NETTCP Drainage & Stormwater Management 2

Question 1

What is the function of an energy dissipator placed at the outlet of a culvert?

Accepted Answer

To reduce flow velocity and prevent scour erosion at the outlet

Answer

To filter pollutants from stormwater before discharge

Answer

To measure discharge volumes for regulatory reporting

Answer

To prevent backflow during high water events

Question 2

A hydraulic gradient line (HGL) that rises above the crown of a drainage pipe indicates:

Accepted Answer

The pipe is flowing full under pressure (pressure flow)

Answer

The pipe is flowing partially full under normal conditions

Answer

Infiltration of groundwater into the system

Answer

The pipe slope is steeper than the critical slope

Question 3

Which underdrain configuration is most effective at lowering the water table beneath a highway pavement to prevent frost heave in New England?

Accepted Answer

Longitudinal perforated pipe underdrain with permeable backfill placed at subgrade elevation

Answer

Surface interceptor ditch along the roadway edge

Answer

Impermeable geocomposite barrier beneath the pavement

Answer

Edge of pavement curb and gutter system

Question 4

When inspecting a stormwater detention basin, which condition requires immediate corrective action?

Accepted Answer

Evidence of overtopping, erosion, or seepage through the embankment

Answer

Vegetation growth on the side slopes below the normal water level

Answer

Accumulation of sediment in the forebay after a storm event

Answer

Standing water in the basin between storm events

Question 5

The time of concentration (Tc) in a drainage watershed is defined as:

Accepted Answer

The time for runoff to travel from the hydraulically most remote point to the design point

Answer

The duration of the design storm event in hours

Answer

The lag time between peak rainfall intensity and peak discharge

Answer

The time required for soil infiltration capacity to reach a steady state

Question 6

What is the minimum recommended slope for a storm drain pipe to maintain self-cleaning velocity and prevent sediment deposition?

Accepted Answer

0.5% (0.5 feet per 100 feet)

Answer

0.1% (1 foot per 1,000 feet)

Answer

2.0% (2 feet per 100 feet)

Answer

5.0% (5 feet per 100 feet)

Question 7

Which New England-specific drainage challenge most often requires the use of deep-sump catch basins rather than standard designs?

Accepted Answer

Freezing and thawing cycles that mobilize sand and road salt into drainage systems

Answer

High annual rainfall totals exceeding 60 inches

Answer

Dense urban development limiting land for surface detention

Answer

Proximity to coastal tidal influence