Primary Sulfur Dioxide NAAQS Implementation Schedule
| Milestone | First Round Designations | Second Round Designations | Third Round Designations | Fourth Round Designations |
|---|---|---|---|---|
| Standard Effective: June 2010 | ||||
| Designation Deadline (4 rounds) | July 2013 | July 2016 | December 2017 | December 2020 |
| Designations Effective | October 2013 | September 2016 | February/March 2018 | March 2021 |
| Infrastructure SIPs Due: June 2013 | ||||
| Attainment Plans (Nonattainment SIPs) Due | April 2015 | March 2018 | August/September 2019 | September 2022 |
| Attainment Date | October 2018 | September 2021 | February/March 2023 | March 2026 |