CC SR 20240716 03 - PVDS Ski Jump Repair
CITY COUNCIL MEETING DATE: 07/16/2024
AGENDA REPORT AGENDA HEADING: Regular Business
AGENDA TITLE:
Consideration and possible action to receive an update on planned repairs to the “ski
jump” on Palos Verdes Drive South in the Greater Portuguese Bend Landslide Complex.
RECOMMENDED COUNCIL ACTION:
(1) Receive and file two options to maintain the traversability of Palos Verdes Drive
South between Narcissa and Peppertree, known locally as the “ski jump;” and,
(2) Direct Staff to return to the City Council with a new agreement to continue with
regular asphalt repairs to smooth out the vertical grade of the area of significant
subsidence on Palos Verdes Drive South between Narcissa Drive and Peppertree
Drive, at the “ski jump,” among other repairs on roadways affected by accelerated
movement of the Greater Portuguese Bend Landslide Complex .
FISCAL IMPACT: There is no fiscal impact to directing the Staff to return with a new
agreement for repairs to the “ski jump.” The fiscal impact of
continuing repairs will be provided as part of the staff report for the
new agreement.
Amount Budgeted: N/A
Additional Appropriation: N/A
Account Number(s): N/A
ORIGINATED BY: Ramzi Awwad, Public Works Director
REVIEWED BY: Same as above
APPROVED BY: Ara Mihranian, AICP, City Manager
ATTACHED SUPPORTING DOCUMENTS:
BACKGROUND:
Following the 2022-23 rainy season, which was approximately 200% of the historical
average rainfall, land movement in the Greater Portuguese Bend Landslide Complex
(Landslide Complex) significantly accelerated, resulting in the formation of landslide
fissures, grabens (i.e. pull-apart zones), thrust features, tensional cracking, and shear
zones. These phenomena, along with land subsidence, have been particularly
pronounced on Palos Verdes Drive South (PVDS), among other areas, within the
Landslide Complex.
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Subsequently, the 2023-2024 rainy season was also significantly wetter than average, at
approximately 170% of historical average rainfall. That season featured severe winter
storms from January 31 to February 9, 2024, for which a federal disaster declaration was
issued by President Biden. The January 31 to February 9, 2024 winter storms resulted in
unprecedented land movement. This land movement has had an unprecedented effect
on PVDS within the Landslide Complex with differential rates of land movement currently
ranging from about 2-7 inches per week across the Klondike Canyon Landslide (KCL), 9-
12 inches per week across the Portuguese Bend Landslide (PBL), and 7-11 inches per
week across the Abalone Cove Landslide (ACL).
Due to the poor condition of PVDS and the pronounced impact on two-wheeled vehicles,
the City Council approved a temporary prohibition on bicycles, motorcycles, and other
two-wheeled vehicles on PVDS within the Landslide Complex for a period of six months
starting on June 18, 2024.
Although many areas of PVDS are experiencing horizontal movement, subsidence, thrust
features, fissures, and cracks, the area between Narcissa Drive and Peppertree Drive,
known locally as the ski jump, has been particularly affected by subsidence. A graben
has formed in this area, which means that the west side and east side are pulling away
from each other adversely impacting the condition of the roadway and warranting the
need to consider options to maintain the drivability of PVDS.
DISCUSSION:
Since the January 31 to February 9, 2024 winter storms, the ground on both sides of the
ski jump has been moving at unprecedented rates, with the east side dropping relatively
faster than the west side. The elevation difference is jeopardizing PVDS. Therefore, Staff
has been developing strategies to keep the ski jump traversable. The following are staff-
identified options for the City Council’s consideration:
Option No. 1 - Complete Regrading of the Ski Jump
This option is considered a complete regrading of the ski jump, bringing it up to a grade
of approximately 3% throughout, which meets current geometric design standards for
vertical grades. This regrading would be accomplished by building up the east side of the
ski jump using geofoam blocks, which are a synthetic lightweight material with similar
compression strength as traditional fill materials. Shoring would be used to surround the
geofoam blocks and an asphalt surface with a roadside barrier would be installed for the
driving surface.
Although a complete regrade would bring the ski jump up to an elevation that meets
current geometric standards and allow room for continued subsidence, based on the
current dynamics of movement, there is a concern that this option may not be durable
over a period of time. This is because according to the City’s Geologist, Mike Phipps of
Cotton, Shires, and Associates, the ski jump is at the boundary of the Abalone Cove
Landslide on the west side and the Western Sub-Slide of the Portuguese Bend Landslide
on the east, where the sub-slides are pulling away from each other and moving at different
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speeds. Therefore, there is a major risk that the east side and west side of the ski jump
will continue to be pulled apart, which could damage the geofoam blocks and require
significant ongoing maintenance.
The ski jump area would continue to be subjected to lateral movement, although this type
of movement is less pronounced in this area when compared to vertical subsidence and
pulling apart.
There would also be significant impacts on traffic during construction of a complete
regrading with intermittent periods of full roadway closure and partial roadway closure
(one-lane traffic). Based on preliminary construction industry feedback, and depending
on whether work would be conducted in 24 -hour or 12-hour shifts, preliminary estimates
indicate that there would be periods of full roadway closure totaling approximately six to
eight weeks and partial roadway closure (one-lane traffic) totaling another approximately
six to eight weeks.
Based on preliminary construction industry feedback, and depending on whether work
would be conducted in 24-hour or 12-hour shifts, preliminary construction cost estimates
indicate that the work is likely to exceed $5 million.
The Los Angeles County Sanitation Districts sewer trunk lines would need to be relocated
to the newly constructed grade so that they can continue to be maintained. Staff is still
evaluating the impact of this work on the construction schedule, and the result may be a
longer duration of a full roadway closure.
Because of the risk that the ski jump will continue to pull apart, damaging the geofoam
blocks and requiring significant maintenance, Staff does not recommend a complete
regrading of the ski jump at this time, and instead recommends waiting for mitigation
measures to significantly slow the landslide movement. Additionally, performing this work
on an emergency basis is likely to result in a higher cost and greater impact to traffic,
whereas taking time to obtain more construction industry feedback will allow for a design
that is tailored to be more efficient and a construction bidding process that is most
competitive.
Option No. 2 - Continued Pavement Smoothing of the Ski Jump
An alternative to the complete regrading of the ski jump is to continue with asphalt repairs
on a regular basis to smooth out the vertical grade to a limited extent. Such repairs would
be modeled after the interim repair performed in May 2024. The City Geologist has
determined that at the current rate of movement, the weight of material estimated to need
to be added over the course of approximately one year is acceptable considering that it
is localized in a relatively small area. The rate of movement is expected to significantly
decrease over time as mitigation measures are implemented, reducing the amount of
asphalt pavement repair needed.
This approach would allow PVDS to continue to be traversable, although not at an ideal
grade. The work would be performed with a one-lane closure during non-peak travel
times, and with a typical duration of approximately one week of construction for each
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repair. The sewer trunk lines would need to continue to be regularly adjusted in this area,
which could also impact traffic.
At the current rate of movement, pavement smoothing would likely need to be repeated
several times a year at an estimated cost in the range of $750,000 to $1 million for the
ski jump alone over the course of a year, after which the rate of movement is expected to
significantly decrease.
Staff recommends continuing with asphalt repairs on a regular basis to smooth out the
vertical grade at the ski jump to a limited extent until such time as land movement has
significantly slowed through mitigation measures and Staff can focus on the most efficient
and cost-effective approach to a long-term solution, with significantly reduced risk.
ADDITIONAL INFORMATION:
Signs and Pavement Markings
Staff (and consultants working on behalf of the City) regularly inspect PVDS and schedule
repairs to maintain access for the approximately 15,000 average daily vehicles that use
PVDS. The assessments include periodic reviews and modifications/additions to the
signs and pavement markings based on recommendations from traffic engineers. An
assessment of truck prohibition signs is currently in progress and may result in additional
truck prohibition signs.
Funding
On April 15, 2024, the Federal Emergency Management Agency (FEMA) announced that
federal disaster assistance has been made available to the state of California, including
Los Angeles County, to supplement recovery efforts in the areas affected by the severe
winter storms from January 31 to February 9, 2024. This declarat ion makes federal
funding available on a cost-sharing basis to local government agencies, including the City,
for emergency work and the repair or replacement of facilities damaged by the st orms.
The cost of repairs to the ski jump on PVDS, both emergency stabilization measures such
as the pavement smoothing and permanent repairs such as a complete regrading, may
be eligible for reimbursement through the FEMA disaster recovery program , with a
minimum City match of 6.25%. It is important to note that the California Governor’s Office
of Emergency Services (CalOES) informed the City that landslides are considered pre -
existing and are typically not considered for damage recovery, but if the City can
demonstrate that the land movement was accelerated due to the January-February 2024
winter storms and meet other requirements, the City may be eligible for damage recovery
costs. Staff continues to work closely with CalOES and FEMA to pursue cost recovery.
CONCLUSION:
Staff recommends the City Council direct Staff to return with a new construction
agreement to continue with asphalt repairs on a regular basis to smooth out the vertical
grade at the ski jump to a limited extent, among other repairs on PVDS, until such time
as land movement has significantly slowed through mitigation measures and Staff can
focus on the most efficient and cost-effective approach to a long-term solution.
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ALTERNATIVES:
In addition to Staff recommendation, the following alternative actions are available for
the City Council’s consideration:
1. Take no action and simply receive and file this report.
2. Take other action, as deemed appropriate.
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