# ES 402 Assignment #3 26 Feb 97 by FyY11D7p

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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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