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Project Grade 7 Engineering & Design

Millbrandt Drainage District: A Nutrient Interception Design

A five-session grade 7 project where teams screen four nitrate-cutting designs against land, budget, and drainage limits, then pitch one to a fictional drainage board.

Objectives

  1. Students will restate a client's wishes as numbered criteria and constraints.
  2. Students will eliminate design options that fail a stated constraint and record why.
  3. Students will score the surviving designs on shared criteria and recommend one.
  4. Students will present a sited, scaled design to a panel and answer challenge questions.

Vocabulary

Nitrate
Nitrate is a form of nitrogen that plants use as food. It gets into water from fertilizer, animal waste, and septic systems, and too much of it is unhealthy for both people and streams.

Also: tile drain, bioreactor, saturated buffer, constraint, criterion, site plan

Teacher overview

Teams act as design consultants to a fictional farm drainage board that wants less nitrate leaving its field drains. Four candidate designs come with real trade-offs in land take, cost, upkeep, and effect on spring drainage, so the work is a screening and scoring problem rather than a build. Over five sessions teams eliminate the designs that break a constraint, size and site the survivors on a scaled plan, score them, and pitch one to a panel. The misconception worth naming early is that the design with the largest nitrate cut is the best design. Students reach for the wetland cell on that basis and only later notice it takes more land out of crops than the board allows, which is a limit and not a preference.

Millbrandt Drainage District: A Nutrient Interception Design — Grade 7 Engineering & Design
Name: ____________________________ Date: ______________

Project Brief

Driving question. Which design should the fictional Millbrandt Drainage District build at the lower end of Cressley Ditch?

The client. You are reporting to the board of a fictional drainage district. Farms in the district drain through buried pipes called tile drains. Those pipes empty into Cressley Ditch. The ditch carries nitrate downstream to a lake. The board wants that nitrate cut.

What the board said at its meeting. These are wishes, not requirements yet. Your first job is to turn them into numbers.

  • "We can spend some money, but not a lot."
  • "We are not giving up much cropland."
  • "Nothing can slow the drains in the spring."
  • "One worker has to be able to keep it up."

The stated limits. The board later put four hard limits in writing.

  • The budget is 40,000 dollars.
  • No more than 1.5 acres may come out of crop production.
  • The design may not raise the water level in the tile drains during March or April.
  • Upkeep must fit two visits a year by one worker.

The four options. Each row is a real practice. The nitrate cut is a range from the board's own file.

Design Cost Land taken Nitrate cut Upkeep Effect on spring drainage
Woodchip bioreactor 26,000 dollars 0.4 acre 25 to 45 percent Refill chips every 10 years, check the control box twice a year None, the flow is split around it
Saturated buffer 14,000 dollars 0.6 acre 20 to 50 percent Adjust the control box twice a year None if the box is opened in March
Wetland cell 62,000 dollars 2.4 acres 40 to 60 percent Mow and manage plants four times a year Raises the water level in nearby drains
Two-stage ditch 38,000 dollars 1.2 acres 10 to 25 percent Mow the benches twice a year None, and it carries flood flows better

What you turn in. Your team submits three things to the board.

  1. A written proposal of two to three pages. It names your design, the limits it meets, and the limits it just barely meets.
  2. A site plan drawn on grid paper at a scale of one inch to forty feet. Label the ditch, the tile drain outlet, your design, and the cropland edge.
  3. A five-minute pitch to the board panel, with one slide or poster.

One more rule. Your proposal must name one thing the board should measure after the build to find out whether the design worked. Say what to measure, where, and how often.

Milestones

Session 1. Turn wishes into numbers. Read the site file. Rewrite each of the four board comments as a numbered requirement with a unit. Mark each one as a limit the design may not cross or a goal the design should reach. Turn in the list. It should have at least six rows.

Session 2. Screen the four options. Check every design against every limit. Use a pass-or-fail grid. Any design that fails one limit is out. Write one sentence per failure naming the limit it broke. Turn in the grid, marking every design still standing.

Session 3. Size it and site it. Draw your site plan at one inch to forty feet. Do this for each surviving design. Show how much land each one takes. Mark the tile drain outlet and the ditch. Turn in one plan for each survivor.

Session 4. Score and choose. Build a scoring table with at least four criteria. Nitrate cut, cost, upkeep, and crop land lost are a good start. Score every surviving design. Total the columns. Pick one. Draft the written proposal. Turn in the scoring table and the draft.

Session 5. Pitch and revise. Present to the panel for five minutes. Take two challenge questions. Afterward write one paragraph naming what you would change and why. Turn in the final proposal, the site plan, and the revision paragraph.

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

Rubric
Criterion 4, exceeds 3, meets 2, approaching 1, beginning
Requirements written with precision Every board comment becomes a requirement with a number and a unit, and limits are separated from goals without error All four comments become numbered requirements and most are sorted correctly Some requirements carry numbers while others stay as wishes Requirements restate the board's wording without numbers
Screening against constraints The pass-or-fail grid is complete and each elimination cites the exact limit and the value that broke it Every failing design is eliminated and the reasons name the right limits Some eliminations are correct while others are missing or misjustified Designs are chosen by preference rather than screened against limits
Site plan and sizing The plan is drawn to the stated scale, labeled fully, and the land take matches the options table The plan uses the stated scale and labels the ditch, outlet, and design The plan is sketched roughly with partial labels or an inconsistent scale The plan is unscaled or missing required features
Scored comparison and recommendation Four or more criteria are scored, totals are shown, and the recommendation follows the totals even when it is not the largest nitrate cut Four criteria are scored and the recommendation follows the table Criteria are listed but scoring is incomplete or the choice ignores the totals A design is named with no scored comparison
Monitoring plan and pitch The proposal names what to measure, where, and how often, and the pitch answers challenge questions with evidence from the team's own tables A monitoring measurement is named with a location, and the pitch covers the required points Monitoring is mentioned in general terms and the pitch is incomplete No monitoring is proposed

Differentiation

Support

Give these teams the six numbered requirements already written so they begin at the screening grid. Provide the pass-or-fail grid with the row headings filled in and one cell worked as a model. Allow a labeled sketch with a written scale statement in place of a fully drawn plan, and shorten the written proposal to a one-page form with headings.

Extension

Ask these teams to price a combination, such as a saturated buffer at one outlet and a woodchip bioreactor at another, and to argue whether splitting the budget beats spending it in one place. Have them prepare a rebuttal to the objection that a smaller nitrate cut is not worth any cropland at all.

ELL supports

Pre-teach tile drain, nitrate, and buffer with a labeled cross section showing a field, a buried pipe, and a ditch. Provide the frames "This design fails because ____ is over the limit of ____" and "We chose ____ because it scored ____." Allow the pitch to be delivered from a written script, and let team members split it so each speaks a short part.

Extensions

Have teams write a one-page letter to a fictional farmer whose field borders the chosen site, explaining in plain language what will be built, what it will look like in five years, and what the farmer is being asked to give up. Comparing this letter with the board proposal shows students that the same design has to be justified differently to different audiences.