What is the average weight of a manhole cover designed to deter unqualified persons from accessing the opening?

Manhole covers designed to deter unqualified persons typically have an average weight of over 100 lbs. The primary purpose of these heavy covers is to prevent unauthorized access while still allowing for necessary maintenance and inspections by qualified personnel. A heavier manhole cover is less likely to be moved or removed by individuals who do not possess the appropriate knowledge or authority, thus enhancing public safety.

Manhole covers that exceed 100 lbs provide significant durability and security against tampering or accidental removal, which is crucial in urban environments where such openings exist on roadways or pedestrian areas. Engineering standards and practices often dictate the weight of these covers based on safety requirements and the specific application, ensuring that they can withstand traffic loads and adverse weather conditions while remaining secure.

For this reason, the correct answer highlights the importance of substantial weight in manhole cover design for safety and security measures.