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 can be established by identifying areas and designing appropriate measures in the erosion control plan.

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.

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

• Areas that do not drain to a sediment trap must be stabilized within 30 days.
• Areas that drain to an appropriately sized Sediment Trap must be stabilized with 90 days.
• Areas left inactive for more than 14 days and those at final grade must be stabilized immediately.