National Grid officials are promising a complete archaeological survey of the site of a planned electricity substation in Hopkinton after Narragansett Indian artifacts were found there. Town Council President Frank Landolfi told The Westerly Sun that about half-dozen ceremonial stones were found at the site off Route 216. National Grid spokesman David Graves said the discovery came at a good time because the substation project is still in the early planning stages. The exact location of the substation has not been determined. The exact location of the artifacts is not being disclosed to protect them.