CSM CSM Urban Stormwater Systems & Infrastructure

Question 1

What is a combined sewer overflow (CSO) and why is it a stormwater concern?

Accepted Answer

A CSO occurs when a combined sewer system carrying both sewage and stormwater exceeds capacity, discharging untreated waste to waterways

Answer

A CSO is a planned release of clean stormwater from municipal retention ponds

Answer

A CSO refers to the overflow of a stormwater detention basin during a 100-year storm

Answer

A CSO is a backup system that routes excess flow to a water treatment plant

Question 2

What distinguishes a detention pond from a retention pond in stormwater management?

Accepted Answer

A detention pond temporarily holds runoff and releases it slowly after a storm; a retention pond permanently holds a standing pool of water

Answer

A detention pond is lined with concrete; a retention pond uses natural soil

Answer

A detention pond is used only in industrial areas; a retention pond is used in residential areas

Answer

A detention pond removes pollutants chemically; a retention pond removes them biologically

Question 3

What is an impervious surface and how does it affect the urban stormwater runoff cycle?

Accepted Answer

A hard surface that prevents infiltration, increasing runoff volume, velocity, and peak discharge compared to natural land

Answer

Any surface that is older than 25 years and requires replacement

Answer

A permeable pavement system that allows water to seep into the subgrade

Answer

A surface treated with waterproof sealant for industrial applications

Question 4

What is the function of a storm drain inlet grate in an urban stormwater system?

Accepted Answer

To collect surface runoff from streets and direct it into the underground storm drain conveyance system

Answer

To filter all pollutants from runoff before it enters the storm drain

Answer

To measure the flow rate entering the storm sewer system

Answer

To prevent backflow from the storm sewer into streets during flooding

Question 5

What is the purpose of a headwall at a storm drain outfall?

Accepted Answer

To stabilize the end of a pipe where it discharges to a channel or receiving water and to prevent erosion around the outlet

Answer

To measure total stormwater discharge volume from the pipe

Answer

To block stormwater from discharging during dry weather conditions

Answer

To raise the discharge elevation to create a ponding effect

Question 6

In the context of urban stormwater infrastructure, what is the purpose of an energy dissipater at a pipe outfall?

Accepted Answer

To reduce the velocity of discharged water to prevent erosion and scour at the receiving channel or water body

Answer

To generate hydroelectric power from stormwater flows

Answer

To filter fine sediment particles from the outfall discharge

Answer

To regulate flow rate so that peak discharge does not exceed pre-development conditions