SW

Stormwater Directory

Quick Summary

California uses a tiered Risk Level system (1–3) based on project location and characteristics. Most projects over 1 acre need a Construction General Permit, a SWPPP developed by a certified QSD, and an on-site QSP for inspections. Risk Level 3 projects face the strictest requirements including a 10 NTU turbidity limit.

State-DelegatedVerified 2026-03

Construction Permit

Permit Document
Permit Name
Construction General Permit (Order 2009-0009-DWQ, as amended)
Threshold
≥ 1 acre of land disturbance (or < 1 acre if part of a larger common plan)
NOI Lead Time
NOI must be filed and permit coverage obtained before grading/construction begins
Application Method
Online via Stormwater Multiple Application and Report Tracking System (SMARTS)
Fee
Annual fee based on acreage: < 5 acres = $900; 5–49 acres = $1,200; ≥ 50 acres = $2,200
Permit Expires
September 1, 2027

SWPPP Requirements

Permit Document
SWPPP Required
Yes
PE Cert Required
No
Template Available
Yes
California uses a Risk Level system (Risk Level 1, 2, or 3) that determines SWPPP complexity and monitoring requirements. Higher risk levels require more rigorous controls.

Inspection Requirements

Permit Document
Frequency
Risk Level 1: Visual inspections every 24 hours during active rain. Risk Level 2–3: Rain Event Action Plans required; inspections during and after qualifying storms
Rain Trigger
Qualifying storm event (QSE) ≥ 0.5 inches: pre-storm inspection required before predicted QSE, during-storm, and within 48 hours after QSE ends; Risk Level 2/3 require Rain Event Action Plans
Inspector Qualification
Qualified SWPPP Practitioner (QSP) for Risk Level 2 and 3 sites; Qualified SWPPP Developer (QSD) must prepare the SWPPP
Accepted Certifications
Qualified SWPPP Practitioner (QSP) REQUIRED for all site inspections; Qualified SWPPP Developer (QSD) required for SWPPP preparation — both are mandatory state credentials (CASQA-administered)

Discharge Standards

Permit Document
Turbidity Limit
Risk Level 3 sites: effluent must meet 10 NTU turbidity limit at discharge point; Risk Level 2: 250 NTU; Risk Level 1: narrative standard
California has some of the most stringent discharge standards in the country, particularly for high-risk sites near sensitive receiving waters.

Post-Construction

SWRCB
Required
Yes
Post-construction requirements depend on local jurisdiction and whether the site is in an MS4 area. Many municipalities require Low Impact Development (LID) features and permanent BMPs.

Impaired Waterbody / TMDL Requirements

Elevated Risk

California's Construction General Permit (CGP, Order 2022-0057-DWQ) explicitly distinguishes requirements based on receiving water impairment status. Projects discharging to 303(d)-listed water bodies for sediment-related causes face Numeric Effluent Limits (NELs) rather than just Numeric Action Levels (NALs). Enhanced monitoring frequency, lower discharge benchmarks, and additional BMP documentation are required. Projects must verify applicable TMDLs and associated Waste Load Allocations through the SWRCB's Statewide TMDL viewer.

State-Specific Notes

California's three-tier Risk Level system is unique among states and drives significantly different requirements for BMPs, monitoring, and reporting. Risk Level is determined by a rainfall erosivity factor and proximity to water bodies.

Disclaimer: This information is provided for general reference only and may not reflect the most current regulatory requirements. Always consult the SWRCB website and applicable regulations before beginning any construction activity.