2015 O3 NAAQS Transport SIP

Develop a consistent technical approach among the LADCO states for producing “Good Neighbor” SIPs for the 2015 ozone (O3) National Ambient Air Quality Standards (NAAQS).


In Attachment A of the March 2018 Transport memo EPA presented a series of options for addressing the four steps of the CSAPR O3 transport framework.  EPA states in the memo that one of the guiding principles for evaluating whether a technical approach is appropriate for use in a transport analysis is that the “…alternative modeling is performed using a credible modeling system which includes “state-of-the-science” and “fit for purpose” models, inputs, and techniques that are relevant to the nature of the ozone problem.” This statement along with the flexibilities presented by EPA in the memo provide the states with multiple approaches for quantifying and reporting interstate O3 transport in their iSIPs.

LADCO, in coordination with the member state air agencies, must investigate the flexibilities presented by EPA, along with other technically defensible options, to find an approach that will be used in the technical support information that will accompany the 2015 O3 NAAQS iSIPs that the states will submit on October 1, 2018.  The approach for the LADCO region in addressing the Good Neighbor SIP obligations of the member states follows:

  • Understand the list of flexibilities presented by EPA; augment this list with additional flexibilities
  • Submit a formal comment from LADCO on the EPA March 2018 memo
  • Identify subgroups of the LADCO Project Team to perform analyses related to the alternative technical analyses with the goal of quantifying how the different approaches alter the interstate ozone contribution results
  • Reach consensus among the LADCO states on the objective(s) of the iSIP technical plan.  For example, is the objective to find a set of analyses that demonstrate the smallest future year contribution from the LADCO states to downwind receptors? Is the objective to highlight the influence of local emissions sources? International emissions?
  • Evaluate the results of the different approaches and develop a protocol for how the LADCO states will collectively use common technical information to support their iSIPs


LADCO 2015 O3 NAAQS Transport Modeling Final Technical Support Document (13 Aug 2018)

LADCO 2015 O3 NAAQS Transport Modeling Draft TSD (31 Jul 2018) | Response to Comments

LADCO CAMx Transport Modeling Protocol | Response to Comments

2023 CAMx APCA Source-Receptor Linkages Excel Spreadsheet


U.S. EPA O3 Transport Resources


LADCO 2015 O3 NAAQS Google Drive


Call Notes

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