PONTIAC, Mich.—Surveillance camera footage shows maintenance workers using a propane torch prior to a blaze that destroyed a century-old clubhouse at a suburban Detroit country club, authorities said Thursday. The Oakland County Sheriff’s Office said the Oakland Hills Country Club has estimated the loss of the clubhouse at about $80 million. The club has hosted the Ryder Cup and other major golf tournaments. The video footage found on a server in a water-logged basement of the clubhouse appears to show the workers attempting to douse a small fire in a wall using a garden hose on Feb. 17, Oakland County Sheriff Michael Bouchard said during a news conference. It also shows firefighters later breaking through the same wall only to be greeted by flame and heavy smoke. The workers had been using the torch to warm rubber flashing as part of a waterproofing process, Bloomfield Township Fire Chief John LeRoy …