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This web page provides links to recent State Implementation Plan (SIP) submissions that Iowa has made to EPA. The web page includes links to information about recent Iowa designation recommendations for National Ambient Air Quality Standards (NAAQs) that were promulgated or revised starting in 2006.
Questions about the information on this web page may be directed to Matthew Johnson at 515-725-9554 or Matthew.Johnson@dnr.iowa.gov; or Jim McGraw at 515-689-1439 or Jim.McGraw@dnr.iowa.gov.
The DNR is currently not making any comments on proposed NAAQs.
The Clean Air Act requires the state to submit designation recommendations to EPA within one year of any NAAQS revision. EPA is responsible for issuing the final designations. EPA's final designations can be found in 40 CFR Part 81.
On February 18, 2014, the Environmental Protection Commission approved a revision to the State Implementation Plan (SIP) to prevent future violations of the 24-hour fine particulate (PM2.5) National Ambient Air Quality Standards (NAAQS) in Muscatine. The SIP revision was forwarded to U.S. EPA on February 18th for federal notice and approval. EPA approved the SIP revision on December 1, 2014.
Iowa is required under the Clean Air Act to develop State Implementation Plans (SIPs) for new and revised National Ambient Air Quality Standards (NAAQs), referred to as infrastructure SIPs. Infrastructure SIPs demonstrate that the state has the authority and resources to implement a new or revised NAAQS.
In 1999, EPA established rules to improve visibility in federally protected Class I areas, such as larger national parks and wilderness areas. The regional haze regulations require all states to periodically submit State Implementation Plan (SIP) revisions to address emissions of visibility impairing pollutants. The first regional haze SIPs were due in 2007 and comprehensive revisions are generally due approximately every 10 years thereafter (EPA provided a one-time extension for the second regional haze SIPs). At the midpoint of each 10-year plan, a 5-year progress report is due.
Iowa currently has one area designated as nonattainment (not meeting) a national ambient air quality standard (NAAQS). This area is in Muscatine County and the nonattainment designation is for the 2010 1-hour sulfur dioxide (SO2) NAAQS. The DNR has submitted a plan, called a nonattainment SIP, that requires emission reductions and other air pollution control measures necessary to attain the 2010 SO2 NAAQS. The plan is being fully implemented and air quality monitoring shows that the Muscatine area is meeting the NAAQS. If EPA approves the nonattainment SIP, the DNR will then submit a maintenance plan as part of the process to redesignate the area to attainment.
Areas that are redesignated from nonattainment to attainment are often called maintenance areas. There is currently one maintenance area in Iowa. in 2018 an area in Council Bluffs was redesignated from nonattainment to attainment for the 2008 lead NAAQS.
On January 21, 2015, the Environmental Protection Commission (EPC) approved a revision to the State Implementation Plan (SIP) to attain the 2008 Lead National Ambient Air Quality Standards (NAAQS) in Council Bluffs. The transmittal letter and SIP revision are dated January 30, 2015, and were forwarded to the U.S. EPA on February 3rd for federal review. EPA fully approved the Council Bluffs lead nonattainment sip on February 26, 2016.
On september 18, 2017, the State of Iowa requested that EPA redesignate to attainment the portion of council bluffs designated nonattainment for the 2008 lead NAAQS. A maintenance sip developed by the DNR accompanied the State of Iowa's request. EPA approved the maintenance sip and processed the redesignation request on October 4, 2018. The area is now designated "attainment" for the 2008 lead NAAQS. (Note, areas that have been redesignated from nonattainment to attainment are often referred to as "maintenance" areas. That is not an official designation, it is just common terminology.)
On May 17, 2016, the Environmental Protection Commission approved a revision to the State Implementation Plan (SIP) to attain the 1-hour SO2 National Ambient Air Quality Standards (NAAQS) in Muscatine County. the SIP revision was forwarded to U.S. EPA on May 17, 2016 for federal notice and approval. EPA fully approved the Muscatine nonattainment SIP on November 17, 2020.
In a letter dated November 12, 2021, the State of Iowa requested that EPA redesignate to attainment the portion of Muscatine County designated nonattainment for the 2010 1-hour SO2 NAAQS. A maintenance SIP developed by the DNR accompanied the redesignation request. Both were submitted to EPA on November 17, 2021. Even though air quality meets the federal 1-hour SO2 NAAQS, the Muscatine area will retain the nonattainment designation until EPA completes its review of the maintenance plan and officially redesignates the area to attainment.
Round 1: Muscatine Nonattainment Area
Round 1: Remainder of State
On March 2, 2015, the U.S. district court for the northern district of California accepted a consent decree to resolve litigation concerning the deadline for completing designation for the 2010 1-hour SO2 NAAQS. The consent decree requires that designations for all remaining undesignated areas in the Country be completed in three additional rounds: the first round by July 2, 2016, the second round by December 31, 2017, and the final round by December 31, 2020.
A summary of actions undertaken in these new rounds of designations are provided below. Additional information regarding the consent decree and the 1-hour SO2 designations process can be found on EPA’s website: https://www.epa.gov/sulfur-dioxide-designations.
Round 2: July 2, 2016 Deadline
The State has provided to EPA updated designation recommendations for three counties in Iowa (Des Moines, Wapello, and Woodbury) affected by this round of designations. EPA has not yet finalized designations under this round, but must do so by July 2, 2016.
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. EPA must consider the State’s amendment and finalize 1-hr SO2 designations for round 3 by December 31, 2017.
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" (DRR, 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 were 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.
The infrastructure SIP the 2015 Ozone NAAQS was submitted to EPA on November 30, 2018.
The infrastructure SIP for the 2012 PM2.5 NAAQS was submitted to EPA on December 15, 2015.
The infrastructure SIP for the 2010 NO2 NAAQS was submitted to EPA on July 23, 2013.
A revision to the 2010 NO2 infrastructure SIP to address the interstate transport requirements of Clean Air Act Section 110(a)(2)(D)(i)(I) was submitted to EPA on March 1, 2017.
The infrastructure SIP for the 2010 SO2 NAAQS was submitted to EPA on July 23, 2013.
The infrastructure SIP for the 2008 ozone NAAQS was submitted to EPA on December 12, 2012. An amended infrastructure SIP was submitted on January 11, 2013.
The infrastructure SIP for the 2006 PM2.5 NAAQS was submitted to EPA on July 23, 2013.