, Question 1
A proposed subsurface system site has a seasonal high water table at 12 inches
below the surface and a restrictive horizon at 18 inches. Under SCDES
Regulation 61-56, which vertical separation is required between the trench
bottom and the seasonal high water table?
A. 6 inches
B. 12 inches
C. 18 inches
D. 24 inches
Correct Answer: B - 12 inches
RATIONALE
Regulation 61-56 requires a minimum of 12 inches of unsaturated soil
between the trench bottom and the seasonal high water table. Options
A, C, and D are incorrect because they do not reflect the regulatory
minimum for vertical separation.
Question 2
During a percolation test, a test hole shows a fall of 1 inch in 45 minutes. What
is the percolation rate in minutes per inch, and how does it affect system
sizing?
A. 45 min/in; requires larger drainfield area
B. 45 min/in; requires smaller drainfield area
C. 0.022 min/in; requires smaller drainfield area
D. 0.022 min/in; requires larger drainfield area
Correct Answer: A - 45 min/in; requires larger drainfield area
Page 2
, RATIONALE
Percolation rate is calculated as time (minutes) divided by fall
(inches): 45 minutes ÷ 1 inch = 45 min/in. A slower rate (higher
min/in) requires a larger drainfield absorption area. Options B, C, and
D misapply the calculation or invert the sizing relationship.
Question 3
A contractor plans to install a septic tank with a 1,000-gallon capacity for a
3-bedroom home. According to Regulation 61-56, what is the minimum
required septic tank capacity for a 3-bedroom dwelling?
A. 750 gallons
B. 1,000 gallons
C. 1,200 gallons
D. 1,500 gallons
Correct Answer: B - 1,000 gallons
RATIONALE
Regulation 61-56 sets the minimum septic tank capacity at 1,000
gallons for a 3-bedroom home. Options A, C, and D do not match the
regulatory minimum for this bedroom count.
Question 4
A soil profile exhibits a clayey texture with a plasticity index of 25 and a linear
extensibility of 6.0. How does this affect the suitability for a conventional
subsurface system?
A. Suitable if a sand liner is used
B. Suitable if the system is oversized by 20%
C. Unsuitable due to high shrink-swell potential
D. Suitable if the water table is lowered
Correct Answer: C - Unsuitable due to high shrink-swell potential
Page 3
, RATIONALE
High shrink-swell potential (indicated by high plasticity index and
linear extensibility) makes the soil unsuitable for conventional
systems because of structural damage risk. Options A, B, and D do not
adequately address the shrink-swell hazard.
Question 5
A septic system is failing due to excessive solids carryover into the drainfield.
Which component is most likely malfunctioning?
A. Inlet baffle
B. Outlet baffle
C. Distribution box
D. Drainfield laterals
Correct Answer: B - Outlet baffle
RATIONALE
The outlet baffle prevents scum and solids from exiting the tank; a
malfunction allows solids to clog the drainfield. Options A, C, and D
are less directly responsible for solids carryover.
Question 6
Under Regulation 61-56, what is the minimum horizontal separation between a
septic tank and a private drinking water well?
A. 25 feet
B. 50 feet
C. 75 feet
D. 100 feet
Correct Answer: B - 50 feet
Page 4
A proposed subsurface system site has a seasonal high water table at 12 inches
below the surface and a restrictive horizon at 18 inches. Under SCDES
Regulation 61-56, which vertical separation is required between the trench
bottom and the seasonal high water table?
A. 6 inches
B. 12 inches
C. 18 inches
D. 24 inches
Correct Answer: B - 12 inches
RATIONALE
Regulation 61-56 requires a minimum of 12 inches of unsaturated soil
between the trench bottom and the seasonal high water table. Options
A, C, and D are incorrect because they do not reflect the regulatory
minimum for vertical separation.
Question 2
During a percolation test, a test hole shows a fall of 1 inch in 45 minutes. What
is the percolation rate in minutes per inch, and how does it affect system
sizing?
A. 45 min/in; requires larger drainfield area
B. 45 min/in; requires smaller drainfield area
C. 0.022 min/in; requires smaller drainfield area
D. 0.022 min/in; requires larger drainfield area
Correct Answer: A - 45 min/in; requires larger drainfield area
Page 2
, RATIONALE
Percolation rate is calculated as time (minutes) divided by fall
(inches): 45 minutes ÷ 1 inch = 45 min/in. A slower rate (higher
min/in) requires a larger drainfield absorption area. Options B, C, and
D misapply the calculation or invert the sizing relationship.
Question 3
A contractor plans to install a septic tank with a 1,000-gallon capacity for a
3-bedroom home. According to Regulation 61-56, what is the minimum
required septic tank capacity for a 3-bedroom dwelling?
A. 750 gallons
B. 1,000 gallons
C. 1,200 gallons
D. 1,500 gallons
Correct Answer: B - 1,000 gallons
RATIONALE
Regulation 61-56 sets the minimum septic tank capacity at 1,000
gallons for a 3-bedroom home. Options A, C, and D do not match the
regulatory minimum for this bedroom count.
Question 4
A soil profile exhibits a clayey texture with a plasticity index of 25 and a linear
extensibility of 6.0. How does this affect the suitability for a conventional
subsurface system?
A. Suitable if a sand liner is used
B. Suitable if the system is oversized by 20%
C. Unsuitable due to high shrink-swell potential
D. Suitable if the water table is lowered
Correct Answer: C - Unsuitable due to high shrink-swell potential
Page 3
, RATIONALE
High shrink-swell potential (indicated by high plasticity index and
linear extensibility) makes the soil unsuitable for conventional
systems because of structural damage risk. Options A, B, and D do not
adequately address the shrink-swell hazard.
Question 5
A septic system is failing due to excessive solids carryover into the drainfield.
Which component is most likely malfunctioning?
A. Inlet baffle
B. Outlet baffle
C. Distribution box
D. Drainfield laterals
Correct Answer: B - Outlet baffle
RATIONALE
The outlet baffle prevents scum and solids from exiting the tank; a
malfunction allows solids to clog the drainfield. Options A, C, and D
are less directly responsible for solids carryover.
Question 6
Under Regulation 61-56, what is the minimum horizontal separation between a
septic tank and a private drinking water well?
A. 25 feet
B. 50 feet
C. 75 feet
D. 100 feet
Correct Answer: B - 50 feet
Page 4
