ETL 1110-2-533
30 Sep 94
batteries and generators. Fortunately, many
If they are not already in place, essential
of the mitigation measures can be done at
service telephone lines (class A service for
low cost if key elements are identified and
some telephone companies) should be
standard fixes or procedures are developed
requested for some of the commercial tele-
for the entire system. While not all system
phone lines that service the facility. These
and equipment configurations can be antici-
lines should be identified, and a procedure
pated, the majority of the potential problems
for accessing them through the PBX at the
can probably be mitigated in this way.
damsite should be established.
Systems and equipment discussed in para-
If water for vital services is needed at a
graph B-5 should be reviewed and imple-
facility, such as for air conditioning of com-
mented when practical. The priority would
puters, the vulnerability of the water system
be determined by the need for continuity of
should be assessed. The high potential for
power generation.
liquefaction resulting in the damage of out-
side plant water lines means that special
The evaluation of seismic vulnerabilities
attention must be paid to valves to isolate
should be made by means of a facility walk-
damaged parts of the system to ensure that
through. While personnel at each facility
water can be delivered to the facility.
could use the guidelines to do an initial
walk-through, each facility should be
Dam operators and other plant personnel are
reviewed by an individual or small group of
a valuable resource in determining priorities
individuals with experience in evaluating
for mitigation measures. In the course of the
facilities. The expert review could be done
review, for many of the systems which were
by an individual from within the Corps or
pointed out as being vulnerable, plant person-
from outside personnel. The evaluation
nel indicated that the system had failed in the
guide can be useful for evaluating systems,
past and that they had "worked around" the
but it is not a substitute for an individual
problems associated with their failure. In the
with broad experience in the evaluation of
cases cited, the various problems arose, one
seismic vulnerabilities.
at a time, when overall system operations
were undisturbed. An earthquake may cause
The use of informed engineering judgment in
several of these systems to fail or malfunc-
the evaluation and retrofit of facilities is
tion at the same time that the generators are
suggested rather than a formal risk analysis
isolated from the power network. The con-
approach. By using this approach, it is pos-
trol of the dam under these conditions may
sible to implement significant improvements
present significant problems. Past earthquake
in seismic performance for what it would
experience has also indicated that unantici-
cost to just formulate and execute a formal
pated events occur that can further exacerbate
risk analysis.
emergency response actions. While dam
operators are the best qualified to control the
Independent, redundant sources of emer-
dam under adverse conditions, and their input
gency power for critical systems needed for
is needed in determining which systems
the control and shutdown of the dam should
should be given highest priority for mitiga-
be considered.
tion, the types of disturbances that can be
brought about by an earthquake are outside
It would be desirable for the Corps to adopt
most operators' experience. It is vital that
a primary communication system for all
operators understand the complexity of the
Corps facilities so that seismic consideration
earthquake scenario in assessing the impor-
could be applied uniformly. For example,
tance of various systems on dam
nodes would be located in seismically ade-
performance.
quate structures, emergency power would be
available, and the facilities would be manned
at all times.
B-26
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