TCEQ Wastewater Class D License Exam
ACTUAL EXAM 2026/2027 | Complete
Exam-Style Questions | Verified Q&A |
Pass Guaranteed - A+ Graded
SECTION 1: SAFETY & BASIC MATH
(20 Questions)
Q1: During a morning plant round, you notice a strong rotten-egg odor near the headworks building.
What is the most likely gas present, and what is your first action?
A. Carbon monoxide; immediately enter the building to investigate the source.
B. Hydrogen sulfide (H₂S); evacuate the area and notify your supervisor. *CORRECT+
C. Methane; continue your round but increase ventilation.
D. Chlorine gas; don your SCBA and enter immediately.
Correct Answer: B
Rationale: H₂S has a characteristic rotten-egg odor at low concentrations (0.0005–0.3 ppm) but
becomes odorless at lethal levels (>100 ppm) due to olfactory paralysis—never rely on smell for safety.
Evacuation and supervisor notification follow TCEQ and OSHA confined space protocols. Distractor A:
CO is odorless and colorless; entering without PPE is fatal. Distractor C: Methane is odorless; continuing
the round ignores the immediate hazard. Distractor D: Chlorine has a pungent bleach-like odor, not
rotten-egg; premature SCBA entry without assessment violates lockout/tagout procedures.
Q2: What is the minimum oxygen level (%) required for safe entry into a confined space in a wastewater
facility per OSHA 1910.146?
A. 15.5%
B. 19.5% [CORRECT]
C. 21.0%
D. 23.5%
,Correct Answer: B
Rationale: OSHA 1910.146 defines a confined space as having an oxygen concentration below 19.5% as
"hazardous" and requiring respiratory protection. Normal atmospheric oxygen is ~20.9%. Distractor A:
15.5% is severely oxygen-deficient and immediately dangerous to life/health (IDLH). Distractor C: 21% is
normal ambient air, not the minimum safe threshold. Distractor D: 23.5% is oxygen-enriched, increasing
combustion risk and also hazardous.
Q3: You are asked to perform maintenance on a pump. The lockout/tagout (LOTO) procedure requires
you to:
A. Turn off the pump switch and place a "Do Not Operate" sign nearby.
B. Shut down the pump, isolate all energy sources, apply your personal lock and tag, and verify zero
energy state. [CORRECT]
C. Ask the operator on the previous shift to lock out the equipment for you.
D. Disconnect the power cord and begin work immediately if the pump is not running.
Correct Answer: B
Rationale: OSHA 1910.147 requires isolation of ALL energy sources (electrical, hydraulic, pneumatic,
gravitational), application of a personal lock/tag by the person performing the work, and verification of
zero energy before work begins. Distractor A: A sign alone does not constitute LOTO; the switch could
be accidentally activated. Distractor C: Another person's lock does not protect you; only your personal
lock ensures your safety. Distractor D: Stored energy (capacitors, pressure) remains hazardous even
when disconnected.
Q4: A rectangular sedimentation tank measures 40 feet long, 20 feet wide, and 10 feet deep. What is
the volume of the tank in gallons?
A. 59,840 gallons
B. 64,960 gallons
C. 69,696 gallons
D. 74,800 gallons
Correct Answer: A
Rationale: Volume = L × W × D × 7.48 gal/ft³ = 40 × 20 × 10 × 7.48 = 59,840 gallons. Distractor B: Uses
8.34 lb/gal (weight conversion) instead of 7.48 gal/ft³. Distractor C: Uses 8.7 gal/ft³ (incorrect conversion
factor). Distractor D: Rounds 7.48 to 7.5 and makes an arithmetic error.
Q5: A pump delivers 250 gallons per minute (gpm). How many million gallons per day (MGD) does this
represent?
, A. 0.25 MGD
B. 0.36 MGD
C. 0.50 MGD
D. 0.75 MGD
Correct Answer: B
Rationale: 250 gpm × 1,440 min/day = 360,000 gpd = 0.36 MGD. Distractor A: Confuses gpm with MGD
directly. Distractor C: Uses 1,000 min/day instead of 1,440. Distractor D: Uses 2,000 min/day or doubles
the flow rate.
Q6: The influent flow to a primary clarifier is 1.5 MGD. The clarifier diameter is 50 feet. What is the
surface overflow rate in gallons per day per square foot (gpd/ft²)?
A. 582 gpd/ft²
B. 764 gpd/ft² [CORRECT]
C. 1,528 gpd/ft²
D. 2,356 gpd/ft²
Correct Answer: B
Rationale: Surface area = π × (25 ft)² = 1,963.5 ft². Overflow rate = 1,500,000 gpd ÷ 1,963.5 ft² = 764
gpd/ft². Distractor A: Uses diameter instead of radius (π × 50² = 7,854 ft²). Distractor C: Forgets to
convert MGD to gallons (uses 1.5 instead of 1,500,000). Distractor D: Uses circumference instead of
area.
Q7: You discover a coworker unconscious inside a wet well. The gas monitor reads 18.0% oxygen. What
is your immediate action?
A. Enter the wet well immediately to rescue your coworker.
B. Call 911, ventilate the space, and do not enter until rescue personnel arrive with proper equipment.
[CORRECT]
C. Send another operator in with a rope tied around their waist.
D. Turn on the ventilation fan and enter after 2 minutes.
Correct Answer: B
Rationale: 18.0% oxygen is below the 19.5% safe threshold. OSHA prohibits untrained rescue attempts;
70% of confined space fatalities are would-be rescuers. Distractor A: Entering without SCBA and rescue
equipment makes you the next victim. Distractor C: A rope does not provide respiratory protection; this
is an outdated and dangerous practice. Distractor D: Two minutes of ventilation is insufficient;
atmospheric testing must confirm safe levels before entry.
ACTUAL EXAM 2026/2027 | Complete
Exam-Style Questions | Verified Q&A |
Pass Guaranteed - A+ Graded
SECTION 1: SAFETY & BASIC MATH
(20 Questions)
Q1: During a morning plant round, you notice a strong rotten-egg odor near the headworks building.
What is the most likely gas present, and what is your first action?
A. Carbon monoxide; immediately enter the building to investigate the source.
B. Hydrogen sulfide (H₂S); evacuate the area and notify your supervisor. *CORRECT+
C. Methane; continue your round but increase ventilation.
D. Chlorine gas; don your SCBA and enter immediately.
Correct Answer: B
Rationale: H₂S has a characteristic rotten-egg odor at low concentrations (0.0005–0.3 ppm) but
becomes odorless at lethal levels (>100 ppm) due to olfactory paralysis—never rely on smell for safety.
Evacuation and supervisor notification follow TCEQ and OSHA confined space protocols. Distractor A:
CO is odorless and colorless; entering without PPE is fatal. Distractor C: Methane is odorless; continuing
the round ignores the immediate hazard. Distractor D: Chlorine has a pungent bleach-like odor, not
rotten-egg; premature SCBA entry without assessment violates lockout/tagout procedures.
Q2: What is the minimum oxygen level (%) required for safe entry into a confined space in a wastewater
facility per OSHA 1910.146?
A. 15.5%
B. 19.5% [CORRECT]
C. 21.0%
D. 23.5%
,Correct Answer: B
Rationale: OSHA 1910.146 defines a confined space as having an oxygen concentration below 19.5% as
"hazardous" and requiring respiratory protection. Normal atmospheric oxygen is ~20.9%. Distractor A:
15.5% is severely oxygen-deficient and immediately dangerous to life/health (IDLH). Distractor C: 21% is
normal ambient air, not the minimum safe threshold. Distractor D: 23.5% is oxygen-enriched, increasing
combustion risk and also hazardous.
Q3: You are asked to perform maintenance on a pump. The lockout/tagout (LOTO) procedure requires
you to:
A. Turn off the pump switch and place a "Do Not Operate" sign nearby.
B. Shut down the pump, isolate all energy sources, apply your personal lock and tag, and verify zero
energy state. [CORRECT]
C. Ask the operator on the previous shift to lock out the equipment for you.
D. Disconnect the power cord and begin work immediately if the pump is not running.
Correct Answer: B
Rationale: OSHA 1910.147 requires isolation of ALL energy sources (electrical, hydraulic, pneumatic,
gravitational), application of a personal lock/tag by the person performing the work, and verification of
zero energy before work begins. Distractor A: A sign alone does not constitute LOTO; the switch could
be accidentally activated. Distractor C: Another person's lock does not protect you; only your personal
lock ensures your safety. Distractor D: Stored energy (capacitors, pressure) remains hazardous even
when disconnected.
Q4: A rectangular sedimentation tank measures 40 feet long, 20 feet wide, and 10 feet deep. What is
the volume of the tank in gallons?
A. 59,840 gallons
B. 64,960 gallons
C. 69,696 gallons
D. 74,800 gallons
Correct Answer: A
Rationale: Volume = L × W × D × 7.48 gal/ft³ = 40 × 20 × 10 × 7.48 = 59,840 gallons. Distractor B: Uses
8.34 lb/gal (weight conversion) instead of 7.48 gal/ft³. Distractor C: Uses 8.7 gal/ft³ (incorrect conversion
factor). Distractor D: Rounds 7.48 to 7.5 and makes an arithmetic error.
Q5: A pump delivers 250 gallons per minute (gpm). How many million gallons per day (MGD) does this
represent?
, A. 0.25 MGD
B. 0.36 MGD
C. 0.50 MGD
D. 0.75 MGD
Correct Answer: B
Rationale: 250 gpm × 1,440 min/day = 360,000 gpd = 0.36 MGD. Distractor A: Confuses gpm with MGD
directly. Distractor C: Uses 1,000 min/day instead of 1,440. Distractor D: Uses 2,000 min/day or doubles
the flow rate.
Q6: The influent flow to a primary clarifier is 1.5 MGD. The clarifier diameter is 50 feet. What is the
surface overflow rate in gallons per day per square foot (gpd/ft²)?
A. 582 gpd/ft²
B. 764 gpd/ft² [CORRECT]
C. 1,528 gpd/ft²
D. 2,356 gpd/ft²
Correct Answer: B
Rationale: Surface area = π × (25 ft)² = 1,963.5 ft². Overflow rate = 1,500,000 gpd ÷ 1,963.5 ft² = 764
gpd/ft². Distractor A: Uses diameter instead of radius (π × 50² = 7,854 ft²). Distractor C: Forgets to
convert MGD to gallons (uses 1.5 instead of 1,500,000). Distractor D: Uses circumference instead of
area.
Q7: You discover a coworker unconscious inside a wet well. The gas monitor reads 18.0% oxygen. What
is your immediate action?
A. Enter the wet well immediately to rescue your coworker.
B. Call 911, ventilate the space, and do not enter until rescue personnel arrive with proper equipment.
[CORRECT]
C. Send another operator in with a rope tied around their waist.
D. Turn on the ventilation fan and enter after 2 minutes.
Correct Answer: B
Rationale: 18.0% oxygen is below the 19.5% safe threshold. OSHA prohibits untrained rescue attempts;
70% of confined space fatalities are would-be rescuers. Distractor A: Entering without SCBA and rescue
equipment makes you the next victim. Distractor C: A rope does not provide respiratory protection; this
is an outdated and dangerous practice. Distractor D: Two minutes of ventilation is insufficient;
atmospheric testing must confirm safe levels before entry.
