Manways and covers for sumps are typically much larger in diameter then manways and covers for spill containment buckets. Sump manways and covers are usually between 36" and 48" in diameter.
If fills for tanks are located inside tank containment sumps then the covers for the manway must follow the color coding requirements of API RP 1637 and COMM 10, section 10.230(12).
Sump manways and covers are designed to resist the heavy loads of transport vehicles traveling across the covers.
Older style sump manways and covers were typically constructed from steel and were very heavy.
Newer style manways and covers are typically constructed from composite materials to save weight and reduce the possibility of back injury when removing the covers from the manways.