PLT OF AN SMA SEL PVT ACFT FELL INTO A HOLE WHILE PARKING OFF THE RAMP IN A GRASSY PARKING AREA RESULTING IN STRIKING AND DAMAGING THE PROP.

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WE MADE AN UNEVENTFUL TRIP AND LNDG. WHILE SLOWLY TAXIING TO PARK ALONGSIDE OTHER PARKED AIRPLANES IN A MOWED GRASS AREA; MY NOSEWHEEL ENTERED A HOLE CAUSING THE PROP TO CONTACT THE GND. FORWARD TRAVEL CEASED; AND THE ENG STOPPED AFTER SEVERAL ROTATIONS. WITH HELP FROM SEVERAL LCLS; WE EXTRICATED THE NOSEWHEEL FROM THE HOLE AND FOUND A HOLE MEASURING APPROX 10 INCHES IN DIAMETER BY 6 FT DEEP. THIS HOLE WAS UNMARKED; AND WAS INVISIBLE OVER THE NOSE FROM THE COCKPIT PERSPECTIVE. UPON INVESTIGATION; SEVERAL OTHER HOLE SITES WERE LOCATED; BUT ALL OTHERS HAD BEEN FILLED. LCL OBSERVERS STATED THAT SOIL TESTING HAD RECENTLY BEEN PERFORMED IN PREPARATION FOR A RADAR INSTALLATION. NONE OF THE LCL HANGAR TENANTS (AT LEAST 10 WERE PRESENT) WERE AWARE OF THE EXISTENCE OF THIS UNFILLED HOLE; AND ONE STATED THAT HE REGULARLY TAXIED ACROSS THE GRASS IN THE SAME AREA. THE ARPT MGR SEEMED SURPRISED THAT ACFT WERE TAXIING IN GRASS AREAS. HOWEVER; SEVERAL OTHER AIRPLANES WERE PARKED IN A ROW IN THE SAME AREA. IN FACT; ON THE NEXT DAY A FLY-IN ACTIVITY WAS HELD IN THE SAME AREA; AND MANY ACFT WERE OPERATING ROUTINELY IN THE GRASS AREAS (WE HAD MARKED THE HOLE FOR SAFETY). IT IS EXTREMELY COMMON FOR ARPTS TO USE GRASS AREAS FOR PARKING AND TAXIING OF LIGHT ACFT. ARPT OPERATORS SHOULD BE AWARE THAT IF UNPAVED AREAS ARE NOT SUITABLE FOR OP OF ACFT AND IT IS NOT OTHERWISE OBVIOUS; THAT THIS INFO SHOULD BE MADE AVAILABLE BY SIGN; NOTAM; FLAGS; OR OTHERWISE.