Alternatives to incineration in remediation of soil and sediments assessed

Contamination of soil and sediment by pollutants represents a major environmental challenge. Remediation of soil during the original Superfund years consisted primarily of dig and haul, capping, or containment. The 1986 amendments to CERCLA—SARA—provided the incentive for treatment and permanent remedies during site remediation. Thermal treatment, which routinely achieves the low cleanup criteria required by RCRA land-ban regulations, became one of the major technologies used for cleanup under the concept of ARAR. As the remediation industry matured and recognized specific market niches in soil remediation, a number of new technologies emerged. Thermal desorption, bioremediation, soil vapor extraction, soil washing, and soil extraction are being used on sites at which the technology offers advantages over incineration. In addition, a continuing stream of emerging technologies is being presented that requires careful evaluation relative to existing cleanup methods. Each of these technologies offers a range of options for achieving appropriate cleanup criteria, application to different soil matrices, cost, time of remediation, and public acceptability. Balancing cleanup criteria defined by regulation or risk assessment with technology cost and capability affords the opportunity to solve these problems with appropriate balance of cost and protection of human health and the environment.     

Risk assessment and accepted regulatory cleanup levels

The determination of cleanup levels at a CERCLA or RCRA site is often the single most important decision made by risk managers. This decision can have a major impact on the costs and time required for remediation, as well as on the selection of remedial technologies. The object of this article is to provide a critical review of the methods used by regulatory agencies and the regulated community to calculate chemical-specific cleanup goals for inactive hazardous waste sites, focusing on those cleanup goals that are designed to protect human health from the effects of chemicals. In addition to this analysis of historical methods that have been used, this article discusses some innovative solutions to the problem of calculating cleanup levels and presents an analysis of controversial topics related to cleanup levels currently under debate by regulatory agencies, industry, environmentalists, and legislative bodies.     

Development of a site‐specific cleanup goal for PAHs in soil based on anthropogenic background levels

During removal of an industrial landfill in Folsom, California, fill material was excavated and processed through a mechanical screening plant to segregate soil from construction and demolition debris. The segregated soil was stockpiled and analyzed for a wide range of chemical groups to determine if the soil could be backfilled on‐site. The analytical results indicated many of the stockpiles had concentrations of polycyclic aromatic hydrocarbons (PAHs) that exceeded US EPA Regional Screening Levels, and a large quantity of soil was initially classified as requiring off‐site disposal at considerable cost. Because PAHs are ubiquitous in urban settings and the landfill did not contain a significant source of PAHs, development of a site‐specific PAH cleanup goal was proposed to regulators. Cal/EPA guidance for using on‐site data to develop a background threshold for metals was applied to the development of the PAH cleanup goal. The Cal/EPA approach involves demonstrating whether the data belong to a single population or multiple populations based on data distribution tests and probability plots. This article explains the statistical and graphical methods that were used to demonstrate that the Cal/EPA approach was valid for PAHs and that the calculated cleanup level was consistent with published anthropogenic background levels of PAHs in California and across the United States. The site‐specific PAH cleanup goal enabled most of the soil to be backfilled on‐site, saving about $227,000 in transportation and disposal costs, and regulators subsequently approved unrestricted future use of the property. © 2010 Wiley Periodicals, Inc.     

Technical feasibility and conceptual design for using supercritical fluid to extract pesticides from aged soil

The demand for processes to clean up contaminated soils without introducing additional contaminants is increasing. One approach to solving this problem is the use of supercritical fluids like carbon dioxide, alone or with cosolvents, to extract contaminants from the soil. Carbon dioxide is readily available, inexpensive, and nonpolluting. Gases exhibit unique properties under supercritical conditions. They retain the ability to diffuse through the interstitial spaces of solid materials, plus they have the solvating power of liquids. Soil cleanup using supercritical fluid extraction (SFE) is being investigated as an alternative/complementary technology to other cleanup methods such as incineration and bioremediation. The objective of the studies included in this article was to collect and analyze data to support use of the SFE technology and to provide the conceptual design and operational processes needed for building a portable treatment unit.     

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.     

Alternative method of groundwater sparging for petroleum hydrocarbon remediation

An alternative method of in-situ groundwater sparging, termed density-driven convection (patent pending), is presented. This method has been successfully used to remediate eight underground storage tank releases involving a wide distillation range of petroleum hydrocarbons (gasoline to waste oil) and in a variety of site soils (clay to sandy gravel). Application of the density-driven convection method is detailed in a case study. The system, installed to remediate a gasoline and diesel release from an underground storage tank, was operated and monitored for a period of one year. Monitoring data indicate reductions in total petroleum hydrocarbon concentrations in groundwater and in soil. Concentrations of aromatic hydrocarbons (benzene, toluene, ethylbenzene, xylenes, and naphthalene) also decreased in both media. Stimulation of natural biodegradation, the primary mechanism of removal, occurred rapidly. Natural biological activity gradually declined over the subsequent 150 days. After one year of operation, the sparging system has achieved or is rapidly approaching the regulatory cleanup goals for both soil and groundwater, including reduction of dissolved concentrations below maximum contaminant levels established under the Safe Drinking Water Act.     

Impact: A Model for calculation of soil cleanup levels

The establishment of soil cleanup levels is a primary concern in site remediation projects. Soil cleanup levels provide targets that drive the remediation process from technology selection through closure. Several state regulatory agencies are currently in the process of developing scientifically based soil cleanup standards. The underlying premise in the derivation of such standards is to ensure that the site will not pose a threat to human health and the environment after remediation has been completed. To accomplish this, remediation project managers must consider several contaminant transport pathways. This article presents the salient features of a model named IMPACT, which was developed to assist in the derivation of soil cleanup levels. IMPACT considers the soil-to-groundwater pathway and predicts the cleanup levels in a contaminated soil layer in the vadose zone such that groundwater quality standards are met at any point in the aquifer.     

A Practical Guide to Estimating Cleanup Costs

Cost estimates are frequently developed to evaluate hazardous‐waste‐site cleanup options in support of a site investigation, remedy selection decision, or assessment of environmental liabilities. The accuracy of the cost estimate depends largely on the quality of the information available at the time it is prepared. This article presents a practical guide to developing a cleanup cost estimate. It includes information on how to document assumptions, use the latest technical resources, and perform basic adjustments to account for uncertainty and the time value of money. The content is based upon a recent guidance document issued by the U.S. Environmental Protection Agency and U.S. Army Corps of Engineers entitled A Guide to Developing and Documenting Cost Estimates during the Feasibility Study (USEPA, 2000). © 2001 John Wiley & Sons, Inc.     

Best management practices for environmental restoration programs

Based on a review of hundreds of environmental restoration program optimization reviews, this article describes management tools found in successful and efficient remediation programs. Projects that consistently struggled to achieve their objectives were observed to be missing certain, or to have inadequately used, these tools. The tools are articulated as best practices because when they are present and actively used, project shortcomings were minimal. Priority objectives for site owners and project managers include improving efficiency and effectiveness through performance management, reducing resource usage and energy consumption, ensuring protectiveness, and reducing uncertainty in management decision making. Restoring environmental resources damaged by historic waste management practices began in earnest in the late 1960s and early 1970s with the broad recognition of the problems caused by environmental discharges and spills when wastes are not managed appropriately. Under new regulations, soil and groundwater remediation projects could be, and were, conducted within a defined framework. The number and variety of restoration projects that were launched resulted in a slew of projects progressing through the stages of characterization, decision, and cleanup, and more were added to the cleanup process each year. In the 1990s, the Department of Defense noted that many cleanup efforts were projected to incur substantial operational, maintenance, and monitoring costs for decades into the future. This was correctly perceived as an opportunity to optimize those systems and programs, minimize costs, and reduce health and environmental risks. The best practices outlined in this article address management tools that were identified in optimization efforts that led to effective and efficient environmental remediation projects. © 2010 Wiley Periodicals, Inc.     

Successful solid-phase bioremediation of petroleum-contaminated soil

Biological processes have been used to remediate petroleum hydrocarbons, pesticides, chlorinated solvents, and halogenated aromatic hydrocarbons. Biological treatment of contaminated soils may involve solid-phase, slurry-phase, or in situ treatment techniques. This article will review the general principle of solid-phase bioremediation and discuss the application of this technique for the cleanup of total petroleum hydrocarbons on two sites. These remedial programs will reduce total petroleum hydrocarbon contamination from the mean concentration of 2,660 ppm to under the 200-ppm cleanup criteria for soil and under the 15-ppm cleanup criteria for groundwater. Over 32,000 yards of soil have been treated by solid-phase treatment to date. The in situ system operation is effectively producing biodegradation in the subsurface. The project is approximately one-third complete.     

A dynamic methodology for estimating cleanup efforts for mercury in soil at gas utility gate stations

This article provides an overview of a dynamic methodology leading to the estimation of the level of mercury concentration in soil and soil cleanup volumes associated with a large number of gate stations suspected of having mercury in their soil. The methodology uses a unique screening approach that has been developed for relating measurements of volatile mercury near the surface to mercury concentration in the upper soil subsurface (about twelve inches deep). The screening approach was used in an effort to reduce the number of sites that are subject to extensive multimedia environmental sampling and analysis. The approach helps to focus on a small number of sites that are suspected of having the highest mercury concentration in soil, perform multimedia environmental sampling at these sites, use the field data to perform risk assessment, and determine the cleanup action levels and the volume of hot spots soil to be cleaned at these sites. The information obtained for the most contaminated sites is used to determine, if required, the level of cleanup for less contaminated sites.     

Radiological risks and cleanup costs: A remediation case study

Potential health risks and cleanup costs are primary factors for measuring the effectiveness of a remediation project concerning a site contaminated with residual radioactive materials. Demanding cleanup of a contaminated site to its original condition, while eliminating any health risks after cleanup, can require prohibitive costs. However, by setting practical remediation objectives and by performing realistic but conservative risk assessments, health risks can be acceptable and cleanup costs can be reasonable. This article uses the South-Middle and Southeast Vaults Decontamination and Demolition Project at Argonne National Laboratory to demonstrate how negligible health risks can result after cleanup with minimal cleanup costs. Substantial cost savings of approximately $2 million was realized by implementing in-place decontamination and demolition (D&D) on the basis of acceptable risk, instead of requiring cleanup of the site to its original condition. By using the RESRAD computer program as a modeling tool, we show the maximum projected radiation dose (0.1 mrem per year) and the potential lifetime cancer risk (on the order of 10⁶) to an individual from exposure to the residual radioactivities are negligibly small. In addition to aiding in the selection of a preferred remediation alternative, results of the RESRAD modeling were also used to guide the implementation of the selected alternative to reduce exposures from the dominant pathway and to ensure that exposures from all pathways would be as low as reasonably achievable.     

Case study: Using soil washing/leaching for the removal of heavy metal at the twin cities army ammunition plant

COGNIS TERRAMET® soil leaching and Bescorp soil washing systems have been successfully combined to remediate an ammunition test burn area at the Twin Cities Army Ammunition Plant (TCAAP), New Brighton, Minnesota. This cleanup is the first in the country to successfully combine these two technologies, and it offers a permanent solution to heavy metal remediation. Over 20,000 tons of soil were treated in the project. The cleaned soil remained on-site, and the heavy metal contaminants were removed, recovered, and recycled. Eight heavy metals were removed from the contaminated soil achieving the very stringent cleanup criteria of <175 ppm for residual lead and achieving background concentrations for seven other project metals (antimony, cadmium, chromium, copper, mercury, nickel, and silver). Initial contaminant levels were measured as high as 86,000 ppm lead and 100,000 ppm copper, with average concentrations over 1,600 ppm each. In addition, both live and spent ordnance were removed in the soil treatment plant to meet the cleanup criteria. By combining soil washing and leaching, COGNIS and Bescorp were able to assemble a process which effectively treats all the soil fractions so that all soil material can be returned on-site, no wastewater is generated, and the heavy metals are recovered and recycled. No hazardous waste requiring landfill disposal was generated during the entire remedial operation.     

Accounting for Science and Uncertainty in Cleanup Levels: The Use of 1 μg/kg as the Cleanup Criterion for Dioxin in Soil

At hazardous waste sites, a 1 μg/kg (ppb) cleanup level has commonly been used for dioxin in residential soil. This article outlines reasons for the continued use of this value in site remediation. Dioxin, one of the most toxic compounds known, has been a focus of scientific study for many years. However, controversy continues to surround its regulation, with some scientists arguing that new scientific results support decreasing risk estimates for dioxin and others taking the opposite view. Part of this controversy appears to involve a decreasing emphasis on cancer and an increased concern about non-cancer and ecological impacts of dioxin. The 1 ppb soil cleanup level represents a reasonable generic value for dioxin, with higher or lower values required on a case-by-case basis to protect specific populations.     

Techniques for rapidly evaluating the progress of in-situ remediation

Although standard methods of monitoring the progress of in-situ remediation may provide general results for the most permeable zones affected by soil vapor extraction or bioventing, they are essentially unsuccessful at providing information on the degree of heterogeneity within the remediation zone and on the existence of “hot spots.” Data are presented that suggest that monitoring the concentrations of fixed and biogenic gases and measuring soil permeability on a small-scale basis may circumvent the common problems associated with assessing the progress of in-situ remediation. The costs of these monitoring techniques are minor compared to those of designing and operating an in-situ remediation system, and may save additional time and costs by identifying problem areas early in the cleanup process.     

Assessing cleanup levels for industrial sites under state risk reduction programs

Many states are promoting the cleanup and reuse of industrial sites. The reasons stem from the need to implement cost-effective risk reduction programs that show reasonable progress in the cleanup of contaminated sites and from the need to make effective use of industrial sites instead of abandoning them and making use of greenfield sites for new industrial facilities. The industrial land-use cleanup criteria developed by states are primarily risk-based. Several EPA regional offices also have developed similar risk-based cleanup criteria. This article addresses methodologies employed for assessing and evaluating the level of cleanup at several industrial sites in Texas, Michigan, and Ohio. This includes defining the regulatory framework, estimating the level and extent of contamination of soil and groundwater, assessing migration pathways, performing health risk assessments, and estimating cleanup requirements and associated costs. The implications associated with the various types of risk reduction options available for these states also are addressed.     

Facilitating brownfields transactions using Triad and environmental insurance

A significant hindrance to reuse of brownfields properties is the risk associated with redevelopment,specifically the uncertainty associated with environmental cleanup. This article explores an approach tomanaging environmental risk through a combination of risk quantification, environmental insurance, and theTriad Approach to site sampling and data interpretation. The expected costs of environmental liabilities areestimated using the Marsh Peer ReviewSM risk quantification process that employs statistical techniques andhighly experienced technical staff. The outputs of the process indicate premiums and attachment points forinsurance products, but they also point to “critical uncertainties” that drive the insurancepremiums. Insurance premiums are often linked to site delineation deficiencies, such as the magnitude ofimpacted soil or the size of a groundwater plume. The Triad Approach is an integrated site characterizationprocess developed by the Environmental Protection Agency that combines systematic planning, dynamic or adaptivefield decision making and field analytical methods (FAMs). The real‐time data produced by FAMsallow for in‐field resolution of uncertainty about sample location, which in turn provides morerepresentative delineation of contaminant distribution. The trade‐off of using slightly less accuratebut substantially lower cost FAMs is an increase in sampling frequency or density, thereby reducing the risk ofincomplete detection or delineation while yielding a “data set” that is more powerful than fewerindividual data points analyzed through traditional methods. Employing the Triad Approach to analyze the“critical uncertainties” identified in the Peer Review Process can impact insurance premiums andallow for better terms of coverage. The combination of using the Triad Approach and environmental insuranceproducts can lead to more predictable and profitable Brownfield transactions. © 2003 Wiley Peridicals,Inc.     

Waste management project's alternatives: A risk-based multi-criteria assessment (RBMCA) approach

This paper examines the evaluation of a waste management project’s alternatives through a quantitative risk analysis. Cost benefit analysis is a widely used method, in which the investments are mainly assessed through the calculation of their evaluation indicators, namely benefit/cost (B/C) ratios, as well as the quantification of their financial, technical, environmental and social risks. Herein, a novel approach in the form of risk-based multi-criteria assessment (RBMCA) is introduced, which can be used by decision makers, in order to select the optimum alternative of a waste management project. Specifically, decision makers use multiple criteria, which are based on the cumulative probability distribution functions of the alternatives’ B/C ratios. The RBMCA system is used for the evaluation of a waste incineration project’s alternatives, where the correlation between the criteria weight values and the decision makers’ risk preferences is analyzed and useful conclusions are discussed.     

Enhanced land treatment of petroleum-contaminated soils using solid peroxygen materials

A pilot field study evaluated whether adding solid peroxygen materials during land treatment could cost effectively accelerate cleanup at a site contaminated with petroleum-related compounds. Five test cells were constructed containing approximately five cubic yards of soil contaminated with 300–400 mg/kg of total petroleum hydrocarbons (TPH). Three cells received treatment with solid peroxygen materials (either MgO₂ or CaO₂), while the other two cells served as controls (no peroxygen amendment). Adding solid peroxygen compounds effectively reduced the hydrocarbon contamination in the soils and decreased the treatment time. During this time, the concentration of TPH in soil in the three treatment cells decreased. In contrast, there was little loss of TPH from the two control cells simulating traditional land treatment. Adding the solid peroxygen materials reduced the total site remediation time, thereby reducing the overall costs.     

Triad case study: Marine Corps Base Camp Pendleton

The U.S. Navy Public Works Center (PWC) Environmental Department, San Diego, California, is home to the Navy West Coast Site Characterization and Analysis Penetrometer System (SCAPS). SCAPS has been extensively used at several Navy sites since 1995 to provide real‐time, high‐density data sets. The U.S. Environmental Protection Agency's Triad approach provided an ideal framework for optimizing the use of the Navy SCAPS during a volatile organic compound (VOC) source investigation at Installation Restoration Site 1114 at Marine Corps Base Camp Pendleton. All three elements of Triad—systematic planning, dynamic work strategy, and use of real‐time measurement tools—were implemented to manage decision uncertainty and expedite the site management process. The investigation was conducted using the Navy SCAPS, outfitted with a cone penetrometer, membrane interface probe, and a direct sampling ion trap mass spectrometry detector, which allowed for real‐ time collection of over 690 feet of continuous lithologic information and VOC concentration data. These data were used collaboratively with 24‐hour turnaround US EPA 8260B VOC groundwater results from temporary direct‐ push wells to support the conclusion of a limited source area. Implementation of the Triad approach for this investigation provided an expedited high‐density data set and a refined conceptual site model (CSM) in real time that resulted in cost savings estimated at $2.5M and reduction of the site characterization and cleanup schedule by approximately three years. This project demonstrates how the US EPA's Triad approach can be applied to streamline the site characterization and cleanup process while appropriately managing decision uncertainty in support of defensible site decisions. © 2004 Wiley Periodicals, Inc.