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EPA's Region 6 Office

Serving: Arkansas, Louisiana, New Mexico, Oklahoma, Texas, and 66 Tribal Nations

RCRA - Risk Assessment Program


The Region 6 RCRA Risk Assessment Team provides technical assistance in the areas of toxicological document review, risk calculations, risk assessment training and guidance on state-of-the-art science.

1) Region 6 Corrective Action Stategy (formerly the Risk Management Stategy)

Region 6 has developed a new Corrective Action Strategy for the RCRA Program that is designed to expedite cleanups at facilities where releases have occurred through the use of a risk-based priority screen.

2) Developed a risk-based program for the delisting of RCRA listed wastes

Background: A listed RCRA waste may be petitioned for exemption from requirements of Subtitle C hazardous waste program under §40 Part 260.22 of the Code of Federal Regulations. Authorization of the RCRA delisting program was delegated to the Regional Administrator of EPA Regional Offices by EPA Administrator Browner on October 10, 1995 (61 FR 32798).

Region 6 toxicologists have developed a risk-based program to determine the toxicity of wastes petitioned for delisting under §40 Part 260.22 of the Code of Federal Regulations. The program is comprised of three (3) components:

1) the Delisting Risk Assessment Software (DRAS) program;
2) the Delisting Technical Support Document (DTSD) and;
3) the DRAS User's Guide (PDF). (21 pp. 609kb pdf)

The DRAS is a user-friendly, stand-alone software program that calculates the potential risks associated with disposing a given waste stream to a landfill or surface impoundment. For a given waste stream, the DRAS calculates both the waste's aggregate risks and also back-calculates each waste constituent's maximum allowable waste constituent concentration permissible for delisting. The DRAS is a risk assessment tool and, therefore, can only provide risk analyses based on the information input into the program. The risk assessment results are only one factor in a delisting decision. The risk-based approach combines state-of-the-art fate and transport modeling with standardized exposure assessment algorithms to provide sound risk assessment.

The Delisting Technical Support Document (DTSD) is the documentation that thoroughly and accurately describes the supporting technical methodology (i.e., fate and transport modeling, exposure pathway algorithms, etc.) employed by the DRAS program to perform the risk assessment. This documentation is available in Acrobat .pdf format. The DRAS User's Guide describes how to use the DRAS and provides minimum and recommended PC system requirements.

For information on the risk-based process, please contact:

    Michelle Peace
    RCRA Corrective Action (6PD-C)
    Multimedia Planning and Permitting Division
    1445 Ross Avenue
    Dallas, Texas 75202
    (214)665-7430 or E-Mail Address: peace.michelle@epa.gov
3) Developing human health and ecological combustion risk assessment guidance.

The current guidance document for human health combustion risk assessments describes the evaluation of direct inhalation risk, but primarily focuses on the procedures used to estimate risk resulting from indirect pathways. The guidance is titled Human Health Risk Assessment Protocol for Hazardous Waste Combustion Facilities and is available for download. Also available is an additional document entitled, Region 6 Risk Management Addendum - Draft Human Health Risk Assessment Protocol for Hazardous Waste Combustion Facilities which provides specific risk management guidance to combustion facilities located in Region 6. Detailed guidance on the methods and processes required to complete screening level combustion risk assessment for ecological receptors has not been presented prior to the development of the new ecological risk assessment guidance. The new ecological risk assessment is titled Screening Level Ecological Risk Assessment Protocol for Hazardous Waste Combustion Facilites. For additional Information related to Combustion Risk Assessment, please see the Center for Combustion Science and Engineering web page.

For information on the above documents, please contact:

    Kishor Fruitwala, Chief
    RCRA Facility Assessment Section (6PD-A)
    Multimedia Planning and Permitting Division
    1445 Ross Avenue
    Dallas, Texas 75202
    (214) 665-6669 or E-Mail Address: fruitwala.kishor

4) Regional Screening Levels (Formerly HHMSSL - Human Health Medium-Specific Screening Levels)

The Regional Screening Levels (RSL) for evaluating contaminated hazardous waste sites are available in two downloadable formats, PDF and Excel. The RSL tables are frequently requested and provide information on levels of contamination in the soil, air and/or water that may be of concern for human health. The User's Guide provides general understanding of the screening tables and explains the rational and equations used to derive the screening values. Along with the User's Guide and Frequently Asked Questions can be viewed, the Screening Level Calculator is included to assist in calculating site-specific screening values.

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