Lobster:
Sounds like the springs are formed from overpressured groundwater escaping through relatively higher permeability zones caused by a sandy zone in the shale (path of least resistance). Remember the aquifer is producing the sum flow of springs (was it 36 gpm) and is probably capable of much more. The fact that the springs all produce 12 gpm is more likely due to the relatively uniform hydraulic properties of the sandy zone in the shale, which is leaking water to the surface rather than the actual confined aquifer. The maximum flow possible is controlled by the cross sectional area of the confined aquifer and the head created by the elevation difference between the upland area and your location. If the aquifer is not the limiting factor, your actual flow is dependent on the diameter of the well and it's placement. The help of a professional is advisable for the best results and to make sure that you do not adversely affect other wells or ponds in your area. If I was working on your project, the first thing I would do is obtain water well records from the health department, which would probably give you a good idea of the thickness of the confining unit, the confined aquifer, and the difference in hydraulic head between the upland source area and your location. Get records from all these locations with several from your surrounding area. Best of all, the records will only cost you a few hours of your time and some copying charges. You might be able to get significant flow with the right well installed correctly. Sounds like you have a pretty good handle on it, hope that helps.
