Water for Schools
Menu

Classroom activity Grade 10 Art & Music

Storm Drain Stencil Campaign: A Grade 10 Scale-Design Activity

A grade 10 design activity where teams create a storm-drain stencil warning, scale it to full size, calculate paint needed, and pitch it as a real civic campaign.

Objectives

  1. Design a storm-drain stencil that communicates a specific nonpoint-source pollution message.
  2. Calculate the scale factor and area relationship between a small sketch and a full-size stencil.
  3. Calculate the paint quantity needed for a multi-stencil neighborhood campaign.

Vocabulary

Storm drain
A storm drain is the grate at the edge of a street that swallows rainwater and sends it through pipes to the nearest creek or river. That water is usually not treated, so only rain belongs down the drain.
Stormwater
Stormwater is rain or melted snow that flows off roofs, streets, and parking lots. In most towns it goes into storm drains and flows to a stream without being treated, carrying whatever it picked up.
Impervious surface
An impervious surface is any hard surface, like a road, roof, or parking lot, that rain cannot soak through. The more impervious surface a town has, the more stormwater rushes off it.
Nonpoint source pollution
Nonpoint source pollution is pollution that washes off the land a little at a time from many places, like lawns, streets, and farms, instead of coming out of one pipe. It is the hardest kind of water pollution to control.

Teacher overview

This is a small-team design activity for groups of three or four, in which each team designs a storm-drain stencil, scales it up mathematically to full size, and pitches it as a proposal a city's public works department could actually fund, mirroring the real stencil and mural campaigns many utilities sponsor. The core mechanic is that every design decision runs through a genuine scale-factor calculation before it becomes a full-size stencil, so students practice geometric modeling and civic communication in the same task.

Activity Directions

  1. Open by explaining the concept every stencil must communicate: storm drains carry rainwater, and anything sitting on the street, such as motor oil, pet waste, fertilizer, or litter, directly to the nearest stream or river, without passing through a treatment plant first.
  2. Divide the class into teams of three or four. Assign or let each team choose one specific pollution source to target: motor oil, pet waste, yard fertilizer, or litter.
  3. Give each team a 6-inch-by-6-inch grid handout. Teams sketch a design (one image plus a phrase of eight words or fewer) inside that 6-inch square.
  4. Explain the constraint: the fictional city's public works department requires all stencils to measure 24 inches by 24 inches. Teams calculate the scale factor between their 6-inch sketch and the required 24-inch stencil, and use it to plan how each part of their sketch will enlarge.
  5. Teams calculate the area, in square feet, of one full-size stencil, then the total area needed if the campaign paints 15 stencils around a neighborhood, and finally how many quarts of stencil paint the campaign needs, given that one quart covers 32 square feet.
  6. Each team delivers a 60-second civic pitch to the class, presented as if pitching the design and its costs to the city's public works department for approval and funding.
  7. The activity ends once every team has delivered its pitch; close with the debrief questions below.
Storm Drain Stencil Campaign: A Grade 10 Scale-Design Activity — Grade 10 Art & Music
Name: ____________________________ Date: ______________

Student Handout

Design brief: Your team's stencil must include one image and a message of eight words or fewer warning that storm drains lead directly to a stream or river untreated. Sketch it inside the 6-inch grid provided.

Scale-up worksheet:

  1. Your sketch is 6 inches by 6 inches. The required full-size stencil is 24 inches by 24 inches. What is the scale factor between your sketch and the full-size stencil?
  2. What is the area, in square inches, of your original 6-inch sketch? What is the area, in square inches, of the 24-inch stencil?
  3. Divide the stencil's area by the sketch's area. How does this number compare with the scale factor you found in question 1?
  4. Convert the 24-inch-by-24-inch stencil's dimensions to feet, and find its area in square feet.
  5. If the campaign paints 15 stencils around the neighborhood, what is the total area, in square feet, that needs paint?
  6. One quart of stencil paint covers 32 square feet. How many quarts does the campaign need for all 15 stencils? Round up to a whole number of quarts, since paint cannot be purchased in fractional cans.

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: 4.
    A scale factor of 4. 24 inches ÷ 6 inches = 4, so every inch on the sketch becomes 4 inches on the full-size stencil.

  2. Answer: 36 square inches (sketch); 576 square inches (stencil).
    The sketch's area is 36 square inches (6 × 6), and the stencil's area is 576 square inches (24 × 24).

  3. Answer: 16.
    576 ÷ 36 = 16, which is the scale factor squared (4² = 16), not the scale factor itself. Enlarging a shape by a linear scale factor of 4 increases its area by a factor of 16, since area scales with the square of the linear scale factor.

  4. Answer: 4 square feet.
    24 inches equals 2 feet, so the stencil is 2 feet by 2 feet, giving an area of 4 square feet (2 × 2).

  5. Answer: 60 square feet.
    15 stencils × 4 square feet each = 60 square feet total.

  6. Answer: 2 quarts.
    60 square feet ÷ 32 square feet per quart = 1.875 quarts, which rounds up to 2 whole quarts, since a partial can of paint cannot be purchased.

Debrief question: Why does the area increase by more than the scale factor itself when a design is enlarged? Answer: Because area is a two-dimensional measurement, both the length and the width of the design grow by the scale factor, so the area grows by the scale factor multiplied by itself.

Debrief question: What made a stencil design effective for this civic pitch? Answer: Answers will vary, but strong pitches connect the image and short phrase directly to one specific pollution source and explain, in plain terms, that storm drains lead untreated to a real body of water.

Differentiation

Support (below grade level)

Provide the scale factor (4) already calculated before question 1, and give students a printed reference showing "small square area × scale factor² = large square area" as a labeled rule before question 3.

Extension (above grade level)

Ask teams to calculate how many quarts of paint the campaign would need if it instead painted 40 stencils, then explain, without recalculating from scratch, how the paint needed would change if each stencil were also enlarged by a scale factor of 1.5.

ELL supports

Provide the design brief and scale-up worksheet with icons alongside each pollution source (a car for motor oil, a paw print for pet waste, a leaf for fertilizer, a wrapper for litter). Allow the civic pitch to be delivered with visual aids and short rehearsed phrases rather than an extemporaneous speech.