CPESC Site Assessment & Planning 4 — Questions and Answers
Question 1: Which site condition would most significantly increase the required size of a sediment basin during the design phase?
- High clay content in the contributing watershed soils
- Large contributing drainage area with steep slopes (Correct answer)
- Dense existing vegetation in the contributing area
- Low rainfall intensity during the construction period
Correct answer: Large contributing drainage area with steep slopes
Larger drainage areas and steeper slopes generate greater runoff volumes and sediment loads, directly increasing the required storage volume and surface area of a sediment basin.
Question 2: A site plan review reveals that a proposed access road crosses a perennial stream without an existing culvert. The FIRST step the CPESC practitioner should recommend is:
- Design a temporary ford crossing for construction equipment
- Determine if a Section 404 permit is required from the Army Corps of Engineers (Correct answer)
- Install a temporary silt fence across the stream channel
- Calculate the culvert size needed for the 25-year storm
Correct answer: Determine if a Section 404 permit is required from the Army Corps of Engineers
Any fill or structure placed in waters of the US, including stream crossings, requires evaluation for Section 404 permit requirements before construction begins.
Question 3: When evaluating a site for potential groundwater contamination risk during construction, which site feature is most significant?
- Depth to bedrock greater than 20 feet
- Shallow water table within 5 feet of the surface (Correct answer)
- Presence of clay soils with low permeability
- Distance from nearest municipal water supply well
Correct answer: Shallow water table within 5 feet of the surface
A shallow water table increases the risk that surface pollutants from construction activities can quickly reach and contaminate groundwater resources.
Question 4: The 'Curve Number' (CN) used in the TR-55 method for runoff estimation primarily reflects:
- The curvature of the land surface and topographic relief
- Soil hydrologic group, land use, and antecedent moisture conditions (Correct answer)
- The curvature of the intensity-duration-frequency curve
- Drainage density and stream channel slope
Correct answer: Soil hydrologic group, land use, and antecedent moisture conditions
The NRCS Curve Number integrates soil hydrologic group (A through D), land use/cover, and antecedent soil moisture to estimate rainfall-runoff relationships.
Question 5: During site assessment, which observation most strongly suggests the presence of a seasonal high water table (SHWT)?
- Dark colored A horizon greater than 12 inches deep
- Mottled gray and brown (redoximorphic) features in the subsoil (Correct answer)
- Rock fragments throughout the soil profile
- Well-developed soil structure in the B horizon
Correct answer: Mottled gray and brown (redoximorphic) features in the subsoil
Redoximorphic features (mottling) in the subsoil indicate periodic saturation and are the primary field indicator of seasonal high water table depth.
Question 6: A construction site SWPPP must be updated when which of the following occurs?
- The project superintendent changes
- There is a change in design, construction, or operation that introduces new pollutant sources (Correct answer)
- The construction schedule is extended by more than 30 days
- A new subcontractor is added to the project
Correct answer: There is a change in design, construction, or operation that introduces new pollutant sources
NPDES Construction General Permits require SWPPP amendments whenever changes in design, construction, or operation alter the types or amounts of pollutants that could be discharged.
Question 7: Which site assessment finding would trigger a requirement to implement 'enhanced' or 'more stringent' sediment controls under most state construction general permits?
- Project area greater than 1 acre
- Site drainage to impaired waters or sensitive receiving waters (Correct answer)
- Presence of fill soils from a previous construction project
- Slopes greater than 5% on any portion of the site
Correct answer: Site drainage to impaired waters or sensitive receiving waters
Most CGPs require enhanced BMPs when construction sites drain to waters listed as impaired (303(d) list) or designated as sensitive, high-quality, or special protection waters.
CPESC Site Assessment & Planning 4
Which site condition would most significantly increase the required size of a sediment basin during the design phase?