Regulatory Update   |   Sep 9th, 2015 SO2 Data Requirements Rule is Final


The New Rule is less stringent, but gives the agencies more flexibility

On August 21, 2015 the U.S. Environmental Protection Agency (EPA) published the final Sulfur Dioxide (SO2) Data Requirements Rule (DRR). It requires that state and tribal air agencies (air agencies) provide data to EPA that will be used to characterize one hour average SO2 concentrations near large sources of emissions. These data will be used to demonstrate compliance with the 1-hour average National Ambient Air Quality Standard (NAAQS). The final rule differs from the proposed rule in several ways. The final DRR:

  • Establishes 2000 tons per year (t/y) of actual emissions as the minimum that air agencies must consider for identifying large sources of SO2 emissions
  • Extends the due date to submit monitoring plans or modeling protocols for areas and sources to be evaluated
  • Gives air agencies flexibility in determining which sources and areas must be characterized via ambient air monitoring or modeling procedures or reduce emissions to avoid the rule requirements

Targeted Sources

The map below shows over 400 sources that exceed the 2000 t/y threshold and may be subject to the final rule. However, air agencies and EPA may include other sources and areas that in their opinion warrant characterization. Air agencies are required to develop and submit a list of sources exceeding the threshold, based on the most recent year of available SO2 emissions data, and indicate the areas that will be characterized.

Compliance Schedule

The final rule establishes the following timeline and milestones for implementation:

  • January 15, 2016: List of targeted sources must be defined and submitted to EPA.
  • July 1, 2016: For each source on the target list, air agencies must indicate whether air quality will be characterized through air quality modeling, ambient monitoring or if federally enforceable emission limits will be established. Appropriate modeling protocols, monitoring plans or planned emission limits must be submitted by this date. (This is a six month extension from the proposed rule schedule)
  • January 1, 2017: New ambient air monitors must be installed and operational.
  • January 13, 2017: Air quality modeling analyses must be submitted to EPA. For sources seeking exemption from the rule, federally enforceable emission limits rulemaking must be complete.
  • May 2020: Collection and certification of three years of ambient monitored data (2017 – 2019) must be complete.

What should sources do now?

SO2 emissions from targeted DRR sources may be affected by other recently finalized EPA rules, e.g., Mercury and Air Toxics Standards (MATS) and Clean Power Plan, or proposed rules. The impact of these rules on future SO2 emissions to specific sources should be considered to determine the feasibility of reducing emissions to below 2000 t/y and avoid being subject to the DRR. In addition to examining solutions through emission reductions, a modeling analysis should be undertaken to determine if compliance with the NAAQS can be demonstrated with current or reduced emissions. These analyses and results will be helpful in discussions with the air agency in selecting the most appropriate compliance strategy for your facility.

Contact us for assistance

TRC’s staff of permitting engineers, modelers and ambient monitoring experts can identify and evaluate the most appropriate option for your plant and emission sources. It is not too early to determine the best strategy for your sources.