There's no limestone anywhere near Crabtree Valley as this whole region has a bedrock of metamorphic nature, mostly gneisses and schists and then to the east of this is a granite pluton. I'm afraid the only ground water flowing through these rocks is just that which happens to pass through the many fissures in this otherwise solid bedrock - not a bad source at all when Raleigh was much smaller and at one time had numerous wells and water towers too, but the potential supply of ground water here today is no match for the needs of the present expansion since then.
Limestone?
Here is a generalized geologic map of North Carolina:
http://geology.about.com/library/bl/maps/n_statemap_NC2000.htm
There's no limestone anywhere near Crabtree Valley as this whole region has a bedrock of metamorphic nature, mostly gneisses and schists and then to the east of this is a granite pluton. I'm afraid the only ground water flowing through these rocks is just that which happens to pass through the many fissures in this otherwise solid bedrock - not a bad source at all when Raleigh was much smaller and at one time had numerous wells and water towers too, but the potential supply of ground water here today is no match for the needs of the present expansion since then.