Round 1: Muscatine Nonattainment Area
1-Hour SO2 Designations Consent Decree
Within three years of any NAAQS revision, the Clean Air Act requires EPA to finalize designations for that pollutant for all areas of the U.S. However, for the 2010 1-hour SO2 NAAQS, by 2013 EPA has only designated areas with ambient monitors measuring NAAQS violations, leaving most of the U.S. undesignated. On March 2, 2015, the U.S. district court for the northern district of California accepted a consent decree to resolve the delay. The consent decree required that designations for all remaining undesignated areas in the country be completed in three additional rounds: the first new round by July 2, 2016, the second new round by December 31, 2017, and the final new round by December 31, 2020. Those new rounds would eventually be referred to as rounds 2, 3, and 4, with round 1 representing the initial round of nonattainment designations that occurred in 2013 (which included Muscatine, Iowa).
A summary of state and related actions undertaken in the additional rounds of designation is provided below. Additional information is found on EPA’s website: https://www.epa.gov/sulfur-dioxide-designations.
Round 2: July 2, 2016 Deadline
The State provided to EPA updated designation recommendations for three counties in Iowa (Des Moines, Wapello, and Woodbury) affected by this round of designations.
Round 3: December 31, 2017 Deadline
On January 5, 2017, the State provided to EPA an amended designation recommendation for all areas in the State not yet designated for the 2010 1-hour SO2 NAAQS. A technical support document that also addressed information required to be submitted under the data requirements rule accompanied the updated recommendation.
Round 4: December 31, 2020 Deadline
No areas in Iowa were designated in Round 4. (EPA completed the initial designations process for Iowa in Round 3.)
Data Requirements Rule (DRR)
On August 21, 2015, the U.S. Environmental Protection Agency (EPA) published the "Data Requirements Rule for the 2010 1-Hour Sulfur Dioxide Primary National Ambient Air Quality Standard" (80 FR 51052). The DRR first required states to identify sources not located in a nonattainment area that had actual annual sulfur dioxide (SO2) emissions of at least 2,000 tons, or were deemed by the air agency as requiring further air quality characterization. States were later required to select an evaluation method to characterize SO2 air quality around each affected source, using either modeling, ambient monitoring, or limiting a source’s SO2 emissions to less than 2,000 tons per year. The letters below addressed those requirements for Iowa.
Annual Reporting Requirements
The DRR also added provisions in 40 CFR 51.1205(b) requiring air agencies to submit an annual report to EPA documenting SO2 emissions in areas where modeling of actual SO2 emissions served as the basis for designating the area attainment for the 2010 1-hour SO2 NAAQS. As required, each report below includes an assessment of the cause of any emissions increases from the previous year and a recommendation regarding whether additional modeling is needed in each applicable area.
2017 report
2018 Report
2019 Report
2020 report
2021 Report
2022 Report
2023 Report
2024 Report