The project is the first phase of a wider development on the site to include two wind turbines, a new hotel and commercial development and BP service station.
Client Cornish Gateway Services gave the firm the green light to archaeological investigation this week at the site ahead of building work starting up.
A spokesman for Cornish Gateway Services said: “This much needed facility has taken over 8 years to come to fruition.
At the moment there isn’t a comprehensive service station on the 118 mile stretch of A30 from Exeter to Penzance, which is ridiculous given Cornwall’s main industry now is tourism as well as the requirements of the general travelling public.
“It should have been built years ago.”