NPDES LEVEL 1A PRACTICE TEST
50+ (Updated for 2026) Exam Prep Pack | A+ Questions & Verified
Answers
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📋 DOCUMENT OVERVIEW 50 Qs
This document, "NPDES Level 1A Practice Test," covers specific topics related to water pollution and
environmental management, including slope gradients, stormwater management, erosion and
sedimentation, and regulations such as those set by the USDA and SWCD. The document provides 50
questions with correct answers and detailed explanations, serving as a comprehensive review tool for
exam preparation. Students can utilize this document to study, review, and understand key concepts,
thereby enhancing their knowledge and preparation for NPDES Level 1A exams.
✓ Verified Answers ✓ Exam Ready ✓ Study Guide
Trusted by thousands of students and professionals worldwide
EXAM QUESTIONS
QUESTION 1
A slope gradient of 25% (4:1) would indicate that in a horizontal length of 100 feet, the vertical rise
would be ______ feet.
A) 2.5
B) 12.5
C) 25
D) 4
CORRECT ANSWER
C) 25
RATIONALE: A slope gradient of 25% (4:1) means that for every 4 feet of horizontal distance, there is a 1 foot
vertical rise. To find the total vertical rise in 100 feet, divide 100 by 4 (the horizontal ratio) to get 25, which represents
the number of times the 4-foot horizontal distance fits within 100 feet.
QUESTION 2
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, As rain falls to the earth, what is the very first function of vegetation?
A) It reduces detachment
B) It increases infiltration
C) It absorbs rain drop impact
D) Roots hold soil in place
CORRECT ANSWER
A) It reduces detachment
RATIONALE: As rain falls to the earth, the very first function of vegetation is to reduce detachment of soil particles
from the surface, allowing the water to interact with the soil more effectively and increasing its chances of infiltrating.
This happens because the presence of vegetation and its roots helps to stabilize the soil, preventing erosion and
runoff, and allowing the rainwater to penetrate the surface more easily.
QUESTION 3
Because of the likelihood of thunderstorms which is the worst month to schedule land disturbing
activities?
A) April
B) July
C) September
D) October
CORRECT ANSWER
B) July
RATIONALE: In regions prone to thunderstorms, July is typically the month with the highest frequency and intensity
of storms due to its peak summer season, making it the worst month to schedule land disturbing activities. This is
because thunderstorms can cause soil instability, erosion, and other hazards that compromise the safety and integrity
of land disturbing activities.
QUESTION 4
Which of the following is not a stage in Erosion and Sedimentation?
A) Detachment
B) Solubility
C) Transport
D) Deposition
CORRECT ANSWER
B) Solubility
RATIONALE: Solubility refers to the ability of a substance to dissolve in a solvent, which is a fundamental concept in
chemistry, but it is not a stage in the physical process of erosion and sedimentation where particles are broken down,
transported, and deposited. In the context of erosion and sedimentation, the correct stages involve physical processes
such as detachment, transport, and deposition, making solubility an outlier in this specific context.
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, QUESTION 5
At what depth must sediment be removed from a silt fence barrier?
A) 12 Inches
B) 16 Inches
C) 1/4 full
D) 1/2 full
CORRECT ANSWER
D) 1/2 full
RATIONALE: A silt fence barrier works by allowing water to pass through while trapping sediment, and removing
sediment at the midpoint allows for optimal filtration and prevents clogging. By removing sediment at half capacity,
sediment can continue to be trapped and filtered out as water flows through the barrier without excessive buildup.
QUESTION 6
When straw mulch is used to cover disturbed soil it must be maintained at a depth of ________
inches.
A) 1-2
B) 1-3
C) 2-3
D) 2-4
CORRECT ANSWER
D) 2-4
RATIONALE: The correct answer is D) 2-4 because maintaining a 2-4 inch depth of straw mulch allows for sufficient
soil cover to prevent erosion and retain moisture, while also preventing the mulch from suffocating the underlying
vegetation. This depth range provides an optimal balance between soil protection and allowing for adequate root
growth and air circulation.
QUESTION 7
If it is necessary to wash vehicle tires to remove excess sediment, the sediment run-off must be:
A) Kept at the construction exit pad
B) Filtered with hay bales
C) Directed away from the road with a diversion
D) Directed into an approved sediment trap or sediment basin
CORRECT ANSWER
C) Directed away from the road with a diversion
RATIONALE: This answer is correct because sediment run-off from washing vehicle tires can contain pollutants and
contaminants that can harm the environment, and directing it away from the road minimizes the risk of soil erosion
and protects waterways and aquatic ecosystems. A diversion is a more effective and environmentally friendly solution
than the other options, as it ensures that the sediment run-off is not released into the environment without proper
treatment or containment.
Trusted by thousands of students and professionals worldwide Page 3 of 16
50+ (Updated for 2026) Exam Prep Pack | A+ Questions & Verified
Answers
100% Guarantee Pass
📋 DOCUMENT OVERVIEW 50 Qs
This document, "NPDES Level 1A Practice Test," covers specific topics related to water pollution and
environmental management, including slope gradients, stormwater management, erosion and
sedimentation, and regulations such as those set by the USDA and SWCD. The document provides 50
questions with correct answers and detailed explanations, serving as a comprehensive review tool for
exam preparation. Students can utilize this document to study, review, and understand key concepts,
thereby enhancing their knowledge and preparation for NPDES Level 1A exams.
✓ Verified Answers ✓ Exam Ready ✓ Study Guide
Trusted by thousands of students and professionals worldwide
EXAM QUESTIONS
QUESTION 1
A slope gradient of 25% (4:1) would indicate that in a horizontal length of 100 feet, the vertical rise
would be ______ feet.
A) 2.5
B) 12.5
C) 25
D) 4
CORRECT ANSWER
C) 25
RATIONALE: A slope gradient of 25% (4:1) means that for every 4 feet of horizontal distance, there is a 1 foot
vertical rise. To find the total vertical rise in 100 feet, divide 100 by 4 (the horizontal ratio) to get 25, which represents
the number of times the 4-foot horizontal distance fits within 100 feet.
QUESTION 2
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, As rain falls to the earth, what is the very first function of vegetation?
A) It reduces detachment
B) It increases infiltration
C) It absorbs rain drop impact
D) Roots hold soil in place
CORRECT ANSWER
A) It reduces detachment
RATIONALE: As rain falls to the earth, the very first function of vegetation is to reduce detachment of soil particles
from the surface, allowing the water to interact with the soil more effectively and increasing its chances of infiltrating.
This happens because the presence of vegetation and its roots helps to stabilize the soil, preventing erosion and
runoff, and allowing the rainwater to penetrate the surface more easily.
QUESTION 3
Because of the likelihood of thunderstorms which is the worst month to schedule land disturbing
activities?
A) April
B) July
C) September
D) October
CORRECT ANSWER
B) July
RATIONALE: In regions prone to thunderstorms, July is typically the month with the highest frequency and intensity
of storms due to its peak summer season, making it the worst month to schedule land disturbing activities. This is
because thunderstorms can cause soil instability, erosion, and other hazards that compromise the safety and integrity
of land disturbing activities.
QUESTION 4
Which of the following is not a stage in Erosion and Sedimentation?
A) Detachment
B) Solubility
C) Transport
D) Deposition
CORRECT ANSWER
B) Solubility
RATIONALE: Solubility refers to the ability of a substance to dissolve in a solvent, which is a fundamental concept in
chemistry, but it is not a stage in the physical process of erosion and sedimentation where particles are broken down,
transported, and deposited. In the context of erosion and sedimentation, the correct stages involve physical processes
such as detachment, transport, and deposition, making solubility an outlier in this specific context.
Trusted by thousands of students and professionals worldwide Page 2 of 16
, QUESTION 5
At what depth must sediment be removed from a silt fence barrier?
A) 12 Inches
B) 16 Inches
C) 1/4 full
D) 1/2 full
CORRECT ANSWER
D) 1/2 full
RATIONALE: A silt fence barrier works by allowing water to pass through while trapping sediment, and removing
sediment at the midpoint allows for optimal filtration and prevents clogging. By removing sediment at half capacity,
sediment can continue to be trapped and filtered out as water flows through the barrier without excessive buildup.
QUESTION 6
When straw mulch is used to cover disturbed soil it must be maintained at a depth of ________
inches.
A) 1-2
B) 1-3
C) 2-3
D) 2-4
CORRECT ANSWER
D) 2-4
RATIONALE: The correct answer is D) 2-4 because maintaining a 2-4 inch depth of straw mulch allows for sufficient
soil cover to prevent erosion and retain moisture, while also preventing the mulch from suffocating the underlying
vegetation. This depth range provides an optimal balance between soil protection and allowing for adequate root
growth and air circulation.
QUESTION 7
If it is necessary to wash vehicle tires to remove excess sediment, the sediment run-off must be:
A) Kept at the construction exit pad
B) Filtered with hay bales
C) Directed away from the road with a diversion
D) Directed into an approved sediment trap or sediment basin
CORRECT ANSWER
C) Directed away from the road with a diversion
RATIONALE: This answer is correct because sediment run-off from washing vehicle tires can contain pollutants and
contaminants that can harm the environment, and directing it away from the road minimizes the risk of soil erosion
and protects waterways and aquatic ecosystems. A diversion is a more effective and environmentally friendly solution
than the other options, as it ensures that the sediment run-off is not released into the environment without proper
treatment or containment.
Trusted by thousands of students and professionals worldwide Page 3 of 16
