A 100,000 liter underground storage tank (UST) has leaked its entire contents into the surrounding subsurface. A portion of the spill remained hung up in the vadose zone due to negative pressures (matric potential), while the remaining amount came to float on top of the water table (groundwater surface) which is more than 10 meters below ground. Show a graphic that depicts this situation and complete the following calculations. Provide graphic depictions and annotated calculations to supporting your response as necessary. a) Several weeks after the event, contaminant geohydrologist investigators determined that at least some part of the spill was contained in a volume of soil in the vadose zone with approximate rectangular top and sides measuring 3 meters wide by 20 meters long at the ground surface, by 6 meters deep (measured from the visibly affected ground surface area). This volume contained gasoline suspended immobile in the vadose soil pores due to negative pore pressure conditions and surface tension. Using the 5% rule, what volume of gasoline (in liters) would be suspended in the vadose zone? Show your calculations and explain your assumptions. b) Based on your answer to a), how much gasoline might be expected to have reached the groundwater table likely to be found floating on the groundwater table surface 4 meters below the affected vadose zone? State the assumptions inherent in your calculation.
A 100,000 liter underground storage tank (UST) has leaked its entire contents into the surrounding subsurface. A portion of the spill remained hung up in the vadose zone due to negative pressures (matric potential), while the remaining amount came to float on top of the water table (groundwater surface) which is more than 10 meters below ground. Show a graphic that depicts this situation and complete the following calculations. Provide graphic depictions and annotated calculations to supporting your response as necessary.
a) Several weeks after the event, contaminant geohydrologist investigators determined that at least some part of the spill was contained in a volume of soil in the vadose zone with approximate rectangular top and sides measuring 3 meters wide by 20 meters long at the ground surface, by 6 meters deep (measured from the visibly affected ground surface area). This volume contained gasoline suspended immobile in the vadose soil pores due to negative pore pressure conditions and surface tension. Using the 5% rule, what volume of gasoline (in liters) would be suspended in the vadose zone? Show your calculations and explain your assumptions.
b) Based on your answer to a), how much gasoline might be expected to have reached the groundwater table likely to be found floating on the groundwater table surface 4 meters below the affected vadose zone? State the assumptions inherent in your calculation.
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