40 C.F.R. § 52.2304
Visibility protection
(a) Reasonably Attributable Visibility Impairment. The requirements of section 169A of the Clean Air Act are not met because the plan does not include fully approvable measures for meeting the requirements of 40 CFR 51.305 for protection of visibility in mandatory Class I Federal areas.
(b) [Reserved]
(c) Regional Haze. The requirements of section 169A of the Clean Air Act are not met because the regional haze plan submitted by Texas on March 31, 2009, does not include fully approvable measures for meeting the requirements of 40 CFR 51.308(d)(3) and 51.308(e) with respect to emissions of NO
(d) Portions of SIPs addressing noninterference with measures required to protect visibility in any other state are disapproved for the 1997 PM
(e) [Reserved]
(f) Measures addressing disapproval associated with NO
(2) The deficiencies associated with SO