ยง 7509. Modification of award by arbitrator. On written application of a party to the arbitrators within twenty days after delivery of the award to the applicant, the arbitrators may modify the award upon the grounds stated in subdivision (c) of section 7511. Written notice of the application shall be given to other parties to the arbitration. Written objection to modification must be served on the arbitrators and other parties to the arbitration within ten days of receipt of the notice. The arbitrators shall dispose of any application made under this section in writing, signed and acknowledged by them, within thirty days after either written objection to modification has been served on them or the time for serving said objection has expired, whichever is earlier. The parties may in writing extend the time for such disposition either before or after its expiration.