A PROPANE LEAK UNDER A ROTONDA HOME WAS QUICKLY CAPPED ON WEDNESDAY.  THE ENGLEWOOD FIRE CONTROL DISTRICT WAS ON SCENE WITHIN TWO MINUTES OF THE FIRST CALL JUST AFTER 2PM WEDNESDAY, AND THEY QUICKLY ASCERTAINED THAT THE LEAK WAS COMING FROM AN UNDERGROUND STORAGE TANK.  RESIDENTS IN THE HOME AND WITHIN 300 FEET WERE EVACUATED AND FIREFIGHTERS APPLIED WATER THROUGH A FOG NOZZLE, AN ESTABLISHED METHOD THAT HAS BEEN PROVEN TO DISSIPATE PROPANE VAPORS.  HORIZON GAS ARRIVED ON SCENE JUST AFTER 3:30PM AND ASSEMBLED A BURN-OFF KIT TO GET RID OF THE REST OF THE GAS.  ABOUT SIXTY GALLONS OF PROPANE HAD TO BE BURNED OFF, AND OFFICIALS DETERMINED THE GAS HAD LEAKED THROUGH A RUSTED AREA IN THE 18-YEAR OLD UNDERGROUND STORAGE TANK.  FIRE OFFICIALS ADVISED THE RESIDENT THAT THE TANK WOULD HAVE TO BE REPLACED.