County of Asotin

Regional Stormwater Program

Inform. Educate. Prevent.

Medium Construction Projects

Local Stormwater Permit Required:

  • Development or re-development project where land disturbing activities are ≥ 5,000 sq ft and < 1 acre
  • Land disturbing activity has the potential to disturb or change natural drainage patterns
  • Requires Erosion & Sediment Control (ESC) Plan and map
  • ESC practices must be installed to reduce erosion prior to land disturbing activities
  • Stormwater staff will conduct inspections
  • Post-Construction best management practice monitoring waived


Projects meeting the Medium Project threshold shall prepare an Erosion and Sediment Control (ESC) Plan for construction activity. The ESC Plan shall be implemented beginning with initial soil disturbance and continue until final stabilization.

The ESC Plan Shall Include The Following Elements:

  • Project schedule including sequencing/phasing a project as appropriate and plan for site stabilization.
  • Boundary of clearing and land disturbing activities (including access and egress).
  • Project/construction site access/egress control, stabilization and management. Off-site tracking of materials is prohibited.
  • Stabilize soils during and after project activities, including disturbed areas and stockpiles. Plan should include erosion and sediment controls utilizing BMPs, acknowledging site run-on and run-off and dust control.
  • Identify and protect stormwater control facilities that may be impacted.
  • Control of pollutants such as demolition debris, waste materials, oils, greases, concrete wastes and chemicals.
  • Maintenance of BMPs and the ESC Plan.

ESC Plan Map

The ESC Plan shall also include a legible site map (or maps) showing the entire construction site. The following features shall be identified, unless not applicable due to site conditions:

  • The direction of north, property lines, and existing structures and roads;
  • Cut and fill slopes indicating the top and bottom of slope catch lines;
  • Approximate slopes, contours, and direction of stormwater flow before and after major grading activities;
  • Areas of soil disturbance and areas that will not be disturbed;
  • Locations of structural and nonstructural controls (BMPs) identified in the ESC Plan;
  • Locations of off-site material, stockpiles, waste storage, borrow areas, and vehicle/equipment storage areas;
  • Locations of all adjacent surface water bodies, including wetlands;
  • Locations where stormwater or non-stormwater discharges off-site and/or to a surface water body, including wetlands;
  • Location and dimensions of stormwater facilities