LAKE CHABOT ROAD
ONE-WAY
CIRCULATION
EVALUATION
February 3, 2025
February 3, 2025 City Council Meeting 1
1 Agenda
Supplemental Geotechnical Investigation
One-Way Circulation Evaluation
2 February 3, 2025 City Council Meeting 2
February 3, 2025 City Council Meeting 3
DATE LEGISLATIVE BODY ACTION/DISCUSSION TOPIC
2/20/2018 City Council Award consultant design contract for roadway stabilization 10/5/2022 Facilities & Transportation Committee Roadway Stabilization Roadway Configuration 2/1/2023 Facilities & Transportation Committee Storm Damage Assessment 5/3/2023 Facilities & Transportation Committee Damaged Roadway Interim Options 7/5/2023 Facilities & Transportation Committee Funding request for roadway storm damage repair 7/17/2023 City Council Accelerated construction award for upslope repair 4/15/2024 City Council Accept federal grant funding for emergency repair 7/15/2024 City council Award environmental consultant contract 9/9/2024 City Council Council Referral: Repair Status Update Presentation 11/6/2024 Facilities & Transportation Committee Council Follow Up: Alternating One-Way, Traffic Calming, Additional Grant Funding, Emergency access/response
12/4/2024 Facilities & Transportation Committee Committee Follow Up: Supplemental geotechnical investigation fee proposal 12/16/2024 City Council Award consultant design contract 1/14/2025 Facilities & Transportation Committee Committee Follow Up: Supplemental geotechnical investigation, one-way circulation, mitigation measures
One-Way
Circulation Evaluation
1 February 3, 2025 City Council Meeting 4
Westbound One-Way Operations
February 3, 2025 City Council Meeting 5
Challenges
Detour of Eastbound Traffic
Inbound access restricted to
certain residences
Reduced Emergency Access
Unacceptable Sight Lines
Westbound One-Way Operations
February 3, 2025 City Council Meeting 6
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
February 3, 2025 City Council Meeting 7
Challenges
Lake Chabot Rd & Estudillo Ave intersection not
suitable for U-Turns
Delivery Truck Bus Semi Trailer Truck
Westbound One-Way Operations
February 3, 2025 City Council Meeting 8
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
EMERGENCY VEHICLE ACCESS
1 3
2 4
5 6
8 9
7 February 3, 2025 City Council Meeting 9
Westbound One-Way Operations
February 3, 2025 City Council Meeting 10
Challenges
Driveway Sightlines
Construction Zone
One-Way WB Operation
Sight Triangle
Eastbound One-Way Operations
February 3, 2025 City Council Meeting 11
Challenges
Detour of Westbound Traffic
Reduced Emergency Access
Detour Route
One-Way EB Operation
Two-Way Operation
Supplemental
Geotechnical
Investigation
2 February 3, 2025 City Council Meeting 12
PREVIOUS GEOTECHNICAL INVESTIGATIONS
February 3, 2025 City Council Meeting 13
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
February 3, 2025 14
1 2
3 4
Pre-storm erosion
Additional erosion
#
#
Boring location
City Council 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
February 3, 2025 City Council Meeting 15
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
February 3, 2025 City Council Meeting 16
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
February 3, 2025 City Council Meeting 17
1 2
3 February 3, 2025 City Council Meeting 18
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
Schedule
10 to 12 weeks
February 3, 2025 City Council Meeting 19
SUPPLEMENTAL GEOTECHNICAL INVESTIGATION
December 2024
Scope & Fee Proposal
Treadwell & Rollo (Langan)
Fee
$89,500
Not eligible for FEMA reimbursement
Topographic survey ($40k) would have been eligible
Current budget earmarked for construction and FEMA local match Additional funds would need to be allocated
February 3, 2025 City Council Meeting 20
ESTIMATED COST TO REPAIR ALL SLIDES
ITEM ESTIMATED COSTS
Slide 1 and Slide 4 Repair Costs $3M
Stabilize Erosion Sites 2 and 3 $6M
Reconstruct Pavement $2M
Total $11M
LAKE CHABOT ROAD
Repair Funded by Grant
Repair Funded by Grant
Pre-storm erosion
Additional erosion
1 2 3
#
#
February 3, 2025 City Council Meeting 21
CITYWIDE ROAD
FUNDING NEEDS
0.5 mi LAKE CHABOT ROAD REPAIR COSTS AMOUNT
(est.)
Slide 1 and Slide 4 Repair Costs (estimate) $3M
Stabilize Erosion Sites 2 and 3 (estimate) $6M
Reconstruct Pavement (estimate) $2M
Total $11M
CITYWIDE ROAD REPAIR NEEDS AMOUNT
43 miles of Failed roads (red, PCI<25) $96
26 miles of Poor roads (orange, PCI<50) $51M
29 miles of Fair roads, (yellow, PCI<65) $18M
Total (98 miles) $165M
February 3, 2025 City Council Meeting 22
Lake Chabot Road PCI = 37 (poor, orange)
NEXT STEPS
Summer 2026
(earliest)
Construction
Environmental
Studies and Design
Hillside
Protection
February 3, 2025 City Council Meeting 23
December 2024
Design Contract Awarded
November 2024
Completed
OPTIONS AND STAFF RECOMMENDATION
February 3, 2025 City Council Meeting 24
Direct staff to design one-way circulation (~$20,000) AND Award Agreement to perform Supplemental
Geotechnical Investigation ($89,500)
Select Direction: Westbound OR Eastbound
Keep road closed to allow staff to focus on repairing slides 1 and 4
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
February 3, 2025 City Council Meeting 25
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