[ApplegateRanch]

water from 970 feet down has been filtered by 970 feet of ground

Actually, no. The aquifer is beneath impervious layers. It is filtered by about 40-50 miles of rock, between the well site, and the recharge zone.

The tilt of the beds means that the cap is missing in the recharge area; not that the aquifer layer itself is exposed.

First, the surface water has to percolate down to the aquifer, doing a first-filtration.

Next it spends several years slowly moving, mainly by osmotic pressure, through the miles of fine-grained filtration to the well site.

A few PPM of dissolved minerals, but that's it. The bacteria of surface water rarely get past the first 10-20 feet of surface & sub soils.

[GeronL]

do I have to pay for that lesson Professor? =o)