During the construction of original nuclear reactors at North Anna, the utility learned of the existence of fault lines within the construction site of the proposed plants from its outside independent engineering firm, Stone & Webster, who had been hired by the utility to assess the proposed nuclear plant locations.
According to the Huffington Post, this 1977 Justice Department memo "..focused on how the power company and federal regulatory officials went to efforts to not make public the knowledge of geologic faulting at North Anna.