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EPA On-line Tools for Site Assessment Calculation


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Alternate form of access to OnSite examples, as required by the US EPA Office of Environmental Information

Pulse Source Model Example 1

Purpose How to set up the pulse source model.
Summary of Approach The contaminant source releases mass into the aquifer at a constant concentration for a known duration.
Boundary condition illustration.

The source concentration and duration are entered along with aquifer transport parameters.
Data Distance Unit ft Most commonly used distance unit in U.S.
Time Unit days Times expressed in days.
porosity 0.25 Estimated effective porosity for sandy aquifer.
Fraction organic carbon 0.0001 Assumed low fraction of organic carbon aquifer.
Hydraulic Conductivity 10 ft/day Assumed input value.
Gradient 0.002 Assumed gradient.
Distance (from source to receptor) 250 ft Assumed distance from source to receptor.
Concentration distribution illustration.
Half Life 730 days Two year half life.
Source Concentration 10 mg/L Assumed constant source concentration for the duration of the pulse.
Beginning Date October 3, 1998 Beginning date of the pulse.
Ending Date December 13, 1999 Ending date of the pulse.
Results Hydraulic Conductivity 10 ft/day Same as input as no unit conversion was requested.
Seepage velocity 0.80 ft/day Velocited associated with contaminant movement.
Retardation Factor 1.07 Calculated retardation factor for benzene.
Longitudinal Dispersivity 13.0 ft Estimated longitudinal dispersivity for 250 ft distance.
Source Duration 436.0 days Difference in days between beginning and ending dates.
Advective Travel Time 3331 days Advective travel time to receptor at 250 feet from source.
Advective Travel Date November 17, 2007 Date associated with advective travel time.
Concentration 1.80 mg/L Estimated concentration at selected distance (250 feet) on the advective travel date.
Additional Concentrations Time Concentration Additional times to better view transport of pulse.
2500 0.18 Decreasing concentrations with time (pulse has passed location).
3000 0.15
5500 0.091

Scaled Gradient Example 1

Purpose Example one shows how to use distances directly, without scaling from a map.
Summary of Approach Measurement Units and Map Units are both set to one foot.

The distance between the wells is then entered directly using the selected "Map Unit."
Data Wells 200 ft apart
Heads 20 ft upgradient
19 ft down gradient
Results Gradient - 0.005

Scaled Gradient Example 2

Purpose Example two illustrates use of the map scale with differing measurement and map units.
Summary of Approach The map has a scale of one inch to 100 feet.

The distance between the wells is then entered as the number of inches between the wells.
Data Measurement Units 1 in
Map Units 100 ft
Distance Between Wells 20 in apart
Head Unit ft
Heads 20 ft upgradient
19 ft down gradient
Results Distance Between Wells 2000 ft
Gradient - 0.0005

Scaled Gradient Example 3

Purpose Example two illustrates use of the map scale with differing measurement and map units. Map measurements using fractional inches.
Summary of Approach The map has a scale of one and 3/8th inches to 100 feet.

The distance between the wells is then entered as the number of inches between the wells.
Data Measurement Units 1 3/8 in
Map Units 100 ft
Distance Between Wells 20 7/8 in
Head Unit ft
Heads 20 ft upgradient
19 ft down gradient
Results Distance Between Wells 1520 ft
Gradient - 0.00065
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