LAKE CHABOT ROAD
Update
January 14, 2025
January 14, 2025 Facilities and Transportation Committee Meeting 1 1 Agenda
Supplemental Geotechnical Investigation
One-Way Circulation Evaluation
2 3
Traffic Calming
January 14, 2025 Facilities and Transportation Committee Meeting 2 Supplemental
Geotechnical
Investigation
1 January 14, 2025 Facilities and Transportation Committee Meeting 3
PREVIOUS GEOTECHNICAL INVESTIGATIONS
January 14, 2025 Facilities and Transportation Committee Meeting 4 Nov 2011 Geological & Geotechnical Investigation Lake Chabot Stabilization Treadwell & Rollo (Langan)
Jan 2019 Materials Report Lake Chabot Road Embankment Stabilization Cal Engineering & Geology
Mar 2019 Design Alternatives Report Lake Chabot Road Embankment Stabilization Cal Engineering & Geology
PREVIOUS GEOTECHNICAL INVESTIGATIONS
November 2011
Geological & Geotechnical Investigation
Lake Chabot Stabilization
Treadwell & Rollo (Langan)
Advanced six (6) borings
13.3’ – 39.5’ depth
January 14, 2025 5
1 2
3 4
Pre-storm erosion
Additional erosion
#
#
Boring location
Facilities and Transportation Committee Meeting
PREVIOUS GEOTECHNICAL INVESTIGATIONS
November 2011
Geological & Geotechnical Investigation Lake Chabot Stabilization Treadwell & Rollo (Langan)
Conclusions
Observed roadway distress result of settlement of fill & fill slope creep movement Landslides triggered by excessive precipitation or earthquake may cause displacement of road
Recommended Mitigation
Stitch Pier Retention System
January 14, 2025 Facilities and Transportation Committee Meeting 6
PREVIOUS GEOTECHNICAL INVESTIGATIONS
January – March 2019
Cal Engineering & Geology
Materials Report Lake Chabot Road
Embankment Stabilization
Design Alternatives Report Lake
Chabot Road Embankment
Stabilization
Topographic Survey
Seismic refraction profiles
Seven (7) additional locations
January 14, 2025 Facilities and Transportation Committee Meeting 7 2 3
4 Pre-storm erosion
Additional erosion
#
#
Boring location
1 Refraction profile
PREVIOUS GEOTECHNICAL INVESTIGATIONS
January – March 2019
Cal Engineering & Geology
Materials Report Lake Chabot Road Embankment Stabilization Design Alternatives Report Lake Chabot Road Embankment Stabilization Conclusions
Substantiated conclusions in 2011 Treadwell & Rollo report Identified areas of embankment failure; downslope creep; loss of lateral support Recommended Mitigation
CIDH Piles
Soldier Pile & Lagging Retaining Wall
Drainage Improvements
January 14, 2025 Facilities and Transportation Committee Meeting 8 1 2
3 January 14, 2025 Facilities and Transportation Committee Meeting 9
PREVIOUS GEOTECHNICAL INVESTIGATIONS
Pavement failure limits
1 2
3 SUPPLEMENTAL GEOTECHNICAL INVESTIGATION
December 2024
Scope & Fee Proposal
Treadwell & Rollo (Langan)
Scope
Topographic survey; Lidar scan
Perform slope stability evaluation
Geotechnical criteria for stability/safety
Develop short-term mitigation recommendations
Fee & Schedule
$89,500
10 to 12 weeks
January 14, 2025 Facilities and Transportation Committee Meeting 10 Traffic Calming
2 January 14, 2025 Facilities and Transportation Committee Meeting 11 Speed Bumps – 85th% speed < 31 mph, steep grades (> 8%) Rumble strips – Not installed on residential streets due to noise Roadway striping improvements
Centerline striping
Right edge line striping
Centerline plus edge line
+ Less costly to construct
+ Flexibility to meet future changes
+ No adverse impact on drainage
+ Can successfully reduce speeds
+ Less impacts to emergency response
+ No noise pollution from acceleration/deceleration
January 14, 2025 Facilities and Transportation Committee Meeting 12
TRAFFIC CALMING MEASURES
Before
After
TRAFFIC CALMING MEASURES
January 14, 2025 Facilities and Transportation Committee Meeting 13 Proposed
Improvements
• Center and Parking Lane
Striping
• Optical Speed Bars
TRAFFIC CALMING MEASURES
January 14, 2025 Facilities and Transportation Committee Meeting 14 Proposed Improvements
25mph Speed Limit
Signs & Pavement Markings
Delineators
Astor Drive & View Drive
One-Way
Circulation Options
3 January 14, 2025 Facilities and Transportation Committee Meeting 15 Westbound One-Way Operations
January 14, 2025 Facilities and Transportation Committee Meeting 16 Challenges
Detour of Eastbound Traffic
Inbound access restricted to
certain residences
Reduced Emergency Access
Unacceptable Sight Lines
Westbound One-Way Operations
January 14, 2025 Facilities and Transportation Committee Meeting 17 Challenges
• Errant eastbound vehicles
likely detour to local streets
• Restricted inbound access to
certain residences
Turn Around Route
One-Way WB Operation
Two-Way Operation
Inbound Access Restricted
Transition at Estudillo Ave
Westbound One-Way Operations
January 14, 2025 Facilities and Transportation Committee Meeting 18 Challenges
Lake Chabot Rd & Estudillo Ave intersection not
suitable for U-Turns
Delivery Truck Bus Semi Trailer Truck
Westbound One-Way Operations
January 14, 2025 Facilities and Transportation Committee Meeting 19 Challenges
Residents with restricted
inbound access increases
Emergency access to
residents further restricted
Detour Route
One-Way WB Operation
Two-Way Operation
Inbound Access Restricted
Transition at Benedict Dr
Westbound One-Way Operations
January 14, 2025 Facilities and Transportation Committee Meeting 20 Challenges
Driveway Sightlines
Construction Zone
One-Way WB Operation
Sight Triangle
Eastbound One-Way Operations
January 14, 2025 Facilities and Transportation Committee Meeting 21 Challenges
Detour of Westbound Traffic
Reduced Emergency Access
Detour Route
One-Way EB Operation
Two-Way Operation
NEXT STEPS
Summer 2026
(earliest)
Construction
Environmental
Studies and Design
Hillside
Protection
January 14, 2025 Facilities and Transportation Committee Meeting 22 December 2024
Design Contract Awarded
November 2024
Completed
STAFF RECOMMENDATIONS
DEPARTMENT JUSTIFICATION
City Manager’s Office 1. Risks associated with unrepaired storm damage at 2 slide locations
2. Risks associated natural geological hazard and erosion/slide history Public Works Department 3. Minimizes vehicle cut-through traffic and waiting queues
4. Preserves pavement structural integrity
5. Streamlines environmental studies, design, and road/hillside inspections
6. Will allow uninterrupted road construction/repair
7. Current temporary traffic control is the lowest cost to implement and maintain Fire and Police Department 8. Allows emergency vehicle access
9. Minimizes conflict with vehicles in the event of an emergency response
10. Allows public use in emergency circumstances
January 14, 2025 Facilities and Transportation Committee Meeting 23
1. KEEP LAKE CHABOT ROAD CLOSED, AS CONFIGURED.
2. FOCUS ON COMPLETING ROAD REPAIRS, AS REQUIRED BY FHWA GRANT.
3. EVALUATE AND IMPLEMENT APPLICABLE TRAFFIC CALMING MEASURES.