While looking into swimming pool options, I got a copy of the 2004 soil report from Sigma Prime - originally created for the planning of the Tuscan villa that the prev. owners designed for the lot.
It suggests that a small fault is crossing the property way down in the meadow. Actually, the fact that it is somewhat green down there in the midst of an otherwise dried out grass meadow may confirm it: I read that the fault forces water from the clay uphill to rise. Of the 6 borings they did, only one (#4) came up with ground water present (at 2') and only one did not have Whiskey Hill formation (#5) as a 2-8 feet layer between rock and surface soil.
Later I learned from Ron Morris that WH fm was a big trouble maker due to its extreme expandability and unpredictable run. He used the term that it "serpentine'd" - that water saturation in places where it was covered/concealed by upper layers might cause the water to move to other places in the layer where it could cause swelling. So it sounds like you cannot just assume that water travels downhill when it is embedded in the clay layer.
Now all that is bad for planning new construction. As to the existing house, it has been sitting there since 1957, and it has only minor settling in the SW corner.
But I wonder: would it be an idea to make a well down near the fault where the water table is really close to the surface? The water could be used for irrigation.
I have contacted a couple of well drillers. One of them will come by next week.
I am a bit uneasy about the project though. I had thought it would be a simple digging of a 3-6 feet hole, securing the walls and then attaching some pump and piping. But according to the well driller, they would go down 200 feet and create a concrete walled well. Sounds like overkill relative to the use I had in mind. I wonder if there would be some other kind of specialist to consult?
Just to get a sense of my current water usage and how much of that goes into irrigation: My monthly usage with minimal irrigation (oct-mar/apr)is 10 ccf; irrigation starts kicking in around May, topping in August, with an avg. of 20 ccf/mo.
[10 ccf = 7480 gal)
