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
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Purpose
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How to set up the pulse source model. |
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Summary of Approach
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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. |
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Data
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Distance Unit |
ft |
Most commonly used distance unit in U.S. |
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Time Unit |
days |
Times expressed in days. |
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porosity |
0.25 |
Estimated effective porosity for sandy aquifer. |
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Fraction organic carbon |
0.0001 |
Assumed low fraction of organic carbon aquifer. |
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Hydraulic Conductivity |
10 ft/day |
Assumed input value. |
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Gradient |
0.002 |
Assumed gradient. |
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Distance (from source to receptor) |
250 ft |
Assumed distance from source to receptor.
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Half Life |
730 days |
Two year half life. |
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Source Concentration |
10 mg/L |
Assumed constant source concentration for the duration of the pulse. |
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Beginning Date |
October 3, 1998 |
Beginning date of the pulse. |
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Ending Date |
December 13, 1999 |
Ending date of the pulse. |
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Results
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Hydraulic Conductivity |
10 ft/day |
Same as input as no unit conversion was requested. |
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Seepage velocity |
0.80 ft/day |
Velocited associated with contaminant movement. |
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Retardation Factor |
1.07 |
Calculated retardation factor for benzene. |
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Longitudinal Dispersivity |
13.0 ft |
Estimated longitudinal dispersivity for 250 ft distance. |
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Source Duration |
436.0 days |
Difference in days between beginning and ending dates. |
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Advective Travel Time |
3331 days |
Advective travel time to receptor at 250 feet from source. |
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Advective Travel Date |
November 17, 2007 |
Date associated with advective travel time. |
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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. |
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2500 |
0.18 |
Decreasing concentrations with time (pulse has passed location). |
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3000 |
0.15 |
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5500 |
0.091 |
Scaled Gradient Example 1
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Purpose
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Example one shows how to use distances directly, without scaling from a map. |
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Summary of Approach
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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." |
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Data
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Wells |
200 ft apart |
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Heads |
20 ft upgradient |
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19 ft down gradient |
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Results
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Gradient |
- 0.005 |
Scaled Gradient Example 2
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Purpose
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Example two illustrates use of the map scale with differing measurement and map units. |
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Summary of Approach
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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. |
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Data
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Measurement Units |
1 in |
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Map Units |
100 ft |
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Distance Between Wells |
20 in apart |
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Head Unit |
ft |
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Heads |
20 ft upgradient |
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19 ft down gradient |
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Results
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Distance Between Wells |
2000 ft |
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Gradient |
- 0.0005 |
Scaled Gradient Example 3
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Purpose
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Example two illustrates use of the map scale with differing measurement and map units. Map measurements using fractional inches. |
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Summary of Approach
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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. |
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Data
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Measurement Units |
1 3/8 in |
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Map Units |
100 ft |
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Distance Between Wells |
20 7/8 in |
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Head Unit |
ft |
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Heads |
20 ft upgradient |
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19 ft down gradient |
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Results
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Distance Between Wells |
1520 ft |
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Gradient |
- 0.00065 |
