Lab 8 Complete
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School
University of Houston *
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Course
2301
Subject
Geology
Date
Dec 6, 2023
Type
Pages
4
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Student Name: __________________________
GEOL1403
– Lab #8 (Groundwater)
Figure on next page shows a geologic cross-section of layers/formation under the town you live in. This
morning you overheard on the news that a local factory reported an ongoing significant leak from one of their
underground storage tanks. The leaked substance, according to the preliminary reports, is Ethylene Dibromide
(Dibromoethane). Subsequent monitoring confirmed the presence of Ethylene Dibromide plume (red color) in the
aquifer. Examine the figure and use your knowledge from Chapter 11 (Groundwater) to answer the following
questions. You can also search online for information, but always express the answers in your own words.
Explanation of Issues:
1)
Is there a reason to be concerned about human exposure to Ethylene Dibromide? Explain.
2)
What
two factors
affect groundwater
velocity
? Briefly define/describe each factor.
3)
Why is cleaning of heavily contaminated groundwater usually not practical for towns or municipalities?
Analysis:
4)
What geologic formation (layer) contains the
unconfined
aquifer?
____________________________
5)
What geologic formation (layer) contains the
confined
aquifer?
______________________________
6)
What geologic formations are the
confining layers
of the confined aquifer?
_____________________
_____________________
7)
In Figure 1 label the following
a.
Flow of groundwater
in the confined aquifer (use arrows)
b.
Flow of groundwater
in the unconfined aquifer (use arrows)
c.
Recharge
(use letter R) and
discharge area
of the confined aquifer (use letter D)
8)
What can you deduce about the
density
of the pollutant plume (see figure), based on its position within
the saturated zone of the aquifer? Explain and justify your answer.
Student Name: __________________________
Answer
question 7
directly into
this figure
Student Name: __________________________
Evaluation:
9)
The leading edge of the contaminant plume has been located
0.21 miles
away from the current town water
well. Assuming the flow rate of groundwater in Terry Sandstone to be
0.83 ft/day
, when should you expect
the town well to get contaminated?
Express your answer in years!
Show all your work. Hint: 1 mile =
5280 ft, 1 year = 365 days.
10)
The factory where the leak occurred alleges that the leak has been going for a of couple of years only.
Can you convincingly show that may not be telling the truth? Estimate how long the leak must have been
going on.
Express your answer in years!
Hints: 1 mile = 5280 ft, 1 year = 365 days. Use the same flow
rate (0.83 ft/day) as in the previous question. The distance scale is at the bottom of the figure to help you
with this question.
11)
Is it safe to assume that (for the most part) the contaminant plume will remain inside the Terry
Sandstone? Why yes or why not? Make sure your answer is well reasoned and supported by evidence.
Synthesis:
The town has decided to be proactive and drill a new well to draw drinking water from. 5 different drilling
companies put in a bid for the contract, but each of them proposed their well in a different location (labeled
Proposed Well A, B, C, D and E in the figure). No one in the mayor’s office took geology in college and therefore
have no idea how to choose the best location for the new well. Finally, you are also asked the evaluate the rough
cost of each well, knowing that the cost of the well depends on how many feet are drilled.
Hint: Look at the
“Anatomy of a well” sketch in the figure and keep in mind that a well only takes in water through the well screen.)
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Student Name: __________________________
12)
Answer the following questions with
Yes or No
to help the mayor make the right decision.
Proposed
Well
Would this well provide
a reliable supply of
water to the town?
Is this well safe (long term)
from the contaminant
plume discussed above?
Rate the cost to drill the
well from 1 (cheapest) to
5 (most expensive)
A
B
C
D
E
Conclusions and related outcomes
13)
Best on your answers in the table above, the best candidates for the new well are _______ and ________.
14)
After you narrowed the well locations down to two, the town came back and told you they would wont to
keep the future pumping costs down, and would like the new well to be “
free flowing
”, meaning it is
providing water without pumping. Which one of the two choices you already made satisfies this condition
and what do we call this type of well?
15)
A developer is proposing a new suburban development (with fantastic views) in the Precinct Mountains.
The town has yet to vote on the proposal, but once again, they have asked you for your opinion. Does it
make sense to protect the Precinct Mountain from development and potential sources pollution? Justify
your answer!