NGWA Master Groundwater Contractor
Certification Practice Exam Questions
And Correct Answers (Verified Answers)
Plus Rationales 2026 Q&A | Instant
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1. What is the primary purpose of a sanitary well seal?
A. To increase pump efficiency
B. To prevent surface contaminants from entering the well
C. To stabilize the casing during drilling
D. To reduce aquifer drawdown
Answer: B
Rationale: Sanitary seals are designed to protect groundwater by
blocking contaminants from entering the well from the surface.
2. Which aquifer type is confined between impermeable layers?
A. Unconfined aquifer
B. Perched aquifer
C. Confined aquifer
D. Alluvial aquifer
Answer: C
Rationale: Confined aquifers are bounded above and below by
low-permeability materials.
,3. What drilling method is most suitable for unconsolidated
formations?
A. Cable tool drilling
B. Rotary drilling with mud
C. Air rotary drilling
D. Reverse circulation drilling
Answer: B
Rationale: Rotary drilling with drilling mud stabilizes
unconsolidated formations.
4. What is the main function of drilling mud?
A. Cooling the drill bit only
B. Increasing penetration rate only
C. Removing cuttings and stabilizing the borehole
D. Preventing corrosion of casing
Answer: C
Rationale: Drilling mud carries cuttings to the surface and
supports borehole walls.
5. Which casing material is most commonly used for potable water
wells?
A. Steel
B. Aluminum
C. PVC
D. Copper
Answer: C
Rationale: PVC is corrosion-resistant and widely approved for
potable water wells.
, 6. What is the purpose of a gravel pack?
A. Increase drilling speed
B. Seal off surface water
C. Improve well yield and filter sediments
D. Anchor the casing
Answer: C
Rationale: Gravel packs enhance water flow while preventing
fine sediments from entering the well.
7. Drawdown refers to:
A. Total depth of the well
B. Difference between static and pumping water levels
C. Pump setting depth
D. Aquifer thickness
Answer: B
Rationale: Drawdown is the lowering of water level during
pumping.
8. What parameter best indicates aquifer permeability?
A. Porosity
B. Transmissivity
C. Specific capacity
D. Storage coefficient
Answer: B
Rationale: Transmissivity measures the ability of an aquifer to
transmit water.
9. Which test is used to evaluate well performance?
A. Slug test
B. Pumping test
Certification Practice Exam Questions
And Correct Answers (Verified Answers)
Plus Rationales 2026 Q&A | Instant
Download Pdf
1. What is the primary purpose of a sanitary well seal?
A. To increase pump efficiency
B. To prevent surface contaminants from entering the well
C. To stabilize the casing during drilling
D. To reduce aquifer drawdown
Answer: B
Rationale: Sanitary seals are designed to protect groundwater by
blocking contaminants from entering the well from the surface.
2. Which aquifer type is confined between impermeable layers?
A. Unconfined aquifer
B. Perched aquifer
C. Confined aquifer
D. Alluvial aquifer
Answer: C
Rationale: Confined aquifers are bounded above and below by
low-permeability materials.
,3. What drilling method is most suitable for unconsolidated
formations?
A. Cable tool drilling
B. Rotary drilling with mud
C. Air rotary drilling
D. Reverse circulation drilling
Answer: B
Rationale: Rotary drilling with drilling mud stabilizes
unconsolidated formations.
4. What is the main function of drilling mud?
A. Cooling the drill bit only
B. Increasing penetration rate only
C. Removing cuttings and stabilizing the borehole
D. Preventing corrosion of casing
Answer: C
Rationale: Drilling mud carries cuttings to the surface and
supports borehole walls.
5. Which casing material is most commonly used for potable water
wells?
A. Steel
B. Aluminum
C. PVC
D. Copper
Answer: C
Rationale: PVC is corrosion-resistant and widely approved for
potable water wells.
, 6. What is the purpose of a gravel pack?
A. Increase drilling speed
B. Seal off surface water
C. Improve well yield and filter sediments
D. Anchor the casing
Answer: C
Rationale: Gravel packs enhance water flow while preventing
fine sediments from entering the well.
7. Drawdown refers to:
A. Total depth of the well
B. Difference between static and pumping water levels
C. Pump setting depth
D. Aquifer thickness
Answer: B
Rationale: Drawdown is the lowering of water level during
pumping.
8. What parameter best indicates aquifer permeability?
A. Porosity
B. Transmissivity
C. Specific capacity
D. Storage coefficient
Answer: B
Rationale: Transmissivity measures the ability of an aquifer to
transmit water.
9. Which test is used to evaluate well performance?
A. Slug test
B. Pumping test
