Haw. Rev. Stat. § 48E-15: Exemption from taxation by county property.

All revenues derived by the county from any project agreement shall be exempt from all state and county taxation. Any right, title, and interest of the county in any pollution control project shall also be exempt from all state and county taxation. Except as otherwise provided by law, the interest of the project party or user of such project in a pollution control project or under the project agreement or related agreement shall not be exempt from taxation to a greater extent than it would be if the costs of the pollution control project were directly financed by the project party or other user.