Introduction%20to%20Ground%20Water%20Flow%20and%20Contamination

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Introduction to Ground Water Flow and
Contamination

• Philip B. Bedient
• Rice University, Houston, TX

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Vertical Distribution of GW
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Vertical Zones of Subsurface Water

• Soil water zone extends from the ground surface
  down through the major root zone, varies with
  soil type and vegetation but is usually a few
  feet in thickness
• Vadose zone (unsaturated zone) extends from the
  surface to the water table through the root zone,
  intermediate zone, and the capillary zone
• Capillary zone extends from the water table up
  to the limit of capillary rise, which varies
  inversely with the pore size of the soil and
  directly with the surface tension

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Porosity

Water
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Soil Classification Based on Particle Size(after
Morris and Johnson)
Material Particle Size, mm
Clay lt0.004
Silt 0.004 - 0.062
Very fine sand 0.062 - 0.125
Fine sand 0.125 - 0.25
Medium sand 0.25 - 0.5
Coarse sand 0.5 - 1.0
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Darcys Law
V - K dh/dl Q - KA dh/dl
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Aquifer Systems
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Ground Water Use in the U.S.A.
Waste Sites
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U.S. Ground Water Regions
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Contamination and Remediation

• Advective transport
• Diffusion and dispersion
• Volatilization
• Adsorption
• Biodegradation processes
• Chemical Reaction
• NAPLs
• Remediation Processes

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Sources of Contamination

• Industrial spills and leaks
• Surface impoundments
• Storage tanks and pipes
• Landfills
• Burial areas and dumps
• Injection wells

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Areas of Industrial Contamination

• Surface soils
• Subsurface soils
• Shallow ground water
• Deep ground water
• Vapors above water table
• Drinking water wells
• Receiving streams/lakes

Shallow
Deep
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Contamination of Ground Water
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Typical Leaking UST - BTEX
Tank
Floats on water table
Soluble Plume
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Typical DNAPL Spill Zone
Sinks to lower layer
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DNAPL Our Most Difficult Challenge

• DNAPL source
• Residual phase
• Trapped on lenses
• Pools in low areas
• Creates soluble plumes for years
• Extremely hard to remediate

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Typical Industrial Site
Source

• Buried fuel tanks
• Above ground chem tanks
• Ponds and Impoundments
• Buried drums (older)
• Landfill area (hidden)
• Waste process area
• Receiving streams/lakes
• Nearby residential area

Plume
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Typical Contaminated Site
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Objectives of a Field Site Study
Monitoring Well Location

• Evaluate
• Surface soils
• Subsurface soils
• Shallow ground water
• Deep ground water
• Vapors in subsurface
• Drinking water wells
• Receiving streams/lakes

Contour Lines
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AMOCO REFINERY
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AMOCO REFINERY
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AMOCO REFINERY
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AMOCO REFINERY
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3D-View Topography Max Benzene Tanks
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The Major Aquifers of Texas
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The Edwards Group
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Chlorinated Solvents
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Chlorinated Solvents (cont)
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BTEX-Related Compounds