ENVIRONMENTAL ENGINEERING ( Practice Questions) a). Suppose a well 0.36m in diameter has been pumped at a rate of 3,000cu.m/day for a long enough time that steady-state conditions apply. An observation well located 30m from the pumped well has been drawn down by 1.0m, and another well at 120m is drawn down by 0.4m. The pumped well extends completely through an unconfined aquifer 60.0m thick. GIVEN: For an unconconfined aquifer, Q = πK(h2c1 – h2c2) / [Ln(r1 / r2)] Determine the hydraulic conductivity, K. (7 marks) (ii) Estimate the drawdown at the pumped well. State any assumptions made. b). A confined aquifer 40.0 m thick has two monitoring wells spaced 400m apart along the direction of groundwater flow. The difference in water level in the wells is 4.0m (the difference in piezometric head). The hydraulic conductivity is 40m/day. Estimate the rate of flow per meter of distance perpendicular to the flow. C). Suppose the aquifer, which has a porosity of 0.25, becomes contaminated and the up-gradient well is used as a monitoring well, whose purpose is to provide early detection of the approaching contaminant plume. How long after the monitoring well is contaminated would the drinking water from the second well become contaminated. State any assumptions made.
ENVIRONMENTAL ENGINEERING ( Practice Questions)
a). Suppose a well 0.36m in diameter has been pumped at a rate of 3,000cu.m/day for a long enough time that steady-state conditions apply. An observation well located 30m from the pumped well has been drawn down by 1.0m, and another well at 120m is drawn down by 0.4m. The pumped well extends completely through an unconfined aquifer 60.0m thick.
GIVEN: For an unconconfined aquifer, Q = πK(h2c1 – h2c2) / [Ln(r1 / r2)]
- Determine the hydraulic conductivity, K. (7 marks)
(ii) Estimate the drawdown at the pumped well. State any assumptions made.
b). A confined aquifer 40.0 m thick has two monitoring wells spaced 400m apart along the direction of groundwater flow. The difference in water level in the wells is 4.0m (the difference in piezometric head). The hydraulic conductivity is 40m/day. Estimate the rate of flow per meter of distance perpendicular to the flow.
C). Suppose the aquifer, which has a porosity of 0.25, becomes contaminated and the up-gradient well is used as a monitoring well, whose purpose is to provide early detection of the approaching contaminant plume. How long after the monitoring well is contaminated would the drinking water from the second well become contaminated. State any assumptions made.
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