Who needs a SWP3 in Indiana?
Any construction project that disturbs one acre or more — or is part of a larger common plan of development reaching one acre — needs a SWP3 under Indiana permit INRA00000.
Indiana runs its own delegated stormwater program. Operators obtain coverage from Indiana Department of Environmental Management (IDEM), Office of Water Quality under Construction Stormwater General Permit (INRA00000), not directly from the EPA. A small subdivision, a solar pad, and a road-widening project all clear the same one-acre line.
Indiana adds requirements worth flagging early: Submit the construction plan/SWP3 to the soil and water conservation district, MS4, or (when directed) IDEM for review before any land disturbance; the NOI carries the reviewer’s sufficiency notice, or proof of delivery if no review came within 28 days (Sections 4.2, 4.3(e), 5.2(a)(11)); Notify the public before the NOI: a signed notice posted at the site 10 calendar days before NOI submittal, a 10-day agency web posting, or a newspaper notice, documented in the project management log (Section 3.7(a)); Submit the NOI at least 48 hours before land disturbance, and send a copy to the plan review agency (SWCD and/or MS4) (Sections 5.3(a) and 5.3(c)); Post a notice near the main entrance with the NOI information, the NPDES permit number once received, and the SWP3 location if it is not kept on site (Section 3.3(a)(13)); Maintain a project management log with self-monitoring reports, regulatory inspections, compliance responses, off-site borrow/disposal/staging areas, and the dates, authors, and summaries of all SWP3 modifications (Section 3.7(b)); Inform personnel of the permit and SWP3 terms (e.g., pre-construction meetings) and document it (Section 3.3(a)(12)); Remove sediment tracked onto roadways open to traffic by the end of the same day (Section 3.3(a)(1)(C)); Only anionic polymers may be used, and only when identified in the SWP3 or after notifying IDEM or the MS4 (Section 3.5(a)); Post-construction SWP3 with an operation and maintenance manual for the permanent measures, unless an exemption in Section 4.1(a)(9) applies (Sections 4.1(a)(9)–(10)); Coverage lasts five years from the date it begins; renewal information is due 90 days before coverage ends (Section 5.4).
What the plan must contain
An Indiana SWP3is the site's compliance binder — the document an inspector opens first. It documents:
- 1Site & project descriptionTotal and disturbed acreage, soils, slopes, and the sequence of construction.
- 2Receiving waters & discharge pointsWhere stormwater leaves the site and the waterbodies it reaches.
- 3Erosion & sediment control BMPsSilt fence, stabilized entrances, inlet protection, and stabilization measures.
- 4Inspection schedule & recordsDated, signed inspection logs and the corrective actions taken.
- 5Operator certificationThe SWP3 is signed by the legally responsible party before work begins.
Required and conditional BMPs
| Best management practice | Category | Status |
|---|---|---|
| Perimeter silt fence / sediment barrier | Sediment control | Required |
| Stabilized construction entrance | Tracking control | Required |
| Storm drain inlet protection | Sediment control | Required |
| Soil stabilization (seeding, mulch, blankets) | Erosion control | Required |
| Concrete washout containment | Good housekeeping | Required |
| Sediment basin or trap | Sediment control | Conditional |
| Dewatering / turbidity controls | Pollution prevention | Conditional |
Filing your Notice of Intent
Submit the NOI, supporting documents, and processing fee online through the IDEM Regulatory ePortal (Section 5.6), after the plan review agency has verified the construction plan/SWP3.
A Notice of Termination closes coverage once the site reaches final stabilization. Keeping the SWP3 and its inspection records on site is what keeps a project clear of stop-work orders.
Inspection requirements
Inspect at least once every calendar week and 24 hours prior to, or by the end of the next business day following, a storm producing 0.5 inch of rain or more within a 24-hour period (the weekly evaluation is counted per work week and is required when no rain event occurs within the work week; accumulated snow events are excluded; no more than three evaluations per work week are required when several qualifying events occur; a written evaluation of the entire site by a trained individual) (INRA00000 Section 3.6(a)(1)(A); Appendix B definition 40 (“measurable storm event”)). Stabilized areas, stabilized common areas, basins, conveyances, outfalls, and inactive building sites may drop to monthly evaluations (INRA00000 Section 3.6(a)(1)(B)). Every inspection is dated and signed, and any failed control is corrected before the next storm.
| Trigger | Requirement |
|---|---|
| Routine | At least once every calendar week and 24 hours prior to, or by the end of the next business day following, a storm producing 0.5 inch of rain or more within a 24-hour period (the weekly evaluation is counted per work week and is required when no rain event occurs within the work week; accumulated snow events are excluded; no more than three evaluations per work week are required when several qualifying events occur; a written evaluation of the entire site by a trained individual) |
How Indiana differs from the federal permit
| Indiana | Federal (EPA) | |
|---|---|---|
| Authority | Indiana Department of Environmental Management (IDEM), Office of Water Quality | U.S. EPA |
| Permit | INRA00000 | EPA CGP |
| Disturbance threshold | 1 acre | 1 acre |
| Plan name | SWP3 | SWPPP |
Because Indiana 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
Does Indiana require an engineer to prepare the SWP3?+–
No. Indiana does not require a licensed PE stamp on a construction SWP3 statewide. The operator certifies the plan; engineer review is optional for complex sites.
What is the disturbance threshold in Indiana?+–
One acre — including sites under an acre that are part of a larger common plan of development totaling one acre or more.
How often must inspections happen in Indiana?+–
Inspect at least once every calendar week and 24 hours prior to, or by the end of the next business day following, a storm producing 0.5 inch of rain or more within a 24-hour period (the weekly evaluation is counted per work week and is required when no rain event occurs within the work week; accumulated snow events are excluded; no more than three evaluations per work week are required when several qualifying events occur; a written evaluation of the entire site by a trained individual) (INRA00000 Section 3.6(a)(1)(A); Appendix B definition 40 (“measurable storm event”)). Stabilized areas, stabilized common areas, basins, conveyances, outfalls, and inactive building sites may drop to monthly evaluations (INRA00000 Section 3.6(a)(1)(B)).
Is a SWP3 the same as a SWPPP?+–
Yes. Indiana uses the term "SWP3" for what other states call a SWPPP — the same plan and the same requirements.
What is a Trained individual and does my site need one?+–
The SWP3 must be signed by a "trained individual", and trained individuals must be used for SWP3 development and design, measure implementation, self-monitoring, and project management (Sections 4.1 and 3.0(c)). A trained individual is trained and experienced in stormwater management, including erosion and sediment control, as demonstrated by coursework, state registration, professional certification, or annual training (Appendix B, definition 66).
Indiana-ready in minutes
Siltworks fills in your site data automatically, applies the Indiana requirements, and hands you an inspection-ready SWP3 — at 70–90% less than a consultant.
Requirements summarized from the publicly available Construction Stormwater General Permit (INRA00000) for planning purposes. The operator must review and certify every SWP3 before use.