Modeling Natural Attenuation with BIOSCREEN GROUNDWATER SERVICES INC

Modeling Natural Attenuation with BIOSCREEN GROUNDWATER SERVICES, INC.

BIOSCREEN Natural Attenuation Model Objectives How Far Will Plume Migrate? How Long Will Plume Be There? ? ?

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

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

Air Force Natural Attenuation Initiative Products Protocol Technical Field Data Modeling Tools

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

Source Term Configuration Location: Downstream of Affected Soil Zone Concentration th d i W Depth

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

Where to Get BIOSCREEN EPA Center for Subsurface Modeling Support (R. S. Kerr Lab) Web: http: //www. epa. gov/ada/bioscreen. html Phone (405) 436 8718