Headlines
Nepal quake rekindles fears on Tehri dam, Jaitpur n-plant
By
K.S. JayaramanBengaluru, May 5
The devastating quake in
Nepal has revived the controversy in India over the Tehri dam in
Uttarakhand that was commissioned in 2006-07 and a nuclear plant
proposed to be set up at Jaitapur in Maharashtra.
Both the dam
and the site for the nuclear plant were approved in spite of advice to
the contrary by independent seismologists, the Rome-based International
Association for Promoting Geoethics (IAPG) has said.
The
260.5-metre-high Tehri dam, the tallest in India, and the 9,900 MW
nuclear plant, the world's largest, are among the controversial projects
cited by IAPG in its latest publication "Geoethics, Ethical Challenges
and Case Studies in Earth Sciences".
The two case studies from
India "relate to future risks to engineering structures and concern
fundamental ethical issues", Vinod Gaur, former director of Hyderabad's
National Geophysical Research Institute and the author of the study,
told IANS.
The Tehri dam is located in the central Himalayan fold
created by the Tibetan plate advancing southward over India at about
two metres per century. Its 2.6 cubic km reservoir floods a narrow 30
km-long valley. Controlled release of reservoir water currently
generates 1,000 MW of power.
According to Gaur, the Tehri dam was
designed in 1972 when evidence of the ongoing deformation in the
Himalayas was not available. The design was based on the assumption that
a maximum credible earthquake at the site would have a magnitude of 7.2
on the Richter scale and a peak ground acceleration of 0.25g (where "g"
is the acceleration due to gravity).
The project was the subject
of three decades of debate due to concerns over the wisdom of
constructing a major earth and rockfill dam in the Himalayas, which have
seen three devastating earthquakes in the first half of the 20th
century.
Gaur said that around the mid-1980s, the maximum
credible magnitude was raised from 7.2 to 8.5 but the Tehri project's
consultants retained the 0.25g value as the dam's design basis.
According
Gaur, the dam should have been redesigned to withstand a peak ground
acceleration of 0.56g, but the government gave the green signal for the
dam's construction after ignoring the majority advice of an expert
committee it had set up in 1996.
Four of the five members of the
committee recommended a 3-D simulation of the dam for long-duration
shaking appropriate for an 8-magnitude quake. Also recommended, before
the beginning of construction, was a simulated dam failure analysis to
evaluate the consequences of its hypothetical breach.
"No 3-D simulation responding to a great rupture beneath the dam has so far been undertaken," Gaur said.
"The
completed dam, therefore, falls short of the recommended compliance
with international standards," says the IAPG report. "Thus, there is a
real concern whether expert committee members have betrayed their
ethical obligations to the public at risk from catastrophic damage in a
future earthquake."
The IAPG case-study of the Jaitapur site says
Indian authorities ignored the presence of a 35-km-long "possibly
active fault" just 10 km south of the site in spite of concerns raised
by scientists not involved in the project.
"No paleoseismic
investigations have been undertaken across this fault to determine when
it last slipped," Gaur said, adding: "It has not been trenched to
determine what magnitude earthquakes this fault may be capable of."
In response, the state-owned Nuclear Power Corporation has said that "all concerns have been accounted for" by its experts.
"The
discounting of the possible occurrence of a damaging earthquake nearby
is clearly imprudent," Gaur said, adding: "Should the fault slip, the
nuclear plant would lie less than 10 kilometres from the rupture."
"Shortcuts
in seismic hazard assessments for nuclear power plants are not
acceptable," Max Wyss, a renowned seismologist with Geneva's
International Centre for Earth Simulation, has said in a commentary on
Gaur's study. He fears that the cases reported in the IAPG publication
"represent only the tip of the iceberg of similar cases worldwide, which
raise serious questions about research integrity."
The 7.9
magnitude Nepal quake on April 29 has claimed over 7,000 lives and
injured thousands more, besides causing large-scale destruction of
houses and other buildings.
(K.S. Jayaraman can be contacted at [email protected]