"Will we have to perform air dispersion modeling for toxic air contaminants at our facility?" is a frequent question and one of the most common concerns from our clients. The objective of this Trinity eNews article is to discuss if air dispersion modeling for toxic air contaminants may (or may not) be required in order to comply with 6 CRR-NY Part 212 (Part 212) at your facility. The potential to model as per Part 212 may apply to a wide-range of industry types and facility sizes and can be triggered by a new or modified permit or registration, or issuance of a renewal for an existing permit or registration.

Part 212 generally requires modeling of compounds emitted at low emission rate potentials and High Toxicity Air Contaminants (HTACs) from specific emission sources. Additionally, the results of modeling can influence a contaminant's Environmental Rating. To provide guidance on Part 212 implementation, including modeling, the New York State Department of Environmental Conservation's (NYSDEC) finalized the Division of Air Resources (DAR) DAR-1: Guidelines for the Evaluation and Control of Ambient Air Contaminants under Part 212 in August of 2016. It has now been two years since DAR-1 was published and facilities ranging from Minor Facility Registrations to Title V Facility Permits have all experienced the impacts of Part 212 implementation. In particular, the multifaceted DAR-1 has caused facilities to consider air dispersion modeling for evaluating toxic air contaminants.

The first step in determining if air dispersion modeling is required is evaluating the emissions of individual contaminants from process emission sources subject to Part 212. The evaluation should consider the following special cases for which modeling may not be required:

  • Emission sources that are not process emission sources (as defined in Part 212) or are not subject to Part 212. For example, contaminants emitted only from "combustion installations" are not required to meet control requirements of Part 212.
  • Sources that are exempt from permitting are not subject to the provisions of Part 212 requirements per §212-1.4(a).
  • Compounds for which site-wide emissions of HTAC are below the Mass Emission Limit (MEL) in 6 CRR-NY 212-2.2 Table 2.
  • HTAC regulated by an applicable NESHAP for which the facility is in compliance.
    • For these compounds, a Toxic Impact Assessment (TIA) must be completed illustrating that off-site impact falls below appropriate guideline concentrations and the Persistent & Bioaccumulative (PB) Trigger cannot be exceeded, per §212-1.5(e)(2).
  • Non-HTAC hazardous air pollutant (HAP) regulated by an applicable NESHAP for which the facility is in compliance. For these compounds, Part 212 is satisfied per §212-1.5(e)(2).
  • Non-HTAC, compounds with an emission rate potential (ERP) <100 lb/yr. For these compounds, there are no substantive Part 212 requirements as described in DAR-1.

Through the evaluation of any of these special cases, it is possible to reduce the requirements to complete air dispersion modeling for your process emission sources and facility. If modeling is required at your facility, the results of each modeled contaminant will be compared to the Annual and Short-term Guideline Concentrations (AGC and SGC) threshold in DAR-1.

Facilities that are required to perform air dispersion modeling should submit a modeling protocol if using AERMOD, EPA's preferred model to use for multiple industrial sources. This protocol must describe the modeling procedures used in refined modeling to predict the maximum offsite ambient air concentration. The protocol should be approved by NYSDEC prior to submitting a final modeling report as part of your permit application.

Trinity Consultants is available to assist you with any of your air permitting and compliance needs. If you have any questions about air dispersion modeling for toxic air contaminants at your facility, please contact Simone Gleicher, Senior Consultant, of our Albany office at (518) 205-9000 or Chris Whitehead, BD Supervisor Northeast, at (609) 318-5500 for more information.