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Lesson plan Grade 6 Engineering & Design

Netherstone Salt Shed Runoff Containment Lesson

A 55-minute lesson in which students size a containment curb and a roof for a fictional town's road-salt pile, then budget the monitoring visits that follow construction.

Objectives

  1. Students will calculate the volume a containment curb can hold in cubic feet and in gallons.
  2. Students will convert a rainfall depth into a runoff volume using a stated area and conversion factor.
  3. Students will allocate a fixed construction budget across a roof, a curb, and monitoring visits.

Vocabulary

Key words: containment, chloride, runoff, curb, monitoring

Teacher overview

Netherstone is a fictional town whose public works yard keeps its winter road salt in an uncovered pile beside Torrin Brook, and every dimension and price in this lesson was invented for that scenario. Rain washes salty water off the pile and into the brook, where chloride stays dissolved and is not removed by ordinary drinking water or wastewater treatment. Students size a containment curb around a new salt pad, decide whether a roof is affordable, and plan how many monitoring visits the leftover money will fund. The misconception this lesson addresses is the belief that a containment volume in gallons can be compared directly with a rainfall depth in inches, when the rainfall has to be turned into a volume first by using the area of the pad.

Procedure

Every figure used in this fictional Netherstone scenario is invented for teaching.

  • Hook (5 min): Show a picture or sketch of an open salt pile beside a stream and ask what happens to the pile during a February rain. Collect answers, then state the problem: chloride that reaches the brook stays there.
  • Define criteria and constraints (10 min): Build two lists on the board. Criteria: keep salty water out of the brook, and be able to show it worked. Constraints: a fixed construction budget, a pad that must be 40 feet by 30 feet to fit the yard, and a curb no higher than half a foot so a loader can drive over it. Point out that the loader requirement is what makes the curb height a design constraint rather than a free choice.
  • Model the volume calculation (8 min): Work one example at the board with numbers that do not appear on the handout. Suppose a different yard poured a pad 20 feet by 10 feet with a curb 0.5 feet high. Ask for the containment volume, then confirm 20 x 10 x 0.5 = 100 cubic feet, and convert it with 100 x 7.48 = 748 gallons. Say plainly that one cubic foot holds 7.48 gallons.
  • Handout (22 min): Students work items 1 through 10 of the Student Handout in pairs. Circulate and check that item 3 uses the pad area of 1,200 square feet rather than the curb volume.
  • Formative check (5 min): Collect item 4 on a half sheet partway through the work time and read the answers quickly. If more than one third of the class did not divide the containment gallons by the gallons a one-inch storm produces, stop and rework item 3 and item 4 with the whole class.
  • Debrief (5 min): Ask which does more for the brook, the roof or the curb, and require a reason drawn from the numbers. Close by asking why a design that reduces pollution still needs monitoring visits afterward.
Netherstone Salt Shed Runoff Containment Lesson — Grade 6 Engineering & Design
Name: ____________________________ Date: ______________

Student Handout

Netherstone, Torrin Brook, and every number below are fictional, invented for this exercise. The new salt pad will be 40 feet long and 30 feet wide, which is an area of 1,200 square feet. A curb 0.5 feet high will run all the way around the outside of the pad.

Rain that falls on a surface can be turned into gallons with this rule: area in square feet, times rainfall in inches, times 0.623.

  1. What volume, in cubic feet, can the curb hold on the pad?
  2. One cubic foot holds 7.48 gallons. How many gallons can the curb hold?
  3. How many gallons does a 1-inch storm put on the 1,200-square-foot pad? Round to the nearest gallon.
  4. Using your answers to items 2 and 3, how many inches of rain would it take to fill the curb to the top? Round to the nearest whole inch.
  5. A roof over the pad costs $9.50 for each square foot of pad. What does the roof cost?
  6. Netherstone budgeted $15,000 for the whole project. How much is left after the roof?
  7. The curb costs $22 for each foot of its length, and the curb runs 140 feet around the pad. What does the curb cost?
  8. How much of the budget is left after the roof and the curb are paid for?
  9. Each monitoring visit to Torrin Brook costs $40. How many whole visits can the town pay for with the money left in item 8?
  10. Explain why a roof over the pile does more to protect Torrin Brook than a curb by itself.

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: 600 cubic feet. The pad is 40 feet by 30 feet with a curb 0.5 feet high, so 40 x 30 x 0.5 = 600 cubic feet.
  2. Answer: 4,488 gallons. Each cubic foot holds 7.48 gallons, so 600 x 7.48 = 4,488 gallons.
  3. Answer: 748 gallons. Using the rule, 1,200 x 1 x 0.623 = 747.6 gallons, which rounds to 748 gallons.
  4. Answer: 6 inches. Each inch of rain puts about 747.6 gallons on the pad, and 4,488 / 747.6 = 6.0, so about 6 inches of rain would fill the curb.
  5. Answer: $11,400. The pad is 1,200 square feet at 9.50 dollars each, so 1,200 x 9.50 = 11,400 dollars.
  6. Answer: $3,600. The budget is 15,000 dollars, so 15,000 - 11,400 = 3,600 dollars left.
  7. Answer: $3,080. The curb runs 140 feet at 22 dollars each, so 140 x 22 = 3,080 dollars.
  8. Answer: $520. After the curb, 3,600 - 3,080 = 520 dollars remain.
  9. Answer: 13 visits. Each visit costs 40 dollars, and 520 / 40 = 13 whole visits.
  10. Answer: A roof keeps rain off the salt in the first place, so far less salty water is ever created. The curb only holds back water that has already picked up salt, and once the curb fills, as item 4 shows it would in about a 6-inch rain, the rest runs toward the brook. Accept any answer that says the roof prevents contact between rain and salt while the curb only stores what is already contaminated.

Differentiation

Support

Give these students the handout with the pad area of 1,200 square feet already written beside items 3 and 5, and a worked model of the volume formula with three labeled blanks. Provide the conversion for cubic feet to gallons on a card they can keep at the desk.

Extension

Ask students to redesign the fictional pad for a yard that can only spare a 30-foot by 30-foot area, keeping the same half-foot curb, and to report how many inches of rain that smaller containment would hold and whether the roof would still fit the same budget.

ELL supports

Provide a labeled drawing of the pad in cross-section with the curb height, the pad width, and the roof drawn and named. Allow students to write item 10 as two labeled arrows on that drawing, one showing rain hitting salt and one showing rain hitting the roof.

Extensions

Have students find out how their own town or county stores road salt, using a public works web page or a photograph taken from a public road, and write a short paragraph comparing that storage with the fictional Netherstone design without transferring any of the invented figures to the real site.