FE Civil Practice Question Solution included after investigation
CASE E-110 · FE

The Watershed That Sent 60.5 cfs, Not 100.8

The rainfall intensity and drainage area were correct, but the runoff coefficient was omitted. The design peak runoff was 60.5 cfs, not 100.8 cfs.

▶ INTERACTIVE CASE FILE • 5–10 MIN • CLICK TO INVESTIGATE

Inspect, commit, prove, fix, and sign off.

Case E-110 engineering failure visual
HOW THIS WORKS

Think like
a real engineer.

Follow the investigation process used in the field — in five guided steps.

1

Inspect

Review the problem, diagram, and evidence.

2

Commit

Choose your hypothesis.

3

Prove

Run calculations and test your idea.

4

Fix

Select and validate a safe correction.

5

Sign Off

See the full debrief and key takeaways.

Case Brief

SAME PRINCIPLES. HIGHER STANDARDS.
PROBLEM STATEMENT

A 40-acre watershed has runoff coefficient C=0.60. The design rainfall intensity for the time of concentration is 2.5 in/hr. Using Q=1.008CiA, estimate peak runoff in cfs. A note omits C and reports 100.8 cfs.

Water Resources Environmental Engineering Civil Design Verification Root Cause Analysis Safe Correction
E-110
INVESTIGATION WORKSPACE WORK THROUGH THE CASE — YOUR CHOICES MATTER.
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DEBRIEF (LOCKED)

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Find the root cause, confirm the fix, and see how this connects to the exam.

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🔒Exam takeawayComplete the case
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CASE CLOSED · ENGINEERING VERDICT

What actually failed — and what should change.

What failed

The runoff coefficient was omitted.

What was missed

Not all rainfall becomes direct peak runoff.

Corrected model

Use Q=1.008CiA with consistent USCS units.

QUICK ANSWER

Q=1.008CiA=1.008(0.60)(2.5)(40)=60.48 cfs.

ENGINEERING TAKEAWAY

Use Q=1.008CiA for USCS units when i is in in/hr and A is in acres.

CASE QUESTIONS

Questions this case should settle.

What is the USCS Rational Method equation used here?

Q=1.008CiA with i in in/hr and A in acres.

NEXT FE PRACTICE QUESTION

The Aquifer That Moved 1,500 ft³/day, Not 72,000

Water Resources Environmental Engineering · 5–10 min

Continue Practice →
WHAT YOU’LL LEARN

Real failures. Lasting skills.

Each case is designed to build the judgment, analysis, and confidence you need for engineering exams — and beyond.

  • Apply core engineering concepts to real-world problems
  • Practice structured troubleshooting and analysis
  • Strengthen exam-ready thinking through realistic scenarios
COMMON QUESTIONS
Do I need prior knowledge to use these cases?

Basic subject familiarity helps, but every case is designed to teach through the investigation itself.

How long does a case take?

Most cases are designed for a focused 5–10 minute investigation.

Are the cases aligned with engineering exams?

Each case is mapped to a verified exam, subject, topic, and misconception before publication.

What happens after I complete a case?

The sealed debrief unlocks with the root cause, corrected reasoning, fix, and takeaway.