OSSF DR (Texas TCEQ) | High-Yield Questions, Site
Evaluation, Soil Science, Calculations & Designated
Representative Exam | Well Rationalized ,Calculations
expressed well | Verified Questions with Maths
Formulae |Brand new Version!!!
_______ and ________ soil textural classes are always unsuitable for standard
absorptive OSSF
Correct Answer:
class IA and IV
List each of the major soil horizons
Correct Answer:
surface soil A, surface soil B, and parent material
_____________ is a term describing the ability of water to migrate through a soil
profile under either _________ or __________ conditions.
Correct Answer:
Hydraulic conductivity, saturated, unsaturated
Interconnected pores in the soil profile allow ______ and _______ to enter the soil
at its surface and migrate downward
Correct Answer:
air, water
List the four components of soil
Correct Answer:
air, water, organics, inorganics
,A drainfield is 50 feet by 90 feet and must be covered with an average of 15
inches of sand loam. How many cubic yards of sandy loam soil must be
purchased?
Correct Answer: 208.3 cubic yards
Rationalization (Step-by-Step):
1. Convert depth to feet:
15 inches ÷ 12 = 1.25 ft
2. Find volume in cubic feet:
50 × 90 × 1.25 = 5,625 cubic feet
3. Convert to cubic yards:
5,625 ÷ 27 = 208.3 cubic yards
Always convert inches → feet and cubic feet → cubic yards (÷27).
Pump Tank Volume (Cylinder)
What is the volume of a 5-foot-diameter pump tank that is 5 feet tall, with the inlet
1 foot below the rim?
Correct Answer: 587 gallons
Rationalization:
1. Radius = 5 ÷ 2 = 2.5 ft
2. Liquid height = 5 – 1 = 4 ft
3. Volume formula (cylinder):
V = πr²h
= 3.14 × (2.5²) × 4
= 3.14 × 6.25 × 4 = 78.5 cubic ft
4. Convert to gallons:
78.5 × 7.48 = 587 gallons
Always subtract freeboard (space above liquid).
Percent Slope
What is the percent slope on a lot 250 feet deep that drops 20 feet in elevation?
Correct Answer: 8%
,Rationalization:
Formula:
Slope (%) = (Vertical Drop ÷ Horizontal Distance) × 100
= (20 ÷ 250) × 100
= 0.08 × 100 = 8%
Slope measures steepness—critical for drainage and system design.
Gravel Volume in Ditch
How many cubic yards of gravel are needed to fill a ditch 3 ft deep, 10 ft wide, 12
ft long, with 18 inches of gravel?
Correct Answer: 6.67 cubic yards
Rationalization:
1. Convert depth:
18 inches = 1.5 ft
2. Volume (cubic feet):
10 × 12 × 1.5 = 180 cubic ft
3. Convert to cubic yards:
180 ÷ 27 = 6.67 cubic yards
: Only use gravel depth, not full ditch depth.
:Septic Tank Capacity (Half Full)
A septic tank is 6 feet in diameter and 8 feet deep. How many gallons will it hold
if the overflow line is halfway up?
Correct Answer: 846 gallons
Rationalization:
1. Radius = 3 ft
2. Liquid height = 8 ÷ 2 = 4 ft
3. Volume (cylinder):
V = 3.14 × (3²) × 4
= 3.14 × 9 × 4 = 113.04 cubic ft
, 4. Convert to gallons:
113.04 × 7.48 = 846 gallons
: Only calculate liquid portion (half full).
Working Liquid Capacity
Calculate the working liquid capacity of the septic tank.
Correct Answer: 1,077 gallons
Rationalization:
This refers to the usable liquid volume below the outlet level, not total tank size.
Using standard tank dimensions and working depth:
• Apply cylinder volume formula
• Convert cubic feet → gallons
“Working capacity” excludes sludge/scum space and freeboard.
Evapotranspiration System Area
What is the surface area of an evapotranspiration system 40 ft wide and 65 ft
long?
Correct Answer: 2,600 sq ft
Rationalization:
Area = Length × Width
= 40 × 65 = 2,600 sq ft
Area calculations are critical for system sizing.
Acreage Calculation (Square Property)
A property measures 256 ft on each side. What is the acreage?
Correct Answer: 1.5 acres
Rationalization:
1. Area = 256 × 256 = 65,536 sq ft
2. Convert to acres:
65,536 ÷ 43,560 = 1.5 acres
Evaluation, Soil Science, Calculations & Designated
Representative Exam | Well Rationalized ,Calculations
expressed well | Verified Questions with Maths
Formulae |Brand new Version!!!
_______ and ________ soil textural classes are always unsuitable for standard
absorptive OSSF
Correct Answer:
class IA and IV
List each of the major soil horizons
Correct Answer:
surface soil A, surface soil B, and parent material
_____________ is a term describing the ability of water to migrate through a soil
profile under either _________ or __________ conditions.
Correct Answer:
Hydraulic conductivity, saturated, unsaturated
Interconnected pores in the soil profile allow ______ and _______ to enter the soil
at its surface and migrate downward
Correct Answer:
air, water
List the four components of soil
Correct Answer:
air, water, organics, inorganics
,A drainfield is 50 feet by 90 feet and must be covered with an average of 15
inches of sand loam. How many cubic yards of sandy loam soil must be
purchased?
Correct Answer: 208.3 cubic yards
Rationalization (Step-by-Step):
1. Convert depth to feet:
15 inches ÷ 12 = 1.25 ft
2. Find volume in cubic feet:
50 × 90 × 1.25 = 5,625 cubic feet
3. Convert to cubic yards:
5,625 ÷ 27 = 208.3 cubic yards
Always convert inches → feet and cubic feet → cubic yards (÷27).
Pump Tank Volume (Cylinder)
What is the volume of a 5-foot-diameter pump tank that is 5 feet tall, with the inlet
1 foot below the rim?
Correct Answer: 587 gallons
Rationalization:
1. Radius = 5 ÷ 2 = 2.5 ft
2. Liquid height = 5 – 1 = 4 ft
3. Volume formula (cylinder):
V = πr²h
= 3.14 × (2.5²) × 4
= 3.14 × 6.25 × 4 = 78.5 cubic ft
4. Convert to gallons:
78.5 × 7.48 = 587 gallons
Always subtract freeboard (space above liquid).
Percent Slope
What is the percent slope on a lot 250 feet deep that drops 20 feet in elevation?
Correct Answer: 8%
,Rationalization:
Formula:
Slope (%) = (Vertical Drop ÷ Horizontal Distance) × 100
= (20 ÷ 250) × 100
= 0.08 × 100 = 8%
Slope measures steepness—critical for drainage and system design.
Gravel Volume in Ditch
How many cubic yards of gravel are needed to fill a ditch 3 ft deep, 10 ft wide, 12
ft long, with 18 inches of gravel?
Correct Answer: 6.67 cubic yards
Rationalization:
1. Convert depth:
18 inches = 1.5 ft
2. Volume (cubic feet):
10 × 12 × 1.5 = 180 cubic ft
3. Convert to cubic yards:
180 ÷ 27 = 6.67 cubic yards
: Only use gravel depth, not full ditch depth.
:Septic Tank Capacity (Half Full)
A septic tank is 6 feet in diameter and 8 feet deep. How many gallons will it hold
if the overflow line is halfway up?
Correct Answer: 846 gallons
Rationalization:
1. Radius = 3 ft
2. Liquid height = 8 ÷ 2 = 4 ft
3. Volume (cylinder):
V = 3.14 × (3²) × 4
= 3.14 × 9 × 4 = 113.04 cubic ft
, 4. Convert to gallons:
113.04 × 7.48 = 846 gallons
: Only calculate liquid portion (half full).
Working Liquid Capacity
Calculate the working liquid capacity of the septic tank.
Correct Answer: 1,077 gallons
Rationalization:
This refers to the usable liquid volume below the outlet level, not total tank size.
Using standard tank dimensions and working depth:
• Apply cylinder volume formula
• Convert cubic feet → gallons
“Working capacity” excludes sludge/scum space and freeboard.
Evapotranspiration System Area
What is the surface area of an evapotranspiration system 40 ft wide and 65 ft
long?
Correct Answer: 2,600 sq ft
Rationalization:
Area = Length × Width
= 40 × 65 = 2,600 sq ft
Area calculations are critical for system sizing.
Acreage Calculation (Square Property)
A property measures 256 ft on each side. What is the acreage?
Correct Answer: 1.5 acres
Rationalization:
1. Area = 256 × 256 = 65,536 sq ft
2. Convert to acres:
65,536 ÷ 43,560 = 1.5 acres
