Preliminary Report for Proposed Na‘alehu Wastewater Treatment Plant

October 31, 2018, 8:57 AM HST
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The County of Hawai‘i reports that a Preliminary Engineering Report (PER) for the proposed Nā‛ālehu Wastewater Treatment Facility was submitted to the United States Environmental Protection Agency (USEPA) on Thursday, Oct. 25, 2018, as required by the Administrative Order on Consent (AOC) signed by the County of Hawaiʻi (COH) and finalized on June 22, 2017.

In 1998, the USEPA promulgated regulations—40 Code of Federal Regulations (CFR) 144.14—which required the elimination of Large Capacity Cesspools (LCCs). As a result, the County of Hawaiʻi will close the existing LCCs in Nāʻālehu and construct a new sewer collection system located primarily within public right-of-way (ROW) and replace the existing LCCs with a wastewater treatment plant (WWTP) to address the wastewater treatment and disposal needs of the community.

The Nāʻālehu PER:

  • Summarizes the evaluations carried out to design and locate a proposed WWTP in Nā‛ālehu, which will be constructed to treat and dispose of the wastewater flow that is currently discharged untreated to the LCCs, plus accommodate additional sewer connections in support of the Kaʻū Community Development Plan (CDP);
  • Recommends a collection, treatment, and disposal system in compliance with the State of Hawaiʻi Department of Health and EPA requirements for the replacement of the three LCCs and deteriorating collection system in Nā‛ālehu;
  • Studied technology options for the proposed wastewater treatment system in Nā‛ālehu; and
  • Recommends a preferred site and conceptual layout for the new facility.




The next step is preparation of a Draft Environmental Assessment (DEA) in accordance with Chapter 343, Hawaiʻi Revised Statutes. The PER will be part of the DEA framework. The DEA is targeted for completion by the end of May 2019 Public comment on the DEA will be solicited.



A new preferred site for the Nāʻālehu wastewater treatment plant is described in detail in the October 2018 PER. Siting was and is a critical factor for the community, and the PER considered community input. A total of 32 sites were evaluated in Nā‛ālehu. The sites were each ranked based on 21 physical, cultural and social factors, including, but not limited to, soil type, locations of subsurface and surface water resources, archaeological and cultural resources, and social implications, such as land ownership and proximity to public uses.

For further information, call the Department of Environmental Management at (808) 961-8083 or view and/or download the PER at the County website.

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