EPA 625/R-00/004 October 2000 IN SITU TREATMENT OF SOIL AND GROUNDWATER CONTAMINATED WITH CHROMIUM TECHNICAL RESOURCE GUIDE Center for Environmental Research Information National Risk Management Research Laboratory Office of Research and Development U.S. Environmental Protection Agency Cincinnati, Ohio 45268Notice The U.S. Environmental Protection Agency through its Office of Research and Development funded and managed the research described here under Contract No. 68-C7-0011, Work Assignment 27, to Science Applications International Corporation (SAIC). It has been subjected to the Agency’s peer and administrative review and has been approved for publication as an EPA document. Mention of trade names or commercial products does not constitute endorsement or recommendation for use. iForeward The U.S. Environmental Protection Agency is charged by Congress with protecting the Nation’s land, air, and water resources. Under a mandate of national environmental laws, the Agency strives to formulate and implement actions leading to a compatible balance between human activities and the ability of natural systems to support and nurture life. To meet this mandate, EPA’s research program is providing data and technical support for solving environmental problems today and building a science knowledge base necessary to manage our ecological resources wisely, understand how pollutants affect our health, and prevent or reduce environmental risks in the future. The National Risk Management Research Laboratory is the Agency’s center for investigation of technological and management approaches for reducing risks from threats to human health and the environment. The focus of the Laboratory’s research program is on methods for the prevention and control of pollution to air, land, water and subsurface resources; protection of water quality in public water systems; remediation of contaminated sites and ground water; and prevention and control of indoor air pollution. The goal of this research effort is to catalyze development and implementation of innovative, cost-effective environmental technologies; develop scientific and engineering information needed by EPA to support regulatory and policy decisions; and provide technical support and information transfer to ensure effective implementation of environmental regulations and strategies. This publication has been produced as part of the Laboratory’s strategic long-term research plan. It is published and made available by EPA’s Office of Research and Development to assist the user community and to link researchers with their clients. E. Timothy Oppelt, Director National Risk Management Research Laboratory iiAbstract Chromium is the second most common metal found at sites for which Records of Decision have been signed. At many industrial and waste disposal locations, chromium has been released to the environment via leakage and poor storage during manufacturing or improper disposal practices. Industrial applications most commonly use chromium in the hexavalent chromium [Cr(VI)] form, which is acutely toxic and very mobile in groundwater. Groundwater extraction and treatment has traditionally been used to remediate chromium-contaminant plumes. This method, while providing interception and hydraulic containment of the plume, may require long-term application to meet Cr(VI) remediation goals and may not be effective at remediating source-zone Cr(VI). New information and treatment approaches have been developed for chromium-contaminated soil and groundwater treatment. The purpose of this report is to bring together the most current information pertaining to the science of chromium contamination and the in situ treatment and control of sites with groundwater and/or soil contaminated with chromium. A number of available in situ technologies or treatment approaches use chemical reduction and fixation for chromium remediation. These include geochemical fixation, permeable reactive barriers (PRBs), and reactive zones. Other types of in situ treatment that are under development include enhanced extraction, electrokinetics, biological processes that can be used within PRBs and reactive zones, natural attenuation, and phytoremediation. Detailed discussions of these in situ technologies are contained in the report. Each discussion consists of a technology description with its advantages and disadvantages, status, and performance and cost data. A comparative summary of the status of the technologies is presented in Table 3-1. More conventional ex situ approaches and other proven and well-documented technologies for chromium treatment or control are not reviewed within this report. The emphasis in this report is on innovative in situ approaches for chromium remediation that are not as well documented, but have been demonstrated or are being developed. It should be noted that this report is not a design document, but a resource guide. Although it does contain design and cost information, it is primarily intended to enable concerned parties, regulators, scientists, and engineers to evaluate the potential use of various treatment technologies, or combinations of these technologies, to clean up chromium-contaminated sites effectively. iiiTable of Contents Section Page Notice ............................................................. i Foreward ........................................................... ii Abstract............................................................ iii Figures ............................................................ vi Tables ............................................................. v i i Acronyms, Abbreviations, and Symbols ................................... v i i i Acknowledgments .................................................... xi 1 – INTRODUCTION 1.1 Purpose ...................................................... 1 1.2 Background and Regulatory Overview ............................... 1 1.3 Scope of the Guide .............................................. 3 2 – CHROMIUM IN THE ENVIRONMENT ................................. 4 2.1 Sources and Extent of Contamination ................................ 4 2.2 Chromium Chemistry ............................................ 5 2.3 Chromium Treatment and Remediation Approaches .................... 11 2.4 Site Characterization Requirements ................................. 14 3 – TECHNOLOGIES FOR IN SITU TREATMENT