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 bsm@sandag.org

Allie DeVaux Project Manager adev@sandag.org

Design Project TeamTricia McColl HNTB Project Manager pmccoll@hntb.com

Sean Colorado Leighton Geotech scolorado@leightongroup.com

David Olson Leighton Geotech dolson@leightongroup.com

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