Revitalizing the Economy by Simplifying Timelines and Assuring Regulatory Transparency Act or the RESTART Act This bill limits, accelerates timelines under, or otherwise modifies several environmental laws. Specifically, it accelerates, coordinates, and limits the environmental review of federal actions under the National Environmental Policy Act of 1969. For example, it (1) establishes deadlines for completing any Environmental Assessment or Environmental Impact Statement (EIS), (2) directs agencies to prepare a single environmental document (e.g., EIS), and (3) limits judicial review. The bill also prohibits agencies from using estimates for the social cost of greenhouse gases when taking agency actions if such use may increase the cost of energy or prolong the timeline for taking actions. It also revises the Clean Air Act, including to allow existing facilities to make certain modifications without obtaining new permits under the New Source Review program. The bill also revises the Clean Water Act, including to (1) provide statutory authority for the definition of waters of the United States in the 2020 navigable waters protection rule, and (2) limit the scope of water quality certifications. It also modifies the underground injection control program to accelerate the review of state applications to obtain responsibility under the Safe Drinking Water Act for regulating Class VI wells, which are used to store captured carbon. In addition, the bill accelerates the timelines for the consultation process under the Endangered Species Act of 1973. Finally, the bill establishes requirements to expedite the completion of the Mountain Valley Pipeline.