The concept is simple. 
At 0640 hours on Saturday, we will start a race around the 4.166667 mile Big Trail. 
The time limit will be one hour.
At 0740 hours, we will begin another race around the trail.
We will do the same at 0840, 0940, and so on, 
every hour,
until only one runner can complete a race within the time limit.
Any runner not in the starting corral for any race, is not eligible to continue.
No late starts!
If no single runner can complete a race at the end, 
there will be no winner.