IN JANUARY 2014, LOS ANGELES Mayor Eric Garcetti and Dr. Lucy Jones of the United States Geolog-ical
Survey (USGS) partnered to develop a citywide Seismic Resilience Program focusing on building
structures, communications, and water. The Los Angeles Department of Water and Power (LADWP) be-gan
working with this program and encouraged by the mayor’s leadership, developed the comprehensive
system-wide Water System Seismic Resilience Program (WSSRP), which both the USGS and the Mayor’s
Office drew from in developing their Resilience by Design report. LADWP is currently undertaking recommen-dations
in Resilience by Design as high priority while continuing to address the more comprehensive aspects
The WSSRP goal is to continually improve the city’s water
system, building on one hundred years of seismic improvement
efforts, to ensure resilience and sustainability. Objectives include
limiting the number of service losses after a seismic event and
restoring interrupted water deliveries as rapidly as possible. Pro-gram
development was accomplished through a management
team effort investigating three requisites: 1) defining characteris-tics
of a seismically resilient Los Angeles Water System, 2) iden-tifying
the current status of Water System seismic resilience, and
3) recognizing aspects that may improve Water System seismic
resilience. LADWP appointed a Resilience Program Manager to
implement the WSSRP and is currently in the process of imple-menting
the following priority items in addition to improving its
emergency response capabilities:
• Fortifying imported water supplies and water storage.
• Increasing local water sources.
• Creating a seismic-resilient pipe network.
• Improving the Water System’s firefighting water supply.
Fortify the Imported Water Supplies and Water Storage
All water imported to the City of Los Angeles crosses the
San Andreas Fault (SAF). A number of potential SAF scenarios,
including the ShakeOut Scenario, have the potential to cause dam-age
to all three water delivery aqueducts simultaneously. Prima-ry
actions being undertaken to ensure adequate post-earthquake
water supplies are: 1) investigating/implementing cost-effective
measures to increase resiliency where the Los Angeles Aqueduct
(LAA) crosses the SAF, 2) performing a systematic seismic assess-ment
of the LAA, 3) establishing a seismic resilient water supply
task force in partnership with the Metropolitan Water District of
Southern California (MWD) and Department of Water Resources
(DWR), and 4) using risk-based methods to enhance the Water Sys-tem
Dam Safety Program for LADWP water system dams in the
city and along the LAA.
A five-mile-long by nine-foot-wide section of the LAA’s Eliz-abeth
Tunnel crosses the SAF nearly perpendicularly. Figure 1
shows a cross-section of the tunnel, completed in 1913. This sec-tion
is vulnerable to seismic shaking and may be subject to fault
movements ranging from a relatively small offset to as much as
30 feet if an event occurs in this area. This range of fault rupture
could damage the tunnel to the point of failure, making it unus-able
for water delivery. To address this, two approaches are being
undertaken: a short-term risk reduction solution that will increase
the likelihood of providing water to Los Angeles after a SAF event,
and a long-term engineered solution to accommodate the larg-est
potential offset. The diagram in Figure 1 shows the proposed
risk-reduction method, which involves installing steel tunnel sup-ports
to reduce the risk of collapse and installation of a highly duc-tile
high-density polyethylene (HDPE) pipe within tunnel sections
in the SAF zone to maintain water flow in the event of small fault
movement or liner collapse.
Because this solution does not prevent loss of water flow in
the case of large fault movements, other alternatives are being
considered including mining a new tunnel, widening the existing
tunnel, and excavating a bypass tunnel in the SAF zone. All three
would be planned to accommodate the maximum offset. Other
options may include upstream connections to the California
Aqueduct West Branch, realigning the LAA, and installing buried
pipe that can be accessed for more rapid post-earthquake repair,
each of which would require pumping the current gravity flow
aqueduct system.
Increase Local Water Resources
Enhanced development of local water resources contributes
of its WSSRP.
Seismic Preparation at the Retail Level:
LADWP’s Water System Seismic Resilience Program
By Craig A. Davis
22 SOURCE fall 2017
Figure 1.