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Lesson plan Grade 11 Social Studies & Civics

Trading Nitrogen on the Quarrington: Permits, Farms, and Credits

A grade 11 lesson on why the Clean Water Act permits point sources but not farm runoff, using a fictional nutrient credit trade priced by students.

Objectives

  1. Students will explain why the Clean Water Act permits point sources while farm runoff is largely unpermitted.
  2. Students will calculate the cost of meeting a nitrogen limit by plant upgrade and by purchased credits.
  3. Students will identify who bears the legal risk when an unpermitted party supplies a credit.

Vocabulary

Key words: point source, nonpoint source, nutrient credit, trading ratio, discharge permit

Teacher overview

The Clean Water Act built its permit system around pipes, so a treatment plant that discharges into a river holds an enforceable permit while the fields upstream generally do not. When a state caps the nitrogen a river may receive, that asymmetry produces an odd result: the party with the permit must pay for reductions that are cheaper to achieve on land it does not own. Students price that trade for a fictional plant and county, then decide who is accountable when the cheaper reduction fails. The misconception to name at the start is the assumption that farm runoff is unregulated because nobody has noticed it; the exemption is a design choice written into the statute, and trading programs are one attempt to work around it.

Procedure

Hook (5 min): Show two photographs or sketches, one of a discharge pipe and one of a plowed field beside a creek, and ask students which one a federal inspector can cite for a violation. Take answers, then state that the pipe is a point source with a permit and the field usually is not.

Direct instruction (12 min): Explain the permit structure. A point source discharges from a discrete conveyance and needs a permit with numeric limits. Runoff from farm fields is treated as a nonpoint source and is addressed mainly through voluntary programs and state plans. Introduce the water quality problem: nitrogen feeds algae, algae decay consumes oxygen, and most fish need dissolved oxygen above 5 mg/L. Explain that a state may cap the total nitrogen a river receives and divide that cap among sources.

Modeled example (8 min): Work one trade on the board using numbers the students will not see again. In a fictional basin, a plant must cut 4,000 pounds of nitrogen a year. Upgrading the plant costs $20 for each pound removed each year. Farm practices in the same basin cost $6 for each pound reduced each year, and the state requires 2 pounds of farm reduction for every 1 pound of credit. Show that the plant route costs $80,000, that covering the cut through trading requires 8,000 pounds of farm reduction at a cost of $48,000, and that the difference is $32,000. Ask what the doubled ratio is for, and establish that it discounts an unmeasured reduction against a metered one.

Handout work (20 min): Students complete the eight items on the handout in pairs, with one partner computing and the other checking. Circulate and require pairs to state the units on every answer.

Closing discussion (10 min): Trace the loop on the board. Fertilizer and treated effluent add nitrogen to the river, algae growth lowers dissolved oxygen, the state responds with a cap, the cap changes what farmers plant in the fall and what the plant builds, and those changes alter the river again. Then take the accountability question from item 8 and ask which party a court could actually reach.

Formative check and exit ticket (5 min): Each student writes one sentence naming the strongest reason to allow trading and one sentence naming the strongest reason to refuse it. Collect and sort into three piles before the next class: both reasons sound, one sound, neither. If more than a quarter of the cards land in the third pile, reteach the permit asymmetry with the handout numbers.

Trading Nitrogen on the Quarrington: Permits, Farms, and Credits — Grade 11 Social Studies & Civics
Name: ____________________________ Date: ______________

Student Handout

The situation (fictional). The town of Ashby Fen operates the Ashby Fen Water Reclamation Facility, which discharges to the Quarrington River under a state permit. The state has capped nitrogen in the basin, and the plant's share of the cut is 18,000 pounds a year. Farms in Weddell County upstream can reduce nitrogen through cover crops and streamside buffers, and they hold no discharge permit. The state's fictional trading rule requires 2 pounds of verified farm reduction for every 1 pound of credit the plant may claim.

  1. The plant must cut 18,000 pounds of nitrogen a year, and upgrading the plant costs $34 for each pound removed each year. What does meeting the whole cut at the plant cost per year?
  2. The trading rule requires 2 pounds of farm reduction for every 1 pound of credit. How many pounds of farm reduction must the plant buy to cover 18,000 pounds?
  3. Farm practices cost $9 for each pound reduced each year. Using your answer to item 2, what does the plant pay the farms per year?
  4. Compare your answers to items 1 and 3. How much does the plant save per year by trading?
  5. The plant claims 18,000 pounds of credit and pays the amount you found in item 3. What is the effective cost of each pound of credit?
  6. At the 2-for-1 ratio, the plant is indifferent between trading and upgrading when the two routes cost the same. Upgrading costs $34 per pound. What farm price per pound makes the two routes equal?
  7. Suppose the state raises the ratio to 3 pounds of farm reduction for every 1 pound of credit, and farm practices still cost $9 per pound. What does the plant pay per year to cover the same 18,000 pounds?
  8. The plant holds an enforceable permit and the farms do not. If a farm plows its buffer strip in year three and the reduction stops, who is legally accountable for the shortfall?

From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.

Answer Key
  1. Answer: $612,000 per year. 18,000 pounds times $34 per pound equals $612,000.
  2. Answer: 36,000 pounds. The rule requires 2 pounds of farm reduction per pound of credit, and 18,000 times 2 equals 36,000.
  3. Answer: $324,000 per year. 36,000 pounds times $9 per pound equals $324,000.
  4. Answer: $288,000 per year. $612,000 minus $324,000 equals $288,000, so trading costs a little more than half as much as upgrading.
  5. Answer: $18 per pound of credit. $324,000 divided by 18,000 pounds of credit equals $18, which is also the farm price of $9 doubled by the 2-for-1 ratio.
  6. Answer: $17 per pound. At the 2-for-1 ratio the plant pays twice the farm price per pound of credit, so the routes are equal when 2 times the farm price equals $34, giving $17.
  7. Answer: $486,000 per year. The plant must buy 3 times 18,000, or 54,000 pounds of farm reduction, and 54,000 times $9 equals $486,000. Trading still costs less than the $612,000 plant route, though the margin narrows.
  8. Answer: The plant, because the permit obligation stays with the permit holder. The farm has no permit and no federal discharge limit to violate, so the state enforces against the plant, which then has only its contract with the farm to fall back on. Accept answers naming the plant and identifying the contract as the plant's only remedy.

Differentiation

Support

Give students a partially completed cost table for this fictional program with the pounds column filled in, so items 1 through 4 require only the multiplication and the subtraction. Provide the ratio rule restated as a sentence beside item 2.

Extension

Have students find the ratio at which trading in this fictional program stops saving money at a farm price of $9 per pound, then write two sentences explaining why a state might set a ratio that high even though it ends trading.

ELL supports

Pre-teach "point source," "nonpoint source," "credit," and "ratio" with a labeled sketch showing a pipe, a field, and an arrow into the river. Provide the frame "The plant pays ___ per pound of credit because the ratio is ___, which is ___ than the ___ per pound it would pay to upgrade."

Extensions

Students compare this fictional program with a real state nutrient trading program described on a state environmental agency website, listing which features appear in both and which appear only in the real program.