Drainage & Storm Water Systems Flashcards

Under KDOT's NPDES permit requirements, what must be in place before earth-disturbing activities begin on a highway construction project?

Answer: A completed stormwater pollution prevention plan (SWPPP)

KDOT projects must have an approved SWPPP in place before any earth disturbance to comply with NPDES stormwater permit requirements.

What is the purpose of a check dam installed in a roadside swale?

Answer: To slow flow velocity and reduce erosion in steep swales

Check dams are low barriers placed across swales to reduce flow velocity on steeper grades, thereby limiting erosion and allowing sediment to settle.

A KDOT inspector notes that a storm sewer manhole lid is sunken 3 inches below the pavement surface. What hazard does this primarily present?

Answer: Vehicle damage and potential loss of vehicle control

A sunken manhole lid creates a roadway hazard that can cause vehicle damage, tire impact, and possible loss of vehicle control.

What is the Manning's roughness coefficient (n) used to calculate in open channel and culvert hydraulics?

Answer: The frictional resistance affecting flow velocity in a channel or pipe

Manning's n quantifies the frictional resistance of the channel boundary, directly affecting the calculated flow velocity and discharge.

During a post-storm inspection, a KDOT inspector finds that a silt fence has been breached and sediment has entered an adjacent waterway. What must be done first?

Answer: Stop additional discharge, contain the spill, and notify the appropriate environmental contacts

A sediment discharge to a waterway is a potential NPDES permit violation requiring immediate containment of further discharge and notification of environmental contacts.

What is the primary difference between a retention basin and a detention basin in highway storm water management?

Answer: Retention basins maintain a permanent pool of water; detention basins drain completely between storms

Retention basins hold a permanent water pool and provide water quality benefits, while detention basins temporarily store runoff and drain completely after each storm.

Which measurement is used to determine whether a culvert has adequate hydraulic opening for the design storm without exceeding allowable headwater?

Answer: Discharge capacity at the design headwater elevation

The culvert's discharge capacity at the allowable headwater elevation is compared to the design storm discharge to verify adequate hydraulic opening.