Enforcement notices were served during tunnel construction
The Health and Safety Executive (HSE) is investigating how a vehicle overturned at a dam, leaving its operator with broken legs.
Emergency services were called to the Glendoe hydro-electric construction site near Fort Augustus on Wednesday.
The injured man was taken to Raigmore Hospital in Inverness for treatment.
HSE said a report would be sent to the procurator fiscal once an investigation into the death of a worker at Glendoe in September was completed.
Ondrej Hladik, 46, from Prague, died in an accident involving a forklift.
Since work began on the project two years ago, the main contractor Hochtief Glendoe JV has been served with four enforcement notices by HSE.
Three related to explosives and were served at the time of tunnel digging.
The executive said each notice had been complied with.