Vault privies shall be constructed to include a fly-tight vault; a superstructure affording complete privacy; an earth mound around the top of the vault and below the floor level, which slopes downward away from the vault; a floor and riser of reinforced concrete at least 4 inches in thickness, or other impervious material; and a hinged, self-closing, fly-proof seat and lid of easily cleanable impervious material. All venting shall be fly-proofed with Number 16 or smaller mesh screening. The vault shall be located in an area accessible for the removal of its contents. The vaults shall be durable, with corrosion-resistant material on the interior and exterior.