EP 1110-2-13
28 Jun 96
Emergency Management Agency 1985b). These criteria,
along with current state-of-the-art techniques, are
intended to be used in such studies and analyses.
Criteria levels, safety factors, and design methods are
the same as that for new projects.
(3) Since judgment of ground motion
parameters for design is based on geologic and seismic
history, future strong seismic events may raise the
design values against which stability should be
analyzed. Should such a situation occur, the district,
if convinced that the ground motion parameters have
changed significantly enough to affect the safety of the
project, shall prepare an evaluation report as detailed
in paragraph 5-4.a.
(4) Strong motion accelerometers that have
been placed on or around Corps dams are intended as
a check on the design seismic resistance of the
structure. If these instruments record ground motion
parameters that, after analysis, are found to be below
the values used in design but yet the structure received
damage, a letter report (in the case of no expected
future remedial action) or an evaluation report (in the
case of anticipated remedial action) shall be written
describing the situation and containing the district's
recommendation.
(5) Seismic stability of auxiliary structures and
devices, such as regulating outlet towers, spillway
gates, retaining walls, hydraulic equipment, and
electric lines, shall be upgraded where necessary to
provide for dam safety, including requirements for
dams to remain operational following the OBE.
Auxiliary structures that do not affect dam safety or
operational safety shall be judged for modification on
economic or other grounds rather than dam safety.
(6) Seismic stability assessment for dam safety
may also involve reservoir rim slides, effects of dam
overtopping, movements of critical retaining walls,
foundation or abutment changes, susceptibility of
embankment dams to liquefaction, or any other feature
that might contribute to dam failure.
5-4. Procedural Requirements
In order to identify and process work for inclusion in
the Dam Safety Assurance Program, reporting and
5-3
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