The Ofu Coastal Storm Damage Reduction Study was a federal study to evaluate and identify emergency shoreline protection measures at the west end of the Ofu Airport runway located on the island of Ofu in American Samoa.
The study was authorized under Section 14 of the Flood Control Act of 1946 (P.L. 79-525), as amended (33 USC 701r) for emergency shoreline protection under the Continuing Authorities Program. This two-year feasibility study began in March 2022 and concluded upon approval of a Final Integrated Feasibility Report and Environmental Assessment (IFR/EA) and Finding of No Significant Impact (FONSI) in July 2024.
The non-Federal sponsor for the study was the American Samoa Government, represented by the Department of Port Administration (DPA). Following application of a Section 1156 waiver, the balance of study costs were cost shared 50/50 between the U.S. Army Corps of Engineers (USACE) and the non-Federal sponsor. Upon conclusion of the feasibility phase, the study will move to the Design & Implementation phase once study funds are received.
Ofu Airport is located on the southern coast of Ofu in the Manuʻa Island group of American Samoa. The 18-acre public airport is operated by DPA on property leased from local families. The airport serves the aviation needs for residents of both Ofu and Olosega islands and is the primary means of transportation for people and critical goods between the islands.
In 1986, USACE constructed a rock revetment on the east end of the runway for shoreline protection under the Section 14 authority. In June 2019, DPA submitted request for Federal assistance of shoreline protection on the west end of the airport runway. The west end shoreline was rapidly receding, eroding into the FAA-mandated runway safety area due to storm surge and wave attack. This condition was further exacerbated by Tropical Storm Evans in 2012 and Tropical Storm Evans in 2018. In July 2023, king tides damaged the newly re-paved airport runway, shutting down airport operations for two weeks until repairs were made. Without protection from wave attack and erosion, the runway would continue to sustain damage and impacts to airport operations. A feasibility cost sharing agreement was signed in March 2022, initiating the feasibility phase for this study.
In May 2023, USACE published a Draft IFR/EA outlining the planning process, engineering and cost analysis, identification of a tentatively selected plan, and associated National Environmental Policy Act (NEPA) analysis. A hybrid public meeting was held 31 May 2023 at the Ofu Airport ARFF Building, Pago Pago International Airport Conference Room, and virtually through Google Meet. The study used public and agency feedback to further refine the tentatively selected plan and finalize the IFR/EA. The Ofu Final IFR/EA was approved by the Major Subordinate Command in July 2024, concluding the feasibility phase.
The Recommended Plan presented in the IFR/EA is a 450 ft-long Tribar Revetment. The structure consists of a concrete toe, geotextile base, double layer of underlayer stone, and a single layer of 1-ton concrete tribar (interlocking) units. At a horizontal to vertical slope of 1.5 to 1, the revetment is expected to be 29 feet wide with a crest elevation of +13 feet above mean sea level. This design meets the USACE coastal engineering criteria for expected design life and adaptability to relative sea level change. At federal fiscal year (FY) 2024 price levels, the total project cost (fully funded) of the Recommended Plan is approximately $10.1 million.
