Lesson plan Grade 6 Engineering & Design

Wrenfield Lead Service Line Replacement Plan Lesson

A grade 6 engineering lesson where students design a phased plan to replace a town's lead service lines on a deadline and budget, then check it with rate and percent.

Grade: Grade 6
Subject: Engineering & Design
Material: Lesson plan
Time: 55 min
Prep: Low prep
Materials: Printed student handout, Chart paper, Markers

Standards

MS-ETS1-1 NGSS

Define the criteria and constraints of a design problem with sufficient precision to ensure a successful solution, taking into account relevant scientific principles and potential impacts on people and the natural environment that may limit possible solutions.

How this material aligns: Students state the criteria and constraints of the replacement plan, the ten-year deadline, the town budget, and the lead level target, in the procedure and handout, exactly the problem-defining work this standard requires.

All materials for MS-ETS1-1 →

6.RP.A.3 Common Core Math

Use ratio and rate reasoning to solve real-world and mathematical problems, e.g., by reasoning about tables of equivalent ratios, tape diagrams, double number line diagrams, or equations, including finding a percent of a quantity and converting measurement units.

How this material aligns: Handout questions 1, 2, and 5 use rate and percent reasoning to find lines per year and the share of the total already replaced, the ratio reasoning this standard targets.

All materials for 6.RP.A.3 →

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This material is in the public domain (CC0) and may be copied, edited, and shared freely, without attribution. Updated 2026-07-23.

Objectives

Students will define the criteria and constraints of a lead service line replacement plan.
Students will calculate a yearly replacement rate and check whether a plan meets a deadline and budget.

Vocabulary

Lead service line: A lead service line is an old water pipe made of lead metal that connects a house to the water main. Lead can get into the drinking water, so these pipes are being dug up and replaced across the country.
Action level: A trigger number in lead and copper testing. If too many homes test above this level, the utility must take steps like improving treatment and telling the public.

Also: parts per billion, phased plan

Teacher overview

Old water pipes made of lead can add lead to drinking water, which is why utilities are replacing lead service lines. Under the federal Lead and Copper Rule Improvements, the lead action level is 15 ppb and drops to 10 ppb in 2027, and systems must replace nearly all lead service lines within 10 years. EPA's health-based goal for lead in drinking water is zero, so the action level is a trigger for utility action, not a safe level. EPA estimates that about 4 million lead service lines remain across the country. This lesson frames that work as an engineering problem with a deadline, a budget, and an action-level target.

Students design a phased replacement plan for a fictional town and then check it with rate and percent math. A common misconception is that any plan finishing "someday" is good enough. The lesson makes the deadline a hard constraint, so students must show that their yearly pace actually reaches the goal in time.

Procedure

Hook (5 min): Show a short cross-section sketch of a service line, the pipe that carries water from the street main into a house. Ask why a town would spend money to dig up and replace pipes that still carry water. Record ideas without judging them.

Background and constraints (10 min): Explain the fictional town of Wrenfield and the rules it must follow. Together, list the criteria and constraints on chart paper: finish within 10 years, stay within the yearly budget, and lower tap lead below the action level. Name these as the engineering criteria the plan must meet.

Model the math (10 min): Using a different sample number than the handout, model finding a yearly rate. If a town had 800 lines and 10 years, show 800 divided by 10 equals 80 lines per year. Model finding a percent: 40 lines replaced out of 800 is 40 divided by 800, which is 5 percent. This is teacher modeling, not a handout answer.

Student handout work (20 min): Students complete the handout for Wrenfield in pairs. They calculate the required yearly rate, track progress, check the budget, and compare tap lead to the action level. Circulate and check that pairs use the total of 1,200 lines as the base for their percents.

Share and evaluate (7 min): Two pairs present their plan. The class checks each plan against the three constraints listed earlier and marks whether it meets all three.

Exit ticket (3 min): Students answer one question on a card: "Name one constraint Wrenfield's plan must meet, and one number from your work that shows the plan meets it." Collect and scan before dismissal.

Wrenfield Lead Service Line Replacement Plan Lesson — Grade 6 Engineering & Design

Name: ____________________________ Date: ______________

Student Handout

Use these facts about the fictional town of Wrenfield. Wrenfield has 1,200 lead service lines to replace. The rule gives the town 10 years. Replacing one line costs $5,000. Wrenfield's 90th-percentile tap result is 18 ppb of lead (1 in every 10 homes tested had 18 ppb or more). The action level is 15 ppb now and 10 ppb in 2027.

To finish in 10 years, how many lines must Wrenfield replace per year on average?
In the first year, the crew replaced 90 lines. What percent of the 1,200 total is that?
After the first year, how many lines still remain?
At $5,000 per line, what is the total cost to replace all 1,200 lines?
Wrenfield has $600,000 for replacements this year. At $5,000 per line, how many lines can it replace this year?
Does replacing 120 lines each year meet the 10-year goal for 1,200 lines? Show why.
Wrenfield's 90th-percentile tap result is 18 ppb. The action level is 15 ppb now. Is Wrenfield above the current action level, and by how much?
After 2027, the action level drops to 10 ppb. How far above the new level is Wrenfield's 18 ppb?

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

Answer Key

All Wrenfield figures below are part of this fictional scenario. Handout questions are keyed 1 to 8 in order.

Answer: 120 lines per year. 1,200 lines / 10 years = 120 lines each year.
Answer: 7.5 percent. 90 / 1,200 = 0.075, or 7.5 percent of the total.
Answer: 1,110 lines. 1,200 - 90 = 1,110 lines still remain.
Answer: $6,000,000. 1,200 lines x $5,000 per line = $6,000,000.
Answer: 120 lines. $600,000 / $5,000 per line = 120 lines this year.
Answer: Yes. 120 lines per year x 10 years = 1,200 lines, which matches the total, so the pace meets the goal.
Answer: 3 ppb above. 18 ppb - 15 ppb = 3 ppb above the current action level.
Answer: 8 ppb above. 18 ppb - 10 ppb = 8 ppb above the 2027 action level.

Differentiation

Support

Give students a partly filled plan table with the total lines and the deadline already entered, so they only find the yearly rate. Provide the percent step in question 2 set up as 90 divided by 1,200. Allow a calculator for every division.

Extension

Ask students to redesign the plan for a town whose yearly budget covers only 80 lines. They must decide whether the town can still finish in 10 years and propose one change that would close the gap.

ELL supports

Pre-teach "service line," "action level," and "phased" with a simple street-to-house diagram and a number line showing 10, 15, and 18 so students can see where the lead levels fall. Provide a sentence frame for the exit ticket: "One constraint is ___, and my number ___ shows the plan meets it."