Location
Grand Rapids, Michigan
Start Date
16-5-2024 11:00 AM
End Date
16-5-2024 11:30 AM
Description
EPA’s Updated Toxicity Criteria for Arsenic: Implications on Coal Ash Sites Authors Mr. Todd Bernhardt - United States - Haley & Aldrich Inc. Mr. Jay Peters - United States - Haley & Aldrich Inc. Abstract In October 2023, the United States Environmental Protection Agency (EPA) released a draft Integrated Risk Information System (IRIS) Toxicological Review of Inorganic Arsenic in which updated toxicity criteria were proposed that are significantly more conservative than the current values. Adoption of the proposed toxicity criteria could have significant implications on risk-based levels for arsenic. Although the Coal Combustion Residuals (CCR) Rule relies on EPA Maximum Contaminant Levels (MCLs) as groundwater protection standards, in recognition that groundwater represented by the monitoring well network may not be used as drinking water, risk assessment has been applied at many coal ash sites to help inform stakeholders of the potential risks posed by CCR constituents. Furthermore, states may require risk-based evaluation of soils beneath CCR units after ash removal to demonstrate that soil is ‘clean’. Using the updated toxicity criteria, risk-based levels for arsenic in soil, for multiple land use scenarios including commercial/industrial, are likely to fall below typical background values (in contrast to the current state, where risk-based levels for commercial/industrial use are typically higher than background levels). To aid in stakeholder communications and to support evaluation of post-remedial conditions for soil, site-specific background values may need to be established, and rigorous statistical approaches may be required to evaluate consistency with background. This presentation will provide hypothetical case studies that illustrate the potentially significant implications adoption of the proposed toxicity criteria could have on the risk management of inorganic arsenic at coal ash sites.
Document Type
Event
EPA’s Updated Toxicity Criteria for Arsenic-Implications on Coal Ash Sites
Grand Rapids, Michigan
EPA’s Updated Toxicity Criteria for Arsenic: Implications on Coal Ash Sites Authors Mr. Todd Bernhardt - United States - Haley & Aldrich Inc. Mr. Jay Peters - United States - Haley & Aldrich Inc. Abstract In October 2023, the United States Environmental Protection Agency (EPA) released a draft Integrated Risk Information System (IRIS) Toxicological Review of Inorganic Arsenic in which updated toxicity criteria were proposed that are significantly more conservative than the current values. Adoption of the proposed toxicity criteria could have significant implications on risk-based levels for arsenic. Although the Coal Combustion Residuals (CCR) Rule relies on EPA Maximum Contaminant Levels (MCLs) as groundwater protection standards, in recognition that groundwater represented by the monitoring well network may not be used as drinking water, risk assessment has been applied at many coal ash sites to help inform stakeholders of the potential risks posed by CCR constituents. Furthermore, states may require risk-based evaluation of soils beneath CCR units after ash removal to demonstrate that soil is ‘clean’. Using the updated toxicity criteria, risk-based levels for arsenic in soil, for multiple land use scenarios including commercial/industrial, are likely to fall below typical background values (in contrast to the current state, where risk-based levels for commercial/industrial use are typically higher than background levels). To aid in stakeholder communications and to support evaluation of post-remedial conditions for soil, site-specific background values may need to be established, and rigorous statistical approaches may be required to evaluate consistency with background. This presentation will provide hypothetical case studies that illustrate the potentially significant implications adoption of the proposed toxicity criteria could have on the risk management of inorganic arsenic at coal ash sites.
