Contributions of common sources of polycyclic aromatic hydrocarbons to soil contamination

Asphalt products, particularly sealants, are prepared using petroleum products that contain a com‐plex mixture of aliphatic and aromatic hydrocarbons, including polycyclic aromatic hydrocarbons (PAHs). Clearly, these products are ubiquitous in urban environments, which raises an issue regard‐ing the potential for PAHs to be transported from parking lots to underlying or adjacent soil, surface‐water bodies, or groundwater. Based on a literature review, there are limited studies focus‐ing on this issue; however, the studies that have been published have fascinating conclusions. The literature shows, as expected, that asphalt‐based products contain PAHs. The highest PAH concen‐trations are present in asphalt sealants, particularly those manufactured using coal tar. Furthermore, due to the low solubility and high partition coefficients of PAHs, the potential for PAHs to leach from asphalt surfaces is negligible, which has been confirmed by leachability studies. Thus, there is little risk that PAHs will be present in stormwater runoff or leach into groundwater from asphalt‐paved areas in a dissolved form. However, asphalt pavement and sealants produce particulate matter that can contain concentrations of PAHs in the sub‐percent range (100s to 1,000s mg/kg total PAHs) that is transported in stormwater runoff. Some studies show that this can cause soil and sediment con‐tamination with total PAH concentrations in the range of 1 to 10 mg/kg. From a remediation per‐spective, many site cleanups are conducted to remediate the presence of PAHs to cleanup goals below 1 mg/kg or, in some cases, 0.1 mg/kg or lower. From a total risk perspective, remediating sites to low PAH cleanup goals may be unwarranted in light of the risk of transportable PAHs produced from paved parking surfaces. In other words, is it reasonable to conduct a cleanup to remediate low PAH concentrations and then redevelop the area with asphalt pavement and sealant, which may pose a greater PAH‐related risk? © 2006 Wiley Periodicals, Inc.     

Field Performance of Point Velocity Probes at a Tidally Influenced Site

Conventional methods to estimate groundwater velocity that rely on Darcy's Law and average hydrogeologic parameter values are insensitive to local‐scale heterogeneities and anisotropy that control advective flow velocity and direction. Furthermore, at sites that are tidally influenced or have extraction wells with variable pumping schedules, infrequent water‐level measurements may not adequately characterize the range and significance of transient hydraulic conditions. The point velocity probe (PVP) is a recently developed instrument capable of directly measuring local‐scale groundwater flow velocity and direction. In particular, PVPs may offer distinct advantages for sites with complex groundwater–surface water interactions and/or with spatially and temporally variable groundwater flow conditions. The PVP utilizes a small volume of saline tracer and inexpensive sensors to directly measure groundwater flow direction and velocity in situ at the centimeter‐scale and discrete times. The probes are installed in conventional direct‐push borings, rather than in wells, thus minimizing the changes and biases in the local flow field caused by well installation and construction. Six PVPs were installed at a tidally influenced site in North Carolina to evaluate their implementability, performance, and potential value as a new site characterization tool. For this study, a new PVP prototype was developed using a rapid prototyping machine (i.e., a “three‐dimensional printer'') and included both horizontally and vertically oriented tracer detectors. A site‐specific testing protocol was developed to account for the spatially and temporally variable hydraulic conditions and groundwater salinity. The PVPs were tested multiple times, and the results were compared to the results of several different groundwater flux and velocity estimation tools and methods, including a heat‐pulse flowmeter, passive flux meters, single‐well tracer tests, and high‐resolution hydraulic gradient analysis. Overall, the results confirmed that the PVP concept is valid and demonstrated that reliable estimates of groundwater velocity and direction can be obtained in simple settings. Also, PVPs can be successfully installed by conventional methods at sites where the formation consists primarily of noncohesive soils and the water table is relatively shallow. Although some PVP tests yielded consistent and reliable results, several tests did not. This is likely due to the highly transient flow conditions and limitations associated with the PVP design and testing procedures. PVPs offer particular advantages over, and can effectively complement, other groundwater flow characterization techniques for certain conditions, and objectives may be useful for characterizing complex flow patterns under steady conditions; however, this study suggests that PVPs are best suited for conditions where the flow hydraulics are not highly transient. For sites where the hydraulic conditions are highly transient, the most reliable approach for understanding groundwater flow behavior and groundwater–surface water interactions would generally involve both a high‐resolution hydraulic gradient analysis and another local‐scale method, such as tracer testing. This study also highlighted some aspects of the current PVP design and testing protocol that can be improved upon, including a more robust connection between the PVP and injection line and further assessment of tracer solution density effects on vertical flow. © 2013 Wiley Periodicals, Inc.     

Addressing soil gas vapor intrusion using sustainable building solutions

Soil gas vapor intrusion (VI) emerged in the 1990s as one of the most important problems in the investigation and cleanup of thousands of sites across the United States. A common practice for sites where VI has been determined to be a significant pathway is to implement interim building engineering controls to mitigate exposure of building occupants to VI while the source of contamination in underlying soil and groundwater is assessed and remediated. Engineering controls may include passive barriers, passive or active venting, subslab depressurization, building pressurization, and sealing the building envelope. Another recent trend is the emphasis on “green” building practices, which coincidentally incorporate some of these same engineering controls, as well as other measures such as increased ventilation and building commissioning for energy conservation and indoor air quality. These green building practices can also be used as components of VI solutions. This article evaluates the sustainability of engineering controls in solving VI problems, both in terms of long‐term effectiveness and “green” attributes. Long‐term effectiveness is inferred from extensive experience using similar engineering controls to mitigate intrusion of radon, moisture, mold, and methane into structures. Studies are needed to confirm that engineering controls to prevent VI can have similar long‐term effectiveness. This article demonstrates that using engineering controls to prevent VI is “green” in accelerating redevelopment of contaminated sites, improving indoor air quality, and minimizing material use, energy consumption, greenhouse gas emissions, and waste generation. It is anticipated that engineering controls can be used successfully as sustainable solutions to VI problems at some sites, such as those deemed technically impracticable to clean up, where remediation of underlying soil or groundwater contamination will not be completed in the foreseeable future. Furthermore, green buildings to be developed in areas of potential soil or groundwater contamination may be designed to incorporate engineering controls to prevent VI. © 2009 Wiley Periodicals, Inc.     

Accelerating environmental cleanup at DOE sites: Monitored natural attenuation/enhanced attenuation—A basis for a new paradigm

The U.S. Department of Energy is conducting a project to accelerate remediation through the use of monitored natural attenuation and enhanced attenuation for chlorinated ethenes in soils and groundwater. Better monitoring practices, improved scientific understanding, and an advanced regulatory framework are being sought through a team effort that engages technology developers from academia, private industry, and government laboratories; site cleanup managers; stakeholders; and federal and state regulators. The team works collaboratively toward the common goals of reducing risk, accelerating cleanup, reducing cost, and minimizing environmental disruption. Cutting‐edge scientific advances are being combined with experience and sound environmental engineering in a broadly integrated and comprehensive approach that exemplifies socalled “third‐generation R&D.” The project is potentially a model for other cleanup activities. © 2004 Wiley Periodicals, Inc.     

Developing Life‐Cycle Environmental Response Costs for Leaking Underground Storage Systems at Service Station Sites

Leaking underground storage tank systems at service stations have resulted in tens of thousands of petroleum releases and associated groundwater chemical plumes often extending hundreds of feet off‐site. Technical and engineering approaches to assess and clean up releases from underground tanks, product lines, and dispensers using technologies such as soil vapor extraction, air sparging, biostimulation, and monitored natural attenuation are well understood and widely published throughout the literature. This article summarizes life‐cycle environmental response costs typically encountered using site‐specific cost estimation or metric‐based cost categories considering the overall complexity of site conditions: (1) simple sites where response actions require smaller scale assessments and/or remediation and have limited or no off‐site impacts; (2) average sites where response actions require larger scale assessments and/or remediation typical of petroleum releases; (3) complex sites where response actions require greater on‐site and/or off‐site remediation efforts; and (4) mega sites where petroleum plumes have impacted public or private water supplies or where petroleum vapors have migrated into occupied buildings. Associated cleanup cost estimates rely upon appropriate combinations of individual work elements and the duration of operation, maintenance, and monitoring activities. These cost estimates can be offset by state reimbursement funds, coverage in purchase agreements, and insurance policies. A case study involving a large service station site portfolio illustrates the range of site complexity and life‐cycle environmental response costs. © 2014 Wiley Periodicals, Inc.     

Phytopumping for hydraulic control of an arsenic plume

Phytoremediation, the use of plants for in situ contaminant cleanup, is gaining new appreciation as an aesthetically pleasing, sustainable method that naturally makes use of solar power. Hybrid poplars are widely used because they grow rapidly and have high transpiration rates, making them advantageous for hydraulic control of groundwater. However, the tendency for trees and other vegetation to uptake metals may be a disadvantage in some settings due to potential redistribution of metals from groundwater to the ground surface. Therefore, a pilot test in the upper midwestern United States was implemented to evaluate the applicability of poplars to groundwater withdrawal and metals transport. © 2009 Wiley Periodicals, Inc.     

Natural attenuation of chlorinated solvent plumes at Texas dry cleaners

Dry cleaners are the largest users of perchloroethene (PCE) solvents in the United States. Releases from dry cleaners to soil and groundwater, however, remain largely unstudied. This article presents a database of 137 chlorinated solvent plumes at dry cleaners in Texas. The data indicate that PCE plumes are generally shorter in extent than those from industrial sites. Degradation products were observed at more than 80 percent of the sites with groundwater contamination. Calculated attenuation rates are on the order of one‐to‐three‐year half‐lives for PCE and its degradation products. The estimated cleanup timeframe for calculated attenuation rates is < 50 years. More research is needed to understand the presence of organic carbon sources at dry cleaners and its implications for natural attenuation. © 2004 Wiley Periodicals, Inc.     

Coupling surfactants/cosolvents with oxidants for enhanced DNAPL removal: A review

Surfactants and cosolvents are useful for enhancing the apparent solubility of dense nonaqueous‐phase liquid (DNAPL) compounds during surfactant‐enhanced aquifer remediation (SEAR). In situ chemical oxidation (ISCO) with permanganate, persulfate, and catalyzed hydrogen peroxide has proven to be a cost‐effective and viable remediation technology for the treatment of a wide range of organic contaminants. Coupling compatible remedial technologies either concurrently or sequentially in a treatment train is an emerging concept for more effective cleanup of DNAPL‐contaminated sites. Surfactants are effective for DNAPL mass removal but not useful for dissolved plume treatment. ISCO is effective for plume control and treatment but can be less effective in areas where large masses of DNAPL are present. Therefore, coupling SEAR with ISCO is a logical next step for source‐zone treatment. This article provides a critical review of peer‐reviewed scientific literature, nonreviewed professional journals, and conference proceedings where surfactants/cosolvents and oxidants have been utilized, either concurrently or sequentially, for DNAPL mass removal. © 2010 Wiley Periodicals, Inc.     

Reductive dechlorination of a chlorinated solvent plume in Houston,Texas

Chlorinated solvents such as tetrachloroethene (perchloroethene, PCE) and trichloroethene (TCE) have been extensively used in various industrial applications for many years. Because neither are typically consumed through their various uses, they are often released to the environment through industrial application or disposal. Once released, PCE and TCE tend to migrate downward into groundwater, where they persist. In the current case study, cheese whey was used as a groundwater amendment to facilitate the reductive dechlorination of a chlorinated solvent plume underlying an auto dealer/repair shop in Harris County, Texas. From September 2010 to January 2014, over 32,000 gallons of cheese whey were injected into the subsurface resulting in a marked reduction in oxidation–reduction potential (ORP) and nitrate concentrations, coupled with an increase in ferrous iron concentrations. Statistical trend analyses indicate the primary contaminants, PCE and TCE, as well as the daughter product cis‐1,2‐dichloroethene (cDCE), all exhibited a positive response, as evidenced by statistically decreasing trends, and/or reversal in concentration trends, subsequent to cheese whey injections. Maximum concentrations of PCE and TCE in key test wells decreased by as much as 98.97 percent and 99.17 percent, respectively. In addition, the bacterial genus Dehalococcoides, capable of complete reduction of PCE to non‐toxic ethene, was found to be more abundant in the treatment area, as compared to background concentrations. Because cheese whey is a by‐product of the cheese making process, the cost of the product is essentially limited to transport. This study demonstrates cheese whey to be an effective groundwater amendment at a cost which is orders of magnitude lower than popular industry alternatives.     

In situ thermal remediation of DNAPL and LNAPL using electrical resistance heating

Electrical resistance heating (ERH) is an in situ treatment for soil and groundwater remediation that can reduce the time to clean up volatile organic compounds (VOCs) from years to months. The technology is now mature enough to provide site owners with both performance and financial certainty in their site‐closure process. The ability of the technology to remediate soil and groundwater impacted by chlorinated solvents and petroleum hydrocarbons regardless of lithology proves to be beneficial over conventional in situ technologies that are dependent on advective flow. These conventional technologies include: soil vapor recovery, air sparging, and pumpand‐treat, or the delivery of fluids to the subsurface such as chemical oxidization and bioremediation. The technology is very tolerant of subsurface heterogeneities and actually performs as well in low‐permeability silts and clay as in higher‐ permeability sands and gravels. ERH is often implemented around and under buildings and public access areas without upsetting normal business operations. ERH may also be combined with other treatment technologies to optimize and enhance their performance. This article describes how the technology was developed, how it works, and provides two case studies where ERH was used to remediate complex lithologies. © 2005 Wiley Periodicals, Inc.     

Sensitivity analysis for setting soil cleanup standards

In recent years, many states have sought to set soil standards for hazardous waste sites. For example, Michigan and Oregon have had soil standards for several years, and within the last three years Massachusetts, New Jersey, Pennsylvania, and Texas have derived soil standards; while Illinois and several other states are in the process of developing soil standards. In general, soil cleanup standards are set to protect against leaching to groundwater and direct contact with soil. This article reviews several agencies' protocols and presents a sensitivity analysis of parameters used to establish these soil cleanup standards. Major issues examined in this article include land use (residential versus commercial/industrial) and exposure parameters used for deriving soil cleanup standards for direct contact. Soil cleanup standards are developed considering exposure routes such as ingestion, dermal contact, inhalation of vapors, and fugitive dust. Other factors such as chemical/physical properties are also considered. For example, many states use Toxicity Characteristic Leaching Procedure (TCLP) or EPA Method 1312 Synthetic Precipitation Leaching Procedure (SPLP) to derive soil standards protective of leaching to groundwater. The results indicate that factors such as leaching and certain exposure assumptions play a key role in determining soil cleanup standards. Exposure pathways were examined by performing a sensitivity analysis using a generic equation to consider exposure from ingestion, dermal contact, and inhalation of soil in deriving soil cleanup standards. The sensitivity analysis indicates that selection of exposure parameters such as toxicity values and soil-to-skin adherence factors contribute more substantially than others. These two factors are also among those values with the greatest uncertainty. Selection of exposure pathways is also important for the derivation of soil cleanup standards. For example, inhalation is the most significant exposure pathway for volatile organic compounds such as toluene, yet many states do not evaluate this exposure route. These findings are based on the mathematical models used by the agencies, and no judgments are made on the validity of the models. The results of this analysis can help focus attention on the most sensitive parameters as federal government reforms environment policies (i.e., CERCLA and RCRA) and the development of national soil cleanup standards is debated.     

Evolution of predictive tools for in situ bioremediation and natural attenuation evaluations

Proving the viability of in situ bioremediation technologies and gathering data for its full‐scale implementation typically involves collecting multiple rounds of data and often completing microcosm studies. Collecting these data is cumbersome, time‐consuming, costly, and typically difficult to scale. A new method of completing microcosm studies in situ using an amendable sampling device deployed and incubated in groundwater monitoring wells provides actionable data to expedite site cleanup. The device, referred to as a Bio‐Trap® sampler, is designed to collect actively colonizing microbes and dissolved organic compounds from groundwater for analysis using conventional analytical techniques and advanced diagnostic tools that can answer very specific design and viability questions relating to bioremediation. Key data that can be provided by in situ microcosm studies using Bio‐Trap® samplers include definitively demonstrating contaminant destruction by using compound‐specific isotope analysis and providing data on the mechanism of the degradation by identifying the responsible microbes. Three case studies are presented that demonstrate the combined flexibility of Bio‐Trap® samplers and advanced site diagnostics. The applications include demonstrating natural attenuation of dissolved chlorinated solvents, demonstrating natural attenuation of dissolved petroleum compounds, and using multiple Bio‐Trap® samplers to comparatively assess the viability of bioaugmentation at a chlorinated solvent release site. At each of these sites, the in situ microcosm studies quickly and cost‐effectively answered key design and viability questions, allowing for regulatory approval and successful full‐scale implementation. © 2010 Wiley Periodicals, Inc.     

Full‐scale in‐situ biobarrier demonstration for containment and treatment of MTBE

The Naval Facilities Engineering Service Center (NFESC), Arizona State University, and Equilon Enterprises LLC are partners in an innovative Environmental Security Technology Certification Program cleanup technology demonstration designed to contain dissolved MTBE groundwater plumes. This full‐scale demonstration is being performed to test the use of an oxygenated biobarrier at Naval Base Ventura County, in Port Hueneme, California. Surprisingly, few cost‐effective in‐situ remedies are known for the cleanup of MTBE‐impacted aquifers, and remediation by engineered in‐situ biodegradation was thought to be an unlikely candidate just a few years ago. This project demonstrates that MTBE‐impacted groundwater can be remediated in‐situ through engineered aerobic biodegradation under natural‐flow conditions. With respect to economics, the installation and operation costs associated with this innovative biobarrier system are at least 50 percent lower than those of a conventional pump and treat system. Furthermore, although it has been suggested that aerobic MTBE biodegradation will not occur in mixed MTBE‐BTEX dissolved plumes, this project demonstrates otherwise. The biobarrier system discussed in this article is the largest of its kind ever implemented, spanning a dissolved MTBE plume that is over 500 feet wide. This biobarrier system has achieved an in‐situ treatment efficiency of greater than 99.9 percent for dissolved MTBE and BTEX concentrations. Perhaps of greater importance is the fact that extensive performance data has been collected, which is being used to generate best‐practice design and cost information for this biobarrier technology. © 2001 John Wiley & Sons, Inc.     

Phytoremediation of a Petroleum‐Hydrocarbon Contaminated Shallow Aquifer in Elizabeth City,North Carolina,USA

A former bulk fuel terminal in North Carolina is a groundwater phytoremediation demonstration site where 3,250 hybrid poplars, willows, and pine trees were planted from 2006 to 2008 over approximately 579,000 L of residual gasoline, diesel, and jet fuel. Since 2011, the groundwater altitude is lower in the area with trees than outside the planted area. Soil‐gas analyses showed a 95 percent mass loss for total petroleum hydrocarbons (TPH) and a 99 percent mass loss for benzene, toluene, ethylbenzene, and xylenes (BTEX). BTEX and methyl tert‐butyl ether concentrations have decreased in groundwater. Interpolations of free‐phase, fuel product gauging data show reduced thicknesses across the site and pooling of fuel product where poplar biomass is greatest. Isolated clusters of tree mortalities have persisted in areas with high TPH and BTEX mass. Toxicity assays showed impaired water use for willows and poplars exposed to the site's fuel product, but Populus survival was higher than the willows or pines on‐site, even in a noncontaminated control area. All four Populus clones survived well at the site. © 2014 Wiley Periodicals, Inc.*     

Fenton's in-situ reagent chemical oxidation of hydrocarbon contamination in soil and groundwater

Industry and regulatory demands for rapid and cost-effective clean up of hydrocarbon and other contamination in soil and groundwater has prompted development and improvement of in-situ remediation technologies. In-situ technologies offer many advantages over ex-situ treatment alternatives, including lower initial capital and long-term operation and maintenance costs, less site disruption, no Resource Conservation and Recovery Act (RCRA) liability, and shorter treatment time necessary to achieve cleanup objectives. Fenton's reagent, a mixture of hydrogen peroxide and ferrous iron that generates a hydroxyl free radical as an oxidizing agent, is widely accepted for chemical oxidation of organic contaminants in the wastewater industry. In-situ implementation of Fenton's reagent for chemical oxidation of organic contaminants in soil and groundwater continues to grow in acceptance and application to a wide variety of environmental contaminants and hydrogeologic conditions (EPA, 1998).     

Groundwater geochemistry diagnostics during in situ ERH remediation

In situ remediation represents a series of challenges in interpreting the monitoring data on remedial progress. Among these challenges are problems in determining the progress of the remediation and the mechanisms responsible, so that the process can be optimized. The release of organic pollutants to groundwater systems and in situ remediation technologies alter the groundwater chemistry, but outside of natural attenuation studies using inorganic chemical analyses as indicators of intrinsic biodegradation, typically little attention has been paid to the changes in inorganic groundwater chemistry. Smith (2008) noted that during an electrical resistance heating remediation that took place at a confidential site in Chicago, a two‐orders‐of‐magnitude increase in chloride concentrations occurred during the remediation. This increase in chloride resulted in a corresponding increase in calcium as a result of what is known as the common ion effect. Carbon dioxide is the gas found in highest concentrations in natural groundwater (Stumm & Morgan, 1981), and its fugacity (partial pressure) corresponds directly with calcium concentrations. Carbon dioxide at supersaturation in groundwater is capable of dissolving organic compounds, such as trichloroethene, facilitating removal of nonaqueous‐phase liquids at temperatures below the boiling point of water. One means of diagnosing these reactions is through the use of compound‐specific isotopic analysis, which is capable of distinguishing between evaporation, biodegradation, and differences in sources. The appropriate diagnosis has the potential to optimize the benefits from these reactions, lower energy costs for removal of nonaqueous‐phase liquids, and direct treatment where it is needed most. © 2010 Wiley Periodicals, Inc.     

Treatment technologies for 1,4‐Dioxane: Fundamentals and field applications

1,4‐Dioxane is a synthetic industrial chemical frequently found at contaminated sites where 1,1,1‐trichloroethane was used for degreasing. It is a probable human carcinogen and has been found in groundwater at sites throughout the United States. The physical and chemical properties and behavior of 1,4‐dioxane create challenges for its characterization and treatment. It is highly mobile and has not been shown to readily biodegrade in the environment. In December 2006, the U.S. Environmental Protection Agency's Office of Superfund Remediation and Technology Innovation (OSRTI) prepared a report titled “Treatment Technologies for 1,4‐Dioxane: Fundamentals and Field Applications.” The report provides information about the chemistry of dioxane, cleanup goals, analytical methods, available treatment technologies, and site‐specific treatment performance data. The information may be useful to project managers, technology providers, consulting engineers, and members of academia faced with addressing dioxane at cleanup sites or in drinking water supplies. This article provides a synopsis of the US EPA report, which is available at http://cluin.org/542R06009 . © 2007 Wiley Periodicals, Inc.     

Arsenic and thallium data in environmental samples: Fact or fiction?

Matrix effects may increasingly lead to erroneous environmental decisions as regulatory limits or risk‐based concentrations of concern for trace metals move lower toward the limits of analytical detection. A U.S. Environmental Protection Agency Office of Technical Standards Alert estimated that environmental data reported using inductively coupled plasma spectrometry (ICP‐AES) has a false‐positive rate for thallium of 99.9 percent and for arsenic of 25 to 50 percent. Although this does not seem to be widely known in the environmental community, using three case studies, this article presents data in environmental samples that demonstrate severe matrix effects on the accuracy of arsenic and thallium results. Case Study 1 involves soil results with concentrations that approached or exceeded the applicable regulatory soil cleanup objectives of 13 mg/kg for arsenic and 2 mg/kg for thallium. Reanalysis using ICP coupled with a mass spectrometer (ICP‐MS) confirmed all thallium results were false positives and all arsenic results were biased high, concluding no action was required for soil remediation. Case Study 2 involves groundwater results for thallium at a Superfund site, where thallium was detected in groundwater up to 21.6 μ g/L using ICP‐AES. Reanalysis by ICP‐MS reported thallium as nondetect below the applicable regulatory level in all samples. ICP‐MS is usually a more definitive and accurate method of analysis compared to ICP‐AES; however, this is not always the case, as we demonstrate in Case Study 3, using data from groundwater samples at an industrial site. Through a weight‐of‐evidence approach, it is demonstrated that although method quality control results were acceptable, interferences in some groundwater samples caused biased high results for arsenic using ICP‐MS, which were significantly lower when reanalyzed using hydride generation atomic fluorescence spectrometry. Causes of these interference effects and conclusions from the three case studies to obtain accurate metal data for site assessment, risk characterization, and remedy selection are discussed. © 2010 Wiley Periodicals, Inc.     

Stratigraphic flux—A method for determining preferential pathways for complex sites

Experience with groundwater remediation over several decades has demonstrated that successful outcomes depend on quantitative conceptual site models (CSMs). Over the last 30 years, we have progressed from groundwater pump‐and‐treat remedies, which were largely designed based on a water supply perspective, to in situ and combined remedy strategies, which are only beginning to benefit from understanding the aquifer architecture and distribution of contaminant mass to assess plume maturity, mass flux, and more reliable means of fate and transport assessment. The U.S. Air Force funded the development of the Stratigraphic Flux approach to provide a framework for understanding contaminant transport pathways at its complex sites and enable more reliable and cost‐effective remediation. Stratigraphic Flux enables the development of quantitative, flux‐based CSMs that are founded in sequence stratigraphy, and high‐resolution hydraulic conductivity and contaminant distribution measurements. The result is a three‐dimensional graphical mapping of relative contaminant flux and classification of transport potential that is easy for all stakeholders to understand. The Stratigraphic Flux graphical model is based on a hydrofacies classification system that describes transport potential in three segments of the aquifer: transport zones—where the majority of groundwater flow occurs and transport rates are measured in feet per day; slow advection zones—where transport rates are measured in feet per year; and storage zones—where typically less than 1% of flow occurs, and diffusion dominates contaminant transport. The hydrofacies architectures are based on stratigraphy and transport potential is defined by grouping facies by orders of magnitude classes in hydraulic conductivity. By combining the hydrofacies architecture with contaminant concentration distributions, one can map relative contaminant flux to define and target the complex pathways that control contaminant transport and cleanup behavior. In this article, we describe the Stratigraphic Flux framework, focusing on the key information needed and the methods of analysis. We illustrate the results of its application to evaluate migration pathways for trichlorethylene and chromium at a former chrome pit at Air Force Plant 4 in Fort Worth, Texas. A comprehensive guidance document that describes the approach with a broad spectrum of tools and several site examples can be requested from the authors.