Critical Infrastructure Act of 2019 This bill (1) requires specified power administrations to disclose all estimated costs and factors affecting total power costs, such as costs for complying with environmental laws impacting the conservation of fish and wildlife, (2) prohibits the Department of the Interior from designating critical habitat in certain water infrastructure areas, and (3) provides exemptions from environmental review requirements for certain electrical power projects or construction projects that may affect prairie dogs. Specifically, the bill requires the Bonneville Power Administration, the Western Area Power Administration, the Southwestern Power Administration, and the Southeastern Power Administration to include in monthly billing statements sent to each customer estimates of all costs and factors affecting total power costs. The estimates must include the customer's share of such administration's costs for compliance with any relevant federal environmental laws impacting the conservation of fish and wildlife. Each administration must report each year on (1) all estimated costs and factors affecting total power costs, including estimates of its total compliance costs; and (2) sources of replacement power. The bill prohibits Interior from designating critical habitat for endangered or threatened species in certain water storage, diversion, or delivery facilities. In addition, the bill exempts projects to install or maintain electrical transmission poles or power lines from environmental review requirements. The bill also exempts from such review construction projects that include buffer areas if the projects would otherwise only require an environmental assessment because of the presence of prairie dogs in such buffer areas.