Del Mar Bluffs Stabilization Project Update Del Mar Bluff Stabilization Update to Del Mar City Council, March 5 th 2018 by Bruce Smith of SANDAG and Patricia McColl of HNTB
Coast Boulevard to Del Mar Bluffs Project Area Torrey Pines Overhead Bridge
Del Mar Bluffs Projects 1998 Drainage Outfall & Soil Cement Stabilization at 11 th Street (NCTD) • • 2000 DMB Geotech Study (NCTD) 2001 Emergency Repairs at 8 th 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)
Soil Cement Buttress 11 th 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
Stabilization Alternatives Considered 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
Priorities from Slope Stability Analysis
Sub Drainage Improvements Interceptor Trench Drain
Subsurface Drainage Improvements
Soldier Pile Alternative • Viable for all stabilization areas C L Existing Track Grade Beam Original Ground Vertical Pile Tieback Anchor (Optional)
Soil Cement Buttress Alternative • Viable for most stabilization areas C L Existing Track Soil Cement Buttress Original Ground Shotcrete Stepped Facing Excavation (Optional Seawall)
Soil Nail Alternative • Viable for SA-7, SA-9 and SA-6B C L Existing Track Original Ground Shotcrete Facing (Optional) Soil Nail Typ
Seawall / Retaining Wall Alternative • Viable for SA-1, SA-3 and SA-10 (East) C L Existing Track Original Ground Reinforced Concrete Seawall Back Cut
Alternative Evaluation Evaluation Criteria Stabilization Rank Environmental Alternative Overall Constructability Cost Considerations Soldier Pile Best Best Best Best Soil Cement Worst Mid-Level Worst Worst Buttress Soil Nail Mid-Level Best Mid-Level Mid-Level Reinforcement Seawall Worst Mid-Level Worst Worst Retaining Wall Mid-Level Mid-Level Best Mid-Level
2001 Wall Slid Down Bluff at 8 th 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 12 th Street
DMB1 Drainage Improvements Replaced headwall Installed new pipe and outlet on beach improved drainage capacity MP 244.7 – Near 8 th Street.
DMB1 Construction of Sub-drains at 7 th Street
Del Mar Bluffs Surface and Sub-Surface Runoff
DMB1 Drainage Improvements at 4 th Street
DMB1 Drainage Improvements Drainage flume at 12 th St. Grouted underneath and hand repaired
DMB1 Hydroauger Installation
DMB1 Hydroauger Installation
DMB1 Slope Monitoring and Landslide Warning System
Del Mar Bluffs 2 and 3 Stabilization Track 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 Area Station Importance Length (Feet) Designation Ranking (IR) DMB3 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 783 Proposed All areas will be environmentally cleared * Indicates proposed with DMB 4 but not yet funded
Del Mar Bluffs 4 Urgent Repairs • Repair Drainage Structures • Install piling to increase factors of safety • Stabilize structures threatened by erosion and corrosion
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 7 th Street
Piling at Timber Retaining Walls CIDH pile supports for 200-foot long section below 13 th Street
Storm Chute MP 244.4 Below 12 th St. Stabilize end of outfall with concrete
New Drainage Channel 6 th Street to 8 th Street
Slope Failure at 7 th Street
Slope Stabilization at 7 th Street Original Ground Line Failed Slope Slurry Backfill Match Bluff Color 41
Replace Drainage Channel at 8 th Street
Grade Path Upper Bluff 6 th to 8 th Street Add Stabilized Decomposed Granite Surfacing
Slope Stabilization at Anderson Canyon CIDH piles and lagging wall
Repair drain and wall North of 10 th Street
Support drain with wall at 10 th Street CIDH piles and lagging wall to support drainage channel
10 th Street Wall Repair CIDH piles and lagging wall to support drainage channel
9 th Street – Repair erosion at flood wall
Remove Hydro-auger Debris
DMB4 Construction Staging and Access Beach Access Right of Way 9 th Street • Life Guard Tower (17 th Street) • • Coast Boulevard 8 th Street • • • State Park State Park 7 th Street • 12 th Street • • Penny Lane 10 th Street •
Access 17 th Street to 12 th Street
Access 11 th Street to 7 th 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 Team Tricia McColl HNTB Project Manager pmccoll@hntb.com Sean Colorado Leighton Geotech scolorado@leightongroup.com David Olson Leighton Geotech dolson@leightongroup.com
DMB 50 Year Stabilization Estimate ($36m - $82m) 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
Bluff Retreat Rates A retreat rate of 6 inches per year assumed for DMB 2 and 3
Atmospheric River
Sorrento Valley Station – December 2010 5 inches rainfall in 3 days
Del Mar Bluffs Stabilization Project Update Del Mar Bluffs History of Rail Service
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