On April 8, 2021, the EPA published proposed clarifications and technical revisions to the National Emission Standards for Hazardous Air Pollutants (NESHAP) for municipal solid waste landfills (MSWLs) established in the March 26, 2020, final rule.
The changes correct errors and clarify:
- Wellhead monitoring requirements for the purpose of identifying excess air infiltration;
- Delegation of authority to state, local, or tribal agencies for “emission standards”;
- Applicability of the General Provisions under 40 CFR 63, Subpart A to affected MSWLs;
- Handling of monitoring data for combustion devices during periods of monitoring system breakdowns, repairs, calibration checks, and adjustments.
The EPA also proposes further revisions to MSWL New Source Performance Standards (NSPS) “to clarify the timing of compliance for certain requirements for existing MSW landfills that have modified, but previously triggered, the requirement to install a gas collection and control system under related MSW landfill rules,” according to the EPA. Previously, “on October 13, 2020, EPA corrected inadvertent errors in the cross-referencing and formatting in the Federal Register” and clarified “two operational and reporting requirements in the March 26, 2020, final rule.”
The final rule applies to both major and area sources. It added “startup, shutdown, and malfunction (SSM) requirements, adds operating condition deviations for out-of-bounds monitoring parameters, requires timely control of bioreactor landfills, and changes the reporting frequency for one type of report,” the EPA adds.
Hazardous pollutants emitted by MSWLs include:
- Vinyl chloride
- Ethyl benzene
Approximately 738 MSWLs in the United States are subject to NESHAP.
NESHAP standards are developed in two phases. Per the EPA, “[t]he first phase is ‘technology-based’ where EPA develops standards for controlling the emissions of air toxics from sources in an industry group or ‘source category.’” These technology-based standards are referred to as maximum achievable control technology (MACT) standards, which are based on emissions levels that are already being achieved by the best-controlled and lower-emitting sources in an industry.
The second phase of NESHAP development is a “risk-based” approach called residual risk assessment. Within 8 years of setting the MACT standards, the Clean Air Act (CAA) directs the EPA to assess the remaining health risks from each source category to determine whether the MACT standards protect public health with an ample margin of safety and protect against adverse environmental effects. “The CAA requires EPA to review and revise the standards, if necessary, to account for improvements in air pollution controls and/or prevention and to address any residual risks that still remain after the MACT is implemented,” according to SCS Engineers, an environmental consulting and contracting firm.
The March 26, 2020, final rule completed the residual risk and technology review (RTR) conducted for the MSWL source category, as required under the CAA.