Our MS4 Permit

[NEW] Regional Phase I Municipal Separate Storm Sewer System (MS4) National Pollutant Discharge Elimination System (NPDES) Permit

The Los Angeles Regional Water Quality Control Board (Regional Board) adopted a new regional permit, Order R4-2021-0105 (Regional Permit), on July 23, 2021, that covers Ventura and Los Angeles Counties and all the incorporated cities therein. As of its effective date, September 11, 2021, the regional permit supersedes the three Orders that covered the Permittees in the region: R4-2010-0108 (Ventura County), R4-2012-0175 (Los Angeles County except for the City of Long Beach), and R4-2014-0024 (City of Long Beach). Many decisions and actions are required of the permittees in the first 30 months following the Permit effective date. Key among them are deciding whether to implement a Watershed Management Program, Monitoring Program coordination, and filing the corresponding Notices of Intent. Significant dates for action include:

September 11, 2021:    Permit Effective Date
December 13, 2021:     File Notice of Intent (NOI) for Watershed Management Programs (WMP)
December 13, 2021:      File NOI for Monitoring Plans
March 11, 2022:             Implement new/modified minimum requirements if not doing a WMP
September 11, 2023:    Submit WMP and Monitoring Program for approval

Information on the development of the Regional Permit is available on the Regional Board's website under "Regional Permit (in development)".


[NEW] Regional Phase I Municipal Separate Storm Sewer System (MS4) Permit, Order R4-2021-0105, effective September 11, 2021


Regional NPDES Municipal Stormwater Permit (R4-2021-0105)

Attachment A       Definitions
Attachment B       Watershed Management Area Maps
Attachment C       MS4 Maps
Attachment D       Standard Provisions
Attachment E       Monitoring and Reporting Program
Attachment F       Fact Sheet
Attachment G       Aquatic Toxicity
Attachment H-a    Reporting Forms (PDF)
Attachment H-b    WMP Progress Report Form (MS Word zip)
Attachment H-c    Annual Report Form (MS Word zip)
Attachment I-a     Trash Reporting Forms (PDF)
Attachment I-b     Trash Reporting Forms (MS Excel zip)
Attachment I-c     Trash Reporting Forms (MS Excel zip)
Attachment J        Permittees & TMDL Matrix
Attachment K        Ventura River TMDLs (Ventura County)
Attachment L        VC Miscellaneous Coastal Watersheds (MCW) TMDLs (Ventura County)
Attachment M        SCR TMDLs (Ventura and Los Angeles Counties)
Attachment N        Calleguas Creek TMDLs (Ventura County)
Attachment O        SMB TMDLs (Ventura and Los Angeles Counties)
Attachment P        Dominguez Channel TMDLs (Los Angeles County)
Attachment Q        Los Angeles River TMDLs (Los Angeles County)
Attachment R        San Gabriel River TMDLs (Los Angeles County)
Attachment S        LCC-AB TMDLs (Los Angeles County)


Ventura Countywide MS4 Stormwater Permit, R4-2010-0108, (2010 - September 11, 2021)

Ventura Countywide Stormwater Permit Order No. R4-2010-0108 was adopted in 2010 for a five year term. The Permit expired on July 8, 2015, but continued on administrative extension until the new Regional Permit effective date: September 11, 2021. As required by the Permit, Ventura County Permittees submitted a Report of Waste Discharge (ROWD) to the Los Angeles Regional Water Quality Control Board (Regional Board) in January 2015. The ROWD summarizes the accomplishments and challenges of the Permittees under this permit.

Documents regarding the Ventura Countywide Stormwater Permit are available at the Regional Board website here: Ventura Countywide Municipal Stormwater Permit


Countywide NPDES Municipal Stormwater Permit (R4-2010-0108)

Attachment A (Watershed Management Areas)
Attachment B (Pollutants of Concern)
Attachment C (Treatment BMP Performance Standards and Effluent Concentrations as Median Values)
Attachment D (Critical Sources Categories)
Attachment E (Determination of Erosion Potential)
Attachment F (Monitoring Program)
Attachment G (Constituents with Associated Minimum Levels)
Attachment H (Major Outfall Stations)
Attachment I (Reporting Program Requirements)


Previous Ventura Countywide MS4 Stormwater Permits

Countywide NPDES Municipal Stormwater Permit (R4-09-0057, 2009)

Countywide NPDES Municipal Stormwater Permit (R4-00-108, 2000-2009)