(1) After establishment of external critical water supply service area boundaries, those boundaries may not be altered until the coordinated water system plan is completed.

(2) Alteration of external critical water supply service area boundaries may be initiated by the department or county legislative authority(ies) in accordance with the procedures and criteria identified in WAC 248-56-600 and 248-56-610. In addition:

(a) The department or county legislative authority(ies), whichever initiates alteration of external boundaries, shall prepare a brief report documenting the need for such alteration, and

(b) The department or county legislative authority(ies), whichever initiates preparation of the report, shall reconvene the water utility coordinating committee and present the report to the committee, together with instructions for committee action.

(3) The coordinated water system plan shall be revised as necessary, due to alteration of external critical water supply service area boundaries, within six months of the date of such action taken by the county legislative authority(ies), unless an extended schedule is approved by the department.