Project Grade 3 Engineering & Design
Camp Alder Creek Filter Challenge: A Grade 3 Design Project
A four-session grade 3 engineering project where teams design and fair-test a sand and gravel filter for a fictional camp's muddy creek water on a fixed budget.
Objectives
- Students will define criteria and constraints for a creek-water filter design using a fixed token budget.
- Students will build and test two different filter designs and compare their results.
- Students will calculate the total token cost of a filter design using addition and multiplication.
Vocabulary
- Filtration
- Filtration is the step where water passes through layers of sand, gravel, or other materials that trap the small particles still left in it. It works like a very fine strainer.
- Turbidity
- Turbidity is a measure of how cloudy or murky water looks because of tiny particles floating in it. Clear water has low turbidity, and muddy water has high turbidity.
Teacher overview
Camp Alder Creek (a fictional summer camp used for this project) has an outdoor wash station where campers rinse dishes and muddy hands using water carried up from a nearby creek, and after a rainstorm that creek water looks cloudy and brown. The camp director has asked student engineers to design a simple sand and gravel filter that makes the wash-station water look clearer, working within a fixed supply budget spent in "supply tokens." Over four sessions, teams define the problem, build and fair-test two filter designs, and present a recommendation, always being clear that a classroom filter makes water look clearer but does not make it safe to drink.
Project Brief
Driving question: How can we build a filter that makes muddy creek water clear? It must get clear enough to read a letter through. We can spend no more than 20 supply tokens.
Scenario: Camp Alder Creek's director needs a filter for the outdoor wash station. Student teams will design it. After it rains, the creek water looks cloudy. Cloudy water is called turbid water. Its cloudiness has a name: turbidity. In this project, water runs through layers that trap dirt. That is called filtration. The filter only needs to make the water look clearer for washing. It does not make the water safe to drink. Safe drinking water needs more steps, such as adding chlorine. A classroom filter cannot do those steps.
Constraints:
- Budget: 20 supply tokens total. The tokens are made up for this project. Sand costs 2 tokens per cup. Gravel or small pebbles cost 1 token per cup. A cotton ball layer costs 3 tokens. A coffee filter layer costs 4 tokens.
- Container: the filter must fit inside a 2-liter bottle cut in half. Turn the top half upside down into the bottom half to catch the filtered water.
- Layers: the filter may use no more than 4 layers total.
- Clarity target: filter the water first. Then a classmate must be able to read a printed capital letter through it. They look through a clear plastic cup. They stand about 12 inches away.
Final deliverable: A finished filter design. A labeled picture showing its layers in order. A budget sheet showing the total token cost. A short team talk for the camp director. The team says which of the two tested designs works best, and why.
Milestones
Session 1 — Define the problem: Teams talk about the wash-station water. After a storm, it needs to look clearer. Teams read the rules above. Each team then writes a problem statement. It names the clarity target, the 20-token budget, and the 4-layer limit. Output: a written problem statement.
Session 2 — Build and test Design 1: The teacher gives each team a muddy water sample. Each team builds its first filter design inside the cut bottle. Teams pour the muddy water through. They test the result with the letter card. No one drinks any of the water, and everyone washes hands after the test. On a data sheet, teams write their layer order, total token cost, and test result. Output: Design 1 data sheet.
Session 3 — Build and test Design 2 (fair test): Teams build a second design. It changes one layer, or the layer order, from Design 1, and nothing else. The muddy water sample stays the same, so the test is fair. Teams test Design 2 with the same letter card. They write down the results. Output: Design 2 data sheet and a written comparison of both designs.
Final session (Session 4) — Choose and present: Teams choose their better design. They check that it cost 20 tokens or fewer. Teams show the class the labeled picture, budget sheet, and comparison. One student plays the camp director. Output: final presentation and completed budget sheet.
From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.
Rubric
| Criterion | Emerging | Developing | Proficient | Advanced |
|---|---|---|---|---|
| Design & clarity target | Filter design does not address the letter-card clarity target | Design references the clarity target but test results are missing or unclear | Design is tested against the clarity target with clear, recorded results | Design meets the clarity target and the team explains which layer made the biggest difference |
| Budget constraint | Total cost exceeds 20 tokens with no correction | Total cost is close to 20 tokens but not shown with itemized costs | Total cost is 20 tokens or fewer, shown with an itemized list of layers and costs | Total cost is 20 tokens or fewer, itemized, with a brief explanation of a tradeoff the team made to stay within budget |
| Fair testing | Design 2 changes so many things at once that the comparison to Design 1 is not fair | Design 2 changes one layer, but the muddy water sample or test method is not kept the same | Design 2 changes exactly one layer or layer order while keeping the water sample and test method the same | Design 2's single change is clearly identified, and the team explains what the fair test showed about that one change |
| Presentation | Presentation is incomplete or difficult to follow | Presentation covers the design but does not explain the reasoning behind it | Presentation clearly explains how the chosen design meets both the clarity target and the budget | Presentation clearly explains both constraints and anticipates a likely question from the camp director |
Differentiation
Support (below grade level)
Provide a completed example budget sheet for a sample filter (1 cup gravel, 1 cup sand, 1 coffee filter) with its total cost already calculated, so teams can check their own math against a model. Shorten the planning time by suggesting one starting recipe for Design 1, leaving Design 2 open for the team's own fair-test change.
Extension (above grade level)
Ask teams to plan the cheapest three-layer filter they think could still pass the letter test, work out how many of the 20 tokens would be left over, and explain whether spending those leftover tokens on a fourth layer would likely help or hurt the filter's performance.
ELL supports
Provide a labeled diagram of a cut-bottle filter with each layer (coffee filter, sand, gravel) named in both English and, where possible, students' home languages. Allow the Session 1 problem statement and Session 4 presentation to include labeled sketches alongside shorter sentences rather than full paragraphs.
Extensions
Invite a local water or wastewater operator to describe, in simple terms, what additional steps a real treatment plant uses to make water safe to drink, such as adding a measured amount of chlorine, and compare those extra steps to what the classroom filter alone can and cannot do.