(1) All board hearings shall be open to the public unless a party requests that part or all of a hearing be conducted in closed session in accordance with subsection (2) of this section.

(2) If one of the parties intends to introduce evidence obtained under RCW 84.40.340 or confidential income data exempted from public inspection pursuant to RCW 42.17.310 and requests that the hearing be closed to the public, the board shall conduct the hearing in closed session, to the extent necessary to protect and preserve confidentiality.