If you find yourself facing this dilemma, here are some guidelines from Dominion for making a proper identification:
Dominion employees carry ID and their contractors typically carry Mt. Storm-Doubs (MS-D) fact sheets and/or MS-D business cards with them or other means to show they are affiliated with Dominion. Dominion has provided these handouts to those they know are going into the field. These documents have Dominion's website, email, and contact 800 number printed on them so employees and contractors can let folks know where/how to get their questions answered.
When Dominion or their contractors take soil samples, they mail the property owners in advance. Before they begin construction, they will mail you again. A few property owners in Jefferson County, WV have already been mailed and contacted about soil sampling.
If you catch someone sneaking around your property who cannot produce identification that satisfies you (or you find something fishy about the story or identification you are shown), contact Dominion at 1-888-291-0190.