Graphic organizer Grade 8 Engineering & Design
Durnsley's Lead Service Lines: A Three-Option Trade-Off Frame
A grade 8 trade-off matrix organizer for comparing full lead line replacement, corrosion control, and point-of-use filters against five stated criteria.
Objectives
- Students will compare three lead-reduction options against five shared criteria in a single matrix.
- Students will state the trade-off that each option forces a utility to accept.
- Students will recommend one option and cite the criteria rows that support the recommendation.
Vocabulary
- Service line
- A service line is the small pipe that connects the water main under the street to the plumbing inside one home or building. It is the last leg of the trip water makes to your tap.
- Corrosion control
- Treatment that keeps water from slowly eating away at the inside of pipes. It helps stop metals like lead from getting into drinking water.
- Orthophosphate
- A chemical that utilities add to water in very small amounts. It coats the inside of pipes so lead cannot easily get into the water.
- Point-of-use filter
- A small filter at a single faucet, like a pitcher filter or one that attaches to the tap. Certified filters can remove lead or PFAS from the water a family drinks.
- 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: trade-off
Teacher overview
This organizer is a three-column trade-off matrix with a criteria row for each thing the utility cares about, a row naming the trade-off each option forces, and a closing recommendation line. It maps the choice facing the fictional town of Durnsley, which has about 1,850 lead service lines still in the ground. Federal rules set the lead action level at 15 ppb, dropping to 10 ppb in 2027, and require systems to replace nearly all lead service lines within 10 years, so Durnsley cannot simply do nothing. Eighth graders often assume one option must be best on every row, and they stop comparing as soon as they find a favorite. The matrix is designed to interrupt that, because each option here wins some rows and loses others.
Organizer
The decision. The fictional town of Durnsley must lower lead at residents' taps. Three options are on the table, and the town can fund one of them fully this year.
- Option A, full replacement. Dig up and replace every lead service line, at a cost the town estimates at $9,000 per line, working through the list over ten years.
- Option B, corrosion control. Add orthophosphate at the treatment plant so a protective coating forms inside the pipes, at a cost the town estimates at $140,000 per year, starting within about six months.
- Option C, point-of-use filters. Give every affected household a certified filter for the kitchen tap, at a cost the town estimates at $95 per household per year, delivered within about three months.
Fill in one cell for each option in every row.
| Criterion | Option A: full replacement | Option B: corrosion control | Option C: point-of-use filters |
|---|---|---|---|
| How much lead it removes from the water path | |||
| How soon residents see a benefit | |||
| What it costs the town | |||
| What residents must do for it to work | |||
| How permanent the protection is | |||
| The trade-off this option forces |
Our recommendation and the rows that support it:
From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.
Completed Exemplar
| Criterion | Option A: full replacement | Option B: corrosion control | Option C: point-of-use filters |
|---|---|---|---|
| How much lead it removes from the water path | Removes the lead pipe itself, so the source of the lead is gone | Leaves the lead pipe in place and coats it, so lead is reduced but still present | Leaves the lead pipe in place and catches lead at one tap |
| How soon residents see a benefit | Slowest, because the town estimates ten years to finish the list | Fast, once the feed starts in about six months, with the coating building over the following months | Fastest, as soon as filters arrive within about three months |
| What it costs the town | Highest, at an estimated $9,000 per line for 1,850 lines | Lowest yearly cost, at an estimated $140,000 per year, ongoing for as long as the feed runs | About $175,750 a year for 1,850 households at $95 each, more than corrosion control, and it never ends |
| What residents must do for it to work | Allow crews onto the property and into the basement | Nothing, because the treatment happens at the plant | Change the cartridge on schedule and use only the treated tap for drinking and cooking |
| How permanent the protection is | Permanent once a line is replaced | Lasts only while the feed keeps running and water chemistry stays stable | Lasts only while each household keeps replacing cartridges |
| The trade-off this option forces | Best long-term result, paid for with the longest wait and the highest cost | Quick, affordable protection bought by leaving the lead pipes in the ground | Fastest relief, bought by shifting the daily work and the risk of failure onto residents |
Our recommendation and the rows that support it: Start Option B now and fund Option A on the required ten-year schedule, using Option C for households with an infant or a pregnant resident until their line is replaced. Rows one and five support replacement as the end goal, while rows two and three explain why the town cannot wait ten years with no other protection.
Differentiation
Support
Give these students the matrix with the "How soon residents see a benefit" row already completed as a model, and supply a short word bank for each remaining row, such as permanent, temporary, ongoing, and one-time. Ask them to complete three rows rather than all six.
Extension
Ask students to add a seventh row for fairness, considering which households benefit first under each option and which are asked to do the most work, then revise the recommendation if that row changes the balance. Strong responses connect the fairness row to the observation that lead service lines are concentrated in lower-income communities.
ELL supports
Provide a labeled cross-section sketch of a service line running from the water main to a house, with the words main, service line, meter, and tap marked. Offer sentence frames such as "Option ___ is faster, but it does not ___" and "I recommend ___ because rows ___ and ___ show ___."
Extensions
Have students write a one-paragraph notice to residents explaining the recommended plan, including what the household is asked to do and when. Comparing two groups' notices side by side usually surfaces disagreements about how much of the work a utility should hand to residents, which is the same argument utilities have in public meetings.