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From dianne Mon Dec 6 16:25:50 1999
Date: Mon, 6 Dec 1999 16:25:49 -0500 (EST)
From: "D. Murray" <dianne@sandelman.ottawa.on.ca>
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To: dianne@sandelman.ottawa.on.ca
Subject: letters.html
World Rivers Review
Volume 10, Number 4/January 1996
Letters: An Open Forum
If the number and length of letters we're receiving from hydropower
industry representatives is any indication, World Rivers Review is
being taken ever more seriously by the industry. We will be reprinting
those that are particularly worthy of response or offer insight into
the industry and its work. Here, then, is a letter from Jan Veltrop,
the former president of the International Committee On Large Dams
(ICOLD) and former vice president of Harza Engineering.
Patrick McCully's "Fear of Failure" in World Rivers Review (May 1995)
is a peculiar mixture of facts and half truths. "New dams have become
progressively less likely to collapse" is a fact, but "Humankind would
do better to harbor a healthy fear of failure" is a grossly
exaggerated opinion. The generalization on what can go wrong with dams
is outright misleading.
Dam safety: McCully acknowledges the thorough and careful approach to
design of dams outlined by Robert Jansen, but then undermines this by
stating that ultimately "economics" decide the "degree of defensive
engineering". Dam engineers do not cut corners to trade off on safety.
Concern for safety exceeds all other considerations. Codes of ethics
for engineers hold sacred the protection of the public welfare.
Lifespan and dam removal: When raising the specter of dam removal, he
completely bypasses current trends towards prolonging dam and
reservoir lifespan through safety monitoring, sediment control and
management, rehabilitation of components affected by aging, addition
of spillway capacity to accommodate large floods and strengthening of
dams against more severe earthquakes. In addition, he seems to be
unaware of the development of guidelines to identify, evaluate, and
describe engineering, environmental, and socioeconomic factors
affecting the retirement of hydroelectric facilities.
Aging of dams: To say that "aging of dams has long been largely
ignored" is not correct. After an eleven-year study started in 1972,
ICOLD published "Deterioration of Dams and Reservoirs" in 1983,
followed in 1994 by "Aging of Dams and Appurtenant Works."
Dam failures: No dam over 125 meters high ever failed. Furthermore,
when considering the number of years of successful operation of all
dams in Europe and the USA over 15m high, the decrease in the number
of incidents per 10,000 years of combined operation is spectacular;
from 29 incidents in the decade 1910-20 to less than four between 1960
and 1970.
In conclusion, generalizations cloud the article and mislead the
uninformed reader. For example, the sentence "Some dams may remain
safe for a thousand years, others may show signs of danger such as
cracks and leaks after less than a decade" implies that man should
live in fear of the potential failure of ANY dam. A number of
countries, including the US, have established hazard ratings for dams,
distinguishing those with high hazard from the vast majority not
listed. People who benefit from the services supplied by dams are
entitled to be properly informed about dam safety. "Fear of Failure"
does not meet this objective.
Jan A. Veltrop
Patrick McCully replies:
To imply that economics do not affect dam design and hence dam safety
is, at best, naive. ICOLD itself recognizes the conflict, stating in
its 1987 guidelines on dam safety that: "To a certain degree, an
increase in dam safety involves an increase in cost. For every dam
project, a balance has to be found between dam safety and economy."
It is also not realistic to hold that all engineers in all cases
follow the engineering codes of ethics. Further, there is no
internationally accepted code of ethics for dam builders, rather a
mish-mash of national and state engineering codes with ambiguous
applicability to international projects. Appeals from IRN and others
for ICOLD to adopt an international code were turned down by Dr.
Veltrop during his term as president.
Many of the methods to prolong dam lifespan are largely unproven, will
in many cases not be economically viable, and will rarely be able to
prolong dam life indefinitely. ICOLD's reports on dam ageing
notwithstanding, few governments or dam-building agencies have started
to consider the cost and techniques of monitoring, maintaining and
eventually taking down dams.
The following quote, found in Water Power and Dam Construction,
illustrates the industry's attitude about decommissioning: "Some key
industry figures had a good laugh informally discussing powerplant
decommissioning and dam removal. They shook their heads, saying that
they would leave such activities up to their grandchildren; it simply
was not going to happen in a serious way during their lives."
Individual dams may be safer than before, but the huge increase in the
number of dams means that the risk of destruction from dam failure
remains significant. While it is true that no dam over 125m high has
yet "failed," the 261m Vaiont Dam in northern Italy (the world's
fourth highest) was overtopped in 1963 by a massive wave caused by a
landslide into its reservoir. The dam withstood the force of the wave
­p; but 2,600 people downstream were swept away to their deaths.
Most high dams are still relatively young and are yet to be tested by
the maximum flood or earthquake likely to occur during their lifespan.
Some significant near misses ­p; for example in 1974 at Tarbela,
Pakistan, and in 1983 at Glen Canyon, US ­p; give warning that it
is only a matter of time before a catastrophic failure of a very high
dam occurs. The 80,000 to 230,000 deaths believed to have been caused
by the failures of Banqiao and Shimantan Dams in China in 1975 give an
indication of the scale of disaster likely if a major dam above a
heavily populated area were to fail.
As Dr. Veltrop should know, the hazard ratings of dams in the US are
not based on an engineering assessment of the soundness of the
structures, but on the height of the dam, size of its reservoir and
whether people live below it. According to a 1994 report by the US
Association of State Dam Safety Officials, there are more than 9,500
"high-hazard" dams in the US, and more than 1,800 dams which have been
inspected and found to be unsafe.
If ICOLD were indeed concerned that people should be "properly
informed about dam safety" it would publicly admit that all large dams
have the potential to fail. It would insist on maps showing downstream
areas at risk of flooding for all large dams, complete with evacuation
plans. To pretend that dam builders can build dams which cannot break
is hubris equal to that of the builders of the "unsinkable" Titanic.
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