The Bullwinkle GC-65A platform was upgraded throughout the last 20 years in a piecemeal approach, such that nine Programmable Logic Controllers (PLC) were integrated together in a haphazard fashion.   Process and safety functions were both physically and logically comingled together with no redundancy.  The complex interrelationship of nine obsolete and overloaded PLC(s) contributed to a continuous and unacceptable large number of nuisance shutdowns.  Shutdown durations were exacerbated by the system complexity.   The PLC Upgrade Project replaced the existing PLC(s) and PLC network with a dual/redundant set of process and safety PLC(s).  The new PLC(s) were arranged in a redundant fiber optic Ethernet ring with star hubs at each of the existing field panels / Local Control Panels (LCP).  Remote I/O (RIO) adapters were installed in each field panel using CAT6 Ethernet cabling in lieu of the legacy Data Highway Plus wiring.  The PLC logic (software) was reverse engineered from the existing code and validated against the current platform installed hardware.  Obsolete, Out Of Service (OOS), and decommissioned equipment was removed from the PLC software to create a clean install without useless overhead logic.  Existing Redi-Panels and Panelviews were removed and five new HMI LCP(s) were installed to support deck/local monitoring by operations, but set to read-only.   In addition to the hardware upgrade, the platform HMI and Historian were also upgraded to support the new software.  Stand-alone skid packages (e.g.: compressor) were also incorporated into the HMI to allow full operator surveillance and control of the entire production system.  The new system modified the existing field intensive monitoring and control to a central control room operator with oversight responsibility for the entire platform.  The design life of the new system is expected to be 20 years.