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Lesson plan Grade 7 Social Studies & Civics

Farriday's Boil-Water Notice: Who Gets Told First

A grade 7 civics lesson in which students study how a fictional water department must notify customers under a boil-water notice, then compute the percentages and costs.

Objectives

  1. Students will explain why a water utility is required to notify customers when water may be unsafe.
  2. Students will calculate what percent of affected customers each notification method reaches.
  3. Students will evaluate which notification methods reach people the others miss.

Vocabulary

Pressure zone
A pressure zone is a section of a water system that a utility manages separately because it sits at a different elevation than the rest of the town. Utilities create pressure zones so that water pressure stays safe and steady for everyone, whether they live at the bottom of a hill or near the top.
Water main
A big underground pipe that carries drinking water beneath the streets to a neighborhood. Smaller service lines branch off it to reach each building.

Also: boil-water notice, public notification, service area

Teacher overview

When pressure in a water main drops far enough, dirty water can be pulled into the pipe through cracks and joints, so state rules require the utility to tell affected customers to boil their water before drinking it. The demanding part of that rule is the notifying rather than the boiling, because the utility has a fixed number of hours to reach every affected account and no single method reaches everyone. This lesson puts students inside the fictional town of Farriday, where a broken main forces a notice on one pressure zone and the water department has to work through three notification methods in order. A misconception worth correcting directly is that sending one automated phone call counts as notifying the public; students will see in the arithmetic that the first method leaves a large share of accounts untouched.

Procedure

Hook (5 min): Post this question and take answers without commenting: "If your town had to tell 3,000 households something urgent about their water in the next 24 hours, how would it reach all of them?" Write the methods students name on the board, then keep the list visible for the rest of the lesson.

Direct instruction (12 min): Explain the rule behind the scenario. Distribution systems normally run at 40 to 80 psi, and most states require at least 20 psi so that contaminated water cannot be drawn into a pipe. When pressure falls below that floor, the utility issues a boil-water notice to the affected area and must notify those customers within a set number of hours. Introduce the fictional town of Farriday and its water department, which serves 12,000 accounts across four pressure zones, and describe the break that drops pressure in one zone. Name the three methods the department uses in order: an automated phone call, a text message, and a door hanger delivered by a crew.

Guided example (10 min): Model one calculation on the board using a different zone than the one on the handout. Suppose a notice covered 2,000 accounts and the automated call reached 1,500 of them. Work through 1,500 divided by 2,000 as a decimal and then as a percent, and ask students what the remaining 25 percent means in practical terms for the crew that has to go door to door. Do not work any handout item; students need those to be new.

Independent work (20 min): Students complete the eight items on the student handout. Circulate and check that students are dividing by the number of accounts under the notice, not by all 12,000 accounts, on items 2 and 3. This is the most common error in the set.

Closure and exit ticket (8 min): Collect the handout and ask each student to answer one question on an index card: "Name one group of Farriday residents that all three notification methods could still miss, and say why." Read the cards before the next class. If fewer than two thirds of the cards name a specific group with a reason, such as renters whose account is in a landlord's name or households where nobody is home during delivery hours, discuss the exit-ticket question as a class at the start of the next period.

Farriday's Boil-Water Notice: Who Gets Told First — Grade 7 Social Studies & Civics
Name: ____________________________ Date: ______________

Student Handout

The fictional Farriday Water Department serves 12,000 accounts. A broken main drops pressure in one pressure zone below the 20 psi floor, so the department issues a boil-water notice for that zone. The zone contains 3,000 accounts. The department notifies customers in three steps: an automated phone call, then a text message, then door hangers delivered by a crew. State rules give the department 24 hours to reach every account under the notice.

  1. The notice covers 3,000 of Farriday's 12,000 accounts. What percent of all accounts are under the notice?
  2. In the first hour the automated phone call reaches 1,800 of the 3,000 accounts under the notice. What percent of the affected accounts is that?
  3. Text messages reach another 600 of the affected accounts. What percent of the 3,000 affected accounts have now been reached by phone or text?
  4. A crew delivers a door hanger to every affected account not yet reached by phone or text. How many door hangers does the crew need?
  5. Each door hanger costs the fictional department $3 to print and deliver. What is the total cost of the door hangers?
  6. The phone calls and texts went out at hour 1. Door hanger delivery took 10 more hours. How many hours of the 24-hour limit were left when the last door hanger was delivered?
  7. A coffee shop in Farriday sold 400 cups of coffee during the notice, down from 500 cups the same week before. What was the percent decrease?
  8. Some Farriday residents do not answer calls from numbers they do not know and do not read door hangers. Name one other method the department could use, and explain why it would reach people the first three methods missed.

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: 25 percent.
    3,000 divided by 12,000 equals 0.25, which is 25 percent of all accounts.

  2. Answer: 60 percent.
    1,800 divided by 3,000 equals 0.60, which is 60 percent of the accounts under the notice. Students who divide by 12,000 and get 15 percent have used the wrong whole.

  3. Answer: 80 percent.
    1,800 plus 600 equals 2,400 accounts reached. 2,400 divided by 3,000 equals 0.80, which is 80 percent.

  4. Answer: 600 door hangers.
    3,000 accounts under the notice minus 2,400 already reached leaves 600 accounts needing a door hanger.

  5. Answer: $1,800.
    600 door hangers times $3 each equals $1,800.

  6. Answer: 13 hours.
    The calls went out at hour 1 and delivery took 10 more hours, finishing at hour 11. 24 minus 11 leaves 13 hours.

  7. Answer: 20 percent.
    500 minus 400 equals 100 fewer cups. 100 divided by 500 equals 0.20, which is a 20 percent decrease.

  8. Answer: Answers will vary. Reasonable answers name a method and the gap it fills: a sign posted at the entrance to the zone reaches people who are out during delivery hours; a notice on local radio or a news site reaches renters whose account is in a landlord's name; a knock on the door reaches households that never look at a hanger. Credit any method paired with a specific group it would reach.

Differentiation

Support

Give these students a handout with the division already set up for items 1 through 3, so that item 1 reads "3,000 divided by 12,000 equals ___" and the student supplies the decimal and the percent. Provide a reminder card showing that 0.25 equals 25 percent. Allow a calculator throughout, and let items 7 and 8 be answered orally.

Extension

Ask students to design a notification plan for the same fictional zone under a tighter deadline of 8 hours instead of 24. They should state how many crews are needed, in what order the methods run, and what the plan costs at the same $3 per door hanger, then explain which part of their plan is most likely to fail.

ELL supports

Pre-teach "boil-water notice," "pressure zone," "account," and "door hanger" with a labeled drawing showing a street, a broken pipe, and a hanger on a doorknob. Provide a reference card listing the three fictional quantities students need most, which are 12,000 total accounts, 3,000 accounts under the notice, and $3 per door hanger. Allow item 8 to be answered in short phrases, and supply the frame "A ___ would reach people who ___."

Extensions

Have students find the public notification page on their own utility's website or in its annual water quality report and list the methods it says it will use. They can then compare that list with the three methods the fictional Farriday department used and write one sentence naming a method their own utility has that Farriday did not.