HW#1 - Head Calculations, Darcy's Law

1. A piezometer is placed in the ground at a site. The screen on the piezometer is at a depth of 266.5 ft. The elevation of the ground surface where the piezometer is located is 3049.0 ft above mean sea level. The pore pressure measured by the piezometer is 52.7 psi. Assume that sea level is the datum. At the location of the piezometer screen:

a) What is the elevation head? [ft]

b) What is the pressure head? [ft]

c) What is the total head? [ft]

2. A flow path computed from a particle tracking analysis is shown below.  Point A represents a potential spill location. Water travels from the river to point A along the path shown.  The length of the flow path is approximately 500 ft.  The aquifer has a relatively uniform thickness.  The water table elevation of point A is 1284 ft.  Estimate the travel time (in days) from point A to the river.


3. At a site owned by Company X, it is decided to remediate a plume using a double trench system as shown below.  A plume lies between the two trenches in a sand layer that is capped by a relatively impermeable clay layer.  Nutrient and oxygen laden water will be injected in the trench on the right.  The water will flush from right to left and be pumped out of the left trench.  To ensure maximum biodegradation, it is best if the sand layer stays saturated.  Thus, the trench on the left will be pumped just enough to keep the sand layer saturated.  The trench on the right will be kept as full as possible.  For the sand layer, assume than n = 0.35 and k = 0.01 cm/s.

a)  For a one ft thick slice of the sand layer, how much water would need to be pumped to flush through one pore volume?

b)  How long would it take (in days) to pump five pore volumes of water through the sand?


Submittal Instructions

Do your calculations in Excel.  Show as much of your work as you can.

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