Section 9. The parties to any controversy described in section five may submit it in writing to a local board of conciliation and arbitration, which may be composed either of three members mutually agreed upon, or of a member chosen by the employer, a member chosen by the employees or their authorized representative, and a third, who shall be chairman, chosen by the other two. Such local board shall have and exercise, relative to matters referred to it, all the powers of the state board, and its decision shall have such binding effect as may be agreed upon in the written submission. Such local board shall have exclusive jurisdiction of the controversy submitted to it, but it may ask the advice and assistance of the state board. The decision of such local board shall be rendered within ten days after the close of any hearing held by it, and shall forthwith be filed with the clerk of the city or town where the controversy arose, and a copy thereof shall be forwarded by said clerk to the state board. Each of such arbitrators shall be entitled to receive from the treasury of the city or town where the controversy arose, with the approval in writing of the mayor of the city or the selectmen of the town, the sum of fifteen dollars for each day of actual service, not exceeding fifty dollars for any one arbitration.