MODEL WATER QUALITY MANAGEMENT PLAN AND TECHNICAL GUIDANCE DOCUMENT BACKGROUND

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Municipal Separate Storm Sewer System (MS4) permits issued by the Santa Ana and San Diego Regional Water Quality Control Boards (RWQCBs) require municipalities to condition “priority” new development and significant redevelopment projects to ensure they incorporate structural controls into their design which capture and infiltrate, treat, reuse, and/or evapotranspirate stormwater runoff from impervious surfaces. A Model Water Quality Management Plan (WQMP) and Technical Guidance Document (TGD) for both North and South Orange County have been prepared as guidance for “priority” new development and significant redevelopment projects within the jurisdiction of Orange County cities, unincorporated Orange County, and the right of way of the Orange County Flood Control District.  

Requirements may vary slightly between jurisdictions so it is important that project proponents contact the entity which has legal authority where the proposed project will occur.  

For projects within County of Orange/Orange County Flood Control District jurisdiction, please refer to the  County/OCFCD BMP Design Manual. 

North Orange County Project Guidance

Prepared for proposed projects located in north and central Orange County (areas north of El Toro Road): 

• Model WQMP 05.2011 - May 2011 

• Technical Guidance Document 12.2013 - December 2013 

South Orange County Project Guidance Documents

Prepared for proposed projects located in south Orange County (areas south of El Toro Road). Collectively these documents function as the “BMP Design Manual” for jurisdictions in South Orange County: 

• Model WQMP 09.2017 - September 2017 

• Technical Guidance Document 12.2013 - September 2017 

• Hydromodification Management Plan - September 2017  

• Water Quality Equivalency Guidance Document - 2018 Update 

• SOCHM Download and Guidance Document - A hydrologic model called the south Orange County Hydrology Model (SOCHM) has been developed to assist project proponents in selecting and sizing hydromodification controls where applicable.

OTHER TOOLS AND RESOURCES

The following OC Stormwater Program tools and resources are available to assist project proponents.  

Land Development Tool Web App 

• The link above will open the Land Development Tool Web App which is intended to assist with the preparation of a water quality management plans (WQMPs) for priority new development and significant redevelopment projects by providing access to site specific data based on the project location. Data attributes available through this web app include the following: 

  • The jurisdiction that has land use authority over the project and links to their requirements for priority new development and significant redevelopment projects 

  • The regional subbasin and watershed as well as downstream receiving waters  

  • Downstream impaired (Clean Water Act Section 303(d) listed) water bodies and the associated pollutants of concern 

  • Soil groups, infiltration constraints, and soil susceptibility to rill and sheet erosion (K Factor) 

  • 85th percentile rainfall amount 

  • Local groundwater information 

OC Stormwater Program Land Development Help Desk 

• The above link will open the County of Orange’s MyOCeServices website where you can submit questions on preparing a water quality management plan (WQMP). Select the “Service Request and Complaints” button from the main menu and submit an “Information and Data Request” service request form. Please include “OC Stormwater Program Land Development Help Desk Request” in the description of the service request. 

OC Public Works GIS Open Data Portal 

• OC Public Works GIS Open Data Portal includes feature layers that can assist with preparing WQMPs.