, Question 1
A confined aquifer in the Coastal Plain of Virginia has a transmissivity of
1,200 ft²/day and a storativity of 0.0005. A well pumping at 150 gpm has been
operating for 30 days. Using the Theis equation, what is the approximate
drawdown at an observation well located 500 feet from the pumping well?
(Assume u < 0.01 and use the Jacob-Lohman approximation.)
A. 12.5 ft
B. 18.7 ft
C. 24.3 ft
D. 31.2 ft
Correct Answer: B - 18.7 ft
RATIONALE
Using the Jacob-Lohman approximation s = (2.303Q/4T)
log(2.25Tt/r²S), with Q=150 gpm = 28,800 ft³/day, T=1,200 ft²/day,
t=30 days, r=500 ft, S=0.0005, the calculated drawdown is
approximately 18.7 ft. Options A, C, and D result from common errors
such as misplacing decimal points, using incorrect unit conversions, or
omitting the 2.303 factor.
Question 2
When drilling a well in Virginia's Piedmont region where fractured crystalline
bedrock is the primary aquifer, which of the following geophysical logging
methods is most effective for identifying water-producing fractures and
guiding casing placement?
A. Spontaneous potential (SP) logging
B. Caliper logging
C. Borehole televiewer (BHTV) imaging
D. Gamma-gamma density logging
Correct Answer: C - Borehole televiewer (BHTV) imaging
Page 2
, RATIONALE
The borehole televiewer provides high-resolution acoustic imaging of
the borehole wall, directly identifying open fractures and their
orientation, which is critical for siting casing and screen in fractured
rock. SP logging is better for sand/shale boundaries, caliper measures
hole diameter, and gamma-gamma density measures bulk density,
none of which directly image fractures.
Question 3
A community water system in Virginia withdraws groundwater from a well
field. The Virginia Department of Health requires a minimum separation
distance between a new production well and a septic system drainfield. What is
the required minimum separation distance under current regulations?
A. 50 feet
B. 100 feet
C. 200 feet
D. 300 feet
Correct Answer: B - 100 feet
RATIONALE
Virginia regulations (12VAC5-590-450) require a minimum 100-foot
separation between a public water supply well and a septic system
drainfield to prevent contamination. Distances of 50 feet are
insufficient, while 200 and 300 feet exceed the minimum but are not
required unless site-specific conditions dictate.
Question 4
A submersible pump installed in a Virginia well is experiencing frequent
cycling (short cycling) despite a correctly sized pressure tank. Which of the
following is the most likely cause?
A. The pump is oversized for the well's yield.
B. The pressure switch is set too wide.
Page 3
, C. The check valve is stuck open.
D. The well screen is partially clogged.
Correct Answer: C - The check valve is stuck open.
RATIONALE
A stuck-open check valve allows water to drain back into the well
after the pump shuts off, causing rapid pressure loss and frequent
pump restarts. An oversized pump would cause rapid drawdown but
not necessarily short cycling if the tank is adequate; a wide pressure
switch setting would lengthen cycle times, and a clogged screen would
reduce flow but not typically cause rapid cycling.
Question 5
A water sample from a Virginia well shows a pH of 5.8, alkalinity of 15 mg/L
as CaCO, and elevated copper levels. Which treatment sequence is most
appropriate to address both corrosion and copper contamination?
A. Anion exchange followed by reverse osmosis
B. Calcite pH adjustment followed by cation exchange
C. Chlorination followed by granular activated carbon
D. Sediment filtration followed by UV disinfection
Correct Answer: B - Calcite pH adjustment followed by cation
exchange
RATIONALE
Low pH and alkalinity cause corrosive water that dissolves copper
from plumbing; calcite contactors raise pH and alkalinity, while cation
exchange removes dissolved copper. Anion exchange and RO are not
optimal for copper removal, chlorination and GAC address organics,
and sediment/UV do not correct corrosion or remove metals.
Page 4
A confined aquifer in the Coastal Plain of Virginia has a transmissivity of
1,200 ft²/day and a storativity of 0.0005. A well pumping at 150 gpm has been
operating for 30 days. Using the Theis equation, what is the approximate
drawdown at an observation well located 500 feet from the pumping well?
(Assume u < 0.01 and use the Jacob-Lohman approximation.)
A. 12.5 ft
B. 18.7 ft
C. 24.3 ft
D. 31.2 ft
Correct Answer: B - 18.7 ft
RATIONALE
Using the Jacob-Lohman approximation s = (2.303Q/4T)
log(2.25Tt/r²S), with Q=150 gpm = 28,800 ft³/day, T=1,200 ft²/day,
t=30 days, r=500 ft, S=0.0005, the calculated drawdown is
approximately 18.7 ft. Options A, C, and D result from common errors
such as misplacing decimal points, using incorrect unit conversions, or
omitting the 2.303 factor.
Question 2
When drilling a well in Virginia's Piedmont region where fractured crystalline
bedrock is the primary aquifer, which of the following geophysical logging
methods is most effective for identifying water-producing fractures and
guiding casing placement?
A. Spontaneous potential (SP) logging
B. Caliper logging
C. Borehole televiewer (BHTV) imaging
D. Gamma-gamma density logging
Correct Answer: C - Borehole televiewer (BHTV) imaging
Page 2
, RATIONALE
The borehole televiewer provides high-resolution acoustic imaging of
the borehole wall, directly identifying open fractures and their
orientation, which is critical for siting casing and screen in fractured
rock. SP logging is better for sand/shale boundaries, caliper measures
hole diameter, and gamma-gamma density measures bulk density,
none of which directly image fractures.
Question 3
A community water system in Virginia withdraws groundwater from a well
field. The Virginia Department of Health requires a minimum separation
distance between a new production well and a septic system drainfield. What is
the required minimum separation distance under current regulations?
A. 50 feet
B. 100 feet
C. 200 feet
D. 300 feet
Correct Answer: B - 100 feet
RATIONALE
Virginia regulations (12VAC5-590-450) require a minimum 100-foot
separation between a public water supply well and a septic system
drainfield to prevent contamination. Distances of 50 feet are
insufficient, while 200 and 300 feet exceed the minimum but are not
required unless site-specific conditions dictate.
Question 4
A submersible pump installed in a Virginia well is experiencing frequent
cycling (short cycling) despite a correctly sized pressure tank. Which of the
following is the most likely cause?
A. The pump is oversized for the well's yield.
B. The pressure switch is set too wide.
Page 3
, C. The check valve is stuck open.
D. The well screen is partially clogged.
Correct Answer: C - The check valve is stuck open.
RATIONALE
A stuck-open check valve allows water to drain back into the well
after the pump shuts off, causing rapid pressure loss and frequent
pump restarts. An oversized pump would cause rapid drawdown but
not necessarily short cycling if the tank is adequate; a wide pressure
switch setting would lengthen cycle times, and a clogged screen would
reduce flow but not typically cause rapid cycling.
Question 5
A water sample from a Virginia well shows a pH of 5.8, alkalinity of 15 mg/L
as CaCO, and elevated copper levels. Which treatment sequence is most
appropriate to address both corrosion and copper contamination?
A. Anion exchange followed by reverse osmosis
B. Calcite pH adjustment followed by cation exchange
C. Chlorination followed by granular activated carbon
D. Sediment filtration followed by UV disinfection
Correct Answer: B - Calcite pH adjustment followed by cation
exchange
RATIONALE
Low pH and alkalinity cause corrosive water that dissolves copper
from plumbing; calcite contactors raise pH and alkalinity, while cation
exchange removes dissolved copper. Anion exchange and RO are not
optimal for copper removal, chlorination and GAC address organics,
and sediment/UV do not correct corrosion or remove metals.
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