CE 473/573 Groundwater
Fall 2012
Homework 10
Due December 5
57. A well is placed in a confined aquifer with thickness 8 m, storativity 3 × 10−5 , and
hydraulic conductivity 4 × 10−4 m/s. The well starts pumping at 500 gpm.
a. Plot the drawdown as a function of time (for one day) at an observation well 250
m away.
b. Plot the drawdown as a function of distance from the well 6 hours after the well
starts pumping.
*58. A confined aquifer of thickness 30 m is pumped at a rate of 150 L/s from a well of
radius 0.3 m. The drawdowns measured 100 m away at 100, 1000, 104 , 105 , and 2×105
seconds are 4.02, 123.6, 366.4, 627.6, and 705 cm, respectively.
a. Determine the aquifer’s storativity, transmissivity, and hydraulic conductivity.
b. Use the Jacob approximation to determine the storativity, transmissivity, and
hydraulic conductivity of the aquifer. Compare to the answers in part a.
*59. An unconfined aquifer is pumped at 0.08 m3 /s The aquifer has an initial saturated
thickness of 30 m, a horizontal hydraulic conductivity of 1.3 × 10−3 m/s, a vertical
hydraulic conductivity of 3 × 10−5 m/s, a storativity of 2 × 10−3 , and a specific yield
of 0.03. An observation well is 88 m away.
a. What is the drawdown 0.1 hours after the pumping starts?
b. When will the drawdown be 0.25 m?
*59. Consider the effect of Γ = r 2 Kv /b2 Kh on the drawdown caused by unsteady flow to
a well in an unconfined aquifer.
a. As Γ increases, does the drawdown become larger or smaller? Explain your
answer.
b. For which value of Γ does the behavior approach that for a confined aquifer?
Explain your answer.
60. Leaking gasoline tanks are a source of the BTEX compounds: benzene, toluene, ethylbenzene, and xylene. Rank them in order of increasing solute velocity if all experience
the same average linear velocity of groundwater flow.
*61. Approximate half-lives for the benzene, toluene, ethylbenzene, and xylene are 300, 20,
120, and 190 days, respectively. The EPA maximum contaminant levels for these compounds are 5, 1000, 700, and 10, 000 µg/L, respectively. Suppose the concentrations
of all four in a leaking tank is 30 mg/L and use an average linear velocity of 2 m/d,
a bulk density of 2 g/cm3 , a soil organic fraction of 0.5%, and an effective porosity of
22%.
a. Compute the plume lengths assuming steady flow and no dispersion.
b. Compute the plume lengths assuming steady flow. Include dispersion.
c. Compute the plume lengths after 1, 5, 10, 50, and 100 years.
d. Compare the estimates from parts a, b, and c.
e. Estimate the ratios of the terms in the full transport equation. Explain how these
ratios indicate the important processes in the transport of the four compounds.
62. To prepare for exam 2, solve problem 1 of 2007 exam 2. Ignore the reference to
problem 36.
63. To prepare for exam 2, solve problem 2 of 2007 exam 2. Change the reference to
problem 28 of HW 5 to problem 40.
64. To prepare for exam 2, solve problem 3 of 2007 exam 2.
65. To prepare for exam 2, solve problem 4 of 2007 exam 2.
66. To prepare for exam 2, solve problem 2 of the 2007 final exam.
67. To prepare for exam 2, solve problem 3 of the 2007 final exam.
68. To prepare for exam 2, solve problem 1 of 2008 exam 2.
69. To prepare for exam 2, solve problem 2 of 2008 exam 2.
70. To prepare for exam 2, solve problem 3 of 2008 exam 2.
71. To prepare for exam 2, solve problem 4 of 2008 exam 2.
72. To prepare for exam 2, solve problem 1 of 2009 exam 2.
73. To prepare for exam 2, solve problem 2 of 2009 exam 2.
74. To prepare for exam 2, solve problem 3 of 2009 exam 2.
75. To prepare for exam 2, solve problem 4 of 2009 exam 2.
76. To prepare for exam 2, solve problem 3 of the 2009 final exam.
77. To prepare for exam 2, solve problem 2 of 2010 exam 2.
78. To prepare for exam 2, solve problem 3 of 2010 exam 2.
79. To prepare for exam 2, solve problem 4 of 2010 exam 2.
80. To prepare for exam 2, solve problem 1 of 2011 exam 2.
81. To prepare for exam 2, solve problem 2 of 2011 exam 2.
82. To prepare for exam 2, solve problem 3 of 2011 exam 2.
83. To prepare for the final exam, solve problem 1 of the 2007 final exam.
84. To prepare for the final exam, solve problem 4 of the 2007 final exam.
85. To prepare for the final exam, solve problem 2 of the 2008 final exam.
86. To prepare for the final exam, solve problem 3 of the 2008 final exam.
87. To prepare for the final exam, solve problem 2 of the 2009 final exam.
88. To prepare for the final exam, solve problem 4 of the 2009 final exam.
89. To prepare for the final exam, solve problem 5 of the 2009 final exam.
90. To prepare for the final exam, solve problem 1 of 2010 exam 2.
91. To prepare for the final exam, solve problem 1 of the 2010 final exam.
92. To prepare for the final exam, solve problem 2 of the 2010 final exam.
93. To prepare for the final exam, solve problem 3 of the 2010 final exam.
94. To prepare for the final exam, solve problem 4 of the 2010 final exam.
95. To prepare for the final exam, solve problem 2 of the 2011 final exam.
96. To prepare for the final exam, solve problem 3 of the 2011 final exam.
97. To prepare for the final exam, solve problem 4 of the 2011 final exam.