At the end of the day I have it two/thirds done. Will finish it easily in the morning because the thickest part is done.
Putting plastic on it should help to keep it from drying out. I hauled between 50 and 80 gallons of sand up out of the arroyo to get this much done. I think I can finish with another 20-25 gallons. I carry half a 5-gallon bucket out at a time, then dump it into the wheelbarrow and roll it to the site. I don't keep a tally of the gallons, but usually use 15 to 20 gallons per batch mixed. So I not only don't remember how many gallons, but I don't remember how many batches I mixed either. That's why my estimate spans such a large gap.