Texas Commission on Environmental Quality (TCEQ)
On-Site Sewage Facility (OSSF) licensing exam EXAM
QUESTIONS AND CORRECT ANSWERS VEriFIED ANSWERS
PLUS RAIONALES 2025/2026 Q&A | INSTANT DOWNLOAD
PDF
1. What is the minimum depth of suitable soil (below the bottom of the proposed
excavation) for a standard absorptive drainfield in Texas?
A. 12 inches
B. 18 inches
C. 24 inches
D. 30 inches
Answer: C. 24 inches — The rules require at least 24 in of acceptable soil below the
bottom of the drainfield excavation for a standard system.
2. Which soil textural classes are always unsuitable for standard absorptive OSSF systems
in Texas?
A. IA and II
B. IV and V
C. IA and IV
D. IB and III
Answer: C. IA and IV — Class IA (sand or loamy sand) and Class IV (clay) are identified as
unsuitable for standard systems. Docsity+1
3. An excavated trench for a standard drainfield must be level within 1 inch per 25 feet or a
maximum of how many inches?
A. 1 inch
B. 2 inches
C. 3 inches
D. 4 inches
Answer: C. 3 inches — The rule sets a maximum of 3 inches difference even when using
the 1 inch per 25 feet guideline. Docsity
,4. Which of the following is the least treatment level (i.e., poorest) of domestic wastewater
treatment?
A. Aerobic treatment unit
B. Two-compartment septic tank
C. Municipal sewage treatment plant
D. Secondary treatment plant
Answer: B. Two-compartment septic tank — Primary treatment (septic tank) provides the
least level of treatment compared to secondary/tertiary options. Docsity
5. The person licensed by TCEQ to perform site evaluations (soil & site survey) for OSSFs is
called a(n):
A. Installer I
B. Site Evaluator
C. Designated Representative
D. Maintenance Technician
Answer: B. Site Evaluator — A site evaluator conducts pre-construction evaluations
including soils and site surveys. TCEQ+1
6. What is the minimum slope on a lot that drops 20 feet over a depth of 250 feet?
A. 6%
B. 7%
C. 8%
D. 9%
Answer: C. 8% — (20 ÷ 250) × 100 = 8%.
7. When installing a gravelless pipe drainfield, what classes of soil fill are allowed for
backfilling?
A. Only Class I a & b
B. Class Ib, II or III
C. Class IV only
D. Any class if geotextile is used
Answer: B. Class Ib, II or III — Gravelless chambers may be backfilled with these soil
classes. Docsity
8. For proper protection of a work-site excavation over a certain depth, OSHA requires that
it be sloped, shored, or otherwise supported. That depth is:
A. 3 feet
B. 4 feet
C. 5 feet
D. 6 feet
, Answer: C. 5 feet — OSHA’s general rule for trench excavations requiring protective
systems applies at 5 ft depth or greater.
9. When is a maintenance contract required for a single-family residence OSSF using
surface application or subsurface drip irrigation?
A. When the system is older than 10 years
B. Always, regardless of system type
C. For surface and subsurface drip irrigation systems only
D. Only if the home has more than 4 bedrooms
Answer: C. For surface and subsurface drip irrigation systems only — These
higher-maintenance disposal methods require contracts. Docsity
10. Which of the following microorganisms are not typically considered when discussing
pathogens in domestic wastewater?
A. Bacteria
B. Viruses
C. Protozoa
D. Algae
Answer: D. Algae — Pathogens of concern include bacteria, viruses, protozoa and
helminths. Algae are not pathogens in this context. Docsity
11. Which license classification allows an individual to install all types of on-site sewage
facilities (OSSFs) in Texas?
A. Installer I
B. Installer II
C. Apprentice
D. Maintenance Provider
Answer: B. Installer II — Installer II licensees are authorized to install all types of OSSF
systems. TCEQ
12. The permitting process for a new OSSF typically begins with a site evaluation, then what
is the next step?
A. Construction begins
B. System must be planned (designed)
C. Permit application is submitted
D. System inspection during installation
Answer: B. System must be planned (designed) — After site evaluation comes system
selection and design planning before permit application. Docsity+1
On-Site Sewage Facility (OSSF) licensing exam EXAM
QUESTIONS AND CORRECT ANSWERS VEriFIED ANSWERS
PLUS RAIONALES 2025/2026 Q&A | INSTANT DOWNLOAD
1. What is the minimum depth of suitable soil (below the bottom of the proposed
excavation) for a standard absorptive drainfield in Texas?
A. 12 inches
B. 18 inches
C. 24 inches
D. 30 inches
Answer: C. 24 inches — The rules require at least 24 in of acceptable soil below the
bottom of the drainfield excavation for a standard system.
2. Which soil textural classes are always unsuitable for standard absorptive OSSF systems
in Texas?
A. IA and II
B. IV and V
C. IA and IV
D. IB and III
Answer: C. IA and IV — Class IA (sand or loamy sand) and Class IV (clay) are identified as
unsuitable for standard systems. Docsity+1
3. An excavated trench for a standard drainfield must be level within 1 inch per 25 feet or a
maximum of how many inches?
A. 1 inch
B. 2 inches
C. 3 inches
D. 4 inches
Answer: C. 3 inches — The rule sets a maximum of 3 inches difference even when using
the 1 inch per 25 feet guideline. Docsity
,4. Which of the following is the least treatment level (i.e., poorest) of domestic wastewater
treatment?
A. Aerobic treatment unit
B. Two-compartment septic tank
C. Municipal sewage treatment plant
D. Secondary treatment plant
Answer: B. Two-compartment septic tank — Primary treatment (septic tank) provides the
least level of treatment compared to secondary/tertiary options. Docsity
5. The person licensed by TCEQ to perform site evaluations (soil & site survey) for OSSFs is
called a(n):
A. Installer I
B. Site Evaluator
C. Designated Representative
D. Maintenance Technician
Answer: B. Site Evaluator — A site evaluator conducts pre-construction evaluations
including soils and site surveys. TCEQ+1
6. What is the minimum slope on a lot that drops 20 feet over a depth of 250 feet?
A. 6%
B. 7%
C. 8%
D. 9%
Answer: C. 8% — (20 ÷ 250) × 100 = 8%.
7. When installing a gravelless pipe drainfield, what classes of soil fill are allowed for
backfilling?
A. Only Class I a & b
B. Class Ib, II or III
C. Class IV only
D. Any class if geotextile is used
Answer: B. Class Ib, II or III — Gravelless chambers may be backfilled with these soil
classes. Docsity
8. For proper protection of a work-site excavation over a certain depth, OSHA requires that
it be sloped, shored, or otherwise supported. That depth is:
A. 3 feet
B. 4 feet
C. 5 feet
D. 6 feet
, Answer: C. 5 feet — OSHA’s general rule for trench excavations requiring protective
systems applies at 5 ft depth or greater.
9. When is a maintenance contract required for a single-family residence OSSF using
surface application or subsurface drip irrigation?
A. When the system is older than 10 years
B. Always, regardless of system type
C. For surface and subsurface drip irrigation systems only
D. Only if the home has more than 4 bedrooms
Answer: C. For surface and subsurface drip irrigation systems only — These
higher-maintenance disposal methods require contracts. Docsity
10. Which of the following microorganisms are not typically considered when discussing
pathogens in domestic wastewater?
A. Bacteria
B. Viruses
C. Protozoa
D. Algae
Answer: D. Algae — Pathogens of concern include bacteria, viruses, protozoa and
helminths. Algae are not pathogens in this context. Docsity
11. Which license classification allows an individual to install all types of on-site sewage
facilities (OSSFs) in Texas?
A. Installer I
B. Installer II
C. Apprentice
D. Maintenance Provider
Answer: B. Installer II — Installer II licensees are authorized to install all types of OSSF
systems. TCEQ
12. The permitting process for a new OSSF typically begins with a site evaluation, then what
is the next step?
A. Construction begins
B. System must be planned (designed)
C. Permit application is submitted
D. System inspection during installation
Answer: B. System must be planned (designed) — After site evaluation comes system
selection and design planning before permit application. Docsity+1
