a Permeable Reactive Barrier: Cotter Corporation's Canyon City, Colorado, Uranium Mill
DOE-LM/GJ816-2005, ESL-RPT-2005-02, 130 pp, 2005

A ZVI PRB was installed in 2000 to treat molybdenum and uranium at the currently operating Cotter Corporation mill site. Though the barrier eventually failed for Mo, U concentrations remained at less than 0.006 mg/L. The ZVI became clogged by mineral precipitants, and modifications (e.g., a pretreatment zone composed of coarse gravel and ZVI) were suggested. Given the conditions experienced at the PRB in 2003, Cotter evaluated the system at years' end and subsequently initiated pumping of upgradient groundwater to the site's primary impoundment.

Permeable Reactive Barrier Facility at the Bodo Canyon Disposal Cell, Durango, Colorado
U.S. DOE, Office of Legacy Management, Grand Junction, CO.

A PRB facility was constructed at the Durango, Colorado, Disposal Site in 1995 to test PRB designs for passive remediation of uranium-contaminated groundwater via treatment of contaminated tailings water (leachate) issuing from a seep into a subsurface engineered collection gallery and drained by gravity to a lined retention basin for treatment at the site's downgradient boundary. Several PRBs (ZVI, copper wool, and steel wool) were used to treat As, Mo, Se, U, V, and Zn. The ZVI barrier operated from August 1999 until June 2004, when flow ceased from the seep and remediation was no longer needed. It maintained effluent uranium concentrations of less than 0.01 mg/L, and was highly effective in treating contaminants.

Permeable Reactive Barrier at the Monticello Mill Tailings Site, Monticello, Utah
U.S. DOE, Office of Legacy Management, Grand Junction, CO.

In 1999, DOE installed a ZVI-containing PRB downgradient of the former uranium milling site at Monticello, UT. The PRB has been effective in reducing concentrations of As, Se, U, and V to nondetectable levels on the PRB's downgradient side, and Mo and nitrate to near nondetect. Soil-bentonite slurry walls direct groundwater to the PRB, but some contaminated groundwater is flowing around the south slurry wall. Methods that might be used to mend the gap on the south end of the slurry wall were investigated. There has been some evidence of barrier clogging, and chemical flushing of the barrier to remedy the clogging was investigated. In 2005, a supplemental treatment cell containing a mixture of ZVI and gravel was installed at the site. The project has generated the following reports:

Permeable Reactive Barriers Projects Page

Permeable Reactive Barriers for Inorganic and Radionuclide Contamination
2005

This document was prepared by Kate Bronstein, a National Network of Environmental Management studies grantee, under a fellowship from the U.S. Environmental Protection Agency. This paper is meant to be an updated reference for project managers, engineers, students, and others interested in a review of case studies of the instances where permeable reactive barriers have been used to remediate sites contaminated with inorganics and radionuclides. This paper mainly focuses on case studies, but a brief overview is given on topics such as: treatment media types, reactive processes, site characterization, configuration, and the nature of contamination.

Permeable Reactive Wall Remediation of Chlorinated Hydrocarbons in Groundwater: ESTCP Cost and Performance Report (CU-9604)
1999, ESTCP

Remediation of TNT and RDX in Groundwater Using Zero-Valent Iron Permeable Reactive Barriers: Cost and Performance Report
ESTCP, Project ER-0223, 66 pp, 2008

A mixed iron/sand PRB was installed to remove TNT and RDX contamination from groundwater at the Cornhusker Army Ammunition Plant near Grand Island, Nebraska. Performance was evaluated over a 20-month period. Installation costs for the pilot-scale barrier (50 ft long by 15 ft deep by 3 ft thick) were $138,000, ~$180 per square ft.

Report for Full-Scale Mulch Wall Treatment of Chlorinated Hydrocarbon-Impacted Groundwater
2004. Groundwater Services, Inc., Houston, TX. DTIC: ADA422621, 97 pp.

Technical Final Report: LIFE Project MULTIBARDEM, LIFE06 ENV/B/000359
VITO, Flemish Institute for Technological Research, 42 pp, 2010

A multibarrier consists of a site-tailored combination of different types of PRBs and reactive zones. This report describes 3 pilot studies of the multibarrier concept. Two separate multibarriers were installed at a landfill to treat leachate containing ammonium, COD, and AOX. The 5 sequential sections of multibarrier 1 (2008) included a clinoptilolite buffer for abiotic removal of ammonium (ion exchange), a nitrification/denitrification for removing ammonium, and sorption to remove AOC and COD. The system was installed in a container 9 meters in length that was partially installed in the subsurface. Via a controlling unit, groundwater was pumped through the system, and oxygen and a carbon source (butyrate) were added. The simplified multibarrier 2 (2009) had 3 sequential sections: 1) a sorption area to remove AOX and COD, 2) an aerobic biological nitrification area, and 3) an anoxic denitrification area. Multibarrier 3 (2008) was installed at an industrial site to address groundwater containing a mixture of chlorinated hydrocarbons via a combination of aerobic and anaerobic zones designed to degrade the mixture of chlorinated compounds. It incorporated (sequentially) pulse dosing of carbon source and a solid slow-release carbon source. See the final report at the bottom of the MULTIBARDEM project page.

Treatment of RDX & HMX Plumes Using Mulch Biowalls
C. Newell. ESTCP Project ER-0426, 77 pp, 2008

The field demonstration conducted at the Pueblo Chemical Depot in Colorado represents the first ever application of mulch PRBs for the treatment of explosives contamination in groundwater. The state-mandated, site-specific cleanup criteria of 0.55 ppb RDX and 602 ppb HMX was used as the project goal. A pilot-scale organic mulch/pea gravel biowall 100 ft long and 2 ft thick was installed using one-pass trenching. The PRB was in place by November 16, 2005, and all performance objectives were met by June 2006, when the system appeared to have reached a pseudo steady state. See also the ESTCP Cost and Performance Report

The Trench and Gate Groundwater Remediation System
1997. Marc W. Bowles, Master's thesis, University of Calgary, 250 pp.

The trench-and-gate PRB is a modified funnel-and-gate system suitable for installation in tills. Modifications include the addition of high hydraulic conductivity trenches along the upgradient side of the funnel walls and a reinfiltration gallery down-gradient of the treatment gate. Preferential groundwater flow through the added high permeability infrastructure prevents mounding and induces a capture zone both horizontally, and vertically larger than the cross-sectional funnel area. Coupled with bioremediation catalyzed by biosparging, or other remediation technologies, the system constitutes an economical, long-term, in situ method for contaminant plume capture and treatment, suitable for low to moderate permeability sediments. A prototype trench and gate was successfully installed at the East Garrington Gas Plant, Alberta, Canada.

Permeable Treatment Zones

Cost and Performance Case Studies from the Federal Remediation Technologies Roundtable

(The) Evolution of Field Application of Nano Scale Zero Valent Iron (nZVI) in a Deep Low Permeability Aquifer
Austrins, L.M.
REMTECH 2010: The Remediation Technologies Symposium, Banff, AB, Canada, 20-22 Oct 2010. Environmental Services Association of Alberta, Edmonton, AB (Canada), 29 slides, 2010

NZVI was selected as a test remedial application to reduce the mass contained in the source area at an EPA Superfund site located in Goodyear, AZ, the source of a 3-mile-long plume (TCE and perchlorate) in the groundwater. A bench test determined the percentage of nZVI to be applied in the first of 3 nZVI application pilot tests but failed to consider how to place the nZVI into the aquifer, with repercussions in the field pilot tests. In pilot test 1, low-pressure addition of a 21 g/L solution of nZVI (50 lbs nZVI) was applied before pressure refusal at 300 lbs prevented further addition of iron. Agglomeration was determined to be the limiting factor in application. Pilot test 2 involved a more complex mixing procedure, reduction of percent by weight of the nZVI solution to 2.5 g/L, addition of a dispersant (sodium hexametaphosphate), and immediate application to the subsurface after mixing. After addition of 2,700 gallons of solution to the aquifer, the net mass of nZVI applied to the aquifer was still 50 lbs upon pressure refusal and injection well plugging. Pilot test 3 utilized high-pressure fracture and injection pulsing techniques to deliver 8,000 gallons of 21 g/L nZVI (1,400 lbs nZVI) into the aquifer. Groundwater samples indicated both increases and decreases in TCE. Increases mainly in the immediate area of the injection points are attributed to fracturing improving the permeability of the target formation and releasing previously contained mass to the groundwater. TCE decreases correlate to chemical reduction of TCE and correspond to increases in both hydrogen and chloride concentrations. Lessons learned from the 3 pilot tests are informing the design of a larger scale application.

The Ashumet Pond Reactive Barrier
Massachusetts Military Reservation, Cape Cod.

A geochemical barrier was applied in the groundwater discharge zone of a kettle-hole pond to address the well-defined discharge of a dissolved phosphorus plume. In August 2004, ZVI was mixed into near-shore pond-bottom sediment (3% by weight) to a depth of about 0.6 m, extending 12.2 m offshore along 91.4 m of shoreline in the area of highest observed pond-bottom phosphorus. The sediment mixture was created by excavating the pond-bottom material while the pond was locally dewatered using a cofferdam and large pumps. An excavator mixing bucket blended the pond-bottom sediment and iron filings prior to placement of the mixture on the pond bottom. The ZVI barrier is ~300 ft long, 40 ft wide, and 3 ft thick. Excavation of the dewatered pond bottom provided a unique opportunity to install instrumentation for barrier performance monitoring. Monitoring the performance of a remediation system at this interface required adapting sampling strategies similar to those used in groundwater/surface-water interaction studies. Additional information: McCobb et al. 2009a, McCobb et al. 2009b

Attenuated Anaerobic Dechlorination of Groundwater Using HRC�. Mactec - Harding ESE: Demonstration Bulletin
U.S. EPA, Risk Management Research Laboratory, Cincinnati, OH.
EPA 540-R-08-003, 2 pp, 2008

An in situ PRB was designed that utilizes Hydrogen Release Compound (HRC�) to treat ground water contaminated with chlorinated compounds. A demonstration of this technology was conducted in 2000 near the Fisherville Mill brownfields site in South Grafton, MA, to determine its effectiveness in eliminating TCE and daughter products from the ground water. The cleanup criteria were not achieved at the downgradient monitoring wells over a period of 2 years despite extensive conversion of TCE to DCE.

Demonstration of In Situ Dehalogenation of DNAPL Through Injection of Emulsified Zero-Valent Iron at Launch Complex 34 in Cape Canaveral Air Force Station, Florida: Innovative Technology Evaluation Report
A. Gavaskar, W.-S. Yoon, M. Gaberell, E. Drescher, L. Cumming, J. Sminchak, J. Hicks, B. Buxton, M. Morara, T. Wilk, and L. Bahn.
EPA 540-R-07-006, 223 pp, 2004

The field demonstration of emulsified zero-valent iron (EZVI) technology for treatment of a TCE DNAPL source zone began at Launch Complex 34 in June 2002 and ended in January 2003. Long-term ground-water monitoring results collected in December 2003 and March 2004 indicate that the EZVI treatment had a long-lasting effect on the chlorinated contaminants in the subsurface. TCE, cis-1,2-DCE, and (eventually) VC levels declined sharply in the one year following EZVI injection, and ethene levels increased substantially.

Demonstration/Validation of Electrolytic Reactive Barriers for Treatment of Energetic Compounds in Groundwater at the Pueblo Chemical Depot (ESTCP ER-0519)
D Gilbert, T. Sale, and M. Petersen.
SERDP/ESTCP Partners in Environmental Technology Technical Symposium & Workshop, 2008

An e-barrier was installed at the Pueblo Chemical Depot (Pueblo, CO) to intercept groundwater affected by explosives constituents. The demonstration e-barrier consists of 15 individual panels of expanded titanium/mixed metal oxide mesh electrodes mounted to vinyl sheet pile. Power is supplied to the electrodes by a 2 kW solar power supply. Contaminated groundwater flowing through the e-barrier is subjected to two sequences of electrolytic oxidation/reduction for degrading the dissolved explosives and intermediates. At the current voltage setting (6.2 V), the system uses ~500 W total power. Performance monitoring will continue through fall 2008. July 2009 Update; January 2010 Update; ESTCP Cost & Performance Report

Development of Permeable Reactive Barriers (PRB) Using Edible Oils
R.C. Borden.
SERDP Project ER-1205, 159 pp, 2008

A detailed field pilot test was conducted to evaluate the use of an emulsified oil biobarrier to enhance the in situ anaerobic biodegradation of perchlorate and chlorinated solvents in groundwater. The biobarrier was installed by injecting 380 L of commercially available soybean oil-in-water emulsion through 10 direct-push injection wells over a 2-day period. Field monitoring results over a 2.5 year period following emulsion injection indicates the oil injection generated strongly reducing conditions in the oil-treated zone with depletion of dissolved oxygen, nitrate, and sulfate, and increases in dissolved iron, manganese, and methane. Perchlorate at 3,100 to 20,000 µg/L was degraded to below detection (<4 µg/L) in the injection and nearby monitor wells within 5 days of injection. Two years after the single emulsion injection, perchlorate was less than 6 µg/L in every downgradient well compared to an average upgradient concentration of 13,100 µg/L. Emulsion injection stimulated reductive dechlorination of 1,1,1-TCA, PCE, and TCE during groundwater migration through the biobarrier but did not reduce them to target treatment levels.

Edible Oil Barriers for Treatment of Chlorinated Solvent Contaminated Groundwater
M.T. Lieberman and R.C. Borden.
ESTCP Project ER-0221, 228 pp, 2009

A pilot test was conducted between 2003 and 2007 at Charleston Naval Weapons Station, SC, to evaluate the effectiveness of EOS�, a commercially available emulsified oil substrate, for enhancing the biodegradation of dissolved-phase chlorinated VOCs in groundwater and aquifer material in a treatment cell. The cell contained 4,000 cubic ft of contaminated aquifer material with up to 16,000 �g/kg TCE in soil and >20,000 �g/L TCE in groundwater. Phase I involved site characterization, baseline sampling, EOS injection, and monitoring for 28 months. Phase II involved a bench-scale treatability study, development and injection of a newly formulated pH-buffered substrate to overcome a pH problem, and an additional 11 months of monitoring to measure the effect of the second substrate. The buffered EOS raised the pH and alkalinity of the aquifer, which allowed the native dehalorespiring populations to re-initiate their metabolism of TCE and DCE and biodegrade TCE throughout the test cell. Over the entire 41-month monitoring period in Phases I and II, the total chlorinated VOC concentration decreased from 198 �M to 17 �M, a decline of 91%. See also the ESTCP Cost and Performance Report.

Edible Oil Barriers for Treatment of Perchlorate Contaminated Groundwater
2005

This final technical report documents the demonstration of emulsified edible oil barriers for groundwater remediation at a confidential perchlorate site in Maryland. The general purpose of the demonstration was to evaluate the efficacy of emulsified oils for treating perchlorate contaminated groundwater. A second demonstration was performed as part of this project to evaluate the use of emulsified oils for remediation of chlorinated solvent impacted groundwater at the Charleston Naval Weapons Station (NWS) in South Carolina. The work at the Charleston NWS is still ongoing and will be reported separately. In addition, a technical protocol document is being written under this demonstration project which describes in detail the use of emulsified oils for enhanced anaerobic bioremediation of perchlorate and chlorinated solvents. See also the Technical Report Addendum (2008) and the ESTCP Cost and Performance Report.

Electrically Induced Redox Barriers for Treatment of Groundwater
T. Sale, M. Petersen, and D. Gilbert.
Environmental Security Technology Certification Program (ESTCP), CU-0112, NTIS: ADA438421, 187 pp, 2005

Closely spaced permeable electrodes can be installed through a ground-water contaminant plume in the format of a permeable reactive barrier, called an e-barrier. An e-barrier was installed at F.E. Warren Air Force Base in August 2002 in the path of a shallow alluvial TCE plume. This report documents results from a three-year collaboration between ESTCP and Colorado State University on the development and testing of this innovative electrolytic approach for managing redox-sensitive contaminants in ground water. According to the Final Report Addendum (2008), the initial project was completed in March 2005, and two additional studies were conducted: screening of titanium-mixed metal oxide electrodes for e-barriers (2003-2005) and extended operation of the e-barrier field demonstration for TCE remediation at F.E. Warren AFB (2004-2006).

FY2003 Annual Summary Report for the In Situ Redox Manipulation Operations
R.F. Raidl and G.G. Kelty.
DOE/RL-2004-06, OSTI: DE00825446, 85 pp, May 2004

This progress and performance report discusses the in situ redox manipulation (ISRM) interim remedial action at the Hanford 100-HR-3 Operable Unit to address the hexavalent chromium plume in the southwest portion of the 100-D Area. Implementation of the ISRM technology involves creating a permeable subsurface treatment zone by injecting sodium dithionite into the aquifer, which creates a chemically reduced environment. Hexavalent chromium passing through the treatment zone is reduced to less toxic and less mobile trivalent chromium.

Field Study of Enhanced TCE Reductive Dechlorination by a Full-Scale Whey PRB
Semkiw, E.S. and M.J. Barcelona.
Ground Water Monitoring & Remediation 31(1):68-78(2011)

At an industrial site located near Battle Creek, Michigan, a full-scale PRB 81 m wide was configured by injection of dairy whey in the downgradient region of a contaminant source zone to enhance the in situ biodegradation of high concentrations (102 to 103 �g/L) of chlorinated ethenes. Ten biannual whey injections were completed in a 3.5-year pilot phase and 1.5-year operational phase, achieving significantly improved and sustained dechlorination at extraction/injection and downgradient wells. The authors discuss carbon substrate cost comparisons and implications for efficient in situ treatment design. Longer abstract

Fracture-Emplacement and 3-D Mapping of a Microiron/Carbon Amendment in TCE-Impacted Sedimentary Bedrock
Bures, G.H., J.A. Skog, D. Swift, J. Rothermel, R. Starr, and J. Moreno.
Proceedings of the Seventh International Conference on Remediation of Chlorinated and Recalcitrant Compounds (Monterey, CA; May 2010). Battelle Press, ISBN: 978-0-9819730-2-9, Paper & presentation D-067, 9 pp + 23 slides, 2010

An in situ pilot remediation project was carried out on behalf of the U.S. Army Corps of Engineers (Omaha District) at the F.E. Warren AFB in Colorado. The pilot featured an innovative application of drilling, fracture emplacement, treatment, and geophysical technologies to mitigate impacts from chlorinated solvents. The former missile site complex is underlain by silty sandstone bedrock sediments affected by TCE >2,000 µg/L and associated VOCs. Pilot tests of biotic and abiotic in situ chemical reduction (ISCR) were conducted in the source area and dissolved plume to evaluate technology performance prior to developing the proposed remedy. The pilot involved the emplacement of over 100 tons of EHC^™, a micro-iron/complex-carbon treatment amendment, into deep bedrock sediments to attain optimal distribution throughout the contaminant plume, including beneath the former Launch and Service Building. The radius of fracture emplacement in the bedrock was up to 60 ft, with a typical fracture overlap of 30 to 50%. Following placement of the amendment, physical, chemical, and microbiological processes combined to create very strong reducing conditions that stimulated chemical and microbiological dehalogenation of the contaminants. View longer abstract. Additional information: Presentation Slides, Field Profile

Hydrogen Release Compound (HRC�) Barrier Application at the North of Basin F Site, Rocky Mountain Arsenal: Innovative Technology Evaluation Report
EPA 540-R-09-004, 95 pp, 2009

The primary objective of the evaluation in the plume study area was to determine the ability of the technology to reduce concentrations of the following contaminants: di-isopropylmethylphosphonate (DIMP), chlorophenylmethyl sulfide, chlorophenylmethyl sulfone, dieldrin, dicyclopentadiene (DCPD), chloroform, methylene chloride, and PCE. Benzene, TCE, 1,2-dibromo-3-chloropropane, and n-nitroso-dimethylamine were also evaluated. Results showed decreasing trends for PCE, TCE, DIMP, DCPD, and benzene.

In Situ Bioremediation of MTBE in Groundwater
P. Johnson, C. Bruce, and K. Miller.
TR-2222-ENV, 118 pp, 2003

A biologically reactive ground-water flow-through barrier (a 'biobarrier') was established at the Naval Base Ventura County, Port Hueneme, CA, to prevent further contamination of ground water by MTBE leaching from gasoline-contaminated soils. The biobarrier was installed downgradient of a gasoline-spill source zone. Ground water containing dissolved MTBE flowed to and through the biobarrier, and the microorganisms in the treatment zone converted MTBE to carbon dioxide and water. Gas injection wells were installed to introduce oxygen into the treatment zone.

In Situ Chemical Reduction of Cr(VI) in Groundwater Using a Combination of Ferrous Sulfate and Sodium Dithionite: A Field Investigation
R.D. Ludwig, C. Su, T.R. Lee, R.T. Wilkin, S.D. Acree, R.R. Ross, and A. Keeley.
Environmental Science & Technology, Vol 41 No 15, p 5299-5305, 2007

A field study was conducted to evaluate the performance of an in situ redox zone for the treatment of a dissolved-phase hexavalent chromium (Cr[VI]) plume at a former industrial site. The in situ redox zone was created by injecting a blend of 0.2M ferrous sulfate and 0.2M sodium dithionite into the path of the plume within a shallow, unconfined aquifer formation of medium-to-fine sand. Monitoring data collected over a period of 1,020 days after more than 100 m of linear ground-water flow through the treatment zone indicated sustained treatment of dissolved-phase Cr(VI) from initial concentrations between 4 and 8 mg/L to less than 0.015 mg/L.

In Situ Reactive Zones (IRZ) Data Sheet
U.S. Navy, Naval Facilities Engineering Command, Environmental Restoration Technology Transfer, Multimedia Training Tools website, 16 pp, 2005.

In Situ Redox Manipulation Permeable Reactive Barrier Emplacement: Final Report, Frontier Hard Chrome Superfund Site, Vancouver, WA
V.R. Vermeul, M.L. Rockhold, B.N. Bjornstad, J.E. Szecsody, C.J. Murray, M.D. Williams, D.R. Newcomer, and Y. Xie.
PNWD-3361, 107 pp + separate appendices, 2004

This report documents results from the emplacement of an in situ redox manipulation (ISRM) treatment zone for the remediation of chromate-contaminated ground water. Additional information: Groundwater Monitoring Network Optimization (2007); 5-Year Review (2008).

Nease Chemical Site, Columbiana County, Ohio - Technology Update #2: Nanotechnology
U.S. EPA Region 5, 2 pp, June 2007

A field study was conducted at the site in November 2006 to confirm the effectiveness of injecting nanoscale zero-valent iron (NZVI) to treat highly contaminated ground water in fractured sedimentary bedrock and to support the design of the full-scale treatment approach. One hundred kg of NZVI in 2,665 gallons of clean water were injected into a highly contaminated portion of the aquifer. The iron was injected in batches containing powdered soy as an organic dispersant, and most batches contained a small amount of palladium. Substantial reductions of PCE (38 to 88% of initial concentrations) and TCE (30 to 70%) were noted in all wells.

Remediation System Evaluation (RSE), Moss-American Superfund Site, Milwaukee, Wisconsin
U.S. EPA, Office of Solid Waste and Emergency Response.
EPA 540-R-11-018, 60 pp, 2011

The 88-acre site comprises a former wood treating facility plus several miles of the Little Menomonee River and its adjacent floodplain. The facility used creosote for wood preservation, and site contaminants include anthracene, benzene, benzo(a)pyrene, benzo(b)fluoranthene, chrysene, fluoranthene, fluorene, naphthalene, and pyrene. The groundwater remedy consists of a funnel-and-gate system to capture and treat the contaminated groundwater prior to discharge to the Little Menomonee River. A sheet-pile containment wall funnels the groundwater through two sets of treatment gates. These permeable treatment zones consist of an area backfilled with a mixture of clean sand/soil pierced by a line of injection wells at the upgradient edge of the gate area. A solution containing potassium nitrate and potassium phosphate was added at Gate 1 from June 2001 through October 2002 using, but nutrient augmentation was discontinued due to inconclusive evidence that it enhanced biodegradation. Air injection has been the only treatment since that time. This report focuses on optimizing system performance and addressing the stagnant groundwater zone that is limiting flow through the treatment gates and elevated contaminant concentrations in the vicinity of one monitoring well. This report provides a brief background on the site and then discusses current operations and recommendations for changes, with potential cost impacts.

Remediation of Explosives in Groundwater Using Zero-Valent Iron In Situ Treatment Wells
R. Johnson and P. Tratnyek.
ESTCP, Project ER-0223, 48 pp, 2008

This report describes the advantages and limitations of a treatment approach for explosives contamination in groundwater tested at Cornhusker Army Ammunition Plant. Granular iron was placed outside of the screens in a pair of dual-screened wells and groundwater circulation was promoted between the wells. Water circulated between the two treatment wells relatively quickly, and explosives concentrations decreased. The cost of each of the two wells was approximately $40,000.

Additional Information Bibliography

McCobb, T.D., D.R. LeBlanc, and A.J. Massey. 2009a. Monitoring the removal of phosphate from ground water discharging through a pond-bottom permeable reactive barrier. Ground Water Monitoring and Remediation 29(2):43-55.

McCobb, T.D., D.R. LeBlanc, L.A. Parsons, and J.G. Blount. 2009b. Distribution of Treated-Wastewater Constituents in Pore Water at a Pond-Bottom Reactive Barrier, Cape Cod, Massachusetts. USGS Scientific Investigations Map 3078, 1 sheet.

Wilkin, R.T., S.D. Acree, R.R Ross, D.G. Beak, and T.R. Lee. 2009. Performance of a Zero-Valent Iron Reactive Barrier for the Treatment of Arsenic in Groundwater: Part 1. Hydrogeochemical Studies. Journal of Contaminant Hydrology 106(1-2):1-14.

U.S. EPA Contaminated Site Cleanup Information (CLU-IN)

Permeable Reactive Barriers, Permeable Treatment Zones, and Application of Zero-Valent Iron

Application