PRIOR TO THE FLT, THE PLT & PASSENGERS WERE OBSERVED DRINKING BEER IN A LOUNGE. THEY TOLD WITNESSES THAT THEY WERE GOING TO THE ARPT TO EAT & WERE LATER SEEN AT A RESTAURANT ON THE ARPT. AFTER THAT, THEY DECIDED TO FLY. THE TAKEOFF TIME & PURPOSE OF THE FLT WAS NOT DETERMINED. AT ABOUT 1920 CDT, THE ACFT COLLIDED WITH A SUPPORT CABLE OF A LARGE ROTARY IRRIGATION SYS & CRASHED. THE COLLISION OCCURRED AT AN ALT OF APRX 20 FT AGL. NO KNOWN WITNESSES SAW THE ACCIDENT, BUT AN UNIDENTIFIED WITNESS TOLD LAW ENFORCEMENT PERSONNEL THAT HE SAW THE ACFT FLYING THRU THE SPRINKLER SPRAY PRIOR TO THE COLLISION. TWO OTHER WITNESSES SAW THE ACFT FLING LOW IN THE VICINITY. WITH THE IRRIGATION SPRINKLERS OPERATING, THE SUPPORT CABLES WERE HARD TO SEE. THE PLT'S BLOOD WAS CHECKED & AN ALCOHOL LEVEL OF 0.108% WAS FOUND. ALSO, THE PLT HAD A POSITIVE TEST FOR MARIJUANA.