Page 39 - Practical Design Ships and Floating Structures

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These changes, while initiated in the 1960’s continued to influence tanker designs and tanker safety
into the first half of the 1970’s. However a single event in March 1967 began a shift from primarily
economic driven change to primarily regulatory change.
That event was the grounding of the 119,000 DWT tanker, Torrey Canyon, off the southwest coast of
England. For the first time the tanker industry and the public realized the unfortunate impact of a large
tanker grounding on the marine environment. Also in a one week period in December 1969, three very
large tankers experienced significant explosions while water washing crude oil tanks during the ballast
voyage. One of the ships was severely damaged that it sunk, the other two were badly damaged.
Studies later indicated that the large cargo tanks could actually have layers of hydrocarbon vapors,
which were in the explosive range. It was also leamed that water washing could build up charges of
static electricity to cause such explosions to occur. A concerned industry would soon develop Inert
Gas Systems as the solution to the explosion problem.
These events, the grounding of the Torrey Canyon and the VLCC explosions, changed the primary
driving force for technical safety changes in tanker design from economic to regulatory.

2 TANKER DESIGN AND THE MARPOL CONVENTION
Following the grounding of the Torrey Canyon, public pressures began to build on governments to
revise the standards for designing and operating oil tankers. As a result, the International Convention
for the prevention of Pollution from Ships was held in London in 1973.
The resulting MARPOL 73 Convention and amendments established the need for segregated ballast
tank capacity for new tankers over 73,000 deadweight tons, to be implemented in a phased manner by
1979. The amendments placed a limit on the size of cargo oil tanks, set limits on the oil outflow in the
event of a collision or grounding, and set other operational requirements to minimize pollution.

In December 1976, the oil tanker ARGO MERCHANT ran aground off the East Coast of the United
States. The vessel subsequently broke up releasing all of its cargo, which fortunately, did not pollute
the U.S. shores. However, in the next three months there were 14 more tanker related incidents off the
U.S. coast, of which eight were serious.
Following these incidents, the U.S. government threatened unilateral action to require double bottoms
to reduce accidental oil outflow, if the international shipping community did not improve tanker
regulations and pollution prevention measures. In response, the International Maritime Organization
(IMO) scheduled the Tanker Safety and Pollution Prevention Conference for February 1978.

Shortly after the opening of that conference, the 250,000 ton AMOCO CADI2 grounded off the coast
of Brittany, releasing its entire cargo into the English Channel and onto the beaches of France. This
insured the decade of the 70’s would be one of unprecedented regulatory change for the tanker
industry.

The Convention on Tanker Safety and Pollution Prevention of 1978 dealt with a wide range of issues
involving requirements for segregated ballast tanks, clean ballast tanks, crude oil washing and inert gas
systems. These changes were directed at both new and existing tankers.
The outcome was a complex compromise that established protocols to both MARPOL 73 and SOLAS
74. Protective location of segregated ballast was accepted as a substitute for a double bottom
requirement on new tankers, which was being proposed by the US. Inert gas systems and crude oil
washing were also required for new tankers. Inert gas systems or crude oil washing were required to