Which of the following is NOT included in the APM list of manholes?

The correct answer identifies an item that is not classified as a manhole within the context of the APM (Asset Performance Management) terminology. Manholes generally refer to underground access points used for utilities, such as sewer or electrical systems, allowing for maintenance and inspections.

Transformers, while more complex structures often related to electrical distribution, are typically housed in manholes or vaults for access purposes. Water tanks and chemical storage tanks can also relate to underground utilities but may not be classified strictly as manholes.

Gas storage tanks, however, are fundamentally different in their purpose and design. They are structures intended for storing gas, typically above ground or in specialized underground facilities, rather than serving as access points for maintenance or inspection. Therefore, they do not fit the definition of a manhole within the APM framework, which leads to the conclusion that gas storage tanks are the item that is NOT included in the list of manholes.