SWPPP Requirements in Colorado

Who needs a SWMP in Colorado?

Any construction project that disturbs one acre or more — or is part of a larger common plan of development reaching one acre — needs a SWMP under Colorado permit COR400000.

Colorado runs its own delegated stormwater program. Operators obtain coverage from Colorado Department of Public Health and Environment (CDPHE), Water Quality Control Division under CDPS General Permit COR400000 — Stormwater Discharges Associated with Construction Activity (COR400000), not directly from the EPA. A small subdivision, a solar pad, and a road-widening project all clear the same one-acre line.

Colorado adds requirements worth flagging early: The plan is a Stormwater Management Plan (SWMP); the owner and the operator are co-permittees and both sign the application (COR400000 Parts I.A.3.b and I.C); Apply through CEOS at least 10 days before construction begins and receive written notice of coverage before construction (public emergency sites: within 14 days after starting) (COR400000 Part I.A.3.b); Include a copy of COR400000, the site’s certification, and any applicable low-risk discharge guidance in the SWMP, and list other CDPS and Section 404 permits (COR400000 Part I.C.2.b); Describe the percent cover of native vegetation (and its source or method), and the site’s stream crossings and receiving waters, in the SWMP site description (COR400000 Part I.C.2.c); Include a spill prevention and response plan and design specifications for every control measure in use (COR400000 Parts I.C.2.g–h); Chemical treatment of stormwater (flocculants, polymers, coagulants) is not authorized (COR400000 Part I.A.2); Discharges to Outstanding Waters must be short-term with a long-term benefit, and require inspections at least every 7 calendar days (COR400000 Parts I.B.2.b and I.D.3); Sign each inspection report with the verification statement once corrective actions are complete (COR400000 Part I.D.5.c).

What the plan must contain

A Colorado SWMPis 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 SWMP is signed by the legally responsible party before work begins.

Required and conditional BMPs

Filing your Notice of Intent

Owner and operator submit a complete, signed permit application through the Colorado Environmental Online Services (CEOS) portal at least 10 days before construction begins; the division must grant coverage in writing before construction starts.

A Notice of Termination closes coverage once the site reaches final stabilization. Keeping the SWMP 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 (COR400000 Part I.D.2.a); or (b) 14-day schedule with post-storm inspections — inspect at least once every 14 calendar days and within 24 hours after the end of any precipitation or snowmelt event that causes surface erosion (post-storm inspections may be used to fulfill the 14-day routine inspection) (COR400000 Part I.D.2.b). Inspections start within 7 calendar days of commencing construction (Part I.D). Every inspection is dated and signed, and any failed control is corrected before the next storm.

How Colorado differs from the federal permit

Because Colorado 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