Coeur d'Alene, ID Environmental Rules: Stormwater Management (2026)

Chapter 13.30, the Stormwater Management Ordinance, applies to all land disturbing activities, including grading, site development, parking lot paving and street improvement (§ 13.30.030). The drainage utility administrator runs it. Every regulated project needs a comprehensive stormwater management plan reviewed by the city and approved by a qualified, licensed professional (§ 13.30.040). New single-family structures and additions to them are excused from the licensed-professional requirement, but the administrator can demand a registered civil engineer's signature when off site drainage or adjacent property rights are affected.

The core performance rule in § 13.30.050 keeps water on your own site. Runoff cannot be accelerated, concentrated or conveyed beyond the exterior property lines, off site public street drainage is detained separately from on site drainage, and every required facility must sit inside the project boundary. Runoff can leave the site only under a joint stormwater management agreement approved in writing by the city, where the downstream property already received drainage before development, or onto a public right of way where needed for driveway or curb cut access. Even then, there can be no measurable increase in the peak runoff rate for a 25-year storm compared with the undeveloped state.

All collected runoff must be directed to infiltration basins or an approved BMP. Runoff from roofs, and runoff from new impervious surface under 3,000 square feet, can go straight into dry wells. Design standards in § 13.30.060 require conveyance facilities sized for a 25-year storm, or a 50-year storm when on site facilities carry off site drainage. Peak flows use the rational method for areas of 10 acres or less and the SCS TR-55 method above that. Infiltration basins must retain and treat one-half inch of runoff over the tributary impervious area, or infiltrate 0.1 inch per hour, and must keep a minimum infiltration rate of 0.5 inch per hour.

No building permit, final plat approval or other discretionary approval issues until the plan is approved (§ 13.30.070). Owners maintain on site facilities, and the abutting owner maintains infiltration basins in city rights of way (§ 13.30.100). Only the city council can grant a variance, and only for undue hardship from unique site characteristics (§ 13.30.130).