In 2003, under the Clean Air Act (CAA), the EPA established the National Emissions Standards for Hazardous Air Pollutants (NESHAP) for Site Remediation (40 CFR Part 63, Subpart GGGGG). In 2006, the rule was revised to address questions and clarifications, as well as technical errors in the original version. Many years later, in 2019, the EPA recommended further amendments to the NESHAP to reflect over a decade of technological advancements that would enable stricter standards. The amendments originally proposed in 2019 were signed in March 2020 as Final Amendments: Air Toxics Standards for Site Remediation—Risk and Technology Review and are summarized below.

NESHAP—A brief history

2003: Original NESHAP for site remediation

The site remediation NESHAP was originally promulgated in 2003 to regulate major sources of hazardous air pollutants (HAPs) when performing remediation activities to clean up environmental contamination (e.g., contaminated groundwater or soil cleanup or emissions during the disposal or containment of contaminated or hazardous media).

The NESHAP was to be implemented in two phases.

The first phase required the EPA to develop technology-based standards for controlling toxic air emissions and promulgate the use of maximum achievable control technology (MACT) standards based on existing industry best practices. As a result, NESHAPs under 40 CFR 63 are often referred to as MACT standards.

The second phase required that within 8 years of setting MACT standards, the EPA conduct a Residual Risk Assessment (RRA) to determine if Phase I’s MACT standards were effective in protecting public health with an ample margin of safety or whether more “health-protective” standards were necessary.

Additionally, every 8 years, the EPA was to review and revise NESHAP standards “to account for improvements in air pollution controls and prevention practices and technologies.”

2006: Clarifications to the original version

Not surprisingly, shortly after the implementation of NESHAP, questions arose on the intent or applicability of several provisions to specific remediation situations. Subsequently, in 2006, the EPA issued an amendment to the NESHAP with clarifications, and technical/editorial corrections, on applying and implementing specific provisions of the rule.

The 2006 amendment included clarifications addressing applicability determinations for certain oil and natural gas production facilities, various exemptions, and requirements for equipment leaks.

2020: Risk and technology review final amendments

In 2019, the EPA proposed further amendments to the NESHAP to reflect a decade of technological improvements that would allow stricter HAP standards and to address residual risks. After a period of public comment, the EPA finalized amendments to the NESHAP for site remediation.

Here is a summary of the key provisions of Final Amendments: Air Toxics Standards for Site Remediation—Risk and Technology Review:

• The NESHAP applies to active remediation projects at sites that are major sources of HAPs subject to another MACT standard.
• The NESHAP does not apply to remediation projects at Resource Conservation and Recovery Act (RCRA) and Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA, also known as Superfund) sites.
• After conducting a residual risk and technology review under the CAA, the EPA lowered the leak threshold for valves and pumps and instituted specific work practices.
• To be consistent with court rulings, the EPA rescinded its earlier exemption from NESHAP standards for periods of startup, shutdown, and malfunction (SSM) and maintenance.
• The NESHAP now requires electronic reporting of performance test results and compliance reports.

Assessment of residual risks to human health under NESHAP standards

The CAA called upon the EPA to conduct an RRA of risks to human health at sites where remediations were conducted in compliance with NESHAP’s final standards on air toxicity.

Cancer risk of 1 in 1 million. The RRA found that NESHAP’s allowable emissions standards reduced the maximum individual risk (MIR) for cancer from inhalation to 1 in 1 million. In other words, if 1 million people were equally exposed—continuously for 24 hours every day over a 70-year life span—to air that met NESHAP standards for HAP emissions, no more than 1 person would likely contract cancer specifically from breathing this air. This would be in addition to the normal incidence of cancer cases in 1 million unexposed people.

Accordingly, the risk of cancer from chronic inhalation of actual and allowable emissions was below a hazard index of 1. A hazard index of 1 or less implies that the level of air toxicity is unlikely to cause adverse noncancer health effects over a lifetime of exposure.

On completion of its RRA and based on available health information, as well as associated uncertainties, the EPA affirmed that NESHAP standards for site remediations lower risks to human health to acceptable levels and provide a more-than-adequate margin of safety in terms of protecting public health.

Leak thresholds lowered to reflect technological advances

The CAA mandates that the EPA keep track of technological advances in practices, processes, and control technologies relevant to NESHAPs and assess, review, and revise air toxics standards, as necessary.

In line with that mandate, the EPA’s technology review identified more stringent leak detection thresholds for valves and pumps in the National Emissions Standards for Equipment Leaks under 40 CFR 63, Subpart UU, and concluded that use of these thresholds would be cost-effective while significantly lowering leak thresholds for valves and pumps under the site remediation NESHAP.

Accordingly, in its Final Amendments: Air Toxics Standards for Site Remediation—Risk and Technology Review, the EPA lowered the leak threshold.

Other amendments

In its original 2003 version, the EPA cut operators some slack by allowing an exemption whereby remediation activities did not have to meet NESHAP standards during periods of SSM and maintenance.

In its 2020 Final Amendments, the EPA takes cognizance of a 2008 court ruling and scraps the SSM exemption. Accordingly, site remediations now have to follow NESHAP standards at all times, including during periods of SSM and maintenance.

However, to ensure compliance after the removal of SSM exemptions, the EPA requires the monitoring of pressure relief devices. In addition, the amendments require adherence to specific work practices for pressure relief devices and maintenance protocols for storage vessel control devices.

In a move toward increased digitization of compliance workflows, the NESHAP now mandates electronic submission of required performance tests and compliance reports. These submissions should be made through the Compliance and Emissions Data Reporting Interface (CEDRI) of the EPA’s Central Data Exchange.

The aforementioned final amendments will go into effect on the day the rule is published in the Federal Register.