New Hampshire Septic Installer Exam 3
Site Conditions, Setbacks, EDAs & Troubleshooting
Questions and Answers
actual NHDES licensing exam items. They are based on NHDES Env-Wq 1000 and
RSA 485-A as publicly available. NHDES proposed amendments to Env-Wq 1000.
1. Why is a test pit excavated within the proposed effluent disposal
area (EDA)?
A. To locate the septic tank before installation
B. To determine the property line
C. To measure the flow rate of the household water supply
D. To observe soil horizons, texture, color, redoximorphic features,
restrictive layers, and bedrock directly
Answer: D. To observe soil horizons, texture, color, redoximorphic
features, restrictive layers, and bedrock directly
Rationale: A test pit shows the soil profile in place, which lets the evaluator
determine seasonal high water table indicators, receiving layer depth, and
limiting layers. A boring or probe alone does not give the same information.
,2. Which field indicator is most commonly used to estimate the
seasonal high water table (SHWT) in soil?
A. The color of the topsoil
B. Redoximorphic features such as mottles
C. The number of roots in the pit
D. The depth at which water is standing on the day of digging
Answer: B. Redoximorphic features such as mottles
Rationale: Mottling and gleying result from repeated saturation, so they
record the long-term high water level. Water seen on one day may be
above or below the SHWT depending on the season and recent rainfall.
3. Which tool is used to describe soil matrix and mottle colors in a
test pit?
A. A pocket penetrometer
B. A hand level
C. Munsell Soil Color Charts
D. A pH meter
Answer: C. Munsell Soil Color Charts
Rationale: Munsell notation (hue, value, chroma) is the standard for
documenting soil color, which supports hydric soil and redox interpretations.
4. What does a percolation rate of 20 minutes per inch mean?
A. The soil is 20 inches deep
B. The hole drained in 20 minutes total
C. The hole drains 20 inches per hour
D. The water level in the test hole drops one inch every 20 minutes
Answer: D. The water level in the test hole drops one inch every 20
minutes
Rationale: Percolation rate is the number of minutes needed for water to
drop one inch in a percolation test hole. It is used to estimate the soil’s
ability to receive and disperse effluent.
,5. The sidewalls of a percolation test hole in clayey soil appear
smooth and glazed after digging. What should the tester do?
A. Leave the walls as they are
B. Add sand to the bottom only
C. Roughen the sidewalls and remove loose material before testing
D. Line the hole with plastic
Answer: C. Roughen the sidewalls and remove loose material before
testing
Rationale: Smearing seals pores and gives a falsely slow rate. Scarifying
the walls restores natural permeability before the test.
6. Why is the percolation test hole presoaked?
A. To make the hole deeper
B. To approach saturated conditions so readings are stable and
representative
C. To raise the water table
D. To kill vegetation
Answer: B. To approach saturated conditions so readings are stable
and representative
Rationale: Dry soils absorb water unusually quickly at first. Presoaking
reduces that effect and produces a more representative rate.
7. A site has very rapidly draining coarse sand. What is the main
concern?
A. Effluent will pond on the surface
B. Effluent may move through the soil too quickly to be adequately treated
before reaching groundwater
C. The system will never need maintenance
D. The soil will freeze more easily
Answer: B. Effluent may move through the soil too quickly to be
adequately treated before reaching groundwater
Rationale: Fast soils transmit effluent with limited treatment time. Designs
must protect groundwater, for example by using approved technologies or
meeting required separation distances.
, 8. How does a slower percolation rate generally affect the sizing of a
conventional EDA?
A. A tank twice as large is required
B. No change in size is needed
C. A smaller basal area is required
D. A larger basal area is required
Answer: D. A larger basal area is required
Rationale: Sizing is based on the soil’s loading rate, which is lower in
slower soils. Slower soils therefore need more area to disperse the same
daily flow.
9. Which field test estimates the clay content of a soil sample?
A. A moisture meter reading
B. The ribbon (texture-by-feel) test
C. The smell test
D. The float test
Answer: B. The ribbon (texture-by-feel) test
Rationale: Squeezing a moist sample into a ribbon between thumb and
finger indicates how much clay is present. Longer, stronger ribbons indicate
higher clay content.
10. A dense, compact glacial till layer in the test pit restricts
downward water movement. How should it be treated in design?
A. As a restrictive layer or impermeable substratum for separation
distance purposes
B. As topsoil
C. As acceptable fill
D. As a receiving layer
Answer: A. As a restrictive layer or impermeable substratum for
separation distance purposes
Rationale: Dense till can perch water and prevents effluent from
percolating. Required separations to impermeable substratum are
measured from this layer.
Site Conditions, Setbacks, EDAs & Troubleshooting
Questions and Answers
actual NHDES licensing exam items. They are based on NHDES Env-Wq 1000 and
RSA 485-A as publicly available. NHDES proposed amendments to Env-Wq 1000.
1. Why is a test pit excavated within the proposed effluent disposal
area (EDA)?
A. To locate the septic tank before installation
B. To determine the property line
C. To measure the flow rate of the household water supply
D. To observe soil horizons, texture, color, redoximorphic features,
restrictive layers, and bedrock directly
Answer: D. To observe soil horizons, texture, color, redoximorphic
features, restrictive layers, and bedrock directly
Rationale: A test pit shows the soil profile in place, which lets the evaluator
determine seasonal high water table indicators, receiving layer depth, and
limiting layers. A boring or probe alone does not give the same information.
,2. Which field indicator is most commonly used to estimate the
seasonal high water table (SHWT) in soil?
A. The color of the topsoil
B. Redoximorphic features such as mottles
C. The number of roots in the pit
D. The depth at which water is standing on the day of digging
Answer: B. Redoximorphic features such as mottles
Rationale: Mottling and gleying result from repeated saturation, so they
record the long-term high water level. Water seen on one day may be
above or below the SHWT depending on the season and recent rainfall.
3. Which tool is used to describe soil matrix and mottle colors in a
test pit?
A. A pocket penetrometer
B. A hand level
C. Munsell Soil Color Charts
D. A pH meter
Answer: C. Munsell Soil Color Charts
Rationale: Munsell notation (hue, value, chroma) is the standard for
documenting soil color, which supports hydric soil and redox interpretations.
4. What does a percolation rate of 20 minutes per inch mean?
A. The soil is 20 inches deep
B. The hole drained in 20 minutes total
C. The hole drains 20 inches per hour
D. The water level in the test hole drops one inch every 20 minutes
Answer: D. The water level in the test hole drops one inch every 20
minutes
Rationale: Percolation rate is the number of minutes needed for water to
drop one inch in a percolation test hole. It is used to estimate the soil’s
ability to receive and disperse effluent.
,5. The sidewalls of a percolation test hole in clayey soil appear
smooth and glazed after digging. What should the tester do?
A. Leave the walls as they are
B. Add sand to the bottom only
C. Roughen the sidewalls and remove loose material before testing
D. Line the hole with plastic
Answer: C. Roughen the sidewalls and remove loose material before
testing
Rationale: Smearing seals pores and gives a falsely slow rate. Scarifying
the walls restores natural permeability before the test.
6. Why is the percolation test hole presoaked?
A. To make the hole deeper
B. To approach saturated conditions so readings are stable and
representative
C. To raise the water table
D. To kill vegetation
Answer: B. To approach saturated conditions so readings are stable
and representative
Rationale: Dry soils absorb water unusually quickly at first. Presoaking
reduces that effect and produces a more representative rate.
7. A site has very rapidly draining coarse sand. What is the main
concern?
A. Effluent will pond on the surface
B. Effluent may move through the soil too quickly to be adequately treated
before reaching groundwater
C. The system will never need maintenance
D. The soil will freeze more easily
Answer: B. Effluent may move through the soil too quickly to be
adequately treated before reaching groundwater
Rationale: Fast soils transmit effluent with limited treatment time. Designs
must protect groundwater, for example by using approved technologies or
meeting required separation distances.
, 8. How does a slower percolation rate generally affect the sizing of a
conventional EDA?
A. A tank twice as large is required
B. No change in size is needed
C. A smaller basal area is required
D. A larger basal area is required
Answer: D. A larger basal area is required
Rationale: Sizing is based on the soil’s loading rate, which is lower in
slower soils. Slower soils therefore need more area to disperse the same
daily flow.
9. Which field test estimates the clay content of a soil sample?
A. A moisture meter reading
B. The ribbon (texture-by-feel) test
C. The smell test
D. The float test
Answer: B. The ribbon (texture-by-feel) test
Rationale: Squeezing a moist sample into a ribbon between thumb and
finger indicates how much clay is present. Longer, stronger ribbons indicate
higher clay content.
10. A dense, compact glacial till layer in the test pit restricts
downward water movement. How should it be treated in design?
A. As a restrictive layer or impermeable substratum for separation
distance purposes
B. As topsoil
C. As acceptable fill
D. As a receiving layer
Answer: A. As a restrictive layer or impermeable substratum for
separation distance purposes
Rationale: Dense till can perch water and prevents effluent from
percolating. Required separations to impermeable substratum are
measured from this layer.
