A key piece of water infrastructure in fire-stricken Altadena is back online, as the 4.1-million-gallon Allen Reservoir has returned to full service following repairs tied to damage from the Eaton Fire. That restoration means additional storage capacity is once again available for customers in Altadena and Pasadena, helping support reliable water pressure and emergency fire flow when the system is under stress. Here's what to know Built in the 1…