Part I walked through one complete design chain end to end. This guide is structured differently — as a mock exam problem set: four independent, fully worked, multi-concept scenarios of the kind you should expect to see mixed together on the actual Class 4 exam. Work each one before reading the solution, then check your process against the worked steps.
Mock Problem 1: Capacity Buildout Under Growth
Problem: A trunk sewer currently carries a measured peak flow of 300 gpm. The service area is growing at 3% per year. The trunk is a 12-inch pipe (n=0.013) laid at 0.25% slope. In 10 years, what percentage of the pipe's full-flow capacity will the peak flow represent? Step 1 — Project the future peak flow using compound growth.
Future Peak=Current Peak×(1+r)t=300×(1.03)10
(1.03)10≈1.344
$$\text{Future Peak} \approx