Whenever a reasonable price cannot be agreed upon, or whenever the owner is legally incapacitated, or is absent, or is unable to convey valid title, or is unknown, the Water and Power Resources Board is hereby authorized and empowered to acquire, by condemnation, any lands, rights, easements, franchises and other property deemed necessary or convenient for the completion or efficient operation of the purposes hereinbefore set forth.
32 P.S. § 751.8