Based on NMFS’s receipt of an application from the Interstate Bridge Replacement Program (IBRP) for incidental take regulations and a Letter of Authorization (LOA) under the Marine Mammal Protection Act, this action proposes regulations to govern the unintentional taking of marine mammals incidental to construction activities associated with the replacement of the I-5 bridge over the North Portland Harbor and the Columbia River, connecting the cities of Portland, Oregon, and Vancouver, Washington. The IBRP plans to conduct necessary work, including impact and vibratory pile driving, to replace the existing bridge. The proposed regulations would set forth the permissible methods of taking; means of effecting the least practicable adverse impact on the affected species or stocks and their habitats; and requirements pertaining to the monitoring and reporting of such taking. Letters of Authorization issued under the regulations would authorize the take of marine mammals incidental to the specified activities for a 5-year period.