Sand Island Climate Change Vulnerability Assessment and Resilience Plan

The Sand Island Sewer Basin in Honolulu, HI, faced increasing threats from climate change, particularly flooding and coastal erosion, which endangered its 17 wastewater pump stations and a 65 mgd wastewater treatment plant. To address these vulnerabilities and protect critical infrastructure, the City of Honolulu engaged Carollo Engineers to conduct a Climate Change Vulnerability Assessment and Resilience Plan. This initiative aimed to evaluate the risks posed by various climate scenarios, including sea level rise, inland flooding, hurricane storm surges and tsunami run-up inundation, and to develop strategies to enhance the resilience of the wastewater facilities.

Carollo’s assessment involved site visits and analysis of record drawings to identify critical flood pathways and other vulnerable components. The team utilized local climate planning requirements, advanced modeling resources, and the latest scientific data to characterize flooding and erosion threats up to the year 2100. By evaluating expected inundation depths and erosion extents, Carollo identified the degree to which these threats could impact the wastewater facilities. This evaluation led to the recommendation of specific adaptation measures designed to increase the resilience of these facilities to both immediate and long-term climate threats.

As a result, the City of Honolulu is better prepared to protect its wastewater infrastructure from the impacts of climate change. The recommended climate adaptation measures were integrated with other project considerations, such as capacity and lifespan of aging infrastructure, to develop a capital improvement program. This approach not only enhances the resilience of Honolulu’s wastewater system but also maintains the continued safety and reliability of essential services for the community in the face of evolving climate challenges.