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Crescent City, California Tsunami Damage and Lessons Learned
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Crescent City, CA Tsunami Damage and Lessons Learned Ted Trenkwalder, PE, SE Ben C. Gerwick, Inc. Oakland, CA
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Crescent City – Project Location & Tsunami History
Tsunami Damage and Lessons Learned – Tsunami Damage – Emergency Response & Recovery – Marina Replacement Project – Lessons Learned
Questions and Answers
Presentation outline
Project Location
Questions and Answers
Project Overview & Approach
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Project Location
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Crescent City has a history of tsunamis
• 1964 Alaska • 2005 Eureka • 2006 Kuril Islands • 2011 Tohoku
Two primary factors
Factor 2 Wave amplification in
the 20-min range
Factor 1 Presence of the Mendocino
escarpment
Tsunami History
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FEMA Map Design Tsunami
Marina is completely submerged: search for maximum current may
not be appropriate design factor
Tsunami History
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Project Location
Crescent City Harbor Waterfront
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Hydrodynamic Model of 15-ft Tsunami
Tsunami Damage
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Hydrodynamic Model of 15-ft Tsunami
Tsunami Damage
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Tsunami Damage
B Street Pedestrian Pier
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Tsunami Damage
Citizens Dock
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Tsunami Damage
Inner Harbor Marina
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Tsunami Response Plan
Three Phases: Immediate (6-8 weeks)
Assess Damage Marina Temporary Float Outreach Contractor Outreach Permitting Issues & Restrictions Temporary Moorings Intermediate Plan Development
Intermediate (8-12 weeks) Dredging Contract Temporary Float Furnish & Install Power & PW Access
Long Term (12 weeks) Marina Replacement Design Contractor Qualification & Selection
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Why build a tsunami resistant marina? "We do not want to simply replace what was there." Dr. Richard Young (CCHD)
Marina Replacement Project
All Photographs Courtesy Ernie Perry (CCHD Permit Specialist)
Before March 2011
March 12, 2011
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• History of Tsunami Activity
• Major source of revenue for Del Norte County
Marina Replacement Project
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How do you design a tsunami resistant marina? Determine key design parameters • Determine Peak wave heights
and velocities • 14-ft above astronomical tide • 20.3 ft/s (6.2 m/s)
Marina Replacement Project
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Calculate tsunami loads • Extreme High Water + tsunami = +14.3
belowDdesign
pilefloat ACVg
LForFF ×××××= 2
21 γ
where LF = design load factor of 1.0 for strength design γdesign = density of seawater with 1.05 factor to account for suspended sediment = 1.05 x 64 pcf = 67.2 pcf g = gravitational acceleration V = design velocity due to design tsunami event CD = drag coefficient Abelow = below water projected area of potential berthed craft and floating docks or guide pile
Marina Replacement Project
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• Shallow Rock • 30"Ø Pipe Pile • Drilled Sockets • Corrosion Resistance
Construction Considerations
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Permitting Considerations • Pinnipeds & Salmon • Construction Windows • Mitigation Measures
Marina Replacement Project
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What does a tsunami resistant marina look like?
Marina Replacement Project
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Larger Rock Slope Protection
Marina Replacement Project
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Larger piles
Marina Replacement Project
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Larger Floats
Marina Replacement Project
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Larger Floats
Marina Replacement Project
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• Critical Financial Asset for Community & County • Do not simply replace waterfront asset • Have a Tsunami Response Plan • Define design goals and understand critical elements • Pre ASCE 7 Tsunami Loads & Effects Subcommittee
Lessons Learned
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Questions and Answers