The Metropolitan Transportation Authority New York City Transit (MTA NYCT) is proposing a change to the approved Canarsie Tunnel Project. The Project includes rehabilitation, resiliency, state of good repair and capacity improvement activities related to the Canarsie Tunnel, which is located in New York under the East River and connects Manhattan and Brooklyn. The purpose of the proposed change is to provide transportation alternatives, known as the Alternative Service Plan (ASP), to the greatest number of diverted L train riders while the Canarsie Tunnel is undergoing rehabilitation. The Tunnel was damaged during Hurricane Sandy in 2012 and needs to be repaired in a safe and expeditious manner to minimize risk of unexpected structural failure and service disruptions. At the time of FTA’s previous environmental review, the Project included a preliminary concept of a service plan to provide transportation alternatives. The ASP has been refined and FTA and MTA NYCT have prepared a Supplemental Environmental Assessment to present the potential environmental impacts of the proposed ASP.