Addendum to the Final Mitigated Negative Declaration. The Approved Project, as described in the Final MND/IS entailed improvements at the San Ysidro Rail Yard (Rail Yard), included construction of two new track extensions and revisions to track alignment for additional rail car storage, a new truck access road, and drainage improvements. The two new track extensions provide additional storage capacity, as well as the ability to switch rail cars outside of the constrained operating windows without interrupting the trolley line. The improved truck access to the Rail Yard provides additional opportunities for cargo transfer (transloading) and eliminates some regional truck traffic trips on freeways in the region. Truck access to the Rail Yard is provided from East Beyer Boulevard via a new one-way, entrance-only driveway that connects to an internal access road that parallels the railroad tracks to the east. Trucks exit the Rail Yard utilizing the existing driveway off East Beyer Boulevard, north of East San Ysidro Boulevard. Other improvements, such lighting and fencing, were installed for improved safety and security. The Approved Project also included drainage improvements to alleviate flooding and siltation that occurred at the Rail Yard. Because of the Rail Yard's adjacency to steeper topography of the undeveloped hillsides to the east, it is subject to inundation by water and silt during storm events. The Approved Project corrected the drainage deficiencies by constructing storm drain facilities to accommodate flows during storm events, including detention and desiltation basins, grated catch basins, drainage - ditches and storm drain pipelines.