Soil loss generated from gentle and moderate slopes subject to sheet and rill erosion can be determined using the Universal Soil Loss Equation (USLE) model. Steep slopes and areas of concentrated flows cannot be modeled using the USLE methodology, and instead, are subject to prescriptive compliance.

Prescriptive compliance should be established by designing and including appropriate measures in the erosion control plan. Compliance with the soil loss standard can be assumed at prescriptive compliance locations where appropriate measures are used.

Specific areas where prescriptive compliance should be followed are:

• Slopes exceeding 33% (Note difference from DNR guidance of 20%)
• Areas of concentrated flows
  • Swales
  • Pipe outfalls
  • Street grading
• Soil stockpiles
• Utility trench excavations
• Side slopes of storm water management practices

Once areas identified as needing prescriptive compliance are identified and clearly defined in the plan, appropriate measures and specifications need to be designed, as detailed below.

• Areas that do not drain to sediment traps must limit the duration of soil exposure to no more than 30 days.
• Areas that drain to sediment traps must limit the duration of soil exposure to no more than 90 days.

• Design and implement approved stabilization practices, typically Erosion Matting.
• Provide stable diversion of off-site runoff around slopes.
• Provide slope interruption devices on slopes.

• Areas left inactive for more than 14 days must be stabilized immediately.
• Areas at final grade must be stabilized immediately.