The number of board members required to make a decision on a case differs depending on the type of case.

(1) Short-board appeals. Pursuant to RCW 90.58.185, petitions for review that involve a single-family residence or an appurtenance to a single-family residence, including a dock or pier for a single-family residence, and petitions for review involving a penalty of fifteen thousand dollars or less, may be heard by a panel of three board members. The chair of the hearings board may also designate other cases for review by a short-board appeal panel. In designating these cases, the chair shall consider factors such as the complexity and precedential nature of the case and the efficiency and cost-effectiveness of using a short board versus a full board. A short-board appeal panel must have at least one but not more than two members of the pollution control hearings board. Two members of the panel must agree to issue a final decision. The decision of the panel is the final decision of the full board.

(2) Full-board appeals. All other appeals are full-board appeals. Four members of the board constitute a quorum for making a decision and may act even if the other two members are unavailable or have not yet been appointed.

(3) Administrative appeals judges. For both full-board and short-board cases, the chairperson may appoint an administrative appeals judge from the environmental and land use hearings office to be the presiding officer.