Piedmont and Blue Ridge

Crystalline rocks with glacial cover

Paleozoic history of southern Piedmont

From Hatcher

http://geoweb.gg.utk.edu/Geology/Faculty/Hatcher/Hatcher.html

Metamorphic and igneous rock

Sandstone and diabase in rift basins

Limestone

Piedmont

Chimney rock

Blue Ridge Province

flow through fractures

Transition

Fractured metamorphic

and igneous rock

Saprolite

Gneiss, schist bedrock

Granite or other intrusive bedrock

Distinct transition

Gradational transition

Storage and transmission

properties

High porosity

Sy?

porosity

Low storage

10-5 10-4 cm/s

Saprolite sampled at different depths. Measure density and chemical composition.

S.G. decreases from 2.1 in rock to 1.6 in shallow saprolite. S.G. decreases as minerals are altered and mass is removed. 0.5 gm/cc removed during weathering.

Chemical concentrations indicate S.G. change largely due to weathering of feldspar to kaolinite as a two-stage reaction.

PorositySpecific

yieldK

cm/sec

Granitic Gneiss 0.015 0.007 3.47E-08

Mica Schist 0.028 0.017 1.74E-09

Hornblende-feldspar gneiss 0.007 0 1.74E-09

Quartzite 0.022 0.012 1.39E-09

Amphibolite 0.02 0.017 1.39E-09

Laboratory determinations of properties of crystalline rocks.

from Randall and others 1966

Saprolite thickness

Typically 50 ft, but variable 10-100 ft

w.t. 20-60 ft bgs

Frx zones in valleys

Flat-lying frx

Saprolite thickness

Greatest over valley or highland? Could be either

Ground watersheds

Open Hole

Multi-level completion

Important: Exception to the Conceptual Model

Specific capacity

Well Performance and Lineaments

Lineaments

Effects of lineaments on well yields in the Piedmont

Other effects of location on well yield

Factor of 2 to 7 difference in yield

Factors from 3 to 25 between valley

and hill

Well yields in different rock types and regions in

the Piedmont

15-30 gpm typical

Roughly 20 gpm

Effects of well depth and diameter on yield in the Piedmont. Based on Daniels

Glaciated crystalline rocks in northern

Appalachians

Other Hydrogeologic Settings in the Piedmont

     Stockton Fm.      Lockatong Fm.      Passaic Fm.      Orange Mt. Basalt      Feltville Fm.      Preakness Basalt      Towaco Fm.      Hook Mt. Basalt      Boonton Fm.      Conglomerates      Palisade sill

Newark Basin, NJ

Mesozoic Basins• Sandstone aquifers• Shale confining unitsRedbeds in the Hartford Basin, Conn

Conglomerate

Basalt

Arkose

Carbonate rock aquifers

Water Chemistry Reminder

• Major Cations: Na+, K+, Ca2+, Mg2+

• Major Anions: HCO3-, Cl-,SO4

2-

• TDS: Total Dissolved SolidsMCL= 500 mg/l Values: Fresh < 1000 mg/l; brackish 1000-10,000; saline; 10,000-100,000 mg/lSeawater: 35,000 mg/l

• Hardness: Ca and Mg scaled to Ca on a meq basis– Soft water < 60 mg/l total hardness– Use water softener= 80-100 mg/l– Very hard >150 mg/l

Milliequivalent

• Charges/volumes

Conc mgmillimol

e valence charge meq millimole charge

literMole weight mg liter

Water quality in Crystalline Rock aquifers

Crystalline rock Triassic BasinCarbonate rock

meq/L

Crystalline Rock

Triassic Basins

Carbonate Aquifers

SC, GA, Al =100 Mgpd