Posted: July 8, 2024
EPA-ORD's Engineering Issue Papers (EIPs) are a series of technology transfer documents that summarize the latest information on selected waste treatment and site remediation technologies and related issues and present it in a conveniently accessible manner to the user community. EIPs are designed to help remedial project managers (RPMs), on-scene coordinators (OSCs), contractors, and other contaminated sites technical staff and site managers understand the type of data and site characteristics that are needed to evaluate a technology for a specific site, as well as ways to design and optimize a technology for a particular application. This latest EIP summarizes the current knowledge on electrokinetic (EK)-enhanced in situ remediation technologies that are available for addressing contaminants in low-permeability (low-k) subsurface environments where conventional hydraulic delivery technologies often face challenges.
Posted: April 11, 2024
The updated guidance reflects the latest, best available science to provide information that managers of PFAS wastes can use to evaluate the most appropriate destruction, disposal, or storage method among those currently available.
Posted: March 12, 2024
The Federal Remediation Technologies Roundtable (FRTR) Matrix is a user-friendly tool for screening potentially applicable technologies for a remediation project. The matrix allows you to screen 49 in situ and ex situ technologies for either soil or groundwater remediation. Variables used in screening include contaminants, development status, overall cost, and cleanup time. Detailed information on each technology is also available, including direct links to the database of cost and performance reports written by FRTR members.
Posted: March 12, 2024
AMDTreat 6.0 Beta is a computer application for estimating the long-term costs of the abatement of mine drainage discharge, commonly referred to as Acid Mine Drainage (AMD). AMDTreat 6.0 Beta can assist a user in estimating costs and sizing facilities to abate water pollution, using passive or chemical treatment technologies. Treatment systems, vertical flow ponds, anoxic limestone drains, anaerobic wetlands, bioreactors, caustic soda, hydrated lime, pebble quicklime, soda ash treatment and other systems can be evaluated.
Posted: March 12, 2024
To support EPA's Per- and Poly-Fluoroalkyl (PFAS) Strategic Roadmap, the Agency is compiling and integrating a collection of data that can be used to evaluate what is known about PFAS manufacture, release, and occurrence in communities. As part of this effort, EPA is integrating data available nationally with other information from states, Tribes, and localities that are testing for PFAS pursuant to their own regulatory or voluntary data collection initiatives. The data included in the PFAS Analytic Tools have a wide range of location-specific data and, in general, are based on national scope, and readily accessible, public information repositories.
Posted: March 12, 2024
This website provides an updated spreadsheet tool developed by the EPA for estimating indoor air concentrations and associated health risks from subsurface vapor intrusion into buildings. The tool is based on the analytical solutions of Johnson and Ettinger for contaminant partitioning and subsurface vapor transport into buildings.
Posted: March 12, 2024
The Matrix Diffusion Toolkit, developed for the Department of Defense's Environmental Security Technology Certification Program (ESTCP), is a free software tool that can assist site personnel to effectively and efficiently estimate the effects matrix diffusion will have at their site, and share the results with stakeholders. The Toolkit is Microsoft Excel-based and provides the following tools to calculate and evaluate matrix diffusion effects:
- Square Root Model - this module provides planning-level estimates of the mass discharge (in units of grams per day) caused by release from a low-k diffusion-dominated unit (typically silt or clay) into a high permeability advection-dominated unit (typically sand or gravel).
- Dandy-Sale Model - this module allows users to perform contaminant transport via advection and transverse diffusion in the transmissive layer, and transport via transverse diffusion in the low-k zone. The module also provides planning-level estimates of the low-k zone and the transmissive zone.
- Matrix Diffusion Related Tools - Additional tools related to matrix diffusion are provided, including the NAPL Dissolution Calculator, Plume Magnitude Information, Low-k Zone Remediation Alternatives, and a 14-Compartment Model.
Posted: March 11, 2024
PHAST is a computer program that simulates multicomponent, reactive solute transport in three-dimensional saturated groundwater flow systems. PHAST is a versatile groundwater flow and solute-transport simulator capable of modeling a wide range of equilibrium and kinetic geochemical reactions. The flow and transport calculations are based on a modified version of HST3D that is restricted to constant fluid density and constant temperature. The geochemical reactions are simulated with the geochemical model PHREEQC, which is embedded in PHAST.
PHAST can be used in studies of migration of nutrients, inorganic and organic contaminants, and radionuclides; in projects such as aquifer storage and recovery or engineered remediation; and in investigations of the natural rock/water interactions in aquifers.
Posted: March 11, 2024
MODFLOW is a modular hydrologic model and is considered an international standard for simulating and predicting groundwater conditions and groundwater/surface-water interactions. MODFLOW programs are capable of simulating coupled groundwater/surface-water systems, solute transport, variable-density flow (including saltwater), aquifer-system compaction and land subsidence, parameter estimation, and groundwater management.
Posted: March 11, 2024
The GSI Mann-Kendall Toolkit is a free, simple, easy-to-use software tool to help environmental professionals efficiently conduct concentration trend analyses for any groundwater constituent. The tool can be used to demonstrate the plume stability condition (expanding, stable, or decreasing) and track the progress of remediation efforts, in a quantitative and consistent manner.
Posted: August 19, 2024
This presentation discusses the effects of increasing the temperature of thermal remediation technologies, electrical resistance heating, and thermal conductive heating on the recoverability of contaminants. Challenges of remediation in low permeability soils include limitations to injecting and extracting liquids and/or gases to facilitate the treatment or recovery of organic compounds. For many legacy contaminated sites, there can be decades or more between when the contamination occurred and when efforts are undertaken to remediate the site. While migration of contaminants into low permeability soils is slow, the delays between when the contamination occurs and when remediation is undertaken provide ample opportunity for the low permeability soils to become contaminated. Remediation efforts generally attempt to recover or treat the contaminants in much less time. Lower groundwater flow rates in low permeability soils means the contaminants are not flushed out rapidly. While the low permeability limits liquid flow in these soils, they can readily be heated. The presentation includes two case studies where thermal treatments were used to remediate PCE in soil.
Posted: August 19, 2024
A novel three-layer permeable reactive barrier (PRB) material incorporating Fe0 and coconut shell biochar was field-scale tested at a chlorinated hydrocarbon (CH)-contaminated site. Monitoring data revealed conditions conducive to reductive dechlorination (low oxygen levels and a relatively neutral pH in the groundwater). The engineered PRB material consistently released organic carbon and iron, fostering CH-dechlorinating bacteria proliferation. Over 250 days, the pilot-scale PRB achieved CH removal efficiencies from 21.9%-99.6% for various CH compounds. Initially, CHs were predominantly eliminated through adsorption and iron-mediated reductive dechlorination, but microbial reductive dechlorination emerged as the predominant mechanism for sustained and long-term CH removal. See the introduction and section snippets at
Posted: August 19, 2024
A study investigated the effects of waste-based biochars on PFAS leaching from sandy soil at a former fire-fighting facility with a low total organic carbon content (TOC, 0.57 ± 0.04%) impacted by PFAS from AFFF. Six different biochars (pyrolyzed at 700-900°C) made from clean wood chips (CWC), waste timber (WT), activated waste timber (aWT), two digested sewage sludges (DSS-1 and DSS-2), and de-watered raw sewage sludge (DWSS) were tested. Up-flow column percolation tests (15 days and 16 pore volume replacements) with 1% biochar indicated that PFOS was retained best by the aWT biochar (99.9% reduction) in the leachate, followed by sludge-based DWSS (98.9%) and DSS-2 (97.8%) and DSS-1 (91.6%). The non-activated wood-based biochars (CWC and WT) reduced leaching by < 42.4 %. Extrapolating this to field conditions, 90% leaching of PFOS would occur after 15 y for unamended soil and after 1200 y and 12,000 y, respectively, for soil amended with 1% DWSS-amended and aWT biochar. The high effectiveness of aWT and the three sludge-based biochars in reducing PFAS leaching from the soil was attributed largely to high porosity in a pore size range (>1.5 nm) that can accommodate the large PFAS molecules (>1.02-2.20 nm) combined with a high affinity to the biochar matrix. Other factors, like anionic exchange capacity, could play a contributing role. Sorbent effectiveness was better for long-chain than short-chain PFAS due to weaker apolar interactions between the biochar and the latter's shorter hydrophobic CF2-tails.
Posted: September 5, 2024
Surfactant Enhanced Aquifer Remediation (SEAR) and in situ chemical oxidation (S-ISCO) were employed in the LIFE SURFING Project to remediate an aquifer contaminated with DNAPL from nearby lindane production at the Bailin Landfill in Sabinanigo, Spain. The project overcame traditional extraction limitations and prevented groundwater contamination from reaching the river. Two SEAR interventions involved injecting 9.3 m3 (SEAR-1) and 6 m3 (SEAR-2) of aqueous solutions containing 20 g/L of the non-ionic surfactant E-Mulse 3®, with bromide (~150 mg/L) serving as a conservative tracer. In SEAR-1 and SEAR-2, 7.1 and 6.0 m3 were extracted, respectively, 60-70% of the injected bromide and 30-40 % of the surfactant were recovered, confirming surfactant soil adsorption. About 130 kg of DNAPL were removed, with >90% mobilized and 10% solubilized. A surfactant-to-DNAPL recovery mass ratio of 2.6 was obtained, a successful value for a fractured aquifer. The S-ISCO phase entailed injecting 22 m3 of a solution containing persulfate (40 g/L), E-Mulse 3 (4 g/L), and NaOH (8.75 g/L) in pulses over 48 h, oxidizing ~20 kg of DNAPL and ensuring low toxicity levels. Preceding the SEAR and S-ISCO trials, time was dedicated to detailed groundwater flow characterizations, including hydrological and tracer studies, which allowed the design of a barrier zone between 317 and 557 m from the test cell and the river, situated 900 m from the site. This zone, which integrated alkali dosing, aeration, vapor extraction, and oxidant injection, effectively prevented fluid escape. Neither surfactants nor contaminants were detected in river waters post-treatment. No residual phase in test cell wells and reduced chlorinated compounds in groundwater were detected until one year after S-ISCO.
Posted: September 17, 2024
An innovative technology combining ISCO and enhanced desorption was applied at a petroleum hydrocarbon-contaminated site to treat residual LNAPL and enhance the effectiveness of groundwater extraction and the treatment systems. The enhanced remediation system included reagent injections of PetroCleanze® (a desorbent) and RegenOx® (an oxidizer) into the subsurface to stimulate the desorption and oxidation of residual hydrocarbons, mobilizing them for subsequent extraction. Real-time subsurface dynamics were investigated through geophysical monitoring, employing electrical resistivity tomography (ERT) to trace reagent migration pathways via their effect on bulk electrical conductivity. Integrating groundwater sampling data aimed to provide additional insights into the transformations of contaminants in the spatiotemporal context. Vivid 2D time-lapse ERT sections showcased the evolution of resistivity anomalies, providing high-resolution evidence of heterogeneity, dispersion pathways of desorbent and oxidant, and residual LNAPL mobilization. Hydrochemical analyses revealed effective mobilization processes with increasing groundwater concentrations of TPH over time. Speciation analysis showed the interplay of desorption and oxidation, portraying the dynamic fractionation of hydrocarbon components. The hydrogeophysical and data-driven framework provided qualitative and quantitative insights into reagent and contaminant distribution, enhancing the understanding of spatial and temporal physio-chemical changes during the remediation process. Coupling hydrogeophysical and chemical findings provided insight into the transformation of contaminants following the sequence of product injection and the push and pull activities, capturing the removal of mobilized contaminants through hydraulic barrier wells. This enhanced understanding proves instrumental in optimizing and tailoring remediation efforts, especially in heterogeneous environmental settings.
Posted: September 17, 2024
Subslab soil gas (SSSG) samples were collected as part of an investigation to evaluate vapor intrusion (VI) into a building and will be used to provide input into future OSWER VI Guidance documents on SSSG sample collection, as the June 2015 OSWER VI Guide does not provide specific, detailed recommendations regarding how to collect SSSG samples. Three different subslab sampling port types were constructed with various sampling techniques within a hexagon-shaped grid near each other. Conventional-, Vapor Pin-, and California-style ports were established in duplicate for continual analysis by onsite gas chromatography-electron capture detection. Triplicate ports were established to evaluate active and passive long-term sampling methods to determine short-range temporal differences. Active sampling methods included evacuated stainless-steel canisters fitted with capillary flow controllers and sorbent tubes collected using a syringe. Samples were analyzed using EPA TO-17 (Modified) using sorbent tube samplers as the passive sampling method. No systematic differences in sample results between conventional, Vapor Pin, and CA-style probes used in SSSG sampling were identified. Site management decisions would likely be the same for data from any subslab port style, active or passive sampling techniques over durations less than 2 weeks.
Posted: September 17, 2024
This paper summarizes current vapor intrusion (VI) guidance, petroleum hydrocarbon-specific VI guidance, and/or media-specific volatilization criteria in broader regulatory programs. Since 2018, 30 states have revised their guidance, issued new guidance or updated criteria or other VI-related information. For each state and the District of Columbia, the review includes tabulations of the available types of screening values (e.g., soil, groundwater, soil gas, and indoor air), the screening values for selected chemicals that commonly drive VI investigations (e.g., TCE, PCE, benzene, and other selected VOCs), and the basis of risk levels used for cancer and non-cancer risk. Federal values are also included for comparison. It also summarizes available key policy criteria for each state, including trigger distances, default subsurface to indoor air attenuation factors, policies for evaluation of petroleum VI, strategies for preferential pathways, and policies for mitigation of VI.
Posted: October 17, 2024
This article reports outcomes of lysimeter investigations conducted across three sites and 18 lysimeters within fine-textured soil profiles. Soil cores from the same locations were recovered. PFAS concentrations in soils and lysimeter porewater were compared with prior lab investigations. Variable concentration distributions with depth of PFAS in soils were found with a max PFAS sum of ~56 mg/kg, dominated by PFOS. The max PFAS sum in porewater was 13.5 mg/L. Comparison across all collocated soil and porewater concentrations did not provide consistent trends. PFAS mass fractions within lysimeter porewater samples were much higher for most PFAS than mass fractions determined from lab investigations, but the fraction was lower for PFOS. Results indicate preferential recovery of individual shorter chain PFAS via leaching at lower liquid: soil ratios such as those experienced under suction during recovery of porewater by lysimeters. Suggestions are offered to advance the use of suction lysimeters in promoting porewater PFAS concentrations as an alternative for regulatory compliance and closing the gap between field and lab approaches.
Posted: October 17, 2024
The presence of PFAS in woven and nonwoven polypropylene geotextiles and four nonwoven polyester geotextiles commonly used in modern geosynthetic composite lining systems for waste containment facilities such as landfills was investigated. Targeted analysis for 23 environmentally significant PFAS molecules and methods for examining "PFAS total" concentrations were used to assess their occurrence. Most geotextile specimens contained PFPrA with concentrations ranging from non-detect to 10.84 µg/g. Average PFPrA concentrations of PFPrA were higher in polypropylene than in polyester geotextiles. PFAS total parameters comprising total fluorine and total oxidizable precursors indicated no significant precursor mass or untargeted intermediates were present in geotextiles. The study identified geotextiles as a possible source of ultrashort PFAS in engineered lined waste containment facilities, which may contribute to the overall PFAS total concentrations in leachates or liquors they are in contact with. Findings may lead to further implications on the fate and migration of PFAS in geosynthetic composite liners, as previously unidentified concentrations, particularly of ultrashort-chain PFAS, may impact the extent of PFAS migration through and attenuation by constituents of geosynthetic composite liner systems.
Posted: October 17, 2024
This guidance updates the UK Environment Agency's technical guidance for monitored natural attenuation (MNA) published in 2000. It captures significant scientific advances that have been made in understanding contaminant behavior and reactive transport in the subsurface, alongside ongoing developments in site characterization, monitoring, and predictive modeling approaches and technologies. These evolving methods enhance contaminant and process-specific understanding required to develop advanced conceptual site models for MNA, addressing complexities and uncertainties that were previously challenging to deal with. These advancements further support the development of three lines of evidence typically considered to demonstrate the effectiveness of natural attenuation for risk management in groundwater:
- Primary: reduction in contaminant concentration, mass and/or mass discharge in groundwater;
- Secondary: geochemical data and modeling that provides indirect evidence of the natural attenuation processes likely causing the observed reductions in contamination (primary line of evidence); and
- Tertiary: contaminant and/or process-specific evidence to support the primary and secondary lines of evidence.
The phased approach described in this guidance supports the identification of contaminant plumes for which MNA is likely feasible, then demonstrates the ability of natural attenuation to protect receptors now and in the future, before undertaking a monitoring program to confirm MNA will achieve remedial objectives within a timeframe suitable for all stakeholders.