Classroom activity Grade 10 Math

Briarcliff Creek PFAS Spill: A Contamination Response Relay

A grade 10 station-rotation activity where teams calculate dilution, travel time, and treatment effectiveness for a fictional PFAS spill nearing a water intake.

Grade: Grade 10
Subject: Math
Material: Classroom activity
Time: 45 min
Prep: Low prep
Materials: 4 station signs with scenario cards (Spill Concentration, Travel Time, Compliance Check, Treatment Reduction), Calculator per team, Timer or stopwatch, Recording sheet per team

Standards

HSN-Q.A.1 Common Core Math

Use units as a way to understand problems and to guide the solution of multi-step problems; choose and interpret units consistently in formulas; choose and interpret the scale and the origin in graphs and data displays.

How this material aligns: Teams carry units through dilution, travel-time, and treatment calculations at each station, choosing consistent units exactly as this standard requires for multi-step modeling.

All materials for HSN-Q.A.1 →

HSA-CED.A.1 Common Core Math

Create equations and inequalities in one variable and use them to solve problems. Include equations arising from linear and quadratic functions, and simple rational and exponential functions.

How this material aligns: Teams solve a one-variable distance-rate-time equation at the travel-time station to find how long the plume takes to reach the water intake.

All materials for HSA-CED.A.1 →

Download Word file

This material is in the public domain (CC0) and may be copied, edited, and shared freely, without attribution. Updated 2026-07-16.

Objectives

Students will calculate a diluted contaminant concentration using a stated mixing ratio.
Students will calculate travel time from a distance and a current speed.
Students will compare calculated concentrations to a real EPA compliance limit before and after treatment.

Vocabulary

Parts per trillion: A unit for measuring extremely small amounts of a chemical in water. PFAS limits are set in parts per trillion because these chemicals matter even in tiny doses.

Also: dilution, compliance limit, removal percent

Teacher overview

This is a four-station, team-based activity for groups of 3 to 4 students that simulates a utility's math-based response to a contamination event on Briarcliff Creek (a fictional creek used for this activity). Each station represents one calculation a real water system would need after an upstream spill: how diluted the contaminant becomes, how long it takes to reach the drinking-water intake, whether the diluted concentration violates a real EPA limit, and how much a treatment barrier would need to remove. Teams rotate through all four stations, recording their work on a shared sheet, and the activity ends with a debrief connecting the math to the real regulatory limit for PFAS.

Activity Directions

Before class, post four station signs around the room: Spill Concentration, Travel Time, Compliance Check, and Treatment Reduction. Each station's card includes the scenario numbers and the question teams must answer. Stations 3 and 4 use the Station 1 result, so give each team a copy of the Station 1 card to complete first, then let teams rotate through Stations 2 to 4 in any order.
Setup (5 min): Divide the class into teams of 3 to 4 students and give each team a recording sheet. Explain the scenario once as a whole class: an industrial spill of PFOA, one type of PFAS, has entered Briarcliff Creek (a fictional creek used for this activity) upstream of the town's drinking-water intake.
Station 1, Spill Concentration (8 min): The spill creates an initial concentration of 3,600 parts per trillion (ppt) at the point it enters the creek. By the time it reaches the monitoring point downstream, it has mixed with clean tributary water in a ratio of 1 part spill water to 5 parts clean water (a hypothetical mixing ratio set for this activity). Teams calculate the diluted concentration by dividing the spill concentration by the total number of parts (1 + 5 = 6), then move to the next station.
Station 2, Travel Time (8 min): The spill point is 4.5 miles upstream of the water intake, and the creek's current moves at 1.5 miles per hour. Teams write and solve a one-variable equation (distance = rate × time) to find how many hours, and then how many minutes, the plume takes to reach the intake.
Station 3, Compliance Check (8 min): Using the diluted concentration from Station 1, teams compare it to the real EPA maximum contaminant level (MCL) for PFOA and PFOS, 4.0 ppt, and calculate how many times over the limit the diluted concentration is.
Station 4, Treatment Reduction (8 min): The intake's treatment barrier removes a hypothetical 98 percent of the contaminant. Teams calculate the concentration remaining after treatment and check whether that remaining concentration still exceeds the 4.0 ppt MCL, and by how much.
Debrief (8 min): Bring the class back together and discuss the questions in the Answer Key below, connecting the Station 4 result to why utilities cannot rely on dilution or a single treatment step to guarantee compliance with a very low ppt-level standard.

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

Answer Key

Answer: 600 ppt.
3,600 ppt ÷ 6 total parts (1 spill + 5 clean) = 600 ppt at the monitoring point.
Answer: 180 minutes.
Time = distance ÷ speed = 4.5 miles ÷ 1.5 mph = 3 hours, which is 3 × 60 = 180 minutes.
Answer: 150 times over the limit.
600 ppt ÷ 4.0 ppt = 150, meaning the diluted concentration is 150 times the real MCL for PFOA and PFOS.
Answer: 12 ppt, still over the limit.
600 ppt × (1 − 0.98) = 12 ppt remaining after treatment. Since 12 ppt is still greater than the 4.0 ppt MCL, the treated water would still exceed the limit, by 12 − 4.0 = 8 ppt.
Debrief question: "Why does a 98 percent removal rate still leave the water out of compliance?" Answer: Because the starting concentration (600 ppt) is so far above the 4.0 ppt limit, even removing 98 percent of it leaves 12 ppt, three times the limit; a contaminant regulated at such a low ppt level requires either a much higher removal percentage or preventing the spill from reaching the intake at that concentration in the first place.
Debrief question: "Which station's result most changed your idea of how a spill is handled?" Answer: Answers will vary; look for students connecting a specific number, such as being 150 times over the limit or 98 percent removal still falling short, to their reasoning.

Differentiation

Support (below grade level)

At each station in this fictional scenario, provide the calculation set up with the operation already chosen (for example, "600 ÷ 4.0 = ___"), so students focus on computing and interpreting the result rather than deciding which operation to use.

Extension (above grade level)

Ask teams to find the minimum removal percentage the treatment barrier at Station 4 would need to bring the fictional spill's diluted 600 ppt concentration below the 4.0 ppt MCL, working backward from the concentration found at Station 1.

ELL supports

Provide each station's card with a simple icon (a spill drop, a clock, a checkmark or X, and a filter) alongside the text, and pre-teach "dilution," "concentration," and "compliance" with a one-sentence plain-language definition posted at each relevant station.