GroundWater Movement and Discharge into Rottenwood Creek

1
Ground-Water Movement and Discharge into
Rottenwood Creek

• November 6, 2007
• Georgia Water Science Center

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Presentation Objectives

• Discuss the geologic controls for off-site
  ground-water movement in AFP-6 area
• Present trends and most recent diffusion sampling
  results for Rottenwood Creek and tributaries
• Baseflow measurements (Aug-07)
• Recommendations for future monitoring

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Location
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GW Contamination at AFP-6

• Chlorinated solvents, acids, lubricants, oils,
  paints, hydrocarbons and other chemicals have
  been used in Aircraft production and repair
• Trichloroethene (TCE) is the principal
  contaminant of concern

Southern Poly U
B4
Life College
B90
B10
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Typical Piedmont Aquifer Model

• Fracture controlled
• Weathered rock, saprolite, alluvium
• Bedrock
• Recharge from above

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Major Controls on Ground Water Movement in
Igneous and Metamorphic Rocks

• Rock type
• Structure
• Topography
• Depth of weathering
• Nature and extent of recharge area

II
IV
III
I-B
I
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Influence of Geologic Structures

• Joints and fractures enhance the permeability
• Parallel partings enhance permeability
• Combination of the two gives you a network of
  fractures

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Lithologic Units
q
IV

• I biotite schist cross-mica biotite gniess
  pegmatite
• I-B amp
• II biotite gneiss and amphibolite
• III biotite schist pegmatite
• IV orange gneiss
• V granite

III
peg
V
I-B
I
II
III
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Lithologic and StructuralControl

• Regolith
• Variable weathering
• Foliation/Layering
• NE-SW Strike
• Dip SE
• Joints
• Dip joints
• Strike joints

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SCT1
regolith
transition zone
80 flow
PWR

• Located on flood plain
• Casing to 85
• 605 deep
• 70 gal/min
• Most of yield from transition zone
• Parting planes

p
jnts
p
bedrock
p
p
p
P parting plane
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SCT1- Transition Zone

• Strikes northeast-southwest
• Dips to southeast

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SCT1- Single Joint

• Strikes NW-SE
• Dips 66 degrees to SW
• cross-joints

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SCT1 - Pegmatite
schist

• Overall fabric is NE-SW
• Schist (dark) in contact with pegmatite sill
  (coarse)

parting
pegmatite
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SCT1- Parting

• Parting at contact between pegmatite and biotite
  gneiss/schist

parting
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SCT1 Deep partings

• Set of parallel partings

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SCT2 Weathered Zones

• Weathered rock
• Strike NE-SW
• Dip to SE

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Bedrock Potentiometric Surface 2004
MWOS-02R
From CH2Mhill 2005
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TCE (2004)
From Seve Mahar 2004
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TCE 2006
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TCE (2006)
DRAFT
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Contaminant Movement (TCE)
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Diffusion Sampler TCE Results 2000
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Diffusion Sampler TCE Results 2001
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Diffusion Sampler TCE Results 2002
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Diffusion Sampler TCE Results 2007
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Seepage Measurement Locations
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Seepage Results
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Aquifer Test

• Drawdown greater parallel to layering than
  perpendicular to it
• Down dip responses
• Demonstrates influence of geologic structure

Down dip response
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Drawdown Near Pumping (RW203)

• Greatest drawdown appears to extend NE-SW
  expanding out parallel to rock layering