BOSTON (AP) — Gov. Deval Patrick has proclaimed Aug. 11 as “811 Day” in Massachusetts, reminding residents to dial before they dig to avoid hitting utility lines.

Patrick says Saturday should remind homeowners and contractors that state law requires them to dial 811 at least three days before an excavation project.

Callers to 811 will be able to arrange for professional locators to come to their house free of charge and mark where power, cable, telecommunication and water lines run. Homeowners need to mark the intended dig site or route.

Officials say installing a mailbox, building a deck, planting a tree or laying a patio are examples of digging projects that need a call to 811 before starting.

Violators can cause injury, repair costs and outages. They can be fined up to $10,000.