(a) In a letter dated January 30, 1987, the Mississippi Department of Natural Resources certified that no emission limits in the State's plan are based on dispersion techniques not permitted by EPA's stack height rules. This certification does not apply to: Mississippi Power-Daniel; South Mississippi Electric Power, Hattiesburg-Morrow; E.I. Dupont, Delisle Boilers 1 & 2; and International Paper, Vicksburg.

(b) Disapproval. EPA is disapproving portions of Mississippi's Infrastructure SIP for the 1997 annual and 2006 24-hour PM2.5 NAAQS addressing section 110(a)(2)(E)(ii) that requires the State to comply with section 128 of the CAA.