Johnson County, IA Environmental Rules: Erosion Control (2026)

7, the Board of Supervisors cannot approve a preliminary plat, and the Board or Zoning Administrator cannot approve a site plan, without an adequate soil erosion and sediment control plan. For building permits, the plan is mandatory only when the project meets one of three thresholds: a new dwelling, a dwelling addition with a footprint of 1,000 square feet or more, or total ground disturbance exceeding one quarter acre. A Soil Erosion and Sediment Control Permit is issued alongside the building permit and stays in effect until the site reaches substantial final stabilization.

Grading permits and demolition permits carry the same plan requirement regardless of project size, and any conditional use conditioned on erosion control cannot commence until a plan is approved and implemented. 7(B)(1). Approved plans must follow the Iowa Statewide Urban Design and Specifications (SUDAS) standard design criteria, preserve and reapply existing topsoil in an uncompacted, uniform layer, and stay in place until the County confirms final stabilization, meaning a sufficient uniform perennial vegetative cover or an equivalent permanent measure covers all disturbed, non-hard-surface ground. Owners remain responsible for compliance with the approved plan, any State NPDES General Permit #2, and all other state or federal permitting in effect at the time of application; a site is not in conformance unless it matches the plan the Zoning Administrator approved.