The manhole covers and frames shall unless otherwise described, be cast iron coated flat covers and frames, clear opening of 500 mm diameter grade 'B' single seal type, complying in all respect with B.S.497: Part 1 (1976) and acceptable by the local authority.Interior manholes shall be filled with recessed cast iron covers and frames suitable for accepting the floor finish specified for the surrounding areas.Exterior manholes in roadways and driveways shall be provided with heavy-duty cast iron covers.
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