If it was a boatyard, particularly one used for repair or rebuilding older boats, they’d probably have a process for every repair job. As each boat came in, it would be one team’s job to remove all the old ballast, and they’d probably have their own “spot” for doing it, near the area of the beach where the boats were pulled out of the water (so they didn’t have to move the now very-bouyant and difficult to control hull all that far to get it beached), but not where it would be a hazard to boats being re-launched.
I don't think ISO 9000 is that old :-) The process would be controlled by a specific master that happened to do the work, and those masters would be changing as lifespans back then were not that great.
The monument, which is made off large boulders, has the shape of a cone and an estimated weight of around 60,000 tons.
I doubt they needed much ballast for the boats that they were building. Those would be probably Egyptian type boats made from reed and other local stuff. Not particularly Titanic-like. So let's say each boat had 100 kg of ballast in it. 60,000 tons then yields 600,000 boats. That's probably more than the total number of boats built since Noah's time anywhere on Earth.
The local economy wouldn't need that many boats, so if we assume that they were indeed built there it had to take centuries, if not millennia. However why would the dumping location be so well preserved across all that time and hundreds of generations of boat builders? They had no GPS to know where to dump stones, and they had no particularly good reason to do it at one point. If you have a facility on shore then you'd be dumping ballast in an arc, not at a single point - that would have to be triangulated from onshore markers. It's a lot of work. Also people are not stupid; they would have started dumping rocks as close to the shore as possible, and only after a few close calls with incoming boats they would grudgingly move the dumping point a bit farther - but not before they used up the entire arc. On top of that, why would you go out of your way to create an artificial reef that *is* a danger for heavier boats? The top of the mound is only 5 feet below the surface. I'd buy it if it was done by an apprentice, in one afternoon and without oversight - an impossibility, of course.
There is yet another issue. The mound is built out of "basalt boulders up to 1 m (3.2 feet) long." Ok, take one of these and put it into a reed boat. What will happen? It will break the bottom of the boat because it is too dense - and too large anyway. If you want a ballast, you'd use gravel that is sewn into bags and spread along the bottom, to even the pressure out.
But there is yet another issue. Why would a shipbuilder discard the ballast? Ballast is used in new boats too. If you unload it and sink, where do you get a new one? I guess there are stones around, but why would you go for miles to nearest hills, using expensive equines and a cart, and get stone if you can reuse the old one that sits right next to the boat, just where you left it? Or maybe the boat is sitting on ballast - you need to raise it to work on it. I cannot imagine an irrational hatred toward perfectly peaceful blocks of stone, to the extent that thousands of shipbuilders took time to cart them away in boats and sink them over one very specific place.
The pointy tip of the mound indicates that last stones were thrown very accurately and with good grouping. This is hard to do from a boat, looking into a dark water. This means that the mound was assembled on land, where the tip was clearly visible to anyone - but only the strongest could climb up there and deposit the load. Weaker workers (or believers?) would leave the stones pretty far from the tip. The profile of the mound even shows from what direction the delivery was occurring (from the right, in the plane of the drawing.) The opposite end was formed by the stones that fell over all by themselves because it is too steep for climbing. The offset of the tip shows that contributors were coming from at least 270° of the circle.
I would be thinking it’s there to cover over something you don’t want dug up.