Stormwater Management Practices Flashcards
7 cards from real CESSWI practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Stormwater Management Practices flashcards as text
Which type of detention basin is designed to drain completely between storm events, providing no permanent pool of water?
Answer: Dry detention basin
Dry detention basins (also called dry ponds) temporarily store runoff and drain completely between storms, providing only flood control without water quality benefits from a permanent pool.
What is the primary purpose of an extended detention basin compared to a standard dry detention basin?
Answer: Provide longer residence time to settle fine sediments
Extended detention basins hold runoff for 24–40 hours, allowing finer sediment particles that would not settle in a standard detention period to be removed before release.
A bioretention cell (rain garden) treats stormwater primarily through which combination of processes?
Answer: Filtration, infiltration, and biological uptake
Bioretention cells use engineered soil media for filtration, underlying native soil for infiltration, and plants for biological nutrient uptake to achieve pollutant removal.
Under the NPDES Construction General Permit, what minimum rainfall threshold typically triggers the requirement to inspect a construction site for BMPs?
Answer: 0.25 inch
Most NPDES Construction General Permits require post-storm inspections following rainfall events of 0.25 inch or greater within a 24-hour period.
Which outlet structure configuration is best suited to control two separate design storms (e.g., 2-year and 100-year) from a single detention basin?
Answer: Riser with multiple orifices at different elevations
A multi-stage riser with orifices at different elevations independently controls smaller, more frequent storms at lower stages and larger storms at higher stages.
What term describes the volume of runoff that must be captured and treated to meet water quality objectives under many state stormwater programs?
Answer: Water quality volume (WQv)
The Water Quality Volume (WQv) is the runoff volume associated with a small, frequent storm (often the 90th percentile event) that must be captured and treated to achieve pollutant load reductions.
Permeable pavement systems reduce stormwater runoff volume primarily by:
Answer: Allowing water to infiltrate through voids into underlying storage layers
Permeable pavement contains open-graded voids that allow rainfall to pass through the surface and into a stone reservoir base, where it infiltrates into the subgrade or is slowly released.