Amigos 805
June 10th, 2025
by
VENTURA — The Ventura Countywide Stormwater Quality Management Program (VCSQMP) is pleased to announce the availability of the Ventura County Technical Guidance Manual for Stormwater Quality Control Measures 2025 Reissuance (2025 TGM). The 2025 TGM is a comprehensive resource that provides sizing and design guidance for post-construction stormwater quality control measures that comply with requirements in the Regional Phase I Municipal Separate Storm Sewer System (MS4) Permit for stormwater and non-stormwater discharges within the coastal watersheds of Los Angeles and Ventura Counties (CAS004004, Order No. R4-2021-0105, 2021 Regional MS4 Permit).
2021 Regional MS4 Permit post-construction stormwater quality control measure requirements can be found in the Planning and Land Development Program of the Permit. The 2025 TGM completely replaced previous TGM versions, as Permit requirements changed. Several major changes within the 2021 Regional MS4 Permit Planning and Land Development Program include:
- Projects applicable to structural controls
- Hydromodification Management requirements
- Water Quality/Flow Reduction requirements
- Technical infeasibility considerations
- Onsite Flow-based approvals
The 2025 TGM includes all 2021 Regional MS4 Permit requirements, updated calculations and worksheets for BMP sizing, restructuring of TGM sections for easier use, and updated maps/web interface.
“The 2025 Technical Guidance Manual reflects Ventura County’s continued leadership in promoting water quality and sustainable growth,” said Peter Shellenbarger, Environmental Compliance Supervisor, City of Ventura Public Works Department. “It offers consistent, science-based guidance to help the development community design stormwater systems to control potential pollution at its source and comply with regulatory requirements.”
The 2025 TGM should be utilized for all new and redevelopment projects that are subject to the Planning and Land Development Program of the 2021 Regional MS4 Permit. The Permit’s Planning and Land Development Program became effective on May 12, 2025, following the approval letter issued by the Los Angeles Regional Water Quality Control Board for the VCSQMP’s Watershed Management Program.
For more information about the 2021 Regional Permit, and to access 2025 TGM documents, please visit https://www.vcstormwater.org/ The VCSQMP will be hosting an online training webinar Summer 2025 to help the development community understand requirements within the 2021 Regional MS4 Permit and present how these requirements were integrated into the 2025 TGM.
The VCSQMP includes the Cities of Camarillo, Fillmore, Moorpark, Ojai, Oxnard, Port Hueneme, Simi Valley, Santa Paula, Thousand Oaks, Ventura, the County of Ventura, and the Ventura County Watershed Protection District. These agencies work together to improve dry and wet weather runoff quality, monitor the health of our watersheds, and meet compliance requirements contained in the 2021 Regional MS4 Permit. More information about VCSQMP and ways to reduce pollution locally, please visit https://www.vcstormwater.org/ and http://www.cleanwatershed.org/\
