On The ‘Shores’ Of The LA River. On August 21, 2017, UP Y2731 (3GS21B, NRE) was mid-train as it approach Union Pacific Railway’s 4th Street Yard after serving the Los Angeles Times. This was late in the day as the golden hour descends upon Los Angeles, California. UP once rostered 59 3GS21Bs (Y2701-Y2760), all have been withdrawn from service.