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

In Situ Chemical Oxidation: Lessons Learned at Multiple Sites

Posted: April 18, 2019

This paper compiles a detailed set of in situ chemical oxidation (ISCO) lessons learned pertaining to design, execution, and safety based on global experiences over the last 20 years. While the benefits of a correct application are known, history also provides examples of a variety of incorrect applications that provide an opportunity to highlight recurring themes that resulted in failures. This paper combines a thorough discussion of lessons learned through decades of ISCO implementation throughout all aspects of ISCO projects with an analysis of changes to the ISCO remediation market. By discussing the interplay of these two themes and providing recommendations from collective lessons learned, the future of safe, cost-effective, and successful applications of ISCO can be improved.

Post-Remediation Evaluation of Evo Treatment: How Can We Improve Performance?

Posted: April 18, 2019

Conclusions and lessons learned in this demonstration project were integrated with prior lab and field studies to generate a general conceptual model of enhanced reductive dechlorination (ERD) with emulsified vegetable oil (EVO) and pH buffer. The conceptual model on which this design tool is based provides a relatively concise summary of the current understanding of ERD with EVO, including (1) ERD microbiology and organohalide respiration; (2) environmental requirements for efficient dechlorination; (3) EVO properties, transport and retention in the subsurface; (4) EVO consumption during ERD; (5) aquifer pH and buffering; and (6) injection system design. Additional information: Excel Spreadsheet Design Tool

Demonstration/Validation of More Cost-Effective Methods for Mitigating Radon and VOC Subsurface Vapor Intrusion to Indoor Air

Posted: April 18, 2019

New lines of evidence and mathematical modeling were developed to aid in the design and performance monitoring of subslab venting systems for mitigation of radon and VOC vapor intrusion to protect the health of building occupants from inhalation exposures. Results indicate that system performance depends strongly on the relative permeability of the floor slab and the material below the floor slab, and that both parameters can be determined with reasonable confidence using tests and analysis that are rapid and affordable. Where coarse granular fill is present below a high quality floor slab, the radius of influence may extend to considerable distances, which reduces the number of suction points required and the associated capital cost. Where a system already exists, mass emission monitoring may help reduce the operation, maintenance, and monitoring costs.

Source Barrier Tool: Contaminant Flux Reduction Barriers for Managing Difficult-To-Treat Source Zones in Unconsolidated Media

Posted: April 18, 2019

This tool explains the potential benefits of a physical barrier around a chlorinated solvent source zone and helps the user understand if a barrier would work at a particular site. The overall objective of this project was to evaluate if inexpensive flow reduction agents delivered via permeation grouting technology could help manage difficult-to-treat chlorinated solvent source zones, or any other source zone comprising contaminants that degrade primarily via anaerobic biodegradation processes inhibited by naturally occurring competing electron acceptors, such as oxygen and sulfate. Additional information: Source Barrier Tool

First Five-Year Review Report Holden Mine Site Okanogan-Wenatchee National Forest Chelan County, Washington

Posted: February 1, 2019

The Holden Mine produced about 200 million lbs of Cu, 40 million lbs of Zn, two million ounces of Ag, and 600,000 ounces of Au from ~10 million tons of ore. Excavation of 60 miles of underground tunnels produced 8.5 million tons of mill tailings placed on 90 acres of U.S. National Forest lands as well as 300,000 yd3 of waste rock piles. Direct release of hazardous materials from the mine, including acid mine drainage, heavy metals (Al, Cd, Cu, Fe, Pb, and Zn), and iron sulfide, affected about 125 acres of land. The remedy is being conducted in 2 phases. Phase 1, which began in 2013 with completion expected in 2018, includes regrading and capping the tailings and main waste rock piles, constructing a groundwater barrier wall and groundwater collection system around Tailings Pile 1 and the Lower West Area, constructing a new groundwater treatment facility, beginning in situ soil treatment (e.g., application of agricultural lime) in areas of interest, implementing institutional controls, and initiating performance verification monitoring. Phase 2 is expected to begin in 2023. In situ treatment is still under technical review and consideration for implementation due to environmental constraints, potential destruction of established forests and habitats, rough topography, and practicability of the remedy.

How to Assess Potential Biological Effects of Subaqueous Disposal of Mine Tailings: Literature Review and Recommended Tools and Methodologies

Posted: February 1, 2019

Subaqueous disposal (SAD) or flooding of sulfide-rich tailings in constructed facilities is a method used at some mine sites to mitigate the formation of acid mine drainage. The primary SAD mitigation mechanism is limitation of oxygen ingress into water-filled pores, which greatly reduces sulfide oxidation, minimizes metal leaching, and prevents acidic drainage development. The overall biological performance of such facilities is not well understood. In particular, a major gap in understanding relates to the biological colonization of such facilities, the health of biological communities that are established, and the influence of those communities on water and sediment geochemistry. This report contains an introduction, an extensive literature review (Sections 2-7), and a set of recommendations on tools and methodologies that might be used to assess the biological effects of submerged tailings.

Global Cover System Design: Technical Guidance Document

Posted: February 1, 2019

Designed primarily for those investigating the use of cover systems on mine sites, this document offers a "best practice" summary to assist mine operators, designers, and regulators to address the role cover systems play over the life of the mine, from early conceptualization to long-term performance monitoring. A conceptual model illuminates how cover system designs might affect contaminant and acidity loading. The model attempts to determine when the varying roles of cover system design (e.g., control of net percolation or oxygen ingress) might influence loadings. Acknowledgment of these unique relationships provides an opportunity to optimize cost-effective management of metal loading and acid rock drainage. The cover system design tool walks users through relevant climatic factors to optimize cover system design alternatives and meet desired performance design criteria.

Sewers and Utility Tunnels as Preferential Pathways for Volatile Organic Compound Migration Into Buildings: Risk Factors and Investigation Protocol

Posted: February 7, 2019

The objectives of this demonstration project were to (1) develop and validate an effective protocol to determine the presence or absence of a sewer/utility tunnel preferential pathway during a vapor intrusion (VI) investigation (i.e., is a sewer/utility transporting VOCs from a subsurface source causing unacceptable buildings impacts?); (2) apply the validated protocol at VI sites to evaluate how often sewer/utility preferential pathways play a role in VOC transport into buildings; and (3) use the results to develop a detailed conceptual model for preferential pathways that identifies the types of sites at risk and the key mechanisms and processes involved in VOC transport through preferential pathways. The following reports have been completed: Final Report (790 pp); Executive Summary (26 pp); Conceptual Model (20 pp); and Investigation Protocol (27 pp).

Evaluating the Efficacy of Bioaugmentation for In-Situ Treatment of PCB Impacted Sediments

Posted: February 7, 2019

The project objective was to demonstrate and validate a recently developed in situ treatment for degrading PCBs in contaminated sediments under field conditions. The innovative aspect of the technology is the application of activated carbon pellets as a solid substrate for: 1) delivery of microorganisms into sediments and 2) sequestration and concentration of hydrophobic PCBs in close proximity to the PCB-transforming bacteria. Both anaerobic halorespiring and aerobic PCB-degrading bioamendments were mass cultured, transported to a site, and delivered through a water column to sediments without loss of viability. Treatment with the bioamendment mixture reduced the mean total PCB concentration by an average of 52% and the aqueous PCB fraction by 95% after 13.5 months. Costs of the treatment were less than thick caps and dredging, and the approach is suited to treat ecologically sensitive and difficult to reach areas.

Technical Measurement Guidance for Lnapl Natural Source Zone Depletion

Posted: February 7, 2019

Natural source zone depletion (NSZD) is a term used to extend the traditional understanding of natural attenuation to the LNAPL source zone. It describes the collective, naturally occurring processes of dissolution, volatilization, and biodegradation that result in mass losses of LNAPL petroleum hydrocarbon constituents from the subsurface. This document provides a knowledge base and procedures for consistency in the measurement of NSZD by a variety of methods, including aqueous, soil gas flux, biogenic heat, and LNAPL compositional change method based on chemical analysis of oil. The guide is generally applicable to a wide range of environmental remediation sites containing petroleum hydrocarbon impacts in the subsurface. It is intended for use at sites that have a need for theoretical, qualitative, or quantitative understanding of NSZD processes.

Mineral Processing Technologies for the Remediation of Soils Polluted by Trace Elements

Posted: February 7, 2019

Soil washing is usually conducted in mobile plants on site; however, prior to field implementation of the treatment, detailed soil characterization and trials are required to optimize the process. In this work, soils affected by heavy metals as a result of mining, metallurgical, and industrial activities were evaluated and treated at pilot scale. The diversity of soils and residues treated in combination with the variety of the methodologies employed enabled the elaboration of a general feasibility protocol for pilot-scale soil washing studies.

Per- and Polyfluoroalkyl Substances in Source and Treated Drinking Waters of the United States

Posted: February 19, 2019

Scientists measured 17 per- and polyfluoroalkyl substances (PFASs) in source and treated water from 25 drinking water treatment plants (DWTPs) as part of a broader study of contaminants of emerging concern (CECs) in drinking water across the United States. PFAS were quantitatively detected in all 50 samples, with summed concentrations of the 17 PFAS ranging from <1 ng/L to 1102 ng/L. The median total PFAS concentration was 21.4 ng/L in the source water and 19.5 ng/L in the treated drinking water. Comparing the total PFAS concentration in source and treated water at each location, only five locations demonstrated statistically significant differences (i.e., P <0.05) between the source and treated water. When PFOA and PFOS concentrations in the treated drinking water were compared to the existing U.S. EPA's PFOA and PFOS drinking water heath advisory of 70 ng/L for each chemical or their sum, one DWTP exceeded the threshold. Six of the 25 DWTPs were along two large rivers. The DWTPs within each of the river systems had specific PFAS profiles, with three DWTPs from the first river dominated by PFOA, while three DWTPs on the second river were dominated by perfluorobutyric acid (PFBA). This paper is Open Access at

EPA's Per- and Polyfluoroalkyl Substances (PFAS) Action Plan

Posted: February 19, 2019

Per- and polyfluoroalkyl substances (PFASs), a group of synthetic chemicals that have been in use since the 1940s, are found in a wide array of consumer and industrial products. Evidence indicates that continued exposure above specific levels to certain PFASs may lead to adverse health effects. This Action Plan describes EPA's approach to identifying and understanding PFASs, approaches to addressing current PFAS contamination, preventing future contamination, and effectively communicating with the public about PFASs. The Action Plan describes broad actions underway to address challenges with PFASs in the environment, including next steps on four PFAS management actions: (1) initiating steps to evaluate the need for an MCL for PFOA and PFOS; (2) beginning the necessary steps to propose designating PFOA and PFOS as "hazardous substances" through one of the available federal statutory mechanisms; (d) developing groundwater cleanup recommendations for PFOA and PFOS at contaminated sites; and (4) developing toxicity values or oral RfDs for GenX chemicals and perfluorobutane sulfonic acid (PFBS). In addition to these actions, EPA's PFAS Action Plan identifies other short- and long-term actions currently being implemented to understand and address PFASs.

Data Review and Validation Guidelines for Perfluoroalkyl Substances (PFASs) Analyzed Using EPA Method 537

Posted: February 19, 2019

This document contains guidance to aid the data reviewer in determining the usability of analytical data generated for perfluoroalkyl substances. It is primarily based on EPA Method 537 and the general validation approach developed under EPA's Contract Laboratory Program. This guide is intended to be applicable to data gathered using EPA Method 537 for investigative purposes. Data users evaluating drinking water sample results or assessing potential human exposure relative to published drinking water health advisory levels should not qualify or use analytical result data that fail Method 537 quality control criteria. To make appropriate judgments, the reviewer needs a complete understanding of the intended use of the data and is strongly encouraged to establish a dialogue with the data user prior to and following the data review, to discuss usability issues and resolve questions regarding the review.

Long-Term Stewardship of Three Evapotranspirative Covers: 15 Years

Posted: March 6, 2019

Summer 2018 marked the 15th anniversary of effective, compliant evapotranspiration (ET) landfill cover performance at Sandia National Laboratories (SNL). From 2003 to 2009, SNL constructed three ET covers ranging from 2.2 to 4.1 acres in Sandia's Technical Area 3 on Kirtland AFB, south of Albuquerque, New Mexico. The evaporation potential is optimal in Albuquerque due to low humidity and generally warm temperatures. The average annual precipitation in this area is 8.72 inches, with half of that accumulation occurring from intense, brief thunderstorms during the months of June through August. New Mexico Environment Department (NMED) post-closure care, long-term monitoring, and maintenance requirements call for quarterly cover inspections, any follow-on maintenance within 60 days, and annual reporting. All three SNL ET Covers meet successful revegetation permit requirements. NMED has approved all SNL annual reports. To facilitate exchange of lessons learned between cover projects, a single SNL team performs all three covers inspections. Likewise, maintenance activities are grouped under a single task order contract. All maintenance work is verified by a biologist and project lead. This presentation notes best practices and lessons learned from SNL's 15 years of experience with ET cover construction, preventive care, and maintenance.

Demonstration of New Tools for Improved Source and Recontamination Potential Assessment

Posted: March 6, 2019

A family of technologies adapted from the oceanographic and environmental arenas was combined to improve DoD's ability to address sediment contaminant source exposure, transport, and fate challenges at coastal sites in a relatively simple and cost-effective way. The demonstration focused on the following three key technologies: (1) Drifting Exposure System - a surface global positioning system (GPS) drifter with position data telemetry, composite sample collection, and passive sampler capabilities for exposure characterization. (2) Drifting Particle Simulator - a GPS drifter with position data telemetry, buoyancy control, bottom detection, and passive sampling capability for measurement of depositional footprints and sampling of source related particles. (3) Sediment Deposition Detector - a sediment bed scour sensor with high resolution differential pressure sensor, shore cable or in situ data logging, and coupled sediment trap capabilities. Field demonstrations were conducted at Naval Base San Diego (Paleta Creek) and Joint Base Pearl Harbor Hickam (Oscar Pier and Waiau Power Plant Area).

Alternatives Evaluation Report: Penobscot River Phase III Engineering Study, Penobscot River Estuary, Maine

Posted: March 6, 2019

Beginning in 1967, a chlor-alkali facility located in Orrington, Maine, released mercury into the Penobscot River Estuary. Hg releases at overall declining concentrations continued throughout facility operation and ceased with facility closure in 2000. The slow rate of Hg concentrations decline in the area is attributable, in part, to the presence in the Estuary of a large pool of Hg-affected mobile sediment, which is retained in the Estuary by natural processes that result in the landward flow of both bottom water and associated sediment under the influence of tides. Following several extensive studies of this contamination issue, six remedial alternatives were evaluated for this report: (1) monitored natural recovery; (2) enhanced monitored natural recovery; (3) dredging; (4) thin layer capping in Mendall Marsh; (5) amendment application in Mendall Marsh; (6) dredging in intertidal and subtidal zones plus thin layer capping in Mendall Marsh. Bench-scale treatability studies were conducted to provide data for the development and evaluation of alternatives.

Assessment and Management of Stormwater Impacts On Sediment Recontamination: Guidance Document

Posted: March 6, 2019

The recommended approach in this guide to assess and evaluate stormwater discharges and sediment recontamination is based upon the implementation of those practices in SERDP Project ER-2428 [

Overview of In Situ and Ex Situ Technologies in Development for the Treatment of Per- and Polyfluoroalkyl Substances

Posted: April 18, 2019

This webinar covers conventional and innovative technologies to address PFASs in water and soil. Remediation of groundwater often requires a treatment train, combining conventional sorbents and engineered filtration with more innovative and emerging remediation solutions for PFASs. While in situ soil stabilization is a promising technique, ongoing research and development is being conducted to evaluate the longevity of fixation amidst circumneutral pH and biotransformation, which may enhance PFAS dissolution. Remediation of PFAS source zones and the associated groundwater plumes presently requires multiple technologies to protect human health in a cost-conscious manner. See a recording of the presentation at