Balboa Islands Seawall Rehabilitation Project Challenges Planning Direction

Balboa Islands Seawall Rehabilitation Project Challenges & Planning Direction Tidelands Management Committee February 18, 2015

Public and Private Seawalls (20 linear miles)

City-Owned Seawalls

Low-Lying Areas Around the Harbor

Seawall Requirements Structurally-sound seawall system B. Islands protected from flooding C. Provide access to piers and beaches A.

Presentation Outline 1. 2. 3. 4. 5. 6. 7. Review of challenges a. Seawall structural condition b. Islands’ flood potential Top-of-wall elevation options Seawall rehabilitation options a. Materials for new seawalls b. Rehab options (new seawall, cap extension, retrofit, sand banking) Rehabilitation costs Beach and pier access Jetty gate option Other design considerations

1 a. - Seawalls Structural Condition � 80 to 86 year-old walls. (Original lifespan approximately 75 years. ) �Walls are exhibiting obvious signs of deterioration and stress.

Floating Sidewalk – West End of Balboa Island

Ballast placed at West End in 1985.

Wall Movement (West End)

Corroded Tie Rods Existing Seawall at Balboa Island West End Constructed: pre-1935 Rock reinforcement installed 1985

Newport Marina Villas Townhomes ~1995 Seawall Failure – Shallow Pile Embedment

Pile Crack (West End)

Pile Crack (Close-up)

Grand Canal Seawall Concerns

Grand Canal: Spalled Veneer

Soldier Pile: Spalled Veneer

Close up of crumbling cap

Cap Spalled Beneath Veneer?

Balboa Islands Seawalls – Condition Summary � 80 -86 year old walls. �Walls are exhibiting obvious signs of deterioration and stress. �Existing walls subject to seismic risk. �Grand Canal: Depth of wall below mudline is very shallow. �Many unknowns: seawall rebar, sheetpile condition below mudline, tiebacks. �Estimated useful lifetime: 6 -21 years.

1 b. Islands’ Flood Potential State requirement that our coastal projects consider potential sea level rise. The conservative projection by the US Army Corps of Engineers is 55 inch rise by 2100.

Overtopping along southern side of Balboa Island - December 2010

Flooding at Balboa Island Ferry Landing (2005)

Seawall Overtopping The low-lying Balboa Islands need protection from rising tides, storm surges and wind waves.

Flooding Potential: 2025 - Highest 1% Tides with Wind Waves

2025: No Flooding with Sandbags

Existing Top of Wall Elevations

Storyboard

Sign installed on north side of Balboa Island

2. Top of Seawall Elevations Options with Estimated Flood Protection Option Top Elevation (NAVD 88) Flood Protection 1 Until: (Approximate!) 1 10. 0’ 2060 2 9. 5‘ 2055 3 9. 5’(south)/9. 0’(north) 2045 4 9. 0’ 2040 1 Projections by 2100. based on a conservative sea-level rise of 55 inches

3. Seawall Rehabilitation Options Materials for new seawall b. Rehab options (new seawall, cap extension, retrofit, sand banking) a.

3 a. New Seawall Material – Option 1 H-piles and Concrete Wall (Lag) Panels (No tiebacks)

Bay Island: Steel Sheet Piles and Cap

Bay Island Sheet Piles and Cap

3 b. Seawall Rehabilitation Options: New Seawalls (pink) and Cap Extensions (blue) (designed for 14’wall)

Little Balboa Seawall Cap Extension

3 b. continued: What about a Seawall Retrofit? Q: If the seawalls along the West End or Grand Canal are reinforced, can we expect another 2025 years of service? A: Maybe. The success any retrofit is dependent upon the structural integrity of existing walls. The seawall will need to be tested first. Cost for core samples, lab tests & report: $150, 000 to $200, 000

Along Grand Canal: H-Pile Supports

More 3 b. - What about periodically placing sand up along the Grand Canal walls?

Potential Costs to Periodically Bank Sand along the Grand Canal �Frequency: 2 to 3 times per year �Permit Renewal: Every 2 to 4 years �Cost for single hydraulic dredging: $100, 000 to $150, 000 �Costs for periodic mitigation: $300 k-900 k �Total cost over 25 years: $7 to 10 million �Conclusion: Even if permit-able, it is not cost effective.

4. Projected Costs Rehabilitation Option Useful Lifetime Initial Cost 1 New Seawalls around both Islands 100 years. $76 million New Seawalls along West End and Grand Canal + Capping elsewhere. Top Elevation: 9. 0 feet 100 years. $31 million New Seawall along West End 100 years. + H-Pile supports along Grand Canal + Capping elsewhere. 15 -20 years? ? Then construct new wall. (>$60 million) 1 New 20 -25 years. (20352040) Then construct new walls. (> $45 million) $20 million seawalls costs based on the Naples Seawall project. Costs include flood protection upgrades at Ferry Landing and Collins Island. Costs for extending height of new seawalls is not included.

Top of Seawall Elevations Options with Estimated Flood Protection Option Top Elevation (NAVD 88) Flood Protection 1 Until: (Approximate!) 1 10. 0’ 2060 2 9. 5‘ 2055 3 9. 5’(south)/9. 0’(north) 2045 4 9. 0’ 2040 1 Projections by 2100. based on a conservative sea-level rise of 55 inches

5. Private Pier Access over New Seawalls with steps down.

Public Pier and Beach Access

Beach Access Concept

6. What about a tide gate at the jetty? �Operationally, tide gate would be best if sea level rise is in the range of 2 to 3 feet. For sea level rise > 4 feet, tide gate would be closed the majority of the time. �Cost for gate: $350 to $500 million. �Annual costs for operation and maintenance. �Beach elevations along the peninsula would need to be raised. �Groundwater intrusion along the peninsula may require higher seawalls on the harbor side.

Jetty Gate: Staff Recommendations Approved by TMC: Verify sea level rise predictions Ø By about 2020, king tides could be 2 -3 inches higher than today – on track for a 55” rise in sea level by 2100. 2. Set new harbor-wide standard for top of seawall elevation, e. g. , 10 feet NAVD 88 3. Set new requirements for finish floor elevations for new construction and/or major remodels. 1.

7. Other Items Under Consideration 1. 2. 3. 4. 5. Flood Protection at the Ferry Landing Collins Island Bridge Replacement Protection from Rising Groundwater Raising Boardwalk (as opportunities arise) Funding

Staff Recommendations Construct new seawalls on the West End and the Grand Canal to 9. 0 feet (NAVD 88). Use steel sheetpiles and concrete cap. 2. Extend cap on remaining walls to top-ofwall elevation of 9. 0 feet. 3. Cost: ~$31 million 1. Location Increase in Wall Height South Side of B. I. 7 to 10 inches North Side of B. I. ~ 14 inches Grand Canal 4 to 6 inches East Side of Little B. I. < 4 inches

Webpage and Community Comments City Webpage: http: //www. newportbeachca. gov/seawall s Comments and concerns: seawalls@newportbeachca. gov Staff contact: Bob Stein, 949 -644 -3322

Emergency Repair of Failed Seawall

Areas below elevation 12 feet at risk of periodic flooding by ~2090 if no protective measures taken.