Writing prompt Grade 8 English Language Arts
Explaining Bellwether Shoals' Earthy Tap Water Taste
A grade 8 informative writing prompt in which students draft the bill insert a fictional utility sends when late-summer algae leave the tap water tasting earthy.
Objectives
- Students will explain a cause chain in order, from nutrients to bloom to taste.
- Students will define technical terms in plain words for a non-technical audience.
- Students will distinguish a taste problem from a health problem in writing.
Vocabulary
- Algal bloom
- An algal bloom is a fast, thick growth of algae that can turn a lake green and scummy. Blooms happen when the water gets lots of nutrients and warm sunshine, and some blooms make toxins.
- Activated carbon
- Activated carbon is a special charcoal full of microscopic holes that grab and hold chemicals as water flows past. It is the same material used in many home water filter pitchers.
Also: geosmin, nutrients, intake
Teacher overview
Taste and odor complaints put a utility in an awkward position, because the honest answer is that the water is safe and that something is genuinely different about it. That combination makes a good informative writing task, since a student who reaches for reassurance alone will not have explained anything. This prompt gives students a fictional town, a cause chain with three linked steps, and an audience of residents who have already picked up the phone. The exemplar and rubric reward writers who keep the explanation in order and define their terms rather than writers who simply insist the water is fine.
Prompt
Background: Bellwether Shoals is a fictional town that takes its drinking water from Copperloch Reservoir. Every year in late August, residents call the water department to report that the tap water tastes and smells earthy, like a freshly dug garden or a damp basement. The water looks the same as always, and the tests come back the same as always.
Here is what causes it. Lawn fertilizer, farm fields, and septic systems around the reservoir send small amounts of nitrogen and phosphorus into the water all summer. Those two elements are nutrients, meaning they feed growth. When the reservoir warms in August, the nutrients feed a heavy growth of algae and related bacteria near the surface, which is called an algal bloom. Some of those organisms release a compound named geosmin. Geosmin is the same compound that gives soil its smell after rain. The human nose detects it at very small concentrations, far below any level that could affect a person's health.
Chlorine does not remove geosmin, so the plant's usual treatment leaves the taste in place. The fictional utility has two tools. It adds powdered activated carbon at the plant, which works like a sponge with an enormous surface, holding the geosmin so it can be filtered out. Carbon costs money, and the plant uses more of it during a bloom. The utility can also lower its intake pipe to draw from deeper, cooler water where the bloom is thinner. Neither tool removes every trace, so the taste usually fades over a few weeks rather than overnight.
The department also tests for the toxins that some blooms can produce. In this fictional town, those tests have come back with nothing detected every year the reservoir has been sampled. The taste itself is not a health problem, and the water meets every standard the state sets.
Writing task: Write the one-page insert that will go out with the September water bill in Bellwether Shoals. Your readers are residents, and many of them have already called to ask whether the water is safe. Your insert must explain the cause in order, from nutrients to bloom to taste; define "geosmin" and one other technical term in plain words where you first use them; explain why the water is safe to drink; describe what the utility is doing about the taste; and close by telling readers what they can do. Write to inform, not to persuade, and do not tell readers how to feel.
Planning Organizer
Fill in every row before you draft. Each row matches one line of the rubric.
| Category | Your notes |
|---|---|
| Audience and purpose (who reads this, and what do they need from it) | |
| Cause chain step 1: where the nutrients come from | |
| Cause chain step 2: what the warm water and nutrients do | |
| Cause chain step 3: how that reaches the tap | |
| Term 1: geosmin, defined in plain words | |
| Term 2: your choice, defined in plain words | |
| Why the water is safe to drink | |
| What the utility is doing | |
| What readers can do, and your closing line |
From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.
Exemplar & Rubric
Exemplar response:
Why Your Water Tastes Earthy This Month
If your tap water has smelled or tasted like damp soil in the past few weeks, you are not the only resident who has noticed it, because the water department has received calls from across town. This insert explains what causes the taste, why the water is still safe, and what we are doing about it.
The cause begins on land. Fertilizer from lawns, runoff from farm fields, and older septic systems all send small amounts of nitrogen and phosphorus into Copperloch Reservoir through the summer. Those two elements are called nutrients because they feed plant growth, in a reservoir just as in a garden. When the reservoir warms in August, the nutrients feed a heavy growth of algae near the surface, called an algal bloom. Some of the organisms in that bloom release a compound named geosmin. Geosmin is the chemical that gives freshly turned soil its smell, and the human nose is unusually good at detecting it. People notice geosmin at amounts far below anything that could affect health, which is why water that passes every test can still taste like a garden.
That is the part worth repeating. Geosmin changes how water tastes and smells. It does not make water unsafe. Our results have met every state standard this year, and our tests for the toxins that some blooms can produce have detected none.
We are treating the taste in two ways. At the plant we add powdered activated carbon, which acts like a sponge with an enormous surface and holds the geosmin so our filters can remove it. We use more carbon during a bloom, which is the main added cost of an August like this one. We have also lowered our intake pipe, the opening that draws water out of the reservoir, so we pull from deeper and cooler water where the bloom is thinner. Neither step catches every trace, so expect the taste to fade over a few weeks rather than in a day.
Residents can help in two ways. Keeping fertilizer off driveways and away from the shoreline keeps nutrients out of the reservoir, and reporting a failing septic system early keeps the same nutrients out of the groundwater that reaches it. If you would like to know more, our reservoir sampling results are posted at the town office and on the department's page.
Rubric:
| Criterion | Emerging | Developing | Proficient | Advanced |
|---|---|---|---|---|
| Cause chain | Names the taste without explaining a cause | States one cause with the steps out of order or incomplete | States all three steps in order, from nutrients to bloom to taste | States all three steps in order and shows how each step depends on the one before it |
| Precise language and defined terms | Uses technical words without defining them, or avoids them entirely | Defines one term, or defines a term inaccurately | Defines geosmin and one other term accurately in plain words at first use | Defines both terms accurately and chooses wording a resident could repeat to a neighbor |
| Safety explanation | Does not address safety, or claims safety with no reason | Says the water is safe without connecting it to the evidence given | Explains that geosmin changes taste rather than safety and cites the testing | Explains the distinction and anticipates the follow-up question a caller would ask next |
| Organization for the audience | No clear order; reads as scattered notes | Some order, but the reader must hunt for the answer to the main question | Clear sections, an opening that names the purpose, and a closing with reader actions | Clear sections and transitions that carry the reader from cause to response to action without repeating |
| Conventions | Errors block meaning | Errors are frequent and noticeable | Few errors; sentences are varied | Nearly error-free, with sentence variety that suits a public notice |
Differentiation
Support
Give these students the cause chain as three sentence starters in the correct order, such as "The cause begins on land, where ___," and allow the insert to run four paragraphs instead of five. Provide a definition of geosmin they may adapt rather than compose from nothing.
Extension
Ask students to write a second, much shorter version of the same insert for a printed door hanger of no more than eighty words, then to write a paragraph explaining which details they cut and why a door hanger reader needs less than a bill reader does.
ELL supports
Pre-teach "nutrient," "bloom," "intake," and "carbon" with a simple cross-section drawing of the fictional reservoir showing the warm surface layer, the bloom, and the intake pipe at two depths. Allow the Planning Organizer to be completed in short phrases or in a first language before drafting in English, and provide a word bank of sequence transitions.