Utility Today, Resilience Tomorrow:Balancing Near-Term and Long-Term Needs in New Pier Design

Abstract: In 2025, the University of Rhode Island (URI) Graduate School of Oceanography (GSO) will begin operating a new research vessel, the R/V Narragansett Dawn. The new vessel will be home-ported at URI’s Narragansett Bay Campus (NBC). The NBC facilities include a pier, which served as the home port for Narragansett Dawn’s predecessor.

Design of a replacement for the NBC pier began in 2019, after URI determined the old pier was approaching the end of its service life and could not be modified to support the new vessel.

The new pier includes a pier head, mooring dolphins, and new mooring, berthing, and utility systems servicing two berths. There is a research shed founded on the pier deck. The project also includes a new access trestle, abutment, approach roadway, and a pumphouse and seawater intake system for the GSO aquariums.

The new pier’s design life is 50 years, which matches that of the new vessel. The project team determined the pier must be able to withstand the 100 year storm event, which has a 40% chance of occurrence in 50 years.

This proved challenging due to the extreme environmental exposure of the site. The new pier will be subjected to large ocean swells, heavy wind-driven chop from a 10-mile fetch, a strong ebb current, and intense coastal floods. The FEMA 100-year wave elevation at NBC is 10.50 feet above the old pier’s deck. State regulators directed the team to design for an additional 5.35 feet of sea level rise by 2073.

Given the vessel’s low main deck, the team concluded that setting the new pier more than 15 feet above the old pier would be impractical for loading operations, and construction of such a large facility would have a range of negative impacts.

The new pier deck is 5.35 feet above the old deck. This is low enough for optimal loading operations during normal weather. Several overtopping events will likely occur over the service life of the new pier; however, these events will be less frequent and less severe than the old pier would have faced. With projected sea level rise, the new pier will not have the same chances of flooding that the old pier had in 2023 until approximately 2073. The permitting agencies accepted this rationale.

The new pier is designed to be overtopped and fully submerged. The deck is sized to resist extreme uplift forces. There are vents underdeck to release air trapped by rising waves. The research shed is designed to break-away at its foundation, and the seawater intake lines are lashed to the trestle piles at the mudline. The pumphouse is built on high ground, and its walls are armored.

The project team also established heavy weather mooring protocols. If wind speed and sea state exceed set limits, the vessel will cast off the pier and seek an alternate berth, returning when the storm subsides.

The new pier was opened in late 2023. It performed well during its first New England winter, which included several storms.

How does this project / topic contribute to the advancement of the industry and profession?: This design struck a delicate balance to accommodate the unusually low freeboard of the design vessel and the extreme exposure and projected sea levels at the site.

If regulators and insurers continue to push more aggressive design allowances for sea level rise and coastal flooding, many other projects involving new port facilities will need to strike a similar balance.

This project presents a middle road that yielded a satisfactory outcome for all stakeholders. It also models several unique analysis methods and structural details related to designing the pier to withstand more than 10 feet of wave overtopping.

Does the project / topic implement new and innovative techniques, materials, technologies, and delivery methods?: The design included innovative solutions to account for the combined effects of a base flood, wave loads, and sea level rise. Vents were installed through the pile caps and edge beams to exhaust air compressed by larger ocean swells. The research shed was a breakaway design, and it was outfitted with quick disconnect utilities.

There were unique features related to the pier’s secondary function as a research platform. The research shed was outfitted with thru-deck port holes to accommodate specialized research equipment. A custom davit system was installed to raise and lower the seawater intake lines for cleaning and maintenance.

What was the most challenging aspect of your project / topic and how did you handle it to ensure success?: Vertical wave forces presented a challenge. An iterative analysis was performed to find at what base flood elevation the design wave would impart maximum uplift forces to the deck. The maximum unfactored wave uplift effect was 750 psf! For structural efficiency, the deck system was designed to have continuous spans in the uplift load condition, which was achieved through careful detailing.

Lateral wave forces were also challenging. The research shed has a semi-isolated foundation, where the whole timber structure can break away without major damage to the pier, and the utilities can be quickly disconnected in advance of a storm.

Who is the target audience for this paper?: 1. Engineers who are tasked with designing a new port facility outside of a traditionally sheltered harbor
2. Facility managers who are planning for replacement of a waterfront asset
3. Any party in a capital improvement project who is seeking to balance current operational needs with projected future conditions, especially those related to sea level rise or wave loading