The Environmental Protection Agency (EPA) is approving a State Implementation Plan (SIP) revision submitted by the State of Connecticut. This revision addresses source monitoring in Connecticut. The principal revision is replacement of Regulations of Connecticut State Agencies (RCSA) section 22a-174-4 (source monitoring, record keeping and reporting) with a new regulation section 22a-174-4a, also called "source monitoring, record keeping and reporting," in the Connecticut SIP. This source monitoring SIP revision provides monitoring, recordkeeping and reporting requirements to ensure that certain sources comply with applicable emissions limitations. This action is being taken in accordance with the Clean Air Act.