Section 52.690 - Visibility protection(a) The requirements of section 169A of the Clean Air Act are not met, because the plan does not include approvable procedures for protection of visibility in mandatory Class I Federal areas.50 FR 28553, July 12, 1985; 51 FR 23759, July 1, 1986, as amended at 52 FR 45137, Nov. 24, 1987; 82 FR 3129 , Jan. 10, 2017