represents a basic solution. Pure water has a pH of 7, while rainwater and
stream water are slightly acidic. Most organisms can tolerate minor
acidity, but higher levels of acidity can significantly reduce the health of
ecosystems. Acid rain includes precipitation with a pH lower than 5.6.
Some of the most acidic rains have reported pH ratings as low as 2.4.
Basic solution: A
solution with a pH
rating above 7.
Chapter 26
616
Social Studies: The Exxon Valdez and Oil Spills
On March 24, 1989, the supertanker Exxon Valdez strayed from its course in Prince William
Sound and slammed into rocks underneath the surface. See Figure 26-A. The result of the
disaster was an oil spill that took more than three years to clean up. Approximately 11
million gallons of oil were spilled over an area that grew to reach hundreds of square miles.
More than 1300 miles of shoreline were affected. Of those, about 200 miles were moderately
to heavily oiled, with the remainder receiving a lighter coating to only trace amounts of oil.
See Figure 26-B.
A team of more than 10,000 workers used various techniques to clean the shoreline of the
oil until 1992, when the U.S. Coast Guard declared the cleanup operations complete. Despite
the fact that many fish and birds were killed by the oil spill, Prince William Sound continues
to yield record harvests for salmon. The Exxon Valdez disaster remains one of the worst acci-
dental oil spills in American waters and cost more than $2.1 billion to clean up, according to
Exxon. As of 2003, the Exxon Valdez spill was no longer considered to be one of the top 50 oil
spills worldwide. It is still widely considered to be the worst spill, however, in terms of
environmental damage, due to the pristine nature of Prince William Sound and the abun-
dance of unique fish and wildlife found there.
One of the major lessons learned by the Exxon Valdez disaster was that spill prevention,
response, and containment procedures were totally inadequate. Since the time of the
accident, the following improvements have been made to oil shipping through Prince
William Sound:
Figure 26-A. The Exxon Valdez tanker
aground in Prince William Sound.
(National Oceanic and Atmospheric
Administration)
Figure 26-B. Workers cleaning the shore-
line of oil from the Exxon Valdez oil spill.
(National Oceanic and Atmospheric
Administration)