EPA On-line Tools for Site Assessment Calculation

Transport and Leaching from a Release of Fresh Fuel

One Dimensional Transport Equation

This calculator generates a breakthrough curve^* at a receptor and uses a one-dimensional model to determine the

First arrival time for a contaminant (above a specified threshold concentration),
Maximum Concentration, and
Duration of Contaminantion above the specified threshold

^*The breakthrough curve is the time history of concentration at a receptor located a specified distance from the contaminant source.

Example breakthrough curve.

See bottom of page for equations solved.>

Inputs

Site Name

Date
Distance Unit

Time Unit

Chemical

Example Fuel

Solubility (S) mg/L

Optional Revised Solubility (S) mg/L

Porosity

Water Saturation Fraction of the pore space filled with water

NAPL Saturatio Fraction of the pore space filled with NAPL

Fraction Organic Carbon

Lens diameter

Smear zone thickness

Recharge rate

Soil type

Hydraulic Conductivity (K)

Gradient (absolute value) (−i)

Distance (x)

Halflife T _1/2

Year Month Day

Beginning Date

Min. Concentration of Concern mg/L mg/l

Default Parameters

Fuel composition note:

Average Molecular Weight of Fuel (MW _o )

Percent Mass Fraction

Intermediate Results

Effective Solubility (C _w ) mg/L

Bulk Density(ρ _B )

Hydraulic Conductivity (K)

Seepage Velocity (q _s = v)

Retardation factor (R)

Estimated dispersivity α

Beginning Time of Breakthrough Curve

First Arrival

Breakthrough Curve Through Maximum Concentration

Mid Point

Additional Point

Maximum

Completion of Breakthrough Curve (for Pulse Sources)

Additional Point

Mid Point

Ending

Duration Above Threshold

Advective Travel Time

Advective Travel Time

First arrival time is earlier than the advective travel time

Ratio advective to first arrival time

One Dimensional Transport Equation

One-dimensional transport equation

R = retardation factor []
D = dispersion constant [L2/T]
v = seepage velocity [L/T]
μ = first order decay constant [1/T]

with the initial and boundary conditions

retardation factor R = 1 + ρ _b k _d /θ

R = retardation factor
ρ _b = bulk density = ρ _s (1-θ)
ρ _s = solids density
θ = porosity
k _d = (soil) distribution coefficient = f _{o c} K _{o c}
f _{o c} = fraction organic carbon
K _{o c} = organic carbon/water partition coefficient

travel time t _{t r} = x R / q _s

t _{t r} = advective travel time^*
q _s = seepage velocity
R = retardation factor
x = distance
^* assuming one-dimensional, steady flow, constant gradient

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