Upon review of a petition for reservation, related data and the results from the departmental investigation, the director shall notify the petitioner of action pertaining to the petition, to withdraw affected waters under RCW 90.54.050(2), or to reserve water(s). If reservation is deemed appropriate, the director shall take action to adopt a regulation or amend an existing regulation established pursuant to chapter 173-500 WAC to reserve water for a future public water supply for the general geographic area described in the petition or for a general area the director determines appropriate. (RCW 90.54.050 mandates the department to conduct a public hearing, prior to adoption of a rule to withdraw or to reserve in each county in which waters relating to the rule are located.)

The amount of the reservation shall be determined by the director and may be more or less than the amount requested in the petition. The total reservation amount may be prorated to specific subareas of service in the proposed development area. Appropriate map may be appended to regulation.