Haw. Rev. Stat. § 101-18
Whenever two or more parcels of real property, or different interests in the same parcel of real property or improvements on real property or personal property in connection therewith, are to be acquired by eminent domain proceedings by two or more governmental agencies, and the properties to be so acquired are contiguous or are so interrelated that the taking of one of the properties or interests by one agency or the improvement contemplated in connection with the taking may affect the amount of the award which may be adjudged for the other of the properties, or vice versa, proceeding for the taking may be consolidated or the taking may be effected in one action brought in the name of one or more of the governmental agencies concerned in the taking pursuant to an agreement between the agencies. In such case the awards, when made, shall be apportioned in such manner as is agreed upon between the agencies, or, if not determined by agreement, then the apportionment shall be made by the court in such manner as it deems equitable, based upon the evidence given in the action or upon the same and such additional evidence as may be necessary or proper to determine the apportionment.
As used in this section, the term "governmental agency" includes the State, and any county, and any department, division, board, commission, public corporation, or other agency or instrumentality of the State or of any county.
Notwithstanding any other provision of law to the contrary, any governmental agency having by law the power to acquire any properties by the exercise of the power of eminent domain, may enter into agreements with any other governmental agency to effect the consolidation or to join in one action for the acquisition of the properties as provided in this section.
HRS § 101-18