Optimizing remediation strategies for a former dry‐cleaner site

Residual tetrachloroethene (PCE) contamination at the former Springvilla Dry Cleaners site in Springfield, Oregon, posed a potential risk through the vapor intrusion, direct contact, and off‐site beneficial groundwater uses. The Oregon Department of Environmental Quality utilized the State Dry Cleaner Program funds to help mitigate the risks posed by residual contamination. After delineation activities were complete, the source‐area soils were excavated and treated on‐site with ex situ vapor extraction to reduce disposal costs. Residual source‐area contamination was then chemically oxidized using sodium permanganate. Dissolved‐phase contamination was subsequently addressed with in situ enhanced reductive dechlorination (ERD). ERD achieved treatment goals across more than 4 million gallons of aquifer impacted with PCE concentrations up to 7,800 micrograms per liter prior to remedial activities. The ERD remedy introduced electron donors and nutrient amendments through groundwater recirculation and slug injection across two aquifers over the course of 24 months. Adaptive and mass‐targeted strategies reduced total remedy costs to approximately $18 per ton within the treatment areas. © 2010 Wiley Periodicals, Inc.     

Successful application of monitored natural attenuation in a surficial aquifer

Groundwater investigations conducted since 1988 at a Tennessee Department of Environment and Conservation (TDEC) Voluntary Oversight and Assistance Program (VOAP) site located in Millington, Tennessee, have defined the lateral and vertical extent of site chemicals of concern (COCs) consisting of tetrachloroethene (PCE), trichloroethene (TCE), and associated degradation products. Results of a groundwater remedial investigation determined that aquifer conditions were favorable for anaerobic degradation of COCs through reductive dechlorination. A subsequent groundwater feasibility study determined that monitored natural attenuation (MNA) coupled with long‐term groundwater monitoring was the most effective and suitable remedial option for the site. A Record of Decision was issued by the TDEC VOAP approving MNA and long‐term groundwater monitoring as the remedial option for the site, a first for such a site in Tennessee involving chlorinated organics. A groundwater fate and transport model (the 1998 model) developed during the RI was used as the basis for the MNA remedy. Analytical data from 1998 to 2008 indicate COCs in former high‐concentration areas continue to degrade at rates consistent with or ahead of the 1998 model predictions. Evidence of reductive dechlorination is also supported by the continued presence of breakdown products—specifically, vinyl chloride and ethene (terminal endpoint of PCE breakdown through reductive dechlorination). The continued detection of breakdown products along the flow‐path wells also confirms the effectiveness of the MNA remedy at the site. Current analytical data indicate that COC plumes beneath the site are not migrating and are actually retracting. © 2010 Wiley Periodicals, Inc.     

In situ soil stabilization for source control of a lithium and bromate groundwater plume

Historic mineral ore processing operations at the former Cyprus Foote Mineral Site located in East Whiteland Township, Pennsylvania, have resulted in the creation of an approximately 10,000‐foot‐long off‐site groundwater plume impacted with lithium and bromate. The plume emanating from the site is impacting the groundwater quality of downgradient private residences. As an early part of the remedial implementation, the private residences were provided with public water connections while the source control efforts were being designed and implemented. Bromate and lithium have recently emerged as groundwater contaminants subjected to increased regulatory scrutiny. This is evidenced in a recently lowered Federal Maximum Contaminant Level (MCL) for bromate of 0.010 milligrams per liter and a Medium‐Specific Concentration (MSC) of 0.005 mg/L for lithium recently proposed by the Pennsylvania Department of Environmental Protection (PADEP) for all groundwater within the Commonwealth. Elevated concentrations for bromate and lithium were detected above the Proposed Remediation Goals (PRGs) for the site, MCLs, and MSCs at a distance of 7,300 feet and 9,200 feet from the source area, respectively. To reduce the contaminant concentrations within the groundwater plume, which will ultimately result in a regressing plume, and to enable the Brownfield redevelopment of this Superfund site, auger‐based, in situ soil stabilization (ISS) with depths of up to 75 feet below ground surface (bgs) was selected as the remedy. The remedial implementation required the temporary removal and relocation of over 100,000 cubic yards of overburden to expose the lithium‐bearing tailings prior to treatment. Using customized 90‐foot‐long, 9‐foot‐diameter augers attached to cranes and drilling platforms, ancillary support excavators, and approximately 21,000 tons of reagent; 2,019 ISS columns were advanced to depths ranging from 10 to 74 feet bgs. This resulted in the creation of an in situ low‐permeablity 117,045‐yd³ “quasi‐monolith,” which encompasses a lateral extent of approximately three acres. The integration of a comprehensive ISS design with a comprehensive long‐term groundwater‐monitoring plan ensured the success of the ISS implementation and will enable a continued evaluation of the off‐site groundwater quality. © 2009 Wiley Periodicals, Inc.     

Use of mixed technologies to remediate chlorinated DNAPL at a Brownfields site

A former chlorofluorocarbon manufacturing facility in northern New Jersey was purchased for redevelopment as a warehousing/distribution center as part of the New Jersey Department of Environmental Protection's Brownfields redevelopment initiative. Soil and groundwater at the site were impacted with dense nonaqueous‐phase liquids (chlorinated organic compounds) and light nonaqueous‐phase liquids (petroleum hydrocarbons). The initial remedial strategy (excavation and offsite disposal) developed by prior site owners would have been cost‐prohibitive to the new site owners and made redevelopment infeasible. Mixed remedial technologies were employed to reduce the cost of remediation while meeting regulatory contaminant levels that are protective of human health and the environment. The most heavily impacted soils (containing greater than 95 percent of the contaminant mass) were excavated and treated onsite by the addition of calcium oxide and lime kiln dust coupled with physical mixing. Treated soils were reused onsite as part of the redevelopment. Residual soil and groundwater contamination was treated via in situ injections of emulsified oil to enhance anaerobic biodegradation, and emulsified oil/zero‐valent iron to chemically reduce residual contaminants. Engineering (cap) and administrative (deed restriction) controls were used as part of the final remedy. The remedial strategy presented in this article resulted in a cost reduction of 50 percent of the initial remedial cost estimate. © 2008 Wiley Periodicals, Inc.     

Historical analysis of monitored natural attenuation: A survey of 191 chlorinated solvent sites and 45 solvent plumes

A survey of experts in the application of natural attenuation was conducted to better understand how monitored natural attenuation (MNA) is being applied at chlorinated solvent sites. Thirty‐four remediation professionals provided general information for 191 sites where MNA was evaluated, and site‐specific data for 45 chlorinated solvent plumes being remediated by MNA. Respondents indicated that MNA was precluded as a remedy at only 23 percent of all sites where evaluated as a remedial option. Leading factors excluding MNA as a remedial approach were the presence of an expanding plume and an unreasonably long estimated remediation time frame. MNA is being used as the sole remedy at about 30 percent of the sites, and 33 percent are implementing MNA in conjunction with source zone remediation. The remaining sites are implementing MNA with plume remediation (13 percent), source containment (9 percent), or some other strategy (16 percent). © 2004 Wiley Periodicals, Inc.     

A practical approach to steam‐enhanced dual‐phase extraction: A case study

This article presents the results of a pilot test that was conducted to determine the effectiveness of using steam‐enhanced dual‐phase extraction (DPE) at a former industrial site in New York. The pilot test proved that steam‐enhanced DPE was very effective at removing significant contaminant mass from the subsurface in a relatively short time period. Concentrations of volatile organic compounds and semivolatile organic compounds in the vapor stream and groundwater were successfully reduced, in some cases by orders of magnitude. Based on the results of the steam‐enhanced DPE pilot test, the final remedy for the site includes implementing this technology at selected areas as an alternative to DPE alone or other remedial alternatives, such as excavation or groundwater pump and treat. © 2003 Wiley Periodicals, Inc.     

Biogeochemical gradients as a framework for understanding waste‐site evolution

The migration of biogeochemical gradients is a useful framework for understanding the evolution of biogeochemical conditions in groundwater at waste sites contaminated with metals and radionuclides. This understanding is critical to selecting sustainable remedies and evaluating sites for monitored natural attenuation, because most attenuation mechanisms are sensitive to geochemical conditions, such as pH and redox potential. Knowledge of how gradients in these parameters evolve provides insights into the behavior of contaminants with time and guides characterization, remedy selection, and monitoring efforts. An example is a seepage basin site at the Savannah River Site in South Carolina where low‐level acidic waste has seeped into groundwater. The remediation of this site relies, in part, on restoring the natural pH of the aquifer by injecting alkaline solutions. The remediation will continue until the pH upflow of the treatment zone increases to an acceptable value. The time required to achieve this objective depends on the time it takes the trailing pH gradient, the gradient separating the plume from influxing natural groundwater, to reach the treatment zone. Predictions of this length of time will strongly influence long‐term remedial decisions. © 2008 Wiley Periodicals, Inc.     

Quantitative analysis of remedial approaches,costs, and time required to remediate dry cleaner sites

This article presents an analysis of remedial approaches, costs, and time required to remediate dry cleaner sites in the United States based on data compiled by the State Coalition for the Remediation of Dry Cleaners (SCRD). Trends in soil and groundwater remedy selection are identified and discussed. Median costs and the time required to remediate dry cleaner sites are presented. In addition, median costs and the duration of soil and groundwater remediation for the most widely used remedial approaches are reported. The analysis is intended to serve the needs of stakeholders, including responsible parties, consultants, regulators, and litigants, as well as real estate developers, banks, and other holders of portfolios of impacted dry cleaner sites by providing quantitative results useful for planning and transactional analysis. © 2011 Wiley Periodicals, Inc.     

Evaluating a Site for Natural Attenuation: EPA Region IV's New Guidance

Natural attenuation has recently been recognized by the U.S. Environmental Protection Agency (EPA) as an appropriate remedy for sites contaminated with chlorinated solvents. Because natural attenuation does not require active remediation, it is considerably less expensive than other groundwater remedies. However, as laid out in EPA's recently released guidance, careful, systematic evaluation of natural attenuation must be conducted to ensure that the remedial approach is appropriate for a given site. The guidance requires that data be collected to demonstrate that natural attenuation is occurring and a fate-and-transport model must be conducted to estimate the extent to which a contaminated plume will ultimately migrate. Finally, the proponent of natural attenuation must be prepared to conduct long-term groundwater monitoring to verify that natural attenuation is controlling plume migration and that human health and the environment are not adversely affected.     

Insufficient source area remediation results in the rebound of TCE breakdown products in groundwater

In the early 1990s, a soil removal action was completed at a former disposal pit site located in southern Michigan. This action removed waste oil, cutting oil, and chlorinated solvents from the unsaturated zone. To contain groundwater contaminant migration at the site, a groundwater pump‐and‐treat system comprised of two extraction wells operating at a combined flow of 50 gallons per minute, carbon treatment, and a permitted effluent discharge was designed, installed, and operated for over 10 years. Groundwater monitoring for natural attenuation parameters and contaminant attenuation modeling demonstrated natural attenuation of the contaminant plume was adequate to attain site closure. As a result of incomplete contaminant source removal, a rebound of contaminants above the levels established in the remedial action plan (RAP) has occurred in the years following system shutdown and site closure. Groundwater concentrations have raised concerns regarding potential indoor air quality at adjacent residential properties constructed in the past 9 to 10 years. The only remedial option available in the original RAP is to resume groundwater pump‐and‐treat. To remediate the source area, an alternate remediation strategy using an ozone sparge system was developed. The ozone sparge remediation strategy addresses the residual saturated zone contaminants beneath the former disposal pit and reestablishes site closure requirements without resumption of the pump‐and‐treat system. A pilot study was completed successfully; and the final system design was subsequently approved by the Michigan Department of Environmental Quality. The system was installed and began operations in July 2010. As of the January 2011 monitoring event, the system has shown dramatic improvement in site contaminant concentrations. The system will continue to operate until monitoring results indicate that complete treatment has been obtained. The site will have achieved the RAP objectives when the system has been shut down and meets groundwater residential criteria for four consecutive quarters. © 2011 Wiley Periodicals, Inc.     

Creosote DNAPL Recovery‐Well Design for Mass Removal

Sites with dense nonaqueous‐phase liquid (DNAPL) contamination present significant remediation challenges in terms of technical practicability and cost. Remedial approaches to DNAPL sites often follow a management approach rather than removal or eradication approaches, particularly due to the uncertainties associated with the benefits of partial source mass removal, as complete source removal is unlikely. Mass‐removal technologies should be evaluated for all DNAPL sites, although implementation of recovery technologies will be limited to a few sites based upon site‐specific factors. Sitewide remedial strategies that employ source reduction, where applicable, and incorporate associated risk‐reduction technologies, including monitored natural attenuation, are advised. Creosote DNAPL sites are particularly challenging, as they are predominantly composed of low‐solubility polycyclic aromatic hydrocarbons that form long‐term continuing sources. Additionally, the physical properties of creosote DNAPL, including high viscosity and relatively low density, result in significant migration potential and considerable dissolved‐phase groundwater impacts. An innovative creosote DNAPL source recovery well design was developed to achieve separate‐phase removal of pooled creosote DNAPL. The design presented herein employs modified circulation‐well technology to mobilize DNAPL to the engineered recovery well, where it is gravity‐settled into a sump to permit separate‐phase mass removal of the emplaced DNAPL source without groundwater production or treatment. A discharge mass flux protocol was developed to verify dissolved‐phase plume stability and the benefit of the source mass removal. © 2013 Wiley Periodicals, Inc.     

In situ biofilm barriers: Case study of a nitrate groundwater plume,Albuquerque, New Mexico

A new use for biofilm barriers was developed and successfully applied to treat nitrate‐contaminated groundwater down to drinking water standards. The barrier was created by stimulating indigenous bacteria with injections of molasses as the carbon donor and a combination of yeast extract and trimetaphosphate as nutrients. This injection of amendments results in bacterial growth in the aquifer, which attaches to the sand grains to create a reactive semipermeable biofilm. The biofilm barrier presented in this article reduced the migration of contaminants and provided an active zone for remediation. The cylindrical biobarrier was constructed using eight wells on the perimeter forming a 60‐foot‐diameter reactive biodenitrification region. Another well at the center was installed to continuously extract the treated water. The intent was to produce a continuous source of nitrate‐free water. The system operated for over one year, and during this period, the biobarrier was revived multiple times by reinjecting molasses in the perimeter wells. Nitrate concentrations of treated water decreased from 275 mg/L (as nitrogen) to < 1 mg/L. © 2005 Wiley Periodicals, Inc.     

Metrics for integrating sustainability evaluations into remediation projects

The US Sustainable Remediation Forum (SURF) created a compilation of metrics (Metrics Toolbox) in response to a need for a broad set of metrics that could be used to assess and monitor the effectiveness of remedies in achieving sustainability goals. Metrics are the key impacts, outcomes, or burdens that are to be assessed or balanced to determine the influences and impacts of a remedial action. Metrics can reflect any of the three aspects of sustainability (i.e., environmental, social, or economic) or a combination of these aspects. Regardless, metrics represent the most critical sustainable outcomes from the perspective of the key stakeholders. The Metrics Toolbox is hosted online at www.sustainableremediation.org/library/guidance‐tools‐and‐other‐resources . By selecting metrics from the Metrics Toolbox as a starting point and considering a potentially wider suite of metrics in remedial program decisions, appropriate assessments can be made. Qualitative and quantitative metrics are tabulated for each remedial phase: remedial investigation, remedy selection, remedial design, remedial construction, operation and maintenance, and closure. Attributes for each metric are described so that remediation practitioners and key stakeholders can view the universe of metrics available and select the most relevant, site‐specific metrics for a particular site. For this reason, SURF recommends that remediation practitioners consider the metrics compiled in the Metrics Toolbox as a companion to the sustainable remediation framework published elsewhere in this journal and other sustainability evaluations. © 2011 Wiley Periodicals, Inc.     

Life‐cycle assessment of in situ thermal remediation

A detailed cradle‐to‐grave life‐cycle assessment (LCA) of an in situ thermal treatment remedy for a chlorinated‐solvent‐contaminated site was performed using process LCA. The major materials and activities necessary to install, operate, monitor, and deconstruct the remedy were included in the analysis. The analysis was based on an actual site remedy design and implementation to determine the potential environmental impacts, pinpoint major contributors to impacts, and identify opportunities for improvements during future implementation. The Electro‐Thermal Dynamic Stripping Process (ET‐DSP?) in situ thermal technology coupled with a dual‐phase extraction and treatment system was evaluated for the remediation of 4,400 yd³ of tetrachloroethene‐ and trichloroethene‐impacted soil, groundwater, and bedrock. The analysis was based on an actual site with an estimated source mass of 2,200 lbs of chlorinated solvents. The remedy was separated into four stages: remedy installation, remedy operation, monitoring, and remedy deconstruction. Environmental impacts were assessed using Sima Pro software, the ecoinvent database, and the ReCiPe midpoint and endpoint methods. The operation stage of the remedy dominated the environmental impacts across all categories due to the large amount of electricity required by the thermal treatment technology. Alternate sources of electricity could significantly reduce the environmental impacts of the remedy across all impact categories. Other large impacts were observed in the installation stage resulting from the large amount of diesel fuel, steel, activated carbon, and asphalt materials required to implement the technology. These impacts suggest where opportunities for footprint reductions can be found through best management practices such as increased materials reuse, increased recycled‐content materials use, and clean fuels and emission control technologies. Smaller impacts were observed in the monitoring and deconstruction stages. Normalized results show the largest environmental burdens to fossil depletion, human toxicity, particulate matter formation, and climate‐change categories resulting from activities associated with mining of fossil fuels for use in electricity production. In situ thermal treatment can reliably remediate contaminated source areas with contaminants located in low‐permeability zones, providing complete destruction of contaminants in a short amount of time, quick return of the site to productive use, and minimized quantities of hazardous materials stored in landfills for future generations to remediate. However, this remediation strategy can also result in significant emissions over a short period of time. It is difficult to quantify the overall value of short‐term cleanups with intense treatment emissions against longer‐term cleanups with lower treatment emissions because of the environmental, social, and economic trade‐offs that need to be considered and understood. LCA is a robust, quantitative tool to help inform stakeholder discussions related to the remedy selection process, trade‐off considerations, and environmental footprint‐reduction opportunities, and to complement a broader toolbox for the evaluation of sustainable remediation strategies. © 2012 Wiley Periodicals, Inc.     

Remediating groundwater using a hydraulic containment system for pump and treat

Twenty years of waste disposal operations at the Conservation Chemical Company (CCC) site in Kansas City, Missouri, led to contamination of soils and groundwater on a six-acre site. As a result of this contamination, the site was listed on the federal government's National Priorities List. Following extensive litigation initiated in 1982, more than 200 contributors to the site (Potentially Responsive Parties or PRPs), CCC's insurance companies, and the government ultimately reached a settlement to fund the remedial action. The remedy that was agreed upon included: (1) a permeable cap to allow water intrusion to assist groundwater cleanup; (2) a with drawal well system to achieve an inward groundwater gradient; and (3) a groundwater treatment system employing several unit operations. Containment of the contaminated plume relied on hydraulic, rather than structural, containment to prevent mitigation of contaminants from the site. ABB Environmental Services, Inc. (ABB-ES) was retained to perform treatability tests and to design, construct, and start up the groundwater treatment plant after the installation of the permeable cap by others.     

When the Going Gets Tough,Communities Believe It's Time to Optimize and Adapt

The people who live in the communities where complex groundwater sites are located are as diverse as the country itself, but those who fight for the cleanup of our groundwater recognize that total cleanup may be difficult, if not impossible, in our lifetimes. Still, as explained in a December 2013 joint letter to US EPA, we want those who are responsible for environmental protection, be they polluters, developers, or regulatory agencies, to try harder before admitting defeat. In Mountain View, California, community activists have developed criteria for the adaptive cleanup of the Moffett‐MEW Regional Plume of TCE groundwater contamination that emphasizes areas with high contaminant mass, source areas, locations that reduce the need for long‐term vapor intrusion mitigation, properties where the detectable plume encroaches on residential areas, schools, and other sensitive uses, and areas planned for reuse. In many other communities, trust is the key to developing community support for remedial strategies. Communities that are listened to tend to feel more empowered. Empowered communities tend to offer more constructive advice. Decision makers tend to listen to communities that offer constructive advice. In summary, when the cleanup going gets tough, empowered communities believe that it is time to optimize and adapt, not to give up. © 2014 Wiley Periodicals, Inc.     

Carbon isotope forensics for methane source identification

Methane (CH₄) in ecosystems originates from ancient petroleum formed deep within the earth and/or via microbial fermentation of organic carbon and subsequent reduction of carbon dioxide (CO₂). Given the complexity of different ecosystems, origins of CH₄ present can be difficult to determine. This issue was realized in a situation where an antimethanogenic in situ chemical reduction (ISCR) remedial amendment containing organic carbon plus zero‐valent iron was applied to treat chlorinated solvents in groundwater at a former dry cleaner facility. The technology rapidly and effectively reduced the concentration of tetrachloroethene in groundwater thus meeting project goals without the stoichiometric accumulation of catabolites such as trichloroethene (TCE), cis‐1,2‐dichloroethene, or vinyl chloride and without excessive methanogenesis (e.g., <2 mg/L) in the treated area. However, approximately 9 months after treatment, increased levels of CH₄ (from 5 to 10 mg/L) were observed downgradient from the treated area. The applied remedial amendment contained approximately 60% (weight basis) fermentation organic carbon and was therefore a potential source of this CH₄. However, there was <500 mg/L total organic carbon in groundwater emanating from the upgradient treatment area which was unlikely sufficient to produce that much CH₄. Moreover, the soil gas also contained benzene, toluene, ethylbenzene, and xylenes and other gasoline constituents. These data suggested that the presence of three gasoline/diesel underground storage tanks that were previously closed in place with no active remediation performed could be the source of elevated CH₄. Thirdly, there were sewer lines, utilities, multiple gasoline stations, and industrial activities in the immediate area. With an initial assumption that CH₄ source(s) could include the ISCR amendment over stimulation of production, gasoline sourced CH₄ from nearby leaking lines, or sewage from local fractured pipes, carbon isotope analyses—radiocarbon (Δ¹⁴C) and stable carbon (δ¹³C)—were coupled with CH₄ and CO₂ concentration data from groundwater samples to determine the origin of respired carbon. The δ¹³C range for carbon sources respired in the process would be approximately ?26.5‰ to ?33.0‰ for the ISCR amendment and total petroleum hydrocarbons (TPH) residuals, respectively. Δ¹⁴C is approximately 0‰ and ?999‰ for the ISCR amendment (young carbon) and TPH (old carbon), respectively. The isotopic signature of respired gasses confirmed that elevated CH₄ downgradient of the treated area originated primarily from sewer gasses (or fermentation of liquids released from sewer lines). This study provides an overview of the capability to apply carbon isotope geochemistry to confirmation of remedial protocols and sources of anthropogenic carbon pools that conclusively identify the origin of CH₄ in a complex ecosystem undergoing a remedial action.     

Complete Degradation of Hexahydro‐1,3,5‐Trinitro‐1,3,5‐Triazine (RDX) by a Co‐Culture of Gordonia sp. KTR9 and Methylobacterium sp. JS178

The presence of hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX) in soil and groundwater is a major contamination issue at many military facilities around the world. Gordonia sp. KTR9 metabolizes RDX as a nitrogen source for growth producing 4‐nitro‐2,4‐diazabutanal (NDAB) as a dead‐end product. Methylobacterium sp. strain JS178 degrades NDAB as a sole source of nitrogen for growth. A mixed culture of strains KTR9 and JS178 was able to completely degrade RDX. There was no difference in rate of RDX degradation by KTR9 alone or in co‐culture with JS178. The first‐order degradation coefficients of RDX and NDAB in the co‐culture were 0.08 hr^?1 and 0.002 hr^?1, respectively. In the co‐culture that initially contained RDX plus NDAB, strain JS178 degraded the NDAB that was produced by KTR9 as shown by a decrease in the molar yield of NDAB (from RDX) from 1.0 to –0.11. Co‐cultures of strains KTR9 and JS178 could be used to promote complete degradation of RDX in soils or groundwater. ©2016 Wiley Periodicals, Inc.     

Best Available Treatment Technologies Applied to Groundwater Circulation Wells

Groundwater circulation wells (GCWs) are a quasi‐in‐situ method for remediating groundwater in areas where remediation techniques that limit the water available for municipal, domestic, industrial, or agricultural purposes are inappropriate. The inherently resource‐conservative nature of groundwater circulation wells is also philosophically appealing in today's culture, which is supportive of green technologies. Groundwater circulation wells involve the circulation of groundwater through a dual‐screen well, with treatment occurring between the screens. The wells are specifically designed so that one well screen draws in groundwater and the second returns the groundwater after it has been treated within the well. Historically, the treatment has been performed with specialized equipment proprietary to GCW vendors. Two full‐scale pilot systems at a formerly used Defense Superfund site in Nebraska used best available technologies for treatment components. A multiple‐tray, low‐profile air stripper typically used for pump‐and‐treat remediation systems was successfully adapted for the GCW pilot system located in a trichloroethylene (TCE) hot spot. An ultraviolet water disinfection system was successfully adapted for the GCW pilot system located in a hot spot contaminated with the explosive compound hexhydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX). The pilot systems showed that GCW technology is competitive with a previously considered pump‐and‐treat alternative for focused extraction, and the regulatory community was supportive of additional GCW applications. A remedial design for the site includes 12 more GCW systems to complete focused remediation requirements. © 2002 Wiley Periodicals, Inc.