2026/2027 TEXAS CLASS D WATER LICENSE (COMPLETE) QUESTIONS AND ANSWERS!! 2026/2027 2026/2027 | Page 1 | Passing Score: 75%
TEXAS COMMISSION ON ENVIRONMENTAL QUALITY
2026/2027 TEXAS CLASS D WATER LICENSE
(COMPLETE) QUESTIONS AND ANSWERS!!
2026/2027
CLASS D WATER LICENSE · Official Exam 2026/2027
100 75% CERTIFIED
QUESTIONS PASSING SCORE RECERTIFICATION
TABLE OF CONTENTS
Section 1 Water Sources and Supply Q1-20
Section 2 Water Treatment Processes Q21-40
Section 3 Water Distribution Systems Q41-60
Section 4 Water Quality and Monitoring Q61-80
Section 5 Regulations, Safety, and Administration Q81-100
Instructions: Select the single best answer for each question. This exam is designed for Texas Class D Water License certification
preparation. Passing score: 75% (75 questions correct).
,ECTION 1 | Water Sources and Supply | Q1-Q20 | 2026/2027 TEXAS CLASS D WATER LICENSE (COMPLETE) QUESTIONS AND ANSWERS!! 2026/2027 2026/202
Q1 Question 1 of 100
A water system operator in West Texas is evaluating a new well field to supplement the
municipal supply. The geologic formation beneath the proposed site consists primarily of
limestone with extensive solution channels and cavities. Which type of aquifer is most likely
present at this location?
A. Karst aquifer characterized by solution-enhanced fractures and conduits in soluble
rock
B. Unconfined sand and gravel aquifer with intergranular pore spaces
C. Confined artesian aquifer bounded by impermeable clay layers above and below
D. Fractured crystalline rock aquifer with minimal primary porosity
Correct Answer: A
Rationale:
Limestone with solution channels and cavities is the hallmark of a karst aquifer, where slightly acidic water dissolves
soluble rock over time, creating enlarged conduits that can transmit water rapidly. Sand and gravel aquifers rely on
intergranular flow, not solution channels. Confined artesian aquifers are bounded by impermeable layers. Crystalline
rock aquifers have minimal primary porosity and lack the solution features described.
Q2 Question 2 of 100
A small community water system draws water from a lake that experiences seasonal algal
blooms. Residents have reported earthy, musty taste and odor in their drinking water during
late summer. Which compounds are most likely responsible for these taste and odor
issues?
A. Geosmin and 2-methylisoborneol produced by cyanobacteria during algal blooms
B. Trihalomethanes formed by the reaction of chlorine with natural organic matter
C. Hydrogen sulfide gas generated by anaerobic bacteria in the lake sediment
D. Iron and manganese dissolved from the lake bed under reducing conditions
Correct Answer: A
Rationale:
Geosmin and MIB are organic compounds produced by cyanobacteria (blue-green algae) that cause earthy, musty
tastes and odors at extremely low concentrations, often during warm-weather algal blooms. THMs are disinfection
byproducts, not taste-causing compounds. Hydrogen sulfide produces a rotten egg odor. Iron and manganese cause
metallic taste and discoloration, not earthy/musty flavors.
2026/2027 TEXAS CLASS D WATER LICENSE (COMPLETE) QUESTIONS AND ANSWERS!! 2026/2027 2026/2027 | Passing Score: 75% | Page 2 of 1
,Q3 Question 3 of 100
A water utility manager is reviewing well construction records and notices that the sanitary
seal around the well casing extends only 5 feet below ground surface instead of the
required depth. The well draws from an unconfined aquifer with a water table at 30 feet.
Which risk does this inadequate sanitary seal pose?
A. Contamination from surface water and shallow pollutants can enter the well along the
casing
B. The well pump will cavitate due to insufficient head pressure above the aquifer
C. The aquifer yield will decrease because the seal does not extend to the water table
D. No risk exists because the water table is well below the seal depth
Correct Answer: A
Rationale:
An inadequate sanitary seal allows surface water, bacteria, and contaminants to migrate downward along the outside
of the casing into the aquifer. The seal must extend deep enough to prevent this pathway, typically through the first
impermeable layer. Pump cavitation relates to suction head, not seal depth. The seal does not affect aquifer yield.
Shallow seals are a contamination risk regardless of water table depth.
Q4 Question 4 of 100
An operator is calculating the specific capacity of a well that produces 600 gallons per
minute with a drawdown of 30 feet after 24 hours of pumping. Which calculation correctly
determines the specific capacity?
A. 20 gpm per foot of drawdown calculated as 600 gpm divided by 30 feet of drawdown
B. 18,000 gallons per day calculated by multiplying flow rate by drawdown
C. 0.05 feet per gpm calculated by dividing drawdown by the pumping rate
D. 30 feet of drawdown which is the only measurement needed for specific capacity
Correct Answer: A
Rationale:
Specific capacity equals the pumping rate divided by the drawdown: 600 gpm / 30 ft = 20 gpm/ft. It measures well
efficiency and productivity per foot of water level decline. Multiplying flow by drawdown gives total volume but not
specific capacity. Dividing drawdown by rate gives the inverse. Drawdown alone does not express the relationship
between yield and water level decline.
2026/2027 TEXAS CLASS D WATER LICENSE (COMPLETE) QUESTIONS AND ANSWERS!! 2026/2027 2026/2027 | Passing Score: 75% | Page 3 of 1
, Q5 Question 5 of 100
A utility is considering developing a spring as a water source for a rural community. The
spring flows from a hillside where a permeable limestone layer overlies an impermeable
shale layer. Which type of spring is described in this scenario?
A. Contact spring where a permeable layer meets an impermeable layer at the ground
surface
B. Artesian spring where water flows upward under pressure through a confining layer
C. Volcanic spring where groundwater is heated by magma near the surface
D. Seepage spring where water slowly oozes from a large area of unconsolidated material
Correct Answer: A
Rationale:
A contact spring occurs where groundwater flowing through a permeable layer (limestone) encounters an impermeable
layer (shale) and emerges at the surface. The impermeable layer forces the water to exit at the contact point. Artesian
springs involve upward flow under pressure. Volcanic springs involve geothermal heating. Seepage springs involve
diffuse flow through unconsolidated material.
Q6 Question 6 of 100
A water system operator measures the static water level in a well at 45 feet below ground
surface. After 8 hours of pumping at 400 gpm, the water level drops to 85 feet. Which value
represents the drawdown?
A. 40 feet calculated as the difference between the pumping level and the static water level
B. 85 feet which is the depth to water during pumping
C. 45 feet which is the original static water level
D. 125 feet calculated by adding the static level and pumping level
Correct Answer: A
Rationale:
Drawdown is the difference between the static (non-pumping) water level and the pumping water level: 85 ft - 45 ft = 40
ft. The pumping level alone (85 ft) is not the drawdown. The static level (45 ft) is the starting point. Adding the two
values has no hydrological meaning.
2026/2027 TEXAS CLASS D WATER LICENSE (COMPLETE) QUESTIONS AND ANSWERS!! 2026/2027 2026/2027 | Passing Score: 75% | Page 4 of 1
TEXAS COMMISSION ON ENVIRONMENTAL QUALITY
2026/2027 TEXAS CLASS D WATER LICENSE
(COMPLETE) QUESTIONS AND ANSWERS!!
2026/2027
CLASS D WATER LICENSE · Official Exam 2026/2027
100 75% CERTIFIED
QUESTIONS PASSING SCORE RECERTIFICATION
TABLE OF CONTENTS
Section 1 Water Sources and Supply Q1-20
Section 2 Water Treatment Processes Q21-40
Section 3 Water Distribution Systems Q41-60
Section 4 Water Quality and Monitoring Q61-80
Section 5 Regulations, Safety, and Administration Q81-100
Instructions: Select the single best answer for each question. This exam is designed for Texas Class D Water License certification
preparation. Passing score: 75% (75 questions correct).
,ECTION 1 | Water Sources and Supply | Q1-Q20 | 2026/2027 TEXAS CLASS D WATER LICENSE (COMPLETE) QUESTIONS AND ANSWERS!! 2026/2027 2026/202
Q1 Question 1 of 100
A water system operator in West Texas is evaluating a new well field to supplement the
municipal supply. The geologic formation beneath the proposed site consists primarily of
limestone with extensive solution channels and cavities. Which type of aquifer is most likely
present at this location?
A. Karst aquifer characterized by solution-enhanced fractures and conduits in soluble
rock
B. Unconfined sand and gravel aquifer with intergranular pore spaces
C. Confined artesian aquifer bounded by impermeable clay layers above and below
D. Fractured crystalline rock aquifer with minimal primary porosity
Correct Answer: A
Rationale:
Limestone with solution channels and cavities is the hallmark of a karst aquifer, where slightly acidic water dissolves
soluble rock over time, creating enlarged conduits that can transmit water rapidly. Sand and gravel aquifers rely on
intergranular flow, not solution channels. Confined artesian aquifers are bounded by impermeable layers. Crystalline
rock aquifers have minimal primary porosity and lack the solution features described.
Q2 Question 2 of 100
A small community water system draws water from a lake that experiences seasonal algal
blooms. Residents have reported earthy, musty taste and odor in their drinking water during
late summer. Which compounds are most likely responsible for these taste and odor
issues?
A. Geosmin and 2-methylisoborneol produced by cyanobacteria during algal blooms
B. Trihalomethanes formed by the reaction of chlorine with natural organic matter
C. Hydrogen sulfide gas generated by anaerobic bacteria in the lake sediment
D. Iron and manganese dissolved from the lake bed under reducing conditions
Correct Answer: A
Rationale:
Geosmin and MIB are organic compounds produced by cyanobacteria (blue-green algae) that cause earthy, musty
tastes and odors at extremely low concentrations, often during warm-weather algal blooms. THMs are disinfection
byproducts, not taste-causing compounds. Hydrogen sulfide produces a rotten egg odor. Iron and manganese cause
metallic taste and discoloration, not earthy/musty flavors.
2026/2027 TEXAS CLASS D WATER LICENSE (COMPLETE) QUESTIONS AND ANSWERS!! 2026/2027 2026/2027 | Passing Score: 75% | Page 2 of 1
,Q3 Question 3 of 100
A water utility manager is reviewing well construction records and notices that the sanitary
seal around the well casing extends only 5 feet below ground surface instead of the
required depth. The well draws from an unconfined aquifer with a water table at 30 feet.
Which risk does this inadequate sanitary seal pose?
A. Contamination from surface water and shallow pollutants can enter the well along the
casing
B. The well pump will cavitate due to insufficient head pressure above the aquifer
C. The aquifer yield will decrease because the seal does not extend to the water table
D. No risk exists because the water table is well below the seal depth
Correct Answer: A
Rationale:
An inadequate sanitary seal allows surface water, bacteria, and contaminants to migrate downward along the outside
of the casing into the aquifer. The seal must extend deep enough to prevent this pathway, typically through the first
impermeable layer. Pump cavitation relates to suction head, not seal depth. The seal does not affect aquifer yield.
Shallow seals are a contamination risk regardless of water table depth.
Q4 Question 4 of 100
An operator is calculating the specific capacity of a well that produces 600 gallons per
minute with a drawdown of 30 feet after 24 hours of pumping. Which calculation correctly
determines the specific capacity?
A. 20 gpm per foot of drawdown calculated as 600 gpm divided by 30 feet of drawdown
B. 18,000 gallons per day calculated by multiplying flow rate by drawdown
C. 0.05 feet per gpm calculated by dividing drawdown by the pumping rate
D. 30 feet of drawdown which is the only measurement needed for specific capacity
Correct Answer: A
Rationale:
Specific capacity equals the pumping rate divided by the drawdown: 600 gpm / 30 ft = 20 gpm/ft. It measures well
efficiency and productivity per foot of water level decline. Multiplying flow by drawdown gives total volume but not
specific capacity. Dividing drawdown by rate gives the inverse. Drawdown alone does not express the relationship
between yield and water level decline.
2026/2027 TEXAS CLASS D WATER LICENSE (COMPLETE) QUESTIONS AND ANSWERS!! 2026/2027 2026/2027 | Passing Score: 75% | Page 3 of 1
, Q5 Question 5 of 100
A utility is considering developing a spring as a water source for a rural community. The
spring flows from a hillside where a permeable limestone layer overlies an impermeable
shale layer. Which type of spring is described in this scenario?
A. Contact spring where a permeable layer meets an impermeable layer at the ground
surface
B. Artesian spring where water flows upward under pressure through a confining layer
C. Volcanic spring where groundwater is heated by magma near the surface
D. Seepage spring where water slowly oozes from a large area of unconsolidated material
Correct Answer: A
Rationale:
A contact spring occurs where groundwater flowing through a permeable layer (limestone) encounters an impermeable
layer (shale) and emerges at the surface. The impermeable layer forces the water to exit at the contact point. Artesian
springs involve upward flow under pressure. Volcanic springs involve geothermal heating. Seepage springs involve
diffuse flow through unconsolidated material.
Q6 Question 6 of 100
A water system operator measures the static water level in a well at 45 feet below ground
surface. After 8 hours of pumping at 400 gpm, the water level drops to 85 feet. Which value
represents the drawdown?
A. 40 feet calculated as the difference between the pumping level and the static water level
B. 85 feet which is the depth to water during pumping
C. 45 feet which is the original static water level
D. 125 feet calculated by adding the static level and pumping level
Correct Answer: A
Rationale:
Drawdown is the difference between the static (non-pumping) water level and the pumping water level: 85 ft - 45 ft = 40
ft. The pumping level alone (85 ft) is not the drawdown. The static level (45 ft) is the starting point. Adding the two
values has no hydrological meaning.
2026/2027 TEXAS CLASS D WATER LICENSE (COMPLETE) QUESTIONS AND ANSWERS!! 2026/2027 2026/2027 | Passing Score: 75% | Page 4 of 1
