Following an aerial search for two people missing in the Dingo area, the pilot stopped the aircraft to let the observers deplane. He then taxied his aircraft along a grassed taxiway to the hangar. During this taxying, the left main wheel entered a deep hole, which had not been sighted by the pilot. The owner/pilot had recently had a "pop-up" sprinkler system installed along the taxiway. The work involved lengthy excavation. The aircraft had been taxied into a hole inadvertently left by the contractor. The pilot had been in the habit of leaving the aircraft near the strip while the work was in progress, but on this occasion he decided to hangar the aircraft to avoid any unnecessary risk of damage to the parked aircraft by stock. This accident was not the subject of an on-site investigation.