Keystone provided controls and automation engineering services for the PLC-Based Subsea Leak Detection project at two offshore facilities. The detection algorithms included meter-in/meter-out, conditional rate of change, and hydrostatic. The benefits of the PLC-based subsea leak detection include the following: can be installed in existing PLC/HMI or as a standalone PLC, configurable for any combinations of well/flowline alignment, configurable for multiple drill centers, alarms, and shutdown triggers available, and can be installed typically without downtime. Additional benefits include minimal subsea data required- pressures and valve statuses, user-configurable timers for all functions, automatic and manual inhibits and degrades, low processor overhead, and abort and abandon logs.