ETL 1110-2-533
30 Sep 94
and summarize the earthquake evaluations
(3) Central region, which consists of the area
performed to date on Corps dams and appurtenant
between the regions just described and the Rocky
structures under ER 1110-2-1806.
Mountains (Figure A-4).
(4) Southwestern region, including New Mexico
b. Legislation. PL 101-614, enacted on
and Arizona (Figure A-5).
16 November 1990, reauthorized the National
Earthquake Hazards Reduction Act of 1977. The
(5) Northwestern region, including Washington,
purpose of the law is to develop a national program
Oregon, Montana, and Idaho (Figure A-6).
to reduce risks to life and property from future
earthquakes. One of the stated objectives is "the
(6) California (Figure A-7).
development of technologically and economically
feasible design and construction methods and
(7) Hydroelectric power plant facilities at risk.
procedures to make new and existing structures, in
The disposition of Corps hydroelectric power plant
areas of seismic risk, earthquake resistant, giving
facilities with respect to the various UBC seismic
priority to the development of such methods and
zones is provided in Table A-1. This table also
procedures for power generating plants, dams,
provides information on the power-producing
hospitals, schools, public utilities and other lifelines,
capacity, the plant location, the river system, and
public safety structures, high occupancy buildings,
the responsible Corps district and division. The
and other structures which are especially needed in
Corps has 8 hydroelectric power plants located in
time of disaster." According to PL 101-614, the
zones of high seismic risk (zones 3 or 4) and 27
term "lifeline" means: "public works and utilities,
plants in zones of moderate seismic risk (zones 2A
including transportation facilities and infrastructure,
and 2B).
oil and gas pipelines, electrical power and
communication facilities, and water supply and
(8) Guidance and evaluation of major structural
sewage treatment facilities."
features of projects with lifeline systems. Corps of
Engineers dams, for the most part, were designed
c. Corps projects with lifeline systems in mod-
by the traditional seismic coefficient method which
erate and high risk seismic areas. Moderate, as
does not realistically account for the inertial forces
well as severe or high intensity earthquakes, can
and stresses generated in a dam due to earthquake
cause significant damage to communities and
ground motions. However, in the past 10 years, all
lifeline systems. Moderate earthquakes can be
Corps dams in seismic zones 2, 3, and 4 were
especially devastating when structures are founded
reevaluated for a maximum credible earthquake
on soft clays which amplify earthquake motions or
using the latest state-of-the-art dynamic analysis
founded on saturated, fine-grained materials which
procedures. The reevaluation effort included all
liquefy. The scope of the lifeline evaluation effort,
earth-fill, rock-fill, and concrete dams; appurtenant
therefore, includes Corps projects located in regions
structures; navigation structures; and levees. The
of moderate and high intensity earthquake risk.
Corps has developed a new, state-of-the-art seismic
Regions of seismic risk for this report are described
evaluation procedures for intake towers (ETL 1110-
by the Uniform Building Code (UBC) seismic zone
2-339). Based on ETL 1110-2-339 procedures,
map (Figure A-1). For the purpose of this report,
towers designed by the old seismic coefficient
zones 2A and 2B represent regions of moderate
method and located in seismic zones 2, 3, and 4
risk, and zones 3 and 4 represent regions of high
will be reevaluated. The status of all seismic
seismic risk. Figures A-2 through A-7 show the
reevaluations will be included in Lifeline Report
Corps projects located in regions of moderate and
No. 3. Dams were reevaluated in accordance with
high seismic risk. The regions identified by these
ETL 1110-2-301, ER 1110-2-1806, and
figures are:
ETL 1110-2-303.
(1) Northeastern region, including New England
and New York (Figure A-2).
(2) Southeastern region, including the central
Appalachian seismic region activity and the area
near Charleston, South Carolina (Figure A-3).
A-2
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