Double Hull Regulation Changed After the MT. Exxon Valdez Incident?

On March 24, 1989, on a bright Saturday amidst the white Alaskan landscape, one of the largest ecological and maritime disasters in history unfolded. The waters of Alaska turned pitch black after a massive oil tanker, captained by Joseph Hazelwood, MT. Exxon Valdez (IMO number: 8414520), measuring 301 meters in length and 51 meters in width, struck Bligh Reef in Prince William Sound, Alaska, resulting in one of the largest oil spills in history. Over 11 million gallons of crude oil spilled into the sea, causing severe environmental damage.

Marine ecosystems, including fish, birds, and marine mammals, were drastically affected, and cleaning up the spill took years. A large-scale cleanup effort involving thousands of people was eventually launched. In a National Geographic article titled Exxon Valdez changed the oil industry forever—but new threats emerge, the final death toll included 250,000 seabirds, nearly 3,000 sea otters, 300 harbor seals, 250 bald eagles, 22 killer whales, and billions of salmon eggs. The population of Pacific herring, essential to the local fishing industry, plummeted, leaving many local fishermen bankrupt.

Following the incident, the United States responded by issuing the Oil Pollution Act (OPA) 1990, signed into law by President George H.W. Bush on August 18, 1990. A critical point in OPA 1990 mandated all new tankers to have a double hull, featuring two layers of hull to prevent oil spills in the event of damage to the outer hull. This regulation was subsequently adopted globally, including by the IMO, to prevent similar accidents and protect the environment. Additionally, OPA 1990 imposed heavy penalties on parties violating oil spill regulations, including significant financial fines and liability for environmental restoration costs.

What is a Double Hull?

A double hull is a design where a vessel has two layers of hull: an outer hull (external hull) that acts as an additional layer outside the inner hull, providing extra protection. If a leak or damage occurs to the inner hull, the outer hull serves as a barrier to prevent oil or hazardous substances from spilling into the sea. The inner hull separates the cargo tanks from the sea and holds the ship’s cargo, such as oil or other hazardous liquids. This design enhances the safety of ships, particularly tankers carrying oil or other dangerous goods. Between these two hull layers is an empty space known as the void space. The main advantage of the double hull is that if the outer layer is damaged in a collision or grounding, the inner layer can still protect the cargo tanks from leaking. This reduces the risk of oil spills into the sea.

With the increasing production and need for new tankers, as well as greater awareness of environmental safety risks posed by single-hull ships, single-hull tankers have been gradually phased out and banned in many international waters since 2010.