Self-study
P1
A major problem facing industrial societies is their exponentially increasing production of toxic waste. █████████████ ███████████ ███ ████████ ███ █████████ ███ ████████████ ████ █████████ █████████████ ██ ██████ ██████ ███
Main Problem ·
Toxic waste disposal
Solution ·
Deep well injection
Details of Solution ·
Details of deep well injection
Waste injected into rock layers, out of reach of underground drinking water (aquifers)
problem ·
Three problems with deep well injection
P2
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Problem 1 ·
Wells can still leak into aquifers, polluting drinking water
Problem 2 ·
Human error can cause wells to fail
Example of human error threatening drinking water supply
P3
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Problem 3 ·
Very difficult to predict how waste will flow underground
P4
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Reiteration of 3 problems ·
Uncertainty of flow (problem 3), mechanical failure (problem 1), human error (problem 2)
Passage Style
Problem-analysis
Single position
7.
Based on the passage, which ███ ██ ███ █████████ ████ ██████████ █████████ ███ █████ ███████████████ ██ ██ ███████████ ████ ████████ ███ ███ █████████ █████████ ██ █████████ ███████
Question Type
Implied
We’re looking for an answer that describes the ideal conditions for deep-well injection of hazardous wastes. Let’s keep in mind the risks identified by such injection. We can anticipate that the correct answer might be one that best helps minimize these risks. We might also need to keep in mind the potential cost of the injection site, as cost-effectiveness is something that industries consider when determining whether to use deep-well injection.
a
At 300 meters ██ ████ █████ ███ ████████ ███ ████ ████████ █ █████ ██ ███████████ ████ █████ █████ █████ ███ ██ █████████ ███████
This isn’t ideal, because we want to protect drinking water from contamination. The drinking water would typically be above areas in which waste is injected, so we want an impermeable layer above the area in which waste is injected. It doesn’t matter whether there aren’t any permeable layers below the impermeable rock. We want impermeable rock between the drinking water and the area in which waste is injected.
b
At 300 meters ██ ████ █████ ███ ████████ ███ ████ ████████ █ █████ ██ █████████ ████ █████ █████ █████ ██ █ █████ ██ ███████████ █████
We’re told that “under the best conditions,” wastes are injected into areas with salt water and “
c
The area contains ███ ██ ████ ██████ ██ ███████████ ████ █████████ ████ ████ ███ ███████ ██ █ █████ ██ ██ █████ ███ ███████
We want to protect drinking water from waste, so we want an impermeable layer above the waste and below the drinking water. (C) doesn’t describe a layer of impermeable rock below drinking water and above the area in which waste is injected. In addition, deep-well injection does require
d
At a depth ██ ███ ██████ ██ █████ ███ ████ ████████ ██ ███████ ████ █████ █████ ██████
A depth of 300 meters or less isn’t ideal, because
e
The area contains █ █████ ██ ███████████ ████ ████████ ██ █ █████ ██ █████████ ████ ██ █ █████ ██ █████ ██████ ██ █████
A depth of 1,800 meters or more isn’t ideal, because this is the depth at which