Do You Need a SWPPP in Idaho? | Idaho CGP Coverage Checklist

Fast coverage checklist (most common trigger)

The most common question is whether your project is a construction activity that needs CGP coverage. This screening flow matches the way contractors and owners usually evaluate coverage before building a SWPPP.

1) Disturbance area Are you disturbing 1 acre or more of land?

2) Common plan Is your site part of a common plan of development that will disturb 1 acre or more total (even if your piece is smaller)?

3) Stormwater discharge Will stormwater leave the site (ditch, storm drain, creek/canal, conveyance, or direct flow)?

4) Operator responsibility Do you (or your client) control plans/specs or day-to-day construction activities? That typically makes you an “operator.”

If you answered “yes” to the main triggers, you generally proceed with (1) CGP coverage/NOI steps and (2) a SWPPP that matches your site conditions.

If the answer is “yes”

You likely need CGP coverage and a SWPPP that matches your site conditions.
Coverage is commonly initiated with an NOI (Notice of Intent).
Ongoing compliance typically includes inspections, corrective actions, stabilization tracking, and recordkeeping.

NOI basics (Idaho) CGP requirements checklist Use the app workflow

If the answer is “no”

You may not need CGP coverage, but you can still have local erosion-control requirements, contract specs, or owner requirements.

Local agency rules can apply even below 1 acre.
BMPs still matter (track-out, inlet protection, stabilization, concrete washout).

BMPs that matter Ask a question

Small sites: rainfall erosivity waiver (R-factor) + reference tool

Idaho’s CGP includes a concept for small construction waivers (e.g., 1–5 acres) where a project may qualify for a waiver in lieu of permit coverage under certain conditions — including a rainfall erosivity waiver where the “R” factor is below a threshold for the construction period (earth disturbance through stabilization).

Open EPA Rainfall Erosivity Calculator EPA guidance page

Important: the tool is a reference. Whether you can rely on a waiver depends on the permit’s waiver instructions and your project’s facts. If you pursue a waiver, document your basis and follow the CGP’s notification requirements.

CGP reference: Appendix B (Small Construction Waivers) describes the rainfall erosivity waiver concept and points to the EPA tool.

What your SWPPP typically includes (Idaho CGP-aligned)

A SWPPP isn’t just a form — it’s a site-specific plan that documents how you will control erosion/sediment, prevent pollution, inspect, correct problems, and stabilize the site. Auto-SWPPP organizes the output around a practical, permit-aligned structure.

Coverage checklist Inspections Stabilization R-factor tool

Template reference: This section list mirrors your SWPPP template’s structure (Sections 1–9).

Erosion & sediment controls

Document BMPs like perimeter controls, track-out, inlet protection, stockpile controls, buffers near waters, and dewatering practices.

Idaho BMPs overview

Inspections & corrective action

Choose an inspection schedule, document rain data sources, and log corrective actions when BMPs fail or conditions change.

Inspection requirements

Stabilization

Track when areas go inactive, apply temporary stabilization, and meet final stabilization criteria.

Stabilization timelines

Inspections: the two common schedules (plus dewatering)

The Idaho CGP allows a minimum inspection schedule of either: (A) once every 7 calendar days, or (B) once every 14 calendar days plus storm-related inspections tied to a rainfall/discharge threshold. If you are discharging dewatering water, inspection frequency increases for the affected portion of the site.

Option A — 7-day schedule Inspect at least once every seven (7) calendar days.

Option B — 14-day + storm/discharge schedule Inspect at least once every fourteen (14) calendar days and within the required window when a qualifying storm produces discharge (threshold discussed in the permit).

Dewatering discharge If the site is discharging dewatering water, you must inspect once each day the discharge occurs for the affected portion of the site.

Rain data Maintain an on-site rain gauge or use a representative weather station and record qualifying rainfall days during business hours.

In the Auto-SWPPP output, inspection schedules, rain data sources, inspector qualifications, and logs are documented under the inspections/corrective action section and appendices.

CGP reference: inspection frequencies and dewatering inspection increase are in the CGP inspection section.

Stabilization: timelines + final stabilization criteria

Stabilization is one of the most enforced parts of construction stormwater compliance. The CGP includes deadlines for initiating and completing temporary stabilization after work stops, plus a definition of what “final stabilization” means.

Temporary stabilization (when work pauses) For many scenarios, temporary non-vegetative measures must be initiated and completed within specific calendar-day deadlines after cessation of work.

Final stabilization (what “done” looks like) Final stabilization can be achieved by establishing uniform perennial vegetation providing 70% or more of native cover, and/or by implementing permanent non-vegetative stabilization (e.g., riprap/gravel/geotextiles).

Special conditions (e.g., drought/seasonally dry periods, unforeseen circumstances, impaired waters/antidegradation tiers) can change stabilization expectations and documentation requirements.

CGP reference: stabilization exceptions/deadlines and final stabilization criteria are in the stabilization section.

Work near waters: buffers and documentation

If your earth disturbance is close to waters, the CGP has specific expectations for documenting buffer width and what controls you’re using when a full buffer isn’t feasible.

Screen for proximity Are there surface waters within a short distance of disturbance? If so, document how you will protect them and show it on the site plan.

Document feasibility + controls If constraints limit buffer retention, document rationale and describe supplemental erosion/sediment controls used to achieve equivalent protection.

CGP reference: buffer appendix discusses exceptions, measurement concepts, and required SWPPP documentation.

Dewatering: why it gets extra attention

Dewatering discharges can transport sediment quickly and create visible water quality issues. That’s why the permit increases inspection frequency for active dewatering discharges and expects controls and monitoring to be documented.

See CGP requirements checklist Build a SWPPP in the app

CGP reference: dewatering discharge inspection frequency is addressed in the inspection section.

Related Idaho SWPPP resources

These pages help with internal discovery and provide deeper detail by topic.

Idaho SWPPP generator

How Auto-SWPPP works and what you get.

Open page

Idaho SWPPP inspections

Inspection schedules, storm thresholds, and logs.

Open page

Idaho CGP requirements

A checklist-style view of major permit elements.

Open page

Want the app workflow?

Auto-SWPPP guides you through the inputs that matter and generates a narrative PDF preview you can review before checkout. After purchase, we finalize and deliver the full SWPPP PDF package aligned to the Idaho CGP workflow.

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