Reading Comprehension

PT158 · S1 · P1 · Q7 Deep Well Injection

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A major problem facing industrial societies is their exponentially increasing production of toxic waste.

Topic

The risks and problems associated with deep-well injection as a method for hazardous waste disposal in industrial societies.

Framework

Problem / Solution

Main Point

Although deep-well injection is increasingly used to dispose of hazardous waste due to cost and regulatory pressures, it poses significant risks—including mechanical failure, human error, and unpredictable underground movement of waste—that make it a problematic and potentially dangerous solution. Most Valuable Sentence: Last paragraph:

P1: Introduction to Deep-Well Injection and Its Controversy

This paragraph introduces the growing problem of toxic waste in industrial societies, describes how regulations and costs have led to the increased use of deep-well injection for hazardous-waste disposal, and notes that this method is controversial, especially as more people depend on underground water sources. It ends by foreshadowing that there are three key problems with this method.

P2: Mechanical Failures and Human Error

Here, the passage explains the first two major problems: wells can leak, allowing dangerous chemicals into drinking water sources, and human error (like faulty well construction) can have dire consequences. Example: a well with a casing gap almost contaminated water for 100,000 people, and such issues might go unnoticed for a long time.

P3: Unpredictable Movement of Underground Waste

This paragraph details the third problem: it’s extremely difficult to predict how wastes will move underground due to complex, variable pressure gradients. Wastewater can travel in any direction, sometimes over great distances, making containment unpredictable.

7.

Based on the passage, which one of the following most accurately describes the ideal characteristics of an underground area suitable for the deep-well injection of hazardous wastes?

  1. At 300 meters or more

    Below is Not a Concern

    We inject the waste at a minimum depth of 300m, because we're trying to make sure it's beneath any of our precious water supplies, which are found above that. So it doesn't really matter to the author if the rock below the injection site is impermeable, because the author isn't really worried about waste leaking down into the Earth's mantle. She's worried about it leaking up into our precious aquifers.

    19% picked this

  2. Correct

    At 300 meters or more

    Why this is right

    We inject the waste at a minimum depth of 300m, because we're trying to make sure it's beneath any of our precious water supplies, which are found above that. So if the rock above the injection site is impermeable, then there's no way for the waste to leak up and get into the aquifers above. This answer is similar to what's being described in the first sentence of the 2nd paragraph. The other fact we need to understand it is in the middle of the 1st paragraph: wells are drilled to a minimum depth of 300 meters -- the minimum depth that generally puts the injected waste as a safe distance below any aquifer.

    Skill tested: Application · how this choice captures the passage's function is the move to repeat next time.

    58% picked this

  3. The area contains one or

    Everything is Impermeable

    This one is tricky. Whether something is permeable or impermeable refers to whether or not it's completely solid, or whether liquid can pass through it (and essentially be stored in it). The first sentence of the 2nd paragraph is saying that we inject the waste into rock strata that is saturated with salt water. If we're injecting into rock strata that is saturated with salt water, then we're injecting into permeable rock. This makes some common sense. If we drilled into solid rock, then we would only be able to dump our liquid waste into that column we've drilled. But if we drill down into a permeable layer of rock strata, we can dump a lot more waste in there, because it will seep into all the nooks and crannies of that rock strata (mixing with the salt water). So this answer choice is describing an area with lots and lots of impermeable rock, and the problem is we need a permeable strata in order for it to hold a bunch of our liquid waste, but we need that permeable strata walled off from other things so that it doesn't leak and ooze into other strata where we don't want waste.

    15% picked this

  4. At a depth of 300

    Opposite, if anything

    We're normally injecting waste at a minimum depth of 300m because generally water is always found above that. But this answer is talking about water that is below 300m, putting it at greater risk of getting tainted by leakage from the waste well.

    4% picked this

  5. The area contains a layer

    Too Deep

    We're told near the end of the 1st paragraph that "wells are rarely deeper than 1800 meters, because it's too expensive". So this answer seems to be talking about what's going on below 1800 meters, which is too deep for affordable drilling, so not an ideal area.

    5% picked this

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