Countywide Model SUSMP July 17, 2008

Topics SUSMP Timeline Goals Approach to Compliance NPDES Permit Requirements NPDES Permit Requirements Model SUSMP Features Model SUSMP Features

Model SUSMP Timeline 12/06 Bay Area presentations to Hydromodification Work Group 5/07 Consultant team selected 10/07 Discussed Proposed SUSMP Approach with Hydromodification Work Group 11/07 Prepared interim updates to Model SUSMP 2/08 Presented SUSMP Approach to TAC and Water Board 3/08 Presented SUSMP Approach to Development Community 4/08 Received task order to prepare the SUSMP 5/08 Discussed detailed outline and principal issues with Hydromodification Work Group 6/08 Drafts dated June 12 and June 26 7/08 July 16 draft and July 24 submittal

Goals for SUSMP Make it easier for applicants to prepare submittals Make it easier for municipal staff to review submittals for compliance Promote consistent and fair implementation countywide Integrate LID, treatment, and hydrograph modification management requirements

SUSMP Compliance Approach Comply with new requirements: Low Impact Development Low Impact Development Treatment Treatment Hydromodification management Hydromodification management Provide options and flexibility Municipalities Municipalities Developers Developers Create option to use integrated design approach Promote consistent and complete presentation of design information and calculations

Low Impact Development D.1.d.(4) NPDES Permit: Use LID site design principles Use LID site design principles Drain a portion of impervious areas to pervious areas Drain a portion of impervious areas to pervious areas Use permeable surfaces Use permeable surfaces Model SUSMP—LID Design Guide Guidance for applying site design principles and using pervious pavements Guidance for applying site design principles and using pervious pavements Divide the site into Drainage Management Areas Divide the site into Drainage Management Areas Identify surface cover for each DMA Identify surface cover for each DMA Account for drainage from each DMA Account for drainage from each DMA Design criteria for LID features and facilities Design criteria for LID features and facilities Design recommendations learned from experience Design recommendations learned from experience

Treatment Controls D.1.d.(6) NPDES Permit Infiltrate, filter, or treat flow from all developed portions of the project Infiltrate, filter, or treat flow from all developed portions of the project Select more effective controls including bioretention Select more effective controls including bioretention Correctly size and design to achieve MEP Correctly size and design to achieve MEP Model SUSMP LID Design Guide ensures integrated LID design meets treatment criteria LID Design Guide ensures integrated LID design meets treatment criteria SUSMP specifies selection and design criteria if applicant chooses not to use the integrated approach SUSMP specifies selection and design criteria if applicant chooses not to use the integrated approach

Hydromodification (D.1.d.10) NPDES Permit: Apply criteria so runoff rates, durations, and velocities are controlled (all projects) Apply criteria so runoff rates, durations, and velocities are controlled (all projects) Interim criteria for projects 50 acres and up Interim criteria for projects 50 acres and up To be superseded by HMP (D.1.g.) To be superseded by HMP (D.1.g.) Model SUSMP Integrated LID design controls runoff rates Integrated LID design controls runoff rates Facility designs will be updated for HMP Facility designs will be updated for HMP Option to perform continuous simulation Option to perform continuous simulation

Source Controls (D.1.d.(5)) NPDES Permit: Implement source control BMPs to minimize pollutants of concern Implement source control BMPs to minimize pollutants of concern Model SUSMP: Appendix lists sources to be controlled and specifies the control measures to be used Appendix lists sources to be controlled and specifies the control measures to be used

Implementation Process (D.1.d.(9)) NPDES Permit: Each Copermittee shall implement a process Each Copermittee shall implement a process Identify measures necessary for implementation Identify measures necessary for implementation Model SUSMP: Acknowledges each municipality will apply their own requirements Acknowledges each municipality will apply their own requirements Provides a general model for preparing project submittals Provides a general model for preparing project submittals Facilitates countywide consistency and streamlined reviews Facilitates countywide consistency and streamlined reviews

Pollutants of Concern (D.1.d.(3)) NPDES Permit Local SUSMPs shall include a procedure to identify Pollutants of Concern Local SUSMPs shall include a procedure to identify Pollutants of Concern Model SUSMP Pragmatic approach Pragmatic approach Identify Pollutants of Concern countywide Identify Pollutants of Concern countywide Specify practicable and effective source controls and treatment controls Specify practicable and effective source controls and treatment controls Allow for rare circumstances when controls should be tailored to land use or watershed Allow for rare circumstances when controls should be tailored to land use or watershed

Summary Pro-active approach to compliance with new NPDES Permit requirements Flexibility for municipalities and developers Detailed support for an integrated design option applicable to most developments Promotes consistency and streamlined preparation and review of submittals Incorporates design knowledge and lessons learned from LID implementation