100 members of the emergency services will be carrying out an emergency planning exercise tomorrow.
Police, the Isle of Man Fire and Rescue Service, Ambulance Service, Civil Defence and Coastguard will be at Groudle Glen in the evening.
People are being told not to be alarmed at the large numbers of personnel and vehicles in the vicinity.
The event is organised by the Isle of Man Government's Emergency Planning Unit – all roads will remain open as normal.