A SEVERE THUNDERSTORM DROPPED 2.04 INCHES OF RAIN OVER A 2 HOUR PERIOD. WATER RUNOFF BUILT UP ON A SPOIL DUMP. IT EVENTUALLY BREACHED THE DUMP BERM, AND FLOWED DOWN INTO THE COAL PIT ACCESS RA MP. THE 24K MOTORGRADER HAD ENTERED THE PIT (WITH 2' OF WATER IN THE BOTTOM) TO PICK UP THE COAL SHOVEL OPERATOR. AS THEY WERE EXITING THE PIT, WATER ENGULFED THE GRADER. TWO EE'S WERE RESCUE