Though three hull designs exist which minimize cargo outflow in a grounding and/or collision, the USCG allows only one within US waters. Which design is it?

• A. Coulombi Egg Design
• B. Double Hull
• C. Mid-Deck Tanker
• D. Another design not listed

Answer: (B)

The main idea is that a physical barrier between cargo and the sea greatly lowers the chance of a spill if the hull is damaged. A double-hull design provides two complete hull layers with a space between them. If the outer hull is breached in a grounding or collision, the inner hull still contains the cargo, dramatically reducing outflow and giving more time for response. This robust protection is why the U.S. Coast Guard allows this design in U.S. waters and why regulations worldwide have moved toward double-hull tankers to prevent oil spills. Other concepts, like Coulombi Egg designs or mid-deck arrangements, were developed to reduce outflow in accidents, but they have not become the standard permitted within U.S. waters.