The EPA partially approves and partially disapproves revisions to the State Implementation Plan (SIP) submitted by the Governor of Wyoming on May 21, 1999. The submittal incorporates revisions to the following sections of the Wyoming Air Quality Standards and Regulations (WAQSR): Section 2 Definitions, Section 4 Sulfur oxides, Section 5 Sulfuric acid mist, Section 8 Ozone, Section 9 Volatile organic compounds, Section 10 Nitrogen oxides, Section 14 Control of particulate emissions, and Section 21 Permit requirements for construction, modification and operation. We partially approve these SIP revisions because they are consistent with Federal requirements. We are also partially disapproving the provisions of the State submittal that allow the Administrator of the Wyoming Air Quality Division (WAQD) to approve alternative test methods to those required in the SIP, (in sections 2, 4, 5, 10, and 14 of the WAQSR) because such provisions are inconsistent with section 110(i) of the Clean Air Act (Act) and the requirement that SIP provisions can only be modified through revisions to the SIP and must be approved by EPA. We are taking this action under section 110 of the Act.