1. Modeling Natural Attenuation with GROUNDWATER SERVICES, INC.
BIOSCREEN
GROUNDWATER SERVICES, INC.

2. ? ? Objectives BIOSCREEN Natural Attenuation Model
 How Far Will Plume Migrate?
 How Long Will Plume Be There? ? ?

3. Groundwater Transport Modeling
Groundwater Transport Processes
Groundwater Transport Modeling
All groundwater transport models are based on the advective-dispersive-reactive equations.
rate of change in HC conc. at any point
net rate of advective transport to that point
net rate of dispersive transport to that point
net rate of degradation at that point = + -
Transport at time t with dispersion & degradation
Transport at time t advection only
Transport at time t with dispersion

4. Fate and Transport Modeling Options
GOAL: Predict steady-state NAF between source and receptor.
Types of Models:
• 1-D vs. 2-D vs. 3-D Advection
• 1-D vs. 2-D vs. 3-D Dispersion
• Deterministic vs. Statistical
• Numerical vs. Analytical
• Transient vs. Steady State
• Constant Source vs. Changing Source

5. Products Air Force Natural Attenuation Initiative
 Technical Protocol
 Field Data
 Modeling Tools

6. Transport: Groundwater in Source Zone Groundwater at Receptor
Concentration at Downgradient Distance x Away from Source
First-Order Decay Constant
Groundwater
Source Width and Depth
Conc (x) = {
1/ 2 } [ ( ) ] [ ] [ ] x
4  x Sw Sd
exp
1 -
1 +
erf
erf
2 x
Vs/R
4 y x
4 z x
Retardation
Coefficient
Error
Function
Transverse
Dispersivity
Vertical
Dispersivity
Longitudinal Dispersivity
Hydraulic
Conductivity
Groundwater Seepage Velocity
Hydraulic Gradient
K i
Vs =
Effective Soil Porosity ne

7. Location: Downstream of Affected Soil Zone
Source Term Configuration
Location: Downstream of Affected Soil Zone
Concentration
Width
Depth

8. BIOSCREEN Model: Other Features
 Single Vertical
Plane Source
 Superimposed Sources
(Connor et al., 1995)
Source 1
Source 2
Source 3

9. Where to Get BIOSCREEN
EPA Center for Subsurface Modeling Support (R. S. Kerr Lab)
 Web:
 Phone (405)