You have determined that your underground cable design requires three maintenance holes (MHs). One is 4.3 m (14 ft), one is 6 m (20 ft), and one is 6.7 m (22 ft) in length. How many MH covers are requ

Three assumes one cover per MH regardless of length, which violates BICSI length-based cover allocation rules for MHs exceeding 15 ft.

Four undercounts because it does not account for the additional covers required for the 6.7m (22 ft) MH.

Six would only be correct if every MH required exactly two covers, but a 14 ft MH only requires one and a 22 ft MH requires four.

Per BICSI TDMM outside plant standards, MH cover allocation is length-dependent: a 4.3m (14 ft) MH requires 1 cover, a 6m (20 ft) MH requires 2 covers, and a 6.7m (22 ft) MH requires 4 covers, yielding a total of 7. The longer the MH, the more access covers are needed to meet safe entry and emergency egress requirements.

Nine overcounts the total; no combination of the three MH lengths produces a nine-cover requirement under BICSI standards.