#1傻 LOFU COASTAL STORM DAMAGE REDUCTION SECTION 14 Public Meeting 31 May 2023 " 50400 STARWAY DUFT Natalia Palamo, Engineer (DPA) EL.473.09 Cindy Acpal, Project Manager (POH Nick Emilio, Planner (POH) Lauren Molina, Engineer (POH) MOORING PING TARTER G US Army Corps U.S. ARMY of Engineers® DEPARTMENT AMERICAN PORT SAMOA ADMINISTR STRATION GOVERNMENT 3050 6724 It I#2U.S. ARMY 2 AGENDA: PUBLIC MEETING 1. Study Overview and Background 2. Existing and Future-Without-Project Conditions 3. Alternatives Analysis 4. Description of the Tentatively Selected Plan 5. How to Participate#3U.S. ARMY STUDY OVERVIEW Authority: Section 14 of the Flood Control Act of 1946, as amended Non-Federal Sponsor: American Samoa Government, represented by the Department of Port Administration Plan Selection (EP 1105-2-58, Para. 10.d.): "Formulation and Justification. Following a finding of eligibility, and given the narrow geographic focus, low cost of these projects, and the imminent threat to the facilities, the formulation and evaluation will focus on the least-cost alternative solution. The least-cost alternative plan is considered to be justified if the total cost of the proposed alternative is less than the costs to relocate the threatened facility." 3#4U.S. ARMY CAP PLANNING AND IMPLEMENTATION TIMELINE LOI 7 23 Feasibility Phase 4 5 Design & Implementation Phase 67 Operations & Maintenance Phase 8 1. Letter of interest (LOI) from non-federal sponsor 2. Federal Interest Determination 3. Feasibility Cost Share Agreement (FCSA) 4. Prepare Feasibility Report with NEPA document 5. Project Partnership Agreement (PPA) 6. Design 7. Construction 8. Operations & Maintenance (O&M) 4#5U.S. ARMY FEASIBILITY STUDY PROCESS 2022 2023 2024 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC JAN FEB MAR APR MAY Study Scoping, Alternative Development, Environmental Consultation, and Initial Analysis Prepare Draft Public Review IFR/EA for Release Period Feasibility Level Analysis • . FCSA Tentatively Selected Plan Milestone Release Draft IFR/EA Release Final IFR/EA The Draft Integrated Feasibility Report and Environmental Assessment (IFR/EA) was released for public and agency review on May 22, 2023. The public review and comment period will end on June 21, 2023. Comments from the public will be considered as we move into the last phase of the feasibility study where we will refine our analyses and prepare a final report. LO 5 LO 5 Ⓡ#6U.S. ARMY Nu'utele STUDY AREA: OFU AIRPORT, AMERICAN SAMOA American Samoa Tutuila Fagamalo o Pagio Tutuila Pago Pago Manu'a Group MI KM Cape Matatula Aunu'u Pago Pago Harbor Fagatele Bay Ofu Olosega Manu'a Group 0 5 MI KM 25 Hawaii • • • American Samoa: U.S. Territory located roughly 2,300 miles southwest of Hawaii Ofu and Olosega islands: Manu'a Island group located about 66 miles east of Tutuila Ofu Airport (study area) is located on the southern coast of Ofu Island KM Ta'u MI Ofu American Samoa Ofu-Olosega Olosega NeG0505211120 2021 Copyright © Ontheworldmap.com • Population (2020 Census): Ofu: 132 Olosega: 147 6#7U.S. ARMY STUDY AREA: OFU AIRPORT, AMERICAN SAMOA N 7 Current Project Area 0 250 PROJECT AREA Ofu Airport, American Samoa US Army Corps Existing Federal SPP and Study Area of Engineers Honolulu District ofu Airport Tutuila K EXISTING USACE SHORELINE PROTECTION PROJECT (SPP) Olosega Ofu American Samoa Tau 500 750 1000 Scale: 1.577,791 PACIFIC OCEAN Project Area feet Zoom Level: 10 170 AM-14414 Degrees#8U.S. ARMY PROBLEMS IDENTIFIED IN STUDY AREA Shoreline along the west bank of Ofu airport runway is experiencing erosion due to wave attack and storm surge. Without emergency shoreline protection, the runway will continue to sustain damage during high wave and storm events, leading to the imminent closure of the runway • Disruption of airport operations will affect the primary means of transporting people and essential goods and supplies to and from both Ofu and Olosega islands. • Due to the isolation of the Manu'a Islands, air travel is especially important in the event of an emergency when transport of food, supplies, and medical evacuation are needed urgently. Closure of the airport due to damage following a storm will result in detrimental impacts to health and safety as well as a significant delay in travel and transport of vital resources to the island.#9U.S. ARMY EXISTING CONDITIONS • • . Waves: Seas and swell waves of up to 13 feet predominantly from the southeast. Less frequent, more energetic tropical cyclone wave energy typically approaches from the north, waves up to 16 feet. Winds: Prevailing winds throughout year are southeasterly trades. Winds tend to approach Samoa more directly from east during December through March, but during remainder of the year, they originate predominantly from east-southeast and southeast. Tropical Storms: Exacerbating coastal erosion in project area - Notable Storms (Damages and fatalities are for all affected areas): • . Cyclone Val (1991): 17 fatalities; $368 million in damages Cyclone Heta (2004): 1 fatality; $110-150 million in damages Cyclone Gita (2018) 2 fatalities; over $200 million in damages Sea Level Change: Rising sea levels globally and locally exacerbate existing problem. 2009 earthquake caused rapid land subsidence resulting in accelerated RSLC rates. Environmental Condition: Diverse coastal habitat in close proximity to project area - Notable Species: Coral, Hawksbill Sea Turtle, Green Sea Turtle 9#10U.S. ARMY EXISTING CONDITIONS – KING TIDES Prior to king tides July 13, 2022 Post king tides damage July 14, 2022 10#11U.S. ARMY FUTURE WITHOUT PROJECT CONDITIONS . . Threat of storm damage in American Samoa will become more frequent and severe over time Long-term sea level rise will increase damage to runway Ofu Airport and runway will continue to sustain significant damage, leading to imminent risk of airport closure and/or relocation Loss of sandy beach habitat in the project area is expected due to climate change impacts Impacts of sea level rise to hawksbill and green sea turtles: > Loss of nesting beaches and increased nest "wash out" due to rising sea levels can lead to overall decreases in nesting success Climate change stressors to coral reefs: - Enhanced reef sedimentation due to increased coastal erosion from wave action Warmer sea temperatures may lead to more frequent and intense coral bleaching events More frequent and intense tropical storms can damage coral and alter nutrient delivery processes to affect viability 11#12U.S. ARMY ALTERNATIVES: INITIAL ARRAY Alternative Alt 0: No Action Yes Alt 1: Rock Revetment Yes Alt 2: Tribar Revetment Carried Forward to Final Array? Alt 3: CRM Seawall Alt 4: Sheetpile Wall Alt 5: Precast Concrete Seawall Yes No; concerns with constructability, performance, and maintenance No; highest cost alternative and not environmentally acceptable No; concerns with constructability, performance, and maintenance 12#13U.S. ARMY ALTERNATIVES: FINAL ARRAY Final Array of Alternatives: Alt. 0: No Action Alt. 1: Rock Revetment Alt. 2: Tribar Revetment 13#14U.S. ARMY ALTERNATIVE 1 DESIGN: ROCK REVETMENT Existing Ground Surface - Runway, ELEV +10' ELEV +10.0' Backfill UNDERLAYER 2 STONES THICK- 675-1,125 LB STONE GEOTEXTILE AND FILL SPLASH APRON ARMOR LAYER -2 STONES THICK 3.4-5.6 TON STONE -Existing Ground Surface ▼MSL ELEV VARIES TOE TRENCHED INTO HARD SUBSTRATE 6.75 TON TOE STONE 14#15U.S. ARMY ALTERNATIVE 2 DESIGN: TRIBAR REVETMENT EXISTING GROUND SURFACE RUNWAY, ELEV +10' 777 BACKFILL -GROUT FILLED GEOTEXTILE BAG ELEV +10.0' 1-TON CONCRETE TRIBAR ARMOR SINGLE LAYER, UNIFORM PLACEMENT UNDERLAYER 2 STONES THICK 100-300 LB STONE GEOTEXTILE AND FILL- 1.5 -EXISTING GROUND SURFACE ▼MSL ELEV VARIES 18" DEEP (MIN) TOE TRENCH EXCAVATED INTO HARD SUBSTRATE AND FILLED WITH CONCRETE AFTER TRIBAR PLACEMENT 15#16U.S. ARMY COST TABLE: FINAL ARRAY Meets Alternative Project First Cost (FY23 Q1) Federal Share Non-Federal Share Participation Limits* Airport Relocation $91,000,000 N/A N/A N/A 0. No Action N/A N/A N/A N/A 1. Rock Revetment $11,700,000 $8,300,000 $3,400,000 Yes 2. Tribar Revetment $8,200,000 $6,000,000 $2,200,000 Yes Note: Numbers may not add due to rounding *Section 14 has a Federal per-project limit of $10M. 16#17U.S. ARMY TENTATIVELY SELECTED PLAN EP 1105-2-58: "The least-cost alternative plan is considered to be justified if the total cost of the proposed alternative is less than the costs to relocate the threatened facility." TSP Identified: TRIBAR REVETMENT (Alternative 2) Estimated Construction Cost: $8.2M ➤ Less than the cost of facility relocation ($91M) - Supported by the Non-Federal Sponsor - Meets Project Design Requirements · Environmentally acceptable - Estimated Construction Time: 12-18 months 17#18U.S. ARMY HOW TO PARTICIPATE Visit the study website at https://www.poh.usace.army.mil/Missions/Civil-Works/Civil-Works- Projects/Ofu-Section-14/ Download the Draft Integrated Feasibility Report and Environmental Assessment (Draft IFR/EA) ➤ Provide comment by June 21, 2023: . • Verbally: Provide verbal comment here at this meeting Written: - Provide comment in the chat (for those online) - - Provide written comment on comment card (for those attending in-person meetings) Email your comment to [email protected] (subject line: Ofu Draft Report) Mail your comment to: U.S. Army Corps of Engineers, Honolulu District Attn: CEPOH-PPC (Ofu) 230 Otake St. Fort Shafter, HI 96858-5440 18#19U.S. ARMY QUESTIONS? 19