Shemya Island - Surviving the Storm - Rebuilding for the Future

Abstract: Eareckson Air Force Station (EAS) is located near the western end of the Aleutian Island chain in Alaska. Its location is strategically important to the U.S. Military, being closer to Russia than mainland Alaska. The remote island location is exposed to extreme weather and is subject to unique construction challenges. Access to the island is essentially limited to two options: a four-hour flight from Anchorage or a one-month sail by barge from Seattle.

A severe storm in the winter of 2020 caused severe damage to EAS’s waterfront infrastructure, with reported 30-to-40-foot waves overtopping the fuel pier. One year later, a bomb cyclone rocked the Aleutians again with the most powerful storm ever recorded in the North Pacific. Exacerbating a history of storm damage, these recent events left the fuel pier and adjacent shoreline in a critical state. The importance of constructing a long-term repair was clear, but the myriad obstacles to overcome were daunting.

The shoreline to the west of the pier was eroding at a rate that would soon cut off landside access and compromise the Station’s sole lifeline for mission-critical deliveries of fuel and heavy construction materials and equipment. Close partnering of coastal/marine/port engineering and construction experts through a design-build contract for the US Army Corps of Engineers led to innovative designs to provide long-term repairs to the fuel pier and adjacent shoreline. This paper focusses on the design of the shoreline protection works.

The design-build team developed an engineered revetment to protect the shoreline and guard the pier access drive and landside facilities from further damage and erosion. Preliminary empirical calculations indicated that wave forces would require armor stone that is too large to procure and transport to site. An alternative design using concrete armor units (CAUs) was developed; however, the design-build team had concerns with this approach due to the requirement for a deep (excavated) toe and significant challenges with excavation at this site.

Advanced design development for the project was supported through a three-dimensional physical model study at HR Wallingford in the UK; the model study included testing of solutions using CAUs, a hybrid design with CAUs and an armor stone toe berm, and a unique “berm” design concept comprised solely of armor stone. The site-specific physical model study supported the development of a unique shoreline protection design that mitigates the key design and construction risks associated with the unique site and provides the required level of protection to the shoreline‘s harsh and unforgiving environment. A risk-based reliability assessment was undertaken to predict the performance of the structure over its 50 year design life, including consideration of the anticipated effects of future climate change.

This paper enlightens the engineering community with the design of shoreline protection for extreme wave events. It showcases the complexities of developing effective engineering solutions in a landscape of uncertainties, risks, and constraints. The design process led to discoveries that were not initially anticipated. It is this knowledge and unique experience that we are excited to share with coastal/marine practitioners.

How does this project / topic contribute to the advancement of the industry and profession?: This project contributes to the industry’s body of knowledge in the following ways:
• State of the art practice in the physical modeling of a shoreline in an extreme wave environment. Many of the lessons gained on this project will illuminate the industry's process for other designs.
• Close partnering between engineering and construction experts on a design-build project resulted in a creative solution that was not initially envisioned, and the process is repeatable on other projects.

Does the project / topic implement new and innovative techniques, materials, technologies, and delivery methods?: This project demonstrates a process of combining empirical design practices informed through physical modeling to develop a solution at a site with many site-specific constraints. The unique set of challenges demanded nothing short of the finest engineering tools, state-of-the-art equipment, and top-notch materials. The process led to remarkable design evolution through physical modeling backed by the engineers, constructers, and client. The approaches taken to address challenges in this remote and extreme location are beneficial for other projects and locations facing similar types of constraints.

What was the most challenging aspect of your project / topic and how did you handle it to ensure success?: The unique and remote site location with severe weather, limited construction windows, major wave forces, limited site data, and known presence of Munitions and Explosives of Concern (MEC). We conducted extensive research of other historic failures and successes to learn for this project. We worked closely with our expert partners, and as a team, transformed adversity into ingenuity.

Who is the target audience for this paper?: Design engineers, maritime contractors, and owners stand to gain valuable insights from learning about this project challenges, design approach, and outcomes.