EPA is promulgating interim approval of the operating permits program submitted by Maryland for the purpose of complying with federal requirements for an approvable program to issue operating permits to all major stationary sources, and to certain other sources. Maryland has substantially, but not fully, met the requirements for an operating permits program set out in title V of the Clean Air Act (CAA) and 40 CFR part 70. Upon the effective date of this program approval, those sources must comply with Maryland's regulatory requirements to submit an application for an operating permit pursuant to the state's submittal schedule.