NGWA Master Groundwater Contractor
Certification Exam – 100 Questions And
Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant
Download Pdf
1. Which type of aquifer is confined by impermeable layers above and
below the water-bearing layer?
a. Unconfined aquifer
b. Confined aquifer
c. Perched aquifer
d. Artesian aquifer
Rationale: A confined aquifer is trapped between impermeable
layers, which restricts water flow and creates pressure.
2. What is the minimum distance a well should be located from a septic
tank to prevent contamination?
, a. 10 feet
b. 25 feet
c. 50 feet
d. 100 feet
Rationale: Standard guidelines recommend at least 50 feet to
prevent microbial contamination from septic systems.
3. Which method is commonly used to determine the safe yield of a
well?
a. Pump test
b. Step drawdown test
c. Constant rate pumping test
d. Chemical analysis
Rationale: Constant rate pumping tests help determine the
sustainable yield of a well by measuring drawdown over time.
4. What is the purpose of a well casing?
a. To increase water flow
b. To prevent the well from collapsing and protect water quality
c. To filter water
d. To mark property boundaries
Rationale: Casings stabilize the well bore and prevent contamination
from surface or shallow water.
5. Which drilling method is best suited for rocky formations?
a. Cable tool drilling
, b. Auger drilling
c. Rotary drilling
d. Air rotary drilling
Rationale: Rotary drilling, especially with a roller bit or diamond bit,
can penetrate hard rock efficiently.
6. What is the primary reason for disinfecting a new well?
a. To increase yield
b. To eliminate harmful microorganisms
c. To remove sediment
d. To prevent casing corrosion
Rationale: Disinfection, usually with chlorine, ensures the well is free
from bacteria before use.
7. Which type of pump is commonly used for deep wells?
a. Centrifugal pump
b. Jet pump
c. Submersible pump
d. Hand pump
Rationale: Submersible pumps are installed below the water surface,
making them ideal for deep wells.
8. What is the effect of high total dissolved solids (TDS) in groundwater?
a. Increases pH
b. Reduces iron content
c. Makes water taste salty or unpalatable
, d. Improves water clarity
Rationale: High TDS affects taste, may cause scaling, and can make
water unsuitable for drinking or industrial use.
9. When installing a well in a sandy aquifer, which screen type is
preferred?
a. Continuous slot screen
b. Wire-wound screen
c. Slot-type well screen
d. Perforated casing
Rationale: Slot-type screens allow water entry while minimizing sand
intrusion.
10. What is the primary cause of well interference?
a. Pump malfunction
b. Proximity of nearby wells
c. Chemical contamination
d. Low water demand
Rationale: Wells too close together can lower each other’s water
levels due to overlapping cones of depression.
11. Which water quality parameter indicates potential
corrosiveness?
a. Turbidity
b. Hardness
c. pH and alkalinity
Certification Exam – 100 Questions And
Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant
Download Pdf
1. Which type of aquifer is confined by impermeable layers above and
below the water-bearing layer?
a. Unconfined aquifer
b. Confined aquifer
c. Perched aquifer
d. Artesian aquifer
Rationale: A confined aquifer is trapped between impermeable
layers, which restricts water flow and creates pressure.
2. What is the minimum distance a well should be located from a septic
tank to prevent contamination?
, a. 10 feet
b. 25 feet
c. 50 feet
d. 100 feet
Rationale: Standard guidelines recommend at least 50 feet to
prevent microbial contamination from septic systems.
3. Which method is commonly used to determine the safe yield of a
well?
a. Pump test
b. Step drawdown test
c. Constant rate pumping test
d. Chemical analysis
Rationale: Constant rate pumping tests help determine the
sustainable yield of a well by measuring drawdown over time.
4. What is the purpose of a well casing?
a. To increase water flow
b. To prevent the well from collapsing and protect water quality
c. To filter water
d. To mark property boundaries
Rationale: Casings stabilize the well bore and prevent contamination
from surface or shallow water.
5. Which drilling method is best suited for rocky formations?
a. Cable tool drilling
, b. Auger drilling
c. Rotary drilling
d. Air rotary drilling
Rationale: Rotary drilling, especially with a roller bit or diamond bit,
can penetrate hard rock efficiently.
6. What is the primary reason for disinfecting a new well?
a. To increase yield
b. To eliminate harmful microorganisms
c. To remove sediment
d. To prevent casing corrosion
Rationale: Disinfection, usually with chlorine, ensures the well is free
from bacteria before use.
7. Which type of pump is commonly used for deep wells?
a. Centrifugal pump
b. Jet pump
c. Submersible pump
d. Hand pump
Rationale: Submersible pumps are installed below the water surface,
making them ideal for deep wells.
8. What is the effect of high total dissolved solids (TDS) in groundwater?
a. Increases pH
b. Reduces iron content
c. Makes water taste salty or unpalatable
, d. Improves water clarity
Rationale: High TDS affects taste, may cause scaling, and can make
water unsuitable for drinking or industrial use.
9. When installing a well in a sandy aquifer, which screen type is
preferred?
a. Continuous slot screen
b. Wire-wound screen
c. Slot-type well screen
d. Perforated casing
Rationale: Slot-type screens allow water entry while minimizing sand
intrusion.
10. What is the primary cause of well interference?
a. Pump malfunction
b. Proximity of nearby wells
c. Chemical contamination
d. Low water demand
Rationale: Wells too close together can lower each other’s water
levels due to overlapping cones of depression.
11. Which water quality parameter indicates potential
corrosiveness?
a. Turbidity
b. Hardness
c. pH and alkalinity
