Stormwater & Erosion Control
Stormwater Pollution Prevention Plans (SWPPP)
A site-specific plan, written by a Qualified SWPPP Developer, so your site can obtain Construction General Permit coverage before any clearing, grading or demolition.
What is a SWPPP?
A stormwater pollution prevention plan (SWPPP) is a site-specific document, required for California construction sites covered by the State's Construction General Permit, that identifies pollutant sources and the erosion, sediment and housekeeping controls crews will install, inspect and maintain.
Sometimes spelled “storm water pollution prevention plan,” a SWPPP is uploaded to SMARTS, the State Water Board's online permit system, to obtain coverage under the 2022 Construction General Permit (CGP; Order WQ 2022-0057-DWQ). The site team follows it from the first day of ground disturbance until coverage ends.
It is separate from the erosion control sheet your city or county reviews with a grading permit, often called an erosion and sediment control plan. Both show erosion and sediment control best management practices (BMPs), and the requirements overlap; some agencies accept the SWPPP in place of that plan.
Deliverables
What's included in a SWPPP
The permit lists what every SWPPP must contain (CGP §IV.O.2). A typical package covers:
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Site-specific SWPPP
Pollutant sources, BMP selection, spill response and housekeeping measures, with the QSD's signed title sheet.
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Risk level determination
Sediment and receiving-water risk from SMARTS maps or site-specific soils and slope data.
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SWPPP drawings
Pre-earthwork and construction drawings showing drainage areas, discharge points and BMP locations.
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Monitoring program
Inspection locations and procedures, plus sampling and chain-of-custody steps where required.
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Registration documents
Notice of Intent data, site maps and attachments for the Legally Responsible Person to certify.
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Post-construction plans
Plans and calculations submitted to your local agency, or the permit's runoff-volume calculations outside municipal permit areas.
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Amendments & updates
QSD revisions as grading, phasing or dates change, with Change of Information support.
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Termination package
Final site map, stabilization photos and post-construction BMP maintenance plan for the Notice of Termination.
When do you need a SWPPP?
Any project needing Construction General Permit coverage needs a SWPPP first. Common cases:
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Subdivisions and tract homes
Every phase of a common plan, from rough grading to vertical construction, stays covered.
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Commercial, multifamily and industrial sites
Clearing, grading, demolition and stockpiling that disturb one acre or more of soil.
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Pipelines, utilities and sewer extensions
Sewer, storm drain and utility work shown on improvement plans follows the permit's linear-project rules.
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Caltrans construction contracts
Caltrans specifications require a QSD-developed SWPPP; jobs not needing one use a QSP-prepared Water Pollution Control Program.
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Taking over a site mid-construction
Coverage doesn't transfer; a new owner files new registration documents and a SWPPP.
Sites of one to five acres may qualify for a Small Construction Rainfall Erosivity Waiver if the rainfall erosivity (R) factor for the construction period is less than 5; within a larger common plan, the whole project must qualify. The waiver must be issued through SMARTS before work starts. A waiver site needs no SWPPP, but if the end date moves and R reaches 5 or more, it needs permit coverage.
Process
How SWPPP preparation works
From confirming coverage to closing it out.
Confirm coverage
We count all disturbed area, including staging, stockpiles and later phases, and check for a common plan or waiver.
Set the risk level
Construction dates, soils and slopes set sediment risk; receiving waters are screened. A topographic survey can refine the slope factor.
Write the SWPPP
The QSD assesses pollutant sources, selects BMPs keyed to the grading plans, and prepares drawings and the monitoring program.
File for coverage
The Legally Responsible Person certifies the registration documents, including post-construction calculations, in SMARTS. Construction waits for the WDID.
Keep it current
The QSD visits the site and revises the plan after SWPPP inspections, sampling results or schedule changes.
Close out coverage
After final stabilization, the Notice of Termination is filed; it is approved automatically after 30 days unless the Regional Water Board acts.
California rules
California requirements for SWPPPs
The current permit took effect September 1, 2023 and expires August 31, 2028. Key rules:
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CGP §II.A–B
Coverage starts at one acre
Construction that disturbs one acre or more of soil, or less than one acre within a larger common plan of development or sale totaling one acre or more, needs coverage before work starts. Clearing, grading, excavation, stockpiling and demolition count; routine maintenance restoring a facility's original line, grade or capacity does not.
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CGP §III.A
No construction before the WDID
The Legally Responsible Person files the Notice of Intent, risk level, site maps, SWPPP, post-construction plans and calculations, and fee. Construction cannot begin until SMARTS issues a Waste Discharge Identification (WDID) number, which must be posted where the public can see it (or kept readily available on request if public posting isn't possible).
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CGP §IV.O.1, §V.A.2
The SWPPP stays on site
A current copy of the SWPPP, developed by a QSD, stays at the site for federal, State and municipal inspectors. It may be electronic if it can be produced during an inspection, but all maps must be legible hard copies.
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CGP Att. D, D.1
Risk level sets the workload
Each traditional construction site is assigned Risk Level 1, 2 or 3 by combining sediment risk with receiving-water risk; linear projects get Type 1, 2 or 3. Sites at Risk Level 2 or 3 also sample storm discharges during qualifying storms for pH and turbidity.
Requirements vary by city and county: local agencies approve their own erosion control plans and wet-season rules differ. Lake Tahoe Hydrologic Unit projects use the Lahontan Regional Board's permit instead.
Sources & references
- Order WQ 2022-0057-DWQ, Construction Stormwater General Permit (State Water Resources Control Board)
- 2022 CGP Attachment D.1, Risk Determination Worksheet (State Water Resources Control Board)
- 2022 Construction Stormwater General Permit FAQ (State Water Resources Control Board)
- 2025 Standard Specifications, Section 13: Water Pollution Control (California Department of Transportation)
- Phase II Small MS4 General Permit, Order WQ 2013-0001-DWQ (conformed), Section E.10 (State Water Resources Control Board)
Last reviewed .
SWPPP FAQs
Do I need a SWPPP if my project disturbs less than one acre?
A SWPPP is required for a site under one acre when it is part of a larger common plan of development or sale that disturbs one acre or more, such as a builder's half-acre share of a 20-acre subdivision. An individual homeowner building a custom home on a private lot under one acre does not need Construction General Permit coverage, though local erosion rules still apply.
Who can prepare a SWPPP in California?
A SWPPP in California must be written and amended by a Qualified SWPPP Developer (QSD). QSDs qualify through the California Stormwater Quality Association's program, which requires a prerequisite credential, a course and an exam; California-licensed civil engineers, professional geologists and engineering geologists may instead self-register through SMARTS. The discharger's Legally Responsible Person certifies the finished documents.
Does a SWPPP include site inspections and sampling?
A SWPPP includes the monitoring program that sets inspection and sampling procedures, but carrying out that program is separate work that continues until coverage ends. A Qualified SWPPP Practitioner (QSP) carries out the SWPPP, including inspections, sampling and BMP implementation, and a Qualified SWPPP Developer (QSD) may do any QSP task. Trained delegates may do the weekly, during-storm and post-storm inspections.
How often does a SWPPP need to be updated?
A SWPPP must be revised by the QSD whenever inspections, sampling data, QSP comments or the QSD's own site observations show a problem, and whenever site conditions, acreage or schedule change. The Construction General Permit requires each amendment to be uploaded to SMARTS within 30 calendar days, and a Change of Information at least 14 days before a construction start or end date changes, unless that is infeasible.
What affects the cost and schedule of a SWPPP?
The cost and schedule of a SWPPP depend on disturbed acreage and phasing, the risk level, whether work spans the wet season, any TMDL, dewatering or treatment requirements, the post-construction calculations, and how complete the grading plans are. Share the site location, disturbed acreage, construction schedule and current plans; the proposal then sets scope and timing.