NETTCP Drainage & Stormwater Management 3

Question 1

When installing a corrugated metal pipe (CMP) culvert, the minimum cover depth over the crown of the pipe under a roadway is typically determined by:

Accepted Answer

The pipe material strength, diameter, and expected live load (vehicle loading)

Answer

The pipe diameter only

Answer

State DOT standard of exactly 12 inches regardless of pipe size

Answer

The depth of the frost line in the project area

Question 2

A French drain (blind drain) differs from a standard storm drain primarily because it:

Accepted Answer

Collects and conveys subsurface groundwater without a defined inlet structure

Answer

Is constructed without outlet pipe connections

Answer

Uses French-manufactured geotextile fabric only

Answer

Is designed exclusively for residential applications

Question 3

According to typical MassDOT and NHDOT specifications, what maximum pipe deflection is acceptable for flexible pipe (HDPE/PVC) after installation and backfilling?

Accepted Answer

5% of the pipe inside diameter

Answer

1% of the pipe inside diameter

Answer

10% of the pipe inside diameter

Answer

15% of the pipe inside diameter

Question 4

What is the purpose of a geotextile filter fabric wrapped around underdrain aggregate?

Accepted Answer

To prevent migration of fine soil particles into the aggregate while allowing water to pass

Answer

To increase the hydraulic conductivity of the drain trench

Answer

To provide structural reinforcement for the drain pipe

Answer

To insulate the drain from frost penetration

Question 5

During a post-storm inspection of a highway drainage system, you find a catch basin sump filled to within 6 inches of the outlet pipe invert. The appropriate action is to:

Accepted Answer

Clean the catch basin immediately to restore design sediment storage capacity

Answer

Schedule cleaning within the next annual maintenance cycle

Answer

Replace the catch basin with a deeper sump model

Answer

Install an additional catch basin upstream to reduce loading

Question 6

Which hydrologic method is most appropriate for computing peak runoff from large complex watersheds (greater than 2,000 acres) for culvert and bridge design in New England?

Accepted Answer

NRCS (SCS) Curve Number Method with unit hydrograph

Answer

Rational Method (Q = CiA)

Answer

Manning's equation applied to the watershed

Answer

Statistical regression equations only

Question 7

When a stormwater outfall discharges directly to a classified cold-water fishery stream in New England, additional design requirements typically include:

Accepted Answer

Thermal impact analysis and possible temperature mitigation measures to protect aquatic habitat

Answer

Reducing stormwater volume by 100% through infiltration only

Answer

Prohibition of any stormwater discharge within 1,000 feet of the stream

Answer

Installation of a water quality vault treating 100% of the 100-year storm