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ES 402 Assignment #3 Due 17 & 18th Mar 2008 (Part 1(a) due on the 17th at the beginning of class; the rest on the 18th, in lab) 1. (3 pt) Darcy’s Law and hydraulic conductivity: Hand in completed copies of Tables 1-4 from lab #6. Use the measurements made in Lab. Exercises #6 and 7 to answer the following questions: (a) Calculate the average hydraulic conductivity for the sample or samples you analyzed in labs #6 and 7. Refer to Fig. 11.4 and 11.6 in your textbook to answer these questions: Are the results reasonable? Would an aquifer 50 m thick (i.e., its vertical dimension) made of either the sand or the gravel from Lab #6 provide a useful source for a well? What about the gravel-sand mixtures you tested? (b) Prepare an ORAL PRESENTATION on Darcy’s Law for lab on March 18th. Your team’s presentation should take about 10 minutes. Use of visual aids is preferred – I can make transparencies for you but need 2 days advanced notice. Give a general introduction to Darcy’s Law and cover the results of BOTH Labs #6 and 7. Discuss the material from (a), including the hydraulic conductivities and Reynolds numbers estimated for each material used. How did your team measure the hydraulic conductivities for the materials in the groundwater model (Lab #7) and what were the results? How did they compare to the measurements from Lab #6? What experiment did your team perform on the aquifer model and what were the results? 2. (1 pt) You have been asked to investigate a confined aquifer that has been used for several years for a municipal well. The well is pumped at a constant rate of 695 L/minute. You supervise the installation of 2 piezometer tubes, one 10 m and the other 50 m from the well. The potentiometric heads in the piezometers are measured as 30 and 30.8 m, respectively, and are unchanged 2 and 4 days later. Use these data to determine the transmissivity of the aquifer. What assumptions do you need to make? If the aquifer is 100 m thick, what is its average hydraulic conductivity? How would you rate this well’s potential for municipal water supply? 3. (1 pt) A test well is drilled through the full thickness of a confined aquifer, 20 feet. The aquifer is horizontal, homogenous and isotropic, with K = 25 ft/day and S (coefficient of storage or storativity) of 0.0004. The test well is pumped at a constant rate of 30,000 ft3/day for 2 days. What would be the drawdown of the potentiometric surface in a piezometer 100 ft from the test well after one hour? At the end of the 2 days of pumping?
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