ETL 1110-2-533
30 Sep 94
Appendix B: Guidelines for Evaluating the Seismic Vulnerability
of Lifelines and Ancillary Systems Required for the
Operation of Dams
and
Mitigation Measures for Reducing Seismic Vulnerability
B-1. Introduction
United States and foreign. In the past, there has been
a strong dependance on informed engineering judg-
ment rather than detailed analysis and formal
a.
Background.
calculation.
(1) In response to the 1971 San Francisco earth-
quake, a Federal initiative addressed seismic vulnera-
bilities of Federal facilities. This resulted in the
vulnerability of dam lifelines and ancillary systems is
Earthquake Hazard Reduction Act of 1977. The
divided into five parts. The first part reviews the
interagency Committee for Seismic Safety and Con-
general effects of earthquakes and the impact on
struction was formed in 1978 in response to this act.
lifelines and dam ancillary systems. The second part
The Earthquake Hazard Reduction Program was
identifies systems critical to dam operation and the
initiated and managed by the Office of Science and
emergency response after a damaging earthquake.
Technology Policy, and a letter was issued to Federal
The third part describes the vulnerabilities and mea-
agencies suggesting that good seismic practices be
sures to improve the seismic response of those sys-
used for Federal facilities. In January 1990, Exec-
tems needed for the protection and safe shutdown of
utive Order 12699 was issued which requires new
the dam after an earthquake. The fourth part
Federal construction to comply with seismic require-
describes the vulnerabilities and measures to improve
ments. Under these requirements Federal facilities
the seismic response of those systems needed for the
and facilities that use Federal funds must conform to
continued operation of the dam. The fifth part dis-
the seismic requirements of the American National
cusses issues related to disaster response plans and
Standards Institute Standards A58, Minimum Design
their exercise. It should be noted that when mitiga-
Loads for Buildings and Other Structures. Seismic
tion measures are discussed in one section of the
requirements for lifeline buildings must be established
report, they will not be repeated in subsequent sec-
within 3 years after the issue of the Executive Order.
tions when similar equipment is discussed.
(2) Hydropower provides about 10 percent of the
B-2. Earthquakes and Their Impact on Life-
total power-generating capacity in the United States,
lines and Dam Ancillary Facilities
and the Corps of Engineers supplies about 30 percent
of this. The Corps is the largest producer of hydro-
electricity and operates 70 projects housing 344 tur-
Knowledge of the effects of earthquakes and their
bine generators. Many of these facilities are located
impact on lifelines has been gained from observing
in moderate to high seismic zones.
earthquakes that have occurred in many parts of the
world. Several phenomena are associated with earth-
quakes: ground vibrations, soil liquefaction, subsi-
b. Scope. The procedures outlined herein are
dence, ground faulting, landslides, and tsunamis. The
for the evaluation of lifelines and operating systems
significance that any phenomenon has for a particular
that may impact the seismic performance of dams and
region depends on the characteristics of the region
ancillary systems. The procedures do not include the
and the facilities in the area. Each of the following
evaluation of structural aspects of the dam or other
sections will discuss one of the phenomena associated
structural elements or systems. The outline is based
with earthquakes and give an example of its impact
on a 2-day review of two facilities.
on lifelines.
c. Approach to vulnerability evaluation and
a.
Ground vibration.
vulnerability has been based primarily on the seismic
(1) When an earthquake occurs, seismic energy
performance of similar equipment at power and
radiates away from the causal fault in the form of
industrial facilities during earthquakes, both in the
B-1
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