Section 52.150 - Yavapai-Apache Reservation(a) The provisions for prevention of significant deterioration of air quality at 40 CFR 52.21 are applicable to the Yavapai-Apache Reservation, pursuant to § 52.21(a) .(b) In accordance with section 164 of the Clean Air Act and the provisions of 40 CFR 52.21(g) , the Yavapai-Apache Indian Reservation is designated as a Class I area for the purposes of preventing significant deterioration of air quality.61 FR 56470, Nov. 1, 1996