What is the standard size of an underground tank opening?

The standard size of an underground tank opening is typically 4 inches in diameter. This size is designed to accommodate various maintenance and operational functions, such as filling and sampling of the tank contents. A 4-inch opening strikes a balance between being large enough for access and maintenance while still maintaining structural integrity and minimizing potential leaks or spillage. This standard is widely accepted in the industry to ensure safety and compliance with regulations governing underground storage tanks.

Larger openings might allow for easier access but could also increase the risks associated with leaks, spills, and unauthorized access. Meanwhile, smaller openings may limit access for necessary maintenance activities, which could lead to issues with tank monitoring or servicing. Therefore, a 4-inch opening is deemed appropriate for the effective functioning and risk management of underground storage tanks.