What is the minimum diameter for round access openings in a manhole?

The minimum diameter for round access openings in a manhole is 26 inches. This standard is established to ensure that maintenance personnel can safely access the manhole for inspection, cleaning, or repair without difficulty. Access openings must be large enough to accommodate both personnel and any tools or equipment they might need to bring inside while also maintaining a certain level of safety. A diameter of 26 inches provides sufficient room for entering and exiting a manhole, which is critical for safe operations in confined spaces.

The other options suggest larger diameters, which, while potentially providing even more space, are not required by the established standards for minimum access openings, making 26 inches the specified requirement. Hence, it's important for professionals in the field to adhere to these dimensions to comply with safety regulations and ensure effective functionality of manholes.