Illinois EPA Class C Ultimate Exam
**Question 1.** Which component of a well prevents surface contaminants from
entering the well bore?
A) Casing
B) Screen
C) Grout
D) Pitless adapter
Answer: A
Explanation: The casing is a sealed pipe that isolates the borehole from surface
soils and groundwater, preventing contaminants from traveling down the well.
**Question 2.** In the hydrologic cycle, what process describes water moving
from the land surface into underground aquifers?
A) Evaporation
B) Transpiration
C) Infiltration
D) Precipitation
Answer: C
Explanation: Infiltration is the movement of water through soil and rock layers
into the saturated zone, recharging groundwater.
**Question 3.** The static water level in a well is measured when:
A) The pump is running at full capacity
B) The well is being drawn down
C) No water is being pumped and the water surface is at rest
D) The well is being flushed
,Illinois EPA Class C Ultimate Exam
Answer: C
Explanation: Static water level is the height of the water column in the well when
the pump is off and the water is undisturbed.
**Question 4.** Which of the following is a common biological threat to
groundwater sources?
A) Nitrate
B. Lead
C) E. coli
D) Iron
Answer: C
Explanation: E. coli is an indicator of fecal contamination, a biological threat to
groundwater quality.
**Question 5.** A “cone of depression” forms when:
A) The well screen becomes clogged
B) The water table rises above the static level
C) Pumping creates a lowered water surface around the well
D) The well casing collapses
Answer: C
Explanation: Pumping removes water faster than it can be replenished, creating a
cone-shaped drawdown in the water table.
**Question 6.** Which chemical is most commonly used for breakpoint
chlorination in Class C operations?
A) Calcium hypochlorite
,Illinois EPA Class C Ultimate Exam
B) Sodium hypochlorite
C) Chlorine gas
D) Chlorine dioxide
Answer: C
Explanation: Chlorine gas is used for breakpoint chlorination because it provides
free chlorine that can achieve the breakpoint where combined chlorine is
eliminated.
**Question 7.** Free chlorine residual is measured in:
A) mg/L as CaCO₃
B) ppm as Cl₂
C) pH units
D) mg/L as Fe²⁺
Answer: B
Explanation: Free chlorine is reported as parts per million (ppm) of elemental
chlorine (Cl₂).
**Question 8.** Which of the following is a safety requirement when handling
chlorine gas?
A) Store in open containers outdoors
B) Use a gas detector and wear respiratory protection
C) Dilute with water before use
D) Keep near combustible materials
Answer: B
Explanation: Chlorine gas is toxic; a detector and proper respiratory protection
are required to prevent inhalation hazards.
, Illinois EPA Class C Ultimate Exam
**Question 9.** Hydrofluosilicic acid (H₂SiF₆) is used for:
A) pH adjustment
B) Fluoridation
C) Corrosion control
D) Disinfection
Answer: B
Explanation: Hydrofluosilicic acid is a fluoridation chemical that provides fluoride
ions for dental health benefits.
**Question 10.** In corrosion control, a pH range of 7.2-7.8 is recommended
because:
A) It maximizes chlorine residual
B) It minimizes pipe scale formation
C) It reduces the solubility of lead and copper
D) It enhances iron oxidation
Answer: C
Explanation: Maintaining pH within 7.2-7.8 reduces the corrosion potential of lead
and copper pipes, limiting metal leaching.
**Question 11.** Polyphosphate sequestration primarily targets which
contaminant?
A) Chlorine
B) Iron and manganese
C) Fluoride
D) Nitrate
**Question 1.** Which component of a well prevents surface contaminants from
entering the well bore?
A) Casing
B) Screen
C) Grout
D) Pitless adapter
Answer: A
Explanation: The casing is a sealed pipe that isolates the borehole from surface
soils and groundwater, preventing contaminants from traveling down the well.
**Question 2.** In the hydrologic cycle, what process describes water moving
from the land surface into underground aquifers?
A) Evaporation
B) Transpiration
C) Infiltration
D) Precipitation
Answer: C
Explanation: Infiltration is the movement of water through soil and rock layers
into the saturated zone, recharging groundwater.
**Question 3.** The static water level in a well is measured when:
A) The pump is running at full capacity
B) The well is being drawn down
C) No water is being pumped and the water surface is at rest
D) The well is being flushed
,Illinois EPA Class C Ultimate Exam
Answer: C
Explanation: Static water level is the height of the water column in the well when
the pump is off and the water is undisturbed.
**Question 4.** Which of the following is a common biological threat to
groundwater sources?
A) Nitrate
B. Lead
C) E. coli
D) Iron
Answer: C
Explanation: E. coli is an indicator of fecal contamination, a biological threat to
groundwater quality.
**Question 5.** A “cone of depression” forms when:
A) The well screen becomes clogged
B) The water table rises above the static level
C) Pumping creates a lowered water surface around the well
D) The well casing collapses
Answer: C
Explanation: Pumping removes water faster than it can be replenished, creating a
cone-shaped drawdown in the water table.
**Question 6.** Which chemical is most commonly used for breakpoint
chlorination in Class C operations?
A) Calcium hypochlorite
,Illinois EPA Class C Ultimate Exam
B) Sodium hypochlorite
C) Chlorine gas
D) Chlorine dioxide
Answer: C
Explanation: Chlorine gas is used for breakpoint chlorination because it provides
free chlorine that can achieve the breakpoint where combined chlorine is
eliminated.
**Question 7.** Free chlorine residual is measured in:
A) mg/L as CaCO₃
B) ppm as Cl₂
C) pH units
D) mg/L as Fe²⁺
Answer: B
Explanation: Free chlorine is reported as parts per million (ppm) of elemental
chlorine (Cl₂).
**Question 8.** Which of the following is a safety requirement when handling
chlorine gas?
A) Store in open containers outdoors
B) Use a gas detector and wear respiratory protection
C) Dilute with water before use
D) Keep near combustible materials
Answer: B
Explanation: Chlorine gas is toxic; a detector and proper respiratory protection
are required to prevent inhalation hazards.
, Illinois EPA Class C Ultimate Exam
**Question 9.** Hydrofluosilicic acid (H₂SiF₆) is used for:
A) pH adjustment
B) Fluoridation
C) Corrosion control
D) Disinfection
Answer: B
Explanation: Hydrofluosilicic acid is a fluoridation chemical that provides fluoride
ions for dental health benefits.
**Question 10.** In corrosion control, a pH range of 7.2-7.8 is recommended
because:
A) It maximizes chlorine residual
B) It minimizes pipe scale formation
C) It reduces the solubility of lead and copper
D) It enhances iron oxidation
Answer: C
Explanation: Maintaining pH within 7.2-7.8 reduces the corrosion potential of lead
and copper pipes, limiting metal leaching.
**Question 11.** Polyphosphate sequestration primarily targets which
contaminant?
A) Chlorine
B) Iron and manganese
C) Fluoride
D) Nitrate
