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Free NGICP Practice Questions

10 free, exam-style National Green Infrastructure Certification Program (NGICP) practice questions with answers and explanations. No signup required. Work through them below, then take the full free NGICP practice test to study every exam domain.

Question 1

A wooded lot is redeveloped into a paved parking area with no stormwater controls. Compared to the original wooded condition, how does the new surface most affect stormwater?

  1. It allows more rainfall to soak in and recharge groundwater
  2. It raises the share of water lost to evaporation and plant uptake
  3. It increases both the volume and rate of runoff
  4. It has little effect on how water leaves the developed site
Show answer & explanation

Correct answer: C - It increases both the volume and rate of runoff

Question 2

In a bioretention cell built over slow-draining native soils, what is the purpose of the underdrain?

  1. To collect and remove treated water the slow native soil cannot infiltrate in time
  2. To deliver and distribute incoming stormwater runoff across the cell surface
  3. To store the captured stormwater for later use in site irrigation
  4. To form a barrier that stops plant roots from spreading into the media
Show answer & explanation

Correct answer: A - To collect and remove treated water the slow native soil cannot infiltrate in time

Question 3

A practice consists of a load-bearing surface that lets water pass through into a stone reservoir below, where it is stored and infiltrated. Which practice is this?

  1. A stormwater wetland that treats runoff with wetland plants
  2. A cistern that stores roof runoff for later reuse
  3. A green roof that holds and evapotranspires precipitation
  4. Permeable pavement with an aggregate reservoir beneath the surface
Show answer & explanation

Correct answer: D - Permeable pavement with an aggregate reservoir beneath the surface

Question 4

While cleaning a bioswale, a maintenance worker finds a stormwater inlet with its grate missing. What should the worker do first?

  1. Begin removing the accumulated trash from the inlet
  2. Secure and barricade the open inlet
  3. Photograph the inlet for the inspection report
  4. Note the location and finish the route before reporting it
Show answer & explanation

Correct answer: B - Secure and barricade the open inlet

Question 5

Which factor is the leading cause of premature failure in green infrastructure practices?

  1. Sediment clogging the media, underdrain, or surface
  2. Occasional vandalism of surface features
  3. Overgrowth of the established vegetation
  4. Pedestrian foot traffic across the surface
Show answer & explanation

Correct answer: A - Sediment clogging the media, underdrain, or surface

Question 6

A specification calls for washed AASHTO #57 stone in an aggregate storage reservoir. Why is washed stone required instead of unwashed stone?

  1. Washed stone is heavier and resists being displaced by flowing water
  2. The fine particles left in unwashed stone help bind the aggregate together for added load-bearing strength
  3. Fines in unwashed stone fill the voids, reducing storage and drainage capacity
  4. Washed stone has a cleaner appearance that improves the finished look
Show answer & explanation

Correct answer: C - Fines in unwashed stone fill the voids, reducing storage and drainage capacity

Question 7

A crew is excavating the bottom of a bioretention cell that is meant to infiltrate stormwater. To protect the cell's function, the crew should:

  1. Compact the bottom firmly with a roller to provide a stable, uniform base
  2. Avoid driving heavy equipment across the infiltration surface
  3. Wet the soil thoroughly before excavating to ease digging
  4. Run the equipment over the bottom repeatedly to smooth it
Show answer & explanation

Correct answer: B - Avoid driving heavy equipment across the infiltration surface

Question 8

A plan specifies a 2:1 (horizontal:vertical) side slope. For every 2 feet of horizontal distance, how much does the elevation change?

  1. 1 foot
  2. 2 feet
  3. 4 feet
  4. 0.5 foot
Show answer & explanation

Correct answer: A - 1 foot

Question 9

A bioretention cell is designed to drain ponded water within 48 hours, but three days after a storm water is still standing in it. What does this most likely indicate?

  1. The cell is draining normally and performing exactly as it was designed
  2. The cell simply received too little rainfall during the recent storm
  3. The cell needs additional plantings installed to take up the extra water
  4. The media or underdrain is clogged, or the soil is compacted
Show answer & explanation

Correct answer: D - The media or underdrain is clogged, or the soil is compacted

Question 10

During inspection, water is observed entering a bioswale and flowing straight through a single eroded channel to the outlet without spreading across the practice. This is best described as:

  1. Healthy infiltration across the swale
  2. An overflow structure that is sized too large
  3. Short-circuiting caused by improper grading
  4. Excess vegetation slowing the flow
Show answer & explanation

Correct answer: C - Short-circuiting caused by improper grading

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