CPESC Site Assessment & Planning 2 — Questions and Answers
Question 1: During a pre-construction site assessment, which soil characteristic most directly predicts erodibility under rainfall impact?
- Soil color and organic matter content
- Aggregate stability and texture (Correct answer)
- Cation exchange capacity
- Soil pH and nutrient level
Correct answer: Aggregate stability and texture
Aggregate stability and texture determine how well soil particles resist detachment by raindrop impact and surface runoff.
Question 2: Which topographic feature on a site plan indicates where concentrated flow is most likely to develop during a storm event?
- Ridgelines shown as convex contours
- Swales and valleys shown as concave contours (Correct answer)
- Uniformly spaced contours on planar slopes
- Hilltops with widely spaced contours
Correct answer: Swales and valleys shown as concave contours
Concave contour patterns (swales/valleys) are natural drainage pathways where overland flow converges into concentrated flow.
Question 3: A CPESC practitioner reviewing a grading plan notices a proposed cut slope of 2H:1V in sandy loam soil. What is the primary concern?
- The slope is too gentle for proper drainage
- The slope may be unstable and highly erosive without protection (Correct answer)
- Sandy loam is not suitable for cut slopes
- The slope angle exceeds regulatory maximums universally
Correct answer: The slope may be unstable and highly erosive without protection
A 2H:1V slope in sandy loam can be unstable and highly susceptible to erosion without adequate stabilization measures.
Question 4: When assessing a construction site adjacent to a stream, which buffer zone measurement is typically used to define the no-disturbance area?
- Measured from the ordinary high water mark (Correct answer)
- Measured from the centerline of the stream
- Measured from the edge of the 100-year floodplain
- Measured from the bankfull discharge width
Correct answer: Measured from the ordinary high water mark
Regulatory buffers are typically measured from the ordinary high water mark (OHWM), which defines the active stream channel boundary.
Question 5: Which factor in the Revised Universal Soil Loss Equation (RUSLE) accounts for the erosion-reducing effect of vegetation and surface cover?
- K factor (soil erodibility)
- LS factor (slope length and steepness)
- C factor (cover-management) (Correct answer)
- P factor (support practice)
Correct answer: C factor (cover-management)
The C factor in RUSLE represents the ratio of soil loss from land with specific cover and management to that from bare, cultivated soil.
Question 6: A site assessment reveals that existing topsoil is 6 inches deep over clay subsoil. What is the recommended best practice for erosion control planning?
- Strip and stockpile topsoil separately for later replacement (Correct answer)
- Mix topsoil and subsoil to improve drainage
- Remove topsoil entirely to expose stable subsoil
- Leave topsoil in place and grade over it
Correct answer: Strip and stockpile topsoil separately for later replacement
Stripping and stockpiling topsoil preserves its organic matter and seed bank for use in final stabilization after grading is complete.
Question 7: During site planning, the concept of 'phased disturbance' primarily serves to:
- Reduce overall project cost by spreading work over time
- Limit the area of exposed soil at any one time to reduce erosion risk (Correct answer)
- Allow regulatory inspections between construction phases
- Provide time for equipment to be mobilized between areas
Correct answer: Limit the area of exposed soil at any one time to reduce erosion risk
Phased disturbance minimizes the total area of bare soil exposed at any given time, directly reducing the potential for erosion and sediment discharge.
CPESC Site Assessment & Planning 2
During a pre-construction site assessment, which soil characteristic most directly predicts erodibility under rainfall impact?