Mauna Lahilahi Beach Park

To mitigate and reverse damage caused by Sea Level Rise (SLR) and increasing wave action at Mauna Lahilahi Beach Park, Oceanit worked with City and State entities to solve difficult coastal engineering problems presented by this project. The actions undertaken were to restore public safety, protect cultural sites and burial grounds, and protect private properties along the shoreline.

For more than 50 years, the beach and shoreline at Mauna Lahilahi Beach Park in Wai’anae, on Oahu, eroding due to sea level rise. All of the beach sand and some of the back shore substrate were lost along a 350-foot shoreline cove during the previous decades.

Oceanit, under contract with the City and County of Honolulu, worked in several stages to design temporary and then permanent coastal engineering solutions for the city park and nearby threatened sites and properties. First, in early project stages, a temporary sandbag revetment was implemented to protect inland areas. In 2003, Oceanit designed and installed a rock breakwater to reduce wave energy, and oversaw a large scale beach restoration and nourishment. Finally, the temporary revetment was then replaced by a permanent, granite revetment.

The breakwater is a rubble structure extending about 250 feet parallel to the eroding shoreline. The beach was built with 10,000 cubic yards of sand from an inland quarry.

The Makaha Surfside Apartments on Oahu are located just landward of beach park’s eroding shoreline and have been damaged on several occasions by hurricanes and seasonal high waves at Mauna Lahilahi Beach Park. The city park was effectively split in two as erosion carried away land in the middle of the site. This eroded inlet began to threaten the safety of the building and residents.

Tasks included bathymetric surveys, characteristics of wave and current conditions to optimize design, and plans and specifications for a shore protection structure. Oceanit completed benthic marine biological surveys, environmental assessments, and all permits required for the project. The project spanned several decades and required collaboration across many State and City & County agencies to align all stakeholders on the final project.

The Mauna Lahilahi beach project wrapped in 2021 with the completion of the final revetment fronting the Makaha Surfside Apartments. The final revetment and greenway reconnected the beach park into a single, traversable park once more.

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Mauna Lahilahi Park and the Makaha Surfside apartments in the early 1990s
Final rock revetment installation work
Mauna Lahilahi park and Makaha Surfside apartments in 2021