Graphic organizer Grade 8 Engineering & Design
Calderstone Fields Runoff: A Criteria and Constraints Frame
A grade 8 definition organizer that separates measurable criteria from hard constraints before students propose any fix for nutrient runoff from school athletic fields.
Objectives
- Students will sort statements about a runoff problem into design criteria and design constraints.
- Students will write a measurable target, a unit, and a measurement method for each criterion.
- Students will name the source of each constraint, such as a budget, a schedule, or a staffing limit.
Vocabulary
- Eutrophication
- Eutrophication is what happens when a lake or bay gets overfed with nutrients: algae grows out of control, and when it dies and rots, the water loses the oxygen that fish need.
Also: criterion, constraint, nutrient, phosphorus, runoff, buffer strip
Teacher overview
This organizer is a three-part definition frame: a criteria table, a constraints table, and a short list of ideas already ruled out. Students fill it in for the fictional town of Calderstone, where the middle school's athletic fields drain into Tiverbrook Creek, and where a volunteer group measured phosphorus at 0.03 mg/L upstream of the fields and 0.11 mg/L downstream. Two mistakes are common when eighth graders meet this frame. They treat criteria and constraints as the same kind of statement, and they write goals with no measurable target, such as "make the creek cleaner," which no test can confirm or refute. Press every criterion until it names a quantity, a unit, and a method someone could actually carry out.
Organizer
The design problem. The school district in the fictional town of Calderstone wants to reduce the phosphorus leaving its athletic fields and reaching Tiverbrook Creek. Before anyone sketches a solution, the problem has to be defined. The district has told you this much: a grounds crew of two people fertilizes the fields twice a year; the fields must stay playable through the fall season; the district has set aside $4,000 for the work; any digging or planting must be finished before the first frost; and the volunteers' field test kit reads phosphorus to the nearest 0.01 mg/L.
Part 1. Criteria: what a successful solution must achieve
| # | Criterion (what success looks like) | How we will measure it | Target value and unit | Why it matters to people or to the creek |
|---|---|---|---|---|
| 1 | ||||
| 2 | ||||
| 3 |
Part 2. Constraints: limits the solution cannot exceed
| # | Constraint (a limit we cannot exceed) | The stated limit | Where the limit comes from |
|---|---|---|---|
| 1 | |||
| 2 | |||
| 3 | |||
| 4 |
Part 3. Ideas already ruled out
| Idea we considered | The criterion or constraint it fails |
|---|---|
From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.
Completed Exemplar
Part 1. Criteria
| # | Criterion (what success looks like) | How we will measure it | Target value and unit | Why it matters to people or to the creek |
|---|---|---|---|---|
| 1 | Phosphorus below the fields moves back toward the upstream reading | Three samples upstream and three downstream on the same morning, using the volunteers' field kit | Downstream at or below 0.05 mg/L | Less phosphorus means less late-summer algae growth in Tiverbrook Creek |
| 2 | The fields stay playable all fall | The grounds crew walks each field after a rain and records soft or muddy spots | No new soft spots inside the marked playing surface | Teams and gym classes use the fields every week of the season |
| 3 | The existing crew can maintain the fix | The crew logs minutes spent on the new work each month | No more than 4 added hours per month | A crew of two already maintains the whole campus |
Part 2. Constraints
| # | Constraint (a limit we cannot exceed) | The stated limit | Where the limit comes from |
|---|---|---|---|
| 1 | Money available for the project | $4,000 total | The amount the district set aside this year |
| 2 | Schedule for digging and planting | Complete before the first frost | Seed and sod will not establish in frozen ground |
| 3 | Changes to the playing surface | No regrading inside the marked field boundaries | The fall season is already scheduled on those fields |
| 4 | Labor available afterward | Maintained by the existing crew of two | No new staff position was approved |
Part 3. Ideas already ruled out
| Idea we considered | The criterion or constraint it fails |
|---|---|
| Replace the turf with gravel so nothing needs fertilizer | Fails criterion 2, because gravel is not a playable surface |
| Hire a contractor to sweep and vacuum the fields monthly | Fails constraint 1, because monthly contractor visits cost more than the money set aside |
| Rebuild the fields with buried drain pipe and a new soil profile | Fails constraint 2 and constraint 3, because the work cannot finish before frost and it regrades the playing surface |
Differentiation
Support
Give these students the statements from the design problem already written on separate slips, and ask them only to sort each slip into the criteria table or the constraints table before writing targets. Fill in row 1 of Part 1 as a worked model, including its unit, so the level of detail is visible.
Extension
Ask students to rank their three criteria and justify the ranking, then explain what would have to change about the site or the budget before a ruled-out idea could move back onto the table. Strong responses name the specific constraint that would have to move and by how much.
ELL supports
Provide a short bilingual glossary for criterion, constraint, runoff, nutrient, and buffer strip, and post the plain-language contrast that a criterion is a goal we can measure while a constraint is a limit we cannot cross. Offer sentence frames such as "This is a constraint because the limit comes from ___" and "We will measure this by ___, and the target is ___."
Extensions
Have students carry the completed frame into a second class period and sketch two solutions that satisfy every constraint, such as a mowed buffer strip along the creek bank or a change in fertilizer timing. Each sketch should be labeled with the criterion it serves best and the constraint that most limits it, which sets up a later comparison of competing designs.