OSSF DR FINAL EXAM NEWEST EXAM PREPARATION NEWEST WITH COMPLETE
QUESTIONS AND CORRECT DETAILED ANSWERS| BRAND NEW VERSION
Question 1
Which soil classes are generally considered unsuitable for a standard drainfield without further
enhancement or alternative design?
A) Class I and II
B) Class II and III
C) Class IA and IV
D) Class III and IV
E) Class IB and II
Correct Answer: C) class IA and IV
Rationale: Class IA soils (gravelly sands) are too coarse and allow effluent to migrate too
quickly for proper treatment, while Class IV soils (clays) are too tight and do not allow for
adequate hydraulic conductivity, leading to surface ponding.
Question 2
What are the three major soil horizons typically identified during a site evaluation?
A) O, A, and E
B) Topsoil, Rock, and Sand
C) Surface soil A, subsoil B, and parent material C
D) Humus, Clay, and Silt
E) Crust, Core, and Mantle
Correct Answer: C) Surface soil A, subsoil B, and parent material C
Rationale: In OSSF site evaluations, technicians look at Horizon A (the surface layer),
Horizon B (the subsoil layer where accumulation occurs), and Horizon C (the parent
material from which the soil developed). Identifying these is crucial for determining the
depth of suitable soil.
Question 3
Which term describes the ability of water to migrate through a soil profile under either saturated
or unsaturated conditions?
A) Soil porosity
B) Hydraulic conductivity
C) Evapotranspiration
D) Capillary action
E) Percolation rate
Correct Answer: B) Hydraulic conductivity
Rationale: Hydraulic conductivity is the measure of how easily water can move through
pore spaces in the soil. It is a critical factor in determining the loading rate for a drainfield.
Question 4
Interconnected pores in the soil profile are essential for allowing which two substances to enter
the soil and migrate downward?
, 2
A) Nitrogen and Phosphorus
B) Air and Water
C) Organics and Inorganics
D) Bacteria and Viruses
E) Sand and Silt
Correct Answer: B) air, water
Rationale: Without interconnected pores, soil becomes anaerobic and impermeable. Air is
necessary for the aerobic bacteria that treat the wastewater, and water movement is
necessary for the disposal of the liquid effluent.
Question 5
What are the four primary components of soil?
A) Sand, Silt, Clay, and Rock
B) Bacteria, Viruses, Protozoa, and Helminths
C) Air, Water, Organics, and Inorganics
D) Nitrogen, Oxygen, Carbon, and Hydrogen
E) Roots, Insects, Fungi, and Minerals
Correct Answer: C) air, water, organics, inorganics
Rationale: Soil is a complex medium consisting of inorganic mineral particles
(sand/silt/clay), organic matter (decaying plants/animals), and the pore spaces filled with
varying amounts of air and water.
Question 6
A drainfield measures 50 feet by 90 feet and must be covered with an average of 15 inches of
sandy loam. How many cubic yards of soil must be purchased?
A) 150.5 cubic yards
B) 208.3 cubic yards
C) 250.0 cubic yards
D) 5,625 cubic yards
E) 125.8 cubic yards
Correct Answer: B) 208.3 cubic yards
Rationale: Volume = Length × Width × Depth. First, convert 15 inches to feet (15/12 = 1.25
ft). Volume = 50 × 90 × 1.25 = 5,625 cubic feet. To convert to cubic yards, divide by 27
(5, = 208.33).
Question 7
What is the volume of a 5-foot-diameter pump tank that stands 5 feet tall, with the inlet located 1
foot below the rim?
A) 440 gals
B) 587 gals
C) 733 gals
, 3
D) 920 gals
E) 1,200 gals
Correct Answer: B) 587 gals
Rationale: Volume of a cylinder =
𝜋 × 𝑟2 × ℎ
. Radius is 2.5 ft. The "working" height is 4 feet (5 total - 1 below rim).
𝑉 = 3.14 × (2.5)2 × 4 = 78.5 cubic feet
. Multiply by 7.48 gallons per cubic foot to get 587.18 gallons.
Question 8
Calculate the percent slope on a lot that is 250 feet deep and drops 20 feet in elevation over that
distance.
A) 2%
B) 5%
C) 8%
D) 12%
E) 20%
Correct Answer: C) 8%
Rationale: Percent slope = (Rise / Run) × 100. In this case, () × 100 = 0.08 × 100 =
8%.
Question 9
How many cubic yards of gravel are needed to fill a ditch 3 feet deep, 10 feet wide, and 12 feet
long with 18 inches of gravel?
A) 4.50 cubic yards
B) 6.67 cubic yards
C) 13.33 cubic yards
D) 18.00 cubic yards
E) 27.00 cubic yards
Correct Answer: B) 6.67 cubic yards
Rationale: Only the gravel depth (18 inches = 1.5 feet) matters for the volume of gravel.
𝑉 = 10 × 12 × 1.5 = 180 cubic feet
. Divide by 27 to get cubic yards:
180/27 = 6.666. ..
or 6.67 cubic yards.
, 4
Question 10
A septic tank is 6 feet in diameter and 8 feet deep. How many gallons will it hold if the overflow
line is located exactly halfway up from the bottom?
A) 423 gals
B) 846 gals
C) 1,692 gals
D) 2,100 gals
E) 550 gals
Correct Answer: B) 846 gals
Rationale: The radius is 3 ft. The working depth is 4 ft (half of 8).
𝑉 = 3.14 × (3)2 × 4 = 113.04 cubic feet
.
113.04 × 7.48 gal/cu ft = 845.5
gallons.
Question 11
What is the surface area in square feet of an evapotranspiration (ET) system that is 40 feet wide
and 65 feet long?
A) 105 sqft
B) 210 sqft
C) 1,300 sqft
D) 2,600 sqft
E) 3,200 sqft
Correct Answer: D) 2,600 sqft
Rationale: Area = Length × Width.
40 ft × 65 ft = 2,600 square feet
.
Question 12
Calculate the acreage for a square piece of property that measures 256 feet on each of its four
sides.
A) 0.5 acres
B) 1.0 acres
C) 1.5 acres
) 2.2 acres
E) 3.0 acres
QUESTIONS AND CORRECT DETAILED ANSWERS| BRAND NEW VERSION
Question 1
Which soil classes are generally considered unsuitable for a standard drainfield without further
enhancement or alternative design?
A) Class I and II
B) Class II and III
C) Class IA and IV
D) Class III and IV
E) Class IB and II
Correct Answer: C) class IA and IV
Rationale: Class IA soils (gravelly sands) are too coarse and allow effluent to migrate too
quickly for proper treatment, while Class IV soils (clays) are too tight and do not allow for
adequate hydraulic conductivity, leading to surface ponding.
Question 2
What are the three major soil horizons typically identified during a site evaluation?
A) O, A, and E
B) Topsoil, Rock, and Sand
C) Surface soil A, subsoil B, and parent material C
D) Humus, Clay, and Silt
E) Crust, Core, and Mantle
Correct Answer: C) Surface soil A, subsoil B, and parent material C
Rationale: In OSSF site evaluations, technicians look at Horizon A (the surface layer),
Horizon B (the subsoil layer where accumulation occurs), and Horizon C (the parent
material from which the soil developed). Identifying these is crucial for determining the
depth of suitable soil.
Question 3
Which term describes the ability of water to migrate through a soil profile under either saturated
or unsaturated conditions?
A) Soil porosity
B) Hydraulic conductivity
C) Evapotranspiration
D) Capillary action
E) Percolation rate
Correct Answer: B) Hydraulic conductivity
Rationale: Hydraulic conductivity is the measure of how easily water can move through
pore spaces in the soil. It is a critical factor in determining the loading rate for a drainfield.
Question 4
Interconnected pores in the soil profile are essential for allowing which two substances to enter
the soil and migrate downward?
, 2
A) Nitrogen and Phosphorus
B) Air and Water
C) Organics and Inorganics
D) Bacteria and Viruses
E) Sand and Silt
Correct Answer: B) air, water
Rationale: Without interconnected pores, soil becomes anaerobic and impermeable. Air is
necessary for the aerobic bacteria that treat the wastewater, and water movement is
necessary for the disposal of the liquid effluent.
Question 5
What are the four primary components of soil?
A) Sand, Silt, Clay, and Rock
B) Bacteria, Viruses, Protozoa, and Helminths
C) Air, Water, Organics, and Inorganics
D) Nitrogen, Oxygen, Carbon, and Hydrogen
E) Roots, Insects, Fungi, and Minerals
Correct Answer: C) air, water, organics, inorganics
Rationale: Soil is a complex medium consisting of inorganic mineral particles
(sand/silt/clay), organic matter (decaying plants/animals), and the pore spaces filled with
varying amounts of air and water.
Question 6
A drainfield measures 50 feet by 90 feet and must be covered with an average of 15 inches of
sandy loam. How many cubic yards of soil must be purchased?
A) 150.5 cubic yards
B) 208.3 cubic yards
C) 250.0 cubic yards
D) 5,625 cubic yards
E) 125.8 cubic yards
Correct Answer: B) 208.3 cubic yards
Rationale: Volume = Length × Width × Depth. First, convert 15 inches to feet (15/12 = 1.25
ft). Volume = 50 × 90 × 1.25 = 5,625 cubic feet. To convert to cubic yards, divide by 27
(5, = 208.33).
Question 7
What is the volume of a 5-foot-diameter pump tank that stands 5 feet tall, with the inlet located 1
foot below the rim?
A) 440 gals
B) 587 gals
C) 733 gals
, 3
D) 920 gals
E) 1,200 gals
Correct Answer: B) 587 gals
Rationale: Volume of a cylinder =
𝜋 × 𝑟2 × ℎ
. Radius is 2.5 ft. The "working" height is 4 feet (5 total - 1 below rim).
𝑉 = 3.14 × (2.5)2 × 4 = 78.5 cubic feet
. Multiply by 7.48 gallons per cubic foot to get 587.18 gallons.
Question 8
Calculate the percent slope on a lot that is 250 feet deep and drops 20 feet in elevation over that
distance.
A) 2%
B) 5%
C) 8%
D) 12%
E) 20%
Correct Answer: C) 8%
Rationale: Percent slope = (Rise / Run) × 100. In this case, () × 100 = 0.08 × 100 =
8%.
Question 9
How many cubic yards of gravel are needed to fill a ditch 3 feet deep, 10 feet wide, and 12 feet
long with 18 inches of gravel?
A) 4.50 cubic yards
B) 6.67 cubic yards
C) 13.33 cubic yards
D) 18.00 cubic yards
E) 27.00 cubic yards
Correct Answer: B) 6.67 cubic yards
Rationale: Only the gravel depth (18 inches = 1.5 feet) matters for the volume of gravel.
𝑉 = 10 × 12 × 1.5 = 180 cubic feet
. Divide by 27 to get cubic yards:
180/27 = 6.666. ..
or 6.67 cubic yards.
, 4
Question 10
A septic tank is 6 feet in diameter and 8 feet deep. How many gallons will it hold if the overflow
line is located exactly halfway up from the bottom?
A) 423 gals
B) 846 gals
C) 1,692 gals
D) 2,100 gals
E) 550 gals
Correct Answer: B) 846 gals
Rationale: The radius is 3 ft. The working depth is 4 ft (half of 8).
𝑉 = 3.14 × (3)2 × 4 = 113.04 cubic feet
.
113.04 × 7.48 gal/cu ft = 845.5
gallons.
Question 11
What is the surface area in square feet of an evapotranspiration (ET) system that is 40 feet wide
and 65 feet long?
A) 105 sqft
B) 210 sqft
C) 1,300 sqft
D) 2,600 sqft
E) 3,200 sqft
Correct Answer: D) 2,600 sqft
Rationale: Area = Length × Width.
40 ft × 65 ft = 2,600 square feet
.
Question 12
Calculate the acreage for a square piece of property that measures 256 feet on each of its four
sides.
A) 0.5 acres
B) 1.0 acres
C) 1.5 acres
) 2.2 acres
E) 3.0 acres
