Del Mar Bluff Stabilization

Transcription

1 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

2 Coast Boulevard to Del Mar Bluffs Project Area Torrey Pines Overhead Bridge

3 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) 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) DMB 5.. (Improvements for 50 year Design Life)

4 Soil Cement Buttress 11 th Street in 1998 New Drainage Outfall

5 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 Erosion rates up to 6 per year and episodic

6 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

7 Priorities from Slope Stability Analysis

8 Sub Drainage Improvements Interceptor Trench Drain

9 Subsurface Drainage Improvements

10 Soldier Pile Alternative Viable for all stabilization areas CL Existing Track Grade Beam Vertical Pile Original Ground Tieback Anchor (Optional)

11 Soil Cement Buttress Alternative Viable for most stabilization areas CL Existing Track Soil Cement Buttress Original Ground Facing Shotcrete (Optional Seawall) Stepped Excavation

12 Soil Nail Alternative Viable for SA-7, SA-9 and SA-6B CL Existing Track Shotcrete Facing (Optional) Original Ground Soil Nail Typ

13 Seawall / Retaining Wall Alternative Viable for SA-1, SA-3 and SA-10 (East) CL Existing Track Reinforced Concrete Seawall Original Ground Back Cut

14 Alternative Evaluation Stabilization Alternative Constructability Evaluation Criteria Cost Environmental Considerations Rank Overall Soldier Pile Best Best Best Best Soil Cement Buttress Soil Nail Reinforcement Worst Mid-Level Worst Worst Mid-Level Best Mid-Level Mid-Level Seawall Worst Mid-Level Worst Worst Retaining Wall Mid-Level Mid-Level Best Mid-Level

15 2001 Wall Slid Down Bluff at 8 th St.

16 2001 Emergency Project Piling installation

17 Sculpted Pile Cap 2001 Emergency Project

18 Del Mar Bluffs Stabilization Project Drainage Improvements and Landslide Warning System

19 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

20 DMB1 Drainage Improvements Replaced headwall Installed new pipe and outlet on beach improved drainage capacity MP Near 8 th Street.

21 DMB1 Construction of Sub-drains at 7 th Street

22 DMB1 Drainage Improvements at 4 th Street

23 DMB1 Drainage Improvements Drainage flume at 12 th St. Grouted underneath and hand repaired

24 DMB1 Hydroauger Installation

25 DMB1 Hydroauger Installation

26 DMB1 Slope Monitoring and Landslide Warning System

27 Del Mar Bluffs 2 and 3 Stabilization Track side piles

28 Soldier Pile Installation

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31 Del Mar Bluffs Existing and Future Stabilization with piles west of track * *

32 Del Mar Bluffs 4 Urgent Repairs Repair Drainage structures Install piling to increase factors of safety Stabilize structures threatened by erosion and corrosion

33 Failed Storm Drain Headwall MP Add Stabilized Decomposed Granite Surfacing

34 Timber Retaining Walls 70-foot long section below 7 th Street

35 Piling at Timber Retaining Walls 200-foot long section below 13 th Street

36 Storm Chute MP Below 12 th St. Support outlet in DMB4 and design new piped outlet for DMB5

37 6 th Street to 8 th Street

38 Slope Repair at 7 th Street Original Ground Line Failed Slope Slurry Backfill Match Bluff Color 38

39 Drainage Channel Repair 8 th Street

40 Grade Path Upper Bluff 6 th to 8 th Street Add Stabilized Decomposed Granite Surfacing

41 Slope Failure at 7 th Street

42 Slope Repair at Anderson Canyon

43 Repair drain and wall North of 10 th Street

44 Support drain with wall at 10 th Street

45 10 th Street Wall Repair

46 9 th Street Repair erosion at flood wall

47 Remove Hydro-auger Debris

48 DMB4 Construction Staging and Access Beach Access Life Guard Tower (17 th Street) State Park Right of Way Coast Boulevard State Park 12 th Street Penny Lane 10 th Street 9 th Street 8 th Street 7 th Street

49 Access Coast Blvd to 12 th Street

50 Access 11 th Street to 6 th Street

51 Bluff top access

52 Bluff access from State Park

53 DMB 50 Year Stabilization Estimate 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 ($36m - $82m) A combination of the above

54 Del Mar Bluffs Proposed Future Stabilization Area Designation Station Importance Ranking (IR) DMB3 Length (Feet) SA-9* SA-8* SA SA SA-6N Total Proposed 783 All areas will be environmentally cleared * Indicates proposed with DMB 4 but not yet funded

55 Questions and Contacts SANDAG Bruce Smith Corridor Director Allie DeVaux Project Manager Design project Team Tricia McColl HNTB Sean Colorado Leighton Geotech David Olson Leighton Geotech

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57 Del Mar Bluffs Stabilization Project Update Del Mar Bluffs History of Rail Service