After conducting research, I could not find any information about a boat ramp named Granite Lake Dam Road in Valley County, Idaho. It is possible that the location may be a small or private boat ramp that is not listed on public databases or websites.

However, there is a Granite Creek boat ramp located in Valley County, Idaho, which could be a possible alternative. This boat ramp services the Payette Lake, which is a popular destination for boaters and anglers. The Granite Creek boat ramp is said to be a concrete ramp with a width of 20 feet. It is designed for small boats, canoes, and kayaks, and is suitable for launching and retrieving watercraft.

It is important to note that regulations and restrictions for boating may vary depending on the location and body of water. It is recommended to check for local laws, permits, and guidelines before launching any watercraft.