del mar bluffs stabilization project update del mar...
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Del Mar Bluffs Stabilization Project UpdateDel Mar Bluff Stabilization
Update to Del Mar City Council, March 5th 2018 by Bruce Smith of SANDAG and Patricia McColl of HNTB
Torrey Pines Overhead Bridge
Coast Boulevard to
Del Mar Bluffs Project Area
• 1998 Drainage Outfall & Soil Cement Stabilization at 11th Street (NCTD)
• 2000 DMB Geotech Study (NCTD)
• 2001 Emergency Repairs at 8th Street (NCTD)
• 2001 Drainage Study
• 2003 Drainage Improvements & Landslide Warning System (NCTD)
• 2007 Del Mar Bluffs 2 stabilization with Soldier Piles (SANDAG)
• 2009 Del Mar Bluffs 3 stabilization with Soldier Piles (SANDAG)
Future Planning
• 2017 Del Mar Bluffs 4 (PSR prepared for Urgent Repairs)
• 2020-2030 DMB 5….. (Improvements for 50 year Design Life)
Del Mar Bluffs Projects
Soil Cement Buttress 11th Street in 1998
New Drainage Outfall
Del Mar Bluffs Geotechnical Study
• NCTD Prioritized areas in need of stabilization
• Presented full range of stabilization alternatives
• Del Mar City Council Review -May 2001
• Approved by NCTD Board in July 2001 after incorporating City Review comments
1. Maintain and Improve drainage
• Repair culverts and drainage swales
• Add sub-drains and hydro-augers
2. Landslide warning system until funds available for stabilization
3. Bluff stabilization with;
• Soldier Piles
• Soil cement buttress
• Soil nails
• Sea walls
Stabilization Alternatives Considered
Priorities from Slope Stability Analysis
Sub Drainage Improvements
Interceptor Trench Drain
Subsurface Drainage Improvements
Soldier Pile Alternative
• Viable for all stabilization areas
Tieback Anchor (Optional)
L Existing TrackC
OriginalGround
Grade Beam
Vertical Pile
L Existing TrackC
Soil Cement Buttress
Soil Cement Buttress Alternative
• Viable for most stabilization areas
OriginalGround
L Existing TrackC
ExcavationStepped
Soil Cement Buttress
FacingShotcrete
(OptionalSeawall)
Soil Nail Alternative
• Viable for SA-7, SA-9 and SA-6B
Ground
ExcavationStepped
FacingShotcrete
(Optional)
OriginalGround
L Existing TrackC
Facing(Optional)
Shotcrete
Soil Nail Typ
Seawall / Retaining Wall Alternative
• Viable for SA-1, SA-3 and SA-10 (East)
L Existing TrackC
SeawallConcrete
ReinforcedGroundOriginal
Back Cut
Alternative Evaluation
Stabilization
Alternative
Evaluation CriteriaRank
Overall Constructability CostEnvironmental
Considerations
Soldier Pile Best Best Best Best
Soil Cement
ButtressWorst Mid-Level Worst Worst
Soil Nail
ReinforcementMid-Level Best Mid-Level Mid-Level
Seawall Worst Mid-Level Worst Worst
Retaining Wall Mid-Level Mid-Level Best Mid-Level
2001 Wall Slid Down Bluff at 8th St.
2001 Emergency Project
Piling installation
2001 Emergency Project
Sculpted Pile Cap
Del Mar Bluffs Stabilization Project 1 – 2003
Drainage Improvements and Landslide Warning System
DMB1 Drainage Improvements
Many drainage improvements included:
• Installed and repaired new drainage structures
• Relined concrete ditches
• River stone energy dissipators
• Storm water filtering system at street ends
• Hydro-augers at several locations on bluff face
• Interceptor Trench Sub Drains east of tracks
• Supported large drainage chute at 12th Street
DMB1 Drainage Improvements
Replaced headwall
Installed new pipe and outlet on beach improved drainage capacity
MP 244.7 – Near 8th Street.
DMB1 Construction of Sub-drains at 7th Street
Del Mar Bluffs
Surface and Sub-Surface
Runoff
DMB1 Drainage Improvements at 4th Street
DMB1 Drainage Improvements
Grouted underneath and hand repaired
Drainage flume at 12th St.
DMB1 Hydroauger Installation
DMB1 Hydroauger Installation
DMB1 Slope Monitoring and Landslide Warning System
Del Mar Bluffs 2 and 3 StabilizationTrack side piles
Soldier Pile and Tieback
Drilling Soldier Pile Drilling
Placing Concrete from Low Railer
Del Mar Bluffs Existing and Future Stabilization with piles west of track
**
Del Mar Bluffs Proposed Future Stabilization
All areas will be environmentally cleared* Indicates proposed with DMB 4 but not yet funded
Area Designation
Station Importance Ranking (IR) DMB3
Length (Feet)
SA-9* 1479+82 4 160
SA-8* 1482+25 5 135
SA-5 1512+15 6 90
SA-3 1517+06 6 198
SA-6N 1493+77 7 200
Total Proposed
783
• Repair Drainage Structures
• Install piling to increase factors of safety
• Stabilize structures threatened by erosion and corrosion
Del Mar Bluffs 4 Urgent Repairs
Stabilize Storm Drain Headwall MP 244.3
Rockscaped headwall with soil nail tiebacks
Piling at Timber Retaining Walls
CIDH pile supports for 70-foot long section below 7th Street
Piling at Timber Retaining Walls
CIDH pile supports for 200-foot long section below 13th Street
Storm Chute MP 244.4 Below 12th St.
Stabilize end of outfall with concrete
New Drainage Channel 6th Street to 8th Street
Slope Failure at 7th Street
Slope Stabilization at 7th Street
41
Original Ground Line
Slurry Backfill Match Bluff Color
Failed Slope
Replace Drainage Channel at 8th Street
Grade Path Upper Bluff 6th to 8th Street
Add Stabilized Decomposed Granite Surfacing
Slope Stabilization at Anderson Canyon
CIDH piles and lagging wall
Repair drain and wall North of 10th Street
Support drain with wall at 10th Street
CIDH piles and lagging wall to support drainage channel
10th Street Wall Repair
CIDH piles and lagging wall to support drainage channel
9th Street – Repair erosion at flood wall
Remove Hydro-auger Debris
Beach Access• Life Guard Tower (17th Street)• State Park
Right of Way • Coast Boulevard• State Park• 12th Street• Penny Lane• 10th Street
DMB4 Construction Staging and Access
• 9th Street• 8th Street• 7th Street
Access 17th Street to 12th Street
Access 11th Street to 7th Street
Access from State Park
Access from State Park
Questions and Contacts
SANDAG Bruce Smith Corridor Director [email protected]
Allie DeVaux Project Manager [email protected]
Design Project TeamTricia McColl HNTB Project Manager [email protected]
Sean Colorado Leighton Geotech [email protected]
David Olson Leighton Geotech [email protected]
Assuming continued bluff retreat from erosion additional stabilization measures will be needed including:
• Replacement and repair of aging structures
• Bluff stabilization based on erosion events by either;
• Stabilize local erosion areas
• Additional piles and tie backs
• Lagging between piles
• Bluff toe protection
• A combination of the above
DMB 50 Year Stabilization Estimate ($36m - $82m)
Bluff Retreat Rates
A retreat rate of 6 inches per year assumed for DMB 2 and 3
Atmospheric River
Sorrento Valley Station – December 20105 inches rainfall in 3 days
Del Mar Bluffs Stabilization Project UpdateDel Mar BluffsHistory of Rail Service