SWPPP Requirements in Wyoming

Who needs a SWPPP in Wyoming?

Any construction project that disturbs one acre or more — or is part of a larger common plan of development reaching one acre — needs a SWPPP under Wyoming permit WYR100000 (large construction general permit (lcgp)), or WYR10-A000 (small construction general permit (scgp)).

Wyoming runs its own delegated stormwater program. Operators obtain coverage from Wyoming Department of Environmental Quality (WDEQ), Water Quality Division under WYPDES Large Construction General Permit (WYR100000) (WYR100000 / WYR10-A000), not directly from the EPA. A small subdivision, a solar pad, and a road-widening project all clear the same one-acre line.

Wyoming adds requirements worth flagging early: Before starting, determine whether any part of the project lies in a Sage-Grouse Core Area, connectivity or winter concentration area, within two miles of a non-core lek (Executive Order 2019-3), or in a designated mule deer/antelope migration corridor (Executive Order 2020-1); if so, obtain a Wyoming Game and Fish Department consistency or de minimis letter (Part 8); The SWPPP must follow the Part 9.2 format — SWPPP administrator, site description narrative, site maps, BMPs, maintenance, inspections, signature; WDEQ provides a SWPPP template (Part 9.2); Identify 303(d)-listed or TMDL waters for sediment, suspended solids, or turbidity within 2,000 feet of the site (Part 9.2.2.8); Train employees on their SWPPP responsibilities at least annually and as new employees are hired (Part 9.2.4.3.e); Sites on the Wind River Indian Reservation are not covered; they fall under the EPA CGP; Submit a complete application package — NOI with original signature, a complete SWPPP, the permit fee, and a map showing access from a public road — at least 30 days before construction begins, and receive a Letter of Authorization before discharging (WYR100000 Parts 3.2 and 3.8) (WYR100000); Post a copy of the authorization letter at the site in a prominent, safe place for public viewing during business hours (WYR100000 Part 7.19) (WYR100000); No NOI is filed: coverage is authorized when the operator develops the SWPPP before land disturbance and complies with the permit (WYR10-A000 Part 3.1) (WYR10-A000); A rainfall erosivity (R-factor under 5) waiver may be requested at least 30 days before construction (WYR10-A000 Part 4) (WYR10-A000).

What the plan must contain

A Wyoming SWPPPis the site's compliance binder — the document an inspector opens first. It documents:

1. 1Site & project descriptionTotal and disturbed acreage, soils, slopes, and the sequence of construction.
2. 2Receiving waters & discharge pointsWhere stormwater leaves the site and the waterbodies it reaches.
3. 3Erosion & sediment control BMPsSilt fence, stabilized entrances, inlet protection, and stabilization measures.
4. 4Inspection schedule & recordsDated, signed inspection logs and the corrective actions taken.
5. 5Operator certificationThe SWPPP is signed by the legally responsible party before work begins.

Required and conditional BMPs

Filing your Notice of Intent

Large sites (5+ acres): submit the NOI, complete SWPPP, fee, and access map at least 30 days before construction — WDEQ’s WYIMS system is the preferred submission route (fillable PDF via the Electronic Documents Submittal portal otherwise) — and receive a Letter of Authorization before discharging. Small sites (1 to under 5 acres): no application; develop the SWPPP before disturbance.

A Notice of Termination closes coverage once the site reaches final stabilization. Keeping the SWPPP and its inspection records on site is what keeps a project clear of stop-work orders.

Inspection requirements

The permit allows 2 inspection schedules; the operator follows one and records the choice in this plan: (a) 7-day schedule — inspect at least once every 7 calendar days (during active construction) (WYR100000 Part 10.2.1.2); or (b) 14-day schedule with storm inspections — inspect at least once every 14 calendar days and within 24 hours of a storm producing more than 0.5 inch of rain (during active construction; the trigger is any precipitation and/or snowmelt event exceeding 0.5 inches, measured with an on-site rain gauge, localized radar estimates, or the nearest representative National Weather Service gauge) (WYR100000 Part 10.2.1.1). Inactive sites where earthwork is complete and stabilization measures required by Part 7.12 are installed may be inspected once every 30 days (WYR100000 Part 10.2.2). Every inspection is dated and signed, and any failed control is corrected before the next storm.

How Wyoming differs from the federal permit

Because Wyoming administers its own program, the federal EPA Construction General Permit does not apply directly here — the state permit governs. Sites inside a regulated municipal storm sewer system may carry additional local ordinance requirements on top of the state permit.

Frequently asked questions