CPWM Utility Systems 4 — Questions and Answers
Question 1: A city's water system pressure zone has static pressure of 95 psi at the lowest point. What is the PRIMARY concern for system managers?
- Insufficient fire flow capacity
- Excessive pressure causing main breaks and customer plumbing damage (Correct answer)
- Inadequate chlorine residual maintenance
- Poor velocity for self-cleaning in mains
Correct answer: Excessive pressure causing main breaks and customer plumbing damage
Pressures above approximately 80 psi can cause accelerated pipe joint failure, increased leak rates, and damage to customer plumbing fixtures and appliances.
Question 2: What is the function of a pressure reducing valve (PRV) in a water distribution system?
- To boost pressure in low-pressure zones
- To step down higher inlet pressure to a set lower downstream pressure (Correct answer)
- To prevent air from entering the main
- To isolate segments during repairs
Correct answer: To step down higher inlet pressure to a set lower downstream pressure
A PRV automatically reduces and maintains downstream pressure at a preset level regardless of fluctuating upstream pressure, protecting pipes and customers in lower pressure zones.
Question 3: Which federal regulation requires utilities to develop Emergency Response Plans (ERPs) for drinking water systems serving more than 3,300 people?
- Clean Water Act Section 319
- America's Water Infrastructure Act (AWIA) of 2018 (Correct answer)
- Safe Drinking Water Act 1974 original text
- Resource Conservation and Recovery Act
Correct answer: America's Water Infrastructure Act (AWIA) of 2018
AWIA 2018 requires community water systems serving more than 3,300 people to conduct Risk and Resilience Assessments and develop Emergency Response Plans.
Question 4: What does BOD₅ measure in a wastewater sample?
- Biological oxygen demand over 50 days at 20°C
- Biochemical oxygen demand over 5 days at 20°C (Correct answer)
- Bacterial oxygen density at 5 meters depth
- Base oxygen demand at pH 5.0
Correct answer: Biochemical oxygen demand over 5 days at 20°C
BOD₅ is the standard 5-day biochemical oxygen demand test conducted at 20°C that measures the amount of oxygen microorganisms consume while decomposing organic matter.
Question 5: A cathodic protection system is installed on a buried steel natural gas main. What is its purpose?
- To increase gas pressure in the distribution system
- To prevent electrochemical corrosion by making the pipe a cathode (Correct answer)
- To detect gas leaks electronically
- To reduce operating pressure during peak demand
Correct answer: To prevent electrochemical corrosion by making the pipe a cathode
Cathodic protection applies electrical current to make the pipe the cathode of an electrochemical cell, preventing the oxidation (corrosion) reactions that would otherwise consume the metal.
Question 6: In a gravity sewer system, what minimum pipe slope is generally required for an 8-inch sewer to achieve self-cleansing velocity?
- 0.01% (0.0001 ft/ft)
- 0.40% (0.004 ft/ft) (Correct answer)
- 2.00% (0.02 ft/ft)
- 5.00% (0.05 ft/ft)
Correct answer: 0.40% (0.004 ft/ft)
An 8-inch sewer requires approximately 0.40% minimum slope to achieve the 2 fps self-cleansing velocity needed to prevent solids deposition and buildup.
Question 7: Which method is MOST effective for rehabilitating a deteriorated gravity sewer without open-cut excavation?
- Pipe bursting with HDPE replacement
- Cured-in-place pipe (CIPP) lining (Correct answer)
- Complete pipe replacement with PVC
- Epoxy spot repairs at joints only
Correct answer: Cured-in-place pipe (CIPP) lining
CIPP lining inserts a resin-saturated felt tube and cures it in place to create a new pipe within the old host pipe, restoring structural integrity without excavation.
CPWM Utility Systems 4
A city's water system pressure zone has static pressure of 95 psi at the lowest point.
What is the PRIMARY concern for system managers?