Mouth of the Columbia River Jetties Major Rehabilitation

MCR North Jetty - Construction and Repair History (Receded approximately 1800’ in length since 1916)

MCR South Jetty - Construction and Repair History (Receded approximately 5000’ in length since )

Design Development Least cost, most reliable repair, environmentally acceptable. Jetty cross section options: –Dimensions: crest elevation, crestwidth, sideslope –Material types: stone, concrete, combination Due to the variability in design climate and repair history, design applications will vary: –Between the three structures –Along the length of each structure. Both physical and two numerical modeling are used to assess and fine tune the designs.

Physical Modeling of Cross Design Options – Optimize Reliability Jetty Resilience Compromised by Wave Action

= reliability-based decision point

Reach of North Jetty NOT Repaired Since 1917 Original Construction Severe Deterioration of Jetty Heads MCR Jetty Breach Feb 2006 Threatened Jetty Section Progressive Damage 2005 North Jetty = 58,000 tons Armor Stone (5-12 tons) 2006 – 2007 South Jetty = 160,000 tons Armor Stone (5-30 tons)

Sand infill from north side through damaged structure. Submerged head of north jetty helping to hold Peacock Spit and Benson Beach.

Major Rehab Considerations Engineering Features –Lagoon Fill –Spur Groins –Capping

Repaired in 2005 Sep 2002 MCR North Jetty

12 m 10 m 8 m 14 m SOUTH JETTY 6 m MCR Navigation channel Existing spur groins on south jetty.

North Jetty South Jetty Clatsop Spit MCR Channel Peacock Spit NJS Use the NJS to reduce the scour rate along the southern toe of the north jetty (place Mcy/yr) Use the SWS to feed material onto Peacock Spit and Sustain the sediment budget north of MCR (place Mcy/yr): SWS

1939 Benson Beach Shoreline 1913 North Head * * hea d of jett y in North Head Shoreline receded 2,000 ft since 1939 North Jetty Shoreline 1913 * As shoals recede, jetties become vulnerable to foundation scour and wave attack

South Jetty Head – 4000 ft loss in length

Major Rehab Alternatives Scheduled Repair Immediate Rehab –Minimum Template –Large Template –Composite Template Scheduled Rehab

N = spur groin NORTH JETTY MAJOR REHABILATION

Selected Plan Reliability: Major feature restoration consisting of structural work on Corps operated and maintained facility Goal: Develop the most cost-effective reliable structure that serves the purpose for the navigation channel

Applicable Environmental Laws NEPA (National Environmental Policy Act) –Mitigated FONSI Environmental Assessment CWA (Clean Water Act) CZMA (Coastal Zone Management Act) ESA (Endangered Species Act) –Biological Assessment –Biological Opinion Marine Mammal Protection Act Magnuson-Stevens Act

Potential Impacts Listed Species and Critical Habitat Impacts to Aquatic Organisms Impacts to Commercial and Recreational Fisheries Essential Fish Habitat Cultural Resources Socio-Economic Section 404 Waters and Wetlands

ESA Species in Project Vicinity 13 Runs of Salmonids Chinook Salmon

Juvenile Fish Studies North Jetty Disposal Site Jetty A

ESA Species in Project Vicinity Pelagic Mammals and Turtles Right Whale Green Sea Turtle

ESA Species in Project Vicinity Birds (Pelican, Eagle, Murrelet, Plover) Pelican Plover Eagle Murrelet

ESA Species in Project Vicinity Steller Sea Lions

Other Species of Concern Dungeness Crab California Sea Lion