Civil Engineering PE Environmental Engineering and Stormwater Management 2 — Questions and Answers
Question 1: Biochemical oxygen demand (BOD) measures:
- Total organic carbon concentration in wastewater
- Oxygen consumed by microorganisms decomposing organic matter (Correct answer)
- Chemical oxygen demand of inorganic compounds
- Dissolved oxygen concentration in a receiving stream
Correct answer: Oxygen consumed by microorganisms decomposing organic matter
BOD quantifies dissolved oxygen consumed by biological processes decomposing organic matter, typically measured over 5 days at 20°C (BOD₅).
Question 2: The Streeter-Phelps DO sag curve downstream of a wastewater outfall shows:
- Immediate increase in DO due to reaeration
- A dissolved oxygen deficit that deepens then recovers downstream (Correct answer)
- Constant DO at saturation throughout
- An irreversible drop in DO with no recovery
Correct answer: A dissolved oxygen deficit that deepens then recovers downstream
The DO sag model predicts a critical minimum at the point where deoxygenation rate equals reaeration rate, after which DO recovers as organic demand decreases.
Question 3: An NPDES permit under the Clean Water Act regulates:
- Nonpoint source pollution from agricultural fields
- Point source discharges of pollutants to navigable waters of the US (Correct answer)
- Underground injection of industrial wastes
- Atmospheric deposition of nitrogen to water bodies
Correct answer: Point source discharges of pollutants to navigable waters of the US
NPDES requires permits for any discrete point source discharging pollutants into waters of the United States, setting effluent limits and monitoring requirements.
Question 4: A bioretention cell (rain garden) removes stormwater pollutants primarily through:
- Sedimentation in a permanent pool
- Filtration through engineered soil media combined with plant uptake (Correct answer)
- Chlorination of captured runoff
- UV disinfection of stormwater
Correct answer: Filtration through engineered soil media combined with plant uptake
Bioretention systems filter runoff through an engineered soil mix, removing TSS, metals, and nutrients via physical filtration, adsorption, and plant/microbial uptake.
Question 5: A Total Maximum Daily Load (TMDL) establishes:
- The maximum stream flow rate allowable below a dam
- The maximum pollutant load a water body can receive and still meet water quality standards (Correct answer)
- The daily BOD limit for a single industrial discharger
- The maximum design storm intensity for a watershed
Correct answer: The maximum pollutant load a water body can receive and still meet water quality standards
A TMDL is the total pollutant loading capacity of a water body, allocated among point sources (WLA), nonpoint sources (LA), and a margin of safety (MOS).
Question 6: NPDES Construction General Permits require a Stormwater Pollution Prevention Plan (SWPPP) for land disturbance areas of:
- Any size
- 0.25 acres or more
- 1 acre or more (Correct answer)
- 5 acres or more
Correct answer: 1 acre or more
Federal NPDES CGP requirements apply to construction sites disturbing 1 acre or more, requiring a SWPPP with erosion and sediment controls.
Civil Engineering PE Environmental Engineering and Stormwater Management 2
Biochemical oxygen demand (BOD) measures: