This proposed action will address the agency’s directive to review and revise the New Source Performance Standards (NSPS) for Volatile Organic Liquid Storage Vessels (Including Petroleum Liquid Storage Vessels) for which Construction, Reconstruction, or Modification Commenced after July 23, 1984 (NSPS Kb) per the consent decree deadline in Environmental Integrity Project, et al. v. Regan, No. 20-cv-03119-TNM (D.D.C.). The action consent decree deadline is September 30, 2024, for a final rule. The Volatile Organic Liquid Storage Vessels NSPS, Subpart Kb, was promulgated pursuant to section 111(1)(B) of the Clean Air Act (CAA) on April 8, 1987, with updates promulgated on August 11, 1989; October 8, 1997; October 17, 2000; December 14, 2000; October 15, 2003; and January 19, 2021. The rule was last amended in January 2021, to incorporate the requirements of 40 CFR section 65, subpart WW as an alternative means of compliance to satisfy 40 CFR section 60.112b through 40 CFR section 60.117b for storage vessels applicable under 40 CFR section 60.110b(e)(5)(i) through (iv). EPA has obligations under the Clean Air Act (CAA) section 111(b)(1)(B), 42 U.S.C. section 7411(b)(1)(B), to “review and, if appropriate revise” the NSPS including NSPS Kb. In particular, the agency plans to review the requirements of NSPS Kb, and if appropriate, promulgate new requirements under NSPS Kc.