SWPPP Requirements for California Construction Sites: A Guide to the 2022 Construction General Permit

Stormwater rules shape a California construction project long before the first rain. Disturbed acreage decides whether a site needs coverage. Soils, slopes, construction dates and downstream waters decide how much inspection and sampling it owes. This guide follows the 2022 Construction General Permit (CGP) in the order a project meets it.

Who needs coverage under California's Construction General Permit?

The CGP covers construction and land disturbance of one acre or more. It also covers smaller disturbances that are part of a larger common plan of development or sale totaling one acre or more.

Linear underground and overhead projects, such as pipelines, fall under the same permit with their own requirements. Sites of one to five acres may instead qualify for a Small Construction Rainfall Erosivity Waiver, but only if the rainfall erosivity factor for the construction window is below 5 and the waiver is issued in SMARTS before work starts. A small site that is part of a larger common plan qualifies only if the whole project does, and the waiver carries its own fee.

Cities and counties enforce their own grading and stormwater ordinances separately. A local grading permit can require an erosion and sediment control plan whether or not the site needs CGP coverage, and rules vary by agency.

What has to be filed before construction can start?

The discharger's Legally Responsible Person certifies and submits Permit Registration Documents (PRDs) through SMARTS, the State Water Board's online permit system. The PRDs are:

• A Notice of Intent
• A risk assessment (the risk level determination)
• A site map
• Post-construction plans and calculations
• The SWPPP
• A signed certification statement
• The first annual fee, set each year by regulation

Post the WDID notification form, with the correct construction start and end dates, where the public can see it. If public posting isn't possible, keep it readily available on request.

The SWPPP lists the site's pollutant sources and the best management practices (BMPs) crews will install and maintain, from housekeeping to erosion and sediment control. A QSD must write it and every amendment, and amendments go into SMARTS within 30 calendar days. Our SWPPP preparation page describes what a plan contains.

How is a site's risk level determined?

Risk has two parts. Sediment risk is the rainfall erosivity (R) factor times soil erodibility (K) times the length-slope (LS) factor, in tons per acre. Below 15 is low, 15 up to 75 is medium, and 75 or more is high. The R factor depends on the construction start and end dates, so a schedule that runs through the wet season raises it.

Receiving water risk is high if the site drains, directly or indirectly, to a water body on the 303(d) list as impaired by sediment. It is also high if the receiving water has the COLD, SPAWN and MIGRATORY beneficial uses, or if the site drains to an unlisted tributary of a sediment-sensitive water in the same HUC 10 watershed. SMARTS combines the two into Risk Level 1, 2 or 3, with 3 the most demanding.

How a site's risk level is set

Illustrative diagram — not to scale

1. 1Sediment risk: the rainfall erosivity (R) factor times soil erodibility (K) times the length-slope (LS) factor, in tons per acre. Below 15 is low, 15 up to 75 is medium, and 75 or more is high.
2. 2Receiving water risk: high if the site drains, directly or indirectly, to a water body on the 303(d) list as impaired by sediment, or meets one of the other conditions described above.
3. 3Risk level: SMARTS combines the two into Risk Level 1, 2 or 3, with 3 the most demanding.

SMARTS can fill in the K factor, LS factor and receiving water risk from the site's coordinates. The determination must cover every phase of construction, from demolition to final landscaping.

Who is responsible: the discharger, the QSD or the QSP?

The discharger is responsible for compliance, including work done by the QSD, the Qualified SWPPP Practitioner (QSP) and any trained delegates.

• QSD: Writes and amends the SWPPP and stays on the project until the Notice of Termination is approved. The QSD visits the site within 30 days of the start of construction, twice a year (August to October and January to March), and within 14 days of a numeric action level exceedance.
• QSP: Personally inspects the site every calendar month and before each forecast qualifying storm, and confirms BMPs are installed and maintained. Those inspections cannot be delegated. Trained delegates may do the weekly, during-storm and post-storm inspections, but a QSP must first confirm they are competent and list them in a training log uploaded to SMARTS.

QSDs and QSPs qualify through the California Stormwater Quality Association (CASQA) training and exam program, which requires a prerequisite credential. Instead, California-licensed civil engineers, professional geologists and engineering geologists can self-register as a QSD or QSP through SMARTS after reviewing the State Water Board's self-directed training materials. CASQA-certified QSDs and QSPs need six hours of continuing education a year and renew every two years.

What inspections, sampling and reports does the permit require?

Every risk level now does weekly inspections plus inspections before and during each qualifying precipitation event (QPE), and after it when the site's rain gauge records 0.5 inch or more. The 2009 permit's Rain Event Action Plan is gone. A QPE is a National Weather Service forecast of at least a 50 percent chance of precipitation and 0.5 inch or more within 24 hours. Our guide to rainy-season SWPPP inspections covers timing and paperwork, and our SWPPP inspection services page explains the field work.

Sampling

Risk Level 2 and 3 sites take one sample from each discharge location in every 24-hour period of a QPE while water is discharging, and test it for pH and turbidity. The numeric action levels (NALs) are a pH range of 6.5 to 8.5 and turbidity of 250 NTU.

Going over an NAL is not a permit violation by itself. Failing to report it, or failing to improve BMPs afterward, is.

Reporting deadlines

TMDL, dewatering and treatment sites

Extra requirements apply to:

• Sites that drain to a water with a total maximum daily load (TMDL) assigning a load to construction stormwater, listed in Attachment H, and have that TMDL's pollutant on site.
• Sites discharging dewatering water (Attachment J).
• Sites using active or passive treatment (Attachments F and G).

How does a project end its permit coverage?

Coverage ends with a Notice of Termination (NOT) submitted in SMARTS. Before filing, the site must reach final stabilization. The permit accepts three ways to show it:

• Permanent vegetation evenly covering 70 percent of disturbed soil
• A RUSLE or RUSLE2 soil-loss calculation
• A custom method the Regional Water Board approves

The NOT package also needs:

• A QSP's final NOT inspection (with the QSP's name and certificate number)
• A final site map
• Photos of final stabilization and the installed post-construction BMPs
• A long-term maintenance plan for those BMPs covering at least five years

The NOT is approved automatically after 30 calendar days unless the Regional Water Board acts first, and every permit requirement stays in force until then.

Post-construction requirements

Post-construction requirements depend on location. Inside a municipal separate storm sewer system (MS4) permit area, the local agency's standards apply. Outside one, the CGP requires the site to match its pre-construction runoff volume for storms up to the 85th percentile 24-hour event. Sites disturbing more than two acres must also preserve pre-construction drainage density and keep runoff time of concentration at least as long as before.

Either way, the PRDs include post-construction plans, so post-construction and LID stormwater calculations are best settled in design. Our article on the July 2026 draft Small MS4 permit covers what may change locally.

What does noncompliance cost?

Under Water Code section 13385, the State or a Regional Water Board can impose administrative civil liability of up to $10,000 per day of violation, plus up to $10 per gallon discharged beyond 1,000 gallons that is not cleaned up. Courts can impose up to $25,000 per day and $25 per gallon.

The section's $3,000 mandatory minimum penalties apply mainly to effluent limitation violations.

The same lapses are violations under the 2022 permit. Other common gaps that break a specific 2022 permit requirement include:

• Grading before the WDID number is issued
• Construction dates in SMARTS that do not match the real schedule, which skews the risk level and waiver eligibility
• BMPs shown on the SWPPP but not installed before the first forecast storm, or a SWPPP not amended as the drainage changes
• Missed storm inspections or sampling, or forecasts not saved with inspection reports

What this means for your project

Most CGP problems start in design and scheduling. Before you file:

• Count every disturbed area, including staging, stockpiles, access roads and later phases, and check for a larger common plan.
• Enter realistic start and end dates. A longer wet-season window can raise the R factor and the risk level.
• Coordinate the SWPPP with your grading plans: stabilized entrances, perimeter controls, and a 50-foot natural buffer (or equivalent controls) where disturbance comes within 50 feet of a water of the U.S. Start stabilizing right away wherever work stops for good or will pause more than 14 days.
• Start post-construction calculations early, especially where a local agency has to approve them.
• Budget for the wet season: monthly and pre-storm QSP visits, delegate inspections and, on Risk Level 2 and 3 sites, sampling.
• Plan the Notice of Termination from the start, including how you will show final stabilization.

We prepare SWPPPs, erosion and sediment control plans and stormwater calculations, and provide SWPPP inspections for construction sites in California. As the permit requires, a QSD develops the SWPPP, and the QSD's site visits and the QSP's monthly and pre-storm inspections are done by those certified individuals. Weekly, during-storm and post-storm inspections can be done by a QSP or a QSP-trained delegate. Send us your site location, disturbed acreage and schedule to start a SWPPP or stormwater inspection request.