PVT PLT GOV EMPLOYEE LANDED HIS C170 ON A DRY LAKE BED IN ORDER TO DETERMINE THE SURFACE CHARACTERISTICS FOR A POSSIBLE EXPERIMENTAL ACFT LNDG SITE. HOWEVER; HE GOT TEMPORARILY STRANDED IN THE MUD AND FOUND OUT LATER THAT IT HAD BEEN INCLUDED IN A UNITED STATES NATL PARK; WHICH WOULD RESTRICT FLYING OVER IT AT LESS THAN 2000 FT AND LNDG INSIDE THE PARK. HE CHKED THE LATEST AERONAUTICAL CHARTS AND FOUND NO SUCH INCLUSION OF THE NATL PARK.

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AS PART OF MY JOB (FLT TEST ENGINEER) I FLEW OUT TO BALLARAT DRY LAKE BED TO PERFORM A PRELIMINARY SURVEY TO DETERMINE THE POTENTIAL OF USING IT AS AN ALTERNATE (EMER ONLY) LNDG SITE FOR AN EXPERIMENTAL ACFT. UPON TOUCHDOWN; I QUICKLY DISCOVERED THAT THE SMOOTH; DRY LAKE BED WAS ONLY DRY FOR THE FIRST 1/4 OF AN INCH. IT TOOK 3 HRS AND THE HELP OF 2 OTHERS TO FREE THE PLANE ENOUGH TO WHERE I COULD ADD FULL PWR AND TAKE OFF. I LANDED ON A NEARBY ROAD AND WAITED FOR MY PAX TO ARRIVE (2 OTHERS). PRIOR TO FLYING THE AREA I STUDIED WAC CG-18 AND THE LAS VEGAS SECTIONALS (BOTH CURRENT EDITIONS) TO CHK FOR RESTR AREAS AND NATIONAL PARK AND WILDERNESS AREAS. THE LAKE BED IS NOT WITHIN EITHER OF THESE. I'VE SINCE LEARNED THAT THE DEATH VALLEY NATL PARK HAS RECENTLY BEEN EXPANDED AND NOW ENCOMPASSES BALLARAT DRY LAKE. THE GOV CHARTS DO NOT REFLECT THIS CHANGE. UNTIL THE CHARTS ARE CHANGED; PLTS WILL NOT KNOW IF THEY ARE WITHIN THE DEATH VALLEY NATIONAL PARK AREA. THE CHARTS NEED TO BE UPDATED. I LANDED ON BALLARAT TO INVESTIGATE THE SURFACE HARDNESS VIA A PRELIMINARY PENETROMETER TEST. UPON LNDG I LEARNED THAT THE TEST WAS NOT NECESSARY NOR WAS A FULL-BLOWN PENETROMETER TEST BY A LICENSED PROFESSIONAL GEOLOGIST.