Project Grade 12 Engineering & Design
Marrowgate Main Replacement: A Capital Plan Project
A grade 12 project where teams rank six aging water mains in a fictional town with a weighted scoring matrix, select a portfolio within budget, and pitch a capital plan.
Objectives
- Students will compute replacement costs and break rates for pipe segments from length and break-history data.
- Students will build a weighted scoring matrix and defend the weights they choose.
- Students will select a replacement portfolio within a fixed budget and justify the deferrals in writing.
Vocabulary
- Capital improvement plan
- A utility's long-term to-do list of big construction projects, such as replacing old pipes or building new tanks. It shows what will be built, when, and how it will be paid for.
- Deferred maintenance
- Repair work that keeps getting put off to save money now. The longer it waits, the worse and more expensive the problems become.
Also: criticality, break rate, weighted scoring
Teacher overview
A water main breaks somewhere in the US roughly every two minutes, and EPA estimates that $625 billion in drinking-water investment is needed over 20 years, most of it for distribution pipe. No utility can replace everything at once, so deciding which segments to replace first is the engineering problem this project puts to students. In this five-session project, teams act as the engineering staff of the fictional town of Marrowgate, ranking six aging mains with a weighted scoring matrix, selecting the portfolio that fits a two-year budget, and defending the plan before a role-played utility board. The final deliverable is a one-page capital improvement memo with a completed scoring matrix and a short board presentation.
Project Brief
Driving question: With a two-year budget of $1.8 million, which of the fictional town of Marrowgate's six aging water mains should be replaced first, and how do we defend the choice?
Scenario: Marrowgate's utility board has asked the engineering staff (your team) for a two-year main replacement plan. Replacement of any segment costs $240 per foot installed, a planning figure set for this project. The board will fund at most $1.8 million and expects the plan to name what is deferred as clearly as what is funded.
Segment data:
| Segment | Length (ft) | Material and install year | Breaks, past 5 years | Criticality note |
|---|---|---|---|---|
| A | 2,400 | Cast iron, 1948 | 9 | Feeds the hospital corridor |
| B | 3,100 | Cast iron, 1954 | 6 | Serves two schools |
| C | 1,850 | Ductile iron, 1988 | 2 | Residential loop |
| D | 4,200 | Cast iron, 1951 | 7 | Downtown commercial district |
| E | 2,900 | Asbestos cement, 1963 | 4 | Residential, parallel main exists |
| F | 1,200 | Cast iron, 1946 | 8 | Low point, breaks flood the street |
Constraints:
- Total selected replacement cost must not exceed $1.8 million at $240 per foot.
- The plan must use a weighted scoring method with at least three criteria, and the weights must be justified in the memo.
- At least one funded segment must address a high-criticality customer (the hospital corridor or the schools).
- Every unfunded segment must appear in the memo with a one-sentence risk statement.
Final deliverable: A one-page capital improvement memo to the Marrowgate utility board, the completed scoring matrix, and a presentation of no more than six minutes delivered to classmates role-playing the board.
Milestones
- Session 1, data analysis: Teams compute each segment's replacement cost at $240 per foot and its break rate per 1,000 feet (breaks ÷ length in thousands of feet). Output: a completed data sheet with both computed columns. (For instance, Segment F runs 8 ÷ 1.2 = 6.7 breaks per 1,000 feet, the worst in the system.)
- Session 2, criteria and weights: Teams choose at least three scoring criteria, such as break rate, criticality, age or material, and cost efficiency, and assign percentage weights totaling 100. Output: a written weighting scheme with a one-sentence justification per criterion.
- Session 3, scoring and selection: Teams score all six segments, rank them, and select a portfolio whose total cost fits the $1.8 million budget. Output: the completed matrix, the ranked list, and the selected portfolio with its exact total cost.
- Session 4, memo drafting: Teams draft the one-page memo: recommended segments, total cost, the scoring logic, and a risk statement for each deferred segment. Output: a complete memo draft exchanged with another team for structured peer comment.
- Session 5, board presentation: Teams revise the memo and present to the class-as-board, answering at least one challenge question about a deferred segment. Output: final memo, final matrix, and the delivered presentation.
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 |
|---|---|---|---|---|
| Data analysis | Costs or break rates are missing or largely incorrect | Costs and break rates are computed with some errors that affect the ranking | All six segments' costs and break rates are correct and used in the scoring | All computations are correct, and the memo cites specific values to justify rankings |
| Budget constraint | Selected portfolio exceeds $1.8 million or lacks a cost total | Portfolio total is stated but contains arithmetic errors | Portfolio is at or under $1.8 million with an accurate itemized total | Portfolio is at or under budget, itemized, and the memo explains a trade-off made to stay within it |
| Scoring method and trade-offs | No weighted method is evident | A matrix exists but weights are unjustified or applied inconsistently | Weighted matrix with justified weights is applied consistently to all six segments | Matrix is consistent and the team tests how a weight change would alter the ranking |
| Memo and presentation | Memo is incomplete or deferred segments are unaddressed | Memo covers funded segments but deferral risks are thin | Memo covers funded and deferred segments clearly within one page, and the presentation answers the board's question | Memo is clear and complete, and the presentation anticipates a board objection before it is asked |
Differentiation
Support
Provide the Session 1 cost column pre-computed for the fictional data set so teams begin at break rates, and supply a starter matrix with two criteria already named, leaving the team to add and weight the third.
Extension
After Session 3, give teams a revised scenario: suppose the board adds $300,000 to the budget on condition that Segment E is included. Teams must determine whether the enlarged budget accommodates E alongside their portfolio, and write a three-sentence addendum accepting or contesting the condition with numbers.
ELL supports
Pre-teach "criticality," "deferred," and "portfolio" with a matching card set tied to the segment table, and provide a memo skeleton with labeled sections (recommendation, cost, method, deferrals) so language load goes to the justifications rather than the format.
Extensions
Invite a guest from a local public works department, in person or by video call, to hear the top presentations and describe how their agency actually sequences replacements, or have students compare their weighting scheme with the criteria named in a real utility's published capital improvement plan and write a paragraph on one difference they would defend.