Protecting Newport Harbor from Sea Level Rise Cost

Protecting Newport Harbor from Sea Level Rise: Cost Considerations and Option Tidelands Management Committee May 29, 2014

Harbor Protection Costs What factors should be considered in estimating costs for protecting facilities and property around the harbor from flooding due to sea level rise? 2. Is a tide gate at the harbor jetty viable and could it reduce overall harbor protection costs? 3. (What sea level rise protection measures need to be considered for Balboa Peninsula? ) 1.

Estimating costs for Harbor protection including jetty gate 1. Estimate costs for harbor flood protection measures including raising seawalls, sand replenishment, groundwater protection measures, raising finish floor elevations, maintaining vehicular/pedestrian access including access to piers and beaches, and maintaining utility systems viability. 2. Assume the design of peninsula (and jetty gate) will withstand projected sea level rise to Year 2100 including projected storm surge and wave overtopping. 3. Estimate to include costs for planning, design, environmental clearances and studies, construction, mitigation and O&M. Estimate to breakout costs for public and private improvements. Assume phased construction as needed. 4. Provide separate estimates with and without a jetty tide gate. 5. Incorporate small craft lock into jetty tide gate design to allow oceangoing transit when gates are in operation. 6. Evaluate hydraulics and need for ocean water mixing when gates are closed to maintain ecological balance in harbor.

Is a tide gate at the harbor jetty viable? Two types of gates were proposed by a consultant last year: Inflatable flap gate 2. Wicket gate with prop 1.

Inflatable Flap Gate (Obermeyer Type) 5

Schematic Obermeyer Bottom Hinge Gate 6 JANUARY 25, 2012 PORT OF WEST SACRAMENTO PRESENTATION

Wicket Gate (Raised) Protected Side Flood Side Flap Gate: Steel or Ltwt. Conc. Steel Prop 35 ft o 55 ft 60 Channel Bed Piles Driven "in-the-wet" Sheet Pile Wall Driven "in-the-wet" Seal Bag Float-In Foundation 7

Conceptual 600 -ft Pass Bottom Hinge Gate Barrier

New Bedford Hurricane Protection Barrier

Raise Beach Elevation for Flood Protection

What if: 55” Sea Level Rise?

Groundwater Pumping on Peninsula? �Appropriate geology for 20’ wells? If not, need many more shallow wells. �Where will groundwater be discharged? Ocean? OCSD? Into Bay with treatment? Initial Conclusion: Raising finish floor elevations is the better option for preventing groundwater intrusion into houses and businesses.

Peninsula Flood Protection Requirements (55 -inch Sea Level Rise) Raise beach sand elevation to ~15 feet (raise beach 0 to 5 feet) 2. Raise Finish Floor elevations above MHHW to ~11+ feet (raise finish floor 1 to 4+ feet) 3. To restrict groundwater incursion into bay, raise Peninsula seawalls to ~11+ feet (raise seawall 2 to 3+ feet) 1.

Areas below elevation 10 feet at risk of periodic flooding by 2064 if no protective measures taken.

Areas below elevation 12 feet at risk of periodic flooding by ~2094 if no protective measures taken.

When would tide gate be closed?

Preliminary Design Values › Major Assumption: 55 -inch sea level rise by 2100 › Required freeboard: 1'-0" for Future Case Present Req'd top of Gate EL. Flood Side Water EL. Protected Side Water EL. Future MSL Future MLLW Tide Future MHHW Tide Future 14. 0’ 9. 0’ 13. 0’ 6. 0’ 7. 2’ 4. 7’ 9. 7’ Tide gate would be closed most of the time. Boats could only avoid the Lock System at low tide.

Fox River Lock System

Mississippi Lock and Dam

Initial Findings �If sea level rise is ~4 feet, tide gate would typically be closed for most of the day. �If long term sea level rise is ~3 feet, a tide gate would operate on a daily basis. �If sea level rise will only be ~2 feet, likely more cost effective to construct seawalls to 10 feet.

Cost Advantage If sea level rise over the long term is No Jetty Tide modest (~3 feet) Gate Construct Jetty Tide Gate Peninsul a All Islands & Landside Replace aging walls Construct new higher seawalls maybe Raise ocean-side beaches Raise finish floors maybe Raise streets and adjust utilities maybe Construct storm water pump system maybe Operate storm drain tide gates maybe Construct jetty tide gate Jetty tide gate operation and maintenance

Estimating costs for Harbor protection including jetty gate 1. Estimate costs for harbor flood protection measures including raising seawalls, sand replenishment, groundwater protection measures, raising finish floor elevations, maintaining vehicular/pedestrian access including access to piers and beaches, and maintaining utility systems viability. 2. Assume the design of peninsula (and jetty gate) will withstand projected sea level to Year 2100 including projected storm surge and wave overtopping. 3. Estimate to include costs for planning, design, environmental clearances and studies, construction, mitigation and O&M. Estimate to breakout costs for public and private improvements. Assume phased construction as needed. 4. Provide separate estimates with and without a jetty tide gate. 5. Incorporate small craft lock into jetty tide gate design to allow oceangoing transit when gates are in operation. 6. Evaluate hydraulics and need for ocean water mixing when gates are closed to maintain ecological balance in harbor.

How to proceed? Verify sea level rise predictions Ø By about 2020, king tides could be ~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 1.

Harbor Protection Options: Comments and Directions