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Kawainui Marsh Bird Habitat

Project Description

Kawainui Marsh has played a highly significant role in Hawaii’s history and culture, and continues as a central focus of the surrounding community. The construction (1966) and enhancement (1990-92) of the Kawainui flood control levee by the USACD offered the opportunity to secure federal funds through the USACD Section 1135 for an ecosystem restoration project.

Challenges

  • 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.

Oceanit Solutions

  • Oceanit was contacted in 2003 to conduct engineering and environment studies, design and obtain all permits.
  • The ponds were designed to meet the biological requirements of the Hawaii Stilt while also accommodating other water birds.
  • Water was supplied form wells and distributed through a side channel, allowing individual fill and drain for each pond using a simple board and weir control system.
  • Construction was completed during the dry season. During the following rainy season the ponds filled, and hundreds of waterfowl are currently using this new habitat.