Approval and Promulgation of Implementation Plans; Illinois Emission Test Averaging

EPA is approving revisions to Illinois rules for averaging of emission tests. Illinois requested these revisions on October 9, 2001. For sources with steady emission rates, these revisions provide for assessing compliance with mass emission limits on the basis of an average of three test runs. EPA proposed to approve these revisions on April 15, 2002, at 67 FR 18115. The Environmental Law & Policy Center and others submitted a comment letter objecting to this proposed approval. The comments observed that averaging three test runs yields a less stringent compliance test than assessing compliance based on each test run individually. The commenters thus view the submittal as an inappropriate relaxation. The comments further object that the State's rules provide for insufficient information on case-specific test protocol revisions to be able to judge how these revisions would affect test results. EPA concludes that averaging of three mass measurement test runs is standard practice, and concludes that Illinois is formalizing its pre- existing approach and not relaxing its compliance assessments. EPA concludes further that Illinois has adopted an appropriate approach to differentiating between major and minor test method revisions and to addressing minor revisions.