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Muscatine Sulfur Dioxide Maintenance Plan

Background of the Plan: In 1991 and 1992 there were violations of the primary Sulfur Dioxide (SO2) National Ambient Air Quality Standards (NAAQS) at one of three state air monitors in Muscatine, Iowa. This resulted in designation of a portion of Muscatine County as nonattainment in 1994. The state determined that there were two major emission sources contributing to the violations of the NAAQS. They were Grain Processing Corporation (GPC), a wet grain milling facility, and Muscatine Power and Water (MPW), a municipal power plant. In the course of modeling the impacts of these emission sources, it was also determined that a third source, Monsanto Corporation, contributed to a modeled violation of the SO2 NAAQS in the vicinity of its own facility.

The Iowa Department of Natural Resources (IDNR) negotiated emission reductions with GPC, MPW, and Monsanto. The reductions were incorporated into revised construction permits. These permits were submitted as a part of the section 110 State Implementation Plan (SIP) revision and thus are federally enforceable. EPA approved this SIP revision on December 1, 1997 (62 FR 63454). EPA approved a redesignation request and maintenance plan for the area on March 19, 1998 (63 FR 13343).

Summary of the Plan: The state SIP provides for expeditious attainment of the SO2 NAAQS through the emission limits and operating restrictions that are set forth in the permits issued by the state.

Stationary Source Control Measures: The emission limits imposed upon the sources are contained in the following permits:

Emission Reductions: The state, GPC, and MPW negotiated reductions of allowable emissions of 24 percent and 60 percent, respectively, and reductions of actual emissions of 4 percent and 13 percent, respectively. These emission reductions were incorporated into revised construction permits for each source.

Stationary Source Regulations:

Maintenance Plan Provisions: The state has a comprehensive program to identify sources of violations of the SO2 NAAQS and to undertake an aggressive follow-up for compliance and enforcement. The state has statutory authority to address any exceedances and resultant violations of the NAAQS that may be identified.

The state will continue to maintain the network of the three SO2 ambient air monitoring stations in the nonattainment area. The state is committed to quickly identifying when exceedances occur and evaluating which sources may be contributing to such occurrences. Direct source monitoring, using CEMs as required in the permits issued to MPW and GPC under this plan, is designed to ensure that the emissions limitations in the permit are not exceeded.

Reporting requirements established in those permits provide the state with a mechanism to consistently monitor the operations of those sources.

Attainment Date: The state permits required compliance (and attainment) by March 15, 1996. The sources met this compliance date.

Additional Information: The implemented control strategy was effective in preventing further violations of the SO2 NAAQS. Consequently, the state requested that the area be redesignated to attainment. EPA redesignated the area to attainment and approved the maintenance plan on March 19, 1998 (63 FR 13343).

EPA Region 7 Contact: Wayne Kaiser, (913) 551-7603, kaiser.wayne@epa.gov

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