Drainage & Stormwater Management Flashcards

What is the primary purpose of a stormwater detention basin in a public infrastructure project?

Answer: To temporarily hold stormwater runoff and release it at a controlled rate

Detention basins temporarily hold stormwater runoff and release it at a controlled rate to prevent downstream flooding.

According to standard drainage design, what does the term 'return period' or 'recurrence interval' refer to?

Answer: The frequency with which a given storm event is statistically expected to occur

Return period (recurrence interval) expresses the statistical probability that a storm of a given magnitude will occur in any given year.

When inspecting a culvert, which condition is considered the most structurally critical defect?

Answer: Joint separation or cracking at the crown

Joint separation or cracking at the crown indicates structural failure that can lead to collapse and loss of hydraulic capacity.

What is the minimum slope typically recommended for concrete-lined drainage channels to maintain self-cleaning velocities?

Answer: 0.5%

A minimum slope of 0.5% is typically required in concrete-lined channels to achieve the minimum velocity needed to prevent sediment deposition.

Which federal regulation primarily governs stormwater discharges from construction sites disturbing one or more acres?

Answer: NPDES Construction General Permit under the Clean Water Act

The NPDES Construction General Permit issued under the Clean Water Act requires stormwater pollution prevention plans for construction sites disturbing one or more acres.

During a storm drain inspection, an inspector observes water pooling above a catch basin grate during moderate rainfall. What is the MOST likely cause?

Answer: The grate is undersized or clogged, restricting inlet capacity

Ponding above a catch basin grate during moderate rain typically indicates the grate openings are clogged with debris or the grate is undersized for the drainage area.

What is a Stormwater Pollution Prevention Plan (SWPPP) required to include as a primary component?

Answer: Best Management Practices (BMPs) to minimize pollutant discharge

A SWPPP must identify and describe the Best Management Practices to be implemented to prevent pollutants from entering stormwater discharges.