Kawainui Marsh has played a highly significant role in Hawaii’s history and culture, and continues its story today as a central part of the surrounding Kailua community as a wetland resource and waterbird sanctuary. The construction (1966) and enhancement (1990-92) of the Kawainui flood control levee by the US Army Corps of Engineering (USACE) offered the initial opportunity to secure federal funds through the USACE Section 1135 for this ecosystem restoration project.
The marsh is located on the island of O‘ahu, and bordered by major highways such as Kalaniana‘ole Highway, Kailua Road, and Kapa‘a Quarry Road.
Kawainui Marsh is recognized by the U.S. Fish and Wildlife Service (FWS) as a waterbird recovery area, providing habitat for four endemic and endangered Hawaiian waterbirds. It also plays a role in the Ko‘olau Poko watershed as an important source of flood control and sediment filtration, protecting the urbanized areas of Kailua and the Kailua Bay ecosystem.
Oceanit was contracted in 2003 to conduct engineering and environmental studies, design pond drainage and water management improvements, and conduct all necessary permitting for construction of the designs. Oceanit’s solutions were designed to meet the biological requirements of the Hawaii Stilt waterbird, while also accommodating many other water birds.
The new designs included water supplied from wells and distributed through a side channel, allowing individual fill and drain for each pond using a simple board and weir control system. Construction of Oceanit’s designs was completed during the dry season, and during the following rainy season, the ponds filled and hundreds of waterbirds returned to the area and began reestablishing and using this modified habitat.
You can learn more about the Kawainui Marsh, and the endemic and endangered species that make up the ecosystem there, by visiting https://dlnr.hawaii.gov/wildlife/sanctuaries/kawainui/
- The design was required to meet operational and ease of maintenance requirements while fitting aesthetically within the natural surroundings and social context.
- Land ownership of the entire marsh was not transferred from the City to the State until 2007, challenging the design process.
- The known presence of archaeological features (loi rock walls buried beneath surface soils) limited grading lift to less than six inches.
- Discovery of archaeological rock wall features near the end of construction period resulted in delays until decisions were reached on how to mitigate the findings in a socially acceptable fashion.
- Several sections of pond berm foundations were not stable under heavy equipment loads due to high groundwater elevations and very silty soils. These berm areas required re-design with geogrid and geotextiles included to improve stability.
- Drain and fill pipelines installed connecting ponds to the transfer channel, were found to be less dense than water, causing them to bend and float up as the ponds filled. Problem remedied by fixing the pipe ends to small concrete pads already present in the ponds.