Environmental Modeling Community of Practice

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. 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.
	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 3/8^th 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

EPA On-line Tools for Site Assessment Calculation

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

Pulse Source Model Example 1

Scaled Gradient Example 1

Scaled Gradient Example 2

Scaled Gradient Example 3