Final answer:
The inspection of drains aboard ships is a standard requirement, and the frequency of inspections can vary depending on the ship type and regulations. Tankers and bulkers often have higher frequencies of overseas ballast water (BW) discharge events, while container ships are frequent arrivals on the East coast.
Step-by-step explanation:
The inspection of drains is a standard requirement aboard ships in order to ensure proper functioning and safety. The frequency of drain inspections can vary depending on the ship type and regulations. For example, tankers and bulkers reported the highest frequency of overseas ballast water (BW) discharge events, with over 10,000 discharge events by tankers and 6,582 by bulkers on the Gulf coast during a specific period. On the East coast, container ships were the most frequent arrivals, with 2,931 discharge events.