CESSWI Stormwater Runoff Management 4 — Questions and Answers
Question 1: Which stormwater management approach focuses on managing runoff at or near its source to mimic predevelopment hydrology?
- End-of-pipe treatment
- Low Impact Development (LID) (Correct answer)
- Traditional gray infrastructure
- Regional retention basins
Correct answer: Low Impact Development (LID)
Low Impact Development (LID) uses distributed, small-scale practices to infiltrate, evapotranspire, and reuse stormwater close to where it falls, mimicking natural hydrology.
Question 2: A bioretention cell is designed to treat stormwater through which primary set of processes?
- Filtration, adsorption, biological uptake, and infiltration (Correct answer)
- Chemical coagulation and flocculation
- Gravity settling in a quiescent pool
- UV disinfection and chlorination
Correct answer: Filtration, adsorption, biological uptake, and infiltration
Bioretention cells treat runoff through physical filtration through engineered media, adsorption to soil particles, biological uptake by plants, and infiltration into native soils.
Question 3: Under what condition should a CESSWI inspector recommend immediate corrective action for a stormwater BMP?
- When the BMP was installed more than 2 years ago
- When the BMP is functioning within 10% of design capacity
- When BMP failure poses an imminent threat to water quality or public safety (Correct answer)
- When sediment has accumulated to 25% of the design storage volume
Correct answer: When BMP failure poses an imminent threat to water quality or public safety
Immediate corrective action is warranted when a BMP failure poses an imminent threat to water quality, downstream flooding, or public safety, regardless of maintenance schedules.
Question 4: Which design element of a wet detention pond is specifically intended to increase sediment removal efficiency?
- Emergency spillway
- Forebay at the inlet (Correct answer)
- Rip-rap outlet protection
- Anti-seep collar on the barrel
Correct answer: Forebay at the inlet
A forebay is a pre-settling chamber at the pond inlet that captures coarse sediment before it reaches the main pool, reducing maintenance frequency and improving overall efficiency.
Question 5: What is the primary regulatory driver for municipalities to develop Stormwater Management Programs (SWMPs) under the MS4 program?
- Clean Air Act Section 112
- Safe Drinking Water Act
- NPDES Phase I and Phase II regulations under the Clean Water Act (Correct answer)
- Resource Conservation and Recovery Act
Correct answer: NPDES Phase I and Phase II regulations under the Clean Water Act
MS4 stormwater programs are required under NPDES Phase I (large/medium municipalities) and Phase II (small municipalities) regulations promulgated under the Clean Water Act.
Question 6: Which scenario represents an illicit discharge to a storm sewer system?
- Stormwater runoff entering an inlet during a rainstorm
- Sanitary sewer overflow entering a storm drain through a cross-connection (Correct answer)
- Groundwater infiltration into a storm drain pipe
- Clean water from a firefighting operation draining to a storm inlet
Correct answer: Sanitary sewer overflow entering a storm drain through a cross-connection
A sanitary sewer cross-connection that allows sewage to enter the storm drain is a classic illicit discharge, introducing pathogens and pollutants into waterways.
Question 7: When computing peak discharge using the Rational Method (Q = CiA), what units must drainage area 'A' be expressed in for the formula to yield flow in cubic feet per second?
- Square feet
- Square miles
- Acres (Correct answer)
- Hectares
Correct answer: Acres
In the Rational Method as commonly applied in the US, area must be in acres, rainfall intensity in inches per hour, and C is dimensionless, yielding Q in cubic feet per second.
CESSWI Stormwater Runoff Management 4
Which stormwater management approach focuses on managing runoff at or near its source to mimic predevelopment hydrology?