The United States Environmental Protection Agency (EPA) is proposing to update the selenium criteria applicable to marine and estuarine waters of the San Francisco Bay and Delta, to ensure that the criteria are protective of aquatic life and aquatic-dependent wildlife in the Bay and Delta. This report provides estimates of the potential incremental compliance actions and costs that may be associated with the proposed regulation. The purpose of this analysis is to identify, using available water quality and discharge data and information, the incremental compliance actions and costs that publicly owned wastewater treatment works (POTWs) and industrial point source dischargers may incur as a result of EPA’s proposed selenium criteria for the Bay and Delta.