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

U.S. Environmental Protection Agency
U.S. EPA Technology Innovation and Field Services Division

Recent Additions

Determination of the Biologically Relevant Sampling Depth for Ecological Risk Assessments

Posted: January 25, 2016

Ecological risk assessors are frequently faced with the challenge of defining the biologically active zone, or biotic zone, in soils and sediments during the design and interpretation of soil and sediment sampling programs. With respect to terrestrial assessments, this study uses a meta-analysis approach to quantify the zone of highest biological activity for soil-dwelling ecological receptors commonly utilized in ecological risk assessments. For decisions related to ecological assessment or remediation in aquatic scenarios, we develop practical default values for the depth of the biotic zone (i.e., biologically relevant sampling depth) in various habitats based on the 80th percentile of abundance or biomass depth distributions. In areas populated by a high density of deep dwelling organisms such as those listed in this paper, the biotic zone may be somewhat deeper than our recommended values.

Development and Validation of a Quantitative Framework and Management Expectation Tool for the Selection of Bioremediation Approaches at Chlorinated Ethene Sites

Posted: January 6, 2016

The overarching project objective was to develop and validate a framework for making bioremediation decisions based on site-specific physical and biogeochemical characteristics and constraints. The key deliverable is called BioPIC, an easy-to-use decision tool for estimating and integrating the impact of quantifiable parameters on natural attenuation and microbial remedies to achieve detoxification of chlorinated ethenes. The quantitative framework and BioPIC were beta-tested for chlorinated ethenes (mainly PCE, TCE, and daughter products) degradation at multiple sites: (1) NAS North Island, Site 5, Unit 2 (complete anaerobic biological reductive dechlorination); (2) Kings Bay, Site 11 (reductive dechlorination in the source zone leading to subsequent oxidation of degradation products downgradient); (3) Hill AFB OU-10 (aerobic oxidation); and (4) Plattsburgh AFB, Fire Training Area 2 (abiotic reductive dechlorination or elimination reactions).

Passive PE Sampling in Support of In Situ Remediation of Contaminated Sediments: Final Report

Posted: January 6, 2016

This project sought to demonstrate (a) polyethylene (PE) passive sampling effectively evaluates porewater concentrations of contaminants; (b) PE can delineate the horizontal and vertical extent of contamination; (c) PE is suited for long-term monitoring; and (d) the PE passive sampling approach is commercially viable. Lab tests showed the PE samplers measured pore waters more accurately than the common commercial practice of using sediment concentrations. PE sampling readily revealed the distribution of sediment contamination by PCBs at the demonstration site. PE samplers showed the site had pg/L levels of individual PCBs in pore waters and bottom waters. Sand-cap data indicated no upward PCB fluxes through the caps. Finally, QA/QC, sensitivity, ease of use, and cost metrics all supported the conclusion that PE passive sampling is commercially viable.

Methods for Minimization and Management of Variability in Long-Term Groundwater Monitoring Results: ESTCP Cost and Performance Report

Posted: January 6, 2016

The project purpose was to (1) validate sample collection methods and procedures that minimize variability in groundwater monitoring results, and (2) validate improved methods to optimize monitoring frequency and assess long-term concentration trends that better account for short-term variability in groundwater monitoring results. The field demonstration was conducted in eight monitoring wells each at a Texas and a California demonstration site. Results indicated that the sample method (except active no-purge) has only a modest impact on monitoring variability and concentration, suggesting sampling methods could be selected based on factors such as cost, ease of implementation, and sample volume requirements rather than concerns regarding data quality. Low-flow standard (purging to parameter stability) and low-flow alternative (small volume) showed the lowest variability at both sites. Results were consistent between the two sites except for the active no-purge (HydraSleeve) method, which was more variable at the California site than the Texas site. Low-flow small-volume purge and passive no-purge (SNAP sampler) were the two most effective sampling methods based on the combined goals of minimizing monitoring cost and minimizing variability in monitoring results.

Arsenic Cycling in Hydrocarbon Plumes: Secondary Effects of Natural Attenuation

Posted: January 21, 2016

At hydrocarbon spill sites, natural attenuation (NA) relies on biodegradation of hydrocarbons coupled with reduction of electron acceptors, including solid-phase ferric iron (Fe(III)). Because arsenic (As) adsorbs to Fe-hydroxides, a potential secondary effect of hydrocarbon NA coupled with Fe(III) reduction is a release of naturally occurring As to groundwater. In a long-term study of anaerobic biodegradation of hydrocarbons coupled to Fe(III) reduction at a crude-oil-contaminated aquifer near Bemidji, Minnesota, groundwater samples collected at the site annually from 2009 to 2013 showed As concentrations in groundwater in the plume reached 230 µg/L, whereas groundwater outside the plume contained <5 µg/L As. Results suggest that (1) naturally occurring As is associated with Fe-hydroxides present in the glacially derived aquifer sediments; (2) introduction of hydrocarbons results in reduction of Fe-hydroxides, releasing As and Fe to groundwater; (3) at the leading edge of the plume, As and Fe are removed from groundwater and retained on sediments; and (4) downgradient from the plume, patterns of As and Fe in groundwater are similar to background. A conceptual model of secondary As release due to hydrocarbon NA can be applied to other sites where an influx of biodegradable organic carbon promotes Fe(III) reduction. This paper is Open Access at

Phytoremediation of Explosive-Contaminated Soils

Posted: January 21, 2016

A considerable amount of information on phytotoxicity and metabolism of TNT and RDX in plants and microorganisms has been collected over the past few decades. This review identifies phytoremediation species that show promise for application to TNT and RDX contamination. Among the plant species that have shown efficient TNT uptake, only a few have been found—i.e., Eurasian water milfoil (Myriophyllum spicatum) and vetiver grass (Chrysopogon zizanioides)—that can do so in a variety of environments. For RDX, reed canary grass, fox sedge, and rice show promise, although degradation of RDX in the plant tissue is limited.

Determination of the Biologically Relevant Sampling Depth for Terrestrial and Aquatic Ecological Risk Assessments

Posted: January 21, 2016

Based upon an extensive review of ecological literature, this report attempts to provide defensible approximations for identification of the depth of the biotic zone in soils and sediments. Actual sampling depths may be modified by the assessor based on the purpose of the assessment. The primary audience for this document is Superfund staff and contractors and ecological risk assessors. The methods used in this study differ somewhat between Part 1 (Terrestrial Biotic Zone) and Part 2 (Aquatic Biotic Zone). In Part 1, biological activity was quantified in forests and grasslands as a function of depth across selected metrics. In Part 2, the reviewers based the biotic zone(s) in various habitats on the 80th percentile of abundance or on biomass depth distributions.

The Fishrand Spatially-Explicit Bioaccumulation Model

Posted: January 21, 2016

Predictive models are required to evaluate the impact of potential contaminated sediment management alternatives. This project demonstrated the application at two Army sites of a probabilistic, spatially explicit, and dynamic bioaccumulation model, referred to as FishRand. Those results were compared to the currently accepted practice of a deterministic application and a probabilistic but not spatially explicit application. An application was developed for total PCBs, two individual PCB congeners, and three homologue groups at one site, and for DDT, DDE, and DDD at the other site. Since completion of this effort, the model has been updated to provide direct linkage to GIS files (go to

Remediation of Ddt and Its Metabolites in Contaminated Sediment

Posted: January 21, 2016

Sediment characteristics, positioning, and overlying water column must be considered relevant to the release and transport of DDT and its degradation products (DDTR) when evaluating appropriate remediation options. DDTR and other co-contaminants are not necessarily fixed permanently in the sediments. Changes in geochemical and physical parameters (e.g., ORP or anoxic environment, seepage, water table fluctuation) can mobilize these species. Remobilization processes can include the diffusion of DDTR into the water body due to concentration gradients, oxidation of anoxic sediments by bioturbation, or resuspension caused by flooding. DDTR can be transformed or partially degraded in sediments under appropriate environmental conditions; however, the degradation products often are as toxic and persistent as the original pesticides or chlorinated organics. The authors review five technologies that have been applied to remediate DDT-contaminated sediments: dredging, sediment washing, phytoremediation, in situ capping, and natural attenuation.

Engineering Issue: Challenges in Bulk Soil Sampling and Analysis for Vapor Intrusion Screening of Soil

Posted: January 21, 2016

This engineering issue paper discusses the benefits and limitations of using bulk soil samples to assess vapor intrusion (VI) risks from soil containing VOCs. Analyses of factors controlling the VOC concentration distribution in soil and the sensitivity of current laboratory methods are used to show that while bulk soil sampling and analysis may help delineate source areas and determine the gross mass of contamination present in a source area, they cannot adequately assess potential VI exposures for most VOCs in undisturbed soil or in soil remaining after excavation. To address this information gap, this paper also describes alternatives for monitoring soil VOCs and for enhancing remedies at sites where excavation is being considered or used for VOC-contaminated soil.

Permitting of Landfill Bioreactor Operations: Ten Years After the Rd&D Rule

Posted: January 21, 2016

To formally promote innovative landfill technologies, including adoption of alternative cover systems and bioreactor technology, EPA published the Research, Development, and Demonstration (RD&D) Permit Rule on March 22, 2004. The Rule allows Subtitle D landfills a variance option for adding bulk free liquids if a demonstration can be made that such a variance will not increase risk to human health and the environment relative to standard permit conditions for the landfill. Prior to promulgation of the Rule, about 20 full-scale bioreactor landfill projects were underway in North America, including one in Canada. By March 2014, 40 bioreactor projects were reported. Wisconsin features the largest number of projects at 13. Only 16 of 50 states had adopted the Rule in 2014, with a further seven reportedly in the process of Rule adoption.

Groundwater Remediation Startup Report, Site Monitoring & Performance Evaluation Report, Revision 1.0: Chemical Injections & Attenuation Monitoring, 2nd & Kirby Site, Hutchinson, Kansas

Posted: February 3, 2016

A truck transportation facility has been operated at the 2nd & Kirby intersection since the 1950s. Dissolved-phase TCE and related contaminants have been found in the site groundwater. The site contractor used direct-push injections to introduce emulsified vegetable oil (EVO) to provide the electron donor needed to produce the reducing and anaerobic conditions that stimulate contaminant biodegradation. A total of ~9,000 gal of EVO-water solution (900 gal EVO product, specifically SRS®-FRL) was injected throughout the course of the project. The presence of cDCE as a degradation product of TCE indicates some degree of ongoing reductive dechlorination. This report details the specific measures applied to accelerate the chemical and biological degradation of TCE in the site groundwater.

In Situ Wetland Restoration Demonstration: ESTCP Cost and Performance Report

Posted: February 3, 2016

Specific objectives of the demonstration performed at Aberdeen Proving Ground, Maryland, were to evaluate the ability of activated carbon (AC) to reduce PCB bioavailability and associated risks in Canal Creek wetland habitats using a variety of AC delivery systems; provide cost and performance data; obtain regulatory agency and trustee acceptance; and disseminate lessons learned. Sequestration agents were mechanically deployed over the surface of a wetland and allowed to integrate into the surface layer of the hydric soil through natural mixing processes (e.g., bioturbation, tidal cycles, root mixing). The technologies deployed comprised a powder-activated carbon (PAC) slurry (the Slurry Spray), two pelletized AC products (AquaBlok® and SediMite™), and an engineered manufactured soil cover system (the Sand control). The goal was risk reduction, not mass removal; hence, performance was gauged through post-treatment evaluation of reduction in PCB bioavailability. While the findings of the overall program suggest that AC addition can sequester PCBs, the field demonstration findings were not conclusive in demonstrating effective reductions in bioavailability. See this report and the project summary presentation at the bottom of