Highbeam,
I agree with you one hundred percent that his issues are coming from the water table. But he also said it's not a daily problem, but something that comes and goes. Heavy rains raise the water table and increase hydralic preasure forcing it out through the point of least resistance.
There is a good chance that this is what's happening. We're just guessing, but if this is the case, than the water is still going to do this. Adding rock wont solve anything. Sand is better, but it will still be just a cover.
Since it's not a static level, but a variable one, this means the water table is below his footings. Draining it out will allow it to dry faster and cut down on soil saturation. When it rains, the water table rises and he has standing water. After things dry out, the water prolem is gone.
Your example of digging a hole and seeing where it fills is a good example of where the water table is at that time. He already has a very large hole in the ground, and it's dry most of the time.
What has me really curious is why would a builder go to all the additional expense in time, effort and material to build such a deep footing? How many more hours on a tractor do dig these footings and walls? How much more time in labor and materails to frame up the walls? Rebar, concrete and labor add up. Just guessing, but his foundation could easily cost 4 times as much to have built as a standard one.
Do homes require permits there? Was there a blueprint or soil study done? Some places in California require the footings to go down over 20 feet. Who signed off on the permits?
THERE IS A REASON for his footing being so deep. No builder with half a brain is gonna triple the amount of concrete he wants to put in the ground just to pay his crews extra money. The only way this makes sencse is the builder knows something we don't. Investorguy needs to find out what the builder knows and why it was built that way.
If you can't find the builder, find the inspector. Somebody made the builder do it this way, and somebody inspected it and signed off on it. Is there a local cement company? Start asking around when you see a crew pouring concrete. I bet this foundation is different enough that people will remember doing it.
Putting fill in there, either sand, rock or dirt, will aslo act as a sponge to some degree and keep moisture there allot longer. This will increase the saturation of the soil that the house sits on. This is bad. I think ther's a reason this wasn't done when the house was built. I do not think it was a mistake or an oversight. They dug the dirt out for a reason. It was sitting right there. If they wanted it back in there, they could have done that allot cheaper than hauling it off.
Another point to consider is why didnt' the builder just dig down the depth he had to go and pour the footings there. WHY DIG DOWN THE ENTIRE CRAWLSPACE?????
Idealy, I think he needs a perimiter drain to keep runnoff away from the house, and a drain in the bottom of the crawlspace to get the moisture out as imediately.
Eddie