CPESC Soil Science 4

Question 1

Which soil characteristic most directly determines whether a soil will be classified as 'hydric' under wetland regulations?

Accepted Answer

Presence of redoximorphic features indicating seasonal saturation

Answer

Hydric soils are identified by redoximorphic features such as mottles, iron depletions, and gleyed matrices that form under conditions of prolonged seasonal saturation.

Question 2

When evaluating a cut slope for erosion potential, a geotechnical investigation reveals a fragipan at 24 inches depth. This layer would:

Accepted Answer

Promote lateral water movement and perched water tables increasing instability

Answer

A fragipan is a brittle, cemented layer with very low permeability that causes perched water tables and lateral flow, potentially destabilizing slopes above it.

Question 3

The 'dispersivity' of a soil refers to its tendency to:

Accepted Answer

Break apart and disperse in water without mechanical agitation

Answer

Dispersive soils deflocculate in the presence of water due to high exchangeable sodium, causing particles to separate and making these soils extremely erodible.

Question 4

In which situation would you expect soil erodibility (K factor) to be HIGHEST?

Accepted Answer

Fine sandy loam with low organic matter content

Answer

Fine sandy loams with low organic matter have moderate-to-high silt content combined with weak aggregation, making them highly susceptible to raindrop detachment and transport.

Question 5

What does a soil's 'field capacity' represent in the context of stormwater management?

Accepted Answer

The water content held after gravitational drainage ceases (approximately -1/3 bar)

Answer

Field capacity is the water content remaining in soil 2–3 days after saturation when gravitational drainage has essentially stopped, representing the upper limit of plant-available water storage.

(CPESC) Certified Professional in Erosion and Sediment Control Practice Test

(CPESC) Certified Professional in Erosion and Sediment Control Practice Test

CPESC Soil Science 4