Nearshore Buttress: Seismic Adaptation Measure - TYPE TEMPLATE


Example of sheet pile and fill installation © Jacobs


SHORELINE STABILIZATION:
Geotechnical

SHORELINE LOCATION:
Nearshore


DESIGN LIFE
ADAPTABILITY
IMPACT ON THE WATERFRONT
CONSTRUCTION COST
100+ Years
High
Major Intervention
Very High


SEISMIC HAZARDS MITIGATED:SEISMIC PERFORMANCE IMPROVED:
Lateral Spreading
Liquefaction
StructuresUtilities & Transportation


MEASURES COMPATIBILITY:
Flood
Seismic
Floodwalls
Levees

Seawalls (Rip Rap Revetment)

Liquefaction Mitigation

Utility Retrofit


DESCRIPTION:
Strengthened in situ soils supporting new fill bayward of the existing shoreline. This would create a soil block which is strong enough and stiff enough to buttress the liquefiable fills acting on the rock dike and thus reduce lateral ground displacements that would otherwise damage the Embarcadero, the promendade, the light rail, utilites, and waterfront structures.


CONSIDERATIONS:
ADVANTAGES:
DISADVANTAGES:
  • Width of buttress defined by depth of Young Bay Mud which varies along the waterfront.
  • Effective in areas of deep Young Bay Mud.
  • Less construction impact to the Embarcadero and promenade compared to landside shoreline stabilization measures.
  • Replaces deteriorated wharf structures.
  • Provides foundation for future sea level rise protection.
  • Provides additional waterfront public space.


  • Construction would require vacating and temporary relocation of waterfront building when the work occurs at an occupied pier
  • Construction duration likely longer than other shoreline stabilization measures.
  • Requires fill within the Bay
  • Does not mitigate liquefaction-induced settlements In-water work requires measures to protect water quality.


CONSTRUCTION IMPACTS TO THE PUBLIC:
SEA LEVEL RISE ADAPTATION OPPORTUNITIES:
  • Construction would require vacating and temporary relocation of waterfront building when the work occurs at an occupied pier.
  • Impacts would be most noticeable to the occupants of the affected pier.
  • Most construction work would be done from the water-side of the seawall.
  • Impacts to users of the promenade and the Embarcadero would be limited.
  • The new engineered land could serve as a foundation for a future levee to protect the Embarcadero and the City from sea level rise.
  • Also, the new land would provide an inherent barrier to limit the influence of rising sea levels on groundwater elevations.




DESIGN CONSIDERATIONS:

  • The width of added land necessary to effectively buttress the existing seawall would depend upon the depth from the ground surface to the competent soil layers below. As this depth varies along the waterfront, the width of the added shoreline would vary.

SITE-SPECIFIC CONSIDERATIONS:

  • Special procedures would be required in the Fisherman’s Wharf area since contaminated soils below the water surface would be disturbed by construction operations.
  • Extension of existing outfalls through the added land would be required in some locations

URBAN DESIGN CONSIDERATIONS:

  • The added shoreline could provide additional open spaces on the waterfront for users of the Embarcadero and promenade.
  • The added shoreline would separate the promenade from the waters edge.

HISTORICAL RESOURCE CONSIDERATIONS:

  • Historic pier-supported buildings would need to be removed temporarily during construction and replaced once the work is complete.

INSTALLATION AND CONSTRUCTABILITY CONSIDERATIONS:

  • Mixing of the soil below the water surface with cement to strengthen it would require controls to protect water quality.
  • Soil mixing would be accomplished by barge-supported equipment.
  • Existing piles would need to be removed to ensure proper mixing of the soil with cement.
  • Timber piles could be salvaged and repurposed


Download the Nearshore Buttress Factsheet.

Learn about other types of measures from our Measures Explorer page.



Example of sheet pile and fill installation © Jacobs


SHORELINE STABILIZATION:
Geotechnical

SHORELINE LOCATION:
Nearshore


DESIGN LIFE
ADAPTABILITY
IMPACT ON THE WATERFRONT
CONSTRUCTION COST
100+ Years
High
Major Intervention
Very High


SEISMIC HAZARDS MITIGATED:SEISMIC PERFORMANCE IMPROVED:
Lateral Spreading
Liquefaction
StructuresUtilities & Transportation


MEASURES COMPATIBILITY:
Flood
Seismic
Floodwalls
Levees

Seawalls (Rip Rap Revetment)

Liquefaction Mitigation

Utility Retrofit


DESCRIPTION:
Strengthened in situ soils supporting new fill bayward of the existing shoreline. This would create a soil block which is strong enough and stiff enough to buttress the liquefiable fills acting on the rock dike and thus reduce lateral ground displacements that would otherwise damage the Embarcadero, the promendade, the light rail, utilites, and waterfront structures.


CONSIDERATIONS:
ADVANTAGES:
DISADVANTAGES:
  • Width of buttress defined by depth of Young Bay Mud which varies along the waterfront.
  • Effective in areas of deep Young Bay Mud.
  • Less construction impact to the Embarcadero and promenade compared to landside shoreline stabilization measures.
  • Replaces deteriorated wharf structures.
  • Provides foundation for future sea level rise protection.
  • Provides additional waterfront public space.


  • Construction would require vacating and temporary relocation of waterfront building when the work occurs at an occupied pier
  • Construction duration likely longer than other shoreline stabilization measures.
  • Requires fill within the Bay
  • Does not mitigate liquefaction-induced settlements In-water work requires measures to protect water quality.


CONSTRUCTION IMPACTS TO THE PUBLIC:
SEA LEVEL RISE ADAPTATION OPPORTUNITIES:
  • Construction would require vacating and temporary relocation of waterfront building when the work occurs at an occupied pier.
  • Impacts would be most noticeable to the occupants of the affected pier.
  • Most construction work would be done from the water-side of the seawall.
  • Impacts to users of the promenade and the Embarcadero would be limited.
  • The new engineered land could serve as a foundation for a future levee to protect the Embarcadero and the City from sea level rise.
  • Also, the new land would provide an inherent barrier to limit the influence of rising sea levels on groundwater elevations.




DESIGN CONSIDERATIONS:

  • The width of added land necessary to effectively buttress the existing seawall would depend upon the depth from the ground surface to the competent soil layers below. As this depth varies along the waterfront, the width of the added shoreline would vary.

SITE-SPECIFIC CONSIDERATIONS:

  • Special procedures would be required in the Fisherman’s Wharf area since contaminated soils below the water surface would be disturbed by construction operations.
  • Extension of existing outfalls through the added land would be required in some locations

URBAN DESIGN CONSIDERATIONS:

  • The added shoreline could provide additional open spaces on the waterfront for users of the Embarcadero and promenade.
  • The added shoreline would separate the promenade from the waters edge.

HISTORICAL RESOURCE CONSIDERATIONS:

  • Historic pier-supported buildings would need to be removed temporarily during construction and replaced once the work is complete.

INSTALLATION AND CONSTRUCTABILITY CONSIDERATIONS:

  • Mixing of the soil below the water surface with cement to strengthen it would require controls to protect water quality.
  • Soil mixing would be accomplished by barge-supported equipment.
  • Existing piles would need to be removed to ensure proper mixing of the soil with cement.
  • Timber piles could be salvaged and repurposed


Download the Nearshore Buttress Factsheet.

Learn about other types of measures from our Measures Explorer page.