If the improvement includes the construction of improvement of a water system, the county board of water supply may assume and pay out of its funds available for these purposes, all or any part of the costs of construction or improvement of the water system. The amount and nature of the costs to be borne by the county board of water supply shall be as mutually agreed to between the authority and the county board of water supply.
Haw. Code R. § 15-19-13