e emphasis has shifted from prevention and clean up, to understanding the long term effects of oils spills. There is still a "before and after" mentality about engineering and oil spills. In science and engineering, where an inevitability is involved such as an oil spill, it is better to work towards greater understanding of related consequences, rather than deny that failure may occur.
In a "low energy" grounding, in which a ship barely scrapes over an underwater reef, the outer hull may be punctured by sharp rocks but the inner hull in a double hulled ship, nested six feet or more within the outer skin, should remain intact. Although the Exxon Valdez was not a double hulled ship, the circumstances of its grounding may have proved double hulling ineffective. Because of pressure differences, a double hulled ship can hit a rock or reef that will rip both hulls apart, In these cases, oil will flow out unobstructed until its pressure equals that of the water (Skerrett, 1992).
Japanese boat builders champion another technique. The intermediate deck design consists of a fluid tight deck that divides the inside of a ship into upper and lower compartments. the oil is kept in both parts, with the lower section below the ocean surface. If the ship runs aground, a punctured compartment would fill with water flowing in, rather than oil flowing out (Skerrett, 1992).
Boat builders have come up with two other techniques that may be adapted. One technique requires shippers to stop adding oil to storage tanks before capacity is reached, so that the oil would remain below the water level in the event of an underwater grounding. This technique relies on pressurization to keep most oil from being lost. The other technique depends on a created vacuum above the stored oil to create a positive imbalance of pressure. The truth is, all the models examined still allow leakage due to the rolling motion of the oceans (Skerrett, 1992).
Th...